Author(s) ID,Title,Year,DOI,Link,Abstract
"7103271625;8733579800;6701618837;7103206141;7006306835;55286185400;6701752471;57208462871;57208455668;35514163500;7402093416;42961002600;7102665209;6701379896;6603396333;7401477391;6603715895;7005808242;6508244744;7402064802;7003554208;57081464900;57054407300;25823927100;6603779823;7005884486;7006003831;56244473600;7103033590;57205867148;6603173671;56744278700;6603171355;8733579000;6508004743;7103366892;7101632204;57199296506;7003802133;6602864692;54382704000;","The dynamical core, physical parameterizations, and basic simulation characteristics of the atmospheric component AM3 of the GFDL global coupled model CM3",2011,"10.1175/2011JCLI3955.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955044421&doi=10.1175%2f2011JCLI3955.1&partnerID=40&md5=67c12e311444a23337eabd4464ea18ec","The Geophysical Fluid Dynamics Laboratory (GFDL) has developed a coupled general circulation model (CM3) for the atmosphere, oceans, land, and sea ice. The goal of CM3 is to address emerging issues in climate change, including aerosol-cloud interactions, chemistry-climate interactions, and coupling between the troposphere and stratosphere. The model is also designed to serve as the physical system component of earth system models and models for decadal prediction in the near-term future-for example, through improved simulations in tropical land precipitation relative to earlier-generation GFDL models. This paper describes the dynamical core, physical parameterizations, and basic simulation characteristics of the atmospheric component (AM3) of this model. Relative to GFDL AM2, AM3 includes new treatments of deep and shallow cumulus convection, cloud droplet activation by aerosols, subgrid variability of stratiform vertical velocities for droplet activation, and atmospheric chemistry driven by emissions with advective, convective, and turbulent transport. AM3 employs a cubed-sphere implementation of a finite-volume dynamical core and is coupled to LM3, a new land model with ecosystem dynamics and hydrology. Its horizontal resolution is approximately 200 km, and its vertical resolution ranges approximately from 70 m near the earth's surface to 1 to 1.5 km near the tropopause and 3 to 4 km in much of the stratosphere. Most basic circulation features in AM3 are simulated as realistically, or more so, as in AM2. In particular, dry biases have been reduced over South America. In coupled mode, the simulation of Arctic sea ice concentration has improved. AM3 aerosol optical depths, scattering properties, and surface clear-sky downward shortwave radiation are more realistic than in AM2. The simulation of marine stratocumulus decks remains problematic, as in AM2. The most intense 0.2% of precipitation rates occur less frequently in AM3 than observed. The last two decades of the twentieth century warm in CM3 by 0.328C relative to 1881-1920. The Climate Research Unit (CRU) and Goddard Institute for Space Studies analyses of observations show warming of 0.568 and 0.528C, respectively, over this period. CM3 includes anthropogenic cooling by aerosol-cloud interactions, and its warming by the late twentieth century is somewhat less realistic than in CM2.1, which warmed 0.668C but did not include aerosol-cloud interactions. The improved simulation of the direct aerosol effect (apparent in surface clear-sky downward radiation) in CM3 evidently acts in concert with its simulation of cloud-aerosol interactions to limit greenhouse gas warming. © 2011 American Meteorological Society."
"7102953444;","Global dimming and brightening: A review",2009,"10.1029/2008JD011470","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954336394&doi=10.1029%2f2008JD011470&partnerID=40&md5=d0d4d2c96e6a3c8e57a72c6045e1cf2e","There is increasing evidence that the amount of solar radiation incident at the Earth's surface is not stable over the years but undergoes significant decadal variations. Here I review the evidence for these changes, their magnitude, their possible causes, their representation in climate models, and their potential implications for climate change. The various studies analyzing long-term records of surface radiation measurements suggest a widespread decrease in surface solar radiation between the 1950s and 1980s (""global dimming""), with a partial recovery more recently at many locations (""brightening""). There are also some indications for an ""early brightening"" in the first part of the 20th century. These variations are in line with independent long-term observations of sunshine duration, diurnal temperature range, pan evaporation, and, more recently, satellite-derived estimates, which add credibility to the existence of these changes and their larger-scale significance. Current climate models, in general, tend to simulate these decadal variations to a much lesser degree. The origins of these variations are internal to the Earth's atmosphere and not externally forced by the Sun. Variations are not only found under cloudy but also under cloud-free atmospheres, indicative of an anthropogenic contribution through changes in aerosol emissions governed by economic developments and air pollution regulations. The relative importance of aerosols, clouds, and aerosol-cloud interactions may differ depending on region and pollution level. Highlighted are further potential implications of dimming and brightening for climate change, which may affect global warming, the components and intensity of the hydrological cycle, the carbon cycle, and the cryosphere among other climate elements. Copyright 2009 by the American Geophysical Union."
"37032346000;35464731600;7102517130;7003591311;7004174939;57189585133;6701597468;10139397300;6701465132;7005135473;15724620800;7201463831;56249704400;7004364155;35510362500;57205638870;7202079615;55448830800;","A review of measurement-based assessments of the aerosol direct radiative effect and forcing",2006,"10.5194/acp-6-613-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645805647&doi=10.5194%2facp-6-613-2006&partnerID=40&md5=5fc9dce112678486813be314880a9f43","Aerosols affect the Earth's energy budget directly by scattering and absorbing radiation and indirectly by acting as cloud condensation nuclei and, thereby, affecting cloud properties. However, large uncertainties exist in current estimates of aerosol forcing because of incomplete knowledge concerning the distribution and the physical and chemical properties of aerosols as well as aerosol-cloud interactions. In recent years, a great deal of effort has gone into improving measurements and datasets. It is thus feasible to shift the estimates of aerosol forcing from largely model-based to increasingly measurement-based. Our goal is to assess current observational capabilities and identify uncertainties in the aerosol direct forcing through comparisons of different methods with independent sources of uncertainties. Here we assess the aerosol optical depth (τ), direct radiative effect (DRE) by natural and anthropogenic aerosols, and direct climate forcing (DCF) by anthropogenic aerosols, focusing on satellite and ground-based measurements supplemented by global chemical transport model (CTM) simulations. The multi-spectral MODIS measures global distributions of aerosol optial depth (τ) on a daily scale, with a high accuracy of ±0.03±0.05τ over ocean. The annual average τ is about 0.14 over global ocean, of which about 21%±7% is contributed by human activities, as estimated by MODIS fine-mode fraction. The multi-angle MISR derives an annual average AOD of 0.23 over global land with an uncertainty of ∼20% or ±0.05. These high-accuracy aerosol products and broadband flux measurements from CERES make it feasible to obtain observational constraints for the aerosol direct effect, especially over global the ocean. A number of measurment-based approaches estimate the clear-sky DRE (on solar radiation) at the top-of-atmosphere (TOA) to be about -5.5±0.2 Wm-2 (median ± standard error from various methods) over the global ocean. Accounting for thin cirrus contamination of the satellite derived aerosol field will reduce the TOA DRE to -5.0 Wm-2. Because of a lack of measurements of aerosol absorption and difficulty in characterizing land surface reflection, estimates of DRE over land and at the ocean surface are currently realized through a combination of satellite retrievals, surface measurements, and model simulations, and are less constrained. Over the oceans the surface DRE is estimated to be -8.8±0.7 Wm-2. Over land, an integration of satellite retrievals and model simulations derives a DRE of -4.9±0.7 Wm-2 and -11.8±1.9 Wm-2 at the TOA and surface, respectively. CTM simulations derive a wide range of DRE estimates that on average are smaller than the measurement-based DRE by about 30-40%, even after accounting for thin cirrus and cloud contamination. A number of issues remain. Current estimates of the aerosol direct effect over land are poorly constrained. Uncertainties of DRE estimates are also larger on regional scales than on a global scale and large discrepancies exist between different approaches. The characterization of aerosol absorption and vertical distribution remains challenging. The aerosol direct effect in the thermal infrared range and in cloudy conditions remains relatively unexplored and quite uncertain, because of a lack of global systematic aerosol vertical profile measurements. A coordinated research strategy needs to be developed for integration and assimilation of satellite measurements into models to constrain model simulations. Enhanced measurements capabilities in the next few years and high-level scientific cooperation will further advance our knowledge. © 2006 Author(s). This work is licensed under a Creative Commons License."
"7202079615;10240710000;8979277400;35330367300;7404243086;","Simulation of climate response to aerosol direct and indirect effects with aerosol transport-radiation model",2005,"10.1029/2004JD005029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16444367564&doi=10.1029%2f2004JD005029&partnerID=40&md5=448d2f38be65ab70aaff2774e93a85a7","With a global aerosol transport-radiation model coupled to a general circulation model, changes in the meteorological parameters of clouds, precipitation, and temperature caused by the direct and indirect effects of aerosols are simulated, and its radiative forcing are calculated. A microphysical parameterization diagnosing the cloud droplet number concentration based on the Köhler theory is introduced into the model, which depends not only on the aerosol particle number concentration but also on the updraft velocity, size distributions, and chemical properties of each aerosol species and saturation condition of the water vapor. The simulated cloud droplet effective radius, cloud radiative forcing, and precipitation rate, which relate to the aerosol indirect effect, are in reasonable agreement with satellite observations. The model results indicate that a decrease in the cloud droplet effective radius by anthropogenic aerosols occurs globally, while changes in the cloud water and precipitation are strongly affected by a variation of the dynamical hydrological cycle with a temperature change by the aerosol direct and first indirect effects rather than the second indirect effect itself. However, the cloud water can increase and the precipitation can simultaneously decrease in regions where a large amount of anthropogenic aerosols and cloud water exist, which is a strong signal of the second indirect effect. The global mean radiative forcings of the direct and indirect effects at the tropopause by anthropogenic aerosols are calculated to be -0.1 and -0.9 W m -2, respectively. It is suggested that aerosol particles approximately reduce 40% of the increase in the surface air temperature by anthropogenic greenhouse gases on the global mean. Copyright 2005 by the American Geophysical Union."
"35561911800;9242540400;56203249800;6604021707;7401548835;9242539000;57191598636;22978151200;24538369000;7004177660;7004409909;36851768400;55339475000;6603552777;57193132723;6505881672;12240390300;7404334532;7006224475;57191693467;56249704400;7006399110;8954866200;57191692422;12241892400;7102967367;7201837768;36705143500;6506806004;35094442700;55403720400;8414341100;8687063000;7006550762;12763470600;7405727977;7004214645;56528677800;56126782200;55408944000;6507308842;14829673100;22986631300;7403318365;57203378018;","Configuration and assessment of the GISS ModelE2 contributions to the CMIP5 archive",2014,"10.1002/2013MS000265","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893558445&doi=10.1002%2f2013MS000265&partnerID=40&md5=e1b1350cc5695cd9ae8b4eec93742aec","We present a description of the ModelE2 version of the Goddard Institute for Space Studies (GISS) General Circulation Model (GCM) and the configurations used in the simulations performed for the Coupled Model Intercomparison Project Phase 5 (CMIP5). We use six variations related to the treatment of the atmospheric composition, the calculation of aerosol indirect effects, and ocean model component. Specifically, we test the difference between atmospheric models that have noninteractive composition, where radiatively important aerosols and ozone are prescribed from precomputed decadal averages, and interactive versions where atmospheric chemistry and aerosols are calculated given decadally varying emissions. The impact of the first aerosol indirect effect on clouds is either specified using a simple tuning, or parameterized using a cloud microphysics scheme. We also use two dynamic ocean components: the Russell and HYbrid Coordinate Ocean Model (HYCOM) which differ significantly in their basic formulations and grid. Results are presented for the climatological means over the satellite era (1980-2004) taken from transient simulations starting from the preindustrial (1850) driven by estimates of appropriate forcings over the 20th Century. Differences in base climate and variability related to the choice of ocean model are large, indicating an important structural uncertainty. The impact of interactive atmospheric composition on the climatology is relatively small except in regions such as the lower stratosphere, where ozone plays an important role, and the tropics, where aerosol changes affect the hydrological cycle and cloud cover. While key improvements over previous versions of the model are evident, these are not uniform across all metrics. Key Points Description of the GISS ModelE2 contribution to CMIP5 Impact on evaluation of structural changes in composition and ocean treatment Ocean model choice is an important structural uncertainty © 2014. American Geophysical Union. All Rights Reserved."
"7203001286;","A parameterization of sea-salt aerosol source function for sub- and super-micron particles",2003,"10.1029/2003gb002079","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642365865&doi=10.1029%2f2003gb002079&partnerID=40&md5=c011aadb4db6820c3595aec9824b694c","A parameterization of a sea-salt source function for both sub- and super-micron particles was developed based on the semi-empirical formulation of Monahan et al. [1986]. This new parameterization extends the range of Monahan's equation to below 0.2 μm in diameter where it has been found to overestimate submicron sea-salt aerosols, especially the sea-salt number concentrations. The new parameterization was used in a one-dimensional (1-D) column model to predict the number size distributions and compared with reasonable agreement to the observed distributions at various wind speeds reported by O'Dowd et at. [1997]. A global 3-D sea-salt simulation with this parameterization was also made and a much better dependence of sea-salt on surface wind speed was predicted than other schemes compared to observations. For an indirect impact assessment of sea-salt aerosols on climate where submicron particles may have a dominant contribution to aerosol-cloud interactions, this scheme provides the most realistic number flux of sea-salt particles between ocean and atmosphere. Copyright 2003 by the American Geophysical Union."
"7402822814;7102783229;","From molecular clusters to nanoparticles: Role of ambient ionization in tropospheric aerosol formation",2001,"10.1029/2000JD900539","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034950753&doi=10.1029%2f2000JD900539&partnerID=40&md5=aa967edc270bf9b45e5c9ffdb8332449","We investigate the role of background ionization, associated mainly with galactic cosmic radiation, in the generation and evolution of ultrafine particles in the marine boundary layer. We follow the entire course of aerosol evolution, from the initial buildup of molecular clusters (charged and uncharged) through their growth into stable nanoparticles. The model used for this purpose is based on a unified collisional (kinetic) mechanism that treats the interactions between vapors, neutral and charged clusters, and particles at all sizes. We show that air ions are likely to play a central role in the formation of new ultrafine particles. The nucleation of aerosols under atmospheric conditions involves a series of competing processes, including molecular aggregation, evaporation, and scavenging by preexisting particles. In this highly sensitive nonlinear system, electrically charged embryos have a competitive advantage over similar neutral embryos. The charged clusters experience enhanced growth and stability as a consequence of electrostatic interactions. Simulations of a major nucleation event observed during the Pacific Exploratory Mission (PEM) Tropics-A can explain most of the observed features in the ultrafine particle behavior. The key parameters controlling this behavior are the concentrations of precursor vapors and the surface area of preexisting particles, as well as the background ionization rate. We find that systematic variations in ionization levels due to the modulation of galactic cosmic radiation by the solar cycle are sufficient to cause a notable variation in aerosol production. This effect is greatest when the ambient nucleation rate is limited principally by the availability of ions. Hence we conclude that the greatest influence of such ionization is likely to occur in and above the marine boundary layer. While a systematic change in the ultrafine particle production rate is likely to affect the population of cloud condensation nuclei and hence cloud optical properties, the magnitude of the effect cannot be directly inferred from the present analysis, and requires additional analysis based on specific aerosol-cloud interactions. Copyright 2001 by the American Geophysical Union."
"6602600408;7006306835;7201837768;7202079615;56162305900;7102604282;25031430500;57203053317;10139397300;57203200427;18635289400;56920790500;14035836100;7003591311;24398842400;35183351400;55717074000;6701597468;7103271625;57208462871;57208121852;35221443100;7003931528;6603140753;22978151200;56249704400;7103353990;35221524700;56250250300;12139310900;7006270084;7003666669;7006705919;7103158465;7102976560;7003311618;56270311300;57205638870;","Aerosol indirect effects ĝ€"" general circulation model intercomparison and evaluation with satellite data",2009,"10.5194/acp-9-8697-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70450257537&doi=10.5194%2facp-9-8697-2009&partnerID=40&md5=e73ec0fd8f381e057a288edbc08cafd8","Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterises aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth (τ a) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (Nd) compares relatively well to the satellite data at least over the ocean. The relationship between τa and liquid water path is simulated much too strongly by the models. This suggests that the implementation of the second aerosol indirect effect mainly in terms of an autoconversion parameterisation has to be revisited in the GCMs. A positive relationship between total cloud fraction (fcld) and τ a as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strongfcldĝ€""τa relationship, our results indicate that none can be identified as a unique explanation. Relationships similar to the ones found in satellite data between τa and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLRĝ€""τ a relationship show a strong positive correlation between τa andf</ i>cld. The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of τa, and parameterisation assumptions such as a lower bound onNd. Nevertheless, the strengths of the statistical relationships are good predictors for the aerosol forcings in the models. An estimate of the total short-wave aerosol forcing inferred from the combination of these predictors for the modelled forcings with the satellite-derived statistical relationships yields a global annual mean value of −1.5±0.5 Wm−2. In an alternative approach, the radiative flux perturbation due to anthropogenic aerosols can be broken down into a component over the cloud-free portion of the globe (approximately the aerosol direct effect) and a component over the cloudy portion of the globe (approximately the aerosol indirect effect). An estimate obtained by scaling these simulated clear- and cloudy-sky forcings with estimates of anthropogenic τa and satellite-retrievedNd</ i>ĝ€""τa regression slopes, respectively, yields a global, annual-mean aerosol direct effect estimate of −0.4±0.2 Wm−2 and a cloudy-sky (aerosol indirect effect) estimate of −0.7±0.5 Wm−2, with a total estimate of −1.2±0. 4 Wm−2."
"7201504886;23019327900;7004084412;7202185413;7006901405;7004106194;55896920900;7004479957;7004393835;7004165697;7101888953;6602514643;7006202844;6603770689;7004965049;23047834100;6508268711;7003606341;7004484563;8586682800;7402049334;7202252296;16178543600;7004838931;7005859154;6602874667;7402956927;57209341911;7003415852;7004198777;7006494557;56350405800;","Dynamics and Chemistry of Marine Stratocumulus - DYCOMS-II",2003,"10.1175/BAMS-84-5-579","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038275770&doi=10.1175%2fBAMS-84-5-579&partnerID=40&md5=0bd0feef242fdc1c5ae2054188b34cb2","The second Dynamics and Chemistry of Marine Stratocumulus (DYCOMS-II) field study is described. The field program consisted of nine flights in marine stratocumulus west-southwest of San Diego, California. The objective of the program was to better undersland the physics and dynamics of marine stratocumulus. Toward this end special flight strategies, including predominantly nocturnal flights, were employed to optimize estimates of entrainment velocities at cloud-top, large-scale divergence within the boundary layer, drizzle processes in the cloud, cloud microstructure, and aerosol-cloud interactions. Cloud conditions during DYCOMS-II were excellent with almost every flight having uniformly overcast clouds topping a well-mixed boundary layer. Although the emphasis of the manuscript is on the goals and methodologies of DYCOMS-II, some preliminary findings are also presented - the most significant being that the cloud layers appear to entrain less and drizzle more than previous theoretical work led investigators to expect. (Page 579)."
"55896920900;6701596624;56706602500;8380252900;7404369915;6603892183;","Radiative properties of boundary layer clouds: Droplet effective radius versus number concentration",2000,"10.1175/1520-0469(2000)057<0803:RPOBLC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034062157&doi=10.1175%2f1520-0469%282000%29057%3c0803%3aRPOBLC%3e2.0.CO%3b2&partnerID=40&md5=51cf96fa43e4d4df86c7dbd3b172f97f","The plane-parallel model for the parameterization of clouds in global climate models is examined in order to estimate the effects of the vertical profile of the microphysical parameters on radiative transfer calculations for extended boundary layer clouds. The vertically uniform model is thus compared to the adiabatic stratified one. The validation of the adiabatic model is based on simultaneous measurements of cloud microphysical parameters in situ and cloud radiative properties from above the cloud layer with a multispectral radiometer. In particular, the observations demonstrate that the dependency of cloud optical thickness on cloud geometrical thickness is larger than predicted with the vertically uniform model and that it is in agreement with the prediction of the adiabatic one. Numerical simulations of the radiative transfer have been performed to establish the equivalence between the two models in terms of the effective radius. They show that the equivalent effective radius of a vertically uniform model is between 80% and 100% of the effective radius at the top of an adiabatic stratified model. The relationship depends, in fact, upon the cloud geometrical thickness and droplet concentration. Remote sensing measurements of cloud radiances in the visible and near infrared are then examined at the scale of a cloud system for a marine case and the most polluted case sampled during the second Aerosol Characterization Experiment. The distributions of the measured values are significantly different between the two cases. This constitutes observational evidence of the aerosol indirect effect at the scale of a cloud system. Finally, the adiabatic stratified model is used to develop a procedure for the retrieval of cloud geometrical thickness and cloud droplet number concentration from the measurements of cloud radiances. It is applied to the marine and to the polluted cases. The retrieved values of droplet concentration are significantly underestimated with respect to the values measured in situ. Despite this discrepancy the procedure is efficient at distinguishing the difference between the two cases.The plane-parallel model for the parameterization of clouds in global climate models is examined in order to estimate the effects of the vertical profile of the microphysical parameters on radiative transfer calculations for extended boundary layer clouds. The vertically uniform model is thus compared to the adiabatic stratified one. The validation of the adiabatic model is based on simultaneous measurements of cloud microphysical parameters in situ and cloud radiative properties from above the cloud layer with a multispectral radiometer. In particular, the observations demonstrate that the dependency of cloud optical thickness on cloud geometrical thickness is larger than predicted with the vertically uniform model and that it is in agreement with the prediction of the adiabatic one. Numerical simulations of the radiative transfer have been performed to establish the equivalence between the two models in terms of the effective radius. They show that the equivalent effective radius of a vertically uniform model is between 80% and 100 of the effective radius at the top of an adiabatic stratified model. The relationship depends, in fact, upon the cloud geometrical thickness and droplet concentration. Remote sensing measurements of cloud radiances in the visible and near infrared are then examined at the scale of a cloud system for a marine case and the most polluted case sampled during the second Aerosol Characterization Experiment. The distributions of the measured values are significantly different between the two cases. This constitutes observational evidence of the aerosol indirect effect at the scale of a cloud system. Finally, the adiabatic stratified model is used to develop a procedure for the retrieval of cloud geometrical thickness and cloud droplet number concentration from the measurements of cloud radiances. It is applied to the marine and to the polluted cases. The retrieved values of droplet concentration are significantly underestimated with respect to the values measured in situ. Despite this discrepancy the procedure is efficient at distinguishing the difference between the two cases."
"10139397300;18134523600;7407104838;7405666962;7102805852;57203200427;","Aerosol forcing in the Climate Model Intercomparison Project (CMIP5) simulations by HadGEM2-ES and the role of ammonium nitrate",2011,"10.1029/2011JD016074","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80455150395&doi=10.1029%2f2011JD016074&partnerID=40&md5=04260d7410aff283c9f74572d66382d9","The latest Hadley Centre climate model, HadGEM2-ES, includes Earth system components such as interactive chemistry and eight species of tropospheric aerosols. It has been run for the period 1860-2100 in support of the fifth phase of the Climate Model Intercomparison Project (CMIP5). Anthropogenic aerosol emissions peak between 1980 and 2020, resulting in a present-day all-sky top of the atmosphere aerosol forcing of -1.6 and -1.4 W m-2 with and without ammonium nitrate aerosols, respectively, for the sum of direct and first indirect aerosol forcings. Aerosol forcing becomes significantly weaker in the 21st century, being weaker than -0.5 W m-2 in 2100 without nitrate. However, nitrate aerosols become the dominant species in Europe and Asia and decelerate the decrease in global mean aerosol forcing. Considering nitrate aerosols makes aerosol radiative forcing 2-4 times stronger by 2100 depending on the representative concentration pathway, although this impact is lessened when changes in the oxidation properties of the atmosphere are accounted for. Anthropogenic aerosol residence times increase in the future in spite of increased precipitation, as cloud cover and aerosol-cloud interactions decrease in tropical and midlatitude regions. Deposition of fossil fuel black carbon onto snow and ice surfaces peaks during the 20th century in the Arctic and Europe but keeps increasing in the Himalayas until the middle of the 21st century. Results presented here confirm the importance of aerosols in influencing the Earth's climate, albeit with a reduced impact in the future, and suggest that nitrate aerosols will partially replace sulphate aerosols to become an important anthropogenic species in the remainder of the 21st century. Copyright 2011 by the American Geophysical Union."
"57203053317;57208121852;24398842400;16444232500;55916925700;7003979342;55879827400;","Cloud microphysics and aerosol indirect effects in the global climate model ECHAM5-HAM",2007,"10.5194/acp-7-3425-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547341225&doi=10.5194%2facp-7-3425-2007&partnerID=40&md5=c240596013273b0907ea4dc8232c7406","The double-moment cloud microphysics scheme from ECHAM4 that predicts both the mass mixing ratios and number concentrations of cloud droplets and ice crystals has been coupled to the size-resolved aerosol scheme ECHAM5-HAM. ECHAM5-HAM predicts the aerosol mass, number concentrations and mixing state. The simulated liquid, ice and total water content and the cloud droplet and ice crystal number concentrations as a function of temperature in stratiform mixed-phase clouds between 0 and -35° C agree much better with aircraft observations in the ECHAM5 simulations. ECHAM5 performs better because more realistic aerosol concentrations are available for cloud droplet nucleation and because the Bergeron-Findeisen process is parameterized as being more efficient. The total anthropogenic aerosol effect includes the direct, semi-direct and indirect effects and is defined as the difference in the top-of-the-atmosphere net radiation between present-day and pre-industrial times. It amounts to -1.9 W m-2 in ECHAM5, when a relative humidity dependent cloud cover scheme and aerosol emissions representative for the years 1750 and 2000 from the AeroCom emission inventory are used. The contribution of the cloud albedo effect amounts to -0.7 W m-2. The total anthropogenic aerosol effect is larger when either a statistical cloud cover scheme or a different aerosol emission inventory are employed because the cloud lifetime effect increases."
"55570248000;6701379896;7102620639;7005808242;7006306835;36599032700;7006199823;7006354215;7402401574;8583350800;14036209800;7004613089;7003961970;55194361500;","Have aerosols caused the observed atlantic multidecadal variability?",2013,"10.1175/JAS-D-12-0331.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873417864&doi=10.1175%2fJAS-D-12-0331.1&partnerID=40&md5=c8e958eb2911277599183f356b1d8ff2","Identifying the prime drivers of the twentieth-century multidecadal variability in the Atlantic Ocean is crucial for predicting how the Atlantic will evolve in the coming decades and the resulting broad impacts on weather and precipitation patterns around the globe. Recently, Booth et al. showed that the Hadley Centre Global Environmental Model, version 2, Earth system configuration (HadGEM2-ES) closely reproduces the observed multidecadal variations of area-averaged North Atlantic sea surface temperature in the twentieth century. The multidecadal variations simulated in HadGEM2-ES are primarily driven by aerosol indirect effects thatmodify net surface shortwave radiation. On the basis of these results, Booth et al. concluded that aerosols are a prime driver of twentieth-century North Atlantic climate variability. However, here it is shown that there are major discrepancies between the HadGEM2-ES simulations and observations in the North Atlantic upper-ocean heat content, in the spatial pattern of multidecadal SST changes within and outside the NorthAtlantic, and in the subpolar NorthAtlantic sea surface salinity. These discrepanciesmay be strongly influenced by, and indeed in large part caused by, aerosol effects. It is also shown that the aerosol effects simulated in HadGEM2-ES cannot account for the observed anticorrelation between detrended multidecadal surface and subsurface temperature variations in the tropical North Atlantic. These discrepancies cast considerable doubt on the claim that aerosol forcing drives the bulk of this multidecadal variability. © 2013 American Meteorological Society."
"7003591311;7007175302;6604017350;8846887600;","First measurements of the Twomey indirect effect using ground-based remote sensors",2003,"10.1029/2002GL016633","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042691727&doi=10.1029%2f2002GL016633&partnerID=40&md5=3a03e34723acec7d20e36f59d53e5321","We demonstrate first measurements of the aerosol indirect effect using ground-based remote sensors at a continental US site. The response of nonprecipitating, icefree clouds to changes in aerosol loading is quantified in terms of a relative change in cloud-drop effective radius for a relative change in aerosol extinction under conditions of equivalent cloud liquid water path. This is done in a single column of air at a temporal resolution of 20 s (spatial resolution of ∼ 100 m). Cloud-drop effective radius is derived from a cloud radar and microwave radiometer. Aerosol extinction is measured below cloud base by a Raman lidar. Results suggest that aerosols associated with maritime or northerly air trajectories tend to have a stronger effect on clouds than aerosols associated with northwesterly trajectories that also have local influence. There is good correlation (0.67) between the cloud response and a measure of cloud turbulence."
"7203001286;7006084942;27267529400;6603613067;57203053317;6603452105;6701553081;16173929000;7003908632;55807293800;7801611677;7003371432;7007067997;16444196600;","Canadian Aerosol Module: A size-segregated simulation of atmospheric aerosol processes for climate and air quality models 1. Module development",2003,"10.1029/2001jd002002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347269076&doi=10.1029%2f2001jd002002&partnerID=40&md5=4d6ca4ea531045897e125adb7bee107e","A size-segregated multicomponent aerosol algorithm, the Canadian Aerosol Module (CAM), was developed for use with climate and air quality models. It includes major aerosol processes in the atmosphere: generation, hygroscopic growth, coagulation, nucleation, condensation, dry deposition/sedimentation, below-cloud scavenging, aerosol activation, a cloud module with explicit microphysical processes to treat aerosol-cloud interactions and chemical transformation of sulphur species in clear air and in clouds. The numerical solution was optimized to efficiently solve the complicated size-segregated multicomponent aerosol system and make it feasible to be included in global and regional models. An internal mixture is assumed for all types of aerosols except for soil dust and black carbon which are assumed to be externally mixed close to sources. To test the algorithm, emissions to the atmosphere of anthropogenic and natural aerosols are simulated for two aerosol types: sea salt and sulphate. A comparison was made of two numerical solutions of the aerosol algorithm: process splitting and ordinary differential equation (ODE) solver. It was found that the process-splitting method used for this model is within 15% of the more accurate ODE solution for the total sulphate mass concentration and <1% accurate for sea-salt concentration. Furthermore, it is computationally more than 100 times faster. The sensitivity of the simulated size distributions to the number of size bins was also investigated. The diffusional behavior of each individual process was quantitatively characterized by the difference in the mode radius and standard deviation of a lognormal curve fit of distributions between the approximate solution and the 96-bin reference solution. Both the number and mass size distributions were adequately predicted by a sectional model of 12 bins in many situations in the atmosphere where the sink for condensable matter on existing aerosol surface area is high enough that nucleation of new particles is negligible. Total mass concentration was adequately simulated using lower size resolution of 8 bins. However, to properly resolve nucleation mode size distributions and minimize the numerical diffusion, a sectional model of 18 size bins or greater is needed. The number of size bins is more important in resolving the nucleation mode peaks than in reducing the diffusional behavior of aerosol processes. Application of CAM in a study of the global cycling of sea-salt mass accompanies this paper [Gong et al, 2002]."
"6701378450;57196499374;","Parameterization of cloud droplet formation in global climate models",2003,"10.1029/2002jd002911","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0742287914&doi=10.1029%2f2002jd002911&partnerID=40&md5=271d066b3d68ebe7c2cebd63a909f56d","An aerosol activation parameterization has been developed based on a generalized representation of aerosol size and composition within the framework of an ascending adiabatic parcel; this allows for parameterizing the activation of chemically complex aerosol with an arbitrary size distribution and mixing state. The new parameterization introduces the concept of ""population splitting,"" in which the cloud condensation nuclei (CCN) that form droplets are treated as two separate populations: those that have a size close to their critical diameter and those that do not. Explicit consideration of kinetic limitations on droplet growth is introduced. Our treatment of the activation process unravels much of its complexity. As a result of this, a substantial number of conditions of droplet formation can be treated completely free of empirical information or correlations; there are, however, some conditions of droplet activation for which an empirically derived correlation is utilized. Predictions of the parameterization are compared against extensive cloud parcel model simulations for a variety of aerosol activation conditions that cover a wide range of chemical variability and CCN concentrations. The parameterization tracks the parcel model simulations closely and robustly. The parameterization presented here is intended to allow for a comprehensive assessment of the aerosol indirect effect in general circulation models."
"8511991900;24081888700;7006303509;7003666669;7005742394;7202048112;7409080503;16507384700;55405340400;","Dominant role by vertical wind shear in regulating aerosol effects on deep convective clouds",2009,"10.1029/2009JD012352","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049112292&doi=10.1029%2f2009JD012352&partnerID=40&md5=f63aef430a9208b3ac259981089bfb42","Aerosol-cloud interaction is recognized as one of the key factors influencing cloud properties and precipitation regimes across local, regional, and global scales and remains one of the largest uncertainties in understanding and projecting future climate changes. Deep convective clouds (DCCs) play a crucial role in the general circulation, energy balance, and hydrological cycle of our climate system. The complex aerosol-DCC interactions continue to be puzzling as more ""aerosol effects"" unfold, and systematic assessment of such effects is lacking. Here we systematically assess the aerosol effects on isolated DCCs based on cloud-resolving model simulations with spectral bin cloud microphysics. We find a dominant role of vertical wind shear in regulating aerosol effects on isolated DCCs, i.e., vertical wind shear qualitatively determines whether aerosols suppress or enhance convective strength. Increasing aerosols always suppresses convection under strong wind shear and invigorates convection under weak wind shear until this effect saturates at an optimal aerosol loading. We also found that the decreasing rate of convective strength is greater in the humid air than that in the dry air when wind shear is strong. Our findings may resolve some of the seemingly contradictory results among past studies by considering the dominant effect of wind shear. Our results can provide the insights to better parameterize aerosol effects on convection by adding the factor of wind shear to the entrainment term, which could reduce uncertainties associated with aerosol effects on climate forcing. Copyright 2009 by the American Geophysical Union."
"7202516876;7003591311;","Large-eddy simulations of trade wind cumuli: Investigation of aerosol indirect effects",2006,"10.1175/JAS3706.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33144473316&doi=10.1175%2fJAS3706.1&partnerID=40&md5=2350602d8e753b5b6d86e01a8be94aa0","The effects of aerosol on warm trade cumulus clouds are investigated using a large-eddy simulation with size-resolved cloud microphysics. It is shown that, as expected, increases in aerosols cause a reduction in precipitation and an increase in the cloud-averaged liquid water path (LWP). However, for the case under study, cloud fraction, cloud size, cloud-top height, and depth decrease in response to increasing aerosol concentration, contrary to accepted hypotheses associated with the second aerosol indirect effect. It is found that the complex responses of clouds to aerosols are determined by competing effects of precipitation and droplet evaporation associated with entrainment. As aerosol concentration increases, precipitation suppression tends to maintain the clouds and lead to higher cloud LWP, whereas cloud droplets become smaller and evaporate more readily, which tends to dissipate the clouds and leads to lower cloud fraction, cloud size, and depth. An additional set of experiments with higher surface latent heat flux, and hence higher LWP and drizzle rate, was also performed. Changes in cloud properties due to aerosols have the same trends as in the base runs, although the magnitudes of the changes are larger. Evidence for significant stabilization (or destabilization) of the subcloud layer due to drizzle is not found, mainly because drizzling clouds cover only a small fraction of the domain. It is suggested that cloud fraction may only increase with increasing aerosol loading for larger clouds that are less susceptible to entrainment and evaporation. Finally, it is noted that at any given aerosol concentration the dynamical variability in bulk cloud parameters such as LWP tends to be larger than the aerosol-induced changes in these parameters, indicating that the second aerosol indirect effect may be hard to measure in this cloud type. The variability in cloud optical depth is, however, dominated by changes in aerosol, rather than dynamics. © 2006 American Meteorological Society."
"36722732500;7404243086;8067118800;25723426400;6603930943;7102084129;7005930090;7201473447;","A study of the direct and indirect effects of aerosols using global satellite data sets of aerosol and cloud parameters",2003,"10.1029/2002jd003359","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342308709&doi=10.1029%2f2002jd003359&partnerID=40&md5=fbec56f0c5cab6e76095da907a8e863b","The present study investigated the correlations between aerosol and cloud parameters derived from satellite remote sensing for evaluating the radiative forcing of the aerosol indirect effect. The global statistics showed that the effective particle radius and the optical thickness of low clouds correlate well with the column number concentration of the aerosol particles, indicating an aerosol indirect effect. A correlation of the cloud fraction with the aerosol number was also seen, whereas we could not find a significant correlation of the cloud-top temperature with the column aerosol number. Furthermore, the regional statistics presented that positive correlations between the cloud optical thickness and cloud fraction with the aerosol column number concentration exist in most regions consistent with the global mean statistics. However, the effective cloud particle radius showed a tendency similar to the global correlation only around the seashore regions. Using these correlations and assuming that the aerosol column number concentration has increased by 30% from the preindustrial era, the total radiative forcing of the aerosol indirect effect was evaluated to be about -0.6 to -1.2 W m-2. The radiative forcing of the aerosol direct effect from the satellite-retrieved parameters was also evaluated as -0.4 W m-2 over the ocean. The cloud-top temperature was found to be insensitive to the change in the aerosol number, although there was a distinct negative correlation between the aerosol number and cloud temperature at which the cloud particle grows to a radius of 14 μm. This particular dependency of the cloud temperature suggests that aerosols acts on clouds so as to change cloud particle size near the cloud top, optical thickness, and fraction but to keep their cloud-top temperature without causing a significant longwave radiative forcing. Copyright 2003 by the American Geophysical Union."
"7201837768;57193132723;56249704400;6603422104;","GCM simulations of the aerosol indirect effect: Sensitivity to cloud parameterization and aerosol burden",2002,"10.1175/1520-0469(2002)059%3C0692%3AGSOTAI%3E2.0.C","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036330162&doi=10.1175%2f1520-0469%282002%29059%253C0692%253AGSOTAI%253E2.0.C&partnerID=40&md5=a32c17834136febfeb3571b437a3d8f7","In this paper the coupling of the Goddard Institute for Space Studies (GISS) general circulation model (GCM) to an online sulfur chemistry model and source models for organic matter and sea salt that is used to estimate the aerosol indirect effect is described. The cloud droplet number concentration is diagnosed empirically from field experiment datasets over land and ocean that observe droplet number and all three aerosol types simultaneously; corrections are made for implied variations in cloud turbulence levels. The resulting cloud droplet number is used to calculate variations in droplet effective radius, which in turn allows one to predict aerosol effects on cloud optical thickness and microphysical process rates. The aerosol indirect effect is calculated by differencing the top-of-the-atmosphere net cloud radiative forcing for simulations with present-day versus preindustrial emissions. Both the first and second indirect effects are explored. The sensitivity of the results presented here to cloud parameterization assumptions that control the vertical distribution of cloud occurrence, the autoconversion rate, and the aerosol scavenging rate, each of which feeds back significantly on the model aerosol burden, are tested. The global mean aerosol indirect effect for all three aerosol types ranges from 21.55 to 24.36 W m22 in the simulations. The results are quite sensitive to the preindustrial background aerosol burden, with low preindustrial burdens giving strong indirect effects, and to a lesser extent to the anthropogenic aerosol burden, with large burdens giving somewhat larger indirect effects. Because of this dependence on the background aerosol, model diagnostics such as albedo-particle size correlations and column cloud susceptibility, for which satellite validation products are available, are not good predictors of the resulting indirect effect. © 2002 American Meteorological Society."
"8511991900;57200702127;7102084129;55717074000;","Review of aerosol-cloud interactions: Mechanisms, significance, and challenges",2016,"10.1175/JAS-D-16-0037.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84994128820&doi=10.1175%2fJAS-D-16-0037.1&partnerID=40&md5=dd9192fd64bbcb582393bfd509b2efa5","Over the past decade, the number of studies that investigate aerosol-cloud interactions has increased considerably. Although tremendous progress has been made to improve the understanding of basic physical mechanisms of aerosol-cloud interactions and reduce their uncertainties in climate forcing, there is still poor understanding of 1) some of the mechanisms that interact with each other over multiple spatial and temporal scales, 2) the feedbacks between microphysical and dynamical processes and between local-scale processes and large-scale circulations, and 3) the significance of cloud-aerosol interactions on weather systems as well as regional and global climate. This review focuses on recent theoretical studies and important mechanisms on aerosol-cloud interactions and discusses the significances of aerosol impacts on radiative forcing and precipitation extremes associated with different cloud systems. The authors summarize the main obstacles preventing the science from making a leap-for example, the lack of concurrent profile measurements of cloud dynamics, microphysics, and aerosols over a wide region on the observation side and the large variability of cloud microphysics parameterizations resulting in a large spread of modeling results on the modeling side. Therefore, large efforts are needed to escalate understanding. Future directions should focus on obtaining concurrent measurements of aerosol properties and cloud microphysical and dynamic properties over a range of temporal and spatial scales collected over typical climate regimes and closure studies, as well as improving understanding and parameterizations of cloud microphysics such as ice nucleation, mixed-phase properties, and hydrometeor size and fall speed. © 2016 American Meteorological Society."
"36538539800;","Online-coupled meteorology and chemistry models: History, current status, and outlook",2008,"10.5194/acp-8-2895-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45349092233&doi=10.5194%2facp-8-2895-2008&partnerID=40&md5=c3298fcf3f33a63551b0bbd6e4946f80","The climate-chemistry-aerosol-cloud-radiation feedbacks are important processes occurring in the atmosphere. Accurately simulating those feedbacks requires fully-coupled meteorology, climate, and chemistry models and presents significant challenges in terms of both scientific understanding and computational demand. This paper reviews the history and current status of the development and application of online-coupled meteorology and chemistry models, with a focus on five representative models developed in the US including GATOR-GCMOM, WRF/Chem, CAM3, MIRAGE, and Caltech unified GCM. These models represent the current status and/or the state-of-the science treatments of online-coupled models worldwide. Their major model features, typical applications, and physical/chemical treatments are compared with a focus on model treatments of aerosol and cloud microphysics and aerosol-cloud interactions. Aerosol feedbacks to planetary boundary layer meteorology and aerosol indirect effects are illustrated with case studies for some of these models. Future research needs for model development, improvement, application, as well as major challenges for online-coupled models are discussed."
"24398842400;7005955015;22953153500;","How important is biological ice nucleation in clouds on a global scale?",2010,"10.1088/1748-9326/5/2/024009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958538314&doi=10.1088%2f1748-9326%2f5%2f2%2f024009&partnerID=40&md5=3b2e4533d1f7814aa891419c2fbefcbb","The high ice nucleating ability of some biological particles has led to speculations about living and dead organisms being involved in cloud ice and precipitation formation, exerting a possibly significant influence on weather and climate. In the present study, the role of primary biological aerosol particles (PBAPs) as heterogeneous ice nuclei is investigated with a global model. Emission parametrizations for bacteria, fungal spores and pollen based on recent literature are introduced, as well as an immersion freezing parametrization based on classical nucleation theory and laboratory measurements. The simulated contribution of PBAPs to the global average ice nucleation rate is only 10-5%, with an uppermost estimate of 0.6%. At the same time, observed PBAP concentrations in air and biological ice nucleus concentrations in snow are reasonably well captured by the model. This implies that 'bioprecipitation' processes (snow and rain initiated by PBAPs) are of minor importance on the global scale. © 2010 IOP Publishing Ltd."
"26643041500;46461636700;6603850285;9235235300;17433905200;35459245100;24480463300;7006182491;23995325300;7005287667;57214957433;6602506226;56472932500;35461255500;8871497700;","Cloud condensation nuclei production associated with atmospheric nucleation: A synthesis based on existing literature and new results",2012,"10.5194/acp-12-12037-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871261113&doi=10.5194%2facp-12-12037-2012&partnerID=40&md5=46dde0556a5a709434aaa5a156ef2542","This paper synthesizes the available scientific information connecting atmospheric nucleation with subsequent cloud condensation nuclei (CCN) formation. We review both observations and model studies related to this topic, and discuss the potential climatic implications. We conclude that CCN production associated with atmospheric nucleation is both frequent and widespread phenomenon in many types of continental boundary layers, and probably also over a large fraction of the free troposphere. The contribution of nucleation to the global CCN budget spans a relatively large uncertainty range, which, together with our poor understanding of aerosol-cloud interactions, results in major uncertainties in the radiative forcing by atmospheric aerosols. In order to better quantify the role of atmospheric nucleation in CCN formation and Earth System behavior, more information is needed on (i) the factors controlling atmospheric CCN production and (ii) the properties of both primary and secondary CCN and their interconnections. In future investigations, more emphasis should be put on combining field measurements with regional and large-scale model studies. © 2012 Author(s)."
"55717244800;7004479957;7006705919;","Integrating cloud processes in the Community Atmosphere Model, version 5",2014,"10.1175/JCLI-D-14-00087.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907050064&doi=10.1175%2fJCLI-D-14-00087.1&partnerID=40&md5=46da5c6b75eab58ee94f083ad4229dca","This paper provides a description of the integrated representation for the cloud processes in the Community Atmosphere Model, version 5 (CAM5). CAM5 cloud parameterizations add the following unique characteristics to previous versions: 1) a cloud macrophysical structure with horizontally nonoverlapped deep cumulus, shallow cumulus, and stratus in each grid layer, where each of which has its own cloud fraction, and mass and number concentrations for cloud liquid droplets and ice crystals; 2) stratus-radiation-turbulence interactions that allow CAM5 to simulate marine stratocumulus solely from grid-mean relative humidity without relying on a stability-based empirical formula; 3) prognostic treatment of the number concentrations of stratus liquid droplets and ice crystals, with activated aerosols and detrained in-cumulus condensates as the main sources and with evaporation, sedimentation, and precipitation of stratus condensate as the main sinks; and 4) radiatively active cumulus and snow. By imposing consistency between diagnosed stratus fraction and prognosed stratus condensate, unrealistically empty or highly dense stratus is avoided in CAM5. Because of the activation of the prognostic aerosols and the parameterizations of the radiation and stratiform precipitation production as a function of the cloud droplet size, CAM5 simulates various aerosol indirect effects as well as the direct effects: that is, aerosols affect both the radiation budget and the hydrological cycle. Detailed analysis of various simulations indicates that CAM5 improves upon CAM3/CAM4 in global performance as well as in physical formulation. However, several problems are also identified in CAM5, which can be attributed to deficient regional tuning, inconsistency between various physics parameterizations, and incomplete treatment of physics. Efforts are continuing to further improve CAM5. © 2014 American Meteorological Society."
"56162305900;7102604282;","Aerosol indirect forcing in a global model with particle nucleation",2009,"10.5194/acp-9-239-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60649107034&doi=10.5194%2facp-9-239-2009&partnerID=40&md5=eefcc1cb2794ebd8ae50fcd45bbd7d61","The number concentration of cloud condensation nuclei (CCN) formed as a result of anthropogenic emissions is a key uncertainty in the study of aerosol indirect forcing and global climate change. Here, we use a global aerosol model that includes an empirical boundary layer nucleation mechanism, the use of primary-emitted sulfate particles to represent sub-grid scale nucleation, as well as binary homogeneous nucleation to explore how nucleation affects the CCN concentration and the first aerosol indirect effect (AIE). The inclusion of the boundary layer nucleation scheme increases the global average CCN concentrations in the boundary layer by 31.4% when no primary-emitted sulfate particles are included and by 5.3% when they are included. Particle formation with the boundary layer nucleation scheme decreases the first indirect forcing over ocean, and increases the first indirect forcing over land when primary sulfate particles are included. This suggests that whether particle formation from aerosol nucleation increases or decreases aerosol indirect effects largely depends on the relative change of primary particles and SO2 emissions from the preindustrial to the present day atmosphere. Including primary-emitted sulfate particle significantly increases both the anthropogenic fraction of CCN concentrations and the first aerosol indirect forcing. The forcing from various treatments of aerosol nucleation ranges from-1.22 to-2.03 w/m2. This large variation shows the importance of better quantifying aerosol nucleation mechanisms for the prediction of CCN concentrations and aerosol indirect effects."
"7404062492;56604618200;7003786872;57205479513;35547807400;7403531523;","An observationally based energy balance for the Earth since 1950",2009,"10.1029/2009JD012105","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71149102287&doi=10.1029%2f2009JD012105&partnerID=40&md5=559599278397c1213cfc9683e7790878","We examine the Earth's energy balance since 1950, identifying results that can be obtained without using global climate models. Important terms that can be constrained using only measurements and radiative transfer models are ocean heat content, radiative forcing by long-lived trace gases, and radiative forcing from volcanic eruptions. We explicitly consider the emission of energy by a warming Earth by using correlations between surface temperature and satellite radiant flux data and show that this term is already quite significant. About 20% of the integrated positive forcing by greenhouse gases and solar radiation since 1950 has been radiated to space. Only about 10% of the positive forcing (about 1/3 of the net forcing) has gone into heating the Earth, almost all into the oceans. About 20% of the positive forcing has been balanced by volcanic aerosols, and the remaining 50% is mainly attributable to tropospheric aerosols. After accounting for the measured terms, the residual forcing between 1970 and 2000 due to direct and indirect forcing by aerosols as well as semidirect forcing from greenhouse gases and any unknown mechanism can be estimated as -1.1 ± 0.4 W m-2 (1σ). This is consistent with the Intergovernmental Panel on Climate Change's best estimates but rules out very large negative forcings from aerosol indirect effects. Further, the data imply an increase from the 1950s to the 1980s followed by constant or slightly declining aerosol forcing into the 1990s, consistent with estimates of trends in global sulfate emissions. An apparent increase in residual forcing in the late 1990s is discussed. Copyright 2009 by the American Geophysical Union."
"35464731600;7004174939;55947099700;57198938123;7801610570;7006421484;7404061081;7005793702;7005399437;7003397919;24578264300;35887706900;","A critical examination of the residual cloud contamination and diurnal sampling effects on MODIS estimates of aerosol over ocean",2005,"10.1109/TGRS.2005.858430","https://www.scopus.com/inward/record.uri?eid=2-s2.0-29044438735&doi=10.1109%2fTGRS.2005.858430&partnerID=40&md5=9d0fb14678c61d8f98a802715be18be1","Observations of the aerosol optical thickness (AOT) by the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments aboard Terra and Aqua satellites are being used extensively for applications to climate and air quality studies. Data quality is essential for these studies. Here we investigate the effects of unresolved clouds on the MODIS measurements of the AOT. The main cloud effect is from residual cirrus that increases the AOT by 0.015 ± 0.003 at 0.55 μm. In addition, lower level clouds can add contamination. We examine the effect of lower clouds using the difference between simultaneously measured MODIS and AERONET AOT. The difference is positively correlated with the cloud fraction. However, interpretation of this difference is sensitive to the definition of cloud contamination versus aerosol growth. If we consider this consistent difference between MODIS and AERONET to be entirely due to cloud contamination we get a total cloud contamination of 0.025 ± 0.005, though a more likely estimate is closer to 0.020 after accounting for aerosol growth. This reduces the difference between MODIS-observed global aerosol optical thickness over the oceans and model simulations by half, from 0.04 to 0.02. However it is insignificant for studies of aerosol cloud interaction. We also examined how representative are the MODIS data of the diurnal average aerosol. Comparison to monthly averaged sunphotometer data confirms that either the Terra or Aqua estimate of global AOT is a valid representation of the daily average. Though in the vicinity of aerosol sources such as fires, we do not expect this to be true. © 2005 IEEE."
"7102604282;6602600408;13403622000;7202079615;57203200427;57208698992;12139043600;7005955015;12139310900;","Model intercomparison of indirect aerosol effects",2006,"10.5194/acp-6-3391-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33747695940&doi=10.5194%2facp-6-3391-2006&partnerID=40&md5=8fb8fb35c57571baa9b5a3d48d6b7589","Modeled differences in predicted effects are increasingly used to help quantify the uncertainty of these effects. Here, we examine modeled differences in the aerosol indirect effect in a series of experiments that help to quantify how and why model-predicted aerosol indirect forcing varies between models. The experiments start with an experiment in which aerosol concentrations, the parameterization of droplet concentrations and the autoconversion scheme are all specified and end with an experiment that examines the predicted aerosol indirect forcing when only aerosol sources are specified. Although there are large differences in the predicted liquid water path among the models, the predicted aerosol first indirect effect for the first experiment is rather similar, about -0.6 Wm-2 to -0.7 Wm-2. Changes to the autoconversion scheme can lead to large changes in the liquid water path of the models and to the response of the liquid water path to changes in aerosols. Adding an autoconversion scheme that depends on the droplet concentration caused a larger (negative) change in net outgoing shortwave radiation compared to the 1st indirect effect, and the increase varied from only 22% to more than a factor of three. The change in net shortwave forcing in the models due to varying the autoconversion scheme depends on the liquid water content of the clouds as well as their predicted droplet concentrations, and both increases and decreases in the net shortwave forcing can occur when autoconversion schemes are changed. The parameterization of cloud fraction within models is not sensitive to the aerosol concentration, and, therefore, the response of the modeled cloud fraction within the present models appears to be smaller than that which would be associated with model ""noise"". The prediction of aerosol concentrations, given a fixed set of sources, leads to some of the largest differences in the predicted aerosol indirect radiative forcing among the models, with values of cloud forcing ranging from -0.3 Wm-2 to -1.4 Wm-2. Thus, this aspect of modeling requires significant improvement in order to improve the prediction of aerosol indirect effects."
"43661479500;8942524900;36134816800;35810775100;57208121852;8942525300;13405658600;7004469744;","The magnitude and causes of uncertainty in global model simulations of cloud condensation nuclei",2013,"10.5194/acp-13-8879-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876930346&doi=10.5194%2facp-13-8879-2013&partnerID=40&md5=431b083226b8dd68b6e21bc3507fcb45","Aerosol-cloud interaction effects are a major source of uncertainty in climate models so it is important to quantify the sources of uncertainty and thereby direct research efforts. However, the computational expense of global aerosol models has prevented a full statistical analysis of their outputs. Here we perform a variance-based analysis of a global 3-D aerosol microphysics model to quantify the magnitude and leading causes of parametric uncertainty in model-estimated present-day concentrations of cloud condensation nuclei (CCN). Twenty-eight model parameters covering essentially all important aerosol processes, emissions and representation of aerosol size distributions were defined based on expert elicitation. An uncertainty analysis was then performed based on a Monte Carlo-type sampling of an emulator built for each model grid cell. The standard deviation around the mean CCN varies globally between about ±30% over some marine regions to ±40-100% over most land areas and high latitudes, implying that aerosol processes and emissions are likely to be a significant source of uncertainty in model simulations of aerosol-cloud effects on climate. Among the most important contributors to CCN uncertainty are the sizes of emitted primary particles, including carbonaceous combustion particles from wildfires, biomass burning and fossil fuel use, as well as sulfate particles formed on sub-grid scales. Emissions of carbonaceous combustion particles affect CCN uncertainty more than sulfur emissions. Aerosol emission-related parameters dominate the uncertainty close to sources, while uncertainty in aerosol microphysical processes becomes increasingly important in remote regions, being dominated by deposition and aerosol sulfate formation during cloud-processing. The results lead to several recommendations for research that would result in improved modelling of cloud-active aerosol on a global scale. © Author(s) 2013. CC Attribution 3.0 License."
"8942525300;7004469744;55942083800;12753162000;35547807400;","Global cloud condensation nuclei influenced by carbonaceous combustion aerosol",2011,"10.5194/acp-11-9067-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052490994&doi=10.5194%2facp-11-9067-2011&partnerID=40&md5=871cf0bbd447f5d5d7701c7d67174f83","Black carbon in carbonaceous combustion aerosol warms the climate by absorbing solar radiation, meaning reductions in black carbon emissions are often perceived as an attractive global warming mitigation option. However, carbonaceous combustion aerosol can also act as cloud condensation nuclei (CCN) so they also cool the climate by increasing cloud albedo. The net radiative effect of carbonaceous combustion aerosol is uncertain because their contribution to CCN has not been evaluated on the global scale. By combining extensive observations of CCN concentrations with the GLOMAP global aerosol model, we find that the model is biased low (normalised mean bias =-77 %) unless carbonaceous combustion aerosol act as CCN. We show that carbonaceous combustion aerosol accounts for more than half (52-64 %) of global CCN with the range due to uncertainty in the emitted size distribution of carbonaceous combustion particles. The model predicts that wildfire and pollution (fossil fuel and biofuel) carbonaceous combustion aerosol causes a global mean cloud albedo aerosol indirect effect of-0.34Wm-2, with stronger cooling if we assume smaller particle emission size. We calculate that carbonaceous combustion aerosol from pollution sources cause a global mean aerosol indirect effect of-0.23Wm-2. The small size of carbonaceous combustion particles from fossil fuel sources means that whilst pollution sources account for only onethird of the emitted mass they cause two-thirds of the cloud albedo aerosol indirect effect that is due to carbonaceous combustion aerosol. This cooling effect must be accounted for, along with other cloud effects not studied here, to ensure that black carbon emissions controls that reduce the high number concentrations of fossil fuel particles have the desired net effect on climate. © 2011 Author(s)."
"8550791300;8586682800;7005848261;35307109700;15072064200;9332706900;9432343100;56374442600;7005968859;7006415284;","Towards closing the gap between hygroscopic growth and activation for secondary organic aerosol: Part 1-Evidence from measurements",2009,"10.5194/acp-9-3987-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69949132619&doi=10.5194%2facp-9-3987-2009&partnerID=40&md5=03b2fc0d33997ac74e5b15d2cadca98d","Secondary Organic Aerosols (SOA) studied in previous laboratory experiments generally showed only slight hygroscopic growth, but a much better activity as a CCN (Cloud Condensation Nucleus) than indicated by the hygroscopic growth. This discrepancy was examined at LACIS (Leipzig Aerosol Cloud Interaction Simulator), using a portable generator that produced SOA particles from the ozonolysis of α-pinene, and adding butanol or butanol and water vapor during some of the experiments. The light scattering signal of dry SOA-particles was measured by the LACIS optical particle spectrometer and was used to derive a refractive index for SOA of 1.45. LACIS also measured the hygroscopic growth of SOA particles up to 99.6% relative humidity (RH), and a CCN counter was used to measure the particle activation. SOA-particles were CCN active with critical diameters of e.g. 100 nm and 55 nm at super-saturations of 0.4% and 1.1%, respectively. But only slight hygroscopic growth with hygroscopic growth factors ≤1.05 was observed at RH<98% RH. At RH>98%, the hygroscopic growth increased stronger than would be expected if a constant hygroscopicity parameter for the particle/droplet solution was assumed. An increase of the hygroscopicity parameter by a factor of 4-6 was observed in the RH-range from below 90% to 99.6%, and this increase continued for increasingly diluted particle solutions for activating particles. This explains an observation already made in the past: that the relation between critical super-saturation and dry diameter for activation is steeper than what would be expected for a constant value of the hygroscopicity. Combining measurements of hygroscopic growth and activation, it was found that the surface tension that has to be assumed to interpret the measurements consistently is greater than 55 mN/m, possibly close to that of pure water, depending on the different SOA-types produced, and therefore only in part accounts for the discrepancy between hygroscopic growth and CCN activity observed for SOA particles in the past."
"55713905400;57200702127;7404865816;","Implementation of a two-moment bulk microphysics scheme to the WRF model to investigate aerosol-cloud interaction",2008,"10.1029/2007JD009361","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53749089891&doi=10.1029%2f2007JD009361&partnerID=40&md5=f5891864693afcf3268e0fab846755fa","A two-moment bulk microphysical scheme has been implemented into the Weather Research and Forecasting (WRF) model to investigate the aerosol-cloud interaction. The microphysical scheme calculates the mass mixing ratios and number concentrations of aerosols and five types of hydrometeors and accounts for various cloud processes including warm and mixed phase microphysics. The representation of the aerosol size distribution is evaluated, showing that the three-moment modal method produces results better in agreement with the sectional approach than the two-moment modal method for variable supersaturation conditions in clouds. The effects of aerosols on cloud processes are investigated using the two-moment bulk microphysical scheme in a convective cumulus cloud event occurring on 24 August 2000 in Houston, Texas. The modeled evolution of the distribution of radar reflectivity in the y-z section, the cell lifetime, and averaged accumulated precipitation with the aerosol concentration under the polluted urban condition are qualitatively consistent with the measurements. Sensitivity simulations are initialized using a set of aerosol profiles with the number concentrations ranging from 200 to 50,000 cm -3 and mass ranging from 1 to 10 μg m-3 at the surface level. The response of precipitation to the increase of aerosol concentrations is nonmonotonic, because of the complicated interaction between cloud microphysics and dynamics. The precipitation increases with aerosol concentrations from clean maritime to continental background conditions, but is considerably reduced and completely suppressed under highly polluted conditions, indicating that the aerosol concentration exhibits distinct effects on the precipitation efficiency under different aerosol conditions. The maximal cloud cover, core updraft, and maximal vertical velocity exhibit similar responses as precipitation. Comparison is made to evaluate the effects of different autoconversion parameterizations and bulk microphysical schemes on cloud properties. Because of its broad application in numerical weather prediction, implementation of the two-moment microphysical scheme to the WRF model will greatly facilitate assessment of aerosol-cloud interaction from individual cumulus to mesoscale convective systems. Copyright 2008 by the American Geophysical Union."
"8225489800;57206332144;7003398947;7004174939;7801610570;","3-D aerosol-cloud radiative interaction observed in collocated MODIS and ASTER images of cumulus cloud fields",2007,"10.1029/2006JD008267","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548610646&doi=10.1029%2f2006JD008267&partnerID=40&md5=f966eda6430b8cb224d10ed7b56539f3","Three-dimensional (3-D) aerosol-cloud interaction is examined by analyzing two images containing cumulus clouds in biomass-burning regions in Brazil. The research consists of two parts. The first part focuses on identifying 3-D cloud impacts on reflectances for the pixels selected for the MODIS aerosol retrieval based purely on observations. The second part of the research combines the observations with radiative transfer computations to identify key parameters in the 3-D aerosol-cloud interaction. We find that 3-D cloud-induced enhancement depends on the optical properties of nearby clouds as well as on wavelength. The enhancement is too large to be ignored. Associated bias error in one-dimensional (1-D) aerosol optical thickness retrieval ranges from 50 to 140% depending on wavelength and the optical depth of nearby clouds, as well as aerosol optical thickness. We caution the community to be prudent when applying 1-D approximations in computing solar radiation in clear regions adjacent to clouds or when using traditional retrieved aerosol optical thickness in aerosol indirect effect research. Copyright 2007 by the American Geophysical Union."
"7404243086;36722732500;7202079615;7006159471;6603930943;55574223708;7005650812;7404104414;35330367300;7402025009;7005931768;7102797196;25723426400;","Significance of direct and indirect radiative forcings of aerosols in the East China Sea region",2003,"10.1029/2002jd003261","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342333135&doi=10.1029%2f2002jd003261&partnerID=40&md5=600b8f2dd8d7b68fcccf4d464606a7b2","Radiative forcings of aerosols and clouds in the East China Sea region are studied using data from surface radiation measurements, satellite remote sensing, and model simulation conducted in April 2001 as a study of Asian Atmospheric Particle Environmental Change Studies (APEX) cooperating with International Global Atmospheric Chemistry (IGAC)/ACE-Asia project. The monthly mean whole sky radiative forcing of the aerosol direct effect is derived from various methods as -5 to -8 W/M2 at the top of atmosphere (TOA) and -10 to -23 W/m2 at Earth's surface of Gosan (33.28N, 127.17E) and Amami-Oshima (28.15N, 129.30E) sites, though there is a large regional difference caused by changes in the aerosol optical thickness and single scattering albedo. The cloud forcing is estimated as -20 to -40 W/m2, so that the aerosol direct forcing can be comparable to the cloud radiative forcing at surface. However, the estimate of the aerosol direct forcing thus obtained strongly depends on the estimation method of the aerosol properties, especially on the single scattering albedo, generating a method difference about 40%. The radiative forcing of the aerosol indirect effect is roughly estimated from satellite method and SPRINTARS model as -1 to -3 W/m2 at both TOA and surface. © 2003 by the American Geophysical Union."
"7202485447;7101899854;56016057500;7201381456;7003377766;16551540700;7102221568;13104873000;34969663100;8452628000;7404548584;35092526000;57218650887;57154893200;7103294028;18635289400;7005399437;49662784300;55781534800;6505894650;7410255240;55273729800;57154891500;7404967662;7401797911;24308208100;7101933764;7407038710;7403967484;7402628473;8080680100;13608654700;55936005100;36672614700;55781688500;7404861364;7501460689;","An overview of regional experiments on biomass burning aerosols and related pollutants in Southeast Asia: From BASE-ASIA and the Dongsha Experiment to 7-SEAS",2013,"10.1016/j.atmosenv.2013.04.066","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882628507&doi=10.1016%2fj.atmosenv.2013.04.066&partnerID=40&md5=ca57d2a950a08669d29e0b11f7aec65d","By modulating the Earth-atmosphere energy, hydrological and biogeochemical cycles, and affecting regional-to-global weather and climate, biomass burning is recognized as one of the major factors affecting the global carbon cycle. However, few comprehensive and wide-ranging experiments have been conducted to characterize biomass-burning pollutants in Southeast Asia (SEA) or assess their regional impact on meteorology, the hydrological cycle, the radiative budget, or climate change. Recently, BASE-ASIA (Biomass-burning Aerosols in South-East Asia: Smoke Impact Assessment) and the 7-SEAS (7-South-East Asian Studies)/Dongsha Experiment were conducted during the spring seasons of 2006 and 2010 in northern SEA, respectively, to characterize the chemical, physical, and radiative properties of biomass-burning emissions near the source regions, and assess their effects. This paper provides an overview of results from these two campaigns and related studies collected in this special issue, entitled ""Observation, modeling and impact studies of biomass burning and pollution in the SE Asian Environment"". This volume includes 28 papers, which provide a synopsis of the experiments, regional weather/climate, chemical characterization of biomass-burning aerosols and related pollutants in source and sink regions, the spatial distribution of air toxics (atmospheric mercury and dioxins) in source and remote areas, a characterization of aerosol physical, optical, and radiative properties, as well as modeling and impact studies. These studies, taken together, provide the first relatively complete dataset of aerosol chemistry and physical observations conducted in the source/sink region in the northern SEA, with particular emphasis on the marine boundary layer and lower free troposphere (LFT). The data, analysis and modeling included in these papers advance our present knowledge of source characterization of biomass-burning pollutants near the source regions as well as the physical and chemical processes along transport pathways. In addition, we raise key questions to be addressed by a coming deployment during springtime 2013 in northern SEA, named 7-SEAS/BASELInE (Biomass-burning Aerosols & Stratocumulus Environment: Lifecycles and Interactions Experiment). This campaign will include a synergistic approach for further exploring many key atmospheric processes (e.g., complex aerosol-cloud interactions) and impacts of biomass burning on the surface-atmosphere energy budgets during the lifecycles of biomass-burning emissions. © 2013 The Authors."
"6603711967;7403364008;55916925700;8570871900;7004063850;24168358300;57213743966;7102976560;7004885872;","Aerosol impacts on climate and biogeochemistry",2011,"10.1146/annurev-environ-042009-094507","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80155192400&doi=10.1146%2fannurev-environ-042009-094507&partnerID=40&md5=593fbce92b12fe53752584144c3978bb","Aerosols are suspensions of solid and/or liquid particles in the atmosphere and modify atmospheric radiative fluxes and chemistry. Aerosols move mass from one part of the earth system to other parts of the earth system, thereby modifying biogeochemistry and the snow surface albedo. This paper reviews our understanding of the impacts of aerosols on climate through direct radiative changes, aerosol-cloud interactions (indirect effects), atmospheric chemistry, snow albedo, and land and ocean biogeochemistry. Aerosols play an important role in the preindustrial (natural) climate system and have been perturbed substantially over the anthropocene, often directly by human activity. The most important impacts of aerosols, in terms of climate forcing, are from the direct and indirect effects, with large uncertainties. Similarly large impacts of aerosols on land and ocean biogeochemistry have been estimated, but these have larger uncertainties. © 2011 by Annual Reviews. All rights reserved."
"7004479957;8882641700;24538177600;","Cloud droplet sedimentation, entrainment efficiency, and subtropical stratocumulus albedo",2007,"10.1029/2006GL027648","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548049274&doi=10.1029%2f2006GL027648&partnerID=40&md5=c92fc16a00d41a8e66f198899737902e","The effect of cloud droplet sedimentation on the entrainment rate and liquid water path of a nocturnal nondrizzling stratocumulus layer is examined using large-eddy simulations (LES) with bulk microphysics. In agreement with a prior study by Ackerman et al. (2004), sedimentation is found to decrease entrainment rate and thereby increase liquid water path. They suggested this is due to reduction of boundary-layer turbulence. Our simulations suggest otherwise. Instead, sedimentation reduces entrainment by removing liquid water from the entrainment zone. This inhibits two mechanisms that promote the sinking of entrained air into the cloud layer-entrainment-induced evaporative cooling and longwave radiative cooling. A sensitivity study shows that the radiative effect is less important than the reduced evaporation. A possible parameterization of the effect of sedimentation on entrainment rate in a mixed layer model is proposed and tested. Since the droplet sedimentation rate is inversely related to cloud droplet (and presumably aerosol) concentration and nearly nondrizzling marine stratocumulus are widespread, sedimentation impacts on stratocumulus entrainment efficiency should be considered in climate model simulations of the aerosol indirect effect. Copyright 2007 by the American Geophysical Union."
"6602600408;57203200427;57203053317;","Constraining the total aerosol indirect effect in the LMDZ and ECHAM4 GCMs using MODIS satellite data",2006,"10.5194/acp-6-947-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646492457&doi=10.5194%2facp-6-947-2006&partnerID=40&md5=8fdd8401657631637dbdff36b587d92b","Aerosol indirect effects are considered to be the most uncertain yet important anthropogenic forcing of climate change. The goal of the present study is to reduce this uncertainty by constraining two different general circulation models (LMDZ and ECHAM4) with satellite data. We build a statistical relationship between cloud droplet number concentration and the optical depth of the fine aerosol mode as a measure of the aerosol indirect effect using MODerate Resolution Imaging Spectroradiometer (MODIS) satellite data, and constrain the model parameterizations to match this relationship. We include here ""empirical"" formulations for the cloud albedo effect as well as parameterizations of the cloud lifetime effect. When fitting the model parameterizations to the satellite data, consistently in both models, the radiative forcing by the combined aerosol indirect effect is reduced considerably, down to -0.5 and -0.3 Wm-2, for LMDZ and ECHAM4, respectively. © Author(s) 2006. This work is licensed under a Creative Commons License."
"8511991900;7202048112;7409080503;7103158465;57138743300;35114405700;55802246600;57200702127;","Aerosol impacts on clouds and precipitation in eastern China: Results from bin and bulk microphysics",2012,"10.1029/2011JD016537","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863012201&doi=10.1029%2f2011JD016537&partnerID=40&md5=b9a38f1a075d2a0096793d34f934df7f","Using the Weather Research and Forecasting model coupled with a spectral-bin microphysics (""SBM"") and measurements from the Atmospheric Radiation Measurement Mobile Facility field campaign in China (AMF-China), the authors examine aerosol indirect effects (AIE) in the typical cloud regimes of the warm and cold seasons in Southeast China: deep convective clouds (DCC) and stratus clouds (SC), respectively. Comparisons with a two-moment bulk microphysics (""Bulk"") are performed to gain insights for improving bulk schemes in estimating AIE in weather and climate simulations. For the first time, measurements of aerosol and cloud properties acquired in China are used to evaluate model simulations to better understand aerosol impact on clouds in the southeast of China. It is found that changes in cloud condensation nuclei (CCN) concentration significantly change the timing of storms, the spatial and temporal distributions of precipitation, the frequency distribution of precipitation rate, as well as cloud base and top heights for the DCC, but not for the SC. Increasing CCN increases cloud droplet number (N<inf>c</inf>) and mass concentrations, decreases raindrop number concentration, and delays the onset of precipitation. Compared with SBM, Bulk predicts much higher N<inf>c</inf> and the opposite CCN effects on convection and heavy rain, stemming from the fixed CCN prescribed in Bulk. CCN have a significant effect on ice microphysical properties with SBM but not Bulk and different condensation/deposition freezing parameterizations employed could be the main reason. This study provided insights to further improve the bulk scheme to better account for aerosol-cloud interactions in regional and global climate simulations, which will be the focus for a follow-on paper. Copyright 2012 by the American Geophysical Union."
"56691914800;8586682800;7004715270;7005968859;8550791300;18437651200;25624725200;35798085000;7006415284;35798985200;55730602600;6602085876;","Irreversible loss of ice nucleation active sites in mineral dust particles caused by sulphuric acid condensation",2010,"10.5194/acp-10-11471-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649814978&doi=10.5194%2facp-10-11471-2010&partnerID=40&md5=dbed589957addd02f526bc19dc632e2f","During the FROST-2 (FReezing Of duST) measurement campaign conducted at the Leipzig Aerosol Cloud Interaction Simulator (LACIS), we investigated changes in the ice nucleation properties of 300 nm Arizona Test Dust mineral particles following thermochemical processing by varying amounts and combinations of exposure to sulphuric acid vapour, ammonia gas, water vapour, and heat. The processed particles' heterogeneous ice nucleation properties were determined in both the water subsaturated and supersaturated humidity regimes at -30 °C and -25 °C using Colorado State University's continuous flow diffusion chamber. The amount of sulphuric acid coating material was estimated by an aerosol mass spectrometer and from CCN-derived hygroscopicity measurements. The condensation of sulphuric acid decreased the dust particles' ice nucleation ability in proportion to the amount of sulphuric acid added. Heating the coated particles in a thermodenuder at 250 °C- intended to evaporate the sulphuric acid coating - reduced their freezing ability even further. We attribute this behaviour to accelerated acid digestion of ice active surface sites by heat. Exposing sulphuric acid coated dust to ammonia gas produced particles with similarly poor freezing potential; however a portion of their ice nucleation ability could be restored after heating in the thermodenuder. In no case did any combination of thermochemical treatments increase the ice nucleation ability of the coated mineral dust particles compared to unprocessed dust. These first measurements of the effect of identical chemical processing of dust particles on their ice nucleation ability under both water subsaturated and mixed-phase supersaturated cloud conditions revealed that ice nucleation was more sensitive to all coating treatments in the water subsaturated regime. The results clearly indicate irreversible impairment of ice nucleation activity in both regimes after condensation of concentrated sulphuric acid. This implies that the sulphuric acid coating caused permanent chemical and/or physical modification of the ice active surface sites; the possible dissolution of the coating during droplet activation did not restore all immersion/condensation-freezing ability. © 2010 Author(s)."
"12645767500;7202899330;7004114883;","Multisensor satellite observations of aerosol effects on warm clouds",2008,"10.1029/2008JD009876","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66949131489&doi=10.1029%2f2008JD009876&partnerID=40&md5=11c24396e4506791d4412b9262afb2df","A global multisensor satellite examination of aerosol indirect effects on warm oceanic clouds is presented. The study centers on the water path response of cloud to aerosol burden. A unique element of the study is a rigorous rain screening methodology that is utilized to separate the responses of nonraining and raining clouds. It is demonstrated that high aerosol environments are associated with reduced liquid water path in nonprecipitating clouds and that the reduction in liquid water path reduces the albedo enhancement expected from decreasing effective radius. Furthermore the reduction in liquid water path is greater in thermodynamically unstable environments than in stable environments suggesting a greater sensitivity of cumulus cloud than stratiform cloud liquid water path to aerosol. In sharp contrast with nonprecipitating clouds, the cloud liquid water path of transitional and precipitating clouds increases dramatically with aerosol, which may be indicative of an inhibited coalescence process. The evidence further indicates that increasing aerosol requires greater amounts of cloud condensate before the onset of precipitation. Additional support for this hypothesis is found in a reduction in the probability of precipitation by as much as 10% depending on the thermodynamical state of the environment. Independent estimates of the broadband cloudy-sky albedo are used to confirm that the cloud albedo responds to the trends that are identified in the liquid water path. In particular, it is found that the water path effect dominates the cloud albedo response for precipitating and transitional clouds. Finally, regional analysis demonstrates that the magnitude of the relationship between aerosol and cloud albedo is greatest in the extratropics and subtropical stratus regions primarily in the winter hemisphere. These relationships are used to estimate the magnitude of the first indirect effect as -0.42 W/m 2. Copyright 2008 by the American Geophysical Union."
"7003591311;7004174939;57127099400;35464731600;","Analysis of smoke impact on clouds in Brazilian biomass burning regions: An extension of Twomey's approach",2001,"10.1029/2001JD000732","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034758282&doi=10.1029%2f2001JD000732&partnerID=40&md5=e19fa9c09b5c2353bed1643efcb2acfe","Satellite remote sensing of smoke aerosol-cloud interaction during the recent Smoke, Clouds, and Radiation-Brazil (SCAR-B) experiment is analyzed to explore the factors that determine the magnitude of the cloud response to smoke aerosol. Analysis of 2 years worth of data revealed that the response is greatest in the north of Brazil where aerosol optical depth is smallest, and tends to decrease as one moves southward, and as aerosol optical depth increases. Saturation in this response occurs at an aerosol optical depth of 0.8 in 1987 and 0.4 in 1995. To explore the reasons for this, a framework is developed in which the satellite-measured response can be compared to simple analytical models of this response and to numerical models of smoke aerosol-cloud interaction. Three types of response are identified: (1) cloud droplet concentrations increase with increasing aerosol loading, followed by saturation in the response at high concentrations; (2) as in type 1, followed by increasing droplet concentrations with further increases in aerosol loading. This increase in droplet concentration is due to the suppression of supersaturation by abundant large particles, which prevents the activation of smaller particles. This enables renewed activation of larger particles when smoke loadings exceed some threshold; (3) as in type 1, followed by a decrease in droplet number concentrations with increasing aerosol loading as intense competition for vapor evaporates the smaller droplets. The latter implies an unexpected increase in drop size with increasing smoke loading. The conditions under which each of these responses are expected to occur are discussed. It is shown that although to first-order smoke optical depth is a good proxy for aerosol indirect forcing, under some conditions the size distribution and hygroscopicity can be important factors. We find no evidence that indirect forcing depends on precipitable water vapor."
"7201665727;7103206141;35514163500;7006306835;6701752471;56244473600;56744278700;","The roles of aerosol direct and indirect effects in past and future climate change",2013,"10.1002/jgrd.50192","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879936647&doi=10.1002%2fjgrd.50192&partnerID=40&md5=1c1e2af93c699f10e6bda452eac8de9c","Using the Geophysical Fluid Dynamics Laboratory's (GFDL's) fully coupled chemistry-climate (ocean/atmosphere/land/sea ice) model (CM3) with an explicit physical representation of aerosol indirect effects (cloud-water droplet activation), we find that the dramatic emission reductions (35%-80%) in anthropogenic aerosols and their precursors projected by Representative Concentration Pathway (RCP) 4.5 result in ~1 °C of additional warming and ~0.1 mm day-1 of additional precipitation, both globally averaged, by the end of the 21st century. The impact of these reductions in aerosol emissions on simulated global mean surface temperature and precipitation becomes apparent by mid-21st century. Furthermore, we find that the aerosol emission reductions cause precipitation to increase in East and South Asia by ~1.0 mm day-1 through the second half of the 21st century. Both the temperature and the precipitation responses simulated by CM3 are significantly stronger than the responses previously simulated by our earlier climate model (CM2.1) that only considered direct radiative forcing by aerosols. We conclude that the indirect effects of sulfate aerosol greatly enhance the impacts of aerosols on surface temperature in CM3; both direct and indirect effects from sulfate aerosols dominate the strong precipitation response, possibly with a small contribution from carbonaceous aerosols. Just as we found with the previous GFDL model, CM3 produces surface warming patterns that are uncorrelated with the spatial distribution of 21st century changes in aerosol loading. However, the largest precipitation increases in CM3 are colocated with the region of greatest aerosol decrease, in and downwind of Asia. Key Points Aerosol reductions (RCP4.5) cause 1K warming and +0.1 mm/day of precipitation.Sulfate indirect effects greatly enhance aerosol impacts on surface temperature.Aerosol reductions increase precipitation in Asia by 0.5-1.0 mm/day by 2100. ©2013. American Geophysical Union. All Rights Reserved."
"7004198777;8586682800;7004838931;7201504886;6506966551;7006494557;7202252296;7004393835;","Evaluation of the aerosol indirect effect in marine stratocumulus clouds: Droplet number, size, liquid water path, and radiative impact",2005,"10.1029/2004JD005116","https://www.scopus.com/inward/record.uri?eid=2-s2.0-21244493561&doi=10.1029%2f2004JD005116&partnerID=40&md5=42948d6214669cbe6a60b85db176bdb3","Data from nine stratocumulus clouds in the northeastern Pacific Ocean were analyzed to determine the effect of aerosol particles on cloud microphysical and radiative properties. Seven nighttime and two daytime cases were included. The number concentration of below-cloud aerosol particles (&gt;0.10 μm diameter) was highly correlated with cloud droplet number concentration. Droplet number concentrations were typically about 75% of particle number concentration in the range of particle concentrations studied (≤400 cm-3). Particle number was anticorrelated with droplet size and with liquid water content in drizzle-sized drops. Radiative impact also depends upon cloud liquid water content and geometric thickness. Although most variability in these macroscopic properties of the clouds could be attributed to variability in the large-scale environment, a weak anticorrelation between particle concentration and cloud geometric thickness was observed. Because of these variations, no correlation between calculated cloud optical thickness or albedo and particle concentration was detectable for the data set as a whole. For regions with comparable liquid water contents in an individual cloud, higher particle concentrations did correspond to increased cloud optical thickness. These results verify that higher particle concentrations do directly affect the microphysics of stratiform clouds. However, the constant liquid water path assumption usually invoked in the Twomey aerosol indirect effect may not be valid. Copyright 2005 by the American Geophysical Union."
"7201504886;","Rethinking the lower bound on aerosol radiative forcing",2015,"10.1175/JCLI-D-14-00656.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941121923&doi=10.1175%2fJCLI-D-14-00656.1&partnerID=40&md5=389902a1e913cfde4f2cfe38df888fb2","Based on research showing that in the case of a strong aerosol forcing, this forcing establishes itself early in the historical record, a simple model is constructed to explore the implications of a strongly negative aerosol forcing on the early (pre-1950) part of the instrumental record. This model, which contains terms representing both aerosol-radiation and aerosol-cloud interactions, well represents the known time history of aerosol radiative forcing as well as the effect of the natural state on the strength of aerosol forcing. Model parameters, randomly drawn to represent uncertainty in understanding, demonstrate that a forcing more negative than -1.0Wm-2 is implausible, as it implies that none of the approximately 0.3-K temperature rise between 1850 and 1950 can be attributed to Northern Hemisphere forcing. The individual terms of the model are interpreted in light of comprehensive modeling, constraints from observations, and physical understanding to provide further support for the less negative (-1.0Wm-2) lower bound. These findings suggest that aerosol radiative forcing is less negative and more certain than is commonly believed. © 2015 American Meteorological Society."
"24398842400;57203053317;57201904116;56250185400;","The global influence of dust mineralogical composition on heterogeneous ice nucleation in mixed-phase clouds",2008,"10.1088/1748-9326/3/2/025003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45749115495&doi=10.1088%2f1748-9326%2f3%2f2%2f025003&partnerID=40&md5=35af98de1e4b546c179ab1d9aced1a4b","Mineral dust is the dominant natural ice nucleating aerosol. Its ice nucleation efficiency depends on the mineralogical composition. We show the first sensitivity studies with a global climate model and a three-dimensional dust mineralogy. Results show that, depending on the dust mineralogical composition, coating with soluble material from anthropogenic sources can lead to quasi-deactivation of natural dust ice nuclei. This effect counteracts the increased cloud glaciation by anthropogenic black carbon particles. The resulting aerosol indirect effect through the glaciation of mixed-phase clouds by black carbon particles is small (+0.1 W m-2 in the shortwave top-of-the-atmosphere radiation in the northern hemisphere). © IOP Publishing Ltd."
"18437230800;6603779272;57203052274;55716092000;57196499374;6701378450;57211106013;7006461606;55605765360;7006550762;","Climatic effects of 1950-2050 changes in US anthropogenic aerosols-Part 1: Aerosol trends and radiative forcing",2012,"10.5194/acp-12-3333-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859557746&doi=10.5194%2facp-12-3333-2012&partnerID=40&md5=fe34d6ab523f648d0b07dc321153cc81","We calculate decadal aerosol direct and indirect (warm cloud) radiative forcings from US anthropogenic sources over the 1950-2050 period. Past and future aerosol distributions are constructed using GEOS-Chem and historical emission inventories and future projections from the IPCC A1B scenario. Aerosol simulations are evaluated with observed spatial distributions and 1980-2010 trends of aerosol concentrations and wet deposition in the contiguous US. Direct and indirect radiative forcing is calculated using the GISS general circulation model and monthly mean aerosol distributions from GEOS-Chem. The radiative forcing from US anthropogenic aerosols is strongly localized over the eastern US. We find that its magnitude peaked in 1970-1990, with values over the eastern US (east of 100° W) of-2.0 W m -2 for direct forcing including contributions from sulfate (-2.0 W m -2), nitrate (-0.2 W m -2), organic carbon (-0.2 W m -2), and black carbon (+0.4 W m -2). The uncertainties in radiative forcing due to aerosol radiative properties are estimated to be about 50%. The aerosol indirect effect is estimated to be of comparable magnitude to the direct forcing. We find that the magnitude of the forcing declined sharply from 1990 to 2010 (by 0.8 W m -2 direct and 1.0 W m -2 indirect), mainly reflecting decreases in SO 2 emissions, and project that it will continue declining post-2010 but at a much slower rate since US SO 2 emissions have already declined by almost 60% from their peak. This suggests that much of the warming effect of reducing US anthropogenic aerosol sources has already been realized. The small positive radiative forcing from US BC emissions (+0.3 W m -2 over the eastern US in 2010; 5% of the global forcing from anthropogenic BC emissions worldwide) suggests that a US emission control strategy focused on BC would have only limited climate benefit. © 2012 Author(s)."
"55683727600;12753162000;8942525300;35547807400;7004469744;35810775100;8942524900;24385307600;35461255500;23995325300;6506180220;","The direct and indirect radiative effects of biogenic secondary organic aerosol",2014,"10.5194/acp-14-447-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892609423&doi=10.5194%2facp-14-447-2014&partnerID=40&md5=dfa8993b57dc26e1b2efebd41279b578","We use a global aerosol microphysics model in combination with an offline radiative transfer model to quantify the radiative effect of biogenic secondary organic aerosol (SOA) in the present-day atmosphere. Through its role in particle growth and ageing, the presence of biogenic SOA increases the global annual mean concentration of cloud condensation nuclei (CCN; at 0.2% supersaturation) by 3.6-21.1%, depending upon the yield of SOA production from biogenic volatile organic compounds (BVOCs), and the nature and treatment of concurrent primary carbonaceous emissions. This increase in CCN causes a rise in global annual mean cloud droplet number concentration (CDNC) of 1.9-5.2%, and a global mean first aerosol indirect effect (AIE) of between +0.01 W m -2 and -0.12 W m-2. The radiative impact of biogenic SOA is far greater when biogenic oxidation products also contribute to the very early stages of new particle formation; using two organically mediated mechanisms for new particle formation, we simulate global annual mean first AIEs of -0.22 W m-2 and -0.77 W m-2. The inclusion of biogenic SOA substantially improves the simulated seasonal cycle in the concentration of CCN-sized particles observed at three forested sites. The best correlation is found when the organically mediated nucleation mechanisms are applied, suggesting that the first AIE of biogenic SOA could be as large as -0.77 W m-2. The radiative impact of SOA is sensitive to the presence of anthropogenic emissions. Lower background aerosol concentrations simulated with anthropogenic emissions from 1750 give rise to a greater fractional CCN increase and a more substantial first AIE from biogenic SOA. Consequently, the anthropogenic indirect radiative forcing between 1750 and the present day is sensitive to assumptions about the amount and role of biogenic SOA. We also calculate an annual global mean direct radiative effect of between -0.08 W m-2 and -0.78 W m-2 in the present day, with uncertainty in the amount of SOA produced from the oxidation of BVOCs accounting for most of this range."
"24722339600;","Cancellation of aerosol indirect effects in marine stratocumulus through cloud thinning",2007,"10.1175/JAS3942.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547754428&doi=10.1175%2fJAS3942.1&partnerID=40&md5=15b35d6b86b59d90dd8653a7d6eab49e","Applying perturbation theory within a mixed layer framework, the response of the marine boundary layer (MBL) cloud thickness h to imposed increases of the cloud droplet concentration Nd as a surrogate for increases in cloud condensation nuclei (CCN) concentrations is examined. An analytical formulation is used to quantify the response and demonstrate theoretically that for the range of environmental conditions found over the subtropical eastern oceans, on time scales of less than a day, the cloud thickness feedback response is largely determined by a balance between the moistening/cooling of the MBL resulting from the suppression of surface precipitation, and the drying/warming resulting from enhanced entrainment resulting from increased turbulent kinetic energy. Quantifying the transient cloud response as a ratio of the second to the first indirect effects demonstrates that the nature of the feedback is critically dependent upon the nature of the unperturbed state, with the cloud-base height zcb being the single most important determinant. For zcb &lt; 400 m, increasing Nd leads to cloud thickening in accordance with the Albrecht hypothesis. However, for zcb &gt; 400 m, cloud thinning occurs, which results in a feedback effect that increasingly cancels the Twomey effect as zcb increases. The environmental conditions favoring an elevated cloud base are relatively weak lower-tropospheric stability and a dry free troposphere, although the former is probably more important over the subtropical eastern oceans. On longer time scales an invariable thickening response is found, and thus accurate quantification of the aerosol indirect effects will require a good understanding of the processes that control the time scale over which aerosol perturbations are modified. © 2007 American Meteorological Society."
"36701716800;7005659017;6604005739;36006968000;","Absorbing aerosols facilitate transition of Indian monsoon breaks to active spells",2011,"10.1007/s00382-010-0971-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81455148141&doi=10.1007%2fs00382-010-0971-3&partnerID=40&md5=b87c2c7e619a416c552c5f17ebeaccd1","While some long breaks of monsoon intraseasonal oscillations (MISOs) are followed by active spells (BFA), some others are not (BNFA). The circulation during BFA (BNFA) cases helps (prevents) accumulation of absorbing aerosols over central India (CI) resulting in almost three times larger Aerosol Index (AI) over CI, during BFA cases compared to BNFA cases. A seminal role played by the absorbing aerosols in the transition from break to active spells is unraveled through modification of the north-south temperature gradient at lower levels. The meridional gradient of temperature at low level ({increment}T) between aerosol-rich CI and pristine equatorial Indian Ocean is large (>6°C) and sustains for long time (>10 days) during BFA leading to significant moisture convergence to CI. The stability effect arising from surface cooling by the aerosols is overcome by the enhanced moisture convergence creating a moist static unstable atmosphere conducive for the large-scale organized convection over the CI region leading to the resurgence of active spells. The moisture convergence induced by {increment}T was also able to overcome possible aerosol indirect effect (Twomey effect) and initiate deep convection and transition to active condition. During BNFA cases, however the maximum {increment}T, which was weaker than the BFA cases by more than 1. 5°C, could not sustain required moisture convergence and failed to lead to a sustained active spell. Using data from MODIS (MODerate resolution Imaging Spectroradiometer) onboard Terra and several other input parameters from various satellites for the period 2000-2009, the aerosol induced radiative forcing representative of two regions-the CI to the north and the pristine ocean to the south-were estimated and support the differences in observed {increment}T during the two cases. Our results highlight the need for proper inclusion of absorbing aerosols in dynamical models for simulation of the observed variability of MISOs and their extended range prediction. © 2010 Springer-Verlag."
"35264934000;7004885872;7003591311;55017656900;","Can aerosol decrease cloud lifetime?",2009,"10.1029/2009GL038888","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71949119419&doi=10.1029%2f2009GL038888&partnerID=40&md5=576f6a97e8226ff6ec6d6e75fd0eef21","Cloud responses to changes in aerosol remain a dominant uncertainty in the radiative forcing of climate. Two main constructs related to aerosol effects on clouds have been postulated: (i) the ""albedo effect"" whereby anthropogenic aerosol results in increased droplet concentrations mat generate increases in cloud albedo, all else (particularly cloud water) being equal; (ii) the ""lifetime effect"" whereby anthropogenic aerosol suppresses precipitation and results in clouds witii more liquid water, higher fractional cloudiness, and longer lifetimes. Based on new observations presented here, and supported by previous fine-scale modeling studies, we suggest that the balance of evidence shows mat non-precipitating cumulus clouds can experience an evaporation-entrainment feedback, and respond to aerosol perturbations in a manner inconsistent with the traditional ""lifetime effect."" Because most cumulus clouds evaporate without producing significant precipitation, this is particularly relevant to estimates of aerosol indirect effects on climate. Copyright 2009 by the American Geophysical Union."
"6701596624;55896920900;","An observational study of drizzle formation in stratocumulus clouds for general circulation model (GCM) parameterizations",2003,"10.1029/2002jd002679","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342269923&doi=10.1029%2f2002jd002679&partnerID=40&md5=93020ec07e62c9d0588982e8f33fc695","Climate model parameterization of precipitation formation in boundary layer stratocumulus clouds is a challenge that needs to be carefully addressed for simulations of the aerosol impact on precipitation and on cloud life time and extent, the so-called second indirect effect of aerosol on climate. Existing schemes are generally tuned against global observations of the liquid water path, as very few in situ observations are available for their validation. This issue is addressed here with data collected during the second Aerosol Characterization Experiment. The methodology is different from previous experimental studies in the sense that each case study is first analyzed for retrieving properties that are representative of the observed cloud system as a whole, such as the cloud system geometrical thickness, droplet concentration, precipitation flux, etc. Special attention is given to the characterization of the droplet number concentration by deriving a value that is representative of the aerosol activation process instead of the mean value over the cloud system. The analysis then focuses on the variability of these cloud system values for eight case studies with different aerosol backgrounds. The data set reveals that precipitation forms when the maximum mean volume droplet radius in the cloud layer reaches values >10 μm, the same critical value as previously used in cloud resolving models. This maximum radius can be predicted with an adiabatic diagnostic on the basis of cloud geometrical thickness and droplet number concentration. The measured reduction rate of drizzle water content by precipitation is also compared to predictions of auto-conversion and accretion production rates derived from existing bulk parameterizations initialized with the measured values of cloud droplet and drizzle water content. The good agreement with the parameterizations suggests that the cloud layer reaches a nearly steady state characterized by a balance between the production and reduction rates of cloud and drizzle water content. Finally, it is shown that the cloud system precipitation rate can be expressed as a power law of cloud geometrical thickness and cloud droplet number concentration, hence providing a simple large-scale parameterization of the precipitation process in boundary layer clouds. Copyright 2003 by the American Geophysical Union."
"7004198777;7102290666;6506966551;","Effect of changes in relative humidity on aerosol scattering near clouds",2009,"10.1029/2008JD010991","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65849231086&doi=10.1029%2f2008JD010991&partnerID=40&md5=79e10ef5b35e95171d8ae809ba09a544","Many investigations using satellite data have determined that aerosol optical depth and cloud cover are correlated and some have interpreted the correlation as evidence of an aerosol indirect effect on clouds. This study uses in situ aircraft observations taken during the Indian Ocean Experiment (INDOEX), February-March 1999, and mostly over the northern Indian Ocean, to show that on average, relative humidity increases as distance to the boundaries of small marine trade cumulus decreases. The increase is sufficient to cause substantial growth of hygroscopic aerosol particles and consequently greatly enhance particle scattering cross sections near clouds. The measured increase is from a relative humidity of about 90% at 1-km horizontal distance from the cloud to about 94-96% at 100 m from cloud edge. This increase would result in about a 40-80% increase in aerosol scattering cross section based on the composition used to model the aerosol. Observations of scattering in the vicinity of clouds using 30-m-resolution imagery from the Multichannel Cloud Radiometer (MCR) indicated that the increase in scattering within 1-2 km of cloud edge was about 50%, comparable to the increase calculated for the particle scattering cross sections. On the basis of these findings, global average estimates of the aerosol direct radiative effect as derived from satellite observations of cloud-free oceans is estimated to be 35-65% larger than that inferred for large (>20 km) cloud-free ocean regions. This enhancement is consistent with those derived from satellite observations. Copyright 2009 by the American Geophysical Union."
"55017656900;7003591311;","Effect of aerosol on warm convective clouds: Aerosol-cloud surface flux feedbacks in a new coupled large eddy model",2006,"10.1029/2005JD006138","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33144474859&doi=10.1029%2f2005JD006138&partnerID=40&md5=ffbed21661548b64a8fb8c373a8da843","We present a new large eddy simulation model that comprises coupled components representing size-resolved aerosol and cloud microphysics, radiative properties of aerosol and clouds, dynamics, and a surface soil and vegetation model. The model is used to investigate the effect of increases in aerosol on liquid water path LWP, cloud fraction, optical depth, and precipitation formation in warm, continental cumulus clouds. Sets of simulations that either neglect, or include the radiative properties of a partially absorbing aerosol are performed. In the absence of aerosol radiative effects, an increase in aerosol loading results in a reduction in precipitation. However, the clouds do not experience significant changes in LWP, cloud fraction and cloud depth; aerosol effects on LWP and cloud fraction are small compared to the dynamical variability of the clouds at any given aerosol concentration. Reasons for this response are discussed. When aerosol radiative effects are included, the modification in atmospheric heating profiles, and the reduction in surface latent and sensible heat fluxes resulting from the presence of these particles, have a significant effect on cloud parameters and boundary layer evolution. For the case considered, there is a significant reduction in the strength of convection, LWP, cloud fraction and cloud depth. Cloud optical depth responds non-monotonically to the increase in aerosol. These results indicate that in continental regions surface processes must be included in calculations of aerosol-cloud-precipitation interactions. Neglect of these surface processes may result in an overestimate of the second aerosol indirect effect. Copyright 2006 by the American Geophysical Union."
"53880473700;6602080205;12787547600;","The influence of anthropogenic aerosol on multi-decadal variations of historical global climate",2013,"10.1088/1748-9326/8/2/024033","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880874790&doi=10.1088%2f1748-9326%2f8%2f2%2f024033&partnerID=40&md5=edc0b207f942f3424842a8e5cd8bcc4c","Analysis of single forcing runs from CMIP5 (the fifth Coupled Model Intercomparison Project) simulations shows that the mid-twentieth century temperature hiatus, and the coincident decrease in precipitation, is likely to have been influenced strongly by anthropogenic aerosol forcing. Models that include a representation of the indirect effect of aerosol better reproduce inter-decadal variability in historical global-mean near-surface temperatures, particularly the cooling in the 1950s and 1960s, compared to models with representation of the aerosol direct effect only. Models with the indirect effect also show a more pronounced decrease in precipitation during this period, which is in better agreement with observations, and greater inter-decadal variability in the inter-hemispheric temperature difference. This study demonstrates the importance of representing aerosols, and their indirect effects, in general circulation models, and suggests that inter-model diversity in aerosol burden and representation of aerosol-cloud interaction can produce substantial variation in simulations of climate variability on multi-decadal timescales. © 2013 IOP Publishing Ltd."
"56162305900;7003666669;55405340400;55717074000;7006270084;8608733900;55802246600;7103158465;","Aerosol indirect effects in a multi-scale aerosol-climate model PNNL-MMF",2011,"10.5194/acp-11-5431-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960187362&doi=10.5194%2facp-11-5431-2011&partnerID=40&md5=c7ac6b672679b092e40fdecdfaae907e","Much of the large uncertainty in estimates of anthropogenic aerosol effects on climate arises from the multi-scale nature of the interactions between aerosols, clouds and dynamics, which are difficult to represent in conventional general circulation models (GCMs). In this study, we use a multi-scale aerosol-climate model that treats aerosols and clouds across multiple scales to study aerosol indirect effects. This multi-scale aerosol-climate model is an extension of a multi-scale modeling framework (MMF) model that embeds a cloud-resolving model (CRM) within each vertical column of a GCM grid. The extension allows a more physically-based treatment of aerosol-cloud interactions in both stratiform and convective clouds on the global scale in a computationally feasible way. Simulated model fields, including liquid water path (LWP), ice water path, cloud fraction, shortwave and longwave cloud forcing, precipitation, water vapor, and cloud droplet number concentration are in reasonable agreement with observations. The new model performs quantitatively similar to the previous version of the MMF model in terms of simulated cloud fraction and precipitation. The simulated change in shortwave cloud forcing from anthropogenic aerosols is 0.77 W mg-2, which is less than half of that (1.79 W mg-2) calculated by the host GCM (NCAR CAM5) with traditional cloud parameterizations and is also at the low end of the estimates of other conventional global aerosol-climate models. The smaller forcing in the MMF model is attributed to a smaller (3.9 %) increase in LWP from preindustrial conditions (PI) to present day (PD) compared with 15.6 % increase in LWP in stratiform clouds in CAM5. The difference is caused by a much smaller response in LWP to a given perturbation in cloud condensation nuclei (CCN) concentrations from PI to PD in the MMF (about one-third of that in CAM5), and, to a lesser extent, by a smaller relative increase in CCN concentrations from PI to PD in the MMF (about 26 % smaller than that in CAM5). The smaller relative increase in CCN concentrations in the MMF is caused in part by a smaller increase in aerosol lifetime from PI to PD in the MMF, a positive feedback in aerosol indirect effects induced by cloud lifetime effects from aerosols. The smaller response in LWP to anthropogenic aerosols in the MMF model is consistent with observations and with high resolution model studies, which may indicate that aerosol indirect effects simulated in conventional global climate models are overestimated and point to the need to use global high resolution models, such as MMF models or global CRMs, to study aerosol indirect effects. The simulated total anthropogenic aerosol effect in the MMF is 1.05 W mg-2, which is close to the Murphy et al. (2009) inverse estimate of 1.1±0.4 W mg-2 (1&amp;sigma;) based on the examination of the Earth's energy balance. Further improvements in the representation of ice nucleation and low clouds in MMF are needed to refine the aerosol indirect effect estimate. © 2011 Author(s)."
"6505932008;7202899330;7202962414;","Aerosol indirect effects on tropical convection characteristics under conditions of radiative-convective equilibrium",2011,"10.1175/2010JAS3603.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954995826&doi=10.1175%2f2010JAS3603.1&partnerID=40&md5=4a6de032e0587f25b984ffa34f3015b0","The impacts of enhanced aerosol concentrations such as those associated with dust intrusions on the trimodal distribution of tropical convection have been investigated through the use of large-domain (10 000 grid points), fine-resolution (1 km), long-duration (100 days), two-dimensional idealized cloud-resolving model simulations conducted under conditions of radiative-convective equilibrium (RCE). The focus of this research is on those aerosols that serve primarily as cloud condensation nuclei (CCN). The results demonstrate that the large-scale organization of convection, the domain-averaged precipitation, and the total cloud fraction show only show a weak response to enhanced aerosol concentrations. However, while the domainwide responses to enhanced aerosol concentrations are weak, aerosol indirect effects on the three tropical cloud modes are found to be quite significant and often opposite in sign, a fact that appears to contribute to the weaker domain response. The results suggest that aerosol indirect effects associated with shallow clouds may offset or compensate for the aerosol indirect effects associated with congestus and deep convection systems and vice versa, thus producing a more moderate domainwide response to aerosol indirect forcing. Finally, when assessing the impacts of aerosol indirect forcing associated with CCN on the characteristics of tropical convection, several aspects need to be considered, including which cloud mode or type is being investigated, the field of interest, and whether localized or systemwide responses are being examined. © 2011 American Meteorological Society."
"7003663305;7202043942;7006041988;57203233100;6603431534;7402480218;19337612500;7402934750;6701873414;","A focus on mixed-phase clouds",2008,"10.1175/2008BAMS2378.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60849086477&doi=10.1175%2f2008BAMS2378.1&partnerID=40&md5=8809366460b731a57169cf0da601fc27","The phase composition and microphysical structure of clouds define the manner in which they modulate atmospheric radiation and contribute to the hydrologic cycle. Issues regarding cloud phase partitioning and transformation come to bear directly in mixed-phase clouds, and have been difficult to address within current modeling frameworks. Ground-based, remote-sensing observations of mixed-phase clouds can contribute a significant body of knowledge with which to better understand, and thereby more accurately model, clouds and their phase-defining processes. Utilizing example observations from the Mixed-Phase Arctic Cloud Experiment (MPACE), which occurred at the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program's Climate Research Facility in Barrow, Alaska, during autumn 2004, we review the current status of ground-based observation and retrieval methods used in characterizing the macrophysical, microphysical, radiative, and dynamical properties of stratiform mixed-phase clouds. In general, cloud phase, boundaries, ice properties, liquid water path, optical depth, and vertical velocity are available from a combination of active and passive sensors. Significant deficiencies exist in our ability to vertically characterize the liquid phase, to distinguish ice crystal habits, and to understand aerosol-cloud interactions. Further validation studies are needed to evaluate, improve, and expand our retrieval abilities in mixed-phase clouds. © 2008 American Meteorological Society."
"8570871900;","Arctic climate sensitivity to local black carbon",2013,"10.1002/jgrd.50176","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875744968&doi=10.1002%2fjgrd.50176&partnerID=40&md5=34bd35670a041613c684652a3663e971","Recent attention has focused on the impact of black carbon (BC) on Arctic climate. Here, idealized equilibrium climate experiments are conducted to explore the dependence of Arctic temperature change on the altitude and season of local BC forcing. BC residing in the lowest atmospheric layer produces very strong Arctic warming per unit mass and forcing [ 2.8 ± 0.5 K (Wm -2)-1] because of low cloud and sea-ice feedbacks that amplify both summer and winter warming. BC operating only within Arctic snow and sea-ice also effectively warms the surface, but forcings at 400-750mbar and 210-250mbar cause weak surface warming and cooling, respectively, despite increasing atmospheric moist static energy. This is a consequence of stable atmospheric conditions in the Arctic limiting vertical mixing, and of higher-altitude BC reducing surface insolation, increasing stability and summer low-cloud cover, and decreasing poleward energy transport. The current simulated distribution of Arctic atmospheric BC slightly cools the surface, supporting an earlier study, while local atmospheric and cryosphere-deposited BC warms the Arctic with a sensitivity of + 0.5 ± 0.4 K (Wm-2) -1. By season, April-May tropospheric BC induces the greatest mass-normalized Arctic warming [0.18 K (Gg yr) -1] because high insolation and surface albedo facilitate large specific forcing during this season. Forcing efficacy, however, increases with summer progression because of decreasing atmospheric stability, leading to a narrow range of mass-normalized response with season. Although limited by exclusion of aerosol indirect effects, changes in ocean heat transport and forcing by co-emitted species, these experiments show that Arctic climate response is sensitive to the vertical distribution and deposition efficiency of BC reaching the Arctic. Key PointsSurface climate change from Arctic black carbon depends strongly on its altitudeNear-surface BC causes strong warming because of cloud and sea-ice feedbacksCurrent Arctic atmosphere + snow BC warms the surface while atmospheric BC may not © 2013. American Geophysical Union. All Rights Reserved."
"6603453147;57206332144;","MODIS observations of enhanced clear sky reflectance near clouds",2009,"10.1029/2008GL037089","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66949159442&doi=10.1029%2f2008GL037089&partnerID=40&md5=a01fa37847d33835fe92a5a1741d1e62","Several recent studies have found that the brightness of clear sky systematically increases near clouds. Understanding this increase is important both for a correct interpretation of observations and for improving our knowledge of aerosol-cloud interactions. However, while the studies suggested several processes to explain the increase, the significance of each process is yet to be determined. This study examines one of the suggested processes-three-dimensional (3-D) radiative interactions between clouds and their surroundings-by analyzing a large dataset of MODIS (Moderate Resolution Imaging Spectroradiometer) observations over the Northeast Atlantic Ocean. The results indicate that 3-D effects are responsible for a large portion of the observed increase, which extends to about 15 km away from clouds and is stronger (z) at shorter wavelengths (ii) near optically thicker clouds and (Ui) near illuminated cloud sides. This implies that it is important to account for 3-D radiative effects in the interpretation of solar reflectance measurements over clear regions in the vicinity of clouds. Copyright 2009 by the American Geophysical Union."
"7202485288;7004540083;7402094372;7201914101;","Global Survey of the Relationships of Cloud Albedo and Liquid Water Path with Droplet Size Using ISCCP",1998,"10.1175/1520-0442(1998)011<1516:GSOTRO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0001120393&doi=10.1175%2f1520-0442%281998%29011%3c1516%3aGSOTRO%3e2.0.CO%3b2&partnerID=40&md5=afed3d57f7109a0ee56044a3bdc0eebe","The most common approach used to model the aerosol indirect effect on clouds holds the cloud liquid water path constant. In this case, increasing aerosol concentration increases cloud droplet concentration, decreases cloud droplet size, and increases cloud albedo. The expected decrease in cloud droplet size associated with larger aerosol concentrations has been found to be larger over land than over water and larger in the Northern than in the Southern Hemisphere, but the corresponding cloud albedo increase has not been found. Many previous studies have shown that cloud liquid water path varies with changing cloud droplet size, which may alter the behavior of clouds when aerosols change. This study examines the relationship between geographic and seasonal variations of cloud effective droplet size and cloud albedo, as well as cloud liquid water path, in low-level clouds using International Satellite Cloud Climatology Project data. The results show that cloud albedo increases with decreasing droplet size for most clouds over continental areas and for all optically thicker clouds, but that cloud albedo decreases with decreasing droplet size for optically thinner clouds over most oceans and the tropical rain forest regions. For almost all clouds, the liquid water path increases with increasing cloud droplet size."
"16444028600;7202865036;16443985900;7403384594;6701378450;","Investigation of molar volume and surfactant characteristics of water-soluble organic compounds in biomass burning aerosol",2008,"10.5194/acp-8-799-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39449126548&doi=10.5194%2facp-8-799-2008&partnerID=40&md5=1832aa96d7c059ad81a643dc0dd45305","In this study, we characterize the CCN activity of the water-soluble organics in biomass burning aerosol. The aerosol after collection upon filters is dissolved in water using sonication. Hydrophobic and hydrophilic components are fractionated from a portion of the original sample using solid phase extraction, and subsequently desalted. The surface tension and CCN activity of these different samples are measured with a KSV CAM 200 goniometer and a DMT Streamwise Thermal Gradient CCN Counter, respectively. The measurements show that the strongest surfactants are isolated in the hydrophobic fraction, while the hydrophilics exhibit negligible surface tension depression. The presence of salts (primarily (NH4)2SO4) in the hydrophobic fraction substantially enhances surface tension depression; their synergistic effects considerably enhance CCN activity, exceeding that of pure (NH 4)2SO4. From our analysis, average thermodynamic properties (i.e, molar volume) are determined for samples using our newly developed Köhler Theory Analysis (KTA) method. The molar mass of the hydrophilic and hydrophobic aerosol components is estimated to be 87±26gmol-1 and 780±231gmol-1, respectively. KTA also suggests that the relative proportion (in moles) of hydrophobic to hydrophilic compounds in the original sample to be 1:3. For the first time, KTA is applied to an aerosol with this level of complexity and displays its potential for providing physically-based constraints for GCM parameterizations of the aerosol indirect effect."
"6602600408;7201504886;57208121852;57203053317;","Interpreting the cloud cover-Aerosol optical depth relationship found in satellite data using a general circulation model",2010,"10.5194/acp-10-6129-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954498624&doi=10.5194%2facp-10-6129-2010&partnerID=40&md5=ea7c4546ea6f8af9ebeb4bc0744c9283","Statistical analysis of satellite data shows a positive correlation between aerosol optical depth (AOD) and total cloud cover (TCC). Reasons for this relationship have been disputed in recent literature. The aim of this study is to explore how different processes contribute to one model's analog of the positive correlation between aerosol optical depth and total cloud cover seen in the satellite retrievals. We compare the slope of the linear regression between the logarithm of TCC and the logarithm of AOD, or the strength of the relationship, as derived from three satellite data sets to the ones simulated by a global aerosol-climate model. We analyse model results from two different simulations with and without a parameterisation of aerosol indirect effects, and using dry compared to humidified AOD. Perhaps not surprisingly we find that no single one of the hypotheses discussed in the literature is able to uniquely explain the positive relationship. However the dominant contribution to the model's AOD-TCC relationship can be attributed to aerosol swelling in regions where humidity is high and clouds are coincidentally found. This finding leads us to hypothesise that much of the AOD-TCC relationship seen in the satellite data is also carried by such a process, rather than the direct effects of the aerosols on the cloud fields themselves. © Author(s) 2010."
"18437651200;25624725200;7402538754;7005254328;6602354484;55730602600;9432343100;35798985200;6601974344;35798085000;7202779940;35307109700;8550791300;14523061300;7006415284;","Heterogeneous freezing of droplets with immersed mineral dust particles - Measurements and parameterization",2010,"10.5194/acp-10-3601-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860389733&doi=10.5194%2facp-10-3601-2010&partnerID=40&md5=783107771c9f1083bd07906f7330f8c0","During the measurement campaign FROST (FReezing Of duST), LACIS (Leipzig Aerosol Cloud Interaction Simulator) was used to investigate the immersion freezing behavior of size selected, coated and uncoated Arizona Test Dust (ATD) particles with a mobility diameter of 300 nm. Particles were coated with succinic acid (C4H6O4), sulfuric acid (H 2SO4) and ammonium sulfate ((NH4)) 2SO4). Ice fractions at mixed-phase cloud temperatures ranging from 233.15K to 239.15K (±0.60 K) were determined for all types of particles. In this temperature range, pure ATD particles and those coated with C4H6O4 or small amounts of H 2SO4 were found to be the most efficient ice nuclei (IN). ATD particles coated with (NH4)2SO4 were the most inefficient IN. Since the supercooled droplets were highly diluted before freezing occurred, a freezing point suppression due to the soluble material on the particles (and therefore in the droplets) cannot explain this observation. Therefore, it is reasonable to assume that the coatings lead to particle surface alterations which cause the differences in the IN abilities. Two different theoretical approaches based on the stochastic and the singular hypotheses were applied to clarify and parameterize the freezing behavior of the particles investigated. Both approaches describe the experimentally determined results, yielding parameters that can subsequently be used to compare our results to those from other studies. How-ever, we cannot clarify at the current state which of the two approaches correctly describes the investigated immersion freezing process. But both approaches confirm the assumption that the coatings lead to particle surface modifications lowering the nucleation efficiency. The stochastic approach interprets the reduction in nucleation rate from coating as primarily due to an increase in the thermodynamic barrier for ice formation (i.e., changes in interfacial free energies). The singular approach interprets the reduction as resulting from a reduced surface density of active sites. © 2010 Author(s)."
"57203053317;24398842400;","Sensitivity studies of different aerosol indirect effects in mixed-phase clouds",2009,"10.5194/acp-9-8917-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71149116178&doi=10.5194%2facp-9-8917-2009&partnerID=40&md5=ae19a66ae9b0a6e201c9974ab1e3bcba","Aerosols affect the climate system by changing cloud characteristics. Using the global climate model ECHAM5-HAM, we investigate different aerosol effects on mixed-phase clouds: The glaciation effect, which refers to a more frequent glaciation due to anthropogenic aerosols, versus the de-activation effect, which suggests that ice nuclei become less effective because of an anthropogenic sulfate coating. The glaciation effect can partly offset the indirect aerosol effect on warm clouds and thus causes the total anthropogenic aerosol effect to be smaller. It is investigated by varying the parameterization for the Bergeron-Findeisen process and the threshold coating thickness of sulfate (SO4-crit), which is required to convert an externally mixed aerosol particle into an internally mixed particle. Differences in the net radiation at the top-of-the-atmosphere due to anthropogenic aerosols between the different sensitivity studies amount up to 0.5 W m&amp;minus;2. This suggests that the investigated mixed-phase processes have a major effect on the total anthropogenic aerosol effect."
"14035836100;7003591311;7005591218;7402934750;55740664200;25624545600;7004057920;7006634316;","An assessment of aerosol-cloud interactions in marine stratus clouds based on surface remote sensing",2009,"10.1029/2008JD011006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68249126568&doi=10.1029%2f2008JD011006&partnerID=40&md5=dc6220f225ea6b81d9571c7c3a4579df","[1] An assessment of aerosol-cloud interactions (ACI) from ground-based remote sensing under coastal stratiform clouds is presented. The assessment utilizes a long-term, high temporal resolution data set from the Atmospheric Radiation Measurement (ARM) Program deployment at Pt. Reyes, California, United States, in 2005 to provide statistically robust measures of ACI and to characterize the variability of the measures based on variability in environmental conditions and observational approaches. The average ACI N (= dlnN<inf>d</inf>/dlnα, the change in cloud drop number concentration with aerosol concentration) is 0.48, within a physically plausible range of 0-1.0. Values vary between 0.18 and 0.69 with dependence on (1) the assumption of constant cloud liquid water path (LWP), (2) the relative value of cloud LWP, (3) methods for retrieving N<inf>d</inf>, (4) aerosol size distribution, (5) updraft velocity, and (6) the scale and resolution of observations. The sensitivity of the local, diurnally averaged radiative forcing to this variability in ACI<inf>N</inf> values, assuming an aerosol perturbation of 500 cm-3 relative to a background concentration of 100 cm-3, ranges between - 4 and - 9 W m-2. Further characterization of ACI and its variability is required to reduce uncertainties in global radiative forcing estimates. Copyright 2009 by the American Geophysical Union."
"7004838931;14060155500;7004611350;7003276832;","Aerosol activation in marine stratocumulus clouds: 2. Köhler and parcel theory closure studies",2003,"10.1029/2002jd002692","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342291176&doi=10.1029%2f2002jd002692&partnerID=40&md5=6c285ef16e0672f58a8f1840812c3e95","Aerosol properties and vertical velocities relevant to cloud droplet concentrations in marine stratocumulus clouds are presented. Data were collected at a coastal surface site, and on an aircraft that flew north (upwind) of the surface site during the CLOUDYCOLUMN portion of the second Aerosol Characterization Experiment (ACE-2). In a closure study we compare observations, from five study days, and predictions based on Köhler and parcel theory. Measured and predicted cloud condensation nuclei (CCN) do agree after accounting for differences between the mobility equivalent (Dme) and sphere equivalent (Dse) diameters, but only when considering results from two study days unaffected by continental pollution. After applying the Dme - Dse correction, cloud droplet concentration closure was also achieved, or nearly achieved, on three study days. Discrepancies between predicted and measured CCN, or between predicted and measured droplet concentration, were always in the direction of predicted values being larger than that measured. Although theoretical studies do specify scenarios where droplet concentration and CCN overestimation can occur, the observed disparities may also be due to multiple and poorly characterized experimental biases. Copyright 2003 by the American Geophysical Union."
"36124786200;7004479395;","Aerosol indirect effect on warm clouds over South-East Atlantic, from co-located MODIS and CALIPSO observations",2013,"10.5194/acp-13-69-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872102043&doi=10.5194%2facp-13-69-2013&partnerID=40&md5=711a42fb782649b6f77a3593001efe64","In this study, we provide a comprehensive analysis of aerosol interaction with warm boundary layer clouds over the South-East Atlantic. We use aerosol and cloud parameters derived from MODIS observations, together with co-located CALIPSO estimates of the layer altitudes, to derive statistical relationships between aerosol concentration and cloud properties. The CALIPSO products are used to differentiate between cases of mixed cloud-aerosol layers from cases where the aerosol is located well-above the cloud top. This technique allows us to obtain more reliable estimates of the aerosol indirect effect than from simple relationships based on vertically integrated measurements of aerosol and cloud properties. Indeed, it permits us to somewhat distinguish the effects of aerosol and meteorology on the clouds, although it is not possible to fully ascertain the relative contribution of each on the derived statistics. Consistently with the results from previous studies, our statistics clearly show that aerosol affects cloud microphysics, decreasing the Cloud Droplet Radius (CDR). The same data indicate a concomitant strong decrease in cloud Liquid Water Path (LWP), which is inconsistent with the hypothesis of aerosol inhibition of precipitation (Albrecht, 1989). We hypothesise that the observed reduction in LWP is the consequence of dry air entrainment at cloud top. The combined effect of CDR decrease and LWP decrease leads to rather small sensitivity of the Cloud Optical Thickness (COT) to an increase in aerosol concentration. The analysis of MODIS-CALIPSO coincidences also evidences an aerosol enhancement of low cloud cover. Surprisingly, the Cloud Fraction (CLF) response to aerosol invigoration is much stronger when (absorbing) particles are located above cloud top than in cases of physical interaction. This result suggests a relevant aerosol radiative effect on low cloud occurrence: absorbing particles above the cloud top may heat the corresponding atmosphere layer, decrease the vertical temperature gradient, increase the low tropospheric stability and provide favourable conditions for low cloud formation. <br><br> We also analyse the impact of anthropogenic aerosols on precipitation, through the statistical analysis of CDR-COT co-variations. A COT value of 10 is found to be the threshold beyond which precipitation is mostly formed, in both clean and polluted environments. For larger COT, polluted clouds show evidence of precipitation suppression. <br><br> Results suggest the presence of two competing mechanisms governing LWP response to aerosol invigoration: a drying effect due to aerosol enhanced entrainment of dry air at cloud top (predominant for optically thin clouds) and a moistening effect due to aerosol inhibition of precipitation (predominant for optically thick clouds). © 2013 Author(s)."
"56162305900;7003666669;55717074000;6701606453;56384704800;7103158465;55405340400;7006270084;7101959253;7006643234;55802246600;7102604282;","Constraining cloud lifetime effects of aerosols using A-Train satellite observations",2012,"10.1029/2012GL052204","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865473923&doi=10.1029%2f2012GL052204&partnerID=40&md5=a4e2ed1ebf77ff3762a698c2b41acc71","Aerosol indirect effects have remained the largest uncertainty in estimates of the radiative forcing of past and future climate change. Observational constraints on cloud lifetime effects are particularly challenging since it is difficult to separate aerosol effects from meteorological influences. Here we use three global climate models, including a multi-scale aerosol-climate model PNNL-MMF, to show that the dependence of the probability of precipitation on aerosol loading, termed the precipitation frequency susceptibility (S <inf>pop</inf>), is a good measure of the liquid water path response to aerosol perturbation (&), as both S<inf>pop</inf> and & strongly depend on the magnitude of autoconversion, a model representation of precipitation formation via collisions among cloud droplets. This provides a method to use satellite observations to constrain cloud lifetime effects in global climate models. S<inf>pop</inf> in marine clouds estimated from CloudSat, MODIS and AMSR-E observations is substantially lower than that from global climate models and suggests a liquid water path increase of less than 5% from doubled cloud condensation nuclei concentrations. This implies a substantially smaller impact on shortwave cloud radiative forcing over ocean due to aerosol indirect effects than simulated by current global climate models (a reduction by one-third for one of the conventional aerosol-climate models). Further work is needed to quantify the uncertainties in satellite-derived estimates of S<inf>pop</inf> and to examine S<inf>pop</inf> in high-resolution models. © 2012. American Geophysical Union. All Rights Reserved."
"55893823700;7102976560;7004347243;6701511321;15755995900;55717074000;7003666669;16027966800;56757625500;7003717604;6507575165;7004643405;7101671456;57207899038;8147766700;8293692200;","Description and evaluation of tropospheric chemistry and aerosols in the Community Earth System Model (CESM1.2)",2015,"10.5194/gmd-8-1395-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929358848&doi=10.5194%2fgmd-8-1395-2015&partnerID=40&md5=5a63f1945ad6b26aa44934f8dda10541","The Community Atmosphere Model (CAM), version 5, is now coupled to extensive tropospheric and stratospheric chemistry, called CAM5-chem, and is available in addition to CAM4-chem in the Community Earth System Model (CESM) version 1.2. The main focus of this paper is to compare the performance of configurations with internally derived ""free running"" (FR) meteorology and ""specified dynamics"" (SD) against observations from surface, aircraft, and satellite, as well as understand the origin of the identified differences. We focus on the representation of aerosols and chemistry. All model configurations reproduce tropospheric ozone for most regions based on in situ and satellite observations. However, shortcomings exist in the representation of ozone precursors and aerosols. Tropospheric ozone in all model configurations agrees for the most part with ozonesondes and satellite observations in the tropics and the Northern Hemisphere within the variability of the observations. Southern hemispheric tropospheric ozone is consistently underestimated by up to 25%. Differences in convection and stratosphere to troposphere exchange processes are mostly responsible for differences in ozone in the different model configurations. Carbon monoxide (CO) and other volatile organic compounds are largely underestimated in Northern Hemisphere mid-latitudes based on satellite and aircraft observations. Nitrogen oxides (NO<inf>x</inf>) are biased low in the free tropical troposphere, whereas peroxyacetyl nitrate (PAN) is overestimated in particular in high northern latitudes. The present-day methane lifetime estimates are compared among the different model configurations. These range between 7.8 years in the SD configuration of CAM5-chem and 8.8 years in the FR configuration of CAM4-chem and are therefore underestimated compared to observational estimations. We find that differences in tropospheric aerosol surface area between CAM4 and CAM5 play an important role in controlling the burden of the tropical tropospheric hydroxyl radical (OH), which causes differences in tropical methane lifetime of about half a year between CAM4-chem and CAM5-chem. In addition, different distributions of NO<inf>x</inf> from lightning explain about half of the difference between SD and FR model versions in both CAM4-chem and CAM5-chem. Remaining differences in the tropical OH burden are due to enhanced tropical ozone burden in SD configurations compared to the FR versions, which are not only caused by differences in chemical production or loss but also by transport and mixing. For future studies, we recommend the use of CAM5-chem configurations, due to improved aerosol description and inclusion of aerosol-cloud interactions. However, smaller tropospheric surface area density in the current version of CAM5-chem compared to CAM4-chem results in larger oxidizing capacity in the troposphere and therefore a shorter methane lifetime. © Author(s) 2015."
"7003777747;7003614389;8708955900;35464731600;7102084129;13403622000;7005955015;6603749963;7003434501;7003927831;","Aerosol-cloud interaction inferred from MODIS satellite data and global aerosol models",2007,"10.5194/acp-7-3081-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250779349&doi=10.5194%2facp-7-3081-2007&partnerID=40&md5=1093f57679b5721886612af49a338ced","We have used the MODIS satellite data and two global aerosol models to investigate the relationships between aerosol optical depth (AOD) and cloud parameters that may be affected by the aerosol concentration. The relation-ships that are studied are mainly between AOD, on the one hand, and cloud cover, cloud liquid water path, and water vapour, on the other. Additionally, cloud droplet effective radius, cloud optical depth, cloud top pressure and aerosol Ångström exponent, have been analysed in a few cases. In the MODIS data we found, as in earlier studies, an enhancement in the cloud cover with increasing AOD. We find it likely that most of the strong increase in cloud cover with AOD, at least for AOD<0.2, is a result of aerosol-cloud interactions and a prolonged cloud lifetime. Large and mesoscale weather systems seem not to be a cause for the increase in cloud cover with AOD in this range. Sensitivity simulations show that when water uptake of the aerosols is not taken into account in the models the modelled cloud cover mostly decreases with AOD. Part of the relationship found in the MODIS data for AOD>0.2 can be explained by larger water uptake close to the clouds since relative humidity is higher in regions with higher cloud cover. The efficiency of the hygroscopic growth depends on aerosol type, the hygroscopic nature of the aerosol, the relative humidity, and to some extent the cloud screening. By analysing the Ångström exponent we find that the hygroscopic growth of the aerosol is not likely to be a main contributor to the cloud cover increase with AOD. Since the largest increase in cloud cover with AOD is for low AOD (∼0.2) and thus also for low cloud cover, we argue that cloud contamination is not likely to play a large role. However, interpretation of the complex relationships between AOD and cloud parameters should be made with great care and further work is clearly needed."
"8684037700;7006837187;7403682442;7004479957;24722339600;8724962900;56363596200;55454856700;36183151300;35232912700;6602582342;57213358341;36145445200;7006839912;7003875967;26643510900;57203798762;6701562043;6507501796;35593636200;23570437900;7401773666;22034655600;7201572145;9332706900;7006377579;37089603000;21933618400;22834248200;9043417100;24537168200;7005254328;7006901405;7202252296;41361927700;41361010200;7006252685;36076994600;7006643234;","South East Pacific atmospheric composition and variability sampled along 20° S during VOCALS-REx",2011,"10.5194/acp-11-5237-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79957955954&doi=10.5194%2facp-11-5237-2011&partnerID=40&md5=6a279c399fcaf7dccbae9ffd2a1dfbde","The VAMOS Ocean-Cloud-Atmosphere-Land Regional Experiment (VOCALS-REx) was conducted from 15 October to 15 November 2008 in the South East Pacific (SEP) region to investigate interactions between land, sea and atmosphere in this unique tropical eastern ocean environment and to improve the skill of global and regional models in representing the region. This study synthesises selected aircraft, ship and surface site observations from VOCALS-REx to statistically summarise and characterise the atmospheric composition and variability of the Marine Boundary Layer (MBL) and Free Troposphere (FT) along the 20° S parallel between 70° W and 85° W. Significant zonal gradients in mean MBL sub-micron aerosol particle size and composition, carbon monoxide, sulphur dioxide and ozone were seen over the campaign, with a generally more variable and polluted coastal environment and a less variable, more pristine remote maritime regime. Gradients in aerosol and trace gas concentrations were observed to be associated with strong gradients in cloud droplet number. The FT was often more polluted in terms of trace gases than the MBL in the mean; however increased variability in the FT composition suggests an episodic nature to elevated concentrations. This is consistent with a complex vertical interleaving of airmasses with diverse sources and hence pollutant concentrations as seen by generalised back trajectory analysis, which suggests contributions from both local and long-range sources. Furthermore, back trajectory analysis demonstrates that the observed zonal gradients both in the boundary layer and the free troposphere are characteristic of marked changes in airmass history with distance offshore ĝ€"" coastal boundary layer airmasses having been in recent contact with the local land surface and remote maritime airmasses having resided over ocean for in excess of ten days. Boundary layer composition to the east of 75° W was observed to be dominated by coastal emissions from sources to the west of the Andes, with evidence for diurnal pumping of the Andean boundary layer above the height of the marine capping inversion. Analysis of intra-campaign variability in atmospheric composition was not found to be significantly correlated with observed low-frequency variability in the large scale flow pattern; campaign-average interquartile ranges of CO, SO2 and O3 concentrations at all longitudes were observed to dominate over much smaller differences in median concentrations calculated between periods of different flow regimes. The campaign climatology presented here aims to provide a valuable dataset to inform model simulation and future process studies, particularly in the context of aerosol-cloud interaction and further evaluation of dynamical processes in the SEP region for conditions analogous to those during VOCALS-REx. To this end, our results are discussed in terms of coastal, transitional and remote spatial regimes in the MBL and FT and a gridded dataset are provided as a resource. © 2011 Author(s)."
"7201496259;7102604282;7007020226;7201699997;7101909186;25723426400;","Cloud susceptibility and the first aerosol indirect forcing: Sensitivity to black carbon and aerosol concentrations",2002,"10.1029/2000JD000215","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36448977286&doi=10.1029%2f2000JD000215&partnerID=40&md5=6adb3c94dd662000fbafd55d2ac774e2","Present-day global anthropogenic emissions contribute more than half of the mass in submicron particles primarily due to sulfate and carbonaceous aerosol components derived from fossil fuel combustion and biomass burning. These anthropogenic aerosols increase cloud drop number concentration and cloud albedo. Here, we use an improved version of the fully coupled climate/chemistry models to investigate cloud susceptibility and the first indirect effect of anthropogenic aerosols (the Twomey effect). We examine the correspondence between the model simulation of cloud susceptibility and that inferred from satellite measurements to test whether our simulated aerosol concentrations and aerosol/cloud interactions give a faithful representation of these features. This comparison provides an overall measure of the adequacy of cloud cover and drop concentrations. We also address the impact of black carbon absorption in clouds on the first indirect forcing and examine the sensitivity of the forcing to different representations of natural aerosols. We find that including this absorption does not change the global forcing by more than 0.07 W m-2, but that locally it could decrease the forcing by as much as 0.7 W m-2 in regions where black carbon emissions are pronounced. Because of the nonlinear relationship between cloud drop number and aerosol number concentrations, the total forcing does not equal the sum of the forcing from each individual source. Our estimated total first indirect forcing is -1.85 W m-2, with -0.30 W m-2 associated with anthropogenic sulfate, -1.16 W m-2 associated with carbonaceous aerosols from biomass burning, and -0.52 W m-2 associated with carbonaceous aerosols from fossil fuel combustion. Estimates of forcing by sulfate and total carbonaceous aerosols increase to -0.31 and -1.67 W m-2, respectively, if natural emissions of organic aerosols are only 8.4 tg yr-1, but decrease to -0.26 and -1.27 W m-2 if they are as large as 42 Tg yr-1. Even larger estimates of forcing are derived if dust and sea-salt emissions are not included. The effect of aerosol abundance on cloud life cycle may be important but is not treated in this Study. Copyright 2002 by the American Geophysical Union."
"55802246600;7006592026;","Interactive coupling of regional climate and sulfate aerosol models over eastern Asia",1999,"10.1029/98JD02347","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033608679&doi=10.1029%2f98JD02347&partnerID=40&md5=77f080006be9d0f586e91a3a793bc6d7","The NCAR regional climate model (RegCM) is interactively coupled to a simple radiatively active sulfate aerosol model over eastern Asia. Both direct and indirect aerosol effects are represented. The coupled model system is tested for two simulation periods, November 1994 and July 1995, with aerosol sources representative of present-day anthropogenic sulfur emissions. The model sensitivity to the intensity of the aerosol source is also studied. The main conclusions from our work are as follows: (1) The aerosol distribution and cycling processes show substantial regional spatial variability, and temporal variability varying on a range of scales, from the diurnal scale of boundary layer and cumulus cloud evolution to the 3-10 day scale of synoptic scale events and the interseasonal scale of general circulation features; (2) both direct and indirect aerosol forcings have regional effects on surface climate; (3) the regional climate response to the aerosol forcing is highly nonlinear, especially during the summer, due to the interactions with cloud and precipitation processes; (4) in our simulations the role of the aerosol indirect effects is dominant over that of direct effects; (5) aerosol-induced feedback processes can affect the aerosol burdens at the subregional scale. This work constitutes the first step in a long term research project aimed at coupling a hierarchy of chemistry/aerosol models to the RegCM over the eastern Asia region. Copyright 1999 by the American Geophysical Union."
"11940188700;6603749963;7003777747;55636322183;10243536500;17434636400;","Anthropogenic radiative forcing time series from pre-industrial times until 2010",2011,"10.5194/acp-11-11827-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-82355184402&doi=10.5194%2facp-11-11827-2011&partnerID=40&md5=d16d2a29249f6f05b6d2631bdb03abec","In order to use knowledge of past climate change to improve our understanding of the sensitivity of the climate system, detailed knowledge about the time development of radiative forcing (RF) of the earth atmosphere system is crucial. In this study, time series of anthropogenic forcing of climate from pre-industrial times until 2010, for all well established forcing agents, are estimated. This includes presentation of RF histories of well mixed greenhouse gases, tropospheric ozone, direct-and indirect aerosol effects, surface albedo changes, stratospheric ozone and stratospheric water vapour. For long lived greenhouse gases, standard methods are used for calculating RF, based on global mean concentration changes. For short lived climate forcers, detailed chemical transport modelling and radiative transfer modelling using historical emission inventories is performed. For the direct aerosol effect, sulphate, black carbon, organic carbon, nitrate and secondary organic aerosols are considered. For aerosol indirect effects, time series of both the cloud lifetime effect and the cloud albedo effect are presented. Radiative forcing time series due to surface albedo changes are calculated based on prescribed changes in land use and radiative transfer modelling. For the stratospheric components, simple scaling methods are used. Long lived greenhouse gases (LLGHGs) are the most important radiative forcing agent with a RF of 2.83±0.28 W m-2 in year 2010 relative to 1750. The two main aerosol components contributing to the direct aerosol effect are black carbon and sulphate, but their contributions are of opposite sign. The total direct aerosol effect was-0.48±0.32 W m -22 in year 2010. Since pre-industrial times the positive RF (LLGHGs and tropospheric O3) has been offset mainly by the direct and indirect aerosol effects, especially in the second half of the 20th century, which possibly lead to a decrease in the total anthropogenic RF in the middle of the century. We find a total anthropogenic RF in year 2010 of 1.4 W m -22. However, the uncertainties in the negative RF from aerosols are large, especially for the cloud lifetime effect. © 2011 Author(s)."
"21742333400;57218971411;22933265100;7004337213;6701378450;","On the effect of dust particles on global cloud condensation nuclei and cloud droplet number",2011,"10.1029/2011JD016283","https://www.scopus.com/inward/record.uri?eid=2-s2.0-83655192891&doi=10.1029%2f2011JD016283&partnerID=40&md5=0ce1b2978bb5e12dbe345b4a90be1cf8","Aerosol-cloud interaction studies to date consider aerosol with a substantial fraction of soluble material as the sole source of cloud condensation nuclei (CCN). Emerging evidence suggests that mineral dust can act as good CCN through water adsorption onto the surface of particles. This study provides a first assessment of the contribution of insoluble dust to global CCN and cloud droplet number concentration (CDNC). Simulations are carried out with the NASA Global Modeling Initiative chemical transport model with an online aerosol simulation, considering emissions from fossil fuel, biomass burning, marine, and dust sources. CDNC is calculated online and explicitly considers the competition of soluble and insoluble CCN for water vapor. The predicted annual average contribution of insoluble mineral dust to CCN and CDNC in cloud-forming areas is up to 40 and 23.8%, respectively. Sensitivity tests suggest that uncertainties in dust size distribution and water adsorption parameters modulate the contribution of mineral dust to CDNC by 23 and 56%, respectively. Coating of dust by hygroscopic salts during the atmospheric aging causes a twofold enhancement of the dust contribution to CCN; the aged dust, however, can substantially deplete in-cloud supersaturation during the initial stages of cloud formation and can eventually reduce CDNC. Considering the hydrophilicity from adsorption and hygroscopicity from solute is required to comprehensively capture the dust-warm cloud interactions. The framework presented here addresses this need and can be easily integrated in atmospheric models. Copyright 2011 by the American Geophysical Union."
"36705143500;35561911800;56203249800;55408944000;22978151200;57193132723;9242540400;12241892400;6604021707;7004214645;9242539000;57191598636;7004177660;7004409909;36851768400;55339475000;6603552777;12240390300;7404334532;7006224475;57191693467;56249704400;7006399110;8954866200;57191692422;7201837768;6506806004;55928817500;55403720400;8414341100;7006550762;12763470600;7401548835;7405727977;56528677800;6507308842;14829673100;22986631300;7403318365;57203378018;","CMIP5 historical simulations (1850-2012) with GISS ModelE2",2014,"10.1002/2013MS000266","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904868424&doi=10.1002%2f2013MS000266&partnerID=40&md5=827f11e855a90250b2a011134186ddc8","Observations of climate change during the CMIP5 extended historical period (1850-2012) are compared to trends simulated by six versions of the NASA Goddard Institute for Space Studies ModelE2 Earth System Model. The six models are constructed from three versions of the ModelE2 atmospheric general circulation model, distinguished by their treatment of atmospheric composition and the aerosol indirect effect, combined with two ocean general circulation models, HYCOM and Russell. Forcings that perturb the model climate during the historical period are described. Five-member ensemble averages from each of the six versions of ModelE2 simulate trends of surface air temperature, atmospheric temperature, sea ice and ocean heat content that are in general agreement with observed trends, although simulated warming is slightly excessive within the past decade. Only simulations that include increasing concentrations of long-lived greenhouse gases match the warming observed during the twentieth century. Differences in twentieth-century warming among the six model versions can be attributed to differences in climate sensitivity, aerosol and ozone forcing, and heat uptake by the deep ocean. Coupled models with HYCOM export less heat to the deep ocean, associated with reduced surface warming in regions of deepwater formation, but greater warming elsewhere at high latitudes along with reduced sea ice. All ensembles show twentieth-century annular trends toward reduced surface pressure at southern high latitudes and a poleward shift of the midlatitude westerlies, consistent with observations. Key Points The model simulates many observed climate trends during the twentieth century Contrasting warming trends among different model configurations can be related to differences in climate sensitivity, aerosol and ozone forcing, and ocean heat uptake Total forcing at the end of the CMIP5 historical period is larger than forcing within the previous (CMIP3) version of the model, due to greater greenhouse gas forcing with a smaller aerosol offset © 2014. The Authors."
"14035836100;7003591311;","The scale problem in quantifying aerosol indirect effects",2012,"10.5194/acp-12-1031-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861326076&doi=10.5194%2facp-12-1031-2012&partnerID=40&md5=191b49e20111a40c4945b61f41f2cc09","A wide range of estimates exists for the radiative forcing of the aerosol effect on cloud albedo. We argue that a component of this uncertainty derives from the use of a wide range of observational scales and platforms. Aerosol influences cloud properties at the microphysical scale, or the ""process scale"", but observations are most often made of bulk properties over a wide range of resolutions, or ""analysis scales"". We show that differences between process and analysis scales incur biases in quantification of the albedo effect through the impact that data aggregation and computational approach have on statistical properties of the aerosol or cloud variable, and their covariance. Measures made within this range of scales are erroneously treated as equivalent, leading to a large uncertainty in associated radiative forcing estimates. Issues associated with the coarsening of observational resolution particular to quantifying the albedo effect are discussed. Specifically, the omission of the constraint on cloud liquid water path and the separation in space of cloud and aerosol properties from passive, space-based remote sensors dampen the measured strength of the albedo effect. We argue that, because of this lack of constraints, many of these values are in fact more representative of the full range of aerosol-cloud interactions and their associated feedbacks. Based on our understanding of these biases we propose a new observationally- based and process-model-constrained, method for estimating aerosol-cloud interactions that can be used for radiative forcing estimates as well as a better characterization of the uncertainties associated with those estimates. © Author(s) 2012."
"7407104838;7102805852;57203200427;","Climate impacts of geoengineering marine stratocumulus clouds",2009,"10.1029/2008JD011450","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67650456686&doi=10.1029%2f2008JD011450&partnerID=40&md5=11a8ffea6d4ad2655404db10f0a0d867","Theoretical potential geoengineering solutions to the global warming problem have recently been proposed. Here, we present an idealized study of the climate response to deliberately seeding large-scale stratocumulus cloud decks in the North Pacific, South Pacific, and South Atlantic, thereby inducing cooling via aerosol indirect effects. Atmosphere-only, atmosphere/mixed-layer ocean, and fully coupled atmosphere/ocean versions of the Met Office Hadley Centre model are used to investigate the radiative forcing, climate efficacy, and regional response of temperature, precipitation, and net primary productivity to such geoengineering. The radiative forcing simulations indicate that, for our parameterization of aerosol indirect effects, up to 35% of the radiative forcing due to current levels of greenhouse gases could be offset by stratocumulus modification. Equilibrium simulations with the atmosphere/mixed-layer ocean model, wherein each of the three stratocumulus sheets is modified in turn, reveal that the most efficient cooling per unit radiative forcing occurs when the South Pacific stratocumulus sheet is modified. Transient coupled model simulations suggest that geoengineering all three stratocumulus areas delays the simulated global warming by about 25 years. These simulations also indicate that, while some areas experience increases in precipitation and net primary productivity, sharp decreases are simulated in South America, with particularly detrimental impacts on the Amazon rain forest. These results show that, while some areas benefit from geoengineering, there are significant areas where the response could be very detrimental with implications for the practical applicability of such a scheme."
"57190893918;6701752471;7201665727;","Cloud tuning in a coupled climate model: Impact on 20th century warming",2013,"10.1002/grl.50232","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879987149&doi=10.1002%2fgrl.50232&partnerID=40&md5=5cf8ec85018e6af16ae56b17ebde518e","Climate models incorporate a number of adjustable parameters in their cloud formulations. They arise from uncertainties in cloud processes. These parameters are tuned to achieve a desired radiation balance and to best reproduce the observed climate. A given radiation balance can be achieved by multiple combinations of parameters. We investigate the impact of cloud tuning in the CMIP5 GFDL CM3 coupled climate model by constructing two alternate configurations. They achieve the desired radiation balance using different, but plausible, combinations of parameters. The present-day climate is nearly indistinguishable among all configurations. However, the magnitude of the aerosol indirect effects differs by as much as 1.2 Wm -2, resulting in significantly different temperature evolution over the 20th century. © 2013 American Geophysical Union. All Rights Reserved."
"25031430500;55717074000;22933265100;57203053317;57200319057;","Climate impacts of ice nucleation",2012,"10.1029/2012JD017950","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868019284&doi=10.1029%2f2012JD017950&partnerID=40&md5=760e0c7ffad4207d37247e4d286217c6","Several different ice nucleation parameterizations in two different General Circulation Models (GCMs) are used to understand the effects of ice nucleation on the mean climate state, and the Aerosol Indirect Effects (AIE) of cirrus clouds on climate. Simulations have a range of ice microphysical states that are consistent with the spread of observations, but many simulations have higher present-day ice crystal number concentrations than in-situ observations. These different states result from different parameterizations of ice cloud nucleation processes, and feature different balances of homogeneous and heterogeneous nucleation. Black carbon aerosols have a small (-0.06 Wm-2) and not statistically significant AIE when included as ice nuclei, for nucleation efficiencies within the range of laboratory measurements. Indirect effects of anthropogenic aerosols on cirrus clouds occur as a consequence of increasing anthropogenic sulfur emissions with different mechanisms important in different models. In one model this is due to increases in homogeneous nucleation fraction, and in the other due to increases in heterogeneous nucleation with coated dust. The magnitude of the effect is the same however. The resulting ice AIE does not seem strongly dependent on the balance between homogeneous and heterogeneous ice nucleation. Regional effects can reach several Wm -2. Indirect effects are slightly larger for those states with less homogeneous nucleation and lower ice number concentration in the base state. The total ice AIE is estimated at 0.27 ± 0.10 Wm-2 (1σ uncertainty). This represents a 20% offset of the simulated total shortwave AIE for ice and liquid clouds of -1.6 Wm-2. © 2012. American Geophysical Union. All Rights Reserved."
"7402565763;6506828940;","Cloud condensation nuclei near marine stratus",1991,"10.1029/91jd02212","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026267466&doi=10.1029%2f91jd02212&partnerID=40&md5=8670079e57db52f6e96736875083606f","Extensive airborne measurements of cloud condensation nucleus (CCN) spectra and concentrations of total particles, or condensation nuclei (CN), below, in, and above the stratus cloud decks off the southern California coast point to important aerosol-cloud interactions. Consistently low CCN concentrations below cloud appear to be due to cloud scavenging processes which include Brownian coagulation, nucleation, coalescence, and drizzle. The higher CCN and CN concentrations above cloud are associated with ambient ozone concentrations which suggest a link with continental, probably anthropogenic, sources, even at distances of 500 km from the California coast. -Authors"
"36740698600;6505932008;7202899330;","Modeling aerosol impacts on convective storms in different environments",2010,"10.1175/2010JAS3363.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651105255&doi=10.1175%2f2010JAS3363.1&partnerID=40&md5=632fd1540f97403a6113ea0ecc9393b0","Aerosols are known to have both direct and indirect effects on clouds through their role as cloud condensation nuclei. This study examines the effects of differing aerosol concentrations on convective storms developing under different environments. The Regional Atmospheric Modeling System (RAMS), a cloud-resolving model with sophisticated microphysical and aerosol parameterization schemes, was used to achieve the goals of this study. A sounding that would produce deep convection was chosen and consistently modified to obtain a variety of CAPE values. Additionally, the model was initiated with varying concentrations of aerosols that were available to act as cloud condensation nuclei. Each model run produced long-lived convective storms with similar storm development, but they differed slightly based on the initial conditions. Runs with higher initial CAPE values produced the strongest storms overall, with stronger updrafts and larger amounts of accumulated surface precipitation. Simulations initiated with larger concentrations of aerosols developed similar storm structures but showed some distinctive dynamical and microphysical changes because of aerosol indirect effects. Many of the changes seen because of varying aerosol concentrations were of either the same order or larger magnitude than those brought about by changing the convective environment. © 2010 American Meteorological Society."
"55896920900;7004885872;6603892183;56128808100;6701599239;6701596624;7006577245;56706602500;7202408184;7004838931;","An overview of the ACE-2 CLOUDYCOLUMN closure experiment",2000,"10.1034/j.1600-0889.2000.00047.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034070781&doi=10.1034%2fj.1600-0889.2000.00047.x&partnerID=40&md5=70c819e0e0d4599c6461b05d7ef74967","CLOUDYCOLUMN is one of the 6 ACE-2 projects which took place in June-July 1997, between Portugal and the Canary Islands. It was specifically dedicated to the study of changes of cloud radiative properties resulting from changes in the properties of those aerosols which act as cloud condensation nuclei. This process is also refered to as the aerosol indirect effect on climate. CLOUDYCOLUMN is focused on the contribution of stratocumulus clouds to that process. In addition to the basic aerosol measurements performed at the ground stations of the ACE-2 project, 5 instrumented aircraft carried out in situ characterization of aerosol physical, chemical and nucleation properties and cloud dynamical and microphysical properties. Cloud radiative properties were also measured remotely with radiometers and a lidar. 11 case studies have been documented, from pure marine to significantly polluted air masses. The simultaneity of the measurements with the multi-aircraft approach provides a unique data set for closure experiments on the aerosol indirect effect. In particular CLOUDYCOLUMN provided the 1st experimental evidence of the existence of the indirect effect in boundary layer clouds forming in polluted continental outbreaks. This paper describes the objectives of the project, the instrumental setup and the sampling strategy. Preliminary results published in additional papers are briefly summarized."
"24398842400;7005955015;56250250300;12139043600;12139310900;25031430500;","Constraining cloud droplet number concentration in GCMs suppresses the aerosol indirect effect",2009,"10.1029/2009GL038568","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68749088350&doi=10.1029%2f2009GL038568&partnerID=40&md5=29655103f69ba5e1425613dc49ec992a","Global aerosol-climate models with prognostic treatment of cloud droplet number concentration (CDNC) often prescribe lower bounds for CDNC or aerosol concentrations. Here we demonstrate that this possibly unphysical constraint reduces the simulated aerosol indirect effect by up to 80%, caused by extensively uniform CDNCs. In present-day conditions, the impact of the prescribed lower bound for CDNC is mainly visible over oceans, while with preindustrial emissions, large parts of both land and ocean areas are influenced. We furthermore show that imposing the same constraints on aerosol instead of on CDNC reduces the aerosol indirect effect to a lesser extent. Copyright 2009 by the American Geophysical Union."
"55896920900;6701596624;56706602500;","Cloud microphysical and radiative properties for parameterization and satellite monitoring of the indirect effect of aerosol on climate",2003,"10.1029/2002jd002682","https://www.scopus.com/inward/record.uri?eid=2-s2.0-19244377495&doi=10.1029%2f2002jd002682&partnerID=40&md5=c4aab2f5e8e2787127adcbe1a888f78d","The spatial variability of the microphysical fields in stratocumulus clouds is documented in this paper with statistics of droplet number concentration, droplet mean volume radius, and liquid water content for eight cases of the second Aerosol Characterization Experiment. Statistics are calculated in five sublayers, from cloud base to cloud top, and they are utilized for deriving estimates of cloud optical thickness and liquid water path, by assuming either random or maximum overlap. The resulting in situ frequency distributions of optical thickness and liquid water path are validated against distributions of these two parameters retrieved from independent remote sensing measurements of cloud radiances. They are also used for testing parameterizations of optical thickness based on liquid water path and either the droplet effective radius or the cloud droplet number concentration. This unique data set of extensive, concomitant, and independent measurements of cloud microphysical and radiative properties is finally used for assessing the detectability of the aerosol indirect effect through examination of the correlation between cloud optical thickness and droplet effective radius. If only cases of comparable values of geometrical thickness are considered, the correlation between optical thickness and effective radius is negative, as anticipated by Twomey [1977]. However, if the most polluted cases are also accounted for, the trend suggests a positive correlation. In fact, the most polluted cloud systems sampled during ACE-2 were slightly drier, hence thinner, than the marine and intermediate cases, hence producing a positive correlation between optical thickness and droplet effective radius. This study demonstrates that the monitoring of the aerosol indirect effect with satellite observations requires an independent retrieval of the liquid water path together with the cloud optical thickness and droplet effective radius. Copyright 2003 by the American Geophysical Union."
"8701353900;24173130300;57205867148;7201504886;","Large-eddy simulation of the transient and near-equilibrium behavior of precipitating shallow convection",2015,"10.1002/2015MS000489","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950291715&doi=10.1002%2f2015MS000489&partnerID=40&md5=1deb7085fab0cafdfb4694b2bf853a2e","Large-eddy simulation is used to study the sensitivity of trade wind cumulus clouds to perturbations in cloud droplet number concentrations. We find that the trade wind cumulus system approaches a radiative-convective equilibrium state, modified by net warming and drying from imposed large-scale advective forcing. The system requires several days to reach equilibrium when cooling rates are specified but much less time, and with less sensitivity to cloud droplet number density, when radiation depends realistically on the vertical distribution of water vapor. The transient behavior and the properties of the near-equilibrium cloud field depend on the microphysical state and therefore on the cloud droplet number density, here taken as a proxy for the ambient aerosol. The primary response of the cloud field to changes in the cloud droplet number density is deepening of the cloud layer. This deepening leads to a decrease in relative humidity and a faster evaporation of small clouds and cloud remnants constituting a negative lifetime effect. In the near-equilibrium regime, the decrease in cloud cover compensates much of the Twomey effect, i.e., the brightening of the clouds, and the overall aerosol effect on the albedo of the organized precipitating cumulus cloud field is small. © 2015. The Authors."
"8422280800;7005968859;7004715270;6603385031;7005848261;6602974799;7003591311;","Water activity and activation diameters from hygroscopicity data - Part II: Application to organic species",2006,"10.5194/acp-6-795-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645818750&doi=10.5194%2facp-6-795-2006&partnerID=40&md5=196db785bba5316476720c55efbffd73","A method has been developed for using particle hygroscopicity measurements made with a humidified tandem differential mobility analyzer (HTDMA) to determine water activity as a function of solute weight percent. In Part I, the method was tested for particles composed of sodium chloride and ammonium sulfate. Here, we report results for several atmospherically-relevant organic species: glutaric acid, malonic acid, oxalic acid and levoglucosan. Predicted water activities for aqueous dicarboxylic acid solutions are quite similar in some cases to published estimates and the simplified predictions of Köhler theory, while in other cases substantial differences are found, which we attribute primarily to the semivolatile nature of these compounds that makes them difficult to study with the HTDMA. In contrast, estimates of water activity for levoglucosan solutions compare very well with recently-reported measurements and with published data for aqueous glucose and fructose solutions. For all studied species, the critical dry diameters active at supersaturations between 0.2 and 1% that are computed with the HTDMA-derived water activities are generally within the experimental error (∼20%) estimated in previously-published direct measurements using cloud condensation nuclei counters. For individual compounds, the variations in reported solution water activity lead to uncertainties in critical dry diameters of 5-25%, not significantly larger than the uncertainty in the direct measurements. To explore the impact of these uncertainties on modeled aerosol-cloud interactions, we incorporate the variations in estimates of solution water activities into the description of hygroscopic growth of aerosol particles in an adiabatic parcel model and examine the impact on the predicted drop number concentrations. For the limited set of initial conditions examined here, we find that the uncertainties in critical dry diameters for individual species lead to 0-21% changes in drop number concentration, with the largest effects at high aerosol number concentration and slow updraft velocities. Ammonium sulfate, malonic acid and glutaric acid have similar activation behavior, while glutaric acid and levoglucosan are somewhat less hygroscopic and lead to lower drop number concentrations; sodium chloride is the most easily activated compound. We explain these behaviors in terms of a parameter that represents compound hygroscopicity, and conclude that this parameter must vary by more than a factor of 2 to induce more than a 15% change in activated drop number concentrations. In agreement with earlier studies, our results suggest that the number concentration of activated drops is more sensitive to changes in the input aerosol size and number concentrations and the applied updraft velocity than to modest changes in the aerosol composition and hygroscopic properties. © 2006 Author(s). This work is licensed under a Creative Commons License."
"6602600408;57203200427;7004479395;","Aerosol indirect effects in POLDER satellite data and the Laboratoire de Météorologie Dynamique-Zoom (LMDZ) general circulation model",2004,"10.1029/2003JD004317","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042713102&doi=10.1029%2f2003JD004317&partnerID=40&md5=1c37fc8d7129b2486fb497666f33adec","The POLDER-1 instrument was able to measure aerosol and cloud properties for eight months in 1996-1997. We use these observational data for aerosol concentration (the aerosol index), cloud optical thickness, and cloud droplet effective radius to establish statistical relationships among these parameters in order to analyze the first and second aerosol indirect effects. We also evaluate the representation of these effects as parameterized in the Laboratoire de Métæorologie Dynamique-Zoom (LMDZ) general circulation model. We find a decrease in cloud top droplet radius with increasing aerosol index in both the model and the observations. Our results are only slightly changed if the analysis is done at fixed cloud liquid water path (LWP) instead of considering all LWP conditions. We also find a positive correlation between aerosol index and cloud liquid water path, which is particularly pronounced over the Northern Hemisphere midlatitudes. This may be interpreted as observational evidence for the second aerosol indirect effect on a large scale. The model-simulated relationship agrees well with that derived from POLDER data. Model simulations show a rather small change in the two relationships if preindustrial rather than present-day aerosol distributions are used. However, when entirely switching off the second aerosol indirect effect in our model, we find a much steeper slope than we do when including it. Copyright 2004 by the American Geophysical Union."
"22133985200;6602215448;23019619200;55405013100;25923565300;7003414581;15926468600;","Optical properties of long-range transported Saharan dust over Barbados as measured by dual-wavelength depolarization Raman lidar measurements",2015,"10.5194/acp-15-11067-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943616737&doi=10.5194%2facp-15-11067-2015&partnerID=40&md5=b468a41db93d65bcdfb70c8378299666","Dual-wavelength Raman and depolarization lidar observations were performed during the Saharan Aerosol Long-range Transport and Aerosol-Cloud interaction Experiment in Barbados in June and July 2013 to characterize the optical properties and vertical distribution of long-range transported Saharan dust after transport across the Atlantic Ocean. Four major dust events were studied during the measurements from 15 June to 13 July 2013 with aerosol optical depths at 532 nm of up to 0.6. The vertical aerosol distribution was characterized by a three-layer structure consisting of the boundary layer, the entrainment or mixing layer and the pure Saharan dust layer. The upper boundary of the pure dust layer reached up to 4.5 km in height. The contribution of the pure dust layer was about half of the total aerosol optical depth at 532 nm. The total dust contribution was about 50-70 % of the total aerosol optical depth at 532 nm. The lidar ratio within the pure dust layer was found to be wavelength independent with mean values of 53 ± 5 sr at 355 nm and 56 ± 7 sr at 532 nm. For the particle linear depolarization ratio, wavelength-independent mean values of 0.26 ± 0.03 at 355 nm and 0.27 ± 0.01 at 532 nm have been found."
"24764483400;7003591311;55017656900;","The influence of entrainment and mixing assumption on aerosol-cloud interactions in marine stratocumulus",2009,"10.1175/2008JAS2909.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68749102757&doi=10.1175%2f2008JAS2909.1&partnerID=40&md5=ae4fe3971e33505badeda114d5969618","This study uses large-eddy simulation with bin microphysics to investigate the influence of entrainment and mixing on aerosol-cloud interactions in the context of idealized, nocturnal, nondrizzling marine stratocumulus (Sc). Of particular interest are (i) an evaporation - entrainment effect and a sedimentation - entrainment effect that result from increasing aerosol concentrations and (ii) the nature of mixing between clear and cloudy air, where homogeneous and extreme inhomogeneous mixing represent the bounding mixing types. Simulations are performed at low resolution (Δz = 20 m; Δx, y = 40 m) and high resolution (Δz = 10 m; Δx, y = 20 m). It is demonstrated that an increase in aerosol from clean conditions (100 cm-3) to polluted conditions (1000 cm-3) produces both an evaporation-entrainment and a sedimentation-entrainment effect, which couple to cause about a 10% decrease in liquid water path (LWP) when all warm microphysical processes are included. These dynamical effects are insensitive to both the resolutions tested and the mixing assumption. Regardless of resolution, assuming extreme inhomogeneous rather than homogeneous mixing results in a small reduction in cloud-averaged drop number concentration, a small increase in cloud drop effective radius, and ∼1% decrease in cloud optical depth. For the case presented, these small changes play a negligible role when compared to the impact of increasing aerosol and the associated entrainment effects. Finally, it is demonstrated that although increasing resolution causes an increase in LWP and number concentration, the relative sensitivity of cloud optical depth to changes in aerosol is unaffected by resolution. © 2009 American Meteorological Society."
"26645289600;24329376600;35547807400;57210518852;","Quantifying components of aerosol-cloud-radiation interactions in climate models",2014,"10.1002/2014JD021710","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904727875&doi=10.1002%2f2014JD021710&partnerID=40&md5=8aecd7d7dac5eb65c857a78b365a2e94","The interaction of anthropogenic aerosols with radiation and clouds is the largest source of uncertainty in the radiative forcing of the climate during the industrial period. Here we apply novel techniques to diagnose the contributors to the shortwave (SW) effective radiative forcing (ERF) from aerosol-radiation-interaction (ERFari) and from aerosol cloud interaction (ERFaci) in experiments performed in phase 5 of the Coupled Model Intercomparison Project. We find that the ensemble mean SW ERFari+aci of -1.40±0.56 W m-2 comes roughly 25% from ERFari (-0.35±0.20 W m-2) and 75% from ERFaci (-1.04±0.67 W m-2). ERFari is made up of -0.62±0.30 W m-2 due to aerosol scattering opposed by +0.26 ± 0.12 W m-2 due to aerosol absorption and is largest near emission sources. The ERFari from nonsulfate aerosols is +0.13 ± 0.09 W m-2, consisting of -0.15±0.11 W m-2 of scattering and +0.29 ± 0.15 W m-2 of absorption. The change in clear-sky flux is a negatively biased measure of ERFari, as the presence of clouds reduces the magnitude and intermodel spread of ERFari by 40-50%. ERFaci, which is large both near and downwind of emission sources, is composed of -0.99±0.54 W m-2 from enhanced cloud scattering, with much smaller contributions from increased cloud amount and absorption. In models that allow aerosols to affect ice clouds, large increases in the optical depth of high clouds cause substantial longwave and shortwave radiative anomalies. Intermodel spread in ERFaci is dominated by differences in how aerosols increase cloud scattering, but even if all models agreed on this effect, over a fifth of the spread in ERFaci would remain due solely to differences in total cloud amount. Key Points We compute effective forcings from aerosol-cloud-radiation interactions in GCMs Total aerosol forcing is 25% direct effect and 75% indirect effect Indirect effect comes mostly from enhanced cloud scattering ©2014. American Geophysical Union. All Rights Reserved."
"7403564495;15032788000;","Effects of Arctic haze on surface cloud radiative forcing",2015,"10.1002/2014GL062015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923533017&doi=10.1002%2f2014GL062015&partnerID=40&md5=d5d741fe30b3267a66f1d2656864b9df","From 4years of observations from Barrow, Alaska, it is shown that the cloud radiative impact on the surface is a net warming effect between October and May and a net cooling in summer. During episodes of high surface haze aerosol concentrations and cloudy skies, both the net warming and net cooling are amplified, ranging from +12.2 Wm-2 in February to -11.8 Wm-2 in August. In liquid clouds, approximately 50%-70% of this change is caused by changes in cloud particle effective radius, with the remainder being caused by unknown atmospheric feedbacks that increase cloud water path. While the yearly averaged warming and cooling effects nearly cancel, the timing of the forcing may be a relevant control of the amplitude and timing of sea ice melt. © 2015. American Geophysical Union. All Rights Reserved."
"56244473600;7103206141;7102447698;57208462871;24481931900;16027961900;7201665727;","Impact of preindustrial to present-day changes in short-lived pollutant emissions on atmospheric composition and climate forcing",2013,"10.1002/jgrd.50608","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882769517&doi=10.1002%2fjgrd.50608&partnerID=40&md5=2c0b37899dbbe1303c5f9e02446a0339","We describe and evaluate atmospheric chemistry in the newly developed Geophysical Fluid Dynamics Laboratory chemistry-climate model (GFDL AM3) and apply it to investigate the net impact of preindustrial (PI) to present (PD) changes in short-lived pollutant emissions (ozone precursors, sulfur dioxide, and carbonaceous aerosols) and methane concentration on atmospheric composition and climate forcing. The inclusion of online troposphere-stratosphere interactions, gas-aerosol chemistry, and aerosol-cloud interactions (including direct and indirect aerosol radiative effects) in AM3 enables a more complete representation of interactions among short-lived species, and thus their net climate impact, than was considered in previous climate assessments. The base AM3 simulation, driven with observed sea surface temperature (SST) and sea ice cover (SIC) over the period 1981-2007, generally reproduces the observed mean magnitude, spatial distribution, and seasonal cycle of tropospheric ozone and carbon monoxide. The global mean aerosol optical depth in our base simulation is within 5% of satellite measurements over the 1982-2006 time period. We conduct a pair of simulations in which only the short-lived pollutant emissions and methane concentrations are changed from PI (1860) to PD (2000) levels (i.e., SST, SIC, greenhouse gases, and ozone-depleting substances are held at PD levels). From the PI to PD, we find that changes in short-lived pollutant emissions and methane have caused the tropospheric ozone burden to increase by 39% and the global burdens of sulfate, black carbon, and organic carbon to increase by factors of 3, 2.4, and 1.4, respectively. Tropospheric hydroxyl concentration decreases by 7%, showing that increases in OH sinks (methane, carbon monoxide, nonmethane volatile organic compounds, and sulfur dioxide) dominate over sources (ozone and nitrogen oxides) in the model. Combined changes in tropospheric ozone and aerosols cause a net negative top-of-the-atmosphere radiative forcing perturbation (-1.05 W m-2) indicating that the negative forcing (direct plus indirect) from aerosol changes dominates over the positive forcing due to ozone increases, thus masking nearly half of the PI to PD positive forcing from long-lived greenhouse gases globally, consistent with other current generation chemistry-climate models. Key Points Document and evaluate atmospheric chemistry in GFDL-AM3 Net forcing from PI to PD short-lived pollutant emission changes is -1.05 Wm-2 ©2013. American Geophysical Union. All Rights Reserved."
"55522563200;55207447000;55740664200;7004057920;","Effective radius of cloud droplets by ground-based remote sensing: Relationship to aerosol",2003,"10.1029/2003jd003721","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342269721&doi=10.1029%2f2003jd003721&partnerID=40&md5=392fdcd2130a0e662a223b02c6c68bd0","Enhancement of cloud droplet number concentration by anthropogenic aerosols has previously been demonstrated by in-situ measurements, but there remains large uncertainty in the resultant enhancement of cloud optical depth and reflectivity. Detection of this effect is made difficult by the large inherent variability in cloud liquid water path (LWP); the dominant influence of LWP on optical depth and albedo masks any aerosol influences. Here we use ground-based remote sensing of cloud optical depth (τc) by narrowband radiometry and LWP by microwave radiometry to determine the dependence of optical depth on LWP, thereby permitting examination of aerosol influence; the method is limited to complete overcast conditions with single layer clouds, as determined mainly by millimeter wave cloud radar. Measurements in north central Oklahoma on 13 different days in the year 2000 show wide variation in LWP and optical depth on any given day, but with near linear proportionality between the two quantities; variance in LWP accounts as much as 97% of the variance in optical depth on individual days and for about 63% of the variance in optical depth for the whole data set. The slope of optical depth vs. LWP is inversely proportional to the effective radius of cloud droplets (re); event-average cloud droplet effective radius ranged from 5.6 ± 0.1 to 12.3 ± 0.6 μm (average ± uncertainty in the mean . This effective radius is negatively correlated with aerosol light scattering coefficient at the surface as expected for the aerosol indirect effect; the weak correlation (R2 = 0.24) might be due in part to vertically decoupled structure of aerosol particle concentration and possible meteorological influence such as vertical wind shear. Cloud albedo and radiative forcing for a given LWP are highly sensitive to effective radius; for solar zenith angle 60° and typical LWP of 100 g m-2, as effective radius decreases from 10.2 to 5.8 μm determined on different days, the resultant decrease in calculated net shortwave irradiance at the top of the atmosphere (Twomey forcing) is about 50 W m-2. © 2003 by the American Geophysical Union."
"25031430500;7103158465;56479980800;6506848305;36856321600;","Advanced two-moment bulk microphysics for global models. Part II: Global model solutions and aerosol-cloud interactions",2015,"10.1175/JCLI-D-14-00103.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923025690&doi=10.1175%2fJCLI-D-14-00103.1&partnerID=40&md5=b14398b7928f561f2194b3c50f2d3f29","A modified microphysics scheme is implemented in the Community AtmosphereModel, version 5 (CAM5). The new scheme features prognostic precipitation. The coupling between the microphysics and the rest of the model is modified to make it more flexible. Single-column tests show the new microphysics can simulate a constrained drizzling stratocumulus case. Substepping the cloud condensation (macrophysics) within a time step improves single-column results. Simulations of mixed-phase cases are strongly sensitive to ice nucleation. The new microphysics alters process rates in both single-column and global simulations, even at low (200 km) horizontal resolution. Thus, prognostic precipitation can be important, even in low-resolution simulations where advection of precipitation is not important. Accretion dominates as liquid water path increases in agreement with cloud-resolving model simulations and estimates from observations. The new microphysics with prognostic precipitation increases the ratio of accretion over autoconversion. The change in process rates appears to significantly reduce aerosol-cloud interactions and indirect radiative effects of anthropogenic aerosols by up to 33% (depending on substepping) to below 1Wm-2 of cooling between simulations with preindustrial (1850) and present-day (2000) aerosol emissions. © 2015 American Meteorological Society."
"56384704800;57202299549;55717074000;7003666669;55519994900;15755995900;7006705919;23095483400;57203053317;","Technical note: On the use of nudging for aerosol-climate model intercomparison studies",2014,"10.5194/acp-14-8631-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906657160&doi=10.5194%2facp-14-8631-2014&partnerID=40&md5=b1b10d7c8b595b25f2b26a170c014dd4","Nudging as an assimilation technique has seen increased use in recent years in the development and evaluation of climate models. Constraining the simulated wind and temperature fields using global weather reanalysis facilitates more straightforward comparison between simulation and observation, and reduces uncertainties associated with natural variabilities of the large-scale circulation. On the other hand, the forcing introduced by nudging can be strong enough to change the basic characteristics of the model climate. In the paper we show that for the Community Atmosphere Model version 5 (CAM5), due to the systematic temperature bias in the standard model and the sensitivity of simulated ice formation to anthropogenic aerosol concentration, nudging towards reanalysis results in substantial reductions in the ice cloud amount and the impact of anthropogenic aerosols on long-wave cloud forcing. In order to reduce discrepancies between the nudged and unconstrained simulations, and meanwhile take the advantages of nudging, two alternative experimentation methods are evaluated. The first one constrains only the horizontal winds. The second method nudges both winds and temperature, but replaces the long-term climatology of the reanalysis by that of the model. Results show that both methods lead to substantially improved agreement with the free-running model in terms of the top-of-atmosphere radiation budget and cloud ice amount. The wind-only nudging is more convenient to apply, and provides higher correlations of the wind fields, geopotential height and specific humidity between simulation and reanalysis. Results from both CAM5 and a second aerosol-climate model ECHAM6-HAM2 also indicate that compared to the wind-and-temperature nudging, constraining only winds leads to better agreement with the free-running model in terms of the estimated shortwave cloud forcing and the simulated convective activities. This suggests nudging the horizontal winds but not temperature is a good strategy for the investigation of aerosol indirect effects since it provides well-constrained meteorology without strongly perturbing the model's mean climate. © 2014 Author(s)."
"36740698600;6505932008;","Microphysical processes evident in aerosol forcing of tropical deep convective clouds",2013,"10.1175/JAS-D-12-076.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874982348&doi=10.1175%2fJAS-D-12-076.1&partnerID=40&md5=11bec24fd64d9418b65d0a03fde425c6","This study investigates the effects of aerosols on tropical deep convective clouds (DCCs). A series of largescale, two-dimensional cloud-resolving model simulations was completed, differing only in the concentration of aerosols available to act as cloud condensation nuclei (CCN). Polluted simulations contained more DCCs, wider storms, higher cloud tops, and more convective precipitation domainwide. Differences in warm cloud microphysics were largely consistent with the first and second aerosol indirect effects. The average surface precipitation produced in each DCC column decreased with increasing aerosol concentration. A detailed microphysical budget analysis showed that the reduction in collision and coalescence largely dominated the trend in average precipitation. The production of rain from ice, though it also decreased, became a more important contribution to precipitation as the aerosol concentration increased. The DCCs in polluted simulations contained more frequent extreme values of vertical velocity, but the average updraft speed decreased with increasing aerosols in DCCs above 6 km. An examination of the buoyancy term of the vertical velocity equation demonstrates that the drag associated with condensate loading is an important factor in determining the average updraft strength. The largest contributions to latent heating in DCCs were cloud nucleation and vapor deposition onto water and ice, but changes in latent heating were, on average, an order of magnitude smaller than those in the condensate loading term. The average updraft speed was largely affected by increased drag from condensate loading in more mature updrafts, while early storm updrafts experienced convective invigoration from increased latent heating. © 2013 American Meteorological Society."
"8511991900;7102084129;54788887200;7202048112;7409080503;","Potential aerosol indirect effects on atmospheric circulation and radiative forcing through deep convection",2012,"10.1029/2012GL051851","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861140684&doi=10.1029%2f2012GL051851&partnerID=40&md5=6bf6489d17c66ef7d79304f07014bff8","Aerosol indirect effects, i.e., the interactions of aerosols with clouds by serving as cloud condensation nuclei or ice nuclei constitute the largest uncertainty in climate forcing and projection. Previous IPCC reported negative aerosol indirect forcing, which does not account for aerosol-convective cloud interactions because the complex processes involved are poorly understood and represented in climate models. Here we elucidated how aerosols change convective intensity, diabatic heating, and regional circulation under different environmental conditions. We found that aerosol indirect effect on deep convective cloud systems could lead to enhanced regional convergence and a strong top-of-atmosphere warming. Aerosol invigoration effect occurs mainly in warmed-based convection with weak shear. This could result in a strong radiative warming in the atmosphere (up to +5.6 W m-2), a lofted latent heating, and a reduced diurnal temperature difference, all of which could potentially impact regional circulation and modify weather systems. The positive aerosol radiative forcing on deep clouds could offset the negative aerosol radiative forcing on low clouds to an unknown extent. © 2012 by the American Geophysical Union."
"35849722200;7004469744;7003591311;","Vertical transport and processing of aerosols in a mixed-phase convective cloud and the feedback on cloud development",2005,"10.1256/qj.03.186","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23044443730&doi=10.1256%2fqj.03.186&partnerID=40&md5=a6160fbcdbc9c5250b38079858598ca7","A modelling study of vertical transport and processing of sulphate aerosol by a mixed-phase convective cloud, and the feedback of the cloud-processed aerosols on the development of cloud microphysical properties and precipitation is presented. An axisymmetric dynamic cloud model with bin-resolved microphysics and aqueous-phase chemistry is developed and is used to examine the relative importance of microphysical and chemical processes on the aerosol budget, the fate of the aerosol material inside hydrometeors, and the size distributions of cloud-processed sulphate aerosols. Numerical simulations are conducted for a moderately deep convective cloud observed during the Cooperative Convective Precipitation Experiments. The results show that aerosol particles that have been transported from the boundary layer, detrained, and then re-entrained at midcloud levels account for a large fraction of the aerosol inside hydrometeors (∼40% by mass). Convective transport by the simulated cloud enhances upper-tropospheric aerosol number and mass concentrations by factors of 2-3 and 3-4, respectively. Sensitivity studies suggest that, for the simulated case, aqueous chemistry does not modify the evolution of the cloud significantly. Finally, ice-phase hydrometeor development is very sensitive to aerosol concentrations at midcloud levels. The latter result suggests that the occurrence of mid-tropospheric aerosol layers that have been advected through long-range transport could strongly affect cloud microphysical processes and precipitation formation. © Royal Meteorological Society, 2005."
"55377690600;12753162000;49261186800;55683727600;8942524900;36134816800;23019544500;24463029300;29068082700;7408623694;36623061000;35291021400;8963601100;7801595201;15047358600;6602136905;35221661700;56573417400;26026483100;35547807400;8942525300;","The impact of residential combustion emissions on atmospheric aerosol, human health, and climate",2016,"10.5194/acp-16-873-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956634945&doi=10.5194%2facp-16-873-2016&partnerID=40&md5=0d361b545f1699adf5fd3a67426186b6","Combustion of fuels in the residential sector for cooking and heating results in the emission of aerosol and aerosol precursors impacting air quality, human health, and climate. Residential emissions are dominated by the combustion of solid fuels. We use a global aerosol microphysics model to simulate the impact of residential fuel combustion on atmospheric aerosol for the year 2000. The model underestimates black carbon (BC) and organic carbon (OC) mass concentrations observed over Asia, Eastern Europe, and Africa, with better prediction when carbonaceous emissions from the residential sector are doubled. Observed seasonal variability of BC and OC concentrations are better simulated when residential emissions include a seasonal cycle. The largest contributions of residential emissions to annual surface mean particulate matter (PM2.5) concentrations are simulated for East Asia, South Asia, and Eastern Europe. We use a concentration response function to estimate the human health impact due to long-term exposure to ambient PM2.5 from residential emissions. We estimate global annual excess adult (&gt; 30 years of age) premature mortality (due to both cardiopulmonary disease and lung cancer) to be 308 000 (113 300-497 000, 5th to 95th percentile uncertainty range) for monthly varying residential emissions and 517 000 (192 000-827 000) when residential carbonaceous emissions are doubled. Mortality due to residential emissions is greatest in Asia, with China and India accounting for 50 % of simulated global excess mortality. Using an offline radiative transfer model we estimate that residential emissions exert a global annual mean direct radiative effect between -66 and +21 mW m-2, with sensitivity to the residential emission flux and the assumed ratio of BC, OC, and SO2 emissions. Residential emissions exert a global annual mean first aerosol indirect effect of between -52 and -16 mW m-2, which is sensitive to the assumed size distribution of carbonaceous emissions. Overall, our results demonstrate that reducing residential combustion emissions would have substantial benefits for human health through reductions in ambient PM2.5 concentrations. © Author(s) 2016."
"6701752471;35611334800;7103271625;7103206141;7006306835;55286185400;","Sensitivity of the aerosol indirect effect to subgrid variability in the cloud parameterization of the GFDL atmosphere general circulation model AM3",2011,"10.1175/2010JCLI3945.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960302456&doi=10.1175%2f2010JCLI3945.1&partnerID=40&md5=7ca791880346d6d1d05bb79fde42f6db","The recently developed GFDL Atmospheric Model version 3 (AM3), an atmospheric general circulation model (GCM), incorporates a prognostic treatment of cloud drop number to simulate the aerosol indirect effect. Since cloud drop activation depends on cloud-scale vertical velocities, which are not reproduced in present-day GCMs, additional assumptions on the subgrid variability are required to implement a local activation parameterization into a GCM. This paper describes the subgrid activation assumptions in AM3 and explores sensitivities by constructing alternate configurations. These alternate model configurations exhibit only small differences in their present-day climatology. However, the total anthropogenic radiative flux perturbation (RFP) between present-day and preindustrial conditions varies by ±50% from the reference, because of a large difference in the magnitude of the aerosol indirect effect. The spread in RFP does not originate directly from the subgrid assumptions but indirectly through the cloud retuning necessary to maintain a realistic radiation balance. In particular, the paper shows a linear correlation between the choice of autoconversion threshold radius and the RFP. Climate sensitivity changes only minimally between the reference and alternate configurations. If implemented in a fully coupled model, these alternate configurations would therefore likely produce substantially different warming from preindustrial to present day. © 2011 American Meteorological Society."
"55688930000;6701335949;7003591311;","Evaluation of scalar advection schemes in the advanced research WRF model using large-eddy simulations of aerosol-cloud interactions",2009,"10.1175/2009MWR2820.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350303196&doi=10.1175%2f2009MWR2820.1&partnerID=40&md5=b355487dd5b0fd1dc796c2eac5975af3","In the Advanced Research Weather Research and Forecasting Model (ARW), versions 3.0 and earlier, advection of scalars was performed using the Runge-Kutta time-integration scheme with an option of using a positive-definite (PD) flux limiter. Large-eddy simulations of aerosol-cloud interactions using the ARW model are performed to evaluate the advection schemes. The basic Runge-Kutta scheme alone produces spurious oscillations and negative values in scalar mixing ratios because of numerical dispersion errors. The PD flux limiter assures positive definiteness but retains the oscillations with an amplification of local maxima by up to 20% in the tests. These numerical dispersion errors contaminate active scalars directly through the advection process and indirectly through physical and dynamical feedbacks, leading to a misrepresentation of cloud physical and dynamical processes. A monotonic flux limiter is introduced to correct the generally accurate but dispersive solutions given by high-order Runge-Kutta scheme. The monotonic limiter effectively minimizes the dispersion errors with little significant enhancement of numerical diffusion errors. The improvement in scalar advection using the monotonic limiter is discussed in the context of how the different advection schemes impact the quantification of aerosol-cloud interactions. The PD limiter results in 20% (10%) fewer cloud droplets and 22% (5%) smaller cloud albedo than the monotonic limiter under clean (polluted) conditions. Underprediction of cloud droplet number concentration by the PD limiter tends to trigger the early formation of precipitation in the clean case, leading to a potentially large impact on cloud albedo change. © 2009 American Meteorological Society."
"15926468600;7003414581;7007020226;6701697023;12242009800;56737226500;57192168375;55883785100;57195527621;6602215448;26023140500;22133985200;57097521200;56060986400;22979686100;55511965400;6602765265;57214160655;55967153600;14058796400;25923565300;23019619200;57113269700;56250185400;55405013100;57192172364;","The Saharan aerosol long-range transport and aerosol-cloud-interaction experiment: Overview and selected highlights",2017,"10.1175/BAMS-D-15-00142.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028593192&doi=10.1175%2fBAMS-D-15-00142.1&partnerID=40&md5=65c1bf807e371579929bf8cf92f4317e",[No abstract available]
"54397207800;7004242319;35572096100;8373634800;25629339800;55663817800;7401651197;6602681732;7004462227;21739304600;","The dependence of ice microphysics on aerosol concentration in arctic mixed-phase stratus clouds during ISDAC and M-PACE",2012,"10.1029/2012JD017668","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865371575&doi=10.1029%2f2012JD017668&partnerID=40&md5=5d4a492d4d303be2b7047a491df5730a","Cloud and aerosol data acquired by the National Research Council of Canada (NRC) Convair-580 aircraft in, above, and below single-layer arctic stratocumulus cloud during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) in April 2008 were used to test three aerosol indirect effects hypothesized to act in mixed-phase clouds: the riming indirect effect, the glaciation indirect effect, and the thermodynamic indirect effect. The data showed a correlation of R = 0.78 between liquid drop number concentration, N<inf>liq</inf> inside cloud and ambient aerosol number concentration N<inf>PCASP</inf> below cloud. This, combined with increasing liquid water content LWC with height above cloud base and the nearly constant vertical profile of N<inf>liq</inf>, suggested that liquid drops nucleated from aerosol at cloud base. No evidence of a riming indirect effect was observed, but a strong correlation of R = 0.69 between ice crystal number concentration N<inf>i</inf> and N<inf>PCASP</inf> above cloud was noted. Increases in ice nuclei (IN) concentration with N<inf>PCASP</inf> above cloud for 2 flight dates combined with the subadiabatic LWC profiles suggest possible mixing of IN from cloud top consistent with the glaciation indirect effect. The lower N<inf>ice</inf> and lower effective radius r<inf>el</inf> for the more polluted ISDAC cases compared to data collected in cleaner single-layer stratocumulus conditions during the Mixed-Phase Arctic Cloud Experiment is consistent with the operation of the thermodynamic indirect effect. However, more data in a wider variety of meteorological and surface conditions, with greater variations in aerosol forcing, are required to identify the dominant aerosol forcing mechanisms in mixed-phase arctic clouds. © 2012 by the American Geophysical Union."
"57188966058;8922308700;57193213111;55688930000;7006270084;7103158465;57203798762;7101909551;16550482700;18437850800;","Assessing regional scale predictions of aerosols, marine stratocumulus, and their interactions during VOCALS-REx using WRF-Chem",2011,"10.5194/acp-11-11951-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-82955184523&doi=10.5194%2facp-11-11951-2011&partnerID=40&md5=dd384e127bf02cbadacd917e13844e55","This study assesses the ability of the recent chemistry version (v3.3) of the Weather Research and Forecasting (WRF-Chem) model to simulate boundary layer structure, aerosols, stratocumulus clouds, and energy fluxes over the Southeast Pacific Ocean. Measurements from the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) and satellite retrievals (i.e., products from the MODerate resolution Imaging Spectroradiometer (MODIS), Clouds and Earth's Radiant Energy System (CERES), and GOES-10) are used for this assessment. The Morrison double-moment microphysics scheme is newly coupled with interactive aerosols in the model. The 31-day (15 October-16 November 2008) WRF-Chem simulation with aerosol-cloud interactions (AERO hereafter) is also compared to a simulation (MET hereafter) with fixed cloud droplet number concentrations in the microphysics scheme and simplified cloud and aerosol treatments in the radiation scheme. The well-simulated aerosol quantities (aerosol number, mass composition and optical properties), and the inclusion of full aerosol-cloud couplings lead to significant improvements in many features of the simulated stratocumulus clouds: cloud optical properties and microphysical properties such as cloud top effective radius, cloud water path, and cloud optical thickness. In addition to accounting for the aerosol direct and semi-direct effects, these improvements feed back to the simulation of boundary-layer characteristics and energy budgets. Particularly, inclusion of interactive aerosols in AERO strengthens the temperature and humidity gradients within the capping inversion layer and lowers the marine boundary layer (MBL) depth by 130 m from that of the MET simulation. These differences are associated with weaker entrainment and stronger mean subsidence at the top of the MBL in AERO. Mean top-of-atmosphere outgoing shortwave fluxes, surface latent heat, and surface downwelling longwave fluxes are in better agreement with observations in AERO, compared to the MET simulation. Nevertheless, biases in some of the simulated meteorological quantities (e.g., MBL temperature and humidity) and aerosol quantities (e.g., underestimations of accumulation mode aerosol number) might affect simulated stratocumulus and energy fluxes over the Southeastern Pacific, and require further investigation. The well-simulated timing and outflow patterns of polluted and clean episodes demonstrate the model's ability to capture daily/synoptic scale variations of aerosol and cloud properties, and suggest that the model is suitable for studying atmospheric processes associated with pollution outflow over the ocean. The overall performance of the regional model in simulating mesoscale clouds and boundary layer properties is encouraging and suggests that reproducing gradients of aerosol and cloud droplet concentrations and coupling cloud-aerosol-radiation processes are important when simulating marine stratocumulus over the Southeast Pacific. © 2011 Author(s)."
"6602097544;6701378450;57196499374;","Black carbon radiative heating effects on cloud microphysics and implications for the aerosol indirect effect. 1. Extended Köhler theory",2002,"10.1029/2002JD002094","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751266317&doi=10.1029%2f2002JD002094&partnerID=40&md5=7cf0b63dac10dce70f952363751fca36","Black carbon (BC) aerosol absorbs sunlight that might have otherwise been reflected to space and changes the radiative heating of the atmosphere and surface. These effects may alter the dynamical and hydrological processes governing cloud formation. A new, microphysical, effect of BC on climate is identified here, in which solar heating within BC-containing cloud condensation nuclei (CCN) slows or prevents the activation of these CCN into cloud drops. Solar-heated BC-containing droplets are elevated in temperature by fractions of a degree above the ambient, thus raising the droplet vapor pressure and inhibiting activation of the most absorptive CCN. This paper develops the theory describing the alteration of the Köhler curve (i.e., the equilibrium vapor pressure over a droplet as a function of water uptake) as a function of CCN size and BC fraction. The effect is most significant in those CCN that contain volumes of BC larger than a 500 nm diameter sphere. For an aerosol population with 10% BC mass fraction per particle, solar heating can cause a 10% reduction in the CCN concentration at 0.01% critical supersaturation. On the other hand, the effect of heating by BC absorption on CCN activation above ∼0.1% critical supersaturation is negligible. Copyright 2002 by the American Geophysical Union."
"7102953444;","Decadal changes in radiative fluxes at land and ocean surfaces and their relevance for global warming",2016,"10.1002/wcc.372","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957725522&doi=10.1002%2fwcc.372&partnerID=40&md5=628a2e1272bc2377a0359dc14a37358b","Anthropogenic interference with climate occurs primarily through modification of radiative fluxes in the climate system. Increasing releases of greenhouse gases into the atmosphere lead to an enhancement of thermal radiation from the atmosphere to the surface by presently about 2 W m-2 per decade, thereby causing global warming. Yet not only thermal radiation undergoes substantial decadal changes at the Earth surface, but also incident solar radiation (SSR), often in line with changes in aerosol emissions. Land-based observations suggest widespread declines in SSR from 1950s to 1980s ('global dimming'), a partial recovery ('brightening') since mid-1980s, and indication for an 'early' brightening in 1930s and 1940s. No similar extended observational records are available over oceans. However, modeling studies, conceptual frameworks and available satellite-derived records point to the existence of decadal SSR variations also over oceans. SSR changes overall match with decadal variations in observed warming rates, suggesting that SSR variations may effectively modulate greenhouse gas-induced warming. Specifically, on the Northern Hemisphere, the lack of warming from 1950s to 1980s and its subsequent acceleration in the 1990s fits to the trend reversal from dimming to brightening and associated changes in air pollution levels. From the 1950s to 1980s no warming was also observed over Northern Hemispheric Oceans, in line with conceptual ideas that subtle aerosol changes in pristine ocean areas, effectively amplified by aerosol-cloud interactions, can substantially alter SSR, thereby modulating Sea Surface Temperatures. On the Southern Hemisphere, the absence of significant aerosol levels fits to the observed stable (greenhouse gas-induced) warming rates since the 1950s. © 2016 Wiley Periodicals, Inc."
"55390690800;8404544300;7101855239;55547119523;36560691800;24554058600;6701822771;","Quantifying water diffusion in high-viscosity and glassy aqueous solutions using a raman isotope tracer method",2014,"10.5194/acp-14-3817-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906351892&doi=10.5194%2facp-14-3817-2014&partnerID=40&md5=3e280c517d5d8546349196d4c36611ba","Recent research suggests that under certain temperature and relative humidity conditions atmospheric aerosol may be present in the form of a glassy solid. In order to understand the impacts that this may have on aerosol-cloud interactions and atmospheric chemistry, knowledge of water diffusion within such aerosol particles is required. Here, a method is described in which Raman spectroscopy is used to observe D2O diffusion in high-viscosity aqueous solutions, enabling a quantitative assessment of water diffusion coefficients,Dwater, as a function of relative humidity. Results for sucrose solutions compare well with literature data at 23.5 ± 0.3 °C, and demonstrate that water diffusion is slow (Dwater ∼5 × 10&minus;17 m2 s&minus;1), but not arrested, just below the glass transition at a water activity of 0.2. Room temperature water diffusion coefficients are also presented for aqueous levoglucosan and an aqueous mixture of raffinose, dicarboxylic acids and ammonium sulphate: at low humidity, diffusion is retarded but still occurs on millisecond to second timescales in atmospherically relevant-sized particles. The effect of gel formation on diffusion in magnesium sulfate solutions is shown to be markedly different from the gradual decrease in diffusion coefficients of highly viscous liquids. We show that using the Stokes-Einstein equation to determine diffusion timescales from viscosity leads to values which are more than 5 orders of magnitude too big, which emphasises the need to make measurements of diffusion coefficients. In addition, comparison of bounce fraction data for levoglucosan with measured diffusion data reveals that even when particles bounce the diffusion timescales for water are a fraction of a second for a 100 nm particle. This suggests a high bounce fraction does not necessarily indicate retarded water diffusion. © Author(s) 2014. CC Attribution 3.0 License."
"7003875148;7003740015;34976155900;7006544721;7201572145;7005753600;6602718303;8950640300;7006960661;24329085500;25633867100;56104763800;6508148129;7007155334;7005228425;57210237373;57159442900;7402074810;6701349778;57217726421;6603577900;8696069500;57193320073;56266071600;7006384026;7004462114;7003900383;9038337500;35299142800;7801369477;7004239407;24472110700;7003663305;6602085876;6602211117;55367706300;8728866200;7005287667;7801558983;56037741700;6602565669;56509328700;55327762400;","The Arctic Summer Cloud Ocean Study (ASCOS): Overview and experimental design",2014,"10.5194/acp-14-2823-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897838395&doi=10.5194%2facp-14-2823-2014&partnerID=40&md5=e2de6aa0e1b9232da2b215c5bd45f33a","The climate in the Arctic is changing faster than anywhere else on earth. Poorly understood feedback processes relating to Arctic clouds and aerosol-cloud interactions contribute to a poor understanding of the present changes in the Arctic climate system, and also to a large spread in projections of future climate in the Arctic. The problem is exacerbated by the paucity of research-quality observations in the central Arctic. Improved formulations in climate models require such observations, which can only come from measurements in situ in this difficult-to-reach region with logistically demanding environmental conditions. <br><br> The Arctic Summer Cloud Ocean Study (ASCOS) was the most extensive central Arctic Ocean expedition with an atmospheric focus during the International Polar Year (IPY) 2007-2008. ASCOS focused on the study of the formation and life cycle of low-level Arctic clouds. ASCOS departed from Longyearbyen on Svalbard on 2 August and returned on 9 September 2008. In transit into and out of the pack ice, four short research stations were undertaken in the Fram Strait: two in open water and two in the marginal ice zone. After traversing the pack ice northward, an ice camp was set up on 12 August at 87°21′ N, 01°29′ W and remained in operation through 1 September, drifting with the ice. During this time, extensive measurements were taken of atmospheric gas and particle chemistry and physics, mesoscale and boundary-layer meteorology, marine biology and chemistry, and upper ocean physics. <br><br> ASCOS provides a unique interdisciplinary data set for development and testing of new hypotheses on cloud processes, their interactions with the sea ice and ocean and associated physical, chemical, and biological processes and interactions. For example, the first-ever quantitative observation of bubbles in Arctic leads, combined with the unique discovery of marine organic material, polymer gels with an origin in the ocean, inside cloud droplets suggests the possibility of primary marine organically derived cloud condensation nuclei in Arctic stratocumulus clouds. Direct observations of surface fluxes of aerosols could, however, not explain observed variability in aerosol concentrations, and the balance between local and remote aerosols sources remains open. Lack of cloud condensation nuclei (CCN) was at times a controlling factor in low-level cloud formation, and hence for the impact of clouds on the surface energy budget. ASCOS provided detailed measurements of the surface energy balance from late summer melt into the initial autumn freeze-up, and documented the effects of clouds and storms on the surface energy balance during this transition. In addition to such process-level studies, the unique, independent ASCOS data set can and is being used for validation of satellite retrievals, operational models, and reanalysis data sets. © Author(s) 2014."
"17433905200;6701378450;8349977900;6602715033;6602097544;7101846027;55438848700;16308514000;6508259172;6602832585;7006572336;57196499374;","Aerosol-cloud drop concentration closure for clouds sampled during the International Consortium for Atmospheric Research on Transport and Transformation 2004 campaign",2007,"10.1029/2006JD007272","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547577197&doi=10.1029%2f2006JD007272&partnerID=40&md5=4520eecc9c6c95809c028cadf4aa13ac","This study analyzes 27 cumuliform and stratiform clouds sampled aboard the CIRPAS Twin Otter during the 2004 International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) experiment. The data set was used to assess cloud droplet closure using (1) a detailed adiabatic cloud parcel model and (2) a state-of-the-art cloud droplet activation parameterization. A unique feature of the data set is the sampling of highly polluted clouds within the vicinity of power plant plumes. Remarkable closure was achieved (much less than the 20% measurement uncertainty) for both parcel model and parameterization. The highly variable aerosol did not complicate the cloud droplet closure, since the clouds had low maximum supersaturation and were not sensitive to aerosol variations (which took place at small particle sizes). The error in predicted cloud droplet concentration was mostly sensitive to updraft velocity. Optimal closure is obtained if the water vapor uptake coefficient is equal to 0.06, but can range between 0.03 and 1.0. The sensitivity of cloud droplet prediction error to changes in the uptake coefficient, organic solubility and surface tension depression suggest that organics exhibit limited solubility. These findings can serve as much needed constraints in modeling of aerosol-cloud interactions in the North America; future in situ studies will determine the robustness of our findings. Copyright 2007 by the American Geophysical Union."
"7403577184;7006614696;7005968859;35453054300;7202772927;7102517130;35464731600;","Satellite-based assessment of marine low cloud variability associated with aerosol, atmospheric stability, and the diurnal cycle",2006,"10.1029/2005JD006097","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847016854&doi=10.1029%2f2005JD006097&partnerID=40&md5=019de672ee7692951561777b78bb94cb","This study examines variability in marine low cloud properties derived from semiglobal observations by the Tropical Rainfall Measuring Mission (TRMM) satellite, as linked to the aerosol index (AI) and lower-tropospheric stability (LTS). AI is derived from the Moderate Resolution Imaging Spectroradiometer (Terra MODIS) sensor and the Goddard Chemistry Aerosol Radiation and Transportation (GOCART) model and is used to represent column-integrated aerosol concentrations. LTS is derived from the NCEP/NCAR reanalysis and represents the background thermodynamic environment in which the clouds form. Global statistics reveal that cloud droplet size tends to be smallest in polluted (high-AI) and strong inversion (high-LTS) environments. Statistical quantification shows that cloud droplet size is better correlated with AI than it is with LTS. Simultaneously, the cloud liquid water path (CLWP) tends to decrease as AI increases. This correlation does not support the hypothesis or assumption that constant or increased CLWP is associated with high aerosol concentrations. Global variability in corrected cloud albedo (CCA), the product of cloud optical depth and cloud fraction, is very well explained by LTS, while both AI and LTS are needed to explain local variability in CCA. Most of the local correlations between AI and cloud properties are similar to the results from the global statistics, while weak anomalous aerosol-cloud correlations appear locally in the regions where simultaneous high (low) AI and low (high) LTS compensate each other. Daytime diurnal cycles explain additional variability in cloud properties. CCA has the largest diurnal cycle in high-LTS regions. Cloud droplet size and CLWP have weak diurnal cycles that differ between clean and polluted environments. The combined results suggest that investigations of marine low cloud radiative forcing and its relationship to hypothesized aerosol indirect effects must consider the combined effects of aerosols, thermodynamics, and the diurnal cycle. Copyright 2006 by the American Geophysical Union."
"55173596300;6602600408;10139397300;","Constraining the aerosol influence on cloud fraction",2016,"10.1002/2015JD023744","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84963894683&doi=10.1002%2f2015JD023744&partnerID=40&md5=bf33c273c4cc9e6d2de37cef5dbed243","Aerosol-cloud interactions have the potential to modify many different cloud properties. There is significant uncertainty in the strength of these aerosol-cloud interactions in analyses of observational data, partly due to the difficulty in separating aerosol effects on clouds from correlations generated by local meteorology. The relationship between aerosol and cloud fraction (CF) is particularly important to determine, due to the strong correlation of CF to other cloud properties and its large impact on radiation. It has also been one of the hardest to quantify from satellites due to the strong meteorological covariations involved. This work presents a new method to analyze the relationship between aerosol optical depth (AOD) and CF. By including information about the cloud droplet number concentration (CDNC), the impact of the meteorological covariations is significantly reduced. This method shows that much of the AOD-CF correlation is explained by relationships other than that mediated by CDNC. By accounting for these, the strength of the global mean AOD-CF relationship is reduced by around 80%. This suggests that the majority of the AOD-CF relationship is due to meteorological covariations, especially in the shallow cumulus regime. Requiring CDNC to mediate the AOD-CF relationship implies an effective anthropogenic radiative forcing from an aerosol influence on liquid CF of -0.48Wm-2 (-0.1 to -0.64Wm-2), although some uncertainty remains due to possible biases in the CDNC retrievals in broken cloud scenes. © 2016. American Geophysical Union. All Rights Reserved."
"8550791300;7004715270;16200336000;25624725200;56195201600;35798085000;55802292700;18437651200;7006415284;","Kaolinite particles as ice nuclei: Learning from the use of different kaolinite samples and different coatings",2014,"10.5194/acp-14-5529-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901916182&doi=10.5194%2facp-14-5529-2014&partnerID=40&md5=f8032c8b9b05be7a999628113facd4b6","Kaolinite particles from two different sources (Fluka and Clay Minerals Society (CMS)) were examined with respect to their ability to act as ice nuclei (IN). This was done in the water-subsaturated regime where often deposition ice nucleation is assumed to occur, and for water-supersaturated conditions, i.e., in the immersion freezing mode. Measurements were done using a flow tube (the Leipzig Aerosol Cloud Interaction Simulator, LACIS) and a continuous-flow diffusion chamber (CFDC). Pure and coated particles were used, with coating thicknesses of a few nanometers or less, where the coating consisted of levoglucosan, succinic acid or sulfuric acid. In general, it was found that the coatings strongly reduced deposition ice nucleation. Remaining ice formation in the water-subsaturated regime could be attributed to immersion freezing, with particles immersed in concentrated solutions formed by the coatings. In the immersion freezing mode, ice nucleation rate coefficients het from both instruments agreed well with each other, particularly when the residence times in the instruments were accounted for. Fluka kaolinite particles coated with either levoglucosan or succinic acid showed the same IN activity as pure Fluka kaolinite particles; i.e., it can be assumed that these two types of coating did not alter the ice-active surface chemically, and that the coatings were diluted enough in the droplets that were formed prior to the ice nucleation, so that freezing point depression was negligible. However, Fluka kaolinite particles, which were either coated with pure sulfuric acid or were first coated with the acid and then exposed to additional water vapor, both showed a reduced ability to nucleate ice compared to the pure particles. For the CMS kaolinite particles, the ability to nucleate ice in the immersion freezing mode was similar for all examined particles, i.e., for the pure ones and the ones with the different types of coating. Moreover, het derived for the CMS kaolinite particles was comparable to het derived for Fluka kaolinite particles coated with sulfuric acid. This is suggestive for the Fluka kaolinite possessing a type of ice-nucleating surface feature which is not present on the CMS kaolinite, and which can be destroyed by reaction with sulfuric acid. This might be potassium feldspar. © 2014 Author(s)."
"24081888700;7004174939;57203386948;","Microphysical, macrophysical and radiative signatures of volcanic aerosols in trade wind cumulus observed by the A-Train",2011,"10.5194/acp-11-7119-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960682774&doi=10.5194%2facp-11-7119-2011&partnerID=40&md5=ac828a7f1f193fe1f4bc09c0dfbba796","Increased aerosol concentrations can raise planetary albedo not only by reflecting sunlight and increasing cloud albedo, but also by changing cloud amount. However, detecting aerosol effect on cloud amount has been elusive to both observations and modeling due to potential buffering mechanisms and convolution of meteorology. Here through a natural experiment provided by long-term degassing of a low-lying volcano and use of A-Train satellite observations, we show modifications of trade cumulus cloud fields including decreased droplet size, decreased precipitation efficiency and increased cloud amount are associated with volcanic aerosols. In addition we find significantly higher cloud tops for polluted clouds. We demonstrate that the observed microphysical and macrophysical changes cannot be explained by synoptic meteorology or the orographic effect of the Hawaiian Islands. The ""total shortwave aerosol forcin"", resulting from direct and indirect forcings including both cloud albedo and cloud amount, is almost an order of magnitude higher than aerosol direct forcing alone. Furthermore, the precipitation reduction associated with enhanced aerosol leads to large changes in the energetics of air-sea exchange and trade wind boundary layer. Our results represent the first observational evidence of large-scale increase of cloud amount due to aerosols in a trade cumulus regime, which can be used to constrain the representation of aerosol-cloud interactions in climate models. The findings also have implications for volcano-climate interactions and climate mitigation research. © 2011 Author(s)."
"8550791300;8849246700;6604016408;8710280200;7202779940;7102680152;15072064200;7006595513;7006415284;","Hygroscopic growth and measured and modeled critical super-saturations of an atmospheric HULIS sample",2007,"10.1029/2006GL028260","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548025326&doi=10.1029%2f2006GL028260&partnerID=40&md5=0c34f5f77c21609c89d35f006b1a66ed","An atmospheric HULIS (humic-like substance) sample dissolved in water was used to generate particles with different dry diameters. A HHTDMA (High Humidity Tandem Differential Mobility Analyzer) and LACIS (Leipzig Aerosol Cloud Interaction Simulator) were used to measure hygroscopic growth of the HULIS particles. LACIS also was used to measure the critical super-saturation for the activation of HULIS particles with dry diameters of 50, 75, 100, and 125 nm. Simple Köhler theory was used to simulate the measured hygroscopic growth factors. For this, a new technique was used, where the ionic density (ρion) was defined as a combination of the HULIS physical properties for which values could not be reliably determined. By adjusting ρion in the Köhler equation, modeled hygroscopic growth could be brought into agreement with the measurements, even without the explicit knowledge of the different HULIS properties. It was demonstrated that the values of ρion determined with our procedure can be reproduced from combinations of physically realistic values of the physical properties represented by ρion. Adjustments of the ionic density were done for two different surface tensions, that of water as the upper limit, and the lowest value that had been measured for this HULIS sample (published previously) as the lower limit. The two adjusted values of ρion were used in the Köhler model to derive critical super-saturations. For more dilute droplets, measured and modeled critical super-saturations were in agreement for both values of the surface tension, whereas for the less dilute solutions, agreement only could be achieved when a lowering of the surface tension due to HULIS was taken into account. Copyright 2007 by the American Geophysical Union."
"13403622000;7005955015;57203053317;","Aerosol influence on mixed-phase clouds in CAM-Oslo",2008,"10.1175/2008JAS2430.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42149193942&doi=10.1175%2f2008JAS2430.1&partnerID=40&md5=fd17fa2600d387d5283b4683c77fd0f5","A new treatment of mixed-phase cloud microphysics has been implemented in the general circulation model, Community Atmosphere Model (CAM)-Oslo, which combines the NCAR CAM2.0.1 and a detailed aerosol module. The new treatment takes into account the aerosol influence on ice phase initiation in stratiform clouds with temperatures between 0° and -40°C. Both supersaturation and cloud ice fraction, that is, the fraction of cloud ice compared to the total cloud water in a given grid box, are now determined based on a physical reasoning in which not only temperature but also the ambient aerosol concentration play a role. Included in the improved microphysics treatment is also a continuity equation for ice crystal number concentration. Ice crystal sources are heterogeneous and homogeneous freezing processes and ice multiplication. Sink terms are collection processes and precipitation formation, that is, melting and sublimation. Instead of using an idealized ice nuclei concentration for the heterogeneous freezing processes, a common approach in global models, the freezing processes are here dependent on the ability of the ambient aerosols to act as ice nuclei. Additionally, the processes are dependent on the cloud droplet number concentration and hence the aerosols' ability to act as cloud condensation nuclei. Sensitivity simulations based on the new microphysical treatment of mixed-phase clouds are presented for both preindustrial and present-day aerosol emissions. Freezing efficiency is found to be highly sensitive to the amount of sulphuric acid available for ice nuclei coating. In the simulations, the interaction of anthropogenic aerosols and freezing mechanisms causes a warming of the earth-atmosphere system, counteracting the cooling effect of aerosols influencing warm clouds. The authors find that this reduction of the total aerosol indirect effect amounts to 50%-90% for the specific assumptions on aerosol properties used in this study. However, many microphysical processes in mixed-phase clouds are still poorly understood and the results must be interpreted with that in mind. © 2008 American Meteorological Society."
"8511991900;6603333885;7006303509;7005877775;7005742394;","Ice formation in arctic mixed-phase clouds: Insights from a 3-D cloud-resolving model with size-resolved aerosol and cloud microphysics",2009,"10.1029/2008JD010782.","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66249120359&doi=10.1029%2f2008JD010782.&partnerID=40&md5=7a948d777f38a845fce7bc2fbac25fc7","The single-layer mixed-phase clouds observed during the Atmospheric Radiation Measurement (ARM) program's Mixed-Phase Arctic Cloud Experiment (MPACE) are simulated with a three-dimensional cloud-resolving model, the System for Atmospheric Modeling (SAM), coupled with an explicit bin microphysics scheme and a radar simulator. By implementing an aerosol-dependent and a temperature- and supersaturation-dependent ice nucleation scheme and treating IN size distribution prognostically, the link between ice crystal and aerosol properties is established to study aerosol indirect effects. Two possible ice enhancement mechanisms, activation of droplet evaporation residues by condensation followed by freezing and droplet evaporation freezing by contact freezing inside out, are scrutinized by extensive comparisons with the in situ and remote sensing measurements. Simulations with either mechanism agree well with the in situ and remote sensing measurements of ice microphysical properties but liquid water content is slightly underpredicted. These two mechanisms give similar cloud properties, although ice nucleation occurs at very different rates and locations. Ice nucleation from activation of evaporation nuclei occurs mostly near cloud top areas, while ice nucleation from the drop freezing during evaporation has no significant location preference. Both ice enhancement mechanisms contribute dramatically to ice formation with ice particle concentration of 10-15 times higher relative to the simulation without either of them. Ice nuclei (IN) recycling from ice sublimation contributes significantly to maintaining concentrations of IN and ice particles in this case, implying an important role to maintain the observed long-term existence of mixed-phase clouds. Cloud can be very sensitive to IN initially but become much less sensitive as cloud evolves to a steady mixed-phase condition. © 2009 by the American Geophysical Union."
"16480175700;6603872903;7003591311;22949331500;10144282600;21734765600;8280879000;7003741536;7006783796;7004008609;34769606600;6602126007;","Effect of biomass burning on marine stratocumulus clouds off the California coast",2009,"10.5194/acp-9-8841-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71149103037&doi=10.5194%2facp-9-8841-2009&partnerID=40&md5=cd8dd6d3a1f44cc517ed14fb59c7bd23","Aerosol-cloud interactions are considered to be one of the most important and least known forcings in the climate system. Biomass burning aerosols are of special interest due to their radiative impact (direct and indirect effect) and their potential to increase in the future due to climate change. Combining data from Geostationary Operational Environmental Satellite (GOES) and MODerate-resolution Imaging Spectroradiometer (MODIS) with passive tracers from the FLEXPART Lagrangian Particle Dispersion Model, the impact of biomass burning aerosols on marine stratocumulus clouds has been examined in June and July of 2006ĝ€""2008 off the California coast. Using a continental tracer, the indirect effect of biomass burning aerosols has been isolated by comparing the average cloud fraction and cloud albedo for different meteorological situations, and for clean versus polluted (in terms of biomass burning) continental air masses at 14:00 local time. Within a 500 km-wide band along the coast of California, biomass burning aerosols, which tend to reside above the marine boundary layer, increased the cloud fraction by 0.143, and the cloud albedo by 0.038. Absorbing aerosols located above the marine boundary layer lead to an increase of the lower tropospheric stability and a reduction in the vertical entrainment of dry air from above, leading to increased cloud formation. The combined effect was an indirect radiative forcing of &minus;7.5% &plusmn;1.7% (cooling effect) of the outgoing radiative flux at the top of the atmosphere on average, with a bias due to meteorology of +0.9%. Further away from the coast, the biomass burning aerosols, which were located within the boundary layer, reduced the cloud fraction by 0.023 and the cloud albedo by 0.006, resulting in an indirect radiative forcing of +1.3% &plusmn;0.3% (warming effect) with a bias of +0.5%. These results underscore the dual role that absorbing aerosols play in cloud radiative forcing."
"36124786200;7004479395;","Analysis of aerosol-cloud interaction from multi-sensor satellite observations",2010,"10.1029/2009GL041828","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953568989&doi=10.1029%2f2009GL041828&partnerID=40&md5=02cf81c1c0ffcada652bb992ec7273d3","Aerosol interaction with clouds is the main uncertainty for the quantification of the anthropogenic forcing on climate. The first step of the so-called ""aerosol indirect effect"" is the change of cloud droplet size distribution when seeded by anthropogenic aerosols. Satellite data provide the density and diversity of observations needed for a statistical estimate of this effect. Numerous such studies have demonstrated the correlation between aerosol load and Cloud Droplet Radius (CDR) and a few have quantified the impact of aerosol on the microphysics. Here, we go one step further by using the profiles from the spaceborne CALIPSO lidar that indicates the respective position of aerosol and cloud layers. The results show that, when aerosol and cloud layers are clearly separated, there is no correlation between aerosol load and CDR. On the other hand, when the lidar profile indicates mixing, there is a strong correlation. We focus on the stratocumulus cloud fields off the coast of Namibia and Angola that are seeded by biomass burning aerosols from Africa. The log-log slope of CDR and a proxy of the condensation nuclei number are-0.24 in excellent agreement with theoretical estimate. When the vertical profile information is not used, the slope is significantly smaller. Copyright © 2010 by the American Geophysical Union."
"7006705919;35552588700;57200319057;","Geoengineering by cloud seeding: Influence on sea ice and climate system",2009,"10.1088/1748-9326/4/4/045112","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76149088442&doi=10.1088%2f1748-9326%2f4%2f4%2f045112&partnerID=40&md5=74c69675f789e31996e18de7b390ef14","General circulation model computations using a fully coupled ocean-atmosphere model indicate that increasing cloud reflectivity by seeding maritime boundary layer clouds with particles made from seawater may compensate for some of the effects on climate of increasing greenhouse gas concentrations. The chosen seeding strategy (one of many possible scenarios) can restore global averages of temperature, precipitation and sea ice to present day values, but not simultaneously. The response varies nonlinearly with the extent of seeding, and geoengineering generates local changes to important climatic features. The global tradeoffs of restoring ice cover, and cooling the planet, must be assessed alongside the local changes to climate features. © 2009 IOP Publishing Ltd."
"55522563200;55740664200;55207447000;56611366900;7004057920;","The role of adiabaticity in the aerosol first indirect effect",2008,"10.1029/2007JD008961","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43449102178&doi=10.1029%2f2007JD008961&partnerID=40&md5=904b90c2e4eefe7a5feb4cc55db04090","Aerosol indirect effects are the most uncertain of the climate forcing mechanisms that have operated through the industrial period. Several studies have demonstrated modifications of cloud properties due to aerosols and corresponding changes in shortwave and longwave radiative fluxes under specific cloud conditions, but some recent studies have indicated that cloud dynamical processes such as entrainment-mixing may be the primary modulator of cloud optical properties in certain situations. For example, day-to-day variations of the cloud drop effective radius (r<inf>e</inf>) determined from the ground-based remote sensing at the Southern Great Plains were found to be weakly associated with the variations in aerosol loading as characterized by its light-scattering coefficient at the surface, implying that other processes were impacting the cloud radiative properties. To study these other impacts, we extend a previous study to investigate the role of changes in liquid water path (LWP) and r<inf>e</inf> in single layer stratiform clouds that are induced by entrainment-mixing processes and their effects on cloud radiative properties. We quantify the degree of entrainment-mixing in terms of the adiabaticity defined as the ratio of the observed cloud liquid water path to the corresponding adiabatic value. The cloud optical depth is, as expected, governed primarily by LWP, but that adiabaticity is the next most influential factor. In contrast, r<inf>e</inf> is found to be equally sensitive to adiabaticity and LWP. In adiabatic clouds the aerosol first indirect effect is clearly observed and related to independent measures of aerosol loading. In sub-adiabatic clouds the aerosol first indirect effect is not readily observed; this may in some circumstances be due to interference from heterogeneous mixing processes that change the droplet number density in a manner that attenuates the effect. Copyright 2008 by the American Geophysical Union."
"7006306835;56744278700;7103271625;7101752236;7402064802;57208462871;7103206141;","Modeling the interactions between aerosols and liquid water clouds with a self-consistent cloud scheme in a general circulation model",2007,"10.1175/JAS3874.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247554922&doi=10.1175%2fJAS3874.1&partnerID=40&md5=89cc99b1aa4e69f61ff628c9b5fd0da7","To model aerosol-cloud interactions in general circulation models (GCMs), a prognostic cloud scheme of cloud liquid water and amount is expanded to include droplet number concentration (Nd) in a way that allows them to be calculated using the same large-scale and convective updraft velocity field. In the scheme, the evolution of droplets fully interacts with the model meteorology. An explicit treatment of cloud condensation nuclei (CCN) activation enables the scheme to take into account the contributions to Nd of multiple aerosol species (i.e., sulfate, organic, and sea-salt aerosols) and to consider kinetic limitations of the activation process. An implementation of the prognostic scheme in the Geophysical Fluid Dynamics Laboratory (GFDL) AM2 GCM yields a vertical distribution of Nd with a characteristic maximum in the lower troposphere; this feature differs from the profile that would be obtained if Nd is diagnosed from the sulfate mass concentration based on an often-used empirical relationship. Prognosticated Nd exhibits large variations with respect to the sulfate mass concentration. The mean values are generally consistent with the empirical relationship over ocean, but show negative biases over the Northern Hemisphere midlatitude land, perhaps owing to the neglect of subgrid variations of large-scale ascents and inadequate convective sources. The prognostic scheme leads to a substantial improvement in the agreement of model-predicted present-day liquid water path (LWP) and cloud forcing with satellite measurements compared to using the empirical relationship. The simulations with preindustrial and present-day aerosols show that the combined first and second indirect effects of anthropogenic sulfate and organic aerosols give rise to a steady-state global annual mean flux change of -1.8 W m-2, consisting of -2.0 W m-2 in shortwave and 0.2 W m-2 in longwave. The ratios of the flux changes in the Northern Hemisphere (NH) to that in Southern Hemisphere (SH) and of the flux changes over ocean to that over land are 2.9 and 0.73, respectively. These estimates are consistent with the averages of values from previous studies stated in a recent review. The model response to higher Nd alters the cloud field; LWT and total cloud amount increase by 19% and 0.6%, respectively. Largely owing to high sulfate concentrations from fossil fuel burning, the NH midlatitude land and oceans experience strong radiative cooling. So does the tropical land, which is dominated by biomass burning-derived organic aerosol. The computed annual, zonal-mean flux changes are determined to be statistically significant, exceeding the model's natural variations in the NH low and midlatitudes and in the SH low latitudes. This study reaffirms the major role of sulfate in providing CCN for cloud formation. © 2007 American Meteorological Society."
"6701463335;7202258620;7003498065;36538539800;7006304904;9738422100;9239331500;8625148400;54941580100;55938109300;6701342931;7202595372;55879681300;8067250600;13007286600;55807448700;56109007900;39361670300;56489746200;7403143315;14719880500;24767977600;22635720500;7003862871;54982705800;6505947323;55720332500;7003658498;","Feedbacks between air pollution and weather, part 2: Effects on chemistry",2015,"10.1016/j.atmosenv.2014.10.021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937861018&doi=10.1016%2fj.atmosenv.2014.10.021&partnerID=40&md5=aa299d67d7f3fb35aea2fe091d152747","Fully-coupled air-quality models running in ""feedback"" and ""no-feedback"" configurations were compared against each other and observation network data as part of Phase 2 of the Air Quality Model Evaluation International Initiative. In the ""no-feedback"" mode, interactions between meteorology and chemistry through the aerosol direct and indirect effects were disabled, with the models reverting to climatologies of aerosol properties, or a no-aerosol weather simulation, while in the ""feedback"" mode, the model-generated aerosols were allowed to modify the models' radiative transfer and/or cloud formation processes. Annual simulations with and without feedbacks were conducted for domains in North America for the years 2006 and 2010, and for Europe for the year 2010. Comparisons against observations via annual statistics show model-to-model variation in performance is greater than the within-model variation associated with feedbacks. However, during the summer and during intense emission events such as the Russian forest fires of 2010, feedbacks have a significant impact on the chemical predictions of the models. The aerosol indirect effect was usually found to dominate feedbacks compared to the direct effect. The impacts of direct and indirect effects were often shown to be in competition, for predictions of ozone, particulate matter and other species. Feedbacks were shown to result in local and regional shifts of ozone-forming chemical regime, between NOx- and VOC-limited environments. Feedbacks were shown to have a substantial influence on biogenic hydrocarbon emissions and concentrations: North American simulations incorporating both feedbacks resulted in summer average isoprene concentration decreases of up to 10%, while European direct effect simulations during the Russian forest fire period resulted in grid average isoprene changes of -5 to +12.5%. The atmospheric transport and chemistry of large emitting sources such as plumes from forest fires and large cities were shown to be strongly impacted by the presence or absence of feedback mechanisms in the model simulations. Summertime model performance for ozone and other gases was improved through the inclusion of indirect effect feedbacks, while performance for particulate matter was degraded, suggesting that current parameterizations for in- and below cloud processes, once the cloud locations become more directly influenced by aerosols, may over- or under-predict the strength of these processes. Process parameterization-level comparisons of fully coupled feedback models are therefore recommended for future work, as well as further studies using these models for the simulations of large scale urban/industrial and/or forest fire plumes. © 2014."
"15071907100;","Why are climate models reproducing the observed global surface warming so well?",2008,"10.1029/2008GL034932","https://www.scopus.com/inward/record.uri?eid=2-s2.0-55849085902&doi=10.1029%2f2008GL034932&partnerID=40&md5=991c0ee177a8b69893c0567853ccd16f","Climate models reproduce the observed surface warming better than one would expect given the uncertainties in radiative forcing, climate sensitivity and ocean heat uptake, suggesting that different models show similar warming for different reasons. It is shown that while climate sensitivity and radiative forcing are indeed correlated across the latest ensemble of models, eliminating this correlation would not strongly change the uncertainty range of long-term temperature projections. However, since most models do not incorporate the aerosol indirect effects, model agreement with observations may be partly spurious. The incorporation of more detailed aerosol effects in future models could lead to inconsistencies between simulated and observed past warming, unless the effects are small or compensated by additional forcings. It is argued that parameter correlations across models are neither unexpected nor problem if the models are interpreted as conditional on observations. Copyright 2008 by the American Geophysical Union."
"35430069600;57211106013;26643036500;","Elicitation of expert judgments of aerosol forcing",2006,"10.1007/s10584-005-9025-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745018916&doi=10.1007%2fs10584-005-9025-y&partnerID=40&md5=fb9e26474e14c081424df94567238747","A group of twenty-four leading atmospheric and climate scientists provided subjective probability distributions that represent their current judgment about the value of planetary average direct and indirect radiative forcing from anthropogenic aerosols at the top of the atmosphere. Separate estimates were obtained for the direct aerosol effect, the semi-direct aerosol effect, cloud brightness (first aerosol indirect effect), and cloud lifetime/distribution (second aerosol indirect effect). Estimates were also obtained for total planetary average forcing at the top of the atmosphere and for surface forcing. Consensus was strongest among the experts in their assessments of the direct aerosol effect and the cloud brightness indirect effect. Forcing from the semi-direct effect was thought to be small (absolute values of all but one of the experts' best estimates were ≤0.5 W/m2). There was not agreement about the sign of the best estimate of the semi-direct effect, and the uncertainty ranges some experts gave for this effect did not overlap those given by others. All best estimates of total aerosol forcing were negative, with values ranging between -0.25 W/m2 and -2.1 W/m2. The range of uncertainty that a number of experts associated with their estimates, especially those for total aerosol forcing and for surface forcing, was often much larger than that suggested in 2001 by the IPCC Working Group 1 summary figure (IPCC, 2001). © Springer 2006."
"7405459515;7202418453;35472747700;7402226589;7102707632;24611027600;6603098675;","Tropical high cloud characteristics derived from SAGE II extinction measurements",1994,"10.1016/0169-8095(94)90081-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0003088329&doi=10.1016%2f0169-8095%2894%2990081-7&partnerID=40&md5=b8d930728198ea29631516f321f8be25","This work investigates the characteristics of tropical high clouds based on the 1989 Stratospheric Aerosol and Gas Experiment (SAGE II) particulate extinction measurements and the National Meteorological Center (NMC) temperature data. A discussion is also provided of the cloud measurement constraints of the SAGE II instrument, including optical limitation, sensitivity of the measurement to particle sizes, and uncertainty due to the spatial resolution of the sampling volume. Because of the viewing geometry of the solar occultation technique, the SAGE II instrument is very sensitive to thin cirrus clouds. The results of this study indicate that (1) the tropical high cloud data can be distinguished approximately from aerosol data by using the ratio of the extinction at 0.525 μm to that at 1.02 μm as an indicator, the 1989 cloud data being characterized by an extinction ratio less than 2.1; (2) the background aerosol size distribution in the tropical tropopause region is bimodal with the small mode extending even below a radius of 0.075 μm and the large mode centered at a radius of 0.6 μm; (3) SAGE II cloud extinction data reveal various degrees of wavelength dependency, which suggests specific progressive changes in particle size distribution during cloud development; and (4) aerosol nucleation and ice nucleation as well as coagulation growth of small particles are important processes in the tropical cirrus cloud evolution. The specific characteristics of the aerosol-cloud interaction as manifested in the multiwavelength SAGE II high cloud extinctions in the tropical tropopause region can be useful information for model studies of the cirrus cloud evolution. © 1994."
"56867812800;8211380400;7202839433;","Simulating aerosol-radiation-cloud feedbacks on meteorology and air quality over eastern China under severe haze conditionsin winter",2015,"10.5194/acp-15-2387-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929298697&doi=10.5194%2facp-15-2387-2015&partnerID=40&md5=0e74ed878f5e0f1186a9990a71c89e14","The aerosol-radiation-cloud feedbacks on meteorology and air quality over eastern China under severe winter haze conditions in January 2013 are simulated using the fully coupled online Weather Research and Forecasting/Chemistry (WRF-Chem) model. Three simulation scenarios including different aerosol configurations are undertaken to distinguish the aerosol's radiative (direct and semi-direct) and indirect effects. Simulated spatial and temporal variations of PM2.5 are generally consistent with surface observations, with a mean bias of -18.9 μg m-3 (-15.0%) averaged over 71 big cities in China. Comparisons between different scenarios reveal that aerosol radiative effects (direct effect and semi-direct effects) result in reductions of downward shortwave flux at the surface, 2 m temperature, 10 m wind speed and planetary boundary layer (PBL) height by up to 84.0 W m-2, 3.2°C, 0.8 m s-1, and 268 m, respectively. The simulated impact of the aerosol indirect effects is comparatively smaller. Through reducing the PBL height and stabilizing lower atmosphere, the aerosol effects lead to increases in surface concentrations of primary pollutants (CO and SO<inf>2</inf>). Surface O<inf>3</inf> mixing ratio is reduced by up to 6.9 ppb (parts per billion) due to reduced incoming solar radiation and lower temperature, while the aerosol feedbacks on PM<inf>2.5</inf> mass concentrations show some spatial variations. Comparisons of model results with observations show that inclusion of aerosol feedbacks in the model significantly improves model performance in simulating meteorological variables and improves simulations of PM<inf>2.5</inf> temporal distributions over the North China Plain, the Yangtze River delta, the Pearl River delta, and central China. Although the aerosol-radiation-cloud feedbacks on aerosol mass concentrations are subject to uncertainties, this work demonstrates the significance of aerosol-radiation-cloud feedbacks for real-time air quality forecasting under haze conditions. © Author(s) 2015."
"6701562113;8631239200;6602572031;7005751636;55665687100;55536747200;7006030430;7003495982;","Introducing subgrid-scale cloud feedbacks to radiation for regional meteorological and climate modeling",2012,"10.1029/2012GL054031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871574295&doi=10.1029%2f2012GL054031&partnerID=40&md5=2ee3719f45dd089e5bddafaa275b4a51","Convective systems and associated cloudiness directly influence regional and local atmospheric radiation budgets, as well as dynamics and thermodynamics, through feedbacks. However, most subgrid-scale convective parameterizations in regional weather and climate models do not consider cumulus cloud feedbacks to radiation, resulting in biases in several meteorological parameters. We have incorporated this key feedback process into a convective parameterization and a radiation scheme in the Weather Research and Forecasting model, and evaluated the impacts of including this process in short-term weather and multiyear climate simulations. Introducing subgrid-scale convective cloud-radiation feedbacks leads to a more realistic simulation of attenuation of downward surface shortwave radiation. Reduced surface shortwave radiation moderates the surface forcing for convection and results in a notable reduction in precipitation biases. Our research reveals a need for more in-depth consideration of the effects of subgrid-scale clouds in regional meteorology/climate and air quality models on radiation, photolysis, cloud mixing, and aerosol indirect effects. © 2012. American Geophysical Union. All Rights Reserved."
"16444006500;55326237100;7005035762;7203034123;7003444634;55915206300;57206330745;57126848900;25624545600;35069282600;23970271800;57217266035;7003591311;6506545080;35114996800;57200390260;6603431534;57206332144;56457851700;55827521500;35095482200;36680583100;7102084129;7003972559;22954523900;57194682576;57208121852;22635999400;57190209035;56363987000;24722339600;56722821200;6602600408;","Remote Sensing of Droplet Number Concentration in Warm Clouds: A Review of the Current State of Knowledge and Perspectives",2018,"10.1029/2017RG000593","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050376815&doi=10.1029%2f2017RG000593&partnerID=40&md5=a96d6fe5d591c2d81c76d6c3126dbdd0","The cloud droplet number concentration (Nd) is of central interest to improve the understanding of cloud physics and for quantifying the effective radiative forcing by aerosol-cloud interactions. Current standard satellite retrievals do not operationally provide Nd, but it can be inferred from retrievals of cloud optical depth (τc) cloud droplet effective radius (re) and cloud top temperature. This review summarizes issues with this approach and quantifies uncertainties. A total relative uncertainty of 78% is inferred for pixel-level retrievals for relatively homogeneous, optically thick and unobscured stratiform clouds with favorable viewing geometry. The uncertainty is even greater if these conditions are not met. For averages over 1° ×1° regions the uncertainty is reduced to 54% assuming random errors for instrument uncertainties. In contrast, the few evaluation studies against reference in situ observations suggest much better accuracy with little variability in the bias. More such studies are required for a better error characterization. Nd uncertainty is dominated by errors in re, and therefore, improvements in re retrievals would greatly improve the quality of the Nd retrievals. Recommendations are made for how this might be achieved. Some existing Nd data sets are compared and discussed, and best practices for the use of Nd data from current passive instruments (e.g., filtering criteria) are recommended. Emerging alternative Nd estimates are also considered. First, new ideas to use additional information from existing and upcoming spaceborne instruments are discussed, and second, approaches using high-quality ground-based observations are examined. ©2018. The Authors."
