Author(s) ID,Title,Year,DOI,Link,Abstract
[No author id available],"Clouds and aerosols",2013,"10.1017/CBO9781107415324.016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928638179&doi=10.1017%2fCBO9781107415324.016&partnerID=40&md5=2aba26645b513c96ab7b6a1cce93f293","Executive Summary. Clouds and aerosols continue to contribute the largest uncertainty to estimates and interpretations of the Earth’s changing energy budget. This chapter focuses on process understanding and considers observations, theory and models to assess how clouds and aerosols contribute and respond to climate change. The following conclusions are drawn. Progress in Understanding. Many of the cloudiness and humidity changes simulated by climate models in warmer climates are now understood as responses to large-scale circulation changes that do not appear to depend strongly on sub-grid scale model processes, increasing confidence in these changes. For example, multiple lines of evidence now indicate positive feedback contributions from circulation-driven changes in both the height of high clouds and the latitudinal distribution of clouds (medium to high confidence). However, some aspects of the overall cloud response vary substantially among models, and these appear to depend strongly on sub-grid scale processes in which there is less confidence. {7.2.4, 7.2.5, 7.2.6, Figure 7.11}. Climate-relevant aerosol processes are better understood, and climate-relevant aerosol properties better observed, than at the time of AR4. However, the representation of relevant processes varies greatly in global aerosol and climate models and it remains unclear what level of sophistication is required to model their effect on climate. Globally, between 20 and 40% of aerosol optical depth (medium confidence) and between one quarter and two thirds of cloud condensation nucleus concentrations (low confidence) are of anthropogenic origin. © Intergovernmental Panel on Climate Change 2014."
"7003408439;7004470971;6603145318;","Zonal and vertical structure of the Madden-Julian oscillation",2005,"10.1175/JAS3520.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23644437569&doi=10.1175%2fJAS3520.1&partnerID=40&md5=795fd84eb54fd96578d602c0f3cb096a","A statistical study of the three-dimensional structure of the Madden-Julian oscillation (MJO) is carried out by projecting dynamical fields from reanalysis and radiosonde data onto space-time filtered outgoing longwave radiation (OLR) data. MJO convection is generally preceded by low-level convergence and upward motion in the lower troposphere, while subsidence, cooling, and drying prevail aloft. This leads to moistening of the boundary layer and the development of shallow convection, followed by a gradual and then more rapid lofting of moisture into the middle troposphere at the onset of deep convection. After the passage of the heaviest rainfall, a westerly wind burst region is accompanied by stratiform precipitation, where lower tropospheric subsidence and drying coincide with continuing upper tropospheric upward motion. The evolution of the heating field leads to a temperature structure that favors the growth of the MJO. The analysis also reveals distinct differences in the vertical structure of the MJO as it evolves, presumably reflecting changes in its vertical heating profile, phase speed, or the basic-state circulation that the MJO propagates through. The dynamical structure and the evolution of cloud morphology within the MJO compares favorably in many respects with other propagating convectively coupled equatorial waves. One implication is that the larger convective envelopes within the Tropics tend to be composed of more shallow convection along their leading edges, a combination of deep convection and stratiform rainfall in their centers, and then a preponderance of stratiform rainfall along their trailing edges, regardless of scale or propagation direction. While this may ultimately be the factor that governs the dynamical similarities across the various wave types, it raises questions about how the smaller-scale, higher-frequency disturbances making up the MJO conspire to produce its heating and dynamical structures. This suggests that the observed cloud morphology is dictated by fundamental interactions with the large-scale circulation. © 2005 American Meteorological Society."
"57204253860;7006432091;","Stratiform rain in the tropics as seen by the TRMM precipitation radar",2003,"10.1175/1520-0442(2003)016<1739:SRITTA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037594725&doi=10.1175%2f1520-0442%282003%29016%3c1739%3aSRITTA%3e2.0.CO%3b2&partnerID=40&md5=b26a2a530d813efc82b3346b767def41","Across the Tropics (20°N-20°S). the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) indicates that for reflectivities ≥ 17 dBZ, stratiform precipitation accounts for 73% of the area covered by rain and 40% of the total rain amount over a 3-yr period (1998-2000). The ratio of the convective rain rate to the stratiform rain rate is 4.1 on average at the horizontal resolution of the PR data. Convective rain rates remain constant or decrease as the strati form contribution to total rain increases, implying that stratiform rain production is not very dependent on the strength of convection. This relationship is especially evident over the ocean, where there are weaker convective rain rates than over land but relatively larger stratiform rain amounts. The ocean environment appears more efficient in the production of stratiform precipitation through either the sustainability of convection by a warm, moist boundary layer with only a weak diurnal variation and/or by the near-moist adiabatic stratification of the free atmosphere. Factors such as wind shear and the relative humidity of the large-scale environment can also affect the production of stratiform rain. Over land, higher stratiform rain fractions often occur during the season of maximum insolation and with the occurrence of very large, organized precipitation systems (i.e., mesoscale convective complexes). Monsoon regions show the largest seasonal variations in stratiform rain fraction, with very low values in the season before the monsoon and higher values during the monsoon. A strong gradient in stratiform rain fraction exists across the Pacific, with a minimum ∼25% over the Maritime Continent and a maximum ∼60% in the intertropical convergence zone (ITCZ) of the eastern-central Pacific. This near-equatorial trans-Pacific gradient becomes exaggerated during El Niño. A higher stratiform rain fraction concentrates latent heating at upper levels, which implies a stronger upper-level circulation response to the heating. Thus, the variations in stratiform rain fraction that occur before the monsoon and during the monsoon, across the Pacific basin, and between La Niña and El Niño imply vertical variations in the large-scale circulation response to tropical precipitating systems that would not occur if the stratiform rain fraction was temporally and spatially uniform across the Tropics."
"7410255460;7006432091;6701670597;","Multiscale variability of deep convection in relation to large-scale circulation in TOGA COARE",1996,"10.1175/1520-0469(1996)053<1380:MVODCI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029769393&doi=10.1175%2f1520-0469%281996%29053%3c1380%3aMVODCI%3e2.0.CO%3b2&partnerID=40&md5=c53dd2132379c20e90adc0545b6aa83a","Deep convection over the Indo-Pacific oceanic warm pool in the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) occurred in cloud clusters, which grouped together in regions favoring their occurrence. These large groups of cloud clusters produced large-scale regions of satellite-observed cold cloud-top temperature. This paper investigates the manner in which the cloud clusters were organized on time and space scales ranging from the seasonal mean pattern over the whole warm-pool region to the scale of individual cloud clusters and their relationship to the large-scale circulation and sea surface temperature (SST). The dominant convective variability was associated with the intraseasonal oscillation (ISO). A large eastward propagating ensemble of cloud clusters marked the ISO's progress. The meridional structure of the ISO was strongly affected by the seasonal cycle with a southward shift from the Northern Hemisphere in October-November to the Southern Hemisphere in January-February. The SST had an intraseasonal signal in lagged quadrature with the cold cloudiness and rainfall in COARE. The SST increased (decreased) during the convectively suppressed (active) phases of the ISO. Enhanced low-level westerly winds occurred toward the later stages of the enhanced-convection periods of the ISO, though not always centered at the equator. The strongest westerlies tended to be located between two synoptic-scale cyclonic gyres, which were often not symmetric about the equator in the low-level wind field. This asymmetry in the anomalous equatorial low-level westerlies may have different implications for the oceanic response in the coupled atmosphere-ocean system than those centered on the equator. The cyclonic gyres contained highly concentrated deep convection, and, in four cases, the gyres developed into tropical cyclones. Within the envelope marking the convectively active phase of the ISO, cloud clusters were frequently concentrated into westward-propagating disturbances with a local periodicity of ∼2 days. These 2-day disturbances have been identified in earlier spectral studies and appear to be related to westward propagating inertio-gravity waves. In COARE, they typically contained numerous cloud clusters, which underwent a distinct diurnal cycle. Most of the cloud clusters embedded in the 2-day disturbances moved westward, though some were stationary, and a few moved eastward. A cloud-cluster tracking program identified groups of clusters (time clusters) that exhibited continuity in time and space. In the most convectively active period of the ISO, the tracking program identified almost the entire ISO cloud ensemble as a long-lasting, trackable superconvective system. This observation indicates the lack of a distinct scale-separation between convection and large-scale disturbances during the most intense convective periods in COARE."
"35509639400;7004714030;56283400100;24322005900;7004764167;","On dynamic and thermodynamic components of cloud changes",2004,"10.1007/s00382-003-0369-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2142829554&doi=10.1007%2fs00382-003-0369-6&partnerID=40&md5=182fc9541143b753cda33fce1a45a768","Clouds are sensitive to changes in both the large-scale circulation and the thermodynamic structure of the atmosphere. In the tropics, temperature changes that occur on seasonal to decadal time scales are often associated with circulation changes. Therefore, it is difficult to determine the part of cloud variations that results from a change in the dynamics from the part that may result from the temperature change itself. This study proposes a simple framework to unravel the dynamic and non-dynamic (referred to as thermodynamic) components of the cloud response to climate variations. It is used to analyze the contrasted response, to a prescribed ocean warming, of the tropically-averaged cloud radiative forcing (CRF) simulated by the ECMWF, LMD and UKMO climate models. In each model, the dynamic component largely dominates the CRF response at the regional scale, but this is the thermodynamic component that explains most of the average CRF response to the imposed perturbation. It is shown that this component strongly depends on the behaviour of the low-level clouds that occur in regions of moderate subsidence (e.g. in the trade wind regions). These clouds exhibit a moderate sensitivity to temperature changes, but this is mostly their huge statistical weight that explains their large influence on the tropical radiation budget. Several propositions are made for assessing the sensitivity of clouds to changes in temperature and in large-scale motions using satellite observations and meteorological analyses on the one hand, and mesoscale models on the other hand. © Springer-Verlag 2004."
"35894581100;","Atmospheric simulations using a GCM with simplified physical parametrizations. I: Model climatology and variability in multi-decadal experiments",2003,"10.1007/s00382-002-0268-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037273134&doi=10.1007%2fs00382-002-0268-2&partnerID=40&md5=41309f6f22069828d8ec71ee18b3b4d2","This work describes the formulation and climatology of an atmospheric general circulation model (GCM) of intermediate complexity, based on a spectral primitive-equation dynamical core and a set of simplified physical parametrization schemes. The parametrization package has been specially designed to work in models with just a few vertical levels, and is based on the same physical principles adopted in the schemes of state-of-the art GCMs. The parametrized processes include large-scale condensation, convection, clouds, short-wave and long-wave radiation, surface fluxes and vertical diffusion. In the current configuration, the model (nicknamed SPEEDY, from Simplified Parametrizations, primitivE-Equation DYnamics"") has five vertical levels and a spectral truncation at total wave number 30 (T30L5). The top vertical level (crudely) represents the stratosphere, the bottom one the planetary boundary layer. Computationally, SPEEDY requires (at least) one order of magnitude less CPU time than a state-of-the-art GCM at the same horizontal resolution, and is therefore suitable for studies of inter-decadal or inter-centennial variability. Statistics of the model mean state and variability are computed from an ensemble of 41-year simulations forced by observed sea-surface temperatures in the period 1952-1992. The model mean state is closer to the observed climatology during the (boreal) winter than during summer. In winter (i.e. December to February, DJF), the model underestimates the amplitude of the Northern Hemisphere stationary wave pattern, particularly in the European-Atlantic sector. Some aspects of the systematic error of SPEEDY are in fact typical of many GCMs, although the error amplitude is stronger than in state-of-the-art models. On the other hand, the global distribution of precipitation in DJF is quite realistic, and compares well with that of more complex GCMs. In summer (June to August), a strong negative bias in the mid-tropospheric temperature generates a Northern Hemisphere circulation with some springtime characteristics. In particular, the position of the Tropical Convergence Zone in the Indian Ocean remains too far south, leading to a deficient simulation of the monsoon circulation over South Asia. The simulated variability during the northern winter is reasonably realistic as far as the spatial distribution is concerned, although some underestimation in the intensity can be found, particularly in the low-frequency range and in the Atlantic sector. The atmospheric response to ENSO events is also weaker than observed, although the spatial patterns of the rainfall and geopotential response in the Pacific sector are in phase with their observed counterparts. In the Atlantic/Eurasian region, the spatial patterns associated with the interdecadal trends in the simulated and observed large-scale circulation show a clear positive correlation, consistent with the hypothesis of a positive ocean-atmosphere feedback on decadal time scales."
"7201504886;25953950400;7003591311;7004061048;","Large-eddy simulations of strongly precipitating, shallow, stratocumulus-topped boundary layers",1998,"10.1175/1520-0469(1998)055<3616:LESOSP>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033489845&doi=10.1175%2f1520-0469%281998%29055%3c3616%3aLESOSP%3e2.0.CO%3b2&partnerID=40&md5=92c296ef389ff41576279d2650863711","Large-eddy simulations that incorporate a size-resolving representation of cloud water are used to study the effect of heavy drizzle on PBL structure. Simulated surface precipitation rates average about 1 mm day-1. Heavily drizzling simulations are compared to nondrizzling simulations under two nocturnal PBL regimes - one primarily driven by buoyancy and the other driven equally by buoyancy and shear. Drizzle implies a net latent heating in the cloud that leads to sharp reductions to both entrainment and the production of turbulent kinetic energy by buoyancy (particulariy in downdrafts). Drizzle, which evaporates below cloud base, promotes a cooler and moister subcloud layer that further inhibits deep mixing. The cooling and moistening is in quantitative agreement with some observations and is shown to favuor the formation of cumuli rising out of the subcloud layer. The cumuli, which are local in space and time, are responsible for most of the heat and moisture transport. They also appear to generate a larger-scale circulation that differs dramatically from the regularity typically found in nonprecipitating stratocumulus. Time-averaged turbulent fluxes of heat and moisture increase in the presence of precipitation, suggesting that drizzle (and drizzle-induced stratification) should not necessarily be taken as a sign of decoupling. Because drizzle primarily affects the vertical distribution of buoyancy, shear production of turbulent kinetic energy mitigates some of the effects described above. Based on large-eddy simulation the authors hypothersize that shallow, well-mixed, radiatively driven stratocumulus cannot persist in the presence of heavy drizzle. In accord with some simpler models, the simulated case with heavy percipitation promotes a reduction in both liquid-water path and entrainment. However, the simulations suggest that time-intergrated cloud fraction may increase as a result of drizzle because thinner percipitating clouds may persist longer if the boundary layer does not deepen as rapidly. These somewhat more complicated dynamics have important implications for a number of hypotheses suggesting that changes in acrosol concerntrations, when metabolized by stratocumulus, have a significant effort on climate."
"7202208382;57203400519;6603565405;6507777841;","Interactions among radiation, convection, and large-scale dynamics in a general circulation model",1989,"10.1175/1520-0469(1989)046<1943:IARCAL>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024830046&doi=10.1175%2f1520-0469%281989%29046%3c1943%3aIARCAL%3e2.0.CO%3b2&partnerID=40&md5=dcf3cdd2ebac58614bbd29eac117185c","We have analyzed the effects of radiatively active clouds on the climate simulated by the UCLA/GLA GCM, with particular attention to the effects of the upper tropospheric stratiform clouds associated with deep cumulus convection, and the interactions of these clouds with convection and the large-scale circulation. Taken together, our results show that upper tropospheric clouds associated with moist convection, whose importance has recently been emphasized in observational studies, play a very complex and powerful role in determining the model results. -from Authors"
"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."
"7103321545;57192049430;","Multi-scale features of Baiu, the summer monsoon over Japan and the East Asia",1992,"10.2151/jmsj1965.70.1B_467","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049104812&doi=10.2151%2fjmsj1965.70.1B_467&partnerID=40&md5=43e96ed361aa91045cb06d7045b3a3dc","This review paper summarizes the authors' recent studies on the Baiu, the summer monsoon, over the Japan Islands and the adjacent areas. The most important feature of the Baiu is the formation of the Baiu front, which is a long quasistationary precipitation belt extending from the southeastern foot of the Tibetan Plateau to Japan and further to the northwestern Pacific. The cold Baiu trough, the polar front and the Pacific subtropical anticyclone are the major large-scale circulation systems which have influence on the Baiu front. The frontogenesis and the generation of convective instability in the southwesterly flows along the westnorthwest periphery of the Pacific subtropical anticyclone are the primary factors for the formation of the Baiu front. The structure of the Baiu front and the associated Baiu low-level jet stream, and the water vapor budget during the peak Baiu period are studied. The generation and release of the convective instability in the intense Baiu precipitation area are also analyzed. The features of the meso-α-scale disturbances in the Baiu frontal zone are studied by the spectral analysis of the relative vorticity field and the cloud amount. The meso-β-and meso-γ-scale fine structures within the meso-a-scale disturbances are demonstrated. The most outstanding feature of the Baiu is that the motions of many scales (planetary, synoptic, meso-α-, meso-β-and meso-γ-scales) are interacting with each other. The multi-scale aspects of the Baiu are stressed in this review paper. © 1992, Meteorological Society of Japan."
"7402944490;56424145700;","Multi-stage onset of the summer monsoon over the western North Pacific",2001,"10.1007/s003820000118","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034842480&doi=10.1007%2fs003820000118&partnerID=40&md5=80b7002dc1cd7fe5c0d5d765709313a0","The climatological summer monsoon onset displays a distinct step wise northeastward movement over the South China Sea and the western North Pacific (WNP) (110°-160°E, 10°-20°N). Monsoon rain commences over the South China Sea-Philippines region in mid-May, extends abruptly to the southwestern Philippine Sea in early to mid-June, and finally penetrates to the northeastern part of the domain around mid-July. In association, three abrupt changes are identified in the atmospheric circulation. Specifically, the WNP subtropical high displays a sudden eastward retreat or quick northward displacement and the monsoon trough pushes abruptly eastward or northeastward at the onset of the three stages. The step wise movement of the onset results from the slow northeastward seasonal evolution of large-scale circulation and the phase-locked intraseasonal oscillation (ISO). The seasonal evolution establishes a large-scale background for the development of convection and the ISO triggers deep convection. The ISO over the WNP has a dominant period of about 20-30 days. This determines up the time interval between the consecutive stages of the monsoon onset. From the atmospheric perspective, the seasonal sea surface temperature (SST) change in the WNP plays a critical role in the northeastward advance of the onset. The seasonal northeastward march of the warmest SST tongue (SST exceeding 29.5 °C) favors the northeastward movement of the monsoon trough and the high convective instability region. The seasonal SST change, in turn, is affected by the monsoon through cloud-radiation and wind-evaporation feedbacks."
"56014511300;7003266014;","A model of transport across the tropical tropopause",2001,"10.1175/1520-0469(2001)058<0765:AMFTAT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035308257&doi=10.1175%2f1520-0469%282001%29058%3c0765%3aAMFTAT%3e2.0.CO%3b2&partnerID=40&md5=729bb5f3698a045eccaeaf5dc137f424","A model of convective and advective transport across the tropical tropopause is described. In this model overshooting convective turrets inject dehydrated tropospheric air into a tropical ""tropopause layer"" (TTL) bounded approximately by the 50- and 150-hPa surfaces, a layer similar to the ""entrainment zone"" at the top of the planetary boundary layer. The overshooting process occurs only in limited regions. In the TTL, mixtures of overshooting and ambient air undergo buoyancy-driven settling, then slowly loft through the TTL and eventually enter the main stratosphere throughout the Tropics. It is found that for reasonable parameter settings the combined action of convection, isentropic mixing, and advection by the large-scale circulation in the model can produce realistic water vapor and ozone profiles while balancing the energy budget. Some of the observed peculiarities that can be simulated are (i) the widespread absence of vapor saturation at the tropopause despite tropical mean upward motion, (ii) an ozone minimum below the mean tropopause, and (iii) the typical location of stratiform cloud tops below the mean tropopause. In contrast to inferences from typical ""cold trap"" models, the relative humidity of air crossing the tropopause is found to be sensitive to ice microphysics."
"35509639400;7401559815;7004160106;","Sea surface temperature and large-scale circulation influences on tropical greenhouse effect cloud radiative forcing",1997,"10.1175/1520-0442(1997)010<2055:SSTALS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031200764&doi=10.1175%2f1520-0442%281997%29010%3c2055%3aSSTALS%3e2.0.CO%3b2&partnerID=40&md5=a91eda0716fe5255448df729c71487eb","Two independent sets of meteorological reanalyses are used to investigate relationships between the tropical sea surface temperature (SST) and the large-scale vertical motion of the atmosphere for spatial and seasonal variations, as well as for El Niño/La Niña episodes of 1987-88. Supergreenhouse effect (SGE) situations are found to be linked to the occurrence of enhanced large-scale rising motion associated with increasing SST. In regions where the large-scale atmospheric motion is largely decoupled from the local SST due to internal or remote forcings, the SGE occurrence is weak. On seasonal and interannual timescales, such regions are found mainly over equatorial regions of the Indian Ocean and western Pacific, especially for SSTs exceeding 29.5°C. In these regions, the activation of feedback processes that regulate the ocean temperature is thus likely to be more related to the large-scale remote processes, such as those that govern the monsoon circulations and the low-frequency variability of the atmosphere, than to the local SST change. The relationships among SST, clouds, and cloud radiative forcing inferred from satellite observations are also investigated. In large-scale subsidence regimes, regardless of the SST range, the cloudiness, the cloud optical thickness, and the shortwave cloud forcing decrease with increasing SST. In convective regions maintained by the large-scale circulation, the strong dependence of both the longwave (LW) and shortwave (SW) cloud forcing on SST mainly results from changes in the large-scale vertical motion accompanying the SST changes. Indeed, for a given large-scale rising motion, the cloud optical thickness decreases with SST, and the SW cloud forcing remains essentially unaffected by SST changes. However, the LW cloud forcing still increases with SST because the detrainment height of deep convection, and thus the cloud-top altitude, tend to increase with SST. The dependence of the net cloud radiative forcing on SST may thus provide a larger positive climate feedback when the ocean warming is associated with weak large-scale circulation changes than during seasonal or El Niño variations."
"23094223900;25228634000;6701847229;6701571700;7003748648;7003499456;","Analysis of ERA 40-driven CLM simulations for Europe",2008,"10.1127/0941-2948/2008/0301","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049101915&doi=10.1127%2f0941-2948%2f2008%2f0301&partnerID=40&md5=7c5da5ba9bfc6e39a2ae82e2dfcd3073","The Climate Local Model (CLM) is a community Regional Climate Model (RCM) based on the COSMO weather forecast model. We present a validation of long-term ERA40-driven CLM simulations performed with differentmodel versions. In particular we analyse three simulations with differences in boundary nudging and horizontal resolution performed for the EU-project ENSEMBLES with the model version 2.4.6, and one with the latest version 4.0. Moreover, we include for comparison a long-term simulation with the RCM CHRM previously used at ETH Zurich. We provide a thorough validation of temperature, precipitation, net radiation, cloud cover, circulation, evaporation and terrestrial water storage for winter and summer. For temperature and precipitation the interannual variability is additionally assessed. While simulations with CLM version 2.4.6 are generally too warm and dry in summer but still within the typical error of PRUDENCE simulations, version 4.0 has an anomalous cold and wet bias. This is partly due to a strong underestimation of the net radiation associated with cloud cover overestimation. Two similar CLM 2.4.6 simulations with different spatial resolutions (0.44° and 0.22°) reveal for the analysed fields no clear benefit of the higher resolution except for better resolved fine-scale structures. While the large-scale circulation is represented more realistically with spectral nudging, temperature and precipitation are not. Overall, CLM performs comparatively to other state-of-the-art RCMs over Europe. © by Gebrüder Borntraeger 2008."
"56016514800;6602598448;36239282800;16203322900;7005939834;55762874000;26643300800;22836772900;53871288800;7005776035;35490828000;12767251100;7003627515;6603873829;","Improved representation of East Antarctic surface mass balance in a regional atmospheric climate model",2014,"10.3189/2014JoG14J051","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84909986649&doi=10.3189%2f2014JoG14J051&partnerID=40&md5=28b512d847f67cd79ea8896570c532d0","This study evaluates the impact of a recent upgrade in the physics package of the regional atmospheric climate model RACMO2 on the simulated surface mass balance (SMB) of the Antarctic ice sheet. The modelled SMB increases, in particular over the grounded ice sheet of East Antarctica (+44Gt a-1), with a small change in West Antarctica. This mainly results from an increase in precipitation, which is explained by changes in the cloud microphysics, including a new parameterization for ice cloud supersaturation, and changes in large-scale circulation patterns, which alter topographically forced precipitation. The spatial changes in SMB are evaluated using 3234 in situ SMB observations and ice-balance velocities, and the temporal variability using GRACE satellite retrievals. The in situ observations and balance velocities show a clear improvement of the spatial representation of the SMB in the interior of East Antarctica, which has become considerably wetter. No improvements are seen for West Antarctica and the coastal regions. A comparison of model SMB temporal variability with GRACE satellite retrievals shows no significant change in performance."
"26645901500;7004468723;26431037300;","European temperatures in CMIP5: Origins of present-day biases and future uncertainties",2013,"10.1007/s00382-013-1731-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888021902&doi=10.1007%2fs00382-013-1731-y&partnerID=40&md5=79b88e48c533a2a6bfc707e294255816","European temperatures and their projected changes under the 8.5 W/m2 Representative Concentration Pathway scenario are evaluated in an ensemble of 33 global climate models participating in the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Respective contributions of large-scale dynamics and local processes to both biases and changes in temperatures, and to the inter-model spread, are then investigated from a recently proposed methodology based on weather regimes. On average, CMIP5 models exhibit a cold bias in winter, especially in Northern Europe. They overestimate summer temperatures in Central Europe, in association with a greater diurnal range than observed. The projected temperature increase is stronger in summer than in winter, with the highest summer warming occurring over Mediterranean regions. Links between biases and sensitivities are evidenced in winter, suggesting a potential influence of snow cover biases on the projected surface warming. A brief analysis of daily temperature extremes suggests that the intra-seasonal variability is projected to decrease (slightly increase) in winter (summer). Then, in order to understand model discrepancies in both present-day and future climates, we disentangle effects of large-scale atmospheric dynamics and regional physical processes. In particular, in winter, CMIP5 models simulate a stronger North-Atlantic jet stream than observed and, in contrast with CMIP3 results, the majority of them suggests an increased frequency of the negative phase of the North-Atlantic Oscillation under future warming. While large-scale circulation only has a minor contribution to ensemble-mean biases or changes, which are primarily dominated by non-dynamical processes, it substantially affects the inter-model spread. Finally, other sources of uncertainties, including the North-Atlantic warming and local radiative feedbacks related to snow cover and clouds, are briefly discussed. © 2013 Springer-Verlag Berlin Heidelberg."
"7004540083;6603422104;10242482700;7006698304;","Tropical climate described as a distribution of weather states indicated by distinct mesoscale cloud property mixtures",2005,"10.1029/2005GL024584","https://www.scopus.com/inward/record.uri?eid=2-s2.0-29344471030&doi=10.1029%2f2005GL024584&partnerID=40&md5=7dd1b0d959adeb389f554bf2f96c18f4","An analysis approach that uses the patterns of cloud property joint distributions at mesoscale (cloud type mixtures) from the International Satellite Cloud Climatology Project to identify distinct weather states of the tropical atmosphere is extended to the whole tropics covering the period 1983-2004. These patterns can be used as the basis for multi-scale, multi-variate compositing of other observations to understand how tropical cloud systems affect the atmospheric diabatic heating and interact with the large scale circulation. We illustrate how variations of the tropical climate on longer time scales can be described in terms of the changes in the frequency of occurrence of these weather states with their associated multivariate relationships. Copyright 2005 by the American Geophysical Union."
"6602744181;55722586400;55678879300;","Sources of systematic errors in the climatology of a regional climate model over Europe",1998,"10.1007/s003820050249","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032435734&doi=10.1007%2fs003820050249&partnerID=40&md5=13361cbebf95b136e05e2414f5aebc8f","Two 10-year simulations made with a European regional climate model (RCM) are compared. They are driven by the same observed sea surface temperatures but use different lateral boundary forcing. For one simulation, RCM ASSIM, it is derived from a time series of operational analyses. The archive of analysis fields (surface pressure plus winds and temperatures on various pressure levels) is not sufficiently comprehensive to provide directly the full set of driving fields required for the RCM (in particular, no moisture fields are present), so these are obtained via a GCM integration, GCM ASSIM, in which the model is continuously relaxed towards the analysis fields using a data assimilation technique. Errors in RCM AMIP can arise either from the internal RCM physics or from errors in the lateral boundary forcing inherited from GCM AMIP. Errors in RCM ASSIM can arise from the internal RCM physics or the boundary moisture forcing but not from the driving circulation. Although previous studies have considered RCM integrations driven either by output from standard GCM integrations or operational analyses, our study is the first to compare parallel integrations of each type. This allows the total systematic error in an RCM integration driven by standard GCM output to be partitioned into components arising from the driving circulation and the internal RCM physics. These components indicate the scope for reducing regional simulation biases by improving either the driving GCM or the RCM itself. The results relate mainly to elements of surface climate likely to be influenced by both the driving circulation and regional physical processes operating in the RCM. For cloud cover, errors are found to arise largely from the internal RCM physics. Values are too low despite a positive relative humidity bias, indicating shortcomings in the parametrisation scheme used to calculate cloud cover. In summer, surface temperature and precipitation errors are also explained principally by regional processes. For example excessive solar heating leads to anomalously high surface temperatures over southern Europe and excessive drying of the soil reduces precipitation in the south eastern sector of the domain. The lateral boundary forcing reduces precipitation in the south eastern sector of the domain. The lateral boundary forcing also exerts some influence, mainly via a tropospheric cold bias which partially offsets the warming over southern Europe and also increases precipitation. In other seasons the lateral boundary forcing and the regional physics both contribute significantly to the errors in surface temperature and precipitation. In winter the boundary forcing (apart from moisture) is responsible for about 60% of the total error variance for temperature and about 40% for precipitation, due to the cold bias and circulation errors such as a southward shift in the storm track. The remaining errors arise from the regional physics, although for precipitation an excessive supply of moisture from the lateral boundaries also contributes. The skill of the mesoscale component of the surface temperature and precipitation distributions exceeds previous estimates, due to more realistic observed climatology. The mesoscale patterns are very similar in the two RCM simulations indicating that errors in the simulation of fine scale detail arise mainly from inadequate representations of local forcings rather than errors in the large-scale circulation. Circulation errors in RCM AMIP (e.g. cold bias, southward shift of storm track) are also present in GCM AMIP, but are largely absent in RCM ASSIM except in summer. This confirms evidence from previous work that the key to reducing most circulation errors in the RCM lies in improving the driving GCM. Regional processes only make a major contribution to circulation errors in summer, when reduced advection from the boundaries allows errors in surface temperature to be transmitted more effectively into the troposphere. Finally, we find evidence of error balances in the GCM which act to minimise biases in important climatological variables. This reflects tuning of the model physics at GCM resolution. In order to achieve simultaneous optimisation of the RCM and GCM at widely differing resolutions it may be necessary to introduce explicit scale dependences into some aspects of the physics."
"57193882808;7006095466;","Moisture-convection feedback in the tropics",2004,"10.1256/qj.03.135","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042709640&doi=10.1256%2fqj.03.135&partnerID=40&md5=a50a277549f412b3f10efc24272ebc79","This paper discusses the large-scale moisture-convection feedback in the tropics, where spatial fluctuations of deep convection cause perturbations of free-tropospheric moisture which, in turn, affect the spatial distribution of deep convection. A simple heuristic argument using the timescale of free-tropospheric humidity change explains why moisture-convection feedback is particularly relevant for tropical intraseasonal oscillations. The large-scale dynamical context for moist ure-convection feedback is investigated in idealized rotating constant-sea-surface-temperature ('tropics everywhere') aquaplanet using cloud-resolving convection parametrization (CRCP; super-parametrization) and a traditional convective parametrization (the Emanuel scheme). The large-scale organization of convection within the equatorial waveguide takes the form of MJO-like (Madden-Julian Oscillation) coherent structures. First, CRCP simulations are performed in which development of large-scale free-tropospheric moisture perturbations is artificially suppressed using relaxation with a timescale of one day. As in previous simulations where much shorter relaxation timescale was used, MJO-Iike coherences do not develop and, if already present, they disintegrate rapidly. Second, CRCP simulations that start from planetary-scale moisture perturbation in the free troposphere are conducted. The ensuing large-scale velocity perturbations have e-folding times of five and seven days, respectively, for interactive and prescribed radiation simulations. This supports the conjecture that interactive radiation enhances moisture-convection feedback; an enhanced large-scale circulation results from differences in radiative cooling between areas having enhanced and suppressed convectively-generated moisture and cloudiness. Additional support for the role of moisture-convection feedback in intraseasonal oscillations is seen in simulations that apply the Emanuel scheme. The standard configuration of the Emanuel scheme is insensitive to free-tropospheric humidity and results in weak MJO-Iike coherences. A simple modification of the Emanuel scheme that enhances its sensitivity to free-tropospheric humidity dramatically improves the simulated MJO-like coherences. © Royal Meteorological Society, 2004."
"36705143500;","Tropical thermostats and low cloud cover",1997,"10.1175/1520-0442(1997)010<0409:TTALCC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031445221&doi=10.1175%2f1520-0442%281997%29010%3c0409%3aTTALCC%3e2.0.CO%3b2&partnerID=40&md5=406c597a380776f73060ddb7ebce333b","The ability of subtropical stratus low cloud cover to moderate or amplify the tropical response to climate forcing such as increased CO2 is considered. Cloud radiative forcing over the subtropics is parameterized using an empirical relation between stratus cloud cover and the difference in potential temperature between 700 mb (a level that is above the trade inversion) and the surface. This relation includes the empirical negative correlation between SST and low cloud cover and is potentially a positive feedback to climate forcing. Since potential temperature above the trade inversion varies in unison across the Tropics as a result of the large-scale circulation and because moist convection relates tropospheric temperature within the convecting region to variations in surface temperature and moisture, the subtropical potential temperature at 700 mb depends upon surface conditions within the convecting region. As a result, subtropical stratus cloud cover and the associated feedback depend upon the entire tropical climate and not just the underlying SST. A simple tropical model is constructed, consisting of separate budgets of dry static energy and moisture for the convecting region (referred to as the ""warm"" pool) and the subtropical descending region (the ""cold"" pool). The cold pool is the location of stratus low clouds in the model. Dynamics is implicitly included through the assumption that temperature above the boundary layer is horizontally uniform as a result of the large-scale circulation. The tropopause and warm pool surface are shown to be connected by a moist adiabat in the limit of vanishingly narrow convective updrafts. Stratus low cloud cover is found to be a negative feedback, increasing in response to doubled CO2 and reducing the tropically averaged warming in comparison to the warming with low cloud cover held fixed. Increased low cloud cover is shown to result from the increased difference in surface temperature between the warm and cold pools, and the increased low-level static stability over the warm pool, equal to the increase in potential temperature along the moist adiabat originating in the warm pool mixed layer."
"57204297539;7404441387;6701623059;24074386100;7102707599;57202245193;6603760227;7201903057;7006359209;","Recent declines in warming and vegetation greening trends over pan-arctic tundra",2013,"10.3390/rs5094229","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884690956&doi=10.3390%2frs5094229&partnerID=40&md5=d37f1167da59cf9b9c695a913ca8ad08","Vegetation productivity trends for the Arctic tundra are updated for the 1982-2011 period and examined in the context of land surface temperatures and coastal sea ice. Understanding mechanistic links between vegetation and climate parameters contributes to model advancements that are necessary for improving climate projections. This study employs remote sensing data: Global Inventory Modeling and Mapping Studies (GIMMS) Maximum Normalized Difference Vegetation Index (MaxNDVI), Special Sensor Microwave Imager (SSM/I) sea-ice concentrations, and Advanced Very High Resolution Radiometer (AVHRR) radiometric surface temperatures. Spring sea ice is declining everywhere except in the Bering Sea, while summer open water area is increasing throughout the Arctic. Summer Warmth Index (SWI-sum of degree months above freezing) trends from 1982 to 2011 are positive around Beringia but are negative over Eurasia from the Barents to the Laptev Seas and in parts of northern Canada. Eastern North America continues to show increased summer warmth and a corresponding steady increase in MaxNDVI. Positive MaxNDVI trends from 1982 to 2011 are generally weaker compared to trends from 1982-2008. So to better understand the changing trends, break points in the time series were quantified using the Breakfit algorithm. The most notable break points identify declines in SWI since 2003 in Eurasia and 1998 in Western North America. The Time Integrated NDVI (TI-NDVI, sum of the biweekly growing season values of MaxNDVI) has declined since 2005 in Eurasia, consistent with SWI declines. Summer (June-August) sea level pressure (slp) averages from 1999-2011 were compared to those from 1982-1998 to reveal higher slp over Greenland and the western Arctic and generally lower pressure over the continental Arctic in the recent period. This suggests that the large-scale circulation is likely a key contributor to the cooler temperatures over Eurasia through increased summer cloud cover and warming in Eastern North America from more cloud-free skies. © 2013 by the authors; licensee MDPI, Basel, Switzerland."
"24528488100;7003278104;7103293232;","The influence of the Madden-Julian Osicllation on ocean surface heat fluxes and sea surface temperature",1998,"10.1175/1520-0442(1998)011<1057:TIOTMJ<2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031683681&doi=10.1175%2f1520-0442%281998%29011%3c1057%3aTIOTMJ%3c2.0.CO%3b2&partnerID=40&md5=849797955dd4a91aad922c0667da5b55","The Madden-Julian oscillation (MJO) involves pronounced variations in convection and large-scale circulation throughout the tropical troposphere. In addition, the MJO is also related to dynamic and thermodynamic variability near the surface and the upper ocean. This study uses observational data to characterize the changes in surface heat fluxes and sea surface temperature (SST) during the life cycle of the MJO. Variations in convective activity are described with outgoing longwave radiation (OLR) during the period January 1985 through September 1994. International Satellite Cloud Climatology Project data (January 1985-April 1991) and European Centre for Medium-Range Weather Forecasts surface analyses (January 1985-December 1994) are used to derive surface fluxes of net shortwave radiation (SW) latent heat (E), their difference (Q = SW - E), and SST. The spatial patterns of OLR, SW, E, Q and SST anomalies reveal that the region of positive OLR anomalies that precede the occurrence of enhanced convection is associated with positive SW and negative E anomalies, which result in positive Q anomalies. The prevailing conditions in the region of positive Q anomalies favor the development of positive SST anomalies, which lead to variations of enhanced convection. In contrast the region of negative OLR anomalies is associated with negative SW and positive E anomalies. These conditions induce negative Q anomalies, which favor the formation of negative SST anomalies. The above results suggest a possible feedback between the oscillation and intraseasonal variations in SST and this may be an important mechanism for numerical simulations of the life cycle of the MJO."
"55976927000;","Radial mixing in protoplanetary accretion disks IV. Metamorphosis of the silicate dust complex",2004,"10.1051/0004-6361:20031554","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347285598&doi=10.1051%2f0004-6361%3a20031554&partnerID=40&md5=336732abecaff6829fc8f5a222f7d8f1","The outer regions of protoplanetary accretion discs are formed by material from the parent molecular cloud of the freshly forming stars. The interstellar dust in this material is a mixture of species which does not correspond to any kind of chemical equilibrium state between the solid and gaseous phases. Mass accretion carries this material into the warm inner disc zones where chemical and physical processes are activated which convert the non-equilibrium solid-gas mixture into a chemical equilibrium mixture. Part of the equilibrated material is then mixed outwards by turbulent diffusion and large-scale circulation currents. This work specifically considers the evolution of the main dust components, viz. from the interstellar mixture of amorphous Mg-Fe-silicates, into a chemical equilibrium mixture of crystalline Mg-silicates, and iron. The basic set of equations for calculating the evolution of a mixture of silicates and iron is derived. Model calculations based on stationary, one-zone α-discs are combined with the advection-diffusion-reaction equations for the dust evolution to study the interstellar to equilibrium dust conversion and the radial mixing of equilibrated dust into the outer disc regions. This determines the mixture of the main dust components which form the mineral inventory of planetesimals. It is found that the results of the model calculation for the resulting mineral mixture are in rough agreement with the composition of matrix material of primitive meteorites and dust in cometary nuclei."
"6603412788;36848436500;57211224269;35997064100;7402345338;15761630100;7403544649;36655323000;7102193013;","Present-day climate and climate sensitivity in the Meteorological Research Institute coupled GCM version 2.3 (MRI-CGCM2.3)",2006,"10.2151/jmsj.84.333","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745189806&doi=10.2151%2fjmsj.84.333&partnerID=40&md5=0b981b77bbfc359eedf10df6a5827f3e","A new version of the Meteorological Research Institute (MRI) coupled general circulation model MRI-CGCM2 (MRI2.3) is developed and compared with the previous version (MRI2.0). The cloud scheme includes diagnostic function for cloud amount separately specified for convective and layer clouds, which is one of the major modifications contributing to the improved model performance. MRI2.3 exhibits better agreement with the observations in many aspects of present-day climate simulations, including the global energy budget, meridional distributions of shortwave and longwave radiation at the top of the atmosphere, and geographical distributions of surface air temperature and precipitation. The effective climate sensitivity of each version is evaluated based on an experiment with a transient (1%/year) increase of carbon dioxide concentration. The effective climate sensitivity of MRI2.3 (2.9 K) is about twice that of MRI2.0 (1.4 K). The change in the cloud-forcing response, particularly for shortwave cloud forcing, is essential for increasing climate sensitivity. A difference in tropical low-level clouds over the subsidence regions contributes significantly to the difference in cloud-forcing changes in response to a climate change. Analyses based on circulation regimes, defined by the vertical velocity at the mid-troposphere, suggest that the cloud-forcing response in the tropics is controlled more by thermodynamic characteristics, such as changes of the stability in the lower troposphere, rather than by large-scale circulation changes, such as a change in the subsidence strength. © 2006, Meteorological Society of Japan."
"6701653010;7101685611;7406215388;7005490049;7004884101;","Tropical rainfall associated with convective and stratiform clouds: Intercomparison of disdrometer and profiler measurements",1999,"10.1175/1520-0450(1999)038<0302:TRAWCA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032718255&doi=10.1175%2f1520-0450%281999%29038%3c0302%3aTRAWCA%3e2.0.CO%3b2&partnerID=40&md5=9c5e36a1ab5f17adb2e5211cf7f17ac6","The motivation for this research is to move in the direction of improved algorithms for the remote sensing of rainfall, which are crucial for meso- and large-scale circulation studies and climate applications through better determinations of precipitation type and latent heating profiles. Toward this end a comparison between two independent techniques, designed to classify precipitation type from 1) a disdrometer and 2) a 915-MHz wind profiler, is presented, based on simultaneous measurements collected at the same site during the Intensive Observing Period of the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment. Disdrometer-derived quantities such as differences in drop size distribution parameters, particularly the intercept parameter N0 and rainfall rate, were used to classify rainfall as stratiform or convective. At the same time, profiler-derived quantities, namely, Doppler velocity, equivalent reflectivity, and spectral width, from Doppler spectra were used to classify precipitation type in four categories: shallow convective, deep convective, mixed convective-stratiform, and stratiform. Overall agreement between the two algorithms is found to be reasonable. Given the disdrometer stratiform classification, the mean profile of reflectivity shows a distinct bright band and associated large vertical gradient in Doppler velocity, both indicators of stratiform rain. For the disdrometer convective classification the mean profile of reflectivity lacks a bright band, while the vertical gradient in Doppler velocity below the melting level is opposite to the stratiform case. Given the profiler classifications, in the order shallow-deep-mixed-stratiform, the composite raindrop spectra for a rainfall rate of 5 mm h-1 show an increase in D0, the median volume diameter, consistent with the dominant microphysical processes responsible for drop formation. Nevertheless, the intercomparison does reveal some limitations in the classification methodology utilizing the disdrometer or profiler algorithms in isolation. In particular, 1) the disdrometer stratiform classification includes individual cases in which the vertical profiles appear convective, but these usually occur at times when the disdrometer classification is highly variable; 2) the profiler classification scheme also appears to classify precipitation too frequently as stratiform by including cases that have small vertical Doppler velocity gradients at the melting level but no bright band; and 3) the profiler classification scheme includes a category of mixed (stratiform-convective) precipitation that has some features in common with deep convection (e.g., enhanced spectral width above the melting level) but other features in common with stratiform precipitation (e.g., well-developed melting layer signature). Comparison of the profiler-derived vertical structure with disdrometer-determined rain rates reveals that almost all cases of rain rates greater than 10 mm h-1 are convective. For rain rates less than 5 mm h-1 all four profiler-determined precipitation classes are well represented."
"16029674800;6701346974;6507017020;55431666500;7101851249;7202208382;6601970557;7102486629;","An ocean-atmosphere climate simulation with an embedded cloud resolving model",2010,"10.1029/2009GL040822","https://www.scopus.com/inward/record.uri?eid=2-s2.0-75749145021&doi=10.1029%2f2009GL040822&partnerID=40&md5=569c704d727d46d9c9e7784986df726a","Mean climate and intraseasonal to interannual variability of two versions of the Community Climate System Model (CCSM) coupled atmosphere-ocean general circulation model (CGCM) are analyzed. The first version is the standard CCSM, in which cloud effects on the large-scale circulation are represented via parameterizations. The second version includes ""super- parameterization"" (SP) of convective processes by replacing parameterized cloud processes with a two-dimensional (2D) cloud-process resolving model (CRM) at each CGCM grid column. The SP-CCSM improves several shortcomings of the CCSM simulation, including mean precipitation patterns, equatorial SST cold tongue structure and associated double intertropical convergence zone (ITCZ), the Asian monsoon, periodicity of the El Nio-Southern Oscillation, and the intraseasonal Madden-Julian Oscillation. These improvements were obtained without the retuning of the coupled model, which is surprising in view of previous experience with other coupled models. Copyright 2010 by the American Geophysical Union."
"7005634455;6603749411;7004993886;7005717609;23490353300;","Comprehensive evaluation of polar weather research and forecasting model performance in the antarctic",2013,"10.1029/2012JD018139","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884879780&doi=10.1029%2f2012JD018139&partnerID=40&md5=983f38460a5cd21e0a6093593ba3d8c6","Recent versions of the Polar Weather Research and Forecasting model are evaluated over the Antarctic to assess the impact of model improvements, resolution, large-scale circulation variability, and uncertainty in initial and lateral boundary conditions. The model skill differs more between forecasts using different sources of lateral boundary data than between forecasts from different model versions or simulated years. Using the ERA-Interim reanalysis for initial and lateral boundary conditions produces the best skill. The forecasts have a cold summer and a warm winter bias in 2m air temperatures, with similar but smaller bias in dew point temperatures. Upper air temperature biases are small and remain less than 1 °C except at the tropopause in summer. Geopotential height biases increase with height in both seasons. Deficient downward longwave radiation in all seasons and an under representation of clouds enhance radiative loss, leading to the cold summer bias. Excess summer surface incident shortwave radiation plays a secondary role, because 80% of it is reflected, leading to greater skill for clear compared with cloudy skies. The positive wind speed bias produces a warm surface bias in winter resulting from anomalously large downward flux of sensible heat toward the surface. Low temperatures on the continent limit sublimation and hence the precipitable water amounts over the ice sheet. ERA-Interim experiments with higher precipitable water showed reduced biases in downwelling shortwave and longwave radiation. Increasing horizontal resolution from 60 to 15 km improves the skill of surface wind forecasts. © 2012. American Geophysical Union."
"12801073500;6603581315;55708686800;9233141100;7004168515;56102017200;9250463400;7202489497;35372923700;57214536094;35509639400;57196135849;56813351300;7003339749;","Process-evaluation of tropospheric humidity simulated by general circulation models using water vapor isotopic observations: 2. Using isotopic diagnostics to understand the mid and upper tropospheric moist bias in the tropics and subtropics",2012,"10.1029/2011JD016623","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863246372&doi=10.1029%2f2011JD016623&partnerID=40&md5=3c588eb1387b3c9c481f767f2a274e2b","Evaluating the representation of processes controlling tropical and subtropical tropospheric relative humidity (RH) in atmospheric general circulation models (GCMs) is crucial to assess the credibility of predicted climate changes. GCMs have long exhibited a moist bias in the tropical and subtropical mid and upper troposphere, which could be due to the mis-representation of cloud processes or of the large-scale circulation, or to excessive diffusion during water vapor transport. The goal of this study is to use observations of the water vapor isotopic ratio to understand the cause of this bias. We compare the three-dimensional distribution of the water vapor isotopic ratio measured from space and ground to that simulated by several versions of the isotopic GCM LMDZ. We show that the combined evaluation of RH and of the water vapor isotopic composition makes it possible to discriminate the most likely cause of RH biases. Models characterized either by an excessive vertical diffusion, an excessive convective detrainment or an underestimated in situ cloud condensation will all produce a moist bias in the free troposphere. However, only an excessive vertical diffusion can lead to a reversed seasonality of the free tropospheric isotopic composition in the subtropics compared to observations. Comparing seven isotopic GCMs suggests that the moist bias found in many GCMs in the mid and upper troposphere most frequently results from an excessive diffusion during vertical water vapor transport. This study demonstrates the added value of water vapor isotopic measurements for interpreting shortcomings in the simulation of RH by climate models. Copyright 2012 by the American Geophysical Union."
"6603335688;26323963700;6602241511;56276813400;","Stable carbon isotopes from Torneträsk, northern Sweden provide a millennial length reconstruction of summer sunshine and its relationship to Arctic circulation",2013,"10.1016/j.quascirev.2012.11.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871894705&doi=10.1016%2fj.quascirev.2012.11.014&partnerID=40&md5=62c6deb9b371499512733a1b5825eb3f","This paper presents results from the first 1100 years of a long stable carbon isotope chronology currently in development from Scots Pine (Pinus sylvestris L.) trees growing in the Torneträsk region of northern Sweden. The isotope record currently comprises a total of 74 trees with a mean annual replication of &gt;12, thereby enabling it to be compared directly with other tree-ring based palæoclimate reconstructions from this region. In developing the reconstruction, several key topics in isotope dendroclimatology (chronology construction, replication, CO2 adjustment and age trends) were addressed. The resulting carbon isotope series is calibrated against instrumental data from the closest meteorological station at Abisko (AD1913-2008) to provide a record of June-August sunshine for northern Fennoscandia. This parameter is closely linked to the direct control of assimilation rate; Photosynthetically Active Radiation (PAR) and the indirect measures; mean July-August temperature and percent cloud cover. The coupled response of summer sunshine and temperature in this region permits a multi-parameter comparison with a local reconstruction of past temperature variability based upon tree growth proxies to explore the stability of this coupling through time. Several periods are identified where the temperature (X-ray density) and sunshine (stable carbon isotope ratio) records diverge. The most significant and sustained of these occur between c AD1200-1380 and c AD1550-1780, providing evidence for a cool, sunny, two-phase ""Little Ice Age"". Whilst summer sunshine reconstructed for the 20th century is significantly different from the mean of the last 1100 years (P &lt; 0.01), conditions during the early mediæval period are similar to those experienced in northern Fennoscandia during the 20th century (P &gt; 0.01), so it is the 17th-18th, and to a lesser extent, the 13th centuries rather than the early mediæval period that appear anomalous when viewed within the context of the last 1100 years. The observed departures between temperature and sunshine are interpreted as indicating a change in large-scale circulation associated with a southward migration of the Polar Front. Such a change, affecting the Northern Annular Mode (Arctic Oscillation) would result in more stable anticyclonic conditions (cool, bright, summers) over northern Fennoscandia, thus providing a testable mechanism for the development of a multi-phase, time-transgressive ""Little Ice Age"" across Europe. © 2012 Elsevier Ltd."
"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)."
"7409522591;7005453346;","Role of convective scale momentum transport in climate simulation",1995,"10.1029/94JD02519","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028977718&doi=10.1029%2f94JD02519&partnerID=40&md5=331f923f162e9a6f2a5947540ec15c33","A unique feature of the scheme is the inclusion of the perturbation pressure field induced by convection and its effect on the cloud momentum transport. Through two experiments of seasonal simulations, it is shown that the perturbation pressure forcing on the cloud momentum transport accounts for a significant part of the total convective momentum source/sink, indicating that the cloud momentum field is substantially modulated by the convection-induced pressure field. The overall effect of convective momentum transport is to reduce the vertical wind shear in both the zonal and the meridional directions. The response of the large-scale circulation to convective momentum transport is very significant. -from Authors"
"55940978200;7407016988;","Diurnally modulated cumulus moistening in the preonset stage of the Madden-Julian oscillation during DYNAMO",2015,"10.1175/JAS-D-14-0218.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923100216&doi=10.1175%2fJAS-D-14-0218.1&partnerID=40&md5=18d6f51c45fa0c77e60073c1514df576","Atmospheric soundings, radar, and air-sea flux measurements collected during Dynamics of the Madden-Julian Oscillation (DYNAMO) are employed to study MJO convective onset (i.e., the transition from shallow to deep convection) in the tropical Indian Ocean. The findings indicate that moistening of the low-midtroposphere during the preonset stage of the MJO is achieved by simultaneous changes in the convective cloud population and large-scale circulation. Namely, cumuliform clouds deepen and grow in areal coverage as the drying by large-scale subsidence and horizontal (westerly) advection wane. The reduction of large-scale subsidence is tied to the reduction of column radiative cooling during the preonset stage, which ultimately links back to the evolving cloud population. While net column moistening in the preonset stage is tied to large-scale circulation changes, a new finding of this study is the high degree to which the locally driven diurnal cycle invigorates convective clouds and cumulus moistening each day. This diurnal cycle is manifest in a daytime growth of cumulus clouds (in both depth and areal coverage) in response to oceanic diurnal warm layers, which drive a daytime increase of the air-sea fluxes of heat and moisture. This diurnally modulated convective cloud field exhibits prominent mesoscale organization in the form of open cells and horizontal convective rolls. It is hypothesized that the diurnal cycle and mesoscale cloud organization characteristic of the preonset stage of the MJO represent two manners in which local processes promote more vigorous daily-mean column moistening than would otherwise occur. © 2015 American Meteorological Society."
"56537463000;7404829395;22959252400;16553368000;7006417494;7202899330;7005973015;","Weakening and strengthening structures in the Hadley Circulation change under global warming and implications for cloud response and climate sensitivity",2014,"10.1002/2014JD021642","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902839438&doi=10.1002%2f2014JD021642&partnerID=40&md5=b1bb998c9545aaddedfbd0fd3fdddd6f","It has long been recognized that differences in climate model-simulated cloud feedbacks are a primary source of uncertainties for the model-predicted surface temperature change induced by increasing greenhouse gases such as CO2. Large-scale circulation broadly determines when and where clouds form and how they evolve. However, the linkage between large-scale circulation change and cloud radiative effect (CRE) change under global warming has not been thoroughly studied. By analyzing 15 climate models, we show that the change of the Hadley Circulation exhibits meridionally varying weakening and strengthening structures, physically consistent with the cloud changes in distinct cloud regimes. The regions that experience a weakening (strengthening) of the zonal-mean circulation account for 54% (46%) of the multimodel-mean top-of-atmosphere (TOA) CRE change integrated over 45°S-40°N. The simulated Hadley Circulation structure changes per degree of surface warming differ greatly between the models, and the intermodel spread in the Hadley Circulation change is well correlated with the intermodel spread in the TOA CRE change. This correlation underscores the close interactions between large-scale circulation and clouds and suggests that the uncertainties of cloud feedbacks and climate sensitivity reside in the intimate coupling between large-scale circulation and clouds. New model performance metrics proposed in this work, which emphasize how models reproduce satellite-observed spatial variations of zonal-mean cloud fraction and relative humidity associated with the Hadley Circulation, indicate that the models closer to the satellite observations tend to have equilibrium climate sensitivity higher than the multimodel mean. © 2014. American Geophysical Union. All Rights Reserved."
"56014511300;","Maintenance of the free-tropospheric tropical water vapor distribution. Part II: Simulation by large-scale advection",1996,"10.1175/1520-0442(1996)009<2919:MOTFTT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030419098&doi=10.1175%2f1520-0442%281996%29009%3c2919%3aMOTFTT%3e2.0.CO%3b2&partnerID=40&md5=4cd3d9777fb0afd888038c6d0bec57ff","Analyzed wind fields are used to perform a simple advection of moisture by the large-scale circulation in three dimensions at 2.5° resolution. The unresolved moisture sink Q2 due to convection is neglected, except in regions of strong ascent where it is used to enforce a 90% relative humidity ceiling, as determined from sounding and geostationary satellite observations. The result is a simulation of water vapor that agrees quantitatively with satellite (Special Sensor Microwave Water Vapor) and sounding observations over the tropical oceans, in both arid and moist regions, to within 10% relative humidity or better from 700 to 300 mb inclusively. Horizontal transport into arid regions from convective regions is accomplished by large coherent structures. Implications of the results for the role of convection in maintaining the observed humidity distribution, and for the interpretation of observed correlations between cloud cover and vapor, are discussed."
"6602908667;6602513090;7202772927;36165663600;","Shallow and deep latent heating modes over tropical oceans observed with TRMM PR spectral latent heating data",2010,"10.1175/2009JCLI3110.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953722044&doi=10.1175%2f2009JCLI3110.1&partnerID=40&md5=b3db837df1fda5cec4937a1be30d0f56","Three-dimensional distributions of the apparent heat source (Q1) 2 radiative heating (QR) estimated from Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) utilizing the spectral latent heating (SLH) algorithm are analyzed. Mass-weighted and vertically integrated Q1 2 QR averaged over the tropical oceans is estimated as ~72.6 J s21 (~2.51 mm day-1) and that over tropical land is;73.7 J s-1 (~2.55 mm day-1) for 30°N-30°S. It is shown that nondrizzle precipitation over tropical and subtropical oceans consists of two dominant modes of rainfall systems: deep systems and congestus. A rough estimate of the shallow-heating contribution against the total heating is about 46.7% for the average tropical oceans, which is substantially larger than the 23.7% over tropical land. Although cumulus congestus heating linearly correlates with SST, deep-mode heating is dynamically bounded by large-scale subsidence. It is notable that a substantial amount of rain, as large as 2.38 mm day-1 on average, is brought from congestus clouds under the large-scale subsiding circulation. It is also notable that, even in the region with SSTs warmer than 28°C, large-scale subsidence effectively suppresses the deep convection, with the remaining heating by congestus clouds. The results support that the entrainment of mid-lower-tropospheric dry air, which accompanies the large-scale subsidence, is the major factor suppressing the deep convection. Therefore, a representation of the realistic entrainment is very important for proper reproduction of precipitation distribution and the resultant large-scale circulation. © 2010 American Meteorological Society."
"7501757094;57198472289;55462121400;","A regional model simulation of the 1991 severe precipitation event over the Yangtze-Huai River valley. Part I: Precipitation and circulation statistics",2000,"10.1175/1520-0442(2000)013<0074:ARMSOT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034030643&doi=10.1175%2f1520-0442%282000%29013%3c0074%3aARMSOT%3e2.0.CO%3b2&partnerID=40&md5=fa5e1a07b94da8c44e4bb2fb8779e465","The summer Mei-yu event over eastern China, which is strongly influenced by large-scale circulation, is an important aspect of East Asian climate; for example, the Mei-yu frequently brings heavy precipitation to the Yangtze-Huai River valley (YHRV). Both observations and a regional model were used to study the Mei-yu front and its relation to large-scale circulation during the summer of 1991 when severe floods occurred over YHRV. This study has two parts: the first part, presented here, analyzes the association between heavy Mei-yu precipitation and relevant large-scale circulation, while the second part, documented by W. Gong and W.-C. Wang, examines the model biases associated with the treatment of lateral boundary conditions (the objective analyses and coupling schemes) used as the driving fields for the regional model. Observations indicate that the Mei-yu season in 1991 spans 18 May-14 July, making it the longest Mei-yu period during the last 40 yr. The heavy precipitation over YHRV is found to be intimately related to the western Pacific subtropical high, upper-tropospheric westerly jet at midlatitudes, and lower-tropospheric southwest wind and moisture flux. The regional model simulates reasonably well the regional mean surface air temperature and precipitation, in particular the precipitation evolution and its association with the large-scale circulation throughout the Mei-yu season. However, the model simulates smaller precipitation intensity, which is due partly to the colder and drier model atmosphere resulting from excessive low-level clouds and the simplified land surface process scheme used in the present study.The summer Mei-yu event over eastern China, which is strongly influenced by large-scale circulation, is an important aspect of East Asian climate; for example, the Mei-yu frequently brings heavy precipitation to the Yangtze-Huai River valley (YHRV). Both observations and a regional model were used to study the Mei-yu front and its relation to large-scale circulation during the summer of 1991 when severe floods occurred over YHRV. This study has two parts: the first part, presented here, analyzes the association between heavy Mei-yu precipitation and relevant large-scale circulation, while the second part, documented by W. Gong and W.-C. Wang, examines the model biases associated with the treatment of lateral boundary conditions (the objective analyses and coupling schemes) used as the driving fields for the regional model. Observations indicate that the Mei-yu season in 1991 spans 18 May-14 July, making it the longest Mei-yu period during the last 40 yr. The heavy precipitation over YHRV is found to be intimately related to the western Pacific subtropical high, upper-tropospheric westerly jet at midlatitudes, and lower-tropospheric southwest wind and moisture flux. The regional model simulates reasonably well the regional mean surface air temperature and precipitation, in particular the precipitation evolution and its association with the large-scale circulation throughout the Mei-yu season. However, the model simulates smaller precipitation intensity, which is due partly to the colder and drier model atmosphere resulting from excessive low-level clouds and the simplified land surface process scheme used in the present study."
"7005634455;7005133082;55474342800;","Modeling the ENSO modulation of Antarctic climate in the late 1990s with the Polar MM5",2004,"10.1175/1520-0442(2004)017<0109:MTEMOA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1442291177&doi=10.1175%2f1520-0442%282004%29017%3c0109%3aMTEMOA%3e2.0.CO%3b2&partnerID=40&md5=906e5ad3ef1710d3cc795c6e38cde497","The Polar fifth-generation Pennsylvania State University-NCAR Mesoscale Model (MM5) is employed to examine the El Nin̄o-Southern Oscillation (ENSO) modulation of Antarctic climate for July 1996-June 1999, which is shown to be stronger than for the mean modulation from 1979 to 1999 and appears to be largely due to an eastward shift and enhancement of convection in the tropical Pacific Ocean. This study provides a more comprehensive assessment than can be achieved with observational datasets by using a regional atmospheric model adapted for high-latitude applications (Polar MM5). The most pronounced ENSO response is observed over the Ross Ice Shelf-Marie Byrd Land and over the Weddell Sea-Ronne/Filchner Ice Shelf. In addition to having the largest climate variability associated with ENSO, these two regions exhibit anomalies of opposite sign throughout the study period, which supports and extends similar findings by other investigators. The dipole structure is observed in surface temperature, meridional winds, cloud fraction, and precipitation. The ENSO-related variability is primarily controlled by the large-scale circulation anomalies surrounding the continent, which are consistent throughout the troposphere. When comparing the El Niña/La Niña phases of this late 1990s ENSO cycle, the circulation anomalies are nearly mirror images over the entire Antarctic, indicating their significant modulation by ENSO. Large temperature anomalies, especially in autumn, are prominent over the major ice shelves. This is most likely due to their relatively low elevation with respect to the continental interior making them more sensitive to shifts in synoptic forcing offshore of Antarctica, especially during months with considerable open water. The Polar MM5 simulations are in broad agreement with observational data, and the simulated precipitation closely follows the European Centre for Medium-Range Weather Forecasts Tropical Ocean-Global Atmosphere precipitation trends over the study period. The collective findings of this work suggest the Polar MM5 is capturing ENSO-related atmospheric variability with good skill and may be a useful tool for future climate studies."
