Author(s) ID,Title,Year,DOI,Link,Abstract
"6603435063;","A comprehensive mass flux scheme for cumulus parameterization in large-scale models",1989,"10.1175/1520-0493(1989)117<1779:ACMFSF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024907516&doi=10.1175%2f1520-0493%281989%29117%3c1779%3aACMFSF%3e2.0.CO%3b2&partnerID=40&md5=0a5a2643fd8c897a45e5559e6cca9fbf","In this paper the question is addressed whether simple schemes can provide realistic values of the thermal forcing by convection under various synoptic conditions. This is done through verifying such a scheme first on data from field experiments for periods of tropical penetrative convection, tradewind cumuli and extratropical organized convection and then in a NWP model. The scheme considers a population of clouds where the cloud ensemble is described by a one-dimensional bulk model. Cumulus scale downdrafts are included. Various types of convection are represented. The closure assumptions for determining the bulk cloud mass flux are: penetrative convection and midlevel convection are maintained by large-scale moisture convergence and shallow convection by supply of moisture due to surface evaporation. The parameterization produces realistic fields of convective heating and appears to be in fair balance with real data for NWP as it does not initiate strong adjustment processes (spinup) in global forecasts. -from Author"
"7006184606;","A scheme for representing cumulus convection in large-scale models",1991,"10.1175/1520-0469(1991)048<2313:asfrcc>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026305596&doi=10.1175%2f1520-0469%281991%29048%3c2313%3aasfrcc%3e2.0.co%3b2&partnerID=40&md5=42af52240bb4a52cb23a28bf92f7f0ff","Air from the subcloud layer is lifted to each level i between cloud base and the level of neutral buoyancy for undilute air. A fraction (εi) of the condensed water is then converted to precipitation, which falls and partially or completely evaporates in an unsaturated downdraft. The remaining cloudy air is then assumed to form a uniform spectrum of mixtures with environmental air at level i; these mixtures ascend or descend according to their buoyancy. The main closure parameters in this scheme are the parcel precipitation efficiencies, εi, which determine the fraction of condensed water in a parcel lifted to level i that is converted to precipitation, and the fraction σsi of precipitation that falls through unsaturated air. One-dimensional radiative-convective equilibrium experiments with this scheme produce reasonable profiles of buoyancy and relative humidity. When large-scale descent is imposed, a trade-cumulus regime is produced, including a trade inversion and mixing-line structure in the cloud layer. -fron Author"
"7202899330;","Cloud feedbacks in the climate system: A critical review",2005,"10.1175/JCLI-3243.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14644413562&doi=10.1175%2fJCLI-3243.1&partnerID=40&md5=3790274149375e7189dcd50ae4f15bcf","This paper offers a critical review of the topic of cloud-climate feedbacks and exposes some of the underlying reasons for the inherent lack of understanding of these feedbacks and why progress might be expected on this important climate problem in the coming decade. Although many processes and related parameters come under the influence of clouds, it is argued that atmospheric processes fundamentally govern the cloud feedbacks via the relationship between the atmospheric circulations, cloudiness, and the radiative and latent heating of the atmosphere. It is also shown how perturbations to the atmospheric radiation budget that are induced by cloud changes in response to climate forcing dictate the eventual response of the global-mean hydrological cycle of the climate model to climate forcing. This suggests that cloud feedbacks are likely to control the bulk precipitation efficiency and associated responses of the planet's hydrological cycle to climate radiative forcings. The paper provides a brief overview of the effects of clouds on the radiation budget of the earth-atmosphere system and a review of cloud feedbacks as they have been defined in simple systems, one being a system in radiative-convective equilibrium (RCE) and others relating to simple feedback ideas that regulate tropical SSTs. The systems perspective is reviewed as it has served as the basis for most feedback analyses. What emerges is the importance of being clear about the definition of the system. It is shown how different assumptions about the system produce very different conclusions about the magnitude and sign of feedbacks. Much more diligence is called for in terms of defining the system and justifying assumptions. In principle, there is also neither any theoretical basis to justify the system that defines feedbacks in terms of global-time-mean changes in surface temperature nor is there any compelling empirical evidence to do so. The lack of maturity of feedback analysis methods also suggests that progress in understanding climate feedback will require development of alternative methods of analysis. It has been argued that, in view of the complex na ture of the climate system, and the cumbersome problems encountered in diagnosing feedbacks, understanding cloud feedback will be gleaned neither from observations nor proved from simple theoretical argument alone. The blueprint for progress must follow a more arduous path that requires a carefully orchestrated and systematic combination of model and observations. Models provide the tool for diagnosing processes and quantifying feedbacks while observations provide the essential test of the model's credibility in representing these processes. While GCM climate and NWP models represent the most complete description of all the interactions between the processes that presumably establish the main cloud feedbacks, the weak link in the use of these models lies in the cloud parameterization imbedded in them. Aspects of these parameterizations remain worrisome, containing levels of empiricism and assumptions that are hard to evaluate with current global observations. Clearly observationally based methods for evaluating cloud parameterizations are an important element in the road map to progress. Although progress in understanding the cloud feedback problem has been slow and confused by past analysis, there are legitimate reasons outlined in the paper that give hope for real progress in the future. © 2005 American Meteorological Society."
"7005616688;7006738371;7402288130;","Planetary radii across five orders of magnitude in mass and stellar insolation: Application to transits",2007,"10.1086/512120","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34248398073&doi=10.1086%2f512120&partnerID=40&md5=c4ce4b30407ac9a0573ace9d9b88e544","To aid in the physical interpretation of planetary radii constrained through observations of transiting planets, or eventually direct detections, we compute model radii of pure hydrogen-helium, water, rock, and iron planets, along with various mixtures. Masses ranging from 0.01 Earth masses to 10 Jupiter masses at orbital distances of 0.02-10 AU are considered. For hydrogen-helium rich planets, our models are the first to couple planetary evolution to stellar irradiation over a wide range of orbital separations (0.02-10 AU ) through a nongray radiative-convective equilibrium atmosphere model. Stellar irradiation retards the contraction of giant planets, but its effect is not a simple function of the irradiation level: a planet at 1 AU contracts as slowly as a planet at 0.1 AU. We confirm the assertion of Guillot that very old giant planets under modest stellar irradiation (like that received by Jupiter and Saturn) develop isothermal atmospheric radiative zones once the planet's intrinsic flux drops to a small fraction of the incident flux. For hydrogenhelium planets, we consider cores up to 90% of the total planet mass, comparable to those of Uranus and Neptune. If ""hot Neptunes"" have maintained their original masses and are not remnants of more massive planets, radii of ∼0.300.45 RJ are expected. Water planets are ∼40%-50% larger than rocky planets, independent of mass. Finally, we provide tables of planetary radii at various ages and compositions, and for ice-rock-iron planets we fit our results to analytic functions, which will allow for quick composition estimates, given masses and radii, or mass estimates, given only planetary radii. These results will assist in the interpretation of observations for both the current transiting planet surveys as well as upcoming space missions, including COROT and Kepler. © 2007. The American Astronomical Society. All rights reserved."
"7006380976;7102609291;6602645956;6701538799;","Inferences of predictability associated with warm season precipitation episodes",2002,"10.1175/1520-0469(2002)059<2033:IOPAWW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036647310&doi=10.1175%2f1520-0469%282002%29059%3c2033%3aIOPAWW%3e2.0.CO%3b2&partnerID=40&md5=f49067e3a9eb853d62f8965916fc81ef","Herein preliminary findings are reported from a radar-based climatology of warm season precipitation ""episodes."" Episodes are defined as time-space clusters of heavy precipitation that often result from sequences of organized convection such as squall lines, mesoscale convective systems, and mesoscale convective complexes. Episodes exhibit coherent rainfall patterns, characteristics of propagating events, under a broad range of atmospheric conditions. Such rainfall patterns are most frequent under ""weakly forced"" conditions in midsummer. The longevity of episodes, up to 60 h, suggests an intrinsic predictability of warm season rainfall that significantly exceeds the lifetime of individual convective systems. Episodes are initiated primarily in response to diurnal and semidiurnal forcings. Diurnal forcing is dominant near the Rocky and Appalachian Mountains, whereas semidiurnal forcing is dominant between these cordilleras. A most common longitude of origin is at or near the east slope of the Continental Divide (105°W). These observations are consistent with a condition of continual thermal forcing, widespread hydrodynamic instability, and the existence of other processes that routinely excite, maintain, and regenerate organized convection. The propagation speed of major episodes is often in excess of rates that are easily attributable either to the phase speeds of large-scale forcing or to advection from low- to midlevel ""steering"" winds. It is speculated that wavelike mechanisms, in the free troposphere and/or the planetary boundary layer, may contribute to the rates of motion observed. Once understood, the representation of such mechanisms in forecast models offers the opportunity for improved predictions of warm season rainfall."
"7006399110;7006630889;7202175203;","Radiative forcing of climate by changes in the vertical distribution of ozone",1990,"10.1029/JD095iD07p09971","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025691053&doi=10.1029%2fJD095iD07p09971&partnerID=40&md5=6ce782d15855fe52ad7003884ceb45e9","The method employs a parameterization based on one-dimensional radiative-convective equilibrium calculations; these calculations predict that the surface temperature should warm in response to both decreases in ozone above 30km and increases in ozone below 30km. We show that observed ozone trends, taken at face value, suggest a cooling of the surface temperature at northern mid-latitudes during the 1970s equal in magnitude to about half the warming predicted for CO2 for the same time period. However, the measurement uncertainty of the observed trends is large, with the best estimates for mid-latitude cooling being -0.05±0.05°C. The surface cooling is caused by ozone decreases in the lower stratosphere, which outweigh the warming effects of ozone increases in the troposphere. -from Authors"
"35509639400;7201504886;15026371500;7006698304;7007181954;57205867148;7103294731;56014511300;6603566335;7102567936;55686667100;7201485519;","Clouds, circulation and climate sensitivity",2015,"10.1038/ngeo2398","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926359595&doi=10.1038%2fngeo2398&partnerID=40&md5=3cc991046f3922dab00d63d9f51143a1","Fundamental puzzles of climate science remain unsolved because of our limited understanding of how clouds, circulation and climate interact. One example is our inability to provide robust assessments of future global and regional climate changes. However, ongoing advances in our capacity to observe, simulate and conceptualize the climate system now make it possible to fill gaps in our knowledge. We argue that progress can be accelerated by focusing research on a handful of important scientific questions that have become tractable as a result of recent advances. We propose four such questions below; they involve understanding the role of cloud feedbacks and convective organization in climate, and the factors that control the position, the strength and the variability of the tropical rain belts and the extratropical storm tracks."
"7403672902;7407016988;","Organizational modes of midlatitude mesoscale convective systems",2000,"10.1175/1520-0493(2001)129<3413:OMOMMC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033662723&doi=10.1175%2f1520-0493%282001%29129%3c3413%3aOMOMMC%3e2.0.CO%3b2&partnerID=40&md5=8aacc6b1e6332439566487b25c46597e","This paper discusses common modes of mesoscale convective organization. Using 2-km national composite reflectivity data, the authors investigated linear mesoscale convective systems (MCSs) that occurred in the central United States during May 1996 and May 1997. Based upon the radar-observed characteristics of 88 linear MCSs, the authors propose a new taxonomy comprising convective lines with trailing (TS), leading (LS), and parallel (PS) stratiform precipitation. While the TS archetype was found to be the dominant mode of linear MCS organization, the LS and PS archetypes composed nearly 40% of the studied population. In this paper, the authors document the characteristics of each linear MCS class and use operational surface and upper air data to describe their different environments. In particular, wind profiler data reveal that the stratiform precipitation arrangement associated with each class was roughly consistent with the advection of hydrometeors implied by the mean middle- and upper-tropospheric storm-relative winds, which were significantly different among the three MCS modes. Case study examples are presented for both the LS and PS classes, which have received relatively little attention to this point. As well, the authors give a general overview of the synoptic-scale meteorology accompanying linear MCSs in this study, which was generally similar to that observed by previous investigators."
"7102696626;7003314664;","The Maritime Continent and its role in the global climate: A GCM study",2003,"10.1175/1520-0442(2003)016<0834:TMCAIR>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038288165&doi=10.1175%2f1520-0442%282003%29016%3c0834%3aTMCAIR%3e2.0.CO%3b2&partnerID=40&md5=a51c21fdfabf38a95d2009b8f1935474","The Maritime Continent, with its complex system of islands and shallow seas, presents a major challenge to models, which tend to systematically underestimate the precipitation in this region. Experiments with a climate version of the Met Office model (HadAM3) show that even with a threefold increase in horizontal resolution there is no improvement in the dry bias. It is argued that the diurnal cycle over the islands and the complex circulation patterns generated by land-sea contrasts are crucial for the energy and hydrological cycles of the Maritime Continent and for determining the mean climate. It is shown that the model has substantial errors in its simulation of the diurnal cycle over the islands, which can rectify onto the seasonal mean climate. It is further argued that deficient rainfall over the Maritime Continent could be a driver for other systematic errors, such as the excess precipitation over the western Indian Ocean. To demonstrate the sensitivity of global systematic model errors to the heating in this region, two experiments have been performed, one with the existing distribution of islands and a second where the island grid points are replaced by ocean grid points. In the absence of the islands of the Maritime Continent, the local precipitation increases by 15%, reducing the existing dry bias and bringing the model closer to observations. In response to this improved heating distribution, precipitation decreases over the west Indian Ocean and South Pacific convergence zone, reducing the systematic wet bias in these regions. This supports the hypothesis that tropical systematic errors are often related through vertical (Walker) circulations. The extratropical response to changes in the Maritime Continent heat source is also well demonstrated by these experiments. The enhanced heating and, hence, divergent outflow generates Rossby waves, which have a significant impact on the winter circulation and surface temperatures across much of North America and the northeast Eurasian region. These changes are such as to substantially reduce model systematic error in these regions. These results reinforce the critical role played by the Maritime Continent in the global circulation. It emphasizes the need for better representation of convective organization over regions of complex land-sea terrains and the importance of considering the global context of model systematic errors in which biases in the Tropics may be a key factor."
"6701670597;","Convective inhibition, subgrid-scale triggering energy, and stratiform instability in a toy tropical wave model",2000,"10.1175/1520-0469(2000)057<1515:CISSTE>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034193907&doi=10.1175%2f1520-0469%282000%29057%3c1515%3aCISSTE%3e2.0.CO%3b2&partnerID=40&md5=0f569080b7b956f9c4b088477f2fac63","A toy model of large-scale deep convection variations is constructed around a radiative-convective equilibrium climate, with an observed mean sounding as its thermodynamic basic state. Vertical structure is truncated at two modes, excited by convective (one-signed) and stratiform (two-signed) heating processes in tropical deep convection. Separate treatments of deep and shallow convection are justified by observations that deep convection is more variable. Deep convection intensity is assumed to be modulated by convective available potential energy (CAPE), while occurrence frequency is modulated by the ratio of convective inhibition (CIN) to 'triggering energy' K, a scalar representing the intensity of subgrid-scale fluctuations. Deep convective downdrafts cool and dry the boundary layer but also increase K. Variations of K make the relationship between convection and thermodynamic variables (CAPE, CIN, θ(e)) nonunique and amplify the deep convective response to temperature waves of small (~1°C) amplitude. For a parameter set in which CAPE variations control convection, moist convective damping destroys all variability. When CIN/K variations have dominant importance (the 'inhibition-controlled' regime), a mechanism termed 'stratiform instability' generates large-scale waves. This mechanism involves lower-tropospheric cooling by stratiform precipitation, which preferentially occurs where the already cool lower troposphere favors deep convection, via smaller CIN. Stratiform instability has two subregimes, based on the relative importance of the two opposite effects of downdrafts: When boundary layer θ(e) reduction (a local negative feedback) is stronger, small-scale waves with frequency based on the boundary layer recovery time are preferred. When the K-generation effect (positive feedback) is stronger, very large scales (low wavenumbers of the domain) develop. A mixture of these scales occurs for parameter choices based on observations. Model waves resemble observed waves, with a phase speed ~20 m s-1 (near the dry wave speed of the second internal mode), and a 'cold boomerang' vertical temperature structure. Although K exhibits 'quasi-equilibrium' with other convection variables (correlations &gt; 0.99), replacing the prognostic K equation with diagnostic equations based on these relationships can put the model into wildly different regimes, if small time lags indicative of causality are distorted. The response of model convection to climatological spatial anomalies of θ(e) (proxy for SST) and K (proxy for orographic and coastal triggering) is considered. Higher SST tends broadly to favor convection under either CAPE-controlled or inhibition-controlled regimes, but there are dynamical embellishments in the inhibition-controlled regime. The Kelvin wave seems to be the preferred structure when the model is run on a uniform equatorial β plane.A toy model of large-scale deep convection variations is constructed around a radiative-convective equilibrium climate. This article reviews a general body of ideas and observations intended to modify and justify the model."
"7004479957;8882641700;6701346974;","An energy-balance analysis of deep convective self-aggregation above uniform SST",2005,"10.1175/JAS3614.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-31144456989&doi=10.1175%2fJAS3614.1&partnerID=40&md5=d9bc208a4393d9a4f2a3c9f0c2fad483","The spatial organization of deep moist convection in radiative-convective equilibrium over a constant sea surface temperature is studied. A 100-day simulation is performed with a three-dimensional cloud-resolving model over a (576 km)2 domain with no ambient rotation and no mean wind. The convection self-aggregates within 10 days into quasi-stationary mesoscale patches of dry, subsiding and moist, rainy air columns. The patches ultimately merge into a single intensely convecting moist patch surrounded by a broad region of very dry subsiding air. The self-aggregation is analyzed as an instability of a horizontally homogeneous convecting atmosphere driven by convection-water vapor-radiation feedbacks that systematically dry the drier air columns and moisten the moister air columns. Column-integrated heat, water, and moist static energy budgets over (72 km)2 horizontal blocks show that this instability is primarily initiated by the reduced radiative cooling of air columns in which there is extensive anvil cirrus, augmented by enhanced surface latent and sensible heat fluxes under convectively active regions due to storm-induced gustiness. Mesoscale circulations intensify the later stages of self-aggregation by fluxing moist static energy from the dry to the moist regions. A simple mathematical model of the initial phase of self-aggregation is proposed based on the simulations. In accordance with this model, the self-aggregation can be suppressed by horizontally homogenizing the radiative cooling or surface fluxes. Lower-tropospheric wind shear leads to slightly slower and less pronounced self-aggregation into bands aligned along the shear vector. Self-aggregation is sensitive to the ice microphysical parameterization, which affects the location and extent of cirrus clouds and their radiative forcing. Self-aggregation is also sensitive to ambient Coriolis parameter f, and can induce spontaneous tropical cyclogenesis for large f. Inclusion of an interactive mixed-layer ocean slows but does not prevent self-aggregation. © 2005 American Meteorological Society."
"57188744345;","Precipitation Extremes Under Climate Change",2015,"10.1007/s40641-015-0009-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84989851610&doi=10.1007%2fs40641-015-0009-3&partnerID=40&md5=346b59f96051bcd94efcc930d30d16e6","The response of precipitation extremes to climate change is considered using results from theory, modeling, and observations, with a focus on the physical factors that control the response. Observations and simulations with climate models show that precipitation extremes intensify in response to a warming climate. However, the sensitivity of precipitation extremes to warming remains uncertain when convection is important, and it may be higher in the tropics than the extratropics. Several physical contributions govern the response of precipitation extremes. The thermodynamic contribution is robust and well understood, but theoretical understanding of the microphysical and dynamical contributions is still being developed. Orographic precipitation extremes and snowfall extremes respond differently from other precipitation extremes and require particular attention. Outstanding research challenges include the influence of mesoscale convective organization, the dependence on the duration considered, and the need to better constrain the sensitivity of tropical precipitation extremes to warming. © 2015, The Author(s)."
"43361566800;7005616688;7006738371;8513269500;7003524601;7005053078;","Neglected clouds in T and y dwarf atmospheres",2012,"10.1088/0004-637X/756/2/172","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865607435&doi=10.1088%2f0004-637X%2f756%2f2%2f172&partnerID=40&md5=85eb39e9cccfaccb12b6f9412c86d983","As brown dwarfs cool, a variety of species condense in their atmospheres, forming clouds. Iron and silicate clouds shape the emergent spectra of Ldwarfs, but these clouds dissipate at the L/T transition. A variety of other condensates are expected to form in cooler Tdwarf atmospheres. These include Cr, MnS, Na2S, ZnS, and KCl, but the opacity of these optically thinner clouds has not been included in previous atmosphere models. Here, we examine their effect on model T and Y dwarf atmospheres. The cloud structures and opacities are calculated using the Ackerman &amp; Marley cloud model, which is coupled to an atmosphere model to produce atmospheric pressure-temperature profiles in radiative-convective equilibrium. We generate a suite of models between T eff = 400 and 1300K, log g = 4.0 and 5.5, and condensate sedimentation efficiencies from f sed = 2 to 5. Model spectra are compared to two red Tdwarfs, Ross 458C and UGPS 0722-05; models that include clouds are found to match observed spectra significantly better than cloudless models. The emergence of sulfide clouds in cool atmospheres, particularly Na2S, may be a more natural explanation for the ""cloudy"" spectra of these objects, rather than the reemergence of silicate clouds that wane at the L-to-T transition. We find that sulfide clouds provide a mechanism to match the near- and mid-infrared colors of observed Tdwarfs. Our results indicate that including the opacity of condensates in Tdwarf atmospheres is necessary to accurately determine the physical characteristics of many of the observed objects. © 2012. The American Astronomical Society. All rights reserved."
"7003406400;","Organization of tropical convection in low vertical wind shears: The role of water vapor",2001,"10.1175/1520-0469(2001)058<0529:OOTCIL>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035868028&doi=10.1175%2f1520-0469%282001%29058%3c0529%3aOOTCIL%3e2.0.CO%3b2&partnerID=40&md5=9af3fa4aa1d7f5229ede5020057beb4b","A modeling study is conducted to gain insight into the factors that control the intensity and organization of tropical convection, and in particular to examine if organization occurs in the absence of factors such as vertical wind shear or underlying sea surface temperature (SST) gradient. The control experiment integrates a cloud-resolving model for 15 days using a 3D domain exceeding 1000 km in length, with no imposed winds, and horizontally uniform SST and forcing for convection. After 2 days of random activity, the convection organizes into clusters with dimensions of approximately 200 km. Convective systems propagate through the clusters at speeds of 2-3 m s-1, while the clusters themselves propagate at minimal speeds of around 0.5 m s-1. Examining the thermodynamic structure of the model domain, it is found that the convective free bands separating the clusters are very dry throughout the troposphere, and due to virtual temperature effects, are correspondingly warmer in the lower troposphere and boundary layer. This suggests a positive feedback between convection and water vapor, where convective moistening of the local atmosphere renders it more favorable to future convection. The existence of this feedback is demonstrated by experiments in which the free-tropospheric water vapor is perturbed in convective regions, and it is found that the lower-atmospheric water vapor is most critical in controlling convection, most likely through the role of downdrafts. Examination of the boundary layer in the control experiment also indicated that convectively generated cold pools also play a key role in the organization of convection, possibly by their influence on the boundary layer water vapor field. In order to see how the water vapor feedback modifies established convective organization, a further experiment was conducted with an SST gradient imposed, which established a mock Walker cell type circulation, with ascending motion over the warmest SSTs. After 5 days, the SST gradient is reversed to see how the convection would establish itself over the new SST maximum. This highly idealized experiment therefore represents a surrogate for the atmospheric response to SST ""hotspots,"" that observations have shown to form under the descending branch of large-scale tropical circulations such as the Madden-Jullian oscillation, due to increased incident solar radiation and decreased latent heat fluxes at the surface. It is found that the convection does not spontaneously initiate over the new SST maximum, but instead must propagate toward it. After a further 5 days, much longer than the boundary layer adjustment timescale, the warmest SSTs are still completely free from convection. This is directly due to the dryness of the atmosphere caused by the initial period of subsidence. A further set of experiments examines the robustness of the feedback in cases of imposed vertical wind shear. It is found that strong wind shears prevent the feedback by effectively mixing water vapor. However, the feedback is still very important in cases of weak wind shears."
"7006095466;","Organized Convective Systems: Archetypal Dynamical Models, Mass and Momentum Flux Theory, and Parametrization",1992,"10.1002/qj.49711850703","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027069248&doi=10.1002%2fqj.49711850703&partnerID=40&md5=5e83567d4376fafc1167f81ceab029a0","A dynamical basis is established for understanding the structure and transport properties of organized convection and for expediting its parametrization in large‐scale models. A two‐dimensional model provides an exact theory of the momentum transport by mesoscale convective systems and similar phenomena. the system‐scale dynamics are supposed to dominate local processes and are modelled by a stationary triple‐branch airflow regime consisting of a double‐branch updraught and a downdraught. It is argued that a jump updraught is essential and has a fundamental effect on the momentum transport. the triple‐branch model degenerates into a form of conservative density current; another limiting case consists of a propagating positive pressure jump of maximum amplitude‐an overturning updraught but no downdraught. the functional relationship among dynamical parameters is determined by a characteristic regime equation derived from elementary nonlinear Lagrangian conservation properties and the volume integral of the horizontal‐momentum equation. The inflow to the archetypal jump updraught is constant. an example shows that the inclusion of shear in this region alters the detailed shape of the momentum flux profile but its fundamental character, namely the negative values of momentum flux for a system travelling in the positive x‐direction, is retained. This result, together with recent numerical simulations, implies that low‐level shear directly influences the initiation and evolution of convective elements, whereas the mature‐state fluxes for which the system‐scale flow organization and tilt is paramount is a product of the distribution of heat sources/sinks and deep tropospheric shear. the universal nature of the momentum flux profiles is explained in elementary terms by appealing to dynamical theory. The physical basis of the model and the momentum flux profiles are validated by using published results. the archetype emulates the basic character of the mass and momentum fluxes by mesoscale convective systems. For example an upper‐tropospheric flow deceleration is consistent with the observed effect of tropical cloud clusters on the mean flow but is distinct from the balanced response due to diabatic heating. The theory is used to develop a dynamical approach to the parametrization of organized convective processes that have hitherto been neglected in global models. Mass and momentum fluxes are obtained from the archetypal model in an approach that is fundamentally different from the statistical or averaging approximations that characterize present techniques. the activation of the parametrization scheme is also studied. Mass‐flux criteria are used to define an amplitude function for the mesoscale flux divergence to incorporate the flux laws into the large‐scale equations. the work can be extended to include thermodynamic fluxes by using generalized conservation properties. Copyright © 1992 Royal Meteorological Society"
"7006083502;7003926380;6701538799;","The role of environmental shear and thermodynamic conditions in determining the structure and evolution of mesoscale convective systems during TOGA COARE",1998,"10.1175/1520-0469(1998)055<3493:troesa>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033490970&doi=10.1175%2f1520-0469%281998%29055%3c3493%3atroesa%3e2.0.co%3b2&partnerID=40&md5=d8c84b0fafb54bf6e6f541862063a230","A collection of case studies is used to clucidate the influence of environment soundings on the structure and evolution of the convection in the mesoscale convective systems sampled by the turboprop aircraft in the Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean-Atmosphere Response Experiment (COARE). The soundings were constructed primarily from aircraft data below 5-6 km and primarily from radiosonde data at higher altitudes. The well-documented role of the vertical shear of the horizontal wind in determining the mesoscale structure of tropical convection is confirmed and extended. As noted by earlier investigators, nearly all convective bands occurring in environments with appreciable shear below a low-level wind maximum are oriented nearly normal to the shear beneath the wind maximum and propagate in the directions of the low-level shear at a speed close to the wind maximum: when there is appreciable shear at middle levels (800-400 mb), convective bands from parallel to the shear. With appreciable shear at both levels, the lower-level shear determines the orientations of the primary convective bands. If the midlevel shear is opppsite the low-level shear, secondery bands parallel to the midlevel shear will extend rearward from the primary band in later stages of its evolution; if the midlevel shear is 90 degrees to the low-level shear, the primary band will ratain its two-dimentional mesoscale structure. Convection has no obvious mesoscale organization on days with little shear or days with widespread convection. Environmental temperatures and humidites have no obvious effect on the mesoscale convective pattern, but they affect COARE convection in other ways. The high tops of COARE convection are related to high parcel equilibrium levels, which approach 100 mb in some cases. Convective available potential energies are larger than those in the GARP (Global Atmospheric Research Program) Atlantic Troptcal Experimental (GATE) mainly because of the higher equilibrium levels. The buoyancy integreated over the lowest 500 mb is similar for the two experiments. Convective inhibitions are small, enabling convection to propagate with only weak forcing. Comparison of slow-moving shear-parallel bands in COARE and GATE suggests that lower relative humidities between the top of the mixed layer and 500 mb can shorten their lifetimes significantly. COARE mesoscale organization and evelution differs from what was observed in GATE. Less-organized convection is more common in COARE. Of the convective bands observed, a greater fraction in COARE are faster-moving, shear-perpendicular squall lines. GATE slow-moving lines tend to be longer lived than than those COARE. The differences are probably traceable to differences in environmental shear and relative humidity, respectively."