"36145802300;35253921800;7005427503;24725828400;57203663638;","Monitoring spatio-temporal variations in aerosols and aerosol-cloud interactions over Pakistan using MODIS data",2010,"10.1016/j.asr.2010.06.025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960132689&doi=10.1016%2fj.asr.2010.06.025&partnerID=40&md5=1add43f4b8c36fff3cb23152aa04fb2f","Clouds are important elements in climatic processes and interactions between aerosols and clouds are therefore a hot topic for scientific research. Aerosols show both spatial and temporal variations, which can lead to variations in the microphysics of clouds. In this research, we have examined the spatial and temporal variations in aerosol particles over Pakistan and the impact of these variations on various optical properties of clouds, using Moderate Resolution Imaging Spectroradiometer (MODIS) data from the Terra satellite. We used the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model for trajectory analysis to reveal the origins of air masses, with the aim of understanding these spatial and temporal variabilities in aerosol concentrations. We also documented seasonal variations in patterns of aerosol optical depth (AOD) over Pakistan, for which the highest values occur during the monsoon season (June-August). We then analyzed the relationships between AOD and four other cloud parameters, namely water vapour (WV), cloud fraction (CF), cloud top temperature (CTT) and cloud top pressure (CTP). Regional correlation maps and time series plots for aerosol (AOD) and cloud parameters were produced to provide a better understanding of aerosol-cloud interaction. The analyses showed strong positive correlations between AOD and WV for all of the eight cities investigated. The correlation between AOD and CF was positive for those cities where the air masses were predominantly humid, but negative for those cities where the air masses were relatively dry and carried a low aerosol abundance. These correlations were clearly dependent on the meteorological conditions for all of the eight cities investigated. Because of the observed AOD-CF relationship, the co-variation of AOD with CTP and CTT may be attributable to large-scale meteorological variations: AOD showed a positive correlation with CTP and CTT in northern regions of Pakistan and a negative correlation in southern regions. © 2010 Elsevier Ltd. All rights reserved."
"7006354036;7005601996;55984424900;6603417217;6603063133;","Soluble organic compounds in fog and cloud droplets: What have we learned over the past few years?",2002,"10.1016/S0169-8095(02)00082-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036742617&doi=10.1016%2fS0169-8095%2802%2900082-0&partnerID=40&md5=a80da29442cf0a78c976dc954eb103c5","We have recently set up a new procedure for characterising the water soluble organic compounds (WSOC) in fog water, for which information is still rather limited. Fog samples collected during the 1998-1999 fall-winter season in the Po Valley (Italy) were analysed following this procedure, which allows a quantitative determination of three main classes of organic compounds (neutral species, mono- and di-carboxylic acids, polycarboxylic acids), together accounting for ca. 85% of the total WSOC. This procedure also provides information on the main chemical characteristics of these three classes of compounds (functional groups, aliphatic vs. aromatic character, etc.). The enhanced chemical knowledge on fog/cloud chemical composition opens new scenarios as far as chemical and microphysical processes in clouds and fogs are concerned. © 2002 Elsevier Science B.V. All rights reserved."
"7005955015;","Studies of the aerosol indirect effect from sulfate and black carbon aerosols",2002,"10.1029/2001JD000887","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347811386&doi=10.1029%2f2001JD000887&partnerID=40&md5=e219ae921a4fbb080404483019bd0613","The indirect effect of anthropogenic aerosols is investigated using the global climate model National Center for Atmospheric Research Community Climate Model Version 3 (NCAR CCM3). Two types of anthropogenic aerosols are considered, i.e., sulfate and black carbon aerosols. The concentrations and horizontal distributions of these aerosols were obtained from simulations with a life-cycle model incorporated into the global climate model. They are then combined with size-segregated background aerosols. The aerosol size distributions are subjected to condensation, coagulation, and humidity swelling. By making assumptions on supersaturation, we determine cloud droplet number concentrations in water clouds. Cloud droplet sizes and top of atmosphere (TOA) radiative fluxes are in good agreement with satellite observations. Both components of the indirect effect, i.e., the radius and lifetime effects, are computed as pure forcing terms. Using aerosol data for 2000 from the Intergovernmental Panel on Climate Change (IPCC), we find, globally averaged, a 5% decrease in cloud droplet radius and a 5% increase in cloud water path due to. anthropogenic aerosols. The largest changes are found over SE Asia, followed by the North Atlantic, Europe, and the eastern United States. This is also the case for the radiative forcing (""indirect effect""), which has a global average of -1.8 W m-2. When the experiment is repeated using data for 2100 from the IPCC A2 scenario, an unchanged globally averaged radiative forcing is found, but the horizontal distribution has been shifted toward the tropics. Sensitivity experiments show that the radius effect is ∼3 times as important as the lifetime effect and that black carbon only contributes marginally to the overall indirect effect. Copyright 2002 by the American Geophysical Union."
"56203249800;35561911800;36705143500;55408944000;9242540400;6604021707;7401548835;9242539000;57191598636;22978151200;7004177660;7004409909;55339475000;6603552777;57193132723;12240390300;7404334532;7006224475;57191693467;56249704400;7006399110;8954866200;57191692422;12241892400;7201837768;6506806004;55403720400;8414341100;7006550762;12763470600;7405727977;7004214645;56528677800;6507308842;14829673100;22986631300;7403318365;57203378018;","Future climate change under RCP emission scenarios with GISS ModelE2",2015,"10.1002/2014MS000403","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928814435&doi=10.1002%2f2014MS000403&partnerID=40&md5=a09054e13edbe0b876d903beba94aabf","We examine the anthropogenically forced climate response for the 21st century representative concentration pathway (RCP) emission scenarios and their extensions for the period 2101-2500. The experiments were performed with ModelE2, a new version of the NASA Goddard Institute for Space Sciences (GISS) coupled general circulation model that includes three different versions for the atmospheric composition components: a noninteractive version (NINT) with prescribed composition and a tuned aerosol indirect effect (AIE), the TCAD version with fully interactive aerosols, whole-atmosphere chemistry, and the tuned AIE, and the TCADI version which further includes a parameterized first indirect aerosol effect on clouds. Each atmospheric version is coupled to two different ocean general circulation models: the Russell ocean model (GISS-E2-R) and HYCOM (GISS-E2-H). By 2100, global mean warming in the RCP scenarios ranges from 1.0 to 4.5°C relative to 1850-1860 mean temperature in the historical simulations. In the RCP2.6 scenario, the surface warming in all simulations stays below a 2°C threshold at the end of the 21st century. For RCP8.5, the range is 3.5-4.5°C at 2100. Decadally averaged sea ice area changes are highly correlated to global mean surface air temperature anomalies and show steep declines in both hemispheres, with a larger sensitivity during winter months. By the year 2500, there are complete recoveries of the globally averaged surface air temperature for all versions of the GISS climate model in the low-forcing scenario RCP2.6. TCADI simulations show enhanced warming due to greater sensitivity to CO<inf>2</inf>, aerosol effects, and greater methane feedbacks, and recovery is much slower in RCP2.6 than with the NINT and TCAD versions. All coupled models have decreases in the Atlantic overturning stream function by 2100. In RCP2.6, there is a complete recovery of the Atlantic overturning stream function by the year 2500 while with scenario RCP8.5, the E2-R climate model produces a complete shutdown of deep water formation in the North Atlantic. © 2015. The Authors."
"56422246700;8550791300;56421834400;55857180100;18437651200;56533851600;25961216800;7006415284;","The immersion mode ice nucleation behavior of mineral dusts: A comparison of different pure and surface modified dusts",2014,"10.1002/2014GL061317","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911393945&doi=10.1002%2f2014GL061317&partnerID=40&md5=c06c8b354c7dba7764884e98a6b9127c","In this study we present results from immersion freezing experiments with size-segregated mineral dust particles. Besides two already existing data sets for Arizona Test Dust (ATD), and Fluka kaolinite, we show two new data sets for illite-NX, which consists mainly of illite, a clay mineral, and feldspar, a common crustal material. The experiments were carried out with the Leipzig Aerosol Cloud Interaction Simulator. After comparing the different dust samples, it became obvious that the freezing ability was positively correlated with the K-feldspar content. Furthermore, a comparison of the composition of the ATD, illite-NX, and feldspar samples suggests that within the K-feldspars, microcline is more ice nucleation active than orthoclase. A coating with sulfuric acid leads to a decrease in the ice nucleation ability of all mineral dusts, with the effect being more pronounced for the feldspar sample. Key Points The freezing ability of mineral dusts correlated with the K-feldspar contentAmong feldspars, microcline shows a better ice nucleation ability than orthoclaseAfter coating, all investigated dusts feature a similar ice nucleation ability ©2014. The Authors."
"35221443100;57208121852;","A critical look at spatial scale choices in satellite-based aerosol indirect effect studies",2010,"10.5194/acp-10-11459-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649842858&doi=10.5194%2facp-10-11459-2010&partnerID=40&md5=04ff2678b6b60dc20f9fab33399feb83","Analysing satellite datasets over large regions may introduce spurious relationships between aerosol and cloud properties due to spatial variations in aerosol type, cloud regime and synoptic regime climatologies. Using MODerate resolution Imaging Spectroradiometer data, we calculate relationships between aerosol optical depth τa derived liquid cloud droplet effective number concentration Ne and liquid cloud droplet effective radius r e at different spatial scales. Generally, positive values of dlnNe/dlnta are found for ocean regions, whilst negative values occur for many land regions. The spatial distribution of dlnr e/dlnta shows approximately the opposite pattern, with generally postive values for land regions and negative values for ocean regions. We find that for region sizes larger than 4° × 4°, spurious spatial variations in retrieved cloud and aerosol properties can introduce widespread significant errors to calculations of dlnNedlnt a and dlnre/dlnta. For regions on the scale of 60° × 60°, these methodological errors may lead to an overestimate in global cloud albedo effect radiative forcing of order 80% relative to that calculated for regions on the scale of 1° × 1°. © 2010 Author(s)."
"14035836100;7003591311;","Quantifying error in the radiative forcing of the first aerosol indirect effect",2008,"10.1029/2007GL032667","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40849126797&doi=10.1029%2f2007GL032667&partnerID=40&md5=84b4d363c0d73963cfe85dd44e476e91","Anthropogenic aerosol plays a major role in the Earth's radiation budget, particularly via effects on clouds. The Intergovernmental Panel on Climate Change lists the uncertainty in aerosol modification of cloud albedo as the largest unknown in the radiative forcing of climate change. Common measures of aerosol effects on clouds, Aerosol-Cloud Interaction (ACI = -∂lnre/∂lnα, where re is drop size and a aerosol burden), cover an enormous range and, as these measures are now being used as parameterizations in global-scale models, this has large implications for radiative forcing. We quantify the relationship between radiative forcing and changes in ACI over the range of values found in the literature. Depending on anthropogenic aerosol perturbation, radiative forcing ranges from -3 to -10 W m-2 for each 0.05 increment in ACI. Narrowing uncertainty in measures of ACI to an accuracy of 0.05 would place estimated cloud radiative forcing on a sounder footing. Copyright 2008 by the American Geophysical Union."
"55113736500;","Development of mixed-phase clouds from multiple aerosol size distributions and the effect of the clouds on aerosol removal",2003,"10.1029/2002jd002691","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642305715&doi=10.1029%2f2002jd002691&partnerID=40&md5=a085af30d1a46a0fb874e11efabef411","This paper provides numerics for cloud and precipitation development from multiple aerosol size distributions and examines the effect of clouds and precipitation on aerosol removal. Numerical techniques are given for (1) simultaneous liquid and ice growth onto multiple aerosol size distributions, (2) diffusiophoretic, thermophoretic, gravitational, etc., coagulation among liquid, ice, and graupel, and their aerosol components, (3) contact freezing (CF) of drops by size-resolved interstitial aerosols, (4) heterogeneous plus homogeneous freezing, (5) liquid drop breakup, (6) coagulation of cloud hydrometeors and incorporated aerosols with interstitial aerosols, (7) coagulation of precipitation hydrometeors with interstitial and below-cloud aerosols (washout), (8) removal of precipitation and incorporated aerosols (rainout), (9) below-cloud evaporation/sublimation to smaller hydrometeors and aerosol cores, (10) gas washout, and (11) aqueous chemistry. Major conclusions are (1) hydrometeor-hydrometeor coagulation appears to play a substantial role in controlling aerosol-particle number globally, (2) washout (aerosol-hydrometeor coagulation) may be a more important in-plus below-cloud removal mechanism of aerosol number than rainout (the opposite is true for aerosol mass), (3) close-in diameter dual peaks in observed cloud distributions may be in part due to different activation characteristics of different aerosol distributions, (4) evaporative cooling at liquid drop surfaces in subsaturated air may be a mechanism of drop freezing (termed ""evaporative freezing"" here), and (5) heterogeneous-homogeneous freezing may freeze more upper-tropospheric drops than CF, but neither appears to affect warm-cloud hydrometeor distributions or aerosol scavenging substantially."
"7201504886;56324515500;56270311300;7402786837;56154540200;57193157387;57193073844;8696069500;","MACv2-SP: A parameterization of anthropogenic aerosol optical properties and an associated Twomey effect for use in CMIP6",2017,"10.5194/gmd-10-433-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85011263995&doi=10.5194%2fgmd-10-433-2017&partnerID=40&md5=ac004681fe90c4c54abc2f12f8cd3b58","A simple plume implementation of the second version (v2) of the Max Planck Institute Aerosol Climatology, MACv2-SP, is described. MACv2-SP provides a prescription of anthropogenic aerosol optical properties and an associated Twomey effect. It was created to provide a harmonized description of post-1850 anthropogenic aerosol radiative forcing for climate modeling studies. MACv2-SP has been designed to be easy to implement, change and use, and thereby enable studies exploring the climatic effects of different patterns of aerosol radiative forcing, including a Twomey effect. MACv2-SP is formulated in terms of nine spatial plumes associated with different major anthropogenic source regions. The shape of the plumes is fit to the Max Planck Institute Aerosol Climatology, version 2, whose present-day (2005) distribution is anchored by surface-based observations. Two types of plumes are considered: one predominantly associated with biomass burning, the other with industrial emissions. These differ in the prescription of their annual cycle and in their optical properties, thereby implicitly accounting for different contributions of absorbing aerosol to the different plumes. A Twomey effect for each plume is prescribed as a change in the host model's background cloud-droplet population density using relationships derived from satellite data. Year-to-year variations in the amplitude of the plumes over the historical period (1850-2016) are derived by scaling the plumes with associated national emission sources of SO2 and NH3. Experiments using MACv2-SP are performed with the Max Planck Institute Earth System Model. The globally and annually averaged instantaneous and effective aerosol radiative forcings are estimated to be -0.6 and -0.5 W m-2, respectively. Forcing from aerosol-cloud interactions (the Twomey effect) offsets the reduction of clear-sky forcing by clouds, so that the net effect of clouds on the aerosol forcing is small; hence, the clear-sky forcing, which is more readily measurable, provides a good estimate of the total aerosol forcing. © Author(s) 2017."
"10139397300;35810775100;24463029300;7405666962;7004469744;12806941900;","Impact of the modal aerosol scheme GLOMAP-mode on aerosol forcing in the hadley centre global environmental model",2013,"10.5194/acp-13-3027-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880534397&doi=10.5194%2facp-13-3027-2013&partnerID=40&md5=e2efc3bbcf9778017599d6e4c3a7ce1f","The Hadley Centre Global Environmental Model (HadGEM) includes two aerosol schemes: the Coupled Large-scale Aerosol Simulator for Studies in Climate (CLASSIC), and the new Global Model of Aerosol Processes (GLOMAP-mode). GLOMAP-mode is a modal aerosol microphysics scheme that simulates not only aerosol mass but also aerosol number, represents internally-mixed particles, and includes aerosol microphysical processes such as nucleation. In this study, both schemes provide hindcast simulations of natural and anthropogenic aerosol species for the period 2000-2006. HadGEM simulations of the aerosol optical depth using GLOMAP-mode compare better than CLASSIC against a data-assimilated aerosol re-analysis and aerosol ground-based observations. Because of differences in wet deposition rates, GLOMAP-mode sulphate aerosol residence time is two days longer than CLASSIC sulphate aerosols, whereas black carbon residence time is much shorter. As a result, CLASSIC underestimates aerosol optical depths in continental regions of the Northern Hemisphere and likely overestimates absorption in remote regions. Aerosol direct and first indirect radiative forcings are computed from simulations of aerosols with emissions for the year 1850 and 2000. In 1850, GLOMAP-mode predicts lower aerosol optical depths and higher cloud droplet number concentrations than CLASSIC. Consequently, simulated clouds are much less susceptible to natural and anthropogenic aerosol changes when the microphysical scheme is used. In particular, the response of cloud condensation nuclei to an increase in dimethyl sulphide emissions becomes a factor of four smaller. The combined effect of different 1850 baselines, residence times, and abilities to affect cloud droplet number, leads to substantial differences in the aerosol forcings simulated by the two schemes. GLOMAP-mode finds a presentday direct aerosol forcing of -0.49Wm-2 on a global average, 72% stronger than the corresponding forcing from CLASSIC. This difference is compensated by changes in first indirect aerosol forcing: the forcing of -1.17Wm-2 obtained with GLOMAP-mode is 20% weaker than with CLASSIC. Results suggest that mass-based schemes such as CLASSIC lack the necessary sophistication to provide realistic input to aerosol-cloud interaction schemes. Furthermore, the importance of the 1850 baseline highlights how model skill in predicting present-day aerosol does not guarantee reliable forcing estimates. Those findings suggest that the more complex representation of aerosol processes in microphysical schemes improves the fidelity of simulated aerosol forcings. © Author(s) 2013."
"7103158465;57193882808;","Cloud-system resolving model simulations of aerosol indirect effects on tropical deep convection and its thermodynamic environment",2011,"10.5194/acp-11-10503-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80055060836&doi=10.5194%2facp-11-10503-2011&partnerID=40&md5=0da6287bbe60b070022f035f47df9c56","This paper presents results from 240-member ensemble simulations of aerosol indirect effects on tropical deep convection and its thermodynamic environment. Simulations using a two-dimensional cloud-system resolving model are run with pristine, polluted, or highly polluted aerosol conditions and large-scale forcing from a 6-day period of active monsoon conditions during the 2006 Tropical Warm Pool-International Cloud Experiment (TWP-ICE). Domain-mean surface precipitation is insensitive to aerosols primarily because the large-scale forcing is prescribed and dominates the water and static energy budgets. The spread of the top-of-atmosphere (TOA) shortwave and longwave radiative fluxes among different ensemble members for the same aerosol loading is surprisingly large, exceeding 25 W m-2 even when averaged over the 6-day period. This variability is caused by random fluctuations in the strength and timing of individual deep convective events. The ensemble approach demonstrates a small weakening of convection averaged over the 6-day period in the polluted simulations compared to pristine. Despite this weakening, the cloud top heights and anvil ice mixing ratios are higher in polluted conditions. This occurs because of the larger concentrations of cloud droplets that freeze, leading directly to higher ice particle concentrations, smaller ice particle sizes, and smaller fall velocities compared to simulations with pristine aerosols. Weaker convection in polluted conditions is a direct result of the changes in anvil ice characteristics and subsequent upper-tropospheric radiative heating and weaker tropospheric destabilization. Such a conclusion offers a different interpretation of recent satellite observations of tropical deep convection in pristine and polluted environments compared to the hypothesis of aerosol-induced convective invigoration. Sensitivity tests using the ensemble approach with modified microphysical parameters or domain configuration (horizontal gridlength, domain size) produce results that are similar to baseline, although there are quantitative differences in estimates of aerosol impacts on TOA radiative fluxes. © 2011 Author(s)."
"55501554900;36538539800;56149492300;57206910481;7004713805;","Implementation and initial application of new chemistry-aerosol options in WRF/Chem for simulating secondary organic aerosols and aerosol indirect effects for regional air quality",2015,"10.1016/j.atmosenv.2014.12.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926161331&doi=10.1016%2fj.atmosenv.2014.12.007&partnerID=40&md5=9459085261737b902077c7bfef1c473e","Atmospheric aerosols play important roles in affecting regional meteorology and air quality through aerosol direct and indirect effects. Two new chemistry-aerosol options have been developed in WRF/Chem v3.4.1 by incorporating the 2005 Carbon Bond (CB05) mechanism and coupling it with the existing aerosol module MADE with SORGAM and VBS modules for simulating secondary organic aerosol (SOA), aqueous-phase chemistry in both large scale and convective clouds, and aerosol feedback processes (hereafter CB05-MADE/SORGAM and CB05-MADE/VBS). As part of the Air Quality Model Evaluation International Initiative (AQMEII) Phase II model intercomparison that focuses on online-coupled meteorology and chemistry models, WRF/Chem with the two new options is applied to an area over North America for July 2006 episode. The simulations with both options can reproduce reasonably well most of the observed meteorological variables, chemical concentrations, and aerosol/cloud properties. Compared to CB05-MADE/SORGAM, CB05-MADE/VBS greatly improves the model performance for organic carbon (OC) and PM2.5, reducing NMBs from -81.2% to -13.1% and from -26.1% to -15.6%, respectively. Sensitivity simulations show that the aerosol indirect effects (including aqueous-phase chemistry) can reduce the net surface solar radiation by up to 53 W m-2 with a domainwide mean of 12 W m-2 through affecting cloud formation and radiation scattering and reflection by increasing cloud cover, which in turn reduce the surface temperature, NO2 photolytic rate, and planetary boundary layer height by up to 0.3 °C, 3.7 min-1, and 64 m, respectively. The changes of those meteorological variables further impact the air quality through the complex chemistry-aerosol-cloud-radiation interactions by reducing O3 mixing ratios by up to 5.0 ppb. The results of this work demonstrate the importance of aerosol indirect effects on the regional climate and air quality. For comparison, the impacts of aerosol direct effects on both regional meteorology and air quality are much lower with the reduction on net surface solar radiation only by up to 17 W m-2 and O3 only by up to 1.4 ppb, which indicates the importance and necessity to accurately represent the aerosol indirect effects in the online-couple regional models. © 2014 Elsevier Ltd."
"55682691500;8550791300;18437651200;55682811900;7004364676;25624725200;55802292700;35798085000;55885038100;55925722100;7006415284;","Immersion freezing of birch pollen washing water",2013,"10.5194/acp-13-10989-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887483973&doi=10.5194%2facp-13-10989-2013&partnerID=40&md5=b3c51f2c29a5e74f873f010663a84c41","Birch pollen grains are known to be ice nucleating active biological particles. The ice nucleating activity has previously been tracked down to biological macromolecules that can be easily extracted from the pollen grains in water. In the present study, we investigated the immersion freezing behavior of these ice nucleating active (INA) macromolecules. Therefore we measured the frozen fractions of particles generated from birch pollen washing water as a function of temperature at the Leipzig Aerosol Cloud Interaction Simulator (LACIS). Two different birch pollen samples were considered, with one originating from Sweden and one from the Czech Republic. For the Czech and Swedish birch pollen samples, freezing was observed to start at-19 and-17 °C, respectively. The fraction of frozen droplets increased for both samples down to-24 °C. Further cooling did not increase the frozen fractions any more. Instead, a plateau formed at frozen fractions below 1. This fact could be used to determine the amount of INA macromolecules in the droplets examined here, which in turn allowed for the determination of nucleation rates for single INA macromolecules. The main differences between the Swedish birch pollen and the Czech birch pollen were obvious in the temperature range between-17 and-24 °C. In this range, a second plateau region could be seen for Swedish birch pollen. As we assume INA macromolecules to be the reason for the ice nucleation, we concluded that birch pollen is able to produce at least two different types of INA macromolecules. We were able to derive parameterizations for the heterogeneous nucleation rates for both INA macromolecule types, using two different methods: a simple exponential fit and the Soccer ball model. With these parameterization methods we were able to describe the ice nucleation behavior of single INA macromolecules from both the Czech and the Swedish birch pollen. © 2013 Author(s)."
"55519994900;23991212200;7003666669;56162305900;55411439700;7202252296;","Constraining the influence of natural variability to improve estimates of global aerosol indirect effects in a nudged version of the Community Atmosphere Model 5",2012,"10.1029/2012JD018588","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870917592&doi=10.1029%2f2012JD018588&partnerID=40&md5=aca35edc6a9188042f750b53d13c5f17","Natural modes of variability on many timescales influence aerosol particle distributions and cloud properties such that isolating statistically significant differences in cloud radiative forcing due to anthropogenic aerosol perturbations (indirect effects) typically requires integrating over long simulations. For state-of-the-art global climate models (GCM), especially those in which embedded cloud-resolving models replace conventional statistical parameterizations (i.e., multiscale modeling framework, MMF), the required long integrations can be prohibitively expensive. Here an alternative approach is explored, which implements Newtonian relaxation (nudging) to constrain simulations with both pre-industrial and present-day aerosol emissions toward identical meteorological conditions, thus reducing differences in natural variability and dampening feedback responses in order to isolate radiative forcing. Ten-year GCM simulations with nudging provide a more stable estimate of the global-annual mean net aerosol indirect radiative forcing than do conventional free-running simulations. The estimates have mean values and 95% confidence intervals of -1.19 0.02 W/m2 and -1.37 0.13 W/m 2 for nudged and free-running simulations, respectively. Nudging also substantially increases the fraction of the world's area in which a statistically significant aerosol indirect effect can be detected (66% and 28% of the Earth's surface for nudged and free-running simulations, respectively). One-year MMF simulations with and without nudging provide global-annual mean net aerosol indirect radiative forcing estimates of -0.81 W/m2 and -0.82 W/m2, respectively. These results compare well with previous estimates from three-year free-running MMF simulations (-0.83 W/m2), which showed the aerosol-cloud relationship to be in better agreement with observations and high-resolution models than in the results obtained with conventional cloud parameterizations. © 2012. American Geophysical Union. All Rights Reserved."
"35264611800;7003591311;7101846027;7004885872;24341429500;7006572336;57196499374;","Aerosol-cloud relationships in continental shallow cumulus",2008,"10.1029/2007JD009354","https://www.scopus.com/inward/record.uri?eid=2-s2.0-50849112002&doi=10.1029%2f2007JD009354&partnerID=40&md5=01ee3f99d25f008b0e226ab8a0ce7615","Aerosol-cloud relationships are derived from 14 warm continental cumuli cases sampled during the 2006 Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS) by the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft. Cloud droplet number concentration is clearly proportional to the subcloud accumulation mode aerosol number concentration. An inverse correlation between cloud top effective radius and subcloud aerosol number concentration is observed when cloud depth variations are accounted for. There are no discernable aerosol effects on cloud droplet spectral dispersion; the averaged spectral relative dispersion is 0.30 ± 0.04. Aerosol-cloud relationships are also identified from comparison of two isolated cloud cases that occurred under different degrees of anthropogenic influence. Cloud liquid water content, cloud droplet number concentration, and cloud top effective radius exhibit subadiabaticity resulting from entrainment mixing processes. The degree of LWC subadiabaticity is found to increase with cloud depth. Impacts of subadiabaticity on cloud optical properties are assessed. It is estimated that owing to entrainment mixing, cloud LWP, effective radius, and cloud albedo are decreased by 50-85%, 5-35%, and 2-26%, respectively, relative to adiabatic values of a plane-parallel cloud. The impact of subadiabaticity on cloud albedo is largest for shallow clouds. Results suggest that the effect of entrainment mixing must be accounted for when evaluating the aerosol indirect effect. Copyright 2008 by the American Geophysical Union."
"35264611800;57196499374;","Study of the aerosol indirect effect by large-eddy simulation of marine stratocumulus",2005,"10.1175/JAS3584.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28844433671&doi=10.1175%2fJAS3584.1&partnerID=40&md5=9fe19475a2d23dc76a190b35f5401af5","A total of 98 three-dimensional large-eddy simulations (LESs) of marine stratocumulus clouds covering both nighttime and daytime conditions were performed to explore the response of cloud optical depth (τ) to various aerosol number concentrations (Na = 50-2500 cm-3) and the covarying meteorological conditions (large-scale divergence rate and SST). The idealized First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE) and the Atlantic Stratocumulus Transition Experiment (ASTEX) Lagrangian 1 sounding profiles were used to represent the lightly and heavily drizzling cases, respectively. The first and second aerosol indirect effects are identified. Through statistical analysis, τ is found be to both positively correlated with Na and cloud liquid water path (LWP) with a higher correlation associated with LWP, which is predominantly regulated by large-scale subsidence and SST. Clouds with high LWP occur under low SST or weak large-scale subsidence. Introduction of a small amount of giant sea salt aerosol into the simulation lowers the number of cloud droplets activated, results in larger cloud droplets, and initiates precipitation for nondrizzling polluted clouds or precedes the precipitation process for drizzling clouds. However, giant sea salt aerosol is found to have a negligible effect on τ for lightly precipitating cases, while resulting in a relative reduction of τ of 3%-77% (increasing with Na, for Na = 1000-2500 cm-3) for heavily precipitating cases, suggesting that the impact of giant sea salt is only important for moist and potentially convective clouds. Finally, a regression analysis of the simulations shows that the second indirect effect is more evident in clear than polluted cases. The second indirect effect is found to enhance (reduce) the overall aerosol indirect effect for heavily (lightly) drizzling clouds; that is, τ is larger (smaller) for the same relative change in Na than considering the Twomey (first indirect) effect alone. The aerosol indirect effect (on τ) is lessened in the daytime afternoon conditions and is dominated by the Twomey effect; however, the effect in the early morning is close but slightly smaller than that in the nocturnal run. Diurnal variations of the aerosol indirect effect should be considered to accurately assess its magnitude. © 2005 American Meteorological Society."
"55879681300;54941580100;55938109300;6701342931;7006304904;39361670300;13007286600;55807448700;55490048900;8625148400;24767977600;22635720500;7003862871;54982705800;6505947323;9738422100;","Analysis of the WRF-Chem contributions to AQMEII phase2 with respect to aerosol radiative feedbacks on meteorology and pollutant distributions",2015,"10.1016/j.atmosenv.2014.10.056","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937151502&doi=10.1016%2fj.atmosenv.2014.10.056&partnerID=40&md5=898d32d2bae5aa6fd509900ec98ae2b0","As a contribution to phase2 of the Air Quality Model Evaluation International Initiative (AQMEII), eight different simulations for the year 2010 were performed with WRF-Chem for the European domain. The four simulations using RADM2 gas-phase chemistry and the MADE/SORGAM aerosol module are analyzed in this paper. The simulations included different degrees of aerosol-meteorology feedback, ranging from no aerosol effects at all to the inclusion of the aerosol direct radiative effect as well as aerosol cloud interactions and the aerosol indirect effect. In addition, a modification of the RADM2 gas phase chemistry solver was tested. The yearly simulations allow characterizing the average impact of the consideration of feedback effects on meteorology and pollutant concentrations and an analysis of the seasonality. Pronounced feedback effects were found for the summer 2010 Russian wildfire episode, where the direct aerosol effect lowered the seasonal mean solar radiation by 20Wm-3 and seasonal mean temperature by 0.25°. This might be considered as a lower limit as it must be taken into account that aerosol concentrations were generally underestimated by up to 50%. The high aerosol concentrations from the wildfires resulted in a 10%-30% decreased precipitation over Russia when aerosol cloud interactions were taken into account. The most pronounced and persistent feedback due to the indirect aerosol effect was found for regions with very low aerosol concentrations like the Atlantic and Northern Europe. The low aerosol concentrations in this area result in very low cloud droplet numbers between 5 and 100dropletscm-1 and a 50-70% lower cloud liquid water path. This leads to an increase in the downward solar radiation by almost 50%. Over Northern Scandinavia, this results in almost one degree higher mean temperatures during summer. In winter, the decreased liquid water path resulted in increased long-wave cooling and a decrease of the mean temperature by almost the same amount. Precipitation over the Atlantic Ocean was found to be enhanced by up to 30% when aerosol cloud interactions were taken into account. The inclusion of aerosol cloud interactions can reduce the bias or improve correlations of simulated precipitation for some episodes and regions. However, the domain and time averaged performance statistics do not indicate a general improvement when aerosol feedbacks are taken into account. Except for conditions with either very low or very high aerosol concentrations, the impact of aerosol feedbacks on pollutant distributions was found to be smaller than the effect of the choice of the chemistry module or wet deposition implementation. © 2014 The Authors."
"7007067997;7004346367;57203053317;13406672500;35464731600;6603452105;7402565763;13406162800;35273334200;","Aerosol indirect effect over the Indian Ocean",2006,"10.1029/2005GL025397","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646444906&doi=10.1029%2f2005GL025397&partnerID=40&md5=ec5131c7c9c7ea07541de754347c25f7","We analyze the MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data over the seas adjacent to the Indian sub-continent to investigate the effect of aerosols on the size distribution of cloud droplets and ice crystals (indirect aerosol effect). During the winter months of increased anthropogenic pollution we observe smaller sizes of cloud droplets in water clouds in agreement with the expected aerosol indirect effect. However, contrary to our expectations, we find that during episodes of increased pollution the effective radius of ice crystals is shifted toward the larger rather than smaller sizes. We propose a combination of natural seasonal variability of meteorological conditions and an ""inverse aerosol indirect effect"" caused by heterogeneous ice nucleation as a possible explanation of observed ice crystal growth. The ECHAM4 (European Center for Medium-Range Weather Forecast Hamburg version 4th generation GCM) results with heterogeneous ice nucleation reproduce the observed increase in ice crystal size during the enhanced pollution episodes. Copyright 2006 by the American Geophysical Union."
"8309699900;6701378450;6505919411;","Chemical and dynamical effects on cloud droplet number: Implications for estimates of the aerosol indirect effect",2004,"10.1029/2004JD004596","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14344262447&doi=10.1029%2f2004JD004596&partnerID=40&md5=d348a8a766d9d2f7c67ff511fe8f2323","Most aerosol-cloud-climate assessment studies use empirical aerosol number/droplet number relationships, which are subject to large variability. Historically, this variability has been attributed to unresolved variations in updraft velocity. We revisit this postulation and assess the effects of both updraft velocity and chemical composition on this variability. In doing so we utilize an inverse modeling approach. Using a detailed numerical cloud parcel model and published aerosol characteristics, with published correlations of cloud droplet versus sulfate and cloud droplet versus aerosol number as constraints, we determine a most probable size distribution and updraft velocity for polluted and clean conditions of cloud formation. A sensitivity analysis is then performed to study the variation in cloud droplet number with changes in aerosol chemistry and updraft velocities. This addresses the need to estimate the importance of chemical effects on spatial scales relevant for global climate models. Our analysis suggests that the effect of organic surfactants can introduce as much variability in cloud droplet number as the effect of expected variations in updraft velocity. In addition, the presence of organics seems to further enhance the sensitivity of droplet concentration to vertical velocity variability. The variability from organic surfactants is seen to be insensitive to variations in aerosol number concentration, implying that such effects can affect cloud droplet number consistently over large spatial scales. Our findings suggest that organics can be as important to the aerosol indirect effect as the effect of unresolved cloud dynamics, and they illustrate the potential and complex role of chemical effects on aerosol-cloud interactions. Copyright 2004 by the American Geophysical Union."
"6602600408;57203200427;","Constraining the first aerosol indirect radiative forcing in the LMDZ GCM using POLDER and MODIS satellite data",2005,"10.1029/2005GL023850","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27544439576&doi=10.1029%2f2005GL023850&partnerID=40&md5=711845df2d2017f97876aecc0ee98a67","The indirect effects of anthropogenic aerosols are expected to cause a significant radiative forcing of the Earth's climate whose magnitude, however, is still uncertain. Most climate models use parameterizations for the aerosol indirect effects based on so-called ""empirical relationships"" which link the cloud droplet number concentration to the aerosol concentration. New satellite datasets such as those from the POLDER and MODIS instruments are well suited to evaluate and improve such parameterizations at a global scale. We derive statistical relationships of cloud-top droplet radius and aerosol index (or aerosol optical depth) from satellite retrievals and fit an empirical parameterization in a general circulation model to match the relationships. When applying the fitted parameterizations in the model, the simulated radiative forcing by the first aerosol indirect effect is reduced by 50% as compared to our baseline simulation (down to -0.3 and -0.4 Wm-2 when using MODIS and POLDER satellite data, respectively). Copyright 2005 by the American Geophysical Union."
"55487674700;57203053317;57214899685;56139519000;8611379900;6603452105;","Contribution of changes in sea surface temperature and aerosol loading to the decreasing precipitation trend in southern China",2005,"10.1175/JCLI3341.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20444469599&doi=10.1175%2fJCLI3341.1&partnerID=40&md5=8b78b4545f99a6b6a5105b5c7a93ba62","The effects of increasing sea surface temperature (SST) and aerosol loading in a drought region in Southern China are studied using aerosol optical depth (AOD), low-level cloud cover (LCC), visibility, and precipitation from observed surface data; wind, temperature, specific humidity, and geopotential height from the NCEP-NCAR reanalysis fields; and SST from the NOAA archive data. The results show a warming of the SST in the South China Sea and the Indian Ocean, and a strengthening of the West Pacific Subtropical High (WPSH) in the early summer during the last 40 yr, with the high pressure system extending farther westward over the continent in Southern China. Because the early summer average temperature contrast between the land and ocean decreased, the southwesterly monsoon from the ocean onto mainland China weakened and a surface horizontal wind divergence anomaly occurred over Southern China stabilizing the boundary layer. Thus, less moisture was transported to Southern China, causing a drying trend. Despite this, surface observations show that AOD and LCC have increased, while visibility has decreased. Precipitation has decreased in this region in the early summer, consistent with both the second aerosol indirect effect (reduction in precipitation efficiency caused by the more numerous and smaller cloud droplets) and dynamically induced changes from convective to more stratiform clouds. The second aerosol indirect effect and increases in SST and greenhouse gases (GHG) were simulated separately with the ECHAM4 general circulation model (GCM). The GCM results suggest that both effects contribute to the changes in LCC and precipitation in the drought region in Southern China. The flooding trend in Eastern China, however, is more likely caused by strengthened convective precipitation associated with increases in SST and GHG. © 2005 American Meteorological Society."
"7006415284;7202779940;6701843835;7005174340;7005228425;7006307463;7005465800;8550791300;56612704000;","Laboratory studies and numerical simulations of cloud droplet formation under realistic supersaturation conditions",2004,"10.1175/1520-0426(2004)021<0876:LSANSO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3242666767&doi=10.1175%2f1520-0426%282004%29021%3c0876%3aLSANSO%3e2.0.CO%3b2&partnerID=40&md5=73c4320cb14326827d029d2014f25345","In this paper, a new device is introduced to study the formation and growth of cloud droplets under near-atmospheric supersaturations. The new device, called the Leipzig Aerosol Cloud Interaction Simulator (LACIS), is based on a laminar flow tube. It has been designed to reproduce the thermodynamic conditions of atmospheric clouds as realistically as possible. A series of experiments have been conducted that prove the definition and stability of the flow field inside the LACIS as well as the stability and reproducibility of the generated droplet size distributions as a function of the applied thermodynamic conditions. Measured droplet size distributions are in good agreement with those determined by a newly developed Eulerian particle-droplet dynamical model. Further investigations will focus on the influences of latent heat release during vapor condensation on the tube walls and the development of a more suitable optical particle counter for droplet size determination. © 2004 American Meteorological Society."
"57151771800;7401776640;7102953444;","Evaluation of multidecadal variability in CMIP5 surface solar radiation and inferred underestimation of aerosol direct effects over Europe, China, Japan, and India",2013,"10.1002/jgrd.50426","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880896083&doi=10.1002%2fjgrd.50426&partnerID=40&md5=765c056bfd5e617ec3cadeed8c430318","Observations from the Global Energy Balance Archive indicate regional decreases in all sky surface solar radiation from ∼1950s to 1980s, followed by an increase during the 1990s. These periods are popularly called dimming and brightening, respectively. Removal of the radiative effects of cloud cover variability from all sky surface solar radiation results in a quantity called ""clear sky proxy"" radiation, in which multidecadal trends can be seen more distinctly, suggesting aerosol radiative forcing as a likely cause. Prior work has shown climate models from the Coupled Model Intercomparison Project 3 (CMIP3) generally underestimate the magnitude of these trends, particularly over China and India. Here we perform a similar analysis with 173 simulations from 42 climate models participating in the new CMIP5. Results show negligible improvement over CMIP3, as CMIP5 dimming trends over four regions - Europe, China, India, and Japan - are all underestimated. This bias is largest for both India and China, where the multimodel mean yields a decrease in clear sky proxy radiation of -1.3±0.3 and -1.2±0.2 W m-2decade -1, respectively, compared to observed decreases of -6.5±0.9 and -8.2±1.3 W m-2decade-1. Similar underestimation of the observed dimming over Japan exists, with the CMIP5 mean dimming ∼20% as large as observed. Moreover, not a single simulation reproduces the magnitude of the observed dimming trend for these three regions. Relative to dimming, CMIP5 models better simulate the observed brightening, but significant underestimation exists for both China and Japan. Overall, no individual model performs particularly well for all four regions. Model biases do not appear to be related to the use of prescribed versus prognostic aerosols or to aerosol indirect effects. However, models exhibit significant correlations between clear sky proxy radiation and several aerosol-related fields, most notably aerosol optical depth (AOD) and absorption AOD. This suggests model underestimation of the observed trends is related to underestimation of aerosol direct radiative forcing and/or deficient aerosol emission inventories. Key Points CMIP5 models underestimate the magnitude of observed dimming and brightening Models exhibit correlations between solar radiation and several aerosol fields Underestimation is related to aerosol direct forcing and/or emissions © 2013. American Geophysical Union. All Rights Reserved."
"7004198777;57202521210;","Droplet nuclei in non-precipitating clouds: Composition and size matter",2008,"10.1088/1748-9326/3/4/045002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62749163061&doi=10.1088%2f1748-9326%2f3%2f4%2f045002&partnerID=40&md5=98188710542b7a30d780d10a0dd8d7cd","The composition of cloud droplet nuclei was compared to the composition of ambient aerosol particles in non-precipitating clouds in different regions. Single-particle electron microscope techniques were used to identify particle types. The smallest particles (<0.2νm diameter) exhibited a dependence of composition on nucleating ability, with salts (chlorides and sulfates of Na, K, Ca and Mg) being preferred nuclei types, followed by ammonium sulfates and organics. Crustal and industrial metals were less likely to be incorporated into cloud droplets. However, for experiments where only larger particles were sampled, a weaker dependence on composition was found. This suggests that larger particles have sufficient soluble material to nucleate despite their primary type. Both size and composition seem to be important, with composition becoming increasingly important as smaller particles activate at higher supersaturations in the cloudy environment. © 2008 IOP Publishing Ltd."
"7102084129;","Aerosol-cloud interactions control of earth radiation and latent heat release budgets",2006,"10.1007/s11214-006-9053-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847321222&doi=10.1007%2fs11214-006-9053-6&partnerID=40&md5=7ef8ce57fc4ef5aa136b0c8d4e202704","Aircraft observations and model simulations show that cloud development is strongly modulated by the impact of cloud-aerosol interactions on precipitation forming processes. New insights into the mechanisms by which aerosols dominate the cloud cover of marine shallow clouds suggest that feedbacks between the cloud microstructure and cloud dynamics through precipitation processes play a major role in determining when a solid cloud cover will break up into a field of trade wind cumulus. Cloud-aerosol interactions dominate not only the dynamics of marine shallow clouds, but also the lifetime and the vertical disposition of latent heat of deep convective clouds over ocean and even more strongly over land. Recent coincident satellite measurements of aerosols and cloud properties quantify the aerosol effects on cloud cover and radiative forcing on regional and global scales. The shapes of the satellite retrieved relations between aerosols and cloud properties are consistent with the suggested ways by which aerosols affect clouds via precipitation processes, particularly by affecting the intensity of the cloud vertical air motions and its vertical development. © Springer Science+Business Media, Inc. 2007."
"7403577184;7006614696;35453054300;7202772927;","Impact of aerosols and atmospheric thermodynamics on cloud properties within the climate system",2004,"10.1029/2003gl019287","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18544403362&doi=10.1029%2f2003gl019287&partnerID=40&md5=b0c7fd25563f45e6d1af147a9f7d56df","A combination of cloud-top and columnar droplet sizes derived from the multi Tropical Rainfall Measurement Mission (TRMM) sensors reveals the sensitivity of the aerosols effect on cloud-precipitation processes due to environmental vertical thermodynamic structure. First, the magnitude of aerosol indirect effect could be larger with the analysis of columnar droplet sizes than that derived from the cloud-top droplet sizes since column-droplet size can account for the broader droplet spectra in the cloud layers. Second, a combination of cloud-top and columnar droplet sizes reveals that the warm rain process is prevented regardless of the aerosols concentration under high static stability such as when a strong temperature inversion exists, while a high aerosol concentration suppresses the warm rain formulation under low static stability. Copyright 2004 by the American Geophysical Union."
"7402565763;","Cloud condensation nuclei near marine cumulus",1993,"10.1029/92JD02169","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027505162&doi=10.1029%2f92JD02169&partnerID=40&md5=e61c889b6e8a11d61dd4e17ef3a8fb44","Extensive airborne measurements of cloud condensation nucleus (CCN) spectra and condensation nuclei below, in, between, and above the cumulus clouds near Hawaii point to important aerosol-cloud interactions. Consistent particle concentrations of 200 cm-3 were found above the marine boundary layer and within the noncloudy marine boundary layer. Lower and more variable CCN concentrations within the cloudy boundary layer, especially very close to the clouds, appear to be a result of cloud scavenging processes. Gravitational coagulation of cloud droplets may be the principal cause of this difference in the vertical distribution of CCN. The results suggest a reservoir of CCN in the free troposphere which can act as a source for the marine boundary layer. -Author"
"55574865800;8953662800;55720362700;56135632400;57206424059;56610909100;56610914500;55822242600;24755928100;","Multi-sensor quantification of aerosol-induced variability in warm clouds over eastern China",2015,"10.1016/j.atmosenv.2015.04.063","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928725849&doi=10.1016%2fj.atmosenv.2015.04.063&partnerID=40&md5=eff4b09f9daf9ae444bcf9e1cc55c252","Aerosol-cloud (AC) interactions remain uncharacterized due to difficulties in obtaining accurate aerosol and cloud observations. In this study, we quantified the aerosol indirect effects (AIE) on warm clouds over Eastern China based on near-simultaneous retrievals from MODIS/AQUA, CALIOP/CALIPSO, and CPR/CLOUDSAT between June 2006 and December 2010. The seasonality of aerosols from ground-based PM<inf>10</inf> (aerosol particles with diameter of 10μm or less) significantly differed from that estimated using MODIS aerosol optical depth (AOD). This result was supported by the lower level frequency profile of aerosol occurrence from CALIOP, indicative of the significant role of CALIOP in the AC interaction. To focus on warm clouds, cloud layers with base (top) altitudes above 7 (10) km were excluded. The combination of CALIOP and CPR was applied to determine the exact position of warm clouds relative to aerosols out of the following six scenarios in terms of AC mixing states: 1) aerosol only (AO); 2) cloud only (CO); 3) single aerosol layer-single cloud layer (SASC); 4) single aerosol layer-double cloud layers (SADC); 5) double aerosol layers - single cloud layer (DASC); and 6) others. The cases with vertical distance between aerosol and cloud layer less (more) than 100m (700m) were marked mixed (separated), and the rest as uncertain. Results showed that only 8.95% (7.53%) belonged to the mixed (separated and uncertain) state among all of the collocated AC overlapping cases, including SASC, SADC, and DASC. Under mixed conditions, the cloud droplet effective radius (CDR) decreased with increasing AOD at moderate aerosol loading (AOD<0.4), and then became saturated at an AOD of around 0.5, followed by an increase in CDR with increasing AOD, known as boomerang shape. Under separated conditions, no apparent changes in CDR with AOD were observed. We categorized the AC dataset into summer- and winter-season subsets to determine how the boomerang shape varied with season. The response of CDR to AOD in summer exhibited similar but much more deepened boomerang shape, as compared with the all year round case. In contrast, CDR in winter did not follow the boomerang shape for its continued decreasing with increasing AOD, even after the saturation zone (AOD around 0.5) of a cloud droplet. © 2015 Elsevier Ltd."
"8726272900;7005304841;7005712238;56250250300;12139043600;7003827051;12139310900;35600074800;","The effect of sea ice loss on sea salt aerosol concentrations and the radiative balance in the Arctic",2011,"10.5194/acp-11-3459-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954447911&doi=10.5194%2facp-11-3459-2011&partnerID=40&md5=1754f3c5fe6aa7c6327a5e0939aec725","Understanding Arctic climate change requires knowledge of both the external and the local drivers of Arctic climate as well as local feedbacks within the system. An Arctic feedback mechanism relating changes in sea ice extent to an alteration of the emission of sea salt aerosol and the consequent change in radiative balance is examined. A set of idealized climate model simulations were performed to quantify the radiative effects of changes in sea salt aerosol emissions induced by prescribed changes in sea ice extent. The model was forced using sea ice concentrations consistent with present day conditions and projections of sea ice extent for 2100. Sea salt aerosol emissions increase in response to a decrease in sea ice, the model results showing an annual average increase in number emission over the polar cap (70-90° N) of 86 × 106 m-2 s-1 (mass emission increase of 23 μgm-2 s-1). This in turn leads to an increase in the natural aerosol optical depth of approximately 23%. In response to changes in aerosol optical depth, the natural component of the aerosol direct forcing over the Arctic polar cap is estimated to be between -0.2 and -0.4 W m-2 for the summer months, which results in a negative feedback on the system. The model predicts that the change in first indirect aerosol effect (cloud albedo effect) is approximately a factor of ten greater than the change in direct aerosol forcing although this result is highly uncertain due to the crude representation of Arctic clouds and aerosol-cloud interactions in the model. This study shows that both the natural aerosol direct and first indirect effects are strongly dependent on the surface albedo, highlighting the strong coupling between sea ice, aerosols, Arctic clouds and their radiative effects. © 2011 Author(s)."
"7003880283;7003708056;","A review of our understanding of the aerosol-cloud interaction from the perspective of a bin resolved cloud scale modelling",2010,"10.1016/j.atmosres.2010.05.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955771077&doi=10.1016%2fj.atmosres.2010.05.008&partnerID=40&md5=a32e1d3b145989dd408518391f655638","This review compiles the main results obtained using a mesoscale cloud model with bin resolved cloud micophysics and aerosol particle scavenging, as developed by our group over the years and applied to the simulation of shallow and deep convective clouds. The main features of the model are reviewed in different dynamical frameworks covering parcel model dynamics, as well as 1.5D, 2D and 3D dynamics. The main findings are summarized to yield a digested presentation which completes the general understanding of cloud-aerosol interaction, as currently available from textbook knowledge. Furthermore, it should provide support for general cloud model development, as it will suggest potentially minor processes that might be neglected with respect to more important ones and can support development of parameterizations for air quality, chemical transport and climate models.Our work has shown that in order to analyse dedicated campaign results, the supersaturation field and the complex dynamics of the specific clouds needs to be reproduced. Only 3D dynamics represents the variation of the supersaturation over the entire cloud, the continuous nucleation and deactivation of hydrometeors, and the dependence upon initial particle size distribution and solubility.However, general statements on certain processes can be obtained also by simpler dynamics. In particular, we found:. Nucleation incorporates about 90% of the initial aerosol particle mass inside the cloud drops. Collision and coalescence redistributes the scavenged aerosol particle mass in such a way that the particle mass follows the main water mass. Small drops are more polluted than larger ones, as pollutant mass mixing ratio decreases with drops size. Collision and coalescence mixes the chemical composition of the generated drops. Their complete evaporation will release processed particles that are mostly larger and more hygroscopic than the initial particles. An interstitial aerosol is left unactivated between the cloud drops which is reduced in number and almost devoid of large particles. Consequently, impaction scavenging can probably be neglected inside clouds. Below clouds, impaction scavenging contributes around 30% to the particle mass reaching the ground by a rainfall event. The exact amount depends on the precise case studied. Nucleation and impaction scavenging directly by the ice phase in mixed phase clouds seems to play a minor role with respect to the particle mass that enters the ice particles via freezing of the liquid phase.The aerosol scavenging efficiency generally follows rather closely the precipitation scavenging value. The nucleation scavenging efficiency is around 90% for the liquid phase clouds and impaction scavenging generally contributed to about 30% of the particle mass in the rain. Clouds are very efficient in pumping up the boundary layer aerosol which essentially determines the cloud properties. For a marine case studied the net pumping depleted about 70% of the aerosol from the section of the boundary layer considered. The larger particles (and thus 70% of the mass vented up) got activated inside the cloud. A weak net import through cloud top and the upwind side was found, as well as a larger net export at the downwind side. The outside cloud subsidence can add to the replenishment of the boundary layer and eventually cause a recycling of the particles into the cloud.The results of the parcel model studies seem to indicate that increasing particulate pollution and decreasing solubility suppresses rain formation. In individual and short time cloud simulations this behaviour was even confirmed in our 3D model studies. However, taking into account entire cloud fields over longer periods of time yields the strong spatial and temporal variability of the results with isolated regions of inverse correlation of the effects. Even though in general initially the expected behaviour was found, after several hours of simulation, the overall precipitation amounts of the more polluted cases caught up. This suggests that a changing pollution will affect the spatial and temporal pattern of precipitation, but will probably not reduce the overall long term precipitation amount which might be entirely governed by the moisture state of the atmosphere. Our results regarding mixed phase precipitation with respect to ""all liquid"" cases seem to confirm this idea, as with increasing modelling time the precipitation mass of both cases also become similar. © 2010 Elsevier B.V."
"8282268700;35464731600;35887706900;57198938123;","Aerosol-cloud interaction - Misclassification of MODIS clouds in heavy aerosol",2005,"10.1109/TGRS.2005.844662","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16444362816&doi=10.1109%2fTGRS.2005.844662&partnerID=40&md5=2672ec4f912d622d4d796351b00a799b","The accuracy of the spaceborne Moderate Resolution Imaging Spectroradiometer (MODIS) cloud mask was evaluated for possible contamination by areas of heavy aerosol that may be misclassified as clouds. Analysis for several aerosol types shows that the cloud mask and products can be safely used in the presence of aerosol up to optical thickness of 0.6. Here we define as cloudy all MODIS 1-km (at nadir) pixels that were used to derive the cloud effective radius and optical thickness of water and ice clouds. The findings make it possible to study aerosols-cloud interaction from the MODIS aerosol and cloud products. © 2005 IEEE."
"7004556087;35477504600;6602238735;15734577800;6601942466;15735037500;22952188100;7005893321;","Black carbon (BC) in alpine aerosols and cloud water - Concentrations and scavenging efficiencies",2001,"10.1016/S1352-2310(01)00312-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034848873&doi=10.1016%2fS1352-2310%2801%2900312-0&partnerID=40&md5=76596cf65e680303d00d998bb0a386f4","During April 1999 and March 2000, intensive field campaigns were performed on a mid-level mountain (Rax, 1644 m a.s.l.) in Central Europe both under out-of-cloud and in-cloud conditions. The black carbon (BC) content of both aerosol and cloud water as well as BC scavenging efficiencies of Rax clouds were measured. As a tracer for the non-carbonaceous aerosol, sulfate was used. Although BC concentrations on Rax were low (April 1999 out-of-cloud average: 0.43 μg/m3, March 2000: 0.72 μg/m3), the BC mass fraction of the aerosol was fairly high (1999: 3.5%, 2000: 6.4%). Average BC concentrations in cloud water were 1.09 μg/ml (1999) and 1.4 μg/ml (2000). These values are far higher than literature values, but comparable to those found in an earlier study (J. Geophys. Res. 105 (D20) (2000) 24637) at a high-level mountain (Sonnblick, 3106 m a.s.l.) some 200 km distant from Rax. The average BC scavenging efficiency of the Rax clouds in March 2000 was 0.54. The increase of scavenging efficiency with increasing liquid water content of the clouds found earlier on Sonnblick for sulfate and aerosol carbon (J. Atmos. Chem 35 (2000) 33), organic carbon (J. Geophys. Res. 105 (2000) 19857), and BC (J. Geophys. Res. 105 (D20) (2000) 24637) was also confirmed on Rax. © 2001 Elsevier Science Ltd. All rights reserved."
"16185051500;","Aerosol-cloud interactions",1993,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027811314&partnerID=40&md5=a2774da7cbbeb5aabb9df6b1b9ea2a2b","Various aspects of the effects of aerosol on clouds have been studied for many years. This is because the aerosol on which cloud droplets form determine the initial concentrations and sizes of the droplets. Aerosol may also play a role in the formation of ice in clouds. Thus, through their effects on both the nature (water or ice) and the size distribution of cloud particles, aerosol can play a role in determining whether or not clouds precipitate and the radiative properties of clouds. These topics are reviewed in the first part of this chapter. Clouds and precipitation are important sinks for atmospheric aerosol. This affects both the size distribution and chemical nature of atmospheric aerosol, as well as the chemical composition of clouds and precipitation. In addition to modifying existing aerosol, some recent research indicates that clouds can be involved in the nucleation of new aerosol. -from Author"
"8067118800;6701752471;7202899330;","Evaluating cloud tuning in a climate model with satellite observations",2013,"10.1002/grl.50874","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883197442&doi=10.1002%2fgrl.50874&partnerID=40&md5=5f00ce00d8f0ea1974ce56828cdd34c6","This study examines the validity of a tunable cloud parameter, the threshold particle radius triggering the warm rain formation, in a climate model. Alternate values of the model's particular parameter within uncertainty have been shown to produce severely different historical temperature trends due to differing magnitude of aerosol indirect forcing. Three different threshold radii are evaluated against satellite observations in terms of the statistics depicting microphysical process signatures of the warm rain formation. The results show that the simulated temperature trend best matches to observed trend when the model adopts the threshold radius that worst reproduces satellite-observed microphysical statistics and vice versa. This inconsistency between the ""bottom-up"" process-based constraint and the ""top-down"" temperature trend constraint implies the presence of compensating errors in the model. Key Points Evaluating a tunable cloud parameter in a climate model Exposing inconsistency between process-based and temperature-based constraints Implying compensating errors in the climate model. © 2013. American Geophysical Union. All Rights Reserved."
"28568055900;16550482700;7102294773;18437850800;57188966058;57213358341;57210590791;7004838931;7006901405;7101799663;55156148900;8247122100;35208232500;8684037700;22834248200;21933618400;6701562043;","Evaluating WRF-chem aerosol indirect effects in southeast pacific marine stratocumulus during VOCALS-REx",2012,"10.5194/acp-12-3045-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859153497&doi=10.5194%2facp-12-3045-2012&partnerID=40&md5=f0d7ee8e599735734b6a18c7eeb5a1f0","We evaluate a regional-scale simulation with the WRF-Chem model for the VAMOS (Variability of the American Monsoon Systems) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx), which sampled the Southeast Pacific's persistent stratocumulus deck. Evaluation of VOCALS-REx ship-based and three aircraft observations focuses on analyzing how aerosol loading affects marine boundary layer (MBL) dynamics and cloud microphysics. We compare local time series and campaign-averaged longitudinal gradients, and highlight differences in model simulations with (W) and without (NW) wet deposition processes. The higher aerosol loadings in the NW case produce considerable changes in MBL dynamics and cloud microphysics, in accordance with the established conceptual model of aerosol indirect effects. These include increase in cloud albedo, increase in MBL and cloud heights, drizzle suppression, increase in liquid water content, and increase in cloud lifetime. Moreover, better statistical representation of aerosol mass and number concentration improves model fidelity in reproducing observed spatial and temporal variability in cloud properties, including top and base height, droplet concentration, water content, rain rate, optical depth (COD) and liquid water path (LWP). Together, these help to quantify confidence in WRF-Chem's modeled aerosol-cloud interactions, especially in the activation parameterization, while identifying structural and parametric uncertainties including: irreversibility in rain wet removal; overestimation of marine DMS and sea salt emissions, and accelerated aqueous sulfate conversion. Our findings suggest that WRF-Chem simulates marine cloud-aerosol interactions at a level sufficient for applications in forecasting weather and air quality and studying aerosol climate forcing, and may do so with the reliability required for policy analysis. © 2012 Author(s)."
"8309699900;7003663305;7003591311;7005284577;9271096600;7202050065;57209647985;6701378450;24477694300;8147766700;6602890253;7404062492;16480175700;6603872903;7006107059;15833742800;","Cloud condensation nuclei as a modulator of ice processes in Arctic mixed-phase clouds",2011,"10.5194/acp-11-8003-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051631900&doi=10.5194%2facp-11-8003-2011&partnerID=40&md5=241412a8dad0646e585de27c768e3bb0","We propose that cloud condensation nuclei (CCN) concentrations are important for modulating ice formation of Arctic mixed-phase clouds, through modification of the droplet size distribution. Aircraft observations from the Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) study in northern Alaska in April 2008 allow for identification and characterization of both aerosol and trace gas pollutants, which are then compared with cloud microphysical properties. Consistent with previous studies, we find that the concentration of precipitating ice particles (>400 μ) is correlated with the concentration of large droplets (>30 μ). We are further able to link the observed microphysical conditions to aerosol pollution, originating mainly from long range transport of biomass burning emissions. The case studies demonstrate that polluted mixed-phase clouds have narrower droplet size distributions and contain 1-2 orders of magnitude fewer precipitating ice particles than clean clouds at the same temperature. This suggests an aerosol indirect effect leading to greater cloud lifetime, greater cloud emissivity, and reduced precipitation. This result is opposite to the glaciation indirect effect, whereby polluted clouds are expected to precipitate more readily due to an increase in the concentration of particles acting as ice nuclei. © 2011 Author(s)."
"56611366900;7005862399;57208698992;19638935200;","Dispersion bias, dispersion effect, and the aerosol-cloud conundrum",2008,"10.1088/1748-9326/3/4/045021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67651127549&doi=10.1088%2f1748-9326%2f3%2f4%2f045021&partnerID=40&md5=78781302b6239418467ec85d7cef6482","This work examines the influences of relative dispersion (the ratio of the standard deviation to the mean radius of the cloud droplet size distribution) on cloud albedo and cloud radiative forcing, derives an analytical formulation that accounts explicitly for the contribution from droplet concentration and relative dispersion, and presents a new approach to parameterize relative dispersion in climate models. It is shown that inadequate representation of relative dispersion in climate models leads to an overestimation of cloud albedo, resulting in a negative bias of global mean shortwave cloud radiative forcing that can be comparable to the warming caused by doubling CO2 in magnitude, and that this dispersion bias is likely near its maximum for ambient clouds. Relative dispersion is empirically expressed as a function of the quotient between cloud liquid water content and droplet concentration (i.e., water per droplet), yielding an analytical formulation for the first aerosol indirect effect. Further analysis of the new expression reveals that the dispersion effect not only offsets the cooling from the Twomey effect, but is also proportional to the Twomey effect in magnitude. These results suggest that unrealistic representation of relative dispersion in cloud parameterization in general, and evaluation of aerosol indirect effects in particular, is at least in part responsible for several outstanding puzzles of the aerosol-cloud conundrum: for example, overestimation of cloud radiative cooling by climate models compared to satellite observations; large uncertainty and discrepancy in estimates of the aerosol indirect effect; and the lack of interhemispheric difference in cloud albedo. © 2008 IOP Publishing Ltd."
"6603393151;7004008268;7004434383;7005287667;7102496779;7003748130;7004462114;7003566416;57214957433;7005088845;7005228425;","Phase partitioning of aerosol constituents in cloud based on single-particle and bulk analysis",1997,"10.1016/S1352-2310(96)00298-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030616217&doi=10.1016%2fS1352-2310%2896%2900298-1&partnerID=40&md5=829529cb7e807f0ea7777e4220b1a70c","Single-particle analysis, performed by laser microprobe mass spectrometry and bulk analytical techniques were used to study aerosol-cloud interactions within the third field campaign of the EUROTRAC subproject 'ground-based cloud experiments' at the Great Dun Fell, Cumbria, U.K. in spring 1993. The shape of the ridge made it possible for ground-based instrumentation to sample similar parcels of air before, during and after their transit through the cloud. A single jet five-stage minicascade impactor was used for sampling particles of the interstitial aerosol. A second impactor worked in tandem with a counter-flow virtual impactor and collected residues of cloud droplets. Considering marine conditions largest droplets nucleated on sea-salt particles, whereas smaller droplets were formed on sulphate and methane sulphonate containing particles. This clearly indicates chemical inhomogeneities in the droplet phase. Particles, which were disfavoured by droplet formation, often contained the highest amounts of water-insoluble carbonaceous matter. For the submicron size range we found that the carbonaceous matter was always internally mixed with sulphate. The fraction of carbonaceous matter increased with decreasing size. A detectable fraction of particles remained in the cloud interstitial air, although they were in size as well as in composition suitable to form cloud droplets. The findings confirm that nucleation is the most important process affecting phase partitioning in cloud, but that spatial and temporal variations of water vapour supersaturation have also an influence on the observed phase partitioning. Proton induced X-ray emission analysis and light absorption measurements of filter samples showed that the average scavenged fraction was 0.77 for sulphur and 0.57 for soot in clouds formed by continental influenced air and 0.62 and 0.44, respectively, for marine influenced clouds."
"24385643100;36128620700;26638618800;7202252296;7005858285;7403401100;35208232500;56177971000;7006204597;52664748600;10038895100;7004027519;55480310900;6701378450;55481275400;23491184100;16308514000;7005088845;7101846027;57196499374;6602504147;35556482500;7003430284;","Primary marine aerosol-cloud interactions off the coast of California",2015,"10.1002/2014JD022963","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930382428&doi=10.1002%2f2014JD022963&partnerID=40&md5=e64f10deb41c2dd27178880f61eff92b","Primary marine aerosol (PMA)-cloud interactions off the coast of California were investigated using observations of marine aerosol, cloud condensation nuclei (CCN), and stratocumulus clouds during the Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE) and the Stratocumulus Observations of Los-Angeles Emissions Derived Aerosol-Droplets (SOLEDAD) studies. Based on recently reportedmeasurements of PMA size distributions, a constrained lognormal-mode-fitting procedure was devised to isolate PMA number size distributions fromtotal aerosol size distributions and applied to E-PEACEmeasurements. During the 12 day E-PEACE cruise on the R/V Point Sur, PMA typically contributed less than 15% of total particle concentrations. PMA number concentrations averaged 12 cm-3 during a relatively calmer period (average wind speed 12m/s1) lasting 8 days, and 71 cm-3 during a period of higher wind speeds (average 16m/s1) lasting 5 days. On average, PMA contributed less than 10% of total CCN at supersaturations up to 0.9% during the calmer period; however, during the higher wind speed period, PMA comprised 5-63% of CCN (average 16-28%) at supersaturations less than 0.3%. Sea salt was measured directly in the dried residuals of cloud droplets during the SOLEDAD study. The mass fractions of sea salt in the residuals averaged 12 to 24% during three cloud events. Comparing the marine stratocumulus clouds sampled in the two campaigns, measured peak supersaturations were 0.2 ± 0.04% during E-PEACE and 0.05-0.1% during SOLEDAD. The availablemeasurements show that cloud droplet number concentrations increased with &gt; 100 nmparticles in E-PEACE but decreased in the three SOLEDAD cloud events. © 2015. American Geophysical Union. All Rights Reserved."
"7202485447;18635289400;16551540700;23012437100;24344262300;7003377766;7103294028;7101899854;24172779500;","Interactions between biomass-burning aerosols and clouds over Southeast Asia: Current status, challenges, and perspectives",2014,"10.1016/j.envpol.2014.06.036","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908622881&doi=10.1016%2fj.envpol.2014.06.036&partnerID=40&md5=68e277eb4a6ca2e1e53230ed3e00de81","The interactions between aerosols, clouds, and precipitation remain among the largest sources of uncertainty in the Earth's energy budget. Biomass-burning aerosols are a key feature of the global aerosol system, with significant annually-repeating fires in several parts of the world, including Southeast Asia (SEA). SEA in particular provides a ”natural laboratory” for these studies, as smoke travels from source regions downwind in which it is coupled to persistent stratocumulus decks. However, SEA has been under-exploited for these studies. This review summarizes previous related field campaigns in SEA, with a focus on the ongoing Seven South East Asian Studies (7-SEAS) and results from the most recent BASELInE deployment. Progress from remote sensing and modeling studies, along with the challenges faced for these studies, are also discussed. We suggest that improvements to our knowledge of these aerosol/cloud effects require the synergistic use of field measurements with remote sensing and modeling tools. © 2014 Elsevier Ltd. All rights reserved."
"7003591311;19337074400;6603800142;7004174939;7004057920;7101846027;","Aerosol indirect effect studies at Southern Great Plains during the May 2003 Intensive Operations Period",2006,"10.1029/2004JD005648","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646356728&doi=10.1029%2f2004JD005648&partnerID=40&md5=23b3c15a41a14f17d4132d47bd6ede31","During May 2003, the Department of Energy's Atmospheric Radiation Measurement Program conducted an Intensive Operations Period (IOP) to measure the radiative effects of aerosol and clouds. A suite of both in situ and remote sensing measurements were available to measure aerosol and cloud parameters. This paper has three main goals: First, it focuses on comparison between in situ retrievals of the radiatively important drop effective radius r<inf>e</inf> and various satellite, airborne, and surface remote sensing retrievals of the same parameter. On 17 May 2003, there was a fortuitous, near-simultaneous sampling of a stratus cloud by five different methods. The retrievals of r<inf>e</inf> agree with one another to within ∼20%, which is approximately the error estimate for most methods. Second, a methodology for deriving a best estimate of r<inf>e</inf> from these different instruments, with their different physical properties and sampling volumes, is proposed and applied to the 17 May event. Third, the paper examines the response of r<inf>e</inf> to changes in aerosol on 3 days during the experiment and examines the consistency of remote sensing and in situ measurements of the effect of aerosol on r<inf>e</inf>. It is shown that in spite of the generally good agreement in derived re, the magnitude of the response of r<inf>e</inf> to changes in aerosol is quite sensitive to the method of retrieving r<inf>e</inf> and to the aerosol proxy for cloud condensation nuclei. Nonphysical responses are sometimes noted, and it is suggested that further work needs to be done to refine these techniques. Copyright 2006 by the American Geophysical Union."
"7202485288;7004540083;35070788500;7201914101;","Three different behaviors of liquid water path of water clouds in aerosol-cloud interactions",2002,"10.1175/1520-0469(2002)059%3C0726%3ATDBOLW%3E2.0.C","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036330192&doi=10.1175%2f1520-0469%282002%29059%253C0726%253ATDBOLW%253E2.0.C&partnerID=40&md5=47fd9437039d4b7d74db80f841f8edd2","Estimates of the indirect aerosol effect in GCMs assume that either cloud liquid water path is constant (Twomey effect) or increases with increased droplet number concentration (drizzle-suppression or Albrecht effect). On the other hand, if cloud thermodynamics and dynamics are considered, cloud liquid water path may also decrease with increasing droplet number concentration, which has been predicted by model calculations and observed in ship track and urban influence studies. This study examines the different changes of cloud liquid water path associated with changes of cloud droplet number concentration. Satellite data (January, April, July, and October 1987) are used to determine the cloud liquid water sensitivity, defined as the ratio of changes of liquid water path and changes of column droplet number concentration. The results of a global survey for water clouds (cloud-top temperature .273 K, optical thickness ≤ τ ≤ 15) reveal all three behaviors of cloud liquid water path with aerosol changes: increasing, approximately constant, or decreasing as cloud column number concentration increases. The authors find that 1) in about one-third of the cases, predominantly in warmer locations or seasons, the cloud liquid water sensitivity is negative, and the regional and seasonal variations of the negative liquid water sensitivity are consistent with other observations; 2) in about one-third of the cases, a minus onethird (21/3) power-law relation between effective droplet radius and column number concentration is found, consistent with a nearly constant cloud water path; and 3) in the remaining one-third of the cases, the cloud liquid water sensitivity is positive. These results support the suggestion that it is possible for an increase of cloud droplet number concentration to both reduce cloud droplet size and enhance evaporation just below cloud base, which decouples the cloud from the boundary layer in warmer locations, decreasing water supply from surface and reducing cloud liquid water. Results of this study also suggest that the current evaluations of the negative aerosol indirect forcing by GCMs, which are based on either the Twomey or Albrecht effects, may be overestimated in magnitude. © 2002 American Meteorological Society."
"55817400800;55802246600;55476830600;7202048112;7406500188;","A case study of urbanization impact on summer precipitation in the greater Beijing metropolitan area: Urban heat island versus aerosol effects",2015,"10.1002/2015JD023753","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84954360880&doi=10.1002%2f2015JD023753&partnerID=40&md5=6af55dd913c8f19042e0acd2062886d6","Convection-resolving ensemble simulations using the WRF-Chem model coupled with a single-layer Urban Canopy Model are conducted to investigate the individual and combined impacts of land use and anthropogenic pollutant emissions from urbanization on a heavy rainfall event in the Greater Beijing Metropolitan Area (GBMA) in China. The simulation with the urbanization effect included generally captures the spatial pattern and temporal variation of the rainfall event. An improvement of precipitation is found in the experiment including aerosol effect on both clouds and radiation. The expanded urban land cover and increased aerosols have an opposite effect on precipitation processes, with the latter playing a more dominant role, leading to suppressed convection and rainfall over the upstream (northwest) area, and enhanced convection and more precipitation in the downstream (southeast) region of the GBMA. In addition, the influence of aerosol indirect effect is found to overwhelm that of direct effect on precipitation in this rainfall event. Increased aerosols lead to more cloud droplets with smaller size, which favor evaporative cooling and reduce updrafts and suppress convection over the upstream (northwest) region in the early stage of the rainfall event. As the rainfall system propagates southeastward, more latent heat is released due to the freezing of larger number of smaller cloud drops that are lofted above the freezing level, which is responsible for the increased updraft strength and convective invigoration over the downstream (southeast) area. © 2015. American Geophysical Union. All Rights Reserved."
"55574865800;8953662800;55960948400;56068376200;55822242600;24755928100;55720362700;57188867135;","Satellite observed aerosol-induced variability in warm cloud properties under different meteorological conditions over eastern China",2014,"10.1016/j.atmosenv.2013.11.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890103177&doi=10.1016%2fj.atmosenv.2013.11.018&partnerID=40&md5=dad82f07661419a0da4e430f7913ee3b","By taking meteorological conditions into account, this paper studies aerosol indirect effect on summertime warm clouds over the Yangtze River Delta (YRD) and East China Sea (ECS). The observed aerosol and cloud data are from MODIS/Aqua Level 2 datasets, and meteorological variables are from NCEP Final Analyses Operational Global Analysis datasets. To minimize meteorological effect on statistical analyses of aerosol-warm cloud interaction, several meteorological variables such as cloud top pressure (CTP), relative humidity (RH), pressure vertical velocity (PVV) and lower tropospheric stability (LTS) are considered in this study.Results show that cloud droplet radius (CDR) decreases with increasing aerosol optical depth (AOD) over ECS, while increases with increasing aerosol abundance over YRD. By taking CTP and RH into account, aerosol effects on cloud fraction (CF) are investigated. When aerosol loading is relatively small, CF is found to increase more sharply over YRD than over ECS in response to aerosol enhancement regardless of RH conditions. Therefore, we argue that the horizontal extension of cloud is prone to be driven by aerosol rather than meteorological conditions. Meanwhile, joint correlative analysis of AOD-CF and AOD-CTP reveals that CTP effect on AOD-CF is not significant, indicating CTP makes little contribution to observed AOD-CF relationship. Constrained by lower tropospheric stability (LTS) and pressure vertical velocity (750hPa), CDR variation in response to AOD is analyzed. In general, CDR tends to decrease as aerosol increases over both ECS and YRD under stable conditions (higher LTS value). In contrast, CDR positively responds to aerosol over land under unstable conditions. Dynamically, CDR has stronger effects on than the ascending motion than on the sinking motion with the same aerosol loading over both land and ocean. The reason can be partially explained by the phenomena that updrafts favor the growth of cloud droplets. Overall, the observed cloud variations can be extremely difficult to be attributed to aerosol particles alone due to dynamical and thermodynamical processes in cloud systems. © 2013 Elsevier Ltd."
"7006643234;24722339600;7003666669;56162305900;55405340400;7006705919;55476786400;6602379332;35115244100;","Aerosol optical depth increase in partly cloudy conditions",2012,"10.1029/2012JD017894","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866665497&doi=10.1029%2f2012JD017894&partnerID=40&md5=b21b5a5f5d3db1f37dca683f0af39c21","Remote sensing observations of aerosol from surface and satellite instruments are extensively used for atmospheric and climate research. From passive sensors, the apparent cloud-free atmosphere in the vicinity of clouds often appears to be brighter than further away from the clouds, leading to an increase in the retrieved aerosol optical depth (τ). Mechanisms contributing to this enhancement or increase, including contamination by undetected clouds, hygroscopic growth of aerosol particles, and meteorological conditions, have been debated in recent literature, but the extent to which each of these factors influence the observed enhancement (δ τ) is poorly known. Here we used 11 years of daily global observations at 10 × 10 km <inf>2</inf>resolution from the MODIS on the NASA Terra satellite to quantify τ as a function of cloud fraction (CF). Our analysis reveals that, averaged over the globe, the clear sky τ is enhanced by δ τ = 0.05 in cloudy conditions (CF = 0.8-0.9). This enhancement in δ τ corresponds to relative enhancement of 25% in cloudy conditions (CF = 0.8-0.9) compared with relatively clear conditions (CF = 0.1-0.2). Unlike the absolute enhancement δ τ the relative increase in τ is rather consistent in all seasons and is 25-35% in the subtropics and 15-25% at mid and higher latitudes. Using a simple Gaussian probability density function model to connect cloud cover and the distribution of relative humidity, we argue that much of the enhancement is consistent with aerosol hygroscopic growth in the humid environment surrounding clouds. Consideration of these cloud-dependent τ effects will facilitate understanding aerosol-cloud interactions and reduce the uncertainty in estimates of aerosol radiative forcing by global climate models. © 2012. American Geophysical Union. All Rights Reserved."
"35232705600;7003696133;57189498750;7402027161;","Regional scale effects of the aerosol cloud interaction simulated with an online coupled comprehensive chemistry model",2011,"10.5194/acp-11-4411-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955880319&doi=10.5194%2facp-11-4411-2011&partnerID=40&md5=9cd76ff728fa0ce237ffdf807b7ef903","We have extended the coupled mesoscale atmosphere and chemistry model COSMO-ART to account for the transformation of aerosol particles into cloud condensation nuclei and to quantify their interaction with warm cloud microphysics on the regional scale. The new model system aims to fill the gap between cloud resolving models and global scale models. It represents the very complex microscale aerosol and cloud physics as detailed as possible, whereas the continental domain size and efficient codes will allow for both studying weather and regional climate. The model system is applied in a first extended case study for Europe for a cloudy five day period in August 2005. The model results show that the mean cloud droplet number concentration of clouds is correlated with the structure of the terrain, and we present a terrain slope parameter TS to classify this dependency. We propose to use this relationship to parameterize the probability density function, PDF, of subgrid-scale cloud updraft velocity in the activation parameterizations of climate models. The simulations show that the presence of cloud condensation nuclei (CCN) and clouds are closely related spatially. We find high aerosol and CCN number concentrations in the vicinity of clouds at high altitudes. The nucleation of secondary particles is enhanced above the clouds. This is caused by an efficient formation of gaseous aerosol precursors above the cloud due to more available radiation, transport of gases in clean air above the cloud, and humid conditions. Therefore the treatment of complex photochemistry is crucial in atmospheric models to simulate the distribution of CCN. The mean cloud droplet number concentration and droplet diameter showed a close link to the change in the aerosol. To quantify the net impact of an aerosol change on the precipitation we calculated the precipitation susceptibility β for the whole model domain over a period of two days with an hourly resolution. The distribution function of β is slightly skewed to positive values and has a mean of 0.23. Clouds with a liquid water path LWP of approximately 0.85 kg m-2 are on average most susceptible to aerosol changes in our simulations with an absolute value of β of 1. The average β for LWP between 0.5 kg m-2 and 1 kg m-2 is approximately 0.4. © 2011 Author(s)."
"7201837768;14829673100;56249704400;7201706787;15032788000;6603140753;7004214645;7006461606;","Aerosol climate effects and air quality impacts from 1980 to 2030",2008,"10.1088/1748-9326/3/2/024004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-46749133626&doi=10.1088%2f1748-9326%2f3%2f2%2f024004&partnerID=40&md5=1a92417f14d38ea958960c5de373445f","We investigate aerosol effects on climate for 1980, 1995 (meant to reflect present day) and 2030 using the NASA Goddard Institute for Space Studies climate model coupled to an on-line aerosol source and transport model with interactive oxidant and aerosol chemistry. Aerosols simulated include sulfates, organic matter (OM), black carbon (BC), sea-salt and dust and, additionally, the amount of tropospheric ozone is calculated, allowing us to estimate both changes to air quality and climate for different time periods and emission amounts. We include both the direct aerosol effect and indirect aerosol effects for liquid-phase clouds. Future changes for the 2030 A1B scenario are examined, focusing on the Arctic and Asia, since changes are pronounced in these regions. Our results for the different time periods include both emission changes and physical climate changes. We find that the aerosol indirect effect (AIE) has a large impact on photochemical processing, decreasing ozone amount and ozone forcing, especially for the future (2030-1995). Ozone forcings increase from 0 to 0.12 W m -2 and the total aerosol forcing decreases from -0.10 to -0.94 W m-2 (AIE decreases from -0.13 to -0.68 W m-2) for 1995-1980 versus 2030-1995. Over the Arctic we find that compared to ozone and the direct aerosol effect, the AIE contributes the most to net radiative flux changes. The AIE, calculated for 1995-1980, is positive (1.0 W m-2), but the magnitude decreases (-0.3 W m-2) considerably for the future scenario. Over Asia, we evaluate the role of biofuel- and transportation-based emissions (for BC and OM) via a scenario (2030A) that includes a projected increase (factor of 2) in biofuel- and transport-based emissions for 2030 A1B over Asia. Projected changes from present day due to the 2030A emissions versus 2030 A1B are a factor of 4 decrease in summertime precipitation in Asia. Our results are sensitive to emissions used. Uncertainty in present-day emissions suggests that future climate projections warrant particular scrutiny. © IOP Publishing Ltd."
"13403622000;7005955015;7003666669;12139043600;12139310900;56250250300;","Predicting cloud droplet number concentration in Community Atmosphere Model (CAM)-Oslo",2006,"10.1029/2005JD006300","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547915206&doi=10.1029%2f2005JD006300&partnerID=40&md5=0c1db48f9ba92ef333deabe1a621a108","A new framework for calculating cloud droplet number, including a continuity equation for cloud droplet number concentration, has been developed and implemented in an extended version of the National Center for Atmospheric Research (NCAR) Community Atmosphere Model version 2.0.1 (CAM-2.0.1). The new continuity equation for cloud droplet number concentration consists of a nucleation term and several microphysical sink terms. The nucleation term is calculated on the basis of a parameterization of activation of cloud condensation nuclei (CCN). A subgrid distribution of vertical velocity is used to calculate the range of supersaturations determining the activation within each model grid box. The aerosol types considered in this study are sea salt, sulfate, black carbon, organic carbon, and mineral dust. The horizontal and vertical distributions of sulfate and carbonaceous aerosols are calculated on the basis of AEROCOM (http://nansen.ipsl.jussieu.fr/ AEROCOM) sources. Microphysical sink terms for cloud droplets are obtained from a prognostic cloud water scheme, assuming a direct proportionality between loss of cloud water and loss of cloud droplets. On the basis of the framework described above, the cloud droplet number concentration and cloud droplet effective radius are determined. Cloud microphysical and radiative properties compare reasonably well with satellite observations, giving an indication of the soundness of our approach. Our method of fitting the aerosol size distribution with lognormal modes has been evaluated and was found not to introduce systematic errors in our approach. The aerosol indirect effect estimated in the new framework ranges from -0.13 W/m2 to -0.72 W/m2, which is significantly smaller than in most other comparable studies. This is largely due to the introduction of microphysical sinks for cloud droplets and a cloud droplet activation scheme which accounts for the so-called competition effect among CCN. As we are not allowing aerosol effects on cloud microphysics and radiation to feed back on the model meteorology, our estimates of the aerosol indirect effect do not include changes in relative humidity and cloud cover. Copyright 2006 by the American Geophysical Union."
"8953662800;55822242600;8511991900;7409080503;57189634238;55543826100;56159334700;24755928100;","Precipitation and air pollution at mountain and plain stations in northern China: Insights gained from observations and modeling",2014,"10.1002/2013JD021161","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900525812&doi=10.1002%2f2013JD021161&partnerID=40&md5=68a6f2314a781e4f16f655ff85d665dd","We analyzed 40 year data sets of daily average visibility (a proxy for surface aerosol concentration) and hourly precipitation at seven weather stations, including three stations located on the Taihang Mountains, during the summertime in northern China. There was no significant trend in summertime total precipitation at almost all stations. However, light rain decreased, whereas heavy rain increased as visibility decreased over the period studied. The decrease in light rain was seen in both orographic-forced shallow clouds and mesoscale stratiform clouds. The consistent trends in observed changes in visibility, precipitation, and orographic factor appear to be a testimony to the effects of aerosols. The potential impact of large-scale environmental factors, such as precipitable water, convective available potential energy, and vertical wind shear, on precipitation was investigated. No direct links were found. To validate our observational hypothesis about aerosol effects, Weather Research and Forecasting model simulations with spectral-bin microphysics at the cloud-resolving scale were conducted. Model results confirmed the role of aerosol indirect effects in reducing the light rain amount and frequency in the mountainous area for both orographic-forced shallow clouds and mesoscale stratiform clouds and in eliciting a different response in the neighboring plains. The opposite response of light rain to the increase in pollution when there is no terrain included in themodel suggests that orography is likely a significant factor contributing to the opposite trends in light rain seen in mountainous and plain areas. © 2014. American Geophysical Union. All Rights Reserved."
"25031430500;7103158465;55232897900;24722339600;","Microphysical process rates and global aerosol-cloud interactions",2013,"10.5194/acp-13-9855-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885998549&doi=10.5194%2facp-13-9855-2013&partnerID=40&md5=ff3965e5b44b2440da7f050ce293ac98","Cloud microphysical process rates control the amount of condensed water in clouds and impact the susceptibility of precipitation to cloud-drop number and aerosols. The relative importance of different microphysical processes in a climate model is analyzed, and the autoconversion and accretion processes are found to be critical to the condensate budget in most regions. A simple steady-state model of warm rain formation is used to illustrate that the diagnostic rain formulations typical of climate models may result in excessive contributions from autoconversion, compared to observations and large eddy simulation models with explicit bin-resolved microphysics and rain formation processes. The behavior does not appear to be caused by the bulk process rate formulations themselves, because the steady-state model with the same bulk accretion and autoconversion has reduced contributions from autoconversion. Sensitivity tests are conducted to analyze how perturbations to the precipitation microphysics for stratiform clouds impact process rates, precipitation susceptibility and aerosol-cloud interactions (ACI). With similar liquid water path, corrections for the diagnostic rain assumptions in the GCM based on the steady-state model to boost accretion indicate that the radiative effects of ACI may decrease by 20% in the GCM. Links between process rates, susceptibility and ACI are not always clear in the GCM. Better representation of the precipitation process, for example by prognosticating precipitation mass and number, may help better constrain these effects in global models with bulk microphysics schemes. © Author(s) 2013."
"26632168400;57203053317;","Sensitivity studies of aerosol-cloud interactions in mixed-phase orographic precipitation",2009,"10.1175/2009JAS3001.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73549087000&doi=10.1175%2f2009JAS3001.1&partnerID=40&md5=0d474209bc4775c5a494295abe34f689","Anthropogenic aerosols serve as a source of both cloud condensation nuclei (CCN) and ice nuclei (IN) and affect microphysical properties of clouds. Increasing aerosol number concentration is assumed to retard the cloud droplet coalescence and the riming process in mixed-phase orographic clouds, thereby decreasing orographic precipitation. In this study, idealized 3D simulations are conducted to investigate aerosol-cloud interactions in mixed-phase orographic clouds and the possible impact of anthropogenic and natural aerosols on orographic precipitation. Two different types of aerosol anomalies are considered: naturally occurring mineral dust and anthropogenic black carbon. In the simulations with a dust aerosol anomaly, the dust aerosols serve as efficient ice nuclei in the contact mode, leading to an early initiation of the ice phase in the orographic cloud. As a consequence, the riming rates in the cloud are increased, leading to increased precipitation efficiency and enhancement of orographic precipitation. The simulations with an anthropogenic aerosol anomaly suggest that the mixing state of the aerosols plays a crucial role because coating and mixing may cause the aerosols to initiate freezing in the less efficient immersion mode rather than by contact nucleation. It is found that externally mixed black carbon aerosols increase riming in orographic clouds and enhance orographic precipitation. In contrast, internally mixed black carbon aerosols decrease the riming rates, leading in turn to a decrease in orographic precipitation. © 2009 American Meteorological Society."
"12138847300;7102290666;6506966551;","Aerosol and cloud property relationships for summertime stratiform clouds in the northeastern Atlantic from Advanced Very High Resolution Radiometer observations",2005,"10.1029/2005JD006165","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31644445180&doi=10.1029%2f2005JD006165&partnerID=40&md5=e62e4ea751789f6e011fa1b1e3d63a99","Advanced Very High Resolution Radiometer (AVHRR) 4-km data collected over the northeastern Atlantic off the coast of the Iberian Peninsula for May to August 1995 were used to investigate the feasibility of empirically deriving estimates of the aerosol indirect radiative forcing. A retrieval scheme was used to derive cloud visible optical depth, droplet effective radius, cloud layer altitude, and pixel-scale fractional cloud cover. A two-channel aerosol retrieval scheme was used to determine aerosol optical depth in cloud-free pixels. Mean aerosol optical depths derived from the cloud-free pixels in 1° × 1° latitude-longitude regions on a given satellite overpass were associated with mean cloud properties derived from the cloudy pixels in the same region for the same satellite overpass. The analysis was restricted to 1° regions that contained only single-layered, low-level cloud systems. Because aerosol and cloud properties are highly variable, results for the 4-month period were composited into 5° × 5° latitude-longitude regions and averaged to obtain reliable trends in the cloud properties as functions of aerosol burden. Consistent with expectations for the aerosol indirect effect, in some 5° regions, droplet effective radii decreased, and cloud visible optical depths increased as aerosol optical depths increased. The hypothesis that drizzle is suppressed in polluted clouds predicts that liquid water path should increase as aerosol burden increases. In three of the thirteen 5° regions studied, the liquid water path increased as aerosol optical depth increased, but in none of the regions was the increase in cloud liquid water statistically significant. In the remaining regions, cloud liquid water remained constant or even decreased with increasing aerosol optical depth. In many of the 5° regions, the retrieved aerosol optical depth increased as the percentage of cloudy pixels increased. Consistent with expectations from adiabatic cloud parcel models, droplet effective radius, cloud optical depth, and cloud liquid water path also increased as fractional cloud cover increased. The simultaneous increase in retrieved aerosol and cloud optical depths with increasing fractional cloud cover might have been due to the aerosol indirect effect, but it might also have resulted from processes that affect both the cloud and aerosol properties as cloud cover changes. The dependence on fractional cloud cover suggests that some of the trends between aerosol optical depth and the cloud properties cannot be solely attributed to the effects of the aerosols. For comparison with previous studies, the simultaneous changes in aerosol and cloud properties were used to estimate the daily average aerosol indirect forcing for overcast conditions in the summertime northeastern Atlantic. The magnitude of the indirect forcing relative to that of the direct forcing reported here is smaller than estimates reported by others. Copyright 2005 by the American Geophysical Union."
"55261195800;56724696200;6602080205;","Impacts of 20th century aerosol emissions on the South Asian monsoon in the CMIP5 models",2015,"10.5194/acp-15-6367-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84935839203&doi=10.5194%2facp-15-6367-2015&partnerID=40&md5=85904afe59dd6a36608a5b790b9d5429","Comparison of single-forcing varieties of 20th century historical experiments in a subset of models from the Fifth Coupled Model Intercomparison Project (CMIP5) reveals that South Asian summer monsoon rainfall increases towards the present day in Greenhouse Gas (GHG)-only experiments with respect to pre-industrial levels, while it decreases in anthropogenic aerosol-only experiments. Comparison of these single-forcing experiments with the all-forcings historical experiment suggests aerosol emissions have dominated South Asian monsoon rainfall trends in recent decades, especially during the 1950s to 1970s. The variations in South Asian monsoon rainfall in these experiments follows approximately the time evolution of inter-hemispheric temperature gradient over the same period, suggesting a contribution from the large-scale background state relating to the asymmetric distribution of aerosol emissions about the equator. By examining the 24 available all-forcings historical experiments, we show that models including aerosol indirect effects dominate the negative rainfall trend. Indeed, models including only the direct radiative effect of aerosol show an increase in monsoon rainfall, consistent with the dominance of increasing greenhouse gas emissions and planetary warming on monsoon rainfall in those models. For South Asia, reduced rainfall in the models with indirect effects is related to decreased evaporation at the land surface rather than from anomalies in horizontal moisture flux, suggesting the impact of indirect effects on local aerosol emissions. This is confirmed by examination of aerosol loading and cloud droplet number trends over the South Asia region. Thus, while remote aerosols and their asymmetric distribution about the equator play a role in setting the inter-hemispheric temperature distribution on which the South Asian monsoon, as one of the global monsoons, operates, the addition of indirect aerosol effects acting on very local aerosol emissions also plays a role in declining monsoon rainfall. The disparity between the response of monsoon rainfall to increasing aerosol emissions in models containing direct aerosol effects only and those also containing indirect effects needs to be urgently investigated since the suggested future decline in Asian anthropogenic aerosol emissions inherent to the representative concentration pathways (RCPs) used for future climate projection may turn out to be optimistic. In addition, both groups of models show declining rainfall over China, also relating to local aerosol mechanisms. We hypothesize that aerosol emissions over China are large enough, in the CMIP5 models, to cause declining monsoon rainfall even in the absence of indirect aerosol effects. The same is not true for India. © Author(s) 2015."
"53880473700;6602080205;8633783900;7004469744;","Quantifying sources of inter-model diversity in the cloud albedo effect",2015,"10.1002/2015GL063301","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925835176&doi=10.1002%2f2015GL063301&partnerID=40&md5=f3ab9945e410318a3cb9f4bbd53f4eea","There is a large diversity in simulated aerosol forcing among models that participated in the fifth Coupled Model Intercomparison Project, particularly related to aerosol interactions with clouds. Here we use the reported model data and fitted aerosol-cloud relations to separate the main sources of inter-model diversity in the magnitude of the cloud albedo effect. There is a large diversity in the global load and spatial distribution of sulfate aerosol, as well as in global mean cloud top effective radius. The use of different parameterizations of aerosol-cloud interactions makes the largest contribution to diversity in modeled radiative forcing (-39%, +48% about the mean estimate). Uncertainty in preindustrial sulfate load also makes a substantial contribution (-15%, +61% about the mean estimate), with smaller contributions from inter-model differences in the historical change in sulfate load and in mean cloud fraction. © 2015. The Authors."
"7005304841;","Do sophisticated parameterizations of aerosol-cloud interactions in CMIP5 models improve the representation of recent observed temperature trends?",2014,"10.1002/2013JD020511","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900605777&doi=10.1002%2f2013JD020511&partnerID=40&md5=9d819c2fb059935f76d1529bca29df0d","Model output from the Coupled Model Inter comparison Project phase 5 (CMIP5) archive was compared with the observed latitudinal distribution of surface temperature trends between the years 1965 and 2004. By comparing model simulations that only consider changes in greenhouse gas forcing (GHG) with simulations that also consider the time evolution of anthropogenic aerosol emissions (GHGAERO), the influence of aerosol forcing on modeled surface temperature trends, and the dependence of the forcing on the model representation of aerosols and aerosol indirect effects, was evaluated. One group of models include sophisticated parameterizations of aerosol activation into cloud droplets; viz., the cloud droplet number concentration (CDNC) is a function of the modeled supersaturation as well as the aerosol concentration. In these models, the temperature trend bias was reduced in GHGAERO compared to GHG in more regions than in the other models. The ratio between high- and low-latitude warming also improved compared to observations. In a second group of models, the CDNC is diagnosed using an empirical relationship between the CDNC and the aerosol concentration. In this group, the temperature trend bias was reduced in more regions than in the model group where no aerosol indirect effects are considered. No clear difference could be found between models that include an explicit aerosol module and the ones that utilize prescribed aerosol. There was also no clear difference between models that include aerosol effects on the precipitation formation rate and the ones that do not. The results indicate that the best representation of recent observed surface temperature trends is obtained if the modeled CDNC is a function of both the aerosol concentration and the supersaturation. © 2013. American Geophysical Union. All Rights Reserved."
"55718911800;56349223500;37105039700;37105327100;56888287100;35975306400;","Cloud residues and interstitial aerosols from non-precipitating clouds over an industrial and urban area in northern China",2011,"10.1016/j.atmosenv.2011.02.044","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953296132&doi=10.1016%2fj.atmosenv.2011.02.044&partnerID=40&md5=af134da629cfafcb39fe4b489ef959a5","Most studies of aerosol-cloud interactions have been conducted in remote locations; few have investigated the characterization of cloud condensation nuclei (CCN) over highly polluted urban and industrial areas. The present work, based on samples collected at Mt. Tai, a site in northern China affected by nearby urban and industrial air pollutant emissions, illuminates CCN properties in a polluted atmosphere. High-resolution transmission electron microscopy (TEM) was used to obtain the size, composition, and mixing state of individual cloud residues and interstitial aerosols. Most of the cloud residues displayed distinct rims which were found to consist of soluble organic matter (OM). Nearly all (91.7%) cloud residues were attributed to sulfate-related salts (the remainder was mostly coarse crustal dust particles with nitrate coatings). Half the salt particles were internally mixed with two or more refractory particles (e.g., soot, fly ash, crustal dust, CaSO4, and OM). A comparison between cloud residues and interstitial particles shows that the former contained more salts and were of larger particle size than the latter. In addition, a somewhat high number scavenging ratio of 0.54 was observed during cloud formation. Therefore, the mixtures of salts with OMs account for most of the cloud-nucleating ability of the entire aerosol population in the polluted air of northern China. We advocate that both size and composition - the two influential, controlling factors for aerosol activation - should be built into all regional climate models of China. © 2011."
"16444669600;16444028600;57200763615;6701378450;","Inferring thermodynamic properties from CCN activation experiments: Single-component and binary aerosols",2007,"10.5194/acp-7-5263-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35348855754&doi=10.5194%2facp-7-5263-2007&partnerID=40&md5=42c3c8281b1ad2bdd82a7f9c62d8fbbc","This study presents a new method, Köhler Theory Analysis (KTA), to infer the molar volume and solubility of organic aerosol constituents. The method is based on measurements of surface tension, chemical composition, and CCN activity coupled with Köhler theory. KTA is evaluated by inferring the molar volume of six known organics (four dicarboxylic acids, one amino acid, and one sugar) in pure form and in mixtures with ammonium sulfate ((NH 4)2SO4). The average error in inferred molar volumes are to within 18% of their expected value for organic fractions between 50 and 90%. This suggests that KTA is a potentially powerful tool for determining the CCN characteristic of ambient water soluble organic carbon (WSOC), providing physically-based constraints for aerosol-cloud interaction parameterizations."
"15050523700;36006968000;55667257200;","Role of interactions between aerosol radiative effect, dynamics, and cloud microphysics on transitions of monsoon intraseasonal oscillations",2013,"10.1175/JAS-D-12-0179.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880436653&doi=10.1175%2fJAS-D-12-0179.1&partnerID=40&md5=5407b73e6920f64a1917dca0720c486d","Extended-range prediction of monsoon intraseasonal oscillations (MISOs), crucial for agriculture and water management, is limited by their event-to-event variability. Here, the authors propose a hypothesis supported by a number of model simulations involving detailed cloud microphysical processes indicating that aerosols contribute significantly to the transitions from ""break"" to ""active"" phases of MISO. The role of aerosol indirect effect in the process of invi oration of precipitation is demonstrated with a high-resolution regional model for Indian summer monsoon breaks that are followed by an active condition (BFA) and contrasted with breaks that are not followed by an active condition (BNFA). The BFA are characterized by higher concentrations of absorbing aerosols that lead to a stronger north-south low-level temperature gradient and strong moisture convergence. Forced uplift beyond the freezing level initiates the cold-rain process involving mixed-phase microphysics and latent heat release at higher levels, thereby invigorating convection, enhancing precipitation, and resulting in an active condition. While more aerosols tend to reduce the cloud drop size and delay the warm rain, it is overcome by the higher moisture convergence during BFA and invigoration by cold-rain processes. The net production of rainfall is sensitive to cloud structure as it depends on the relative strength of the warm-and cold-rain initiation processes. The results indicate the importance of aerosols on transitions of MISO and a pathway by which they influence the transitions involving complex interactions between direct radiative forcing, large-scale dynamics, and cloud microphysics. Broader implications of these results in event-to-event variability of MISO and its predictability are also highlighted. © 2013 American Meteorological Society."
"24757696000;6701490531;7004154626;7003495982;7005217679;55612523600;36006968000;","Impact of elevated aerosol layer on the cloud macrophysical properties prior to monsoon onset",2013,"10.1016/j.atmosenv.2012.12.036","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874517043&doi=10.1016%2fj.atmosenv.2012.12.036&partnerID=40&md5=6734c1bea372460e4fea3ff734e8d985","Atmospheric aerosols alter the radiation balance by absorption/scattering of solar radiation, and indirectly by modifying the cloud microphysical properties. Observations during the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) provide a unique opportunity to investigate the aerosol-cloud interaction in a dry to wet transition phase prior to the onset of southwest monsoon. It is observed that aerosol loading increased over the central Indian region in spite of the increase in surface rainfall. This aerosol loading was observed mainly in the 2-5 km level above surface. The origin and influence of elevated aerosol layer have been investigated with the help of WRF-Chem simulations by conducting sensitivity experiments for dust emissions, modified based on the satellite observations. To enhance the dust emissions, the erodible fraction over the Thar Desert region is enhanced to an average factor of 1.7 based on TOMS aerosol index (AI) and USGS land use category, which contributed to enhanced dust emissions by a factor of 1.25 over the study region. This enhancement of dust emission from Thar Desert can result in an increased radiative heating due to elevated aerosol layers, which leads to an increase in the ice mixing ratio and ice water content in the regions of dry to wet transition. It is shown that even natural dust emissions (without changes in anthropogenic emissions) may also influence the spatial and temporal distribution of cloud and precipitation and the hydrological cycle. © 2013 Elsevier Ltd."
"18437651200;25624725200;35798085000;8550791300;7202779940;56691914800;7004715270;8586682800;35798985200;55730602600;36955999600;6602085876;8728866200;8915492800;23048728700;7402538754;57193537889;6602354484;7006415284;","Experimental study of the role of physicochemical surface processing on the in ability of mineral dust particles",2011,"10.5194/acp-11-11131-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79961104485&doi=10.5194%2facp-11-11131-2011&partnerID=40&md5=23d9333835e201d77ae712f75cb710ae","During the measurement campaign FROST 2 (FReezing Of duST 2), the Leipzig Aerosol Cloud Interaction Simulator (LACIS) was used to investigate the influence of various surface modifications on the ice nucleating ability of Arizona Test Dust (ATD) particles in the immersion freezing mode. The dust particles were exposed to sulfuric acid vapor, to water vapor with and without the addition of ammonia gas, and heat using a thermodenuder operating at 250 °C. Size selected, quasi monodisperse particles with a mobility diameter of 300 nm were fed into LACIS and droplets grew on these particles such that each droplet contained a single particle. Temperature dependent frozen fractions of these droplets were determined in a temperature range between-40 °C ≤ T ≤-28 °C. The pure ATD particles nucleated ice over a broad temperature range with their freezing behavior being separated into two freezing branches characterized through different slopes in the frozen fraction vs. temperature curves. Coating the ATD particles with sulfuric acid resulted in the particles' IN potential significantly decreasing in the first freezing branch (T >-35 °C) and a slight increase in the second branch (T ≤-35 °C). The addition of water vapor after the sulfuric acid coating caused the disappearance of the first freezing branch and a strong reduction of the IN ability in the second freezing branch. The presence of ammonia gas during water vapor exposure had a negligible effect on the particles' IN ability compared to the effect of water vapor. Heating in the thermodenuder led to a decreased IN ability of the sulfuric acid coated particles for both branches but the additional heat did not or only slightly change the IN ability of the pure ATD and the water vapor exposed sulfuric acid coated particles. In other words, the combination of both sulfuric acid and water vapor being present is a main cause for the ice active surface features of the ATD particles being destroyed. A possible explanation could be the chemical transformation of ice active metal silicates to metal sulfates. The strongly enhanced reaction between sulfuric acid and dust in the presence of water vapor and the resulting significant reductions in IN potential are of importance for atmospheric ice cloud formation. Our findings suggest that the IN concentration can decrease by up to one order of magnitude for the conditions investigated. © 2011 Author(s)."
"26632168400;57203053317;","Sensitivity studies of the role of aerosols in warm-phase orographic precipitation in different dynamical flow Regimes",2008,"10.1175/2007JAS2492.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51749111165&doi=10.1175%2f2007JAS2492.1&partnerID=40&md5=07a1cd4ac04c6df1d96a0cb8ab9949a1","Aerosols serve as a source of cloud condensation nuclei (CCN) and influence the microphysical properties of clouds. In the case of orographic clouds, it is suspected that aerosol-cloud interactions reduce the amount of precipitation on the upslope side of the mountain and enhance the precipitation on the down-slope side when the number of aerosols is increased. The net effect may lead to a shift of the precipitation distribution toward the leeward side of mountain ranges, which affects the hydrological cycle on the local scale. In this study aerosol-cloud interactions in warm-phase clouds and the possible impact on the orographic precipitation distribution are investigated. Herein, simulations of moist orographic flow over topography are conducted and the influence of anthropogenic aerosols on the orographic precipitation formation is analyzed. The degree of aerosol pollution is prescribed by different aerosol spectra that are representative for central Switzerland. The simulations are performed with the Consortium for Small-Scale Modeling's mesoscale nonhydrostatic limited-area weather prediction model (COSMO) with a horizontal grid spacing of 2 km and a fully coupled aerosol-cloud parameterization. It is found that an increase in the aerosol load leads to a downstream shift of the orographic precipitation distribution and to an increase in the spillover factor. A reduction of warm-phase orographic precipitation is observed at the upslope side of the mountain. The downslope precipitation enhancement depends critically on the width of the mountain and on the flow dynamics. In the case of orographic precipitation induced by stably stratified unblocked flow, the loss in upslope precipitation is not compensated by leeward precipitation enhancement. In contrast, flow blocking may lead to leeward precipitation enhancement and eventually to a compensation of the upslope precipitation loss. The simulations also indicate that latent heat effects induced by aerosol-cloud-precipitation interactions may considerably affect the orographic flow dynamics and consequently feed back on the orographic precipitation development. © 2008 American Meteorological Society."
"57097521200;7003414581;6701697023;55933175300;22133985200;6602215448;55405013100;16642991200;55883785100;57195682689;7801401670;7101707186;26023140500;8927405700;24366038500;","Triple-wavelength depolarization-ratio profiling of Saharan dust over Barbados during SALTRACE in 2013 and 2014",2017,"10.5194/acp-17-10767-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019669642&doi=10.5194%2facp-17-10767-2017&partnerID=40&md5=74dd50a50043459604347e7d88e9b781","Triple-wavelength polarization lidar measurements in Saharan dust layers were performed at Barbados (13.1°N, 59.6°W), 5000-8000km west of the Saharan dust sources, in the framework of the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE-1, June-July 2013, SALTRACE-3, June-July 2014). Three case studies are discussed. High quality was achieved by comparing the dust linear depolarization ratio profiles measured at 355, 532, and 1064nm with respective dual-wavelength (355, 532nm) depolarization ratio profiles measured with a reference lidar. A unique case of long-range transported dust over more than 12000km is presented. Saharan dust plumes crossing Barbados were measured with an airborne triple-wavelength polarization lidar over Missouri in the midwestern United States 7 days later. Similar dust optical properties and depolarization features were observed over both sites indicating almost unchanged dust properties within this 1 week of travel from the Caribbean to the United States. The main results of the triple-wavelength polarization lidar observations in the Caribbean in the summer seasons of 2013 and 2014 are summarized. On average, the particle linear depolarization ratios for aged Saharan dust were found to be 0.252±0.030 at 355nm, 0.280±0.020 at 532nm, and 0.225±0.022 at 1064nm after approximately 1 week of transport over the tropical Atlantic. Based on published simulation studies we present an attempt to explain the spectral features of the depolarization ratio of irregularly shaped mineral dust particles, and conclude that most of the irregularly shaped coarse-mode dust particles (particles with diameters &gt; 1μm) have sizes around 1.5-2μm. The SALTRACE results are also set into the context of the SAMUM-1 (Morocco, 2006) and SAMUM-2 (Cabo Verde, 2008) depolarization ratio studies. Again, only minor changes in the dust depolarization characteristics were observed on the way from the Saharan dust sources towards the Caribbean."
"25652188900;24077600000;10139397300;8982748700;","Impacts of increasing the aerosol complexity in the Met Office global numerical weather prediction model",2014,"10.5194/acp-14-4749-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901022863&doi=10.5194%2facp-14-4749-2014&partnerID=40&md5=6da6479001f9c930683b1cc1c22825dd","The inclusion of the direct and indirect radiative effects of aerosols in high-resolution global numerical weather prediction (NWP) models is being increasingly recognised as important for the improved accuracy of short-range weather forecasts. In this study the impacts of increasing the aerosol complexity in the global NWP configuration of the Met Office Unified Model (MetUM) are investigated. A hierarchy of aerosol representations are evaluated including three-dimensional monthly mean speciated aerosol climatologies, fully prognostic aerosols modelled using the CLASSIC aerosol scheme and finally, initialised aerosols using assimilated aerosol fields from the GEMS project. The prognostic aerosol schemes are better able to predict the temporal and spatial variation of atmospheric aerosol optical depth, which is particularly important in cases of large sporadic aerosol events such as large dust storms or forest fires. Including the direct effect of aerosols improves model biases in outgoing long-wave radiation over West Africa due to a better representation of dust. However, uncertainties in dust optical properties propagate to its direct effect and the subsequent model response. Inclusion of the indirect aerosol effects improves surface radiation biases at the North Slope of Alaska ARM site due to lower cloud amounts in high-latitude clean-air regions. This leads to improved temperature and height forecasts in this region. Impacts on the global mean model precipitation and large-scale circulation fields were found to be generally small in the short-range forecasts. However, the indirect aerosol effect leads to a strengthening of the low-level monsoon flow over the Arabian Sea and Bay of Bengal and an increase in precipitation over Southeast Asia. Regional impacts on the African Easterly Jet (AEJ) are also presented with the large dust loading in the aerosol climatology enhancing of the heat low over West Africa and weakening the AEJ. This study highlights the importance of including a more realistic treatment of aerosol-cloud interactions in global NWP models and the potential for improved global environmental prediction systems through the incorporation of more complex aerosol schemes. © 2014 Author(s)."
"7004154626;24757696000;6701490531;6603926727;7005618829;36006968000;","Aerosol effect on droplet spectral dispersion in warm continental cumuli",2012,"10.1029/2011JD016532","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865463192&doi=10.1029%2f2011JD016532&partnerID=40&md5=3dd05b6f3bcfb59f820d6f28aa95eee4","In situ aircraft measurements of cloud microphysical properties and aerosol during the 1st phase of the Cloud Aerosol Interaction and Precipitation Enhancement EXperiment (CAIPEEX-I) over the Indian sub-continent provided initial opportunities to investigate the dispersion effect and its implications for estimating aerosol indirect effects in continental cumuli. In contrast to earlier studies on continental shallow cumuli, it is found that not only the cloud droplet number concentration but also the relative dispersion increases with the aerosol number concentration in continental cumuli. The first aerosol indirect effect estimated from the relative changes in droplet concentration and effective radius with aerosol number concentration are 0.13 and 0.07, respectively. In-depth analysis reveals that the dispersion effect could offset the cooling by enhanced droplet concentration by 39% in these continental cumuli. Adiabaticity analysis revealed aerosol indirect effect is lesser in subadiabatic clouds possibly due to inhomogeneous mixing processes. This study shows that adequate representation of the dispersion effect would help in accurately estimating the cloud albedo effect for continental cumuli and can reduce uncertainty in aerosol indirect effect estimates. © 2012 by the American Geophysical Union."
"35798985200;6601974344;6602354484;9432343100;8550791300;14523061300;18437651200;25624725200;35798085000;7006415284;56691914800;7004715270;8586682800;6602085876;55730602600;","Surface modification of mineral dust particles by sulphuric acid processing: Implications for ice nucleation abilities",2011,"10.5194/acp-11-7839-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79961101012&doi=10.5194%2facp-11-7839-2011&partnerID=40&md5=3f85224ed3a202b3c2f6353f33c7b582","The ability of coated mineral dust particles to act as ice nuclei (IN) was investigated at LACIS (Leipzig Aerosol Cloud Interaction Simulator) during the FROST1-and FROST2-campaigns (Freezing dust). Sulphuric acid was condensed on the particles which afterwards were optionally humidified, treated with ammonia vapour and/or heat. By means of aerosol mass spectrometry we found evidence that processing of mineral dust particles with sulphuric acid leads to surface modifications of the particles. These surface modifications are most likely responsible for the observed reduction of the IN activation of the particles. The observed particle mass spectra suggest that different treatments lead to different chemical reactions on the particle surface. Possible chemical reaction pathways and products are suggested and the implications on the IN efficiency of the treated dust particles are discussed. © 2011 Author(s)."
"7402177459;7004020627;7403204849;7004538458;6602157151;57196282021;6701842515;7202380672;15072064200;7004047498;7006595513;7004613032;55954833500;7004100461;8616954900;8631323300;8960080000;7101799663;8507974400;23996266700;8645916500;22837162400;8631323200;8507974900;8616955900;7201695681;8711886600;7005465800;56060986400;6602339197;6603230487;8631673500;8631673200;6701843835;6504549639;56619200900;7402078417;","FEBUKO and MODMEP: Field measurements and modelling of aerosol and cloud multiphase processes",2005,"10.1016/j.atmosenv.2005.02.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-22144449537&doi=10.1016%2fj.atmosenv.2005.02.004&partnerID=40&md5=8501884a644d2523f1c8bc485fb965c2","An overview of the two FEBUKO aerosol-cloud interaction field experiments in the Thüringer Wald (Germany) in October 2001 and 2002 and the corresponding modelling project MODMEP is given. Experimentally, a variety of measurement methods were deployed to probe the gas phase, particles and cloud droplets at three sites upwind, downwind and within an orographic cloud with special emphasis on the budgets and interconversions of organic gas and particle phase constituents. Out of a total of 14 sampling periods within 30 cloud events three events (EI, EII and EIII) are selected for detailed analysis. At various occasions an impact of the cloud process on particle chemical composition such as on the organic compounds content, sulphate and nitrate and also on particle size distributions and particle mass is observed. Moreover, direct phase transfer of polar organic compound from the gas phase is found to be very important for the understanding of cloudwater composition. For the modelling side, a main result of the MODMEP project is the development of a cloud model, which combines a complex multiphase chemistry with detailed microphysics. Both components are described in a fine-resolved particle/drop spectrum. New numerical methods are developed for an efficient solution of the entire complex model. A further development of the CAPRAM mechanism has lead to a more detailed description of tropospheric aqueous phase organic chemistry. In parallel, effective tools for the reduction of highly complex reaction schemes are provided. Techniques are provided and tested which allow the description of complex multiphase chemistry and of detailed microphysics in multidimensional chemistry-transport models. © 2005 Elsevier Ltd. All rights reserved."
"55620143100;57211681908;12782055300;35422938600;55683310400;55615346700;57192954165;57149740600;56789763900;55683113200;7005773698;15061542200;35291021400;14067215000;7005968859;7004715270;","A dynamic link between ice nucleating particles released in nascent sea spray aerosol and oceanic biological activity during two mesocosm experiments",2017,"10.1175/JAS-D-16-0087.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85009364983&doi=10.1175%2fJAS-D-16-0087.1&partnerID=40&md5=558af85fca0302e8f05a986c0a2e6eab","Emission rates and properties of ice nucleating particles (INPs) are required for proper representation of aerosol-cloud interactions in atmospheric models. Few investigations have quantified marine INP emissions, a potentially important INP source for remote oceanic regions. Previous studies have suggested INPs in sea spray aerosol (SSA) are linked to oceanic biological activity. This proposed link was explored in this study by measuring INP emissions from nascent SSA during phytoplankton blooms during two mesocosm experiments. In a Marine Aerosol Reference Tank (MART) experiment, a phytoplankton bloom was produced with chlorophyll-a (Chl a) concentrations reaching 39 μg L-1, while Chl a concentrations more representative of natural ocean conditions were obtained during the Investigation into Marine Particle Chemistry and Transfer Science (IMPACTS; peak Chl a of 5 μg L-1) campaign, conducted in the University of California, San Diego, wave flume. Dynamic trends in INP emissions occurred for INPs active at temperatures &gt; -30°C. Increases in INPs active between -25° and -15°C lagged the peak in Chl a in both studies, suggesting a consistent population of INPs associated with the collapse of phytoplankton blooms. Trends in INP emissions were also compared to aerosol composition, abundances of microbes, and enzyme activity. In general, increases in INP concentrations corresponded to increases in organic species in SSA and the emissions of heterotrophic bacteria, suggesting that both microbes and biomolecules contribute to marine INP populations. INP trends were not directly correlated with a single biological marker in either study. Direct measurements of INP chemistry are needed to accurately identify particles types contributing to marine INP populations. © 2017 American Meteorological Society."
"56682032300;55683727600;36026436300;55588510300;54402966300;6601941399;13405658600;","Uncertainties in global aerosols and climate effects due to biofuel emissions",2015,"10.5194/acp-15-8577-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938633742&doi=10.5194%2facp-15-8577-2015&partnerID=40&md5=4d83645e7b15ed79c881463098a18b78","Aerosol emissions from biofuel combustion impact both health and climate; however, while reducing emissions through improvements to combustion technologies will improve health, the net effect on climate is largely unconstrained. In this study, we examine sensitivities in global aerosol concentration, direct radiative climate effect, and cloud-albedo aerosol indirect climate effect to uncertainties in biofuel emission factors, optical mixing state, and model nucleation and background secondary organic aerosol (SOA). We use the Goddard Earth Observing System global chemical-transport model (GEOS-Chem) with TwO Moment Aerosol Sectional (TOMAS) microphysics. The emission factors include amount, composition, size, and hygroscopicity, as well as optical mixing-state properties. We also evaluate emissions from domestic coal use, which is not biofuel but is also frequently emitted from homes. We estimate the direct radiative effect assuming different mixing states (homogeneous, core-shell, and external) with and without absorptive organic aerosol (brown carbon). We find the global-mean direct radiative effect of biofuel emissions ranges from -0.02 to +0.06 W m-2 across all simulation/mixing-state combinations with regional effects in source regions ranging from -0.2 to +0.8 W m-2. The global-mean cloud-albedo aerosol indirect effect (AIE) ranges from +0.01 to -0.02 W m-2 with regional effects in source regions ranging from -1.0 to -0.05 W m-2. The direct radiative effect is strongly dependent on uncertainties in emissions mass, composition, emissions aerosol size distributions, and assumed optical mixing state, while the indirect effect is dependent on the emissions mass, emissions aerosol size distribution, and the choice of model nucleation and secondary organic aerosol schemes. The sign and magnitude of these effects have a strong regional dependence. We conclude that the climate effects of biofuel aerosols are largely unconstrained, and the overall sign of the aerosol effects is unclear due to uncertainties in model inputs. This uncertainty limits our ability to introduce mitigation strategies aimed at reducing biofuel black carbon emissions in order to counter warming effects from greenhouse gases. To better understand the climate impact of particle emissions from biofuel combustion, we recommend field/laboratory measurements to narrow constraints on (1) emissions mass, (2) emission size distribution, (3) mixing state, and (4) ratio of black carbon to organic aerosol. © Author(s) 2015."
"7405728922;7202180152;6701497749;36932594300;6603262263;6701562113;55476830600;55717074000;","Aerosol indirect effect on the grid-scale clouds in the two-way coupled WRF-CMAQ: Model description, development, evaluation and regional analysis",2014,"10.5194/acp-14-11247-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908410171&doi=10.5194%2facp-14-11247-2014&partnerID=40&md5=c0f357a4b6dcf716ac04683bc90dbae3","This study implemented first, second and glaciation aerosol indirect effects (AIE) on resolved clouds in the two-way coupled Weather Research and Forecasting Community Multiscale Air Quality (WRF-CMAQ) modeling system by including parameterizations for both cloud drop and ice number concentrations on the basis of CMAQpredicted aerosol distributions and WRF meteorological conditions. The performance of the newly developed WRF- CMAQ model, with alternate Community Atmospheric Model (CAM) and Rapid Radiative Transfer Model for GCMs (RRTMG) radiation schemes, was evaluated with observations from the Clouds and the See http://ceres.larc. nasa.gov/. Earth's Radiant Energy System (CERES) satellite and surface monitoring networks (AQS, IMPROVE, CASTNET, STN, and PRISM) over the continental US (CONUS) (12 km resolution) and eastern Texas (4 km resolution) during August and September of 2006. The results at the Air Quality System (AQS) surface sites show that in August, the normalized mean bias (NMB) values for PM2.5 over the eastern US (EUS) and the western US (WUS) are 5.3% (-0.1 %) and 0.4% (-5.2 %) for WRF-CMAQ/CAM (WRF-CMAQ/RRTMG), respectively. The evaluation of PM2.5 chemical composition reveals that in August, WRF-CMAQ/CAM (WRF-CMAQ/RRTMG) consistently underestimated the observed SO2-4 by -23.0% (-27.7 %), -12.5% (-18.9 %) and -7.9% (-14.8 %) over the EUS at the Clean Air Status Trends Network (CASTNET), Interagency Monitoring of Protected Visual Environments (IMPROVE) and Speciated Trends Network (STN) sites, respectively. Both configurations (WRF-CMAQ/CAM, WRF-CMAQ/RRTMG) overestimated the observed mean organic carbon (OC), elemental carbon (EC) and and total carbon (TC) concentrations over the EUS in August at the IMPROVE sites. Both configurations generally underestimated the cloud field (shortwave cloud forcing, SWCF) over the CONUS in August due to the fact that the AIE on the subgrid convective clouds was not considered when the model simulations were run at the 12 km resolution. This is in agreement with the fact that both configurations captured SWCF and longwave cloud forcing (LWCF) very well for the 4 km simulation over eastern Texas, when all clouds were resolved by the finer resolution domain. The simulations of WRF-CMAQ/CAM and WRF-CMAQ/RRTMG show dramatic improvements for SWCF, LWCF, cloud optical depth (COD), cloud fractions and precipitation over the ocean relative to those of WRF default cases in August. The model performance in September is similar to that in August, except for a greater overestimation of PM2.5 due to the overestimations of SO2-4 , NH+4 , NO-3 , and TC over the EUS, less underestimation of clouds (SWCF) over the land areas due to the lower SWCF values, and fewer convective clouds in September. This work shows that inclusion of indirect aerosol effect treatments in WRF-CMAQ represents a significant advancement and milestone in air quality modeling and the development of integrated emissions control strategies for air quality management and climate change mitigation. © 2014 Author(s)."
"56119479900;55717074000;24398842400;56424145700;","Different contact angle distributions for heterogeneous ice nucleation in the community atmospheric model version 5",2014,"10.5194/acp-14-10411-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907936517&doi=10.5194%2facp-14-10411-2014&partnerID=40&md5=f0bdde44d0de8184ddcd8538d90dea87","In order to investigate the impact of different treatments for the contact angle (&alpha;) in heterogeneous ice nucleating properties of natural dust and black carbon (BC) particles, we implement the classical-nucleation-theory-based parameterization of heterogeneous ice nucleation (Hoose et al., 2010) in the Community Atmospheric Model version 5 (CAM5) and then improve it by replacing the original single-contact-angle model with the probability-density-function-of-(-PDF) model to better represent the ice nucleation behavior of natural dust found in observations. We refit the classical nucleation theory (CNT) to constrain the uncertain parameters (i.e., onset and activation energy in the single-model; mean contact angle and standard deviation in the-PDF model) using recent observation data sets for Saharan natural dust and BC (soot). We investigate the impact of the time dependence of droplet freezing on mixed-phase clouds and climate in CAM5 as well as the roles of natural dust and soot in different nucleation mechanisms. Our results show that, when compared with observations, the potential ice nuclei (IN) calculated by the-PDF model show better agreement than those calculated by the single-model at warm temperatures (T &minus;20 °C). More ice crystals can form at low altitudes (with warm temperatures) simulated by the-PDF model than compared to the single-model in CAM5. All of these can be attributed to different ice nucleation efficiencies among aerosol particles, with some particles having smaller contact angles (higher efficiencies) in the-PDF model. In the sensitivity tests with the-PDF model, we find that the change in mean contact angle has a larger impact on the active fraction at a given temperature than a change in standard deviation, even though the change in standard deviation can lead to a change in freezing behavior. Both the single-and the-PDF model indicate that the immersion freezing of natural dust plays a more important role in the heterogeneous nucleation than that of soot in mixed-phase clouds. The new parameterizations implemented in CAM5 induce more significant aerosol indirect effects than the default parameterization. © 2014 Author(s)."
"24390528000;6602600408;35611334800;7102953444;","Pollution trends over Europe constrain global aerosol forcing as simulated by climate models",2014,"10.1002/2013GL058715","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896406949&doi=10.1002%2f2013GL058715&partnerID=40&md5=2202db9b6f8fb2e3d500f48f8705d9cf","An increasing trend in surface solar radiation (solar brightening) has been observed over Europe since the 1990s, linked to economic developments and air pollution regulations and their direct as well as cloud-mediated effects on radiation. Here, we find that the all-sky solar brightening trend (1990-2005) over Europe from seven out of eight models (historical simulations in the Fifth Coupled Model Intercomparison Project) scales well with the regional and global mean effective forcing by anthropogenic aerosols (idealized ""present- day"" minus ""preindustrial"" runs). The reason for this relationship is that models that simulate stronger forcing efficiencies and stronger radiative effects by aerosol-cloud interactions show both a stronger aerosol forcing and a stronger solar brightening. The all-sky solar brightening is the observable from measurements (4.06±0.60 W m-2 decade-1), which then allows to infer a global mean total aerosol effective forcing at about -1.30 W m-2 with standard deviation ±0.40 W m-2. © 2014. American Geophysical Union. All Rights Reserved."
"7201656946;7102447698;56244473600;7103206141;7101823091;","Climate versus emission drivers of methane lifetime against loss by tropospheric OH from 1860-2100",2012,"10.5194/acp-12-12021-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871265119&doi=10.5194%2facp-12-12021-2012&partnerID=40&md5=81381b065fde9d60b0ef0786ba6dedc4","With a more-than-doubling in the atmospheric abundance of the potent greenhouse gas methane (CH4) since preindustrial times, and indications of renewed growth following a leveling off in recent years, questions arise as to future trends and resulting climate and public health impacts from continued growth without mitigation. Changes in atmospheric methane lifetime are determined by factors which regulate the abundance of OH, the primary methane removal mechanism, including changes in CH4 itself. We investigate the role of emissions of short-lived species and climate in determining the evolution of methane lifetime against loss by tropospheric OH, (τCH4OH), in a suite of historical (1860-2005) and future Representative Concentration Pathway (RCP) simulations (2006-2100), conducted with the Geophysical Fluid Dynamics Laboratory (GFDL) fully coupled chemistry-climate model (CM3). From preindustrial to present, CM3 simulates an overall 5% increase in τCH4OH due to a doubling of the methane burden which offsets coincident increases in nitrogen oxide (NO x emissions. Over the last two decades, however, the τCH4OH declines steadily, coinciding with the most rapid climate warming and observed slow-down in CH4 growth rates, reflecting a possible negative feedback through the CH4 sink. Sensitivity simulations with CM 3 suggest that the aerosol indirect effect (aerosol-cloud interactions) plays a significant role in cooling the CM3 climate. The projected decline in aerosols under all RCPs contributes to climate warming over the 21st century, which influences the future evolution of OH concentration and τCH4OH. Projected changes in τCH4OH from 2006 to 2100 range from-13% to +4%. The only projected increase occurs in the most extreme warming case (RCP8.5) due to the near-doubling of the CH4 abundance, reflecting a positive feedback on the climate system. The largest decrease occurs in the RCP4.5 scenario due to changes in short-lived climate forcing agents which reinforce climate warming and enhance OH. This decrease is more-than-halved in a sensitivity simulation in which only well-mixed greenhouse gas radiative forcing changes along the RCP4.5 scenario (5% vs. 13%). © 2012 Author(s)."
"55173596300;57208121852;","Regime-based analysis of aerosol-cloud interactions",2012,"10.1029/2012GL053221","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868623630&doi=10.1029%2f2012GL053221&partnerID=40&md5=c02e040d3c539a89668e75189bc49406","Previous global satellite studies into the indirect aerosol effect have relied on determining the sensitivity of derived Cloud Droplet Number Concentration (N<inf>d</inf>) to co-located Aerosol Optical Depth (AOD). These studies generally find a positive N<inf>d</inf> sensitivity to AOD changes over ocean, but some find a negative sensitivity over land, in contrast to that predicted by models and theory. Here we investigate the N<inf>d</inf> sensitivity to AOD in different cloud regimes, determined using a k-means clustering process on retrieved cloud properties. We find the strongest positive N<inf>d</inf> sensitivity in the stratiform regimes over both land and ocean, providing the majority of the total sensitivity. The negative sensitivity previously observed over land is generated by the low cloud fraction regimes, suggesting that it is due to the difficulty of retrieving N<inf>d</inf> at low cloud fractions. When considering a mean sensitivity, weighted by liquid cloud fraction to account for sampling biases, we find an increased sensitivity over land, in some regions becoming positive. This highlights the importance of regime based analysis when studying aerosol indirect effects. © 2012. American Geophysical Union. All Rights Reserved."
"7102680152;22959375000;7202779940;6604015058;6601927317;6602354484;57193537889;6601974344;36730485900;36812255500;8084443000;7006415284;","Hygroscopic growth and droplet activation of soot particles: Uncoated, succinic or sulfuric acid coated",2012,"10.5194/acp-12-4525-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861555046&doi=10.5194%2facp-12-4525-2012&partnerID=40&md5=941c192cdd9cd7c857494d8d0cacf41a","The hygroscopic growth and droplet activation of uncoated soot particles and such coated with succinic acid and sulfuric acid were investigated during the IN-11 campaign at the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) facility. A GFG-1000 soot generator applying either nitrogen or argon as carrier gas and a miniCAST soot generator were utilized to generate soot particles. Different organic carbon (OC) to black carbon (BC) ratios were adjusted for the CAST-soot by varying the fuel to air ratio. The hygroscopic growth was investigated by means of the mobile Leipzig Aerosol Cloud Interaction Simulator (LACIS-mobile) and two different Hygroscopicity Tandem Differential Mobility Analyzers (HTDMA, VHTDMA). Two Cloud Condensation Nucleus Counter (CCNC) were applied to measure the activation of the particles. For the untreated soot particles neither hygroscopic growth nor activation was observed at a supersaturation of 1%, with exception of a partial activation of GFG-soot generated with argon as carrier gas. Coatings of succinic acid lead to a detectable hygroscopic growth of GFG-soot and enhanced the activated fraction of GFG-(carrier gas: argon) and CAST-soot, whereas no hygroscopic growth of the coated CAST-soot was found. Sulfuric acid coatings led to an OC-content dependent hygroscopic growth of CAST-soot. Such a dependence was not observed for activation measurements. Coating with sulfuric acid decreased the amount of Polycyclic Aromatic Hydrocarbons (PAH), which were detected by AMS-measurements in the CAST-soot, and increased the amount of substances with lower molecular weight than the initial PAHs. We assume that these reaction products increased the hygroscopicity of the coated particles in addition to the coating substance itself. © 2012 Author(s)."
"26661481400;7409080503;","Separating real and apparent effects of cloud, humidity, and dynamics on aerosol optical thickness near cloud edges",2010,"10.1029/2009JD013547","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650585340&doi=10.1029%2f2009JD013547&partnerID=40&md5=31e7f2c4cf518f3f729f05f7be2eb339","Aerosol optical thickness (AOT) is one of aerosol parameters that can be measured on a routine basis with reasonable accuracy from Sun-photometric observations at the surface. However, AOT-derived near clouds is fraught with various real effects and artifacts, posing a big challenge for studying aerosol and cloud interactions. Recently, several studies have reported correlations between AOT and cloud cover, pointing to potential cloud contamination and the aerosol humidification effect; however, not many quantitative assessments have been made. In this study, various potential causes of apparent correlations are investigated in order to separate the real effects from the artifacts, using well-maintained observations from the Aerosol Robotic Network, Total Sky Imager, airborne nephelometer, etc., over the Southern Great Plains site operated by the U.S. Department of Energy's Atmospheric Radiation Measurement Program. It was found that aerosol humidification effects can explain about one fourth of the correlation between the cloud cover and AOT. New particle genesis, cloud-processed particles, atmospheric dynamics, and aerosol indirect effects are likely to be contributing to as much as the remaining three fourth of the relationship between cloud cover and AOT. Copyright 2010 by the American Geophysical Union."
"57151771800;8542741400;8633783900;","Interhemispheric aerosol radiative forcing and tropical precipitation shifts during the late Twentieth Century",2015,"10.1175/JCLI-D-15-0148.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945474745&doi=10.1175%2fJCLI-D-15-0148.1&partnerID=40&md5=dcff66163ff42aef2965a788781e53ee","Through the latter half of the twentieth century, meridional shifts in tropical precipitation have been associated with severe droughts. Although linked to a variety of causes, the origin of these shifts remains elusive. Here, it is shown that they are unlikely to arise from internal variability of the climate system alone, as simulated by coupled ocean-atmosphere climate models. Similar to previous work, the authors find that anthropogenic and volcanic aerosols are the dominant drivers of simulated twentieth-century tropical precipitation shifts. Models that include the cloud-albedo and lifetime aerosol indirect effects yield significantly larger shifts than models that lack aerosol indirect effects and also reproduce most of the southward tropical precipitation shift in the Pacific. However, all models significantly underestimate the magnitude of the observed shifts in the Atlantic sector, unless driven by observed SSTs. Mechanistically, tropical precipitation shifts are driven by interhemispheric sea surface temperature variations, which are associated with hemispherically asymmetric changes in low-latitude surface pressure, winds, and low clouds, as well as the strength, location, and cross-equatorial energy transport of the Hadley cells. Models with a larger hemispheric aerosol radiative forcing gradient yield larger hemispheric temperature contrasts and, in turn, larger meridional precipitation shifts. The authors conclude that aerosols are likely the dominant driver of the observed southward tropical precipitation shift in the Pacific. Aerosols are also significant drivers of the Atlantic shifts, although one cannot rule out a contribution from natural variability to account for the magnitude of the observed shifts. © 2015 American Meteorological Society."
"24173873500;7004174939;55113736500;","Microphysical and radiative effects of aerosols on warm clouds during the Amazon biomass burning season as observed by MODIS: Impacts of water vapor and land cover",2011,"10.5194/acp-11-3021-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953693609&doi=10.5194%2facp-11-3021-2011&partnerID=40&md5=96434bdb0fbe01fc5344128e87f0b8b1","Aerosol, cloud, water vapor, and temperature profile data from the Moderate Resolution Imaging Spectroradiometer (MODIS) are utilized to examine the impact of aerosols on clouds during the Amazonian biomass burning season in Rondnia, Brazil. It is found that increasing background column water vapor (CWV) throughout this transition season between the Amazon dry and wet seasons likely exerts a strong effect on cloud properties. As a result, proper analysis of aerosol-cloud relationships requires that data be stratified by CWV to account better for the influence of background meteorological variation. Many previous studies of aerosol-cloud interactions over Amazonia have ignored the systematic changes to meteorological factors during the transition season, leading to possible misinterpretation of their results. Cloud fraction (CF) is shown to increase or remain constant with aerosol optical depth (AOD), depending on the value of CWV, whereas the relationship between cloud optical depth (COD) and AOD is quite different. COD increases with AOD until AOD ∼ 0.3, which is assumed to be due to the first indirect (microphysical) effect. At higher values of AOD, COD is found to decrease with increasing AOD, which may be due to: (1) the inhibition of cloud development by absorbing aerosols (radiative effect/semi-direct effect) and/or (2) a possible retrieval artifact in which the measured reflectance in the visible is less than expected from a cloud top either from the darkening of clouds through the addition of carbonaceous biomass burning aerosols within or above clouds or subpixel dark surface contamination in the measured cloud reflectance. If (1) is a contributing mechanism, as we suspect, then an empirically-derived increasing function between cloud drop number and aerosol concentration, assumed in a majority of global climate models, is inaccurate since these models do not include treatment of aerosol absorption in and around clouds. The relationship between aerosols and both CWV and clouds over varying land surface types is also analyzed. The study finds that the difference in CWV between forested and deforested land is not correlated with aerosol loading, supporting the assumption that temporal variation of CWV is primarily a function of the larger-scale meteorology. However, a difference in the response of CF to increasing AOD is observed between forested and deforested land. This suggests that dissimilarities between other meteorological factors, such as atmospheric stability, may have an impact on aerosol-cloud correlations between different land cover types. © 2011 Author(s)."
"36856321600;7004479957;","Response of a subtropical stratocumulus-capped mixed layer to climate and aerosol changes",2009,"10.1175/2008JCLI1967.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60749119482&doi=10.1175%2f2008JCLI1967.1&partnerID=40&md5=8b2bd37705ef28edea2b890cfe7f1904","In this paper, an idealized framework based on a cloud-topped mixed layer model is developed for investigating feedbacks between subtropical stratocumulus (Sc) and global warming. The two principal control parameters are Sc-region sea surface temperature (SST) and intertropical convergence zone (ITCZ) SST (which controls the temperature and mean subsidence profiles above the Sc). The direct effect of CO2 doubling (leaving all other parameters fixed) is tested and found to somewhat reduce liquid water path; discussion of this effect on the SST-change simulations is included. The presence of a cold boundary layer is found to significantly affect the temperature and subsidence rate just above cloud top by enhancing lower-tropospheric diabatic cooling in this region. A simple representation of this effect (easily generalizable to a more realistic boundary layer model) is developed. Steady-state solutions are analyzed as a function of local and ITCZ SST. Two climate change scenarios are considered. The first scenario is an equal increase of local and ITCZ SSTs. In this case, predicted boundary layer depth and cloud thickness increase. This is found in a simplified context to result from subsidence and entrainment decreases due to increased static stability in a warmer climate. In the second case, local SST change is diagnosed from a surface energy balance under the assumption that ocean heat transport remains unchanged. In this case, predicted boundary layer depth decreases. Cloud continues to thicken with rising ITCZ SST, but at a rate much reduced in comparison to the equal-warming scenario. This cloud shading feedback keeps SST in the Sc region nearly constant as the ITCZ SST increases. Model sensitivity to aerosol indirect effects is also considered by varying the assumed droplet concentration. The resulting change in liquid water path is small, suggesting a weaker dependence on second indirect effect than found in previous studies. © 2009 American Meteorological Society."
"7102084129;7003591311;","Explanation of discrepancies among satellite observations of the aerosol indirect effects",2003,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141942130&partnerID=40&md5=b0685a7e71624d36948c14bc30e96975","Satellite-based remote sensing instruments for measuring the aerosol indirect effect (IE = -d ln re/d ln Ta where re is the cloud drop effective radius and Ta is the aerosol optical depth) show large disparities in the magnitude of the effect for similar regions of the globe. Over the oceans, the Advanced Very High Resolution Radiometer (AVHRR) measures an indirect effect twice that measured by the POLarization and Directionality of the Earth Reflectances (POLDER) (0.17 vs. 0.085). We address possible reasons for these disparities. It is argued that AVHRR misses the optically thin and broken clouds, especially over land, while POLDER misses clouds with variable top heights in its field of view. POLDER is also biased to thinner, less turbulent clouds. The sensitivity of the indirect effect to cloud turbulence therefore biases POLDER to lower values. POLDER measures an indirect effect over the ocean that is about twice that over the land (0.085 vs. 0.04). By considering factors such as dynamics, variability in cloud liquid water path, decoupling of the boundary layer, and the effect of salt particles, we argue that this could be an artifact, and that the indirect effect on cloud microstructure may be stronger over land than over the ocean."
"55896920900;7004393835;57112070700;","Cloud optical thickness and liquid water path-does the k coefficient vary with droplet concentration?",2011,"10.5194/acp-11-9771-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052983143&doi=10.5194%2facp-11-9771-2011&partnerID=40&md5=5b7317f6753c2462f5395acd5d7c90cf","Cloud radiative transfer calculations in general circulation models involve a link between cloud microphysical and optical properties. Indeed, the liquid water content expresses as a function of the mean volume droplet radius, while the light extinction is a function of their mean surface radius. There is a small difference between these two parameters because of the droplet spectrum width. This issue has been addressed by introducing an empirical multiplying correction factor to the droplet concentration. Analysis of in situ sampled data, however, revealed that the correction factor decreases when the concentration increases, hence partially mitigating the aerosol indirect effect. <br><br> Five field experiments are reanalyzed here, in which standard and upgraded versions of the droplet spectrometer were used to document shallow cumulus and stratocumulus topped boundary layers. They suggest that the standard probe noticeably underestimates the correction factor compared to the upgraded versions. The analysis is further refined to demonstrate that the value of the correction factor derived by averaging values calculated locally along the flight path overestimates the value derived from liquid water path and optical thickness of a cloudy column, and that there is no detectable relationship between the correction factor and the droplet concentration. It is also shown that the droplet concentration dilution by entrainment-mixing after CCN activation is significantly stronger in shallow cumuli than in stratocumulus layers. These various effects are finally combined to produce the today best estimate of the correction factor to use in general circulation models. © 2011 Author(s)."
"7102805852;10139397300;7407104838;57203200427;7102953444;7004942632;","The roles of aerosol, water vapor and cloud in future global dimming/brightening",2011,"10.1029/2011JD016000","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80055055695&doi=10.1029%2f2011JD016000&partnerID=40&md5=715be3349a82b9842ef7d644ac0eced6","Observational evidence indicates significant regional trends in solar radiation at the surface in both all-sky and cloud-free conditions. Negative trends in the downwelling solar surface irradiance (SSI) have become known as dimming while positive trends have become known as brightening. We use the Met Office Hadley Centre HadGEM2 climate model to model trends in cloud-free and total SSI from the pre-industrial to the present-day and compare these against observations. Simulations driven by CMIP5 emissions are used to model the future trends in dimming/brightening up to the year 2100. The modeled trends are reasonably consistent with observed regional trends in dimming and brightening which are due to changes in concentrations in anthropogenic aerosols and, potentially, changes in cloud cover owing to the aerosol indirect effects and/or cloud feedback mechanisms. The future dimming/brightening in cloud-free SSI is not only caused by changes in anthropogenic aerosols: aerosol impacts are overwhelmed by a large dimming caused by increases in water vapor. There is little trend in the total SSI as cloud cover decreases in the climate model used here, and compensates the effect of the change in water vapor. In terms of the surface energy balance, these trends in SSI are obviously more than compensated by the increase in the downwelling terrestrial irradiance from increased water vapor concentrations. However, the study shows that while water vapor is widely appreciated as a greenhouse gas, water vapor impacts on the atmospheric transmission of solar radiation and the future of global dimming/brightening should not be overlooked. Copyright © 2011 by the American Geophysical Union."
"26661481400;7409080503;36000595000;7101899854;","Effect of aerosol humidification on the column aerosol optical thickness over the Atmospheric Radiation Measurement Southern Great Plains site",2007,"10.1029/2006JD007176","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547611955&doi=10.1029%2f2006JD007176&partnerID=40&md5=adf3347b9ea8f7a4ff9fd803676ddf71","This study investigates the aerosol humidification effect (AHE) using 70 profiles of the aerosol scattering coefficients at high (∼80%) and low (∼40%) relative humidity (RH) levels and absorption coefficient at a low RH level obtained by a light aircraft (Cessna C-172N) over the Southern Great Plains (SGP) site from April 2003 to June 2004. The column aerosol humidification factor, R(RH), defined as the ratio of the aerosol optical thickness (AOT) at the ambient RH to that at RH = 40% throughout the column rarely exceeded 1.3 (mean, 1.09 ± 0.12) over the SGP site. However, for an atmospheric column of a constant RH = 85%, R(RH) is greater than 1.5 for the majority of cases (mean, 1.57 ± 0.28). R(RH) was fitted to a function of column RH based on this unique aerosol data set. Several methods were proposed to estimate R(RH) for use when direct measurements of R(RH) are not available. It was found that the relationship between R(RH) and aerosol extinction coefficient weighted column-mean RH works best. Performance of other methods depends on the measurements available. Sensitivity of R(RH) to a very humid (RH = 99%) layer with varying thickness values (0.1-0.3 km) is examined. The results indicate that the AHE on the AOT over the SGP site is not likely to exceed 50% on the average. The methods and results of this study may be utilized with caution to remove the AHE from the AOT retrieved from satellite or automated Sun photometer measurements, which will be useful for studies on aerosol indirect effect or quantifying cloud contamination in aerosol retrievals. Copyright 2007 by the American Geophysical Union."
"7006705919;7401936984;15755995900;8859530100;55688930000;25629055800;22953153500;36856321600;56384704800;7006270084;9434771700;55544607500;57202299549;6701752471;55418728800;57188758598;6701431208;7005920812;15044268700;55802246600;57202522440;7202048112;52464731300;57210671633;6507492100;36876405100;25637373000;35617453500;7102696626;12761052200;55317177900;6603400519;7102450474;8570871900;57209779308;55165863400;24534445300;7402064802;55717074000;7004245252;13007924700;55720018700;","An Overview of the Atmospheric Component of the Energy Exascale Earth System Model",2019,"10.1029/2019MS001629","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068580236&doi=10.1029%2f2019MS001629&partnerID=40&md5=f2b9c692b04e0646e34f11b45b76a5ea","The Energy Exascale Earth System Model Atmosphere Model version 1, the atmospheric component of the Department of Energy's Energy Exascale Earth System Model is described. The model began as a fork of the well-known Community Atmosphere Model, but it has evolved in new ways, and coding, performance, resolution, physical processes (primarily cloud and aerosols formulations), testing and development procedures now differ significantly. Vertical resolution was increased (from 30 to 72 layers), and the model top extended to 60 km (~0.1 hPa). A simple ozone photochemistry predicts stratospheric ozone, and the model now supports increased and more realistic variability in the upper troposphere and stratosphere. An optional improved treatment of light-absorbing particle deposition to snowpack and ice is available, and stronger connections with Earth system biogeochemistry can be used for some science problems. Satellite and ground-based cloud and aerosol simulators were implemented to facilitate evaluation of clouds, aerosols, and aerosol-cloud interactions. Higher horizontal and vertical resolution, increased complexity, and more predicted and transported variables have increased the model computational cost and changed the simulations considerably. These changes required development of alternate strategies for tuning and evaluation as it was not feasible to “brute force” tune the high-resolution configurations, so short-term hindcasts, perturbed parameter ensemble simulations, and regionally refined simulations provided guidance on tuning and parameterization sensitivity to higher resolution. A brief overview of the model and model climate is provided. Model fidelity has generally improved compared to its predecessors and the CMIP5 generation of climate models. ©2019. The Authors."
"57208121852;","Limitations of passive remote sensing to constrain global cloud condensation nuclei",2016,"10.5194/acp-16-6595-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84973569070&doi=10.5194%2facp-16-6595-2016&partnerID=40&md5=5973d3f321a160b8e388f096f8710cd6","Aerosol-cloud interactions are considered a key uncertainty in our understanding of climate change (Boucher et al., 2013). Knowledge of the global abundance of cloud condensation nuclei (CCN) is fundamental to determine the strength of the anthropogenic climate perturbation. Direct measurements are limited and sample only a very small fraction of the globe so that remote sensing from satellites and ground-based instruments is widely used as a proxy for cloud condensation nuclei (Nakajima et al., 2001; Andreae, 2009; Clarke and Kapustin, 2010; Boucher et al., 2013). However, the underlying assumptions cannot be robustly tested with the small number of measurements available so that no reliable global estimate of cloud condensation nuclei exists. This study overcomes this limitation using a self-consistent global model (ECHAM-HAM) of aerosol radiative properties and cloud condensation nuclei. An analysis of the correlation of simulated aerosol radiative properties and cloud condensation nuclei reveals that common assumptions about their relationships are violated for a significant fraction of the globe: 71% of the area of the globe shows correlation coefficients between CCN0.2% at cloud base and aerosol optical depth (AOD) below 0.5, i.e. AOD variability explains only 25% of the CCN variance. This has significant implications for satellite based studies of aerosol-cloud interactions. The findings also suggest that vertically resolved remote-sensing techniques, such as satellite-based high spectral resolution lidars, have a large potential for global monitoring of cloud condensation nuclei. © 2016 Author(s)."
"57161358100;56162305900;7003666669;7102010848;55688930000;56384704800;23095483400;57203053317;16444232500;7202079615;25031430500;7103158465;55588510300;7004214645;57163988800;57208121852;49861577800;7402803216;","On the characteristics of aerosol indirect effect based on dynamic regimes in global climate models",2016,"10.5194/acp-16-2765-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84960414965&doi=10.5194%2facp-16-2765-2016&partnerID=40&md5=6b5f9028ea1d74c05cf4baaee72e5cc9","Aerosol-cloud interactions continue to constitute a major source of uncertainty for the estimate of climate radiative forcing. The variation of aerosol indirect effects (AIE) in climate models is investigated across different dynamical regimes, determined by monthly mean 500 hPa vertical pressure velocity (<i>‰</i>500), lower-tropospheric stability (LTS) and large-scale surface precipitation rate derived from several global climate models (GCMs), with a focus on liquid water path (LWP) response to cloud condensation nuclei (CCN) concentrations. The LWP sensitivity to aerosol perturbation within dynamic regimes is found to exhibit a large spread among these GCMs. It is in regimes of strong large-scale ascent (<i>‰</i>500g€¯ &lt; g€¯g'25 hPa dayg'1) and low clouds (stratocumulus and trade wind cumulus) where the models differ most. Shortwave aerosol indirect forcing is also found to differ significantly among different regimes. Shortwave aerosol indirect forcing in ascending regimes is close to that in subsidence regimes, which indicates that regimes with strong large-scale ascent are as important as stratocumulus regimes in studying AIE. It is further shown that shortwave aerosol indirect forcing over regions with high monthly large-scale surface precipitation rate (&gt; 0.1 mm dayg'1) contributes the most to the total aerosol indirect forcing (from 64 to nearly 100 %). Results show that the uncertainty in AIE is even larger within specific dynamical regimes compared to the uncertainty in its global mean values, pointing to the need to reduce the uncertainty in AIE in different dynamical regimes. © 2016 Author(s) . CC Attribution 3.0 License."
"13405658600;57217801354;55683727600;55683891800;13403849600;7005287667;8942525300;","Weak global sensitivity of cloud condensation nuclei and the aerosol indirect effect to Criegee+SO2 chemistry",2013,"10.5194/acp-13-3163-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901346317&doi=10.5194%2facp-13-3163-2013&partnerID=40&md5=dabef9b4e96c287b30c1da2aa602b2cc","H2SO4 vapor is important for the nucleation of atmospheric aerosols and the growth of ultrafine particles to cloud condensation nuclei (CCN) sizes with important roles in the global aerosol budget and hence planetary radiative forcing. Recent studies have found that reactions of stabilized Criegee intermediates (CIs, formed from the ozonolysis of alkenes) with SO2 may be an important source of H2SO4 that has been missing from atmospheric aerosol models. For the first time in a global model, we investigate the impact of this new source of H 2SO4 in the atmosphere. We use the chemical transport model, GEOS-Chem, with the online aerosol microphysics module, TOMAS, to estimate the possible impact of CIs on present-day H2SO4, CCN, and the cloud-albedo aerosol indirect effect (AIE). We extend the standard GEOS-Chem chemistry with CI-forming reactions (ozonolysis of isoprene, methyl vinyl ketone, methacrolein, propene, and monoterpenes) from the Master Chemical Mechanism. Using a fast rate constant for CI+SO2, we find that the addition of this chemistry increases the global production of H 2SO4 by 4 %. H2SO4 concentrations increase by over 100% in forested tropical boundary layers and by over 10-25% in forested NH boundary layers (up to 100% in July) due to CI+SO2 chemistry, but the change is generally negligible elsewhere. The predicted changes in CCN were strongly dampened to the CI+SO2 changes in H 2SO4 in some regions: less than 15% in tropical forests and less than 2% in most mid-latitude locations. The global-mean CCN change was less than 1% both in the boundary layer and the free troposphere. The associated cloud-albedo AIE change was less than 0.03Wm-2. The model global sensitivity of CCN and the AIE to CI+SO2 chemistry is significantly (approximately one order-of-magnitude) smaller than the sensitivity of CCN and AIE to other uncertain model inputs, such as nucleation mechanisms, primary emissions, SOA (secondary organic aerosol) and deposition. Similarly, comparisons to size-distribution measurements show that uncertainties in other model parameters dominate model biases in the model predicted size distributions. We conclude that improvement in the modeled CI+SO2 chemistry would not likely lead to significant improvements in present-day CCN and AIE predictions. © Author(s) 2013."
"7403564495;7402064802;7401936984;55717074000;7401974644;52464731300;","Aerosol first indirect effects on non-precipitating low-level liquid cloud properties as simulated by CAM5 at ARM sites",2012,"10.1029/2012GL051213","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861322251&doi=10.1029%2f2012GL051213&partnerID=40&md5=604260f7a8b6c27421756679165aa6d5","We quantitatively examine the aerosol first indirect effects (FIE) for non-precipitating low-level single-layer liquid phase clouds simulated by the Community Atmospheric Model version 5 (CAM5) running in the weather forecast mode at three DOE Atmospheric Radiation Measurement (ARM) sites. The FIE is quantified in terms of a relative change in cloud droplet effective radius for a relative change in accumulation mode aerosol number concentration under conditions of fixed liquid water content (LWC). CAM5 simulates aerosol-cloud interactions reasonably well for this specific cloud type, and the simulated FIE is consistent with the long-term observations at the examined locations. The FIE in CAM5 generally decreases with LWC at coastal ARM sites, and is larger by using cloud condensation nuclei rather than accumulation mode aerosol number concentration as the choice of aerosol amount. However, it has no significant variations with location and has no systematic strong seasonal variations at examined ARM sites. Copyright 2012 by the American Geophysical Union."
"14066601400;7003469326;7005899926;6506389946;55238619300;35487016600;25923454000;55951906300;7102113229;","CIAO: The CNR-IMAA advanced observatory for atmospheric research",2011,"10.5194/amt-4-1191-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81055147763&doi=10.5194%2famt-4-1191-2011&partnerID=40&md5=295ec413e7d66c0df0ba9e28d5671945","Long-term observations of aerosol and clouds are of crucial importance to understand the weather climate system. At the Istituto di Metodologie per l'Analisi Ambientale of the Italian National Research Council (CNR-IMAA) an advanced atmospheric observatory, named CIAO, is operative. CIAO (CNR-IMAA Atmospheric Observatory) main scientific objective is the long term measurement for the climatology of aerosol and cloud properties. Its equipment addresses the state-of-the-art for the ground-based remote sensing of aerosol, water vapour and clouds including active and passive sensors, like lidars, ceilometers, radiometers, and a radar. This paper describes the CIAO infrastructure, its scientific activities as well as the observation strategy. The observation strategy is mainly organized in order to provide quality assured measurements for satellite validation and model evaluation and to fully exploit the synergy and integration of the active and passive sensors for the improvement of atmospheric profiling. Data quality is ensured both by the application of protocols and dedicated quality assurance programs mainly related to the projects and networks in which the infrastructure is involved. The paper also introduces examples of observations performed at CIAO and of the synergies and integration algorithms (using Raman lidar and microwave profiler data) developed and implemented at the observatory for the optimization and improvement of water vapour profiling. CIAO database represents an optimal basis to study the synergy between different sensors and to investigate aerosol-clouds interactions, and can give a significant contribution to the validation programs of the incoming new generation satellite missions. © 2012 Author(s)."
"6603453147;57206332144;","Global CALIPSO observations of aerosol changes near clouds",2011,"10.1109/LGRS.2010.2049982","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650927865&doi=10.1109%2fLGRS.2010.2049982&partnerID=40&md5=73a264166ce6e39c422813caace4785f","Several recent studies have found that clouds are surrounded by a transition zone of rapidly changing aerosol optical properties and particle size. Characterizing this transition zone is important for better understanding aerosolcloud interactions and aerosol radiative effects, and also for improving satellite retrievals of aerosol properties. This letter presents a statistical analysis of a monthlong global data set of CloudAerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar observations over oceans. The results show that the transition zone is ubiquitous over all oceans and extends up to 15 km away from clouds. They also show that near-cloud enhancements in backscatter and particle size are strongest at low altitudes, slightly below the top of the nearest clouds. Also, the enhancements are similar near illuminated and shadowy cloud sides, which confirms that the asymmetry of Moderate Resolution Imaging Spectroradiometer reflectances found in an earlier study comes from 3-D radiative processes and not from differences in aerosol properties. Finally, the effects of CALIPSO aerosol detection and cloud identification uncertainties are discussed. The findings underline the importance of accounting for the transition zone to avoid potential biases in studies of satellite aerosol products, aerosolcloud interactions, and aerosol direct radiative effects. © 2010 IEEE."
"55754495900;7404976222;","Weakening trend in the atmospheric heat source over the Tibetan Plateau during recent decades. Part II: Connection with climate warming",2009,"10.1175/2009JCLI2699.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69249104934&doi=10.1175%2f2009JCLI2699.1&partnerID=40&md5=a203b1f775e78ecf0e46072344ce829d","In Part I the authors have shown that heating sources in spring over the Tibetan Plateau (TP), and in particular the sensible heat flux (SHF), exhibit a significant weakening trend since the mid-1980s that is induced mainly by decreased surface wind speed. The possible reason of such a change is further investigated in Part II by analyzing historical observations and the NCEP/Department of Energy (DOE) reanalysis. The steady declining trend in the surface wind speed over the TP after the 1970s arises mainly from the zonal component. Since the mean altitude of the TP is about 600 hPa and the surface flow is controlled by the East Asian subtropical westerly jet (EASWJ) for most parts of the year, the substantial tropospheric warming in the mid- and high latitudes to the north of the plateau results in a decrease of the meridional pressure gradient in the subtropics. As a result, the EASWJ and the surface winds over the TP are decelerated. Moreover, changes of the general circulation in the twentieth century simulated by 16 coupled climate models driven by natural and anthropogenic forcings are examined. Intercomparison results suggest that sulfate aerosol indirect effects and ozone may be important in reproducing the weakening trend in EASWJ. Although nearly half of the models can successfully reproduce the observed trends in the EASWJ during the last two decades, there is an obvious spread in simulation of the spatial patterns of twentieth-century tropospheric temperatures, suggesting significant room still exists for improvement of the current state-of-the-art coupled climate models. © 2009 American Meteorological Society."
"22959375000;8550791300;35600074800;6604016408;8710280200;8849246700;15072064200;7006415284;","Hygroscopic growth and activation of HULIS particles: Experimental data and a new iterative parameterization scheme for complex aerosol particles",2008,"10.5194/acp-8-1855-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41449116966&doi=10.5194%2facp-8-1855-2008&partnerID=40&md5=3cccdfbf57605707f3ecfc1491fe0e66","The hygroscopic growth and activation of two HULIS (HUmic LIke Substance) and one Aerosol-Water-Extract sample, prepared from urban-type aerosol, were investigated. All samples were extracted from filters, redissolved in water and atomized for the investigations presented here. The hygroscopic growth measurements were done using LACIS (Leipzig Aerosol Cloud Interaction Simulator) together with a HH-TDMA (High Humidity Tandem Differential Mobility Analyzer). Hygroscopic growth was determined for relative humidities (RHs) up to 99.75%. The critical diameters for activation were measured for supersaturations between 0.2 and 1%. All three samples showed a similar hygroscopic growth behavior, and the two HULIS samples also were similar in their activation behavior, while the Aerosol-Water-Extract turned out to be more CCN active than the HULIS samples. The experimental data was used to derive parameterizations for the hygroscopic growth and activation of HULIS particles. The concept of ρion (Wex et al., 2007a) and the Szyszkowski-equation (Szyszkowski, 1908; Facchini, 1999) were used for parameterizing the Raoult and the Kelvin (surface tension) terms of the K ¶hler equation, respectively. This concept proved to be very successful for the HULIS samples in the saturation range from RHs larger than 98% up to activation. It was also shown to work well with data on HULIS taken from literature. Here, different atmospheric life-times and/or different sources for the different samples showed up in different coefficients for the parameterization. However, the parameterization did not work out well for the Aerosol-Water-Extract."
"9043417100;7006235542;57195257572;7006377579;7201787800;7003445775;","Cloud-resolving simulations of intense tropical Hector thunderstorms: Implications for aerosol-cloud interactions",2006,"10.1256/qj.05.86","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34848837269&doi=10.1256%2fqj.05.86&partnerID=40&md5=107b394119dc3af9b5584d31432fd4a9","The Hector thunderstorm is studied with a numerical cloud-resolving model. Special attention is given to modelling the mixed-phase and glaciated cloud microphysical processes (along with the implications of aerosols) and their influence on the resulting microphysical and dynamical storm structure. Radiative impacts are also calculated. Simulations are performed for a typical storm case from the EMERALD-II convective cloud experiment in November and December 2002. It is found that, for intense thunderstorms, aerosol indirect effects are generally modified from recently proposed theoretical considerations. Specifically, the proposed 'glaciation' indirect effect, resulting from increasing ice nuclei concentrations, is small for intense convection. More importantly, increasing ice number concentrations results in a 'collection' indirect effect (where aggregation and accretion processes lead to precipitation) rather than the 'glaciation', Bergeron-Findeisen process. There is a 'thermodynamic' indirect effect for Hector, as increasing the cloud droplet number concentration from maritime to continental values resulted in a suppression of the heterogeneous freezing process. However, for extreme continental cases, liquid and raindrop freezing by collection processes acquires higher importance; hence there is an optimal value for strong cumulonimbus development. The 'glaciation' indirect effect is found to be similar to increasing the rate of ice production by the Hallett-Mossop process. Another aspect of this study shows that there is a significant impact of microphysics on cloud dynamics, and so studying aerosol-cloud effects must also consider dynamical feedback, a strong component of which arises from the latent heat released during homogeneous freezing. The important indirect effects may be well described by recent theory for smaller, more common stratiform and cumulus clouds; however, in the tropics, the importance of Hector-type storms cannot be ignored as they, and other similar storms, provide a mechanism for the production of widespread cirrus and the release of a large amount of precipitation. © Royal Meteorological Society, 2006."
"8045690700;7005275092;7202079615;","Tropospheric aerosol impacts on trace gas budgets through photolysis",2003,"10.1029/2002jd002743","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342279003&doi=10.1029%2f2002jd002743&partnerID=40&md5=20dd8f4ba3d98e68a76434669d25615e","Aerosols affect the global budgets Of O3, OH, and CH4 in part through their alteration of photolysis rates and in part through their direct chemical interactions with gases (i.e., ""heterogeneous chemistry""). The first effect is evaluated here with a global tropospheric chemistry transport model using recently developed global climatologies of tropospheric aerosols: a satellite-derived aerosol climatology over the oceans by advanced very high resolution radiometer and a model-generated climatology for land plus oceans by the Center for Climate System Research. Globally averaged, the impact of aerosols on photolysis alone is to increase tropospheric O3 by 0.63 Dobson units and increase tropospheric CH4 by 130 ppb (via tropospheric OH decreases of 8%). These greenhouse gas increases lead to an aerosol indirect effect (counting both natural and anthropogenic aerosols) of +0.08 W/m2 . Although the CH4 increases are, of course, global, the changes in tropospheric OH and O3 are mainly regional, with the largest impacts in northwest Affica for January and in India and southern Affica for July. The influence of aerosols is greater in July than in January and greater in the Northern Hemisphere than in the Southern Hemisphere, as expected given the pollution sources in the Northern Hemisphere. The predominant impact is due to the aerosols over land; aerosols over the ocean contribute less than a third to globally integrated changes."
"56502199700;8067118800;30767858100;7202079615;","The source of discrepancies in aerosol-cloud-precipitation interactions between GCM and A-Train retrievals",2016,"10.5194/acp-16-15413-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006321444&doi=10.5194%2facp-16-15413-2016&partnerID=40&md5=0bbdfbc1102f2edc3d871fca633473c6","Aerosol-cloud interactions are one of the most uncertain processes in climate models due to their nonlinear complexity. A key complexity arises from the possibility that clouds can respond to perturbed aerosols in two opposite ways, as characterized by the traditional ""cloud lifetime"" hypothesis and more recent ""buffered system"" hypothesis. Their importance in climate simulations remains poorly understood. Here we investigate the response of the liquid water path (LWP) to aerosol perturbations for warm clouds from the perspective of general circulation model (GCM) and A-Train remote sensing, through process-oriented model evaluations. A systematic difference is found in the LWP response between the model results and observations. The model results indicate a near-global uniform increase of LWP with increasing aerosol loading, while the sign of the response of the LWP from the A-Train varies from region to region. The satellite-observed response of the LWP is closely related to meteorological and/or macrophysical factors, in addition to the microphysics. The model does not reproduce this variability of cloud susceptibility (i.e., sensitivity of LWP to perturbed aerosols) because the parameterization of the autoconversion process assumes only suppression of rain formation in response to increased cloud droplet number, and does not consider macrophysical aspects that serve as a mechanism for the negative responses of the LWP via enhancements of evaporation and precipitation. Model biases are also found in the precipitation microphysics, which suggests that the model generates rainwater readily even when little cloud water is present. This essentially causes projections of unrealistically frequent and light rain, with high cloud susceptibilities to aerosol perturbations. © Author(s) 2016."
"7801565183;7006434689;14034301300;56238026000;23670554500;9846154100;6701810892;7004923073;7005069415;","A review of more than 20 years of aerosol observation at the high altitude research station Jungfraujoch, Switzerland (3580 m asl)",2016,"10.4209/aaqr.2015.05.0305","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959358521&doi=10.4209%2faaqr.2015.05.0305&partnerID=40&md5=82ae1168294e44b8f6aa296fd7f35e2d","Among the worldwide existing long-term aerosol monitoring sites, the Jungfraujoch (JFJ) belongs to the category where both free tropospheric (FT) conditions and influence from planetary boundary layer (PBL) injections can be observed. Thus, it is possible to characterize free tropospheric aerosol as well as the effects of vertical transport of more polluted air from the PBL. This paper summarizes the current knowledge of the key properties for the JFJ aerosol, gained from the large number of in-situ studies from more than 20 years of aerosol measurements at the site. This includes physical, chemical and optical aerosol properties as well as aerosol-cloud interactions and cloud characteristics. It is illustrated that the aerosol size distribution and the aerosol chemical composition are fairly constant in time due to the long distance from aerosol sources, and that many climate relevant aerosol properties can be derived due to this behavior. © Taiwan Association for Aerosol Research."
"7003666669;57193073844;56162305900;56384704800;8942524900;7004469744;13405658600;22978151200;57211106013;","A simple model of global aerosol indirect effects",2013,"10.1002/jgrd.50567","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880882329&doi=10.1002%2fjgrd.50567&partnerID=40&md5=44498e396d270ae107db9718920e930f","Most estimates of the global mean indirect effect of anthropogenic aerosol on the Earth's energy balance are from simulations by global models of the aerosol lifecycle coupled with global models of clouds and the hydrologic cycle. Extremely simple models have been developed for integrated assessment models, but lack the flexibility to distinguish between primary and secondary sources of aerosol. Here a simple but more physically based model expresses the aerosol indirect effect (AIE) using analytic representations of cloud and aerosol distributions and processes. Although the simple model is able to produce estimates of AIEs that are comparable to those from some global aerosol models using the same global mean aerosol properties, the estimates by the simple model are sensitive to preindustrial cloud condensation nuclei concentration, preindustrial accumulation mode radius, width of the accumulation mode, size of primary particles, cloud thickness, primary and secondary anthropogenic emissions, the fraction of the secondary anthropogenic emissions that accumulates on the coarse mode, the fraction of the secondary mass that forms new particles, and the sensitivity of liquid water path to droplet number concentration. Estimates of present-day AIEs as low as -5 W m-2 and as high as -0.3 W m-2 are obtained for plausible sets of parameter values. Estimates are surprisingly linear in emissions. The estimates depend on parameter values in ways that are consistent with results from detailed global aerosol-climate simulation models, which adds to understanding of the dependence on AIE uncertainty on uncertainty in parameter values. Key Points A simple physically-based model represents aerosol indirect effects The model estimates depend on parameters in ways like detailed global models The aerosol indirect effect is surprisingly linear in emissions © 2013. American Geophysical Union. All Rights Reserved."
"35280798500;57203053317;13403622000;","Modelling the impact of fungal spore ice nuclei on clouds and precipitation",2013,"10.1088/1748-9326/8/1/014029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876189955&doi=10.1088%2f1748-9326%2f8%2f1%2f014029&partnerID=40&md5=33164e5744bdabd528112b338998faa4","Some fungal spore species have been found in laboratory studies to be very efficient ice nuclei. However, their potential impact on clouds and precipitation is not well known and needs to be investigated. Fungal spores as a new aerosol species were introduced into the global climate model (GCM) ECHAM5-HAM. The inclusion of fungal spores acting as ice nuclei in a GCM leads to only minor changes in cloud formation and precipitation on a global level; however, changes in the liquid water path and ice water path as well as stratiform precipitation can be observed in the boreal regions where tundra and forests act as sources of fungal spores. Although fungal spores contribute to heterogeneous freezing, their impact is reduced by their low numbers as compared to other heterogeneous ice nuclei. © 2013 IOP Publishing Ltd."
"7004057920;57201726470;56521864800;55510976200;54783781000;7005862399;26643510900;36076994600;57203798762;","Comparison of MODIS cloud microphysical properties with in-situ measurements over the Southeast Pacific",2012,"10.5194/acp-12-11261-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870538467&doi=10.5194%2facp-12-11261-2012&partnerID=40&md5=fa12b9d4f7db3f6169d2bd9c75947aac","Utilizing the unique characteristics of the cloud over the Southeast Pacific (SEP) off the coast of Chile during the VOCALS field campaign, we compared satellite remote sensing of cloud microphysical properties against in-situ data from multi-aircraft observations, and studied the extent to which these retrieved properties are sufficiently constrained and consistent to reliably quantify the influence of aerosol loading on cloud droplet sizes. After constraining the spatial-temporal coincidence between satellite retrievals and in-situ measurements, we selected 17 non-drizzle comparison pairs. For these cases the mean aircraft profiling times were within one hour of Terra overpasses at both projected and un-projected (actual) aircraft positions for two different averaging domains of 5 km and 25 km. Retrieved quantities that were averaged over a larger domain of 25 km compared better statistically with in-situ observations than averages over a smaller domain of 5 km. Comparison at projected aircraft positions was slightly better than un-projected aircraft positions for some parameters. Overall, both MODIS-retrieved effective radius and LWP were larger but highly correlated with the in-situ measured effective radius and LWP, e.g., for averaging domains of 5 km, the biases are up to 1.75 μm and 0.02 mm whilst the correlation coefficients are about 0.87 and 0.85, respectively. The observed effective radius difference between the two decreased with increasing cloud drop number concentration (CDNC), and increased with increasing cloud geometrical thickness. Compared to the absolute effective radius difference, the correlations between the relative effective radius difference and CDNC or cloud geometric thickness are weaker. For averaging domains of 5 km and 25 km, the correlation coefficients between MODIS-retrieved and in-situ measured CDNC are 0.91 and 0.93 with fitting slopes of 1.23 and 1.27, respectively. If the cloud adiabaticity is taken into account, better agreements are achieved for both averaging domains (the fitting slopes are 1.04 and 1.07, respectively). Our comparison and sensitivity analysis of simulated retrievals demonstrate that both cloud geometrical thickness and cloud adiabaticity are important factors in satellite retrievals of effective radius and cloud drop number concentration. The large variabilities in cloud geometrical thickness and adiabaticity, the dependencies of cloud microphysical properties on both quantities (as demonstrated in our sensitivity study of simulated retrievals), and the inability to accurately account for either of them in retrievals lead to some uncertainties and biases in satellite retrieved cloud effective radius, cloud liquid water path, and cloud drop number concentration. However, strong correlations between satellite retrievals and in-situ measurements suggest that satellite retrievals of cloud effective radius, cloud liquid water path, and cloud drop number concentration can be used to investigate aerosol indirect effects qualitatively. © 2012 Author(s)."
"55259114100;6603156461;7004862277;","Detailed heterogeneous oxidation of soot surfaces in a particle-resolved aerosol model",2011,"10.5194/acp-11-4505-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79956108825&doi=10.5194%2facp-11-4505-2011&partnerID=40&md5=80e4eb36b522fd4ebb5ecf97cfbba970","Using the particle-resolved aerosol model PartMC-MOSAIC, we simulate the heterogeneous oxidation of a monolayer of polycyclic aromatic hydrocarbons (PAHs) on soot particles in an urban atmosphere. We focus on the interaction of the major atmospheric oxidants (O3, NO2, OH, and NO 3) with PAHs and include competitive co-adsorption of water vapour for a range of atmospheric conditions. For the first time detailed heterogeneous chemistry based on the P-schl-Rudich-Ammann (PRA) framework is modelled on soot particles with a realistic size distribution and a continuous range of chemical ages. We find PAHs half-lives, τ, on the order of seconds during the night, when the PAHs are rapidly oxidised by the gas-surface reaction with NO 3. During the day, τ is on the order of minutes and determined mostly by the surface layer reaction of PAHs with adsorbed O3. Such short half-lives of surface-bound PAHs may lead to efficient conversion of hydrophobic soot into more hygroscopic particles, thus increasing the particles' aerosol-cloud interaction potential. Despite its high reactivity OH appears to have a negligible effect on PAH degradation which can be explained by its very low concentration in the atmosphere. An increase of relative humidity (RH) from 30 % to 80 % increases PAH half-lives by up to 50 % for daytime degradation and by up to 100 % or more for nighttime degradation. Uptake coefficients, averaged over the particle population, are found to be relatively constant over time for O3 (∼2 × 107 to 2 × 106) and NO2 (∼5 × 106 to ∼105) at the different levels of NOx emissions and RH considered in this study. In contrast, those for OH and NO3 depend strongly on the surface concentration of PAHs. We do not find a significant influence of heterogeneous reactions on soot particles on the gas phase composition. The derived half-lives of surface-bound PAHs and the time and particle population averaged uptake coefficients for O3 and NO2 presented in this paper can be used as parameterisations for the treatment of heterogeneous chemistry in large-scale atmospheric chemistry models. © 2011 Author(s)."
"25624725200;18437651200;55885038100;35798085000;7402538754;8550791300;7202779940;7006415284;","Homogeneous and heterogeneous ice nucleation at LACIS: Operating principle and theoretical studies",2011,"10.5194/acp-11-1753-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952085129&doi=10.5194%2facp-11-1753-2011&partnerID=40&md5=b7a5704f400fb478a9ef392bee3f8165","At the Leipzig Aerosol Cloud Interaction Simulator (LACIS) experiments investigating homogeneous and heterogeneous nucleation of ice (particularly immersion freezing in the latter case) have been carried out. Here both the physical LACIS setup and the numerical model developed to design experiments at LACIS and interpret their results are presented in detail. <br><br> Combining results from the numerical model with experimental data, it was found that for the experimental parameter space considered, classical homogeneous ice nucleation theory is able to predict the freezing behavior of highly diluted ammonium sulfate solution droplets, while classical heterogeneous ice nucleation theory, together with the assumption of a constant contact angle, fails to predict the immersion freezing behavior of surrogate mineral dust particles (Arizona Test Dust, ATD). The main reason for this failure is the compared to experimental data apparently overly strong temperature dependence of the nucleation rate coefficient. <br><br> Assuming, in the numerical model, Classical Nucleation Theory (CNT) for homogeneous ice nucleation and a CNT-based parameterization for the nucleation rate coefficient in the immersion freezing mode, recently published by our group, it was found that even for a relatively effective ice nucleating agent such as pure ATD, there is a temperature range where homogeneous ice nucleation is dominant. The main explanation is the apparently different temperature dependencies of the two freezing mechanisms. Finally, reviewing the assumptions made during the derivation of the CNT-based parameterization for immersion freezing, it was found that the assumption of constant temperature during ice nucleation and the chosen ice nucleation time were justified, underlining the applicability of the method to determine the fitting coefficients in the parameterization equation. © 2011 Author(s)."
"18437651200;8550791300;13407676600;7006415284;7004538458;7202779940;57213549839;7005228425;","LACIS-measurements and parameterization of sea-salt particle hygroscopic growth and activation",2008,"10.5194/acp-8-579-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-39349104171&doi=10.5194%2facp-8-579-2008&partnerID=40&md5=c0a7d1fa141bc0ee74a64a9dc7301f68","The Leipzig Aerosol Cloud Interaction Simulator (LACIS) was used to investigate the hygroscopic growth and activation of sea-salt particles which were generated from three different sea-water samples. The measurements showed that the sea-salt particles exhibit a slightly reduced hygroscopic growth compared to pure NaCl particles. Köhler theory was utilized to model the hygroscopic growth of these particles. Some parameters used in this model are unknown for sea-salt. These parameters are combined in an ""ionic density"" ρion. For each sea-salt sample an average ρion was determined by fitting the Köhler equation to the data from the hygroscopic growth measurements. LACIS was also used to measure the activation of the sea-salt particles at three different supersaturations: 0.11%, 0.17% and 0.32%. A CCN-closure was tested by calculating the critical diameters Dcrit for the sea-salt particles at these supersaturations, using the Köhler model and the corresponding ρion as derived from the hygroscopic growth data. These calculated critical diameters were compared to the measured ones. Measured and calculated values of D crit agree within the level of uncertainty. Based on this successful closure, a new parameterization to describe sea-salt-particle hygroscopic growth (at RH&gt;95%) and activation has been developed."
"7403564495;57192164648;55497853400;7410041005;19638935200;57212399558;39862411700;57216713239;","Negative Aerosol-Cloud re Relationship From Aircraft Observations Over Hebei, China",2018,"10.1002/2017EA000346","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040977762&doi=10.1002%2f2017EA000346&partnerID=40&md5=940bad7c2fbae338a8616b1be4d0702c","Using six flights observations in September 2015 over Hebei, China, this study shows a robust negative aerosol-cloud droplet effective radius (re) relationship for liquid clouds, which is different from previous studies that found positive aerosol-cloud re relationship over East China using satellite observations. A total of 27 cloud samples was analyzed with the classification of clean and polluted conditions using lower and upper 1/3 aerosol concentration at 200 m below the cloud bases. By normalizing the profiles of cloud droplet re, we found significant smaller values under polluted than under clean condition at most heights. Moreover, the averaged profiles of cloud liquid water content (LWC) show larger values under polluted than clean conditions, indicating even stronger negative aerosol-cloud re relationship if LWC is kept constant. The droplet size distributions further demonstrate that more droplets concentrate within smaller size ranges under polluted conditions. Quantitatively, the aerosol-cloud interaction is found around 0.10–0.19 for the study region. ©2018. The Authors."
"56457851700;12801992200;57193327928;7202145115;24722339600;16444006500;","The global aerosol-cloud first indirect effect estimated using MODIS, MERRA, and AeroCom",2017,"10.1002/2016JD026141","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85012993562&doi=10.1002%2f2016JD026141&partnerID=40&md5=2a2a5a92fed4f68857492a82ce3f273d","Aerosol-cloud interactions (ACI) represent a significant source of forcing uncertainty in global climate models (GCMs). Estimates of radiative forcing due to ACI in Fifth Assessment Report range from -0.5 to -2.5Wm-2. A portion of this uncertainty is related to the first indirect, or Twomey, effect whereby aerosols act as nuclei for cloud droplets to condense upon. At constant liquid water content this increases the number of cloud droplets (Nd) and thus increases the cloud albedo. In this study we use remote-sensing estimates of Nd within stratocumulus regions in combination with state-of-the-art aerosol reanalysis from Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA2) to diagnose how aerosols affect Nd. As in previous studies, Nd is related to sulfate mass through a power law relationship. The slope of the log-log relationship between Nd and SO4 in maritime stratocumulus is found to be 0.31, which is similar to the range of 0.2-0.8 from previous in situ studies and remote-sensing studies in the pristine Southern Ocean. Using preindustrial emissions models, the change in Nd between preindustrial and present day is estimated. Nd is inferred to have more than tripled in some regions. Cloud properties from Moderate Resolution Imaging Spectroradiometer (MODIS) are used to estimate the radiative forcing due to this change in Nd. The Twomey effect operating in isolation is estimated to create a radiative forcing of -0.97 ± 0.23Wm-2 relative to the preindustrial era. © 2017. American Geophysical Union. All Rights Reserved."
"25031430500;","Putting the clouds back in aerosol-cloud interactions",2015,"10.5194/acp-15-12397-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942682922&doi=10.5194%2facp-15-12397-2015&partnerID=40&md5=0f9c67cb086c1d89de8d0d3784a6de87","Aerosol-cloud interactions (ACI) are the consequence of perturbed aerosols affecting cloud drop and crystal number, with corresponding microphysical and radiative effects. ACI are sensitive to both cloud microphysical processes (the ""C"" in ACI) and aerosol emissions and processes (the ""A"" in ACI). This work highlights the importance of cloud microphysical processes, using idealized and global tests of a cloud microphysics scheme used for global climate prediction. Uncertainties in key cloud microphysical processes examined with sensitivity tests cause uncertainties of nearly g'30 to +60 % in ACI, similar to or stronger than uncertainties identified due to natural aerosol emissions (-30 to +30 %). The different dimensions and sensitivities of ACI to microphysical processes identified in previous work are analyzed in detail, showing that precipitation processes are critical for understanding ACI and that uncertain cloud lifetime effects are nearly one-third of simulated ACI. Buffering of different processes is important, as is the mixed phase and coupling of the microphysics to the condensation and turbulence schemes in the model. © Author(s) 2015."
"15755995900;7006705919;56162305900;55688930000;7003666669;7006270084;8922308700;55717074000;52464731300;22635190100;","How does increasing horizontal resolution in a global climate model improve the simulation of aerosol-cloud interactions?",2015,"10.1002/2015GL064183","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948711317&doi=10.1002%2f2015GL064183&partnerID=40&md5=969ff8f82b189d40e8245bf6f679da5f","The Community Atmosphere Model Version 5 is run at horizontal grid spacing of 2, 1, 0.5, and 0.25°, with the meteorology nudged toward the Year Of Tropical Convection analysis, and cloud simulators and the collocated A-Train satellite observations are used to explore the resolution dependence of aerosol-cloud interactions. The higher-resolution model produces results that agree better with observations, showing an increase of susceptibility of cloud droplet size, indicating a stronger first aerosol indirect forcing (AIF), and a decrease of susceptibility of precipitation probability, suggesting a weaker second AIF. The resolution sensitivities of AIF are attributed to those of droplet nucleation and precipitation parameterizations. The annual average AIF in the Northern Hemisphere midlatitudes (where most anthropogenic emissions occur) in the 0.25° model is reduced by about 1 W m-2 (-30%) compared to the 2° model, leading to a 0.26 W m-2 reduction (-15%) in the global annual average AIF. © 2015. American Geophysical Union. All Rights Reserved."
"15070038800;21734131700;57192107995;7006347751;","Generation of internally mixed insoluble and soluble aerosol particles to investigate the impact of atmospheric aging and heterogeneous processing on the CCN activity of mineral dust aerosol",2007,"10.1080/02786820701557222","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548567823&doi=10.1080%2f02786820701557222&partnerID=40&md5=3845e7e100b5de81209f850a1ff7bcd2","Heterogeneous reactions of trace gases with mineral dust aerosol not only impact the chemical balance of the atmosphere but also the physicochemical properties of the dust particle and the ability of the particle to act as a cloud condensation nuclei (CCN). Recent field studies have shown that carbonate minerals are preferentially associated with nitrates whereas aluminum silicates (i.e., clay minerals) are preferentially associated with sulfates. To better understand how this association can impact the climate effects of mineral dust particles, we have measured the CCN activity of a number of pure and internal mixtures of aerosols relevant to these recent field studies. The CCN activity of CaCO3-Ca(NO3)2 aerosol, simulating the activity of mineral dust aerosol that has been partially processed by nitrogen oxides in the atmosphere, is significantly enhanced relative to CaCO3 aerosol of the same diameter. Similar results are obtained for a clay mineral, kaolinite, internally mixed with (NH4)2SO4. For example, at 0.3% supersaturation, a 200 nm particle containing a soluble nitrate or sulfate component is 2 to 4 times more active than an unreacted particle. The results presented here show that when determining the contribution of mineral dust aerosol to the overall impact of the aerosol indirect effect on radiative forcing, changes in chemical composition due to atmospheric processing cannot be ignored. Copyright © American Association for Aerosol Research."
"7201837768;6603809220;","The radiative influence of aerosol effects on liquid-phase cumulus and stratiform clouds based on sensitivity studies with two climate models",2006,"10.1007/s00382-006-0139-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745698744&doi=10.1007%2fs00382-006-0139-3&partnerID=40&md5=492065d1f688e7980d76573f13cd8b5a","Aerosol effects on warm (liquid-phase) cumulus cloud systems may have a strong radiative influence via suppression of precipitation in convective systems. A consequence of this suppression of precipitation is increased liquid water available for large-scale stratiform clouds, through detrainment, that in turn affect their precipitation efficiency. The nature of this influence on radiation, however, is dependent on both the treatment of convective condensate and the aerosol distribution. Here, we examine these issues with two climate models - CSIRO and GISS, which treat detrained condensate differently. Aerosol-cloud interactions in warm stratiform and cumulus clouds (via cloud droplet formation and autoconversion) are treated similarly in both models. The influence of aerosol-cumulus cloud interactions on precipitation and radiation are examined via simulations with present-day and pre-industrial aerosol emissions. Sensitivity tests are also conducted to examine changes to climate due to changes in cumulus cloud droplet number (Nc); the main connection between aerosols and cumulus cloud microphysics. Results indicate that the CSIRO GCM is quite sensitive to changes in aerosol concentrations such that an increase in aerosols increases Nc cloud cover, total liquid water path (LWP) and reduces total precipitation and net cloud radiative forcings. On the other hand, the radiative fluxes in the GISS GCM appear to have minimal changes despite an increase in aerosols and Nc. These differences between the two models - reduced total LWP in the GISS GCM for increased aerosols, opposite to that seen in CSIRO - appear to be more sensitive to the detrainment of convective condensate, rather than to changes in Nc. If aerosols suppress convective precipitation as noted in some observationally based studies (but not currently treated in most climate models), the consequence of this change in LWP suggests that: (1) the aerosol indirect effect (calculated as changes to net cloud radiative forcing from anthropogenic aerosols) may be higher than previously calculated or (2) lower than previously calculated. Observational constrains on these results are difficult to obtain and hence, until realistic cumulus-scale updrafts are implemented in models, the logic of detraining non-precipitating condensate at appropriate levels based on updrafts and its effects on radiation, will remain an uncertainty. © Springer-Verlag 2006."
"7004242319;55688930000;","Effects of aerosols on trade wind cumuli over the Indian Ocean: Model simulations",2006,"10.1256/qj.04.179","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745021144&doi=10.1256%2fqj.04.179&partnerID=40&md5=be12746c743dbff9bc8e6207d28881ba","An Eulerian non-hydrostatic anelastic fluid model using a warm cloud bulk parametrization is used to study responses of trade wind cumuli to increased cloud drop concentrations produced by enhanced aerosol numbers and to absorption from aerosols containing soot. Simulations are initialized using temperature and moisture profiles measured during the Indian Ocean Experiment (INDOEX) and sea surface temperatures retrieved from the Tropical Rainfall Measuring Mission microwave imager. Cloud covers between 4 and 10% and cloud-averaged liquid water contents of between 0.01 and 0.6 g m-3 more closely match values retrieved and measured in situ during INDOEX than those modelled in past studies; previous studies found larger cloud coverage associated with cloud spreading below a strong inversion not present in the INDOEX soundings. As in previous studies, a diurnal cycle with reductions of cloud cover and liquid water path (LWP) after sunrise is seen, with absorbing aerosols within cloud augmenting the decrease in cloud cover. Variations in aerosol vertical profiles can change semi-direct radiative forcing at the surface (top of the atmosphere) from + 1.6 (+1.3) W m-2 when aerosols are confined to cloud compared to -0.4 (-0.6) W m-2 when aerosols occur below cloud. Low-level water-vapour mixing ratios decrease as vertical motions increase, the vertical motions being enhanced by below-cloud solar heating and cloud-top radiative cooling and suppressed by in-cloud heating. Cloud cover and LWP are larger for stronger vertical motions, explaining the dependence of radiative forcing on aerosol profile. In the late afternoon and evening, increases in radiative cooling and sensible and latent heat flux, occurring due to reductions in mixed-layer temperature and vapour, allow cloud cover and LWP to recover to values like those found in simulations without absorbing aerosols. © Royal Meteorological Society, 2006."
"36538539800;7006270084;7003666669;6602973136;","Impact of aerosol size representation on modeling aerosol-cloud interactions",2002,"10.1109/AERO.2002.1036876","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16444385482&doi=10.1109%2fAERO.2002.1036876&partnerID=40&md5=ebc8abfe06589d9bbeebd3bd2268d2d5","We use a one-dimensional version of a climate-aerosol-chemistry model with both modal and sectional aerosol size representations to evaluate the impact of aerosol size representation on modeling aerosol-cloud interactions in shallow stratiform clouds observed during the second Aerosol Characterization Experiment. Both the modal (with prognostic aerosol number and mass or prognostic aerosol number, surface area and mass, referred to as the Modal-NM and Modal-NSM) and the sectional approaches (with 12 and 36 sections) predict total number and mass for interstitial and activated particles that are generally within several percent of references from a high-resolution 108-section approach. The modal approach with prognostic aerosol mass but diagnostic number (referred to as the Modal-M) cannot accurately predict the total particle number and surface areas, with deviations from the references ranging from 7 to 161%. The particle size distributions are sensitive to size representations, with normalized absolute differences of up to 12% and 37% for the 36- and 12-section approaches, and 30%, 39%, and 179% for the Modal-NSM, Modal-NM, and Modal-M, respectively. For the Modal-NSM and Modal-NM, differences from the references are primarily due to the inherent assumptions and limitations of the modal approach. In particular, they cannot resolve the abrupt size transition between the interstitial and activated aerosol fractions. For the 12- and 36-section approaches, differences are largely due to limitations of the parameterized activation for nonlognormal size distributions, plus the coarse resolution for the 12-section case. Differences are larger both with higher aerosol (i.e., less complete activation) and higher SO<inf>2</inf> concentrations (i.e., greater modification of the initial aerosol distribution). Copyright 2002 by the American Geophysical Union."
"57202163835;6506101358;57203200427;24511929800;","Sulfate Aerosol Indirect Effect and CO2 Greenhouse Forcing: Equilibrium Response of the LMD GCM and Associated Cloud Feedbacks",1998,"10.1175/1520-0442(1998)011<1673:saieac>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0001733727&doi=10.1175%2f1520-0442%281998%29011%3c1673%3asaieac%3e2.0.co%3b2&partnerID=40&md5=fe5f577fffe3bfe82cc93c068cf4ce19","The climate sensitivity to various forcings, and in particular to changes in CO2 and sulfate aerosol concentrations, imposed separately or in a combined manner, is studied with an atmospheric general circulation model coupled to a simple slab oceanic model. The atmospheric model includes a rather detailed treatment of warm cloud microphysics and takes the aerosol indirect effects into account explicitly, although in a simplified manner. The structure of the model response appears to be organized at a global scale, with a partial independence from the geographical structure of the forcing. Atmospheric and surface feedbacks are likely to explain this feature. In particular the cloud feedbacks play a very similar role in the CO2 and aerosol experiments, but with opposite sign. These results strengthen the idea, already apparent from other studies, that, in spite of their different nature and their different geographical and vertical distributions, aerosol may have substantially counteracted the climate effect of greenhouse gases, at least in the Northern Hemisphere, during the twentieth century. When the effects of the two forcings are added, the model response is not symmetric between the two hemispheres. This feature is also consistent with the findings of other modeling groups and has implications for the detection of future climate changes."
"57097521200;7003414581;26023140500;22979686100;6701697023;24366038500;56814955200;55883785100;","Dry versus wet marine particle optical properties: RH dependence of depolarization ratio, backscatter, and extinction from multiwavelength lidar measurements during SALTRACE",2017,"10.5194/acp-17-14199-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029479627&doi=10.5194%2facp-17-14199-2017&partnerID=40&md5=37ad2a9823183fae1c7aa713e4d3dd62","Triple-wavelength lidar observations of the depolarization ratio and the backscatter coefficient of marine aerosol as a function of relative humidity (RH) are presented with a 5ĝ€min time resolution. The measurements were performed at Barbados (13°ĝ€N, 59°ĝ€W) during the Saharan Aerosol Long-range Transport and Aerosol-Cloud interaction Experiment (SALTRACE) winter campaign in February 2014. The phase transition from spherical sea salt particles to cubic-like sea salt crystals was observed with a polarization lidar. The radiosonde and water-vapor Raman lidar observations show a drop in RH below 50ĝ€% in the marine aerosol layer simultaneously with a strong increase in particle linear depolarization ratio, which reaches values up to 0.12ĝ€±ĝ€0.08 (at 355ĝ€nm), 0.15ĝ€±ĝ€0.03 (at 532ĝ€nm), and 0.10ĝ€±ĝ€0.01 (at 1064ĝ€nm). The lidar ratio (extinction-To-backscatter ratio) increased from 19 and 23ĝ€sr for spherical sea salt particles to 27 and 25ĝ€sr (at 355 and 532ĝ€nm, respectively) for cubic-like particle ensembles. Furthermore the scattering enhancement due to hygroscopic growth of the marine aerosol particles under atmospheric conditions was measured. Extinction enhancement factors from 40 to 80ĝ€% RH of 1.94ĝ€±ĝ€0.94 at 355ĝ€nm, 3.70ĝ€±ĝ€1.14 at 532ĝ€nm, and 5.37ĝ€±ĝ€1.66 at 1064ĝ€nm were found. The enhanced depolarization ratios and lidar ratios were compared to modeling studies of cubic sea salt particles. © Author(s) 2017. This work is distributed under the Creative Commons Attribution 4.0 License."
"16642991200;7003414581;","Potential of polarization/Raman lidar to separate fine dust, coarse dust, maritime, and anthropogenic aerosol profiles",2017,"10.5194/amt-10-3403-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019675039&doi=10.5194%2famt-10-3403-2017&partnerID=40&md5=adb46a3efa7125d189cdec425f68b406","We applied the recently introduced polarization lidar-photometer networking (POLIPHON) technique for the first time to triple-wavelength polarization lidar measurements at 355, 532, and 1064 nm. The lidar observations were performed at Barbados during the Saharan Aerosol Long-Range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) in the summer of 2014. The POLIPHON method comprises the traditional lidar technique to separate mineral dust and non-dust backscatter contributions and the new, extended approach to separate even the fine and coarse dust backscatter fractions. We show that the traditional and the advanced method are compatible and lead to a consistent set of dust and non-dust profiles at simplified, less complex aerosol layering and mixing conditions as is the case over the remote tropical Atlantic. To derive dust mass concentration profiles from the lidar observations, trustworthy extinction-to-volume conversion factors for fine, coarse, and total dust are needed and obtained from an updated, extended Aerosol Robotic Network sun photometer data analysis of the correlation between the fine, coarse and total dust volume concentration and the respective fine, coarse, and total dust extinction coefficient for all three laser wavelengths. Conversion factors (total volume to extinction) for pure marine aerosol conditions and continental anthropogenic aerosol situations are presented in addition. As a new feature of the POLIPHON data analysis, the Raman lidar method for particle extinction profiling is used to identify the aerosol type (marine or anthropogenic) of the non-dust aerosol fraction. The full POLIPHON methodology was successfully applied to a SALTRACE case and the results are discussed. We conclude that the 532 nm polarization lidar technique has many advantages in comparison to 355 and 1064 nm polarization lidar approaches and leads to the most robust and accurate POLIPHON products. © 2017 Author(s)."
"7103180783;7402401574;6506298579;","Understanding the rapid summer warming and changes in temperature extremes since the mid-1990s over Western Europe",2017,"10.1007/s00382-016-3158-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84966292302&doi=10.1007%2fs00382-016-3158-8&partnerID=40&md5=a366b71fbde36e8772284a48561593ee","Analysis of observations indicates that there was a rapid increase in summer (June–August) mean surface air temperature (SAT) since the mid-1990s over Western Europe. Accompanying this rapid warming are significant increases in summer mean daily maximum temperature, daily minimum temperature, annual hottest day temperature and warmest night temperature, and an increase in frequency of summer days and tropical nights, while the change in the diurnal temperature range (DTR) is small. This study focuses on understanding causes of the rapid summer warming and associated temperature extreme changes. A set of experiments using the atmospheric component of the state-of-the-art HadGEM3 global climate model have been carried out to quantify relative roles of changes in sea surface temperature (SST)/sea ice extent (SIE), anthropogenic greenhouse gases (GHGs), and anthropogenic aerosols (AAer). Results indicate that the model forced by changes in all forcings reproduces many of the observed changes since the mid-1990s over Western Europe. Changes in SST/SIE explain 62.2 ± 13.0 % of the area averaged seasonal mean warming signal over Western Europe, with the remaining 37.8 ± 13.6 % of the warming explained by the direct impact of changes in GHGs and AAer. Results further indicate that the direct impact of the reduction of AAer precursor emissions over Europe, mainly through aerosol-radiation interaction with additional contributions from aerosol-cloud interaction and coupled atmosphere-land surface feedbacks, is a key factor for increases in annual hottest day temperature and in frequency of summer days. It explains 45.5 ± 17.6 % and 40.9 ± 18.4 % of area averaged signals for these temperature extremes. The direct impact of the reduction of AAer precursor emissions over Europe acts to increase DTR locally, but the change in DTR is countered by the direct impact of GHGs forcing. In the next few decades, greenhouse gas concentrations will continue to rise and AAer precursor emissions over Europe and North America will continue to decline. Our results suggest that the changes in summer seasonal mean SAT and temperature extremes over Western Europe since the mid-1990s are most likely to be sustained or amplified in the near term, unless other factors intervene. © 2016, The Author(s)."
"55512941600;57203053317;7102988363;26643250500;","Dust ice nuclei effects on cirrus clouds",2014,"10.5194/acp-14-3027-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897419824&doi=10.5194%2facp-14-3027-2014&partnerID=40&md5=e92b0cec80f3ad7e871083889e6c163a","In order to study aerosol-cloud interactions in cirrus clouds, we apply a new multiple-mode ice microphysical scheme to the general circulation model ECHAM5-HAM. The multiple-mode ice microphysical scheme allows for analysis of the competition between homogeneous freezing of solution droplets, deposition nucleation of pure dust particles, and immersion freezing of coated dust particles and pre-existing ice. We base the freezing efficiencies of coated and pure dust particles on the most recent laboratory data. The effect of pre-existing ice, which has been neglected in previous ice nucleation parameterizations, is to deplete water vapour by depositional growth and thus prevent homogeneous and heterogeneous freezing from occurring. As a first step, we extensively tested the model and validated the results against in situ measurements from various aircraft campaigns. The results compare well with observations; properties such as ice crystal size and number concentration as well as supersaturation are predicted within the observational spread. We find that heterogeneous nucleation on mineral dust particles and the consideration of pre-existing ice in the nucleation process may lead to significant effects: globally, ice crystal number and mass are reduced by 10 and 5%, whereas the ice crystals' size is increased by 3%. The reductions in ice crystal number are most pronounced in the tropics and mid-latitudes in the Northern Hemisphere. While changes in the microphysical and radiative properties of cirrus clouds in the tropics are mostly driven by considering pre-existing ice, changes in the northern hemispheric mid-latitudes mainly result from heterogeneous nucleation. The so-called negative Twomey effect in cirrus clouds is represented in ECHAM5-HAM. The net change in the radiation budget is-0.94 W mg-2, implying that both heterogeneous nucleation on dust and pre-existing ice have the potential to modulate cirrus properties in climate simulations and thus should be considered in future studies. ©Author(s) 2014."
"23052016900;6506718302;6507755223;26643041500;7007039218;17345303300;6701620591;35459245100;","Direct and indirect effects of sea spray geoengineering and the role of injected particle size",2012,"10.1029/2011JD016428","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856603398&doi=10.1029%2f2011JD016428&partnerID=40&md5=3b20328a824af5e031e15ce31b2c7d91","Climate-aerosol model ECHAM5.5-HAM2 was used to investigate how geoengineering with artificial sea salt emissions would affect marine clouds and the Earth's radiative balance. Prognostic cloud droplet number concentration and interaction of aerosol particles with clouds and radiation were calculated explicitly, thus making this the first time that aerosol direct effects of sea spray geoengineering are considered. When a wind speed dependent baseline geoengineering flux was applied over all oceans (total annual emissions 443.9 Tg), we predicted a radiative flux perturbation (RFP) of -5.1 W m-2, which is enough to counteract warming from doubled CO<inf>2</inf> concentration. When the baseline flux was limited to three persistent stratocumulus regions (3.3% of Earth's surface, total annual emissions 20.6 Tg), the RFP was -0.8 Wm-2 resulting mainly from a 74-80% increase in cloud droplet number concentration and a 2.5-4.4 percentage point increase in cloud cover. Multiplying the baseline mass flux by 5 or reducing the injected particle size from 250 to 100 nm had comparable effects on the geoengineering efficiency with RFPs -2.2 and -2.1 Wm-2, respectively. Within regions characterized with persistent stratocumulus decks, practically all of the radiative effect originated from aerosol indirect effects. However, when all oceanic regions were seeded, the direct effect with the baseline flux was globally about 29% of the total radiative effect. Together with previous studies, our results indicate that there are still large uncertainties associated with the sea spray geoengineering efficiency due to variations in e.g., background aerosol concentration, updraft velocity, cloud altitude and onset of precipitation. Copyright 2012 by the American Geophysical Union."
"37089417300;56151703900;13402933200;7102988363;8718425100;35998927000;","Climate impact of biofuels in shipping: Global model studies of the aerosol indirect effect",2011,"10.1021/es1036157","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954474909&doi=10.1021%2fes1036157&partnerID=40&md5=18da1f7dbac404ae6a7f03654cdb6dcd","Aerosol emissions from international shipping are recognized to have a large impact on the Earth's radiation budget, directly by scattering and absorbing solar radiation and indirectly by altering cloud properties. New regulations have recently been approved by the International Maritime Organization (IMO) aiming at progressive reductions of the maximum sulfur content allowed in marine fuels from current 4.5% by mass down to 0.5% in 2020, with more restrictive limits already applied in some coastal regions. In this context, we use a global bottom-up algorithm to calculate geographically resolved emission inventories of gaseous (NOx, CO, SO2) and aerosol (black carbon, organic matter, sulfate) species for different kinds of low-sulfur fuels in shipping. We apply these inventories to study the resulting changes in radiative forcing, attributed to particles from shipping, with the global aerosol-climate model EMAC-MADE. The emission factors for the different fuels are based on measurements at a test bed of a large diesel engine. We consider both fossil fuel (marine gas oil) and biofuels (palm and soy bean oil) as a substitute for heavy fuel oil in the current (2006) fleet and compare their climate impact to that resulting from heavy fuel oil use. Our simulations suggest that ship-induced surface level concentrations of sulfate aerosol are strongly reduced, up to about 40-60% in the high-traffic regions. This clearly has positive consequences for pollution reduction in the vicinity of major harbors. Additionally, such reductions in the aerosol loading lead to a decrease of a factor of 3-4 in the indirect global aerosol effect induced by emissions from international shipping. © 2011 American Chemical Society."
"7004022660;7102653983;7101688723;7006508549;","Land use change suppresses precipitation",2009,"10.5194/acp-9-6531-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71849117529&doi=10.5194%2facp-9-6531-2009&partnerID=40&md5=d7404f88c620e2244da252e4e5fec956","A feedback loop between regional scale deforestation and climate change was investigated in an experiment using novel, small size airborne platforms and instrument setups. Experiments were performed in a worldwide unique natural laboratory in Western Australia, characterized by two adjacent homogeneous observation areas with distinctly different land use characteristics. Conversion of several ten thousand square km of forests into agricultural land began more than a century ago. Changes in albedo, surface roughness, the soil water budget and the planetary boundary layer evolved over decades. Besides different meteorology, we found a significant up to now overlooked source of aerosol over the agriculture area. The enhanced number of cloud condensation nuclei is coupled through the hydrological groundwater cycle with deforestation. Modification of surface properties and aerosol number concentrations are key factors for the observed reduction of precipitation. The results document the importance of aerosol indirect effects on climate due to nanometer size biogenic aerosol and human impact on aerosol sources."
"16639418500;57203053317;","Influence of Giant CCN on warm rain processes in the ECHAM5 GCM",2008,"10.5194/acp-8-3769-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-47549102019&doi=10.5194%2facp-8-3769-2008&partnerID=40&md5=5d76f77b279900265ca561583de19c8c","Increased Cloud Condensation Nuclei (CCN) load due to anthropogenic activity might lead to non-precipitating clouds because the cloud drops become smaller (for a constant liquid water content) and, therefore, less efficient in rain formation (aerosol indirect effect). Adding giant CCN (GCCN) into such a cloud can initiate precipitation (namely, drizzle) and, therefore, might counteract the aerosol indirect effect. The effect of GCCN on global climate on warm clouds and precipitation within the ECHAM5 General Circulation Model (GCM) is investigated. Therefore, the newly introduced prognostic rain scheme (Posselt and Lohmann, 2007) is applied so that GCCN are directly activated into rain drops. The ECHAM5 simulations with incorporated GCCN show that precipitation is affected only locally. On the global scale, the precipitation amount does not change. Cloud properties like total water (liquid + rain water) and cloud drop number show a larger sensitivity to GCCN. Depending on the amount of added GCCN, the reduction of total water and cloud drops account for up to 20% compared to the control run without GCCN. Thus, the incorporation of the GCCN accelerate the hydrological cycle so that clouds precipitate faster (but not more) and less condensed water is accumulated in the atmosphere. An estimate of the anthropogenic aerosol indirect effect on the climate is obtained by comparing simulations for present-day and pre-industrial climate. The introduction of the prognostic rain scheme lowered the anthropogenic aerosol indirect effect significantly compared to the standard ECHAM5 with the diagnostic rain scheme. The incorporation of the GCCN changes the model state, especially the cloud properties like TWP and Nl. The precipitation changes only locally but globally the precipitation is unaffected because it has to equal the global mean evaporation rate. Changing the cloud properties leads to a local reduction of the aerosol indirect effect and, hence, partly compensating for the increased anthropogenic CCN concentrations in that regions. Globally, the aerosol indirect effect is nearly the same for all simulations."
"56373027800;15032788000;7006107059;","Evaluation of the aerosol indirect effect using satellite, tracer transport model, and aircraft data from the International Consortium for Atmospheric Research on Transport and Transformation",2007,"10.1029/2006JD007581","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547609628&doi=10.1029%2f2006JD007581&partnerID=40&md5=34eeff62ac10acdcbdd9a646cb8c74ed","The magnitudes of the ""indirect effects"" that anthropogenic aerosols have on clouds and climate remain uncertain. Past space-based characterizations have compared satellite retrievals of cloud properties with satellite- or model-derived aerosol quantities. The two fields have been taken from air masses displaced from each other either horizontally or vertically. Thus, almost by definition, the cloud retrievals have come from different meteorological regimes than the aerosol to which ostensibly they are related. Because cloud properties depend foremost on meteorology, the difference introduces undesired ambiguity in the comparisons. In this study, we compare Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) cloud retrievals with high spatial and temporal resolution output from a tracer transport model (FLEXPART), enabling colocation of fields of pollution and clouds both vertically and horizontally. Anthropogenic carbon monoxide (CO) is used as a passive pollution tracer, because its concentrations are tied to mixing and pollutant source strength, and they are independent of atmospheric oxidation and removal processes on timescales of weeks to months. Cloud and pollution fields are compared along a downwind axis from the U.S. northeastern seaboard for the duration of the summer 2004 International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) mission. Where the transport model indicates air as being polluted, cloud r<inf>e</inf> is smaller and cloud optical depth is in some cases higher, at least close to primary source regions. However, within 4 ± 1 days advection time from the northeastern seaboard, cloud perturbations become negligible, probably because of wet-scavenging of CCN. No conclusive evidence was found for any perturbation to cloud liquid water path by pollution. Copyright 2007 by the American Geophysical Union."
"7006306835;7202252296;","Organic aerosol effects on fog droplet spectra",2004,"10.1029/2003JD004427","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4143137504&doi=10.1029%2f2003JD004427&partnerID=40&md5=895653bfc0b535294307c3167dd493e0","Organic aerosol alters cloud and fog properties through surface tension and solubility effects. This study characterizes the role of organic compunds in affecting fog droplet number concentration by initializing and comparing detailed particle microphysical simulations with two field campaigns in the Po Valley. The size distribution and chemical composition of aerosol were based on the measurements made in the Po Valley Fog Experiments in 1989 and 1998-1999. Two types of aerosol with different hygroscopicity were considered: the less hygroscopic particles, composed mainly of organic compounds, and the more hygroscopic particles, composed mainly of inorganic salts. The organic fraction of aerosol mass explicitly modeled as a mixture of seven soluble compounds [Fuzzi et al., 2001] by employing a functional group-based thermodynamic model [Ming and Russell, 2002}. Condensable gases in the vapor phase included nitric acid, sulfuric acid, and ammonia. The maximum supersaturation in the simulation is 0.030% and is comparable to the calculation by Noone et al. [2002] inferred from measured residual particle fractions. The minimum activation diameters of the less and more hygroscopic particles are 0.49 μm and 0.40 μm, respectively. The predicted residual particle fractions are in agreement with measurements. The organic components of aerosol account for 34% of the droplet residual particle mass and change the average droplet number concentration by -10-6%, depending on the lowering o droplet surface tension and the interactions among dissolving ions. The hygroscopic growth of particles due to the presence of water-soluble organic compounds enhances the condensation of nitric acid and ammonia due to the increased surface area, resulting in a 9% increase in the average droplet number concentration. Assuming ideal behavior of aqueous solutions of water-soluble organic compounds overestimates the hygroscopic growth of particles and increases droplet numbers by 6%. The results are sensitive to microphysical processes such as condensation of soluble gases, which increases the average droplet number concentration by 26%. Wet deposition plays an important role in controlling liquid water content in this shallow fog. Copyright 2004 by the Geophysical Union."
"36678944300;57202078062;56158622800;55545601500;7403564495;25723426400;57201618856;57202070352;","Long-term variation of cloud droplet number concentrations from space-based Lidar",2018,"10.1016/j.rse.2018.05.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047068432&doi=10.1016%2fj.rse.2018.05.011&partnerID=40&md5=d7a0a4089d90d3c4527273693c2f1b56","This study presents a new 10 year of liquid water cloud droplet number concentration (Nd) climatology, and analyzes its long-term variation on both regional and global scales based on accurate depolarization ratio measurement from CALIPSO and 3.7 μm cloud effective radius retrieval from MODIS. Compared with the widely used passive retrieval method (e.g., MODIS retrieval), which considers Nd as function of cloud optical depth, geometry thickness and effective radius, retrieval method of the new Nd dataset has a weak dependence upon the cloud adiabatic assumption and eliminates the possible bias caused by multilayer clouds. Statistical results show that the annual cycle and long-term variability of Nd retrieved by CALIPSO agree reasonably well with those obtained from MODIS retrieval method, especially over the stratocumulus regions (correlation coefficient &gt;0.9). Multiple regression models and contribution calculation verify that the variability of sulfate mass concentration dominates the long-term variation of Nd over most regions, even though the contribution factors and rates vary with different regions, temperatures and methods. In addition, our study also indicates that the impact of BC and OC on Nd should not be ignored, especially for supercooled water clouds over those important biomass burning regions. These results demonstrate the temperature-dependent Nd climatology derived from CALIOP has potential to be beneficial to climate research and reduce the uncertainties in estimates of the aerosol indirect effect in the model simulations. © 2018 Elsevier Inc."
"7103180783;7402401574;6602080205;53880473700;","Preferred response of the East Asian summer monsoon to local and non-local anthropogenic sulphur dioxide emissions",2016,"10.1007/s00382-015-2671-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959113205&doi=10.1007%2fs00382-015-2671-5&partnerID=40&md5=6db0e8ae1c59616de9278aa629883383","In this study, the atmospheric component of a state-of-the-art climate model (HadGEM2-ES) that includes earth system components such as interactive chemistry and eight species of tropospheric aerosols considering aerosol direct, indirect, and semi-direct effects, has been used to investigate the impacts of local and non-local emissions of anthropogenic sulphur dioxide on the East Asian summer monsoon (EASM). The study focuses on the fast responses (including land surface feedbacks, but without sea surface temperature feedbacks) to sudden changes in emissions from Asia and Europe. The initial responses, over days 1–40, to Asian and European emissions show large differences. The response to Asian emissions involves a direct impact on the sulphate burden over Asia, with immediate consequences for the shortwave energy budget through aerosol–radiation and aerosol–cloud interactions. These changes lead to cooling of East Asia and a weakening of the EASM. In contrast, European emissions have no significant impact on the sulphate burden over Asia, but they induce mid-tropospheric cooling and drying over the European sector. Subsequently, however, this cold and dry anomaly is advected into Asia, where it induces atmospheric and surface feedbacks over Asia and the Western North Pacific (WNP), which also weaken the EASM. In spite of very different perturbations to the local aerosol burden in response to Asian and European sulphur dioxide emissions, the large scale pattern of changes in land–sea thermal contrast, atmospheric circulation and local precipitation over East Asia from days 40 onward exhibits similar structures, indicating a preferred response, and suggesting that emissions from both regions likely contributed to the observed weakening of the EASM. Cooling and drying of the troposphere over Asia, together with warming and moistening over the WNP, reduces the land–sea thermal contrast between the Asian continent and surrounding oceans. This leads to high sea level pressure (SLP) anomalies over Asia and low SLP anomalies over the WNP, associated with a weakened EASM. In response to emissions from both regions warming and moistening over the WNP plays an important role and determines the time scale of the response. © 2015, The Author(s)."
"56571063800;13403627400;43661479500;53879778800;7006728825;7004469744;","Evaluating uncertainty in convective cloud microphysics using statistical emulation",2015,"10.1002/2014MS000383","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928804697&doi=10.1002%2f2014MS000383&partnerID=40&md5=398c3b5f8c9d90505530e06c4a8eeb1d","The microphysical properties of convective clouds determine their radiative effects on climate, the amount and intensity of precipitation as well as dynamical features. Realistic simulation of these cloud properties presents a major challenge. In particular, because models are complex and slow to run, we have little understanding of how the considerable uncertainties in parameterized processes feed through to uncertainty in the cloud responses. Here we use statistical emulation to enable a Monte Carlo sampling of a convective cloud model to quantify the sensitivity of 12 cloud properties to aerosol concentrations and nine model parameters representing the main microphysical processes. We examine the response of liquid and ice-phase hydrometeor concentrations, precipitation, and cloud dynamics for a deep convective cloud in a continental environment. Across all cloud responses, the concentration of the Aitken and accumulation aerosol modes and the collection efficiency of droplets by graupel particles have the most influence on the uncertainty. However, except at very high aerosol concentrations, uncertainties in precipitation intensity and amount are affected more by interactions between drops and graupel than by large variations in aerosol. The uncertainties in ice crystal mass and number are controlled primarily by the shape of the crystals, ice nucleation rates, and aerosol concentrations. Overall, although aerosol particle concentrations are an important factor in deep convective clouds, uncertainties in several processes significantly affect the reliability of complex microphysical models. The results suggest that our understanding of aerosol-cloud interaction could be greatly advanced by extending the emulator approach to models of cloud systems. © 2015. The Authors."
"34876658200;56612517400;55802355600;36538539800;6701378450;","Incorporation of advanced aerosol activation treatments into CESM/CAM5: Model evaluation and impacts on aerosol indirect effects",2014,"10.5194/acp-14-7485-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904891921&doi=10.5194%2facp-14-7485-2014&partnerID=40&md5=cf68fa67da60214d366044044360d8b8","One of the greatest sources of uncertainty in the science of anthropogenic climate change is from aerosol-cloud interactions. The activation of aerosols into cloud droplets is a direct microphysical linkage between aerosols and clouds; parameterizations of this process link aerosol with cloud condensation nuclei (CCN) and the resulting indirect effects. Small differences between parameterizations can have a large impact on the spatiotemporal distributions of activated aerosols and the resulting cloud properties. In this work, we incorporate a series of aerosol activation schemes into the Community Atmosphere Model version 5.1.1 within the Community Earth System Model version 1.0.5 (CESM/CAM5) which include factors such as insoluble aerosol adsorption and giant cloud condensation nuclei (CCN) activation kinetics to understand their individual impacts on global-scale cloud droplet number concentration (CDNC). Compared to the existing activation scheme in CESM/CAM5, this series of activation schemes increase the computation time by ∼10% but leads to predicted CDNC in better agreement with satellite-derived/in situ values in many regions with high CDNC but in worse agreement for some regions with low CDNC. Large percentage changes in predicted CDNC occur over desert and oceanic regions, owing to the enhanced activation of dust from insoluble aerosol adsorption and reduced activation of sea spray aerosol after accounting for giant CCN activation kinetics. Comparison of CESM/CAM5 predictions against satellite-derived cloud optical thickness and liquid water path shows that the updated activation schemes generally improve the low biases. Globally, the incorporation of all updated schemes leads to an average increase in column CDNC of 150% and an increase (more negative) in shortwave cloud forcing of 12%. With the improvement of model-predicted CDNCs and better agreement with most satellite-derived cloud properties in many regions, the inclusion of these aerosol activation processes should result in better predictions of radiative forcing from aerosol-cloud interactions. © Author(s) 2014. CC Attribution 3.0 License."
"25652188900;8670472000;36161386500;7404747615;23484340400;7407104838;24329376600;23968109800;56487420600;10139397300;7405666962;7404142321;16444006500;56457851700;","Improved Aerosol Processes and Effective Radiative Forcing in HadGEM3 and UKESM1",2018,"10.1029/2018MS001464","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048133744&doi=10.1029%2f2018MS001464&partnerID=40&md5=3b3d766cd050e712d82e8a9e856d1a22","Aerosol processes and, in particular, aerosol-cloud interactions cut across the traditional physical-Earth system boundary of coupled Earth system models and remain one of the key uncertainties in estimating anthropogenic radiative forcing of climate. Here we calculate the historical aerosol effective radiative forcing (ERF) in the HadGEM3-GA7 climate model in order to assess the suitability of this model for inclusion in the UK Earth system model, UKESM1. The aerosol ERF, calculated for the year 2000 relative to 1850, is large and negative in the standard GA7 model leading to an unrealistic negative total anthropogenic forcing over the twentieth century. We show how underlying assumptions and missing processes in both the physical model and aerosol parameterizations lead to this large aerosol ERF. A number of model improvements are investigated to assess their impact on the aerosol ERF. These include an improved representation of cloud droplet spectral dispersion, updates to the aerosol activation scheme, and black carbon optical properties. One of the largest contributors to the aerosol forcing uncertainty is insufficient knowledge of the preindustrial aerosol climate. We evaluate the contribution of uncertainties in the natural marine emissions of dimethyl sulfide and organic aerosol to the ERF. The combination of model improvements derived from these studies weakens the aerosol ERF by up to 50% of the original value and leads to a total anthropogenic historical forcing more in line with assessed values. ©2018. Crown copyright. This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland."
"57196436816;23095483400;15840467900;57196441587;57196439738;35194679200;35772803100;57196442534;","Unveiling aerosol-cloud interactions - Part 1: Cloud contamination in satellite products enhances the aerosol indirect forcing estimate",2017,"10.5194/acp-17-13151-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85033218029&doi=10.5194%2facp-17-13151-2017&partnerID=40&md5=46a4bbd8e6f89004f4fa00cc5846f3d5","Increased concentrations of aerosol can enhance the albedo of warm low-level cloud. Accurately quantifying this relationship from space is challenging due in part to contamination of aerosol statistics near clouds. Aerosol retrievals near clouds can be influenced by stray cloud particles in areas assumed to be cloud-free, particle swelling by humidification, shadows and enhanced scattering into the aerosol field from (3-D radiative transfer) clouds. To screen for this contamination we have developed a new cloud-aerosol pairing algorithm (CAPA) to link cloud observations to the nearest aerosol retrieval within the satellite image. The distance between each aerosol retrieval and nearest cloud is also computed in CAPA. <br></br> Results from two independent satellite imagers, the Advanced Along-Track Scanning Radiometer (AATSR) and Moderate Resolution Imaging Spectroradiometer (MODIS), show a marked reduction in the strength of the intrinsic aerosol indirect radiative forcing when selecting aerosol pairs that are located farther away from the clouds (ĝ'0.28±0.26ĝ€Wĝ€mĝ'2) compared to those including pairs that are within 15ĝ€km of the nearest cloud (ĝ'0.49±0.18ĝ€Wĝ€mĝ'2). The larger aerosol optical depths in closer proximity to cloud artificially enhance the relationship between aerosol-loading, cloud albedo, and cloud fraction. These results suggest that previous satellite-based radiative forcing estimates represented in key climate reports may be exaggerated due to the inclusion of retrieval artefacts in the aerosol located near clouds."
"55934190000;55879681300;8618282100;7003907127;7006770362;8263760300;12544502800;55938109300;54941580100;8670222900;7006304904;39361670300;13007286600;55807448700;8625148400;24767977600;22635720500;7003862871;6701742258;6602893779;54982705800;6505947323;9738422100;7003658498;","Analysis of meteorology-chemistry interactions during air pollution episodes using online coupled models within AQMEII phase-2",2015,"10.1016/j.atmosenv.2014.09.020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937918358&doi=10.1016%2fj.atmosenv.2014.09.020&partnerID=40&md5=ecedf6e18d71b9edf1ae5f3958873819","This study reviews the top ranked meteorology and chemistry interactions in online coupled models recommended by an experts' survey conducted in COST Action EuMetChem and examines the sensitivity of those interactions during two pollution episodes: the Russian forest fires 25 Jul-15 Aug 2010 and a Saharan dust transport event from 1 Oct to 31 Oct 2010 as a part of the AQMEII phase-2 exercise. Three WRF-Chem model simulations were performed for the forest fire case for a baseline without any aerosol feedback on meteorology, a simulation with aerosol direct effects only and a simulation including both direct and indirect effects. For the dust case study, eight WRF-Chem and one WRF-CMAQ simulations were selected from the set of simulations conducted in the framework of AQMEII. Of these two simulations considered no feedbacks, two included direct effects only and five simulations included both direct and indirect effects. The results from both episodes demonstrate that it is important to include the meteorology and chemistry interactions in online-coupled models. Model evaluations using routine observations collected in AQMEII phase-2 and observations from a station in Moscow show that for the fire case the simulation including only aerosol direct effects has better performance than the simulations with no aerosol feedbacks or including both direct and indirect effects. The normalized mean biases are significantly reduced by 10-20% for PM10 when including aerosol direct effects. The analysis for the dust case confirms that models perform better when including aerosol direct effects, but worse when including both aerosol direct and indirect effects, which suggests that the representation of aerosol indirect effects needs to be improved in the model. © 2014 Published by Elsevier Ltd."
"55173596300;57208121852;35221443100;","Cloud fraction mediates the aerosol optical depth-cloud top height relationship",2014,"10.1002/2014GL059524","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900934922&doi=10.1002%2f2014GL059524&partnerID=40&md5=b2f7243073cb4faf2cf75d0b879f5a79","The observed strong link between aerosol optical depth (τ) and cloud top pressure (ptop) has frequently been interpreted as the invigoration of convective clouds by aerosol, with increased τ being strongly correlated with decreases in ptop (increases in cloud top height). A strong correlation between τ and cloud fraction (fc) has also been observed. Using satellite-retrieved data, here we show that p top is also strongly correlated to fc, and when combined with the strong sensitivity between fc and τ, a large proportion of the relationship between ptop and τcan be reconstructed. Given the uncertainties about the influence of aerosol-cloud interactions on the τ-fc relationship, this suggests that a large fraction of the τ-ptop correlation may not be due to aerosol effects. Influences such as aerosol humidification and meteorology play an important role and should therefore be considered in studies of aerosol-cloud interactions. © 2014. American Geophysical Union. All Rights Reserved."
"17345303300;26643041500;35459245100;55800347700;23051160600;6701620591;23991203900;6507755223;35461255500;6506718302;","Evaluation of the sectional aerosol microphysics module SALSA implementation in ECHAM5-HAM aerosol-climate model",2012,"10.5194/gmd-5-845-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869050669&doi=10.5194%2fgmd-5-845-2012&partnerID=40&md5=df4361f277fde83d8775aac8be62edc1","We present the implementation and evaluation of a sectional aerosol microphysics module SALSA within the aerosol-climate model ECHAM5-HAM. This aerosol microphysics module has been designed to be flexible and computationally efficient so that it can be implemented in regional or global scale models. The computational efficiency has been achieved by minimising the number of variables needed to describe the size and composition distribution. The aerosol size distribution is described using 10 size classes with parallel sections which can have different chemical compositions. Thus in total, the module tracks 20 size sections which cover diameters ranging from 3 nm to 10 μm and are divided into three subranges, each with an optimised selection of processes and compounds. <br><br> The implementation of SALSA into ECHAM5-HAM includes the main aerosol processes in the atmosphere: emissions, removal, radiative effects, liquid and gas phase sulphate chemistry, and the aerosol microphysics. The aerosol compounds treated in the module are sulphate, organic carbon, sea salt, black carbon, and mineral dust. In its default configuration, ECHAM5-HAM treats aerosol size distribution using the modal method. In this implementation, the aerosol processes were converted to be used in a sectional model framework. <br><br> The ability of the module to describe the global aerosol properties was evaluated by comparing against (1) measured continental and marine size distributions, (2) observed variability of continental number concentrations, (3) measured sulphate, organic carbon, black carbon and sea-salt mass concentrations, (4) observations of aerosol optical depth (AOD) and other aerosol optical properties from satellites and AERONET network, (5) global aerosol budgets and concentrations from previous model studies, and (6) model results using M7, which is the default aerosol microphysics module in ECHAM5-HAM. <br><br> The evaluation shows that the global aerosol properties can be reproduced reasonably well using a coarse resolution of 10 sections in size space. The simulated global aerosol budgets are within the range of previous studies. Surface concentrations of sulphate and carbonaceous species have an annual mean within a factor of two of the observations. The simulated sea-salt concentrations reproduce the observations within a factor of two, apart from the Southern Ocean over which the concentrations are within a factor of five. Regionally, AOD is in a relatively good agreement with the observations (within a factor of two). At mid-latitudes the observed AOD is captured well, while at high-latitudes as well as in some polluted and dust regions the modelled AOD is significantly lower than observed. <br><br> Regarding most of the investigated aerosol properties, the SALSA and the modal aerosol module M7 perform comparably well against observations. However, SALSA reproduces the observed number concentrations and the size distribution of CCN sized particles much more accurately than M7, and is therefore a good choice for aerosol-cloud interaction studies in global models. Our study also shows that when activation type nucleation in the boundary layer is included, the observed concentration of particles under 50 nm in diameter are reproduced much better compared to when only binary nucleation in the free troposphere is assumed. © Author(s) 2012."
"6603385031;7004715270;7202865036;56691914800;7005968859;7402049334;","Biomass burning as a potential source for atmospheric ice nuclei: Western wildfires and prescribed burns",2012,"10.1029/2012GL051915","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862542180&doi=10.1029%2f2012GL051915&partnerID=40&md5=42b1dc0e0cfbf7f95db4689062dcf81c","The sources, abundance and nature of atmospheric particles that serve as ice nuclei (IN) for cold cloud formation remain some of the most important, yet poorly-characterized, features of aerosol-cloud interactions that indirectly affect climate. Although a great deal of effort has focused on characterizing the ice nucleating ability of mineral dusts, less is known about carbonaceous particles. A primary source for carbonaceous IN is from biomass combustion. Here we report new measurements of IN activity at-30°C and above water saturation from biomass burning generated particles from prescribed burns and wildfires in the western US. These measurements suggest a range of IN activity, with variability largely dependent on the intensity of the fire. Although the fraction of particles generated during burns which serve as IN is quite small, the large numbers of particles generated in fires make biomass burning a potentially important source of IN to the atmosphere. © 2012. American Geophysical Union. All Rights Reserved."