"7003329628;7102781936;6603955469;7006689276;13406672500;7103081525;35419560700;6602565779;7006086673;","Tropospheric water-vapour and ozone cross-sections in a zonal plane over the central equatorial Pacific Ocean",1997,"10.1256/smsqj.54311","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031395718&doi=10.1256%2fsmsqj.54311&partnerID=40&md5=27e0a45712c57f17f549902dc24affb6","Tropospheric water-vapour and ozone measurements, using calibrated balloon-borne sensors, are reported from the Central Equatorial Pacific Experiment (CEPEX). The sensors were launched from the Research Vessel Vickers along 2°S latitude between 156°E (west of the international date line) and 155°W (east of the date line). These measurements are combined with those from water-vapour sondes launched over the western Pacific warm pool, during the Coupled Ocean-Atmosphere Response Experiment (TOGA-COARE). Taking the two experiments CEPEX and TOGA-COARE together, the sensors included frost-point hygrometers, Humicap-A Väisälä sondes, Humicap-H Väisälä sondes and electrochemical ozone-sondes. Taken together, the CEPEX and TOGA-CO ARE data provide over 150 vertical profiles of water vapour within the troposphere in varied conditions of convective activity ranging from disturbed to suppressed. The primary motivation behind the present analyses is to understand the role of tropical deep convection in the vertical distribution of water-vapour. With this in mind, the profiles have been analysed in relation to occasions of recent deep convection and occasions when convection was suppressed. We employ three different criteria to identify the profiles influenced by deep convection: brightness temperature in the infrared-window channel of the Japanese Geostationary Meteorological Satellite (GMS); ozone as a quasi-conservative tracer for deep convection; and using water vapour itself, that is the wettest versus the driest soundings. Irrespective of the criteria used, we report here that the atmosphere, while under the influence of active deep convection, was found to have relative humidities in excess of 75% over most of the troposphere between the surface and about 14 km. The sondes were launched routinely over a period of 45 days (between CEPEX and TOGA-COARE), without biasing the sample towards convectively disturbed conditions. A feature of the convectively disturbed profile is a distinct minimum in relative humidity at about 700 hPa, where it was as low as 65%. The low relative humidity was accompanied by relatively high ozone mixing ratios, which raises the possibility of long-range transport of dry sub-tropical air into the warm, convectively disturbed, regions of the equatorial Pacific Ocean. Inspection of the analysed fields, and the wind fields from the sondes, supports this assertion. It then follows that the omnipresent minimum of moist static energy and minimum relative humidity at 700 hPa in the inner tropics may be the result of long-range, inclined, transport of dry air from non-convective regions. This detection suggests a linkage between the large-scale circulation, deep convection and the thermodynamic structure within the equatorial troposphere. The results presented here demonstrate the applicability of ozone as a quasi-conservative tracer of transport in the context of deep convection. The ozone-based criterion is used to diagnose recent deep convection, independent of the GMS satellite observations, and allows one to follow the evolution of relative humidity and of water-vapour mixing ratio after the dissipation of the cloud anvil to optically thin conditions. We show that the troposphere dries to low humidity soon after anvil dissipation. This observation leads to the hypothesis that moistening of the atmosphere, away from the core of Cb convection, occurs by evaporation of precipitation falling out of the anvils. After anvil dissipation, the ensuing subsidence in clear air causes the relative humidity and the water mixing ratio to decrease."
"6603060770;","Numerical simulations of forced shallow-water turbulence: Effects of moist convection on the large-scale circulation of Jupiter and Saturn",2007,"10.1175/JAS4007.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34948873714&doi=10.1175%2fJAS4007.1&partnerID=40&md5=0190a8b9a507ef0e822b1d109d2c9872","To test the hypothesis that the zonal jets on Jupiter and Saturn result from energy injected by thunderstorms into the cloud layer, forced-dissipative numerical simulations of the shallow-water equations in spherical geometry are presented. The forcing consists of sporadic, isolated circular mass pulses intended to represent thunderstorms; the damping, representing radiation, removes mass evenly from the layer. These results show that the deformation radius provides strong control over the behavior. At deformation radii &lt;2000 km (0.03 Jupiter radii), the simulations produce broad jets near the equator, but regions poleward of 15°-30° latitude instead become dominated by vortices. However, simulations at deformation radii &gt;4000 km (0.06 Jupiter radii) become dominated by barotropically stable zonal jets with only weak vortices. The lack of midlatitude jets at a small deformation radii results from the suppression of the beta effect by column stretching; this effect has been previously documented in the quasigeostrophic system but never before in the full shallow-water system. In agreement with decaying shallow-water turbulence simulations, but in disagreement with Jupiter and Saturn, the equatorial flows in these forced simulations are always westward. In analogy with purely two-dimensional turbulence, the size of the coherent structures (jets and vortices) depends on the relative strengths of forcing and damping; stronger damping removes energy faster as it cascades upscale, leading to smaller vortices and more closely spaced jets in the equilibrated state. Forcing and damping parameters relevant to Jupiter produce flows with speeds up to 50-200 m s-1 and a predominance of anticyclones over cyclones, both in agreement with observations. However, the dominance of vortices over jets at deformation radii thought to be relevant to Jupiter (1000-3000 km) suggests that either the actual deformation radius is larger than previously believed or that three-dimensional effects, not included in the shallow-water equations, alter the dynamics in a fundamental manner. © 2007 American Meteorological Society."
"8900751100;7501757094;57198472289;","Model and observational analysis of the northeast U.S. regional climate and its relationship to the PNA and NAO patterns during early winter",2006,"10.1175/MWR3234.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845451213&doi=10.1175%2fMWR3234.1&partnerID=40&md5=1d2373a6680e8ce03b38f293dd7175b0","The relationship between the large-scale circulation and regional climate of the northeast United States is investigated for early winter using observational data and the State University of New York at Albany regional climate model. Simulated patterns of temperature, precipitation, and atmospheric circulation compare well with observations, despite a cold, dry bias. Ten December runs are analyzed to investigate the impact of the Pacific-North American (PNA) pattern on temperature, precipitation, clouds, and circulation features. During a positive PNA pattern, the simulated and observed eastern U.S. jet shifts to the southeast, coinciding with cold, dry conditions in the Northeast. This shift and intensification of the upper-level jet stream during a positive PNA pattern coincides with a greater frequency of cyclones and anticyclones along a distinct southwest-northeast track. Despite increased cyclone activity, total wintertime precipitation is below normal during a positive PNA pattern because of enhanced stability and subsidence over land, along with lower-atmospheric moisture content. Lower surface air temperatures during a positive PNA pattern result in enhanced simulated cloud cover over the Great Lakes and Atlantic Ocean due to increased thermal contrast and fluxes of sensible and latent heat, and a reduction in clouds over land. Interactions between the PNA and North Atlantic Oscillation (NAO) patterns impact the Northeast winter climate. Observed frontal passages through New York are most abundant during a negative PNA and positive NAO pattern, with a zonal upper-level jet positioned over New York. A positive PNA pattern is frequently characterized by an earlier observed Great Lakes ice season, while the greatest lake-effect snowfall occurs during a positive PNA and negative NAO pattern. The NAO pattern has the largest impact on northeast U.S. temperatures and the eastern U.S. upper-level jet during a positive PNA pattern. © 2006 American Meteorological Society."
"8866821900;7201504886;35509639400;","Using aquaplanets to understand the robust responses of comprehensive climate models to forcing",2015,"10.1007/s00382-014-2138-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939873329&doi=10.1007%2fs00382-014-2138-0&partnerID=40&md5=69761b7cc5058381a2ff428415301b3f","Idealized climate change experiments using fixed sea-surface temperature are investigated to determine whether zonally symmetric aquaplanet configurations are useful for understanding climate feedbacks in more realistic configurations. The aquaplanets capture many of the robust responses of the large-scale circulation and hydrologic cycle to both warming the sea-surface temperature and quadrupling atmospheric CO<inf>2</inf>. The cloud response to both perturbations varies across models in both Earth-like and aquaplanet configurations, and this spread arises primarily from regions of large-scale subsidence. Most models produce a consistent cloud change across the subsidence regimes, and the feedback in trade-wind cumulus regions dominates the tropical response. It is shown that these trade-wind regions have similar cloud feedback in Earth-like and aquaplanet warming experiments. The tropical average cloud feedback of the Earth-like experiment is captured by five of eight aquaplanets, and the three outliers are investigated to understand the discrepancy. In two models, the discrepancy is due to warming induced dissipation of stratocumulus decks in the Earth-like configuration which are not represented in the aquaplanet. One model shows a circulation response in the aquaplanet experiment accompanied by a cloud response that differs from the Earth-like configuration. Quadrupling atmospheric CO<inf>2</inf> in aquaplanets produces slightly greater adjusted forcing than in Earth-like configurations, showing that land-surface effects dampen the adjusted forcing. The analysis demonstrates how aquaplanets, as part of a model hierarchy, help elucidate robust aspects of climate change and develop understanding of the processes underlying them. © 2014, The Author(s)."
"7401559815;7006329926;7201844203;7202772927;","An inquiry into the cirrus‐cloud thermostat effect for tropical sea surface temperature",1994,"10.1029/94GL00222","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028592859&doi=10.1029%2f94GL00222&partnerID=40&md5=2e5b95c0039bcfb11e2c666477e5ace3","In this paper, we investigate the relative importance of local vs remote control on cloud radiative forcing using a cumulus ensemble model. It is found that cloud and surface radiation forcings are much more sensitive to the mean vertical motion associated with large scale tropical circulation than to the local SST. When the local SST is increased with the mean vertical motion held constant, increased surface latent and sensible heat flux associated with enhanced moisture recycling is found to be the primary mechanism for cooling the ocean surface. Large changes in surface shortwave fluxes are related to changes in cloudiness induced by changes in the large scale circulation. These results are consistent with a number of earlier empirical studies, which raised concerns regarding the validity of the cirrus‐thermostat hypothesis (Ramanathan and Collins, 1991). It is argued that for a better understanding of cloud feedback, both local and remote controls need to be considered and that a cumulus ensemble model is a powerful tool that should be explored for such purpose. Copyright 1994 by the American Geophysical Union."
"7003610507;7006449261;14820677200;57203209031;7005706662;8279747600;","Marine fog: A review",2014,"10.1016/j.atmosres.2013.12.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84895725534&doi=10.1016%2fj.atmosres.2013.12.012&partnerID=40&md5=263f7ccdc1d156bc8d60d2bc549ee1c7","The objective of this review is to discuss physical processes over a wide range of spatial scales that govern the formation, evolution, and dissipation of marine fog. We consider marine fog as the collective combination of fog over the open sea along with coastal sea fog and coastal land fog. The review includes a history of sea fog research, field programs, forecasting methods, and detection of sea fog via satellite observations where similarity in radiative properties of fog top and the underlying sea induce further complexity. The main thrust of the study is to provide insight into causality of fog including its initiation, maintenance, and destruction. The interplay between the various physical processes behind the several stages of marine fog is among the most challenging aspects of the problem. An effort is made to identify this interplay between processes that include the microphysics of fog formation and maintenance, the influence of large-scale circulations and precipitation/clouds, radiation, turbulence (air-sea interaction), and advection. The environmental impact of marine fog is also addressed. The study concludes with an assessment of our current knowledge of the phenomenon, our principal areas of ignorance, and future lines of research that hold promise for advances in our understanding. © 2013."
"7006614696;6701606453;7004114883;","Variability in the characteristics of precipitation systems in the tropical pacific. Part I: Spatial structure",2005,"10.1175/JCLI-3304.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17144404919&doi=10.1175%2fJCLI-3304.1&partnerID=40&md5=f8d95c9f084b1eb5e0486932f8872b7d","Regional and temporal variability in the vertical and horizontal characteristics of tropical precipitating clouds are investigated using the Precipitation Radar (PR) and the Visible and Infrared Scanner (VIRS) on board the Tropical Rainfall Measuring Mission (TRMM) satellite. The present study focuses on the three oceanic regions (west, central, and east Pacific) together with two continental regions for comparison and the two separate time periods (February 1998 and February 2000) under different phases of the El Niño-Southern Oscillation (ENSO) in order to examine regional and ENSO-related variations. The height spectrums of storms are investigated in terms of radar echo-top height and infrared brightness temperature. The variability in the spectrum clearly correlates with the large-scale circulation and its ENSO-related change. On the basis of the height spectrum, storm systems are classified into the four categories of shallow, cumulus congestus, deep stratiform, and deep convective. The deep stratiform and deep convective categories, both of which have very cold cloud tops, are differentiated by radar echo-top heights so that deep convective systems are accompanied with an appreciable amount of large frozen particles aloft. While shallow events are dominant in the probability of occurrence over relatively cold oceans, deep convective systems take their place for warmer sea surface temperatures (SSTs). The turnover occurs at the SST threshold of 28°-29°C for all the oceanic regions and years investigated except the west Pacific in 2000, for which deep convective systems prevail over the entire range of SST. Rain correlation-scale length (RCSL) and cloud correlation-scale length (CCSL) are introduced as statistical indicators of the horizontal scale of storms. While the RCSL is 8-18 km for shallow- and cumulus congestus-type clouds without significant regional and temporal variations, the RCSL and CCSL associated with deep stratiform and deep convective systems consistently exceed 100 km and exhibit a systematic variability. The RCSL and CCSL in the central and east Pacific, particularly, increase significantly in the El Nño year. © 2005 American Meteorological Society."
"57034069700;35509639400;","Physical mechanisms controlling the initiation of convective self-aggregation in a General Circulation Model",2015,"10.1002/2015MS000571","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959576864&doi=10.1002%2f2015MS000571&partnerID=40&md5=6d729f7b1ea968f6b4a8a35ef810bf37","Cloud-resolving models have shown that under certain conditions, the Radiative-Convective Equilibrium (RCE) could become unstable and lead to the spontaneous organization of the atmosphere into dry and wet areas, and the aggregation of convection. In this study, we show that this ""self-aggregation"" behavior also occurs in nonrotating RCE simulations performed with the IPSL-CM5A-LR General Circulation Model (GCM), and that it exhibits a strong dependence on sea surface temperature (SST). We investigate the physical mechanisms that control the initiation of self-aggregation in this model, and their dependence on temperature. At low SSTs, the onset of self-aggregation is primarily controlled by the coupling between low-cloud radiative effects and shallow circulations and the formation of ""radiatively driven cold pools"" in areas devoid of deep convection, while at high SSTs it is primarily controlled by the coupling between surface fluxes and circulation within convective areas. At intermediate temperatures, the occurrence of self-aggregation is less spontaneous and depends on initial conditions, but it can arise through a combination of both mechanisms. Through their coupling to circulation and surface fluxes, the radiative effects of low-level clouds play a critical role in both initiation mechanisms, and the sensitivity of boundary layer clouds to surface temperature explains to a large extent the temperature dependence of convective self-aggregation. At any SST, the presence of cloud-radiative effects in the free troposphere is necessary to the initiation, growth, and maintenance of convective aggregation. © 2015. The Authors."
"16025402200;7202583200;","Dynamics of the West African monsoon under mid-Holocene precessional forcing: Regional climate model simulations",2007,"10.1175/JCLI4013.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847417518&doi=10.1175%2fJCLI4013.1&partnerID=40&md5=be9f6ebc03e0fe4e9c066c46a3bb696f","The African Humid Period (AHP), about 14 800 yr ago [14.8-5.5 ka (ka ≡ 1000 yr ago)], was a time of increased humidity over Africa. Paleoclimate evidence suggests that the West African summer monsoon was stronger and more extensive 6 ka than today, and that the Saharan Desert was green. Here, a regional climate model that produces an excellent simulation of today's climate over northern Africa is used to study the dynamics of the monsoon 6 ka. Changes in insolation, atmospheric CO2, and vegetation are used to impose 6-ka conditions, and the role of each forcing is isolated. Vegetation is not interactive, and the large-scale circulation and SSTs are fixed at present-day values for the 6-ka simulations. The regional model produces precipitation increases across the Sahel and Sahara that are in good agreement with the paleodata. However, unobserved drying is simulated over the Guinean coast region where paleodata are sparse. Precipitation increases in the Sahel are related to a northward shift of the monsoon, the elimination of the African easterly jet, and an intensification and deepening of the low-level westerly jet on the west coast. The thermal low-Saharan high system of the present-day climate is replaced by a deep thermal low. When this system becomes fully developed in midsummer, cyclonic circulations transport moisture north into the Sahara, and rainfall increases there. Surface temperatures decrease despite the increased solar forcing 6 ka because of an increase in cloudiness. A moist static energy budget analysis shows that increased low-level moisture dominates the cooling to destabilize the vertical column and enhance convection. Even though solar forcing is the ultimate cause of the AHP, the model responds more strongly to the vegetation forcing, especially early in the summer season, emphasizing the importance of vegetation in maintaining the intensified monsoon system. © 2007 American Meteorological Society."
"7006957668;6603244291;7402942478;7409376438;57202803751;35425197200;7101600167;7004114883;","Assimilation of SSM/I-derived surface rainfall and total precipitable water for improving the GEOS analysis for climate studies",2000,"10.1175/1520-0493(2000)128<0509:AOSIDS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034014765&doi=10.1175%2f1520-0493%282000%29128%3c0509%3aAOSIDS%3e2.0.CO%3b2&partnerID=40&md5=1fd7e7e393c87a291147d73091fc4324","This article describes a variational framework for assimilating the SSM/I-derived surface rain rate and total precipitable water (TPW) and examines their impact on the analysis produced by the Goddard Earth Observing System (GEOS) Data Assimilation System (DAS). The SSM/I observations consist of tropical rain rates retrieved using the Goddard Profiling Algorithm and tropical TPW estimates produced by Wentz. In a series of assimilation experiments for December 1992. results show that the SSM/I-derived rain rate, despite current uncertainty in its intensity, is better than the model-generated precipitation. Assimilating rainfall data improves cloud distributions and the cloudy-sky radiation, while assimilating TPW data reduces a moisture bias in the lower troposphere to improve the clear-sky radiation. Together, the two data types reduce the monthly mean spatial bias by 46% and the error standard deviation by 26% in the outgoing longwave radiation (OLR) averaged over the Tropics, as compared with the NOAA OLR observation product. The improved cloud distribution, in turn, improves the solar radiation at the surface. There is also evidence that the latent heating change associated with the improved precipitation improves the large-scale circulation in the Tropics. This is inferred from a comparison of the clear-sky brightness temperatures for TIROS Operational Vertical Sounder channel 12 computed from the GEOS analyses with the observed values, suggesting that rainfall assimilation reduces a prevailing moist bias in the upper-tropospheric humidity in the GEOS system through enhanced subsidence between the major convective centers. This work shows that assimilation of satellite-derived precipitation and TPW can reduce state-dependent systematic errors in the OLR, clouds, surface radiation, and the large-scale circulation in the assimilated dataset. The improved analysis also leads to better short-range forecasts, but the impact is modest compared with improvements in the time-averaged signals in the analysis. The study shows that, in the presence of biases and other errors of the forecast model, it is possible to improve the time-averaged ""climate contentin the data without comparable improvements in forecast. The full impact of these data types on the analysis cannot be measured solely in terms of forecast skills."
"57193882808;35572026100;7006095466;","Cloud resolving modeling of tropical circulations driven by large-scale SST gradients",2000,"10.1175/1520-0469(2000)057<2022:crmotc>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034233811&doi=10.1175%2f1520-0469%282000%29057%3c2022%3acrmotc%3e2.0.co%3b2&partnerID=40&md5=f16f6dd6b37c8fb865e15a81b367356d","This paper considers interactions between the moist atmospheric convection and the large-scale flow driven by the large-scale gradient of sea surface temperature. A two-dimensional computational framework is used with the horizontal domain size of 4000 km in which both the convective dynamics and the large-scale flow are resolved. Rotational effects are not considered. Simulations are performed using either a prescribed temperature tendency mimicking the effects of radiative processes or a fully interactive radiation transfer model. The simulations are performed for a period of 60 days with quasi-equilibrium conditions attained after about a month. The time-mean large-scale flow in the simulations features an ascending branch occupied by moist convection over a warm ocean and a cloud-free descending branch over a cold ocean. The time-mean flow for the prescribed radiation case features a complex vertical structure characterized by two somewhat decoupled circulations in the lower and upper troposphere. This is in stark contrast with the predominant first-baroclinic-mode structure typical of the observed large-scale tropical circulations, which is characterized by a single cell. An idealized dry model featuring prescribed convective heat source suggests that the complex vertical structure is directly related to the deviation of the model temperature profile from the climatology. Quasi-two-day oscillations are a major transient feature of the simulations. The oscillations are associated with radiation of gravity waves from the convective branch into the descending branch. Inclusion of the interactive radiation results in a significant modification of the large-scale flow and has a dramatic impact on the strength and horizontal extent of convection. Water vapor and cloud condensate strongly interact with radiative processes to induce these paramount effects on the tropical large-scale circulations.This paper considers interactions between the moist atmospheric convection and the large-scale flow driven by the large-scale gradient of sea surface temperature. A two-dimensional computational framework is used with the horizontal domain size of 4000 km in which both the convective dynamics and the large-scale flow are resolved. Rotational effects are not considered. Simulations are performed using either a prescribed temperature tendency mimicking the effects of radiative processes or a fully interactive radiation transfer model. The simulations are performed for a period of 60 days with quasi-equilibrium conditions attained after about a month. The time-mean large-scale flow in the simulations features an ascending branch occupied by moist convection over a warm ocean and a cloud-free descending branch over a cold ocean. The time-mean flow for the prescribed radiation case features a complex vertical structure characterized by two somewhat decoupled circulations in the lower and upper troposphere. This is in stark contrast with the predominant first-baroclinic-mode structure typical of the observed large-scale tropical circulations, which is characterized by a single cell. An idealized dry model featuring prescribed convective heat source suggests that the complex vertical structure is directly related to the deviation of the model temperature profile from the climatology. Quasi-two-day oscillations are a major transient feature of the simulations. The oscillations are associated with radiation of gravity waves from the convective branch into the descending branch. Inclusion of the interactive radiation results in a significant modification of the large-scale flow and has a dramatic impact on the strength and horizontal extent of convection. Water vapor and cloud condensate strongly interact with radiative processes to induce these paramount effects on the tropical large-scale circulations."
"35741200300;57203142176;24492504500;","The role of atmosphere feedbacks during ENSO in the CMIP3 models. Part II: Using AMIP runs to understand the heat flux feedback mechanisms",2011,"10.1007/s00382-010-0895-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053326490&doi=10.1007%2fs00382-010-0895-y&partnerID=40&md5=6ceb630c568bee18877693d8100be375","Several studies using ocean-atmosphere general circulation models (GCMs) suggest that the atmospheric component plays a dominant role in the modelled El Niño-Southern Oscillation (ENSO). To help elucidate these findings, the two main atmosphere feedbacks relevant to ENSO, the Bjerknes positive feedback (μ) and the heat flux negative feedback (α), are here analysed in nine AMIP runs of the CMIP3 multimodel dataset. We find that these models generally have improved feedbacks compared to the coupled runs which were analysed in part I of this study. The Bjerknes feedback, μ, is increased in most AMIP runs compared to the coupled run counterparts, and exhibits both positive and negative biases with respect to ERA40. As in the coupled runs, the shortwave and latent heat flux feedbacks are the two dominant components of α in the AMIP runs. We investigate the mechanisms behind these two important feedbacks, in particular focusing on the strong 1997-1998 El Niño. Biases in the shortwave flux feedback, αSW, are the main source of model uncertainty in α. Most models do not successfully represent the negative αSW in the East Pacific, primarily due to an overly strong low-cloud positive feedback in the far eastern Pacific. Biases in the cloud response to dynamical changes dominate the modelled αSW biases, though errors in the large-scale circulation response to sea surface temperature (SST) forcing also play a role. Analysis of the cloud radiative forcing in the East Pacific reveals model biases in low cloud amount and optical thickness which may affect αSW. We further show that the negative latent heat flux feedback, αLH, exhibits less diversity than αSW and is primarily driven by variations in the near-surface specific humidity difference. However, biases in both the near-surface wind speed and humidity response to SST forcing can explain the inter-model αLH differences. © 2010 Springer-Verlag."
"23502460300;7004540083;","Effects of cloud vertical structure on atmospheric circulation in the GISS GCM",1998,"10.1175/1520-0442(1998)011<3010:EOCVSO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032216219&doi=10.1175%2f1520-0442%281998%29011%3c3010%3aEOCVSO%3e2.0.CO%3b2&partnerID=40&md5=e0c47114fc14fafe6ffe8ed2b70ae66c","Thirteen experiments have been performed using the Goddard Institute for Space Studies General Circulation Model (GISS GCM) to investigative the response of the large-scale circulation to different macroscale cloud vertical structures (CVS). The overall effect of clouds, the role of their geographic variations, and difference between the transient and equilibrium responses of the atmospheric circulation are also studied. Clouds act to suppress the Hadley circulation in the transient response, but intensify it in the equilibrium state. Changing CVS affects the atmospheric circulation directly by modifying the radiative cooling profile and atmospheric static stability, but the effect is opposed, on average, by an indirect effect on the latent heating profile produced by deep (moist) convection. Different interactions of radiation and convection with land and ocean surfaces mean that this cancellation of CVS effects on radiative and latent heating is not the same at all locations. All three parameters of the CVS seem equally important: the cloud-top height of the uppermost cloud layer, the presence of multiple layers, and the separation distance between two consecutive layers in a multilayered cloud system. In experiments with a globally uniform, single-layered cloud, the one with the cloud located somewhere at middle levels (720-550 mb in this model) results in the strongest Hadley circulation; with a single-layered cloud located above or below this level, both the circulation intensity and its vertical extent decrease. Inserting another cloud layer below a cloud in the upper troposphere also intensifies the Hadley circulation, the effect increasing with decreasing separation distance. Separately, vertical gradients in the cloud distribution appear to be more important to the circulation strength than horizontal gradients, but horizontal variations in the CVs are needed to explain the strength of the mean circulation in the model atmosphere. The results also suggest that explicity resolving cloud-top radiative cooling and base warming for each cloud layer is important to modeling the Hadley circulation.Thirteen experiments have been performed using the Goddard Institute for Space Studies General Circulation Model (GISS GCM) to investigate the responce of the large-scale circulation to different macroscale cloud vertical structures (CVS). The overall effect of clouds, the role of their geographic variations, and difference between the transient and equilibrium responses of the atmospheric circulation are also studied. Clouds act to suppress the Hadley circulation in the transient response, but intensify it in the equilibrium state. Separately, vertical gradients in the cloud distribution appear to be more important to the circulation strength than horizontal gradients, but horizontal variations in the CVS are needed to explain the strength of the mean circulation in the model atmosphere."
"57001165400;55803043300;7403968239;","Cloud and water vapor feedbacks to the El Niño warming: Are they still biased in CMIP5 models?",2013,"10.1175/JCLI-D-12-00575.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876438721&doi=10.1175%2fJCLI-D-12-00575.1&partnerID=40&md5=e52bca17aac459ae1591997e0c7c6a9b","Previous evaluations of model simulations of the cloud and water vapor feedbacks in response to El Niño warming have singled out two common biases in models from phase 3 of the Coupled Model Intercomparison Project (CMIP3): an underestimate of the negative feedback from the shortwave cloud radiative forcing (SWCRF) and an overestimate of the positive feedback from the greenhouse effect of water vapor. Here, the authors check whether these two biases are alleviated in the CMIP5 models. While encouraging improvements are found, particularly in the simulation of the negative SWCRF feedback, the biases in the simulation of these two feedbacks remain prevalent and significant. It is shown that bias in the SWCRF feedback correlates well with biases in the corresponding feedbacks from precipitation, large-scale circulation, and longwave radiative forcing of clouds (LWCRF). By dividing CMIP5 models into two categories-high score models (HSM) and low score models (LSM)-based on their individual skills of simulating the SWCRF feedback, the authors further find that ocean-atmosphere coupling generally lowers the score of the simulated feedbacks of water vapor and clouds but that the LSM is more affected by the coupling than the HSM. They also find that the SWCRF feedback is simulated better in the models that have a more realistic zonal extent of the equatorial cold tongue, suggesting that the continuing existence of an excessive cold tongue is a key factor behind the persistence of the feedback biases in models. ©2013 American Meteorological Society."
"55182712000;6603850393;","Atmospheric circulation anomalies during episodes of enhanced and reduced convective cloudiness over Uruguay",2003,"10.1175/1520-0442(2003)016<3171:ACADEO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0344552897&doi=10.1175%2f1520-0442%282003%29016%3c3171%3aACADEO%3e2.0.CO%3b2&partnerID=40&md5=d1d4b0cb8f5e35a84d6081aebda9ca04","Regional and large-scale circulation anomalies associated with periods of enhanced and reduced convective cloudiness over Uruguay are studied for austral spring and summer, when rainfall associated with deep convection is more frequent in this region. The analysis was performed at a submonthly timescale, considering that the essential nature of the mechanisms producing rainfall is not well captured by anomalies calculated on a monthly or seasonal basis in regions where precipitation is highly episodic. Periods of enhanced and reduced convective cloudiness over Uruguay are characterized by a marked dipolar structure in the outgoing longwave radiation anomaly field along eastern South America from 10° to 40°S, with the centers of the dipole located over the South Atlantic convergence zone (SACZ) and over a broad region including Uruguay, southern Brazil, and northeastern Argentina. This dipole, which corresponds to one of the key factors of climate dynamics in South America during spring and summer, seems to be part of a much larger wavelike quasi-barotropic structure that includes alternating centers of negative and positive geopotential height and temperature anomalies in the southern portion of the continent, and farther upstream in the southern Pacific. At the regional scale, periods of enhanced convection and rainfall over Uruguay are associated with the following features: a warm-core anticyclonic circulation anomaly in the middle and upper troposphere, centered on 34°S, 45°W, approximately: an intensified Chaco low in northwestern Argentina that favors a reinforced northwesterly flow of warm and moist air from the Amazon basin; and an anomalously strong subtropical jet along eastern South America. Periods with reduced convective cloudiness over Uruguay are characterized by circulation anomalies that are broadly opposite to those described before, although some significant asymmetries in their intensity are documented. No major differences were detected in the circulation anomaly patterns between spring and summer, although some changes in the wavelike structure associated to the dipole were found. Considering the extent of circulation anomalies described here for the austral summer semester, it seems plausible that they also characterize rainfall anomalies over a broader region in southeastern South America."
"7004160106;7402390191;7401559815;","Mechanisms regulating sea-surface temperatures and deep convection in the tropics",1999,"10.1029/1999GL900197","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033560507&doi=10.1029%2f1999GL900197&partnerID=40&md5=bb2a19891262ed82a2973dde90544a7f","Scientific basis for the emergence of deep convection in the tropics at or above 28°C sea-surface temperature (SST), and its proximity to the highest observed SST of about 30°C, is explained from first principles of moist convection and TOGA-COARE data. Our calculations show that SST of 28-29°C is needed for charging the cloud-base airmass with the required moist static energy for clouds to reach the upper troposphere (i.e., 200 hPa). Besides reducing solar irradiation by cloud-cover, moist convection also produces cool and dry downdrafts, which promote oceanic cooling by increased sensible and latent heat fluxes at the surface. Consequently, the tropical ocean seesaws between the states of net energy absorber before, and net energy supplier after, the deep moist convection, which causes the SST to vacillate between 28° and 30°C. While dynamics of the large-scale circulation embodying the easterly waves and Madden-Julian Oscillations (MJOs) modulate moist convection, we show that the quasi-stationary vertical profile of moist static energy of the tropics is the ultimate cause of the upper limit on tropical SSTs. Copyright 1999 by the American Geophysical Union."
"7004129006;7003292889;","A global view of large-scale precipitation variability",1993,"10.1175/1520-0442(1993)006<1495:AGVOLS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027799632&doi=10.1175%2f1520-0442%281993%29006%3c1495%3aAGVOLS%3e2.0.CO%3b2&partnerID=40&md5=8c48d8dc46594f0a5f71d79e69fec8ee","Rainfall in the deep tropics is particularly important as a forcing mechanism for the atmosphere's large-scale circulation and climate. Analysis of systematic space-based observations and surface marine data over the past three decades has vastly improved our understanding of tropical convective regimes and their relationship to sea surface temperature field and the general circulation of the tropics are reviewed. The hierarchal nature of tropical precipitation variability on time/space scales ranging from synoptic cloud clusters through the intraseasonal Madden-Julian Oscillation to multiyear El Nino-Southern Oscillation cycle is discussed. Links between tropical convection and extratropical precipitation on time scales ranging from synoptic to multiyear are examined, with emphasis on conditions over the North Pacific-North American sector during winter. -from Authors"
"7006874359;7005461477;","Vertical motion, diabatic heating, and rainfall characteristics in north Australia convective systems",1998,"10.1256/smsqj.54805","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031707797&doi=10.1256%2fsmsqj.54805&partnerID=40&md5=a8c612692b39a01280eb0b6b7bd187d4","Very-high-frequency wind-profiler data are used to study the vertical draught structure within 13 tropical Mesoscale Convective Systems (MCSs) near Darwin, Australia during the 1989-90 and 1990-91 wet seasons. These studies are supported by single-Doppler radar, soundings, and surface rainfall data to correlate radar reflectivity, thermal buoyancy, and surface rainfall patterns with vertical air-motion structures. Because of Darwin's unique location at the southern tip of the Maritime Continent, vertical draughts in both the monsoon (maritime) and monsoon break (continental) convective regimes can be observed. The break-regime MCSs (six in total) were all squall lines, characterized by a leading line of convection with heavy precipitation and trailing stratiform rainfall containing a characteristic radar bright band. These MCSs exhibited a pronounced life-cycle pattern and were all sampled by the profiler in the mature to dissipating stages. In contrast, the monsoon systems (seven in total) were composed of regions of stratiform cloud with embedded convective bands which moved on-shore in the monsoonal flow. Results from the Darwin rain-gauge network indicated that the majority of the total rainfall in each MCS (break and monsoon) was associated with the convective portion of the system. The break-regime MCSs were all characterized by a low-level (4 km) updraught peak associated with convective cells on the leading edge of each squall line, trailed by deeper convective updraughts in the middle and upper troposphere. For the monsoon cases, the lower-troposphere convective updraughts were typically less than those in the squall lines, yet were stronger in the upper troposphere. The low-level differences in the convective updraughts were consistent with the smaller virtual-temperature excess in the monsoon soundings, as well as the larger vertical radar-reflectivity gradients observed in monsoon convection. Consistent with the differences in vertical air-motion patterns, diabatic heating and moistening profiles for the monsoon MCSs were characterized by a higher-level heating and drying peak compared with the break MCSs. The results have important implications for cumulus parametrizations in numerical models since the large-scale circulation is sensitive to the vertical distribution of diabatic heating in tropical MCSs."
"7406543625;","Large-scale circulations associated with the east asian summer monsoon and the Mei-Yu over South China and Taiwan",1994,"10.2151/jmsj1965.72.6_959","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0006396031&doi=10.2151%2fjmsj1965.72.6_959&partnerID=40&md5=cbe3a74d52eefcd86d5e3413ba041fe9","Grid point data, visible and infrared cloud imageries, and cloud top temperatures during the period of May-June 1981-1986 were used to study the large-scale circulations in Asian monsoon region. Stream function, velocity potential, divergent part of the wind, convection index, cloud top temperature index, and moisture field were analyzed. The distribution of the half-monthly mean of these parameters is presented and discussed to reveal the characteristics of the evolution of large-scale circulations from the pre-Mei-Yu season (1-15 May) to the post-Mei-Yu season (16-30 June) in South China and Taiwan region. Also, convectively active and inactive Mei-Yu seasons and fronts were selected to study the interannual and intraseasonal variations of the large-scale circulation patterns. The results can be summarized as follows: (1) The Mei-Yu over South China and Taiwan occurred concurrently with the onset of the summer southwest monsoon over the South China Sea during the period of May 16-31 (Phase I). (2) The northward advance of the area of deep convection, ITCZ, and subtropical ridge at the post-Mei- Yu season (June 16-30) occurred concurrently with the establishment of the quasi-stationary position of Mei-Yu front over the Yangtze Valley and Japan. At the same time, a quasi-equivalent barotropic monsoon circulation system was well developed with the low-level cyclone under the upper-level anticyclone over northeastern Indian and Burma area. (3) The active Mei-Yu season was characterized by the further southward penetration of the northern (baroclinic) system and moisture flux convergence over the Mei-Yu region. The reversed situations were observed for the inactive Mei-Yu season. (4) The difference for the active and inactive Mei-Yu fronts was mainly controlled by the low-level flows. The active Mei-Yu front was accompanied by the southwest monsoonal flows originating from the Bay of Bengal and the tropical western Pacific, whereas the inactive front the southeasterly or easterly flows of the Pacific high circulation prevailed over the Mei-Yu region. Higher mixing ratio, stronger moisture flux, and flux convergence were observed over the Mei-Yu region for the active front as compared to those for the inactive one. (5) More frequent occurrence of the active fronts led to an active Mei-Yu season and the reverse was true for an inactive one. © 1994, Meteorological Society of Japan."
"22936054800;25649651700;7004480520;6701751765;","Gravity waves, cold pockets and CO2 clouds in the Martian mesosphere",2012,"10.1029/2011GL050343","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856138054&doi=10.1029%2f2011GL050343&partnerID=40&md5=a19f69a58f287af3551681fb0f78d926","Many independent measurements have shown that extremely cold temperatures are found in the Martian mesosphere. These mesospheric ""cold pockets"" may result from the propagation of atmospheric waves. Recent observational achievements also hint at such cold pockets by revealing mesospheric clouds formed through the condensation of CO2, the major component of the Martian atmosphere. Thus far, modeling studies addressing the presence of cold pockets in the Martian mesosphere have explored the influence of large-scale circulations. Mesoscale phenomena, such as gravity waves, have received less attention. Here we show through multiscale meteorological modeling that mesoscale gravity waves could play a key role in the formation of mesospheric cold pockets propitious to CO2 condensation. © 2012 by the American Geophysical Union."
"55812409300;7004540083;","Interaction of tropical deep convection with the large-scale circulation in the MJO",2010,"10.1175/2009JCLI3240.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953695065&doi=10.1175%2f2009JCLI3240.1&partnerID=40&md5=139fd0ed165d9aa6180bfd6c7b694165","To better understand the interaction between tropical deep convection and the Madden-Julian oscillation (MJO), tropical cloud regimes are defined by cluster analysis of International Satellite Cloud Climatology Project (ISCCP) cloud-top pressure-optical thickness joint distributions from the D1 dataset covering 21.5 yr. An MJO index based solely on upper-level wind anomalies is used to study variations of the tropical cloud regimes. The MJO index shows that MJO events are present almost all the time; instead of the MJO event being associated with ""on or off"" deep convection, it is associated with weaker or stronger mesoscale organization of deep convection. Atmospheric winds and humidity from NCEP-NCAR reanalysis 1 are used to characterize the large-scale dynamics of the MJO; the results show that the large-scale motions initiate an MJO event by moistening the lower troposphere by horizontal advection. Increasingly strong convection transports moisture into the upper troposphere, suggesting a reinforcement of the convection itself. The change of convection organization shown by the cloud regimes indicates a strong interaction between the large-scale circulation and deep convection. The analysis is extended to the complete atmospheric diabatic heating by precipitation, radiation, and surface fluxes. The wave organizes stronger convective heating of the tropical atmosphere, which results in stronger winds, while there is only a passive response of the surface, directly linked to cloud radiative effects. Overall, the results suggest that an MJO event is an amplification of large-scale wave motions by stronger convective heating, which results from a dynamic reorganization of scattered deep convection into more intense mesoscale systems. © 2010 American Meteorological Society."
"7405489798;6506328135;","Bi-modal structure and variability of large-scale diabatic heating in the tropics",2009,"10.1175/2009JAS3089.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949422454&doi=10.1175%2f2009JAS3089.1&partnerID=40&md5=79a30ee324c7005824143e382929efe6","Tropical diabatic heating profiles estimated using sounding data from eight field campaigns were diagnosed to document their common and prevailing structure and variability that are relevant to the large-scale circulation. The first two modes of a rotated empirical orthogonal function analysis-one deep, one shallow-explain 85% of the total variance of all data combined. These two modes were used to describe the heating evolution, which led to three composited heating profiles that are considered as prevailing large-scale heating structures. They are, respectively, shallow, bottom heavy (peak near 700 hPa); deep, middle heavy (peak near 400 hPa); and stratiform-like, top heavy (heating peak near 400 hPa and cooling peak near 700 hPa). The amplitudes and occurrence frequencies of the shallow, bottom-heavy heating profiles are comparable to those of the stratiform-like, top-heavy ones. The sequence of the most probable heating evolution is deep tropospheric cooling to bottom-heavy heating, to middle heavy heating, to stratiform-like heating, then back to deep tropospheric cooling. This heating transition appears to occur on different time scales. Each of the prevailing heating structures is interpreted as being composed of particular fractional populations of various types of precipitating cloud systems, which are viewed as the building blocks for the mean. A linear balanced model forced by the three prevailing heating profiles produces rich vertical structures in the circulation with multiple overturning cells, whose corresponding moisture convergence and surface wind fields are very sensitive to the heating structures. © 2009 American Meteorological Society."
"48661551300;7403931916;7201826462;6701606453;6603081424;6602513845;7005729142;7102018821;","Influence of ice particle surface roughening on the global cloud radiative effect",2013,"10.1175/JAS-D-13-020.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884940988&doi=10.1175%2fJAS-D-13-020.1&partnerID=40&md5=7af5e18f0ff4ba4d72f83f5a62960936","Ice clouds influence the climate system by changing the radiation budget and large-scale circulation. Therefore, climate models need to have an accurate representation of ice clouds and their radiative effects. In this paper, new broadband parameterizations for ice cloud bulk scattering properties are developed for severely roughened ice particles. The parameterizations are based on a general habit mixture that includes nine habits (droxtals, hollow/solid columns, plates, solid/hollow bullet rosettes, aggregate of solid columns, and small/large aggregates of plates). The scattering properties for these individual habits incorporate recent advances in light-scattering computations. The influence of ice particle surface roughness on the ice cloud radiative effect is determined through simulations with the Fu-Liou and the GCM version of the Rapid Radiative Transfer Model (RRTMG) codes and the National Center for Atmospheric Research Community Atmosphere Model (CAM, version 5.1). The differences in shortwave (SW) and longwave (LW) radiative effect at both the top of the atmosphere and the surface are determined for smooth and severely roughened ice particles. While the influence of particle roughening on the single-scattering properties is negligible in the LW, the results indicate that ice crystal roughness can change the SW forcing locally by more than 10Wm-2 over a range of effective diameters. The global-averaged SW cloud radiative effect due to ice particle surface roughness is estimated to be roughly 1-2Wm-22. The CAM results indicate that ice particle roughening can result in a large regional SW radiative effect and a small but nonnegligible increase in the global LW cloud radiative effect. © 2013 American Meteorological Society."
"24070687500;7102745183;","Probing regional orographic controls of precipitation and cloudiness in the Central Andes using satellite data",2009,"10.1175/2008JHM973.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65349169002&doi=10.1175%2f2008JHM973.1&partnerID=40&md5=9795b5d239c0e1ef989c1a378b61e364","Data obtained from NOAA's Geostationary Operational Environmental Satellite (GOES) and NASA's Tropical Rainfall Measuring Mission (TRMM) satellites were used to investigate the relationships between topography, large-scale circulation, and the climatology of precipitation and cloudiness in the Andes - specifically over Peru and the Altiplano Plateau - at diurnal, seasonal, and interannual time scales. The spatial variability of cloudiness was assessed through empirical orthogonal function (EOF) analysis of GOES brightness temperatures. Results indicate that landform is the principal agent of the space-time variability of moist atmospheric processes in the Andes, with the first mode explaining up to 70% of all observed variability. These results substantiate the differences between ""continental"" (Andes and Himalayas) and ""maritime"" (Western Cordillera) orographic precipitation regimes, reflecting the degree to which upwind landmasses modulate moisture transport toward and across mountain barriers. GOES brightness temperatures show that afternoon convective activity during the rainy season is more intense on wet hydrometeorological years such as 2001, whereas the space-time structure of nighttime cloudiness at the foothills and outlets of deep interior valleys does not change during the monsoon and from one year to another independently of large-scale conditions. This suggests that daytime cloud formation and precipitation is strongly dependent on large-scale moisture transport. Interactions between mesoscale and ridge-valley circulations, which are locked to the topography, determine the space-time organization of clouds and precipitation at nighttime. This leads to strong clustering of precipitation features associated with enhanced convection at high elevations along the ridges and near the headwaters of the major river systems in the TRMM data. © 2009 American Meteorological Society."
"7006184606;","A simple model of multiple climate regimes",2002,"10.1029/2001jd001002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0345782225&doi=10.1029%2f2001jd001002&partnerID=40&md5=dd3ca89201c4f3655f92ff76f1b96f93","Among the most intriguing enigmas of the climate system is that on the one hand, the Earth's climate appears to be exquisitely sensitive to relatively minor variations in the distribution of insolation owing to orbital variations, but on the other hand, it is in a grosser sense stable, in that it has varied only moderately in response to a roughly 30% increase in solar insolation over the life of the planet. To this enigma may be added the evidence that climate may undergo extraordinarily abrupt transitions. An attractive idea to help explain these characteristics is the notion that the Earth possesses a limited number of stable climate regimes that may overlap to produce multiple equilibrium states for the same solar forcing. Here we present a simple model that produces such overlapping stable equilibria, based on a few key feedback processes. These include control of atmospheric clouds and water vapor by the large-scale circulation of the atmosphere, control of the depth and intensity of the ocean's thermohaline circulation by tropical cyclones, and the dependence of atmospheric CO2 content on ocean temperature and the strength of the thermohaline circulation. We will show that these key feedback processes produce a climate with two or three stable, overlapping climate regimes. Subjecting this system to variations in climate forcing can account for several observed features of the climate system, including abrupt transitions, sensitivity to orbital variations, arctic warmth and high bottom water temperature during the Eocene and late Cretaceous, tempestites, and possible episodes of deep ocean anoxia during the Cretaceous."
"7201605742;","A Further Study of the Tropical Cyclone without Parameterizing the Effects of Cumulus Convection",1983,"10.2467/mripapers.34.221","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85004561017&doi=10.2467%2fmripapers.34.221&partnerID=40&md5=7fc0cbf995d611aed9b54a2abe00a44e","As a continuation of previous studies (Yamasaki, 1977a, b) numerical experiments of axially symmetric tropical cyclones are performed. As in the previous studies, a fine resolution model is used in which convective clouds are not parameterized but explicitly resolved. A recent advance in the computer has enabled us to deal with the tropical cyclone with realistic horizontal scale even when a sufficiently small grid size is used. Although assumption of axial symmetry restricts very realistic simulation of real tropical cyclones, it seems that the numerical experiments have revealed many important aspects of the formation and intensification processes and the structures of the tropical cyclone and their mechanisms. At the early stage before the tangential velocity attains about 10 ms-2 the area of convective activity and the vortex size expand with time because convection at the outermost part of the convective area propagates outward. Individual convective clouds are usually organized as a convective system with a time scale of about 3 hours, which is referred to as ‘mesoscale convection’ in this paper. As one mesoscale convection-weakens, another forms at some distance. As a result of successive formation, convective activity and rainfall propagate outward or inward and persist for a long period of time. A large-scale (cyclone-scale) meridional circulation is intensified by an ensemble of several mesoscale convections, whereas the continuous formation of mesoscale convection is maintained by the large-scale circulation. The mechanism of such cooperative interaction between moist convection and large-scale motion at this stage, however, is different from that of the original CISK found by Ooyama (1964) and Charney and Eliassen (1964). That is, surface friction does not play any significant role, but instead, the downdraft and cooling due to evaporation of rainwater play an essential role. Such a new type of CISK was also discussed in Yamasaki (1975, 1979). When the rotational winds are intensified, surface friction becomes important. That is, the radial positions of the outermost convection and of maximum tangential velocity begin to shift inward by frictional inflow. Such an inward shift occurs when the tangential velocity attains 10-15 ms-2 Even at this stage it appears that cooling due to evaporation of rainwater and downdraft have significant effects on the large-scale dynamics. When the tangential velocity near the vortex center exceeds about 20 ms2 an eye and eyewall are formed. Then rapid fall of the central surface pressure as well as rapid intensification of the tangential winds takes place. Surface friction plays an essential role in the formation and maintenance of the eye and eyewall. Several small-scale features, which have not been studied with coarse grid models with parameterized convection, are found in the eye and eyewall, including time variation with a period of about 10 minutes. It is suggested that the long-lasting convections obtained in this study may correspond to observed spiral rainbands, which have been interpreted by many authors as internal gravity waves modified by convective heating. The structure and the phase velocity of the long-lasting convections are different from those of internal gravity waves. © 1983, Japan Meteorological Agency/Meteorological Research Institute. All rights reserved."
"7401936984;55745955800;7401974644;6701464294;7102268722;8859530100;","Impact of a revised convective triggering mechanism on community atmosphere model, version 2, simulations: Results from short-range weather forecasts",2004,"10.1029/2004JD004692","https://www.scopus.com/inward/record.uri?eid=2-s2.0-5444272242&doi=10.1029%2f2004JD004692&partnerID=40&md5=addef7b3bf156c51deec9c526c6f9984","This study implements a revised convective triggering condition in the National Center for Atmospheric Research (NCAR) Community Atmosphere Model, Version 2 (CAM2), model to reduce its excessive warm season daytime precipitation over land. The new triggering mechanism introduces a simple dynamic constraint on the initiation of convection that emulates the collective effects of lower level moistening and upward motion of the large-scale circulation. It requires a positive contribution from the large-scale advection of temperature and moisture to the existing positive convective available potential energy (CAPE) for model convection to start. In contrast, the original convection triggering function in CAM2 assumes that convection is triggered whenever there is positive CAPE, which results in too frequent warm season convection over land arising from strong diurnal variation of solar radiation. We examine the impact of the new trigger on CAM2 simulations by running the climate model in numerical weather prediction (NWP) mode so that more available observations and high-frequency NWP analysis data can be used to evaluate model performance. We show that the modified triggering mechanism has led to considerable improvements in the simulation of precipitation, temperature, moisture, clouds, radiations, surface temperature, and surface sensible and latent heat fluxes when compared to the data collected from the Atmospheric Radiation Measurement (ARM) Program at its Southern Great Plains (SGP) site. Similar improvements are also seen over other parts of the globe. In particular, the surface precipitation simulation has been significantly improved over both the continental United States and around the globe; the overestimation of high clouds in the equatorial tropics has been substantially reduced; and the temperature, moisture, and zonal wind are more realistically simulated. Results from this study also show that some systematic errors in the CAM2 climate simulations can be detected in the early stage of model integration. Examples are the extremely overestimated high clouds in the tropics in the vicinity of Intertropical Convergence Zone and the spurious precipitation maximum to the east of the Rockies. This has important implications in studies of these model errors since running the climate model in NWT mode allows us to perform a more in-depth analysis during a short time period where more observations are available and different model errors from various processes have not compensated for the systematic errors. Copyright 2004 by the American Geophysical Union."
"36065603800;7401945370;56962915800;16309604700;9535769800;7406372329;25647939800;57207415190;7006614696;7402205043;6602546234;","An MJO simulated by the NICAM at 14- and 7-km resolutions",2009,"10.1175/2009MWR2965.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70449115282&doi=10.1175%2f2009MWR2965.1&partnerID=40&md5=c8ec218766bf596964fcefb25b2acc76","This study discloses detailed Madden-Julian oscillation (MJO) characteristics in the two 30-day integrations of the global cloud-system-resolving Nonhydrostatic Icosahedral Atmospheric Model (NICAM) using the all-season real-time multivariate MJO index of Wheeler and Hendon. The model anomaly is derived by excluding the observed climatology because the simulation is sufficiently realistic. Results show that the MJO has a realistic evolution in amplitude pattern, geographical locations, eastward propagation, and baroclinic- and westward-tilted structures. In the central Indian Ocean, convection develops with the low-level easterly wind anomaly then matures where the low-level easterly and westerly anomalies meet. Anomalous moisture tilts slightly with height. In contrast, over the western Pacific, the convection grows with a low-level westerly anomaly. Moisture fluctuations, leading convection in eastward propagation, tilt clearly westward with height. The frictional moisture convergence mechanism operates to maintain the MJO. Such success can be attributed to the explicit representation of the interactions between convection and large-scale circulations. The simulated event, however, grows faster in phases 2 and 3, and peaks with 30% higher amplitude than that observed, although the 7-km version shows slight improvement. The fast-growth phases are induced by the fast-growing low-level convergence in the IndianOcean and the strongly biased ITCZ in the west Pacific when the model undergoes a spinup. The simulated OLR has a substantial bias in the tropics. Possible solutions to the deficiencies are discussed. © 2009 American Meteorological Society."
"57200702127;7404829395;56537463000;","Atmospheric responses to the redistribution of anthropogenic aerosols",2015,"10.1002/2015JD023665","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944907910&doi=10.1002%2f2015JD023665&partnerID=40&md5=142ca91428058514e0f36b51d7b4bf3f","The geographical shift of global anthropogenic aerosols fromthe developed countries to the Asian continent since the 1980s could potentially perturb the regional and global climate due to aerosol-cloud-radiation interactions. We use an atmospheric general circulation model with different aerosol scenarios to investigate the radiative and microphysical effects of anthropogenic aerosols from different regions on the radiation budget, precipitation, and large-scale circulations. An experiment contrasting anthropogenic aerosol scenarios in 1970 and 2010 shows that the altered cloud reflectivity and solar extinction by aerosols results in regional surface temperature cooling in East and South Asia, and warming in the US and Europe, respectively. These aerosol-induced temperature changes are consistent with the relative temperature trends from 1980 to 2010 over different regions in the reanalysis data. A reduced meridional streamfunction and zonal winds over the tropics as well as a poleward shift of the jet stream suggest weakened and expanded tropical circulations, which are induced by the redistributed aerosols through a relaxing of the meridional temperature gradient. Consequently, precipitation is suppressed in the deep tropics and enhanced in the subtropics. Our assessments of the aerosol effects over the different regions suggest that the increasing Asian pollution accounts for the weakening of the tropics circulation, while the decreasing pollution in Europe and US tends to shift the circulation systems southward. Moreover, the aerosol indirect forcing is predominant over the total aerosol forcing in magnitude, while aerosol radiative and microphysical effects jointly shape the meridional energy distributions and modulate the circulation systems. © 2015. American Geophysical Union. All Rights Reserved."
"7401776640;","Interannual and interdecadal variability in the storm track, cloudiness, and sea surface temperature over the summertime North Pacific",2000,"10.1175/1520-0442(2000)013<0422:IAIVIT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034117792&doi=10.1175%2f1520-0442%282000%29013%3c0422%3aIAIVIT%3e2.0.CO%3b2&partnerID=40&md5=7e87182aa22d3eb9f71806138531471e","Interannual and interdecadal variability in the summertime mean North Pacific storm track is examined in relation to summertime mean sea surface temperature (SST), nimbostratus, and marine stratiform cloudiness (MSC) (stratus, stratocumulus, fog). The storm track is diagnosed by root-mean-squared daily vertical velocity at 500 mb during the summer season (rms ω) obtained from the National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis. The cloud and SST data are obtained from surface observations. Year-to-year variations in the storm track exhibit significant coupling to variations in cloudiness and SST across the North Pacific. These correspond to coincident latitudinal shifts in the storm track, SST gradient, and MSC gradient. Moreover, both rms ω and nimbostratus show that the storm track moved equatorward and intensified between 1952 and 1995, consistent with the previously documented upward trend in MSC and downward trend in SST. Lead-lag relationships suggest variability in the storm track has a large role in forcing variability in SST. Boundary layer cloudiness responds to and adds a positive feedback to variability in SST. Weak relationships are observed with the summertime mean large-scale circulation, as diagnosed by sea level pressure. This suggests summertime North Pacific atmosphere-ocean interaction is dominated by local processes operating in the storm track and over the SST gradient, unlike the situation during winter.Interannual and interdecadal variability in the summertime mean North Pacific storm track is examined in relation to summertime mean sea surface temperature (SST), nimbostratus, and marine stratiform cloudiness (MSC) (stratus, stratocumulus, fog). The storm track is diagnosed by root-mean-squared daily vertical velocity at 500 mb during the summer season (rms ω) obtained from the National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis. The cloud and SST data are obtained from surface observations. Year-to-year variations in the storm track exhibit significant coupling to variations in cloudiness and SST across the North Pacific. These correspond to coincident latitudinal shifts in the storm track, SST gradient, and MSC gradient. Moreover, both rms ω and nimbostratus show that the storm track moved equatorward and intensified between 1952 and 1995, consistent with the previously documented upward trend in MSC and downward trend in SST. Lead-lag relationships suggest variability in the storm track has a large role in forcing variability in SST. Boundary layer cloudiness responds to and adds a positive feedback to variability in SST. Weak relationships are observed with the summertime mean large-scale circulation, as diagnosed by sea level pressure. This suggests summertime North Pacific atmosphere-ocean interaction is dominated by local processes operating in the storm track and over the SST gradient, unlike the situation during winter."
"7005702722;8882641700;7004479957;","A new approach for 3D cloud-resolving simulations of large-scale atmospheric circulation",2005,"10.1029/2004GL021024","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16344375107&doi=10.1029%2f2004GL021024&partnerID=40&md5=4217b7afa9cddd93096d68504310fd04","We present a computationally efficient new method for simulating the interactions of large-scale atmospheric circulations with deep convection in a 3D cloud-resolving model. This is accomplished by reducing the scale difference between the large-scale and convective circulations. Our method, Diabatic Acceleration and REscaling (DARE), consists of accelerating all diabatic processes, reducing the planetary radius and increasing its rotation rate. A second useful interpretation of this rescaling, Reduced Acceleration in the VErtical (RAVE) is also presented briefly. The DARE/RAVE approach is expected to be useful for a wide range of problems involving interactions between large-scale circulation, deep convection, and associated cloud and radiation processes, whose investigation has long been plagued by deficiencies in cumulus/cloud parameterizations. Initial results from a near-global scale equatorial β-plane simulation using the DARE approach are briefly presented. Copyright 2005 by the American Geophysical Union."
"57193010470;7201375498;6701729202;57194466775;6602551610;","Meteorological conditions in a thinner Arctic sea ice regime from winter to summer during the Norwegian Young sea ice expedition (N-ICE2015)",2017,"10.1002/2016JD026034","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85022175479&doi=10.1002%2f2016JD026034&partnerID=40&md5=35abc6c075f2560f752be51411b41e7d","Atmospheric measurements were made over Arctic sea ice north of Svalbard from winter to early summer (January-June) 2015 during the Norwegian Young Sea Ice (N-ICE2015) expedition. These measurements, which are available publicly, represent a comprehensive meteorological data set covering the seasonal transition in the Arctic Basin over the new, thinner sea ice regime. Winter was characterized by a succession of storms that produced short-lived (less than 48 h) temperature increases of 20 to 30 K at the surface. These storms were driven by the hemispheric scale circulation pattern with a large meridional component of the polar jet stream steering North Atlantic storms into the high Arctic. Nonstorm periods during winter were characterized by strong surface temperature inversions due to strong radiative cooling (“radiatively clear state”). The strength and depth of these inversions were similar to those during the Surface Heat Budget of the Arctic Ocean (SHEBA) campaign. In contrast, atmospheric profiles during the “opaquely cloudy state” were different to those from SHEBA due to differences in the synoptic conditions and location within the ice pack. Storm events observed during spring/summer were the result of synoptic systems located in the Barents Sea and the Arctic Basin rather than passing directly over N-ICE2015. These synoptic systems were driven by a large-scale circulation pattern typical of recent years, with an Arctic Dipole pattern developing during June. Surface temperatures became near-constant 0°C on 1 June marking the beginning of summer. Atmospheric profiles during the spring and early summer show persistent lifted temperature and moisture inversions that are indicative of clouds and cloud processes. © 2017. The Authors."
"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)."
"7005804830;37012936800;35577008300;7404080553;","The influence of eastern Pacific tropical cyclone remnants on the southwestern United States",2011,"10.1175/2010MWR3389.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951606974&doi=10.1175%2f2010MWR3389.1&partnerID=40&md5=c419e5eacbe9483838127a7c80cd7a00","Forty-three eastern North Pacific tropical cyclone remnants with varying impact on the southwestern United States during the period 1992-2005 are investigated.Of these, 35 remnants (81%) brought precipitation to some part of the southwestern United States and the remaining 8 remnants (19%) had precipitation that was almost entirely restricted to Mexico, although cloud cover did advect over the southwestern United States in some of these cases.Although the tropical cyclone-strength winds rapidly diminish upon making landfall, these systems still carry a large quantity of tropicalmoisture and, upon interaction withmountainous topography, are found to drop up to 30% of the local annual precipitation. Based on common rainfall patterns and large-scale circulation features, the tropical cyclones are grouped into five categories. These include a northern recurving pattern that is more likely to bring rainfall to the southwestern United States; a southern recurving pattern that brings rainfall across northern Mexico and the Gulf Coast region; a largely north and/or northwestward movement pattern that brings rainfall to the west coast of the United States; a group that is blocked from the southwest by a ridge, which limits rainfall to Mexico; and a small group of cases that are not clearly any of the previous four types. Composites of the first four groups are shown and forecasting strategies for each are described. © 2011 American Meteorological Society."