"7005808242;6701618837;56744278700;","Radiative-convective equilibrium with explicit two-dimensional moist convection",1993,"10.1175/1520-0469(1993)050<3909:RCEWET>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027837535&doi=10.1175%2f1520-0469%281993%29050%3c3909%3aRCEWET%3e2.0.CO%3b2&partnerID=40&md5=d9418fb08fc95890966c479722e1827a","Radiative-convective statistical equilbria are obtained using a two-dimensional model in which radiative transfer is interactive with the predicted moisture and cloud fields. The domain is periodic in x, with a width of 640 km, and extends from the ground to 26 km. The lower boundary is a fixed-temperature water-saturated surface. The model produces a temperature profile resembling the mean profile observed in the tropics. The model generates a QBO-like oscillation in the x-averaged winds with an apparent period of ~60 days. This oscillation extends into the troposphere and influences the convective organization. In order to avoid the associated large vertical wind shears, calculations are also performed in which the x-averaged winds are constrained to vanish. The convection then evolves into a pattern in which rain falls only within a small part of the domain. The moisture field appears to provide the memory that localizes the convection. If the vertical shears are fixed at a modest nonzero value, this localization is avoided. -from Authors"
"36724322000;7006186794;6603130624;7003937114;6602113713;7103311365;6603244946;6602863880;7202642044;7403068412;7003958615;7402390888;6506354630;57213941483;7003507545;57197077309;6602570835;","BOBMEX: The Bay of Bengal Monsoon experiment",2001,"10.1175/1520-0477(2001)082<2217:BTBOBM>2.3.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0000339443&doi=10.1175%2f1520-0477%282001%29082%3c2217%3aBTBOBM%3e2.3.CO%3b2&partnerID=40&md5=09310fc75ceae64e3399edbf36f61181","The first observational experiment under the Indian Climate Research Programme, called the Bay of Bengal Monsoon Experiment (BOBMEX), was carried out during July-August 1999. BOBMEX was aimed at measurements of important variables of the atmosphere, ocean, and their interface to gain deeper insight into some of the processes that govern the variability of organized convection over the bay. Simultaneous time series observations were carried out in the northern and southern Bay of Bengal from ships and moored buoys. About 80 scientists from 15 different institutions in India collaborated during BOBMEX to make observations in most-hostile conditions of the raging monsoon. In this paper, the objectives and the design of BOBMEX are described and some initial results presented. During the BOBMEX field phase there were several active spells of convection over the bay, separated by weak spells. Observation with high-resolution radiosondes, launched for the first time over the northern bay, showed that the magnitudes of the convective available potential energy (CAPE) and the convective inhibition energy were comparable to those for the atmosphere over the west Pacific warm pool. CAPE decreased by 2-3 kJ kg-1 following convection, and recovered in a time period of 1-2 days. The surface wind speed was generally higher than 8 m s-1. The thermohaline structure as well as its time evolution during the BOBMEX field phase were found to be different in the northern bay than in the southern bay. Over both the regions, the SST decreased during rain events and increased in cloud-free conditions. Over the season as a whole, the upper-layer salinity decreased for the north bay and increased for the south bay. The variation in SST during 1999 was found to be of smaller amplitude than in 1998. Further analysis of the surface fluxes and currents is expected to give insight into the nature of coupling."
"6701448540;7402115506;6601982038;","Regional differences in tropical lightning distributions",2000,"10.1175/1520-0450(2001)040<2231:rditld>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034463725&doi=10.1175%2f1520-0450%282001%29040%3c2231%3arditld%3e2.0.co%3b2&partnerID=40&md5=8c2426c3d446da163cce6d250bee2ead","Observations from the National Aeronautics and Space Administration Optical Transient Detector (OTD) and Tropical Rainfall Measuring Mission (TRMM)-based Lightning Imaging Sensor (LIS) are analyzed for variability between land and ocean, various geographic regions, and different (objectively defined) convective ""regimes."" The bulk of the order-of-magnitude differences between land and ocean regional flash rates are accounted for by differences in storm spacing (density) and/or frequency of occurrence, rather than differences in storm instantaneous flash rates, which only vary by a factor of 2 on average. Regional variability in cell density and cell flash rates closely tracks differences in 85-GHz microwave brightness temperatures. Monotonic relationships are found with the gross moist stability of the tropical atmosphere, a large-scale ""adjusted state"" parameter. This result strongly suggests that it will be possible, using TRMM observations, to objectively test numerical or theoretical predictions of how mesoscale convective organization interacts with the larger-scale environment. Further parameters are suggested for a complete objective definition of tropical convective regimes."
"57193882808;57203012011;7006095466;56216811200;","Cloud-resolving modeling of cloud systems during phase III of GATE. Part II: Effects of resolution and the third spatial dimension",1998,"10.1175/1520-0469(1998)055<3264:CRMOCS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033232461&doi=10.1175%2f1520-0469%281998%29055%3c3264%3aCRMOCS%3e2.0.CO%3b2&partnerID=40&md5=13e9dc279fc90f6c4f5fad71cbae51a7","Two- and three-dimensional simulations of cloud systems for the period of 1-7 September 1974 in phase III of the Global Atmospheric Research Programme (GARP) Atlantic Tropical Experiment (GATE) are performed using the approach discussed in Part I of this paper. The aim is to reproduce cloud systems over the GATE B-scale sounding array. Comparison is presented between three experiments driven by the same large-scale conditions: (i) a fully three-dimensional experiment, (ii) a two-dimensional experiment that is an east-west section of the three-dimensional case, and (iii) a high-resolution version of the two-dimensional experiment Differences between two- and three-dimensional frameworks and those related to spatial resolution are analyzed. The three-dimensional experiment produced a qualitatively realistic organization of convection: nonsquall clusters, a squall line, and scattered convection and transitions between regimes were simulated. The two-dimensional experiments produced convective organization similar to that discussed in Part I. The thermodynamic fields evolved very similarly in all three experiments, although differences between model fields and observations did occur. When averaged over a few hours, surface sensible and latent heat fluxes and surface precipitation evolved very similarly in all three experiments and evaluated well against observations. Model resolution had some effect on the upper-troposheric cloud cover and consequently on the upper-tropospheric temperature ten-dency due to radiative flux divergence. When compared with the fully three-dimensional results, the two-dimensional simulations produced a much higher temporal variability of domain-averaged quantities The results support the notion that, as long as high-frequency temporal variability is not of primary importance, low-resolution two-dimensional simulations can be used as realizations of tropical cloud systems in the climate problem and for improving and/or testing cloud parameterizations for large-scale models."
"6602999057;7202803069;","Mineral dust aerosols over the Sahara: Meteorological controls on emission and transport and implications for modeling",2012,"10.1029/2011RG000362","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84856947014&doi=10.1029%2f2011RG000362&partnerID=40&md5=e769a1c09105ca07949fafc0445c2eae","Atmospheric mineral dust has recently become an important research field in Earth system science because of its impacts on radiation, clouds, atmospheric dynamics and chemistry, air quality, and biogeochemical cycles. Studying and modeling dust emission and transport over the world's largest source region, the Sahara, is particularly challenging because of the complex meteorology and a very sparse observational network. Recent advances in satellite retrievals together with ground-and aircraft-based field campaigns have fostered our understanding of the spatiotemporal variability of the dust aerosol and its atmospheric drivers. We now have a more complete picture of the key processes in the atmosphere associated with dust emission. These cover a range of scales from (1) synoptic scale cyclones in the northern sector of the Sahara, harmattan surges and African easterly waves, through (2) low-level jets and cold pools of mesoscale convective systems (particularly over the Sahel), to (3) microscale dust devils and dusty plumes, each with its own pronounced diurnal and seasonal characteristics. This paper summarizes recent progress on monitoring and analyzing the dust distribution over the Sahara and discusses implications for numerical modeling. Among the key challenges for the future are a better quantification of the relative importance of single processes and a more realistic representation of the effects of the smaller-scale meteorological features in dust models. In particular, moist convection has been recognized as a major limitation to our understanding because of the inability of satellites to observe dust under clouds and the difficulties of numerical models to capture convective organization. Copyright 2012 by the American Geophysical Union."
"6602908667;7201468792;","3-5 day-period disturbances coupled with convection over the tropical Pacific Ocean",1993,"10.2151/jmsj1965.71.2_221","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0001483858&doi=10.2151%2fjmsj1965.71.2_221&partnerID=40&md5=2a736fd5e623e6a7783e203c522836df","Convection-associated disturbance systems that propagate westward over the equatorial Pacific with a period of 3-5 days are studied utilizing the GMS IR equivalent blackbody temperature (TBB) data and the ECMWF global analysis data. The period of analysis is JJA 1980-1989 excluding 1984. Spectral analysis, lag-correlation analysis and composite analysis are utilized for the study. The dominance of 3-5 day variations with convective activity is statistically confirmed in the equatorial Pacific ITCZ region for the boreal summer season. It is shown, in a climatological sense, that these convective variations are associated with mixed Rossby-gravity (MRG)-wave-type disturbances in the central Pacific near the dateline, while they are associated with tropical depression (TD)-type disturbances in the tropical western north Pacific. It is suggested that the changes of dominant disturbance types are attributed to variations in large-scale environmental conditions, such as the mean vertical wind shear, the speed of mean zonal wind as well as the SST distribution. This hypothesis is supported by comparing disturbance structures in an El Niño year with those in a La Niña year at the same longitude. Three-dimensional structures and characteristic values are examined for these two types of disturbances associated with organized convection. The characteristics of MRG-wave-type disturbances correspond well with MRG waves with the equivalent depth of ~30m. A fairly large amplitude is observed in a limited longitudinal region of about a half-wavelength width (~4000km) near the dateline. The convection and wave convergence exhibit relatively ""loose"" coupling. The vertical phase structure for MRG waves coincides with the result of Yanai et al. (1968) and what was proposed by Hayashi (1970). However, it is not clear that the system can be described in the framework of wave-CISK. The characteristics of TD-type disturbances, on the other hand, coincide with the classical ""easterly waves"" as described by Reed &amp; Recker (1971) and exhibit ""tight"" coupling with convection. They do not correspond to any linear equatorial waves. It is shown that both types of disturbances obtain the kinetic energy through energy conversion from the available potential energy. © 1993, Meteorological Society of Japan."
"57034458200;7403566096;","Diurnal cycles of surface winds and temperatures as simulated by five boundary layer parameterizations",2004,"10.1175/1520-0450(2004)043<0157:DCOSWA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342310492&doi=10.1175%2f1520-0450%282004%29043%3c0157%3aDCOSWA%3e2.0.CO%3b2&partnerID=40&md5=89f181d04ab588929203406d79fc3913","Although most of the planetary boundary layer (PBL) parameterizations have demonstrated the capability to reproduce many meteorological phenomena in the lowest few kilometers, little attention has been paid to the prediction of the diurnal cycles of surface wind speed (VSFC) in relation to surface temperature (TSFC). In this study, the performance of five widely used PBL parameterizations in reproducing the diurnal cycles of VSFC and TSFC is evaluated using the 3-day mesoscale simulations of summertime weak-gradient flows over the central United States where little organized convection and topographical forcing were present. The time series of area-averaged VSFC and TSFC, as well as the vertical wind and thermal profiles from the five sensitivity simulations, are compared with hourly surface observations and other available data. The hourly surface observations reveal that the diurnal cycles of VSFC, are in phase (but surface wind directions are 5-6 h out of phase) with those of TSFC. It is shown that both VSFC and TSFC are very sensitive to the PBL parameterizations, given the identical conditions for all of the other model parameters. It is found that all five of the PBL schemes can reproduce the diurnal phases of TSFC (and wind directions), albeit with different amplitudes. However, all of the schemes underestimate the strength of VSFC during the daytime, and most of them overestimate it at night. Moreover, some PBL schemes produce pronounced phase errors in VSFC or substantially weak VSFC all of the time, despite their well-simulated diurnal cycle of TSFC. The results indicate that a perfect simulation of the diurnal TSFC cycle (and the thermal structures above) does not guarantee the reproduction of the diurnal cycles of VSFC. The final outcome would depend on how various physical processes, such as the vertical turbulent exchanges of the mass and momentum under different stability conditions, are parameterized. Because the upper portion of the PBL flow is often nearly opposite in phase to VSPC under weak-gradient conditions, the results have significant implications for the predictability of diurnal precipitation and the studies of air quality, wind energy, and other environmental problems. © 2004 American Meteorological Society."
"7003406400;7101867299;","Radiative-convective equilibrium in a three-dimensional cloud-ensemble model",1998,"10.1256/smsqj.55012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032413083&doi=10.1256%2fsmsqj.55012&partnerID=40&md5=36909d95742e9c2801c4f05424d642f2","A knowledge of radiative convective interactions is key to an understanding of the tropical climate. In an attempt to address this a cloud-resolving model has been run to a radiative-convective equilibrium state in three dimensions. The model includes a three-phase bulk microphysical scheme and a fully interactive two-stream broadband radiative-transfer scheme for both the infrared and solar radiation. The simulation is performed using a fixed sea surface temperature, and cyclic lateral boundary conditions. No 'large-scale' convergence, mean wind shear or background vorticity was imposed. The total integration lasted 70 days, and a statistical equilibrium state was reached at all heights after 30 days of simulation in all model variables. It is seen that some variables, such as vertical mass flux, adjust quickly to their equilibrium values while others, such as column-integrated water amount, domain-mean temperature and convective available potential energy (CAPE) display variation on a longer 30 day time-scale. The equilibrium state had a column-integrated vapour amount of 42.3 km m-2, a mean temperature of 258.7 K and a pseudo-adiabatic CAPE value of 1900 J kg-1. The equilibrium-state statistics are consistent with tropical observations. The convection does not remain randomly distributed but instead becomes organized, aligning in a band structure associated with high moisture values in the boundary layer. This organization seems to result from interactions between radiation, convection and surface fluxes. The surface-flux feedback is due to higher boundarylayer winds, associated with convection, increasing surface fluxes of moisture feedback is due to higher boundary winds, associated with convection, increasing surface fluxes of moisture locally. Horizontally inhomogeneous radiation can act to make clouds longer lasting and also increase convergence into cloudy region. Replacing the wind-sensitive surface-flux calculation with a linear relaxation to surface values appeared to largely destroy this organization, as did the use of an imposed horizontally uniform radiative-heating rate."
"15124698700;7401836526;","The hydrological cycle over a wide range of climates simulated with an idealized GCM",2008,"10.1175/2007JCLI2065.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53649098155&doi=10.1175%2f2007JCLI2065.1&partnerID=40&md5=b59fb841598f1760e89cc68ab899f1a7","A wide range of hydrological cycles and general circulations was simulated with an idealized general circulation model (GCM) by varying the optical thickness of the longwave absorber. While the idealized GCM does not capture the full complexity of the hydrological cycle, the wide range of climates simulated allows the systematic development and testing of theories of how precipitation and moisture transport change as the climate changes. The simulations show that the character of the response of the hydrological cycle to variations in longwave optical thickness differs in different climate regimes. The global-mean precipitation increases linearly with surface temperature for colder climates, but it asymptotically approaches a maximum at higher surface temperatures. The basic features of the precipitation-temperature relation, including the rate of increase in the linear regime, are reproduced in radiative-convective equilibrium simulations. Energy constraints partially account for the precipitation-temperature relation but are not quantitatively accurate. Large-scale condensation is most important in the midlatitude storm tracks, and its behavior is accounted for using a stochastic model of moisture advection and condensation. The precipitation associated with large-scale condensation does not scale with mean specific humidity, partly because the condensation region moves upward and meridionally as the climate warms, and partly because the mean condensation rate depends on isentropic specific humidity gradients, which do not scale with the specific humidity itself. The local water vapor budget relates local precipitation to evaporation and meridional moisture fluxes, whose scaling in the subtropics and extratropics is examined. A delicate balance between opposing changes in evaporation and moisture flux divergence holds in the subtropical dry zones. The extratropical precipitation maximum follows the storm track in warm climates but lies equatorward of the storm track in cold climates. © 2008 American Meteorological Society."
"12240204600;7003611656;7003926380;","Mesoscale convective systems over southeastern South America and their relationship with the South American low-level jet",2007,"10.1175/MWR3305.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34248360373&doi=10.1175%2fMWR3305.1&partnerID=40&md5=abc5c227b6897f5f499ac4d0c423823f","Prior studies have shown that the low-level jet is a recurrent characteristic of the environment during the initiation and mature stages of mesoscale convective systems (MCSs) over the Great Plains of the United States. The South American low-level jet (SALLJ) over southeastern South America (SESA) has an analogous role, advecting heat and moisture from the Amazon basin southward into the central plains of southeastern South America, generating ideal environmental conditions for convection initiation and growth into MCSs. This research has two purposes. One is to describe the characteristics of a 3-yr MCS sample in South America, south of the equator, and its related geographical distribution of convection frequency. The other is to advance the knowledge of the evolution of favorable environmental conditions for the development of large MCSs, specifically those that mature under SALLJ conditions. High horizontal and temporal resolution satellite images are used to detect MCSs in the area for the period 1 September 2000-31 May 2003. Operational 1° horizontal resolution fields from NCEP are used to examine the environment associated with the systems and for the same period. Differences between tropical and subtropical MCSs in terms of size, diurnal cycle, and duration are found. Tropical MCSs are smaller, shorter in duration, and are characterized by a diurnal cycle mainly controlled by diurnal radiative heating. Subtropical MCSs show a preference for a nocturnal phase at maturity over Argentina, which contrasts with a tendency for a daytime peak over Uruguay and southern Brazil. In all seasons, at least one subtropical MCS developed in 41% of the SALLJ days, whereas in the days with no SALLJ conditions this percentage dropped to 12%. This result shows the importance of the synoptic conditions provided by the SALLJ for the development of MCSs and motivates the study of the atmospheric large-scale structure that evolves in close coexistence between SALLJ and subtropical organized convection at the mature stage. The large-scale environment associated with large long-lived MCSs during SALLJ events over SESA evolves under thermodynamic and dynamic forcings that are well captured by the compositing analysis. Essential features are low-level convergence generated by an anomalous all-day-long strong low-level jet prior to the development of the system, overlapped by high-level divergence associated with the anticyclonic flank of the entrance of an upper-level jet streak. This provides the dynamical forcing for convection initiation in an increasingly convectively unstable atmosphere driven by an intense and persistent horizontal advection of heat and moisture at low levels. These processes act during at least one diurnal cycle, enabling gradual building of optimal conditions for the formation of the largest organized convection in the subtropical area. The frequency of convection culminates in a geographically concentrated nocturnal maximum over northeast Argentina on the following day (MCS-SALLJ day). The northeastward displacement and later dissipation of subtropical convection are affected by a northward advance of a baroclinic zone, which is related to horizontal cold advection and divergence of moisture flux at low levels, both contributing to the stabilization of the atmosphere. © 2007 American Meteorological Society."
"7401559815;7006329926;","Mechanisms of short-term sea surface temperature regulation: Observations during TOGA COARE",1997,"10.1175/1520-0442(1997)010<0465:MOSTSS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030789371&doi=10.1175%2f1520-0442%281997%29010%3c0465%3aMOSTSS%3e2.0.CO%3b2&partnerID=40&md5=efeac64584ba1d91c595fc5394518fa6","Analyses of ocean-atmpsphere data from Tropical Oceans Global Atmosphere Coupled Ocean-Atmosphere Response Experiment indicate that short-term (weekly to monthly) fluctuations of SST in the western Pacific warm pool are closely linked to the alternation of wet and dry spell driven by the Madden-Julian oscillation (MJO). The dry phase is characterized by increased convection over the Indian Ocean, a prolonged period of atmospheric subsidence, and surface easterlies over the western Pacific warm pool. During this place, increased surface shortwave radiation and reduced evaporation contribute about equally to the warming of the warm pool. Pronounced diurnal variations in SST observed during the dry phase may be instrumental in leading to the prolonged warming. The dry phase is followed by the wet phase, in which the SST warming trend is arrested and a cooling trend initiated by a reduction in surface shortwave radiation accompanying the buildup of organized convection. Subsequently, the continued cooling of the upper ocean is accelerated by increased westerly surface wind leading to enhanced surface evaporation and increased entrainment of cold water from below the thermocline. At this stage, the increased surface shortwave radiation due to the diminished cloud cover from reduced convection opposes the cooling by evaporation. The cooling trend is reversed as soon as the westerly phase terminates and the dry phase is reinitiated by the establishment of new organized convection over the Indian Ocean. The authors' results suggest that short-term SST variability in the western Pacific warm pool is closely linked to surface fluxes, which are strongly modulated by atmospheric low-frequency variability associated with the MJO. The implications of the present results on the dynamics of the MJO and the possible role of coupled SST in influencing the MJO variability are also discussed."
"7102577095;57198369060;","Cloud optical thickness feedbacks in the CO2 climate problem.",1984,"10.1029/JD089iD06p09668","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021641125&doi=10.1029%2fJD089iD06p09668&partnerID=40&md5=f8a0113751021717f0f048ee78a20949","A radiative-convective equilibrium model is developed and applied to study cloud optical thickness feedbacks in the CO2 climate problem. The basic hypothesis is that in the warmer and moister CO2-rich atmosphere, cloud liquid water content will generally be larger too. For clouds other than thin cirrus the result is to increase the albedo more than to increase the greenhouse effect.-from Authors"
"16644246500;7006184606;","Physical mechanisms controlling self-aggregation of convection in idealized numerical modeling simulations",2014,"10.1002/2013MS000269","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899059181&doi=10.1002%2f2013MS000269&partnerID=40&md5=6c78a372969162337ae852f1151b23ff","We elucidate the physics of self-aggregation by applying a new diagnostic technique to the output of a cloud resolving model. Specifically, the System for Atmospheric Modeling is used to perform 3- D cloud system resolving simulations of radiative-convective equilibrium in a nonrotating framework, with interactive radiation and surface fluxes and fixed sea surface temperature (SST). We note that self-aggregation begins as a dry patch that expands, eventually forcing all the convection into a single clump. Thus, when examining the initiation of self-aggregation, we focus on processes that can amplify this initial dry patch. We introduce a novel method to quantify the magnitudes of the various feedbacks that control self-aggregation within the framework of the budget for the spatial variance of column-integrated frozen moist static energy. The absorption of shortwave radiation by atmospheric water vapor is found to be a key positive feedback in the evolution of aggregation. In addition, we find a positive wind speed-surface flux feedback whose role is to counteract a negative feedback due to the effect of air-sea enthalpy disequilibrium on surface fluxes. The longwave radiation feedback can be either positive or negative in the early and intermediate stages of aggregation; however, it is the dominant positive feedback that maintains the aggregated state once it develops. Importantly, the mechanisms that maintain the aggregate state are distinct from those that instigate the evolution of self-aggregation. Key Points A new analysis method is used to quantify feedbacks governing self-aggregation Feedbacks that establish the cluster are different than those that maintain it Positive WISHE feedback opposes a negative surface flux disequilibrium feedback ©2013. American Geophysical Union. All Rights Reserved."
"56272964700;7005808242;","Detailed investigation of the self-aggregation of convection in cloud-resolving simulations",2012,"10.1175/JAS-D-11-0257.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867920582&doi=10.1175%2fJAS-D-11-0257.1&partnerID=40&md5=ff2201a7c8bebb1c457db29980f6c8f7","In models of radiative-convective equilibrium it is known that convection can spontaneously aggregate into one single localized moist region if the domain is large enough. The large changes in the mean climate state and radiative fluxes accompanying this self-aggregation raise questions as to what simulations at lower resolutions with parameterized convection, in similar homogeneous geometries, should be expected to produce to be considered successful in mimicking a cloud-resolving model. The authors investigate this self-aggregation in a nonrotating, three-dimensional cloud-resolving model on a square domain without large-scale forcing. It is found that self-aggregation is sensitive not only to the domain size, but also to the horizontal resolution. With horizontally homogeneous initial conditions, convective aggregation only occurs on domains larger than about 200 km and with resolutions coarser than about 2 km in the model examined. The system exhibits hysteresis, so that with aggregated initial conditions, convection remains aggregated even at our finest resolution, 500 m, as long as the domain is greater than 200-300 km. The sensitivity of self-aggregation to resolution and domain size in this model is due to the sensitivity of the distribution of low clouds to these two parameters. Indeed, the mechanism responsible for the aggregation of convection is the dynamical response to the longwave radiative cooling from low clouds. Strong longwave cooling near cloud top in dry regions forces downward motion, which by continuity generates inflow near cloud top and near-surface outflow from dry regions. This circulation results in the net export of moist static energy from regions with low moist static energy, yielding a positive feedback. © 2012 American Meteorological Society."
"35509639400;12801073500;22949118500;","Influence of convective processes on the isotopic composition (δ18O and δD) of precipitation and water vapor in the tropics: 1. Radiative-convective equilibrium and Tropical Ocean-Global Atmosphere-Coupled Ocean-Atmosphere Response Experiment (TOGA-COARE) simulations",2008,"10.1029/2008JD009942","https://www.scopus.com/inward/record.uri?eid=2-s2.0-59749092885&doi=10.1029%2f2008JD009942&partnerID=40&md5=eb76721b562757bc16e371235c0ad50e","Cumulus convection constitutes a key process in the control of tropical precipitation and the vertical transport of atmospheric water. To better understand the influence of convective processes on the isotopic composition of precipitation and water vapor, water stable isotopes (H2 18O and HDO) are introduced into a single column model including the Emanuel convective parameterization. This paper analyzes unidimensional simulations of the tropical atmosphere in a state of radiative-convective equilibrium, and simulations forced by data from the Tropical Ocean-Global Atmosphere-Coupled Ocean-Atmosphere Response Experiment (TOGA-COARE). This study shows that deep convective atmospheres are associated with robust isotopic features such as an isotopic composition of the air below the tropical tropopause layer (around 12-13 km) close to the typical values observed in the lower tropical stratosphere, and an isotopic enrichment of the upper tropospheric water that starts well below the tropopause. It highlights the critical role of condensate lofting and convective detrainment in these features, and the role of convective unsaturated downdrafts in the control of the isotopic composition of precipitation. Finally, it shows that the so-called ""amount effect"" primarily reveals the influence of large-scale atmospheric circulation changes on the isotopic composition of the precipitation, and that temperature changes not associated with circulation changes lead to an ""anti-amount effect"". The detailed analysis of the physical processes underlying the ""amount effect"" is presented in a companion paper. Copyright 2008 by the American Geophysical Union."
"6603263640;7005808242;","Entropy budget of an atmosphere in radiative-convective equilibrium. Part I: Maximum work and frictional dissipation",2002,"10.1175/1520-0469(2002)059<0125:EBOAAI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036330172&doi=10.1175%2f1520-0469%282002%29059%3c0125%3aEBOAAI%3e2.0.CO%3b2&partnerID=40&md5=f17473b256b3964a1f9897379de5f8d8","The entropy budget of an atmosphere in radiative-convective equilibrium is analyzed here. The differential heating of the atmosphere, resulting from surface heat fluxes and tropospheric radiative cooling, corresponds to a net entropy sink. In statistical equilibrium, this entropy sink is balanced by the entropy production due to various irreversible processes such as frictional dissipation, diffusion of heat, diffusion of water vapor, and irreversible phase changes. Determining the relative contribution of each individual irreversible process to the entropy budget can provide important information on the behavior of convection. The entropy budget of numerical simulations with a cloud ensemble model is discussed. In these simulations, it is found that the dominant irreversible entropy source is associated with irreversible phase changes and diffusion of water vapor. In addition, a large fraction of the frictional dissipation results from falling precipitation, and turbulent dissipation accounts for only a small fraction of the entropy production. This behavior is directly related to the fact that the convective heat transport is mostly due to the latent heat transport. In such cases, moist convection acts more as an atmospheric dehumidifier than as a heat engine. The amount of work available to accelerate convective updrafts and downdrafts is much smaller than predicted by studies that assume that moist convection behaves mostly as a perfect heat engine."
"7006095466;","A theory of organized steady convection and its transport properties",1981,"10.1002/qj.49710745103","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019353155&doi=10.1002%2fqj.49710745103&partnerID=40&md5=44b863f6318f061d181c5efb4bf9d3e1","A dynamical classification of organized convection is presented, and previously published and additional models are collated in a more general theory. the transport properties of each type are represented by flux laws, the motivation being to understand convective transports in the context of parametrization schemes for organized convection. Five distinct models, derived as analytic solutions to a general displacement equation obtained from conservation properties of the Boussinesq equations, are necessary to describe the dynamics. These models, designated propagating, steering‐level, jump, cellular and classical, have very distinctive dynamical structures, and can be combined to represent more complex types of organized convection. The propagating and steering‐level types export a significant amount of kinetic energy, momentum and entropy, while the jump and cellular types store a considerable amount of energy as work done on the environment by the pressure field. the classical type does not transport momentum, and is a representation of the classical thunderstorm in weakly sheared flow. Apart from the cellular model, although the entropy transports are broadly similar, the momentum and kinetic energy transports are very distinctive, with counter‐gradient momentum transport the rule rather than the exception. Thus by effecting organized updraught/downdraught circulations, a completely different transport problem from small‐scale cumulus and mixed‐layer convection is posed, with fundamental inferences regarding parametrization. the dynamical necessity of a mesoscale response in the cellular and propagating types suggests that this scale may, in certain cases, need to be represented explicitly in convective parametrization schemes for large‐scale models. These prototypes have been deliberately simplified for the sake of elucidating fundamental principles, and to give a dynamical basis for experimentation and generalization, through exploiting both cloud‐scale and larger‐scale numerical simulation models, as well as providing guidance in observational analyses, budget studies in particular. Copyright © 1981 Royal Meteorological Society"
"24492188100;6602908667;","The development of organized convection associated with the MJO during TOGA COARE IOP: Trimodal characteristics",2004,"10.1029/2004GL019601","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4143063583&doi=10.1029%2f2004GL019601&partnerID=40&md5=1bc0c4e87f97473d7a45a255941a26cd","We constructed a composite lifecycle of the Madden-Julian oscillation (MJO) with cloud-top information and atmospheric temperature and moisture profiles. Japanese Geostationary Meteorological Satellite (GMS/IR TBB) histograms and upper-soundings from the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) intensive observation period (IOP) were analyzed around Ujung Pandang (119°E, 5°S) and Kupang (123°E, 10°S), which encountered the mature phase of MJO from January to February, 1993. Under a large-scale boundary layer (BL) convergence, convection developed in stages: 1) 'suppressed stage' with suppressed clouds, 2) 'shallow convection stage' (2-3 days) with clouds confined under the trade inversion level, 3) 'developing stage' (3-4 days) with most clouds stopped at the mid-troposphere but some tall convective clouds developing 4) 'mature stage' (4-5 days) with large anvil cloud shields, and 5) 'decaying stage' with decaying anvils. These stages of MJO were related to three stable layers; trade inversion, 0°C level, and tropopause. It is suggested that staged convective development associated with the MJO was strongly affected by the interaction among convection, stable layers, and atmospheric moistening. Copyright 2004 by the American Geophysical Union."