"24329545900;7004154626;24757696000;","Aerosol indirect effect during successive contrasting monsoon seasons over Indian subcontinent using MODIS data",2010,"10.1016/j.atmosenv.2010.02.015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951091554&doi=10.1016%2fj.atmosenv.2010.02.015&partnerID=40&md5=2ca20b1e93c5a1e799ee0a960f00bbba","Aerosol indirect effect (AIE) was estimated over six Indian regions, which have been identified as main source regions of absorbing aerosol emissions, for four successive contrasting monsoon years, 2001 (normal monsoon rainfall year), 2002 (drought year), 2003 (excess monsoon rainfall year) and 2004 (below normal rainfall year). The AIE has been estimated both for fixed cloud liquid water path (CLWP) and for fixed cloud ice path (CIP) bins, ranging from 1 to 350 gm-2 at 25 gm-2 intervals obtained from Moderate resolution imaging spectroradiometer (MODIS). In 2002 and 2004, AIE found to be of positive (Twomey effect) in majority of the fixed CLWP and CIP bins, while in 2001 and 2003 majority of the bins were found to be showing negative indirect effect (Anti-Twomey effect). Changes in circulation patterns during contrasting monsoon seasons, bringing up air mass containing aerosols of different source origins may be the main reason for this positive and negative AIE. The study suggests that AIE could be one of the factors in modulating Indian summer monsoon. However, further research on this topic is to be carried out to establish the relationship between AIE and Indian monsoon rainfall and also AIE values may be parameterized in climate models for better prediction of monsoon. © 2010 Elsevier Ltd."
"9432343100;56374442600;8586682800;8550791300;35307109700;7005696579;15072064200;7005968859;7006415284;","Towards closing the gap between hygroscopic growth and CCN activation for secondary organic aerosols-Part 3: Influence of the chemical composition on the hygroscopic properties and volatile fractions of aerosols",2010,"10.5194/acp-10-3775-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951562805&doi=10.5194%2facp-10-3775-2010&partnerID=40&md5=fb6d4acadc0706f2459c0ed77e332a4f","The influence of varying levels of water mixing ratio,r during the formation of secondary organic aerosol (SOA) from the ozonolysis of α-pinene on the SOA hygroscopicity and volatility was investigated. The reaction proceeded and aerosols were generated in a mixing chamber and the hygroscopic characteristics of the SOA were determined with the Leipzig Aerosol Cloud Interaction Simulator (LACIS) and a Cloud Condensation Nuclei counter (CCNc). In parallel, a High-Resolution Time-of-Flight Aerodyne Aerosol Mass Spectrometer (HR-ToF-AMS) located downstream of a thermodenuder (TD) sampling from the mixing chamber, to collect mass spectra of particles from the volatile and less-volatile fractions of the SOA. Results showed that both hygroscopic growth and the volatile fraction of the SOA increased with increases in r inside the mixing chamber during SOA generation. An effective density of 1.40 g cm-3 was observed for the generated SOA when the reaction proceeded with &lt;1 g kg-1. Changes in the concentrations of the fragment CO2+ and the sum of CxH+y(short name CHO) and CxH+y (short name CH) fragments as measured by the HR-ToF-AMS were used to estimate changes in the oxidation level of the SOA with reaction conditions, using the ratios CO2 + to CH and CHO to CH. Under humid conditions, both ratios increased, corresponding to the presence of more oxygenated functional groups (i.e., multifunctional carboxylic acids). This result is consistent with the α-pinene ozonolysis mechanisms which suggest that water interacts with the stabilized Criegee intermediate. The volatility and the hygroscopicity results show that SOA generation via ozonolysis of &amp;alpha;-pinene in the presence of water vapour (r &lt;16.9 g kg-1) leads to the formation of more highly oxygenated compounds that are more hygroscopic and more volatile than compounds formed under dry conditions. © 2010 Author(s)."
"56706602500;55896920900;6701596624;","Retrieval of microphysical, geometrical, and radiative properties of marine stratocumulus from remote sensing",2003,"10.1029/2002jd002680","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342333730&doi=10.1029%2f2002jd002680&partnerID=40&md5=aa44e6032cf297b2b9397009334df0a8","Radiative transfer calculations in boundary layer stratocumulus are performed and used to retrieve cloud properties from remotely measured reflected radiances in the visible and near-infrared. Calculations based on the vertically uniform plane-parallel cloud model have been currently used for the retrieval of cloud optical thickness and droplet effective radius. They were extended in a previous work to the retrieval of cloud droplet number concentration and cloud geometrical thickness, by assuming a vertically stratified cloud model, with prescribed droplet spectrum. The retrieved values of cloud droplet number concentration though were substantially underestimated. Improvements are presented here with a more realistic parameterization of the droplet size distribution, based on the theory of droplet growth by vapor diffusion. The retrieval technique is applied to eight case studies of the second Aerosol Characterization Experiment and the retrieved values are compared to estimates derived from in situ cloud microphysical measurements. The technique provides accurate retrievals of cloud droplet number concentration, with no bias. The retrieval of cloud geometrical thickness though is systematically overestimated compared to that directly measured. This bias partly reflects the difference of cloud sampling between the two strategies. Remote sensing measurements, which are continuous, are capable of detecting the thickest cells of the cloud layer within the field of view of the radiometer, while discontinuous in situ vertical profiles provide a statistical average of the geometrical thickness. Part of the bias could also reflect three-dimensional effects of the radiative transfer in spatially heterogeneous clouds, which are not accounted for by the plane-parallel models. The data are then processed for deriving statistics of the retrieved values of cloud droplet number concentration, optical thickness, and liquid water path, for validation of large-scale parameterizations of the aerosol indirect effect. Copyright 2003 by the American Geophysical Union."
"36106370400;7102680152;55984424900;57194237061;55901167900;8084443000;8657171200;57189368623;55683878900;16479877100;6603256829;15065491600;37162122100;23479194900;57200679067;57203052406;55984712000;22979663900;7004296083;46461233500;7801565183;17433787100;55960891600;26658060000;9846154100;7402177459;55888251800;57195355957;35461255500;7006058570;6701378450;7006708207;8871497700;24081268200;35774441900;55942083800;9432343100;7005287667;35461763400;7004864963;7006595513;7006634316;7201496735;7003842561;7006415284;7005069415;14034301300;","Long-term cloud condensation nuclei number concentration, particle number size distribution and chemical composition measurements at regionally representative observatories",2018,"10.5194/acp-18-2853-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042731217&doi=10.5194%2facp-18-2853-2018&partnerID=40&md5=d10df45a94673b4318a2bed15b846f37","Aerosol-cloud interactions (ACI) constitute the single largest uncertainty in anthropogenic radiative forcing. To reduce the uncertainties and gain more confidence in the simulation of ACI, models need to be evaluated against observations, in particular against measurements of cloud condensation nuclei (CCN). Here we present a data set - ready to be used for model validation - of long-term observations of CCN number concentrations, particle number size distributions and chemical composition from 12 sites on 3 continents. Studied environments include coastal background, rural background, alpine sites, remote forests and an urban surrounding. Expectedly, CCN characteristics are highly variable across site categories. However, they also vary within them, most strongly in the coastal background group, where CCN number concentrations can vary by up to a factor of 30 within one season. In terms of particle activation behaviour, most continental stations exhibit very similar activation ratios (relative to particles 20nm) across the range of 0.1 to 1.0% supersaturation. At the coastal sites the transition from particles being CCN inactive to becoming CCN active occurs over a wider range of the supersaturation spectrum. Several stations show strong seasonal cycles of CCN number concentrations and particle number size distributions, e.g. at Barrow (Arctic haze in spring), at the alpine stations (stronger influence of polluted boundary layer air masses in summer), the rain forest (wet and dry season) or Finokalia (wildfire influence in autumn). The rural background and urban sites exhibit relatively little variability throughout the year, while short-term variability can be high especially at the urban site. The average hygroscopicity parameter, calculated from the chemical composition of submicron particles was highest at the coastal site of Mace Head (0.6) and lowest at the rain forest station ATTO (0.2-0.3). We performed closure studies based on -Köhler theory to predict CCN number concentrations. The ratio of predicted to measured CCN concentrations is between 0.87 and 1.4 for five different types of . The temporal variability is also well captured, with Pearson correlation coefficients exceeding 0.87. Information on CCN number concentrations at many locations is important to better characterise ACI and their radiative forcing. But long-term comprehensive aerosol particle characterisations are labour intensive and costly. Hence, we recommend operating migrating-CCNCs to conduct collocated CCN number concentration and particle number size distribution measurements at individual locations throughout one year at least to derive a seasonally resolved hygroscopicity parameter. This way, CCN number concentrations can only be calculated based on continued particle number size distribution information and greater spatial coverage of long-term measurements can be achieved. © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License."
"56610909100;8953662800;7409080503;7403564495;56610914500;8839875600;55574865800;57189621839;","A CloudSat perspective on the cloud climatology and its association with aerosol perturbations in the vertical over eastern China",2016,"10.1175/JAS-D-15-0309.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84988411029&doi=10.1175%2fJAS-D-15-0309.1&partnerID=40&md5=f870912b76f8da8ba3ea5fd78f57fc66","Many efforts have been taken to investigate aerosol-cloud interactions from space, but only a few studies have examined the response of vertical cloud structure to aerosol perturbations. Three-dimensional cloud climatologies of eight different cloud types identified from the CloudSat level-2 cloud product during the warm season (May-September) in 2008-10 over eastern China were first generated and analyzed. Using visibility as a proxy for cloud condensation nuclei, in combination with satellite-observed radar reflectivity, normalized contoured frequency by altitude diagrams of the differences in cloud radar reflectivity Z profiles under polluted and clean conditions were constructed. For shallow cumulus clouds (shallow Cu) Z tends to be inhibited, and it is enhanced in the upper layers for deep cumulus (deep Cu), nimbostratus (Ns), and deep convective clouds (DCC) under polluted conditions. Overall, analyses of the modified center of gravity (MCOG) and cloud-top height (CTH) also point to a similar aerosol effect, except for the nonsignificant changes in MCOGs and CTHs in deep Cu. The impacts of environmental factors such as lower-tropospheric stability and vertical velocity are also discussed for these types of clouds. Although consistent aerosol-induced elevations in MCOGs and CTHs for Ns and DCC clouds are observed, the effect of meteorology cannot be completely ruled out, which merits further analysis. © 2016 American Meteorological Society."
"36988140900;7403577184;7202772927;57206456336;6701845806;7102517130;7005054220;57194974100;7401701196;55787994000;","Implementation of an aerosol-cloud-microphysics-radiation coupling into the NASA unified WRF: Simulation results for the 6-7 August 2006 AMMA special observing period",2014,"10.1002/qj.2286","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922943045&doi=10.1002%2fqj.2286&partnerID=40&md5=521bd43aed5fb1923c3a76918c287b0d","Aerosols affect the Earth's radiation balance directly and cloud microphysical processes indirectly via the activation of cloud condensation and ice nuclei. These two effects have often been considered separately and independently, hence the need to assess their combined impact given the differing nature of their effects on convective clouds. To study both effects, an aerosol-microphysics-radiation coupling, including Goddard microphysics and radiation schemes, was implemented into the NASA Unified Weather Research and Forecasting model (NU-WRF). Fully coupled NU-WRF simulations were conducted for a mesoscale convective system (MCS) that passed through the Niamey, Niger area on 6-7 August 2006 during an AMMA special observing period. The results suggest that rainfall is reduced when aerosol indirect effects are included, regardless of the aerosol direct effect. Daily mean radiation heating profiles in the area traversed by the MCS showed the aerosol (mainly mineral dust) direct effect had the largest impact near cloud tops just above 200 hPa where short-wave heating increased by about 0.8 K day-1; the weakest long-wave cooling was at around 250 hPa. It was also found that more condensation and ice nuclei as a result of higher aerosol/dust concentrations led to increased amounts of all cloud hydrometeors because of the microphysical indirect effect, and the radiation direct effect acts to reduce precipitating cloud particles (rain, snow and graupel) in the middle and lower cloud layers while increasing the non-precipitating particles (ice) in the cirrus anvil. However, when the aerosol direct effect was activated, regardless of the indirect effect, the onset of MCS precipitation was delayed about 2 h, in conjunction with the delay in the activation of cloud condensation and ice nuclei. Overall, for this particular environment, model set-up and physics configuration, the effect of aerosol radiative heating due to mineral dust overwhelmed the effect of the aerosols on microphysics. © 2014 Royal Meteorological Society."
"57199321052;8586682800;55892420400;55892427900;22940676000;","Minimal cooling rate dependence of ice nuclei activity in the immersion mode",2013,"10.1002/jgrd.50810","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886068952&doi=10.1002%2fjgrd.50810&partnerID=40&md5=0a7cfe1066637da2ab0bde12c8ee4a6a","We present new measurements of the time dependence of the ice-nucleating ability of a wide range of materials including the minerals montmorillonite and kaolinite, the biological proxy ice nuclei Icemax, and flame soot generated from the incomplete combustion of ethylene gas. We also present time dependence for ambient ice nuclei collected from rainwater samples. Our data show that the time dependence for all materials studied here is weak, suggesting that the modified singular approximation is valid over the range of times and temperatures encountered for mixed phase clouds. Key Points Cooling rate dependent measurements of ice nuclei present in rainwaterCooling rate dependence for heterogeneous ice nucleation is minimalFifty hours exposure changes median freezing temperatures by less than 3K ©2013. American Geophysical Union. All Rights Reserved."
"35232818000;55258950300;25630924500;36810195000;10738896100;7403079681;55388515800;","An examination of parameterizations for the CCN number concentration based on in situ measurements of aerosol activation properties in the North China Plain",2013,"10.5194/acp-13-6227-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880754200&doi=10.5194%2facp-13-6227-2013&partnerID=40&md5=684b936c7abaea9fcf2e071f4879410d","Precise quantification of the cloud condensation nuclei (CCN) number concentration is crucial for understanding aerosol indirect effects and characterizing these effects in models. An evaluation of various methods for CCN parameterization was carried out in this paper based on in situ measurements of aerosol activation properties within HaChi (Haze in China) project. Comparisons were made by closure studies between methods using CCN spectra, bulk activation ratios, cut-off diameters and size-resolved activation ratios. The estimation of CCN number concentrations by the method using aerosol size-resolved activation ratios, either averaged over a day or with diurnal variation, was found to be most satisfying and straightforward. This could be well expected since size-resolved activation ratios include information regarding the effects of size-resolved chemical compositions and mixing states on aerosol activation properties. The method using the averages of critical diameters, which were inferred from measured CCN number concentrations and particle number size distributions, also provided a good prediction of the CCN number concentration. Based on comparisons of all these methods in this paper, it was recommended that the CCN number concentration be predicted using particle number size distributions with inferred critical diameters or size-resolved activation ratios. © 2012 Author(s)."
"57209647985;21742333400;24167564500;36026458100;6701378450;","Droplet number uncertainties associated with CCN: An assessment using observations and a global model adjoint",2013,"10.5194/acp-13-4235-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876898632&doi=10.5194%2facp-13-4235-2013&partnerID=40&md5=a5d5071dd14b1f62bf07641587a0cbd2","We use the Global Modelling Initiative (GMI) chemical transport model with a cloud droplet parameterisation adjoint to quantify the sensitivity of cloud droplet number concentration to uncertainties in predicting CCN concentrations. Published CCN closure uncertainties for six different sets of simplifying compositional and mixing state assumptions are used as proxies for modelled CCN uncertainty arising from application of those scenarios. It is found that cloud droplet number concentrations (Nd) are fairly insensitive to the number concentration (Na) of aerosol which act as CCN over the continents (∂ lnNd/∂ lnNa ̃ 10-30 %), but the sensitivities exceed 70% in pristine regions such as the Alaskan Arctic and remote oceans. This means that CCN concentration uncertainties of 4-71% translate into only 1- 23% uncertainty in cloud droplet number, on average. Since most of the anthropogenic indirect forcing is concentrated over the continents, this work shows that the application of Köhler theory and attendant simplifying assumptions in models is not a major source of uncertainty in predicting cloud droplet number or anthropogenic aerosol indirect forcing for the liquid, stratiform clouds simulated in these models. However, it does highlight the sensitivity of some remote areas to pollution brought into the region via long-range transport (e.g., biomass burning) or from seasonal biogenic sources (e.g., phytoplankton as a source of dimethylsulfide in the southern oceans). Since these transient processes are not captured well by the climatological emissions inventories employed by current large-scale models, the uncertainties in aerosol-cloud interactions during these events could be much larger than those uncovered here. This finding motivates additional measurements in these pristine regions, for which few observations exist, to quantify the impact (and associated uncertainty) of transient aerosol processes on cloud properties. © Author(s) 2013."
"36701716800;7005659017;16506538300;7103352790;","Aerosol indirect effect during the aberrant Indian Summer Monsoon breaks of 2009",2012,"10.1016/j.atmosenv.2012.06.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863732702&doi=10.1016%2fj.atmosenv.2012.06.007&partnerID=40&md5=1524fbf5529dc54f2e4546b793ffb06c","The significant role of aerosol-cloud interaction during the large-scale drought producing breaks of 2009 Indian Summer Monsoon is investigated in the present paper. This mega drought had already been attributed to two long breaks, one in June and the other in July-August. While Central India (CI) and northern parts of the country experienced deficient rainfall, the rainfall over the southern Peninsular India (PI) remained close to normal. During the first break in June, which was associated with mid-latitude intrusion of dry air, the Twomey effect (positive aerosol indirect effect - AIE) was a dominant factor inhibiting efficient precipitation over CI region, as compared to that over PI. Moreover, the number of days that experienced significant (at 5% level of significance) positive AIE during the first break was more over CI compared to the same during the second break. The AIE on ice clouds was not as significant as that of the low-clouds. The resulting cloud properties during both break and active phases over CI differ significantly from that over PI for the corresponding periods. The positive AIE mentioned here is attributed to the large-scale deficit of moisture supply to the CI region due to dynamical reasons. However, it is shown that under ample availability of moisture, more aerosols could invigorate deep clouds over specific regions even during the break spells. © 2012 Elsevier Ltd."
"8891521600;7004364155;7403282069;7201953443;7801693068;","An estimate of aerosol indirect effect from satellite measurements with concurrent meteorological analysis",2010,"10.1029/2010JD013948","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957557975&doi=10.1029%2f2010JD013948&partnerID=40&md5=b4c953e66b4b204a3e904bd0d1c789ea","Many studies have used satellite retrievals to investigate the effect of aerosols on cloud properties, but these retrievals are subject to artifacts that can confound interpretation. Additionally, large-scale meteorological differences over a study region dominate cloud dynamics and must be accounted for when studying aerosol and cloud interactions. We have developed an analysis method which minimizes the effect of retrieval artifacts and large-scale meteorology on the assessment of the aerosol indirect effect. The method divides an oceanic study region into 1° × 1° grid boxes and separates the grid boxes into two populations according to back trajectory analysis: one population contains aerosols of oceanic origin, and the other population contains aerosols of continental origin. We account for variability in the large-scale dynamical and thermodynamical conditions by stratifying these two populations according to vertical velocity (at 700 hPa) and estimated inversion strength and analyze differences in the aerosol optical depths, cloud properties, and top of atmosphere (TOA) albedos. We also stratify the differences by cloud liquid water path (LWP) in order to quantify the first aerosol indirect effect. We apply our method to a study region off the west coast of Africa and only consider single-layer low-level clouds. We find that grid boxes associated with aerosols of continental origin have higher cloud fraction than those associated with oceanic origin. Additionally, we limit our analysis to those grid boxes with cloud fractions larger than 80% to ensure that the two populations have similar retrieval biases. This is important for eliminating the retrieval biases in our difference analysis. We find a significant reduction in cloud droplet effective radius associated with continental aerosols relative to that associated with oceanic aerosols under all LWP ranges; the overall reduction is about 1.0 μm, when cloud fraction is not constrained, and is about 0.5 μm, when cloud fraction is constrained to be larger than 80%. We also find significant increases in cloud optical depth and TOA albedo associated with continental aerosols relative to those associated with oceanic aerosols under all LWP ranges. The overall increase in cloud optical depth is about 0.6, and the overall increase in TOA albedo is about 0.021, when we do not constrained cloud fraction. The overall increases in cloud optical depth and TOA albedo are 0.4 and 0.008, when we only use grid boxes with cloud fraction larger than 80%. Copyright 2010 by the American Geophysical Union."
"13403622000;7005955015;57203053317;56250250300;12139043600;12139310900;","Modeling of the wegener-bergeron-findeisen process - Implications for aerosol indirect effects",2008,"10.1088/1748-9326/3/4/045001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62749158649&doi=10.1088%2f1748-9326%2f3%2f4%2f045001&partnerID=40&md5=d4af2525a41e3eb2668d9430ec772fba","A new parameterization of the Wegener-Bergeron-Findeisen (WBF) process has been developed, and implemented in the general circulation model CAM-Oslo. The new parameterization scheme has important implications for the process of phase transition in mixed-phase clouds. The new treatment of the WBF process replaces a previous formulation, in which the onset of the WBF effect depended on a threshold value of the mixing ratio of cloud ice. As no observational guidance for such a threshold value exists, the previous treatment added uncertainty to estimates of aerosol effects on mixed-phase clouds. The new scheme takes subgrid variability into account when simulating the WBF process, allowing for smoother phase transitions in mixed-phase clouds compared to the previous approach. The new parameterization yields a model state which gives reasonable agreement with observed quantities, allowing for calculations of aerosol effects on mixed-phase clouds involving a reduced number of tunable parameters. Furthermore, we find a significant sensitivity to perturbations in ice nuclei concentrations with the new parameterization, which leads to a reversal of the traditional cloud lifetime effect. © 2008 IOP Publishing Ltd."
"7003613864;26643251000;7102578937;6506033170;56078142500;7006967825;","Simultaneous determination of aerosol- and surface characteristics from top-of-atmosphere reflectance using MERIS on board of ENVISAT",2006,"10.1016/j.asr.2006.03.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745726991&doi=10.1016%2fj.asr.2006.03.017&partnerID=40&md5=ea15f772bb3ab69f5d0bb9bd69a253db","The determination of aerosol optical thickness (AOT) from nadir scanning multi-spectral radiometers, like SeaWiFS, MERIS or MODIS, requires the separation of spectral atmospheric and surface properties. Since SeaWiFS and MERIS do not provide information at 2.1 μm, like MODIS, the estimation of the surface reflectance cannot be made by the cross correlation approach described by Kaufman et al., 1997. The BAER approach (Bremen AErosol Retrieval), von Hoyningen-Huene et al., 2003, uses a linear mixing model of spectra for 'green vegetation' and 'bare soil', tuned by the NDVI, determining an apparent surface to enable this separation of aerosol and surface properties from VIS and NIR channels. Thus AOT can be derived over a wide range of land surfaces for wavelengths &lt;0.67 μm. Using MERIS L1 data over Europe, the AOT retrieved is comparable with ground-based observations, provided by AERONET. Regional variation of AOT can be observed, showing the atmospheric variability for clear sky conditions by: large scale variation of aerosol turbidity, regional pollution, urban regions, effects of contrails and cases of aerosol-cloud interaction. Simultaneously with the spectral AOT also spectral surface reflectance is obtained, where all atmospheric influences have been considered (molecules, aerosols and absorbing gases (O 3 )) for channels with wavelengths &lt;0.67 μm. The AOT is extrapolated by Angström power law to NIR channels and the atmospheric correction for land surface properties is performed, enabling the further investigation of land use and spectral land properties. © 2006 COSPAR."
"17434337000;7102111067;13606163100;7006592184;","Potential for a biogenic influence on cloud microphysics over the ocean: A correlation study with satellite-derived data",2012,"10.5194/acp-12-7977-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866109011&doi=10.5194%2facp-12-7977-2012&partnerID=40&md5=98755b4395ccf8949ef7a7e04dcad8fc","Aerosols have a large potential to influence climate through their effects on the microphysics and optical properties of clouds and, hence, on the Earth's radiation budget. Aerosol-cloud interactions have been intensively studied in polluted air, but the possibility that the marine biosphere plays an important role in regulating cloud brightness in the pristine oceanic atmosphere remains largely unexplored. We used 9 yr of global satellite data and ocean climatologies to derive parameterizations of the temporal variability of (a) production fluxes of sulfur aerosols formed by the oxidation of the biogenic gas dimethylsulfide emitted from the sea surface; (b) production fluxes of secondary organic aerosols from biogenic organic volatiles; (c) emission fluxes of biogenic primary organic aerosols ejected by wind action on sea surface; and (d) emission fluxes of sea salt also lifted by the wind upon bubble bursting. Series of global monthly estimates of these fluxes were correlated to series of potential cloud condensation nuclei (CCN) numbers derived from satellite (MODIS). More detailed comparisons among weekly series of estimated fluxes and satellite-derived cloud droplet effective radius (r e) data were conducted at locations spread among polluted and clean regions of the oceanic atmosphere. The outcome of the statistical analysis was that positive correlation to CCN numbers and negative correlation to r e were common at mid and high latitude for sulfur and organic secondary aerosols, indicating both might be important in seeding cloud droplet activation. Conversely, primary aerosols (organic and sea salt) showed widespread positive correlations to CCN only at low latitudes. Correlations to r e were more variable, non-significant or positive, suggesting that, despite contributing to large shares of the marine aerosol mass, primary aerosols are not widespread major drivers of the variability of cloud microphysics. Validation against ground measurements pointed out that the parameterizations used captured fairly well the variability of aerosol production fluxes in most cases, yet some caution is warranted because there is room for further improvement, particularly for primary organic aerosol. Uncertainties and synergies are discussed, and recommendations of research needs are given. © 2012 Author(s)."
"57203793097;7005135473;6602600408;","A six year satellite-based assessment of the regional variations in aerosol indirect effects",2009,"10.5194/acp-9-4091-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950285633&doi=10.5194%2facp-9-4091-2009&partnerID=40&md5=54e78c356773dee680a0a49f8d97015c","Aerosols act as cloud condensation nuclei (CCN) for cloud water droplets, and changes in aerosol concentrations have significant microphysical impacts on the corresponding cloud properties. Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol and cloud properties are combined with NCEP Reanalysis data for six different regions around the globe between March 2000 and December 2005 to study the effects of different aerosol, cloud, and atmospheric conditions on the aerosol indirect effect (AIE). Emphasis is placed in examining the relative importance of aerosol concentration, type, and atmospheric conditions (mainly vertical motion) to AIE from region to region. Results show that in most regions, AIE has a distinct seasonal cycle, though the cycle varies in significance and period from region to region. In the Arabian Sea (AS), the sixyear mean anthropogenic + dust AIE is-0.27Wm-2 and is greatest during the summer months (&lt;-2.0Wm-2) during which aerosol concentrations (from both dust and anthropogenic sources) are greatest. Comparing AIE as a function of thin (LWP&lt;20 gm-2) vs. thick (LWP≥20 gm-2) clouds under conditions of large scale ascent or decent at 850 hPa showed that AIE is greatest for thick clouds during periods of upward vertical motion. In the Bay of Bengal, AIE is negligible owing to less favorable atmospheric conditions, a lower concentration of aerosols, and a non-alignment of aerosol and cloud layers. In the eastern North Atlantic, AIE is weakly positive (+0.1Wm-2) with dust aerosol concentration being much greater than the anthropogenic or sea salt components. However, elevated dust in this region exists above the maritime cloud layers and does not have a hygroscopic coating, which occurs in AS, preventing the dust from acting as CCN and limiting AIE. The Western Atlantic has a large anthropogenic aerosol concentration transported from the eastern United States producing a modest anthropogenic AIE (-0.46Wm-2). Anthropogenic AIE is also present off the West African coast corresponding to aerosols produced from seasonal biomass burning (both natural and man-made). Interestingly, atmospheric conditions are not particularly favorable for cloud formation compared to the other regions during the times where AIE is observed; however, clouds are generally thin (LWP&lt;20 gm-2) and concentrated very near the surface. Overall, we conclude that vertical motion, aerosol type, and aerosol layer heights do make a significant contribution to AIE and that these factors are often more important than total aerosol concentration alone and that the relative importance of each differs significantly from region to region."
"6603081424;57208765879;","Radiative susceptibility of cloudy atmospheres to droplet number perturbations: 2. Global analysis from MODIS",2008,"10.1029/2007JD009655","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52949120297&doi=10.1029%2f2007JD009655&partnerID=40&md5=0300e957ca9478e9ae8d1c0808d80040","Global distributions of albedo susceptibility for areas covered by liquid clouds are presented for 4 months in 2005. The susceptibility estimates are based on expanded definitions presented in a companion paper and include relative cloud droplet number concentration (CDNC) changes, perturbations in cloud droplet asymmetry parameter and single-scattering albedo, atmospheric/surface effects, and incorporation of the full solar spectrum. The cloud properties (optical thickness and effective radius) used as input in the susceptibility calculations come from MODIS Terra and Aqua Collection 5 gridded data. Geographical distributions of susceptibility corresponding to absolute (""absolute cloud susceptibility"") and relative (""relative cloud susceptibility"") CDNC changes are markedly different indicating that the detailed nature of the cloud microphysical perturbation is important for determining the radiative forcing associated with the first indirect aerosol effect. However, both types of susceptibility exhibit common characteristics such as significant reductions when perturbations in single-scattering properties are omitted, significant increases when atmospheric absorption and surface albedo effects are ignored, and the tendency to decrease with latitude, to be higher over ocean than over land, and to be statistically similar between the morning and afternoon MODIS overpasses. The satellite-based susceptibility analysis helps elucidate the role of present-day cloud and land surface properties in indirect aerosol forcing responses. Our realistic yet moderate CDNC perturbations yield forcings on the order of 1 -2 W m-2 for cloud optical property distributions and land surface spectral albedos observed by MODIS. Since susceptibilities can potentially be computed from model fields, these results have practical application in assessing the reasonableness of model-generated estimates of the aerosol indirect radiative forcing. Copyright 2008 by the American Geophysical Union."
"35227762400;7003591311;","The Radiative Forcing of Aerosol–Cloud Interactions in Liquid Clouds: Wrestling and Embracing Uncertainty",2018,"10.1007/s40641-018-0089-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85051798980&doi=10.1007%2fs40641-018-0089-y&partnerID=40&md5=507b4dd07cb271c00d8ee9a51957cb07","This article discusses some of the challenges that have limited progress in quantifying the radiative forcing associated with aerosol–cloud interactions (ACI) in warm (liquid-water) clouds. It reviews recent progress and suggests new ways of viewing the problem that might accelerate progress. It calls for much greater attention to the scale problem, both in terms of aerosol–cloud process representation in models and comparison with observations. It suggests careful consideration of the balance in detail with which processes are represented, and proposes a merging of detailed process understanding and system-wide behavior. In this spirit, it advocates tackling the problem with models of varying complexity that consider both the depth and breadth of the complex dynamical system. Finally, it considers shifting attention from untangling aerosol and meteorological effects on cloud systems towards understanding the co-variability of key aerosol and meteorological drivers of cloud systems. © 2018, The Author(s)."
"56623693700;57193206897;57193214426;7003541446;57192373652;57191308597;6701845055;16203284500;18437651200;7402538754;","A laboratory facility to study gas-aerosol cloud interactions in a turbulent environment: The π chamber",2016,"10.1175/BAMS-D-15-00203.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85011672048&doi=10.1175%2fBAMS-D-15-00203.1&partnerID=40&md5=cbf2880dec2b82317885a8d9b432fb3d","We have developed a facility capable of generating cloud conditions in two ways. The first is by reducing the pressure in the chamber, thereby simulating an updraft in the atmosphere, and the second is by forcing a temperature difference between two parallel, water-coated plates, inducing moist Rayleigh-Bénard convection. The more traditional mode via expansion produces a cloud lifetime limited by how long the expansion can be maintained (on the order of 10 min). Cloud formation through mixing allows the cloud to be sustained as long as the temperature difference is maintained and cloud condensation nuclei are supplied; in practice, such cloud conditions have been maintained for many days during extended measurement studies. Operation using both modes simultaneously is also possible. Laboratory experiments have the advantage of allowing us to decouple the full complexity of the atmosphere. Often, model comparisons with field results, as important as these are, are confounded by the lack of steady conditions, poor characterization of initial and boundary conditions, relatively sparse measurements, and the sheer level of complexity for many days during extended measurement studies. Operation using both modes simultaneously is also possible. Laboratory experiments have the advantage of allowing us to decouple the full complexity of the atmosphere. Often, model comparisons with field results, as important as these are, are confounded by the lack of steady conditions, poor characterization of initial and boundary conditions, relatively sparse measurements, and the sheer level of complexity. © 2016 American Meteorological Society."
"7202258620;6701463335;55720332500;9239331500;8067250600;7003298573;35556482500;7003430284;","Modelling aerosol-cloud-meteorology interaction: A case study with a fully coupled air quality model (GEM-MACH)",2015,"10.1016/j.atmosenv.2015.05.062","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939773088&doi=10.1016%2fj.atmosenv.2015.05.062&partnerID=40&md5=b29d45adc95b573f823000cb88e54176","A fully coupled on-line air quality forecast model, GEM-MACH, was used to study aerosol-cloud interactions for a case of an urban-industrial plume impacting stratocumulus. The aerosol effect on the cloud microphysics was achieved by the use of parameterization of cloud droplet nucleation predicted from the on-line size- and composition-resolved aerosols and coupled with a double-moment cloud microphysics parameterization. The model simulations with and without the on-line aerosol effect on cloud microphysics were compared and evaluated against in-situ aerosol and cloud observations from ICARTT 2004. Inclusion of the on-line aerosol interaction with cloud resulted in an increase in modelled cloud amount and cloud liquid water content (LWC) due to increased cloud droplet number concentration (Nd), a decrease in cloud droplet size and a reduction in warm precipitation. The modelled LWC and Nd agreed more closely with the observations when the on-line aerosol was allowed to affect the cloud than when aerosol effects on cloud were not explicitly simulated. The increased cloud amount due to the aerosol effects reduced the modelled downward shortwave radiative flux and air temperature at the surface, contributing to a decrease in ozone over the region of enhanced cloud and an increase in particle sulphate from an increased capacity for aqueous-phase production. Aerosol activation is shown to have a significant influence on the cloud microphysics and cloud processing of trace gases and aerosols. The importance of reasonable parameterization of cloud updraft speed is demonstrated. © 2015."
"36059595100;8511991900;7202048112;15755995900;55544607500;55476830600;36538539800;57207176515;16246205000;","Investigation of aerosol indirect effects using a cumulus microphysics parameterization in a regional climate model",2014,"10.1002/2013JD020958","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900620563&doi=10.1002%2f2013JD020958&partnerID=40&md5=a264bc5e18113673404179e0061b28d5","A new Zhang and McFarlane (ZM) cumulus scheme includes a two-moment cloud microphysics parameterization for convective clouds. This allows aerosol effects to be investigated more comprehensively by linking aerosols with microphysical processes in both stratiform clouds that are explicitly resolved and convective clouds that are parameterized in climate models. This new scheme is implemented in the Weather Research and Forecasting model, coupled with the physics and aerosol packages from the Community Atmospheric Model version 5. A case of July 2008 during the East Asian summer monsoon is selected to evaluate the performance of the new ZM and to investigate aerosol effects on monsoon precipitation. The precipitation and radiative fluxes simulated by the new ZM show a better agreement with observations compared to simulations with the original ZM that does not include convective cloud microphysics and aerosol-convective cloud interactions. Detailed analysis suggests that an increase in detrained cloud water and ice mass by the new ZM is responsible for this improvement. Aerosol impacts on cloud properties, precipitation, and radiation are examined by reducing the primary aerosols and anthropogenic emissions to 30% of those in the present (polluted) condition. The simulated surface precipitation is reduced by 9.8% from clean to polluted environment, and the reduction is less significant when microphysics processes are excluded from the cumulus clouds. Cloud fraction is reduced by the increased aerosols due to suppressed convection, except during some heavy precipitation periods when cloud fraction, cloud top height, and rain rate are increased due to enhanced convection. © 2013. American Geophysical Union. All Rights Reserved."
"57188966058;8922308700;57193213111;55688930000;7006270084;56162305900;7003666669;7102266120;7202048112;7103158465;","Impact of natural and anthropogenic aerosols on stratocumulus and precipitation in the Southeast Pacific: A regional modelling study using WRF-Chem",2012,"10.5194/acp-12-8777-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867658091&doi=10.5194%2facp-12-8777-2012&partnerID=40&md5=f2ccecef52e9b2d825d1408661c4cc62","Cloud-system resolving simulations with the chemistry version of the Weather Research and Forecasting (WRF-Chem) model are used to quantify the relative impacts of regional anthropogenic and oceanic emissions on changes in aerosol properties, cloud macro-and microphysics, and cloud radiative forcing over the Southeast Pacific (SEP) during the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) (15 October-16 November 2008). Two distinct regions are identified. The near-coast polluted region is characterized by low surface precipitation rates, the strong suppression of non-sea-salt particle activation due to sea-salt particles, a predominant albedo effect in aerosol indirect effects, and limited impact of aerosols associated with anthropogenic emissions on clouds. Opposite sensitivities to natural marine and anthropogenic aerosol perturbations are seen in cloud properties (e.g., cloud optical depth and cloud-top and cloud-base heights), precipitation, and the top-of-atmosphere and surface shortwave fluxes over this region. The relatively clean remote region is characterized by large contributions of aerosols from non-regional sources (lateral boundaries) and much stronger drizzle at the surface. Under a scenario of five-fold increase in regional anthropogenic emissions, this relatively clean region shows large cloud responses, for example, a 13% increase in cloud-top height and a 9% increase in albedo in response to a moderate increase (25% of the reference case) in cloud condensation nuclei (CCN) concentration. The reduction of precipitation due to this increase in anthropogenic aerosols more than doubles the aerosol lifetime in the clean marine boundary layer. Therefore, the aerosol impacts on precipitation are amplified by the positive feedback of precipitation on aerosol, which ultimately alters the cloud micro-and macro-physical properties, leading to strong aerosol-cloud-precipitation interactions. The high sensitivity is also related to an increase in cloud-top entrainment rate (by 16% at night) due to the increased anthropogenic aerosols. The simulated aerosol-cloud- precipitation interactions due to the increased anthropogenic aerosols have a stronger diurnal cycle over the clean region compared to the near-coast region with stronger interactions at night. During the day, solar heating results in more frequent decoupling of the cloud and sub-cloud layers, thinner clouds, reduced precipitation, and reduced sensitivity to the increase in anthropogenic emissions. This study shows the importance of natural aerosols in accurately quantifying anthropogenic forcing within a regional modeling framework. The results of this study also imply that the energy balance perturbations from increased anthropogenic emissions are larger in the more susceptible clean environment than in already polluted environment and are larger than possible from the first indirect effect alone. © 2012 Author(s)."
"35113492400;56611366900;24765069600;6701333444;","Observed impacts of vertical velocity on cloud microphysics and implications for aerosol indirect effects",2012,"10.1029/2012GL053599","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869409594&doi=10.1029%2f2012GL053599&partnerID=40&md5=bc5ebc16dc7a540b6d1d6a25f9952000","The simultaneous measurements of vertical velocity and cloud droplet size distributions in cumuli collected during the RACORO field campaign over the Atmospheric Radiation Measurement Program's Southern Great Plains site near Lamont, Oklahoma, US, are analyzed to determine the effects of vertical velocity on droplet number concentration, relative dispersion (the ratio of standard deviation to mean radius), and their relationship. The results show that with increasing vertical velocity the droplet number concentration increases while the relative dispersion decreases. The data also exhibit a negative correlation between relative dispersion and droplet number concentration. These empirical relationships can be fitted well with power law functions. This observational study confirms the theoretical and numerical expectations of the effects of vertical velocity on cloud microphysics by analyzing the data of vertical velocity directly. The effects of vertical velocity on relative dispersion and its relationship with droplet number concentration are opposite to that associated with aerosol loading, posing a confounding challenge for separating aerosol indirect effects from dynamical effects. © 2012. American Geophysical Union. All Rights Reserved."
"13403622000;57203053317;55915206300;","What governs the spread in shortwave forcings in the transient IPCC AR4 models?",2009,"10.1029/2008GL036069","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62749189133&doi=10.1029%2f2008GL036069&partnerID=40&md5=dadeb2a9a387d4bf6a36298aa8bfbb03","The coupled global atmospheric-ocean models used for transient simulations in the IPCC AR4 report differences in the present-day shortwave forcing of more than 2 W/m2. We show here that about 1.3 W/m of this spread could be explained by the different methods used to calculate cloud droplet number concentration (CDNC) from aerosol mass concentrations. Although we cannot rule out that other forcing agents could yield comparable uncertainties, this strongly points to the aerosol indirect effect as the main contributor to the wide spread in the shortwave forcing reported in IPCC AR4. © 2009 by the American Geophysical Union."
"6507984183;6701378450;57211106013;57196499374;","Cloud condensation nuclei prediction error from application of Köhler theory: Importance for the aerosol indirect effect",2007,"10.1029/2006JD007834","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547819313&doi=10.1029%2f2006JD007834&partnerID=40&md5=c9101f5878240732fb45bf0135a3ec18","In situ observations of aerosol and cloud condensation nuclei (CCN) and the GISS GCM Model II' with an online aerosol simulation and explicit aerosol-cloud interactions are used to quantify the uncertainty in radiative forcing and autoconversion rate from application of Köhler theory. Simulations suggest that application of Köhler theory introduces a 10-20% uncertainty in global average indirect forcing and 2-11% uncertainty in autoconversion. Regionally, the uncertainty in indirect forcing ranges between 10-20%, and 5-50% for autoconversion. These results are insensitive to the range of updraft velocity and water vapor uptake coefficient considered. This study suggests that Köhler theory (as implemented in climate models) is not a significant source of uncertainty for aerosol indirect forcing but can be substantial for assessments of aerosol effects on the hydrological cycle in climatically sensitive regions of the globe. This implies that improvements in the representation of GCM subgrid processes and aerosol size distribution will mostly benefit indirect forcing assessments. Predictions of autoconversion, by nature, will be subject to considerable uncertainty; its reduction may require explicit representation of size-resolved aerosol composition and mixing state. Copyright 2007 by the American Geophysical Union."
"7201837768;55896920900;57203200427;8606869000;57193132723;7003931528;7003666669;14060155500;55717074000;57203053317;6701596624;7102604282;6602600408;57198966831;56706602500;7004838931;","Evaluating aerosol/cloud/radiation process parameterizations with single-column models and Second Aerosol Characterization Experiment (ACE-2) cloudy column observations",2003,"10.1029/2003jd003902","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642286841&doi=10.1029%2f2003jd003902&partnerID=40&md5=de725877252a9ec8a9c2914ff9a00156","The Second Aerosol Characterization Experiment (ACE-2) data set along with ECMWF reanalysis meteorological fields provided the basis for the single column model (SCM) simulations, performed as part of the PACE (Parameterization of the Aerosol Indirect Climatic Effect) project. Six different SCMs were used to simulate ACE-2 case studies of clean and polluted cloudy boundary layers, with the objective being to identify limitations of the aerosol/cloud/radiation interaction schemes within the range of uncertainty in in situ, reanalysis and satellite retrieved data. The exercise proceeds in three steps. First, SCMs are configured with the same fine vertical resolution as the ACE-2 in situ data base to evaluate the numerical schemes for prediction of aerosol activation, radiative transfer and precipitation formation. Second, the same test is performed at the coarser vertical resolution of GCMs to evaluate its impact on the performance of the parameterizations. Finally, SCMs are run for a 24-48 hr period to examine predictions of boundary layer clouds when initialized with large-scale meteorological fields. Several schemes were tested for the prediction of cloud droplet number concentration (N). Physically based activation schemes using vertical velocity show noticeable discrepancies compared to empirical schemes due to biases in the diagnosed cloud base vertical velocity. Prognostic schemes exhibit a larger variability than the diagnostic ones, due to a coupling between aerosol activation and drizzle scavenging in the calculation of N. When SCMs are initialized at a fine vertical resolution with locally observed vertical profiles of liquid water, predicted optical properties are comparable to observations. Predictions however degrade at coarser vertical resolution and are more sensitive to the mean liquid water path than to its spatial heterogeneity. Predicted precipitation fluxes are severely underestimated and improve when accounting for sub-grid liquid water variability. Results from the 24-48 hr runs suggest that most models have problems in simulating boundary layer cloud morphology, since the large-scale initialization fields do not accurately reproduce observed meteorological conditions. As a result, models significantly overestimate optical properties. Improved cloud morphologies were obtained for models with subgrid inversions and subgrid cloud thickness schemes. This may be a result of representing subgrid scale effects though we do not rule out the possibility that better large-forcing data may also improve cloud morphology predictions. Copyright 2003 by the American Geophysical Union."
"55386235300;56355030000;7102290666;7202162685;36058918500;7003415852;","Retrieval of cloud droplet size from visible and microwave radiometric measurements during INDOEX: Implication to aerosols' indirect radiative effect",2003,"10.1029/2001jd001395","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347899406&doi=10.1029%2f2001jd001395&partnerID=40&md5=6c5356dddaad0fc553f6af919ac76a12","The effective radius of water cloud droplets is retrieved using remotely sensed passive microwave and visible data collected by aircraft during the Indian Ocean Experiment. The purpose of this study is to assess the aerosols' effect on cloud microphysical and radiative properties. To study this effect, we investigate the relationships among effective radius, liquid water path and number concentration of cloud droplets. The effective radius retrieval uses imager observations of reflected sunlight at 0.64 μm and liquid water path derived from microwave measurements. Results of an error analysis show that retrieval error is the largest for thin clouds having small visible reflectances and small liquid water path. For this reason, only pixels with visible reflectances greater than 0.2 are used in our data analysis, so that the maximum RMS error in effective radius is limited to about 4 μm. The relation between liquid water path and effective radius is examined for four different latitudinal regions. Results show that for the same liquid water path, effective radii are significantly smaller in the north than in the south, in correspondence to the north-south gradient of aerosol concentration in this region. In situ aircraft observations reveal larger cloud droplet number concentrations in the north than in the south. The north-south gradient of these variables are consistent with the aerosols' effect on cloud microphysics, that is, higher aerosol concentration increases the number concentration of cloud droplets, which, in turn, reduces droplet sizes given the same liquid water path and cloud thickness. Results based on comparison between data collected from northern and southern hemispheres suggest that the increase in aerosol number concentration alters cloud droplet numbers and sizes while leaving liquid water contents approximately the same."
"55923546200;8942524900;8633783900;43661479500;35810775100;55480654300;24463029300;12753162000;36134816800;7004469744;","Uncertainty in the magnitude of aerosol-cloud radiative forcing over recent decades",2014,"10.1002/2014GL062029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921790880&doi=10.1002%2f2014GL062029&partnerID=40&md5=40ba027986211b72331273f6acce10e1","Aerosols and their effect on the radiative properties of clouds are one of the largest sources of uncertainty in calculations of the Earth's energy budget. Here the sensitivity of aerosol-cloud albedo effect forcing to 31 aerosol parameters is quantified. Sensitivities are compared over three periods; 1850-2008, 1978-2008, and 1998-2008. Despite declining global anthropogenic SO2 emissions during 1978-2008, a cancelation of regional positive and negative forcings leads to a near-zero global mean cloud albedo effect forcing. In contrast to existing negative estimates, our results suggest that the aerosol-cloud albedo effect was likely positive (0.006 to 0.028Wm-2) in the recent decade, making it harder to explain the temperature hiatus as a forced response. Proportional contributions to forcing variance from aerosol processes and natural and anthropogenic emissions are found to be period dependent. To better constrain forcing estimates, the processes that dominate uncertainty on the timescale of interest must be better understood. Key Points Forcing sensitivity to aerosol parameters is strongly period dependentUnderstanding near-future climate is limited if a single period is consideredIn recent decades, parametric uncertainty is smaller than model diversity ©2014. The Authors."
"55366700000;7102084129;","Decomposing aerosol cloud radiative effects into cloud cover, liquid water path and Twomey components in marine stratocumulus",2014,"10.1016/j.atmosres.2013.12.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891794013&doi=10.1016%2fj.atmosres.2013.12.008&partnerID=40&md5=d023409c7f57e86396c26ef9dc9d2c68","A method for separating the three components of the marine stratocumulus (MSC) aerosol cloud interactions radiative effects, i.e., the cloud cover, liquid water path (LWP) and cloud drop radius (Twomey), was developed and tested. It is based on the assumption that changes in MSC cloud regimes that occur at short distance in homogeneous meteorological conditions are related to respective changes in the concentration of cloud condensation nuclei (CCN). The method was applied to 50 cases of well defined transitions from closed to open cells. It was found that the negative cloud radiative effect (CRE) over the closed cells is on average higher by 109±18Wm-2 than that over the adjacent open cells. This large negative CRE is composed of the cloud cover (42±8%), LWP (32±8%) and Twomey (26±6%) effects. This shows that the Twomey effect, which is caused by change in droplet concentration for a given LWP, contributes only a quarter of the difference in CRE, whereas the rest is contributed by added cloud water to the open cells both in the horizontal (cloud cover effect) and in the vertical (LWP effect) dimensions. The results suggest the possibility that anthropogenic aerosols that affect MSC-regime-changes might incur large negative radiative forcing on the global scale, mainly due to the cloud cover effect. © 2013 Elsevier B.V."
"7103180783;7402401574;6602080205;53880473700;","The impacts of European and Asian anthropogenic sulfur dioxide emissions on Sahel rainfall",2014,"10.1175/JCLI-D-13-00769.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907048188&doi=10.1175%2fJCLI-D-13-00769.1&partnerID=40&md5=c0133ce077f0baf94bdddd3e07d8fdd9","In this study, the atmospheric component of a state-of-the-art climate model [the Hadley Centre Global Environment Model, version 2-Earth System (HadGEM2-ES)] has been used to investigate the impacts of regional anthropogenic sulfur dioxide emissions on boreal summer Sahel rainfall. The study focuses on the transient response of the West African monsoon (WAM) to a sudden change in regional anthropogenic sulfur dioxide emissions, including land surface feedbacks but without sea surface temperature (SST) feedbacks. The response occurs in two distinct phases: 1) fast adjustment of the atmosphere on a time scale of days to weeks (up to 3 weeks) through aerosol-radiation and aerosol-cloud interactions with weak hydrological cycle changes and surface feedbacks and 2) adjustment of the atmosphere and land surface with significant local hydrological cycle changes and changes in atmospheric circulation (beyond 3 weeks). European emissions lead to an increase in shortwave (SW) scattering by increased sulfate burden, leading to a decrease in surface downwardSWradiation that causes surface cooling over North Africa, a weakening of the Saharan heat low and WAM, and a decrease in Sahel precipitation. In contrast, Asian emissions lead to very little change in sulfate burden over North Africa, but they induce an adjustment of the Walker circulation, which leads again to a weakening of theWAMand a decrease in Sahel precipitation. The responses to European and Asian emissions during the second phase exhibit similar large-scale patterns of anomalous atmospheric circulation and hydrological variables, suggesting a preferred response. The results support the idea that sulfate aerosol emissions contributed to the observed decline in Sahel precipitation in the second half of the twentieth century. © 2014 American Meteorological Society."
"55332372700;6505932008;6602805147;","Mineral dust indirect effects and cloud radiative feedbacks of a simulated idealized nocturnal squall line",2013,"10.5194/acp-13-4467-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877858403&doi=10.5194%2facp-13-4467-2013&partnerID=40&md5=4386ccf306feb6a9cb3ea6ed00c42387","Mineral dust is arguably the most abundant aerosol species in the world and as such potentially plays a large role in aerosol indirect effects (AIEs). This study assesses and isolates the individual responses in a squall line that arise (1) from radiation, (2) from dust altering the microphysics, as well as (3) from the synergistic effects between (1) and (2). To accomplish these tasks, we use the Regional Atmospheric Modeling System (RAMS) set up as a cloudresolving model (CRM). The CRM contains aerosol and microphysical schemes that allow mineral dust particles to nucleate as cloud drops and ice crystals, replenish upon evaporation and sublimation, be tracked throughout hydrometeor transition, and be scavenged by precipitation and dry sedimentation. Factor separation is used on four simulations of the squall line in order to isolate the individual roles of radiation (RADIATION), microphysically active dust (DUST MICRO), and the nonlinear interactions of those factors (SYNERGY). Results indicate that RADIATION acts to increase precipitation, intensify the cold pool, and enhance the mesoscale organization of the squall line due to changes in microphysics originating from cloud top cooling. Conversely, DUST MICRO decreases precipitation, weakens the cold pool, and weakens the mesoscale organization of the squall line due to an enhancement of the warm rain process. SYNERGY shows little impact on the squall line, except near the freezing level, where an increase in mesoscale organization takes place. The combined effect of the mineral dust AIE due to both DUST MICRO and SYNERGY is to weaken the squall line. © Author(s) 2013."
"20435752700;35974951200;55885039800;35887706900;","Relative humidity and its effect on aerosol optical depth in the vicinity of convective clouds",2013,"10.1088/1748-9326/8/3/034025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885653399&doi=10.1088%2f1748-9326%2f8%2f3%2f034025&partnerID=40&md5=6356baf323f1430151a3c16af65521d5","The hygroscopic growth of aerosols is controlled by the relative humidity (RH) and changes the aerosols' physical and hence optical properties. Observational studies of aerosol-cloud interactions evaluate the aerosol concentration using optical parameters, such as the aerosol optical depth (AOD), which can be affected by aerosol humidification. In this study we evaluate the RH background and variance values, in the lower cloudy atmosphere, an additional source of variance in AOD values beside the natural changes in aerosol concentration. In addition, we estimate the bias in RH and AOD, related to cloud thickness. This provides the much needed range of RH-related biases in studies of aerosol-cloud interaction. Twelve years of radiosonde measurements (June-August) in thirteen globally distributed stations are analyzed. The estimated non-biased AOD variance due to day-to-day changes in RH is found to be around 20% and the biases linked to cloud development around 10%. Such an effect is important and should be considered in direct and indirect aerosol effect estimations but it is inadequate to account for most of the AOD trend found in observational studies of aerosol-cloud interactions. © 2013 IOP Publishing Ltd."
"24480690400;23502556500;35171424700;6603384123;55007493900;15830196600;53865535800;6602948193;6701691417;35577097300;25926681100;","Spatio-temporal variations in aerosol optical and cloud parameters over Southern India retrieved from MODIS satellite data",2012,"10.1016/j.atmosenv.2011.10.032","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84155163091&doi=10.1016%2fj.atmosenv.2011.10.032&partnerID=40&md5=bcd006cd0c84739a1fbd43a1ed2c4f19","Remote sensing of global aerosols has generated a great scientific interest in a variety of applications related to global warming and climate change. The spatial and temporal variations in aerosol particles over Southern India were described in the present study and the impact of these variations on various optical properties of clouds, using Moderate Resolution Imaging Spectroradiometer (MODIS) data retrieved from the Terra satellite. High mean Aerosol Optical Depth (AOD) values were observed in almost all regions during the summer season, whereas in Pune, Visakhapatnam and Hyderabad, high AOD values were noticed during the monsoon season. The ångström exponent that increases with AOD is opposite to what would be the case if swelling of particles due to hygroscopic growth near cloudy areas played a major role in the MODIS data. We then analyzed the relationships between AOD and four other cloud parameters, namely water vapor (WV), cloud fraction (CF), cloud top temperature (CTT) and cloud top pressure (CTP). Regional correlation maps and time series plots for aerosol (AOD) and cloud parameters were produced to provide a better understanding of aerosol-cloud interaction. The correlation between AOD and CF was greater than 0.51 in Visakhapatnam, 0.45 in Thiruvanantapuram, 0.42 in Pune and whereas in Bangalore, Hyderabad and Anantapur, it is 0.17, 0.39 and 0.12, respectively. The analyses showed strong positive correlations between AOD and WV for all cities investigated. The correlation between AOD and CF was positive for all selected cities. AOD showed a negative correlation with CTP and CTT in Southern Indian regions. © 2011 Elsevier Ltd."
"55915206300;8511991900;36680583100;7202048112;6603631763;","Pollution from China increases cloud droplet number, suppresses rain over the East China Sea",2011,"10.1029/2011GL047235","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955794828&doi=10.1029%2f2011GL047235&partnerID=40&md5=9d7f61dcf9f66260b0c9467c55417b86","Rapid economic growth over the last 30 years in China has led to a significant increase in aerosol loading, which is mainly due to the increased emissions of its precursors such as SO<inf>2</inf> and NO<inf>x</inf>. Here we show that these changes significantly affect wintertime clouds and precipitation over the East China Sea downwind of major emission sources. Satellite observations show an increase of cloud droplet number concentration from less than 200 cm-3 in the 1980s to more than 300 cm-3 in 2005. In the same time period, precipitation frequency reported by voluntary ship observers was reduced from more than 30% to less than 20% of the time. A back trajectory analysis showed the pollution in the investigation area to originate from the Shanghai-Nanjing and Jinan industrial areas. A model sensitivity study was performed, isolating the effects of changes in emissions of the aerosol precursors SO<inf>2</inf> and NO<inf>x</inf> on clouds and precipitation using a state-of-the-art mesocale model including chemistry and aerosol indirect effects. Similar changes in cloud droplet number concentration over the East China Sea were obtained when the current industrial emissions in China were reduced to the 1980s levels. Simulated changes in precipitation were somewhat smaller than the observed changes but still significant. © 2011 by the American Geophysical Union."
"16308514000;7003591311;12645767500;55017656900;7202899330;","Deconstructing the precipitation susceptibility construct: Improving methodology for aerosol-cloud precipitation studies",2010,"10.1029/2009JD013426","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956486060&doi=10.1029%2f2009JD013426&partnerID=40&md5=e334f50add110b0203382daead47bb71","It is generally thought that an increase in aerosol particles suppresses precipitation in warm clouds. The nature and magnitude of this effect are highly uncertain owing to numerous microphysical and macrophysical processes that influence clouds over a wide range of spatial and temporal scales. This work addresses the need to improve the evidence for and quantification of aerosol effects on precipitation by using observational data. Previous work introduced the concept of precipitation susceptibility as a metric for changes in precipitation that result from aerosol perturbations. Motivated by the difficulty in obtaining statistically significant aerosol measurements in the vicinity of clouds, this study explores breaking up the precipitation susceptibility construct into separate components: an aerosol-cloud interaction component and a cloud-precipitation component. These are used to quantify precipitation susceptibility, while also accounting for meteorological factors that could obfuscate the response of clouds to aerosol perturbations. The utility of this technique is demonstrated using a diverse set of tools, including data from NASA's A-Train constellation of satellites, aircraft measurements, and models of various complexities. Employing this method results in increased confidence in causal relationships between aerosol perturbations and precipitation. © Copyright 2010 by the American Geophysical Union."
"56032511300;7102604282;6602805147;","Aerosol effects on liquid-water path of thin stratocumulus clouds",2009,"10.1029/2008JD010513","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649128741&doi=10.1029%2f2008JD010513&partnerID=40&md5=9a4555e3ee2793f146ab14736499fa7d","Thin clouds with mean liquid water path (LWP) of ∼50 g m-2 cover 27.5% of the globe and thus play an important role in Earth's-radiation budget. Radiative fluxes at Earth's surface and top of atmosphere are very sensitive to the LWP variation when the LWP becomes smaller than ∼50 g m-2. This indicates that aerosol effects on thin clouds can have a substantial impact on the variation of global radiative forcing if LWP changes. This study examines the aerosol indirect effect through changes in the LWP in three cases of thin warm stratocumulus clouds with LWP &lt; 50 gm-2 . We use a cloudsystem resolving model coupled with a double-moment representation of cloud microphysics. Intensified interactions among the cloud droplet number concentration, condensation, and dynamics at high aerosol play a critical role in the LWP responses to aerosol increases. Increased aerosols lead to increased CDNC, providing the increased surface area of droplets where water vapor condenses. This increases condensation, and thus condensational heating, to produce stronger updrafts, leading to an increased LWP with increased aerosols in two of the cases where precipitation reaches the surface. In a case with no surface precipitation, LWP decreases with increases in aerosols. In this case, most of precipitation evaporates just below the cloud base. With decreases in aerosols, precipitation increases and leads to increasing evaporation of precipitation, thereby increasing instability around the cloud base. This leads to increased updrafts, and thus condensation, from which increased LWP results. Copyright 2009 by the American Geophysical Union."
"7005703744;35302065900;","Evidence of the cloud lifetime effect from wildfire-induced thunderstorms",2008,"10.1029/2008GL035680","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60149097387&doi=10.1029%2f2008GL035680&partnerID=40&md5=794ee83a3880fd7bfae8fc0750571b13","A case study is presented of pyro-cumulonimbi (pyroCbs) forming over Canadian forest fires. Cloud-top ice effective radius values of these pyroCbs are significantly smaller than are those within surrounding convection. The smoke provides a massive source of cloud condensation nuclei (CCN), resulting in smaller cloud droplets which freeze homogeneously at temperatures around -40°C and produce very small ice crystals. It is also shown that the pyroCb anvils persist 6-12 hours longer than convectively-generated cirrus anvils from nearby convection. This provides evidence for the so-called cloud lifetime effect, an aerosol indirect effect identified by the most recent Intergovernmental Panel on Climate Change (IPCC) report."
"56611366900;6701590980;55740664200;7005862399;7005263785;","Threshold radar reflectivity for drizzling clouds",2008,"10.1029/2007GL031201","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41849135059&doi=10.1029%2f2007GL031201&partnerID=40&md5=56b46ace9d328488efb4714190de71e7","Empirical studies have suggested the existence of a threshold radar reflectivity between nonprecipitating and precipitating clouds; however, there has been neither a rigorous theoretical basis for the threshold reflectivity nor a sound explanation as to why empirically determined threshold reflectivities differ among studies. Here we present a theory for the threshold reflectivity by relating it to the autoconversion process. This theory not only demonstrates the sharp transition from cloud to rain when the radar reflectivity exceeds some value (threshold reflectivity) but also reveals that the threshold reflectivity is an increasing function of the cloud droplet concentration. The dependence of threshold reflectivity on droplet concentration suggests that the differences in empirically determined threshold reflectivity arise from the differences in droplet concentration. The favorable agreement with measurements collected over a wide range of conditions further provides observational support for the theoretical formulation. The results have many potential applications, especially to remote sensing of cloud properties and studies of the second aerosol indirect effect. Copyright 2008 by the American Geophysical Union."
"14060155500;7004838931;7004611350;","Aerosol activation in marine stratocumulus clouds: 1. Measurement validation for a closure study",2003,"10.1029/2002jd002678","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342288981&doi=10.1029%2f2002jd002678&partnerID=40&md5=c0149a9027db9629c3dbd2e8ce4b68e6","This paper is the first of a series dedicated to an observational study of the aerosol indirect effect in marine stratocumulus clouds. The data were collected in 1997, during the second Aerosol Characterization Experiment (ACE-2) CLOUDYCOLUMN experiment, conducted over the eastern Atlantic Ocean, in the vicinity of the Canary Islands. Here we compare measurements made both on aircraft and at the surface, including condensation nuclei (CN) and accumulation mode aerosol concentrations, and aerosol size spectra. We also compare measured and predicted wet aerosol size spectra and examine statistics of vertical velocity within and below stratocumulus clouds. In general, aircraft and surface measurements of CN concentration, accumulation mode aerosol concentration and size spectra agree within expected uncertainties. However, a substantial disparity is documented in the comparison of predicted and observed wet aerosol spectra. We attribute this to either bias in the wet aerosol measurements, made with an FSSP-300, or to error in the sizing of dry aerosol particles. The analysis of vertical velocity indicates that the first and third moments of the vertical velocity frequency distribution do not change substantially between below-cloud and in-cloud flight segments; however, an increase in the second moment of the distribution across cloud base is documented. Overall, the results lend confidence to the use of surface site aerosol physical and chemical property data, as well as airborne measurements of vertical velocity, for modeling of the aerosol activation process, as described by Snider et al. [2003] (hereinafter referred to as part 2) in the special section. Here, and in the paper by Snider et al. [2003] (hereinafter referred to as part 2), we examine how sensitive the predictions are to the common assumption that the aerosol particles are compact spheres. Copyright 2003 by the American Geophysical Union."
"55173596300;55366700000;55326237100;6602600408;35227762400;24757696000;37078354100;25031430500;35069282600;","Constraining the aerosol influence on cloud liquid water path",2019,"10.5194/acp-19-5331-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064744918&doi=10.5194%2facp-19-5331-2019&partnerID=40&md5=f9cc2bdc2e3efb9263872ea341634561","The impact of aerosols on cloud properties is one of the largest uncertainties in the anthropogenic radiative forcing of the climate. Significant progress has been made in constraining this forcing using observations, but uncertainty remains, particularly in the magnitude of cloud rapid adjustments to aerosol perturbations. Cloud liquid water path (LWP) is the leading control on liquid-cloud albedo, making it important to observationally constrain the aerosol impact on LWP. Previous modelling and observational studies have shown that multiple processes play a role in determining the LWP response to aerosol perturbations, but that the aerosol effect can be difficult to isolate. Following previous studies using mediating variables, this work investigates use of the relationship between cloud droplet number concentration (Nd) and LWP for constraining the role of aerosols. Using jointprobability histograms to account for the non-linear relationship, this work finds a relationship that is broadly consistent with previous studies. There is significant geographical variation in the relationship, partly due to role of meteorological factors (particularly relative humidity). The Nd-LWP relationship is negative in the majority of regions, suggesting that aerosol-induced LWP reductions could offset a significant fraction of the instantaneous radiative forcing from aerosol-cloud interactions (RFaci). However, variations in the Nd-LWP relationship in response to volcanic and shipping aerosol perturbations indicate that the Nd-LWP relationship overestimates the causal Nd impact on LWP due to the role of confounding factors. The weaker LWP reduction implied by these ""natural experiments"" means that this work provides an upper bound to the radiative forcing from aerosol-induced changes in the LWP. © 2019 Author(s)."
"57191227191;55717074000;7404544551;55577875600;57201942906;57192212652;57191226379;55438848700;57190497058;","Radiative effect and climate impacts of brown carbon with the Community Atmosphere Model (CAM5)",2018,"10.5194/acp-18-17745-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058503201&doi=10.5194%2facp-18-17745-2018&partnerID=40&md5=c1c68b9796583870529216d870f72f1d","A recent development in the representation of aerosols in climate models is the realization that some components of organic aerosol (OA), emitted from biomass and biofuel burning, can have a significant contribution to shortwave radiation absorption in the atmosphere. The absorbing fraction of OA is referred to as brown carbon (BrC). This study introduces one of the first implementations of BrC into the Community Atmosphere Model version 5 (CAM5), using a parameterization for BrC absorptivity described in Saleh et al. (2014). Nine-year experiments are run (2003-2011) with prescribed emissions and sea surface temperatures to analyze the effect of BrC in the atmosphere. Model validation is conducted via model comparison to single-scatter albedo and aerosol optical depth from the Aerosol Robotic Network (AERONET). This comparison reveals a model underestimation of single scattering albedo (SSA) in biomass burning regions for both default and BrC model runs, while a comparison between AERONET and the model absorption Ångström exponent shows a marked improvement with BrC implementation. Global annual average radiative effects are calculated due to aerosol-radiation interaction (REari; 0:13±0:01Wm -2 ) and aerosol-cloud interaction (REaci; 0:01±0:04Wm -2 ). REari is similar to other studies' estimations of BrC direct radiative effect, while REaci indicates a global reduction in low clouds due to the BrC semidirect effect. The mechanisms for these physical changes are investigated and found to correspond with changes in global circulation patterns. Comparisons of BrC implementation approaches find that this implementation predicts a lower BrC REari in the Arctic regions than previous studies with CAM5. Implementation of BrC bleaching effect shows a significant reduction in REari (0:06±0:008Wm -2 ). Also, variations in OA density can lead to differences in REari and REaci, indicating the importance of specifying this property when estimating the BrC radiative effects and when comparing similar studies. © Author(s) 2018."
"55620143100;8657171200;21834810800;38760907700;6603093035;10739566100;7005461772;57211681908;57203053317;15923105200;7006708207;7005968859;7004715270;","Marine and Terrestrial Organic Ice-Nucleating Particles in Pristine Marine to Continentally Influenced Northeast Atlantic Air Masses",2018,"10.1029/2017JD028033","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048961714&doi=10.1029%2f2017JD028033&partnerID=40&md5=85c47e5014e4aadea85729c2456ebb40","Sea spray aerosol (SSA) generated by bubble bursting at the ocean surface is an important component of aerosol-cloud interactions over remote oceans, providing the atmosphere with ice-nucleating particles (INPs) or particles required for heterogeneous ice nucleation. Studies have shown that organic INPs are emitted during phytoplankton blooms, but changes in INP number concentrations (nINPs) due to ocean biological activity have not been directly demonstrated in natural SSA. In this study, a clean sector sampler was used to differentiate ice nucleation and composition of pristine SSA from terrestrial aerosol at the Mace Head Research Station in August 2015. Average nINPs active at −15 °C (nINPs,−15 °C) were 0.0011 L−1, and large variability (up to a factor of 200) was observed for INPs active warmer than −22 °C. Highest nINPs in the clean sector occurred during a period of elevated marine organic aerosol from offshore biological activity (M1, nINPs,−15 °C = 0.0077 L−1). A peak in nINPs was also observed in terrestrial organic aerosol (T1, nINPs,−15 °C = 0.0076 L−1). The impacts of heating and hydrogen peroxide digestion on nINPs indicate that INPs at Mace Head Research Station were largely organic and that INPs observed during M1 and T1 were biological (i.e., protein containing). Complexities of predicting increases in nINPs due to offshore biological activity are explored. A parameterization for pristine SSA INPs over the North Atlantic Ocean was developed, illustrating that SSA is associated with a factor of 1,000 fewer ice-nucleating sites per surface area of aerosol compared to mineral dust. ©2018. American Geophysical Union. All Rights Reserved."
"35519380200;6603779272;57203052274;18133397500;57192695511;55850540800;8728433200;7102795549;7203040996;56140087300;56914807500;7004289296;57204699163;7003798647;36047973900;","Multidecadal trends in aerosol radiative forcing over the Arctic: Contribution of changes in anthropogenic aerosol to Arctic warming since 1980",2017,"10.1002/2016JD025321","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85015299463&doi=10.1002%2f2016JD025321&partnerID=40&md5=1131f6c7e7e566fc5d5a94845da4b7af","Arctic observations show large decreases in the concentrations of sulfate and black carbon (BC) aerosols since the early 1980s. These near-term climate-forcing pollutants perturb the radiative balance of the atmosphere and may have played an important role in recent Arctic warming. We use the GEOS-Chem global chemical transport model to construct a 3-D representation of Arctic aerosols that is generally consistent with observations and their trends from 1980 to 2010. Observations at Arctic surface sites show significant decreases in sulfate and BC mass concentrations of 2-3% per year. We find that anthropogenic aerosols yield a negative forcing over the Arctic, with an average 2005-2010 Arctic shortwave radiative forcing (RF) of -0.19 ± 0.05Wm-2 at the top of atmosphere (TOA). Anthropogenic sulfate in our study yields more strongly negative forcings over the Arctic troposphere in spring (1.17 ± 0.10Wm 2) than previously reported. From 1980 to 2010, TOA negative RF by Arctic aerosol declined, from -0.67 ± 0.06Wm-2 to 0.19 ± 0.05Wm 2, yielding a net TOA RF of +0.48 ± 0.06Wm-2. The net positive RF is due almost entirely to decreases in anthropogenic sulfate loading over the Arctic. We estimate that 1980-2010 trends in aerosol-radiation interactions over the Arctic and Northern Hemisphere midlatitudes have contributed a net warming at the Arctic surface of +0.27 ± 0.04 K, roughly one quarter of the observed warming. Our study does not consider BC emissions from gas flaring nor the regional climate response to aerosol-cloud interactions or BC deposition on snow. © 2017. American Geophysical Union."
"10739072200;6603478665;42662973900;6602493466;57204496157;34568413600;","Continental anthropogenic primary particle number emissions",2016,"10.5194/acp-16-6823-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84970992144&doi=10.5194%2facp-16-6823-2016&partnerID=40&md5=d823ed255d9dff47ba31ccb783f4140b","Atmospheric aerosol particle number concentrations impact our climate and health in ways different from those of aerosol mass concentrations. However, the global, current and future anthropogenic particle number emissions and their size distributions are so far poorly known. In this article, we present the implementation of particle number emission factors and the related size distributions in the GAINS (Greenhouse Gas-Air Pollution Interactions and Synergies) model. This implementation allows for global estimates of particle number emissions under different future scenarios, consistent with emissions of other pollutants and greenhouse gases. In addition to determining the general particulate number emissions, we also describe a method to estimate the number size distributions of the emitted black carbon particles. The first results show that the sources dominating the particle number emissions are different to those dominating the mass emissions. The major global number source is road traffic, followed by residential combustion of biofuels and coal (especially in China, India and Africa), coke production (Russia and China), and industrial combustion and processes. The size distributions of emitted particles differ across the world, depending on the main sources: in regions dominated by traffic and industry, the number size distribution of emissions peaks in diameters range from 20 to 50 nm, whereas in regions with intensive biofuel combustion and/or agricultural waste burning, the emissions of particles with diameters around 100 nm are dominant. In the baseline (current legislation) scenario, the particle number emissions in Europe, Northern and Southern Americas, Australia, and China decrease until 2030, whereas especially for India, a strong increase is estimated. The results of this study provide input for modelling of the future changes in aerosol-cloud interactions as well as particle number related adverse health effects, e.g. in response to tightening emission regulations. However, there are significant uncertainties in these current emission estimates and the key actions for decreasing the uncertainties are pointed out. © Author(s) 2016."
"57213947466;7409080503;56158622800;8839875600;55875842200;","Long-term aerosol-mediated changes in cloud radiative forcing of deep clouds at the top and bottom of the atmosphere over the Southern Great Plains",2014,"10.5194/acp-14-7113-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904332778&doi=10.5194%2facp-14-7113-2014&partnerID=40&md5=2da48f356c232978737276924838e3ed","Aerosols can alter the macro- and micro-physical properties of deep convective clouds (DCCs) and their radiative forcing (CRF). This study presents what is arguably the first long-term estimate of the aerosol-mediated changes in CRF (AMCRF) for deep cloud systems derived from decade-long continuous ground-based and satellite observations, model simulations, and reanalysis data. Measurements were made at the US Department of Energy's Atmospheric Radiation Measurement Program's Southern Great Plains (SGP) site. Satellite retrievals are from the Geostationary Operational Environmental Satellite. Increases in aerosol loading were accompanied by the thickening of DCC cores and the expansion and thinning of anvils, due presumably to the aerosol invigoration effect (AIV) and the aerosol microphysical effect. Meteorological variables dictating these cloud processes were investigated. Consistent with previous findings, the AIV is most significant when the atmosphere is moist and unstable with weak wind shear. Such aerosol-mediated systematic changes in DCC core thickness and anvil size alter CRF at the top of atmosphere (TOA) and at the surface. Using extensive observations, ∼300 DCC systems were identified over a 10 years period at the SGP site (2000-2011) and analyzed. Daily mean AMCRF at the TOA and at the surface are 29.3 W mg-2 and 22.2 W mg -2, respectively. This net warming effect due to changes in DCC microphysics offsets the cooling resulting from the first aerosol indirect effect. © Author(s) 2014."
"7102266120;7005520001;26665326700;6603079013;6701562043;","Observations of the first aerosol indirect effect in shallow cumuli",2011,"10.1029/2010GL046047","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79751489112&doi=10.1029%2f2010GL046047&partnerID=40&md5=83945355536af9327c1e384dae586908","Data from the Cumulus Humilis Aerosol Processing Study (CHAPS) are used to estimate the impact of both aerosol indirect effects and cloud dynamics on the microphysical and optical properties of shallow cumuli observed in the vicinity of Oklahoma City, Oklahoma. Not surprisingly, we find that the amount of light scattered by clouds is dominated by their liquid water content (LWC), which in turn is driven by buoyancy and cloud dynamics. However, removing the effect of cloud dynamics by examining the scattering normalized by LWC shows a statistically significant sensitivity of scattering to pollutant loading (increasing at a rate of 0.002 m2 g-1 ppbv-1). These results suggest that even moderately sized cities, like Oklahoma City, can have a measureable impact on the optical properties of shallow cumuli. Copyright 2011 by the American Geophysical Union."
"56032511300;7103271625;7102604282;","Thunderstorm and stratocumulus: How does their contrasting morphology affect their interactions with aerosols?",2010,"10.5194/acp-10-6819-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954894867&doi=10.5194%2facp-10-6819-2010&partnerID=40&md5=308c238669a8021726a2b656354bdf7e","It is well-known that aerosols affect clouds and that the effect of aerosols on clouds is critical for understanding human-induced climate change. Most climate model studies have focused on the effect of aerosols on warm stratiform clouds (e.g., stratocumulus clouds) for the prediction of climate change. However, systems like the Asian and Indian Monsoon, storm tracks, and the intertropical convergence zone, play important roles in the global hydrological cycle and in the circulation of energy and are driven by thunderstorm-type convective clouds. Here, we show that the different morphologies of these two cloud types lead to different aerosol-cloud interactions. Increasing aerosols are known to suppress the conversion of droplets to rain (i.e., so-called autoconversion). This increases droplets as a source of evaporative cooling, leading to an increased intensity of downdrafts. The acceleration of the intensity of downdrafts is larger in convective clouds due to their larger cloud depths (providing longer paths for downdrafts to follow to the surface) than in stratiform clouds. More accelerated downdrafts intensify the gust front, leading to significantly increased updrafts, condensation and thus the collection of cloud liquid by precipitation, which offsets the suppressed autoconversion. This leads to an enhancement of precipitation with increased aerosols in convective clouds. However, the downdrafts are less accelerated in stratiform clouds due to their smaller cloud depths, and they are not able to induce changes in updrafts as large as those in convective clouds. Thus, the offset is not as effective, and this allows the suppression of precipitation with increased aerosols. Thus aerosols affect these cloud systems differently. The dependence of the effect of aerosols on clouds on the morphology of clouds should be taken into account for a more complete assessment of climate change. © Author(s) 2010."
"7004838931;8550791300;13407563600;6603256829;7006415284;8849246700;7102680152;7202779940;57214957727;16177371300;6602128405;56251307100;16833315000;6602354484;8586682800;55942083800;","Intercomparison of cloud condensation nuclei and hygroscopic fraction measurements: Coated soot particles investigated during the LACIS Experiment in November (LExNo)",2010,"10.1029/2009JD012618","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953786492&doi=10.1029%2f2009JD012618&partnerID=40&md5=442e0e6f874b82414e42a510a6e8f390","Four cloud condensation nuclei (CCN) instruments were used to sample size-selected particles prepared at the Leipzig Aerosol Cloud Interaction Simulator facility. Included were two Wyoming static diffusion CCN instruments, the continuous flow instrument built by Droplet Measurement Technologies, and the continuous flow Leipzig instrument. The aerosols were composed of ammonium sulfate, levoglucosan, levoglucosan and soot, and ammonium hydrogen sulfate and soot. Comparisons are made among critical supersaturation values from the CCN instruments and derived from measurements made with a humidified tandem differential mobility system. The comparison is quite encouraging: with few exceptions the reported critical supersaturations agree within known experimental uncertainty limits. Also reported are CCN- and hygroscopicity-based estimates of the soot particles' solute fraction. Relative differences between these are as large as 40%, but an error analysis demonstrates that agreement within experimental uncertainty is achieved. We also analyze data from the Droplet Measurement Technologies and the two Wyoming static diffusion instruments for evidence of size distribution broadening and investigate levoglucosan particle growth kinetics in the Wyoming CCN instrument. Copyright 2010 by the American Geophysical Union."
"6603850285;56037741700;8705440100;7007182077;23995325300;26643041500;7006712143;","Size-dependent activation of aerosols into cloud droplets at a subarctic background site during the second Pallas Cloud Experiment (2nd PaCE): Method development and data evaluation",2009,"10.5194/acp-9-4841-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-74049161004&doi=10.5194%2facp-9-4841-2009&partnerID=40&md5=c1253d2a2cd3294ce2f2530027de198a","In situ measurements of aerosol water uptake and activation of aerosols into cloud droplets provide information on how aerosols influence the microphysical properties of clouds. Here we present a computational scheme that can be used in connection with such measurements to assess the influence of the particle hygroscopicity and mixing state (in terms of the water uptake) on the cloud nucleating ability of particles. Additionally, it provides an estimate for the peak supersaturation of water vapour reached during the formation of the observed cloud(s). The method was applied in interpreting results of a measurement campaign that focused on aerosol-cloud interactions taking place at a subarctic background site located in Northern Finland (second Pallas Cloud Experiment, 2nd PaCE). A set of case studies was conducted, and the observed activation behavior could be successfully explained by a maximum supersaturation that varied between 0.18 and 0.26% depending on the case. In these cases, the diameter corresponding to the activated fraction of 50% was in the range of 110-140 nm, and the particles were only moderately water soluble with hygroscopic growth factors varying between 1.1 and 1.4. The conducted analysis showed that the activated fractions and the total number of particles acting as CCN are expected to be highly sensitive to the particle hygroscopic growth properties. For example, the latter quantity varied over a factor between 1.8 and 3.1, depending on the case, when the mean hygroscopic growth factors were varied by 10%. Another important conclusion is that size-dependent activation profiles carries information on the mixing state of particles. © 2009 Author(s)."
"7202516876;7003591311;","A modeling study of the effect of nitric acid on cloud properties",2004,"10.1029/2004JD004750","https://www.scopus.com/inward/record.uri?eid=2-s2.0-10244236527&doi=10.1029%2f2004JD004750&partnerID=40&md5=b31cc9815a6015faa69610145b778a2b","The effect of nitric acid (HNO<inf>3</inf>) on cloud microphysical and radiative properties is studied using an adiabatic cloud parcel model for a range of aerosol size distributions, different water vapor mass accommodation coefficients, and HNO<inf>3</inf> concentrations. Results show that HNO<inf>3</inf> not only increases cloud drop number concentration N<inf>d</inf>, but also leads to significantly broader droplet size spectra at both the small- and large-size ends. The broader spectra are generally the result of competition for H<inf>2</inf>O and HNO<inf>3</inf> among the polydisperse droplets. The increase in the number of activated cloud droplets in the presence of HNO<inf>3</inf>, and the deactivation of some of the small cloud droplets due to the outgasing of HNO<inf>3</inf>, lead to spectral broadening at the small-size end. At the large-size end the broadening is caused by an increase in the driving force for growth. For small drops the driving force tends to be decreased by the presence of HNO<inf>3</inf>. Although N<inf>d</inf> increases with increasing HNO<inf>3</inf> concentration, the increases in cloud optical depth and albedo due to HNO<inf>3</inf> cannot necessarily be predicted by the commonly used relationships for cloud optical properties. The dependence of the cloud optical depth on N<inf>d</inf> to the one-third power is shown to be an overestimate because droplet spectra are significantly broadened by HNO<inf>3</inf>. We show that broadening effects due to HNO<inf>3</inf> and other chemical or microphysical factors need to be considered when estimating cloud optical properties and their effect on climate."
"56462887500;35069282600;57203596463;10139397300;","Volcano and Ship Tracks Indicate Excessive Aerosol-Induced Cloud Water Increases in a Climate Model",2017,"10.1002/2017GL075280","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85039152778&doi=10.1002%2f2017GL075280&partnerID=40&md5=9f9971db1e185af314d668ef84e12caf","Aerosol-cloud interaction is the most uncertain mechanism of anthropogenic radiative forcing of Earth's climate, and aerosol-induced cloud water changes are particularly poorly constrained in climate models. By combining satellite retrievals of volcano and ship tracks in stratocumulus clouds, we compile a unique observational data set and confirm that liquid water path (LWP) responses to aerosols are bidirectional, and on average the increases in LWP are closely compensated by the decreases. Moreover, the meteorological parameters controlling the LWP responses are strikingly similar between the volcano and ship tracks. In stark contrast to observations, there are substantial unidirectional increases in LWP in the Hadley Centre climate model, because the model accounts only for the decreased precipitation efficiency and not for the enhanced entrainment drying. If the LWP increases in the model were compensated by the decreases as the observations suggest, its indirect aerosol radiative forcing in stratocumulus regions would decrease by 45%. ©2017. American Geophysical Union. All Rights Reserved."
"55683113200;7006960329;35422938600;55683310400;35423527600;7005773698;","Phytoplankton blooms weakly influence the cloud forming ability of sea spray aerosol",2016,"10.1002/2016GL069922","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84992360126&doi=10.1002%2f2016GL069922&partnerID=40&md5=4545fdd1303713d0ea27370be9818132","After many field studies, the establishment of connections between marine microbiological processes, sea spray aerosol (SSA) composition, and cloud condensation nuclei (CCN) has remained an elusive challenge. In this study, we induced algae blooms to probe how complex changes in seawater composition impact the ability of nascent SSA to act as CCN, quantified by using the apparent hygroscopicity parameter (κapp). Throughout all blooms, κapp ranged between 0.7 and 1.4 (average 0.95 ± 0.15), consistent with laboratory investigations using algae-produced organic matter, but differing from climate model parameterizations and in situ SSA generation studies. The size distribution of nascent SSA dictates that changes in κapp associated with biological processing induce less than 3% change in expected CCN concentrations for typical marine cloud supersaturations. The insignificant effect of hygroscopicity on CCN concentrations suggests that the SSA production flux and/or secondary aerosol chemistry may be more important factors linking ocean biogeochemistry and marine clouds. ©2016. American Geophysical Union. All Rights Reserved."
"7103180783;7402401574;57087451200;56228672600;7402969850;55737749900;","Abrupt summer warming and changes in temperature extremes over Northeast Asia since the mid-1990s: Drivers and physical processes",2016,"10.1007/s00376-016-5247-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84979079606&doi=10.1007%2fs00376-016-5247-3&partnerID=40&md5=41dbd80727b36a5c9e8aba401f5b2123","This study investigated the drivers and physical processes for the abrupt decadal summer surface warming and increases in hot temperature extremes that occurred over Northeast Asia in the mid-1990s. Observations indicate an abrupt increase in summer mean surface air temperature (SAT) over Northeast Asia since the mid-1990s. Accompanying this abrupt surface warming, significant changes in some temperature extremes, characterized by increases in summer mean daily maximum temperature (Tmax), daily minimum temperature (Tmin), annual hottest day temperature (TXx), and annual warmest night temperature (TNx) were observed. There were also increases in the frequency of summer days (SU) and tropical nights (TR). Atmospheric general circulation model experiments forced by changes in sea surface temperature (SST)/sea ice extent (SIE), anthropogenic greenhouse gas (GHG) concentrations, and anthropogenic aerosol (AA) forcing, relative to the period 1964–93, reproduced the general patterns of observed summer mean SAT changes and associated changes in temperature extremes, although the abrupt decrease in precipitation since the mid-1990s was not simulated. Additional model experiments with different forcings indicated that changes in SST/SIE explained 76% of the area-averaged summer mean surface warming signal over Northeast Asia, while the direct impact of changes in GHG and AA explained the remaining 24% of the surface warming signal. Analysis of physical processes indicated that the direct impact of the changes in AA (through aerosol–radiation and aerosol–cloud interactions), mainly related to the reduction of AA precursor emissions over Europe, played a dominant role in the increase in TXx and a similarly important role as SST/SIE changes in the increase in the frequency of SU over Northeast Asia via AA-induced coupled atmosphere–land surface and cloud feedbacks, rather than through a direct impact of AA changes on cloud condensation nuclei. The modelling results also imply that the abrupt summer surface warming and increases in hot temperature extremes over Northeast Asia since the mid-1990s will probably sustain in the next few decades as GHG concentrations continue to increase and AA precursor emissions over both North America and Europe continue to decrease. © 2016, Science Press."
"6506383700;55803773100;21935606200;6508260037;11539061800;","Seasonal inhomogeneity in cloud precursors over Gangetic Himalayan region during GVAX campaign",2015,"10.1016/j.atmosres.2014.11.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919935217&doi=10.1016%2fj.atmosres.2014.11.022&partnerID=40&md5=58eea05f25d6a7c6325a6a9ac02eca35","Atmospheric aerosols are key elements in cloud microphysics, the hydrological cycle and climate by serving as cloud condensation nuclei (CCN). The present work analyzes simultaneous measurements of number concentration of CCN (NCCN) and condensation nuclei (NCN) obtained at Nainital, in the Gangetic-Himalayan (GH) region, during the frameworks of Ganges Valley Aerosol Experiment (GVAX), June 2011 to March 2012. The NCCN, NCN and activation (AR=NCCN/NCN) at 0.31-0.33% S (supersaturation ratio), exhibit significant daily, monthly and seasonal variations within a range of 684-2065cm-3 for NCCN, 1606-4124cm-3 for NCN, and 0.38-0.60 for AR, suggesting large inhomogeneity in aerosol properties, types and sources, which control the degree of aerosol potential activation. Thus, transported aerosols from the Ganges valley and abroad, the boundary-layer dynamics and atmospheric modification processes play an important role in aerosol-cloud interactions over the GH region. The NCN and NCCN show monthly-dependent diurnal variations with afternoon maxima due to transported aerosols from the Ganges valley up to the Himalayan foothills, while the AR is lower during these hours implying lower hygroscopicities or smaller sizes of the transported aerosols. The dependence of NCCN on S is highest during Dec-Mar and lowest during monsoon (Jun-Sep), suggesting different aerosol chemical composition. Comparison between Nainital and Kanpur shows that NCN and NCCN are much lower at Nainital, while the similarity in AR suggests aerosols of similar type, source and chemical composition uplifted from the Ganges valley to the Himalayan foothills. © 2014 Elsevier B.V."
"7102423967;8629713500;7401796996;","Aerosol properties and their influences on marine boundary layer cloud condensation nuclei at the ARM mobile facility over the Azores",2014,"10.1002/2013JD021288","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900556177&doi=10.1002%2f2013JD021288&partnerID=40&md5=688678fce980a5fc183e81d0bdfb87ba","A multiplatform data set fromthe Clouds, Aerosol, and Precipitation in the Marine Boundary Layer (MBL) Graciosa, Azores, 2009-2010 field campaign was used to investigate how continental aerosols can influenceMBL cloud condensation nuclei (CCN) number concentration (NCCN). The seasonal variations of aerosol properties have shown that the winter and early spring months had the highest mean surface wind speed (&gt; 5ms-1) and greatest contribution of sea salt to aerosol optical depth (AOD), while continental fine mode aerosols were the main contributors to AOD during the warm season months (May-September). Five aerosol events consisting of mineral dust, pollution, biomass smoke, and volcanic ash particles were selected as case studies using Atmospheric Radiation Measurement (ARM) mobile facility measurements. The aerosols in Case I were found to primarily consist of coarsemode, Saharan mineral dust. For Case II, the aerosols were also coarse mode but consisted of volcanic ash. Case III had fine mode biomass smoke and pollution aerosol influences while Cases IV and V consisted ofmixtures of North American pollution and Saharan dust that was advected by an extratropical cyclone to the Azores. Cases I, IV, and V exhibited weak correlations between aerosol loading and NCCN due to mineral dust influences, while Cases II and III had a strong relationship with NCCN likely due to the sulfate content in the volcanic ash and pollution particles. The permanent Eastern North Atlantic ARM facility over the Azores will aid in a future long-term study of aerosol effects on NCCN. © 2014. American Geophysical Union. All Rights Reserved."
"55800936800;7801565183;14034301300;35195849700;17434636400;36776963300;7005069415;7006434689;","Investigation of the effective peak supersaturation for liquid-phase clouds at the high-alpine site Jungfraujoch, Switzerland (3580 m a.s.l.)",2014,"10.5194/acp-14-1123-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893311414&doi=10.5194%2facp-14-1123-2014&partnerID=40&md5=d70b7083ba1c4188ff4a8d22f3984740","Aerosols influence the Earth's radiation budget directly through absorption and scattering of solar radiation in the atmosphere but also indirectly by modifying the properties of clouds. However, climate models still suffer from large uncertainties as a result of insufficient understanding of aerosol-cloud interactions. At the high altitude research station Jungfraujoch (JFJ; 3580 m a.s.l., Switzerland) cloud condensation nuclei (CCN) number concentrations at eight different supersaturations (SS) from 0.24% to 1.18% were measured using a CCN counter during Summer 2011. Simultaneously, in-situ aerosol activation properties of the prevailing ambient clouds were investigated by measuring the total and interstitial (non-activated) dry particle number size distributions behind two different inlet systems. Combining all experimental data, a new method was developed to retrieve the so-called effective peak supersaturation SSpeak, as a measure of the SS at which ambient clouds are formed. A 17-month CCN climatology was then used to retrieve the SSpeak values also for four earlier summer campaigns (2000, 2002, 2004 and 2010) where no direct CCN data were available. The SSpeak values varied between 0.01% and 2.0% during all campaigns. An overall median SSpeak of 0.35% and dry activation diameter of 87 nm was observed. It was found that the difference in topography between northwest and southeast plays an important role for the effective peak supersaturation in clouds formed in the vicinity of the JFJ, while differences in the number concentration of potential CCN only play a minor role. Results show that air masses coming from the southeast (with the slowly rising terrain of the Aletsch Glacier) generally experience lower SSpeak values than air masses coming from the northwest (steep slope). The observed overall median values were 0.41% and 0.22% for northwest and southeast wind conditions, respectively, corresponding to literature values for cumulus clouds and shallow-layer clouds. These cloud types are consistent with weather observations routinely performed at the JFJ. © 2014 Author(s)."
"55286034300;7003926380;11940701600;","An investigation of the aerosol indirect effect on convective intensity using satellite observations",2014,"10.1175/JAS-D-13-0158.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891654226&doi=10.1175%2fJAS-D-13-0158.1&partnerID=40&md5=42fd0eafb4780a3aac73f50a20415b73","The effect of the environment on individual clouds makes it difficult to isolate the signal of the aerosolindirect effect, particularly at larger spatial and temporal scales. This study uses observations from theTropical Rainfall Measuring Mission (TRMM), CloudSat, and Aqua satellites to identify convective cloudsystems in clean and dirty environments. The Moderate Resolution Imaging Spectroradiometer (MODIS)aerosol index is collocated with radar precipitation features (RPFs) from TRMM and congestus cloud features(CFs) from CloudSat. The Interim ECMWF Re-Analysis (ERA-Interim) is interpolated to identify theenvironmental profile surrounding each feature. Regions in Africa, the Amazon, the Atlantic Ocean, and thesouthwestern United States are examined. TRMM features in the Africa and Amazon regions are moreintense and have higher lightning flash rates under dirty background conditions. RPFs in the southwesternUnited States are more intense under clean background conditions. The Atlantic region shows little differencein intensity. The differences found in the mean thermodynamic profile for RPFs forming in clean anddirty environments could explain these differences in convective intensity. Congestus identified with CloudSat show smaller differences between clouds forming in clean and dirtyenvironments in Africa and the Amazon. Congestus in clean environments have higher reflectivities andgenerally larger widths, but no trend is seen in cloud-top height. The signal of the aerosol indirect effect is sosmall that it is very difficult to detect confidently using these methods. The environment must be considered inany study of the aerosol indirect effect, because important environmental changes can occur as aerosols areintroduced to an air mass. © 2014 American Meteorological Society."
"24390528000;7005129538;6602600408;25648525300;","GCM simulations of anthropogenic aerosol-induced changes in aerosol extinction, atmospheric heating and precipitation over India",2013,"10.1002/jgrd.50298","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882374599&doi=10.1002%2fjgrd.50298&partnerID=40&md5=faf426c44e1a53b614711b6f9560fec8","The influence of anthropogenic emissions on aerosol distributions and the hydrological cycle are examined with a focus on monsoon precipitation over the Indian subcontinent, during January 2001 to December 2005, using the European Centre for Medium-Range Weather Forecasts-Hamburg (ECHAM5.5) general circulation model extended by the Hamburg Aerosol Module (HAM). The seasonal variability of aerosol optical depth (AOD) retrieved from the MODerate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua satellite is broadly well simulated (R≈0.6-0.85) by the model. The spatial distribution and seasonal cycle of the precipitation observed over the Indian region are reasonably well simulated (R≈0.5 to 0.8) by the model, while in terms of absolute magnitude, the model underestimates precipitation, in particular in the south-west (SW) monsoon season. The model simulates significant anthropogenic aerosol-induced changes in clear-sky net surface solar radiation (dimming greater than -7 W m-2), which agrees well with the observed trends over the Indian region. A statistically significant decreasing precipitation trend is simulated only for the SWmonsoon season over the central-north Indian region, which is consistent with the observed seasonal trend over the Indian region. In the model, this decrease results from a reduction in convective precipitation, where there is an increase in stratiform cloud droplet number concentration (CDNC) and solar dimming that resulted from increased stability and reduced evaporation. Similarities in spatial patterns suggest that surface cooling, mainly by the aerosol indirect effect, is responsible for this reduction in convective activity. When changes in large-scale dynamics are allowed by slightly disturbing the initial state of the atmosphere, aerosol absorption in addition leads to a further stabilization of the lower troposphere, further reducing convective precipitation. © 2013. American Geophysical Union. All Rights Reserved."
"25624545600;57206332144;7003907406;8266297500;7003289221;","Physical interpretation of the spectral radiative signature in the transition zone between cloud-free and cloudy regions",2009,"10.5194/acp-9-1419-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60849105999&doi=10.5194%2facp-9-1419-2009&partnerID=40&md5=1283f6bc7b02a38d460b7c0e0cca39d3","One-second-resolution zenith radiance measurements from the Atmospheric Radiation Measurement program's new shortwave spectrometer (SWS) provide a unique opportunity to analyze the transition zone between cloudy and cloud-free air, which has considerable bearing on the aerosol indirect effect. In the transition zone, we find a remarkable linear relationship between the sum and difference of radiances at 870 and 1640 nm wavelengths. The intercept of the relationship is determined primarily by aerosol properties, and the slope by cloud properties. We then show that this linearity can be predicted from simple theoretical considerations and furthermore that it supports the hypothesis of inhomogeneous mixing, whereby optical depth increases as a cloud is approached but the effective drop size remains unchanged."
"55017656900;7003591311;7101846027;35264611800;7004885872;7006572336;57196499374;","Statistical comparison of properties of simulated and observed cumulus clouds in the vicinity of Houston during the Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS)",2008,"10.1029/2007JD009304","https://www.scopus.com/inward/record.uri?eid=2-s2.0-50849142581&doi=10.1029%2f2007JD009304&partnerID=40&md5=7209a6724e9677fb1e579b848bab79cc","We present statistical comparisons of properties of clouds generated by Large Eddy Simulations (LES) with aircraft observations of nonprecipitating, warm cumulus clouds made in the vicinity of Houston, TX during the Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS), carried out in the summer of 2006. Aircraft data were sampled with the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter airplane. Five flights (days) that are most suitable for studying aerosol-cloud interactions are selected from the 22 flights. The model simulations are initiated with observed environmental profiles. The simulations are used to generate an ensemble of thousands of cumulus clouds for statistically meaningful evaluations. Statistical comparisons focus on the properties of a set of dynamical and thermodynamical variables, sampled either in the cloud or the cloud updraft core. The set of variables includes cloud liquid water content (LWC), number mixing ratio of cloud droplets (N<inf>d</inf>), cloud effective radius (r<inf>e</inf>), updraft velocity (w), and the distribution of cloud sizes. In general, good agreement between the simulated and observed clouds is achieved in the normalized frequency distribution functions, the profiles averaged over the cloudy regions, the cross-cloud averages, and the cloud size distributions, despite big differences in sample size between the model output and the aircraft data. Some unresolved differences in frequency distributions of w and possible differences in cloud fraction are noted. These comparisons suggest that the LES is able to successfully generate the cumulus cloud populations that were present during GoMACCS. The extent to which this is true will depend on the specific application. Copyright 2008 by the American Geophysical Union."
"8922308700;7102266120;7006270084;7003666669;","The Explicit-Cloud Parameterized-Pollutant hybrid approach for aerosol-cloud interactions in multiscale modeling framework models: Tracer transport results",2008,"10.1088/1748-9326/3/2/025005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-46749087994&doi=10.1088%2f1748-9326%2f3%2f2%2f025005&partnerID=40&md5=95a4e7a980357336f4704696e89319ce","All estimates of aerosol indirect effects on the global energy balance have either completely neglected the influence of aerosol on convective clouds or treated the influence in a highly parameterized manner. Embedding cloud-resolving models (CRMs) within each grid cell of a global model provides a multiscale modeling framework for treating both the influence of aerosols on convective as well as stratiform clouds and the influence of clouds on the aerosol, but treating the interactions explicitly by simulating all aerosol processes in the CRM is computationally prohibitive. An alternate approach is to use horizontal statistics (e.g., cloud mass flux, cloud fraction, and precipitation) from the CRM simulation to drive a single-column parameterization of cloud effects on the aerosol and then use the aerosol profile to simulate aerosol effects on clouds within the CRM. Here, we present results from the first component of the Explicit-Cloud Parameterized-Pollutant parameterization to be developed, which handles vertical transport of tracers by clouds. A CRM with explicit tracer transport serves as a benchmark. We show that this parameterization, driven by the CRM's cloud mass fluxes, reproduces the CRM tracer transport significantly better than a single-column model that uses a conventional convective cloud parameterization. © IOP Publishing Ltd."
"7202733689;7003543851;","Hemispheric climate shifts driven by anthropogenic aerosol-cloud interactions",2017,"10.1038/NGEO2988","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85026633666&doi=10.1038%2fNGEO2988&partnerID=40&md5=bcba428997f518993831d3f7e21f5da3","The contrasting rainfall between the wet tropics and the dry subtropics largely determines the climate of the tropical zones. A southward shift of these rain belts has been observed throughout the latter half of the twentieth century, with profound societal consequences. Although such large-scale shifts in rainfall have been linked to interhemispheric temperature gradients from anthropogenic aerosols, a complete understanding of this mechanism has been hindered by the lack of explicit information on aerosol radiative effects. Here we quantify the relative contributions of radiative forcing from anthropogenic aerosols to the interhemispheric asymmetry in temperature and precipitation change for climate change simulations.We show that in model simulations the vast majority of the precipitation shift does not result from aerosols directly through their absorption and scattering of radiation, but rather indirectly through their modification of cloud radiative properties. Models with larger cloud responses to aerosol forcing are found to better reproduce the observed interhemispheric temperature changes and tropical rain belt shifts over the twentieth century, suggesting that aerosol-cloud interactions will play a key role in determining future interhemispheric shifts in climate. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved."
"46461636700;26643041500;14034301300;7004296083;35461763400;24480463300;7005069415;16479877100;8568391400;56251307100;56333104300;16549600900;8720897100;35224765000;35085069400;35195849700;24558717100;34868441100;6603256829;23995325300;35461255500;57203053317;57189372185;6603172418;7006058570;6701378450;7006708207;8657171200;8871497700;55942083800;7403401100;13407563600;57214957433;7005287667;7006434689;8576496400;7006595513;55789354000;6602085876;","A synthesis of cloud condensation nuclei counter (CCNC) measurements within the EUCAARI network",2015,"10.5194/acp-15-12211-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946238238&doi=10.5194%2facp-15-12211-2015&partnerID=40&md5=edb3c88efc04694d43a08a186f482f16","Cloud condensation nuclei counter (CCNC) measurements performed at 14 locations around the world within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) framework have been analysed and discussed with respect to the cloud condensation nuclei (CCN) activation and hygroscopic properties of the atmospheric aerosol. The annual mean ratio of activated cloud condensation nuclei (NCCN) to the total number concentration of particles (NCN), known as the activated fraction A, shows a similar functional dependence on supersaturation S at many locations - exceptions to this being certain marine locations, a free troposphere site and background sites in south-west Germany and northern Finland. The use of total number concentration of particles above 50 and 100 nm diameter when calculating the activated fractions (A50 and A100, respectively) renders a much more stable dependence of A on S; A50 and A100 also reveal the effect of the size distribution on CCN activation. With respect to chemical composition, it was found that the hygroscopicity of aerosol particles as a function of size differs among locations. The hygroscopicity parameter κ decreased with an increasing size at a continental site in south-west Germany and fluctuated without any particular size dependence across the observed size range in the remote tropical North Atlantic and rural central Hungary. At all other locations κ increased with size. In fact, in Hyytiälä, Vavihill, Jungfraujoch and Pallas the difference in hygroscopicity between Aitken and accumulation mode aerosol was statistically significant at the 5 % significance level. In a boreal environment the assumption of a size-independent κ can lead to a potentially substantial overestimation of NCCN at S levels above 0.6 %. The same is true for other locations where κ was found to increase with size. While detailed information about aerosol hygroscopicity can significantly improve the prediction of NCCN, total aerosol number concentration and aerosol size distribution remain more important parameters. The seasonal and diurnal patterns of CCN activation and hygroscopic properties vary among three long-term locations, highlighting the spatial and temporal variability of potential aerosol-cloud interactions in various environments. © Author(s) 2015."
"42263280300;55796506900;36628695400;","Improvement of cloud microphysics in the aerosolclimate model BCC_AGCM2.0.1_CUACE/AERO, evaluation against observations, and updated aerosol indirect effect",2014,"10.1002/2014JD021886","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921332525&doi=10.1002%2f2014JD021886&partnerID=40&md5=4c8338e7c0ff5f691c3d459670299595","A two-moment cloud microphysical scheme, to predict both the mass and number concentrations of cloud droplets and ice crystals, is implemented into the aerosol-climate model BCC_AGCM2.0.1_CUACE/Aero. The model results for aerosols, cloud properties, and meteorological fields are evaluated, and the anthropogenic aerosol indirect effect (AIE) is estimated. The new model simulates more realistic aerosol mass concentrations and optical depth compared with the original version using a one-moment bulk cloud microphysical scheme. The global annual mean column cloud droplet number concentration (CDNC) from the new model is 3.3 × 1010 m-2, which is comparable to the 4.0 × 1010 m-2 from satellite retrieval. The global annual mean cloud droplet effective radius at the cloud top from the new model is 8.1 μm, which is smaller than the 10.5 μm from observation. The simulated liquid water path (LWP) in the new model is significantly lower than that in the original model. In particular, the annual mean LWP is lower in the new model by more than 100 g m-2 in some midlatitude regions and hence much more consistent with satellite retrievals. Cloud radiative forcing and precipitation are improved to some extent in the new model. The global annual mean radiation budget at the top of the atmosphere is 0.6 W m-2, which is considerably different from the value of 1.8 W m-2 in the original model. The global annual mean anthropogenic AIE is estimated to be 1.9 W m-2 without imposing a lower bound of CDNC, whereas it is reduced significantly when a higher lower bound of CDNC is prescribed. © 2014. American Geophysical Union. All rights reserved."
"8067118800;7202899330;12645767500;","Aerosol effect on the warm rain formation process: Satellite observations and modeling",2013,"10.1002/jgrd.50043","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877979910&doi=10.1002%2fjgrd.50043&partnerID=40&md5=85df091b8980561c71cd57d0505d26b3","This study demonstrates how aerosols influence the liquid precipitation formation process. This demonstration is provided by the combined use of satellite observations and global high-resolution model simulations. Methodologies developed to examine the warm cloud microphysical processes are applied to both multi-sensor satellite observations and aerosol-coupled global cloud-resolving model (GCRM) results to illustrate how the warm rain formation process is modulated under different aerosol conditions. The observational analysis exhibits process-scale signatures of rain suppression due to increased aerosols, providing observational evidence of the aerosol influence on precipitation. By contrast, the corresponding statistics obtained from the model show a much faster rain formation even for polluted aerosol conditions and much weaker reduction of precipitation in response to aerosol increase. It is then shown that this reduced sensitivity points to a fundamental model bias in the warm rain formation process that in turn biases the influence of aerosol on precipitation. A method of improving the model bias is introduced in the context of a simplified single-column model (SCM) that represents the cloud-to-rain water conversion process in a manner similar to the original GCRM. Sensitivity experiments performed by modifying the model assumptions in the SCM and their comparisons to satellite statistics both suggest that the auto-conversion scheme has a critical role in determining the precipitation response to aerosol perturbations and also provide a novel way of constraining key parameters in the auto-conversion schemes of global models. Key Points Satellite observation analysis of aerosol effect on precipitation Global model evaluation of aerosol effect on precipitation Proposing a way of constraining microphysics parameterizations ©2013. American Geophysical Union. All Rights Reserved."
"25227357000;7102018821;7404829395;56537463000;55717074000;","Dust aerosol impact on North Africa climate: A GCM investigation of aerosol-cloud-radiation interactions using A-Train satellite data",2012,"10.5194/acp-12-1667-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880592785&doi=10.5194%2facp-12-1667-2012&partnerID=40&md5=cd93ba810dc85c9828e35ac2798652da","The climatic effects of dust aerosols in North Africa have been investigated using the atmospheric general circulation model (AGCM) developed at the University of California, Los Angeles (UCLA). The model includes an efficient and physically based radiation parameterization scheme developed specifically for application to clouds and aerosols. Parameterization of the effective ice particle size in association with the aerosol first indirect effect based on ice cloud and aerosol data retrieved from A-Train satellite observations have been employed in climate model simulations. Offline simulations reveal that the direct solar, IR, and net forcings by dust aerosols at the top of the atmosphere (TOA) generally increase with increasing aerosol optical depth. When the dust semi-direct effect is included with the presence of ice clouds, positive IR radiative forcing is enhanced since ice clouds trap substantial IR radiation, while the positive solar forcing with dust aerosols alone has been changed to negative values due to the strong reflection of solar radiation by clouds, indicating that cloud forcing associated with aerosol semi-direct effect could exceed direct aerosol forcing. With the aerosol first indirect effect, the net cloud forcing is generally reduced in the case for an ice water path (IWP) larger than 20 g m2. The magnitude of the reduction increases with IWP. AGCM simulations show that the reduced ice crystal mean effective size due to the aerosol first indirect effect results in less OLR and net solar flux at TOA over the cloudy area of the North Africa region because ice clouds with smaller size trap more IR radiation and reflect more solar radiation. The precipitation in the same area, however, increases due to the aerosol indirect effect on ice clouds, corresponding to the enhanced convection as indicated by reduced OLR. Adding the aerosol direct effect into the model simulation reduces the precipitation in the normal rainfall band over North Africa, where precipitation is shifted to the south and the northeast produced by the absorption of sunlight and the subsequent heating of the air column by dust particles. As a result, rainfall is drawn further inland to the northeast. This study represents the first attempt to quantify the climate impact of the aerosol indirect effect using a GCM in connection with A-Train satellite data. The parameterization for the aerosol first indirect effect developed in this study can be readily employed for application to other GCMs. © 2012 Author(s)."
"8309699900;","Coincidence errors in a cloud droplet probe (CDP) and a cloud and aerosol spectrometer (CAS), and the improved performance of a modified CDP",2012,"10.1175/JTECH-D-11-00208.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868028005&doi=10.1175%2fJTECH-D-11-00208.1&partnerID=40&md5=af3fb5e142ebd550bc70785f47fbe8bc","Central to the aerosol indirect effect on climate is the relationship between cloud droplet concentrations Nd and cloud condensation nuclei (CCN) concentrations. There are valid reasons to expect a sublinear relationship between measured Nd and CCN, and such relationships have been observed for clouds in a variety of locations. However, a measurement artifact known as ""coincidence""can also produce a sublinear trend. The current paper shows that two commonly used instruments, the cloud droplet probe (CDP) and the cloud and aerosol spectrometer (CAS), can be subject to significantly greater coincidence errors than are typically recognized, with an undercounting bias of at least 27% and an oversizing bias of 20%-30% on average at Nd = 500 cm-3, and with an undercounting bias of as much as 44% at Nd = 1000 cm-3. This type of systematic error may have serious implications for interpretation of in situ cloud observations. It is shown that a simple optical modification of the CDP dramatically reduces oversizing and undercounting biases due to coincidence. Guidance is provided for diagnosing coincidence errors in CAS and CDP instruments. © 2012 American Meteorological Society."
"15032788000;8502218100;7103119050;57196263581;","Acceleration by aerosol of a radiative-thermodynamic cloud feedback influencing Arctic surface warming",2009,"10.1029/2009GL040195","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049106104&doi=10.1029%2f2009GL040195&partnerID=40&md5=117a84ea88a68d206e92e8e63342bc10","Recent work suggests that short-lived pollutants with mid-latitude origins are contributing to observed warming of the Arctic surface. Candidate mechanisms include an ""aerosol indirect effect"" associated with increases in cloud longwave emissivity: small cloud droplets associated with polluted conditions are efficient absorbers and emitters of longwave radiation. Here, we argue that the associated surface warming can be temporarily amplified: particulate pollution, by increasing cloud emissivity, additionally accelerates a preexisting positive feedback loop between cloud top radiative cooling and new droplet condensation. Copyright 2009 by the American Geophysical Union."
"9132948500;7201504886;7006452341;","On the diurnal cycle and susceptibility to aerosol concentration in a stratocumulus-topped mixed layer",2005,"10.1256/qj.04.103","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27644441425&doi=10.1256%2fqj.04.103&partnerID=40&md5=df83e349dc29d99da1ead0716b29af82","Mixed-layer theory is used to study the diurnal cycle of the stratocumulus-topped boundary layer and its susceptibility to perturbations in atmospheric aerosol concentration. Our results show that the diurnal evolution of cloud thickness is sensitive to the entrainment efficiency. For high entrainment efficiencies, the cloud base tends to descend at a faster rate than the cloud top; this difference in descent rates leads to cloud thickening during the daytime, which is inconsistent with observations. For low entrainment efficiencies, variations in cloud-top height dominate in the cloud-thickness evolution, while cloud-base height remains almost constant; this behaviour is in better agreement with available data. We explain these effects through a consideration of the equilibrium state of cloud boundaries and their adjustment time-scales. Liquid-water path and cloud albedo are both sensitive to the entrainment efficiency; still, the susceptibility of cloud albedo to droplet number density dominates the entrainment effects. This result has significant implications for climate-sensitivity studies: it suggests that estimates of aerosol indirect effects from stratocumulus clouds will not be particularly sensitive to the way entrainment is represented in large-scale models. © Royal Meteorological Society, 2005."
"7203001286;7006084942;","Simulating the impact of sea salt on global nss sulphate aerosols",2003,"10.1029/2002jd003181","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342289969&doi=10.1029%2f2002jd003181&partnerID=40&md5=ec8d35d60aabcd15eda5b2c5ec941a5c","The Canadian Aerosol Module coupled with the Canadian third generation Global Climate Model was used to simulate the global distributions of size-segregated sea salt and sulphate aerosols of both anthropogenic and natural origins in the atmosphere. A sectional model of 12 size bins was used to treat the size distribution of sea salt and sulphate, which is assumed to be internally mixed in each size bin. The spatial and temporal distributions predicted by the model compare reasonably well with observations. The mixed aerosol simulations yield number and volume size distributions in the marine boundary layer (MBL) comparable with observations. Sea salt particles redistribute the mass and number distributions of sulphate aerosols by serving as a quenching agent to nucleation and as an additional surface area for condensation and by changing the cloud properties in the MBL. By differential simulations of global sea salt and sulphate it is found that the presence of sea salt increases the mass mean diameter of sulphate aerosols by up to a factor of 2 over the MBL with high sea salt concentrations and reduces the global sulphate aerosol mass in the surface MBL layer from 5 to 75% depending on the sea salt distributions. The high impacts are in the midlatitudes of both Northern and Southern Hemispheres with a minimum in the equatorial regions. In the polluted anthropogenic regions of North Pacific and Atlantic, sea salt reduces the sulphate concentration from 10 to 30%. The peak reductions of 50-75% occur in the roaring 40s of the Southern Hemisphere in spring and fall. The impact of sea salt on the annual global mass and number loading is estimated to be 9.13 and 0.76%, respectively. A reduction of 20-60% in the marine cloud droplet number concentrations (CDNC) was predicted because of the presence of sea salt, with greatest reductions in the roaring 40s south (40-70%) and in the midlatitude north (20-40%) where the sea salt concentrations were high. Along the equatorial regions some enhancement of total CDNC was simulated because of the presence of sea salt aerosols. Copyright 2003 by the American Geophysical Union."
"49261186800;7201488063;7003666669;57203049177;7201443624;24329376600;16027966800;15724543600;35547807400;25031430500;7003786872;56604618200;7006329853;","Volcanic Radiative Forcing From 1979 to 2015",2018,"10.1029/2018JD028776","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056711815&doi=10.1029%2f2018JD028776&partnerID=40&md5=16019d14a44fb06811db84fae9d26a18","Using volcanic sulfur dioxide emissions in an aerosol-climate model, we derive a time series of global-mean volcanic effective radiative forcing (ERF) from 1979 to 2015. For 2005–2015, we calculate a global multiannual mean volcanic ERF of −0.08 W/m2 relative to the volcanically quiescent 1999–2002 period, due to a high frequency of small-to-moderate-magnitude explosive eruptions after 2004. For eruptions of large magnitude such as 1991 Mt. Pinatubo, our model-simulated volcanic ERF, which accounts for rapid adjustments including aerosol perturbations of clouds, is less negative than that reported in the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) that only accounted for stratospheric temperature adjustments. We find that, when rapid adjustments are considered, the relation between volcanic forcing and volcanic stratospheric optical depth (SAOD) is 13–21% weaker than reported in IPCC AR5 for large-magnitude eruptions. Further, our analysis of the recurrence frequency of eruptions reveals that sulfur-rich small-to-moderate-magnitude eruptions with column heights ≥10 km occur frequently, with periods of volcanic quiescence being statistically rare. Small-to-moderate-magnitude eruptions should therefore be included in climate model simulations, given the &gt;50% chance of one or two eruptions to occur in any given year. Not all of these eruptions affect the stratospheric aerosol budget, but those that do increase the nonvolcanic background SAOD by ~0.004 on average, contributing ~50% to the total SAOD in the absence of large-magnitude eruptions. This equates to a volcanic ERF of about −0.10 W/m2, which is about two thirds of the ERF from ozone changes induced by ozone-depleting substances. ©2018. American Geophysical Union. All Rights Reserved."
"55620143100;57211681908;54962189200;57195803278;23477978100;7004680257;7201563100;15054885700;57201388540;56471122700;6602675912;57195946518;57204562706;6603826855;6602579613;6701754792;7005968859;7004715270;","Observations of Ice Nucleating Particles Over Southern Ocean Waters",2018,"10.1029/2018GL079981","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056192435&doi=10.1029%2f2018GL079981&partnerID=40&md5=668c32067889d51d5a59580cc6f95a8b","A likely important feature of the poorly understood aerosol-cloud interactions over the Southern Ocean (SO) is the dominant role of sea spray aerosol, versus terrestrial aerosol. Ice nucleating particles (INPs), or particles required for heterogeneous ice nucleation, present over the SO have not been studied in several decades. In this study, boundary layer aerosol properties and immersion freezing INP number concentrations (nINPs) were measured during a ship campaign that occurred south of Australia (down to 53°S) in March–April 2016. Ocean surface chlorophyll a concentrations ranged from 0.11 to 1.77 mg/m3, and nINPs were a factor of 100 lower than historical surveys, ranging from 0.38 to 4.6 m−3 at −20 °C. The INP population included organic heat-stable material, with contributions from heat-labile material. Lower INP source potentials of SO seawater samples compared to Arctic seawater were consistent with lower ice nucleating site densities in this study compared to north Atlantic air masses. ©2018. American Geophysical Union. All Rights Reserved."
"56422246700;8550791300;56495287900;25624725200;55730602600;56612704000;55857180100;7006415284;","Laboratory-generated mixtures of mineral dust particles with biological substances: Characterization of the particle mixing state and immersion freezing behavior",2016,"10.5194/acp-16-5531-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84969528754&doi=10.5194%2facp-16-5531-2016&partnerID=40&md5=eaef1a62d39f20d712f5e6e31c927726","Biological particles such as bacteria, fungal spores or pollen are known to be efficient ice nucleating particles. Their ability to nucleate ice is due to ice nucleation active macromolecules (INMs). It has been suggested that these INMs maintain their nucleating ability even when they are separated from their original carriers. This opens the possibility of an accumulation of such INMs in soils, resulting in an internal mixture of mineral dust and INMs. If particles from such soils which contain biological INMs are then dispersed into the atmosphere due to wind erosion or agricultural processes, they could induce ice nucleation at temperatures typical for biological substances, i.e., above-20 up to almost 0 °C, while they might be characterized as mineral dust particles due to a possibly low content of biological material. We conducted a study within the research unit INUIT (Ice Nucleation research UnIT), where we investigated the ice nucleation behavior of mineral dust particles internally mixed with INM. Specifically, we mixed a pure mineral dust sample (illite-NX) with ice active biological material (birch pollen washing water) and quantified the immersion freezing behavior of the resulting particles utilizing the Leipzig Aerosol Cloud Interaction Simulator (LACIS). A very important topic concerning the investigations presented here as well as for atmospheric application is the characterization of the mixing state of aerosol particles. In the present study we used different methods like single-particle aerosol mass spectrometry, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray analysis (EDX), and a Volatility-Hygroscopicity Tandem Differential Mobility Analyser (VHTDMA) to investigate the mixing state of our generated aerosol. Not all applied methods performed similarly well in detecting small amounts of biological material on the mineral dust particles. Measuring the hygroscopicity/volatility of the mixed particles with the VH-TDMA was the most sensitive method.We found that internally mixed particles, containing ice active biological material, follow the ice nucleation behavior observed for the pure biological particles. We verified this by modeling the freezing behavior of the mixed particles with the Soccerball model (SBM). It can be concluded that a single INM located on a mineral dust particle determines the freezing behavior of that particle with the result that freezing occurs at temperatures at which pure mineral dust particles are not yet ice active. © 2016 Author(s)."
"56426612900;35759254100;7202619752;6603172418;","Aerosol-radiation-cloud interactions in a regional coupled model: The effects of convective parameterisation and resolution",2016,"10.5194/acp-16-5573-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84968835130&doi=10.5194%2facp-16-5573-2016&partnerID=40&md5=b49551b90e4af323f296ad80880f2efe","The Weather Research and Forecasting model with Chemistry (WRF-Chem) has been used to simulate a region of Brazil heavily influenced by biomass burning. Nested simulations were run at 5 and 1 km horizontal grid spacing for three case studies in September 2012. Simulations were run with and without fire emissions, convective parameterisation on the 5 km domain, and aerosol-radiation interactions in order to explore the differences attributable to the parameterisations and to better understand the aerosol direct effects and cloud responses. Direct aerosol-radiation interactions due to biomass burning aerosol resulted in a net cooling, with an average short-wave direct effect of-4.08 ± 1.53 Wm-2. However, around 21.7 Wm-2 is absorbed by aerosol in the atmospheric column, warming the atmosphere at the aerosol layer height, stabilising the column, inhibiting convection, and reducing cloud cover and precipitation. The changes to clouds due to radiatively absorbing aerosol (traditionally known as the semi-direct effects) increase the net short-wave radiation reaching the surface by reducing cloud cover, producing a secondary warming that counters the direct cooling. However, the magnitude of the semi-direct effect was found to be extremely sensitive to the model resolution and the use of convective parameterisation. Precipitation became organised in isolated convective cells when not using a convective parameterisation on the 5 km domain, reducing both total cloud cover and total precipitation. The SW semi-direct effect varied from 6.06 ± 1.46 with convective parameterisation to 3.61 ± 0.86 Wm-2 without. Convective cells within the 1 km domain are typically smaller but with greater updraft velocity than equivalent cells in the 5 km domain, reducing the proportion of the domain covered by cloud in all scenarios and producing a smaller semi-direct effect. Biomass burning (BB) aerosol particles acted as cloud condensation nuclei (CCN), increasing the droplet number concentration of clouds. However, the changes to cloud properties had negligible impact on the net radiative balance in either domain, with or without convective parameterisation. The sensitivity to the uncertainties relating to the semi-direct effect was greater than any other observable indirect effects. Although the version of WRF-Chem distributed to the community currently lacks aerosol-cloud interactions in parameterised clouds, the results of this study suggest a greater priority for the development is to improve the modelling of semi-direct effects by reducing the uncertainties relating to the use of convective parameterisation and resolution before WRF-Chem can reliably quantify the regional impacts of aerosols. © 2016 Author(s)."
"57142867400;56611366900;55745955800;19638935200;","New understanding and quantification of the regime dependence of aerosol-cloud interaction for studying aerosol indirect effects",2016,"10.1002/2016GL067683","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977829941&doi=10.1002%2f2016GL067683&partnerID=40&md5=ab902e1fac84fff7ef2f1ffe5f6573c3","Aerosol indirect effects suffer from large uncertainty in climate models and among observations. This study focuses on two plausible factors: regime dependence of aerosol-cloud interactions and the effect of cloud droplet spectral shape. We show, using a new parcel model, that combined consideration of droplet number concentration (Nc) and relative dispersion (ε, ratio of standard deviation to mean radius of the cloud droplet size distribution) better characterizes the regime dependence of aerosol-cloud interactions than considering Nc alone. Given updraft velocity (w), ε increases with increasing aerosol number concentration (Na) in the aerosol-limited regime, peaks in the transitional regime, and decreases with further increasing Na in the updraft-limited regime. This new finding further reconciles contrasting observations in literature and reinforces the compensating role of dispersion effect. The nonmonotonic behavior of ε further quantifies the relationship between the transitional Na and w that separates the aerosol- and updraft-limited regimes. ©2016. The Authors."
"57151771800;57190184992;","Future aerosol reductions and widening of the northern tropical belt",2016,"10.1002/2016JD024803","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84978204674&doi=10.1002%2f2016JD024803&partnerID=40&md5=b9b7027900e37afc2d6a4e952bc48150","Observations show that the tropical belt has widened over the past few decades, a phenomenon associated with poleward migration of subtropical dry zones and large-scale atmospheric circulation. Although part of this signal is related to natural climate variability, studies have identified an externally forced contribution primarily associated with greenhouse gases (GHGs) and stratospheric ozone loss. Here we show that the increase in aerosols over the twentieth century has led to contraction of the northern tropical belt, thereby offsetting part of the widening associated with the increase in GHGs. Over the 21st century, however, when aerosol emissions are projected to decrease, the effects of aerosols and GHGs reinforce one another, both contributing to widening of the northern tropical belt. Models that have larger aerosol forcing, by including aerosol indirect effects on cloud albedo and lifetime, yield significantly larger Northern Hemisphere (NH) tropical widening than models with direct aerosol effects only. More targeted simulations show that future reductions in aerosols can drive NH tropical widening as large as greenhouse gases, and idealized simulations show the importance of NH midlatitude aerosol forcing. Mechanistically, the 21st century reduction in aerosols peaks near 40°N, which results in a corresponding maximum increase in surface solar radiation, NH midlatitude tropospheric warming amplification, and a poleward shift in the latitude of maximum baroclinicity, implying a corresponding shift in atmospheric circulation. If models with aerosol indirect effects better represent the real world, then future aerosol changes are likely to be an important-if not dominant-driver of NH tropical belt widening. © 2016. American Geophysical Union. All Rights Reserved."
"7501627905;","Anthropogenic aerosols and the distribution of past large-scale precipitation change",2015,"10.1002/2015GL066416","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955195119&doi=10.1002%2f2015GL066416&partnerID=40&md5=bd6e581bb4c18134425d20787704555d","The climate response of precipitation to the effects of anthropogenic aerosols is a critical while not yet fully understood aspect in climate science. Results of selected models that participated the Coupled Model Intercomparison Project Phase 5 and the data from the Twentieth Century Reanalysis Project suggest that, throughout the tropics and also in the extratropical Northern Hemisphere, aerosols have largely dominated the distribution of precipitation changes in reference to the preindustrial era in the second half of the last century. Aerosol-induced cooling has offset some of the warming caused by the greenhouse gases from the tropics to the Arctic and thus formed the gradients of surface temperature anomaly that enable the revealed precipitation change patterns to occur. Improved representation of aerosol-cloud interaction has been demonstrated as the key factor for models to reproduce consistent distributions of past precipitation change with the reanalysis data. © 2015. American Geophysical Union. All Rights Reserved."
"55173596300;57208121852;55417497600;49861577800;","Wet scavenging limits the detection of aerosol effects on precipitation",2015,"10.5194/acp-15-7557-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937037713&doi=10.5194%2facp-15-7557-2015&partnerID=40&md5=394a423a9b2af8a5fa4c01d08c625cb8","Satellite studies of aerosol-cloud interactions usually make use of retrievals of both aerosol and cloud properties, but these retrievals are rarely spatially co-located. While it is possible to retrieve aerosol properties above clouds under certain circumstances, aerosol properties are usually only retrieved in cloud-free scenes. Generally, the smaller spatial variability of aerosols compared to clouds reduces the importance of this sampling difference. However, as precipitation generates an increase in spatial variability of aerosols, the imperfect co-location of aerosol and cloud property retrievals may lead to changes in observed aerosol-cloud-precipitation relationships in precipitating environments. In this work, we use a regional-scale model, satellite observations and reanalysis data to investigate how the non-coincidence of aerosol, cloud and precipitation retrievals affects correlations between them. We show that the difference in the aerosol optical depth (AOD)-precipitation relationship between general circulation models (GCMs) and satellite observations can be explained by the wet scavenging of aerosol. Using observations of the development of precipitation from cloud regimes, we show how the influence of wet scavenging can obscure possible aerosol influences on precipitation from convective clouds. This obscuring of aerosol-cloud-precipitation interactions by wet scavenging suggests that even if GCMs contained a perfect representation of aerosol influences on convective clouds, the difficulty of separating the ""clear-sky"" aerosol from the ""all-sky"" aerosol in GCMs may prevent them from reproducing the correlations seen in satellite data. © Author(s) 2015."
"56192746700;6505932008;6507731482;6602805147;25953950400;","Aerosol indirect effects on idealized tropical cyclone dynamics",2014,"10.1175/JAS-D-13-0202.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901759268&doi=10.1175%2fJAS-D-13-0202.1&partnerID=40&md5=a0164caef882793d72f00ea841716daf","The desire to improve the forecasting skill of the intensity and size of tropical cyclones has prompted the investigation into numerous physical processes that can impact these quantities. The modification of cloud properties via aerosols injected into a tropical cyclone can initiate interactions between cloud microphysics and storm dynamics that ultimately lead to appreciable changes in the large-scale features of the storm. In this modeling study it is shown that the introduction of aerosols at the periphery of an idealized tropical cyclone can impact both the intensity and size of the storm. In general, the storm intensity increases and the storm size decreases with increasing aerosol number concentration. Results from a sensitivity study to the aerosol number concentration in a source located at the storm periphery reveal that the storm intensity is increased up to 17%, and the storm size is reduced up to roughly 16% for aerosol concentrations ranging from 100 to 2000 cm-3. The storm response is approximately a monotonic function of the aerosol concentration amounts. Despite the increase in storm intensity for the heavily polluted case, the overall destructive potential of this case is reduced due to the significant decrease in the storm size. © 2014 American Meteorological Society."
"7005485117;55968364300;7003366215;14070768100;7403882699;56391331800;","Impacts of enhanced CCN on the organization of convection and recent reduced counts of monsoon depressions",2013,"10.1007/s00382-012-1638-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879499929&doi=10.1007%2fs00382-012-1638-z&partnerID=40&md5=ba38531cb041ced64ed27ac806854fb6","Monsoon depressions, that form during the Indian summer monsoon season (June to September) are known to be baroclinic disturbances (horizontal scale 2,000-3,000 km) and are driven by deep convection that carries a very large vertical slope towards cold air aloft in the upper troposphere. Deep convection is nearly always organized around the scale of these depressions. In the maintenance of the monsoon depression the generation of eddy kinetic energy on the scale of the monsoon depression is largely governed by the ""in scale"" covariance of heating and temperature and of vertical velocity and temperature over the region of the monsoon depression. There are normally about 6-8 monsoon depressions during a summer monsoon season. Recent years 2009, 2010 and 2011 saw very few (around 1, 0 and 1 per season respectively). The best numerical models such as those from ECMWF and US (GFS) carried many false alarms in their 3-5 day forecasts, more like 6-8 disturbances. Even in recent years with fewer observed monsoon depressions a much larger number of depressions is noted in ECMWF forecasts. These are fairly comprehensive models that carry vast data sets (surface and satellite based), detailed data assimilation, and are run at very high resolutions. The monsoon depression is well resolved by these respective horizontal resolutions in these models (at 15 and 35 km). These models carry complete and detailed physical parameterizations. The false alarms in their forecasts leads us to suggest that some additional important ingredient may be missing in these current best state of the art models. This paper addresses the effects of pollution for the enhancement of cloud condensation nuclei and the resulting disruption of the organization of convection in monsoon depressions. Our specific studies make use of a high resolution mesoscale model (WRF/CHEM) to explore the impacts of the first and second aerosol indirect effects proposed by Twomey and Albrecht. We have conducted preliminary studies including examination of the evolution of radar reflectivity (computed inversely from the model hydrometeors) for normal and enhanced CCN effects (arising from enhanced monsoon pollution). The time lapse histories show a major disruption in the organization of convection of the monsoon depressions on the time scale of a week to 10 days in these enhanced CCN scenarios. © 2012 Springer-Verlag Berlin Heidelberg."
"35095482200;7005035762;","The first aerosol indirect effect quantified through airborne remote sensing during VOCALS-REx",2013,"10.5194/acp-13-917-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873024475&doi=10.5194%2facp-13-917-2013&partnerID=40&md5=fb87e4da3465eb096e2f3924e895ca3d","The first aerosol indirect effect (1AIE) is investigated using a combination of in situ and remotely-sensed aircraft (NCAR C-130) observations acquired during VOCALS-REx over the southeast Pacific stratocumulus cloud regime. Satellite analyses have previously identified a high albedo susceptibitility to changes in cloud microphysics and aerosols over this region. The 1AIE was broken down into the product of two independently-estimated terms: the cloud aerosol interaction metric ACI τ Combining double low linτ Na|LWP , and the relative albedo (A) susceptibility S Rτ Combining double low line A/3dτ|LWP, with τ/and N a denoting retrieved cloud optical thickness and in situ aerosol concentration respectively and calculated for fixed intervals of liquid water path (LWP). ACI τ was estimated by combining in situ N/a sampled below the cloud, with τ and LWP derived from, respectively, simultaneous upward-looking broadband irradiance and narrow field-of-view millimeter-wave radiometer measurements, collected at 1 Hz during four eight-hour daytime flights by the C-130 aircraft. ACIτ values were typically large, close to the physical upper limit (0.33), with a modest increase with LWP. The high ACI τ values slightly exceed values reported from many previous in situ airborne studies in pristine marine stratocumulus and reflect the imposition of a LWP constraint and simultaneity of aerosol and cloud measurements. S Rτ increased with LWP and τ, reached a maximum SR τ (0.086) for LWP (τ) of 58 g m-2 (∼14), and decreased slightly thereafter. The 1AIE thus increased with LWP and is comparable to a radiative forcing of-3.2-3.8 W m-2 for a 10% increase in Na, exceeding previously-reported global-range values. The aircraft-derived values are consistent with satellite estimates derived from instantaneous, collocated Clouds and the Earth's Radiant Energy System (CERES) albedo and MOderate resolution Imaging Spectroradiometer (MODIS)-retrieved droplet number concentrations at 50 km resolution. The consistency of the airborne and satellite estimates, despite their independent approaches, differences in observational scales, and retrieval assumptions, is hypothesized to reflect the ideal remote sensing conditions for these homogeneous clouds. We recommend the southeast Pacific for regional model assessments of the first aerosol indirect effect on this basis. This airborne remotely-sensed approach towards quantifying 1AIE should in theory be more robust than in situ calculations because of increased sampling. However, although the technique does not explicitly depend on a remotely-derived cloud droplet number concentration (Nd), the at-times unrealistically-high Nd values suggest more emphasis on accurate airborne radiometric measurements is needed to refine this approach. © 2013 Author(s)."
"50261552200;6701752471;7103271625;","Aerosol effects on stratocumulus water paths in a PDF-based parameterization",2011,"10.1029/2011GL048611","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052725662&doi=10.1029%2f2011GL048611&partnerID=40&md5=bb5322ae5f27ef0beba90dbe33d79c55","Successful simulation of aerosol indirect effects in climate models requires parameterizations that capture the full range of cloud-aerosol interactions, including positive and negative liquid water path (LWP) responses to increasing aerosol concentrations, as suggested by large eddy simulations (LESs). A parameterization based on multi-variate probability density functions with dynamics (MVD PDFs) has been incorporated into the single-column version of GFDL AM3, extended to treat aerosol activation, and coupled with a two-moment microphysics scheme. We use it to explore cloud-aerosol interactions. In agreement with LESs, our single-column simulations produce both positive and negative LWP responses to increasing aerosol concentrations, depending on precipitation and free atmosphere relative humidity. We have conducted sensitivity tests to vertical resolution and droplet sedimentation parameterization. The dependence of sedimentation on cloud droplet size is essential to capture the full LWP responses to aerosols. Further analyses reveal that the MVD PDFs are able to represent changes in buoyancy profiles induced by sedimentation as well as enhanced entrainment efficiency with aerosols comparable to LESs. Copyright 2011 by the American Geophysical Union."
"7102680152;8550791300;8849246700;7202779940;7004838931;13407563600;6602128405;56251307100;55942083800;6603256829;57214957727;6602443410;16833315000;6602354484;23971773000;55730602600;36168844500;7006415284;","Soluble mass, hygroscopic growth, and droplet activation of coated soot particles during LACIS Experiment in November (LExNo)",2010,"10.1029/2009JD012626","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953748764&doi=10.1029%2f2009JD012626&partnerID=40&md5=fb366742aef7ec2e07b4967a665b9186","The LACIS Experiment in November (LExNo) campaign was conducted in November 2005 at the Atmospheric Composition Change the European Network of Excellence (ACCENT) site Leipzig Aerosol Cloud Interaction Simulator (LACIS). The goal of LExNo was to provide deeper insight into the activation properties of coated soot particles imitating aged combustion aerosol particles. The aerosols were prepared by starting with spark-generated soot particles. In some experiments the soot particles were compacted by exposure to propanol vapor; in others this step was bypassed. The soot was thermally coated with ammonium sulfate, levoglucosan, or a mixture of both ammonium sulfate and levoglucosan. The synthesized particles were investigated using aerosol mass spectrometry, a Hygroscopicity Tandem differential mobility analyzer, two Wyoming static diffusion cloud condensation nuclei (CCN) instruments, a Droplet Measurement Technologies continuous flow CCN instrument, and LACIS. A close correlation between the hygroscopic growth factor at 98% relative humidity and the critical supersaturation of CCN activation was observed. Closure between hygroscopic growth, CCN activation, and chemical composition of the investigated particles was achieved with two different single-parameter Köhler model approaches and with a third approach, a standard Köhler model using as input parameter the soluble mass as determined by aerosol mass spectrometry. Copyright 2010 by the American Geophysical Union."
"8349977900;7004174939;57208765879;16245558300;57202661839;6508138919;","Exploring the differences in cloud properties observed by the Terra and Aqua MODIS Sensors",2009,"10.5194/acp-9-3461-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72449171063&doi=10.5194%2facp-9-3461-2009&partnerID=40&md5=d269d40d274d8bd02b23ed8e6dfa4dac","The aerosol-cloud interaction in different parts of the globe is examined here using multi-year statistics of remotely sensed data from two MODIS sensors aboard NASA's Terra (morning) and Aqua (afternoon) satellites. Simultaneous retrievals of aerosol loadings and cloud properties by the MODIS sensor allowed us to explore morning-to-afternoon variation of liquid cloud fraction (CF) and optical thickness (COT) for clean, moderately polluted and heavily polluted clouds in different seasons. Data analysis for seven-years of MODIS retrievals revealed strong temporal and spatial patterns in morning-to-afternoon variation of cloud fraction and optical thickness over different parts of the global oceans and the land. For the vast areas of stratocumulus cloud regions, the data shows that the days with elevated aerosol abundance were also associated with enhanced afternoon reduction of CF and COT pointing to the possible reduction of the indirect climate forcing. A positive correlation between aerosol optical depth and morning-to-afternoon variation of trade wind cumulus cloud cover was also found over the northern Indian Ocean, though no clear relationship between the concentration of Indo-Asian haze and morning-to-afternoon variation of COT was established. Over the Amazon region during wet conditions, aerosols are associated with an enhanced convective process in which morning shallow warm clouds are organized into afternoon deep convection with greater ice cloud coverage. Analysis presented here demonstrates that the new technique for exploring morning-to-afternoon variability in cloud properties by using the differences in data products from the two daily MODIS overpasses is capable of capturing some of the major features of diurnal variations in cloud properties and can be used for better understanding of aerosol radiative effects."
"56452429200;7003430284;7004027519;","Processes Controlling the Composition and Abundance of Arctic Aerosol",2018,"10.1029/2018RG000602","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056107925&doi=10.1029%2f2018RG000602&partnerID=40&md5=d92a7b0d0affcc3048b55a113b014831","The Arctic region is a harbinger of global change and is warming at a rate higher than the global average. While Arctic warming is driven by increases in anthropogenic greenhouse gases' in combination with local feedback mechanisms, short-lived climate forcing agents, such as tropospheric aerosol, are also important drivers of Arctic climate. Arctic aerosol-climate impacts vary seasonally as a result of the interplay between aerosol and different cloud types, available solar radiation, sea ice, surface albedo, Arctic and lower latitude removal processes, and atmospheric transport patterns. Photochemistry and efficient wet aerosol removal have low impact in winter but become important in spring to summer, dramatically altering aerosol chemical composition, and driving the size distribution from a pronounced accumulation mode toward a dominance of smaller particles. Retreating sea ice, increasing solar insolation and warmer temperatures in summer result in enhanced emissions from Arctic marine and terrestrial ecosystems, and anthropogenic sources, with impacts on the composition of gas and particle phases. Fractional cloud cover reaches a maximum in Arctic summer, in parallel with decreasing sea ice extent and surface albedo. This seasonal variation corresponds to significant changes in the net cloud radiative effect; changes that are affected by aerosol. This review summarizes our current knowledge of processes that control Arctic aerosol properties. We highlight both natural and anthropogenic processes that will be impacted by current and future sea ice loss. Efforts are needed to better constrain aerosol removal rates, characterize aerosol precursors, and constrain the seasonality and magnitude of aerosol-cloud-climate impacts. ©2018. The Authors."
"55827521500;23970271800;23006117300;22954523900;","Investigation of the adiabatic assumption for estimating cloud micro- and macrophysical properties from satellite and ground observations",2016,"10.5194/acp-16-933-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956702078&doi=10.5194%2facp-16-933-2016&partnerID=40&md5=79491e18457575c29bb1b876eaae4aad","Cloud properties from both ground-based as well as from geostationary passive satellite observations have been used previously for diagnosing aerosol-cloud interactions. In this investigation, a 2-year data set together with four selected case studies are analyzed with the aim of evaluating the consistency and limitations of current ground-based and satellite-retrieved cloud property data sets. The typically applied adiabatic cloud profile is modified using a sub-adiabatic factor to account for entrainment within the cloud. Based on the adiabatic factor obtained from the combination of ground-based cloud radar, ceilometer and microwave radiometer, we demonstrate that neither the assumption of a completely adiabatic cloud nor the assumption of a constant sub-adiabatic factor is fulfilled (mean adiabatic factor 0.63±0.22). As cloud adiabaticity is required to estimate the cloud droplet number concentration but is not available from passive satellite observations, an independent method to estimate the adiabatic factor, and thus the influence of mixing, would be highly desirable for global-scale analyses. Considering the radiative effect of a cloud described by the sub-adiabatic model, we focus on cloud optical depth and its sensitivities. Ground-based estimates are here compared vs. cloud optical depth retrieved from the Meteosat SEVIRI satellite instrument resulting in a bias of -4 and a root mean square difference of 16. While a synergistic approach based on the combination of ceilometer, cloud radar and microwave radiometer enables an estimate of the cloud droplet concentration, it is highly sensitive to radar calibration and to assumptions about the moments of the droplet size distribution. Similarly, satellite-based estimates of cloud droplet concentration are uncertain. We conclude that neither the ground-based nor satellite-based cloud retrievals applied here allow a robust estimate of cloud droplet concentration, which complicates its use for the study of aerosol-cloud interactions. © Author(s) 2016."
"56612517400;36538539800;","Improvement and further development in CESM/CAM5: Gas-phase chemistry and inorganic aerosol treatments",2014,"10.5194/acp-14-9171-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907010428&doi=10.5194%2facp-14-9171-2014&partnerID=40&md5=072ef2a52fb4f0bf958efea72c77f89f","Gas-phase chemistry and subsequent gas-to-particle conversion processes such as new particle formation, condensation, and thermodynamic partitioning have large impacts on air quality, climate, and public health through influencing the amounts and distributions of gaseous precursors and secondary aerosols. Their roles in global air quality and climate are examined in this work using the Community Earth System Model version 1.0.5 (CESM1.0.5) with the Community Atmosphere Model version 5.1 (CAM5.1) (referred to as CESM1.0.5/CAM5.1). CAM5.1 includes a simple chemistry that is coupled with a 7-mode prognostic Modal Aerosol Model (MAM7). MAM7 includes classical homogenous nucleation (binary and ternary) and activation nucleation (empirical first-order power law) parameterizations, and a highly simplified inorganic aerosol thermodynamics treatment that only simulates particulate-phase sulfate and ammonium. In this work, a new gas-phase chemistry mechanism based on the 2005 Carbon Bond Mechanism for Global Extension (CB05-GE) and several advanced inorganic aerosol treatments for condensation of volatile species, ion-mediated nucleation (IMN), and explicit inorganic aerosol thermodynamics for sulfate, ammonium, nitrate, sodium, and chloride have been incorporated into CESM/CAM5.1-MAM7. Compared to the simple gas-phase chemistry, CB05-GE can predict many more gaseous species, and thus could improve model performance for PM2.5, PM10, PM components, and some PM gaseous precursors such as SO2 and NH3 in several regions as well as aerosol optical depth (AOD) and cloud properties (e.g., cloud fraction (CF), cloud droplet number concentration (CDNC), and shortwave cloud forcing, SWCF) on the global scale. The modified condensation and aqueous-phase chemistry could further improve the prediction of additional variables such as HNO3, NO2, and O3 in some regions, and new particle formation rate (&lt;i&gt;J&lt;/i&gt;) and AOD on the global scale. IMN can improve the prediction of secondary PM2.5 components, PM2.5, and PM10 over Europe as well as AOD and CDNC on the global scale. The explicit inorganic aerosol thermodynamics using the ISORROPIA II model improves the prediction of all major PM2.5 components and their gaseous precursors in some regions as well as downwelling shortwave radiation, SWCF, and cloud condensation nuclei at a supersaturation of 0.5% on the global scale. For simulations of 2001-2005 with all the modified and new treatments, the improved model predicts that on global average, SWCF increases by 2.7 W m-2, reducing the normalized mean bias (NMB) of SWCF from -5.4 to 1.2%. Uncertainties in emissions can largely explain the inaccurate prediction of precursor gases (e.g., SO2, NH3, and NO) and primary aerosols (e.g., black carbon and primary organic matter). Additional factors leading to the discrepancies between model predictions and observations include assumptions associated with equilibrium partitioning for fine particles assumed in ISORROPIA II, irreversible gas/particle mass transfer treatment for coarse particles, uncertainties in model treatments such as dust emissions, secondary organic aerosol formation, multi-phase chemistry, cloud microphysics, aerosol-cloud interaction, dry and wet deposition, and model parameters (e.g., accommodation coefficients and prefactors of the nucleation power law) as well as uncertainties in model configuration such as the use of a coarse-grid resolution."
"8942525300;12753162000;","Natural aerosol-climate feedbacks suppressed by anthropogenic aerosol",2013,"10.1002/2013GL057966","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885562447&doi=10.1002%2f2013GL057966&partnerID=40&md5=1686b5b6979cbe85f3f34454da7b9875","The natural environment is an important source of atmospheric aerosol such as dust, sea spray, and wildfire smoke. Climate controls many of these natural aerosol sources, which, in turn, can alter climate through changing the properties of clouds and the Earth's radiative balance. However, the Earth's atmosphere is now heavily modified by anthropogenic pollution aerosol, but how this pollution may alter these natural aerosol-climate feedbacks has not been previously explored. Here we use a global aerosol microphysics model to analyze how anthropogenic aerosol alters one link within these feedbacks, namely, the sensitivity of cloud albedo to changes in natural aerosol. We demonstrate that anthropogenic aerosol in the Northern Hemisphere has halved the hemispheric mean cloud albedo radiative effect that occurs due to changes in natural aerosol emissions. Such a suppression has not occurred in the more pristine Southern Hemisphere. Key Points Cloud droplet number concentrations have increased in NH due to pollution Aerosol indirect effect due to natural aerosol is suppressed by pollution Natural aerosol-climate feedbacks more important before pollution aerosol ©2013. American Geophysical Union. All Rights Reserved."
"9534896800;7401776640;55905970100;","Is there evidence for an aerosol indirect effect during the recent aerosol optical depth decline in Europe?",2010,"10.1029/2009JD012867","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952264501&doi=10.1029%2f2009JD012867&partnerID=40&md5=21b70c677a1611759656b84594a37634","Aerosol indirect effects are some of the largest uncertainties of anthropogenic climate change. To estimate the first aerosol indirect radiative effect (or cloud albedo effect), we analyzed global solar irradiance measurements under completely overcast skies during the recent period of aerosol optical depth decline in Europe. Although measurements from 15 Swiss and 8 northern German sites show clear evidence for an aerosol direct radiative effect under cloud-free skies, trends of transmitted solar irradiance (SW tran) under overcast skies are ambiguous. Time series from 1981 to 2005 of SWtran for all overcast conditions show slightly negative, but nonsignificant trends. SWtran under overcast conditions with ""thick"" clouds (SWtran smaller than the long-term mean) exhibit on average an increasing trend of +0.29 [+0.01 to +0.57] W m -2 / decade. The increase of SWtran under ""thick"" overcast skies, however, is about nine times smaller than the increase under cloud-free skies. Since cirrus clouds are generally excluded from and low-level stratiform clouds are more frequently represented by ""thick"" overcast skies, the slight increase in SWtran may possibly result from a weak aerosol indirect effect. Alternatively, the increase in SWtran may be due to a decreasing trend in low-level stratiform cloud amount under overcast conditions observed for these sites. We further find that solar irradiance changes caused by decreasing aerosol direct effect and increasing sunshine duration can account for most of the observed increasing all-sky solar radiation trend. This suggests that the first aerosol indirect effect makes little contribution to surface solar radiation changes over Europe. Copyright 2010 by the American Geophysical Union."
"26654888600;7101846027;7409175472;6603684590;7006572336;57196499374;6701378450;","On the representation of droplet coalescence and autoconversion: Evaluation using ambient cloud droplet size distributions",2009,"10.1029/2008JD010502","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649133595&doi=10.1029%2f2008JD010502&partnerID=40&md5=d7f8f41b4d86818f7bdff2ef81d508c5","In this study, we evaluate eight autoconversion parameterizations against integration of the Kinetic Collection Equation (KCE) for cloud size distributions measured during the NASA CRYSTAL-FACE and CSTRIPE campaigns. KCE calculations are done using both the observed data and fits of these data to a gamma distribution function; it is found that the fitted distributions provide a good approximation for calculations of total coalescence but not for autoconversion because of fitting errors near the drop-drizzle separation size. Parameterizations that explicitly compute autoconversion tend to be in better agreement with KCE but are subject to substantial uncertainty, about an order of magnitude in autoconversion rate. Including turbulence effects on droplet collection increases autoconversion by a factor of 1.82 and 1.24 for CRYSTAL-FACE and CSTRIPE clouds, respectively; this enhancement never exceeds a factor of 3, even under the most aggressive collection conditions. Shining the droplet-drizzle separation radius from 20 to 25 μm results in about a twofold uncertainty in autoconversion rate. The polynomial approximation to the gravitation.collection kernel used to develop parameterizations provides computation of autoconversion that agree to within 30%. Collectively, these uncertainties have an important impact on autoconversion but are all within the factor of 10 uncertainty of autoconversion parameterizations. Incorporating KCE calculations in GCM simulations of aerosol-cloud interactions studies is computationally feasible by using precalculated collection kernel tables and can quantify the autoconversion uncertainty associated with application of parameterizations. Copyright 2009 by the American Geophysical Union."
"21935606200;7003831855;7402866430;","Aerosol indirect effect over Indo-Gangetic plain",2007,"10.1016/j.atmosenv.2007.05.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34748822366&doi=10.1016%2fj.atmosenv.2007.05.007&partnerID=40&md5=7525777ccc67a6aefe6957ba23fe5edb","Moderate resolution imaging spectroradiometer (MODIS) data are analyzed over the Indo-Gangetic plain (IGP) to study the effect of aerosol optical depth (AOD) on the water (Reff,w) and ice (Reff,i) cloud effective radius for the period 2001-2005. The temporal variation of Reff,w and Reff,i shows reverse trend as that of AOD for most of the time. The intensity of positive indirect effect (i.e. increase of Reff,w/i with decrease of AOD and vice versa) is the highest in winter (ΔReff,w/ΔAOD∼-9.67 μm and ΔReff,i/ΔAOD∼-12.15 μm), when the role of meteorology is the least. The positive indirect effect is significant in 43%, 37%, 68% and 54% of area for water clouds in winter, pre-monsoon, monsoon and post-monsoon seasons, respectively, whereas the corresponding values for ice clouds are 42%, 35%, 53% and 53% for the four seasons, respectively. On the contrast, Reff,i in some locations shows increment with the increase in AOD (negative indirect effect). The negative indirect effect is significant at 95% confidence level in 7%, 18%, 9% and 6% grids for winter, pre-monsoon, monsoon and post-monsoon seasons, respectively. The restricted spatial distribution of negative indirect effect in IGP shows that the cloud microphysical processes are very complex. Our analyses clearly identify the contrasting indirect effect, which requires further in situ investigations for better understanding of the aerosol-cloud interaction in the region. © 2007 Elsevier Ltd. All rights reserved."
"6604099174;24281186100;6602840804;55999772700;7403221533;","Influence of aerosol particles from biomass burning on cloud microphysical properties and radiative forcing",2006,"10.1016/j.atmosres.2005.10.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749134850&doi=10.1016%2fj.atmosres.2005.10.010&partnerID=40&md5=5216c3d5989d5c5cb149b9051dde7ebe","Aerosol from biomass burning has been shown to strongly modify cloud microphysical properties and cloud lifetime through the so-called ""indirect effect."" However, in the case of a lack of wet scavenging, it stays suspended for days to weeks and can be transported to considerable distances within an elevated layer above low-level cloud tops with minimal aerosol-cloud interactions. The observations carried out during the Southern African Regional Science Initiative (SAFARI) 2000 dry season field campaign often revealed the presence of an elevated biomass-burning aerosol layer above a semi-permanent stratiform cloud deck off the southern African coasts. MODerate-resolution Imaging Spectroradiometer (MODIS) cloud products were used to investigate the existence of an aerosol indirect effect on convective clouds. Results are presented documenting cloud effective radius and cloud radiative forcing variations due to the presence of the aerosol during the development of convective clouds. Radiative transfer simulations in the visible (0.8 μm, VIS) and near-infrared (1.6, 2.1 and 3.7 μm, NIR) wavelengths were instrumental in establishing the extent of the influence of a biomass-burning aerosol layer overlying a water cloud sheet on the MODIS satellite retrieval of cloud parameters, in particular the effective radius and the optical thickness. The radiative transfer simulations suggest that the presence of the aerosol induces a significant underestimation of the cloud optical thickness, whereas an underestimation of the retrieved effective radius is more pronounced in the retrieval that makes use of the 1.6 μm waveband than the 2.1 and 3.7 μm wavebands. The MODIS cloud products of 3 days of the SAFARI 2000 campaign were analyzed to determine whether the aerosol induced biases evidenced by the simulations also affect the operational cloud property retrieval. Cloud parameters, in particular the effective radius, are usually employed as indicators of the occurrence of aerosol-cloud interaction according to the ""indirect effect."" However, these results highlight some of the difficulties associated with satellite retrievals of cloud properties and show the importance of an accurate sighting of the cloud and aerosol layer top and bottom heights in order to prevent erroneous detections of indirect effects. © 2006 Elsevier B.V. All rights reserved."
"13403622000;7005955015;7003777747;8708955900;7003614389;","Combined observational and modeling based study of the aerosol indirect effect",2006,"10.5194/acp-6-3583-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748298912&doi=10.5194%2facp-6-3583-2006&partnerID=40&md5=faba03cdaed29f245f36bf78ce262219","The indirect effect of aerosols via liquid clouds is investigated by comparing aerosol and cloud characteristics from the Global Climate Model CAM-Oslo to those observed by the MODIS instrument onboard the TERRA and AQUA satellites (http://modis.gsfc.nasa.gov). The comparison is carried out for 15 selected regions ranging from remote and clean to densely populated and polluted. For each region, the regression coefficient and correlation coefficient for the following parameters are calculated: Aerosol Optical Depth vs. Liquid Cloud Optical Thickness, Aerosol Optical Depth vs. Liquid Cloud Droplet Effective Radius and Aerosol Optical Depth vs. Cloud Liquid Water Path. Modeled and observed correlation coefficients and regression coefficients are then compared for a 3-year period starting in January 2001. Additionally, global maps for a number of aerosol and cloud parameters crucial for the understanding of the aerosol indirect effect are compared for the same period of time. Significant differences are found between MODIS and CAM-Oslo both in the regional and global comparison. However, both the model and the observations show a positive correlation between Aerosol Optical Depth and Cloud Optical Depth in practically all regions and for all seasons, in agreement with the current understanding of aerosol-cloud interactions. The correlation between Aerosol Optical Depth and Liquid Cloud Droplet Effective Radius is variable both in the model and the observations. However, the model reports the expected negative correlation more often than the MODIS data. Aerosol Optical Depth is overall positively correlated to Cloud Liquid Water Path both in the model and the observations, with a few regional exceptions."
"8550791300;7202779940;7006415284;10142434600;6602832585;","Measured and modeled equilibrium sizes of NaCl and (NH4)2SO4 particles at relative humidities up to 99.1%",2005,"10.1029/2004JD005507","https://www.scopus.com/inward/record.uri?eid=2-s2.0-29244444004&doi=10.1029%2f2004JD005507&partnerID=40&md5=d85f7fce36d5833235719298e74a8482","The Leipzig Aerosol Cloud Interaction Simulator (LACIS) was used to measure equilibrium sizes of particles at relative humidities (RHs) up to 99.1%. Particles of substances with well-known hygroscopic behavior (NaCl and (NH4)2SO4) were used for the measurements. The intention was to check the proper functionality of LACIS for this measurement mode. Equilibrium sizes were also simulated on the basis of Köhler theory, by (1) assuming ideal solutions and (2) accounting for the nonideality of the droplets by using osmotic coefficients from the open literature. Measured and simulated equilibrium diameters were compared to measured values published in the open literature. For sodium chloride, model approaches 1 and 2 and all measured values were in good agreement. For ammonium sulfate, the results of model approach 2 (nonideal solution) were in good agreement with the measured diameters, whereas assuming an ideal solution yields equilibrium diameters that are too large by up to 20%. Measured hygroscopic growth factors were used to derive scattering coefficients and visibilities for two exemplary atmospheric dry number size distributions at different RHs. For both salts, at 90% RH the scattering coefficient increased by about a factor of 5 compared to that of the dry aerosol; at 99% RH the increase was about 21-fold. If instead the hygroscopic growth was assumed to follow the growth factors that were simulated for an ideal ammonium sulfate solution, the increase of the scattering coefficient is overestimated by ∼40%. This highlights the need to account for the nonideal solution behavior of droplets when calculating equilibrium diameters, even at high RHs. Copyright 2005 by the American Geophysical Union."
"13402835300;25652188900;24329376600;7404142321;7003976079;7103016965;25924878400;","Strong Dependence of Atmospheric Feedbacks on Mixed-Phase Microphysics and Aerosol-Cloud Interactions in HadGEM3",2019,"10.1029/2019MS001688","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067486765&doi=10.1029%2f2019MS001688&partnerID=40&md5=f3c8706352832e655af6185f7246ce99","We analyze the atmospheric processes that explain the large changes in radiative feedbacks between the two latest climate configurations of the Hadley Centre Global Environmental model. We use a large set of atmosphere-only climate change simulations (amip and amip-p4K) to separate the contributions to the differences in feedback parameter from all the atmospheric model developments between the two latest model configurations. We show that the differences are mostly driven by changes in the shortwave cloud radiative feedback in the midlatitudes, mainly over the Southern Ocean. Two new schemes explain most of the differences: the introduction of a new aerosol scheme and the development of a new mixed-phase cloud scheme. Both schemes reduce the strength of the preexisting shortwave negative cloud feedback in the midlatitudes. The new aerosol scheme dampens a strong aerosol-cloud interaction, and it also suppresses a negative clear-sky shortwave feedback. The mixed-phase scheme increases the amount of cloud liquid water path (LWP) in the present day and reduces the increase in LWP with warming. Both changes contribute to reducing the negative radiative feedback of the increase of LWP in the warmer climate. The mixed-phase scheme also enhances a strong, preexisting, positive cloud fraction feedback. We assess the realism of the changes by comparing present-day simulations against observations and discuss avenues that could help constrain the relevant processes. ©2019 Crown copyright. This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland."
"55577875600;7406500188;55717074000;56138686500;55727880700;56162305900;7102010848;8720083500;7402803216;","Anthropogenic aerosol effects on east asian winter monsoon: The role of black carbon-induced tibetan plateau warming",2017,"10.1002/2016JD026237","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020754305&doi=10.1002%2f2016JD026237&partnerID=40&md5=67b3a75bbebac2b6985e90297821e9b4","This study investigates anthropogenic aerosol effects on East Asian winter monsoon (EAWM) with Community Atmospheric Model version 5. In winter, the anthropogenic aerosol optical depth is the largest over southern East Asia and adjacent oceans. The associated EAWM change, however, is the most significant in northern East Asia, which is characterized by a significant surface cooling in northern East Asia and an acceleration of the jet stream around 40°N, indicating an intensification of the EAWM northern mode. Such an intensification is attributed to anthropogenic black carbon (BC)-induced Tibetan Plateau (TP) warming. The BC is mostly transported from northern South Asia by wintertime westerly and southwesterly and then deposited on snow, giving rise to a reduction of surface albedo and an increase of surface air temperature via the snow-albedo feedback. The TP warming increases meridional temperature gradient and lower tropospheric baroclinicity over northern East Asia, leading to the jet stream acceleration around 40°N and the westward shift of East Asian major trough via the transient eddy-mean flow feedback. Such upper tropospheric pattern favors more cold air outbreak, leading to a large surface cooling in northern East Asia. In southern East Asia, the effect of nonabsorbing aerosols is dominant. The solar flux at surface is significantly reduced directly by scattering of nonabsorbing aerosols and indirectly by intensification of short wave cloud forcing. Accordingly, the surface air temperature in southern East Asia is reduced. The precipitation is also significantly reduced in South China and Indo-China Peninsula, where the aerosol indirect effect is the largest. © 2017. The Authors."
"35069282600;57044397100;7202899330;","Aerosol indirect effect dictated by liquid clouds",2016,"10.1002/2016JD025245","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007404014&doi=10.1002%2f2016JD025245&partnerID=40&md5=e5d71edc085f9384458f17811d9db18e","Anthropogenic aerosols have been shown to enhance the solar reflection from warm liquid clouds and mask part of the warming due to the buildup of greenhouse gases. However, very little is known about the effects of aerosol on mixed-phase stratiform clouds as well as other cloud regimes including cumulus, altocumulus, nimbostratus, deep convection, and anvil cirrus. These additional cloud categories are ubiquitous and typically overlooked in satellite-based assessments of the global aerosol indirect forcing. Here we provide their contribution to the aerosol indirect forcing estimate using satellite data collected from several colocated sensors in the A-train for the period 2006-2010. Cloud type is determined according to the 2B-CLDCLASS-LIDAR CloudSat product, and the observations are matched to the radiative flux measurements from CERES (Clouds and the Earth’s Radiant Energy System) and aerosol retrievals from MODIS (MODerate resolution Imaging Spectroradiometer). The oceanic mean aerosol indirect forcing is estimated to be -0.20 ± 0.31Wm-2 with warm low-level cloud largely dictating the strength of the response (-0.36 ± 0.21Wm-2) due to their abundance and strong cloud albedo effect. Contributions from mixed-phase low-level cloud (0.01 ± 0.06Wm-2) and convective cloud (0.15 ± 0.23Wm-2) are positive and buffer the system due to strong aerosol-cloud feedbacks that reduce the cloud albedo effect and/or lead to convective invigoration causing a countering positive longwave warming response. By combining all major cloud categories together, aerosol indirect forcing decreases and now contains positive values in the uncertainty estimate. © 2016. American Geophysical Union. All Rights Reserved."
"8836278700;36984127300;35577097300;","Aerosol number size distributions over a coastal semi urban location: Seasonal changes and ultrafine particle bursts",2016,"10.1016/j.scitotenv.2016.03.246","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84966320702&doi=10.1016%2fj.scitotenv.2016.03.246&partnerID=40&md5=d00aad26ed343f1b9db026597faa2581","Number-size distribution is one of the important microphysical properties of atmospheric aerosols that influence aerosol life cycle, aerosol-radiation interaction as well as aerosol-cloud interactions. Making use of one-yearlong measurements of aerosol particle number-size distributions (PNSD) over a broad size spectrum (~15-15,000 nm) from a tropical coastal semi-urban location-Trivandrum (Thiruvananthapuram), the size characteristics, their seasonality and response to mesoscale and synoptic scale meteorology are examined. While the accumulation mode contributed mostly to the annual mean concentration, ultrafine particles (having diameter &lt;100 nm) contributed as much as 45% to the total concentration, and thus constitute a strong reservoir, that would add to the larger particles through size transformation. The size distributions were, in general, bimodal with well-defined modes in the accumulation and coarse regimes, with mode diameters lying in the range 141 to 167 nm and 1150 to 1760 nm respectively, in different seasons. Despite the contribution of the coarse sized particles to the total number concentration being meager, they contributed significantly to the surface area and volume, especially during transport of marine air mass highlighting the role of synoptic air mass changes. Significant diurnal variation occurred in the number concentrations, geometric mean diameters, which is mostly attributed to the dynamics of the local coastal atmospheric boundary layer and the effect of mesoscale land/sea breeze circulation. Bursts of ultrafine particles (UFP) occurred quite frequently, apparently during periods of land-sea breeze transitions, caused by the strong mixing of precursor-rich urban air mass with the cleaner marine air mass; the resulting turbulence along with boundary layer dynamics aiding the nucleation. These ex-situ particles were observed at the surface due to the transport associated with boundary layer dynamics. The particle growth rates from ultrafine particles to accumulation sizes varied between 1 and 15 nm h-1, with mean growth rate of ~7.35 ± 2.93 nm h-1. © 2016 Elsevier B.V."
"56587124900;36538539800;55624488227;7202010686;","Application of online-coupled WRF/Chem-MADRID in East Asia: Model evaluation and climatic effects of anthropogenic aerosols",2016,"10.1016/j.atmosenv.2015.03.052","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949624899&doi=10.1016%2fj.atmosenv.2015.03.052&partnerID=40&md5=af65825aa08ead1f7971dceb85e99542","The online-coupled Weather Research and Forecasting model with Chemistry with the Model of Aerosol Dynamics, Reaction, Ionization, and Dissolution (referred to as WRF/Chem-MADRID) is applied to simulate meteorological fields, air quality, and the direct and indirect effects of anthropogenic aerosols over East Asia in four months (January, April, July, and October) in 2008. Model evaluation against available surface and satellite measurements shows that despite some model biases, WRF/Chem-MADRID is able to reproduce reasonably well the spatial and seasonal variations of most meteorological fields and chemical concentrations. Large model biases for chemical concentrations are attributed to uncertainties in emissions and their spatial and vertical allocations, simulated meteorological fields, imperfectness of model representations of aerosol formation processes, uncertainties in the observations based on air pollution index, and the use of a coarse grid resolution. The results show that anthropogenic aerosols can reduce net shortwave flux at the surface by up to 40.5-57.2 W m-2, Temperature at 2-m by up to 0.5-0.8 °C, NO2 photolytic rates by up to 0.06-0.1 min-1 and the planetary boundary layer height by up to 83.6-130.4 m. Anthropogenic aerosols contribute to the number concentrations of aerosols by up to 6.2-8.6 × 104 cm-3 and the surface cloud concentration nuclei at a supersaturation of 0.5% by up to 1.0-1.6 × 104 cm-3. They increase the column cloud droplet number concentrations by up to 3.6-11.7 × 108 cm-2 and cloud optical thickness by up to 19.8-33.2. However, anthropogenic aerosols decrease daily precipitation in most areas by up to 3.9-18.6 mm during the 4 months. These results indicate the importance of anthropogenic aerosols in modulating regional climate changes in East Asia through aerosol direct and indirect effects, as well as the need to further improve the performance of online-coupled models. © 2015 Elsevier Ltd."
"55683727600;8942525300;13405658600;9235235300;55683891800;12753162000;7004469744;35547807400;7004864963;35461255500;7102830450;7005287667;35810775100;8942524900;","Impact of gas-to-particle partitioning approaches on the simulated radiative effects of biogenic secondary organic aerosol",2015,"10.5194/acp-15-12989-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948187324&doi=10.5194%2facp-15-12989-2015&partnerID=40&md5=8162df7eeba2f6ad1ac4607cd3b7caaa","The oxidation of biogenic volatile organic compounds (BVOCs) gives a range of products, from semi-volatile to extremely low-volatility compounds. To treat the interaction of these secondary organic vapours with the particle phase, global aerosol microphysics models generally use either a thermodynamic partitioning approach (assuming instant equilibrium between semi-volatile oxidation products and the particle phase) or a kinetic approach (accounting for the size dependence of condensation). We show that model treatment of the partitioning of biogenic organic vapours into the particle phase, and consequent distribution of material across the size distribution, controls the magnitude of the first aerosol indirect effect (AIE) due to biogenic secondary organic aerosol (SOA). With a kinetic partitioning approach, SOA is distributed according to the existing condensation sink, enhancing the growth of the smallest particles, i.e. those in the nucleation mode. This process tends to increase cloud droplet number concentrations in the presence of biogenic SOA. By contrast, an approach that distributes SOA according to pre-existing organic mass restricts the growth of the smallest particles, limiting the number that are able to form cloud droplets. With an organically mediated new particle formation mechanism, applying a mass-based rather than a kinetic approach to partitioning reduces our calculated global mean AIE due to biogenic SOA by 24 %. Our results suggest that the mechanisms driving organic partitioning need to be fully understood in order to accurately describe the climatic effects of SOA. © 2015 Author(s)."
"24764483400;7801353107;23484340400;","How sensitive are aerosol-precipitation interactions to the warm rain representation?",2015,"10.1002/2014MS000422","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945490310&doi=10.1002%2f2014MS000422&partnerID=40&md5=7c60b1c34e83af04bbb867bc869f0dd5","It is widely acknowledged that aerosol-cloud interactions are a major uncertainty in climate and numerical weather prediction. One of the sources of uncertainty is the sensitivity of the cloud microphysics parameterization to changes in aerosol, in particular the response of precipitation. In this work, we conduct an idealized, dynamically consistent, intercomparison of warm rain microphysics schemes to understand this source of uncertainty. The aims of this investigation are: (i) investigate how sensitive precipitation susceptibility (S0) is to cloud microphysics representation and (ii) use S0 to determine the minimum complexity of microphysics required to produce a consistent precipitation response to changes in cloud drop number concentration (Nd). The main results from this work are: (i) over a large range of liquid water path and Nd, all the bulk schemes, but particularly the single moment schemes, artificially produce rain too rapidly. Relative to a reference bin microphysics scheme, this leads to a low in-cloud S0 and impacts the evolution of S0 over time. (ii) Rain evaporation causes surface S0 from all schemes to be larger than the cloud base S0. The magnitude of the change in S0 with altitude is dependent on the scheme and the representation of the rain drop size distribution. Overall, we show that single-moment schemes produce the largest range in the sensitivity of precipitation to changes in Nd. Modifying rain production parameterization alone does not reduce this spread. Instead, increasing the complexity of the rain representation to double-moment significantly improves this behavior and the overall consistency between schemes. © 2015. The Authors."
"8640375700;22837162400;7403204849;16689399100;8740849900;7101799663;7402177459;","Trace metal characterization of aerosol particles and cloud water during HCCT 2010",2015,"10.5194/acp-15-8751-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938941552&doi=10.5194%2facp-15-8751-2015&partnerID=40&md5=7d1fd2c9d09a59e1b2677ac5962dea0b","Trace metal characterization of bulk and size-resolved aerosol and cloud water samples were performed during the Hill Cap Cloud Thuringia (HCCT) campaign. Cloud water was collected at the top of Mt. Schmücke while aerosol samples were collected at two stations upwind and downwind of Mt. Schmücke. Fourteen trace metals including Ti, V, Fe, Mn, Co, Zn, Ni, Cu, As, Sr, Rb, Pb, Cr, and Se were investigated during four full cloud events (FCEs) that fulfilled the conditions of a continuous air mass flow through the three stations. Aerosol particle trace metal concentrations were found to be lower than those observed in the same region during previous field experiments but were within a similar range to those observed in other rural regions in Europe. Fe and Zn were the most abundant elements with concentration ranges of 0.2-111.6 and 1.1-32.1 ng m-3, respectively. Fe, Mn, and Ti were mainly found in coarse mode aerosols while Zn, Pb, and As were mostly found in the fine mode. Correlation and enrichment factor analysis of trace metals revealed that trace metals such as Ti and Rb were mostly of crustal origin while trace metals such as Zn, Pb, As, Cr, Ni, V, and Cu were of anthropogenic origin. Trace metals such as Fe and Mn were of mixed origins including crustal and combustion sources. Trace metal cloud water concentration decreased from Ti, Mn, Cr, to Co with average concentrations of 9.18, 5.59, 5.54, and 0.46 μg L-1, respectively. A non-uniform distribution of soluble Fe, Cu, and Mn was observed across the cloud drop sizes. Soluble Fe and Cu were found mainly in cloud droplets with diameters between 16 and 22 μm, while Mn was found mostly in larger drops greater than 22 μm. Fe(III) was the main form of soluble Fe especially in the small and larger drops with concentrations ranging from 2.2 to 37.1 μg L-1. In contrast to other studies, Fe(II) was observed mainly in the evening hours, implying its presence was not directly related to photochemical processes. Aerosol-cloud interaction did not lead to a marked increase in soluble trace metal concentrations; rather it led to differences in the chemical composition of the aerosol due to preferential loss of aerosol particles through physical processes including cloud drop deposition to vegetative surfaces. © Author(s) 2015."
"7003459696;8633783900;34568038900;55940504500;7403100147;45061126700;56488642100;","Influence of aerosols in multidecadal SST variability simulations over the North Pacific",2015,"10.1002/2014JD021933","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923138937&doi=10.1002%2f2014JD021933&partnerID=40&md5=f07b7bfd88d45790dab4ce98a155e082","The influence of aerosol emissions on North Pacific sea surface temperature (SST) variability during the twentieth century is investigated using a comparison between historical simulations with and without anthropogenic aerosol changes. The historical simulations using the Hadley Global Environment Model version 2 show that there is a common externally forced component in relation to the twentieth century North Pacific SST variability. This matches a number of important temporal and spatial characteristics of the observed multidecadal SST variability from the 1920s to 1990s, which is not found in experiments without aerosol changes. This paper explores both direct and indirect aerosol influences, and finds that in this model the aerosol-cloud interactions dominate the total aerosol forcing of the surface energy budget. These aerosol-cloud processes were not commonly included in most models in the previous (Coupled Model Intercomparison Project phase 3) generation, which may explain why the potential role of aerosols in Pacific variability has not been previously discussed. However, unlike recently reported aerosol drivers of Atlantic SST variability, the aerosol surface radiative forcing pattern does not map directly onto the historical spatial surface radiative and SST changes but is instead modulated by circulation changes to the Aleutian Low. These circulation changes share common features with previously reported studies of natural drivers of Pacific variability, suggesting that both forced and internally generated SST variability may be modulated via the same circulation response. © 2014. The Authors."
"6602878057;7004479957;24722339600;7102294773;7403682442;57193213111;36183151300;8922308700;36876405100;8718425100;56521864800;25823927100;25652188900;28568055900;16550482700;57188966058;","Global and regional modeling of clouds and aerosols in the marine boundary layer during VOCALS: The VOCA intercomparison",2015,"10.5194/acp-15-153-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920728055&doi=10.5194%2facp-15-153-2015&partnerID=40&md5=c282a1d4ffd2934fac94356cbdbb963a","A diverse collection of models are used to simulate the marine boundary layer in the southeast Pacific region during the period of the October-November 2008 VOCALS REx (VAMOS Ocean Cloud Atmosphere Land Study Regional Experiment) field campaign. Regional models simulate the period continuously in boundary-forced free-running mode, while global forecast models and GCMs (general circulation models) are run in forecast mode. The models are compared to extensive observations along a line at 20° S extending westward from the South American coast. Most of the models simulate cloud and aerosol characteristics and gradients across the region that are recognizably similar to observations, despite the complex interaction of processes involved in the problem, many of which are parameterized or poorly resolved. Some models simulate the regional low cloud cover well, though many models underestimate MBL (marine boundary layer) depth near the coast. Most models qualitatively simulate the observed offshore gradients of SO2, sulfate aerosol, CCN (cloud condensation nuclei) concentration in the MBL as well as differences in concentration between the MBL and the free troposphere. Most models also qualitatively capture the decrease in cloud droplet number away from the coast. However, there are large quantitative intermodel differences in both means and gradients of these quantities. Many models are able to represent episodic offshore increases in cloud droplet number and aerosol concentrations associated with periods of offshore flow. Most models underestimate CCN (at 0.1% supersaturation) in the MBL and free troposphere. The GCMs also have difficulty simulating coastal gradients in CCN and cloud droplet number concentration near the coast. The overall performance of the models demonstrates their potential utility in simulating aerosol-cloud interactions in the MBL, though quantitative estimation of aerosol-cloud interactions and aerosol indirect effects of MBL clouds with these models remains uncertain. © © Author(s) 2015."
"57151771800;","A 21st century northward tropical precipitation shift caused by future anthropogenic aerosol reductions",2015,"10.1002/2015JD023623","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945459346&doi=10.1002%2f2015JD023623&partnerID=40&md5=fe2f648c02edf4204248b5ccb2ee52f5","The tropical rain belt is a narrow band of clouds near the equator, where the most intense rainfall on the planet occurs. On seasonal timescales, the rain moves across the equator following the Sun, resulting in wet and dry seasons in the tropics. The position of the tropical rain belt also varies on longer timescales. Through the latter half of the twentieth century, for example, shifts in tropical rainfall have been associated with severe droughts, including the African Sahel and Amazon droughts. Here I show that climate models project a northward migration of the tropical rain belt through the 21st century, with future anthropogenic aerosol reductions driving the bulk of the shift. Models that include both aerosol indirect effects yield significantly larger northward shifts than models that lack aerosol indirect effects. Moreover, the rate of the shift corresponds to the rate of the decrease of anthropogenic aerosol emissions across different time periods and future emission scenarios. This response is consistent with relative warming of the Northern Hemisphere, a decrease in northward cross-equatorial moist static energy transport, and a northward shift of the Hadley circulation, including the tropical rain belt. The shift is relatively weak in the Atlantic sector, consistent with both a smaller decrease in aerosol emissions and a larger reduction in northward cross-equatorial ocean heat flux. Although aerosol effects remain uncertain, I conclude that future reductions in anthropogenic aerosol emissions may be the dominant driver of a 21st century northward shift of the tropical rain belt. © 2015. American Geophysical Union. All Rights Reserved."
"7003871110;8945984800;8055301200;7201400583;11940634500;35305397000;35746915400;7102578937;8581789300;","Particles and iodine compounds in coastal Antarctica",2015,"10.1002/2015JD023301","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939260144&doi=10.1002%2f2015JD023301&partnerID=40&md5=c3f284ffe696488c747091fc0c7f2fc1","Aerosol particle number concentrations have been measured at Halley and Neumayer on the Antarctic coast, since 2004 and 1984, respectively. Sulphur compounds known to be implicated in particle formation and growth were independently measured: sulphate ions and methane sulphonic acid in filtered aerosol samples and gas phase dimethyl sulphide for limited periods. Iodine oxide, IO, was determined by a satellite sensor from 2003 to 2009 and by different ground-based sensors at Halley in 2004 and 2007. Previous model results and midlatitude observations show that iodine compounds consistent with the large values of IO observed may be responsible for an increase in number concentrations of small particles. Coastal Antarctica is useful for investigating correlations between particles, sulphur, and iodine compounds, because of their large annual cycles and the source of iodine compounds in sea ice. After smoothing all the measured data by several days, the shapes of the annual cycles in particle concentration at Halley and Neumayer are approximated by linear combinations of the shapes of sulphur compounds and IO but not by sulphur compounds alone. However, there is no short-term correlation between IO and particle concentration. The apparent correlation by eye after smoothing but not in the short term suggests that iodine compounds and particles are sourced some distance offshore. This suggests that new particles formed from iodine compounds are viable, i.e., they can last long enough to grow to the larger particles that contribute to cloud condensation nuclei, rather than being simply collected by existing particles. If so, there is significant potential for climate feedback near the sea ice zone via the aerosol indirect effect. © 2015. The Authors."
"55879571100;57203439874;35849722200;56145499000;14326501100;","Correlation analysis between AOD and cloud parameters to study their relationship over china using MODIS data (2003–2013): Impact on cloud formation and climate change",2015,"10.4209/aaqr.2014.08.0168","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929666720&doi=10.4209%2faaqr.2014.08.0168&partnerID=40&md5=0661f37d70dac1f288d89672ef4c9e6c","In the present study, we examined the spatial and temporal variations in aerosol optical depth (AOD) at 550 nm and its relationship with various cloud parameters derived from the Moderate resolution Imaging Spectroradiometer (MODIS) sensor onboard Terra satellite. The data have been analyzed for the period of 10-years between March 2003 and February 2013 over 12 major cities in China. The results revealed that high AOD noticed over low latitude regions influenced with high anthropogenic activities and the low AOD observed for the high altitude and mountainous areas, since AOD accounts for the slant path which reduces the aerosol emissions. In addition, the aerosol variations in the atmosphere are complicated by several factors in emissions (natural and anthropogenic) as well as stagnant synoptic meteorology. From the temporal studies, it is clear that the maximum AOD was found during summer followed by spring and autumn with a minimum AOD in winter season for all the regions of study in China. Furthermore, we studied the relationship between AOD versus water vapor (WV), cloud fraction (CF), cloud optical thickness (COT), cloud effective radius (CER), cloud top pressure (CTP), and cloud top temperature (CTT) for the selected regions in China. Additionally, regression analysis and one paired student’s t-Test were applied to represent the probability of data significant at 95% confidence for the derived AOD values and cloud parameters in order to provide a better understanding of aerosol-cloud interaction. © Taiwan Association for Aerosol Research."
"55173596300;57208121852;36171703500;","Links between satellite-retrieved aerosol and precipitation",2014,"10.5194/acp-14-9677-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906945263&doi=10.5194%2facp-14-9677-2014&partnerID=40&md5=e56473f53c456db89b9b45f6aa772868","Many theories have been proposed detailing how aerosols might impact precipitation, predicting both increases and decreases depending on the prevailing meteorological conditions and aerosol type. In convective clouds, increased aerosol concentrations have been speculated to invigorate convective activity. Previous studies have shown large increases in precipitation with increasing aerosol optical depth, concluding an aerosol effect on precipitation. Our analysis reveals that these studies may have been influenced by cloud effects on the retrieved aerosol, as well as by meteorological covariations. We use a regime-based approach to separate out different cloud regimes, allowing for the study of aerosol-cloud interactions in individual cloud regimes. We account for the influence of cloud properties on the aerosol retrieval and make use of the diurnal sampling of the TRMM satellite and the TRMM merged precipitation product to investigate the precipitation development. We find that whilst there is little effect on precipitation at the time of the aerosol retrieval, in the 6 h after the aerosol retrieval, there is an increase in precipitation from cloud in high-aerosol environments, consistent with the invigoration hypothesis. Increases in lightning flash count with increased aerosol are also observed in this period. The invigoration effect appears to be dependent on the cloud-top temperature, with clouds with tops colder than 0 °C showing increases in precipitation at times after the retrieval, as well as increases in wet scavenging. Warm clouds show little change in precipitation development with increasing aerosol, suggesting ice processes are important for the invigoration of precipitation. © 2014 Author(s)."
"57206273805;6701378450;","Understanding the contributions of aerosol properties and parameterization discrepancies to droplet number variability in a global climate model",2014,"10.5194/acp-14-4809-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900819346&doi=10.5194%2facp-14-4809-2014&partnerID=40&md5=a5a26cbfae03877735c97f25b337be4b","Aerosol indirect effects in climate models strongly depend on the representation of the aerosol activation process. In this study, we assess the process-level differences across activation parameterizations that contribute to droplet number uncertainty by using the adjoints of the Abdul-Razzak and Ghan (2000) and Fountoukis and Nenes (2005) droplet activation parameterizations in the framework of the Community Atmospheric Model version 5.1 (CAM5.1). The adjoint sensitivities ofNd to relevant input parameters are used to (i) unravel the spatially resolved contribution of aerosol number, mass, and chemical composition to changes inNd between present-day and pre-industrial simulations and (ii) identify the key variables responsible for the differences inNd fields and aerosol indirect effect estimates when different activation schemes are used within the same modeling framework. The sensitivities are computed online at minimal computational cost. Changes in aerosol number and aerosol mass concentrations were found to contribute toNd differences much more strongly than chemical composition effects. The main sources of discrepancy between the activation parameterizations considered were the treatment of the water uptake by coarse mode particles, and the sensitivity of the parameterizedNd accumulation mode aerosol geometric mean diameter. These two factors explain the different predictions ofNd over land and over oceans when these parameterizations are employed. Discrepancies in the sensitivity to aerosol size are responsible for an exaggerated response to aerosol volume changes over heavily polluted regions. Because these regions are collocated with areas of deep clouds, their impact on shortwave cloud forcing is amplified through liquid water path changes. The same framework is also utilized to efficiently explore droplet number uncertainty attributable to hygroscopicity parameter of organic aerosol (primary and secondary). Comparisons between the parameterization-derived sensitivities of droplet number against predictions with detailed numerical simulations of the activation process were performed to validate the physical consistency of the adjoint sensitivities. © 2014 Author(s)."
"35096299800;35547807400;7407104838;7004299063;36600036800;57203200427;57197325620;35459245100;7005955015;53878006900;6506373162;23052016900;7006705919;55688930000;9249627300;","Sea spray geoengineering experiments in the geoengineering model intercomparison project (GeoMIP): Experimental design and preliminary results",2013,"10.1002/jgrd.50856","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887193183&doi=10.1002%2fjgrd.50856&partnerID=40&md5=5a7484b98771130196bf0dac0634afd5","Marine cloud brightening through sea spray injection has been proposed as a method of temporarily alleviating some of the impacts of anthropogenic climate change, as part of a set of technologies called geoengineering. We outline here a proposal for three coordinated climate modeling experiments to test aspects of sea spray geoengineering, to be conducted under the auspices of the Geoengineering Model Intercomparison Project (GeoMIP). The first, highly idealized, experiment (G1ocean-albedo) involves a uniform increase in ocean albedo to offset an instantaneous quadrupling of CO2 concentrations from preindustrial levels. Results from a single climate model show an increased land-sea temperature contrast, Arctic warming, and large shifts in annual mean precipitation patterns. The second experiment (G4cdnc) involves increasing cloud droplet number concentration in all low-level marine clouds to offset some of the radiative forcing of an RCP4.5 scenario. This experiment will test the robustness of models in simulating geographically heterogeneous radiative flux changes and their effects on climate. The third experiment (G4sea-salt) involves injection of sea spray aerosols into the marine boundary layer between 30°S and 30°N to offset 2 W m-2 of the effective radiative forcing of an RCP4.5 scenario. A single model study shows that the induced effective radiative forcing is largely confined to the latitudes in which injection occurs. In this single model simulation, the forcing due to aerosol-radiation interactions is stronger than the forcing due to aerosol-cloud interactions. Key Points Outline of three marine cloud brightening experiments Land-sea contrast is an important feature of marine cloud brightening Direct effect of sea salt injection may be greater than indirect effect ©2013. American Geophysical Union. All Rights Reserved."
"6603453147;57206332144;57198593283;","Multi-satellite aerosol observations in the vicinity of clouds",2013,"10.5194/acp-13-3899-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899009280&doi=10.5194%2facp-13-3899-2013&partnerID=40&md5=580ed95a1770bbea83ce906c4cdf07d5","Improved characterization of aerosol properties in the vicinity of clouds is important for better understanding two critical aspects of climate: aerosol-cloud interactions and the direct radiative effect of aerosols. Satellite measurements have provided important insights into aerosol properties near clouds, but also suggested that the observations can be affected by 3-D radiative processes and instrument blurring not considered in current data interpretation methods. This study examines systematic cloud-related changes in particle properties and radiation fields that influence satellite measurements of aerosols in the vicinity of low-level maritime clouds. For this, the paper presents a statistical analysis of a yearlong global dataset of co-located MODIS and CALIOP observations and theoretical simulations. The results reveal that CALIOP-observed aerosol particle size and optical thickness, and MODIS-observed solar reflectance increase systematically in a wide transition zone around clouds. It is estimated that near-cloud changes in particle populations - including both aerosols and undetected cloud particles - are responsible for roughly two thirds of the observed increase in 0.55 μm MODIS reflectance. The results also indicate that 3-D radiative processes significantly contribute to near-cloud reflectance enhancements, while instrument blurring contributes significantly only within 1 km from clouds and then quickly diminishes with distance from clouds. © Author(s) 2013."
"6603453147;57206332144;","Analysis of co-located MODIS and CALIPSO observations near clouds",2012,"10.5194/amt-5-389-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866615047&doi=10.5194%2famt-5-389-2012&partnerID=40&md5=cdb22ccd8075cd00d6d38fd9d075248c","This paper aims at helping synergistic studies in combining data from different satellites for gaining new insights into two critical yet poorly understood aspects of anthropogenic climate change, aerosol-cloud interactions and aerosol radiative effects. In particular, the paper examines the way cloud information from the MODIS (MODerate resolution Imaging Spectroradiometer) imager can refine our perceptions based on CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar measurements about the systematic aerosol changes that occur near clouds. The statistical analysis of a yearlong dataset of co-located global maritime observations from the Aqua and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) satellites reveals that MODIS's multispectral imaging ability can greatly help the interpretation of CALIOP observations. The results show that imagers on Aqua and CALIPSO yield very similar pictures, and that the discrepancies-due mainly to wind drift and differences in view angle-do not significantly hinder aerosol measurements near clouds. By detecting clouds outside the CALIOP track, MODIS reveals that clouds are usually closer to clear areas than CALIOP data alone would suggest. The paper finds statistical relationships between the distances to clouds in MODIS and CALIOP data, and proposes a rescaling approach to statistically account for the impact of clouds outside the CALIOP track even when MODIS cannot reliably detect low clouds, for example at night or over sea ice. Finally, the results show that the typical distance to clouds depends on both cloud coverage and cloud type, and accordingly varies with location and season. In maritime areas perceived cloud free, the global median distance to clouds below 3 km altitude is in the 4-5 km range. © 2012 Author(s)."
"14829673100;","Global climate forcing by criteria air pollutants",2012,"10.1146/annurev-environ-082310-100824","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879912241&doi=10.1146%2fannurev-environ-082310-100824&partnerID=40&md5=7a31f0fedfb057d111afa12b06b2ec31","Ambient air pollution has significant impacts on global climate change in complex ways, involving both warming and cooling, and causes an estimated one million deaths every year. Modeling studies and observations from a suite of platforms, including those that are space based, have revealed that air pollution is a widespread global phenomenon. The net effect of air pollution is a global cooling that is masking 50% of the committed greenhouse gas (GHG) warming from the Industrial Revolution. Aggressive air pollution abatement and climate stabilization strategies that reduce cooling pollutants may lead to a short-term warming surge that is unsafe for ecosystems and the human population, imposing complex trade-offs in policy making. Conversely, selective reduction of warming air pollutants to mitigate near-term climate change may offer opportunities for synergistic policy development. Reducing and preventing the accumulation of fossil-fuel carbon dioxide (CO2) in the atmosphere is the only sustainable way to protect climate safety in the long term. Here, the current understanding of air pollution effects on global climate change is reviewed, including assessment by individual pollutant, precursor emission, economic sector, and policy-relevant scenarios. © Copyright ©2012 by Annual Reviews. All rights reserved."
"6602600408;57203200427;7407104838;7004024532;35221700500;35221494300;","Exploiting the weekly cycle as observed over Europe to analyse aerosol indirect effects in two climate models",2009,"10.5194/acp-9-8493-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70450280475&doi=10.5194%2facp-9-8493-2009&partnerID=40&md5=41b92a7bf57ac9c371626f0de2ef572f","A weekly cycle in aerosol pollution and some meteorological quantities is observed over Europe. In the present study we exploit this effect to analyse aerosol-cloud-radiation interactions. A weekly cycle is imposed on anthropogenic emissions in two general circulation models that include parameterizations of aerosol processes and cloud microphysics. It is found that the simulated weekly cycles in sulfur dioxide, sulfate, and aerosol optical depth in both models agree reasonably well with those observed indicating model skill in simulating the aerosol cycle. A distinct weekly cycle in cloud droplet number concentration is demonstrated in both observations and models. For other variables, such as cloud liquid water path, cloud cover, top-of-the-atmosphere radiation fluxes, precipitation, and surface temperature, large variability and contradictory results between observations, model simulations, and model control simulations without a weekly cycle in emissions prevent us from reaching any firm conclusions about the potential aerosol impact on meteorology or the realism of the modelled second aerosol indirect effects."
"6602873453;","A model study of smoke-haze influence on clouds and warm precipitation formation in Indonesia 1997/1998",2007,"10.1016/j.atmosenv.2007.04.050","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548805440&doi=10.1016%2fj.atmosenv.2007.04.050&partnerID=40&md5=2e9a34f10bafdb23f7fd97d4d23bb45f","In the last few decades, fire and smoke-haze occurrence increased in Indonesia by intentionally set land clearing fires and higher fire susceptibility of disturbed forests. Particularly, during El Niño years with prolonged droughts in Indonesia, land clearing fires become uncontrolled wildfires and produce large amounts of gaseous and particulate emissions. This paper investigates the influence of smoke-haze aerosols from such fires on clouds and precipitation over Indonesia during the El Niño event 1997/1998 by numerical modelling. Warm precipitation formation in both layered and convective clouds is calculated dependent on the atmospheric aerosol concentration. In the smoke-haze affected regions of Indonesia, aerosol-cloud interactions induce events with both precipitation suppression and increase compared to a reference simulation without aerosol-cloud interactions. The effect of precipitation suppression is found to dominate with about 2/3 of all precipitation modification events pointing to a prolongation of smoke-haze episodes. The corresponding convective cloud top height of shallow clouds is increased whereas distinct lower deep convective cloud top heights are found. The remaining about 1/3 events are characterised by increased precipitation and cloud liquid water content, accompanied by lower convective cloud top heights of shallow clouds and higher deep convective clouds. © 2007 Elsevier Ltd. All rights reserved."
"6507984183;7402370453;6701378450;","CCN predictions: Is theory sufficient for assessments of the indirect effect?",2006,"10.1029/2005GL025148","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646351964&doi=10.1029%2f2005GL025148&partnerID=40&md5=9666b3ec5849b6648d44c74d7b181f61","This study quantitatively assesses the sensitivity of cloud droplet number (CDNC) to errors in cloud condensation nuclei (CCN) predictions that arise from application of Köhler theory. The CDNC uncertainty is assessed by forcing a droplet activation parameterization with a comprehensive dataset of CCN activity and aerosol size and chemical composition obtained during the ICARTT field campaign in August 2004. Our analysis suggests that, for a diverse range of updraft velocity, droplet growth kinetics and airmass origin, the error in predicted CDNC is (at most) half of the CCN prediction error. This means that the typical 20-50% error in ambient CCN closure studies would result in a 10-25% error in CDNC. For the first time, a quantitative link between aerosol and CDNC prediction errors is available, and can be the basis of a robust uncertainty analysis of the first aerosol indirect effect. Copyright 2006 by the American Geophysical Union."
"6602600408;57203200427;7004714030;56283400100;","Impacts of greenhouse gases and aerosol direct and indirect effects on clouds and radiation in atmospheric GCM simulations of the 1930-1989 period",2004,"10.1007/s00382-004-0475-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-12744272116&doi=10.1007%2fs00382-004-0475-0&partnerID=40&md5=a7d3104fc717dcad0a3dbce07137e41b","Among anthropogenic perturbations of the Earth's atmosphere, greenhouse gases and aerosols are considered to have a major impact on the energy budget through their impact on radiative fluxes. We use three ensembles of simulations with the LMDZ general circulation model to investigate the radiative impacts of five species of greenhouse gases (CO2, CH4, N2O, CFC-11 and CFC-12) and sulfate aerosols for the period 1930-1989. Since our focus is on the atmospheric changes in clouds and radiation from greenhouse gases and aerosols, we prescribed sea-surface temperatures in these simulations. Besides the direct impact on radiation through the greenhouse effect and scattering of sunlight by aerosols, strong radiative impacts of both perturbations through changes in cloudiness are analysed. The increase in greenhouse gas concentration leads to a reduction of clouds at all atmospheric levels, thus decreasing the total greenhouse effect in the longwave spectrum and increasing absorption of solar radiation by reduction of cloud albedo. Increasing anthropogenic aerosol burden results in a decrease in high-level cloud cover through a cooling of the atmosphere, and an increase in the low-level cloud cover through the second aerosol indirect effect. The trend in low-level cloud lifetime due to aerosols is quantified to 0.5 min day-1 decade-1 for the simulation period. The different changes in high (decrease) and low-level (increase) cloudiness due to the response of cloud processes to aerosols impact shortwave radiation in a contrariwise manner, and the net effect is slightly positive. The total aerosol effect including the aerosol direct and first indirect effects remains strongly negative. © Springer-Verlag 2004."
"55417497600;55173596300;57208121852;7103158465;7403077486;49861577800;","Uncertainty from the choice of microphysics scheme in convection-permitting models significantly exceeds aerosol effects",2017,"10.5194/acp-17-12145-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85031315792&doi=10.5194%2facp-17-12145-2017&partnerID=40&md5=7c7b246e49120deb2c008a2db459c367","This study investigates the hydrometeor development and response to cloud droplet number concentration (CDNC) perturbations in convection-permitting model configurations. We present results from a real-data simulation of deep convection in the Congo basin, an idealised supercell case, and a warm-rain large-eddy simulation (LES). In each case we compare two frequently used double-moment bulk microphysics schemes and investigate the response to CDNC perturbations. We find that the variability among the two schemes, including the response to aerosol, differs widely between these cases. In all cases, differences in the simulated cloud morphology and precipitation are found to be significantly greater between the microphysics schemes than due to CDNC perturbations within each scheme. Further, we show that the response of the hydrometeors to CDNC perturbations differs strongly not only between microphysics schemes, but the inter-scheme variability also differs between cases of convection. Sensitivity tests show that the representation of autoconversion is the dominant factor that drives differences in rain production between the microphysics schemes in the idealised precipitating shallow cumulus case and in a subregion of the Congo basin simulations dominated by liquid-phase processes. In this region, rain mass is also shown to be relatively insensitive to the radiative effects of an overlying layer of ice-phase cloud. The conversion of cloud ice to snow is the process responsible for differences in cold cloud bias between the schemes in the Congo. In the idealised supercell case, thermodynamic impacts on the storm system using different microphysics parameterisations can equal those due to aerosol effects. These results highlight the large uncertainty in cloud and precipitation responses to aerosol in convection-permitting simulations and have important implications not only for process studies of aerosol-convection interaction, but also for global modelling studies of aerosol indirect effects. These results indicate the continuing need for tighter observational constraints of cloud processes and response to aerosol in a range of meteorological regimes. © 2017 Author(s)."
"23019619200;56060986400;56250185400;","Harmattan, Saharan heat low, and West African monsoon circulation: Modulations on the Saharan dust outflow towards the North Atlantic",2017,"10.5194/acp-17-10223-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028702917&doi=10.5194%2facp-17-10223-2017&partnerID=40&md5=9425a0cc2571eed443bc2af47955e731","The outflow of dust from the northern African continent towards the North Atlantic is stimulated by the atmospheric circulation over North Africa, which modulates the spatio-temporal distribution of dust source activation and consequently the entrainment of mineral dust into the boundary layer, as well as the transport of dust out of the source regions. The atmospheric circulation over the North African dust source regions, predominantly the Sahara and the Sahel, is characterized by three major circulation regimes: (1) the harmattan (trade winds), (2) the Saharan heat low (SHL), and (3) the West African monsoon circulation. The strength of the individual regimes controls the Saharan dust outflow by affecting the spatio-temporal distribution of dust emission, transport pathways, and deposition fluxes.<br><br>This study aims at investigating the atmospheric circulation pattern over North Africa with regard to its role favouring dust emission and dust export towards the tropical North Atlantic. The focus of the study is on summer 2013 (June to August), during which the SALTRACE (Saharan Aerosol Long-range TRansport and Aerosol-Cloud interaction Experiment) field campaign also took place. It involves satellite observations by the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) flying on board the geostationary Meteosat Second Generation (MSG) satellite, which are analysed and used to infer a data set of active dust sources. The spatio-temporal distribution of dust source activation frequencies (DSAFs) allows for linking the diurnal cycle of dust source activations to dominant meteorological controls on dust emission. In summer, Saharan dust source activations clearly differ from dust source activations over the Sahel regarding the time of day when dust emission begins. The Sahara is dominated by morning dust source activations predominantly driven by the breakdown of the nocturnal low-level jet. In contrast, dust source activations in the Sahel are predominantly activated during the second half of the day, when downdrafts associated with deep moist convection are the major atmospheric driver. Complementary to the satellite-based analysis on dust source activations and implications from their diurnal cycle, simulations on atmosphere and dust life cycle were performed using the mesoscale atmosphere-dust model system COSMO-Muscat (COSMO: COnsortium for Small-scale MOdelling; Muscat: MUltiScale Chemistry Aerosol Transport Model). Fields from this simulation were analysed regarding the variability of the harmattan, the Saharan heat low, and the monsoon circulation as well as their impact on the variability of the Saharan dust outflow towards the North Atlantic. This study illustrates the complexity of the interaction among the three major circulation regimes and their modulation of the North African dust outflow. Enhanced westward dust fluxes frequently appear following a phase characterized by a deep SHL. Ultimately, findings from this study contribute to the quantification of the interannual variability of the atmospheric dust burden. © Author(s) 2017."
"37062135300;6603624776;57041028000;6603615831;","LIMA (v1.0): A quasi two-moment microphysical scheme driven by a multimodal population of cloud condensation and ice freezing nuclei",2016,"10.5194/gmd-9-567-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84958171379&doi=10.5194%2fgmd-9-567-2016&partnerID=40&md5=76c56eebb2644d2cbf24ebaeede43460","The paper describes the LIMA (Liquid Ice Multiple Aerosols) quasi two-moment microphysical scheme, which relies on the prognostic evolution of an aerosol population, and the careful description of the nucleating properties that enable cloud droplets and pristine ice crystals to form from aerosols. Several modes of cloud condensation nuclei (CCN) and ice freezing nuclei (IFN) are considered individually. A special class of partially soluble IFN is also introduced. These ""aged"" IFN act first as CCN and then as IFN by immersion nucleation at low temperatures. All the CCN modes are in competition with each other, as expressed by the single equation of maximum supersaturation. The IFN are insoluble aerosols that nucleate ice in several ways (condensation, deposition and immersion freezing) assuming the singular hypothesis. The scheme also includes the homogeneous freezing of cloud droplets, the Hallett-Mossop ice multiplication process and the freezing of haze at very low temperatures. LIMA assumes that water vapour is in thermodynamic equilibrium with the population of cloud droplets (adjustment to saturation in warm clouds). In ice clouds, the prediction of the number concentration of the pristine ice crystals is used to compute explicit deposition and sublimation rates (leading to free under/supersaturation over ice). The autoconversion, accretion and self-collection processes shape the raindrop spectra. The initiation of the large crystals and aggregates category is the result of the depositional growth of large crystals beyond a critical size. Aggregation and riming are computed explicitly. Heavily rimed crystals (graupel) can experience a dry or wet growth mode. An advanced version of the scheme includes a separate hail category of particles forming and growing exclusively in the wet growth mode. The sedimentation of all particle types is included. The LIMA scheme is inserted into the Meso-NH cloudresolving mesoscale model. The flexibility of LIMA is illustrated by two 2-D experiments. The first one highlights the sensitivity of orographic ice clouds to IFN types and IFN concentrations. Then a squall line case discusses the microstructure of a mixed-phase cloud and the impacts of pure CCN and IFN polluting plumes. The experiments show that LIMA responds well to the complex nature of aerosol-cloud interactions, leading to different pathways for cloud and precipitation formation. © 2016 Author(s)."
"55416060200;55802355600;56942554300;36538539800;56095429600;55624488227;7004444634;7202010686;7405728922;","Incorporation of new particle formation and early growth treatments into WRF/Chem: Model improvement, evaluation, and impacts of anthropogenic aerosols over East Asia",2016,"10.1016/j.atmosenv.2015.05.046","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949626196&doi=10.1016%2fj.atmosenv.2015.05.046&partnerID=40&md5=86e91806323ca58fcdf30f9fca24845c","New particle formation (NPF) provides an important source of aerosol particles and cloud condensation nuclei, which may result in enhanced cloud droplet number concentration (CDNC) and cloud shortwave albedo. In this work, several nucleation parameterizations and one particle early growth parameterization are implemented into the online-coupled Weather Research and Forecasting model coupled with chemistry (WRF/Chem) to improve the model's capability in simulating NPF and early growth of ultrafine particles over East Asia. The default 8-bin over the size range of 39 nm-10 μm used in the Model for Simulating Aerosol Interactions and Chemistry aerosol module is expanded to the 12-bin over 1 nm-10 μm to explicitly track the formation and evolution of new particles. Although model biases remain in simulating H2SO4, condensation sink, growth rate, and formation rate, the evaluation of July 2008 simulation identifies a combination of three nucleation parameterizations (i.e., COMB) that can best represent the atmospheric nucleation processes in terms of both surface nucleation events and the resulting vertical distribution of ultrafine particle concentrations. COMB consists of a power law of Wang et al. (2011) based on activation theory for urban areas in planetary boundary layer (PBL), a power law of Boy et al. (2008) based on activation theory for non-urban areas in PBL, and the ion-mediated nucleation parameterization of YU10 for above PBL. The application and evaluation of the improved model with 12-bin and the COMB nucleation parameterization in East Asia during January, April, July, and October in 2001 show that the model has an overall reasonably good skill in reproducing most observed meteorological variables and surface and column chemical concentrations. Relatively large biases in simulated precipitation and wind speeds are due to inaccurate surface roughness and limitations in model treatments of cloud formation and aerosol-cloud-precipitation interactions. Large biases in the simulated surface concentrations of PM10, NOx, CO, SO2, and VOCs at some sites are due in part to possible underestimations of emissions and in part to inaccurate meteorological predictions. The simulations of 2001 show that anthropogenic aerosols can increase aerosol optical depth by 64.0-228.3%, CDNC by 40.2-76.4%, and cloud optical thickness by 14.3-25.3%; they can reduce surface net shortwave radiation by up to 42.5-52.8 W m-2, 2-m temperature by up to 0.34-0.83 °C, and PBL height by up to 76.8-125.9 m. Such effects are more significant than those previously reported for the U.S. and Europe. © 2015 Elsevier Ltd."
"56974294800;35223783100;7003942283;","Snow-borne nanosized particles: Abundance, distribution, composition, and significance in ice nucleation processes",2015,"10.1002/2015JD023773","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955170451&doi=10.1002%2f2015JD023773&partnerID=40&md5=bf16f1e05a5cb8df5b1ea4c1ecd3e1b9","Physicochemical processes of nucleation constitute a major uncertainty in understanding aerosol-cloud interactions. To improve the knowledge of the ice nucleation process, we characterized physical, chemical, and biological properties of fresh snow using a suite of state-of-the-art techniques based on mass spectrometry, electron microscopy, chromatography, and optical particle sizing. Samples were collected at two North American Arctic sites, as part of international campaigns (2006 and 2009), and in the city of Montreal, Canada, over the last decade. Particle size distribution analyses, in the range of 3 nm to 10 μm, showed that nanosized particles are the most numerous (38–71%) in fresh snow, with a significant portion (11 to 19%) less than 100nm in size. Particles with diameters less than 200nm consistently exhibited relatively high ice-nucleating properties (on average ranged from -19.6 ± 2.4 to -8.1 ± 2.6°C). Chemical analysis of the nanosized fraction suggests that they contain bioorganic materials, such as amino acids, as well as inorganic compounds with similar characteristics to mineral dust. The implication of nanoparticle ubiquity and abundance in diverse snow ecosystems are discussed in the context of their importance in understanding atmospheric nucleation processes. © 2015. American Geophysical Union. All Rights Reserved."
"22635081500;7004160106;6603081424;7409322518;7402933297;7203062717;","Modeling the influences of aerosols on pre-monsoon circulation and rainfall over Southeast Asia",2014,"10.5194/acp-14-6853-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903849552&doi=10.5194%2facp-14-6853-2014&partnerID=40&md5=101776cb7500d9d4a8357c732f7ffaab","We conduct several sets of simulations with a version of NASA's Goddard Earth Observing System, version 5, (GEOS-5) Atmospheric Global Climate Model (AGCM) equipped with a two-moment cloud microphysical scheme to understand the role of biomass burning aerosol (BBA) emissions in Southeast Asia (SEA) in the pre-monsoon period of February-May. Our experiments are designed so that both direct and indirect aerosol effects can be evaluated. For climatologically prescribed monthly sea surface temperatures, we conduct sets of model integrations with and without biomass burning emissions in the area of peak burning activity, and with direct aerosol radiative effects either active or inactive. Taking appropriate differences between AGCM experiment sets, we find that BBA affects liquid clouds in statistically significantly ways, increasing cloud droplet number concentrations, decreasing droplet effective radii (i.e., a classic aerosol indirect effect), and locally suppressing precipitation due to a deceleration of the autoconversion process, with the latter effect apparently also leading to cloud condensate increases. Geographical re-arrangements of precipitation patterns, with precipitation increases downwind of aerosol sources are also seen, most likely because of advection of weakly precipitating cloud fields. Somewhat unexpectedly, the change in cloud radiative effect (cloud forcing) at surface is in the direction of lesser cooling because of decreases in cloud fraction. Overall, however, because of direct radiative effect contributions, aerosols exert a net negative forcing at both the top of the atmosphere and, perhaps most importantly, the surface, where decreased evaporation triggers feedbacks that further reduce precipitation. Invoking the approximation that direct and indirect aerosol effects are additive, we estimate that the overall precipitation reduction is about 40% due to the direct effects of absorbing aerosols, which stabilize the atmosphere and reduce surface latent heat fluxes via cooler land surface temperatures. Further refinements of our two-moment cloud microphysics scheme are needed for a more complete examination of the role of aerosol-convection interactions in the seasonal development of the SEA monsoon. © 2014 Author(s)."
"57194679347;23991203900;16444006500;27067996900;6701620591;15519671300;56262351900;6603796496;6603729297;8705440100;55800347700;7006712143;6507755223;","Long-term measurements of cloud droplet concentrations and aerosol–cloud interactions in continental boundary layer clouds",2013,"10.3402/tellusb.v65i0.20138","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893304396&doi=10.3402%2ftellusb.v65i0.20138&partnerID=40&md5=1e69ad48316b1406f0ccfef34e9d334f","The effects of aerosol on cloud droplet effective radius (Reff), cloud optical thickness and cloud droplet number concentration (Nd) are analysed both from long-term direct ground-based in situ measurements conducted at the Puijo measurement station in Eastern Finland and from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument onboard the Terra and Aqua satellites. The mean in situ Nd during the period of study was 217 cm–3, while the MODIS-based Nd was 171 cm–3. The absolute values, and the dependence of both Nd observations on the measured aerosol number concentration in the accumulation mode (Nacc), are quite similar. In both data sets Nd is clearly dependent on Nacc, for Nacc values lower than approximately 450 cm–3. Also, the values of the aerosol–cloud-interaction parameter [ACI=(1/3)*d ln(Nd)/d ln(Nacc)] are quite similar for Nacc&lt;400 cm–3 with values of 0.16 and 0.14 from in situ and MODIS measurements, respectively. With higher Nacc (&gt;450 cm–3) N d increases only slowly. Similarly, the effect of aerosol on MODIS-retrieved Reff is visible only at low Nacc values. In a sub set of data, the cloud and aerosol properties were measured simultaneously. For that data the comparison between MODIS-derived Nd and directly measured Nd, or the cloud droplet number concentration estimated from Nacc values (Nd,p), shows a correlation, which is greatly improved after careful screening using a ceilometer to make sure that only single cloud layers existed. This suggests that such determination of the number of cloud layers is very important when trying to match ground-based measurements to MODIS measurements. © 2013 I. Ahmad et al."
"23995325300;26643041500;7004174939;","Aerosol-cloud interaction determined by both in situ and satellite data over a northern high-latitude site",2010,"10.5194/acp-10-10987-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649428866&doi=10.5194%2facp-10-10987-2010&partnerID=40&md5=7a0a6bb78c066dff505a01c0702c442e","The first aerosol indirect effect over a clean, northern high-latitude site was investigated by determining the aerosol cloud interaction (ACI) using three different approaches; ground-based in situ measurements, combined ground-based in situ measurements and satellite retrievals and using only satellite retrievals. The obtained values of ACI were highest for in situ ground-based data, clearly lower for combined ground-based and satellite data, and lowest for data relying solely on satellite retrievals. One of the key findings of this study was the high sensitivity of ACI to the definition of the aerosol burden. We showed that at least a part of the variability in ACI can be explained by how different investigators have related different cloud properties to ""aerosol burden"". © 2010 Author(s)."
"23568239000;55917711400;","Relationships between mineral dust and cloud properties in the West African Sahel",2010,"10.5194/acp-10-6901-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955043396&doi=10.5194%2facp-10-6901-2010&partnerID=40&md5=495fdb018ef723368d70353f816db0ae","Aerosol cloud interactions are known to be of great importance to many parts of the climate system. Five years of observations from three different satellites (Aqua, ENVISAT and Meteosat Second Generation) are used to statistically analyse the relationship of mineral dust aerosol, separated from other aerosol species, with monsoon season cloud state in the West African Sahel domain. Additionally, observations of the Tropical Rainfall Measuring Mission are used for discrimination of dry and wet seasons. The aerosol-cloud- interactions are analysed separately by season and air mass in order to minimise spurious correlations with meteorological conditions. The detailed analysis uncovers different counteracting relationships of the mineral dust aerosol with the cloud state, which is also evident from an analysis of the spatial distribution patterns of cloud properties changes with dust activity. The aerosol-cloud relationships found from the analysis of this multiple year dataset are mainly consistent with the hypothesis of a suppression of convective activity, but also indications of lifetime enhancement and thus increased cloud cover and convective intensity are found in some subsets. © 2010 Author(s)."
"6603796496;27067996900;8705440100;7004935190;6701620591;23995325300;6602753217;7006712143;7007039218;","Overview of the research activities and results at Puijo semi-urban measurement station",2009,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-69949105266&partnerID=40&md5=9e989c73953c2fea2903e4b1171172ad","We introduce a new measurement station that we established in 2005 in an observation tower at Puijo in Kuopio. At Puijo we measure several meteorological parameters, aerosol and cloud droplet size distribution, aerosol optical properties and trace gas concentrations. We summarize the research activities at the station during its three-year history and present overall results. We compare the results from Puijo with those measured at the ground level in Kuopio and at the Finnish background stations. We also characterize the measured parameters according to the wind direction and air mass origins, based on trajectory analysis, for the effects of local and remote sources. Our conclusion is that the Puijo tower is a very good place to gather experimental data on cloud formation and aerosol-cloud interaction. In addition to cloud experiments, we would suggest the Puijo measurement station for studies of particle formation, which we also observed frequently. © 2009."
"6603164079;7006708207;35498501900;56128808100;","Time-scale analysis of marine boundary layer aerosol evolution: Lagrangian case studies under clean and polluted cloudy conditions",2000,"10.3402/tellusb.v52i2.16169","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034083985&doi=10.3402%2ftellusb.v52i2.16169&partnerID=40&md5=3bd1a8ed5138dd85b80c13394bc3efb6","Significant changes were observed in the sub-micron aerosol size distribution during a clean and a polluted Lagrangian study of marine boundary layer (MBL) aerosol and meteorological evolution during ACE-2. These changes were accompanied by significant alterations in boundary layer meteorology and structure. The clean case (LAG1) shows a reduction in the fine mode aerosol from 1050 cm-3 to 750 cm-3 and an increase in the accumulation mode concentration from 76 cm-3 to 162 cm-3 over 26 h. Dominant meteorological features during the same period comprised a reduction in boundary layer height from ~1500 m to ~800 m and an increase in the surface layer wind speed from 5 m s-1 to 15 m s-1. A detailed time-scale analysis, based upon measured data and including processes such as coagulation, condensation, deposition, chemical processing, sea-salt flux and entrainment, suggests that the dominant loss process for fine mode aerosol is coagulation, while the enhancement of accumulation mode aerosol can be almost totally ascribed to enhanced sea-salt aerosol flux into the reduced mixed layer volume. Aerosol size distributions from the polluted Lagrangian (LAG2) indicated little growth in particle diameter, and both fine and accumulation mode were observed to decrease in concentration from 2700 cm-3 to 1150 cm-3 and from 670 cm-3 to 430 cm-3 in 26 h, respectively. Dilution with cleaner free tropospheric air as the boundary layer height increased from ~500 m to &gt;1000 m is suggested to be the primary factor relating to reduced aerosol concentrations in this case. To a smaller extent, coagulation and precipitation scavenging were calculated to be of some importance. For both Lagrangian case studies, meteorological changes, followed by physical aerosol-cloud interactions, appear to have the greatest influence on the MBL aerosol size distribution and number concentration over the given time-scale."
"49864573500;57194491444;35740180800;57203315797;56536745100;57203318983;23978405300;24764483400;7801353107;18635820300;6507755223;37051480000;7006712143;35459245100;57205787051;57203053317;24398842400;7005304841;7004469744;7103016965;","A model intercomparison of CCN-limited tenuous clouds in the high Arctic",2018,"10.5194/acp-18-11041-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85051253863&doi=10.5194%2facp-18-11041-2018&partnerID=40&md5=ae8600d0035007297d3c99d2e35e6857","We perform a model intercomparison of summertime high Arctic (&gt; 80° N) clouds observed during the 2008 Arctic Summer Cloud Ocean Study (ASCOS) campaign, when observed cloud condensation nuclei (CCN) concentrations fell below 1 cm-3. Previous analyses have suggested that at these low CCN concentrations the liquid water content (LWC) and radiative properties of the clouds are determined primarily by the CCN concentrations, conditions that have previously been referred to as the tenuous cloud regime. The intercomparison includes results from three large eddy simulation models (UCLALES-SALSA, COSMO-LES, and MIMICA) and three numerical weather prediction models (COSMO-NWP, WRF, and UM-CASIM). We test the sensitivities of the model results to different treatments of cloud droplet activation, including prescribed cloud droplet number concentrations (CDNCs) and diagnostic CCN activation based on either fixed aerosol concentrations or prognostic aerosol with in-cloud processing. There remains considerable diversity even in experiments with prescribed CDNCs and prescribed ice crystal number concentrations (ICNC). The sensitivity of mixed-phase Arctic cloud properties to changes in CDNC depends on the representation of the cloud droplet size distribution within each model, which impacts autoconversion rates. Our results therefore suggest that properly estimating aerosol-cloud interactions requires an appropriate treatment of the cloud droplet size distribution within models, as well as in situ observations of hydrometeor size distributions to constrain them. The results strongly support the hypothesis that the liquid water content of these clouds is CCN limited. For the observed meteorological conditions, the cloud generally did not collapse when the CCN concentration was held constant at the relatively high CCN concentrations measured during the cloudy period, but the cloud thins or collapses as the CCN concentration is reduced. The CCN concentration at which collapse occurs varies substantially between models. Only one model predicts complete dissipation of the cloud due to glaciation, and this occurs only for the largest prescribed ICNC tested in this study. Global and regional models with either prescribed CDNCs or prescribed aerosol concentrations would not reproduce these dissipation events. Additionally, future increases in Arctic aerosol concentrations would be expected to decrease the frequency of occurrence of such cloud dissipation events, with implications for the radiative balance at the surface. Our results also show that cooling of the sea-ice surface following cloud dissipation increases atmospheric stability near the surface, further suppressing cloud formation. Therefore, this suggests that linkages between aerosol and clouds, as well as linkages between clouds, surface temperatures, and atmospheric stability need to be considered for weather and climate predictions in this region. © 2018 Author(s)."
"55577875600;57192212652;55717074000;55802246600;56384704800;57200055610;7406500188;","Impacts of global open-fire aerosols on direct radiative, cloud and surface-albedo effects simulated with CAM5",2016,"10.5194/acp-16-14805-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85001000760&doi=10.5194%2facp-16-14805-2016&partnerID=40&md5=57c72589147298ee90b68f856cb98436","Aerosols from open-land fires could significantly perturb the global radiation balance and induce climate change. In this study, Community Atmosphere Model version 5 (CAM5) with prescribed daily fire aerosol emissions is used to investigate the spatial and seasonal characteristics of radiative effects (REs, relative to the case of no fires) of open-fire aerosols including black carbon (BC) and particulate organic matter (POM) from 2003 to 2011. The global annual mean RE from aerosol-radiation interactions (REari) of all fire aerosols is 0.16±0.01Wm-2 (1σ uncertainty), mainly due to the absorption of fire BC (0.25±0.01Wm-2), while fire POM induces a small effect (-0.05 and 0.04±0.01Wm-2 based on two different methods). Strong positive REari is found in the Arctic and in the oceanic regions west of southern Africa and South America as a result of amplified absorption of fire BC above low-level clouds, in general agreement with satellite observations. The global annual mean RE due to aerosol-cloud interactions (REaci) of all fire aerosols is -0.70±0.05Wm-2, resulting mainly from the fire POM effect (-0.59±0.03Wm-2). REari (0.43±0.03Wm-2) and REaci (-1.38±0.23Wm-2) in the Arctic are stronger than in the tropics (0.17±0.02 and -0.82±0.09Wm-2 for REari and REaci), although the fire aerosol burden is higher in the tropics. The large cloud liquid water path over land areas and low solar zenith angle of the Arctic favor the strong fire aerosol REaci (up to -15Wm-2) during the Arctic summer. Significant surface cooling, precipitation reduction and increasing amounts of low-level cloud are also found in the Arctic summer as a result of the fire aerosol REaci based on the atmosphere-only simulations. The global annual mean RE due to surface-albedo changes (REsac) over land areas (0.03±0.10Wm-2) is small and statistically insignificant and is mainly due to the fire BC-in-snow effect (0.02Wm-2) with the maximum albedo effect occurring in spring (0.12Wm-2) when snow starts to melt. © Author(s) 2016. CC Attribution 3.0 License."
"57193798535;56422246700;25624725200;57191955465;35459535800;25961216800;7006415284;8550791300;","The immersion freezing behavior of ash particles from wood and brown coal burning",2016,"10.5194/acp-16-13911-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84995520558&doi=10.5194%2facp-16-13911-2016&partnerID=40&md5=2dbbf496223168080bb1713e51f68a18","It is generally known that ash particles from coal combustion can trigger ice nucleation when they interact with water vapor and/or supercooled droplets. However, data on the ice nucleation of ash particles from different sources, including both anthropogenic and natural combustion processes, are still scarce. As fossil energy sources still fuel the largest proportion of electric power production worldwide, and biomass burning contributes significantly to the global aerosol loading, further data are needed to better assess the ice nucleating efficiency of ash particles. In the framework of this study, we found that ash particles from brown coal (i.e., lignite) burning are up to 2 orders of magnitude more ice active in the immersion mode below ĝ'32ĝ€°C than those from wood burning. Fly ash from a coal-fired power plant was shown to be the most efficient at nucleating ice. Furthermore, the influence of various particle generation methods on the freezing behavior was studied. For instance, particles were generated either by dispersion of dry sample material, or by atomization of ash-water suspensions, and then led into the Leipzig Aerosol Cloud Interaction Simulator (LACIS) where the immersion freezing behavior was examined. Whereas the immersion freezing behavior of ashes from wood burning was not affected by the particle generation method, it depended on the type of particle generation for ash from brown coal. It was also found that the common practice of treating prepared suspensions in an ultrasonic bath to avoid aggregation of particles led to an enhanced ice nucleation activity. The findings of this study suggest (a) that ash from brown coal burning may influence immersion freezing in clouds close to the source and (b) that the freezing behavior of ash particles may be altered by a change in sample preparation and/or particle generation. © The Author(s) 2016."
"55258548500;57200702127;56158925300;56158523800;56611366900;7404865816;","Distinct impacts of aerosols on an evolving continental cloud complex during the RACORO field campaign",2016,"10.1175/JAS-D-15-0361.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84988318561&doi=10.1175%2fJAS-D-15-0361.1&partnerID=40&md5=a290aee1fe086fa38c564f6bffc0ab14","A continental cloud complex, consisting of shallow cumuli, a deep convective cloud (DCC), and stratus, is simulated by a cloud-resolving Weather Research and Forecasting Model to investigate the aerosol microphysical effect (AME) and aerosol radiative effect (ARE) on the various cloud regimes and their transitions during the Department of Energy Routine Atmospheric Radiation Measurement Aerial Facility Clouds with Low Optical Water Depths Optical Radiative Observations (RACORO) campaign. Under an elevated aerosol loading with AME only, a reduced cloudiness for the shallow cumuli and stratus resulted from more droplet evaporation competing with suppressed precipitation, but an enhanced cloudiness for the DCC is attributed to more condensation. With the inclusion of ARE, the shallow cumuli are suppressed owing to the thermodynamic effects of light-absorbing aerosols. The responses of DCC and stratus to aerosols are monotonic with AME only but nonmonotonic with both AME and ARE. The DCC is invigorated because of favorable convection and moisture conditions at night induced by daytime ARE, via the so-called aerosol-enhanced conditional instability mechanism. The results reveal that the overall aerosol effects on the cloud complex are distinct from the individual cloud types, highlighting that the aerosol-cloud interactions for diverse cloud regimes and their transitions need to be evaluated to assess the regional and global climatic impacts. © 2016 American Meteorological Society."
"7404548584;6507631512;7101846027;7004444946;35520130200;6602448665;53870839800;7102069638;55241984000;8359591200;55470017900;7004124427;7005399437;7101984634;6603652793;57092490700;6603775815;6701718281;7202201947;8544522500;55725404100;56518420000;7404164395;57203378050;","Observations of the temporal variability in aerosol properties and their relationships to meteorology in the summer monsoonal South China Sea/East Sea: The scale-dependent role of monsoonal flows, the Madden-Julian Oscillation, tropical cyclones, squall lines and cold pools",2015,"10.5194/acp-15-1745-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923358749&doi=10.5194%2facp-15-1745-2015&partnerID=40&md5=6ae1f6e7579e7f56dd152cc8e3104904","In a joint NRL/Manila Observatory mission, as part of the Seven SouthEast Asian Studies program (7-SEAS), a 2-week, late September 2011 research cruise in the northern Palawan archipelago was undertaken to observe the nature of southwest monsoonal aerosol particles in the South China Sea/East Sea (SCS/ES) and Sulu Sea region. Previous analyses suggested this region as a receptor for biomass burning from Borneo and Sumatra for boundary layer air entering the monsoonal trough. Anthropogenic pollution and biofuel emissions are also ubiquitous, as is heavy shipping traffic. Here, we provide an overview of the regional environment during the cruise, a time series of key aerosol and meteorological parameters, and their interrelationships. Overall, this cruise provides a narrative of the processes that control regional aerosol loadings and their possible feedbacks with clouds and precipitation. While 2011 was a moderate El Ninõ-Southern Oscillation (ENSO) La Ninã year, higher burning activity and lower precipitation was more typical of neutral conditions. The large-scale aerosol environment was modulated by the Madden-Julian Oscillation (MJO) and its associated tropical cyclone (TC) activity in a manner consistent with the conceptual analysis performed by Reid et al. (2012). Advancement of the MJO from phase 3 to 6 with accompanying cyclogenesis during the cruise period strengthened flow patterns in the SCS/ES that modulated aerosol life cycle. TC inflow arms of significant convection sometimes span from Sumatra to Luzon, resulting in very low particle concentrations (minimum condensation nuclei CN &lt; 150 cm-3, non-sea-salt PM2.5 &lt; 1 μg m-3). However, elevated carbon monoxide levels were occasionally observed suggesting passage of polluted air masses whose aerosol particles had been rained out. Conversely, two drier periods occurred with higher aerosol particle concentrations originating from Borneo and Southern Sumatra (CN &gt; 3000 cm-3 and non-sea-salt PM2.5 10-25 μg m-3). These cases corresponded with two different mechanisms of convection suppression: lower free-tropospheric dry-air intrusion from the Indian Ocean, and large-scale TC-induced subsidence. Veering vertical wind shear also resulted in aerosol transport into this region being mainly in the marine boundary layer (MBL), although lower free troposphere transport was possible on the western sides of Sumatra and Borneo. At the hourly time scale, particle concentrations were observed to be modulated by integer factors through convection and associated cold pools. Geostationary satellite observations suggest that convection often takes the form of squall lines, which are bowed up to 500 km across the monsoonal flow and 50 km wide. These squall lines, initiated by cold pools from large thunderstorms and likely sustained by a veering vertical wind shear and aforementioned mid-troposphere dry layers, propagated over 1500 km across the entirety of the SCS/ES, effectively cutting large swaths of MBL aerosol particles out of the region. Our conclusion is that while large-scale flow patterns are very important in modulating convection, and hence in allowing long-range transport of smoke and pollution, more short-lived phenomena can modulate cloud condensation nuclei (CCN) concentrations in the region, resulting in pockets of clean and polluted MBL air. This will no doubt complicate large scale comparisons of aerosol-cloud interaction. © 2015 Author(s)."