"55260519600;7005137442;15026371500;7006328089;","The impact of methane thermodynamics on seasonal convection and circulation in a model Titan atmosphere",2009,"10.1016/j.icarus.2009.03.043","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68749094068&doi=10.1016%2fj.icarus.2009.03.043&partnerID=40&md5=b03ac9ee60ca7dabed93976bb126219c","We identify mechanisms controlling the distribution of methane convection and large-scale circulation in a simplified, axisymmetric model atmosphere of Titan forced by gray radiation and moist (methane) convection. The large-scale overturning circulation, or Hadley cell, is global in latitudinal extent and provides fundamental control of precipitation and tropospheric winds. The precipitating, large-scale updraft regularly oscillates in latitude with seasons. The distance of greatest poleward excursion of the Hadley cell updraft is set by the mass of the convective layer of the atmosphere; convection efficiently communicates seasonal warming of the surface through the cold and dense lower atmosphere, increasing the heat capacity of the system. The presence of deep, precipitating convection introduces three effects relative to the case with no methane latent heating: (1) convection is narrowed and enhanced in the large-scale updraft of the Hadley cell; (2) the latitudinal amplitude of Hadley cell updraft oscillations is decreased; and (3) a time lag is introduced. These effects are observable in the location and timing of convective methane clouds in Titan's atmosphere as a function of season. A comparison of simulations over a range of convective regimes with available observations suggest methane thermodynamic-dynamic feedback is important in the Titan climate. © 2009 Elsevier Inc. All rights reserved."
"7601492669;57202301596;56962915800;55703823500;","Large-scale atmospheric forcing by southeast Pacific boundary layer clouds: A regional model study",2005,"10.1175/JCLI3302.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13844277289&doi=10.1175%2fJCLI3302.1&partnerID=40&md5=051646259f9aca69d14b113597980dd2","A regional model is used to study the radiative effect of boundary layer clouds over the southeast Pacific on large-scale atmosphere circulation during August-October 1999. With the standard settings, the model simulates reasonably well the large-scale circulation over the eastern Pacific, precipitation in the intertropical convergence zone (ITCZ) north of the equator, and marine boundary layer stratocumulus clouds to the south. In a sensitivity experiment with the radiative effect of liquid clouds south of the equator over the eastern Pacific artificially removed, boundary layer clouds south of the equator almost disappear and precipitation in the ITCZ is reduced by 15%-20%, indicating that the stratocumulus clouds over the southeast Pacific have both local and cross-equatorial effects. Examination of the differences between the control and sensitivity experiments indicates that clouds exert a net diabatic cooling in the inversion layer. In response to this cloud-induced cooling, an in situ anomalous high pressure system develops in the boundary layer and an anomalous shallow meridional circulation develops in the lower troposphere over the equatorial eastern Pacific. At the lower branch of this shallow circulation, anomalous boundary layer southerlies blow from the boundary layer high toward the northern ITCZ where the air ascends. An anomalous returning flow (northerly) just above the cloud layer closes the shallow circulation. This low-level anomalous shallow circulation enhances the subsidence over the southeast Pacific above the cloud layer, helping to maintain boundary layer clouds and temperature inversion there. Meanwhile, the strengthened cross-equatorial flow near the surface enhances moisture convergence and convection in the ITCZ north of the equator. This in turn strengthens the local, deep Hadley circulation and hence the large-scale subsidence and boundary layer clouds over the southeast Pacific. This positive feedback therefore enhances the interhemispheric climate asymmetry over the tropical eastern Pacific. © 2005 American Meteorological Society."
"35509639400;7201504886;16444240700;24723648200;56212055700;6603868770;23017945100;7006184606;55883785100;35551238800;22133985200;57206156792;6603418610;57202531041;23492864500;55940978200;23768540500;6603566335;6602115663;56198145500;35621058500;56567409000;57190209035;7201423091;","EUREC4A: A Field Campaign to Elucidate the Couplings Between Clouds, Convection and Circulation",2017,"10.1007/s10712-017-9428-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030099198&doi=10.1007%2fs10712-017-9428-0&partnerID=40&md5=df9180e49db240179718c7784676b9d6","Trade-wind cumuli constitute the cloud type with the highest frequency of occurrence on Earth, and it has been shown that their sensitivity to changing environmental conditions will critically influence the magnitude and pace of future global warming. Research over the last decade has pointed out the importance of the interplay between clouds, convection and circulation in controling this sensitivity. Numerical models represent this interplay in diverse ways, which translates into different responses of trade-cumuli to climate perturbations. Climate models predict that the area covered by shallow cumuli at cloud base is very sensitive to changes in environmental conditions, while process models suggest the opposite. To understand and resolve this contradiction, we propose to organize a field campaign aimed at quantifying the physical properties of trade-cumuli (e.g., cloud fraction and water content) as a function of the large-scale environment. Beyond a better understanding of clouds-circulation coupling processes, the campaign will provide a reference data set that may be used as a benchmark for advancing the modelling and the satellite remote sensing of clouds and circulation. It will also be an opportunity for complementary investigations such as evaluating model convective parameterizations or studying the role of ocean mesoscale eddies in air–sea interactions and convective organization. © 2017, The Author(s)."
"55622713800;7005035762;","The role of the southern African easterly jet in modifying the southeast Atlantic aerosol and cloud environments",2016,"10.1002/qj.2765","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981763297&doi=10.1002%2fqj.2765&partnerID=40&md5=2fcfe2237ac376801a8e31757d816299","The westward transport of biomass-burning (BB) aerosols by mid-tropospheric winds over the southeast Atlantic stratocumulus deck has long been recognized, but the coupling to the large-scale circulation has yet to be investigated fully. This goal is furthered here using satellite observations and reanalysis datasets spanning 2001-2012, as well as 10 day forward trajectory calculations of satellite-detected smoke emissions. The results highlight the important role of a mid-tropospheric zonal wind maximum, the Southern African Easterly Jet (AEJ-S), in transporting BB aerosol west off the African continent. The AEJ-S, defined through daily-mean 600 hPa easterly wind speeds exceeding 6 m s-1 between 5°S and 15°S and centred zonally on the coastline, is most pronounced during September-October. The AEJ-S is part of a meridional circulation that is diabatically forced by the temperature-moisture gradient between the southern hot-dry and northern cool-moist convective structures over land. 45% of 24 264 total identified smoke trajectories exit the continent to its west between 5°S and 15°S. These thereafter follow three major pathways: northwestward (8%), directly westward (55%) and anticyclonically recirculated (37%). The AEJ-S induces an upward motion directly below the jet that enhances prevailing updraughts over land, lifting emissions and transporting aerosols more efficiently over the southeast Atlantic. Offshore, the prevailing large-scale mean subsidence is reduced, with an associated increase in the nearby cloud-top heights and reduction in the nearby marine low-level cloud fraction. Further from the jet, increased warm continental temperature advection at 800 hPa associated with the strengthened land-based anticyclone decreases mean low-level cloud heights. Westward-moving 600 hPa winds at the northern edge of a land-based anticyclone become the southern African easterly jet (AEJ-S, blue contours, 6-10 m/s) in September-October. 10-day smoke trajectories (red to yellow indicating age), for September of 2007, visualize shortwave-absorbing aerosol transport from satellite-detected fire emissions (fire-counts in maroon) far offshore, over the southeast Atlantic stratocumulus deck (greyscale, cloud fractions of 0.5 to 1.0). We further examine the impact of the AEJ-S's secondary circulation on the stratocumulus clouds and aerosol distribution. © 2016 Royal Meteorological Society."
"7006614696;7004114883;","Observations of tropical precipitating clouds ranging from shallow to deep convective systems",2006,"10.1029/2006GL026547","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845669908&doi=10.1029%2f2006GL026547&partnerID=40&md5=55ab8fd542b757ae0bdb0e5709b5752a","Regional and temporal variability in a broad spectrum of tropical precipitation systems is investigated in conjunction with the large-scale environment. The analysis utilizes four storm categories (Shallow, Cumulus Congestus, Deep Stratiform, and Deep Convective) determined from Tropical Rainfall Measuring Mission (TRMM) measurements. Deep Stratiform and Deep Convective systems are found to be clearly correlated with large-scale circulation deduced from a reanalysis data set, and are modulated by a distinct seasonal cycle over land. The Shallow category is practically the only component of tropical oceanic rainfall for cold sea surfaces, while it gives way to deeper systems as SST exceeds 28-29°C. The cloud horizontal scale of organized rainfall systems tends to be increasingly extensive relative to the raining portion as the system becomes larger. The present results are discussed in light of existing relevant studies. Copyright 2006 by the American Geophysical Union."
"7004149770;6602504047;57196396429;","Land effect on the diurnal cycle of clouds over the TOGA COARE area, as observed from GMS IR Data",2001,"10.1175/1520-0493(2001)129<1500:LEOTDC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035359980&doi=10.1175%2f1520-0493%282001%29129%3c1500%3aLEOTDC%3e2.0.CO%3b2&partnerID=40&md5=a46b8f5932ed6a59b635016fc9f19871","The diurnal cycle of clouds over the western equatorial Pacific region (15°S-15°N, 130°E-180°) is studied analyzing hourly GMS-4 infrared brightness temperature images during the intensive observation period (Nov 1992-Feb 1993) of TOGA COARE. Although the area studied is essentially (93%) oceanic, differences of diurnal behavior of the clouds are noticed over different ocean subareas, depending both on the general circulation conditions and on the vicinity of landmasses. This study focuses on the effects of New Guinea and other major islands on the diurnal cycle within the surrounding ocean areas, as for example, the TOGA COARE Intensive Flux Array. The major observable feature of the influence of land is the presence of a diurnal, rather than semidiurnal, average cycle of cloudiness with a high day-to-day repetitivity. The signal is observed up to 600 km off the coast of New Guinea and it is characterized by a variable phase propagating at an average speed of about 15 m s-1. For smaller islands, the effect extends over a distance approximately comparable to their size. The genesis of the propagating cloud systems is assumed as due to the low-level convergence between the large-scale flow and a possible land breeze. This conceptual model has been previously proposed to explain a similar signal observed offshore of Borneo. Within this framework, the influence of the large-scale circulation on the intensity and spatial organization of the propagating cloud systems is discussed. The diurnal signal vanishes when the expected convergence is weaker or when overshadowed by large-scale disturbances crossing over the considered area. In the first 3 months of the period such disturbances are nearly always cloud clusters accompanying the active phase of the Madden-Julian oscillation. Finally it is shown that the small islands in the TOGA COARE domain can corrupt the ""oceanic"" signal by as much as 10% of the diurnal cycle."
"56919125400;7102567936;","Responses of tropical deep convection to the QBO: Cloud-resolving simulations",2015,"10.1175/JAS-D-15-0035.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945157073&doi=10.1175%2fJAS-D-15-0035.1&partnerID=40&md5=2662f8b672e00cd972336ae0221b8c0c","Observational studies suggest that the stratospheric quasi-biennial oscillation (QBO) can modulate tropical deep convection. The authors use a cloud-resolving model with a limited domain, representing a convective column in the tropics, to study the mechanisms of this modulation. The large-scale circulation is parameterized using the weak temperature gradient (WTG) approximation, under which the parameterized large-scale vertical motion acts to relax the horizontal-mean temperature toward a specified reference profile. Temperature variations typically seen in easterly and westerly phases are imposed in the upper troposphere and lower stratosphere of this reference profile. The responses of convection are studied over different sea surface temperatures, holding the reference temperature profile fixed. This can be thought of as studying the response of convection to the QBO over different ""relative SSTs"" and also corresponds to different equilibrium precipitation rates in the control simulation. The equilibrium precipitation rate shows slight increases in response to a QBO easterly phase temperature perturbation over small SST anomalies and strong decreases over large SST anomalies, and vice versa for the QBO westerly phase perturbation. A column moist static energy budget analysis reveals that the QBO modulates the convective precipitation through two pathways: it changes the high-cloud properties and thus the column radiative cooling, and it alters the shape of the large-scale vertical motion and thus the efficiency of energy transport by the large-scale flow. The nonmonotonicity of the precipitation response with respect to relative SST results from the competition of these two effects. � 2015 American Meteorological Society."
"6603684258;7005742190;","Heavy rainfall episodes in Ecuador during El Niño events and associated regional atmospheric circulation and SST patterns",2006,"10.5194/adgeo-6-43-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646355470&doi=10.5194%2fadgeo-6-43-2006&partnerID=40&md5=cc5167c53f71f0849d834cef4da3a489","To date very little is known about the relation between regional circulation patterns and sea surface temperature development in the Niño 1,2 region and the occurrence of heavy precipitation in Ecuador and northern Peru. The current study uses a comprehensive data set of 2544 Meteosat-3 imagery to investigate the dynamics of heavy precipitation during El Niño in 1991/92. Rainfall maps are retrieved by means of an adjusted version of the Convective Stratiform Technique (CST) and Cloud Motion Winds (CMW) are extracted from image sequences by using a special cross-correlation approach. A spatial factor analysis is applied to extract specific weather situations with heavy precipitation during El Niño events. The factor analysis yielded 16 factors. It has been proven that the factor patterns with the highest variance explanation also occur during the rainy season of non-El Niño years. However, 6 El Niño-specific situations could be derived which cause heavy rainfall, especially in coastal Ecuador and northern Peru. Multi-channel Sea Surface Temperatures (MCSST) and cloud motion winds are used to describe atmospheric and oceanic dynamics for these specific weather situations. The analysis shows that high SSTs in combination with strong SST gradients off the coast and warm SST bubbles lead to regional differences in moist instability and heavy rainfall. Both large scale circulation (reversal of the Walker cell) and regional dynamics (extended land-sea-breeze system) have been proven to contribute to El Niño rainfall."
"7402583463;7406633839;7407184643;","Arctic sea ice drift from wavelet analysis of NSCAT and special sensor microwave imager data",1999,"10.1029/1998jc900115","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033562263&doi=10.1029%2f1998jc900115&partnerID=40&md5=12b2e60935efc3b1f1848b0b607ddf6a","Wavelet analysis of NASA scatterometer (NSCAT) backscatter and DMSP special sensor microwave imager (SSM/I) radiance data can be used to obtain daily sea ice drift information for the Arctic region. This technique provides improved spatial coverage over the existing array of Arctic Ocean buoys and better temporal resolution over techniques utilizing data from satellite synthetic aperture radars. Comparisons with ice motion derived from ocean buoys give good quantitative agreement. Both comparison results from NSCAT and SSM/I are compatible, and the results from NSCAT can definitely complement that from SSM/I when there are cloud or surface effects. Then, three sea ice drift daily results from NSCAT, SSM/I, and buoy data can be merged as a composite map by some data fusion techniques. The ice flow streamlines are highly correlated with surface air pressure contours. Examples of derived ice drift maps in December 1996 illustrate large-scale circulation reversals over a period of 4 days. These calibrated/validated results indicate that NSCAT, SSM/I merged daily ice motions are suitably accurate to identify and closely locate sea ice processes and to improve our current knowledge of sea ice drift and related processes through the data assimilation of ocean-ice numerical model. Copyright 1999 by the American Geophysical Union."
"57192049430;","Large, synoptic and meso scale variations of the Baiu Front, during July 1982 part ii: Frontal structure and disturbances",1990,"10.2151/jmsj1965.68.5_557","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0000389414&doi=10.2151%2fjmsj1965.68.5_557&partnerID=40&md5=0813967f48d6cb271e1824244124805b","In part I of this study, cloud variations in/around the Baiu front in July 1982 were studied. The purpose of Part II is to clarify inclusively the structure of the Baiu frontal zone and features of the Baiu frontal disturbances which would be related to the cloud variations studied in Part I, analyzing relative vorticity fields in July 1982. Attention is focused on the relationship and interaction between the upper westerly jet (W-jet) in 40°N~50°N and the Baiu low-level jet (B-jet) in 30°N~40°N. In monthly mean, the Baiu frontal cloud zone, which was formed in 30°N~40°N, coincided with a low-level positive vorticity zone associated with a B-jet. Over the continent, the positive vorticity zone was confined to the lower layer. The zone merged with the positive vorticity zone associated with the W-jet around the east coast (~120°E) of the continent. Over the region east of 120°E (Japan~the northwestern Pacific), the deep positive vorticity zone of a baroclinic structure was formed in the Baiu frontal zone. This will account for the difference in cloud features of the Baiu frontal mesoscale systems between the continent and the Japan~northwestern Pacific region described in Part I. With the change of large-scale circulation in East Asia, the relationship between the W-jet and the B-jet changed during the analysis period. Concurrently, the frontal structure, features of disturbances and cloud amounts in the Baiu front, also changed significantly in the 120° E~140° E region. Three situations of the Baiu front ((1) active-deep, (2) active-shallow and (3) inactive phases) are classified. The vertical structure of the Baiu front and features of the disturbances in these three phases are studied in detail. Over 120°E~140°E, the Baiu frontal mesoscale disturbances showed a deep-baroclinic structure in the active-deep phase, while in the active-shallow phases they showed a shallow structure and located to south of the deep mesoscale disturbances in the northern frontal zone of the W-jet. In both active phases, the mesoscale disturbances in the Baiu frontal zone began to develop around the east coast (~120°E) of the continent under the influence of the upper-level disturbances in the W-jet propagated from Central Asia. © 1990, Meteorological Society of Japan."
"6603875926;6701735773;35509639400;7004714030;6602080773;10143232600;","Impact of different convective cloud schemes on the simulation of the tropical seasonal cycle in a coupled ocean-atmosphere model",2007,"10.1007/s00382-007-0244-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547918025&doi=10.1007%2fs00382-007-0244-y&partnerID=40&md5=1526e982901952ac81f93672d0fd1cfb","The simulation of the mean seasonal cycle of sea surface temperature (SST) remains a challenge for coupled ocean - atmosphere general circulation models (OAGCMs). Here we investigate how the numerical representation of clouds and convection affects the simulation of the seasonal variations of tropical SST. For this purpose, we compare simulations performed with two versions of the same OAGCM differing only by their convection and cloud schemes. Most of the atmospheric temperature and precipitation differences between the two simulations reflect differences found in atmosphere-alone simulations. They affect the ocean interior down to 1,000 m. Substantial differences are found between the two coupled simulations in the seasonal march of the Intertropical Convergence Zone in the eastern part of the Pacific and Atlantic basins, where the equatorial upwelling develops. The results confirm that the distribution of atmospheric convection between ocean and land during the American and African boreal summer monsoons plays a key role in maintaining a cross equatorial flow and a strong windstress along the equator, and thereby the equatorial upwelling. Feedbacks between convection, large-scale circulation, SST and clouds are highlighted from the differences between the two simulations. In one case, these feedbacks maintain the ITCZ in a quite realistic position, whereas in the other case the ITCZ is located too far south close to the equator. © Springer-Verlag 2007."
"7003324794;23987208900;6603767909;22233766500;7102322882;55960562700;28267551200;","Cassini observations reveal a regime of zonostrophic macroturbulence on Jupiter",2014,"10.1016/j.icarus.2013.08.030","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890038690&doi=10.1016%2fj.icarus.2013.08.030&partnerID=40&md5=989973a0e176de83ff001296ece21c24","In December 2000, the Cassini fly-by near Jupiter delivered high-resolution images of Jupiter's clouds over the entire planet in a band between 50°N and 50°S. Three daily-averaged two-dimensional velocity snapshots extracted from these images are used to perform spectral analysis of jovian atmospheric macroturbulence. A similar analysis is also performed on alternative data documented by Choi and Showman (Choi, D., Showman, A. [2011]. Icarus 216, 597-609), based on a different method of image processing. The inter-comparison of the products of both analyses ensures a better constraint of the spectral estimates. Both analyses reveal strong anisotropy of the kinetic energy spectrum. The zonal spectrum is very steep and most of the kinetic energy resides in slowly evolving, alternating zonal (west-east) jets, while the non-zonal, or residual spectrum obeys the Kolmogorov-Kraichnan law specific to two-dimensional turbulence in the range of the inverse energy cascade. The spectral data is used to estimate the inverse cascade rate {small element of} and the zonostrophy index Rβ for the first time. Although both datasets yield somewhat different values of {small element of}, it is estimated to be in the range 0.5-1.0×10-5m2s-3. The ensuing values of Rβ≳5 belong well in the range of zonostrophic turbulence whose threshold corresponds to Rβ≃2.5. We infer that the large-scale circulation is maintained by an anisotropic inverse energy cascade. The removal of the Great Red Spot from both datasets has no significant effect upon either the spectra or the inverse cascade rate. The spectral data are used to compute the rate of the energy exchange, W, between the non-zonal structures and the large-scale zonal flow. It is found that instantaneous values of W may exceed {small element of} by an order of magnitude. Previous numerical simulations with a barotropic model suggest that W and {small element of} attain comparable values only after averaging of W over a sufficiently long time. Near-instantaneous values of W that have been routinely used to infer the rate of the kinetic energy supply to Jupiter's zonal flow may therefore significantly overestimate {small element of}. This disparity between W and {small element of} may resolve the long-standing conundrum of an unrealistically high rate of energy transfer to the zonal flow. The meridional diffusivity Kφ in the regime of zonostrophic turbulence is given by an expression that depends on {small element of}. The value of Kφ estimated from the spectra is compared against data from the dispersion of stratospheric gases and debris resulting from the Shoemaker-Levy 9 comet and Wesley asteroid impacts in 1994 and 2009 respectively. Not only is Kφ found to be consistent with estimates for both impacts, but the eddy diffusivity found from observations appears to be scale-independent. This behaviour could be a consequence of the interaction between anisotropic turbulence and Rossby waves specific to the regime of zonostrophic macroturbulence. © 2013 Elsevier Inc."
"56293796000;36054921000;7102567936;","Response of atmospheric convection to vertical wind shear: Cloud-system-resolving simulations with parameterized large-scale circulation: Part I: Specified radiative cooling",2014,"10.1175/JAS-D-13-0320.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904893904&doi=10.1175%2fJAS-D-13-0320.1&partnerID=40&md5=2307ab8740723872d2f73d6916d9a0e4","It is well known that vertical wind shear can organize deep convective systems and greatly extend their lifetimes. Much less is known about the influence of shear on the bulk properties of tropical convection in statistical equilibrium. To address the latter question, the authors present a series of cloud-resolving simulations on a doubly periodic domain with parameterized large-scale dynamics based on the weak temperature gradient (WTG) approximation. The horizontal-mean horizontal wind is relaxed strongly in these simulations toward a simple unidirectional linear vertical shear profile in the troposphere. The strength and depth of the shear layer are varied as control parameters. Surface enthalpy fluxes are prescribed. The results fall in two distinct regimes. For weak wind shear, time-averaged rainfall decreases with shear and convection remains disorganized. For larger wind shear, rainfall increases with shear, as convection becomes organized into linear mesoscale systems. This nonmonotonic dependence of rainfall on shear is observed when the imposed surface fluxes are moderate. For larger surface fluxes, convection in the unsheared basic state is already strongly organized, but increasing wind shear still leads to increasing rainfall. In addition to surface rainfall, the impacts of shear on the parameterized large-scale vertical velocity, convective mass fluxes, cloud fraction, and momentum transport are also discussed. © 2014 American Meteorological Society."
"7401559815;7404653593;7201844203;","Water vapor and cloud feedback over the tropical oceans: Can we use ENSO as a surrogate for climate change?",1996,"10.1029/96GL02414","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030265162&doi=10.1029%2f96GL02414&partnerID=40&md5=61cf076a112f64903dd4439c914ea5ce","Based on experiments with the Goddard Earth Observing System (GEOS) global climate model, we find that the basic patterns of anomalous water vapor greenhouse effect and cloud radiative forcing during ENSO are primarily determined by the basin-wide dynamical response to large scale sea surface temperature (SST) forcing. There is no supergreenhouse effect in the sense of unstable interaction due to local thermodynamics and water vapor radiative feedback on interannual time scales. About 80% of the clear sky water vapor greenhouse sensitivity to SST deduced from ENSO anomalies are due to the transport of water vapor by the large scale circulation. The sensitivity of water vapor greenhouse effect to SST due to radiative feedback is found to be about 1.8 Wm-2/°C, much smaller than the values of 6-9 Wn-2/°C previously estimated from satellite observations from ENSO conditions. Our results show that regionally based interannual variability should not be used to infer radiative feedback sensitivity for climate change unless proper corrections are made for the effect of the large scale circulation. Copyright 1996 by the American Geophysical Union."
"56447586200;36913865000;","Relationship between middle stratiform clouds and large scale circulation over eastern China",2006,"10.1029/2005GL025615","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745699432&doi=10.1029%2f2005GL025615&partnerID=40&md5=06d5a4a1f016cf74346ec2d9ea24d4fe","Eastern China is the globally unique land region with lots of middle stratiform clouds in cold seasons. The distribution of this specific stratiform cloud is determined by three main factors, viz, relative humidity, stable stratification, and ascending motions. The large relative humidity in cold seasons provides a basic moisture condition for clouds, the ascending motions generated by the convergence in the low atmosphere and divergence in the middle troposphere provide a favorable dynamical condition for middle clouds, and the midlatitude temperature inversion provides a favorable stable stratification for the stratiform clouds. In addition, the co-effects of the divergence in the low and middle atmosphere dominate the middle stratiform cloud amount over eastern China. Copyright 2006 by the American Geophysical Union."
"7004450611;6603461810;","Variations of the cosmic rays as one of the possible links between the solar activity and the lower atmosphere",1996,"10.1016/0273-1177(95)00745-Z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029767383&doi=10.1016%2f0273-1177%2895%2900745-Z&partnerID=40&md5=3a4f5cf2ba7fe14c1963f475edc00e83","Effects of the solar and galactic cosmic ray variations on the large-scale circulation of the lower atmosphere have been investigated. The results obtained show that these effects do really exist both on the time scale of a few days and in the 11-year solar cycle. Thus, the variations of the cosmic rays, both solar and galactic, may be responsible for the changes in the large-scale atmospheric circulation associated with solar activity phenomena, the energy of cosmic particles being ∼0.1-1 GeV. A possible mechanism of the cosmic ray effects on the lower atmosphere involves changes in the atmospheric transparency and cloud cover due to the changes in the stratospheric ionization produced by the considered cosmic particles. Experimental evidence of the cosmic ray influence on the high-level cloud formation is provided."
"36908840200;7202048112;55476830600;57188966058;57111001300;6506328135;57210180554;9845949200;6602858513;13406399300;","Exploring a multiresolution approach using AMIP simulations",2015,"10.1175/JCLI-D-14-00729.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942910911&doi=10.1175%2fJCLI-D-14-00729.1&partnerID=40&md5=c75909a1f6cffa8b79441ecc22cc6b1f","This study presents a diagnosis of a multiresolution approach using the Model for Prediction Across Scales-Atmosphere (MPAS-A) for simulating regional climate. Four Atmospheric Model Intercomparison Project (AMIP) experiments were conducted for 1999-2009. In the first two experiments, MPAS-A was configured using global quasi-uniform grids at 120- and 30-km grid spacing. In the other two experiments, MPAS-A was configured using variable-resolution (VR) mesh with local refinement at 30km over North America and South America and embedded in a quasi-uniform domain at 120km elsewhere. Precipitation and related fields in the four simulations are examined to determine how well the VRs reproduce the features simulated by the globally high-resolution model in the refined domain. In previous analyses of idealized aquaplanet simulations, characteristics of the global high-resolution simulation in moist processes developed only near the boundary of the refined region. In contrast, AMIP simulations with VR grids can reproduce high-resolution characteristics across the refined domain, particularly in South America. This finding indicates the importance of finely resolved lower boundary forcings such as topography and surface heterogeneity for regional climate and demonstrates the ability of the MPAS-A VR to replicate the large-scale moisture transport as simulated in the quasi-uniform high-resolution model. Upscale effects from the high-resolution regions on a large-scale circulation outside the refined domain are observed, but the effects are mainly limited to northeastern Asia during the warm season. Together, the results support the multiresolution approach as a computationally efficient and physically consistent method formodeling regional climate. © 2015 American Meteorological Society."
"7006518289;7005965757;","Cloud albedo feedback and the super greenhouse effect in a global coupled GCM",1995,"10.1007/BF00209514","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029542789&doi=10.1007%2fBF00209514&partnerID=40&md5=f8963871e3b3a6c4b30d75a83670228b","Two competing cloud-radiative feedbacks identified in previous studies i.e., cloud albedo feedback and the super greenhouse effect, are examined in a sensitivity study with a global coupled ocean-atmosphere general circulation model. Cloud albedo feedback is strengthened in a sensitivity experiment by lowering the sea-surface temperature (SST) threshold in the specified cloud albedo feedback scheme. This simple parameterization requires coincident warm SSTs and deep convection for upper-level cloud albedos to increase. The enhanced cloud albedo feedback in the sensitivity experiment results in decreased maximum values of SST and cooler surface temperatures over most areas of the planet. There is also a cooling of the tropical troposphere with attendant global changes of atmospheric circulation reminiscent of those observed during La Niña or cold events in the Southern Oscillation. The strengthening of the cloud albedo feedback only occurs over warm tropical oceans (e.g., the western Pacific warm pool), where there is increased albedo, decreased absorbed solar radiation at the surface, stronger surface westerlies, enhanced westward currents, lower temperatures, and decreased precipitation and evaporation. However, the weakened convection over the tropical western Pacific Ocean alters the large-scale circulation in the tropics such that there is increased upper-level divergence over tropical land areas and the tropical Indian Ocean. This results in increased precipitation in those regions and intensified monsoonal regimes. The enhanced precipitation over tropical land areas produces increased clouds and albedo and wetter and cooler land surfaces. These additional contributions to decreased absorbed solar input at the surface combine with similar changes over the tropical oceans to produce the global cooling associated with the stronger cloud albedo feedback. Increased low-level moisture convergence and precipitation over the tropical Indian Ocean enhance slightly the super greenhouse effect there. But the stronger cloud albedo feedback is still the dominant effect, although cooling of SSTs in that region is less than in the tropical western Pacific Ocean. The sensitivity experiment demonstrates how a regional change of radiative forcing is quickly transmitted globally through a combination of radiative and dynamical processes in the coupled model. This study points to the uncertainties involved with the parameterization of cloud albedo and the major implications of such parameterizations concerning the maximum values of SST, global climate sensitivity, and climate change. © 1995 Springer-Verlag."
"36017879100;36077992900;56339079100;55731174900;55993981800;","Heat wave frequency variability over North America: Two distinct leading modes",2012,"10.1029/2011JD016908","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862965925&doi=10.1029%2f2011JD016908&partnerID=40&md5=c9544c78535ed40a32f86bf5086f331f","Seasonal prediction of heat wave variability is a scientific challenge and of practical importance. This study investigates the heat wave frequency (HWF) variability over North America (NA) during the past 53 summers (1958-2010). It is found that the NA HWF is dominated by two distinct modes: the interdecadal (ID) mode and the interannual (IA) mode. The ID mode primarily depicts a HWF increasing pattern over most of the NA continent except some western coastal areas. The IA mode resembles a tripole HWF anomaly pattern with three centers over the northwestern, central, and southern NA. The two leading modes have different dynamic structures and predictability sources. The ID mode is closely associated with the prior spring sea surface temperature anomaly (SSTA) in the tropical Atlantic and tropical western Pacific that can persist throughout the summer, whereas the IA mode is linked to the development of El Niño-Southern Oscillation. A simplified general circulation model is utilized to examine the possible physical mechanism. For the ID mode the tropical Atlantic SSTA can induce a Gill-type response which extends to NA, while the northwestern Pacific SSTA excites a Rossby wave train propagating eastward toward NA. These two flow patterns jointly contribute to the formation of the large-scale circulation anomalies associated with the ID mode. For the IA mode the corresponding circulation anomalies are basically similar to a Pacific-North America pattern. The subsidence associated with high-pressure anomalies warms and dries the boundary layer, inhibiting cloud formation. The resulting surface radiative heating further warms the surface. For the low-pressure anomalies the situation is just opposite. Through such processes these SSTAs can exert profound influences on the HWF variability over NA. Copyright 2012 by the American Geophysical Union."
"25823927100;7103271625;7003582587;7003554893;7401974644;7402064802;35169960300;15766838300;20435098200;57199180379;55286185400;7401936984;7005877775;57204253860;","TWP-ICE global atmospheric model intercomparison: Convection responsiveness and resolution impact",2012,"10.1029/2011JD017018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861137836&doi=10.1029%2f2011JD017018&partnerID=40&md5=a2eea2dee467a207bb6cdc4ca0501ec6","Results are presented from an intercomparison of atmospheric general circulation model (AGCM) simulations of tropical convection during the Tropical Warm Pool-International Cloud Experiment (TWP-ICE). The distinct cloud properties, precipitation, radiation, and vertical diabatic heating profiles associated with three different monsoon regimes (wet, dry, and break) from available observations are used to evaluate 9 AGCM forecasts initialized daily from realistic global analyses. All models captured well the evolution of large-scale circulation and thermodynamic fields, but cloud properties differed substantially among models. Compared with the relatively well simulated top-heavy heating structures during the wet and break period, most models had difficulty in depicting the bottom-heavy heating profiles associated with cumulus congestus during the dry period. The best performing models during this period were the ones whose convection scheme was most responsive to the free tropospheric humidity. Compared with the large impact of cloud and convective parameterizations on model cloud and precipitation characteristics, resolution has relatively minor impact on simulated cloud properties. However, one feature that was influenced by resolution in several models was the diurnal cycle of precipitation. Peaking at a different time from convective precipitation, large-scale precipitation generally increases in high resolution forecasts and modulates the total precipitation diurnal cycle. Overall, the study emphasizes the need for convection parameterizations that are more responsive to environmental conditions as well as the substantial diversity among large-scale cloud and precipitation schemes in current AGCMs. This experiment has demonstrated itself to be a very useful test bed for those developing cloud and convection schemes for AGCMs. Copyright 2012 by the American Geophysical Union."
"6602176524;6701481007;","Satellite-based climatology of Mediterranean cloud systems and their association with large-scale circulation",2006,"10.1029/2005JD006460","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33144468186&doi=10.1029%2f2005JD006460&partnerID=40&md5=8a26e5eee6f8874f1d9e99e649d56efb","The variability of Mediterranean cloud systems is investigated using 8.5 years (from (January 1987 to June 1995) of TIROS-N Operational Vertical Sounder (TOVS) observations acquired aboard the National Oceanic and Atmospheric Administration (NOAA) series of operational polar satellites. Cloud systems and troughs are automatically detected with the retrievals of the cloud top pressure (CTP) and the temperature of lower stratosphere (TLS). Observed cloud systems have a typical size of few hundred kilometres with a larger occurrence between March and October. A threefold cloud system typology reveals the presence of an upper-level anomaly for about 30% of the cloud systems in winter, 26% in spring and 7% in autumn (but 23% in October). During summer, in contrast, the forcing is very likely local, and according to the composite analysis, weakly related to upper-level anomaly. During the cold seasons (15 October to 15 April), more cloud systems are found during negative North Atlantic Oscillation (NAO) phase when the north Atlantic storm track takes its southernmost position. Consistently, more systems are observed during the Greenland Anticyclone and the Atlantic Ridge regimes, compared to the Zonal and Blocking regimes. Finally, severe precipitation events over the Alpine region are associated with a warm TLS anomaly upstream the cloud system, showing once more the impact of the upper levels on the weather over this area. Copyright 2006 by the American Geophysical Union."
"42661692800;7202048112;6506328135;6508063123;57210180554;6602858513;7406243250;","The dependence of ITCZ structure on model resolution and dynamical core in aquaplanet simulations",2014,"10.1175/JCLI-D-13-00269.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896075417&doi=10.1175%2fJCLI-D-13-00269.1&partnerID=40&md5=b9529dbe1094c5f5a0091b3aec8fddc0","Aquaplanet simulations using the Community Atmosphere Model, version 4 (CAM4), with the Model for Prediction Across Scales-Atmosphere (MPAS-A) and High-Order Method Modeling Environment (HOMME) dynamical cores and using zonally symmetric sea surface temperature (SST) structure are studied to understand the dependence of the intertropical convergence zone (ITCZ) structure on resolution and dynamical core. While all resolutions in HOMME and the low-resolution MPAS-A simulations give a single equatorial peak in zonal mean precipitation, the high-resolution MPAS-A simulations give a double ITCZ with precipitation peaking around 28-38 on either side of the equator. This study reveals that the structure of ITCZ is dependent on the feedbacks between convection and large-scale circulation. It is shown that the difference in specific humidity betweenHOMMEandMPAS-A can lead to different latitudinal distributions of the convective available potential energy (CAPE) by influencing latent heat release by clouds and the upper-tropospheric temperature. With lower specific humidity, the high-resolution MPAS-A simulation has CAPE increasing away from the equator that enhances convection away from the equator and, through a positive feedback on the circulation, results in a double ITCZ structure. In addition, it is shown that the dominance of antisymmetric waves in the model is not enough to cause double ITCZ, and the lateral extent of equatorial waves does not play an important role in determining the width of the ITCZ but rather the latter may influence the former. © 2014 American Meteorological Society."
"6701718281;6505932008;7202899330;54983414800;","Changes in the interaction between tropical convection, radiation, and the large-scale circulation in a warming environment",2012,"10.1175/2011JCLI4167.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856948197&doi=10.1175%2f2011JCLI4167.1&partnerID=40&md5=392cf36094b5b7cdebc95a3f221625a6","This paper explores the response of the tropical hydrologic cycle to surface warming through the lens of large-domain cloud-system-resolving model experiments run in a radiative-convective equilibrium framework. Simulations are run for 55 days and are driven with fixed insolation and constant sea surface temparatures (SSTs) of 298 K, 300 K, and 302 K. In each experiment, convection organizes into coherent regions of large-scale ascent separated by areas with relatively clear air and troposphere-deep descent. Aspects of the simulations correspond to observed features of the tropical climate system, including the transition to large precipitation rates above a critical value of total column water vapor, and an increase in convective intensity with SST amidst weakening of the large-scale overturning circulation. However, the authors also find notable changes to the interaction between convection and the environment as the surface warms. In particular, organized convection in simulations with SSTs of 298 and 300 K is inhibited by the presence of a strong midtropospheric stable layer and dry upper troposphere. As a result, there is a decrease in the vigor of deep convection and an increase in stratiform precipitation fraction with an increase in SST from 298 to 300 K. With an increase in SST to 302 K, moistening of the middletroposphere and increase in lower-tropospheric buoyancy serve to overcome these limitations, leading to an overall increase in convective intensity and larger increase in upper-tropospheric relative humidity. The authors conclude that, while convective intensity increases with SST, the aggregate nature of deep convection is strongly affected by the details of the thermodynamic environment in which it develops. In particular, the positive feedback between increasing SST and a moistening upper troposphere found in the simulations, operates as a nonmonotonic function of SST and is modulated by a complex interaction between deep convection and the environmental relative humidity and static stability profile. The results suggest that projected changes in convection that assume a monotonic dependence on SST may constitute an oversimplification. © 2012 American Meteorological Society."
"6602908667;14520108800;7103201242;","A diagnostic study on interactions between atmospheric thermodynamic structure and cumulus convection over the tropical western Pacific Ocean and over the Indochina Peninsula",2006,"10.2151/jmsj.84A.151","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748443582&doi=10.2151%2fjmsj.84A.151&partnerID=40&md5=14e2afd7e6f70a0b2a507d500fa68b50","Interactions between the convective activity and the atmospheric thermodynamic structures are analyzed utilizing upper-air rawinsonde observations obtained by R/V Mirai, R/V Kaiyo, R/V Natsushima, of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) over the western tropical Pacific Ocean, and those over three GEWEX Asian Monsoon Experiment (GAME) stations: Chiang Mai, Non Khai, and Ubon Ratchathani. Special emphases are placed on understanding the correlation between convection and the atmospheric thermodynamic structures in relation to the recent findings of trimodal cloud levels over the warm ocean (e.g., Johnson et al. 1999) and to the cloud diagnostics proposed by Raymond and Blyth (1992). We first examine the relationships between a convection index and thermodynamic structure indices. A large correlation is found between the convective activity and lower-tropospheric (600-800 hPa) humidity, while there is no significant correlation between the convective activity and Convective Available Potential Energy (CAPE) or Convective Inhibition (CIN). Next, we apply a cloud diagnostic model introduced by Raymond and Blyth (1992) (referred to as RB92) to the observed profiles. As a result, it is shown that there are fundamentally 3 peaks of detrainment levels, which are lower-troposphere (near 900 hPa), mid-troposphere (near 450 hPa), and upper-troposphere (near 150 hPa), over ocean as well as over land. In the soundings over ocean, when the lower-troposphere (600-800 hPa) is dry, there is a tendency for simultaneous existence of stable layers both in the lower-troposphere and in the mid-troposphere. Such atmospheric thermodynamic structure is diagnosed as favorable for strengthened detrainments in the low- and mid-troposphere and weakened in the upper-troposphere. Finally, meridional winds are composited to the north and to the south of the maximum convective activity in the Inter Tropical Convergence Zone (ITCZ) region, respectively, over the tropical western Pacific Ocean. It is confirmed with upper-air soundings that there is a significant meridional divergence near the melting layer level in the mid-troposhere around 500-600 hPa and a significant meridional convergece near 350-400 hPa, in addition to the lower-tropospheric convergence and the upper-tropospheric divergence of the local Hadley Circulation. These additional circulations in the mid-troposphere are consistent with detrainment profiles diagnosed for observed atmospheric profiles utilizing RB92 cloud model. After all, it is strongly suggested that the cloud microphysics, such as melting and freezing, play significant roles in determining the large-scale circulation. © 2006, Meteorological Society of Japan."
"7006198994;","An intraseasonal oscillation composite life cycle in the NCAR CCM3.6 with modified convection",2002,"10.1175/1520-0442(2002)015<0964:AIOCLC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036572602&doi=10.1175%2f1520-0442%282002%29015%3c0964%3aAIOCLC%3e2.0.CO%3b2&partnerID=40&md5=b8d17e5f1ee24ea9336e678d1498e89a","The NCAR CCM3.6 with microphysics of clouds with relaxed Arakawa-Schubert convection produces an intraseasonal oscillation that is highly dependent on lower-tropospheric moistening by surface convergence. Model intraseasonal convection is most highly correlated with surface convergence at zero lag, causing enhanced convection to be associated with 850-mb easterly anomalies, where surface convergence is strongest. The tendency for surface convergence to maximize within 850-mb easterly anomalies is consistent with meridional frictional convergence into equatorial surface pressure troughs associated with planetary-scale tropical wave circulations. Anomalous vertical advection associated with meridional surface convergence influences model convection by moistening the lower troposphere. Observed Madden-Julian oscillation (MJO) convection and lower-tropospheric specific humidity are also significantly correlated with surface convergence, although correlations are weaker than in the model, and convergence leads convection anomalies. Observed MJO enhanced convection tends to fall closer to the point of maximum convergence in the 850-mb equatorial zonal wind anomaly field. Although surface convergence appears important for both observed and model intraseasonal convection, the significant differences between observed and modeled intraseasonal variability suggest that interactions between convection and the large-scale circulation in the model are not completely realistic. The wind-induced surface heat exchange (WISHE) mechanism cannot explain the preference for model intraseasonal enhanced convection to coincide with 850-mb easterly anomalies. When the effects of WISHE are removed by fixing the surface wind speed in the calculation of surface latent heat fluxes, the phase relationship between model intraseasonal wind and convection anomalies does not change. Removing WISHE may produce a more robust model intraseasonal oscillation, however. Model intraseasonal oscillation circulation features are better defined, and spectral power in the MJO band is more prominent when WISHE is removed."
"24074386100;57204297539;7404441387;6701623059;57202245193;7102707599;6603760227;7201903057;15319527800;36679171400;7004154240;55680480300;57203378018;7801678853;","Climate drivers linked to changing seasonality of Alaska Coastal tundra vegetation productivity",2015,"10.1175/EI-D-15-0013.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949895066&doi=10.1175%2fEI-D-15-0013.1&partnerID=40&md5=8d85e49f05d8e7714a2d04d789abf5d8","The mechanisms driving trends and variability of the normalized difference vegetation index (NDVI) for tundra in Alaska along the Beaufort, east Chukchi, and east Bering Seas for 1982–2013 are evaluated in the context of remote sensing, reanalysis, and meteorological station data as well as regional modeling. Over the entire season the tundra vegetation continues to green; however, biweekly NDVI has declined during the early part of the growing season in all of the Alaskan tundra domains. These springtime declines coincide with increased snow depth in spring documented in northern Alaska. The tundra region generally has warmed over the summer but intraseasonal analysis shows a decline in midsummer land surface temperatures. The midsummer cooling is consistent with recent large-scale circulation changes characterized by lower sea level pressures, which favor increased cloud cover. In northern Alaska, the sea-breeze circulation is strengthened with an increase in atmospheric moisture/cloudiness inland when the land surface is warmed in a regional model, suggesting the potential for increased vegetation to feedback onto the atmospheric circulation that could reduce midsummer temperatures. This study shows that both large- and local-scale climate drivers likely play a role in the observed seasonality of NDVI trends. © 2015."
"7003460432;16445063600;55912769000;56308032100;56221423400;24331185200;7402989545;8661012100;7003683808;7102011023;","Variability of large-scale atmospheric circulation indices for the northern hemisphere during the past 100 years",2009,"10.1127/0941-2948/2009/0389","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949391434&doi=10.1127%2f0941-2948%2f2009%2f0389&partnerID=40&md5=794fc4f833ef00b36f5ec994dc8886c8","We present an analysis of the large-scale atmospheric circulation variability since 1900 based on various circulation indices. They represent the main features of the zonal mean circulation in the northern hemisphere in boreal winter (such as the Hadley circulation, the subtropical jet, and the polar vortex in the lower stratosphere) as well as aspects of the regional and large-scale circulation (the Pacific Walker Circulation, the Indian monsoon, the North Atlantic Oscillation, NAO, and the Pacific North American pattern, PNA). For the past decades we calculate the indices from different reanalyses (NCEP/NCAR, ERA-40, JRA-25, ERAInterim). For the first half of the 20 th century the indices are statistically reconstructed based on historical upper-air and surface data as well as calculated from the Twentieth Century Reanalysis. The indices from all these observation-based data sets are compared to indices calculated from a 9-member ensemble of ""all forcings"" simulations performed with the chemistry-climate model SOCOL. After discussing the agreement among different data products, we analyse the interannual-to-decadal variability of the indices in the context of possible driving factors, such as El Niño/Southern Oscillation (ENSO), volcanic eruptions, and solar activity. The interannual variability of the Hadley cell strength, the subtropical jet strength, or the PNA is well reproduced by the model ensemble mean, i.e., it is predictable in the context of the specified forcings. The source of this predictability is mainly related to ENSO (or more generally, tropical sea-surface temperatures). For other indices such as the strength of the stratospheric polar vortex, the NAO, or the poleward extent of the Hadley cell the correlations between observations and model ensemble mean are much lower, but so are the correlations within the model ensemble. Multidecadal variability and trends in the individual series are discussed in the context of the underlying anthropogenic and natural forcings. While consistent trends were found for some of the indices, results also indicate that care should be taken when analysing trends in reconstructions or reanalysis data. © by Gebrüder Borntraeger 2009."
"36862677400;7202145115;","Interactions among cloud, water vapor, radiation, and large-scale circulation in the tropical climate. Part I: Sensitivity to uniform sea surface temperature changes",2003,"10.1175/1520-0442-16.10.1425","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038128200&doi=10.1175%2f1520-0442-16.10.1425&partnerID=40&md5=4fd899fd3cb01714efe20d919927dcf8","The responses of tropical clouds and water vapor to SST variations are investigated with simple numerical experiments. The fifth-generation Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) Mesoscale Model is used with doubly periodic boundary conditions and a uniform constant sea surface temperature (SST). The SST is varied and the equilibrium statistics of cloud properties, water vapor, and circulation at different temperatures are compared. The top of the atmosphere (TOA) radiative fluxes have the same sensitivities to SST as in observations averaged from 20°N to 20°S over the Pacific, suggesting that the model sensitivities are realistic. As the SST increases, the temperature profile approximately follows a moist-adiabatic lapse rate. The rain rate and cloud ice amounts increase with SST. The average relative humidity profile stays approximately constant, but the upper-tropospheric relative humidity increases slightly with SST. The clear-sky mean temperature and water vapor feedbacks have similar magnitudes to each other and opposite signs. The net clear-sky feedback is thus about equal to the lapse rate feedback, which is about -2 W m-2 K-1. The clear-sky outgoing longwave radiation (OLR) thus increases with SST, but the high cloud-top temperature is almost constant with SST, and the high cloud amount increases with SST. The result of these three effects is an increase of cloud longwave forcing with SST and a mean OLR that is almost independent of SST. The high cloud albedo remains almost constant with increasing SST, but the increase in high cloud area causes a negative shortwave cloud radiative forcing feedback, which partly cancels the longwave cloud feedback. The net radiation decreases slightly with SST, giving a small net negative feedback, implying a stable, but very sensitive climate."
"56537463000;7410255460;7004479957;","Three-Dimensional Week-Long Simulations of TOGA COARE Convective Systems Using the MM5 Mesoscale Model",1999,"10.1175/1520-0469(1999)056<2326:TDWLSO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032761941&doi=10.1175%2f1520-0469%281999%29056%3c2326%3aTDWLSO%3e2.0.CO%3b2&partnerID=40&md5=ecdad8878722fd131353958d8ccc996b","A three-dimensional nonhydrostatic mesoscale model, the Pennsylvania State University/National Center for Atmospheric Research mesoscale model (MM5), is used to simulate the evolution of convective systems over the intensive flux array (IFA) during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment, during 19-26 December 1992. The model is driven by a time-varying ""IFA mean forcing"" based on the average advcctive tendencies of temperature and moisture over the IFA. The domain-averaged horizontal wind is kept close to the observed IFA mean using Newtonian relaxation. Periodic lateral boundary conditions are imposed. Simulations with three horizontal grid spacings, 2, 15, and 60 km, are conducted. With 15- and 60-km resolution, subgrid-scale cumulus convection is parameterized while mesoscale convective organization is explicitly resolved over a (600 km)! domain. With 2-km resolution, convection is fully resolved over a (210 km)2 domain. Despite their different horizontal resolution and different treatment of moist convection, the simulations all produce very similar temporal variability in domain-averaged temperature and relative humidity profiles. They also closely resemble each other in various statistical properties of convective systems. A comprehensive comparison of the 15- and 2-km model results against observations is performed. The domain-averaged cloud amount and precipitation agree well with observations. Some shortcomings are noted. During suppressed convective periods, the model tends to have greater areal coverage of rainfall and more cirrus anvil clouds than observed. Over the 8-day period, both models produce mean temperature drifts about 2 K colder than observed. A histogram of modeled cloud-top temperature captures the observed breaks between convective episodes but shows excessive and persistent cold cirrus clouds. A radar reflectivity histogram shows that the 15-km model slightly overpredicts radar reflectivity and that the 2-km model has too high and temporally homogeneous reflectivities. The modelsimulated cloud cluster size is somewhat smaller than the observed. Surface sensible and latent heat fluxes are overestimated by 50%-100%, due both to shortcomings in the surface flux calculations in the model and modelproduced mean temperature and humidity biases. Downwelling solar flux at the surface is underestimated mainly because of the simple shortwave radiation scheme. This study suggests that large-domain simulations using the MM5 with 15-km resolution can be a useful tool for further study of tropical convective organization and its interaction with large-scale circulation. © 1999 American Meteorological Society."
"7201605742;","A numerical experiment of the interaction between cumulus convection and larger-scale motion",1975,"10.2467/mripapers1950.26.3_63","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84998307049&doi=10.2467%2fmripapers1950.26.3_63&partnerID=40&md5=ee4a9f2e09615a719ca732c3fe5a38e0","As an approach to study the interaction between the cumulus convection and the large-scale motion, a numerical experiment is performed with the use of a sufficiently fine space resolution by which the behavior of individual cumulus clouds as well as the evolution of large-scale motions can be explicitly described. For computational limitations a rectilinear two-dimensional model is adopted in which both cloud-scale and large-scale motions are uniform in one horizontal direction. We deal with a meso-like disturbance such that the horizontal scale of a large-scale ascending area where cumulus clouds are formed is only several tens of kilometers. Some cloud-microphysical processes such as autoconversion, collection and so on are incorporated, using parameterizations which have been adopted in many numerical experiments on precipitating clouds in recent years. Buoyancy perturbations are given initially so that cumulus clouds may be initiated and thereby a large-scale meridional circulation is induced. The time integration indicates that cumulus clouds are formed one after another in the large-scale convergence field and that the large-scale circulation is intensified and maintained by the effects of cumulus clouds for a period of about 15 hours. The time variation of the large-scale field and the processes of formation, growth and decay of many individual cumulus clouds are presented and discussed. © 1975, Japan Meteorological Agency. All rights reserved."
"55868743000;56158622800;55802246600;24168479200;35206916200;","Effects of aerosols on autumn precipitation over Mid-Eastern China",2014,"10.16555/j.1006-8775.2014.03.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84979768192&doi=10.16555%2fj.1006-8775.2014.03.007&partnerID=40&md5=b5275b6c5bc274f113b00fb65a9665cd","Long-term observational data indicated a decreasing trend for the amount of autumn precipitation (i.e. 54.3 mm per decade) over Mid-Eastern China, especially after the 1980s (~ 5.6% per decade). To examine the cause of the decreasing trend, the mechanisms associated with the change of autumn precipitation were investigated from the perspective of water vapor transportation, atmospheric stability and cloud microphysics. Results show that the decrease of convective available potential energy (i.e. 12.81 J kg-1/ decade) and change of cloud microphysics, which were closely related to the increase of aerosol loading during the past twenty years, were the two primary factors responsible for the decrease of autumn precipitation. Our results showed that increased aerosol could enhance the atmospheric stability thus weaken the convection. Meanwhile, more aerosols also led to a significant decline of raindrop concentration and to a delay of raindrop formation because of smaller size of cloud droplets. Thus, increased aerosols produced by air pollution could be one of the major reasons for the decrease of autumn precipitation. Furthermore, we found that the aerosol effects on precipitation in autumn was more significant than in other seasons, partly due to relatively more stable synoptic systems in autumn. The impact of large-scale circulation dominant in autumn and the dynamic influence on precipitation was more important than the thermodynamic activity. © 2014, Journal of Tropical Meteorology Press. All rights reserved."
"56032511300;","Effect of aerosol on circulations and precipitation in deep convective clouds",2012,"10.1175/JAS-D-11-0111.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864839520&doi=10.1175%2fJAS-D-11-0111.1&partnerID=40&md5=17c35afbe821acef4d78fc964520a925","This study examines the effect of a mesoscale perturbation of aerosol on a larger-scale cloud system driven by deep convective clouds. An aerosol-perturbed domain of size 120 km is prescribed in the middle of the larger-scale domain of size 1100 km. Aerosol perturbations in the mesoscale domain result in an intensification of convection in a mesoscale convective system (MCS). This leads to an intensification of the larger-scale circulations, which in turn leads to an intensification of the larger-scale subsidence. While the invigorated convection enhances precipitation in the MCS, the intensified larger-scale subsidence acts to increase the larger-scale stability and thus to suppress convection and precipitation in the larger-scale domain. The suppression of precipitation in the larger-scale domain outweighs the enhancement of precipitation in the mesoscale domain, leading to suppressed precipitation over the entire domain. The ramifications of aerosol perturbations therefore need to be considered on scales much larger than the scale of the perturbation. © 2012 American Meteorological Society."
"9535769800;25647939800;7401945370;57212988186;13404664500;","Multi-scale organization of convection in a global numerical simulation of the December 2006 MJO event using explicit moist processes",2009,"10.2151/jmsj.87.335","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68949099880&doi=10.2151%2fjmsj.87.335&partnerID=40&md5=a390e810e3272bf74f963bb790f47650","Multi-scale convective organization in a Madden-Julian Oscillation (MJO) event that occurred during December 2006 and January 2007 was studied by global numerical experiments using explicit moist physics. The simulations successfully reproduced the eastward-propagating (̃5 m s -1) convective envelope of the MJO with a zonal scale of 5000-10,000 km, which included eastward-propagating (10-15 m s -1) disturbances (EPDs) and westward-propagating cloud clusters (CCs) with zonal scales of 1000-2000 km and O (100 km), respectively. The simulated EPDs were composed of CCs, with new clusters growing to the east of older ones. When the large-scale circulation associated with the MJO intensified, the EPDs formed well-organized squall-type clusters (rainbands). The dynamical structure of the simulated EPDs was reminiscent of moist Kelvin waves. Relevance of westward-propagating wave disturbances including cross-equatorial flow to convective organization in the EPDs was also suggested. © 2009, Meteorological Society of Japan."
"7202048112;7202152636;55802246600;35187572900;","Evaluation of regional climate simulations of the 1998 and 1999 East Asian summer monsoon using the GAME/HUBEX observational data",2004,"10.2151/jmsj.82.1695","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13844253667&doi=10.2151%2fjmsj.82.1695&partnerID=40&md5=615b1a4a5d61c6c41211263b78ca7fa8","A regional climate model based on the Penn State/NCAR Mesoscale Model (MM5) was used to simulate the 1998 and 1999 East Asian summer monsoon conditions. Simulations were performed for 1 April-31 August of each year, with initial and lateral boundary conditions provided by the ECMWF analysis. Observations from the 1998 and 1999 GAME/HUBEX experiments were used to evaluate the regional climate simulations. Based on observations, large differences can be found between the 1998 and 1999 meteorological conditions and surface energy budgets at the Shouxian station during the IOPs, with much higher rain intensity but only slightly higher rain frequency in 1998 than 1999. For 1998, although the regional climate model was able to reproduce the general spatial distribution of monthly mean rainfall quite well during the summer monsoon season, large discrepancies can be found in comparing the observed and simulated surface climate and energy fluxes in the HUBEX region. By using Four Dimensional Data Assimilation (FDDA) technique, which constrains the simulated large-scale circulation with observations from 21 soundings in the HUBEX α-scale region, both the root mean square error and mean bias in rainfall were greatly reduced. The improvements in simulating rainfall were related to both reduction in errors of precipitation amount and timing. In the control simulation, a mean bias of -63 W/M2 (-36%) was found in the simulated surface net radiation at Shouxian, which suggest large errors in simulating clouds in the region. With FDDA, the bias was significantly reduced to -23 W/ m2 (-13%), with corresponding reduction of bias in the latent heat flux. This suggests that at least part of the model bias in simulating net radiation is related to errors in simulating the large-scale circulation, which can affect cloud amount and vertical distribution. Comparing the 1998 and 1999 simulations, both without FDDA, smaller biases were found in the surface fluxes during 1999. Percentage biases in the net radiation and latent heat flux were -18% and -33% in 1999 and -36% and -50% in 1998 respectively. Based on observations, large differences in the net surface radiation, and small differences in cloud fraction between the two years suggest that cloud optical depth and/or vertical distribution were very different, with more cloudy conditions observed during 1999. Although the 1999 simulations were sensitive to the cumulus convective parameterizations (Grell scheme versus Kain-Fritsch scheme) as shown by the sensitivity experiments, the large differences in simulation skill between the 1998 and 1999 cases, regardless of the convection schemes used, suggest possible dependence of model errors on cloud properties that deserve further investigations. © 2004, Meteorological Society of Japan."
"23094149200;7003278104;9249239700;24485218400;","On the annual cycle, variability, and correlations of oceanic low-topped clouds with large-scale circulation using aqua MODIS and ERA-interim",2012,"10.1175/JCLI-D-11-00478.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867194292&doi=10.1175%2fJCLI-D-11-00478.1&partnerID=40&md5=f2ec8537df82285cfc7d61367887e3d9","Eight years of Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) level-3 cloud data in conjunction with collocated Interim ECMWF Re-Analysis are used to investigate relationships between isolated low-topped cloud fraction (LCF) and dynamics/thermodynamics versus averaging time scale. Correlation coefficients between LCF and 2SST exceed 0.70 over 56%of ocean regions from 25 oS to 25 oN for 90-day running means and exceed 0.70 between LCF and 500-hPa omega ( ω500) for over one-third of oceans from 50 oS to 50 oN. Correlations increase most dramatically by increasing the averaging time scale from 1 day to about 15, owing to the large LCF synoptic variability and random effects that are suppressed by averaging. In five regions selected with monthly mean SSTs between 291 and 303 K, SST decreases by 20.13K% -1 low-cloud cover increase. Monthly LCF is also correlated with estimated inversion strength (EIS), which is SST dominated in low latitudes and free tropospheric temperature dominated in the northeast Atlantic, Pacific, and midlatitudes, though SST and stability are poor predictors of LCF over the southern oceans. Where the fraction of variance explained by the annual LCF harmonic is high, maximum LCF tends to leadminimum SST by ~15-30 days such that clouds can amplify the SST annual cycle, especially when LCF maxima coexist with insolation minima. Monthly mean LCF tends to scale with ω500 exponentially over the convective margins and offshore of the Pacific Northwest, but daily climatology relationships indicate that LCF levels off and even diminishes for ω500 &gt;0.05 Pa s -1, suggesting a limit through, perhaps, a too strong suppression of boundary layer heights. This suggests the need for dynamic-regime analysis in diagnosing low cloud/circulation feedbacks. © 2012 American Meteorological Society."
"24464437300;12765807300;7003627515;57210198318;","Comparison of the meteorology and surface energy balance at Storbreen and Midtdalsbreen, two glaciers in southern Norway",2009,"10.5194/tc-3-57-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70749113520&doi=10.5194%2ftc-3-57-2009&partnerID=40&md5=64122c503052fd9ecf5b4461c5bf265b","We compare 5 years of meteorological records from automatic weather stations (AWSs) on Storbreen and Midtdalsbreen, two glaciers in southern Norway, located approximately 120 km apart. The records are obtained from identical AWSs with an altitude difference of 120 m and cover the period September 2001 to September 2006. Air temperature at the AWS locations is found to be highly correlated, even with the seasonal cycle removed. The most striking difference between the two sites is the difference in wind climate. Midtdalsbreen is much more under influence of the large-scale circulation with wind speeds on average a factor 1.75 higher. On Storbreen, weaker katabatic winds are dominant. The main melt season is from May to September at both locations. During the melt season, incoming and net solar radiation are larger on Midtdalsbreen, whereas incoming and net longwave radiation are larger on Storbreen, primarily caused by thicker clouds on the latter. The turbulent fluxes are a factor 1.7 larger on Midtdalsbreen, mainly due to the higher wind speeds. Inter-daily fluctuations in the surface energy fluxes are very similar at the AWS sites. On average, melt energy is a factor 1.3 larger on Midtdalsbreen, a result of both larger net radiation and larger turbulent fluxes. The relative contribution of net radiation to surface melt is larger on Storbreen (76%) than on Midtdalsbreen (66%). As winter snow depth at the two locations is comparable in most years, the larger amount of melt energy results in an earlier disappearance of the snowpack on Midtdalsbreen and 70% more ice melt than on Storbreen. We compare the relative and absolute values of the energy fluxes on Storbreen and Midtdalsbreen with reported values for glaciers at similar latitudes. Furthermore, a comparison is made with meteorological variables measured at two nearby weather stations, showing that on-site measurements are essential for an accurate calculation of the surface energy balance and melt rate. © 2009 Author(s)."