"7006019301;6603795286;","Distribution and statistics of african mesoscale convective weather systems based on the ISCCP meteosat imagery",1997,"10.1175/1520-0493(1997)125<2821:DASOAM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0000628769&doi=10.1175%2f1520-0493%281997%29125%3c2821%3aDASOAM%3e2.0.CO%3b2&partnerID=40&md5=b3c39e0da6a4a7f19a71b568638093c5","This paper provides for the first time an objective short-term (8 yr) climatology of African convective weather systems based on satellite imagery. Eight years of infrared International Satellite Cloud Climatology Project-European Space Agency's Meteorological Satellite (ISCCP-Meteosat) satellite imagery has been analyzed using objective feature identification, tracking, and statistical techniques for the July, August, and September periods and the region of Africa and the adjacent Atlantic ocean. This allows various diagnostics to be computed and used to study the distribution of mesoscale and synoptic-scale convective weather systems from mesoscale cloud clusters and squall lines to tropical cyclones. An. 8-yr seasonal climatology (1983-90) and the seasonal cycle of this convective activity are presented and discussed. Also discussed is the dependence of organized convection for this region, on the orography, convective, and potential instability and vertical wind shear using European Centre for Medium-Range Weather Forecasts reanalysis data."
"7403008073;","Dust in the photospheric environment: Unified cloudy models of M, L, and T dwarfs",2002,"10.1086/341262","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0001649096&doi=10.1086%2f341262&partnerID=40&md5=41d1c82084bae30927b7b132c9952509","We report an attempt to construct unified cloudy models of M, L, and T dwarfs. For this purpose, we first discuss opacities as well as thermochemical properties of the cool and dense matter. Below about 2000 K, refractory material condenses, and dust will play a major role as a source of opacity. Then a major problem in modeling the photospheres of very cool dwarfs is how to treat dust and, especially, how dust could be sustained in the static photosphere for a long time. Under the high density of the photospheres of cool dwarfs, dust forms easily at the condensation temperature, Tcond, but the dust will soon grow larger than its critical radius rer (at which the Gibbs free energy of condensation attains the maximum) at the critical temperature TV Such large dust grains with rgr ≳ r cr will soon segregate from the gas and precipitate below the photosphere. For this reason, dust exists effectively only in the limited region of Tcr ≲ T ≲ Tcond in the photosphere, and this means that a dust cloud is formed deep in the photosphere rather than in the cooler surface region. With this simple model of the dust cloud, we show that the nongray model photosphere in radiative-convective equilibrium can be extended to Teff values as low as 800 K. Since Tcond ≈ 2000 K for the first condensates such as corundum and iron, the dust cloud is rather warm and necessarily located deeper in the photosphere (τ &gt; 1) for the cooler objects (note that T ≈ Teff at τ ≈ 1)). This explains why dust apparently shows little observable effect in T dwarfs. For warmer objects, the dust cloud, which is always formed at the same temperature range of Tcr ≲ T ≲ Tcond, can be located nearer the surface (τ &lt; 1) and, for this reason, L dwarfs appear to be dusty. We show that the recently proposed spectral classification of L and T dwarfs can consistently be interpreted by a single grid of our unified cloudy models with the thin dust cloud deep in the photosphere."
"56272964700;15124698700;8043701900;","Intensification of precipitation extremes with warming in a cloud-resolving model",2011,"10.1175/2011JCLI3876.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79251510318&doi=10.1175%2f2011JCLI3876.1&partnerID=40&md5=497199fd78d46323e062da380c1c9d13","A cloud-resolving model is used to investigate the effect of warming on high percentiles of precipitation (precipitation extremes) in the idealized setting of radiative-convective equilibrium.While this idealized setting does not allow for several factors that influence precipitation in the tropics, it does allow for an evaluation of the response of precipitation extremes to warming in simulations with resolved rather than parameterized convection. The methodology developed should also be applicable to less idealized simulations. Modeled precipitation extremes are found to increase in magnitude in response to an increase in sea surface temperature. A dry static energy budget is used to relate the changes in precipitation extremes to changes in atmospheric temperature, vertical velocity, and precipitation efficiency. To first order, the changes in precipitation extremes are captured by changes in the mean temperature structure of the atmosphere. Changes in vertical velocities play a secondary role and tend to weaken the strength of precipitation extremes, despite an intensification of updraft velocities in the upper troposphere. The influence of changes in condensate transports on precipitation extremes is quantified in terms of a precipitation efficiency; it does not change greatly with warming. Tropical precipitation extremes have previously been found to increase at a greater fractional rate than the amount of atmospheric water vapor in observations of present-day variability and in some climate model simulations with parameterized convection. But the fractional increases in precipitation extremes in the cloud-resolving simulations are comparable in magnitude to those in surface water vapor concentrations (owing to a partial cancellation between dynamical and thermodynamical changes), and are substantially less than the fractional increases in column water vapor. © 2011 American Meteorological Society."
"8658853400;7006380976;55999772700;7102609291;","The propagation and diurnal cycles of deep convection in northern tropical Africa",2008,"10.1002/qj.194","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41949088049&doi=10.1002%2fqj.194&partnerID=40&md5=36ea6aa5e8a355e465564bf41fc32b4e","The propagation and diurnal cycle of organized convection in northern tropical Africa are examined using five years (1999-2003) of digital infrared imagery for May-August. Reduced-dimension techniques are used to document the properties of cold clouds - proxies for deep convection and precipitation. Large-scale environments are diagnosed from global analyses. Organized convection in Africa consists of coherent sequences or episodes which span an average distance of about 1000 km and last about 25 h. A substantial fraction of events exhibits systematic propagation at regional to continental scales while undergoing decay and regeneration. Episodes with 36 h duration and 1472 km span recur at a one-per-day interval. Most episodes have phase speed of 10-20 m s-1, which is faster than most African easterly waves. Convective episodes tend to initiate in the lee of high terrain, consistent with thermal forcing from elevated heat sources. Average diurnal frequency maxima result from the superposition of local diurnal maximum with the delayed-phase arrival of systems propagating from the east. Propagation occurs with moderate low- to mid-tropospheric shear, which varies with the African easterly jet migration and West African monsoon phases. Frequent deep convection occurs with local shear maxima near high terrain. For the peak monsoon period and for 10 °W-10 °E, where easterly waves and convective systems are frequent, 35% of cold cloud episodes occur cast of the wave trough compared with about 24% to the west. Based on the coherent behaviour of organized, propagating convection, inferences may be made regarding the prediction of precipitation beyond one or two days. Copyright © 2008 Royal Meteorological Society."
"7006184606;","On thermally direct circulations in moist atmospheres",1995,"10.1175/1520-0469(1995)052<1529:OTDCIM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029412340&doi=10.1175%2f1520-0469%281995%29052%3c1529%3aOTDCIM%3e2.0.CO%3b2&partnerID=40&md5=99d8bda50555e9ba2e163d7194f4d809","An expression is derived for the critical horizontal gradient of subcloud-layer θe in radiative-convective equilibrium, sufficient for the onset of thermally direct, zonally symmetric circulations. The expression is then generalized to nonsymmetric flows under the approximation that the corresponding radiative-convective equilibrium state is in geostrophic balance. Scale analysis shows that actual moist entropy distributions cannot be far from critical in large-scale Hadley, Walker, and monsoon circulations. The balanced component of the surface winds can be calculated from the supercriticality of the surface θe, distribution, and the secondary circulation can then be estimated from the surface stress. -from Author"
"7403109784;55712772000;57207341888;","A study on the ""runaway greenhouse effect' with a one-dimensional radiative-convective equilibrium model",1992,"10.1175/1520-0469(1992)049<2256:ASOTGE>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027088162&doi=10.1175%2f1520-0469%281992%29049%3c2256%3aASOTGE%3e2.0.CO%3b2&partnerID=40&md5=e038a981668607724e25597e0dcbdb11","An upper limit of the outgoing infrared radiation is found to exist. The existence of the upper limit is characterized by the radiation limits that appear when the optical depth of the entire atmosphere becomes sufficiently deep and the temperature structure around the levels where the optical depth is about unity approaches a fixed profile. This appearance of an upper limit differs from that found by Komabayashi and Ingersoll, which is obtained from the constraint of the stratospheric radiation balance. As one of those radiation limits, the outgoing infrared radiation has an asymptotic limit as the surface temperature increases. This is caused by the tropospheric structure approaching the water vapor saturation curve. -from Authors"
"7006095466;6701809158;","Organized convective systems in the tropical western Pacific as a process in general circulation models: A TOGA COARE case-study",1997,"10.1256/smsqj.54001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030828613&doi=10.1256%2fsmsqj.54001&partnerID=40&md5=982055cfa42cf018e4e38759ba7b22ae","We examine the large-scale effects of organized convective systems in the tropical western Pacific observed during the Tropical-Ocean Global-Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). In a case-study approach, we examine realizations of a supercluster, associated with the onset of the December 1992 westerly wind burst, in the T213 operational medium-range weather forecasting model of the European Centre for Medium-Range Weather Forecasts (ECMWF). We idealize a supercluster as a hierarchy of three interacting scales, namely organized cumulonimbus script c sign1, mesoscale convective systems script c sign2, and the supercluster component script c sign3. It is shown that the ECMWF model represents this hierarchy as a script c sign3-like surrogate whose influence dominates the effect of parametrized convection. This causes over-prediction of the model tendencies which, in the case of zonal momentum, is explained in elementary terms. The structure of the resolved-scale momentum flux is explained by Moncrieff's (1992) archetypal theory of organized convection which has been verified against observations and cloud-resolving model data-sets. The parametrization of subgrid-scale convective momentum-flux in the ECMWF model, based on a momentum mixing concept, produces subgrid-scale tendencies that are physically different from transport associated with cumulonimbus convection in a shear flow. We outline a strategy for parametrizing the momentum flux by the script c sign1 component based on the archetypal model. The script c sign2 component, which is part-resolved and part-parametrized, is at odds with the assumptions of scale separation underpinning parametrization. It is argued that this component should be represented as part of the prognostic treatment of convectively generated cirrus. Finally, we suggest cloud-resolving modelling studies to further quantify the structure and large-scale impact of superclusters in a westerly-wind-burst environment, ranging from idealized models to models having data assimilation capability."
"6701670597;7102696626;","Parameterizing convective organization to escape the entrainment dilemma",2011,"10.1029/2011MS000042","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051826033&doi=10.1029%2f2011MS000042&partnerID=40&md5=f6eee0845319cb5247c9ee94553f97da","Lateral mixing parameters in buoyancy-driven deep convection schemes are among the most sensitive and important unknowns in atmosphere models. Unfortunately, there is not a true optimum value for plume mixing rate, but rather a dilemma or tradeoff: Excessive dilution of updrafts leads to unstable stratification bias in the mean state, while inadequate dilution allows deep convection to occur too easily, causing poor space and time distributions and variability. In this too-small parameter space, compromises are made based on competing metrics of model performance. We attempt to escape this ""entrainment dilemma"" by making bulk plume parameters (chiefly entrainment rate) depend on a new prognostic variable (""organization,"" org) meant to reflect the rectified effects of subgrid-scale structure in meteorological fields. We test an org scheme in the Community Atmosphere Model (CAM5) with a new unified shallow-deep convection scheme (UW-ens, a 2-plume version of the University of Washington scheme). Since buoyant ascent involves natural selection, subgrid structure makes convection systematically deeper and stronger than the pure unorganized case: plumes of average (or randomly sampled) air rising in the average environment. To reflect this, org is nonnegative, but we leave it dimensionless. A time scale characterizes its behavior (here ,3 h for a 2o model). Currently its source is rain evaporation, but other sources can be added easily. We also let org be horizontally transported by advection, as a mass-weighted mean over the convecting layer. Linear coefficients link org to a plume ensemble, which it assists via: 1) plume base warmth above the mean temperature 2) plume radius enhancement (reduced mixing), and 3) increased probability of overlap in a multi-plume scheme, where interactions benefit later generations (this part has only been implemented in an offline toy column model). Since rain evaporation is a source for org, it functions as a time-lagged but positive feedback on deep convection development. This evades the entrainment dilemma, since fully developed org-enhanced convection is not overly dilute, avoiding stability bias, while the pioneering updrafts of new convection are suppressed by entrainment, encouraging more large-scale variability."
"7003674085;7102389805;","The role of inertial instability in determining the location and strength of near-equatorial convection",1997,"10.1256/smsqj.54201","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031426327&doi=10.1256%2fsmsqj.54201&partnerID=40&md5=96453c6b9a9eee2b06267f54a9608530","There are two major organized cloud configurations in the vicinity of the equator. Where there is a small cross-equatorial surface pressure gradient, convection is close to the equator and is generally tied to the location of the lowest sea-level pressure (SLP) and warmest sea-surface temperature (SST), in agreement with arguments based upon simple thermodynamical considerations. However, when there is a substantial cross-equatorial pressure gradient, such as occurs in the monsoon regions, organized convection appears off the equator in the summer hemisphere, equatorward of the SLP minimum and not necessarily collocated with the warmest SSTs. Thus, in this instance, simple thermodynamical considerations alone cannot explain the location of the convection. In this situation, the zero absolute vorticity contour (η = 0) also lies in the summer hemisphere. Therefore, between the equator and the η = 0 contour is a region of locally-anticyclonic absolute vorticity and an inertially unstable regime. It is argued that the convection results from the low-level divergence-convergence doublet centred about the η = 0 contour which is the mitigating response to the inertial instability. The associated latitude-height secondary circulation should provide subsidence (suppressed convection) over the equator and rising motion (enhanced convection) to the north of the zero absolute vorticity contour. Signatures of the inertial instability predicted by theory are found in observations supporting the hypothesis. Wherever a strong cross-equatorial pressure gradient exists, the η = 0 contour bisects a maximum in the divergent wind field. Divergence is found equatorward of the zero contour and convergence on the poleward side. Latitude-height cross sections show strong local meridional circulations with maximum rising motion on the poleward side of η = 0. As the regions where the rising motions occur are conditionally unstable, there is deep convection and the vertical circulations extend throughout the troposphere. It is noted that the intensity of the off-equator convection is deeper (and probably stronger) than convection located at the equator. This is probably because the convection associated with the inertial instability is more efficient. Necessary conditions for the location of near-equatorial convection are listed. Arguments are presented whereby inertial instability is established as the cause, rather than an effect, of off-equatorial convection. These include an outline of the sequence of processes leading up to the convection. The factors that limit the encroachment of the η = 0 contour into the summer hemisphere are discussed and an explanation for the existence of the low-level westerly monsoon wind maximum is suggested. The possible role played by the instability mechanism (or the lack of it) in coupled model simulations that produce seasonally migrating and/or double ITCZs in the eastern Pacific Ocean is discussed. Finally, it is proposed that the instability mechanism is important in the initiation of westward-moving disturbances found in the eastern Pacific and in determining active and break periods in the summer Indian monsoon."
"55418382000;35509639400;7006861646;","Observational evidence for relationships between the degree of aggregation of deep convection, water vapor, surface fluxes, and radiation",2012,"10.1175/JCLI-D-11-00258.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867686898&doi=10.1175%2fJCLI-D-11-00258.1&partnerID=40&md5=6d4fcce8b9f689521571cb4f5753524e","Tropical deep convection exhibits complex organization over a wide range of scales. This study investigates the relationships between the spatial organization of deep convection and the large-scale atmospheric state. By using several satellite datasets and reanalyses, and by defining a simple diagnostic of convective aggregation, relationships between the degree of convective aggregation and the amount of water vapor, turbulent surface fluxes, and radiation are highlighted above tropical oceans. When deep convection is more aggregated, the middle and upper troposphere are drier in the convection-free environment, turbulent surface fluxes are enhanced, and the low-level and midlevel cloudiness is reduced in the environment. Humidity and cloudiness changes lead to a large increase in outgoing longwave radiation. Cloud changes also result in reduced reflected shortwave radiation. Owing to these opposing effects, the sensitivity of the radiative budget at the top of the atmosphere to convective aggregation turns out to be weak, but the distribution of radiative heating throughout the troposphere is affected. These results suggest that feedbacks between convective aggregation and the large-scale atmospheric state might influence large-scale dynamics and the transports of water and energy and, thus, play a role in the climate variability and change. These observational findings are qualitatively consistent with previous cloud-resolvingmodel results, except for the effects on cloudiness and reflected shortwave radiation. The proposed methodology may be useful for assessing the representation of convective aggregation and its interaction with the large-scale atmospheric state in various numerical models. © 2012 American Meteorological Society."
"36701716800;7005659017;6604005739;36006968000;","Absorbing aerosols facilitate transition of Indian monsoon breaks to active spells",2011,"10.1007/s00382-010-0971-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81455148141&doi=10.1007%2fs00382-010-0971-3&partnerID=40&md5=b87c2c7e619a416c552c5f17ebeaccd1","While some long breaks of monsoon intraseasonal oscillations (MISOs) are followed by active spells (BFA), some others are not (BNFA). The circulation during BFA (BNFA) cases helps (prevents) accumulation of absorbing aerosols over central India (CI) resulting in almost three times larger Aerosol Index (AI) over CI, during BFA cases compared to BNFA cases. A seminal role played by the absorbing aerosols in the transition from break to active spells is unraveled through modification of the north-south temperature gradient at lower levels. The meridional gradient of temperature at low level ({increment}T) between aerosol-rich CI and pristine equatorial Indian Ocean is large (>6°C) and sustains for long time (>10 days) during BFA leading to significant moisture convergence to CI. The stability effect arising from surface cooling by the aerosols is overcome by the enhanced moisture convergence creating a moist static unstable atmosphere conducive for the large-scale organized convection over the CI region leading to the resurgence of active spells. The moisture convergence induced by {increment}T was also able to overcome possible aerosol indirect effect (Twomey effect) and initiate deep convection and transition to active condition. During BNFA cases, however the maximum {increment}T, which was weaker than the BFA cases by more than 1. 5°C, could not sustain required moisture convergence and failed to lead to a sustained active spell. Using data from MODIS (MODerate resolution Imaging Spectroradiometer) onboard Terra and several other input parameters from various satellites for the period 2000-2009, the aerosol induced radiative forcing representative of two regions-the CI to the north and the pristine ocean to the south-were estimated and support the differences in observed {increment}T during the two cases. Our results highlight the need for proper inclusion of absorbing aerosols in dynamical models for simulation of the observed variability of MISOs and their extended range prediction. © 2010 Springer-Verlag."
"7006095466;","Analytic representation of the large-scale organization of tropical convection",2004,"10.1175/1520-0469(2004)061<1521:AROTLO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943097454&doi=10.1175%2f1520-0469%282004%29061%3c1521%3aAROTLO%3e2.0.CO%3b2&partnerID=40&md5=65036231b5621308474539fdce3782ff","The pivotal role of mesoscale organization on the large-scale coherence of tropical convection is represented by a nonlinear dynamical model. The general model consists of two interlocked systems: a mesoscale parameterization of organized convection and a two-layer model of large-scale equatorial dynamics. The lower-layer dynamics is Rossby gyre-like, whereas outflow from organized convection maintains the upper-layer circulation. The transports of zonal momentum in the vertical and meridional directions are key processes. An archetype of the general model, in spite of being brutally simplified, represents the convective organization, momentum transport, and equatorial superrotation realized by the cloud-resolving convection parameterization or superparameterization explicit, approach developed by Grabowski. The mesoscale parameterization is an analytic equivalent of the cloud-system-resolving models used in this computational approach. Finally, issues in parameterizing convective organization are discussed. © 2004 American Meteorological Society."
"35578543700;23486505900;7006184606;","Tropical cyclogenesis sensitivity to environmental parameters in radiative-convective equilibrium",2007,"10.1002/qj.170","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38849165938&doi=10.1002%2fqj.170&partnerID=40&md5=18018fed0193274461a2918b7391dd8a","In this study, the relationship between the likelihood of tropical cyclogenesis and external environmental forcings is explored in the simplest idealized modelling framework possible: radiative-convective equilibrium on a doubly periodic f-plane. In such an environment, control of the equilibrium environmental sounding is reduced to three parameters: the sea-surface temperature, the Coriolis parameter, and the imposed background surface wind speed. Cloud-resolving mesoscale model simulations are used to generate environments of radiative-convective equilibrium determined by these three factors. The favourability of these environments for tropical cyclogenesis is measured in three ways: in terms of the maximum potential intensity (MPI) of the sounding, based on the thermodynamic theory of Emanuel; in terms of the 'genesis potential' determined by an empirical genesis parameter; and in terms of the propensity of weak initial vortices in these environments to form into tropical cyclones. The simulated environments of radiative - convective equilibrium with no vertical wind shear are found to be very favourable for tropical cyclogenesis. Weak initial vortices always transition to a tropical cyclone, even for rather low sea-surface temperatures. However, the time required for these vortices to make the transition from a weak, mid-level vortex to a rapidly developing tropical cyclone decreases as the MPI increases, indicating the importance of MPT in enhancing the frequency of cyclogenesis. The relationship between this 'time to genesis' and the thermodynamic parameters is explored. The time to genesis is found to be very highly (negatively) correlated to MPI, with little or no relationship to convective instability, Coriolis parameter, mid-level humidity, or the empirical genesis parameter. In some cases, tropical cyclones are found to form spontaneously from random convection. This formation is due to a cooperative interaction between large-scale moisture, long-wave radiation, and locally enhanced sea-surface fluxes, similar to the 'aggregation' of convection found in previous studies. Copyright © 2007 Royal Meteorological Society."
"7006119444;7202505945;","On the interaction of tropical‐cyclone‐scale vortices. I: Observations",1993,"10.1002/qj.49711951406","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027804860&doi=10.1002%2fqj.49711951406&partnerID=40&md5=129331166fa2b8028647db0053da50bf","A detailed analysis is made of the observed behaviour in interaction, tropical‐cyclone‐scale vortices in the western North Pacific region. It is found that all multiple‐vortex interactions can be broken down into a common model of binary interaction. The classical Fujiwhara model of converging cyclonic rotation about a centroid followed by merger is rarely followed. Capture tends to occur rapidly, within several hours, and is followed by a period of relatively stable cyclonic orbit. Cyclone merger occurs by one vortex experiencing a loss of convective organization, followed by horizontal shearing and incorporation into the outer circulation of the other vortex. However, a substantial proportion of interacting cyclones escape from the interaction, and the changeover from a stable orbiting configuration occurs rapidly. A model of binary interaction is presented. Cases where swarms of mesoscale vortices are formed in convectively active regions without tropical cyclones are also documented. These vortices have a much narrower range of influence (a few hundred kilometres) then that observed for tropical cyclones. When groups of vortices come within this range they are observed to conform to the same interaction model as observed for tropical cyclones. Copyright © 1993 Royal Meteorological Society"
"7404847071;6701749915;","Stratospheric ozone in the lower troposphere -I. Presentation and interpretation of aircraft measurements",1981,"10.1016/0004-6981(81)90325-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019389888&doi=10.1016%2f0004-6981%2881%2990325-5&partnerID=40&md5=331bdaeac07041e68b8bc842d8362328","The United States has instituted a number of air pollution regulations to control ozone, including an air quality standard for oxidants of 120 ppb for one hour. Accordingly, there is considerable interest in determining the magnitude of the natural (i.e. nonanthropogenic) component of ozone concentration near the ground, much of which is generally believed to come from the stratosphere. Toward this end, an extensive program of aircraft measurements of tropospheric ozone originating from the stratosphere was carried out over the Central U.S. in spring and fall 1978. On 10 of these flights, the vertical structure of stratospheric ozone intrusions was well mapped by aircraft penetrations at several altitudes extending between 2 and 8 km above sea level (ASL) in the southern portions of tropospheric low-pressure troughs. The field measurements show that stratospheric ozone intrusions into the troposphere occur more frequently than earlier studies had indicated. Ozone intrusions were found in virtually every trough, regardless of intensity, within which suitable measurements were taken. A close relationship was found between: 1. (1) maximum ozone concentrations in the intrusion; and 2. (2) trough intensity as characterized by maximum wind speed at 300 mb (approximately 10 km ASL). The intrusions typically are characterized by peak ozone concentrations at higher altitudes (6-8 km ASL) in the range of 240-400 ppb, diminishing to 100-200 ppb at lower altitudes as mixing with surrounding air occurs. Measured concentrations during spring were almost twice as high as those measured during fall, but the intrusion structures were very similar during both seasons. The data show that stratospheric ozone intrusions are typically 100-300 km wide in the crosswind direction, are several hundreds of kilometers long, and can be tracked down at least as far as the top of the atmospheric boundary layer (about 2 km ASL). Possible mechanisms for downward transport within the boundary layer include normal convective mixing, organized convection associated with cloud and precipitation processes, and organized downward motion within frontal zones. © 1981."
"6505932008;7202899330;7202962414;","Aerosol indirect effects on tropical convection characteristics under conditions of radiative-convective equilibrium",2011,"10.1175/2010JAS3603.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954995826&doi=10.1175%2f2010JAS3603.1&partnerID=40&md5=4a6de032e0587f25b984ffa34f3015b0","The impacts of enhanced aerosol concentrations such as those associated with dust intrusions on the trimodal distribution of tropical convection have been investigated through the use of large-domain (10 000 grid points), fine-resolution (1 km), long-duration (100 days), two-dimensional idealized cloud-resolving model simulations conducted under conditions of radiative-convective equilibrium (RCE). The focus of this research is on those aerosols that serve primarily as cloud condensation nuclei (CCN). The results demonstrate that the large-scale organization of convection, the domain-averaged precipitation, and the total cloud fraction show only show a weak response to enhanced aerosol concentrations. However, while the domainwide responses to enhanced aerosol concentrations are weak, aerosol indirect effects on the three tropical cloud modes are found to be quite significant and often opposite in sign, a fact that appears to contribute to the weaker domain response. The results suggest that aerosol indirect effects associated with shallow clouds may offset or compensate for the aerosol indirect effects associated with congestus and deep convection systems and vice versa, thus producing a more moderate domainwide response to aerosol indirect forcing. Finally, when assessing the impacts of aerosol indirect forcing associated with CCN on the characteristics of tropical convection, several aspects need to be considered, including which cloud mode or type is being investigated, the field of interest, and whether localized or systemwide responses are being examined. © 2011 American Meteorological Society."
"7202326662;7004160585;7103201242;","The evolution of the tropical western Pacific atmosphere-ocean system following the arrival of a dry intrusion",2000,"10.1002/qj.49712656307","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034092090&doi=10.1002%2fqj.49712656307&partnerID=40&md5=5bfde8ea504a2ead15f2579bca79c1fe","Recent studies using TOGA COARE data have found that extremely dry air from middle-latitude waves frequently intrudes into the equatorial troposphere over the western Pacific. Using sounding data taken during the COARE, the magnitude of the advection of water vapour for one event is calculated, and it is estimated that the time for the atmosphere to recover to moist conditions was ~10-20 days. From the magnitude of the drying and from the frequency of these events, it is proposed that dry intrusions must be a major contributor to the tropospheric moisture budget over the region during the COARE, making it difficult for the atmosphere to reach a radiative-convective equilibrium. Intrusions, instead, can help to recharge the tropical atmosphere by decreasing convective activity and, thus, driving the atmosphere toward unusually large values of convective available potential energy. A variety of atmospheric and oceanic measurements are also used to study the recovery process in detail. A conceptual model is proposed based on this work and previous investigations. As in past studies, the recovery of the atmosphere to moist conditions is accomplished through detrainment from convective clouds that began to form soon after the arrival of the dry air mass and slowly deepen in height as the recovery progresses. Previous investigators concluded that the entrainment of dry air into convective cells is generally the factor that tends to suppress convective activity and limits the height of any convection that does develop under these adverse conditions. The idea that entrainment limits convective activity is consistent with the commonly held perception that the western Pacific is a region where there is little inhibition to deep convection and, when inhibition does occur, it can be removed by surface fluxes within hours. In contrast, it is found that convective inhibition can be large enough to suppress convection following dry intrusions, and that the diurnal variation in rainfall is due partly to modulations in convective inhibition. The modulations in convective inhibition are, in turn, caused by diurnal variations in the vertical profiles of radiation, in surface fluxes, and perhaps in large-scale subsidence, leading to a minimum in convective inhibition during the late afternoon. In contrast, studies of this type of convection have generally emphasized diurnal variations in the surface fluxes, and often ignored convective inhibition and diurnal variations in atmospheric radiative heating."
"57212215393;7202208382;","Global-scale convective aggregation: Implications for the Madden-Julian Oscillation",2015,"10.1002/2015MS000498","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959507321&doi=10.1002%2f2015MS000498&partnerID=40&md5=7e568dbb87702269f13d0e6864171738","Previous work has shown that convection will self-organize in cloud-system-resolving model simulations of radiative-convective equilibrium, and it has been suggested that the convective envelope of the Madden-Julian oscillation (MJO) may be organized by similar processes on a much larger scale. Here we present support for that hypothesis based on simulations with SP-CAM with globally uniform SST. Without rotation, convection self-organizes into large (-4000 km) clusters surrounded by dry regions, while with Earth-like rotation the model produces a robust MJO. The nonrotating aggregation and MJO are found to have similar budgets of moist static energy, both being supported by diabatic feedbacks, particularly cloud-longwave interaction. Mechanism denial experiments show that longwave heating anomalies associated with high clouds are essential to the nonrotating aggregation, and amplify the MJO. Simulations using the conventional CAM show a weaker MJO and a much weaker tendency for nonrotating aggregation, and both MJO activity and aggregation intensity are found to increase with the entrainment rate in the deep convection parameterization. © 2015. The Authors."