"35069282600;8067118800;56418532300;7202899330;","Ship track observations of a reduced shortwave aerosol indirect effect in mixed-phase clouds",2014,"10.1002/2014GL061320","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911426422&doi=10.1002%2f2014GL061320&partnerID=40&md5=8b6824ac42c69b4b411b37c435ca994e","Aerosol influences on clouds are a major source of uncertainty to our understanding of forced climate change. Increased aerosol can enhance solar reflection from clouds countering greenhouse gas warming. Recently, this indirect effect has been extended from water droplet clouds to other types including mixed-phase clouds. Aerosol effects on mixed-phase clouds are important because of their fundamental role on sea ice loss and polar climate change, but very little is known about aerosol effects on these clouds. Here we provide the first analysis of the effects of aerosol emitted from ship stacks into mixed-phase clouds. Satellite observations of solar reflection in numerous ship tracks reveal that cloud albedo increases 5 times more in liquid clouds when polluted and persist 2 h longer than in mixed-phase clouds. These results suggest that seeding mixed-phase clouds via shipping aerosol is unlikely to provide any significant counterbalancing solar radiative cooling effects in warming polar regions. Key Points Ship tracks discovered in ice clouds reveal a reduced aerosol indirect effectShip emissions enhance ice production in low-level clouds ©2014. American Geophysical Union. All Rights Reserved."
"14019100300;35068194500;22978151200;55915206300;55717074000;56384704800;7006306835;50261552200;7404829395;","Evaluating clouds, aerosols, and their interactions in three global climate models using satellite simulators and observations",2014,"10.1002/2014JD021722","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018214798&doi=10.1002%2f2014JD021722&partnerID=40&md5=12e3540e32a99b594282f463a7c16e07","Accurately representing aerosol-cloud interactions in global climate models is challenging. As parameterizations evolve, it is important to evaluate their performance with appropriate use of observations. In this investigation we compare aerosols, clouds, and their interactions in three global climate models (Geophysical Fluid Dynamics Laboratory-Atmosphere Model 3 (AM3), National Center for Atmospheric Research-Community Atmosphere Model 5 (CAM5), and Goddard Institute for Space Studies-ModelE2) to Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations. Modeled cloud properties are diagnosed using a MODIS simulator. Cloud droplet number concentrations (N) are computed identically from satellite-simulated and MODIS-observed values of liquid cloud optical depth and droplet effective radius. We find that aerosol optical depth (τa) simulated by models is similar to observations in many regions around the globe. For N, AM3 and CAM5 capture the observed spatial pattern of higher values in coastal marine stratocumulus versus remote ocean regions, though modeled values, in general, are higher than observed. Aerosol-cloud interactions were computed as the sensitivity of ln(N) to ln(τa) for coastal marine liquid clouds near South Africa (SAF) and Southeast Asia where τa varies in time. AM3 and CAM5 are more sensitive than observations, while the sensitivity for ModelE2 is statistically insignificant. This widely used sensitivity could be subject to misinterpretation due to the confounding influence of meteorology on both aerosols and clouds. A simple framework for assessing the sensitivity of ln(N) to ln(τa) at constant meteorology illustrates that observed sensitivity can change from positive to statistically insignificant when including the confounding influence of relative humidity. Satellite-simulated versus standard model values of N are compared; for CAM5 in SAF, standard model values are significantly lower than satellite-simulated values with a bias of 83 cm3. © 2014. American Geophysical Union. All rights reserved."
"7005304841;57198208348;57196600097;","Impact of two-way aerosol-cloud interaction and changes in aerosol size distribution on simulated aerosol-induced deep convective cloud sensitivity",2011,"10.1175/2010JAS3651.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955006055&doi=10.1175%2f2010JAS3651.1&partnerID=40&md5=454f0eebd537161dab4abf8e9895c255","Recent cloud-resolving model studies of single (isolated) deep convective clouds have shown contradicting results regarding the response of the deep convection to changes in the aerosol concentration. In the present study, a cloud-resolving model including explicit aerosol physics and chemistry is used to examine how the complexity of the aerosolmodel, the size of the aerosols, and the aerosol activation parameterization influence the aerosol-induced deep convective cloud sensitivity. Six sensitivity series are conducted. A significant difference in the aerosol-induced deep convective cloud sensitivity is found when using different complexities of the aerosol model and different aerosol activation parameterizations. In particular, graupel impaction scavenging of aerosols appears to be a crucial process because it efficiently may limit the number of cloud condensation nuclei (CCN) at a critical stage of cloud development and thereby dampen the convection. For the simulated case, a 100%increase in aerosol concentration results in a difference in average updraft between the various sensitivity series that is as large as the average updraft increase itself. The change in graupel and rain formation also differs significantly. The sign of the change in precipitation is not always directly proportional to the change in updraft velocity and several of the sensitivity series display a decrease of the rain amount with increasing updraft velocity. This result illustrates the need to account for changes in evaporation processes and subsequent cooling when assessing aerosol effects on deep convective strength. The model simulations also show that an increased number of aerosols in the Aitken mode (here defined by 23 ≤ d ≤ 100.0 nm) results in a larger impact on the convective strength compared to an increased number of aerosols in the accumulation mode (here defined by 100 ≤ d ≤ 900.0 nm).When accumulation mode aerosols are activated and grow at the beginning of the cloud cycle, the supersaturation near the cloud base is lowered, which to some extent limits further aerosol activation. The simulations indicate a need to better understand and represent the two-way interaction between aerosols and clouds when studying aerosol-induced deep convective cloud sensitivity. © 2011 American Meteorological Society."
"6603333885;7006270084;","Nonlinear advection algorithms applied to interrelated tracers: Errors and implications for modeling aerosol-cloud interactions",2009,"10.1175/2008MWR2626.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68249158191&doi=10.1175%2f2008MWR2626.1&partnerID=40&md5=38aa51b73686d1d064fcee81b994e5e2","Monotonicity constraints and gradient-preserving flux corrections employed by many advection algorithms used in atmospheric models make these algorithms nonlinear. Consequently, any relations among model variables transported separately are not necessarily preserved in such models. These errors cannot be revealed by traditional algorithm testing based on advection of a single tracer. New types of tests are developed and conducted to evaluate the monotonicity of a sum of several number mixing ratios advected independently of each other - as is the case, for example, in models using bin or sectional representations of aerosol or cloud particle size distributions. The tests show that when three tracers with an initially constant sum are advected separately in one-dimensional constant velocity flow, local errors in their sum can be on the order of 10%.When cloudlike interactions are allowed among the tracers in the idealized ""cloud base"" test, errors in the sum of three mixing ratios can reach 30%. Several approaches to eliminate the error are suggested, all based on advecting the sum as a separate variable and then using it to normalize the sum of the individual tracers' mixing ratios or fluxes.Asimple scalar normalization ensures the monotonicity of the total number mixing ratio and positive definiteness of the variables, but the monotonicity of individual tracers is no longer maintained. More involved flux normalization procedures are developed for the flux-based advection algorithms to maintain the monotonicity for individual scalars and their sum. © 2009 American Meteorological Society."
"56611366900;7005862399;7005263785;55740664200;24765069600;","Theoretical expression for the autoconversion rate of the cloud droplet number concentration",2007,"10.1029/2007GL030389","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35948953542&doi=10.1029%2f2007GL030389&partnerID=40&md5=042e1e54269173b5b4848818c93ff68e","Accurate parameterization of the autoconversion rate of the cloud droplet concentration (number autoconversion rate in cm-3 s-1) is critical for evaluating aerosol indirect effects using climate models; however, existing parameterizations are empirical at best. A theoretical expression is presented in this contribution that analytically relates the number autoconversion rate to the liquid water content, droplet concentration and relative dispersion of the cloud droplet size distribution. The analytical expression is theoretically derived by generalizing the analytical formulation previously developed for the autoconversion rate of the cloud liquid water content (mass autoconversion rate in g cm-3 s-1). Further examination of the theoretical number and mass autoconversion rates reveals that the former is not linearly proportional to the latter as commonly assumed in existing parameterizations. The formulation forms a solid theoretical basis for developing multi-moment representation of the autoconversion process in atmospheric models in general. Copyright 2007 by the American Geophysical Union."
"7003591311;7004174939;57127099400;35464731600;","Analysis of smoke impact on clouds in Brazilian biomass burning regions: An extension of Twomey's approach",2001,"10.1029/2001JD000732","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983108497&doi=10.1029%2f2001JD000732&partnerID=40&md5=d1c64bc68b37d97bfe38ac14965627dd","Satellite remote sensing of smoke aerosol-cloud interaction during the recent Smoke, Clouds, and Radiation-Brazil (SCAR-B) experiment is analyzed to explore the factors that determine the magnitude of the cloud response to smoke aerosol. Analysis of 2 years worth of data revealed that the response is greatest in the north of Brazil where aerosol optical depth is smallest, and tends to decrease as one moves southward, and as aerosol optical depth increases. Saturation in this response occurs at an aerosol optical depth of 0.8 in 1987 and 0.4 in 1995. To explore the reasons for this, a framework is developed in which the satellite-measured response can be compared to simple analytical models of this response and to numerical models of smoke aerosol-cloud interaction. Three types of response are identified: (1) cloud droplet concentrations increase with increasing aerosol loading, followed by saturation in the response at high concentrations; (2) as in type 1, followed by increasing droplet concentrations with further increases in aerosol loading. This increase in droplet concentration is due to the suppression of supersaturation by abundant large particles, which prevents the activation of smaller particles. This enables renewed activation of larger particles when smoke loadings exceed some threshold; (3) as in type 1, followed by a decrease in droplet number concentrations with increasing aerosol loading as intense competition for vapor evaporates the smaller droplets. The latter implies an unexpected increase in drop size with increasing smoke loading. The conditions under which each of these responses are expected to occur are discussed. It is shown that although to first-order smoke optical depth is a good proxy for aerosol indirect forcing, under some conditions the size distribution and hygroscopicity can be important factors. We find no evidence that indirect forcing depends on precipitable water vapor."
"56699083600;36179218000;42263280300;57203654591;57139379600;57202301596;","Changes in Extreme Rainfall Over India and China Attributed to Regional Aerosol-Cloud Interaction During the Late 20th Century Rapid Industrialization",2018,"10.1029/2018GL078308","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052557103&doi=10.1029%2f2018GL078308&partnerID=40&md5=8de2b92fcd08e12e401dcf4ec6ce2ca3","Both mean and extreme rainfall decreased over India and Northern China during 1979–2005 at a rate of 0.2%/decade. The aerosol dampening effects on rainfall has also been suggested as a main driver of mean rainfall shift in India and China. Conflicting views, however, exist on whether aerosols enhance or suppress hazardous extreme heavy rainfall. Using Coupled Model Intercomparison Project phase 5 (CMIP5) multimodel ensemble, here we show that only a subset of models realistically reproduces the late-20th-century trend of extreme rainfall for the three major regions in Asia: drying in India and Northern China and wetting in Southern China, all consistent with mean rainfall change. As a common feature, this subset of models includes an explicit treatment of the complex physical processes of aerosol-cloud interaction (i.e., both cloud-albedo and cloud-lifetime effects), while simulation performance deteriorates in models that include only aerosol direct effect or cloud-albedo effect. The enhanced aerosol pollution during this rapid industrialization era is the leading cause of the spatially heterogeneous extreme rainfall change by dimming surface solar radiation, cooling adjacent ocean water, and weakening moisture transport into the continental region, while GHG warming or natural variability alone cannot explain the observed changes. Our results indicate that the projected intensification of regional extreme rainfall during the early-to-mid 21st-century, in response to the anticipated aerosol reduction, may be underestimated in global climate models without detailed treatment of complex aerosol-cloud interaction. ©2018. The Authors."
"55940667800;7103016965;24764483400;55226243300;7801353107;18635820300;55838069100;7006728825;","Aerosol-cloud interactions in mixed-phase convective clouds - Part 1: Aerosol perturbations",2018,"10.5194/acp-18-3119-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85043498589&doi=10.5194%2facp-18-3119-2018&partnerID=40&md5=f8914a4b7645cfa68873b8e32d2af370","Changes induced by perturbed aerosol conditions in moderately deep mixed-phase convective clouds (cloud top height ĝ1/4 g 5g km) developing along sea-breeze convergence lines are investigated with high-resolution numerical model simulations. The simulations utilise the newly developed Cloud-AeroSol Interacting Microphysics (CASIM) module for the Unified Model (UM), which allows for the representation of the two-way interaction between cloud and aerosol fields. Simulations are evaluated against observations collected during the COnvective Precipitation Experiment (COPE) field campaign over the southwestern peninsula of the UK in 2013. The simulations compare favourably with observed thermodynamic profiles, cloud base cloud droplet number concentrations (CDNC), cloud depth, and radar reflectivity statistics. Including the modification of aerosol fields by cloud microphysical processes improves the correspondence with observed CDNC values and spatial variability, but reduces the agreement with observations for average cloud size and cloud top height. <br><br> Accumulated precipitation is suppressed for higher-aerosol conditions before clouds become organised along the sea-breeze convergence lines. Changes in precipitation are smaller in simulations with aerosol processing. The precipitation suppression is due to less efficient precipitation production by warm-phase microphysics, consistent with parcel model predictions. <br><br> In contrast, after convective cells organise along the sea-breeze convergence zone, accumulated precipitation increases with aerosol concentrations. Condensate production increases with the aerosol concentrations due to higher vertical velocities in the convective cores and higher cloud top heights. However, for the highest-aerosol scenarios, no further increase in the condensate production occurs, as clouds grow into an upper-level stable layer. In these cases, the reduced precipitation efficiency (PE) dominates the precipitation response and no further precipitation enhancement occurs. Previous studies of deep convective clouds have related larger vertical velocities under high-aerosol conditions to enhanced latent heating from freezing. In the presented simulations changes in latent heating above the 0°C are negligible, but latent heating from condensation increases with aerosol concentrations. It is hypothesised that this increase is related to changes in the cloud field structure reducing the mixing of environmental air into the convective core. <br><br> The precipitation response of the deeper mixed-phase clouds along well-established convergence lines can be the opposite of predictions from parcel models. This occurs when clouds interact with a pre-existing thermodynamic environment and cloud field structural changes occur that are not captured by simple parcel model approaches. © Author(s) 2018."
"56531367400;55628589750;56735478500;15071907100;57203053317;","Understanding the drivers of marine liquid-water cloud occurrence and properties with global observations using neural networks",2017,"10.5194/acp-17-9535-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027217508&doi=10.5194%2facp-17-9535-2017&partnerID=40&md5=58863096bffbd0ae426068af5449bf78","The role of aerosols, clouds and their interactions with radiation remain among the largest unknowns in the climate system. Even though the processes involved are complex, aerosol-cloud interactions are often analyzed by means of bivariate relationships. In this study, 15 years (2001-2015) of monthly satellite-retrieved near-global aerosol products are combined with reanalysis data of various meteorological parameters to predict satellite-derived marine liquid-water cloud occurrence and properties by means of region-specific artificial neural networks. The statistical models used are shown to be capable of predicting clouds, especially in regions of high cloud variability. On this monthly scale, lower-tropospheric stability is shown to be the main determinant of cloud fraction and droplet size, especially in stratocumulus regions, while boundary layer height controls the liquid-water amount and thus the optical thickness of clouds. While aerosols show the expected impact on clouds, at this scale they are less relevant than some meteorological factors. Global patterns of the derived sensitivities point to regional characteristics of aerosol and cloud processes. © 2017 Author(s)."
"55241800100;13403622000;","Testing the sensitivity of past climates to the indirect effects of dust",2017,"10.1002/2017GL072584","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020462950&doi=10.1002%2f2017GL072584&partnerID=40&md5=cd6b52540df13888ac49eddb6693ad6f","Mineral dust particles are important ice nuclei (IN) and as such indirectly impact Earth's radiative balance via the properties of cold clouds. Using the Community Earth System Model version 1.0.6, and Community Atmosphere Model version 5.1, and a new empirical parameterization for ice nucleation on dust particles, we investigate the radiative forcing induced by dust IN for different dust loadings. Dust emissions are representative of global conditions for the Last Glacial Maximum and the mid-Pliocene Warm Period. Increased dust leads to smaller and more numerous ice crystals in mixed phase clouds, impacting cloud opacity, lifetime, and precipitation. This increases the shortwave cloud radiative forcing, resulting in significant surface temperature cooling and polar amplification—which is underestimated in existing studies relative to paleoclimate archives. Large hydrological changes occur and are linked to an enhanced dynamical response. We conclude that dust indirect effects could potentially have a significant impact on the model-data mismatch that exists for paleoclimates. ©2017. American Geophysical Union. All Rights Reserved."
"16444006500;7103016965;24764483400;7801353107;","The relative importance of macrophysical and cloud albedo changes for aerosol-induced radiative effects in closed-cell stratocumulus: Insight from the modelling of a case study",2017,"10.5194/acp-17-5155-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018482794&doi=10.5194%2facp-17-5155-2017&partnerID=40&md5=5b78d88048547a9cf41386b9a1e65e21","Aerosol-cloud interactions are explored using 1 km simulations of a case study of predominantly closedcell SE Pacific stratocumulus clouds. The simulations include realistic meteorology along with newly implemented cloud microphysics and sub-grid cloud schemes. The model was critically assessed against observations of liquid water path (LWP), broadband fluxes, cloud fraction (fc), droplet number concentrations (Nd), thermodynamic profiles, and radar reflectivities. Aerosol loading sensitivity tests showed that at low aerosol loadings, changes to aerosol affected shortwave fluxes equally through changes to cloud macrophysical characteristics (LWP, fc) and cloud albedo changes due solely to Nd changes. However, at high aerosol loadings, only the Nd albedo change was important. Evidence was also provided to show that a treatment of sub-grid clouds is as important as order of magnitude changes in aerosol loading for the accurate simulation of stratocumulus at this grid resolution. Overall, the control model demonstrated a credible ability to reproduce observations, suggesting that many of the important physical processes for accurately simulating these clouds are represented within the model and giving some confidence in the predictions of the model concerning stratocumulus and the impact of aerosol. For example, the control run was able to reproduce the shape and magnitude of the observed diurnal cycle of domain mean LWP to within ∼10 gm-2 for the nighttime, but with an overestimate for the daytime of up to 30 gm-2. The latter was attributed to the uniform aerosol fields imposed on the model, which meant that the model failed to include the low-Nd mode that was observed further offshore, preventing the LWP removal through precipitation that likely occurred in reality. The boundary layer was too low by around 260 m, which was attributed to the driving global model analysis. The shapes and sizes of the observed bands of clouds and open-cell-like regions of low areal cloud cover were qualitatively captured. The daytime fc frequency distribution was reproduced to within Δfc = 0.04 for fc &gt;∼ 0.7 as was the domain mean nighttime fc (at a single time) to within δfc = 0.02. Frequency distributions of shortwave top-of-the-atmosphere (TOA) fluxes from the satellite were well represented by the model, with only a slight underestimate of the mean by 15 %; this was attributed to near-shore aerosol concentrations that were too low for the particular times of the satellite overpasses. TOA long-wave flux distributions were close to those from the satellite with agreement of the mean value to within 0.4 %. From comparisons of Nd distributions to those from the satellite, it was found that the Nd mode from the model agreed with the higher of the two observed modes to within ∼15 %. © Author(s) 2017."
"56210720700;55481275400;16308514000;7004885872;37021250300;54784169900;7003361863;7403247998;7101846027;35340122000;7006572336;57196499374;","Stratocumulus cloud clearings and notable thermodynamic and aerosol contrasts across the clear-cloudy interface",2016,"10.1175/JAS-D-15-0137.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84962236682&doi=10.1175%2fJAS-D-15-0137.1&partnerID=40&md5=85536fb9cd55098cd29a0b77e8fe7fe8","Data from three research flights, conducted over water near the California coast, are used to investigate the boundary between stratocumulus cloud decks and clearings of different sizes. Large clearings exhibit a diurnal cycle with growth during the day and contraction overnight and a multiday life cycle that can include oscillations between growth and decay, whereas a small coastal clearing was observed to be locally confined with a subdiurnal lifetime. Subcloud aerosol characteristics are similar on both sides of the clear-cloudy boundary in the three cases, while meteorological properties exhibit subtle, yet important, gradients, implying that dynamics, and not microphysics, is the primary driver for the clearing characteristics. Transects, made at multiple levels across the cloud boundary during one flight, highlight the importance of microscale (~1 km) structure in thermodynamic properties near the cloud edge, suggesting that dynamic forcing at length scales comparable to the convective eddy scale may be influential to the larger-scale characteristics of the clearing. These results have implications for modeling and observational studies of marine boundary layer clouds, especially in relation to aerosol-cloud interactions and scales of variability responsible for the evolution of stratocumulus clearings. © 2016 American Meteorological Society."
"55577875600;7406500188;55717074000;","Seasonality in anthropogenic aerosol effects on East Asian climate simulated with CAM5",2015,"10.1002/2015JD023451","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84954391203&doi=10.1002%2f2015JD023451&partnerID=40&md5=019f9095bec229e234e305fb100b357d","This study investigates the seasonality in anthropogenic aerosol optical depth (AOD) distributions and their effects on clouds and precipitation in East Asia with the Community Atmospheric Model version 5. The differences between the model experiments with and without anthropogenic emissions exhibit a northward shift of the maximal AOD change in East Asia from March to July and then a southward withdrawal from September to November, which are induced by East Asian monsoon circulation. Associated with the shift, the direct and semidirect effects of the anthropogenic aerosols are the most pronounced in spring and summer, with a maximum center in North China during summer and a secondary center in South China during spring. The cloud liquid water path and shortwave cloud forcing changes, however, are the weakest in North China during summer. The indirect effect is the strongest in South China during spring, which is related to the large amount of middle-low level clouds in cold seasons in East China. A positive feedback between aerosol induced surface cooling and low-level cloud increase is identified in East China, which acts to enforce the aerosol indirect effect in spring. Accordingly, the climate response to the anthropogenic aerosols is also characterized by a northward shift of reduced precipitation from spring to summer, leading to a spring drought in South China and a summer drought in North China. The spring drought is attributed to both direct and indirect effects of the anthropogenic aerosols, while the summer drought is primarily determined by the aerosols’ direct effect. © 2015. American Geophysical Union. All Rights Reserved."
"56612517400;36538539800;55462884000;7202418289;55915206300;36680583100;57204359029;","Decadal simulation and comprehensive evaluation of CESM/CAM5.1 with advanced chemistry, aerosol microphysics, and aerosol-cloud interactions",2015,"10.1002/2014MS000360","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928789260&doi=10.1002%2f2014MS000360&partnerID=40&md5=dad06294dc5400cf90478f3edd0a7ed2","Earth system models have been used for climate predictions in recent years due to their capabilities to include biogeochemical cycles, human impacts, as well as coupled and interactive representations of Earth system components (e.g., atmosphere, ocean, land, and sea ice). In this work, the Community Earth System Model (CESM) with advanced chemistry and aerosol treatments, referred to as CESM-NCSU, is applied for decadal (2001-2010) global climate predictions. A comprehensive evaluation is performed focusing on the atmospheric component - the Community Atmosphere Model version 5.1 (CAM5.1) by comparing simulation results with observations/reanalysis data and CESM ensemble simulations from the Coupled Model Intercomparison Project phase 5 (CMIP5). The improved model can predict most meteorological and radiative variables relatively well with normalized mean biases (NMBs) of -14.1 to -9.7% and 0.7-10.8%, respectively, although temperature at 2 m (T2) is slightly underpredicted. Cloud variables such as cloud fraction (CF) and precipitating water vapor (PWV) are well predicted, with NMBs of -10.5 to 0.4%, whereas cloud condensation nuclei (CCN), cloud liquid water path (LWP), and cloud optical thickness (COT) are moderately-to-largely underpredicted, with NMBs of -82.2 to -31.2%, and cloud droplet number concentration (CDNC) is overpredictd by 26.7%. These biases indicate the limitations and uncertainties associated with cloud microphysics (e.g., resolved clouds and subgrid-scale cumulus clouds). Chemical concentrations over the continental U.S. (CONUS) (e.g., SO42-, Cl-, OC, and PM2.5) are reasonably well predicted with NMBs of -12.8 to -1.18%. Concentrations of SO2, SO42-, and PM10 are also reasonably well predicted over Europe with NMBs of -20.8 to -5.2%, so are predictions of SO2 concentrations over the East Asia with an NMB of -18.2%, and the tropospheric ozone residual (TOR) over the globe with an NMB of -3.5%. Most meteorological and radiative variables predicted by CESM-NCSU agree well overall with those predicted by CESM-CMIP5. The performance of LWP and AOD predicted by CESM-NCSU is better than that of CESM-CMIP5 in terms of model bias and correlation coefficients. Large biases for some chemical predictions can be attributed to uncertainties in the emissions of precursor gases (e.g., SO2, NH3, and NOx) and primary aerosols (black carbon and primary organic matter) as well as uncertainties in formulations of some model components (e.g., online dust and sea-salt emissions, secondary organic aerosol formation, and cloud microphysics). Comparisons of CESM simulation with baseline emissions and 20% of anthropogenic emissions from the baseline emissions indicate that anthropogenic gas and aerosol species can decrease downwelling shortwave radiation (FSDS) by 4.7 W m-2 (or by 2.9%) and increase SWCF by 3.2 W m-2 (or by 3.1%) in the global mean. © 2015. The Authors."
"36451754500;7102436094;56434996400;55506050200;","Dust aerosol effects on cirrus and altocumulus clouds in Northwest China",2015,"10.1007/s13351-015-4116-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007201937&doi=10.1007%2fs13351-015-4116-9&partnerID=40&md5=9b86f10a0cbe0e394a50dd3ace1c863d","Dust aerosol effects on the properties of cirrus and altocumulus cloud in Northwest China were studied for the period March–May 2007 by using the satellite data of Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), Aqua, and CloudSat. Dusty clouds were defined as those mixed with dust aerosols or existing in dust aerosol conditions, while pure clouds were those in a dust-free environment. For dusty altocumulus clouds, the mean values of cloud optical depth (OPD), cloud liquid water path (LWP), cloud ice water path (IWP), cloud effective particle radius (Re), and cloud effective particle diameter (De) were 6.40, 40.23 g m−2, 100.70 g m−2, 8.76 μm, and 40.72 μm, respectively. For pure altocumulus clouds, the corresponding mean values were 9.28, 76.70 g m−2, 128.75 g m−2, 14.03 μm, and 48.92 μm, respectively. These results show a significant decrease of OPD, LWP, IWP, Re, and De of approximately 31%, 48%, 22%, 38%, and 17% because of the effects of dust aerosols. Moreover, the effects of dust aerosols on liquid-phase altocumulus clouds were greater than on ice-phase altocumulus clouds. Regarding dusty cirrus clouds, the mean values of OPD, IWP, and De were 5.11, 137.53 g m−2, and 60.44 μm, respectively. In contrast, the mean values were 6.69, 156.17 g m−2, and 66.63 μm, respectively, for pure cirrus clouds, with a 24% decrease in OPD, a 12% decrease in IWP, and a 9% decrease in De. These results indicate that dust aerosols can significantly change cloud properties, leading to a reduction of OPD, LWP, and effective particle size for both altocumulus and cirrus clouds in Northwest China. © The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2015."
"7404330190;15755362800;55870068500;7404210314;8703963700;41362078500;7403393030;","Advances in cloud physics and weather modification in China",2015,"10.1007/s00376-014-0006-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919715260&doi=10.1007%2fs00376-014-0006-9&partnerID=40&md5=4fa5be8c7f099c568a4fe0ef00dfa2ce","The capabilities of cloud-resolving numerical models, observational instruments and cloud seeding have improved greatly over recent years in China. The subject of this review focuses on the main progresses made in China in the areas of cloud modeling, field observations, aerosol-cloud interactions, the effects of urbanization on cloud and precipitation, and weather modification.Despite important progress having been made, many critical issues or challenges remain to be solved, or require stronger scientific evidence and support, such as the chain of physical events involved in the effects induced by cloud seeding. Current important progresses in measurements and seeding techniques provide the opportunity and possibility to reduce these deficiencies. Long-term scientific projects aimed at reducing these key uncertainties are extremely urgent and important for weather-modification activities in China.Well-equipped aircraft and ground-based advanced Doppler and polarized radars have been rapidly applied in cloud-seeding operations. The combined use of modern techniques such as the Global Positioning System, remote sensing, and Geographical Information Systems has greatly decreased the blindness and uncertainties in weather-modification activities. Weather-modification models based on state-of-the-art cloud-resolving models are operationally run at the National Weather Modification Centre in China for guiding weather-modification programs. © Institute of Atmospheric Physics/Chinese Academy of Sciences, and Science Press and Springer-Verlag Berlin Heidelberg 2015."
"57094306300;8072265400;","Evaluating aerosol direct radiative effects on global terrestrial ecosystem carbon dynamics from 2003 to 2010",2014,"10.3402/tellusb.v66.21808","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923364156&doi=10.3402%2ftellusb.v66.21808&partnerID=40&md5=3e6fcac08a274dc968039bb72f6a9191","An integrated terrestrial ecosystem model and an atmospheric radiative transfer module are developed and applied to evaluate aerosol direct radiative effects on carbon dynamics of global terrestrial ecosystems during 2003-2010. The Moderate-Resolution Imaging Spectroradiometer measurements of key atmosphere parameters have been used to quantify aerosol effects on downward solar radiation. Simulations with and without considering the aerosol loadings show that aerosol affects terrestrial ecosystem carbon dynamics through the effects on plant phenology, thermal and hydrological conditions as well as solar radiation. The simulations also show that aerosol enhances the terrestrial gross primary production by 4.9 Pg C yr-1, the net primary production by 3.8 Pg C yr-1, the net ecosystem production by 3.9 Pg C yr-1, and the plant respiration by 1.1 Pg C yr-1 during the period. The aerosol loading at a magnitude of 0.1 Pg C yr-1 reduces ecosystem heterotrophic respiration. These results support previous findings of the positive effects of aerosol light scattering on plant production, but suggest there is a strong spatial variation due to cloud cover. This study suggests that both direct and indirect aerosol radiative effects through aerosol-cloud interactions should be considered to quantify the global carbon cycle. © 2014 M. Chen and Q. Zhuang."
"7402786837;57208121852;6602600408;7006689276;","Aerosol indirect effects from shipping emissions: Sensitivity studies with the global aerosol-climate model ECHAM-HAM",2012,"10.5194/acp-12-5985-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864227470&doi=10.5194%2facp-12-5985-2012&partnerID=40&md5=6d1879e0761718c794f6eeefc891981f","In this study, we employ the global aerosol-climate model ECHAM-HAM to globally assess aerosol indirect effects (AIEs) resulting from shipping emissions of aerosols and aerosol precursor gases. We implement shipping emissions of sulphur dioxide (SO2), black carbon (BC) and particulate organic matter (POM) for the year 2000 into the model and quantify the model's sensitivity towards uncertainties associated with the emission parameterisation as well as with the shipping emissions themselves. Sensitivity experiments are designed to investigate (i) the uncertainty in the size distribution of emitted particles, (ii) the uncertainty associated with the total amount of emissions, and (iii) the impact of reducing carbonaceous emissions from ships. <br><br> We use the results from one sensitivity experiment for a detailed discussion of shipping-induced changes in the global aerosol system as well as the resulting impact on cloud properties. From all sensitivity experiments, we find AIEs from shipping emissions to range from ĝ̂'0.32 0.01 W mĝ'2 to ĝ'0.07 ± 0.01 W mĝ̂'2 (global mean value and inter-annual variability as a standard deviation). The magnitude of the AIEs depends much more on the assumed emission size distribution and subsequent aerosol microphysical interactions than on the magnitude of the emissions themselves. It is important to note that although the strongest estimate of AIEs from shipping emissions in this study is relatively large, still much larger estimates have been reported in the literature before on the basis of modelling studies. We find that omitting just carbonaceous particle emissions from ships favours new particle formation in the boundary layer. These newly formed particles contribute just about as much to the CCN budget as the carbonaceous particles would, leaving the globally averaged AIEs nearly unaltered compared to a simulation including carbonaceous particle emissions from ships."
"56082867500;7004057920;8343401100;","A case study: The indirect aerosol effects of mineral dust on warm clouds",2010,"10.1175/2009JAS3235.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953338715&doi=10.1175%2f2009JAS3235.1&partnerID=40&md5=ed88c8edca16f3055878d4ccaf5efc69","The indirect aerosol effect (Twomey effect) is studied during a Saharan dust-transport event that presented an unusually favorable combination of a dust-loading gradient across clouds with warm cloud-top temperatures. Standard retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS), the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E), and the Clouds and the Earth's Radiant Energy System (CERES) provide cloud-top temperature (a surrogate for height), liquid water path (LWP), classification of precipitation regime, and radiation flux. The authors correlate a retrieved mean effective droplet radius (re) versus the number concentration of cloud condensation nuclei (NCCN), using the regressed slope d lnre/d lnNCCN as the estimator of the aerosol indirect effect (AIE). Results demonstrate statistically significant AIE for only some of the segregated cloud classes. For nonprecipitating clouds (the most direct test of Twomey effect), the estimated AIE is effectively 20.07 over all wider temperature bands and is statistically significant from 1.1 to 1.9σ. Further classification by LWP strengthens both the AIE (for all LWP. 150 g m-2) to approximately -0.16, and substantially increases the statistical significance, to better than 5σ. Shortwave radiation forcing of dust aerosols is also estimated directly from satellite measurements. The direct shortwave (SW) radiation effect of Saharan dusts at solar zenith angle 21.6° is 53.48 ± 8.56 W m-2 per unit aerosol optical depth, with a correlation coefficient of 0.92. The indirect SW forcing of Saharan dust is 29.88 ± 2.42 W m-2 per unit AOD for clouds with LWP of 100 g m-2. © 2010 American Meteorological Society."
"56082867500;7004057920;","Impacts of mineral dust on the vertical structure of precipitation",2010,"10.1029/2009JD011925","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905339031&doi=10.1029%2f2009JD011925&partnerID=40&md5=ecb57ecd0e1ed1de1d0b9d8a927d2b70","Characteristics of precipitation vertical structure in deep convective cloud systems are compared using measurements from sensors on board multiple satellites over the equatorial Atlantic under dust-laden and dust-free conditions. Both case and statistical studies consistently show that the impacts of mineral dust on tropical cloud and precipitation systems are highly dependent on rain type. For convective rain, the pattern of rainfall profiles above the dust layer is mainly determined by updraft intensity. For similar updraft intensity, the convective rain at and below the dust layer exhibits enhancement of the breakup process of raindrops due to mineral dust and associated warm air with strong wind shear. For stratiform rain, dust-induced microphysical effects are more evident. For similar storm height (or the rain top), precipitation at altitudes above 6 km is enhanced under dust-laden conditions, suggesting an enhancement of ice heterogeneous nucleation. For warm rain with similar storm height, precipitation is systematically weaker under dust-laden conditions. Furthermore, the ratio of precipitation water to the total amount of atmospheric hydrometeors is smaller under dust-laden conditions. Our study suggests that mineral dust exhibits a second aerosol indirect effect on cloud and precipitation systems. Copyright © 2010 by the American Geophysical Union."
"55716092000;6701378450;55714712500;57211106013;9249239700;57196499374;","Global climate response to anthropogenic aerosol indirect effects: Present day and year 2100",2010,"10.1029/2008JD011619","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954530206&doi=10.1029%2f2008JD011619&partnerID=40&md5=3908226512830464c18cf3ae68f95c86","Aerosol indirect effects (AIE) are a principal source of uncertainty in future climate predictions. The present study investigates the equilibrium response of the climate system to present-day and future AIE using the general circulation model (GCM), Goddard Institute for Space Studies (GISS) III. A diagnostic formulation correlating cloud droplet number concentration (N <inf>c</inf>) with concentrations of aerosol soluble ions is developed as a basis for the calculation. Explicit dependence on N<inf>c</inf> is introduced in the treatments of liquid-phase stratiform clouds in GISS III. The model is able to reproduce the general patterns of present-day cloud frequency, droplet size, and radiative balance observed by CloudSat, Moderate Resolution Imaging Spectroradiometer, and Earth Radiation Budget Experiment. For perturbations of N<inf>c</inf> from preindustrial to present day, a net AIE forcing of-1.67 W m-2 is estimated, with a global mean surface cooling of 1.12 K, precipitation reduction of 3.36%, a southward shift of the Intertropical Convergence Zone, and a hydrological sensitivity of +3.00% K-1. For estimated perturbations of N<inf>c</inf> from present day to year 2100, a net AIE forcing of-0.58 W m-2, a surface cooling of 0.47 K, and a decrease in precipitation of 1.7% are predicted. Sensitivity calculations show that the assumption of a background minimum N<inf>c</inf> value has more significant effects on AIE forcing in the future than on that in present day. When AIE-related processes are included in the GCM, a decrease in stratiform precipitation is predicted over future greenhouse gas (GHG)-induced warming scenario, as opposed to the predicted increase when only GHG and aerosol direct effects are considered. Copyright 2010 by the American Geophysical Union."
"40461229800;57195578500;57203108617;25124619600;42361350100;7006041988;24308208100;55067058700;","Marine and terrestrial influences on ice nucleating particles during continuous springtime measurements in an Arctic oilfield location",2018,"10.5194/acp-18-18023-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058967263&doi=10.5194%2facp-18-18023-2018&partnerID=40&md5=806334c89f51f1dbfa2f35db957ee5ce","Aerosols that serve as ice nucleating particles (INPs) have the potential to modulate cloud microphysical properties and can therefore impact cloud radiative forcing (CRF) and precipitation formation processes. In remote regions such as the Arctic, aerosol-cloud interactions are severely understudied yet may have significant implications for the surface energy budget and its impact on sea ice and snow surfaces. Further, uncertainties in model representations of heterogeneous ice nucleation are a significant hindrance to simulating Arctic mixed-phase cloud processes. We present results from a campaign called INPOP (Ice Nucleating Particles at Oliktok Point), which took place at a US Department of Energy Atmospheric Radiation Measurement (DOE ARM) facility in the northern Alaskan Arctic. Three time-and size-resolved aerosol impactors were deployed from 1 March to 31 May 2017 for offline ice nucleation and chemical analyses and were co-located with routine measurements of aerosol number and size. The largest particles (i.e., ≥3 μ m or coarse mode) were the most efficient INPs by inducing freezing at the warmest temperatures. During periods with snow-and ice-covered surfaces, coarse mode INP concentrations were very low (maximum of 6 × 10 -4 L -1 at-15 °C), but higher concentrations of warm-temperature INPs were observed during late May (maximum of 2 × 10 -2 L -1 at 15 °C). These higher concentrations were attributed to air masses originating from over open Arctic Ocean water and tundra surfaces. To our knowledge, these results represent the first INP characterization measurements in an Arctic oilfield location and demonstrate strong influences from mineral and marine sources despite the relatively high springtime pollution levels. Ultimately, these results can be used to evaluate the anthropogenic and natural influences on aerosol composition and Arctic cloud properties. © 2018 Author(s)."
"7102604282;55245030000;7006525200;23065650200;","Anthropogenic Aerosol Indirect Effects in Cirrus Clouds",2018,"10.1029/2018JD029204","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055731603&doi=10.1029%2f2018JD029204&partnerID=40&md5=9b8190c740388bed3a0a14c7ef8ac84c","We have implemented a parameterization for forming ice in large-scale cirrus clouds that accounts for the changes in updrafts associated with a spectrum of waves acting within each time step in the model. This allows us to account for the frequency of homogeneous and heterogeneous freezing events that occur within each time step of the model and helps to determine more realistic ice number concentrations as well as changes to ice number concentrations. The model is able to fit observations of ice number at the lowest temperatures in the tropical tropopause but is still somewhat high in tropical latitudes with temperatures between 195°K and 215°K. The climate forcings associated with different representations of heterogeneous ice nuclei (IN or INPs) are primarily negative unless large additions of IN are made, such as when we assumed that all aircraft soot acts as an IN. However, they can be close to zero if it is assumed that all background dust can act as an INP irrespective of how much sulfate is deposited on these particles. Our best estimate for the forcing of anthropogenic aircraft soot in this model is −0.2 ± 0.06 W/m2, while that from anthropogenic fossil/biofuel soot is −0.093 ± 0.033 W/m2. Natural and anthropogenic open biomass burning leads to a net forcing of −0.057 ± 0.05 W/m2. ©2018. The Authors."
"55326237100;55173596300;7402838215;55366700000;23017945100;6506848120;57204179735;6602600408;","Ice crystal number concentration estimates from lidar-radar satellite remote sensing - Part 1: Method and evaluation",2018,"10.5194/acp-18-14327-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054864630&doi=10.5194%2facp-18-14327-2018&partnerID=40&md5=611c529bd9e2f9e33b4b06357c288035","The number concentration of cloud particles is a key quantity for understanding aerosol-cloud interactions and describing clouds in climate and numerical weather prediction models. In contrast with recent advances for liquid clouds, few observational constraints exist regarding the ice crystal number concentration (N). This study investigates how combined lidar-radar measurements can be used to provide satellite estimates of N, using a methodology that constrains moments of a parameterized particle size distribution (PSD). The operational liDAR-raDAR (DARDAR) product serves as an existing base for this method, which focuses on ice clouds with temperatures 30&thinsp;°C. Theoretical considerations demonstrate the capability for accurate retrievals of N, apart from a possible bias in the concentration in small crystals when 50&thinsp;°C, due to the assumption of a monomodal PSD shape in the current method. This is verified via a comparison of satellite estimates to coincident in situ measurements, which additionally demonstrates the sufficient sensitivity of lidar-radar observations to N. Following these results, satellite estimates of N are evaluated in the context of a case study and a preliminary climatological analysis based on 10 years of global data. Despite a lack of other large-scale references, this evaluation shows a reasonable physical consistency in N spatial distribution patterns. Notably, increases in N are found towards cold temperatures and, more significantly, in the presence of strong updrafts, such as those related to convective or orographic uplifts. Further evaluation and improvement of this method are necessary, although these results already constitute a first encouraging step towards large-scale observational constraints for N. Part 2 of this series uses this new dataset to examine the controls on. © 2018 Copernicus GmbH. All Rights Reserved."
"55620143100;57214277644;35422938600;54796767100;56316545900;55615346700;57192954165;55694114200;7005968859;7005773698;7006347751;7004715270;","A mesocosm double feature: Insights into the chemical makeup of marine ice nucleating particles",2018,"10.1175/JAS-D-17-0155.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048993475&doi=10.1175%2fJAS-D-17-0155.1&partnerID=40&md5=e92ba43ae4949257422d3d655e99dd7c","The abundance of atmospheric ice nucleating particles (INPs) is a source of uncertainty for numerical representation of ice-phase transitions in mixed-phase clouds. While sea spray aerosol (SSA) exhibits less ice nucleating (IN) ability than terrestrial aerosol, marine INP emissions are linked to oceanic biological activity and are potentially an important source of INPs over remote oceans. Inadequate knowledge of marine INP identity limits the ability to parameterize this complex INP source. A previous manuscript described abundances of marine INPs in relation to several aerosol composition and ocean biology observations during two laboratory mesocosm experiments. In this study, the abundances and chemical and physical properties of INPs found during the same mesocosm experiments were directly probed in SSA, seawater, and surface microlayer samples. Two unique marine INP populations were found: 1) dissolved organic carbon INPs are suggested to be composed of IN-active molecules, and 2) particulate organic carbon INPs are attributed as intact cells or IN-active microbe fragments. Both marine INP types are likely to be emitted into SSA following decay of phytoplankton biomass when 1) the surface microlayer is significantly enriched with exudates and cellular detritus and SSA particles are preferentially coated with IN-active molecules or 2) diatom fragments and bacteria are relatively abundant in seawater and therefore more likely transferred into SSA. These findings inform future efforts for incorporating marine INP emissions into numerical models and motivate future studies to quantify specific marine molecules and isolate phytoplankton, bacteria, and other species that contribute to these marine INP types. © 2018 American Meteorological Society."
"57187615700;7004214645;6602988199;57203200427;35547807400;36894599500;7003777747;23101759100;22986631300;24329376600;12240390300;57110426700;56250250300;57189524073;7006462819;12139043600;7102976560;6602414959;57109884900;24472400800;7202079615;","Dynamical response of Mediterranean precipitation to greenhouse gases and aerosols",2018,"10.5194/acp-18-8439-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048843153&doi=10.5194%2facp-18-8439-2018&partnerID=40&md5=5d74da974ab6cf1f7388c41c938151f5","Atmospheric aerosols and greenhouse gases affect cloud properties, radiative balance and, thus, the hydrological cycle. Observations show that precipitation has decreased in the Mediterranean since the beginning of the 20th century, and many studies have investigated possible mechanisms. So far, however, the effects of aerosol forcing on Mediterranean precipitation remain largely unknown. Here we compare the modeled dynamical response of Mediterranean precipitation to individual forcing agents in a set of global climate models (GCMs). Our analyses show that both greenhouse gases and aerosols can cause drying in the Mediterranean and that precipitation is more sensitive to black carbon (BC) forcing than to well-mixed greenhouse gases (WMGHGs) or sulfate aerosol. In addition to local heating, BC appears to reduce precipitation by causing an enhanced positive sea level pressure (SLP) pattern similar to the North Atlantic Oscillation-Arctic Oscillation, characterized by higher SLP at midlatitudes and lower SLP at high latitudes. WMGHGs cause a similar SLP change, and both are associated with a northward diversion of the jet stream and storm tracks, reducing precipitation in the Mediterranean while increasing precipitation in northern Europe. Though the applied forcings were much larger, if forcings are scaled to those of the historical period of 1901-2010, roughly one-third (31±17g%) of the precipitation decrease would be attributable to global BC forcing with the remainder largely attributable to WMGHGs, whereas global scattering sulfate aerosols would have negligible impacts. Aerosol-cloud interactions appear to have minimal impacts on Mediterranean precipitation in these models, at least in part because many simulations did not fully include such processes; these merit further study. The findings from this study suggest that future BC and WMGHG emissions may significantly affect regional water resources, agricultural practices, ecosystems and the economy in the Mediterranean region. ©Author(s) 2018."
"56324515500;7201504886;8696069500;","On the sensitivity of anthropogenic aerosol forcing to model-internal variability and parameterizing a Twomey effect",2017,"10.1002/2017MS000932","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020097992&doi=10.1002%2f2017MS000932&partnerID=40&md5=cd2a03a6396f301baeb830a8df4a2bf4","Despite efforts to accurately quantify the effective radiative forcing (ERF) of anthropogenic aerosol, the historical evolution of ERF remains uncertain. As a further step toward a better understanding of ERF uncertainty, the present study systematically investigates the sensitivity of the shortwave ERF at the top of the atmosphere to model-internal variability and spatial distributions of the monthly mean radiative effects of anthropogenic aerosol. For this, ensembles are generated with the atmospheric model ECHAM6.3 that uses monthly prescribed optical properties and changes in cloud-droplet number concentrations designed to mimic that associated with the anthropogenic aerosol using the new parameterization MACv2-SP. The results foremost highlight the small change in our best estimate of the global averaged all-sky ERF associated with a substantially different pattern of anthropogenic aerosol radiative effects from the mid-1970s (–0.51 Wm–2) and present day (–0.50 Wm–2). Such a small change in ERF is difficult to detect when model-internal year-to-year variability (0.32 Wm–2 standard deviation) is considered. A stable estimate of all-sky ERF requires ensemble simulations, the size of which depends on the targeted precision, confidence level, and the magnitude of model-internal variability. A larger effect of the pattern of the anthropogenic aerosol radiative effects on the globally averaged all-sky ERF (15%) occurs with a strong Twomey effect through lowering the background aerosol optical depth in regions downstream of major pollution sources. It suggests that models with strong aerosol-cloud interactions could show a moderate difference in the global mean ERF associated with the mid-1970s to present-day change in the anthropogenic aerosol pattern. © 2017. The Authors."
"56734151000;7006960661;26643041500;55720362700;57169368500;8438057200;56083968500;56165373000;55515518300;7102010848;56415384100;57192169322;35461255500;8871497700;","Analysis of aerosol effects on warm clouds over the Yangtze River Delta from multi-sensor satellite observations",2017,"10.5194/acp-17-5623-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018777864&doi=10.5194%2facp-17-5623-2017&partnerID=40&md5=8aa3fdc4b7724938d7bb6590507dcfb4","Aerosol effects on low warm clouds over the Yangtze River Delta (YRD, eastern China) are examined using co-located MODIS, CALIOP and CloudSat observations. By taking the vertical locations of aerosol and cloud layers into account, we use simultaneously observed aerosol and cloud data to investigate relationships between cloud properties and the amount of aerosol particles (using aerosol optical depth, AOD, as a proxy). Also, we investigate the impact of aerosol types on the variation of cloud properties with AOD. Finally, we explore how meteorological conditions affect these relationships using ERA-Interim reanalysis data. This study shows that the relation between cloud properties and AOD depends on the aerosol abundance, with a different behaviour for low and high AOD (i.e. AOD< 0.35 and AOD> 0.35). This applies to cloud droplet effective radius (CDR) and cloud fraction (CF), but not to cloud optical thickness (COT) and cloud top pressure (CTP). COT is found to decrease when AOD increases, which may be due to radiative effects and retrieval artefacts caused by absorbing aerosol. Conversely, CTP tends to increase with elevated AOD, indicating that the aerosol is not always prone to expand the vertical extension. It also shows that the COT-CDR and CWP (cloud liquid water path)-CDR relationships are not unique, but affected by atmospheric aerosol loading. Furthermore, separation of cases with either polluted dust or smoke aerosol shows that aerosol-cloud interaction (ACI) is stronger for clouds mixed with smoke aerosol than for clouds mixed with dust, which is ascribed to the higher absorption efficiency of smoke than dust. The variation of cloud properties with AOD is analysed for various relative humidity and boundary layer thermodynamic and dynamic conditions, showing that high relative humidity favours larger cloud droplet particles and increases cloud formation, irrespective of vertical or horizontal level. Stable atmospheric conditions enhance cloud cover horizontally. However, unstable atmospheric conditions favour thicker and higher clouds. Dynamically, upward motion of air parcels can also facilitate the formation of thicker and higher clouds. Overall, the present study provides an understanding of the impact of aerosols on cloud properties over the YRD. In addition to the amount of aerosol particles (or AOD), evidence is provided that aerosol types and ambient environmental conditions need to be considered to understand the observed relationships between cloud properties and AOD. © Author(s) 2017."
"57192164648;7403564495;8953662800;36678944300;","8-Year ground-based observational analysis about the seasonal variation of the aerosol-cloud droplet effective radius relationship at SGP site",2017,"10.1016/j.atmosenv.2017.06.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020280544&doi=10.1016%2fj.atmosenv.2017.06.002&partnerID=40&md5=20e933d4cc152a7bf86e918c129e4e49","Previous studies have shown the negative or positive relationship between cloud droplet effective radius (re) and aerosol amount based on limited observations, indicative of the uncertainties of this relationship caused by many factors. Using 8-year ground-based cloud and aerosol observations at Southern Great Plain (SGP) site in Oklahoma, US, we here analyze the seasonal variation of aerosol effect on low liquid cloud re. It shows positive instead of negative AOD- re relationship in all seasons except summer. Potential contribution to AOD- re relationship from the precipitable water vapor (PWV) has been analyzed. Results show that the AOD- re relationship is indeed negative in low PWV condition regardless of seasonality, but it turns positive in high PWV condition for all seasons other than summer. The most likely explanation for the positive AOD-re relationship in high PWV condition for spring, fall and winter is that high PWV could promote the growth of cloud droplets by providing sufficient water vapor. The different performance of AOD- re relationship in summer could be related to the much heavier aerosol loading, which makes the PWV not sufficient any more so that the droplets compete water with each other. By limiting the variation of other meteorological conditions such as low tropospheric stability and wind speed near cloud bases, further analysis shows that higher PWVs not only help change AOD- re relationship from negative to positive, but also make cloud depth and cloud top height higher. © 2017 Elsevier Ltd"
"57203104770;7004862277;","Analysis of isothermal and cooling-rate-dependent immersion freezing by a unifying stochastic ice nucleation model",2016,"10.5194/acp-16-2083-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959387684&doi=10.5194%2facp-16-2083-2016&partnerID=40&md5=8cc721ec9b53d247195d38110820753d","Immersion freezing is an important ice nucleation pathway involved in the formation of cirrus and mixed-phase clouds. Laboratory immersion freezing experiments are necessary to determine the range in temperature, T, and relative humidity, RH, at which ice nucleation occurs and to quantify the associated nucleation kinetics. Typically, isothermal (applying a constant temperature) and cooling-rate-dependent immersion freezing experiments are conducted. In these experiments it is usually assumed that the droplets containing ice nucleating particles (INPs) all have the same INP surface area (ISA); however, the validity of this assumption or the impact it may have on analysis and interpretation of the experimental data is rarely questioned. Descriptions of ice active sites and variability of contact angles have been successfully formulated to describe ice nucleation experimental data in previous research; however, we consider the ability of a stochastic freezing model founded on classical nucleation theory to reproduce previous results and to explain experimental uncertainties and data scatter. A stochastic immersion freezing model based on first principles of statistics is presented, which accounts for variable ISA per droplet and uses parameters including the total number of droplets, Ntot, and the heterogeneous ice nucleation rate coefficient, Jhet(T). This model is applied to address if (i) a time and ISA-dependent stochastic immersion freezing process can explain laboratory immersion freezing data for different experimental methods and (ii) the assumption that all droplets contain identical ISA is a valid conjecture with subsequent consequences for analysis and interpretation of immersion freezing. The simple stochastic model can reproduce the observed time and surface area dependence in immersion freezing experiments for a variety of methods such as: droplets on a cold-stage exposed to air or surrounded by an oil matrix, wind and acoustically levitated droplets, droplets in a continuous-flow diffusion chamber (CFDC), the Leipzig aerosol cloud interaction simulator (LACIS), and the aerosol interaction and dynamics in the atmosphere (AIDA) cloud chamber. Observed time-dependent isothermal frozen fractions exhibiting non-exponential behavior can be readily explained by this model considering varying ISA. An apparent cooling-rate dependence of Jhet is explained by assuming identical ISA in each droplet. When accounting for ISA variability, the cooling-rate dependence of ice nucleation kinetics vanishes as expected from classical nucleation theory. The model simulations allow for a quantitative experimental uncertainty analysis for parameters Ntot, T, RH, and the ISA variability. The implications of our results for experimental analysis and interpretation of the immersion freezing process are discussed. © 2016 Author(s)."
"25624725200;8550791300;35798085000;56422246700;18437651200;56195201600;7006415284;","Immersion freezing of kaolinite: Scaling with particle surface area",2016,"10.1175/JAS-D-15-0057.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957630946&doi=10.1175%2fJAS-D-15-0057.1&partnerID=40&md5=35f5289a8b94c9af5f2173baf7b3883e","This study presents an analysis showing that the freezing probability of kaolinite particles from Fluka scales exponentially with particle surface area for different atmospherically relevant particle sizes. Immersion freezing experiments were performed at the Leipzig Aerosol Cloud Interaction Simulator (LACIS). Size-selected kaolinite particles with mobility diameters of 300, 700, and 1000 nm were analyzed with one particle per droplet. First, it is demonstrated that immersion freezing is independent of the droplet volume. Using the mobility analyzer technique for size selection involves the presence of multiply charged particles in the quasi-monodisperse aerosol, which are larger than singly charged particles. The fractions of these were determined using cloud droplet activation measurements. The development of a multiple charge correction method has proven to be essential for deriving ice fractions and other quantities for measurements in which the here-applied method of size selection is used. When accounting for multiply charged particles (electric charge itself does not matter), both a time-independent and a time-dependent description of the freezing process can reproduce the measurements over the range of examined particle sizes. Hence, either a temperature-dependent surface site density or a single contact angle distribution was sufficient to parameterize the freezing behavior. From a comparison with earlier studies using kaolinite samples from the same provider, it is concluded that the neglect of multiply charged particles and, to a lesser extent, the effect of time can cause a significant overestimation of the ice nucleation site density of one order of magnitude, which translates into a temperature bias of 5-6 K. © 2016 American Meteorological Society."
"56457851700;7202145115;","Observations of a substantial cloud-aerosol indirect effect during the 2014-2015 Bár arbunga-Vei IVötn fissure eruption in Iceland",2015,"10.1002/2015GL067070","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84953635064&doi=10.1002%2f2015GL067070&partnerID=40&md5=11d11aa94f8ce074cb8627cd34776fcc","The Bárarbunga-Vei ivötn fissure eruption lasted from 31 August 2014 to 28 February 2015, during which its sulfur emissions dwarfed anthropogenic emissions from Europe. This natural experiment offers an excellent opportunity to investigate the aerosol indirect effect and the effect of effusive volcanic eruptions on climate. During the eruption cloud droplet effective radius (re) over the region surrounding Iceland was at the lowest value in the 14 year Moderate Imaging Spectroradiometer data record during September and October 2014. The change in reflected solar radiation due to increased cloud reflectivity during September and October is estimated to exceed 2 W m-2 over the region surrounding Iceland, with increases of 1 W m-2 extending as far south as the Açores. The strength of the aerosol indirect effect diagnosed here reaffirms the ability of volcanic aerosols to affect cloud properties and ultimately the planetary albedo. © 2015. American Geophysical Union. All Rights Reserved."
"55501554900;56149492300;36538539800;7003498065;6602931427;35119188100;35285676700;7003862871;24767977600;39361670300;55938109300;6701463335;55915206300;","A multi-model assessment for the 2006 and 2010 simulations under the Air Quality Model Evaluation International Initiative (AQMEII) Phase 2 over North America: Part II. Evaluation of column variable predictions using satellite data",2015,"10.1016/j.atmosenv.2014.07.044","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939772321&doi=10.1016%2fj.atmosenv.2014.07.044&partnerID=40&md5=5d6b8de053243d8b825a890cbef3edf9","Within the context of the Air Quality Model Evaluation International Initiative Phase 2 (AQMEII2) project, this part II paper performs a multi-model assessment of major column abundances of gases, radiation, aerosol, and cloud variables for 2006 and 2010 simulations with three online-coupled air quality models over the North America using available satellite data. It also provides the first comparative assessment of the capabilities of the current generation of online-coupled models in simulating column variables. Despite the use of different model configurations and meteorological initial and boundary conditions, most simulations show comparable model performance for many variables. The evaluation results show an excellent agreement between all simulations and satellite-derived radiation variables including downward surface solar radiation, longwave radiation, and top-of-atmospheric outgoing longwave radiation, as well as precipitable water vapor with domain-average normalized mean biases (NMBs) of typically less than 5% and correlation coefficient (R) typically more than 0.9. Most simulations perform well for column-integrated abundance of CO with domain-average NMBs of -9.4% to -2.2% in 2006 and -12.1% to 4.6% in 2010 and from reasonably well to fair for column NO2, HCHO, and SO2, with domain-average NMBs of -37.7% to 2.1%, -27.3% to 59.2%, and 16.1% to 114.2% in 2006, respectively, and, 12.9% to 102.1%, -25.0% to 87.6%, -65.2% to 7.4% in 2010, respectively. R values are high for CO and NO2 typically between 0.85 and 0.9 (i.e., R2 of 0.7-0.8). Tropospheric ozone residuals are overpredicted by all simulations due to overestimates of ozone profiles from boundary conditions. Model performance for cloud-related variables is mixed and generally worse compared to gases and radiation variables. Cloud fraction (CF) is well reproduced by most simulations. Other aerosol/cloud related variables such as aerosol optical depth (AOD), cloud optical thickness, cloud liquid water path, cloud condensation nuclei, and cloud droplet number concentration (CDNC) are moderately to largely underpredicted by most simulations, due to underpredictions of aerosol loadings and also indicating high uncertainties associated with the current model treatments of aerosol-cloud interactions and the need for further model development. Negative correlations are found for AOD for most simulations due to large negative biases over the western part of the domain. Inter-model discrepancies also exist for a few variables such as column abundances of HCHO and SO2 and CDNC due likely to different chemical mechanisms, biogenic emissions, and treatments of aerosol indirect effects. Most simulations can also capture the inter-annual trend observed by satellites between 2006 and 2010 for several variables such as column abundance of NO2, AOD, CF, and CDNC. Results shown in this work provide the important benchmark for future online-couple air quality model development. © 2014 Elsevier Ltd."
"55588510300;13405658600;57211106013;","Representation of nucleation mode microphysics in a global aerosol model with sectional microphysics",2013,"10.5194/gmd-6-1221-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883154207&doi=10.5194%2fgmd-6-1221-2013&partnerID=40&md5=a2ce9e485a499a5262eda2c1ad724737","In models, nucleation mode (1 nm &lt; Dp 10 nm) particle microphysics can be represented explicitly with aerosol microphysical processes or can be parameterized to obtain the growth and survival of nuclei to the model's lower size boundary. This study investigates how the representation of nucleation mode microphysics impacts aerosol number predictions in the TwO-Moment Aerosol Sectional (TOMAS) aerosol microphysics model running with the GISS GCM II-prime by varying its lowest diameter boundary: 1 nm, 3 nm, and 10 nm. The model with the 1 nm boundary simulates the nucleation mode particles with fully resolved microphysical processes, while the model with the 10 nm and 3 nm boundaries uses a nucleation mode dynamics parameterization to account for the growth of nucleated particles to 10 nm and 3 nm, respectively. We also investigate the impact of the time step for aerosol microphysical processes (a 10 min versus a 1 h time step) to aerosol number predictions in the TOMAS models with explicit dynamics for the nucleation mode particles (i.e., 3 nm and 1 nm boundary). The model with the explicit microphysics (i.e., 1 nm boundary) with the 10 min time step is used as a numerical benchmark simulation to estimate biases caused by varying the lower size cutoff and the time step. Different representations of the nucleation mode have a significant effect on the formation rate of particles larger than 10 nm from nucleated particles (J 10) and the burdens and lifetimes of ultrafine-mode (10 nm ≤ Dp ≤ 70 nm) particles but have less impact on the burdens and lifetimes of CCN-sized particles. The models using parameterized microphysics (i.e., 10 nm and 3 nm boundaries) result in higher J10 and shorter coagulation lifetimes of ultrafine-mode particles than the model with explicit dynamics (i.e., 1 nm boundary). The spatial distributions of CN10 (Dp ≥ 10 nm) and CCN(0.2%) (i.e., CCN concentrations at 0.2% supersaturation) are moderately affected, especially CN10 predictions above ∼ 700 hPa where nucleation contributes most strongly to CN10 concentrations. The lowermost-layer CN10 is substantially improved with the 3 nm boundary (compared to 10 nm) in most areas. The overprediction in CN10 with the 3 nm and 10 nm boundaries can be explained by the overprediction of J10 or J3 with the parameterized microphysics, possibly due to the instantaneous growth rate assumption in the survival and growth parameterization. The errors in CN10 predictions are sensitive to the choice of the lower size boundary but not to the choice of the time step applied to the microphysical processes. The spatial distribution of CCN(0.2%) with the 3 nm boundary is almost identical to that with the 1 nm boundary, but that with the 10 nm boundary can differ more than 10-40% in some areas. We found that the deviation in the 10 nm simulations is partly due to the longer time step (i.e., 1 h time step used in the 10 nm simulations compared to 10 min time step used in the benchmark simulations), but, even with the same time step, the 10 nm cutoff showed noticeably higher errors than the 3 nm cutoff. In conclusion, we generally recommend using a lower diameter boundary of 3 nm for studies focused on aerosol indirect effects but down to 1 nm boundary for studies focused on CN10 predictions or nucleation. © 2013 Author(s)."
"7006415284;57214957727;6602128405;56251307100;8849246700;7102680152;16833315000;7202779940;6603256829;6602336063;6602354484;55942083800;13407563600;55730602600;7004838931;6602443410;23971773000;8550791300;","Examination of laboratory-generated coated soot particles: An overview of the LACIS Experiment in November (LExNo) campaign",2010,"10.1029/2009JD012628","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953754747&doi=10.1029%2f2009JD012628&partnerID=40&md5=b42c53874af82e19e22b3658f6115afb","In the suite of laboratory measurements described here and in companion articles we deal with the hygroscopic growth and activation behavior of coated soot particles synthesized to mimic those of an atmospheric aerosol originating from biomass combustion. The investigations were performed during the measurement campaign LACIS Experiment in November (LExNo) which took place at the Leipzig Aerosol Cloud Interaction Simulator (LACIS). The specific goals of this campaign were (1) to perform a critical supersaturation measurement intercomparison using data sets from three different cloud condensation nucleus (CCN) instruments (two static thermal gradient type, one stream-wise thermal gradient type) and LACIS, (2) to examine particle hygroscopic growth (hydrated particle size as function of relative humidity) for particle characteristics such as aerosol mass spectrometer (AMS) measured soluble mass and particle morphology, and (3) to relate critical supersaturations derived from both measurements of soluble mass and high-humidity tandem differential mobility analyzer (HH-TDMA) determined growth factors to critical supersaturations measured by means of the CCN instruments. This paper provides information on the particle synthesis techniques used during LExNo, an overview concerning the particle characterization measurements performed, and, by proving relations between measured composition, hygroscopic growth, and activation data, lay the foundations for the detailed investigations described in the companion studies. In the context of the present paper, excellent agreement of the critical supersaturations measured with three different CCN instruments and LACIS was observed. Furthermore, clear relations between coating masses determined with AMS and both hygroscopic growth factors at 98% RH and measured critical supersaturations could be seen. Also, a strong correlation between measured hygroscopic growth (growth factors at 98%) and measured critical supersaturation for all of the differently coated soot particles (coating substances being levoglucosan and/or ammonium (hydrogen) sulfate) was found. This is clearly indicative of the possibility of predicting the critical supersaturation of coated soot particles based on hygroscopic growth measurements using Köhler theory. Copyright 2010 by the American Geophysical Union."
"7003566416;56251307100;6603577857;7101751527;7003748130;6602332621;7005287667;7405551904;7201787800;7006377579;7006235542;7103021308;7004713188;57203088526;","Validation of very high cloud droplet number concentrations in air masses transported thousands of kilometres over the ocean",2000,"10.1034/j.1600-0889.2000.00020.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18744429641&doi=10.1034%2fj.1600-0889.2000.00020.x&partnerID=40&md5=363e39a09b3565c15de52ee0eb71d075","The microstructure of orographic clouds related to the aerosol present was studied during the second Aerosol Characterisation Experiment (ACE-2). Very high cloud droplet number concentrations (almost 3000 cm-3) were observed. These high concentrations occurred when clouds formed on a hill slope at Tenerife in polluted air masses originating in Europe that had transported the order of 1000 km over the Atlantic Ocean. The validity of the measured droplet number concentrations was investigated by comparing with measurements of the aerosol upstream of the cloud and cloud interstitial aerosol. Guided by distributions of the ratios between the measurements, three criteria of typically 30% in maximum deviation were applied to the measurements to test their validity. Agreement was found for 88% of the cases. The validated data set spans droplet number concentrations of 150-3000 cm-3. The updraught velocity during the cloud formation was estimated to 2.2 m s-1 by model calculations, which is typical of cumuliform clouds. The results of the present study are discussed in relation to cloud droplet number concentrations previously reported in the literature. The importance of promoting the mechanistic understanding of the aerosol/cloud interaction and the use of validation procedures of cloud microphysical parameters is stressed in relation to the assessment of the indirect climatic effect of aerosols."
"36497832500;16644478700;57204727310;55728968600;7103325318;24802123400;8720083500;55703449100;24725566100;56689323900;55938857300;","PM2.5 Pollution Modulates Wintertime Urban Heat Island Intensity in the Beijing-Tianjin-Hebei Megalopolis, China",2020,"10.1029/2019GL084288","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078241251&doi=10.1029%2f2019GL084288&partnerID=40&md5=bd41ea05a215723e3a5e2479dab50be1","Heavy PM2.5 (particulate matter with aerodynamic diameter equal to or less than 2.5 μm) pollution and urban heat island (UHI) pose increasing threats to human health and living environment in populated cities. However, how PM2.5 pollution affects the UHI intensity (UHII) has not been fully understood. The impacts of PM2.5 on the wintertime UHII in the Beijing-Tianjin-Hebei megalopolis of China are explored during 2013–2017. The results show that the UHII at the time of daily maximum/minimum temperature (UHIImax/UHIImin) exhibits a decreasing/increasing tendency as PM2.5 concentration increases, causing a continuous decrease in the diurnal temperature range. These effects are mediated via aerosol-radiation interaction (aerosol-cloud interaction) under clear-sky (cloudy) condition. The changes in PM2.5 concentration further cause different relative trends of UHIImax/UHIImin/diurnal temperature range across different cities in the Beijing-Tianjin-Hebei region, which are likely related to the differences in both the PM2.5 composition and city size. This study provides insights on how air pollution affects urban climate and would help to design effective mitigation strategies. © 2019. The Authors."
"55717244800;57208660400;57206183419;57206200324;57190740194;","Global climate simulated by the Seoul National University Atmosphere Model version 0 with a unified convection scheme (SAM0-UNICON)",2019,"10.1175/JCLI-D-18-0796.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065036989&doi=10.1175%2fJCLI-D-18-0796.1&partnerID=40&md5=eab8f2bd5a72f0c2887a381532b106cf","As a contribution to phase 6 of the Coupled Model Intercomparison Project (CMIP6), the global climate simulated by an atmospheric general circulationmodel (GCM), the Seoul NationalUniversityAtmosphere Model version 0 with a Unified Convection Scheme (SAM0-UNICON), is compared with observation and climates simulated by the Community Atmosphere Model version 5 (CAM5) and Community Earth System Model version 1 (CESM1), on which SAM0-UNICON is based. Both SAM0-UNICON and CESM1 successfully reproduce observed global warming after 1970. The global mean climate simulated by SAM0-UNICON is roughly similar to that of CAM5/CESM1. However, SAM0-UNICON improves the simulations of the double intertropical convergence zone, shortwave cloud forcing, near-surface air temperature, aerosol optical depth, sea ice fraction, and sea surface temperature (SST), but is slightly poorer for the simulation of tropical relative humidity, Pacific surface wind stress, and ocean rainfall. Two important biases in the simulated mean climate in both models are a set of horseshoe-shaped biases of SST, sea level pressure, precipitation, and cloud radiative forcings in the central equatorial Pacific and a higher sea ice fraction in the Arctic periphery and Southern Hemispheric circumpolar regions. Both SAM0- UNICON and CESM1 simulate the observed El Niño-Southern Oscillation (ENSO) reasonably well. However, compared with CAM5/CESM1, SAM0-UNICON performs better in simulating the Madden- Julian oscillation (MJO), diurnal cycle of precipitation, and tropical cyclones. The aerosol indirect effect (AIE) simulated by SAM0-UNICON is similar to that from CAM5 but the magnitudes of the individual shortwave and longwave AIEs are substantially reduced. © 2019 American Meteorological Society."
"56898331700;25227357000;7102018821;57200702127;55717074000;55814053500;7404829395;56537463000;","Type-Dependent Responses of Ice Cloud Properties to Aerosols From Satellite Retrievals",2018,"10.1002/2018GL077261","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045908368&doi=10.1002%2f2018GL077261&partnerID=40&md5=4a4bb62928ac1204299525aa7bfc5b1f","Aerosol-cloud interactions represent one of the largest uncertainties in external forcings on our climate system. Compared with liquid clouds, the observational evidence for the aerosol impact on ice clouds is much more limited and shows conflicting results, partly because the distinct features of different ice cloud and aerosol types were seldom considered. Using 9-year satellite retrievals, we find that, for convection-generated (anvil) ice clouds, cloud optical thickness, cloud thickness, and cloud fraction increase with small-to-moderate aerosol loadings (<0.3 aerosol optical depth) and decrease with further aerosol increase. For in situ formed ice clouds, however, these cloud properties increase monotonically and more sharply with aerosol loadings. An increase in loading of smoke aerosols generally reduces cloud optical thickness of convection-generated ice clouds, while the reverse is true for dust and anthropogenic pollution aerosols. These relationships between different cloud/aerosol types provide valuable constraints on the modeling assessment of aerosol-ice cloud radiative forcing. ©2018. American Geophysical Union. All Rights Reserved."
"55802355600;55624488227;42761459200;56720568200;55053146200;57214419797;56500741100;56068376200;","Enhancement of PM2.5 Concentrations by Aerosol-Meteorology Interactions Over China",2018,"10.1002/2017JD027524","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041011306&doi=10.1002%2f2017JD027524&partnerID=40&md5=dfd32a5f2efa254af3d6180e21f2a69f","Aerosol-meteorology interactions can change surface aerosol concentrations via different mechanisms such as altering radiation budget or cloud microphysics. However, few studies investigated the impacts of different mechanisms on temporal and spatial distribution of PM2.5 concentrations over China. Here we used the fully coupled Weather Research and Forecasting model with online chemistry (WRF-Chem) to quantify the enhancement of PM2.5 concentrations by aerosol-meteorology feedback in China in 2014 for different seasons and separate the relative impacts of aerosol radiation interactions (ARIs) and aerosol-cloud interactions (ACIs). We found that ARIs and ACIs could increase population-weighted annual mean PM2.5 concentration over China by 4.0 μg/m3 and 1.6 μg/m3, respectively. We found that ARIs play a dominant role in aerosol-meteorology interactions in winter, while the enhancement of PM2.5 concentration by ARIs and ACIs is comparable in other three seasons. ARIs reduced the wintertime monthly mean wind speed and planetary boundary layer (PBL) height by up to 0.1 m/s and 160 m, respectively, but increased the relative humidity by up to 4%, leading to accumulation of pollutants within PBL. Also, ARIs reduced dry deposition velocity of aerosols by up to 20%, resulting in an increase in PM2.5 lifetime and concentrations. ARIs can increase wintertime monthly mean surface PM2.5 concentration by a maximum of 30 μg/m3 in Sichuan Basin. ACIs can also increase PM2.5 concentration with more significant impacts in wet seasons via reduced wet scavenging and enhanced in-cloud chemistry. Dominant processes in PM2.5 enhancement are also clarified in different seasons. Results show that physical process is more important than chemical processes in winter in ARIs, while chemical process of secondary inorganic aerosols production may be crucial in wet seasons via ACIs. ©2017. American Geophysical Union. All Rights Reserved."
"57132509000;23003259600;55495632500;57189378782;57216168952;16481561000;57131646800;57191334192;56375286600;55689034100;56068376200;","Evaluation of radiosonde, MODIS-NIR-Clear, and AERONET precipitable water vapor using IGS ground-based GPS measurements over China",2017,"10.1016/j.atmosres.2017.07.021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85026861405&doi=10.1016%2fj.atmosres.2017.07.021&partnerID=40&md5=7f1d0032e1b1059aea5a8f13c03a9031","Water vapor is one of the major greenhouse gases in the atmosphere and also the key parameter affecting the hydrological cycle, aerosol properties, aerosol-cloud interactions, the energy budget, and the climate. This study analyzed the temporal and spatial distribution of precipitable water vapor (PWV) in China using MODerate resolution Imaging Spectroradiometer near-infrared (MODIS-NIR)-Clear PWV products from 2011 to 2013. We then compared the four PWV products (Global Positioning System PWV (GPS-PWV), radiosonde PWV (RS-PWV), MODIS-NIR-Clear PWV, and Aerosol Robotic Network sunphotometer PWV (AERONET-PWV)) at six typical sites in China from 2011 to 2013. The analysis of the temporal and spatial distribution showed that the PWV distribution in China has clear geographical differences, and its basic distribution characteristics gradually change from the coast in the southeast to inland in the northwest. Affected by the East Asian monsoon, the PWV over China showed clear seasonal distribution features, with highest values in the summer, followed by autumn and spring, and the lowest values in winter. Intercomparison results showed that GPS-PWV and RS-PWV had a slightly higher correlation (R2 = 0.975) at 0000 UTC than that at 1200 UTC (R2 = 0.967). The mean values of Bias, SD, and RMSE between GPS-PWV and RS-PWV (GPS-RS) were − 0.03 mm, 2.36 mm, and 2.60 mm at 0000 UTC, and − 0.23 mm, 2.76 mm, and 2.95 mm at 1200 UTC, respectively. This showed that GPS-PWV was slightly lower than RS-PWV, and this difference was more obvious during the nighttime. The MODIS-NIR-Clear PWV product showed a similar correlation coefficient (R2 = 0.88) with GPS-PWV compared with RS-PWV. In addition, MODIS-NIR-Clear PWV was greater than GPS-PWV and RS-PWV. The MODIS-NIR-Clear PWV showed a larger deviation from GPS-PWV (MODIS-GPS Bias = 1.50 mm, RMSE = 5.76 mm) compared with RS PWV (MODIS-RS Bias = 0.75 mm, RMSE = 5.31 mm). The correlation coefficients between AERONET-PWV and the PWV from GPS, RS, and MODIS-NIR-Clear were 0.970, 0.963, and 0.923 (with RMSE of 2.53 mm, 3.67 mm, and 4.39 mm), respectively. In the Beijing area, the overall mean bias of the AERONET-PWV product with GPS-PWV, RS-PWV and MODIS-NIR-Clear PWV was − 0.09 mm, − 1.82 mm, and − 1.54 mm, respectively, which shows that the AERONET-PWV product was lower than the other three PWV products. © 2017 Elsevier B.V."
"57206330745;6603258995;6603566335;","Impact of aerosols and clouds on decadal trends in all-sky solar radiation over the Netherlands (1966-2015)",2017,"10.5194/acp-17-8081-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85022217951&doi=10.5194%2facp-17-8081-2017&partnerID=40&md5=25b5b3ee1cb7bb0f9145efbe1d7feff2","A 50-year hourly data set of global shortwave radiation, cloudiness and visibility over the Netherlands was used to quantify the contribution of aerosols and clouds to the trend in yearly-averaged all-sky radiation (1.81±1.07Wm-2decade-1). Yearly-averaged clear-sky and cloud-base radiation data show large year-to-year fluctuations caused by yearly changes in the occurrence of clear and cloudy periods and cannot be used for trend analysis. Therefore, proxy clear-sky and cloud-base radiations were computed. In a proxy analysis hourly radiation data falling within a fractional cloudiness value are fitted by monotonic increasing functions of solar zenith angle and summed over all zenith angles occurring in a single year to produce an average. Stable trends can then be computed from the proxy radiation data. A functional expression is derived whereby the trend in proxy all-sky radiation is a linear combination of trends in fractional cloudiness, proxy clear-sky radiation and proxy cloud-base radiation. Trends (per decade) in fractional cloudiness, proxy clear-sky and proxy cloud-base radiation were, respectively, 0.0097±0.0062, 2.78±0.50 and 3.43±1.17Wm-2. To add up to the all-sky radiation the three trends have weight factors, namely the difference between the mean cloud-base and clear-sky radiation, the clear-sky fraction and the fractional cloudiness, respectively. Our analysis clearly demonstrates that all three components contribute significantly to the observed trend in all-sky radiation. Radiative transfer calculations using the aerosol optical thickness derived from visibility observations indicate that aerosol-radiation interaction (ARI) is a strong candidate to explain the upward trend in the clear-sky radiation. Aerosol-cloud interaction (ACI) may have some impact on cloud-base radiation, but it is suggested that decadal changes in cloud thickness and synoptic-scale changes in cloud amount also play an important role. © Author(s) 2017."
"36822103700;7201463831;8643993200;6506458269;57203776263;26643054400;7004242319;6701378450;6603372665;6602356428;6506424404;18134565600;","Aircraft-measured indirect cloud effects from biomass burning smoke in the Arctic and subarctic",2016,"10.5194/acp-16-715-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957311125&doi=10.5194%2facp-16-715-2016&partnerID=40&md5=3ec7c09c07ef3916bb0849befaef46e8","The incidence of wildfires in the Arctic and subarctic is increasing; in boreal North America, for example, the burned area is expected to increase by 200-300g% over the next 50-100 years, which previous studies suggest could have a large effect on cloud microphysics, lifetime, albedo, and precipitation. However, the interactions between smoke particles and clouds remain poorly quantified due to confounding meteorological influences and remote sensing limitations. Here, we use data from several aircraft campaigns in the Arctic and subarctic to explore cloud microphysics in liquid-phase clouds influenced by biomass burning. Median cloud droplet radii in smoky clouds were g1/4 g40-60g% smaller than in background clouds. Based on the relationship between cloud droplet number (Nliq) and various biomass burning tracers (BBt) across the multi-campaign data set, we calculated the magnitude of subarctic and Arctic smoke aerosol-cloud interactions (ACIs, where ACI Combining double low line (1g•3) × dln(Nliq)g•dln(BBt)) to be g1/4 g0.16 out of a maximum possible value of 0.33 that would be obtained if all aerosols were to nucleate cloud droplets. Interestingly, in a separate subarctic case study with low liquid water content ( g1/4 g0.02gggmg'3) and very high aerosol concentrations (2000-3000gcmg'3) in the most polluted clouds, the estimated ACI value was only 0.05. In this case, competition for water vapor by the high concentration of cloud condensation nuclei (CCN) strongly limited the formation of droplets and reduced the cloud albedo effect, which highlights the importance of cloud feedbacks across scales. Using our calculated ACI values, we estimate that the smoke-driven cloud albedo effect may decrease local summertime short-wave radiative flux by between 2 and 4gWgmg'2 or more under some low and homogeneous cloud cover conditions in the subarctic, although the changes should be smaller in high surface albedo regions of the Arctic. We lastly explore evidence suggesting that numerous northern-latitude background Aitken particles can interact with combustion particles, perhaps impacting their properties as cloud condensation and ice nuclei. © Author(s) 2016."
"35868180800;7005477332;7004315232;6701416358;","Human-caused fires limit convection in tropical Africa: First temporal observations and attribution",2015,"10.1002/2015GL065063","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940448515&doi=10.1002%2f2015GL065063&partnerID=40&md5=9ac628267e7a8697ebb976fe383a1244","It is well established that smoke particles modify clouds, which in turn affects climate. However, no study has quantified the temporal dynamics of aerosol-cloud interactions with direct observations. Here for the first time, we use temporally offset satellite observations from northern Africa between 2006 and 2010 to quantitatively measure the effect of fire aerosols on convective cloud dynamics. We attribute a reduction in cloud fraction during periods of high aerosol optical depths to a smoke-driven inhibition of convection. We find that higher smoke burdens limit upward vertical motion, increase surface pressure, and increase low-level divergence - meteorological indicators of convective suppression. These results are corroborated by climate simulations that show a smoke-driven increase in regionally averaged shortwave tropospheric heating and decrease in convective precipitation during the fire season. Our results suggest that in tropical regions, anthropogenic fire initiates a positive feedback loop where increased aerosol emissions limit convection, dry the surface, and enable increased fire activity via human ignition. ©2015. American Geophysical Union. All Rights Reserved."
"57217772325;7410041005;54783792600;55717074000;56119479900;7202708481;","Global dust distribution from improved thin dust layer detection using A-train satellite lidar observations",2015,"10.1002/2014GL062111","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923543866&doi=10.1002%2f2014GL062111&partnerID=40&md5=abb1088e773592433e1ba1cfc27fd764","A new dust detection algorithm was developed to take advantage of strong dust signals in the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) 532 nm perpendicular channel to more accurately identify optically thin dust layer boundaries. Layer mean particulate depolarization ratios and improved thin ice cloud detections by combining CALIPSO and CloudSat products were used to further refine the dust mask. Three year global mean results show that the new method detects dust occurrences total detected dust case numbertotal observation number of 0.12 and 0.028 below and above 4 km altitudes, while CALIPSO Level 2 products reported 0.07 and 0.012, respectively. The improvements are mainly in weak source and transporting regions, and the upper troposphere, where optically thin, but significant dust layers from the point of view of aerosol-cloud interactions are dominated. The results can help us to better understand global dust transportation and dust-cloud interactions and improve model simulations. © 2015. American Geophysical Union. All Rights Reserved."
"35798085000;7202779940;25624725200;55682691500;57189024386;18437651200;8550791300;7006415284;","Application of linear polarized light for the discrimination of frozen and liquid droplets in ice nucleation experiments",2013,"10.5194/amt-6-1041-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882744486&doi=10.5194%2famt-6-1041-2013&partnerID=40&md5=790085070a802c8d91e5c3d153ed259e","We report on the development and test results of the new optical particle counter TOPS-Ice (Thermostabilized Optical Particle Spectrometer for the detection of Ice). The instrument uses measurements of the cross-polarized scattered light by single particles into the near-forward direction (42.5° ± 12.7°) to distinguish between spherical and non-spherical particles. This approach allows the differentiation between liquid water droplets (spherical) and ice particles (non-spherical) having similar volume-equivalent sizes and therefore can be used to determine the fraction of frozen droplets in a typical immersion freezing experiment. We show that the numerical simulation of the light scattered on non-spherical particles (spheroids in random orientation) considering the actual scattering geometry used in the instrument supports the validity of the approach, even though the cross-polarized component of the light scattered by spherical droplets does not vanish in this scattering angle. For the separation of the ice particle mode from the liquid droplet mode, we use the width of the pulse detected in the depolarization channel instead of the pulse height. Exploiting the intrinsic relationship between pulse height and pulse width for Gaussian pulses allows us to calculate the fraction of frozen droplets even if the liquid droplet mode dominates the particle ensemble. We present test results obtained with TOPS-Ice in the immersion freezing experiments at the laminar diffusion chamber LACIS (Leipzig Aerosol Cloud Interaction Simulator) and demonstrate the excellent agreement with the data obtained in similar experiments with a different optical instrument. Finally, the advantages of using the cross-polarized light measurements for the differentiation of liquid and frozen droplets in the realistic immersion freezing experiments are discussed. © Author(s) 2013."
"57203793097;7005135473;","Statistical properties of aerosol-cloud-precipitation interactions in South America",2010,"10.5194/acp-10-2287-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860389175&doi=10.5194%2facp-10-2287-2010&partnerID=40&md5=7da2a78729b1a849d6e779f5ee03c782","Given the complex interaction between aerosol, cloud, and atmospheric properties, it is difficult to extract their individual effects to observed rainfall amount. This research uses principle component analysis (PCA) that combines Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol and cloud products, NCEP Reanalysis atmospheric products, and rainrate estimates from the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) to assess if aerosols affect warm rain processes. Data collected during September 2006 over the Amazon basin in South America during the biomass-burning season are used. The goal of this research is to combine these observations into a smaller number of variables through PCA with each new variable having a unique physical interpretation. In particular, we are concerned with PC variables whose weightings include aerosol optical thickness (AOT), as these may be an indicator of aerosol indirect effects. If they are indeed occurring, then PC values that include AOT should change as a function of rainrate. To emphasize the advantage of PCA, changes in aerosol, cloud, and atmospheric observations are compared to rainrate. Comparing no-rain, rain, and heavy rain only (&gt;5mmh?1) samples, we find that cloud thicknesses, humidity, and upward motion are all greater during rain and heavy rain conditions. However, no statistically significant difference in AOT exists between each sample, indicating that atmospheric conditions are more important to rainfall than aerosol concentrations as expected. If aerosols are affecting warm process clouds, it would be expected that stratiform precipitation would decrease as a function increasing aerosol concentration through either Twomey and/or semidirect effects. PCA extracts the latter signal in a variable labeled PC2, which explains 15% of the total variance and is second in importance the variable (PC1) containing the broad atmospheric conditions. PC2 contains weightings showing that AOT is inversely proportional to low-level humidity and cloud optical thickness. Increasing AOT is also positively correlated with increasing low-level instability due to aerosol absorption. The nature of these weightings is strongly suggestive that PC2 is an indicator of the semi-direct effect with larger values associated with lower rainfall rates. PC weightings consistent with the Twomey effect (an anti-correlation between AOT and cloud droplet effective radius) are only present in higher order PC variables that explain less than 1% of the total variance, and do not vary significantly as a function of rainrate. If the Twomey effect is occurring, it is highly non-linear and/or being overshadowed by other processes. Using the raw variables alone, these determinations could not be made; thus, we are able to show the advantage of using advanced statistical techniques such as PCA for analysis of aerosols impacts on precipitation in South America. © 2010 Author(s)."
"6602244257;7202252296;56744278700;","A microphysics-based investigation of the radiative effects of aerosol-cloud interactions for two MAST experiment case studies",2001,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035045731&partnerID=40&md5=dfecfcbcf4c02a0655a77bd197779119","We use a size- and composition-resolved externally mixed aerosol microphysical model and a delta-Eddington exponential-sum-fit radiation algorithm to examine the interactions between aerosol particles and cloud drops, and their influence on solar radiation. Both the aerosol model and the radiation code are designed to explicitly handle external and internal aerosol particle and cloud drop mixtures. Using observations from the Monterey Area Ship Track (MAST) Experiment, we model changes in aerosol and cloud drop size distributions for a clean marine cloud and ship track and a continentally influenced marine cloud and ship track. Linking these results to the radiation algorithm with a Miescattering subroutine, we investigate the corresponding changes in cloud albedo, cloud absorption, and transmission. The differences in 0.3-3.0 μm albedo and transmission between the clouds and ship tracks as a result of the changes in drop size distribution and composition are found to be substantial, and the composition of the cloud drops is found to be important particularly in the continentally influenced case. Both the clouds and ship tracks enhance atmospheric absorption with respect to a clear sky, with a cloud forcing ratio ranging from 1.15 to 1.37, where the clear sky is defined to be cloud- and aerosol-free. Sensitivity studies are performed with respect to the updraft velocity, the updraft area fraction, dilution of the ship emissions, and the composition of supermicron continental particles. The radiation results are also compared with Meteorological Research Flight (MRF) C-130 in situ aircraft measurements and with parameterizations of the Twomey effect."
"6603936062;7102743829;23047834100;","Evaluation of sulfate aerosols indirect effect in marine stratocumulus clouds using observation-derived cloud climatology",1996,"10.1029/96GL01793","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030199798&doi=10.1029%2f96GL01793&partnerID=40&md5=eebb020d68b7fe87fc85cbccd977f06d","The indirect shortwave effect of anthropogenic sulfate aerosol augmentation in marine stratocumulus clouds has been evaluated using global cloud climatology, sulfate aerosol data from a chemical model, and cloud albedo augmentation obtained from a large-eddy simulation (LES) cloud model with explicit microphysics. It is found that the annually and globally (over the oceans) averaged indirect shortwave forcing is -1.1 Wm-2, with a hemispheric difference of 0.4 Wm-2. Given the many uncertainties in the aerosol-CCN-cloud microstructure links, this estimate, most likely, should be considered as an upper limit of the aerosol indirect forcing. The hemispheric forcing has a strong seasonal cycle with the Northern Hemisphere (NH) forcing exceeding the Southern Hemisphere (SH) forcing during the NH spring and summer and the SH forcing prevailing during the SH spring and summer. We also estimate that the single layer St/Sc contributes most to the aerosol indirect forcing (60%) with an additional 25% from the St/Sc overlapped with Ci/Cs/Cc, and 15% from St/Sc overlapped with As/Ac. Copyright 1996 by the American Geophysical Union."
"57217266035;57204216001;35232912700;57201215838;57204209556;57213358341;57140859500;35405390200;28568055900;24722339600;","Time-dependent entrainment of smoke presents an observational challenge for assessing aerosol-cloud interactions over the southeast Atlantic Ocean",2018,"10.5194/acp-18-14623-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054958865&doi=10.5194%2facp-18-14623-2018&partnerID=40&md5=e70dcd518bcd5ef123dacac5c4bffec0","The colocation of clouds and smoke over the southeast Atlantic Ocean during the southern African biomass burning season has numerous radiative implications, including microphysical modulation of the clouds if smoke is entrained into the marine boundary layer. NASA's ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) campaign is studying this system with aircraft in three field deployments between 2016 and 2018. Results from ORACLES-2016 show that the relationship between cloud droplet number concentration and smoke below cloud is consistent with previously reported values, whereas cloud droplet number concentration is only weakly associated with smoke immediately above cloud at the time of observation. By combining field observations, regional chemistry-climate modeling, and theoretical boundary layer aerosol budget equations, we show that the history of smoke entrainment (which has a characteristic mixing timescale on the order of days) helps explain variations in cloud properties for similar instantaneous above-cloud smoke environments. Precipitation processes can obscure the relationship between above-cloud smoke and cloud properties in parts of the southeast Atlantic, but marine boundary layer carbon monoxide concentrations for two case study flights suggest that smoke entrainment history drove the observed differences in cloud properties for those days. A Lagrangian framework following the clouds and accounting for the history of smoke entrainment and precipitation is likely necessary for quantitatively studying this system; an Eulerian framework (e.g., instantaneous correlation of A-train satellite observations) is unlikely to capture the true extent of smoke-cloud interaction in the southeast Atlantic. © 2018 Author(s)."
"57196414931;7003414581;8927405700;55933600200;24366038500;36620394700;56270311300;","Profiling of Saharan dust from the Caribbean to western Africa-Part 1: Layering structures and optical properties from shipborne polarization/Raman lidar observations",2017,"10.5194/acp-17-12963-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032948395&doi=10.5194%2facp-17-12963-2017&partnerID=40&md5=8444bee4a793070116e4e5310da7923e","We present final and quality-assured results of multiwavelength polarization/Raman lidar observations of the Saharan air layer (SAL) over the tropical Atlantic. Observations were performed aboard the German research vessel R/V Meteor during the 1-month transatlantic cruise from Guadeloupe to Cabo Verde over 4500 km from 61.5 to 20 W at 14-15 N in April-May 2013. First results of the shipborne lidar measurements, conducted in the framework of SALTRACE (Saharan Aerosol Long-range Transport and Aerosol-Cloud Interaction Experiment), were reported by Kanitz et al. (2014). Here, we present four observational cases representing key stages of the SAL evolution between Africa and the Caribbean in detail in terms of layering structures and optical properties of the mixture of predominantly dust and aged smoke in the SAL. We discuss to what extent the lidar results confirm the validity of the SAL conceptual model which describes the dust long-range transport and removal processes over the tropical Atlantic. Our observations of a clean marine aerosol layer (MAL, layer from the surface to the SAL base) confirm the conceptual model and suggest that the removal of dust from the MAL, below the SAL, is very efficient. However, the removal of dust from the SAL assumed in the conceptual model to be caused by gravitational settling in combination with large-scale subsidence is weaker than expected. To explain the observed homogenous (heightindependent) dust optical properties from the SAL base to the SAL top, from the African coast to the Caribbean, we have to assume that the particle sedimentation strength is reduced and dust vertical mixing and upward transport mechanisms must be active in the SAL. Based on lidar observations on 20 nights at different longitudes in May 2013, we found, on average, MAL and SAL layer mean values (at 532 nm) of the extinction-to-backscatter ratio (lidar ratio) of 17-5 sr (MAL) and 43±8 sr (SAL), of the particle linear depolarization ratio of 0:025±0:015 (MAL) and 0:19±0:09 (SAL), and of the particle extinction coefficient of 67±45Mm..1 (MAL) and 68±37Mm..1 (SAL). The 532 nm optical depth of the lofted SAL was found to be, on average, 0:15±0:13 during the ship cruise. The comparably low values of the SAL mean lidar ratio and depolarization ratio (compared to typical pure dust values of 50-60 sr and 0.3, respectively) in combination with backward trajectories indicate a smoke contribution to light extinction of the order of 20% during May 2013, at the end of the burning season in central-western Africa. 1. © 2017 Author(s)."
"57195966145;8550791300;26424128800;25624725200;57193798535;57191955465;56369730900;38760907700;7006415284;15923105200;","Leipzig Ice Nucleation chamber Comparison (LINC): Intercomparison of four online ice nucleation counters",2017,"10.5194/acp-17-11683-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030542875&doi=10.5194%2facp-17-11683-2017&partnerID=40&md5=a4aae7be15f1499c03f0815f2e7d8b52","Ice crystal formation in atmospheric clouds has a strong effect on precipitation, cloud lifetime, cloud radiative properties, and thus the global energy budget. Primary ice formation above 235 K is initiated by nucleation on seed aerosol particles called ice-nucleating particles (INPs). Instruments that measure the ice-nucleating potential of aerosol particles in the atmosphere need to be able to accurately quantify ambient INP concentrations. In the last decade several instruments have been developed to investigate the ice-nucleating properties of aerosol particles and to measure ambient INP concentrations. Therefore, there is a need for intercomparisons to ensure instrument differences are not interpreted as scientific findings. In this study, we intercompare the results from parallel measurements using four online ice nucleation chambers. Seven different aerosol types are tested including untreated and acid-treated mineral dusts (microcline, which is a K-feldspar, and kaolinite), as well as birch pollen washing waters. Experiments exploring heterogeneous ice nucleation above and below water saturation are performed to cover the whole range of atmospherically relevant thermodynamic conditions that can be investigated with the intercompared chambers. The Leipzig Aerosol Cloud Interaction Simulator (LACIS) and the Portable Immersion Mode Cooling chAmber coupled to the Portable Ice Nucleation Chamber (PIMCA-PINC) performed measurements in the immersion freezing mode. Additionally, two continuous-flow diffusion chambers (CFDCs) PINC and the Spectrometer for Ice Nuclei (SPIN) are used to perform measurements below and just above water saturation, nominally presenting deposition nucleation and condensation freezing. The results of LACIS and PIMCA-PINC agree well over the whole range of measured frozen fractions (FFs) and temperature. In general PINC and SPIN compare well and the observed differences are explained by the ice crystal growth and different residence times in the chamber. To study the mechanisms responsible for the ice nucleation in the four instruments, the FF (from LACIS and PIMCA-PINC) and the activated fraction, AF (from PINC and SPIN), are compared. Measured FFs are on the order of a factor of 3 higher than AFs, but are not consistent for all aerosol types and temperatures investigated. It is shown that measurements from CFDCs cannot be assumed to produce the same results as those instruments exclusively measuring immersion freezing. Instead, the need to apply a scaling factor to CFDCs operating above water saturation has to be considered to allow comparison with immersion freezing devices. Our results provide further awareness of factors such as the importance of dispersion methods and the quality of particle size selection for intercomparing online INP counters. © 2017 Author(s)."
"55462884000;56612517400;36538539800;","Impact of future climate policy scenarios on air quality and aerosol-cloud interactions using an advanced version of CESM/CAM5: Part I. model evaluation for the current decadal simulations",2017,"10.1016/j.atmosenv.2016.12.035","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007452347&doi=10.1016%2fj.atmosenv.2016.12.035&partnerID=40&md5=71ff1f23fc5e41415791d2702cfdcd0a","A version of the Community Earth System Model modified at the North Carolina State University (CESM-NCSU) is used to simulate the current and future atmosphere following the representative concentration partway scenarios for stabilization of radiative forcing at 4.5 W m−2(RCP4.5) and radiative forcing of 8.5 W m−2(RCP8.5). Part I describes the results from a comprehensive evaluation of current decadal simulations. Radiation and most meteorological variables are well simulated in CESM-NCSU. Cloud parameters are not as well simulated due in part to the tuning of model radiation and general biases in cloud variables common to all global chemistry-climate models. The concentrations of most inorganic aerosol species (i.e., SO42-, NH4+, and NO3−) are well simulated with normalized mean biases (NMBs) typically less than 20%. However, some notable exceptions are European NH4+, which is overpredicted by 33.0–42.2% due to high NH3emissions and irreversible coarse mode condensation, and Cl−, that is negatively impacted by errors in emissions driven by wind speed and overpredicted HNO3. Carbonaceous aerosols are largely underpredicted following the RCP scenarios due to low emissions of black carbon, organic carbon, and anthropogenic volatile compounds in the RCP inventory and efficient wet removal. This results in underpredictions of PM2.5and PM10by 6.4–55.7%. The column mass abundances are reasonably well simulated. Larger biases occur in surface mixing ratios of trace gases in CESM-NCSU, likely due to numerical diffusion from the coarse grid spacing of the CESM-NCSU simulations or errors in the magnitudes and vertical structure of emissions. This is especially true for SO2and NO2. The mixing ratio of O3is overpredicted by 38.9–76.0% due to the limitations in the O3deposition scheme used in CESM and insufficient titration resulted from large underpredictions in NO2. Despite these limitations, CESM-NCSU reproduces reasonably well the current atmosphere in terms of radiation, clouds, meteorology, trace gases, aerosols, and aerosol-cloud interactions, making it suitable for future climate simulations. © 2016 Elsevier Ltd"
"22834248200;57189089842;9846154100;17434636400;7006377579;9043417100;7201787800;7102603429;7006235542;57195257572;","Observations of fluorescent aerosol-cloud interactions in the free troposphere at the High-Altitude Research Station Jungfraujoch",2016,"10.5194/acp-16-2273-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959387781&doi=10.5194%2facp-16-2273-2016&partnerID=40&md5=409826e314be92d826172e0730dd17b3","The fluorescent nature of aerosol at a high-altitude Alpine site was studied using a wide-band integrated bioaerosol (WIBS-4) single particle multi-channel ultraviolet - light-induced fluorescence (UV-LIF) spectrometer. This was supported by comprehensive cloud microphysics and meteorological measurements with the aims of cataloguing concentrations of bio-fluorescent aerosols at this high-altitude site and also investigating possible influences of UV-fluorescent particle types on cloud-aerosol processes. Analysis of background free tropospheric air masses, using a total aerosol inlet, showed there to be a minor increase in the fluorescent aerosol fraction during in-cloud cases compared to out-of-cloud cases. The size dependence of the fluorescent aerosol fraction showed the larger aerosol to be more likely to be fluorescent with 80% of 10 μm particles being fluorescent. Whilst the fluorescent particles were in the minority (NFl/NAll = 0.27 ± 0.19), a new hierarchical agglomerative cluster analysis approach, Crawford et al. (2015) revealed the majority of the fluorescent aerosols were likely to be representative of fluorescent mineral dust. A minor episodic contribution from a cluster likely to be representative of primary biological aerosol particles (PBAP) was also observed with a wintertime baseline concentration of 0.1 ± 0.4 L-1. Given the low concentration of this cluster and the typically low ice-active fraction of studied PBAP (e.g. pseudomonas syringae), we suggest that the contribution to the observed ice crystal concentration at this location is not significant during the wintertime. © Author(s) 2016."
"25031430500;7004214645;7102976560;","Impact of aerosol radiative effects on 2000–2010 surface temperatures",2015,"10.1007/s00382-014-2464-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943819596&doi=10.1007%2fs00382-014-2464-2&partnerID=40&md5=93d13d29a8717dcf966ae7a4e789eaa4","Aerosol radiative forcing from direct and indirect effects of aerosols is examined over the recent past (last 10–15 years) using updated sulfate aerosol emissions in two Earth System Models with very different surface temperature responses to aerosol forcing. The hypothesis is that aerosol forcing and in particular, the impact of indirect effects of aerosols on clouds (Aerosol–Cloud Interactions, or ACI), explains the recent ‘hiatus’ in global mean surface temperature increases. Sulfate aerosol emissions increase globally from 2000 to 2005, and then decrease slightly to 2010. Thus the change in anthropogenic sulfate induced net global radiative forcing is small over the period. Regionally, there are statistically significant forcings that are similar in both models, and consistent with changes in simulated emissions and aerosol optical depth. Coupled model simulations are performed to look at impacts of the forcing on recent surface temperatures. Temperature response patterns in the models are similar, and reflect the regional radiative forcing. Pattern correlations indicate significant correlations between observed decadal surface temperature changes and simulated surface temperature changes from recent sulfate aerosol forcing in an equilibrium framework. Sulfate ACI might be a contributor to the spatial patterns of recent temperature forcing, but not to the global mean ‘hiatus’ itself. © 2015, Springer-Verlag Berlin Heidelberg."
"55938109300;39361670300;54941580100;7006304904;55879681300;7004713805;13007286600;55807448700;56489746200;24767977600;22635720500;7003862871;54982705800;6505947323;9738422100;","Sensitivity analysis of the microphysics scheme in WRF-Chem contributions to AQMEII phase 2",2015,"10.1016/j.atmosenv.2015.01.047","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937132465&doi=10.1016%2fj.atmosenv.2015.01.047&partnerID=40&md5=c566ad2cfaf97e677f45ab87b32865c0","The parameterization of cloud microphysics is a crucial part of fully-coupled meteorology-chemistry models, since microphysics governs the formation, growth and dissipation of hydrometeors and also aerosol cloud interactions. The main objective of this study, which is based on two simulations for Europe contributing to Phase 2 of the Air Quality Model Evaluation International Initiative (AQMEII) is to assess the sensitivity of WRF-Chem to the selection of the microphysics scheme. Two one-year simulations including aerosol cloud interactions with identical physical-chemical parameterizations except for the microphysics scheme (Morrison -MORRAT vs Lin -LINES) are compared. The study covers the difference between the simulations for two three-month periods (cold and a warm) during the year 2010, allowing thus a seasonal analysis. Overall, when comparing to observational data, no significant benefits from the selection of the microphysical schemes can be derived from the results. However, these results highlight a marked north-south pattern of differences, as well as a decisive impact of the aerosol pollution on the results. The MORRAT simulation resulted in higher cloud water mixing ratios over remote areas with low CCN concentrations, whereas the LINES simulation yields higher cloud water mixing ratios over the more polluted areas. Regarding the droplet number mixing ratio, the Morrison scheme was found to yield higher values both during winter and summer for nearly the entire model domain. As smaller and more numerous cloud droplets are more effective in scattering shortwave radiation, the downwelling shortwave radiation flux at surface was found to be up to 30 W m-2 lower for central Europe for the MORRAT simulation as compared to the simulation using the LINES simulation during wintertime. Finally, less convective precipitation is simulated over land with MORRAT during summertime, while no almost difference was found for the winter. On the other hand, non-convective precipitation was up to 4 mm lower during wintertime over Italy and the Balkans for the case of including Lin microphysics as compared to the MORRAT simulation. © 2015 Elsevier Ltd."
"13405658600;8728433200;56682032300;55683891800;7501381728;","The importance of interstitial particle scavenging by cloud droplets in shaping the remote aerosol size distribution and global aerosol-climate effects",2015,"10.5194/acp-15-6147-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930959649&doi=10.5194%2facp-15-6147-2015&partnerID=40&md5=59be22da4edca63c2ffda224be02d802","In this paper, we investigate the coagulation of interstitial aerosol particles (particles too small to activate to cloud droplets) with cloud drops, a process often ignored in aerosol-climate models. We use the GEOS-Chem-TOMAS (Goddard Earth Observing System-Chemistry TwO-Moment Aerosol Sectional) global chemical transport model with aerosol microphysics to calculate the changes in the aerosol size distribution, cloud-albedo aerosol indirect effect, and direct aerosol effect due to the interstitial coagulation process. We find that inclusion of interstitial coagulation in clouds lowers total particle number concentrations by 15-21% globally, where the range is due to varying assumptions regarding activation diameter, cloud droplet size, and ice cloud physics. The interstitial coagulation process lowers the concentration of particles with dry diameters larger than 80 nm (a proxy for larger CCN) by 10-12%. These 80 nm particles are not directly removed by the interstitial coagulation but are reduced in concentration because fewer smaller particles grow to diameters larger than 80 nm. The global aerosol indirect effect of adding interstitial coagulation varies from +0.4 to +1.3 W m-2 where again the range depends on our cloud assumptions. Thus, the aerosol indirect effect of this process is significant, but the magnitude depends greatly on assumptions regarding activation diameter, cloud droplet size, and ice cloud physics. The aerosol direct effect of the interstitial coagulation process is minor (< 0.01 W m-2) due to the shift in the aerosol size distribution at sizes where scattering is most effective being small. We recommend that this interstitial scavenging process be considered in aerosol models when the size distribution and aerosol indirect effects are important."
"56556953400;6506718750;7003501766;","Sensitivity of PARASOL multi-angle photopolarimetric aerosol retrievals to cloud contamination",2015,"10.5194/amt-8-1287-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925002714&doi=10.5194%2famt-8-1287-2015&partnerID=40&md5=175d5e7e4ce0d0813bd9013773e7dfdd","An important problem in satellite remote sensing of aerosols is related to the need to perform an adequate cloud screening. If a cloud screening is applied that is not strict enough, the ground scene has the probability of residual cloud cover which causes large errors on the retrieved aerosol parameters. On the other hand, if the cloud-screening procedure is too strict, too many clear sky cases, especially near-cloud scenes, will falsely be flagged cloudy. The detrimental effects of cloud contamination as well as the importance of aerosol cloud interactions that can be studied in these near-cloud scenes call for new approaches to cloud screening. Multi-angle multi-wavelength photopolarimetric measurements have a unique capability to distinguish between scattering by (liquid) cloud droplets and aerosol particles. In this paper the sensitivity of aerosol retrievals from multi-angle photopolarimetric measurements to cloud contamination is investigated and the ability to intrinsically filter the cloud-contaminated scenes based on a goodness-of-fit criteria is evaluated. Hereto, an aerosol retrieval algorithm is applied to a partially clouded over-ocean synthetic data set as well as non-cloud-screened over-ocean POLDER-3/PARASOL observations. It is found that a goodness-of-fit filter, together with a filter on the coarse mode refractive index ( > 1.335) and a cirrus screening, adequately rejects the cloud-contaminated scenes. No bias or larger SD are found in the retrieved parameters for this intrinsic cloud filter compared to the parameters retrieved in a priori cloud-screened data set (using MODIS/AQUA cloud masks) of PARASOL observations. Moreover, less high-aerosol load scenes are misinterpreted as cloud contaminated. The retrieved aerosol optical thickness, single scattering albedo and Ångström exponent show good agreement with AERONET observations. Furthermore, the synthetic retrievals give confidence in the ability of the algorithm to correctly retrieve the micro-physical aerosol parameters. © 2015 Author(s)."
"36538539800;55802355600;56942554300;56612517400;7202048112;8511991900;6701378450;","Incorporating an advanced aerosol activation parameterization into WRF-CAM5: Model evaluation and parameterization intercomparison",2015,"10.1002/2014JD023051","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939256583&doi=10.1002%2f2014JD023051&partnerID=40&md5=132e8f6b284723b341be37700e3e330f","Aerosol activation into cloud droplets is an important process that governs aerosol indirect effects. The advanced treatment of aerosol activation by Fountoukis and Nenes (2005) and its recent updates, collectively called the FN series, have been incorporated into a newly developed regional coupled climate-air quality model based on the Weather Research and Forecasting model with the physics package of the Community Atmosphere Model version 5 (WRF-CAM5) to simulate aerosol-cloud interactions in both resolved and convective clouds. The model is applied to East Asia for two full years of 2005 and 2010. A comprehensive model evaluation is performed for model predictions of meteorological, radiative, and cloud variables, chemical concentrations, and column mass abundances against satellite data and surface observations from air quality monitoring sites across East Asia. The model performs overall well for major meteorological variables including near-surface temperature, specific humidity, wind speed, precipitation, cloud fraction, precipitable water, downward shortwave and longwave radiation, and column mass abundances of CO, SO2, NO2, HCHO, and O3 in terms of both magnitudes and spatial distributions. Larger biases exist in the predictions of surface concentrations of CO and NOx at all sites and SO2, O3, PM2.5, and PM10 concentrations at some sites, aerosol optical depth, cloud condensation nuclei over ocean, cloud droplet number concentration (CDNC), cloud liquid and ice water path, and cloud optical thickness. Compared with the default Abdul-Razzack Ghan (2000) parameterization, simulations with the FN series produce ~107-113% higher CDNC, with half of the difference attributable to the higher aerosol activation fraction by the FN series and the remaining half due to feedbacks in subsequent cloud microphysical processes. With the higher CDNC, the FN series are more skillful in simulating cloud water path, cloud optical thickness, downward shortwave radiation, shortwave cloud forcing, and precipitation. The model evaluation identifies several areas of improvements including emissions and their vertical allocation as well as model formulations such as aerosol formation, cloud droplet nucleation, and ice nucleation. © 2015. American Geophysical Union. All Rights Reserved."
"24757981500;57217352376;37561891300;55570627500;56260099600;57193840197;7004154626;","Aerosol characteristics at a rural station in southern peninsular India during CAIPEEX-IGOC: physical and chemical properties",2015,"10.1007/s11356-014-3836-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925484413&doi=10.1007%2fs11356-014-3836-1&partnerID=40&md5=57490ff91141e45eafee192783859667","To understand the boundary layer characteristics and pathways of aerosol–cloud interaction, an Integrated Ground Observational Campaign, concurrent with Cloud Aerosol Interaction and Precipitation Enhancement Experiment, was conducted by the Indian Institute of Tropical Meteorology, Pune, under Ministry of Earth Sciences at Mahabubnagar (a rural environment, which is ~100 km away from an urban city Hyderabad in Andhra Pradesh), during the period of July–November 2011. Collected samples of PM2.5 and PM10 were analyzed for water-soluble ionic species along with organic carbon (OC) and elemental carbon (EC). During study period, the average mass concentrations of PM2.5 and PM10 were about 50(±10) and 69(±14) μg m−3, respectively, which are significantly higher than the prescribed Indian National Ambient Air Quality Standards values. The chemical species such as sum of anions and cations from measured chemical constituents were contributed to be 31.27 and 38.49 % in PM2.5 and 6.35 and 5.65 % to the PM10, whereas carbonaceous species contributed ~17.3 and 20.47 % for OC and ~3.0 and 3.10 % for EC, respectively. The average ratio of PM2.5/PM10 during study period was ~0.73(±0.2), indicating that the dominance of fine size particles. Carbonaceous analysis results showed that the average concentration of OC was 14 and 8.7 μg m−3, while EC was 2.1 and 1.5 μg m−3 for PM10 and PM2.5, respectively. The ratios between OC and EC were estimated, which were 6.6 and 5.7 for PM10 and PM2.5, suggesting the presence of secondary organic aerosol. Total carbonaceous aerosol accounts 23 % of PM10 in which the contribution of OC is 20 % and EC is 3 %, while 20 % of PM2.5 mass in which the contribution of OC is 17 % and EC is 3 %. Out of the total aerosols mass, water-soluble constituents contributed an average of 45 % in PM10 and 38 % in PM2.5 including about 39 % anions and 6 % cations in PM10, while 31 % anions and 7 % cations in PM2.5 aerosol mass collectively at study site. © 2014, Springer-Verlag Berlin Heidelberg."
"13007924700;7102266120;57193213111;7006270084;7004462227;7101909551;8922308700;55796504300;7005520001;","Modeling aerosols and their interactions with shallow cumuli during the 2007 CHAPS field study",2013,"10.1029/2012JD018218","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880302327&doi=10.1029%2f2012JD018218&partnerID=40&md5=9cd45465fd8c6abec765b9e81e428f4c","The Weather Research and Forecasting model coupled with chemistry, using 2 km horizontal grid spacing, is used to simulate two important relationships between aerosols and clouds in the vicinity of Oklahoma City during the June 2007 Cumulus Humilis Aerosol Processing Study (CHAPS). First, the model reproduces the trends of higher nitrate volume fractions in cloud droplet residuals compared to interstitial nonactivated aerosols, as measured using an aerosol mass spectrometer. Comparing simulations with cloud chemistry turned on and off, we show that nitric acid vapor uptake by cloud droplets explains the higher nitrate content of cloud droplet residuals. Second, the model reasonably represents the observations of the first aerosol indirect effect where pollutants in the vicinity of Oklahoma City increase cloud droplet number concentrations and decrease the droplet effective radius. In addition, as documented using an offline optical code, simulated aerosol optical properties depend on several compensating effects including aerosol water content, size-resolved chemical composition, and refractory index of various particle chemical species. All of our four sensitivity test cases clearly show an increase in simulated absorption and a decrease in single scattering albedo within the Oklahoma City plume relative to conditions outside the plume. While previous studies have often focused on cloud-aerosol interactions in stratiform and deep convective clouds, this study highlights the ability of regional-scale models to represent some of the important aspects of cloud-aerosol interactions associated with fields of short-lived shallow cumuli. ©2013. American Geophysical Union. All Rights Reserved."
"7004559579;14018610000;7003886299;","The effects of mineral dust particles, aerosol regeneration and ice nucleation parameterizations on clouds and precipitation",2012,"10.5194/acp-12-9303-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869025506&doi=10.5194%2facp-12-9303-2012&partnerID=40&md5=b7a8d2d01c990d2f37f9798e4114404a","This study focuses on the effects of aerosol particles on the formation of convective clouds and precipitation in the Eastern Mediterranean Sea, with a special emphasis on the role of mineral dust particles in these processes. We used a new detailed numerical cloud microphysics scheme that has been implemented in the Weather Research and Forecast (WRF) model in order to study aerosol-cloud interaction in 3-D configuration based on 1° × 1° resolution reanalysis meteorological data. Using a number of sensitivity studies, we tested the contribution of mineral dust particles and different ice nucleation parameterizations to precipitation development. In this study we also investigated the importance of recycled (regenerated) aerosols that had been released to the atmosphere following the evaporation of cloud droplets. The results showed that increased aerosol concentration due to the presence of mineral dust enhanced the formation of ice crystals. The dynamic evolution of the cloud system sets the time periods and regions in which heavy or light precipitation occurred in the domain. The precipitation rate, the time and duration of precipitation were affected by the aerosol properties only at small spatial scales (with areas of about 20 km 2). Changes of the ice nucleation scheme from ice supersaturation-dependent parameterization to a recent approach of aerosol concentration and temperature-dependent parameterization modified the ice crystals concentrations but did not affect the total precipitation in the domain. Aerosol regeneration modified the concentration of cloud droplets at cloud base by dynamic recirculation of the aerosols but also had only a minor effect on precipitation. The major conclusion from this study is that the effect of mineral dust particles on clouds and total precipitation is limited by the properties of the atmospheric dynamics and the only effect of aerosol on precipitation may come from significant increase in the concentration of accumulation mode aerosols. In addition, the presence of mineral dust had a much smaller effect on the total precipitation than on its spatial distribution. © 2012 Author(s)."
"24081888700;7004174939;8045690700;35585284200;13408938100;7005054220;6603081424;7402115506;57203386948;7404327420;","Aerosol indirect effect on tropospheric ozone via lightning",2012,"10.1029/2012JD017723","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867201595&doi=10.1029%2f2012JD017723&partnerID=40&md5=bdf44b39f320a91e12c73d32fcf3018d","[1] Tropospheric ozone (O<inf>3</inf>) is a pollutant and major greenhouse gas and its radiative forcing is still uncertain. Inadequate understanding of processes related to O<inf>3</inf> production, in particular those natural ones such as lightning, contributes to this uncertainty. Here we demonstrate a new effect of aerosol particles on O<inf>3</inf> production by affecting lightning activity and lightning-generated NOx (LNOx). We find that lightning flash rate increases at a remarkable rate of 30 times or more per unit of aerosol optical depth. We provide observational evidence that indicates the observed increase in lightning activity is caused by the influx of aerosols from a volcano. Satellite data analyses show O<inf>3</inf> is increased as a result of aerosol-induced increase in lightning and LNOx, which is supported by modle simulations with prescribed lightning change. O<inf>3</inf> production increase from this aerosollightning- ozone link is concentrated in the upper troposphere, where O<inf>3</inf> is most efficient as a greenhouse gas. In the face of anthropogenic aerosol increase our findings suggest that lightning activity, LNOx and O<inf>3</inf>, especially in the upper troposphere, have all increased substantially since preindustrial time due to the proposed aerosol-lightning- ozone link, which implies a stronger O<inf>3</inf> historical radiative forcing. Aerosol forcing therefore has a warming component via its effect on O <inf>3</inf> production and this component has mostly been ignored in previous studies of climate forcing related to O<inf>3</inf> and aerosols. Sensitivity simulations suggest that 4-8% increase of column tropospheric ozone, mainly in the tropics, is expected if aerosol-lighting-ozone link is parameterized, depending on the background emission scenario. We note, however, substantial uncertainties remain on the exact magnitude of aerosol effect on tropospheric O<inf>3</inf> via lightning. The challenges for obtaining a quantitative global estimate of this effect are also discussed. Our results have significant implications for understanding past and projecting future tropospheric O <inf>3</inf> forcing as well as wildfire changes and call for integrated investigations of the coupled aerosol-cloud-chemistry system. © 2012. American Geophysical Union. All Rights Reserved."
"8550791300;7006415284;8849246700;25624725200;18437651200;35600074800;8710280200;13407563600;6604016408;22959375000;","Connecting hygroscopic growth at high humidities to cloud activation for different particle types",2008,"10.1088/1748-9326/3/3/035004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-54749128205&doi=10.1088%2f1748-9326%2f3%2f3%2f035004&partnerID=40&md5=f8d2ad48f3620c8c8210d4c533fc1991","This work recompiles studies that have been done with respect to hygroscopic growth in the regime of high relative humidities and with respect to activation for different kinds of particle at LACIS (Leipzig Aerosol Cloud Interaction Simulator) during the last few years. The particles examined consisted of a mixture of succinic acid and ammonium sulfate, seawater samples, soot coated with an organic and/or an inorganic substance, and two different atmospheric HULIS (HUmic LIke Substance) samples. An influence of changing non-ideal behavior and of slightly soluble substances on the hygroscopic growth was found in varying degrees in the subsaturation regime. The measured hygroscopic growth was extrapolated towards supersaturation, using a simple form of the Köhler equation, and assuming a constant number of molecules/ions in solution for high relative humidities (≥95% or ≥98%, depending on the particles). When the surface tension of water was used, the modeled critical supersaturations reproduced the measured ones for the seawater samples and for the coated soot particles. To reach agreement between measured and modeled critical supersaturations for the HULIS particles, a concentration-dependent surface tension had to be used, with values of the surface tension that were lower than that of water, but larger than those that had been reported for bulk measurements in the past. © 2008 IOP Publishing Ltd."
"7005035762;7202516876;7003591311;","Shortwave radiative impacts from aerosol effects on marine shallow cumuli",2008,"10.1175/2007JAS2447.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45849105990&doi=10.1175%2f2007JAS2447.1&partnerID=40&md5=b0b1da9d8445f72fc4011d687f20db4e","The net shortwave radiative impact of aerosol on simulations of two shallow marine cloud cases is investigated using a Monte Carlo radiative transfer model. For a shallow cumulus case, increased aerosol concentrations are associated not only with smaller droplet sizes but also reduced cloud fractions and cloud dimensions, a result of evaporation-induced mixing and a lack of precipitation. Three-dimensional radiative transfer (3DRT) effects alter the fluxes by 10%-20% from values calculated using the independent column approximation for these simulations. The first (Twomey) aerosol indirect effect is dominant but the decreased cloud fraction reduces the magnitude of the shortwave cloud forcing substantially. The 3DRT effects slightly decrease the sensitivity of the cloud albedo to changes in droplet size under an overhead sun for the two ranges of cloud liquid water paths examined, but not strongly so. A popular two-stream radiative transfer approximation to the cloud susceptibility overestimates the more directly calculated values for the low liquid-water-path clouds within pristine aerosol conditions by a factor of 2 despite performing well otherwise, suggesting caution in its application to the cloud albedos within broken cloud fields. An evaluation of the influence of cloud susceptibility and cloud fraction changes to a ""domain"" area-weighted cloud susceptibility found that the domain cloud albedo is more likely to increase under aerosol loading at intermediate aerosol concentrations than under the most pristine conditions, contrary to traditional expectations. The second simulation (cumulus penetrating into stratus) is characterized by higher cloud fractions and more precipitation. This case has two regimes: a clean, precipitating regime where cloud fraction increases with increasing aerosol, and a more polluted regime where cloud fraction decreases with increasing aerosol. For this case the domain-mean cloud albedo increases steadily with aerosol loading under clean conditions, but increases only slightly after the cloud coverage decreases. Three-dimensional radiative transfer effects are mostly negligible for this case. Both sets of simulations suggest that aerosol-induced cloud fraction changes must be considered in tandem with the Twomey effect for clouds of small dimensions when assessing the net radiative impact, because both effects are drop size dependent and radiatively significant. © 2008 American Meteorological Society."
"36241582600;57203231853;10141775500;7102111067;56224593400;","Sea-surface dimethylsulfide (DMS) concentration from satellite data at global and regional scales",2018,"10.5194/bg-15-3497-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048628298&doi=10.5194%2fbg-15-3497-2018&partnerID=40&md5=2d49e9f961d518472f09ce467ab25b06","The marine biogenic gas dimethylsulfide (DMS) modulates climate by enhancing aerosol light scattering and seeding cloud formation. However, the lack of time-and space-resolved estimates of DMS concentration and emission hampers the assessment of its climatic effects. Here we present DMSSAT, a new remote sensing algorithm that relies on macroecological relationships between DMS, its phytoplanktonic precursor dimethylsulfoniopropionate (DMSPt) and plankton light exposure. In the first step, planktonic DMSPt is estimated from satellite-retrieved chlorophyll a and the light penetration regime as described in a previous study (Galí et al., 2015). In the second step, DMS is estimated as a function of DMSPt and photosynthetically available radiation (PAR) at the sea surface with an equation of the form: log10DMS Combining double low line α + βlog10DMSPt + 3PAR. The two-step DMSSAT algorithm is computationally light and can be optimized for global and regional scales. Validation at the global scale indicates that DMSSAT has better skill than previous algorithms and reproduces the main climatological features of DMS seasonality across contrasting biomes. The main shortcomings of the global-scale optimized algorithm are related to (i) regional biases in remotely sensed chlorophyll (which cause underestimation of DMS in the Southern Ocean) and (ii) the inability to reproduce high DMS • DMSPt ratios in late summer and fall in specific regions (which suggests the need to account for additional DMS drivers). Our work also highlights the shortcomings of interpolated DMS climatologies, caused by sparse and biased in situ sampling. Time series derived from MODIS-Aqua in the subpolar North Atlantic between 2003 and 2016 show wide interannual variability in the magnitude and timing of the annual DMS peak(s), demonstrating the need to move beyond the classical climatological view. By providing synoptic time series of DMS emission, DMSSAT can leverage atmospheric chemistry and climate models and advance our understanding of plankton-aerosol-cloud interactions in the context of global change. © 2018 Author(s)."
"55622713800;7005035762;","Low cloud cover sensitivity to biomass-burning aerosols and meteorology over the Southeast Atlantic",2018,"10.1175/JCLI-D-17-0406.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047075177&doi=10.1175%2fJCLI-D-17-0406.1&partnerID=40&md5=ccae8608333d1f0ffbaa9411dd28b899","Shortwave-absorbing aerosols seasonally cover and interact with an expansive low-level cloud deck over the southeast Atlantic. Daily anomalies of the MODIS low cloud fraction, fine-mode aerosol optical depth (AODf), and six ERA-Interim meteorological parameters (lower-tropospheric stability, 800-hPa subsidence, 600-hPa specific humidity, 1000- and 800-hPa horizontal temperature advection, and 1000-hPa geopotential height) are constructed spanning July-October (2001-12). A standardized multiple linear regression, whereby the change in the low cloud fraction to each component's variability is normalized by one standard deviation, facilitates comparison between the different variables. Most cloud-meteorology relationships follow expected behavior for stratocumulus clouds. Of interest is the low cloud-subsidence relationship, whereby increasing subsidence increases low cloud cover between 10° and 20°S but decreases it elsewhere. Increases in AODf increase cloudiness everywhere, independent of other meteorological predictors. The cloud-AODf effect is partially compensated by accompanying increases in the midtropospheric moisture, which is associated with decreases in low cloud cover. This suggests that the free-tropospheric moisture affects the low cloud deck primarily through longwave radiation rather than mixing. The low cloud cover is also more sensitive to aerosol when the vertical distance between the cloud and aerosol layer is relatively small, which is more likely to occur early in the biomass burning season and farther offshore. A parallel statistical analysis that does not include AODf finds altered relationships between the low cloud cover changes and meteorology that can be understood through the aerosol cross-correlations with the meteorological predictors. For example, the low cloud-stability relationship appears stronger if aerosols are not explicitly included. © 2018 American Meteorological Society."
"37051480000;56418561200;23978405300;6506718302;56262351900;6507755223;","UCLALES-SALSA v1.0: A large-eddy model with interactive sectional microphysics for aerosol, clouds and precipitation",2017,"10.5194/gmd-10-169-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85009437837&doi=10.5194%2fgmd-10-169-2017&partnerID=40&md5=8a85707d0214d8bb2ac63eefae36de2c","Challenges in understanding the aerosol-cloud interactions and their impacts on global climate highlight the need for improved knowledge of the underlying physical processes and feedbacks as well as their interactions with cloud and boundary layer dynamics. To pursue this goal, increasingly sophisticated cloud-scale models are needed to complement the limited supply of observations of the interactions between aerosols and clouds. For this purpose, a new large-eddy simulation (LES) model, coupled with an interactive sectional description for aerosols and clouds, is introduced. The new model builds and extends upon the well-characterized UCLA Large-Eddy Simulation Code (UCLALES) and the Sectional Aerosol module for Large-Scale Applications (SALSA), hereafter denoted as UCLALES-SALSA. Novel strategies for the aerosol, cloud and precipitation bin discretisation are presented. These enable tracking the effects of cloud processing and wet scavenging on the aerosol size distribution as accurately as possible, while keeping the computational cost of the model as low as possible. The model is tested with two different simulation set-ups: a marine stratocumulus case in the DYCOMS-II campaign and another case focusing on the formation and evolution of a nocturnal radiation fog. It is shown that, in both cases, the size-resolved interactions between aerosols and clouds have a critical influence on the dynamics of the boundary layer. The results demonstrate the importance of accurately representing the wet scavenging of aerosol in the model. Specifically, in a case with marine stratocumulus, precipitation and the subsequent removal of cloud activating particles lead to thinning of the cloud deck and the formation of a decoupled boundary layer structure. In radiation fog, the growth and sedimentation of droplets strongly affect their radiative properties, which in turn drive new droplet formation. The size-resolved diagnostics provided by the model enable investigations of these issues with high detail. It is also shown that the results remain consistent with UCLALES (without SALSA) in cases where the dominating physical processes remain well represented by both models. © Author(s) 2017."
"55221209400;57203474131;","Modeling urban precipitation modification by spatially heterogeneous aerosols",2017,"10.1175/JAMC-D-16-0320.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027467696&doi=10.1175%2fJAMC-D-16-0320.1&partnerID=40&md5=557541bd6ca833a0663792d3c8d64a7b","This study introduces a methodology to simulate how spatially heterogeneous urban aerosols modify a precipitating thunderstorm in a numerical weather model. An air quality model (simple photochemical model) was coupled with a high-resolution mesoscale weather model (the Regional Atmospheric Modeling System) and generated variable urban cloud condensation nuclei values consistent with those measured in previous field studies. The coupled emission model was used to simulate the passage of a synoptic low pressure system with embedded thunderstorms over an idealized city using the real-atmosphere idealized land surface (RAIL) method. Experiments were conducted to calibrate the surface formation of cloud-nucleating aerosols in an urban environment and then to assess the specific response of different aerosol loads on simulated precipitation. The model response to aerosol heterogeneity reduced the total precipitation but significantly increased simulated rain rates. High-aerosol-loading scenarios produced a peak city-edge precipitation rate of over 100 mm h-1 greater than a control containing only a city land surface with no emissions. In comparing the control with a scenario with no city, it was seen that the land surface effect produced a rain rate increase of up to 20 mm h-1. Results indicate, within the limits of the model framework, that the urban rainfall modification is a combination of land heterogeneity causing the dynamical lifting of the air mass and aerosols, with rainfall enhancement being maintained and synergistically increased because of the aerosol indirect effects on cloud properties. © 2017 American Meteorological Society."
"56682032300;13405658600;","Important global and regional differences in aerosol cloud-albedo effect estimates between simulations with and without prognostic aerosol microphysics",2017,"10.1002/2016JD025886","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85017420458&doi=10.1002%2f2016JD025886&partnerID=40&md5=2687e45eb5f5a9384c60b0c31f71f36b","Aerosol-cloud interactions are among the most uncertain climate forcings, in part due to the strong sensitivity of cloud droplet number concentration (CDNC) to changes in the size distribution of potential cloud condensation nuclei. Despite this sensitivity of simulated aerosol-cloud interactions to variations in size-resolved aerosol concentrations being well established, many chemistry-climate and chemical-transport models do not include explicit treatment of the aerosol size distribution. We use a global chemical-transport model to estimate the aerosol cloud-albedo effect (CAE) due to anthropogenic emissions with prognostic sectional aerosol microphysics and compare this to the CAE calculated when the simulated aerosol mass of each species is remapped onto a prescribed size distribution. We find that although both the prescribed and prognostic methods compare similarly well with present-day size-distribution observations, there are substantial differences in the relative CDNC and CAE due to anthropogenic emissions. When using the prognostic size-distribution method, anthropogenic emissions yield a 25-75% larger increase in CDNC over most land masses but a 50-75% smaller increase in some remote-marine regions than in the prescribed size-distribution methods. Simulations using the prognostic scheme yield a global mean anthropogenic CAE of -0.87 W m-2, while the simulations with the prescribed scheme predict -0.66 W m-2. In South America and South Asia, differences in the CAE exceed 3.0 W m-2. These differences suggest that simulations with prescribed size-distribution mapping are unable to capture regional and temporal variability in size-resolved aerosol number and thus may lead to biases in estimates of the CAE. © 2017. American Geophysical Union. All Rights Reserved."
"56682032300;57189624682;7102795549;6602352339;13405658600;","The aerosol radiative effects of uncontrolled combustion of domestic waste",2016,"10.5194/acp-16-6771-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84973488177&doi=10.5194%2facp-16-6771-2016&partnerID=40&md5=ce1300965c5464237b312e5f3b070709","Open, uncontrolled combustion of domestic waste is a potentially significant source of aerosol; however, this aerosol source is not generally included in many global emissions inventories. To provide a first estimate of the aerosol radiative impacts from domestic-waste combustion, we incorporate theWiedinmyer et al. (2014) emissions inventory into GEOS-Chem-TOMAS, a global chemical-transport model with online aerosol microphysics. We find domestic-waste combustion increases global-mean black carbon and organic aerosol concentrations by 8 and 6 %, respectively, and by greater than 40% in some regions. Due to uncertainties regarding aerosol optical properties, we estimate the globally averaged aerosol direct radiative effect to range from-5 to-20mWm-2; however, this range increases from-40 to +4mWm-2 when we consider uncertainties in emission mass and size distribution. In some regions with significant waste combustion, such as India and China, the aerosol direct radiative effect may exceed-0.4Wm-2. Similarly, we estimate a cloud-albedo aerosol indirect effect of-13mWm-2, with a range of-4 to-49mWm-2 due to emission uncertainties. In the regions with significant waste combustion, the cloud-albedo aerosol indirect effect may exceed-0.4Wm-2. © Author(s) 2016."
"36679904200;18635289400;7103353990;7005396592;23977685500;","Systematic satellite observations of the impact of aerosols from passive volcanic degassing on local cloud properties",2014,"10.5194/acp-14-10601-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907937863&doi=10.5194%2facp-14-10601-2014&partnerID=40&md5=185c99789c56cbb70ace222a815e359f","The impact of volcanic emissions, especially from passive degassing and minor explosions, is a source of uncertainty in estimations of aerosol indirect effects. Observations of the impact of volcanic aerosol on clouds contribute to our understanding of both present-day atmospheric properties and of the pre-industrial baseline necessary to assess aerosol radiative forcing. We present systematic measurements over several years at multiple active and inactive volcanic islands in regions of low present-day aerosol burden. The time-averaged indirect aerosol effects within 200 km downwind of island volcanoes are observed using Moderate Resolution Imaging Spectroradiometer (MODIS, 2002-2013) and Advanced Along-Track Scanning Radiometer (AATSR, 2002-2008) data. Retrievals of aerosol and cloud properties at Klauea (Hawai'i), Yasur (Vanuatu) and Piton de la Fournaise (la Réunion) are rotated about the volcanic vent to be parallel to wind direction, so that upwind and downwind retrievals can be compared. The emissions from all three volcanoes-including those from passive degassing, Strombolian activity and minor explosions-lead to measurably increased aerosol optical depth downwind of the active vent. Average cloud droplet effective radius is lower downwind of the volcano in all cases, with the peak difference ranging from 2-8 1/4m at the different volcanoes in different seasons. Estimations of the difference in Top of Atmosphere upward Short Wave flux upwind and downwind of the active volcanoes from NASA's Clouds and the Earth's Radiant Energy System (CERES) suggest a downwind elevation of between 10 and 45 Wmg-2 at distances of 150-400 km from the volcano, with much greater local (&lt; 80 km) effects. Comparison of these observations with cloud properties at isolated islands without degassing or erupting volcanoes suggests that these patterns are not purely orographic in origin. Our observations of unpolluted, isolated marine settings may capture processes similar to those in the pre-industrial marine atmosphere. © 2014 Author (s)."
"56032970700;7401945370;7202954964;56959736200;","Simultaneous evaluation of ice cloud microphysics and nonsphericity of the cloud optical properties using hydrometeor video sonde and radiometer sonde in situ observations",2014,"10.1002/2013JD021086","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903288905&doi=10.1002%2f2013JD021086&partnerID=40&md5=6b01073ad46968546f57ada9ecc21355","This study utilizes hydrometeor sonde and radiometer sonde in situ observations to simultaneously evaluate ice cloud microphysics and radiative fluxes. In addition, the impact of nonsphericity and heterogeneous ice nucleation schemes on radiative fluxes are examined using a double-moment bulk cloud microphysics scheme on a midlatitude frontal system. The distribution of simulated outgoing longwave radiation (OLR) is systematically reduced by assuming the presence of columnar ice crystals instead of planar ice crystals because of the difference in the effective radii (the projected area) between the two shapes. However, the choice of the heterogeneous ice nucleation schemes drastically changes the distribution of OLR by modifying the number concentration of the cloud ice (Ni) (more than tenfold). The observed shortwave fluxes are useful for evaluating the simulated number concentration of cloud ice when nonspherical single scattering properties are used instead of spherical single scattering properties. The dependence of the asymmetry factor on the effective radius is the key to quantitatively estimating the ice cloud radiative forcing and determining the aerosol indirect effect on ice clouds. Based on the comparison of shortwave fluxes, the cloud microphysics scheme was found to underestimate the Ni near the cloud base (a robust bias). A possible method of modifying the bias is discussed. © 2014. American Geophysical Union. All Rights Reserved."
"8225489800;57206332144;7404061081;7004174939;7004364155;6603453147;7003398947;","Improvement of MODIS aerosol retrievals near clouds",2013,"10.1002/jgrd.50617","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885141091&doi=10.1002%2fjgrd.50617&partnerID=40&md5=aa7e0c526b7f475dd2246f697ffde12b","The retrieval of aerosol properties near clouds from reflected sunlight is challenging. Sunlight reflected from clouds can effectively enhance the reflectance in nearby clear regions. Ignoring cloud 3-D radiative effects can lead to large biases in aerosol retrievals, risking an incorrect interpretation of satellite observations on aerosol-cloud interaction. Earlier, we developed a simple model to compute the cloud-induced clear-sky radiance enhancement that is due to radiative interaction between boundary layer clouds and the molecular layer above. This paper focuses on the application and implementation of the correction algorithm. This is the first time that this method is being applied to a full Moderate Resolution Imaging Spectroradiometer (MODIS) granule. The process of the correction includes converting Clouds and the Earth's Radiant Energy System broadband flux to visible narrowband flux, computing the clear-sky radiance enhancement, and retrieving aerosol properties.We find that the correction leads to smaller values in aerosol optical depth (AOD), Ångström exponent, and the small mode aerosol fraction of the total AOD. It also makes the average aerosol particle size larger near clouds than far away from clouds, which is more realistic than the opposite behavior observed in operational retrievals.We discuss issues in the current correction method as well as our plans to validate the algorithm. © 2013. Her Majesty the Queen in Right of Canada. American Geophysical Union."
"23980042500;7003371432;","Aerosol-cloud interactions in a mesoscale model. Part I: Sensitivity to activation and collision-coalescence",2008,"10.1175/2007JAS2207.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40949114685&doi=10.1175%2f2007JAS2207.1&partnerID=40&md5=e165ab84f2b9111e0f1f664b27b590f4","High-resolution numerical simulations of the aerosol-cloud feedbacks are performed with a mesoscale model. The multimodal aerosol species, added to the model, and the cloud species were represented by two spectral moments. The aerosol sources include particle activation, solute transfer between drops due to collision, and coalescence of drops, and particle regeneration. A summertime case was simulated consisting of a cold frontal cloud system and a postfrontal stratus. Experiments with both simple and mechanistic activation parameterization of aerosol and with one and two aerosol modes were performed. Verification was made of the stratus properties against measurements taken during the Radiation Aerosol and Cloud Experiment (RACE). The results demonstrate a significant sensitivity of the stratus and of the frontal system to the aerosol and a moderate impact on the particle spectrum of drop collision-coalescence. The stratus simulation with mechanistic activation and unimodal aerosol showed the best agreement of droplet concentration with the observations, and the simulations with mechanistic activation and a bimodal aerosol and with simple activation underestimated the droplet concentration. A similar high sensitivity was found for the frontal precipitation intensity. Drop collision-coalescence in the frontal system was found to have an impact on the particle mean radius whose magnitude amounted to 10% and 15% for one and multiple cloud cycles, respectively. This impact was also found to be highly variable in space. The modified particle spectrum, following activation in clouds, was found to increase droplet concentration. © 2008 American Meteorological Society."
"13407676600;7006415284;18437651200;8550791300;7202779940;","Mass accommodation coefficient of water: A combined computational fluid dynamics and experimental data analysis",2007,"10.1029/2007JD008604","https://www.scopus.com/inward/record.uri?eid=2-s2.0-37349030360&doi=10.1029%2f2007JD008604&partnerID=40&md5=ae4c3df1abf922e05ba310f83d627e5d","The mass accommodation coefficient α<inf>mass</inf> of water vapor in NaCl solutions has been studied for realistic lower atmospheric conditions. To determine α<inf>mass</inf>, a combination of experimental data and computational fluid dynamics (CFD) modeling has been applied. Experiments were performed at the Leipzig Aerosol Cloud Interaction Simulator (LACIS), a laminar flow diffusion tube for measurements of both hygroscopic growth and cloud condensation nuclei (CCN) activation. Quasi-monodisperse sodium chloride particles with 54 nm and 108 nm in diameter have been used as condensation nuclei. To characterize particle growth, mean droplet diameters have been measured at the outlet of LACIS with a white-light optical particle spectrometer. Measurements were performed for different saturation ratios in the range between 1.0 and 1.02. Experiments have been modeled using the Computational Fluid Dynamics Code (CFD-Code) FLUENT6 combined with the Fine Particle Model (FPM). For determination of α<inf>mass</inf>, measured droplet diameters have been compared with calculated ones. The accommodation coefficient in the theoretical calculations was varied to achieve a quantitative comparison with the measurements. Experimental data shown in this study are consistent with α<inf>mass</inf> > 0.30. Therefore our results support previous studies applying different experimental techniques. Copyright 2007 by the American Geophysical Union."
"7201837768;57193132723;","Evaluating the impacts of carbonaceous aerosols on clouds and climate",2007,"10.1017/CBO9780511619472.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927118713&doi=10.1017%2fCBO9780511619472.005&partnerID=40&md5=d51f0c017369800459bd45e63a844ba2","Any attempt to reconcile observed surface temperature changes within the past 150 years to changes simulated by climate models that include various atmospheric forcings is sensitive to the changes attributed to aerosols and aerosol–cloud–climate interactions, which are the main contributors that may well balance the positive forcings associated with greenhouse gases, absorbing aerosols, ozone related changes, etc. These aerosol effects on climate, from various modeling studies discussed in Menon (2004), range from + 0.8 to − 2.4 W/m2, with an implied value of − 1.0 W/m2 (range from − 0.5 to − 4.5 W/m2) for the aerosol indirect effects. Quantifying the contribution of aerosols and aerosol–cloud interactions remains complicated for several reasons, some of which are related to aerosol distributions and some to the processes used to represent their effects on clouds. Aerosol effects on low-lying marine stratocumulus clouds that cover much of the Earth’s surface (about 70%) have been the focus of most prior simulations of aerosol–cloud interaction effects. Since cumulus clouds (shallow and deep convective) are short-lived and cover about 15 to 20% of the Earth’s surface, they are not usually considered as radiatively important. However, the large amount of latent heat released from convective towers, and corresponding changes in precipitation, especially in biomass regions owing to convective heating effects (Graf et al., 2004), suggest that these cloud systems, and aerosol effects on them, must be examined more closely. © Cambridge University Press 2007, Cambridge University Press, 2010."
"25723426400;7005602760;7404243086;7006461606;7401753043;","Examining the aerosol indirect effect over China using an SO2 emission inventory",2004,"10.1016/j.atmosres.2004.03.028","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8644277060&doi=10.1016%2fj.atmosres.2004.03.028&partnerID=40&md5=4dcd367fc248d9341b71b3c67256252c","The relationship between SO2 emissions and the effective particle radius of low-level water clouds (re) over China was investigated to determine anthropogenic effects on clouds. Sulfur dioxide emission values were obtained from a statistical inventory, and re origins were retrieved by satellite remote sensing on a 0.5° grid. Comparisons between annual mean SO2 emissions and re showed generally decreasing re values, explained by the Twomey effect. The existence of the Twomey effect is supported by comparisons with simulated aerosol optical depths. Results further suggest that clouds over land show sensitivity to the Twomey effect as well as clouds over the ocean. © 2004 Elsevier B.V. All rights reserved."
"7103180783;53880473700;6602080205;7402401574;","Impacts of recent decadal changes in Asian aerosols on the East Asian summer monsoon: roles of aerosol–radiation and aerosol–cloud interactions",2019,"10.1007/s00382-019-04698-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062783893&doi=10.1007%2fs00382-019-04698-0&partnerID=40&md5=8b9d762e92a500606ac1c6ff306ccfae","Anthropogenic aerosols (AA) can affect cloud and precipitation through aerosol–radiation interaction (ARI) and aerosol–cloud interaction (ACI). Over the past few decades, anthropogenic aerosol emissions have exhibited remarkable changes in the magnitude and in spatial pattern. The most significant changes are the increased emissions over both South Asia and East Asia. In this study, the atmospheric component of a state-of-the-art climate model that includes eight species of tropospheric aerosols, coupled to a multi-level mixed-layer ocean model, has been used to investigate the impacts of Asian anthropogenic aerosol precursor emission changes from 1970s to 2000s on large scale circulation and precipitation in boreal summer over East Asia. Results reveal significant changes in circulation and clouds over East Asia and over the tropical and western North Pacific (WNP). Increased Asian AA emissions lead to anomalous cyclonic circulation over the Maritime continent (MC) and anomalous anticyclonic circulation over the WNP, resulting in anomalous moisture transport convergence over the MC and therefore increased precipitation. They also lead to anomalous moisture flux divergence over both the WNP and large land areas of East Asia, especially over northern China, and therefore decreased precipitation there. These large scale circulation anomalies over the adjacent oceans are related to aerosol change induced ocean feedbacks, predominantly through ACI. It is the slow responses over the adjacent oceans (e.g., SST changes) through coupled atmosphere–ocean interaction in pre-monsoon seasons and summer that shape the changes of the East Asian summer monsoon and local precipitation. The results in this study suggest that increased Asian AA emissions from 1970s to 2000s may have played an important role for the observed southward shift of the Pacific intertropical convergence zone and precipitation belt, weakening of East Asian summer monsoon and reduced precipitation over northern China in East Asia during the latter half of the twentieth century. © 2019, The Author(s)."
"6602740671;7003489918;6701378450;22978151200;17345303300;7004469744;6507533363;56540693200;56571063800;21742333400;12139043600;56682032300;57203053317;9275665400;23051160600;49662076300;23095483400;13405658600;36106370400;57208121852;6507308842;55885662200;55688930000;36462180600;36969949500;55720018700;56377286600;16425152300;55984424900;57189748029;15065491600;55717074000;6603711967;23485829700;36469200100;12804476900;21744073500;57201942906;38762392200;","Evaluation of global simulations of aerosol particle and cloud condensation nuclei number, with implications for cloud droplet formation",2019,"10.5194/acp-19-8591-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068570626&doi=10.5194%2facp-19-8591-2019&partnerID=40&md5=f7bc6775c7c03a158c0056f7de33aaa6","A total of 16 global chemistry transport models and general circulation models have participated in this study; 14 models have been evaluated with regard to their ability to reproduce the near-surface observed number concentration of aerosol particles and cloud condensation nuclei (CCN), as well as derived cloud droplet number concentration (CDNC). Model results for the period 2011-2015 are compared with aerosol measurements (aerosol particle number, CCN and aerosol particle composition in the submicron fraction) from nine surface stations located in Europe and Japan. The evaluation focuses on the ability of models to simulate the average across time state in diverse environments and on the seasonal and short-term variability in the aerosol properties. There is no single model that systematically performs best across all environments represented by the observations. Models tend to underestimate the observed aerosol particle and CCN number concentrations, with average normalized mean bias (NMB) of all models and for all stations, where data are available, of -24% and -35% for particles with dry diameters >50 and >120nm, as well as -36% and -34% for CCN at supersaturations of 0.2% and 1.0%, respectively. However, they seem to behave differently for particles activating at very low supersaturations (<0.1%) than at higher ones. A total of 15 models have been used to produce ensemble annual median distributions of relevant parameters. The model diversity (defined as the ratio of standard deviation to mean) is up to about 3 for simulated N3 (number concentration of particles with dry diameters larger than 3nm) and up to about 1 for simulated CCN in the extra-polar regions. A global mean reduction of a factor of about 2 is found in the model diversity for CCN at a supersaturation of 0.2% (CCN0.2) compared to that for N3, maximizing over regions where new particle formation is important. An additional model has been used to investigate potential causes of model diversity in CCN and bias compared to the observations by performing a perturbed parameter ensemble (PPE) accounting for uncertainties in 26 aerosol-related model input parameters. This PPE suggests that biogenic secondary organic aerosol formation and the hygroscopic properties of the organic material are likely to be the major sources of CCN uncertainty in summer, with dry deposition and cloud processing being dominant in winter. Models capture the relative amplitude of the seasonal variability of the aerosol particle number concentration for all studied particle sizes with available observations (dry diameters larger than 50, 80 and 120nm). The short-term persistence time (on the order of a few days) of CCN concentrations, which is a measure of aerosol dynamic behavior in the models, is underestimated on average by the models by 40% during winter and 20% in summer. In contrast to the large spread in simulated aerosol particle and CCN number concentrations, the CDNC derived from simulated CCN spectra is less diverse and in better agreement with CDNC estimates consistently derived from the observations (average NMB -13% and -22% for updraft velocities 0.3 and 0.6ms-1, respectively). In addition, simulated CDNC is in slightly better agreement with observationally derived values at lower than at higher updraft velocities (index of agreement 0.64 vs. 0.65). The reduced spread of CDNC compared to that of CCN is attributed to the sublinear response of CDNC to aerosol particle number variations and the negative correlation between the sensitivities of CDNC to aerosol particle number concentration (Nd=Na) and to updraft velocity (Nd=w). Overall, we find that while CCN is controlled by both aerosol particle number and composition, CDNC is sensitive to CCN at low and moderate CCN concentrations and to the updraft velocity when CCN levels are high. Discrepancies are found in sensitivities Nd=Na and Nd=w; models may be predisposed to be too ""aerosol sensitive"" or ""aerosol insensitive"" in aerosol-cloud-climate interaction studies, even if they may capture average droplet numbers well. This is a subtle but profound finding that only the sensitivities can clearly reveal and may explain intermodel biases on the aerosol indirect effect. © Author(s) 2019."
"57193798535;56422246700;57204063990;55857180100;57204067817;57204074025;27467630500;7003897194;55730602600;57204073106;7006415284;26424128800;8550791300;","Coal fly ash: Linking immersion freezing behavior and physicochemical particle properties",2018,"10.5194/acp-18-13903-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053778082&doi=10.5194%2facp-18-13903-2018&partnerID=40&md5=23382b1441a77636ae93fcea6719db6d","To date, only a few studies have investigated the potential of coal fly ash particles to trigger heterogeneous ice nucleation in cloud droplets. The presented measurements aim at expanding the sparse dataset and improving process understanding of how physicochemical particle properties can influence the freezing behavior of coal fly ash particles immersed in water. Firstly, immersion freezing measurements were performed with two single particle techniques, i.e., the Leipzig Aerosol Cloud Interaction Simulator (LACIS) and the SPectrometer for Ice Nuclei (SPIN). The effect of suspension time on the efficiency of the coal fly ash particles when immersed in a cloud droplet is analyzed based on the different residence times of the two instruments and employing both dry and wet particle generation. Secondly, two cold-stage setups, one using microliter sized droplets (Leipzig Ice Nucleation Array) and one using nanoliter sized droplets (WeIzmann Supercooled Droplets Observation on Microarray setup) were applied. We found that coal fly ash particles are comparable to mineral dust in their immersion freezing behavior when being dry generated. However, a significant decrease in immersion freezing efficiency was observed during experiments with wet-generated particles in LACIS and SPIN. The efficiency of wet-generated particles is in agreement with the cold-stage measurements. In order to understand the reason behind the deactivation, a series of chemical composition, morphology, and crystallography analyses (single particle mass spectrometry, scanning electron microscopy coupled with energy dispersive X-ray microanalysis, X-ray diffraction analysis) were performed with dry- and wet-generated particles. From these investigations, we conclude that anhydrous CaSO4 and CaO - which, if investigated in pure form, show the same qualitative immersion freezing behavior as observed for dry-generated coal fly ash particles - contribute to triggering heterogeneous ice nucleation at the particle-water interface. The observed deactivation in contact with water is related to changes in the particle surface properties which are potentially caused by hydration of CaSO4 and CaO. The contribution of coal fly ash to the ambient population of ice-nucleating particles therefore depends on whether and for how long particles are immersed in cloud droplets. © 2018 Mohsen Lutephy, published by Sciendo."
"57189368623;24448185400;50562006500;15925588200;57203005068;55539832600;55683878900;23479194900;15724233200;7006495018;55893745600;16549600900;57203142421;22979686100;7003854090;57192645486;57203161526;6507532116;57189372185;36955999600;36930720800;57211811362;13407563600;24172248700;42361807800;56879845700;36076994600;56572131500;7006790175;7004864963;35461763400;55942083800;35774441900;","Long-term observations of cloud condensation nuclei over the Amazon rain forest - Part 2: Variability and characteristics of biomass burning, long-range transport, and pristine rain forest aerosols",2018,"10.5194/acp-18-10289-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050698943&doi=10.5194%2facp-18-10289-2018&partnerID=40&md5=498d65a311f3fe4a91ee609e5baa5af4","Size-resolved measurements of atmospheric aerosol and cloud condensation nuclei (CCN) concentrations and hygroscopicity were conducted over a full seasonal cycle at the remote Amazon Tall Tower Observatory (ATTO, March 2014-February 2015). In a preceding companion paper, we presented annually and seasonally averaged data and parametrizations (Part 1; Pöhlker et al., 2016a). In the present study (Part 2), we analyze key features and implications of aerosol and CCN properties for the following characteristic atmospheric conditions: Empirically pristine rain forest (PR) conditions, where no influence of pollution was detectable, as observed during parts of the wet season from March to May. The PR episodes are characterized by a bimodal aerosol size distribution (strong Aitken mode with DAit ≈ 70nm and NAit ≈ 160cm-3, weak accumulation mode with Dacc ≈ 160nm and Nacc ≈ 90cm-3), a chemical composition dominated by organic compounds, and relatively low particle hygroscopicity (ΚAit ≈ 0.12, Κacc ≈ 0.18). Long-range-transport (LRT) events, which frequently bring Saharan dust, African biomass smoke, and sea spray aerosols into the Amazon Basin, mostly during February to April. The LRT episodes are characterized by a dominant accumulation mode (DAit ≈ 80nm, NAit ≈ 120cm-3 vs. Dacc ≈ 180nm, Nacc ≈ 310cm-3), an increased abundance of dust and salt, and relatively high hygroscopicity (ΚAit ≈ 0.18, Κacc ≈ 0.35). The coarse mode is also significantly enhanced during these events. Biomass burning (BB) conditions characteristic for the Amazonian dry season from August to November. The BB episodes show a very strong accumulation mode (DAit ≈ 70nm, NAit ≈ 140cm-3 vs. Dacc ≈ 170nm, Nacc ≈ 3400cm-3), very high organic mass fractions (∼ 90%), and correspondingly low hygroscopicity (ΚAit ≈ 0.14, Κacc ≈ 0.17). Mixed-pollution (MPOL) conditions with a superposition of African and Amazonian aerosol emissions during the dry season. During the MPOL episode presented here as a case study, we observed African aerosols with a broad monomodal distribution (D ≈ 130nm, NCN, 10 ≈ 1300cm-3), with high sulfate mass fractions (∼ 20%) from volcanic sources and correspondingly high hygroscopicity (Κ < 100 nm ≈ 0.14, Κ > 100 nm ≈ 0.22), which were periodically mixed with fresh smoke from nearby fires (D ≈ 110nm, NCN, 10 ≈ 2800cm-3) with an organic-dominated composition and sharply decreased hygroscopicity (Κ < 150 nm ≈ 0.10, Κ > 150 nm ≈ 0.20). Insights into the aerosol mixing state are provided by particle hygroscopicity (Κ) distribution plots, which indicate largely internal mixing for the PR aerosols (narrow Κ distribution) and more external mixing for the BB, LRT, and MPOL aerosols (broad Κ distributions). The CCN spectra (CCN concentration plotted against water vapor supersaturation) obtained for the different case studies indicate distinctly different regimes of cloud formation and microphysics depending on aerosol properties and meteorological conditions. The measurement results suggest that CCN activation and droplet formation in convective clouds are mostly aerosol-limited under PR and LRT conditions and updraft-limited under BB and MPOL conditions. Normalized CCN efficiency spectra (CCN divided by aerosol number concentration plotted against water vapor supersaturation) and corresponding parameterizations (Gaussian error function fits) provide a basis for further analysis and model studies of aerosol-cloud interactions in the Amazon. . © Author(s) 2018."
"56637900300;7003961970;56037285200;","Fast Adjustments of the Asian Summer Monsoon to Anthropogenic Aerosols",2018,"10.1002/2017GL076667","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040964737&doi=10.1002%2f2017GL076667&partnerID=40&md5=c0712d748944e4f1359fd4f8782a750e","Anthropogenic aerosols are a major factor contributing to human-induced climate change, particularly over the densely populated Asian monsoon region. Understanding the physical processes controlling the aerosol-induced changes in monsoon rainfall is essential for reducing the uncertainties in the future projections of the hydrological cycle. Here we use multiple coupled and atmospheric general circulation models to explore the physical mechanisms for the aerosol-driven monsoon changes on different time scales. We show that anthropogenic aerosols induce an overall reduction in monsoon rainfall and circulation, which can be largely explained by the fast adjustments over land north of 20∘N. This fast response occurs before changes in sea surface temperature (SST), largely driven by aerosol-cloud interactions. However, aerosol-induced SST feedbacks (slow response) cause substantial changes in the monsoon meridional circulation over the oceanic regions. Both the land-ocean asymmetry and meridional temperature gradient are key factors in determining the overall monsoon circulation response. ©2018. The Authors."
"6506848305;25031430500;36876405100;7005920812;7102696626;7102239370;57200319057;","The path to CAM6: Coupled simulations with CAM5.4 and CAM5.5",2018,"10.5194/gmd-11-235-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040767785&doi=10.5194%2fgmd-11-235-2018&partnerID=40&md5=34ecd3e50cba161004fb75f8cc4509b7","This paper documents coupled simulations of two developmental versions of the Community Atmosphere Model (CAM) towards CAM6. The configuration called CAM5.4 introduces new microphysics, aerosol, and ice nucleation changes, among others to CAM. The CAM5.5 configuration represents a more radical departure, as it uses an assumed probability density function (PDF)-based unified cloud parameterization to replace the turbulence, shallow convection, and warm cloud macrophysics in CAM. This assumed PDF method has been widely used in the last decade in atmosphere-only climate simulations but has never been documented in coupled mode. Here, we compare the simulated coupled climates of CAM5.4 and CAM5.5 and compare them to the control coupled simulation produced by CAM5.3. We find that CAM5.5 has lower cloud forcing biases when compared to the control simulations. Improvements are also seen in the simulated amplitude of the Niño-3.4 index, an improved representation of the diurnal cycle of precipitation, subtropical surface wind stresses, and double Intertropical Convergence Zone biases. Degradations are seen in Amazon precipitation as well as slightly colder sea surface temperatures and thinner Arctic sea ice. Simulation of the 20th century results in a credible simulation that ends slightly colder than the control coupled simulation. The authors find this is due to aerosol indirect effects that are slightly stronger in the new version of the model and propose a solution to ameliorate this. Overall, in these early coupled simulations, CAM5.5 produces a credible climate that is appropriate for science applications and is ready for integration into the National Center for Atmospheric Research's (NCAR's) next-generation climate model. © Author(s) 2018."
"56447276100;57095410800;55361287700;57193091858;7403253796;7404865816;8075033200;57037223300;7409080503;","Uncertainty in Predicting CCN Activity of Aged and Primary Aerosols",2017,"10.1002/2017JD027058","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032937974&doi=10.1002%2f2017JD027058&partnerID=40&md5=afd0f5e9a621e2671910ddf0a6116199","Understanding particle CCN activity in diverse atmospheres is crucial when evaluating aerosol indirect effects. Here aerosols measured at three sites in China were categorized as different types for attributing uncertainties in CCN prediction in terms of a comprehensive data set including size-resolved CCN activity, size-resolved hygroscopic growth factor, and chemical composition. We show that CCN activity for aged aerosols is unexpectedly underestimated ~22% at a supersaturation (S) of 0.2% when using κ-Kohler theory with an assumption of an internal mixture with measured bulk composition that has typically resulted in an overestimate of the CCN activity in previous studies. We conclude that the underestimation stems from neglect of the effect of aging/coating on particle hygroscopicity, which is not considered properly in most current models. This effect enhanced the hygroscopicity parameter (κ) by between ~11% (polluted conditions) and 30% (clean days), as indicated in diurnal cycles of κ based on measurements by different instruments. In the urban Beijing atmosphere heavily influenced by fresh emissions, the CCN activity was overestimated by 45% at S = 0.2%, likely because of inaccurate assumptions of particle mixing state and because of variability of chemical composition over the particle size range. For both fresh and aged aerosols, CCN prediction exhibits very limited sensitivity to κSOA, implying a critical role of other factors like mixing of aerosol components within and between particles in regulating CCN activity. Our findings could help improving CCN parameterization in climate models. ©2017. American Geophysical Union. All Rights Reserved."
"35731251200;26434854300;55481489700;57190072737;56213282800;7005773698;","Laboratory Studies of the Cloud Droplet Activation Properties and Corresponding Chemistry of Saline Playa Dust",2017,"10.1021/acs.est.6b04487","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020405126&doi=10.1021%2facs.est.6b04487&partnerID=40&md5=c29a087416492542916ac2c8f6ccb9e1","Playas emit large quantities of dust that can facilitate the activation of cloud droplets. Despite the potential importance of playa dusts for cloud formation, most climate models assume that all dust is nonhygroscopic; however, measurements are needed to clarify the role of dusts in aerosol-cloud interactions. Here, we report measurements of CCN activation from playa dusts and parameterize these results in terms of both κ-Köhler theory and adsorption activation theory for inclusion in atmospheric models. κ ranged from 0.002 ± 0.001 to 0.818 ± 0.094, whereas Frankel-Halsey-Hill (FHH) adsorption parameters of AFHH = 2.20 ± 0.60 and BFHH = 1.24 ± 0.14 described the water uptake properties of the dusts. Measurements made using aerosol time-of-flight mass spectrometry (ATOFMS) revealed the presence of halite, sodium sulfates, and sodium carbonates that were strongly correlated with κ underscoring the role that mineralogy, including salts, plays in water uptake by dust. Predictions of κ made using bulk chemical techniques generally showed good agreement with measured values. However, several samples were poorly predicted suggesting that chemical heterogeneities as a function of size or chemically distinct particle surfaces can determine the hygroscopicity of playa dusts. Our results further demonstrate the importance of dust in aerosol-cloud interactions. © 2016 American Chemical Society."
"57194833104;57203053317;","Constraining precipitation susceptibility of warm-, ice-, and mixed-phase clouds with microphysical equations",2016,"10.1175/JAS-D-16-0008.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85015326597&doi=10.1175%2fJAS-D-16-0008.1&partnerID=40&md5=d4f0a0980238684a6367ab9f1ea799f5","The strength of the effective anthropogenic climate forcing from aerosol-cloud interactions is related to the susceptibility of precipitation to aerosol effects. Precipitation susceptibility d lnP/d lnN has been proposed as a metric to quantify the effect of aerosol-induced changes in cloud droplet number N on warm precipitation rate P. Based on the microphysical rate equations of the Seifert and Beheng two-moment bulk microphysics scheme, susceptibilities of warm-, mixed-, and ice-phase precipitation and cirrus sedimentation to cloud droplet and ice crystal number are estimated. The estimation accounts for microphysical adjustments to the initial perturbation in N. For warm rain, d lnP/d lnN < -2aut/(aut + acc) is found, which depends on the rates of autoconversion (aut) and accretion (acc). Cirrus sedimentation susceptibility corresponds to the exponent of crystal sedimentation velocity with a value of -0.2. For mixed-phase clouds, several microphysical contributions that explain low precipitation susceptibilities are identified: (i) Because of the larger hydrometeor sizes involved, mixed-phase collection processes are less sensitive to changes in hydrometeor size than autoconversion. (ii) Only a subset of precipitation formation processes is sensitive to droplet or crystal number. (iii) Effects on collection processes and diffusional growth compensate. (iv) Adjustments in cloud liquid and ice amount compensate the effect of changes in ice crystal and cloud droplet number. (v) Aerosol perturbations that simultaneously affect ice crystal and droplet number have opposing effects. © 2016 American Meteorological Society."
"56989640500;21935606200;36915461700;7102913661;","Aerosol-cloud associations over gangetic basin during a typical monsoon depression event using WRF-Chem simulation",2015,"10.1002/2015JD023634","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84954379322&doi=10.1002%2f2015JD023634&partnerID=40&md5=c7543a39936b98bff00cc24c24fc2ce7","To study aerosol-cloud interactions over the Gangetic Basin of India, the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) has been applied to a typical monsoon depression event prevalent between the 23 and 29 August 2009. This event was sampled during the Cloud Aerosol Interaction and Precipitation Enhancement EXperiment (CAIPEEX) aircraft campaign, providing measurements of aerosol and cloud microphysical properties from two sorties. Comparison of the simulated meteorological, thermodynamical, and aerosol fields against satellite and in situ aircraft measurements illustrated that the westward propagation of the monsoon depression and the cloud, aerosol, and rainfall spatial distribution was simulated reasonably well using anthropogenic emission rates from Monitoring Atmospheric Composition and Climate project along with cityZEN projects (MACCity)+Intercontinental Chemical Transport Experiment Phase B anthropogenic emission rates. However,the magnitude of aerosol optical depth was underestimated by up to 50%. A simulation with aerosol emissions increased by a factor of 6 over the CAIPEEX campaign domain increased the simulated aerosol concentrations to values close to the observations, mainly within boundary layer. Comparison of the low-aerosol simulation and high-aerosol simulation for the two sorties illustrated that more anthropogenic aerosols increased the cloud condensing nuclei (CCN) and cloud droplet mass concentrations. The number of simulated cloud droplets increased while the cloud droplet effective radii decreased, highlighting the importance of CCN-cloud feedbacks over this region. The increase in simulated anthropogenic aerosols (including absorbing aerosols) also increased the temperature of air parcels below clouds and thus the convective available potential energy (CAPE). The increase in CAPE intensified the updraft and invigorated the cloud, inducing formation of deeper clouds with more ice-phase hydrometeors for both cases. These case studies provide evidence of aerosol-induced cloud invigoration over the Gangetic Basin. © 2015. American Geophysical Union. All Rights Reserved."
"55025909400;7003414581;55444637900;7003375617;","Strong aerosol-cloud interaction in altocumulus during updraft periods: Lidar observations over central Europe",2015,"10.5194/acp-15-10687-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942596965&doi=10.5194%2facp-15-10687-2015&partnerID=40&md5=dc1331c9357ca8074d023f93ab16242d","For the first time, a liquid-water cloud study of the aerosol-cloud-dynamics relationship, solely based on lidar, was conducted. Twenty-nine cases of pure liquid-water altocumulus layers were observed with a novel dual-field-of-view Raman lidar over the polluted central European site of Leipzig, Germany, between September 2010 and September 2012. By means of the novel Raman lidar technique, cloud properties such as the droplet effective radius and cloud droplet number concentration (CDNC) in the lower part of altocumulus layers are obtained. The conventional aerosol Raman lidar technique provides the aerosol extinction coefficient (used as aerosol proxy) below cloud base. A collocated Doppler lidar measures the vertical velocity at cloud base and thus updraft and downdraft occurrence. Here, we present the key results of our statistical analysis of the 2010-2012 observations. Besides a clear aerosol effect on cloud droplet number concentration in the lower part of the altocumulus layers during updraft periods, turbulent mixing and entrainment of dry air is assumed to be the main reason for the found weak correlation between aerosol proxy and CDNC higher up in the cloud. The corresponding aerosol-cloud interaction parameter based on changes in cloud droplet number concentration with aerosol loading was found to be close to 0.8 at 30-70 m above cloud base during updraft periods and below 0.4 when ignoring vertical-wind information in the analysis. Our findings are extensively compared with literature values and agree well with airborne observations. © 2015. CC Attribution 3.0 License."
"56531367400;55628589750;","How thermodynamic environments control stratocumulus microphysics and interactions with aerosols",2015,"10.1088/1748-9326/10/2/024004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923787514&doi=10.1088%2f1748-9326%2f10%2f2%2f024004&partnerID=40&md5=549e35ed195c5f3d04ced75c3aab66df","Aerosol-cloud interactions are central to climate system changes and depend on meteorological conditions. This study identifies distinct thermodynamic regimes and proposes a conceptual framework for interpreting aerosol effects. In the analysis, ten years (2003-2012) of daily satellite-derived aerosol and cloud products are combined with reanalysis data to identify factors controlling Southeast Atlantic stratocumulus microphysics. Considering the seasonal influence of aerosol input from biomass burning, thermodynamic environments that feature contrasting microphysical cloud properties and aerosol-cloud relations are classified. While aerosol impact is stronger in unstable environments, it is mostly confined to situations with low aerosol loading (aerosol index AI ≲ 0.15), implying a saturation of aerosol effects. Situations with high aerosol loading are associated with weaker, seasonally contrasting aerosol-droplet size relationships, likely caused by thermodynamically induced processes and aerosol swelling. © 2015 IOP Publishing Ltd."
"6603453147;57206332144;","Effect of cloud fraction on near-cloud aerosol behavior in the MODIS atmospheric correction ocean color product",2015,"10.3390/rs70505283","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930016598&doi=10.3390%2frs70505283&partnerID=40&md5=1300827c1edb2586929445889fe73982","Characterizing the way satellite-based aerosol statistics change near clouds is important for better understanding both aerosol-cloud interactions and aerosol direct radiative forcing. This study focuses on the question of whether the observed near-cloud increases in aerosol optical thickness and particle size may be explained by a combination of two factors: (i) Near-cloud data coming from areas with higher cloud fractions than far-from-cloud data and (ii) Cloud fraction being correlated with aerosol optical thickness and particle size. This question is addressed through a statistical analysis of aerosol parameters included in the MODIS (MODerate resolution Imaging Spectroradiometer) ocean color product. Results from ten Septembers (2002-2011) over part of the northeast Atlantic Ocean confirm that the combination of these two factors working together explains a significant but not dominant part (in our case, 15%-30%) of mean optical thickness changes near clouds. Overall, the findings show that cloud fraction plays a large role in shaping the way aerosol statistics change with distance to clouds. This implies that both cloud fraction and distance to clouds are important to consider when aerosol-cloud interactions or aerosol direct radiative effects are examined in satellite or modeling studies. © 2015 by the authors."
"57044397100;35069282600;7005477332;7004315232;","Aerosol-cloud interactions in ship tracks using Terra MODIS/MISR",2015,"10.1002/2014JD022736","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928624091&doi=10.1002%2f2014JD022736&partnerID=40&md5=121a938e97e1445788aa70a867e68917","Simultaneous ship track observations fromTerra Moderate Resolution Imaging Spectroradiometer (MODIS) and Multiangle Imaging Spectroradiometer (MISR) have been compiled to investigate how ship-injected aerosols affect marine warm boundary layer clouds for different cloud types and environmental conditions. By taking advantage of the high spatial resolution multiangle observations available from MISR, we utilized the retrieved cloud albedo, cloud top height, and cloudmotion vectors to examine cloud property responses in ship-polluted and nearby unpolluted clouds. The strength of the cloud albedo response to increased aerosol level is primarily dependent on cloud cell structure, dryness of the free troposphere, and boundary layer depth, corroborating a previous study by Chen et al. (2012) where A-Train satellite data were utilized. Under open cell cloud structure the cloud properties are more susceptible to aerosol perturbations as compared to closed cells. Aerosol plumes caused an increase in liquid water amount (+38%), cloud top height (+13%), and cloud albedo (+49%) for open cell clouds, whereas for closed cell clouds, little change in cloud properties was observed. Further capitalizing on MISR’s unique capabilities, the MISR cross-track cloud speed was used to derive cloud top divergence. Statistically averaging the results from the identified plume segments to reduce random noise, we found evidence of cloud top divergence in the ship-polluted clouds, whereas the nearby unpolluted clouds showed cloud top convergence, providing observational evidence of a change in local mesoscale circulation associated with enhanced aerosols. Furthermore, open cell polluted clouds revealed stronger cloud top divergence as compared to closed cell clouds, consistent with different dynamical mechanisms driving their responses. These results suggest that detailed cloud responses, classified by cloud type and environmental conditions, must be accounted for in global climate modeling studies to reduce uncertainties in calculations of aerosol indirect forcing. © 2015. American Geophysical Union. All Rights Reserved."
"7402370453;6701378450;","Effects of film-forming compounds on the growth of giant cloud condensation nuclei: Implications for cloud microphysics and the aerosol indirect effect",2004,"10.1029/2004JD004666","https://www.scopus.com/inward/record.uri?eid=2-s2.0-11844276988&doi=10.1029%2f2004JD004666&partnerID=40&md5=b6276809ddfd4db19188179a15378e8b","The presence of giant cloud condensation nuclei (GCCN) within stratocumulus clouds can help the formation of drizzle by acting as collector drops. We propose that the presence of film-forming compounds (FFCs) on GCCN may decrease their growth enough to cease this drizzle formation mechanism. We systematically explore the accommodation properties and amount of FFCs necessary to have a significant impact on GCCN size under realistic conditions of growth inside typical stratocumulus clouds. It is found that even low mass fractions (as low as 0.2%) of FFCs with a modest effect on water vapor accommodation can significantly reduce GCCN size and their potential to act as collector drops. Our conclusions apply to both pristine and polluted aerosol conditions, which suggest that in the presence of FFCs, GCCN may be influencing the microphysical evolution of clouds to a lesser extent than previously thought. Copyright 2004 by the American Geophysical Union."
"57203053317;6603452105;","Comparing continental and oceanic cloud susceptibilities to aerosols",2003,"10.1029/2003GL017828","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0242368920&doi=10.1029%2f2003GL017828&partnerID=40&md5=d7cd969b95e13a4b5480384625c5074b","A common practice in remote sensing studies of the aerosol indirect effect is to consider the correlation between the droplet effective radius and the aerosol index. However, this correlation is not unique as the relationship depends also on the liquid water path. Moreover, it differs for oceanic and continental clouds because clouds over land generally have higher cloud bases, are thinner and have a higher average cloud droplet number concentration for a given aerosol index than marine clouds. Only when using aerosol number concentration at cloud base instead of aerosol index and using an effective radius representative for the whole cloud rather than just at cloud top, do the defined susceptibilities of oceanic and continental clouds obtained from ECHAM4 climate model simulations agree within the standard errors. This has important consequences for properly interpreting the magnitude of the anthropogenic indirect aerosol effect on climate."
"36538539800;7006270084;7003666669;6602973136;","Impact of aerosol size representation on modeling aerosol-cloud interactions",2002,"10.1029/2001JD001549","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36448987568&doi=10.1029%2f2001JD001549&partnerID=40&md5=a0fb9c063d750b54dc8d4ed9fdba6189","[1] We use a one-dimensional version of a climate-aerosol-chemistry model with both modal and sectional aerosol size representations to evaluate the impact of aerosol size representation on modeling aerosol-cloud interactions in shallow stratiform clouds observed during the second Aerosol Characterization Experiment. Both the modal (with prognostic aerosol number and mass or prognostic aerosol number, surface area and mass, referred to as the Modal-NM and Modal-NSM) and the sectional approaches (with 12 and 36 sections) predict total number and mass for interstitial and activated particles that are generally within several percent of references from a high-resolution 108-section approach. The modal approach with prognostic aerosol mass but diagnostic number (referred to as the Modal-M) cannot accurately predict the total particle number and surface areas, with deviations from the references ranging from 7 to 161%. The particle size distributions are sensitive to size representations, with normalized absolute differences of up to 12% and 37% for the 36- and 12-section approaches, and 30%, 39%, and 179% for the Modal-NSM, Modal-NM, and Modal-M, respectively. For the Modal-NSM and Modal-NM, differences from the references are primarily due to the inherent assumptions and limitations of the modal approach. In particular, they cannot resolve the abrupt size transition between the interstitial and activated aerosol fractions. For the 12- and 36-section approaches, differences are largely due to limitations of the parameterized activation for nonlognormal size distributions, plus the coarse resolution for the 12-section case. Differences are larger both with higher aerosol (i.e., less complete activation) and higher SO2 concentrations (i.e., greater modification of the initial aerosol distribution). Copyright 2002 by the American Geophysical Union."
"57205479655;6602890253;7003786872;7006329853;10144282600;16027966800;7005284577;57211636621;34769585100;15822293900;36864033800;25629654200;57205581157;7404062492;57205479513;55263254000;24477694300;55683611000;","Efficient In-Cloud Removal of Aerosols by Deep Convection",2019,"10.1029/2018GL080544","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060638069&doi=10.1029%2f2018GL080544&partnerID=40&md5=1ad04d059f16599c74f59c28b4b4731f","Convective systems dominate the vertical transport of aerosols and trace gases. The most recent in situ aerosol measurements presented here show that the concentrations of primary aerosols including sea salt and black carbon drop by factors of 10 to 10,000 from the surface to the upper troposphere. In this study we show that the default convective transport scheme in the National Science Foundation/Department of Energy Community Earth System Model results in a high bias of 10–1,000 times the measured aerosol mass for black carbon and sea salt in the middle and upper troposphere. A modified transport scheme, which considers aerosol activation from entrained air above the cloud base and aerosol-cloud interaction associated with convection, dramatically improves model agreement with in situ measurements suggesting that deep convection can efficiently remove primary aerosols. We suggest that models that fail to consider secondary activation may overestimate black carbon's radiative forcing by a factor of 2. ©2018. The Authors."
"57200702127;7404829395;56537463000;12040335900;55814053500;8953662800;7005973015;","Elucidating the role of anthropogenic aerosols in Arctic sea ice variations",2018,"10.1175/JCLI-D-17-0287.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040538052&doi=10.1175%2fJCLI-D-17-0287.1&partnerID=40&md5=ccf04daf42547a690e767a2347c85767","Observations show that the Arctic sea ice cover has been shrinking at an unprecedented rate since the 1970s. Even though the accumulation of greenhouse gases in the atmosphere has been closely linked with the loss of Arctic sea ice, the role of atmospheric aerosols in past and future Arctic climate change remains elusive. Using a state-of-the-art fully coupled climate model, the authors assess the equilibrium responses of the Arctic sea ice to the different aerosol emission scenarios and investigate the pathways by which aerosols impose their influence in the Arctic. These sensitivity experiments show that the impacts of aerosol perturbations on the pace of sea ice melt effectively modulate the ocean circulation and atmospheric feedbacks. Because of the contrasting evolutions of particulate pollution in the developed and developing countries since the 1970s, the opposite aerosol forcings from different midlatitude regions are nearly canceled out in the Arctic during the boreal summer, resulting in a muted aerosol effect on the recent sea ice changes. Consequently, the greenhouse forcing alone can largely explain the observed Arctic sea ice loss up to the present. In the next few decades, the projected alleviation of particulate pollution in the Northern Hemisphere can contribute up to 20% of the total Arctic sea ice loss and 0.7°C surface warming over the Arctic. The authors' model simulations further show that aerosol microphysical effects on the Arctic clouds are the major component in the total aerosol radiative forcing over the Arctic. Compared to the aerosol-induced energy imbalance in lower latitudes outside the Arctic, the local radiative forcing by aerosol variations within the Arctic, due to either local emissions or long-range transports, is more efficient in determining the sea ice changes and Arctic climate change. © 2018 American Meteorological Society."
"57192373652;7003541446;57191308597;57194151357;57194152771;7402538754;","Aerosol removal and cloud collapse accelerated by supersaturation fluctuations in turbulence",2017,"10.1002/2017GL072762","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018868904&doi=10.1002%2f2017GL072762&partnerID=40&md5=9b1ad421e44ffea1ee16cd08d903d8b7","Prior observations have documented the process of cloud cleansing, through which cloudy, polluted air from a continent is slowly transformed into cloudy, clean air typical of a maritime environment. During that process, cloud albedo changes gradually, followed by a sudden reduction in cloud fraction and albedo as drizzle forms and convection changes from closed to open cellular. Experiments in a cloud chamber that generates a turbulent environment show a similar cloud cleansing process followed by rapid cloud collapse. Observations of (1) cloud droplet size distribution, (2) interstitial aerosol size distribution, (3) cloud droplet residual size distribution, and (4) water vapor supersaturation are all consistent with the hypothesis that turbulent fluctuations of supersaturation accelerate the cloud cleansing process and eventual cloud collapse. Decay of the interstitial aerosol concentration occurs slowly at first then more rapidly. The accelerated cleansing occurs when the cloud phase relaxation time exceeds the turbulence correlation time. ©2017. American Geophysical Union. All Rights Reserved."
"55624399200;6505932008;","The importance of the shape of cloud droplet size distributions in shallow cumulus clouds. Part II: Bulk microphysics simulations",2017,"10.1175/JAS-D-15-0383.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85009347588&doi=10.1175%2fJAS-D-15-0383.1&partnerID=40&md5=c402fb3837f2d3833f267c6f6ba3e8d8","In this two-part study, relationships between the cloud gamma size distribution shape parameter, microphysical processes, and cloud characteristics of nonprecipitating shallow cumulus clouds are investigated using large-eddy simulations. In Part I, the dependence of the shape parameter (which is closely related to the distribution width) on cloud properties and processes was investigated. However, the distribution width also impacts cloud process rates and in turn cloud properties, and it is this aspect of the relationship that is explored in Part II and is discussed in the context of aerosol-cloud interactions. In simulations with a bulk microphysics scheme, it is found that the evaporation rates are much more sensitive to the value of the shape parameter than to the condensation rates. This is due to changes in both the rate of removal of mass and the rate of removal of fully evaporated droplets. As a result, cloud properties such as droplet number concentration, mean droplet diameter, and cloud fraction are strongly impacted by the value of the shape parameter, particularly in the subsaturated regions of the clouds. These changes can be on the same order of magnitude as changes due to increasing or decreasing the aerosol concentration by a factor of 16. Particular attention is paid to the impact of the shape parameter on cloud albedo. The cloud albedo increases as the shape parameter is increased as a result of the changes in evaporation. The magnitude of the increase is about 4 times larger than previous estimates. However, this increase in cloud albedo is largely offset by a decrease in the cloud fraction, which results in only small increases to the domain-average albedo. Implications for the aerosol relative dispersion effect are discussed. © 2017 American Meteorological Society."
"10139397300;26867472700;36894599500;6602414959;24390528000;56604012500;6602988199;14630194200;37090362900;6602600408;7003777747;","Regional and seasonal radiative forcing by perturbations to aerosol and ozone precursor emissions",2016,"10.5194/acp-16-13885-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84975029792&doi=10.5194%2facp-16-13885-2016&partnerID=40&md5=aa51c2646354cc3d3269739ff6c0a8c9","Predictions of temperature and precipitation responses to changes in the anthropogenic emissions of climate forcers require the quantification of the radiative forcing exerted by those changes. This task is particularly difficult for near-term climate forcers like aerosols, methane, and ozone precursors because their short atmospheric lifetimes cause regionally and temporally inhomogeneous radiative forcings. This study quantifies specific radiative forcing, defined as the radiative forcing per unit change in mass emitted, for eight near-term climate forcers as a function of their source regions and the season of emission by using dedicated simulations by four general circulation and chemistry-transport models. Although differences in the representation of atmospheric chemistry and radiative processes in different models impede the creation of a uniform dataset, four distinct findings can be highlighted. Firstly, specific radiative forcing for sulfur dioxide and organic carbon are stronger when aerosol-cloud interactions are taken into account. Secondly, there is a lack of agreement on the sign of the specific radiative forcing of volatile organic compound perturbations, suggesting they are better avoided in climate mitigation strategies. Thirdly, the strong seasonalities of the specific radiative forcing of most forcers allow strategies to minimise positive radiative forcing based on the timing of emissions. Finally, European and shipping emissions exert stronger aerosol specific radiative forcings compared to East Asia where the baseline is more polluted. This study can therefore form the basis for further refining climate mitigation options based on regional and seasonal controls on emissions. For example, reducing summertime emissions of black carbon and wintertime emissions of sulfur dioxide in the more polluted regions is a possible way to improve air quality without weakening the negative radiative forcing of aerosols."
"37089417300;7102988363;7004194999;","The global impact of the transport sectors on atmospheric aerosol in 2030 - Part 2: Aviation",2016,"10.5194/acp-16-4481-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84964550163&doi=10.5194%2facp-16-4481-2016&partnerID=40&md5=4ffaf563b06c105c9d820b6ededffeb2","We use the EMAC (ECHAM/MESSy Atmospheric Chemistry) global climate-chemistry model coupled to the aerosol module MADE (Modal Aerosol Dynamics model for Europe, adapted for global applications) to simulate the impact of aviation emissions on global atmospheric aerosol and climate in 2030. Emissions of short-lived gas and aerosol species follow the four Representative Concentration Pathways (RCPs) designed in support of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. We compare our findings with the results of a previous study with the same model configuration focusing on year 2000 emissions. We also characterize the aviation results in the context of the other transport sectors presented in a companion paper. In spite of a relevant increase in aviation traffic volume and resulting emissions of aerosol (black carbon) and aerosol precursor species (nitrogen oxides and sulfur dioxide), the aviation effect on particle mass concentration in 2030 remains quite negligible (on the order of a few ngm-3), about 1 order of magnitude less than the increase in concentration due to other emission sources. Due to the relatively small size of the aviation-induced aerosol, however, the increase in particle number concentration is significant in all scenarios (about 1000cm-3), mostly affecting the northern mid-latitudes at typical flight altitudes (7-12km). This largely contributes to the overall change in particle number concentration between 2000 and 2030, which also results in significant climate effects due to aerosol-cloud interactions. Aviation is the only transport sector for which a larger impact on the Earth's radiation budget is simulated in the future: the aviation-induced radiative forcing in 2030 is more than doubled with respect to the year 2000 value of -15mWm-2 in all scenarios, with a maximum value of -63mWm-2 simulated for RCP2.6. © Author(s) 2016."
"36538539800;55802355600;56942554300;55624488227;7004444634;7202010686;","Application of WRF/Chem over East Asia: Part II. Model improvement and sensitivity simulations",2016,"10.1016/j.atmosenv.2015.07.023","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949626339&doi=10.1016%2fj.atmosenv.2015.07.023&partnerID=40&md5=af5ad6763e275894dd59e726f5eae6a3","To address the problems and limitations identified through a comprehensive evaluation in Part I paper, several modifications are made in model inputs, treatments, and configurations and sensitivity simulations with improved model inputs and treatments are performed in this Part II paper. The use of reinitialization of meteorological variables reduces the biases and increases the spatial correlations in simulated temperature at 2-m (T2), specific humidity at 2-m (Q2), wind speed at 10-m (WS10), and precipitation (Precip). The use of a revised surface drag parameterization further reduces the biases in simulated WS10. The adjustment of only the magnitudes of anthropogenic emissions in the surface layer does not help improve overall model performance, whereas the adjustment of both the magnitudes and vertical distributions of anthropogenic emissions shows moderate to large improvement in simulated surface concentrations and column mass abundances of species in terms of domain mean performance statistics, hourly and monthly mean concentrations, and vertical profiles of concentrations at individual sites. The revised and more advanced dust emission schemes can help improve PM predictions. Using revised upper boundary conditions for O3 significantly improves the column O3 abundances. Using a simple SOA formation module further improves the predictions of organic carbon and PM2.5. The sensitivity simulation that combines all above model improvements greatly improves the overall model performance. For example, the sensitivity simulation gives the normalized mean biases (NMBs) of -6.1% to 23.8% for T2, 2.7-13.8% for Q2, 22.5-47.6% for WS10, and -9.1% to 15.6% for Precip, comparing to -9.8% to 75.6% for T2, 0.4-23.4% for Q2, 66.5-101.0% for WS10, and 11.4%-92.7% for Precip from the original simulation without those improvements. It also gives the NMBs for surface predictions of -68.2% to -3.7% for SO2, -73.8% to -20.6% for NO2, -8.8%-128.7% for O3, -61.4% to -26.5% for PM2.5, and -64.0% to 7.2% for PM10, comparing to -84.2% to -44.5% for SO2, -88.1% to -44.0% for NO2, -11.0%-160.3% for O3, -63.9% to -25.2% for PM2.5, and -68.9%-33.3% for PM10 from the original simulation. The improved WRF/Chem is applied to estimate the impact of anthropogenic aerosols on regional climate and air quality in East Asia. Anthropogenic aerosols can increase cloud condensation nuclei, aerosol optical depth, cloud droplet number concentrations, and cloud optical depth. They can decrease surface net radiation, temperature at 2-m, wind speed at 10-m, planetary boundary layer height, and precipitation through various direct and indirect effects. These changes in turn lead to changes in chemical predictions in a variety of ways. © 2015 Elsevier Ltd."
"54931083200;57193953105;26434217100;7003753501;24315205000;","Common summertime total cloud cover and aerosol optical depth weekly variabilities over Europe: Sign of the aerosol indirect effects?",2015,"10.1016/j.atmosres.2014.07.031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906252278&doi=10.1016%2fj.atmosres.2014.07.031&partnerID=40&md5=a2dca8fe5e7630382a1205b3ab4a1856","In this study, the summer total cloud cover (TCC) weekly cycle over Europe is investigated using MODIS and ISCCP satellite data in conjunction with aerosol optical depth (AOD) MODIS data. Spatial weekly patterns are examined at a 1° × 1° (MODIS) and 250 × 250 km2 (ISCCP) resolution. Despite the noise in the TCC weekly cycle patterns, their large-scale features show similarities with the AOD550 patterns. Regions with a positive (higher values during midweek) weekly cycle appear over Central Europe, while a strong negative (higher values during weekend) weekly plume appears over the Iberian Peninsula and the North-Eastern Europe. The TCC weekly variability exhibits a very good agreement with the AOD550 weekly variability over Central, South-Western Europe and North-Eastern Europe and a moderate agreement for Central Mediterranean. The MODIS derived TCC weekly variability shows reasonable agreement with the independent ISCCP observations, thus supporting the credibility of the results. TCC and AOD550 correlations exhibit a strong slope for the total of the 6 regions investigated in this work with the slopes being higher for regions with common TCC-AOD550 weekly variabilities. The slope is much stronger for AOD550 values less than 0.2 for Central and South-Western Europe, in line with previous studies around the world. Possible scenarios that could explain the common weekly variability of aerosols and cloud cover through the aerosol indirect effects are discussed here also taking into account the weekly variability appearing in ECA&amp;D E-OBS rainfall data. © 2014 Elsevier B.V."
"6602085876;8950640300;7003740015;7003900383;57203053317;","Single-particle characterization of the high-Arctic summertime aerosol",2014,"10.5194/acp-14-7409-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904677912&doi=10.5194%2facp-14-7409-2014&partnerID=40&md5=e386c5412e73bf54903be596eabdd547","Single-particle mass-spectrometric measurements were carried out in the high Arctic north of 80° during summer 2008. The campaign took place onboard the icebreaker Oden and was part of the Arctic Summer Cloud Ocean Study (ASCOS). The instrument deployed was an aerosol time-of-flight mass spectrometer (ATOFMS) that provides information on the chemical composition of individual particles and their mixing state in real time. Aerosols were sampled in the marine boundary layer at stations in the open ocean, in the marginal ice zone, and in the pack ice region. The largest fraction of particles detected for subsequent analysis in the size range of the ATOFMS between approximately 200 and 3000 nm in diameter showed mass-spectrometric patterns, indicating an internal mixing state and a biomass burning and/or biofuel source. The majority of these particles were connected to an air mass layer of elevated particle concentration mixed into the surface mixed layer from the upper part of the marine boundary layer. The second largest fraction was represented by sea salt particles. The chemical analysis of the over-ice sea salt aerosol revealed tracer compounds that reflect chemical aging of the particles during their long-range advection from the marginal ice zone, or open waters south thereof prior to detection at the ship. From our findings we conclude that long-range transport of particles is one source of aerosols in the high Arctic. To assess the importance of long-range particle sources for aerosol-cloud interactions over the inner Arctic in comparison to local and regional biogenic primary aerosol sources, the chemical composition of the detected particles was analyzed for indicators of marine biological origin. Only a minor fraction showed chemical signatures of potentially ocean-derived primary particles of that kind. However, a chemical bias in the ATOFMS's detection capabilities observed during ASCOS might suggest the presence of a particle type of unknown composition and source. In general, the study suffered from low counting statistics due to the overall small number of particles found in this pristine environment, the small sizes of the prevailing aerosol below the detection limit of the ATOFMS, and its low hit rate. To our knowledge, this study reports on the first in situ single-particle mass-spectrometric measurements in the marine boundary layer of the high-Arctic pack ice region. © 2014 Author(s)."
"7402786837;6602600408;57208121852;7006689276;","Processes limiting the emergence of detectable aerosol indirect effects on tropical warm clouds in global aerosol-climate model and satellite data",2014,"10.3402/tellusb.v66.24054","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901999818&doi=10.3402%2ftellusb.v66.24054&partnerID=40&md5=9135cb87ecf763961778aa343cc3eb46","We use data from simulations performed with the global aerosol-climate model ECHAM5-HAM to test the proposition that shipping emissions do not have a statistically significant effect on water clouds over tropical oceans on climate scales put forward in earlier satellite based work. We analyse a total of four sensitivity experiments, three of which employ global shipping emissions and one simulation which only employs shipping emissions in the mid-Atlantic Ocean. To ensure comparability to earlier results from observations, we sample the model data using a method previously applied to satellite data aimed at separating 'clean' from 'polluted' oceanic regions based on i) the location of main shipping routes and ii) wind direction at 10 mabove sea level. The model simulations run with realistic present-day shipping emissions show changes in the lower tropospheric aerosol population attributable to shipping emissions across major shipping corridors over tropical oceans. However, we find the resulting effect on cloud properties to be non-distinguishable from natural gradients and variability, that is, gradients of cloud properties sampled across major shipping corridors over tropical oceans are very similar among those simulations. Our results therefore compare well to the earlier findings from satellite observations. Substantial changes of the aerosol population and cloud properties only occur when shipping emissions are increased 10-fold. We find that aerosol advection and rapid aerosol removal from the atmosphere play an important role in determining the non-significant response in i) column integrated aerosol properties and ii) cloud microphysical properties in the realistic simulations. Additionally, high variability and infrequent occurrence of simulated low-level clouds over tropical oceans in ECHAM5-HAM limit the development of aerosol indirect effects because i) in-cloud production of sulphate from ship-emitted sulphuric species via aqueous oxidation pathways is very low and ii) a possible observational signal is blurred out by high variability in simulated clouds. Our results highlight i) the importance of adequately accounting for atmospheric background conditions when determining climate forcings from observations and ii) the effectiveness of buffering mechanisms on micro-and macroscopic scales which limit the emergence of such climate forcings. © 2014 K. Peters et al."
"57211236228;","Variability of aerosol optical depth and cloud parameters over North Eastern regions of India retrieved from MODIS satellite data",2013,"10.1016/j.jastp.2013.03.025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877693566&doi=10.1016%2fj.jastp.2013.03.025&partnerID=40&md5=24597d3b9b0f7ccbf5f80f5f7c862202","In the present study, the Moderate Resolution Imaging Spectroradiometer (MODIS) data retrieved from Terra satellite has been used to investigate the spatial and temporal variations in aerosol particles over North Eastern region of India for the period (2001-2010). Aerosol optical depths have found to be increased >15% across North Eastern part of India during the last decade (2001-2010). During the summer season, the mean AOD values (0.60±0.07) were observed whereas during the post monsoon season, mean AOD values were observed to be 0.07±0.02. Highest annual mean increase of AOD (> 79%) has been found over Guwahati. We then studied the relationship between AOD and five other cloud parameters namely water vapor, cloud fraction, cloud top temperature, cloud top pressure and cloud optical depth over North Eastern part of India so as to provide a better understanding of aerosol-cloud interaction. © 2013 Elsevier Ltd."
"35075717400;57204986042;7003603120;","Summer/winter variability of the surfactants in aerosols from Grenoble, France",2012,"10.1016/j.atmosenv.2011.10.040","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84155172744&doi=10.1016%2fj.atmosenv.2011.10.040&partnerID=40&md5=823b18eddbb39f8a538d398f626f9cc4","Many atmospheric aerosols seem to contain strong organic surfactants likely to enhance their cloud-forming properties. Yet, few techniques allow for the identification and characterization of these compounds. Recently, we introduced a double extraction method to isolate the surfactant fraction of atmospheric aerosol samples, and evidenced their very low surface tension (≤30mNm -1). In this work, this analytical procedure was further optimized. In addition to an optimized extraction and a reduction of the analytical time, the improved method led to a high reproducibility in the surface tension curves obtained (shapes and minimal values), illustrated by the low uncertainties on the values, ±10% or less. The improved method was applied to PM 10 aerosols from the urban area of Grenoble, France collected from June 2009 to January 2010. Significant variability was observed between the samples. The minimum surface tension obtained from the summer samples was systematically lower (30mNm -1) than that of the winter samples (35-45mNm -1). Sharp transitions in the curves together with the very low surface tensions suggested that the dominating surfactants in the summer samples were biosurfactants, which would be consistent with the high biogenic activity in that season. One group of samples from the winter also displayed sharp transitions, which, together with the slightly higher surface tension, suggested the presence of weaker, possibly man-made, surfactants. A second group of curves from the winter did not display any clear transition but were similar to those of macromolecular surfactants such as polysaccharides or humic substances from wood burning. These surfactants are thus likely to originate from wood burning, the dominating source for aerosols in Grenoble in winter. These observations thus confirm the presence of surfactants from combustion processes in urban aerosols reported by other groups and illustrates the ability of our method to distinguish between different types of surfactants in atmospheric samples. © 2011 Elsevier Ltd."
"55522563200;35193567500;7404653593;","Weekly periodicities of meteorological variables and their possible association with aerosols in Korea",2009,"10.1016/j.atmosenv.2009.08.023","https://www.scopus.com/inward/record.uri?eid=2-s2.0-71049161779&doi=10.1016%2fj.atmosenv.2009.08.023&partnerID=40&md5=658577ded59bcfbc14a7d103a1b9f0bb","The weekly periodicities in meteorological variables and its association with aerosols in Korea are investigated using long-term surface measurements of meteorology (1975-2005) and aerosols (1999-2005). Through an analysis of the annual (and/or seasonal) values averaged over 10 stations, we identified distinct weekly periodicities in the daily minimum temperature (Tmin), diurnal temperature range (DTR), cloud fraction, and solar insolation, although they have different characteristics from each other. The weekly association among variables is discussed in this study. Positive anomalies of the cloud fraction and Tmin and negative anomalies of solar insolation and DTR are seen for the second half of the week and the reverse for the first half of the week, i.e., more cloudiness and less insolation for Wednesday-Thursday and less cloudiness and more insolation for Monday-Tuesday. Furthermore, seasonal dependence of weekly anomalies shows that the weekly periodicities are enhanced especially in autumn, more than 2-3 times as great as those of the annual mean. The weekly cycles in such variables are most likely driven by changes in cloud fraction, possibly through aerosol-cloud interactions induced by aerosol variations between working weekdays and Sunday, which are clearly identified in PM10 weekly cycles. This study also suggests that the weekly periodicities in meteorological variables are possibly associated with long-range transport of weekly periodicities, as well as aerosol-cloud-precipitation interactions over the region. © 2009 Elsevier Ltd. All rights reserved."
"27067996900;8705440100;6603796496;6507755223;7006712143;7007039218;","Observations of aerosol-cloud interactions at the Puijo semi-urban measurement station",2009,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-69949094345&partnerID=40&md5=59d5d01e87920ed4e5148e98dfff4a45","The Puijo measurement station has produced continuous data on aerosol-cloud interactions since June 2006. The station is located on the top floor of an observation tower in a semi-urban environment near the town of Kuopio in central Finland. The top of the tower (306 m a.s.l.) has been detected to be in-cloud approximately 10% of the time. We analysed continuous weather, particle size distribution and cloud droplet size distribution measurements. The effects of local pollutant sources and air mass origin on aerosol-cloud interaction were examined in detail. We were able to find clear evidence of the aerosol indirect effects at the Puijo site. There is a positive correlation between cloud droplet number concentration and particle number concentration. Higher cloud droplet concentration led to a smaller average cloud droplet size. Furthermore, the ratio of cloud droplet number concentration to accumulation mode particle number concentration is smaller when the particle number concentration is higher. Results from our trajectory analysis indicated that at our site marine air masses had higher particle concentrations and the continental aerosols are more effective in acting as cloud condensation nuclei than marine aerosols, probably due to their larger mean size. We could also distinguish the effect of local pollutant sources. © 2009."
"56355030000;55386235300;","A critical examination of the observed first aerosol indirect effect",2009,"10.1175/2008JAS2812.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69849092294&doi=10.1175%2f2008JAS2812.1&partnerID=40&md5=2ccc3813917b6f0df9f0ac6398893769","The relative change in cloud droplet number concentration with respect to the relative change in aerosol number concentration, α, is an indicator of the strength of the aerosol indirect effect and is commonly used in models to parameterize this effect. Based on Twomey's analytical expression, the values of α derived from measurements of an individual cloud (i.e., αT) can be as large as 0.60-0.90. In contrast, the values of α derived from direct measurements of polluted and clean clouds (i.e., α Δ) typically range from 0.25 to 0.85, corresponding to a weaker but more uncertain cooling effect. Clearly, reconciling αΔ with αT is necessary to properly calculate the indirect aerosol forcing. In this study, the terms that are involved in determining αT and αΔ are first analytically examined. Then, by analyzing satellite data over subtropical oceans, the satellite-observed αΔ can be successfully related to Twomey's analytical solution. It is found that except for the dust-influenced region of the northeastern Atlantic Ocean, injecting continental aerosols into a marine background may significantly reduce the average aerosols' ability to act as cloud condensation nuclei. Taking this competing effect into account may reduce the cooling effect proposed by Twomey from 0.76 to 0.28. It is also found that the variability of the adiabaticity (i.e., the cloud dilution state with respect to adiabatic cloud) among different clouds accounts for ∼50% uncertainty in αΔ. Based on these results, the authors explain the claimed discrepancies in the first aerosol indirect effect (AIE) from different methods and on different scales and present an improved parameterization of the first AIE that can be used in global climate models. © 2009 American Meteorological Society."
"14829673100;7201837768;56249704400;7004214645;","Impacts of aerosol-cloud interactions on past and future changes in tropospheric composition",2009,"10.5194/acp-9-4115-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950213026&doi=10.5194%2facp-9-4115-2009&partnerID=40&md5=394c266659ac9b5445b64c2d62de6c49","The development of effective emissions control policies that are beneficial to both climate and air quality requires a detailed understanding of all the feedbacks in the atmospheric composition and climate system. We perform sensitivity studies with a global atmospheric composition-climate model to assess the impact of aerosols on tropospheric chemistry through their modification on clouds, aerosol-cloud interactions (ACI). The model includes coupling between both tropospheric gas-phase and aerosol chemistry and aerosols and liquid-phase clouds. We investigate past impacts from preindustrial (PI) to present day (PD) and future impacts from PD to 2050 (for the moderate IPCC A1B scenario) that embrace a wide spectrum of precursor emission changes and consequential ACI. The aerosol indirect effect (AIE) is estimated to be-2.0Wm-2 for PD-PI and-0.6Wm-2 for 2050-PD, at the high end of current estimates. Inclusion of ACI substantially impacts changes in global mean methane lifetime across both time periods, enhancing the past and future increases by 10% and 30%, respectively. In regions where pollution emissions increase, inclusion of ACI leads to 20% enhancements in in-cloud sulfate production and ∼10% enhancements in sulfate wet deposition that is displaced away from the immediate source regions. The enhanced in-cloud sulfate formation leads to larger increases in surface sulfate across polluted regions (∼10-30%). Nitric acid wet deposition is dampened by 15-20% across the industrialized regions due to ACI allowing additional re-release of reactive nitrogen that contributes to 1-2 ppbv increases in surface ozone in outflow regions. Our model findings indicate that ACI must be considered in studies of methane trends and projections of future changes to particulate matter air quality."
"8718425100;7601492669;7101752236;6602582342;55915206300;7403682442;","Simulating marine boundary layer clouds over the eastern Pacific in a regional climate model with double-moment cloud microphysics",2009,"10.1029/2009JD012201","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049117875&doi=10.1029%2f2009JD012201&partnerID=40&md5=5b6c3d2fc56e429b719d9ce0a70a521a","A double-moment cloud microphysics scheme with a prognostic treatment of aerosols inside clouds has been implemented into the International Pacific Research Center Regional Atmospheric Model (iRAM) to simulate marine boundary layer clouds over the eastern Pacific and to study aerosol-cloud interactions, including the aerosol indirect effect. This paper describes the new model system and presents a comparison of model results with observations. The results show that iRAM with the double-moment cloud microphysics scheme is able to reproduce the major features, including the geographical patterns and vertical distribution of the basic cloud parameters such as cloud droplet number, liquid water content, or droplet effective radii over the eastern Pacific reasonably well. However, the model tends to underestimate cloud droplet number concentrations near the coastal regions strongly influenced by advection of continental aerosols and precursor gases. In addition, the average location of the stratocumulus deck off South America is shifted to the northwest compared with the satellite observations. We apply the new model system to assess the indirect aerosol effect over the eastern Pacific by comparing a simulation with preindustrial aerosol to an otherwise identical simulation with present-day aerosol. Resulting changes in the cloud droplet number concentration are particularly pronounced in Gulf of Mexico and along the Pacific coastlines with local changes up to 70 cm-3 (50% of the present-day value). The modeled domain-averaged 3-month (August-October) mean change in top-of-atmosphere net cloud forcing over the ocean owing to changes in the aerosol burden by anthropogenic activities is - 1.6 W m-2. Copyright 2009 by the American Geophysical Union."
"7003398293;7005729142;7202057166;7403361959;22954523900;","Aerosol indirect effects as a function of cloud top pressure",2007,"10.1029/2006JD007383","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249744334&doi=10.1029%2f2006JD007383&partnerID=40&md5=976695edb0a187bd3db4aa82846efe3c","Aerosol indirect effects are quantified as a function of cloud top pressure over India and the Indian Ocean in February and March 2003-2005 from analyses of moderate resolution imaging spectroradiometer (MODIS) radiances, reflectance, and aerosol optical depth data. We test the hypothesis that aerosol indirect effects are present throughout the troposphere. Theoretical cloud reflectance values are calculated by application of the discrete-ordinate DISORT multiple scattering program, as a function of cloud top pressure, aerosol optical depth, and cloud phase (i.e., liquid droplets and cloud ice), and are compared to MODIS cloud reflectance data at 1.38 and 3.75 μm. Aerosol indirect effects are apparent for pressure levels associated with liquid droplets; that is, derivatives of cloud reflectance with respect to aerosol optical depth at 3.75 μm for liquid droplets over land and ocean are larger than corresponding derivatives associated with theoretical aerosol direct effects. Aerosol indirect effects are not apparent for pressure levels associated with tropospheric ice crystals. Copyright 2007 by the American Geophysical Union."
"57190445508;6602221672;56682032300;8728433200;37040691400;56177971000;57203776263;13405658600;","The potential role of methanesulfonic acid (MSA) in aerosol formation and growth and the associated radiative forcings",2019,"10.5194/acp-19-3137-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062569518&doi=10.5194%2facp-19-3137-2019&partnerID=40&md5=30901c1005616a082bb911cf7f5b4811","Atmospheric marine aerosol particles impact Earth's albedo and climate. These particles can be primary or secondary and come from a variety of sources, including sea salt, dissolved organic matter, volatile organic compounds, and sulfur-containing compounds. Dimethylsulfide (DMS) marine emissions contribute greatly to the global biogenic sulfur budget, and its oxidation products can contribute to aerosol mass, specifically as sulfuric acid and methanesulfonic acid (MSA). Further, sulfuric acid is a known nucleating compound, and MSA may be able to participate in nucleation when bases are available. As DMS emissions, and thus MSA and sulfuric acid from DMS oxidation, may have changed since pre-industrial times and may change in a warming climate, it is important to characterize and constrain the climate impacts of both species. Currently, global models that simulate aerosol size distributions include contributions of sulfate and sulfuric acid from DMS oxidation, but to our knowledge, global models typically neglect the impact of MSA on size distributions. In this study, we use the GEOS-Chem-TOMAS (GCTOMAS) global aerosol microphysics model to determine the impact on aerosol size distributions and subsequent aerosol radiative effects from including MSA in the sizeresolved portion of the model. The effective equilibrium vapor pressure of MSA is currently uncertain, and we use the Extended Aerosol Inorganics Model (E-AIM) to build a parameterization for GC-TOMAS of MSA's effective volatility as a function of temperature, relative humidity, and available gas-phase bases, allowing MSA to condense as an ideally nonvolatile or semivolatile species or too volatile to condense. We also present two limiting cases for MSA's volatility, assuming that MSA is always ideally nonvolatile (irreversible condensation) or that MSA is always ideally semivolatile (quasi-equilibrium condensation but still irreversible condensation). We further present simulations in which MSA participates in binary and ternary nucleation with the same efficacy as sulfuric acid whenever MSA is treated as ideally nonvolatile. When using the volatility parameterization described above (both with and without nucleation), including MSA in the model changes the global annual averages at 900 hPa of submicron aerosol mass by 1.2 %, N3 (number concentration of particles greater than 3 nm in diameter) by-3:9 % (non-nucleating) or 112.5 % (nucleating), N80 by 0.8 % (non-nucleating) or 2.1 % (nucleating), the cloud-albedo aerosol indirect effect (AIE) by-8:6 mW m-2 (non-nucleating) or-26 mW m-2 (nucleating), and the direct radiative effect (DRE) by-15 mW m-2 (non-nucleating) or-14 mW m-2 (nucleating). The sulfate and sulfuric acid from DMS oxidation produces 4-6 times more submicron mass than MSA does, leading to an ∼ 10 times stronger cooling effect in the DRE. But the changes in N80 are comparable between the contributions from MSA and from DMS-derived sulfate/sulfuric acid, leading to comparable changes in the cloud-albedo AIE. Model-measurement comparisons with the Heintzenberg et al. (2000) dataset over the Southern Ocean indicate that the default model has a missing source or sources of ultrafine particles: the cases in which MSA participates in nucle ation (thus increasing ultrafine number) most closely match the Heintzenberg distributions, but we cannot conclude nucleation from MSA is the correct reason for improvement. Model-measurement comparisons with particle-phase MSA observed with a customized Aerodyne high-resolution timeof-flight aerosol mass spectrometer (AMS) from the ATom campaign show that cases with the MSA volatility parameterizations (both with and without nucleation) tend to fit the measurements the best (as this is the first use of MSA measurements from ATom, we provide a detailed description of these measurements and their calibration). However, no one model sensitivity case shows the best model-measurement agreement for both Heintzenberg and the ATom campaigns. As there are uncertainties in both MSA's behavior (nucleation and condensation) and the DMS emissions inventory, further studies on both fronts are needed to better constrain MSA's past, current, and future impacts upon the global aerosol size distribution and radiative forcing. © 2019 Author(s)."
"56898396100;23028245500;55574869900;7102423967;57204185658;","Examining Intrinsic Aerosol-Cloud Interactions in South Asia Through Multiple Satellite Observations",2018,"10.1029/2017JD028232","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054869454&doi=10.1029%2f2017JD028232&partnerID=40&md5=43784faa11b2e848e71fc6d2a8d5975f","Changes in anthropogenic aerosol loading affect cloud albedo and the Earth's radiative balance with a low level of scientific understanding. Aerosol-cloud interaction and its effects on climate are mainly evaluated using passive observations in a global scale. Here this study estimated the intrinsic response of clouds to aerosols by combining active and passive satellite observations from July 2006 to February 2011 in South Asia. We evaluate the average radiative forcing by the intrinsic aerosol-cloud interaction for warm liquid clouds as 0.63 ± 0.19, −0.34 ± 0.40, and 1.11 ± 0.08 W/m2 during the annual, monsoon, and nonmonsoon periods in South Asia, respectively. Relationships derived among liquid water path, cloud droplet number concentration, and consequent cloud albedo are assessed as a function of aerosol concentration. The intensity of the aerosol-cloud interaction gradually weakens with increasing cloud base height above ground level in South Asia, is associated with aerosol vertical distribution and vertical atmospheric upward motion. Moreover, distinct regional and seasonal variations in the aerosol-cloud interaction are observed for liquid water path, cloud droplet number concentration, and the resulting cloud albedo in South Asia. These variations are associated with water vapor and aerosol absorption levels. Results contribute to the understanding and modeling of aerosol-cloud interactions and determining their effects on radiative forcing and climate in South Asia. ©2018. American Geophysical Union. All Rights Reserved."
"42062523800;","Erroneous attribution of deep convective invigoration to aerosol concentration",2018,"10.1175/JAS-D-17-0217.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047102039&doi=10.1175%2fJAS-D-17-0217.1&partnerID=40&md5=2cf0d61cd75481e2c58284d7c6cf4dd6","Contiguous time-height cloud objects at the Department of Energy Atmospheric Radiation Measurement Southern Great Plains (SGP) site are matched with surface condensation nuclei (CN) concentrations and retrieved thermodynamic and kinematic vertical profiles for warm-cloud-base, cold-cloud-top systems in convectively unstable environments. Statistical analyses show that previously published conclusions that increasing CN concentrations cause a decrease in minimum cloud-top temperature (CTT) at the SGP site through the aerosol convective invigoration effect are unfounded. The CN-CTT relationship is statistically insignificant, while correlations between convective available potential energy (CAPE), level of neutral buoyancy (LNB), and CN concentration account for most of the change in the CN-CTT positive correlation. Removal of clouds with minimum CTTs > -36°C from the analysis eliminates the CN-CTT correlation. Composited dirty conditions at the SGP have ~1°C-warmer low levels and ~1°C-cooler upper levels than clean conditions. This correlation between aerosol concentrations and thermodynamic profiles may be caused by an increase in regional rainfall preceding deep convective conditions as CN concentration decreases. Increased rainfall can be expected to increase wet deposition of aerosols, cool low-level temperatures, and warm upper-level temperatures. The masking of a potential aerosol effect by such small thermodynamic changes implies that the strategy of analyzing subsets of aerosol data by binned meteorological factor values is not a valid method for discerning an aerosol effect in some situations. These findings highlight the need for more careful, detailed, and strategic observations to confidently isolate and quantify an aerosol deep convective invigoration effect. © 2018 American Meteorological Society."
"56457851700;12801992200;16444006500;57193327928;7202145115;24722339600;7103016965;","Predicting decadal trends in cloud droplet number concentration using reanalysis and satellite data",2018,"10.5194/acp-18-2035-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042009402&doi=10.5194%2facp-18-2035-2018&partnerID=40&md5=b9a9a2bfc6ed183450a0363a2d273d9f","Cloud droplet number concentration (CDNC) is the key state variable that moderates the relationship between aerosol and the radiative forcing arising from aerosol-cloud interactions. Uncertainty related to the effect of anthropogenic aerosol on cloud properties represents the largest uncertainty in total anthropogenic radiative forcing. Here we show that regionally averaged time series of the Moderate-Resolution Imaging Spectroradiometer (MODIS) observed CDNC of low, liquid-topped clouds is well predicted by the MERRA2 reanalysis near-surface sulfate mass concentration over decadal timescales. A multiple linear regression between MERRA2 reanalyses masses of sulfate (SO4), black carbon (BC), organic carbon (OC), sea salt (SS), and dust (DU) shows that CDNC across many different regimes can be reproduced by a simple power-law fit to near-surface SO4, with smaller contributions from BC, OC, SS, and DU. This confirms previous work using a less sophisticated retrieval of CDNC on monthly timescales. The analysis is supported by an examination of remotely sensed sulfur dioxide (SO2) over maritime volcanoes and the east coasts of North America and Asia, revealing that maritime CDNC responds to changes in SO2 as observed by the ozone monitoring instrument (OMI). This investigation of aerosol reanalysis and top-down remote-sensing observations reveals that emission controls in Asia and North America have decreased CDNC in their maritime outflow on a decadal timescale. © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License."
"56797942500;11339401400;55965624000;57193695551;55976582900;15019752400;6701413579;7006084942;7005219614;","Sensitivity of transatlantic dust transport to chemical aging and related atmospheric processes",2017,"10.5194/acp-17-3799-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85015872714&doi=10.5194%2facp-17-3799-2017&partnerID=40&md5=ec92915445881a20c1cdd3bdeefba8fc","We present a sensitivity study on transatlantic dust transport, a process which has many implications for the atmosphere, the ocean and the climate. We investigate the impact of key processes that control the dust outflow, i.e., the emission flux, convection schemes and the chemical aging of mineral dust, by using the EMAC model following Abdelkader et al. (2015). To characterize the dust outflow over the Atlantic Ocean, we distinguish two geographic zones: (i) dust interactions within the Intertropical Convergence Zone (ITCZ), or the dust-ITCZ interaction zone (DIZ), and (ii) the adjacent dust transport over the Atlantic Ocean (DTA) zone. In the latter zone, the dust loading shows a steep and linear gradient westward over the Atlantic Ocean since particle sedimentation is the dominant removal process, whereas in the DIZ zone aerosol-cloud interactions, wet deposition and scavenging processes determine the extent of the dust outflow. Generally, the EMAC simulated dust compares well with CALIPSO observations; however, our reference model configuration tends to overestimate the dust extinction at a lower elevation and underestimates it at a higher elevation. The aerosol optical depth (AOD) over the Caribbean responds to the dust emission flux only when the emitted dust mass is significantly increased over the source region in Africa by a factor of 10. These findings point to the dominant role of dust removal (especially wet deposition) in transatlantic dust transport. Experiments with different convection schemes have indeed revealed that the transatlantic dust transport is more sensitive to the convection scheme than to the dust emission flux parameterization. To study the impact of dust chemical aging, we focus on a major dust outflow in July 2009. We use the calcium cation as a proxy for the overall chemical reactive dust fraction and consider the uptake of major inorganic acids (i.e., H2SO4, HNO3 and HCl) and their anions, i.e., sulfate (SO42-), bisulfate (HSO4-), nitrate (NO3-) and chloride (Cl-), on the surface of mineral particles. The subsequent neutralization reactions with the calcium cation form various salt compounds that cause the uptake of water vapor from the atmosphere, i.e., through the chemical aging of dust particles leading to an increase of 0.15 in the AOD under subsaturated conditions (July 2009 monthly mean). As a result of the radiative feedback on surface winds, dust emissions increased regionally. On the other hand, the aged dust particles, compared to the non-aged particles, are more efficiently removed by both wet and dry deposition due to the increased hygroscopicity and particle size (mainly due to water uptake). The enhanced removal of aged particles decreases the dust burden and lifetime, which indirectly reduces the dust AOD by 0.05 (monthly mean). Both processes can be significant (major dust outflow, July 2009), but the net effect depends on the region and level of dust chemical aging. © The Author(s) 2017."
"57205842560;55683372600;57031671300;57188806149;7004239407;56471122700;6602675912;7404477860;6701547852;56923805700;","Composition, size and cloud condensation nuclei activity of biomass burning aerosol from northern Australian savannah fires",2017,"10.5194/acp-17-3605-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85015374229&doi=10.5194%2facp-17-3605-2017&partnerID=40&md5=ae00bfc85b923ead5abc4c49ca41d96f","The vast majority of Australia's fires occur in the tropical north of the continent during the dry season. These fires are a significant source of aerosol and cloud condensation nuclei (CCN) in the region, providing a unique opportunity to investigate the biomass burning aerosol (BBA) in the absence of other sources. CCN concentrations at 0.5 % supersaturation and aerosol size and chemical properties were measured at the Australian Tropical Atmospheric Research Station (ATARS) during June 2014. CCN concentrations reached over 104 cmĝ'3 when frequent and close fires were burning - up to 45 times higher than periods with no fires. Both the size distribution and composition of BBA appeared to significantly influence CCN concentrations. A distinct diurnal trend in the proportion of BBA activating to cloud droplets was observed, with an activation ratio of 40 ± 20 % during the night and 60 ± 20 % during the day. BBA was, on average, less hygroscopic during the night (K = 0. 04 ± 0.03) than during the day (K = 0.07 ± 0.05), with a maximum typically observed just before midday. Size-resolved composition of BBA showed that organics comprised a constant 90 % of the aerosol volume for aerodynamic diameters between 100 and 200 nm. While this suggests that the photochemical oxidation of organics led to an increase in the hygroscopic growth and an increase in daytime activation ratios, it does not explain the decrease in hygroscopicity after midday. Modelled CCN concentrations assuming typical continental hygroscopicities produced very large overestimations of up to 200 %. Smaller, but still significant, overpredictions up to ∼ 100 % were observed using aerosol mass spectrometer (AMS)- and hygroscopicity tandem differential mobility analyser (H-TDMA)-derived hygroscopicities as well as campaign night and day averages. The largest estimations in every case occurred during the night, when the small variations in very weakly hygroscopic species corresponded to large variations in the activation diameters. Trade winds carry the smoke generated from these fires over the Timor Sea, where aerosol-cloud interactions are likely to be sensitive to changes in CCN concentrations, perturbing cloud albedo and lifetime. Dry season fires in northern Australia are therefore potentially very important in cloud processes in this region. © Author(s) 2017."
"55243352000;25959992900;","Aerosol impacts on radiative and microphysical properties of clouds and precipitation formation",2017,"10.1016/j.atmosres.2016.10.021","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84993982834&doi=10.1016%2fj.atmosres.2016.10.021&partnerID=40&md5=71c11d126a2c3f43357c05711dfa82c2","Through modifying the number concentration and size of cloud droplets, aerosols have intricate impacts on radiative and microphysical properties of clouds, which together influence precipitation processes. Aerosol-cloud interactions for a mid-latitude convective cloud system are investigated using a two-moment aerosol-aware bulk microphysical scheme implemented into the Weather Research and Forecasting (WRF) model. Three sensitivity experiments with initial identical dynamic and thermodynamic conditions, but different cloud-nucleating aerosol concentrations were conducted. Increased aerosol number concentration has resulted in more numerous cloud droplets of overall smaller sizes, through which the optical properties of clouds have been changed. While the shortwave cloud forcing is significantly increased in more polluted experiments, changes in the aerosol number concentration have negligible impacts on the longwave cloud forcing. For the first time, it is found that polluted clouds have higher cloud base heights, the feature that is caused by more surface cooling due to a higher shortwave cloud forcing, as well as a drier boundary layer in the polluted experiment compared to the clean. The polluted experiment was also associated with a higher liquid water content (LWC), caused by an increase in the number of condensation of water vapor due to higher concentration of hygroscopic aerosols acting as condensation nuclei. The domain-averaged accumulated precipitation is little changed under both polluted and clean atmosphere. Nevertheless, changes in the rate of precipitation are identified, such that under polluted atmosphere light rain is reduced, while both moderate and heavy rain are intensified, confirming the fact that if an ample influx of water vapor exists, an increment of hygroscopic aerosols can increase the amount of precipitation. © 2016 Elsevier B.V."
"42261193100;57203176082;7006828530;56035904300;","Sources and formation processes of water-soluble dicarboxylic acids, α-oxocarboxylic acids, α-dicarbonyls, and major ions in summer aerosols from eastern central India",2017,"10.1002/2016JD026246","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85017339466&doi=10.1002%2f2016JD026246&partnerID=40&md5=5295758237aa9b0ac1088ac13d14034a","The sources and formation processes of dicarboxylic acids are still under investigation. Size-segregated aerosol (nine-size) samples collected in the urban site (Raipur: 21.2°N and 82.3°E) in eastern central India during summer of 2013 were measured for water-soluble diacids (C2-C12), ω-oxoacids (ωC2-ωC9), α-dicarbonyls (C2-C3), and inorganic ions to better understand their sources and formation processes. Diacids showed the predominance of oxalic acid (C2), whereas ω-oxoacids showed the predominance of glyoxylic acid (ωC2), and glyoxal (Gly) was a major α-dicarbonyl in all the sizes. Diacids, ω-oxoacids, and α-dicarbonyls as well as SO24, NO3, and NH+4 were enriched in coarse mode, where Ca2+ peaked, suggesting that they are preferentially produced in coarse mode via adsorption as well as heterogeneous and aqueous-phase oxidation reaction of precursors on the surface of water-soluble mineral dust particles having more alkaline species. Strong correlations of diacids and related compounds with NO3 (r = 0.66-0.91) and aerosol water content (AWC) (r = 0.63-0.93) further suggest the importance of heterogeneous and aqueous-phase production in coarse mode. We found strong correlations of C2/(C2-C12), C2/ωC2, and C2/Gly ratios with AWC in coarse mode (r = 0.83, 0.86, and 0.85, respectively), indicating that enhanced AWC is favorable for the production of C2 diacid through aqueous-phase oxidation of its higher homologous diacids, ωC2, and Gly. These results demonstrates unique reactivity of water-soluble mineral dust particles for the enhanced production of diacids and related compounds in aqueous-phase, having implications on the aerosol-cloud interaction, solubility, and hygroscopicity of a dominant fraction of water-soluble organic aerosol mass. © 2017. American Geophysical Union."
"57003839000;55542885500;57191733258;57131535300;7102010848;8438057200;26666356300;35239166400;35975306400;","Evolution of trace elements in the planetary boundary layer in southern China: Effects of dust storms and aerosol-cloud interactions",2017,"10.1002/2016JD025541","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016428730&doi=10.1002%2f2016JD025541&partnerID=40&md5=abf12127f330bdbdfb026db7983ba336","Aerosols and cloud water were analyzed at a mountaintop in the planetary boundary layer in southern China during March-May 2009, when two Asian dust storms occurred, to investigate the effects of aerosol-cloud interactions (ACIs) on chemical evolution of atmospheric trace elements. Fe, Al, and Zn predominated in both coarse and fine aerosols, followed by high concentrations of toxic Pb, As, and Cd. Most of these aerosol trace elements, which were affected by dust storms, exhibited various increases in concentrations but consistent decreases in solubility. Zn, Fe, Al, and Pb were the most abundant trace elements in cloud water. The trace element concentrations exhibited logarithmic inverse relationships with the cloud liquid water content and were found highly pH dependent with minimum concentrations at the threshold of pH ~5.0. The calculation of Visual MINTEQ model showed that 80.7-96.3% of Fe(II), Zn(II), Pb(II), and Cu(II) existed in divalent free ions, while 71.7% of Fe(III) and 71.5% of Al(III) were complexed by oxalate and fluoride, respectively. ACIs could markedly change the speciation distributions of trace elements in cloud water by pH modification. The in-cloud scavenging of aerosol trace elements likely reached a peak after the first 2-3 h of cloud processing, with scavenging ratios between 0.12 for Cr and 0.57 for Pb. The increases of the trace element solubility (4-33%) were determined in both in-cloud aerosols and postcloud aerosols. These results indicated the significant importance of aerosol-cloud interactions to the evolution of trace elements during the first several cloud condensation/evaporation cycles. © 2017. American Geophysical Union."