"7410041005;7202899330;7005126327;7004678728;7103278864;7004485096;7003865921;56978385600;25227465100;","Association of Antarctic polar stratospheric cloud formation on tropospheric cloud systems",2008,"10.1029/2008GL034209","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53749089272&doi=10.1029%2f2008GL034209&partnerID=40&md5=1bf653e54d92ee6766d06bfc71a4e87e","The formation of polar stratospheric clouds (PSCs) is critical to the development of polar ozone loss. However, the mechanisms of PSC formation remain poorly understood, which affects ozone loss models. Here, based on observations by the NASA A-train satellites, we show that 66% ± 16% and 52% ± 17% of PSCs over west and east Antarctica during the period June-October 2006 were associated with deep tropospheric cloud systems, with maximum depths exceeding 7 km. The development of such deep tropospheric cloud systems should cool the lower stratosphere through adiabatic and radiative processes, favoring PSC development. These deep systems also transport lower tropospheric air into the upper troposphere and lower stratosphere. These new findings suggest that Antarctic PSC formation is closely connected to tropospheric meteorology and thus governed by synoptic scale dynamics, local topography, and large-scale circulation. More dedicated studies are still needed to better understand Antarctic PSC formation. Copyright 2008 by the American Geophysical Union."
"6603139566;7005256983;","Modulation of the Great Plains low-level jet and moisture transports by orography and large-scale circulations",2003,"10.1029/2002jd003005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342289983&doi=10.1029%2f2002jd003005&partnerID=40&md5=5c33dfcf899772026b8c17b75968acd2","This paper describes orographic processes that modulate the Great Plains low-level jet (LLJ) and related hydrology of the Mississippi River basin. Mechanical flow deflection by the Rocky Mountains is diagnosed in 50 years of monthly averaged National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) Reanalysis fields and in a series of integrations using a primitive equation version of the Utah Global Model (UGM). Although the mountain profiles are fixed over periods of short-to medium-range climate changes, their influence on the LLJ is not stationary because evolving ambient flows produce changing LLJ responses. Ensembles of medium-range forecasts are made for the 1993 U.S. floods and for the 1988 U.S. drought. The forecasts distinguish some of the observed precipitation differences between these years, but the magnitude of the differences is underestimated. Seasonal and longer-term changes of the ambient flow occur on large scales, while the response of the LLJ occurs on smaller scales that may promote cloud generation and precipitation. Month-long simulations with monthly averaged conditions suggest that the Great Plains LLJ is a component of the large-scale circulation associated with the topography of the western United States. Orography thus provides a scale transfer mechanism that focuses global-scale features into the regional-scale responses. These are relevant to precipitation distribution and to moisture budgets of the larger individual river basins comprising the GCIP domain. A theoretical interpretation of the large-scale, mechanical influence of orography on surrounding low-level circulations is proposed. Copyright 2003 by the American Geophysical Union."
"55627873255;57014496500;55980179900;57204391699;55727776500;56997948800;57204391899;57204391463;","Evaluation and intercomparison of high-resolution satellite precipitation estimates-GPM, TRMM, and CMORPH in the Tianshan Mountain Area",2018,"10.3390/rs10101543","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055457698&doi=10.3390%2frs10101543&partnerID=40&md5=aae63bd55882ca206943c47b8cea64a3","With high resolution and wide coverage, satellite precipitation products like Global Precipitation Measurement (GPM) could support hydrological/ecological research in the Tianshan Mountains, where the spatial heterogeneity of precipitation is high, but where rain gauges are sparse and unevenly distributed. Based on observations from 46 stations from 2014-2015, we evaluated the accuracies of three satellite precipitation products: GPM, Tropical Rainfall Measurement Mission (TRMM) 3B42, and the Climate Prediction Center morphing technique (CMORPH), in the Tianshan Mountains. The satellite estimates significantly correlated with the observations. They showed a northwest-southeast precipitation gradient that reflected the effects of large-scale circulations and a characteristic seasonal precipitation gradient that matched the observed regional precipitation pattern. With the highest correlation (R = 0.51), the lowest error (RMSE = 0.85 mm/day), and the smallest bias (1.27%), GPM outperformed TRMM and CMORPH in estimating daily precipitation. It performed the best at both regional and sub-regional scales and in low and mid-elevations. GPM had relatively balanced performances across all seasons, while CMORPH had significant biases in summer (46.43%) and winter (-22.93%), and TRMM performed extremely poorly in spring (R = 0.31; RMSE = 1.15 mm/day; bias = -20.29%). GPM also performed the best in detecting precipitation events, especially light and moderate precipitation, possibly due to the newly added Ka-band and high-frequency microwave channels. It successfully detected 62.09% of the precipitation events that exceeded 0.5 mm/day. However, its ability to estimate severe rainfall has not been improved as expected. Like other satellite products, GPM had the highest RMSE and bias in summer, suggesting limitations in its way of representing small-scale precipitation systems and isolated deep convection. It also underestimated the precipitation in high-elevation regions by 16%, suggesting the difficulties of capturing the orographic enhancement of rainfall associated with cap clouds and feeder-seeder cloud interactions over ridges. These findings suggest that GPM may outperform its predecessors in the mid-/high-latitude dryland, but not the tropical mountainous areas. With the advantage of high resolution and improved accuracy, the GPM creates new opportunities for understanding the precipitation pattern across the complex terrains of the Tianshan Mountains, and it could improve hydrological/ecological research in the area. © 2018 by the authors."
"55519994900;23991212200;55411439700;","The response of US summer rainfall to quadrupled CO2 climate change in conventional and superparameterized versions of the NCAR community atmosphere model",2015,"10.1002/2014MS000306","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930677124&doi=10.1002%2f2014MS000306&partnerID=40&md5=232bc47ef7f3dc27c6012b6a2e7845a8","Observations and regional climate modeling (RCM) studies demonstrate that global climate models (GCMs) are unreliable for predicting changes in extreme precipitation. Yet RCM climate change simulations are subject to boundary conditions provided by GCMs and do not interact with large-scale dynamical feedbacks that may be critical to the overall regional response. Limitations of both global and regional modeling approaches contribute significant uncertainty to future rainfall projections. Progress requires a modeling framework capable of capturing the observed regional-scale variability of rainfall intensity without sacrificing planetary scales. Here the United States summer rainfall response to quadrupled CO2 climate change is investigated using conventional (CAM) and superparameterized (SPCAM) versions of the NCAR Community Atmosphere Model. The superparameterization approach, in which cloud-resolving model arrays are embedded in GCM grid columns, improves rainfall statistics and convective variability in global simulations. A set of 5 year time-slice simulations, with prescribed sea surface temperature and sea ice boundary conditions harvested from preindustrial and abrupt four times CO2 coupled Community Earth System Model (CESM/CAM) simulations, are compared for CAM and SPCAM. The two models produce very different changes in mean precipitation patterns, which develop from differences in large-scale circulation anomalies associated with the planetary-scale response to warming. CAM shows a small decrease in overall rainfall intensity, with an increased contribution from the weaker parameterized convection and a decrease from large-scale precipitation. SPCAM has the opposite response, a significant shift in rainfall occurrence toward higher precipitation rates including more intense propagating Central United States mesoscale convective systems in a four times CO2 climate. Key Points Large-scale dynamics are critical to regional rainfall climate change responses Superparameterization captures expected increases in rain and storm intensity Extreme rain may be decoupled from key climate change drivers in standard GCMs © 2014. American Geophysical Union. All Rights Reserved."
"55545874600;7005446873;6507112497;16426378500;55324953800;7102567936;36054921000;57204886915;8977001000;12761291000;19934163800;57000268800;6603566335;35369402500;","Intercomparison of methods of coupling between convection and large-scale circulation: 1. Comparison over uniform surface conditions",2015,"10.1002/2015MS000468","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959539835&doi=10.1002%2f2015MS000468&partnerID=40&md5=7f4bf8e5f23a7b614f6aee5ac128f19d","As part of an international intercomparison project, a set of single-column models (SCMs) and cloud-resolving models (CRMs) are run under the weak-temperature gradient (WTG) method and the damped gravity wave (DGW) method. For each model, the implementation of the WTG or DGW method involves a simulated column which is coupled to a reference state defined with profiles obtained from the same model in radiative-convective equilibrium. The simulated column has the same surface conditions as the reference state and is initialized with profiles from the reference state. We performed systematic comparison of the behavior of different models under a consistent implementation of the WTG method and the DGW method and systematic comparison of the WTG and DGW methods in models with different physics and numerics. CRMs and SCMs produce a variety of behaviors under both WTG and DGW methods. Some of the models reproduce the reference state while others sustain a large-scale circulation which results in either substantially lower or higher precipitation compared to the value of the reference state. CRMs show a fairly linear relationship between precipitation and circulation strength. SCMs display a wider range of behaviors than CRMs. Some SCMs under the WTG method produce zero precipitation. Within an individual SCM, a DGW simulation and a corresponding WTG simulation can produce different signed circulation. When initialized with a dry troposphere, DGW simulations always result in a precipitating equilibrium state. The greatest sensitivities to the initial moisture conditions occur for multiple stable equilibria in some WTG simulations, corresponding to either a dry equilibrium state when initialized as dry or a precipitating equilibrium state when initialized as moist. Multiple equilibria are seen in more WTG simulations for higher SST. In some models, the existence of multiple equilibria is sensitive to some parameters in the WTG calculations. © 2015. The Authors."
"35119304200;7005804830;","Lightning flash rates as an indicator of tropical cyclone genesis in the Eastern North Pacific",2009,"10.1175/2009MWR2822.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70449102418&doi=10.1175%2f2009MWR2822.1&partnerID=40&md5=d22f64a56be69e844b6e73b54053b372","Lightning flashes in convective tropical clusters of the eastern North Pacific Ocean are detected by the Long-Range Lightning Detection Network and are analyzed for temporal patterns in electrical activity. The rates of lightning flash discharge in the 2006 season are analyzed for both tropical cyclones and nondeveloping cloud clusters to 1) determine if there is a difference in the convective activity of these two populations and 2) find a level of electrical activity that constitutes development in a particular system. Convective activity is associated with tropical cyclogenesis and thus we use the rate of electrical discharge as a proxy for convection associated with the likelihood of organization of individual cloud clusters into a tropical depression strength system. On the basis of the rates of lightning flashes in the cloud clusters, four levels of development are defined, ranging from non- and partially developing to fully developing cloud clusters. The levels of development are further supported by the analysis of other remotely sensed observations, such as surface scatterometer winds, that allow for the description of the mesoscale and large-scale circulation patterns in which the cloud clusters are embedded. It is found that lightning flash rates distinguish those cloud clusters that do not fully develop into tropical depressions from those that do. Receiver operating characteristic curves for these groupings are calculated, and a level of flash rate can be chosen that gives a probability of detection of 67% for a false-alarm rate of 24%. © 2009 American Meteorological Society."
"9249239700;7404829395;7003278104;7003406400;","Assessing consistency between EOS MLS and ECMWF analyzed and forecast estimates of cloud ice",2007,"10.1029/2006GL029022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250725928&doi=10.1029%2f2006GL029022&partnerID=40&md5=8dd81af25eb4b066a52746bff5963bf9","Cloud ice water content (IWC) from MLS retrievals and ECMWF analyses and forecasts are compared for August 2004 to July 2005. ECMWF data are sampled along MLS tracks and filtered according to MLS sensitivity. At 147 hPa, there is good spatial agreement with the analyses biased high by 10%. Over landmasses, the analyses are biased low up to 50%. This underestimation grows in the forecasts, with a 40% reduction by day 10. At 215 hPa, the analyses are biased low by 10-60%. However, at this level the forecast IWC undergoes little change. These biases, in conjunction with those in precipitation and top of the atmosphere radiative fluxes, along with consideration of the changes in vertical velocity, cumulus cloud mass flux and cloud top detrainment, indicates a systematic reduction of the modeled deep convection over the warm pool in conjunction with a weakened large-scale circulation and enhanced upper-level vertical stratification. Copyright 2007 by the American Geophysical Union."
"7402933297;7405584618;7004160106;7402390191;","Effects of cloud microphysics on tropical atmospheric hydrologic processes and intraseasonal variability",2005,"10.1175/JCLI3561.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30144444974&doi=10.1175%2fJCLI3561.1&partnerID=40&md5=fbed61aacf07059ab4d54748d6c85863","The sensitivity of tropical atmospheric hydrologic processes to cloud microphysics is investigated using NASA Goddard Earth Observing System (GEOS) general circulation model (GCM). Results show that a faster autoconversion rate leads to (a) enhanced deep convection in the climatological convective zones anchored to tropical land regions; (b) more warm rain, but less cloud over oceanic regions; and (c) an increased convective-to-stratiform rain ratio over the entire Tropics. Fewer clouds enhance longwave cooling and reduce shortwave heating in the upper troposphere, while more warm rain produces more condensation heating in the lower troposphere. This vertical differential heating destabilizes the tropical atmosphere, producing a positive feedback resulting in more rain and an enhanced atmospheric water cycle over the Tropics. The feedback is maintained via secondary circulations between convective tower and anvil regions (cold rain), and adjacent middle-to-low cloud (warm rain) regions. The lower cell is capped by horizontal divergence and maximum cloud detrainment near the freezing-melting (0°C) level, with rising motion (relative to the vertical mean) in the warm rain region connected to sinking motion in the cold rain region. The upper cell is found above the 0°C level, with induced subsidence in the warm rain and dry regions, coupled to forced ascent in the deep convection region. It is that warm rain plays an important role in regulating the time scales of convective cycles, and in altering the tropical large-scale circulation through radiative-dynamic interactions. Reduced cloud-radiation feedback due to a faster autoconversion rate results in intermittent but more energetic eastward propagating Madden-Julian oscillations (MJOs). Conversely, a slower autoconversion rate, with increased cloud radiation produces MJOs with more realistic westward-propagating transients embedded in eastward-propagating supercloud clusters. The implications of the present results on climate change and water cycle dynamics research are discussed. © 2005 American Meteorological Society."
"7402933297;57201725986;7405584618;","Evolution of the large scale circulation, cloud structure and regional water cycle associated with the South China Sea Monsoon during May-June, 1998",2002,"10.2151/jmsj.80.1129","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036823353&doi=10.2151%2fjmsj.80.1129&partnerID=40&md5=a75f1008d19742252dccff4efec35ee4","This paper studies the evolution of the South China Sea (SCS) monsoon during May-June 1998, to elucidate relationships among the large scale circulation, organization of convection, cloud structures, and fluctuations of the regional water cycle of the SCS. Primary data used include field observations from the South China Sea Monsoon Experiment (SCSMEX), and the satellite rain products from the Tropical Rainfall Measuring Mission (TRMM). Prior to the onset of the SCS monsoon, enhanced convective activities associated with the Madden and Julian Oscillation were detected over the equatorial Indian Ocean in early May while the SCS was under the influence of the West Pacific Anticyclone with prevailing low level easterlies and suppressed convection. Subsquently, a bifurcation of the MJO convection near 90°E led to the development of strong convection over the Bay of Bengal, which spawned low-level westerlies across Indo-China and contributed to the initial build-up of moisture and convective available potential energy over the northern SCS. The onset of the SCS monsoon occurred around May 18-20, and appeared to be triggered by the equatorward penetration of extratropical frontal disturbances, originating from the continental regions of East Asia. Analysis of TRMM microwave and precipitation radar data revealed that during the onset phase, convection over the northern SCS consisted of squall-type rain cells embedded in meso-scale complexes similar to extratropical systems. The radar Z-factor intensity indicated that SCS clouds possessed a bimodal distribution, with a pronounced signal (>30 dBz) at a height of 2-3 km, and another one (>25 dBz) at the 8-10 km level, separated by a well-defined melting level signaled by a bright band at around 5-km level. The most convectively active phase of the SCS monsoon, as measured by the abundance of convective and stratiform hydrometeor types, inferred from the radar vertical profile, was found to occur when the large scale vertical wind shear was weakest. The fluctuation of the water cycle over the northern SCS was found to be closely linked to the large-scale dynamical and SST forcings. Before onset and during the break, the northern SCS was relatively warm and served as a moisture source (E - P > O) to the overlying atmosphere. During the active phase, the northern SCS was cooled, providing a strong sink (E - P « O) for atmospheric moisture, with the primary source of moisture coming from regions further west over Indo-China and the eastern Indian Ocean. Vigorous water recycling by convective systems in the northern SCS occurred during the mature phase of the SCS monsoon, with precipitation efficiency (defined as the ratio of the surface precipitation to the sum of large scale moisture convergence and surface evaporation from the ocean) approaching 96%. Westward transport of moisture from Indo-China into, and northward transport out of, the northern SCS provided the main source of moisture for the torrential rain over the YRV in mid-June 1998. The present results suggest that the SCS may play an important role in regulating the SCS monsoon active and break cycles through charge and discharge of moisture, and convective available potential energy."
"7006957668;7409376438;7402942478;57211301037;","Improving assimilated global datasets using TMI rainfall and columnar moisture observations",2000,"10.1175/1520-0442(2000)013<4180:IAGDUT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034351743&doi=10.1175%2f1520-0442%282000%29013%3c4180%3aIAGDUT%3e2.0.CO%3b2&partnerID=40&md5=0401755feace52fdc83d92f780f4c30d","A global analysis that optimally combines observations from diverse sources with physical models of atmospheric and land processes can provide a comprehensive description of the climate systems. Currently, such data products contain significant errors in primary hydrological fields such as precipitation and evaporation, especially in the Tropics. In this study it is demonstrated that assimilating precipitation and total precipitable water (TPW) derived from the Tropical Rainfall Measuring Mission Microwave Imager (TMI) can significantly improve the quality of global analysis. It is shown that assimilating the 6-h averaged TMI rainfall and TPW retrievals improves not only the hydrological cycle, but also key climate parameters such as clouds, radiation, and the large-scale circulation produced by the Goddard Earth Observing System (GEOS) data assimilation system (DAS). Notably, assimilating TMI rain rates improves clouds and radiation in areas of active convection, as well as the latent heating distribution and the large-scale motion field in the Tropics, while assimilating TMI TPW retrievals leads to reduced moisture biases and improved radiative fluxes in clear-sky regions. Assimilating these data also improves the instantaneous wind and temperature fields in the analysis, leading to better short-range forecasts in the Tropics. Ensemble forecasts initialized with analyses incorporating TMI rain rates and TPW yield smaller biases in tropical precipitation forecasts beyond 1 day, better 500-hPa geopotential height forecasts up to 5 days, and better 200-hPa divergent winds up to 2 days. These results demonstrate the potential of using high quality spaceborne rainfall and moisture observations to improve the quality of assimilated global data for climate analysis and weather forecasting applications."
"7202899330;7404288437;7401513327;","A comparison of SSM/I and TOVS column water vapor data over the global oceans",1994,"10.1007/BF01030059","https://www.scopus.com/inward/record.uri?eid=2-s2.0-21844500145&doi=10.1007%2fBF01030059&partnerID=40&md5=e109e460bd00126a582f216d883ba02f","This paper presents a comparison of column water vapor (CWV) information derived from both infrared measurements as part of the TIROS-N Operational Vertical Sounder (TOVS) and Special Sensor Microwave/Imager (SSM/I) in an attempt to assess the relative merits of each kind of data. From the analyses presented in this paper, it appears that both types of satellite data closely reproduce the bulk climatological relationships introduced in earlier studies using different data. This includes both the bulk relationship between CWV and the sea surface temperature and the annual variation of CWV over the world's oceans. The TOVS water vapor data tends to be systematically smaller than the SSM/I data and when averaged over the ocean covered regions of the globe this difference is between 2-3 kgm-2. Using a cloud liquid water threshold technique to establish clear sky values of SSM/I water vapor, we conclude that the differences between TOVS and SSM/I are largely a result of the clear sky bias in TOVS sampling except in the subsidence regions of the subtropics. The clear sky bias is considerably smaller than previously reported and we attribute this improvement to the new physical retrieval scheme implemented by NOAA NESDIS. While there is considerable agreement between the two types of satellite data, there are also important differences. In regions where there is drying associated with large scale subsidence of the atmosphere, the TOVS CWV's are too moist relative to both radiosonde and SSM/I data and this difference may exceed 10 kgm-2. The explanation for this difference lies in the limitations of infrared radiative transfer. By contrast, in regions of deep convection, such as in the ITCZ, TOVS CWV is systematically lower than the SSM/I CWV. Both TOVS and SSM/I data demonstrate similar kinds of gross effects of large scale circulation on the water vapor except in these subsidence regions where TOVS data leads to an under-prediction of the effects of subsidence drying. © 1994 Springer-Verlag."
"36663291700;6603060770;","Global-mean Vertical Tracer Mixing in Planetary Atmospheres. I. Theory and Fast-rotating Planets",2018,"10.3847/1538-4357/aada85","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055146271&doi=10.3847%2f1538-4357%2faada85&partnerID=40&md5=6fd6b89545c85260c47e39a6b375fdf8","Most chemistry and cloud formation models for planetary atmospheres adopt a one-dimensional (1D) diffusion approach to approximate the global-mean vertical tracer transport. The physical underpinning of the key parameter in this framework, eddy diffusivity K zz, is usually obscure. Here we analytically and numerically investigate vertical tracer transport in a 3D stratified atmosphere and predict K zz as a function of the large-scale circulation strength, horizontal mixing due to eddies and waves and local tracer sources and sinks. We find that K zz increases with tracer chemical lifetime and circulation strength but decreases with horizontal eddy mixing efficiency. We demarcated three K zz regimes in planetary atmospheres. In the first regime where the tracer lifetime is short compared with the transport timescale and horizontal tracer distribution under chemical equilibrium () is uniformly distributed across the globe, global-mean vertical tracer mixing behaves diffusively. But the traditional assumption in current 1D models that all chemical species are transported via the same eddy diffusivity generally breaks down. We show that different chemical species in a single atmosphere should in principle have different eddy diffusion profiles. In the second regime where the tracer is short-lived but is non-uniformly distributed, a significant non-diffusive component might lead to a negative K zz under the diffusive assumption. In the third regime where the tracer is long-lived, global-mean vertical tracer transport is also largely influenced by non-diffusive effects. Numerical simulations of 2D tracer transport on fast-rotating zonally symmetric planets validate our analytical K zz theory over a wide parameter space. © 2018. The American Astronomical Society. All rights reserved.."
"14325218600;24576706500;7005449794;","Improving the simulation of the West African monsoon using the MIT regional climate model",2014,"10.1175/JCLI-D-13-00188.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896077818&doi=10.1175%2fJCLI-D-13-00188.1&partnerID=40&md5=8483ca384a06f012416392874a14284b","This paper presents an evaluation of the performance of the Massachusetts Institute of Technology (MIT) regional climate model (MRCM) in simulating the West African monsoon. The MRCM is built on the Regional Climate Model, version 3 (RegCM3), but with several improvements, including coupling of Integrated Biosphere Simulator (IBIS) land surface scheme, a new surface albedo assignment method, new convective cloud and convective rainfall autoconversion schemes, and a modified scheme for simulating boundary layer height and boundary layer clouds. To investigate the impact of these more physically realistic representations when incorporated into MRCM, a series of experiments were carried out implementing two land surface schemes [IBIS with a new albedo assignment, and the Biosphere-Atmosphere Transfer Scheme (BATS)] and two convection schemes (Grell with the Fritsch-Chappell closure, and Emanuel in both the default form and modified with the new convective cloud cover and a rainfall autoconversion scheme). The analysis primarily focuses on comparing the rainfall characteristics, surface energy balance, and large-scale circulations against various observations. This work documents significant sensitivity in simulation of the West African monsoon to the choices of the land surface and convection schemes. Despite several deficiencies, the simulation with the combination of IBIS and the modified Emanuel scheme with the new convective cloud cover and a rainfall autoconversion scheme shows the best performance with respect to the spatial distribution of rainfall and the dynamics of the monsoon. The coupling of IBIS leads to representations of the surface energy balance and partitioning that show better agreement with observations compared to BATS. The IBIS simulations also reasonably reproduce the dynamical structures of the West African monsoon circulation. © 2014 American Meteorological Society."
"7004764167;","Comparison of mechanisms of cloud-climate feedbacks in GCMs",1999,"10.1175/1520-0442(1999)012<1480:comocc>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032883626&doi=10.1175%2f1520-0442%281999%29012%3c1480%3acomocc%3e2.0.co%3b2&partnerID=40&md5=d79ecfbd9ee23ef20e01ace019f2fdd2","International model comparisons of cloud-climate feedbacks have typically been restricted to assessing only the radiative effect of changes in clouds and have not attempted to explain the mechanisms for differences in cloud feedbacks. This paper uses different versions of the U.K. Meteorological Office GCM run at the Hadley Centre to illustrate the usefulness of a detailed comparison of microphysical cloud properties in understanding cloud feedback mechanisms and their effect on the regional distribution of the predicted warming in simulations of climate change. The inclusion of interactive cloud radiative properties explains much of the difference in the spatial patterns of cloud feedback and leads to a marked difference in the response of the large-scale circulation and in the resulting meridional gradient of surface temperature changes. In the model versions that include interactive radiative properties, the strength of the related feedback is determined by the water path of the cloud in the control experiment. Difficulties in performing such a detailed comparison on a wider range of models may arise from the lack of diagnostics in a common format being available from different models and because of the range of assumptions about how clouds are treated by different radiation schemes. A suggestion is put forward for a possible common format that would enable comparison of such diagnostics."
"57198472289;7501757094;","A regional model simulation of the 1991 severe precipitation event over the Yangtze-Huai River valley. Part II: Model bias",2000,"10.1175/1520-0442(2000)013<0093:ARMSOT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034081711&doi=10.1175%2f1520-0442%282000%29013%3c0093%3aARMSOT%3e2.0.CO%3b2&partnerID=40&md5=e8a84b791e196e7c5371c2d0b09407dd","This is the second part of a study investigating the 1991 severe precipitation event over the Yangtze-Huai River valley (YHRV) in China using both observations and regional model simulations. While Part I reported on the Mei-yu front and its association with large-scale circulation, this study documents the biases associated with the treatment of the lateral boundary in the regional model. Two aspects of the biases were studied: the driving field, which provides large-scale boundary forcing, and the coupling scheme, which specifies how the forcing is adopted by the model. The former bias is defined as model uncertainty because it is not related to the model itself, while the latter bias (as well as those biases attributed to other sources) is referred to as model error. These two aspects were examined by analyzing the regional model simulations of the 1991 summer severe precipitation event over YHRV using different driving fields (ECMWF-TOGA objective analysis, ECMWF reanalysis, and NCEP-NCAR reanalysis) and coupling scheme (distribution function of the nudging coefficient and width of the buffer zone). Spectral analysis was also used to study the frequency distribution of the bias. The analyses suggest that the 200-hPa winds. 500-hPa geopotential height, and 850-hPa winds and water vapor mixing ratio, which have dominant influences on Mei-yu evolution, are sensitive to large-scale boundary forcing. In particular the 500-hPa geopotential height, and 850-hPa water vapor mixing ratio near the Tibetan Plateau and over the western Pacific Oceans are highly dependent on the driving field. On the other hand, the water vapor in the lower troposphere, wind at all levels, and precipitation pattern are much more affected by the treatment of nudging in the coupling scheme. It is interesting to find that the two commonly used coupling schemes, the lateral boundary coupling and the spectral coupling, provide similar large-scale information to the simulation domain when the former scheme used a wider buffer zone and stronger nudging coefficient. Systematical model errors, existing in the north of the simulation domain, are caused by the overprediction of low-level inversion stratiform clouds. The analyses further indicate that the model mesoscale signal is not significantly influenced by the different treatments of the nudging procedure. However, it is also shown that the model performance, especially the monthly mean precipitation and its spatial pattern, is substantially improved with the increase of buffer zone width and nudging coefficient.This is the second part of a study investigating the 1991 severe precipitation event over the Yangtze-Huai River valley (YHRV) in China using both observations and regional model simulations. While Part I reported on the Mei-yu front and its association with large-scale circulation, this study documents the biases associated with the treatment of the lateral boundary in the regional model. Two aspects of the biases were studied: the driving field, which provides large-scale boundary forcing, and the coupling scheme, which specifies how the forcing is adopted by the model. The former bias is defined as model uncertainty because it is not related to the model itself, while the latter bias (as well as those biases attributed to other sources) is referred to as model error. These two aspects were examined by analyzing the regional model simulations of the 1991 summer severe precipitation event over YHRV using different driving fields (ECMWF-TOGA objective analysis, ECMWF reanalysis, and NCEP-NCAR reanalysis) and coupling scheme (distribution function of the nudging coefficient and width of the buffer zone). Spectral analysis was also used to study the frequency distribution of the bias. The analyses suggest that the 200-hPa winds, 500-hPa geopotential height, and 850-hPa winds and water vapor mixing ratio, which have dominant influences on Mei-yu evolution, are sensitive to large-scale boundary forcing. In particular the 500-hPa geopotential height, and 850-hPa water vapor mixing ratio near the Tibetan Plateau and over the western Pacific Oceans are highly dependent on the driving field. On the other hand, the water vapor in the lower troposphere, wind at all levels, and precipitation pattern are much more affected by the treatment of nudging in the coupling scheme. It is interesting to find that the two commonly used coupling schemes, the lateral boundary coupling and the spectral coupling, provide similar large-scale information to the simulation domain when the former scheme used a wider buffer zone and stronger nudging coefficient. Systematical model errors, existing in the north of the simulation domain, are caused by the overprediction of low-level inversion stratiform clouds. The analyses further indicate that the model mesoscale signal is not significantly influenced by the different treatments of the nudging procedure. However, it is also shown that the model performance, especially the monthly mean precipitation and its spatial pattern, is substantially improved with the increase of buffer zone width and nudging coefficient."
"36663291700;6603060770;","Global-mean Vertical Tracer Mixing in Planetary Atmospheres. II. Tidally Locked Planets",2018,"10.3847/1538-4357/aada7c","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055159545&doi=10.3847%2f1538-4357%2faada7c&partnerID=40&md5=9990177474c7859d0a1647aefd660a79","In Zhang &amp; Showman, we developed an analytical theory of 1D eddy diffusivity K zz for global-mean vertical tracer transport in a 3D atmosphere. We also presented 2D numerical simulations on fast-rotating planets to validate our theory. On a slowly rotating planet such as Venus or a tidally locked planet (not necessarily a slow-rotator) such as a hot Jupiter, the tracer distribution could exhibit significant longitudinal inhomogeneity and tracer transport is intrinsically 3D. Here we study the global-mean vertical tracer transport on tidally locked planets using 3D tracer-transport simulations. We find that our analytical K zz theory in Zhang &amp; Showman is validated on tidally locked planets over a wide parameter space. K zz strongly depends on the large-scale circulation strength, horizontal mixing due to eddies, and waves, and local tracer sources and sinks due to chemistry and microphysics. As our analytical theory predicted, K zz on tidally locked planets also exhibit three regimes. In Regime I where the chemical and microphysical processes are uniformly distributed across the globe, different chemical species should be transported via different eddy diffusivity. In Regime II where the chemical and microphysical processes are nonuniform - for example, photochemistry or cloud formation that exhibits strong day-night contrast - the global-mean vertical tracer mixing does not always behave diffusively. In the third regime where the tracer is long-lived, non-diffusive effects are significant. Using species-dependent eddy diffusivity, we provide a new analytical theory of the dynamical quench points for disequilibrium tracers on tidally locked planets from first principles. © 2018. The American Astronomical Society. All rights reserved."
"27467537200;37090362900;6603749963;56379892200;56284543100;9636594900;7004942632;","Emission metrics for quantifying regional climate impacts of aviation",2017,"10.5194/esd-8-547-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85023196288&doi=10.5194%2fesd-8-547-2017&partnerID=40&md5=46c6b958eb2ee0c72cdc570f6744c023","This study examines the impacts of emissions from aviation in six source regions on global and regional temperatures. We consider the NOx-induced impacts on ozone and methane, aerosols and contrail-cirrus formation and calculate the global and regional emission metrics global warming potential (GWP), global temperature change potential (GTP) and absolute regional temperature change potential (ARTP). The GWPs and GTPs vary by a factor of 2-4 between source regions. We find the highest aviation aerosol metric values for South Asian emissions, while contrail-cirrus metrics are higher for Europe and North America, where contrail formation is prevalent, and South America plus Africa, where the optical depth is large once contrails form. The ARTP illustrate important differences in the latitudinal patterns of radiative forcing (RF) and temperature response: the temperature response in a given latitude band can be considerably stronger than suggested by the RF in that band, also emphasizing the importance of large-scale circulation impacts. To place our metrics in context, we quantify temperature change in four broad latitude bands following 1 year of emissions from present-day aviation, including CO2. Aviation over North America and Europe causes the largest net warming impact in all latitude bands, reflecting the higher air traffic activity in these regions. Contrail cirrus gives the largest warming contribution in the short term, but remain important at about 15% of the CO2 impact in several regions even after 100 years. Our results also illustrate both the short- and long-term impacts of CO2: while CO2 becomes dominant on longer timescales, it also gives a notable warming contribution already 20 years after the emission. Our emission metrics can be further used to estimate regional temperature change under alternative aviation emission scenarios. A first evaluation of the ARTP in the context of aviation suggests that further work to account for vertical sensitivities in the relationship between RF and temperature response would be valuable for further use of the concept. © 2017 Author(s)."
"7202358048;7102101132;","An examination of two pathways to tropical cyclogenesis occurring in idealized simulations with a cloud-resolving numerical model",2013,"10.5194/acp-13-5999-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879989155&doi=10.5194%2facp-13-5999-2013&partnerID=40&md5=bc1d4cec25391a505fc8b05c547b32d4","Simulations are conducted with a cloud-resolving numerical model to examine the transformation of a weak incipient mid-level cyclonic vortex into a tropical cyclone. Results demonstrate that two distinct pathways are possible and that development along a particular pathway is sensitive to model physics and initial conditions. One pathway involves a steady increase of the surface winds to tropical cyclone strength as the radius of maximum winds gradually decreases. A notable feature of this evolution is the creation of small-scale lower tropospheric cyclonic vorticity anomalies by deep convective towers and subsequent merger and convergence by the low-level secondary circulation. The second pathway also begins with a strengthening low-level circulation, but eventually a significantly stronger mid-level circulation develops. Cyclogenesis occurs subsequently when a small-scale surface concentrated vortex forms abruptly near the center of the larger-scale circulation. The small-scale vortex is warm core throughout the troposphere and results in a fall in local surface pressure of a few millibars. It usually develops rapidly, undergoing a modest growth to form a small tropical cyclone. Many of the simulated systems approach or reach tropical cyclone strength prior to development of a prominent mid-level vortex so that the subsequent formation of a strong small-scale surface concentrated vortex in these cases could be considered intensification rather than genesis. <br><br> Experiments are performed to investigate the dependence on the inclusion of the ice phase, radiation, the size and strength of the incipient mid-level vortex, the amount of moisture present in the initial vortex, and the sea surface temperature. Notably, as the sea surface temperature is raised, the likelihood of development along the second pathway is increased. This appears to be related to an increased production of ice. The sensitivity of the pathway taken to model physics and initial conditions revealed by these experiments raise the possibility that the solution to this initial value problem is near a bifurcation point. Future improvements to model parameterizations and more accurate observations of the transformation of disturbances to tropical cyclones should clarify the conditions that favor a particular pathway when starting from a mid-level vortex. © 2013 Author(s)."
"24764834600;7004035832;7102739935;","Cloud frequency climatology at the Andes/Amazon transition: 1. Seasonal and diurnal cycles",2012,"10.1029/2012JD017770","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870612636&doi=10.1029%2f2012JD017770&partnerID=40&md5=19204e86ba3ff60b2e27f54095fd10f4","Tropical montane regions present a complex local climate but one that may be very sensitive to local and global change. Therefore, it is important to assess their current climatological state, and to understand how the large-scale circulation may affect local-scale cloud patterns. We examine the cloud climatology of a tropical Andean montane region in the context of tropical South American climate in terms of seasonal/diurnal cycles using a corrected ISCCP (International Satellite Cloud Climatology Project) DX cloud product (1983-2008), MODIS (Moderate Resolution Imaging Spectroradiometer) MOD35 visible cloud flags (2000-2008) and ground-based cloud observations. Cloud climatologies were compared for three elevation zones: highlands (puna grassland), eastern slope (the montane forest) and lowlands. We found that in the dry season (JJA) the study area is part of a localized region of higher cloud frequency relative to other parts the eastern slope, and also relative to the adjacent highlands and lowlands. The highlands exhibited the greatest amplitude mean annual cycle of cloud frequency, with a minimum in June for all times of day. There were contrasts between the three zones with regard to the month in which the minimum cloud frequency occurs between different times of day. Higher lowland and eastern slope cloud frequencies compared with those on the puna in the early hours in the wet season suggest low-level convergence at lower elevations. Comparisons between satellite products show that ISCCP and MODIS produce very similar annual cycles although the absolute cloud frequencies are higher in ISCCP data. © 2012. American Geophysical Union. All Rights Reserved."
"16309604700;7601492669;7401945370;9535769800;25647939800;7801685271;","Multiscale interactions in the life cycle of a tropical cyclone simulated in a global cloud-system-resolving model. Part II: System-scale and mesoscale processes",2010,"10.1175/2010MWR3475.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651071307&doi=10.1175%2f2010MWR3475.1&partnerID=40&md5=c87cde94623ed3a4c6a64aaf4b70306b","The life cycle of Tropical Storm Isobel was simulated reasonably well in the Nonhydrostatic Icosahedral Atmospheric Model (NICAM), a global cloud-system-resolving model. The evolution of the large-scale circulation and the storm-scale structure change was discussed in Part I. Both the mesoscale and system-scale processes in the life cycle of the simulated Isobel are documented in this paper. In the preconditioned favorable environment over the Java Sea, mesoscale convective vortices (model MCVs) developed in the mesoscale convective systems (MCSs) and convective towers with cyclonic potential vorticity (PV) anomalies throughout the troposphere [model vortical hot towers (VHTs)] appeared in the model MCVs. Multiple model VHTs strengthened cyclonic PV in the interior of the model MCV and led to the formation of an upright monolithic PV core at the center of the concentric MCV (primary vortex enhancement). As the monolithic PV core with a warm core developed near the circulation center, the intensification and the increase in horizontal size of the cyclonic PV were enhanced through the system-scale intensification (SSI) process (the secondary vortex enhancement), leading to the genesis of Isobel over the Timor Sea. The SSI process can be well explained by the balanced dynamics. After its genesis, the subsequent evolution of the simulated Isobel was controlled by both the external influence and the internal dynamics. Under the unfavorable environmental conditions, the development of asymmetric structure reduced the axisymmetric diabatic heating in the inner core and the SSI process became ineffective and the storm weakened. Later on, as the eyewall reformed as a result of the axisymmetrization of an inward-propagating outer spiral rainband, the SSI process became effective again, leading to the reintensification of Isobel. Therefore, the large-scale environmental flow provided the precondition for the genesis of Isobel and the triggering mechanism for subsequent storm-scale structure change as discussed in Part I. The system-scale and mesoscale processes, such as the evolution of MCVs and merging VHTs, were responsible for the genesis, while the eyewall processes were critical to the storm intensity change through the SSI process. © 2010 American Meteorological Society."
"24070687500;7102745183;","A remote sensing survey of the role of land form on the organization of orographic precipitation in Central and Southern Mexico",2008,"10.1175/2008JHM947.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-47049119907&doi=10.1175%2f2008JHM947.1&partnerID=40&md5=e996a53b4c6ac3f7798ee46f5bc4a985","Data from NASA's TRMM satellite and NOAA's GOES satellites were used to survey the orographic organization of cloud precipitation in central and southern Mexico during the monsoon with two main objectives: 1) to investigate large-scale forcing versus local landform controls, and 2) to compare the results with previous work in the Himalayas. At large scales, the modes of spatial variability of cloudiness were estimated using the empirical orthogonal function (EOF) analysis of GOES brightness temperatures. Terrain modulation of synoptic-scale high-frequency variability (3-5- and 6-9-day cycles normally associated with the propagation of easterly waves) was found to cause higher dispersion in the EOF spectrum, with the first mode explaining less than 30% of the spatial variability in central and southern Mexico as opposed to 50% and higher in the Himalayas. A detailed analysis of the first three EOFs for 1999, an average La Niña year with above average rainfall, and for 2001, a weak La Niña year with below average rainfall, shows that landform (mountain peaks and land-ocean contrast) and large-scale circulation (moisture convergence) alternate as the key controls of regional hydrometeorology in dry and wet years, or as active and break (midsummer drought) phases of the monsoon, respectively. The diurnal cycle is the dominant time scale of variability in 2001, as it is during the midsummer drought in all years. Strong variability at time scales beyond two weeks is only present during the active phases of the monsoon. At the river basin scale, the data show increased cloudiness over the mountain ranges during the afternoon, which moves over the low-lying regions at the foot of the major orographic barriers [the Sierra Madre Occidental (SMO)/Sierra Madre del Sur (SMS) and Trans-Mexican Volcanic Belt (TMVB)], specifically the Balsas and the Rio de Santiago basins at nighttime and in the early morning. At the ridge-valley scale (∼ 100-200 km), robust day-night (ridge-valley) asymmetries suggest strong local controls on cloud and precipitation, with convective activity along the coastal region of the SMO and topographically forced convection at the foothills of headwater ridges in the Altiplano and the SMS. These day-night spatial shifts in cloudiness and precipitation are similar to those found in the Himalayas at the same spatial scales. © 2008 American Meteorological Society."
"7003625225;6505752137;7003601758;","Monthly mean upper tropospheric humidities in cloud‐free areas from meteosat observations",1991,"10.1002/joc.3370110802","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026268573&doi=10.1002%2fjoc.3370110802&partnerID=40&md5=d647b95eeabf7517477a3a737f3169dc","The purpose of this paper is to study the annual variation of the upper tropospheric relative humidity fields extracted from radiance measurements in the water vapour channel (in the thermal infra‐red at wavelengths around 6.3 μm) aboard the geostationary satellite METEOSAT. Monthly mean fields for April, July and October 1988 and January 1989 have been created from the operational Upper Tropospheric Humidity (hereafter UTH) product derived routinely at the European Space Operations Centre (ESOC). The present product retrieval is confined to cloud‐free areas in the upper troposphere, thus the monthly means represent an average over cloud‐free cases. Principally the patterns of the monthly mean UTH fields reflect the large‐scale circulation of the atmosphere. In the low latitudes, belts with relatively high and low UTH values are located over the ascending and descending branches of the ‘Hadley cell’, respectively. The distinct patterns of monthly mean UTH fields can be used to characterize the geographical structure of the Hadley cell. The UTH fields complement existing data on atmospheric humidity for use in numerical weather prediction and climatological research. The monthly mean fields presented in this paper may be useful for validating upper tropospheric water vapour fields in climate models. Copyright © 1991 John Wiley & Sons, Ltd"
"7102718675;7202772927;7101801476;56122626400;6701845806;","The NASA-Goddard Multi-scale Modeling Framework-Land Information System: Global land/atmosphere interaction with resolved convection",2013,"10.1016/j.envsoft.2012.02.023","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870301611&doi=10.1016%2fj.envsoft.2012.02.023&partnerID=40&md5=f4476ff6bbffc2090d6c821398fdce33","The present generation of general circulation models (GCM) use parameterized cumulus schemes and run at hydrostatic grid resolutions. To improve the representation of cloud-scale moist processes and land-atmosphere interactions, a global, Multi-scale Modeling Framework (MMF) coupled to the Land Information System (LIS) has been developed at NASA-Goddard Space Flight Center. The MMF-LIS has three components, a finite-volume (fv) GCM (Goddard Earth Observing System Ver. 4, GEOS-4), a 2D cloud-resolving model (Goddard Cumulus Ensemble, GCE), and the LIS, representing the large-scale atmospheric circulation, cloud processes, and land surface processes, respectively. The non-hydrostatic GCE model replaces the single-column cumulus parameterization of fvGCM. The model grid is composed of an array of fvGCM gridcells each with a series of embedded GCE models. A horizontal coupling strategy, GCE ↔ fvGCM ↔ Coupler ↔ LIS, offered significant computational efficiency, with the scalability and I/O capabilities of LIS permitting land-atmosphere interactions at cloud-scale. Global simulations of 2007-2008 and comparisons to observations and reanalysis products were conducted. Using two different versions of the same land surface model but the same initial conditions, divergence in regional, synoptic-scale surface pressure patterns emerged within two weeks. The sensitivity of large-scale circulations to land surface model physics revealed significant functional value to using a scalable, multi-model land surface modeling system in global weather and climate prediction. © 2012."
"6505995301;7004432098;","Laboratory simulations of radiatively induced entrainment in stratiform clouds",1998,"10.1029/98JD00344","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032571687&doi=10.1029%2f98JD00344&partnerID=40&md5=4db13a26b1360cd843263b7709630323","Laboratory experiments have been conducted to simulate entrainment in stratiform clouds. In particular, the case of entrainment across a capping temperature inversion and induced by cloud top cooling has been simulated. This geometry is termed interfacial convection, and its physics differ from the more thoroughly studied case of penetrative convection. The dimensionless entrainment rate associated with interfacial convection has been found to vary inversely with a bulk Richardson number over a broad range of Richardson numbers. A dependence of the entrainment rate on the diffusivity of the stratifying agent has also been found. This dependence is explained in terms of Taylor layers. A physical model for the dynamics of interfacial convection is proposed. In the laboratory case, a stably stratifield interface separates two fluid layers. Convection is driven in the upper layer by the deposition of raeiation near the interface. After sufficient energy has been deposited, buoyant fluid rises and induces formation of entraining cusps at the interface. The spacing between cusps is determined by equating a buoyancy instability timescale with a heating timescale. When the depth of the convecting layer is large compared to the distance separating the cusps, a larger-scale circulation also develops. In such cases, eddies of size comparable to the depth of the convecting layer advect the cusps horizontally. Despite Raynolds numbers that differ by four orders of magnitude or more between the laboratory simulation and the real atmosphere, it is argued that the entrainment dynamics are analogous. Dimensionaless entrainment rates measured in the laboratory are within one order of magnitude of those measured in the atmosphere for a given Richardson number. Thinner Taylor layers and the lack of evaporative effects in the laboratory may account for the difference."
"7103321545;","Cloud distribution over East Asia during Baiu period of 1979",1989,"10.2151/jmsj1965.67.4_639","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0040189187&doi=10.2151%2fjmsj1965.67.4_639&partnerID=40&md5=53aee86713aa7d9e9b9b449fbc3ed875","The cloud distribution over the East Asia and the northwestern Pacific, during the pre-Baiu, Baiu and post-Baiu periods of 1979 are studied in relation to the large-scale circulations. The distribution of the following cloud systems is studied; 1) major cloud system including deep convective clouds (MCS-CON), 2) major cloud system of layer and shallow convective clouds (MCS-LAY), 3) cloud system including deep convective clouds (CS-CON), and 4) cloud system of layer and shallow convective clouds (CS-LAY). The following features are found in the present study; (1) The area and period of the largest Baiu precipitation coincide with the area and period of most frequent MCS-CON’s occurrence. This indicates that MCS-CON is the most important cloud system in the production of Baiu precipitation. (2) During the pre-Baiu period, CS-LAY’s cover is large over southern China. With the rapid change in the static stability from the convectively stable to the unstable condition, CS-LAY’s cover decreases around the end of May, and CS-CON’S cover increases. (3) During the pre-Baiu period, a zone of MCS-CON results from the passage of polar frontal depressions in the vicinity of Japan. (4) The large-scale circulations change rapidly around the beginning of June. The polar jet stream shifts northward. The Baiu ridge and Baiu trough form in this period. A zone of MCS-CON associated with the Baiu frontal depressions forms along the NW~N rim of the Pacific subtropical anticyclone which grows and shifts westward in June. (5) During the Baiu period, the Baiu trough cloud zone exists apart from the Baiu frontal cloud zone in the 130~150ºE area. The Baiu trough cloud zone is located 1000~1500km north of the Baiu frontal cloud zone. (6) Large cover of CS-LAY and a convectively stable condition are seen over the northwester Pacific throughout the pre-Baiu and Baiu period. (7) During the peak Baiu period, the Baiu frontal cloud zone attains its maximum extension and maximum cloud cover. The notable regional (W to E) difference is seen in the Baiu frontal cloud zone. The western part of the cloud zone (over China), which forms in the proximity of the Baiu trough, is characterized by CS-CON, strong convectively unstable conditions and very weak baroclinicity. The central part of the cloud zone (in the vicinity of Japan), which forms along NW~N rim of the Pacific anticyclone, is characterized by MCS-CON, weak convectively unstable conditions and fairly strong baroclinicity. The eastern part of the cloud zone (over the NW Pacific) is characterized by MCS-LAY, convectively stable condition and strong baroclinicity. (8) Around the end of July, the Baiu ridge and the Baiu trough weaken. The height and thermal fields change into a zonal pattern with weak meridional gradient. The pacific anticyclone shifts northward. The Baiu frontal cloud zone shifts northward, and the cloud cover decreases. (9) The zone of MCS-CON is the essential part of the Baiu frontal cloud zone. The zone of MCSCON forms under the coexistence of weak convectively unstable conditions and moderately strong baroclinicity in the lower troposphere. The aforementioned condition is seen only in the peak Baiu period in the 120~150ºE region. © 1989, Meteolorogical Society of Japan."
"7103158465;57193882808;","Response of tropical deep convection to localized heating perturbations: Implications for aerosol-induced convective invigoration",2013,"10.1175/JAS-D-13-027.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888021288&doi=10.1175%2fJAS-D-13-027.1&partnerID=40&md5=39665fe820e4e2d616922ff9d58c2d7b","A cloud-system-resolving model is used to investigate the effects of localized heating/cooling perturbations on tropical deep convection, in the context of the aerosol ""invigoration effect."" This effect supposes that a reduction of droplet collision-coalescence in polluted conditions leads to lofting of cloud water in convective updrafts and enhanced freezing, latent heating, and buoyancy. To specifically isolate and test this mechanism, heating perturbations were applied to updrafts with corresponding cooling applied in downdrafts. Ensemble simulations were run with either perturbed or unperturbed conditions and large-scale forcing from a 7.5-day period of active monsoon conditions during the 2006 Tropical Warm Pool-International Cloud Experiment. In the perturbed simulations there was an initial invigoration of convective updrafts and surface precipitation, but convection returned to its unperturbed state after about 24 h because of feedback with the larger-scale environment. This feedback led to an increase in the horizontally averaged mid-/upper-tropospheric temperature of about 1 K relative to unperturbed simulations. When perturbed conditions were applied to only part of the domain, gravity waves rapidly dispersed buoyancy anomalies in the perturbed region to the rest of the domain, allowing convective invigoration from the heating perturbations to be sustained over the entire simulation period. This was associated with a mean mesoscale circulation consisting of ascent (descent) at mid-/upper levels in the perturbed (unperturbed) region. In contrast to recent studies, it is concluded that the invigoration effect is intimately coupled with larger-scale dynamics through a two-way feedback, and in the absence of alterations in the larger-scale circulation there is limited invigoration beyond the convective adjustment time scale. © 2013 American Meteorological Society."
"7103246957;7005206400;6507871748;57201177267;7410009029;57213606287;7004436916;","The Amazonian boundary layer and mesoscale circulations",2009,"10.1029/2008GM000725","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899856969&doi=10.1029%2f2008GM000725&partnerID=40&md5=1c693fbc1e8fb14bd249d5d1357524d1","The interactions between the Amazonian boundary layer, the surface, atmospheric convection, aerosols, and larger-scale circulations are complex. The field experiments in Amazonia have provided rich insights into the daytime and nighttime boundary layer in different regions and seasons over both forest and pasture and into the coupling between the surface fluxes, the boundary layer, precipitation, and cloud radiative forcing. We discuss the typical diurnal cycle of Amazonian convection, the self-organization into mesoscale systems in different synoptic regimes, and the role of forest and river breeze circulations. We review the coupling between aerosols, smoke, and convection in the dry season; ozone transports by deep convection; and microphysical and electrical impacts on convection. © Copyright 2009 by the American Geophysical Union."
"7405459515;7006783796;7004325649;7403531523;6701464149;","Satellite observations of long-term changes in tropical cloud and outgoing longwave radiation from 1985 to 1998",2002,"10.1029/2001gl014264","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037095940&doi=10.1029%2f2001gl014264&partnerID=40&md5=ee1d1755dc1da1b50c7390fcbbf9d19b","Cloud vertical distributions and radiation data from satellites taken between 1985 and 1998 were analyzed to determine the impact of clouds on outgoing longwave radiation (OLR) in the Tropics. Clouds with a 1-μm optical depth greater than 0.025 above 12 km decreased, while those below 12 km increased. The OLR mean and decadal trend were 254 Wm-2 and 3.9 Wm-2/decade, respectively. The mean cloud and OLR results were used to derive a value of 0.36 for the tropical mean cloud longwave effective emissivity. Changes in cloud vertical distributions account for 40% of the OLR trend. A change in cloud effective emissivity of -0.026/decade cloud account for the remainder of the OLR changes. These changes suggest reduced mean cloud opacity, a drier troposphere, and a strengthened large-scale circulation in the Tropics during the period."
"8525144100;55738957800;13406672500;","Heat balance in the pacific warm pool atmosphere during TOGA COARE and CEPEX",2001,"10.1175/1520-0442(2001)014<1881:HBITPW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035870116&doi=10.1175%2f1520-0442%282001%29014%3c1881%3aHBITPW%3e2.0.CO%3b2&partnerID=40&md5=ec032dc5a69a74589417ea6ccf0901af","The atmosphere above the western equatorial Pacific warm pool (WP) is an important source for the dynamic and thermodynamic forcing of the atmospheric general circulation. This study uses a high-resolution reanalysis and several observational datasets including Global Precipitation Climatology Project precipitation, Tropical Ocean Global Atmosphere (TOGA) Tropical Atmosphere Ocean moored buoys, and Earth Radiation Budget Experiment, TOGA Coupled Ocean-Atmosphere Response Experiment (COARE), and Central Equatorial Pacific Experiment (CEPEX) radiation data to examine the details of the dynamical processes that lead to this net positive forcing. The period chosen is the period of two field experiments: TOGA COARE and CEPEX during December 1992-March 1993. The four months used in the study were sufficient to establish that the warm pool atmosphere (WPA) was close to a state of radiative-convective-dynamic equilibrium. The analysis suggests that the large-scale circulation imports about 200 W m-2 of sensible heat and about 140 W m-2 of latent energy into the WPA mainly through the low-level mass convergence and exports about 420 W m-2 potential energy mainly through the upper-level mass divergence. Thus the net effect of the large-scale dynamics is to export about 80 W m-2 energy out of the WPA and cool the WPA by about 0.8 K day-1. The dynamic cooling in addition to the radiative cooling of about 0.4 K day-1 or 40 W m-2 leads to a net radiative-dynamic cooling of about 1.2 K day-1 or 120 W m-2. which should be balanced by convective heating of the same magnitude. The WPA radiative cooling is only about 0.4 K day-1, which is considerably smaller than previously cited values in the Tropics. This difference is largely due to the cloud radiative forcing (CRF). about 70 W m-2. associated with the deep convective cirrus clouds in the WPA, which compensates the larger clear sky radiative cooling. Thus moist convection heats the WPA, not only through the direct convective heating, that is, the vertical eddy sensible heat and latent energy transport, but also through the indirect convective heating, that is, the CRF of deep convective clouds. The CRF of the deep convective clouds has a dipole structure, in other words, strong heating of the atmosphere through convergence of longwave radiation and a comparable cooling of the surface through the reduction of shortwave radiation at the surface. As a result, the deep convective clouds enhance the required atmospheric heat transport and reduce the required oceanic heat transport significantly in the WP.A more detailed understanding of these convective processes is required to improve our understanding of the heat transport by the large-scale circulation in the Tropics."
"7402681852;","The preliminary syudy of medium-scale cloud clusters over the Changjiang basin in summer",1985,"10.1007/BF02677249","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51249177609&doi=10.1007%2fBF02677249&partnerID=40&md5=779fa7c8cb38b8b85037259f1cc737d0","It is shown that the medium-scale could cluster is a major one of precipitation systems from analysing the rainstorms along the Changjiang River during the plum rain period of 1980-1983. The medium-scale cloud clusters do not always correspond to the moving vortex, but they are in good agreement with the convergence center for the divergent component of wind at 850 hPa. The favourable environmental conditions for the genesis and development of medium-scale cloud cluster, such as the large-scale circulation situation, patterns of temperature and moisture, potential instability, and the structure of cloud cluster are given. A model on large-scale cloud pattern for the genesis of medium-scale cloud cluster is presented. © 1985 Advances in Atmospheric Sciences."
"24472110700;7003875148;","Clouds, warm air, and a climate cooling signal over the summer Arctic",2017,"10.1002/2016GL071959","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85010533631&doi=10.1002%2f2016GL071959&partnerID=40&md5=35a9709c13dfe3683c579772e5c08ab0","While the atmospheric greenhouse effect always results in a warming at the surface, outgoing longwave radiation (OLR) to space always represents a cooling. During events of heat and moisture advection into the Arctic, increases in tropospheric temperature and moisture impact clouds, in turn impacting longwave (LW) radiation. State-of-the-art satellite measurements and atmospheric reanalysis consistently reveal an enhancement of summer Arctic monthly OLR cooling ranging 1.5–4 W m−2 during months with anomalously high thermodynamic advection. This cooling anomaly is found to be of the same magnitude or slightly larger than associated downwelling LW surface warming anomalies. We identify a relationship between large-scale circulation variability and changing cloud properties permitting LW radiation at both the surface and top of the atmosphere to respond to variability in atmospheric thermodynamics. Driven by anomalous advection of warm air, the corresponding enhanced OLR cooling signal on monthly time scales represents an important buffer to regional Arctic warming. ©2017. American Geophysical Union. All Rights Reserved."
"6507495053;8669401600;57203260074;6602137606;12645700600;55030182900;","European heatwave in July 2006: Observations and modeling showing how local processes amplify conducive large-scale conditions",2014,"10.1002/2014GL060205","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905303249&doi=10.1002%2f2014GL060205&partnerID=40&md5=2e509bfc596fe8a062b74634add1edd8","July 2006 was particularly warm in Europe. The consistency of this kind of anomaly with large-scale circulation conditions or local processes is a key issue for regional climate evolution. Using observations from space and ground-based observatory, together with simulations from regional model, shows that two concomitant but disconnected drivers explain this heatwave. The first driver corresponds to large-scale conditions (specific atmospheric condition with advection of continental air favoring clear sky). The second condition relates to local processes (dry soil, amplifying surface temperature in heatwave for first 5days, and making this event warm enough to induce a monthly mean anomaly). This large-scale event is studied at a site in northern France, where comprehensive observation data carefully reanalyzed are available. A regional model is able to produce the amplitude of the event, for both temperature and cloud large-scale anomalies. Coupling model and observations allow discriminating the surface contribution to the temperature anomaly. Key Point Heatwave can be studied in a precise location © 2014. American Geophysical Union. All Rights Reserved."
"55545874600;6507112497;7005446873;","Cloud-resolving model simulations with one- and two-way couplings via the weak temperature gradient approximation",2012,"10.1175/JAS-D-12-058.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871941796&doi=10.1175%2fJAS-D-12-058.1&partnerID=40&md5=15eb5031b7a57743b2ed0cc9956a1ea3","A cloud-resolving model is modified to implement the weak temperature gradient approximation in order to simulate the interactions between tropical convection and the large-scale tropical circulation. The instantaneous domain-mean potential temperature is relaxed toward a reference profile obtained from a radiative-convective equilibrium simulation of the cloud-resolving model. For homogeneous surface conditions, the model state at equilibrium is a large-scale circulation with its descending branch in the simulated column. This is similar to the equilibrium state found in some other studies, but not all. For this model, the development of such a circulation is insensitive to the relaxation profile and the initial conditions. Two columns of the cloud-resolving model are fully coupled by relaxing the instantaneous domain-mean potential temperature in both columns toward each other. This configuration is energetically closed in contrast to the reference-column configuration. No mean large-scale circulation develops over homogeneous surface conditions, regardless of the relative area of the two columns. The sensitivity to nonuniform surface conditions is similar to that obtained in the reference-column configuration if the two simulated columns have very different areas, but it is markedly weaker for columns of comparable area. The weaker sensitivity can be understood as being a consequence of a formulation for which the energy budget is closed. The referencecolumn configuration has been used to study the convection in a local region under the influence of a largescale circulation. The extension to a two-column configuration is proposed as a methodology for studying the influence on local convection of changes in remote convection.©2012 American Meteorological Society."
"56301517800;8558370300;8866821900;23393212200;56014511300;36089222400;7102567936;7003991093;28367935500;6507253177;","Model Hierarchies for Understanding Atmospheric Circulation",2019,"10.1029/2018RG000607","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85066888992&doi=10.1029%2f2018RG000607&partnerID=40&md5=25c8d6a5ce796bab80c011238762f2f3","In this review, we highlight the complementary relationship between simple and comprehensive models in addressing key scientific questions to describe Earth's atmospheric circulation. The systematic representation of models in steps, or hierarchies, connects our understanding from idealized systems to comprehensive models and ultimately the observed atmosphere. We define three interconnected principles that can be used to characterize the model hierarchies of the atmosphere. We explore the rich diversity within the governing equations in the dynamical hierarchy, the ability to isolate and understand atmospheric processes in the process hierarchy, and the importance of the physical domain and resolution in the hierarchy of scale. We center our discussion on the large-scale circulation of the atmosphere and its interaction with clouds and convection, focusing on areas where simple models have had a significant impact. Our confidence in climate model projections of the future is based on our efforts to ground the climate predictions in fundamental physical understanding. This understanding is, in part, possible due to the hierarchies of idealized models that afford the simplicity required for understanding complex systems. ©2019. American Geophysical Union. All Rights Reserved."
"55940978200;11939918300;","Diurnal circulation adjustment and organized deep convection",2018,"10.1175/JCLI-D-17-0693.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047099793&doi=10.1175%2fJCLI-D-17-0693.1&partnerID=40&md5=25defdc7efbc3c6dfea8572423c572ec","This study investigates the diurnal cycle of tropical organized deep convection and the feedback in large-scale circulation. By considering gravity wave phase speeds, we find that the circulation adjustment into weak temperature gradient (WTG) balance occurs rapidly (<6 h) relative to diurnal diabatic forcing on the spatial scales typical of organized convection (≤500 km). Convection-permitting numerical simulations of self-aggregation in diurnal radiative-convective equilibrium (RCE) are conducted to explore this further. These simulations depict a pronounced diurnal cycle of circulation linked to organized convection, which indeed maintains WTG balance to first order. A set of sensitivity experiments is conducted to assess what governs the diurnal cycle of organized convection. We find that the ""direct radiation-convection interaction"" (or lapse-rate) mechanism is of primary importance for diurnal precipitation range, while the ""dynamic cloudy-clear differential radiation"" mechanism amplifies the range by approximately 30%, and delays the nocturnal precipitation peak by around 5 h. The differential radiation mechanism therefore explains the tendency for tropical heavy rainfall to peak in the early morning, while the lapse-rate mechanism primarily governs diurnal amplitude. The diurnal evolution of circulation can be understood as follows. While nocturnal deep convection invigorated by cloud-top cooling (i.e., the lapse-rate mechanism) leads to strong bottom-heavy circulation at nighttime, the localized (i.e., differential) top-heavy shortwave warming in the convective region invigorates circulation at upper levels in daytime. A diurnal evolution of the circulation therefore arises, from bottom heavy at nighttime to top heavy in daytime, in a qualitatively consistent manner with the observed diurnal pulsing of the Hadley cell driven by the ITCZ. © 2018 American Meteorological Society."