"6506647236;8934032500;7006235116;57209596880;7005008970;","Recurrent daily OLR patterns in the Southern Africa/Southwest Indian ocean region, implications for South African rainfall and teleconnections",2009,"10.1007/s00382-008-0426-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58849126502&doi=10.1007%2fs00382-008-0426-2&partnerID=40&md5=05ed7cd39c6c1940920ef81b990e5095","A cluster analysis of daily outgoing longwave radiation (OLR) anomalies from 1979 to 2002 over the Southern Africa/Southwest Indian Ocean (SWIO) region for the November to February season reveals seven robust and statistically well separated recurrent patterns of large-scale organized convection. Among them are three regimes indicative of well defined tropical-temperate interactions linking the hinterland parts of Southern Africa to the mid-latitudes of the SWIO. Preferred transitions show a tendency for an eastward propagation of these systems. Analysis of daily rainfall records for South Africa shows that six of the OLR regimes are associated with spatially coherent and significant patterns of enhanced or reduced daily rainfall over the country. Atmospheric anomalies from the NCEP/DOE II reanalysis dataset show that the OLR regimes are associated with either regional or near-global adjustments of the atmospheric circulation, the three regimes representative of tropical-temperate interactions being in particular related to a well-defined wave structure encompassing the subtropical and temperate latitudes, featuring strong vertical anomalies and strong poleward export of momentum in the lee of the location of the cloud-band. The time-series of OLR regimes seasonal frequency are correlated to distinctive anomaly patterns in the global sea-surface-temperature field, among which are shown to be those corresponding to El Nino and La Nina conditions. The spatial signature of El Nino Southern Oscillation's (ENSO) influence is related to the combination of an increased/decreased frequency of these regimes. It is shown in particular that the well-known ""dipole"" in convection anomalies contrasting Southern Africa and the SWIO during ENSO events arises as an effect of seasonal averaging and is therefore not valid at the synoptic scale. This study also provides a framework to better understand the observed non-linearities between ENSO and the seasonal convection and rainfall anomalies over the region. © Springer-Verlag 2008."
"7006380976;55619308081;7102746335;7102653983;","Tropical island convection in the absence of significant topography. Part I: Life cycle of diurnally forced convection",2000,"10.1175/1520-0493(2000)128<3459:TICITA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033659336&doi=10.1175%2f1520-0493%282000%29128%3c3459%3aTICITA%3e2.0.CO%3b2&partnerID=40&md5=039bb00de48f6becfcf8e59fbe2ef2cd","Diurnally forced convection was observed over the Tiwi Islands, north of the Australian continent, as part of the Maritime Continent Thunderstorm Experiment. Immature peninsula-scale (5-15 km) sea breezes were observed to initiate moist convection early each day, principally through convergence that results from the confluence or collision of peninsula breeze fronts. Convection initiated by peninsula-scale breezes usually fails to organize beyond a small cluster of cells and dissipates as a local event. Mature island-scale (∼100 km) breezes develop by late morning and subsequently play a pivotal role in the forcing and evolution of organized convection. The initiation of mesoscale convective systems (MCSs) is observed to be a direct consequence of breeze front collisions for only ∼20% of the days on which organized convection develops. This is referred to as ""type A"" forcing and it occurs when normal convective development is delayed or otherwise suppressed. Type A forcing is nature's backup mechanism and it is less likely to produce large or strong mesoscale convective systems when compared to the general population of events. On approximately 80% of days during which organized convection develops, a multiple-stage forcing process evolves through complex interactions between preferred sea breezes and convectively generated cold pools. Socalled type B forcing emerges 1-3 h before penetration of the sea-breeze fronts to the interior island. Type B evolution has at least four stages: 1) leeward- or other preferred-coast sea-breeze showers that develop small cold pools, 2) showers that travel inland when their cold pools become denser than the marine boundary layer, 3) westward propagation of squalls that result from a merge or maturation of small cold pools, and 4) interaction between a gust front and a zonally oriented sea-breeze front of island scale (∼100 km). A collision of gust fronts, emanating from separate convective areas over Bathurst and Melville Islands, can excite a fifth stage of development associated with many of the strongest systems. A principal finding of this study is that all MCSs over the Tiwi Islands can be traced backward in time to the initiation of convection by island-scale sea breezes, usually of type B near leeward coasts. Subsequent convective evolution is characteristic of traveling free convection elsewhere in that it organizes according to cold pool, shear balance, and mean flow factors. The presence of a critical level in the lower troposphere is a unique aspect of the theoretical ""optimal condition"" associated with island convection in a low-level jet regime; however, the data presented here suggest that the effects of surface layer stagnation may be of greater practical importance. Since the aforestated conclusions are based on time series of rather limited duration, the reader is cautioned as to uncertainty associated with the climatological frequency of events as described herein. Furthermore, the authors have not examined external forcings, which may be associated with large-scale circulations."
"7006095466;7103119050;7201783608;7004160585;7202772927;","GEWEX Cloud System Study (GCSS) Working Group 4: Precipitating Convective Cloud Systems",1997,"10.1175/1520-0477(1997)078<0831:GCSSGW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031399069&doi=10.1175%2f1520-0477%281997%29078%3c0831%3aGCSSGW%3e2.0.CO%3b2&partnerID=40&md5=be0ed22364f3142adfaa5bed189d69d8","The authors present the objectives of the working group on precipitating convective cloud systems. These center on developing physically based parameterizations for global models in which basic research into the large-scale role of cloud systems is an important part. The approach calls on a range of expertise: cloud-resolving modeling and contributing research, observational evaluation of the model results, and tests of parameterizations in single-column models. Ongoing studies focus on oceanic cloud systems in Tropical Oceans Global Atmosphere Coupled Ocean-Atmosphere Research Experiment (TOGA COARE). First, cloud-resolving modeling of organized convection on a timescale of a few hours concentrates on momentum transport and surface fluxes. Results are evaluated against data obtained during the 22 February 1993 Intensive Observation Period, which include airborne Doppler radar measurements of a squall line. Second, multiday simulations focus on the environmental effects of cloud systems as they respond to changes in specified (observed) large-scale tendencies and sea surface temperature. In this case, observational data on the scale of the entire TOGA COARE Intensive Flux Array are used in model evaluations. Results and recommendations from the first model intercomparison workshop, as well as the next steps in the intercomparison, are summarized. In the longer term, cloud system research in Working Group 4 will contribute to the Climate Variability and Predictability-Global Ocean-Atmosphere-Land System program, as regards the large-scale effects of cloud systems up to intraseasonal timescales. Another contribution will be to space-borne measurements; for example, cloud-profiling capability will provide data critical to the comprehensive evaluation of upper-tropospheric moisture distribution in cloud-resolving models. Besides additional studies in tropical cloud systems, convection in cold air outbreaks and convection over continents have a high priority."
"26536569500;7005702722;","Do undiluted convective plumes exist in the upper tropical troposphere?",2010,"10.1175/2009JAS3184.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953248803&doi=10.1175%2f2009JAS3184.1&partnerID=40&md5=29f4e7e724d6058f3c2e982fba7b0c0a","Using a passive tracer, entrainment is studied in cloud-resolving simulations of deep convection in radiative-convective equilibrium. It is found that the convective flux of undiluted parcels decays with height exponentially, indicating a constant probability per vertical distance of mixing with environmental air. This probability per distance is sufficiently large that undiluted updrafts are negligible above a height of 4-5 km and virtually absent above 10 km. These results are shown to be independent of the horizontal grid size within the range of 3.2 km to 100 m. Plumes that do reach the tropopause are found to be highly diluted. An equivalent potential temperature is defined that is exactly conserved for all reversible adiabatic transformations, including those with ice. Using this conserved variable, it is shown that the latent heat of fusion (from both freezing and deposition) causes only a small increase in the level of neutral buoyancy near the tropopause. In fact, when taken to sufficiently low pressures, a parcel with an ice phase ends up colder than it would without an ice phase. Nevertheless, the contribution from fusion to a parcel's kinetic energy is quite large. Using an ensemble of tracers, information is encoded in parcels at the cloud base and decoded where the parcel is observed in the free troposphere. Using this technique, clouds at the tropopause are diagnosed for their cloud-base temperature, specific humidity, and vertical velocity. Using these as the initial values for a Lagrangian parcel model, it is shown that fusion provides the kinetic energy required for diluted parcels to reach the tropopause. © 2010 American Meteorological Society."
"57217923852;7006184606;","The effects of vertical wind shear on radiative-convective equilibrium states",2001,"10.1175/1520-0469(2001)058<1427:TEOVWS<2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035359799&doi=10.1175%2f1520-0469%282001%29058%3c1427%3aTEOVWS%3c2.0.CO%3b2&partnerID=40&md5=5a6abc14a1734c28af4b0be977268a23","Using a three-dimensional cloud ensemble model, a systematic exploration is undertaken of radiative-convective equilibrium states as a function of the structure and magnitude of an imposed background flow with vertical shear. In such simulations, mesoscale organization appears naturally, independent of the particulars of the initial condition. As the magnitude of an imposed low-level shear increases, the convection becomes increasingly organized in lines or arcs, propagating broadly downshear, as predicted by earlier work. When the shear is very strong, the convection tends to organize into lines at an angle to the shear, such that the line-normal component is not far from its theoretical optimal value. Midlevel shear favors shear-parallel lines, but if it occurs in conjunction with sufficiently strong low-level shear, the convection can become very strongly organized into lines or arcs generally orthogonal to the low-level shear. Optimal organization occurs when the depth of the shear layer is comparable to that of the cold pools associated with the convective downdrafts. As the vertical shear is increased, the domain-averaged convective available potential energy (CAPE) at first increases but then decreases at stronger shear values. Associated with these changes, the lower to middle troposphere becomes drier at low shear values and more humid when the shear is strong. This relationship between humidity and CAPE is broadly consistent with recently developed CAPE theories. The authors also confirm previous work that shows that the transport of momentum by the simulated convection, though usually down the gradient of the background flow, is nonlocal in character. Finally, some simulations are performed with an imposed hodograph taken from a tropical cyclone. Convective arcs form with an orientation similar to observed outer spiral bands, but the simulated bands propagate more rapidly than observed, perhaps because of a dry middle troposphere in the simulations."
"7006738371;7101952183;","Thermal Structure of Uranus' Atmosphere",1999,"10.1006/icar.1998.6071","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033107498&doi=10.1006%2ficar.1998.6071&partnerID=40&md5=be5d459fa60bef4d16594122a844db40","Application of a radiative-convective equilibrium model to the thermal structure of Uranus'atmosphere evaluates the role of hazes in the planet's stratospheric energy budget and places a lower limit on the internal energy flux. The model is constrained by Voyager and post-Voyager observations of the vertical aerosol and radiatively active gas profiles. Our baseline model generally reproduces the observed tropospheric and stratospheric temperature profile. However, as in past studies, the model stratosphere from about 10-3to 10-1bar is too cold. We find that the observed stratospheric hazes do not warm this region appreciably and that any postulated hazes capable of warming the stratosphere sufficiently are inconsistent with Voyager and ground-based constraints. We explore the roles played by the stratospheric methane abundance, the H2pressure-induced opacity, photochemical hazes, and C2H2and C2H6in controlling the temperature structure in this region. Assuming a vertical methane abundance profile consistent with that found by the Voyager UVS occultation observations, the model upper stratosphere, from 10 to 100μbar, is also too cold. Radiation in the 7.8-μm band from a small abundance of hot methane in the lower thermosphere absorbed in this region can warm the atmosphere and bring models into closer agreement with observations. Finally, we find that internal heat fluxes 60 erg cm-2sec-1are inconsistent with the observed tropospheric temperature profile. © 1999 Academic Press."
"7006184606;16644246500;54995785000;","Radiative-convective instability",2014,"10.1002/2013MS000270","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899097230&doi=10.1002%2f2013MS000270&partnerID=40&md5=d4ca3891ff2a63b723f9fe326d72bf2a","Radiative-moist-convective equilibrium (RCE) is a simple paradigm for the statistical equilibrium the earth's climate would exhibit in the absence of lateral energy transport. It has generally been assumed that for a given solar forcing and long-lived greenhouse gas concentration, such a state would be unique, but recent work suggests that more than one stable equilibrium may be possible. Here we show that above a critical specified sea surface temperature, the ordinary RCE state becomes linearly unstable to large-scale overturning circulations. The instability migrates the RCE state toward one of the two stable equilibria first found by Raymond and Zeng (2000). It occurs when the clear-sky infrared opacity of the lower troposphere becomes so large, owing to high water vapor concentration, that variations of the radiative cooling of the lower troposphere are governed principally by variations in upper tropospheric water vapor. We show that the instability represents a subcritical bifurcation of the ordinary RCE state, leading to either a dry state with large-scale descent, or to a moist state with mean ascent; these states may be accessed by finite amplitude perturbations to ordinary RCE in the subcritical state, or spontaneously in the supercritical state. As first suggested by Raymond (2000) and Sobel et al. (2007), the latter corresponds to the phenomenon of self-aggregation of moist convection, taking the form of cloud clusters or tropical cyclones. We argue that the nonrobustness of self-aggregation in cloud system resolving models may be an artifact of running such models close to the critical temperature for instability. Key Points Radiative-convective equilibrium becomes unstable at high temperature ©2013. American Geophysical Union. All Rights Reserved."
"7006095466;7003278104;16441664100;57195139224;7004563395;36664254400;","Multiscale convective organization and the YOTC virtual global field campaign",2012,"10.1175/BAMS-D-11-00233.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84866382215&doi=10.1175%2fBAMS-D-11-00233.1&partnerID=40&md5=f12f8cd779a2fe12bdb975a2ed542376","The Year of Tropical Convection (YOTC) project recognizes that major improvements are needed in how the tropics are represented in climate models. Tropical convection is organized into multiscale precipitation systems with an underlying chaotic order. These organized systems act as building blocks for meteorological events at the intersection of weather and climate (time scales up to seasonal). These events affect a large percentage of the world's population. Much of the uncertainty associated with weather and climate derives from incomplete understanding of how meteorological systems on the mesoscale (~1-100 km), synoptic scale (~1,000 km), and planetary scale (~10,000 km) interact with each other. This uncertainty complicates attempts to predict high-impact phenomena associated with the tropical atmosphere, such as tropical cyclones, the Madden-Julian oscillation, convectively coupled tropical waves, and the monsoons. These and other phenomena influence the extratropics by migrating out of the tropics and by the remote effects of planetary waves, including those generated by the MJO. The diurnal and seasonal cycles modulate all of the above. It will be impossible to accurately predict climate on regional scales or to comprehend the variability of the global water cycle in a warmer world without comprehensively addressing tropical convection and its interactions across space and time scales. ©2012 American Meteorological Society."
"7409953339;57203054708;7103119050;","The macroscopic behavior of cumulus ensembles simulated by a cumulus ensemble model",1992,"10.1175/1520-0469(1992)049<2402:tmboce>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027086190&doi=10.1175%2f1520-0469%281992%29049%3c2402%3atmboce%3e2.0.co%3b2&partnerID=40&md5=0084f9e14d84fd12035cb342cdb5d9b4","In all simulations, cumulus convection is rather strongly modulated by large-scale advective processes in spite of the existence of some nonmodulated high-frequency fluctuations. The modulation exhibits some phase delays, however, when the basic wind shear is strong. This is presumably associated with the existence of mesoscale convective organization. The EKE budget analysis shows that the net eddy buoyancy generation rate is nearly zero for a wide range of cumulus ensembles. -from Authors"
"7004978125;6602424416;","Models for stratiform instability and convectively coupled waves",2001,"10.1175/1520-0469(2001)058<1567:MFSIAC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035875631&doi=10.1175%2f1520-0469%282001%29058%3c1567%3aMFSIAC%3e2.0.CO%3b2&partnerID=40&md5=e5ad7dfd053a9727ba8e0b05d87175c9","A simplified intermediate model for analyzing and parameterizing convectively coupled tropical waves is introduced here. This model has two baroclinic modes of vertical structure: a direct heating mode and a stratiform mode. The key essential parameter in these models is the area fraction occupied by deep convection, σc. The unstable convectively coupled waves that emerge from perturbation of a radiative convective equilibrium are discussed in detail through linearized stability analysis. Without any mean flow, for an overall cooling rate of 1 K day-1 as the area fraction parameter increases from σc = 0.0010 to σc = 0.0014 the waves pass from a regime with stable moist convective damping to a regime of ""stratiform"" instability with convectively coupled waves propagating at speeds of roughly 15 m s-1; instabilities for a band of wavelengths in the supercluster regime, O(1000)-O(2000) km: and a vertical structure with a ""wave tilt"" where the temperature structure in the upper troposphere lags behind that in the lower troposphere. Thus, these convectively coupled waves in the model reproduce several key features of convectively coupled waves in the troposphere processed from recent observational data by Wheeler and Kiladis. As the parameter σc is increased further to values such as σc = 0.01, the band of unstable waves increases and spreads toward a mesoscale wavelength of O(100) km while the same wave structure and quantitative features mentioned above are retained for O(1000) km. A detailed analysis of the temporal development of instability of these convectively coupled waves is presented here. In the first stage of instability, a high convective available potential energy (CAPE) region generates deep convection and a front-to-rear ascending flow with enhanced vertical shear in a stratiform wake region. Thus, these intermediate models may be useful prototypes for studying the parameterization of upscale convective momentum transport due to organized convection. In the second stage of instability, detailed analysis of the CAPE budget establishes that the effects of the second baroclinic mode in the stratiform wake produce new CAPE, which regenerates the first half of the wave cycle. Finally, since these convectively coupled stratiform waves do not require a barotropic mean flow, a barotropic mean flow, which alters the surface fluxes, is added to study its effect on their stability. These effects of a barotropic mean flow are secondary; an easterly mean flow enhances instability of the eastward-propagating convectively coupled waves and diminishes the instability of the westward-propagating waves through a wind-induced surface heat exchange mechanism."
"56272964700;35509639400;","What favors convective aggregation and why?",2015,"10.1002/2015GL064260","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938150157&doi=10.1002%2f2015GL064260&partnerID=40&md5=da978a7d9f99816a1314c97c199fb6f1","The organization of convection is ubiquitous, but its physical understanding remains limited. One particular type of organization is the spatial self-aggregation of convection, taking the form of cloud clusters, or tropical cyclones in the presence of rotation. We show that several physical processes can give rise to self-aggregation and highlight the key features responsible for it, using idealized simulations. Longwave radiative feedbacks yield a ""radiative aggregation."" In that case, sufficient spatial variability of radiative cooling rates yields a low-level circulation, which induces the upgradient energy transport and radiative-convective instability. Not only do vertically integrated radiative budgets matter but the vertical profile of cooling is also crucial. Convective aggregation is facilitated when downdrafts below clouds are weak (""moisture-memory aggregation""), and this is sufficient to trigger aggregation in the absence of longwave radiative feedbacks. These results shed some light on the sensitivity of self-aggregation to various parameters, including resolution or domain size. Key Points Longwave radiative feedbacks can trigger a radiative aggregation The vertical profile of radiative cooling is crucial for self-aggregation Conditions favoring weak downdrafts can trigger a moisture-memory aggregation. © 2015. American Geophysical Union. All Rights Reserved."
"55436842300;7003656857;6603566335;57193882808;","Influence of the subcloud layer on the development of a deep convective ensemble",2012,"10.1175/JAS-D-11-0317.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867951271&doi=10.1175%2fJAS-D-11-0317.1&partnerID=40&md5=6577e7b7816578e0902d6ce7839a7204","The rapid transition from shallow to deep convection is investigated using large-eddy simulations. The role of cold pools, which occur due to the evaporation of rainfall,is explored using a series of experiments in which their formation is suppressed.A positive feedback occurs: the presence of cold pools promotes deeper, wider, and more buoyant clouds with higher precipitation rates, which in turn lead to stronger cold pools. To assess the influence of the subcloud layer on the development of deep convection, the coupling between the cloud layer and the subcloud layer is explored using Lagrangian particle trajectories. As shown in previous studies,particles that enter clouds have properties that deviate significantly from the mean state. However, the differences between particles that enter shallow and deep clouds are remarkably small in the subcloud layer, and become larger in the cloud layer, indicating different entrainment rates. The particles that enter the deepest clouds also correspond to the widest cloud bases, which points to the importance of convective organization within the subcloud layer. © 2012 American Meteorological Society."
"6603263640;7005808242;","Entropy budget of an atmosphere in radiative-convective equilibrium. Part II: Latent heat transport and moist processes",2002,"10.1175/1520-0469(2002)059<0140:EBOAAI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036322275&doi=10.1175%2f1520-0469%282002%29059%3c0140%3aEBOAAI%3e2.0.CO%3b2&partnerID=40&md5=a2b4ca63464946794c37827296fc77b7","In moist convection, atmospheric motions transport water vapor from the earth's surface to the regions where condensation occurs. This transport is associated with three other aspects of convection: the latent heat transport, the expansion work performed by water vapor, and the irreversible entropy production due to diffusion of water vapor and phase changes. An analysis of the thermodynamic transformations of atmospheric water yields what is referred to as the entropy budget of the water substance, providing a quantitative relationship between these three aspects of moist convection. The water vapor transport can be viewed as an imperfect heat engine that produces less mechanical work than the corresponding Carnot cycle because of diffusion of water vapor and irreversible phase changes. The entropy budget of the water substance provides an alternative method of determining the irreversible entropy production due to phase changes and diffusion of water vapor. This method has the advantage that it does not require explicit knowledge of the relative humidity or of the molecular flux of water vapor for the estimation of the entropy production. Scaling arguments show that the expansion work of water vapor accounts for a small fraction of the work that would be produced in the absence of irreversible moist processes. It is also shown that diffusion of water vapor and irreversible phase changes can be interpreted as the irreversible counterpart to the continuous dehumidification resulting from condensation and precipitation. This leads to a description of moist convection where it acts more as an atmospheric dehumidifier than as a heat engine."
"7403672902;","Response of simulated squall lines to low-level cooling",2008,"10.1175/2007JAS2507.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45849125794&doi=10.1175%2f2007JAS2507.1&partnerID=40&md5=2a53e506460cc1c519ca4f2204d6ac8a","Organized convection has long been recognized to have a nocturnal maximum over the central United States. The present study uses idealized numerical simulations to investigate the mechanisms for the maintenance, propagation, and evolution of nocturnal-like convective systems. As a litmus test for the basic governing dynamics, the experiments use horizontally homogeneous initial conditions (i.e., they include neither fronts nor low-level jet streams). The simulated storms are allowed to mature as surface-based convective systems before the boundary layer is cooled. In this case it is then surprisingly difficult to cut the mature convective systems off from their source of near-surface inflow parcels. Even when 10 K of the low-level cooling has been applied, the preexisting system cold pool is sufficient to lift boundary layer parcels to their levels of free convection. The present results suggest that many of the nocturnal convective systems that were previously thought to be elevated may actually be surface based. With additional cooling, the simulated systems do, indeed, become elevated. First, the CAPE of the near-surface air goes to zero: second, as the cold pool's temperature deficit vanishes, the lifting mechanism evolves toward a bore atop the nocturnal inversion. Provided that air above the inversion has CAPE, the system then survives and begins to move at the characteristic speed of the bore. Interestingly, as the preconvective environment is cooled and approaches the temperature of the convective outflow, but before the system becomes elevated, yet another distinct behavior emerges. The comparatively weaker cold pool entails slower system motion but also more intense lifting, apparently because it is more nearly balanced by the lower-tropospheric shear. This could explain the frequent observation of intensifying convective systems in the evening hours without the need for a nocturnal low-level jet. The governing dynamics of the simulated systems, as well as the behavior of low-level tracers and parcel trajectories, are addressed for a variety of environments and degrees of stabilization. © 2008 American Meteorological Society."
"7003406400;","The impact of dimensionality on long-term cloud-resolving model simulations",2000,"10.1175/1520-0493(2000)128<1521:TIODOL>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033926625&doi=10.1175%2f1520-0493%282000%29128%3c1521%3aTIODOL%3e2.0.CO%3b2&partnerID=40&md5=edff9302db96c8252597f1d0a17ad039","Cloud-resolving model simulations of radiative-convective equilibrium are conducted in both two and three dimensions (2D and 3D) to examine the effect of dimensionality on the equilibrium statistics. Convection is forced by a fixed imposed profile of radiative cooling and surface fluxes from fixed temperature ocean. In the control experiment, using the same number of grid points in both 2D and 3D and a zero mean wind, the temperature and moisture profiles diverge considerably after a few days of simulations. Two mechanisms are shown to be responsible for this. First, 2D geometry causes higher perturbation surface winds resulting from deep convective downdrafts, which lead to a warmer, moister boundary layer and a warmer tropospheric mean temperature state. Additionally, 2D geometry encourages spontaneous large-scale organization, in which areas far away from convection become very dry and thus inhibit further convection there, leading to a drier mean atmosphere. Further experiments were conducted in which horizontal mean winds were applied, adopting both constant and sheared vertical profiles. With mean surface winds that are of the same magnitude as downdraft outflow velocities or greater, convection can no longer increase mean surface fluxes, and the temperature differences between 2D and 3D are greatly reduced. However, the organization of convection still exists with imposed wind profiles. Repeating the experiments on a small 2D domain produced similar equilibrium profiles to the 3D investigations, since the limited domain artificially reduces surface wind speeds, and also restricts mesoscale organization. The main conclusions are that for modeling convection that is highly two-dimensionally organized, such as squall lines or Walker-type circulations over strong SST gradients, and for which a reasonable mean surface wind exists, it is possible that a 2D model can be used. However, for random or clustered convection, and especially in low wind environments, it is highly preferable to use a 3D cloud model."
"8701353900;24173130300;57205867148;7201504886;","Large-eddy simulation of the transient and near-equilibrium behavior of precipitating shallow convection",2015,"10.1002/2015MS000489","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950291715&doi=10.1002%2f2015MS000489&partnerID=40&md5=1deb7085fab0cafdfb4694b2bf853a2e","Large-eddy simulation is used to study the sensitivity of trade wind cumulus clouds to perturbations in cloud droplet number concentrations. We find that the trade wind cumulus system approaches a radiative-convective equilibrium state, modified by net warming and drying from imposed large-scale advective forcing. The system requires several days to reach equilibrium when cooling rates are specified but much less time, and with less sensitivity to cloud droplet number density, when radiation depends realistically on the vertical distribution of water vapor. The transient behavior and the properties of the near-equilibrium cloud field depend on the microphysical state and therefore on the cloud droplet number density, here taken as a proxy for the ambient aerosol. The primary response of the cloud field to changes in the cloud droplet number density is deepening of the cloud layer. This deepening leads to a decrease in relative humidity and a faster evaporation of small clouds and cloud remnants constituting a negative lifetime effect. In the near-equilibrium regime, the decrease in cloud cover compensates much of the Twomey effect, i.e., the brightening of the clouds, and the overall aerosol effect on the albedo of the organized precipitating cumulus cloud field is small. © 2015. The Authors."
"35435635000;7102101132;8285351400;7410290189;","Asymmetric and axisymmetric dynamics of tropical cyclones",2013,"10.5194/acp-13-12299-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890153637&doi=10.5194%2facp-13-12299-2013&partnerID=40&md5=0b4715b6b51cb676d8ae3528d1aed438","We present the results of idealized numerical experiments to examine the difference between tropical cyclone evolution in three-dimensional (3-D) and axisymmetric (AX) model configurations. We focus on the prototype problem for intensification, which considers the evolution of an initially unsaturated AX vortex in gradient-wind balance on an f plane. Consistent with findings of previous work, the mature intensity in the 3-D model is reduced relative to that in the AX model. In contrast with previous interpretations invoking barotropic instability and related horizontal mixing processes as a mechanism detrimental to the spin-up process, the results indicate that 3-D eddy processes associated with vortical plume structures can assist the intensification process by contributing to a radial contraction of the maximum tangential velocity and to a vertical extension of tangential winds through the depth of the troposphere. These plumes contribute significantly also to the azimuthally averaged heating rate and the corresponding azimuthal-mean overturning circulation. The comparisons show that the resolved 3-D eddy momentum fluxes above the boundary layer exhibit counter-gradient characteristics during a key spin-up period, and more generally are not solely diffusive. The effects of these eddies are thus not properly represented by the subgrid-scale parameterizations in the AX configuration. The resolved eddy fluxes act to support the contraction and intensification of the maximum tangential winds. The comparisons indicate fundamental differences between convective organization in the 3-D and AX configurations for meteorologically relevant forecast timescales. While the radial and vertical gradients of the system-scale angular rotation provide a hostile environment for deep convection in the 3-D model, with a corresponding tendency to strain the convective elements in the tangential direction, deep convection in the AX model does not suffer this tendency. Also, since during the 3-D intensification process the convection has not yet organized into annular rings, the azimuthally averaged heating rate and radial gradient thereof is considerably less than that in the AX model. This lack of organization results broadly in a slower intensification rate in the 3-D model and leads ultimately to a weaker mature vortex after 12 days of model integration. While azimuthal mean heating rates in the 3-D model are weaker than those in the AX model, local heating rates in the 3-D model exceed those in the AX model and at times the vortex in the 3-D model intensifies more rapidly than AX. Analyses of the 3-D model output do not support a recent hypothesis concerning the key role of small-scale vertical mixing processes in the upper-tropospheric outflow in controlling the intensification process. In the 3-D model, surface drag plays a particularly important role in the intensification process for the prototype intensification problem on meteorologically relevant timescales by helping foster the organization of convection in azimuth. There is a radical difference in the behaviour of the 3-D and AX simulations when the surface drag is reduced or increased from realistic values. Borrowing from ideas developed in a recent paper, we give a partial explanation for this difference in behaviour. Our results provide new qualitative and quantitative insight into the differences between the asymmetric and symmetric dynamics of tropical cyclones and would appear to have important consequences for the formulation of a fluid dynamical theory of tropical cyclone intensification and mature intensity. In particular, the results point to some fundamental limitations of strict axisymmetric theory and modelling for representing the azimuthally averaged behaviour of tropical cyclones in three dimensions. © Author(s) 2013."