"55462884000;36538539800;","Impact of future climate policy scenarios on air quality and aerosol-cloud interactions using an advanced version of CESM/CAM5: Part II. Future trend analysis and impacts of projected anthropogenic emissions",2017,"10.1016/j.atmosenv.2016.12.034","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85009136692&doi=10.1016%2fj.atmosenv.2016.12.034&partnerID=40&md5=c8da550870fc44976d09247501e5f0a6","Following a comprehensive evaluation of the Community Earth System Model modified at the North Carolina State University (CESM-NCSU), Part II describes the projected changes in the future state of the atmosphere under the representative concentration partway scenarios (RCP4.5 and 8.5) by 2100 for the 2050 time frame and examine the impact of climate change on future air quality under both scenarios, and the impact of projected emission changes under the RCP4.5 scenario on future climate through aerosol direct and indirect effects. Both the RCP4.5 and RCP8.5 simulations predict similar changes in air quality by the 2050 period due to declining emissions under both scenarios. The largest differences occur in O3which decreases by global mean of 1.4 ppb under RCP4.5 but increases by global mean of 2.3 ppb under RCP8.5 due to differences in methane levels, and PM10, which decreases by global mean of 1.2 μg m−3under RCP4.5 and increases by global mean of 0.2 μg m−3under RCP8.5 due to differences in dust and sea-salt emissions under both scenarios. Enhancements in cloud formation in the Arctic and Southern Ocean and increases of aerosol optical depth (AOD) in central Africa and South Asia dominate the change in surface radiation in both scenarios, leading to global average dimming of 1.1 W m−2and 2.0 W m−2in the RCP4.5 and RCP8.5 scenarios, respectively. Declines in AOD, cloud formation, and cloud optical thickness from reductions of emissions of primary aerosols and aerosol precursors under RCP4.5 result in near surface warming of 0.2 °C from a global average increase of 0.7 W m−2in surface downwelling solar radiation. This warming leads to a weakening of the Walker Circulation in the tropics, leading to significant changes in cloud and precipitation that mirror a shift in climate towards the negative phase of the El Nino Southern Oscillation. © 2016 Elsevier Ltd"
"56149492300;56942554300;56003666300;55462884000;56612517400;36538539800;","Decadal evaluation of regional climate, air quality, and their interactions over the continental US and their interactions using WRF/Chem version 3.6.1",2016,"10.5194/gmd-9-671-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959088700&doi=10.5194%2fgmd-9-671-2016&partnerID=40&md5=a89632cada4d16fda50fccdd0b004d62","The Weather Research and Forecasting model with Chemistry (WRF/Chem) v3.6.1 with the Carbon Bond 2005 (CB05) gas-phase mechanism is evaluated for its first decadal application during 2001-2010 using the Representative Concentration Pathway 8.5 (RCP 8.5) emissions to assess its capability and appropriateness for long-term climatological simulations. The initial and boundary conditions are downscaled from the modified Community Earth System Model/Community Atmosphere Model (CESM/CAM5) v1.2.2. The meteorological initial and boundary conditions are bias-corrected using the National Center for Environmental Protection's Final (FNL) Operational Global Analysis data. Climatological evaluations are carried out for meteorological, chemical, and aerosol-cloud-radiation variables against data from surface networks and satellite retrievals. The model performs very well for the 2 m temperature (T2) for the 10-year period, with only a small cold bias of - '0.3 °C. Biases in other meteorological variables including relative humidity at 2 m, wind speed at 10 m, and precipitation tend to be site-and season-specific; however, with the exception of T2, consistent annual biases exist for most of the years from 2001 to 2010. Ozone mixing ratios are slightly overpredicted at both urban and rural locations with a normalized mean bias (NMB) of 9.7 % but underpredicted at rural locations with an NMB of-8.8 %. PM2.5 concentrations are moderately overpredicted with an NMB of 23.3 % at rural sites but slightly underpredicted with an NMB of-10.8 % at urban/suburban sites. In general, the model performs relatively well for chemical and meteorological variables, and not as well for aerosol-cloud-radiation variables. Cloud-aerosol variables including aerosol optical depth, cloud water path, cloud optical thickness, and cloud droplet number concentration are generally underpredicted on average across the continental US. Overpredictions of several cloud variables over the eastern US result in underpredictions of radiation variables (such as net shortwave radiation-GSW-with a mean bias-MB-of-5.7 W m-2) and overpredictions of shortwave and longwave cloud forcing (MBs of-7 to 8 W m-2), which are important climate variables. While the current performance is deemed to be acceptable, improvements to the bias-correction method for CESM downscaling and the model parameterizations of cloud dynamics and thermodynamics, as well as aerosol-cloud interactions, can potentially improve model performance for long-term climate simulations. © 2016 Author(s)."
"56963229300;7403364008;6603711967;","The sensitivity of global climate to the episodicity of fire aerosol emissions",2015,"10.1002/2015JD024068","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955192101&doi=10.1002%2f2015JD024068&partnerID=40&md5=8492ec40f33007ab1af553c88c000f9f","Here we explore the sensitivity of the global radiative forcing and climate response to the episodicity of fire emissions. We compare the standard approach used in present day and future climate modeling studies, in which emissions are not episodic but smoothly interpolated between monthly mean values and that contrast to the response when fires are represented using a range of approximations of episodicity. The range includes cases with episodicity levels matching observed fire day and fire event counts, as well as cases with extreme episodicity. We compare the different emissions schemes in a set of Community Atmosphere Model (CAM5) simulations forced with reanalysis meteorology and a set of simulations with online dynamics designed to calculate aerosol indirect effect radiative forcings. We find that using climatologically observed fire frequency improves model estimates of cloud properties over the standard scheme, particularly in boreal regions, when both are compared to a simulation with meteorologically synchronized emissions. Using these emissions schemes leads to a range in global indirect effect radiative forcing of fire aerosols between −1.1 and −1.3 W m−2. In cases with extreme episodicity, we see increased transport of aerosols vertically, leading to longer lifetimes and less negative indirect effect radiative forcings. In general, the range in climate impacts that results from the different realistic fire emissions schemes is smaller than the uncertainty in climate impacts due to other aspects of modeling fire emissions. © 2015. American Geophysical Union. All Rights Reserved."
"7003836546;24437444900;36621776000;6507607421;22635944500;56059425100;55765335000;","Natural and anthropogenic aerosols in the Eastern Mediterranean and Middle East: Possible impacts",2014,"10.1016/j.scitotenv.2014.02.035","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901654332&doi=10.1016%2fj.scitotenv.2014.02.035&partnerID=40&md5=5ec65c38e48961a72a6f217bd40d7581","The physical and chemical properties of airborne particles have significant implications on the microphysical cloud processes. Maritime clouds have different properties than polluted ones and the final amounts and types of precipitation are different. Mixed phase aerosols that contain soluble matter are efficient cloud condensation nuclei (CCN) and enhance the liquid condensate spectrum in warm and mixed phase clouds. Insoluble particles such as mineral dust and black carbon are also important because of their ability to act as efficient ice nuclei (IN) through heterogeneous ice nucleation mechanisms. The relative contribution of aerosol concentrations, size distributions and chemical compositions on cloud structure and precipitation is discussed in the framework of RAMS/ICLAMS model. Analysis of model results and comparison with measurements reveals the complexity of the above links. Taking into account anthropogenic emissions and all available aerosol-cloud interactions the model precipitation bias was reduced by 50% for a storm simulation over eastern Mediterranean. © 2014 Elsevier B.V."
"55025909400;7003414581;55444637900;24366038500;7003375617;7403361959;36846877900;","Dual-FOV raman and Doppler lidar studies of aerosol-cloud interactions: Simultaneous profiling of aerosols, warm-cloud properties, and vertical wind",2014,"10.1002/2013JD020424","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901704135&doi=10.1002%2f2013JD020424&partnerID=40&md5=16b96b01207ce7bd4c16204ad8c97415","For the first time, colocated dual-field of view (dual-FOV) Raman lidar and Doppler lidar observations (case studies) of aerosol and cloud optical and microphysical properties below and within thin layered liquid water clouds are presented together with an updraft and downdraft characterization at cloud base. The goal of this work is to investigate the relationship between aerosol load close to cloud base and cloud characteristics of warm (purely liquid) clouds and the study of the influence of vertical motions and turbulent mixing on this relationship. We further use this opportunity to illustrate the applicability of the novel dual-FOV Raman lidar in this field of research. The dual-FOV lidar combines the well-established multiwavelength Raman lidar technique for aerosol retrievals and the multiple-scattering Raman lidar technique for profiling of the single-scattering extinction coefficient, effective radius, number concentration of the cloud droplets, and liquid water content. Key findings of our 3 year observations are presented in several case studies of optically thin altocumulus layers occurring in the lower free troposphere between 2.5 and 4 km height over Leipzig, Germany, during clean and polluted situations. For the clouds that we observed, the most direct link between aerosol proxy (particle extinction coefficient) and cloud proxy (cloud droplet number concentration) was found at cloud base during updraft periods. Above cloud base, additional processes resulting from turbulent mixing and entrainment of dry air make it difficult to determine the direct impact of aerosols on cloud processes. © 2014. American Geophysical Union. All Rights Reserved."
"55683037100;35232705600;7003696133;7402027161;57189498750;","Impact of aerosol on post-frontal convective clouds over Germany",2014,"10.3402/tellusb.v66.22528","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930616414&doi=10.3402%2ftellusb.v66.22528&partnerID=40&md5=4e1a7fed58bab56fddaca8ab2faf99c3","We carried out simulations with predefined and simulated aerosol distributions in order to investigate the improvement in the forecasting capabilities of an operational weather forecast model by the use of an improved aerosol representation. This study focuses on convective cumulus clouds developing after the passage of a cold front on 25 April 2008 over Germany. The northerly flow after the cold front leads to increased sea salt aerosol concentrations compared to prefrontal conditions. High aerosol number concentrations are simulated in the interactive scenario representing typically polluted conditions. Nevertheless, due to the presence of sea salt particles, effective radii of cloud droplets reach values typical of pristine clouds (between 7μm and 13 μm) at the same time. Compared to the predefined continental and maritime aerosol scenarios, the simulated aerosol distribution leads to a significant change in cloud properties such as cloud droplet radii and number concentrations. Averaged over the domain covered by the convective cumuli clouds, we found a systematic decrease in precipitation with increasing aerosol number concentrations. Differences in cloud cover, short wave radiation and cloud top heights are buffered by systematic differences in precipitation and the related diabatic effects. Comparisons with measured precipitation show good agreement for the interactive aerosol scenario as well as for the extreme maritime aerosol scenario. © 2014 D. Rieger et al."
"22982270700;56228672600;19638935200;57193017893;54413450200;55831300600;","Numerical simulation of clouds and precipitation depending on different relationships between aerosol and cloud droplet spectral dispersion",2013,"10.3402/tellusb.v65i0.19054","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882597788&doi=10.3402%2ftellusb.v65i0.19054&partnerID=40&md5=a34179e4e8cc6d06c0d820cb4a18fdd5","The aerosol effects on clouds and precipitation in deep convective cloud systems are investigated using the Weather Research and Forecast (WRF) model with the Morrison two-moment bulk microphysics scheme. Considering positive or negative relationships between the cloud droplet number concentration (Nc) and spectral dispersion (ε), a suite of sensitivity experiments are performed using an initial sounding data of the deep convective cloud system on 31 March 2005 in Beijing under either a maritime ('clean') or continental ('polluted') background. Numerical experiments in this study indicate that the sign of the surface precipitation response induced by aerosols is dependent on the ε-Nc relationships, which can influence the autoconversion processes from cloud droplets to rain drops. When the spectral dispersion o is an increasing function of Nc, the domainaverage cumulative precipitation increases with aerosol concentrations from maritime to continental background. That may be because the existence of large-sized rain drops can increase precipitation at high aerosol concentration. However, the surface precipitation is reduced with increasing concentrations of aerosol particles when o is a decreasing function of Nc. For the ε-Nc negative relationships, smaller spectral dispersion suppresses the autoconversion processes, reduces the rain water content and eventually decreases the surface precipitation under polluted conditions. Although differences in the surface precipitation between polluted and clean backgrounds are small for all the ε-Nc relationships, additional simulations show that our findings are robust to small perturbations in the initial thermal conditions. © 2013 X. Xie et al."
"13403622000;","Uncertainties in aerosol direct and indirect effects attributed to uncertainties in convective transport parameterizations",2012,"10.1016/j.atmosres.2012.06.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865324734&doi=10.1016%2fj.atmosres.2012.06.022&partnerID=40&md5=bc5a072bfe403cbc4a51792ff2097c37","Deep convection is an important transport mechanism for aerosol particles, allowing them to be lifted to levels where they are subject to long-range transport from source regions to remote regions. The sensitivity of regional aerosol effects to the rate of entrainment in deep moist convection has been explored in a global modeling framework, and found to be crucial for the radiative balance both at the surface and at the top of the atmosphere. The fact that regions where deep convection is frequent often coincide with regions of particularly high black carbon emissions is found to be an important factor in understanding this sensitivity to entrainment. More entrainment leads to shallower convective plumes and less aerosol transport from the boundary layer to the upper troposphere in source regions. As a result, boundary layer aerosol concentrations are increased in source regions, while upper tropospheric aerosol concentrations are reduced globally. This generally leads to stronger aerosol effects in polluted regions and weaker aerosol effects in remote regions. Because black carbon particles have the ability to absorb solar radiation, reducing their concentration leads to more solar radiation reflected back to space, especially over bright surfaces. Conversely, at the surface more entrainment means more downwelling shortwave radiation everywhere but in source regions. Regions that experience increased aerosol concentrations in the boundary layer in response to increased entrainment observed a stronger aerosol indirect effect, while the opposite was true everywhere else. This study highlights that the relative strengths of the aerosol direct and indirect effects in clean versus polluted regions depend crucially on the rate of entrainment in deep convective clouds, a process that is presently not well understood and quantified. © 2012 Elsevier B.V."
"36600036800;35183351400;24398842400;","Do anthropogenic aerosols enhance or suppress the surface cloud forcing in the Arctic?",2010,"10.1029/2010JD014015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78249253759&doi=10.1029%2f2010JD014015&partnerID=40&md5=c30068e27b5dc10825c9e4b3a4e46051","Earlier studies suggest that aerosol-cloud interactions may have contributed to the increase in surface air temperature recently observed in the Arctic. While those studies focused on longwave effects of strong pollution events around Barrow, Alaska, we use a global climate model (CAM-Oslo) to study the annual and seasonal net radiative effect of aerosol-cloud interactions over the entire Arctic region. The model is validated against and adjusted to match observations from the Surface Heat Budget of the Arctic Ocean campaign along with measuring stations within the Arctic region. Several sensitivity experiments were conducted which included changes in both cloud properties and aerosol concentrations. Results show that the longwave indirect effect at the surface lies between 0.10 and 0.85 W/m2 averaged annually north of 71°N, while the shortwave indirect effect lies between -1.29 W/m2 and -0.52 W/m2. Due to longwave dominance in winter, 6 of 11 simulations give a positive change in net cloud forcing between October and May (-0.16 to 0.29 W/m2), while the change in forcing averaged over the summer months is negative for all model simulations (from -2.63 to -0.23 W/m2). The annually averaged change in net cloud forcing at the surface is negative in 10 of 11 simulations, lying between -0.98 and 0.12 W/m2. In conclusion, our results point to a small decrease in the surface radiative flux due to the aerosol indirect effect in the Arctic, but these estimates are subject to uncertainties in the frequency of thin clouds and biases in the estimated cloud cover. © 2010 by the American Geophysical Union."
"6507755223;6603172418;7006377579;55454856700;7006837187;7006235542;","A comparison between trajectory ensemble and adiabatic parcel modeled cloud properties and evaluation against airborne measurements",2009,"10.1029/2008JD011286","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66449115539&doi=10.1029%2f2008JD011286&partnerID=40&md5=7c5b964e9771af9c1c1cf0ff846cc9aa","A trajectory ensemble model (TEM) and an adiabatic air parcel model have been used to study the sensitivity of cloud droplet number concentration on aerosol chemical composition and vertical wind speed variations in the case of stratocumulus clouds. Cloud droplet number concentrations predicted using the TEM approach, in which trajectories are produced by large eddy simulation, and those derived from an air parcel model fed with a probability density function of measured updraft velocities, are compared to cloud droplet measurements conducted during the Cloud Processing of Regional Air Pollution Advecting Over Land and Sea (CLOPAP) campaign. It was found that much better agreement can be achieved using TEM than with the adiabatic air parcel model. The reason for this is the ripening process decreasing the cloud droplet number concentration in the air parcels having long in-cloud residence time. It was also found that the sensitivity of cloud droplet number concentration to aerosol properties is much smaller with TEM than expected from the adiabatic air parcel model simulations. As current parameterizations used to estimate cloud droplet number concentration in many large-scale models are based on adiabatic air parcel models, it is possible that the aerosol indirect effect for stratocumulus and stratus clouds with low vertical wind speeds is overestimated unless the sink resulting from ripening is taken into account. Copyright 2009 by the American Geophysical Union."
"35592560600;57192460006;23020321400;","Aerosol effects on clouds and precipitation during the 1997 smoke episode in Indonesia",2009,"10.5194/acp-9-743-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950283719&doi=10.5194%2facp-9-743-2009&partnerID=40&md5=c41b4ec32b4e7575abab4be05c125545","In 1997/1998 a severe smoke episode due to extensive biomass burning, especially of peat, was observed over Indonesia. September 1997 was the month with the highest aerosol burden. This month was simulated using the limited area model REMOTE driven at its lateral boundaries by ERA40 reanalysis data. REMOTE was extended by a new convective cloud parameterization mimicking individual clouds competing for instability energy. This allows for the interaction of aerosols, convective clouds and precipitation. Results show that in the monthly mean convective precipitation is diminished at nearly all places with high aerosol loading, but at some areas with high background humidity precipitation from large-scale clouds may over-compensate the loss in convective rainfall. The simulations revealed that both large-scale and convective clouds' microphysics are in-fluenced by aerosols. Since aerosols are washed and rained out by rainfall, high aerosol concentrations can only persist at low rainfall rates. Hence, aerosol concentrations are not independent of the rainfall amount and in the mean the maximum absolute effects on rainfall from large scale clouds are found at intermediate aerosol concentrations. The reason for this behavior is that at high aerosol concentrations rainfall rates are small and consequently also the anomalies are small. For large-scale as well as for convective rain negative and positive anomalies are found for all aerosol concentrations. Negative anomalies dominate and are highly statistically significant especially for convective rainfall since part of the precipitation loss from large-scale clouds is compensated by moisture detrained from the convective clouds. The mean precipitation from large-scale clouds is less reduced (however still statistically significant) than rain from convective clouds. This effect is due to detrainment of cloud water from the less strongly raining convective clouds and because of the generally lower absolute amounts of rainfall from large-scale clouds. With increasing aerosol load both, convective and large scale clouds produce less rain. At very few individual time steps cases were found when polluted convective clouds produced intensified rainfall via mixed phase microphysics. However, these cases are not unequivocal and opposite results were also simulated, indicating that other than aerosol-microphysics effects have important impact on the results. Overall, the introduction of the new cumulus parameterization and aerosol-cloud interaction reduced some of the original REMOTE biases of precipitation patterns and total amount."
"8550791300;22959375000;7202779940;7102680152;7006415284;","Deliquescence and hygroscopic growth of succinic acid particles measured with LACIS",2007,"10.1029/2007GL030185","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35948958984&doi=10.1029%2f2007GL030185&partnerID=40&md5=b7ec1f976fd1cbcde31f206526325079","Succinic acid, a dicarboxylic acid which is only slightly soluble in water, was examined with regard to its deliquescence process and its hygroscopic growth in comparison with simple Köhler theory. Investigations were done at LACIS (Leipzig Aerosol Cloud Interaction Simulator), which can measure hygroscopic growth of aerosol particles at relative humidities up to values close to 100%. The deliquescence relative humidity of dry succinic acid particles with diameters of 200 nm was found at 99% (±0.2%). Deliquescence took place on a time scale faster than 0.3 seconds, for some measurements even faster than 0.15 seconds. Comparison of the measured equilibrium sizes of the succinic acid particles with modeled hygroscopic growth revealed evaporation of succinic acid from the deliquesced particles, an effect, which has been described in literature previously. Copyright 2007 by the American Geophysical Union."
"12138847300;7102290666;6506966551;","Multiyear Advanced Very High Resolution Radiometer observations of summertime stratocumulus collocated with aerosols in the northeastern Atlantic",2006,"10.1029/2005JD006890","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845951911&doi=10.1029%2f2005JD006890&partnerID=40&md5=0db66528e60f72d22d0d8f60347a1cc2","Advanced Very High Resolution Radiometer (AVHRR) 4-km data were collected over the northeast Atlantic for May-August 1995-1999. Aerosol optical depth at 0.55 μm was retrieved in pixels identified as being cloud-free ocean. In pixels identified as containing clouds from single-layered, low-level cloud systems over oceans, the following cloud properties were retrieved: 0.64-μm cloud optical depth, droplet effective radius, cloud layer altitude, pixel-scale fractional cloud cover, column liquid water amount and column droplet concentration. Aerosol and cloud properties were averaged in 1° × 1° latitude-longitude regions. Regions that contained clouds were limited to those in which all the clouds were part of a single-layered, low-level cloud system. Aerosol and cloud properties were compared only in 1° regions that had sufficient numbers of both cloud-free pixels that yielded aerosol retrievals and cloudy pixels that yielded retrievals of cloud properties within a single overpass. The comparisons were collected in 5° × 5° latitude-longitude regions to determine trends. Within each 5° region the cloud properties were similar from year to year, permitting the data to be composited for all 5 years. Aerosol optical depth decreased systematically with time, probably as a result of the increase in solar zenith angle due to the precession of the satellite orbit. Within the 5° regions, as aerosol optical depth increased, droplet effective radius decreased, cloud optical depth increased, and droplet column number concentration increased, qualitatively consistent with the trends expected for the aerosol indirect effect. In some regions, liquid water path decreased as aerosol optical depth increased, contrary to the trends expected for the suppression of drizzle. Within each 5° region, clouds in clean air, as indicated by their collocation with relatively small aerosol optical depths, had larger droplets and smaller cloud optical depths than clouds in polluted air, as indicated by their collocation with relatively large aerosol optical depths. On average, the aerosol indirect radiative forcing for overcast conditions was about twice as large as the direct radiative forcing for cloud-free conditions. In most of the 5° regions increases in cloud liquid water with increasing aerosol optical depth enhanced the ratios by 20-30% over those calculated from the changes in droplet effective radius and an assumption of constant cloud liquid water. In some 5° regions, however, like those just to the west of the Iberian peninsula, the column amount of cloud liquid water decreased with increasing aerosol optical depth. Copyright 2006 by the American Geophysical Union."
"57203053317;35887706900;35464731600;","Disentangling the role of microphysical and dynamical effects in determining cloud properties over the Atlantic",2006,"10.1029/2005GL024625","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745713477&doi=10.1029%2f2005GL024625&partnerID=40&md5=c108a64e8be245a4a009ee17c4e1523e","MODIS satellite data reveal that over the Atlantic Ocean (20°S-30°N) in June-August 2002 indirect aerosol effects cause a decrease in the cloud top effective radius of stratiform clouds of 2.9 μm and an increase in cloud fraction of 21%, when increasing the aerosol optical thickness (AOT) from the cleanest 5 percentile to an AOT of 0.2. Thus, indirect aerosol effects are responsible for 72% (-8.8 W m-2) of the -12.2 W m-2 decrease in the shortwave radiation at the top-of-the atmosphere (TOA). Global climate model simulations with and without indirect aerosol effects confirm a decrease in TOA shortwave cloud forcing of -9 W m-2 over the Atlantic from the cleanest to the highest AOT due to indirect aerosol effects. While MODIS shows an increase in cloud fraction due to aerosols, in the model aerosols cause primarily an increase in cloud water. Thus, unlike the analysis from MODIS, the increase in cloud fraction with increasing AOT is dominated by changes in dynamical regimes, not by aerosol indirect effects. Copyright 2006 by the American Geophysical Union."
"57203837174;55279955100;57209290429;14012040000;57207924967;55413425000;55674516400;56810629000;57205064972;57089985200;57129789700;25655132600;57200701209;56893048100;36089962000;57213316186;56998026500;57210207151;55268427500;55730541100;","Observed Interactions Between Black Carbon and Hydrometeor During Wet Scavenging in Mixed-Phase Clouds",2019,"10.1029/2019GL083171","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85069919595&doi=10.1029%2f2019GL083171&partnerID=40&md5=4c55e276e37b2e7258c89fae46cebd1c","Wet scavenging of black carbon (BC) has been subject to large uncertainty, which importantly determines its atmospheric lifetime and indirect forcing impact on cloud microphysics. This study reveals the complex BC-hydrometeor interactions in mixed-phase clouds via single particle measurements in the real-world environment, by capturing precipitation processes throughout cloud formation, cold rain/graupel, and subsequent snow events at a mountain site influenced by anthropogenic sources in wintertime. We found highly efficient BC wet scavenging during cloud formation, with large and thickly coated BC preferentially incorporated into droplets. During snow processes, BC core sizes in the interstitial phase steadily increased. A mechanism was proposed whereby the BC mass within each droplet was accumulated through droplet collision, leading to larger BC cores, which were then released back to the interstitial air through the Wegener-Bergeron-Findeisen processes when ice dominated. These results provide fundamental basis for constraining BC wet scavenging. © 2019. American Geophysical Union. All Rights Reserved."
"55355176000;8067118800;","The Impact of Process-Based Warm Rain Constraints on the Aerosol Indirect Effect",2018,"10.1029/2018GL079956","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054665254&doi=10.1029%2f2018GL079956&partnerID=40&md5=4eb4c7b22f46ee0b4411037cf96924c9","Many global climate models have been found to generate warm rain too frequently. This study, with a particular global climate model, found that the problem can be mitigated via altering the autoconversion process so as to inhibit rain formation under conditions of a large cloud number concentration and small droplet sizes. However, this improvement was found to cause an overly large aerosol indirect effect. This dichotomy between the constraint on warm-rain formation process and the energy-budget requirement on aerosol indirect effect was found to result from a pronounced cloud-water response to aerosol perturbations, which is amplified through the wet scavenging feedback to an extent depending on precipitation-formation parameterization. Thus, critical compensating errors exist between warm-rain formation and other key processes, and better constraint on these processes, particularly wet scavenging, is required to mitigate the dichotomy. The results have broad implication for models that suffer from the aforementioned too-frequent warm-rain formation bias. ©2018. The Authors."
"12139043600;6507533363;6602414959;12139310900;36600036800;55682938700;57194590416;15042618500;55717074000;23051160600;16308931200;14051743300;57205638870;56250250300;","A production-tagged aerosol module for earth system models, OsloAero5.3-extensions and updates for CAM5.3-Oslo",2018,"10.5194/gmd-11-3945-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054305977&doi=10.5194%2fgmd-11-3945-2018&partnerID=40&md5=8ff41dcf31282b52846186934e121833","We document model updates and present and discuss modeling and validation results from a further developed production-Tagged aerosol module, OsloAero5.3, for use in Earth system models. The aerosol module has in this study been implemented and applied in CAM5.3-Oslo. This model is based on CAM5.3-CESM1.2 and its own predecessor model version CAM4-Oslo. OsloAero5.3 has improved treatment of emissions, aerosol chemistry, particle life cycle, and aerosol-cloud interactions compared to its predecessor OsloAero4.0 in CAM4-Oslo. The main new features consist of improved aerosol sources; the module now explicitly accounts for aerosol particle nucleation and secondary organic aerosol production, with new emissions schemes also for sea salt, dimethyl sulfide (DMS), and marine primary organics. Mineral dust emissions are updated as well, adopting the formulation of CESM1.2. The improved model representation of aerosol-cloud interactions now resolves heterogeneous ice nucleation based on black carbon (BC) and mineral dust calculated by the model and treats the activation of cloud condensation nuclei (CCN) as in CAM5.3. Compared to OsloAero4.0 in CAM4-Oslo, the black carbon (BC) mass concentrations are less excessive aloft, with a better fit to observations. Near-surface mass concentrations of BC and sea salt aerosols are also less biased, while sulfate and mineral dust are slightly more biased. Although appearing quite similar for CAM5.3-Oslo and CAM4-Oslo, the validation results for organic matter (OM) are inconclusive, since both of the respective versions of OsloAero are equipped with a limited number of OM tracers for the sake of computational efficiency. Any information about the assumed mass ratios of OM to organic carbon (OC) for different types of OM sources is lost in the transport module. Assuming that observed OC concentrations scaled by 1.4 are representative for the modeled OM concentrations, CAM5.3-Oslo with OsloAero5.3 is slightly inferior for the very sparsely available observation data. Comparing clear-sky column-integrated optical properties with data from ground-based remote sensing, we find a negative bias in optical depth globally; however, it is not as strong as in CAM4-Oslo, but has positive biases in some areas typically dominated by mineral dust emissions. Aerosol absorption has a larger negative bias than the optical depth globally. This is reflected in a lower positive bias in areas where mineral dust is the main contributor to absorption. Globally, the low bias in absorption is smaller than in CAM4-Oslo. The Ångström parameter exhibits small biases both globally and regionally, suggesting that the aerosol particle sizes are reasonably well represented. Cloud-Top droplet number concentrations over oceans are generally underestimated compared to satellite retrievals, but seem to be overestimated downwind of major emissions of dust and biomass burning sources. Finally, we find small changes in direct radiative forcing at the top of the atmosphere, while the cloud radiative forcing due to anthropogenic aerosols is now more negative than in CAM4-Oslo, being on the strong side compared to the multi-model estimate in IPCC AR5. Although not all validation results in this study show improvement for the present CAM5.3-Oslo version, the extended and updated aerosol module OsloAero5.3 is more advanced and applicable than its predecessor OsloAero4.0, as it includes new parameterizations that more readily facilitate sensitivity and process studies and use in climate and Earth system model studies in general. © 2018 Copernicus GmbH. All Rights Reserved."
"6504067346;57193882808;6701596624;","Broadening of cloud droplet spectra through eddy hopping: Turbulent entraining parcel simulations",2018,"10.1175/JAS-D-18-0078.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85057402782&doi=10.1175%2fJAS-D-18-0078.1&partnerID=40&md5=95831939f30505e3f62741dee843d403","This paper discusses the effects of cloud turbulence, turbulent entrainment, and entrained cloud condensation nuclei (CCN) activation on the evolution of the cloud droplet size spectrum. We simulate an ensemble of idealized turbulent cloud parcels that are subject to entrainment events modeled as a random process. Entrainment events, subsequent turbulent mixing inside the parcel, supersaturation fluctuations, and the resulting stochastic droplet activation and growth by condensation are simulated using aMonte Carlo scheme. Quantities characterizing the turbulence intensity, entrainment rate, CCN concentration, and the mean fraction of environmental air entrained in an event are all specified as independent external parameters. Cloud microphysics is described by applying Lagrangian particles, the so-called superdroplets. These are either unactivated CCN or cloud droplets that grow from activated CCN. The model accounts for the addition of environmental CCN into the cloud by entraining eddies at the cloud edge. Turbulent mixing of the entrained dry air with cloudy air is described using the classical linear relaxation to the mean model. We show that turbulence plays an important role in aiding entrained CCN to activate, and thus broadening the droplet size distribution. These findings are consistent with previous large-eddy simulations (LESs) that consider the impact of variable droplet growth histories on the droplet size spectra in small cumuli. The scheme developed in this work is ready to be used as a stochastic subgrid-scale scheme in LESs of natural clouds. © 2018 American Meteorological Society."
"56798441100;36606783400;7004351010;","Aerosols characteristics, trends and their climatic implications over northeast india and adjoining South Asia",2018,"10.1002/joc.5240","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045913681&doi=10.1002%2fjoc.5240&partnerID=40&md5=4ee7846f4acd2d05e11ac65bfe7e498e","Aerosol characteristics and climatic implications derived for selected locations of the north-eastern region of India and adjoining locations Thimphu (THM), Dhaka (DAC) and Banmauk between 22-30°N and 88-98°E are reported. The region is found to reveal a distinct spatio-temporal variability in aerosol distribution, with highest climatological mean aerosol optical depth at 550 nm (AOD550) at DAC (0.65 ± 0.07) and lowest at the high altitude location THM (0.19 ± 0.02). Seasonally the maximum AOD550 is observed in the pre-monsoon season. Moderate resolution imaging spectroradiometer Level-3 Collection 6 AOD550 and Ångström exponent (AE) exhibit a significant and simultaneous increasing trend in the range of ∼0.003 year−1 to 0.012 year−1 and ∼−0.001 year−1 to 0.020 year−1, respectively, during the period 2001-2014. Together with AE, increasing trend of total ozone mapping spectrometer and ozone monitoring instrument-retrieved aerosol index (∼0.001 year−1 to 0.007 year−1 during 1979-2014) signifies an increase in anthropogenic aerosol loading, leading to an increase in number density of cloud condensation nuclei and decrease/increase of cloud effective radius /cloud optical depth (COD). This is further associated with overall decreasing trends of rainfall rate over this complex monsoon region. A slow increase in maximum temperature (Tmax) (∼0.008 ∘C year−1 to 0.049 ∘C year−1) compared to that in minimum temperature (Tmin) (∼0.007 ∘C year−1 to 0.068 ∘C year−1) is attributed to solar dimming due to increasing aerosol loading and COD (∼0.056 year−1 to 0.15 year−1). A decrease in high-level cloud (CODhigh) counteracts decreasing trends of ground reaching solar radiation over a few locations, including Dibrugarh. This study is important from an aerosol radiation interaction and aerosol cloud interaction viewpoint, which facilitates in reaching a closure of model simulated present day climate change and future climate projections. © 2017 Royal Meteorological Society."
"6508333712;34868499700;24398842400;","Sensitivity of the 2014 Pentecost storms over Germany to different model grids and microphysics schemes",2017,"10.1002/qj.3019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018892688&doi=10.1002%2fqj.3019&partnerID=40&md5=4907a3be011f8767d795cb1ffed10cdf","At Pentecost 2014, following a period of hot weather, northwestern Germany was affected by a series of severe convective storms leading to fatalities and significant damage from strong winds, heavy precipitation, hail, and lightning. We present convection-permitting numerical simulations for 2 days of this event (8 and 9 June) using the COnsortium for Small-scale MOdeling (COSMO) model. Whereas a control run in a nearly operational configuration successfully reproduced the convective events of the first day, it failed to adequately reproduce the events of the second day. To further assess the predictability of this event, sensitivity studies with an enlarged model domain, finer horizontal and vertical grid spacing, and a double-moment microphysics scheme were performed. Results show that enlarging the model domain improved the results over France and the Netherlands by better resolving deep convection and secondary cell initiation in that area, but the model failed to simulate deep convection over Germany. The increase of model resolution from 2.8 km to 2.2 and 1 km had minor effects only. However, the errors of accumulated precipitation were diminished independently of the model domain and grid resolution on the first day when using the double-moment microphysics scheme. A better result for 9 June was obtained by using later initialization times (0300 and 0600 UTC instead of 0000 UTC). The control run initialized at 0000 UTC produced one cell, which decayed while travelling over the Netherlands. In contrast, the runs initialized later produced thunderstorms over Germany as well, due to outflow triggering or cell splitting. Finally, different cloud condensation nuclei (CCN) assumptions revealed a systematic relationship for condensate amounts of cloud water, rain and ice with increasing CCN. However, the evaporation of raindrops at lower levels led to a non-systematic response of accumulated precipitation to CCN. In addition, grid spacing effects on aerosol–cloud interactions were assessed. © 2017 Royal Meteorological Society"
"56536745100;7005304841;57203053317;","Cloud response and feedback processes in stratiform mixed-phase clouds perturbed by ship exhaust",2017,"10.1002/2016GL071358","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85013382124&doi=10.1002%2f2016GL071358&partnerID=40&md5=1fe8ce558d585fe2f699f463fa3614a5","Stratiform mixed-phase clouds (MPCs), which contain both supercooled liquid and ice, play a key role in the energy balance of the Arctic and are a major contributor to surface precipitation. As Arctic shipping is projected to increase with climate change, these clouds may frequently be exposed to local aerosol perturbations of up to 15,000 cm−3. Yet little consensus exists within the community regarding the key feedback mechanisms induced in MPCs perturbed by ship exhaust, or aerosol in general. Here we show that many known processes identified in the warm-phase stratocumulus regime can be extrapolated to the MPC regime. However, their effect may be compensated, or even undermined, by the following two most relevant processes unique to the MPC regime: (i) increased cloud glaciation via immersion freezing due to cloud condensation nuclei (CCN) induced cloud top radiative cooling and (ii) the continued cycling of ice nucleating particles (INPs) through the cloud and subcloud layer. ©2017. The Authors."
"26634244600;14035836100;7003591311;","A long-term study of aerosol-cloud interactions and their radiative effect at the Southern Great Plains using ground-based measurements",2016,"10.5194/acp-16-11301-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84987762581&doi=10.5194%2facp-16-11301-2016&partnerID=40&md5=2a4e9c4cd65b9b6061d52f52e3a85564","Empirical estimates of the microphysical response of cloud droplet size distribution to aerosol perturbations are commonly used to constrain aerosol-cloud interactions in climate models. Instead of empirical microphysical estimates, here macroscopic variables are analyzed to address the influence of aerosol particles and meteorological descriptors on instantaneous cloud albedo and the radiative effect of shallow liquid water clouds. Long-term ground-based measurements from the Atmospheric Radiation Measurement (ARM) program over the Southern Great Plains are used. A broad statistical analysis was performed on 14 years of coincident measurements of low clouds, aerosol, and meteorological properties. Two cases representing conflicting results regarding the relationship between the aerosol and the cloud radiative effect were selected and studied in greater detail. Microphysical estimates are shown to be very uncertain and to depend strongly on the methodology, retrieval technique and averaging scale. For this continental site, the results indicate that the influence of the aerosol on the shallow cloud radiative effect and albedo is weak and that macroscopic cloud properties and dynamics play a much larger role in determining the instantaneous cloud radiative effect compared to microphysical effects. On a daily basis, aerosol shows no correlation with cloud radiative properties (correlation D =-0.01±0.03), whereas the liquid water path shows a clear signal (correlation D =-0.56± .02). © 2016 Author(s)."
"57189038577;15032788000;8680433600;7102944401;7006107059;","Effects of long-range aerosol transport on the microphysical properties of low-level liquid clouds in the Arctic",2016,"10.5194/acp-16-4661-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84964853581&doi=10.5194%2facp-16-4661-2016&partnerID=40&md5=d925472b6d7489d38f5170059d579ff2","The properties of low-level liquid clouds in the Arctic can be altered by long-range pollution transport to the region. Satellite, tracer transport model, and meteorological data sets are used here to determine a net aerosol-cloud interaction (ACInet) parameter that expresses the ratio of relative changes in cloud microphysical properties to relative variations in pollution concentrations while accounting for dry or wet scavenging of aerosols en route to the Arctic. For a period between 2008 and 2010, ACInet is calculated as a function of the cloud liquid water path, temperature, altitude, specific humidity, and lower tropospheric stability. For all data, ACInet averages 0.12 ± 0.02 for cloud-droplet effective radius and 0.16 ± 0.02 for cloud optical depth. It increases with specific humidity and lower tropospheric stability and is highest when pollution concentrations are low. Carefully controlling for meteorological conditions we find that the liquid water path of arctic clouds does not respond strongly to aerosols within pollution plumes. Or, not stratifying the data according to meteorological state can lead to artificially exaggerated calculations of the magnitude of the impacts of pollution on arctic clouds. © 2016 Author(s)."
"55973913400;7006434689;55999273500;56442378900;35751142400;14034301300;56533839200;55554016600;6701842515;7005069415;","The Ice Selective Inlet: A novel technique for exclusive extraction of pristine ice crystals in mixed-phase clouds",2015,"10.5194/amt-8-3087-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938635314&doi=10.5194%2famt-8-3087-2015&partnerID=40&md5=19e61d2e844854be5130b84fbd3fb9ef","Climate predictions are affected by high uncertainties partially due to an insufficient knowledge of aerosol-cloud interactions. One of the poorly understood processes is formation of mixed-phase clouds (MPCs) via heterogeneous ice nucleation. Field measurements of the atmospheric ice phase in MPCs are challenging due to the presence of much more numerous liquid droplets. The Ice Selective Inlet (ISI), presented in this paper, is a novel inlet designed to selectively sample pristine ice crystals in mixed-phase clouds and extract the ice residual particles contained within the crystals for physical and chemical characterization. Using a modular setup composed of a cyclone impactor, droplet evaporation unit and pumped counterflow virtual impactor (PCVI), the ISI segregates particles based on their inertia and phase, exclusively extracting small ice particles between 5 and 20 andmu;m in diameter. The setup also includes optical particle spectrometers for analysis of the number size distribution and shape of the sampled hydrometeors. The novelty of the ISI is a droplet evaporation unit, which separates liquid droplets and ice crystals in the airborne state, thus avoiding physical impaction of the hydrometeors and limiting potential artefacts. The design and validation of the droplet evaporation unit is based on modelling studies of droplet evaporation rates and computational fluid dynamics simulations of gas and particle flows through the unit. Prior to deployment in the field, an inter-comparison of the optical particle size spectrometers and a characterization of the transmission efficiency of the PCVI was conducted in the laboratory. The ISI was subsequently deployed during the Cloud and Aerosol Characterization Experiment (CLACE) 2013 and 2014-two extensive international field campaigns encompassing comprehensive measurements of cloud microphysics, as well as bulk aerosol, ice residual and ice nuclei properties. The campaigns provided an important opportunity for a proof of concept of the inlet design. In this work we present the setup of the ISI, including the modelling and laboratory characterization of its components, as well as field measurements demonstrating the ISI performance and validating the working principle of the inlet. Finally, measurements of biological aerosol during a Saharan dust event (SDE) are presented, showing a first indication of enrichment of bio-material in sub-2 μm ice residuals. © 2015 Author(s)."
"55253694900;7102084129;55389396600;6508061772;7004222436;","Effects of aerosol sources and chemical compositions on cloud drop sizes and glaciation temperatures",2015,"10.1002/2015JD023270","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944909397&doi=10.1002%2f2015JD023270&partnerID=40&md5=b2e5b542efdc31d8bdb7cc9607f53fba","The effect of aerosols on cloud properties, such as its droplet sizes and its glaciation temperatures, depends on their compositions and concentrations. In order to examine these effects,we collected rain samples in northern Israel during five winters (2008-2011 and 2013) and determined their chemical composition, which was later used to identify the aerosols’ sources. By combining the chemical data with satellite-retrieved cloud properties, we linked the aerosol types, sources, and concentrations with the cloud glaciation temperatures (Tg). The presence of dust increased Tg from -26°C to -12°C already at relatively low dust concentrations. This result is in agreement with the conventional wisdom that desert dust serves as good ice nuclei (INs). With higher dust concentrations, Tg saturated at -12°C, even though cloud droplet sizes decreased as a result of the cloud condensation nucleating (CCN) activity of the dust. Marine air masses also encouraged freezing, but in this case, freezing was enhanced by the larger cloud droplet sizes in the air masses (caused by low CCN concentrations) and not by IN concentrations or by aerosol type. An increased fraction of anthropogenic aerosols in marine air masses caused a decrease in Tg, indicating that these aerosols served as poor IN. Anthropogenic aerosols reduced cloud droplet sizes, which further decreased Tg. Our results could be useful in climate models for aerosol-cloud interactions, aswe investigated the effects of aerosols of different sources on cloud properties. Such parameterization can simplify these models substantially. © 2015. American Geophysical Union. All Rights Reserved."
"35095482200;7006783796;8723505700;","Aerosol variability, synoptic-scale processes, and their link to the cloud microphysics over the northeast pacific during MAGIC",2015,"10.1002/2015JD023175","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84932147074&doi=10.1002%2f2015JD023175&partnerID=40&md5=ce527dba53d94a44072956fbdcea5724","Shipborne aerosol measurements collected from October 2012 to September 2013 along 36 transects between the port of Los Angeles, California (33.7°N, 118.2°), and Honolulu, Hawaii (21.3°N, 157.8°W), during the Marine ARM GPCI (Global Energy and Water Cycle Experiment (GEWEX)-Cloud System Study (GCSS)-Pacific Cross-section Intercomparison) Investigation of Clouds campaign are analyzed to determine the circulation patterns that modulate the synoptic and monthly variability of cloud condensation nuclei (CCN) in the boundary layer. Seasonal changes in CCN are evident, with low magnitudes during autumn/winter, and high CCN during spring/summer accompaniedwith a characteristic westward decrease. CCNmonthly evolution is consistent with satellite-derived cloud droplet number concentration Ndfrom the Moderate Resolution Imaging Spectroradiometer. One-point correlation (r) analysis between the 1000 hPa zonal wind time series over a region between 125°Wand 135°W, 35°N and 45°N, and the Ndfield yields a negative r (up to -0.55) over a domain that covers a zonal extent of at least 20° from the California shoreline, indicating that Nddecreases when the zonal wind intensifies. The negative r expands southwestward as the zonal wind precedes Ndby up to 3 days, suggesting a transport mechanism from the coast of North America mediated by the California low-coastal jet, which intensifies in summer when the aerosol concentration and Ndreach a maximum. A first assessment of aerosol-cloud interaction (ACI) is performed by combining CCN and satellite Ndvalues from the Fifteenth Geostationary Operational Environmental Satellite. The CCN-Ndcorrelation is 0.66–0.69, and the ACI metric defined as ACI= ∂ln(Nd)/∂ln(CCN) is high at 0.9, similar to other aircraft-based studies and substantially greater than those inferred from satellites and climate models. © 2015. American Geophysical Union. All rights reserved."
"57211236228;","Long term (2003-2012) spatio-temporal MODIS (Terra/Aqua level 3) derived climatic variations of aerosol optical depth and cloud properties over a semi arid urban tropical region of Northern India",2014,"10.1016/j.atmosenv.2013.10.030","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890106250&doi=10.1016%2fj.atmosenv.2013.10.030&partnerID=40&md5=8434dfd036003a922fc5035b10559d39","Aerosol optical depth (AOD) values at 550nm derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard NASA's Terra and Aqua satellites, for the 10 years period of 2003-2012 have been analyzed in the present study. The retrieved satellite data (Terra/Aqua) has been used to investigate the temporal heterogeneity in columnar aerosol characteristics over a semi arid urban tropical Delhi zone (28° 34', 77° 07', 233m ASL) of Northern India with a resolution of 1°×1° grid in magnitude. Aerosol optical depths have found to be increased >25% across Delhi region of India during the study period of 2003-2012. Yearly mean Terra/Aqua AOD values have shown an increasing trend at a rate of 0.005/0.009 per year respectively. However, seasonally winter means Terra/Aqua AOD values exhibit an increasing trend at a rate of ~0.012/0.007 per year respectively. In order to provide a better understanding of aerosol-cloud interaction, a single paired one tailed distribution student's t-Test has been applied to the Terra AOD values and cloud parameters. The results extracted in the present study are compared with the earlier studies as well as with the AOD values over various other Indian regions. © 2013 Elsevier Ltd."
"36491930900;8696318000;7404462869;6507979420;57193840197;55570627500;","Influence of aerosol on clouds over the Indo-Gangetic Plain, India",2013,"10.1007/s00382-013-1775-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881026409&doi=10.1007%2fs00382-013-1775-z&partnerID=40&md5=5f183eb41b6c928eb30514e525869a9c","Using Total Ozone Mapping Spectrometer Aerosol Index (AI) and NCEP/NCAR reanalysis clouds data for the period 1979-1992, the influence of aerosol on the clouds (low and high cloud cover) over the Indo-Gangetic Plain (IGP) in India has been brought out for the first time in the present study. AI shows increasing tendency over the IGP suggesting that aerosol loading over this region increased significantly during the study period. In our analysis, High Cloud Cover (HCC) shows increasing trend and Low Cloud Cover (LCC) shows decreasing trend over the IGP during the same period. During pre-monsoon season when aerosol loading is more, HCC increases in positive correlation with AI. On the other hand, LCC show decreasing trend and is anti-correlated with AI. During summer monsoon, aerosol shows increasing trend but their effect on HCC and LCC is not seen to be significant. Similarly, the role of humidity on aerosol induced changes in HCC and LCC over the IGP region was also analyzed. In the low to moderate humid areas of IGP region (western and middle IGP), increasing AI leads to increase in HCC and decrease in LCC. On the other hand, in high humid areas (eastern IGP), increase in AI does not show any significant effect on HCC, but LCC shows positive trend. Therefore, we strongly argue that increasing aerosol loading enhances Cloud Condensation Nuclei over the region which in turn, alters the microphysical properties of clouds by reducing the size of cloud droplets, and atmospheric humidity controls the aerosol effect on clouds. During the recent period (2005-2010), similar features have also been observed over the IGP region. © 2013 Springer-Verlag Berlin Heidelberg."
"37051480000;7006146719;57203259976;6701511324;35392584500;","Cloud base vertical velocity statistics: A comparison between an atmospheric mesoscale model and remote sensing observations",2011,"10.5194/acp-11-9207-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052681135&doi=10.5194%2facp-11-9207-2011&partnerID=40&md5=bdc66e881958f28baacd0a8a0f3f5e25","The statistics of cloud base vertical velocity simulated by the non-hydrostatic mesoscale model AROME are compared with Cloudnet remote sensing observations at two locations: the ARM SGP site in central Oklahoma, and the DWD observatory at Lindenberg, Germany. The results show that AROME significantly underestimates the variability of vertical velocity at cloud base compared to observations at their nominal resolution; the standard deviation of vertical velocity in the model is typically 4-8 times smaller than observed, and even more during the winter at Lindenberg. Averaging the observations to the horizontal scale corresponding to the physical grid spacing of AROME (2.5 km) explains 70-80% of the underestimation by the model. Further averaging of the observations in the horizontal is required to match the model values for the standard deviation in vertical velocity. This indicates an effective horizontal resolution for the AROME model of at least 10 km in the presented case. Adding a TKE-term on the resolved grid-point vertical velocity can compensate for the underestimation, but only for altitudes below approximately the boundary layer top height. The results illustrate the need for a careful consideration of the scales the model is able to accurately resolve, as well as for a special treatment of sub-grid scale variability of vertical velocities in kilometer-scale atmospheric models, if processes such as aerosol-cloud interactions are to be included in the future. © Author(s) 2011."
"8550791300;7202779940;22959375000;7006415284;","Calibration of LACIS as a CCN detector and its use in measuring activation and hygroscopic growth of atmospheric aerosol particles",2006,"10.5194/acp-6-4519-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749556423&doi=10.5194%2facp-6-4519-2006&partnerID=40&md5=26bcf5e9b999cd9a937be5c6512a0b92","A calibration for LACIS (Leipzig Aerosol Cloud Interaction Simulator) for its use as a CCN (cloud condensation nuclei) detector has been developed. For this purpose, sodium chloride and ammonium sulfate particles of known sizes were generated and their grown sizes were detected at the LACIS outlet. From these signals, the effective critical super-saturation was derived as a function of the LACIS wall temperature. With this, LACIS is calibrated for its use as a CCN detector. The applicability of LACIS for measurements of the droplet activation, and also of the hygroscopic growth of atmospheric aerosol particles was tested. The activation of the urban aerosol particles used in the measurements was found to occur at a critical super-saturation of 0.46% for particles with a dry diameter of 75 nm, and at 0.42% for 85 nm, respectively. Hygroscopic growth was measured for atmospheric aerosol particles with dry diameters of 150, 300 and 350 nm at relative humidities of 98 and 99%, and it was found that the larger dry particles contained a larger soluble volume fraction of about 0.85, compared to about 0.6 for the 150 nm particles."
"7102655202;7102862273;35593636200;6602914876;35998927000;7006211890;56187256200;6603738264;55684491100;7004292082;","Aerosol-cirrus interactions: A number based phenomenon at all?",2004,"10.5194/acp-4-293-2004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3242730519&doi=10.5194%2facp-4-293-2004&partnerID=40&md5=484fb1eb6b3a2a10a3b3c7a5adca54a9","In situ measurements of the partitioning of aerosol particles within cirrus clouds were used to investigate aerosol-cloud interactions in ice clouds. The number density of interstitial aerosol particles (non-activated particles in between the cirrus crystals) was compared to the number density of cirrus crystal residuals. The data was obtained during the two INCA (Interhemispheric Differences in Cirrus Properties from Anthropogenic Emissions) campaigns, performed in the Southern Hemisphere (SH) and Northern Hemisphere (NH) midlatitudes. Different aerosol-cirrus interactions can be linked to the different stages of the cirrus lifecycle. Cloud formation is linked to positive correlations between the number density of interstitial aerosol (Nint) and crystal residuals (Ncvi), whereas the correlations are smaller or even negative in a dissolving cloud. Unlike warm clouds, where the number density of cloud droplets is positively related to the aerosol number density, we observed a rather complex relationship when expressing Ncvi as a function of Nint for forming clouds. The data sets are similar in that they both show local maxima in the Nint range 100 to 200 cm-3, where the SH- maximum is shifted towards the higher value. For lower number densities Nint and Ncvi are positively related. The slopes emerging from the data suggest that a ten-fold increase in the aerosol number density corresponds to a 3 to 4 times increase in the crystal number density. As Nint increases beyond the ca. 100 to 200 cm-3, the mean crystal number density decreases at about the same rate for both data sets. For much higher aerosol number densities, only present in the NH data set, the mean Ncvi remains low. The situation for dissolving clouds allows us to offer two possible, but at this point only speculative, alternative interactions between aerosols and cirrus: evaporating clouds might be associated with a source of aerosol particles, or air pollution (high aerosol number density) might retard ice particle evaporation rates. © European Geosciences Union 2004."
"23095483400;16444232500;56039057300;57208121852;36171703500;56250185400;57206038917;35235146400;6506718302;57203053317;","The global aerosol-climate model ECHAM6.3-HAM2.3-Part 2: Cloud evaluation, aerosol radiative forcing, and climate sensitivity",2019,"10.5194/gmd-12-3609-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85071235195&doi=10.5194%2fgmd-12-3609-2019&partnerID=40&md5=5b46beb191002250765800ba146684d3","The global aerosol-climate model ECHAM6.3-HAM2.3 (E63H23) as well as the previous model versions ECHAM5.5-HAM2.0 (E55H20) and ECHAM6.1-HAM2.2 (E61H22) are evaluated using global observational datasets for clouds and precipitation. In E63H23, the amount of low clouds, the liquid and ice water path, and cloud radiative effects are more realistic than in previous model versions. E63H23 has a more physically based aerosol activation scheme, improvements in the cloud cover scheme, changes in the detrainment of convective clouds, changes in the sticking efficiency for the accretion of ice crystals by snow, consistent ice crystal shapes throughout the model, and changes in mixed-phase freezing; an inconsistency in ice crystal number concentration (ICNC) in cirrus clouds was also removed. Common biases in ECHAM and in E63H23 (and in previous ECHAM-HAM versions) are a cloud amount in stratocumulus regions that is too low and deep convective clouds over the Atlantic and Pacific oceans that form too close to the continents (while tropical land precipitation is underestimated). There are indications that ICNCs are overestimated in E63H23. Since clouds are important for effective radiative forcing due to aerosol-radiation and aerosol-cloud interactions (ERFariCaci) and equilibrium climate sensitivity (ECS), differences in ERFariCaci and ECS between the model versions were also analyzed. ERFariCaci is weaker in E63H23 (-1:0 W m-2) than in E61H22 (-1:2 W m-2) (or E55H20;-1:1 W m-2). This is caused by the weaker shortwave ERFariCaci (a new aerosol activation scheme and sea salt emission parameterization in E63H23, more realistic simulation of cloud water) overcompensating for the weaker longwave ERFariCaci (removal of an inconsistency in ICNC in cirrus clouds in E61H22). The decrease in ECS in E63H23 (2.5 K) compared to E61H22 (2.8 K) is due to changes in the entrainment rate for shallow convection (affecting the cloud amount feedback) and a stronger cloud phase feedback. Experiments with minimum cloud droplet number concentrations (CDNCmin) of 40 cm-3 or 10 cm-3 show that a higher value of CDNCmin reduces ERFariCaci as well as ECS in E63H23. © 2019 The Author(s)."
"57208796935;56682032300;57190445508;55790615000;30667482600;13405658600;","Effects of near-source coagulation of biomass burning aerosols on global predictions of aerosol size distributions and implications for aerosol radiative effects",2019,"10.5194/acp-19-6561-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065839963&doi=10.5194%2facp-19-6561-2019&partnerID=40&md5=dbbb569915fd027af1fdc204f0d1b0b5","Biomass burning is a significant global source of aerosol number and mass. In fresh biomass burning plumes, aerosol coagulation reduces aerosol number and increases the median size of aerosol size distributions, impacting aerosol radiative effects. Near-source biomass burning aerosol coagulation occurs at spatial scales much smaller than the grid boxes of global and many regional models. To date, these models have ignored sub-grid coagulation and instantly mixed fresh biomass burning emissions into coarse grid boxes. A previous study found that the rate of particle growth by coagulation within an individual smoke plume can be approximated using the aerosol mass emissions rate, initial size distribution median diameter and modal width, plume mixing depth, and wind speed. In this paper, we use this parameterization of sub-grid coagulation in the GEOS-Chem-TOMAS (TwO-Moment Aerosol Sectional) global aerosol microphysics model to quantify the impacts on global aerosol size distributions, the direct radiative effect, and the cloud-albedo aerosol indirect effect. We find that inclusion of biomass burning sub-grid coagulation reduces the biomass burning impact on the number concentration of particles larger than 80&thinsp;nm (a proxy for CCN-sized particles) by 37&thinsp;% globally. This cloud condensation nuclei (CCN) reduction causes our estimated global biomass burning cloud-albedo aerosol indirect effect to decrease from -76 to -43&thinsp;mW&thinsp;m-2. Further, as sub-grid coagulation moves mass to sizes with more efficient scattering, including it increases our estimated biomass burning all-sky direct effect from -224 to -231&thinsp;mW&thinsp;m-2, with assumed external mixing of black carbon and from -188 to -197&thinsp;mW&thinsp;m-2 and with assumed internal mixing of black carbon with core-shell morphology. However, due to differences in fire and meteorological conditions across regions, the impact of sub-grid coagulation is not globally uniform. We also test the sensitivity of the impact of sub-grid coagulation to two different biomass burning emission inventories to various assumptions about the fresh biomass burning aerosol size distribution and to two different timescales of sub-grid coagulation. The impacts of sub-grid coagulation are qualitatively the same regardless of these assumptions. © Author(s) 2019."
"56300206800;57192962897;57192298390;56888287100;55486117400;56411079900;57145546300;8075033200;56520903100;35265615300;36836439900;55718911800;","Cloud scavenging of anthropogenic refractory particles at a mountain site in North China",2018,"10.5194/acp-18-14681-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054993443&doi=10.5194%2facp-18-14681-2018&partnerID=40&md5=7bb03b47925840a0e70c0dd6908792d2","Aerosol-cloud interactions remain a major source of uncertainty in climate forcing estimates. Few studies have been conducted to characterize the aerosol-cloud interactions in heavily polluted conditions worldwide. In this study, cloud residual and cloud interstitial particles were collected during cloud events under different pollution levels from 22 July to 1 August 2014 at Mt. Tai (1532 m above sea level) located in the North China Plain (NCP). A transmission electron microscope was used to investigate the morphology, size, and chemical composition of individual cloud residual and cloud interstitial particles, and to study mixing properties of different aerosol components in individual particles. Our results show that S-rich particles were predominant (78 %) during clean periods (PM2.5&lt; 15 μ3), but a large number of anthropogenic refractory particles (e.g., soot, fly ash, and metal) and their mixtures with S-rich particles (defined as ""S-refractory"") were observed during polluted periods. Cloud droplets collected during polluted periods were found to become an extremely complicated mixture by scavenging abundant refractory particles. We found that 76 % of cloud residual particles were S-refractory particles and that 26 % of cloud residual particles contained two or more types of refractory particles. Soot-containing particles (i.e., S-soot and S-fly ash/metal-soot) were the most abundant (62 %) among cloud residual particles, followed by fly ash/metal-containing particles (i.e., S-fly ash/metal and Sfly ash/metal-soot, 37 %). These complicated cloud droplets have not been reported in clean continental or marine air before. Our findings provide an insight into the potential impacts on cloud radiative forcing from black carbon and metal catalyzed reactions of SO2 in micro-cloud droplets containing soluble metals released from fly ash and metals over polluted air. © 2018 Author(s)."
"36106335800;15318900900;7501627905;","On the representation of aerosol activation and its influence on model-derived estimates of the aerosol indirect effect",2018,"10.5194/acp-18-7961-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048243812&doi=10.5194%2facp-18-7961-2018&partnerID=40&md5=9e7853a8ed4676262a96abca52438789","Interactions between aerosol particles and clouds contribute a great deal of uncertainty to the scientific community's understanding of anthropogenic climate forcing. Aerosol particles serve as the nucleation sites for cloud droplets, establishing a direct linkage between anthropogenic particulate emissions and clouds in the climate system. To resolve this linkage, the community has developed parameterizations of aerosol activation which can be used in global climate models to interactively predict cloud droplet number concentrations (CDNCs). However, different activation schemes can exhibit different sensitivities to aerosol perturbations in different meteorological or pollution regimes. To assess the impact these different sensitivities have on climate forcing, we have coupled three different core activation schemes and variants with the CESM-MARC (two-Moment, Multi-Modal, Mixing-state-resolving Aerosol model for Research of Climate (MARC) coupled with the National Center for Atmospheric Research's (NCAR) Community Earth System Model (CESM; version 1.2)). Although the model produces a reasonable present-day CDNC climatology when compared with observations regardless of the scheme used, ΔCDNCs between the present and preindustrial era regionally increase by over 100% in zonal mean when using the most sensitive parameterization. These differences in activation sensitivity may lead to a different evolution of the model meteorology, and ultimately to a spread of over 0.8Wm-2 in global average shortwave indirect effect (AIE) diagnosed from the model, a range which is as large as the intermodel spread from the AeroCom intercomparison. Modelderived AIE strongly scales with the simulated preindustrial CDNC burden, and those models with the greatest preindustrial CDNC tend to have the smallest AIE, regardless of their 1CDNC. This suggests that present-day evaluations of aerosol-climate models may not provide useful constraints on the magnitude of the AIE, which will arise from differences in model estimates of the preindustrial aerosol and cloud climatology. © Author(s) 2018."
"56294931300;7005742394;7006446865;18438598900;","Relationship between aerosols, hail microphysics, and ZDR columns",2018,"10.1175/JAS-D-17-0127.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048406791&doi=10.1175%2fJAS-D-17-0127.1&partnerID=40&md5=20c06cca867c926b7cedb0b20cd14fbb","Mechanisms of formation of differential reflectivity columns are investigated in simulations of a midlatitude summertime hailstorm with hailstones up to several centimeters in diameter. Simulations are performed using a new version of the Hebrew University Cloud Model (HUCM) with spectral bin microphysics. A polarimetric radar forward operator is used to calculate radar reflectivity and differential reflectivity ZDR. It is shown that ZDR columns are associated with raindrops and with hail particles growing in a wet growth regime within convective updrafts. The height and volume of ZDR columns increases with an increase in aerosol concentration. Small hail forming under clean conditions grows in updrafts largely in a dry growth regime corresponding to low ZDR. Characteristics of ZDR columns are highly correlated with vertical velocity, hail size, and aerosol concentration. © 2018 American Meteorological Society."
"57142867400;56611366900;55745955800;19638935200;","Height Dependency of Aerosol-Cloud Interaction Regimes",2018,"10.1002/2017JD027431","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040238032&doi=10.1002%2f2017JD027431&partnerID=40&md5=ab33e66243ad4c15ec9674333d7b9be6","This study investigates the height dependency of aerosol-cloud interaction regimes in terms of the joint dependence of the key cloud microphysical properties (e.g., cloud droplet number concentration and cloud droplet relative dispersion) on aerosol number concentration (Na) and vertical velocity (w). The three distinct regimes with different microphysical features are the aerosol-limited regime, the updraft-limited regime, and the transitional regime. The results reveal two new phenomena in updraft-limited regime: (1) the “condensational broadening” of cloud droplet size distribution in contrast to the well-known “condensational narrowing” in the aerosol-limited regime and (2) above the level of maximum supersaturation; some cloud droplets are deactivated into interstitial aerosols in the updraft-limited regime, whereas all droplets remain activated in the aerosol-limited regime. Further analysis shows that the particle equilibrium supersaturation plays important role in understanding these unique features. Also examined is the height of warm rain initiation and its dependence on Na and w. The rain initiation height is found to depend primarily on either Na or w or both in different Na-w regimes, suggesting a strong regime dependence of the second aerosol indirect effect. ©2017. American Geophysical Union. All Rights Reserved."
"57189038577;15032788000;56460968300;8680433600;","High Sensitivity of Arctic Liquid Clouds to Long-Range Anthropogenic Aerosol Transport",2018,"10.1002/2017GL075795","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040084987&doi=10.1002%2f2017GL075795&partnerID=40&md5=0d393ce7c6f66bb1219f1cfe81f29ce0","The rate of warming in the Arctic depends upon the response of low-level microphysical and radiative cloud properties to aerosols advected from distant anthropogenic and biomass-burning sources. Cloud droplet cross-section density increases with higher concentrations of cloud condensation nuclei, leading to an increase of cloud droplet absorption and scattering radiative cross sections. The challenge of assessing the magnitude of the effect has been decoupling the aerosol impacts on clouds from how clouds change solely due to natural meteorological variability. Here we address this issue with large, multi-year satellite, meteorological, and tracer transport model data sets to show that the response of low-level clouds in the Arctic to anthropogenic aerosols lies close to a theoretical maximum and is between 2 and 8 times higher than has been observed elsewhere. However, a previously described response of arctic clouds to biomass-burning plumes appears to be overstated because the interactions are rare and modification of cloud radiative properties appears better explained by coincident changes in temperature, humidity, and atmospheric stability. ©2017. American Geophysical Union. All Rights Reserved."
"56925245400;55447210800;6701490531;","Aerosol-cloud interaction in deep convective clouds over the Indian Peninsula using spectral (bin) microphysics",2017,"10.1175/JAS-D-17-0034.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85031128277&doi=10.1175%2fJAS-D-17-0034.1&partnerID=40&md5=da050d141736891e5338d0358f5aa95a","The Weather Research and Forecasting (WRF) Model coupled with a spectral bin microphysics (SBM) scheme is used to investigate aerosol effects on cloud microphysics and precipitation over the Indian peninsular region. The main emphasis of the study is in comparing simulated cloud microphysical structure with in situ aircraft observations from the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX). Aerosol-cloud interaction over the rain-shadow region is investigated with observed and simulated size distribution spectra of cloud droplets and ice particles in monsoon clouds. It is shown that size distributions as well as other microphysical characteristics obtained from simulations such as liquid water content, cloud droplet effective radius, cloud droplet number concentration, and thermodynamic parameters are in good agreement with the observations. It is seen that in clouds with high cloud condensation nuclei (CCN) concentrations, snow and graupel size distribution spectra were broader compared to clouds with low concentrations of CCN, mainly because of enhanced riming in the presence of a large number of droplets with a diameter of 10-30 μm. The Hallett-Mossop ice multiplication process is illustrated to have an impact on snow and graupel mass. The changes in CCN concentrations have a strong effect on cloud properties over the domain, amounts of cloud water, and the glaciation of the clouds, but the effects on surface precipitation are small when averaged over a large area. Overall enhancement of cold-phase cloud processes in the high- CCN case contributed to slight enhancement (5%) in domain-averaged surface precipitation. © 2017AmericanMeteorological Society."
"56167179800;57194339496;23095483400;57203053317;","Impact of Saharan dust on North Atlantic marine stratocumulus clouds: Importance of the semidirect effect",2017,"10.5194/acp-17-6305-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019724220&doi=10.5194%2facp-17-6305-2017&partnerID=40&md5=92dc0971bd4f1be1d09c4dbc2379f53d","One component of aerosol-cloud interactions (ACI) involves dust and marine stratocumulus clouds (MSc). Few observational studies have focused on dust-MSc interactions, and thus this effect remains poorly quantified. We use observations from multiple sensors in the NASA A-Train satellite constellation from 2004 to 2012 to obtain estimates of the aerosol-cloud radiative effect, including its uncertainty, of dust aerosol influencing Atlantic MSc off the coast of northern Africa between 45°W and 15° E and between 0 and 35± N. To calculate the aerosol-cloud radiative effect, we use two methods following Quaas et al. (2008) (Method 1) and Chen et al. (2014) (Method 2). These two methods yield similar results of-1.5±1.4 and 1.5±1.6Wm-2, respectively, for the annual mean aerosol-cloud radiative effect. Thus, Saharan dust modifies MSc in a way that acts to cool the planet. There is a strong seasonal variation, with the aerosol-cloud radiative effect switching from significantly negative during the boreal summer to weakly positive during boreal winter. Method 1 (Method 2) yields-3.8±2.5 (-4.3±4.1) during summer and 1±2.9 (0.6±1)Wm-2 during winter. In Method 1, the aerosol-cloud radiative effect can be decomposed into two terms, one representing the first aerosol indirect effect and the second representing the combination of the second aerosol indirect effect and the semidirect effect (i.e., changes in liquid water path and cloud fraction in response to changes in absorbing aerosols and local heating). The first aerosol indirect effect is relatively small, varying from 0.7±0.6 in summer to 0.1±0.5Wm-2 in winter. The second term, however, dominates the overall radiative effect, varying from 3.2±2.5 in summer to 0.9±2.9Wm-2 during winter. Studies show that the semidirect effect can result in a negative (i.e., absorbing aerosol lies above low clouds like MSc) or positive (i.e., absorbing aerosol lies within low clouds) aerosol-cloud radiative effect. The semipermanent MSc are low and confined within the boundary layer. CALIPSO shows that 61.8±12.6% of Saharan dust resides above North Atlantic MSc during summer for our study area. This is consistent with a relatively weak first aerosol indirect effect and also suggests the second aerosol indirect effect plus semidirect effect (the second term in Method 1) is dominated by the semidirect effect. In contrast, the percentage of Saharan dust above North Atlantic MSc in winter is 11.9±10.9 %, which is much lower than in summer. CALIPSO also shows that 88.3±8.5% of dust resides below 2.2 km the winter average of MSc top height. During summer, however, there are two peaks, with 35.6±13% below 1.9 km (summer average of MSc top height) and 44.4±9.2%between 2 and 4 km. Because the aerosol-cloud radiative effect is positive during winter, and is also dominated by the second term, this again supports the importance of the semidirect effect.We conclude that Saharan dust-MSc interactions off the coast of northern Africa are likely dominated by the semidirect effect. © Author(s) 2017. CC Attribution 3.0 License."
"22982270700;57190227631;56228672600;19638935200;56611366900;","Sensitivity study of cloud parameterizations with relative dispersion in CAM5.1: Impacts on aerosol indirect effects",2017,"10.5194/acp-17-5877-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019187622&doi=10.5194%2facp-17-5877-2017&partnerID=40&md5=14dff2fde9639f6adfab1a885dd57cb6","Aerosol-induced increase of relative dispersion of cloud droplet size distribution ϵ exerts a warming effect and partly offsets the cooling of aerosol indirect radiative forcing (AIF) associated with increased droplet concentration by increasing the cloud droplet effective radius (Re) and enhancing the cloud-to-rain autoconversion rate (Au) (labeled as the dispersion effect), which can help reconcile global climate models (GCMs) with the satellite observations. However, the total dispersion effects on both Re and Au are not fully considered in most GCMs, especially in different versions of the Community Atmospheric Model (CAM). In order to accurately evaluate the dispersion effect on AIF, the new complete cloud parameterizations of Re and Au explicitly accounting for ϵ are implemented into the CAM version 5.1 (CAM5.1), and a suite of sensitivity experiments is conducted with different representations of ϵ reported in the literature. It is shown that the shortwave cloud radiative forcing is much better simulated with the new cloud parameterizations as compared to the standard scheme in CAM5.1, whereas the influences on longwave cloud radiative forcing and surface precipitation are minimal. Additionally, consideration of the dispersion effect can significantly reduce the changes induced by anthropogenic aerosols in the cloud-top effective radius and the liquid water path, especially in the Northern Hemisphere. The corresponding AIF with the dispersion effect considered can also be reduced substantially by a range of 0.10 to 0.21 W m-2 at the global scale and by a much bigger margin of 0.25 to 0.39 W m-2 for the Northern Hemisphere in comparison with that of fixed relative dispersion, mainly dependent on the change of relative dispersion and droplet concentrations (Δϵ/ΔNc). © Author(s) 2017."
"35345729700;16444949400;57208121047;16425152300;6603818654;6603848988;55718857500;27467537200;7003777747;6602414959;55702982900;11940188700;57202142004;6505805689;8388968100;10139397300;55545335600;7003489918;42662973900;6603478665;23485829700;6602600408;23968109800;57205638870;24390528000;57203180094;56151334000;23161713000;36021733300;","Multi-model evaluation of short-lived pollutant distributions over east Asia during summer 2008",2016,"10.5194/acp-16-10765-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84984920622&doi=10.5194%2facp-16-10765-2016&partnerID=40&md5=0c4411a2aa9ec719d38bb94c196f1e0c","The ability of seven state-of-the-art chemistry-aerosol models to reproduce distributions of tropospheric ozone and its precursors, as well as aerosols over eastern Asia in summer 2008, is evaluated. The study focuses on the performance of models used to assess impacts of pollutants on climate and air quality as part of the EU ECLIPSE project. Models, run using the same ECLIPSE emissions, are compared over different spatial scales to in situ surface, vertical profiles and satellite data. Several rather clear biases are found between model results and observations, including overestimation of ozone at rural locations downwind of the main emission regions in China, as well as downwind over the Pacific. Several models produce too much ozone over polluted regions, which is then transported downwind. Analysis points to different factors related to the ability of models to simulate VOC-limited regimes over polluted regions and NO<i>x</i> limited regimes downwind. This may also be linked to biases compared to satellite NO2, indicating overestimation of NO2 over and to the north of the northern China Plain emission region. On the other hand, model NO2 is too low to the south and west of this region and over South Korea/Japan. Overestimation of ozone is linked to systematic underestimation of CO particularly at rural sites and downwind of the main Chinese emission regions. This is likely to be due to enhanced destruction of CO by OH. Overestimation of Asian ozone and its transport downwind implies that radiative forcing from this source may be overestimated. Model-observation discrepancies over Beijing do not appear to be due to emission controls linked to the Olympic Games in summer 2008.<br><br>With regard to aerosols, most models reproduce the satellite-derived AOD patterns over eastern China. Our study nevertheless reveals an overestimation of ECLIPSE model mean surface BC and sulphate aerosols in urban China in summer 2008. The effect of the short-term emission mitigation in Beijing is too weak to explain the differences between the models. Our results rather point to an overestimation of SO2 emissions, in particular, close to the surface in Chinese urban areas. However, we also identify a clear underestimation of aerosol concentrations over northern India, suggesting that the rapid recent growth of emissions in India, as well as their spatial extension, is underestimated in emission inventories. Model deficiencies in the representation of pollution accumulation due to the Indian monsoon may also be playing a role. Comparison with vertical aerosol lidar measurements highlights a general underestimation of scattering aerosols in the boundary layer associated with overestimation in the free troposphere pointing to modelled aerosol lifetimes that are too long. This is likely linked to too strong vertical transport and/or insufficient deposition efficiency during transport or export from the boundary layer, rather than chemical processing (in the case of sulphate aerosols). Underestimation of sulphate in the boundary layer implies potentially large errors in simulated aerosol-cloud interactions, via impacts on boundary-layer clouds.<br><br>This evaluation has important implications for accurate assessment of air pollutants on regional air quality and global climate based on global model calculations. Ideally, models should be run at higher resolution over source regions to better simulate urban-rural pollutant gradients and/or chemical regimes, and also to better resolve pollutant processing and loss by wet deposition as well as vertical transport. Discrepancies in vertical distributions require further quantification and improvement since these are a key factor in the determination of radiative forcing from short-lived pollutants."
"55995261600;35849722200;41362078500;14326501100;56649594800;55567649200;56939103900;","A closure study of aerosol optical properties at a regional background mountainous site in Eastern China",2016,"10.1016/j.scitotenv.2016.01.205","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956628194&doi=10.1016%2fj.scitotenv.2016.01.205&partnerID=40&md5=d26efbf726eecaa4e5930adb8245d7b8","There is a large uncertainty in evaluating the radiative forcing from aerosol-radiation and aerosol-cloud interactions due to the limited knowledge on aerosol properties. In-situ measurements of aerosol physical and chemical properties were carried out in 2012 at Mt. Huang (the Yellow Mountain), a continental background mountainous site in eastern China. An aerosol optical closure study was performed to verify the model outputs by using the measured aerosol optical properties, in which a spherical Mie model with assumptions of external and core-shell mixtures on the basis of a two-component optical aerosol model and high size-segregated element carbon (EC) ratio was applied. Although the spherical Mie model would underestimate the real scattering with increasing particle diameters, excellent agreement between the calculated and measured values was achieved with correlation coefficients above 0.98. Sensitivity experiments showed that the EC ratio had a negligible effect on the calculated scattering coefficient, but largely influenced the calculated absorption coefficient. The high size-segregated EC ratio averaged over the study period in the closure was enough to reconstruct the aerosol absorption coefficient in the Mie model, indicating EC size resolution was more important than time resolution in retrieving the absorption coefficient in the model. The uncertainties of calculated scattering and absorption coefficients due to the uncertainties of measurements and model assumptions yielded by a Monte Carlo simulation were ±. 6% and ±. 14% for external mixture and ±. 9% and ±. 31% for core-shell mixture, respectively. This study provided an insight into the inherent relationship between aerosol optical properties and physicochemical characteristics in eastern China, which could supplement the database of aerosol optical properties for background sites in eastern China and provide a method for regions with similar climate. © 2016 Elsevier B.V."
"36106335800;7501627905;","Metamodeling of droplet activation for global climate models",2016,"10.1175/JAS-D-15-0223.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84962217145&doi=10.1175%2fJAS-D-15-0223.1&partnerID=40&md5=bad283e8b3b920ad9034502ce354e8ac","The nucleation of cloud droplets from the ambient aerosol is a critical physical process that must be resolved for global models to faithfully predict aerosol-cloud interactions and aerosol indirect effects on climate. To better represent droplet nucleation from a complex, multimodal, and multicomponent aerosol population within the context of a global model, a new metamodeling framework is applied to derive an efficient and accurate activation parameterization. The framework applies polynomial chaos expansion to a detailed parcel model in order to derive an emulator that maps thermodynamic and aerosol parameters to the supersaturation maximum achieved in an adiabatically ascending parcel and can be used to diagnose droplet number from a single lognormal aerosol mode. The emulator requires much less computational time to build, store, and evaluate than a high-dimensional lookup table. Compared to large sample sets from the detailed parcel model, the relative error in the predicted supersaturation maximum and activated droplet number computed with the best emulator is -:6%±9:9% and 0:8%±17:8% and (one standard deviation), respectively. On average, the emulators constructed here are as accurate and between 10 and 17 times faster than a leading physically based activation parameterization. Because the underlying parcel model being emulated resolves size-dependent droplet growth factors, the emulator captures kinetic limitations on activation. The results discussed in this work suggest that this metamodeling framework can be extended to accurately account for the detailed activation of a complex aerosol population in an arbitrary coupled global aerosol-climate model. © 2016 American Meteorological Society."
"55732558900;7202252296;22953153500;","Potential sea salt aerosol sources from frost flowers in the pan-Arctic region",2016,"10.1002/2015JD024713","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84988876275&doi=10.1002%2f2015JD024713&partnerID=40&md5=5ca93ec7aafcb4eafba50a2a66d36546","In order to better represent observed wintertime aerosol mass and number concentrations in the pan-Arctic (60°N–90°N) region, we implemented an observationally based parameterization for estimating sea salt production from frost flowers in the Community Earth System Model (CESM, version 1.2.1). In this work, we evaluate the potential influence of this sea salt source on the pan-Arctic climate. Results show that frost flower salt emissions increase the modeled surface sea salt aerosol mass concentration by roughly 200% at Barrow and 100% at Alert and accumulation-mode number concentration by about a factor of 2 at Barrow and more than a factor of 10 at Alert in the winter months when new sea ice and frost flowers are present. The magnitude of sea salt aerosol mass and number concentrations at the surface in Barrow during winter simulated by the model configuration that includes this parameterization agrees better with observations by 48% and 12%, respectively, than the standard CESM simulation without a frost flower salt particle source. At Alert, the simulation with this parameterization overestimates observed sea salt aerosol mass concentration by 150% during winter in contrast to the underestimation of 63% in the simulation without this frost flower source, while it produces particle number concentration about 14% closer to observation than the standard CESM simulation. However, because the CESM version used here underestimates transported sulfate in winter, the reference accumulation-mode number concentrations at Alert are also underestimated. Adding these frost flower salt particle emissions increases sea salt aerosol optical depth by 10% in the pan-Arctic region and results in a small cooling at the surface. The increase in salt aerosol mass concentrations of a factor of 8 provides nearly two times the cloud condensation nuclei concentration at supersaturation of 0.1%, as well as 10% increases in cloud droplet number and 40% increases in liquid water content near coastal regions adjacent to continents. These cloud changes reduce longwave cloud forcing at the top of the atmosphere by 3% and cause a small surface warming, increasing the downward longwave flux at the surface by 1.8 W m-2 in the pan-Arctic under the present-day climate. This regional average longwave warming due to the presence of clouds attributed to frost flower sea salts is roughly half of previous observed surface longwave fluxes and cloud-forcing estimates reported in Alaska, implying that the longwave enhancement due to frost flower salts may be comparable to those estimated for anthropogenic aerosol emissions. Since the potential frost flower area is parameterized as the maximum possible region on which frost flowers grow for the modeled atmospheric temperature and sea ice conditions and the model underestimates the number of accumulation-mode particles from midlatitude anthropogenic sources transported in winter, the calculated aerosol indirect effect of frost flower sea salts in this work can be regarded an upper bound. © 2016. American Geophysical Union. All Rights Reserved."
"25031430500;56699083600;8866821900;57212416832;","Climate feedback variance and the interaction of aerosol forcing and feedbacks",2016,"10.1175/JCLI-D-16-0151.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84987958800&doi=10.1175%2fJCLI-D-16-0151.1&partnerID=40&md5=57781a3a466a4184c577c4fe45f0e4ba","Aerosols can influence cloud radiative effects and, thus, may alter interpretation of how Earth's radiative budget responds to climate forcing. Three different ensemble experiments from the same climate model with different greenhouse gas and aerosol scenarios are used to analyze the role of aerosols in climate feedbacks and their spread across initial condition ensembles of transient climate simulations. The standard deviation of global feedback parameters across ensemble members is low, typically 0.02 W m-2 K-1. Feedbacks from high (8.5 W m-2) and moderate (4.5 W m-2) year 2100 forcing cases are nearly identical. An aerosol kernel is introduced to remove effects of aerosol cloud interactions that alias into cloud feedbacks. Adjusted cloud feedbacks indicate an ""aerosol feedback"" resulting from changes to climate that increase sea-salt emissions, mostly in the Southern Ocean. Ensemble simulations also indicate higher tropical cloud feedbacks with higher aerosol loading. These effects contribute to a difference in cloud feedbacks of nearly 50% between ensembles of the same model. These two effects are also seen in aquaplanet simulations with varying fixed drop number. Thus aerosols can be a significant modifier of cloud feedbacks, and different representations of aerosols and their interactions with clouds may contribute to multimodel spread in climate feedbacks and climate sensitivity in multimodel archives. © 2016 American Meteorological Society."
"6602600408;","Approaches to Observe Anthropogenic Aerosol-Cloud Interactions",2015,"10.1007/s40641-015-0028-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85025628600&doi=10.1007%2fs40641-015-0028-0&partnerID=40&md5=79261fa69eb8e357362d692784521f8c","Anthropogenic aerosol particles exert an—quantitatively very uncertain—effective radiative forcing due to aerosol-cloud interactions via an immediate altering of cloud albedo on the one hand and via rapid adjustments by alteration of cloud processes and by changes in thermodynamic profiles on the other hand. Large variability in cloud cover and properties and the therefore low signal-to-noise ratio for aerosol-induced perturbations hamper the identification of effects in observations. Six approaches are discussed as a means to isolate the impact of anthropogenic aerosol on clouds from natural cloud variability to estimate or constrain the effective forcing. These are (i) intentional cloud modification, (ii) ship tracks, (iii) differences between the hemispheres, (iv) trace gases, (v) weekly cycles and (vi) trends. Ship track analysis is recommendable for detailed process understanding, and the analysis of weekly cycles and long-term trends is most promising to derive estimates or constraints on the effective radiative forcing. © 2015, The Author(s)."
"55800936800;7801565183;7202607188;57203053317;6603409139;7006434689;7005069415;17434636400;","Sensitivity estimations for cloud droplet formation in the vicinity of the high-alpine research station Jungfraujoch (3580 m a.s.l.)",2015,"10.5194/acp-15-10309-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941923101&doi=10.5194%2facp-15-10309-2015&partnerID=40&md5=f0b90eada43a2752c08bba5464a7c801","Aerosol radiative forcing estimates suffer from large uncertainties as a result of insufficient understanding of aerosol-cloud interactions. The main source of these uncertainties is dynamical processes such as turbulence and entrainment but also key aerosol parameters such as aerosol number concentration and size distribution, and to a much lesser extent, the composition. From June to August 2011 a Cloud and Aerosol Characterization Experiment (CLACE2011) was performed at the high-alpine research station Jungfraujoch (Switzerland, 3580 m a.s.l.) focusing on the activation of aerosol to form liquid-phase clouds (in the cloud base temperature range of -8 to 5 °C). With a box model the sensitivity of the effective peak supersaturation (SS<inf>peak</inf>), an important parameter for cloud activation, to key aerosol and dynamical parameters was investigated. The updraft velocity, which defines the cooling rate of an air parcel, was found to have the greatest influence on SS<inf>peak</inf>. Small-scale variations in the cooling rate with large amplitudes can significantly alter CCN activation. Thus, an accurate knowledge of the air parcel history is required to estimate SS<inf>peak</inf>. The results show that the cloud base updraft velocities estimated from the horizontal wind measurements made at the Jungfraujoch can be divided by a factor of approximately 4 to get the updraft velocity required for the model to reproduce the observed SS<inf>peak</inf>. The aerosol number concentration and hygroscopic properties were found to be less important than the aerosol size in determining SSpeak. Furthermore turbulence is found to have a maximum influence when SS<inf>peak</inf> is between approximately 0.2 and 0.4 %. Simulating the small-scale fluctuations with several amplitudes, frequencies and phases, revealed that independently of the amplitude, the effect of the frequency on SS<inf>peak</inf> shows a maximum at 0.46 Hz (median over all phases) and at higher frequencies, the maximum SS<inf>peak</inf> decreases again. © Author(s) 2015."
"55683891800;56229494700;36026436300;55683727600;12753162000;13403849600;8942525300;9235235300;13405658600;","Aerosol size distribution and radiative forcing response to anthropogenically driven historical changes in biogenic secondary organic aerosol formation",2015,"10.5194/acp-15-2247-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923865363&doi=10.5194%2facp-15-2247-2015&partnerID=40&md5=c7ccf804ae0eb16a57bda76e2c77b567","Emissions of biogenic volatile organic compounds (BVOCs) have changed in the past millennium due to changes in land use, temperature, and CO2 concentrations. Recent reconstructions of BVOC emissions have predicted that global isoprene emissions have decreased, while monoterpene and sesquiterpene emissions have increased; however, all three show regional variability due to competition between the various influencing factors. In this work, we use two modeled estimates of BVOC emissions from the years 1000 to 2000 to test the effect of anthropogenic changes to BVOC emissions on secondary organic aerosol (SOA) formation, global aerosol size distributions, and radiative effects using the GEOS-Chem-TOMAS (Goddard Earth Observing System; TwO-Moment Aerosol Sectional) global aerosol microphysics model. With anthropogenic emissions (e.g., SO2, NOx, primary aerosols) turned off and BVOC emissions changed from year 1000 to year 2000 values, decreases in the number concentration of particles of size Dp &gt; 80 nm (N80) of &gt; 25% in year 2000 relative to year 1000 were predicted in regions with extensive land-use changes since year 1000 which led to regional increases in the combined aerosol radiative effect (direct and indirect) of &gt; 0.5 W m-2 in these regions. We test the sensitivity of our results to BVOC emissions inventory, SOA yields, and the presence of anthropogenic emissions; however, the qualitative response of the model to historic BVOC changes remains the same in all cases. Accounting for these uncertainties, we estimate millennial changes in BVOC emissions cause a global mean direct effect of between +0.022 and +0.163 W m-2 and the global mean cloud-albedo aerosol indirect effect of between -0.008 and -0.056 W m-2. This change in aerosols, and the associated radiative forcing, could be a largely overlooked and important anthropogenic aerosol effect on regional climates. © Author(s) 2015."
"37051480000;35392584500;6701511324;","Explicit representation of subgrid variability in cloud microphysics yields weaker aerosol indirect effect in the ECHAM5-HAM2 climate model",2015,"10.5194/acp-15-703-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921348913&doi=10.5194%2facp-15-703-2015&partnerID=40&md5=33ba3e089306e150c92d06dfea71611d","The impacts of representing cloud microphysical processes in a stochastic subcolumn framework are investigated, with emphasis on estimating the aerosol indirect effect. It is shown that subgrid treatment of cloud activation and autoconversion of cloud water to rain reduce the impact of anthropogenic aerosols on cloud properties and thus reduce the global mean aerosol indirect effect by 19%, from g-1.59 to g-1.28 W mg-2. This difference is partly related to differences in the model basic state; in particular, the liquid water path (LWP) is smaller and the shortwave cloud radiative forcing weaker when autoconversion is computed separately for each subcolumn. However, when the model is retuned so that the differences in the basic state LWP and radiation balance are largely eliminated, the global-mean aerosol indirect effect is still 14% smaller (i.e. g-1.37 W mg-2) than for the model version without subgrid treatment of cloud activation and autoconversion. The results show the importance of considering subgrid variability in the treatment of autoconversion. Representation of several processes in a self-consistent subgrid framework is emphasized. This paper provides evidence that omitting subgrid variability in cloud microphysics contributes to the apparently chronic overestimation of the aerosol indirect effect by climate models, as compared to satellite-based estimates. © 2015 Author(s)."
"55232897900;24722339600;23094149200;","Satellite estimates of precipitation susceptibility in low-level marine stratiform clouds",2015,"10.1002/2015JD023319","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943370195&doi=10.1002%2f2015JD023319&partnerID=40&md5=0860524d068361d7d6bb1910c4dd3f47","Quantifying the sensitivity of warm rain to aerosols is important for constraining climate model estimates of aerosol indirect effects. In this study, the precipitation sensitivity to cloud droplet number concentration (Nd) in satellite retrievals is quantified by applying the precipitation susceptibility metric to a combined CloudSat/Moderate Resolution Imaging Spectroradiometer data set of stratus and stratocumulus clouds that cover the tropical and subtropical Pacific Ocean and Gulf of Mexico. Consistent with previous observational studies of marine stratocumulus, precipitation susceptibility decreases with increasing liquid water path (LWP), and the susceptibility of the mean precipitation rate R is nearly equal to the sum of the susceptibilities of precipitation intensity and of probability of precipitation. Consistent with previous modeling studies, the satellite retrievals reveal that precipitation susceptibility varies not only with LWP but also with Nd. Puzzlingly, negative values of precipitation susceptibility are found at low LWP and high Nd. There is marked regional variation in precipitation susceptibility values that cannot simply be explained by regional variations in LWP and Nd. This suggests other controls on precipitation apart from LWP and Nd and that precipitation susceptibility will need to be quantified and understood at the regional scale when relating to its role in controlling possible aerosol-induced cloud lifetime effects. © 2015. American Geophysical Union. All Rights Reserved."
"55793449600;21935606200;7103243257;57217352376;7403906746;","Quantifying the importance of galactic cosmic rays in cloud microphysical processes",2013,"10.1016/j.jastp.2013.05.017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880142703&doi=10.1016%2fj.jastp.2013.05.017&partnerID=40&md5=fd5f987e675d14c9e0c64082fadfdf8e","Galactic Cosmic Rays are one of the major sources of ion production in the troposphere and stratosphere. Recent studies have shown that ions form electrically charged clusters which may grow to become cloud droplets. Aerosol particles charge by the attachment of ions and electrons. The collision efficiency between a particle and a water droplet increases, if the particle is electrically charged, and thus aerosol-cloud interactions can be enhanced. Because these microphysical processes may change radiative properties of cloud and impact Earth's climate it is important to evaluate these processes' quantitative effects. Five different models developed independently have been coupled to investigate this. The first model estimates cloud height from dew point temperature and the temperature profile. The second model simulates the cloud droplet growth from aerosol particles using the cloud parcel concept. In the third model, the scavenging rate of the aerosol particles is calculated using the collision efficiency between charged particles and droplets. The fourth model calculates electric field and charge distribution on water droplets and aerosols within cloud. The fifth model simulates the global electric circuit (GEC), which computes the conductivity and ionic concentration in the atmosphere in altitude range 0-45. km. The first four models are initially coupled to calculate the height of cloud, boundary condition of cloud, followed by growth of droplets, charge distribution calculation on aerosols and cloud droplets and finally scavenging. These models are incorporated with the GEC model. The simulations are verified with experimental data of charged aerosol for various altitudes. Our calculations showed an effect of aerosol charging on the CCN concentration within the cloud, due to charging of aerosols increase the scavenging of particles in the size range 0.1μm to 1μm. © 2013 Elsevier Ltd."
"55703106400;55522563200;55740664200;7004057920;23028717700;","Enhanced aerosol-cloud relationships in more stable and adiabatic clouds",2012,"10.1007/s13143-012-0028-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871063471&doi=10.1007%2fs13143-012-0028-0&partnerID=40&md5=89cf2b50c8870b57c14731888c451fc1","Modification of cloud microphysics and cloud albedo by cloud-active aerosol is generally identified and accepted, but the nature and magnitude of aerosol-cloud interactions are vaguely understood and thought to include a myriad of processes that vary regionally and confound the application of simple physical models of cloud-aerosol sensitivity. This paper presents observations demonstrating that cloud top stability through its regulation of mixing and vertical development is one of the critical mechanisms that regulate cloud response to cloud-active aerosol in some cloud systems. Strong above-cloud inversions are shown to buffer marine stratocumulus from the effects of mixing with drier, warmer inversion air. This buffering reduces the variability of the cloud liquid water path (LWP) and enables the clouds to remain nearly adiabatic. While weaker above-cloud inversions in continental stratocumulus promote variability in the LWP and sub-adiabatic LWPs, stronger inversions in marine stratocumulus enables a relatively adiabatic existence that increases the relationship of cloud microphysical alteration to cloudactive aerosol. This study has important implications for Geoengineering in that it demonstrates that cloud systems overlain by strong thermal inversions are more likely to respond predictably to intentional manipulation of the in-cloud concentration of cloud-active aerosol. © The Korean Meteorological Society and Springer 2012."
"55470017900;35463545000;35551376300;7404291795;54796931400;35302065900;","Likely seeding of cirrus clouds by stratospheric Kasatochi volcanic aerosol particles near a mid-latitude tropopause fold",2012,"10.1016/j.atmosenv.2011.09.027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-82955247824&doi=10.1016%2fj.atmosenv.2011.09.027&partnerID=40&md5=41ef2fcda5a306826b8ea3b9f3b46b9c","Following the explosive 7-8 August 2008 Mt. Kasatochi volcanic eruption in southwestern Alaska, a segment of the dispersing stratospheric aerosol layer was profiled beginning 16 August in continuous ground-based lidar measurements over the Mid-Atlantic coast of the eastern United States. On 17-18 August, the layer was displaced downward into the upper troposphere through turbulent mixing near a tropopause fold. Cirrus clouds and ice crystal fallstreaks were subsequently observed, having formed within the entrained layer. The likely seeding of these clouds by Kasatochi aerosol particles is discussed. Cloud formation is hypothesized as resulting from either preferential homogenous freezing of relatively large sulfate-based solution droplets deliquesced after mixing into the moist upper troposphere or through heterogeneous droplet activation by volcanic ash. Satellite-borne spectrometer measurements illustrate the evolution of elevated Kasatochi SO2 mass concentrations regionally and the spatial extent of the cirrus cloud band induced by likely particle seeding. Satellite-borne polarization lidar observations confirm ice crystal presence within the clouds. Geostationary satellite-based water vapor channel imagery depicts strong regional subsidence, symptomatic of tropopause folding, along a deepening trough in the sub-tropical westerlies. Regional radiosonde profiling confirms both the position of the fold and depth of upper-tropospheric subsidence. These data represent the first unambiguous observations of likely cloud seeding by stratospheric volcanic aerosol particles after mixing back into the upper troposphere. © 2011."
"22933265100;6507984183;6701378450;","Global distribution of cloud droplet number concentration, autoconversion rate, and aerosol indirect effect under diabatic droplet activation",2011,"10.1029/2010JD015274","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051850330&doi=10.1029%2f2010JD015274&partnerID=40&md5=eab509d90773ce6e8e9fe69bc6b9b7f8","This study presents a global assessment of the sensitivity of droplet number to diabatic activation (i.e., including effects from entrainment of dry air) and its first-order tendency on indirect forcing and autoconversion. Simulations were carried out with the NASA Global Modeling Initiative (GMI) atmospheric and transport model using climatological metereorological fields derived from the former NASA Data Assimilation Office (DAO), the NASA Finite volume GCM (FVGCM) and the Goddard Institute for Space Studies version II’ (GISS) GCM. Cloud droplet number concentration (CDNC) is calculated using a physically based prognostic parameterization that explicitly includes entrainment effects on droplet formation. Diabatic activation results in lower CDNC, compared to adiabatic treatment of the process. The largest decrease in CDNC (by up to 75%) was found in the tropics and in zones of moderate CCN concentration. This leads to a global mean effective radius increase between 0.2-0.5 µm (up to 3.5 µm over the tropics), a global mean autoconversion rate increase by a factor of 1.1 to 1.7 (up to a factor of 4 in the tropics), and a 0.2-0.4 W m-2 decrease in indirect forcing. The spatial patterns of entrainment effects on droplet activation tend to reduce biases in effective radius (particularly in the tropics) when compared to satellite retrievals. Considering the diabatic nature of ambient clouds, entrainment effects on CDNC need to be considered in GCM studies of the aerosol indirect effect. © 2011 by the American Geophysical Union."
"42263280300;55796506900;7402721790;7203001286;56068376200;","Modeling study of aerosol indirect effects on global climate with an AGCM",2010,"10.1007/s00376-010-9120-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955821707&doi=10.1007%2fs00376-010-9120-5&partnerID=40&md5=97397a7a1a334bf3aea022c899437e25","Aerosol indirect effects (AIEs) on global climate were quantitatively investigated by introducing aerosol-cloud interaction parameterizations for water stratus clouds into an AGCM (BCC_AGCM2. 0.1), which was developed by the National Climate Center of the China Meteorological Administration. The study yielded a global annual mean of -1.14 W m-2 for the first indirect radiative forcing (IRF), with an obvious seasonal change. In summer, large forcing mainly occurred in mid to high latitudes of the Northern Hemisphere, whereas in winter, large values were found at 60°S. The second indirect effect led to global annual mean changes in net shortwave flux of -1.03 W m-2 at the top of the atmosphere (TOA), which was relatively significant in mid-latitude regions of both hemispheres. The total AIE reduced the global annual means of net shortwave flux at the TOA and of surface temperature by 1.93 W m-2 and 0. 12 K, respectively. Change in surface temperature induced by the total AIE was clearly larger in the Northern Hemisphere (-0. 23 K) than in the Southern Hemisphere, where changes were negligible. The interhemispheric asymmetry in surface cooling resulted in significant differences in changes of the interhemispheric annual mean precipitation rate, which could lead to a tendency for the ITCZ to broaden. The total AIE decreased the global annual mean precipitation rate by 0.055 mm d-1. © 2010 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"6603315547;6701762451;","Aerosol-cloud interactions - A challenge for measurements and modeling at the cutting edge of cloud-climate interactions",2008,"10.1088/1748-9326/3/2/025002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-46749140614&doi=10.1088%2f1748-9326%2f3%2f2%2f025002&partnerID=40&md5=7ab65433a6dcaebc3b7378e9515f740a",[No abstract available]
"57208698992;7102604282;57210717445;6701596624;","Examination of the aerosol indirect effect under contrasting environments during the ACE-2 experiment",2007,"10.5194/acp-7-535-2007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846613208&doi=10.5194%2facp-7-535-2007&partnerID=40&md5=60b3c1749a3bf5184cb094573aacad5a","The Active Tracer High-resolution Atmospheric Model (ATHAM) has been adopted to examine the aerosol indirect effect in contrasting clean and polluted cloudy boundary layers during the Second Aerosol Characterization Experiment (ACE-2). Model results are in good agreement with available in-situ observations, which provides confidence in the results of ATHAM. Sensitivity tests have been conducted to examine the response of the cloud fraction (CF), cloud liquid water path (LWP), and cloud optical depth (COD) to changes in aerosols in the clean and polluted cases. It is shown for two cases that CF and LWP would decrease or remain nearly constant with an increase in aerosols, a result which shows that the second aerosol indirect effect is positive or negligibly small in these cases. Further investigation indicates that the background meteorological conditions play a critical role in the response of CF and LWP to aerosols. When large-scale subsidence is weak as in the clean case, the dry overlying air above the cloud is more efficiently entrained into the cloud, and in so doing, removes cloud water more efficiently, and results in lower CF and LWP when aerosol burden increases. However, when the large-scale subsidence is strong as in the polluted case, the growth of the cloud top is suppressed and the entrainment drying makes no significant difference when aerosol burden increases. Therefore, the CF and LWP remain nearly constant. In both the clean and polluted cases, the COD tends to increase with aerosols, and the total aerosol indirect effect (AIE) is negative even when the CF and LWP decrease with an increase in aerosols. Therefore, the first AIE dominates the response of the cloud to aerosols."
"56355030000;55386235300;","Why is the satellite observed aerosol's indirect effect so variable?",2005,"10.1029/2005GL023260","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25844477949&doi=10.1029%2f2005GL023260&partnerID=40&md5=d1a329969a12b401bfd04ac7efe9ccfa","Although evidence has shown that enhanced aerosol concentration reduces cloud drop size and increases cloud albedo, this phenomenon is not always observed by satellite. Satellite derived correlation between cloud drop size and aerosol concentration can be either negative, insignificant or even positive, depending on the location of the clouds. In this study, we propose an analytical model describing the coupled effects of aerosol concentration and cloud depth on cloud drop size and explain one major cause of the puzzling correlation. Marine stratocumulus observed over northeastern Pacific during summer is analyzed to support the proposed explanation. The result also reassures the aerosol indirect radiative effect being still at work even for the regions where it appears no negative correlation between aerosol concentration and cloud drop size observed by satellite. Copyright 2005 by the American Geophysical Union."
"6701596624;55896920900;6603892183;7005550877;6701323933;6603100667;7404369915;35551238800;6602107874;7006211890;57197784699;7102661133;6701599239;7006577245;56706602500;","Microphysical and radiative properties of stratocumulus clouds: The EUCREX mission 206 case study",2000,"10.1016/S0169-8095(00)00058-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-6744248663&doi=10.1016%2fS0169-8095%2800%2900058-2&partnerID=40&md5=5d3b24bbdc3707fae1695c699e54f5ac","In this conclusion paper, remote sensing retrievals of cloud optical thickness performed during the EUCREX mission 206 are analyzed. The comparison with estimates derived from in situ measurements demonstrates that the adiabatic model of cloud microphysics is more realistic than the vertically uniform plane parallel model (VUPPM) for parameterization of optical thickness. The analysis of the frequency distributions of optical thickness in the cloud layer then shows that the adiabatic model provides a good prediction when the cloud layer is thick and homogeneous, while it overestimates significantly the optical thickness when the layer is thin and broken. Finally, it is shown that the effective optical thickness over the whole sampled cloud is smaller than the adiabatic prediction based on the mean geometrical thickness of the cloud layer. The high sensitivity of the optical thickness on cloud geometrical thickness suggests that the effect of aerosol and droplet concentration on precipitation efficiency, and therefore on cloud extent and lifetime, is likely to be more significant than the Twomey effect. (C) 2000 Elsevier Science B.V. All rights reserved."
"7202485288;7004540083;7402094372;7201914101;","Near-global survey of cloud column susceptibilities using ISCCP data",2000,"10.1029/2000GL011543","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033625942&doi=10.1029%2f2000GL011543&partnerID=40&md5=80ae5166194fa1a0a503e15a75776112","A new parameter, cloud column susceptibility, is introduced to study the aerosol indirect effect, which describes the aerosol indirect effect more directly without assuming how cloud droplet size will respond to changes of droplet number concentration. Between the two approaches that used to retrieve cloud column susceptibilities, the one that makes no assumption of constant liquid water content leads to smaller, even negative cloud column susceptibilities. This finding is consistent with results of model studies and observations from the 1998-1999 Indian Ocean Experiment (INDOEX) that suggest that cloud liquid water content may be reduced during aerosol-cloud interactions. The results of this survey suggest that using constant liquid water content in models may lead to significant overestimation of the aerosol indirect effect."
"56159672300;56996271000;","Does the modern-era retrospective analysis for research and applications-2 aerosol reanalysis introduce an improvement in the simulation of surface solar radiation over China?",2019,"10.1002/joc.5881","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055520334&doi=10.1002%2fjoc.5881&partnerID=40&md5=7bbdda44eb431673a5e95496222b3a83","Surface incident solar radiation (R s ) is a key parameter of energy and water cycles of the Earth. Reanalyses represent important sources of information on R s . However, reanalyses R s may have important bias due to their imperfect parameterizations and input errors of cloud and aerosol. NASA's Global Modelling and Assimilation Office has recently released Version 2 of the Modern-Era Retrospective Analysis for Research and Applications (MERRA2), which incorporates a reanalysis of atmospheric optical depth for the first time. In this study, we evaluate R s from MERRA2 and its predecessor (MERRA) in China from 1980 to 2014. We first compare three possible reference data sources: (a) observed R s at 122 stations, (b) satellite retrievals of R s and (c) R s values derived from sunshine durations measured at 2,400 weather stations. We find sunshine duration derived R s is a reliable reference and use it to evaluate MERRA and MERRA2. Our results show that both MERRA and MERRA2 have a high mean bias of 38.63 and 43.86 W/m 2 over China due to their underestimation of cloud fraction, which is greater in southern China. MERRA2 displays improved capability in reproducing monthly and annual variability, and national mean trend of R s . MERRA overestimates the trend of R s by 3.23 W/m 2 in eastern China. MERRA2 reduced this trend bias over the North China Plain likely due to its aerosol assimilation. However, MERRA2 show a negative bias in trend of R s (−3.44 W/m 2 ) in the south China likely due to its overestimation of atmospheric aerosols loading and aerosol-cloud interaction. The results provide guidance for future development of reanalysis and its scientific applications for ecological and hydrological models. © 2018 The Authors. International Journal of Climatology published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"7403564495;57205349803;55497853400;","A case study of stratus cloud properties using in situ aircraft observations over Huanghua, China",2019,"10.3390/atmos10010019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059680562&doi=10.3390%2fatmos10010019&partnerID=40&md5=6badee555e7a6411804a36cb9ec8ac59","Cloud liquid water content (LWC) and droplet effective radius (r e ) have an important influence on cloud physical processes and optical characteristics. The microphysical properties of a three-layer pure liquid stratus were measured by aircraft probes on 26 April 2014 over a coastal region in Huanghua, China. Vertical variations in aerosol concentration (Na), cloud condensation nuclei (CCN) at supersaturation (SS) 0.3%, cloud LWC and cloud r e are examined. Large Na in the size range of 0.1-3 μm and CCN have been found within the planetary boundary layer (PBL) below 1150 m. However, Na and CCN decrease quickly with height and reach a level similar to that over marine locations. Corresponding to the vertical distributions of aerosols and CCN, the cloud re is quite small (3.0-6 μm) at heights below 1150 m, large (7-13 μm) at high altitudes. In the PBL cloud layer, cloud r e and aerosol Na show a negative relationship, while they show a clear positive relationship in the upper layer above PBL with much less aerosol Na. It also shows that the relationship between cloud r e and aerosol Na changes from negative to positive when LWC increases. These results imply that the response of cloud r e to aerosol Na depends on the combination effects of water-competency and collision-coalescence efficiency among droplets. The vertical structure of aerosol Na and cloud r e implies potential cautions for the study of aerosol-cloud interaction using aerosol optical depth for cloud layers above the PBL altitude. © 2019 by the authors."
"36106370400;57203815874;57212216605;7102680152;57212220256;55923546200;55440534900;57201305884;26424128800;23967608200;55293421800;57212217948;55903815100;24385643100;35794658100;56571063800;7402548443;56442378900;6602892883;57212218365;7801565183;7006415284;6603825422;57212219835;7003968166;7102084129;57189748029;7004469744;","Overview of the antarctic circumnavigation expedition: Study of preindustrial-like aerosols and their climate effects (ACE-SPACE)",2019,"10.1175/BAMS-D-18-0187.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074602846&doi=10.1175%2fBAMS-D-18-0187.1&partnerID=40&md5=f8f7086b3f2acd60b28507ccc18991ec","The first results from ACE-SPACE highlight that the Southern Ocean is a region with highly heterogeneous aerosol properties. The areas around the strong westerly wind belt are characterized by significant sea spray contributions to the total particle and CCN number concentrations in the MBL. Future work will link detailed wave and wind observations to sea spray production. In the Ross and Amundsen Sea polynyas (leg 2), biogenic emissions appear to play an important role for CCN abundance. There are a number of open questions associated with this observation. First, even though this particular region was probed during a phytoplankton bloom period, it was not the only region with microbial activity but showed the clearest link to high CCN concentrations. Hence, either DMS production from dimethylsulfoniopropionate in the water and/or DMS fluxes into the atmosphere were enhanced. Second, the major pathway of how MSA is added to the particle phase remains to be identified. There are two possibilities: It can condense from the gas into the particle phase, or it can be added during cloud processing. The latter process would be consistent with the reduced efficiency of wet removal because of droplet evaporation or snowflake sublimation in the cold and dry airmasses from Antarctica. Our results also indicate that the absence of MSA-related processes in the aerosol model could explain the underestimation of CCN concentration, particularly in high aerosol-MSA regions. Given that the number of CCN influence Nd, this is an important issue to solve, especially close to the coast of Antarctica where clouds could impact the surface snow mass balance by influencing both the surface energy budget and precipitation. Further studies are planned that more closely investigate the linkages between CCN number concentrations and model simulations that take DMS emissions fluxes and particle phase MSA into account. A comparison of satellite-retrieved Nd90 and ship-based measurements of CCN shows a clear underestimation of CCN from remote sensing, even for coupled cloud cases. This is a strong indication of the importance of surface sources as opposed to the free troposphere for particle origin. Further investigation is underway to understand the cause of the discrepancy between the remote sensing and in situ measurements. We did not find direct evidence for new particle formation as an important source of CCN. However, some nucleation events were observed and a nucleation mode was present in the clustered particle size distributions. A dedicated study will investigate the gases involved in these events and the fate of the nucleation mode in the atmosphere. Our ice nucleating particle findings suggest that concentrations are lower than in Northern Hemisphere marine airmasses and that concentrations decreased from summer toward fall with only small differences between open-ocean and coastal Antarctic samples. The ACE-SPACE INP concentrations are also consistent with findings of a recent study in the Southern Ocean (McCluskey et al. 2018a), but much lower than results from several decades ago (Bigg 1973). More detailed studies including information on potential island effects, long-range transport and fluorescent and microbial particles are underway. The ACE-SPACE project is motivated by the idea of constraining uncertainty in anthropogenic radiative forcing from aerosol-cloud interactions through measurement of preindustrial-like aerosol-cloud interactions. We have shown that the in situ data are suitable for constraining the aerosol model for preindustrial-like conditions. After a detailed model-measurement comparison, we will use the aerosol model to further constrain uncertainties of global radiative forcing from aerosol-cloud interactions. © 2019 American Meteorological Society."
"55355176000;8067118800;56502199700;","The key role of warm rain parameterization in determining the aerosol indirect effect in a global climate model",2019,"10.1175/JCLI-D-18-0789.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068079553&doi=10.1175%2fJCLI-D-18-0789.1&partnerID=40&md5=b5cd92c86b593f08dc4b1d5dea5d04d2","Global climate models (GCMs) have been found to share the common too-frequent bias in the warm rain formation process. In this study, five different autoconversion schemes are incorporated into a single GCM, to systematically evaluate the warm rain formation processes in comparison with satellite observations and investigate their effects on the aerosol indirect effect (AIE). It is found that some schemes generate warm rain less efficiently under polluted conditions in the manner closer to satellite observations, while the others generate warm rain too frequently. Large differences in AIE are found among these schemes. It is remarkable that the schemes with more observation-like warm rain formation processes exhibit larger AIEs that far exceed the uncertainty range reported in IPCC AR5, to an extent that can cancel much of the warming trend in the past century, whereas schemes with too-frequent rain formations yield AIEs that are well bounded by the reported range. The power-law dependence of the autoconversion rate on the cloud droplet number concentration β is found to affect substantially the susceptibility of rain formation to aerosols: the more negative β is, the more difficult it is for rain to be triggered in polluted clouds, leading to larger AIE through substantial contributions from the wet scavenging feedback. The appropriate use of a droplet size threshold can mitigate the effect of a less negative β. The role of the warm rain formation process on AIE in this particular model has broad implications for others that share the too-frequent rain-formation bias. © 2019 American Meteorological Society."
"57201942906;55717074000;16173929000;57191226379;57192212652;15755995900;55688930000;55893823700;6603711967;49662076300;7006270084;","Impacts of Aerosol Dry Deposition on Black Carbon Spatial Distributions and Radiative Effects in the Community Atmosphere Model CAM5",2018,"10.1029/2017MS001219","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046535166&doi=10.1029%2f2017MS001219&partnerID=40&md5=0a67f49b0f16345a88306352ac812009","Dry deposition is an important process affecting the lifetime and spatial distributions of atmospheric aerosols. Black carbon (BC) plays an important role in the Earth's climate, but is subject to large bias in remote regions in model simulations. In this study, to improve the BC simulations, the scheme of Petroff and Zhang () (PZ10) is implemented into the Community Atmospheric Model version 5 (CAM5), and model simulations using PZ10 are compared with the one using the default scheme of Zhang et al. () (Z01) and observations. The PZ10 scheme predicts much lower dry deposition velocity (Vd) than Z01 for fine particles in Aitken, primary carbon, and accumulation modes, resulting in 73.0% lower of global mean BC dry deposition fluxes and 23.2% higher of global mean BC column burdens. CAM5 with PZ10 increases modeled BC concentrations at all altitudes and latitudes compared to Z01, which improves the agreement with observations of BC profiles in the lower troposphere in the Arctic. It also improves the simulation of surface BC concentrations in high-latitudes remote regions and its seasonality in the Arctic. The global annual mean radiative effects due to aerosol-radiation interactions (REari) and aerosol-cloud interactions (REaci) of BC from the CAM5 experiment using Z01 are 0.61 ± 0.007 and −0.11 ± 0.02 W m−2, respectively, compared to slightly larger REari (0.75 ± 0.01 W m−2) and REaci (–0.14 ± 0.02 W m−2) from CAM5 using PZ10. The results suggest that Brownian diffusion efficiency is a key factor for the predictions of Vd, which requires better representation in the global climate models. © 2018. The Authors."
"57194285910;6506340624;8633783900;12787547600;6602087140;55357516200;8606857600;","Do differences in future sulfate emission pathways matter for near-term climate? A case study for the Asian monsoon",2018,"10.1007/s00382-017-3726-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019543352&doi=10.1007%2fs00382-017-3726-6&partnerID=40&md5=d7ac8a8e674e25c7fd2aefa122ad2762","Anthropogenic aerosols could dominate over greenhouse gases in driving near-term hydroclimate change, especially in regions with high present-day aerosol loading such as Asia. Uncertainties in near-future aerosol emissions represent a potentially large, yet unexplored, source of ambiguity in climate projections for the coming decades. We investigated the near-term sensitivity of the Asian summer monsoon to aerosols by means of transient modelling experiments using HadGEM2-ES under two existing climate change mitigation scenarios selected to have similar greenhouse gas forcing, but to span a wide range of plausible global sulfur dioxide emissions. Increased sulfate aerosols, predominantly from East Asian sources, lead to large regional dimming through aerosol-radiation and aerosol-cloud interactions. This results in surface cooling and anomalous anticyclonic flow over land, while abating the western Pacific subtropical high. The East Asian monsoon circulation weakens and precipitation stagnates over Indochina, resembling the observed southern-flood-northern-drought pattern over China. Large-scale circulation adjustments drive suppression of the South Asian monsoon and a westward extension of the Maritime Continent convective region. Remote impacts across the Northern Hemisphere are also generated, including a northwestward shift of West African monsoon rainfall induced by the westward displacement of the Indian Ocean Walker cell, and temperature anomalies in northern midlatitudes linked to propagation of Rossby waves from East Asia. These results indicate that aerosol emissions are a key source of uncertainty in near-term projection of regional and global climate; a careful examination of the uncertainties associated with aerosol pathways in future climate assessments must be highly prioritised. © 2017, The Author(s)."
"24450860900;","A numerical investigation of the potential effects of aerosol-induced warming and updraft width and slope on updraft intensity in deep convective clouds",2018,"10.1175/JAS-D-16-0368.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042228675&doi=10.1175%2fJAS-D-16-0368.1&partnerID=40&md5=bb37d818d2a9264fed395b16bda987dc","The effects of aerosol perturbations on deep convective clouds have received considerable attention in the recent literature, especially from a modeling perspective. The published responses in precipitation amount and updraft strength vary in both sign and magnitude and may be the result of different models and parameterizations. Here, a simple numerical framework is employed to determine the potential effects of warming both below the freezing level (warm invigoration) and above the freezing level (mixed-phase invigoration) due to increased aerosol loading. The role of updraft width and slope in the same framework is also examined, highlighting the relative importance of each factor on the resulting updraft strength. The results show that the potential effects of warm invigoration are 2-3 times larger than for mixed-phase invigoration. However, a relatively small response in updraft velocity to warming is found, especially in comparison with the predicted changes in updraft velocity due to small differences in system slope and width, with 87.7% and 96.4% of the subadiabatic and adiabatic realizations, respectively, showing changes in updraft velocity of less than 15% for warmings of no more than 2°C. This result suggests that observations of the aerosol effect will be largely muddled by the natural variability of convective updraft width and slope (which are related to environmental wind shear). © 2018 American Meteorological Society."
"55462884000;56612517400;36538539800;","Improving organic aerosol treatments in CESM/CAM5: Development, application, and evaluation",2017,"10.1002/2016MS000874","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007436816&doi=10.1002%2f2016MS000874&partnerID=40&md5=765ff3d7fb6466ed7d089207ac5711ad","New treatments for organic aerosol (OA) formation have been added to a modified version of the CESM/CAM5 model (CESM-NCSU). These treatments include a volatility basis set treatment for the simulation of primary and secondary organic aerosols (SOAs), a simplified treatment for organic aerosol (OA) formation from glyoxal, and a parameterization representing the impact of new particle formation (NPF) of organic gases and sulfuric acid. With the inclusion of these new treatments, the concentration of oxygenated organic aerosol increases by 0.33 µg m−3 and that of primary organic aerosol (POA) decreases by 0.22 µg m−3 on global average. The decrease in POA leads to a reduction in the OA direct effect, while the increased OOA increases the OA indirect effects. Simulations with the new OA treatments show considerable improvement in simulated SOA, oxygenated organic aerosol (OOA), organic carbon (OC), total carbon (TC), and total organic aerosol (TOA), but degradation in the performance of HOA. In simulations of the current climate period, despite some deviations from observations, CESM-NCSU with the new OA treatments significantly improves the magnitude, spatial pattern, seasonal pattern of OC and TC, as well as, the speciation of TOA between POA and OOA. Sensitivity analysis reveals that the inclusion of the organic NPF treatment impacts the OA indirect effects by enhancing cloud properties. The simulated OA level and its impact on the climate system are most sensitive to choices in the enthalpy of vaporization and wet deposition of SVOCs, indicating that accurate representations of these parameters are critical for accurate OA-climate simulations. © 2017. The Authors."
"55855213300;55826210400;6504793116;8326989900;55705803300;7006960661;","Estimates of the aerosol indirect effect over the Baltic Sea region derived from 12 years of MODIS observations",2017,"10.5194/acp-17-3133-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85014143520&doi=10.5194%2facp-17-3133-2017&partnerID=40&md5=11d9d4c6a691b13cc0bb5e181465cae6","Retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) on-board the Aqua satellite, 12 years (2003-2014) of aerosol and cloud properties were used to statistically quantify aerosol-cloud interaction (ACI) over the Baltic Sea region, including the relatively clean Fennoscandia and the more polluted central-eastern Europe. These areas allowed us to study the effects of different aerosol types and concentrations on macro-and microphysical properties of clouds: cloud effective radius (CER), cloud fraction (CF), cloud optical thickness (COT), cloud liquid water path (LWP) and cloud-top height (CTH). Aerosol properties used are aerosol optical depth (AOD), Ångström exponent (AE) and aerosol index (AI). The study was limited to low-level water clouds in the summer. The vertical distributions of the relationships between cloud properties and aerosols show an effect of aerosols on low-level water clouds. CF, COT, LWP and CTH tend to increase with aerosol loading, indicating changes in the cloud structure, while the effective radius of cloud droplets decreases. The ACI is larger at relatively low cloud-top levels, between 900 and 700hPa. Most of the studied cloud variables were unaffected by the lower-tropospheric stability (LTS), except for the cloud fraction. The spatial distribution of aerosol and cloud parameters and ACI, here defined as the change in CER as a function of aerosol concentration for a fixed LWP, shows positive and statistically significant ACI over the Baltic Sea and Fennoscandia, with the former having the largest values. Small negative ACI values are observed in central-eastern Europe, suggesting that large aerosol concentrations saturate the ACI. © 2017 The Author(s)."
"15050523700;15047538100;26436096300;55667257200;","Role of interactions between cloud microphysics, dynamics and aerosol in the heavy rainfall event of June 2013 over Uttarakhand, India",2017,"10.1002/qj.2983","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85013356503&doi=10.1002%2fqj.2983&partnerID=40&md5=e3012ae528e333560cb3f0a1f7539096","In this study, we propose a hypothesis, supported by numerical model simulations, concerning the role of cloud microphysical processes and aerosols in the invigoration of an extreme rainfall event over Uttarakhand in June 2013. The interactions among dynamics, thermodynamics and microphysical processes and their feedbacks play a vital role in the occurrence of extreme events. To test the proposed hypothesis, Weather Research and Forecasting (WRF) simulations are carried out with three different microphysical schemes (i.e. WDM6, Morrison, and CLR). The role of aerosol indirect effects in the process of invigoration of precipitation is demonstrated with a high-resolution regional model for the extreme event over the foothills of the Himalayas. The extreme event is characterized by the strong north–south tropospheric temperature gradient and strong moisture convergence. Forced uplift beyond the freezing level initiates a precipitation process which involves cloud ice and mixed-phase cloud microphysics and latent heat release; further, it invigorates convection and enhances precipitation. Results pinpoint that the role of microphysical processes are very crucial during such a type of extreme event. Additionally, the result accentuates the importance of aerosols on the deep convective cloud systems which have influence through invigoration and involvement of complex interactions between aerosol, large-scale dynamics and cloud microphysics. © 2016 Royal Meteorological Society"
"56400726900;7004154626;57190215589;6701874937;35253736000;7801642681;57190218552;57190216755;","Investigation of aerosol indirect effects on monsoon clouds using ground-based measurements over a high-altitude site in Western Ghats",2016,"10.5194/acp-16-8423-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84978370291&doi=10.5194%2facp-16-8423-2016&partnerID=40&md5=5a9d7fb9541b6b94a116612f0302c2d4","The effect of aerosols on cloud droplet number concentration and droplet effective radius is investigated from ground-based measurements over a high-altitude site where clouds pass over the surface. First aerosol indirect effect (AIE) estimates were made using (i) relative changes in cloud droplet number concentration (AIEn/and (ii) relative changes in droplet effective radius (AIEs/with relative changes in aerosol for different cloud liquid water contents (LWCs). AIE estimates from two different methods reveal that there is systematic overestimation in AIEn as compared to that of AIEs. Aerosol indirect effects (AIEn and AIEs/and dispersion effect (DE) at different LWC regimes ranging from 0.05 to 0.50 gm-3 were estimated. The analysis demonstrates that there is overestimation of AIEn as compared to AIEs, which is mainly due to DE. Aerosol effects on spectral dispersion in droplet size distribution play an important role in altering Twomey's cooling effect and thereby changes in climate. This study shows that the higher DE in the medium LWC regime offsets the AIE by 30 %."
"57207185960;15724233200;35488819200;15069732800;22953153500;6603315547;26531584300;35461763400;55942083800;24172248700;","Comprehensive mapping and characteristic regimes of aerosol effects on the formation and evolution of pyro-convective clouds",2015,"10.5194/acp-15-10325-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942134846&doi=10.5194%2facp-15-10325-2015&partnerID=40&md5=6bf39757eb6a8f50911d7ad0086e7f38","A recent parcel model study (Reutter et al., 2009) showed three deterministic regimes of initial cloud droplet formation, characterized by different ratios of aerosol concentrations (N<inf>CN</inf>) to updraft velocities. This analysis, however, did not reveal how these regimes evolve during the subsequent cloud development. To address this issue, we employed the Active Tracer High Resolution Atmospheric Model (ATHAM) with full microphysics and extended the model simulation from the cloud base to the entire column of a single pyro-convective mixed-phase cloud. A series of 2-D simulations (over 1000) were performed over a wide range of N<inf>CN</inf> and dynamic conditions. The integrated concentration of hydrometeors over the full spatial and temporal scales was used to evaluate the aerosol and dynamic effects. The results show the following. (1) The three regimes for cloud condensation nuclei (CCN) activation in the parcel model (namely aerosol-limited, updraft-limited, and transitional regimes) still exist within our simulations, but net production of raindrops and frozen particles occurs mostly within the updraft-limited regime. (2) Generally, elevated aerosols enhance the formation of cloud droplets and frozen particles. The response of raindrops and precipitation to aerosols is more complex and can be either positive or negative as a function of aerosol concentrations. The most negative effect was found for values of N<inf>CN</inf> of ∼ 1000 to 3000 cm-3. (3) The nonlinear properties of aerosol-cloud interactions challenge the conclusions drawn from limited case studies in terms of their representativeness, and ensemble studies over a wide range of aerosol concentrations and other influencing factors are strongly recommended for a more robust assessment of the aerosol effects. © Author(s) 2015."
"56502199700;25723426400;7202079615;","The effects of aerosols on water cloud microphysics and macrophysics based on satellite-retrieved data over East Asia and the North Pacific",2014,"10.5194/acp-14-11935-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922116401&doi=10.5194%2facp-14-11935-2014&partnerID=40&md5=a359ec17eccdcf8b3656364a1086281a","This study examines the characteristics of the microphysics and macrophysics of water clouds from East Asia to the North Pacific, using data from active CloudSat radar measurements and passive MODerate-resolution Imaging Spectroradiometer (MODIS) retrievals. Our goals are to clarify differences in microphysics and macrophysics between land and oceanic clouds, seasonal differences unique to the midlatitudes, characteristics of the drizzling process, and cloud vertical structure. In pristine oceanic areas, fractional occurrences of cloud optical thickness (COT) and cloud droplet effective radius (CDR) increase systematically with an increase in drizzle intensity, but these characteristics of the COT and CDR transition are less evident in polluted land areas. In addition, regional and seasonal differences are identified in terms of drizzle intensity as a function of the liquid water path (LWP) and cloud droplet number concentration (Nc). The correlations between drizzle intensity and LWP, and between drizzle intensity and Nc, are both more robust over oceanic areas than over land areas. We also demonstrate regional and seasonal characteristics of the cloud vertical structure. Our results suggest that aerosol-cloud interaction mainly occurs around the cloud base in polluted land areas during the winter season. In addition, a difference between polluted and pristine areas in the efficiency of cloud droplet growth is confirmed. These results suggest that water clouds over the midlatitudes exhibit a different drizzle system to those over the tropics. © Author(s) 2014."
"37032042300;7005287667;7005712238;35461255500;","A long-term satellite study of aerosol effects on convective clouds in Nordic background air",2014,"10.5194/acp-14-2203-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896832628&doi=10.5194%2facp-14-2203-2014&partnerID=40&md5=7f3cf43557be6b0bc726180c92f474f3","Aerosol-cloud interactions constitute a major uncertainty in future climate predictions. This study combines 10 years of ground-based aerosol particle measurements from two Nordic background stations (Vavihill and Hyytiälä) with MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data of convective clouds. The merged data are used to examine how aerosols affect cloud droplet sizes and precipitation from convective clouds over the Nordic countries. From the satellite scenes, vertical profiles of cloud droplet effective radius (re) are created by plotting retrieved cloud top re against cloud top temperature for the clouds in a given satellite scene. The profiles have been divided according to aerosol number concentrations but also meteorological reanalysis parameters from the ECMWF (European Centre for Medium-Range Forecasts). Furthermore, weather radar data from the BALTEX (Baltic Sea Experiment) and precipitation data from several ground-based meteorological measurement stations have been investigated to determine whether aerosols affect precipitation intensity and amount. Small re throughout the entire cloud profiles is associated with high aerosol number concentrations at both stations. However, aerosol number concentrations seem to affect neither the cloud optical thickness nor the vertical extent of the clouds in this study. Cloud profiles with no or little precipitation have smaller droplets than those with more precipitation. Moreover, the amount of precipitation that reaches the ground is affected by meteorological conditions such as the vertical extent of the clouds, the atmospheric instability and the relative humidity in the lower atmosphere rather than the aerosol number concentration. However, lower precipitation rates are associated with higher aerosol number concentrations for clouds with similar vertical extent. The combination of these ground-based and remote-sensing datasets provides a unique long-term study of the effects of aerosols on convective clouds over the Nordic countries."
"56032511300;7202772927;55923143300;","Aerosol effects on instability, circulations, clouds, and precipitation",2014,"10.1155/2014/683950","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893759938&doi=10.1155%2f2014%2f683950&partnerID=40&md5=ea2656af4d732ac9c867b9f1500956d5","It is well known that increasing aerosol and associated changes in aerosol-cloud interactions and precipitation since industrialization have been playing an important role in climate change, but this role has not been well understood. This prevents us from predicting future climate with a good confidence. This review paper presents recent studies on the changes in the aerosol-cloud interactions and precipitation particularly in deep convective clouds. In addition, this review paper discusses how to improve our understanding of these changes by considering feedbacks among aerosol, cloud dynamics, cloud and its embedded circulations, and microphysics. Environmental instability basically determines the dynamic intensity of clouds and thus acts as one of the most important controls on these feedbacks. As a first step to the improvement of the understanding, this paper specifically elaborates on how to link the instability to the feedbacks. © 2014 Seoung-Soo Lee et al."
"36183151300;24722339600;7004479957;55802199600;","Development and impact of hooks of high droplet concentration on remote southeast Pacific stratocumulus",2013,"10.5194/acp-13-6305-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880637937&doi=10.5194%2facp-13-6305-2013&partnerID=40&md5=a4bba7ad389e2e50c2495b8fcda774f5","Over the southeastern Pacific (SEP), droplet concentration (Nd) in the typically unpolluted marine stratocumulus west of 80° W (&gt; 1000 km offshore) is periodically strongly enhanced in zonally elongated ""hook""-shaped features that increase albedo. Here, we examine three hook events using the chemistry version of the Weather Research and Forecasting model (WRF-Chem) with 14 km horizontal resolution, satellite data, and aircraft data from the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx). A particularly strong hook yields insights into the development, decay, and radiative impact of these features. Hook development occurs with Nd increasing to polluted levels over the remote ocean primarily due to entrainment of cloud condensation nuclei (CCN) from the lower free troposphere (FT). The feature advects northwestward until the FT CCN source is depleted, after which Nd decreases over a few days due to precipitation and dilution. The model suggests that the FT CCN source supplying the hook consists of high concentrations of small accumulation-mode aerosols that contribute a relatively small amount of aerosol mass to the MBL, in agreement with near-coast VOCALS measurements of polluted layers in the FT. The aerosol particles in this hook originate mainly from a pulse of offshore flow that transports Santiago-region (33-35° S) emissions to the remote marine FT. To provide pollution CCN that can sustain hooks, the FT transport of pollution plumes to the remote ocean requires strong, deep offshore flow. Such flow is favored by a trough approaching the South American coast and a southeastward shift of the climatological subtropical high-pressure system. The model simulations show precipitation suppression in the hook and a corresponding increase in liquid water path (LWP) compared with a simulation without anthropogenic sources. LWP also increases as the hook evolves over time due to increasing stability and decreasing subsidence. WRF-Chem suggests that dimethyl sulfide (DMS) significantly influences the aerosol number and size distributions in a hook, but that hooks do not form without FT CCN. The Twomey effect contributes ∼ 50-70% of the albedo increase due to the presence of the hook, while secondary aerosol indirect effects and meteorological influences also contribute significantly. The source of hook aerosols is difficult to determine with the available observations alone. The model provides further explanation of the factors influencing hook formation. Two other weaker hooks during VOCALS-REx are not as well simulated but are also associated with FT offshore flow near Santiago. Hooks demonstrate the importance of free-tropospheric transport of aerosols in modulating the droplet concentration in the southeastern Pacific stratocumulus deck, and present a formidable challenge to simulate accurately in large-scale models. © Author(s) 2013."
"6701346974;56590724100;","Cloud-resolving modelling of aerosol indirect effects in idealised radiative-convective equilibrium with interactive and fixed sea surface temperature",2013,"10.5194/acp-13-4133-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882787274&doi=10.5194%2facp-13-4133-2013&partnerID=40&md5=12e03ea47bcc2245c6db13cf2253828f","The study attempts to evaluate the aerosol indirect effects over tropical oceans in regions of deep convection applying a three-dimensional cloud-resolving model run over a doubly-periodic domain. The Tropics are modelled using a radiative-convective equilibrium idealisation when the radiation, turbulence, cloud microphysics and surface fluxes are explicitly represented while the effects of large-scale circulation are ignored. The aerosol effects are modelled by varying the number concentration of cloud condensation nuclei (CCN) at 1% supersaturation, which serves as a proxy for the aerosol amount in the environment, over a wide range, from pristine maritime (50 cm-3) to polluted (1000 cm-3) conditions. No direct effects of aerosol on radiation are included. Two sets of simulations have been run: fixed (noninteractive) sea surface temperature (SST) and interactive SST as predicted by a simple slab-ocean model responding to the surface radiative fluxes and surface enthalpy flux. Both sets of experiments agree on the tendency of increased aerosol concentrations to make the shortwave cloud forcing more negative and reduce the longwave cloud forcing in response to increasing CCN concentration. These, in turn, tend to cool the SST in interactive-SST case. It is interesting that the absolute change of the SST and most other bulk quantities depends only on relative change of CCN concentration; that is, same SST change can be the result of doubling CCN concentration regardless of clean or polluted conditions. It is found that the 10-fold increase of CCN concentration can cool the SST by as much as 1.5 K. This is quite comparable to 2.1-2.3K SST warming obtained in a simulation for clean maritime conditions, but doubled CO2 concentration. Assuming the aerosol concentration has increased from preindustrial time by 30 %, the radiative forcing due to indirect aerosol effects is estimated to be -0.3Wm-2. It is found that the indirect aerosol effect is dominated by the first (Twomey) effect. Qualitative differences between the interactive and fixed SST cases have been found in sensitivity of the hydrological cycle to the increase in CCN concentration; namely, the precipitation rate shows some tendency to increase in fixed SST case, but robust tendency to decrease in interactive SST case. © Author(s) 2013."
"36059595100;7405763496;","Investigation of aerosol indirect effects on simulated flash-flood heavy rainfall over Korea",2012,"10.1007/s00703-012-0216-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868624753&doi=10.1007%2fs00703-012-0216-6&partnerID=40&md5=309318fd81d3a2334dba5f6a462af09e","This study investigates aerosol indirect effects on the development of heavy rainfall near Seoul, South Korea, on 12 July 2006, focusing on precipitation amount. The impact of the aerosol concentration on simulated precipitation is evaluated by varying the initial cloud condensation nuclei (CCN) number concentration in the Weather Research and Forecasting (WRF) Double-Moment 6-class (WDM6) microphysics scheme. The simulations are performed under clean, semi-polluted, and polluted conditions. Detailed analysis of the physical processes that are responsible for surface precipitation, including moisture and cloud microphysical budgets shows enhanced ice-phase processes to be the primary driver of increased surface precipitation under the semi-polluted condition. Under the polluted condition, suppressed auto-conversion and the enhanced evaporation of rain cause surface precipitation to decrease. To investigate the role of environmental conditions on precipitation response under different aerosol number concentrations, a set of sensitivity experiments are conducted with a 5 % decrease in relative humidity at the initial time, relative to the base simulations. Results show ice-phase processes having small sensitivity to CCN number concentration, compared with the base simulations. Surface precipitation responds differently to CCN number concentration under the lower humidity initial condition, being greatest under the clean condition, followed by the semi-polluted and polluted conditions. © 2012 Springer-Verlag Wien."
"37032042300;7005712238;6506180220;7005287667;35461255500;23995325300;","A study of the indirect aerosol effect on subarctic marine liquid low-level clouds using MODIS cloud data and ground-based aerosol measurements",2012,"10.1016/j.atmosres.2011.09.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865152069&doi=10.1016%2fj.atmosres.2011.09.014&partnerID=40&md5=a254ac92cbfbbc2aa9b8631b66e53f10","Cloud microphysics is substantially affected by aerosol loading and the resulting changes in the reflective properties of the clouds can significantly affect the global radiation budget. A study of how marine low-level clouds over Barents Sea and the northern parts of the Norwegian Sea are affected by air mass origin has been performed by combining ground-based aerosol measurements with satellite cloud retrievals. Aerosol number size distributions have been obtained from measurement stations in northern Finland, and a trajectory model has been used to estimate the movement of the air masses. To identify anthropogenic influences on the clouds, the dataset has been divided according to aerosol loading. The clean air masses arrived to the investigation area from the north and the polluted air masses arrived from the south. Satellite derived microphysical and optical cloud parameters from the Moderate Resolution Imaging Spectrometer (MODIS) have then been analyzed for days when the trajectories coincided with marine low-level clouds over the investigated area. The cloud optical thickness (τ), cloud depth (H) and droplet number concentration (N d) were significantly higher for the polluted days compared to the clean conditions, while the opposite was found for the cloud droplet effective radius (r e). The H and N d were derived from the satellite retrievals of τ and r e. Furthermore, calculations of the aerosol cloud interaction relationship (ACI), relating N d to boundary layer aerosol concentrations, resulted in a value of 0.17, which is in line with previous remote sensing studies. The results demonstrate that ground-based aerosol measurements can be combined with satellite cloud observations to study the indirect aerosol effect, and that the microphysics of marine sub-polar clouds can be considerably affected by continental aerosols. © 2011 Elsevier B.V."
"6507755223;6701620591;6506718302;7004047498;6603948265;26643041500;6701511324;7410177774;35459245100;7006712143;","Effect of aerosol size distribution changes on AOD, CCN and cloud droplet concentration: Case studies from Erfurt and Melpitz, Germany",2012,"10.1029/2011JD017091","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859709794&doi=10.1029%2f2011JD017091&partnerID=40&md5=f96f3a70c47bcb98a74f3ef2439be5bc","For the period of 1990 to 2000, atmospheric particulate mass concentrations have decreased in Central Europe. Simultaneously, the amount of shortwave radiation reaching the ground increased during clear sky conditions. The aerosol indirect effect has not been seen as clearly, as the radiation reaching the ground during overcast conditions has not increased as much as might be expected. Here we show that this may be caused by the condensation kinetics of water during cloud droplet formation. The decrease in the particulate mass led to a clear decrease in the number concentration of cloud condensation nuclei (CCN). However, in urban areas a relatively larger decrease in the number of particles in the upper end of the accumulation mode has led to slower condensation of water. As a result, a higher maximum supersaturation is reached during the cloud droplet formation. This compensates for the effect of decreased CCN concentrations. For example in Erfurt between 1991 and 1996, the aerosol properties changed so that aerosol optical depth decreased by 58% and CCN concentration decreased by 25 to 50%. These led to a 4 to 12% reduction in cloud droplet number concentration (CDNC) and less than a 2 Wm-2 increase in shortwave radiation during overcast conditions. These results demonstrate that locally the aerosol direct effect can be much larger than the aerosol indirect effect. Furthermore, even though AOD appears to be a valid proxy for CCN, the correlation between AOD and CDNC is not straightforward and thus AOD cannot be used as a proxy for CDNC."
"22982270700;56228672600;","Effects of spectral dispersion on clouds and precipitation in mesoscale convective systems",2011,"10.1029/2010JD014598","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953002076&doi=10.1029%2f2010JD014598&partnerID=40&md5=e974a5242c67345e5ad131d37d4675b1","The effects of spectral dispersion on clouds and precipitation in mesoscale convective systems have been studied by conducting 10 numerical simulations with different values of spectral dispersion (ε = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0) in the clean, semipolluted, and polluted backgrounds. The simulation results show that spectral dispersion affects cloud microphysical properties markedly in each aerosol regime. With an increase in spectral dispersion, both the raindrop concentration and the rainwater content increase, while the mean radius of the raindrops diminishes substantially. Moreover, it is found that the effects of spectral dispersion on simulated precipitation differ in these three aerosol backgrounds and relative humidity. In the clean background and at relatively lower humidity, the average accumulated precipitation is reduced significantly with an increase in spectral dispersion. Precipitation varies nonmonotonically in the semipolluted background, increasing with spectral dispersion at smaller values, while decreasing at larger values. In the mean time, precipitation is continuously enhanced with increasing spectral dispersion in the polluted background. Furthermore, sensitivity tests demonstrate that the possible impacts of spectral dispersion on precipitation varies depending on the relative humidity. For instance, at high relative humidity, an increase in spectral dispersion even in a clean atmosphere leads to more precipitation. Our results could shed light on understanding the influences of aerosols on clouds and precipitation, especially the second aerosol indirect effect. Copyright 2011 by the American Geophysical Union."
"7006246996;6701333444;","Observational quantification of a total aerosol indirect effect in the Arctic",2010,"10.1111/j.1600-0889.2010.00460.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649393451&doi=10.1111%2fj.1600-0889.2010.00460.x&partnerID=40&md5=5cef240d6d489eb32b92eaa11fe5093d","We use 6 yr of multisensor radiometric data (1998-2003) from the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program to provide an observational quantification of the short-wave aerosol first indirect effect in the Arctic. Combined with the previously determined long-wave indirect effect, the total (short-wave and long-wave) first indirect effect in the high Arctic is found to yield a transition from surface warming of +3 W m-2 during March to a cooling of -11 W m-2 during May, therefore altering the seasonal cycle of energy input to the Arctic Earth-atmosphere system. These data also reveal evidence of a first indirect effect that affects optically thinner clouds during summer, which may represent an additional negative climate feedback that responds to a warming Arctic Ocean with retreating sea ice. © 2010 The Authors Journal compilation © 2010 Blackwell Munksgaard."
"57208698992;56611366900;7102604282;","Does the threshold representation associated with the autoconversion process matter?",2008,"10.5194/acp-8-1225-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40449092529&doi=10.5194%2facp-8-1225-2008&partnerID=40&md5=4a0ea87588ec94b43c7bfb68d6afef17","Different ad hoc threshold functions associated with the autoconversion process have been arbitrarily used in atmospheric models. However, it is unclear how these ad hoc functions impact model results. Here systematic investigations of the sensitivities of climatically-important properties: CF (cloud fraction), LWP (liquid water path), and AIE (aerosol indirect effect) to threshold functions have been performed using a 3-D cloud-resolving model. It is found that the effect of threshold representations is larger on instantaneous values than on daily averages; and the effect depends on the percentage of clouds in their transitional stages of converting cloud water to rain water. For both the instantaneous values and daily averages, the sensitivity to the specification of critical radius is more significant than the sensitivity to the ""smoothness"" of the threshold representation (as embodied in the relative dispersion of droplet size distribution) for drizzling clouds. Moreover, the impact of threshold representations on the AIE is stronger than that on CF and LWP."
"7004160106;22635081500;","Parameterization of aerosol indirect effect to complement McRAS cloud scheme and its evaluation with the 3-year ARM-SGP analyzed data for single column models",2007,"10.1016/j.atmosres.2007.03.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35148831597&doi=10.1016%2fj.atmosres.2007.03.007&partnerID=40&md5=fff94e67958006cadcf69429dee2e61d","Microphysics of clouds with the Relaxed Arakawa-Schubert Scheme (McRAS) was upgraded for simulating the Aerosol Indirect Effects (AIE) for water clouds. The AIE comprises of i) Fountoukis and Nenes aerosol activation module for obtaining cloud condensation nuclei; ii) Seifert and Beheng algorithms for precipitation microphysics but with modified accretion constant for the coarse vertical-resolution typical of a global general circulation model (GCM); and iii) Khvorostyanov and Curry parameterization for computing the effective radius (re) of cloud drops. The upgraded package, named McRAS-AC, was evaluated using the 3-year ARM-SGP Single Column Model (SCM) data. Invoking only the most dominant sulfate aerosols over the region, McRAS-AC simulated realistic annual mean and annual cycles of cloud water, cloud optical thicknesses, cloud drop number concentration, and re. The follow-on SCM-sensitivity simulations showed that accretion of cloud water is sensitive to i) the terminal velocity of hydrometeors produced by autoconversion and ii) cloud height increases due to in-cloud condensation heating. The impact of aerosol mass concentration on the resultant column cloud water, and bulk optical properties of clouds were assessed by using 1/8 to 8 times the average monthly aerosol mass concentration estimates of GOCART aerosol climatology. A log-linear relation between cloud-radiative forcing and aerosol-mass concentration emerged in the simulated data. © 2007 Elsevier B.V. All rights reserved."
"14019399400;35473805400;6603431534;7101846027;7004171585;","Cloud seeding as a technique for studying aerosol-cloud interactions in marine stratocumulus",2007,"10.1029/2007GL029748","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548595672&doi=10.1029%2f2007GL029748&partnerID=40&md5=ea827fc1b353147c8277706086a3ac2d","Giant hygroscopic aerosols were introduced into a solid marine stratocumulus cloud (200 m thick) by burning hygroscopic flares mounted on an aircraft. The cloud microphysical response in two parallel seeding plumes was observed using an instrumented aircraft making 16 transects of the plumes. The cloud drop size distribution width increased in the plumes due to an increased number of small cloud drops (3-5 μm) on the earlier transects and a 5-fold increase in the number of large drops (20-40 μm) relative to the background cloud 30 minutes later. The cloud effective diameter increased from about 11 μm in the background to 13 μm in the plumes. Although the giant nuclei were only a small fraction of the total aerosols produced by the flares, they dominated the cloud response. The merit of the seeding approach for controlled observational studies of aerosol-cloud interactions in marine stratocumulus was demonstrated. Copyright 2007 by the American Geophysical Union."
"6602729528;57203053317;","A comparison of surface observations and ECHAM4-GCM experiments and its relevance to the indirect aerosol effect",2001,"10.1175/1520-0442(2001)014<1078:ACOSOA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035869801&doi=10.1175%2f1520-0442%282001%29014%3c1078%3aACOSOA%3e2.0.CO%3b2&partnerID=40&md5=7c0f70d34177596522888eb35618c07d","The observations of solar irradiance at the surface, total cloud cover, and precipitation rates have been used to evaluate aerosol-cloud interactions in a GCM. Records from Germany and the United States were available for the time period from 1985 to 1990 and 1960 to 1990. The model used here is the European Centre for Medium-Range Weather Forecasts-Deutsches Klimarechenzentrum: Hamburg (ECHAM4) GCM as run for a 5-yr period with a fully coupled sulfur chemistry-cloud scheme by Lohmann and Feichter. Two experiments- one with an annual mean sulfate load of 0.36 Tg S for the preindustrial simulation and one with 1.05 Tg S for the present day simulation were studied. The goal was to confirm indirectly the existence of the indirect aerosol effect by finding indices for a better agreement of observations with the present-day experiment as compared with the preindustrial experiment. The authors were able to draw such a conclusion only for the German data but not for the United States. The model correctly predicts the annual mean total cloud cover in Germany and the United States, whereas global solar radiation is underestimated by 13 W m-2. This deficiency stems from cloudy conditions. Clouds are either optically too thick or the vertical distribution of clouds is erroneous. This is confirmed by the modeled overcast solar irradiance, which is 27 W m-2 lower than observed, whereas, for the clear sky, model and observations agree. Precipitation rates are underestimated by 42% in the United States. The seasonal cycle of the precipitation rate is incorrect in all U.S. regions. The modeled cloud cover is too low over the central United States in July and August, and consequently the solar irradiance exceeds the observations during these months. The opposite occurs in winter, when the model overestimates the cloud cover and thus underestimates solar irradiance. The nonseasonality of vegetation and soil parameters is suggested as a possible cause for these deficiencies. The convective precipitation formation might also contribute to these discrepancies. On the other hand, this drying out effect of the inner continent is not as pronounced in coastal regions, and, in particular, the comparisons for the German grid box provide indications for the validity of the indirect aerosol effect. The modeled annual cloud cover and solar radiation cycles for the present-day aerosol load are in better agreement with observations. Furthermore, the model shows an interesting shift from low-cloud reduction to cirrus formation in spring as a consequence of the indirect aerosol effect, a result that is confirmed by observational data."
"6602596830;6603463248;7003899504;6603859477;8536879700;","The Aerosol Recirculation and Rainfall Experiment (ARREX): An initial study on aerosol-cloud interactions over South Africa",2000,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034005107&partnerID=40&md5=bde953be449d066ffa9c75da5d0b7054","South Africa, and especially its industrial highveld, is a significant source of anthropogenic and natural aerosols and trace gases. This region produces more than 1 million tonnes of sulfur dioxide (SO2) a year, mainly from the burning of coal. Through atmospheric gas-to-particle conversion, SO2 is transformed into hygroscopic sulfates, which are potentially active as cloud condensation nuclei (CCN). These additional nuclei can affect rainfall formation in clouds. The Aerosol Recirculation and Rainfall Experiment (ARREX) was started in 1998 to investigate the distribution of aerosols and trace gases over southern Africa and their possible effect on rainfall production efficiency. In southern Africa this is an important issue as water is a scarce resource. This paper presents preliminary findings on continental-maritime contrast in aerosol, CCN and cloud droplet properties under typical summer-time conditions that could explain the differences in rainfall production efficiency between the highveld and the eastern seaboard. These results form the basis for evidence to support the hypothesis that SO2 sources affect cloud properties that influence precipitation production efficiency. The complex nature of the processes involved is highlighted and suggestions made for research that should be conducted in future experiments in the region."
"7403058740;24537575000;","A possible link of aerosol and cloud radiations to Asian summer monsoon and its implication in long-range numerical weather prediction",1998,"10.2151/jmsj1965.76.6_965","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0039394498&doi=10.2151%2fjmsj1965.76.6_965&partnerID=40&md5=1125f17557c28e7b4333b11905c6f316","The influence of aerosol and cloud radiations upon the Asian summer monsoon was studied by using the global numerical weather prediction (NWP) model at the Japan Meteorological Agency (JMA). We parameterize both the direct and indirect effects of aerosols on radiative processes. In addition, criteria of cloud diagnosis are modified to enhance the cloud cover over the land in contrast to that over the ocean, considering that clouds form more easily over the land due to surface inhomogeneity and stay longer in the atmosphere due to smaller droplet size over the land than over the ocean. We confirm that the prediction of Asian monsoon activity is very sensitive to inclusions of aerosols and land-cloud enhancement. The control model, which uses the same cloud diagnosis scheme both over the land and over the ocean and does not include any effects of aerosols, systematically overpredicts the absorbed solar radiation (ASR) over land. The test model with these processes fairly reduces the systematic errors of land-ocean contrast of ASR. Over the Eurasian continent, the test model reduces ASR and lowers low-level temperature through land-atmosphere interactions. It suppresses monsoonal circulations in Southeast Asia and significantly delays northward migration of the typical fronts around East Asia, such as the Meiyu, Changma and Baiu fronts. The impact of land-cloud enhancement on one-month forecasts of the Asian monsoon seems to be similar to that of aerosols. Although the reduction of systematic errors of ASR indicates the relevance of the total effects of the two parameterization schemes, relative magnitudes of their impacts in nature are still uncertain. Further studies are required on distributions of aerosols and their optical properties, and cloud formation mechanisms particularly associated with the land-ocean difference, including aerosol-cloud interactions."
"6603414854;39261772800;","The current state of aerosol-radiation interactions: A mini review",2019,"10.1016/j.jaerosci.2018.12.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061106576&doi=10.1016%2fj.jaerosci.2018.12.010&partnerID=40&md5=726f0055cfae6f460db6ee6851f0831c","The study of physico-chemical properties of atmospheric aerosol is important as these influence the Earth's climate directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation nuclei. Nowadays, the physico-chemical properties of aerosols are being measured using space as well as ground-based sensors. Although tremendous progress has been made to improve observation systems, yet till date our understanding of physico-chemical properties of aerosol is limited. A review of available literature indicates that the surface cooling effect of aerosol is strengthened with the increase in absorbing aerosol particles in the atmosphere in response to warming. This effect might change the microphysical properties of the clouds and in due time climate. The current state of knowledge about aerosol processes where it affects climate during interaction with clouds is limited. Because aerosol processes are too complex and couldn't represent accurately in global climate models, so it is crucial in terms of predicting climate. It is therefore pertinent that future research needs to focus on a detailed understanding of physico-chemical properties of aerosols and underlying aerosol processes particularly aerosol-cloud interactions and their effect on climate. © 2019 Elsevier Ltd"
"57193622926;36106370400;37085050600;56387142000;7005069415;57189748029;","Droplet activation behaviour of atmospheric black carbon particles in fog as a function of their size and mixing state",2019,"10.5194/acp-19-2183-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061826927&doi=10.5194%2facp-19-2183-2019&partnerID=40&md5=55cdc664d245f01337a5fd50658dec21","Among the variety of particle types present in the atmosphere, black carbon (BC), emitted by combustion processes, is uniquely associated with harmful effects to the human body and substantial radiative forcing of the Earth. Pure BC is known to be non-hygroscopic, but its ability to acquire a coating of hygroscopic organic and inorganic material leads to increased diameter and hygroscopicity, facilitating droplet activation. This affects BC radiative forcing through aerosol-cloud interactions (ACIs) and BC life cycle. To gain insights into these processes, we performed a field campaign in winter 2015-2016 in a residential area of Zurich which aimed at establishing relations between the size and mixing state of BC particles and their activation to form droplets in fog. This was achieved by operating a CCN counter (CCNC), a scanning mobility particle sizer (SMPS), a single-particle soot photometer (SP2) and an aerosol chemical speciation monitor (ACSM) behind a combination of a total- and an interstitial-aerosol inlet. Our results indicate that in the morning hours of weekdays, the enhanced traffic emissions caused peaks in the number fraction of externally mixed BC particles, which do not act as CCN within the CCNC. The very low effective peak supersaturations (SS peak ) occurring in fog (between approximately 0.03% and 0.06% during this campaign) restrict droplet activation to a minor fraction of the aerosol burden (around 0.5% to 1% of total particle number concentration between 20 and 593nm) leading to very selective criteria on diameter and chemical composition. We show that bare BC cores are unable to activate to fog droplets at such low SS pea , while BC particles surrounded by thick coating have very similar activation behaviour to BC-free particles. Using simplified κ-Köhler theory combined with the ZSR mixing rule assuming spherical core-shell particle geometry constrained with single-particle measurements of respective volumes, we found good agreement between the predicted and the directly observed size- and mixing-state-resolved droplet activation behaviour of BC-containing particles in fog. This successful closure demonstrates the predictability of their droplet activation in fog with a simplified theoretical model only requiring size and mixing state information, which can also be applied in a consistent manner in model simulations. © 2019 Author(s)."
"36497832500;55689034100;56514334400;56514380000;7404433688;57205739818;","TRMM-Based Optical and Microphysical Features of Precipitating Clouds in Summer Over the Yangtze–Huaihe River Valley, China",2019,"10.1007/s00024-018-1940-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061368337&doi=10.1007%2fs00024-018-1940-8&partnerID=40&md5=88928eeae802581471e133c05b13b65c","The optical and microphysical features of precipitating clouds are key information for studying the satellite-based precipitation estimation, cloud radiative effects, aerosol–cloud–precipitation interactions, cloud and precipitation parameterization in weather and climate models. In this study, 15-year synchronous spectral and radar observations from the TRMM satellite were used to statistically explore the optical and microphysical features of precipitating clouds (PCs), including cloud effective radius (CER), cloud optical thickness (COT), cloud water path (CWP), thermal infrared brightness temperature at channel 4 (TB4) of cloud top, and storm top height (STH) and their relationships with surface rain rates in summer over Yangtze–Huaihe River Valley (YHRV). Results show that the optical and microphysical features of PCs/stratiform PCs/convective PCs vary with geographical locations in summer over YHRV, due to the different ambient meteorological and topographical conditions. Higher CER/COT/CWP/STH and lower TB4 mainly locate at areas of bigger rain rates. For PCs, their spatial distribution of CER is mainly dominated by stratiform PCs, while their spatial distribution of COT/CWP is mainly dominated by convective PCs. Moreover, stratiform precipitation is the dominant form in summer over YHRV and, thus, most PCs present vertical structures of optical and microphysical features as stratiform PCs. Stratiform PCs are usually thicker and contain more water vapor with bigger cloud particles than convective PCs (including deep and shallow convective PCs). In addition, existing shallow convective PCs are associated with lower storm heights and warmer cloud tops. Finally, surface rain rates of PCs (convective/stratiform PCs) increase gradually with the increment of CER/COT/CWP/STH, especially under 5 (15/5) mm/h. Similar relationship between surface rain rates and COT/CWP for shallow convective PCs is also found under 0.75 mm/h. Surface rain rate of PCs (convective/stratiform PCs) with cold cloud tops (TB4 < 247 K) obviously increases as TB4 decreases. Differently, for shallow convective PCs with warmer cloud tops (TB4 > 264 K), surface rain rate usually increases as CER decreases, which suggests that aerosol indirect effects are dominant in lower PCs, because over pollution regions abundant aerosols enter into lower clouds more easily and then suppress the development of shallow convective PCs. © 2018, Springer International Publishing AG, part of Springer Nature."
"56735478500;55628589750;56531367400;","Building a cloud in the southeast Atlantic: Understanding low-cloud controls based on satellite observations with machine learning",2018,"10.5194/acp-18-16537-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85057180840&doi=10.5194%2facp-18-16537-2018&partnerID=40&md5=aecd9d62a838cfc0f2d81a6c24255e02","Understanding the processes that determine low-cloud properties and aerosol-cloud interactions (ACIs) is crucial for the estimation of their radiative effects. However, the covariation of meteorology and aerosols complicates the determination of cloud-relevant influences and the quantification of the aerosol-cloud relation. This study identifies and analyzes sensitivities of cloud fraction and cloud droplet effective radius to their meteorological and aerosol environment in the atmospherically stable southeast Atlantic during the biomass-burning season based on an 8-day-averaged data set. The effect of geophysical parameters on clouds is investigated based on a machine learning technique, gradient boosting regression trees (GBRTs), using a combination of satellite and reanalysis data as well as trajectory modeling of air-mass origins. A comprehensive, multivariate analysis of important drivers of cloud occurrence and properties is performed and evaluated. The statistical model reveals marked subregional differences of relevant drivers and processes determining low clouds in the southeast Atlantic. Cloud fraction is sensitive to changes of lower tropospheric stability in the oceanic, southwestern subregion, while in the northeastern subregion it is governed mostly by surface winds. In the pristine, oceanic subregion large-scale dynamics and aerosols seem to be more important for changes of cloud droplet effective radius than in the polluted, near-shore subregion, where free tropospheric temperature is more relevant. This study suggests the necessity to consider distinct ACI regimes in cloud studies in the southeast Atlantic. © Author(s) 2018."
"57192373652;7003541446;7402538754;","Influence of turbulent fluctuations on cloud droplet size dispersion and aerosol indirect effects",2018,"10.1175/JAS-D-18-0006.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052664672&doi=10.1175%2fJAS-D-18-0006.1&partnerID=40&md5=fc1efca6ea582409deb720cdd385c233","Cloud droplet relative dispersion, defined as the standard deviation over the mean cloud droplet size, is of central importance in determining and understanding aerosol indirect effects. In recent work, it was found that cloud droplet size distributions become broader as a result of supersaturation variability and that the sensitivity of this effect is inversely related to cloud droplet number density. The subject is investigated in further detail using an extensive dataset from a laboratory cloud chamber capable of producing steady-state turbulence. An extended stochastic theory is found to successfully describe properties of the droplet size distribution, including an analytical expression for the relative dispersion. The latter is found to depend on the cloud droplet removal time, which in turn increases with the cloud droplet number density. The results show that relative dispersion decreases monotonically with increasing droplet number density, consistent with some recent atmospheric observations. Experiments spanning fast to slow microphysics regimes are reported. The observed dispersion is used to estimate time scales for autoconversion, demonstrating the important role of the turbulence-induced broadening effect on precipitation development. An initial effort is made to extend the stochastic theory to an atmospheric context with a steady updraft, for which autoconversion time is the controlling factor for droplet lifetime. As in the cloud chamber, relative dispersion is found to increase with decreasing cloud droplet number density. © 2018 American Meteorological Society."
"56457851700;7103016965;49261186800;16444006500;12801992200;7801353107;24764483400;18635820300;25924878400;","Aerosol midlatitude cyclone indirect effects in observations and high-resolution simulations",2018,"10.5194/acp-18-5821-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046013294&doi=10.5194%2facp-18-5821-2018&partnerID=40&md5=62b10d3f5fe6731522c5284c9c091173","Aerosol-cloud interactions are a major source of uncertainty in inferring the climate sensitivity from the observational record of temperature. The adjustment of clouds to aerosol is a poorly constrained aspect of these aerosol-cloud interactions. Here, we examine the response of midlatitude cyclone cloud properties to a change in cloud droplet number concentration (CDNC). Idealized experiments in high-resolution, convection-permitting global aquaplanet simulations with constant CDNC are compared to 13 years of remote-sensing observations. Observations and idealized aquaplanet simulations agree that increased warm conveyor belt (WCB) moisture flux into cyclones is consistent with higher cyclone liquid water path (CLWP). When CDNC is increased a larger LWP is needed to give the same rain rate. The LWP adjusts to allow the rain rate to be equal to the moisture flux into the cyclone along the WCB. This results in an increased CLWP for higher CDNC at a fixed WCB moisture flux in both observations and simulations. If observed cyclones in the top and bottom tercile of CDNC are contrasted it is found that they have not only higher CLWP but also cloud cover and albedo. The difference in cyclone albedo between the cyclones in the top and bottom third of CDNC is observed by CERES to be between 0.018 and 0.032, which is consistent with a 4.6-8.3gWmg2 in-cyclone enhancement in upwelling shortwave when scaled by annual-mean insolation. Based on a regression model to observed cyclone properties, roughly 60g% of the observed variability in CLWP can be explained by CDNC and WCB moisture flux. © Author(s) 2018."
"57200602923;8550791300;57193798535;57214957717;57214957723;25624725200;7003459101;8550432800;55555084100;","Effects of Ice Nucleation Protein Repeat Number and Oligomerization Level on Ice Nucleation Activity",2018,"10.1002/2017JD027307","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041826197&doi=10.1002%2f2017JD027307&partnerID=40&md5=81bb7eaf54ae4dd8c60c2590ca46b8d0","Ice nucleation active bacteria have attracted particular attention due to their unique ability to produce specific ice nucleation proteins (INpros), which are the most efficient ice nuclei known as they induce nucleation at temperatures close to 0°C. Our model bacterium Pseudomonas syringae strain R10.79 produced INpros containing 67 tandem repeats, forming the proposed ice-binding surface. To understand the role of the INpro repeats as well as the role of intermolecular interactions between INpros for their ice nucleation behavior, we produced a truncated version of the protein with only 16 tandem repeats (INpro16R). The purified INpro16R produced oligomers of varying sizes. Immersion freezing ice nucleation behavior of purified INpro16R was characterized by droplet-freezing assays and in the Leipzig Aerosol Cloud Interaction Simulator. Predominant INpro16R oligomers introduced into Leipzig Aerosol Cloud Interaction Simulator as single particles with diameters of 50 nm or 70 nm were ice nucleation active at temperatures of −26°C and −24°C, respectively. These are much lower temperatures compared to that of intact INpros (−12°C). The data clearly indicated that the number of repeats determines the ice nucleation temperature. In addition, ice nucleation between −9°C and −10°C, comparable to the activity of intact INpro, was caused by higher-order INpro16R oligomers. This supported previous observations that INpro oligomerization increases the ice-binding surface, thereby affecting ice nucleation activity. In conclusion, both repeat number and oligomerization contribute in a seemingly independent manner to the nucleation mechanism of INpros. ©2018. American Geophysical Union. All Rights Reserved."
"36822103700;57203102974;7102944401;14035836100;24074763000;57209647985;7006107059;","Aerosol indirect effects on the nighttime Arctic Ocean surface from thin, predominantly liquid clouds",2017,"10.5194/acp-17-7311-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021167690&doi=10.5194%2facp-17-7311-2017&partnerID=40&md5=7404747bd572d670a09ba41162148e47","Aerosol indirect effects have potentially large impacts on the Arctic Ocean surface energy budget, but model estimates of regional-scale aerosol indirect effects are highly uncertain and poorly validated by observations. Here we demonstrate a new way to quantitatively estimate aerosol indirect effects on a regional scale from remote sensing observations. In this study, we focus on nighttime, optically thin, predominantly liquid clouds. The method is based on differences in cloud physical and microphysical characteristics in carefully selected clean, average, and aerosol-impacted conditions. The cloud subset of focus covers just g1/4 5g% of cloudy Arctic Ocean regions, warming the Arctic Ocean surface by g1/4g1-1.4gWgmg2 regionally during polar night. However, within this cloud subset, aerosol and cloud conditions can be determined with high confidence using CALIPSO and CloudSat data and model output. This cloud subset is generally susceptible to aerosols, with a polar nighttime estimated maximum regionally integrated indirect cooling effect of g1/4 g0.11gWgmg2 at the Arctic sea ice surface (g1/4g8g% of the clean background cloud effect), excluding cloud fraction changes. Aerosol presence is related to reduced precipitation, cloud thickness, and radar reflectivity, and in some cases, an increased likelihood of cloud presence in the liquid phase. These observations are inconsistent with a glaciation indirect effect and are consistent with either a deactivation effect or less-efficient secondary ice formation related to smaller liquid cloud droplets. However, this cloud subset shows large differences in surface and meteorological forcing in shallow and higher-altitude clouds and between sea ice and open-ocean regions. For example, optically thin, predominantly liquid clouds are much more likely to overlay another cloud over the open ocean, which may reduce aerosol indirect effects on the surface. Also, shallow clouds over open ocean do not appear to respond to aerosols as strongly as clouds over stratified sea ice environments, indicating a larger influence of meteorological forcing over aerosol microphysics in these types of clouds over the rapidly changing Arctic Ocean."
"56612517400;36538539800;56942554300;57213551855;7202048112;8511991900;56991611600;35792776400;55624488227;7004444634;7202010686;","Multi-year application of WRF-CAM5 over East Asia-Part I: Comprehensive evaluation and formation regimes of O3 and PM2.5",2017,"10.1016/j.atmosenv.2017.06.015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021320039&doi=10.1016%2fj.atmosenv.2017.06.015&partnerID=40&md5=3c38661eb0374928be02804caf3e7aac","Accurate simulations of air quality and climate require robust model parameterizations on regional and global scales. The Weather Research and Forecasting model with Chemistry version 3.4.1 has been coupled with physics packages from the Community Atmosphere Model version 5 (CAM5) (WRF-CAM5) to assess the robustness of the CAM5 physics package for regional modeling at higher grid resolutions than typical grid resolutions used in global modeling. In this two-part study, Part I describes the application and evaluation of WRF-CAM5 over East Asia at a horizontal resolution of 36-km for six years: 2001, 2005, 2006, 2008, 2010, and 2011. The simulations are evaluated comprehensively with a variety of datasets from surface networks, satellites, and aircraft. The results show that meteorology is relatively well simulated by WRF-CAM5. However, cloud variables are largely or moderately underpredicted, indicating uncertainties in the model treatments of dynamics, thermodynamics, and microphysics of clouds/ices as well as aerosol-cloud interactions. For chemical predictions, the tropospheric column abundances of CO, NO2, and O3 are well simulated, but those of SO2 and HCHO are moderately overpredicted, and the column HCHO/NO2 indicator is underpredicted. Large biases exist in the surface concentrations of CO, NOx, and PM10 due to uncertainties in the emissions as well as vertical mixing. The underpredictions of NO lead to insufficient O3 titration, thus O3 overpredictions. The model can generally reproduce the observed O3 and PM indicators. These indicators suggest to control NOx emissions throughout the year, and VOCs emissions in summer in big cities and in winter over North China Plain, North/South Korea, and Japan to reduce surface O3, and to control SO2, NH3, and NOx throughout the year to reduce inorganic surface PM. © 2017 Elsevier Ltd"
"56604613900;55720362700;55913139000;7003438566;56604445500;55964480200;","Analysis of aerosol-cloud-precipitation interactions based on MODIS data",2017,"10.1016/j.asr.2016.08.042","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006339816&doi=10.1016%2fj.asr.2016.08.042&partnerID=40&md5=66e3be477fa831dd97d2679a2fd81ea0","Aerosols exert an indirect impact on climate change via its impact on clouds by altering its radiative and optical properties which, in turn, changes the process of precipitation. Over recent years how to study the indirect climate effect of aerosols has become an important research topic. In this study we attempted to understand the complex mutual interactions among aerosols, clouds and precipitation through analysis of the spatial correlation between aerosol optical depth (AOD), cloud effective radius (CER) and precipitation during 2000–2012 in central-eastern China that has one of the highest concentrations of aerosols globally. With the assistance of moderate resolution imaging spectroradiometer (MODIS)-derived aerosol and cloud product data, this analysis focuses on regional differentiation and seasonal variation of the correlation in which in situ observed precipitation was incorporated. On the basis of the achieved results, we proposed four patterns depicting the mutual interactions between aerosols, clouds and precipitation. They characterize the indirect effects of aerosols on the regional scale. These effects can be summarized as complex seasonal variations and north-south regional differentiation over the study area. The relationship between AOD and CER is predominated mostly by the first indirect effect (the negative correlation between AOD and CER) in the north of the study area in the winter and spring seasons, and over the entire study area in the summer season. The relationship between CER and precipitation is dominated chiefly by the second indirect effect (the positive correlation between CER and precipitation) in the northern area in summer and over the entire study area in autumn. It must be noted that aerosols are not the factor affecting clouds and rainfall singularly. It is the joint effect of aerosols with other factors such as atmospheric dynamics that governs the variation in clouds and rainfall. © 2016 COSPAR"
"24722339600;57198616562;36076994600;7004479957;57191663360;57193132723;6506545080;7003666669;14019399400;6603431534;7103119050;7005263785;55740664200;35095482200;7202252296;35584010200;7005035762;","Planning the next decade of coordinated research to better understand and simulate marine low clouds",2016,"10.1175/BAMS-D-16-0160.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84992391438&doi=10.1175%2fBAMS-D-16-0160.1&partnerID=40&md5=46a12459cdd60eb7ed603d9bb1c42bb3","A workshop was held 27-29 January 2016 at Brookhaven National Laboratory to help define research pathways to address outstanding issues related to our understanding of marine low clouds. Discussion centered on four themes where significant progress can be made using ground-based remote sensing, in situ data, and modeling. These included aerosol indirect effects and the cloud condensation nuclei (CCN) budget, precipitation, entrainment and mixing, and mesoscale organization. The response of clouds to aerosol variations in the current climate may not accurately represent the responses of clouds and their radiative forcing to increases in aerosol concentration from anthropogenic emissions since the preindustrial era. Remote marine low cloud systems are particularly susceptible to perturbations in aerosols associated with anthropogenic emissions because of their relatively low optical thicknesses and low background aerosol concentrations. Radar observations have played a critical role in demonstrating that marine low clouds precipitate frequently with rates that are significant for the planetary boundary layer (PBL) moisture budget. Most climate models represent collision?coalescence processes using bulk representations that may result in an artificially strong sensitivity to aerosol. The estimation of entrainment rate from ground-based remote sensing and aircraft measurements to provide observational constraints for models remains a significant challenge."
"56536745100;36141355100;57203053317;7003748648;","Real-case simulations of aerosol-cloud interactions in ship tracks over the Bay of Biscay",2015,"10.5194/acp-15-2185-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924044829&doi=10.5194%2facp-15-2185-2015&partnerID=40&md5=9f50bf5ca2363ecf202b477477feec35","Ship tracks provide an ideal test bed for studying aerosol-cloud interactions (ACIs) and for evaluating their representation in model parameterisations. Regional modelling can be of particular use for this task, as this approach provides sufficient resolution to resolve the structure of the produced track including their meteorological environment whilst relying on the same formulations of parameterisations as many general circulation models. In this work we simulate a particular case of ship tracks embedded in an optically thin stratus cloud sheet which was observed by a polar orbiting satellite at 12:00UTC on 26 January 2003 around the Bay of Biscay. The simulations, which include moving ship emissions, show that the model is indeed able to capture the structure of the track at a horizontal grid spacing of 2 km and to qualitatively capture the observed cloud response in all simulations performed. At least a doubling of the cloud optical thickness was simulated in all simulations together with an increase in cloud droplet number concentration by about 40 cm-3 (300 %) and decrease in effective radius by about 5 μm (40 %). Furthermore, the ship emissions lead to an increase in liquid water path in at least 25% of the track regions. We are confident in the model's ability to capture key processes of ship track formation. However, it was found that realistic ship emissions lead to unrealistic aerosol perturbations near the source regions within the simulated tracks due to grid-scale dilution and homogeneity. Combining the regional-modelling approach with comprehensive field studies could likely improve our understanding of the sensitivities and biases in ACI parameterisations, and could therefore help to constrain global ACI estimates, which strongly rely on these parameterisations. © 2015 Author(s). CC Attribution 3.0 License."
"23003259600;55710921100;57215729754;56093506600;56305468400;55687255900;41462164500;55689034100;16481561000;56068376200;38362385200;","Fine mode aerosol optical properties related to cloud and fog processing over a cluster of cities in Northeast China",2015,"10.4209/aaqr.2014.12.0325","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942280051&doi=10.4209%2faaqr.2014.12.0325&partnerID=40&md5=4566726b030851e7346fc16651167fb9","Fine mode aerosol optical properties were retrieved from sunphotometer measurements, carried out in Shenyang, Anshan, Benxi, and Fushun in Northeast China from 2009–2013. Accumulation mode aerosol size distribution retrievals were investigated for specific situations involving extensive cloud processing during fog or haze. Large fine mode median radii (≥ 0.20 µm) frequently occurred at the four sites in July. At other times, as aerosol optical depths increased so did the fine mode median radii, reaching 0.30–0.40 µm. This was possibly due to aerosol humidification during cloud processing. Instances of large (~1.50) Alpha curvature at the sites also may be associated with cloud processing. When single scattering albedos were ≥ 0.90, the radii distributions were centered round 0.30–0.40 µm at all at sites except Benxi, perhaps due to non-absorbing material from aerosol/cloud interactions. Case studies of size distribution retrievals at each of the four sites showed that large accumulation mode radii (0.40–0.50 µm) may be linked to cloud processing. © Taiwan Association for Aerosol Research."
"56520572300;56162305900;7103158465;55411439700;56384704800;55717074000;9249239700;","Investigating ice nucleation in cirrus clouds with an aerosol-enabled Multiscale Modeling Framework",2014,"10.1002/2014MS000343","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923083516&doi=10.1002%2f2014MS000343&partnerID=40&md5=0c9316cc2e0e756b1dc72bee87c90b99","In this study, an aerosol-dependent ice nucleation scheme has been implemented in an aerosol-enabled Multiscale Modeling Framework (PNNL MMF) to study ice formation in upper troposphere cirrus clouds through both homogeneous and heterogeneous nucleation. The MMF model represents cloud scale processes by embedding a cloud-resolving model (CRM) within each vertical column of a GCM grid. By explicitly linking ice nucleation to aerosol number concentration, CRM-scale temperature, relative humidity and vertical velocity, the new MMF model simulates the persistent high ice supersaturation and low ice number concentration (10-100/L) at cirrus temperatures. The new model simulates the observed shift of the ice supersaturation PDF toward higher values at low temperatures following the homogeneous nucleation threshold. The MMF model predicts a higher frequency of midlatitude supersaturation in the Southern Hemisphere and winter hemisphere, which is consistent with previous satellite and in situ observations. It is shown that compared to a conventional GCM, the MMF is a more powerful model to simulate parameters that evolve over short time scales such as supersaturation. Sensitivity tests suggest that the simulated global distribution of ice clouds is sensitive to the ice nucleation scheme and the distribution of sulfate and dust aerosols. Simulations are also performed to test empirical parameters related to auto-conversion of ice crystals to snow. Results show that with a value of 250 μm for the critical diameter, Dcs, that distinguishes ice crystals from snow, the model can produce good agreement with the satellite-retrieved products in terms of cloud ice water path and ice water content, while the total ice water is not sensitive to the specification of Dcs value. © 2014. The Authors."
"36131958000;57094306300;8072265400;","Aerosol effects on global land surface energy fluxes during 2003-2010",2014,"10.1002/2014GL061640","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923340242&doi=10.1002%2f2014GL061640&partnerID=40&md5=23a68b8447129665f7d5737e8bb5467d","Aerosols affect downward solar radiation, impacting the terrestrial ecosystem carbon dynamics and energy budget. Here we apply a coupled modeling framework of a terrestrial ecosystem model and an atmospheric radiative transfer model to evaluate aerosol direct radiative effects on the surface heat fluxes of global terrestrial ecosystems during 2003-2010. We find that aerosol loadings decrease the mean latent heat flux by 2.4 Wm-2 (or evapotranspiration by 28 mm) and sensible heat flux by 16 Wm-2. As a result, global mean soil moisture and water evaporative fraction have increased by 0.5% and 4%, respectively. Spatially, aerosol effects are significant in tropical forests and temperate broadleaf evergreen forests. This study is among the first quantifications of aerosols' effects on the heat fluxes of the global terrestrial ecosystems. The study further suggests that both direct and indirect aerosol radiative effects through aerosol-cloud interactions should be considered to quantify the energy budget of the global terrestrial ecosystems. © 2014. American Geophysical Union. All Rights Reserved."
"6602639942;6603859477;15319447000;7004171585;7401539646;7004938676;","Individual aerosol particles in ambient and updraft conditions below convective cloud bases in the Oman mountain region",2014,"10.1002/2013JD021165","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898442139&doi=10.1002%2f2013JD021165&partnerID=40&md5=32a5e8106f9175f1c8303767ccf26b49","An airborne study of cloud microphysics provided an opportunity to collect aerosol particles in ambient and updraft conditions of natural convection systems for transmission electron microscopy (TEM). Particles were collected simultaneously on lacey carbon and calcium-coated carbon (Ca-C) TEM grids, providing information on particle morphology and chemistry and a unique record of the particle’s physical state on impact. In total, 22 particle categories were identified, including single, coated, aggregate, and droplet types. The fine fraction comprised up to 90% mixed cation sulfate (MCS) droplets, while the coarse fraction comprised up to 80% mineral-containing aggregates. Insoluble (dry), partially soluble (wet), and fully soluble particles (droplets) were recorded on Ca-C grids. Dry particles were typically silicate grains; wet particles were mineral aggregates with chloride, nitrate, or sulfate components; and droplets were mainly aqueous NaCl and MCS. Higher numbers of droplets were present in updrafts (80% relative humidity (RH)) compared with ambient conditions (60% RH), and almost all particles activated at cloud base (100% RH). Greatest changes in size and shape were observed in NaCl-containing aggregates (>0.3 μm diameter) along updraft trajectories. Their abundance was associated with high numbers of cloud condensation nuclei (CCN) and cloud droplets, as well as large droplet sizes in updrafts. Thus, compositional dependence was observed in activation behavior recorded for coarse and fine fractions. Soluble salts from local pollution and natural sources clearly affected aerosol-cloud interactions, enhancing the spectrum of particles forming CCN and by forming giant CCN from aggregates, thus, making cloud seeding with hygroscopic flares ineffective in this region. © 2014. American Geophysical Union. All rights reserved."
"9043417100;7102132806;7202957110;8670222900;8684037700;7006235542;57195257572;7006377579;21933618400;35740180800;","Can aerosols influence deep tropical convection? Aerosol indirect effects in the Hector island thunderstorm",2013,"10.1002/qj.2083","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890248755&doi=10.1002%2fqj.2083&partnerID=40&md5=31339736dc351fa011d10428e7dd491d","This article addresses the effects of cloud condensation nuclei on the evolution of an intense tropical convective system, known as Hector, using data taken from the ACTIVE and TWP-ICE field campaigns, which were conducted in 2005 and 2006. The Hector thunderstorms were observed in a variety of aerosol conditions so the data serve as an ideal dataset to test whether aerosols have a significant impact on the evolution of convective clouds and precipitation. We find evidence for an aerosol effect on the storm's properties, which are reproduced with a state-of-the-art mesoscale cloud-resolving model. Including the measured aerosol concentration within the model is shown to improve the fractions skill-score metric for every case presented in the article, thus giving us confidence that the deep convection observed during the period was indeed influenced by the aerosol entering the storm's inflow. However, we do not find a general relationship for the way aerosols affect properties such as cloud-top height, precipitation or radiative properties, as has been suggested in previous work. The reasons for this appear to be because of the nonlinearity of interactions between neighbouring cells and because of the variability in the meteorological profiles of temperature, wind and humidity. © 2012 Royal Meteorological Society."
"21739412800;7003479145;","Role of fine mode aerosols in modulating cloud properties over industrial locations in north India",2011,"10.5194/angeo-29-1605-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856012308&doi=10.5194%2fangeo-29-1605-2011&partnerID=40&md5=f72cae1456606f729e58f7780e2a9f43","The influence of aerosols on cloud properties over North India which includes the Indo-Gangetic Plain has been investigated for the years 2000 to 2010. During the years 2004, 2009 and 2010 there has been an abrupt increase in fine mode aerosol optical depth (AOD) inducing a sharp decline in cloud effective radius (CER) in the month of January. The following monsoon during these years was a failure in the region considered for the study. In the year 2010, a highest AOD value of 0.35 was recorded in the month of January. In accordance with the aerosol indirect effect, this large increase in AOD resulted in a significant reduction in CER. The monsoon season in that year was deficient in the study region even though the rest of the country received above normal rainfall. For the years when CER diminished below 12 microns in the month of May, a delay in the advancement of monsoon towards North India is noted even after a normal or early onset in southern peninsula. Meanwhile, a rapid progression took place when it was 12 microns or above. During non-monsoon months an inverse relationship existed between cloud effective radius and liquid water path and a strong positive association occurred in the monsoon months. Present analysis suggests that the excessive aerosol loading and the associated aerosol indirect effects in the months prior to the monsoon season has an effect on the propagation and onset of the south west monsoon over the region. © Author(s) 2011. CC Attribution 3.0 License."
"56032511300;7102604282;","Aerosol effects on ice clouds: Can the traditional concept of aerosol indirect effects be applied to aerosol-cloud interactions in cirrus clouds?",2010,"10.5194/acp-10-10345-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78149271958&doi=10.5194%2facp-10-10345-2010&partnerID=40&md5=b48309b1454a6fe8e45892a062d3f476","Cirrus clouds cover approximately 20g-25% of the globe and thus play an important role in the Earth's radiation budget. Therefore the effect of aerosols on cirrus clouds can have a substantial impact on global radiative forcing if either the ice-water path (IWP) and/or the cloud ice number concentration (CINC) changes. This study examines the aerosol indirect effect (AIE) through changes in the CINC and IWP for a cirrus cloud case. We use a cloud-system resolving model (CSRM) coupled with a double-moment representation of cloud microphysics. Intensified interactions among CINC, deposition and dynamics play a critical role in increasing the IWP as aerosols increase. Increased IWP leads to a smaller change in the outgoing LW radiation relative to that for the SW radiation for increasing aerosols. Increased aerosols lead to increased CINC, providing increased surface area for water vapor deposition. The increased deposition causes depositional heating which produces stronger updrafts, and leads to the increased IWP. The conversion of ice crystals to aggregates through autoconversion and accretion plays a negligible role in the IWP response to aerosols, and the sedimentation of aggregates is negligible. The sedimentation of ice crystals plays a more important role in the IWP response to aerosol increases than the sedimentation of aggregates, but not more than the interactions among the CINC, deposition and dynamics. © 2010 Author(s)."
"24538177600;7004479957;8882641700;","The sensitivity of stratocumulus-capped mixed layers to cloud droplet concentration: Do les and mixed-layer models agree?",2010,"10.5194/acp-10-4097-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951972439&doi=10.5194%2facp-10-4097-2010&partnerID=40&md5=24bdf1d5c12883e1849e090fe32050bf","The sensitivity of a stratocumulus-capped mixed layer to a change in cloud droplet concentration is evaluated with a large-eddy simulation (LES) and a mixed layer model (MLM). The strength of the second aerosol indirect effect simulated by the two model types agrees within 50% for cases in which the LES-simulated boundary layer remains well mixed, if the MLM entrainment closure includes the effects of cloud droplet sedimentation. To achieve this agreement, parameters in the MLM entrainment closure and the drizzle parameterization must be retuned to match the LES. This is because the LES advection scheme and microphysical parameterization significantly bias the entrainment rate and precipitation profile compared to observational best guesses. Before this modifi-cation, the MLM simulates more liquid water path and much more drizzle at a given droplet concentration than the LES and is more sensitive to droplet concentration, even undergoing a drizzle-induced boundary layer collapse at low droplet concentrations. After this modification, both models predict a comparable decrease of cloud liquid water path as droplet concentration increases, cancelling 30-50% of the Twomey effect for our case. The agreement breaks down at the lowest simulated droplet concentrations, for which the boundary layer in the LES is not well mixed. Our results highlight issues with both types of model. Potential LES biases due to inadequate resolution, subgrid mixing and parameterized microphysics must be carefully considered when trying to make a quantitative inference of the second indirect effect from an LES of a stratocumulustopped boundary layer. On the other hand, even slight internal decoupling of the boundary layer invalidates the centralassumption of an MLM, substantially limiting the range of conditions that MLM-predicted sensitivities to droplet concentration are meaningful. © 2010 Author(s)."
"8067118800;7404243086;35330367300;7202899330;","Effect of the droplet activation process on microphysical properties of warm clouds",2010,"10.1088/1748-9326/5/2/024012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78149348460&doi=10.1088%2f1748-9326%2f5%2f2%2f024012&partnerID=40&md5=197cd8909ba5a93d1aba213638fb0c36","This study investigates the effect of the droplet activation process on microphysical characteristics of warm clouds represented by correlation statistics between cloud droplet effective radius re and cloud optical thickness τc. The conceptual adiabatic model is first employed to interpret satellite-observed re-τc correlation statistics over two different regions and to reveal distinctively different increasing patterns of droplet number concentration between these regions. This difference is attributed to a different behavior of the droplet activation process induced by differing microphysical conditions of aerosols. Numerical experiments of changing aerosol size spectrum are then performed with a spectral bin microphysics cloud model. The results show that the slope of the size spectrum controls the re-τc relationship through its effect on increasing pattern of droplet number concentration due to the activation process. The simulated results are also found to reproduce the r e-τc correlation statistics closely resembling those observed when the slope parameter and the aerosol amount are appropriately chosen. These results suggest that the re-τc correlation statistics observed by remote sensing studies contains a signature of how the droplet activation process takes place in the real clouds. © 2010 IOP Publishing Ltd."
"8688004400;57193882808;7103158465;","The impact of atmospheric aerosols on precipitation from deep organized convection: A prescribed-flow model study using double-moment bulk microphysics",2009,"10.1002/qj.450","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350624537&doi=10.1002%2fqj.450&partnerID=40&md5=b7949d9088f235b2e7f4dfffddacedc0","This note discusses the results of numerical simulations in which a prescribed-flow model is merged with a double-moment warm-rain and ice microphysics scheme to investigate the impact of microphysical processes on precipitation from deep organized convection. The prescribed two-dimensional flow mimics an idealized squall line, with a narrow region of strong convective updraft and much wider region of weak stratiform updraft overlaying a stratiform downdraft. To cover the broad range of conditions that are possible for a squall line as well as to explore precipitation dependence on different parameters, 25 pairs of simulations are performed. Simulated cases differ in the dynamics (e.g. changing the updraft strength or large-scale shear), thermodynamics (e.g. changing the inflow sounding) or microphysics (e.g. changing the collision efficiencies). Each pair features cloud condensation nuclei (CCN) in either a pristine or polluted environment. Total surface precipitation and partitioning between convective and stratiform precipitation in each pair appears to be almost the same, with the difference being typically a few tenths of 1%. However, the dynamical and thermodynamical parameters do affect the precipitation significantly. It follows that the surface precipitation from organized convection can differ between pristine and polluted environments only through the feedback of CCN on cloud dynamics. In this feedback, small differences in the latent heating for the same flow pattern lead to different flow patterns in subsequent squall-line evolution. Details of this feedback need to be investigated using a dynamical model. © 2009 Royal Meteorological Society."
"7404294454;7005135473;","Seasonal variation in satellite-derived effects of aerosols on clouds in the Arabian Sea",2008,"10.1029/2007JD009118","https://www.scopus.com/inward/record.uri?eid=2-s2.0-46449111112&doi=10.1029%2f2007JD009118&partnerID=40&md5=52473272e015bdcbe535bafcf2ad5590","Aerosols act as cloud condensation nuclei for cloud water droplets, with changes in aerosol concentrations having significant impacts on the corresponding cloud properties. An increase in aerosol concentration may lead to an increase in CCN, with an associated decrease in cloud droplet size for a given cloud liquid water content. Smaller droplet sizes may then lead to a reduction in precipitation efficiency and an increase in cloud lifetimes. However, these effects are highly dependent on the aerosol concentration, aerosol species, and the meteorological conditions. In the Arabian Sea (10-20°N, 62-72°E), prevailing aerosol type transitions from mostly small-mode anthropogenic aerosols during the winter months to mostly coarse-mode mineral dust and sea salt during the summer due to a change in prevailing wind speed and direction, is likely to impart substantial variability on any associated indirect effects. To examine this variability, we use one year (2004) of MODIS derived aerosol optical thickness (AOT) and cloud products over the Arabian Sea to quantify aerosol indirect effects. Results show that indirect effects in the Arabian Sea are a strong function of season, which is a result of the changing aerosol and moisture (humidity) concentrations during the course of the year. During the winter months (DJF), cloud-droplet size and AOT were found to have a weak positive correlation (r=0.12), opposite of the expected effect. The low atmospheric humidity coupled with wide-spread subsidence and other dynamical factors may prevent these aerosols from being activated. During the summer months (JJA), AOT increases with the addition of mineral dust and sea salt aerosols and the correlation between AOT and cloud droplet size becomes negative (r=-0.22). The magnitude of the first indirect effect corresponds to an increase in low level wind speeds, increasing the concentration of hygroscopic sea salt into the atmosphere. For both periods, a positive correlation (r=0.16, 0.32) was found between AOT and LWP indicating a reduction in precipitation efficiency. Copyright 2008 by the American Geophysical Union."
"25723426400;","Relationships between cloud properties and precipitation amount over the Amazon basin",2006,"10.1016/j.atmosres.2005.10.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749155780&doi=10.1016%2fj.atmosres.2005.10.007&partnerID=40&md5=e1a7b13f92ca6136f160239cafbfda35","Comparisons between the precipitation amount, P, and monthly averaged cloud properties (optical depths of low-level water clouds, τlow, and ""total clouds"", τtot, effective particle radius, re, and columnar-integrated droplet number of low-level water clouds, Nc) over the Amazon basin elucidated the effect of precipitation on low cloud properties and the relationship between precipitation and ""total cloud"" cover. The relationship between re and P was positive, while the relationship between Nc and P was negative. Since low clouds in this region generally produce little precipitation, these relationships may reflect the scavenging of aerosols by precipitation and suggest the aerosol indirect effect of the first kind. The relationship between τtot and P was positive because the ""total clouds"" included actual precipitating clouds. © 2006 Elsevier B.V. All rights reserved."
"35227762400;55173596300;35611334800;15755995900;24757696000;6602600408;","Separating radiative forcing by aerosol-cloud interactions and rapid cloud adjustments in the ECHAM-HAMMOZ aerosol-climate model using the method of partial radiative perturbations",2019,"10.5194/acp-19-15415-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076677100&doi=10.5194%2facp-19-15415-2019&partnerID=40&md5=9298b28c74684157b00df0d160cc7040","Using the method of offline radiative transfer modeling within the partial radiative perturbation (PRP) approach, the effective radiative forcing by aerosol-cloud interactions (ERFaci) in the ECHAM-HAMMOZ aerosol climate model is decomposed into a radiative forcing by anthropogenic cloud droplet number change and adjustments of the liquid water path and cloud fraction. The simulated radiative forcing by anthropogenic cloud droplet number change and liquid water path adjustment are of approximately equal magnitude at-0:52 and-0:53Wm-2, respectively, while the cloud-fraction adjustment is somewhat weaker at-0:31Wm-2 (constituting 38 %, 39 %, and 23% of the total ERFaci, respectively); geographically, all three ERFaci components in the simulation peak over China, the subtropical eastern ocean boundaries, the northern Atlantic and Pacific oceans, Europe, and eastern North America (in order of prominence). Spatial correlations indicate that the temporal-mean liquid water path adjustment is proportional to the temporal-mean radiative forcing, while the relationship between cloud-fraction adjustment and radiative forcing is less direct. While the estimate of warm-cloud ERFaci is relatively insensitive to the treatment of ice and mixedphase cloud overlying warm cloud, there are indications that more restrictive treatments of ice in the column result in a low bias in the estimated magnitude of the liquid water path adjustment and a high bias in the estimated magnitude of the droplet number forcing. Since the present work is the first PRP decomposition of the aerosol effective radiative forcing into radiative forcing and rapid cloud adjustments, idealized experiments are conducted to provide evidence that the PRP results are accurate. The experiments show that using low-frequency (daily or monthly) time-averaged model output of the cloud property fields underestimates the ERF, but 3-hourly mean output is sufficiently frequent. © 2019 Copernicus GmbH. All rights reserved."
"7003414581;16642991200;55444637900;22954523900;8927405700;57202475063;36651412700;38760907700;15923105200;6602085876;8980175400;17341189400;","Ice-nucleating particle versus ice crystal number concentrationin altocumulus and cirrus layers embedded in Saharan dust:a closure study",2019,"10.5194/acp-19-15087-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85072129265&doi=10.5194%2facp-19-15087-2019&partnerID=40&md5=2f85982188e3f23a3577b4da6d87ff59","For the first time, a closure study of the relationship between the ice-nucleating particle concentration (INP; INPC) and ice crystal number concentration (ICNC) in altocumulus and cirrus layers, solely based on groundbased active remote sensing, is presented. Such aerosol- cloud closure experiments are required (a) to better understand aerosol-cloud interaction in the case of mixed-phase clouds, (b) to explore to what extent heterogeneous ice nucleation can contribute to cirrus formation, which is usually controlled by homogeneous freezing, and (c) to check the usefulness of available INPC parameterization schemes, applied to lidar profiles of aerosol optical and microphysical properties up to the tropopause level. The INPC-ICNC closure studies were conducted in Cyprus (Limassol and Nicosia) during a 6-week field campaign in March-April 2015 and during the 17-month CyCARE (Cyprus Clouds Aerosol and Rain Experiment) campaign. The focus was on altocumulus and cirrus layers which developed in pronounced Saharan dust layers at heights from 5 to 11 km. As a highlight, a long-lasting cirrus event was studied which was linked to the development of a very strong dust-infused baroclinic storm (DIBS) over Algeria. The DIBS was associated with strong convective cloud development and lifted large amounts of Saharan dust into the upper troposphere, where the dust influenced the evolution of an unusually large anvil cirrus shield and the subsequent transformation into an cirrus uncinus cloud system extending from the eastern Mediterranean to central Asia, and thus over more than 3500 km. Cloud top temperatures of the three discussed closure study cases ranged from - 20 to -57 °C. The INPC was estimated from polarization/Raman lidar observations in combination with published INPC parameterization schemes, whereas the ICNC was retrieved from combined Doppler lidar, aerosol lidar, and cloud radar observations of the terminal velocity of falling ice crystals, radar reflectivity, and lidar backscatter in combination with the modeling of backscattering at the 532 and 8.5 mm wavelengths. A good-to-acceptable agreement between INPC (observed before and after the occurrence of the cloud layer under investigation) and ICNC values was found in the discussed three proof-of-concept closure experiments. In these case studies, INPC and ICNC values matched within an order of magnitude (i.e., within the uncertainty ranges of the INPC and ICNC estimates), and they ranged from 0.1 to 10 L-1 in the altocumulus layers and 1 to 50 L-1 in the cirrus layers observed between 8 and 11 km height. The successful closure experiments corroborate the important role of heterogeneous ice nucleation in atmospheric ice formation processes when mineral dust is present. The observed longlasting cirrus event could be fully explained by the presence of dust, i.e., without the need for homogeneous ice nucleation processes. © 2019 Author(s)."
"57193572297;42361233000;6507121473;7005207654;57205682408;29567632400;20435752700;56931957400;56193650100;35744191200;7005742394;","Parameterization of vertical profiles of governing microphysical parameters of shallow cumulus cloud ensembles using LES with bin microphysics",2019,"10.1175/JAS-D-18-0046.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062511946&doi=10.1175%2fJAS-D-18-0046.1&partnerID=40&md5=1ec70617f6708c768078574022136b39","Shallow convection is a subgrid process in cloud-resolving models for which their grid box is larger than the size of small cumulus clouds (Cu). At the same time such Cu substantially affect radiation properties and thermodynamic parameters of the low atmosphere. The main microphysical parameters used for calculation of radiative properties of Cu in cloud-resolving models are liquid water content (LWC), effective droplet radius, and cloud fraction (CF). In this study, these parameters of fields of small, warm Cu are calculated using large-eddy simulations (LESs) performed using the System for Atmospheric Modeling (SAM) with spectral bin microphysics. Despite the complexity of microphysical processes, several fundamental properties of Cu were found. First, despite the high variability of LWC and droplet concentration within clouds and between different clouds, the volume mean and effective radii per specific level vary only slightly. Second, the values of effective radius are close to those forming during adiabatic ascent of air parcels from cloud base. These findings allow for characterization of a cloud field by specific vertical profiles of effective radius and of mean liquid water content, which can be calculated using the theoretical profile of adiabatic liquid water content and the droplet concentration at cloud base. Using the results of these LESs, a simple parameterization of cloud-field-averaged vertical profiles of effective radius and of liquid water content is proposed for different aerosol and thermodynamic conditions. These profiles can be used for calculation of radiation properties of Cu fields in large-scale models. The role of adiabatic processes in the formation of microstructure of Cu is discussed. © 2019 American Meteorological Society."
"7006027075;6507506955;6508030754;7004864963;56429387500;6603569074;6603785227;7102866124;57189372185;6701562043;35276210200;36076994600;","Aircraft observations of the chemical composition and aging of aerosol in the Manaus urban plume during GoAmazon 2014/5",2018,"10.5194/acp-18-10773-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050870944&doi=10.5194%2facp-18-10773-2018&partnerID=40&md5=0c89a62c64826f7a448831aefeef9f3f","The Green Ocean Amazon (GoAmazon 2014/5) campaign, conducted from January 2014 to December 2015 in the vicinity of Manaus, Brazil, was designed to study the aerosol life cycle and aerosol-cloud interactions in both pristine and anthropogenically influenced conditions. As part of this campaign, the U.S. Department of Energy (DOE) Gulfstream 1 (G-1) research aircraft was deployed from 17 February to 25 March 2014 (wet season) and 6 September to 5 October 2014 (dry season) to investigate aerosol and cloud properties aloft. Here, we present results from the G-1 deployments focusing on measurements of the aerosol chemical composition and secondary organic aerosol (SOA) formation and aging. In the first portion of the paper, we provide an overview of the data and compare and contrast the data from the wet and dry season. Organic aerosol (OA) dominates the deploymentaveraged chemical composition, comprising 80%of the nonrefractory PM1 aerosol mass, with sulfate comprising 14 %, nitrate 2 %, and ammonium 4 %. This product distribution was unchanged between seasons, despite the fact that total aerosol loading was significantly higher in the dry season and that regional and local biomass burning was a significant source of OA mass in the dry, but not wet, season. However, the OA was more oxidized in the dry season, with the median of the mean carbon oxidation state increasing from -0:45 in the wet season to -0:02 in the dry season. In the second portion of the paper, we discuss the evolution of the Manaus plume, focusing on 13 March 2014, one of the exemplary days in the wet season. On this flight, we observe a clear increase in OA concentrations in the Manaus plume relative to the background. As the plume is transported downwind and ages, we observe dynamic changes in the OA. The mean carbon oxidation state of the OA increases from -0:6 to -0:45 during the 4-5 h of photochemical aging. Hydrocarbon-like organic aerosol (HOA) mass is lost, with ΔHOA/ΔCO values decreasing from 17.6 μgm-3 ppmv-1 over Manaus to 10.6 μgm-3 ppmv-1 95 km downwind. Loss of HOA is balanced out by formation of oxygenated organic aerosol (OOA), with ΔOOA/ΔCO increasing from 9.2 to 23.1 μgm-3 ppmv-1. Because hydrocarbon-like organic aerosol (HOA) loss is balanced by OOA formation, we observe little change in the net Δorg/ΔCO values; Δorg/ΔCO averages 31 μgm-3 ppmv-1 and does not increase with aging. Analysis of the Manaus plume evolution using data from two additional flights in the wet season showed similar trends in Δorg/ΔCO to the 13 March flight; Δorg/ΔCO values averaged 34 μgm-3 ppmv-1 and showed little change over 4-6.5 h of aging. Our observation of constant Δorg/ΔCO are in contrast to literature studies of the outflow of several North American cities, which report significant increases in Δorg/ΔCO for the first day of plume aging. These observations suggest that SOA formation in the Manaus plume occurs, at least in part, by a different mechanism than observed in urban outflow plumes in most other literature studies. Constant Δorg/ΔCO with plume aging has been observed in many biomass burning plumes, but we are unaware of reports of fresh urban emissions aging in this manner. These observations show that urban pollution emitted from Manaus in the wet season forms less particulate downwind as it ages than urban pollution emitted from North American cities. © Author(s) 2018."
"7006550762;35561911800;16304488000;36705143500;56203249800;57202924942;54981446800;","Multicentury Instability of the Atlantic Meridional Circulation in Rapid Warming Simulations With GISS ModelE2",2018,"10.1029/2017JD027149","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049856487&doi=10.1029%2f2017JD027149&partnerID=40&md5=8e615a53d3ddb8d7fd0b0ffda29dd80c","In multimillennial global warming simulations with the GISS-E2-R climate model, we observe multicentennial shutdowns with restoration and fast overshooting in North Atlantic Deep Water production despite the absence of exogenous freshwater input. AMOC (Atlantic Meridional Overturning Circulation) cessation is associated with a sea surface salinity reduction, initiated by increases in precipitation over evaporation as the climate warms. These multicentury shutdowns are the direct result of cooling in the North Atlantic associated with an aerosol indirect effect on cloud cover. The local cooling reduces evaporation within the North Atlantic, while warming elsewhere provides moisture to maintain nearly unperturbed precipitation in this region. As global warming continues, warm temperature (low density) anomalies spread northward at depth in the North Atlantic eventually destabilizing the water column, even though precipitation input at the surface is initially unchanged. Internal ocean freshwater transports do not play an important role in initiating this behavior, as assumed by some standard metrics of AMOC stability. The importance of the aerosol indirect effect in these runs is due to its role in strengthening the sea surface temperature-evaporation feedback; this suggests a renewed focus on surface flux observations to help assess overturning stability. The length of the AMOC reduction, and its rapid recovery, may be relevant to the onset and end of the Younger Dryas, which occurred within a warming climate during the last deglaciation. ©2018. American Geophysical Union. All Rights Reserved. This article has been contributed to by US Government employees and their work is in the public domain in the USA."
"57195281036;7202516876;","The effect of ice nuclei efficiency on Arctic mixed-phase clouds from large-eddy simulations",2017,"10.1175/JAS-D-17-0112.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040370189&doi=10.1175%2fJAS-D-17-0112.1&partnerID=40&md5=76eda03cb6d3553234bddd960806e62d","The effects of ice nuclei (IN) efficiency on the persistent ice formation in Arctic mixed-phase clouds (AMCs) are investigated using a large-eddy simulation model, coupled to a bin microphysics scheme with a prognostic IN formulation. In the three cases where the IN efficiency is high, ice formation and IN depletion are fast. When the IN concentration is 1 and 10 g-1, IN are completely depleted and the cloud becomes purely liquid phase before the end of the 24-h simulation. When the IN concentration is 100 g-1, the IN supply is sufficient but the liquid water is completely consumed so that the cloud dissipates quickly. In the three cases when the IN efficiency is low, ice formation is negligible in the first several hours but becomes significant as the temperature is decreased through longwave cooling. Before the end of the simulation, the cloud is in mixed phase when the IN concentration is 1 and 10 g-1 but dissipates when the IN concentration is 100 g-1. In the case where two types of IN are considered, ice formation persists throughout the simulation. Analysis shows that as the more efficient IN are continuously removed through ice formation, the less efficient IN gradually nucleate more ice crystals because the longwave cooling decreases the cloud temperature. This mechanism is further illustrated with a simple model. These results indicate that a spectrum of IN efficiency is necessary to maintain the persistent ice formation in AMCs. © 2017 American Meteorological Society."
"22834248200;57195257572;7006377579;7006235542;7201787800;56983034700;55581504800;8055301200;6701802669;8581789300;34871751300;12753270700;","Real-time detection of airborne fluorescent bioparticles in Antarctica",2017,"10.5194/acp-17-14291-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85033232327&doi=10.5194%2facp-17-14291-2017&partnerID=40&md5=f4fd2a239f65d056f5e2aad1da641114","We demonstrate, for the first time, continuous real-time observations of airborne bio-fluorescent aerosols recorded at the British Antarctic Survey's Halley VI Research Station, located on the Brunt Ice Shelf close to the Weddell Sea coast (lat 75°34′59′′S, long 26°10′0′′W) during Antarctic summer, 2015. As part of the NERC MAC (Microphysics of Antarctic Clouds) aircraft aerosol cloud interaction project, observations with a real-time ultraviolet-light-induced fluorescence (UV-LIF) spectrometer were conducted to quantify airborne biological containing particle concentrations along with dust particles as a function of wind speed and direction over a 3-week period. <br><br> Significant, intermittent enhancements of both non- and bio-fluorescent particles were observed to varying degrees in very specific wind directions and during strong wind events. Analysis of the particle UV-induced emission spectra, particle sizes and shapes recorded during these events suggest the majority of particles were likely a subset of dust with weak fluorescence emission responses. A minor fraction, however, were likely primary biological particles that were very strongly fluorescent, with a subset identified as likely being pollen based on comparison with laboratory data obtained using the same instrument. <br><br> A strong correlation of bio-fluorescent particles with wind speed was observed in some, but not all, periods. Interestingly, the fraction of fluorescent particles to total particle concentration also increased significantly with wind speed during these events. The enhancement in concentrations of these particles could be interpreted as due to resuspension from the local ice surface but more likely due to emissions from distal sources within Antarctica as well as intercontinental transport. Likely distal sources identified by back trajectory analyses and dispersion modelling were the coastal ice margin zones in Halley Bay consisting of bird colonies with likely associated high bacterial activity together with contributions from exposed ice margin bacterial colonies but also long-range transport from the southern coasts of Argentina and Chile. Dispersion modelling also demonstrated emissions from shipping lanes, and therefore marine anthropogenic sources cannot be ruled out. Average total concentrations of total fluorescent aerosols were found to be 1.9±2.6L-1 over a 3-week period crossing over from November into December, but peak concentrations during intermittent enhancement events could be up to several tens per litre. While this short pilot study is not intended to be generally representative of Antarctic aerosol, it demonstrates the usefulness of the UV-LIF measurement technique for quantification of airborne bioaerosol concentrations and to understand their dispersion. The potential importance for microbial colonisation of Antarctica is highlighted. © Author(s) 2017."
"23095483400;57196436816;15840467900;57203053317;","Unveiling aerosol-cloud interactions - Part 2: Minimising the effects of aerosol swelling and wet scavenging in ECHAM6-HAM2 for comparison to satellite data",2017,"10.5194/acp-17-13165-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85033227771&doi=10.5194%2facp-17-13165-2017&partnerID=40&md5=dd65b35c08abc9b25604112b054c4042","Aerosol-cloud interactions (ACIs) are uncertain and the estimates of the ACI effective radiative forcing (ERFaci) magnitude show a large variability. Within the Aerosol-cci project the susceptibility of cloud properties to changes in aerosol properties is derived from the high-resolution AATSR (Advanced Along-Track Scanning Radiometer) data set using the Cloud-Aerosol Pairing Algorithm (CAPA) (as described in our companion paper) and compared to susceptibilities from the global aerosol climate model ECHAM6-HAM2 and MODIS-CERES (Moderate Resolution Imaging Spectroradiometer - Clouds and the Earth's Radiant Energy System) data. For ECHAM6-HAM2 the dry aerosol is analysed to mimic the effect of CAPA. Furthermore the analysis is done for different environmental regimes. <br></br> The aerosol-liquid water path relationship in ECHAM6-HAM2 is systematically stronger than in AATSR-CAPA data and cannot be explained by an overestimation of autoconversion when using diagnostic precipitation but rather by aerosol swelling in regions where humidity is high and clouds are present. When aerosol water is removed from the analysis in ECHAM6-HAM2 the strength of the susceptibilities of liquid water path, cloud droplet number concentration and cloud albedo as well as ERFaci agree much better with those of AATSR-CAPA or MODIS-CERES. When comparing satellite-derived to model-derived susceptibilities, this study finds it more appropriate to use dry aerosol in the computation of model susceptibilities. <br></br> We further find that the statistical relationships inferred from different satellite sensors (AATSR-CAPA vs. MODIS-CERES) as well as from ECHAM6-HAM2 are not always of the same sign for the tested environmental conditions. In particular the susceptibility of the liquid water path is negative in non-raining scenes for MODIS-CERES but positive for AATSR-CAPA and ECHAM6-HAM2. Feedback processes like cloud-top entrainment that are missing or not well represented in the model are therefore not well constrained by satellite observations. <br></br> In addition to aerosol swelling, wet scavenging and aerosol processing have an impact on liquid water path, cloud albedo and cloud droplet number susceptibilities. Aerosol processing leads to negative liquid water path susceptibilities to changes in aerosol index (AI) in ECHAM6-HAM2, likely due to aerosol-size changes by aerosol processing. <br></br> Our results indicate that for statistical analysis of aerosol-cloud interactions the unwanted effects of aerosol swelling, wet scavenging and aerosol processing need to be minimised when computing susceptibilities of cloud variables to changes in aerosol."
"56735478500;55628589750;56531367400;6701410329;57192064467;","On the Influence of Air Mass Origin on Low-Cloud Properties in the Southeast Atlantic",2017,"10.1002/2017JD027184","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85038015359&doi=10.1002%2f2017JD027184&partnerID=40&md5=506612bd1ff7e8d232ac23669276311e","This study investigates the impact of air mass origin and dynamics on cloud property changes in the Southeast Atlantic (SEA) during the biomass burning season. The understanding of clouds and their determinants at different scales is important for constraining the Earth's radiative budget and thus prominent in climate system research. In this study, the thermodynamically stable SEA stratocumulus cover is observed not only as the result of local environmental conditions but also as connected to large-scale meteorology by the often neglected but important role of spatial origins of air masses entering this region. In order to assess to what extent cloud properties are impacted by aerosol concentration, air mass history, and meteorology, a Hybrid Single-Particle Lagrangian Integrated Trajectory cluster analysis is conducted linking satellite observations of cloud properties (Spinning-Enhanced Visible and Infrared Imager), information on aerosol species (Monitoring Atmospheric Composition and Climate), and meteorological context (ERA-Interim reanalysis) to air mass clusters. It is found that a characteristic pattern of air mass origins connected to distinct synoptical conditions leads to marked cloud property changes in the southern part of the study area. Long-distance air masses are related to midlatitude weather disturbances that affect the cloud microphysics, especially in the southwestern subdomain of the study area. Changes in cloud effective radius are consistent with a boundary layer deepening and changes in lower tropospheric stability (LTS). In the southeastern subdomain cloud cover is controlled by a generally higher LTS, while air mass origin plays a minor role. This study leads to a better understanding of the dynamical drivers behind observed stratocumulus cloud properties in the SEA and frames potentially interesting conditions for aerosol-cloud interactions. ©2017. American Geophysical Union. All Rights Reserved."
"8067118800;7202899330;6701752471;","Significance of aerosol radiative effect in energy balance control on global precipitation change",2017,"10.1002/asl.780","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85031754550&doi=10.1002%2fasl.780&partnerID=40&md5=83f6a5ec14076631af25c90e566f2650","Historical changes of global precipitation in the 20th century simulated by a climate model are investigated. The results simulated with alternate configurations of cloud microphysics are analyzed in the context of energy balance controls on global precipitation, where the latent heat changes associated with the precipitation change is nearly balanced with changes to atmospheric radiative cooling. The atmospheric radiative cooling is dominated by its clear-sky component, which is found to correlate with changes to both column water vapor and aerosol optical depth (AOD). The water vapor-dependent component of the clear-sky radiative cooling is then found to scale with global temperature change through the Clausius–Clapeyron relationship. This component results in a tendency of global precipitation increase with increasing temperature at a rate of approximately 2%K−1. Another component of the clear-sky radiative cooling, which is well correlated with changes to AOD, is also found to vary in magnitude among different scenarios with alternate configurations of cloud microphysics that controls the precipitation efficiency, a major factor influencing the aerosol scavenging process that can lead to different aerosol loadings. These results propose how different characteristics of cloud microphysics can cause different aerosol loadings that in turn perturb global energy balance to significantly change global precipitation. This implies a possible coupling of aerosol–cloud interaction with aerosol–radiation interaction in the context of global energy balance. © 2017 The Authors. Atmospheric Science Letters published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"57193846713;22133756600;55719290500;7403354324;56421304000;57219896610;7103333752;55713905400;","Aerosol effects on the development of cumulus clouds over the Tibetan Plateau",2017,"10.5194/acp-17-7423-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021082110&doi=10.5194%2facp-17-7423-2017&partnerID=40&md5=7d8ef78a3082a01e9bedf1e32ad5288d","The aerosol-cloud interaction over the Tibetan Plateau has been investigated using a cloud-resolving weather research and forecasting model with a two-moment bulk microphysical scheme including aerosol effects on cloud condensation nuclei and ice nuclei. Two types of cumulus clouds with a similar convective available potential energy, occurring over the Tibetan Plateau (Cu-TP) and North China Plain (Cu-NCP) in August 2014, are simulated to explore the response of convective clouds to aerosols. A set of aerosol profiles is used in the simulations, with the surface aerosol number concentration varying from 20 to 9000cm-3 and the sulfate mass concentration varying from 0.02 to 9.0μgcm-3. Increasing aerosol concentrations generally enhances the cloud core updraft and maximum updraft, intensifying convections in Cu-TP and Cu-NCP. However, the core updraft is much stronger in Cu-TP than Cu-NCP, because of the early occurrence of the glaciation process in Cu-TP that is triggered at an elevation above 4000m. The precipitation increases steadily with aerosol concentrations in Cu-NCP, caused by the suppression of the warm rain but occurrence of efficient mix-phased precipitation due to the reduced cloud droplet size. The precipitation in Cu-TP also increases with aerosol concentrations, but the precipitation enhancement is not substantial compared to that in Cu-NCP with high aerosol concentrations. The aerosol-induced intensification of convections in Cu-TP not only facilitates the precipitation but also transports more ice-phase hydrometeors into the upper troposphere to decrease the precipitation efficiency. Considering the very clean atmosphere over the Tibetan Plateau, elevated aerosol concentrations can remarkably enhance convections due to its specific topography, which not only warms the middle troposphere to influence the Asian summer monsoon but also delivers hydrometeors into the upper troposphere to allow more water vapor to travel into the lower stratosphere."
"56754613500;55705948900;14019100300;55709174800;57191034805;57188699861;7202041928;","Potential impacts of urban land expansion on Asian airborne pollutant outflows",2017,"10.1002/2016JD025564","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027693481&doi=10.1002%2f2016JD025564&partnerID=40&md5=c25c190dd75de0d6c7f400436fd2a17b","Eastern part of China (EPC) has experienced rapid urbanization during the past few decades. Here we investigate the impacts of urban land expansion over EPC on the export of Asian pollutants to the western Pacific during January, April, July, and October of 2009 using the Weather Research and Forecasting model coupled to Chemistry (WRF/Chem) and a single-layer urban canopy scheme. Over urbanizing areas, increases in the urban land fraction result in a linearly enhanced uplift of surface primary pollutants to higher altitudes. We further examine how this local effect would change outflows of Asian pollutants to the western Pacific using the tagged black carbon (BC) and carbon monoxide (CO) tracers emitted from EPC (denoted by BCt and COt, respectively). Overall, a 0.1 increase in the fraction of land area that is urban over EPC would linearly (R2 = 0.70-0.96) increase the mean tropospheric eastward export of BCt and COt across meridional planes (i.e., 135°E and 150°E) by 4-40% and 1-6% in different months, respectively. The relative perturbation in exporting efficiency generally maximizes during July while minimizes during April. The urbanization-export relationship is largely driven by the elevation effect and is also impacted by urbanization-forced changes in zonal winds. The spatial pattern of the response of BCt over the downwind Pacific differs from that of COt mainly due to aerosol-cloud interactions. Our findings demonstrate that extensive urban land expansion could substantially impact climate and air quality from a local scale to a regional scale, especially for shorter-lived air pollutants such as BC and other aerosols. © 2017. American Geophysical Union. All Rights Reserved."
"57203053317;","Why does knowledge of past aerosol forcingmatter for future climate change?",2017,"10.1002/2017JD026962","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018913306&doi=10.1002%2f2017JD026962&partnerID=40&md5=424e874ba4037b96467ff15fe0e6a076","Aerosol particles scatter and absorb radiation and interact with cloud particles. The net aerosol forcing since preindustrial times is negative and has offset part of the greenhouse gas warming. It dominates the uncertainty of the overall anthropogenic forcing. This large uncertainty results from gaps in our knowledge on the underlying aerosol and cloud microphysical processes and aerosol-cloud interactions as well as their representation in global coupled aerosol-climate models. A recent paper by Nazarenko et al. (2017) illustrates how the anthropogenic aerosol forcing, especially the effective radiative forcing that includes aerosol-cloud and aerosol-radiation interactions, depends on climate feedbacks and on the employed aerosol model. © 2017. American Geophysical Union. All Rights Reserved."
"57190215031;14421017500;55567649200;35113492400;35849722200;18134578100;56300205000;","Parameterization and comparative evaluation of the CCN number concentration on Mt. Huang, China",2016,"10.1016/j.atmosres.2016.07.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84978427788&doi=10.1016%2fj.atmosres.2016.07.004&partnerID=40&md5=3b6e129d509578e0c61500028db484da","Quantifying regional CCN concentration is important for reliable estimations of aerosol indirect effects. Based on observational data of the number concentrations of total aerosol (NCN) and cloud condensation nuclei (NCCN), particle number size distribution (PNSD) and, size-resolved activation ratio (SRAR) obtained on Mt. Huang in southeast China from September 19 to October 11, 2012, seven parameterization schemes are used to calculate NCCN employing CCN spectra, bulk activation ratio, cut-off diameter and SRAR. The calculations and the observations are compared and analyzed at four supersaturations (S) from 0.109% to 0.67%. Results show that (1) the parameterization using the average cut-off diameter Dm, which is derived from the various measured PNSD and NCCN, provides the best estimate of NCCN, with coefficient of determination, R2 = 0.70–0.90 and NCCN,cal/NCCN,obs = 0.92–1.11, followed by the method of combining an average size-resolved activation curve with the PNSD, with R2 = 0.71–0.91 and NCCN,cal/NCCN,obs = 0.71–0.91; average D50 together with the PNSD also provides a rational scheme for NCCN prediction, with NCCN,cal/NCCN,obs = 0.86–0.94 and R2 = 0.70–0.89; (2) the method of parameterizing CCN spectra, though straightforward, has limits under polluted conditions. Reasonable NCCN estimate could only be obtained at high S (R2 ≥ 0.85 at S = 0.39% and 0.67%). (3) For the method employing the bulk activation ratio ARB(S), NCCN are substantially overestimated by using total mode-based ARB(S) (NCCN,cal/NCCN,obs = 0.94–1.39, R2 = 0.17–0.67), while applying ammonium sulfate-based ARB(S) yields improved CCN predictions (NCCN,cal/NCCN,obs = 0.91–1.11, R2 = 0.70–0.91). In southern China, when determining the parameterization schemes in climate models, it is first recommended to use the method of average cut-off diameter or SRAR, with the various measured PNSD to predict NCCN. Besides, the method using ammonium sulfate-based ARB(S) and parameterizing CCN spectra also provides a viable way to calculate NCCN. © 2016 Elsevier B.V."
"35494005000;57188733928;","Observational evidence for aerosol invigoration in shallow cumulus downstream of Mount Kilauea",2016,"10.1002/2016GL067830","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84979469566&doi=10.1002%2f2016GL067830&partnerID=40&md5=eedc045d2ae6ebdeb7e21121f3fe8ff0","Knowledge of how marine boundary layer (MBL) shallow cumulus clouds respond to changes in aerosol is central to understanding how MBL clouds modulate the climate system. Mount Kilauea on the island of Hawaii began erupting in 2008 injecting substantial SO2 into the marine boundary layer creating a unique natural laboratory. Examining data from approximately 600 passes of the A-Train downstream of Mount Kilauea over a 3 year period and separating data into aerosol optical depth quartiles, we find an unambiguous increase in marine boundary cloud top height and an increase in surface wind speed as aerosol increases while the radar reflectivity does not change substantially. We conclude that increased aerosols may have caused invigoration of the MBL clouds. Additionally, we find that increases in sub 1 km cloud fraction combined with increasing aerosol explain the increased visible reflectance suggesting that evidence for the so-called first aerosol indirect effect should be reexamined. ©2016. American Geophysical Union. All Rights Reserved."
"55875842200;7409080503;8839875600;","Response of marine boundary layer cloud properties to aerosol perturbations associated with meteorological conditions from the 19-month AMF-Azores campaign",2016,"10.1175/JAS-D-15-0364.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84994081865&doi=10.1175%2fJAS-D-15-0364.1&partnerID=40&md5=e3e5d7ef715fd196fdd3e5ff3e8ee8d7","This study investigates the response of marine boundary layer (MBL) cloud properties to aerosol loading by accounting for the contributions of large-scale dynamic and thermodynamic conditions and quantifies the first indirect effect (FIE). It makes use of 19-month measurements of aerosols, clouds, and meteorology acquired during theAtmospheric Radiation Measurement Mobile Facility field campaign over the Azores. Cloud droplet number concentrations Nc and cloud optical depth (COD) significantly increased with increasing aerosol number concentration Na. Cloud droplet effective radius (DER) significantly decreased with increasing Na. The correlations between cloud microphysical properties [Nc, liquid water path (LWP), and DER] and Na were stronger undermore stable conditions. The correlations between Nc, LWP, DER, and Na were stronger under ascendingmotion conditions, while the correlation between COD and Na was stronger under descending-motion conditions. The magnitude and corresponding uncertainty of the FIE (=[-∂ ln(DER)/∂ ln(Na)] at constant LWP) ranged from 0.060 ± 0.022 to 0.101 ± 0.006 depending on the different LWP values. Under more stable conditions, cloud-base heights were generally lower than those under less stable conditions. This enabled a more effective interaction with aerosols, resulting in a larger value for the FIE. However, the dependence of the response of cloud properties to aerosol perturbations on stability varied according to whether ground- or satellite-based DER retrievals were used. The magnitude of the FIE had a larger variation with changing LWP under ascending-motion conditions and tended to be higher under ascending-motion conditions for clouds with low LWP and under descending-motion conditions for clouds with highLWP.Acontrasting dependence of FIE on atmospheric stability estimated fromthe surface and satellite cloud properties retrievals reported in this study underscores the importance of assessing all-level properties of clouds in aerosol-cloud interaction studies. © 2016 American Meteorological Society."
"56999327800;6603631763;12801836100;","Climatology analysis of aerosol effect on marine water cloud from long-term satellite climate data records",2016,"10.3390/rs8040300","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84971602989&doi=10.3390%2frs8040300&partnerID=40&md5=8c7d9f41f0dfbfd8332fa8ccfc6b34bb","Satellite aerosol and cloud climate data records (CDRs) have been used successfully to study the aerosol indirect effect (AIE). Data from the Advanced Very High Resolution Radiometer (AVHRR) now span more than 30 years and allow these studies to be conducted from a climatology perspective. In this paper, AVHRR data are used to study the AIE on water clouds over the global oceans. Correlation analysis between aerosol optical thickness (AOT) and cloud parameters, including cloud droplet effective radius (CDER), cloud optical depth (COD), cloud water path (CWP), and cloud cover fraction (CCF), is performed. For the first time from satellite observations, the long-term trend in AIE over the global oceans is also examined. Three regimes have been identified: (1) AOT < 0.08, where CDER increases with AOT; (2) 0.08 < AOT < 0.3, where CDER generally decreases when AOT increases; and (3) AOT > 0.3, where CDER first increases with AOT and then levels off. AIE is easy to manifest in the CDER reduction in the second regime (named Regime 2), which is identified as the AIE sensitive/effective regime. The AIE manifested in the consistent changes of all four cloud variables (CDER, COD, CWP, and CCF) together is located only in limited areas and with evident seasonal variations. The long-term trend of CDER changes due to the AIE of AOT changes is detected and falls into three scenarios: Evident CDER decreasing (increasing) with significant AOT increasing (decreasing) and evident CDER decreasing with limited AOT increasing but AOT values fall in the AIE sensitive Regime 2. © 2016 by the authors."
"24485369800;57193419761;56746839400;57207403865;57203714946;56395875900;56643794500;55074722200;14032147800;7404331038;57211569167;57188827110;36441407000;","Modelling the effect of aerosol feedbacks on the regional meteorology factors over China",2015,"10.4209/aaqr.2014.11.0272","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938347850&doi=10.4209%2faaqr.2014.11.0272&partnerID=40&md5=cdd490a1c17050b0520579ba19a03beb","The fully coupled online air quality model WRF/chem was used to investigate the aerosol-radiation interaction and aerosol-cloud interaction on the regional meteorological factors over China in 2006.The aerosol-radiation interaction and aerosol-cloud interaction of aerosols influence the various regional meteorological factors in the worst aerosol-polluted regions of China. Domain-wide monthly-mean over all day and night hours incoming solar radiation decreased by –11.03 W/m2, –9.84 W/m2, –5.84 W/m2 and –12.37 W/m2; temperature at 2 meters (T2) decreased by –0.22°C, –0.12°C, –0.06°C and –0.24°C; Planetary boundary layer (PBL) height decreased by –16.44 m, –15.90 m, –5.48 m and –31.59 m in January, April, July and October, respectively. The values of the monthly-mean incoming solar radiation, T2 and PBL height had greater decreases in east China. Due to aerosol feedbacks, a slight increase of the monthly-mean precipitation occurred in southern and south-eastern China. The aerosol-radiation interaction and aerosol-cloud interaction of aerosols were compared for the United States (U.S.) continent, Europe, India and this study. Due to the higher aerosol load in China, the monthly-mean incoming solar radiation, T2 and PBL height exhibited greater decreases in China than in the U.S. continent and in Europe. Aerosol extinction was the dominant effect on the incoming solar radiation for either cloudless or cloudy weather conditions in China, but aerosol extinction was only apparent during cloudless weather in Europe. In India, the incoming solar radiation decreased by –20 W/m2 or more in the most aerosol polluted area, which is close to the value of decrease determined in China. © Taiwan Association for Aerosol Research."
"56735478500;55628589750;","Where Aerosols become clouds-potential for global analysis based on CALIPSO data",2015,"10.3390/rs70404178","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937819347&doi=10.3390%2frs70404178&partnerID=40&md5=bc4000e2160b9d7dc595cf401e8d0b7e","This study evaluates the potential to determine the global distribution of hydrated aerosols based on Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data products. Knowledge of hydrated aerosol global distribution is of high relevance in the study of the radiative impact of aerosol-cloud interactions on Earth's climate. The cloud-aerosol discrimination (CAD) score of the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) instrument on the CALIPSO satellite separates aerosols and clouds according to the probability density functions (PDFs) of attenuated backscatter, total color ratio, volume depolarization ratio, altitude and latitude. The pixels that CAD fails to identify as either cloud or aerosol are used here to pinpoint the occurrence of hydrated aerosols and to globally quantify their relative frequency using data of August from 2006 to 2013. Atmospheric features in this no-confidence range mostly match with aerosol PDFs and imply an early hydration state of aerosols. Their strong occurrence during August above the South-East Atlantic and below an altitude of 4 km coincides with the biomass burning season in southern Africa and South America. © 2015 by the authors."
"27067996900;6603796496;8720897100;34868441100;7004935190;35085069400;7006712143;7007039218;6507755223;8705440100;","The effect of local sources on particle size and chemical composition and their role in aerosol-cloud interactions at Puijo measurement station",2014,"10.5194/acp-14-6021-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902578846&doi=10.5194%2facp-14-6021-2014&partnerID=40&md5=72501370901c62094d70d0999cb0f800","Interactions between aerosols and liquid water clouds were studied during autumns 2010-2011 at a semiurban measurement station on Puijo tower in Kuopio, Finland. Cloud interstitial and total aerosol size distributions, particle chemical composition and hygroscopicity and cloud droplet size distribution were measured, with a focus on comparing clean air masses with those affected by local sources. On average, the polluted air contained more particles than the clean air masses, and generally the concentrations decreased during cloud events. Cloud processing was found to take place, especially in the clean air masses, and to a lesser extent in the polluted air. Some, mostly minor, differences in the average particle chemical composition between the air masses were observed. The average size and number concentration of activating particles were quite similar for both air masses, producing average droplet populations with only minor distinctions. As a case study, a long cloud event was analyzed in detail, with a special focus on the emissions from local sources, including a paper mill and a heating plant. This revealed larger variations in particle and cloud properties than the analysis of the whole data set. Clear differences in the total (between 214 and 2200 cm-3) and accumulation mode particle concentrations (between 62 and 169 cm-3) were observed. Particle chemical composition, especially the concentrations of organics (between 0.42 and 1.28 Î1/4g m-3) and sulfate (between 0.16 and 4.43 Î1/4g m-3), varied considerably. This affected the hygroscopic growth factor: for example, for 100 nm particles the range was from 1.21 to 1.45 at 90% relative humidity. Particularly, large particles, high hygroscopicities and elevated amounts of inorganics were linked with the pollutant plumes. Moreover, the particle hygroscopicity distributions in the polluted air were clearly bimodal, indicating externally mixed aerosol. The variable conditions also had an impact on cloud droplet formation, with the droplet concentration varying between 138 and 240 cm-3 and mean diameter between 9.2 and 12.4 μm. © Author(s) 2014."