"6506286471;36342537900;6508033759;","Fast atmospheric response to a sudden thinning of Arctic sea ice",2016,"10.1007/s00382-015-2629-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957431167&doi=10.1007%2fs00382-015-2629-7&partnerID=40&md5=5575b61e75a456f986cb3b4648ddad0a","In order to understand the influence of a thinner Arctic sea ice on the wintertime atmosphere, idealized ensemble experiments with increased sea ice surface temperature have been carried out with the Integrated Forecast System of the European Centre for Medium-Range Weather Forecasts. The focus is on the fast atmospheric response to a sudden “thinning” of Arctic sea ice to disentangle the role of various different processes. We found that boundary layer turbulence is the most important process that distributes anomalous heat vertically. Anomalous longwave radiation plays an important role within the first few days before temperatures in the lower troposphere had time to adjust. The dynamic response tends to balance that due to boundary layer turbulence while cloud processes and convection play only a minor role. Overall the response of the atmospheric large-scale circulation is relatively small with up to 2 hPa in the mean sea level pressure during the first 15 days; the quasi-equilibrium response reached in the second and third month of the integration is about twice as large. During the first few days the response tends to be baroclinic in the whole Arctic. Already after a few days an anti-cyclonic equivalent-barotropic response develops over north-western Siberia and north-eastern Europe. The structure resembles very much that of the atmospheric equilibrium response indicating that fast tropospheric processes such as fewer quasi-barotropic cyclones entering this continental area are key opposed to slower processes such as those involving, for example, stratosphere-troposphere interaction. © 2015, The Author(s)."
"16430637800;6507958221;8420514500;7401806579;57201958916;57207177305;","A diagnostic study of heavy rainfall in Karachi due to merging of a mesoscale low and a diffused tropical depression during South Asian summer monsoon",2005,"10.1007/BF02918751","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20344380911&doi=10.1007%2fBF02918751&partnerID=40&md5=beda5cd5827d167431181f0354f02752","This paper presents the results of a diagnostic study of a typical case of very heavy rainfall during the South Asian summer monsoon when a mesoscale low in a desert climate merged with a diffused tropical depression. The former low was located over Pakistan's desert region and the latter depression originated over the Bay of Bengal. Surface and NCEP reanalysis data supported by satellite and radar images were incorporated in the diagnosis. The relationship between the heavy precipitation process and large-scale circulations such as monsoon trough, subtropical high, westerly jet, low level jet and water vapor transport were investigated to further understand the mechanism of this peculiar interaction. It was found that: (1) the mesoscale low developed as a result of cold air advection aloft from northern latitudes and strong convection over the region of humidity convergence on 24 July 2003 over the Indian Rajistan area. (2) On the same day, a low that formed over the Bay of Bengal was transformed into a monsoon depression and moved westward to the mesoscale low which existed over southwest India and the adjoining southeastern parts of Pakistan. (3) Initially, the mesoscale low received moisture supply from both the Bay of Bengal as well as the Arabian Sea, whereas the Bay of Bengal maintained the cont)nuous supply of moisture to the monsoon depression. (4) After the depression crossed central India, the Bay's moisture supply was cut off and the Arabian Sea became the only source of moisture to both the closely located systems. On 27 July, both of the systems merged together and the merger resulted in a heavy downpour in the Karachi metropolitan and in its surroundings. (5) With the intensification as well as the southeastward extension of the subtropical high and the shift of the monsoon trough axis from southwest-west to northeast-east, the monsoon depression moved southwestward. In this situation, there existed a very favourable condition for a merger of the two systems in the presence of cross-latitude influence. (6) A number of convective cloud clusters were developed and organized in the mesoscale low. Probably, interactions existed among the multi-scale systems."
"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)."
"57201123684;7401936984;7402064802;22635190100;56763174500;25926762100;14045744500;7003582587;","CAUSES: Diagnosis of the Summertime Warm Bias in CMIP5 Climate Models at the ARM Southern Great Plains Site",2018,"10.1002/2017JD027200","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044292305&doi=10.1002%2f2017JD027200&partnerID=40&md5=5f0828021389dbe59b108b4bfc128d31","All the weather and climate models participating in the Clouds Above the United States and Errors at the Surface project show a summertime surface air temperature (T2 m) warm bias in the region of the central United States. To understand the warm bias in long-term climate simulations, we assess the Atmospheric Model Intercomparison Project simulations from the Coupled Model Intercomparison Project Phase 5, with long-term observations mainly from the Atmospheric Radiation Measurement program Southern Great Plains site. Quantities related to the surface energy and water budget, and large-scale circulation are analyzed to identify possible factors and plausible links involved in the warm bias. The systematic warm season bias is characterized by an overestimation of T2 m and underestimation of surface humidity, precipitation, and precipitable water. Accompanying the warm bias is an overestimation of absorbed solar radiation at the surface, which is due to a combination of insufficient cloud reflection and clear-sky shortwave absorption by water vapor and an underestimation in surface albedo. The bias in cloud is shown to contribute most to the radiation bias. The surface layer soil moisture impacts T2 m through its control on evaporative fraction. The error in evaporative fraction is another important contributor to T2 m. Similar sources of error are found in hindcast from other Clouds Above the United States and Errors at the Surface studies. In Atmospheric Model Intercomparison Project simulations, biases in meridional wind velocity associated with the low-level jet and the 500 hPa vertical velocity may also relate to T2 m bias through their control on the surface energy and water budget. ©2018. The Authors."
"56471429200;55437450100;","Double and single ITCZs with and without clouds",2017,"10.1175/JCLI-D-17-0062.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85031683712&doi=10.1175%2fJCLI-D-17-0062.1&partnerID=40&md5=b14c11d156431ef7a64ee73cde2153c8","A major bias in tropical precipitation over the Pacific in climate simulations stems from the models' tendency to produce two strong distinct intertropical convergence zones (ITCZs) too often. Several mechanisms have been proposed that may contribute to the emergence of two ITCZs, but current theories cannot fully explain the bias. This problem is tackled by investigating how the interaction between atmospheric cloud-radiative effects (ACREs) and the large-scale circulation influences the ITCZ position in an atmospheric general circulation model. Simulations are performed in an idealized aquaplanet setup and the longwave and shortwave ACREs are turned off individually or jointly. The low-level moist static energy (MSE) is shown to be a good predictor of the ITCZ position. Therefore, a mechanism is proposed that explains the changes in MSE and thus ITCZ position due to ACREs consistently across simulations. The mechanism implies that the ITCZ moves equatorward if the Hadley circulation strengthens because of the increased upgradient advection of low-level MSE off the equator. The longwave ACRE increases the meridional heating gradient in the tropics and as a response the Hadley circulation strengthens and the ITCZ moves equatorward. The shortwave ACRE has the opposite effect. The total ACRE pulls the ITCZ equatorward. This mechanism is discussed in other frameworks involving convective available potential energy, gross moist stability, and the energy flux equator. It is thus shown that the response of the large-scale circulation to the shortwave and longwave ACREs is a fundamental driver of changes in the ITCZ position. © 2017 American Meteorological Society."
"55355215900;42962694100;","The influence of urban surface expansion in China on regional climate",2017,"10.1175/JCLI-D-15-0604.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85010874934&doi=10.1175%2fJCLI-D-15-0604.1&partnerID=40&md5=f7a54512693a3ad32a743492f70c1446","Incorporating satellite-based urban surface data for the 1980s, 1990s, 2000s, and 2010s in China, contributions to regional warming, and changes in the precipitation due to urban surface expansion were explored using the nested Fifth-generation Pennsylvania State University-NCAR Mesoscale Model version 3.7 (MM5V3.7) with urban effects considered. The impact on surface air temperature at 2 m (SAT) due to urban surface expansion between the 1980s and the 2010s revealed that annual urban-related warming was lower over East Asia (0.031°C) and China (0.075°C) but higher in eastern China (0.14°C), which experienced dramatic urbanization. Greater warming could be detected over urban surface areas in the three city clusters [Beijing-Tianjin-Hebei (BTH) and the Yangtze and Pearl River deltas (YRD and PRD, respectively)], which reached 1.06°, 0.84°, and 0.92°C, respectively. Urban-related warming was not limited to a single city or city clusters but extended over a SAT-increased belt that covered the eastern coast of China. Further analysis showed that urban-surface-expansion-induced changes in albedo and the total cloud amount contributed to the changes in the radiation budget, which resulted in strong surface radiative forcings in the urban surface (14.5, 11.2, and 11.7 W m-2 for BTH, YRD, and PRD, respectively). However, significant differences could be detected for the transition from nonurban to urban land use compared to those that were classified as urban in both time periods because of the varied albedo changes. The urbanization-related warming, especially in the city cluster areas, also had a further effect on the large-scale circulation and precipitation. The precipitation was weakened in northeastern and northern China but intensified in eastern and southern China, which resulted in the strengthened precipitation over China (0.016 mm day-1, 0.65%) and East Asia (0.011 mm day-1, 0.28%). Therefore, subregional characteristics with marked seasonal, interannual, and decadal variations were detected for the influence of the urban surface expansion."
"57188866963;57210687618;","Moisture-radiative cooling instability",2016,"10.1002/2016MS000763","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84995655013&doi=10.1002%2f2016MS000763&partnerID=40&md5=ce8e3bc769d3fe24fe9d633ad2154cdd","Radiative-convective equilibrium (RCE)—the statistical equilibrium state of the atmosphere where convection and radiation interact in the absence of lateral transport—is widely used as a basic-state model of the tropical atmosphere. The possibility that RCE may be unstable to development of large-scale circulation has been raised by recent modeling, theoretical, and observational studies, and could have profound consequences for our understanding of tropical meteorology and climate. Here, we study the interaction between moisture and radiative cooling as a contributor to instability of RCE. We focus on whether the total atmospheric radiative cooling decreases with column water vapor; this condition, which we call moisture-radiative cooling instability (MRCI), provides the potential for unstable growth of moist or dry perturbations. Analytic solutions to the gray-gas radiative transfer equations show that MRCI is satisfied when the total column optical depth—linked to column water vapor—exceeds a critical threshold. Both the threshold and the growth rate of the instability depend strongly on the shape of the water vapor perturbation. Calculations with a realistic radiative transfer model confirm the existence of MRCI for typical tropical values of column water vapor, but show even stronger dependence on the vertical structure of water vapor perturbation. Finally, we analyze the sensitivity of atmospheric radiative cooling to variability in column water vapor in observed tropical soundings. We find that clear-sky MRCI is satisfied across a range of locations and seasons in the real tropical atmosphere, with a partial growth rate of ∼1 month. © 2016. The Authors."
"52564166000;6602729528;6603584184;7005626683;8571302000;6602699701;","Influence of synoptic weather patterns on solar irradiance variability in northern Europe",2016,"10.1175/JCLI-D-15-0476.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84971426740&doi=10.1175%2fJCLI-D-15-0476.1&partnerID=40&md5=25c552e60945784372960480c4491111","Observations have revealed strong variability of shortwave (SW) irradiance at Earth's surface on decadal time scales, referred to as global dimming and brightening. Previous studies have attributed the dimming and brightening to changes in clouds and atmospheric aerosols. This study assesses the influence of atmospheric circulation on clouds and SW irradiance to separate the influence of ""natural"" SW variability from direct and, to some extent, indirect aerosol effects. The focus is on SW irradiance in northern Europe in summer and spring because there is little high-latitude SW irradiance during winter. As a measure of large-scale circulation the Grosswetterlagen (GWL) dataset, a daily classification of synoptic weather patterns, is used. Empirical models of normalized SW irradiance are constructed based on the GWL, relating the synoptic weather patterns to the local radiative climate. In summer, a temporary SW peak in the 1970s and subsequent dimming is linked to variations in the synoptic patterns over Scandinavia, possibly related to a northward shift in the North Atlantic storm track. In spring, a decrease of anticyclonic and increase of cyclonic weather patterns over northern Europe contributes to the dimming from the 1960s to 1990. At many sites, there is also a residual SW irradiance trend not explained by the GWL model: a weak nonsignificant residual dimming from the 1950s or 1960s to around 1990, followed by a statistically significant residual brightening. It is concluded that factors other than the large-scale circulation (e.g., decreasing aerosol emissions) also play an important role in northern Europe. © 2016 American Meteorological Society."
"6506416572;7006861646;35766145000;56695168500;","Macrophysical, microphysical, and radiative properties of tropical mesoscale convective systems over their life cycle",2016,"10.1175/JCLI-D-15-0551.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84966444592&doi=10.1175%2fJCLI-D-15-0551.1&partnerID=40&md5=455e62f21a968a3bf66fdd7752394391","Mesoscale convective systems (MCSs) are important drivers of the atmospheric large-scale circulation through their associated diabatic heating profile. Taking advantage of recent tracking techniques, this study investigates the evolution of macrophysical, microphysical, and radiative properties over the MCS life cycle by merging geostationary and polar-orbiting satellite data. These observations are performed in three major convective areas: Continental West Africa, the adjacent Atlantic Ocean, and the open Indian Ocean. MCS properties are also investigated according to internal subregions (convective, stratiform, and nonprecipitating anvil). Continental MCSs show a specific life cycle, with more intense convection at the beginning. Larger and denser hydrometeors are thus found at higher altitudes, as well as up to the cirriform subregion. Oceanic MCSs have more constant reflectivity values, suggesting a less intense convective updraft, but more persistent intensity. A layer of small crystals is found in all subregions, but with a depth that varies according to the MCS subregion and life cycle. Radiative properties are also examined. It appears that the evolution of large and dense hydrometeors tends to control the evolution of the cloud albedo and the outgoing longwave radiation. The impact of dense hydrometeors, detrained from the convective towers, is also seen in the radiative heating profiles, in particular in the shortwave domain. A dipole of cooling near the cloud top and heating near the cloud base is found in the longwave; this cooling intensifies near the end of the life cycle. © 2016 American Meteorological Society."
"55522498000;14920052300;55802246600;57169158900;55544020300;","Climatic effects of irrigation over the Huang-Huai-Hai plain in China simulated by the weather research and forecasting model",2016,"10.1002/2015JD023736","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84960847662&doi=10.1002%2f2015JD023736&partnerID=40&md5=7e534805d7e98b77d33a55034a337ced","The climatic effects of irrigation over the Huang-Huai-Hai Plain (3HP) in China are investigated by using the weather research and forecasting model coupled with an operational-like irrigation scheme. Multiple numerical experiments with irrigation off/on during spring, summer, and both spring and summer are conducted. Results show that the warm bias in surface temperature and dry bias in soil moisture are reduced over the 3HP region during the growing seasons by considering the irrigation in the model. The air temperature during nongrowing seasons is also affected by irrigation because of the persistent effects of soil moisture on land-air energy exchanges and ground heat storage. Irrigation can induce significant cooling in the planetary boundary layer (PBL) during the growing seasons and lead to a relatively wet PBL with increased low-level clouds during spring but a relatively dry condition in summer. Further analyses indicate that irrigation leads to increased summer precipitation over the Yangtze River Basin and decreased summer precipitation in southern and northern China. These responses are associated with the changes in the large-scale circulation induced by irrigation. Irrigation tends to cool the atmosphere and forces a possible southward shift of the upper level jet that can further affect the precipitation distribution. Our model results suggest that in addition to local-scale processes, large-scale impacts should also be considered when studying the precipitation response to irrigation over East Asia. ©2016. American Geophysical Union. All Rights Reserved."
"14920137300;","A strategy for representing the effects of convective momentum transport in multiscale models: Evaluation using a new superparameterized version of the Weather Research and Forecast model (SP-WRF)",2015,"10.1002/2014MS000417","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027921791&doi=10.1002%2f2014MS000417&partnerID=40&md5=d235b4b8f88330cd617b47890364ba66","This paper describes a general method for the treatment of convective momentum transport (CMT) in large-scale dynamical solvers that use a cyclic, two-dimensional (2-D) cloud-resolving model (CRM) as a ""superparameterization"" of convective-system-scale processes. The approach is similar in concept to traditional parameterizations of CMT, but with the distinction that both the scalar transport and diagnostic pressure gradient force are calculated using information provided by the 2-D CRM. No assumptions are therefore made concerning the role of convection-induced pressure gradient forces in producing up or down-gradient CMT. The proposed method is evaluated using a new superparameterized version of the Weather Research and Forecast model (SP-WRF) that is described herein for the first time. Results show that the net effect of the formulation is to modestly reduce the overall strength of the large-scale circulation, via ""cumulus friction."" This statement holds true for idealized simulations of two types of mesoscale convective systems, a squall line, and a tropical cyclone, in addition to real-world global simulations of seasonal (1 June to 31 August) climate. In the case of the latter, inclusion of the formulation is found to improve the depiction of key synoptic modes of tropical wave variability, in addition to some aspects of the simulated time-mean climate. The choice of CRM orientation is also found to importantly affect the simulated time-mean climate, apparently due to changes in the explicit representation of wide-spread shallow convective regions. © 2015. The Authors."
"55344913800;6602524412;36615513300;23570158900;","The atmospheric general circulation in thermodynamical coordinates",2014,"10.1175/JAS-D-13-0173.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896777269&doi=10.1175%2fJAS-D-13-0173.1&partnerID=40&md5=502f6752a59db08c69d00219cb0e09b2","The zonal and meridional components of the atmospheric general circulation are used to define a global thermodynamic streamfunction in dry static energy versus latent heat coordinates. Diabatic motions in the tropical circulations and fluxes driven by midlatitude eddies are found to form a single, global thermodynamic cycle. Calculations based on the Interim European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-Interim) dataset indicate that the cycle has a peak transport of 428 Sv (Sv ≡ [109 kgs-1). The thermodynamic cycle encapsulates a globally interconnected heat and water cycle comprising ascent of moist air where latent heat is converted into dry static energy, radiative cooling where dry air loses dry static energy, and a moistening branch where air is warmed and moistened. It approximately follows a tropical moist adiabat and is bounded by the Clausius-Clapeyron relationship for near-surface air. The variability of the atmospheric general circulation is related to ENSO events using reanalysis data from recent years (1979- 2009) and historical simulations from the EC-Earth Consortium (EC-Earth) coupled climate model (1850- 2005). The thermodynamic cycle in both EC-Earth and ERA-Interim widens and weakens with positive ENSO phases and narrows and strengthens during negative ENSO phases with a high correlation coefficient. Weakening in amplitude suggests a weakening of the large-scale circulation, while widening suggests an increase in mean tropical near-surface moist static energy. © 2014 American Meteorological Society."
"36165663600;6602908667;55686667100;7102857642;16645036600;","Role of convective entrainment in spatial distributions of and temporal variations in precipitation over tropical oceans",2014,"10.1175/JCLI-D-13-00701.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919696659&doi=10.1175%2fJCLI-D-13-00701.1&partnerID=40&md5=38503325ad8429d8287d3ab923834d2d","The authors demonstrate that an appropriate treatment of convective entrainment is essential for determining spatial distributions of and temporal variations in precipitation. Four numerical experiments are performed using atmospheric models with different entrainment characteristics: a control experiment (Ctl), a no-entrainment experiment (NoEnt), an original Arakawa-Schubert experiment (AS), and an AS experiment with a simple empirical suppression of convection depending on cloud-layer humidity (ASRH). The fractional entrainment rates of AS and ASRH are constant for each cloud type and are very small in the lower troposphere compared with those in the Ctl, in which half of the buoyancy-generated energy is consumed by entrainment. Spatial and temporal variations in the observed precipitation are satisfactorily reproduced in the Ctl, but their amplitudes are underestimated with a so-called double intertropical convergence zone bias in the NoEnt and AS. The spatial variation is larger in the Ctl because convection is more active over humid ascending regions and more suppressed over dry subsidence regions. Feedback processes involving convection, the large-scale circulation, free tropospheric moistening by congestus, and radiation enhance the variations. The temporal evolution of precipitation events is also more realistic in the Ctl, because congestus moistens the midtroposphere, and large precipitation events occur once sufficient moisture is available. The large entrainment in the lower troposphere, increasing free tropospheric moistening by congestus and enhancing the coupling of convection to free tropospheric humidity, is suggested to be important for the realistic spatial and temporal variations. © 2014 American Meteorological Society."
"6603263640;7006184606;","Numerical instability resulting from infrequent calculation of radiative heating",2004,"10.1175/1520-0493(2004)132<0673:NIRFIC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842735952&doi=10.1175%2f1520-0493%282004%29132%3c0673%3aNIRFIC%3e2.0.CO%3b2&partnerID=40&md5=d159b249f1d4df93ed3ffc4f65d2309e","Owing to its relative expense, radiative heating is often not calculated for every time step in numerical simulations of the atmosphere. This is justified when the radiation field evolves slowly in comparison to the atmospheric flow. However, when the effects of variable water vapor and clouds are taken into account, the radiation field can change rapidly, and the finite time between calls to the radiation scheme can introduce a destabilizing time lag. In the worst case, this lag gives rise to an exponential numerical instability with a growth rate proportional to the time interval between radiative calculations. In less drastic circumstances, in which the radiation would damp oscillations of the real system, numerical instability occurs when the time interval between calls to the radiation scheme exceeds a critical value that depends on the Doppler-shifted natural oscillation frequency and the radiative damping rate. It is shown that this type of instability occurs in a single-column model as well as in an idealized general circulation model. The critical frequency at which the radiative heating rate should be computed is found to depend on several factors, including the large-scale circulation and the model resolution. Several potential remedies are discussed. © 2004 American Meteorological Society."
"55366637500;6603925960;7004714030;","A process oriented characterization of tropical oceanic clouds for climate model evaluation, based on a statistical analysis of daytime A-train observations",2012,"10.1007/s00382-012-1533-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868147271&doi=10.1007%2fs00382-012-1533-7&partnerID=40&md5=5b2bbd5c559c02823975ec9f29d190d7","This paper aims at characterizing how different key cloud properties (cloud fraction, cloud vertical distribution, cloud reflectance, a surrogate of the cloud optical depth) vary as a function of the others over the tropical oceans. The correlations between the different cloud properties are built from 2 years of collocated A-train observations (CALIPSO-GOCCP and MODIS) at a scale close to cloud processes; it results in a characterization of the physical processes in tropical clouds, that can be used to better understand cloud behaviors, and constitute a powerful tool to develop and evaluate cloud parameterizations in climate models. First, we examine a case study of shallow cumulus cloud observed simultaneously by the two sensors (CALIPSO, MODIS), and develop a methodology that allows to build global scale statistics by keeping the separation between clear and cloudy areas at the pixel level (250, 330 m). Then we build statistical instantaneous relationships between the cloud cover, the cloud vertical distribution and the cloud reflectance. The vertical cloud distribution indicates that the optically thin clouds (optical thickness >1.5) dominate the boundary layer over the trade wind regions. Optically thick clouds (optical thickness <3.4) are composed of high and mid-level clouds associated with deep convection along the ITCZ and SPCZ and over the warm pool, and by stratocumulus low level clouds located along the East coast of tropical oceans. The cloud properties are analyzed as a function of the large scale circulation regime. Optically thick high clouds are dominant in convective regions (CF < 80 %), while low level clouds with low optical thickness (>3.5) are present in regimes of subsidence but in convective regimes as well, associated principally to low cloud fractions (CF > 50 %). A focus on low-level clouds allows us to quantify how the cloud optical depth increases with cloud top altitude and with cloud fraction. © 2012 Springer-Verlag Berlin Heidelberg."
"22956930200;7005137442;","Using microwave observations to assess large-scale control of free tropospheric water vapor in the mid-latitudes",2006,"10.1029/2006GL026240","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845642073&doi=10.1029%2f2006GL026240&partnerID=40&md5=c86d80ae512216bd3e27ef108554ca65","The hypothesis of large scale control of midlatitude water vapor is evaluated through reconstructions of the water vapor field using a Lagrangian advectioncondensation model without microphysics or diffusion. The reconstruction is validated against satellite observations in the 183.31 ± 1 GHz band from the AMSU-B radiometer following a model-to-satellite approach. Because microwave radiation can penetrate clouds, the validation can be performed for cloudy as well as clear sky scenes, with the exception of very cold or precipitating clouds, which are screened out. The results show very good agreement between the simulated top of the atmosphere radiation and the observations, in clear as well as cloudy regions, with a general bias of less than 2K. The results suggest that cloud microphysics and small scale mixing play at most a secondary role in determining midlatitude free tropospheric humidity except perhaps indirectly through their effect on large scale circulation. Copyright 2006 by the American Geophysical Union."
"56380621100;8043701900;","Estimating vertical motion profile shape within tropical weather states over the oceans",2014,"10.1175/JCLI-D-13-00602.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907433694&doi=10.1175%2fJCLI-D-13-00602.1&partnerID=40&md5=4e2f09ced9fd46b967d64ce299613eb6","The vertical structure of tropical deep convection strongly influences interactions with larger-scale circulations and climate. This paper focuses on investigating this vertical structure and its relationship with mesoscale tropical weather states. The authors test the hypothesis that latent heating plus turbulent flux convergence varies (in space and time) in association with weather state type. The authors estimate mean-state vertical motion profile shape and latent heating plus turbulent flux convergence for six weather states defined using cloud-top pressure and optical depth properties from the International Satellite Cloud Climatology Project (ISCCP) dataset. Assuming two modes of vertical motion profile variability, these modes are statistically extracted from reanalysis data using a principal component analysis. Using these modes and the relationship between vertical motion, the dry static energy budget, and mass continuity, the authors estimate vertical motion profile shape. In these estimates, the authors use Global Precipitation Climatology Project (GPCP) [and Tropical Rainfall Measuring Mission (TRMM) 3B42] precipitation and Quick Scatterometer (QuikSCAT) surface convergence data in the ITCZ region from 2001 to 2006. Finally, these profile shapes are categorized by weather state type and spatiotemporally averaged to generate mean-state vertical motion profiles and latent heating plus turbulent flux convergence. The authors find that vertical motion profile shape varies by weather state. The isolated systems convective regime exhibits more ""bottom heaviness""than the other convectively active regimes, with maximum upward vertical motion occurring in the lower troposphere rather than the middle to upper troposphere. The variability observed does not coincide with the conventional profile variability based on stratiform rain fraction. © 2014 American Meteorological Society."
"7402944490;7201724255;55499275500;","ENSO contribution to aerosol variations over the maritime continent and the western north pacific during 2000-10",2013,"10.1175/JCLI-D-12-00253.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883167746&doi=10.1175%2fJCLI-D-12-00253.1&partnerID=40&md5=c5b2dac18a2fa3ce80a0def983936686","This study investigates interannual aerosol variations over the Maritime Continent and the western North Pacific Ocean and aerosol-cloud-precipitation relationship during the period 2000-10 based on monthlymean anomalies. The local aerosol-cloud-precipitation relationship displays strong regional characteristics. The aerosol variation is negatively correlated with cloud and precipitation variation over the Maritime Continent, but is positively correlated with cloud and precipitation variation over the region southeast of Japan. Over broad subtropical oceanic regions, the aerosol variation is positively correlated with cloud variation, but has a weak correlation with precipitation variation. Aerosol variations over the Maritime Continent and over the region southeast of Japan display a biennial feature with an obvious phase lag of about 8 months in the latter region during 2001-07. This biennial feature is attributed to the impacts of El Nĩno events on aerosol variations in these regions through large-scale circulation and precipitation changes. Around October of El Nĩno-developing years, the suppressed precipitation over the Maritime Continent favors an aerosol increase by reducing the wet deposition and setting up dry conditions favorable for fire burning. During early summer of El Nĩno-decaying years, suppressed heating around the Philippines as a delayed response to El Nĩno warming induces an anomalous lower-level cyclone over the region to the southeast of Japan through an atmospheric teleconnection, leading to an accumulation of aerosol and increase of precipitation. The aerosol-precipitation relationship shows an obvious change with time over eastern China, leading to an overall weak correlation © 2013 American Meteorological Society."
"7102916561;7003642788;","Interannual variations of boundary layer temperature over the African Sahel associated with vegetation and the upper troposphere",2000,"10.1029/2000JD900048","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16644377186&doi=10.1029%2f2000JD900048&partnerID=40&md5=4036cdf58934bc3dc799c990c7d57d00","The spatial patterns of correlations between the convective boundary layer (CBL) temperature and both vegetation and upper tropospheric temperature over Africa have been detected by a singular value decomposition (SVD) analysis of monthly data for the period 1981-1994. The data used in the present study consist of the National Oceanic and Atmospheric Administration (NOAA)-derived normalized difference vegetation index (NDVI) and the 850 hPa/200 hPa potential temperatures from the National Centers for Environmental Prediction (NCEP) objective reanalysis. In general, greater-than-normal vegetation over the Sahel is related to lower-than-normal CBL temperature aloft, whereas less vegetation corresponds to higher CBL temperature aloft. This vegetation-CBL correlation was extracted as the first SVD mode that has centers of action concentrated over the Sahel. The correlation is strongest during the late dry season (especially during February and April) and is weaker during the rainy season. Typical correlation is observed during April when marked cooling of the CBL occurs in concurrence with positive vegetation anomalies. These anomalies are likely to be produced by an occasional premonsoon rain resulting from a cloud band that propagates from the midlatitudes. During the rainy season the CBL temperature is more strongly associated with upper tropospheric temperatures, which are likely modulated by large-scale circulation, than with the Sahelian vegetation. Copyright 2000 by the American Geophysical Union."
"7201605742;","Towards an understanding of the interaction between convection and the larger-scale in the tropics",1988,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024149810&partnerID=40&md5=e955ca25909f77592b4a75abb3f3340c","It is emphasised that cloud physical and dynamical processes in cumulus convection may play an important role not only in the mesoscale organisation of cumulus convection but also in persistence of mesoscale convective activity and the development of a larger-scale circulation. The well-known CISK mechanism, to which frictional convergence is essential, appears to be applicable only when the vorticity is very large, as in the case of the eyewall of tropical cyclones. It is also suggested that there exists a dynamically significant mode of organised cumulus convection, in this paper this is referred to as Mesoscale Convection (MC). Finally, some results from a numerical model with a new scheme of implicit representation of cumulus convection (but with explicit treatment of mesoscale convection) are presented to show mesoscale and large-scale behaviour in the inter-tropical convergence zone under a simplified situation. -from Author"
"57190683350;26431037300;6701676992;","Contributions of Ice Thickness to the Atmospheric Response From Projected Arctic Sea Ice Loss",2018,"10.1029/2018GL078158","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048976300&doi=10.1029%2f2018GL078158&partnerID=40&md5=d849aa4269e46e0bf18d34967cad4d31","A large ensemble of simulations from a high-top atmospheric general circulation model are conducted to compare the atmospheric responses from loss of Arctic sea ice thickness and sea ice concentration. The response to projected sea ice thickness loss indicates substantial surface warming over the Arctic Ocean and up to 1°C of cooling in Eurasia. While the dynamic circulation response from sea ice thickness loss is smaller in magnitude, it has a similar spatial anomaly pattern as that due to sea ice concentration loss. This pattern resembles the negative phase of the Northern Annular Mode. The simulations reveal that sea ice thickness loss enhances the thermodynamic and large-scale circulation response from sea ice anomalies. These results stress the importance of considering a realistic sea ice thickness distribution in future atmospheric general circulation model sea ice perturbation experiments. ©2018. American Geophysical Union. All Rights Reserved."
"15050523700;15047538100;36242447900;6602135370;","Effect of cloud microphysics on Indian summer monsoon precipitating clouds: A coupled climate modeling study",2017,"10.1002/2016JD026106","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85017390574&doi=10.1002%2f2016JD026106&partnerID=40&md5=e051de3d1ca2ff4c65a1356b2083b5bf","The quest for one of the most dominant processes controlling the large-scale circulations in the tropics is unraveled. The impact of cloud microphysical processes is known to have effects on rainfall and local atmospheric thermodynamics; however, its effect on the prevailing mean circulations is not yet studied. Two sets of coupled global climate model experiments (ICE and NO ICE microphysics) reveal that ice microphysics improves the strength of the Hadley circulation with respect to observation. Results pinpoint that ICE simulation enhances high cloud fraction (global tropics: ~59%, India: ~51%) and stratiform rain (global tropics: ~5%, India: ~15%) contribution. ICE and NO ICE cloud microphysics impacts differently on the outgoing longwave radiation (OLR), tropospheric temperature, and surface shortwave and longwave radiation. The effect of ice microphysics reduces OLR, which signifies deeper convection in the ICE run. The global annual average of the net radiation flux (shortwave and longwave) at the surface in ICE run (108.1W/m2) is close to the observation (106W/m2), which is overestimated in NO ICE run (112W/m2). The result of apparent heat source term over the land and ocean surface eventually modifies regional Hadley circulation. Thus, the effect of ice microphysics in the global coupled model is important not only because of microphysics but also due to the radiation feedbacks. Therefore, better ice-phase microphysics is required in the new generation of climate forecast model, which may lead to improvements in the simulation of monsoon. © 2017. American Geophysical Union. All Rights Reserved."
"36908840200;57111001300;7202048112;55476830600;55656929800;6506328135;","Sources and pathways of the upscale effects on the Southern Hemisphere jet in MPAS-CAM4 variable-resolution simulations",2016,"10.1002/2016MS000743","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85000983826&doi=10.1002%2f2016MS000743&partnerID=40&md5=9025e1dd7fe7c153efcc444a3492668e","Impacts of regional grid refinement on large-scale circulations (“upscale effects”) were detected in a previous study that used the Model for Prediction Across Scales-Atmosphere coupled to the physics parameterizations of the Community Atmosphere Model version 4. The strongest upscale effect was identified in the Southern Hemisphere jet during austral winter. This study examines the detailed underlying processes by comparing two simulations at quasi-uniform resolutions of 30 and 120 km to three variable-resolution simulations in which the horizontal grids are regionally refined to 30 km in North America, South America, or Asia from 120 km elsewhere. In all the variable-resolution simulations, precipitation increases in convective areas inside the high-resolution domains, as in the reference quasi-uniform high-resolution simulation. With grid refinement encompassing the tropical Americas, the increased condensational heating expands the local divergent circulations (Hadley cell) meridionally such that their descending branch is shifted poleward, which also pushes the baroclinically unstable regions, momentum flux convergence, and the eddy-driven jet poleward. This teleconnection pathway is not found in the reference high-resolution simulation due to a strong resolution sensitivity of cloud radiative forcing that dominates the aforementioned teleconnection signals. The regional refinement over Asia enhances Rossby wave sources and strengthens the upper level southerly flow, both facilitating the cross-equatorial propagation of stationary waves. Evidence indicates that this teleconnection pathway is also found in the reference high-resolution simulation. The result underlines the intricate diagnoses needed to understand the upscale effects in global variable-resolution simulations, with implications for science investigations using the computationally efficient modeling framework. © 2016. The Authors."
"6602364115;","Attributing the behavior of low-level clouds in large-scale models to subgrid-scale parameterizations",2015,"10.1002/2015MS000503","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959545996&doi=10.1002%2f2015MS000503&partnerID=40&md5=ac18563cf88f13037d42aac264d6143f","This study explores ways of establishing the characteristic behavior of boundary layer schemes in representing subtropical marine low-level clouds in climate models. To this purpose, parameterization schemes are studied in both isolated and interactive mode with the larger-scale circulation. Results of the EUCLIPSE/GASS intercomparison study for Single-Column Models (SCM) on low-level cloud transitions are compared to General Circulation Model (GCM) results from the CFMIP-2 project at selected grid points in the subtropical eastern Pacific. Low cloud characteristics are plotted as a function of key state variables for which Large-Eddy Simulation results suggest a distinct and reasonably tight relation. These include the Cloud Top Entrainment Instability (CTEI) parameter and the total cloud cover. SCM and GCM results are thus compared and their resemblance is quantified using simple metrics. Good agreement is reported, to such a degree that SCM results are found to be uniquely representative of their GCM, and vice versa. This suggests that the system of parameterized fast boundary layer physics dominates the model state at any given time, even when interactive with the larger-scale flow. This behavior can loosely be interpreted as a unique ""fingerprint"" of a boundary layer scheme, recognizable in both SCM and GCM simulations. The result justifies and advocates the use of SCM simulation for improving weather and climate models, including the attribution of typical responses of low clouds to climate change in a GCM to specific parameterizations. © 2015. The Authors."
"7004157687;","Upscale effects in simulations of tropical convection on an equatorial beta-plane",2006,"10.1016/j.dynatmoce.2006.02.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749650938&doi=10.1016%2fj.dynatmoce.2006.02.006&partnerID=40&md5=5ca88b423f356cf6b71d31f442efba73","A cloud-resolving model is configured to span the full meridional extent of the tropical atmosphere and have sufficient zonal extent to permit the representation of tropical cloud super-clusters. This is made computationally feasible by the use of anisotropic horizontal grids where one horizontal coordinate direction has over an order of magnitude finer resolution than the other direction. Typically, the meridional direction is chosen to have the coarser resolution (40 km grid spacing) and the zonal direction has enough resolution to 'permit' crude convective squall line ascent (1 km grid spacing). The aim was to run in cloud-resolving model (CRM) mode yet still have sufficient meridional resolution and extent to capture the equatorial trapped waves and the Hadley circulation. The large-scale circulation is driven by imposed uniform tropospheric cooling in conjunction with a fixed sea surface temperature distribution. At quasi-equilibrium the flow is characterized by sub-tropical jetstreams, tropical squall line systems that form eastward-propagating super-clusters, tropical depressions and even hurricanes. Two scientific issues are briefly addressed by the simulations: what forces the Hadley circulation and the nature of stratospheric waves appearing in the simulation. It is found that the presence of a meridional sea surface temperature gradient is not sufficient on its own to force a realistic Hadley circulation even though convection communicates the underlying temperature gradient to the atmosphere. It is shown in a simulation that accounts for the observed time and zonal-mean momentum forcing effect of large-scale eddies (originating in middle latitudes) that the heaviest precipitation is concentrated near the equator in association with moisture flux convergence driven by the Trade winds. A spectral analysis of the stratospheric waves found on the equator using the dispersion relation for equatorially-trapped waves provides strong evidence for the existence of a domain-scale Kelvin wave together with eastward and westward propagating inertia-gravity waves. The eastward-propagating stratospheric waves appear to be part of a convectively coupled wave system travelling at about 15 ms-1. Crown Copyright © 2006."
"36862677400;7202145115;","Interactions among cloud, water vapor, radiation, and large-scale circulation in the tropical climate. Part II: Sensitivity to spatial gradients of sea surface temperature",2003,"10.1175/1520-0442-16.10.1441","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038467220&doi=10.1175%2f1520-0442-16.10.1441&partnerID=40&md5=0d094d46996187e46218244188c3a100","The responses of the large-scale circulation, clouds, and water vapor to an imposed sea surface temperature (SST) gradient are investigated. Simulations compare reasonably to averaged observations over the Pacific, considering the simplifications applied to the model. The model responses to sinusoidal SST patterns have distinct circulations in the upper and lower troposphere. The upper circulation is sensitive to the heating from deep convection over the warmest SST. Stronger SST gradients are associated with stronger longwave cooling above stratus clouds in the subsidence region, stronger lower-tropospheric large-scale circulation, a reduction of the rain area, and larger area coverage of low clouds. A similar SST gradient with a warmer mean temperature produces slightly weaker lower-tropospheric circulation, and slightly reduced low cloud coverage. The outgoing longwave radiation (OLR) is not sensitive to the mean SST or the range of the imposed sinusoidal SST gradient. The positive feedbacks of water vapor and decreasing high cloud OLR compensate for the increase in longwave emission with increasing mean temperature in these simulations. As the SST gradient is increased keeping the mean SST constant, the positive high cloud feedback is still active, but the air temperature increases in proportion to the maximum SST in the domain, increasing the clear-sky OLR value and keeping the average OLR constant. The net absorbed shortwave radiation (SWI) is found to be extremely sensitive to the SST gradient. The stronger lower-tropospheric large-scale circulation produces a higher water content in the high and low clouds, increasing the absolute magnitude of the shortwave cloud forcing. A 25% increase in the maximum zonal mass flux of the lower circulation of the 300-K mean, 4-K SST range simulation leads to a 7.4 W m-2 decrease in SWI. Increasing the mean SST creates a positive feedback in these simulations because of the decrease in the lower-tropospheric large-scale circulation and the resultant decrease in cloud optical depth."
"36941575300;8549269500;","CloudSat observations of multi layered clouds across the globe",2017,"10.1007/s00382-016-3345-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84986300653&doi=10.1007%2fs00382-016-3345-7&partnerID=40&md5=6d32fcfeeaa57788671b5a0f3b00fa2d","Vertically resolved multi-layer cloud distributions over the globe using 4 years of CloudSat/CALIPSO observations during 2007–2010 are discussed. The quantitative information on the frequency of occurrence of one- to five-layered clouds across the globe is established, which are of immense importance from the global climate standpoint. After segregating the CloudSat observations into different seasons, the 4 years of mean global maps of frequency of occurrence of one to five-layered clouds are discussed in details. These global maps provide much needed quantification of vertically resolved multi-layer clouds by revealing when and where the frequency of occurrence of multi-layer clouds are maximum including the number of layers. On an average, it is observed that over the globe one-, two-, three-, four- and five-layer clouds occur 53, 20, 3.5, 0.4 and 0.04 % of the time respectively. High fraction of single layer clouds is observed over the descending limbs of Hadley cell where relatively large lower tropospheric stability is found. The regions where multi-layer clouds are more frequent are identified and discussed along with large scale circulation. Apart from quantifying the frequency of occurrence of multi-layer clouds, the latitudinal distribution of zonal mean occurrence of cloud base and top altitudes of each cloud layer is constructed for boreal winter and summer. These analyses provide the cloud base and top altitudes of one to five-layered clouds, which are important to understand the vertical structure of the multi-layered clouds. The significance of the present study lies in establishing the global distribution of vertically resolved multi-layer clouds and the role of large-scale dynamics in controlling their distribution for the first time. © 2016, Springer-Verlag Berlin Heidelberg."
"55545874600;7005446873;6507112497;16426378500;55324953800;7102567936;36054921000;57204886915;8977001000;12761291000;19934163800;57000268800;6603566335;35369402500;","Intercomparison of methods of coupling between convection and large-scale circulation: 2. Comparison over nonuniform surface conditions",2016,"10.1002/2015MS000570","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84978322432&doi=10.1002%2f2015MS000570&partnerID=40&md5=f2948755884286fb0c28e23e41037fe3","As part of an international intercomparison project, the weak temperature gradient (WTG) and damped gravity wave (DGW) methods are used to parameterize large-scale dynamics in a set of cloud-resolving models (CRMs) and single column models (SCMs). The WTG or DGW method is implemented using a configuration that couples a model to a reference state defined with profiles obtained from the same model in radiative-convective equilibrium. We investigated the sensitivity of each model to changes in SST, given a fixed reference state. We performed a systematic comparison of the WTG and DGW methods in different models, and a systematic comparison of the behavior of those models using the WTG method and the DGW method. The sensitivity to the SST depends on both the large-scale parameterization method and the choice of the cloud model. In general, SCMs display a wider range of behaviors than CRMs. All CRMs using either the WTG or DGW method show an increase of precipitation with SST, while SCMs show sensitivities which are not always monotonic. CRMs using either the WTG or DGW method show a similar relationship between mean precipitation rate and column-relative humidity, while SCMs exhibit a much wider range of behaviors. DGW simulations produce large-scale velocity profiles which are smoother and less top-heavy compared to those produced by the WTG simulations. These large-scale parameterization methods provide a useful tool to identify the impact of parameterization differences on model behavior in the presence of two-way feedback between convection and the large-scale circulation. © 2016. The Authors."
"22973752500;7003926380;11940701600;","TRMM-Observed shallow versus deep convection in the eastern Pacific related to large-scale circulations in reanalysis datasets",2014,"10.1175/JCLI-D-13-00315.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904511880&doi=10.1175%2fJCLI-D-13-00315.1&partnerID=40&md5=934f36451eb34247f53893c5e2b8598b","Over the eastern Pacific, recent studies have shown that a shallow large-scale meridional circulation with its return flow just above the boundary layer coexists with a deep Hadley circulation. This study examines how the vertical structure of large-scale circulations is related to satellite-observed individual precipitation properties over the eastern Pacific in boreal autumn. Three reanalysis datasets are used to describe differences in their behavior. The results are compared among reanalyses and three distinctly different convection periods, which are defined according to their radar echo depths. Shallow and deep circulations are shown to often coexist for each of the three periods, resulting in the multicell circulation structure. Deep (shallow) circulations preferentially appear in the mostly deep (shallow) convection period of radar echo depths. Thus, depth of convection basically corresponds to which circulation branch is dominant. This anticipated relationship between the circulation structure and depths of convection is common in all three reanalyses. Notable differences among reanalyses are found in the mid- to upper troposphere in either the time-mean state or the composite analysis based on the convection periods. Reanalyses have large variations in characteristics associated with deep circulations such as the upper-tropospheric divergence and outflows and the midlevel inflows, which are consistent with their different profiles of latent heating in the mid- to upper troposphere. On the other hand, discrepancies in shallow circulations and shallow convection are also found, but they are not as large as those in deep ones. © 2014 American Meteorological Society."
"13403754000;7006614696;7007021059;7004379124;","Reproducibility by climate models of cloud radiative forcing associated with tropical convection",2012,"10.1175/JCLI-D-11-00114.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857027494&doi=10.1175%2fJCLI-D-11-00114.1&partnerID=40&md5=d5c69133b7cfd997c0c98723748df758","In this study, cloud radiative forcing (CRF) associated with convective activity over tropical oceans is analyzed for monthly mean data from twentieth-century simulations of 18 climate models participating in phase 3 of the Coupled Model Intercomparison Project (CMIP3) in comparison with observational and reanalysis data. The analysis is focused on the warm oceanic regions with sea surface temperatures (SSTs) above 27°C to exclude the regions with cold SSTs typically covered by low stratus clouds. CRF is evaluated for different regimes sorted by pressure-coordinated vertical motion at 500 hPa (ω 500) as an index of large-scale circulation. The warm oceanic regions cover the regime of vertical motion ranging from strong ascent to weak descent. The most notable feature found in this study is a systematic underestimation by most models of the ratio of longwave cloud radiative forcing (LWCRF) to shortwave cloud radiative forcing (SWCRF) over the weak vertical motion regime defined as -10, ω500, 20 hPa day -1. The underestimation of the ratio corresponds to the underestimation of LWCRF and the overestimation of SWCRF. Clouds in models seem to be lower in the amount of high clouds but more reflective than those in the observations in this regime. In the weak vertical motion regime, the lower free troposphere is dry. In the large-scale environment condition, the reproducibility of LWCRF is high in models adopting the scheme where the relative humidity- based suppression for deep convection occurrence is implemented. Models adopting the Zhang andMcFarlane scheme show good performance without such a suppression mechanism. © 2012 American Meteorological Society."
"35572026100;57193882808;7006095466;","Mean-state convective circulations over large-scale tropical SST gradients",2002,"10.1175/1520-0469(2002)059<1578:MSCCOL>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036274834&doi=10.1175%2f1520-0469%282002%29059%3c1578%3aMSCCOL%3e2.0.CO%3b2&partnerID=40&md5=873ce721d880537e7bb0368eab6217bc","The dynamical balance of the mean tropical atmospheric circulation maintained over large-scale SST gradients is analyzed. To first order, the strength of the circulation is determined by the subsidence rate in the dry descent region that balances the radiative cooling. The divergent component of the horizontal wind is then proportional to the domain size. The convective intensity is determined by the balance between convective heating and the sum of the radiative cooling and adiabatic cooling by large-scale vertical ascent. A key result is that the amplitude of the SST gradients does not directly determine the strength of the large-scale circulation. A second-order analysis shows that the tropospheric temperature responds to SST only through the residual convective heating, which is the deviation of convective heating from the first-order estimate. This decreases the temperature gradient that drives the observed Walker circulation to only a small fraction of the SST gradient across the Pacific. This argument is analogous to Lindzen and Nigam's ""back pressure."" The suppression of the SST gradients by the residual convective heating further increases with decreasing horizontal extent of the large-scale circulation, as well as with increasing SST contrast. Therefore, the horizontal air temperature gradient required to drive the large-scale circulation is consistent with the first-order estimate. Analyses of cloud-resolving numerical simulations suggest that when the domain size is small, the suppression of SST gradients by residual convective heating is strong enough to generate a secondary convergence in the middle troposphere. This generates a mean circulation consisting of two shallow cells (third baroclinic mode). This shallower circulation maintains a horizontal flow strength comparable to that in a large domain. Two variables remain undetermined: the ratio between the ascending and the descending areas, and a closed expression for the residual heating rate."
"7405459515;7006550762;7004678728;24611027600;7102707632;6603098675;","An empirical model study of the tropospheric meridional circulation based on SAGE II observations",1998,"10.1029/98JD00204","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032572267&doi=10.1029%2f98JD00204&partnerID=40&md5=4279508d53cfa9cecf62cb668406492c","This study investigates the tropospheric mean meridional circulation important to the development of opaque clouds and the measurement opportunity of the 1.02-μm channel of the Stratospheric Aerosol and Gas Experiment (SAGE) II in the troposphere. A simple empirical model is formulated to derive the mean meridional circulation from the 6-year (1985-1990) statistics of the SAGE II tropospheric measurement frequency. The vertical circulation of the model is assumed to be related to the departure field of the zonally averaged SAGE II measurement frequency from the corresponding global mean in a linear fashion. The proportional constant is calibrated with the observed upwelling circulation statistics in the tropics. The obtained model vertical circulation is then used to determine the distribution of meridional velocity according to the continuity equation. The derived model mean circulation features the influence from both the diabatic circulation and the eddy quasi-isentropic transport, with a distinct pattern of material advection into the upper troposphere from both the lower troposphere and the stratosphere. Most significantly, the model circulation is shown to be highly consistent with the observed free tropospheric aerosol and ozone distributions, particularly with their seasonal variations given the aerosol and ozone source regions. This high degree of consistency illustrates the intimate relationship between the large-scale circulation, cloudiness, and the SAGE II tropospheric measurement frequency, and the robust nature of the empirical model despite the model's simplicity. The discussion in relating the model circulation to the conventional Eulerian circulation and the Lagrangian transport, based on isentropic consideration, is also provided. Copyright 1998 by the American Geophysical Union."
"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)."
"55476830600;7202048112;55189671700;6506328135;57111001300;36908840200;55317177900;55418728800;6701335949;26323138400;","Exploring the impacts of physics and resolution on aqua-planet simulations from a nonhydrostatic global variable-resolution modeling framework",2016,"10.1002/2016MS000727","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84996538372&doi=10.1002%2f2016MS000727&partnerID=40&md5=1766255af19e9c0c88ab2a43730acd50","The nonhydrostatic Model for Prediction Across Scales (NH-MPAS) provides a global framework to achieve high resolution using regional mesh refinement. Previous studies using the hydrostatic version of MPAS (H-MPAS) with the physics parameterizations of Community Atmosphere Model version 4 (CAM4) found notable resolution-dependent behaviors. This study revisits the resolution sensitivity using NH-MPAS with both CAM4 and CAM5 physics. A series of aqua-planet simulations at global quasiuniform resolutions and global variable resolution with a regional mesh refinement over the tropics are analyzed, with a primary focus on the distinct characteristics of NH-MPAS in simulating precipitation, clouds, and large-scale circulation features compared to H-MPAS-CAM4. The resolution sensitivity of total precipitation and column integrated moisture in NH-MPAS is smaller than that in H-MPAS-CAM4. This contributes importantly to the reduced resolution sensitivity of large-scale circulation features such as the intertropical convergence zone and Hadley circulation in NH-MPAS compared to H-MPAS. In addition, NH-MPAS shows almost no resolution sensitivity in the simulated westerly jet, in contrast to the obvious poleward shift in H-MPAS with increasing resolution, which is partly explained by differences in the hyperdiffusion coefficients used in the two models that influence wave activity. With the reduced resolution sensitivity, simulations in the refined region of the NH-MPAS global variable resolution configuration exhibit zonally symmetric features that are more comparable to the quasiuniform high-resolution simulations than those from H-MPAS that displays zonal asymmetry in simulations inside the refined region. Overall, NH-MPAS with CAM5 physics shows less resolution sensitivity compared to CAM4. © 2016. The Authors."
"8688004400;6603263640;7004978125;57193882808;","Multiscale interactions in an idealized walker cell: Simulations with sparse space-time superparameterization",2015,"10.1175/MWR-D-14-00082.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928880608&doi=10.1175%2fMWR-D-14-00082.1&partnerID=40&md5=d3ae642fd7bffe879c09052d38c4c621","This paper discusses the sparse space-time superparameterization (SSTSP) algorithm and evaluates its ability to represent interactions between moist convection and the large-scale circulation in the context of aWalker cell flow over a planetary scale two-dimensional domain. The SSTSP represents convective motions in each column of the large-scale model by embedding a cloud-resolving model, and relies on a sparse sampling in both space and time to reduce computational cost of explicit simulation of convective processes. Simulations are performed varying the spatial compression and/or temporal acceleration, and results are compared to the cloud-resolving simulation reported previously. The algorithm is able to reproduce a broad range of circulation features for all temporal accelerations and spatial compressions, but significant biases are identified. Precipitation tends to be too intense and too localized over warm waters when compared to the cloud-resolving simulations. It is argued that this is because coherent propagation of organized convective systems from one large-scale model column to another is difficult when superparameterization is used, as noted in previous studies. The Walker cell in all simulations exhibits low-frequency variability on a time scale of about 20 days, characterized by four distinctive stages: suppressed, intensification, active, and weakening. The SSTSP algorithm captures spatial structure and temporal evolution of the variability. This reinforces the confidence that SSTSP preserves fundamental interactions between convection and the large-scale flow, and offers a computationally efficient alternative to traditional convective parameterizations. © 2015 American Meteorological Society."
"8977001000;7403282069;","An explicit representation of vertical momentum transport in a multiscale modeling framework through its 2-d cloud-resolving model component",2014,"10.1002/2013JD021078","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898465921&doi=10.1002%2f2013JD021078&partnerID=40&md5=cd88028dd366b12a697aa43df0d4a8cd","In this study, an explicit representation of vertical momentum transport by convective cloud systems, including mesoscale convective systems (MCSs), is proposed and tested in a multiscale modeling framework (MMF). The embedded cloud-resolving model (CRM) provides vertical momentum transport in one horizontal direction. The vertical momentum transport in the other direction is assumed to be proportional to the vertical mass flux diagnosed from the CRM in addition to the effects of entrainment and detrainment. In order to represent both upgradient and downgradient vertical momentum transports, the orientation of the embedded CRM must change with time instead of being stationary typically in MMFs. The orientation is determined by the stratification of the lower troposphere and environmental wind shear. Introducing the variation of the orientations of the embedded CRM is responsible for reducing the stationary anomalous precipitation and many improvements. Improvements are strengthened when the CRM simulated vertical momentum transport is allowed to modify the large-scale circulation simulated by the host general circulation model. These include an improved spatial distribution, amplitude, and intraseasonal variability of the surface precipitation in the tropics, more realistic zonal mean diabatic heating and drying patterns, more reasonable zonal mean large-scale circulations and the East Asian summer monsoon circulation, and an improved, annual mean implied meridional ocean transport in the Southern Hemisphere. Further tests of this convective momentum transport parameterization scheme will be performed with a higher-resolution MMF to further understand its roles in the intraseasonal oscillation and tropical waves, monsoon circulation, and zonal mean large-scale circulations. © 2014. American Geophysical Union. All rights reserved."
"7103278864;35305673400;57210590791;","Airborne observations of a catalina eddy",2013,"10.1175/MWR-D-13-00029.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884930985&doi=10.1175%2fMWR-D-13-00029.1&partnerID=40&md5=bbff14bac4c0c4e626e7a4b34141359e","Summertime low-level winds over the ocean adjacent to the California coast are typically from the north, roughly parallel to the coastline. Past Point Conception the flow often turns eastward, thereby generating cyclonic vorticity in the California Bight. Clouds are frequently present when the cyclonic motion is well developed and at such times the circulation is referred to as a Catalina eddy. Onshore flow south of the California Bight associated with the eddy circulation can result in a thickening of the low-level marine stratus adjacent to the coast. During nighttime hours the marine stratus typically expands over a larger area and moves northward along the coast with the cyclonic circulation. A Catalina eddy was captured during the Precision Atmospheric Marine Boundary Layer Experiment in June of 2012. Measurements were made of the cloud structure in the marine layer and the horizontal pressure field associated with the cyclonic circulation using the University of Wyoming King Air research aircraft. Airborne measurements show that the coastal mountains to the south of Los Angeles block the flow, resulting in enhanced marine stratus heights and a local pressure maximum near the coast. The horizontal pressure field also supports a south-north movement of marine stratus. Little evidence of leeside troughing south of Santa Barbara, California, was observed for this case, implying that the horizontal pressure field is forced primarily through topographic blocking by the coastal terrain south of Los Angeles, California, and the ambient large-scale circulation associated with the mean flow. © 2013 American Meteorological Society."
"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."
"9241987300;7004978125;","Test models for filtering and prediction of moisture-coupled tropical waves",2013,"10.1002/qj.1956","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873313708&doi=10.1002%2fqj.1956&partnerID=40&md5=24303dfc6423fadf20724cc4e1936e79","The filtering/data assimilation and prediction of moisture-coupled tropical waves is a contemporary topic with significant implications for extended-range forecasting. The development of efficient algorithms to capture such waves is limited by the unstable multiscale features of tropical convection which can organize large-scale circulations and the sparse observations of the moisture-coupled wave in both the horizontal and vertical. The approach proposed here is to address these difficult issues of data assimilation and prediction through a suite of analogue models which, despite their simplicity, capture key features of the observational record and physical processes in moisture-coupled tropical waves. The analogue models emphasized here involve the multicloud convective parametrization based on three cloud types (congestus, deep, and stratiform) above the boundary layer. Two test examples involving an MJO-like turbulent travelling wave and the initiation of a convectively coupled wave train are introduced to illustrate the approach. A suite of reduced filters with judicious model errors for data assimilation of sparse observations of tropical waves, based on linear stochastic models in a moisture-coupled eigenmode basis is developed here and applied to the two test problems. Both the reduced filter and 3D-Var with a full moist background covariance matrix can recover the unobserved troposphere humidity and precipitation rate; on the other hand, 3D-Var with a dry background covariance matrix fails to recover these unobserved variables. The skill of the reduced filtering methods in recovering the unobserved precipitation, congestus, and stratiform heating rates as well as the front-to-rear tilt of the convectively coupled waves exhibits a subtle dependence on the sparse observation network and the observation time. © 2012 Royal Meteorological Society."
"8229909100;7404587604;","Regional variability of convection over northern India during the pre-monsoon season",2011,"10.1007/s00704-010-0289-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951556277&doi=10.1007%2fs00704-010-0289-4&partnerID=40&md5=1cc9dff29732af7fc90d6733742b17d0","In general, the overall differences in activity and timing of convection are a result of the influence of large-scale regional and synoptic flow patterns on the local mesoscale environment. The linkage between the space-time variability of observed clouds and rainfall, with large-scale circulation patterns and mesoscale variables over north India during the pre-monsoon season (March to May) is the focus of this paper. We use harmonic analysis to identify the first hour of rainfall for 42 stations spread over the north Indian region during the pre-monsoon summer season (March to May), from 1980 to 2000. The variability is observed to be systematic, with large regions having similar timing for occurrence of rainfall. The stations located in the foothills of the Himalayas have a late night to early morning maximum of first hour rainfall. In the northwestern plains, the first hour of rainfall mostly starts in the early afternoon to evening hours. Further eastward, the rainfall occurs in the late evening hours. Overall, there is a gradient in the occurrence of first rainfall events from late afternoon hours in the southern sections of the north Indian region to nocturnal maxima in the higher altitude regions. Five of these stations, located in different regions of homogenous timing of rainfall occurrence, were selected to analyze in detail the variable trigger for convection. Our results indicate that convective episodes occur mostly in association with the passage of westerly troughs over this region. These upper atmosphere troughs enable moisture to flow from the surrounding oceanic regions to the dry inland regions and also provide some dynamic support to the episodes of convection. However, the actual occurrence of convection is triggered by local factors, giving rise to the mesoscale structure of the weather systems during this season. Specifically, over the plains of northwest India, convection is triggered in a moistened environment by diurnal solar heating. The late night to early morning convection over the foothills is triggered by the orography, when the moistened airflow is normally incident on the mountain slopes. Further eastward, the primary trigger for localized moist convection is downdrafts from south-eastward propagating convective systems that originate at a north-south dry line over north India. These systems propagate with a speed of about 15 m s-1. The above results are supported by geostationary satellite brightness temperature data for March to May 2008. © 2010 Springer-Verlag."
"57203012011;57201725986;","A review of cloud-resolving model studies of convective processes",2008,"10.1007/s00376-008-0202-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-55349103799&doi=10.1007%2fs00376-008-0202-6&partnerID=40&md5=bc14760cb1931785269312dda36e4886","Convective processes affect large-scale environments through cloud-radiation interaction, cloud microphysical processes, and surface rainfall processes. Over the last three decades, cloud-resolving models (CRMs) have demonstrated to be capable of simulating convective-radiative responses to an imposed largescale forcing. The CRM-produced cloud and radiative properties have been utilized to study the convective-related processes and their ensemble effects on large-scale circulations. This review summarizes the recent progress on the understanding of convective processes with the use of CRM simulations, including precipitation processes; cloud microphysical and radiative processes; dynamical processes; precipitation efficiency; diurnal variations of tropical oceanic convection; local-scale atmosphere-ocean coupling processes; and tropical convective-radiative equilibrium states. Two different ongoing applications of CRMs to general circulation models (GCMs) are discussed: replacing convection and cloud schemes for studying the interaction between cloud systems and large-scale circulation, and improving the schemes for climate simulations. © Science Press 2008."