"7003848718;","Roll and cell convection in wintertime arctic cold-air outbreaks",1999,"10.1175/1520-0469(1999)056<2613:RACCIW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0345201754&doi=10.1175%2f1520-0469%281999%29056%3c2613%3aRACCIW%3e2.0.CO%3b2&partnerID=40&md5=863cc27bfbd3b6e5a1d18418f07525ec","Cold-air outbreaks from the polar ice caps or winterly continents over the open ocean lead to organized convection that typically starts as longitudinal roll patterns and changes to cellular patterns in downstream direction. During the field experiments ARKTIS 1991 and ARKTIS 1993, aircraft missions were conducted in 13 cold-air outbreak events over the Greenland and Barents Seas to determine the characteristic parameters of both the mean (primary) flow and the superimposed organized convection (secondary flow). The measurements are classified into four categories with respect to the convective pattern form: longitudinal rolls with small and wider horizontal wavelengths, transitional forms between rolls and cells, and cells. Rolls were observed for boundary layer depths h &lt; 1 km with horizontal wavelengths λ &lt; 5 km and aspect ratios λ/h between 2.6 and 6.5. Distinct cellular structures occurred for h &gt; 1.4 km with λ &gt; 8 km and λ/h between 4 and 12. The amplitudes of the secondary flow-scale variations of the temperature θ(R), moisture m(R), and the longitudinal, u(R); transversal, v(R); and vertical, w(R), wind components were on the order of 0.1-0.4 K, 0.03-0.30 g kg-1, 0.6-2.5 m s-1, 0.8-2.5 m s-1, and 0.4-1.8 m s-1, respectively, generally increasing from the roll to the cell region. The same is true for the ratio u(R)/v(R) (from about 0.6 to nearly 1) and for the ratio Lm(R)/c(P)θ(R) (from 0.7 to more than 2), hinting at increasing importance of moisture processes in the cell compared to the roll region. The importance of the secondary-flow transports of heat and momentum in relation to the total vertical transports increases with height and from rolls to cells. Particularly clear is the vertical profile of the vertical moisture transport m(R)w(R), which exhibits a maximum around cloud base and is on the average related to the surface moisture flux as (m(R)w(R))(max) = 0.35(m'w')(o). The thermodynamic conditions of the basic flow are characterized by the Rayleigh number Ra, the stability of the capping inversion, and the net condensation rate in the cloud layer. Here Ra is clearly overcritical in the whole cold-air outbreak region; it is around 105 in the roll region and around 2 X 106 in the cell region. The Monin-Obukhov stability parameter does not appear to be suitable measure to distinguish between roll and cell convection. The stability above the boundary layer is about two to three times larger for rolls than for cells. The net condensation in clouds is three times larger in cell than in roll regions and the resulting heating of the boundary layer exceeds that of the surface heat flux in the cell region. The kinematic conditions of the basic flow are characterized by a larger shear of the longitudinal wind component u in the roll than in the cell region. The curvature of the u profile is mostly overcritical in rolls and always subcritical in cells. The secondary flow-scale kinetic energy E(kin,R) is related to Ra. The best least squares fit is given by E(kin,R) = 3.7Ra0.4.Cold-air outbreaks from the polar ice caps or winterly continents over the open ocean lead to organized convection that typically starts as longitudinal roll patterns and changes to cellular patterns in dowstream direction. This article discusses the ARKTIS 1991 and ARKTIS 1993 field experiments where aircraft missions were conducted in 13 cold-air outbreak events over the Greenland and Barents Seas to determine the characteristic parameters of both the mean flow and the superimposed organized convection. The measurements are classified into four categories with respect to the convective pattern form: longitudinal rolls with small and wider horizontal wavelengths, transitional forms between rolls and cells, and cells."
"56522444900;7101790869;14822021400;","Rainfall types in the West African Sudanian zone during the summer monsoon 2002",2006,"10.1175/MWR3182.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33747785609&doi=10.1175%2fMWR3182.1&partnerID=40&md5=806f3b19cd16358b70867e27f194de75","Enhanced surface and upper-air observations from the field campaign of the Integrated Approach to the Efficient Management of Scarce Water Resources in West Africa (IMPETUS) project are used to partition rainfall amounts over the West African Sudanian zone during the 2002 summer monsoon season into several characteristic types and subtypes of precipitating systems. The most prominent rainfall subtype was fast-moving, long-lived, and extensive cloud clusters that often developed far upstream over the central Nigerian highlands in the afternoon hours and arrived at the Upper Ouémé Valley (UOV) after midnight. These organized convective systems (advective OCSs, subtype Ia) accounted for 50% of the total rain amount in the UOV catchment in Benin. Subtypes Ia and IIa (i.e., locally developing OCSs) were found to pass by or organize when a highly sheared environment with deep and dry midtropospheric layers was present over the UOV. These systems were most frequent outside the peak of the monsoon season. The second major type of organized convection, termed mesoscale convective systems (subtypes Ib, IIb, and IIIb) in the present study, contributed 26% to the annual UOV precipitation. They occurred in a less-sheared and moister tropospheric environment mainly around the height of the rainy season. A third distinct class of rainfall events occurred during an unusual synoptic situation in which a cyclonic vortex to the north of the UOV led to deep westerly flow. During these periods, the African easterly jet was lacking. The so-called vortex-type rainfalls (subtypes IIIa, IIIb, and IIIc) contributed about 9% to the annual rainfall totals. © 2006 American Meteorological Society."
"55932195300;8696069500;28367935500;","Robust increase in equilibrium climate sensitivity under global warming",2013,"10.1002/2013GL058118","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84887879771&doi=10.1002%2f2013GL058118&partnerID=40&md5=3e4164aa83628c138cd2e00b8426dd88","Equilibrium climate sensitivity (ECS) is a widely accepted measure of Earth's susceptibility to radiative forcing. While ECS is often assumed to be constant to a first order of approximation, recent studies suggested that ECS might depend on the climate state. Here it is shown that the latest generation of climate models consistently exhibits an increasing ECS in warmer climates due to a strengthening of the water-vapor feedback with increasing surface temperatures. The increasing ECS is replicated by a one-dimensional radiative-convective equilibrium model, which further shows that the enhanced water-vapor feedback follows from the rising of the tropopause in a warming climate. This mechanism is potentially important for understanding both warm climates of Earth's past and projections of future high-emission scenarios."
"6507400558;7004978125;","Multicloud models for organized tropical convection: Enhanced congestus heating",2008,"10.1175/2007JAS2408.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43149088061&doi=10.1175%2f2007JAS2408.1&partnerID=40&md5=6f73bb8a774038f16896c99ebe6ebea0","Despite the recent advances in supercomputing, the current general circulation models (GCMs) poorly represent the large-scale variability associated with tropical convection. Multicloud model convective parameterizations based on three cloud types (congestus, deep, and stratiform), introduced recently by the authors, have been revealed to be very useful in representing key features of organized convection and convectively coupled waves. Here a new systematic version of the multicloud models is developed with separate upper- and lower-troposphere basis functions for the congestus and stratiform clouds. It naturally leads to a new convective closure for the multicloud models enhancing the congestus heating in order to better pinpoint the congestus preconditioning and moistening mechanisms. The models are studied here for flows above the equator without rotation effects. First, the new model results consist of the usual synopticscale convectively coupled moist gravity wave packets moving at 15-20 m s-1 but, in addition, these packets have planetary-scale envelopes moving in the opposite direction at about 6 m s-1 and have many of the self-similar features of convectively coupled waves, reminiscent of the Madden-Julian oscillation. Second, when a warm pool forcing is imposed, dry regions of roughly 250 km in extent form ""convective barriers"" surrounding the warm pool region where only congestus heating survives. Deep convection and moist gravity waves are thus confined within the warm pool region. Finally, linear analysis reveals that, for sufficiently dry mean states, in addition to the inherent synoptic-scale moist gravity waves, the new model supports a planetary (wavenumber 1) standing congestus mode that provides, within its congestus active phase, a region where moist gravity waves evolve and propagate, which results in a Walker-like circulation over a uniform SST background. © 2008 American Meteorological Society."
"56575724100;","Thermodynamic aspects of tropical cyclone formation",2012,"10.1175/JAS-D-11-0298.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867972799&doi=10.1175%2fJAS-D-11-0298.1&partnerID=40&md5=f2606435e47c80202835108d699d3dba","The thermodynamic aspects of tropical cyclone (TC) formation near the center of the wave pouch, a region of approximately closed Lagrangian circulation within the wave critical layer, are examined through diagnoses of a high-resolution numerical simulation and dropsonde data from a recent field campaign. It is found that the meso-b area near the pouch center is characterized by high saturation fraction, small difference in equivalent potential temperature Θ e between the surface and the middle troposphere, and a short incubation time scale. Updrafts tend to be more vigorous in this region, presumably because of reduced dry air entrainment, while downdrafts are not suppressed. The thermodynamic conditions near the pouch center are thus critically important for TC formation. The balanced responses to convective and stratiform heating at the pregenesis stage are examined using the Sawyer-Eliassen equation. Deep convection is concentrated near the pouch center. The strong radial and vertical gradients of latent heat release effectively force the transverse circulation and spin up a surface protovortex near the pouch center. Stratiform heating induces modest midlevel inflow and very weak lowlevel outflow, which contributes to the midlevel spinup without substantially spinning down the low-level circulation. The analysis of dropsonde data shows that the midlevel Θ e increases significantly near the pouch center one to two days prior to genesis but changes little away from the pouch center. This may indicate convective organization and the impending TC genesis. It also suggests that the critical information of TC genesis near the pouch center may be masked out if a spatial average is taken over the pouch scale. © 2012 American Meteorological Society."
"7102718675;7003926380;","Defining Mesoscale Convective Systems by Their 85-GHz Ice-Scattering Signatures",1996,"10.1175/1520-0477(1996)077<1179:DMCSBT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030424650&doi=10.1175%2f1520-0477%281996%29077%3c1179%3aDMCSBT%3e2.0.CO%3b2&partnerID=40&md5=0b1f4125cd0a5a5820d0f07e8ec78e53","Mesoscale convective systems are composed of numerous deep convective cells with varying amounts of large, convectively produced ice particles aloft. The magnitude of the 85-GHz brightness temperature depression resulting from scattering by large ice is believed to be related to the convective intensity and to the magnitude of the convective fluxes through a deep layer. The 85-GHz ice-scattering signature can be used to map the distribution of organized mesoscale regions of convectively produced large ice particles. The purpose of this article is to demonstrate the usefulness of the 85-GHz ice-scattering signature for describing the frequency, convective intensity, and geographic distribution of mesoscale convective systems. Objective criteria were developed to identify mesoscale convective systems from raw data from January, April, July, and October 1993. To minimize the effects of background contamination and to ensure that bounded areas contained convective elements, a ""mesoscale convective system"" was defined as an area bounded by 250 K of at least 2000 km2 of 85 GHz, with a minimum brightness temperature ≤ 225 K. Mesoscale convective systems extracted from the raw data were sorted and plotted by their areas and by their minimum brightness temperatures. Four area and brightness temperature classes were used to account for a spectrum of organized convection ranging from small to very large and from less organized to highly organized. The populations of mesoscale convective systems by this study's definition were consistent with infrared-based climatologies and large-scale seasonal dynamics. Land/water differences were highlighted by the plots of minimum brightness temperature. Most of the intense mesoscale convective systems were located on or near land and seemed to occur most frequently in particular areas in North America, South America, Africa, and India."
"14012082000;7101867299;56284582200;7402579146;7401584839;","Mesoscale simulations of organized convection: Importance of convective equilibrium",2006,"10.1256/qj.04.84","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745017165&doi=10.1256%2fqj.04.84&partnerID=40&md5=44cf04d514030ecba51b1864b581289a","The validity of convective parametrization breaks down at the resolution of mesoscale models, and the success of parametrized versus explicit treatments of convection is likely to depend on the large-scale environment. In this paper we examine the hypothesis that a key feature determining the sensitivity to the environment is whether the forcing of convection is sufficiently homogeneous and slowly varying that the convection can be considered to be in equilibrium. Two case studies of mesoscale convective systems over the UK, one where equilibrium conditions are expected and one where equilibrium is unlikely, are simulated using a mesoscale forecasting model. The time evolution of area-average convective available potential energy and the time evolution and magnitude of the timescale of convective adjustment are consistent with the hypothesis of equilibrium for case 1 and non-equilibrium for case 2. For each case, three experiments are perfor med with different partitionings between parametrized and explicit convection: fully parametrized convection, fully explicit convection and a simulation with significant amounts of both. In the equilibrium case, bulk properties of the convection such as area-integrated rain rates are insensitive to the treatment of convection. However, the detailed structure of the precipitation field changes; the simulation with parametrized convection behaves well and produces a smooth field that follows the forcing region, and the simulation with explicit convection has a small number of localized intense regions of precipitation that track with the mid-level flow. For the non-equilibrium case, bulk properties of the convection such as area-integrated rain rates are sensitive to the treatment of convection. The simulation with explicit convection behaves similarly to the equilibrium case with a few localized precipitation regions. In contrast, the cumulus parametrization fails dramatically and develops intense propagating bows of precipitation that were not observed. The simulations with both parametrized and explicit convection follow the pattern seen in the other experiments, with a transition over the duration of the run from parametrized to explicit precipitation. The impact of convection on the large-scale flow, as measured by upper-level wind and potential-vorticity perturbations, is very sensitive to the partitioning of convection for both cases. © Royal Meteorological Society, 2006."
"16644246500;57210687618;","Self-aggregation of convection in long channel geometry",2016,"10.1002/qj.2628","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957801196&doi=10.1002%2fqj.2628&partnerID=40&md5=9202f62166457ca3283b0d45df06d465","Cloud cover and relative humidity in the Tropics are strongly influenced by organized atmospheric convection, which occurs across a range of spatial and temporal scales. One mode of organization that is found in idealized numerical modelling simulations is self-aggregation, a spontaneous transition from randomly distributed convection to organized convection despite homogeneous boundary conditions. We explore the influence of domain geometry on the mechanisms, growth rates and length-scales of self-aggregation of tropical convection. We simulate radiative-convective equilibrium with the System for Atmospheric Modeling (SAM), in a non-rotating, highly elongated three-dimensional (3D) channel domain of length &gt;104 km, with interactive radiation and surface fluxes and fixed sea-surface temperature varying from 280-310 K. Convection self-aggregates into multiple moist and dry bands across this full range of temperatures. As convection aggregates, we find a decrease in upper tropospheric cloud fraction but an increase in lower tropospheric cloud fraction; this sensitivity of clouds to aggregation agrees with observations in the upper troposphere but not in the lower troposphere. An advantage of the channel geometry is that a separation distance between convectively active regions can be defined; we present a theory for this distance based on boundary layer. We find that surface fluxes and radiative heating act as positive feedback mechanisms, favouring self-aggregation, but advection of moist static energy acts as a negative feedback, opposing self-aggregation, for nearly all temperatures and times. Early in the process of self-aggregation, surface fluxes are a positive feedback at all temperatures, shortwave radiation is a strong positive feedback at low surface temperatures but weakens at higher temperatures and longwave radiation is a negative feedback at low temperatures but becomes a positive feedback for temperatures greater than 295-300 K. Clouds contribute strongly to the radiative feedback, especially at low temperatures. © 2016 Royal Meteorological Society."
"35766145000;7006861646;","An algorithm for the detection and tracking of tropical mesoscale convective systems using infrared images from geostationary satellite",2013,"10.1109/TGRS.2012.2227762","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880268403&doi=10.1109%2fTGRS.2012.2227762&partnerID=40&md5=70d0f1380202f70de1555cad344246b5","This paper focuses on the tracking of mesoscale convective systems (MCS) from geostationary satellite infrared data in the tropical regions. In the past, several automatic tracking algorithms have been elaborated to tackle this problem. However, these techniques suffer from limitations in describing convection at the 'true' scale and in depicting coherent MCS life cycles (split and merge artifacts). To overcome these issues, a new algorithm called Tracking Of Organized Convection Algorithm through a 3-D segmentatioN has been developed and is presented in this paper. This method operates in a time sequence of infrared images to identify and track MCS and is based on an iterative process of 3-D segmentation of the volume of infrared images. The objective of the new tracking algorithm is to associate the convective core of an MCS to its anvil cloud in the spatiotemporal domain. The technique is applied on various case studies over West Africa, Bay of Bengal, and South America. The efficiency of the new algorithm is established from an analysis of the case studies and via a statistical analysis showing that the cold cloud shield defined by a 235-K threshold in the spatiotemporal domain is decomposed into realistic MCSs. In comparison with an overlap-based tracking algorithm, the analysis reveals that MCSs are detected earlier in life cycle and later in their dissipation stages. Moreover, MCSs identified are not anymore affected by split and merge events along their life cycles, allowing a better characterization of their morphological parameters along their life cycles. © 1980-2012 IEEE."
"6603263640;7103242280;","Sensitivity of radiative-convective equilibrium simulations to horizontal resolution",2006,"10.1175/JAS3705.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746889375&doi=10.1175%2fJAS3705.1&partnerID=40&md5=9caff240bd7ff5f9e9737a9e2933cd7c","This paper investigates the impacts of horizontal resolution on the statistical behavior of convection. An idealized radiative-convective equilibrium is simulated for model resolutions ranging between 2 and 50 km. The simulations are compared based upon the analysis of the mean state, the energy and water vapor transport, and the probability distribution functions for various quantities. It is shown that, at a coarse resolution, the model is unable to capture the mixing associated with shallow clouds. This results in a dry bias in the lower troposphere, and in an excessive amount of water clouds. Despite this deficiency, the coarse resolution simulations are able to reproduce reasonably well the statistical properties of deep convective towers. This is particularly apparent in the cloud ice and vertical velocity distributions that exhibit a very robust behavior. A theoretical scaling for the vertical velocity as function of the grid resolution is derived based upon the behavior of an idealized air bubble. It is shown that the vertical velocity of an ascending air parcel is determined by its aspect ratio, with a wide, flat parcel rising at a much slower pace than a narrow one. This theoretical scaling law exhibits a similar sensitivity to that of the numerical simulations. It is used to renormalize the probability distribution functions for vertical velocity, which show a very good agreement for resolutions up to 16 km. This new scaling law offers a way to improve direct simulations of deep convection in coarse resolution models. © 2006 American Meteorological Society."
"7003406400;7101867299;","Sensitivity of tropical convection to sea surface temperature in the absence of large-scale flow",1999,"10.1175/1520-0442(1999)012<0462:SOTCTS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033080089&doi=10.1175%2f1520-0442%281999%29012%3c0462%3aSOTCTS%3e2.0.CO%3b2&partnerID=40&md5=143927d62fdb4629672545071bd5cdee","The response of convection to changing sea surface temperature (SST) in the absence of large-scale flow is examined, using a three-dimensional cloud resolving model. The model includes a five-category bulk microphysical scheme representing snow, ice, graupel, rain, and cloud amounts in addition to an interactive radiation scheme for the shortwave and infrared. Long integrations are made to achieve a radiative-convective equilibrium state for SSTs of 298, 300, and 302 K, for which cloud and convection statistics are analyzed. The main conclusion of the paper is that, despite significant temperature sensitivities in many of the conversion terms between bulk water categories, convection is very insensitive to changing SST in the absence of large-scale flow. This is a result of the moist adiabatic temperature profile that the tropical atmosphere is constrained to take. A parcel of air rising through a deep convective cloud experiences approximately the same range of temperatures but at higher altitudes as SST increases. Thus the vertical profiles of cloud fraction and other cloud-related related statistics are simply shifted in height, but not changed in overall magnitude. The small changes in cloud properties that do occur lead to a small reduction in cloud fraction as SST increases. This appears to be due to an increase in graupel amounts with respect to snow, giving smaller cloud fractions since graupel has a higher fall velocity. The radiative effects of the changes in atmospheric properties are examined and it is found that the model atmosphere exhibits no supergreenhouse effect since atmospheric relative humidity is not altered significantly by the SST changes. The water vapor feedback effect is largely canceled by the change in temperature. Clouds have a negligibly small, but highly nonlinear, feedback in the model climate, in the absence of large-scale flow.The response of convection to changing sea surface temperature (SST) in the absence of large-scale flow is examined, using a three-dimensional cloud resolving model. The model includes a five-category bulk micro-physical scheme representing snow, ice, graupel, rain, and cloud amounts in addition to an interactive radiation scheme for the shortwave and infrared. Long integrations are made to achieve a radiative-convective equilibrium state for SSTs of 298, 300, and 302 K, for which cloud and convection statistics are analyzed. The main conclusion of the paper is that, despite significant temperature sensitivities in many of the conversion terms between bulk water categories, convection is very insensitive to changing SST in the absence of large-scale flow. This is a result of the moist adiabatic temperature profile that the tropical atmosphere is constrained to take. A parcel of air rising through a deep convective cloud experiences approximately the same range of temperatures but at higher altitudes as SST increases. Thus the vertical profiles of cloud fraction and other cloud-related statistics are simply shifted in height, but not changed in overall magnitude. The small changes in cloud properties that do occur lead to a small reduction in cloud fraction as SST increases. This appears to be due to an increase in graupel amounts with respect to snow, giving smaller cloud fractions since graupel has a higher fall velocity. The radiative effects of the changes in atmospheric properties are examined and it is found that the model atmosphere exhibits no supergreenhouse effect since atmospheric relative humidity is not altered significantly by the SST changes. The water vapor feedback effect is largely canceled by the change in temperature. Clouds have a negligibly small, but highly nonlinear, feedback in the model climate, in the absence of large-scale flow."
"55660926800;7201504886;28367935500;","Climate and climate change in a radiative-convective equilibrium version of ECHAM6",2013,"10.1029/2012MS000191","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876725239&doi=10.1029%2f2012MS000191&partnerID=40&md5=ed1ca72bf5ee40c74531b6324cf3683b","A radiative-convective equilibrium (RCE) configuration of a comprehensive atmospheric general circulation model, ECHAM6, is coupled to a mixed-layer ocean for the purpose of advancing understanding of climate and climate change. This configuration differs from a standard configuration only through the removal of land-surface processes, spatial gradients in solar insolation, and the effects of rotation. Nonetheless, the model produces a climate that resembles the tropical climate in a control simulation of Earth's atmosphere. In the RCE configuration, regional inhomogeneities in surface temperature develop. These inhomogeneities are transient in time but sufficiently long-lived to establish large-scale overturning circulations with a distribution similar to the preindustrial tropics in the standard configuration. The vertical structure of the atmosphere, including profiles of clouds and condensate conditioned on the strength of overturning, also resembles those produced by a control simulation of Earth's tropical atmosphere. The equilibrium climate sensitivity of the RCE atmosphere can explain 50% of the global climate sensitivity of a realistic configuration of ECHAM6. Part of the difference is attributed to the lack of polar amplification in RCE. The remainder appears to be related to a less positive cloud shortwave feedback, which results from an increase in low cloudiness with increasing surface temperatures in the RCE configuration. The RCE configuration shows an increase of climate sensitivity in a warmer climate. The increase in climate sensitivity scales with the degree to which the upper-troposphere temperature departs from a moist adiabat. © 2012. American Geophysical Union. All Rights Reserved."
"7006738371;35185383500;","On the cool side: Modeling the atmospheres of brown dwarfs and giant planets",2015,"10.1146/annurev-astro-082214-122522","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939789092&doi=10.1146%2fannurev-astro-082214-122522&partnerID=40&md5=a4793671f3e1c119078e675395056bcf","The atmosphere of a brown dwarf or extrasolar giant planet controls the spectrum of radiation emitted by the object and regulates its cooling over time. Although the study of these atmospheres has been informed by decades of experience modeling stellar and planetary atmospheres, the distinctive characteristics of these objects present unique challenges to forward modeling. In particular, complex chemistry arising from molecule-rich atmospheres, molecular opacity line lists (sometimes running to 10 billion absorption lines or more), multiple cloud-forming condensates, and disequilibrium chemical processes all combine to create a challenging task for any modeling effort. This review describes the process of incorporating these complexities into one-dimensional radiative-convective equilibrium models of substellar objects. We discuss the underlying mathematics as well as the techniques used to model the physics, chemistry, radiative transfer, and other processes relevant to understanding these atmospheres. The review focuses on methods for creating atmosphere models and briefly presents some comparisons of model predictions to data. Current challenges in the field and some comments on the future conclude the review. © 2015 by Annual Reviews."
"7006861646;6701751100;6506821155;7004160585;","Extratropical dry-air intrusions into the West African monsoon midtroposphere: An important factor for the convective activity over the Sahel",2005,"10.1175/JAS-3366.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14744291461&doi=10.1175%2fJAS-3366.1&partnerID=40&md5=525d9c9fa839e224bc458f558e70af88","This paper investigates the relationship between large-scale dynamics, water vapor, and organized convection over West Africa. Making use of a simplified condensation hypothesis, a back-trajectory model fed by NCEP-analyzed winds is used to reconstruct the midtropospheric humidity field over Africa during July to August 1992. The approach documents both the moisture content and the origin of the air masses. Meteosat satellite infrared imagery is used to characterize the convective systems. A case study analysis reveals that very dry air patches (RH < 5%) are located in the immediate midtropospheric environment of a typical squall line. Such dry-air structures are shown to originate in the upper levels (200-250 hPa) on the anticyclonic side of the polar jet stream at 50°N. Focusing on the Sahel region, dry events are isolated using the time series of the 500-hPa relative humidity distribution during the monsoon period. These dry events are shown to be composed of extratropical air. Composite analysis of the convective activity indicator exhibits a strong positive association between dry intrusions and convection on the eastern side of the Sahelian region. Organized convective systems that are fast moving and long lasting are more likely over this region when a dry intrusion is present. This coincides with the well-established theory that midtropospheric dry air, when combined with sufficient wind shear, can maintain and intensify previously triggered deep convection through rain evaporation that feeds the cold pools, especially within squall lines. This paper suggests that the extratropical dry-air intrusions modulate the occurrence and duration of convective systems and, therefore, the mode of variability of rainfall over West Africa during the monsoon. © 2005 American Meteorological Society."
"34881780600;6506328135;36868795400;37099564300;56583515100;8247122100;","Mechanisms of convective cloud organization by cold pools over tropical warm ocean during the AMIE/DYNAMO field campaign",2015,"10.1002/2014MS000384","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027952454&doi=10.1002%2f2014MS000384&partnerID=40&md5=8709ad51eeaf0dd28137b2ce2cb21759","This paper investigates the mechanisms of convective cloud organization by precipitation-driven cold pools over the warm tropical Indian Ocean during the 2011 Atmospheric Radiation Measurement (ARM) Madden-Julian Oscillation (MJO) Investigation Experiment/Dynamics of the MJO (AMIE/DYNAMO) field campaign. A high-resolution regional model simulation is performed using the Weather Research and Forecasting model during the transition from suppressed to active phases of the November 2011 MJO. The simulated cold pool lifetimes, spatial extent, and thermodynamic properties agree well with the radar and ship-borne observations from the field campaign. The thermodynamic and dynamic structures of the outflow boundaries of isolated and intersecting cold pools in the simulation and the associated secondary cloud populations are examined. Intersecting cold pools last more than twice as long, are twice as large, 41% more intense (measured with buoyancy), and 62% deeper than isolated cold pools. Consequently, intersecting cold pools trigger 73% more convection than do isolated ones. This is due to stronger outflows that enhance secondary updraft velocities by up to 45%. However, cold pool-triggered convective clouds grow into deep convection not because of the stronger secondary updrafts at cloud base, but rather due to closer spacing (aggregation) between clouds and larger cloud clusters that form along the cold pool boundaries when they intersect. The close spacing of large clouds moistens the local environment and reduces entrainment drying, increasing the probability that the clouds further develop into deep convection. Implications for the design of future convective parameterization with cold pool-modulated entrainment rates are discussed. Key Points: Intersecting cold pools trigger more clouds than isolated ones Intersecting cold pools produce larger clouds and closer spacing among them Larger clouds and closer spacing promote deeper convection © 2015. The Authors."
"14020840100;14018910800;7004909806;","Operational implementation of the 1D13D-Var assimilation method of radar reflectivity data in the AROME model",2014,"10.1175/MWR-D-13-00230.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899837110&doi=10.1175%2fMWR-D-13-00230.1&partnerID=40&md5=bed5390987439e30d3771b0406992375","This paper presents results from radar reflectivity data assimilation experiments with the nonhydrostatic limited-area model Application of Research to Operations at Mesoscale (AROME) in an operational context. A one-dimensional (1D) Bayesian retrieval of relative humidity profiles followed by a three-dimensional variational data assimilation (3D-Var) technique is adopted. Several preprocessing procedures of raw reflectivity data are presented and the use of the nonrainy signal in the assimilation is widely discussed and illustrated. This two-step methodology allows the authors to build up a screening procedure that takes into account the evaluation of the results from the 1D Bayesian retrieval. In particular, the 1D retrieval is checked by comparing a pseudoanalyzed reflectivity to the observed reflectivity. Additionally, a physical consistency between the reflectivity innovations and the 1D relative humidity increments is imposed before assimilating relative humidity pseudo-observations with other observations. This allows the authors to counteract the difficulty of the current 3D-Var system to correct strong differences between model and observed clouds from the crude specification of background-error covariances. Assimilation experiments of radar reflectivity data in a preoperational configuration are first performed over a 1-month period. Positive impacts on short-term precipitation forecast scores are systematically found. The evaluation shows improvements on the analysis and also on objective conventional forecast scores, in particular for the model wind field up to 12 h. A case study for a specific precipitating system demonstrates the capacity of the method for improving significantly short-term forecasts of organized convection. © 2014 American Meteorological Society."
"34979145900;","The moisture mode in the quasi-equilibrium tropical circulation model. Part I: Analysis based on the weak temperature gradient approximation",2009,"10.1175/2008JAS2690.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67650543176&doi=10.1175%2f2008JAS2690.1&partnerID=40&md5=781992b561561bb5abdf5373cde8c13a","The moisture mode in a simplified version of the quasi-equilibrium tropical circulation model (QTCM) of Neelin and Zeng is analyzed. Perturbation expansion based on the ratio of temperature tendency to adiabatic cooling simplifies the system and dispersion relationship. The weak temperature gradient (WTG) approximation of Sobel, Nilsson, and Polvani naturally emerges as the dynamical balance of the moisture mode. The condition of the expansion can be phrased in terms of the nondimensional wavenumber and is satisfied in the tropics even for the planetary scale. The WTG growth rate equation demonstrates that the moisture mode is unstable when moist static energy sources such as cloud radiative forcing and gustiness-enhanced evaporation exceed its export. Wind-induced surface heat exchange does not affect the growth rate at the leading order, although it propagates the mode eastward in the mean easterly wind. For typical values of parameters, the time scale of moisture mode instability is several days. Nonlinear WTG calculations show that the moisture mode nonlinearly saturates by a thermodynamic limiting process. In the standard parameter regime, a phase diagram reveals two stable fixed points in addition to the unstable solution of radiative-convective equilibrium. © 2009 American Meteorological Society."