"56611366900;7005862399;35113492400;","Comment on “cloud droplet spectral width relationship to ccn spectra and vertical velocity” by hudson et al",2014,"10.1002/2012JD019207","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896959028&doi=10.1002%2f2012JD019207&partnerID=40&md5=14c242d6560abe2acec1216bb06b1ceb",[No abstract available]
"25648525300;24537421700;","Aerosol-precipitation interactions over India: Review and future perspectives",2013,"10.1155/2013/649156","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893798743&doi=10.1155%2f2013%2f649156&partnerID=40&md5=7fcb733954e3efb29f38664858802116","Atmospheric aerosols can interact with clouds and influence the hydrological cycle by acting as cloud condensation nuclei. The current study reviews the results obtained on aerosol-precipitation interactions over India and the surrounding oceanic regions. An analysis of aerosol and cloud characteristics over the Arabian Sea, India, and the Bay of Bengal during summer monsoon in the last decade reveals large regional, intraseasonal, and interannual variations. Aerosol optical depth (AOD) and aerosol absorbing index (AAI) in 2002 (a drought year) are higher over India when compared to normal monsoon years. Cloud effective radius (CER) and cloud optical thickness exhibit a negative correlation with AOD over India, which agrees well with the indirect radiative effects of aerosols. Over Bay of Bengal CER is positively correlated with AOD suggesting an inverse aerosol indirect effect. In future, observatories to measure aerosol characteristics (amount, size, type, chemical composition, mixing, vertical and horizontal distributions), and cloud properties (number and size) over several locations in India, and intense observational campaigns involving aircraft and ships are crucial to unravel the quantitative impact that aerosols have on Indian monsoon. Satellite remote sensing of aerosol distribution, their chemical composition, microphysical properties of clouds, solar irradiance, and terrestrial longwave radiation is important. © 2013 S. Ramachandran and S. Kedia."
"54684023500;24329545900;55510783800;55817283000;","Estimates of aerosol indirect effect from terra MODIS over Republic of Korea",2013,"10.1155/2013/976813","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893651138&doi=10.1155%2f2013%2f976813&partnerID=40&md5=cc1defa658cdd8d65567414cba11efa1","Moderate resolution imaging spectroradiometer (MODIS) data have been analyzed over four different regions (Yellow sea, Korean inland, East Sea, and South Sea) in Republic of Korea to investigate the seasonal variability of aerosol-cloud properties and aerosol indirect effect during the past decade (2000-2009). Aerosol optical depth (AOD) was found to be consistently high during spring. Cloud ice radius (CIR) also showed higher values during spring, while an enhancement in cloud water radius (CWR) and fine mode fraction (FMF) was observed during summer. AOD and aerosol index (AI) were found to be higher during January to June. However, FMF and CWR showed enhancement during July to December. Aerosol indirect effect (AIE) in each year has been estimated and found to be showing positive and negative indirect effects. The AIE for fixed cloud ice path (CIP) showed positive indirect effect (Twomey effect) over Yellow sea, while the AIE for fixed cloud water path (CWP) showed a major negative indirect effect (anti-Twomey effect) over all regions. During Changma (summer monsoon) period, the AIE for both CIP and CWP showed dominant anti-Twomey effect in middle and low level clouds, indicating the growth of cloud droplet radius with changes in aerosols, enhancing the precipitation. © 2013 Woon-Seon Jung et al."
"24329133800;35608815200;","Aerosol-cloud-interaction variability induced by atmospheric brown clouds during the 2009 Indian summer monsoon drought",2013,"10.4209/aaqr.2012.11.0329","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880583838&doi=10.4209%2faaqr.2012.11.0329&partnerID=40&md5=908df3ce6b7a803088e6e943d1596eaf","Contrasting monsoons of 2008 and 2009 provided a test bed to enhance the understanding of the aerosol variability and aerosol-cloud interaction. Vertical aerosol profiles derived from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) are used to delineate the aerosol properties during the two contrasting Indian summer monsoons. We observed a 30-40% increase in the aerosol occurrence frequency (AOF) in lower altitudes (below 6 km) in 2009 and a 5-8% enhancement in AOF at higher altitudes in 2008. The cloud occurrence frequency also showed more deep convective clouds in 2008 (13-15%) than in 2009. Cloud Fraction, Aerosol Optical Depth and TRMM precipitation data sets have been also used to investigate the aerosol-cloud interaction. We define the microphysical effect as the increase in cloud fraction with increase in aerosols (CCN) and the radiative effect as the decrease of cloud fraction with increase in aerosol loading. We observe a stronger microphysical effect than the radiative effect in 2008 as compared to 2009. In 2009, atmospheric brown clouds were observed from March to September, which slowed down the microphysical effect and enhanced the radiative effect. This resulted in a 30% reduction in the total cloud fraction that may have reduced precipitation, and invigorated the drought conditions during 2009. © Taiwan Association for Aerosol Research."
"7004160106;22635081500;6603081424;22933265100;6701378450;35497573900;","Performance of McRAS-AC in the GEOS-5 AGCM: Aerosol-cloud-microphysics, precipitation, cloud radiative effects, and circulation",2013,"10.5194/gmd-6-57-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872699847&doi=10.5194%2fgmd-6-57-2013&partnerID=40&md5=ea72d0b4a783afb624b0c28fea753123","A revised version of the Microphysics of clouds with Relaxed Arakawa-Schubert and Aerosol-Cloud interaction scheme (McRAS-AC) including, among others, a new ice nucleation parameterization, is implemented in the GEOS-5 AGCM. Various fields from a 10-yr-long integration of the AGCM with McRAS-AC are compared with their counterparts from an integration of the baseline GEOS-5 AGCM, as well as satellite observations. Generally McRAS-AC simulations have smaller biases in cloud fields and cloud radiative effects over most of the regions of the Earth than the baseline GEOS-5 AGCM. Two systematic biases are identified in the McRAS-AC runs: one is underestimation of cloud particle numbers around 40 S-60 S, and one is overestimate of cloud water path during the Northern Hemisphere summer over the Gulf Stream and North Pacific. Sensitivity tests show that these biases potentially originate from biases in the aerosol input. The first bias is largely eliminated in a test run using 50% smaller radius of sea-salt aerosol particles, while the second bias is substantially reduced when interactive aerosol chemistry is turned on. The main weakness of McRAS-AC is the dearth of low-level marine stratus clouds, a probable outcome of lack of explicit dry-convection in the cloud scheme. Nevertheless, McRAS-AC largely simulates realistic clouds and their optical properties that can be improved further with better aerosol input. An assessment using the COSP simulator in a 1-yr integration provides additional perspectives for understanding cloud optical property differences between the baseline and McRAS-AC simulations and biases against satellite data. Overall, McRAS-AC physically couples aerosols, the microphysics and macrophysics of clouds, and their radiative effects and thereby has better potential to be a valuable tool for climate modeling research. © 2013 Author(s)."
"7201496259;55462312300;7401974644;7401936984;","Sensitivity of aerosol indirect effects to cloud nucleation and autoconversion parameterizations in short-range weather forecasts during the May 2003 aerosol IOP",2012,"10.1029/2012MS000161","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867723843&doi=10.1029%2f2012MS000161&partnerID=40&md5=ecfeb091b71c5708aa1656f036bca8d3","Aerosol-cloud interactions begin with the direct involvement of aerosols in cloud nucleation followed by its indirect contribution to the formation of precipitation through autoconversion. Since the treatments of cloud microphysics in climate models are highly parameterized, a thorough study is needed to examine the range of simulations associated with different parameterizations of aerosol-cloud interactions. Unlike previous studies focused on climate-mode simulations, our interest is in shortrange model response before the development of model bias and the compensation of multiple feedback mechanisms. In this study, we modified CAM4 to explore model sensitivity to treatments of cloud nucleation and autoconversion over the Atmospheric Radiation Measurement Southern Great Plains (SGP) facility during the May 2003 Aerosol Intensive Operations Period (IOP) under the Cloud-Associated Parameterizations Testbed framework. Simulated liquid water path and low cloud fraction were sensitive to the choice of parameterization; however, change of modeled precipitation was insignificant with varying parameterization in short-range (̃3 day) simulation. In general, simulated cloud properties were more sensitive to the treatment of autoconversion than nucleation. Calculations of sulfate indirect effects indicate that the change of shortwave fluxes from cloud lifetime effect is much more sensitive to cloud parameterizations than cloud albedo effect. Microphysical feedbacks complicate the local response of the climate system and can yield a positive 2nd indirect sulfate forcing that counters the expectation that increases in aerosol concentration decrease the shortwave fluxes. As a result, the calculated total sulfate indirect forcing over SGP varies widely ranging from 20.1 to 22.1 W m22 during the IOP. © 2012 by the American Geophysical Union."
"55344397300;7006306835;","Nonlinear climate response to regional brightening of tropical marine stratocumulus",2012,"10.1029/2012GL052064","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865404654&doi=10.1029%2f2012GL052064&partnerID=40&md5=178d9196511727789c44136402aa3400","To counteract global warming, there have been suggestions to increase the albedo of low-level marine clouds through the aerosol indirect effects by injecting them with sea salt. However, the full climate response to this geoengineering scheme is currently poorly understood. We simulate cloud seeding in a coupled mixed-layer ocean-atmosphere general circulation model in order to identify the specific physical mechanisms through which seeding could perturb the climate system's radiative balance, and cause temperature and precipitation changes. Seeding stratocumulus decks over three tropical maritime regions in the North Pacific, South Pacific and South Atlantic produces strong local reductions in solar absorption. Over half of the radiative cooling is due to direct scattering of solar radiation by the added sea salt aerosols, while the rest comes from enhancement of the local cloud albedo. The oceanic cooling due to the seeding over the southeastern equatorial Pacific induces a La Nia-like response, with tropical precipitation changes resembling La Nia anomalies and teleconnections occurring in the mid-latitude North Pacific and North America. Additionally, model runs in which only one of the three regions is seeded indicate nonlinearity in the climate response. We identify dynamical and thermodynamical constraints respectively on the temperature and hydrological cycle responses to cloud seeding, but the full response to such geoengineering remains poorly constrained. © 2012. American Geophysical Union. All Rights Reserved."
"35985515200;7102018821;56383477900;7101899854;","Satellite remote sensing of dust aerosol indirect effects on cloud formation over Eastern Asia",2012,"10.1080/01431161.2012.700135","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85014288950&doi=10.1080%2f01431161.2012.700135&partnerID=40&md5=700541bde995ddf376209a7f6c2f521f","The dust aerosol indirect effect of the first kind on ice and liquid water cloud formation has been investigated using available MODIS cloud and aerosol products on the basis of correlation analysis. The variability in the correlation between cloud parameters, including optical depth, effective particle size, cloud water path and cloud particle number concentration, and aerosol variables, including optical depth and number concentration, over Eastern Asia has been studied. Three MODIS scenes that contain a significant presence of local and transported dust and clouds have been selected for comprehensive analysis. For all cases studied, we demonstrate that there is a negative trend regarding the correlation between cloud particle size and aerosol optical depth, which is statistically significant. These results represent a strong evidence of dust and cloud interactions that are consistent with the hypothesis of the Twomey effect for clouds. © 2012, Taylor & Francis Group, LLC."
"7403364008;25953950400;","A method for forecasting cloud condensation nuclei using predictions of aerosol physical and chemical properties from WRF/Chem",2011,"10.1175/2011JAMC2644.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960388815&doi=10.1175%2f2011JAMC2644.1&partnerID=40&md5=85dc032e888f8ee1b1923069762b2ff4","Model investigations of aerosol-cloud interactions across spatial scales are necessary to advance basic understanding of aerosol impacts on climate and the hydrological cycle. Yet these interactions are complex, involving numerous physical and chemical processes. Models capable of combining aerosol dynamics and chemistry with detailed cloud microphysics are recent developments. In this study, predictions of aerosol characteristics from the Weather Research and Forecasting Model with Chemistry (WRF/Chem) are integrated into the Regional Atmospheric Modeling System microphysics package to form the basis of a coupled model that is capable of predicting the evolution of atmospheric aerosols from gas-phase emissions to droplet activation. The new integrated system is evaluated against measurements of cloud condensation nuclei (CCN) from a land-based field campaign and an aircraft-based field campaign in Colorado. The model results show the ability to capture vertical variations in CCN number concentration within an anthropogenic pollution plume. In a remote continental location the model-forecast CCN number concentration exhibits a positive bias that is attributable in part to an overprediction of the aerosol hygroscopicity that results from an underprediction in the organic aerosol mass fraction. In general, the new system for predicting CCN from forecast aerosol fields improves on the existing scheme in which aerosol quantities were user prescribed. © 2011 American Meteorological Society."
"7404544551;13406672500;","Investigation of aerosol-cloud interactions using a chemical transport model constrained by satellite observations",2010,"10.1111/j.1600-0889.2009.00444.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954419515&doi=10.1111%2fj.1600-0889.2009.00444.x&partnerID=40&md5=b5eac2746159d8e565a88efe8b5e0c3f","This study simulates optical depth of marine warm clouds for year 2001 based on interactively predicted aerosol concentrations with a global chemical transport model (CTM) driven by the ERA-40 re-analysis meteorological data. The simulated aerosol and cloud droplet number concentrations (CDNC) largely reproduce the variations between polluted and pristine marine environment as revealed by surface and aircraft measurements. By constraining cloud liquid water path (CLWP) with satellite microwave measurements, the simulated global and southern hemispheric aerosol optical depth (AOD) and cloud optical depth (COD) are well within 10% of the observed values. As a result of larger anthropogenic aerosol loadings over the northern oceans, the simulated CDNC and COD are, respectively, by 51 and 18% higher than those over the southern oceans, while the column-averaged droplet effective radius is 13% smaller. These simulated interhemispheric differences, while qualitatively consistent with satellite observations, are larger than the observations. Inclusion of drizzle effect improved the disparities but not entirely. The constrained CTM generally captures the seasonality in AOD and CLWP observations, and demonstrates that annual cycle of COD is dominated by CLWP. During winter monsoon the simulated and observed COD correlate more strongly with changes in AOD over the N. Indian Ocean. © 2009 The Authors Journal compilation © 2010 Blackwell Munksgaard."
"57212027576;57212023802;57212021393;56162305900;57212020453;57212020923;","Aerosol Indirect Effects on Warm Clouds in the Grid-Point Atmospheric Model of IAP LASG (GAMIL)",2010,"10.1080/16742834.2010.11446871","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876454305&doi=10.1080%2f16742834.2010.11446871&partnerID=40&md5=aec73bcaf5138f0c74e0d3b60fa8a309","Aerosol indirect effects on warm clouds are estimated in the Grid-point Atmospheric Model of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics (IAP LASG) (GAMIL) with a new two-moment cloud microphysics scheme using two different physically-based aerosol activation parameterizations: Abdul-Razzak and Ghan, and Nenes and Seinfeld. The annual global mean changes in shortwave cloud forcing from preindustrial times to present day (a measure of the aerosol indirect effects) estimated from these two parameterizations are remarkably similar: 0.76 W m-2 with the Abdul-Razzak and Ghan parameterization, and 0.78 W m-2 with the Nenes and Seinfeld parameterization. Physically-based parameterizations can provide robust representations of aerosol effects on droplet nucleation, meaning that aerosol activation is no longer the most un-certain factor in modeling aerosol indirect effects. © 2010, © Institute of Atmospheric Physics, Chinese Academy of Sciences."
"57208698992;7102604282;57210717445;7401936984;","Investigation of the first and second aerosol indirect effects using data from the May 2003 Intensive Operational Period at the Southern Great Plains",2007,"10.1029/2006JD007173","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35148868590&doi=10.1029%2f2006JD007173&partnerID=40&md5=31879485a81f0d0212d3f596be247275","The Active Tracer High-Resolution Atmospheric Model is used to examine the aerosol indirect effect (AIE) for a spring continental stratus cloud on the basis of data collected during the 17 May 2003 Aerosol Intensive Operation Period (AIOP) at the Atmospheric Radiation Measurement (ARM) Program Southern Great Plains site. Model results for our base case, which uses observed aerosol concentrations, agree reasonably well with the available observations, giving confidence that the basic model is reasonable. Sensitivity tests are performed to explore the response of the clouds to changes in the aerosol number concentration and surface fluxes. During the major part of the simulation, from 0630 through 1400 local standard time (LST), an increase in the aerosol number concentration (N<inf>a</inf>) results in a decrease of the mean cloud droplet size and an increase of the cloud liquid water path (LWP) until aerosol number concentration levels reach 1200 cm-3. Further increases in aerosol concentration do not increase the liquid water path because the depletion of cloud water by precipitation is negligible above this number concentration. After 1400 LST, the liquid water path decreases when aerosols increase as long as N<inf>a</inf> < 600 cm-3 and remains unchanged for higher aerosol concentrations. The decrease of LWP is associated with the evaporative cooling below cloud base which leads to more condensation of water vapor, a result that is consistent with afternoon satellite observations of the response of continental clouds to increases in droplet concentrations. A sensitivity test with a stronger surface latent flux increases both the cloud geometrical thickness and cloud water content. On the other hand, a sensitivity test with a stronger surface sensible heat flux leads to a higher cloud base and a shallower and drier cloud. The response of the cloud geometrical thickness to changes in surface sensible heat flux dominates that of the cloud water content. The cloud fraction is also reduced at the end of the simulation time period. Because the surface heat fluxes will likely change when aerosol and droplet number concentrations change, these sensitivity tests show that a fully coupled simulation with a land surface model will be needed to fully assess the response of the cloud to changing aerosol concentrations. Nevertheless, since the thermodynamic boundary layer profiles do not change significantly when aerosol concentrations are changed, our results for changing aerosol concentrations are qualitatively correct. Copyright 2007 by the American Geophysical Union."
"57210212520;7006306835;55476830600;57213600227;8953662800;6506340624;57211583321;","Contribution of local and remote anthropogenic aerosols to a record-breaking torrential rainfall event in Guangdong Province, China",2020,"10.5194/acp-20-223-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077872309&doi=10.5194%2facp-20-223-2020&partnerID=40&md5=5aca4ed1240db1c229a43d623a2afa0d","A torrential rainfall case, which happened in Guangdong Province during 14-16 December 2013, broke the historical rainfall record in the province in terms of duration, affected area, and accumulative precipitation. The influence of anthropogenic aerosols on this extreme rainfall event is examined using a coupled meteorology-chemistry-aerosol model. Up to 33.7&thinsp;mm precipitation enhancement in the estuary and near the coast is mainly attributed to aerosol-cloud interactions (ACI), whereas aerosol-radiation interaction partially offsets 14&thinsp;% of the precipitation increase. Our further analysis of changes in hydrometeors and latent heat sources suggests that the ACI effects on the intensification of precipitation can be divided into two stages: cold rain enhancement in the former stage followed by warm rain enhancement in the latter. Responses of precipitation to the changes in anthropogenic aerosol concentration from local (i.e., Guangdong Province) and remote (i.e., outside Guangdong Province) sources are also investigated through simulations with reduced aerosol emissions from either local or remote sources. Accumulated aerosol concentration from local sources aggregates mainly near the ground surface and dilutes quickly after the precipitation initiated. By contrast, the aerosols from remote emissions extend up to 8&thinsp;km above ground and last much longer before decreasing until peak rainfall begins, because aerosols are continuously transported by the strong northerly winds. The patterns of precipitation response to remote and local aerosol concentrations resemble each other. However, compared with local aerosols through warm rain enhancement, remote aerosols contribute more than twice the precipitation increase by intensifying both cold and warm rain, occupying a predominant role. A 10-time emission sensitivity test shows about 10 times the PM<span classCombining double low line""inline-formula"">2.5</span> concentration compared with the control run. Cold (warm) rain is drastically enhanced (suppressed) in the <span classCombining double low line""inline-formula"">10×</span> run. In response to <span classCombining double low line""inline-formula"">10×</span> aerosol emissions, the pattern of precipitation and cloud property changes resembles the differences between CTL and CLEAN, but with a much greater magnitude. The precipitation average over Guangdong decreases by 1.0&thinsp;mm in the <span classCombining double low line""inline-formula"">10×</span> run but increases by 1.4&thinsp;mm in the control run compared with the CLEAN run. We note that the precipitation increase is concentrated within a more narrowed downstream region of the aerosol source, whereas the precipitation decrease is more dispersed across the upstream region. This indicates that the excessive aerosols not<span idCombining double low line""page224""/> only suppress rainfall, but also change the spatial distribution of precipitation, increasing the rainfall range, thereby potentially exacerbating flood and drought elsewhere. This study highlights the importance of considering aerosols in meteorology to improve extreme weather forecasting. Furthermore, aerosols from remote emissions may outweigh those from local emissions in the convective invigoration effect. © 2020. This work is distributed under the Creative Commons Attribution 4.0 License."
"55806957000;6506340624;7003961970;13805883800;","Disentangling the influence of local and remote anthropogenic aerosols on South Asian monsoon daily rainfall characteristics",2019,"10.1007/s00382-018-4512-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055920087&doi=10.1007%2fs00382-018-4512-9&partnerID=40&md5=c897666a00beda5da595a9d8cb3572fe","Wet and dry periods within the South Asian summer monsoon season can have acute societal impacts. Recent studies have identified changes in daily rainfall characteristics of the monsoon, but the underlying causes are poorly understood. In particular, although the dominant role of anthropogenic aerosols in shaping historical changes in seasonal-mean monsoon rainfall has been documented, their influence on daily-scale rainfall remains unconstrained. Using an ensemble of single-forcing climate simulations, we find that anthropogenic aerosols have a stronger influence on late-twentieth century changes in the frequency of wet events, dry events and rainless days, compared with other climate forcings. We also investigate the role of aerosol-cloud interactions (“indirect effects”) in the total aerosol response, and the contribution of aerosols emitted from South Asia versus from remote sources. Based on additional simulations with the GFDL-CM3 climate model, we find that the simulated aerosol response over South Asia is largely associated with aerosol-indirect effects. In addition, local aerosols suppress wet-event frequency and enhance dry-event frequency over eastern-central India, where increases in aerosol loading are the largest. Remote aerosols cause a north–south dipole pattern of change in mean rainfall over India and fewer rainless days over western India. However, the overall spatial response of South Asian rainfall characteristics to total aerosol forcing is substantially influenced by the combined non-linear climate response to local and remote aerosols. Together, our results suggest that understanding the influence of different aerosol emissions trajectories on the regional climate dynamics is critical for effective climate-risk management in this populated, vulnerable region. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature."
"57119983700;57195681934;7003638602;6603174102;55850233200;7006593624;57191159699;6701845055;6701762451;","Laboratory study of the heterogeneous ice nucleation on black-carbon-containing aerosol",2019,"10.5194/acp-19-12175-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85073059629&doi=10.5194%2facp-19-12175-2019&partnerID=40&md5=b095760a1a36dfb09305084dd81787b6","Soot and black carbon (BC) particles are generated in the incomplete combustion of fossil fuels, biomass, and biofuels. These airborne particles affect air quality, human health, aerosol-cloud interactions, precipitation formation, and climate. At present, the climate effects of BC particles are not well understood. Their role in cloud formation is obscured by their chemical and physical variability and by the internal mixing states of these particles with other compounds. Ice nucleation in field studies is often difficult to interpret. Nonetheless, most field studies seem to suggest that BC particles are not efficient ice-nucleating particles (INPs). On the other hand, laboratory measurements show that in some cases, BC particles can be highly active INPs under certain conditions. By working with well-characterized BC particles, our aim is to systematically establish the factors that govern the ice nucleation activity of BC. The current study focuses on laboratory measurements of the effectiveness of BC-containing aerosol in the formation of ice crystals in temperature and ice supersaturation conditions relevant to cirrus clouds. We examine ice nucleation on BC particles under watersubsaturated cirrus cloud conditions, commonly understood as deposition-mode ice nucleation. We study a series of wellcharacterized commercial carbon black particles with varying morphologies and surface chemistries as well as ethylene flame-generated combustion soot. The carbon black particles used in this study are proxies for atmospherically relevant BC aerosols. These samples were characterized by electron microscopy, mass spectrometry, and optical scattering measurements. Ice nucleation activity was systematically examined in temperature and saturation conditions in the ranges of 217 ≤ T ≤ 235 K and 1:0 ≤ Sice ≤ 1:5 and 0:59 ≤ Swater ≤ 0:98, respectively, using a SPectrometer for Ice Nuclei (SPIN) instrument, which is a continuous-flow diffusion chamber coupled with instrumentation to measure light scattering and polarization. To study the effect of coatings on INPs, the BC-containing particles were coated with organic acids found in the atmosphere, namely stearic acid, cis-pinonic acid, and oxalic acid. The results show significant variations in ice nucleation activity as a function of size, morphology, and surface chemistry of the BC particles. The measured ice nucleation activity dependencies on temperature, supersaturation conditions, and the physicochemical properties of the BC particles are consistent with an ice nucleation mechanism of pore condensation followed by freezing. Coatings and surface oxidation modify the initial formation efficiency of pristine ice crystals on BC-containing aerosol. Depending on the BC mate rial and the coating, both inhibition and enhancement in INP activity were observed. Our measurements at low temperatures complement published data and highlight the capability of some BC particles to nucleate ice under low ice supersaturation conditions. These results are expected to help refine theories relating to soot INP activation in the atmosphere. © 2019 Author(s)."
"8633783900;13905919900;7407104838;53880473700;55427995800;7004469744;","Comments on ""Rethinking the lower bound on aerosol radiative forcing""",2018,"10.1175/JCLI-D-17-0369.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056137084&doi=10.1175%2fJCLI-D-17-0369.1&partnerID=40&md5=315f0fd0242e62d25370c9f72c0c69f3",[No abstract available]
"56086444100;36458602300;6603431534;6603196991;","Revisiting Liquid Water Content Retrievals in Warm Stratified Clouds: The Modified Frisch",2018,"10.1029/2018GL079845","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053465381&doi=10.1029%2f2018GL079845&partnerID=40&md5=b0dc36971f22173b349d1e32037a67c8","Accurate observations of liquid water content (LWC) in warm stratiform clouds are important for quantifying their radiative and hydrological effects and for studying aerosol-cloud interactions. Retrieving LWC from radar reflectivity under drizzling or nondrizzling conditions has been investigated for several decades by the cloud remote sensing community. However, no physically plausible framework exists to address the biases introduced by drizzle on existing retrieval techniques. We present the modified Frisch retrieval (ModFrisch), which combines radar and microwave radiometer measurements to retrieve LWC in both nondrizzling and drizzling conditions. It is shown, using a 1-D steady state microphysical model and a radar simulator, that the uncertainty of ModFrisch is up to four times smaller than the uncertainty of similar retrievals under drizzling conditions, enabling LWC profiling with an accuracy of 20%. The performance of the ModFrisch technique is evaluated using 1 year of observations. ©2018. The Authors."
"50562006500;24448185400;24278842600;57203142421;57189368623;23479194900;56879845700;8528352100;55683878900;7006495018;57201792799;57192639459;7102866124;36930720800;57195553709;55730602600;57192173802;56097800400;57190209035;7004864963;55502994400;55942083800;35461763400;35774441900;","African volcanic emissions influencing atmospheric aerosols over the Amazon rain forest",2018,"10.5194/acp-18-10391-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050661319&doi=10.5194%2facp-18-10391-2018&partnerID=40&md5=10eeeeac849bb917d1d28d5198f871db","The long-range transport (LRT) of trace gases and aerosol particles plays an important role for the composition of the Amazonian rain forest atmosphere. Sulfate aerosols originate to a substantial extent from LRT sources and play an important role in the Amazonian atmosphere as strongly light-scattering particles and effective cloud condensation nuclei. The transatlantic transport of volcanic sulfur emissions from Africa has been considered as a source of particulate sulfate in the Amazon; however, direct observations have been lacking so far. This study provides observational evidence for the influence of emissions from the Nyamuragira-Nyiragongo volcanoes in Africa on Amazonian aerosol properties and atmospheric composition during September 2014. Comprehensive ground-based and airborne aerosol measurements together with satellite observations are used to investigate the volcanic event. Under the volcanic influence, hourly mean sulfate mass concentrations in the submicron size range reached up to 3.6&thinsp;μg&thinsp;mĝ'3 at the Amazon Tall Tower Observatory, the highest value ever reported in the Amazon region. The substantial sulfate injection increased the aerosol hygroscopicity with <i>i°</i> values up to 0.36, thus altering aerosol-cloud interactions over the rain forest. Airborne measurements and satellite data indicate that the transatlantic transport of volcanogenic aerosols occurred in two major volcanic plumes with a sulfate-enhanced layer between 4 and 5&thinsp;km of altitude. This study demonstrates how African aerosol sources, such as volcanic sulfur emissions, can substantially affect the aerosol cycling and atmospheric processes in Amazonia. © Author(s) 2018."
"40461229800;57202019283;7006173230;43461316300;6603237119;43461301000;21646972800;57199013699;24308208100;","HOVERCAT: A novel aerial system for evaluation of aerosol-cloud interactions",2018,"10.5194/amt-11-3969-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049724892&doi=10.5194%2famt-11-3969-2018&partnerID=40&md5=319e0670ae91e276beee65c3df4796e6","Aerosols have a profound impact on cloud microphysics through their ability to serve as ice nucleating particles (INPs). As a result, cloud radiative properties and precipitation processes can be modulated by such aerosol-cloud interactions. However, one of the largest uncertainties associated with atmospheric processes is the indirect effect of aerosols on clouds. The need for more advanced observations of INPs in the atmospheric vertical profile is apparent, yet most ice nucleation measurements are conducted on the ground or during infrequent and intensive airborne field campaigns. Here, we describe a novel measurement platform that is less expensive and smaller (&lt;5 kg) when compared to traditional aircraft and tethered balloon platforms and that can be used for evaluating two modes of ice nucleation (i.e., immersion and deposition). HOVERCAT (Honing On VERtical Cloud and Aerosol properTies) flew during a pilot study in Colorado, USA, up to 2.6 km above mean sea level (1.1 km above ground level) and consists of an aerosol module that includes an optical particle counter for size distributions (0.38-17 μm in diameter) and a new sampler that collects up to 10 filter samples for offline ice nucleation and aerosol analyses on a launched balloon platform. During the May 2017 test flight, total particle concentrations were highest closest to the ground (up to 50 cm-3 at &lt; 50 m above ground level) and up to 2 in 102 particles were ice nucleation active in the immersion mode (at-23 °C). The warmest temperature immersion and deposition mode INPs (observed up to-6 and-40.4 °C, respectively) were observed closest to the ground, but overall INP concentrations did not exhibit an inverse correlation with increasing altitude. HOVERCAT is a prototype that can be further modified for other airborne platforms, including tethered balloon and unmanned aircraft systems. The versatility of HOVERCAT affords future opportunities to profile the atmospheric column for more comprehensive evaluations of aerosol-cloud interactions. Based on our test flight experiences, we provide a set of recommendations for future deployments of similar measurement systems and platforms. © 2018 Author(s)."
"57194590416;57202339855;13403622000;36600036800;6507533363;6602414959;12139043600;12139310900;56250250300;57205638870;","Strong impacts on aerosol indirect effects from historical oxidant changes",2018,"10.5194/acp-18-7669-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047953733&doi=10.5194%2facp-18-7669-2018&partnerID=40&md5=595746884abbad45aff5488479c49628","Uncertainties in effective radiative forcings through aerosol-cloud interactions (ERFaci, also called aerosol indirect effects) contribute strongly to the uncertainty in the total preindustrial-to-present-day anthropogenic forcing. Some forcing estimates of the total aerosol indirect effect are so negative that they even offset the greenhouse gas forcing. This study highlights the role of oxidants in modeling of preindustrial-to-present-day aerosol indirect effects. We argue that the aerosol precursor gases should be exposed to oxidants of its era to get a more correct representation of secondary aerosol formation. Our model simulations show that the total aerosol indirect effect changes from -1.32 to -1.07 W m-2 when the precursor gases in the preindustrial simulation are exposed to preindustrial instead of present-day oxidants. This happens because of a brightening of the clouds in the preindustrial simulation, mainly due to large changes in the nitrate radical (NO3). The weaker oxidative power of the preindustrial atmosphere extends the lifetime of the precursor gases, enabling them to be transported higher up in the atmosphere and towards more remote areas where the susceptibility of the cloud albedo to aerosol changes is high. The oxidation changes also shift the importance of different chemical reactions and produce more condensate, thus increasing the size of the aerosols and making it easier for them to activate as cloud condensation nuclei. © 2018 Author(s)."
"57003839000;55542885500;7201796620;55786181800;57212815233;57195935519;36521979100;57190620377;57190618196;","Insights on Chemistry of Mercury Species in Clouds over Northern China: Complexation and Adsorption",2018,"10.1021/acs.est.7b06669","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046465614&doi=10.1021%2facs.est.7b06669&partnerID=40&md5=b643278575bd2828d33a0d23c3c81798","Cloud effects on heterogeneous reactions of atmospheric mercury (Hg) are poorly understood due to limited knowledge of cloudwater Hg chemistry. Here we quantified Hg species in cloudwater at the summit of Mt. Tai in northern China. Total mercury (THg) and methylmercury (MeHg) in cloudwater were on average 70.5 and 0.15 ng L-1, respectively, and particulate Hg (PHg) contributed two-thirds of THg. Chemical equilibrium modeling simulations suggested that Hg complexes by dissolved organic matter (DOM) dominated dissolved Hg (DHg) speciation, which was highly pH dependent. Hg concentrations and speciation were altered by cloud processing, during which significant positive correlations of PHg and MeHg with cloud droplet number concentration (Nd) were observed. Unlike direct contribution to PHg from cloud scavenging of aerosol particles, abiotic DHg methylation was the most likely source of MeHg. Hg adsorption coefficients Kad (5.9-362.7 L g-1) exhibited an inverse-power relationship with cloud residues content. Morphology analyses indicated that compared to mineral particles, fly ash particles could enhance Hg adsorption due to more abundant carbon binding sites on the surface. Severe particulate air pollution in northern China may bring substantial Hg into cloud droplets and impact atmospheric Hg geochemical cycling by aerosol-cloud interactions. © 2018 American Chemical Society."
"36931958000;6602075440;7401666571;9434771700;35098801000;","Influence of dimethyl sulfide on the carbon cycle and biological production",2018,"10.1007/s10533-018-0430-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042605209&doi=10.1007%2fs10533-018-0430-5&partnerID=40&md5=d3cb7ef63f82d7a6ae6e553968b46725","Dimethyl sulfide (DMS) is a significant source of marine sulfate aerosol and plays an important role in modifying cloud properties. Fully coupled climate simulations using dynamic marine ecosystem and DMS calculations are conducted to estimate DMS fluxes under various climate scenarios and to examine the sign and strength of phytoplankton-DMS-climate feedbacks for the first time. Simulation results show small differences in the DMS production and emissions between pre-industrial and present climate scenarios, except for some areas in the Southern Ocean. There are clear changes in surface ocean DMS concentrations moving into the future, and they are attributable to changes in phytoplankton production and competition driven by complex spatially varying mechanisms. Comparisons between parallel simulations with and without DMS fluxes into the atmosphere show significant differences in marine ecosystems and physical fields. Without DMS, the missing subsequent aerosol indirect effects on clouds and radiative forcing lead to fewer clouds, more solar radiation, and a much warmer climate. Phaeocystis, a uniquely efficient organosulfur producer with a growth advantage under cooler climate states, can benefit from producing the compound through cooling effects of DMS in the climate system. Our results show a tight coupling between the sulfur and carbon cycles. The ocean carbon uptake declines without DMS emissions to the atmosphere. The analysis indicates a weak positive phytoplankton-DMS-climate feedback at the global scale, with large spatial variations driven by individual autotrophic functional groups and complex mechanisms. The sign and strength of the feedback vary with climate states and phytoplankton groups. This highlights the importance of a dynamic marine ecosystem module and the sulfur cycle mechanism in climate projections. © 2018, The Author(s)."
"56125686700;6602974799;","A microphysical parameterization of aqSOA and sulfate formation in clouds",2017,"10.1002/2017GL074233","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85026294462&doi=10.1002%2f2017GL074233&partnerID=40&md5=f27716ca926a88ddd7c9f623ffe91fa4","Sulfate and secondary organic aerosol (cloud aqSOA) can be chemically formed in cloud water. Model implementation of these processes represents a computational burden due to the large number of microphysical and chemical parameters. Chemical mechanisms have been condensed by reducing the number of chemical parameters. Here an alternative is presented to reduce the number of microphysical parameters (number of cloud droplet size classes). In-cloud mass formation is surface and volume dependent due to surface-limited oxidant uptake and/or size-dependent pH. Box and parcel model simulations show that using the effective cloud droplet diameter (proportional to total volume-to-surface ratio) reproduces sulfate and aqSOA formation rates within ≤30% as compared to full droplet distributions; other single diameters lead to much greater deviations. This single-class approach reduces computing time significantly and can be included in models when total liquid water content and effective diameter are available. ©2017. American Geophysical Union. All Rights Reserved."
"57194833104;56536745100;57189498750;7402027161;57203053317;","A comparison of two chemistry and aerosol schemes on the regional scale and the resulting impact on radiative properties and liquid- and ice-phase aerosol-cloud interactions",2017,"10.5194/acp-17-8651-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85024902745&doi=10.5194%2facp-17-8651-2017&partnerID=40&md5=3eb4260ed923c50c88da888a8e5828a7","The complexity of atmospheric aerosol causes large uncertainties in its parameterization in atmospheric models. In a process-based comparison of two aerosol and chemistry schemes within the regional atmospheric modeling framework COSMO-ART (Consortium for Small-Scale Modelling, Aersosol and Reactive Trace gases extension), we identify key sensitivities of aerosol parameterizations. We consider the aerosol module MADE (Modal Aerosol Dynamics model for Europe) in combination with full gas-phase chemistry and the aerosol module M7 in combination with a constant-oxidant-field-based sulfur cycle. For a Saharan dust outbreak reaching Europe, modeled aerosol populations are more sensitive to structural differences between the schemes, in particular the consideration of aqueous-phase sulfate production, the selection of aerosol species and modes, and modal composition, than to parametric choices like modal standard deviation and the parameterization of aerosol dynamics. The same observation applies to aerosol optical depth (AOD) and the concentrations of cloud condensation nuclei (CCN). Differences in the concentrations of ice-nucleating particles (INPs) are masked by uncertainties between two ice-nucleation parameterizations and their coupling to the aerosol scheme. Differences in cloud droplet and ice crystal number concentrations are buffered by cloud microphysics as we show in a susceptibility analysis."
"56592712200;15846270900;8836278700;","CCN characteristics over a tropical coastal station during south-west monsoon: observations and closure studies",2017,"10.1016/j.atmosenv.2017.06.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020828594&doi=10.1016%2fj.atmosenv.2017.06.012&partnerID=40&md5=39db3654d880d72108c616bc1f0f871d","Number concentration measurements of cloud condensation nuclei (CCN) at five supersaturation values between 0.2 and 1.0% were made from a coastal site (Thiruvananthapuram) of peninsular India using a single column CCN counter during the summer monsoon period (June–September) of 2013 and 2014. The CCN concentration over this site showed diurnal variations of high values during nighttime and low values during daytime in association with the change in mesoscale circulation patterns. The inter-annual variations of CCN (CCN0.4% = 2,232 ± 672 cm−3 during August 2013 and CCN0.4% = 941 ± 325 cm−3 during August 2014) are mostly associated with the varying intensity of monsoon rainfall. The variation of CCN number concentration with supersaturation is found to be steeper during nighttime (indicating a less CCN active aerosol system) than during daytime (CCN active system). The CCN activation ratio estimated using simultaneous measurements of CCN and aerosol number (CN) concentration clearly depict the role of land-sea breeze circulations with higher values during daytime than the nighttime. The CCN number concentration predicted for different supersaturations, from measured aerosol number size distribution using Kohler theory, indicate the importance of the change in aerosol composition associated with different airmasses in a coastal environment. © 2017 Elsevier Ltd"
"35302065900;26538561700;7005975931;","Dust-infused baroclinic cyclone storm clouds: The evidence, meteorology, and some implications",2016,"10.1002/2016GL071801","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007439480&doi=10.1002%2f2016GL071801&partnerID=40&md5=daf503c306529e7b1b127354e92a8fd0","Desert mineral dust is a critical yet still poorly understood component of atmospheric composition, weather, and climate. Long-range transport of dust is well known, yet uncertainty persists regarding the pathway from the desert floor to the free troposphere. Here we will show that a recurrent pathway for dust into the uppermost troposphere involves passage through an extratropical baroclinic cyclonic storm. The evidence derives from a synergistic use of satellite-based, multispectral nadir-image data and lidar. The dust-infused baroclinic storm (DIBS) exhibits peculiar cirrus cloud top reflected and emitted radiance from the UV through thermal IR, involving positive UV absorbing aerosol index, muted visible reflectivity, visible cumuliform texture, and systematically intense visible lidar backscatter on a synoptic scale. Proof that the DIBS is microphysically impacted by storm-scale dust infusion is the occurrence of anomalously large daytime 3.9–11μm brightness temperature difference indicative of small ice crystals. We present multispectral snapshots of two DIBS, over two desert source regions, in comparison with a pristine baroclinic storm cloud. Each storm snapshot is presented in the context of the baroclinic cyclone's lifetime and dust source region (the Gobi desert and the Sahara). These and other cases discussed show that the DIBS is a recurring conduit for long-range transport and a natural experiment in dust-related aerosol indirect effects. ©2016. American Geophysical Union. All Rights Reserved."
"56531367400;55628589750;56735478500;57192064467;","Global observations of cloud-sensitive aerosol loadings in low-levelmarine clouds",2016,"10.1002/2016JD025614","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84996567106&doi=10.1002%2f2016JD025614&partnerID=40&md5=6c552d86e65c40f47c9983b0af4d04d0","Aerosol-cloud interaction is a key component of the Earth’s radiative budget and hydrological cycle, but many facets of its mechanisms are not yet fully understood. In this study, global satellite-derived aerosol and cloud products are used to identify at what aerosol loading cloud droplet size shows the greatest sensitivity to changes in aerosol loading (ACSmax). While, on average, cloud droplet size is most sensitive at relatively low aerosol loadings, distinct spatial and temporal patterns exist. Possible determinants for these are identified with reanalysis data. The magnitude of ACSmax is found to be constrained by the total columnar water vapor. Seasonal patterns of water vapor are reflected in the seasonal patterns of ACSmax. Also, situations with enhanced turbulent mixing are connected to higher ACSmax, possibly due to intensified aerosol activation. Of the analyzed aerosol species, dust seems to impact ACSmax the most, as dust particles increase the retrieved aerosol loading without substantially increasing the concentration of cloud condensation nuclei. © 2016. American Geophysical Union. All Rights Reserved."
"56539196700;57205872550;","Dust induced changes in ice cloud and cloud radiative forcing over a high altitude site",2016,"10.4209/aaqr.2015.05.0325","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84979944498&doi=10.4209%2faaqr.2015.05.0325&partnerID=40&md5=957fc51473a3dc493adf443ea453b2c9","Aerosol-cloud interaction is the subject of considerable scientific research, due to the importance of clouds in controlling climate. In the present study, three years (2011-2013) satellite observations are used to investigate the aerosol indirect effect (AIE) over Dehradun. The low values of Angstrom exponent (α) during March-July are attributed to the loading of dust-like coarse particles in the atmosphere, whereas the analysis of aerosol type and Spectral Radiation Transport Model for Aerosol species (SPRINTARS) simulated aerosol species variation supports the fact. Moderate Resolution Imaging Spectroradiometer (MODIS) derived AOD data are associated to the cloud product to examine the dust impact on properties of liquid cloud and ice cloud. The positive values of aerosol cloud interaction effect (ACI) for ice cloud during pre-monsoon (March-May) and monsoon (June-August) seasons reveal the significant impact of dust on ice clouds over Dehradun, which is maximum during May (~0.24 ± 0.05). The present study shows that ice cloud effective radius (ICER) decrease with AOD during dust period. The increase in ice water path (IWP) and ice cloud optical depth (ICOD) reveals the impact of dust on heterogeneous ice generation in low level clouds. However, there is no relation between dust and liquid water cloud during dust period. It is difficult to provide definite conclusions that the dust and cloud changes are driven by the same meteorological conditions. Cloud and the Earth’s Radiant Energy System (CERES) derived flux data are used to examine the associated changes in TOA cloud radiative forcing. The diminution in effective size of ice crystal due to aerosol first indirect effect traps more longwave radiation and reflects more solar radiation. Both first and second indirect effects enhance cloud cooling, whereas the dust induced cloud warming is mainly the result of the semi-direct effect. © Taiwan Association for Aerosol Research."
"55462884000;36538539800;7004046707;7006461606;","Changes in future air quality, deposition, and aerosol-cloud interactions under future climate and emission scenarios",2016,"10.1016/j.atmosenv.2016.05.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84976649872&doi=10.1016%2fj.atmosenv.2016.05.008&partnerID=40&md5=bf979edcf316b5e36874f128b3c6132b","The prospect of global climate change will have wide scale impacts, such as ecological stress and human health hazards. One aspect of concern is future changes in air quality that will result from changes in both meteorological forcing and air pollutant emissions. In this study, the GU-WRF/Chem model is employed to simulate the impact of changing climate and emissions following the IPCC AR4 SRES A1B scenario. An average of 4 future years (2020, 2030, 2040, and 2050) is compared against an average of 2 current years (2001 and 2010). Under this scenario, by the Mid-21st century global air quality is projected to degrade with a global average increase of 2.5 ppb in the maximum 8-hr O3 level and of 0.3 μg m-3 in 24-hr average PM2.5. However, PM2.5 changes are more regional due to regional variations in primary aerosol emissions and emissions of gaseous precursor for secondary PM2.5. Increasing NOx emissions in this scenario combines with a wetter climate elevating levels of OH, HO2, H2O2, and the nitrate radical and increasing the atmosphere's near surface oxidation state. This differs from findings under the RCP scenarios that experience declines in OH from reduced NOx emissions, stratospheric recovery of O3, and increases in CH4 and VOCs. Increasing NOx and O3 levels enhances the nitrogen and O3 deposition, indicating potentially enhanced crop damage and ecosystem stress under this scenario. The enhanced global aerosol level results in enhancements in aerosol optical depth, cloud droplet number concentration, and cloud optical thickness. This leads to dimming at the Earth's surface with a global average reduction in shortwave radiation of 1.2 W m-2. This enhanced dimming leads to a more moderate warming trend and different trends in radiation than those found in NCAR's CCSM simulation, which does not include the advanced chemistry and aerosol treatment of GU-WRF/Chem and cannot simulate the impacts of changing climate and emissions with the same level of detailed treatments. This study indicates that effective climate mitigation and emission control strategies are needed to prevent future health impact and ecosystem stress. Further, studies that are used to develop these strategies should use fully coupled models with sophisticated chemical and aerosol-interaction treatments that can provide a more realistic representation of the atmosphere. © 2016 Elsevier Ltd."
"7003480967;57204252724;6602765265;","History of aerosol-cloud interactions derived from observations in mountaintop clouds in Puerto Rico",2016,"10.4209/aaqr.2015.05.0359","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959319892&doi=10.4209%2faaqr.2015.05.0359&partnerID=40&md5=761c3c6bc76f899c5357c8be782e9ac6","Aerosol particles in the atmosphere play a fundamental role in the formation of cloud droplets. Moreover, cloudprocessing of aerosols is an important component of the changes observed in aerosol composition and size. In this study we present measurements of the physical and optical properties of interstitial and droplet residual particles in clouds made at a tropical mountain site. The measurements were made with the Aerosol Particle Spectrometer with Polarization Detection (APSPD) that was deployed at the mountaintop observatory of Pico del Este in Puerto Rico, between 25 August and 10 September, 2011 as part of the Puerto Rico African Dust and Cloud Study (PRADACS).We evaluate the optical signatures and equivalent optical diameters of the sampled aerosol with respect to the origin and meteorological history of the air mass in which the aerosol were embedded. Additionally, the aerosol properties are related to the liquid water content present in the cloud. The origin of the air mass is the most important factor that modulates the optical signatures, volume size distributions and total volume concentration of the sampled aerosol. Differences in the aerosol volume concentrations were significant (up to a factor of 4) between air masses originating in Africa, the North Atlantic and the South Atlantic. In addition, African aerosols have a much higher ratio of residual to interstitial volume concentration, suggesting that these particles had a higher fraction of cloud condensation nuclei than in the other air masses. Finally, the amount of precipitation along the air mass trajectories impacts the aerosol volume concentration, as does the residence time of the air mass in the moist, oceanic boundary layer, below 500 m. © Taiwan Association for Aerosol Research."
"36538539800;57195938097;55612831900;34876658200;","Sensitivity of simulated chemical concentrations and aerosol-meteorology interactions to aerosol treatments and biogenic organic emissions in WRF/Chem",2016,"10.1002/2016JD024882","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029386857&doi=10.1002%2f2016JD024882&partnerID=40&md5=86be630c322a13fe3dd3f816f0de694c","Coupled air quality and climate models can predict aerosol concentrations and properties, as well as aerosol direct and indirect effects that depend on aerosol chemistry and microphysics treatments. In this study, Weather Research and Forecasting with Chemistry (WRF/Chem) simulations are conducted over continental U.S. (CONUS) for January and July 2001 with the same gas-phase mechanism (CB05) but three aerosol modules (Modal Aerosol Dynamics Model for Europe/Secondary Organic Aerosol Model (MADE/ SORGAM),Model for Simulating Aerosol Interactions and Chemistry (MOSAIC), andModel of Aerosol Dynamics, Reaction, Ionization and Dissolution (MADRID)) to examine the impacts of aerosol treatments on predictions of aerosols and their effects on cloud properties and radiation. The simulations with the three aerosol modules give similar domain mean predictions of surface PM2.5 concentrations but exhibit a strong spatial variation in magnitudes with large differences in eastern U.S. Large discrepancies are found in the predicted concentrations of sulfate and organicmatter due to different treatments in secondary inorganic and secondary organic aerosol (SOA) formation. In particular, the nucleation calculation in MADE/SORGAM causes mass buildup of sulfate which results in much higher sulfate concentrations that those predicted by WRF/Chem with the other two aerosol modules. Different PM mass concentrations and size representations lead to differences in the predicted aerosol number concentrations. The above differences in PM concentrations lead to large differences in simulated condensation nuclei (CCN) and cloud properties in both months. The simulated ranges of domain mean are (1.9-14.3) × 109m-3 and (1.4-5.4) × 109m-3 for PM2.5 number concentration, (1.6-3.9) × 108cm-2 and (1.9-3.9) × 108cm-2 for CCN, 102.9-208.2 cm-3 and 143.7-202.2 cm-3 for column cloud droplet number concentration (CDNC), and 4.5-6.4 and 3.6-6.7 for cloud optical depths (COT) in January and July, respectively. The sensitivity simulation for July 2001 using online biogenic emissions increases isoprene concentrations but decreases terpene concentrations, leading to a domain mean increase in O3 (1.5 ppb) and a decrease in biogenic SOA (-0.07 µgm-3) and PM2.5 (-0.2 µgm-3). Anthropogenic emissions contribute to O3, biogenic SOA (BSOA), and PM2.5 concentrations by 38.0%, 44.2%, and 53.6% domain mean and by up to 78.5%, 89.7%, and 96.3%, respectively, indicating that a large fraction of BSOA is controllable through controlling atmospheric oxidant levels in CONUS. Anthropogenic emissions also contribute to a decrease in downward shortwave flux at ground surface (-5.8Wm-2), temperature at 2m (-0.05°C), wind speed at 10m (-0.02ms-1), planetary boundary layer height (-6.6m), and precipitation (-0.08mm), as well as an increase in CCN (+5.7 × 10-7cm-2), in-cloud CDNC (+40.4 cm-3), and COT (+0.6). This work indicates the need for an accurate representation of several aerosol processes such as SOA formation and aerosol-cloud interactions in simulating aerosol direct and indirect effects in the online-coupled models. © 2016. American Geophysical Union. All Rights Reserved."
"56536745100;36141355100;57203053317;7003748648;","The resolution dependence of cloud effects and ship-induced aerosol-cloud interactions in marine stratocumulus",2016,"10.1002/2015JD024685","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84966344397&doi=10.1002%2f2015JD024685&partnerID=40&md5=d5a05fe26449b489be2a47984b0b0e0d","Measures of aerosol-cloud interactions in stratocumulus have been shown to depend on the resolution of the applied data set. In order to contrast resolution with emission dilution effects in models, a regional numerical weather prediction model is used to simulate ship tracks at a range of spatiotemporal resolutions ranging from the global climate modeling scale (Δx = 50 km, Δt = 180 s) to the convection-resolving scale (Δx = 1 km, Δt = 20 s). The background simulations without ship emissions display a high degree of similarity in the planetary boundary layer and cloud properties at all spatiotemporal resolutions. Simulations assessing the impact of emission dilution show an increasing overestimation of the shortwave (SW) cloud radiative effect (CRE) with degenerating emission resolution. Although mean perturbations in the activation-sized aerosol number concentration (Nact) are similar for all dilution experiments, the variability in Nact is increasingly lost with stronger emission dilution. The enhanced Nact homogeneity in turn leads to an overestimated SW CRE. We show that emission dilution alone accounts for 47% of the overestimated SW CRE simulated at low resolutions. The remainder of the differences is attributed to a combination of locally enhanced aerosol concentrations due to weaker vertical mixing simulated at coarse resolutions, in combination with a faster conversion rate of Aitken to accumulation mode particles by redistribution in these regions. © 2016. American Geophysical Union. All rights reserved."
"7401471372;7201587909;55718857500;7404243086;23161713000;","The effect of aerosol representation on cloud microphysical properties in Northeast Asia",2014,"10.1007/s00703-013-0288-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893292550&doi=10.1007%2fs00703-013-0288-y&partnerID=40&md5=e6c40d5548faf872eec703f6d99d18c4","This study performed a three-dimensional regional-scale simulation of aerosol and cloud fields using a meso-scale non-hydrostatic model with a bin-based cloud microphysics. The representation of aerosols in the model has been improved to account for more realistic multi-modal size distribution and multiple chemical compositions. Two case studies for shallow stratocumulus over Northeast Asia in March 2005 were conducted with different aerosol conditions to evaluate model performance. Improved condensation nuclei (CN) and cloud condensation nuclei (CCN) are attributable to the newly constructed aerosol size distribution. The simulated results of cloud microphysical properties (cloud droplet effective radius, liquid water path, and optical thickness) with improved CN/CCN number are close to the retrievals from satellite-based observation. The effects of aerosol on the microphysical properties of shallow stratocumulus are investigated by model simulation, in terms of columnar aerosol number concentration. Enhanced aerosol number concentration results in increased liquid water path in humid case, but invariant liquid water path in dry case primarily due to precipitation occurrence. The changes of cloud microphysical properties are more predominant for small aerosol burden than for large aerosol burden with the retarded changes in cloud mass and size due to inactive condensation and collision-coalescence processes. Quantitative evaluation of sensitivity factor between aerosol and cloud microphysical properties indicates a strong aerosol-cloud interaction in Northeast Asian region. © 2013 Springer-Verlag Wien."
"23051160600;6507755223;6506718302;57208121852;6701511324;56154540200;7003931528;35461255500;7006712143;","Brightening of the global cloud field by nitric acid and the associated radiative forcing",2012,"10.5194/acp-12-7625-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869034863&doi=10.5194%2facp-12-7625-2012&partnerID=40&md5=31b9a9e9aeabd511a3bfad3053f5bdea","Clouds cool Earth's climate by reflecting 20% of the incoming solar energy, while also trapping part of the outgoing radiation. The effect of human activities on clouds is poorly understood, but the present-day anthropogenic cooling via changes of cloud albedo and lifetime could be of the same order as warming from anthropogenic addition in CO2. Soluble trace gases can increase water condensation to particles, possibly leading to activation of smaller aerosols and more numerous cloud droplets. We have studied the effect of nitric acid on the aerosol indirect effect with the global aerosol-climate model ECHAM5.5-HAM2. Including the nitric acid effect in the model increases cloud droplet number concentrations globally by 7%. The nitric acid contribution to the present-day cloud albedo effect was found to be-0.32 W m -2 and to the total indirect effect-0.46 W m -2. The contribution to the cloud albedo effect is shown to increase to-0.37 W m -2 by the year 2100, if considering only the reductions in available cloud condensation nuclei. Overall, the effect of nitric acid can play a large part in aerosol cooling during the following decades with decreasing SO2 emissions and increasing NOx and greenhouse gases. © 2012 Author(s)."
"11539061800;55613308500;23493942300;7202434960;6603837066;55262544600;","Development of a ground based remote sensing approach for direct evaluation of Aerosol-Cloud interaction",2012,"10.3390/atmos3040468","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874563180&doi=10.3390%2fatmos3040468&partnerID=40&md5=5c241cc8a601d5dfbad6e22251c8f1bc","The possible interaction and modification of cloud properties due to aerosols is one of the most poorly understood mechanisms within climate studies, resulting in the most significant uncertainty as regards radiation budgeting. In this study, we explore direct ground based remote sensing methods to assess the Aerosol-Cloud Indirect Effect directly, as space-borne retrievals are not directly suitable for simultaneous aerosol/cloud retrievals. To illustrate some of these difficulties, a statistical assessment of existing multispectral imagers on geostationary (e.g., GOES)/Moderate Resolution Imaging Spectroradiometer (MODIS) satellite retrievals of the Cloud Droplet Effective Radius (Reff) showed significant biases especially at larger solar zenith angles, further motivating the use of ground based remote sensing approaches. In particular, we discuss the potential of using a combined Microwave Radiometer (MWR)-Multi-Filter Rotating Shadowband Radiometer (MFRSR) system for real-time monitoring of Cloud Optical Depth (COD) and Cloud Droplet Effective Radius (Reff), which are combined with aerosol vertical properties from an aerosol lidar. An iterative approach combining the simultaneous observations from MFRSR and MWR are used to retrieve the COD and Reff for thick cloud cases and are extensively validated using the DoE Southern Great Plains (SGP) retrievals as well as regression based parameterized model retrievals. In addition, we account for uncertainties in background aerosol, surface albedo and the combined measurement uncertainties from the MWR and MFRSR in order to provide realistic uncertainty estimates, which is found to be ~10% for the parameter range of interest in Aerosol-Cloud Interactions. Finally, we analyze a particular case of possible aerosol-cloud interaction described in the literature at the SGP site and demonstrate that aerosol properties obtained at the surface can lead to inconclusive results in comparison to lidar-derived aerosol properties near the cloud base. © 2012 by the authors."
"55245030000;7102604282;7006306835;8953038700;","Aerosol forcing based on CAM5 and AM3 meteorological fields",2012,"10.5194/acp-12-9629-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869067380&doi=10.5194%2facp-12-9629-2012&partnerID=40&md5=f0d0004fc2f4f7adf458945fa5bd2e92","We use a single aerosol model to explore the effects of the differing meteorological fields from the NCAR CAM5 and GFDL AM3 models. We simulate the global distributions of sulfate, black carbon, organic matter, dust and sea salt using the University of Michigan IMPACT model and use these fields to calculate aerosol direct and indirect forcing, thereby isolating the impacts of the differing meteorological fields. Over all, the IMPACT-AM3 model predicts larger burdens and longer aerosol lifetimes than the IMPACT-CAM5 model. However, the IMPACT-CAM5 simulations transport more black carbon to the polar regions and more dust from Asia towards North America. These differences can mainly be attributed to differences in: (1) the vertical cloud mass flux and large-scale precipitation fields which determine the wet deposition of aerosols; (2) the in-cloud liquid water content and the cloud coverage which determine the wet aqueous phase production of sulfate. The burden, lifetime and global distribution, especially black carbon in polar regions, are strongly affected by choice of the parameters used for wet deposition. The total annual mean aerosol optical depth (AOD) at 550 nm ranges from 0.087 to 0.122 for the IMPACT-AM3 model and from 0.138 to 0.186 for the IMPACT-CAM5 model (range is due to different parameters used for wet deposition). Even though IMPACT-CAM5 has smaller aerosol burdens, its AOD is larger due to the much higher relative humidity in CAM5 which leads to more hygroscopic growth. The corresponding global annual average anthropogenic and all-sky aerosol direct forcing at the top of the atmosphere ranges from-0.25 W m-2 to-0.30 W m-2 for IMPACT-AM3 and from-0.48 W m-2 to-0.64 W m-2 for IMPACT-CAM5. The global annual average anthropogenic 1st aerosol indirect effect at the top of the atmosphere ranges from-1.26 W m-2 to-1.44 W m -2 for IMPACT-AM3 and from-1.74 W m-2 to-1.77 W m -2 for IMPACT-CAM5. © 2012 Author(s)."
"56032511300;7102604282;","Dependence of aerosol-cloud interactions in stratocumulus clouds on liquid-water path",2011,"10.1016/j.atmosenv.2011.08.050","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052971227&doi=10.1016%2fj.atmosenv.2011.08.050&partnerID=40&md5=4219870626ad0aefe43f940494c540f3","A recent study showed that aerosol-induced feedbacks between microphysics and dynamics predominantly determined the cloud-mass response to aerosols in thin clouds with liquid-water path (LWP) of ∼50 g m-2 or less; in this paper, cloud mass represents the time- and area-averaged LWP and LWP is the column-integrated cloud liquid content (LWC); LWC is the mass of cloud liquid per unit volume of air. This is contrary to studies which have shown that aerosol-induced inefficient conversion and sedimentation play an important role in the determination of the effect of aerosols on cloud mass. These studies are generally based on clouds with LWP &gt;50 g m-2. Hence, it is important to understand whether the role of aerosol-induced feedbacks in the effect of aerosols on cloud mass depends on the level of LWP. Pairs of numerical experiments for high and low-aerosol cases are run for four cases of stratiform clouds with different LWPs. All of these cases show that the role of condensation or evaporation of cloud liquid in the cloud-mass response to aerosol is more important than that of conversion of cloud liquid to rain and sedimentation (or precipitation). This indicates that focusing only on parameterization of autoconversion and sedimentation to represent aerosol effects on cloud mass in climate models can be misleading. Also, this study finds that the effect of aerosol-induced sedimentation suppression on the cloud-mass response to aerosol becomes less important as LWP lowers. Instead, the effect of aerosol-induced changes in condensation or evaporation on the cloud-mass response becomes more important with the decreasing LWP. These changes in condensation (and associated changes in evaporation) are caused by interactions (or feedbacks) among aerosol, droplet surface area, supersaturation, and instability around cloud base. © 2011 Elsevier Ltd."
"37114958000;7202516876;15724722300;8700927900;","A study of shallow cumulus cloud droplet dispersion by large eddy simulations",2011,"10.1007/s13351-011-0024-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955550738&doi=10.1007%2fs13351-011-0024-9&partnerID=40&md5=ff2f38ae2514549b0d71f5a681fb263c","Cloud droplet dispersion is an important parameter in estimating aerosol indirect effect on climate in general circulation models (GCMs). This study investigates droplet dispersion in shallow cumulus clouds under different aerosol conditions using three-dimensional large eddy simulations (LES). It is found that cloud droplet mean radius, standard deviation, and relative dispersion generally decrease as aerosol mixing ratio increases from 25 mg-1 (clean case) to 100 mg-1 (moderate case), and to 2000 mg-1 (polluted case). Under all the three simulated aerosol conditions, cloud droplet mean radius and standard deviation increase with height. However, droplet relative dispersion increases with height only in the polluted case, and does not vary with height in the clean and moderate cases. The mechanisms for cloud droplet dispersion are also investigated. An additional simulation without considering droplet collision-coalescence and sedimentation under the aerosol mixing ratio of 25 mg-1 shows smaller values of droplet mean radius, standard deviation, and relative dispersion as compared to the base clean case. This indicates that droplet collision-coalescence plays an important role in broadening droplet spectra. Results also suggest that the impact of homogeneous mixing on cumulus cloud droplet spectra is significant under all the three simulated aerosol conditions. In weak mixing (strong updraft) regions where clouds are closer to be adiabatic, cloud droplets tend to have larger mean radius, smaller standard deviation, and hence smaller relative dispersion than those in stronger mixing (downdraft or weak updraft) regions. The parameterized cloud optical depth in terms of cloud liquid water content, droplet number concentration, and relative dispersion is only slightly smaller than the result calculated from detailed droplet spectra, indicating that current parameterization of cloud optical depth as used in many GCMs is plausible for low clouds. © The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2011."
"57192615132;55717074000;7401936984;7401974644;7005877775;","Testing ice microphysics parameterizations in the NCAR Community Atmospheric Model Version 3 using Tropical Warm Pool-International Cloud Experiment data",2009,"10.1029/2008JD011220","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350064177&doi=10.1029%2f2008JD011220&partnerID=40&md5=b1ba6dff07ee879910d349ea5d2e9163","Cloud properties have been simulated with a new double-moment microphysics scheme under the framework of the single-column version of NCAR Community Atmospheric Model version 3 (CAM3). For comparison, the same simulation was made with the standard single-moment microphysics scheme of CAM3. Results from both simulations compared favorably with observations during the Tropical Warm Pool-International Cloud Experiment by the U.S. Department of Energy Atmospheric Radiation Measurement Program in terms of the temporal variation and vertical distribution of cloud fraction and cloud condensate. Major differences between the two simulations are in the magnitude and distribution of ice water content within the mixed-phase cloud during the monsoon period, though the total frozen water (snow plus ice) contents are similar. The ice mass content in the mixed-phase cloud from the new scheme is larger than that from the standard scheme, and ice water content extends 2 km further downward, which is in better agreement with observations. The dependence of the frozen water mass fraction on temperature from the new scheme is also in better agreement with available observations. Outgoing longwave radiation (OLR) at the top of the atmosphere (TOA) from the simulation with the new scheme is, in general, larger than that with the standard scheme, while the surface downward longwave radiation is similar. Sensitivity tests suggest that different treatments of the ice crystal effective radius contribute significantly to the difference in the calculations of TOA OLR, in addition to cloud water path. Numerical experiments show that cloud properties in the new scheme can respond reasonably to changes in the concentration of aerosols and emphasize the importance of correctly simulating aerosol effects in climate models for aerosol-cloud interactions. Further evaluation, especially for ice cloud properties based on in situ data, is needed."
"6602178158;55885662200;7408519438;6603710604;36098422200;6603002398;","On the increased climate sensitivity in the EC-Earth model from CMIP5 to CMIP6",2020,"10.5194/gmd-13-3465-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089582341&doi=10.5194%2fgmd-13-3465-2020&partnerID=40&md5=4aee4b5434c505cfb111b9f7131c10ee","Many modelling groups that contribute to CMIP6 (Coupled Model Intercomparison Project Phase 6) have found a larger equilibrium climate sensitivity (ECS) with their latest model versions compared with the values obtained with the earlier versions used in CMIP5. This is also the case for the EC-Earth model. Therefore, in this study, we investigate what developments since the CMIP5 era could have caused the increase in the ECS in this model. Apart from increases in the horizontal and vertical resolution, the EC-Earth model has also substantially changed the representation of aerosols; in particular, it has introduced a more sophisticated description of aerosol indirect effects. After testing the model with some of the recent updates switched off, we find that the ECS increase can be attributed to the more advanced treatment of aerosols, with the largest contribution coming from the effect of aerosols on cloud microphysics (cloud lifetime or second indirect effect). The increase in climate sensitivity is unrelated to model tuning, as all experiments were performed with the same tuning parameters and only the representation of the aerosol effects was changed. These results cannot be generalised to other models, as their CMIP5 and CMIP6 versions may differ with respect to aspects other than the aerosol-cloud interaction, but the results highlight the strong sensitivity of ECS to the details of the aerosol forcing. © 2020 Copernicus GmbH. All rights reserved."
"56983008100;57196577048;8670213100;6701796418;6507681572;","Global vertically resolved aerosol direct radiation effect from three years of CALIOP data using the FORTH radiation transfer model",2019,"10.1016/j.atmosres.2019.03.024","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063376697&doi=10.1016%2fj.atmosres.2019.03.024&partnerID=40&md5=f644c249885df3875cb9238f3084f6dc","We use global aerosol optical depth data from CALIOP with a radiation transfer model to investigate the aerosol direct radiative effect (DRE) and its sensitivity to the aerosol vertical resolution. Our study spans three years (2007–2009) and uses cloud data from ISCCP D2 to take into account cloud-aerosol radiative interactions on a monthly 2.5° × 2.5° resolution. The three-year global average all-sky aerosol DRE at the surface, in the atmosphere, and at the top of atmosphere (TOA) was calculated to be −4.23, 2.40, and −1.83 Wm −2 , respectively. As expected, local DREs and atmospheric heating rates are shown to vary significantly. The largest magnitudes of the DREs are observed in regions with heavy aerosol load consisting of both natural and anthropogenic particles, such as desert dust, biomass burning and urban/industrial pollution. At TOA the aerosol effect is generally of negative sign, though a planetary heating effect is found in regions characterized by both absorbing aerosol and large surface albedo, such as deserts. Clouds scatter and absorb solar radiation, which generally decreases the aerosol cooling at the surface and the aerosol warming in the atmosphere. However, the latter effect is attenuated due to the enhancement of radiation absorption by the above-cloud aerosols. As a result, clouds decrease the aerosol TOA (planetary) cooling, and sometimes even cause aerosol warming (e.g. over the tropical South Atlantic). The cloud effect on the aerosol DRE depends strongly on the aerosol optical properties and the aerosol load fraction above low clouds. Comparing the effect of the observed aerosol vertical profile against an exponentially decreasing profile, we find a small sensitivity for the surface DRE, but larger for the atmospheric column and the top of the atmosphere. Under all-sky conditions, when continental aerosols are lifted higher in the atmosphere, the outgoing shortwave radiation at TOA decreases, due to the increase of UV and visible radiation absorption by particles while higher oceanic aerosols generally increase the outgoing shortwave radiation through more efficient backscatter and decrease of the NIR radiation absorption by atmospheric gases below aerosol particles. © 2019 Elsevier B.V."
"55894087900;25648525300;9249255600;57205095740;","Black carbon linked aerosol hygroscopic growth: Size and mixing state are crucial",2019,"10.1016/j.atmosenv.2018.12.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058517900&doi=10.1016%2fj.atmosenv.2018.12.001&partnerID=40&md5=3cae7597ff68fffb1fab80a979d8d170","The objective of this study is to characterise urban refractory black carbon (rBC) mixing state relative to hygroscopic growth factor (HGF) of size selective aerosols to better constrain the aerosol indirect effect. The Aitken mode range (≤100 nm) is dominated by particles that have relatively low hygroscopicity and comprised freshly emitted hydrophobic rBC, however, our observations suggest that BC mixing states in Aitken range (down to 70 nm) still govern the hygroscopic properties. Conversely, the accumulation mode range (>100 nm) dominated by particles that have relatively high hygroscopicity consisted of oxidized organic compounds and inorganic salts. Single particle soot photometer (SP2) measurement further revealed that particles at lower size are mostly incandescent type dominated by refractory component whereas higher size particles are mostly scattering type dominated by nonrefractory component. The lower hygroscopicity parameter (κ) (0.26 ± 0.08) obtained for Aitken mode particles suggests that they may contain levoglucosan and levoglucosan-OH oxidation products, and are possibly from biomass burning sources whereas accumulation range particles with higher κ value (0.39 ± 0.03) have ammonium sulfate, ammonium bisulfate and malonic acid in their composition and their possible source would be secondary in origin. These findings are important because for the first time, BC mixing state and the impact of size selective rBC on HGF are determined directly over an urban region which have implications to precipitation. © 2018 Elsevier Ltd"
"53879901600;7103180783;55582587700;55211425200;","Anthropogenically Forced Decadal Change of South Asian Summer Monsoon Across the Mid-1990s",2019,"10.1029/2018JD029195","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060801270&doi=10.1029%2f2018JD029195&partnerID=40&md5=5029d6deba654a291d30a100414ba662","Analysis of observations indicates that there was a significant decadal change in summer (June–August) mean rainfall over South Asia and Southeast Asia across the mid-1990s, which is characterized by less rainfall over central-northern India and northern Indo-China Peninsula. This study investigates impacts of anthropogenic forcing on the observed decadal change across the mid-1990s. A set of experiments using the coupled atmosphere-ocean-mixed-layer model MetUM-GOML2 has been performed to quantify the relative roles of changes in anthropogenic greenhouse gases and anthropogenic aerosols (AA). Results indicate a dominant role of anthropogenic changes in the observed decadal changes. Separately, the changes in greenhouse gases forcing play an important role in the reduction of rainfall over central-northern India through the changes of atmospheric circulation (i.e., the local Hadley circulation and the Walker circulation), with additional contribution from changes in AA forcing. The changes in AA forcing dominate the reduction of rainfall over northern Indo-China Peninsula due to high-pressure anomalies over northern South Asia and the western subtropical Pacific. These high-pressure anomalies are induced by the surface cooling, mainly via aerosol-radiation interaction that decreases downward clear-sky shortwave radiation over South Asia during summer and aerosol-radiation interaction and aerosol-cloud interaction that decrease downward shortwave radiation over the western subtropical Pacific during presummer seasons. ©2018. American Geophysical Union. All Rights Reserved."
"54982705800;55879760100;37017289300;55554574300;23990442300;26665602100;55532508600;6507896695;","Implementation of aerosol-cloud interaction within WRF-CHIMERE online coupled model: Evaluation and investigation of the indirect radiative effect from anthropogenic emission reduction on the Benelux Union",2019,"10.3390/atmos10010020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059683079&doi=10.3390%2fatmos10010020&partnerID=40&md5=615d57db4a94ae4b7aecc527452756b2","The indirect effects of aerosol are particularly important over regions where meteorological conditions and aerosol content are favourable to cloud formation. This was observed during the Intensive Cloud Aerosol Measurement Campaign (IMPACT) (European Integrated project on Aerosol Cloud Climate and Air quality Interaction (EUCAARI) project) in the Benelux Union during May 2008. To better understand this cloud formation variability, the indirect effects of aerosol have been included within the WRF-CHIMERE online model. By comparing model results to the aircraft measurements of IMPACT, to surface measurements from EMEP and AIRBASE and to MODIS satellite measurements, we showed that the model is able to simulate the variability and order of magnitude of the observed number of condensation nuclei (CN), even if some differences are identified for specific aerosol size and location. To quantify the impact of the local anthropogenic emissions on cloud formation, a sensitivity study is performed by halving the surface emissions fluxes. It is shown that the indirect radiative effect (IRE) at the surface is positive for both shortwave and longwave with a net warming of +0.99 W/m 2 . In addition, important instantaneous changes are modelled at local scale with up to ±6 °C for temperatures and ±50 mm/day for precipitation. © 2019 by the authors."
"56001297600;57203174863;55417816200;","A 12-year long global record of optical depth of absorbing aerosols above the clouds derived from the OMI/OMACA algorithm",2018,"10.5194/amt-11-5837-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055565346&doi=10.5194%2famt-11-5837-2018&partnerID=40&md5=8dbdfc1a82bd7bbfc1e760b186cc5f65","Aerosol-cloud interaction continues to be one of the leading uncertain components of climate models, primarily due to the lack of adequate knowledge of the complex microphysical and radiative processes of the aerosol- cloud system. Situations when light-absorbing aerosols such as carbonaceous particles and windblown dust overlay lowlevel cloud decks are commonly found in several regions of the world. Contrary to the known cooling effects of these aerosols in cloud-free scenario over darker surfaces, an overlapping situation of the absorbing aerosols over the cloud can lead to a significant level of atmospheric absorption exerting a positive radiative forcing (warming) at the top of the atmosphere. We contribute to this topic by introducing a new global product of above-cloud aerosol optical depth (ACAOD) of absorbing aerosols retrieved from the near-UV observations made by the Ozone Monitoring Instrument (OMI) onboard NASA's Aura platform. Physically based on an unambiguous ""color ratio"" effect in the near-UV caused by the aerosol absorption above the cloud, the OMACA (OMI above-cloud aerosols) algorithm simultaneously retrieves the optical depths of aerosols and clouds under a prescribed state of the atmosphere. The OMACA algorithm shares many similarities with the twochannel cloud-free OMAERUV algorithm, including the use of AIRS carbon monoxide for aerosol type identification, CALIOP-based aerosol layer height dataset, and an OMI-based surface albedo database. We present the algorithm architecture, inversion procedure, retrieval quality flags, initial validation results, and results from a 12-year long OMI record (2005-2016) including global climatology of the frequency of occurrence, ACAOD, and aerosolcorrected cloud optical depth. A comparative analysis of the OMACA-retrieved ACAOD, collocated with equivalent accurate measurements from the HSRL-2 lidar for the ORACLES Phase I operation (August-September 2016), revealed a good agreement (R D0.77, RMSED0.10). The long-term OMACA record reveals several important regions of the world, where the carbonaceous aerosols from the seasonal biomass burning and mineral dust originated over the continents are found to overlie low-level cloud decks with moderate (0.3 ACAOD 0.5, away from the sources) to higher levels of ACAOD (> 0.8 in the proximity to the sources), including the southeastern Atlantic Ocean, southern Indian Ocean, Southeast Asia, the tropical Atlantic Ocean off the coast of western Africa, and northern Arabian sea. No significant long-term trend in the frequency of occurrence of aerosols above the clouds and ACAOD is noticed when OMI observations that are free from the ""row anomaly"" throughout the operation are considered. If not accounted for, the effects of aerosol absorption above the clouds introduce low bias in the retrieval of cloud optical depth with a profound impact on increasing ACAOD and cloud brightness. The OMACA aerosol product from OMI presented in this paper offers a crucial missing piece of information from the aerosol loading above cloud that will help us to quantify the radiative effects of clouds when overlaid with aerosols and their resultant impact on cloud properties and climate. © 2018 Author."
"36822103700;57203102974;25230018900;7006107059;7102944401;","A satellite-based estimate of combustion aerosol cloud microphysical effects over the Arctic Ocean",2018,"10.5194/acp-18-14949-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055311978&doi=10.5194%2facp-18-14949-2018&partnerID=40&md5=a3a066463ba2515340f356824ff71964","Climate predictions for the rapidly changing Arctic are highly uncertain, largely due to a poor understanding of the processes driving cloud properties. In particular, cloud fraction (CF) and cloud phase (CP) have major impacts on energy budgets, but are poorly represented in most models, often because of uncertainties in aerosol-cloud interactions. Here, we use over 10 million satellite observations coupled with aerosol transport model simulations to quantify large-scale microphysical effects of aerosols on CF and CP over the Arctic Ocean during polar night, when direct and semi-direct aerosol effects are minimal. Combustion aerosols over sea ice are associated with very large (∼ 10Wmg-2) differences in longwave cloud radiative effects at the sea ice surface. However, co-varying meteorological changes on factors such as CF likely explain the majority of this signal. For example, combustion aerosols explain at most 40% of the CF differences between the full dataset and the clean-condition subset, compared to between 57% and 91% of the differences that can be predicted by co-varying meteorology. After normalizing for meteorological regime, aerosol microphysical effects have small but significant impacts on CF, CP, and precipitation frequency on an Arctic-wide scale. These effects indicate that dominant aerosol-cloud microphysical mechanisms are related to the relative fraction of liquid-containing clouds, with implications for a warming Arctic. © Author(s) 2018."
"55875842200;7409080503;","Significant Underestimation in the Optically Based Estimation of the Aerosol First Indirect Effect Induced by the Aerosol Swelling Effect",2018,"10.1029/2018GL077679","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048973187&doi=10.1029%2f2018GL077679&partnerID=40&md5=e5dbfd42a32a358bf94c894d5ccb699d","Aerosol optical quantities have been widely employed as the proxy variables of cloud condensation nuclei concentration to study aerosol indirect effects (AIE). Due to the aerosol swelling effect, cloud condensation nuclei and aerosol optical quantities do not vary in harmony, leading to a bias in the estimation of the AIE. To identify and quantify this artifact, we employ extensive measurements of aerosol and cloud properties made at four sites in different continents that have distinct aerosol properties in terms of size and composition. One-unit enhancement in aerosol scattering coefficient by swelling effect is found to lead to a systematic underestimation of the first indirect effect (FIE) by about 23% that can result in an underestimation in the FIE-related radiative forcing by several W/m2 depending on aerosol properties and relative humidity. This likely contributes significantly to the systematic difference between satellite-based estimates of the FIE and those simulated by general circulation models. Recommendations are made to make more sound comparisons of the AIE estimated from observations and model simulations. ©2018. American Geophysical Union. All Rights Reserved."
"56818565600;7410041005;7409080503;57217772325;7003729315;56978385600;55488312400;7402727711;55806891500;56447276100;57095410800;","Retrieval of Cloud Condensation Nuclei Number Concentration Profiles From Lidar Extinction and Backscatter Data",2018,"10.1029/2017JD028102","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048952733&doi=10.1029%2f2017JD028102&partnerID=40&md5=b4e87d4784b6a575d88f645539d2b511","The vertical distribution of aerosols and their capability of serving as cloud condensation nuclei (CCN) are important for improving our understanding of aerosol indirect effects. Although ground-based and airborne CCN measurements have been made, they are generally scarce, especially at cloud base where it is needed most. We have developed an algorithm for profiling CCN number concentrations using backscatter coefficients at 355, 532, and 1,064 nm and extinction coefficients at 355 and 532 nm from multiwavelength lidar systems. The algorithm considers three distinct types of aerosols (urban industrial, biomass burning, and dust) with bimodal size distributions. The algorithm uses look-up tables, which were developed based on the ranges of aerosol size distributions obtained from the Aerosol Robotic Network, to efficiently find optimal solutions. CCN number concentrations at five supersaturations (0.07–0.80%) are determined from the retrieved particle size distributions. Retrieval simulations were performed with different combinations of systematic and random errors in lidar-derived extinction and backscatter coefficients: systematic errors range from −20% to 20% and random errors are up to 15%, which fall within the typical error ranges for most current lidar systems. The potential of this algorithm to retrieve CCN concentrations is further evaluated through comparisons with surface-based CCN measurements with near-surface lidar retrievals. This retrieval algorithm would be valuable for aerosol-cloud interaction studies for which virtually none has employed CCN at cloud base because of the lack of such measurements. ©2018. American Geophysical Union. All Rights Reserved."
"55915364000;7403401100;54279446400;57189377456;16023843200;7006708207;","Vertical wind velocity measurements using a five-hole probe with remotely piloted aircraft to study aerosol-cloud interactions",2018,"10.5194/amt-11-2583-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046770454&doi=10.5194%2famt-11-2583-2018&partnerID=40&md5=52e5eed2fb024c27d030f2923a2acfb6","The importance of vertical wind velocities (in particular positive vertical wind velocities or updrafts) in atmospheric science has motivated the need to deploy multi-hole probes developed for manned aircraft in small remotely piloted aircraft (RPA). In atmospheric research, lightweight RPAs ( < 2.5kg) are now able to accurately measure atmospheric wind vectors, even in a cloud, which provides essential observing tools for understanding aerosol-cloud interactions. The European project BACCHUS (impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: Towards a Holistic UnderStanding) focuses on these specific interactions. In particular, vertical wind velocity at cloud base is a key parameter for studying aerosol-cloud interactions. To measure the three components of wind, a RPA is equipped with a five-hole probe, pressure sensors, and an inertial navigation system (INS). The five-hole probe is calibrated on a multi-axis platform, and the probe-INS system is validated in a wind tunnel. Once mounted on a RPA, power spectral density (PSD) functions and turbulent kinetic energy (TKE) derived from the five-hole probe are compared with sonic anemometers on a meteorological mast. During a BACCHUS field campaign at Mace Head Atmospheric Research Station (Ireland), a fleet of RPAs was deployed to profile the atmosphere and complement ground-based and satellite observations of physical and chemical properties of aerosols, clouds, and meteorological state parameters. The five-hole probe was flown on straight-and-level legs to measure vertical wind velocities within clouds. The vertical velocity measurements from the RPA are validated with vertical velocities derived from a ground-based cloud radar by showing that both measurements yield model-simulated cloud droplet number concentrations within 10%. The updraft velocity distributions illustrate distinct relationships between vertical cloud fields in different meteorological conditions. © Author(s) 2018."
"57192915106;55938109300;7006770362;54941580100;12544502800;55879681300;13007286600;55807448700;56998535300;57196082964;24767977600;22635720500;7003862871;24333054700;6505947323;7004020627;9738422100;39361670300;","An assessment of aerosol optical properties from remote-sensing observations and regional chemistry-climate coupled models over Europe",2018,"10.5194/acp-18-5021-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045392738&doi=10.5194%2facp-18-5021-2018&partnerID=40&md5=cfc2b2982732b0f7e1e498ffcf454f3e","Atmospheric aerosols modify the radiative budget of the Earth due to their optical, microphysical and chemical properties, and are considered one of the most uncertain climate forcing agents. In order to characterise the uncertainties associated with satellite and modelling approaches to represent aerosol optical properties, mainly aerosol optical depth (AOD) and Ångström exponent (AE), their representation by different remote-sensing sensors and regional online coupled chemistry-climate models over Europe are evaluated. This work also characterises whether the inclusion of aerosol-radiation (ARI) or/and aerosol-cloud interactions (ACI) help improve the skills of modelling outputs. Two case studies were selected within the EuMetChem COST Action ES1004 framework when important aerosol episodes in 2010 all over Europe took place: a Russian wildfire episode and a Saharan desert dust outbreak that covered most of the Mediterranean Sea. The model data came from different regional air-quality-climate simulations performed by working group 2 of EuMetChem, which differed according to whether ARI or ACI was included or not. The remote-sensing data came from three different sensors: MODIS, OMI and SeaWIFS. The evaluation used classical statistical metrics to first compare satellite data versus the ground-based instrument network (AERONET) and then to evaluate model versus the observational data (both satellite and ground-based data). Regarding the uncertainty in the satellite representation of AOD, MODIS presented the best agreement with the AERONET observations compared to other satellite AOD observations. The differences found between remote-sensing sensors highlighted the uncertainty in the observations, which have to be taken into account when evaluating models. When modelling results were considered, a common trend for underestimating high AOD levels was observed. For the AE, models tended to underestimate its variability, except when considering a sectional approach in the aerosol representation. The modelling results showed better skills when ARI+ACI interactions were included; hence this improvement in the representation of AOD (above 30 % in the model error) and AE (between 20 and 75 %) is important to provide a better description of aerosol-radiation-cloud interactions in regional climate models. © 2018 Copernicus GmbH. All rights reserved."
"56942554300;36538539800;55802355600;8511991900;7202048112;35792776400;55624488227;7202010686;","Fine-scale application of WRF-CAM5 during a dust storm episode over East Asia: Sensitivity to grid resolutions and aerosol activation parameterizations",2018,"10.1016/j.atmosenv.2017.12.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85038242085&doi=10.1016%2fj.atmosenv.2017.12.014&partnerID=40&md5=3bf2341d33c1fa8ef6fcf9587573f125","An advanced online-coupled meteorology and chemistry model WRF-CAM5 has been applied to East Asia using triple-nested domains at different grid resolutions (i.e., 36-, 12-, and 4-km) to simulate a severe dust storm period in spring 2010. Analyses are performed to evaluate the model performance and investigate model sensitivity to different horizontal grid sizes and aerosol activation parameterizations and to examine aerosol-cloud interactions and their impacts on the air quality. A comprehensive model evaluation of the baseline simulations using the default Abdul-Razzak and Ghan (AG) aerosol activation scheme shows that the model can well predict major meteorological variables such as 2-m temperature (T2), water vapor mixing ratio (Q2), 10-m wind speed (WS10) and wind direction (WD10), and shortwave and longwave radiation across different resolutions with domain-average normalized mean biases typically within ±15%. The baseline simulations also show moderate biases for precipitation and moderate-to-large underpredictions for other major variables associated with aerosol-cloud interactions such as cloud droplet number concentration (CDNC), cloud optical thickness (COT), and cloud liquid water path (LWP) due to uncertainties or limitations in the aerosol-cloud treatments. The model performance is sensitive to grid resolutions, especially for surface meteorological variables such as T2, Q2, WS10, and WD10, with the performance generally improving at finer grid resolutions for those variables. Comparison of the sensitivity simulations with an alternative (i.e., the Fountoukis and Nenes (FN) series scheme) and the default (i.e., AG scheme) aerosol activation scheme shows that the former predicts larger values for cloud variables such as CDNC and COT across all grid resolutions and improves the overall domain-average model performance for many cloud/radiation variables and precipitation. Sensitivity simulations using the FN series scheme also have large impacts on radiations, T2, precipitation, and air quality (e.g., decreasing O3) through complex aerosol-radiation-cloud-chemistry feedbacks. The inclusion of adsorptive activation of dust particles in the FN series scheme has similar impacts on the meteorology and air quality but to lesser extent as compared to differences between the FN series and AG schemes. Compared to the overall differences between the FN series and AG schemes, impacts of adsorptive activation of dust particles can contribute significantly to the increase of total CDNC (∼45%) during dust storm events and indicate their importance in modulating regional climate over East Asia. © 2017 Elsevier Ltd"
"7102423967;","Anomalous Lightning Behavior During the 26–27 August 2007 Northern Great Plains Severe Weather Event",2018,"10.1002/2017JD027750","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041724977&doi=10.1002%2f2017JD027750&partnerID=40&md5=65236ab962bac5ced3f533209391fd10","Positive polarity lightning strokes can be useful indicators of thunderstorm behavior. A combination of National Lightning Detection Network and Next Generation Radar retrievals is used to analyze the anomalous positive cloud-to-ground (CG) lightning behavior of a rare, late summer severe weather event that occurred on 26–27 August 2007 in the Northern Great Plains region of the United States and southern Canada. Seven discrete supercells (SC1–SC7) exhibiting frequent and intense lightning were responsible for numerous reports of severe weather (e.g., severe hail and 16 tornadoes) including catastrophic damage to the town of Northwood, North Dakota, caused by SC2. Biomass burning smoke from wildfires in Idaho and Montana was present prior to convective initiation. A positive CG lightning stroke rate of nearly 30 strokes per minute was observed 10 min before the EF4 tornado struck Northwood. SC2 was also responsible for all the reports of tornadoes exceeding an EF2 rating. The strongest peak currents (>200 kA) were observed in SC1–SC4 with SC2 having a maximum value of 280 kA. SC2 dominated the statistics of the line of supercells accounting for 27% of all CG lightning strokes. Positive CG lightning accounted for over 40% of all CG lightning strokes in SC4–SC7 on average, and the maximum exceeded 90% in SC6 and SC7. Increasing positive CG lightning dominance was correlated with an increasing northward gradient of smoke aerosol loading in addition to severe weather being reported before the maximum in positive CG lighting stroke rate (SC5 and SC6). This suggests that a complex combination of synoptic forcing and aerosol perturbation likely led to the observed anomalous positive CG lightning behavior in the supercells. ©2018. American Geophysical Union. All Rights Reserved."
"55875842200;7409080503;","First surface-based estimation of the aerosol indirect effect over a site in southeastern China",2018,"10.1007/s00376-017-7106-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040370894&doi=10.1007%2fs00376-017-7106-2&partnerID=40&md5=2e6bb82ecd4a3a3ebc658d32fd3ca9d8","The deployment of the U.S. Atmospheric Radiation Measurement mobile facility in Shouxian from May to December 2008 amassed the most comprehensive set of measurements of atmospheric, surface, aerosol, and cloud variables in China. This deployment provided a unique opportunity to investigate the aerosol–cloud interactions, which are most challenging and, to date, have not been examined to any great degree in China. The relationship between cloud droplet effective radius (CER) and aerosol index (AI) is very weak in summer because the cloud droplet growth is least affected by the competition for water vapor. Mean cloud liquid water path (LWP) and cloud optical depth (COD) significantly increase with increasing AI in fall. The sensitivities of CER and LWP to aerosol loading increases are not significantly different under different air mass conditions. There is a significant correlation between the changes in hourly mean AI and the changes in hourly mean CER, LWP, and COD. The aerosol first indirect effect (FIE) is estimated in terms of relative changes in both CER (FIECER) and COD (FIECOD) with changes in AI for different seasons and air masses. FIECOD and FIECER are similar in magnitude and close to the typical FIE value of ∼ 0.23, and do not change much between summer and fall or between the two different air mass conditions. Similar analyses were done using spaceborne Moderate Resolution Imaging Spectroradiometer data. The satellite-derived FIE is contrary to the FIE estimated from surface retrievals and may have large uncertainties due to some inherent limitations. © 2018, Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag GmbH Germany, part of Springer Nature."
"56188306800;57197808707;7409080503;14018770700;8636990400;7406073187;55806891500;8953662800;8839875600;","Potential influences of neglecting aerosol effects on the NCEP GFS precipitation forecast",2017,"10.5194/acp-17-13967-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85034969191&doi=10.5194%2facp-17-13967-2017&partnerID=40&md5=0eb1c7ef72fcadc6cad6d09f2309cdba","Aerosol-cloud interactions (ACIs) have been widely recognized as a factor affecting precipitation. However, they have not been considered in the operational National Centers for Environmental Predictions Global Forecast System model. We evaluated the potential impact of neglecting ACI on the operational rainfall forecast using ground-based and satellite observations and model reanalysis. The Climate Prediction Center unified gauge-based precipitation analysis and the Modern-Era Retrospective analysis for Research and Applications Version 2 aerosol reanalysis were used to evaluate the forecast in three countries for the year 2015. The overestimation of light rain (47.84 %) and underestimation of heavier rain (31.83, 52.94, and 65.74 % for moderate rain, heavy rain, and very heavy rain, respectively) from the model are qualitatively consistent with the potential errors arising from not accounting for ACI, although other factors cannot be totally ruled out. The standard deviation of the forecast bias was significantly correlated with aerosol optical depth in Australia, the US, and China. To gain further insight, we chose the province of Fujian in China to pursue a more insightful investigation using a suite of variables from gauge-based observations of precipitation, visibility, water vapor, convective available potential energy (CAPE), and satellite datasets. Similar forecast biases were found: over-forecasted light rain and under-forecasted heavy rain. Long-term analyses revealed an increasing trend in heavy rain in summer and a decreasing trend in light rain in other seasons, accompanied by a decreasing trend in visibility, no trend in water vapor, and a slight increasing trend in summertime CAPE. More aerosols decreased cloud effective radii for cases where the liquid water path was greater than 100 g m-2. All findings are consistent with the effects of ACI, i.e., where aerosols inhibit the development of shallow liquid clouds and invigorate warm-base mixed-phase clouds (especially in summertime), which in turn affects precipitation. While we cannot establish rigorous causal relations based on the analyses presented in this study, the significant rainfall forecast bias seen in operational weather forecast model simulations warrants consideration in future model improvements."
"24722339600;57206503877;7006705919;57194858213;","Could geoengineering research help answer one of the biggest questions in climate science?",2017,"10.1002/2017EF000601","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85023599365&doi=10.1002%2f2017EF000601&partnerID=40&md5=26d95a666529a1fc4e16a16ba67c4c79","Anthropogenic aerosol impacts on clouds constitute the largest source of uncertainty in quantifying the radiative forcing of climate, and hinders our ability to determine Earth's climate sensitivity to greenhouse gas increases. Representation of aerosol–cloud interactions in global models is particularly challenging because these interactions occur on typically unresolved scales. Observational studies show influences of aerosol on clouds, but correlations between aerosol and clouds are insufficient to constrain aerosol forcing because of the difficulty in separating aerosol and meteorological impacts. In this commentary, we argue that this current impasse may be overcome with the development of approaches to conduct control experiments whereby aerosol particle perturbations can be introduced into patches of marine low clouds in a systematic manner. Such cloud perturbation experiments constitute a fresh approach to climate science and would provide unprecedented data to untangle the effects of aerosol particles on cloud microphysics and the resulting reflection of solar radiation by clouds. The control experiments would provide a critical test of high-resolution models that are used to develop an improved representation aerosol–cloud interactions needed to better constrain aerosol forcing in global climate models. © 2017 The Authors."
"57192064467;55628589750;56735478500;56531367400;","Mapping the twilight zone-What we are missing between clouds and aerosols",2017,"10.3390/rs9060577","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021107580&doi=10.3390%2frs9060577&partnerID=40&md5=cedad60b773cd2a7011a773ee5875140","Scientific understanding of aerosol-cloud interactions can profit from an analysis of the transition regions between pure aerosol and pure clouds as detected in satellite data. This study identifies and evaluates pixels in this region by analysing the residual areas of aerosol and cloud products from the Moderate Resolution Imaging Radiometer (MODIS) satellite sensor. These pixels are expected to represent the ""twilight zone"" or transition zone between aerosols and clouds. In the analysis period (February and August, 2007-2011), about 20% of all pixels are discarded by both MODIS aerosol and cloud retrievals (""Lost Pixels""). The reflective properties and spatial distribution of Lost Pixels are predominantly in between pure aerosol and cloud. The high amount of discarded pixels underlines the relevance of analyzing the transition zone as a relevant part of the Earth's radiation budget and the importance of considering them in research on aerosol-cloud interactions. © 2017 by the authors."
"55938109300;36661106500;6508026916;39361670300;","Biomass burning aerosol impact on surface winds during the 2010 Russian heat wave",2017,"10.1002/2016GL071484","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85010629691&doi=10.1002%2f2016GL071484&partnerID=40&md5=2ea4d225fa6a58dce704ad4f213ab240","This paper elucidates the impact of biomass burning aerosols (BB) on surface winds for the Russian fires episode during 25 July to 15 August 2010. The methodology consists of three Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) simulations over Europe differing in the inclusion (or not) of aerosol-radiation and aerosol-cloud interactions. The presence of BB reduces the 10 m wind speed over Russia during this fire event by 0.2 m s−1 (10%). Aerosol interactions imply a decrease of the shortwave downwelling radiation at the surface leading to a reduction of the 2 m temperature. This decrease reduces the turbulence flux, developing a more stable planetary boundary layer. Moreover, cooling favors an increase of the surface pressure over Russian area and also it extends nearby northern Europe. ©2016. American Geophysical Union. All Rights Reserved."
"57192915106;55938109300;57148462400;7004607037;12544502800;39361670300;","Evaluating the representation of aerosol optical properties using an online coupled model over the Iberian Peninsula",2017,"10.5194/acp-17-277-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85009115328&doi=10.5194%2facp-17-277-2017&partnerID=40&md5=e2bd61eee240a627694bd6e48ccaaab4","The effects of atmospheric aerosol particles on the Earth's climate mainly depend on their optical, microphysical and chemical properties, which modify the Earth's radiative budget. The aerosol radiative effects can be divided into direct and semi-direct effects, produced by the aerosol-radiation interactions (ARIs), and indirect effects, produced by aerosol-cloud interactions (ACIs). In this sense the objective of this work is to assess whether the inclusion of aerosol radiative feedbacks in the online coupled WRFChem model improves the modelling outputs over the Iberian Peninsula (IP) and surrounding water areas. For this purpose, the methodology is based on the evaluation of modelled aerosol optical properties under different simulation scenarios. The evaluated data come from two WRF-Chem simulations for the IP differing in the inclusion/no-inclusion of ARIs and ACIs (RF/NRF simulations). The case studies cover two episodes with different aerosol types over the IP in 2010, namely a Saharan dust outbreak and a forest fire episode. The evaluation uses observational data from AERONET (Aerosol Robotic Network) stations and MODIS (Moderate Resolution Imaging Spectroradiometer) sensor, including aerosol optical depth (AOD) and Ångström exponent (AE). Experimental data of aerosol vertical distribution from the EARLINET (European Aerosol Research Lidar Network) Granada station are used for checking the models. The results indicate that for the spatial distribution the bestrepresented variable is AOD and the largest improvements when including the aerosol radiative feedbacks are found for the vertical distribution. In the case of the dust outbreak, a slight improvement (worsening) is produced over the areas with medium (high/low) levels of AOD(-9%=C12% of improvement) when including the aerosol radiative feedbacks. For the wildfire episode, improvements of AOD representation (up to 11 %) over areas further away from emission sources are estimated, which compensates for the computational effort of including aerosol feedbacks in the simulations. No clear improvement is observed for the AE representation, the variability of which is largely underpredicted by both simulations. © Author(s) 2017."
"24390528000;6602600408;35611334800;24485834000;","Black carbon indirect radiative effects in a climate model",2017,"10.1080/16000889.2017.1369342","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048909905&doi=10.1080%2f16000889.2017.1369342&partnerID=40&md5=cf153aac5188437b7d4f2982eb2320dc","The aerosol–cloud interactions due to black carbon (BC) aerosols, as well as the implied climate responses, are examined using an aerosol module in the coupled atmosphere–ocean general circulation model MPI-ESM. BC is simulated to enhance cloud droplet number concentration (CDNC) by 10–15% in the BC emission source regions, especially in the Tropics and mid-latitudes. Higher CDNC and reduced auto-conversion from cloud water to rain water explains the increased cloud water path over the tropical regions (30◦S–30◦N) in the model. In the global mean, the cloud water– as well as precipitation changes are negligibly small. The global-mean effective radiative forcing due to aerosol–cloud interactions for BC is estimated at −0.13 ± 0.1Wm−2, which is attributable to the increase in CDNC burden and (regionally) cloud water in the model. Global mean temperature and rainfall response were found to be−0.16 ± 0.04K and−0.004±0.004mmday−1, respectively, with significantly larger regional changes mainly in the downwind regions from BC sources. © 2017, © 2017 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group."
"7003800456;35338710200;55519833300;6504028729;8314917200;","Radiative forcing from aircraft emissions of NOx: Model calculations with CH4 surface flux boundary condition",2017,"10.1127/metz/2016/0776","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85038837949&doi=10.1127%2fmetz%2f2016%2f0776&partnerID=40&md5=c64d62696fc4ba40317cd92108022a3c","Two independent chemistry-transport models with troposphere-stratosphere coupling are used to quantify the different components of the radiative forcing (RF) from aircraft emissions of NOx, i.e., the University of L'Aquila climate-chemistry model (ULAQ-CCM) and the University of Oslo chemistry-transport model (Oslo-CTM3). The tropospheric NOx enhancement due to aircraft emissions produces a short-term O3 increase with a positive RF (+17.3mW/m2) (as an average value of the two models). This is partly compensated by the CH4 decrease due to the OH enhancement (-9.4mW/m2). The latter is a long-term response calculated using a surface CH4 flux boundary condition (FBC), with at least 50 years needed for the atmospheric CH4 to reach steady state. The radiative balance is also affected by the decreasing amount of CO2 produced at the end of the CH4 oxidation chain: an average CO2 accumulation change of -2.2 ppbv/yr is calculated on a 50 year time horizon (-1.6mW/m2). The aviation perturbed amount of CH4 induces a long-term response of tropospheric O3 mostly due to less HO2 and CH3O2 being available for O3 production, compared with the reference case where a constant CH4 surface mixing ratio boundary condition is used (MBC) (-3.9mW/m2). The CH4 decrease induces a long-term response of stratospheric H2O (-1.4mW/m2). The latter finally perturbs HOx and NOx in the stratosphere, with a more efficient NOx cycle for mid-stratospheric O3 depletion and a decreased O3 production from HO2+NO in the lower stratosphere. This produces a long-term stratospheric O3 loss, with a negative RF (-1.2mW/m2), compared with the CH4 MBC case. Other contributions to the net NOx RF are those due to NO2 absorption of UV-A and aerosol perturbations (the latter calculated only in the ULAQ-CCM). These comprise: increasing sulfate due to more efficient oxidation of SO2, increasing inorganic and organic nitrates and the net aerosols indirect effect on warm clouds. According to these model calculations, aviation NOx emissions for 2006 produced globally a net cooling effect of -5.7mW/m2 (-6.2 and -5.1mW/m2, from ULAQ and Oslo models, respectively). When the effects of aviation sulfur emissions are taken into account in the atmospheric NOx balance (via heterogeneous chemistry), the model-average net cooling effects of aviation NOx increases to -6.2mW/m2. Our study applies to a sustained and constant aviation NOx emission and for the given background NOy conditions. The perturbation picture, however, may look different if an increasing trend in aviation NOx emissions would be allowed. © 2017 The authors."
"7401800593;57214786060;57191294058;","Dust load and rainfall characteristics and their relationship over the South Asian monsoon region under various warming scenarios",2017,"10.1002/2017JD027451","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028068896&doi=10.1002%2f2017JD027451&partnerID=40&md5=5eab8fa3cf5e059a44f70dd85f85f0b9","Present study investigates the similarities and differences in the pattern of dust load and rainfall and their relationship over the South Asian monsoon region under various future warming scenarios with respect to the historical period using multiple coupled climate model runs that participated in Coupled Model Inter-comparison Project Phase 5 (CMIP5). Based on statistically robust significance tests, we unravel several likely changes in the pattern of the dust load and rainfall over the South Asia under different future warming scenarios by the end of 21st century compared to the historical period. Kolmogorov-Smirnov test results reveal a significant change (at 5% significance level) in the amount of dust and rainfall under different warming scenarios over the study region. Northern part of the Indian subcontinent is likely to witness increased dust loading in future, and regions with increase in dust load are also likely to be the regions of increased rainfall over North India. Positive correlation between rainfall over the Indian region and dust over the Arabian region is also likely to strengthen in future. Considerable changes in the spatial correlation pattern between dust and rainfall are noted under different representative concentration pathways; however, no noteworthy changes are recorded in their temporal relationship. Notable intermodel differences in the patterns of dust load and rainfall relationship over South Asia are possibly caused by variations in the dust emission schemes among the CMIP5 models as well as the parameterization of aerosol indirect effect in addition to the differences in the meteorology simulated by various models under identical forcing scenarios. © 2017. American Geophysical Union. All Rights Reserved."
"56709590600;6603034566;55937180800;7004472363;10141225800;7801401670;7403076976;8918197800;","Aerosols and lightning activity: The effect of vertical profile and aerosol type",2016,"10.1016/j.atmosres.2016.07.031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981155184&doi=10.1016%2fj.atmosres.2016.07.031&partnerID=40&md5=ccd228d8d0d5cff296d9f2b486c930e8","The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument on board the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite has been utilized for the first time in a study regarding lightning activity modulation due to aerosols. Lightning activity observations, obtained by the ZEUS long range Lightning Detection Network, European Centre for Medium range Weather Forecasts (ECMWF) Convective Available Potential Energy (CAPE) data and Cloud Fraction (CF) retrieved by MODIS on board Aqua satellite have been combined with CALIPSO CALIOP data over the Mediterranean basin and for the period March to November, from 2007 to 2014. The results indicate that lightning activity is enhanced during days characterized by higher Aerosol Optical Depth (AOD) values, compared to days with no lightning. This study contributes to existing studies on the link between lightning activity and aerosols, which have been based just on columnar AOD satellite retrievals, by performing a deeper analysis into the effect of aerosol profiles and aerosol types. Correlation coefficients of R = 0.73 between the CALIPSO AOD and the number of lightning strikes detected by ZEUS and of R = 0.93 between ECMWF CAPE and lightning activity are obtained. The analysis of extinction coefficient values at 532 nm indicates that at an altitudinal range exists, between 1.1 km and 2.9 km, where the values for extinction coefficient of lightning-active and non-lightning-active cases are statistically significantly different. Finally, based on the CALIPSO aerosol subtype classification, we have investigated the aerosol conditions of lightning-active and non-lightning-active cases. According to the results polluted dust aerosols are more frequently observed during non-lightning-active days, while dust and smoke aerosols are more abundant in the atmosphere during the lightning-active days. © 2016 Elsevier B.V."
"23012437100;7101899854;55053404100;22235187200;7004899626;55781534800;18635289400;7202772927;7403577184;","Coupled aerosol-cloud systems over northern vietnam during 7-SEAS/BASELine: A radar and modeling perspective",2016,"10.4209/aaqr.2015.11.0631","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84994079462&doi=10.4209%2faaqr.2015.11.0631&partnerID=40&md5=3e0e2c104856f040017a302d7b08b16f","The 2013 7-SEAS/BASELInE campaign over northern Southeast Asia (SEA) provided, for the first time ever, comprehensive ground-based W-band radar measurements of the low-level stratocumulus (Sc) systems that often exist during the spring over northern Vietnam in the presence of biomass-burning aerosols. Although spatially limited, groundbased remote sensing observations are generally free of the surface contamination and signal attenuation effects that often hinder space-borne measurements of these low-level cloud systems. Such observations permit detailed measurements of structures and lifecycles of these clouds as part of a broader effort to study potential impacts of these coupled aerosolcloud systems on local and regional weather and air quality. Introductory analyses of the W-band radar data show these Sc systems generally follow a diurnal cycle, with peak occurrences during the nighttime and early morning hours, often accompanied by light precipitation. Preliminary results from idealized simulations of Sc development over land based on the observations reveal the familiar response of increased numbers and smaller sizes of cloud droplets, along with suppressed drizzle formation, as aerosol concentrations increase. Slight reductions in simulated W-band reflectivity values also are seen with increasing aerosol concentrations and result primarily from decreased droplet sizes. As precipitation can play a large role in removing aerosol from the atmosphere, and thereby improving air quality locally, quantifying feedbacks between aerosols and cloud systems over this region are essential, particularly given the negative impacts of biomass burning on human health in SEA. Such an endeavor should involve improved modeling capabilities along with comprehensive measurements of time-dependent aerosol and cloud profiles. © Taiwan Association for Aerosol Research."
"24329545900;7004154626;6604005739;6701490531;","Indirect forcing of black carbon on clouds over northeast India",2016,"10.1002/qj.2878","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84997703796&doi=10.1002%2fqj.2878&partnerID=40&md5=3ac448c63fde7bb997e1864d4ca85016","Black carbon (BC) induced indirect radiative forcing and cloud albedo effect has been studied for the first time over northeast India. Measurements of BC and cloud microphysical parameters were carried out during Phase-I of the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) over northeast India (Guwahati) in 2009. Liquid water path (LWP) in the cloud layers coherent with BC on different experimental days was found to be 206–327 g m−2 over the region. Black carbon aerosol indirect effect (BCIE) for fixed LWP is found to be 0.32–0.48 on different days of observations. The indirect forcing corresponding to this BCIE has been estimated using a radiative transfer model for fixed LWP by altering the derived BC-AOD (aerosol optical depth from measured BC profiles) and cloud effective radius (Re) combinations. The estimated average BC-induced indirect forcing (BCIF) was −24 to −37.1 W m−2 at the surface and +2.5 to +14.8 W m−2 at the top of the atmosphere (TOA). The average albedo due to BCIF at TOA was 0.49–0.61. BCIF is found to reduce the cloud reflection by 1.5–2% over the region. The sensitivities of cloud parameters to BCIF and the albedo effect are illustrated. © 2016 Royal Meteorological Society"
"57008250400;7101752236;9535707500;14321759900;55974019700;8684037700;6506385754;8942525300;8942524900;","Aerosol indirect effects on glaciated clouds. Part I: Model description",2016,"10.1002/qj.2791","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84992306091&doi=10.1002%2fqj.2791&partnerID=40&md5=b5730f9effcecbb19dd6799fc574ee53","Various improvements were made to a state-of-the-art aerosol–cloud model and comparison of the model results with observations from field campaigns was performed. The strength of this aerosol–cloud model is in its ability to explicitly resolve all the known modes of heterogeneous cloud droplet activation and ice crystal nucleation. The model links cloud particle activation with the aerosol loading and chemistry of seven different aerosol species. These improvements to the model resulted in more accurate prediction especially of droplet and ice crystal number concentrations in the upper troposphere and enabled the model to directly sift the aerosol indirect effects based on the chemistry and concentration of the aerosols. In addition, continental and maritime cases were simulated for the purpose of validating the aerosol–cloud model and for investigating the critical microphysical and dynamical mechanisms of aerosol indirect effects from anthropogenic solute and solid aerosols, focusing mainly on glaciated clouds. The simulations showed that increased solute aerosols reduced cloud particle sizes by about 5 μm and inhibited warm rain processes. Cloud fractions and their optical thicknesses were increased quite substantially in both cases. Although liquid mixing ratios were boosted, there was however a substantial reduction of ice mixing ratios in the upper troposphere owing to the increase in snow production aloft. These results are detailed in the subsequent parts of this study. © 2016 Royal Meteorological Society"
"56448637100;6603478665;42662973900;23051160600;35459245100;56663244400;7007182077;6602917432;7006712143;23995325300;26643041500;","Impacts of emission reductions on aerosol radiative effects",2015,"10.5194/acp-15-5501-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930203348&doi=10.5194%2facp-15-5501-2015&partnerID=40&md5=50d255a983b3b0368a6b6a198e20573a","The global aerosol-climate model ECHAM-HAMMOZ was used to investigate changes in the aerosol burden and aerosol radiative effects in the coming decades. Four different emissions scenarios were applied for 2030 (two of them applied also for 2020) and the results were compared against the reference year 2005. Two of the scenarios are based on current legislation reductions: one shows the maximum potential of reductions that can be achieved by technical measures, and the other is targeted to short-lived climate forcers (SLCFs). We have analyzed the results in terms of global means and additionally focused on eight subregions. Based on our results, aerosol burdens show an overall decreasing trend as they basically follow the changes in primary and precursor emissions. However, in some locations, such as India, the burdens could increase significantly. The declining emissions have an impact on the clear-sky direct aerosol effect (DRE), i.e. the cooling effect. The DRE could decrease globally 0.06-0.4 W m-2 by 2030 with some regional increases, for example, over India (up to 0.84 W m-2). The global changes in the DRE depend on the scenario and are smallest in the targeted SLCF simulation. The aerosol indirect radiative effect could decline 0.25-0.82 W m-2 by 2030. This decrease takes place mostly over the oceans, whereas the DRE changes are greatest over the continents. Our results show that targeted emission reduction measures can be a much better choice for the climate than overall high reductions globally. Our simulations also suggest that more than half of the near-future forcing change is due to the radiative effects associated with aerosol-cloud interactions. © Author(s) 2015."
"49561700200;7101729096;56370988900;35446906200;7102914417;7004800276;24399990200;7409097241;56265445700;","Chemical compositions of sulfate and chloride salts over the last termination reconstructed from the dome fuji ice core, inland antarctica",2014,"10.1002/2014JD022030","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921417558&doi=10.1002%2f2014JD022030&partnerID=40&md5=d42baa8044463cf5bd9204fcb0dc8d7a","The flux and chemical composition of aerosols impact the climate. Antarctic ice cores preserve the record of past atmospheric aerosols, providing useful information about past atmospheric environments. However, few studies have directly measured the chemical composition of aerosol particles preserved in ice cores. Here we present the chemical compositions of sulfate and chloride salts from aerosol particles in the Dome Fuji ice core. The analysis method involves ice sublimation, and the period covers the last termination, 25.0–11.0 thousand years before present (kyr B.P.), with a 350 year resolution. The major components of the soluble particles are CaSO4, Na2SO4, and NaCl. The dominant sulfate salt changes at 16.8 kyr B.P. from CaSO4, a glacial type, to Na2SO4, an interglacial type. The sulfate salt flux (CaSO4 plus Na2SO4) inversely correlates with δ18O in Dome Fuji over millennial timescales. This correlation is consistent with the idea that sulfate salt aerosols contributed to the last deglacial warming of inland Antarctica by reducing the aerosol indirect effect. Between 16.3 and 11.0 kyr B.P., the presence of NaCl suggests that winter atmospheric aerosols are preserved. A high NaCl/Na2SO4 fraction between 12.3 and 11.0 kyr B.P. indicates that the contribution from the transport of winter atmospheric aerosols increased during this period. © 2014. American Geophysical Union. All Rights Reserved."
"7005766987;7005659017;7801642681;","Type-segregated aerosol effects on regional monsoon activity: A study using ground-based experiments and model simulations",2014,"10.1016/j.atmosenv.2014.10.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908399872&doi=10.1016%2fj.atmosenv.2014.10.022&partnerID=40&md5=ee4e1a608e8251203292e2eb40b5ef49","Classification of observed aerosols into key types [e.g., clean-maritime (CM), desert-dust (DD), urban-industrial/biomass-burning (UI/BB), black carbon (BC), organic carbon (OC) and mixed-type aerosols (MA)] would facilitate to infer aerosol sources, effects, and feedback mechanisms, not only to improve the accuracy of satellite retrievals but also to quantify the assessment of aerosol radiative impacts on climate. In this paper, we report the results of a study conducted in this direction, employing a Cimel Sun-sky radiometer at the Indian Institute of Tropical Meteorology (IITM), Pune, India during 2008 and 2009, which represent two successive contrasting monsoon years. The study provided an observational evidence to show that the local sources are subject to heavy loading of absorbing aerosols (dust and black carbon), with strong seasonality closely linked to the monsoon annual rainfall cycle over Pune, a tropical urban station in India. The results revealed the absence of CM aerosols in the pre-monsoon as well as in the monsoon seasons of 2009 as opposed to 2008. Higher loading of dust aerosols is observed in the pre-monsoon and monsoon seasons of 2009; majority may be coated with fine BC aerosols from local emissions, leading to reduction in regional rainfall. Further, significant decrease in coarse-mode AOD and presence of carbonaceous aerosols, affecting the aerosol-cloud interaction and monsoon-rain processes via microphysics and dynamics, is considered responsible for the reduction in rainfall during 2009. Additionally, we discuss how optical depth, contributed by different types of aerosols, influences the distribution of monsoon rainfall over an urban region using the Monitoring Atmospheric Composition and Climate (MACC) aerosol reanalysis. Furthermore, predictions of the Dust REgional Atmospheric Model (DREAM) simulations combined with HYSPLIT (HYbrid Single Particle Lagrangian Integrated Trajectory) cluster model are also discussed in support of the observed features. © 2014 Elsevier Ltd."
"55726160100;55519994900;23991212200;7202252296;7102577095;","Investigating impacts of forest fires in Alaska and western Canada on regional weather over the northeastern United States using CAM5 global simulations to constrain transport to a WRF-Chem regional domain",2014,"10.1002/2013JD020973","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904767793&doi=10.1002%2f2013JD020973&partnerID=40&md5=35da1d5f4773a92b6c62f915f4017277","An aerosol-enabled globally driven regional modeling system has been developed by coupling the National Center for Atmospheric Research's Community Atmosphere Model version 5 (CAM5) with the Weather Research and Forecasting model with chemistry (WRF-Chem). In this modeling system, aerosol-enabled CAM5, a state-of-the-art global climate model is downscaled to provide coherent meteorological and chemical boundary conditions for regional WRF-Chem simulations. Aerosol particle emissions originating outside the WRF-Chem domain can be a potentially important nonlocal aerosol source. As a test case, the potential impacts of nonlocal forest fire aerosols on regional precipitation and radiation were investigated over the northeastern United States during the summer of 2004. During this period, forest fires in Alaska and western Canada lofted aerosol particles into the midtroposphere, which were advected across the United States. WRF-Chem simulations that included nonlocal biomass burning aerosols had domain-mean aerosol optical depths that were nearly three times higher than those without, which reduced peak downwelling domain-mean shortwave radiation at the surface by ~25 W m-2. In this classic twin experiment design, adding nonlocal fire plume led to near-surface cooling and changes in cloud vertical distribution, while variations in domain-mean cloud liquid water path were negligible. The higher aerosol concentrations in the simulation with the fire plume resulted in a ~10% reduction in domain-mean precipitation coincident with an ~8% decrease in domain-mean CAPE. A suite of simulations was also conducted to explore sensitivities of meteorological feedbacks to the ratio of black carbon to total plume aerosols, as well as to overall plume concentrations. Results from this ensemble revealed that plume-induced near-surface cooling and CAPE reduction occur in a wide range of conditions. The response of moist convection was very complex because of strong thermodynamic internal variability. Key Points Nonlocal fire emissions resulted in ~10% precipitation reduction Nonlocal fire emissions reduced peak surface shortwave radiation at by 25 W m-2 An aerosol-enabled globally driven regional modeling system is developed ©2014. American Geophysical Union. All Rights Reserved."
"35794588800;7102805852;7103016965;24764483400;8724962900;7005056279;7801353107;55630942000;","A method to represent subgrid-scale updraft velocity in kilometer-scale models: Implication for aerosol activation",2014,"10.1002/2013JD021218","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942419022&doi=10.1002%2f2013JD021218&partnerID=40&md5=d3f6f274e8710c0225f5ce7ad06dfcd7","Updraft velocities strongly control the activation of aerosol particles or that component that act as cloud condensation nuclei (CCN). For kilometer-scale models, vertical motions are partially resolved but the subgrid-scale (SGS) contribution needs to be parametrized or constrained to properly represent the activation of CCNs. This study presents a method to estimate the missing SGS (or unresolved) contribution to vertical velocity variability in models with horizontal grid sizes up to ∼2 km. A framework based on Large Eddy Simulations (LES) and high-resolution aircraft observations of stratocumulus and shallow cumulus clouds has been developed and applied to output from the United Kingdom Met Office Unified Model (UM) operating at kilometer-scale resolutions in numerical weather prediction configuration. For a stratocumulus deck simulation, we show that the UM 1 km model underestimates significantly the variability of updraft velocity with an averaged cloud base standard deviation between 0.04 and 0.05 m s−1 compared to LES and aircraft estimates of 0.38 and 0.54 m s−1, respectively. Once the SGS variability is considered, the UM corrected averages are between 0.34 and 0.44 m s−1. Off-line calculations of CCN-activated fraction using an activation scheme have been performed to illustrate the implication of including the SGS vertical velocity. It suggests increased CCN-activated fraction from 0.52 to 0.89 (respectively, 0.10 to 0.54) for a clean (respectively, polluted) aerosol environment for simulations with a 1 km horizontal grid size. Our results highlight the importance of representing the SGS vertical velocity in kilometer-scale simulations of aerosol-cloud interactions. © 2014. American Geophysical Union. All Rights Reserved."
"7006065540;6507906735;55315290600;6603926727;15318942300;7005618829;","Possible evidence of new particle formation and its impact on cloud microphysics from airborne measurements over Bay of Bengal",2014,"10.1016/j.atmosres.2014.01.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893431462&doi=10.1016%2fj.atmosres.2014.01.014&partnerID=40&md5=27c197f87d2187eba956a5c7cf14f60e","Airborne measurements conducted under a special mission over Bay of Bengal (BoB) during the CAIPEEX (Cloud Aerosol Interaction and Precipitation Enhancement EXperiment) in 2011 were analyzed in the present study. Research flights were carried out on 19 and 20 October, 2011 (referred as RF1 and RF2), in the region over BoB, which was influenced by a depression to evaluate the aerosol-cloud interactions over marine environment. The increased concentration of aitken/accumulation mode particles was observed at 500. m above sea surface level over the ocean after the passage of the depression. The source of these particles and their subsequent growth during RF1 at about 200. km from coastline has been attributed to (i) increased production of aerosols due to oxidation of dimethyl sulfide (DMS) because of upwelling of the deep ocean water during the depression and (ii) anthropogenic aerosols transported from inland. Moreover, measurements of accumulation and coarse mode particles with diameter ranging from 0.1 to 3. μm and cloud droplets in the range 3 to 47. μm show systematic growth associated with cloud microphysical/rain formation process. On the other hand, no such evidence of increasing particle concentration and growth has been observed at about 60. km from coastline towards southeast during RF2. Evidently, the rain event observed during the night hours of 19 October caused the washout and scavenging of aerosols which contributed towards the decreased aerosol concentration observed near the coast. © 2014 Elsevier B.V."
"55479808100;7003333258;6602765265;14828772800;56392950900;7005773698;6701842515;6603954179;","Do Cloud Properties in a Puerto Rican Tropical Montane Cloud Forest Depend on Occurrence of Long-Range Transported African Dust?",2014,"10.1007/s00024-014-0830-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908146257&doi=10.1007%2fs00024-014-0830-y&partnerID=40&md5=abc905391bc87b59e0873db028720fc2","We investigated cloud properties of warm clouds in a tropical montane cloud forest at Pico del Este (1,051 m a.s.l.) in the northeastern part of Puerto Rico to address the question of whether cloud properties in the Caribbean could potentially be affected by African dust transported across the Atlantic Ocean. We analyzed data collected during 12 days in July 2011. Cloud droplet size spectra were measured using the FM-100 fog droplet spectrometer that measured droplet size distributions in the range from 2 to 49 µm, primarily during fog events. The droplet size spectra revealed a bimodal structure, with the first peak (D &lt; 6 µm) being more pronounced in terms of droplet number concentrations, whereas the second peak (10 µm &lt; D &lt; 20 µm) was found to be the one relevant for total liquid water content (LWC) of the cloud. We identified three major clusters of characteristic droplet size spectra by means of hierarchical clustering. All clusters differed significantly from each other in droplet number concentration (Ntot), effective diameter (ED), and median volume diameter (MVD). For the cluster comprising the largest droplets and the lowest droplet number concentrations, we found evidence of inhomogeneous mixing in the cloud. Contrastingly, the other two clusters revealed microphysical behavior, which could be expected under homogeneous mixing conditions. For those conditions, an increase in cloud condensation nuclei—e.g., from processed African dust transported to the site—is supposed to lead to an increased droplet concentration. In fact, one of these two clusters showed a clear shift of cloud droplet size spectra towards smaller droplet diameters. Since this cluster occurred during periods with strong evidence for the presence of long-range transported African dust, we hypothesize a link between the observed dust episodes and cloud characteristics in the Caribbean at our site, which is similar to the anthropogenic aerosol indirect effect. © 2014, Springer Basel."
"35221443100;57208121852;7103353990;23020321400;","The contribution of the strength and structure of extratropical cyclones to observed cloud-aerosol relationships",2013,"10.5194/acp-13-10689-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887028194&doi=10.5194%2facp-13-10689-2013&partnerID=40&md5=5c5570cf622b787fb609895af19ef4e5","Meteorological conditions may drive relationships between aerosol and cloud-related properties. It is important to account for the meteorological contribution to observed cloud-aerosol relationships in order to improve understanding of aerosol-cloud-climate interactions. A new method of investigating the contribution of meteorological covariation to observed cloud-aerosol relationships is introduced. Other studies have investigated the contribution of local meteorology to cloud-aerosol relationships. In this paper, a complimentary large-scale view is presented. Extratropical cyclones have been previously shown to affect satellite-retrieved aerosol optical depth (τ), due to enhanced emission of sea salt and sea surface brightness artefacts in regions of higher wind speed. Extratropical cyclones have also been shown to affect cloud-related properties such as cloud fraction (fc) and cloud top temperature (Ttop). Therefore, it seems plausible to hypothesise that extratropical cyclones may drive relationships between cloud-related properties and τ. In this paper, this hypothesis is investigated for extratropical cyclones, henceforth referred to as storms, over the Atlantic Ocean. MODerate resolution Imaging Spectroradiometer (MODIS) retrieved τ, fc and T top data are analysed using a storm-centric coordinate system centred on extratropical cyclones which have been tracked using European Centre for Medium Range Weather Forecasts (ECMWF) reanalysis 850 hPa relative vorticity data. The tracked relative vorticity (ω) is used as a measure of storm strength, while position in the storm-centric domain is used to account for storm structure. Relationships between the cloud-related properties and τ are measured by calculating regression slopes and correlations. The fc-τ relationships are positive, while the Ttop-τ relationships are negative. By shuffling the pairing of the cloud and τ data at each location in the storm-centric domain and within narrow ω bins, the contribution of storm strength and storm structure to the observed relationships can be investigated. It is found that storm strength and storm structure can explain only a small component of the relationships observed in the MODIS data. The primary causes for observed cloud-aerosol relationships are likely to be other factors such as retrieval errors, local meteorology or aerosol-cloud interactions. © 2013 Author(s)."
"6507017517;55017656900;7003591311;39762774100;7801381830;7005310521;7004885872;","A comparative study of the response of modeled non-drizzling stratocumulus to meteorological and aerosol perturbations",2013,"10.5194/acp-13-2507-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874908221&doi=10.5194%2facp-13-2507-2013&partnerID=40&md5=35321fcc5be15f957b1de88e931cb456","The impact of changes in aerosol and cloud droplet concentration (<i>N</i>a and <i>N</i>d) on the radiative forcing of stratocumulus-topped boundary layers (STBLs) has been widely studied. How these impacts compare to those due to variations in meteorological context has not been investigated in a systematic fashion for non-drizzling overcast stratocumulus. In this study we examine the impact of observed variations in meteorological context and aerosol state on daytime, non-drizzling overcast stratiform evolution, and determine how resulting changes in cloud properties compare. <br><br> Using large-eddy simulation (LES) we create a model base case of daytime southeast Pacific coastal stratocumulus, spanning a portion of the diurnal cycle (early morning to near noon) and constrained by observations taken during the VOCALS (VAMOS Ocean-Atmosphere-Land Study) field campaign. We perturb aerosol and meteorological properties around this base case to investigate the stratocumulus response. We determine perturbations in the cloud top jumps in potential temperature θ and total water mixing ratio <i>q</i>t from ECMWF Re-analysis Interim data, and use a set of <i>N</i>d values spanning the observable range. To determine the cloud response to these meteorological and aerosol perturbations, we compute changes in liquid water path (LWP), bulk optical depth (τ) and cloud radiative forcing (CRF). <br><br> We find that realistic variations in the thermodynamic jump properties can elicit a response in the cloud properties of τ and shortwave (SW) CRF that are on the same order of magnitude as the response found due to realistic changes in aerosol state (i.e <i>N</i>d). In response to increases in <i>N</i>d, the cloud layer in the base case thinned due to increases in evaporative cooling and entrainment rate. This cloud thinning somewhat mitigates the increase in τ resulting from increases in <i>N</i>d. On the other hand, variations in θ and <i>q</i>t jumps did not substantially modify <i>N</i>d. The cloud layer thickens in response to an increase in the θ jump and thins in response to an increase in the <i>q</i>t jump, both resulting in a τ and SW CRF response comparable to those found from perturbations in <i>N</i>d. Longwave CRF was not substantially altered by the perturbations we tested. <br><br> We find that realistic variations in meteorological context can elicit a response in CRF and τ on the same order of magnitude as, and at times larger than, that response found due to realistic changes in aerosol state. We estimate the limits on variability of cloud top jump properties required for accurate observation of aerosol SW radiative impacts on stratocumulus, and find strict constraints: less than 1 K and 1 g kg&minus;1 in the early morning hours, and order 0.1 K and 0.1 g kg&minus;1 close to solar noon. These constraints suggest that accurately observing aerosol radiative impacts in stratocumulus may be challenging as co-variation of meteorological properties may obfuscate aerosol-cloud interactions. © Author(s) 2013."
"7006041988;8117864800;7003553324;57203233100;","A numerical study of aerosol influence on mixed-phase stratiform clouds through modulation of the liquid phase",2013,"10.5194/acp-13-1733-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874052437&doi=10.5194%2facp-13-1733-2013&partnerID=40&md5=f584bb3f0dd65bfc2f705f2420d1ee7a","Numerical simulations were carried out in a high-resolution two-dimensional framework to increase our understanding of aerosol indirect effects in mixed-phase stratiform clouds. Aerosol characteristics explored include insoluble particle type, soluble mass fraction, influence of aerosol-induced freezing point depression and influence of aerosol number concentration. Simulations were analyzed with a focus on the processes related to liquid phase microphysics, and ice formation was limited to droplet freezing. Of the aerosol properties investigated, aerosol insoluble mass type and its associated freezing efficiency was found to be most relevant to cloud lifetime. Secondary effects from aerosol soluble mass fraction and number concentration also alter cloud characteristics and lifetime. These alterations occur via various mechanisms, including changes to the amount of nucleated ice, influence on liquid phase precipitation and ice riming rates, and changes to liquid droplet nucleation and growth rates. Alteration of the aerosol properties in simulations with identical initial and boundary conditions results in large variability in simulated cloud thickness and lifetime, ranging from rapid and complete glaciation of liquid to the production of long-lived, thick stratiform mixed-phase cloud. © 2013 Author(s)."
"37056101400;7007010459;","An urban solar flux island: Measurements from London",2011,"10.1016/j.atmosenv.2011.03.045","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79956036345&doi=10.1016%2fj.atmosenv.2011.03.045&partnerID=40&md5=978bd89e000ea1822620b8bb1def85ee","Solar irradiance measurements from a new high density urban network in London are presented. Annual averages demonstrate that central London receives 30 ± 10 W m-2 less solar irradiance than outer London at midday, equivalent to 9 ± 3% less than the London average. Particulate matter and AERONET measurements combined with radiative transfer modelling suggest that the direct aerosol radiative effect could explain 33-40% of the inner London deficit and a further 27-50% could be explained by increased cloud optical depth due to the aerosol indirect effect. These results have implications for solar power generation and urban energy balance models.A new technique using 'Langley flux gradients' to infer aerosol column concentrations over clear periods of 3 h has been developed and applied to three case studies. Comparisons with particulate matter measurements across London have been performed and demonstrate that the solar irradiance measurement network is able to detect aerosol distribution across London and transport of a pollution plume out of London. © 2011 Elsevier Ltd."
"13403622000;7005955015;57203053317;56250250300;12139043600;12139310900;","Erratum: Modeling of the Wegener-Bergeron-Findeisen process - Implications for aerosol indirect effects (Environmental Research Letters (2008) 3 (045001))",2010,"10.1088/1748-9326/5/1/019801","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950661340&doi=10.1088%2f1748-9326%2f5%2f1%2f019801&partnerID=40&md5=102a09ef129282d27443bfb6b4feafc9",[No abstract available]
"12753162000;57197784699;57212870163;","Shepard and Hardy multiquadric interpolation methods for multicomponent aerosol-cloud parameterization",2009,"10.1175/2008JAS2626.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549100647&doi=10.1175%2f2008JAS2626.1&partnerID=40&md5=dfed56f0d74e650fd156964801fa8ce4","This paper presents a novel method based on the application of interpolation techniques to the multi-component aerosol-cloud parameterization for global climate modeling. Quantifying the aerosol indirect effect still remains a difficult task, and thus developing parameterizations for general circulation models (GCMs) of the microphysics of clouds and their interactions with aerosols is a major challenge for climate modelers. Three aerosol species are considered in this paper - namely sulfate, sea salt, and biomass smoke - and a detailed microphysical chemical parcel model is used to obtain a dataset of points relating the cloud droplet number concentration (CDNC) to the three aerosol input masses. The resulting variation of CDNC with the aerosol mass has some nonlinear features that require a complex but efficient parameterization to be easily incorporated into GCMs. In bicomponent systems, simple interpolation techniques may be sufficient to relate the CDNC to the aerosol mass, but with increasing components, simple methods fail. The parameterization technique proposed in this study employs either the modified Shepard interpolation method or the Hardy multiquadrics interpolation method, and the numerical results obtained show that both methods provide realistic results for a wide range of aerosol mass loadings. This is the first application of these two interpolation techniques to aerosol-cloud interaction studies. © 2009 American Meteorological Society."
"56188179500;7102743829;6506537159;","An idealized modeling study of the effect of continental air mass aerosol parameters on marine stratocumulus",2008,"10.1016/j.atmosres.2007.10.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41549133895&doi=10.1016%2fj.atmosres.2007.10.010&partnerID=40&md5=de625893beea5b165a14a791f7794d8b","A series of numerical simulations of a stratocumulus topped marine boundary layer (STBL) affected by advection of CCN from a continental origin were performed using a large eddy simulation (LES) model with explicit microphysics. We investigated the role of these continental air outbreaks as a function of continental aerosol size mode (giant, accumulation, and nucleation), location of the continental air mass in the vertical, and the presence of wind shear across the inversion. It was shown that giant CCN particles entrained into the cloud layer from an elevated continental air mass above the inversion significantly modulates drizzle efficiency, leading to profound effects on stratocumulus cloud layer dynamics and microphysics. These effects include breakup and decoupling of the cloud layer, attenuated turbulence, larger undulation of cloud top, and widening of the entrainment zone. In a marine air mass modified by continental aerosols of predominantly fine mode size, precipitation is suppressed. The suppression is less if the only source for the continental aerosol particles (in accumulation or nucleation mode) is via entrainment from a continental air mass above the inversion. The feedbacks between the continental aerosol forcing and drizzle efficiency, positive for the giant pollution particles and negative for accumulation and nucleation mode particles, are enhanced in the presence of wind shear. We conclude that the aerosol indirect effect cannot be characterized by the total aerosol particle load alone; the vertical variation in aerosol concentration, the size of the dominant particle mode, and the wind shear across the inversion each play significant roles in the physical processes underlying the indirect effect. © 2007 Elsevier B.V. All rights reserved."
"7005955015;","Studies of the aerosol indirect effect from sulfate and black carbon aerosols",2002,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-36448997395&partnerID=40&md5=741b44403b556c61acf95ee1c37ec402","[1] The indirect effect of anthropogenic aerosols is investigated using the global climate model National Center for Atmospheric Research Community Climate Model Version 3 (NCAR CCM3). Two types of anthropogenic aerosols are considered, i.e., sulfate and black carbon aerosols. The concentrations and horizontal distributions of these aerosols were obtained from simulations with a life-cycle model incorporated into the global climate model. They are then combined with size-segregated background aerosols. The aerosol size distributions are subjected to condensation, coagulation, and humidity swelling. By making assumptions on supersaturation, we determine cloud droplet number concentrations in water clouds. Cloud droplet sizes and top of atmosphere (TOA) radiative fluxes are in good agreement with satellite observations. Both components of the indirect effect, i.e., the radius and lifetime effects, are computed as pure forcing terms. Using aerosol data for 2000 from the Intergovernmental Panel on Climate Change (IPCC), we find, globally averaged, a 5% decrease in cloud droplet radius and a 5% increase in cloud water path due to anthropogenic aerosols. The largest changes are found over SE Asia, followed by the North Atlantic, Europe, and the eastern United States. This is also the case for the radiative forcing (""indirect effect""), which has a global average of -1.8 W m-2. When the experiment is repeated using data for 2100 from the IPCC A2 scenario, an unchanged globally averaged radiative forcing is found, but the horizontal distribution has been shifted toward the tropics. Sensitivity experiments show that the radius effect is ∼3 times as important as the lifetime effect and that black carbon only contributes marginally to the overall indirect effect. Copyright 2002 by the American Geophysical Union."
"16308514000;55536734900;57195361786;57126848900;56210720700;7003729315;7005891596;6508356419;57195361985;56016057500;14035836100;57209647985;35095482200;55619886800;57195488312;55350802700;56083852600;55688930000;7403247998;18134565600;7005035762;","Atmospheric Research Over the Western North Atlantic Ocean Region and North American East Coast: A Review of Past Work and Challenges Ahead",2020,"10.1029/2019JD031626","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082333727&doi=10.1029%2f2019JD031626&partnerID=40&md5=dfb25e5b161ae8871df70d24b5d51596","Decades of atmospheric research have focused on the Western North Atlantic Ocean (WNAO) region because of its unique location that offers accessibility for airborne and ship measurements, gradients in important atmospheric parameters, and a range of meteorological regimes leading to diverse conditions that are poorly understood. This work reviews these scientific investigations for the WNAO region, including the East Coast of North America and the island of Bermuda. Over 50 field campaigns and long-term monitoring programs, in addition to 715 peer-reviewed publications between 1946 and 2019, have provided a firm foundation of knowledge for these areas. Of particular importance in this region has been extensive work at the island of Bermuda that is host to important time series records of oceanic and atmospheric variables. Our review categorizes WNAO atmospheric research into eight major categories, with some studies fitting into multiple categories (relative %): aerosols (25%); gases (24%); development/validation of techniques, models, and retrievals (18%); meteorology and transport (9%); air-sea interactions (8%); clouds/storms (8%); atmospheric deposition (7%); and aerosol-cloud interactions (2%). Recommendations for future research are provided in the categories highlighted above. ©2020. American Geophysical Union. All Rights Reserved."
"7201432984;7202429440;7006399419;7406814589;57195570337;57191160338;57210176804;55408314400;7202252296;6603689369;","Variability in Marine Plankton Ecosystems Are Not Observed in Freshly Emitted Sea Spray Aerosol Over the North Atlantic Ocean",2020,"10.1029/2019GL085938","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078277433&doi=10.1029%2f2019GL085938&partnerID=40&md5=b794e4e3903c35292429aa9d769c8992","Sea spray aerosol (SSA) consists of both sea salt and organic components. These aerosols affect Earth's climate by scattering solar radiation and by altering cloud properties. Here we present observations of SSA particles generated at sea using an over-the-side bubbling system (Sea Sweep) and an onboard plunging wave mesocosm (Marine Aerosol Reference Tank—MART) during five cruises in the North Atlantic. The cruises were timed to sample different stages of the North Atlantic plankton bloom and included transects from the oligotrophic Sargasso Sea to the biologically productive western subarctic. The results show that the North Atlantic plankton bloom has little effect on the emission flux, organic fraction, or cloud condensation nuclei (CCN) activity of SSA, and therefore, plankton ecosystems do not need to be included in modeling aerosol indirect effects of primary SSA in global climate models or in chemical transport models. © 2020. The Authors."
"57097521200;57192172364;7003414581;57192168375;6701697023;14058796400;55883785100;15926468600;","Profiles of cloud condensation nuclei, dust mass concentration, and ice-nucleating-particle-relevant aerosol properties in the Saharan Air Layer over Barbados from polarization lidar and airborne in situ measurements",2019,"10.5194/acp-19-13773-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075313623&doi=10.5194%2facp-19-13773-2019&partnerID=40&md5=7c90c93e80a29764a9cc7c8ca481a25b","The present study aims to evaluate lidar retrievals of cloud-relevant aerosol properties by using polarization lidar and coincident airborne in situ measurements in the Saharan Air Layer (SAL) over the Barbados region. Vertical profiles of the number concentration of cloud condensation nuclei (CCN), large particles (diameter d > 500 nm), surface area, mass, and ice-nucleating particle (INP) concentration are derived from the lidar measurements and compared with CCN concentrations and the INP-relevant aerosol properties measured in situ with aircraft. The measurements were performed in the framework of the Saharan Aerosol Longrange Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) in summer 2013. The CCN number concentrations derived from lidar observations were up to a factor of 2 higher than the ones measured in situ aboard the research aircraft Falcon. Possible reasons for the difference are discussed. The number concentration of particles with a dry radius of more than 250 nm and the surface-area concentration obtained from the lidar observations and used as input for the INP parameterizations agreed well (< 30 %-50 % deviation) with the aircraft measurements. In a pronounced lofted dust layer during summer (10 July 2013), the lidar retrieval yielded 100-300 CCN per cubic centimeter at 0.2 % water supersaturation and 10-200 INPs per liter at-25?C. Excellent agreement was also obtained in the comparison of mass concentration profiles. During the SALTRACE winter campaign (March 2014), the dust layer from Africa was mixed with smoke particles which dominated the CCN number concentration. This example highlights the unique lidar potential to separate smoke and dust contributions to the CCN reservoir and thus to identify the sensitive role of smoke in trade wind cumuli developments over the tropical Atlantic during the winter season. © 2017 Georg Thieme Verlag. All rights reserved."
"57204124287;25227357000;7402270607;7404829395;56898331700;","Assessing aerosol indirect effect on clouds and regional climate of East/South Asia and West Africa using NCEP GFS",2019,"10.1007/s00382-018-4476-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054577904&doi=10.1007%2fs00382-018-4476-9&partnerID=40&md5=2170956e1e08b69137ece5d65e3f7cce","Aerosols can act as cloud condensation nuclei and ice nuclei, resulting in changes in cloud droplet/particle number/size, and hence altering the radiation budget. This study investigates the interactions between aerosols and ice clouds by incorporating the latest ice clouds parameterization in an atmospheric general circulation model. The simulation shows a decrease in effective ice cloud crystal size corresponding to aerosol increase, referred to as the aerosol first indirect effect, which has not been comprehensively studied. Ice clouds with smaller particles reflect more shortwave radiation and absorb more infrared radiation, resulting in radiation change by 0.5–1.0 W/m2 at the top of the atmosphere (TOA). The TOA radiation field is also influenced by cloud cover change due to aerosol-induced circulation change. Such aerosol effects on precipitation highly depend on the existence of a deep convection system: interactions between aerosols and ice clouds create dipole precipitation anomalies in the Asian monsoon regions; while in West Africa, enhanced convections are constrained by anticyclone effects at high levels and little precipitation increase is found. We also conduct an experiment to assess interactions between aerosols and liquid clouds and compare the climatic effects with that due to ice clouds. Radiation and temperature changes generated by liquid clouds are normally 1–2 times larger than those generated by ice clouds. The radiation change has a closer relationship to liquid cloud droplet size than liquid cloud cover, in contrast with what we find for ice clouds. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature."
"57200081294;57208389162;57213469031;56691914800;","Role of Feldspar and Pyroxene Minerals in the Ice Nucleating Ability of Three Volcanic Ashes",2019,"10.1021/acsearthspacechem.9b00004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064636609&doi=10.1021%2facsearthspacechem.9b00004&partnerID=40&md5=189ed39e05e6a2a1ee60f1a0bf5252d6","The mineralogical and immersion-mode freezing properties of volcanic ashes from three volcanoes, Volcán de Fuego and Santiaguito in Guatemala, and Soufrière Hills Volcano, in Montserrat, were examined. All ashes (sieved to &lt;37 μm) contained effective ice nuclei, typically freezing over the temperature range of -12 to -25 °C and possessing ice active site densities (ns) spanning ∼10 1 to 10 5 cm-2 over this temperature range. The high freezing activity of the ashes was determined to likely originate from pyroxene minerals, and the ice nucleation properties of pyroxene minerals are also reported here for the first time for comparison. Ca- and Na-rich plagioclase feldspars also contributed to the observed freezing properties. Volcanic glass was present in all of the samples and is theorized to be a much weaker ice nucleant, effectively diluting the freezing ability of the crystalline mineral phases. Smaller particle size fractions of the Volcán de Fuego ash were observed to contain more active ice nucleating particles, attributed to an increase in the amount of pyroxene minerals with decreasing particle size fraction. The particle resuspension and size segregated collection process was also observed to increase the ice nucleating ability of all size fractions, likely due to mechanical ablation removing passivated surfaces and exposing fresher and more ice-active mineral surfaces. Copyright © 2019 American Chemical Society."
"40461229800;35767428100;6603762280;57209715507;57127429600;57200697338;7006498080;10540059100;55093434700;57210255924;57210258643;57210265119;7004715270;","Ice Nucleating Particles Carried From Below a Phytoplankton Bloom to the Arctic Atmosphere",2019,"10.1029/2019GL083039","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070111068&doi=10.1029%2f2019GL083039&partnerID=40&md5=5dd7e04f3928797a003125da5d036596","As Arctic temperatures rise at twice the global rate, sea ice is diminishing more quickly than models can predict. Processes that dictate Arctic cloud formation and impacts on the atmospheric energy budget are poorly understood, yet crucial for evaluating the rapidly changing Arctic. In parallel, warmer temperatures afford conditions favorable for productivity of microorganisms that can effectively serve as ice nucleating particles (INPs). Yet the sources of marine biologically derived INPs remain largely unknown due to limited observations. Here we show, for the first time, how biologically derived INPs were likely transported hundreds of kilometers from deep Bering Strait waters and upwelled to the Arctic Ocean surface to become airborne, a process dependent upon a summertime phytoplankton bloom, bacterial respiration, ocean dynamics, and wind-driven mixing. Given projected enhancement in marine productivity, combined oceanic and atmospheric transport mechanisms may play a crucial role in provision of INPs from blooms to the Arctic atmosphere. ©2019. American Geophysical Union. All Rights Reserved."
"56628141500;6603196127;26667030700;7202079615;7403722047;36522733500;9249627300;6603378233;","Effect of high dust amount on surface temperature during the Last Glacial Maximum: A modelling study using MIROC-ESM",2018,"10.5194/cp-14-1565-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056379733&doi=10.5194%2fcp-14-1565-2018&partnerID=40&md5=53821c6cb7b88a981673fa9b7acf1fc1","The effect of aerosols is one of many uncertain factors in projections of future climate. However, the behaviour of mineral dust aerosols (dust) can be investigated within the context of past climate change. The Last Glacial Maximum (LGM) is known to have had enhanced dust deposition in comparison with the present, especially over polar regions. Using the Model for Interdisciplinary Research on Climate Earth System Model (MIROC-ESM), we conducted a standard LGM experiment following the protocol of the Paleoclimate Modelling Intercomparison Project phase 3 and sensitivity experiments. We imposed glaciogenic dust on the standard LGM experiment and investigated the impacts of glaciogenic dust and non-glaciogenic dust on the LGM climate. Global mean radiative perturbations by glaciogenic and non-glaciogenic dust were both negative, consistent with previous studies. However, glaciogenic dust behaved differently in specific regions; e.g. it resulted in less cooling over the polar regions. One of the major reasons for reduced cooling is the ageing of snow or ice, which results in albedo reduction via high dust deposition, especially near sources of high glaciogenic dust emission. Although the net radiative perturbations in the lee of high glaciogenic dust provenances are negative, warming by the ageing of snow overcomes this radiative perturbation in the Northern Hemisphere. In contrast, the radiative perturbation due to high dust loading in the troposphere acts to warm the surface in areas surrounding Antarctica, primarily via the longwave aerosol-cloud interaction of dust, and it is likely the result of the greenhouse effect attributable to the enhanced cloud fraction in the upper troposphere. Although our analysis focused mainly on the results of experiments using the atmospheric part of the MIROC-ESM, we also conducted full MIROC-ESM experiments for an initial examination of the effect of glaciogenic dust on the oceanic general circulation module. A long-term trend of enhanced warming was observed in the Northern Hemisphere with increased glaciogenic dust; however, the level of warming around Antarctica remained almost unchanged, even after extended coupling with the ocean. © 2018 Author(s)."
"57189038577;8680433600;56460968300;15032788000;","Evidence for Changes in Arctic Cloud Phase Due to Long-Range Pollution Transport",2018,"10.1029/2018GL079873","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054721750&doi=10.1029%2f2018GL079873&partnerID=40&md5=dc31c6bea8c6632ba1c5d9eac41efcf7","Reduced precipitation rates allow pollution within air parcels from midlatitudes to reach the Arctic without being scavenged. We use satellite and tracer transport model data sets to evaluate the degree of supercooling required for 50% of a chosen ensemble of low-level clouds to be in the ice phase for a given meteorological regime. Our results suggest that smaller cloud droplet effective radii are related to higher required amounts of supercooling but that, overall, pollution plumes from fossil fuel combustion lower the degree of supercooling that is required for freezing by approximately 4 °C. The relationship between anthropogenic plumes and the freezing transition temperature from liquid to ice remains to be explained. ©2018. American Geophysical Union. All Rights Reserved."
"57204068836;7003842561;56143929800;55940397300;45061126700;","Polar cooling effect due to increase of phytoplankton and dimethyl-sulfide emission",2018,"10.3390/atmos9100384","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054381902&doi=10.3390%2fatmos9100384&partnerID=40&md5=5d1abda370df52089a5495a0dd02a912","The effects of increased dimethyl-sulfide (DMS) emissions due to increased marine phytoplankton activity are examined using an atmosphere-ocean coupled climate model. As the DMS emission flux from the ocean increases globally, large-scale cooling occurs due to the DMS-cloud condensation nuclei (CCN)-cloud albedo interactions. This cooling increases as DMS emissions are further increased, with the most pronounced effect occurring over the Arctic, which is likely associated with a change in sea-ice fraction as sea ice mediates the air-sea exchange of the radiation, moisture and heat flux. These results differ from recent studies that only considered the bio-physical feedback that led to amplified Arctic warming under greenhouse warming conditions. Therefore, climate negative feedback from DMS-CCN-cloud albedo interactions that involve marine phytoplankton and its impact on polar climate should be properly reflected in future climate models to better estimate climate change, especially over the polar regions. © 2018 by the authors."
"57195267250;7101984634;55916086500;7404548584;56604019400;8665263500;6701718281;","Exploring the first aerosol indirect effect over Southeast Asia using a 10-year collocated MODIS, CALIOP, and model dataset",2018,"10.5194/acp-18-12747-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052894503&doi=10.5194%2facp-18-12747-2018&partnerID=40&md5=ec2f7e1aa584d7b1e00ce28bf89f2890","Satellite observations and model simulations cannot, by themselves, give full insight into the complex relationships between aerosols and clouds. This is especially true over Southeast Asia, an area that is particularly sensitive to changes in precipitation yet poses some of the world's largest observability and predictability challenges. We present a new collocated dataset, the Curtain Cloud-Aerosol Regional A-Train dataset, or CCARA. CCARA includes collocated satellite observations from Aqua's Moderate-resolution Imaging Spectroradiometer (MODIS) and the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) with the Navy Aerosol Analysis and Prediction System (NAAPS). The CCARA dataset is designed with the capability to investigate aerosol-cloud relationships in regions with limited aerosol retrievals due to high cloud amounts by leveraging the NAAPS model reanalysis of aerosol concentration in these regions. This combined aerosol and cloud dataset provides coincident and vertically resolved cloud and aerosol observations for 2006-2016. Using the model reanalysis aerosol fields from the NAAPS and coincident cloud liquid effective radius retrievals from MODIS (cirrus contamination using CALIOP), we investigate the first aerosol indirect effect in Southeast Asia. We find that, as expected, aerosol loading anti-correlates with cloud effective radius, with maximum sensitivity in cumulous mediocris clouds with heights in the 3-4.5km level. The highest susceptibilities in droplet effective radius to modeled perturbations in particle concentrations were found in the more remote and pristine regions of the western Pacific Ocean and Indian Ocean. Conversely, there was much less variability in cloud droplet size near emission sources over both land and water. We hypothesize this is suggestive of a high aerosol background already saturated with cloud condensation nuclei even during the relatively clean periods, in contrast to the remote ocean regions, which have periods where the aerosol concentrations are low enough to allow for larger droplet growth. © 2018 Author(s)."
"56127418900;25227357000;7404829395;56537463000;24074948100;55476830600;55802246600;56898331700;7102018821;12040335900;","Impacts of aerosols on seasonal precipitation and snowpack in California based on convection-permitting WRF-Chem simulations",2018,"10.5194/acp-18-5529-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045931609&doi=10.5194%2facp-18-5529-2018&partnerID=40&md5=cd8e74b1ef19072227047a769536fbeb","A version of the WRF-Chem model with fully coupled aerosol-meteorology-snowpack is employed to investigate the impacts of various aerosol sources on precipitation and snowpack in California. In particular, the impacts of locally emitted anthropogenic and dust aerosols, and aerosols transported from outside California are studied. We differentiate three pathways of aerosol effects: aerosol-radiation interaction (ARI), aerosol-snow interaction (ASI), and aerosol-cloud interaction (ACI). The convection-permitting model simulations show that precipitation, snow water equivalent (SWE), and surface air temperature averaged over the whole domain (34-42°N, 117-124°W, not including ocean points) are reduced when aerosols are included, therefore reducing large biases in these variables due to the absence of aerosol effects in the model. Aerosols affect California water resources through the warming of mountaintops and the reduction of precipitation; however, different aerosol sources play different roles in changing surface temperature, precipitation, and snowpack in California by means of various weights of the three pathways. ARI by all aerosols mainly cools the surface, leading to slightly increased SWE over the mountains. Locally emitted dust aerosols warm the surface of mountaintops through ASI, in which the reduced snow albedo associated with dusty snow leads to more surface absorption of solar radiation and reduced SWE. Transported aerosols and local anthropogenic aerosols play a dominant role in increasing nonprecipitating clouds but reducing precipitation through ACI, leading to reduced SWE and runoff on the Sierra Nevada, as well as the warming of mountaintops associated with decreased SWE and hence lower surface albedo. The average changes in surface temperature from October 2012 to June 2013 are about -0.19 and 0.22K for the whole domain and over mountaintops, respectively. Overall, the averaged reduction during October to June is about 7% for precipitation, 3% for SWE, and 7% for surface runoff for the whole domain, while the corresponding numbers are 12, 10, and 10% for the mountaintops. The reduction in SWE is more significant in a dry year, with 9% for the whole domain and 16% for the mountaintops. The maximum reduction of ∼ 20% in precipitation occurs in May and is associated with the maximum aerosol loading, leading to the largest decrease in SWE and surface runoff over that period. It is also found that dust aerosols can cause early snowmelt on the mountaintops and reduced surface runoff after April. © Author(s) 2018."
"24404522500;14829673100;13403622000;55899443700;55777115000;7007120936;","Global radiative effects of solid fuel cookstove aerosol emissions",2018,"10.5194/acp-18-5219-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045520573&doi=10.5194%2facp-18-5219-2018&partnerID=40&md5=aa9acd25c8c8a8b5debd5df24bdf3d5c","We apply the NCAR CAM5-Chem global aerosolclimate model to quantify the net global radiative effects of black and organic carbon aerosols from global and Indian solid fuel cookstove emissions for the year 2010. Our assessment accounts for the direct radiative effects, changes to cloud albedo and lifetime (aerosol indirect effect, AIE), impacts on clouds via the vertical temperature profile (semidirect effect, SDE) and changes in the surface albedo of snow and ice (surface albedo effect). In addition, we provide the first estimate of household solid fuel black carbon emission effects on ice clouds. Anthropogenic emissions are from the IIASA GAINS ECLIPSE V5a inventory. A global dataset of black carbon (BC) and organic aerosol (OA) measurements from surface sites and aerosol optical depth (AOD) from AERONET is used to evaluate the model skill. Compared with observations, the model successfully reproduces the spatial patterns of atmospheric BC and OA concentrations, and agrees with measurements to within a factor of 2. Globally, the simulated AOD agrees well with observations, with a normalized mean bias close to zero. However, the model tends to underestimate AOD over India and China by ∼19±4% but overestimate it over Africa by ∼25±11% (± represents modeled temporal standard deviations for n D 5 run years). Without BC serving as ice nuclei (IN), global and Indian solid fuel cookstove aerosol emissions have net global cooling radiative effects of-141±4mWm-2 and-12±4mWm-2, respectively (± represents modeled temporal standard deviations for n D 5 run years). The net radiative impacts are dominated by the AIE and SDE mechanisms, which originate from enhanced cloud condensation nuclei concentrations for the formation of liquid and mixedphase clouds, and a suppression of convective transport of water vapor from the lower troposphere to the upper troposphere/ lower stratosphere that in turn leads to reduced ice cloud formation. When BC is allowed to behave as a source of IN, the net global radiative impacts of the global and Indian solid fuel cookstove emissions range from-275 to C154mWm-2 and-33 to C24mWm-2, with globally averaged values of-59±215 and 0.3±29mWm-2, respectively. Here, the uncertainty range is based on sensitivity simulations that alter the maximum freezing efficiency of BC across a plausible range: 0.01, 0.05 and 0.1. BC-ice cloud interactions lead to substantial increases in high cloud (&lt;500 hPa) fractions. Thus, the net sign of the impacts of carbonaceous aerosols from solid fuel cookstoves on global climate (warming or cooling) remains ambiguous until improved constraints on BC interactions with mixed-phase and ice clouds are available. © 2018 Copernicus GmbH. All rights reserved."
"55717074000;55542833500;","Sensitivity of Homogeneous Ice Nucleation to Aerosol Perturbations and Its Implications for Aerosol Indirect Effects Through Cirrus Clouds",2018,"10.1002/2017GL076721","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041800618&doi=10.1002%2f2017GL076721&partnerID=40&md5=9acea77feb0fd42af018d33575d5b938","The magnitude and sign of anthropogenic aerosol impacts on cirrus clouds through ice nucleation are still very uncertain. In this study, aerosol sensitivity (ηα), defined as the sensitivity of the number concentration (Ni) of ice crystals formed from homogeneous ice nucleation to aerosol number concentration (Na), is examined based on simulations from a cloud parcel model. The model represents the fundamental process of ice crystal formation that results from homogeneous nucleation. We find that the geometric dispersion (σ) of the aerosol size distribution used in the model is a key factor for ηα. For a monodisperse size distribution, ηα is close to zero in vertical updrafts (V &lt; 50 cm s−1) typical of cirrus clouds. However, ηα increases to 0.1–0.3 (i.e., Ni increases by a factor of 1.3–2.0 for a tenfold increase in Na) if aerosol particles follow lognormal size distributions with a σ of 1.6–2.3 in the upper troposphere. By varying the input aerosol and environmental parameters, our model reproduces a large range of ηα values derived from homogeneous ice nucleation parameterizations widely used in global climate models (GCMs). The differences in ηα from these parameterizations can translate into a range of anthropogenic aerosol longwave indirect forcings through cirrus clouds from 0.05 to 0.36 W m−2 with a GCM. Our study suggests that a larger ηα (0.1–0.3) is more plausible and the homogeneous nucleation parameterizations should include a realistic aerosol size distribution to accurately quantify anthropogenic aerosol indirect effects. ©2018. American Geophysical Union. All Rights Reserved."
"57216645367;57200583927;56162305900;56722821200;6701606453;","Estimating precipitation susceptibility in warm marine clouds using multi-sensor aerosol and cloud products from A-Train satellites",2018,"10.5194/acp-18-1763-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041740603&doi=10.5194%2facp-18-1763-2018&partnerID=40&md5=2bf39b43480bc763f19647206eb99246","Precipitation susceptibility to aerosol perturbation plays a key role in understanding aerosol-cloud interactions and constraining aerosol indirect effects. However, large discrepancies exist in the previous satellite estimates of precipitation susceptibility. In this paper, multi-sensor aerosol and cloud products, including those from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), CloudSat, Moderate Resolution Imaging Spectroradiometer (MODIS), and Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) from June 2006 to April 2011 are analyzed to estimate precipitation frequency susceptibility SPOP, precipitation intensity susceptibility SI, and precipitation rate susceptibility SR in warm marine clouds. We find that SPOP strongly depends on atmospheric stability, with larger values under more stable environments. Our results show that precipitation susceptibility for drizzle (with a-15 dBZ rainfall threshold) is significantly different than that for rain (with a 0 dBZ rainfall threshold). Onset of drizzle is not as readily suppressed in warm clouds as rainfall while precipitation intensity susceptibility is generally smaller for rain than for drizzle. We find that SPOP derived with respect to aerosol index (AI) is about one-third of SPOP derived with respect to cloud droplet number concentration (CDNC). Overall, SPOP demonstrates relatively robust features throughout independent liquid water path (LWP) products and diverse rain products. In contrast, the behaviors of SI and SR are subject to LWP or rain products used to derive them. Recommendations are further made for how to better use these metrics to quantify aerosol-cloud-precipitation interactions in observations and models."
"35731251200;43561092300;55683113200;55481489700;57200536402;57200535228;7005773698;","The cloud nucleating properties and mixing state of marine aerosols sampled along the Southern California coast",2018,"10.3390/atmos9020052","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041545072&doi=10.3390%2fatmos9020052&partnerID=40&md5=264875a150c916ac0233459b145628a2","Marine aerosols are a globally significant contributor to aerosol-cloud-climate interactions; however, the impact that different sources of pollution and natural emissions from the ocean have on the water uptake properties of marine aerosols remains largely underexplored. Here we present measurements of the cloud condensation nuclei (CCN) activation of marine aerosols taken in a coastal, marine environment impacted by sea spray aerosol and different sources of pollution. The hygroscopicity parameter, κ, was found to range from < 0.1 up to 1.4 with a campaign-average value of 0.22 ± 0.12. Smaller particles were less hygroscopic than larger ones, and κ varied diurnally and temporally as a function of air mass transport conditions. Measurements made using aerosol time-of-flight mass spectrometry (ATOFMS) revealed that heterogeneous reactions, sulfates, and temporal differences in the observed particle types had the largest impacts on the observed κ values. The aerosol mixing-state was also found to affect κ. Temporal differences between freshly-emitted soot and aged soot internally mixed with sulfates, likely emitted from ships, had the largest impact on diurnal variations in κ. Our results further demonstrate the significant impact that pollution and the aerosol mixing-state have on aerosol-cloud interactions in the marine boundary layer. © 2018 by the authors."
"7102423967;7401796996;8629713500;","Aerosol properties and their impacts on surface CCN at the ARM Southern Great Plains site during the 2011 Midlatitude Continental Convective Clouds Experiment",2018,"10.1007/s00376-017-7033-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040333285&doi=10.1007%2fs00376-017-7033-2&partnerID=40&md5=24fa03105ccc16134e15abc73695ef32","Aerosol particles are of particular importance because of their impacts on cloud development and precipitation processes over land and ocean. Aerosol properties as well as meteorological observations from the Department of Energy Atmospheric Radiation Measurement (ARM) platform situated in the Southern Great Plains (SGP) are utilized in this study to illustrate the dependence of continental cloud condensation nuclei (CCN) number concentration (NCCN) on aerosol type and transport pathways. ARM-SGP observations from the 2011 Midlatitude Continental Convective Clouds Experiment field campaign are presented in this study and compared with our previous work during the 2009–10 Clouds, Aerosol, and Precipitation in the Marine Boundary Layer field campaign over the current ARM Eastern North Atlantic site. Northerly winds over the SGP reflect clean, continental conditions with aerosol scattering coefficient (σsp) values less than 20 Mm−1 and NCCN values less than 100 cm−3. However, southerly winds over the SGP are responsible for the observed moderate to high correlation (R) among aerosol loading (σsp &lt; 60 Mm−1) and NCCN, carbonaceous chemical species (biomass burning smoke), and precipitable water vapor. This suggests a common transport mechanism for smoke aerosols and moisture via the Gulf of Mexico, indicating a strong dependence on air mass type. NASA MERRA-2 reanalysis aerosol and chemical data are moderately to highly correlated with surface ARM-SGP data, suggesting that this facility can represent surface aerosol conditions in the SGP, especially during strong aerosol loading events that transport via the Gulf of Mexico. Future long-term investigations will help to understand the seasonal influences of air masses on aerosol, CCN, and cloud properties over land in comparison to over ocean. © 2018, Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag GmbH Germany, part of Springer Nature."
"33067634600;7101928629;","On the CCN (de)activation nonlinearities",2017,"10.5194/npg-24-535-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028863282&doi=10.5194%2fnpg-24-535-2017&partnerID=40&md5=bfcd0677d75da7b59874b6315791d90b","We take into consideration the evolution of particle size in a monodisperse aerosol population during activation and deactivation of cloud condensation nuclei (CCN). Our analysis reveals that the system undergoes a saddle-node bifurcation and a cusp catastrophe. The control parameters chosen for the analysis are the relative humidity and the particle concentration. An analytical estimate of the activation timescale is derived through estimation of the time spent in the saddle-node bifurcation bottleneck. Numerical integration of the system coupled with a simple air-parcel cloud model portrays two types of activation/deactivation hystereses: one associated with the kinetic limitations on droplet growth when the system is far from equilibrium, and one occurring close to equilibrium and associated with the cusp catastrophe. We discuss the presented analyses in context of the development of particle-based models of aerosol-cloud interactions in which activation and deactivation impose stringent time-resolution constraints on numerical integration. © 2017 Author(s). This work is distributed under the Creative Commons Attribution 3.0 License."
"24757696000;6602600408;7004020627;57194586250;26632168400;55326237100;35611334800;56060986400;56250185400;","Implementation of aerosol-cloud interactions in the regional atmosphere-aerosol model COSMO-Muscat(5.0) and evaluation using satellite data",2017,"10.5194/gmd-10-2231-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021101500&doi=10.5194%2fgmd-10-2231-2017&partnerID=40&md5=18a77e2265e0942f40347709d3e61bad","The regional atmospheric model Consortium for Small-scale Modeling (COSMO) coupled to the Multi-Scale Chemistry Aerosol Transport model (Muscat) is extended in this work to represent aerosol-cloud interactions. Previously, only one-way interactions (scavenging of aerosol and in-cloud chemistry) and aerosol-radiation interactions were included in this model. The new version allows for a microphysical aerosol effect on clouds. For this, we use the optional two-moment cloud microphysical scheme in COSMO and the online-computed aerosol information for cloud condensation nuclei concentrations (Cccn), replacing the constant Cccn profile. In the radiation scheme, we have implemented a droplet-size-dependent cloud optical depth, allowing now for aerosol-cloud-radiation interactions. To evaluate the models with satellite data, the Cloud Feedback Model Intercomparison Project Observation Simulator Package (COSP) has been implemented. A case study has been carried out to understand the effects of the modifications, where the modified modeling system is applied over the European domain with a horizontal resolution of 0.25°g × g0.25°. To reduce the complexity in aerosol-cloud interactions, only warm-phase clouds are considered. We found that the online-coupled aerosol introduces significant changes for some cloud microphysical properties. The cloud effective radius shows an increase of 9.5g%, and the cloud droplet number concentration is reduced by 21.5g%."
"35173744200;10141225800;6602087140;6701378450;7801401670;24437444900;55226243300;41361927700;55001699000;24537168200;55520002300;6507312817;7006837187;7004438457;7006058570;","Profiling aerosol optical, microphysical and hygroscopic properties in ambient conditions by combining in situ and remote sensing",2017,"10.5194/amt-10-83-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85009059991&doi=10.5194%2famt-10-83-2017&partnerID=40&md5=b20bd0d3d1ad7006f289bf0a90a6b4ac","We present the In situ/Remote sensing aerosol Retrieval Algorithm (IRRA) that combines airborne in situ and lidar remote sensing data to retrieve vertical profiles of ambient aerosol optical, microphysical and hygroscopic properties, employing the ISORROPIA II model for acquiring the particle hygroscopic growth. Here we apply the algorithm on data collected from the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 research aircraft during the ACEMED campaign in the Eastern Mediterranean. Vertical profiles of aerosol microphysical properties have been derived successfully for an aged smoke plume near the city of Thessaloniki with aerosol optical depth of ∼0.4 at 532 nm, single scattering albedos of ∼0.9-0.95 at 550 nm and typical lidar ratios for smoke of ∼60-80 sr at 532 nm. IRRA retrieves highly hydrated particles above land, with 55 and 80% water volume content for ambient relative humidity of 80 and 90%, respectively. The proposed methodology is highly advantageous for aerosol characterization in humid conditions and can find valuable applications in aerosol-cloud interaction schemes. Moreover, it can be used for the validation of active space-borne sensors, as is demonstrated here for the case of CALIPSO. © 2017 The Author(s)."
"57193803894;7004325649;6506827279;7006783796;","Quantifying the dependence of satellite cloud retrievals on instrument uncertainty",2017,"10.1175/JCLI-D-16-0429.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027247940&doi=10.1175%2fJCLI-D-16-0429.1&partnerID=40&md5=3c90cfe69d4cb3f2e1fdaeada95c190c","Cloud response to Earth's changing climate is one of the largest sources of uncertainty among global climate model (GCM) projections. Two of the largest sources of uncertainty are the spread in equilibrium climate sensitivity (ECS) and uncertainty in radiative forcing due to uncertainty in the aerosol indirect effect. Satellite instruments with sufficient accuracy and on-orbit stability to detect climate change-scale trends in cloud properties will improve confidence in the understanding of the relationship between observed climate change and cloud property trends, thus providing information to better constrain ECS and radiative forcing. This study applies a climate change uncertainty framework to quantify the impact of measurement uncertainty on trend detection times for cloud fraction, effective temperature, optical thickness, and water cloud effective radius. Although GCMs generally agree that the total cloud feedback is positive, disagreement remains on its magnitude. With the climate uncertainty framework, it is demonstrated how stringent measurement uncertainty requirements for reflected solar and infrared satellite measurements enable improved constraint of SW and LW cloud feedbacks and the ECS by significantly reducing trend uncertainties for cloud fraction, optical thickness, and effective temperature. The authors also demonstrate improved constraint on uncertainty in the aerosol indirect effect by reducing water cloud effective radius trend uncertainty. © 2017 American Meteorological Society."
"19933330400;8511991900;7006270084;57188966058;55476830600;7003666669;","Coupling spectral-bin cloud microphysics with the MOSAIC aerosol model in WRF-Chem: Methodology and results for marine stratocumulus clouds",2016,"10.1002/2016MS000676","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983268201&doi=10.1002%2f2016MS000676&partnerID=40&md5=0082ba464c8ab832e751e66e86454262","Aerosol-cloud interaction processes can be represented more physically with bin cloud microphysics relative to bulk microphysical parameterizations. However, due to computational power limitations in the past, bin cloud microphysics was often run with very simple aerosol treatments. The purpose of this study is to represent better aerosol-cloud interaction processes in the Chemistry version of Weather Research and Forecast model (WRF-Chem) at convection-permitting scales by coupling spectral-bin cloud microphysics (SBM) with the MOSAIC sectional aerosol model. A flexible interface is built that exchanges cloud and aerosol information between them. The interface contains a new bin aerosol activation approach, which replaces the treatments in the original SBM. It also includes the modified aerosol resuspension and in-cloud wet removal processes with the droplet loss tendencies and precipitation fluxes from SBM. The newly coupled system is evaluated for two marine stratocumulus cases over the Southeast Pacific Ocean with either a simplified aerosol setup or full-chemistry. We compare the aerosol activation process in the newly coupled SBM-MOSAIC against the SBM simulation without chemistry using a simplified aerosol setup, and the results show consistent activation rates. A longer time simulation reinforces that aerosol resuspension through cloud drop evaporation plays an important role in replenishing aerosols and impacts cloud and precipitation in marine stratocumulus clouds. Evaluation of the coupled SBM-MOSAIC with full-chemistry using aircraft measurements suggests that the new model works realistically for the marine stratocumulus clouds, and improves the simulation of cloud microphysical properties compared to a simulation using MOSAIC coupled with the Morrison two-moment microphysics. © 2016. The Authors."
"22982270700;56228672600;57196429803;56661876600;","Effects of aerosols on radiative forcing and climate over East Asia with different SO2 emissions",2016,"10.3390/atmos7080099","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983797285&doi=10.3390%2fatmos7080099&partnerID=40&md5=670975bdfe7c7a6c8ff356d05879f08a","It is known that aerosol and precursor gas emissions over East Asia may be underestimated by 50% due to the absence of data on regional rural and township industries. As the most important element of anthropogenic emissions, sulphur dioxide (SO2) can form sulfate aerosols through several chemical processes, thus affecting the regional and global climate. In this study, we use the Community Atmospheric Model 5.1 (CAM5.1) to investigate the effects of anthropogenic aerosols on radiative forcing and the climate over East Asia, taking into consideration various SO2 emission levels, including double the amount of SO2 emissions over East Asia. Numerical experiments are performed using high-resolution CAM5.1 with pre-industrial (PI) and present day (PD) aerosol emission levels, and with PD aerosol emission levels with double SO2 emissions over East Asia (PD2SO2). The simulated aerosol optical depth and surface sulfate concentrations over East Asia are significantly increased in PD2SO2, which is in better agreement with the observational results. The simulation results show extensive aerosol direct and indirect radiative forcing for PD-PI (the difference between PI and PD), which significantly weakens the large-scale intensity of the East Asian summer monsoon (EASM) and reduces the summer precipitation. Compared to PD, the aerosol direct radiative forcing is significantly increased in PD2SO2, whereas the aerosol indirect radiative forcing is markedly decreased due to the inhibition of cloud formation, especially over North China. The increase in aerosol direct radiative forcing and decrease in aerosol indirect radiative forcing result in insignificant changes in the total amount of aerosol radiative forcing. These results also show that the large-scale intensity of the EASM and the associated summer precipitation are insensitive to the doubling of current SO2 emissions. © 2016 by the authors."
"36801729300;55315290600;6603926727;7004154626;7004057920;","Aerosol indirect effects from ground-based retrievals over the rain shadow region in Indian subcontinent",2016,"10.1002/2015JD024577","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84960899122&doi=10.1002%2f2015JD024577&partnerID=40&md5=ef0d36e78622470a94c96183c6dd71d5","Aerosol-induced changes in cloud microphysical and radiative properties have been studied for the first time using ground-based and airborne observations over a semiarid rain shadow region. The study was conducted for nonprecipitating, ice-free clouds during monsoon (July to September) and postmonsoon (October) months, when cloud condensation nuclei (CCN) concentrations over the region of interest increased monotonically and exhibited characteristics of continental origin. A multifilter rotating shadowband radiometer and microwave radiometric profiler were used to retrieve the cloud optical depth and liquid water path (LWP), respectively, from which cloud effective radius (CER) was obtained. CER showed wide variability from 10-18 μm and a decreasing trend toward the postmonsoon period. During monsoon, the estimated first aerosol indirect effect (AIE) increased from 0.01 to 0.23 with increase in LWP. AIE at different super saturations (SS) showed maximum value (significant at 95%) at 0.4% SS and higher LWP bin (250-300 g/m2). Also, statistically significant AIE values were found at 0.6% and 0.8% SSs but at lower LWP bin (200-250 g/m2). The relationship between CCN and CER showed high correlation at 0.4% SS at higher LWP bin, while at higher SSs good correlations were observed at lower LWPs. Data combined from ground-based and aircraft observations showed dominance of microphysical effect at aerosol concentrations up to 1500 cm-3 and radiative effect at higher concentrations. This combined cloud microphysical and aerosol radiative effect is more prominent during postmonsoon period due to an increase in aerosol concentration. Key Points High AIE observed over the rain shadow region can also be one of the causative factors for rainfall deficiency AIE is highly variable with CCN super saturation along with available cloud LWP Combined cloud microphysical-aerosol radiative effects is prominent during postmonsoon period. © 2016. American Geophysical Union. All Rights Reserved."
"57212270042;57200055610;36623540900;36537129600;57218357221;7005902263;7006901405;","Surface and free tropospheric sources of methanesulfonic acid over the tropical Pacific Ocean",2014,"10.1002/2014GL060934","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904273532&doi=10.1002%2f2014GL060934&partnerID=40&md5=29ceb7bccf128f2057761f1ab24b956b","The production of sulfate aerosols through sulfur chemistry in marine environments is critical to the tropical climate system. However, not all sulfur compounds have been studied in detail. One such compound is methanesulfonic acid (MSA). In this study, we use a one-dimensional chemical transport model to analyze the observed vertical profiles of gas phase MSA during the Pacific Atmospheric Sulfur Experiment. The observed sharp decrease in MSA from the surface to 600 m implies a surface source of 4.0 × 107 molecules/cm2/s. Evidence suggests that this source is photolytically enhanced in daytime. We also find that the observed large increase of MSA from the boundary layer into the lower free troposphere (1000-2000 m) results mainly from the degassing of MSA from dehydrated aerosols. We estimate a source of 1.2 × 107 molecules/cm2/s to the free troposphere through this pathway. This source of soluble MSA could potentially provide an important precursor for new particle formation in the free troposphere over the tropics, affecting the climate system through aerosol-cloud interactions. © 2014. American Geophysical Union. All Rights Reserved."
"56045224900;","Dust observations and climatology",2014,"10.1007/978-94-017-8978-3_7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930905896&doi=10.1007%2f978-94-017-8978-3_7&partnerID=40&md5=91377d9fceaaf5ee83f8fd33b09c05ef","Along with a growing research interest for aerosols, a variety of methods have been developed in the last two decades to observe airborne mineral dust. Both remote sensing from spaceborne sensors and associated ground-based networks have played important roles. An increasing number of satellite sensors have been used either singly or in association with models, aircraft and ground-based measurements. The relevance of these techniques is to provide regional/global pictures of dust storm activity, allowing significant progress in the identification of dust sources, understanding of transport processes and assessment of variability at different timescales, from the diurnal cycle to interannual changes. More recently the development of lidar techniques has provided further advances in dust monitoring. The vertical profiling allows a 4D view of dust properties, a crucial point for progress on the assessment of aerosol radiative impact and aerosol-cloud interaction research. The algorithms associated to advanced sensors dedicated to aerosols, as well as the reliability of retrievals, have been improved in the last decade, giving more detailed and accurate description of dust properties. This chapter provides a brief review of the main observational techniques that have been used for dust survey (Sect. 7.2) with a focus on remote sensing observations. Applications of these data for research on dust source regions (Sect. 7.3.1), transport (Sect. 7.3.2), climatology (Sect. 7.3.3) and vertical structure (Sect. 7.3.4) are presented. Historical context and recent progress are shown alongside remaining limitations determining the needs for future improvements. © 2014 Springer Science+Business Media Dordrecht. All rights are reserved."
"37032042300;7005287667;7005712238;35461255500;","Aerosol indirect effects on continental low-level clouds over Sweden and Finland",2014,"10.5194/acp-14-12167-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007004577&doi=10.5194%2facp-14-12167-2014&partnerID=40&md5=9d8129a5da6dff270e31ae12047b1783","Aerosol effects on low-level clouds over the Nordic Countries are investigated by combining in situ ground-based aerosol measurements with remote sensing data of clouds and precipitation. Ten years of number size distribution data from two aerosol measurement stations (Vavihill, Sweden and Hyytiälä, Finland) provide aerosol number concentrations in the atmospheric boundary layer. This is combined with cloud satellite data from the Moderate Resolution Imaging Spectroradiometer and weather radar data from the Baltic Sea Experiment. Also, how the meteorological conditions affect the clouds is investigated using reanalysis data from the European Centre for Medium-Range Weather Forecasts. The cloud droplet effective radius is found to decrease when the aerosol number concentration increases, while the cloud optical thickness does not vary with boundary layer aerosol number concentrations. Furthermore, the aerosol- cloud interaction parameter (ACI), a measure of how the effective radius is influenced by the number concentration of cloud active particles, is found to be somewhere between 0.10 and 0.18 and the magnitude of the ACI is greatest when the number concentration of particles with a diameter larger than 130 nm is used. Lower precipitation intensity in the weather radar images is associated with higher aerosol number concentrations. In addition, at Hyytiälä the particle number concentrations is generally higher for non-precipitating cases than for precipitating cases. The apparent absence of the first indirect effect of aerosols on low-level clouds over land raises questions regarding the magnitude of the indirect aerosol radiative forcing. © Author(s) 2014."
"55667257200;7004508767;56521864800;","A statistical-numerical aerosol parameterization scheme",2013,"10.5194/acp-13-10483-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887035380&doi=10.5194%2facp-13-10483-2013&partnerID=40&md5=5e79e541735b8e1bea7d94c759f538c6","A new modal aerosol parameterization scheme, the statistical-numerical aerosol parameterization (SNAP), was developed for studying aerosol processes and aerosol-cloud interactions in regional or global models. SNAP applies statistical fitting on numerical results to generate accurate parameterization formulas without sacrificing details of the growth kernel. Processes considered in SNAP include fundamental aerosol processes as well as processes related to aerosol-cloud interactions. Comparison of SNAP with numerical solutions, analytical solutions, and binned aerosol model simulations showed that the new method performs well, with accuracy higher than that of the high-order numerical quadrature technique, and with much less computation time. The SNAP scheme has been implemented in regional air quality models, producing results very close to those using binned-size schemes or numerical quadrature schemes. © 2013 Author(s)."
"7006041988;22978151200;37018824600;7201837768;6701333444;","Evaluation of aerosol-cloud interaction in the GISS ModelE using ARM observations",2013,"10.1002/jgrd.50460","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880907890&doi=10.1002%2fjgrd.50460&partnerID=40&md5=a725b4a1cb8e391ee127e23ca59926c6","Observations from the US Department of Energy's Atmospheric Radiation Measurement (ARM) program are used to evaluate the ability of the NASA GISS ModelE global climate model in reproducing observed interactions between aerosols and clouds. Included in the evaluation are comparisons of basic meteorology and aerosol properties, droplet activation, effective radius parameterizations, and surface-based evaluations of aerosol-cloud interactions (ACI). Differences between the simulated and observed ACI are generally large, but these differences may result partially from vertical distribution of aerosol in the model, rather than the representation of physical processes governing the interactions between aerosols and clouds. Compared to the current observations, the ModelE often features elevated droplet concentrations for a given aerosol concentration, indicating that the activation parameterizations used may be too aggressive. Additionally, parameterizations for effective radius commonly used in models were tested using ARM observations, and there was no clear superior parameterization for the cases reviewed here. This lack of consensus is demonstrated to result in potentially large, statistically significant differences to surface radiative budgets, should one parameterization be chosen over another. Key Points The GISS ModelE struggles to correctly simulate aerosol-cloud interactions Effective Radius parameterization has a significant impact on simulated climate Long-term atmospheric measurements help in evaluating model performance © 2013. American Geophysical Union. All Rights Reserved."
"36485592900;7003842561;","Anthropogenic radiative forcing of marine stratocumulus clouds under different thermodynamic conditions-An LES model study",2012,"10.1016/j.atmosres.2012.07.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865442266&doi=10.1016%2fj.atmosres.2012.07.018&partnerID=40&md5=27d282c4b77ec68525374a08f9c14728","A LES model with bin microphysics was used to investigate the aerosol indirect effects of marine stratocumulus clouds that develop under different thermodynamic conditions. The diurnal contrasts of cloud development were also examined in detail. Three observed CCN spectra that represent maritime, continental and polluted air masses were used as input CCN spectra. Two observed thermodynamic soundings and two derived ones from the observed soundings to vary the inversion altitude were used as initial thermodynamic conditions. With these initial conditions the model was run for the daytime and nocturnal conditions to make the total number of model runs to be 24. For both daytime and nocturnal conditions, the cloud depth and liquid water path (LWP) varied with the thermodynamic soundings. For a given thermodynamic sounding, LWP tended to be similar or slightly smaller for polluted. However, cloud top radiative cooling is stronger for polluted due to smaller sizes of cloud droplets and therefore turbulent mixing is stronger for polluted. However, there were significant differences in LWP between the daytime and nocturnal clouds. For the daytime condition, the cloud became decoupled from the surface layer and moisture supply was limited for all soundings. In contrast, with the absence of solar radiation, cloud top radiative cooling was much stronger, turbulent mixing was also much stronger and therefore no decoupling occurred and clouds were thicker with greater LWP in the nocturnal runs. To note is the derived thermodynamic sounding (named MH) that produced the thickest clouds: the clouds were too thick to be maintained as a single layer cloud and became multi-layered for the daytime condition while the maritime stratocumulus cloud broke up into a cumuliform cloud due to heavy drizzle for the nocturnal condition. From the daytime run results, the anthropogenic cloud radiative forcing was calculated by subtracting the net cloud radiative forcing for maritime from that for polluted. It amounted to be -21.6Wm -2 for MH but was more than a factor of two larger for all three other soundings, -56.4, -55.4 and -55.7Wm -2. For the MH sounding, the LWP was noticeably smaller for polluted than for maritime, the relative difference of the effective radii between maritime and polluted was small and therefore albedo difference between the two was also small, compared to those for the other three soundings. Notable is the similar magnitude of the anthropogenic cloud radiative forcing for these three soundings despite the significant differences in cloud depths among the clouds produced by these soundings. This may imply that there may be an optimal range of cloud depth that can produce a strong anthropogenic cloud radiative forcing. The cloud depths were smaller than 150m for the thermodynamic sounding that produced the shallowest clouds but it seemed to be within the optimal range. © 2012 Elsevier B.V."
"56032511300;","Dependence of the effect of aerosols on cirrus clouds on background vertical velocity",2012,"10.1016/j.atmosres.2012.03.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860551240&doi=10.1016%2fj.atmosres.2012.03.003&partnerID=40&md5=129eea229ed46f0097c12d80bfc6cc01","Cirrus clouds cover approximately 20-25% of the globe and thus play an important role in the Earth's radiation budget. This important role in the radiation budget played by cirrus clouds indicates that aerosol effects on cirrus clouds can have a substantial impact on the variation of global radiative forcing if the ice-water path (IWP) changes. This study examines the aerosol indirect effect (AIE) through changes in the IWP for cirrus cloud cases. This study also examines the dependence of aerosol-cloud interactions in cirrus clouds on the large-scale vertical motion. We use a cloud-system resolving model (CSRM) coupled with a double-moment representation of cloud microphysics.Intensified interactions among the cloud ice number concentration (CINC), deposition and dynamics play a critical role in the IWP increases due to aerosol increases from the preindustrial (PI) level to the present-day (PD) level with a low large-scale vertical velocity. Increased aerosols lead to an increased CINC, providing an increased surface area for water vapor deposition. The increased surface area leads to increased deposition despite decreased supersaturation with increasing aerosols. The increased deposition causes an increased depositional heating which produces stronger updrafts, and these stronger updrafts lead to the increased IWP. However, with a high large-scale vertical velocity, the effect of increased CINC on deposition was not able to offset the effect of decreasing supersaturation with increasing aerosols. The effect of decreasing supersaturation on deposition dominant over that of increasing CINC leads to smaller deposition and IWP at high aerosol with the PD aerosol than at low aerosol with the PI aerosol.The conversion of ice crystals to aggregates through autoconversion and accretion plays a negligible role in the IWP responses to aerosols, as does the sedimentation of aggregates. The sedimentation of ice crystals plays a more important role in the IWP response to aerosol increases than the sedimentation of aggregates, but, not more important than the interactions among the CINC, supersaturation, deposition and dynamics. These interactions not only determine the effect of aerosols on IWP but also control how this effect varies with varying large-scale vertical velocities. © 2012 Elsevier B.V."
"6602506226;","Weakness of the weekend effect in aerosol number concentrations",2012,"10.1016/j.atmosenv.2012.01.060","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857789692&doi=10.1016%2fj.atmosenv.2012.01.060&partnerID=40&md5=7310a9e708a9eccaf7d139ca932d25e2","Weekday related anthropogenic aerosol emissions have been suggested to affect regional climate via indirect aerosol effects. I studied the variability of potential cloud condensation nuclei using measurements of number size distributions of Cloud Condensation Nuclei (CCN)-sized aerosol particles and CCNs measured at several European regional background stations, located at a wide variety of environments. With notably rare exceptions, there were no statistically significant difference between concentrations on different weekdays. I further analysed the concentration time-series of four long-period datasets in Germany and Finland with wavelet analysis. Outside of urban areas, very little weekday-connected variability was found. The lack of 7-day variability outside of cities is in contrast of earlier studies in this field, which used mostly particle mass as the representative measure of aerosol concentration. A time-scale and variability analysis showed that PM 10 and PM 2.5 are more sensitive for the weekly variation than CCN-sized particles. Using mass-based variations as a proxy for short-term variations of CCN particle numbers can thus overestimate the weekend effect for these particles. The results of this study do not support aerosol indirect effects from 50 to 500 nm diameter particles as a major contributor on potential weekday connected variations in European meteorology. © 2012 Elsevier Ltd."
"36465124400;21933618400;35559590900;7201787800;35224765000;7006235542;7006837187;6603172418;","In situ aerosol measurements taken during the 2007 COPS field campaign at the Hornisgrinde ground site",2011,"10.1002/qj.727","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952001936&doi=10.1002%2fqj.727&partnerID=40&md5=5d1425831023519dde3f1ea1f84421d7","The Convective and Orographically-induced Precipitation Study (COPS) campaign was conducted during the summer of 2007. A suite of instruments housed at the top of the Hornisgrinde Mountain (1156 m) in the Black Forest region of south-west Germany provided datasets that allow an investigation into the physical, chemical and hygroscopic properties of the aerosol particles sampled during COPS. Organic mass loadings were found to dominate the aerosol composition for the majority of the project, exceeding 8 μg m-3 during a period of high pressure, high temperature, and low wind speed. The ratio of organic:sulphate sub-micron mass concentration exceeds 10:1 during the same time period. Back trajectories show air from this time-frame passing slowly over the local forest and not passing over any local anthropogenic sources. Occasional peaks in nitrate mass loadings were associated with changes in the typical wind direction from south-westerly to north-westerly where air had passed over the Stuttgart region. Size distribution data shows a dominant accumulation-mode when the measurement site was free from precipitation events. A sharp increase in ultrafine particle number concentration was seen during most days commencing around noon. The apparent growth of these particles is associated with an increase in organic mass loading, suggesting condensational growth. For the most part, with the exception of the high pressure period, the aerosol properties recorded during COPS were comparable to previous studies of continental aerosol properties. Copyright © 2011 Royal Meteorological Society Copyright © 2011 Royal Meteorological Society."
"6603140753;7201837768;7004242319;","Simulating mixed-phase Arctic stratus clouds: Sensitivity to ice initiation mechanisms",2009,"10.5194/acp-9-4747-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79961199866&doi=10.5194%2facp-9-4747-2009&partnerID=40&md5=42e9c4491dc9302d5601bbf830c1260c","The importance of Arctic mixed-phase clouds on radiation and the Arctic climate is well known. However, the development of mixed-phase cloud parameterization for use in large scale models is limited by lack of both related observations and numerical studies using multidimensional models with advanced microphysics that provide the basis for understanding the relative importance of different microphysical processes that take place in mixed-phase clouds. To improve the representation of mixed-phase cloud processes in the GISS GCM we use the GISS single-column model coupled to a bin resolved microphysics (BRM) scheme that was specially designed to simulate mixed-phase clouds and aerosol-cloud interactions. Using this model with the microphysical measurements obtained from the DOE ARM Mixed-Phase Arctic Cloud Experiment (MPACE) campaign in October 2004 at the North Slope of Alaska, we investigate the effect of ice initiation processes and Bergeron-Findeisen process (BFP) on glaciation time and longevity of single-layer stratiform mixed-phase clouds. We focus on observations taken during 9-10 October, which indicated the presence of a single-layer mixed-phase clouds. We performed several sets of 12-h simulations to examine model sensitivity to different ice initiation mechanisms and evaluate model output (hydrometeors' concentrations, contents, effective radii, precipitation fluxes, and radar reflectivity) against measurements from the MPACE Intensive Observing Period. Overall, the model qualitatively simulates ice crystal concentration and hydrometeors content, but it fails to predict quantitatively the effective radii of ice particles and their vertical profiles. In particular, the ice effective radii are overestimated by at least 50%. However, using the same definition as used for observations, the effective radii simulated and that observed were more comparable. We find that for the single-layer stratiform mixed-phase clouds simulated, process of ice phase initiation due to freezing of supercooled water in both saturated and subsaturated (w.r.t. water) environments is as important as primary ice crystal origination from water vapor. We also find that the BFP is a process mainly responsible for the rates of glaciation of simulated clouds. These glaciation rates cannot be adequately represented by a water-ice saturation adjustment scheme that only depends on temperature and liquid and solid hydrometeors' contents as is widely used in bulk microphysics schemes and are better represented by processes that also account for supersaturation changes as the hydrometeors grow. © 2009 Author(s)."
"57218719165;57218715519;7003777747;57218719136;7402105994;15726663700;57203200427;7004714030;55802221900;6506553245;6603412788;8397494800;23486734100;10241250100;57215857013;7202391479;24339847400;24329376600;36876405100;36705143500;56203249800;55227339000;57199567418;56324515500;15042618500;57218716470;7006577693;57205867148;57218718333;","Effective radiative forcing and adjustments in CMIP6 models",2020,"10.5194/acp-20-9591-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85090172487&doi=10.5194%2facp-20-9591-2020&partnerID=40&md5=7560ef66c8a07ce7c90c2b44c25b388f","The effective radiative forcing, which includes the instantaneous forcing plus adjustments from the atmosphere and surface, has emerged as the key metric of evaluating human and natural influence on the climate. We evaluate effective radiative forcing and adjustments in 17 contemporary climate models that are participating in the Coupled Model Intercomparison Project (CMIP6) and have contributed to the Radiative Forcing Model Intercomparison Project (RFMIP). Present-day (2014) global-mean anthropogenic forcing relative to pre-industrial (1850) levels from climate models stands at 2.00 (0:23) Wm2, comprised of 1.81 (0:09) Wm2 from CO2, 1.08 ( 0.21) Wm2 from other well-mixed greenhouse gases, 1:01 ( 0.23) Wm2 from aerosols and 0:09 (0:13) Wm2 from land use change. Quoted uncertainties are 1 standard deviation across model best estimates, and 90 confidence in the reported forcings, due to internal variability, is typically within 0.1 Wm2. The majority of the remaining 0:21Wm2 is likely to be from ozone. In most cases, the largest contributors to the spread in effective radiative forcing (ERF) is from the instantaneous radiative forcing (IRF) and from cloud responses, particularly aerosol-cloud interactions to aerosol forcing. As determined in previous studies, cancellation of tropospheric and surface adjustments means that the stratospherically adjusted radiative forcing is approximately equal to ERF for greenhouse gas forcing but not for aerosols, and consequentially, not for the anthropogenic total. The spread of aerosol forcing ranges from 0:63 to 1:37Wm2, exhibiting a less negative mean and narrower range compared to 10 CMIP5 models. The spread in 4CO2 forcing has also narrowed in CMIP6 compared to 13 CMIP5 models. Aerosol forcing is uncorrelated with climate sensitivity. Therefore, there is no evidence to suggest that the increasing spread in climate sensitivity in CMIP6 models, particularly related to high-sensitivity models, is a consequence of a stronger negative present-day aerosol forcing and little evidence that modelling groups are systematically tuning climate sensitivity or aerosol forcing to recreate observed historical warming. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License."
"56457851700;7103016965;7201394374;25924878400;16444006500;","Untangling causality in midlatitude aerosol-cloud adjustments",2020,"10.5194/acp-20-4085-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083052650&doi=10.5194%2facp-20-4085-2020&partnerID=40&md5=5ba6048e60d5ef218bb7c9aebfa3dcac","Aerosol-cloud interactions represent the leading uncertainty in our ability to infer climate sensitivity from the observational record. The forcing from changes in cloud albedo driven by increases in cloud droplet number (Nd) (the first indirect effect) is confidently negative and has narrowed its probable range in the last decade, but the sign and strength of forcing associated with changes in cloud macrophysics in response to aerosol (aerosol-cloud adjustments) remain uncertain. This uncertainty reflects our inability to accurately quantify variability not associated with a causal link flowing from the cloud microphysical state to the cloud macrophysical state. Once variability associated with meteorology has been removed, covariance between the liquid water path (LWP) averaged across cloudy and clear regions (here characterizing the macrophysical state) and Nd (characterizing the microphysical) is the sum of two causal pathways linking Nd to LWP: Nd altering LWP (adjustments) and precipitation scavenging aerosol and thus depleting Nd. Only the former term is relevant to constraining adjustments, but disentangling these terms in observations is challenging. We hypothesize that the diversity of constraints on aerosol-cloud adjustments in the literature may be partly due to not explicitly characterizing covariance flowing from cloud to aerosol and aerosol to cloud. Here, we restrict our analysis to the regime of extratropical clouds outside of low-pressure centers associated with cyclonic activity. Observations from MAC-LWP (Multisensor Advanced Climatology of Liquid Water Path) and MODIS are compared to simulations in the Met Office Unified Model (UM) GA7.1 (the atmosphere model of HadGEM3-GC3.1 and UKESM1). The meteorological predictors of LWP are found to be similar between the model and observations. There is also agreement with previous literature on cloud-controlling factors finding that increasing stability, moisture, and sensible heat flux enhance LWP, while increasing subsidence and sea surface temperature decrease it. A simulation where cloud microphysics are insensitive to changes in Nd is used to characterize covariance between Nd and LWP that is induced by factors other than aerosol-cloud adjustments. By removing variability associated with meteorology and scavenging, we infer the sensitivity of LWP to changes in Nd. Application of this technique to UM GA7.1 simulations reproduces the true model adjustment strength. Observational constraints developed using simulated covariability not induced by adjustments and observed covariability between Nd and LWP predict a 25 %-30% overestimate by the UM GA7.1 in LWP change and a 30 %-35% overestimate in associated radiative forcing. © 2020 Copernicus GmbH. All rights reserved."
"55688930000;7006270084;36657850900;15755995900;55544607500;56384704800;57214786060;7006705919;22953153500;7003666669;55317190600;55802246600;55720018700;7404544551;8570871900;7202048112;55717074000;13007924700;56049520900;25629055800;7401936984;55317177900;","Aerosols in the E3SM Version 1: New Developments and Their Impacts on Radiative Forcing",2020,"10.1029/2019MS001851","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078849803&doi=10.1029%2f2019MS001851&partnerID=40&md5=85b34f6275e02272599ab79af8c3cb28","The new Energy Exascale Earth System Model Version 1 (E3SMv1) developed for the U.S. Department of Energy has significant new treatments of aerosols and light-absorbing snow impurities as well as their interactions with clouds and radiation. This study describes seven sets of new aerosol-related treatments (involving emissions, new particle formation, aerosol transport, wet scavenging and resuspension, and snow radiative transfer) and examines how they affect global aerosols and radiative forcing in E3SMv1. Altogether, they give a reduced total aerosol radiative forcing (−1.6 W/m2) and sensitivity in cloud liquid water to aerosols, but an increased sensitivity in cloud droplet size to aerosols. A new approach for H2SO4 production and loss largely reduces a low bias in small particles concentrations and leads to substantial increases in cloud condensation nuclei concentrations and cloud radiative cooling. Emitting secondary organic aerosol precursor gases from elevated sources increases the column burden of secondary organic aerosol, contributing substantially to global clear-sky aerosol radiative cooling (−0.15 out of −0.5 W/m2). A new treatment of aerosol resuspension from evaporating precipitation, developed to remedy two shortcomings of the original treatment, produces a modest reduction in aerosols and cloud droplets; its impact depends strongly on the model physics and is much stronger in E3SM Version 0. New treatments of the mixing state and optical properties of snow impurities and snow grains introduce a positive present-day shortwave radiative forcing (0.26 W/m2), but changes in aerosol transport and wet removal processes also affect the concentration and radiative forcing of light-absorbing impurities in snow/ice. © 2019. The Authors."
"57203098840;55718911800;55999590500;6506180220;6506258154;55366522200;55716266100;56068376200;55431445800;57145546300;","Organic coating on sulfate and soot particles during late summer in the Svalbard Archipelago",2019,"10.5194/acp-19-10433-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070798128&doi=10.5194%2facp-19-10433-2019&partnerID=40&md5=cc4225d941e3327871e63bdfd856d356","Interaction of anthropogenic particles with radiation and clouds plays an important role in Arctic climate change. The mixing state of aerosols is a key parameter to influence aerosol radiation and aerosol-cloud interactions. However, little is known of this parameter in the Arctic, preventing an accurate representation of this information in global models. Here we used transmission electron microscopy with energy-dispersive X-ray spectrometry, scanning electron microscopy, nanoscale secondary ion mass spectrometry, and atomic forces microscopy to determine the size and mixing state of individual sulfate and carbonaceous particles at 100 nm to 2 collected in the Svalbard Archipelago in summer. We found that 74 % by number of non-sea-salt sulfate particles were coated with organic matter (OM); 20 % of sulfate particles also had soot inclusions which only appeared in the OM coating. The OM coating is estimated to contribute 63 % of the particle volume on average. To understand how OM coating influences optical properties of sulfate particles, a Mie core-shell model was applied to calculate optical properties of individual sulfate particles. Our result shows that the absorption cross section of individual OM-coated particles significantly increased when assuming the OM coating as light-absorbing brown carbon. Microscopic observations here suggest that OM modulates the mixing structure of fine Arctic sulfate particles, which may determine their hygroscopicity and optical properties. © 2019 Copernicus GmbH. All rights reserved."
"57203318983;56536745100;57203053317;","Response of Arctic mixed-phase clouds to aerosol perturbations under different surface forcings",2019,"10.5194/acp-19-9847-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85073886826&doi=10.5194%2facp-19-9847-2019&partnerID=40&md5=5774a16663eaaddc27d5e875315008ae","The formation and persistence of low-lying mixed-phase clouds (MPCs) in the Arctic depends on a multitude of processes, such as surface conditions, the environmental state, air mass advection, and the ambient aerosol concentration. In this study, we focus on the relative importance of different instantaneous aerosol perturbations (cloud condensation nuclei and ice-nucleating particles; CCN and INPs, respectively) on MPC properties in the European Arctic. To address this topic, we performed high-resolution large-eddy simulation (LES) experiments using the Consortium for Small-scale Modeling (COSMO) model and designed a case study for the Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA) campaign in March 2013. Motivated by ongoing sea ice retreat, we performed all sensitivity studies over open ocean and sea ice to investigate the effect of changing surface conditions. We find that surface conditions highly impact cloud dynamics, consistent with the ACCACIA observations: over sea ice, a rather homogeneous, optically thin, mixed-phase stratus cloud forms. In contrast, the MPC over the open ocean has a stratocumulus-like cloud structure. With cumuli feeding moisture into the stratus layer, the cloud over the open ocean features a higher liquid (LWP) and ice water path (IWP) and has a lifted cloud base and cloud top compared to the cloud over sea ice. Furthermore, we analyzed the aerosol impact on the sea ice and open ocean cloud regime. Perturbation aerosol concentrations relevant for CCN activation were increased to a range between 100 and 1000 cm-3 and icenucleating particle perturbations were increased by 100% and 300% compared to the background concentration (at every grid point and at all levels). The perturbations are prognostic to allow for fully interactive aerosol-cloud interactions. Perturbations in the INP concentration increase IWP and decrease LWP consistently in both regimes. The cloud microphysical response to potential CCN perturbations occurs faster in the stratocumulus regime over the ocean, where the increased moisture flux favors rapid cloud droplet formation and growth, leading to an increase in LWP following the aerosol injection. In addition, IWP increases through new ice crystal formation by increased immersion freezing, cloud top rise, and subsequent growth by deposition. Over sea ice, the maximum response in LWP and IWP is delayed and weakened compared to the response over the open ocean surface. Additionally, we find the long-term response to aerosol perturbations to be highly dependent on the cloud regime. Over the open ocean, LWP perturbations are efficiently buffered after 18 h simulation time. Increased ice and precipitation formation relax the LWP back to its unperturbed range. On the contrary, over sea ice the cloud evolution remains substantially perturbed with CCN perturbations ranging from 200 to 1000CCNcm-3. © 2019 Author(s)."
"24081888700;55330123800;55816227500;57208765879;7401793588;6603081424;","Automatically Finding Ship Tracks to Enable Large-Scale Analysis of Aerosol-Cloud Interactions",2019,"10.1029/2019GL083441","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068505616&doi=10.1029%2f2019GL083441&partnerID=40&md5=5295e61b029f66f2bd51dc33d3b69818","Ship tracks appear as long winding linear features in satellite images and are produced by aerosols from ship exhausts changing low cloud properties. They are one of the best examples of aerosol-cloud interaction experiments. However, manually finding ship tracks from satellite data on a large scale is prohibitively costly while a large number of samples are required to improve our understanding. Here we train a deep neural network to automate finding ship tracks. The neural network model generalizes well as it not only finds ship tracks labeled by human experts but also detects those that are occasionally missed by humans. It finds more ship tracks than all previous studies combined and produces a map of ship track distributions off the California coast that matches well with known shipping traffic. Our technique will enable studying aerosol effects on low clouds using ship tracks on a large scale, which will potentially narrow the uncertainty of the aerosol-cloud interactions. ©2019. The Authors."
"57194633505;57194464561;57200689896;8631019200;55899884100;8911915900;36021733300;55258950300;","Method to retrieve cloud condensation nuclei number concentrations using lidar measurements",2019,"10.5194/amt-12-3825-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068894982&doi=10.5194%2famt-12-3825-2019&partnerID=40&md5=cac3dd57374a417cce65c9da4dcb16f8","Determination of cloud condensation nuclei (CCN) number concentrations at cloud base is important to constrain aerosol-cloud interactions. A new method to retrieve CCN number concentrations using backscatter and extinction profiles from multiwavelength Raman lidars is proposed. The method implements hygroscopic enhancements of backscatter and extinction with relative humidity to derive dry backscatter and extinction and humidogram parameters. Humidogram parameters, Ångström exponents, and lidar extinction-to-backscatter ratios are then linked to the ratio of CCN number concentration to dry backscatter and extinction coefficient (<span classCombining double low lineAR<i>ζ</i>). This linkage is established based on the datasets simulated by Mie theory and <span classCombining double low line<i>κ</i>-Köhler theory with in-situ-measured particle size distributions and chemical compositions. CCN number concentration can thus be calculated with <span classCombining double low lineAR<i>ζ</i> and dry backscatter and extinction. An independent theoretical simulated dataset is used to validate this new method and results show that the retrieved CCN number concentrations at supersaturations of 0.07%, 0.10%, and 0.20% are in good agreement with theoretical calculated values. Sensitivity tests indicate that retrieval error in CCN arises mostly from uncertainties in extinction coefficients and RH profiles. The proposed method improves CCN retrieval from lidar measurements and has great potential in deriving scarce long-term CCN data at cloud base, which benefits aerosol-cloud interaction studies. © Author(s) 2019."
"57204816417;55917306900;56151545200;7102010848;56195282900;7406500188;57205085158;","Impacts of black carbon on the formation of advection-radiation fog during a haze pollution episode in eastern China",2019,"10.5194/acp-19-7759-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067244959&doi=10.5194%2facp-19-7759-2019&partnerID=40&md5=965b9277ec071d3a160758539a9112d2","Aerosols can not only participate in fog formation by acting as condensation nuclei of droplets but also modify the meteorological conditions such as air temperature and moisture, planetary boundary layer height (PBLH) and regional circulation during haze events. The impact of aerosols on fog formation, yet to be revealed, can be critical in understanding and predicting fog-haze events. In this study, we used the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) to investigate a heavy fog event during a multiday intense haze pollution episode in early December 2013 in the Yangtze River Delta (YRD) region in eastern China. Using the WRF-Chem model, we conducted four parallel numerical experiments to evaluate the roles of aerosol-radiation interaction (ARI), aerosol-cloud interaction (ACI), black carbon (BC) and non-BC aerosols in the formation and maintenance of the heavy fog event. We find that only when the aerosols' feedback processes are considered can the model capture the haze pollution and the fog event well. And the effects of ARI during the fog-haze episode in early December 2013 played a dominant role, while the effects of ACI were negligible. Furthermore, our analyses show that BC was more important in inducing fog formation in the YRD region on 7 December than non-BC aerosols. The dome effect of BC leads to an increase in air moisture over the sea by reducing PBLH and weakening vertical mixing, thereby confining more water vapor to the near-surface layer. The strengthened daytime onshore flow by a cyclonic wind anomaly, induced by contrast temperature perturbation over land and sea, transported moister air to the YRD region, where the suppressed PBLH and weakened daytime vertical mixing maintained the high moisture level. Then heavy fog formed due to the surface cooling at night. This study highlights the importance of anthropogenic emissions in the formation of advection-radiation fog in the polluted coastal areas. © 2019 by ASME."
"57204524766;6506340624;7402383878;","Strong Influence of Aerosol Reductions on Future Heatwaves",2019,"10.1029/2019GL082269","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065980697&doi=10.1029%2f2019GL082269&partnerID=40&md5=7b782771168635a2929bb3a0ca6d10c6","Using the Community Earth System Model Large Ensemble experiments, we investigate future heatwaves under the Representative Concentration Pathway 8.5 scenario, separating the relative roles of greenhouse gas increases and aerosol reductions. We show that there will be more severe heatwaves (in terms of intensity, duration, and frequency) due to mean warming, with minor contributions from future temperature variability changes. While these changes come primarily from greenhouse gas increases, aerosol reductions contribute significantly over the Northern Hemisphere. Furthermore, per degree of global warming, aerosol reductions induce a significantly stronger response in heatwave metrics relative to greenhouse gas increases. The stronger response to aerosols is associated with aerosol-cloud interactions, which are still poorly understood and constrained in current climate models. This suggests that there may exist large uncertainties in future heatwave projections, highlighting the critical significance of reducing uncertainties in aerosol-cloud interactions for reliable projection of climate extremes and effective risk management. ©2019. American Geophysical Union. All Rights Reserved."
"57208745275;6701606453;","Quantifying variations in shortwave aerosol-cloud-radiation interactions using local meteorology and cloud state constraints",2019,"10.5194/acp-19-6251-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065659528&doi=10.5194%2facp-19-6251-2019&partnerID=40&md5=26a865fbd56e1c5d13a00b99d8f96d0c","While many studies have tried to quantify the sign and the magnitude of the warm marine cloud response to aerosol loading, both remain uncertain, owing to the multitude of factors that modulate microphysical and thermodynamic processes within the cloud. Constraining aerosol� cloud interactions using the local meteorology and cloud liquid water may offer a way to account for covarying influences, potentially increasing our confidence in observational estimates of warm cloud indirect effects. A total of 4 years of collocated satellite observations from the NASA A-Train constellation, combined with reanalysis from MERRA-2, are used to partition marine warm clouds into regimes based on stability, the free atmospheric relative humidity, and liquid water path. Organizing the sizable number of satellite observations into regimes is shown to minimize the covariance between the environment or liquid water path and the indirect effect. Controlling for local meteorology and cloud state mitigates artificial signals and reveals substantial variance in both the sign and magnitude of the cloud radiative response, including regions where clouds become systematically darker with increased aerosol concentration in dry, unstable environments. A darkening effect is evident even under the most stringent of constraints. These results suggest it is not meaningful to report a single global sensitivity of cloud radiative effect to aerosol. To the contrary, we find the sensitivity can range from 0:46 to 0.11Wm2 ln(AI)1 regionally. © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 License."
"55462884000;6701562113;56612517400;57194470383;16246205000;57207176515;","The Weather Research and Forecasting Model with Aerosol-Cloud Interactions (WRF-ACI): Development, evaluation, and initial application",2019,"10.1175/MWR-D-18-0267.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065845185&doi=10.1175%2fMWR-D-18-0267.1&partnerID=40&md5=29d15080cbf4a868241d84483226f0a9","The Weather Research and Forecasting Model with Aerosol-Cloud Interactions (WRF-ACI) is developed for studying aerosol effects on gridscale and subgrid-scale clouds using common aerosol activation and ice nucleation formulations and double-moment cloud microphysics in a scale-aware subgrid-scale parameterization scheme. Comparisons of both the standard WRF and WRF-ACI models' results for a summer season against satellite and reanalysis estimates show that the WRF-ACI system improves the simulation of cloud liquid and ice water paths. Correlation coefficients for nearly all evaluated parameters are improved, while other variables show slight degradation. Results indicate a strong cloud lifetime effect from current climatological aerosols increasing domain average cloud liquid water path and reducing domain average precipitation as compared to a simulation with aerosols reduced by 90%. Increased cloud-top heights indicate a thermodynamic invigoration effect, but the impact of thermodynamic invigoration on precipitation is overwhelmed by the cloud lifetime effect. A combination of cloud lifetime and cloud albedo effects increases domain average shortwave cloud forcing by ~3.0 W m-2. Subgrid-scale clouds experience a stronger response to aerosol levels, while gridscale clouds are subject to thermodynamic feedbacks because of the design of the WRF modeling framework. The magnitude of aerosol indirect effects is shown to be sensitive to the choice of autoconversion parameterization used in both the gridscale and subgrid-scale cloud microphysics, but spatial patterns remain qualitatively similar. These results indicate that the WRF-ACI model provides the community with a computationally efficient tool for exploring aerosol-cloud interactions. © 2019 American Meteorological Society."
"54413450200;7102084129;55706490400;36107490600;35794562900;54413425200;57189358333;57196742036;57208499543;57208497697;","Automated Mapping of Convective Clouds (AMCC) thermodynamical, microphysical, and CCN properties from SNPP/VIIRS satellite data",2019,"10.1175/JAMC-D-18-0144.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064896059&doi=10.1175%2fJAMC-D-18-0144.1&partnerID=40&md5=c3ae6e4be230245228ad8840bfb57912","The advent of the Visible Infrared Imager Radiometer Suite (VIIRS) on board the Suomi NPP (SNPP) satellite made it possible to retrieve a new class of convective cloud properties and the aerosols that they ingest. An automated mapping system of retrieval of some properties of convective cloud fields over large areas at the scale of satellite coverage was developed and is presented here. The system is named Automated Mapping of Convective Clouds (AMCC). The input is level-1 VIIRS data and meteorological gridded data. AMCC identifies the cloudy pixels of convective elements; retrieves for each pixel its temperature T and cloud drop effective radius re; calculates cloud-base temperature Tb based on the warmest cloudy pixels; calculates cloud-base height Hb and pressure Pb based on Tb and meteorological data; calculates cloud-base updraft Wb based on Hb; calculates cloud-base adiabatic cloud drop concentrations Nd, a based on the T-re relationship, Tb, and Pb; calculates cloud-base maximum vapor supersaturation S based on Nd, a and Wb; and defines Nd, a/1.3 as the cloud condensation nuclei (CCN) concentration NCCN at that S. The results are gridded 36 km × 36 km data points at nadir, which are sufficiently large to capture the properties of a field of convective clouds and also sufficiently small to capture aerosol and dynamic perturbations at this scale, such as urban and land-use features. The results of AMCC are instrumental in observing spatial covariability in clouds and CCN properties and for obtaining insights from such observations for natural and man-made causes. AMCC-generated maps are also useful for applications from numerical weather forecasting to climate models. © 2019 American Meteorological Society."
"57192915106;39361670300;55938109300;54941580100;6701342931;7006304904;57207570246;22635720500;16480889100;7101820512;54982705800;7003658498;","Aerosol optical properties over Europe: An evaluation of the AQMEII Phase 3 simulations against satellite observations",2019,"10.5194/acp-19-2965-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062611110&doi=10.5194%2facp-19-2965-2019&partnerID=40&md5=33cf9121e160380dd79cb168f754ad02","The main uncertainties regarding the estimation of changes in the Earth's energy budget are related to the role of atmospheric aerosols. These changes are caused by aerosol-radiation (ARIs) and aerosol-cloud interactions (ACIs), which heavily depend on aerosol properties. Since the 1980s, many international modeling initiatives have studied atmospheric aerosols and their climate effects. Phase 3 of the Air Quality Modelling Evaluation International Initiative (AQMEII) focuses on evaluating and intercomparing regional and linked global/regional modeling systems by collaborating with the Task Force on the Hemispheric Transport of Air Pollution Phase 2 (HTAP2) initiative. Within this framework, the main aim of this work is the assessment of the representation of aerosol optical depth (AOD) and the Ångström exponent (AE) in AQMEII Phase 3 simulations over Europe. The evaluation was made using remote-sensing data from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors aboard the Terra and Aqua platforms, and the instruments belonging to the ground-based Aerosol Robotic Network (AERONET) and the Maritime Aerosol Network (MAN). Overall, the skills of AQMEII simulations when representing AOD (mean absolute errors from 0.05 to 0.30) produced lower errors than for the AE (mean absolute errors from 0.30 to 1). Regardless of the models or the emissions used, models were skillful at representing the low and mean AOD values observed (below 0.5). However, high values (around 1.0) were overpredicted for biomass burning episodes, due to an underestimation in the common fires' emissions, and were overestimated for coarse particles-principally desert dust-related to the boundary conditions. Despite this behavior, the spatial and temporal variability of AOD was better represented by all the models than AE variability, which was strongly underestimated in all the simulations. Noticeably, the impact of the model selection when representing aerosol optical properties is higher than the use of different emission inventories. On the other hand, the influence of ARIs and ACIs has a little visible impact compared to the impact of the model used. © 2019 Author(s)."
"57194833104;56482796700;56571063800;24402359000;7004469744;7003591311;","An emulator approach to stratocumulus susceptibility",2019,"10.5194/acp-19-10191-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070613374&doi=10.5194%2facp-19-10191-2019&partnerID=40&md5=b7c5839e25c4562e4ac633cd164b4e4c","The climatic relevance of aerosol-cloud interactions depends on the sensitivity of the radiative effect of clouds to cloud droplet number N, and liquid water path LWP. We derive the dependence of cloud fraction CF, cloud albedo AC, and the relative cloud radiative effect rCRE D CF • AC on N and LWP from 159 large-eddy simulations of nocturnal stratocumulus. These simulations vary in their initial conditions for temperature, moisture, boundary-layer height, and aerosol concentration but share boundary conditions for surface fluxes and subsidence. Our approach is based on Gaussian-process emulation, a statistical technique related to machine learning. We succeed in building emulators that accurately predict simulated values of CF, AC, and rCRE for given values of N and LWP. Emulator-derived susceptibilities @ lnrCRE=@ lnN and @ lnrCRE=@ lnLWP cover the nondrizzling, fully overcast regime as well as the drizzling regime with broken cloud cover. Theoretical results, which are limited to the nondrizzling regime, are reproduced. The susceptibility @ lnrCRE=@ lnN captures the strong sensitivity of the cloud radiative effect to cloud fraction, while the susceptibility @ lnrCRE=@ lnLWP describes the influence of cloud amount on cloud albedo irrespective of cloud fraction. Our emulation-based approach provides a powerful tool for summarizing complex data in a simple framework that captures the sensitivities of cloud-field properties over a wide range of states. © 2019 Author(s)."
"21233445300;35096299800;35794448200;","Quantifying uncertainty from aerosol and atmospheric parameters and their impact on climate sensitivity",2018,"10.5194/acp-18-17529-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058573867&doi=10.5194%2facp-18-17529-2018&partnerID=40&md5=d5de95d4c8dcfdf5dfbd408b3f873e3a","Climate sensitivity in Earth system models (ESMs) is an emergent property that is affected by structural (missing or inaccurate model physics) and parametric (variations in model parameters) uncertainty. This work provides the first quantitative assessment of the role of compensation between uncertainties in aerosol forcing and atmospheric parameters, and their impact on the climate sensitivity of the Community Atmosphere Model, Version 4 (CAM4). Running the model with prescribed ocean and ice conditions, we perturb four parameters related to sulfate and black carbon aerosol radiative forcing and distribution, as well as five atmospheric parameters related to clouds, convection, and radiative flux. In this experimental setup where aerosols do not affect the properties of clouds, the atmospheric parameters explain the majority of variance in climate sensitivity, with two parameters being the most important: one controlling low cloud amount, and one controlling the timescale for deep convection. Although the aerosol parameters strongly affect aerosol optical depth, their impacts on climate sensitivity are substantially weaker than the impacts of the atmospheric parameters, but this result may depend on whether aerosol-cloud interactions are simulated. Based on comparisons to inter-model spread of other ESMs, we conclude that structural uncertainties in this configuration of CAM4 likely contribute 3 times more to uncertainty in climate sensitivity than parametric uncertainties. We provide several parameter sets that could provide plausible (measured by a skill score) configurations of CAM4, but with different sulfate aerosol radiative forcing, black carbon radiative forcing, and climate sensitivity. © Author(s) 2018."
"55938109300;39361670300;56597778200;12544502800;7006304904;55879681300;56339873300;57192915106;7102857809;7004102378;54982705800;57204496157;7003658498;","Evaluating cloud properties in an ensemble of regional online coupled models against satellite observations",2018,"10.5194/acp-18-15183-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055840553&doi=10.5194%2facp-18-15183-2018&partnerID=40&md5=fe91e40998be5fa6f542f21e0c401e45","Online coupled meteorology-chemistry models permit the description of the aerosol-radiation (ARI) and aerosol-cloud interactions (ACIs). The aim of this work is to assess the representation of several cloud properties in regional-scale coupled models when simulating the climate-chemistry-cloud-radiation system. The evaluated simulations are performed under the umbrella of the Air Quality Model Evaluation International Initiative (AQMEII) Phase 2 and include ARI+ACI interactions. Model simulations are evaluated against observational data from the European Space Agency (ESA) Cloud_cci project. The results show an underestimation (overestimation) of cloud fraction (CF) over land (sea) areas by the models. Lower bias values are found in the ensemble mean. Cloud optical depth (COD) and cloud ice water path (IWP) are generally underestimated over the whole European domain. The cloud liquid water path (LWP) is broadly overestimated. The temporal correlation suggests a generally positive correlation between models and satellite observations. Finally, CF gives the best spatial variability representation, whereas COD, IWP, and LWP show less capacity. The differences found can be attributed to differences in the microphysics schemes used; for instance, the number of ice hydrometeors and the prognostic/diagnostic treatment of the LWP are relevant. © 2018 Author(s)."
"57192373652;7003541446;20436169300;7402538754;","Dispersion Aerosol Indirect Effect in Turbulent Clouds: Laboratory Measurements of Effective Radius",2018,"10.1029/2018GL079194","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054800854&doi=10.1029%2f2018GL079194&partnerID=40&md5=60eb29604c5a610d5b2d3020dd46cafc","Cloud optical properties are determined not only by the number density nd and mean radius (Formula presented.) of cloud droplets but also by the shape of the droplet size distribution. The change in cloud optical depth with changing nd, due to the change in distribution shape, is known as the dispersion effect. Droplet relative dispersion is defined as (Formula presented.). For the first time, a commonly used effective radius parameterization is tested in a controlled laboratory environment by creating a turbulent cloud. Stochastic condensation growth suggests d independent of nd for a nonprecipitating cloud, hence nearly zero albedo susceptibility due to the dispersion effect. However, for size-dependent removal, such as in a laboratory cloud or highly clean atmospheric conditions, stochastic condensation produces a weak dispersion effect. The albedo susceptibility due to turbulence broadening has the same sign as the Twomey effect and augments it by order 10%. ©2018. American Geophysical Union. All Rights Reserved."
"16445110800;6506553245;55802221900;23012746800;","Assessment of CNRM coupled ocean-atmosphere model sensitivity to the representation of aerosols",2018,"10.1007/s00382-017-4054-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85039758482&doi=10.1007%2fs00382-017-4054-6&partnerID=40&md5=8ec211af0c4a0e815f6c90044ae0c450","Atmospheric aerosols can significantly affect the Earth’s radiative balance due to absorption, scattering and aerosol-cloud interactions. Although our understanding of aerosol properties has improved over recent decades, aerosol radiative forcing remains as one of the largest uncertainties when attributing recent and projecting future anthropogenic climate change. Ensembles of a coupled ocean-atmosphere general circulation model were used to investigate how the representation of aerosols within the model can affect climate. The control simulation consisted of a 30-year simulation with an interactive aerosol scheme and aerosol emissions that evolve from 1980–2009. The sensitivity tests included using constant 1980 emissions, using prescribed 2-D monthly mean AODs, modifying the aerosol vertical distribution, altering aerosol optical properties, and changing the parameters used for calculating the aerosol first indirect effect. The results of these sensitivity studies show how modifying certain aspects of the aerosol scheme can significantly affect radiative flux and temperature. In particular, it was shown that compared to the control simulation the use of constant 1980 aerosol emissions decreased the average winter surface temperature of the Arctic by 0.2 K and that the use of prescribed 2-D monthly mean AODs reduced the annual global surface temperature by 0.3 K. Increasing the vertical distribution of anthropogenic aerosols in the model and altering aerosol optical properties modified localised radiative fluxes and temperatures, but the most significant change in global surface temperature (1.3 K) was caused by removing sea salt and organic matter from the calculation of cloud droplet number concentration. © 2017, Springer-Verlag GmbH Germany, part of Springer Nature."
"57192064212;10739072200;23051160600;6602671297;7102010848;57204496157;26643041500;35461255500;","Advancing global aerosol simulations with size-segregated anthropogenic particle number emissions",2018,"10.5194/acp-18-10039-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050237255&doi=10.5194%2facp-18-10039-2018&partnerID=40&md5=7524118e4d8d65fc49df1dffdbc650e9","Climate models are important tools that are used for generating climate change projections, in which aerosol-climate interactions are one of the main sources of uncertainties. In order to quantify aerosol-radiation and aerosol-cloud interactions, detailed input of anthropogenic aerosol number emissions is necessary. However, the anthropogenic aerosol number emissions are usually converted from the corresponding mass emissions in pre-compiled emission inventories through a very simplistic method depending uniquely on chemical composition, particle size and density, which are defined for a few, very wide main source sectors. In this work, the anthropogenic particle number emissions converted from the AeroCom mass in the ECHAM-HAM climate model were replaced with the recently formulated number emissions from the Greenhouse Gas and Air Pollution Interactions and Synergies (GAINS) model. In the GAINS model the emission number size distributions vary, for example, with respect to the fuel and technology. Special attention was paid to accumulation mode particles (particle diameter <i>d</i>pĝ€† &gt; ĝ€†100&thinsp;nm) because of (i) their capability of acting as cloud condensation nuclei (CCN), thus forming cloud droplets and affecting Earth's radiation budget, and (ii) their dominant role in forming the coagulation sink and thus limiting the concentration of sub-100&thinsp;nm particles. In addition, the estimates of anthropogenic CCN formation, and thus the forcing from aerosol-climate interactions, are expected to be affected. Analysis of global particle number concentrations and size distributions reveals that GAINS implementation increases CCN concentration compared with AeroCom, with regional enhancement factors reaching values as high as 10. A comparison between modeled and observed concentrations shows that the increase in number concentration for accumulation mode particles agrees well with measurements, but it leads to a consistent underestimation of both nucleation mode and Aitken mode (<i>d</i>pĝ€† &lt; ĝ€†100&thinsp;nm) particle number concentrations. This suggests that revisions are needed in the new particle formation and growth schemes currently applied in global modeling frameworks. © 2018 Copernicus GmbH. All rights reserved."
"57194833104;57203053317;","Precipitation susceptibility and aerosol buffering of warm- and mixed-phase orographic clouds in idealized simulations",2018,"10.1175/JAS-D-17-0254.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047060535&doi=10.1175%2fJAS-D-17-0254.1&partnerID=40&md5=ece7d486828ea49eaeb20d3f3755d9d3","The sensitivity of warm- and mixed-phase orographic precipitation to the aerosol background with simultaneous changes in the abundance of cloud condensation nuclei and ice nucleating particles is explored in an idealized, two-dimensional modeling study. The concept of precipitation susceptibility dlnP/dlnN, where P is the precipitation mixing ratio and N the cloud droplet number, is adapted for orographic clouds. Precipitation susceptibility is found to be low because perturbations to different precipitation formation pathways compensate each other. For mixed-phase conditions, this in particular means a redistribution between warm and cold pathways. The compensating behavior is described as a consequence of a balance equation for the cloud water along parcel trajectories that constrains the total precipitation formation to match the drying from condensation and vapor deposition on ice-phase hydrometeors caused by the mountain flow. For an aerosol-independent condensation rate (saturation adjustment), this balance requirement limits aerosol impacts on orographic precipitation (i) to the evaporation of hydrometeors and (ii) to the glaciation state of the cloud, which controls the contribution of vapor deposition to drying. The redistribution of precipitation formation pathways is coupled to a redistribution of the total hydrometeor mass between hydrometeor categories. Aerosol effects on the glaciation state of the cloud enhance this redistribution effect such that liquid and ice adjustments do not compensate. For the externally constrained, fully adjusted steady-state situation studied, precipitation susceptibility quantifies the redistribution effect rather than changes in precipitation production as in previous studies. © 2018 American Meteorological Society."