"7103321545;36842329100;55619302013;35776608800;","Polar-air outbreak and air-mass transformation over the east coast of Asia as simulated by an AGCM",2006,"10.2151/jmsj.84.47","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646419014&doi=10.2151%2fjmsj.84.47&partnerID=40&md5=7bbc93f36428a04699bca2c51289f30d","The present report studies features of the polar-air outbreak and the associated air-mass transformation over the east coast of Asia simulated in an AGCM (T106L52: a primitive equation spectral model, which has 52 σ-levels and triangular spectral truncation at wave-number 106) that used climatological SST in comparison with the features described in several observational studies. The large-scale circulations are properly reproduced for January Y07 (the 7th year after the spin up integration). A typical case of polar-air outbreak simulated in January is studied in detail. During the polar-air outbreak, cyclonic northwesterly polar-air streams over the Sea of Japan and the northwestern Pacific, and anticyclonic northeasterly polar-air streams over the East China Sea and the South China Sea are reasonably simulated. During the polar-air outbreak, the sensible and latent heat fluxes simulated over the Sea of Japan reach to ∼150 and ∼250 W m-2, while those over the East China Sea reach to ∼75 and ∼250 W m-2, respectively. These simulated fluxes agree with the fluxes evaluated in observational studies. The multi-layer structure of the transformed air-mass, including the unstable surface layer, the subcloud layer, and the cloud layer capped by the stable layer, simulated over the coastal areas of Asia is consistent with the observations for the cases of typical polar-air outbreak. However, the precipitation over the coastal areas of Japan simulated during the polar-air outbreak is significantly small as compared with the observation. This is due to the insufficient horizontal resolution of the T106L52 to simulate mesoscale circulation systems which induce snowfalls. In addition, the duration of the polar-air outbreak simulated in the AGCM is relatively short as compared with that in the real atmosphere, since the anticyclone over the continent tends to extend eastward in the model. © 2006, Meteorological Society of Japan."
"7402717381;7003376335;","On the features of clouds occurring over the Mackenzie River basin",2002,"10.1029/2001JD001559","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14344257191&doi=10.1029%2f2001JD001559&partnerID=40&md5=c3bc08cc660173ea7e01e26c05104678","[1] To better characterize the occurrence of clouds and some of their features over the Mackenzie basin of northwestern Canada, surface-based measurements of cloud fields have been examined from several operational observing sites. This article focuses on the determination of cloud cover fraction, cloud base height, multiple layering, and cloud type as well as the variations of these on temporal scales ranging from diurnal to interannual. In addition, the cloud features were related to the large-scale circulation, large-scale convergence, air mass, and surface temperature. The results indicate that clouds over this region are very common (occurring about 80% of the time and covering an average of about 60% of the sky), are linked with surface temperature variations (such as being less common and higher during winter cold periods), are poorly correlated with large-scale factors (such as El Nino), and may be exhibiting some long-term trends (such as an-increase in cloud cover traction). Copyright 2002 by the American Geophysical Union."
"57204524766;7402383878;6506340624;","The role of anthropogenic aerosols in future precipitation extremes over the Asian Monsoon Region",2019,"10.1007/s00382-018-4514-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055949140&doi=10.1007%2fs00382-018-4514-7&partnerID=40&md5=e9b754b80ddf88a35bc694329cd04981","The role of anthropogenic aerosols in future projections (up to 2100) of summertime precipitation and precipitation extremes over the Asian monsoon region is investigated, by comparing two sets of the Community Earth System Model (CESM1) large ensemble simulations under the Representative Concentration Pathway 8.5 scenario (RCP8.5) and the corresponding scenario with aerosol fixed at 2005 levels (RCP8.5_FixA). The model is verified to be performing well in capturing present-day (1986–2005) climate and precipitation extremes. Our results suggest that the Asian monsoon region would become progressively warmer and wetter in the future under RCP8.5, while precipitation extremes will be significantly aggravated due to anthropogenic aerosol mitigation, particularly over East Asia. Specifically, aerosol reductions are found to shift the distribution of precipitation mean and extremes to larger values. For example, aerosol reductions would result in an increased likelihood of extreme precipitation (e.g. the maximum consecutive 5-day precipitation amount) and related disasters. Sensitivities of changes in precipitation mean and extremes to local warming from aerosol reductions are much larger than that from greenhouse gas increases. This is particularly important over East Asia in accordance with larger magnitudes of aerosol reductions compared to South Asia. Finally, by investigating the response of the climate system to aerosol changes, our findings demonstrate that aerosol induced precipitation changes would be dominated by aerosol–radiation–cloud forcing over northern East Asia and aerosol forcing induced large-scale circulation anomalies over southern East and South Asia. © 2018, The Author(s)."
"57201698175;8953662800;56200000400;25823927100;7403564495;57206424059;57195198884;57188767737;8905764300;56610909100;55543826100;","Mesoscale Convective Systems in the Asian Monsoon Region From Advanced Himawari Imager: Algorithms and Preliminary Results",2019,"10.1029/2018JD029707","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061978867&doi=10.1029%2f2018JD029707&partnerID=40&md5=8eaf579b2bad1823c3e57e3c4590e12e","The knowledge of mesoscale convective system (MCS) in the Asian monsoon region remains still deficient due to the limited available data and less powerful algorithms. Here, using the data from Advanced Himawari Imager onboard Himawari-8 (HW8), an improved algorithm combining the area overlapping with the Kalman filter is developed, which captures much smaller MCSs that are unavailable otherwise. Several influential factors like the overlapping rate and splitting/merging in the area overlapping method, and the initial state variable in the Kalman filter method, all of which were less appreciated, are handled explicitly. The occurrence frequency, and moving trajectory of two types of MCS, including the ordinary MCS and superconvective system, has been comprehensively examined in the Asian monsoon region for the warm season (April to September) of 2016. Comparison analyses with ground precipitation and radar measurements confirm the good performance of our algorithm. In particular, the moving direction of MCS strongly depends on latitudes, so does the horizontal velocity. Compared with over ocean, the frequency of MCSs dominates over land or along coasts in the tropics, where strong moisture flux convergence is frequently observed in the low troposphere. In addition, the MCSs detected in eastern China can roughly capture the meridional propagation over time, which corresponds well to the precipitation belts linked to Meiyu front systems. The superconvective systems dominate over the Bay of Bengal and South China Sea due to the large-scale circulation. Our findings provide new insights to spatiotemporal patterns of MCSs during warm season in the Asian monsoon region. ©2019. The Authors."
"54399869900;7401836526;","Atmospheric dynamics feedback: Concept, simulations, and climate implications",2018,"10.1175/JCLI-D-17-0470.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042849303&doi=10.1175%2fJCLI-D-17-0470.1&partnerID=40&md5=6c8bf7b48ce659940c21bc7aa8229481","The regional climate response to radiative forcing is largely controlled by changes in the atmospheric circulation. It has been suggested that global climate sensitivity also depends on the circulation response, an effect called the ""atmospheric dynamics feedback."" Using a technique to isolate the influence of changes in atmospheric circulation on top-of-the-atmosphere radiation, the authors calculate the atmospheric dynamics feedback in coupled climate models. Large-scale circulation changes contribute substantially to all-sky and cloud feedbacks in the tropics but are relatively less important at higher latitudes. Globally averaged, the atmospheric dynamics feedback is positive and amplifies the near-surface temperature response to climate change by an average of 8% in simulations with coupled models. A constraint related to the atmospheric mass budget results in the dynamics feedback being small on large scales relative to feedbacks associated with thermodynamic processes. Idealized-forcing simulations suggest that circulation changes at high latitudes are potentially more effective at influencing global temperature than circulation changes at low latitudes, and the implications for past and future climate change are discussed. © 2018 American Meteorological Society."
"57194420030;7006306835;7103206141;56744278700;55271575700;","On the seasonality of arctic black carbon",2017,"10.1175/JCLI-D-16-0580.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020040253&doi=10.1175%2fJCLI-D-16-0580.1&partnerID=40&md5=b001b3e811d3ef004102d80b4251ccb6","Arctic haze has a distinct seasonal cycle with peak concentrations in winter but pristine conditions in summer. It is demonstrated that the Geophysical Fluid Dynamics Laboratory (GFDL) atmospheric general circulation model (AM3) can reproduce the observed seasonality of Arctic black carbon (BC), an important component of Arctic haze. The model is used to study how large-scale circulation and removal drive the seasonal cycle of Arctic BC. It is found that despite large seasonal shifts in the general circulation pattern, the transport of BC into the Arctic varies little throughout the year. The seasonal cycle of Arctic BC is attributed mostly to variations in the controlling factors of wet removal, namely the hydrophilic fraction of BC and wet deposition efficiency of hydrophilic BC. Specifically, a confluence of low hydrophilic fraction and weak wet deposition, owing to slower aging process and less efficient mixed-phase cloud scavenging, respectively, is responsible for the wintertime peak of BC. The transition to low BC in summer is the consequence of a gradual increase in the wet deposition efficiency, whereas the increase of BC in late fall can be explained by a sharp decrease in the hydrophilic fraction. The results presented here suggest that future changes in the aging and wet deposition processes can potentially alter the concentrations of Arctic aerosols and their climate effects. © 2017 American Meteorological Society."
"55819549500;57188837293;16506458200;15050523700;7404178566;36006968000;","Seminal role of stratiform clouds in large-scale aggregation of tropical rain in boreal summer monsoon intraseasonal oscillations",2017,"10.1007/s00382-016-3124-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84963769987&doi=10.1007%2fs00382-016-3124-5&partnerID=40&md5=458d25a69aa326ca5364e78dbad33da7","Modification of the vertical structure of non-adiabatic heating by significant abundance of the stratiform rain in the tropics has been known to influence the large-scale circulation. However, the role of the stratiform rain on the space–time evolution of the observed Boreal summer monsoon intraseasonal oscillations (MISO) has so far been ignored. In the present study, we unravel a feedback mechanism through which the stratiform component of the rain leads to aggregation (organization) of rain on the MISO scale, making it an indispensable component of the MISO evolution dynamics. Using TRMM 3A25 monthly mean data (between 1998 and 2013), the ratio between convective and stratiform rain (RCS) is shown to be strongly related to the total rainfall. Further, composites of rainfall and circulation anomalies corresponding to high (low) values of RCS over the Central India or over the Equatorial Indian Ocean show spatial structures remarkably similar to that associated with the MISOs. Analyzing lead–lag relationship between the convective rain, the stratiform rain and the large scale moisture convergence with respect to peak active (break) spells from daily modern era retrospective-analysis for research and applications data, we unravel that the initial isolated convective elements spawn the stratiform rain which in turn modifies the vertical distribution of heating and leads to stronger large scale moisture convergence thereby producing more convective elements and more stratiform rain ultimately leading to aggregation of rain on the MISO scale. Our finding indicates that large and persisting systematic biases in simulating the summer monsoon rainfall over the Asian monsoon region by climate models are likely to be related to the systematic biases in simulating the MISOs which in turn are related to the serious underestimation of stratiform rain in most climate models. © 2016, Springer-Verlag Berlin Heidelberg."
"56038150300;6701606453;","A global assessment of the spatial distribution of precipitation occurrence",2015,"10.1175/JAMC-D-15-0019.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948958928&doi=10.1175%2fJAMC-D-15-0019.1&partnerID=40&md5=37a9ad78c03538cab06bad73fee12eca","The spatial distribution of precipitation occurrence has important implications for numerous applications ranging from defining cloud radiative effects to modeling hydrologic runoff, statistical downscaling, and stochastic weather generation. This paper introduces a new method of describing the spatial characteristics of rainfall and snowfall that takes advantage of the high sensitivity and high resolution of the W-band cloud precipitation radar aboard CloudSat. The resolution dependence of precipitation occurrence is described by a two-parameter exponential function defined by a shape factor that governs the variation in the distances between precipitation events and a scale length that represents the overall probability of precipitation and number density of distinct events. Geographic variations in the shape factor and scale length are consistent with large-scale circulation patterns and correlate with environmental conditions on local scales. For example, a large contrast in scale lengths between land and ocean areas reflects the more extensive, widespread nature of precipitation over land than over ocean. An analysis of warm rain in the southeast Pacific reveals a shift from frequent isolated systems to less frequent but more regularly spaced systems along a transect connecting stratocumulus and trade cumulus cloud regimes.Asimilar analysis during the Amazon wet season reveals a relationship between the size and frequency of convection and zonal wind direction with precipitation exhibiting a more oceanic character during periods of westerly winds. These select examples demonstrate the utility of this approach for capturing the sensitivity of the spatial characteristics of precipitation to environmental influences on both local and larger scales. © 2015 American Meteorological Society."
"55354306200;","Sensitivity of WRF simulated typhoon track and intensity over the Northwest Pacific Ocean to cumulus schemes",2013,"10.1007/s11430-012-4486-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873189220&doi=10.1007%2fs11430-012-4486-0&partnerID=40&md5=0b1c70b37c354991101ec7cd56388198","Here discussed is the sensitivity of simulated typhoon track and intensity over the Northwest Pacific Ocean to different cumulus schemes. The results from the 20 typhoon cases during 2003-2008 show that the simulation of typhoon track and intensity are very sensitive to cumulus schemes. The relationship between simulations of typhoon track and cumulus schemes can be case dependent. Different best tracks obtained from different case studies depend on which cumulus scheme we chose. However, simulations of typhoon intensity exhibit different features. The Kain-Fritsch scheme simulation obtains the most intensive typhoon, whereas the Betts-Miller-Janjic scheme and the Grell-Devenyi scheme obtain weaker typhoons. The sensitivity of simulated typhoon track and intensity to different cumulus schemes is due mainly to different hypotheses and precipitation calculations. The difference of simulated large scale circulations using different cumulus schemes leads to the difference of typhoon tracks. The closer the simulations are compared to observations, the less the errors of simulated typhoon tracks. The difference of simulated typhoon intensity is due mainly to the difference of simulated vertical heating of the atmosphere. These lead to different strengths of convection which causes the difference of cumulus precipitation and latent heat. The KF scheme simulation obtains the strongest vertical convection, the obvious warm core structure, more cumulus precipitation, and stronger intensity. By contrast, the BMJ scheme and the GD scheme obtain weaker convection, less cumulus precipitation, and weaker intensity. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg."
"57200629445;34976226000;55595547400;7201724255;","Diurnal variations of low-level winds and precipitation response to large-scale circulations during a heavy rainfall event",2019,"10.1175/MWR-D-19-0131.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075635262&doi=10.1175%2fMWR-D-19-0131.1&partnerID=40&md5=78520acef8867bb9694e52aefa0d7e4a","A succession of MCSs developed during the last week of October 2016 and produced extreme heavy rainfall in central China. The event underwent an evident shift from a mei-yu-like warm scenario to an autumn cold scenario. Diurnal cycles of rainfall and low-level winds may be modulated by the shifting of large-scale atmospheric conditions. We conducted observational analyses and numerical experiments to examine how large-scale circulations influenced rainfall systems through diurnally varying processes. The results show that, in the first half (warm) period of the event, intense rainfall mostly occurred in eastern-central China with an early morning peak. It was closely related to a nocturnal southwesterly low-level jet (NLLJ) on the flank of the western Pacific subtropical high. The NLLJ formed near midnight in southern China where ageostrophic wind rotated clockwise due to Blackadar’s inertial oscillation. The NLLJ extended downstream to central China during the predawn hours due to the horizontal advection of momentum. Both the formation and extension of the NLLJ were supported by an enhanced subtropical high that provided relatively warm conditions with surface heating for boundary layer inertial oscillation and strong background southwesterly winds for momentum transport. The NLLJ induced MCSs at its northern terminus where the low-level ascent, moisture flux convergence, and convective instability were enhanced during the predawn hours. In the second half period with an intrusion of cold air, the diurnal amplitude of low-level winds became small under relatively cold and cloudy conditions. Moderate rainfall tended to occur in western-central China with a peak after midnight, most likely due to frontogenetic processes, upslope lifting, and nighttime cloud-top cooling. © 2019 American Meteorological Society."
"57033686900;7202145115;56898950300;24322892500;7006783796;","The life cycle of anvil clouds and the top-of-atmosphere radiation balance over the tropical west Pacific",2018,"10.1175/JCLI-D-18-0154.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058196913&doi=10.1175%2fJCLI-D-18-0154.1&partnerID=40&md5=4d4e68872d8876e49663d2178166bb48","Observations from a geostationary satellite are used to study the life cycle of mesoscale convective systems (MCS), their associated anvil clouds, and their effects on the radiation balance over the warm pool of the tropical western Pacific Ocean. In their developing stages, MCS primarily consist of clouds that are optically thick and have a negative net cloud radiative effect (CRE). As MCS age, ice crystals in the anvil become larger, the cloud top lowers somewhat, and cloud radiative effects decrease in magnitude. Shading from anvils causes cool anomalies in the underlying sea surface temperature (SST) of up to 20.68C. MCS often occur in clusters that are embedded within large westward-propagating disturbances, and therefore shading from anvils can cool SSTs over regions spanning hundreds of kilometers. Triggering of convection is more likely to follow a warm SST anomaly than a cold SST anomaly on a time scale of several days. This information is used to evaluate hypotheses for why, over the warm pool, the average shortwave and longwave CRE are individually large but nearly cancel. The results are consistent with the hypothesis that the cancellation in CRE is caused by feedbacks among cloud albedo, large-scale circulation, and SST. © 2018 American Meteorological Society."
"56541522300;6701509222;6701754792;7004462660;56884595900;7102578362;","The isotopic signature of monsoon conditions, cloud modes, and rainfall type",2018,"10.1002/hyp.13140","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050186224&doi=10.1002%2fhyp.13140&partnerID=40&md5=9a1c26098f9b54c584b2f4afeae2cf11","This work provides a comprehensive physically based framework for the interpretation of the north Australian rainfall stable isotope record (δ18O and δ2H). Until now, interpretations mainly relied on statistical relationships between rainfall amount and isotopic values on monthly timescales. Here, we use multiseason daily rainfall stable isotope and high resolution (10 min) ground-based C-band polarimetric radar data and show that the five weather types (monsoon regimes) that constitute the Australian wet season each have a characteristic isotope ratio. The data suggest that this is not only due to changes in regional rainfall amount during these regimes but, more importantly, is due to different rain and cloud types that are associated with the large scale circulation regimes. Negative (positive) isotope anomalies occurred when stratiform rainfall fractions were large (small) and the horizontal extent of raining areas were largest (smallest). Intense, yet isolated, convective conditions were associated with enriched isotope values whereas more depleted isotope values were observed when convection was widespread but less intense. This means that isotopic proxy records may record the frequency of which these typical wet season regimes occur. Positive anomalies in paleoclimatic records are most likely associated with periods where continental convection dominates and convection is sea-breeze forced. Negative anomalies may be interpreted as periods when the monsoon trough is active, convection is of the oceanic type, less electric, and stratiform areas are wide spread. This connection between variability of rainfall isotope anomalies and the intrinsic properties of convection and its large-scale environment has important implications for all fields of research that use rainfall stable isotopes. Copyright © 2018 John Wiley & Sons, Ltd."
"55731064200;57194595597;57194588116;55831305300;","Bjerknes compensation in meridional heat transport under freshwater forcing and the role of climate feedback",2017,"10.1175/JCLI-D-16-0824.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021129057&doi=10.1175%2fJCLI-D-16-0824.1&partnerID=40&md5=5072fcd7637ced1d8261c223692d98ae","Using a coupled Earth climate model, freshwater forcing experiments are performed to study the Bjerknes compensation (BJC) between meridional atmosphere heat transport (AHT) and meridional ocean heat transport (OHT). Freshwater hosing in the North Atlantic weakens the Atlantic meridional overturning circulation (AMOC) and thus reduces the northward OHT in the Atlantic significantly, leading to a cooling (warming) in the surface layer in the Northern (Southern) Hemisphere. This results in an enhanced Hadley cell and northward AHT. Meanwhile, the OHT in the Indo-Pacific is increased in response to the Hadley cell change, partially offsetting the reduced OHT in the Atlantic. Two compensations occur here: compensation between theAHTand the Atlantic OHT, and that between the Indo-PacificOHTand the Atlantic OHT. The AHT change undercompensates the OHT change by about 60% in the extratropics, while the former overcompensates the latter by about 30% in the tropics due to the Indo-Pacific change. The BJC can be understood from the viewpoint of large-scale circulation change. However, the intrinsic mechanism of BJC is related to the climate feedback of the Earth system. The authors' coupled model experiments confirm that the occurrence of BJC is an intrinsic requirement of local energy balance, and local climate feedback determines the extent of BJC, consistent with previous theoretical results. Even during the transient period of climate change, the BJC is well established when the ocean heat storage is slowly varying and its change is much weaker than the net local heat flux change at the ocean surface. The BJC can be deduced from the local climate feedback. Under the freshwater forcing, the overcompensation in the tropics is mainly caused by the positive longwave feedback related to clouds, and the undercompensation in the extratropics is due to the negative longwave feedback related to surface temperature change. Different dominant feedbacks determine different BJC scenarios in different regions, which are in essence constrained by local energy balance. © 2017 American Meteorological Society."
"23990276200;7006256622;23082420800;57193084799;","Model evidence for low-level cloud feedback driving persistent changes in atmospheric circulation and regional hydroclimate",2017,"10.1002/2016GL071978","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85010637404&doi=10.1002%2f2016GL071978&partnerID=40&md5=d480688d2d2cd56a5aaf0da2c5d8c130","Recent studies suggest that low clouds in the Pacific play an important role in the observed decadal climate variability and future climate change. In this study, we implement a novel modeling experiment designed to isolate how interactions between local and remote feedbacks associated with low cloud, SSTs, and the large-scale circulation play a significant role in the observed persistence of tropical Pacific SST and associated North American drought. The modeling approach involves the incorporation of observed patterns of satellite-derived shortwave cloud radiative effect (SWCRE) into the coupled model framework and is ideally suited for examining the role of local and large-scale coupled feedbacks and ocean heat transport in Pacific decadal variability. We show that changes in SWCRE forcing in eastern subtropical Pacific alone reproduces much of the observed changes in SST and atmospheric circulation over the past 16 years, including the observed changes in precipitation over much of the Western Hemisphere. ©2016. The Authors."
"15726427000;57193132723;55802031900;7102171439;6603126554;6701606453;","Responses of tropical ocean clouds and precipitation to the large-scale circulation: Atmospheric-water-budget-related phase space and dynamical regimes",2016,"10.1175/JCLI-D-15-0712.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84991221632&doi=10.1175%2fJCLI-D-15-0712.1&partnerID=40&md5=1d3e32ee679143b23bd3e68f7a1ce625","An atmospheric-water-budget-related phase space is constructed with the tendency terms related to dynamical convergence (QCON = -Q∇ · V) and moisture advection (QADV = -V · ∇Q) in the water budget equation. Over the tropical oceans, QCON accounts for large-scale dynamical conditions related to conditional instability, and QADV accounts for conditions related to lower-tropospheric moisture gradient. Two reanalysis products [MERRA and ERA-Interim (ERAi)] are used to calculate QCON and QADV. Using the phase space as a reference frame, the Moderate Resolution Imaging Spectroradiometer (MODIS) cloud-top pressure (CTP) and cloud optical depth (COD) are used to evaluate simulated clouds in the GISS-E2 general circulation model. In regimes of divergence over the tropical oceans, moist advection yields frequent high- to midlevel medium-thickness to thick clouds associated with moderate stratiform precipitation, while dry advection yields low-level thin clouds associated with shallow convection with lowered cloud tops. In regimes with convergence, moist and dry advection modulate the relative abundance of high-level thick clouds and low-level thin to medium-thickness clouds. GISS-E2 qualitatively reproduces the cloud property dependence on moisture budget tendencies in regimes of convergence but with larger COD compared to MODIS. Low-level thick clouds in GISS-E2 are the most frequent in regimes of near-zero convergence and moist advection instead of those of large-scale divergence. Compared to the Global Precipitation Climatology Project product, MERRA, ERAi, and GISS-E2 have more rain in regimes with deep convection and less rain in regimes with shallow convection. © 2016 American Meteorological Society."
"56293796000;36054921000;7102567936;","Response of atmospheric convection to vertical wind shear: Cloud-system-resolving simulations with parameterized large-scale circulation. Part II: Effect of interactive radiation",2016,"10.1175/JAS-D-15-0151.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957615169&doi=10.1175%2fJAS-D-15-0151.1&partnerID=40&md5=afe79e1bebcd8396546a2543b3b1898b","The authors investigate the effects of cloud-radiation interaction and vertical wind shear on convective ensembles interacting with large-scale dynamics in cloud-resolving model simulations, with the large-scale circulation parameterized using the weak temperature gradient approximation. Numerical experiments with interactive radiation are conducted with imposed surface heat fluxes constant in space and time, an idealized lower boundary condition that prevents wind-evaporation feedback. Each simulation with interactive radiation is compared to a simulation in which the radiative heating profile is held constant in the horizontal and in time and is equal to the horizontal-mean profile from the interactive-radiation simulation with the same vertical shear profile and surface fluxes. Interactive radiation is found to reduce mean precipitation in all cases. The magnitude of the reduction is nearly independent of the vertical wind shear but increases with surface fluxes. Deep shear also reduces precipitation, though by approximately the same amount with or without interactive radiation. The reductions in precipitation due to either interactive radiation or deep shear are associated with strong large-scale ascent in the upper troposphere, which more strongly exports moist static energy and is quantified by a larger normalized gross moist stability. © 2016 American Meteorological Society."
"56883885900;55544443300;36720934300;55823994500;","Sensitivity of the climate response to the altitude of black carbon in the Northern subtropics in an aquaplanet GCM",2015,"10.1175/JCLI-D-15-0037.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942848261&doi=10.1175%2fJCLI-D-15-0037.1&partnerID=40&md5=3315df77f4c10af671f84f5399d4560c","This study explores the dependence of the climate response on the altitude of black carbon in the northern subtropics by employing an atmospheric general circulation model coupled to an aquaplanet mixed layer ocean, with a focus on the pattern changes in the temperature, hydrological cycle, and large-scale circulation. Black carbon added below or within the subtropical low-level clouds tends to suppress convection, which reduces the low cloud amount, resulting in a positive cloud radiative forcing. The warmer northern subtropics then induce a northward shift of the intertropical convergence zone (ITCZ) and a poleward expansion of the descending branch of the northern Hadley cell. As the black carbon-induced local warming is amplified by clouds and is advected by the anomalous Hadley circulation, the entire globe gets warmer. In contrast, black carbon added near the surface increases the buoyancy of air parcels to enhance convection, leading to an increase in the subtropical low cloud amount and a negative cloud radiative forcing. The temperature increase remains local to where black carbon is added and elsewhere decreases, so that the ITCZ is shifted southward and the descending branch of the northern Hadley cell contracts equatorward. Consistent with previous studies, the authors demonstrate that the climate response to black carbon is highly sensitive to the vertical distribution of black carbon relative to clouds; hence, models have to accurately compute the vertical transport of black carbon to enhance their skill in simulating the climatic effects of black carbon. © 2015 American Meteorological Society."
"54893098900;36187387300;55885528600;","Evaluating Marine Stratocumulus Clouds in the CNRM-CM6-1 Model Using Short-Term Hindcasts",2019,"10.1029/2018MS001461","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060167483&doi=10.1029%2f2018MS001461&partnerID=40&md5=0310608cc8a1fc36186a496837b0ee52","The representation of stratocumulus by the atmospheric component of the Centre National de Recherches Météorologiques model version 6 (CNRM-CM6-1) is assessed. An Atmospheric Model Intercomparison Project-type simulation is first used to document the main model errors, namely, a large lack of stratocumulus over the eastern part of tropical ocean basins. Short-term hindcasts, following the Transpose-Atmospheric Model Intercomparison Project framework, are then used to better assess the timescales associated with the cloud bias growth and to highlight the processes leading to them. These biases are shown to appear within only a few hours, independently of errors in the large-scale circulation that set up within a few days. Key processes underlying the low-cloud formation are thus mainly local and, to the first order, do not imply any feedback between the model physics and the large-scale dynamics. As a consequence, short-term hindcasts provide a relevant framework to investigate whether the low-cloud underestimate is related to errors in the large-scale state variables or to errors in the model parameterizations. Sensitivity tests highlight that the involved processes arise (1) mostly from misrepresentation of subgrid effects on cloud formation and (2) partly from biases in drying induced by cloud-top entrainment mixing. Improvements in the representation of stratocumulus in the CNRM-CM6-1 model might thus be expected by including a more realistic subgrid-scale temperature and moisture distribution, that would link convective and turbulence processes. Finally, this study confirms the potential of short-term hindcasts, which provide a trustworthy framework to evaluate and develop climate model parameterizations. ©2018. The Authors."
"57033686900;7202145115;","Balanced Cloud Radiative Effects Across a Range of Dynamical Conditions Over the Tropical West Pacific",2018,"10.1029/2018GL080046","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055937280&doi=10.1029%2f2018GL080046&partnerID=40&md5=009e43eb959694727f843ae90deb2104","Instantaneous relationships between clouds and large-scale vertical motion are used to study the impact of circulation on the near cancellation of cloud radiative effects that is observed over the tropical west Pacific Ocean. The coverage of deep-convective clouds increases with stronger upward motion, but the proportion of thick, medium, and thin anvil cloud remains nearly constant. Thus, when averaging over scales larger than individual storms, the top-of-atmosphere net radiation is only weakly sensitive to the large-scale flow. The balance in cloud radiative effects is therefore maintained across a wide range of large-scale circulations. The ability of the Community Atmosphere Model Version 5 to reproduce the observed cloud-circulation relationships is investigated. The simulated convective clouds substantially overestimate the proportion of deep and optically thick cloud and underestimate the proportion of anvil cirrus. These results demonstrate that simulating key properties of deep-convective clouds remains challenging for some state-of-the-art climate models. ©2018. American Geophysical Union. All Rights Reserved."
"52564166000;6602699701;6602729528;8571302000;","Influence of atmospheric circulation patterns on local cloud and solar variability in Bergen, Norway",2016,"10.1007/s00704-015-1517-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84931864143&doi=10.1007%2fs00704-015-1517-8&partnerID=40&md5=73f6b1af194b4dfaee987564cc237f9c","In a previous paper, we have shown that long-term cloud and solar observations (1965–2013) in Bergen, Norway (60.39°N, 5.33°E) are compatible with a largely cloud dominated radiative climate. Here, we explicitly address the relationship between the large scale circulation over Europe and local conditions in Bergen, identifying specific circulation shifts that have contributed to the observed cloud and solar variations. As a measure of synoptic weather patterns, we use the Grosswetterlagen (GWL), a daily classification of European weather for 1881–2013. Empirical models of cloud cover, cloud base, relative sunshine duration, and normalised global irradiance are constructed based on the GWL frequencies, extending the observational time series by more than 70 years. The GWL models successfully reproduce the observed increase in cloud cover and decrease in solar irradiance during the 1970s and 1980s. This cloud-induced dimming is traced to an increasing frequency of cyclonic and decreasing frequency of anticyclonic weather patterns over northern Europe. The changing circulation patterns in winter can be understood as a shift from the negative to the positive phase of the North Atlantic and Arctic Oscillation. A recent period of increasing solar irradiance is observed but not reproduce by the GWL models, suggesting this brightening is associated with factors other than large scale atmospheric circulation, possibly decreasing aerosol loads and local cloud shifts. © 2015, Springer-Verlag Wien."
"23982847500;36620570600;7006815674;56507246300;56527443200;","Linking the southern annular mode to the diurnal temperature range shifts over southern Africa",2015,"10.1002/joc.4281","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957974145&doi=10.1002%2fjoc.4281&partnerID=40&md5=ca19cb60138aa83f842580de6bd42df7","The link between the diurnal temperature range (DTR) and the southern annular mode (SAM) over southern Africa for the October to December period during 1960 to 2012 is established using observations. The DTR shifts are consistent with the change of moisture and temperature advection over the subregion which is related to the SAM-induced circulation alterations. As such, we consider these changing circulation patterns as playing the dominant role in different types of the DTR development. In fact, for the long-term influence of changes in the large-scale circulation over southern Africa, the SAM circulation may have substantially contributed to the long-term development of cloud cover/precipitation, which can be used as a proxy for the DTR variability in recent decades. Therefore, cloud cover and precipitation changes acted as a disguise rather than the actual cause for the variations in DTR. At the same time, while the mean temperature trends over southern Africa are similar to the global trends that indicate general warming, this increase is superimposed on the significant DTR decadal variability. Consequently, the DTR can be considered as a possible radiative forced index independent of internal climate variations, which is able to provide additional information for the detection and attribution of climate change over southern Africa. © 2015 Royal Meteorological Society."
"6602313880;35247589400;36815870300;","A case study of a winter heavy rainfall event over the Serra do Mar in Brazil",2011,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650761369&partnerID=40&md5=d8de7c7c86f7634d9f4f53341585323c","Serra do Mar is a mountainous region vulnerable to landslides due to frequent summer heavy rainfall and steep slopes. These mountains are located in Southeastern Brazil and lie along the coastal region. Major cities, industries, roads and pipelines are established in the Serra do Mar. A reference of landslides occurred in the winter of 2004. This is a rare case in the dry season and the civil defense was caught unprepared. We investigate the causes of these landslides in order to provide some guidance to forecasters and policy makers. Rain was mainly from stratiform clouds associated with a relatively intense cold front which persisted for about 6 days in the region. The cold front became stationary on the coast of the State of Sao Paulo as the post-frontal anticyclone, which was initially cold, acquired a barotropic structure and, consequently, a semi stationary behavior. The large scale circulation determined the persistence of southerly and southeasterly winds near the surface. After reaching the continent, these winds were lifted by the Serra do Mar mountain chain. The progression of a shortwave trough to upper levels was not the major cause of heavy precipitation, but contributed to enhance the thermodynamic instability and increase rainfall, which caused the landslides in the Serra do Mar."
"8859530100;55745955800;56093699900;","Simulation of low clouds from the CAM and the regional WRF with multiple nested resolutions",2009,"10.1029/2008GL037088","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67449142948&doi=10.1029%2f2008GL037088&partnerID=40&md5=c3c4fadbeffabee8a9f2ed9bc4e8646a","[1] Current climate models have shown systematic simulation biases of low clouds that have cast great uncertainties on the climate sensitivity of these models. Among them is the deficient amount of low clouds over the storm tracks. This study uses the NCAR Community Atmospheric Model (CAM) and the Weather Research and Forecasting model (WRF) to study the cause of the failure of the global model in simulating low clouds associated with a frontal passage over the North Atlantic. The global model is shown to simulate the large-scale circulation that can support the boundary layer instabilities responsible for the observed clouds, but because the global model does not resolve the unstable modes, the instability cannot be realized. The resolution requirement of cloud simulations is discussed. This study also demonstrates the feasibility of cloud parameterization by nesting high resolution models into coarse resolution models to tap into the dynamical properties of the large-scale flows. Copyright 2009 by the American Geophysical Union."
"36024555900;36127012800;7005523706;","Impact of sub-grid variability of precipitation and canopy water storage on hydrological processes in a coupled land - Atmosphere model",2009,"10.1007/s00382-008-0435-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60349101979&doi=10.1007%2fs00382-008-0435-1&partnerID=40&md5=b6ed6427179fd245bf5a7bd4bff2a928","The impact of sub-grid variability of precipitation and canopy water storage is investigated by applying a new canopy interception scheme into the Community Atmosphere Model version 3 (CAM3) coupled with the Community Land Model version 3 (CLM3). Including such sub-grid variability alters the partitioning of net radiation between sensible heat flux and latent heat flux on land surface, which leads to changes in precipitation through various pathways/mechanisms. The areas with most substantial changes are Amazonia and Central Africa where convective rain is dominant and vegetation is very dense. In these areas, precipitation during December - January - February is increased by up to 2 mm/day. This increase is due to the enhanced large-scale circulation and atmospheric instability caused by including the sub-grid variability. Cloud feedback plays an important role in modifying the large-scale circulation and atmospheric instability. Turning off cloud feedback mitigates the changes in surface convergence and boundary layer height caused by inclusion of sub-grid variability of precipitation and water storage canopy, which moderate the effect on precipitation. © Springer-Verlag 2008."
"55870068500;7404330190;7405690800;","Climatic features of cloud water distribution and cycle over China",2008,"10.1007/s00376-008-0437-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-55349105150&doi=10.1007%2fs00376-008-0437-2&partnerID=40&md5=4d1f47fa68234125e0c73097f2d8f853","Analyses of cloud water path (CWP) data over China available from the International Satellite Cloud Climatology Project (ISCCP) are performed for the period 1984-2004. Combined with GPCP precipitation data, cloud water cycle index (CWCI) is also calculated. The climatic distributions of CWP are found to be dependent on large-scale circulation, topographical features, water vapor transport and similar distribution features which are found in CWCI except in the Sichuan Basin. Influenced by the Asia monsoon, CWP over China exhibits very large seasonal variations in different regions. The seasonal cycles of CWCI in different regions are consistent and the largest CWCI occurs in July. The long-term trends of CWP and CWCI are investigated, too. Increasing trends of CWP are found during the period with the largest increase found in winter. The decreasing trends of CWCI dominate most regions of China. The differences in long-term trends between CWP and CWCI suggest that CWP only can influence the variation of CWCI to a certain extent and that other factors need to be involved in cloud water cycle researches. This phenomenon reveals the complexity of the hydrological cycle related to cloud water. © Science Press 2008."
"24784567700;55483511400;7403572534;","The early summer seasonal change of Large-Scale circulation over east asia and its relation to change of the frontal features and frontal rainfall environment during 1991 summer",1995,"10.1007/BF02656829","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51249163930&doi=10.1007%2fBF02656829&partnerID=40&md5=3a334a26269be42bf84a28884e406490","By using the rawinsonde data, upper cloud amount data and objective analysis data for global domain which all were produced by Numerical Prediction Division, JMA and by using daily and mean weather map issued by JMA and daily rainfall data over the Huaihe River Basin from China, an observational study to the early summer seasonal change of large-scale circulation over East Asia and its relation to change of the frontal features and environment for the frontal rainfall has been carried out. Following reaults have been obtained: (1) The early summer seasonal change of large-scale circulation was occurred during 20-23 May 1991, which was about 10 days earlier than the normal. During the period the subtropical westerly jet and tropical easterlies abruptly moved northward; (2) The northward movement of the tropical easterlies was not uniform, it was earlier at 100 hPa level and about 24 hrs late at 200 hPa level. The phenomenon was associated with earlier disappearence of the subtropical westerly jet at 100 hPa level; (3) During the seasonal change there were two westerly jets in the upper level and changed their intensity with the time. Before 18 May 1991, the southern one was more intense and then changed to more intense for the northern one and disappearence of the southern one, the phenomenon seemed to be appeared as northward movement of the southern jet; (4) A faster temperature (T) rising in the upper level over the Tibetan Plateau was associated with the seasonal change. From the T rising the T maximum moved onto the plateau, changing the T gradient from positive to nega-tive to the south flank of the plateau, the effect to reduce and disappear the southern westerlies. Also the T rising was associated with change of the frontal features over East Asia; (5) The seasonal change type during 1991 was same as that during 1992 and 1993, but different from that during 1990; (6) The environment for the frontal rainfall was change in the season, the differences were in the baroclinity in upper level and vertical wind speed and direction shear. © 1995 Advances in Atmospheric Sciences."
"57194420030;7006306835;","The influence of aerosol absorption on the extratropical circulation",2018,"10.1175/JCLI-D-17-0839.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049724365&doi=10.1175%2fJCLI-D-17-0839.1&partnerID=40&md5=595641a7b2379e00d3d0958ef2efc6e1","This study examines how aerosol absorption affects the extratropical circulation by analyzing the response to a globally uniform increase in black carbon (BC) simulated with an atmospheric general circulation model forced by prescribed sea surface temperatures. The model includes aerosol direct and semidirect effects, but not indirect or cloud-absorption effects. BC-induced heating in the free troposphere stabilizes the midlatitude atmospheric column, which results in less energetic baroclinic eddies and thus reduced meridional energy transport at midlatitudes. Upper-tropospheric BC also decreases the meridional temperature gradient on the equatorward flank of the tropospheric jet and yields a weakening and poleward shift of the jet, while boundary layer BC has no significant influence on the large-scale circulation since most of the heating is diffused by turbulence in the boundary layer. The effectiveness of BC in altering circulation generally increases with height. Dry baroclinic eddy theories can explain most of the extratropical response to free-tropospheric BC. Specifically, the decrease in vertical eddy heat flux related to a more stable atmosphere is the main mechanism for reestablishing atmospheric energy balance in the presence of BC-induced heating. Similar temperature responses are found in a dry idealized model, which further confirms the dominant role of baroclinic eddies in driving the extratropical circulation changes. The strong atmospheric-only response to BC suggests that absorbing aerosols are capable of altering synoptic-scale weather patterns. Its height dependence highlights the importance of better constraining model-simulated aerosol vertical distributions with satellite and field measurements. © 2018 American Meteorological Society."
"56127418900;9249239700;56913124000;56130997600;55667257200;","An observationally based evaluation of WRF seasonal simulations over the Central and Eastern Pacific",2015,"10.1002/2015JD023561","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84954400850&doi=10.1002%2f2015JD023561&partnerID=40&md5=ada2e5b2dfc4aa729235afd5b8988478","This study uses multiple satellite data sets to evaluate seasonal simulations of the Weather Research and Forecasting (WRF) model over Central and Eastern Pacific. Experiments with five different convective parameterizations all show reasonably good performance for precipitation simulations. However, large discrepancies exist in the model-simulated ice clouds compared to CloudSat observations. Underestimations of ice clouds, mainly snow and graupel, are present in the Intertropical Convergence Zone (ITCZ) in all the experiments compared to CloudSat. In the ITCZ, all the experiments show a systematic overestimation of outgoing longwave radiation at the top of the atmosphere and downward shortwave radiation at the surface, along with biased cloud cooling in the middle and upper troposphere and biased cloud warming in the lower troposphere. Vertical motion is enhanced in the ITCZ compared to reanalysis. A weaker low-level circulation over themidlatitude oceans is evidenced in all simulations with an eastward overextension of the South Pacific Convergence Zone and overestimated moisture over the Southern Hemisphere oceans when compared to Special Sensor Microwave/Imager observations. Sensitivity experiment demonstrates that doubling the radiative effect of snow can reduce high biases in vertical motion within the ITCZ and improve the large-scale circulation and moisture over the midlatitude oceans. © 2015. American Geophysical Union. All Rights Reserved."
"19933330400;7006329926;","A modeling analysis of rainfall and water cycle by the cloud-resolving WRF model over the western North Pacific",2013,"10.1007/s00376-013-2288-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886937980&doi=10.1007%2fs00376-013-2288-8&partnerID=40&md5=9578aa2525d54f902620d084428edd53","Simulated regional precipitation, especially extreme precipitation events, and the regional hydrologic budgets over the western North Pacific region during the period from May to June 2008 were investigated with the high-resolution (4-km grid spacing) Weather Research and Forecast (WRF v3.2.1) model with explicit cloud microphysics. The model initial and boundary conditions were derived from the National Centers for Environmental Prediction/Department of Energy (NCEP/DOE) Reanalysis 2 data. The model precipitation results were evaluated against the Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis 3B42 product. The results show that the WRF simulations can reasonably reproduce the spatial distributions of daily mean precipitation and rainy days. However, the simulated frequency distributions of rainy days showed an overestimation of light precipitation, an underestimation of moderate to heavy precipitation, but a good representation of extreme precipitation. The downscaling approach was able to add value to the very heavy precipitation over the ocean since the convective processes are resolved by the high-resolution cloud-resolving model. Moreover, the water vapor budget analysis indicates that heavy precipitation is contributed mostly by the stronger moisture convergence; whereas, in less convective periods, the precipitation is more influenced by the surface evaporation. The simulated water vapor budgets imply the importance in the tropical monsoon region of cloud microphysics that affects the precipitation, atmospheric latent heating and, subsequently, the large-scale circulation. © 2013 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"55724139300;55723539100;","Numerical simulations of impacts of urbanization on heavy rainfall in Beijing using different land-use data",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548186511&partnerID=40&md5=9b68b10908b0159ce90c91ea32be8418","A summer strong convective precipitation event on 10 July 2004 over Beijing is numerically simulated in this paper, and the impact of urban heat island (UHI) on summer convective rain is investigated. The analysis reveals that a mesoscale convective cloud cluster system leads to this heavy rainfall event, suggesting the supply of moisture by the large scale circulation before the initiation of precipitation, a generally weaker UHI of 2-3°C existed in the urban area. Much like a sea breeze, the anomalously warm urban air created relatively low pressure, inducing the inflow of cooler rural air towards the urban center, which is favorable to the ascending motion and the formation of convective precipitation over the urban area. In addition, the numerical simulation of the strong convective precipitation event suggests that the simulated result of precipitation using the 2002 LANDSAT-7 land-use data with 30-m resolution is much better than that using the 1992-1993 USGS land-use data with 1-km resolution, whether in the magnitude of rainfall or in the location of precipitation. The simulation confirms to some extent that the UHI has a significant role in causing extreme rainfall event."
"14037770000;","Prediction of severe synoptic events in coastal east Antarctica",2003,"10.1175/1520-0493(2003)131<0354:POSSEI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042926805&doi=10.1175%2f1520-0493%282003%29131%3c0354%3aPOSSEI%3e2.0.CO%3b2&partnerID=40&md5=12afd74fc0eb0a31b8e1af9cada40736","The coastal region of the Antarctic continent is renowned for the frequent, intense blizzards and associated extreme weather that affect it, creating treacherous conditions that place human activities there in often perilous situations. The understanding and prediction of these events are therefore vital for continued safe operations on the continent. Severe wind events are investigated at two Australian coastal sites, Casey and Mawson. A summer case study at Casey and then the climatology of the events at the two stations are studied using station observations and atmospheric analyses. All events are found to be associated with extratropical cyclones that move close to the stations and lead to strong winds and heavy cloud cover. Most events see the passage of a high pressure ridge over the station ahead of the cyclone that blocks the cyclone, forcing it to move farther south close to the coast, thus intensifying the effect of the cyclone on the coastal weather. The ridge also produces calm, clear conditions that allow a pool of cold air to develop inland over the ice sheet. The approach of the cyclone then disrupts the stability of the surface layer inland, and at Mawson, where the katabatic flow is important, strong downslope flow can then add to the severity of the event. Station observations and reanalyses have then been used to investigate the degree to which precursors can be used to predict station wind speeds. Local conditions do not provide useful information on the development of severe winds 24 h later, but patterns in the large-scale circulation and temperature distributions offer potential for predicting the events. Regression analysis with these precursors is used to predict station wind speeds and is successful for many severe wind events, showing that the large-scale atmospheric forcing is dominant in most cases. However, there are cases where the evolution of the circulation and temperatures are more complicated than the typical events described above, and precursors are not sufficient to predict the onset of severe winds."
"56009810800;57034458200;","A numerical study of the along-line variability of a frontal squall line during PRE-STORM",1997,"10.1175/1520-0493(1997)125<2544:ANSOTA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0003207483&doi=10.1175%2f1520-0493%281997%29125%3c2544%3aANSOTA%3e2.0.CO%3b2&partnerID=40&md5=16e85fbf4f84b420454c512f1bd2b099","Despite considerable progress in the understanding of two-dimensional structures of squall lines, little attention has been paid to the along-line variability of these convective systems. In this study, the roles of meso- and larger-scale circulations in the generation of along-line variability of squall lines are investigated, using an 18-h prediction of a frontal squall line that occurred on 26-27 June 1985 during PRE-STORM (Preliminary Regional Experiment for Stormscale Operational Research Meteorology). It is shown that the Canadian regional finite-element (RFE) model reproduces reasonably well a number of surface and vertical circulation structures of the squall system, as verified against available network observations. These include the initiation, propagation, and dissipation of the squall system, surface pressure perturbations, and cold outflow boundaries: a midlevel mesolow and an upper-level mesohigh: a front-to-rear (FTR) ascending flow overlying an intense rear-to-front (RTF) flow: and a leading convective line followed by stratiform precipitation regions. It is found that across-line circulations at the northern segment of the squall line differ significantly from those at its southern segment, including the different types of precipitation, the absence of the RTF flow and midlevel mesolow, and the early dissipation of organized convection in the northern part. The along-line variability of the squall's circulations results primarily from the interaction of convectively generated perturbations with a midlevel baroclinic trough. The large-scale trough provides an extensive RTF flow component in the southern portion of the squall system and an FTR flow component in the north, whereas the midlevel mesolow tends to enhance the RTF flow to the south and the FTR flow to the north of the mesolow during the mature to decaying stages. The along-line variability of the squall's circulations appears to be partly responsible for the generation of different weather conditions along the line, such as the development of an upper-level stratiform region in the southern segment and a midlevel cloud region in the northern portion of the squall line."
"7401559815;7405584618;57202302285;","Large scale dynamics associated with super cloud cluster organization over the tropical western pacific",1994,"10.2151/jmsj1965.72.4_481","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016865069&doi=10.2151%2fjmsj1965.72.4_481&partnerID=40&md5=9cfaee10262180e065d1bc82bb6ca0da","Using a nonlinear primitive equation model of the tropical atmosphere, we have studied the large scale dynamics associated with the organization of super-cloud clusters (SCC) and the effect of nonlinear mean flow interaction and lateral forcing on the evolution of SCC and the Madden and Julian Oscillation (MJO) over the tropical western Pacific. It is found that the nonlinear interaction between convection and the large scale circulation associated with the organization of SCC can excite a variety of symmetric divergent motions along the equator and rotational motions away from the equator. The former can be identified as eastward propagating moist Kelvin waves and westward propagating inertia-gravity waves and the latter as Rossby waves. The interaction between the SCC and a basic flow induced by a northern wintertime heat source distribution gives rise to quasi-stationary modes over the western Pacific which may be identified with mixed Rossby-gravity wave. Westerly vertical wind shear over the western Pacific modifies the vertical tilt of the MJO and favors its growth. During the northern winter, cold surges from the East Asian continent exert strong control on the development of SCC in the equatorial regions by inducing pressure differential across the maritime continent and the western Pacific, leading to enhancement of surface wind convergence. When the influence of the subsidence motion associated with a pre-existing SCC/MJO is weakened, the cold surge-induced pressure anomaly can lead to the development of new SCC with intermediate time scales. The time interval between intermediate SCCs is about 8-10 days which is approximately the transit time of the MJO across the span of the warm pool of the western Pacific. During the northern summer, the SCCs in the equatorial region are much less organized with mixed eastward and westward propagating signals. In the northern subtropics (15°N-20°N), westward propagating synoptic scale waves are found in regions with strong westerly shear. These waves grow by latent heating as well as by extracting wave energy from the mean westerly vertical shear in the lower troposphere. Overall, the results suggest that the organization and location of SCC and the associated multi-scale motions are strongly dependent on the evolving seasonal mean flow. © 1994, Meteorological Society of Japan."
"56304460900;57196143493;","Understanding the atmospheric temperature adjustment to CO2 perturbation at the process level",2020,"10.1175/JCLI-D-19-0032.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074765992&doi=10.1175%2fJCLI-D-19-0032.1&partnerID=40&md5=d6cc72c9bda8e68b4c3c5e51eae9ba49","Climate model comparisons show that there is considerable uncertainty in the atmospheric temperature response to CO2 perturbation. The uncertainty results from both the rapid adjustment that occurs before SST changes and the slow feedbacks that occur after SST changes. The analysis in this paper focuses on the rapid adjustment. We use a novel method to decompose the temperature change in AMIP-type climate simulation in order to understand the adjustment at the process level. We isolate the effects of different processes, including radiation, convection, and large-scale circulation in the temperature adjustment, through a set of numerical experiments using a hierarchy of climate models. We find that radiative adjustment triggers and largely controls the zonal mean atmospheric temperature response pattern. This pattern is characterized by stratospheric cooling, lower-tropospheric warming, and a warming center near the tropical tropopause. In contrast to conventional views, the warming center near the tropopause is found to be critically dependent on the shortwave absorption of CO2. The dynamical processes largely counteract the effect of the radiative process that increases the vertical temperature gradient in the free troposphere. The effect of local convection is to move atmospheric energy vertically, which cools the lower troposphere and warms the upper troposphere. The adjustment due to large-scale circulation further redistributes energy along the isentropic surfaces across the latitudes, which cools the low-latitude lower troposphere and warms the midlatitude upper troposphere and stratosphere. Our results highlight the importance of the radiative adjustment in the overall adjustment and provide a potential method to understand the spread in the models. © 2019 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"23492864500;6603566335;","Boundary Layer Clouds and Convection over Subtropical Oceans in our Current and in a Warmer Climate",2019,"10.1007/s40641-019-00126-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065421570&doi=10.1007%2fs40641-019-00126-x&partnerID=40&md5=6c07875bf284617d00ac375bbd5cffce","Purpose of Review: We review our understanding of mechanisms underlying the response of (sub)tropical clouds to global warming, highlight mechanisms that challenge our understanding, and discuss simulation strategies that tackle them. Recent Findings: Turbulence-resolving models and emergent constraints provide probable evidence, supported by theoretical understanding, that the cooling cloud radiative effect (CRE) of low clouds weakens with warming: a positive low-cloud feedback. Nevertheless, an uncertainty in the feedback remains. Climate models may not adequately represent changing SST and circulation patterns, which determine future cloud-controlling factors and how these couple to clouds. Furthermore, we do not understand what mesoscale organization implies for the CRE, and how moisture-radiation interactions, horizontal advection, and the profile of wind regulate low cloud, in our current and in our warmer climate. Summary: Clouds in nature are more complex than the idealized cloud types that have informed our understanding of the cloud feedback. Remaining major uncertainties are the coupling of clouds to large-scale circulations and to the ocean, and mesoscale aggregation of clouds. © 2019, The Author(s)."
"23975806200;57193848954;57195032810;57195032515;55339562000;25925845500;36109825000;57201483033;57201484008;57195031465;57195037869;57201480769;","Meteorological conditions during a severe, prolonged regional heavy air pollution episode in eastern China from December 2016 to January 2017",2019,"10.1007/s00704-018-2426-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045056863&doi=10.1007%2fs00704-018-2426-4&partnerID=40&md5=29d77f706f69b88770b11a9ae34a2026","A severe, prolonged and harmful regional heavy air pollution episode occurred in eastern China from December 2016 to January 2017. In this paper, the pollutant characteristics and the meteorological formation mechanism of this pollution event, including climate anomalies, surface weather conditions, planetary boundary layer structure and large-scale circulation features, were analysed based on observational pollution data, surface meteorological data, sounding data and ERA-Interim reanalysis data. The results are as follows. (1) Five pollution stages were identified in eastern China. The two most severe episodes occurred from December 27, 2016 to January 4, 2017 and from January 8 to 12 2017. During these two pollution episodes, fine mode particles were major contributors, and hourly PM2.5 concentrations often exceeded 150 μg/m3, reaching a maximum of 333 μg/m3 at Fuyang station. Gaseous pollutants were transformed into secondary aerosols through heterogeneous reactions on the surface of PM2.5. (2) Compared with the same period over the years 2000–2016, 2017 presented meteorological field climate anomalies in conjunction with unfavourable surface conditions (weak winds, high relative humidity, fewer hours of sunshine, high cloud cover) and adverse atmospheric circulation (weak East Asian winter monsoon and an abnormal geopotential height of 500 hPa), which caused poorer visibility in 2017 than in the other analysed years. (3) During the development of heavy pollution event, unfavourable surface weather conditions, including poorer visibility, weaker pressure, higher relative humidity, lower wind speed with unfavourable wind direction and less precipitation suppressed the horizontal diffusion ability of air pollutants. Furthermore, the unfavourable structure of the atmospheric boundary layer was the key cause of the rapid PM2.5 increase. The deep, strong temperature inversion layer and weak vertical wind velocity could have suppressed vertical motion and enhanced the stability of the near-surface atmosphere, causing the air pollutants to accumulate at low levels and exacerbating the air pollution problem. Finally, a persistent stagnant weather system with a weak geopotential height field of 1000 hPa and warm air advection at 850 hPa was the main feature of atmospheric circulation associated with the heavy pollution. © 2018, Springer-Verlag GmbH Austria, part of Springer Nature."
"7404747615;7102805852;55427995800;","Are Changes in Atmospheric Circulation Important for Black Carbon Aerosol Impacts on Clouds, Precipitation, and Radiation?",2019,"10.1029/2019JD030568","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85069807011&doi=10.1029%2f2019JD030568&partnerID=40&md5=3e7bae50546845a5e6fa754b2c5bef60","Black carbon (BC) aerosols strongly absorb solar radiation, but their effective radiative forcing and impacts on regional climate remain highly uncertain owing to strong feedbacks of BC heating on clouds, convection, and precipitation. This study investigates the role of large-scale circulation changes in governing such feedbacks. In the HadGEM3 climate model BC emissions were increased to 10 times present-day values while keeping sea surface temperatures fixed, to assess the rapid adjustments to increased BC absorption. The BC perturbation led to an effective radiative forcing of 2.7 W/m2 and a 0.13-mm/day reduction in global precipitation. There were also large shifts in the spatial distribution of tropical convection, increased low cloud over oceans, and a weakening and poleward shift of midlatitude storm tracks, especially in the Northern Hemisphere. In a parallel experiment, horizontal winds were nudged toward meteorological reanalyses to deliberately suppress circulation responses while allowing changes to the thermodynamic structure of the atmosphere. Surprisingly, BC had approximately the same impact on global-mean radiation and global precipitation in the nudged experiment, even though regional changes in clouds and convection were not fully captured. The results show that large-scale dynamical responses to BC are important for regional impacts but have a limited role in determining the effective radiative forcing and global-mean climate response. The rapid adjustments of clouds, radiation, and global precipitation were primarily a response to increased radiative absorption and atmospheric stability. This implies that short nudged simulations may be sufficient to assess absorbing aerosol impacts on global-mean radiation and precipitation. ©2019 Crown copyright. This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland."
"13405561000;8918407000;35104877900;36655323000;9838847000;","Changes in marine fog in a warmer climate",2016,"10.1002/asl.691","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84984678066&doi=10.1002%2fasl.691&partnerID=40&md5=d379edaefae7deb88b08bc6ff00f8d1d","Changes in marine fog in a warmer climate are investigated through simulations using the atmospheric component of a global climate model, with both observed and perturbed sea surface temperature forcing. Global changes in marine fog occurrence in different seasons are compared. We show that the changes in marine fog occurrence correspond well to changes in horizontal temperature advection near the surface in a warmer climate. Therefore, the changes in marine fog can be well explained by large-scale circulation changes. Regarding changes in the characteristics of marine fog, we show that the in-cloud liquid water content of marine fog is consistently increased in a warmer climate, for a given horizontal surface temperature advection. It is also confirmed that the contribution of changes in marine fog to cloud feedback is not negligible, but is small. © 2016 The Authors. Atmospheric Science Letters published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"7004540083;7601318782;6603422104;","Atmospheric diabatic heating in different weather states and the general circulation",2016,"10.1175/JCLI-D-15-0760.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957824524&doi=10.1175%2fJCLI-D-15-0760.1&partnerID=40&md5=1fdbd2906e4009a96bef1593e4870a8c","Analysis of multiple global satellite products identifies distinctive weather states of the atmosphere from the mesoscale pattern of cloud properties and quantifies the associated diabatic heating/cooling by radiative flux divergence, precipitation, and surface sensible heat flux. The results show that the forcing for the atmospheric general circulation is a very dynamic process, varying strongly at weather space-time scales, comprising relatively infrequent, strong heating events by ""stormy"" weather and more nearly continuous, weak cooling by ""fair"" weather. Such behavior undercuts the value of analyses of time-averaged energy exchanges in observations or numerical models. It is proposed that an analysis of the joint time-related variations of the global weather states and the general circulation on weather space-time scales might be used to establish useful ""feedback like"" relationships between cloud processes and the large-scale circulation. © 2016 American Meteorological Society."
"55545874600;6507112497;7005446873;","Transition from suppressed to active convection modulated by a weak temperature gradient-derived large-scale circulation",2015,"10.1175/JAS-D-14-0041.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923095045&doi=10.1175%2fJAS-D-14-0041.1&partnerID=40&md5=f30394170b9173dc5b1168b8b31328dd","Numerical simulations are performed to assess the influence of the large-scale circulation on the transition from suppressed to active convection. As a model tool, the authors used a coupled-column model. It consists of two cloud-resolving models that are fully coupled via a large-scale circulation that is derived from the requirement that the instantaneous domain-mean potential temperature profiles of the two columns remain close to each other. This is known as the weak temperature gradient approach. The simulations of the transition are initialized from coupled-column simulations over nonuniform surface forcing, and the transition is forced in the dry column by changing the local and/or remote surface forcings to uniform surface forcing across the columns. As the strength of the circulation is reduced to zero, moisture is recharged into the dry column and a transition to active convection occurs once the column is sufficiently moistened to sustain deep convection. Direct effects of changing surface forcing occur over the first few days only. Afterward, it is the evolution of the large-scale circulation that systematically modulates the transition. Its contributions are approximately equally divided between the heating and moistening effects. A transition time is defined to summarize the evolution from suppressed to active convection. It is the time when the rain rate in the dry column is halfway to the mean value obtained at equilibrium over uniform surface forcing. The transition time is around twice as long for a transition that is forced remotely compared to a transition that is forced locally. Simulations in which both local and remote surface forcings are changed produce intermediate transition times. © 2015 American Meteorological Society."
"6602176524;6701481007;","Observed variability of North Atlantic oceanic precipitating systems during winter",2003,"10.1029/2002jd003343","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0742270498&doi=10.1029%2f2002jd003343&partnerID=40&md5=ad56a4673052130d421eb9e468039d5e","The variability of large precipitating weather systems as observed from polar satellites over the North Atlantic Ocean is investigated using a statistical analysis. Nine winters (from 1987 to 1995) have been considered. Cloud systems and troughs over the area 40-60°N, 70-10°W are automatically detected with retrievals of the cloud top pressure, a precipitation index, and the temperature of the lower stratosphere. A classification of the largest precipitating systems as characterized by these variables leads to eight classes, whose occurrence significantly differs over the years. It also shows the systematic presence of a trough upstream of the precipitating area covered by high-level clouds, as expected in the case of baroclinic interaction. In order to understand the large interannual variability an attempt to identify systematic differences in cyclone structures during different flow regimes is then performed. It shows that the large-scale (typically 3000 km wide) and zonally elongated cloud systems are observed mainly to the south of 45°N when the phase of the Arctic Oscillation (AO) is negative (which also corresponds to the Greenland Anticyclone regime). Conversely, zonally elongated cloud systems of smaller scale (1000 km wide) associated with frontal waves are favored also to the south but during the positive AO phase (particularly during zonal regimes). The most tilted weather systems, without any preferential AO phase, are found mostly during the blocking regime. These systems are cyclonically tilted in the northeastern branch of the storm track and anticyclonically tilted in the southwestern branch. It must be noted that similar results are obtained when the AO daily index is replaced by the North Atlantic Oscillation index. This analysis gives observational evidence of previous idealized simulations linking the large-scale circulation to preferential life cycles of weather systems. In addition, a weak response to extreme El Niño Southern Oscillation events has been observed in the location of cyclones but not in their average structure."