"16644246500;7006184606;13411455700;56272964700;","Convective Self-Aggregation in Numerical Simulations: A Review",2017,"10.1007/s10712-017-9408-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85013472940&doi=10.1007%2fs10712-017-9408-4&partnerID=40&md5=526b611a236c74b90b24dd54658e2771","Organized convection in the tropics occurs across a range of spatial and temporal scales and strongly influences cloud cover and humidity. One mode of organization found is “self-aggregation,” in which moist convection spontaneously organizes into one or several isolated clusters despite spatially homogeneous boundary conditions and forcing. Self-aggregation is driven by interactions between clouds, moisture, radiation, surface fluxes, and circulation, and occurs in a wide variety of idealized simulations of radiative–convective equilibrium. Here we provide a review of convective self-aggregation in numerical simulations, including its character, causes, and effects. We describe the evolution of self-aggregation including its time and length scales and the physical mechanisms leading to its triggering and maintenance, and we also discuss possible links to climate and climate change. © 2017, Springer Science+Business Media Dordrecht."
"7102227540;36637844900;34976155900;7201443624;7102128820;6507112497;","Modelling the diurnal cycle of tropical convection across the 'grey zone'",2014,"10.1002/qj.2145","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896045250&doi=10.1002%2fqj.2145&partnerID=40&md5=5ea78f354a1e4895ba1ee54efc8d1757","We present the results of simulations carried out with the Met Office Unified Model at 12, 4 and 1.5 km resolution for a large region centred on West Africa using several different representations of the convection processes. These span a range of resolutions from much coarser than the size of the convection processes to cloud-system-resolving and thus encompass the intermediate 'grey zone'. The diurnal cycle in the extent of convective regions in the models is tested against observations from the Geostationary Earth Radiation Budget instrument on Meteosat-8. By this measure, the two best-performing simulations are a 12 km model without convective parametrization, using Smagorinsky-style subgrid-scale mixing in all three dimensions, and a 1.5 km simulation with two-dimensional Smagorinsky mixing. Of these, the 12 km model produces a better match to the magnitude of the total cloud fraction but the 1.5 km one results in better timing for its peak value. The results suggest that the previously reported improvement in the representation of the diurnal cycle of convective organization in the 4 km model compared with the standard 12 km configuration is principally a result of the convection scheme employed rather than the improved resolution per se. The details of this result and implications for high-resolution model simulations are discussed. © 2013 Royal Meteorological Society."
"7004014731;7003545639;6507915133;8960489000;","Analysis of global cloud imagery from multiple satellites",1991,"10.1175/1520-0477(1991)072<0467:AOGCIF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026266778&doi=10.1175%2f1520-0477%281991%29072%3c0467%3aAOGCIF%3e2.0.CO%3b2&partnerID=40&md5=5f5b1f3008d9c01cef8d7525147fc549","Synoptic images of the global cloud field have been created from infrared measurements taken aboard four geostationary and two polar-orbiting platforms simultaneously observing the earth. A series of spatial and temporal interpolations together with data reliability criteria are used to composite data from the individual satellites into synoptic images of the global cloud pattern. The composite Global Cloud Imagery (GCI) have a horizontal resolution of about half a degree and a temporal resolution of 3 h, providing an unprecedented view of the earth's cloud field. Each composite image represents a nearly instantaneous snapshot of the global cloud pattern. Collectively, the composite imagery resolve, on a global basis, most of the variability associated with organized convection, including several harmonics of the diurnal cycle. Because of its customized architecture and the homogeneous properties of the GCI, the IAS can perform such analyses on the 3-dimensional data with interactive speed. Statistical properties of cloud variability are presented along with other preliminary results derived from the GCI. -from Authors"
"7202899330;6505932008;8266109300;","Radiative-convective feedbacks in idealized states of radiative-convective equilibrium",2008,"10.1175/2008JAS2524.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049221356&doi=10.1175%2f2008JAS2524.1&partnerID=40&md5=c9501164606115ed8bdac95ad74aeade","This paper examines feedbacks between the radiative heating of clouds and convection in the context of numerical radiative-convective equilibrium experiments conducted using both 2D and 3D versions of a cloud-resolving model. The experiments are conducted on a large domain, and equilibria develop as juxtaposed regions of dry and moist air that are connected and sustained by circulations between them. The scales of such variability are large and differ significantly between the 2D and 3D versions of the experiments. Three sensitivity experiments were conducted which, when compared to the control experiment, provide insight into the relative influences of cloud-radiation feedback mechanisms on the equilibrium state achieved. It emerges from the experiments conducted that radiation feedbacks operate via two main pathways, with the radiative heating by high clouds being the governing process of both. The predominant bimodal nature of the moist equilibrium is established by gradients in radiative heating that, in turn, are determined by high cloud differences between wet and dry regions that, in turn, are controlled by convection. Convection, on the other hand, is also influenced by the localized effects of cloud radiative heating by these extended layers of high clouds. The results of the experiments demonstrate how high cloud radiative heating, which is a by-product of the convection itself, provides a feedback that acts to regulate the high clouds produced in the wet convective areas of the equilibrium. © 2008 American Meteorological Society."
"55469523400;15124698700;","Influence of entrainment on the thermal stratification in simulations of radiative-convective equilibrium",2013,"10.1002/grl.50796","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883088629&doi=10.1002%2fgrl.50796&partnerID=40&md5=f2746405e26a10aed2245030adac7a6b","Convective available potential energy (CAPE) is shown to increase rapidly with warming in simulations of radiative-convective equilibrium over a wide range of surface temperatures. The increase in CAPE implies a systematic deviation of the thermal stratification from moist adiabatic that is non-negligible at high temperatures. However, cloud buoyancy remains much smaller than what CAPE would imply because entrainment is more effective in reducing buoyancy in warmer atmospheres. An entraining plume model in the limit of zero cloud buoyancy is shown to reproduce the increase in CAPE with warming if the entrainment rate is held fixed and increases in the vertical extent of convection are taken into account. These model results together with radiosonde observations are used to support a conceptual model in which entrainment plays a role in determining the thermal stratification of the tropical atmosphere. Key Points CAPE increases with warming in simulations of radiative-convective equilibrium Cloud buoyancy remains small because of entrainment Observations suggest entrainment also influences tropical stratification. © 2013. American Geophysical Union. All Rights Reserved."
"7006095466;7409792174;","Representing convective organization in prediction models by a hybrid strategy",2006,"10.1175/JAS3812.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749266472&doi=10.1175%2fJAS3812.1&partnerID=40&md5=4d553fd25f9c51e3fea49ecc86dc6121","The mesoscale organization of precipitating convection is highly relevant to next-generation global numerical weather prediction models, which will have an intermediate horizontal resolution (grid spacing about 10 km). A primary issue is how to represent dynamical mechanisms that are conspicuously absent from contemporary convective parameterizations. A hybrid parameterization of mesoscale convection is developed, consisting of convective parameterization and explicit convectively driven circulations. This kind of problem is addressed for warm-season convection over the continental United States, although it is argued to have more general application. A hierarchical strategy is adopted: cloud-system-resolving model simulations represent the mesoscale dynamics of convective organization explicitly and intermediate resolution simulations involve the hybrid approach. Numerically simulated systems are physically interpreted by a mechanistic dynamical model of organized propagating convection. This model is a formal basis for approximating mesoscale convective organization (stratiform heating and mesoscale downdraft) by a first-baroclinic heating couplet. The hybrid strategy is implemented using a predictor-corrector strategy. Explicit dynamics is the predictor and the first-baroclinic heating couplet the corrector. The corrector strengthens the systematically weak mesoscale downdrafts that occur at intermediate resolution. When introduced to the Betts-Miller-Janjic convective parameterization, this new hybrid approach represents the propagation and dynamical structure of organized precipitating systems. Therefore, the predictor-corrector hybrid approach is an elementary practical framework for representing organized convection in models of intermediate resolution. © 2006 American Meteorological Society."
"7006514964;6602229351;","The stability of climate on Venus",1996,"10.1029/95JE03862","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029729213&doi=10.1029%2f95JE03862&partnerID=40&md5=a778427ccd163c55f7dd0ffa0f019fd8","The climate of Venus is to a large degree controlled by the radiative properties of its massive atmosphere. However, volcanic outgassing and surface-atmosphere interactions may moderate the atmospheric abundances of CO2 and other radiatively important volatiles. Recently, work on the interpretation of the impact cratering record has placed limits on the magnitude of the volcanic flux. Additionally, recent laboratory data on the equilibria and kinetics of possible surface-atmosphere reactions under Venus-like conditions provide important insights into the role that they may play in moderating Venus' climate. The surface temperature and pressure on Venus coincide approximately with the P-T equilibrium of the calcite-wollastonite mineral reaction, and atmospheric sulfur species are probably involved in rapid heterogeneous reactions with the surface. Perturbations to the atmospheric inventory of radiatively active species may have a significant impact on the climate of Venus and upon the stability of the greenhouse effect. Through the use of a Venus climate model that couples atmospheric radiative-convective equilibrium with surface processes, we show that it is likely that Venus' climate is at or near a state of unstable equilibrium. Furthermore, we show that only moderate perturbations in the abundances of radiatively active volatiles may be sufficient to precipitate changes to new climate regimes. Copyright 1990 by the American Geophysical Union."
"6701540733;7006184606;57206416522;","Radiative-convective model with an explicit hydrologic cycle 1. Formulation and sensitivity to model parameters",1994,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028554159&partnerID=40&md5=0f79200d212cd56bd74f7b73279e2704","A hydrological cycle is explicitly included in a one-dimensional radiative-convective equilibrium model which is coupled to a ""swamp' surface and tested with various cumulus convection schemes. The essential difference between our model and other radiative-convective models is that in our model the moisture profile (but not cloudiness) is interactively computed by the cumulus convection scheme. This has a crucial influence on the computation of the radiative fluxes throughout the atmopshere and therefore on the model's sensitivities. Using the Emanuel scheme, we show that clouds with high precipitation efficiency produce cold and dry climates. Clouds with low precipitation efficiency lead to moist and warm climates. The cumulus convection schemes currently in use in GCMs bypass the microphysical processes by making arbitrary moistening assumptions. -Authors"
"55469523400;15124698700;","Influence of microphysics on the scaling of precipitation extremes with temperature",2014,"10.1002/2014GL061222","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906295057&doi=10.1002%2f2014GL061222&partnerID=40&md5=b2240105167f5064c2831e722d1c7d0a","Simulations of radiative-convective equilibrium with a cloud-system resolving model are used to investigate the scaling of high percentiles of the precipitation distribution (precipitation extremes) over a wide range of surface temperatures. At surface temperatures above roughly 295 K, precipitation extremes increase with warming in proportion to the increase in surface moisture, following what is termed Clausius-Clapeyron (CC) scaling. At lower temperatures, the rate of increase of precipitation extremes depends on the choice of cloud and precipitation microphysics scheme and the accumulation period, and it differs markedly from CC scaling in some cases. Precipitation extremes are found to be sensitive to the fall speeds of hydrometeors, and this partly explains the different scaling results obtained with different microphysics schemes. The results suggest that microphysics play an important role in determining the response of convective precipitation extremes to warming, particularly when ice- and mixed-phase processes are important. © 2014. American Geophysical Union."
"57203025900;34870277200;35488045200;36006968000;","Multiscale interaction with topography and extreme rainfall events in the northeast Indian region",2010,"10.1029/2009JD012275","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954502200&doi=10.1029%2f2009JD012275&partnerID=40&md5=27ef5e6c41bbf5fb93ad7ce70dc9d27d","Flash floods associated with extreme rain events are a major hydrological disaster in the northeast Indian (NEI) region because of the unique topographic features of the region as well as increased frequency of occurrence of such events. Knowledge of the spatiotemporal distribution of these events in the region and an understanding of the factors responsible for them, therefore, would be immensely useful for appropriate disaster preparedness. Using daily rainfall data from 15 stations over the region for 32 years (1975-2006), it is shown that the frequency of occurrence of these events is largest not during the premonsoon thunderstorm season but during the peak monsoon months (June-July-August). This fact together with the fact that most of these events occur during long rainy spells indicate that the extreme events in the NEI region largely occur in association with the monsoon synoptic events rather than isolated thunderstorms. We also find that the aggregate of extreme rain events over the region has a significant decreasing trend in contrast to a recent finding of an increasing trend of such events in central India (Goswami et al., 2006). This decreasing trend of extreme events is consistent with observed decreasing trend in convective available potential energy and increasing convective inhibition energy over the region for the mentioned period. Examination of the structure of convection associated with the extreme rain events in the region indicates that they occur through a multiscale interaction of circulation with the local topography. It is found that at all the stations, the events are associated with a mesoscale structure of convection that is embedded in a much larger scale convective organization. We identify that this large-scale organization is a manifestation of certain phases of the tropical convergence zone associated with the northward propagating active-break phases of the summer monsoon intraseasonal oscillation. Further, it is shown that the mesoscale circulation interacting with the local topography generates southward propagating gravity waves with diurnal period. The strong updrafts associated with the gravity waves within the mesoscale organization leads to very deep convective events and the extreme rainfall. The insights provided by our study would be useful when designing models to improve the prediction of extreme events. Copyright 2010 by the American Geophysical Union."
"7006083502;7006095466;","Momentum and mass transport by convective bands: comparisons of highly idealized dynamical models to observations",1994,"10.1175/1520-0469(1994)051<0281:MAMTBC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028554070&doi=10.1175%2f1520-0469%281994%29051%3c0281%3aMAMTBC%3e2.0.CO%3b2&partnerID=40&md5=414fc225a9c5cb6717a57a4c9829dc89","The effects of quasi-two-dimensional convective bands on the environmental flow are investigated by comparing the observed mass and momentum fluxes and horizontal pressure changes to those predicted by the Moncrieff archetypal model (M92). The model idealizes the organized convection as two-dimensional and steady state, with three flow branches - a front-to-rear jump updraft, a front overturning updraft, and a rear overturning current, which can be an updraft or a downdraft. Flow through the branches satisfies mass continuity and Bernoulli's equation. The vertical divergence of line-normal momentum flux averaged over the volume is constrained to be zero. Coriolis and buoyancy effects are neglected. The model predicts the vertical mass flux, the vertical divergence of the vertical flux of line-normal momentum, and the pressure change across the line (independent of height). A simple equation for the vertical transport of line-parallel momentum follows from the model assumptions. -from Authors"
"7004479957;6701346974;","Convective self-aggregation feedbacks in near-global cloud-resolving simulations of an aquaplanet",2015,"10.1002/2015MS000499","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959472519&doi=10.1002%2f2015MS000499&partnerID=40&md5=6026d1d194d6c8d368fb919a915127a4","Positive feedbacks between precipitable water, reduced radiative cooling and enhanced surface fluxes promote convective self-aggregation in limited-area cloud-resolving model (CRM) simulations over uniform sea-surface temperature (SST). Near-global aquaplanet simulations with 4 km horizontal grid spacing and no cumulus or boundary layer parameterization are used to test the importance of these feedbacks to realistically organized tropical convection. A 20,480 × 10,240 km equatorially centered channel with latitudinally varying SST is used. Realistic midlatitude and tropical cloud structures develop. The natural zonal variability of humidity and convection are studied in a 30 day control simulation. The temporal growth of a small white-noise humidity perturbation and intrinsic predictability implications are explored. Atmospheric column budgets of moist-static energy (MSE) quantify its covariation with precipitation, surface heat flux, and radiative energy loss. Zonal Fourier analysis partitions these budgets by length scale. Radiative feedbacks on MSE natural variability and perturbation growth are found to be positive, broadly similar across scales, and comparable to limited-area CRMs, capable of e-folding a column MSE perturbation in 6-14 days. Surface fluxes are highest in synoptic-scale dry intrusions, inhibiting aggregation by damping tropical MSE perturbations. Sub-4-day MSE variations are due mainly to advection. Both tropics and midlatitudes have large-scale intrinsic predictability horizons of 15-30 days. An identical simulation but with 20 km grid spacing has more mesoscale variability and low cloud. © 2015. The Authors."
"6507400558;7004978125;","Equatorial convectively coupled waves in a simple muticlod model",2008,"10.1175/2008JAS2752.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049112928&doi=10.1175%2f2008JAS2752.1&partnerID=40&md5=8a320ba2a20813b45c42ea49a8ca1683","Linear stability results for the multicloud model recently developed by the authors on an equatorial beta plane are presented here. The linearized equations, about a realistic radiative-convective equilibrium (RCE) are projected in the meridional direction via a Galerkin truncation procedure based on the parabolic cylinder functions. In a suitable parameter regime, the multicloud model exhibits convectively coupled Kelvin, M = 0 eastward (Yanai), and M = 1 westward inertia-gravity waves, unstable at the synoptic scales in agreement with the outgoing longwave radiation (OLR) spectral peaks observed by Wheeler and Kiladis. The horizontal wave structure and vertical wavenumber of the unstable waves qualitatively match those of the rotating equatorial shallow water waves but with a reduced phase speed, as in the observations. More importantly, they exhibit the same self-similar front-to-rear vertical tilt in the zonal winds, temperature, and heating fields as observed by Kiladis and colleagues. Similar to the case without rotation (from earlier work) a wave life cycle is identified, once again demonstrating the crucial role, played by congestus clouds and moisture, of preconditioning and moistening prior to deep convection and of triggering and maintaining the instability. When the troposphere is excessively dry, the convective wave instability fades out and an instability of low-frequency modes moving in both eastward and westward directions takes place. The eigenstructure of the low-frequency modes projects heavily on the congestus and moisture components and exhibits a quadruple vortex configuration reminiscent of Rossby waves with strong meridional convergence of warm and moist air toward the equatorial belt, suggesting a moistening and preconditioning role resembling the congestus standing mode seen in the case without rotation. © 2008 American Meteorological Society."
"6603051342;","Nocturnal cloud systems and the diurnal variation of clouds and rainfall in southwestern Amazonia",2004,"10.1175/1520-0493(2004)132<1201:NCSATD>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2442712425&doi=10.1175%2f1520-0493%282004%29132%3c1201%3aNCSATD%3e2.0.CO%3b2&partnerID=40&md5=e4a573d7e615da2975e2405f6589fa5a","This paper examines the origins of a secondary nocturnal maximum in cloudiness and precipitation in southwestern Amazonia, a diurnal feature observed previously by many investigators. Analysis is based on satellite, radar, sounding, and profiler observations of precipitating systems and cloudiness from the Tropical Rainfall Measuring Mission Large-Scale Biosphere-Atmosphere (TRMM-LBA) and the coincident Wet-Season Atmospheric Mesoscale Campaign (WETAMC) field programs during the early 1999 wet season. The general finding is that following the collapse of the nearly ubiquitous and locally generated afternoon (""noon balloon"") convection, organized deep convection contributes to a postmidnight maximum in raining area and high cloudiness, and to a lesser extent rainfall. Nocturnal convective systems have the effect of weakening and delaying the onset of the following afternoon's convection. Many of these nocturnal convective events are traced to large-scale squall lines, which propagate westward thousands of kilometers from their point of origin along the northeast coast of Brazil. In addition, a previously undescribed nocturnal stratiform drizzle phenomenon, generated above the melting layer independently from deep convection, contributes significantly to nocturnal cloud cover. Results from this study underscore the complex influence of propagating large-scale organized convection in locally modulating the diurnal variation in clouds and rain. The greatest significance of the nocturnal drizzle may be the potential effect on the diurnal radiation budget by the extensive midlevel nocturnal clouds rather than their marginal contribution to nocturnal rainfall. © 2004 American Meteorological Society."
"7103008628;","Bow Echoes: A Tribute to T. T. Fujita",2001,"10.1175/1520-0477(2001)082<0097:BEATTT>2.3.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0041819317&doi=10.1175%2f1520-0477%282001%29082%3c0097%3aBEATTT%3e2.3.CO%3b2&partnerID=40&md5=401136dbac640fc23691702e54f5e9cd","Bow echoes represent one of the unique and more well-known forms of severe convective organization, often being responsible for the production of long swaths of damaging surface winds and small tornadoes. They are identified by their characteristic bow shape as seen on radar reflectivity displays. Much of what is known about bow echoes originated with T. T. Fujita, whose observational insights and careful analyses two decades ago still guide research and forecasting of bow-echo phenomena today. This paper reviews Fujita's contributions to our understanding of bow echoes, and also summarizes more recent observational and numerical studies that have built on the foundation that he provided. Perhaps not surprisingly, the life cycle of bow echoes as first described by Fujita, consisting of an evolution from a symmetric line of convective cells to a comma-shaped echo with a dominant cyclonic vortex, is now recognized as one of the fundamental modes of mesoconvective evolution, for both severe and nonsevere convective systems alike."
"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."
"55624399200;54983414800;6505932008;","Make it a double? Sobering results from simulations using single-moment microphysics schemes",2015,"10.1175/JAS-D-14-0107.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923115004&doi=10.1175%2fJAS-D-14-0107.1&partnerID=40&md5=0ef301d82891c93cfe6e0c017277d4cd","Single-moment microphysics schemes have long enjoyed popularity for their simplicity and efficiency. However, in this article it is argued through theoretical considerations, idealized thunderstorm simulations, and radiative-convective equilibrium (RCE) simulations that the assumptions inherent in these parameterizations can induce large errors in the proper representation of clouds and their feedbacks to the atmosphere. For example, precipitation is shown to increase by 200% through changes to fixed parameters in a singlemoment scheme and low-cloud fraction in the RCE simulations drops from about 15% in double-moment simulations to about 2% in single-moment simulations. This study adds to the large body of work that has shown that double-moment schemes generally outperform single-moment schemes. Therefore, it is recommended that future studies, regardless of their focus and especially those employing cloud-resolving models to simulate a realistic atmosphere, strongly consider moving to the exclusive use of multimoment microphysics schemes. © 2015 American Meteorological Society."
"23486505900;35578543700;","The effect of vertical shear orientation on tropical cyclogenesis",2012,"10.1002/qj.977","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861464574&doi=10.1002%2fqj.977&partnerID=40&md5=6735a7a07fffff15c84d6fd1594b339c","The effect of the relative orientation of the vertical wind shear to the surface wind on tropical cyclogenesis is explored in environments of radiative-convective equilibrium (RCE) through numerical simulation. This study serves as a companion paper to an earlier study on the thermodynamics of genesis in RCE. It is found, when the mean surface wind and shear are aligned, a negative surface wind anomaly arises from the superposition of the mean and vortex surface flows left of the shear vector. The resulting weak surface enthalpy fluxes and up-shear quasi-balanced subsidence leads to dry air being located cyclonically down-wind of the down-shear convective anomaly. Thus convection is inhibited from propagating cyclonically around the core leading to a large down-shear vortex tilt. Conversely, in a counter-aligned orientation, the negative surface wind anomaly and driest air is found right of the shear vector. Hence the driest air rotates into the down-shear flank where it moistened by shear-organized convection. Furthermore, the boundary layer is relatively moist left of shear due to the positive surface wind anomaly, therefore promoting the cyclonic propagation from down-shear and constraining the magnitude of the vortex tilt. Genesis is intimately tied to the magnitude of the tilt and is found to occur once the mid-level vortex has precessed into the up-shear flank. For smaller values of maximum tilt, vortex precession is comparatively rapid, aided by ""showerhead"" moistening provided by the up-shear advection of frozen condensate aloft. With the up-shear flank pre-moistened, rapid precession of the mid-level vortex, at smaller radii, leads to near saturation on the mesoscale and the onset of rapid intensification. When the magnitude of the tilt is quite large, precession is much slower and the showerhead effect is significantly reduced until just prior to the emergence of the mid-level vortex in the up-shear flank. © 2011 Royal Meteorological Society."
"7004978125;6507400558;7003408439;7004470971;6602424416;","A model for convectively coupled tropical waves: Nonlinearity, rotation, and comparison with observations",2004,"10.1175/1520-0469(2004)061<2188:AMFCCT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4844223055&doi=10.1175%2f1520-0469%282004%29061%3c2188%3aAMFCCT%3e2.0.CO%3b2&partnerID=40&md5=66f6b08e14931b1a8659337e461716c4","Recent observational analysis of both individual realizations and statistical ensembles identifies moist convectively coupled Kelvin waves in the Tropics with supercluster envelopes of convection. This observational analysis elucidates several key features of these waves including their propagation speed of roughly 15 m s-1 and many aspects of their dynamical structure. This structure includes anomalously cold temperatures in the lower troposphere and warm temperatures in the upper troposphere (below 250 hPa) within and sometimes leading the heating region and strong updrafts in the wave, and an upward and westward tilting structure with height below roughly 250 hPa. Other key features in the wave are that anomalous increases in convective available potential energy (CAPE) and surface precipitation lead the wave while the trailing part of the supercluster is dominated by stratiform precipitation. The main result in this paper is the development of a simple model convective parameterization with nonlinear convectively coupled moist gravity waves, which reproduce many of the features of the observational record listed above in a qualitative fashion. One key feature of the model convective parameterization is the systematic use of two vertical modes with one representing deep convective heating and the other stratiform heating. The other key feature in the model is the explicit parameterization of the separate deep convective and stratiform contribution to the downdrafts, which change equivalent potential temperature in the boundary layer. The effects of rotation on convectively coupled equatorial waves are also included through a suitable linear stability theory for the model convective parameterization about radiative convective equilibrium. © 2004 American Meteorological Society."
"6602847022;6701751100;7004160585;7006861646;","Numerical study of a Sahelian synoptic weather system: Initiation and mature stages of convection and its interactions with the large-scale dynamics",2002,"10.1256/003590002320603467","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036653782&doi=10.1256%2f003590002320603467&partnerID=40&md5=c46bf2c3e5290943ad5a8569119be39d","A 24 h multi-scale simulation of the life cycle of a Sahelian squall line is presented. The initial and coupling. fields have been taken from the Europian Centre for Medium-Range Weather Forecasts re-analysis (ERA-15) after humidity corrections to avoid spurious absolute and conditional convective instabilities. Comparisons of model-synthetic and Meteosat infra-red radiances indicate that the simulated scenario of convection development and structure are realistic, though differences are found concerning the size of the squall line with a delay of 2-3 h. The simulated arc-shaped structure and surface signature fit well with radar and ground station observations. respectively. The mature stage of the simulated squall line presents a cross-line structure similar to conceptual models. An intense rear-to-front flow is generated below the trailing stratiform part. An acceleration of the African easterly jet (AEJ) is simulated behind the system, occurring across its full width. This leads to the generation of a dipole of counter-rotating vortices. The resulting potential-vorticity signature leads to local reinforcement of the barotropic instability on the north flank of the AEJ. This simulation is used to analyse the impact of the convection at synoptic-scales and to compare it with ERA-15. It suggests that the convection contributes to reinforce the monsoon at least up to 500 km. The monsoon inflow moves eastward and westward with time-scales shorter and longer than 24 h, respectively. The tropical easterly jet intensifies to the south-west of the convection area up to 700 km away. The AEJ is strongly intensified ahead of the trough where active convection occurs. Organized convection developing in the vicinity of the AEJ core induces weakening of the AEJ ahead of the squall line and strengthening behind it. A common result in the simulation and in ERA-15 is that the AEJ core moves westward faster due to the convective activity."
"6701538799;7404361000;7102609291;","Long-lived mesoconvective vortices and their environment. Part I: Observations from the central United States during the 1998 warm season",2000,"10.1175/1520-0493(2000)128<3376:LLMVAT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033646299&doi=10.1175%2f1520-0493%282000%29128%3c3376%3aLLMVAT%3e2.0.CO%3b2&partnerID=40&md5=7c9ad8933eafb37ea0fcf932f81e7f94","Observations from the modernized United States National Weather Service (NWS) data network are used to assess the frequency and general characteristics of midtropospheric cyclonic vortices (MCVs) generated by mesoscale convective systems (MCSs). Results from the 1998 convective season (15 May-15 September) over the central United States suggest that long-lived MCVs, which persist after the dissipation of the initiating MCS, are more common than previously documented. These MCVs occur in weaker ambient vertical shear (both in the lower troposphere and through a nominal vortex layer) than MCSs from which no detectable MCVs are spawned. An important aspect of MCVs is that they may focus subsequent convective development within long-lived discontinuous heavy precipitation episodes. Subsequent deep convection is observed in the vicinity of MCVs in slightly greater than 1/2 of the MCV cases. This subsequent convection occurs in thermodynamic environments of moderate-to-large convective available potential energy and small convective inhibition, and is located in a region from the center of the MCV circulation outward to its downshear periphery. This location is consistent with lower-tropospheric ascent arising from the interaction of a quasi-balanced vortex with the ambient vertical shear. Long-lived organized convection near the MCV center is likely crucial in either sustaining or reinvigorating vortices during the relatively rare MCV events that persist longer than a diurnal cycle. Examples from the 1998 convective season are used to illustrate differences in the relationship between the MCV circulation and the organization of subsequent convection among different MCV cases."