"57200702127;57200788113;55258548500;56158925300;56158523800;56611366900;7401796996;7404829395;7005973015;7404865816;","Aerosol microphysical and radiative effects on continental cloud ensembles",2018,"10.1007/s00376-017-7091-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044255560&doi=10.1007%2fs00376-017-7091-5&partnerID=40&md5=5ae2cac82fbbdc6d7e3e793fe9778437","Aerosol–cloud–radiation interactions represent one of the largest uncertainties in the current climate assessment. Much of the complexity arises from the non-monotonic responses of clouds, precipitation and radiative fluxes to aerosol perturbations under various meteorological conditions. In this study, an aerosol-aware WRF model is used to investigate the microphysical and radiative effects of aerosols in three weather systems during the March 2000 Cloud Intensive Observational Period campaign at the US Southern Great Plains. Three simulated cloud ensembles include a low-pressure deep convective cloud system, a collection of less-precipitating stratus and shallow cumulus, and a cold frontal passage. The WRF simulations are evaluated by several ground-based measurements. The microphysical properties of cloud hydrometeors, such as their mass and number concentrations, generally show monotonic trends as a function of cloud condensation nuclei concentrations. Aerosol radiative effects do not influence the trends of cloud microphysics, except for the stratus and shallow cumulus cases where aerosol semi-direct effects are identified. The precipitation changes by aerosols vary with the cloud types and their evolving stages, with a prominent aerosol invigoration effect and associated enhanced precipitation from the convective sources. The simulated aerosol direct effect suppresses precipitation in all three cases but does not overturn the aerosol indirect effect. Cloud fraction exhibits much smaller sensitivity (typically less than 2%) to aerosol perturbations, and the responses vary with aerosol concentrations and cloud regimes. The surface shortwave radiation shows a monotonic decrease by increasing aerosols, while the magnitude of the decrease depends on the cloud type. © 2018, Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag GmbH Germany, part of Springer Nature."
"56999327800;56611366900;38762392200;6603631763;","Using Long-Term Satellite Observations to Identify Sensitive Regimes and Active Regions of Aerosol Indirect Effects for Liquid Clouds Over Global Oceans",2018,"10.1002/2017JD027187","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040228340&doi=10.1002%2f2017JD027187&partnerID=40&md5=f1a8457f5ef93c5e210c943c3a9b9402","Long-term (1981–2011) satellite climate data records of clouds and aerosols are used to investigate the aerosol-cloud interaction of marine water cloud from a climatology perspective. Our focus is on identifying the regimes and regions where the aerosol indirect effects (AIEs) are evident in long-term averages over the global oceans through analyzing the correlation features between aerosol loading and the key cloud variables including cloud droplet effective radius (CDER), cloud optical depth (COD), cloud water path (CWP), cloud top height (CTH), and cloud top temperature (CTT). An aerosol optical thickness (AOT) range of 0.13 < AOT < 0.3 is identified as the sensitive regime of the conventional first AIE where CDER is more susceptible to AOT than the other cloud variables. The first AIE that manifests as the change of long-term averaged CDER appears only in limited oceanic regions. The signature of aerosol invigoration of water clouds as revealed by the increase of cloud cover fraction (CCF) and CTH with increasing AOT at the middle/high latitudes of both hemispheres is identified for a pristine atmosphere (AOT < 0.08). Aerosol invigoration signature is also revealed by the concurrent increase of CDER, COD, and CWP with increasing AOT for a polluted marine atmosphere (AOT > 0.3) in the tropical convergence zones. The regions where the second AIE is likely to manifest in the CCF change are limited to several oceanic areas with high CCF of the warm water clouds near the western coasts of continents. The second AIE signature as represented by the reduction of the precipitation efficiency with increasing AOT is more likely to be observed in the AOT regime of 0.08 < AOT < 0.4. The corresponding AIE active regions manifested themselves as the decline of the precipitation efficiency are mainly limited to the oceanic areas downwind of continental aerosols. The sensitive regime of the conventional AIE identified in this observational study is likely associated with the transitional regime from the aerosol-limited regime to the updraft-limited regime identified for aerosol-cloud interaction in cloud model simulations. Published 2017. This article is a US Government work and is in the public domain in the USA."
"56909903600;24722339600;","A Case Study in Low Aerosol Number Concentrations Over the Eastern North Atlantic: Implications for Pristine Conditions in the Remote Marine Boundary Layer",2017,"10.1002/2017JD027493","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85035226151&doi=10.1002%2f2017JD027493&partnerID=40&md5=6222641df40370c0fa986a394b2d02a7","We present a case study (20 September to 13 October 2015) of synergistic, multi-instrument observations of aerosols, clouds, and the marine boundary layer (MBL) at the Eastern North Atlantic (ENA) Atmospheric Radiation Measurement site centered on a period of exceptionally low (20–50 cm−3) surface accumulation mode (0.1–1 μm) aerosol particle number concentrations. We divide the case study into three regimes (high, clean, and ultraclean) based on daily median number concentrations and compare finer resolution (hourly or less) observations between these regimes. The analysis focuses on the possibility of using these ultraclean events to study pristine conditions in the remote MBL, as well as examining evidence for a recently proposed conceptual model for the large-scale depletion of cloud condensation nuclei-sized particles in postfrontal air masses. Relative to the high and clean regimes, the ultraclean regime tends to exhibit significantly fewer particles between 0.1 and 0.4 μm in diameter and a relatively increased prevalence of larger accumulation mode particles. In addition, supermicron particles tend to dominate total scattering in the ultraclean regime, and there is little evidence for absorbing aerosol. These observations are more in-line with a heavily scavenged but natural marine aerosol population and minimal contribution from continental sources such as anthropogenic pollution, biomass burning, or dust. The air masses with the consistently lowest accumulation mode aerosol number concentrations are largely dominated by heavily drizzling clouds with high liquid water path cores, deep decoupled boundary layers, open cellular organization, and notable surface forcing of subcloud turbulence, even at night. ©2017. American Geophysical Union. All Rights Reserved."
"57193884115;6603109490;","Investigation of aerosol effects on the Arctic surface temperature during the diurnal cycle: part 2 – Separating aerosol effects",2017,"10.1002/joc.5075","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019165663&doi=10.1002%2fjoc.5075&partnerID=40&md5=df3ad83399ee83b8300707d89c545a64","Temperature changes in the Arctic due to anthropogenic climate change are larger in magnitude than those at lower latitudes, with sea ice extent and thickness diminishing since the dawn of the satellite era. Aerosols play a role in determining the changes to the Arctic surface temperature. While Part 1 of this two-part study investigated the changes in Arctic surface temperature due to the total aerosol effect, in Part 2, the total aerosol effect is separated into the changes caused by the aerosol direct effect, the aerosol semi-direct effect, and the aerosol indirect effects through the use of additional Weather Research and Forecasting Chemistry (WRF-Chem) runs. While Part 1 of the study showed that aerosols may have both a cooling and warming effect, largely depending upon the time of day and aerosol concentration, Part 2 of this study shows that the indirect effects are the dominant component of the total aerosol effect on the cooling and warming of the Arctic surface temperature throughout the diurnal cycle. It is also shown that the size distribution of aerosols is important, as smaller aerosols dominate the aerosol indirect effects. The aerosol direct effect contributes to cooling in the region, while the semi-direct effect is negligible. © 2017 Royal Meteorological Society"
"57172833500;7003972559;","Monitoring aerosol-cloud interactions at the CESAR Observatory in the Netherlands",2017,"10.5194/amt-10-1987-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020028807&doi=10.5194%2famt-10-1987-2017&partnerID=40&md5=c1c0c1c6b1435841ffe51f226ec53feb","The representation of aerosol-cloud interaction (ACI) processes in climate models, although long studied, still remains the source of high uncertainty. Very often there is a mismatch between the scale of observations used for ACI quantification and the ACI process itself. This can be mitigated by using the observations from groundbased remote sensing instruments. In this paper we presented a direct application of the aerosol-cloud interaction monitoring technique (ACI monitoring). ACI monitoring is based on the standardised Cloudnet data stream, which provides measurements from ground-based remote sensing instruments working in synergy. For the data set collected at the CESAR Observatory in the Netherlands we calculate ACI metrics. We specifically use attenuated backscatter coefficient (ATB) for the characterisation of the aerosol properties and cloud droplet effective radius (re) and number concentration (Nd) for the characterisation of the cloud properties. We calculate two metrics: ACIr Dln(re)/ln(ATB) and ACIN Dln(Nd)/ln(ATB). The calculated values of ACIr range from 0.001 to 0.085, which correspond to the values reported in previous studies. We also evaluated the impact of the vertical Doppler velocity and liquid water path (LWP) on ACI metrics. The values of ACIr were highest for LWP values between 60 and 105 gm-2. For higher LWP other processes, such as collision and coalescence, seem to be dominant and obscure the ACI processes. We also saw that the values of ACIr are higher when only data points located in the updraught regime are considered. The method presented in this study allow for monitoring ACI daily and further aggregating daily data into bigger data sets. © Author(s) 2017."
"55940397300;7005219614;55976582900;55965624000;15019752400;55460555300;","Aerosol physicochemical effects on CCN activation simulated with the chemistry-climate model EMAC",2017,"10.1016/j.atmosenv.2017.03.036","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019623206&doi=10.1016%2fj.atmosenv.2017.03.036&partnerID=40&md5=468ab4841c9648af230db6e9a4505d3c","This study uses the EMAC atmospheric chemistry-climate model to simulate cloud properties with a prognostic cloud droplet nucleation scheme. We present modeled global distributions of cloud condensation nuclei (CCN) number concentrations and CCN activation rates, together with the effective hygroscopicity parameter κ, to describe the aerosol chemical composition effect on CCN activation. Large particles can easily activate into cloud droplets, even at low κ values due to the dominant size effect in cloud droplet formation. Small particles are less efficiently activated as CCN, and are more sensitive to aerosol composition and supersaturation. Since the dominant fraction of small particles generally originates from anthropogenic precursor emissions over land, this study focuses on the influence of the continental atmosphere, using a prognostic cloud droplet nucleation scheme that considers aerosol-cloud interactions during cloud formation, together with a double-moment cloud microphysics scheme. The agreement of simulated clouds and climate with observations generally improves over the Northern Hemisphere continents, particularly high air pollution regions such as Eastern US, Europe, East Asia by accounting for aerosol-cloud interactions that include impacts of chemical composition on CCN activation. © 2017 The Authors"
"7102805852;","Atmospheric Aerosols and Their Role in Climate Change",2016,"10.1016/B978-0-444-63524-2.00027-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018614959&doi=10.1016%2fB978-0-444-63524-2.00027-0&partnerID=40&md5=96fc1fa90e759434117647ecc8f8e4d4","As in the case for increased emissions of greenhouse gases, increased emissions of atmospheric aerosols from human activity perturb the climate of the Earth. Aerosols exert a significant radiative forcing of climate via aerosol-radiation and aerosol-cloud interactions; these processes will be explained in relatively simple terms by concentrating on the underlying physical processes. We shall see that while the net impact of anthropogenic aerosol emissions is to cool the planet, significance arises from the complexity of aerosol absorption and the impacts of aerosols on cloud microphysics. Aerosols are also implicated in climate feedback mechanisms where atmospheric concentrations of natural aerosols such as sea salt, mineral dust and organic aerosols are potentially perturbed in response to future climate change scenarios. We also briefly investigate the contentious issue of aerosols in potential climate engineering via solar radiation management schemes. © 2016 Elsevier B.V. All rights reserved."
"14520559400;6601927317;35302719200;56442378900;56948738800;55999273500;56463831800;57141453800;57189640729;56164814800;6506424404;6701762451;","Development and characterization of an ice-selecting pumped counterflow virtual impactor (IS-PCVI) to study ice crystal residuals",2016,"10.5194/amt-9-3817-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016139265&doi=10.5194%2famt-9-3817-2016&partnerID=40&md5=1230740e648f8785fdff4c41ee22a4f1","Separation of particles that play a role in cloud activation and ice nucleation from interstitial aerosols has become necessary to further understand aerosol-cloud interactions. The pumped counterflow virtual impactor (PCVI), which uses a vacuum pump to accelerate the particles and increase their momentum, provides an accessible option for dynamic and inertial separation of cloud elements. However, the use of a traditional PCVI to extract large cloud hydrometeors is difficult mainly due to its small cut-size diameters (< 5 μm). Here, for the first time we describe a development of an ice-selecting PCVI (IS-PCVI) to separate ice in controlled mixed-phase cloud system based on the particle inertia with the cut-off diameter ≥10 μm. We also present its laboratory application demonstrating the use of the impactor under a wide range of temperature and humidity conditions. The computational fluid dynamics simulations were initially carried out to guide the design of the IS-PCVI. After fabrication, a series of validation laboratory experiments were performed coupled with the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) expansion cloud simulation chamber. In the AIDA chamber, test aerosol particles were exposed to the ice supersaturation conditions (i.e., RHice > 100 %), where a mixture of droplets and ice crystals was formed during the expansion experiment. In parallel, the flow conditions of the IS-PCVI were actively controlled, such that it separated ice crystals from a mixture of ice crystals and cloud droplets, which were of diameter ≥10 μm. These large ice crystals were passed through the heated evaporation section to remove the water content. Afterwards, the residuals were characterized with a suite of online and offline instruments downstream of the IS-PCVI. These results were used to assess the optimized operating parameters of the device in terms of (1) the critical cut-size diameter, (2) the transmission efficiency and (3) the counterflow-toinput flow ratio. Particle losses were characterized by comparing the residual number concentration to the rejected interstitial particle number concentration. Overall results suggest that the IS-PCVI enables inertial separation of particles with a volume-equivalent particle size in the range of ≥10- 30 μm in diameter with small inadvertent intrusion (≥5 %) of unwanted particles. © Author(s) 2016. CC Attribution 3.0 License."
"7004620320;7201832531;7202772927;55718206700;","Sensitivity of convection to observed variation in aerosol size distributions and composition at a rural site in the southeastern United States",2015,"10.1007/s10874-015-9300-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948716737&doi=10.1007%2fs10874-015-9300-x&partnerID=40&md5=7eed335b5645f97422934556bf5004fa","We present a sensitivity analysis to determine the impact of variations in aerosol physical and chemical characteristics, as observed in the field in the southeastern United States, on convective cloud microphysics. Scenarios reflecting changes in aerosol properties, observed over the Piedmont of Virginia and associated with new particle formation and growth events, were evaluated using the two-dimensional version of the Goddard Cumulus Ensemble Model with detailed spectral-bin microphysics. Two aerosol size distributions represented early and late stages of particle growth, and two aerosol chemical compositions (norpinic acid and ammonium sulfate) represented extremes in aerosol hygroscopicity observed at the field site, for a total of four scenarios. The chosen compositions reflect inferred local changes in aerosol composition over short time scales. Variations in the aerosol size distribution and composition resulted in substantial variation in the total number of cloud condensation nuclei (CCN) produced in the four case studies. Cases with high CCN concentrations developed larger, more vigorous clouds with more precipitation generated by both warm and cold rain processes. Greater numbers of drops were propelled aloft and formed an extensive ice anvil that produced a large area of stratiform rain. Convection was enhanced by increasing aerosols despite decreases in precipitation efficiency. In contrast, lower CCN concentrations developed smaller clouds with suppressed cold rain processes and less total precipitation. The relatively small increase in CCN concentration associated with the increase in aerosol hygroscopicity resulted in an increase in accumulated modeled precipitation of 12 % after 180 min of simulation time in both high and low CCN cases. The increase in accumulated precipitation due to the substantial increase in CCN concentration associated with growth of the aerosol size distribution was 93 % for both aerosol compositions. The timing of the onset of precipitation was not affected by aerosol concentration or composition. © 2015 Springer Science+Business Media Dordrecht."
"7201431739;","Sensitivity of the atmospheric energy budget to two-moment representation of cloud microphysics in idealized simulations of convective radiative quasi-equilibrium",2015,"10.1002/qj.2342","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922812749&doi=10.1002%2fqj.2342&partnerID=40&md5=193e634821f0e693812e7065a1a50218","Sensitivity of the atmospheric energy budget to two-moment (2M) representation of cloud microphysics in idealized convective radiative quasi-equilibrium (CRQE) is studied using partial and full 2M schemes. The focus is especially given to the sensitivity to 2M scheme for large hydrometeors. The atmospheric energy budget is found to be sensitive to the first indirect effect, but the energy budget is more sensitive to the 2M treatment for large hydrometeors. The top and bottom of atmosphere (TOA and BOA) energy budgets depend on 2M treatment especially for large ice hydrometeors (snow and graupel). The predicted number concentration of graupel dominates BOA energy budgets by increasing rain size leading to decrease of sensible heat flux, and that of snow dominates TOA energy budgets by enhancing updraught cloud mass flux in both low and middle clouds. In conclusion, the energy budgets are controlled not only by 2M representation of rain but also by representation of large ice hydrometeors. Sensitivity of the energy budget to 2M treatment for large ice hydrometeors is more significant than that for rain because the treatment impacts properties of surface heat fluxes and both low and mid-level clouds. © 2014 Royal Meteorological Society."
"55480868800;8608660400;57205351494;6701378450;7004027519;","Suppression in droplet growth kinetics by the addition of organics to sulfate particles",2014,"10.1002/2014JD021689","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84913555060&doi=10.1002%2f2014JD021689&partnerID=40&md5=36d29127309b23e30b4d8f3a779b58ba","Aerosol-cloud interactions are affected by the rate at which water vapor condenses onto particles during cloud droplet growth. Changes in droplet growth rates can impact cloud droplet number and size distribution. The current study investigated droplet growth kinetics of acidic and neutral sulfate particles which contained various amounts and types of organic compounds, from model compounds (carbonyls) to complex mixtures (α-pinene secondary organic aerosol and diesel engine exhaust). In most cases, the formed droplet size distributions were shifted to smaller sizes relative to control experiments (pure sulfate particles), due to suppression in droplet growth rates in the cloud condensation nuclei counter. The shift to smaller droplets correlated with increasing amounts of organic material, with the largest effect observed for acidic seed particles at low relative humidity. For all organics incorporated onto acidic particles, formation of high molecular weight compounds was observed, probably by acid-catalyzed Aldol condensation reactions in the case of carbonyls. To test the reversibility of this process, carbonyl experiments were conducted with acidic particles exposed to higher relative humidity. High molecular weight compounds were not measured in this case and no shift in droplet sizes was observed, suggesting that high molecular weight compounds are the species affecting the rate of water uptake. While these results provide laboratory evidence that organic compounds can slow droplet growth rates, the modeled mass accommodation coefficient of water on these particles (α > 0.1) indicates that this effect is unlikely to significantly affect cloud properties, consistent with infrequent field observations of slower droplet growth rates. © 2014. American Geophysical Union. All Rights Reserved."
"7402786837;57208121852;6602600408;7006689276;","Erratum: Aerosol indirect effects from shipping emissions: Sensitivity studies with the global aerosol-climate model ECHAM-HAM (Atmospheric Chemistry and Physics (2012) 12 (5985-6007))",2013,"10.5194/acp-13-6429-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880635398&doi=10.5194%2facp-13-6429-2013&partnerID=40&md5=5ac52512511be34f383664840cf56670",[No abstract available]
"55542833500;56962915800;55717074000;56162305900;","Two-moment bulk stratiform cloud microphysics in the grid-point atmospheric model of IAP LASG (GAMIL)",2013,"10.1007/s00376-012-2072-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876438078&doi=10.1007%2fs00376-012-2072-1&partnerID=40&md5=eb6a4f9a2e9caaa8e81620c1bd9c861f","A two-moment bulk stratiform microphysics scheme, including recently developed physically-based droplet activation/ice nucleation parameterizations has been implemented into the Grid-point Atmospheric Model of IAP LASG (GAMIL) as an effort to enhance the model's capability to simulate aerosol indirect effects. Unlike the previous one-moment cloud microphysics scheme, the new scheme produces a reasonable representation of cloud particle size and number concentration. This scheme captures the observed spatial variations in cloud droplet number concentrations. Simulated ice crystal number concentrations in cirrus clouds qualitatively agree with in situ observations. The longwave and shortwave cloud forcings are in better agreement with observations. Sensitivity tests show that the column cloud droplet number concentrations calculated from two different droplet activation parameterizations are similar. However, ice crystal number concentration in mixed-phased clouds is sensitive to different heterogeneous ice nucleation formulations. The simulation with high ice crystal number concentration in mixed-phase clouds has less liquid water path and weaker cloud forcing. Furthermore, ice crystal number concentration in cirrus clouds is sensitive to different ice nucleation parameterizations. Sensitivity tests also suggest that the impact of pre-existing ice crystals on homogeneous freezing in old clouds should be taken into account. © 2013 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"24343173500;57189215242;8084443000;7403401100;7103337730;7006107059;7004015298;55871322800;55871415400;55871394300;7004393835;24069972000;7004611350;55908042400;57050508600;7006808794;8657166100;","Airborne investigation of the aerosols-cloud interactions in the vicinity and within a marine stratocumulus over the North Sea during EUCAARI (2008)",2013,"10.1016/j.atmosenv.2013.08.035","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884919209&doi=10.1016%2fj.atmosenv.2013.08.035&partnerID=40&md5=fbaabc5d073b190c71f7d2670f8765e3","Within the European Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) project, the Meteo France research aircraft ATR-42 was operated from Rotterdam (Netherlands) airport during May 2008, to perform scientific flights dedicated to the investigation of aerosol-cloud interactions. The objective of this study is to illustrate the impact of cloud processing on the aerosol particle physical and chemical properties. The presented results are retrieved from measurements during flight operation with two consecutive flights, first from Rotterdam to Newcastle (United Kingdom) and subsequently reverse along the same waypoints back to Rotterdam using data measured with compact Time of Flight Aerosol Mass Spectrometer (cToF-AMS) and Scanning Mobility Particle Sizer (SMPS). Cloud-related measurements during these flights were performed over the North Sea within as well as in close vicinity of a marine stratocumulus cloud layer. Particle physical and chemical properties observed in the close vicinity, below and above the stratocumulus cloud, show strong differences: (1) the averaged aerosol size distributions, observed above and below the cloud layer, are of bimodal character with pronounced minima between Aitken and accumulation mode, very likely due to cloud processing. (2) the chemical composition of aerosol particles is strongly dependent on the position relative to the cloud layer (vicinity or below/above cloud). In general, the nitrate and organic relative mass fractions decrease with decreasing distance to the cloud, in the transit from cloud-free conditions towards the cloud boundaries. This relative mass fraction decrease ranges from a factor of three to ten, thus leading to an increase of the sulfate and ammonium relative mass concentrations while approaching the cloud layer. (3), the chemical composition of cloud droplet residuals, analyzed downstream of a Counterflow virtual Impactor (CVI) inlet indicates increased fractions of mainly soluble chemical compounds such as nitrate and organics, compared to non cloud processed particles. Finally, a net overbalance of nitrate aerosol has been revealed by comparing cloud droplet residual and non cloud processed aerosol chemical compositions. Conclusively, this study highlights gaps concerning the sampling strategy that need to be addressed for the future missions. © 2013 Elsevier Ltd."
"55575070500;8502218200;8212878600;55575967900;55629355400;7005901650;7006659222;35595209900;","Multi-wavelength lidar system for the characterization of tropospheric aerosols and clouds",2012,"10.1109/IGARSS.2012.6351839","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873102877&doi=10.1109%2fIGARSS.2012.6351839&partnerID=40&md5=c3dd78929caf24434deb210d5dc60ece","Atmospheric Data Collection Lidar (ADCL) of the Center for Environmental Remote Sensing (CEReS), Chiba University, is a multi-wavelength lidar system designed for measuring tropospheric aerosols and clouds with ancillary data from ground-based aerosol measurement instruments. In this paper, we report on the concept of aerosol and cloud retrieval based on vertical, slant-path, and plan-position indicator (PPI) lidar measurements in combination with aerosol measurements conducted with a three-wavelength integrating nephelometer, an aethalometer, and a particle counter. It is expected that such a combined approach makes it possible to study the detailed features of aerosols in the troposphere, including the aerosol-cloud interaction. © 2012 IEEE."
"26028905900;57201726470;7004057920;","Surface-based observation of aerosol indirect effect in the Mid-Atlantic region",2008,"10.1029/2008GL036064","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60149093579&doi=10.1029%2f2008GL036064&partnerID=40&md5=6742c1fe98e6825700cbf683e3e31208","A method for assessing the aerosol indirect effect based on back trajectory analysis and cloud and aerosol properties derived from a combination of observations from the Multifilter Rotating Shadow Band Radiometer and microwave radiometer at a newly established atmospheric measurement field station in the Baltimore-Washington corridor is reported in this article. Six months of aerosol and cloud optical depth data are segregated according to air mass history based on back trajectory analysis. Under stagnant and polluted conditions where air flow across the region is predominantly from west-southwest, aerosol optical depth is on average three to four times greater than in air masses that advect rapidly from north and east. When sorted by mean cloud liquid water path, cloud-droplet effective radius in polluted air masses is on average 0.9 μm smaller than that observed under more pristine conditions. Analysis is presented to confirm the statistical significance of this result. Copyright 2008 by the American Geophysical Union."
"7201837768;57193132723;56249704400;6603422104;","GCM simulations of the aerosol indirect effect: Sensitivity to cloud parameterization and aerosol Burden",2002,"10.1175/1520-0469(2002)059<0692:gsotai>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086351635&doi=10.1175%2f1520-0469%282002%29059%3c0692%3agsotai%3e2.0.co%3b2&partnerID=40&md5=2b91fe63f72bbc658522e1af83cb8b6e","In this paper the coupling of the Goddard Institute for Space Studies (GISS) general circulation model (GCM) to an online sulfur chemistry model and source models for organic matter and sea salt that is used to estimate the aerosol indirect effect is described. The cloud droplet number concentration is diagnosed empirically from field experiment datasets over land and ocean that observe droplet number and all three aerosol types simultaneously; corrections are made for implied variations in cloud turbulence levels. The resulting cloud droplet number is used to calculate variations in droplet effective radius, which in turn allows one to predict aerosol effects on cloud optical thickness and microphysical process rates. The aerosol indirect is calculated by differencing the top-of-the-atmosphere net cloud radiative forcing for simulations with present-day versus pre-industrial emissions. Both the first and second indirect effects are explored. The sensitivity of the results presented here to cloud parameterization assumptions that control the vertical distribution of cloud occurence, the autoconversion rate, and the aerosol scavenging rate, each of which feeds back significantly on the model aerosol burden. are testes. The global mean aerosol indirect effect for all three aerosol types ranges from - 1.55 to -4.36 W m-2 in the simulations. The results are quite sensitive to the preindustrial background aerosol burden. with low preindustrial burdens giving strong indirect effects, and to a lesser extent to the anthropogenic aerosol burden, with large burdens giving somewhat larger indirect effects. Because of this dependence on the background aerosol, model diagnostics such as albedo-particle size correlations and column cloud susceptibility, for which satellite validation products are available, are not good predictors of the resulting indirect effect."
"55896920900;6603892183;","Introduction to the EUCREX-94 mission 206",2000,"10.1016/S0169-8095(00)00053-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033850677&doi=10.1016%2fS0169-8095%2800%2900053-3&partnerID=40&md5=9249f78a4c87555b708535b73402ce7b","Part of the EUCREX-94 experiment was devoted to the study of the radiative properties of boundary layer clouds in relation with their microphysical and structural properties. Mission 206, on April 18, is particularly attractive because of a general trend in cloud geometrical thickness within the sampled region, with corresponding values of optical thickness between 4 and 70. The cloud system has been extensively documented in situ with an instrumented aircraft, while two other aircraft were measuring its radiative properties with radiometers and a lidar. This paper introduces the scientific objectives of the experiment and describes the instrumental setup. After a presentation of the meteorological situation, the various papers of this series are briefly introduced. (C) 2000 Elsevier Science B.V. All rights reserved."
"8708681500;55897850700;6603926347;7005387225;7005183733;6603610616;","A study of aerosol-cloud interactions with a comprehensive air quality model",2000,"10.1016/s0021-8502(00)90061-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034272001&doi=10.1016%2fs0021-8502%2800%2990061-2&partnerID=40&md5=7f296ba22ed053775fe351cf30fcdb90",[No abstract available]
"7403401100;7004864963;35461763400;","The chemistry and role of cloud condensation nuclei in the Amazon Basin",2000,"10.1016/s0021-8502(00)90069-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034271614&doi=10.1016%2fs0021-8502%2800%2990069-7&partnerID=40&md5=f710eb01ecad4f368a6e4f0874125b76",[No abstract available]
"16185051500;","Aerosol-Cloud Interactions",1993,"10.1016/S0074-6142(08)60211-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956864115&doi=10.1016%2fS0074-6142%2808%2960211-9&partnerID=40&md5=938dc4c246b09b408002cc1b4a8e7c01","This chapter presents a review of two of the aerosol–cloud–climate interactions: the effects of atmospheric aerosol on clouds, and the effects of clouds on atmospheric aerosol. The corresponding aerosol–cloud interactions over the continents are depicted. The main sources of sulfur and nitrogen gases are from anthropogenic and biomass combustion. These gases can be absorbed into cloud particles; they are oxidized to form aerosol, some of which can serve as cloud condensation nuclei (CCN). CCN are also injected directly into the atmosphere from the Earth's surface. Aqueous-phase chemical reactions in clouds can enhance the activity of CCN released from evaporating clouds. Also, in-cloud chemical reactions are probably often the main mechanism for acidifying cloud water and precipitation in polluted air, with nucleation scavenging and below-cloud removal generally playing important but lesser roles. Clouds and precipitation are important sinks for atmospheric aerosol. This affects the size distribution and chemical nature of atmospheric aerosol and the chemical composition of clouds and precipitation. In addition to modifying existing aerosol, some recent research indicates that clouds can be involved in the nucleation of new aerosol. © 1993, Academic Press Inc."
"56823691200;6603412788;9249656500;8918407000;13405561000;10739772300;56797095600;","Global and Arctic effective radiative forcing of anthropogenic gases and aerosols in MRI-ESM2.0",2020,"10.1186/s40645-020-00348-w","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089266171&doi=10.1186%2fs40645-020-00348-w&partnerID=40&md5=0941f8cced5856e40c6e7419d72fff7e","The effective radiative forcing (ERF) of anthropogenic gases and aerosols under present-day conditions relative to preindustrial conditions is estimated using the Meteorological Research Institute Earth System Model version 2.0 (MRI-ESM2.0) as part of the Radiative Forcing Model Intercomparison Project (RFMIP) and Aerosol and Chemistry Model Intercomparison Project (AerChemMIP), endorsed by the sixth phase of the Coupled Model Intercomparison Project (CMIP6). The global mean total anthropogenic net ERF estimate at the top of the atmosphere is 1.96 W m−2 and is composed primarily of positive forcings due to carbon dioxide (1.85 W m−2), methane (0.71 W m−2), and halocarbons (0.30 W m−2) and negative forcing due to the total aerosols (− 1.22 W m−2). The total aerosol ERF consists of 23% from aerosol-radiation interactions (− 0.32 W m−2), 71% from aerosol-cloud interactions (− 0.98 W m−2), and slightly from surface albedo changes caused by aerosols (0.08 W m−2). The ERFs due to aerosol-radiation interactions consist of opposing contributions from light-absorbing black carbon (BC) (0.25 W m−2) and from light-scattering sulfate (− 0.48 W m−2) and organic aerosols (− 0.07 W m−2) and are pronounced over emission source regions. The ERFs due to aerosol-cloud interactions (ERFaci) are prominent over the source and downwind regions, caused by increases in the number concentrations of cloud condensation nuclei and cloud droplets in low-level clouds. Concurrently, increases in the number concentration of ice crystals in high-level clouds (temperatures &lt; –38 °C), primarily induced by anthropogenic BC aerosols, particularly over tropical convective regions, cause both substantial negative shortwave and positive longwave ERFaci values in MRI-ESM2.0. These distinct forcings largely cancel each other; however, significant longwave radiative heating of the atmosphere caused by high-level ice clouds suggests the importance of further studies on the interactions of aerosols with ice clouds. Total anthropogenic net ERFs are almost entirely positive over the Arctic due to contributions from the surface albedo reductions caused by BC. In the Arctic, BC provides the second largest contribution to the positive ERFs after carbon dioxide, suggesting a possible important role of BC in Arctic surface warming. [Figure not available: see fulltext.] © 2020, The Author(s)."
"7005793702;57208460143;9233714800;16834406100;56493777900;57202339891;36169854600;8625545200;35501613900;6603019259;55512674800;7404548584;6701620591;7004299722;55725404100;14052775900;57217333204;7401850582;35396858200;6603372665;6506458269;55718857500;57218132286;","Influence of cloud, fog, and high relative humidity during pollution transport events in South Korea: Aerosol properties and PM2.5 variability",2020,"10.1016/j.atmosenv.2020.117530","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084236505&doi=10.1016%2fj.atmosenv.2020.117530&partnerID=40&md5=c3b97f2eef5a106bab9e544771003414","This investigation examines aerosol dynamics during major fine mode aerosol transboundary pollution events in South Korea primarily during the KORUS-AQ campaign from May 1 – June 10, 2016, particularly when cloud fraction was high and/or fog was present to quantify the change in aerosol characteristics due to near-cloud or fog interaction. We analyze the new AERONET Version 3 data that have significant changes to cloud screening algorithms, allowing many more fine-mode observations in the near vicinity of clouds or fog. Case studies for detailed investigation include May 25–26, 2016 when cloud fraction was high over much of the peninsula, associated with a weak frontal passage and advection of pollution from China. These cloud-influenced Chinese transport dates also had the highest aerosol optical depth (AOD), surface PM2.5 concentrations and fine mode particle sizes of the entire campaign. Another likewise cloud/high relative humidity (RH) case is June 9 and 10, 2016 when fog was present over the Yellow Sea that appears to have affected aerosol properties well downwind over the Korean peninsula. In comparison we also investigated aerosol properties on air stagnation days with very low cloud cover and relatively low RH (May 17 &amp; 18, 2016), when local Korean emissions dominated. Aerosol volume size distributions show marked differences between the transport days (with high RH and cloud influences) and the local pollution stagnation days, with total column-integrated particle fine mode volume being an order of magnitude greater on the pollution transport dates. The PM2.5 over central Seoul were significantly greater than for coastal sites on the transboundary transport days yet not on stagnation days, suggesting additional particle formation from gaseous urban emissions in cloud/fog droplets and/or in the high RH humidified aerosol environment. Many days had KORUS-AQ research aircraft flights that provided observations of aerosol absorption, particle chemistry and vertical profiles of extinction. AERONET retrievals and aircraft in situ measurements both showed high single scattering albedo (weak absorption) on the cloudy or cloud influenced days, plus aircraft profile in situ measurements showed large AOD enhancements (versus dried aerosol) at ambient relative humidity (RH) on the pollution transport days, consistent with the significantly larger fine mode particle radii and weak absorption. © 2020 Elsevier Ltd"
"35113492400;56611366900;7003842561;57142867400;57109569100;57216749259;35849722200;56893048100;57208313489;","Reconciling Contrasting Relationships Between Relative Dispersion and Volume-Mean Radius of Cloud Droplet Size Distributions",2020,"10.1029/2019JD031868","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084436964&doi=10.1029%2f2019JD031868&partnerID=40&md5=2f41f8af4f54b5d1a46ce5548a6ef9e0","Cloud droplet spectral relative dispersion is critical to parameterizations of cloud radiative properties, warm-rain initiation, and aerosol-cloud interactions in models; however, there is no consistent relationship between relative dispersion and volume-mean radius in literature, which hinders improving relative dispersion parameterization and calls for physical explanation. Here we show, by analyzing aircraft observations of cumulus clouds during Routine AAF [Atmospheric Radiation Measurement (ARM) Aerial Facility] Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations, that the correlation between relative dispersion and volume-mean radius changes from positive to negative as volume-mean radius increases. With the new observation, we postulate that the sign of the correlation is determined by whether or not condensation (evaporation) occurs simultaneously with significant new activation (deactivation). The hypothesis is validated by simulations of both an adiabatic cloud parcel model and a parcel model accounting for entrainment-mixing. A new quantity, first bin strength, is introduced to quantify this new observation. Theoretical analysis of truncated gamma and modified gamma size distributions further supports the hypothesis and reconciles the contrasting relationships between relative dispersion and volume-mean radius, including the results in polluted fog observations. The results could shed new light on the so-called “twilight zone” between cloudy and cloud-free air, which in turn affects evaluation of aerosol-cloud interactions and retrieval of aerosol optical depth. ©2020. American Geophysical Union. All Rights Reserved."
"18437651200;55885038100;55159539500;57216560399;7201769159;7402538754;7006415284;","Characterization and first results from LACIS-T: A moist-air wind tunnel to study aerosol-cloud-turbulence interactions",2020,"10.5194/amt-13-2015-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083893805&doi=10.5194%2famt-13-2015-2020&partnerID=40&md5=c4e3ada653a207259e347989865e8080","The interactions between turbulence and cloud microphysical processes have been investigated primarily through numerical simulation and field measurements over the last 10 years. However, only in the laboratory we can be confident in our knowledge of initial and boundary conditions and are able to measure under statistically stationary and repeatable conditions. In the scope of this paper, we present a unique turbulent moist-air wind tunnel, called the Turbulent Leipzig Aerosol Cloud Interaction Simulator (LACIS-T) which has been developed at TROPOS in order to study cloud physical processes in general and interactions between turbulence and cloud microphysical processes in particular. The investigations take place under well-defined and reproducible turbulent and thermodynamic conditions covering the temperature range of warm, mixed-phase and cold clouds (25°C > T >-40°C). The continuous-flow design of the facility allows for the investigation of processes occurring on small temporal (up to a few seconds) and spatial scales (micrometer to meter scale) and with a Lagrangian perspective. The here-presented experimental studies using LACIS-T are accompanied and complemented by computational fluid dynamics (CFD) simulations which help us to design experiments as well as to interpret experimental results. In this paper, we will present the fundamental operating principle of LACIS-T, the numerical model, and results concerning the thermodynamic and flow conditions prevailing inside the wind tunnel, combining both characterization measurements and numerical simulations. Finally, the first results are depicted from deliquescence and hygroscopic growth as well as droplet activation and growth experiments. We observe clear indications of the effect of turbulence on the investigated microphysical processes. © 2018 The Author(s)."
"57140859500;6505576518;57204216001;57213358341;57215835692;35232912700;6602550636;24722339600;7005035762;6602137800;6701378450;","Biomass burning aerosol as a modulator of the droplet number in the southeast Atlantic region",2020,"10.5194/acp-20-3029-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081987598&doi=10.5194%2facp-20-3029-2020&partnerID=40&md5=737112a94de90b5090341af9fb7dfd65","The southeastern Atlantic (SEA) and its associated cloud deck, off the west coast of central Africa, is an area where aerosol-cloud interactions can have a strong radiative impact. Seasonally, extensive biomass burning (BB) aerosol plumes from southern Africa reach this area. The NASA ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) study focused on quantitatively understanding these interactions and their importance. Here we present measurements of cloud condensation nuclei (CCN) concentration, aerosol size distribution, and characteristic vertical updraft velocity (w*) in and around the marine boundary layer (MBL) collected by the NASA P-3B aircraft during the August 2017 ORACLES deployment. BB aerosol levels vary considerably but systematically with time; high aerosol concentrations were observed in the MBL (800-1000 cm-3) early on, decreasing midcampaign to concentrations between 500 and 800 cm-3. By late August and early September, relatively clean MBL conditions were sampled (< 500 cm-3). These data then drive a state-of-the-art droplet formation parameterization from which the predicted cloud droplet number and its sensitivity to aerosol and dynamical parameters are derived. Droplet closure was achieved to within 20 %. Droplet formation sensitivity to aerosol concentration, w*, and the hygroscopicity parameter, k, vary and contribute to the total droplet response in the MBL clouds. When aerosol concentrations exceed ~ 900 cm-3 and maximum supersaturation approaches 0.1 %, droplet formation in the MBL enters a velocity-limited droplet activation regime, where the cloud droplet number responds weakly to CCN concentration increases. Below ~ 500 cm-3, in a clean MBL, droplet formation is much more sensitive to changes in aerosol concentration than to changes in vertical updraft. In the competitive regime, where the MBL has intermediate pollution (500-800 cm-3), droplet formation becomes much more sensitive to hygroscopicity (k) variations than it does in clean and polluted conditions. Higher concentrations increase the sensitivity to vertical velocity by more than 10-fold. We also find that characteristic vertical velocity plays a very important role in driving droplet formation in a more polluted MBL regime, in which even a small shift in w*may make a significant difference in droplet concentrations. Identifying regimes where droplet number variability is driven primarily by updraft velocity and not by aerosol concentration is key for interpreting aerosol indirect effects, especially with remote sensing. The droplet number responds proportionally to changes in characteristic velocity, offering the possibility of remote sensing of w*under velocity-limited conditions. © Author(s) 2020."
"26032229000;42962520400;36117910700;7005659847;35463545000;55470017900;35568326100;36552332100;6701653010;25923454000;7102113229;","Overview of the new version 3 NASA micro-pulse lidar network (MPLNET) automatic precipitation detection algorithm",2020,"10.3390/rs12010071","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082508993&doi=10.3390%2frs12010071&partnerID=40&md5=74db64b0f612823160896a41b7559c1d","Precipitation modifies atmospheric column thermodynamics through the process of evaporation and serves as a proxy for latent heat modulation. For this reason, a correct precipitation parameterization (especially for low-intensity precipitation) within global scale models is crucial. In addition to improving our modeling of the hydrological cycle, this will reduce the associated uncertainty of global climate models in correctly forecasting future scenarios, and will enable the application of mitigation strategies. In this manuscript we present a proof of concept algorithm to automatically detect precipitation from lidar measurements obtained from the National Aeronautics and Space Administration Micropulse lidar network (MPLNET). The algorithm, once tested and validated against other remote sensing instruments, will be operationally implemented into the network to deliver a near real time (latency <1.5 h) rain masking variable that will be publicly available on MPLNET website as part of the new Version 3 data products. The methodology, based on an image processing technique, detects only light precipitation events (defined by intensity and duration) such as light rain, drizzle, and virga. During heavy rain events, the lidar signal is completely extinguished after a few meters in the precipitation or it is unusable because of water accumulated on the receiver optics. Results from the algorithm, in addition to filling a gap in light rain, drizzle, and virga detection by radars, are of particular interest for the scientific community as they help to fully characterize the aerosol cycle, from emission to deposition, as precipitation is a crucial meteorological phenomenon accelerating atmospheric aerosol removal through the scavenging effect. Algorithm results will also help the understanding of long term aerosol-cloud interactions, exploiting the multi-year database from several MPLNET permanent observational sites across the globe. The algorithm is also applicable to other lidar and/or ceilometer network infrastructures in the framework of the Global AerosolWatch (GAW) aerosol lidar observation network (GALION). © 2019 by the authors."
"55225894400;24381474400;57191172390;57211565887;25652188900;57213046638;7004587644;56250119900;35782476600;57212530468;57192180109;","The sensitivity of Southern Ocean aerosols and cloud microphysics to sea spray and sulfate aerosol production in the HadGEM3-GA7.1 chemistry-climate model",2019,"10.5194/acp-19-15447-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076945970&doi=10.5194%2facp-19-15447-2019&partnerID=40&md5=70a9096cb029a3f145cc8bcdbf53b65c","With low concentrations of tropospheric aerosol, the Southern Ocean offers a ""natural laboratory"" for studies of aerosol-cloud interactions. Aerosols over the Southern Ocean are produced from biogenic activity in the ocean, which generates sulfate aerosol via dimethylsulfide (DMS) oxidation, and from strong winds and waves that lead to bubble bursting and sea spray emission. Here, we evaluate the representation of Southern Ocean aerosols in the Hadley Centre Global Environmental Model version 3, Global Atmosphere 7.1 (HadGEM3-GA7.1) chemistry-climate model. Compared with aerosol optical depth (AOD) observations from two satellite instruments (the Moderate Resolution Imaging Spectroradiometer, MODIS-Aqua c6.1, and the Multi-angle Imaging Spectroradiometer, MISR), the model simulates too-high AOD during winter and too-low AOD during summer. By switching off DMS emission in the model, we show that sea spray aerosol is the dominant contributor to AOD during winter. In turn, the simulated sea spray aerosol flux depends on near-surface wind speed. By examining MODIS AOD as a function of wind speed from the ERA-Interim reanalysis and comparing it with the model, we show that the sea spray aerosol source function in HadGEM3-GA7.1 overestimates the wind speed dependency. We test a recently developed sea spray aerosol source function derived from measurements made on a Southern Ocean research voyage in 2018. In this source function, the wind speed dependency of the sea spray aerosol flux is less than in the formulation currently implemented in HadGEM3-GA7.1. The new source function leads to good agreement between simulated and observed wintertime AODs over the Southern Ocean; however, it reveals partially compensating errors in DMS-derived AOD. While previous work has tested assumptions regarding the seawater climatology or sea-air flux of DMS, we test the sensitivity of simulated AOD, cloud condensation nuclei and cloud droplet number concentration to three atmospheric sulfate chemistry schemes. The first scheme adds DMS oxidation by halogens and the other two test a recently developed sulfate chemistry scheme for the marine troposphere; one tests gas-phase chemistry only, while the second adds extra aqueous-phase sulfate reactions. We show how simulated sulfur dioxide and sulfuric acid profiles over the Southern Ocean change as a result and how the number concentration and particle size of the soluble Aitken, accumulation and coarse aerosol modes are affected. The new DMS chemistry scheme leads to a 20&thinsp;% increase in the number concentration of cloud condensation nuclei and cloud droplets, which improves agreement with observations. Our results highlight the importance of atmospheric chemistry for simulating aerosols and clouds accurately over the Southern Ocean. © Author(s) 2019."
"55879760100;54982705800;35551238800;55554574300;15319055900;","The role of aerosol-radiation-cloud interactions in linking anthropogenic pollution over southern west Africa and dust emission over the Sahara",2019,"10.5194/acp-19-14657-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076085036&doi=10.5194%2facp-19-14657-2019&partnerID=40&md5=8fe32203671c08a7e6419caa45887775","The aerosol direct and indirect effects are studied over west Africa in the summer of 2016 using the coupled WRF-CHIMERE regional model including aerosol-cloud interaction parameterization. First, a reference simulation is performed and compared with observations acquired during the Dynamics-aerosol-chemistry-cloud interactions in West Africa (DACCIWA) field campaign which took place in June and July 2016. Sensitivity experiments are also designed to gain insights into the impact of the aerosols dominating the atmospheric composition in southern west Africa (one simulation with halved anthropogenic emissions and one with halved mineral dust emissions). The most important effect of aerosol-cloud interactions is found for the mineral dust scenario, and it is shown that halving the emissions of mineral dust decreases the 2 m temperature by 0.5 K and the boundary layer height by 25 m on a monthly average (July 2016) and over the Saharan region. The presence of dust aerosols also increases (decreases) the shortwave (longwave) radiation at the surface by 25 W m-2. It is also shown that the decrease of anthropogenic emissions along the coast has an impact on the mineral dust load over west Africa by increasing their emissions in the Saharan region. It is due to a mechanism where particulate matter concentrations are decreased along the coast, imposing a latitudinal shift of the monsoonal precipitation and, in turn, an increase of the surface wind speed over arid areas, inducing more mineral dust emissions. © 2019 Author(s)."
"55405013100;24722292100;57202903973;6701697023;22133985200;6603816167;15926468600;26023140500;7003414581;57189706844;36183122600;57212092544;57214160655;57097521200;7004005379;","Sun photometer retrievals of Saharan dust properties over Barbados during SALTRACE",2019,"10.5194/acp-19-14571-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075872703&doi=10.5194%2facp-19-14571-2019&partnerID=40&md5=3866987a62f738c2437933416c68bf44","The Saharan Aerosol Long-Range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) was devoted to the investigation of Saharan dust properties over the Caribbean. The campaign took place in June-July 2013. A wide set of ground-based and airborne aerosol instrumentation was deployed at the island of Barbados for a comprehensive experiment. Several sun photometers performed measurements during this campaign: two AERONET (Aerosol Robotic Network) Cimel sun photometers and the Sun and Sky Automatic Radiometer (SSARA). The sun photometers were co-located with the ground-based multi-wavelength lidars BERTHA (Backscatter Extinction lidar Ratio Temperature Humidity profiling Apparatus) and POLIS (Portable Lidar System). Aerosol properties derived from direct sun and sky radiance observations are analyzed, and a comparison with the co-located lidar and in situ data is provided. The time series of aerosol optical depth (AOD) allows identifying successive dust events with short periods in between in which the marine background conditions were observed. The moderate aerosol optical depth in the range of 0.3 to 0.6 was found during the dust periods. The sun photometer infrared channel at the 1640nm wavelength was used in the retrieval to investigate possible improvements to aerosol size retrievals, and it was expected to have a larger sensitivity to coarse particles. The comparison between column (aerosol optical depth) and surface (dust concentration) data demonstrates the connection between the Saharan Air Layer and the boundary layer in the Caribbean region, as is shown by the synchronized detection of the successive dust events in both datasets. However the differences of size distributions derived from sun photometer data and in situ observations reveal the difficulties in carrying out a column closure study. © 2019 All rights reserved."
"36600735400;57209469105;10739072200;56897131200;36106335800;8550791300;57210592594;25626899800;57201305884;7102680152;57209465284;26424128800;35461255500;7006415284;7402177459;7006595513;","New particle formation and its effect on cloud condensation nuclei abundance in the summer Arctic: A case study in the Fram Strait and Barents Sea",2019,"10.5194/acp-19-14339-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075838612&doi=10.5194%2facp-19-14339-2019&partnerID=40&md5=d4af0429f96db3cff1c37c26c1237c37","In a warming Arctic the increased occurrence of new particle formation (NPF) is believed to originate from the declining ice coverage during summertime. Understanding the physico-chemical properties of newly formed particles, as well as mechanisms that control both particle formation and growth in this pristine environment, is important for interpreting aerosol-cloud interactions, to which the Arctic climate can be highly sensitive. In this investigation, we present the analysis of NPF and growth in the high summer Arctic. The measurements were made on-board research vessel <i>Polarstern</i> during the PS106 Arctic expedition. Four distinctive NPF and subsequent particle growth events were observed, during which particle (diameter in a range 10-50&thinsp;nm) number concentrations increased from background values of approx. 40 up to 4000&thinsp;cm<span classCombining double low line""inline-formula"">-3</span>. Based on particle formation and growth rates, as well as hygroscopicity of nucleation and the Aitken mode particles, we distinguished two different types of NPF events. First, some NPF events were favored by negative ions, resulting in more-hygroscopic nucleation mode particles and suggesting sulfuric acid as a precursor gas. Second, other NPF events resulted in less-hygroscopic particles, indicating the influence of organic vapors on particle formation and growth. To test the climatic relevance of NPF and its influence on the cloud condensation nuclei (CCN) budget in the Arctic, we applied a zero-dimensional, adiabatic cloud parcel model. At an updraft velocity of 0.1&thinsp;m&thinsp;s<span classCombining double low line""inline-formula"">-1</span>, the particle number size distribution (PNSD) generated during nucleation processes resulted in an increase in the CCN number concentration by a factor of 2 to 5 compared to the background CCN concentrations. This result was confirmed by the directly measured CCN number concentrations. Although particles did not grow beyond 50&thinsp;nm in diameter and the activated fraction of 15-50&thinsp;nm particles was on average below 10&thinsp;%, it could be shown that the sheer number of particles produced by the nucleation process is enough to significantly influence the background CCN number concentration. This implies that NPF can be an important source of CCN in the Arctic. However, more studies should be conducted in the future to understand mechanisms of NPF, sources of precursor gases and condensable vapors, as well as the role of the aged nucleation mode particles in Arctic cloud formation. © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 License."
"57209878026;23978736500;57206961398;56989640500;21935606200;","Aerosol-orography-precipitation – A critical assessment",2019,"10.1016/j.atmosenv.2019.116831","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068982091&doi=10.1016%2fj.atmosenv.2019.116831&partnerID=40&md5=0ebb65c11cc1c8aba3a2ff1ce587c44a","The increasing anthropogenic pollution and its interaction with precipitation received much attention from the research community and have been explored extensively for understanding the aerosol-cloud interactions. The impacts of orography and aerosols on the precipitation processes have unveiled the Aerosol-Orography-Precipitation (AOP) interaction as an essential research area. The understanding of AOP interaction is critical for improving the extreme rainfall events prediction over mountainous regions. The phase of clouds (warm or mixed) along with orography has emerged as a significant factor for influencing the AOP relations. The present work reviews the modelling and observational based studies dealing with the relationship between orography and aerosols on the precipitation. The study reveals the principal role of aerosols in shifting the precipitation pattern for orographic regions. The environmental factors, especially ambient temperature, humidity and flow patterns are also identified to affect the orographic precipitation. The review also discovers that AOP studies exist only to limited areas of the world due to limited observations, and mostly with idealised cases in the modelling framework. © 2019 Elsevier Ltd"
"55947922300;7103180783;","Projected near-term changes in three types of heat waves over China under RCP4.5",2019,"10.1007/s00382-019-04743-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064446559&doi=10.1007%2fs00382-019-04743-y&partnerID=40&md5=ed16c01001b4666aae49e55ff1158dc4","The changes in three aspects of frequency, intensity and duration of the compound, daytime and nighttime heat waves (HWs) over China during extended summer (May–September) in a future period of the mid-21st century (FP; 2045–2055) under RCP4.5 scenario relative to present day (PD; 1994–2011) are investigated by two models, MetUM-GOML1 and MetUM-GOML2, which comprise the atmospheric components of two state-of-the-art climate models coupled to a multi-level mixed-layer ocean model. The results show that in the mid-21st century all three types of HWs in China will occur more frequently with strengthened intensity and elongated duration relative to the PD. The compound HWs will change most dramatically, with the frequency in the FP being 4–5 times that in the PD, and the intensity and duration doubling those in the PD. The changes in daytime and nighttime HWs are also remarkable, with the changes of nighttime HWs larger than those of daytime HWs. The future changes of the three types of HWs in China in two models are similar in terms of spatial patterns and area-averaged quantities, indicating these projected changes of HWs over the China under RCP4.5 scenario are robust. Further analyses suggest that projected future changes in HWs over China are determined mainly by the increase in seasonal mean surface air temperatures with change in temperature variability playing a minor role. The seasonal mean temperature increase is due to the increase in surface downward longwave radiation and surface shortwave radiation. The increase in downward longwave radiation results from the enhanced greenhouse effect and increased water vapour in the atmosphere. The increase in surface shortwave radiation is the result of the decreased aerosol emissions, via direct aerosol–radiation interaction and indirect aerosol–cloud interaction over southeastern and northeastern China, and the reduced cloud cover related to a decrease in relative humidity. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature."
"55620143100;7004715270;15755995900;22953153500;","Numerical Representations of Marine Ice-Nucleating Particles in Remote Marine Environments Evaluated Against Observations",2019,"10.1029/2018GL081861","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068893627&doi=10.1029%2f2018GL081861&partnerID=40&md5=ca5d61c54ea18b4cf15c4194d738ef1e","The abundance and sources of ice-nucleating particles, particles required for heterogeneous ice nucleation, are long-standing sources of uncertainty in quantifying aerosol-cloud interactions. In this study, we demonstrate near closure between immersion freezing ice-nucleating particle number concentration (nINPs) observations and nINPs calculated from simulated sea spray aerosol and dust. The Community Atmospheric Model with constrained meteorology was used to simulate aerosol concentrations at the Mace Head Research Station (North Atlantic) and over the Southern Ocean to the south of Tasmania (Clouds, Aerosols, Precipitation, Radiation, and atmospherIc Composition Over the southeRN ocean campaign). Model-predicted nINPs were within a factor of 10 of nINPs observed with an off-line ice spectrometer at Mace Head Research Station and Clouds, Aerosols, Precipitation, Radiation, and atmospherIc Composition Over the southeRN ocean campaign, for 93% and 69% of observations, respectively. Simulated vertical profiles of nINPs reveal that transported dust may be critical to nINPs in remote regions and that sea spray aerosol may be the dominate contributor to primary ice nucleation in Southern Ocean low-level mixed-phase clouds. ©2019. American Geophysical Union. All Rights Reserved."
"57209848570;34876209700;26029479600;55243717000;","Aerosol indirect effects on the predicted precipitation in a global weather forecasting model",2019,"10.3390/atmos10070392","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068932155&doi=10.3390%2fatmos10070392&partnerID=40&md5=2a3e19e18feec55ec5d4371f1370f668","Aerosol indirect effects on precipitation were investigated in this study using a Global/Regional Integrated Model system (GRIMs) linked with a chemistry package devised for reducing the heavy computational burden occurring in common atmosphere-chemistry coupling models. The chemistry package was based on the Goddard Chemistry Aerosol Radiation and Transport scheme of Weather Research and Forecasting with Chemistry (WRF-Chem), and five tracers that are relatively important for cloud condensation nuclei (CCN) formation were treated as prognostic variables. For coupling with the cloud physics processes in the GRIMs, the CCN number concentrations derived from the simplified chemistry package were utilized in the cumulus parameterization scheme (CPS) and the microphysics scheme (MPS). The simulated CCN number concentrations were higher than those used in original cloud physics schemes and, overall, the amount of incoming shortwave radiation reaching the ground was indirectly reduced by an increase in clouds owing to a high CCN. The amount of heavier precipitation increased over the tropics owing to the inclusion of enhanced riming effects under deep precipitating convection. The trend regarding the changes in non-convective precipitation was mixed depending on the atmospheric conditions. The increase in small-size cloud water owing to a suppressed autoconversion led to a reduction in precipitation. More precipitation can occur when ice particles fall under high CCN conditions owing to the accretion of cloud water by snow and graupel, along with their melting. © 2019 by the authors."
"57194682576;22635999400;57126848900;7003444634;57209647985;56210720700;18134565600;","Polarimetric retrievals of cloud droplet number concentrations",2019,"10.1016/j.rse.2019.04.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058147019&doi=10.1016%2fj.rse.2019.04.008&partnerID=40&md5=5db55345566c99eb6ffc65fc1e37aacf","Cloud droplet number concentration (Nd)is an important parameter of liquid clouds and is crucial to understanding aerosol-cloud interactions. It couples boundary layer aerosol composition, size and concentration with cloud reflectivity. It affects cloud evolution, precipitation, radiative forcing, global climate and, through observation, can be used to partially monitor the first indirect effect. With its unique combination of multi-wavelength, multi-angle, total and polarized reflectance measurements, the Research Scanning Polarimeter (RSP)retrieves Nd with relatively few assumptions. The approach involves measuring cloud optical thickness, mean droplet extinction cross-section and cloud physical thickness. Polarimetric observations are capable of measuring the effective variance, or width, of the droplet size distribution. Estimating cloud geometrical thickness is also an important component of the polarimetric Nd retrieval, which is accomplished using polarimetric measurements in a water vapor absorption band to retrieve the amount of in-cloud water vapor and relating this to physical thickness. We highlight the unique abilities and quantify uncertainties of the polarimetric approach. We validate the approach using observational data from the North Atlantic and Marine Ecosystems Study (NAAMES). NAAMES targets specific phases in the seasonal phytoplankton lifecycle and ocean-atmosphere linkages. This study provides an excellent opportunity for the RSP to evaluate its approach of sensing Nd over a range of concentrations and cloud types with in situ measurements from a Cloud Droplet Probe (CDP). The RSP and CDP, along with an array of other instruments, are flown on the NASA C-130 aircraft, which flies in situ and remote sensing legs in sequence. Cloud base heights retrieved by the RSP compare well with those derived in situ (R = 0.83)and by a ceilometer aboard the R.V. Atlantis (R = 0.79). Comparing geometric mean values from 12 science flights throughout the NAAMES-1 and NAAMES-2 campaigns, we find a strong correlation between Nd retrieved by the RSP and CDP (R = 0.96). A linear least squares fit has a slope of 0.92 and an intercept of 0.3 cm−3. Uncertainty in this comparison can be attributed to cloud 3D effects, nonlinear liquid water profiles, multilayered clouds, measurement uncertainty, variation in spatial and temporal sampling, and assumptions used within the method. Radiometric uncertainties of the RSP measurements lead to biases on derived optical thickness and cloud physical thickness, but these biases largely cancel out when deriving Nd for most conditions and geometries. We find that a polarimetric approach to sensing Nd is viable and the RSP is capable of accurately retrieving Nd for a variety of cloud types and meteorological conditions. © 2019 Elsevier Inc."
"57202132498;8543279200;56265041500;","A seasonal analysis of aerosol-cloud-radiation interaction over Indian region during 2000–2017",2019,"10.1016/j.atmosenv.2018.12.044","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059846119&doi=10.1016%2fj.atmosenv.2018.12.044&partnerID=40&md5=76090b9886c4096b90671c445a68ed3f","The present study uses 18 years (March 2000–May 2017) of satellite–derived relevant parameters to examine the impact of aerosols on cloud properties, radiative fluxes and ACI (aerosol-cloud interaction) over Indian region. The study includes consideration of shortwave cloud radiative forcing (SWCRF), longwave cloud radiative forcing (LWCRF) and net cloud radiative forcing (NetCRF) from CERES (Clouds and Earth's Radiant Energy System). Also, aerosol optical depth (AOD) and cloud properties such as ice/liquid CER (Cloud Effective Radius), CF (Cloud Fraction), COD (Cloud Optical Depth), CTP (Cloud Top Pressure) and ice/liquid CWP (Cloud Water Path; i.e., ICWP and LCWP) are also considered. Moderate to high aerosol loading and the significant increasing trend of AOD is observed over several parts of Indian region depending upon the seasons. CF is found to be moderate to higher during monsoon months with increasing trend over several parts of the country. Optically thicker high-level clouds have low SWCRF value; whereas, middle-level and low-level clouds have low to moderate SWCRF value. In the majority of cases, Twomey effect is observed whereas in some scenarios Anti-Twomey effect is seen. © 2019 Elsevier Ltd"
"7202463361;6602338213;7102862273;6506180220;7004692414;7006838702;7005284903;57204252724;35734944400;23485571500;57205141282;8850861200;","Year-Round In Situ Measurements of Arctic Low-Level Clouds: Microphysical Properties and Their Relationships With Aerosols",2019,"10.1029/2018JD029802","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061597757&doi=10.1029%2f2018JD029802&partnerID=40&md5=a9c9a5ed146864386b30702b22abeb4a","Two years of continuous in situ measurements of Arctic low-level clouds have been made at the Mount Zeppelin Observatory (78°56′N, 11°53′E), in Ny-Ålesund, Spitsbergen. The monthly median value of the cloud particle number concentration (N c ) showed a clear seasonal variation: Its maximum appeared in May–July (65 ± 8 cm −3 ), and it remained low between October and March (8 ± 7 cm −3 ). At temperatures warmer than 0 °C, a clear correlation was found between the hourly N c values and the number concentrations of aerosols with dry diameters larger than 70 nm (N 70 ), which are proxies for cloud condensation nuclei (CCN). When clouds were detected at temperatures colder than 0 °C, some of the data followed the summertime N c to N 70 relationship, while other data showed systematically lower N c values. The lidar-derived depolarization ratios suggested that the former (CCN-controlled) and latter (CCN-uncontrolled) data generally corresponded to clouds consisting of supercooled water droplets and those containing ice particles, respectively. The CCN-controlled data persistently appeared throughout the year at Zeppelin. The aerosol-cloud interaction index (ACI = dlnN c /(3dlnN 70 )) for the CCN-controlled data showed high sensitivities to aerosols both in the summer (clean air) and winter–spring (Arctic haze) seasons (0.22 ± 0.03 and 0.25 ± 0.02, respectively). The air parcel model calculations generally reproduced these values. The threshold diameters of aerosol activation (D act ), which account for the N c of the CCN-controlled data, were as low as 30–50 nm when N 70 was less than 30 cm −3 , suggesting that new particle formation can affect Arctic cloud microphysics. ©2019. The Authors."
"57208163987;49662076300;16550482700;37034312700;6602635781;","Impacts of new particle formation on short-term meteorology and air quality as determined by the NPF-explicit WRF-chem in the midwestern United States",2019,"10.4209/aaqr.2018.05.0163","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064010332&doi=10.4209%2faaqr.2018.05.0163&partnerID=40&md5=bea09c60eeaefecf056de0e30db3c408","New particle formation (NPF) from nucleation and subsequent nuclei growth, which is frequently observed in the troposphere, is critical to aerosol-cloud interactions yet difficult to simulate. In this work, regional simulations with the fully coupled NPF-explicit WRF-Chem model link NPF to cloud properties and to changes in both meteorology and air quality in the U.S. Midwest during summer 2008. Simulations that include NPF have higher concentrations of condensation nuclei, as anticipated from the particle production associated with nucleation, leading to enhanced concentrations of cloud condensation nuclei (CCN) at high supersaturations. However, the online-coupled model develops a number of unexpected features that can be traced to a feedback loop involving aqueous (in-cloud) oxidation of sulfur combined with boundary layer NPF. Simulations with NPF (relative to simulations without) exhibit reduced PM2.5 sulfate mass, cloud dimming (reductions in the cloud frequency, CCN concentration at a low supersaturation, cloud optical depth, and cloud droplet number concentration), and enhanced surface-reaching shortwave radiation. This effect of NPF on the PM2.5 mass is mostly absent for other constituents of PM2.5. The implications of this feedback loop, which is not considered in most climate and air quality modeling, are discussed. © Taiwan Association for Aerosol Research."
"56001571800;22133985200;7201423091;55469200300;7402838215;7004944088;","High Depolarization Ratios of Naturally Occurring Cirrus Clouds Near Air Traffic Regions Over Europe",2018,"10.1029/2018GL079345","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058623943&doi=10.1029%2f2018GL079345&partnerID=40&md5=a98a999482201c9770c56408316cc476","Cirrus clouds have a large influence on the Earth's climate and anthropogenic activities such as aviation can alter their properties. Besides the formation of contrails, indirect effects on naturally occurring cirrus like increased heterogeneous freezing due to exhaust soot particles are discussed in the literature. However, hardly any observational study exists. In this work we present cirrus optical properties measured by an airborne lidar over Europe during the Midlatitude Cirrus experiment (ML-CIRRUS). One half of the cloud cases showed elevated depolarization ratios with a mode difference of 10 percentage points indicating differences in the clouds microphysical properties. Their origin can be traced back to highly frequented air traffic regions, and they show lower in-cloud ice supersaturations. Our analysis reveals no influence of embedded contrails and temperature. These results could be explained by an indirect aerosol effect where heterogeneous freezing is caused by aviation exhaust particles. ©2018. The Authors."
"6508333712;24398842400;","Aerosol effects on clouds and precipitation over central Europe in different weather regimes",2018,"10.1175/JAS-D-18-0110.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059264534&doi=10.1175%2fJAS-D-18-0110.1&partnerID=40&md5=eee6d97d6b8bdec51221e5d918d9f2b7","The response of clouds to changes in the aerosol concentration is complex and may differ depending on the cloud type, the aerosol regime, and environmental conditions. In this study, a novel technique is used to systematically modify the environmental conditions in realistic convection-resolving simulations for cases with weak and strong large-scale forcing over central Europe with the Consortium for Small-Scale Modeling (COSMO) model. Besides control runs with quasi-operational settings, initial and boundary temperature profiles are modified with linear increasing temperature increments from 0 to 5K between 3 and 12 km AGL to represent different amounts of convective available potential energy (CAPE) and relative humidity. The results show a systematic decrease of total precipitation with increasing cloud condensation nuclei (CCN) concentrations for the cases with strong synoptic forcing caused by a suppressed warm-rain process, whereas no systematic aerosol effect is simulated for weak synoptic forcing. The effect of increasing CCN tends to be stronger in the simulations with increased temperatures and lower CAPE. While the large-scale domainaveraged responses to increased CCN are weak, the precipitation forming over mountainous terrain reveals a stronger sensitivity for most of the analyzed cases. Our findings also demonstrate that the role of the warmrain process is more important for strong than for weak synoptic forcing. The aerosol effect is largest for weakly forced conditions but more predictable for the strongly forced cases. However, more accurate environmental conditions are much more important than accurate aerosol assumptions, especially for weak largescale forcing. © 2018 American Meteorological Society."
"24398842400;57203902649;6508333712;","Cloud Top Phase Distributions of Simulated Deep Convective Clouds",2018,"10.1029/2018JD028381","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053446606&doi=10.1029%2f2018JD028381&partnerID=40&md5=22a545690822dc56c6ce7bb4b742e704","Space-based observations of the thermodynamic cloud phase are frequently used for the analysis of aerosol indirect effects and other regional and temporal trends of cloud properties; yet they are mostly limited to the cloud top layers. This study addresses the information content in cloud top phase distributions of deep convective clouds during their growing stage. A cloud-resolving model with grid spacings of 300 m and lower is used in two different setups, simulating idealized and semiidealized isolated convective clouds of different strengths. It is found that the cloud top phase distribution is systematically shifted to higher temperatures compared to the in-cloud phase distribution due to lower vertical velocities and a resultingly stronger Wegener-Bergeron-Findeisen process at the cloud top. Sensitivity studies show that heterogeneous freezing can modify the cloud top glaciation temperature (where the ice pixel fraction reaches 50%) and ice multiplication via rime splintering is visible in an early ice onset at temperatures around −10°C. However, if the analyses are repeated with a coarsened horizontal resolution (above 1 km, similar to many satellite data sets), a significant part of this signal is lost, which limits the detectability of these microphysical fingerprints in the observable cloud top phase distribution. In addition, variation in the cloud dynamics also impacts the cloud phase distribution but cannot be quantified easily. ©2018. American Geophysical Union. All Rights Reserved."
"35095482200;","Global Estimates of Changes in Shortwave Low-Cloud Albedo and Fluxes Due to Variations in Cloud Droplet Number Concentration Derived From CERES-MODIS Satellite Sensors",2018,"10.1029/2018GL078880","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053232340&doi=10.1029%2f2018GL078880&partnerID=40&md5=5005c78ed403e6780bb8fd5a08ed95d8","Fifteen years of Aqua Clouds and the Earth's Radiant Energy Systems (CERES) and MOderate resolution Imaging Spectroradiometer (MODIS) observations are combined to derive nearly global maps of shortwave albedo (A) and flux (F) response to changes in cloud droplet number concentration (Nd). Absolute (Sa=∂A/∂Nd) and relative (Sr=∂A/∂In(Nd)) albedo susceptibilities are computed by exploiting the linear relationship between A and ln (Nd) for shallow liquid clouds. Subtropical stratiform clouds over the eastern Pacific, eastern Atlantic, and off the coast of eastern Asia yield the highest Sr, followed by the extratropical oceans during their hemispheric summer. When Sr is cast in terms of F, the eastern Pacific clouds dominate Sr. Sa is mainly governed by Nd, with offshore clouds producing high Sa. While both Sa and Sr are advantageous for understanding radiative aspects of the aerosol indirect effect, Sr is more suitable for calculating changes in A and F due to the linearity of the A-ln (Nd) relationship. ©2018. American Geophysical Union. All Rights Reserved."
"55940667800;7103016965;24764483400;7801353107;18635820300;","Aerosol-cloud interactions in mixed-phase convective clouds - Part 2: Meteorological ensemble",2018,"10.5194/acp-18-10593-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050653192&doi=10.5194%2facp-18-10593-2018&partnerID=40&md5=03e47b5cf6bfcddc94dd057179ed54cb","The relative contribution of variations in meteorological and aerosol initial and boundary conditions to the variability in modelled cloud properties is investigated with a high-resolution ensemble (30 members). In the investigated case, moderately deep convection develops along sea-breeze convergence zones over the southwestern peninsula of the UK. A detailed analysis of the mechanism of aerosol-cloud interactions in this case has been presented in the first part of this study (Miltenberger et al., 2018). The meteorological ensemble (10 members) varies by about a factor of 2 in boundary-layer moisture convergence, surface precipitation, and cloud fraction, while aerosol number concentrations are varied by a factor of 100 between the three considered aerosol scenarios. If ensemble members are paired according to the meteorological initial and boundary conditions, aerosol-induced changes are consistent across the ensemble. Aerosol-induced changes in CDNC (cloud droplet number concentration), cloud fraction, cell number and size, outgoing shortwave radiation (OSR), instantaneous and mean precipitation rates, and precipitation efficiency (PE) are statistically significant at the 5% level, but changes in cloud top height or condensate gain are not. In contrast, if ensemble members are not paired according to meteorological conditions, aerosol-induced changes are statistically significant only for CDNC, cell number and size, outgoing shortwave radiation, and precipitation efficiency. The significance of aerosol-induced changes depends on the aerosol scenarios compared, i.e. an increase or decrease relative to the standard scenario. A simple statistical analysis of the results suggests that a large number of realisations (typically > 100) of meteorological conditions within the uncertainty of a single day are required for retrieving robust aerosol signals in most cloud properties. Only for CDNC and shortwave radiation small samples are sufficient. While the results are strictly only valid for the investigated case, the presented evidence combined with previous studies highlights the necessity for careful consideration of intrinsic predictability, meteorological conditions, and co-variability between aerosol and meteorological conditions in observational or modelling studies on aerosol indirect effects. © Author(s) 2018."
"35491260500;6506730508;7201804746;22933265100;7402942478;6602407753;35547214900;8147766700;","Dust impacts on the 2012 Hurricane Nadine track during the NASA HS3 field campaign",2018,"10.1175/JAS-D-17-0237.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049776429&doi=10.1175%2fJAS-D-17-0237.1&partnerID=40&md5=bf9e89795625b362d43da763d184157d","During the 2012 deployment of the NASA Hurricane and Severe Storm Sentinel (HS3) field campaign, several flights were dedicated to investigating Hurricane Nadine. Hurricane Nadine developed in close proximity to the dust-laden Saharan air layer and is the fourth-longest-lived Atlantic hurricane on record, experiencing two strengthening and weakening periods during its 22-day total life cycle as a tropical cyclone. In this study, the NASA GEOS-5 atmospheric general circulation model and data assimilation system was used to simulate the impacts of dust during the first intensification and weakening phases of Hurricane Nadine using a series of GEOS-5 forecasts initialized during Nadine's intensification phase (12 September 2012). The forecasts explore a hierarchy of aerosol interactions within the model: no aerosol interaction, aerosol-radiation interactions, and aerosol-radiation and aerosol-cloud interactions simultaneously, as well as variations in assumed dust optical properties. When only aerosol-radiation interactions are included, Nadine's track exhibits sensitivity to dust shortwave absorption, as a more absorbing dust introduces a shortwave temperature perturbation that impacts Nadine's structure and steering flow, leading to a northward track divergence after 5 days of simulation time. When aerosol-cloud interactions are added, the track exhibits little sensitivity to dust optical properties. This result is attributed to enhanced longwave atmospheric cooling from clouds that counters shortwave atmospheric warming by dust surrounding Nadine, suggesting that aerosol-cloud interactions are a more significant influence on Nadine's track than aerosol-radiation interactions. These findings demonstrate that tropical systems, specifically their track, can be impacted by dust interaction with the atmosphere. © 2018 American Meteorological Society."
"57198006594;26665602100;35546188200;","Aerosol indirect effects on summer precipitation in a regional climate model for the Euro-Mediterranean region",2018,"10.5194/angeo-36-321-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85043369271&doi=10.5194%2fangeo-36-321-2018&partnerID=40&md5=7231784112748593b4fd59dea413b937","Aerosols affect atmospheric dynamics through their direct and semi-direct effects as well as through their effects on cloud microphysics (indirect effects). The present study investigates the indirect effects of aerosols on summer precipitation in the Euro-Mediterranean region, which is located at the crossroads of air masses carrying both natural and anthropogenic aerosols. While it is difficult to disentangle the indirect effects of aerosols from the direct and semi-direct effects in reality, a numerical sensitivity experiment is carried out using the Weather Research and Forecasting (WRF) model, which allows us to isolate indirect effects, all other effects being equal. The Mediterranean hydrological cycle has often been studied using regional climate model (RCM) simulations with parameterized convection, which is the approach we adopt in the present study. For this purpose, the Thompson aerosol-Aware microphysics scheme is used in a pair of simulations run at 50ĝ€̄km resolution with extremely high and low aerosol concentrations. An additional pair of simulations has been performed at a convection-permitting resolution (3.3ĝ€̄km) to examine these effects without the use of parameterized convection.<br><br> While the reduced radiative flux due to the direct effects of the aerosols is already known to reduce precipitation amounts, there is still no general agreement on the sign and magnitude of the aerosol indirect forcing effect on precipitation, with various processes competing with each other. Although some processes tend to enhance precipitation amounts, some others tend to reduce them. In these simulations, increased aerosol loads lead to weaker precipitation in the parameterized (low-resolution) configuration. The fact that a similar result is obtained for a selected area in the convection-permitting (high-resolution) configuration allows for physical interpretations. By examining the key variables in the model outputs, we propose a causal chain that links the aerosol effects on microphysics to their simulated effect on precipitation, essentially through reduction of the radiative heating of the surface and corresponding reductions of surface temperature, resulting in increased atmospheric stability in the presence of high aerosol loads. © 2018 Author(s)."
"7005968859;8586682800;57203053317;","100 years of progress in cloud physics, aerosols, and aerosol chemistry research",2018,"10.1175/AMSMONOGRAPHS-D-18-0024.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083359556&doi=10.1175%2fAMSMONOGRAPHS-D-18-0024.1&partnerID=40&md5=ffdaab130a54dae0e6db7516cad3aa45","This chapter reviews the history of the discovery of cloud nuclei and their impacts on cloud microphysics and the climate system. Pioneers including John Aitken, Sir John Mason, Hilding Köhler, Christian Junge, Sean Twomey, and Kenneth Whitby laid the foundations of the field. Through their contributions and those of many others, rapid progress has been made in the last 100 years in understanding the sources, evolution, and composition of the atmospheric aerosol, the interactions of particles with atmospheric water vapor, and cloud microphysical processes. Major breakthroughs in measurement capabilities and in theoretical understanding have elucidated the characteristics of cloud condensation nuclei and ice nucleating particles and the role these play in shaping cloud microphysical properties and the formation of precipitation. Despite these advances, not all their impacts on cloud formation and evolution have been resolved. The resulting radiative forcing on the climate system due to aerosol–cloud interactions remains an unacceptably large uncertainty in future climate projections. Process-level understanding of aerosol–cloud interactions remains insufficient to support tech-nological mitigation strategies such as intentional weather modification or geoengineering to accelerating Earth-system-wide changes in temperature and weather patterns. © 2019 American Meteorological Society."
"6603453147;57206332144;7005793702;","Observation-Based Study on Aerosol Optical Depth and Particle Size in Partly Cloudy Regions",2017,"10.1002/2017JD027028","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030215361&doi=10.1002%2f2017JD027028&partnerID=40&md5=9961fbe5f0f95950b7286bc9da7f849a","This study seeks to help better understand aerosol-cloud interactions by examining statistical relationships between aerosol properties and nearby low-altitude cloudiness using satellite data. The analysis of a global data set of Moderate Resolution Imaging Spectroradiometer observations reveals that the positive correlation between cloudiness and aerosol optical depth (AOD) reported in earlier studies is strong throughout the globe and during both winter and summer. Typically, AOD is 30–50% higher on cloudier-than-average days than on less cloudy days. A combination of satellite observations and Modern-Era Retrospective analysis for Research and Applications, Version 2 global reanalysis data reveals that the correlation between cloud cover and AOD is strong for all aerosol types considered: sulfate, dust, carbon, and sea salt. The observations also indicate that in the presence of nearby clouds, aerosol size distributions tend to shift toward smaller particles over large regions of the Earth. This is consistent with a greater cloud-related increase in the AOD of fine-mode than of coarse-mode particles. The greater increase in fine-mode AOD implies that the cloudiness-AOD correlation does not come predominantly from cloud detection uncertainties. Additionally, the results show that aerosol particle size increases near clouds even in regions where it decreases with increasing cloudiness. This suggests that the decrease with cloudiness comes mainly from changes in large-scale environment, rather than from clouds increasing the number or the size of fine-mode aerosols. Finally, combining different aerosol retrieval algorithms demonstrated that quality assessment flags based on local variability can help identifying when the observed aerosol populations are affected by surrounding clouds. ©2017. American Geophysical Union. All Rights Reserved."
"57191220155;25226620200;7102019758;","Role of aerosols in modulating cloud properties during active–break cycle of Indian summer monsoon",2017,"10.1007/s00382-016-3437-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84994718514&doi=10.1007%2fs00382-016-3437-4&partnerID=40&md5=ee0014fdececffcbddb85579a5dd2af0","In this study, the weather research and forecast model coupled with chemistry (WRF-Chem), is used to understand the impact of aerosol–cloud interaction during the active–break cycles of the Indian summer monsoon. Two sets of simulations are performed, one with a fixed aerosol concentration (ConstantAero) and the other with an observation-based prescription of the rate of change of aerosol concentration as a function of precipitation (VaryingAero). This prescription is derived based on satellite-retrieved daily rainrate and concurrent observations of aerosol optical depth from aerosol robotic network. The proposed modification is necessitated by the lack of realistic emission estimates over the Indian region as well as the presence of inherent biases in monsoon simulation in WRF-Chem. In the VaryingAero simulation, unlike in the ConstantAero run, we find that the break-to-active monsoon phase has more cloud liquid water (CLW) and less rain efficiency than in the active-to-break phase. This is primarily due to the indirect effect of increased aerosol loading in the break phase. This result is in accordance with the observed behaviour of CLW estimtes from microwave imager (TRMM 2A12) and radar reflectivity (TRMM precipitation radar). We also find that the proposed interactive aerosol loading results in higher spatial variability in CLW and enhances the likelihood of increased cloud cover via formation of larger clouds. The modification also alters the diurnal cycle of clouds in break and break-to-active phases as compared to other phases due to aerosol loading, with a stronger diurnal cycle of upper level clouds in these phases in the VaryingAero model as compared to ConstantAero model. © 2016, Springer-Verlag Berlin Heidelberg."
"57193884115;6603109490;","Investigation of aerosol effects on the Arctic surface temperature during the diurnal cycle: part 1 – total aerosol effect",2017,"10.1002/joc.5036","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85017355348&doi=10.1002%2fjoc.5036&partnerID=40&md5=ffbcfab58924fbe47f631e6f75f4bbea","Temperature changes in the Arctic due to anthropogenic climate change are larger in magnitude than those at lower latitudes, with sea ice extent and thickness diminishing since the dawn of the satellite era. Aerosols may play a vital role in determining these changes, as the radiation reaching the Arctic surface is impacted directly by aerosol absorption and scattering, as well as the ability of aerosols to act as cloud condensation nuclei (CCN) and ice nuclei (IN). This study uses the Weather Research and Forecasting Chemistry (WRF-Chem) model to show the impact of aerosol absorption, scattering, and CCN contribution on the Arctic surface, with a particular focus on how these effects change throughout the diurnal cycle. Part 1 of this two-part study investigates the changes in surface temperature, radiation, and cloud properties due to the total aerosol effect in the Arctic. A suite of ensemble runs is used to develop a filtering mechanism based upon the t-test to eliminate the effects of meteorological variability. While much has been speculated about the cooling role of aerosols, this study shows that aerosols have both a warming and cooling effect. The warming effect is prominent at night, while the cooling effect dominates during the day. In both cases, the magnitude of the effect is dependent upon aerosol concentration. © 2017 Royal Meteorological Society"
"57217911076;56033070100;26643041500;7102963655;26422498700;57207261095;24446327700;25825715600;23051160600;57192064212;7006960661;35461255500;","Observational evidence for aerosols increasing upper tropospheric humidity",2016,"10.5194/acp-16-14331-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84996587467&doi=10.5194%2facp-16-14331-2016&partnerID=40&md5=b1c9aad6b5ececcf3913e8c8e394de72","Aerosol-cloud interactions are the largest source of uncertainty in the radiative forcing of the global climate. A phenomenon not included in the estimates of the total net forcing is the potential increase in upper tropospheric humidity (UTH) by anthropogenic aerosols via changes in the microphysics of deep convection. Using remote sensing data over the ocean east of China in summer, we show that increased aerosol loads are associated with an UTH increase of 2.2 ± 1.5 in units of relative humidity. We show that humidification of aerosols or other meteorological covariation is very unlikely to be the cause of this result, indicating relevance for the global climate. In tropical moist air such an UTH increase leads to a regional radiative effect of 0.5 ± 0.4 W m-2. We conclude that the effect of aerosols on UTH should be included in future studies of anthropogenic climate change and climate sensitivity. © Author(s) 2016."
"55317177900;7006705919;55688930000;6508063123;57214786060;","The role of carbonaceous aerosols on short-term variations of precipitation over North Africa",2016,"10.1002/asl.672","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977484729&doi=10.1002%2fasl.672&partnerID=40&md5=ca7aa8f7651075fc99286db6c1798b9a","Subtropical North Africa has been subject to extensive droughts in the late 20th century, linked to changes in the sea surface temperature (SST). However, climate models forced by observed SSTs cannot reproduce the magnitude of the observed rainfall reduction. Here, we propose aerosol indirect effects (AIE) as an important positive feedback mechanism. Model results are presented using two sets of sensitivity experiments designed to distinguish the role of aerosol direct/semi-direct and indirect effects on regional precipitation. Changes in cloud properties due to the presence of carbonaceous aerosols are proposed as a key mechanism to explain the reduced rainfall over subtropical North Africa. © 2016 The Authors. Atmospheric Science Letters published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"57008250400;7101752236;9535707500;","Aerosol indirect effects on glaciated clouds. Part 2: Sensitivity tests using solute aerosols",2016,"10.1002/qj.2790","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84971330338&doi=10.1002%2fqj.2790&partnerID=40&md5=991dfa00353e44f96773fc89d5d8f88b","Sensitivity tests were performed on a midlatitude continental case using a state-of-the-art aerosol–cloud model to determine the salient mechanisms of aerosol indirect effects (AIE) from solute aerosols. The simulations showed that increased solute aerosols doubled cloud-droplet number concentrations and hence reduced cloud particle sizes by about 20% and consequently inhibited warm rain processes, thus enhancing the chances of homogeneous freezing of cloud droplets and aerosols. Cloud fractions and their optical thicknesses increased quite substantially with increasing solute aerosols. Although liquid mixing ratios were boosted, there was, however, a substantial reduction of ice mixing ratios in the upper troposphere, owing to the increase in snow production aloft. The predicted total aerosol indirect effect was equal to −9.46 ± 1.4 W m−2. The AIEs of glaciated clouds (−6.33 ± 0.95 W m−2) were greater than those of water-only clouds (−3.13 ± 0.47 W m−2) by a factor of two in this continental case. The higher radiative importance of glaciated clouds compared with water-only clouds emerged from their larger collective spatial extent and their existence above water-only clouds. In addition to the traditional AIEs (glaciation, riming and thermodynamic), the new AIEs sedimentation, aggregation and coalescence were identified. © 2016 Royal Meteorological Society"
"36801729300;55315290600;6603926727;7004154626;7004057920;","Aerosol indirect effects from ground-based retrievals over the rain shadow region in Indian subcontinent",2016,"10.1002/2015JD024577","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029150074&doi=10.1002%2f2015JD024577&partnerID=40&md5=4a9a60768354e2c0a61dc04d3caf2d59","Aerosol-induced changes in cloud microphysical and radiative properties have been studied for the first time using ground-based and airborne observations over a semiarid rain shadow region. The study was conducted for nonprecipitating, ice-free clouds during monsoon (July to September) and postmonsoon (October) months, when cloud condensation nuclei (CCN) concentrations over the region of interest increased monotonically and exhibited characteristics of continental origin. A multifilter rotating shadowband radiometer and microwave radiometric profiler were used to retrieve the cloud optical depth and liquid water path (LWP), respectively, from which cloud effective radius (CER) was obtained. CER showed wide variability from 10–18 μm and a decreasing trend toward the postmonsoon period. During monsoon, the estimated first aerosol indirect effect (AIE) increased from 0.01 to 0.23 with increase in LWP. AIE at different super saturations (SS) showed maximum value (significant at 95%) at 0.4% SS and higher LWP bin (250–300 g/m2). Also, statistically significant AIE values were found at 0.6% and 0.8% SSs but at lower LWP bin (200–250 g/m2). The relationship between CCN and CER showed high correlation at 0.4% SS at higher LWP bin, while at higher SSs good correlations were observed at lower LWPs. Data combined from ground-based and aircraft observations showed dominance of microphysical effect at aerosol concentrations up to 1500 cm-3 and radiative effect at higher concentrations. This combined cloud microphysical and aerosol radiative effect is more prominent during postmonsoon period due to an increase in aerosol concentration. ©2016. American Geophysical Union. All Rights Reserved."
"57161358100;56162305900;7003666669;7102010848;55688930000;56384704800;23095483400;57203053317;16444232500;7202079615;25031430500;7103158465;55588510300;7004214645;36171703500;57208121852;49861577800;7402803216;","On the characteristics of aerosol indirect effect based on dynamic regimes in global climate models",2015,"10.5194/acpd-15-23683-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84993931925&doi=10.5194%2facpd-15-23683-2015&partnerID=40&md5=61c78ef8c06fc32ddd04771f78a7e775","Aerosol-cloud interactions continue to constitute a major source of uncertainty for the estimate of climate radiative forcing. The variation of aerosol indirect effects (AIE) in climate models is investigated across different dynamical regimes, determined by monthly mean 500 hPa vertical pressure velocity (ω500), lower-tropospheric stability (LTS) and large-scale surface precipitation rate derived from several global climate models (GCMs), with a focus on liquid water path (LWP) response to cloud condensation nuclei (CCN) concentrations. The LWP sensitivity to aerosol perturbation within dynamic regimes is found to exhibit a large spread among these GCMs. It is in regimes of strong large-scale ascend (ω500 &lt; -25 hPa d-1) and low clouds (stratocumulus and trade wind cumulus) where the models differ most. Shortwave aerosol indirect forcing is also found to differ significantly among different regimes. Shortwave aerosol indirect forcing in ascending regimes is as large as that in stratocumulus regimes, which indicates that regimes with strong large-scale ascend are as important as stratocumulus regimes in studying AIE. It is further shown that shortwave aerosol indirect forcing over regions with high monthly large-scale surface precipitation rate (&gt; 0.1 mm d-1) contributes the most to the total aerosol indirect forcing (from 64 to nearly 100 %). Results show that the uncertainty in AIE is even larger within specific dynamical regimes than that globally, pointing to the need to reduce the uncertainty in AIE in different dynamical regimes. © Author(s) 2015."
"24472400800;7005955015;","Contrasting influences of recent aerosol changes on clouds and precipitation in Europe and East Asia",2015,"10.1175/JCLI-D-14-00837.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949979685&doi=10.1175%2fJCLI-D-14-00837.1&partnerID=40&md5=c7456ef076d04bd1a124316d25d0144e","Over the last few decades, aerosol loadings have increased greatly over Southeast Asia, while Europe and North America have experienced huge reductions. Previous studies have suggested that these changes may have influenced the temperature trends as well as precipitation patterns due to the direct and semidirect aerosol effects. Here, an Earth system model with parameterized aerosol-radiation and aerosol-cloud interactions is used to investigate changes in cloud properties and precipitation between 1975 and 2005. This is done globally as well as for the two focus areas Europe and East Asia. Despite systematic changes in cloud droplet number concentration and cloud droplet size, changes in stratiform precipitation are less clear. In both regions there is a dominance of autoconversion over liquid water accretion as the primary precipitation release mechanism, which alone should imply a strong sensitivity to changes in cloud droplet size. However, in these areas liquid water paths are relatively low and background concentrations are high, which produce low simulated precipitation susceptibilities. High susceptibilities are instead found over remote ocean regions, in agreement with expectations. For convective precipitation, both regions show statistically significant changes that are consistent with oppositely signed changes in direct aerosol forcing over Europe and East Asia, respectively. © 2015 American Meteorological Society."
"55683899300;6506718302;35459245100;7006712143;7007039218;6507755223;","Reallocation in modal aerosol models: Impacts on predicting aerosol radiative effects",2014,"10.5194/gmd-7-161-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893233113&doi=10.5194%2fgmd-7-161-2014&partnerID=40&md5=18697277ce09b730cc9d9bd203c490a9","Atmospheric models often represent the aerosol particle size distribution with a modal approach, in which particles are described with log-normal modes within predetermined size ranges. This approach reallocates particles numerically from one mode to another for example during particle growth, potentially leading to artificial changes in the aerosol size distribution. In this study we analysed how the modal reallocation affects climate-relevant variables: cloud droplet number concentration (CDNC), aerosol-cloud interaction parameter (ACI) and light extinction coefficient (<i>q</i>ext). The ACI parameter gives the response of CDNC to a change in total aerosol number concentration. We compared these variables between a modal model (with and without reallocation routines) and a high resolution sectional model, which was considered a reference model. We analysed the relative differences in the chosen variables in four experiments designed to assess the influence of atmospheric aerosol processes. We find that limiting the allowed size ranges of the modes, and subsequent remapping of the distribution, leads almost always to an underestimation of cloud droplet number concentrations (by up to 100%) and an overestimation of light extinction (by up to 20%). On the other hand, the aerosol-cloud interaction parameter can be either over- or underestimated by the reallocating model, depending on the conditions. For example, in the case of atmospheric new particle formation events followed by rapid particle growth, the reallocation can cause on average a 10% overestimation of the ACI parameter. Thus it is shown that the reallocation affects the ability of a model to estimate aerosol climate effects accurately, and this should be taken into account when using and developing aerosol models. © Author(s) 2014."
"57212023209;57212020453;57212023802;","The Role of the Aerosol Indirect Effect in the Northern Indian Ocean Warming Simulated by CMIP5 Models",2014,"10.3878/j.issn.1674-2834.14.0032","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075748734&doi=10.3878%2fj.issn.1674-2834.14.0032&partnerID=40&md5=97c652d695225cbd02b53afad4908025","The northern Indian Ocean (NIO) experienced a decadal-scale persistent warming from 1950 to 2000, which has influenced both regional and global climate. Because the NIO is a region susceptible to aerosols emission changes, and there are still large uncertainties in the representation of the aerosol indirect effect (AIE) in CMIP5 (Coupled Model Intercomparison Project Phase 5) models, it is necessary to investigate the role of the AIE in the NIO warming simulated by these models. In this study, the authors select seven CMIP5 models with both the aerosol direct and indirect effects to investigate their performance in simulating the basin-wide decadal-scale NIO warming. The results show that the decreasing trend of the downwelling shortwave flux (FSDS) at the surface has the major damping effect on the SST increasing trend, which counteracts the warming effect of greenhouse gases (GHGs). The FSDS decreasing trend is mostly contributed by the decreasing trend of cloudy-sky surface downwelling shortwave flux (FSDSCL), a metric used to measure the strength of the AIE, and partly by the clear-sky surface downwelling shortwave flux (FSDSC). Models with a relatively weaker AIE can simulate well the SST increasing trend, as compared to observation. In contrast, models with a relatively stronger AIE produce a much smaller magnitude of the increasing trend, indicating that the strength of the AIE in these models may be overestimated in the NIO. © 2014, © Institute of Atmospheric Physics, Chinese Academy of Sciences."
"23065650200;6603133549;","Satellite retrieval of the liquid water fraction in tropical clouds between -20 and -38 °c",2012,"10.5194/amt-5-1683-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864240193&doi=10.5194%2famt-5-1683-2012&partnerID=40&md5=58ae9be14151868ca793ea7a3baaa0d3","This study describes a satellite remote sensing method for directly retrieving the liquid water fraction in mixed phase clouds, and appears unique in this respect. The method uses MODIS split-window channels for retrieving the liquid fraction from cold clouds where the liquid water fraction is less than 50% of the total condensate. This makes use of the observation that clouds only containing ice exhibit effective 12-to-11 μm absorption optical thickness ratios (β eff) that are quasi-constant with retrieved cloud temperature T. This observation was made possible by using two CO2 channels to retrieve T and then using the 12 and 11 μm channels to retrieve emissivities and β eff. Thus for T -40 °C, β eff is constant, but for T -40 °C, β eff slowly increases due to the presence of liquid water, revealing mean liquid fractions of ∼ 10% around -22 °C from tropical clouds identified as cirrus by the cloud mask. However, the uncertainties for these retrievals are large, and extensive in situ measurements are needed to refine and validate these retrievals. Such liquid levels are shown to reduce the cloud effective diameter De such that cloud optical thickness will increase by more than 50% for a given water path, relative to De corresponding to pure ice clouds. Such retrieval information is needed for validation of the cloud microphysics in climate models. Since low levels of liquid water can dominate cloud optical properties, tropical clouds between -25 and -20 °C may be susceptible to the first aerosol indirect effect. © Author(s) 2012."
"55654938600;7404544551;","Iron mobilization in North African dust",2011,"10.1016/j.proenv.2011.05.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857429807&doi=10.1016%2fj.proenv.2011.05.004&partnerID=40&md5=8fef0fc94915998b39cc3e75e6aa402a","Iron is an essential nutrient for phytoplankton. Although iron-containing dust mobilized from arid regions supplies the majority of the iron to the oceans, the key flux in terms of the biogeochemical response to atmospheric deposition is the amount of soluble or bioavailable iron. Atmospheric processing of mineral aerosols by anthropogenic pollutants (e.g. sulfuric acid) may transform insoluble iron into soluble forms. Previous studies have suggested higher iron solubility in smaller particles, as they are subject to more thorough atmospheric processing due to a longer residence time than coarse particles. On the other hand, the specific mineralogy of iron in dust may also influence the particulate iron solubility in size. Compared to mineral dust aerosols, iron from combustion sources could be more soluble, and found more frequently in smaller particles. Internal mixing of alkaline dust with iron-containing minerals could significantly reduce iron dissolution in large dust aerosols due to the buffering effect, which may, in contrast, yield higher solubility in smaller particles externally mixed with alkaline dust (Ito and Feng, 2010). Here, we extend the modeling study of Ito and Feng (2010) to investigate atmospheric processing of mineral aerosols from African dust. In contrast to Asian dust, we used a slower dissolution rate for African dust in the fine mode. We compare simulated fractional iron solubility with observations. The inclusion of alkaline compounds in aqueous chemistry substantially limits the iron dissolution during long-range transport to the Atlantic Ocean: only a small fraction of iron (<0.2%) dissolves from illite in coarsemode dust aerosols with 0.45% soluble iron initially. In contrast, a significant fraction (1-1.5%) dissolves in fine-mode dust aerosols due to the acid mobilization of the iron-containing minerals externally mixed with carbonate minerals. Consequently, the model generally reproduces higher iron solubility in smaller particles as suggested by measurements over the Atlantic Ocean. Our results imply that the dissolution of iron in African dust is generally slower than that in Asian dust. Conventionally, dust is assumed as the major supply of bioavailable iron with a constant solubility at 1-2% to the remote ocean. Therefore, the timing and location of the atmospheric iron input to the ocean with detailed modeling of atmospheric processing could be different from those previously assumed. Past and future changes in aerosol supply of bioavailable iron might play a greater role in the nutrient supply for phytoplankton production in the upper ocean, as global warming has been predicted to intensify stratification and reduce vertical mixing from the deep ocean. Thus the feedback of climate change through ocean uptake of carbon dioxide as well as via aerosol-cloud interaction might be modified by the inclusion of iron chemistry in the atmosphere. © 2011 Published by Elsevier BV."
"35974951200;6603390592;6602244257;","The aerosol-Bénard cell effect on marine stratocumulus clouds and its contribution to glacial-interglacial cycles",2011,"10.1029/2010JD014470","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958066490&doi=10.1029%2f2010JD014470&partnerID=40&md5=85fe36887135fbe3535e1ed9d30e022e","Aerosol-cloud interactions, such as aerosol loading in convective clouds resulting in either precipitation suppression or cloud invigoration, in higher cloud tops, and in longer-lived clouds, are well known. Here we investigate a new aerosol-cloud interaction, the effect of aerosol loading on Bénard cells, on the stratocumulus cloud fraction, and ultimately on the climate over glacial-interglacial cycles, using a two-dimensional model running a million year continuous simulation. This radiative effect is observed only in marine boundary layer stratocumulus clouds that have a convective cellular structure. Recent research suggests that aerosols can switch the direction of convection in Bénard cells (from open cells to closed cells) by suppressing precipitation and therefore dramatically change the cloud fraction. The effect investigated in this work differs from previously known aerosol effects on convective clouds by its intensity and magnitude and has never been taken into account in past climate simulations. The results show that accounting for the aerosol-Bénard cell effect alone contributes a negative radiative forcing, affecting both the Northern Hemisphere mean annual surface temperature and ice volume. Adding the aerosol-Bénard cell effect to the direct radiative effect of dust and to the effect of dust on snow and ice albedo shows that the aerosol-Bénard cell effect plays a significant role in glacial-interglacial climate change, strengthening the earlier glacial cycles and creating a larger glacial-interglacial surface temperature amplitude while preserving the continental ice volume amplitude. Because of the model limitations, there are a number of uncertainties involved. However, the results serve to give a preliminary evaluation of the aerosol-Bénard cell effect at least qualitatively if not quantitatively. Copyright 2011 by the American Geophysical Union."
"35621564700;7004160106;55717074000;7402390191;57217362458;57192695511;","Importance of including ammonium sulfate ((NH4)2SO4) aerosols for ice cloud parameterization in GCMs",2010,"10.5194/angeo-28-621-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649141307&doi=10.5194%2fangeo-28-621-2010&partnerID=40&md5=6f72d2cd476b7c191aa8a2b93292f909","A common deficiency of many cloud-physics parameterizations including the NASA's microphysics of clouds with aerosol-cloud interactions (hereafter called McRAS-AC) is that they simulate lesser (larger) than the observed ice cloud particle number (size). A single column model (SCM) of McRAS-AC physics of the GEOS4 Global Circulation Model (GCM) together with an adiabatic parcel model (APM) for ice-cloud nucleation (IN) of aerosols were used to systematically examine the influence of introducing ammonium sulfate (NH4)2SO 4 aerosols in McRAS-AC and its influence on the optical properties of both liquid and ice clouds. First an (NH4)2SO4 parameterization was included in the APM to assess its effect on clouds vis-á-vis that of the other aerosols. Subsequently, several evaluation tests were conducted over the ARM Southern Great Plain (SGP) and thirteen other locations (sorted into pristine and polluted conditions) distributed over marine and continental sites with the SCM. The statistics of the simulated cloud climatology were evaluated against the available ground and satellite data. The results showed that inclusion of (NH4)2SO4 into McRAS-AC of the SCM made a remarkable improvement in the simulated effective radius of ice cloud particulates. However, the corresponding ice-cloud optical thickness increased even more than the observed. This can be caused by lack of horizontal cloud advection not performed in the SCM. Adjusting the other tunable parameters such as precipitation efficiency can mitigate this deficiency. Inclusion of ice cloud particle splintering invoked empirically further reduced simulation biases. Overall, these changes make a substantial improvement in simulated cloud optical properties and cloud distribution particularly over the Intertropical Convergence Zone (ITCZ) in the GCM."
"35887706900;7501627905;","Cloud-rain interactions: As complex as it gets",2008,"10.1088/1748-9326/3/4/045018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-62749143492&doi=10.1088%2f1748-9326%2f3%2f4%2f045018&partnerID=40&md5=a63d19981976ff85ac22c563008bd0b5","The effect of aerosol on clouds and precipitation poses one of the largest uncertainties in the estimation of the anthropogenic contribution to climate change. Often the local effect of aerosol on the radiation field both directly and indirectly by changing cloud properties can be more than an order of magnitude larger than the effect of greenhouse gases. Recent works also suggest that some of the local aerosol effects such as the heating of the atmosphere from aerosol absorption can have a large-scale impact. However, due to the inhomogeneous distribution and short lifetime of aerosols, the inherent complexity of cloud microphysics and dynamics, and the strong coupling of aerosol-related processes with meteorology, it is still challenging to estimate the overall effect that aerosols exert on the radiation field and climate. The climatic effect of aerosol-cloud interaction is not limited to the radiation field. By changing the cloud microphysical and radiative properties, aerosols may affect precipitation amount and patterns. Precipitation processes are located at the end of the 'food chain' of aerosol-cloud processes. Rain rates and patterns are the final result of many cloud processes and feedbacks, some of which are affected by aerosols. Changes in precipitation patterns could lead to serious hydrological consequences. For example if the same amount of rain precipitates in shorter time, e.g. heavier rain rates, the probability of floods increases, a larger portion of the water is drained by rapid surface run-off and the amount of water penetrating the subsurface and available as an underground reservoir of drinking water is reduced. Moreover, the subsurface water distribution depends heavily on topography and geomorphology. Therefore small changes in the timing or location of precipitation may dramatically alter the surface and subsurface water distribution and affect the water reservoir. In studying aerosol-cloud-precipitation interactions, the largest challenge is determining how to separate the effect of meteorological processes from aerosol effects. Simple statistical correlations between observed or retrieved aerosol and cloud properties do not imply causality. With the help of sophisticated cloud numerical models where certain variables or processes can be controlled in sensitivity simulations, aerosol-precipitation casual relationships could be examined in specific conditions. However, it is not always clear whether such aerosol-precipitation relationships seen in the model could be applied to more general meteorological scenarios. Aerosol-cloud-precipitation interaction is a highly complex problem involving processes and feedbacks that span the size range from an aerosol particle (10-7m) to a cloud (103m), and all the way to synoptic scale systems (106m). These feedbacks determine whether a droplet, initiated at a size of few microns, could grow within the time scale of a cloud's lifetime to reach a raindrop size of a few mm, and whether this raindrop will fall all the way to the surface and be available as fresh water. These feedbacks include dynamic and thermodynamic processes of precipitating particles, which in conjunction with other processes determine the micro and macrophysical properties of the cloud and hence determine the cloud's effect on the regional radiation field and local climate. Thus, aerosol, cloud, precipitation and radiation interactions are inherently linked, and need to be addressed as a single problem when attempting to better understand human-induced changes in the climate system. Focus on Aerosol Precipitation Contents Drizzle rates versus cloud depths for marine stratocumuli A B Kostinski Characteristics of vertical velocity in marine stratocumulus: comparison of large eddy simulations with observations Huan Guo, Yangang Liu, Peter H Daum, Gunnar I Senum and Wei-Kuo Tao Dispersion bias, dispersion effect, and the aerosol-cloud conundrum Yangang Liu, Peter H Daum, Huan Guo and Yiran Peng The impact of smoke from forest fires on the spectral dispersion of cloud droplet size distributions in the Amazonian region J A Martins and M A F Silva Dias A conceptual model for the link between Central American biomass burning aerosols and severe weather over the south central United States Jun Wang, Susan C van den Heever and Jeffrey S Reid © 2008 IOP Publishing Ltd."
"55896920900;","Introduction to Special Section: An experimental study of the aerosol indirect effect for validation of climate model parameterizations",2003,"10.1029/2003jd003849","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342269859&doi=10.1029%2f2003jd003849&partnerID=40&md5=3f45c66b45fb7ec2dcafe52755fb6c8e",[No abstract available]
"57200035729;14063724200;55357667300;57194282107;57204292894;57197781066;","Trends in downward surface shortwave radiation from multi-source data over China during 1984–2015",2020,"10.1002/joc.6408","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076130690&doi=10.1002%2fjoc.6408&partnerID=40&md5=f4596ae23107cdcb36b9fd8617c35474","The clear knowledge of decadal variability of surface solar radiation (SSR) is of vitally significant for understanding hydrological and biological processes and climate prediction. However, existing studies have shown observed SSR over China may have large discrepancies and inhomogeneity in decadal variability due to sensitivity drift, inaccurate calibrations and instrument replacement. Therefore, a new procedure of station selection was proposed to eliminate errors and to derive “true” SSR values in this study. Afterward, two satellite retrieves of SSR, including Clouds and the Earth's Radiant Energy System-energy balanced and filled product (CERES-EBAF) (edition 4) and Global Energy and Water Cycle Experiment-Surface Radiation Budget (GEWEX-SRB) (Version 3.0), and three reanalysis products, including National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR), national centers for environmental prediction-/department of energy (NCEP-DOE) and Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) were evaluated using “true” SSR values at 39 homogeneous stations from the China Meteorological Administration and it was found that although all five products overestimated SSR, two satellite retrieves showed better accuracy with an overall R of 0.95, an root mean squared error (RMSE) of 20.4 W m−2 and mean absolute bias error (MAE) of 14.9 W m−2 for CERES-EBAF and an overall R of 0.92, an RMSE of 27.7 W m−2 and MAE of 21.2 W m−2 for GEWEX-SRB across China. Meanwhile, inter-comparisons between trends of observations and trends of two satellite retrieves in this study showed that the new trends derived from two satellite retrieves (+0.78 W m−2 decade−1) were good agreement with trends of observation (+0.92 W m−2 decade−1) from 1994 to 2015. However, trends of SSR (+5.8 W m−2 decade−1) in situ measurements were still in disagreement with the trends of SSR (−3.7 W m−2 decade−1) derived from two satellite retrieves from 1984 to 1993 because of the sensitivity drift and instrument replacement in this period. The possible reasons for decadal variability of SSR in China were detected and it was found that variations in aerosol optical depth (AOD) and aerosol-cloud interaction, rather than cloud, were suggested to be likely the main influencing factor of decadal variability of SSR across China from 1984 to 2015. © 2019 Royal Meteorological Society"
"57208745275;6701606453;","Quantifying cloud adjustments and the radiative forcing due to aerosol-cloud interactions in satellite observations of warm marine clouds",2020,"10.5194/acp-20-6225-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085660194&doi=10.5194%2facp-20-6225-2020&partnerID=40&md5=57e45b91bccc6d22df982af7cd9cc884","Aerosol-cloud interactions and their resultant forcing remains one of the largest sources of uncertainty in future climate scenarios. The effective radiative forcing due to aerosol-cloud interactions (ERFaci) is a combination of two different effects, namely how aerosols modify cloud brightness (RFaci, intrinsic) and how cloud extent reacts to aerosol (cloud adjustments CA; extrinsic). Using satellite observations of warm clouds from the NASA ATrain constellation from 2007 to 2010 along with MERRA- 2 Reanalysis and aerosol from the SPRINTARS model, we evaluate the ERFaci in warm, marine clouds and its components, the RFaciwarm and CAwarm, while accounting for the liquid water path and local environment. We estimate the ERFaciwarm to be 0:320:16Wm2. The RFaciwarm dominates the ERFaciwarm contributing 80% (0:210:15Wm2), while the CAwarm enhances this cooling by 20% (0:050:03Wm2). Both the RFaciwarm and CAwarm vary in magnitude and sign regionally and can lead to opposite, negating effects under certain environmental conditions.Without considering the two terms separately and without constraining cloud-environment interactions, weak regional ERFaciwarm signals may be erroneously attributed to a damped susceptibility to aerosol. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License."
"55635713200;55326237100;56771374500;24366038500;56125661000;57216886074;47661249200;56287748600;56522555200;57195136271;57211646937;57190733403;36469200100;22954523900;36705265400;56533742600;57189505139;57216877634;8204115900;57193241144;55614754800;57216871998;56284543100;6603868770;24398842400;8701353900;56250185400;6602600408;","Detection and attribution of aerosol-cloud interactions in large-domain large-eddy simulations with the ICOsahedral Non-hydrostatic model",2020,"10.5194/acp-20-5657-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085069138&doi=10.5194%2facp-20-5657-2020&partnerID=40&md5=c76c0ab8648f2237be5562c2dd2187f1","Clouds and aerosols contribute the largest uncertainty to current estimates and interpretations of the Earth's changing energy budget. Here we use a new-generation large-domain large-eddy model, ICON-LEM (ICOsahedral Non-hydrostatic Large Eddy Model), to simulate the response of clouds to realistic anthropogenic perturbations in aerosols serving as cloud condensation nuclei (CCN). The novelty compared to previous studies is that (i) the LEM is run in weather prediction mode and with fully interactive land surface over a large domain and (ii) a large range of data from various sources are used for the detection and attribution. The aerosol perturbation was chosen as peak-aerosol conditions over Europe in 1985, with more than fivefold more sulfate than in 2013. Observational data from various satellite and ground-based remote sensing instruments are used, aiming at the detection and attribution of this response. The simulation was run for a selected day (2 May 2013) in which a large variety of cloud regimes was present over the selected domain of central Europe. It is first demonstrated that the aerosol fields used in the model are consistent with corresponding satellite aerosol optical depth retrievals for both 1985 (perturbed) and 2013 (reference) conditions. In comparison to retrievals from groundbased lidar for 2013, CCN profiles for the reference conditions were consistent with the observations, while the ones for the 1985 conditions were not. Similarly, the detection and attribution process was successful for droplet number concentrations: the ones simulated for the 2013 conditions were consistent with satellite as well as new ground-based lidar retrievals, while the ones for the 1985 conditions were outside the observational range. For other cloud quantities, including cloud fraction, liquid water path, cloud base altitude and cloud lifetime, the aerosol response was small compared to their natural vari ability. Also, large uncertainties in satellite and ground-based observations make the detection and attribution difficult for these quantities. An exception to this is the fact that at a large liquid water path value (LWP &gt; 200 g m-2), the control simulation matches the observations, while the perturbed one shows an LWP which is too large. The model simulations allowed for quantifying the radiative forcing due to aerosol-cloud interactions, as well as the adjustments to this forcing. The latter were small compared to the variability and showed overall a small positive radiative effect. The overall effective radiative forcing (ERF) due to aerosol-cloud interactions (ERFaci) in the simulation was dominated thus by the Twomey effect and yielded for this day, region and aerosol perturbation-2:6 W m-2. Using general circulation models to scale this to a global-mean present-day vs. pre-industrial ERFaci yields a global ERFaci of-0:8 W m-2 © 2020 Author(s)."
"54931083200;7801401670;35173744200;56709590600;36629973600;26434217100;6701363731;22946301100;6602087140;15059495000;10141225800;","A first case study of CCN concentrations from spaceborne lidar observations",2020,"10.3390/rs12101557","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085566497&doi=10.3390%2frs12101557&partnerID=40&md5=38edf0014ae1231c09839dab752f459b","We present here the first cloud condensation nuclei (CCN) concentration profiles derived from measurements with the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), for different aerosol types at a supersaturation of 0.15%. CCN concentrations, along with the corresponding uncertainties, were inferred for a nighttime CALIPSO overpass on 9 September 2011, with coincident observations with the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 research aircraft, within the framework of the Evaluation of CALIPSO's Aerosol Classification scheme over Eastern Mediterranean (ACEMED) research campaign over Thessaloniki, Greece. The CALIPSO aerosol typing is evaluated, based on data from the Copernicus Atmosphere Monitoring Service (CAMS) reanalysis. Backward trajectories and satellite-based fire counts are used to examine the origin of air masses on that day. Our CCN retrievals are evaluated against particle number concentration retrievals at different height levels, based on the ACEMED airborne measurements and compared against CCN-related retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors aboard Terra and Aqua product over Thessaloniki showing that it is feasible to obtain CCN concentrations from CALIPSO, with an uncertainty of a factor of two to three. © 2020 by the authors."
"57203142421;57189368623;56879845700;50562006500;36462896300;56780325800;24448185400;57192173802;57216691532;56097800400;57209471574;7004864963;7006790175;7005941217;56647730800;55683878900;15724233200;57192168375;57219113417;15925588200;35119188100;57203161526;57190128079;6507532116;57215197618;7102866124;22635042200;57191364055;57194460601;14058796400;56187256200;55730602600;24172248700;15926468600;57192172364;57190209035;6603738264;6506126751;55942083800;35461763400;35774441900;","Influx of African biomass burning aerosol during the Amazonian dry season through layered transatlantic transport of black carbon-rich smoke",2020,"10.5194/acp-20-4757-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084309379&doi=10.5194%2facp-20-4757-2020&partnerID=40&md5=f9f42a80a8d6dfcf5ef25d55c911ed6a","Black carbon (BC) aerosols influence the Earth's atmosphere and climate, but their microphysical properties, spatiotemporal distribution, and long-range transport are not well constrained. This study presents airborne observations of the transatlantic transport of BC-rich African biomass burning (BB) smoke into the Amazon Basin using a Single Particle Soot Photometer (SP2) as well as several complementary techniques. We base our results on observations of aerosols and trace gases off the Brazilian coast onboard the HALO (High Altitude and LOng range) research aircraft during the ACRIDICON-CHUVA campaign in September 2014. During flight AC19 over land and ocean at the northeastern coastline of the Amazon Basin, we observed a BCrich layer at ∼ 3:5 km altitude with a vertical extension of ∼ 0:3 km. Backward trajectories suggest that fires in African grasslands, savannas, and shrublands were the main source of this pollution layer and that the observed BB smoke had undergone more than 10 d of atmospheric transport and aging over the South Atlantic before reaching the Amazon Basin. The aged smoke is characterized by a dominant accumulation mode, centered at about 130 nm, with a particle concentration of Nacc D 850±330 cm-3. The rBC particles account for ∼ 15 % of the submicrometer aerosol mass and ∼ 40 % of the total aerosol number concentration. This corresponds to a mass concentration range from 0.5 to 2 μ g m-3 (1st to 99th percentiles) and a number concentration range from 90 to 530 cm-3. Along with rBC, high cCO (150 ± 30 ppb) and cO3 (56 ± 9 ppb) mixing ratios support the biomass burning origin and pronounced photochemical aging of this layer. Upon reaching the Amazon Basin, it started to broaden and to subside, due to convective mixing and entrainment of the BB aerosol into the boundary layer. Satellite observations show that the transatlantic transport of pollution layers is a frequently occurring process, seasonally peaking in August/September. By analyzing the aircraft observations together with the long-term data from the Amazon Tall Tower Observatory (ATTO), we found that the transatlantic transport of African BB smoke layers has a strong impact on the northern and central Amazonian aerosol population during the BBinfluenced season (July to December). In fact, the early BB season (July to September) in this part of the Amazon appears to be dominated by African smoke, whereas the later BB season (October to December) appears to be dominated by South American fires. This dichotomy is reflected in pronounced changes in aerosol optical properties such as the single scattering albedo (increasing from 0.85 in August to 0.90 in November) and the BC-to-CO enhancement ratio (decreasing from 11 to 6 ng m-3 ppb-1). Our results suggest that, despite the high fraction of BC particles, the African BB aerosol acts as efficient cloud condensation nuclei (CCN), with potentially important implications for aerosol-cloud interactions and the hydrological cycle in the Amazon. © 2020 Author(s)."
"8724962900;56363596200;7005035762;57202024872;35069282600;55927053800;55783064400;22834248200;7006377579;7201787800;","Open cells exhibit weaker entrainment of free-tropospheric biomass burning aerosol into the south-east Atlantic boundary layer",2020,"10.5194/acp-20-4059-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083116153&doi=10.5194%2facp-20-4059-2020&partnerID=40&md5=bb2ec9b120c62f3a1c9a712c5173875e","This work presents synergistic satellite, airborne and surface-based observations of a pocket of open cells (POC) in the remote south-east Atlantic. The observations were obtained over and upwind of Ascension Island during the CLouds and Aerosol Radiative Impacts and Forcing (CLARIFY) and the Layered Smoke Interacting with Clouds (LASIC) field experiments. A novel aspect of this case study is that an extensive free-tropospheric biomass burning aerosol plume that had been transported from the African continent was observed to be in contact with the boundary layer inversion over the POC and the surrounding closed cellular cloud regime. The in situ measurements show marked contrasts in the boundary layer thermodynamic structure, cloud properties, precipitation and aerosol conditions between the open cells and surrounding overcast cloud field./ The data demonstrate that the overlying biomass burning aerosol was mixing down into the boundary layer in the stratocumulus cloud downwind of the POC, with elevated carbon monoxide, black carbon mass loadings and accumulation-mode aerosol concentrations measured beneath the trade-wind inversion. The stratocumulus cloud in this region was moderately polluted and exhibited very little precipitation falling below cloud base. A rapid transition to actively precipitating cumulus clouds and detrained stratiform remnants in the form of thin quiescent veil clouds was observed across the boundary into and deep within the POC. The subcloud layer in the POC was much cleaner than that in the stratocumulus region. The clouds in the POC formed within an ultra-clean layer (accumulation-mode aerosol concentrations of approximately a few span classCombining double low line""inline-formula"">cm-3/span>) in the upper region of the boundary layer, which was likely to have been formed via efficient collision-coalescence and sedimentation processes. Enhanced Aitken-mode aerosol concentrations were also observed intermittently in this ultra-clean layer, suggesting that new particle formation was taking place. Across the boundary layer inversion and immediately above the ultra-clean layer, accumulation-mode aerosol concentrations were span classCombining double low line""inline-formula"">ĝ&circ;1/4/span>&thinsp;1000&thinsp;span classCombining double low line""inline-formula"">cm-3/span>. Importantly, the air mass in the POC showed no evidence of elevated carbon monoxide over and above typical background conditions at this location and time of year. As carbon monoxide is a good tracer for biomass burning aerosol that is not readily removed by cloud processing and precipitation, it demonstrates that the open cellular convection in the POC is not able to entrain large quantities of the free-tropospheric aerosol that was sitting directly on top of the boundary layer inversion. This suggests that the structure of the mesoscale cellular convection may play an important role in regulating the transport of aerosol from the free troposphere down into the marine boundary layer./ span idCombining double low line""page4060""/>We then develop a climatology of open cellular cloud conditions in the south-east Atlantic from 19 years of September Moderate Resolution Imaging Spectroradiometer (MODIS) Terra imagery. This shows that the maxima in open cell frequency (span classCombining double low line""inline-formula"">&gt;/span>&thinsp;0.25) occurs far offshore and in a region where subsiding biomass burning aerosol plumes may often come into contact with the underlying boundary layer cloud. If the results from the observational case study applied more broadly, then the apparent low susceptibility of open cells to free-tropospheric intrusions of additional cloud condensation nuclei could have some important consequences for aerosol-cloud interactions in the region./. © 2020 Copernicus GmbH. All rights reserved."
"57215531068;16527798200;57215529063;55408314400;7202429440;7201432984;42260971800;7202252296;6603689369;7401651197;","Ice Nucleation by Marine Aerosols Over the North Atlantic Ocean in Late Spring",2020,"10.1029/2019JD030913","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081073853&doi=10.1029%2f2019JD030913&partnerID=40&md5=530dbae982cda36f8dc5b54b25505719","Here we report the ice nucleating temperatures of marine aerosols sampled in the subarctic Atlantic Ocean during a phytoplankton bloom. Ice nucleation measurements were conducted on primary aerosol samples and phytoplankton isolated from seawater samples. Primary marine aerosol samples produced by a specialized aerosol generator (the Sea Sweep) catalyzed droplet freezing at temperatures between −33.4 °C and − 24.5 °C, with a mean freezing temperature of −28.5 °C, which was significantly warmer than the homogeneous freezing temperature of pure water in the atmosphere (−36 °C). Following a storm-induced deep mixing event, ice nucleation activity was enhanced by two metrics: (1) the fraction of aerosols acting as ice nucleating particles (INPs) and (2) the nucleating temperatures, which were the warmest observed throughout the project. Seawater samples were collected from the ocean's surface and phytoplankton groups, including Synechococcus, picoeukaryotes, and nanoeukaryotes, were isolated into sodium chloride sheath fluid solution using a cell-sorting flow cytometer. Marine aerosol containing Synechococcus, picoeukaryotes, and nanoeukaryotes serves as INP at temperatures significantly warmer than the homogeneous freezing temperature of pure water in the atmosphere. Samples containing whole organisms in 30 g L−1 NaCl had freezing temperatures between −33.8 and − 31.1 °C. Dilution of samples to representative atmospheric aerosol salt concentrations (as low as 3.75 g L−1 NaCl) raised freezing temperatures to as high as −22.1 °C. It follows that marine aerosols containing phytoplankton may have widespread influence on marine ice nucleation events by facilitating ice nucleation. ©2020. American Geophysical Union. All Rights Reserved."
"57211266497;7402866430;","Consistent signal of aerosol indirect and semi-direct effect on water clouds in the oceanic regions adjacent to the Indian subcontinent",2020,"10.1016/j.atmosres.2019.104677","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85073255689&doi=10.1016%2fj.atmosres.2019.104677&partnerID=40&md5=46c73fa0b936481efa15f8f0b600d421","Quantifying aerosol-cloud interaction is one of the most challenging tasks in climate science. Previous studies in the oceanic regions adjacent to the Indian subcontinent providing evidence of aerosol impacts on cloud properties were mostly confined in the winter season. Here we analyze 15 years (March 2000–February 2015) of MODIS aerosol and cloud products and 10 years (October 2004–February 2015) of OMI absorbing aerosol index (AI) over the Arabian Sea (AS), Bay of Bengal (BoB) and South Indian Ocean (SIO) to examine the sensitivity of marine water cloud characteristics to changing aerosol loading. Amidst a monotonous increase in Reff (cloud effective radius) with an increase in LWP (liquid water path) in clean and polluted conditions (an indicator of the meteorological influence), a smaller Reff at higher AOD (aerosol optical depth) bins demonstrates that aerosol signal is detectable and consistent in LWP range of 150–350 g m−2. Furthermore, a faster rate of Reff growth with increasing LWP in clean condition and the pattern of change in cloud fraction (fc) with an increase in AOD that cannot be explained by meteorology alone also provide evidence of the consistency of aerosol indirect effect. Evidence of aerosol semi-direct (decrease of LWP with an increase in AI) is also conspicuous in the AS and BoB. Our results suggest improved representations of aerosol and cloud processes in the models are required to reduce uncertainty in regional climate forcing. © 2019 Elsevier B.V."
"57200201534;57200055610;55802246600;57201951903;55734757600;6701726768;","Using CESM-RESFire to understand climate-fire-ecosystem interactions and the implications for decadal climate variability",2020,"10.5194/acp-20-995-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078758149&doi=10.5194%2facp-20-995-2020&partnerID=40&md5=626a459740abc039c10d914fae992b13","<p>Large wildfires exert strong disturbance on regional and global climate systems and ecosystems by perturbing radiative forcing as well as the carbon and water balance between the atmosphere and land surface, while short- and long-term variations in fire weather, terrestrial ecosystems, and human activity modulate fire intensity and reshape fire regimes. The complex climate-fire-ecosystem interactions were not fully integrated in previous climate model studies, and the resulting effects on the projections of future climate change are not well understood. Here we use the fully interactive REgion-Specific ecosystem feedback Fire model (RESFire) that was developed in the Community Earth System Model (CESM) to investigate these interactions and their impacts on climate systems and fire activity. We designed two sets of decadal simulations using CESM-RESFire for present-day (2001-2010) and future (2051-2060) scenarios, respectively, and conducted a series of sensitivity experiments to assess the effects of individual feedback pathways among climate, fire, and ecosystems. Our implementation of RESFire, which includes online land-atmosphere coupling of fire emissions and fire-induced land cover change (LCC), reproduces the observed aerosol optical depth (AOD) from space-based Moderate Resolution Imaging Spectroradiometer (MODIS) satellite products and ground-based AErosol RObotic NETwork (AERONET) data; it agrees well with carbon budget benchmarks from previous studies. We estimate the global averaged net radiative effect of both fire aerosols and fire-induced LCC at <span classCombining double low line""inline-formula""><math xmlnsCombining double low line""http://www.w3.org/1998/Math/MathML"" idCombining double low line""M1"" displayCombining double low line""inline"" overflowCombining double low line""scroll"" dspmathCombining double low line""mathml""><mrow><mo>-</mo><mn mathvariantCombining double low line""normal"">0.59</mn><mo>±</mo><mn mathvariantCombining double low line""normal"">0.52</mn></mrow></math><span><svg:svg xmlns:svgCombining double low line""http://www.w3.org/2000/svg"" widthCombining double low line""64pt"" heightCombining double low line""10pt"" classCombining double low line""svg-formula"" dspmathCombining double low line""mathimg"" md5hashCombining double low line""81225efbee53d3fa37673b300b31505a""><svg:image xmlns:xlinkCombining double low line""http://www.w3.org/1999/xlink"" xlink:hrefCombining double low line""acp-20-995-2020-ie00001.svg"" widthCombining double low line""64pt"" heightCombining double low line""10pt"" srcCombining double low line""acp-20-995-2020-ie00001.png""/></svg:svg></span></span>&thinsp;W&thinsp;m<span classCombining double low line""inline-formula"">-2</span>, which is dominated by fire aerosol-cloud interactions (<span classCombining double low line""inline-formula""><math xmlnsCombining double low line""http://www.w3.org/1998/Math/MathML"" idCombining double low line""M3"" displayCombining double low line""inline"" overflowCombining double low line""scroll"" dspmathCombining double low line""mathml""><mrow><mo>-</mo><mn mathvariantCombining double low line""normal"">0.82</mn><mo>±</mo><mn mathvariantCombining double low line""normal"">0.19</mn></mrow></math><span><svg:svg xmlns:svgCombining double low line""http://www.w3.org/2000/svg"" widthCombining double low line""64pt"" heightCombining double low line""10pt"" classCombining double low line""svg-formula"" dspmathCombining double low line""mathimg"" md5hashCombining double low line""e6f571c6171863e014b049d815ae960f""><svg:image xmlns:xlinkCombining double low line""http://www.w3.org/1999/xlink"" xlink:hrefCombining double low line""acp-20-995-2020-ie00002.svg"" widthCombining double low line""64pt"" heightCombining double low line""10pt"" srcCombining double low line""acp-20-995-2020-ie00002.png""/></svg:svg></span></span>&thinsp;W&thinsp;m<span classCombining double low line""inline-formula"">-2</span>), in the present-day scenario under climatological conditions of the 2000s. The fire-related net cooling effect increases by <span classCombining double low line""inline-formula"">ĝ1/4170</span>&thinsp;% to <span classCombining double low line""inline-formula""><math xmlnsCombining double low line""http://www.w3.org/1998/Math/MathML"" idCombining double low line""M6"" displayCombining double low line""inline"" overflowCombining double low line""scroll"" dspmathCombining double low line""mathml""><mrow><mo>-</mo><mn mathvariantCombining double low line""normal"">1.60</mn><mo>±</mo><mn mathvariantCombining double low line""normal"">0.27</mn></mrow></math><span><svg:svg xmlns:svgCombining double low line""http://www.w3.org/2000/svg"" widthCombining double low line""64pt"" heightCombining double low line""10pt"" classCombining double low line""svg-formula"" dspmathCombining double low line""mathimg"" md5hashCombining double low line""b35b7b37838dbc67785d3c8c2a132cdb""><svg:image xmlns:xlinkCombining double low line""http://www.w3.org/1999/xlink"" xlink:hrefCombining double low line""acp-20-995-2020-ie00003.svg"" widthCombining double low line""64pt"" heightCombining double low line""10pt"" srcCombining double low line""acp-20-995-2020-ie00003.png""/></svg:svg></span></span>&thinsp;W&thinsp;m<span classCombining double low line""inline-formula"">-2</span> in the 2050s under the conditions of the Representative Concentration Pathway 4.5 (RCP4.5) scenario. Such considerably enhanced radiative effect is attributed to the largely increased global burned area (<span classCombining double low line""inline-formula"">+19</span>&thinsp;%) and fire carbon emissions (<span classCombining double low line""inline-formula"">+100</span>&thinsp;%) from the 2000s to the 2050s driven by climate change. The net ecosystem exchange (NEE) of carbon between the land and atmosphere components in the simulations increases by 33&thinsp;% accordingly, implying that biomass burning is an increasing carbon source at short-term timescales in the future. High-latitude regions with prevalent peatlands would be more vulnerable to increased fire threats due to climate change, and the increase in fire aerosols could counter the projected decrease in anthropogenic aerosols due to air pollution control policies in many regions. We also evaluate two distinct feedback mechanisms that are associated with fire aerosols and fire-induced LCC, respectively. On a global scale, the first mechanism imposes positive feedbacks to fire activity through enhanced droughts with suppressed precipitation by fire aerosol-cloud interactions, while the second one manifests as negative feedbacks due to reduced fuel loads by fire consumption and post-fire tree mortality and recovery processes. These two<span idCombining double low line""page996""/> feedback pathways with opposite effects compete at regional to global scales and increase the complexity of climate-fire-ecosystem interactions and their climatic impacts.</p>. © 2020 Copernicus GmbH. All rights reserved."
"6603081424;56567382200;22635081500;","A Global Survey of Apparent Aerosol-Cloud Interaction Signals",2020,"10.1029/2019JD031287","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078314452&doi=10.1029%2f2019JD031287&partnerID=40&md5=a14dced806d7ce9a44da943cb68fd80d","We update and expand analysis of the apparent responses to aerosol variations of the planet's cloud regimes seen by the Moderate Resolution Imaging Spectroradiometer (MODIS). We distinguish between morning aerosol loadings and afternoon clouds and consider local scales explicitly. Aerosol loading is represented by gridded aerosol optical depth (AOD) from either MODIS or a reanalysis data set, while cloud information comes exclusively from MODIS. The afternoon cloud affected quantities (CAQs) examined in conjunction with morning AOD include precipitation and cloud radiative effect, in addition to cloud properties. One analysis thrust focuses on calculating global means distinguished by morning cloud regime, of afternoon CAQs, for distinct percentiles of grid cell seasonal morning AOD distributions. When the dependence of these global means on AOD is examined, we find persistent increases in cloud radiative fluxes with AOD as predicted by classic aerosol-cloud interaction paradigms, and also deviations from expected cloud responses, especially for precipitation. The other analysis thrust involves calculations at 1° scales of logarithmic CAQ sensitivities to AOD perturbations, approximated by linear regression slopes for distinct morning cloud regime groups. While the calculations are fundamentally local, we concentrate on the prevailing sensitivity signs in statistics of the slopes at global scales. Results from this second analysis approach indicate CAQ directions of change with AOD that are largely consistent with the first approach. When using a rather simple methodology where meteorological variables are treated as if they were CAQs, no conclusive results on the potential influence of meteorology on our findings are inferred. Published 2019. This article is a US Government work and is in the public domain in the USA."
"57192373652;55820893200;56965949500;7003541446;7201520305;7402538754;","Droplet size distributions in turbulent clouds: experimental evaluation of theoretical distributions",2020,"10.1002/qj.3692","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074700496&doi=10.1002%2fqj.3692&partnerID=40&md5=bb0cfa1e289f63b2e688370e6caf633d","Precipitation efficiency and optical properties of clouds, both central to determining Earth's weather and climate, depend on the size distribution of cloud particles. In this work theoretical expressions for cloud droplet size distribution shape are evaluated using measurements from controlled experiments in a convective-cloud chamber. The experiments are a unique opportunity to constrain theory because they are in steady-state and because the initial and boundary conditions are well characterized compared to typical atmospheric measurements. Three theoretical distributions obtained from a Langevin drift-diffusion approach to cloud formation via stochastic condensation are tested: (a) stochastic condensation with a constant removal time-scale; (b) stochastic condensation with a size-dependent removal time-scale; (c) droplet growth in a fixed supersaturation condition and with size-dependent removal. In addition, a similar Weibull distribution that can be obtained from the drift-diffusion approach, as well as from mechanism-independent probabilistic arguments (e.g., maximum entropy), is tested as a fourth hypothesis. Statistical techniques such as the χ2 test, sum of squared errors of prediction, and residual analysis are employed to judge relative success or failure of the theoretical distributions to describe the experimental data. An extensive set of cloud droplet size distributions are measured under different aerosol injection rates. Five different aerosol injection rates are run both for size-selected aerosol particles, and six aerosol injection rates are run for broad-distribution, polydisperse aerosol particles. In relative comparison, the most favourable comparison to the measurements is the expression for stochastic condensation with size-dependent droplet removal rate. However, even this optimal distribution breaks down for broad aerosol size distributions, primarily due to deviations from the measured large-droplet tail. A possible explanation for the deviation is the Ostwald ripening effect coupled with deactivation/activation in polluted cloud conditions. © 2019 Royal Meteorological Society"
"57205168888;6602111828;7202069518;7403296946;","Regional Biases in MODIS Marine Liquid Water Cloud Drop Effective Radius Deduced Through Fusion With MISR",2019,"10.1029/2019JD031063","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076365407&doi=10.1029%2f2019JD031063&partnerID=40&md5=b1e685525015035518b0423526c906ac","Satellite measurements from Terra's Moderate Resolution Imaging Spectroradiometer (MODIS) represent our longest, single-platform, global record of the effective radius (Re) of the cloud drop size distribution. Quantifying its error characteristics has been challenging because systematic errors in retrieved Re covary with the structural characteristics of the cloud and the Sun-view geometry. Recently, it has been shown that the bias in MODIS Re can be estimated by fusing MODIS data with data from Terra's Multi-angle Imaging SpectroRadiometer (MISR). Here, we relate the bias to the observed underlying conditions to derive regional-scale, bias-corrected, monthly-mean Re1.6, Re2.1, and Re3.7 values retrieved from the 1.6, 2.1, and 3.7 μm MODIS spectral channels. Our results reveal that monthly-mean bias in Re2.1 exhibits large regional dependency, ranging from at least ~1 to 10 μm (15 to 60%) varying with scene heterogeneity, optical depth, and solar zenith angle. Regional bias-corrected monthly-mean Re2.1 ranges from 4 to 17 μm, compared to 10 to 25 μm for uncorrected Re2.1, with estimated uncertainties of 0.1 to 1.8 μm. The bias-corrected monthly-mean Re3.7 and Re2.1 show difference of approximately +0.6 μm in the coastal marine stratocumulus regions and down to approximately −2 μm in the cumuliform cloud regions, compared to uncorrected values of about −1 to −6 μm, respectively. Bias-corrected Re values compare favorably to other independent data sources, including field observations, global model simulations, and satellite retrievals that do not use retrieval techniques similar to MODIS. This work changes the interpretation of global Re distributions from MODIS Re products and may further impact studies, which use the original MODIS Re products to study, for example, aerosol-cloud interactions and cloud microphysical parameterization. ©2019. The Authors."
"56798441100;36606783400;7004351010;","Vertical distribution of aerosols and clouds over north-eastern South Asia: Aerosol-cloud interactions",2019,"10.1016/j.atmosenv.2019.116882","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070516828&doi=10.1016%2fj.atmosenv.2019.116882&partnerID=40&md5=a4fb1aa1ede3630f0ef6d33c0aef3644","Eleven years of CALIOP and MODIS data are used to investigate the vertical distribution of aerosols and clouds and their possible interactions over the north-eastern South Asia (22–30°N, 88–98°E). Distinct seasonality in the vertical aerosol structure with the presence of elevated aerosol layers (EALs) is observed. The EALs vary from ~1.4 to 4.8 km in post monsoon to ~4.8–7.4 km in monsoon. Strong convective activities mainly in pre-monsoon and monsoon and upper air transportation of aerosols contribute to the formation of EALs. The contribution of polluted dust, polluted continental/smoke and elevated smoke are found to be predominant in the vertical column during pre-monsoon and monsoon. Contrarily, clean continental, clean marine and dusty marine are dominant during winter and post monsoon. Small spherical particles are abundant during winter while in monsoon hygroscopically grown spherical particles predominate. Seasonally, the cloud occurrence frequency (COF) as a function of altitude is maximum during monsoon. An increase in cloud top height (CTH) is observed within this region corresponding to an increase in number of cloud layers, thus revealing invigoration effect. The occurrence of cirrus and deep convective clouds is maximum in monsoon and minimum in the dry season. Significant inhibition/invigoration is observed for mixed-phase/liquid clouds. © 2019"
"55574869900;57190534239;56898396100;","Four-year ground-based observations of the aerosol effects on cloud base height in Wuhan, China",2019,"10.1016/j.apr.2019.05.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068883703&doi=10.1016%2fj.apr.2019.05.001&partnerID=40&md5=b80bbf84309aae15c99a74e171791153","Aerosols can modify cloud properties by affecting the concentration and size of cloud droplets and the strength of cloud convection. Understanding the effects of aerosol on cloud remains challenging because of the different effects of aerosol on various conditions and regions. In this study, we survey the effect of aerosol on cloud base height (CBH) through four-year ground-based observations in Wuhan, China. A robust positive correlation between aerosol loading and CBH can be found via annual and correlation analyses, which suggest the systematic invigoration of clouds through aerosol loading. The statistical analysis of collocated measurements of PM10 concentrations, meteorological factors, and CBHs suggest that temperature, relative humidity and aerosol particles collectively influence CBH variations. The present finding also demonstrate that the influence of aerosol particles on promoting CBH is prominent under the conditions of relatively high humidity and low temperature. This study provides a new perspective for understanding the response of aerosol-cloud interactions in an urban area, which will play important roles in regional climate change and human life. © 2019"
"56044817200;6701853567;36179218000;26643043700;36767412900;7006591842;","Contributions of aerosol-cloud interactions to mid-Piacenzian seasonally sea ice-free Arctic Ocean",2019,"10.1029/2019GL083960","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85071318750&doi=10.1029%2f2019GL083960&partnerID=40&md5=a759d464372f64227a954a05f46dcad2","Forcings and feedbacks controlling the seasonally sea ice-free Arctic Ocean during the mid-Piacenzian Warm period (3.264–3.025 Ma, MPWP), a period when CO2 level, geography, and topography were similar to present day, remain unclear given that many complex Earth System Models with comparatively higher skills at simulating twentieth century Arctic sea ice tend to produce perennial Arctic sea ice for this period. We demonstrate that explicitly simulating aerosol-cloud interactions and the exclusion of industrial pollutants from model forcing conditions is key to simulating seasonally sea ice-free Arctic Ocean of MPWP. The absence of industrial pollutants leads to fewer and larger cloud droplets over the high-latitude Northern Europe and North Pacific, which allows greater absorption of solar radiation at the surface during the early summer. This enhanced absorption triggers the seasonally runaway sea ice surface albedo feedback that gives rise to September sea ice-free Arctic Ocean and strongly amplified northern high-latitude surface warmth. ©2019. American Geophysical Union. All Rights Reserved."
"57200339651;57192373652;57194152771;7003541446;7402538754;","Aerosol-Mediated Glaciation of Mixed-Phase Clouds: Steady-State Laboratory Measurements",2019,"10.1029/2019GL083503","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85072136501&doi=10.1029%2f2019GL083503&partnerID=40&md5=36c65933014b78798442ec2daa2c3e8b","What concentration of ice-nucleating particles is required to completely glaciate a typical atmospheric supercooled liquid cloud? This seemingly esoteric question has far reaching implications, as the ratio of liquid to ice in these clouds governs, for example, their influence on Earth's radiation budget and their precipitation efficiency. Microphysical properties of steady-state mixed-phase clouds formed in a laboratory convection chamber are observed using digital holography. It is observed that the ratio of ice to total water content of steady-state mixed-phase clouds is determined by the concentration of ice-nucleating aerosol particles. Existing theory is adapted to show such clouds result from a balance between the thermodynamic forcing (i.e., the source of excess water vapor that is condensing to liquid and ice) and the number and size of particles that become ice (i.e., the ice integral radius). The measurements quantitatively support the Korolev-Mazin conditions for existence of mixed-phase clouds. ©2019. American Geophysical Union. All Rights Reserved."
"57202132498;8543279200;36701716800;","A satellite observation-based analysis of aerosol-cloud-precipitation interaction during the february 2016 unseasonal heatwave episode over the Indian region",2019,"10.4209/aaqr.2018.04.0144","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85069707247&doi=10.4209%2faaqr.2018.04.0144&partnerID=40&md5=68291ae617ec6da3ee0c1a15b258a1da","Aerosol-cloud-precipitation (ACP) interaction during the February 2016 unseasonal heatwave episode over India is analyzed and presented. Moderate Resolution Imaging Spectroradiometer (MODIS) datasets from the Aqua satellite are used to examine the relationship between aerosol and cloud parameters, viz., the aerosol optical depth (AOD), Ångström exponent (AE), cloud fraction, ice and liquid cloud effective radius, cloud optical depth, cloud top temperature, and ice and liquid cloud water path. Furthermore, the Tropical Rainfall Measuring Mission (TRMM) dataset is used to analyze the rainfall during the dissipating phase of the heatwave episode. The prevailing meteorological conditions during the pre-mature, mature, and dissipating phases of the episode are identified by analyzing the near-surface temperature, relative humidity, and vertically integrated moisture flux convergence via 0.25°-resolution ERA-Interim datasets. Back-trajectory analysis is conducted to determine the origin of air masses and transported aerosols. Hot and dry westerly winds dominate during the pre-mature and mature phases, and consequently, significant aerosol transport is observed. The AOD reaches a maximum of 1.6 during the three phases, with the AE being in the range of 0.8–1.7, indicating the presence of both fine-and coarse-mode aerosols. Due to microphysical processes, clouds respond fairly strongly to aerosols in the presence of favorable dynamic and thermodynamic atmospheric conditions. The suppression of precipitation during the pre-mature and mature phases is primarily attributable to weak aerosol-cloud interaction. A major rainfall event in the region comprising northern Odisha, eastern Jharkhand, and most parts of West Bengal, which is situated north of the minimum vertically integrated moisture flux zone, occurs during the dissipating phase. This rainfall event results from the unseasonal transport of moisture from the neighboring Bay of Bengal, the presence of appreciable aerosol loading, and the consequent ACP interaction. Copyright © Taiwan Association for Aerosol Research."
"57208534427;8058662600;7006728825;24764483400;7404021119;","How important are aerosol–fog interactions for the successful modelling of nocturnal radiation fog?",2019,"10.1002/wea.3503","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065032492&doi=10.1002%2fwea.3503&partnerID=40&md5=f6b027eb4227f26cad4ca6e6f5f27ec5","Forecasting and modelling fog formation, development, and dissipation is a significant challenge. Fog dynamics involve subtle interactions between small-scale turbulence, radiative transfer and microphysics. Recent studies have highlighted the role of aerosol and related cloud microphysical properties in the evolution of fog. In this article, we investigate this role using very high-resolution large eddy simulations coupled with a newly developed multi-moment cloud microphysics scheme (CASIM), which has been designed to model aerosol–cloud interactions. The simulation results demonstrate the sensitivity of the fog structure to the properties of the aerosol population (e.g. number concentration). This study also demonstrates the importance of the treatment of aerosol activation in fog formation and discusses future work required to improve the representation of aerosol–fog interactions for simulations of fog. © 2019 The Authors. Weather published by John Wiley & Sons Ltd on behalf of Royal Meteorological Society"
"57189712592;55607020000;56611366900;","Exploring aerosol-cloud interaction using VOCALS-REx aircraft measurements",2019,"10.5194/acp-19-7955-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067427009&doi=10.5194%2facp-19-7955-2019&partnerID=40&md5=9c525ba987f1c3a4f9d87482eb5620af","In situ aircraft measurements obtained during the VAMOS (Variability of the American Monsoons) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) field campaign are analyzed to study the aerosol-cloud interactions in the stratocumulus clouds over the southeastern Pacific Ocean (SEP), with a focus on three understudied topics (separation of aerosol effects from dynamic effects, dispersion effects, and turbulent entrainmentmixing processes). Our analysis suggests that an increase in aerosol concentration tends to simultaneously increase both cloud droplet number concentration (Nd) and relative dispersion (ω), while an increase in vertical velocity (w) often increases Nd but decreases ω. After constraining the differences of cloud dynamics, the positive correlation between ω and Nd becomes stronger, implying that perturbations of w could weaken the aerosol influence on ω and hence result in an underestimation of dispersion effect. A comparative analysis of the difference of cloud microphysical properties between the entrainment and non-entrainment zones suggests that the entrainment-mixing mechanism is predominantly extremely inhomogeneous in the stratocumulus that capped by a sharp inversion, whereby the variation in liquid water content (25 %) is similar to that of Nd (29 %) and the droplet size remains approximately constant. In entrainment zone, drier air entrained from the top induces fewer cloud droplets with respect to total in-cloud particles (0:56 ± 0:22) than the case in the non-entrainment zone (0:73 ± 0:13) by promoting cloud droplet evaporation. This study is helpful in reducing uncertainties in dispersion effects and entrainment mixing for stratocumulus, and the results of this study may benefit cloud parameterizations in global climate models to more accurately assess aerosol indirect effects. © 2019 The Author(s)."
"54393349200;14019399400;55626648300;24448185400;57189368623;35774441900;22979686100;26425029500;7201504886;","Remote sensing of sea salt aerosol below trade wind clouds",2019,"10.1175/JAS-D-18-0139.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85066847892&doi=10.1175%2fJAS-D-18-0139.1&partnerID=40&md5=8c46b70a81a28c39d9cd0be9a1289197","Sea salt aerosol in the boundary layer below shallow cumulus clouds is remotely observed with a Ka-band cloud radar at the Barbados Cloud Observatory and is detected in 76% of the measurements over 1 year. Carried by convection, sea salt particles with a diameter larger than 500 nm show an upward motion of 0.2ms-1 below shallow cumulus clouds for a 2-day case study. Caused by an increasing relative humidity with increasing altitude, the sea salt particles become larger as they move closer to the cloud base. By using combined measurements of a Ka-band cloud radar and a Raman lidar, the retrieved equivolumetric diameter of the hygroscopically grown sea salt particles is found to be between 6 and 11 μm with a total number concentration of 20 cm-3 near cloud base. Assuming a fixed shape parameter, a size distribution of sea salt particles under high-relative-humidity conditions below cloud base is estimated and agrees with measurements taken by a dry-deposition sampler and online aerosol observations. The methods outlined in this paper can be used in future studies to get a better understanding of the vertical and temporal sea salt distribution in the boundary layer and sea salt aerosol-cloud interaction processes. © 2019 American Meteorological Society."
"57207823252;7005304841;25631411400;9235235300;7003740015;","Aerosol Indirect Effects in Marine Stratocumulus: The Importance of Explicitly Predicting Cloud Droplet Activation",2019,"10.1029/2018GL081746","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062960186&doi=10.1029%2f2018GL081746&partnerID=40&md5=6bb94f6cb7e343f469f3f557c812e6e7","Climate models generally simulate a unidirectional, positive liquid water path (LWP) response to increasing aerosol number concentration. However, satellite observations and large-eddy simulations show that the LWP may either increase or decrease with increasing aerosol concentration, influencing the overall magnitude of the aerosol indirect effect (AIE). We use large-eddy simulation to investigate the LWP response of a marine stratocumulus cloud and its dependence on different parameterizations for obtaining cloud droplet number concentration (CDNC). The simulations confirm that the LWP response is not always positive—regardless of CDNC treatment. However, the AIE simulated with the model version with prescribed CDNC is almost 3 times larger compared to the version with prognostic CDNC. The reason is that the CDNC in the prognostic scheme varies in time due to supersaturation fluctuations, collection, and other microphysical processes. A substantial spread in simulated AIE may thus arise simply due to the CDNC treatment. © 2019. American Geophysical Union. All Rights Reserved."
"56539196700;56265041500;56502199700;9249255400;","Strengthened Indian Summer Monsoon Precipitation Susceptibility Linked to Dust-Induced Ice Cloud Modification",2019,"10.1029/2018GL081634","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068753253&doi=10.1029%2f2018GL081634&partnerID=40&md5=888efe0ecb9ad88f0ab98a3f687cd1bf","A growing body of research has underscored the radiative impact of mineral dust in influencing Indian summer monsoon rainfall variability. However, the various aerosol-cloud-precipitation interaction mechanisms remain poorly understood. Here we analyze multisatellite observations to examine dust-induced modification in ice clouds and precipitation susceptibility. We show contrasting dust-induced changes in ice cloud regimes wherein despite a 25% reduction in ice particle radius in thin ice clouds, we find ~40% increase in ice particle radius and ice water path in thick ice clouds resulting in the cloud deepening and subsequently strengthened precipitation susceptibility, under strong updraft regimes. The observed dust-ice cloud-precipitation interactions are supported by a strong correlation between the interannual monsoon rainfall variability and dust frequency. This microphysical-dynamical coupling appears to provide negative feedback to aerosol-cloud interactions, which acts to buffer enhanced aerosol wet scavenging. Our results underscore the importance of incorporating meteorological regime-dependent dust-ice cloud-precipitation interactions in climate simulations. ©2019. American Geophysical Union. All Rights Reserved."
"55542833500;55717074000;","Sensitivity Study of Anthropogenic Aerosol Indirect Forcing through Cirrus Clouds with CAM5 Using Three Ice Nucleation Parameterizations",2018,"10.1007/s13351-018-8011-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055346276&doi=10.1007%2fs13351-018-8011-z&partnerID=40&md5=c091453ae065712efa81dcd745668f5d","Quantifying the radiative forcing due to aerosol–cloud interactions especially through cirrus clouds remains challenging because of our limited understanding of aerosol and cloud processes. In this study, we investigate the anthropogenic aerosol indirect forcing (AIF) through cirrus clouds using the Community Atmosphere Model version 5 (CAM5) with a state-of-the-art treatment of ice nucleation. We adopt a new approach to isolate anthropogenic AIF through cirrus clouds in which ice nucleation parameterization is driven by prescribed pre-industrial (PI) and presentday (PD) aerosols, respectively. Sensitivities of anthropogenic ice AIF (i.e., anthropogenic AIF through cirrus clouds) to different ice nucleation parameterizations, homogeneous freezing occurrence, and uncertainties in the cloud microphysics scheme are investigated. Results of sensitivity experiments show that the change (PD minus PI) in global annual mean longwave cloud forcing (i.e., longwave anthropogenic ice AIF) ranges from 0.14 to 0.35 W m–2, the change in global annual mean shortwave cloud forcing (i.e., shortwave anthropogenic ice AIF) from–0.47 to–0.20 W m–2, and the change in net cloud forcing from–0.12 to 0.05 W m–2. Our results suggest that different ice nucleation parameterizations are an important factor for the large uncertainty of anthropogenic ice AIF. Furthermore, improved understanding of the spatial and temporal occurrence characteristics of homogeneous freezing events and the mean states of cirrus cloud properties are also important for constraining anthropogenic ice AIF. © 2018, The Chinese Meteorological Society and Springer-Verlag GmbH Germany, part of Springer Nature."
"8882641700;7004479957;7402781278;23013520400;","Locally Enhanced Aerosols Over a Shipping Lane Produce Convective Invigoration but Weak Overall Indirect Effects in Cloud-Resolving Simulations",2018,"10.1029/2018GL078682","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053454765&doi=10.1029%2f2018GL078682&partnerID=40&md5=63a7a2eec0558fcd3d6952b2c171aa05","The effect of aerosol emissions from an active shipping lane in the Indian Ocean is simulated using an idealized framework in a cloud-resolving model. Increased aerosol concentrations over the modeled shipping lane lead to increased cloud droplet number, cloud liquid mass, ice hydrometeor mass, and simulated radar reflectivity. The invigoration of deep convection induces mesoscale uplift and increased precipitation over the shipping lane. A predicted increase in the prevalence of both strong updrafts and radar echoes aloft is suggestive of enhanced lightning activity over the shipping lane, as observed in a recent study. Cloud radiative effects, both shortwave and longwave, are intensified over the shipping lane, but the change in the net radiative flux at top of atmosphere is not significantly different from zero. ©2018. American Geophysical Union. All Rights Reserved."
"56009184300;55258950300;","Optical levitation measurement on hygroscopic behaviour and SVOC vapour pressure of single organic/inorganic aqueous aerosol",2018,"10.1016/j.atmosenv.2018.06.040","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049336775&doi=10.1016%2fj.atmosenv.2018.06.040&partnerID=40&md5=7996840e00e04e5ad755fe365747f68a","Quantifying the gas/particle partitioning of organic compounds is of great significance to the understanding of atmospheric aerosol indirect effect. Accurate determination of the hygroscopicities and vapour pressures of semi-volatile organic compounds (SVOC) is of crucial importance in studying their partitioning behaviour into atmospheric aerosol, as the influences on SVOCs evaporation from participation of inorganic species remains unclear. In this study we first present thermodynamic quantitative simulation and tweezed single particle measurement of hygroscopicity and volatility of single aerosol droplets. With thermodynamics simulation of the hygroscopicity, SVOC time dependent evaporation and potential chloride depletion reaction in a single trapped droplet, we illustrate influences from different process towards the trapped droplet. In optical tweezers measurement, the trapped droplet in the aerosol optical tweezers acts as a microcavity, which stimulates the cavity enhanced Raman spectroscopy (CERS) signal. Size and composition of the particle are calculated from Mie fit to the positions of the “whispering gallery modes” in the CERS fingerprint. Hygroscopic behaviours and SVOC saturated vapour pressure can then be extracted from the correlation between the changing droplet radius and solute concentration (derived from experimentally determined real part of refractive index (RI)) with good accuracy and reliability. © 2018 Elsevier Ltd"
"57200130699;","Aerosol–cloud interactions",2018,"10.1038/s41558-018-0195-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075553339&doi=10.1038%2fs41558-018-0195-9&partnerID=40&md5=c2c682ae70352ba3a400f7f13b1f894c",[No abstract available]
"22982270700;57190227631;56228672600;19638935200;56611366900;","Role of microphysical parameterizations with droplet relative dispersion in IAP AGCM 4.1",2018,"10.1007/s00376-017-7083-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040328818&doi=10.1007%2fs00376-017-7083-5&partnerID=40&md5=959cfbd0bc5b860dca8e052848dbcd67","Previous studies have shown that accurate descriptions of the cloud droplet effective radius (Re) and the autoconversion process of cloud droplets to raindrops (Ar) can effectively improve simulated clouds and surface precipitation, and reduce the uncertainty of aerosol indirect effects in GCMs. In this paper, we implement cloud microphysical schemes including two-moment Ar and Re considering relative dispersion of the cloud droplet size distribution into version 4.1 of the Institute of Atmospheric Physics’s atmospheric GCM (IAP AGCM 4.1), which is the atmospheric component of the Chinese Academy of Sciences’ Earth System Model. Analysis of the effects of different schemes shows that the newly implemented schemes can improve both the simulated shortwave and longwave cloud radiative forcings, as compared to the standard scheme, in IAP AGCM 4.1. The new schemes also effectively enhance the large-scale precipitation, especially over low latitudes, although the influences of total precipitation are insignificant for different schemes. Further studies show that similar results can be found with the Community Atmosphere Model, version 5.1. © 2018, Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag GmbH Germany, part of Springer Nature."
"56539196700;6602600408;57205872550;","A new statistical approach to improve the satellite-based estimation of the radiative forcing by aerosol-cloud interactions",2017,"10.5194/acp-17-3687-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85015429371&doi=10.5194%2facp-17-3687-2017&partnerID=40&md5=8b125ecc36b75f9cac0b858e2850d679","In a previous study of Quaas et al. (2008) the radiative forcing by anthropogenic aerosol due to aerosol-cloud interactions, RFaci, was obtained by a statistical analysis of satellite retrievals using a multilinear regression. Here we employ a new statistical approach to obtain the fitting parameters, determined using a nonlinear least square statistical approach for the relationship between planetary albedo and cloud properties and, further, for the relationship between cloud properties and aerosol optical depth. In order to verify the performance, the results from both statistical approaches (previous and present) were compared to the results from radiative transfer simulations over three regions for different seasons. We find that the results of the new statistical approach agree well with the simulated results both over land and ocean. The new statistical approach increases the correlation by 21-23% and reduces the error compared to the previous approach. © Author(s) 2017."
"36538539800;56942554300;56612517400;","Multi-year application of WRF-CAM5 over East Asia-Part II: Interannual variability, trend analysis, and aerosol indirect effects",2017,"10.1016/j.atmosenv.2017.06.029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021738137&doi=10.1016%2fj.atmosenv.2017.06.029&partnerID=40&md5=291a6f8237b483efbf6f0e417ac8eb53","Following a comprehensive evaluation of WRF-CAM5 in Part I, Part II describes analyses of interannual variability, multi-year variation trends, and the direct, indirect, and total effects of anthropogenic aerosols. The interannual variations of chemical column and surface concentrations, and ozone (O3)/particulate matter (PM) indicators are strongly correlated to anthropogenic emission changes. Despite model biases, the model captures well the observed interannual variations of temperature at 2-m, cloud fraction, shortwave cloud forcing, downwelling shortwave radiation, cloud droplet number concentration, column O3, and column formaldehyde (HCHO) for the whole domain. While the model reproduces the volatile organic compound (VOC)-limited regimes of O3 chemistry at sites in Hong Kong, Taiwan, Japan, South Korea, and from the Acid Deposition Monitoring Network in East Asia (EANET) and the degree of sulfate neutralization at the EANET sites, it has limited capability in capturing the interannual variations of the ratio of O3 and nitrogen dioxide (O3/NO2) and PM chemical regime indicators, due to uncertainties in the emissions of precursors for O3 and secondary PM, the model assumption for ammonium bisulfate (NH4HSO4) as well as lack of gas/particle partitioning of total ammonia and total nitrate. While the variation trends in multi-year periods in aerosol optical depth and column concentrations of carbon monoxide, sulfur dioxide, and NO2 are mainly caused by anthropogenic emissions, those of major meteorological and cloud variables partly reflect feedbacks of chemistry to meteorological variables. The impacts of anthropogenic aerosol indirect effects either dominate or play an important role in the aerosol total effects for most cloud and chemical predictions, whereas anthropogenic aerosol direct effects influence most meteorological and radiation variables. The direct, indirect, and total effects of anthropogenic aerosols exhibit a strong interannual variability in 2001, 2006, and 2011. © 2017 Elsevier Ltd"
"57212500706;35511486700;57190067960;57190070438;","Cloud — Aerosol interaction during lightning activity over land and ocean: Precipitation pattern assessment",2016,"10.1007/s13143-015-0087-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977106991&doi=10.1007%2fs13143-015-0087-0&partnerID=40&md5=429b17ccb957ffa9ff4bb5265c126cf6","The present study attempts to identify the land - ocean contrast in cloud - aerosol relation during lightning and non-lightning days and its effect on subsequent precipitation pattern. The thermal hypothesis in view of Convective Available Potential Energy (CAPE) behind the land - ocean contrast is observed to be insignificant in the present study region. The result shows that the lightning activities are significantly and positively correlated with aerosols over both land and ocean in case of low aerosol loading whereas for high aerosol loading the correlation is significant but, only over land. The study attempts to comprehend the mechanism through which the aerosol and lightning interact using the concept of aerosol indirect effect that includes the study of cloud effective radius, cloud fraction and precipitation rate. The result shows that the increase in lightning activity over ocean might have been caused due to the first aerosol indirect effect, while over land the aerosol indirect effect might have been suppressed due to lightning. Thus, depending on the region and relation between cloud parameters it is observed that the precipitation rate decreases (increases) over ocean during lightning (non-lightning) days. On the other hand during non-lightning days, the precipitation rate decreases over land. © 2016, Korean Meteorological Society and Springer Science+Business Media Dordrecht."
"57172833500;7003972559;","Ground-based remote sensing scheme for monitoring aerosol-cloud interactions",2016,"10.5194/amt-9-1039-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84960970547&doi=10.5194%2famt-9-1039-2016&partnerID=40&md5=85ccff39ab36d4294fd2e10e0f7213da","A new method for continuous observation of aerosol-cloud interactions with ground-based remote sensing instruments is presented. The main goal of this method is to enable the monitoring of the change of the cloud droplet size due to the change in the aerosol concentration. We use high-resolution measurements from a lidar, a radar and a radiometer, which allow us to collect and compare data continuously. This method is based on a standardised data format from Cloudnet and can be implemented at any observatory where the Cloudnet data set is available. Two example case studies were chosen from the Atmospheric Radiation Measurement (ARM) Program deployment on Graciosa Island, Azores, Portugal, in 2009 to present the method. We use the cloud droplet effective radius (re) to represent cloud microphysical properties and an integrated value of the attenuated backscatter coefficient (ATB) below the cloud to represent the aerosol concentration. All data from each case study are divided into bins of the liquid water path (LWP), each 10 g m-2 wide. For every LWP bin we present the correlation coefficient between ln re and ln ATB, as well as ACIr (defined as ACIr = -d ln re/d ln ATB, change in cloud droplet effective radius with aerosol concentration). Obtained values of ACIr are in the range 0.01-0.1. We show that ground-based remote sensing instruments used in synergy can efficiently and continuously monitor aerosol-cloud interactions. © 2016 Author(s)."
"6602122304;","Dependence of daily aerosol wet deposition on precipitation at appalachian mountains site in the United States",2016,"10.4209/aaqr.2015.05.0322","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959343226&doi=10.4209%2faaqr.2015.05.0322&partnerID=40&md5=ab44fe590e0903aba9b52fd9eab224bc","The wet removal of airborne particulates is a significant component of atmospheric deposition in the Eastern United States. This study analyzed the daily wet deposition of major ions at the Canaan Valley site in Appalachian Mountains in Eastern US, for the time interval 2000-2014. The site is part of the Atmospheric Integrated Research Monitoring Network (AIRMoN), and is significantly impacted by acid precipitation, caused largely by anthropogenic sources of SO2 and NOx. Results show that the precipitation rate, R, varies mainly in the interval [0.01-100] mm day-1, and the daily wet deposition flux, F, varies about two orders of magnitude for most ions. The largest daily wet depositions are for SO42- and NO3- with extreme values over 30 mg m-2 day-1. In the case of NH4+, the largest daily wet depositions are over 10 mg m-2 day-1. Seasonal variations are illustrated by contrasting the winter and summer. In general, there are much larger daily wet deposition fluxes in summer than in winter. For SO42- there is more conversion of SO2 to SO42- in the gas phase and in cloud droplets during summer. Similarly, NH4+ has a distinct seasonal variation with a maximum in summer, consistent with larger sources of NH3 during the growth season. NO3- has a maximum concentration in precipitation during winter, and a maximum daily wet deposition flux during summer, especially during the most intense rain events. The Na+ and Cl- ions have the highest wet deposition in winter due to storms that bring air masses from Atlantic. Analysis shows that precipitation events are more frequent and more intense in summer than in winter. For the Canaan Valley, the summer precipitation events are effective in wet removal of aerosols providing episodes with some of the highest rates of acid deposition. © Taiwan Association for Aerosol Research."
"26424802100;7004020627;8711886600;7402177459;","Treatment of non-ideality in the SPACCIM multiphase model - Part 1: Model development",2016,"10.5194/gmd-9-247-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956533203&doi=10.5194%2fgmd-9-247-2016&partnerID=40&md5=0212c3b47a018e9bfa61205ce323a875","Ambient tropospheric deliquesced particles generally comprise a complex mixture of electrolytes, organic compounds, and water. Dynamic modeling of physical and chemical processes in this complex matrix is challenging. Thus, up-to-date multiphase chemistry models generally do not consider non-ideal solution effects. Therefore, the present study was aimed at presenting further development of the SPACCIM (Spectral Aerosol Cloud Chemistry Interaction Model) through treatment of solution non-ideality, which has not been considered before. The present paper firstly describes the model developments including (i) the implementation of solution non-ideality in aqueous-phase reaction kinetics in the SPACCIM framework, (ii) the advancements in the coupling scheme of microphysics and multiphase chemistry and (iii) the required adjustments of the numerical schemes, especially in the sparse linear solver and the calculation of the Jacobian. Secondly, results of sensitivity investigations are outlined, aiming at the evaluation of different activity coefficient modules and the examination of the contributions of different intermolecular forces to the overall activity coefficients. Finally, first results obtained with the new model framework are presented. The SPACCIM parcel model was developed and, so far, applied for the description of aerosol-cloud interactions. To advance SPACCIM also for modeling physical and chemical processes in deliquesced particles, the solution non-ideality has to be taken into account by utilizing activities in reaction terms instead of aqueous concentrations. The main goal of the extended approach was to provide appropriate activity coefficients for solved species. Therefore, an activity coefficient module was incorporated into the kinetic model framework of SPACCIM. Based on an intercomparison of different activity coefficient models and the comparison with experimental data, the AIOMFAC approach was implemented and extended by additional interaction parameters from the literature for mixed organic-inorganic systems. Moreover, the performance and the capability of the applied activity coefficient module were evaluated by means of water activity measurements, literature data and results of other activity coefficient models. Comprehensive comparison studies showed that the SpactMod (SPACCIM activity coefficient module) is valuable for predicting the thermodynamic behavior of complex mixtures of multicomponent atmospheric aerosol particles. First simulations with a detailed chemical mechanism have demonstrated the applicability of SPACCIM-SpactMod. The simulations indicate that the treatment of solution non-ideality might be needed for modeling multiphase chemistry processes in deliquesced particles. The modeled activity coefficients imply that chemical reaction fluxes of chemical processes in deliquesced particles can be both decreased and increased depending on the particular species involved in the reactions. For key ions, activity coefficients on the order of 0.1-0.8 and a strong dependency on the charge state as well as the RH conditions are modeled, implying a lowered chemical processing of ions in concentrated solutions. In contrast, modeled activity coefficients of organic compounds are in some cases larger than 1 under deliquesced particle conditions and suggest the possibility of an increased chemical processing of organic compounds. Moreover, the model runs have shown noticeable differences in the pH values calculated with and without consideration of solution non-ideality. On average, the predicted pH values of the simulations considering solution non-ideality are -0.27 and -0.44 pH units lower under 90 and 70% RH conditions, respectively. More comprehensive results of detailed SPACCIM-SpactMod studies on the multiphase processing in organic-inorganic mixtures of deliquesced particles are described in a companion paper. © Author(s) 2016."
"55213845300;55885662200;7003501910;6504572295;7003467276;","Global and regional climate impacts of future aerosol mitigation in an RCP6.0-like scenario in EC-Earth",2016,"10.1007/s10584-015-1525-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84951570285&doi=10.1007%2fs10584-015-1525-9&partnerID=40&md5=cf5d0ad8bf1c613eca9b564987f14ca0","Future changes in aerosol concentrations will influence the climate system over the coming decades. In this study we evaluate the equilibrium climate response to aerosol reductions in different parts of the world in 2050, using the global climate model EC-Earth. The aerosol concentrations are based on a set of scenarios similar to RCP6.0, developed using the IMAGE integrated assessment model and exploring stringent and weaker air pollution control. Reductions in aerosol concentrations lead to an increase in downward surface solar radiation under all-sky conditions in various parts of the world, especially in Asia where the local brightening may reach about 10 Wm−2. The associated increase in surface temperature may be as high as 0.5 °C. This signal is dominated by the reduced cooling effect of sulphate which in some areas is partially compensated by the decreased warming effect of black carbon. According to our simulations, the mitigation of BC may lead to decreases in mean summer surface temperature of up to 1 °C in central parts of North America and up to 0.3 °C in northern India. Aerosol reductions could significantly affect the climate at high latitudes especially in the winter, where temperature increases of up to 1 °C are simulated. In the Northern Hemisphere, this strong surface temperature response might be related to changes in circulation patterns and precipitation at low latitudes, which can give rise to a wave train and induce changes in weather patterns at high latitudes. Our model does not include a parameterization of aerosol indirect effects so that responses could be stronger in reality. We conclude that different, but plausible, air pollution control policies can have substantial local climate effects and induce remote responses through dynamic teleconnections. © 2015, Springer Science+Business Media Dordrecht."
"24332905600;55879739300;57207869145;6506718302;7006665163;8670472000;7005635934;9246517900;","Integration of prognostic aerosol-cloud interactions in a chemistry transport model coupled offline to a regional climate model",2015,"10.5194/gmd-8-1885-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84933511408&doi=10.5194%2fgmd-8-1885-2015&partnerID=40&md5=47410bee693a740a51c95941ba1eb392","To reduce uncertainties and hence to obtain a better estimate of aerosol (direct and indirect) radiative forcing, next generation climate models aim for a tighter coupling between chemistry transport models and regional climate models and a better representation of aerosol-cloud interactions. In this study, this coupling is done by first forcing the Rossby Center regional climate model (RCA4) with ERA-Interim lateral boundaries and sea surface temperature (SST) using the standard cloud droplet number concentration (CDNC) formulation (hereafter, referred to as the ""stand-alone RCA4 version"" or ""CTRL"" simulation). In the stand-alone RCA4 version, CDNCs are constants distinguishing only between land and ocean surface. The meteorology from this simulation is then used to drive the chemistry transport model, Multiple-scale Atmospheric Transport and Chemistry (MATCH), which is coupled online with the aerosol dynamics model, Sectional Aerosol module for Large Scale Applications (SALSA). CDNC fields obtained from MATCH-SALSA are then fed back into a new RCA4 simulation. In this new simulation (referred to as ""MOD"" simulation), all parameters remain the same as in the first run except for the CDNCs provided by MATCH-SALSA. Simulations are carried out with this model setup for the period 2005-2012 over Europe, and the differences in cloud microphysical properties and radiative fluxes as a result of local CDNC changes and possible model responses are analysed. Our study shows substantial improvements in cloud microphysical properties with the input of the MATCH-SALSA derived 3-D CDNCs compared to the stand-alone RCA4 version. This model setup improves the spatial, seasonal and vertical distribution of CDNCs with a higher concentration observed over central Europe during boreal summer (JJA) and over eastern Europe and Russia during winter (DJF). Realistic cloud droplet radii (CD radii) values have been simulated with the maxima reaching 13 μm, whereas in the stand-alone version the values reached only 5 μm. A substantial improvement in the distribution of the cloud liquid-water paths (CLWP) was observed when compared to the satellite retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) for the boreal summer months. The median and standard deviation values from the ""MOD"" simulation are closer to observations than those obtained using the stand-alone RCA4 version. These changes resulted in a significant decrease in the total annual mean net fluxes at the top of the atmosphere (TOA) by -5 W m-2 over the domain selected in the study. The TOA net fluxes from the ""MOD"" simulation show a better agreement with the retrievals from the Clouds and the Earth's Radiant Energy System (CERES) instrument. The aerosol indirect effects are estimated in the ""MOD"" simulation in comparison to the pre-industrial aerosol emissions (1900). Our simulations estimated the domain averaged annual mean total radiative forcing of -0.64 W m-2 with a larger contribution from the first indirect aerosol effect (-0.57 W m-2) than from the second indirect aerosol effect (-0.14 W m-2). © Author(s) 2015."
"25031430500;7103158465;55232897900;24722339600;","Erratum: Microphysical process rates and global aerosol-cloud interactions (Atmospheric Chemistry Physics (2013) 13 (9855-9867))",2014,"10.5194/acp-14-9099-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907016682&doi=10.5194%2facp-14-9099-2014&partnerID=40&md5=a3ad8c5d0d83ca4bb8426d3162de74d1",[No abstract available]
"57205026438;55711668600;","Asymmetrical interannual variation in aerosol optical depth over the tropics in terms of aerosol-cloud interaction",2014,"10.2151/sola.2014-039","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920660310&doi=10.2151%2fsola.2014-039&partnerID=40&md5=6fbab076fac75a199293751ad7edc0fa","We statistically investigated an interannual co-variation among aerosol optical depth (AOD), cloud effective radius (CER), and precipitation, focusing on aerosol-cloud interaction over the tropics. A three-month composite analysis for AOD, CER, and precipitation for 2000-2012 based on El Niño-Southern Oscillation phases during September-October-November (SON) and December-January-February shows that an increase (decrease) in AOD in the El Niño (La Niña) years was associated with a decrease (increase) in precipitation, particularly in SON over the Maritime Continent. Additionally, CER decreased in the El Niño years over the same region, which implies that CER was associated with interannual variation in aerosol burden; these results were statistically significant. Interannual variation in AOD and CER in SON in the Maritime Continent was asymmetrical, which can be explained by stronger aerosol-cloud interactions under drier conditions. Specifically, large amounts of aerosols suppressed cloud and precipitation formation, which leads to decreases in wet deposition and increases in emission under warmer and drier surface conditions. This feedback results in asymmetrical variation. Furthermore, the asymmetrical interannual variation was confirmed statistically. © 2014, the Meteorological Society of Japan."
"55706050400;7005602760;","Effects of dust aerosols on warm cloud properties over East Asia and the sahara from satellite data",2014,"10.2151/jmsj.2014-A07","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910005050&doi=10.2151%2fjmsj.2014-A07&partnerID=40&md5=42ce84a4087abe83a93c10de81416384","The effects of dust aerosol particles on the properties of clouds over East Asia and the Sahara are studied using moderate resolution imaging spectroradiometer observations from the Terra and Aqua satellites and simulation results of the chemical weather forecast system (CFORS) model. Dust-contaminated clouds are detected using the brightness temperature difference (BTD) method, in which dust or dust-bearing clouds are detected when the BTD between the 11 μm and 12 μm channels in the window region is negative, and by the CFORS model’s dust vertical profile. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation data are also used to assess the above procedures. For the Sahara region, no obvious changes to effective particle radius (Re) are attributed to dust aerosols. However, for East Asia, dust aerosols are found to change the cloud microphysical properties, decreasing Re by 12 % and increasing the cloud optical depth by 27 % and the liquid water path by 9 %. Re is found to be negatively correlated with sulfate concentration by CFORS in dust-bearing clouds, but not in dust-free clouds, over East Asia. These findings indicate that mineral dust can act as effective cloud condensation nuclei in environments polluted by water-soluble aerosols such as sulfates. We also estimate the indirect radiative effect of dust aerosols in the East Asia region and determine, by radiative transfer calculation, that the net shortwave radiative flux at the top of the atmosphere decreases and the absorption of shortwave radiation by the atmosphere increases with changes in cloud properties due to dust aerosols. © 2014, Meteorological Society of Japan."
"36480030600;57212018317;57212017731;57212026332;57212024252;","Effects of Aerosols on Fogs Observed in the North China Plain",2013,"10.1080/16742834.2013.11447060","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940240281&doi=10.1080%2f16742834.2013.11447060&partnerID=40&md5=316037f46a5dc9f9ccafa3fa7b4e97a2","Fog simulation and prediction are becoming increasingly important in China because of the great impact of fog on traffic and other human activities. More studies are needed to have a better understanding of the formation mechanisms and life cycles of fogs. This work uses data from two fog cases observed in Wuqing, Tianjin, in 2009. The data include aerosol size distribution, fog droplet size distribution, fog liquid water content, and meteorological properties. The results show that increasing aerosols can increase the number concentration of fog droplets and decrease fog droplet size, which is consistent with the first aerosol indirect effect found in clouds. It is also shown that increased aerosols can lead to lower visibility in fogs. This work demonstrates that the first aerosol indirect effect plays an important role in fogs. © 2013, © 2013 Institute of Atmospheric Physics, Chinese Academy of Sciences."
"12801992200;","Aerosol Forcing: Rapporteur's Report and Summary",2012,"10.1007/s10712-011-9160-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862682317&doi=10.1007%2fs10712-011-9160-0&partnerID=40&md5=9d6fece99f718687a931f90897023ded","This paper summarizes the discussions held during the session dedicated to Aerosol forcing at the Workshop Observing and Modelling Earth's Energy Flows. The session Aerosol forcing was convened by P. Ingmann and J. Heintzenberg and included 10 presentations given by R. Kahn, D. Winker, U. Baltensperger, J. Haywood, S. Schwartz, J. Heintzenberg, H. Le Treut, U. Lohmann, R. Wood, and E. Philipona. The presentations given ranged from overviews of current observational capabilities to analyses of aerosol-cloud interactions in observations and models of varying complexity. This paper is organized around a few key points, summarizing the major points of agreement, disagreement, and discussion that the presentations gave rise to. The focus is largely on the uncertainties that remain with regard to aerosol forcing, particularly related to aerosol-cloud interactions and indirect aerosol effects on climate. © 2011 Springer Science+Business Media B.V."
"23980042500;7003371432;","Aerosol-cloud interactions in a mesoscale model. Part II: Sensitivity to aqueous-phase chemistry",2008,"10.1175/2007JAS2276.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40949130534&doi=10.1175%2f2007JAS2276.1&partnerID=40&md5=d096f5d59457faf70a4d0902e48ea9d1","The feedbacks between aerosols, cloud microphysics, and cloud chemistry are investigated in a mesoscale model. A simple bulk aqueous-phase sulfur chemistry scheme was fully coupled to the existing aerosol and microphysics schemes. The representation of aerosol and microphysics follows the explicit bulk double-moment approach. A case of summertime stratocumulus cloud system is simulated at high resolution (3-km grid spacing), and the evolution of an observed continental aerosol spectrum that changes during the course of the simulation as a result of cloud processing is examined. The results demonstrate that the bulk approach to the aerosol and droplet spectra correctly represents the feedbacks in the coupled system. The simulations capture the characteristic bimodal aerosol size spectrum resulting from cloud processing, with the first mode consisting of particles that did not participate as cloud condensation nuclei and the second mode, in the region of 0.08-0.12-υm radii, comprising the particles that were affected by processing. New information is revealed about the impact of the two main processing pathways and about the spatial distribution of the processed aerosol. One cycle of physical processing produced a relatively modest impact of 3%-5% on the processed particlermean radius of the order that was comparable to the impact of chemical processing, while continuous physical recycling produced a much larger impact as high as 30%-50%. A strong constraint on the chemical processing was found to be the initial chemistry input and the assumption of bulk chemical composition. Simple tests with a more slowly depleting primary oxidant (H2O2) and including the droplet chemical heterogeneity effect favor stronger sulfate production, by, respectively, the H2O, and O3 oxidation reaction, and both show a larger impact on the processed particle mean radius of similar magnitude, 10%-20%. Spatially, the impact of processing is found initially in the downdraft regions below cloud and at later times at substantial distances downwind. It is shown that cloud processing can either enhance or suppress the number of activated drops in subsequent cycles. © 2008 American Meteorological Society."
"7102018821;7201844203;7402359452;","Recent progress in atmospheric sciences: Applications to the Asia-Pacific region",2008,"10.1142/9789812818911","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84969641325&doi=10.1142%2f9789812818911&partnerID=40&md5=bb17587d54ea67161dbdad1acf05b8de","This book contains 22 peer-reviewed articles that cover a spectrum of contemporary subjects relevant to atmospheric sciences, with specific applications to the Asia-Pacific region. The majority of these papers consist of a review of a scientific sub-field in atmospheric sciences, while some contain original contributions. All of the accepted papers were subject to scientific reviews and revisions. The book is divided into 2 traditional fields in atmospheric sciences: atmospheric dynamics and meteorology; and atmospheric physics and chemistry. The authors of these papers are distinguished alumni of the Department of Atmospheric Sciences at the National Taiwan University, residing in the USA and Taiwan. This book is dedicated to the 50th anniversary of the Department of Atmospheric Sciences that occurred in 2004. Papers in atmospheric dynamics and meteorology cover the following subjects: El Niño/Southern Oscillation, air/sea interactions, convection in the tropics, meiyu frontal systems, tropical cyclones/typhoons, data assimilations, and mesoscale modeling. In atmospheric physics and chemistry, subjects range from aerosols/clouds interactions, heat budgets in the context of air/sea interactions, atmospheric radiative transfer, remote sensing of the oceans, Asian dust outbreaks and clouds, reviews of cloud microphysics and urban ozone formations, to a satellite GPS system for typhoon studies and weather predictions. © 2008 by World Scientific Publishing Co. Pte. Ltd. All rights reserved."
"7005116139;","Heterogeneous ice nucleation. Comparison with Fletcher theory",2000,"10.1016/s0021-8502(00)90265-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034269629&doi=10.1016%2fs0021-8502%2800%2990265-9&partnerID=40&md5=0fcfef1f3e67050be0b6ff0b0ac86a5b",[No abstract available]
"8140555300;7006212411;36474213000;7404105326;56284543100;57188559483;7005007661;57201134332;35547807400;9636594900;25031430500;16233122400;8314917200;27467537200;56572170400;55754604900;7102604282;7003800456;7005275092;7004194999;53880473700;","The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018",2021,"10.1016/j.atmosenv.2020.117834","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092478510&doi=10.1016%2fj.atmosenv.2020.117834&partnerID=40&md5=eff8484172bbdee6e8077560d8bdb9c5","Global aviation operations contribute to anthropogenic climate change via a complex set of processes that lead to a net surface warming. Of importance are aviation emissions of carbon dioxide (CO2), nitrogen oxides (NOx), water vapor, soot and sulfate aerosols, and increased cloudiness due to contrail formation. Aviation grew strongly over the past decades (1960–2018) in terms of activity, with revenue passenger kilometers increasing from 109 to 8269 billion km yr−1, and in terms of climate change impacts, with CO2 emissions increasing by a factor of 6.8 to 1034 Tg CO2 yr−1. Over the period 2013–2018, the growth rates in both terms show a marked increase. Here, we present a new comprehensive and quantitative approach for evaluating aviation climate forcing terms. Both radiative forcing (RF) and effective radiative forcing (ERF) terms and their sums are calculated for the years 2000–2018. Contrail cirrus, consisting of linear contrails and the cirrus cloudiness arising from them, yields the largest positive net (warming) ERF term followed by CO2 and NOx emissions. The formation and emission of sulfate aerosol yields a negative (cooling) term. The mean contrail cirrus ERF/RF ratio of 0.42 indicates that contrail cirrus is less effective in surface warming than other terms. For 2018 the net aviation ERF is +100.9 milliwatts (mW) m−2 (5–95% likelihood range of (55, 145)) with major contributions from contrail cirrus (57.4 mW m−2), CO2 (34.3 mW m−2), and NOx (17.5 mW m−2). Non-CO2 terms sum to yield a net positive (warming) ERF that accounts for more than half (66%) of the aviation net ERF in 2018. Using normalization to aviation fuel use, the contribution of global aviation in 2011 was calculated to be 3.5 (4.0, 3.4) % of the net anthropogenic ERF of 2290 (1130, 3330) mW m−2. Uncertainty distributions (5%, 95%) show that non-CO2 forcing terms contribute about 8 times more than CO2 to the uncertainty in the aviation net ERF in 2018. The best estimates of the ERFs from aviation aerosol-cloud interactions for soot and sulfate remain undetermined. CO2-warming-equivalent emissions based on global warming potentials (GWP* method) indicate that aviation emissions are currently warming the climate at approximately three times the rate of that associated with aviation CO2 emissions alone. CO2 and NOx aviation emissions and cloud effects remain a continued focus of anthropogenic climate change research and policy discussions. © 2020 Elsevier Ltd"
"57212006310;7004154626;56400726900;","Role of droplet size classes on the cloud droplet spectral dispersion as observed over the Western Ghats",2020,"10.1016/j.atmosres.2020.105104","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087103303&doi=10.1016%2fj.atmosres.2020.105104&partnerID=40&md5=05a0bd0b5ccee22eeb0b2f64b500729b","The aerosol indirect effects (AIE) on cloud microphysical properties have been studied using ground-based in-situ measurements. Aerosol and cloud microphysical properties were collected from a high altitude site in the Western Ghats region of India, where clouds pass over the surface during South West monsoon. The AIE was estimated using cloud droplet number concentration (AIEn) and cloud droplet effective radius (AIEs) at different fixed liquid water content (LWC) bins. The AIE varied in the range 0.01–0.13 for LWC between 0.04 g m−3 and 0.26 g m−3. The maximum AIEn and AIEs (0.125 and 0.119) were observed at the lower LWC bin (0.06–0.07 g m−3). An overestimation in AIEn is due to the dispersion effect. The offset was reduced and AIEn became close to AIEs after dispersion correction. Hence for the correct estimation of AIE using cloud droplet number concentration (Nc), dispersion correction should be considered. At the same time, the AIE estimate obtained using Reff does not need correction as the dispersion effect is implicitly included. Relative dispersion can be viewed not only as the combined effects of σ and Rm, but also as the combined effects of cloud droplets of different sizes. Further, for the first time in India, the relative contribution by the smaller and medium size droplets to the total dispersion of cloud droplet size distribution (CDSD) at lower and higher LWC bins were studied. In lower LWC, the smaller size droplets are contributing maximum (71%) to the total Nc, whereas the medium size droplets are contributing maximum (61%) to the total dispersion. At higher LWC, the contribution to total Nc by the smaller size droplets was reduced by 20%, however contribution by the medium size droplets increased by 17%, compared to the lower LWC case. Hence at higher LWC, both smaller (42%) and medium (55%) size droplets have a significant role in the total dispersion of CDSD. © 2020 Elsevier B.V."
"42961641500;57201854221;57141453800;57201854177;57219338234;7006204597;57214957727;57191031593;7005304841;7003487564;55332349200;7202779940;7003740015;6601927317;8404544300;57189006448;57192264838;34771961300;","The ice-nucleating activity of Arctic sea surface microlayer samples and marine algal cultures",2020,"10.5194/acp-20-11089-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092268295&doi=10.5194%2facp-20-11089-2020&partnerID=40&md5=c5b8e4a2528f419311ecd45cf4d32339","In recent years, sea spray as well as the biological material it contains has received increased attention as a source of ice-nucleating particles (INPs). Such INPs may play a role in remote marine regions, where other sources of INPs are scarce or absent. In the Arctic, these INPs can influence water-ice partitioning in low-level clouds and thereby the cloud lifetime, with consequences for the surface energy budget, sea ice formation and melt, and climate. Marine aerosol is of a diverse nature, so identifying sources of INPs is challenging. One fraction of marine bioaerosol (phytoplankton and their exudates) has been a particular focus of marine INP research. In our study we attempt to address three main questions. Firstly, we compare the ice-nucleating ability of two common phytoplankton species with Arctic seawater microlayer samples using the same instrumentation to see if these phytoplankton species produce ice-nucleating material with sufficient activity to account for the ice nucleation observed in Arctic microlayer samples. We present the first measurements of the ice-nucleating ability of two predominant phytoplankton species: Melosira arctica, a common Arctic diatom species, and Skeletonema marinoi, a ubiquitous diatom species across oceans worldwide. To determine the potential effect of nutrient conditions and characteristics of the algal culture, such as the amount of organic carbon associated with algal cells, on the ice nucleation activity, Skeletonema marinoi was grown under different nutrient regimes. From comparison of the ice nucleation data of the algal cultures to those obtained from a range of sea surface microlayer (SML) samples obtained during three different field expeditions to the Arctic (ACCACIA, NETCARE, and ASCOS), we found that they were not as ice active as the investigated microlayer samples, although these diatoms do produce ice-nucleating material. Secondly, to improve our understanding of local Arctic marine sources as atmospheric INPs we applied two aerosolization techniques to analyse the ice-nucleating ability of aerosolized microlayer and algal samples. The aerosols were generated either by direct nebulization of the undiluted bulk solutions or by the addition of the samples to a sea spray simulation chamber filled with artificial seawater. The latter method generates aerosol particles using a plunging jet to mimic the process of oceanic wave breaking. We observed that the aerosols produced using this approach can be ice active, indicating that the ice-nucleating material in seawater can indeed transfer to the aerosol phase. Thirdly, we attempted to measure ice nucleation activity across the entire temperature range relevant for mixed-phase clouds using a suite of ice nucleation measurement techniques-an expansion cloud chamber, a continuous-flow diffusion chamber, and a cold stage. In order to compare the measurements made using the different instruments, we have normalized the data in relation to the mass of salt present in the nascent sea spray aerosol. At temperatures above 248K some of the SML samples were very effective at nucleating ice, but there was substantial variability between the different samples. In contrast, there was much less variability between samples below 248K. We discuss our results in the context of aerosol-cloud interactions in the Arctic with a focus on furthering our understanding of which INP types may be important in the Arctic atmosphere. © Author(s) 2020."
"35329672300;30767858100;26666431500;8067118800;55702984800;24450766100;55791137300;56959736200;","Global aerosol simulations using NICAM.16 on a 14&thinsp;km grid spacing for a climate study: Improved and remaining issues relative to a lower-resolution model",2020,"10.5194/gmd-13-3731-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088657566&doi=10.5194%2fgmd-13-3731-2020&partnerID=40&md5=c5eeaaa2e913837780d1b6e16f5950f3","High-performance computing resources allow us to conduct numerical simulations with a horizontal grid spacing that is sufficiently high to resolve cloud systems on a global scale, and high-resolution models (HRMs) generally provide better simulation performance than low-resolution models (LRMs). In this study, we execute a next-generation model that is capable of simulating global aerosols using version 16 of the Nonhydrostatic Icosahedral Atmospheric Model (NICAM.16). The simulated aerosol distributions are obtained for 3 years with an HRM using a global 14 km grid spacing, an unprecedentedly high horizontal resolution and long integration period. For comparison, a NICAM with a 56 km grid spacing is also run as an LRM, although this horizontal resolution is still high among current global aerosol climate models. The comparison elucidated that the differences in the various variables of meteorological fields, including the wind speed, precipitation, clouds, radiation fluxes and total aerosols, are generally within 10% of their annual averages, but most of the variables related to aerosols simulated by the HRM are slightly closer to the observations than are those simulated by the LRM. Upon investigating the aerosol components, the differences in the water-insoluble black carbon and sulfate concentrations between the HRM and LRM are large (up to 32 %), even in the annual averages. This finding is attributed to the differences in the aerosol wet deposition flux, which is determined by the conversion rate of cloud to precipitation, and the difference between the HRM and LRM is approximately 20 %. Additionally, the differences in the simulated aerosol concentrations at polluted sites during polluted months between the HRM and LRM are estimated with normalized mean biases of 19% for black carbon (BC), 5% for sulfate and 3% for the aerosol optical thickness (AOT). These findings indicate that the impacts of higher horizontal grid spacings on model performance for secondary products such as sulfate, and complex products such as the AOT, are weaker than those for primary products, such as BC. On a global scale, the subgrid variabilities in the simulated AOT and cloud optical thickness (COT) in the 1 1 domain using 6-hourly data are estimated to be 28.5% and 80.0 %, respectively, in the HRM, whereas the corresponding differences are 16.6% and 22.9% in the LRM. Over the Arctic, both the HRM and the LRM generally reproduce the observed aerosols, but the largest difference in the surface BC mass concentrations between the HRM and LRM reaches 30% in spring (the HRM-simulated results are closer to the observations). The vertical distributions of the HRM-and LRM-simulated aerosols are generally close to the measurements, but the differences between the HRM and LRM results are large above a height of approximately 3 km, mainly due to differences in the wet deposition of aerosols. The global annual averages of the effective radiative forcings due to aerosol radiation and aerosol cloud interactions (ERFari and ERFaci) attributed to anthropogenic aerosols in the HRM are estimated to be 0:2930:001 and 0:9190:004Wm2, respectively, whereas those in the LRM are 0:2390:002 and 1:1010:013Wm2. The differences in the ERFari between the HRM and LRM are primarily caused by those in the aerosol burden, whereas the differences in the ERFaci are primarily caused by those in the cloud expression and performance, which are attributed to the grid spacing. The analysis of interannual variability revealed that the difference in reproducibility of both sulfate and carbonaceous aerosols at different horizontal resolution is greater than their interannual variability over 3 years, but those of dust and sea salt AOT and possibly clouds were the opposite. Because at least 10 times the computer resources are required for the HRM (14 km grid) compared to the LRM (56 km grid), these findings in this study help modelers decide whether the objectives can be achieved using such higher resolution or not under the limitation of available computational resources. © 2020 Copernicus GmbH. All rights reserved."
"57194577188;55720018700;55688930000;36657850900;57218509585;55714712500;","Source attribution of Arctic black carbon and sulfate aerosols and associated Arctic surface warming during 1980-2018",2020,"10.5194/acp-20-9067-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089366641&doi=10.5194%2facp-20-9067-2020&partnerID=40&md5=25e07cd4924b7df59b65a5b2c20b13df","Observations show that the concentrations of Arctic sulfate and black carbon (BC) aerosols have declined since the early 1980s. Previous studies have reported that reducing sulfate aerosols potentially contributed to the recent rapid Arctic warming. In this study, a global aerosol-climate model (Community Atmosphere Model, version 5) equipped with Explicit Aerosol Source Tagging (CAM5-EAST) is applied to quantify the source apportionment of aerosols in the Arctic from 16 source regions and the role of aerosol variations in affecting changes in the Arctic surface temperature from 1980 to 2018. The CAM5-EAST simulated surface concentrations of sulfate and BC in the Arctic had a decrease of 43thinsp; and 23thinsp;, respectively, in 2014-2018 relative to 1980-1984 mainly due to the reduction of emissions from Europe, Russia and local Arctic sources. Increases in emissions from South and East Asia led to positive trends in Arctic sulfate and BC in the upper troposphere. All aerosol radiative impacts are considered including aerosol-radiation and aerosol-cloud interactions, as well as black carbon deposition on snow- and ice-covered surfaces. Within the Arctic, sulfate reductions caused a top-of-atmosphere (TOA) warming of 0.11 and 0.25thinsp;Wthinsp span classCombining double low line inline-formula -2 /span through aerosol-radiation and aerosol-cloud interactions, respectively. While the changes in Arctic atmospheric BC has little impact on local radiative forcing, the decrease in BC in snow and ice led to a net cooling of 0.05thinsp;Wthinspspan classCombining double low line inline-formula -2 /span. By applying climate sensitivity factors for different latitudinal bands, global changes in sulfate and BC during 2014-2018 (with respect to 1980-1984) exerted a span classCombining double low line inline-formula +0.088 /span and 0.057thinsp;K Arctic surface warming, respectively, through aerosol-radiation interactions. Through aerosol-cloud interactions, the sulfate reduction caused an Arctic warming of span classCombining double low line inline-formula +0.193 /spanthinsp;K between the two time periods. The weakened BC effect on snow-ice albedo led to an Arctic surface cooling of span classCombining double low line inline-formula -0.041 /spanthinsp;K. The changes in atmospheric sulfate and BC outside the Arctic produced a total Arctic warming of span classCombining double low line inline-formula + /span0.25thinsp;K, the majority of which is due to the midlatitude changes in radiative forcing. Our results suggest that changes in aerosols over the midlatitudes of the Northern Hemisphere have a larger impact on Arctic temperature than other regions through enhanced poleward heat transport. The combined total effects of sulfate and BC produced an Arctic surface warming of span classCombining double low line inline-formula + /span0.297thinsp;K, explaining approximately 20thinsp; of the observed Arctic warming since the early 1980s. /p. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License."
"49663766700;14036209800;7201443624;8633783900;26031912400;24512349100;57203049177;8583350800;8670472000;8651824700;7003976079;7402401574;53880473700;57218150582;","Aerosol-Forced AMOC Changes in CMIP6 Historical Simulations",2020,"10.1029/2020GL088166","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088586097&doi=10.1029%2f2020GL088166&partnerID=40&md5=d7208485f8614524afef7e431403a4aa","The Atlantic Meridional Overturning Circulation (AMOC) has been, and will continue to be, a key factor in the modulation of climate change both locally and globally. However, there remains considerable uncertainty in recent AMOC evolution. Here, we show that the multimodel mean AMOC strengthened by approximately 10% from 1850–1985 in new simulations from the 6th Coupled Model Intercomparison Project (CMIP6), a larger change than was seen in CMIP5. Across the models, the strength of the AMOC trend up to 1985 is related to a proxy for the strength of the aerosol forcing. Therefore, the multimodel difference is a result of stronger anthropogenic aerosol forcing on average in CMIP6 than CMIP5, which is primarily due to more models including aerosol-cloud interactions. However, observational constraints—including a historical sea surface temperature fingerprint and shortwave radiative forcing in recent decades—suggest that anthropogenic forcing and/or the AMOC response may be overestimated. ©2020. The Authors."
"10139397300;35263614500;57211395413;6602600408;35227762400;57218718333;57191980050;43661479500;55923546200;57203078473;10239512000;36100012200;57203200427;7003777747;","Radiative forcing of climate change from the Copernicus reanalysis of atmospheric composition",2020,"10.5194/essd-12-1649-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85090171235&doi=10.5194%2fessd-12-1649-2020&partnerID=40&md5=9b41c13426111a13e8a62e2c2d499ecc","Radiative forcing provides an important basis for understanding and predicting global climate changes, but its quantification has historically been done independently for different forcing agents, has involved observations to varying degrees, and studies have not always included a detailed analysis of uncertainties. The Copernicus Atmosphere Monitoring Service reanalysis is an optimal combination of modelling and observations of atmospheric composition. It provides a unique opportunity to rely on observations to quantify the monthly and spatially resolved global distributions of radiative forcing consistently for six of the largest forcing agents: carbon dioxide, methane, tropospheric ozone, stratospheric ozone, aerosol-radiation interactions, and aerosol-cloud interactions. These radiative-forcing estimates account for adjustments in stratospheric temperatures but do not account for rapid adjustments in the troposphere. On a global average and over the period 2003-2017, stratospherically adjusted radiative forcing of carbon dioxide has averaged +1.89Wm-2 (5%-95% confidence interval: 1.50 to 2.29Wm-2) relative to 1750 and increased at a rate of 18% per decade. The corresponding values for methane are +0.46 (0.36 to 0.56)Wm-2 and 4% per decade but with a clear acceleration since 2007. Ozone radiative-forcing averages +0.32 (0 to 0.64)Wm-2, almost entirely contributed by tropospheric ozone since stratospheric ozone radiative forcing is only +0.003Wm-2. Aerosol radiative-forcing averages -1.25 (-1.98 to -0.52)Wm-2, with aerosol-radiation interactions contributing -0.56Wm-2 and aerosol-cloud interactions contributing -0.69Wm-2 to the global average. Both have been relatively stable since 2003. Taking the six forcing agents together, there is no indication of a sustained slowdown or acceleration in the rate of increase in anthropogenic radiative forcing over the period. These ongoing radiative-forcing estimates will monitor the impact on the Earth's energy budget of the dramatic emission reductions towards net-zero that are needed to limit surface temperature warming to the Paris Agreement temperature targets. Indeed, such impacts should be clearly manifested in radiative forcing before being clear in the temperature record. In addition, this radiative-forcing dataset can provide the input distributions needed by researchers involved in monitoring of climate change, detection and attribution, interannual to decadal prediction, and integrated assessment modelling. The data generated by this work are available at https://doi.org/10.24380/ads.1hj3y896 (Bellouin et al., 2020b). © Author(s) 2020."
"57201305884;8312732800;56433368600;35219942100;6701313597;55888251800;35114996800;6603382350;57218120225;25626899800;8550791300;16317681900;7006415284;","Wintertime Airborne Measurements of Ice Nucleating Particles in the High Arctic: A Hint to a Marine, Biogenic Source for Ice Nucleating Particles",2020,"10.1029/2020GL087770","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087977919&doi=10.1029%2f2020GL087770&partnerID=40&md5=2da4e121cb0d38308959f20b4fd31663","Ice nucleating particles (INPs) affect the radiative properties of cold clouds. Knowledge concerning their concentration above ground level and their potential sources is scarce. Here we present the first highly temperature resolved ice nucleation spectra of airborne samples from an aircraft campaign during late winter in 2018. Most INP spectra featured low concentration levels (&lt;3 · 10−4 L−1 at −15°C). However, we also found INP concentrations of up to 1.8·10−2 L−1 at −15°C and freezing onsets as high as −7.5°C for samples mainly from the marine boundary layer. Shape and onset temperature of the ice nucleation spectra of those samples as well as heat sensitivity hint at biogenic INP. Colocated measurements additionally indicate a local marine influence rather than long-range transport. Our results suggest that even in late winter above 80°N a local marine source for biogenic INP, which can efficiently nucleate ice at high temperatures, is present. ©2020. The Authors."
"56009507800;24833810000;6701562043;36076994600;55575158300;24491934500;24722339600;6603239456;14035836100;12803904100;56358382600;56495509000;9846347800;","Identifying a regional aerosol baseline in the eastern North Atlantic using collocated measurements and a mathematical algorithm to mask high-submicron-number-concentration aerosol events",2020,"10.5194/acp-20-7553-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087910887&doi=10.5194%2facp-20-7553-2020&partnerID=40&md5=e853a6e7cdf32bc2cdb7f15c2836a82e","High-time-resolution measurements of in situ aerosol and cloud properties provide the ability to study regional atmospheric processes that occur on timescales of minutes to hours. However, one limitation to this approach is that continuous measurements often include periods when the data collected are not representative of the regional aerosol. Even at remote locations, submicron aerosols are pervasive in the ambient atmosphere with many sources. Therefore, periods dominated by local aerosol should be identified before conducting subsequent analyses to understand aerosol regional processes and aerosol-cloud interactions. Here, we present a novel method to validate the identification of regional baseline aerosol data by applying a mathematical algorithm to the data collected at the U.S. Department of Energy's (DOE) Atmospheric Radiation Measurement (ARM) user facility in the eastern North Atlantic (ENA). The ENA central facility (C1) includes an aerosol observing system (AOS) for the measurement of aerosol physical, optical, and chemical properties at time resolutions from seconds to minutes. A second temporary supplementary facility (S1), located ∼0.75km from C1, was deployed for ∼1 year during the Aerosol and Cloud Experiments (ACE-ENA) campaign in 2017. First, we investigate the local aerosol at both locations. We associate periods of high submicron number concentration (Ntot) in the fine-mode condensation particle counter (CPC) and size distributions from the Ultra-High Sensitivity Aerosol Spectrometer (UHSAS) as a function of wind direction using a meteorology sensor with local sources. Elevated concentrations of Aitken-mode (<100nm diameter) particles were observed in correspondence with the wind directions associated with airport operations. At ENA, the Graciosa Airport and its associated activities were found to be the main sources of high-concentration aerosol events at ENA, causing peaks in 1min Ntot that exceeded 8000 and 10000cm-3 at C1, in summer and winter, respectively, and 5000cm-3 at S1 in summer. Periods with high Ntot not associated with these wind directions were also observed. As a result, the diverse local sources at ENA yielded a poor relationship between Ntot measurements collected at C1 and S1 (R2 = 0.03 with a slope = 0.05 ± 0.001). As a first approach to mask these events, the time periods when the wind direction was associated with the airport operations (west to northwest and southeast to south at C1 and east to south at S1) were applied. The meteorological masks removed 38.9% of the data at C1 and 43.4% at S1, and they did not significantly improve the relationship between the two sites (R2 = 0.18 with a slope = 0.06 ± 0.001). Due to the complexity of high-Ntot events observed at ENA, we develop and validate a mathematical ENA Aerosol Mask (ENA-AM) to identify high-Ntot events using 1min resolution data from the AOS CPC at C1 and S1. After its parameterization and application, ENA-AM generated a high correlation between Ntot in the summer at C1 and S1 (R2 = 0.87 with a slope = 0.84 - 0.001). We identified the regional baseline at ENA to be 428±228cm-3 in the summer and 346±223cm-3 in the winter. Lastly, we compared masked measurements from the AOS with the ARM Aerial Facility (AAF) during flights over C1 in the summer to understand submicron aerosol vertical mixing over C1. The high correlation (R2 = 0.71 with a slope of 1.04±0.01) observed between C1 and the AAF Ntot collected within an area of 10km surrounding ENA and at altitudes <500m indicated that the submicron aerosol at ENA was well mixed within the first 500m of the marine boundary layer during the month of July during ACE-ENA. Our novel method for determining a regional aerosol baseline at ENA can be applied to other time periods and at other locations with validation by a secondary site or additional collocated measurements.. © Author(s) 2020."
"56502199700;8067118800;","Reconciling Compensating Errors Between Precipitation Constraints and the Energy Budget in a Climate Model",2020,"10.1029/2020GL088340","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086805202&doi=10.1029%2f2020GL088340&partnerID=40&md5=5dbefdcefc6451dd64a6e45ceb713d34","Precipitation microphysics and the effective radiative forcing due to aerosol-cloud interactions (ERFaci) contribute to some of the largest uncertainties in general circulation models (GCMs) and are closely interrelated. This study shows that a sophisticated, two-moment prognostic precipitation scheme can simultaneously represent both warm rain characteristics consistent with satellite observations and a realistic ERFaci magnitude, thus reconciling compensating errors between precipitation microphysics and ERFaci that are common to many GCMs. The enhancement of accretion from prognostic precipitation and accretion-driven buffering mechanisms in scavenging processes are found to be responsible for mitigating the compensating errors. However, single-moment prognostic precipitation without the explicit prediction of raindrop size cannot capture observed warm rain characteristics. Results underscore the importance of using a two-moment representation of both clouds and precipitation to realistically simulate precipitation-driven buffering of the cloud response to aerosol perturbations. ©2020. The Authors."
"57217068878;18434033000;52364737200;54931083200;56736820800;6701363731;6602537415;","Investigating the sensitivity to resolving aerosol interactions in downscaling regional model experiments with WRFv3.8.1 over Europe",2020,"10.5194/gmd-13-2511-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086022901&doi=10.5194%2fgmd-13-2511-2020&partnerID=40&md5=601fd0bd2e5c01ba0c0fd3aa31fdd5af","In this work we present downscaling experiments with the Weather Research and Forecasting model (WRF) to test the sensitivity to resolving aerosol-radiation and aerosol-cloud interactions on simulated regional climate for the EURO-CORDEX domain. The sensitivities mainly focus on the aerosol-radiation interactions (direct and semi-direct effects) with four different aerosol optical depth datasets (Tegen, MAC-v1, MACC, GOCART) being used and changes to the aerosol absorptivity (single scattering albedo) being examined. Moreover, part of the sensitivities also investigates aerosol-cloud interactions (indirect effect). Simulations have a resolution of 0.44 and are forced by the ERA-Interim reanalysis. A basic evaluation is performed in the context of seasonal-mean comparisons to ground-based (E-OBS) and satellite-based (CM SAF SARAH, CLARA) benchmark observational datasets. The impact of aerosols is calculated by comparing it against a simulation that has no aerosol effects. The implementation of aerosol-radiation interactions reduces the direct component of the incoming surface solar radiation by 20 %-30% in all seasons, due to enhanced aerosol scattering and absorption. Moreover the aerosol-radiation interactions increase the diffuse component of surface solar radiation in both summer (30 %-40 %) and winter (5 %-8 %), whereas the overall downward solar radiation at the surface is attenuated by 3 %-8 %. The resulting aerosol radiative effect is negative and is comprised of the net effect from the combination of the highly negative direct aerosol effect (-17 to-5Wm-2) and the small positive changes in the cloud radiative effect (C5Wm-2), attributed to the semi-direct effect. The aerosol radiative effect is also stronger in summer (-12Wm-2) than in winter (-2Wm-2).We also show that modelling aerosol-radiation and aerosol-cloud interactions can lead to small changes in cloudiness, mainly regarding low-level clouds, and circulation anomalies in the lower and mid-troposphere, which in some cases, mainly close to the Black Sea in autumn, can be of statistical significance. Precipitation is not affected in a consistent pattern throughout the year by the aerosol implementation, and changes do not exceed-5% except for the case of unrealistically absorbing aerosol. Temperature, on the other hand, systematically decreases by-0.1 to-0.5 °C due to aerosol-radiation interactions with regional changes that can be up to-1.5 °C. © 2020 Authors."
"57216957220;55675283100;","Aerosol Indirect Effects on Cirrus Clouds Based on Global Aircraft Observations",2020,"10.1029/2019GL086550","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085497384&doi=10.1029%2f2019GL086550&partnerID=40&md5=3b56c1856866d4570a7a0cf7b165b7a9","Cirrus clouds have large climate impacts, yet aerosol indirect effects on cirrus microphysical properties remain highly uncertain. There is a lack of observational analysis on thermodynamic, dynamical, and aerosol indirect effects simultaneously, which limits the quantification of each effect. Using seven National Science Foundation aircraft campaigns, impacts of temperature, relative humidity, vertical velocity, and aerosols are individually quantified. Nonmonotonic correlations of ice water content, ice crystal number concentration (Ni), and mean diameter (Di) with respect to aerosol number concentrations (Na) are consistently seen at various conditions. Positive correlations become significant when Na &gt; 500 nm (Na500) and &gt;100 nm (Na100) are 3 and 10 times higher than average, respectively. While Na500 are more effective at temperatures closer to −40 °C with small vertical velocity fluctuations and are less sensitive to ice supersaturation, Na100 are more effective at colder temperatures with higher updraft and higher ice supersaturation, indicating heterogeneous and homogeneous nucleation mechanisms, respectively. © 2020. American Geophysical Union. All Rights Reserved."
"57195933651;57194152771;7003541446;7402538754;7004288217;","High Supersaturation in the Wake of Falling Hydrometeors: Implications for Cloud Invigoration and Ice Nucleation",2020,"10.1029/2020GL088055","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085492751&doi=10.1029%2f2020GL088055&partnerID=40&md5=261b35e32260b40c94712f7a79f15bf2","Aerosol particles, cloud droplets, and ice crystals, coupled through the supersaturation field, play an important role in the buoyancy and life cycle of convective clouds. This letter reports laboratory observations of copious cloud droplets and ice crystals formed in the wake of a warm, falling water drop, which is a laboratory surrogate for a relatively warm hydrometeor in atmospheric clouds, such as a graupel particle in the wet growth regime. Aerosols were activated in the regions of very high supersaturation due to mixing in the wake. A mechanism is explored for attaining very high supersaturations capable of activating significant fractions of the interstitial aerosols within the lifetime of a convective cloud. The latent heat released from the activation of interstitial aerosols and subsequent growth may provide an additional source of buoyancy for cloud invigoration and may lead to larger concentrations of ice crystals. ©2020. American Geophysical Union. All Rights Reserved."
"56448942200;55921734500;57202410843;","Evaluation of convective storms using spaceborne radars over the Indo-Gangetic Plains and western coast of India",2020,"10.1002/met.1917","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086989979&doi=10.1002%2fmet.1917&partnerID=40&md5=99df5e2eeffa18893ed40e929bc55a2d","Monsoonal convective systems are examined using four years (2014–2017) of radar reflectivity data from the Precipitation Features (PFs) database of the Global Precipitation Measurement (GPM) Microwave Imager (GMI) and Dual Precipitation Radar (DPR). The study classifies the cumulonimbus tower (PF-CbT) at 12 km, and intense convective clouds at both 3 km (PF-ICC3) and 8 km (PF-ICC8) based on PFs' reflectivity threshold at a reference height over the Indo-Gangetic Plains (IGP) and Indian Western coastal (WG) region, including the Arabian Sea and the Western Ghats. Results show that the regional variations are more enhanced for the PF-ICC3 clouds with high occurrence over the IGP region. In the mixed-phase regime, the median maximum reflectivity is greater for all cloud types over the IGP region. The occurrences of 20 and 40 dBZ echo the top height > 5 km is higher in the IGP region, indicating the deep and intense convection. The aerosol–cloud interaction is examined for warm and mixed-phase clouds. The vertical structure of aerosols shows the suppression of warm rainfall over the IGP region. However, rainfall intensity increases in mixed-phase clouds because of the dominancy of ice processes. The significant positive (negative) correlation is observed between the echo top height and aerosol concentrations over the IGP (WG) region. The value of the novel findings clearly states the region-specific demand for a closer examination of the radar reflectivity–aerosol interaction on regime-dependent clouds over the IGP region as well as contrasts against other regions for similar and contrasting cloud–aerosol-radiation interactions. © 2020 The Authors. Meteorological Applications published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"57212103352;8218839600;57189699116;38761582600;55667257200;24921898800;7004508767;12794036300;56411195600;","Anthropogenic Aerosols Significantly Reduce Mesoscale Convective System Occurrences and Precipitation Over Southern China in April",2020,"10.1029/2019GL086204","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082519352&doi=10.1029%2f2019GL086204&partnerID=40&md5=22416ae46a441d17e88d6b7ceab59977","Precipitation over Southern China in April, largely associated with mesoscale convective systems (MCSs), has declined significantly in recent decades. It is unclear how this decline in precipitation may be related to the concurrent increase of anthropogenic aerosols over this region. Here, using observation analyses and model simulations, we showed that increased levels of anthropogenic aerosols can significantly reduce MCS occurrences by 21% to 32% over Southern China in April, leading to less rainfall. Half of this MCS occurrence reduction was due to the direct radiative scattering of aerosols and the indirect enhancement of non-MCS liquid cloud reflectance by aerosols, which stabilized the regional atmosphere. The other half of the MCS occurrence reduction was due to the microphysical and dynamical responses of the MCS to aerosols. Our results demonstrated the complex effects of aerosols on MCSs via impacts on both the convective systems and on the regional atmosphere. © 2020 The Authors."
"56536745100;16024614000;12801992200;57194833104;","Deconvolution of boundary layer depth and aerosol constraints on cloud water path in subtropical stratocumulus decks",2020,"10.5194/acp-20-3609-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082607757&doi=10.5194%2facp-20-3609-2020&partnerID=40&md5=2e450142d055177761e5cc3705cc8302","The liquid water path (LWP) adjustment due to aerosol-cloud interactions in marine stratocumulus remains a considerable source of uncertainty for climate sensitivity estimates. An unequivocal attribution of LWP adjustments to changes in aerosol concentration from climatology remains difficult due to the considerable covariance between meteorological conditions alongside changes in aerosol concentrations. We utilise the susceptibility framework to quantify the potential change in LWP adjustment with boundary layer (BL) depth in subtropical marine stratocumulus. We show that the LWP susceptibility, i.e. the relative change in LWP scaled by the relative change in cloud droplet number concentration, in marine BLs triples in magnitude from <span classCombining double low line""inline-formula"">-0.1</span> to <span classCombining double low line""inline-formula"">-0.31</span> as the BL deepens from 300 to 1200&thinsp;m and deeper.</p> We further find deep BLs to be underrepresented in pollution tracks, process modelling, and in situ studies of aerosol-cloud interactions in marine stratocumulus. Susceptibility estimates based on these approaches are skewed towards shallow BLs of moderate LWP susceptibility. Therefore, extrapolating LWP susceptibility estimates from shallow BLs to the entire cloud climatology may underestimate the true LWP adjustment within subtropical stratocumulus and thus overestimate the effective aerosol radiative forcing in this region.</p> Meanwhile, LWP susceptibility estimates in deep BLs remain poorly constrained. While susceptibility estimates in shallow BLs are found to be consistent with process modelling studies, they overestimate pollution track estimates. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License."
"55577875600;7406500188;55717074000;57209113113;56384704800;56162305900;56459194500;56119479900;57192212652;","Impacts of wildfire aerosols on global energy budget and climate: The role of climate feedbacks",2020,"10.1175/JCLI-D-19-0572.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089613354&doi=10.1175%2fJCLI-D-19-0572.1&partnerID=40&md5=efd16e60fd75b9b4547894ee35eedf0b","Aerosols emitted from wildfires could significantly affect global climate through perturbing global radiation balance. In this study, the Community Earth System Model with prescribed daily fire aerosol emissions is used to investigate fire aerosols' impacts on global climate with emphasis on the role of climate feedbacks. The total global fire aerosol radiative effect (RE) is estimated to be 20.78 6 0.29 W m22, which is mostly from shortwave RE due to aerosol-cloud interactions (REaci; 20.70 6 0.20 W m22). The associated global annual-mean surface air temperature (SAT) change DT is 20.64 6 0.16 K with the largest reduction in the Arctic regions where the shortwave REaci is strong. Associated with the cooling, the Arctic sea ice is increased, which acts to reamplify the Arctic cooling through a positive ice-albedo feedback. The fast response (irrelevant to DT) tends to decrease surface latent heat flux into atmosphere in the tropics to balance strong atmospheric fire black carbon absorption, which reduces the precipitation in the tropical land regions (southern Africa and South America). The climate feedback processes (associated with DT) lead to a significant surface latent heat flux reduction over global ocean areas, which could explain most (;80%) of the global precipitation reduction. The precipitation significantly decreases in deep tropical regions (58N) but increases in the Southern Hemisphere tropical ocean, which is associated with the southward shift of the intertropical convergence zone and the weakening of Southern Hemisphere Hadley cell. Such changes could partly compensate the interhemispheric temperature asymmetry induced by boreal forest fire aerosol indirect effects, through intensifying the cross-equator atmospheric heat transport. © 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"57211144211;14829673100;55899443700;7007120936;","Global Climate and Human Health Effects of the Gasoline and Diesel Vehicle Fleets",2020,"10.1029/2019GH000240","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082201453&doi=10.1029%2f2019GH000240&partnerID=40&md5=896026483f54721eaf797417ffb1d813","The global gasoline and diesel fuel vehicle fleets impose substantial impacts on air quality, human health, and climate change. Here we quantify the global radiative forcing and human health impacts of the global gasoline and diesel sectors using the NCAR CESM global chemistry-climate model for year 2015 emissions from the IIASA GAINS inventory. Net global radiative effects of short-lived climate forcers (including aerosols, ozone, and methane) from the gasoline and diesel sectors are +13.6 and +9.4 mW m−2, respectively. The annual mean net aerosol contributions to the net radiative effects of gasoline and diesel are −9.6 ± 2.0 and +8.8 ± 5.8 mW m−2. Aerosol indirect effects for the gasoline and diesel road vehicle sectors are −16.6 ± 2.1 and −40.6 ± 4.0 mW m−2. The fractional contributions of short-lived climate forcers to the total global climate impact including carbon dioxide on the 20-year time scale are similar, 14.9% and 14.4% for gasoline and diesel, respectively. Global annual total PM2.5- and ozone-induced premature deaths for gasoline and diesel sectors approach 115,000 (95% CI: 69,000–153,600) and 122,100 (95% CI: 78,500–157,500), with corresponding years of life lost of 2.10 (95% CI: 1.23–2.66) and 2.21 (95% CI: 1.47–2.85) million years. Substantial regional variability of premature death rates is found for the diesel sector when the regional health effects are normalized by the annual total regional vehicle distance traveled. Regional premature death rates for the gasoline and diesel sectors, respectively, vary by a factor of eight and two orders of magnitude, with India showing the highest for both gasoline and diesel sectors. © 2020. The Authors."
"57191172390;7003789044;55225894400;8084443000;57202921054;57211565887;56250119900;","Constraining the Surface Flux of Sea Spray Particles From the Southern Ocean",2020,"10.1029/2019JD032026","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081088467&doi=10.1029%2f2019JD032026&partnerID=40&md5=78f9d5406750561a608c8aa56fe25a29","Modeling the shortwave radiation balance over the Southern Ocean region remains a challenge for Earth system models. To investigate whether this is related to the representation of aerosol-cloud interactions, we compared measurements of the total number concentration of sea spray-generated particles within the Southern Ocean region to model predictions thereof. Measurements were conducted from a container laboratory aboard the R/V Tangaroa throughout an austral summer voyage to the Ross Sea. We used source-receptor modeling to calculate the sensitivity of our measurements to upwind surface fluxes. From this approach, we could constrain empirical parameterizations of sea spray surface flux based on surface wind speed and sea surface temperature. A newly tuned parameterization for the flux of sea spray particles based on the near-surface wind speed is presented. Comparisons to existing model parameterizations revealed that present model parameterizations led to overestimations of sea spray concentrations. In contrast to previous studies, we found that including sea surface temperature as an explanatory variable did not substantially improve model-measurement agreement. To test whether or not the parameterization may be applicable globally, we conducted a regression analysis using a database of in situ whitecap measurements. We found that the key fitting parameter within this regression agreed well with the parameterization of sea spray flux. Finally, we compared calculations from the best model of surface flux to boundary layer measurements collected onboard an aircraft throughout the Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES), finding good agreement overall. ©2020. American Geophysical Union. All Rights Reserved."
"56190076100;7006219023;","Long-Term Trends of High Aerosol Pollution Events and Their Climatic Impacts in North America Using Multiple Satellite Retrievals and Modern-Era Retrospective Analysis for Research and Applications version 2",2020,"10.1029/2019JD031137","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85080982784&doi=10.1029%2f2019JD031137&partnerID=40&md5=e5ff254fe5bcf922ad75061264cf0662","Mean magnitudes and temporal trends in aerosol optical depth (AOD) from satellite observations and an aerosol reanalysis exhibit a negative-positive east-northwest dipole across the contiguous United States with large magnitude negative trends over the eastern United States while small magnitude positive trends over the northwestern states. Based on analyses of Modern-Era Retrospective Analysis for Research and Applications version 2, the AOD reduction over the eastern United States appears to be largely attributable to reductions in aerosol sulfate, while there have been marked increases in aerosol-organic and elemental carbon over almost all of the contiguous United States and particularly the northwestern states. Long-term trends of high aerosol pollution events (HAPEs; days with AOD over the long-term local 90th daily AOD percentile) during 2000–2017 also indicate that over the eastern United States, both the frequency and spatial scale of summer HAPEs exhibit significant negative trends, while those of moderate aerosol events (days with AOD between the local 30th and 70th AOD percentiles) exhibit weak upward trends. Opposing trends, of smaller magnitude, are derived in the northwestern United States and southwestern Canada. Net and shortwave solar radiation show positive trends at the surface and top of atmosphere under clear-sky conditions over the eastern United States consistent with the reduction in AOD. However, skin temperatures do not indicate significant trends during all days or HAPEs, indicating that the aerosol-induced radiation trends are not sufficient to manifest trends in surface temperature. Precipitation during HAPEs appears to have increased during 2000–2017 over the eastern and central United States, indicating that the reduction in aerosol may already be enhancing the precipitation through aerosol-cloud interactions. ©2020. American Geophysical Union. All Rights Reserved."
"56909903600;57217266035;24722339600;","Ultra-clean and smoky marine boundary layers frequently occur in the same season over the southeast Atlantic",2020,"10.5194/acp-20-2341-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85080882878&doi=10.5194%2facp-20-2341-2020&partnerID=40&md5=3264746820de9b99f5d301f147b24a38","We study 41 d with daily median surface accumulation mode aerosol particle concentrations below 50 cm-3 (ultra-clean conditions) observed at Ascension Island (ASI; 7.9_ S, 14.4_ W) between June 2016 and October 2017 as part of the Layered Atlantic Smoke Interactions with Clouds (LASIC) campaign. Interestingly, these days occur during a period of great relevance for aerosol-cloud-radiation interactions, the southeast Atlantic (SEATL) biomass-burning season (approximately June-October). That means that these critical months can feature both the highest surface aerosol numbers, from smoke intrusion into the marine boundary layer, as well as the lowest. While carbon monoxide and refractory black carbon concentrations on ultra-clean days do not approach those on days with heavy smoke, they also frequently exceed background concentrations calculated in the non-burning season from December 2016 to April 2017. This is evidence that even what become ultra-clean boundary layers can make contact with and entrain from an overlying SEATL smoke layer before undergoing a process of rapid aerosol removal. Because many ultra-clean and polluted boundary layers observed at Ascension Island during the biomass burning season follow similar isobaric back trajectories, the variability in this entrainment is likely more closely tied to the variability in the overlying smoke rather than large-scale horizontal circulation through the boundary layer. Since exceptionally low accumulation mode aerosol numbers at ASI do not necessarily indicate the relative lack of other trace pollutants, this suggests the importance of regional variations in what constitutes an ""ultra-clean"" marine boundary layer. Finally, surface drizzle rates, frequencies and accumulation - as well as retrievals of liquid water path - all consistently tend toward higher values on ultraclean days. This implicates enhanced coalescence scavenging in low clouds as the key driver of ultra-clean events in the southeast Atlantic marine boundary layer. These enhancements occur against and are likely mediated by the backdrop of a seasonal increase in daily mean cloud fraction and daily median liquid water path over ASI, peaking in September and October in both LASIC years. Therefore the seasonality in ultra-clean day occurrence seems directly linked to the seasonality in SEATL cloud properties. These results highlight the importance of two-way aerosol-cloud interactions in the region. © 2020 BMJ Publishing Group. All rights reserved."
"7007067997;7003799326;36781333600;7004346367;","CMIP5 Climate Models Overestimate Cooling by Volcanic Aerosols",2020,"10.1029/2020GL087047","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079574776&doi=10.1029%2f2020GL087047&partnerID=40&md5=57fb0a25496fe0e20a1de99c0facbaf9","We compare projections of the observed hemispherical mean surface temperature (HadCRUT4.6.0.0) and the ensemble mean of CMIP5 climate models' simulations on a set of standard regression model forcing variables. We find that the volcanic aerosol regression coefficients of the CMIP5 simulations are consistently significantly larger (by 40–49%) than the volcanic aerosol coefficients of the observed temperature. The probability that the observed differences are caused just by chance is much less than 0.01. The overestimate is due to the climate models' response to volcanic aerosol radiative forcing. The largest overestimate occurs in the winter season of each hemisphere. We hypothesize that the models' parameterization of aerosol-cloud interactions within ice and mixed phase clouds is a likely source of this discrepancy. Furthermore, the models significantly underestimate the effect of solar variability on temperature for both hemispheres. ©2020. American Geophysical Union. All Rights Reserved."
"57189634238;8511991900;35849722200;57195922668;","Aerosol Impacts on Mesoscale Convective Systems Forming Under Different Vertical Wind Shear Conditions",2020,"10.1029/2018JD030027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079461772&doi=10.1029%2f2018JD030027&partnerID=40&md5=f942f1b59ba7d16d644a73d0960de3fd","Following our previous study of wind shear effect on mesoscale convective system (MCS) organization under a clean atmospheric condition using the Weather Research and Forecasting model coupled with spectral-bin microphysics, we conduct sensitivity simulations by increasing cloud condensation nuclei concentration to investigate aerosol impacts on MCSs forming under different wind shear conditions. We find that increased aerosols induce stronger updrafts and downdrafts in all MCSs. The stronger updrafts and enlarged convective core area contribute to larger vertical mass fluxes and enhance precipitation. The enhanced updrafts and vertical mass fluxes indicate convective invigoration. Increased updraft speed below 8-km altitude is attributed to enhanced condensational heating, except for the weak wind shear and strong low-level shear cases in which the enhanced low-level convergence is another contributing factor. Interestingly, above 8-km altitude, we see reduced updraft speed by the increased aerosols due to reduced vertical pressure perturbation gradient force. The accumulated rainfall and mean rain rate are increased with a greater occurrence frequency of heavy rain. Larger rain rate is seen in both convective and stratiform regions. In general, we see a higher frequency of deep clouds in the polluted condition because of invigorated convection, and more stratiform/anvil clouds, but a lower frequency of shallow warm clouds, with a larger significance for more organized MCSs. The consistently invigorated MCSs by aerosols under various wind shear conditions revealed by this study have important implications to weather and climate in warm and humid regions that are influenced by pollution. ©2020. American Geophysical Union. All Rights Reserved."