"35572026100;7006095466;57193882808;","Walker-type mean circulations and convectively coupled tropical waves as an interacting system",2002,"10.1175/1520-0469(2002)059<1566:WTMCAC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036275705&doi=10.1175%2f1520-0469%282002%29059%3c1566%3aWTMCAC%3e2.0.CO%3b2&partnerID=40&md5=db27500829809e7978ab9797761c076f","Interactions between convectively coupled tropical waves and Walker-type mean circulations are examined using a two-dimensional analytic model wherein drying and cooling of the boundary layer by convective and mesoscale downdrafts are in equilibrium with the wind-induced perturbations of surface fluxes. The moist thermodynamic state directly affects the stability of the large-scale circulation by controlling the wind perturbation on surface fluxes and the strength of the convective downdrafts. Stability analyses yield two major conclusions. (i) The mean Walker circulation is linearly unstable, suggesting that it may only exist in a quasi-steady sense through the spontaneous generation of transient waves. The instability is a manifestation of positive feedback: enhanced low-level convergence increases the surface wind speed, which increases the surface flux. As a result, convective heating is increased, which further enhances the low-level convergence. The mean circulation is more unstable when its horizontal extent is small and its depth large. Hence, when the horizontal extent of the mean circulation is a few thousand kilometers, as in the authors' recent cloud-resolving simulations, the deep first-baroclinic mode circulation is too unstable to be maintained even in a quasi-steady sense, realizing a shallow double-cell structure. (ii) The convectively coupled large-scale wave differs from traditional tropical large-scale instabilities of a homogeneous mean state in an important way: the longest waves are the most unstable rather than the shortest. Linear coupling of the waves with the mean state, through wind-induced surface flux perturbations, induces monotonically growing instabilities when the ascent of the mean circulation occupies more than half of the total domain. These instabilities occur only with the odd-wavenumber modes, which have parity with the mean circulation. Otherwise, the system supports linear neutral waves that propagate slower than the dry gravity waves due to the convective coupling in the ascending region. Growing oscillatory modes occur when nonlinear advection is included, which is consistent with the observed spontaneous generation of convectively coupled waves."
"55765742100;6506738607;56256907500;57204527472;6701823396;","Strong dependence of wintertime arctic moisture and cloud distributions on atmospheric large-scale circulation",2019,"10.1175/JCLI-D-19-0242.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076258465&doi=10.1175%2fJCLI-D-19-0242.1&partnerID=40&md5=00f90ac86e4339446ca9e5fb2541981d","This study gives a comprehensive picture of how atmospheric large-scale circulation is related to moisture transport and to distributions of moisture, clouds, and surface downward longwave radiation in the Arctic in winter. Anomaly distributions of the abovementioned variables are compared in 30 characteristic wintertime atmospheric circulation regimes, which are allocated from 15 years (2003-17) of mean sea level pressure data of ERA-Interim reanalysis applying the self-organizing map method. The characteristic circulation regimes are further related to known climate indices-the North Atlantic Oscillation (NAO), the Arctic Oscillation (AO), and Greenland blocking index-as well as to a frequent high pressure pattern across the Arctic Ocean from Siberia to North America, herein called the Arctic bridge. Effects of large-scale circulation on moisture, cloud, and longwave radiation are to a large extent occurring through the impact of horizontal moisture transport. Evaporation is typically not efficient enough to shape those distributions, and much of the moisture evaporated in the Arctic is transported southward. The positive phase of the NAO and AO increases moisture and clouds in northern Europe and the eastern North Atlantic Ocean, and a strong Greenland blocking typically increases those in the southwest of Greenland. When the Arctic bridge is lacking, the amount of moisture, clouds, and downward longwave radiation is anomalously high near the North Pole. Our results reveal a strong dependence of moisture, clouds, and longwave radiation on atmospheric pressure fields, which also appears to be important from a climate change perspective. © 2019 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"57200926820;","Convective Heating Leads to Self-Aggregation by Generating Available Potential Energy",2019,"10.1029/2019GL083805","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074079939&doi=10.1029%2f2019GL083805&partnerID=40&md5=3e0177355114c699653f281a0aa14fe1","The moisture-entrainment-convection (MEC) feedback posits that a moist environment favors deep convection, which further moistens the atmosphere through its associated circulation and detrainment. The MEC feedback has been proposed to be crucial to spontaneous convective aggregation. Here we test this hypothesis by performing minimal cloud-resolving simulations, without the buoyancy effect due to water vapor, evaporation of rain, or radiative and surface-flux feedbacks. Convection can self-aggregate in this minimal simulation, in which the MEC feedback is active. We then switch off this feedback by relaxing moisture to its horizontal mean over a time scale of 3 hr. Convection still self-aggregates in this mechanism-denial experiment, suggesting that the MEC feedback is not essential to self-aggregation. We further show that convective heating coincides with positive temperature anomalies, generating available potential energy. Therefore, we propose that this convective heating-overturning circulation feedback can lead to spontaneous development of large-scale circulations. © 2019. American Geophysical Union. All Rights Reserved."
"57212988186;22934904700;55471474500;7401945370;10243650000;56520853700;","Responses of Clouds and Large-Scale Circulation to Global Warming Evaluated From Multidecadal Simulations Using a Global Nonhydrostatic Model",2019,"10.1029/2019MS001658","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85073787477&doi=10.1029%2f2019MS001658&partnerID=40&md5=ac03f1977ebe0c001bccfb71e52f87f4","This is the first paper that analyzes data from atmosphere model intercomparison project-type climate simulations using a cloud-system-resolving global nonhydrostatic model without cumulus parameterization focussing particulaly on the relationship between clouds and circulation, and their changes due to global warming. The decrease in fractional coverage of low clouds is key to evaluating cloud radiative effects, because changes in shortwave cloud radiative effects overwhelm those of longwave cloud radiative effects. Thus, improved evaluation of low clouds is important, even in high-resolution climate simulations. An analysis of heat redistribution by explicitly computed clouds revealed that column-integrated heating rate due to phase changes correlates highly with vertical velocity at the altitude corresponding to 500 hPa and is closely linked to column water vapor, similar to the present climate result. Using data from year 1 to year 5, the effective climate sensitivity was evaluated to be 3.6−3.7°C. Possible convective aggregation is also examined using an index of modified subsidence fraction and characteristic changes in the number of cold pools. Despite previous idealized-planet simulations showing more aggregated tropical convection under warmer conditions, here we show a decrease in the subsidence fraction and an increase in the number of smaller cold pools, suggesting that it is possible to realize less convective organization with warming under real atmospheric conditions. ©2019. The Authors."
"57209611475;55721580400;56410752500;57199888745;","Improving the simulation of the climatology of the East Asian summer monsoon by coupling the Stochastic Multicloud Model to the ECHAM6.3 atmosphere model",2019,"10.1007/s00382-019-04787-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065027160&doi=10.1007%2fs00382-019-04787-0&partnerID=40&md5=9994a37404bec86d2b0e49e08299dec2","The East Asian summer monsoon (EASM) has significant impacts on local and global hydrological and climatic systems. However, most current atmospheric and coupled models have difficulty in capturing the climatological mean state of the EASM. The present study investigated the possible improvement of EASM simulation via coupling the Stochastic Multicloud Model (SMCM) to the state-of-the-art ECHAM6.3 atmosphere model. Evaluated by the pattern correlation coefficient and root-mean-square error, the modified ECHAM6.3, i.e., with SMCM coupling, showed better performance in simulating the EASM in terms of the precipitation pattern and intensity, the pattern of the western North Pacific subtropical high, the monsoon onset, and its seasonal evolution. Analyses also revealed that the modified ECHAM6.3 outperformed the default ECHAM6.3 in terms of large-scale circulation and vertically integrated moisture transport. Finally, it was that the intensified land–sea thermal contrast in both the meridional and zonal directions, as well as the stronger meridional temperature gradient in the upper troposphere and enhanced diabatic heating over the Tibetan Plateau, which are associated with the stochastic cloud, were the main reasons for the better performance of the modified ECHAM6.3 in simulating the EASM. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature."
"57204107350;8953662800;52264873100;57213521610;55153585300;55184057600;57188767737;55899884100;57195198884;57200751575;55543826100;","Tropopause trend across China from 1979 to 2016: A revisit with updated radiosonde measurements",2019,"10.1002/joc.5866","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054480416&doi=10.1002%2fjoc.5866&partnerID=40&md5=a893e4c1adcf521a55c5fde168fef0bb","The long-term trend in tropopause has profound implications for the expansion of tropical zone and the variation of large-scale circulation. However, the changes of tropopause in China have not been explicitly investigated as yet. In this study, the trend of lapse rate tropopause (LRT) height over China has been comprehensively revisited for the period of 1979–2016, using the newly released quality-controlled radiosonde data from China Meteorological Administration. Results show that the LRT height in most parts of China shows a significant upwards trend with a rate of 370 m/decade, most likely due to global warming. The fastest increase occurs in northwest region, followed by the low-latitude regions (15°–25°N), while the slowest increase occurs in the high-latitude regions (45°–55°N). Overall, the LRT height varies with latitudes, exhibiting a “south high and north low” pattern. In particular, high LRT height over low latitudes is found to be expanding rapidly polewards in recent years, in contrast to almost constant LRT height over mid and high latitudes. In terms of the seasonality, tropopause height reaches the peak in summer and bottom in winter. The frequency distribution in the vertical direction exhibits a bimodal pattern with the major peak mostly occurring at around 15 km and a secondary peak occurring between 8 and 12 km. This bimodal distribution is similar to the findings revealed in previous studies. Our findings offer important circumstantial observational evidence for the polewards expansion of the Tropics under global warming. © 2018 Royal Meteorological Society"
"15047538100;15050523700;6602135370;36242447900;57203816066;","Simulation of extreme Indian summer monsoon years in Coupled Model Intercomparison Project Phase 5 models: Role of cloud processes",2019,"10.1002/joc.5851","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053049500&doi=10.1002%2fjoc.5851&partnerID=40&md5=35dfe5ff54cb5f2948de26bf05f72e7e","The Indian summer monsoon (ISM) is a climate coupled system where cloud processes play a significant role in modulating the thermodynamics and dynamics of the atmosphere. The realistic representation of cloud by coupled model becomes indispensable for the simulation of the rainfall variability dictating the extreme ISM rainfall years. This study pinpoints the importance of correct representation of cloud processes and different types of rainfall in coupled climate model for the realistic simulation of monsoon extreme rainfall years. The study has used historical runs of Coupled Model Intercomparison Project Phase 5 (CMIP5) models. It provided best opportunity to investigate the ISM rainfall characteristics in case of anomalous monsoon and associated physical processes responsible for the modulation of large-scale circulation. The study has identified the mechanism behind the better simulation of anomalous years. Relatively more cloud condensate at upper level and middle level is present in excess monsoon years. Pertaining to phase changes and thermodynamical processes, there will be relatively more tropospheric temperature gradient and it will be conducive for strong monsoon. Proper representation of convective and stratiform rain is seen during extreme years. Precipitable water is also relatively more during excess monsoon years. As a result, total rainfall also enhances and it leads to excess monsoon. In contrast, during deficient monsoon relatively less cloud condensate at upper level and middle level is present. Therefore, the correct representation of cloud condensate vertical profile and stratiform/convective rain are crucial for the better simulation of excess and deficient monsoon, which may further improve the variability of ISM in climate model. This study connotes the urgent need of the improvement of cloud parameterization in coupled climate models for the betterment of monsoon variability and realistic representation of deficient/excess monsoon rainfall patterns over Indian subcontinent. © 2018 Royal Meteorological Society"
"36655445400;57203012011;35849722200;35113492400;41362078500;55601976700;57214076440;","Thermal effects of the surface heat flux on cloud systems over the Tibetan Plateau in boreal summer",2019,"10.1175/JCLI-D-18-0604.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074771494&doi=10.1175%2fJCLI-D-18-0604.1&partnerID=40&md5=0d3f0a15ece0c7baec0c02aa70d17ab9","The influence of surface heat fluxes on the generation and development of cloud and precipitation and its relative importance to the large-scale circulation patterns are investigated via cloud-resolving model (CRM) simulations over the Tibetan Plateau (TP) during boreal summer. Over the lowland (e.g., along the middle and lower reaches of the Yangtze River), the dynamical and thermal properties of the atmosphere take more responsibility than the surface heat fluxes for the triggering of heavy rainfall events. However, the surface thermal driving force is a necessary criterion for the triggering of heavy rainfall in the eastern and western TP (ETP and WTP). Strong surface heat fluxes can trigger shallow convections in the TP. Furthermore, moisture that is mainly transported from the southern tropical ocean has a greater influence on the heavy rainfall events of the WTP than those of the ETP. Cloud microphysical processes are substantially less active and heavy rainfall cannot be produced when surface heat fluxes are weakened by half in magnitude over the TP. In addition, surface heating effects are largely responsible for the high occurrence frequency of convection during the afternoon, and the cloud tops of convective systems show a positive relationship with the intensity of surface heat fluxes. © 2019 American Meteorological Society."
"23492864500;7006184606;7006614696;36161790500;","Implications of Warm Rain in Shallow Cumulus and Congestus Clouds for Large-Scale Circulations",2017,"10.1007/s10712-017-9429-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030087504&doi=10.1007%2fs10712-017-9429-z&partnerID=40&md5=818c2cee1e96257ef1cbea1acd1bad81","Space-borne observations reveal that 20–40% of marine convective clouds below the freezing level produce rain. In this paper we speculate what the prevalence of warm rain might imply for convection and large-scale circulations over tropical oceans. We present results using a two-column radiative–convective model of hydrostatic, nonlinear flow on a non-rotating sphere, with parameterized convection and radiation, and review ongoing efforts in high-resolution modeling and observations of warm rain. The model experiments investigate the response of convection and circulation to sea surface temperature (SST) gradients between the columns and to changes in a parameter that controls the conversion of cloud condensate to rain. Convection over the cold ocean collapses to a shallow mode with tops near 850 hPa, but a congestus mode with tops near 600 hPa can develop at small SST differences when warm rain formation is more efficient. Here, interactive radiation and the response of the circulation are crucial: along with congestus a deeper moist layer develops, which leads to less low-level radiative cooling, a smaller buoyancy gradient between the columns, and therefore a weaker circulation and less subsidence over the cold ocean. The congestus mode is accompanied with more surface precipitation in the subsiding column and less surface precipitation in the deep convecting column. For the shallow mode over colder oceans, circulations also weaken with more efficient warm rain formation, but only marginally. Here, more warm rain reduces convective tops and the boundary layer depth—similar to Large-Eddy Simulation (LES) studies—which reduces the integrated buoyancy gradient. Elucidating the impact of warm rain can benefit from large-domain high-resolution simulations and observations. Parameterizations of warm rain may be constrained through collocated cloud and rain profiling from ground, and concurrent changes in convection and rain in subsiding and convecting branches of circulations may be revealed from a collocation of space-borne sensors, including the Global Precipitation Measurement (GPM) and upcoming Aeolus missions. © 2017, The Author(s)."
"13403754000;7006614696;7004379124;","Evaluation of precipitation and high-level cloud areas associated with large-scale circulation over the tropical Pacific in the CMIP3 models",2009,"10.2151/jmsj.87.771","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349496258&doi=10.2151%2fjmsj.87.771&partnerID=40&md5=de4dcadeb53129ac8aae2cfbacc2c9e8","Precipitation and high-level cloud (HLC) areas in association with the large-scale circulation over the tropical Pacific are analyzed for simulations of nineteen Coupled Model Intercomparison Project Phase 3 (CMIP3) models with observations for 16 years of 1984-1999. The distribution of rainfall and HLC areas are composited around the geographical center of tropospheric upper-level (200 hPa) divergence (DIV) along Intertropical Convergence Zone (ITCZ) using monthly anomaly data. Datasets with a finer temporal sampling than monthly means were not available for the present purposes. The most notable feature is that the horizontal spread of enhanced circulation and the related rainfall and HLC areas are all underestimated around the DIV center in the models compared to the observation. Particularly, the underestimation is pronounced in HLC, presumably owing to difficulties in the physical processes relevant to the spatial distribution of HLC area. In general, a model with a higher correlation between the large-scale circulation field and rainfall tends to have a wider spread of HLC area around the DIV center. © 2009, Meteorological Society of Japan."
"56982420100;56211654900;","Hot gas halo of NGC 3923: Circulation of intergalactic matter",1999,"10.1086/306954","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033110564&doi=10.1086%2f306954&partnerID=40&md5=ac8f8b2308e427a51972e21c3a9a8028","We have observed the X-ray-faint, early-type galaxy NGC 3923 with the X-ray satellite ASCA. The observed images were restored using the Richardson-Lucy algorithm. The total mass of hot gas and the total mass of Fe in the halo have been derived from the restored images. We found that NGC 3923 contains a very small amount of hot gas and Fe compared with X-ray-bright early-type galaxies. The observed mass of the hot gas, Mgas = 5.7 x 107 M⊙, can be produced in 0.063 Gyr by the stellar mass loss; the observed mass of Fe, MFe = 1.2(0.71-2.2) x 105M⊙ can be produced in 0.027 Gyr by Type Ia supernovae. From the short timescales that are inferred, we conclude that NGC 3923 must be in the outflow phase at present. We show that most early-type galaxies are in their outflow phase at present and that the dynamical accretion of gas clouds, which has been expected from the hierarchical clustering theory, is necessary to explain the observed Fe abundances of early-type galaxies. The outflow driven by Type Ia supernovae and gas accretion due to the dynamical interaction of dark matter clouds produce a large-scale circulation of intergalactic matter."
"7003728653;7102432861;6603968676;","Persistent low overcast events in the U.S. upper Midwest: A climatological and case study analysis",1998,"10.1175/1520-0434(1998)013<0640:ploeit>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032172939&doi=10.1175%2f1520-0434%281998%29013%3c0640%3aploeit%3e2.0.co%3b2&partnerID=40&md5=ed43b1d8f8f2c74db19bd42611587786","Persistent low overcast conditions, defined as continuous overcast conditions (100% cloud cover) with ceiling heights at or below 2 km for a minimum of 5 days, are found to occur in the cold season in the U.S. upper Midwest on average slightly more often than once every two years. These occurrences are associated with two primary large-scale circulation patterns. Most commonly, the midlatitude westerlies are split across North America, with downstream confluence of the northwesterly polar and the southwesterly subtropical jet streams. A second, less frequent, pattern features an amplified westerly jet across North America, with a correspondingly rapid progression of weakly developed cyclones through the region. In the case of the split flow pattern, composite surface high pressure is established, occasionally disrupted by the emergence from either stream of relatively weak cyclones. These systems act to moisten the affected region at low levels through horizontal transport of moisture and, to a lesser extent, moisture convergence. Subsidence inversions established following the passage of these systems act to slowly erode the depth of the surface-based moist layer but are insufficient in combination with the weak solar radiative input to dissipate the cloud. The properties of the event structure, from the large scale down to that of the cloud layer itself, are stable. Under such conditions, the mechanism that finally removes the cloud is the passage of a relatively well-developed baroclinic wave and its associated forcing (subsidence, dry air advection, moisture divergence). Correspondingly, the difficult act of forecasting the end of such periods requires an accurate assessment of the sufficiency of that forcing to remove the low-level cloud. It is suggested that a relatively simple one-dimensional boundary layer model employed for the time to be critically tested in conjunction with the standard forecast model guidance (forecast vertical motion, profiles of temperature and moisture, Model Output Statistics cloud cover and ceiling) would provide additional information regarding forecast uncertainty."
"7202746265;","Linear retrieval and global measurement of precipitable water from the SEASAT SMMR data",1992,"10.1007/BF01025615","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33751125142&doi=10.1007%2fBF01025615&partnerID=40&md5=1f51da6318cfbec0e0ec7020e2fde200","The Seasat Scanning Multichannel Microwave Radiometer (SMMR) measurements in the 18.0, 21.0 and 37.0 GHz channels, both horizontal and vertical polarizations, are primarily used for precipitable water, cloud liquid water content and rainfall rate determination. Linear regressions using a leaps and bounds procedure are used for the retrieval of precipitable water. The radiation simulated for all the ten SMMR channels with varied global environmental parameters were used for subset selection for water vapour retrieval. Only subsets with channels having uniform grid size (18, 21 and 37 GHz) were used for the analysis. A total of eight subsets using two to five frequencies of the SMMR are examined to determine their potential in the retrieval of atmospheric water vapour content. Our analysis indicates that the information concerning the 18 and 21 GHz channels are optimum for the water vapour retrieval. An attempt to use all the SMMR channels simultaneously gives no significant improvement. A comparison with the radiosonde observations gave an rms accuracy of 0.4 g/cm2. The rms accuracy of retrieved precipitable water using different subsets was within 10 percent. Global maps of precipitable water over oceans using two and five channels retrieval are given. These maps are generated on a 10 day average basis as well as on monthly basis for the period 7 July to 6 August 1978. An analysis of these Global maps reveals the possibility of global moisture distribution associated with oceanic currents and large scale general circulation in the atmosphere. A stable feature of the large scale circulation is noticed. The precipitable water is maximum over the Bay of Bengal and in the North Pacific over the Kuroshio current and shows general latitudinal pattern. © 1992 Springer-Verlag."
"56905466000;15765165800;25031297200;56043409000;56127371700;8576228100;15766109700;","Climate signals in carbon and oxygen isotope ratios of Pinus cembra tree-ring cellulose from the Călimani Mountains, Romania",2020,"10.1002/joc.6349","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074793257&doi=10.1002%2fjoc.6349&partnerID=40&md5=42f8e3a5711ba7cc55f5199c292adddb","We analyse annually resolved tree-ring stable carbon (δ13C) and oxygen (δ18O) isotopic chronologies from Swiss stone pine (Pinus cembra L.) in Romania. The chronologies cover the period between 1876 and 2012 and integrate data from four individual trees from the Calimani Mts in the eastern Carpathians where climatic records are scarce and starts only from 1961. Calibration trials show that the δ13C values correlate with local April–May relative humidity and with regional to larger scale (European) summer precipitation. δ18O correlates significantly with local relative humidity, cloud cover, maximum temperature, as well as European scale drought conditions. In all cases, the climate effects on δ13C values are weaker than those recorded in the δ18O data, with the latter revealing a tendency toward higher (lower) values of δ18O during extremely dry (wet) years. The most striking signal, however, is the strong link between the interannual δ18O variability recorded in the Calimani Mts and large-scale circulation patterns associated with North Atlantic and Mediteraneean Sea sea surface temperatures. High (low) values of δ18O occur in association with a high (low) pressure system over the central and eastern part of Europe and with a significantly warmer (colder) Mediterranean Sea surface temperature. These results demonstrate the possibility of using tree ring oxygen isotopes from the eastern Carpathians to reconstruct regional drought conditions in eastern Europe on long-term time scales and larger scale circulation dynamics over the preinstrumental periods. © 2019 Royal Meteorological Society"
"36627352900;57195588141;53063975800;35209683700;57207734961;57193516281;35838255300;10144067900;","Impacts of the North Atlantic subtropical high on interannual variation of summertime heat stress over the conterminous United States",2019,"10.1007/s00382-019-04708-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062796728&doi=10.1007%2fs00382-019-04708-1&partnerID=40&md5=a3d83c31d000e0e90bddc360c268ba4a","Heat index (HI) provides a proven indicator of heat stress and discomfort for the general public. The index takes the integrated effects of both temperature and humidity into account, and both factors are regulated by large-scale circulation patterns. This study examines the impacts of the North Atlantic Subtropical High (NASH) on HI over the conterminous United States (CONUS). The analysis suggests that the HI is primarily controlled by surface air temperature over the CONUS; but is negatively correlated with relative humidity in the western and Central US north of 40°N. In addition, winds contribute to the variation of HI in the Midwest and the southeastern US. By regulating these meteorological parameters, the movement of the NASH western ridge significantly impacts HI over the US, especially the Southeast. When the NASH western ridge is located northwest (NW) of its climatological mean position, abnormally high temperatures are observed due to fewer clouds and a precipitation deficit, leading to positive HI anomalies over the southeastern US. In contrast, when the western ridge is located in the southwest (SW), temperature decreases and HI anomaly becomes negative over the Southeast, even though relative humidity increases east of 100°W. NASH has a weaker impact on the HI when it is far from the North American continent, especially during southeast (SE) ridge years. In the future, CMIP5 models project an increase in HI over the entire CONUS, while NASH-induced HI will be weakened during the NW, SE and NE ridge years but strengthened when its ridge moves to the SW quadrant. These results suggest that future increases in heat stress are likely caused by climatological warming and NASH intensification. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature."
"57207697043;55766838600;56463154100;56539258900;57205085158;","Evaluation of the effects of a multiphysics ensemble on the simulation of an extremely hot summer in 2003 over the CORDEX-EA-II region",2019,"10.1002/joc.6028","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062728517&doi=10.1002%2fjoc.6028&partnerID=40&md5=905d043ee7ffe0ed87a8b85e35b67a13","In this paper, we evaluate a 48-member multiphysics ensemble using the Weather Research and Forecasting (WRF) model for the JJA extreme precipitation and temperature in 2003 over the CORDEX-EA-II domain. The simulated precipitation and temperature are reasonable in the subregions controlled by a large-scale circulation, yet the biases for both precipitation and temperature are evident over the subregions where the effects of mesoscale processes are important. The performance of various combinations of WRF physical schemes for simulating the JJA precipitation is dependent on the region. Meanwhile, the cumulus and microphysical schemes have substantial influences on the simulation of precipitation, and the land surface models and cumulus schemes play crucial roles in the surface temperature. Our analysis shows that the combination of Noah for the land surface process, Lin for the microphysics, G3D for the cumulus parameterization, and CAM for the radiation scheme can provide the most reliable reproduction of both precipitation and temperature extremes over China. Ensemble analysis shows that the simulated climate extremes are usually accompanied by a large ensemble spread, implying sensitivities to the model physical processes in some subregions. The simulated wind fields at low-to-middle atmospheric levels display responses to the options of the land surface models and cumulus schemes. The essential impact of the land–atmospheric interaction on simulating the extremes can be largely attributed to the active convective processes. WRF has difficulties in reproducing the observed temporal evolution of the rainfall process, which consists of continuous large rainfall episodes in the observation data set during the simulation period. © 2019 Royal Meteorological Society"
"55510628800;57191754390;56526794400;36994106300;","Simulation of interannual variability of summer rainfall over the Tibetan Plateau by the Weather Research and Forecasting model",2019,"10.1002/joc.5840","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052924484&doi=10.1002%2fjoc.5840&partnerID=40&md5=63ecc212c5757ed9f62043571b6ed494","A realistic simulation of rainfall over the Tibetan Plateau (TP) is a big challenge for both regional and global climate models. In this study, we investigate the simulations of summer rainfall over the TP from 1979 to 2010 by the Weather Research and Forecasting (WRF) model with various horizontal resolutions and cumulus schemes, with a focus on the difference in the model's skill in simulating interannual variability of rainfall between early and high summer. The WRF captures spatial pattern of climatological summer mean rainfall over the TP. However, it produces apparent wet bias, especially in southern and eastern edges of the TP. Despite this climatological bias, WRF skilfully reproduces the interannual variability of summer rainfall over the southeastern TP, where maximum rainfall is located. An increase in horizontal resolution or an appropriate cumulus scheme mostly improves the simulation of climatological mean rainfall. However, the phase of interannual variability of simulated rainfall is not sensitive to horizontal resolution and cumulus scheme. Instead, it is sensitive to mechanisms responsible for interannual variability of rainfall. WRF has a high skill in simulating the interannual variability of rainfall over the southeastern TP in July and August, but a low skill in June. The WRF's high skill is attributed to that the interannual variability of July–August rainfall is largely driven by large-scale circulation, while its low skill for June rainfall may be ascribed to the overestimation of snow and its relationship with rainfall. © 2018 Royal Meteorological Society"
"25924499900;57212988186;22934904700;","The Impact of Hybrid Usage of a Cumulus Parameterization Scheme on Tropical Convection and Large-Scale Circulations in a Global Cloud-System Resolving Model",2018,"10.1029/2018MS001302","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85057125034&doi=10.1029%2f2018MS001302&partnerID=40&md5=dbcf6b2cde27b819ca38e50c81f61b2a","The impact of activating a cumulus parameterization scheme in the global nonhydrostatic icosahedral atmospheric model (NICAM) coupled with a one-dimensional (1-D) mixed-layer ocean model is assessed using a cloud-system-resolving, 14-km mesh. The Chikira-Sugiyama (CS) scheme, which employs an entrainment rate sensitive to the humidity of the environment, can consider congestus clouds in the tropics when used in conventional global climate models. Congestus clouds are underresolved in the default 14-km mesh NICAM. In the present study, boreal summer NICAM simulations are performed with and without the CS scheme, and several different scheme parameters are evaluated. The results show that the horizontal scale of convection and precipitable water increased in the tropics when using the CS scheme. Model adjustments were apparent at two different timescales: a rapid adjustment within the first week and a slower adjustment at 1 to 2 months. Both effects were magnified in the simulations that employed smaller values for the parameter that defines the fractional of loss of buoyancy-generated energy in parameterized convection. The upward branch of the Hadley circulation shifted northward, and the Walker circulation was enhanced when the CS scheme was activated. These large-scale adjustments suggested that increased midtropospheric moisture in the tropics tends to favor larger organized convective activities, which require an abundant supply of moisture, which, in this case, is available to the north of the equatorial West Pacific Ocean. ©2018. The Authors."
"57217352376;57197668622;12782225200;7005659017;","Aerosol characteristics in the UTLS region: A satellite-based study over north India",2016,"10.1016/j.atmosenv.2015.11.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84947710346&doi=10.1016%2fj.atmosenv.2015.11.022&partnerID=40&md5=5c6b00f3a9595b9f6c6de38080a707d4","Vertical profiles of aerosol backscatter coefficient and depolarization ratio, obtained from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite, were studied in the upper troposphere and lower stratosphere (UTLS) region over North India (21-30° N and 72-90° E), covering the highly polluted Indo-Gangetic Plain (IGP) for one-year period from December 2011 to November 2012. An enhanced aerosol layer was observed between 15 and 18 km altitude, in the vicinity of tropopause, with a broad layer depth of about 2 km. The aerosol layer showed strong seasonal, monthly as well as day and night time variability, with a peak value of backscatter coefficient during monsoon season (~5.54 × 10-3 sr-1 in September). The corresponding depolarization ratio indicates anisotropic (non-spherical) nature of particles. The aerosol layer was found to be highly linked with the variability in tropopause height, showing a positive correlation between tropopause height and the height of maximum backscatter coefficient (correlation coefficient of 0.8). However, it was found to be negatively correlated with the integrated backscatter coefficient (IBC), with a correlation coefficient of 0.3. We further analyzed outgoing long-wave radiation (OLR) data during the study period to investigate the link between the observed enhanced aerosol layer in the UTLS region and prevailing deep convective activities over the study region. Low values of OLR during monsoon (about 214 W m-2) indicate the occurrence of deep convection over this region, which may cause a large-scale circulation-driven vertical transport of boundary-layer pollution into the atmosphere of UTLS region. Results may have potential implications for better understanding and assessing the chemical and radiative impacts of these aerosols in the tropical UTLS region. © 2015."
"57197139045;55624487688;26643299500;","Validation and development of a new hailstone formation theory: Numerical simulations of a strong hailstorm occuring over the Qinghai-Tibetan Plateau",2007,"10.1029/2005JD006227","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547903193&doi=10.1029%2f2005JD006227&partnerID=40&md5=d48b577dfcf6ce6e77d68e1468af0c11","Hailstorms occur frequently over the northeastern border of the Qinghai-Tibetan Plateau and its surroundings because of the combined geographical and meteorological features of this region. Formation and growth of the hailstones in a typical hailstorm are simulated using a three-dimensional (3-D) cloud model with hail-bin microphysics developed by the Institute of Atmospheric Physics of the Chinese Academy of Sciences (IAP/CAS). The information of the large-scale circulations for the cloud model was provided by the MM5V3 model. The results show that (1) the water content of each hailstone bin is significantly large in the ""cave channels""; (2) at the initial stage of hail formation, there is another high water content region consisting of small ice particles (D < 1 mm), graupel and hail embryos (1 mm < D < 5 mm), as well as small hailstones (5 mm < D < 10 mm), around the altitude of -30 ∼ -50°C above the high water content center associated with the ""cave channels""; between them there is a gap of lower water content, which means that the main mechanisms of hail formation are different in those two regions; (3) as the hail and rain fall, the maximum center at higher level drops until it merges with a lower equivalent; the larger the hail particles are, the earlier the maximum centers merge with each other; (4) during the hailstorm dissipation period the downdraft occurs in the region of ""cave channels"" and the ""cave channels"" fade; however, it is still the center of high hail water content, even though all updraft airflow turns to downdraft airflow; (5) ""cave channels"" are not the only regions of hailstones formation, but are nonetheless effective in the growth of hailstones, so which should be the main region of suppressing hail growth from small to large. Copyright 2007 by the American Geophysical Union."
"7005828412;","Polar meteorology",1975,"10.1029/RG013i003p00710","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84995044823&doi=10.1029%2fRG013i003p00710&partnerID=40&md5=ff38c72b23e81ebfa1baa8abaeacf851","The general large‐scale circulation of the global atmosphere has its basic driving mechanism in the equator‐poleward temperature gradients in both hemispheres. It has become increasingly obvious over the last few decades that to understand and predict the behavior of the atmosphere at any point, it is essential to understand the behavior of the total global fluid system. The Global Atmospheric Research Project (Garp) is an outcome of this recognition. Studies of the heat sinks (the polar regions) are therefore just as important as studies of the heat source (the equatorial regions) to understand the meteorology of the planet. Interest in polar meteorology has undergone many cyclic fluctuations, peaking during the various international polar years and more recently during the International Geophysical Year (IGY) in 1957–1958. While polar meteorology continues to be studied for its own intrinsic interest, increased attention is given to its role within the framework of Garp. At the present the focus of Garp's first objective (improved extended weather forecasts) is on the tropical heat source, where convection and cloud formation and dissipation are still relatively little understood processes. However, the second Garp objective (better understanding of the physical basis of climate) requires more attention to be devoted to the cryosphere and its long‐term interaction with oceans and atmosphere and its role as indicator of climatic change. The idea of a polar experiment (Polex) in support of Garp was initially introduced by Treshnikov et al. [1968] and by Borisenkov and Treshnikov [1971]. A summary of the early history of Polex was recently given by Weller and Bierly [1973]. The two closely related objectives of Polex that most directly pertain to Garp may be restated in their simplest terms as (1) a better understanding of energy transfer processes and the heat budgets of the polar regions, for the purpose of parameterizing them properly in general circulation models and climate models, and (2) provision of adequate data from the polar regions during the First Garp Global Experiment (FGGE) in 1978. Copyright © 1975 by the American Geophysical Union."
"57212216605;56226894800;55293329700;55262054500;15070408300;55903815100;24177361900;36106370400;8633162900;57190438255;6602892883;7003968166;55293421800;","Meridional and vertical variations of the water vapour isotopic composition in the marine boundary layer over the Atlantic and Southern Ocean",2020,"10.5194/acp-20-5811-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085094617&doi=10.5194%2facp-20-5811-2020&partnerID=40&md5=5f8317ef44a04d78ae8e490803d00157","<span idCombining double low line""page5812""/>Stable water isotopologues (SWIs) are useful tracers of moist diabatic processes in the atmospheric water cycle. They provide a framework to analyse moist processes on a range of timescales from large-scale moisture transport to cloud formation, precipitation and small-scale turbulent mixing. Laser spectrometric measurements on research vessels produce high-resolution time series of the variability of the water vapour isotopic composition in the marine boundary layer. In this study, we present a 5-month continuous time series of such ship-based measurements of δ2H and δ18O from the Antarctic Circumnavigation Expedition (ACE) in the Atlantic and the Southern Ocean in the time period from November 2016 to April 2017. We analyse the drivers of meridional SWI variations in the marine boundary layer across diverse climate zones in the Atlantic and Southern Ocean using Lagrangian moisture source diagnostics and relate vertical SWI differences to near-surface wind speed and ocean surface state. The median values of δ18O, δ2H and deuterium excess during ACE decrease continuously from low to high latitudes. These meridional SWI distributions reflect climatic conditions at the measurement and moisture source locations, such as air temperature, specific humidity and relative humidity with respect to sea surface temperature. The SWI variability at a given latitude is highest in the extratropics and polar regions with decreasing values equatorwards. This meridional distribution of SWI variability is explained by the variability in moisture source locations and its associated environmental conditions as well as transport processes. The westward-located moisture sources of water vapour in the extratropics are highly variable in extent and latitude due to the frequent passage of cyclones and thus widen the range of encountered SWI values in the marine boundary layer. Moisture loss during transport further contributes to the high SWI variability in the extratropics. In the subtropics and tropics, persistent anticyclones lead to well-confined narrow easterly moisture source regions, which is reflected in the weak SWI variability in these regions. Thus, the expected range of SWI signals at a given latitude strongly depends on the large-scale circulation. Furthermore, the ACE SWI time series recorded at 8.0 and 13.5 m above the ocean surface provide estimates of vertical SWI gradients in the lowermost marine boundary layer. On average, the vertical gradients with height found during ACE are <math xmlnsCombining double low line""http://www.w3.org/1998/Math/MathML"" idCombining double low line""M5"" displayCombining double low line""inline"" overflowCombining double low line""scroll"" dspmathCombining double low line""mathml""><mrow><mo>-</mo><mn mathvariantCombining double low line""normal"">0.1</mn><mspace linebreakCombining double low line""nobreak"" widthCombining double low line""0.125em""/><mi mathvariantCombining double low line""normal"">‰</mi><mspace widthCombining double low line""0.125em"" linebreakCombining double low line""nobreak""/><msup><mi mathvariantCombining double low line""normal"">m</mi><mrow><mo>-</mo><mn mathvariantCombining double low line""normal"">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svgCombining double low line""http://www.w3.org/2000/svg"" widthCombining double low line""58pt"" heightCombining double low line""14pt"" classCombining double low line""svg-formula"" dspmathCombining double low line""mathimg"" md5hashCombining double low line""0b021c3fdbdc571a66f4ed883414678c""><svg:image xmlns:xlinkCombining double low line""http://www.w3.org/1999/xlink"" xlink:hrefCombining double low line""acp-20-5811-2020-ie00001.svg"" widthCombining double low line""58pt"" heightCombining double low line""14pt"" srcCombining double low line""acp-20-5811-2020-ie00001.png""/></svg:svg> for δ18O, <math xmlnsCombining double low line""http://www.w3.org/1998/Math/MathML"" idCombining double low line""M7"" displayCombining double low line""inline"" overflowCombining double low line""scroll"" dspmathCombining double low line""mathml""><mrow><mo>-</mo><mn mathvariantCombining double low line""normal"">0.5</mn><mspace widthCombining double low line""0.125em"" linebreakCombining double low line""nobreak""/><mi mathvariantCombining double low line""normal"">‰</mi><mspace widthCombining double low line""0.125em"" linebreakCombining double low line""nobreak""/><msup><mi mathvariantCombining double low line""normal"">m</mi><mrow><mo>-</mo><mn mathvariantCombining double low line""normal"">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svgCombining double low line""http://www.w3.org/2000/svg"" widthCombining double low line""58pt"" heightCombining double low line""14pt"" classCombining double low line""svg-formula"" dspmathCombining double low line""mathimg"" md5hashCombining double low line""9ce754f70dacafdde0e8a8acbee50447""><svg:image xmlns:xlinkCombining double low line""http://www.w3.org/1999/xlink"" xlink:hrefCombining double low line""acp-20-5811-2020-ie00002.svg"" widthCombining double low line""58pt"" heightCombining double low line""14pt"" srcCombining double low line""acp-20-5811-2020-ie00002.png""/></svg:svg> for δ2H and 0.3 ‰ m-1 for deuterium excess. Careful calibration and post-processing of the SWI data and a detailed uncertainty analysis provide a solid basis for the presented gradients. Using sea spray concentrations and sea state conditions, we show that the vertical SWI gradients are particularly large during high wind speed conditions with increased contribution of sea spray evaporation or during low wind speed conditions due to weak vertical turbulent mixing. Although further SWI measurements at a higher vertical resolution are required to validate these findings, the simultaneous SWI measurements at several heights during ACE show the potential of SWIs as tracers for vertical mixing and sea spray evaporation in the lowermost marine boundary layer. © 2020 BMJ Publishing Group. All rights reserved."
"36655445400;57203012011;35849722200;35113492400;","Large-Scale Circulation Environment and Microphysical Characteristics of the Cloud Systems Over the Tibetan Plateau in Boreal Summer",2020,"10.1029/2020EA001154","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085481140&doi=10.1029%2f2020EA001154&partnerID=40&md5=ef8b41f28e32906dfc63366e23f19e99","The Tibetan Plateau (TP) experiences a particular dynamical and thermal environment due to its unique topography, which could affect the generation and development of its cloud and precipitation. Statistical results of 52-year daily precipitation (1961 to 2012) show that the most frequent daily precipitation is about 3 mm day−1 over the eastern TP (ETP) in the warm season while it is less than 1 mm day−1 over the western TP (WTP). Circulation patterns for rainy and rainless conditions over both the ETP and WTP are investigated. The results show that the rainy weather over the TP is usually related to the moisture transported from the warm ocean by the southerly flow. Moreover, rainy weather in WTP can only appear when the strong southerly flow prevails over the Indian subcontinent. When the south flow is weak, the rainy weather can still develop in ETP under favorable conditions due to the local madid environment. CloudSat observations show that the strong convective system can extend to a level as high as 16 km above the sea level with a favorable dynamical and thermal environment. However, the depth of most precipitating convective clouds over the TP is in a range of 6–9 km. Due to the wetter condition, the precipitating convective cloud holds a lower cloud base in August in ETP than WTP. Compared with other regions, the precipitating convective clouds in both the ETP and WTP are thinner in cloud depth, smaller in cloud particles and weaker in precipitation capacity. ©2020. The Authors."
"56591585100;55531609200;7004384155;19639722300;","The Response of Tropical Organized Convection to El Niño Warming",2019,"10.1029/2019JD031026","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070689266&doi=10.1029%2f2019JD031026&partnerID=40&md5=d60f7de27b6dabb65a0358c7ef02c96c","Convective organization has a large impact on precipitation and feeds back on larger-scale circulations in the tropics. The degree of this convective organization changes with modes of climate variability like the El Niño–Southern Oscillation (ENSO), but because organization is not represented in current climate models, a quantitative assessment of these shifts has not been possible. Here, we construct multidecade satellite climatologies of occurrence of tropical convective organization and its properties and assess changes with ENSO phase. The occurrence of organized deep convection becomes more concentrated, increasing threefold in the eastern and central Pacific during El Niño and decreasing twofold outside of these regions. Both horizontal extent of the cold cloud shield and convective depth increase in regions of positive sea surface temperature anomaly (SSTa); however, the regions of greatest convective deepening are those of large-scale ascent, rather than those of warmest SSTa. Extent decreases with SSTa at a rate of about 20 km/K, while the SSTa dependence of depth is only about 0.2 K/K. We introduce two values to describe convective changes with ENSO more succinctly: (1) an information entropy metric to quantify the clustering of convective system occurrences and (2) a growth metric to quantify deepening relative to spreading over the system lifetime. Finally, with collocated precipitation data, we see that rainfall attributable to convective organization jumps up to 5% with warming. Rain intensity and amount increase for a given system size during El Niño, but a given rain amount may actually fall with higher intensity during La Niña. ©2019. American Geophysical Union. All Rights Reserved."
"55545874600;7005446873;6507112497;","Using the Weak-Temperature Gradient Approximation to Evaluate Parameterizations: An Example of the Transition From Suppressed to Active Convection",2017,"10.1002/2017MS000940","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032257589&doi=10.1002%2f2017MS000940&partnerID=40&md5=cf42ab34ea9c8aeaa21a18610351cc73","Two single-column models are fully coupled via the weak-temperature gradient approach. The coupled-SCM is used to simulate the transition from suppressed to active convection under the influence of an interactive large-scale circulation. The sensitivity of this transition to the value of mixing entrainment within the convective parameterization is explored. The results from these simulations are compared with those from equivalent simulations using coupled cloud-resolving models. Coupled-column simulations over nonuniform surface forcing are used to initialize the simulations of the transition, in which the column with suppressed convection is forced to undergo a transition to active convection by changing the local and/or remote surface forcings. The direct contributions from the changes in surface forcing are to induce a weakening of the large-scale circulation which systematically modulates the transition. In the SCM, the contributions from the large-scale circulation are dominated by the heating effects, while in the CRM the heating and moistening effects are about equally divided. A transition time is defined as the time when the rain rate in the dry column is halfway to the value at equilibrium after the transition. For the control value of entrainment, the order of the transition times is identical to that obtained in the CRM, but the transition times are markedly faster. The locally forced transition is strongly delayed by a higher entrainment. A consequence is that for a 50% higher entrainment the transition times are reordered. The remotely forced transition remains fast while the locally forced transition becomes slow, compared to the CRM. © 2017. The Authors."
"22136981600;22734679600;","General circulation of Venus from a long-term synoptic study of tropospheric CO by Venus Express/VIRTIS",2017,"10.1016/j.icarus.2017.02.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85014301918&doi=10.1016%2fj.icarus.2017.02.018&partnerID=40&md5=9bbf6f6a0d2f942dd6b964b22c8c9fa3","The understanding of spatial and temporal variations in tropospheric abundances of the trace gas carbon monoxide (CO) is key to understanding the deep atmospheric circulation on Venus. CO is entrained in the global circulation, as well as being key ingredients in the multi-reaction chemical cycle that creates and destroys the sulfuric acid that is a primary constituent of the clouds. Long-term temporal variations of CO across Venus’ disc would provide critical insights and constraints into the large-scale circulation and cloud forming processes in the troposphere. Here, we present an in-depth look at the CO as a function of latitude, longitude and local time as seen by the VIRTIS-M-IR instrument onboard the Venus Express spacecraft during its three years of operation. We find that CO is slightly enhanced on the dusk hemisphere near the poles (by ∼2 ppmv) and the equatorial concentrations from 22:00 – 03:00 are also elevated. Longitudinal variations of CO are largely absent, except for a potential correlation of anomalous CO around Themis Regio. These observations provide the most stringent constraints yet on global dynamics and CO chemistry of the deep troposphere on Venus. © 2017 Elsevier Inc."
"55683079000;7005461477;35325977100;13405658600;","Interactions between the MJO, Aerosols, and Convection over the Central Indian Ocean",2017,"10.1175/JAS-D-16-0054.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85011633135&doi=10.1175%2fJAS-D-16-0054.1&partnerID=40&md5=fd0b56578068a3815d766f04964bb774","This study examines covariability of boundary layer cloud condensation nuclei (CCN) concentrations [estimated using the GEOS 3D chemical transport model (GEOS-Chem)], convective clouds, precipitation, and lightning observed over the central equatorial Indian Ocean (CIO). Three distinct Madden-Julian oscillation (MJO) episodes were observed during the recent Dynamics of the MJO (DYNAMO; 2011/12) field campaign. Coherent relationships between CCN, rainfall, and lightning are apparent in time series from DYNAMO and more lightning located north of the equator is noted, compared to south of the equator. More-polluted environments north of the equator contained deep convective clouds that had stronger radar reflectivities (~2-3 dB) in the mixed-phase region (5-10-km altitude) compared to south of the equator. Following discussion of the MJO episodes that occurred during DYNAMO, 22 cycles of the MJO observed during boreal cold seasons in the years 2004-11 are examined with the aid of TRMM satellite observations. Climatological results suggest that horizontal transport of continental aerosols from proximal landmasses by the large-scale circulation after active MJO convection reinforces the meridional gradient of CCN concentrations in the CIO. Satellite observations depicted comparable aggregate cold cloud feature area in both regions in similar thermodynamic environments, leading to the suggestion that higher CCN concentrations north of the equator act to invigorate convection. Direct comparisons of convective intensity metrics to CCN support the aerosol hypothesis; however, in line with previous studies, it is acknowledged that conditional instability, vertical wind shear, and environmental moisture can modulate the initial development of deep convection over the CIO during select phases of the MJO. © 2017 American Meteorological Society."
"55176818100;54585176800;7004978125;","Enhanced persistence of equatorial waves via convergence coupling in the stochastic multicloud model",2015,"10.1175/JAS-D-15-0135.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950280678&doi=10.1175%2fJAS-D-15-0135.1&partnerID=40&md5=365e77a1da5532a851bba3e9f4d803b9","Recent observational and theoretical studies show a systematic relationship between tropical moist convection and measures related to large-scale convergence. It has been suggested that cloud fields in the column stochastic multicloud model compare better with observations when using predictors related to convergence rather than moist energetics (e.g., CAPE) as per Peters et al. Here, this work is extended to a fully prognostic multicloud model. A nonlocal convergence-coupled formulation of the stochastic multicloud model is implemented without wind-dependent surface heat fluxes. In a series of idealized Walker cell simulations, this convergence coupling enhances the persistence of Kelvin wave analogs in dry regions of the domain while leaving the dynamics in moist regions largely unaltered. This effect is robust for changes in the amplitude of the imposed sea surface temperature (SST) gradient. In essence, this method provides a soft convergence coupling that allows for increased interaction between cumulus convection and the large-scale circulation but does not suffer from the deleterious wave-conditional instability of the second kind (CISK) behavior of the Kuo-type moisture-convergence closures. © 2015 American Meteorological Society."
"36017183900;55686667100;7102857642;","Superrotation and nonlinear hadley circulation response to zonally asymmetric sea surface temperature in an aquaplanet GCM",2013,"10.2151/jmsj.2013-A10","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886785286&doi=10.2151%2fjmsj.2013-A10&partnerID=40&md5=c224eac4dfb55d77bbd8133b3a7aba5d","The responses of the equatorial zonal wind and the Hadley circulation to the equatorial zonal wavenumber one sea surface temperature (SST) anomaly, Ts*, are examined in an atmospheric general circulation model (AGCM) with an aquaplanet condition. The Hadley cell is weakened as the magnitude of Ts* increases, balancing with a decrease in the zonal-mean diabatic heating over the tropics. The decrease of heating reflects a nonlinear relationship between precipitation and SST; deep convection, such as a super cloud cluster, is significantly suppressed over cold Ts*, whereas is slightly enhanced over warm Ts*. The effective suppression of deep convection is accomplished by the stable boundary layer and the dry subsidence anomaly associated with the Walker cell which is excited by the SST anomaly. And the decreased convection acts to further reinforce the subsidence via thermodynamic balance. Therefore, this positive feedback between large-scale circulation and deep convection determines the nonlinear relationship and controls the strength of the Hadley cell. In terms of the energetics of the tropical circulation, the Hadley cell has to be weakened to compensate for the lack of energy supply caused by an increase of tropical radiative cooling due to the effective suppression of deep convection over cold Ts*. We compared the results of our AGCM with that of other 15 aquaplanet AGCMs integrated with the same SST distribution. While the Hadley cell is weakened in all AGCMs when Ts* is added to the zonal uniform SST, there is a large diversity in the strength. This suggests that the difference in the physical parameterization causes a different sensitivity of the Hadley cell response to zonally asymmetric SST. The magnitude of weakening is approximately proportional to the decreased (increased) amount of the deep convective precipitation (the radiative cooling) over the tropics. This strong relationship suggests that the positive feedback also works in other AGCMs. It is considered that the feedback is also important for understanding the formation of a real tropical climate. © 2013, Meteorological Society of Japan."
"7003278104;7102389501;","Analysis of ocean surface heat fluxes in a NOGAPS climate simulation: Influences from convection, clouds and dynamical processes",2000,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033785916&partnerID=40&md5=eb644c19375fb8c749b97b3ffb44f30e","This study examines the simulation quality of the surface heat flux fields produced during a climate simulation of the Navy Operational Global Atmospheric Prediction System, version 3.4, with a reduced spectral truncation of T63 and 18 levels (herineafter referred to as NOGAPS-CL). Comparisons are made between a 17-year NOGAPS-CL simulation using monthly sea surface temperatures as surface boundary conditions and a number of validating data sets consisting of ship, satellite, and/or reanalysis-based surface heat fluxes, precipitation, top of the atmosphere radiation budget, water vapor, cloud frequency, surface wind stress, and tropospheric winds. In this extended, long-range integration, NOGAPS-CL underpredicts the net surface shortwave flux in much of the subtropical oceans and overpredicts the net shortwave flux in the western Pacific warm pool and the midlatitude oceans, when compared to several satellite-derived climatological data sets. In addition, NOGAPS-CL over predicts the latent heat flux in much of the subtropics and under predicts the latent heat flux over the northern ocean western boundary currents and under the storm track regions that extend eastward from them. These shortwave and evaporation biases combine to produce errors in the surface net heat flux, with too little heat entering the subtropical/tropical oceans and too much heat loss in the midlatitudes oceans. Examination of related quantities indicates that the tropical climate biases are coupled to shortcomings in the convective cloud and/or boundary layer parameterizations which leads to the premature release of moist instability from the boundary layer in regions just outside the deep convective zones. This leads to enhanced climatological cloudiness, rainfall, and surface evaporation, as well as to a reduction in the surface shortwave flux and outgoing longwave radiation (OLR), in the subtropical regions. Furthermore, because of this early release of the moist static energy, there is a reduction in clouds, rainfall and water vapor content, as well as enhanced surface shortwave flux and outgoing longwave radiation, in the deep convective zones. The reduction in rainfall and enhanced OLR reduces the strength of the tropical large-scale circulation, which in turn reduces the strength of the subsidence in the subtropical regions which normally acts to suppress the convection processes in these regions. The implications of these results are discussed in terms of the relationship among the forecast model climatological surface fluxes, convection, clouds, and the dynamical processes, as well as their similarities to other climate models and their possible impact on the simulation of transient systems."
"53664297000;8397494800;7005664339;18635208300;9434771700;24483178600;7006130951;25629055800;","Quantifying CanESM5 and EAMv1 sensitivities to Mt. Pinatubo volcanic forcing for the CMIP6 historical experiment",2020,"10.5194/gmd-13-4831-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092667826&doi=10.5194%2fgmd-13-4831-2020&partnerID=40&md5=bb5b26bfeb0ecf9a7d52454cd23366dc","Large volcanic eruptions reaching the stratosphere have caused marked perturbations to the global climate including cooling at the Earth's surface, changes in large-scale circulation and precipitation patterns and marked temporary reductions in global ocean heat content. Many studies have investigated these effects using climate models; however, uncertainties remain in the modelled response to these eruptions. This is due in part to the diversity of forcing datasets that are used to prescribe the distribution of stratospheric aerosols resulting from these volcanic eruptions, as well as uncertainties in optical property derivations from these datasets. To improve this situation for the sixth phase of the Coupled Model Intercomparison Project (CMIP6), a two-step process was undertaken. First, a combined stratospheric aerosol dataset, the Global Space-based Stratospheric Aerosol Climatology (GloSSAC; 1979-2016), was constructed. Next, GloSSAC, along with information from ice cores and Sun photometers, was used to generate aerosol distributions, characteristics and optical properties to construct a more consistent stratospheric aerosol forcing dataset for models participating in CMIP6. This “version 3” of the stratospheric aerosol forcing has been endorsed for use in all contributing CMIP6 simulations. Recent updates to the underlying GloSSAC from version 1 to version 1.1 affected the 1991-1994 period and necessitated an update to the stratospheric aerosol forcing from version 3 to version 4. As version 3 remains the official CMIP6 input, quantification of the impact on radiative forcing and climate is both relevant and timely for interpreting results from experiments such as the CMIP6 historical simulations. This study uses two models, the Canadian Earth System Model version 5 (CanESM5) and the Energy Exascale Earth System Model (E3SM) Atmosphere Model version 1 (EAMv1), to estimate the difference in instantaneous radiative forcing in simulated post-Pinatubo climate response when using version 4 instead of version 3. Differences in temperature, precipitation and radiative forcings are generally found to be small compared to internal variability. An exception to this is differences in monthly temperature anomalies near 24 km altitude in the tropics, which can be as large as 3 ◦C following the eruption of Mt. Pinatubo. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License."
"57194201247;7004479957;6701346974;","The Role of Multiscale Interaction in Tropical Cyclogenesis and Its Predictability in Near-Global Aquaplanet Cloud-Resolving Simulations",2020,"10.1175/JAS-D-20-0021.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089404752&doi=10.1175%2fJAS-D-20-0021.1&partnerID=40&md5=f71f85b7141a1a8b29b61c59c2265531","Tropical cyclogenesis (TCG) is a multiscale process that involves interactions between large-scale circulation and small-scale convection. A near-global aquaplanet cloud-resolving model (NGAqua) with 4-km horizontal grid spacing that produces tropical cyclones (TCs) is used to investigate TCG and its predictability. This study analyzes an ensemble of three 20-day NGAqua simulations, with initial white-noise perturbations of low-level humidity. TCs develop spontaneously from the northern edge of the intertropical convergence zone (ITCZ), where large-scale flows and tropical convection provide necessary conditions for barotropic instability. Zonal bands of positive low-level absolute vorticity organize into cyclonic vortices, some of which develop into TCs. A new algorithm is developed to track the cyclonic vortices. A vortex-following framework analysis of the low-level vorticity budget shows that vertical stretching of absolute vorticity due to convective heating contributes positively to the vorticity spinup of the TCs. A case study and composite analyses suggest that sufficient humidity is key for convective development. TCG in these three NGAqua simulations undergoes the same series of interactions. The locations of cyclonic vortices are broadly predetermined by planetary-scale circulation and humidity patterns associated with ITCZ breakdown, which are predictable up to 10 days. Whether and when the cyclonic vortices become TCs depend on the somewhat more random feedback between convection and vorticity. © 2020 American Meteorological Society."
"7410069943;22982141200;55220443400;","Distinctive spring shortwave cloud radiative effect and its inter-annual variation over southeastern China",2020,"10.1002/asl.970","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083253005&doi=10.1002%2fasl.970&partnerID=40&md5=866b158957de773408245c522e028ace","The shortwave cloud radiative effect (SWCRE) plays a critical role in the earth's radiation balance, and its global mean magnitude is much larger than the warming effect induced by greenhouse gases. This study investigates the SWCRE at the top of the atmosphere and its inter-annual variation over southeastern China (SEC) using satellite retrievals and ERA-Interim reanalysis data. The results show that in this region the largest SWCRE with the maximum intensity up to −120 W·m−2 occurs in spring and is also the strongest between 60°S and 60°N. The domain-averaged intensity of SWCRE is much larger than the longwave cloud radiative effect (LWCRE), suggesting the dominant cooling role of SWCRE in the regional atmosphere–surface system. The spring SWCRE over SEC shows a weak increasing trend and its anomalies in most years exceed those of LWCRE during 2000–2017. This means that SWCRE also plays a dominant role in the inter-annual variation of regional cloud radiative effects. Over SEC, low- to mid-level ascending motion and water vapor convergence during spring favor the generation and maintenance of cloud water, leading to strong SWCRE. Statistical analysis shows that the spatial pattern and intensity of the spring SWCRE are well correlated with the low- to mid-level ascending motion and water vapor convergence. The temporal correlation coefficient between domain-averaged spring SWCRE and 850–500-hPa vertical velocity is.76 during 2000–2017. The long-term variation in spring SWCRE over SEC can be inferred to some extent from regional ascending motion and associated large-scale circulations. © 2020 The Authors. Atmospheric Science Letters published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"57203874129;13403622000;57200612374;56905280300;14020798200;","Importance of orography for Greenland cloud and melt response to atmospheric blocking",2020,"10.1175/JCLI-D-19-0527.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85090192254&doi=10.1175%2fJCLI-D-19-0527.1&partnerID=40&md5=c1c8f4bfa592eae03fa91579b1f347cf","More frequent high pressure conditions associated with atmospheric blocking episodes over Greenland in recent decades have been suggested to enhance melt through large-scale subsidence and cloud dissipation, which allows more solar radiation to reach the ice sheet surface. Here we investigate mechanisms linking high pressure circulation anomalies to Greenland cloud changes and resulting cloud radiative effects, with a focus on the previously neglected role of topography. Using reanalysis and satellite data in addition to a regional climate model, we show that anticyclonic circulation anomalies over Greenland during recent extreme blocking summers produce cloud changes dependent on orographic lift and descent. The resulting increased cloud cover over northern Greenland promotes surface longwave warming, while reduced cloud cover in southern and marginal Greenland favors surface shortwave warming. Comparison with an idealized model simulation with flattened topography reveals that orographic effects were necessary to produce area-averaged decreasing cloud cover since the mid-1990s and the extreme melt observed in the summer of 2012. This demonstrates a key role for Greenland topography in mediating the cloud and melt response to large-scale circulation variability. These results suggest that future melt will depend on the pattern of circulation anomalies as well as the shape of the Greenland Ice Sheet. © 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"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"
"37107744600;7202208382;6701835010;","Multiple-Instance Superparameterization: 1. Concept, and Predictability of Precipitation",2019,"10.1029/2019MS001610","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075449868&doi=10.1029%2f2019MS001610&partnerID=40&md5=d49e988eaf316361b578c985d60121bc","We have investigated the predictability of precipitation using a new configuration of the superparameterized Community Atmosphere Model (SP-CAM). The new configuration, called the multiple-instance SP-CAM, or MP-CAM, uses the average heating and drying rates from 10 independent two-dimensional cloud-permitting models (CPMs) in each grid column of the global model, instead of a single CPM. The 10 CPMs start from slightly different initial conditions and simulate alternative realizations of the convective cloud systems. By analyzing the ensemble of possible realizations, we can study the predictability of the cloud systems and identify the weather regimes and physical mechanisms associated with chaotic convection. We explore alternative methods for quantifying the predictability of precipitation. Our results show that unpredictable precipitation occurs when the simulated atmospheric state is close to critical points as defined by Peters and Neelin (2006, https://doi.org/10.1038/nphys314). The predictability of precipitation is also influenced by the convective available potential energy and the degree of mesoscale organization. It is strongly controlled by the large-scale circulation. A companion paper compares the global atmospheric circulations simulated by SP-CAM and MP-CAM. ©2019. The Authors."