"7004160585;6701751100;","A three-dimensional simulation of a tropical squall line: convective organization and thermodynamic vertical transport",1988,"10.1175/1520-0469(1988)045<1334:ATDSOA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024220713&doi=10.1175%2f1520-0469%281988%29045%3c1334%3aATDSOA%3e2.0.CO%3b2&partnerID=40&md5=855d9c41518c2151fc274277221079b5","Three-dimensional convective-scale simulations of an African squall line, observed during the French COPT 81 experiment, are presented. The convective region (30km wide) appears as the superposition of several convective cells at different stages of their life cycle. New elements are formed in front of the system and are fed by the forced convergence band along the squall-line front. Mature cells produce precipitation that feeds downdrafts by loading and evaporation. Old convective cells dissipate at the simulated system rear. Between the convective updrafts, intrusions of low equivalent potential temperature (θe) are found. These are unsaturated downdraft cells feeding the gravity current. At low levels (up to 2km), the simulated system has a two-dimensional structure, but it becomes progressively three-dimensional with height. This three-dimensional structure allows the crossing of two inflow layers of high and low θe, respectively between 2 and 6km. This is the crossover zone whose existence was hypothesized by Zipser. A detailed description of the gravity current at small scale is given, showing an inner circulation whose intensity depends on the forcing imposed by the stratiform part. -from Authors"
"12144041700;7102567936;","Effects of relative and absolute sea surface temperature on tropical cyclone potential intensity using a single-column model",2011,"10.1175/2010JCLI3690.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79251575308&doi=10.1175%2f2010JCLI3690.1&partnerID=40&md5=6b0be87d84d5d628615bd330327e089d","The effects of relative and absolute sea surface temperature (SST) on tropical cyclone potential intensity are investigated using the Massachusetts Institute of Technology (MIT) single-column model. The model is run in two modes: (i) radiative-convective equilibrium (RCE) to represent the convective response to uniform warming of the ocean as in a homogeneous aqua planet, and (ii) weak temperature gradient (WTG) to represent the convective response to warming over a limited area of ocean while the SST outside that area remains unchanged. The WTG calculations are taken to represent the sensitivity of the atmospheric state to relative SST changes, while the RCE calculations are taken to represent the sensitivity to absolute SST changes occurring in the absence of relative SST changes. The potential intensity is computed using temperature and moisture profiles from the two sets of experiments for various values of SST. The computed potential intensity is more sensitive to relative SST than to absolute SST, with slopes of between about 7 and 8 m s-1 °C-1 (depending on choice of input parameters in the model's convection scheme and other details of the model configuration) in the WTG calculations and about 1 m s-1 °C-1 in RCE. The sensitivity to relative SST obtained from these calculations is quantitatively similar to that obtained previously by G. Vecchi and B. J. Soden from global climate model output. The greater sensitivity of potential intensity to SST in the WTG simulations (relative to RCE) can be attributed primarily to larger changes in the air-sea thermodynamic disequilibrium in those calculations as SST changes, which results from the inability of the free troposphere to adjust to the SST in WTG as it does in RCE. © 2011 American Meteorological Society."
"7005485117;7006422317;6701493094;6603128956;7005695791;6506581978;7004176604;","The hurricane intensity issue",2005,"10.1175/MWR2954.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-24144483077&doi=10.1175%2fMWR2954.1&partnerID=40&md5=588a981c9d844e0edf36f50ab1668453","The intensity issue of hurricanes is addressed in this paper using the angular momentum budget of a hurricane in storm-relative cylindrical coordinates and a scale-interaction approach. In the angular momentum budget in storm-relative coordinates, a large outer angular momentum of the hurricane is depleted continually along inflowing trajectories. This depletion occurs via surface and planetary boundary layer friction, model diffusion, and ""cloud torques""; the latter is a principal contributor to the diminution of outer angular momentum. The eventual angular momentum of the parcel near the storm center determines the storm's final intensity. The scale-interaction approach is the familiar energetics in the wavenumber domain where the eddy and zonal kinetic energy on the hurricane scale offer some insights on its intensity. Here, however, these are cast in storm-centered local cylindrical coordinates as a point of reference. The wave-numbers include azimuthally averaged wavenumber 0, principal hurricane-scale asymmetries (wavenumbers 1 and 2, determined from datasets) and other scales. The main questions asked here relate to the role of the individual cloud scales in supplying energy to the scales of the hurricane, thus contributing to its intensity. A principal finding is that cloud scales carry most of their variance, via organized convection, directly on the scales of the hurricane. The generation of available potential energy and the transformation of eddy kinetic energy from the cloud scale are in fact directly passed on to the hurricane scale by the vertical overturning processes on the hurricane scale. Less of the kinetic energy is generated on the scales of individual clouds that are of the order of a few kilometers. The other major components of the energetics are the kinetic-to-kinetic energy exchange and available potential-to-available potential energy exchange among different scales. These occur via triad interaction and were noted to be essentially downscale transfer, that is, a cascading process. It is the balance among these processes that seems to dictate the final intensity. © 2005 American Meteorological Society."
"6701670597;","Water's two height scales: The moist adiabat and the radiative troposphere",2001,"10.1256/smsqj.57707","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035473116&doi=10.1256%2fsmsqj.57707&partnerID=40&md5=a57f2c204c271312a42752d0b7fe6798","The temperature structure of the tropical troposphere resembles a moist adiabat, with a lapse-rate transition toward dry adiabatic where water becomes scarce at an altitude Hma - 8 km (350 hPa). Infrared emission by water vapour cools a deeper layer, extending up to Hrad - 14 km (160 hPa). Five consequences of these unequal heights are reviewed. 1. Upper-tropospheric relative humidity is often low, highly variable, and bimodal, due to the rapidity of drying by radiative subsidence. 2. Large-scale divergent circulations (e.g. equatorial u wind) exhibit a two-celled vertical structure, with an elevated convergence layer near 8-10 km in the rising branch. 3. The dominant deep convective heating process changes from latent heating at low levels to eddy heat-flux convergence in the upper troposphere. This requires a substantial updraught-environment temperature difference, which leads to large entrainment near Hma, yielding stratiform anvil clouds which also contribute radiative heating. 4. The rising branches of deep (-Hrad) vertical circulations export more heat than they import as moisture, so that large-scale tropical dynamics can be characterized by a 'gross moist stability'. 5. Divergent motions with a vertical wavelength -8 km, corresponding to Kelvin or gravity wave speeds of -15 m s-1, are excited by simple (e.g. uniform) heating profiles extending through the lapse-rate change near Hma."
"6603263640;9939102400;7005808242;","Frictional dissipation in a precipitating atmosphere",2000,"10.1175/1520-0469(2000)057<0989:FDIAPA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034176113&doi=10.1175%2f1520-0469%282000%29057%3c0989%3aFDIAPA%3e2.0.CO%3b2&partnerID=40&md5=1248ffe189a4213b75fdcbb8e310e5df","The frictional dissipation in the shear zone surrounding falling hydrometeors is estimated to be 2-4 W m-2 in the Tropics. A numerical model of radiative-convective equilibrium with resolved three-dimensional moist convection confirms this estimate and shows that the precipitation-related dissipation is much larger than the dissipation associated with the turbulent energy cascade from the convective scale. Equivalently, the work performed by moist convection is used primarily to lift water rather than generate kinetic energy of the convective airflow. This fact complicates attempts to use the entropy budget to derive convective velocity scales.The frictional dissipation in the shear zone surrounding falling hydrometeors is estimated to be 2-4 W m-2 in the Tropics. A numerical model of radiative-convective equilibrium with resolved three-dimensional moist convection confirms this estimate and shows that the precipitation-related dissipation is much larger than the dissipation associated with the turbulent energy cascade from the convective scale. Equivalently, the work performed by moist convection is used primarily to lift water rather than generate kinetic energy of the convective airflow. This fact complicates attempts to use the entropy budget to derive convective velocity scales."
"8723504500;56003262400;57034458200;","Initiation and organizational modes of an extreme-rain-producing mesoscale convective system along a mei-yu front in East China",2014,"10.1175/MWR-D-13-00111.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892462810&doi=10.1175%2fMWR-D-13-00111.1&partnerID=40&md5=b547bc4dbc0505095f36a2ceedc498b6","The initiation and organization of a quasi-linear extreme-rain-producing mesoscale convective system (MCS) along a mei-yu front in east China during the midnight-to-morning hours of 8 July 2007 are studied using high-resolution surface observations and radar reflectivity, and a 24-h convection-permitting simulation with the nested grid spacing of 1.11 km. Both the observations and the simulation reveal that the quasi-linear MCS forms through continuous convective initiation and organization into west-east-oriented rainbands with life spans of about 4-10 h, and their subsequent southeastward propagation. Results show that the early convective initiation at the western end of the MCS results from moist southwesterly monsoonal flows ascending cold domes left behind by convective activity that develops during the previous afternoon-to-evening hours, suggesting a possible linkage between the early morning and late afternoon peaks of the mei-yu rainfall. Two scales of convective organization are found during the MCS's development: one is the east- to northeastward ""echo training""of convective cells along individual rainbands, and the other is the southeastward ""band training""of the rainbands along the quasi-linear MCS. The two organizational modes are similar within the context of ""training""of convective elements, but they differ in their spatial scales and movement directions. It is concluded that the repeated convective backbuilding and the subsequent echo training along the same path account for the extreme rainfall production in the present case, whereas the band training is responsible for the longevity of the rainbands and the formation of the quasi-linear MCS. © 2014 American Meteorological Society."
"7202772927;7006095466;","Multiscale cloud system modeling",2009,"10.1029/2008RG000276","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957586906&doi=10.1029%2f2008RG000276&partnerID=40&md5=24db6f3f4ec91d7dab1fb0bf518cebb4","The central theme of this paper is to describe how cloud system resolving models (CRMs) of grid spacing ∼1 km have been applied to various important problems in atmospheric science across a wide range of spatial and temporal scales and how these applications relate to other modeling approaches. A long-standing problem concerns the representation of organized precipitating convective cloud systems in weather and climate models. Since CRMs resolve the mesoscale to large scales of motion (i.e., 10 km to global) they explicitly address the cloud system problem. By explicitly representing organized convection, CRMs bypass restrictive assumptions associated with convective parameterization such as the scale gap between cumulus and large-scale motion. Dynamical models provide insight into the physical mechanisms involved with scale interaction and convective organization. Multiscale CRMs simulate convective cloud systems in computational domains up to global and have been applied in place of contemporary convective parameterizations in global models. Multiscale CRMs pose a new challenge for model validation, which is met in an integrated approach involving CRMs, operational prediction systems, observational measurements, and dynamical models in a new international project: the Year of Tropical Convection, which has an emphasis on organized tropical convection and its global effects. © Copyright 2009 by the American Geophysical Union."
"7005038449;14026866700;","Linear Stratospheric Gravity Waves above Convective Thermal Forcing",1999,"10.1175/1520-0469(1999)056<2434:LSGWAC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032762047&doi=10.1175%2f1520-0469%281999%29056%3c2434%3aLSGWAC%3e2.0.CO%3b2&partnerID=40&md5=39a2e8b81b33189e9e29e2265cfa712b","The spectra of linear gravity waves generated by a time-varying tropospheric thermal forcing representing organized convection are compared to the spectra of stratospheric gravity waves generated by organized convection in a fully nonlinear two-dimensional squall line simulation. The resemblance between the spectra in the two simulations suggests that stratospheric gravity waves above convection can be understood primarily in terms of the linear response to a time- and space-dependent thermal forcing. In particular, the linear response to thermal forcing accounts for the correlation between the dominant vertical wavelength of the stratospheric waves and the depth of the tropospheric convection as well as the the fact that the dominant frequency of the stratospheric waves is the same as the frequency of oscillation of the main convective updraft. © 1999 American Meteorological Society."
"7005702722;7202145115;","Testing the fixed anvil temperature hypothesis in a cloud-resolving model",2007,"10.1175/JCLI4124.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33947355386&doi=10.1175%2fJCLI4124.1&partnerID=40&md5=4c52345d3ef86d96ec584a0882c5ab15","Using cloud-resolving simulations of tropical radiative-convective equilibrium, it is shown that the anvil temperature changes by less than 0.5 K with a 2-K change in SST, lending support to the fixed anvil temperature (FAT) hypothesis. The results suggest that for plausible ozone profiles, a decrease in the air's emission capability instead of ozone heating shall remain the control on the detrainment level, and the FAT hypothesis should hold. The anvil temperature also remains unchanged with other changes in the system such as the doubled CO2 mixing ratio, doubled stratospheric water vapor concentration, and dynamical cooling due to the Brewer-Dobson circulations. The results are robust when a different microphysics scheme is used. © 2007 American Meteorological Society."
"7410290189;7102101132;","Observations of the convective environment in developing and non-developing tropical disturbances",2012,"10.1002/qj.1910","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868144443&doi=10.1002%2fqj.1910&partnerID=40&md5=ef1a0c7a006da9342b9dc04da6e04638","Analyses of thermodynamic data gathered from airborne dropwindsondes released from the upper troposphere during the Pre-Depression Investigation of Cloud Systems in the Tropics (PREDICT) experiment are presented. We focus on two systems that finally became hurricanes Karl and Matthew, and one system (Gaston) that attained tropical storm status, but subsequently weakened and never redeveloped during five days of monitoring. Data for all events show that the largest values of total precipitable water are collocated with the surface trough and with values of convective available potential energy that seem high enough to support convective organization. These values coincide mostly with low values of convective inhibition. Vertical profiles of virtual potential temperature show little variability between soundings on a particular day, but the system means from day to day show a slight warming. In contrast, vertical profiles of pseudo-equivalent potential temperature, θ e, show much more variability between soundings on a particular day on account of the variability in moisture. In all systems, there was is a tendency for the lower troposphere to moisten, but in the non-developing system, the troposphere became progressively drier in the height range between approximately 2 and 9 km during the five days of observations. In the developing systems, the troposphere moistened. The most prominent difference between the non-developing system and the two developing systems was the much larger reduction of θ e between the surface and a height of 3 km, typically 25 K in the non-developing system, compared with only 17 K in the developing systems. Conventional wisdom would suggest that, for this reason, the convective downdraughts would be stronger in the non-developing system and would thereby act to suppress the development. Here we propose an alternative hypothesis in which the drier air weakens the convective updraughts and thereby the convective amplification of absolute vorticity necessary for development. © 2012 Royal Meteorological Society."
"7101661890;7007099717;","Convectively generated gravity waves and their effect on the cloud environment",2001,"10.1175/1520-0469(2001)058<2427:CGGWAT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035880403&doi=10.1175%2f1520-0469%282001%29058%3c2427%3aCGGWAT%3e2.0.CO%3b2&partnerID=40&md5=f6b02fd991be589d2834c8b3423c448f","This study uses a two-dimensional cloud-resolving model to examine how convectively generated gravity waves modify the environment of an isolated convective cloud. The model is initialized with an idealized sounding, and the cloud is initiated by adding a locally buoyant perturbation. The modeled convection generates a spectrum of gravity waves with vertical wavelengths that are harmonics of the depth of the troposphere. It is shown that the first three wave modes significantly modify the cloud environment. The modification of the cloud environment is quantified in terms of the convective available potential energy (CAPE) and convective inhibition (CIN). The first two wave modes travel fastest away from the cloud and are responsible for the changes in CAPE, whereas the third wave mode causes low-level lifting and hence a reduction in CIN. The maximum far-field perturbations in CAPE and CIN are approximately 15% and 33% of the initial background values, respectively. These results agree with previous studies of more organized convection, predicting the existence of a region surrounding the convective system that favors the development of new convection."
"7005702722;","Linear response functions of a cumulus ensemble to temperature and moisture perturbations and implications for the dynamics of convectively coupled waves",2010,"10.1175/2009JAS3260.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953350963&doi=10.1175%2f2009JAS3260.1&partnerID=40&md5=6da079244305fe788bc36f308733655c","An approach is presented for the construction of linear response functions of a cumulus ensemble to largescale temperature and moisture perturbations using a cloud system-resolving model (CSRM). A set of timeinvariant, horizontally homogeneous, anomalous temperature and moisture tendencies is added, one at a time, to the forcing of the CSRM. By recording the departure of the equilibrium domain-averaged temperature and moisture profiles from those of a control experiment and through a matrix inversion, a sufficiently complete and accurate set of linear response functions is constructed for use as a parameterization of the cumulus ensemble around the reference mean state represented by the control experiment.This approach is applied to two different mean state conditions in which the CSRM, when coupled with 2D gravity waves, exhibits interestingly different behaviors. With a more strongly convecting mean state forced by the large-scale vertical velocity profile taken from the Tropical Ocean and Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE), spontaneous development of convectively coupled waves requires moisture variations above the boundary layer, whereas with a mean state of radiative- convective equilibrium (RCE) not forced by large-scale vertical advection, the development of convectively coupled waves is stronger and persists even when moisture variations above the boundary layer are removed. The linear response functions were able to reproduce these behaviors of the full CSRMwith some quantitative accuracy. The linear response functions show that both temperature and moisture perturbations at a range of heights can regulate convective heating. The ability for convection to remove temperature anomalies, thus maintaining convective neutrality, decreases considerably fromthe lower troposphere to the middle and upper troposphere. It is also found that the response of convective heating to a lower tropospheric temperature anomaly is more top-heavy in the RCE case than in the TOGA COARE case. Comparing the linear response functions with the treatment of convection in an earlier simple model by the present author indicates general consistency, lending confidence that the instability mechanisms identified in that model provide the correct explanation to the instability seen in the CSRM simulations and the instability's dependence on the mean state. © 2010 American Meteorological Society."
"7005808242;57218978147;8733579800;","Dynamic radiative-convective equilibria using GCM column physics",2007,"10.1175/JAS3825.11","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846485149&doi=10.1175%2fJAS3825.11&partnerID=40&md5=1838da7ddcb99f49c3877c59b2d41c6c","The behavior of a GCM column physics package in a nonrotating, doubly periodic, homogeneous setting with prescribed SSTs is examined. This radiative-convective framework is proposed as a useful tool for studying some of the interactions between convection and larger-scale dynamics and the effects of differing modeling assumptions on convective organization and cloud feedbacks. For the column physics utilized here, from the Geophysical Fluid Dynamics Laboratory (GFDL) AM2 model, many of the properties of the homogeneous, nonrotating model are closely tied to the fraction of precipitation that is large-scale, rather than convective. Significant large-scale precipitation appears above a critical temperature and then increases with further increases in temperature. The amount of large-scale precipitation is a function of horizontal resolution and can also be controlled by modifying the convection scheme, as is illustrated here by modifying assumptions concerning entrainment into convective plumes. Significant similarities are found between the behavior of the homogeneous model and that of the Tropics of the parent GCM when ocean temperatures are increased and when the convection scheme is modified."
"36961988200;8313138100;56900416800;25823927100;","Observed tropical cyclone size revisited",2016,"10.1175/JCLI-D-15-0731.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84964841682&doi=10.1175%2fJCLI-D-15-0731.1&partnerID=40&md5=6e92f23bfd8cdf120d965b8ae2a5ea74","This work revisits the statistics of observed tropical cyclone outer size in the context of recent advances in our theoretical understanding of the storm wind field. The authors create a new dataset of the radius of 12 m s-1 winds based on a recently updated version of the QuikSCAT ocean wind vector database and apply an improved analytical outer wind model to estimate the outer radius of vanishing wind. The dataset is then applied to analyze the statistical distributions of the two size metrics as well as their dependence on environmental parameters, with a specific focus on testing recently identified parameters possessing credible theoretical relationships with tropical cyclone size. The ratio of the potential intensity to the Coriolis parameter is found to perform poorly in explaining variation of size, with the possible exception of its upper bound, the latter of which is in line with existing theory. The rotating radiative-convective equilibrium scaling of Khairoutdinov and Emanuel is also found to perform poorly. Meanwhile, mean storm size is found to increase systematically with the relative sea surface temperature, in quantitative agreement with the results of a recent study of storm size based on precipitation area. Implications of these results are discussed in the context of existing tropical climate theory. Finally, an empirical dependence of the central pressure deficit on outer size is found in line with past work. © 2016 American Meteorological Society."
"56562594400;7005702722;56562157700;","Mechanisms for convection triggering by cold pools",2015,"10.1002/2015GL063227","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927797051&doi=10.1002%2f2015GL063227&partnerID=40&md5=8c1de084d387a1ac766855f1e032141d","Cold pools are fundamental ingredients of deep convection. They contribute to organizing the subcloud layer and are considered key elements in triggering convective cells. It was long known that this could happen mechanically, through lifting by the cold pools' fronts. More recently, it has been suggested that convection could also be triggered thermodynamically, by accumulation of moisture around the edges of cold pools. A method based on Lagrangian tracking is here proposed to disentangle the signatures of both forcings and quantify their importance in a given environment. Results from a simulation of radiative-convective equilibrium over the ocean show that parcels reach their level of free convection through a combination of both forcings, each being dominant at different stages of the ascent. Mechanical forcing is an important player in lifting parcels from the surface, whereas thermodynamic forcing reduces the inhibition encountered by parcels before they reach their level of free convection. Key Points Thermodynamic effect of cold pools crucial in the inhibition layer Gust front lifting is necessary for lifting parcels from the surface No forcing mechanism by cold pools is entirely dominant; cooperation is needed ©2015. American Geophysical Union. All Rights Reserved."
"8658853400;7006380976;55999772700;","Cycles and propagation of deep convection over equatorial Africa",2011,"10.1175/2011MWR3500.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053199993&doi=10.1175%2f2011MWR3500.1&partnerID=40&md5=3828f1734fcdf184fa9e1a944cc16309","Long-term statistics of organized convection are vital to improved understanding of the hydrologic cycle at various scales. Satellite observations are used to understand the timing, duration, and frequency of deep convection in equatorial Africa, a region with some of the most intense thunderstorms. Yet little has been published about the propagation characteristics of mesoscale convection in that region. Diurnal, subseasonal, and seasonal cycles of cold cloud (proxy for convective precipitation) are examined on a continental scale. Organized deep convection consists of coherent structures that are characteristic of systems propagating under a broad range of atmospheric conditions. Convection is triggered by heating of elevated terrain, sea/land breezes, and lake breezes. Coherent episodes of convection result from regeneration of convection through multiple diurnal cycles while propagating westward. They have an average 17.6-h duration and 673 km span; most have zonal phase speeds of 8-16 m s-1. Propagating convection occurs in the presence of moderate low-level shear that is associated with the southwesterly monsoonal flow and midlevel easterly jets. Convection is also modulated by eastward-moving equatorially trapped Kelvin waves, which have phase speeds of 12-22m s-1 over equatorial Africa. Westward propagation of mesoscale convection is interrupted by the dry phase of convectively coupled Kelvin waves. During the wet phase, daily initiation and westward propagation continues within the Kelvin wave and the cold cloud shields are larger. Mesoscale convection is more widespread during the active phase of the Madden-Julian oscillation (MJO) but with limited westward propagation. The study highlights multiscale interaction as a major source of variability in convective precipitation during the critical rainy seasons in equatorial Africa. © 2011 American Meteorological Society."
"7005685786;7102301816;","Convective momentum transport observed during the TOGA COARE IOP. Part II: Case studies",2002,"10.1175/1520-0469(2002)059<2535:CMTODT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036733248&doi=10.1175%2f1520-0469%282002%29059%3c2535%3aCMTODT%3e2.0.CO%3b2&partnerID=40&md5=ec51bbcd2974f1090c8f45b61d25ed11","Convective momentum transport (CMT) associated with the Madden-Julian oscillation (MJO), tropical waves, squall and nonsquall mesoscale convective systems (MCSs), and the diurnal cycle is studied by examining the momentum budget residual X = (X, Y) deduced from the objectively analyzed in situ observations during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) intensive observing period (IOP: November 1992-February 1993). Using wavelet transform, time evolution of signals of these disturbances in the time series of |X| and ITBB (an index for deep convection), averaged over the intensive flux array (IFA), is analyzed. Signals of disturbances with periods ≥ 1 day in |X| generally evolve in phase with those in ITBB. During the convective phase of MJO, signals in both |X| and ITBB with shorter periods are also enhanced. Frequency distribution of IFA-mean E = -V̄ · X in the troposphere is examined. The mean E is positive, that is, kinetic energy (K) transfer is downscale, about 60%-65% of time in the lower troposphere below 500 hPa, and between 200 hPa and the tropopause. However, in the upper troposphere, between 350-200 hPa, upscale and downscale K transfer occur with nearly equal frequency. Different frequency distributions near the surface, the middle troposphere, and near the tropopause suggest the existence of different regimes of K transfer associated with various convective and boundary layer processes. Furthermore, the dependence of the direction of CMT on mesoscale convective organizations documented in many previous observations is found to be detectable at the 2.5° × 2.5° objective analysis. Couplets of vorticity and vorticity budget residual Z appear in the upper levels with monsquall MCSs. Upscale K transfer is found in the linenormal direction of a squall line. During the westerly wind phase of the MJO, convection appears to play dual roles. First, as the westerlies are initiated in the lower troposphere, CMT is typically upgradient and may help maintain middle-level easterly shear. Thus the upscale K transfer may help trigger the westerly wind burst (WWB). Second, at the later stage with strong lower- to middle-level westerlies. CMT is mostly downgradient and reduces the middle-level zonal wind shear."
"6701402902;7005501098;55640225400;","Transformation of a large monsoon depression to a tropical storm during TCM-93",1996,"10.1175/1520-0493(1996)124<2625:TOALMD>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0000225278&doi=10.1175%2f1520-0493%281996%29124%3c2625%3aTOALMD%3e2.0.CO%3b2&partnerID=40&md5=f9707a17fab3eb3a8bbd8fea8a510b6a","Data obtained during two aircraft observing periods (AOP) from the TCM-93 mini field experiment are used to describe the transformation between 5° and 10°N of a large depression in the western North Pacific monsoon trough into a tropical cyclone over a 36-h period. The transformation is defined to occur in three stages. Although a large mesoscale convective system (MCS) was present along the eastern periphery of the monsoon depression during the preorganization stage characterized by observations from the first AOP, the overall convective organization of the broad circulation is weak. The structure of the MCS provided a midlevel subsynoptic contribution to the vorticity of the monsoon depression and contributed to a shift in the center of the monsoon depression circulation between 800 and 600 mb toward the MCS location. However, the presence of unsaturated downdrafts associated with the MCS perturbed the low-level thermodynamic conditions and contributed to the rapid decay of the MCS. Slow intensification of the monsoon depression circulation during the preorganization stage is primarily due to favorable interactions with large-scale mean and eddy circulations at both upper and lower levels. The overall convective signature was observed in hourly satellite imagery to become more organized during a 24-h period between the two AOPs. This organization stage was characterized by the formation of a new MCS near the midlevel circulation of the decaying MCS from the preorganization stage. Satellite imagery indicates that the broad monsoon depression began to organize around the new MCS and the outer convection started to be oriented in large principle bands. During the transformation to a tropical storm during the second AOP, the outer principal bands appear to separate the inner circulation of the monsoon depression from the large-scale monsoon trough environment. Convection rapidly develops along the periphery of the inner circulation that now contains a vigorous central updraft and high values of equivalent potential temperature that extend to the middle troposphere. Although several episodes of MCS generation and decay occurred throughout the development of the monsoon depression, it is hypothesized that the subsynoptic processes in the MCS during the first AOP and the MCSs that formed immediately following the second AOP contributed to the concentration of the monsoon depression center and transformation to a tropical cyclone."
"7003406400;57194110694;","Organization of tropical convection in low vertical wind shears: Role of updraft entrainment",2017,"10.1002/2016MS000802","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018732880&doi=10.1002%2f2016MS000802&partnerID=40&md5=fd4ea53041f91faca46ad35c080c9ddb","Radiative-convective equilibrium simulations with a 2 km horizontal resolution are conducted to investigate the impact on convective organization of different parameterizations for horizontal and vertical subgrid turbulence mixing. Three standard approaches for representing horizontal diffusion produce starkly differing mixing rates, particularly for the entrainment mixing into updrafts, which differ by more than an order of magnitude between the schemes. The simulations demonstrate that the horizontal subgrid mixing of water vapor is key, with high mixing rates a necessary condition for organization of convection to occur, since entrainment of dry air into updrafts suppresses convection. It is argued that diabatic budgets, while demonstrating the role of spatially heterogeneous radiative heating rates in driving organization, can overlook the role of physical processes such as updraft entrainment. These results may partially explain previous studies that showed that organization is more likely to occur at coarser resolutions, when entrainment is solely represented by subgrid-scale turbulence schemes, highlighting the need for benchmark simulations of higher horizontal resolution. The recommendation is for the use of larger ensembles to ensure robustness of conclusions to subgrid-scale parameterization assumptions when numerically investigating convective organization, possibly through a coordinated community model intercomparison effort. © 2017. The Authors."
"15135583300;35467186900;7006083502;7005869171;6701432911;","On how hot towers fuel the hadley cell: An observational and modeling study of line-organized convection in the equatorial trough from TOGA COARE",2009,"10.1175/2009JAS3017.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73549094257&doi=10.1175%2f2009JAS3017.1&partnerID=40&md5=05cc1cd8e9f6e77094da0cf3f01bc1d9","An airflow trajectory analysis was carried out based on an idealized numerical simulation of the nocturnal 9 February 1993 equatorial oceanic squall line observed over the Tropical Ocean and Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) ship array. This simulation employed a nonhydrostatic numerical cloud model, which features a sophisticated 12-class bulk microphysics scheme. A second convective system that developed immediately south of the ship array a few hours later under similar environmental conditions was the subject of intensive airborne quad-Doppler radar observations, allowing observed airflow trajectories to be meaningfully compared to those from the model simulation. The results serve to refine the so-called hot tower hypothesis, which postulated the notion of undiluted ascent of boundary layer air to the high troposphere, which has for the first time been tested through coordinated comparisons with both model output and detailed observations. For parcels originating ahead (north) of the system near or below cloud base in the boundary layer (BL), the model showed that a majority (&gt;62%) of these trajectories were able to surmount the 10-km level in their lifetime, with about 5% exceeding 14-km altitude, which was near the modeled cloud top (15.5 km). These trajectories revealed that during ascent, most air parcels first experienced a quick decrease of equivalent potential temperature (θe) below 5-km MSL as a result of entrainment of lower ambient θe air. Above the freezing level, ascending parcels experienced an increase in θe with height attributable to latent heat release from ice processes consistent with previous hypotheses. Analogous trajectories derived from the evolving observed airflow during the mature stage of the airborne radar-observed system identified far fewer (~5%) near-BL parcels reaching heights above 10 km than shown by the corresponding simulation. This is attributed to both the idealized nature of the simulation and to the limitations inherent to the radar observations of near-surface convergence in the subcloud layer. This study shows that latent heat released above the freezing level can compensate for buoyancy reduction by mixing at lower levels, thus enabling air originating in the boundary layer to contribute to the maintenance of both local buoyancy and the large-scale Hadley cell despite acknowledged dilution by mixing along updraft trajectories. A tropical ""hot tower"" should thus be redefined as any deep convective cloud with a base in the boundary layer and reaching near the upper-tropospheric outflow layer. © 2009 American Meteorological Society."