"56346491900;55255714600;7005143387;","Impacts of some co-dissolved inorganics on in-cloud photochemistry of aqueous brown carbon",2020,"10.1016/j.atmosenv.2019.117250","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077383508&doi=10.1016%2fj.atmosenv.2019.117250&partnerID=40&md5=2884c772c9a9ed11da69d7646bbee125","This experimental study explored the impacts of some codissolved inorganic ions (in particular, sulfate, nitrate and chloride) on the photo-bleaching kinetics of the aqueous solutions of brown carbon (BrC) extracted from rice-straw smoldering aerosol. All the aqueous BrC solutions showed two distinct phases of decreasing mass absorption coefficient (MAC) with irradiation time, where the first phase (0–1h) was 2.4–5.3 times faster than the second phase (1–3h). Interestingly, the photo-bleaching process was slowed down for both phases when SO42− (0–1h: 0.196±0.02 h−1; 1–3h: 0.045±0.01 h−1), NO3− (0–1h: 0.158±0.004 h−1; 1–3h: 0.066±0.007 h−1) and Cl− (0–1h: 0.169±0.007 h−1; 1–3h: 0.032±0.006 h−1) salt solutions were added separately to the BrC extracts (0–1h: 0.27±0.04 h−1; 1–3h: 0.067±0.01 h−1). Alternatively, the corresponding lifetimes of the light-absorbing organic species were enhanced in the salt-added BrC solutions. In addition, the magnitudes of the fluorescence quantum yields were measured to be of the order of 10−3−10−2, implying that most of the absorbed solar energy would convert into heat rather than fluorescing back into the atmosphere. The findings of this study are suggestive of possible increase in heating of BrC containing atmospheric aqueous bodies like cloud-water, resulting in water evaporation and hence reduced precipitation (semi-direct effect). © 2019 Elsevier Ltd"
"55855213300;37032042300;23095483400;6506718302;55826210400;6504793116;6701620591;7006960661;57194590416;7006712143;57203053317;","Evaluation of aerosol and cloud properties in three climate models using MODIS observations and its corresponding COSP simulator, as well as their application in aerosol-cloud interactions",2020,"10.5194/acp-20-1607-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079389644&doi=10.5194%2facp-20-1607-2020&partnerID=40&md5=a95db30090dd126b0b57f1469c137ec8","The evaluation of modelling diagnostics with appropriate observations is an important task that establishes the capabilities and reliability of models. In this study we compare aerosol and cloud properties obtained from three different climate models (ECHAM-HAM, ECHAM-HAMSALSA, and NorESM) with satellite observations using Moderate Resolution Imaging Spectroradiometer (MODIS) data. The simulator MODIS-COSP version 1.4 was implemented into the climate models to obtain MODIS-like cloud diagnostics, thus enabling model-to-model and modelto-satellite comparisons. Cloud droplet number concentrations (CDNCs) are derived identically from MODIS-COSPsimulated and MODIS-retrieved values of cloud optical depth and effective radius. For CDNC, the models capture the observed spatial distribution of higher values typically found near the coasts, downwind of the major continents, and lower values over the remote ocean and land areas. However, the COSP-simulated CDNC values are higher than those observed, whilst the direct model CDNC output is significantly lower than the MODIS-COSP diagnostics. NorESM produces large spatial biases for ice cloud properties and thick clouds over land. Despite having identical cloud modules, ECHAM-HAM and ECHAM-HAM-SALSA diverge in their representation of spatial and vertical distributions of clouds. From the spatial distributions of aerosol optical depth (AOD) and aerosol index (AI), we find that NorESM shows large biases for AOD over bright land surfaces, while discrepancies between ECHAM-HAM and ECHAM-HAM-SALSA can be observed mainly over oceans. Overall, the AIs from the different models are in good agreement globally, with higher negative biases in the Northern Hemisphere. We evaluate the aerosol-cloud interactions by computing the sensitivity parameter ACICDNC D dln.CDNC/=dln.AI/on a global scale. However, 1 year of data may be considered not enough to assess the similarity or dissimilarities of the models due to large temporal variability in cloud properties. This study shows how simulators facilitate the evaluation of cloud properties and expose model deficiencies, which are necessary steps to further improve the parameterisation in climate models. © 2020 Author(s)."
"57208274214;35119188100;14020751800;55704350200;57189294502;57202531041;35461763400;36106033000;15925588200;57191750766;36515307600;35774441900;57189368623;55942083800;7102084129;7004944088;57189215242;57190209035;","The challenge of simulating the sensitivity of the Amazonian cloud microstructure to cloud condensation nuclei number concentrations",2020,"10.5194/acp-20-1591-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079430665&doi=10.5194%2facp-20-1591-2020&partnerID=40&md5=cae25401c7265cdbfe97e32f5ac861c3","The realistic representation of aerosol-cloud interactions is of primary importance for accurate climate model projections. The investigation of these interactions in strongly contrasting clean and polluted atmospheric conditions in the Amazon region has been one of the motivations for several field campaigns, including the airborne ""Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems-Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modeling and to the GPM (Global Precipitation Measurement) (ACRIDICON-CHUVA)"" campaign based in Manaus, Brazil, in September 2014. In this work we combine in situ and remotely sensed aerosol, cloud, and atmospheric radiation data collected during ACRIDICONCHUVA with regional, online-coupled chemistry-transport simulations to evaluate the model's ability to represent the indirect effects of biomass burning aerosol on cloud microphysical and optical properties (droplet number concentration and effective radius). We found agreement between the modeled and observed median cloud droplet number concentration (CDNC) for low values of CDNC, i.e., low levels of pollution. In general, a linear relationship between modeled and observed CDNC with a slope of 0.3 was found, which implies a systematic underestimation of modeled CDNC when compared to measurements. Variability in cloud condensation nuclei (CCN) number concentrations was also underestimated, and cloud droplet effective radii (reff) were overestimated by the model. Modeled effective radius profiles began to saturate around 500 CCN cm-3 at cloud base, indicating an upper limit for the model sensitivity well below CCN concentrations reached during the burning season in the Amazon Basin. Additional CCN emitted from local fires did not cause a notable change in modeled cloud droplet effective radii. Finally, we also evaluate a parameterization of CDNC at cloud base using more readily available cloud microphysical properties, showing that we are able to derive CDNC at cloud base from cloud-side remote-sensing observations. © 2020 Author(s)."
"37111900500;57193877432;7201472576;56597778200;7003861526;","Satellite observations of aerosols and clouds over southern China from 2006 to 2015: Analysis of changes and possible interaction mechanisms",2020,"10.5194/acp-20-457-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078241456&doi=10.5194%2facp-20-457-2020&partnerID=40&md5=2c912f5fff5f5ef582540520df073ac3","Aerosol and cloud properties over southern China during the 10-year period 2006-2015 are analysed based on observations from passive and active satellite sensors and emission data. The results show a strong decrease in aerosol optical depth (AOD) over the study area, accompanied by an increase in liquid cloud cover and cloud liquid water path (LWP). The most significant changes occurred mainly in late autumn and early winter: AOD decreased by about 35%, coinciding with an increase in liquid cloud fraction by 40% and a near doubling of LWP in November and December. Analysis of emissions suggests that decreases in carbonaceous aerosol emissions from biomass burning activities were responsible for part of the AOD decrease, while inventories of other, anthropogenic emissions mainly showed increases. Analysis of precipitation changes suggests that an increase in precipitation also contributed to the overall aerosol reduction. Possible explanatory mechanisms for these changes were examined, including changes in circulation patterns and aerosol-cloud interactions (ACIs). Further analysis of changes in aerosol vertical profiles demonstrates a consistency of the observed aerosol and cloud changes with the aerosol semi-direct effect, which depends on relative heights of the aerosol and cloud layers: fewer absorbing aerosols in the cloud layer would lead to an overall decrease in the evaporation of cloud droplets, thus increasing cloud LWP and cover. While this mechanism cannot be proven based on the present observation-based analysis, these are indeed the signs of the reported changes. © Author(s) 2020."
"8412334000;55957189000;7003696273;7102578937;6603247427;57203054070;57204303593;35336992600;24398842400;6602600408;57201613655;7102807964;7404732357;7006717176;18438817800;57189498750;","The research unit volimpact: Revisiting the volcanic impact on atmosphere and climate - preparations for the next big volcanic eruption",2020,"10.1127/metz/2019/0999","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082491199&doi=10.1127%2fmetz%2f2019%2f0999&partnerID=40&md5=17e2656999f67399e0c4f70bf4ba4853","This paper provides an overview of the scientific background and the research objectives of the Research Unit “VolImpact” (Revisiting the volcanic impact on atmosphere and climate - preparations for the next big volcanic eruption, FOR 2820). VolImpact was recently funded by the Deutsche Forschungsgemeinschaft (DFG) and started in spring 2019. The main goal of the research unit is to improve our understanding of how the climate system responds to volcanic eruptions. Such an ambitious program is well beyond the capabilities of a single research group, as it requires expertise from complementary disciplines including aerosol microphysical modelling, cloud physics, climate modelling, global observations of trace gas species, clouds and stratospheric aerosols. The research goals will be achieved by building on important recent advances in modelling and measurement capabilities. Examples of the advances in the observations include the now daily near-global observations of multi-spectral aerosol extinction from the limb-scatter instruments OSIRIS, SCIAMACHY and OMPS-LP. In addition, the recently launched SAGE III/ISS and upcoming satellite missions EarthCARE and ALTIUS will provide high resolution observations of aerosols and clouds. Recent improvements in modeling capabilities within the framework of the ICON model family now enable simulations at spatial resolutions fine enough to investigate details of the evolution and dynamics of the volcanic eruptive plume using the large-eddy resolving version, up to volcanic impacts on larger-scale circulation systems in the general circulation model version. When combined with state-of-the-art aerosol and cloud microphysical models, these approaches offer the opportunity to link eruptions directly to their climate forcing. These advances will be exploited in VolImpact to study the effects of volcanic eruptions consistently over the full range of spatial and temporal scales involved, addressing the initial development of explosive eruption plumes (project VolPlume), the variation of stratospheric aerosol particle size and radiative forcing caused by volcanic eruptions (VolARC), the response of clouds (VolCloud), the effects of volcanic eruptions on atmospheric dynamics (VolDyn), as well as their climate impact (VolClim). © 2020 The authors"
"57208383202;55277859100;16445036300;54404323500;57195056873;55781928800;56923937200;7201920350;","Simulation of the responses of rainstorm in the Yangtze River Middle Reaches to changes in anthropogenic aerosol emissions",2020,"10.1016/j.atmosenv.2019.117081","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074483177&doi=10.1016%2fj.atmosenv.2019.117081&partnerID=40&md5=4898b02c778fc0d19ed6ac20251a1132","The model WRF-Chem sensitivity simulation experiments with changing intensity of anthropogenic emissions sources were applied to simulate a rainstorm process in the Yangtze River Middle Reaches (YRMR) during June 18–19, 2018 to study the responses of clouds and precipitation in the rainstorm to changes in aerosol concentrations in this region. The simulation experiments revealed that the aerosol-cloud interaction during low and high emission phases tended to inhibit and to enhance the precipitation process with the precipitation peak lagging 1–2 h. In the later period of rainstorm, high concentrations of aerosols improved precipitation efficiency significantly, resulting in more centralized clusters of intense precipitation. The cloud droplet number concentrations and cloud water contents demonstrated an increasing logarithmic relationship with increasing PM2.5 concentrations. The PM2.5 concentration of about 25 μg/m3 was estimated as the response threshold of cloud droplet number concentrations from sharp to smooth changes. Before and after the peak precipitation, the relationship between the average precipitation rates and PM2.5 concentrations presented an inverse power function. Aerosol-induced precipitation changes were sensitive to ambient relative humidity (RH). When 80% ≤ RH &lt; 85%, the response of precipitation to aerosol emissions was in equilibrium. When RH &lt; 80% or RH &gt; 85% increasing anthropogenic aerosol emissions tended to inhibit or enhance precipitation, especially in the case of low (high) aerosol emissions. © 2019 Elsevier Ltd"
"57208313489;24765069600;24080610100;35113492400;57212669015;57095410800;57212669535;57212669565;57203100417;57193679498;","A New Method for Distinguishing Unactivated Particles in Cloud Condensation Nuclei Measurements: Implications for Aerosol Indirect Effect Evaluation",2019,"10.1029/2019GL085379","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077295464&doi=10.1029%2f2019GL085379&partnerID=40&md5=b19723be9db15a8c9e877bd70e11d003","An ongoing challenge for cloud condensation nuclei (CCN) measurements is the inclusion of unactivated particles, which affects droplet activation parameterizations and aerosol indirect effects in models. For the first time, a reciprocal relationship between the critical diameter and critical supersaturation of activated droplets from the κ-Köhler theory is derived to accurately count unactivated particles in CCN measurements. We conducted 4-day continuous observations to simultaneously measure the number concentration of CCN (NCCN) and aerosol. The results show that as supersaturation (SS) decreases from 0.186% at 25 °C, the proportion of the unactivated particles in the CCN measurements increases, reaching 88% at SS of 0.07%. Owing to the NCCN overestimation caused by NCCN-SS parameterizations with uncorrected NCCN, there is significant overestimation of aerosol indirect effects, especially under low SS conditions. After removing unactivated particles, NCCN-SS parameterizations are adjusted accordingly, which can improve simulations of aerosol-cloud-radiation interactions in models. ©2019. The Authors."
"55366700000;6506152198;56482796700;24402359000;7003591311;","Anthropogenic Air Pollution Delays Marine Stratocumulus Breakup to Open Cells",2019,"10.1029/2019GL085412","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076152967&doi=10.1029%2f2019GL085412&partnerID=40&md5=7dc138191373a4d3546477dca9e7f2fe","Marine stratocumulus cloud (Sc) decks with high cloud fraction typically breakup when sufficient drizzle forms. Cloud breakup leads to a lower cloud radiative effect due to the lower cloud amount. Here we use realistic Lagrangian large eddy simulations along a 3-day trajectory, evaluated with satellite observations, to investigate the timing of Sc breakup in response to aerosol conditions. We show that the timing of the breakup is strongly modulated by the diurnal cycle and large-scale meteorology but varies systematically with the initial aerosol concentration: the more polluted the clouds, the later the breakup. This indicates that the cloud radiative effect via cloud cover adjustments is not saturated, in contrast to the effect of aerosol on cloud albedo at fixed cloudiness, which weakens with increasing aerosol levels. The results also show that the cloud radiative impact of anthropogenic aerosol is strongest far from its origin over land. ©2019. The Authors."
"57212032560;7406523040;55962449900;57215439770;57188681995;","Climate impacts of the biomass burning in Indochina on atmospheric conditions over Southern China",2019,"10.4209/aaqr.2019.01.0028","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075786934&doi=10.4209%2faaqr.2019.01.0028&partnerID=40&md5=7a07cfdfeaff1cb00c82de12ecdd85a7","Substantial biomass burning (BB) activities in Indochina during March and April of each year generate aerosols that are transported via westerly winds to southern China. These BB aerosols have both radiative (direct and semi-direct) and indirect effects on the climate. This study evaluates impacts of BB in Indochina during April 2013 on atmospheric conditions in southern China using WRF-Chem sensitivity simulations. We show that the atmosphere becomes drier and hotter under the aerosol radiative effect in southern China, while the changes linked to the indirect effect are opposite. The former (the latter) rises (reduces) surface temperature 0.13°C (0.19°C) and decrease (increase) water vapor mixing ratios 0.23 g kg–1 (0.40 g kg–1) at 700 hPa. Atmospheric responses to aerosols in turn affect aerosol dissipation. Specifically, BB aerosols absorb solar radiation and heat the local atmosphere, which inhibits the formation of clouds (reducing low-level cloud about 7%) related to the aerosol semi-direct effect. Less cloud enhances surface solar radiation flux and temperature. Otherwise, northeasterly winds linked to radiative effect suppress water vapor transport. In this case, precipitation reduces 1.09 mm day–1, diminishing wet removal and westward transport of aerosols. Under the indirect effect, greater cloud coverage is formed, which reduces surface solar radiation flux and increases local latent heat release. This extra heating promotes air convection and diffusion of pollution. Regional mean precipitation increases 0.49 mm d–1, facilitating wet pollution removal. Under indirect effect, aerosol extinction coefficient reduces 0.011 km–1 at 2-km height over southern China. However, it increases around 0.002 km–1 at 3-km height over southernmost China related to radiative effect. Therefore, atmospheric changes linked to indirect effect play a greater role in removing pollutants from the atmosphere than radiative effect over southern China. © Taiwan Association for Aerosol Research."
"57189712592;55607020000;38762392200;56611366900;35849722200;","Distinct Impacts of Increased Aerosols on Cloud Droplet Number Concentration of Stratus/Stratocumulus and Cumulus",2019,"10.1029/2019GL085081","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075448325&doi=10.1029%2f2019GL085081&partnerID=40&md5=d17856bc2a3545d0314e4670ca8ceb3a","In situ aircraft measurements obtained during the RACORO field campaign are analyzed to study the aerosol effects on different cloud regimes. The results show that with increasing cloud condensation nuclei (CCN), cloud droplet number concentration (Nd) significantly increases in stratocumulus (Sc) while remains almost unchanged in cumulus (Cu). By using a new approach to strictly constrain the dynamics in Cu, we found that neither simultaneously changing cloud dynamics nor dilution of cloud water induced by entrainment-mixing can explain the observed insensitivity of Nd. The different degree of reduction in cloud supersaturation caused by increasing aerosols might be responsible for the observed different aerosol indirect effect between Sc and Cu. ©2019. American Geophysical Union. All Rights Reserved."
"55915364000;7403401100;57189377456;17341189400;8084443000;24081268200;8980175400;35771409400;","Aerosol-cloud closure study on cloud optical properties using remotely piloted aircraft measurements during a BACCHUS field campaign in Cyprus",2019,"10.5194/acp-19-13989-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075737330&doi=10.5194%2facp-19-13989-2019&partnerID=40&md5=b0644da5e9f4580b8a7bb9de5e296bfd","<p>In the framework of the EU-FP7 BACCHUS (impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: Towards a Holistic UnderStanding) project, an intensive field campaign was performed in Cyprus (March 2015). Remotely piloted aircraft system (RPAS), ground-based instruments, and remote-sensing observations were operating in parallel to provide an integrated characterization of aerosol-cloud interactions. Remotely piloted aircraft (RPA) were equipped with a five-hole probe, pyranometers, pressure, temperature and humidity sensors, and measured vertical wind at cloud base and cloud optical properties of a stratocumulus layer. Ground-based measurements of dry aerosol size distributions and cloud condensation nuclei spectra, and RPA observations of updraft and meteorological state parameters are used here to initialize an aerosol-cloud parcel model (ACPM) and compare the in situ observations of cloud optical properties measured by the RPA to those simulated in the ACPM. Two different cases are studied with the ACPM, including an adiabatic case and an entrainment case, in which the in-cloud temperature profile from RPA is taken into account. Adiabatic ACPM simulation yields cloud droplet number concentrations at cloud base (approximately 400&thinsp;cm<span classCombining double low line""inline-formula"">-3</span>) that are similar to those derived from a Hoppel minimum analysis. Cloud optical properties have been inferred using the transmitted fraction of shortwave radiation profile measured by downwelling and upwelling pyranometers mounted on a RPA, and the observed transmitted fraction of solar radiation is then compared to simulations from the ACPM. ACPM simulations and RPA observations shows better agreement when associated with entrainment compared to that of an adiabatic case. The mean difference between observed and adiabatic profiles of transmitted fraction of solar radiation is 0.12, while this difference is only 0.03 between observed and entrainment profiles. A sensitivity calculation is then conducted to quantify the relative impacts of 2-fold changes in aerosol concentration, and updraft to highlight the importance of accounting for the impact of entrainment in deriving cloud optical properties, as well as the ability of RPAs to leverage ground-based observations for studying aerosol-cloud interactions.</p>. © 2019 American Institute of Physics Inc.. All rights reserved."
"57202638281;6508333712;24398842400;35219670500;","Relative impact of aerosol, soil moisture, and orography perturbations on deep convection",2019,"10.5194/acp-19-12343-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85073237467&doi=10.5194%2facp-19-12343-2019&partnerID=40&md5=39f2809f2c009dd3574bc3b36c909727","The predictability of deep moist convection depends on many factors, such as the synoptic-scale flow, the geographical region (i.e., the presence of mountains), and land surface-atmosphere as well as aerosol-cloud interactions. This study addresses all these factors by investigating the relative impact of orography, soil moisture, and aerosols on precipitation over Germany in different weather regimes. To this end, we conduct numerical sensitivity studies with the COnsortium for Small-sale MOdelling (COSMO) model at high spatial resolution (500 m grid spacing) for 6 days with weak and strong synoptic forcing. The numerical experiments consist of (i) successive smoothing of topographical features, (ii) systematic changes in the initial soil moisture fields (spatially homogeneous increase/decrease, horizontal uniform soil moisture, different realizations of dry/wet patches), and (iii) different assumptions about the ambient aerosol concentration (spatially homogeneous and heterogeneous fields). Our results show that the impact of these perturbations on precipitation is on average higher for weak than for strong synoptic forcing. Soil moisture and aerosols are each responsible for the maximum precipitation response for three of the cases, while the sensitivity to terrain forcing always shows the smallest spread. For the majority of the analyzed cases, the model produces a positive soil moisture-precipitation feedback when averaged over the entire model domain. Furthermore, the amount of soil moisture affects precipitation more strongly than its spatial distribution. The precipitation response to changes in the CCN concentration is more complex and case dependent. The smoothing of terrain shows weaker impacts on days with strong synoptic forcing because surface fluxes are less important and orographic ascent is still simulated reasonably well, despite missing fine-scale orographic features. We apply an object-based characterization to identify whether and how the perturbations affect the structure, location, timing, and intensity of precipitation. These diagnostics reveal that the structure component, comparing the size and shape of precipitating objects to the reference simulation, is on average highest in the soil moisture and aerosol simulations, often due to changes in the maximum precipitation amounts. This indicates that the dominant mechanisms for convection initiation remain but that precipitation amounts depend on the strength of the trigger mechanisms. Location and amplitude parameters both vary over a much smaller range. Still, the temporal evolution of the amplitude component correlates well with the rain rate. Our results suggest that for quantitative precipitation forecasting, both aerosols and soil moisture are of similar importance and that their inclusion in convective-scale ensemble forecasting containing classical sources of uncertainty should be assessed in the future. © 2019 Author(s). This work is distributed under the Creative Commons Attribution 4.0 License."
"57192226380;57207225911;57217772325;57211500284;57211502431;55718267600;8239701900;12753965200;","New global view of above-cloud absorbing aerosol distribution based on CALIPSO measurements",2019,"10.3390/rs11202396","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074192462&doi=10.3390%2frs11202396&partnerID=40&md5=e0e40bc857e20589dba75010850a5a35","Above-low-level-cloud aerosols (ACAs) have gradually gained more interest in recent years; however, the combined aerosol-cloud radiation effects are not well understood. The uncertainty about the radiative effects of aerosols above cloud mainly stems from the lack of comprehensive and accurate retrieval of aerosols and clouds for ACA scenes. In this study, an improved ACA identification and retrieval methodology was developed to provide a new global view of the ACA distribution by combining three-channel CALIOP (The Cloud-Aerosol Lidar with Orthogonal Polarization) observations. The new method can reliably identify and retrieve both thin and dense ACA layers, providing consistent results between the day- and night-time retrieval of ACAs. Then, new four-year (2007 to 2010) globalACAdatasets were built, and new seasonal mean views of globalACAoccurrence, optical depth, and geometrical thickness were presented and analyzed. Further discussion on the relative position of ACAs to low clouds showed that the mean distance between the ACA layer and the low cloud deck over the tropical Atlantic region is less than 0.2 km. This indicates that the ACAs over this region are more likely to be mixed with low-level clouds, thereby possibly influencing the cloud microphysics over this region, contrary to findings reported from previous studies. The results not only help us better understand global aerosol transportation and aerosol-cloud interactions but also provide useful information for model evaluation and improvements. © 2019 by the authors."
"57202977053;57209296376;57201667638;56544915700;26030052000;15923105200;","A high-speed particle phase discriminator (PPD-HS) for the classification of airborne particles, as tested in a continuous flow diffusion chamber",2019,"10.5194/amt-12-3183-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067259848&doi=10.5194%2famt-12-3183-2019&partnerID=40&md5=ff24ecdc6e7bba88bf2dde7df78ee37f","A new instrument, the High-speed Particle Phase Discriminator (PPD-HS), developed at the University of Hertfordshire, for sizing individual cloud hydrometeors and determining their phase is described herein. PPD-HS performs an in situ analysis of the spatial intensity distribution of near-forward scattered light for individual hydrometeors yielding shape properties. Discrimination of spherical and aspherical particles is based on an analysis of the symmetry of the recorded scattering patterns. Scattering patterns are collected onto two linear detector arrays, reducing the complete 2-D scattering pattern to scattered light intensities captured onto two linear, one-dimensional strips of light sensitive pixels. Using this reduced scattering information, we calculate symmetry indicators that are used for particle shape and ultimately phase analysis. This reduction of information allows for detection rates of a few hundred particles per second. Here, we present a comprehensive analysis of instrument performance using both spherical and aspherical particles generated in a well-controlled laboratory setting using a vibrating orifice aerosol generator (VOAG) and covering a size range of approximately 3-32&thinsp;μm. We use supervised machine learning to train a random forest model on the VOAG data sets that can be used to classify any particles detected by PPD-HS. Classification results show that the PPD-HS can successfully discriminate between spherical and aspherical particles, with misclassification below 5% for diameters &gt;3μm. This phase discrimination method is subsequently applied to classify simulated cloud particles produced in a continuous flow diffusion chamber setup. We report observations of small, near-spherical ice crystals at early stages of the ice nucleation experiments, where shape analysis fails to correctly determine the particle phase. Nevertheless, in the case of simultaneous presence of cloud droplets and ice crystals, the introduced particle shape indicators allow for a clear distinction between these two classes, independent of optical particle size. From our laboratory experiments we conclude that PPD-HS constitutes a powerful new instrument to size and discriminate the phase of cloud hydrometeors. The working principle of PPD-HS forms a basis for future instruments to study microphysical properties of atmospheric mixed-phase clouds that represent a major source of uncertainty in aerosol-indirect effect for future climate projections.. © Author(s) 2019."
"57209173299;57200790124;","Droplet inhomogeneity in shallow cumuli: The effects of in-cloud location and aerosol number concentration",2019,"10.5194/acp-19-7297-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85066743400&doi=10.5194%2facp-19-7297-2019&partnerID=40&md5=029d506b49c268f8dfab3b258fcc10a7","Aerosol-cloud interactions are complex, including albedo and lifetime effects that cause modifications to cloud characteristics. With most cloud-aerosol interactions focused on the previously stated phenomena, there have been no in situ studies that focus explicitly on how aerosols can affect large-scale (centimeters to tens of meters) droplet inhomogeneities within clouds. This research therefore aims to gain a better understanding of how droplet inhomogeneities within cumulus clouds can be influenced by in-cloud droplet location (cloud edge vs. center) and the surrounding environmental aerosol number concentration. The pair-correlation function (PCF) is used to identify the magnitude of droplet inhomogeneity from data collected on board the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft, flown during the 2006 Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS). Time stamps (at 10-4m spatial resolution) of cloud droplet arrival times were measured by the Artium Flight phase-Doppler interferometer (PDI). Using four complete days of data with 81 non-precipitating cloud penetrations organized into two flights of low-pollution (L1, L2) and high-pollution (H1, H2) data shows enhanced inhomogeneities near cloud edge as compared to cloud center for all four cases. Low-pollution clouds are shown to have enhanced overall inhomogeneity, with flight L2 being solely responsible for this enhanced inhomogeneity. Analysis suggests cloud age plays a larger role in the amount of inhomogeneity experienced than the aerosol number concentration, with dissipating clouds showing increased inhomogeneities as compared to growing or mature clouds. Results using a single, vertically developed cumulus cloud demonstrate enhanced droplet inhomogeneity near cloud top as compared to cloud base. © Author(s) 2019."
"57208394173;24398842400;","Aerosol-Cloud-Precipitation Interactions in the Context of Convective Self-Aggregation",2019,"10.1029/2018MS001523","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064667146&doi=10.1029%2f2018MS001523&partnerID=40&md5=f109b1a6953190bb624601fcd5a9ece9","We investigate the sensitivity of self-aggregated radiative-convective-equilibrium cloud-resolving model simulations to the cloud condensation nuclei (CCN) concentration. Experiments were conducted on a long (2,000-km × 120-km) channel domain, allowing the emergence of multiple convective clusters and dry regions of subsidence. Increasing the CCN concentration leads to increased moisture in the dry regions, increased midlevel and upper level clouds, decreased radiative cooling, and decreased precipitation. We find that these trends follow from a decrease in the strength of the self-aggregation as measured by the moist static energy (MSE) variance. In our simulations, precipitation is correlated, both locally and in total, with the distribution of MSE anomalies. We thus quantify changes in the adiabatic/diabatic contributions to MSE anomalies (Wing & Emanuel, 2014, https://doi.org/10.1002/2013MS000269) and relate those changes to changes in precipitation. Through a simple two-column conceptual model, we argue that the reduction in precipitation can be explained thermodynamically by the reduction in mean net radiative cooling and mechanistically by the weakening of the area-weighted radiatively driven subsidence velocity—defined as the ratio of the total radiative cooling over the dry regions and the static stability. We interpret the system's response to increasing CCN as a thermodynamically constrained realization of an aerosol indirect effect on clouds and precipitation. ©2019. The Authors."
"56553589800;8586682800;7102745183;","Understanding aerosol-cloud interactions through modeling the development of orographic cumulus congestus during IPHEx",2019,"10.5194/acp-19-1413-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061075483&doi=10.5194%2facp-19-1413-2019&partnerID=40&md5=7963f62819e99872b54c8a48cd82e61c","A new cloud parcel model (CPM) including activation, condensation, collision-coalescence, and lateral entrainment processes is used to investigate aerosol-cloud interactions (ACIs) in cumulus development prior to rainfall onset. The CPM was applied with surface aerosol measurements to predict the vertical structure of cloud development at early stages, and the model results were evaluated against airborne observations of cloud microphysics and thermodynamic conditions collected during the Integrated Precipitation and Hydrology Experiment (IPHEx) in the inner region of the southern Appalachian Mountains (SAM). Sensitivity analysis was conducted to examine the model response to variations in key ACI physiochemical parameters and initial conditions. The CPM sensitivities mirror those found in parcel models without entrainment and collision-coalescence, except for the evolution of the droplet spectrum and liquid water content with height. Simulated cloud droplet number concentrations (CDNCs) exhibit high sensitivity to variations in the initial aerosol concentration at cloud base, but weak sensitivity to bulk aerosol hygroscopicity. The condensation coefficient ac plays a governing role in determining the evolution of CDNC, liquid water content (LWC), and cloud droplet spectra (CDS) in time and with height. Lower values of ac lead to higher CDNCs and broader CDS above cloud base, and higher maximum supersaturation near cloud base. Analysis of model simulations reveals that competitive interference among turbulent dispersion, activation, and droplet growth processes modulates spectral width and explains the emergence of bimodal CDS and CDNC heterogeneity in aircraft measurements from different cloud regions and at different heights. Parameterization of nonlinear interactions among entrainment, condensational growth, and collision-coalescence processes is therefore necessary to simulate the vertical structures of CDNCs and CDSs in convective clouds. Comparisons of model predictions with data suggest that the representation of lateral entrainment remains challenging due to the spatial heterogeneity of the convective boundary layer and the intricate 3-D circulations in mountainous regions. © Author(s) 2019."
"57195398231;56892889800;7501757094;","Aerosol direct radiative and cloud adjustment effects on surface climate over eastern China: Analyses of WRF model simulations",2019,"10.1175/JCLI-D-18-0236.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061009604&doi=10.1175%2fJCLI-D-18-0236.1&partnerID=40&md5=edbca167f2b1bef440030222e94ce281","The WRF-simulated changes in clouds and climate due to the increased anthropogenic aerosols for the summers of 2002-08 (vs the 1970s) over eastern China were used to offline calculate the radiative forcings associated with aerosol-radiation (AR) and aerosol-cloud-radiation (ACR) interactions, which subsequently facilitated the interpretation of surface temperature changes. During this period, the increases of aerosol optical depth (ΔAOD) averaged over eastern China range from 0.18 in 2004 to 0.26 in 2007 as compared to corresponding cases in the 1970s, and the multiyear means (standard deviations) of AR and ACRforcings at the surface are-6.7 (0.58) and-3.5 (0.63)Wm -2 , respectively, indicating the importance of cloud changes in affecting both the aerosol climate forcing and its interannual variation. The simulated mean surface cooling is 0.35°C, dominated by AR and ACR with a positive (cooling) feedback associated with changes in meteorology (~10%), and two negative (warming) feedbacks associated with decreases in latent (~70%) and sensible (~20%) heat fluxes. More detailed spatial characteristics were analyzed using ensemble simulations for the year 2008. Three regions-Jing-Jin-Ji (ΔAOD;0.63), Sichuan basin (ΔAOD;0.31), and middle Yangtze River valley (ΔAOD ~ 0.26)-at different climate regimes were selected to investigate the relative roles of AR and ACR. While the AR forcing is closely related to ΔAOD values, the ACR forcing presents different regional characteristics owing to cloud changes. In addition, the surface heat flux feedbacks are also different between regions. The study thus illustrates that ACR forcing is useful as a diagnostic parameter to unravel the complexity of climate change to aerosol forcing over eastern China. © 2019 American Meteorological Society."
"56349358200;56349223500;56447862300;55995261600;57211570116;57212325988;","Aircraft measurements of aerosol distribution, warm cloud microphysical properties, and their relationship over the Eastern Loess Plateau in China",2019,"10.1080/16000889.2019.1663994","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85073075090&doi=10.1080%2f16000889.2019.1663994&partnerID=40&md5=dd4362a366e395e91b476d9933baeff7","In situ aircraft measurements of aerosols and clouds were performed over the eastern Loess Plateau in Shanxi Province, China. The microphysical properties of both aerosols and warm clouds, including aerosol number concentration (Na), particle effective diameter (ED), number concentration of cloud droplets (Nc), cloud droplet diameter (Dc), and liquid water content (LWC) of clouds, determined through six flight observations performed in May 2013 were obtained and analysed. The mean magnitude of measured Na over the six flights was 103 cm−3, and accumulation mode particles dominated the majority. Most EDs of aerosol particles were less than 1 μm. Large amounts of fine aerosol particles were constrained to the lower layer, with ED smaller than 0.5 μm, and Na decreased with height. The base heights of warm clouds ranged from 1000 to 2800 m. The maximum and average values of the measured Nc ranged from 147 to 311 cm−3 and 51 to 157 cm−3, respectively. The maximum and average Dc ranged from 13.5 to 28.9 and 5.8 to 13.1 μm, respectively. The average LWC of warm clouds was 0.05 g·m−3. Na was negatively correlated with Nc either in the vertical or horizontal direction. Nc was higher with a smaller size of cloud droplets under high aerosol loading conditions. A small number of cloud droplets with larger size were formed under low aerosol loading conditions. At a certain range of LWC, Nc and Dc showed a negative correlation. The increase in LWC was related to an increase in the size of cloud droplets rather than the number of cloud droplets. The cloud droplet size distribution showed that small droplets dominated the total cloud droplet concentration. A bimodal lognormal distribution function can be efficiently used to describe the average spectrum of warm cloud droplets. © 2019, © 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group."
"57209456809;35422648700;35330742100;6506175295;","Cloud condensation nuclei and immersion freezing abilities of al2o3 and fe2o3 particles measured with the meteorological research institute’s cloud simulation chamber",2019,"10.2151/jmsj.2019-032","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067805233&doi=10.2151%2fjmsj.2019-032&partnerID=40&md5=be26b16be3862d795f165f8d7c5e4135","Aluminum oxide (Al2O3) and iron oxide (Fe2O3) particles have been observed not only in industrial areas and their surroundings, but also in natural atmospheric environments. These types of aerosols can influence aerosol– cloud interactions. In this study, physicochemical properties such as size distribution and the ability to act as cloud condensation nuclei (CCN) as well as ice nucleating particles (INPs) of surrogates of ambient Al2O3 and Fe2O3 particles were investigated using a CCN counter, the Meteorological Research Institute’s (MRI) cloud simulation chamber, the MRI’s continuous-flow-diffusion-chamber-type ice nucleus counter (CFDC-type INC), and an array of aerosol instruments. The results indicated that their hygroscopicity parameter (κ-value) ranged from 0.01 to 0.03. This range is compatible with that of surrogates of mineral dust particles and is smaller than typical κ-values of atmospheric aerosols. On the other hand, based on their ice nucleation active surface site (INAS) densities, these materials may act as effective INPs via immersion freezing (i.e., ice nucleation triggered by particles immersed in water droplets). In the cloud chamber experiments, Al2O3 and Fe2O3 particles continuously nucleated ice crystals at temperatures below −14°C and −20°C, respectively. This result indicates that the Al2O3 particles were better INPs than the Fe2O3 particles were. Moreover, the INAS density of the Al2O3 particles was comparable to that of natural ambient dust. © The Author(s) 2019."
"56734151000;55720362700;57169368500;57189270744;56165373000;57193237418;15836110700;57205290677;56415384100;7006960661;","Satellite-based estimate of the variability of warm cloud properties associated with aerosol and meteorological conditions",2018,"10.5194/acp-18-18187-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059382160&doi=10.5194%2facp-18-18187-2018&partnerID=40&md5=6a13b3439a3faf30c3fbcd89e2ed4153","Aerosol-cloud interaction (ACI) is examined using 10 years of data from the MODIS/Terra (morning orbit) and MODIS/Aqua (afternoon orbit) satellites. Aerosol optical depth (AOD) and cloud properties retrieved from both sensors are used to explore in a statistical sense the morning-to-afternoon variation of cloud properties in conditions with low and high AOD, over both land and ocean. The results show that the interaction between aerosol particles and clouds is more complex and of greater uncertainty over land than over ocean. The variation in d(X), defined as the mean change in cloud property Cloud-X between the morning and afternoon overpasses in high-AOD conditions minus that in low-AOD conditions, is different over land and ocean. This applies to cloud droplet effective radius (CDR), cloud fraction (CF) and cloud top pressure (CTP), but not to cloud optical thickness (COT) and cloud liquid water path (CWP). Both COT and CWP increase over land and ocean after the time step, irrespective of the AOD. However, the initial AOD conditions can affect the amplitude of variation of COT and CWP. The effects of initial cloud fraction and meteorological conditions on the change in CF under low- and high-AOD conditions after the 3h time step over land are also explored. Two cases are considered: (1) when the cloud cover increases and (2) when the cloud cover decreases. For both cases, we find that almost all values of d(CF) are positive, indicating that the variations of CF are larger in high AOD than that in low AOD after the 3h time step. The results also show that a large increase in cloud fraction occurs when scenes experience large AOD and stronger upward motion of air parcels. Furthermore, the increase rate of cloud cover is larger for high AOD with increasing relative humidity (RH) when RH is larger than 20%. We also find that a smaller increase in cloud fraction occurs when scenes experience larger AOD and larger initial cloud cover. Overall, the analysis of the diurnal variation of cloud properties provides a better understanding of aerosol-cloud interaction over land and ocean. © 2017 Copernicus GmbH.All right reserved."
"57008250400;7101752236;9535707500;","Effects of solid aerosols on partially glaciated clouds",2018,"10.1002/qj.3376","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058536082&doi=10.1002%2fqj.3376&partnerID=40&md5=7743e36224e613dcbfde1ac51e4ed95f","Sensitivity tests were conducted using a state-of-the-art aerosol–cloud to investigate the key microphysical and dynamical mechanisms by which solid aerosols affect glaciated clouds. The tests involved simulations of two contrasting cases of deep convection—a tropical maritime case and a midlatitude continental case, in which solid aerosol concentrations were increased from their pre-industrial (1850) to their present-day (2010) levels. In the midlatitude continental case, the boosting of the number concentrations of solid aerosols weakened the updrafts in deep convective clouds, resulting in reduced snow and graupel production. Consequently, the cloud fraction and the cloud optical thickness increased with increasing ice nuclei (IN), causing a negative radiative flux change at the top of the atmosphere (TOA), that is, a cooling effect of −1.96 ± 0.29 W/m 2 . On the other hand, in the tropical maritime case, increased ice nuclei invigorated upper-tropospheric updrafts in both deep convective and stratiform clouds, causing cloud tops to shift upwards. Snow production was also intensified, resulting in reduced cloud fraction and cloud optical thickness, hence a positive radiative flux change at the TOA—a warming effect of 1.02 ± 0.36 W/m 2 was predicted. © 2018 Royal Meteorological Society"
"56126562300;56082867500;55969140000;7404433688;55476830600;","Potential Impacts of Sahara Dust Aerosol on Rainfall Vertical Structure Over the Atlantic Ocean as Identified From EOF Analysis",2018,"10.1029/2018JD028500","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052829931&doi=10.1029%2f2018JD028500&partnerID=40&md5=7f3d077df70f5f943cca675f57546d4a","The current study investigates the potential impacts of Sahara dust on rainfall vertical structure over the Atlantic Ocean by employing multisensor satellite observations. The variabilities in rainfall vertical structure are decomposed by empirical orthogonal function (EOF) analysis. For a given near surface rain rate, the mean storm height of stratiform rain under dust-laden condition is significantly higher than that under the dust-free condition. The stratiform rain rate at the layers well above the freezing level is substantially enhanced under dust-laden condition. Those changes may result from dynamic and thermodynamic effect of Sahara Air Layer effect and/or the effect that dust aerosol acting as additional ice nuclei. For convective rain, there is no significant difference in the leading three normalized EOF modes between the dust-laden and dust-free sectors, implying that dust effect, if exists, is not strong enough to cause evident changes in convective rainfall profiles. For stratiform rain, the EOF1 shows no signals of dust effect either. However, significant difference is found in the EOF2 and EOF3 modes between dust-laden and dust-free conditions. The normalized EOF2 and EOF3 under dust-laden condition both represent enhanced rain rate at the upper layer well above the freezing level, where heterogeneous ice nucleation prevails. The statistical study shows consistent results with the case study, except that the aerosol-related changes in stratiform rainfall vertical structure is isolated in the EOF3 only. This study suggests that EOF analysis is a promising way for isolating the potential and relatively weak aerosol effects on precipitation from the strong dynamic effects. ©2018. American Geophysical Union. All Rights Reserved."
"55606974300;7003666669;56162305900;15755995900;7006270084;55405340400;8511991900;56384704800;55688930000;7006643234;55802246600;","Development and Evaluation of an Explicit Treatment of Aerosol Processes at Cloud Scale Within a Multi-Scale Modeling Framework (MMF)",2018,"10.1029/2018MS001287","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050830348&doi=10.1029%2f2018MS001287&partnerID=40&md5=a2ef4bc1dd31afdb5538e4543e101b1c","Modeling the aerosol lifecycle in traditional global climate models (GCM) is challenging for a variety of reasons, not the least of which is the coarse grid. The multiscale modeling framework (MMF), in which a cloud resolving model replaces conventional parameterizations of cloud processes within each GCM grid column, provides a promising framework to address this challenge. Here we develop a new version of MMF that for the first time treats aerosol processes at cloud scale to improve the aerosol-cloud interaction representation in the model. We demonstrate that the model with the explicit aerosol treatments shows significant improvements of many aspects of the simulated aerosols compared to the previous version of MMF with aerosols parameterized at the GCM grid scale. The explicit aerosol treatments produce a significant increase of the column burdens of black carbon (BC), primary organic aerosol, and sulfate by up to 40% in many remote regions, a decrease of the sea-salt aerosol burdens by 40% in remote regions. These differences are caused by the differences in aerosol convective transport and wet removal between these two models. The new model also shows reduced bias of BC surface concentration in North America and BC vertical profiles in the high latitudes. However, the biased-high BC concentrations in the upper troposphere over the remote Pacific regions remain, requiring further improvements on other process representations (e.g., secondary activation neglected in the model). ©2018. The Authors."
"57189986903;55598938800;55885662200;6504572295;7003501766;","The impact of precipitation evaporation on the atmospheric aerosol distribution in EC-Earth v3.2.0",2018,"10.5194/gmd-11-1443-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045583984&doi=10.5194%2fgmd-11-1443-2018&partnerID=40&md5=d1db562e89b6870692a63fa473219d6f","The representation of aerosol-cloud interaction in global climate models (GCMs) remains a large source of uncertainty in climate projections. Due to its complexity, precipitation evaporation is either ignored or taken into account in a simplified manner in GCMs. This research explores various ways to treat aerosol resuspension and determines the possible impact of precipitation evaporation and subsequent aerosol resuspension on global aerosol burdens and distribution. The representation of aerosol wet deposition by large-scale precipitation in the EC-Earth model has been improved by utilising additional precipitation-related 3- D fields from the dynamical core, the Integrated Forecasting System (IFS) general circulation model, in the chemistry and aerosol module Tracer Model, version 5 (TM5). A simple approach of scaling aerosol release with evaporated precipitation fraction leads to an increase in the global aerosol burden (+7.8 to +15% for different aerosol species). However, when taking into account the different sizes and evaporation rate of raindrops following Gong et al. (2006), the release of aerosols is strongly reduced, and the total aerosol burden decreases by -3.0 to -8.5 %. Moreover, inclusion of cloud processing based on observations by Mitra et al. (1992) transforms scavenged small aerosol to coarse particles, which enhances removal by sedimentation and hence leads to a -10 to -11% lower aerosol burden. Finally, when these two effects are combined, the global aerosol burden decreases by -11 to -19 %. Compared to the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations, aerosol optical depth (AOD) is generally underestimated in most parts of the world in all configurations of the TM5 model and although the representation is now physically more realistic, global AOD shows no large improvements in spatial patterns. Similarly, the agreement of the vertical profile with Cloud- Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite measurements does not improve significantly. We show, however, that aerosol resuspension has a considerable impact on the modelled aerosol distribution and needs to be taken into account. © Author(s) 2018."
"56085419300;7005632987;","Influence of aerosol-cloud interaction on austral summer precipitation over Southern Africa during ENSO events",2018,"10.1016/j.atmosres.2017.11.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85033585917&doi=10.1016%2fj.atmosres.2017.11.011&partnerID=40&md5=ea873c4f1e77a27f6262322eab02056b","In the present study, we are investigating the role of aerosols-and clouds in modulating the austral summer precipitation (December–February) during ENSO events over southern Africa region for the period from 2002 to2012 by using satellite and complimentary data sets. Aerosol radiative forcing (ARF) and Cloud radiative forcing (CRF) shows distinct patterns for El-Nina and La-Nina years. Further analysis were carried out by selecting the four Southern Africa regions where the precipitation shows remarkable difference during El-Nino and La-Nina years. These regions are R1 (33°S–24°S, 18°E–30°E), R2 (17°S–10°S, 24°E–32°E), R3 (19°S–9°S, 33°E–41°E) and R4 (7°S–0°S, 27°E–36°E). Aerosol Optical depth (AOD) shows considerable differences during these events. In region R1, R2 and R3 AOD shows more abundance in El-Nino years as compared to La-Nina years where as in R4 the AOD shows more abundance in La-Nina years. Cloud Droplet Effective radius (CDER) shows higher values during La-Nina years over R1, R2 and R3 regions but in R4 region CDER shows higher values in El-Nino years. Aerosol indirect effect (AIE) is estimated both for fixed cloud liquid water path (CLWP) and for fixed cloud ice path (CIP) bins, ranging from 1 to 300 gm –2 at 25 gm –2 interval over all the selected regions for El-Nino and La-Nina years. The results indicate more influence of positive indirect effect (Twomey effect) over R1 and R3 region during El-Nino years as compared to La-Nina years. This analysis reveals the important role of aerosol on cloud-precipitation interaction mechanism illustrating the interlinkage between dynamics and microphysics during austral summer season over southern Africa. © 2017 Elsevier B.V."
"7402677913;7004862277;7005729142;7103271625;","Modeling of aircraft measurements of ice crystal concentration in the Arctic and a parameterization for mixed-phase cloud",2017,"10.1175/JAS-D-17-0037.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85034785587&doi=10.1175%2fJAS-D-17-0037.1&partnerID=40&md5=48e947bd5d0d23569e3054731a92de7b","In this study, two parameterizations of ice nucleation rate on dust particles are used in a parcel model to simulate aircraft measurements of ice crystal number concentration Ni in the Arctic. The parcel model has detailed microphysics for droplet and ice nucleation, growth, and evaporation with prescribed vertical air velocities. Three dynamic regimes are considered, including large-scale ascent, cloud-top generating cells, and their combination. With observed meteorological conditions and aerosol concentrations, the parcel model predicts the number concentrations of size-resolved ice crystals, which may be compared to aircraft measurements. Model results show rapid changes with height/time in relative humidity, Ni, and thermodynamic phase partitioning, which is not resolved in current climate and weather forecasting models. Parameterizations for ice number and nucleation rate in mixed-phase stratus clouds are thus developed based on the parcel model results to represent the time-integrated effect of some microphysical processes in large-scale models. © 2017 American Meteorological Society."
"6507755223;56418561200;6602785950;57203080601;56862095200;57194679347;37051480000;15519671300;8705440100;56262351900;","Aerosol-landscape-cloud interaction: Signatures of topography effect on cloud droplet formation",2017,"10.5194/acp-17-7955-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021641315&doi=10.5194%2facp-17-7955-2017&partnerID=40&md5=e052faa5ab98f47ed5b8bee43fa506b0","Long-term in situ measurements of aerosol-cloud interactions are usually performed in measurement stations residing on hills, mountains, or high towers. In such conditions, the surface topography of the surrounding area can affect the measured cloud droplet distributions by increasing turbulence or causing orographic flows and thus the observations might not be representative for a larger scale. The objective of this work is to analyse, how the local topography affects the observations at Puijo measurement station, which is located in the 75m high Puijo tower, which itself stands on a 150m high hill. The analysis of the measurement data shows that the observed cloud droplet number concentration mainly depends on the cloud condensation nuclei (CCN) concentration. However, when the wind direction aligns with the direction of the steepest slope of the hill, a clear topography effect is observed. This finding was further analysed by simulating 3-D flow fields around the station and by performing trajectory ensemble modelling of aerosol- and wind-dependent cloud droplet formation. The results showed that in typical conditions, with geostrophic winds of about 10ms-1, the hill can cause updrafts of up to 1ms-1 in the air parcels arriving at the station. This is enough to produce in-cloud supersaturations (SSs) higher than typically found at the cloud base of ∼ 0.2%), and thus additional cloud droplets may form inside the cloud. In the observations, this is seen in the form of a bimodal cloud droplet size distribution. The effect is strongest with high winds across the steepest slope of the hill and with low liquid water contents, and its relative importance quickly decreases as these conditions are relaxed. We therefore conclude that, after careful screening for wind speed and liquid water content, the observations at Puijo measurement station can be considered representative for clouds in a boreal environment."
"7202463361;57201331852;55910010100;57191978244;55791137300;35330367300;","Modulations of aerosol impacts on cloud microphysics induced by the warm kuroshio current under the east asian winter monsoon",2016,"10.1002/2016JD025375","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84995639972&doi=10.1002%2f2016JD025375&partnerID=40&md5=77db7b4243246a0037630500001df742","In our previous aircraft observations, the possible influence of high sea surface temperature (SST) along the Kuroshio Current on aerosol-cloud interactions over the western North Pacific was revealed. The cloud droplet number concentration (Nc) was found to increase with decreasing near-surface static stability (NSS), which was evaluated locally as the difference between the SST and surface air temperature (SAT). To explore the spatial and temporal extent to which this warm SST influence can be operative, the present study analyzed Nc values estimated from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite measurements. The comparison of the local Nc values between the high and low SST-SAT days revealed a marked increase in Nc (up to a factor of 1.8) along the Kuroshio Current in the southern East China Sea, where particularly high SST-SAT values (up to 8 K) were observed in winter under monsoonal cold air outflows from the Asian Continent. This cold airflow destabilizes the atmospheric boundary layer, which leads to enhanced updraft velocities within the well-developed mixed layer and thus greater Nc. The monsoonal northwesterlies also bring a large amount of anthropogenic aerosols from the Asian continent that increase Nc in the first place. These results suggest that the same modulations of cloud microphysics can occur over other warm western boundary currents, including the Gulf Stream, under polluted cool continental airflows. Possibilities of influencing the cloud liquid water path are also discussed. © 2016. American Geophysical Union. All Rights Reserved."
"24172248700;15724233200;25630924500;35369409100;55356838400;57189368623;9846688600;7006595513;55942083800;","A broad supersaturation scanning (BS2) approach for rapid measurement of aerosol particle hygroscopicity and cloud condensation nuclei activity",2016,"10.5194/amt-9-5183-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84992694448&doi=10.5194%2famt-9-5183-2016&partnerID=40&md5=25f51eca42e4c710f4fc9aee2fe343d0","The activation and hygroscopicity of cloud condensation nuclei (CCN) are key to the understanding of aerosol-cloud interactions and their impact on climate. They can be measured by scanning the particle size and supersaturation in CCN measurements. The scanning of supersaturation is often time-consuming and limits the temporal resolution and performance of CCN measurements. Here we present a new approach, termed the broad supersaturation scanning (BS2) method, in which a range of supersaturation is simultaneously scanned, reducing the time interval between different supersaturation scans. The practical applicability of the BS2 approach is demonstrated with nano-CCN measurements of laboratory-generated aerosol particles. Model simulations show that the BS2 approach may also be applicable for measuring CCN activation of ambient mixed particles. Due to its fast response and technical simplicity, the BS2 approach may be well suited for aircraft and long-term measurements. Since hygroscopicity is closely related to the fraction of organics/inorganics in aerosol particles, a BS2-CCN counter can also serve as a complementary sensor for fast detection/estimation of aerosol chemical compositions."
"10739072200;6603478665;42662973900;57200999914;57204496157;34568413600;","Continental anthropogenic primary particle number emissions",2016,"10.5194/acp-2015-1023","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042812264&doi=10.5194%2facp-2015-1023&partnerID=40&md5=7e9c5902191c7f39852f7af2bee3912d","Atmospheric aerosol particle number concentrations impact our climate and health in ways different from those of aerosol mass concentrations. However, the global, current and future, anthropogenic particle number emissions and their size distributions are so far poorly known. In this article, we present the implementation of particle number emission factors and the related size distributions in the GAINS model. This implementation allows for global estimates of particle number emissions under different future scenarios, consistent with emissions of other pollutants and greenhouse gases. In addition to determining the general particulate number emissions, we also describe a method to estimate the number size distributions of the emitted black carbon. The first results show that the sources dominating the particle number emissions are different to those dominating the mass emissions. The major global number source is road traffic, followed by residential combustion of biofuels and coal (especially in China, India and Africa), coke production (Russia and China), and industrial combustion and processes. The size distributions of emitted particles differ across the world, depending on the main sources: in regions dominated by traffic and industry, the number size distribution of emissions peaks in diameters range from 20 to 50 nm, whereas in regions with intensive biofuel combustion and/or agricultural waste burning, the emissions of particles with diameters around 100 nm are dominant. In the baseline (current legislation) scenario, the particle number emissions in Europe, Northern and Southern Americas, Australia, and China decrease until 2030, whereas especially for India, a strong increase is estimated. The results of this study provide input for modelling of the future changes in aerosol-cloud interactions as well as particle number related adverse health effects, e.g., in response to tightening emission regulations. However, there are significant uncertainties in these current emission estimates and the key actions for decreasing the uncertainties are pointed out. © Author(s) 2016."
"56518787700;23493942300;57188561782;7202434960;","Observation of aerosol-cloud interaction over New York City using synergetic ground-based remote sensing systems",2016,"10.1117/1.JRS.10.016023","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84961589871&doi=10.1117%2f1.JRS.10.016023&partnerID=40&md5=3a526449d4fd08e769755110800be67f","Using UV Raman Lidar for aerosol extinction (αext), and combining microwave radiometer-derived liquid water path (LWP) with multifilter rotating shadowband radiometer-derived cloud optical depth (τcod) to retrieve cloud droplet effective radius (Reff), we observe clear signatures of the Twomey aerosol indirect effect (IE) under certain specialized conditions. The aerosol-cloud index (ACI) or IE slope relating cloud droplet radius to aerosol loading is calculated and shown to be quantitatively consistent with theoretical constraints. To demonstrate consistency, we use both a neural network multiband (default) approach and a dual-channel (DC) approach for the LWP and observe that the DC approach is generally more robust with more successful retrievals leading to a reduction of error in our regression analysis. We also perform an uncertainty analysis of the IE regression slope taking into account the major sources of error in cloud property retrieval and demonstrate that only sufficiently high values of the IE slope should be observable. Finally, based on the results of multiple cases, we observe the importance of vertical wind uptake on the IE signature. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)."
"57212024136;57193844239;57212021393;57212019537;","Model Analysis of the Anthropogenic Aerosol Effect on Clouds over East Asia",2012,"10.1080/16742834.2012.11446968","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050557180&doi=10.1080%2f16742834.2012.11446968&partnerID=40&md5=b3006087fb57c23ec219183a90bc46f6","A coupled meteorology and aerosol/chemistry model WRF-Chem (Weather Research and Forecast model coupled with Chemistry) was used to conduct a pair of simulations with present-day (PD) and preindustrial (PI) emissions over East Asia to examine the aerosol indirect effect on clouds. As a result of an increase in aerosols in January, the cloud droplet number increased by 650 cm–3 over the ocean and East China, 400 cm–3 over Central and Southwest China, and less than 200 cm–3 over North China. The cloud liquid water path (LWP) increased by 40–60 g m–2 over the ocean and Southeast China and 30 g m–2 over Central China; the LWP increased less than 5 g m–2 or decreased by 5 g m–2 over North China. The effective radius (Re) decreased by more than 4 µm over Southwest, Central, and Southeast China and 2 µm over North China. In July, variations in cloud properties were more uniform; the cloud droplet number increased by approximately 250–400 cm–3, the LWP increased by approximately 30–50 g m–2, and Re decreased by approximately 3 µm over most regions of China. In response to cloud property changes from PI to PD, shortwave (SW) cloud radiative forcing strengthened by 30 W m–2 over the ocean and 10 W m–2 over Southeast China, and it weakened slightly by approximately 2–10 W m–2 over Central and Southwest China in January. In July, SW cloud radiative forcing strengthened by 15 W m–2 over Southeast and North China and weakened by 10 W m–2 over Central China. The different responses of SW cloud radiative forcing in different regions was related to cloud feedbacks and natural variability. © 2012, © Institute of Atmospheric Physics, Chinese Academy of Sciences."
"57212021918;57212007242;57212023112;57212018934;57212017862;57212024462;","An Evidence of Aerosol Indirect Effect on Stratus Clouds from the Integrated Ground-Based Measurements at the ARM Shouxian Site",2011,"10.1080/16742834.2011.11446905","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940165208&doi=10.1080%2f16742834.2011.11446905&partnerID=40&md5=98c5363e88e6399f7aadc62e66c6de5d","The aerosol effect on clouds was explored using remote sensing of aerosol and cloud data at Shouxian, China. Non-precipitation, ice-free, and overcast clouds were firstly chosen by a combination of sky images from the Total Sky Imager (TSI), cloud base heights from the Ceilometer, and vertical temperature profiles from the Balloon-Borne Sounding System (BBSS). Six cases were chosen in summer, and seven in autumn. The averaged cloud effective radii (re), cloud optical depth (COD), aerosol total light scattering coefficient σ, and liquid water path (LWP) are, respectivey, 6.47 μm, 35.4, 595.9 mm-1, 0.19 mm in summer, and 6.07 μm, 96.0, 471.7 mm-1, 0.37 mm in autumn. The correlation coefficient between (re) and σ was found to change from negative to positive value as LWP increases. © 2011, © Institute of Atmospheric Physics, Chinese Academy of Sciences."
"7101899854;7005399437;","5 Radiation, aerosol joint observations - monsoon experiment in Gangetic-Himalayan area (RAJO-MEGHA): synergy of satellite-surface observations",2007,"10.1016/S0928-2025(06)10005-X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48349146849&doi=10.1016%2fS0928-2025%2806%2910005-X&partnerID=40&md5=13b02856dc0b64f6baa3fbe2253c16e0","Monsoon rainfalls sustain the livelihood of more than half of the world's population. Understanding the mechanism that drives the water cycle and fresh water distribution is highlighted as one of the major short-term goals in NASA's Earth Science Enterprise Strategy, and the interaction between natural/anthropogenic aerosols, clouds, and precipitation is a critical component of that mechanism. In Asia, sheer population density presents a major environmental stress. In addition, economic expansion in this region is accompanied by increases in biomass/biofuel burning, industrial pollution, and land cover and land use changes. With a growth rate of ~8% per year for Indian economy, more than 600 million people from Lahore, Pakistan to Calcutta, India over the Indo-Gangetic Basin have particularly witnessed increased frequencies of floods and droughts, as well as a dramatic increase in atmospheric loading of aerosols (i.e., anthropogenic and natural aerosols) in recent decades. Continuous sun-photometry observations (2001-2004) at Kanpur, India also reveal high values of monthly mean aerosol optical thickness of 0.4-0.8 year-round. The Asian monsoon is a dominant component of the global water and energy cycle, and provides the critical fresh water supply to the Indo-Gangetic Basin. Meltwater from the Himalayas sustains the regional agriculture throughout the dry season. However, recent observations indicate that glaciers are rapidly shrinking, jeopardizing the long-term water supply over the region. The A-Train satellite constellation, Aqua, CALIPSO, CloudSat and Aura are, and will be, deliberately placed in orbit to take synergistic measurements to help provide a better understanding of climate forcing due to trace gases, aerosols, and clouds. As a complement to these satellite capabilities, an initiative to deploy NASA SMART-COMMIT facilities and an array of AERONET sun-photometers, in concert with the A-Train/Terra, will be presented. The GSFC SMART-COMMIT facilities will provide aerosol and radiation measurements from a suite of radiometers, micropulse lidar, trace-gas concentration analyzers, particle sizers, mass analyzers, nephelometers, aethalometer, and standard meteorological probes. These valuable observations will be utilized to address the following scientific questions:(1)What are the spatial and temporal distributions of aerosol properties (e.g., chemical, microphysical, optical and radiative) in the RAJO-MEGHA region during the pre-monsoon and monsoon season?(2)What are anthropogenic aerosols in the regions, and can they be remotely sensed?(3)How accurately can we determine aerosol radiative forcing over the regions?(4)How do the cloud properties evolve as a result of interaction with anthropogenic and natural (or aggregate) aerosols?(5)What are the impacts of aerosol-cloud interactions on the regional hydrological cycle during the pre-monsoon season and break period?The expected close collaboration of RAJO-MEGHA with various research projects in the region (e.g., ABC, CLIVAR, GEWEX, and CEOP) will definitely provide a better understanding of the role that absorbing aerosols (dust and black carbon) play in affecting interannual and intraseasonal variability of the Indian monsoon, in particular, and of global water cycle, in general. © 2007."
"7202577029;35419152500;6701648855;7004210193;7003911760;7101788438;","Development of Raman lidar techniques to address the indirect aerosol effect: Retrieving the liquid water content of clouds",2004,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-3142576985&partnerID=40&md5=005e67ba45e88aa901a730f3d6d68240","This work reports on the development of Raman lidar techniques to measure cloud and aerosol properties involved in the determination of aerosol indirect effect, such as the extinction, liquid water content, droplet size distribution and number density. The study of these physical properties will bring to a better understanding of the aerosol indirect effect and the role that Raman lidars play. A preliminary study of Raman lidar techniques to retrieve cloud liquid water contents will be shown together with a technique to calibrate the liquid water-mixing ratio. This study is part of a broader research by the author towards her PhD studies at the University of Maryland Baltimore County."
"6701843835;7003814396;","Numerical simulations of cloud microphysics and drop freezing as function of drop contamination",2000,"10.1016/s0021-8502(00)90159-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034270401&doi=10.1016%2fs0021-8502%2800%2990159-9&partnerID=40&md5=e15bf9a2770e39c96a731dd665955855",[No abstract available]
"8657166100;6701842515;7005228425;7003708056;","First in situ evidence for Bergeron-Findeisen process",1999,"10.1016/s0021-8502(99)80077-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033189927&doi=10.1016%2fs0021-8502%2899%2980077-9&partnerID=40&md5=b7ce2c839be705a6da8f0a11faa5f1bd","During the Cloud Ice Mountain Experiment (CIME), the ice nucleation and the fate of droplets during ice crystal growth was demonstrated due to the change in cloud residual particle distributions studied with a Counterflow Virtual Impactor (CVI). The CVI captured and evaporated cloud droplets and ice crystals larger than 5 μm in diameter and was complemented by a Round Jet Impactor (RJI) that sampled aerosol particles smaller than 5 μm. A comparison between the residual particles of liquid drops and ice particles and the additional measurements of the interstitial particles in the ambient air illuminated the freezing and growth mechanisms in a mixed phase cloud."
"8657166100;7005228425;6701842515;56506988700;","Size dependency of 25-850 nm aerosol particles incorporated in cloud droplets",1999,"10.1016/s0021-8502(99)80132-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033189042&doi=10.1016%2fs0021-8502%2899%2980132-3&partnerID=40&md5=b159bbc80e13c799978df77ae786fcaf","As part of an experiment of the German Aerosol Research Focus (AFS) on Mt. Brocken, Germany, in autumn 1998, dual Counterflow Virtual Impactor (CVI) systems sampled subsets of the total droplet spectrum at lower cut sizes of 5 μm and 13 μm for the subsequently presented time window of measurements. According to the calibrated CVI collection efficiencies, the first CVI sampled 92% of the total droplet number, while the second one collected a number fraction of 16%."
"41362078500;56404969000;56166950300;57211503922;","Sensitivity of aerosol-cloud interactions to autoconversion schemes in mixed-phase orographic clouds",2021,"10.1016/j.atmosres.2020.105205","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089915162&doi=10.1016%2fj.atmosres.2020.105205&partnerID=40&md5=dbd49901d4a900c16789976c20c7b2f0","Autoconversion is an important role in describing initial formation of raindrops through droplets collision-coalescence, especially in discussing aerosol-cloud interactions. Seven autoconversion schemes have been adopted to investigate aerosol particles severing as cloud condensation nuclei (CCN) effect on mixed-phase orographic cloud. As CCN represented by initial droplet concentration is increased, more cloud droplets caused by a suppression of autoconversion rate benefit for snow growth by accreting droplets, leading to a delay in precipitation. Moreover, the loss of rain growth induced by a decrease in the accretion of cloud droplets by rain with increasing CCN can, to some extent, be offset by an enhancement of snow growth. As the freezing level is decreased, ice-phase particles become more effective, and then the decrease in precipitation becomes less obvious. Compared analysis finds that sensitive degrees of surface precipitation, hydrometeors and their related microphysical processes vary from different autoconversion schemes. Among them, the decrease in precipitation induced by increasing CCN is found to range from 3.2% to 36.3% under different schemes, while the increase in spillover is changed from 2.9% to 86.4%. The decrease in the accretion of cloud droplets by rain varies from 4.47% to 62.5%, and then the increase in snow melting can be changed from 7.32% to 31.8%. Hence, it should be pay attention to autoconversion scheme in estimating aerosol-cloud-precipitation interactions. Finally, based on the SCE (the stochastic collection equation) scheme, Berry scheme and Seifert and Beheng scheme are more appropriate for clean background condition, while Khairoutdinov and Kogan scheme and Liu and Daum scheme are applicable to polluted condition. © 2020 Elsevier B.V."
"55730541100;57209290429;24477694300;56400765800;","Lifecycle of light-absorbing carbonaceous aerosols in the atmosphere",2020,"10.1038/s41612-020-00145-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85093872411&doi=10.1038%2fs41612-020-00145-8&partnerID=40&md5=30441f740fcf8bf07cc4251f76e98cc0","Light-absorbing carbonaceous aerosols (LACs), including black carbon and light-absorbing organic carbon (brown carbon, BrC), have an important role in the Earth system via heating the atmosphere, dimming the surface, modifying the dynamics, reducing snow/ice albedo, and exerting positive radiative forcing. The lifecycle of LACs, from emission to atmospheric evolution further to deposition, is key to their overall climate impacts and uncertainties in determining their hygroscopic and optical properties, atmospheric burden, interactions with clouds, and deposition on the snowpack. At present, direct observations constraining some key processes during the lifecycle of LACs (e.g., interactions between LACs and hydrometeors) are rather limited. Large inconsistencies between directly measured LAC properties and those used for model evaluations also exist. Modern models are starting to incorporate detailed aerosol microphysics to evaluate transformation rates of water solubility, chemical composition, optical properties, and phases of LACs, which have shown improved model performance. However, process-level understanding and modeling are still poor particularly for BrC, and yet to be sufficiently assessed due to lack of global-scale direct measurements. Appropriate treatments of size- and composition-resolved processes that influence both LAC microphysics and aerosol–cloud interactions are expected to advance the quantification of aerosol light absorption and climate impacts in the Earth system. This review summarizes recent advances and up-to-date knowledge on key processes during the lifecycle of LACs, highlighting the essential issues where measurements and modeling need improvement. © 2020, The Author(s)."
"57218705320;","Validation of OMI seasonal and spatio-temporal variations in aerosol-cloud interactions over Banizoumbou using AERONET data",2020,"10.1016/j.jastp.2020.105457","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092480308&doi=10.1016%2fj.jastp.2020.105457&partnerID=40&md5=b4f6f1652951a179675992d88f890c75","Aerosols and cloud interaction remains highly important in the climatic process and its validation with space-based Ozone Monitoring Instrument (OMI) and ground-based observation of Aeronet Robotic Network (AERONET) is therefore essential. OMI and AERONET AODs was logrithmically subset and variations observed in both instruments show spatio-temporal quality of being more noticeable, which could lead to changes in the microphysical scale of clouds and instrumental biases. In this study, we have examined the spatio-temporal OMI AODs variations over Banizoumbou and validated results using AERONET AOD, precipitable water and cloud fraction data from Moderate Resolution Imaging Spectroradiometer (MODIS) from the period between 2014 and 2018. Additionally, estimated the absolute mean bias values of both AODs, correlating the results and performing the mean and standard deviation analysis. To validate instrumental error in retrieving AOD values, we calculated the root mean square error (RMSE) and mean absolute error (MAE) with standard error of measurements and perform 7 day kinematic back trajectories at various initial pressures to estimate zonal and meridional jet winds. Additionally, the seasonal loading of aerosols from the Dust Surface Mass Concentration shows aerosols masking cloud. The results show that winter season has period of good AODs agreement and the absolute bias error and its standard deviation for OMI and AERONET AODs is 0.216 ± 0.08. The correlation results obtained with cloud and precipitable water are 0.51, 0.32 and 0.20, −0.18 which show high monsoon AOD dominance the desert. It could be concluded that instrumental performance has spatio-temporal bias. © 2020 Elsevier Ltd"
"56035170100;12800882800;57202812237;57201720473;57217166311;35612235000;","Cirrus-induced shortwave radiative effects depending on their optical and physical properties: Case studies using simulations and measurements",2020,"10.1016/j.atmosres.2020.105095","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086586410&doi=10.1016%2fj.atmosres.2020.105095&partnerID=40&md5=27f9d150d2a8656c26e3036fcef14563","Cirrus (Ci) clouds play an important role in the atmospheric radiative balance, and hence in Climate Change. In this work, a polarized Micro-Pulse Lidar (P-MPL), standard NASA/Micro Pulse NETwork (MPLNET) system, deployed at the INTA/El Arenosillo station in Huelva (SW Iberian Peninsula) is used for Ci detection and characterization for the first time at this site. Three days were selected on the basis of the predominantly detected Ci clouds in dependence on their cloud optical depth (COD). Hence, three Ci cloud categories were examined at day-times for comparison with solar radiation issues: 19 cases of sub-visuals (svCi, COD: 0.01–0.03) on 1 October 2016, 7 cases of semitransparents (stCi, COD: 0.03–0.30) on 8 May 2017, and 17 cases of opaques (opCi, COD: 0.3–3.0) on 28 October 2016. Their radiative-relevant optical, macro- and micro-physical properties were retrieved. The mean COD for the svCi, stCi and opCi groups was 0.02 ± 0.01, 0.22 ± 0.08 and 0.93 ± 0.40, respectively; in overall, their lidar ratio ranged between 25 and 35 sr. Ci clouds were detected at 11–13 km height (top boundaries) with geometrical thicknesses of 1.7–2.0 km. Temperatures reported at those altitudes corresponded to lower values than the thermal threshold for homogenous ice formation. Volume linear depolarization ratios of 0.3–0.4 (and normalized backscattering ratios higher than 0.9) also confirmed Ci clouds purely composed of ice particles. Their effective radius was within the interval of 9–15 μm size, and the ice water path ranged from 0.02 (svCi) to 9.9 (opCi) g m−2. The Cirrus Cloud Radiative Effect (CCRE) was estimated using a Radiative Transfer (RT) model for Ci-free conditions and Ci-mode (Ci presence) scenarios. RT simulations were performed for deriving the CCRE at the top-of-atmosphere (TOA) and on surface (SRF), and also the atmospheric CCRE, for the overall shortwave (SW) range and their spectral sub-intervals (UV, VIS and NIR). A good agreement was first obtained for the RT simulations as validated against solar radiation measurements under clean conditions for solar zenith angles less than 75° (differences were mainly within ±20 W m−2 and correlation coefficients close to 1). By considering all the Ci clouds, independently on their COD, the mean SW CCRE values at TOA and SRF were, respectively, −30 ± 26 and − 24 ± 19 W m−2, being the mean atmospheric CCRE of −7 ± 7 W m−2; these values are in good agreement with global annual estimates found for Ci clouds. By using linear regression analysis, a Ci-induced enhancing cooling radiative effect was observed as COD increased for all the spectral ranges, with high correlations. In particular, the SW CCRE at TOA and SRF, and the atmospheric CCRE, presented COD-dependent rates of −74 ± 4, −55 ± 5, −19 ± 2 W m−2τ−1, respectively. Additionally, increasing negative rates are found from UV to NIR for each Ci category, reflecting a higher cooling NIR contribution w.r.t. UV and VIS ranges to the SW CCRE, and being also more pronounced at the TOA w.r.t. on SRF, as expected. The contribution of the SW CCRE to the net (SW + LW) radiative balance can be also potentially relevant. These results are especially significant for space-borne photometric/radiometric instrumentation and can contribute to validation purposes of the next ESA's EarthCARE mission, whose principal scientific goal is focused on radiation-aerosol-cloud interaction research. © 2020 Elsevier B.V."
"56502199700;8067118800;7202079615;","Snow-induced buffering in aerosol-cloud interactions",2020,"10.5194/acp-20-13771-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096345077&doi=10.5194%2facp-20-13771-2020&partnerID=40&md5=6702736600aeeb76ab741232b16653ab","Complex aerosol-cloud-precipitation interactions lead to large differences in estimates of aerosol impacts on climate among general circulation models (GCMs) and satellite retrievals. Typically, precipitating hydrometeors are treated diagnostically in most GCMs, and their radiative effects are ignored. Here, we quantify how the treatment of precipitation influences the simulated effective radiative forcing due to aerosol-cloud interactions (ERFaci) using a stateof- the-art GCM with a two-moment prognostic precipitation scheme that incorporates the radiative effect of precipitating particles, and we investigate how microphysical process representations are related to macroscopic climate effects. Prognostic precipitation substantially weakens the magnitude of ERFaci (by approximately 54 %) compared with the traditional diagnostic scheme, and this is the result of the increased longwave (warming) and weakened shortwave (cooling) components of ERFaci. The former is attributed to additional adjustment processes induced by falling snow, and the latter stems largely from riming of snow by collection of cloud droplets. The significant reduction in ERFaci does not occur without prognostic snow, which contributes mainly by buffering the cloud response to aerosol perturbations through depleting cloud water via collection. Prognostic precipitation also alters the regional pattern of ERFaci, particularly over northern midlatitudes where snow is abundant. The treatment of precipitation is thus a highly influential controlling factor of ERFaci, contributing more than other uncertain ""tunable""processes related to aerosol-cloud-precipitation interactions. This change in ERFaci caused by the treatment of precipitation is large enough to explain the existing difference in ERFaci between GCMs and observations. © Author(s) 2020."
"56672215300;15724233200;57218932521;35760600800;57189368623;35774441900;7004864963;13007924700;57219248003;55942083800;24172248700;","Impact of biomass burning aerosols on radiation, clouds, and precipitation over the Amazon: Relative importance of aerosol-cloud and aerosol-radiation interactions",2020,"10.5194/acp-20-13283-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096134206&doi=10.5194%2facp-20-13283-2020&partnerID=40&md5=a751de3802a0034471fd6733deb1f80d","Biomass burning (BB) aerosols can influence regional and global climate through interactions with radiation, clouds, and precipitation. Here, we investigate the impact of BB aerosols on the energy balance and hydrological cycle over the Amazon Basin during the dry season. We performed simulations with a fully coupled meteorology-chemistry model, the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem), for a range of different BB emission scenarios to explore and characterize nonlinear effects and individual contributions from aerosol-radiation interactions (ARIs) and aerosol-cloud interactions (ACIs). The ARIs of BB aerosols tend to suppress low-level liquid clouds by local warming and increased evaporation and to facilitate the formation of high-level ice clouds by enhancing updrafts and condensation at high altitudes. In contrast, the ACIs of BB aerosol particles tend to enhance the formation and lifetime of low-level liquid clouds by providing more cloud condensation nuclei (CCN) and to suppress the formation of high-level ice clouds by reducing updrafts and condensable water vapor at high altitudes (&gt; 8 km). For scenarios representing the lower and upper limits of BB emission estimates for recent years (2002-2016), we obtained total regional BB aerosol radiative forcings of −0.2 and 1.5 W m−2, respectively, showing that the influence of BB aerosols on the regional energy balance can range from modest cooling to strong warming. We find that ACIs dominate at low BB emission rates and low aerosol optical depth (AOD), leading to an increased cloud liquid water path (LWP) and negative radiative forcing, whereas ARIs dominate at high BB emission rates and high AOD, leading to a reduction of LWP and positive radiative forcing. In all scenarios, BB aerosols led to a decrease in the frequency of occurrence and rate of precipitation, caused primarily by ACI effects at low aerosol loading and by ARI effects at high aerosol loading. The dependence of precipitation reduction on BB aerosol loading is greater in a strong convective regime than under weakly convective conditions. Overall, our results show that ACIs tend to saturate at high aerosol loading, whereas the strength of ARIs continues to increase and plays a more important role in highly polluted episodes and regions. This should hold not only for BB aerosols over the Amazon, but also for other light-absorbing aerosols such as fossil fuel combustion aerosols in industrialized and densely populated areas. The importance of ARIs at high aerosol loading highlights the need for accurately characterizing aerosol optical properties in the investigation of aerosol effects on clouds, precipitation, and climate. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License."
"55338801300;6602087140;37056101400;55996365900;49861577800;7404747615;7202060229;57219965866;35547214900;8627503500;56423657500;","Models transport Saharan dust too low in the atmosphere: A comparison of the MetUM and CAMS forecasts with observations",2020,"10.5194/acp-20-12955-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096302531&doi=10.5194%2facp-20-12955-2020&partnerID=40&md5=0eaae725a53db0992c17e414689964dd","We investigate the dust forecasts from two operational global atmospheric models in comparison with in situ and remote sensing measurements obtained during the AERosol properties - Dust (AER-D) field campaign. Airborne elastic backscatter lidar measurements were performed on board the Facility for Airborne Atmospheric Measurements during August 2015 over the eastern Atlantic, and they permitted us to characterise the dust vertical distribution in detail, offering insights on transport from the Sahara. They were complemented with airborne in situ measurements of dust size distribution and optical properties, as well as datasets from the Cloud-Aerosol Transport System (CATS) spaceborne lidar and the Moderate Resolution Imaging Spectroradiometer (MODIS). We compare the airborne and spaceborne datasets to operational predictions obtained from the Met Office Unified Model (MetUM) and the Copernicus Atmosphere Monitoring Service (CAMS). The dust aerosol optical depth predictions from the models are generally in agreement with the observations but display a low bias. However, the predicted vertical distribution places the dust lower in the atmosphere than highlighted in our observations. This is particularly noticeable for the MetUM, which does not transport coarse dust high enough in the atmosphere or far enough away from the source. We also found that both model forecasts underpredict coarse-mode dust and at times overpredict fine-mode dust, but as they are fine-tuned to represent the observed optical depth, the fine mode is set to compensate for the underestimation of the coarse mode. As aerosol-cloud interactions are dependent on particle numbers rather than on the optical properties, this behaviour is likely to affect their correct representation. This leads us to propose an augmentation of the set of aerosol observations available on a global scale for constraining models, with a better focus on the vertical distribution and on the particle size distribution. Mineral dust is a major component of the climate system; therefore, it is important to work towards improving how models reproduce its properties and transport mechanisms. © Author(s) 2020."
"57219925946;57217865914;","Using machine learning to derive cloud condensation nuclei number concentrations from commonly available measurements",2020,"10.5194/acp-20-12853-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096103971&doi=10.5194%2facp-20-12853-2020&partnerID=40&md5=4a8649af36ec39f211d06d7e193b37d7","Cloud condensation nuclei (CCN) number concentrations are an important aspect of aerosol-cloud interactions and the subsequent climate effects; however, their measurements are very limited. We use a machine learning tool, random decision forests, to develop a random forest regression model (RFRM) to derive CCN at 0.4% supersaturation ([CCN0.4]) from commonly available measurements. The RFRM is trained on the long-Term simulations in a global size-resolved particle microphysics model. Using atmospheric state and composition variables as predictors, through associations of their variabilities, the RFRM is able to learn the underlying dependence of [CCN0.4] on these predictors, which are as follows: eight fractions of PM2:5 (NH4, SO4, NO3, secondary organic aerosol (SOA), black carbon (BC), primary organic carbon (POC), dust, and salt), seven gaseous species (NOx , NH3, O3, SO2, OH, isoprene, and monoterpene), and four meteorological variables (temperature (T), relative humidity (RH), precipitation, and solar radiation). The RFRM is highly robust: it has a median mean fractional bias (MFB) of 4:4% with 96:33% of the derived [CCN0.4] within a good agreement range of-60% MFB C60% and strong correlation of Kendall's coefficient 0:88. The RFRM demonstrates its robustness over 4 orders of magnitude of [CCN0.4] over varying spatial (such as continental to oceanic, clean to polluted, and nearsurface to upper troposphere) and temporal (from the hourly to the decadal) scales. At the Atmospheric Radiation Measurement Southern Great Plains observatory (ARM SGP) in Lamont, Oklahoma, United States, long-Term measurements for PM2:5 speciation (NH4, SO4, NO3, and organic carbon (OC)), NOx , O3, SO2, T, and RH, as well as [CCN0.4] are available. We modify, optimize, and retrain the developed RFRM to make predictions from 19 to 9 of these available predictors. This retrained RFRM (RFRM-ShortVars) shows a reduction in performance due to the unavailability and sparsity of measurements (predictors); it captures the [CCN0.4] variability and magnitude at SGP with 67:02% of the derived values in the good agreement range. This work shows the potential of using the more commonly available measurements of PM2:5 speciation to alleviate the sparsity of CCN number concentrations' measurements. © 2020 Copernicus GmbH. All rights reserved."
"55232897900;23991212200;8882641700;7004479957;","The Impact of Resolving Subkilometer Processes on Aerosol-Cloud Interactions of Low-Level Clouds in Global Model Simulations",2020,"10.1029/2020MS002274","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096471375&doi=10.1029%2f2020MS002274&partnerID=40&md5=c814ccd6215804bca809afb29c47a194","Subkilometer processes are critical to the physics of aerosol-cloud interaction (ACI) but have been dependent on parameterizations in global model simulations. We thus report the strength of ACI in the Ultra-Parameterized Community Atmosphere Model (UPCAM), a multiscale climate model that uses coarse exterior resolution to embed explicit cloud-resolving models with enough resolution (250 m horizontal, 20 m vertical) to quasi-resolve subkilometer eddies. To investigate the impact on ACIs, UPCAM's simulations are compared to a coarser multiscale model with 4 km horizontal resolution. UPCAM produces cloud droplet number concentrations (Nd) and cloud liquid water path (LWP) values that are higher than the coarser model but equally plausible compared to observations. Our analysis focuses on the Northern Hemisphere (20–50°N) oceans, where historical aerosol increases have been largest. We find similarities in the overall radiative forcing from ACIs in the two models, but this belies fundamental underlying differences. The radiative forcing from increases in LWP is weaker in UPCAM, whereas the forcing from increases in Nd is larger. Surprisingly, the weaker LWP increase is not due to a weaker increase in LWP in raining clouds, but a combination of weaker increase in LWP in nonraining clouds and a smaller fraction of raining clouds in UPCAM. The implication is that as global modeling moves toward finer than storm-resolving grids, nuanced model validation of ACI statistics conditioned on the existence of precipitation and good observational constraints on the baseline probability of precipitation will become key for tighter constraints and better conceptual understanding. ©2020. The Authors."
"55462884000;6701562113;56612517400;57194470383;16246205000;57207176515;","Studying scale dependency of aerosol-cloud interactions using multiscale cloud formulations",2020,"10.1175/JAS-D-19-0203.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85095862297&doi=10.1175%2fJAS-D-19-0203.1&partnerID=40&md5=ba41a5432f39e1c98140bf3016fd3fb5","The Weather Research and Forecasting Model with Aerosol-Cloud Interactions (WRF-ACI) configuration is used to investigate the scale dependency of aerosol-cloud interactions (ACI) across the ""gray zone""scales for grid-scale and subgrid-scale clouds. The impacts of ACI on weather are examined across regions in the eastern and western United States at 36, 12, 4, and 1 km grid spacing for short-term periods during the summer of 2006. ACI impacts are determined by comparing simulations with current climatological aerosol levels to simulations with aerosol levels reduced by 90%. The aerosol-cloud lifetime effect is found to be the dominant process leading to suppressed precipitation in regions of the eastern United States, while regions in the western United States experience offsetting impacts on precipitation from the cloud lifetime effect and other effects that enhance precipitation. Generally, the cloud lifetime effect weakens with decreasing grid spacing due to a decrease in relative importance of autoconversion compared to accretion. Subgrid-scale ACI are dominant at 36 km, while grid-scale ACI are dominant at 4 and 1 km. At 12 km grid spacing, grid-scale and subgridscale ACI processes are comparable in magnitude and spatial coverage, but random perturbations in grid-scale ACI impacts make the overall grid-scale ACI impact appear muted. This competing behavior of grid- and subgrid-scale clouds complicate the understanding of ACI at 12 km within the current WRF modeling framework. The work implies including subgrid-scale cloud microphysics and ice/mixed-phase-cloud ACI processes may be necessary in weather and climate models to study ACI effectively. © 2020 American Meteorological Society."
"57202945874;35793213300;57218937109;54797474600;56682032300;57212090581;57208796935;57218664100;57218652781;35486838200;13405658600;","Estimated aerosol health and radiative effects of the residential coal ban in the Beijing-Tianjin-Hebei region of China",2020,"10.4209/aaqr.2019.11.0565","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85095407497&doi=10.4209%2faaqr.2019.11.0565&partnerID=40&md5=1dc0d87a55a50f5bfc08d2d564ee7dde","Particle-phase air pollution is a leading risk factor for premature death globally and impacts climate by scattering or absorbing radiation and changing cloud properties. Within the Beijing-Tianjin-Hebei region of China, where there are severe air quality problems, several municipalities have begun implementing a coal-to-electricity program that bans residential coal and provides subsidies for electricity and electric-powered heat pumps. We used GEOS-Chem to evaluate two complete residential coal-to-electricity transitions—a Beijing-off scenario and Beijing-Tianjin-Hebei-off scenario—each relative to a base case. We estimate that within China, the ambient fine particulate matter (PM2.5) reductions in the Beijing-off scenario could lead to 1,900 (95% CI: 1,200-2,700) premature deaths avoided annually, while the Beijing-Tianjin-Hebei-off scenario could lead to 13,700 (95% CI: 8,900-19,600) premature deaths avoided annually. Additionally, we estimate that the residential-coal-ban scenarios will result in a positive top-of-the-atmosphere aerosol direct radiative effect (DRE) (model domain average: Beijing-off: 0.023 W m-2; Beijing-Tianjin-Hebei-off: 0.30 W m-2) and a negligible cloud-albedo aerosol indirect effect (AIE) (Beijing-off: 0.0001 W m-2; Beijing-Tianjin-Hebei-off: 0.0027 W m-2). To evaluate the uncertainty of the radiative effects, we calculated the DRE under four black-carbon mixing-state assumptions and both the DRE and AIE assuming three different black-carbon-to-organic-aerosol (BC:OA) ratios for residential-coal emissions. Although the magnitude of our radiative forcing estimates varied across sensitivity cases, the domain average remained positive. When only considering the aerosol-related effects of the aforementioned coal-ban scenarios, we predict substantial health benefits, but do not anticipate a climate “co-benefit”, because removing aerosol emissions leads to a warming tendency. However, if the coal-to-electricity program results in less net greenhouse gas emissions due to the replacement heaters, the policy may be able to achieve health and climate “co-benefits”. © The Author(s)."
"36822103700;57203102974;","Saharan dust aerosols change deep convective cloud prevalence, possibly by Inhibiting Marine New Particle formation",2020,"10.1175/JCLI-D-20-0083.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092566287&doi=10.1175%2fJCLI-D-20-0083.1&partnerID=40&md5=46c9d0900d167107990d241753298c77","Deep convective clouds (DCCs) are important to global climate, atmospheric chemistry, and precipitation. Dust, a dominant aerosol type over the tropical North Atlantic, has potentially large microphysical impacts on DCCs over this region. However, dust effects are difficult to identify, being confounded by covarying meteorology and other factors. Here, a method is developed to quantify DCC responses to dust and other aerosols at large spatial and temporal scales despite these uncertainties. Over 7 million tropical North Atlantic cloud, aerosol, and meteorological profiles from CloudSat satellite data and MERRA-2 reanalysis products are used to stratify cloud observations into meteorological regimes, objectively select a priori assumptions, and iteratively test uncertainty sensitivity. Dust is robustly associated with a 54% increase in DCC prevalence. However, marine aerosol proxy concentrations are 5 times more predictive of dustassociated increases in DCC prevalence than the dust itself, or any other aerosol or meteorological factor. Marine aerosols are also the most predictive factor for the even larger increases in DCC prevalence (61%-87%) associated with enhanced dimethyl sulfide and combustion and sulfate aerosols. Dust-associated increases in DCC prevalence are smaller at high dust concentrations than at low concentrations. These observations suggest that not only is dust a comparatively ineffective CCN source, but it may also act as a condensation/coagulation sink for chemical precursors to CCN, reducing total CCN availability over large spatial scales by inhibiting new particle formation from marine emissions. These observations represent the first time this process, previously predicted by models, has been supported and quantified by measurements. © 2020 American Meteorological Society."
"54899176600;13403622000;6602988199;24472400800;","Global Radiative Impacts of Black Carbon Acting as Ice Nucleating Particles",2020,"10.1029/2020GL089056","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85094655689&doi=10.1029%2f2020GL089056&partnerID=40&md5=72393143b62c04a19d5a8f00bf3da25a","Black carbon (BC) aerosols from incomplete combustion generally warm the climate, but the magnitudes of their various interactions with climate are still uncertain. A key knowledge gap is their role as ice nucleating particles (INPs), enabling ice formation in clouds. Here we assess the global radiative impacts of BC acting as INPs, using simulations with the Community Earth System Model 2 climate model updated to include new laboratory-based ice nucleation parameterizations. Overall, we find a moderate cooling through changes to stratiform cirrus clouds, counteracting the well-known net warming from BC's direct scattering and absorption of radiation. Our best estimates indicate that BC INPs generally thin cirrus by indirectly inhibiting the freezing of solution aerosol, with a global net radiative impact of −0.13 ± 0.07 W/m2. Sensitivity tests of BC amounts and ice nucleating efficiencies, and uncertainties in the environment where ice crystals form, show a potential range of impacts from −0.30 to +0.02 W/m2. ©2020. The Authors."
"57213136646;57216955263;57211427059;56426612900;35775264900;23476421000;","Minimal Climate Impacts From Short-Lived Climate Forcers Following Emission Reductions Related to the COVID-19 Pandemic",2020,"10.1029/2020GL090326","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85094647901&doi=10.1029%2f2020GL090326&partnerID=40&md5=0cc06d399323ee1f6d87fc5551e123ff","We present an assessment of the impacts on atmospheric composition and radiative forcing of short-lived pollutants following a worldwide decrease in anthropogenic activity and emissions comparable to what has occurred in response to the COVID-19 pandemic, using the global composition-climate model United Kingdom Chemistry and Aerosols Model (UKCA). Emission changes reduce tropospheric hydroxyl radical and ozone burdens, increasing methane lifetime. Reduced SO2 emissions and oxidizing capacity lead to a decrease in sulfate aerosol and increase in aerosol size, with accompanying reductions to cloud droplet concentration. However, large reductions in black carbon emissions increase aerosol albedo. Overall, the changes in ozone and aerosol direct effects (neglecting aerosol-cloud interactions which were statistically insignificant but whose response warrants future investigation) yield a radiative forcing of −33 to −78 mWm−2. Upon cessation of emission reductions, the short-lived climate forcers rapidly return to pre-COVID levels; meaning, these changes are unlikely to have lasting impacts on climate assuming emissions return to pre-intervention levels. ©2020. The Authors."
"16479877100;6701378450;55480310900;7005284577;7004176333;35737484800;6603735912;26424128800;","Drivers of cloud droplet number variability in the summertime in the southeastern United States",2020,"10.5194/acp-20-12163-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85095110842&doi=10.5194%2facp-20-12163-2020&partnerID=40&md5=5a55c4c6b46f7e88adc62283200ca87d","Here we analyze regional-scale data collected on board the NOAA WP-3D aircraft during the 2013 Southeast Nexus (SENEX) campaign to study the aerosol cloud droplet link and quantify the sensitivity of droplet number to aerosol number, chemical composition, and vertical velocity. For this, the observed aerosol size distributions, chemical composition, and vertical-velocity distribution are introduced into a state-of-the-art cloud droplet parameterization to show that cloud maximum supersaturations in the region range from 0.02 % to 0.52 %, with an average of 0:14 ± 0:05 %. Based on these low values of supersaturation, the majority of activated droplets correspond to particles with a dry diameter of 90 nm and above. An important finding is that the standard deviation of the vertical velocity (sw) exhibits considerable diurnal variability (ranging from 0.16 ms-1 during nighttime to over 1.2 ms-1 during day), and it tends to covary with total aerosol number (Na). This sw Na covariance amplifies the predicted response in cloud droplet number (Nd) to Na increases by 3 to 5 times compared to expectations based on Na changes alone. This amplified response is important given that droplet formation is often velocity-limited and therefore should normally be insensitive to aerosol changes. We also find that Nd cannot exceed a characteristic concentration that depends solely on sw. Correct consideration of sw and its covariance with time and Na is important for fully understanding aerosol cloud interactions and the magnitude of the aerosol indirect effect. Given that model assessments of aerosol cloud climate interactions do not routinely evaluate for overall turbulence or its covariance with other parameters, datasets and analyses such as the one presented here are of the highest priority to address unresolved sources of hydrometeor variability, bias, and the response of droplet number to aerosol perturbations. © 2020 Author(s)."
"57204076890;57219546461;57201362212;57214611556;57189685892;8871497700;26643041500;35461255500;6603731262;","Clouds over Hyytiälä, Finland: An algorithm to classify clouds based on solar radiation and cloud base height measurements",2020,"10.5194/amt-13-5595-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85094823134&doi=10.5194%2famt-13-5595-2020&partnerID=40&md5=97ba3f596f6dd09e9a39058114ff0427","We developed a simple algorithm to classify clouds based on global radiation and cloud base height measured by pyranometer and ceilometer, respectively. We separated clouds into seven different classes (stratus, stratocumulus, cumulus, nimbostratus, altocumulus + altostratus, cirrus + cirrocumulus + cirrostratus and clear sky + cirrus). We also included classes for cumulus and cirrus clouds causing global radiation enhancement, and we classified multilayered clouds, when captured by the ceilometer, based on their height and characteristics (transmittance, patchiness and uniformity). The overall performance of the algorithm was nearly 70% when compared with classification by an observer using total-sky images. The performance was best for clouds having well-distinguishable effects on solar radiation: nimbostratus clouds were classified correctly in 100% of the cases. The worst performance corresponds to cirriform clouds (50 %). Although the overall performance of the algorithm was good, it is likely to miss the occurrences of high and multilayered clouds. This is due to the technical limits of the instrumentation: the vertical detection range of the ceilometer and occultation of the laser pulse by the lowest cloud layer. We examined the use of clearness index, which is defined as a ratio between measured global radiation and modeled radiation at the top of the atmosphere, as an indicator of clear-sky conditions. Our results show that cumulus, altocumulus, altostratus and cirriform clouds can be present when the index indicates clear-sky conditions. Those conditions have previously been associated with enhanced aerosol formation under clear skies. This is an important finding especially in the case of low clouds coupled to the surface, which can influence aerosol population via aerosol-cloud interactions. Overall, caution is required when the clearness index is used in the analysis of processes affected by partitioning of radiation by clouds. © Author(s) 2020."
"57207918070;7004091561;24338002400;","Differences in fine particle chemical composition on clear and cloudy days",2020,"10.5194/acp-20-11607-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092779588&doi=10.5194%2facp-20-11607-2020&partnerID=40&md5=0b325d5af1c15b4aa94b1c79dbedcb47","Clouds are prevalent and alter fine particulate matter (PM2.5) mass and chemical composition. Cloud-affected satellite retrievals are subject to higher uncertainty and are often removed from data products, hindering quantitative estimates of tropospheric chemical composition during cloudy times. We examine surface PM2.5 chemical constituent concentrations in the Interagency Monitoring of PROtected Visual Environments (IMPROVE) network in the United States during cloudy and clear-sky times defined using Moderate Resolution Imaging Spectroradiometer (MODIS) cloud flags from 2010 to 2014 with a focus on differences in particle species that affect hygroscopicity and aerosol liquid water (ALW). Cloudy and clear-sky periods exhibit significant differences in PM2.5 mass and chemical composition that vary regionally and seasonally. In the eastern US, relative humidity alone cannot explain differences in ALW, suggesting that emissions and in situ chemistry related to anthropogenic sources exert determining impacts. An implicit clear-sky bias may hinder efforts to quantitatively understand and improve representation of aerosol–cloud interactions, which remain dominant uncertainties in models. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License."
"37016361600;57213701824;57202945874;13405658600;24833804500;36672804000;6601941399;","Emissions and radiative impacts of sub-10 nm particles from biofuel and fossil fuel cookstoves",2020,"10.1080/02786826.2020.1769837","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087012014&doi=10.1080%2f02786826.2020.1769837&partnerID=40&md5=2b5b749c7829a0eb37e5ca3202bb94a4","Combustion sources have been shown to directly emit particles smaller than 10 nm. The emission of 1-3 nm particles from biofuel or fossil fuel cookstoves has not been studied previously, nor have the radiative impacts of these emissions been investigated. In this work, emissions (number of particles) were measured during a water boiling test performed on five different cookstoves (three-stone fire, rocket elbow, gasifier, charcoal, and liquified petroleum gas [LPG]) for particle diameters between ∼1 and ∼1000 nm. We found significant emissions of particles smaller than 10 nm for all cookstoves (&gt;5 × 1015 # kg-fuel−1). Furthermore, cleaner (e.g., LPG) cookstoves emitted a larger fraction of sub-10 nm particles (relative to the total particle counts) than traditional cookstoves (e.g., three-stone fire). Simulations performed with the global chemical transport model GEOS-Chem-TOMAS that were informed by emissions data from this work suggested that sub-10 nm particles were unlikely to significantly influence number concentrations of particles with diameters larger than 80 nm that can serve as cloud condensation nuclei (CCN) (&lt;0.3%, globally averaged) or alter the cloud-albedo indirect effect (absolute value &lt;0.005 W m−2, globally averaged). The largest, but still relatively minor, localized changes in CCN-relevant concentrations (&lt;10%) and the cloud-albedo indirect effect (absolute value &lt;0.5 W m−2) were found in large biofuel combustion source regions (e.g., Brazil, Tanzania, Southeast Asia) and in the Southern Ocean. Enhanced coagulation-related losses of these sub-10 nm particles at sub-grid scales will tend to further reduce their impact on particle number concentrations and the aerosol indirect effect, although they might still be of relevance for human health. Copyright © 2020 American Association for Aerosol Research. © 2020 American Association for Aerosol Research."
"57208192792;36152171200;57217487135;35329672300;15830929400;7202079615;57218628808;38362385200;","Aerosol effective radiative forcing in the online aerosol coupled cas-fgoals-f3-l climate model",2020,"10.3390/atmos11101115","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85095963554&doi=10.3390%2fatmos11101115&partnerID=40&md5=642f7a63fab35eb935ee5bcdfb4491f9","The effective radiative forcing (ERF) of anthropogenic aerosol can be more representative of the eventual climate response than other radiative forcing. We incorporate aerosol–cloud interaction into the Chinese Academy of Sciences Flexible Global Ocean–Atmosphere–Land System (CAS-FGOALS-f3-L) by coupling an existing aerosol module named the Spectral Radiation Transport Model for Aerosol Species (SPRINTARS) and quantified the ERF and its primary components (i.e., effective radiative forcing of aerosol-radiation interactions (ERFari) and aerosol-cloud interactions (ERFaci)) based on the protocol of current Coupled Model Intercomparison Project phase 6 (CMIP6). The spatial distribution of the shortwave ERFari and ERFaci in CAS-FGOALS-f3-L are comparable with that of most available CMIP6 models. The global mean 2014–1850 shortwave ERFari in CAS-FGOALS-f3-L (−0.27 W m−2) is close to the multi-model means in 4 available models (−0.29 W m−2 ), whereas the assessing shortwave ERFaci (−1.04 W m−2 ) and shortwave ERF (−1.36 W m−2 ) are slightly stronger than the multi-model means, illustrating that the CAS-FGOALS-f3-L can reproduce the aerosol radiation effect reasonably well. However, significant diversity exists in the ERF, especially in the dominated component ERFaci, implying that the uncertainty is still large. © 2020 by the authors. Licensee MDPI, Basel, Switzerland."
"57219444062;57213758822;12771338800;7003459696;57203809453;57193751793;7404747615;12806941900;9941600400;57206360338;25652188900;34771463800;56800396300;23101727900;57200623783;55921861500;11339675000;23476421000;57203722524;35740180800;7004469744;57213046638;7202802701;7004587644;","The impacts of aerosol emissions on historical climate in ukesm1",2020,"10.3390/atmos11101095","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092693593&doi=10.3390%2fatmos11101095&partnerID=40&md5=03c13deecc34e7e81b75fd70478d6ba1","As one of the main drivers for climate change, it is important to understand changes in anthropogenic aerosol emissions and evaluate the climate impact. Anthropogenic aerosols have affected global climate while exerting a much larger influence on regional climate by their short lifetime and heterogeneous spatial distribution. In this study, the effective radiative forcing (ERF), which has been accepted as a useful index for quantifying the effect of climate forcing, was evaluated to understand the effects of aerosol on regional climate over a historical period (1850–2014). Eastern United States (EUS), Western European Union (WEU), and Eastern Central China (ECC), are regions that predominantly emit anthropogenic aerosols and were analyzed using Coupled Model Intercomparison Project 6 (CMIP6) simulations implemented within the framework of the Aerosol Chemistry Model Intercomparison Project (AerChemMIP) in the UK’s Earth System Model (UKESM1). In EUS and WEU, where industrialization occurred relatively earlier, the negative ERF seems to have been recovering in recent decades based on the decreasing trend of aerosol emissions. Conversely, the radiative cooling in ECC seems to be strengthened as aerosol emission continuously increases. These aerosol ERFs have been largely attributed to atmospheric rapid adjustments, driven mainly by aerosol-cloud interactions rather than direct effects of aerosol such as scattering and absorption. © 2020 by the authors. Licensee MDPI, Basel, Switzerland."
"57204032243;8705440100;6507755223;7007182077;26643041500;8568391400;","In situ cloud ground-based measurements in the Finnish sub-Arctic: Intercomparison of three cloud spectrometer setups",2020,"10.5194/amt-13-5129-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092610113&doi=10.5194%2famt-13-5129-2020&partnerID=40&md5=33616a97136987ad191ecf7e58936b7b","Continuous, semi-long-term, ground-based in situ cloud measurements were conducted during the Pallas Cloud Experiment (PaCE) in 2013. The measurements were carried out in Finnish sub-Arctic region at Sammaltunturi station (67 58 ′ N, 24 07 ′ E; 560 m a.s.l.), part of Pallas Atmosphere - Ecosystem Supersite and Global Atmosphere Watch (GAW) program. The main motivation of the campaign was to conduct in situ cloud measurements with three different cloud spectrometer probes and perform an evaluation of their ground-based setups. Therefore, we mutually compared the performance of the cloud and aerosol spectrometer (CAS), the cloud droplet probe (CDP) and the forward-scattering spectrometer probe (FSSP-100) (DMT; Boulder, CO, USA). We investigated how different meteorological parameters affect each instrument's ground-based setup operation and quantified possible biases and discrepancies of different microphysical cloud properties. Based on the obtained results we suggested limitations for further use of the instrument setups in campaigns where the focus is on investigating aerosol-cloud interactions. Measurements in this study were made by instruments owned by the Finnish Meteorological Institute and results concern their operation in sub-Arctic conditions with frequently occurring supercooled clouds. The measured parameter from each instrument was the size distribution, and additionally we derived the number concentration, the effective diameter, the median volume diameter and the liquid water content. A complete intercomparison between the CAS probe and the FSSP-100 ground setups and additionally between the FSSP-100 and the CDP probe ground setups was made and presented. Unfortunately, there was not a sufficient amount of common data to compare all three probes together due to operational problems of the CDP ground setup in sub-zero conditions. The CAS probe that was fixed to one direction lost a significant number of cloud droplets when the wind direction was out of wind iso-axial conditions in comparison with the FSSP-100 and the CDP, which were both placed on a rotating platform. We revealed that CAS and FSSP-100 had good agreement in deriving sizing parameters (effective diameter and median volume diameter from 5 to 35 μm ) even though CAS was losing a significant amount of cloud droplets. The most sensitive derived parameter was liquid water content, which was strongly connected to the wind direction and temperature. © 2020 American Institute of Physics Inc.. All rights reserved."
"57216873259;56162305900;7102084129;54413425200;57216645367;57219149392;57219148580;","Evaluation of Cloud and Precipitation Response to Aerosols in WRF-Chem With Satellite Observations",2020,"10.1029/2020JD033108","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091462557&doi=10.1029%2f2020JD033108&partnerID=40&md5=87f76e07807ab5ec54edb6c4a366dace","Large uncertainties remain in the key physical processes associated with aerosol-cloud interactions (ACI) in models. With the help of A-Train satellite observations, the Weather Research and Forecasting Model with chemistry (WRF-Chem) model with two microphysical schemes, Morrison (MOR) and Lin (LIN), is evaluated by quantifying the susceptibilities of cloud properties, precipitation characteristics, and warm rain process to aerosols for marine stratocumulus over the Southeast Pacific. We reduced the meteorological control on clouds by stratifying them using cloud geometric thickness. Our results show that while the cloud fraction increases with increasing cloud droplet number concentration (Nd) in observation and simulations, the susceptibility of cloud fraction to Nd in simulations are only half of that in the observation. The cloud liquid water path increases with Nd in simulations but decreases slightly in the observation. Compared with the observations, the warm rain in WRF-Chem simulations is generally less suppressed by aerosols, and it initiates at a much smaller cloud droplet effective radius (Re). The conversion from cloud to rain is substantially faster in simulations compared to satellite observations. The conversion rate accelerates at Re ≈ 13 μm in observations and at Re ≈ 9 μm in simulations. ©2020. American Geophysical Union. All Rights Reserved."
"57219284485;7102988363;37089417300;56060986400;56250185400;22133985200;14058796400;57192172364;15926468600;","Modelling mineral dust emissions and atmospheric dispersion with MADE3 in EMAC v2.54",2020,"10.5194/gmd-13-4287-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092034781&doi=10.5194%2fgmd-13-4287-2020&partnerID=40&md5=27ff4495019cb651cafb616525c29317","It was hypothesized that using mineral dust emission climatologies in global chemistry climate models (GCCMs), i.e. prescribed monthly-mean dust emissions representative of a specific year, may lead to misrepresentations of strong dust burst events. This could result in a negative bias of model dust concentrations compared to observations for these episodes. Here, we apply the aerosol microphysics submodel MADE3 (Modal Aerosol Dynamics model for Europe, adapted for global applications, third generation) as part of the ECHAM/MESSy Atmospheric Chemistry (EMAC) general circulation model. We employ two different representations of mineral dust emissions for our model simulations: (i) a prescribed monthly-mean climatology of dust emissions representative of the year 2000 and (ii) an online dust parametrization which calculates wind-driven mineral dust emissions at every model time step. We evaluate model results for these two dust representations by comparison with observations of aerosol optical depth from groundbased station data. The model results show a better agreement with the observations for strong dust burst events when using the online dust representation compared to the prescribed dust emissions setup. Furthermore, we analyse the effect of increasing the vertical and horizontal model resolution on the mineral dust properties in our model.We compare results from simulations with T42L31 and T63L31 model resolution (2:8 2:8 and 1:9 1:9 in latitude and longitude, respectively; 31 vertical levels) with the reference setup (T42L19). The different model versions are evaluated against airborne in situ measurements performed during the SALTRACE mineral dust campaign (Saharan Aerosol Longrange Transport and Aerosol-Cloud Interaction Experiment, June-July 2013), i.e. observations of dust transported from the Sahara to the Caribbean. Results show that an increased horizontal and vertical model resolution is able to better represent the spatial distribution of airborne mineral dust, especially in the upper troposphere (above 400 hPa). Additionally, we analyse the effect of varying assumptions for the size distribution of emitted dust but find only a weak sensitivity concerning these changes. The results of this study will help to identify the model setup best suited for future studies and to further improve the representation of mineral dust particles in EMAC-MADE3. © 2020 Copernicus GmbH. All rights reserved."
"36058435800;7003908632;27267529400;57191094832;7202258620;57219121683;7006204597;","CNT parameterization based on the observed INP concentration during arctic summer campaigns in a marine environment",2020,"10.3390/ATMOS11090916","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091343243&doi=10.3390%2fATMOS11090916&partnerID=40&md5=fab58bc0a881afb513d77f4665323c6d","Aerosol-cloud interactions present a large source of uncertainties in atmospheric and climate models. One of the main challenges to simulate ice clouds is to reproduce the right ice nucleating particle concentration. In this study, we derive a parameterization for immersion freezing according to the classical nucleation theory. Our objective was to constrain this parameterization with observations taken over the Canadian Arctic during the Amundsen summer 2014 and 2016 campaigns. We found a linear dependence of contact angle and temperature. Using this approach, we were able to reproduce the scatter in ice nucleated particle concentrations within a factor 5 of observed values with a small negative bias. This parameterization would be easy to implement in climate and atmospheric models, but its representativeness has to first be validated against other datasets. © 2020 by the authors."
"55923546200;36106370400;56571063800;57212217948;57203815874;7102680152;56377286600;7006415284;57189748029;16444006500;7004469744;","The value of remote marine aerosol measurements for constraining radiative forcing uncertainty",2020,"10.5194/acp-20-10063-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091802750&doi=10.5194%2facp-20-10063-2020&partnerID=40&md5=0f163e9a2099f4993ba096596de00445","Aerosol measurements over the Southern Ocean are used to constrain aerosol-cloud interaction radiative forcing (RFaci) uncertainty in a global climate model. Forcing uncertainty is quantified using 1 million climate model variants that sample the uncertainty in nearly 30 model parameters. Measurements of cloud condensation nuclei and other aerosol properties from an Antarctic circumnavigation expedition strongly constrain natural aerosol emissions: default sea spray emissions need to be increased by around a factor of 3 to be consistent with measurements. Forcing uncertainty is reduced by around 7% using this set of several hundred measurements, which is comparable to the 8% reduction achieved using a diverse and extensive set of over 9000 predominantly Northern Hemisphere measurements. When Southern Ocean and Northern Hemisphere measurements are combined, uncertainty in RFaci is reduced by 21 %, and the strongest 20% of forcing values are ruled out as implausible. In this combined constraint, observationally plausible RFaci is around 0.17Wm-2 weaker (less negative) with 95% credible values ranging from-2:51 to-1:17Wm-2 (standard deviation of-2:18 to-1:46Wm-2). The Southern Ocean and Northern Hemisphere measurement datasets are complementary because they constrain different processes. These results highlight the value of remote marine aerosol measurements. © 2020 Laser Institute of America. All rights reserved."
"57192915106;57208121852;36661106500;39361670300;","Quantifying the sensitivity of aerosol optical properties to the parameterizations of physico-chemical processes during the 2010 Russian wildfires and heatwave",2020,"10.5194/acp-20-9679-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85093862165&doi=10.5194%2facp-20-9679-2020&partnerID=40&md5=2339efd5ae60e79043bc5773f46cae17","The impact of aerosol-radiation and aerosol-cloud interactions on the radiative forcing is subject to large uncertainties. This is caused by the limited understanding of aerosol optical properties and the role of aerosols as cloud condensation/ice nuclei (CCN/IN). On the other hand, aerosol optical properties and vertical distribution are highly related, and their uncertainties come from different processes. This work attempts to quantify the sensitivity of aerosol optical properties (i.e. aerosol optical depth; AOD) and their vertical distribution (using the extinction coefficient, backscatter coefficient, and concentrations' species profiles) to key processes. In order to achieve this objective, sensitivity tests have been carried out, using the WRF-Chem regional fully coupled model by modifying the dry deposition, sub-grid convective transport, relative humidity, and wet scavenging. The 2010 Russian heatwave-wildfires episode has been selected as case study. Results indicate that AOD is sensitive to these key processes in the following order of importance: (1) modification of relative humidity, causing AOD differences of up to 0.6; (2) modification of vertical convection transport with AOD differences around 0:4; and (3) the dry deposition with AOD absolute differences of up to 0:35 and 0.3. Moreover, these AOD changes exhibit a nonlinear response. Both a increase and a decrease in the RH result in higher AOD values. On the other hand, both the increase and offset of the sub-grid convective transport lead to a reduction in the AOD over the fire area. In addition, a similar nonlinear response is found when reducing the dry deposition velocity; in particular, for the accumulation mode where the concentration of several species increases (while a decrease might be expected). These nonlinear responses are highly dependent on the equilibrium of the thermodynamics system sulfate-nitrate-SOA (secondary organic aerosol). In this sense, small changes in the concentration of one species can strongly affect others, finally affecting aerosol optical properties. Changes in this equilibrium could come from modifications in relative humidity, dry deposition, or vertical convective transport. By itself, dry deposition also presents a high uncertainty influencing the AOD representation. © 2020 American Society of Civil Engineers (ASCE). All rights reserved."
"56127067100;7003591311;57193321288;24402359000;","Quantification of the radiative effect of aerosol-cloud interactions in shallow continental cumulus clouds",2020,"10.1175/JAS-D-19-0269.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091002318&doi=10.1175%2fJAS-D-19-0269.1&partnerID=40&md5=4db8bb8d46bcaea479f2eb595135186d","The indirect radiative effect of aerosol variability on shallow cumulus clouds is realized in nature with considerable concurrent meteorological variability. Large-eddy simulations constrained by observations at a continental site in Oklahoma are performed to represent the variability of different meteorological states on days with different aerosol conditions. The total radiative effect of this natural covariation between aerosol and other meteorological drivers of total cloud amount and albedo is quantified. The changes to these bulk quantities are used to understand the response of the cloud radiative effect to aerosol-cloud interactions (ACI) in the context of concurrent processes, as opposed to attempting to untangle the effect of individual processes on a case-by-case basis. Mutual information (MI) analysis suggests that meteorological variability masks the strength of the relationship between cloud drop number concentration and the cloud radiative effect. This is shown to be mostly due to variation in solar zenith angle and cloud field horizontal heterogeneity masking the relationship between cloud drop number and cloud albedo. By combining MI and more traditional differential analyses, a framework to identify important modes of covariation between aerosol, clouds, and meteorological conditions is developed. This shows that accounting for solar zenith angle variation and implementing an albedo bias correction increases the detectability of the radiative effects of ACI in simulations of shallow cumulus. © 2020 American Meteorological Society."
"35758711800;","Weather effects of aerosols in theglobal forecast model",2020,"10.3390/ATMOS11080850","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85090040349&doi=10.3390%2fATMOS11080850&partnerID=40&md5=102f3f17148a815400f24e06c4bd94b2","The weather effects of aerosol types were investigated using well-posed aerosol climatology through the aerosol sensitivity test of thermodynamic and hydrometeor fields, and the weather forecast performances in July of 2017. The largest aerosol direct radiative forcing (ADRF) in July was due to dust aerosols at the surface and atmosphere, and sulfate at the top of the atmosphere (TOA), respectively. The ADRF of total aerosols had unilateral tendencies in thermodynamic and hydrometeor fields. The contribution of individual aerosols was linearly additive to those of total aerosols in the heat fluxes, heating rates, humidity, and convective precipitation. However, no such linearity existed in temperature, geopotential height, cloud liquid or ice contents, and large-scale precipitation. Dust was the most influential forcing agent in July among five aerosol types due to the largest light-absorption capacity. Such unilateral tendencies of total aerosols and a part of the linearity of individual aerosols were exerted on the weather systems. The verification of medium-range forecasts showed that aerosols alleviated the overestimation of surface shortwave (SW) downward fluxes, the negative biases of temperature and geopotential heights at TOA and surface, and the underestimation in light and moderate precipitation. In contrast, they enhanced warm biases at the mid-atmosphere and underestimation in heavy precipitations, particularly negative biases in the intertropical convergence zone (ITCZ). Weather forecast scores including current aerosol information were improved in geopotential height (GPH) of the northern hemisphere (NH); however, they got worse in the temperature and the upper atmosphere GPH of the southern hemisphere (SH), which was mostly due to black carbon (BC) aerosols in the tropical regions. The missing mechanisms such as aerosol-cloud interactions, better aerosol spectral optical properties including mixing states and aging, and the near-real-time (NRT) based aerosol loading data are worthwhile to be tried in the near future for fixing the intrinsic underestimation of precipitation in ITCZ and surface radiative fluxes in the desert and biomass burning area. © 2020 by the authors."
"57215902022;19638935200;56611366900;57192560178;22982270700;57218625361;","Understanding Cloud Droplet Spectral Dispersion Effect Using Empirical and Semi-Analytical Parameterizations in NCAR CAM5.3",2020,"10.1029/2020EA001276","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089843043&doi=10.1029%2f2020EA001276&partnerID=40&md5=2c4106d1f9b5e8f3183e2a1408219223","Five parameterizations of cloud droplet spectral shape are implemented in a global climate model to investigate the dispersion effect and aerosol indirect effect (AIE). We design a series of experiments by modifying the microphysical cloud scheme of NCAR CAM5.3 (National Center for Atmospheric Research Community Atmosphere Model Version 5.3). We employ four empirical (Martin94, RLiu03, PengL03, and Liu08) and one semi-analytical (LiuLi15) expressions for cloud droplet spectral shape parameters. Analysis focuses on the instantaneous differences in the simulated cloud microphysical properties and the comparison between model output and satellite data. The results show that RLiu03, PengL03, and LiuLi15 produce wider droplet spectrum and faster autoconversion rate, but Liu08 has a narrower droplet spectrum and slower autoconversion rate than the default parameterization (Martin94) in CAM5.3. Global dispersion effects caused by the five parameterizations modify the aerosol indirect effect by −10% (counteract) to 13% (strengthen). The simulated AIEs and dispersion effects exhibit noticeably spatial inhomogeneity. In the sensitive regions of AIE (Southeast Asia, North Pacific, and West Coast of South America), we decompose the response of shortwave cloud forcing to the change in droplet number for analysis. The varying dispersion effects can be explained by different responses of cloud properties in different spectral parameterizations. © 2020. The Authors."
"57218283496;10139397300;56462887500;","Large-Scale Industrial Cloud Perturbations Confirm Bidirectional Cloud Water Responses to Anthropogenic Aerosols",2020,"10.1029/2020JD032575","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088597530&doi=10.1029%2f2020JD032575&partnerID=40&md5=12bec54de45316dec20b3f5bde35d116","Aerosols offset a poorly quantified fraction of anthropogenic greenhouse gas warming, and the aerosol impact on clouds is the most uncertain mechanism of anthropogenic climate forcing. Here observations of a relatively weak average response of liquid cloud water to aerosol perturbations are extended to much larger areas than in previous studies, with the polluted cloud areas covering hundreds by hundreds of kilometers. Polluted clouds detected in satellite images at the global anthropogenic air pollution hot spot of Norilsk, Russia, and at other various major aerosol source regions show close compensation between aerosol-induced cloud water increases and decreases. In the sampled Norilsk cloud perturbations the decrease in liquid water path offsets 3% of the radiative forcing through the Twomey effect on average. Weak cloud water response on average in large polluted areas is in very good agreement with previous results based on observations of small-scale ship-track-like industrial cloud perturbations, helping to reduce the uncertainty associated with the anthropogenic aerosol impacts on clouds. ©2020. American Geophysical Union. All Rights Reserved."
"57142867400;56611366900;55745955800;","Effects of Lateral Entrainment Mixing With Entrained Aerosols on Cloud Microphysics",2020,"10.1029/2020GL087667","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087945178&doi=10.1029%2f2020GL087667&partnerID=40&md5=36f4c18c5bd16db7b22f059cf6882ecf","The effects of entrained environment air and aerosols on cloud properties remain a critical yet understudied topic. This study first introduces a new entraining cloud parcel model considering entrained aerosols. With entrained aerosols represented by a newly introduced parameter, the impacts of entrainment rate and entrained aerosols on cloud microphysical properties are investigated. The results show that the relationships between entrainment rate and cloud microphysical properties are highly nonlinear when the entrained aerosols vary. With the lateral entrainment mixing, a new phenomenon is revealed that the height of maximum parcel supersaturation cannot be reached when the entrainment rate is beyond a certain critical value. This new critical entrainment rate is different from the critical entrainment rate defined by Barahona and Nenes (2007, https://doi.org/10.1029/2007JD008473), beyond which clouds cannot form. This finding has important implications for developing parameterization of droplet activation, which is based primarily on the assumption of the existence of maximum supersaturation. ©2020. American Geophysical Union. All Rights Reserved."
"57195056873;7201920350;35209683700;56923937200;57202925605;57199068971;57217862195;57217857005;57208383202;57217862422;7401796996;","Localization and Invigoration of Mei-yu Front Rainfall due to Aerosol-Cloud Interactions: A Preliminary Assessment Based on WRF Simulations and IMFRE 2018 Field Observations",2020,"10.1029/2019JD031952","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087728434&doi=10.1029%2f2019JD031952&partnerID=40&md5=721532e2765cf0e7a2ccfe36488c62be","Aerosol-cloud interactions remain a major source of uncertainty in our understanding and modeling of the Earth's hydrological cycle. Based upon a diagnostic and modeling analysis utilizing the latest field measurements from the Integrative Monsoon Frontal Rainfall Experiment (IMFRE) 2018, this paper reports the effects of aerosols on the cloud properties along the Mei-yu front over the Middle Reaches of Yangtze River in China. Numerical experiments with the Weather Research and Forecasting (WRF) model suggest that increasing aerosol number concentration reduces surface precipitation by ~8.8% and delays the onset of rainfall by ~30 min. Furthermore, warm clouds are suppressed but the convective cores are slightly intensified. This corresponds to an overall aerosol effect of “localization and invigoration” of the Mei-yu rainfall and thus an elevated probability of short-term heavy rainfall. The signals of “convective invigoration” with a bulk scheme in this study are relatively weak compared to those simulated by bin microphysics. The increased aerosol concentration strengthens Mei-yu front and changes local morphology of the front, consistent with earlier studies demonstrating positive effects of convective heating on the genesis and maintenance of Mei-yu front via conditional instability of the second kind (CISK) and diabatic generation of potential vorticity. Also discussed are the uncertainties of bulk microphysics in simulating aerosol-cloud interactions, which may shed light on the design of future field campaigns to further understand the impact of aerosol-cloud interactions on weather and climate over China in boreal summer. ©2020. American Geophysical Union. All Rights Reserved."
"57213002882;55984424900;7005601996;6603093035;55943979800;13204951000;57092684000;7005461772;7003993113;8657171200;10739566100;7006708207;57217853456;57189377456;21834810800;","Linking Marine Biological Activity to Aerosol Chemical Composition and Cloud-Relevant Properties Over the North Atlantic Ocean",2020,"10.1029/2019JD032246","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087705734&doi=10.1029%2f2019JD032246&partnerID=40&md5=c5e6f464ee4b1c1efc425d4c46bcbfba","The ways in which marine biological activity affects climate, by modifying aerosol properties, are not completely understood, causing high uncertainties in climate predictions. In this work, in situ measurements of aerosol chemical composition, particle number size distribution, cloud condensation nuclei (CCN), and ice-nucleating particle (INP) number concentrations are combined with high-resolution sea surface chlorophyll-a concentration (CHL) and back-trajectory data to elucidate the relationship between oceanic biological activity and marine aerosol. The measurements were performed during an intensive field campaign conducted in late summer (August–September) 2015 at the Mace Head Research Station (MHD). At the short time scale (1–2 months) of the experiment, we observed a clear dependency of the main aerosol physicochemical and cloud-relevant properties on the patterns of biological activity, in specific oceanic regions with a delayed response of about 1–3 weeks. The oceanic region comprised between 47°–57°N and 14°–30°W was identified as the main source of biogenic aerosols during the campaign, with hints of some minor influence of waters up to the Greenland coast. These spatial and temporal relationships demonstrate that the marine biota influences aerosol properties under a variety of features up to the most cloud-relevant properties. Such dependency of aerosol properties with oceanic biological activity was previously reported over the North Atlantic Ocean only for multiyear data sets, where the correlation may be enhanced by coincident seasonalities. A better knowledge of these short time scale interactions may lead to a significant improvement in understanding the ocean-atmosphere-cloud system, with important impacts on climate science. ©2020. American Geophysical Union. All Rights Reserved."
"56459194500;","Quantifying the impacts of fire aerosols on global terrestrial ecosystem productivity with the fully-coupled Earth system model CESM [火灾气溶胶对全球陆地生态系统生产力的影响]",2020,"10.1080/16742834.2020.1740580","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082405985&doi=10.1080%2f16742834.2020.1740580&partnerID=40&md5=dc0cfa5975311271b86184fbcda7fa1e","Fire is a global phenomenon and a major source of aerosols from the terrestrial biosphere to the atmosphere. Most previous studies quantified the effect of fire aerosols on climate and atmospheric circulation, or on the regional and site-scale terrestrial ecosystem productivity. So far, only one work has quantified their global impacts on terrestrial ecosystem productivity based on offline simulations, which, however, did not consider the impacts of aerosol–cloud interactions and aerosol–climate feedbacks. This study quantitatively assesses the influence of fire aerosols on the global annual gross primary productivity (GPP) of terrestrial ecosystems using simulations with the fully coupled global Earth system model CESM1.2. Results show that fire aerosols generally decrease GPP in vegetated areas, with a global total of −1.6 Pg C yr−1, mainly because fire aerosols cool and dry the land surface and weaken the direct photosynthetically active radiation (PAR). The exception to this is the Amazon region, which is mainly due to a fire-aerosol-induced wetter land surface and increased diffuse PAR. This study emphasizes the importance of the influence of fire aerosols on climate in quantifying global-scale fire aerosols’ impacts on terrestrial ecosystem productivity. © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group."
"57191428317;57195361985;57191430389;56650977600;56210720700;7101846027;7006572336;57196499374;16308514000;","On the relationship between cloud water composition and cloud droplet number concentration",2020,"10.5194/acp-20-7645-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088287341&doi=10.5194%2facp-20-7645-2020&partnerID=40&md5=ddf5aa97540d9e204555b2ab2d21abc2","Aerosol cloud interactions are the largest source of uncertainty in quantifying anthropogenic radiative forcing. The large uncertainty is, in part, due to the difficulty of predicting cloud microphysical parameters, such as the cloud droplet number concentration (Nd). Even though rigorous first-principle approaches exist to calculate Nd, the cloud and aerosol research community also relies on empirical approaches such as relating Nd to aerosol mass concentration. Here we analyze relationships between Nd and cloud water chemical composition, in addition to the effect of environmental factors on the degree of the relationships. Warm, marine, stratocumulus clouds off the California coast were sampled throughout four summer campaigns between 2011 and 2016. A total of 385 cloud water samples were collected and analyzed for 80 chemical species. Single- and multispecies log log linear regressions were performed to predict Nd using chemical composition. Single-species regressions reveal that the species that best predicts Nd is total sulfate (R2 adj D 0:40). Multispecies regressions reveal that adding more species does not necessarily produce a better model, as six or more species yield regressions that are statistically insignificant. A commonality among the multispecies regressions that produce the highest correlation with Nd was that most included sulfate (either total or non-seasalt), an ocean emissions tracer (such as sodium), and an organic tracer (such as oxalate). Binning the data according to turbulence, smoke influence, and in-cloud height allowed for examination of the effect of these environmental factors on the composition Nd correlation. Accounting for turbulence, quantified as the standard deviation of vertical wind speed, showed that the correlation between Nd with both total sulfate and sodium increased at higher turbulence conditions, consistent with turbulence promoting the mixing between ocean surface and cloud base. Considering the influence of smoke significantly improved the correlation with Nd for two biomass burning tracer species in the study region, specifically oxalate and iron. When binning by in-cloud height, non-sea-salt sulfate and sodium correlated best with Nd at cloud top, whereas iron and oxalate correlated best with Nd at cloud base. © 2020 Copernicus GmbH. All rights reserved."
"8866821900;","Aquaplanets as a Framework for Examination of Aerosol Effects",2020,"10.1029/2019MS001874","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088561854&doi=10.1029%2f2019MS001874&partnerID=40&md5=e7a6fe65d4f82a601e5e2552b62e1183","Although fundamental to the planetary radiative balance, aerosol impacts are highly uncertain in climate simulations because of the uneven distribution of aerosol sources and the complex interactions with radiation and clouds that are difficult to represent in climate models. This study proposes that aquaplanet configurations represent an idealized framework to investigate aerosol effects. As a simple demonstration, a series of aquaplanet simulations with the Community Atmosphere Model version 6 shows that the spatial distribution of aerosol emissions changes the aerosol effective radiative forcing even with unchanged total emissions. Some statistical properties of the simulations are presented to show that relatively short model integrations yield robust results. Much of the aerosol effect is shown to arise from aerosol-cloud interactions, especially through rapid adjustments associated with the aerosol lifetime effect that alter the cloud optical thickness. ©2020. The Authors."
"26032229000;35220430700;55470017900;16551540700;","Editorial for special issue ""high resolution active optical remote sensing observations of aerosols, clouds and aerosol-cloud interactions and their implication to climate""",2020,"10.3390/rs12132166","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087563892&doi=10.3390%2frs12132166&partnerID=40&md5=83fe2fd7399ea0efb24182591246a298","This Special Issue contains twelve publications that, through different remote sensing techniques, investigate how the atmospheric aerosol layers and their radiative effects influence cloud formation, precipitation and air-quality. The investigations are carried out analyzing observations obtained from high-resolution optical devices deployed on different platforms as satellite and ground-based observational sites. In this editorial, the published contributions are taken in review to highlight their innovative contribution and research main findings. © 2020 by the authors."
"57201394954;55913339000;57210808619;57201395360;57201392422;","Inconsistent aerosol indirect effects on water clouds and ice clouds over the Tibetan Plateau",2020,"10.1002/joc.6430","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076748124&doi=10.1002%2fjoc.6430&partnerID=40&md5=6b51b76c2ae5de5d3f412d6bb3a43e4f","Recently, satellites have observed that dust events are occurring more frequently over the Tibetan Plateau (TP), which implies a new issue of aerosols influencing cloud properties and presents a new challenge in research on the role of the TP in climate change. In this study, combining satellite observations with Climate Model Intercomparison Project Phase 5 (CMIP5) model simulations, the inconsistent aerosol indirect effects on the properties of water clouds and ice clouds over the TP are compared and quantified. Analyses of satellite observations show that, compared with water clouds, ice clouds are observed more frequently and are more significantly correlated with aerosols over the TP. Correspondingly, the aerosol effect on the radiative forcing of ice clouds is more significant than that on the forcing of water clouds, in which the aerosol indirect effect is dominated by the effect on the shortwave radiative forcing of ice clouds. Both observations and CMIP5 model simulation results show that, due to the variation of aerosols, changes in the ice cloud radiative forcing cover most of the TP, while changes in the water cloud radiative forcing mainly appear over the southern edge of the TP. The CMIP5 simulation results suggest that the aerosol indirect effect on the total radiative forcing of water clouds over the TP is −0.34 (±0.03) W⋅m−2, while that on the forcing of ice clouds is −0.73 (±0.03) W⋅m−2. Overall, both the model simulations and satellite results show that the indirect effect of aerosols on ice clouds is more pronounced than that on water clouds. © 2019 Royal Meteorological Society"
"57204899091;13403622000;56004685100;","Disentangling the Microphysical Effects of Fire Particles on Convective Clouds Through A Case Study",2020,"10.1029/2019JD031890","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086888115&doi=10.1029%2f2019JD031890&partnerID=40&md5=e0f5a66da5c3f896bd70b179fceca308","Aerosol emissions from forest fires may impact cloud droplet activation through an increase in particle number concentrations (“the number effect”) and also through a decrease in the hygroscopicity κ of the entire aerosol population (“the hygroscopicity effect”) when fully internal mixing is assumed in models. This study investigated these effects of fire particles on the properties of simulated deep convective clouds (DCCs), using cloud-resolving simulations with the Weather Research and Forecasting model coupled with Chemistry for a case study in a partly idealized setting. We found that the magnitude of the hygroscopicity effect was in some cases strong enough to entirely offset the number/size effect, in terms of its influence on modeled droplet and ice crystal concentrations. More specifically, in the case studied here, the droplet number concentration was reduced by about 37% or more due solely to the hygroscopicity effect. In the atmosphere, by contrast, fire particles likely have a much weaker impact on the hygroscopicity of the pre-existing background aerosol, as such a strong impact would occur only if the fire particles mixed immediately and uniformly with the background. We also show that the differences in the number of activated droplets eventually led to differences in the optical thickness of the clouds aloft, though this finding is limited to only a few hours of the initial development stage of the DCCs. These results suggest that accurately and rigorously representing aerosol mixing and κ in models is an important step toward accurately simulating aerosol-cloud interactions under the influence of fires. ©2020. The Authors."
"35095482200;35095482200;57217381144;26427916400;7003729315;7101707186;57217380754;57215231856;24322892500;7006783796;7006783796;7404544551;7103072920;7103072920;","Reducing uncertainties in satellite estimates of aerosol-cloud interactions over the subtropical ocean by integrating vertically resolved aerosol observations",2020,"10.5194/acp-20-7167-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087167218&doi=10.5194%2facp-20-7167-2020&partnerID=40&md5=2acaa8b35e3394d006dab9925508ec23","Satellite quantification of aerosol effects on clouds relies on aerosol optical depth (AOD) as a proxy for aerosol concentration or cloud condensation nuclei (CCN). However, the lack of error characterization of satellite-based results hampers their use for the evaluation and improvement of global climate models. We show that the use of AOD for assessing aerosol-cloud interactions (ACIs) is inadequate over vast oceanic areas in the subtropics. Instead, we postulate that a more physical approach that consists of matching vertically resolved aerosol data from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite at the cloud-layer height with Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua cloud retrievals reduces uncertainties in satellite-based ACI estimates. Combined aerosol extinction coefficients (σ) below cloud top (σBC) from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and cloud droplet number concentrations (Nd) from MODIS Aqua yield high correlations across a broad range of σBC values, with sBC quartile correlations ≥ 0.78. In contrast, CALIOP-based AOD yields correlations with MODIS Nd of 0.54-0.62 for the two lower AOD quartiles. Moreover, sBC explains 41 % of the spatial variance in MODIS Nd, whereas AOD only explains 17 %, primarily caused by the lack of spatial covariability in the eastern Pacific. Compared with σBC, near-surface σ weakly correlates in space with MODIS Nd, accounting for a 16 % variance. It is concluded that the linear regression calculated from ln(Nd/-ln(σBC) (the standard method for quantifying ACIs) is more physically meaningful than that derived from the Nd-AOD pair. © Author(s) 2020."
"57198006594;26665602100;35546188200;","Aerosol indirect effects on the temperature-precipitation scaling",2020,"10.5194/acp-20-6207-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085653703&doi=10.5194%2facp-20-6207-2020&partnerID=40&md5=f9edad809df9c0d06c4536f6a490e2f9","Aerosols may impact precipitation in a complex way involving their direct and indirect effects. In a previous numerical study, the overall microphysical effect of aerosols was found to weaken precipitation through reduced precipitable water and convective instability. The present study aims to quantify the relative importance of these two processes in the reduction of summer precipitation using temperature-precipitation scaling. Based on a numerical sensitivity experiment conducted in central Europe aiming to isolate indirect effects, the results show that, all others effects being equal, the scaling of hourly convective precipitation with temperature follows the Clausius-Clapeyron (CC) relationship, whereas the decrease in convective precipitation does not scale with the CC law since it is mostly attributable to increased stability with increased aerosol concentration rather than to decreased precipitable water content. This effect is larger at low surface temperatures at which clouds are statistically more frequent and optically thicker. At these temperatures, the increase in stability is mostly linked to the stronger reduction in temperature in the lower troposphere compared to the upper troposphere, which results in lower lapse rates. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License."
"55813858200;6506545080;6701873414;7202252296;7203034123;","Nonturbulent Liquid-Bearing Polar Clouds: Observed Frequency of Occurrence and Simulated Sensitivity to Gravity Waves",2020,"10.1029/2020GL087099","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085477573&doi=10.1029%2f2020GL087099&partnerID=40&md5=3d670b03f269c0f8513c725b8c5e9ccf","A common feature of polar liquid-bearing clouds (LBCs) is radiatively driven turbulence, which may variously alter cloud lifecycle via vertical mixing, droplet activation, and subsequent feedbacks. However, polar LBCs are commonly initiated under stable, nonturbulent conditions. Using long-term data from the North Slope of Alaska and McMurdo, Antarctica, we show that nonturbulent conditions prevail in ~25% of detected LBCs, surmised to be preferentially early in their lifecycle. We conclude that nonturbulent LBCs are likely common over the polar regions owing primarily to atmospheric temperature and stability. Such stable environments are known to support gravity wave activity. Using large-eddy simulations, we find that short to intermediate period gravity waves may catalyze turbulence formation when aerosol particles available for activation are sufficiently small. We posit that the frequent occurrence of nonturbulent LBCs over the polar regions has implications for polar aerosol-cloud interactions and their parameterization in large-scale models. © 2020, American Geophysical Union. All Rights Reserved."
"26032229000;35463545000;36117910700;55470017900;42962520400;","Features and Characteristics of the new NASA MicroPuLse NETwork (MPLNET) automatic rain detection algorithm",2020,"10.1088/1755-1315/489/1/012028","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086228314&doi=10.1088%2f1755-1315%2f489%2f1%2f012028&partnerID=40&md5=38b020109b577c8e0d11f8122ea9424c","The water cycle strongly influences life on Earth. In particular, the precipitation modifies the atmospheric column thermodynamics through the process of evaporation and serves as a proxy for latent heat modulation. For this reason, a correct precipitation parameterization (especially low-intensity precipitation) at global scale, bedsides improving our understanding of the hydrological cycle, it is crucial to reduce the associated uncertainty of the global climate models to correctly forecast future scenarios, i.e. to apply fast mitigation strategies. In this study we developed an algorithm to automatically detect precipitation from lidar measurements obtained by the National and Aeronautics Space Administration (NASA) Micropulse lidar network (MPLNET) permanent observational site in Goddard. The algorithm, once full operational, will deliver in Near Real Time (latency 1.5h) a new rain mask product that will be publicly available on MPLNET website as part of the new Version 3 Level 1.5 data. The methodology, based on an image processing technique, can detect only light precipitation events (defined by intensity and duration) as the morphological filters used through the detection process are applied on the lidar volume depolarization ratio range corrected composite images, i.e. heavy rain events are unusable as the lidar signal is completely extinguished after few meters in the precipitation or no signal detected because of the water accumulated on the receiver optics. © Published under licence by IOP Publishing Ltd."
"56262351900;6603478665;57194702516;6506718302;36601252500;55359575700;37051480000;57203088526;15765804400;6602917432;55800347700;","Effects of black carbon mitigation on Arctic climate",2020,"10.5194/acp-20-5527-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085115138&doi=10.5194%2facp-20-5527-2020&partnerID=40&md5=2fe071cdb112a236ebcd593501cae098","pWe use the ECHAM-HAMMOZ aerosol-climate model to assess the effects of black carbon (BC) mitigation measures on Arctic climate. To this end we constructed several mitigation scenarios that implement all currently existing legislation and then implement further reductions of BC in a successively increasing global area, starting from the eight member states of the Arctic Council, expanding to its active observer states, then to all observer states, and finally to the entire globe. These scenarios also account for the reduction of the co-emitted organic carbon (OC) and sulfate (SU). We find that, even though the additional BC emission reductions in the member states of the Arctic Council are small, the resulting reductions in Arctic BC mass burdens can be substantial, especially in the lower troposphere close to the surface. This in turn means that reducing BC emissions only in the Arctic Council member states can reduce BC deposition in the Arctic by about 30&thinsp;% compared to the current legislation, which is about 60&thinsp;% of what could be achieved if emissions were reduced globally. Emission reductions further south affect Arctic BC concentrations at higher altitudes and thus only have small additional effects on BC deposition in the Arctic. The direct radiative forcing scales fairly well with the total amount of BC emission reduction, independent of the location of the emission source, with a maximum direct radiative forcing in the Arctic of about span classCombining double low line""inline-formula""-0.4/span&thinsp;W&thinsp;mspan classCombining double low line""inline-formula""-2/span for a global BC emission reduction. On the other hand, the Arctic effective radiative forcing due to the BC emission reductions, which accounts for aerosol-cloud interactions, is small compared to the direct aerosol radiative forcing. This happens because BC-and OC-containing particles can act as cloud condensation nuclei, which affects cloud reflectivity and lifetime and counteracts the direct radiative forcing of BC. Additionally, the effective radiative forcing is accompanied by very large uncertainties that originate from the strong natural variability of meteorology, cloud cover, and surface albedo in the Arctic. We further used the TM5-FASST model to assess the benefits of the aerosol emission reductions for human health. We found that a full implementation in all Arctic Council member and observer states could reduce the annual global number of premature deaths by 329&thinsp;000 by the year 2030, which amounts to 9&thinsp;% of the total global premature deaths due to particulate matter. © Author(s) 2020."
"57211870916;6603926727;55315290600;","System driven changes in aerosol-cloud interactions and its impact on the life-cycle of a monsoon depression",2020,"10.1016/j.atmosres.2019.104765","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075208454&doi=10.1016%2fj.atmosres.2019.104765&partnerID=40&md5=363bc460867ca6968c5a4f51b0eba8b8","This study examines the aerosol effect on the life cycle of a monsoon depression (‘MD’ hereafter), particularly whether it could suppress the system as suggested by previous modeling studies. Airborne aerosol and cloud microphysical observations collected during an MD (24 and 25, August 2009) are analyzed and the interactions between aerosols, cloud microphysics and MD dynamics are discussed. The growth of warm rain processes during the MD life-cycle was also investigated. An absence of rainfall due to the SW-NE orientation of rain belt exposed the northwest region of India to dry conditions and the transport of dust and anthropogenic aerosols through westerlies and north-westerlies heavily increased the aerosol concentration (NAERO) over the region which was favorable to suppress the convection. The results show an increase in regional convergence of zonal wind associated with high NAERO that led to an early transport of moisture to this region. The high NAERO under strong wind shear and dry to humid transition significantly affected the convective activity over the land during the initial phase of the MD. Over Central India, the combination of humid air and aerosols lead to the suppression and later redistribution of rainfall associated with the MD. However, these effects did not sustain for long as the continuous moisture transport part of the mesoscale convective system revitalized the system which is evident from surface latent heat flux. The strong low-level moisture transport supported by large-scale convergence from the Arabian Sea also weakened the aerosol effect helping in the good rainfall. The study also highlights that giant Cloud Condensation Nuclei (CCN) could play a positive role while the smaller CCN contributes to the suppression of rainfall. © 2019 Elsevier B.V."
"57113269700;57192168375;26023140500;57194228711;15926468600;","Flow-induced errors in airborne in situ measurements of aerosols and clouds",2020,"10.5194/amt-13-1963-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083786034&doi=10.5194%2famt-13-1963-2020&partnerID=40&md5=8477d29f5f3f01d92d598efddaa0f400","<p>Aerosols and clouds affect atmospheric radiative processes and climate in many complex ways and still pose the largest uncertainty in current estimates of the Earth's changing energy budget.</p> <p>Airborne in situ sensors such as the Cloud, Aerosol, and Precipitation Spectrometer (CAPS) or other optical spectrometers and optical array probes provide detailed information about the horizontal and vertical distribution of aerosol and cloud properties. However, flow distortions occurring at the location where these instruments are mounted on the outside of an aircraft may directly produce artifacts in detected particle number concentration and also cause droplet deformation and/or breakup during the measurement process.</p> <p>Several studies have investigated flow-induced errors assuming that air is incompressible. However, for fast-flying aircraft, the impact of air compressibility is no longer negligible. In this study, we combine airborne data with numerical simulations to investigate the flow around wing-mounted instruments and the induced errors for different realistic flight conditions. A correction scheme for deriving particle number concentrations from in situ aerosol and cloud probes is proposed, and a new formula is provided for deriving the droplet volume from images taken by optical array probes. Shape distortions of liquid droplets can either be caused by errors in the speed with which the images are recorded or by aerodynamic forces acting at the droplet surface caused by changes of the airflow when it approaches the instrument. These forces can lead to the dynamic breakup of droplets causing artifacts in particle number concentration and size. An estimation of the critical breakup diameter as a function of flight conditions is provided.</p> <p>Experimental data show that the flow speed at the instrument location is smaller than the ambient flow speed. Our simulations confirm the observed difference and reveal a size-dependent impact on particle speed and concentration. This leads, on average, to a 25&thinsp;% overestimation of the number concentration of particles with diameters larger than 10&thinsp;<span classCombining double low line""inline-formula"">μm</span> diameter and causes distorted images of droplets and ice crystals if the flow values recorded at the instrument are used. With the proposed corrections, errors of particle number concentration and droplet volume, as well as image distortions, are significantly reduced by up to 1 order of magnitude.</p> <p>Although the presented correction scheme is derived for the DLR Falcon research aircraft (Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) campaign) and validated for the DLR Falcon (Absorbing aerosol layers in a changing climate: Aging, lifetime and dynamics mission conducted in 2017 (A-LIFE) campaign) and the NASA DC-8 (Atmospheric Tomography Mission (ATom) campaigns), the general conclusions hold for any fast-flying research aircraft.</p>. © 2020 Royal Society of Chemistry. All rights reserved."
"57192915106;6508026916;56998535300;35177669200;36457573700;36661106500;55883983700;39361670300;","Added value of aerosol-cloud interactions for representing aerosol optical depth in an online coupled climate-chemistry model over Europe",2020,"10.3390/atmos11040360","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085121943&doi=10.3390%2fatmos11040360&partnerID=40&md5=909e513988cbb7a3693e80b3d3907acb","Aerosol-cloud interactions (ACI) represent one of the most important sources of uncertainties in climate modelling. In this sense, realistic simulations of ACI are needed for a better understanding of the complex interactions between air pollution and the climate system. This work quantifies the added value of including ACI in an online coupled climate/chemistry model (WRF-Chem, 0.44° horizontal resolution, years 2003 to 2010) in order to assess whether there is an improvement in the representation of aerosol optical depth (AOD). Modelling results for each species have been evaluated against the Copernicus Atmosphere Monitoring Service (CAMS) reanalysis, and AOD at 675 nm has been compared to AERONET data. Results indicate that the improvements of the monthly biases are around 8% for total AOD550 when including ACI, reaching 20% for the monthly bias in AOD550 coming from dust. Moreover, the temporal representation of AOD550 largely improves (increase in the Pearson time correlation coefficients), ranging from 6% to 20% depending on the chemical species considered. The benefits from this improvement overcome the problems derived from the high computational time required in ACI simulations (eight times higher with respect to simulations not including aerosol-cloud interactions). © 2020 by the authors."
"57216645367;56162305900;56722821200;57200208164;","Synergetic Satellite Trend Analysis of Aerosol and Warm Cloud Properties ver Ocean and Its Implication for Aerosol-Cloud Interactions",2020,"10.1029/2019JD031598","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082691070&doi=10.1029%2f2019JD031598&partnerID=40&md5=fec3e0337fb0fefc3901260cdaa7161c","Decadal-scale trends in aerosol and cloud properties provide important ways for understanding aerosol-cloud interactions. In this paper, by using MODIS products (2003–2017), we analyze synergetic trends in aerosol properties and warm cloud properties over global ocean. Cloud droplet number concentration (CDNC) and aerosol parameters (aerosol optical depth, angstrom exponent, and aerosol index) show consistent decreasing trend over East Coast of the United States (EUS), west coast of Europe (WEU), and east coast of China (EC), and no significant trend in liquid water path is found over these regions during the period 2003–2017. Over regions with significant long-term trends of aerosol loading and CDNC (e.g., EUS and WEU), the sensitivity of CDNC to aerosol loading based on the long-term trend is closer to those derived from ground and aircraft observations and larger than those derived from instantaneous satellite observations, providing an alternative way for quantifying aerosol-cloud interactions. A clear shift in the normalized probability density function of CDNC between the first 5 years (2003–2007) and the last 5 years (2013–2017) is found, with a decrease of around 50% in the occurrence frequency of high CDNC (&gt;400 cm−3) over EUS and WEU. The relative variances of cloud droplet effective radius generally decrease with decreasing aerosol loading, providing large-scale evidence for the effects of anthropogenic aerosols on the dispersion of cloud droplet size distribution. The long-term satellite data sets provide great opportunities for quantifying aerosol-cloud interactions and further confronting these interactions in climate models in the future. ©2020. American Geophysical Union. All Rights Reserved."
"26643250500;","Process-Based Simulation of Aerosol-Cloud Interactions in a One-Dimensional Cirrus Model",2020,"10.1029/2019JD031847","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082330737&doi=10.1029%2f2019JD031847&partnerID=40&md5=3b512e08cddfe4db335e5ba5e308e76b","A new microphysical cirrus model to simulate ice crystal nucleation, depositional growth, and gravitational settling is described. The model tracks individual simulation ice particles in a vertical column of air and allows moisture and heat profiles to be affected by turbulent diffusion. Ice crystal size- and supersaturation-dependent deposition coefficients are employed in a one-dimensional model framework. This enables the detailed simulation of microphysical feedbacks influencing the outcome of ice nucleation processes in cirrus. The use of spheroidal water vapor fluxes enables the prediction of primary ice crystal shapes once microscopic models describing the vapor uptake on the surfaces of cirrus ice crystals are better constrained. Two applications addressing contrail evolution and cirrus formation demonstrate the potential of the model for advanced studies of aerosol-cirrus interactions. It is shown that supersaturation in, and microphysical and optical properties of, cirrus are affected by variable deposition coefficients. Vertical variability in ice supersaturation, ice crystal sedimentation, and high turbulent diffusivity all tend to decrease homogeneously nucleated ice number mixing ratios over time, but low ice growth efficiencies counteract this tendency. Vertical mixing induces a tendency to delay the onset of homogeneous freezing. In situations of sustained large-scale cooling, natural cirrus clouds may often form in air surrounding persistent contrails. ©2020. American Geophysical Union. All Rights Reserved."
"57216133573;8629713500;7401796996;7102423967;57200702127;56457152000;","Investigation of aerosol-cloud interactions under different absorptive aerosol regimes using Atmospheric Radiation Measurement (ARM) southern Great Plains (SGP) ground-based measurements",2020,"10.5194/acp-20-3483-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082576784&doi=10.5194%2facp-20-3483-2020&partnerID=40&md5=598ef7cbd2374981ea786a1421fa396f","The aerosol indirect effect on cloud microphysical and radiative properties is one of the largest uncertainties in climate simulations. In order to investigate the aerosol-cloud interactions, a total of 16 low-level stratus cloud cases under daytime coupled boundary-layer conditions are selected over the southern Great Plains (SGP) region of the United States. The physicochemical properties of aerosols and their impacts on cloud microphysical properties are examined using data collected from the Department of Energy Atmospheric Radiation Measurement (ARM) facility at the SGP site. The aerosol-cloud interaction index (<span classCombining double low line""inline-formula"">ACIr</span>) is used to quantify the aerosol impacts with respect to cloud-droplet effective radius. The mean value of <span classCombining double low line""inline-formula"">ACIr</span> calculated from all selected samples is <span classCombining double low line""inline-formula"">0.145±0.05</span> and ranges from 0.09 to 0.24 at a range of cloud liquid water paths (LWPs; <span classCombining double low line""inline-formula"">LWPCombining double low line20</span>-300&thinsp;g&thinsp;m<span classCombining double low line""inline-formula"">-2</span>). The magnitude of <span classCombining double low line""inline-formula"">ACIr</span> decreases with an increasing LWP, which suggests a diminished cloud microphysical response to aerosol loading, presumably due to enhanced condensational growth processes and enlarged particle sizes. The impact of aerosols with different light-absorbing abilities on the sensitivity of cloud microphysical responses is also investigated. In the presence of weak light-absorbing aerosols, the low-level clouds feature a higher number concentration of cloud condensation nuclei (<span classCombining double low line""inline-formula""><i>N</i>CCN</span>) and smaller effective radii (<span classCombining double low line""inline-formula""><i>r</i>e</span>), while the opposite is true for strong light-absorbing aerosols. Furthermore, the mean activation ratio of aerosols to CCN (<span classCombining double low line""inline-formula""><i>N</i>CCNĝ&circ;•<i>N</i>a</span>) for weakly (strongly) absorbing aerosols is 0.54 (0.45), owing to the aerosol microphysical effects, particularly the different aerosol compositions inferred by their absorptive properties. In terms of the sensitivity of cloud-droplet number concentration (<span classCombining double low line""inline-formula""><i>N</i>d</span>) to <span classCombining double low line""inline-formula""><i>N</i>CCN</span>, the fraction of CCN that converted to cloud droplets (<span classCombining double low line""inline-formula""><i>N</i>dĝ&circ;•<i>N</i>CCN</span>) for the weakly (strongly) absorptive regime is 0.69 (0.54). The measured <span classCombining double low line""inline-formula"">ACIr</span> values in the weakly absorptive regime are relatively higher, indicating that clouds have greater microphysical responses to aerosols, owing to the favorable thermodynamic condition. The reduced <span classCombining double low line""inline-formula"">ACIr</span> values in the strongly absorptive regime are due to the cloud-layer heating effect induced by strong light-absorbing aerosols. Consequently, we expect larger shortwave radiative cooling effects from clouds in the weakly absorptive regime than those in the strongly absorptive regime.. © 2020 BMJ Publishing Group. All rights reserved."
"57196309273;7501627905;","The impacts of biomass burning activities on convective systems over the Maritime Continent",2020,"10.5194/acp-20-2533-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081133313&doi=10.5194%2facp-20-2533-2020&partnerID=40&md5=afe7844cdace78b8576365dc26e709e5","Convective precipitation associated with Sumatra squall lines and diurnal rainfall over Borneo is an important weather feature of the Maritime Continent in Southeast Asia. Over the past few decades, biomass burning activities have been widespread during summertime over this region, producing massive fire aerosols. These additional aerosols, when brought into the atmosphere, besides influencing the local radiation budget through directly scattering and absorbing sunlight, can also act as cloud condensation nuclei or ice nuclei to alter convective clouds and precipitation over the Maritime Continent via so-called aerosol indirect effects. Based on 4-month simulations with or without biomass burning aerosols, conducted using the Weather Research and Forecasting model coupled with a chemistry module (WRF-Chem), we have investigated the aerosol-cloud interactions associated with biomass burning aerosols over the Maritime Continent. Results from selected cases of convective events have specifically shown the significant impact of fire aerosols on weak convections by their increasing of the quantities of hydrometeors and rainfall in both the Sumatra and Borneo regions. Statistical analysis over the fire season also suggests that fire aerosols have impacts on the nocturnal convections associated with the local anticyclonic circulation in western Borneo and weaken nocturnal rainfall intensity by about 9 %. Such an effect is likely to have come from the near-surface heating due to absorbing aerosols emitted from fires, which could weaken land breezes and thus the convergence of anticyclonic circulation. © Author(s) 2020."
"56999327800;56611366900;38762392200;6603631763;16305549600;","Climatology perspective of sensitive regimes and active regions of aerosol indirect effect for cirrus clouds over the global oceans",2020,"10.3390/rs12050823","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081897956&doi=10.3390%2frs12050823&partnerID=40&md5=6bc61f075df4e1ac831fa668fab952a6","Long-term satellite climate data records (CDRs) of clouds and aerosols are used to investigate the aerosol indirect effect (AIE) of cirrus clouds over the global oceans from a climatology perspective. Our study focuses on identifying the sensitive regimes and active regions where AIE signatures easily manifest themselves in the sense of the long-term average of cloud and aerosol variables. The aerosol index (AIX) regimes of AIX < 0.18 and 0.18 < AIX < 0.46 are respectively identified as the sensitive regimes for negative and positive aerosol albedos and lifetime effects of cirrus clouds. Relative humidity first decreases (along with upward motions) and then reverses to increase (along with downward motions) in the first regime of negative aerosol albedo and lifetime effects. Relatively wet and strong upward motions are the favorable meteorological conditions for the second regime of positive aerosol albedo and lifetime effects. Two swath regions extending from 15°N to 30°N over the east coastal oceans of China and the USA are the active regions of positive aerosol albedo effects. Positive aerosol lifetime effects are only active or easy to manifest in the regions where a positive aerosol albedo effect is active. The results based on the long-term averaged satellite observations are valuable for the evaluation and improvement of aerosol-cloud interactions for cirrus clouds in global climate models. © 2020 by the authors."
"57194590416;25031430500;13403622000;36600036800;6603749963;","Exploring Impacts of Size-Dependent Evaporation and Entrainment in a Global Model",2020,"10.1029/2019JD031817","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081068692&doi=10.1029%2f2019JD031817&partnerID=40&md5=dfd38a3242356aa8dceeb373af371b57","While most observations indicate well-buffered clouds to aerosol perturbations, global models do not. Among the suggested mechanisms for this discrepancy is the models' lack of connections between cloud droplet size and two processes that can contribute to reduced cloudiness when droplets become more numerous and smaller: evaporation and entrainment. In this study, we explore different implementations of size-dependent evaporation and entrainment in the global atmospheric model CAM5.3-Oslo. We study their impact on the preindustrial-to-present day change in liquid water path ((Formula presented.)) and the corresponding aerosol indirect effect ((Formula presented.)). Impacts of the 2014–2015 fissure eruption in Holuhraun, Iceland, are also presented. Our entrainment modifications only have a moderate effect on (Formula presented.) (changes from (Formula presented.) 1.07 W m (Formula presented.) to (Formula presented.) 0.98 W m (Formula presented.)), and a small impact on the signal from the Holuhraun eruption compared to other suggested compensating mechanisms. Simulations with added size-dependent evaporation in the top of the stratiform clouds also show small evaporation differences between PI and PD. Moderate changes in (Formula presented.) were achieved when also including an entrainment feedback to the evaporation changes, mixing air between the cloudtop layer and the layer above. These changes were not associated with the size dependency, but changes in the cloud susceptibility to aerosols in both PI and PD when adding evaporation. We find that increased evaporation of smaller droplets at stratiform cloud tops can reduce (Formula presented.), but can increase (Formula presented.) in some areas due to enhanced shallow convection caused by destabilization. ©2020. The Authors."
"57194682576;22635999400;57126848900;7003444634;57209647985;18134565600;56210720700;","Observations of Aerosol-Cloud Interactions During the North Atlantic Aerosol and Marine Ecosystem Study",2020,"10.1029/2019GL085851","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079575620&doi=10.1029%2f2019GL085851&partnerID=40&md5=b83f36312e15910e260ea7912fc3e30b","Clouds and their response to aerosols constitute the largest uncertainty in our understanding of 20th-century climate change. We present an investigation that determines linkages between remotely sensed marine cloud properties with in situ measurements of cloud condensation nuclei (CCN) and meteorological properties obtained during the North Atlantic Aerosols and Marine Ecosystems Study. The first two deployments of this campaign have geographically similar domains but occur in different seasons allowing the response of clouds to a range of CCN concentrations and meteorological conditions to be investigated. Well-defined connections between CCN and cloud microphysical properties consistent with the indirect effect are observed, as well as complex, nonlinear secondary effects that are partially supported by previously proposed mechanisms. Using the Research Scanning Polarimeter's remotely sensed effective variance parameter, correlation is found with liquid water path. In general, cloud macrophysical properties are found to better correlate with atmospheric state parameters than changes in CCN concentrations. ©2020. American Geophysical Union. All Rights Reserved."
"12803904100;36076994600;7006303509;57189215242;7402838215;57191750766;7006027075;55730602600;57192173802;7402480218;57190209035;7102866124;7102654014;57192169899;6507506955;6603569074;6603104382;15926468600;57215031466;57189368623;56187256200;56073532500;35461763400;57189372185;56429387500;8511991900;35276210200;6701562043;55942083800;7004864963;35774441900;15925588200;6602914876;6506848120;7005941217;","Comparison of aircraft measurements during GoAmazon2014/5 and ACRIDICON-CHUVA",2020,"10.5194/amt-13-661-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079814234&doi=10.5194%2famt-13-661-2020&partnerID=40&md5=3e04a2d329ab5e7a9aac8e0341c64a34","The indirect effect of atmospheric aerosol particles on the Earth's radiation balance remains one of the most uncertain components affecting climate change throughout the industrial period. The large uncertainty is partly due to the incomplete understanding of aerosol-cloud interactions. One objective of the GoAmazon2014/5 and the ACRIDICON (Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems)-CHUVA (Cloud Processes of the Main Precipitation Systems in Brazil) projects was to understand the influence of emissions from the tropical megacity of Manaus (Brazil) on the surrounding atmospheric environment of the rainforest and to investigate its role in the life cycle of convective clouds. During one of the intensive observation periods (IOPs) in the dry season from 1 September to 10 October 2014, comprehensive measurements of trace gases and aerosol properties were carried out at several ground sites. In a coordinated way, the advanced suites of sophisticated in situ instruments were deployed aboard both the US Department of Energy Gulfstream-1 (G1) aircraft and the German High Altitude and Long-Range Research Aircraft (HALO) during three coordinated flights on 9 and 21 September and 1< page662 October. Here, we report on the comparison of measurements collected by the two aircraft during these three flights. Such comparisons are challenging but essential for assessing the data quality from the individual platforms and quantifying their uncertainty sources. Similar instruments mounted on the G1 and HALO collected vertical profile measurements of aerosol particle number concentrations and size distribution, cloud condensation nuclei concentrations, ozone and carbon monoxide mixing ratios, cloud droplet size distributions, and downward solar irradiance. We find that the above measurements from the two aircraft agreed within the measurement uncertainties. The relative fraction of the aerosol chemical composition measured by instruments on HALO agreed with the corresponding G1 data, although the total mass loadings only have a good agreement at high altitudes. Furthermore, possible causes of the discrepancies between measurements on the G1 and HALO are examined in this paper. Based on these results, criteria for meaningful aircraft measurement comparisons are discussed. © 2020 Author(s)."
"57219284671;35799889800;56920790500;56597778200;35069282600;57198373080;35772803100;23977685500;6701410329;7103353990;","Cloud_cci ATSR-2 and AATSR data set version 3: A 17-year climatology of global cloud and radiation properties",2020,"10.5194/essd-12-2121-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092047248&doi=10.5194%2fessd-12-2121-2020&partnerID=40&md5=8442c379bbc2ffde226e784b5809abe4","We present version 3 (V3) of the Cloud_cci Along-Track Scanning Radiometer (ATSR) and Advanced ATSR (AATSR) data set. The data set was created for the European Space Agency (ESA) Cloud_cci (Climate Change Initiative) programme. The cloud properties were retrieved from the second ATSR (ATSR-2) on board the second European Remote Sensing Satellite (ERS-2) spanning 1995-2003 and the AATSR on board Envisat, which spanned 2002-2012. The data are comprised of a comprehensive set of cloud properties: cloud top height, temperature, pressure, spectral albedo, cloud effective emissivity, effective radius, and optical thickness, alongside derived liquid and ice water path. Each retrieval is provided with its associated uncertainty. The cloud property retrievals are accompanied by high-resolution top- and bottom-of-atmosphere shortwave and longwave fluxes that have been derived from the retrieved cloud properties using a radiative transfer model. The fluxes were generated for all-sky and clear-sky conditions. V3 differs from the previous version 2 (V2) through development of the retrieval algorithm and attention to the consistency between the ATSR-2 and AATSR instruments. The cloud properties show improved accuracy in validation and better consistency between the two instruments, as demonstrated by a comparison of cloud mask and cloud height with co-located CALIPSO data. The cloud masking has improved significantly, particularly in its ability to detect clear pixels. The Kuiper Skill score has increased from 0.49 to 0.66. The cloud top height accuracy is relatively unchanged. The AATSR liquid water path was compared with the Multisensor Advanced Climatology of Liquid Water Path (MAC-LWP) in regions of stratocumulus cloud and shown to have very good agreement and improved consistency between ATSR-2 and AATSR instruments. The correlation with MAC-LWP increased from 0.4 to over 0.8 for these cloud regions. The flux products are compared with NASA Clouds and the Earth's Radiant Energy System (CERES) data, showing good agreement within the uncertainty. The new data set is well suited to a wide range of climate applications, such as comparison with climate models, investigation of trends in cloud properties, understanding aerosol cloud interactions, and providing contextual information for co-located ATSR-2/AATSR surface temperature and aerosol products. © 2020 Author(s)."
"56157798300;9636267700;7801340865;57201193822;7102582535;","An exploration of the aerosol indirect effects in East Asia using a regional climate model",2020,"10.20937/ATM.52604","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079009025&doi=10.20937%2fATM.52604&partnerID=40&md5=6a6b9e77f88c7cc11b7351d7bf66d4bc","In this study, the aerosol direct, semi-direct and indirect effects on the East Asia climate are investigated using the International Center for Theoretical Physics Regional Climate Model v. 4 (RegCM4.1.1), by focusing on the East Asian Summer Monsoon temperature and precipitation. The externally mixed aerosols, including sulfate (SO42-), black carbon and organic carbon, reduced the solar flux reaching the surface directly by scattering solar radiation, and indirectly by increasing the cloud droplet concentration and cloud liquid water path over East China. The combined aerosol effects (direct and indirect) decreased the temperature on the continent and increased it over the oceans, leading to the reduction of rainfall in the central regions of China and an enhancement of rainfall in the adjacent ocean regions. © 2020 Universidad Nacional Autonoma de Mexico."
"25652997700;35849722200;56028694400;55914518400;14018610000;57212755392;57213541099;36655445400;","The Roles of Mineral Dust as Cloud Condensation Nuclei and Ice Nuclei During the Evolution of a Hail Storm",2019,"10.1029/2019JD031403","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077386985&doi=10.1029%2f2019JD031403&partnerID=40&md5=b2d23d3a6fa199c771fdf47665a51ac6","Aerosols play important roles in the evolution of deep convective systems like hailstorms. In this study, the heterogeneous ice nucleation schemes have been improved in the Weather Research and Forecasting model coupled with a spectral bin microphysics (WRF-SBM), which considered aerosols acting as ice nuclei (IN). A hail storm occurred around Tianshan mountains, northwestern China, was simulated with updated WRF-SBM, and the results have been compared with satellite observations. Further, four sensitive simulation tests were conducted with different cloud condensation nuclei (CCN) and IN concentrations to investigate their respective roles during the evolution of the hailstorm. The increase in CCN concentration resulted in larger cloud droplet concentration and cloud water content, as well as enhanced condensational growth, which released more latent heat and led to stronger updraft at lower levels. The increase in IN number almost did not affect warm processes but led to larger ice crystal concentration and enhanced Bergeron process. Larger CCN concentration led to larger supercooled liquid water content, which in turn contributed to the enhanced hail growth by more efficient drop-ice collisions and led to larger size of hail particles, while larger IN number reduced the size of graupel and suppressed the growth of hailstones. An analysis of the mobility of hail indicated increased frequency of larger hail with stronger sedimentation induced by more CCN. A further three ensemble runs with random perturbations on initial temperature and humidity were performed for each aerosol scenario, and the results suggested the robustness of simulated CCN and IN effects. ©2019. The Authors."
"56924085200;7004713188;7102010848;57189442478;55901167900;7004296083;7006495018;56083968500;8438057200;56151545200;8871497700;35461255500;26643041500;","Estimating cloud concentration nuclei number concentrations using aerosol optical properties: Role of particle number size distribution and parameterization",2019,"10.5194/acp-19-15483-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077132008&doi=10.5194%2facp-19-15483-2019&partnerID=40&md5=8a0703d6998ed234339f6c12460c10e4","The concentration of cloud condensation nuclei (CCN) is an essential parameter affecting aerosol-cloud interactions within warm clouds. Long-term CCN number concentration (NCCN) data are scarce; there are a lot more data on aerosol optical properties (AOPs). It is therefore valuable to derive parameterizations for estimating NCCN from AOP measurements. Such parameterizations have already been made, and in the present work a new parameterization is presented. The relationships between NCCN, AOPs, and size distributions were investigated based on in situ measurement data from six stations in very different environments around the world. The relationships were used for deriving a parameterization that depends on the scattering Ångström exponent (SAE), backscatter fraction (BSF), and total scattering coefficient (ssp) of PM10 particles. The analysis first showed that the dependence of NCCN on supersaturation (SS) can be described by a logarithmic fit in the range SS < 1:1 %, without any theoretical reasoning. The relationship between NCCN and AOPs was parameterized as NCCN ≈.286 ± 46/SAE ln(SS/(0:093 ± 0:006))(BSF-BSFmin) C (5:2 ± 3:3))ssp, where BSFmin is the minimum BSF, in practice the 1st percentile of BSF data at a site to be analyzed. At the lowest supersaturations of each site (SS ≈ 0:1 %), the average bias, defined as the ratio of the AOP-derived and measured NCCN, varied from ∼ 0:7 to ∼ 1:9 at most sites except at a Himalayan site where the bias was > 4. At SS > 0:4 % the average bias ranged from ∼ 0:7 to ∼ 1:3 at most sites. For the marine-aerosol-dominated site Ascension Island the bias was higher, ∼ 1:4-1.9. In other words, at SS > 0:4 % NCCN was estimated with an average uncertainty of approximately 30 % by using nephelometer data. The biases were mainly due to the biases in the parameterization related to the scattering Ångström exponent (SAE). The squared correlation coefficients between the AOP-derived and measured NCCN varied from ∼ 0:5 to ∼ 0:8. To study the physical explanation of the relationships between NCCN and AOPs, lognormal unimodal particle size distributions were generated and NCCN and AOPs were calculated. The simulation showed that the relationships of NCCN and AOPs are affected by the geometric mean diameter and width of the size distribution and the activation diameter. The relationships of NCCN and AOPs were similar to those of the observed ones. © 2019 Author(s)."
"57189986903;55598938800;8686475900;7003501766;","Explicit aerosol-cloud interactions in the Dutch Atmospheric Large-Eddy Simulation model DALES4.1-M7",2019,"10.5194/gmd-12-5177-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076683331&doi=10.5194%2fgmd-12-5177-2019&partnerID=40&md5=b7c86dde2ca2b89a3416c107905a815c","Large-eddy simulation (LES) models are an excellent tool to improve our understanding of aerosol-cloud interactions (ACI). We introduce a prognostic aerosol scheme with multiple aerosol species in the Dutch Atmospheric Large-Eddy Simulation model (DALES), especially focused on simulating the impact of cloud microphysical processes on the aerosol population. The numerical treatment of aerosol activation is a crucial element for simulating both cloud and aerosol characteristics. Two methods are implemented and discussed: an explicit activation scheme based on <span classCombining double low line""inline-formula""><i>κ</i></span>-Köhler theory and a more classic approach using updraught strength. Sample model simulations are based on the Rain in Shallow Cumulus over the Ocean (RICO) campaign, characterized by rapidly precipitating warm-phase shallow cumulus clouds.</p> We find that in this pristine ocean environment virtually all aerosol mass in cloud droplets is the result of the activation process, while in-cloud scavenging is relatively inefficient. Despite the rapid formation of precipitation, most of the in-cloud aerosol mass is returned to the atmosphere by cloud evaporation. The strength of aerosol processing through subsequent cloud cycles is found to be particularly sensitive to the activation scheme and resulting cloud characteristics. However, the precipitation processes are considerably less sensitive. Scavenging by precipitation is the dominant source for in-rain aerosol mass. About half of the in-rain aerosol reaches the surface, while the rest is released by evaporation of falling precipitation. The effect of cloud microphysics on the average aerosol size depends on the balance between the evaporation of clouds and rain and ultimate removal by precipitation. Analysis of typical aerosol size associated with the different microphysical processes shows that aerosols resuspended by cloud evaporation have a radius that is only 5&thinsp;% to 10&thinsp;% larger than the originally activated aerosols. In contrast, aerosols released by evaporating precipitation are an order of magnitude larger. © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 License."
"56158523800;7102084129;7006446865;7006640608;57207137435;55491523900;18438598900;7404865816;14032595800;","Polarimetric Radar Convective Cell Tracking Reveals Large Sensitivity of Cloud Precipitation and Electrification Properties to CCN",2019,"10.1029/2019JD030857","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075452737&doi=10.1029%2f2019JD030857&partnerID=40&md5=04debbe21f71b921b34afab1d8cb7c47","Hypotheses have been proposed for decades about the effect of activated cloud condensation nuclei (CCN) on delaying the warm rain process, invigorating deep convective cloud vertical development, and enhancing mixed-phase processes. Observational support has been only qualitative with mixed results due to the lack of regional measurements of CCN concentration (NCCN), while simulations have not produced a robust consensus. Quantitative assessments of these relationships became possible with the advent of NCCN retrievals from satellites; when combined with measurements by polarimetric radar and Lightning Mapping Array (LMA), tracking convective cells observed on radar and examining precipitation properties throughout the cells' life cycle has permitted the study of the impact of NCCN on cloud and precipitation characteristics. We composited more than 2,800 well-tracked cells in the Houston region and stratified them by NCCN, convective available potential energy (CAPE), and urban/rural locations. The results show that increased NCCN invigorates the convection until saturation near NCCN = 1,000 cm3; increasing NCCN from ~400 to an optimum of ~1,000 cm3 increases lightning activity by an order of magnitude. A further increase in CCN decreases lightning rates. Adding CAPE enhances lightning only under low NCCN (e.g., less than 500 cm3). The presence of the urban area enhances lightning for similar NCCN concentrations, although this applies mainly under low NCCN conditions. The urban heat island as manifested by cloud base height cannot explain this observation. It is suspected that the urban ultrafine aerosols contribute to the storm electrification. ©2019. American Geophysical Union. All Rights Reserved."
"24402359000;7003591311;6506152198;","Aerosol-Cloud Interactions in Trade Wind Cumulus Clouds and the Role of Vertical Wind Shear",2019,"10.1029/2019JD031073","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075429785&doi=10.1029%2f2019JD031073&partnerID=40&md5=f7fe1065b50319abe0e18c9b019bacbd","In shallow cumulus clouds, cloud deepening as a dynamical response to increased droplet number concentration has recently been shown to buffer the microphysical suppression of precipitation. In the current study, large eddy simulations with a two-moment bin microphysics model are employed to revisit this buffering and to investigate the role of vertical wind shear in aerosol-cloud interactions in trade wind cumuli. An idealized case is developed based on ship measurements and corresponding reanalysis data over the Sulu Sea in the Philippines in September 2012. A quasi-steady state is reached after roughly 25 – 35 hr for all six simulations performed (three different aerosol concentrations covering 35 – 230 cm−3, with/without vertical wind shear). All simulations show that the aerosol effect is buffered, to first order; increased aerosol results in deeper clouds, a reduced cloud fraction, and an increase in the shortwave cloud radiative effect. For the no-shear cases, positive aerosol perturbations result in a small increase in surface precipitation, while the opposite is true in the presence of vertical wind shear because of muted deepening. Analysis shows competing influences of vertical wind shear; enhanced cloud clustering protects clouds from evaporation and entrainment while tilting of clouds enhances evaporation. In spite of the small responses of surface precipitation to very large changes in aerosol, cloud size and spatial distributions and charge/discharge precipitation cycles differ significantly, expressing changes in the pathways to surface precipitation and a dynamical buffering of the system. ©2019. American Geophysical Union. All Rights Reserved."
"55173596300;55522941400;57211856505;35069282600;57211857960;","The Impact of Ship Emission Controls Recorded by Cloud Properties",2019,"10.1029/2019GL084700","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075189588&doi=10.1029%2f2019GL084700&partnerID=40&md5=68a0b8bab5c970d941a47afcd9aee2b1","The impact of aerosols on cloud properties is one of the leading uncertainties in the human forcing of the climate. Ships are large, isolated sources of aerosol creating linear cloud formations known as shiptracks. These are an ideal opportunity to identify and measure aerosol-cloud interactions. This work uses over 17,000 shiptracks during the implementation of fuel sulfur content regulations to demonstrate the central role of sulfate aerosol in ship exhaust for modifying clouds. By connecting individual shiptracks to transponder data, it is shown that almost half of shiptracks are likely undetected, masking a significant contribution to the climate impact of shipping. A pathway to retrieving ship sulfate emissions is demonstrated, showing how cloud observations could be used to monitor air pollution. ©2019. American Geophysical Union. All Rights Reserved."
"57203825369;15830929400;7501757094;24468389200;7404976222;55119602800;7410069943;57209415860;57209411388;57207883166;54403961000;55220443400;","LASG Global AGCM with a Two-moment Cloud Microphysics Scheme: Energy Balance and Cloud Radiative Forcing Characteristics",2019,"10.1007/s00376-019-8196-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067671764&doi=10.1007%2fs00376-019-8196-9&partnerID=40&md5=b745d7d9b62646ebea0fffac50c1cad5","Cloud dominates influence factors of atmospheric radiation, while aerosol-cloud interactions are of vital importance in its spatiotemporal distribution. In this study, a two-moment (mass and number) cloud microphysics scheme, which significantly improved the treatment of the coupled processes of aerosols and clouds, was incorporated into version 1.1 of the IAP/LASG global Finite-volume Atmospheric Model (FAMIL1.1). For illustrative purposes, the characteristics of the energy balance and cloud radiative forcing (CRF) in an AMIP-type simulation with prescribed aerosols were compared with those in observational/reanalysis data. Even within the constraints of the prescribed aerosol mass, the model simulated global mean energy balance at the top of the atmosphere (TOA) and at the Earth’s surface, as well as their seasonal variation, are in good agreement with the observational data. The maximum deviation terms lie in the surface downwelling longwave radiation and surface latent heat flux, which are 3.5 W m-2 (1%) and 3 W m-2 (3.5%), individually. The spatial correlations of the annual TOA net radiation flux and the net CRF between simulation and observation were around 0.97 and 0.90, respectively. A major weakness is that FAMIL1.1 predicts more liquid water content and less ice water content over most oceans. Detailed comparisons are presented for a number of regions, with a focus on the Asian monsoon region (AMR). The results indicate that FAMIL1.1 well reproduces the summer-winter contrast for both the geographical distribution of the longwave CRF and shortwave CRF over the AMR. Finally, the model bias and possible solutions, as well as further works to develop FAMIL1.1 are discussed. © 2019, Institute of Atmospheric Physics/Chinese Academy of Sciences, and Science Press and Springer-Verlag GmbH Germany, part of Springer Nature."
"7005072865;","Asian dust properties investigated by multi-instruments",2019,"10.1051/e3sconf/20199902003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067832205&doi=10.1051%2fe3sconf%2f20199902003&partnerID=40&md5=9aeea93cdb5b4e1852e451831cdbf914","Dust and many types of aerosols are major pollutants significantly affecting the environment in the East Asia. To identify and classify various types of aerosols is a challenge. In Taiwan and nearby areas, Asian Dust mainly arrive in spring with an average of about 5 dust storms each year. They usually come with some other aerosol sources, therefore it is important to identify these aerosols and their properties. In this paper, we report studying of dust aerosols by using several ground-based and remote sensing measurements. The AERONET data is used to find optical properties of aerosols in 2008-2012. The lidar observations can investigate further properties and atmospheric processes for specific dust events, including observations of aerosol-cloud interactions. These combined with model or space observations can help us to understand long range dust particles transported to distant areas and their interaction with weather systems. A real time case of observation of dust-cloud interaction is provided. © 2019 The Authors, published by EDP Sciences."
"57008250400;9535707500;7101752236;","Modeled aerosol-cloud indirect effects and processes based on an observed partially glaciated marine deep convective cloud case",2019,"10.1016/j.atmosenv.2019.02.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061835292&doi=10.1016%2fj.atmosenv.2019.02.010&partnerID=40&md5=6802bf6eb317aab97478753c7479ad78","A tropical maritime case of deep convective clouds was studied using a state-of-the-art aerosol-cloud model in order to evaluate the microphysical mechanisms of aerosol indirect effects (AIE). The aerosol-cloud scheme used is a hybrid bin/bulk model, which treats all phases of clouds and precipitation allowing a detailed analysis of process-level aerosol indirect effects on targeted cloud types. From the simulations, a substantially huge total AIE on maritime clouds of −17.44 ± 6.1 Wm−2 was predicted primarily because maritime clouds are highly sensitive to perturbations in aerosol concentrations because of their low background aerosol concentrations. This was evidenced by the conspicuous increases in droplet and ice number concentrations and the subsequent reductions in particle mean sizes in the present-day. Both the water-only (−9.08 ± 3.18 Wm−2) and the partially glaciated clouds (−8.36 ± 2.93 Wm−2) contributed equally to the net AIE of these maritime clouds. As for the partially glaciated clouds, the mixed-phase component (−14.12 ± 4.94 Wm−2) of partially glaciated clouds was dominant, whilst the ice-only component (5.76 ± 1.84 Wm−2) actually exhibited a positive radiative forcing at the top of the atmosphere (TOA). This was primarily because ice water contents aloft were diminished significantly owing to increased snow production in the present-day. © 2019 Elsevier Ltd"
"23012437100;","Towards an enhanced droplet activation scheme for multi-moment bulk microphysics schemes",2018,"10.1016/j.atmosres.2018.08.025","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054078338&doi=10.1016%2fj.atmosres.2018.08.025&partnerID=40&md5=4f0bf8b55b0fcdb4cf148433985b28b8","Initial droplet spectra produced upon activation impact the ensuing chain of microphysical processes and therefore play a crucial role in cloud evolution. This work re-examines dependencies of newly formed cloud droplet size distribution (CDSD) characteristics on environmental and aerosol properties via parcel model simulations that serve as the basis for a multi-moment bulk microphysics droplet activation scheme suitable for a cloud-resolving model (CRM). It is found that applying a fixed size threshold to define activated droplets versus employing physical considerations can lead to erroneous activation and overly broad CDSDs for high aerosol concentration and weak updraft conditions. Aerosol distributions characterized by larger median sizes and/or increased solubility can result in greater activated droplet numbers, whereas impacts of these parameters on CDSD spectral width depend on both aerosol number concentration and updraft velocity. An expansion of the activation scheme to include CDSD spectral width is proposed to aid efforts to extend high-order moment prediction to cloud droplet categories in CRMs as well as better represent variability in the activation process on the cloud scale. © 2018 Elsevier B.V."
"7201504886;","Reply to ""Comments on 'Rethinking the lower bound on aerosol radiative forcing'""",2018,"10.1175/JCLI-D-18-0185.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056134713&doi=10.1175%2fJCLI-D-18-0185.1&partnerID=40&md5=470c48edc683845cd8a60fdb5adae9be","This reply addresses a comment questioning one of the lines of evidence I used in a 2015 study (S15) to argue for a less negative aerosol radiative forcing. The comment raises four points of criticism. Two of these have been raised and addressed elsewhere; here I additionally show that even if they have merit the S15 lower bound remains substantially (0.5 W m-2) less negative than that given in the AR5. Regarding the two other points of criticism, one appears to be based on a poor understanding of the nature of S15's argument; the other rests on speculation as to the nature of the uncertainty in historical SO2 estimates. In the spirit of finding possible flaws with the top-down constraints from S15, I instead hypothesize that an interesting-albeit unlikely-way S15 could be wrong is by inappropriately discounting the contribution of biomass burning to radiative forcing through aerosol-cloud interactions. This hypothesis is interesting as it opens the door for a role for the anthropogenic (biomass) aerosol in causing the Little Ice Age and again raises the specter of greater warming from ongoing reductions in SO2 emissions. © 2018 American Meteorological Society."
"57194974081;","Climate impacts of particulate pollutants emitted from international shipping",2018,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053899051&partnerID=40&md5=a02994dc07e0b0b5688aaacc375abdad","International shipping represents a large sector for heavy fuel oil consumption and is an important source of particulate matter (PM) emissions and their precursors, including SO2. PM from international shipping emissions (ISE) could have significant cooling radiative effects on the Earth's climate system through direct (aerosol-radiation) and indirect (aerosol-cloud) interactions. To reduce the pollution and climate impacts of ISE, the International Maritime Organization (IMO) has set various emission caps on the sulfur content of marine fuel oil to be implemented in the future. Concawe commissioned MIT to conduct a modeling study using a state-of-the-art climate model, Community Earth System Model, to address the uncertainties that influence the estimation of cloud radiative effects of ISE. Several scenarios were simulated to quantify the impacts of the IMO's emission regulations on the radiative effects of ISEs. Also, the influence of naturally occurring dimethyl sulfide emissions on the cloud radiative effects of ISE was examined. In this ongoing modeling work, MIT estimates that using 2.7% and 3.5% sulfur content in fuel would cause a global average cooling of 0.2°C or more."
"24343173500;57189215242;8084443000;7403401100;7103337730;7006107059;7004015298;55871322800;55871415400;55871394300;7004393835;24069972000;7004611350;55908042400;57050508600;7006808794;8657166100;","Erratum to “Airborne investigation of the aerosols-cloud interactions in the vicinity and within a marine stratocumulus over the North Sea during EUCAARI (2008)” [Atmos. Environ. 81C (2013) 288-303](S1352231013006444)(10.1016/j.atmosenv.2013.08.035)",2018,"10.1016/j.atmosenv.2018.01.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045202405&doi=10.1016%2fj.atmosenv.2018.01.022&partnerID=40&md5=53f93f2dacaaebfdbb29d031c81dc83d","The publisher regrets there was an error in Table 6 of this article. The incorrect version of Table 6 appears as follows:[Table presented] The correct version of Table should appear as: [Table presented] The publisher would like to apologise for any inconvenience caused. © 2018 Elsevier Ltd"
"56439933300;36628712500;36652057000;","Observed correlation between aerosol and cloud base height for low clouds at Baltimore and New York, United States",2018,"10.3390/atmos9040143","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045303956&doi=10.3390%2fatmos9040143&partnerID=40&md5=9e0994cf0f79f146fe57a932f5098e19","The correlation between aerosol particulate matter with aerodynamic diameter ≤2.5 μm (PM2.5) and cloud base height (CBH) of low clouds (CBH lower than 1.5 km a.g.l.) at Baltimore and New York, United States, for an 8 year period (2007-2014) was investigated using information from the Automated Surface Observing System (ASOS) observations and collocated U.S. Environmental Protection Agency (EPA) observations. The lifting condensation level (LCL) heights were calculated and compared with the CBH. The monthly average observations show that PM2.5 decreases from 2007 to 2014 while there is no significant trend found for CBH and LCL. The variability of the LCL height agrees well with CBH but LCL height is systematically lower than CBH (~180 m lower). There was a significant negative correlation found between CBH-LCL and PM2.5. All of the cloud cases were separated into polluted and clean conditions based on the distribution of PM2.5 values. The distributions of CBH-LCL in the two groups show more cloud cases with smaller CBH-LCL in polluted conditions than in clean conditions. © 2018 by the authors."
"56400726900;7004154626;54901507000;6701874937;35253736000;7801642681;57190218552;6603926727;","Investigation of aerosol indirect effects on monsoon clouds using ground-based measurements over a high-altitude site in Western Ghats",2016,"10.5194/acp-2015-1057","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042813475&doi=10.5194%2facp-2015-1057&partnerID=40&md5=95147a9a374af1a8966d7582c3fb4141","The effect of aerosols on cloud droplet number concentration and droplet effective radius are investigated from ground-based measurements over a high-altitude site where in clouds pass over the surface. First aerosol indirect effect AIE estimates were made using i) relative changes in cloud droplet number concentration (AIEn) and ii) relative changes in droplet effective radius (AIEs) with relative changes in aerosol for different LWC values. AIE estimates from two different methods reveal that there is systematic overestimation in AIEn as compared to that of AIEs. Aerosol indirect effects (AIEn and AIEs) and Dispersion effect (DE) at different liquid water content (LWC) regimes ranging from 0.05 to 0.50 gm-3 were estimated. The analysis demonstrates that there is overestimation of AIEn as compared to AIEs which is mainly due to DE. Aerosol effects on spectral dispersion in droplet size distribution plays an important role in altering Twomey's cooling effect and thereby changes in climate. This study shows that the higher DE in the medium LWC regime which offsets the AIE by 30%. © Author(s) 2016."
"16645334100;9638541400;","Vibration analysis, control and genetic algorithm optimization of a piezoelectric elements bonded rotating spacecraft composite beam",2016,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016467358&partnerID=40&md5=9fe782778c31355f66d87b9264b1511c","The paper reviews the outstanding problems focused on Contrails and Cirrus Cloud, its assessment, consequences and solution synthesis, and identify future directions that could be followed. The Rationale for assessing Clouds, Aerosols and their interactions is associated with the representation of cloud processes in climate models which has been recognized as a dominant source of uncertainty in our understanding of changes in the climate system. Clouds respond to climate forcing mechanisms in multiple ways, and intermodel differences in cloud feedbacks constitute by far the primary source of spread of both equilibrium and transient climate responses simulated by climate models despite the fact that most models agree that the feedback is positive. Thus confidence in climate projections requires a thorough assessment of how cloud processes have been accounted for a radiative forcing (RF) of climate change through their interaction with radiation, and also as a result of their interaction with clouds. Estimate of Effective Radiative Forcing from Combined Aerosol-Radiation and Aerosol-Cloud Interactions is also relevant. There are a large number of satellite surface sensors recently launched or shortly to be launched. Recent satellite instruments such as CHRIS, MERIS, MODIS and ASTER, are essential in obtaining relevant data to that end. Theory, model studies and observations suggest that some Solar Radiation Management Methods (SRM methods) may be able to counteract a portion of global warming effects (on temperature, sea ice and precipitation) due to high concentrations of anthropogenic Green House Gases (GHGs). A new coordinated earth observation, aviation and environment program should be able to bring in at minimal cost the aircraft and ground-based measurement community, the satellite analysis community, the chemistry and climate modeling communities, along with the international research community to participate in specific projects, to deliver realistic outcomes. These initiatives may incorporate Models and Measurements, which in this case describes a critical, objective evaluation of the models used to predict aviation impacts, a unified global data set for contrails and cirrus, with well characterized accuracy and within reach using existing satellite observations, in a coordinated effort within Earth Observation initiatives."
"57189038577;15032788000;8680433600;7102944401;7006107059;","Effects of long-range aerosol transport on the microphysical properties of low-level liquid clouds in the Arctic",2015,"10.5194/acpd-15-31823-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042392524&doi=10.5194%2facpd-15-31823-2015&partnerID=40&md5=5a31185a91e122a2895959c9af294a41","The properties of clouds in the Arctic can be altered by long-range aerosol transport to the region. The goal of this study is to use satellite, tracer transport model, and meteorological data sets to determine the effects of pollution on cloud microphysics due only to pollution itself and not to the meteorological state. Here, A-Train, POLDER-3 and MODIS satellite instruments are used to retrieve low-level liquid cloud microphysical properties over the Arctic between 2008 and 2010. Cloud retrievals are co-located with simulated pollution represented by carbon-monoxide concentrations from the FLEXPART tracer transport model. The sensitivity of clouds to pollution plumes - including aerosols - is constrained for cloud liquid water path, temperature, altitude, specific humidity, and lower tropospheric stability (LTS). We define an Indirect Effect (IE) parameter from the ratio of relative changes in cloud microphysical properties to relative variations in pollution concentrations. Retrievals indicate that, depending on the meteorological regime, IE parameters range between 0 and 0.34 for the cloud droplet effective radius, and between -0.10 and 0.35 for the optical depth, with average values of 0.12 ± 0.02 and 0.15 ± 0.02 respectively. The IE parameter increases with increasing specific humidity and LTS. Further, the results suggest that for a given set of meteorological conditions, the liquid water path of arctic clouds does not respond strongly to pollution. Or, not constraining sufficiently for meteorology may lead to artifacts that exaggerate the magnitude of the aerosol indirect effect. The converse is that the response of arctic clouds to pollution does depend on the meteorologic state. Finally, we find that IE values are highest when pollution concentrations are low, and that they depend on the source of pollution. © Author(s) 2015."
"49561700200;7101729096;56370988900;35446906200;7102914417;7004800276;57203137943;7409097241;56265445700;","Chemical compositions of sulfate and chloride salts over the last termination reconstructed from the dome fuji ice core, inland antarctica",2014,"10.1002/2014JD022030","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018759858&doi=10.1002%2f2014JD022030&partnerID=40&md5=99377c662370a2373179dc0c37be8e15","The flux and chemical composition of aerosols impact the climate. Antarctic ice cores preserve the record of past atmospheric aerosols, providing useful information about past atmospheric environments. However, few studies have directly measured the chemical composition of aerosol particles preserved in ice cores. Here we present the chemical compositions of sulfate and chloride salts from aerosol particles in the Dome Fuji ice core. The analysis method involves ice sublimation, and the period covers the last termination, 25.0–11.0 thousand years before present (kyr B.P.), with a 350 year resolution. The major components of the soluble particles are CaSO4, Na2SO4, and NaCl. The dominant sulfate salt changes at 16.8 kyr B.P. from CaSO4, a glacial type, to Na2 SO4 , an interglacial type. The sulfate salt flux (CaSO4 plus Na2 SO4) inversely correlates with δ18O in Dome Fuji over millennial timescales. This correlation is consistent with the idea that sulfate salt aerosols contributed to the last deglacial warming of inland Antarctica by reducing the aerosol indirect effect. Between 16.3 and 11.0 kyr B.P., the presence of NaCl suggests that winter atmospheric aerosols are preserved. A high NaCl/Na2SO4 fraction between 12.3 and 11.0 kyr B.P. indicates that the contribution from the transport of winter atmospheric aerosols increased during this period. © 2014. American Geophysical Union. All Rights Reserved."
"8953662800;55574865800;56135632400;57203292649;24755928100;","Three dimensional aerosol-cloud structure in China from space: Implications for aerosol indirect effect",2014,"10.1109/IGARSS.2014.6947621","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911370876&doi=10.1109%2fIGARSS.2014.6947621&partnerID=40&md5=d1500f673691988fdbab0c4c51e8851e","In this study, we plot a 3D aerosol map over China mainland based on CALIPSO and MODIS aerosol product combined, which is height-resolved. We can see there are several hot spots in terms of aerosol loadings across China, such as Pearl River Delta, Yangtze River Delta. Also, the maximum height that aerosol can reach were figured out based on the aerosol vertical profiles. Generally, this height is consistent with the planetary boundary layer height, less than 2km. Meanwhile, we attempted to sort out the aerosol indirect effect on cloud, by plotting Contoured Frequency by Altitude Diagram (CFAD) of cloud reflectivity from Cloudsat. It demonstrated that cloud tended to be restrained under heavy aerosol conditions. © 2014 IEEE."
"35221167400;56251307100;55367706300;7003566416;","Inversion of droplet aerosol analyzer data for long-term aerosol-cloud interaction measurements",2014,"10.5194/amt-7-877-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898751730&doi=10.5194%2famt-7-877-2014&partnerID=40&md5=b4bc382dc94b9f792ddc349255848e94","The droplet aerosol analyzer (DAA) was developed to study the influence of aerosol properties on clouds. It measures the ambient particle size of individual droplets and interstitial particles, the size of the dry (residual) particles after the evaporation of water vapor and the number concentration of the dry (residual) particles. A method was developed for the evaluation of DAA data to obtain the three-parameter data set: ambient particle diameter, dry (residual) particle diameter and number concentration. First results from in-cloud measurements performed on the summit of Mt. Brocken in Germany are presented. Various aspects of the cloud-aerosol data set are presented, such as the number concentration of interstitial particles and cloud droplets, the dry residue particle size distribution, droplet size distributions, scavenging ratios due to cloud droplet formation and size-dependent solute concentrations. This data set makes it possible to study clouds and the influence of the aerosol population on clouds. © 2014 Author(s)."
"56370907100;57189333618;8336962200;55901062600;7006609519;36673016000;6602607937;6701453955;8871497700;35461255500;","Atmospheric electricity and aerosol-cloud interactions: Synthesis based on Existing Data Archives and New Results",2014,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086813660&partnerID=40&md5=e1631d97c13f9c284a14f06cfd5918f5","Atmospheric ions play an important role in the fair weather electricity. Atmosphere's fair weather condition concerns the electric field and the electric current in the air as well as the air conductivity. On the other hand, atmospheric ions are important for Earth's climate, due to their potential role in secondary aerosol formation. This can lead to increased number of cloud condensation nuclei (CCN), which in turn can change the cloud properties. Our aim is to quantify the connections between these two important roles of air ions based on field observations and existing data archives. © International Conference on Atmospheric Electricity, ICAE 2014"
"57203102974;","Aerosols",2014,"10.1007/978-0-387-36699-9_4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85051547144&doi=10.1007%2f978-0-387-36699-9_4&partnerID=40&md5=b636dc7ed87943c6e3d2a2ca8f9997cc","Our appreciation of aerosols’ role in climate change has grown over the past 25 years, in part due to the contributions made by remote sensing. First estimates of the impacts transported aerosols have on the atmospheric energy balance, on clouds and the hydrological cycle, on larger-scale atmospheric circulation, and on human health have been made. An understanding has developed for the need to combine detailed physical and chemical measurements from aircraft and ground stations and extensive constraints on aerosol optical depth, type, and vertical distribution from satellites, with numerical models that can simulate present and predict future conditions. However, much remains to be done. For planning purposes, the accuracy of measurements needed to assess aerosol direct radiative effect must be improved, and uncertainties in aerosol indirect effects on clouds must be reduced. Techniques for systematically constraining models with satellite and suborbital data need to be developed, both to test model parameterizations of aerosol sources, cloud processes, etc., and to assess the uncertainties in the resulting simulations. Based on past experience, this can be achieved, provided we continue to develop and deploy the instruments, improve the models, and maintain the research community, which have carried the field to this point. © Springer Science+Business Media New York 2014."
"37088899300;56350198800;55741517200;38762557600;55691665700;55440359400;7202079615;57211223914;","Regional climatic effects according to different estimations of biogenic volatile organic compounds during the asian summer monsoon",2014,"10.1007/s13143-014-0033-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906891267&doi=10.1007%2fs13143-014-0033-6&partnerID=40&md5=fa49547eef70b435f34dc1bbd88c1f13","A series of 60-year numerical experiments starting from 1851 was conducted using a global climate model coupled with an aerosol-cloud-radiation model to investigate the response of the Asian summer monsoon to variations in the secondary organic aerosol (SOA) flux induced by two different estimations of biogenic volatile organic compound (BVOC) emissions. One estimation was obtained from a pre-existing archive and the other was generated by a next-generation model (the Model of Emissions of Gases and Aerosols from Nature, MEGAN). The use of MEGAN resulted in an overall increase of the SOA production through a higher rate of gasto-particle conversion of BVOCs. Consequently, the atmospheric loading of organic carbon (OC) increased due to the contribution of SOA to OC aerosol. The increase of atmospheric OC aerosols was prominent in particular in the Indian subcontinent and Indochina Peninsula (IP) during the pre- and early-monsoon periods because the terrestrial biosphere is the major source of BVOC emissions and the atmospheric aerosol concentration diminishes rapidly with the arrival of monsoon rainfall. As the number of atmospheric OC particles increased, the number concentrations of cloud droplets increased, but their size decreased. These changes represent a combination of aerosol-cloud interactions that were favorable to rainfall suppression. However, the modeled precipitation was slightly enhanced in May over the oceans that surround the Indian subcontinent and IP. Further analysis revealed that a compensating updraft in the surrounding oceans was induced by the thermally-driven downdraft in the IP, which was a result of surface cooling associated with direct OC aerosol radiative forcing, and was able to surpass the aerosolcloud interactions. The co-existence of oceanic ascending motion with the maximum convective available potential energy was also found to be crucial for rainfall formation. Although the model produced statistically significant rainfall changes with locally organized patterns, the suggested pathways should be considered guardedly because in the simulation results, 1) the BVOC-induced aerosol direct effect was marginal; 2) cloud-aerosol interactions were modeldependent; and 3) Asian summer monsoons were biased to a nonnegligible extent. © 2014 Korean Meteorological Society and Springer Science+Business Media Dordrecht."
"23568239000;","Analysis of aerosol-cloud-interactions over semi-arid and arid subtropical land regions from three different satellite datasets (MODIS, AATSR/ENVISAT, IASI)",2014,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905486007&partnerID=40&md5=270d3c7d2a0186414ebc3e6191bd4df8","Indirect aerosol effects, i.e. the change of cloud physical properties by aerosol interactions, have been identified as one of the largest uncertainties in the current understanding of the climate system. Despite the uncertainties of the representations of aerosol-cloud interactions in current climate projections, they have large impact on the climate system itself - in terms of the radiation balance, but also in terms of precipitation, and thus vegetation cover, and re-distribution of water throughout the atmosphere. Nevertheless, so far only very few studies of large-scale statistics of aerosol-cloud interactions over land are available. Moreover most studies on the topic cover liquid water clouds only. Aerosol cloud interactions over arid and semi-arid land regions have been analysed from three different satellite datasets with respect to aerosol type and cloud phase. The regions of the analysis cover Southern Africa, the Sahel domain with the influence of the West African monsoon circulation, the North-Western African Maghreb region and the Arabian Peninsula. These regions have been chosen as they are dominated by one (Maghreb, Arabia) or two (Sahel, Southern Africa) aerosol types and as mineral dust is one of the dominating aerosol types in all of them. The second dominating aerosol type is biomass burning in the Sahel and Southern Africa. These aerosol types can be discriminated by separating the aerosol information into fine mode (biomass burning) and coarse mode (desert dust) aerosol. Thus they can generally also be discriminated from satellite, although these capabilities are limited over land. Over land the diurnal cycle of convection is much stronger and aerosol interactions with deep convective cloud systems over land have been identified to be of great importance not only for precipitation in regions under pressure of desertification, but also with respect to climate change. For liquid water clouds the well-known first indirect aerosol effect (""Twomey effect""), i.e. higher cloud albedo due to smaller droplet sizes, could be confirmed for all regions, if liquid water path is held constant. Nevertheless, liquid water path has been found to be affected by aerosol presence and the aerosol effect on liquid water path dominates the net effect of aerosols on cloud optical depth. For ice phase clouds the same effects are observed with ice water path controlling the net aerosol effect on optical depth. From thermal infrared retrievals of mineral dust and ice clouds an increase of ice particle size with respect to background conditions has been detected. Together with observations at solar wavelengths the differences can be interpreted as indications for an increase of optically thicker clouds at the cost of cirrus coverage. Although the Twomey effect has been identified to be active in all cases, cloud water path and cloud phase transitions could be identified to be of predominant importance for resulting cloud propertiy changes due to aerosol presence. The second indirect aerosol effect (""Albrecht effect"") could not be identified from the statistical analysis. Although cloud cover distributions as functions of aerosol optical depth (AOD) indicate an increase of cloud cover with AOD, these could not be related to any other cloud properties including cloud droplet size. Thus the satellite observations do not support the relatively simple formulation of the second indirect aerosol effect (longer cloud lifetime due to drizzle suppression as a consequence of smaller droplets). An aerosol effect on cloud phase has been identified with respect to cloud water path. It could not be confirmed in terms of cloud coverage. The statistical analysis of cloud macro- and microphysical properties has been performed after the observations have been projected all to the same cloud top temperature distribution. This method allows correcting for effects of the temperature and moisture fields (meteorological conditions), which otherwise would dominate the statistical results. It has been shown that aerosol type is important for aerosol cloud interactions in subtropical land regions. Moreover the cloud water path (liquid and ice) has been identified to be a strong constraint on indirect aerosol effects, outweighing e.g. the optical depth increase by droplet size reduction (""Twomey-effect""). It could moreover be shown that aerosol-cloud interactions are also important for ice cloud properties in subtropical land regions, which have yet not fully been addressed in statistical analyses of indirect aerosol effects and consequently in climate projections. Nevertheless, by means of the large-scale statistical analysis, also some deficits of current satellite datasets have been identified, which have to be solved in order to furthermore reduce the uncertainties of indirect aerosol effects. It has been the first attempt to quantify aerosol-cloud interactions focussed on semiarid and arid land regions, performing the same kind of analysis to liquid water and ice clouds at the same time with the same methods, comparing results from three different independent satellite datasets, using advanced statistical descriptions of the observed deviations from background in order to account for non-linearity and multimodal or non-Gaussian probability distributions of cloud properties, applying a newly developed method to account for variations in cloud top temperature affecting cloud property observations statistically and also introducing a newly developed dataset from IASI which is sensitive to desert dust and ice clouds only, adding information about aerosol type sensitivity of aerosol-cloud interactions."
"24437444900;7003836546;36621776000;6701378450;22933265100;56059425100;","The Role of Aerosol Properties on Cloud Nucleation Processes",2013,"10.1007/978-94-007-5577-2_5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885394883&doi=10.1007%2f978-94-007-5577-2_5&partnerID=40&md5=2b1dd933388f8f7a4aad064295f6635e","The clouds that develop in maritime or polluted environments have significant differences in their properties. A number of modeling sensitivity tests have been performed to describe the physical processes related to aerosol - cloud interactions at various stages of cloud development. Precipitation amounts and cloud structure were found to be very sensitive to changes in the size distribution and number concentrations of the aerosols. Certain combinations of CCN/IN properties and atmospheric properties may lead to significant enhancement of convection and precipitation. These interactions are not linear and it is the synergetic effects between meteorology and atmospheric chemistry that are responsible for the variation of precipitation. © Springer Science+Business Media Dordrecht 2014."
"55574865800;8953662800;55960948400;24755928100;","Satellite based analysis of aerosol effect on cloud droplet size in eastern China",2012,"10.1109/IGARSS.2012.6351125","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873172620&doi=10.1109%2fIGARSS.2012.6351125&partnerID=40&md5=5a800f50f576415bf7ae6603bb9820cb","As concluded by IPCC Fourth Assessment Report, the aerosol first indirect effect, so-called Twomey effect could be climatically important. Seven consecutive summers (2002-2008) of daily observations from MODIS instrument are used to reveal aerosol-cloud relationship over a region of continent, the eastern China(30°N-41°N; 114°E-123°E). The results indicates that AOD effect DER more significantly when the droplet is smaller. Small droplet observations reveal an 'Anti-Twomey' effect while large droplet observations show the contrary Twomey effect. The regions study on scale 1° × 1° also contains results lead to both the Twomey effect and 'Anti-twomey' effect. This phenomenon might be caused by the distribution of aerosol chemical composition and particles size. © 2012 IEEE."
"36538539800;","On-line coupled meteorology and chemistry models in the US",2011,"10.1007/978-3-642-13980-2_2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895199798&doi=10.1007%2f978-3-642-13980-2_2&partnerID=40&md5=c239feced4dab28c5bddbbce52dc5ad0","The climate-chemistry-aerosol-cloud-radiation feedbacks are important processes occurring in the atmosphere. Accurately simulating those feedbacks requires fully-coupled meteorology, climate, and chemistry models and presents significant challenges in terms of both scientific understanding and computational demand. This review focuses on history and current status of development and application of on-line models in the US Several representative on-line coupled meteorology and chemistry models such as GATOR/GCMOM, WRF/Chem, CAM3, MIRAGE, and Caltech unified GCM are included. Major model features, physical/chemical treatments, as well as typical applications are evaluated with a focus on aerosol microphysics treatments, aerosol feedbacks to planetary boundary layer meteorology, and aerosol-cloud interactions. Recommendations for future development and improvement of on-line coupled models are provided. © 2011 Springer Berlin Heidelberg."
"7005822617;57194244669;","Air pollution and climate change progress toward integrated strategies and Co-benefits",2010,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-79952691168&partnerID=40&md5=f584ab36c354f780ea5ebec76eef6a56","The scientific and policy drivers that is critical in developing plans to improve air quality while simultaneously reducing greenhouse gas (GHG) emissions are discussed. A key area of debate is the magnitude of the net warming effect of black carbon once factors such as aerosol-cloud interactions are taken into account. Methane is the second most significant driver of climate warming after CO2, but lasts only for a decade. So, to achieve quick cooling in sensitive regions like the Arctic, methane reductions may be a more powerful tool, even though CO2 reductions are needed over the long run. Existing regional air pollution networks can play an important role in linking the climate and air pollution communities at different scales and in sharing expertise. The GAP Forum partners are considering how to encourage outreach to help developing nations implement best practices for regulation of methane sources with an initial focus on improving regional air quality, but with the clear co-benefit of climate protection."
"23568239000;55917711400;","Satellite observations of Mineral Dust interactions with West-African monsoon clouds",2009,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879927326&partnerID=40&md5=6226e4d4bf2fbc8a1ab695738b07b1c1","A new Bitemporal Mineral Dust Index (BMDI) from MSG infrared channels was used to examine the influence of mineral dust on convective clouds and the monsoon in the West-African Sahel region. Analysing BMDI and contemporary cloud parameter and precipitation retrievals shows that observation density distributions of cloud properties such as cloud cover and Cloud Top Temperature (CTT) are changed significantly in the presence of dust. Besides the strong contrast of cloud properties and precipitation between dusty and dust-free scenes, cloud lifetimes are increased due to precipitation suppression for higher dust loads, which can be seen in increasing cloud cover, decreasing CTT and lower rainfall averages. As other non-dust aerosols are part of background conditions in the statistical analysis, the results strongly indicate to the necessity for different treatment of aerosol species in aerosol-cloud interaction studies."
"55718206700;7202772927;7005742394;35467186900;","Aerosol indirect effect on long-lasting mesoscale convective systems: A modeling study",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868059621&partnerID=40&md5=30a01fe5893419991a175c4c2f0cac14",[No abstract available]
"23109486000;57203053317;","The effect of cloud top entrainment on the aerosol indirect effect",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-75149195879&partnerID=40&md5=c48b5015538e5d5ca012555bc92f3e78",[No abstract available]
"56373027800;15032788000;7006107059;","Evaluation of the aerosol indirect effect using satellite, chemical transport model, and aircraft data during ICARTT",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-75149184086&partnerID=40&md5=70a40301426ce5f0df1cb19da7f204f2",[No abstract available]
"26632168400;57203053317;","Aerosol-cloud interactions and the effects on orographic precipitation",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-75149144409&partnerID=40&md5=1d9f815b4d934292d79013821a31cadc","Anthropogenic and natural aerosols serve as a source of cloud condensation nuclei (CCN) and influence the microphysical properties of clouds. An increase of the aerosol load leads to an increase of the cloud droplet number concentration and, for a given liquid water content, to a decrease of the average cloud droplet size. Since the collision efficiency is small for small droplets, the increased aerosol load induces a deceleration of the cloud drop coalescense process in warm phase clouds. Furthermore, the rain drop development through the (auto-) conversion process is prolongated. This prolongation effect extends the cloud lifetime and leads to a modification of the precipitation formation. Furthermore, the spatial distribution of precipitation at the surface may be altered. In the case of low-level orographic clouds the aerosol-cloud interactions are suspected to reduce the amount of precipitation on the upslope side of the mountain and to enhance the precipitation on the downslope side of the mountain. The net effect may lead to a shift of the precipitation distribution towards the leeward side of mountain ranges which affects the hydrological cycle on the local scale. The main purpose of this study is to investigate aerosol-cloud interactions in warm phase clouds and to quantify the aerosol indirect effect on the hydrological cycle. Herefore, simulations of moist orographic flows over topography are conducted and the influence of aerosol particles on the orographic precipitation formation is analyzed by comparing a polluted case against a clean reference case. The degree of aerosol pollution is simulated by prescribing different number concentrations of CCN which are then available for the cloud drop nucleation. The simulations are performed with the shortrange Local Model (LMK) which is currently developed at the German weather service (DWD) for the purpose of short-range weather prediction and the horizontal resolution of the model is 2.8km. Throughout this study the focus is put on warm phase clouds. The considered microphysical processes are the nucleation of cloud droplets, the selfcollection, the ac-creation and the autoconversion of cloud droplets into rain. These warm phase processes are treated within the framework of a two-moment microphysics scheme."
"25723426400;7005602760;7006159471;9248799600;","The aerosol indirect effects examined by numerically calculated aerosols and satellite derived clouds",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-75149140504&partnerID=40&md5=793ce49ee112a14e0ebf74f436733114",[No abstract available]
"55017656900;7003591311;","Aerosol-cloud-radiation and surface flux interations simulated in a Large-Eddy model",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-75149130501&partnerID=40&md5=7c905b1abd3359613fa0ea99599d6c81","4.1 Simulations with no aerosol-radiative-land surface feedbacks • Increases in Na in these warm cumulus clouds do not lead to statistically significant changes in cloud fraction, LWP and cloud depth. Aerosol effects are well within the dynamical variability in LWP and cloud fraction at any given Na. • Increases in Na result in increases in Nd and cloud optical depth τc. • Increases in Na cause reduction in surface precipitation. 4.2 Simulations including aerosol-radiative-land surface feedbacks: • The radiatively-active aerosol blocks up to 26.5 % of incoming solar radiative flux from reaching the surface (for the most polluted case). The reduction in the surface radiative flux leads to a reduction in the surface heat flux and consequently weaker convection, much shallower clouds and lower cloud cover and LWP. • Cloud optical depth shows non-monotonic behavior with increasing aerosol. We have shown that the sign of the change of aerosol induced effects on LWP and cloud fraction does not follow the common hypothesis known as the second aerosol indirect effect. This study has pointed to the importance of coupling aerosol radiative properties and a surface soil and vegetation model to the microphysical-dynamical model. As shown here, under polluted conditions the surface flux response to the aerosol may be the single most important factor in cloud reduction. We emphasize that further study is required to establish the robustness of these results for different atmospheric soundings."
"7007061674;7003480967;7004052136;57197424614;6602765265;20433889200;6701842515;7005941217;55730602600;23971773000;55477947800;14034301300;6602128405;7401891176;57196669323;","Aerosol-cloud interactions on a mountain peak in Puerto Rico",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-75149122422&partnerID=40&md5=089dbcb75e69998de13e5626e74fbebe","The preliminary analysis of measurements made in a clear and cloudy environment show that the aerosol particle size distributions were independent of the air mass origin, i.e. clean maritime air from the NE or moderately polluted air from the SE. Likewise the CCN (Figure presented) concentrations were insensitive to the wind direction. The CN number and BC mass concentrations were somewhat higher when winds were from the SE, suggesting that the majority of the anthropogenic particles were very small, non-hygroscopic soot. The cloud properties were virtually unaffected by the source of the air and the amount of rain was the same regardless of wind direction. This indicates that the anthropogenic particles do not increase droplet concentration or impact the efficiency of precipitation. Finally, the dominance of sea salt in the cloud water suggests that the clouds that form over the East Peak of Puerto Rico are generated primarily from CCN that originate from natural sources."
"35998927000;","Particle emissions from aviation: Microphysics, chemistry, and climate impact",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751040921&partnerID=40&md5=f83fb9e8b21173c24591a57fd284414c","Particulate emissions from aviation during cruise, their physical and chemical properties and the potential effects on Earth's atmosphere and climate constitute a rich and complex research area. Their relevance for the global climate system was identified in the early 1990s, and gains today increasing attention because of their likely role in the life cycle of upper tropospheric ice clouds or cirrus, respectively. An understanding of the impact mechanisms of aviation-related particle emissions on atmosphere and climate requires research on particle formation in gas turbines, on particle processing in chemically active exhaust plumes, on atmospheric processing and transformation of particles released into the upper troposphere and lowermost stratosphere, and also on the background aerosol of this particular atmospheric layer which forms the sink for the aircraft engine exhaust particles. Simultaneously, techniques have to be developed for improving the available measurement capabilities for relevant particle properties and constituents. The presented experimental work approaches the scientific subject from all necessary directions: The physical and chemical properties of emitted particles were identified under cruise altitude conditions and with more detailed methods during ground-test studies. The quantification of emissions for various aircraft resulted in a validated average emission index for particulate black carbon which is today widely used for the calculation of the aviation-related particle emissions in climate models and impact studies. The results achieved from this extensive experimental field work contributed considerably to the international assessment of the climate effects of aviation at the turn to the 21 st century. A European research programme on the properties and the processing of particles forming in an aircraft engine under controlled test-stand conditions was defined which built on the knowledge gained during the studies on aviation particle emissions at cruise. The project PartEmis was of high relevance also for the European aircraft engine industry and provided extensive new knowledge on particle emissions from aircraft engines. Particularly the connection of particle chemical and physical properties with the potential activation of combustion particles for the formation of cloud droplets will promote the understanding of the aerosol-cloud interaction concerning combustion particles. Furthermore, a robust method for the measurement of aerosol light absorption and thus for black carbon was developed and evaluated. Multi-Angle Absorption Photometry turned out to be widely applicable for measurements in engine exhaust as well as in the remote background atmosphere on mountain sites. Results from a first 2-years data record on black carbon in the free troposphere over central Europe were used in combination with the determined particle emission factors for aircraft engines for estimating the black carbon load of the free troposphere and for assessing the climate impact of particle emissions from aviation. The estimated magnitude of the expected aerosol radiative forcing is in close agreement with recent results from the European project TRADEOFF which represents today's state of knowledge on the subject of aviation radiative forcing."
"6602128405;6602238735;7004326767;7004556087;","CCN activation of pure and coated carbon black particles",2004,"10.1016/s0021-8502(19)30153-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23344451022&doi=10.1016%2fs0021-8502%2819%2930153-3&partnerID=40&md5=618e95dc41e50a3b187840a12ee39541",[No abstract available]
"8657166100;6602417968;7006211890;6701313597;8657165300;57197924923;6602914876;6701862401;7101764967;8657165800;55633197600;7102490158;","Aerosol-cloud interaction during the transition time period of Arctic haze to clean summer conditions",2004,"10.1016/s0021-8502(19)30118-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23344440958&doi=10.1016%2fs0021-8502%2819%2930118-1&partnerID=40&md5=bdd017c72b99a0ef680cd0ffbc36a4c5",[No abstract available]
"57208121852;7003931528;7003363359;55916925700;56370934200;8666820400;6701465132;","Global aerosol modelling with the ECHAM5 GCM",2004,"10.1016/s0021-8502(19)30255-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23344440515&doi=10.1016%2fs0021-8502%2819%2930255-1&partnerID=40&md5=223b40b015e909738ba74982720ea8d5",[No abstract available]
"6504549639;8711886600;7402177459;","Simulation of aerosol-cloud chemistry interactions during a hill CAP cloud passage experiment",2004,"10.1016/s0021-8502(19)30174-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23344438881&doi=10.1016%2fs0021-8502%2819%2930174-0&partnerID=40&md5=283cb7ee6803239b4f6c00648f1e0f67",[No abstract available]
"7202485288;7004540083;35070788500;7201914101;","Three different behaviors of liquid water path of water clouds in aerosol-cloud interactions",2002,"10.1175/1520-0469(2002)059<0726:tdbolw>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086353534&doi=10.1175%2f1520-0469%282002%29059%3c0726%3atdbolw%3e2.0.co%3b2&partnerID=40&md5=2e1b8d702dce8e207ab47db8fa0fb09b","Estimates of the indirect aerosol effect in GCMs assume that either cloud liquid water path is constant (Twomey effect) or increases with increased droplet number concentration (drizzle-suppression or Albrecht effect). On the other hand, if cloud thermodynamics and dynamics are considered, cloud liquid water path may also decrease with increasing droplet number concentration, which has been predicted by model calculations and observed in ship track and urban influence studies. This study examines the different changes of cloud liquid water path associated with changes of cloud droplet number concentration. Satellite data (January, April, July, and October 1987) are used to determine the cloud liquid water sensitivity, defined as the ratio of changes of liquid water path and changes of column droplet number concentration. The results of a global survey for water clouds (cloud-top temperature > 273 K. optical thickness 1 ≤ T < 15) reveal all three behaviors of cloud liquid water path with aerosol changes: increasing, approximately constant, or decreasing as cloud column number concentration increases. The authors find that 1) in about one-third of the cases, predominantly in warmer locations or seasons, the cloud liquid water sensitivity is negative, and the regional and seasonal variations of the negative liquid water sensitivity are consistent with other observations; 2) in about one-third of the cases, a minus one-third (-1/3) power-law relation between effective droplet radius and column number concentration is found, consistent with a nearly constant cloud water path: and 3) in the remaining one-third of the cases, the cloud liquid water sensitivity is positive. These results support the suggestion that it is possible for an increase of cloud droplet number concentration to both reduce cloud droplet size and enhance evaporation just below cloud base, which decouples the cloud from the boundary layer in warmer locations, decreasing water supply from surface and reducing cloud liquid water. Results of this study also suggest that the current evaluations of the negative aerosol indirect forcing by GCMs, which are based on either the Twomey or Albrecht effects, may be overestimated in magnitude."
"7202485288;7004540083;7402652539;7201914101;","Satellite remote sensing of the liquid water sensitivity in water clouds",2001,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035575149&partnerID=40&md5=58c272a3a54b851a277656411c5b500d","In estimation of the aerosol indirect effect, cloud liquid water path is considered either constant (Twomey effect) or increasing with enhanced droplet number concentrations (drizzle-suppression effect, or Albrecht effect) if cloud microphysics is the prevailing mechanism during the aerosol-cloud interactions. On the other hand, if cloud thermodynamics and dynamics are considered, the cloud liquid water path may be decreased with increasing droplet number concentration, which is predicted by model calculations and observed in ship-track and urban influence studies. This study is to examine the different responses of cloud liquid water path to changes of cloud droplet number concentration. Satellite data (January, April, July and October 1987) are used to retrieve the cloud liquid water sensitivity, defined as the changes of liquid water path versus changes of column droplet number concentrations. The results of a global survey reveal that 1) at least one third of the cases the cloud liquid water sensitivity is negative, the regional and seasonal variations of the negative liquid water sensitivity are consistent with other observations; 2) cloud droplet sizes are always inversely proportional to column droplet number concentrations. Our results suggest that an increase of cloud droplet number concentration leads to reduced cloud droplet size and enhanced evaporation, which weakens the coupling between water clouds and boundary layer in warm zones, decreases water supply from surface and desiccates cloud liquid water. Our results also suggest that the current evaluations of negative aerosol indirect forcing by GCMs, which are based on Twomey effect or Albrecht effect, may be overestimated."
"7003814396;","A new method for the solution of the stochastic collection equation in cloud models with multi-component microphysics",2000,"10.1016/s0021-8502(00)90161-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034272003&doi=10.1016%2fs0021-8502%2800%2990161-7&partnerID=40&md5=b3a24395e8d1c66c93f7dd6f193f4db9",[No abstract available]
"7005088845;7005712238;","Cloud droplet redisual particles in cirrus clouds",2000,"10.1016/s0021-8502(00)90011-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034271991&doi=10.1016%2fs0021-8502%2800%2990011-9&partnerID=40&md5=47de90ee574b3e09c02f93732324b162",[No abstract available]
"57201124395;7004494327;55925779800;6603221134;","Ion composition of cloud processed continental aerosol particles",2000,"10.1016/s0021-8502(00)90071-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034271516&doi=10.1016%2fs0021-8502%2800%2990071-5&partnerID=40&md5=3187d13a0d395b67c71b7c4d9f60dfbc",[No abstract available]
"26643250500;56604618200;","Properties of particles in the tropopause region",2000,"10.1016/s0021-8502(00)90603-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034270305&doi=10.1016%2fs0021-8502%2800%2990603-7&partnerID=40&md5=c27bf3d201f5cc1499eab8346323b74f",[No abstract available]
"35998927000;6603164079;26643250500;7006471143;56187256200;","Observation of aerosol properties above ice saturation in the tropopause region",2000,"10.1016/s0021-8502(00)90015-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034269943&doi=10.1016%2fs0021-8502%2800%2990015-6&partnerID=40&md5=124aec8f1d7149d1e8b616af3323ea61",[No abstract available]
"7102680152;7006434689;7005069415;7004923073;","Investigation of the interaction between aerosol and clouds at the jungfraujoch (3580 M ASL)",2000,"10.1016/s0021-8502(00)90019-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034269889&doi=10.1016%2fs0021-8502%2800%2990019-3&partnerID=40&md5=1e0c07f1e97c6b2c8fe034ae72d2d1e0",[No abstract available]
"7202252296;57196499374;","Comparison of modelled particle activation to cloud droplets in clean and anthropogenically-influenced aerosol conditions",1998,"10.1016/S0021-8502(98)90743-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-11544255750&doi=10.1016%2fS0021-8502%2898%2990743-1&partnerID=40&md5=7e00453e765dd75fc12eba32d020e041",[No abstract available]
"6602244257;7202252296;56744278700;","A microphysics-based investigation of aerosol-cloud interactions and their radiative effects",1998,"10.1016/S0021-8502(98)00104-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0040712148&doi=10.1016%2fS0021-8502%2898%2900104-9&partnerID=40&md5=a2bd9f626019793fe5daa49e124e5136",[No abstract available]
"7102495313;57196499374;","Simulations of marine boundary-layer clouds with a coupled aerosol-cloud model",1997,"10.1016/S0021-8502(97)85210-X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0040565273&doi=10.1016%2fS0021-8502%2897%2985210-X&partnerID=40&md5=855c9c9ca64e9f8956d504f9da147270",[No abstract available]
"7801600432;7402094372;7201914101;","Aerosol optical thickness over ocean areas and its relationship with cloud droplet size",1997,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030650215&partnerID=40&md5=cbca0802190f4ce7275a9461d7e46af2","This paper presents the results of retrieved aerosol optical thickness over ocean areas and its relationship with droplet sizes of water clouds. The aerosol optical thickness is retrieved from clear sky radiances of channel 1 of AVHRR from ISCCP dataset. The results show consistent distribution patterns of aerosol optical thickness with other authors' work. The aerosol optical thickness shows a negative relation with cloud droplet size, consistent with expected aerosol indirect effect."
"7405459515;7202418453;35472747700;24611027600;","Potential application of solar occultation extinction measurements to aerosol-cloud-interaction studies",1993,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027874754&partnerID=40&md5=fc9ac98a476a637c14a48891ced1ebac","The objective of this report is to illustrate the potential application of the multiwavelength solar occultation measurements to aerosol-could-interaction studies, with emphasis on the evolution of the particle size distribution of tropical high clouds by using the fall 1989 SAGE II observations."
"7005349646;56270311300;24606987600;","35 P 28 A blue sun observation-an interplay between cloud and aerosol microphysics, and optics",1993,"10.1016/0021-8502(93)90310-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43949172966&doi=10.1016%2f0021-8502%2893%2990310-6&partnerID=40&md5=c4d17208559d7d6b4936d52b9f04fb4a","During a SAGE II tangent path intercept on 19 April 1991 over New Mexico, the NASA DC-8 aircraft inadvertently entered a cirrus cloud at 33000 feet pressure altitude. During a turning climb to get back into clear air, a blue sun at 2.3° elevation was observed near the top of the cloud at 35000 feet. In situ microphysical instruments aboard the aircraft showed, at the time of the blue sun observation, the appearance of three major modes in the particle size range 0.03 &lt; R &lt; 20 μm: An aerosol mode (lognormal parameters N0 = 18.6 cm-3, rg = 0.06 μm, σg = 1.5), a cloud-aerosol mode (N0 = 8.2 cm-3, rg = 0.27 μm, σg = 1.2) and a cloud mode (N0 = 1.1 cm-3, rg = 1.8 μm, σg = 1.9). Mie-calculations showed the atmospheric optics being dominated by the cloud and cloud-aerosol modes. Of these two, only the cloud mode alone shows a slight increase of light extinction with wavelength in the visible, which is a necessary condition for the appearance of a blue sun. In order to explain the blue sun observation, we had to combine actual measurements with a model (Horvath et al., 1993) by which cloud-aerosol interactions as a function of saturation with respect to ice explain the cloud-aerosol mode as a residue of a dissipating cloud mode. This observation points to the importance of multidisciplinary approaches to atmospheric observations, and it is an example of the occasional difficulty of reconciling in situ with remote sensing measurements. © 1993."