"35221494300;","Warm conveyor belts and their role for cloud radiative forcing in the extratropical storm tracks",2019,"10.1175/JCLI-D-18-0802.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074659723&doi=10.1175%2fJCLI-D-18-0802.1&partnerID=40&md5=2d590a251e0babc3a0b7b57e6cd64466","The link between cloud radiative forcing (CRF) and warm conveyor belts (WCBs), which are strongly ascending airstreams in extratropical cyclones, is investigated based on ERA-Interim reanalysis from 1979 to 2011. Clouds associated with WCBs can be liquid, mixed phase, or ice clouds. They interact with the longwave and shortwave radiation in different ways and thus strongly influence Earth's radiative budget in the extratropical storm tracks in a complex way. In this study, WCBs are identified with a Lagrangian method, where WCBs are represented by trajectories that rise at least 600 hPa in 48 h in the vicinity of an extratropical cyclone, and CRF is traced along all WCB trajectories during the considered 30-yr period. The results show that due to the poleward ascent of WCBs, they exhibit negative net cloud forcing (NetCRF) in the southern part of the associated cloud band, whereas in their northern part, NetCRF gets positive due to the lack of sunlight in the winter months. This nonuniform CRF along WCBs from low to high latitudes increases the meridional NetCRF gradient. Furthermore, in their outflow regions in the North Atlantic, where WCBs are mainly associated with ice clouds, WCBs contribute up to 10 W m22 to the global climatological NetCRF maximum in winter. The results highlight the importance of WCBs in modulating the radiative budget in the extratropics. Furthermore, the results emphasize the need for a correct representation of WCBs in climate models to correctly simulate the cloud-circulation coupling. © 2019 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (http://www.ametsoc.org/PUBSReuseLicenses)."
"54391390300;7102567936;7005702722;55469523400;56919125400;","A Moist Entropy Budget View of the South Asian Summer Monsoon Onset",2019,"10.1029/2019GL082089","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064608587&doi=10.1029%2f2019GL082089&partnerID=40&md5=5fc2cb17267a2e2cc35cc6aa9396b264","Using a high-resolution global model with explicit representation of convection, the physical processes involved in the abrupt onset of South Asian summer monsoon are investigated within a moist entropy budget framework. The monsoon onset is a two-stage transition. During the first stage, which starts around 2 months before onset, the source terms of column-integrated moist entropy gradually increase, while the export by the large-scale circulation slowly strengthens. The second stage is marked by a sudden increase of radiative heating and surface latent heat flux 10 days prior to the onset, followed by abrupt strengthening of large-scale export of moist entropy. When either cloud-radiative or wind-evaporation feedback is disabled in numerical experiments, the monsoon experiences much smoother and weaker onset. The evolution of the system in a gross moist stability plane demonstrates that these positive feedbacks destabilize the system and are responsible for the abruptness of the transition. ©2019. American Geophysical Union. All Rights Reserved."
"7202304406;8060634600;15050523700;15047538100;7103352790;","On unravelling mechanism of interplay between cloud and large scale circulation: a grey area in climate science",2019,"10.1007/s00382-018-4211-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045469032&doi=10.1007%2fs00382-018-4211-6&partnerID=40&md5=29cac1aaf54a046daf4a64ba8b9515bd","The interaction between cloud and large scale circulation is much less explored area in climate science. Unfolding the mechanism of coupling between these two parameters is imperative for improved simulation of Indian summer monsoon (ISM) and to reduce imprecision in climate sensitivity of global climate model. This work has made an effort to explore this mechanism with CFSv2 climate model experiments whose cloud has been modified by changing the critical relative humidity (CRH) profile of model during ISM. Study reveals that the variable CRH in CFSv2 has improved the nonlinear interactions between high and low frequency oscillations in wind field (revealed as internal dynamics of monsoon) and modulates realistically the spatial distribution of interactions over Indian landmass during the contrasting monsoon season compared to the existing CRH profile of CFSv2. The lower tropospheric wind error energy in the variable CRH simulation of CFSv2 appears to be minimum due to the reduced nonlinear convergence of error to the planetary scale range from long and synoptic scales (another facet of internal dynamics) compared to as observed from other CRH experiments in normal and deficient monsoons. Hence, the interplay between cloud and large scale circulation through CRH may be manifested as a change in internal dynamics of ISM revealed from scale interactive quasi-linear and nonlinear kinetic energy exchanges in frequency as well as in wavenumber domain during the monsoon period that eventually modify the internal variance of CFSv2 model. Conversely, the reduced wind bias and proper modulation of spatial distribution of scale interaction between the synoptic and low frequency oscillations improve the eastward and northward extent of water vapour flux over Indian landmass that in turn give feedback to the realistic simulation of cloud condensates attributing improved ISM rainfall in CFSv2. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature."
"55716092000;55713076400;57195559046;57212168155;57212168177;","Role of coastal convection to moisture buildup during the South China sea summer monsoon onset",2019,"10.2151/jmsj.2019-065","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076096569&doi=10.2151%2fjmsj.2019-065&partnerID=40&md5=baaae357e197559b3ecf82112e33ed42","In this study, the climatological characteristics of object-based precipitation systems (OPSs) and moisture development are analyzed over the South China Sea (SCS) during the sharp transition of the summer monsoon onset. The satellite-observed statistics of the OPSs showed that over the 20-day pre-onset period, OPSs of small (< 100 km) to medium size (100 – 300 km) are active over the lands surrounding the SCS. The pre-onset composite mean shows a basin-scale (~ 1000 km) local circulation with anomalous subsidence over the ocean, and ocean convection is mostly suppressed. Over the 20-day post-onset period, large (> 300 km) OPSs develop over the coastal ocean and contribute to over 60 % of the total precipitation. The number of large OPSs observed significantly increases along with the sharp moisture buildup within 10 days after the onset. The moisture budget suggests that the local contribution from convective vertical mixing is the major moisture source during the first pentad after the onset. The relationship between moisture buildup and convection organization is then examined using a set of idealized cloud-resolving model (CRM) experiments, with a land–ocean configuration approximating the SCS basin. The CRM appropriately represents the observed development of coastal convection. In the noshear environment, a strong basin-scale circulation is formed, which suppresses the ocean moisture development. When large-scale vertical wind shear is imposed to represent the changes of large-scale circulation during the onset pentad, organized convection systems are increased over the coastal ocean and propagate toward the open ocean, accompanied by fast ocean moistening within 5 – 10 days. © The Author(s) 2019."
"57203225639;6603236154;7005446873;6507112497;","The implications of an idealized large-scale circulation for mechanical work done by tropical convection",2018,"10.1175/JAS-D-17-0314.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050961227&doi=10.1175%2fJAS-D-17-0314.1&partnerID=40&md5=d63c9ee4a5c139d706985cad85048189","A thermodynamic analysis is presented of an overturning circulation simulated by two cloud-resolving models, coupled by a weak temperature gradient parameterization. Taken together, they represent two separated regions over different sea surface temperatures, and the coupling represents an idealized large-scale circulation such as the Walker circulation. It is demonstrated that a thermodynamic budget linking net heat input to the generation of mechanical energy can be partitioned into contributions from the large-scale interaction between the two regions, as represented by the weak temperature gradient approximation, and from convective motions in the active warm region and the suppressed cool region. Model results imply that such thermodynamic diagnostics for the aggregate system are barely affected by the strength of the coupling, even its introduction, or by the SST contrast between the regions. This indicates that the weak temperature gradient parameterization does not introduce anomalous thermodynamic behavior. We find that the vertical kinetic energy associated with the large-scale circulation is more than three orders of magnitude smaller than the typical vertical kinetic energy in each region. However, even with very weak coupling circulations, the contrast between the thermodynamic budget terms for the suppressed and active regions is strong and is relatively insensitive to the degree of the coupling. Additionally, scaling arguments are developed for the relative values of the terms in the mechanical energy budget. © 2018 American Meteorological Society."
"56293796000;36054921000;7102567936;","Coupling with ocean mixed layer leads to intraseasonal variability in tropical deep convection: Evidence from cloud-resolving simulations",2017,"10.1002/2016MS000803","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016581082&doi=10.1002%2f2016MS000803&partnerID=40&md5=a69f1e17bc11fb6fc10ac961ebacf027","The effect of coupling a slab ocean mixed layer to atmospheric convection is examined in cloud-resolving model (CRM) simulations in vertically sheared and unsheared environments without Coriolis force, with the large-scale circulation parameterized using the Weak Temperature Gradient (WTG) approximation. Surface fluxes of heat and moisture as well as radiative fluxes are fully interactive, and the vertical profile of domain-averaged horizontal wind is strongly relaxed toward specified profiles with vertical shear that varies from one simulation to the next. Vertical wind shear is found to play a critical role in the simulated behavior. There exists a threshold value of the shear strength above which the coupled system develops regular oscillations between deep convection and dry nonprecipitating states, similar to those found earlier in a much more idealized model which did not consider wind shear. The threshold value of the vertical shear found here varies with the depth of the ocean mixed layer. The time scale of the spontaneously generated oscillations also varies with mixed layer depth, from 10 days with a 1 m deep mixed layer to 50 days with a 10 m deep mixed layer. The results suggest the importance of the interplay between convection organized by vertical wind shear, radiative feedbacks, large-scale dynamics, and ocean mixed layer heat storage in real intraseasonal oscillations. © 2017. The Authors."
"13403754000;7006614696;7007021059;7004379124;","Analysis of cloud properties associated with tropical convection in climate models and satellite data",2012,"10.2151/jmsj.2012-504","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870478967&doi=10.2151%2fjmsj.2012-504&partnerID=40&md5=573b1ea6a3eb37fd97902247ae44d23d","Cloud properties associated with tropical convection are analyzed for 11 models participating in Cloud Feedback Model Intercomparison Project Phase 1 (CFMIP1) in comparison with International Satellite Cloud Climatology Project (ISCCP) and other satellite observations and reanalysis datasets. Cloud properties are analyzed for different regimes of large-scale circulation field sorted by monthly mean of pressure coordinated vertical velocity at 500 hPa as an index of large-scale circulation. The present analysis is focused on warm oceanic regions with sea surface temperatures above 27°C where convection is active. The warm oceanic regions cover the vertical motion regimes ranging from strong ascent to weak descent. The ISCCP simulator outputs are used to evaluate cloud properties in the models. Cloud amount of optically thick high-clouds with optical thicknesses (τ) ≧ 3.6 and cloud-top pressure (CTP) ≦ 440 hPa is overestimated in the strong ascent regime while that of optically thin high-clouds with τ < 3.6 is underestimated for all the regimes. Cloud amount of optically thick low-clouds with CTP ≧ 680 hPa is overestimated in the weak vertical motion regime as well in some models. The relevance of cloud amount bias to cloud radiative effect bias is discussed. Observations show that optically thick clouds in the strong ascent regime often have tops around 180-310 hPa. In many models, the cloud top often reaches higher altitude compared to the observations. The tendency can especially be seen in the models adopting the moisture accumulation type scheme presumably due to excessively deep convection. Comparison of upward motion strength among the models and reanalyses suggests that cumulus parameterization performs better when entrainment rate is varied with large-scale environmental fields to reduce the convection deepness where necessary. © 2012, Meteorological Society of Japan."
"55738957800;6507972321;","Preliminary Evaluation of a Revised Zhang-McFarlane Convection Scheme Using the NCAR CCM3 GCM",2001,"10.1007/bf03403496","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346789671&doi=10.1007%2fbf03403496&partnerID=40&md5=fdbb67ba115374854ca1eaec89256e5f","This study investigates the interaction between convection, clouds, and the large-scale circulation. By examining the sensitivity of the large-scale fields to a modification of the convective parameterization scheme in the NCAR CCM3, we show that the convective parameterization has a strong impact on the temporal characteristics of the large-scale circulation and clouds. When Convective Available Potential Energy (CAPE) in the atmosphere is used to close the convective parameterization, the simulated convection is continuous, and lacks the observed intermittence. When the CAPE change due to the large-scale forcing in the free troposphere is used, the simulated temporal behavior of convection is in much better agreement with the observations. We attribute this improvement to the enhanced coupling between convection and the large-scale forcing in the convective parameterization."
"7005793728;7003991093;57198369060;","Cloud/climate sensitivity experiments.",1984,"10.1029/gm029p0092","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021535240&doi=10.1029%2fgm029p0092&partnerID=40&md5=c13c0528d433a07090f1028ebe44275b","A study of the relationships between large-scale cloud fields and large-scale circulation patterns is presented. The basic tool is a multi-level numerical model comprising conservation equations for temperature, water vapor and cloud water and appropriate parameterizations for evaporation, condensation, precipitation and radiative feedbacks. It is shown that cloud cover increases with decreased eddy vertical velocity, decreased horizontal advection, decreased atmospheric temperature, increased surface temperature, and decreased precipitation efficiency. -from Authors"
"57217480416;22982141200;57218489399;57218487923;55273023800;57219626063;56596869400;","Changes in cloud amount over the Tibetan Plateau and impacts of large-scale circulation",2021,"10.1016/j.atmosres.2020.105332","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85094327184&doi=10.1016%2fj.atmosres.2020.105332&partnerID=40&md5=484a410816290f836241c3f957efd3ca","Using the Clouds and Earth's Radiant Energy System (CERES) Edition 4 dataset, characteristics and variations of cloud amounts over the Tibetan Plateau (Tibet) during 2001–2019 was analyzed. Our results reveal that the mid–high cloud cover (MHCC) constitutes the major proportion and shows similar seasonal variations and annual cycle to the total cloud cover (TCC). The high cloud cover (HCC) has the greatest seasonal variation, whereas the mid–low cloud cover (MLCC) has the least variation. TCC, MHCC, and HCC exhibit the largest values in summer. The summer TCC, MHCC and MLCC exhibited decreasing trends and MHCC is more significant. The summer HCC shows increasing trend. Clouds at different heights show different correlations with skin temperature, and decreased TCC likely influences recent warming over the Tibet. The increased skin temperature is mainly adjusted by the decreased cloud amount especially MHCC. Cloud amounts are highly responsible for the precipitation, and the summer precipitation over the Tibet is mainly influenced by HCC, followed by MHCC. The decreasing TCC is related to two Rossby wave trains over Eurasia, corresponding to the Eurasian teleconnection pattern and Silk Road pattern. They induce an anomalous anti-cyclone in north Tibet and restrain ascending motions. Meanwhile, the South Asia High weakens and further enhances the sinking movements. © 2020 Elsevier B.V."
"57219396406;36917387900;57219386712;57219379866;","Vegetation-heatwave correlations and contrasting energy exchange responses of different vegetation types to summer heatwaves in the Northern Hemisphere during the 1982–2011 period",2021,"10.1016/j.agrformet.2020.108208","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092467091&doi=10.1016%2fj.agrformet.2020.108208&partnerID=40&md5=bfdfd7123cf2faca43d763fdf980ed07","Heatwave is a serious threat to society and can lead to grave consequences. Although it is well known that persistent large-scale circulation anomalies are the key to generate heatwaves, land-atmosphere interactions have also been suggested to intensify and propagate heatwaves. Vegetation plays a vital role in land-atmosphere interactions, modulating energy and water exchange through various pathways. However, vegetation impacts on surface energy exchange during extreme events such as heatwaves, and the attribution of effects to different vegetation types, is complex and poorly understood. In this study, we found strong interannual correlations between summer heatwaves and various plant function types (PFTs), based on the Global Heatwave and Warm-spell Record (GHWR) and leaf area index (LAI) products from satellites during 1982–2011. In Central Europe and the southern and southeastern part of North America, where the land cover is dominated by grasslands, temperate deciduous forests or temperate needleleaf forests, heatwaves tend to occur more frequently in years with lower LAI. In contrast, in the northwestern and northeastern part of North America, where boreal evergreen forests dominate, higher-than-normal LAI is associated with an increase in heatwave occurrence. These findings are in general supported by composite analyses of extreme LAI years in these PFT regions and heatwave characteristics therein. We speculate that the different surface heat flux responses over different PFTs during heatwaves may explain the above relationships. Focusing on North America, and using various datasets including those generated by the Global Land Data Assimilation System (GLDAS) with three different land surface models (CLM, MOS, NOAH), three reanalysis datasets (MERRA-2, NOAA-CIRES-DOS, NCEP/NCAR), and also observations from an extensive network of flux towers, we found that when temperate and boreal evergreen forests are greener, positive sensible heat anomalies increase significantly during heatwaves. Meanwhile, over boreal evergreen forests, changes in latent heat anomalies are much smaller than the positive sensible heat anomalies, suggesting that a greener boreal evergreen forest may prolong and amplify heatwaves significantly. This generates a positive feedback mechanism that begins with higher LAI in generally warmer years in these temperature-limited regions, thus sustaining the strong positive heatwave-LAI correlation. In contrast, for temperate needleleaf forests, temperate deciduous forests and grasslands, strong positive latent heat anomalies with cloud, precipitation and evaporative cooling feedback during high-LAI years appear to suppress heatwaves regionally. Our study revealed the interannual relationships between heatwaves and vegetation as well as the underlying energy exchange processes for different vegetation types and background climate conditions, with implications for the management of forest resources in view of worsening heatwave severity under the future climate. © 2020 Elsevier B.V."
"56212055700;35621058500;57212452751;35551238800;35509639400;","Trade-wind clouds and aerosols characterized by airborne horizontal lidar measurements during the EUREC4A field campaign",2020,"10.5194/essd-12-2919-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096495077&doi=10.5194%2fessd-12-2919-2020&partnerID=40&md5=49f348d18dc11974f6cc0b9b9aea22d5","From 23 January to 13 February 2020, 20 manned research flights were conducted over the tropical Atlantic, off the coast of Barbados (13◦300 N, 58◦300 W), to characterize the trade-wind clouds generated by shallow convection. These flights were conducted as part of the international EUREC4A (Elucidating the role of cloud–circulation coupling in climate) field campaign. One of the objectives of these flights was to characterize the trade-wind cumuli at their base for a range of meteorological conditions, convective mesoscale organizations and times of the day, with the help of sidewards-staring remote sensing instruments (lidar and radar). This paper presents the datasets associated with horizontal lidar measurements. The lidar sampled clouds from a lateral window of the aircraft over a range of about 8 km, with a horizontal resolution of 15 m, over a rectangle pattern of 20 km by 130 km. The measurements made possible the characterization of the size distribution of clouds near their base and the presence of dust-like aerosols within and above the marine boundary layer. This paper presents the measurements and the different levels of data processing, ranging from the raw Level 1 data (https://doi.org/10.25326/57; Chazette et al., 2020c) to the Level 2 and Level 3 processed data that include a horizontal cloud mask (https://doi.org/10.25326/58; Chazette et al., 2020b) and aerosol extinction coefficients (https://doi.org/10.25326/59; Chazette et al., 2020a). An intermediate level, companion to Level 1 data (Level 1.5), is also available for calibrated and geolocalized data (https://doi.org/10.25326/57; Chazette et al., 2020c). © Author(s) 2020. This work is distributed under"
"22998388600;55511251500;24173639400;57217686030;7402330357;55636235500;","Signatures of monsoon intra-seasonal oscillation and stratiform process in rain isotope variability in northern Bay of Bengal and their simulation by isotope enabled general circulation model",2020,"10.1007/s00382-020-05344-w","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087495608&doi=10.1007%2fs00382-020-05344-w&partnerID=40&md5=e00bd7360ece4e0125379de29654537e","Monsoon intra-seasonal oscillation (MISO) represents a quasi-periodic occurrence of rainfall spells over India during summer monsoon (June–September) associated with large-scale circulation and convection. The connection of MISO with the hydrological cycle has been explored in this study through stable oxygen (δ18O) and hydrogen isotope ratios (δD) in rainwater samples collected from two stations located near the north coast of the Bay of Bengal during 2004–2014. The δ18O and δD values of the samples (total 202) have wide ranges: − 18.2 to 2.8‰ and − 132 to 28‰ (rel. to VSMOW) respectively. Based on northward propagation of negative anomaly in Outgoing Longwave Radiation, 16 convective MISO phases were identified during this period. Out of 69 samples associated with these MISO phases, 46 samples have isotope ratios depleted in heavier isotopes. These ratios are well correlated (R = 0.81) with the MISO propagation speed and enhanced rainfall (R = − 0.71) over the Bay of Bengal. In addition, the isotope ratios also show a significant anti-correlation (R = − 0.94) with satellite-derived stratiform rain fraction. The observed isotopic ratios were compared with the results obtained from an Isotope Enabled Global Spectral Model (IsoGSM). The model simulation reproduces the amplitude of variation in the observed values reasonably well, but on average, the model values are higher in δ18O and δD by about 2‰ and 11‰ respectively. In contrast, the model d-excess values are much lower (by 4.5‰ on average). We speculate that the discrepancies in δ18O, δD and d-excess may arise due to an overestimation of raindrop evaporation effect in the model. Our study thus identifies two major physical processes controlling rain isotope variability in northern Bay of Bengal, namely, the effect of MISO propagation characteristics in inducing isotope depletion through rain out over the ocean and contribution from the stratiform rains. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature."
"57193212469;7402333662;6506476612;","Realistic Simulation of Tropical Atmospheric Gravity Waves Using Radar-Observed Precipitation Rate and Echo Top Height",2020,"10.1029/2019MS001949","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089853984&doi=10.1029%2f2019MS001949&partnerID=40&md5=69427ec5d259e1adad5920c354c4d347","Gravity waves (GWs) generated by tropical convection are important for the simulation of large-scale atmospheric circulations, for example, the quasi-biennial oscillation (QBO), and small-scale phenomena like clear-air turbulence. However, the simulation of these waves still poses a challenge due to the inaccurate representation of convection, and the high computational costs of global, cloud-resolving models. Methods combining models with observations are needed to gain the necessary knowledge on GW generation, propagation, and dissipation so that we may encode this knowledge into fast parameterized physics for global weather and climate simulation or turbulence forecasting. We present a new method suitable for rapid simulation of realistic convective GWs. Here, we associate the profile of latent heating with two parameters: precipitation rate and cloud top height. Full-physics cloud-resolving WRF simulations are used to develop a lookup table for converting instantaneous radar precipitation rates and echo top measurements into a high-resolution, time-dependent latent heating field. The heating field from these simulations is then used to force an idealized dry version of the WRF model. We validate the method by comparing simulated precipitation rates and cloud tops with scanning radar observations and by comparing the GW field in the idealized simulations to satellite measurements. Our results suggest that including variable cloud top height in the derivation of the latent heating profiles leads to better representation of the GWs compared to using only the precipitation rate. The improvement is especially noticeable with respect to wave amplitudes. This improved representation also affects the forcing of GWs on large-scale circulation. © 2020. The Authors."
"25924727700;","A New Lens for Evaluating Dynamic Controls on Shallow Convection",2020,"10.1029/2020MS002249","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089838537&doi=10.1029%2f2020MS002249&partnerID=40&md5=819a1a9cac5698780f2461da4851faab","Rising temperatures and changing dynamics can both moisten the air, making it difficult to disentangle these interrelated drivers of water cycle change. However, work by Camille Risi and colleagues presents a new way to distinguish their effects. Using large-eddy simulations with water isotopic tracers, they show that while warming the sea surface increases the ratio of isotopically heavy-to-light water in the tropical marine subcloud layer, strengthening the moisture flux convergence decreases it. This divergent response provides a new framework for examining the complex mechanisms that regulate the development of convection and, ultimately, cloudiness—a target of the 2020 international field campaign EUREC4A (ElUcidating the RolE of Clouds-Circulation Coupling in ClimAte). Moreover, their findings provide a clearer picture of why water isotopes recorded in tropical paleoproxies are a valuable lens through which to view changes in moisture transport in the past. © 2020. The Authors."
"57201698175;8953662800;57218290237;57218291394;25823927100;","Elucidating the life cycle of warm-season mesoscale convective systems in Eastern China from the Himawari-8 geostationary satellite",2020,"10.3390/rs12142307","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088646729&doi=10.3390%2frs12142307&partnerID=40&md5=5bdc1b3cd97a548bca9f073d29e43a3e","The life cycle of mesoscale convective systems (MCSs) in eastern China is yet to be fully understood, mainly due to the lack of observations of high spatio-temporal resolution and objective methods. Here, we quantitatively analyze the properties of warm-season (from April to September of 2016) MCSs during their lifetimes using the Himawari-8 geostationary satellite, combined with ground-based radars and gauge measurements. Generally, the occurrence of satellite derived MCSs has a noon peak over the land and an early morning peak over the ocean, which is several hours earlier than the precipitation peak. The developing and dissipative stages are significantly longer as total durations of MCSs increase. Aided by three-dimensional radar mosaics, we find the fraction of convective cores over northern China is much lower when compared with those in central United States, indicating that the precipitation produced by broad stratiform clouds may be more important for northern China. When there exists a large amount of stratiform precipitation, it releases a large amount of latent heat and promotes the large-scale circulations, which favors the maintenance of MCSs. These findings provide quantitative results about the life cycle of warm-season MCSs in eastern China based on multiple data sources and large numbers of samples. © 2020 by the authors."
"56893768100;56520921400;51864663400;57136738600;15848674200;","Microphysical Sensitivity of Superparameterized Precipitation Extremes in the Contiguous United States Due to Feedbacks on Large-Scale Circulation",2020,"10.1029/2019EA000731","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088580560&doi=10.1029%2f2019EA000731&partnerID=40&md5=3510fdbd18c5ba331e9bc4fec23137e7","Superparameterized (SP) global climate models have been shown to better simulate various features of precipitation relative to conventional models, including its diurnal cycle as well as its extremes. While various studies have focused on the effect of differing microphysics parameterizations on precipitation within limited-area cloud-resolving models, we examine here the effect on contiguous U.S. (CONUS) extremes in a global SP model. We vary the number of predicted moments for hydrometeor distributions, the character of the rimed ice species, and the representation of raindrop self-collection and breakup. Using a likelihood ratio test and accounting for the effects of multiple hypothesis testing, we find that there are some regional differences, particularly during spring and summer in the Southwest and the Midwest, in both the current climate and a warmer climate with uniformly increased sea surface temperatures. These differences are most statistically significant and widespread when the number of moments is changed. To determine whether these results are due to (fast) local effects of the different microphysics or the (slower) ensuing feedback on the large-scale atmospheric circulation, we run a series of short, 5-day simulations initialized from reanalysis data. We find that the differences largely disappear in these runs and therefore infer that the different parameterizations impact precipitation extremes indirectly via the large-scale circulation. Finally, we compare the present-day results with hourly rain gauge data and find that SP underestimates extremes relative to observations regardless of which microphysics scheme is used given a fixed model configuration and resolution. ©2020. The Authors."
"56539575600;56669652300;56681868600;57211681734;56510058800;8573340700;","Microphysics and dynamics of snowfall associated with a warm conveyor belt over Korea",2020,"10.5194/acp-20-7373-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087937887&doi=10.5194%2facp-20-7373-2020&partnerID=40&md5=5206f5ec1107a81953964e0fa54b7312","On 28 February 2018, 57span classCombining double low line""inline-formula""mm/span of precipitation associated with a warm conveyor belt (WCB) fell within 21span classCombining double low line""inline-formula""h/span over South Korea. To investigate how the large-scale circulation influenced the microphysics of this intense precipitation event, we used radar measurements, snowflake photographs and radiosounding data from the International Collaborative Experiments for Pyeongchang 2018 Olympic and Paralympic Winter Games (ICE-POP 2018). The WCB was identified with trajectories computed with analysis wind fields from the Integrated Forecast System global atmospheric model. The WCB was collocated with a zone of enhanced wind speed of up to 45span classCombining double low line""inline-formula""m s-1/span at 6500span classCombining double low line""inline-formula""m/spana.s.l., as measured by a radiosonde and a Doppler radar. Supercooled liquid water (SLW) with concentrations exceeding 0.2span classCombining double low line""inline-formula""g kg-1/span was produced during the rapid ascent within the WCB. During the most intense precipitation period, vertical profiles of polarimetric radar variables show a peak and subsequent decrease in differential reflectivity as aggregation starts. Below the peak in differential reflectivity, the specific differential phase shift continues to increase, indicating early riming of oblate crystals and secondary ice generation. We hypothesise that the SLW produced in the WCB led to intense riming. Moreover, embedded updraughts in the WCB and turbulence at its lower boundary enhanced aggregation by increasing the probability of collisions between particles. This suggests that both aggregation and riming occurred prominently in this WCB. This case study shows how the large-scale atmospheric flow of a WCB provides ideal conditions for rapid precipitation growth involving SLW production, riming and aggregation. Future microphysical studies should also investigate the synoptic conditions to understand how observed processes in clouds are related to large-scale circulation. © 2020 Copernicus GmbH. All rights reserved."
"57197867114;24450860900;","Linking large-scale circulation patterns to low-cloud properties",2020,"10.5194/acp-20-7125-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086723013&doi=10.5194%2facp-20-7125-2020&partnerID=40&md5=fb995243ca9423be7244438cf5e1f936","The North Pacific High (NPH) is a fundamental meteorological feature present during the boreal warm season. Marine boundary layer (MBL) clouds, which are persistent in this oceanic region, are influenced directly by the NPH. In this study, we combine 11 years of reanalysis and an unsupervised machine learning technique to examine the gamut of 850 hPa synoptic-scale circulation patterns. This approach reveals two distinguishable regimes-a dominant NPH setup and a land-falling cyclone-and in between a spectrum of large-scale patterns. We then use satellite retrievals to elucidate for the first time the explicit dependence of MBL cloud properties (namely cloud droplet number concentration, liquid water path, and shortwave cloud radiative effect-CRESW) on 850 hPa circulation patterns over the northeast Pacific Ocean. We find that CRESW spans from-146.8 to-115.5Wm-2, indicating that the range of observed MBL cloud properties must be accounted for in global and regional climate models. Our results demonstrate the value of combining reanalysis and satellite retrievals to help clarify the relationship between synoptic-scale dynamics and cloud physics. © 2020 Author(s)."
"57218768332;57218768257;55651471000;","A basic effect of cloud radiative effects on tropical sea surface temperature variability",2020,"10.1175/JCLI-D-19-0298.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85090235155&doi=10.1175%2fJCLI-D-19-0298.1&partnerID=40&md5=961a86cf43e672ed9deaccdc0a7d9654","Cloud radiative effects (CREs) are known to play a central role in governing the long-term mean distribution of sea surface temperatures (SSTs). Very recent work suggests that CREs may also play a role in governing the variability of SSTs in the context of El Niño-Southern Oscillation. Here, the authors exploit numerical simulations in the Max Planck Institute Earth System Model with two different representations of CREs to demonstrate that coupling between CREs and the atmospheric circulation has a much more general and widespread effect on tropical climate than that indicated in previous work. The results reveal that coupling between CREs and the atmospheric circulation leads to robust increases in SST variability on time scales longer than a month throughout the tropical oceans. Remarkably, cloud-circulation coupling leads to more than a doubling of the amplitude of decadal-scale variability in tropical-mean SSTs. It is argued that the increases in tropical SST variance derive primarily from the coupling between SSTs and shortwave CREs: Coupling increases the memory in shortwave CREs on hourly and daily time scales and thus reddens the spectrum of shortwave CREs and increases their variance on time scales spanning weeks to decades. Coupling between SSTs and CREs does not noticeably affect the variance of SSTs in the extratropics, where the effects from variability in CREs on the surface energy budget are much smaller than the effects from the turbulent heat fluxes. The results indicate a basic but critical role of CREs in climate variability throughout the tropics. © 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"56567409000;35509639400;7201504886;","Estimating the Shallow Convective Mass Flux from the Subcloud-Layer Mass Budget",2020,"10.1175/JAS-D-19-0135.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85090074290&doi=10.1175%2fJAS-D-19-0135.1&partnerID=40&md5=8ef1c9000a67dda823c2e60331f8f7d1","This paper develops a method to estimate the shallow-convective mass flux M at the top of the subcloud layer as a residual of the subcloud-layer mass budget. The ability of the mass-budget estimate to reproduce the mass flux diagnosed directly from the cloud-core area fraction and vertical velocity is tested using real-case large-eddy simulations over the tropical Atlantic. We find that M reproduces well the magnitude, diurnal cycle, and day-to-day variability of the core-sampled mass flux, with an average root-mean-square error of less than 30% of the mean. The average M across the four winter days analyzed is 12 mm s21, where the entrainment rate E contributes on average 14 mm s21 and the large-scale vertical velocity W contributes 22 mm s21. We find that day-to-day variations in M are mostly explained by variations in W, whereas E is very similar among the different days analyzed. Instead E exhibits a pronounced diurnal cycle, with a minimum of about 10 mm s21 around sunset and a maximum of about 18 mm s21 around sunrise. Application of the method to dropsonde data from an airborne field campaign in August 2016 yields the first measurements of the mass flux derived from the mass budget, and supports the result that the variability in M is mostly due to the variability in W. Our analyses thus suggest a strong coupling between the day-to-day variability in shallow convective mixing (as measured by M) and the large-scale circulation (as measured by W). Application of the method to the EUREC4A field campaign will help evaluate this coupling, and assess its implications for cloud-base cloudiness. Ó 2020 American Meteorological Society."
"57208782662;28367935500;6602999057;","The role of observed cloud-radiative anomalies for the dynamics of the North Atlantic Oscillation on synoptic time-scales",2020,"10.1002/qj.3768","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081667767&doi=10.1002%2fqj.3768&partnerID=40&md5=dafdded94bb8b043278869426344eee2","Clouds shape weather and climate by regulating the latent and radiative heating in the atmosphere. Recent work has demonstrated the importance of cloud-radiative effects (CRE) for the mean circulation of the extratropical atmosphere and its response to global warming. In contrast, little research has been done regarding the impact of CRE on internal variability. Here, we study how clouds and the North Atlantic Oscillation (NAO) couple on synoptic time-scales during Northern Hemisphere winter via CRE within the atmosphere (ACRE). A regression analysis based on 5-day mean data from CloudSat/CALIPSO, CERES and GERB satellite observations and ERA-Interim short-term forecast data reveals a robust dipole of high-level and low-level cloud-incidence anomalies during a positive NAO, with increased high-level cloud incidence along the storm track (near 45°N) and the subpolar Atlantic, and decreased high-level cloud incidence poleward and equatorward of this track. Opposite changes occur for low-level cloud incidence. The cloud anomalies lead to an anomalous column-mean heating from ACRE over the region of the Iceland low, and to a cooling over the region of the Azores high. To quantify the impact of the ACRE anomalies on the NAO, and to thereby test the hypothesis of a cloud-radiative feedback on the NAO persistence, we apply the surface pressure tendency equation for ERA-Interim short-term forecast data. The NAO-generated ACRE anomalies amplify the NAO-related surface pressure anomalies over the Azores high but have no area-averaged impact on the Iceland low. In contrast, diabatic processes as a whole, including latent heating and clear-sky radiation, strongly amplify the NAO-related surface pressure anomalies over both the Azores high and the Iceland low, and their impact is much more spatially coherent. This suggests that, while atmospheric cloud-radiative effects lead to an increase in NAO persistence on synoptic time-scales, their impact is relatively minor and much smaller than other diabatic processes. © 2020 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"45661599100;7402425067;55965925000;16403404400;53878006900;7401934994;","Inequal Responses of Drylands to Radiative Forcing Geoengineering Methods",2019,"10.1029/2019GL084210","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076086859&doi=10.1029%2f2019GL084210&partnerID=40&md5=7f23ced5873a6af72d0d1593009768c0","Climate geoengineering has the potential to reduce global warming. However, the nonlinear responses of Earth's large-scale circulation to climate geoengineering can exacerbate regional climate change, with potential inequality risks. We show noticeable inequality in the responses of drylands when three radiative forcing geoengineering (RFG) methodologies—cirrus cloud thinning (CCT), marine sky brightening (MSB), and stratospheric aerosol injection (SAI)—individually reduce the radiative forcing of the representative concentration pathway 8.5 scenario using a set of the Norwegian Earth system model (NorESM1-ME) experiments. In North America, CCT and SAI alleviate drylands expansion, whereas drylands expand further under MSB. CCT induces significantly wetter conditions over the western Sahel. Wetting over Australia is enhanced and prevented by MSB and SAI, respectively. Our results suggest spatially inequal distributions of benefits and harms of individual RFGs on the projected distribution of drylands, which should be considered before any real-world application of such RFGs. ©2019. The Authors."
"35758810600;54785392500;8882641700;7005702722;6603581315;","Moist Entropy and Water Isotopologues in a Zonal Overturning Circulation Framework of the Madden-Julian Oscillation",2019,"10.1029/2018JD029510","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060870908&doi=10.1029%2f2018JD029510&partnerID=40&md5=c79873c0ba575cb25c7471f159767589","The Madden-Julian oscillation (MJO) is the principal source of tropical intraseasonal variability, yet challenges remain to accurately simulate its observed convective behavior and eastward propagation. There is specific need for evaluating the role of water within the MJO, including evaporation, vertical transport, precipitation, and latent heating of the coupled atmosphere-ocean system. Hydrogen isotope ratios are particularly useful for investigating these aspects of the water cycle. This study complements previous characterization of MJO joint distributions for water vapor and isotopologue concentrations (δD) with consideration of moist entropy in the tropical zonal overturning circulation framework of the MJO. The goals are to distinguish the roles of convective and large-scale dynamic processes through the life cycle of the MJO and identify shortcomings for modeling MJO humidity, clouds, and convection. From MJO composite analyses, wet equivalent potential temperature (θ q ) anomalies are largest at 500 hPa and tilt westward with altitude. A positive θ q anomaly co-occurs with the precipitation maxima, and negative θ q anomalies co-occur with subsidence both trailing and leading the convective center. Out of phase with θ q , δD anomalies are positive east and negative west of the convective center, coherent with the regional zonal overturning stream function. These results point to a decoupling in the MJO between midtroposphere water vapor, which is tied to convective processes, and the isotopologue ratios, which are tied to the large-scale circulation. A conceptual model is presented to describe the physical processes that explain the MJO life-cycle for joint distributions of humidity (q) and water vapor δD. ©2019. American Geophysical Union. All Rights Reserved."
"56293796000;36054921000;19639722300;57198616562;","Probing the response of tropical deep convection to aerosol perturbations using idealized cloud-resolving simulations with parameterized large-scale dynamics",2019,"10.1175/JAS-D-18-0351.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075630551&doi=10.1175%2fJAS-D-18-0351.1&partnerID=40&md5=04c3ef241ca5233ab46f3e9eadeee882","A framework is introduced to investigate the indirect effect of aerosol loading on tropical deep convection using three-dimensional limited-domain idealized cloud-system-resolving model simulations coupled with large-scale dynamics over fixed sea surface temperature. The large-scale circulation is parameterized using the spectral weak temperature gradient (WTG) approximation that utilizes the dominant balance between adiabatic cooling and diabatic heating in the tropics. The aerosol loading effect is examined by varying the number of cloud condensation nuclei (CCN) available to form cloud droplets in the two-moment bulk microphysics scheme over a wide range of environments from 30 to 5000 cm23. The radiative heating is held at a constant prescribed rate in order to isolate the microphysical effects. Analyses are performed over the period after equilibrium is achieved between convection and the large-scale environment. Mean precipitation is found to decrease modestly and monotonically when the aerosol number concentration increases as convection gets weaker, despite the increase in cloud liquid water in the warm-rain region and ice crystals aloft. This reduction is traced down to the reduction in surface enthalpy fluxes as an energy source to the atmospheric column induced by the coupling of the large-scale motion, though the gross moist stability remains constant. Increasing CCN concentration leads to 1) a cooler free troposphere because of a reduction in the diabatic heating and 2) a warmer boundary layer because of suppressed evaporative cooling. This dipole temperature structure is associated with anomalously descending large-scale vertical motion above the boundary layer and ascending motion at lower levels. Sensitivity tests suggest that changes in convection and mean precipitation are unlikely to be caused by the impact of aerosols on cloud droplets and microphysical properties but rather by accounting for the feedback from convective adjustment with the large-scale dynamics. Furthermore, a simple scaling argument is derived based on the vertically integrated moist static energy budget, which enables estimation of changes in precipitation given known changes in surfaces enthalpy fluxes and the constant gross moist stability. The impact on cloud hydrometeors and microphysical properties is also examined, and it is consistent with the macrophysical picture. © 2019 American Meteorological Society."
"56567017600;56526794400;","Analysis of a Late-Autumn Rainstorm in the Sichuan Basin on the Eastern Side of the Tibetan Plateau",2019,"10.1155/2019/8797368","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85066414439&doi=10.1155%2f2019%2f8797368&partnerID=40&md5=1c27e40997c26ef0cc18e9a065c59bab","An abnormal heavy rainfall that occurred on 27 October 2014 in the Sichuan Basin (SB), China, is analyzed. An inverted trough at 850 hPa evolved into a Southwest China Vortex (SWCV), and strong upward motion caused by interaction between the low-level jet (LLJ) at 850 hPa and the upper-level jet (ULJ) at 200 hPa triggered the rainstorm process. Under a large-scale circulation system featuring a westerly trough and subtropical high, there were two cloud bands over the northeast side and south side of the Tibetan Plateau, respectively. Influenced by the eastward-moving trough, the inverted trough, LLJ, and the SWCV, a Mesoscale Convective System (MCS) was generated near the intersection of the two cloud bands, and it was the direct rainstorm system. The MCS strengthened under the situation of the 850 hPa inverted trough, but weakened when the inverted trough evolved to into the SWCV. Eventually, it formed the phenomenon known as ""existing vortex without cloud."" Through analysis of the possible reasons why precipitation strengthened (weakened) under the situation of the inverted trough (SWCV), it was found that the strengthening of precipitation was due to a strong tilting updraft in the area of the ULJ and LLJ intersection. On one hand, the upward motion was related to the vorticity advection variation with height and the low-level warm advection forcing; while on the other hand, the dew-point front near the LLJ also played a lifting role in the upward flow of the lower-layer vertical circulation. Meanwhile, the LLJ ""head"" was a high-value area of water vapor convergence, which provided sufficient water vapor for the rainstorm. During the SWCV, the weakening of precipitation was due to the SWCV weakening gradually; plus, the ULJ was interrupted over the SB, the upper airflow presented downdrafts, and its superposition with the ascending branch of low-level vertical circulation. This airflow structure inhibited the development of strong upward motion, whilst at the same time, the LLJ retreated toward the south and the dew-point front ultimately weakened and disappeared. Subsequently, water vapor convergence weakened and no longer supported the occurrence of heavy rainfall. Therefore, the strong upward motion caused by the ULJ-LLJ intersection and the lower-level dew-point front were the key reasons for the occurrence of this late-autumn rainstorm. © 2019 Yongren Chen and Yueqing Li."
"55838659500;28367935500;6603422104;7004060399;","Model uncertainty in cloud-circulation coupling, and cloud-radiative response to increasing CO2, linked to biases in climatological circulation",2018,"10.1175/JCLI-D-17-0665.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058186453&doi=10.1175%2fJCLI-D-17-0665.1&partnerID=40&md5=17a5ae6834dc10e42400c0c21d41b441","Recent analyses of global climate models suggest that uncertainty in the coupling between midlatitude clouds and the atmospheric circulation contributes to uncertainty in climate sensitivity. However, the reasons behind model differences in the cloud-circulation coupling have remained unclear. Here, we use a global climate model in an idealized aquaplanet setup to show that the Southern Hemisphere climatological circulation, which in many models is biased equatorward, contributes to the model differences in the cloud-circulation coupling. For the same poleward shift of the Hadley cell (HC) edge, models with narrower climatological HCs exhibit stronger midlatitude cloud-induced shortwave warming than models with wider climatological HCs. This cloud-induced radiative warming results predominantly from a subsidence warming that decreases cloud fraction and is stronger for narrower HCs because of a larger meridional gradient in the vertical velocity. A comparison of our aquaplanet results with comprehensive climate models suggests that about half of the model uncertainty in the midlatitude cloud-circulation coupling stems from this impact of the circulation on the large-scale temperature structure of the atmosphere, and thus could be removed by improving the climatological circulation in models. This illustrates how understanding of large-scale dynamics can help reduce uncertainty in clouds and their response to climate change. © 2018 American Meteorological Society."
"57212500706;57213455955;57190976274;35511486700;","An investigation on the dynamic and scale interactive processes for estimating the predictability of cloudburst over elevated orography",2017,"10.1007/s11069-016-2561-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84984914964&doi=10.1007%2fs11069-016-2561-0&partnerID=40&md5=e5024cec7d5c1667bfca7225413b361f","The cloudburst is defined as a heavy downpour at a very high rainfall rate over small spatio-temporal scale. The Indian states of Uttarakhand (30°15′N; 79°15′E) and Himachal Pradesh (32°29′N; 75°10′E) are prone to cloudburst due to its geographical setup. The large-scale monsoon flow along with elevated orography makes cloudburst phenomena frequent a well as severe over the regions. However, cloudburst and the heavy rainfall events occasionally, become difficult to distinguish. The present study attempts to identify the processes associated with cloudburst over elevated orography and compare it with one of the most debated event of 2013 which was reported as heavy rainfall but, not a cloudburst by Indian Meteorological Department (IMD). The temporal variations of rainfall and cloud-top pressure (CTP) are considered to identify the genesis of the event. The vertical developments of the system along with large-scale circulation pattern are estimated in the present study. The result of the study reveals that the mid-tropospheric dry entrainment, low-level temperature inversion and cloud height clearly distinguish the “cloudburst” and “heavy rainfall” events and confirms that the system of 2013 was indeed a heavy rainfall event and not a cloudburst. © 2016, Springer Science+Business Media Dordrecht."
"56818716000;7102353054;18436976900;","Simulation of monsoon precipitation over south-Asia using RegCM3",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-77952890779&partnerID=40&md5=dabd70a7a910a0ffbc2157710e4661a6","The objective of this study was to explore the capability of the regional climate model RegCM3, to predict extreme weather events in south-Asia region with particular reference to precipitation during monsoon season (July, August, September) over northern mountainous and southern plain regions of Pakistan. Different cumulus parameterization schemes in RegCM3 for prediction of convective precipitation were tested for monsoon period during the years 1998 and 2001. The model predicted results compared with the satellite pictures, CRU observational data and the surface synoptic observatories data of the Pakistan Meteorological Department (PMD). This may be mentioned here, that the year 1998 was a dry year and the starting year of a severe drought which lasted up to the year 2000. This may also be added here, that during the year 2001, the precipitation over some parts of the country exceeded the normal and some areas in the northern parts of the country observed exceptionally high rainfall rate. The results indicated that some convective parameterization schemes of RegCM3, well captured the summer monsoon precipitation over south-Asia region. However, the schemes need to be selected carefully depending upon the region of any particular focus. Some interim findings were that the Grell scheme with both closures: Arakawa-Schubert (AS) and Fritsch-Chappell (FC) satisfactorily predicted the total monthly rainfall in the northern mountainous regions of Pakistan. However, both predicted high precipitations over southern and south-eastern plain regions. Both the modified-Kuo and Betts-Miller (BM) schemes substantially under-predicted the rainfall, although the patterns were captured adequately. The modified-Kuo scheme was more close to the observed data when compared with the performance of the BM scheme It is recommended to further test the model schemes, perhaps a further improvement in the modified-Kuo scheme would yield a scheme even better than both of the Grell closures (which predicted exceptionally high precipitation over south-eastern plain regions of Pakistan and the adjoining Indian regions. In a future paper we shall be presenting more results and will try to suggest some modifications in the existing schemes to be able to better capture the summer monsoon precipitation over south-Asia. Due to their coarse resolution General Circulation Models (GCMs) often perform poorly in simulating regional processes, especially in regions with local fine-scale forcing topography (Gates, 1992, Gao et al., 2002). On the other hand, modeling studies with regional climate models also indicated that some cumulus parameterization schemes do not perform well in some specific regions of the world e.g. Asian monsoon regions (Leung et al. 2003, Lee and Suh 2000). Scale interactions are extremely complex in the Asian monsoon regions (Holland 1995), which are further complicated due to the effects of Tibetan plateau, ocean-continent contrast and sea-air interactions. These specific features require special consideration in designing regional climate models to be used in this particular region. The impacts of climate change on food and water resources of a country are linked with the regional climate rather than to the global scale. It is therefore imperative to understand and predict how global climate change is manifested at these regional scales. Using GCM output to drive limited-area atmospheric simulations on regional scales has been reported to be a promising approach for simulating regional climates (Giorgi and Mearns, 1991, 1999). The principle behind this approach is that, given a large-scale atmospheric circulation, a limited-area model with a suitably high-resolution, resolving complex topography, land-sea contrast, land use and detailed description of physical processes can generate realistic high-resolution (both spatial and temporal) information coherent with the driving large-scale circulation. The large-scale circulation can be supplied by either reanalysis data or a GCM output. A critical weakness that needs improvement in both global and regional climate models is the treatment of clouds (Giorgi and Mearns 1999). Although the detailed explicit cloud microphysics parameterization for grid resolved moist processes, is considered in some of the regional climate models, the complex interaction between sub-grid cumulus convection and grid scale moist processes is very crudely treated. Some studies have indicated the improvements in radiation budgets by using cloud microphysics information (Petch and Dudhia, 1998), but the cloud amount is treated in a quite simple way and is usually estimated by the relative humidity in most of the climate model applications (Giorgi et al. 1993, Dudek et al. 1996, Wang et al. 2000). Although some previous studies (Houghton et al., 1992) have shown the capability of regional climate models in reproducing intra-annual variability when driven by good quality driving fields, more analyses are needed to improve model performance in simulating climate variability at short timescales (days to weeks). The increased resolution of regional climate models can allow simulation of a broader spectrum of weather events to improve simulation of the daily to monthly precipitation intensity distributions. We in this work, have studied the capabilities of a regional climate model, RegCM3 (available from http://www.ictp.trieste.it/~pubregcm/RegCM3) to simulate the precipitation intensity/patterns during summer monsoon season in the Indian subcontinent. The summer monsoon systems are originated from the Bay of Bengal, Indian Ocean and some times get accentuated by the juxtaposition of passing westerly disturbances and the Arabian Sea component. We have tried to identify some suitable cumulus parameterization schemes for predicting the summer monsoon precipitation (July to September) over the regions or to access the need of further modification in the model. Different cumulus parameterization schemes in RegCM3 for prediction of convective precipitation were tested for monsoon period during the years 1998 and 2001. This would be interesting to mention here that 1998 was the starting year of a severe drought in Pakistan, which lasted up to the year 2000. Due to this drought the agricultural productivity in the country was badly affected. On the other hand, during the year 2001, the precipitation over some parts of the country exceeded the normal and some areas in the northern parts of the country observed exceptionally high rainfall rate. July 23, of the year 2001 witnessed heavy rainfall in a cloud burst fashion over some of the northern parts of Pakistan (Districts of Mansehra, Abottabad, Rawalpindi and Islamabad). This heavy precipitation exceeded the recorded maximum rainfall in Islamabad, during a single spell and caused severe economic and life loss. In this work, we have tried to explore the capabilities of RegCM3 and the effects of the use of different convective closure schemes on the intensity and spatial patterns of the precipitation during the summer monsoon months (July, August and September) of the selected years. The model was initialized using the NCEP reanalysis data having spatial resolution of 2.5° × 2.5° and temporal resolution of 6 h. The model domain was from 5N to 45N and 55E to 105E with a spatial resolution of 90 km and a 1:3 nesting was provided over a domain from 24N to 36N and 60E to 76E to focus on Pakistan. USGS Topographic data and US Department of Agriculture, land use data of 10 minutes resolution were used (see Figs. 1-2)."
"11941003100;7006565753;","Case studies of low stratus decks in the vicinity of Innsbruck",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-31344477337&partnerID=40&md5=09c62b9eb9e483ad02b95dd470cf3b77","A low stratus cloud can occur in lowlands as well as in valleys. In this work low stratus clouds in the Inn Valley are studied. In 1991 Huntrieser developed a desicion tree for forecasting the onset and dispersion of a low stratus deck('Hochnebel') at Innsbruck. Based on a limited data set, she identified three scenarios leading to such a low stratus deck. This work examines each scenario with a low stratus event correctly forecasted by Huntrieser's algorithm, a false alarm, and a missed event. Considerably more data were available for this study than for Huntrieser's work: a radiosonde at Innsbruck, automatic weather stations, ceilometers, webcams, and a simple radiative transfer model. It is found that forecasts of low stratus in the Inn Valley will be improved by taking explicitly into account the presence and temporal change of the elevated layer of high humidity, which is the required ingredient for the low stratus deck. This in turn requires the correct prediction of the evolution of the interaction of the valley wind system with the larger-scale circulation."
"7003278104;7102389501;","Analysis of ocean surface heat fluxes in a NOGAPS climate simulation: Influences from convection, clouds and dynamical processes",2000,"10.1029/1999JD901028","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046528304&doi=10.1029%2f1999JD901028&partnerID=40&md5=e684c068ba3edb34ff893cac435c2428","This study examines the simulation quality of the surface heat flux fields produced during a climate simulation of the Navy Operational Global Atmospheric Prediction System, version 3.4, with a reduced spectral truncation of T63 and 18 levels (herineafter referred to as NOGAPS-CL). Comparisons are made between a 17-year NOGAPS-CL simulation using monthly sea surface temperatures as surface boundary conditions and a number of validating data sets consisting of ship, satellite, and/or reanalysis-based surface heat fluxes, precipitation, top of the atmosphere radiation budget, water vapor, cloud frequency, surface wind stress, and tropospheric winds. In this extended, long-range integration, NOGAPS-CL underpredicts the net surface shortwave flux in much of the subtropical oceans and overpredicts the net shortwave flux in the western Pacific warm pool and the midlatitude oceans, when compared to several satellite-derived climatological data sets. In addition, NOGAPS-CL over predicts the latent heat flux in much of the subtropics and under predicts the latent heat flux over the northern ocean western boundary currents and under the storm track regions that extend eastward from them. These shortwave and evaporation biases combine to produce errors in the surface net heat flux, with too little heat entering the subtropical/tropical oceans and too much heat loss in the midlatitudes oceans. Examination of related quantities indicates that the tropical climate biases are coupled to shortcomings in the convective cloud and/or boundary layer parameterizations which leads to the premature release of moist instability from the boundary layer in regions just outside the deep convective zones. This leads to enhanced climatological cloudiness, rainfall, and surface evaporation, as well as to a reduction in the surface shortwave flux and outgoing longwave radiation (OLR), in the subtropical regions. Furthermore, because of this early release of the moist static energy, there is a reduction in clouds, rainfall and water vapor content, as well as enhanced surface shortwave flux and outgoing longwave radiation, in the deep convective zones. The reduction in rainfall and enhanced OLR reduces the strength of the tropical large-scale circulation, which in turn reduces the strength of the subsidence in the subtropical regions which normally acts to suppress the convection processes in these regions. The implications of these results are discussed in terms of the relationship among the forecast model climatological surface fluxes, convection, clouds, and the dynamical processes, as well as their similarities to other climate models and their possible impact on the simulation of transient systems. Copyright 2000 by the American Geophysical Union."
"7402933297;","Water vapor and cloud feedback mechanisms: Inferences from satellite observations and numerical modeling",1997,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030720441&partnerID=40&md5=76a604ce8b7864f98f86765c287f8307","The sensitivity of water vapor and cloud forcings to ocean temperature changes and their relationship with large scale circulation regimes (LSCR) were studied using satellite outgoing longwave radiation, sea surface temperature (SST) and LSCR data. On interannual time scales, LSCR changes contribute substantially to anomalies in the water vapor and cloud forcing observed during major climate events such as the El Nino. Experiments show that over 75% of the observed apparent sensitivity are due to changes in the LSCR, with direct radiative feedback accounting for less that 20% of the observed changes. Possible pitfalls in data interpretation are indicated when adjustments are made for changes in the LSCR since runaway greenhouse warming does not exists."
"7005247514;","The role of the subtropical gyres in the heat balance of the Warmwassersphaere",1990,"10.1016/0924-7963(90)90068-L","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025586520&doi=10.1016%2f0924-7963%2890%2990068-L&partnerID=40&md5=75636d1e800fbbf9c7a0a1a319bed569","A coupled oceanic mixed layer-atmospheric subcloud layer model is used to analyze warm water mass formation in subtropical oceans. The influence of large scale circulation is parameterized by prescribing winds and currents, radiant heat gain and loss and air temperature and humidity above cloud base. Boundary layer processes, however, are fully accounted for. The resulting heat and vapor balances reduce to a second order hyperbolic equation, which can be integrated along air- and water-side characteristics. The solution fairly rapidly approach an equilibrium state, through damped ""air-sea interaction waves"". Application of the model as a diagnostic tool to an idealized subtropical gyre leads to the conclusion that net oceanic heat gain (i.e. warm water mass formation) at a rate of the order of 30 W m-2 is possible as a consequence of cold water advection. This verifies meteorological calculations of oceanic heat gain in such oceans as the North Atlantic, where the Warmwassersphaere is flanked by cold surface waters. However, in a completely warm ocean, such as the Northern Indian Ocean, there is no realistic way to square meteorologically calculated heat gains of 60 W m-2 and more with boundary layer resistances to heat transfer. © 1990."
"57196396429;24378650300;35729333400;","Observation of mean dynamic fields from Meteosat large scale water vapor structure motions",1989,"10.1016/0273-1177(89)90147-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45249128429&doi=10.1016%2f0273-1177%2889%2990147-6&partnerID=40&md5=4654b8e88293e6dda87dd392f3ec1daf","With the objective characterizing atmospheric dynamics for particular months, structures appearing at large scales on Meteosat water vapor images are tracked with similar methods as those used for cloud tracking in other channels at smaller scales. For this purpose sampled ISCCP images at resolution 30 km with time intervals of 3 hours are used. Mean monthly ""motion fields"" are computed. These fields are very consistent with the general circulation of the upper troposphere. They are shown to represent the motions of synoptic systems rather than the wind at a particular level. Nevertheless, significant interannual variations of the large scale circulations can be observed. © 1989."
"7005922474;7401928282;7102511773;7404393921;","Observational and theoretical studies of the evolving structure of baroclinic waves.",1984,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021547960&partnerID=40&md5=26e55983010b8f44a86bcb45a330fd53","Dynamical processes involved in comma cloud formation, and passive tracer evolution in a baroclinic wave are discussed. An analytical solution was obtained demonstrating the complex nongeostrophic flow pattern involved in the redistribution of low level constituents in a finite amplitude baroclinic wave, and in the formation of the typical humidity and cloud distributions in such a wave. Conservational and theoretical studies of blocking weather patterns in middle latitude flows were studied. The differences in the energy and enstrophy cascades in blocking and nonblocking situations were shown. It was established that pronounced upscale flow of both of these quantities, from intermediate to planetary scales, occurs during blocking episodes. The upscale flux of enstrophy, in particular, suggests that the persistence of blocking periods may be due to reduced dissipation of the large scale circulation and therefore entail some above normal predictability.-from STAR, 22(24), 1984"
"7102681346;","The role of the general circulation in western Pacific tropical cyclone genesis.",1982,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020227271&partnerID=40&md5=170060d5c1f4d19a0b72d18dfe222b5e","The role that large scale circulation patterns play in tropical cyclone genesis is studied. The problem of defining the important flow features observed prior to cyclone genesis in the northwest Pacific and Australian region is addressed. A combination of case study and compositing was used to identify those weather systems which interact with a pregenesis tropical cloud cluster, enhancing its development potential.-from STAR, 20(15), 1982"
"7005793728;7003991093;57198369060;","Cloud/climate sensitivity experiments.",1982,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040844486&partnerID=40&md5=bdc7e4a8aff91d2a2bab7088e13cc4cf","A study of the relationships between large-scale cloud fields and large scale circulation patterns is presented. The basic tool is a multi-level numerical model comprising conservation equations for temperature, water vapor and cloud water and appropriate parameterizations for evaporation, condensation, precipitation and radiative feedbacks. Incorporating an equation for cloud water in a large-scale model is somewhat novel and allows the formation and advection of clouds to be treated explicitly.-from STAR, 21(11), 1983"
"7403937184;","Cumulus cloud population and its parameterization",1975,"10.1007/BF01592962","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250408610&doi=10.1007%2fBF01592962&partnerID=40&md5=ea05825ae1420d273c103a9257ef9509","The latent heat released by cumulus clouds is very important to the energies of many large-scale tropical disturbances. The number of cumulus clouds involved in these disturbances is usually very large. The collective effects of cumulus clouds must therefore be incorporated into a large-scale model in a parameterized fashion. Present parameterization schemes are briefly reviewed. Recent advances in our understanding of the control and feedback processes between cumulus clouds and the large-scale circulations are discussed. Emphasis is placed on the implications of the results of recent diagnostic studies on the future development of the theory of cumulus parameterization. © 1975 Birkhäuser Verlag."
"16528521600;","Some results of short wave insolation measurements during the IGY along the 10° E meridian and a comparison with theoretical values",1964,"10.1007/BF00879725","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250597266&doi=10.1007%2fBF00879725&partnerID=40&md5=8a25112e802039d7a3e51c13d49897f9","The observational material of 138 stations, which had during the July 1957 to December 1958 IGY period made obervations of global radiation along the longitude 10°E (±10°) between the latitudes 47°S and 70°N, had been evaluated to obtain mean monthly and annual totals of global radiation for 12 different latitudes along the a/n-meridian. The sums are compared with theoretical results obtained by Budyko, Black, and Bernhardt and Philipps. These theoretically computed values are drawn graphically or numerically from charts or tables of the a/n-authors for the coordinates corresponding to the means of the relevant IGY stations. In hardly a case the measured annual totals deviate by more than 10% from theoretical values. In hardly a case the measured annual totals deviate by more than 10% from theoretical values. The Budyko data are the nearest approximation to the measured ones;Black's computation shows the greatest deviation. In the 0 to 47° S zone theoretical values are actually exceeded by to 20%. The annual variation is marked by the following deviations as compared to the theoretical results: In the region north to 50° latitude in October, November and January only 80% of the theoretically computed amount of radiation was observed, while in the remaining months the monthly totals are within a ±10% boundary of the theoretical values; in March about 20% 'above normal' global radiation was observed. Between 30° and 50°N the measured data in autumn, winter and spring 10 to 20% below the theoretical values, in the remaining time of the year the deviation is less than ±10%. A comparison with cloud conditions (relative sunshine duration) suggests that deviations cannot be interpreted merely by deviating cloud conditions of this zone. Between 0° and 30°N only January and February are 10% below theoretical values, while in August to October the totals were 10 to 15% above. South of the equator from October to May (southern summer) the radiation totals were too high by up to 25%, while in the remaining time of the year the data were about 10% below theoretical values; it should be noted that deviation increases with increasing southern latitude. For comparison the Ashbel IGY global radiation charts were used which indicate similar deviations from theoretical values; there are also some differences to microcard values. There is reason to suggest that there is a complex relation between the observed deviations and variation of the large-scale circulation during IGY. The results of the small number of available turbidity measurements (Central European area only) can be interpreted in the same way. To what extent the observed deviations from theoretical values are due to weather conditions deviating during the IGY period from normal or originate from inconsistencies in the theoretical consideration cannot definition be said until inspection of the complete IGY cloud and turbidity data and the availability of the climatological material which served for the theoretical work. The latter was only the case in the Bernhardt and Philipps paper. © 1964 Birkhäuser Verlag."