"35578543700;23486505900;","Increased sensitivity of tropical cyclogenesis to wind shear in higher SST environments",2008,"10.1029/2008GL034147","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53749102980&doi=10.1029%2f2008GL034147&partnerID=40&md5=be0b6cdbe35578a1c37b35803f865001","A new method for evaluating the sensitivity of tropical cyclone (TC) genesis to environmental parameters involves the simulation of tropical cyclone development with a cloud-resolving model in environments of radiative-convective equilibrium (RCE) generated by the same model. This method is extended to allow for the incorporation of mean wind shear into the RCE states, thus providing much more realistic and relevant simulations of TC genesis. The ""finite-amplitude"" nature of tropical cyclogenesis is reproduced, with cyclogenesis resulting only when the initial vortex strength is sufficient, which in turn depends on the environmental parameters. For fixed thermodynamic parameters, the required initial vortex strength necessary for genesis increases with the mean wind shear. However, an unexpected result has been obtained, that increasing sea surface temperature (SST) does not allow TC genesis to overcome greater shear. In fact, the opposite trend is found, that shear is more effective in suppressing TC genesis when the SST is higher. This increased sensitivity can be explained by several factors, such as the higher altitude of the developing mid-level vortex, stronger downdrafts, and increased static stability, all of which allow the shear to be more effective in disrupting the developing cyclone. Copyright 2008 by the American Geophysical Union."
"57209589566;6701744275;","Synoptic wave perturbations and convective systems over equatorial Africa",2008,"10.1175/2008JCLI2409.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-60749085102&doi=10.1175%2f2008JCLI2409.1&partnerID=40&md5=c5ac31c7a10267b0e340bc67e1a160e3","Spectral analysis of the outgoing longwave radiation (OLR) time series over equatorial Africa reveals large oscillations of the convection with periods of between 3 and 6 days. In March and April, when the intertropical convergence zone (ITCZ) migrates northward and crosses equatorial Africa, this periodic behavior is most pronounced with a marked peak at 5-6 days. Robust horizontal and vertical patterns, consistent with a convectively coupled Kelvin wave, can be extracted by a simple composite technique based only on the phase of the convective oscillations over equatorial Africa. The composite reveals differences between continental and adjacent oceanic regions. Over the continent, the stronger oscillation of the convection is associated with larger temperature and moisture anomalies near the surface, suggesting an influence of diabatic processes on the amplitude of the perturbations. Some convective events over equatorial Africa are triggered by waves propagating eastward over the equatorial Atlantic. However, this cannot explain the robust periodic behavior observed over equatorial Africa because the convective variability over the Amazon basin and the equatorial Atlantic have different spectral characteristics with no marked peak at 5-6 days in March and April. The mesoscale convective systems embedded in these synoptic disturbances are studied using satellite brightness temperature at higher spatial (0.5°) and temporal (3 h) resolution than the OLR (respectively, 2.5° and daily average). The diurnal and the wave modulations of occurrence, size, and life cycle of the mesoscale convective systems are inspected. These systems are generated preferentially over the western slopes of the Rift Valley highlands. They propagate west-southwestward over the Congo basin where they reach their maximum size. The 5-6-day perturbations do not modify the diurnal triggering of convective systems notably, but the perturbations do modify their development into larger organized convection, especially over the Congo basin. The implication of these results for understanding the physical source of these 5-6-day perturbations is discussed. © 2008 American Meteorological Society."
"7101667328;","Multiple quasi equilibria of the ITCZ and the origin of monsoon onset",2000,"10.1175/1520-0469(2000)057<0641:mqeoti>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034161745&doi=10.1175%2f1520-0469%282000%29057%3c0641%3amqeoti%3e2.0.co%3b2&partnerID=40&md5=d99d5fd9b7ccbaf22d005f15ad7fe75a","Supported by numerical experiment results, the abrupt change of the location of the intertropical convergence zone (ITCZ), from the equatorial trough flow regime to the monsoon trough flow regime, or the monsoon onset, is interpreted as a subcritical instability. There are two balancing 'forces' acting on the ITCZ. One toward the equator, or an equatorial latitude depending on the convection scheme, due to the earth's rotation, has a nonlinear latitudinal dependence; and the other toward a latitude close to the sea surface temperature peak has a relatively linear latitudinal dependence. The highly nonlinear latitudinal dependence of the first 'force' is crucial for the existence of the multiple equilibria. This work pivots on the finding that the ITCZ and Hadley circulation can still exist without the pole-to-equator gradient of radiative-convective equilibrium temperature. The numerical experiments are done with an atmospheric general circulation model over an aquaplanet with zonally uniform sea surface temperature. The existence of the two flow regimes, the two 'force,' and the abrupt transition are all demonstrated in the experiments. Experimental results show high dependence on the choice of cumulus parameterization scheme, especially during the equatorial trough circulation regime. Although the proposed interpretation is more suitable for explaining the monsoon trough onset in the western Pacific, it is hypothesized that the same basic mechanism is also at the core of monsoon onset in other parts of the Tropics.Supported by numerical experiment results, the abrupt change of the location of the intertropical convergence zone (ITCZ), from the equatorial trough flow regime to the monsoon trough flow regime, or the monsoon onset, is interpreted as a subcritical instability. There are two balancing 'forces' acting on the ITCZ. One toward the equator, or an equatorial latitude depending on the convection scheme, due to the earth's rotation, has a nonlinear latitudinal dependence; and the other toward a latitude close to the sea surface temperature peak has a relatively linear latitudinal dependence. The highly nonlinear latitudinal dependence of the first 'force' is crucial for the existence of the multiple equilibria. This work pivots on the finding that the ITCZ and Hadley circulation can still exist without the pole-to-equator gradient of radiative-convective equilibrium temperature. The numerical experiments are done with an atmospheric general circulation model over an aquaplanet with zonally uniform sea surface temperature. The existence of the two flow regimes, the two 'forces,' and the abrupt transition are all demonstrated in the experiments. Experimental results show high dependence on the choice of cumulus parameterization scheme, especially during the equatorial trough circulation regime. Although the proposed interpretation is more suitable for explaining the monsoon trough onset in the western Pacific, it is hypothesized that the same basic mechanism is also at the core of monsoon onset in other parts of the Tropics."
"7003554893;7004160585;6603853280;7103413199;6602627241;6602080773;7402445326;7201783608;7004854393;7006621789;6602109792;","A GCSS model intercomparison for a tropical squall line observed during TOGA-COARE. II: Intercomparison of single-column models and a cloud-resolving model",2000,"10.1002/qj.49712656405","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034069686&doi=10.1002%2fqj.49712656405&partnerID=40&md5=0b67d75b9cf27ae9f1765d966d9ae8aa","This paper presents single-column model (SCM) simulations of a tropical squall-line case observed during the Coupled Ocean-Atmosphere Response Experiment of the Tropical Ocean/Global Atmosphere Programme. This case-study was part of an international model intercomparison project organized by Working Group 4 'Precipitating Convective Cloud Systems' of the GEWEX (Global Energy and Water-cycle EXperiment) Cloud System Study. Eight SCM groups using different deep-convection parametrizations participated in this project. The SCMs were forced by temperature and moisture tendencies that had been computed from a reference cloud-resolving model (CRM) simulation using open boundary conditions. The comparison of the SCM results with the reference CRM simulation provided insight into the ability of current convection and cloud schemes to represent organized convection. The CRM results enabled a detailed evaluation of the SCMs in terms of the thermodynamic structure and the convective mass flux of the system, the latter being closely related to the surface convective precipitation. It is shown that the SCMs could reproduce reasonably well the time evolution of the surface convective and stratiform precipitation, the convective mass flux, and the thermodynamic structure of the squall-line system. The thermodynamic structure simulated by the SCMs depended on how the models partitioned the precipitation between convective and stratiform. However, structural differences persisted in the thermodynamic profiles simulated by the SCMs and the CRM. These differences could be attributed to the fact that the total mass flux used to compute the SCM forcing differed from the convective mass flux. The SCMs could not adequately represent these organized mesoscale circulations and the microphysical/radiative forcing associated with the stratiform region. This issue is generally known as the 'scale-interaction' problem that can only be properly addressed in fully three-dimensional simulations. Sensitivity simulations run by several groups showed that the time evolution of the surface convective precipitation was considerably smoothed when the convective closure was based on convective available potential energy instead of moisture convergence. Finally, additional SCM simulations without using a convection parametrization indicated that the impact of a convection parametrization in forced SCM runs was more visible in the moisture profiles than in the temperature profiles because convective transport was particularly important in the moisture budget."
"35345503300;7006184606;","Equilibrium atmospheres of a two-column radiative-convective model",1999,"10.1256/smsqj.55813","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032695412&doi=10.1256%2fsmsqj.55813&partnerID=40&md5=00cdc7c5015af41d69b2f62867bb354c","Interaction between steady, large-scale atmospheric circulations and a radiative-convective environment is considered. As a model tool, we use a two-column radiative-convective model with an explicit hydrological cycle that uses clear-sky conditions in the radiation calculation. A flow field is calculated by the linearized, hydrostatic equations of motion in a non-rotating frame of reference. Mechanical damping is represented by vertical diffusion of momentum and surface drag. The flow advects heat and moisture, and thereby modifies the local radiative-convective equilibrium. A dynamically passive ocean mixed layer is situated below the model atmosphere. All externally specified parameters are identical in the two columns, implying that local radiative-convective equilibrium is a steady solution. For weak mechanical damping (or small column length), the local equilibrium is generally unstable due to a positive feedback between large-scale subsidence and infrared cooling, which operates via advective drying. A circulating equilibrium, in which the air ascends in one column and descends in the other, is attained. Due to a reduced content of clear-sky water vapour, which is the major infrared absorber in the model, the circulating equilibrium can emit the absorbed solar radiation at a significantly lower surface temperature than the corresponding local equilibrium. In the limit of a nearly inviscid atmosphere, the intensity of the large-scale circulation is controlled chiefly by the mid-tropospheric radiative cooling in the downdraught column. In this regime, we find two distinct equilibria with circulation that are distinguished by the features of the downdraught column: one branch with deep convection but where the integrated convective heating vanishes due to evaporation of precipitation; and one branch with shallow (or no) convection where the surface boundary layer is disconnected from the free atmosphere."
"7409792174;7006095466;","Sensitivity of cloud-resolving simulations of warm-season convection to cloud microphysics parameterizations",2007,"10.1175/MWR3437.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548257816&doi=10.1175%2fMWR3437.1&partnerID=40&md5=62bcf988b8ce10c2e03df1958227e6e8","This paper investigates the effects of cloud microphysics parameterizations on simulations of warm-season precipitation at convection-permitting grid spacing. The objective is to assess the sensitivity of summertime convection predictions to the bulk microphysics parameterizations (BMPs) at fine-grid spacings applicable to the next generation of operational numerical weather prediction models. Four microphysical parameterization schemes are compared: simple ice (Dudhia), four-class mixed phase (Reisner et al.), Goddard five-class mixed phase (Tao and Simpson), and five-class mixed phase with graupel (Reisner et al.). The experimentation involves a 7-day episode (3-9 July 2003) of U.S. midsummer convection under moderate large-scale forcing. Overall, the precipitation coherency manifested as eastward-moving organized convection in the lee of the Rockies is insensitive to the choice of the microphysics schemes, and the latent heating profiles are also largely comparable among the BMPs. The upper-level condensate and cloudiness, upper-level radiative cooling/ heating, and rainfall spectrum are the most sensitive, whereas the domain-mean rainfall rate and areal coverage display moderate sensitivity. Overall, the three mixed-phase schemes outperform the simple ice scheme, but a general conclusion about the degree of sophistication in the microphysics treatment and the performance is not achievable. © 2007 American Meteorological Society."
"7101673388;","Greenhouse models of the atmosphere of titan",1973,"10.1016/0019-1035(73)90138-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846058132&doi=10.1016%2f0019-1035%2873%2990138-3&partnerID=40&md5=bcdce1f53c1a96f22da5217d3f7cda3a","The greenhouse effect is calculated for a series of model atmospheres of Titan containing varying proportions of methane, hydrogen, helium, and ammonia. The pressure induced transitions of hydrogen and methane are the major sources of infrared opacity. For each model atmosphere we first computed its temperature structure with a radiative-convective equilibrium computer program and then generated its brightness temperature spectrum to compare with observed values. This comparison indicates that the methane-to-hydrogen ratio is 1-.67+2, the surface pressure is at least 0.4atm, and the surface temperature at least 150°K. In addition, except possibly close to the surface, the amount of ammonia is far less than the saturation vapor value. Large amounts of helium may also be present. Many of the successful model atmospheres have methane condensation clouds in the upper troposphere, which help reconcile spectroscopic gas abundances and the observed ultraviolet albedo of Titan with the gas amounts required for the greenhouse effect. The occurrence of large amounts of hydrogen may be a prerequisite for the occurrence of large amounts of methane in the atmosphere and vice versa. This hypothesis may help explain why Titan is the only satellite in our solar system known to have an atmosphere. © 1973."
"16644246500;36992744000;7401945370;7201504886;35509639400;56520853700;","Radiative-convective equilibrium model intercomparison project",2018,"10.5194/gmd-11-793-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042845837&doi=10.5194%2fgmd-11-793-2018&partnerID=40&md5=8b81810be5bcaacc822b1d0c37b0572d","RCEMIP, an intercomparison of multiple types of models configured in radiative-convective equilibrium (RCE), is proposed. RCE is an idealization of the climate system in which there is a balance between radiative cooling of the atmosphere and heating by convection. The scientific objectives of RCEMIP are three-fold. First, clouds and climate sensitivity will be investigated in the RCE setting. This includes determining how cloud fraction changes with warming and the role of self-aggregation of convection in climate sensitivity. Second, RCEMIP will quantify the dependence of the degree of convective aggregation and tropical circulation regimes on temperature. Finally, by providing a common baseline, RCEMIP will allow the robustness of the RCE state across the spectrum of models to be assessed, which is essential for interpreting the results found regarding clouds, climate sensitivity, and aggregation, and more generally, determining which features of tropical climate a RCE framework is useful for. A novel aspect and major advantage of RCEMIP is the accessibility of the RCE framework to a variety of models, including cloud-resolving models, general circulation models, global cloud-resolving models, single-column models, and large-eddy simulation models. © Author(s) 2018."
"36961988200;7006184606;","Equilibrium tropical cyclone size in an idealized state of axisymmetric radiative-convective equilibrium",2014,"10.1175/JAS-D-13-0155.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899741314&doi=10.1175%2fJAS-D-13-0155.1&partnerID=40&md5=ba3756c471fbae57264a55eb61eb35ce","Tropical cyclone size remains an unsolved problem in tropical meteorology, yet size plays a significant role in modulating damage. This work employs the Bryan cloud model (CM1) to systematically explore the sensitivity of the structure of an axisymmetric tropical cyclone at statistical equilibrium to the set of relevant model, initial, and environmental external parameters. The analysis is performed in a highly idealized state of radiative-convective equilibrium(RCE) governed by only four thermodynamic parameters, which are shown to modulate the storm structure primarily via modulation of the potential intensity. Using dimensional analysis, the authors find that the equilibrium radial wind profile is primarily a function of a single nondimensional parameter given by the ratio of the storm radial length scale to the parameterized eddy radial length scale. The former is found to be the ratio of the potential intensity to the Coriolis parameter, matching the prediction for the ''natural'' storm length scale embedded within prevailing axisymmetric tropical cyclone theory; the Rossby deformation radius is shown not to be fundamental. Beyond this primary scaling, a second nondimensional parameter representing the nondimensional Ekman suction velocity is found to modulate the far outer wind field. Implications of the primary nondimensional parameter are discussed, including the critical role of effective turbulence in modulating inner-core structure and new insight into empirical estimates of the radial mixing length. © 2014 American Meteorological Society."
"13411455700;16644246500;35509639400;56272964700;7006614696;36161790500;7402934750;7005035762;","Observing Convective Aggregation",2017,"10.1007/s10712-017-9419-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85025067879&doi=10.1007%2fs10712-017-9419-1&partnerID=40&md5=3aebb39e19c43f386bec273123bc10c4","Convective self-aggregation, the spontaneous organization of initially scattered convection into isolated convective clusters despite spatially homogeneous boundary conditions and forcing, was first recognized and studied in idealized numerical simulations. While there is a rich history of observational work on convective clustering and organization, there have been only a few studies that have analyzed observations to look specifically for processes related to self-aggregation in models. Here we review observational work in both of these categories and motivate the need for more of this work. We acknowledge that self-aggregation may appear to be far-removed from observed convective organization in terms of time scales, initial conditions, initiation processes, and mean state extremes, but we argue that these differences vary greatly across the diverse range of model simulations in the literature and that these comparisons are already offering important insights into real tropical phenomena. Some preliminary new findings are presented, including results showing that a self-aggregation simulation with square geometry has too broad distribution of humidity and is too dry in the driest regions when compared with radiosonde records from Nauru, while an elongated channel simulation has realistic representations of atmospheric humidity and its variability. We discuss recent work increasing our understanding of how organized convection and climate change may interact, and how model discrepancies related to this question are prompting interest in observational comparisons. We also propose possible future directions for observational work related to convective aggregation, including novel satellite approaches and a ground-based observational network. © 2017, The Author(s)."
"35105101800;22980035400;","Microphysical characteristics of overshooting convection from polarimetric radar observations",2015,"10.1175/JAS-D-13-0388.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923112625&doi=10.1175%2fJAS-D-13-0388.1&partnerID=40&md5=85d5684993ea1bf930d93d1ca4daa28b","The authors present observations of the microphysical characteristics of deep convection that overshoots the altitude of the extratropical tropopause from analysis of the polarimetric radar variables of radar reflectivity factor at horizontal polarization ZH, differential reflectivity ZDR, and specific differential phase KDP. Identified overshooting convective storms are separated by their organization and intensity into three classifications: organized convection, discrete ordinary convection, and discrete supercell convection. Composite analysis of identified storms for each classification reveals microphysical features similar to those found in previous studies of deep convection, with deep columns of highly positive ZDR and KDP representing lofting of liquid hydrometeors within the convective updraft and above the melting level. In addition, organized and discrete supercell classifications show distinct near-zero ZDR minima aligned horizontally with and at altitudes higher than the updraft column features, likely indicative of the frequent presence of large hail in each case. Composites for organized convective systems show a similar ZDR minimum throughout the portion of the convective core that is overshooting the tropopause, corresponding to ZH in the range of 15-30 dBZ and negative KDP observations, in agreement with the scattering properties of small hail and/or lump or conical graupel. Additional analyses of the evolution of overshooting storms reveals that the ZDR minima indicative of hail in the middle and upper troposphere and graupel in the overshooting top are associated with the mature and decaying stages of overshooting, respectively, supporting their inferred contributions to the observed polarimetric fields. © 2015 American Meteorological Society."
"55927861900;7006069664;57203474131;7201786471;35768178600;","Simulation of heavy rainfall events over Indian monsoon region using WRF-3DVAR data assimilation system",2010,"10.1007/s00703-009-0054-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949272722&doi=10.1007%2fs00703-009-0054-3&partnerID=40&md5=bca6f9f63a79d5975a8304001808dda6","We present the results of the impact of the 3D variational data assimilation (3DVAR) system within the Weather Research and Forecasting (WRF) model to simulate three heavy rainfall events (25-28 June 2005, 29-31 July 2004, and 7-9 August 2002) over the Indian monsoon region. For each event, two numerical experiments were performed. In the first experiment, namely the control simulation (CNTL), the low-resolution global analyses are used as the initial and boundary conditions of the model. In the second experiment (3DV-ANA), the model integration was carried out by inserting additional observations in the model's initial conditions using the 3DVAR scheme. The 3DVAR used surface weather stations, buoy, ship, radiosonde/rawinsonde, and satellite (oceanic surface wind, cloud motion wind, and cloud top temperature) observations obtained from the India Meteorological Department (IMD). After the successful inclusion of additional observational data using the 3DVAR data assimilation technique, the resulting reanalysis was able to successfully reproduce the structure of convective organization as well as prominent synoptic features associated with the mid-tropospheric cyclones (MTC). The location and intensity of the MTC were better simulated in the 3DV-ANA as compared to the CNTL. The results demonstrate that the improved initial conditions of the mesoscale model using 3DVAR enhanced the location and amount of rainfall over the Indian monsoon region. Model verification and statistical skill were assessed with the help of available upper-air sounding data. The objective verification further highlighted the efficiency of the data assimilation system. The improvements in the 3DVAR run are uniformly better as compared to the CNTL run for all the three cases. The mesoscale 3DVAR data assimilation system is not operational in the weather forecasting centers in India and a significant finding in this study is that the assimilation of Indian conventional and non-conventional observation datasets into numerical weather forecast models can help improve the simulation accuracy of meso-convective activities over the Indian monsoon region. Results from the control experiments also highlight that weather and regional climate model simulations with coarse analysis have high uncertainty in simulating heavy rain events over the Indian monsoon region and assimilation approaches, such as the 3DVAR can help reduce this uncertainty. © Springer-Verlag 2009."
"7103274591;57197046575;","Instability and large-scale circulations in a two-column model of the tropical troposphere",2000,"10.1256/smsqj.57006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034531614&doi=10.1256%2fsmsqj.57006&partnerID=40&md5=49a5abf09bd844093faee27e406afbd0","A two-column model of the tropical atmosphere is developed. The two columns are kept in buoyancy equilibrium by mass exchange driven by the inter-column pressure gradient, and diabatic processes are parameterized by highly simplified schemes. This model is used to investigate whether spontaneous large-scale circulations will develop in the tropical atmosphere when the sea surface temperature and solar radiative forcing are uniform. Such circulations do indeed develop in the model, with ascent in one column and descent in the other, when one of the columns is slightly perturbed from the initial state of radiative-convective equilibrium. A key element of the circulation dynamics is that increased equivalent potential temperature in a column leads to enhanced convection and rainfall in that column, which further increases the equivalent potential temperature there. The latter effect arises because convection enhances surface heat fluxes and decreases outgoing long-wave radiation by virtue of the increase in stratiform cloudiness. These results form an attractive explanation for the observed patchiness of deep convection over warm tropical oceans and suggest that further modelling and observational work be directed towards understanding the budget of equivalent potential temperature in the tropical atmosphere and its relationship to rainfall."
"11939918300;7201504886;","Coupled radiative convective equilibrium simulations with explicit and parameterized convection",2016,"10.1002/2016MS000666","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84990222896&doi=10.1002%2f2016MS000666&partnerID=40&md5=ff4fbe646c4093a5005116e10fe696e2","Radiative convective equilibrium has been applied in past studies to various models given its simplicity and analogy to the tropical climate. At convection-permitting resolution, the focus has been on the organization of convection that appears when using fixed sea surface temperature (SST). Here the SST is allowed to freely respond to the surface energy. The goals are to examine and understand the resulting transient behavior, equilibrium state, and perturbations thereof, as well as to compare these results to a simulation integrated with parameterized cloud and convection. Analysis shows that the coupling between the SST and the net surface energy acts to delay the onset of self-aggregation and may prevent it, in our case, for a slab ocean of less than 1 m. This is so because SST gradients tend to oppose the shallow low-level circulation that is associated with the self-aggregation of convection. Furthermore, the occurrence of self-aggregation is found to be necessary for reaching an equilibrium state and avoiding a greenhouse-like climate. In analogy to the present climate, the self-aggregation generates the dry and clear subtropics that allow the system to efficiently cool. In contrast, strong shortwave cloud radiative effects, much stronger than at convection-permitting resolution, prevent the simulation with parameterized cloud and convection to fall into a greenhouse state. The convection-permitting simulations also suggest that cloud feedbacks, as arising when perturbing the equilibrium state, may be very different, and in our case less negative, than what emerges from general circulation models. © 2016. The Authors."
"35767566800;7006198994;7102567936;15026371500;7103271625;","Tropical intraseasonal variability in version 3 of the GFDL atmosphere model",2013,"10.1175/JCLI-D-12-00103.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872924851&doi=10.1175%2fJCLI-D-12-00103.1&partnerID=40&md5=647d6cdfc647e990baab62b6201a7459","Tropical intraseasonal variability is examined in version 3 of the Geophysical FluidDynamics Laboratory Atmosphere Model (AM3). In contrast to its predecessorAM2, AM3 uses a new treatment of deep and shallow cumulus convection and mesoscale clouds. The AM3 cumulus parameterization is a massflux-based scheme but also, unlike that in AM2, incorporatessubgrid-scale vertical velocities; these play a key role in cumulus microphysical processes. The AM3 convection scheme allows multiphase water substance produced in deep cumuli to be transported directly into mesoscale clouds, which strongly influence large-scale moisture and radiation fields. The authors examine four AM3 simulations using a control model and three versions with different modifications to the deep convection scheme. In the control AM3, using a convective closure based on CAPE relaxation, both MJO and Kelvin waves are weak relative to those in observations. By modifying the convective closure and trigger assumptions to inhibit deep cumuli, AM3 produces reasonable intraseasonal variability but a degraded mean state. MJO-like disturbances in the modified AM3 propagate eastwardat roughly the observed speed in the Indian Ocean but up to 2 times the observed speed inthe west Pacific Ocean. Distinct differences in intraseasonal convective organization andpropagation exist among the modified AM3 versions. Differences in vertical diabatic heating profiles associated with the MJO are also found. The two AM3 versions with the strongest intraseasonal signals have a more prominent ""bottom heavy"" heating profile leading the disturbance center and ""top heavy"" heating profile following the disturbance. The more realistic heating structures are associated with an improved depiction of moisture convergence and intraseasonal convective organization in AM3. © 2013 American Meteorological Society."
"15319530000;7101755461;","Tropical cyclogenesis associated with Kelvin waves and the Madden-Julian oscillation",2011,"10.1175/MWR-D-10-05060.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053177122&doi=10.1175%2fMWR-D-10-05060.1&partnerID=40&md5=111cf5aacfe33d1637aab9554e77ffa1","The Madden-Julian oscillation (MJO) influences tropical cyclone formation around the globe. Convectively coupled Kelvin waves are often embedded within the MJO, but their role in tropical cyclogenesis remains uncertain. This case study identifies the influences of the MJO and a series of Kelvin waves on the formation of two tropical cyclones. Typhoons Rammasun and Chataan developed in the western North Pacific on 28 June 2002. Two weeks earlier, conditions had been unfavorable for tropical cyclogenesis because of uniform trade easterlies and a lack of organized convection. The easterlies gave way to equatorial westerlies as the convective envelope of the Madden-Julian oscillation moved into the region. A series of three Kelvin waves modulated the development of the westerlies. Cyclonic potential vorticity (PV) developed in a strip between the growing equatorial westerlies and the persistent trade easterlies farther poleward. Rammasun and Chataan emerged from the apparent breakdown of this strip. The cyclonic PV developed in association with diabatic heating from both the MJO and the Kelvin waves. The tropical cyclones also developed during the largest superposition of equatorial westerlies from the MJO and the Kelvin waves. This chain of events suggests that the MJO and the Kelvin waves each played a role in the development of Rammasun and Chataan. © 2011 American Meteorological Society."
"14319126400;7101867299;","Fluctuations in an equilibrium convective ensemble. Part II: Numerical experiments",2006,"10.1175/JAS3710.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745038373&doi=10.1175%2fJAS3710.1&partnerID=40&md5=21c5e37534d49d9ac8ff168011cbd6db","The theoretical predictions derived in Part I of this study for the equilibrium fluctuations of an idealized ensemble of noninteracting, pointlike cumulus clouds are tested against three-dimensional cloud resolving model (CRM) simulations of radiative-convective equilibrium. Simulations with different radiative cooling rates are used to give a range of cloud densities, while imposed vertical wind shear of different strengths is used to produce different degrees of convective organization. The distribution of mass flux of individual clouds is found to be exponential in all simulations, in agreement with the theory. The distribution of total mass flux over a finite region also agrees well (to within around 10%) with the theoretical prediction for all simulations, but only after a correction to the modeled variance to take account of the finite size of clouds has been made. In the absence of imposed vertical wind shear, some spatial clustering of convective cells is observed at lower forcings (-2 and -4 K day-1) on a scale of 10-20 km, while at higher forcings (-8, -12, and -16 K day-1), there is a tendency toward spatial regularity on the same scale. These localized cloud interactions, however, appear to have little effect on the magnitude of the mass flux variability. Surprisingly, the convective organization obtained in the simulations with vertical wind shear has only a small effect on the mass flux statistics, even though it shows clearly in the location of the clouds. © 2006 American Meteorological Society."
"7003406400;","Time-scales of adjustment to radiative-convective equilibrium in the tropical atmosphere",1998,"10.1002/qj.49712455208","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032455784&doi=10.1002%2fqj.49712455208&partnerID=40&md5=94b29f23db5e6f0c90228f13b978e1b4","In the tropics the assumed existence of a balanced atmospheric state of radiative-convective equilibrium is a useful and widely utilized concept. Given an atmospheric state of radiative-convective equilibrium which is perturbed, this paper attempts to identify the mechanisms that determine the time-scale for the restoration of the balanced state. The perturbation could arise from large-scale atmospheric wave motions, local-scale convective downdraughts or sea surface temperature perturbations for example. The resulting state immediately after the perturbation is applied can be one of suppressed or convective conditions, and it is the complex response under convective conditions that is explored in this paper. A three-dimensional cloud resolving model is operated to a radiative-convective equilibrium state to which sea surface temperature perturbations are then applied. It is found that the variability of the model state variables, such as temperature and total water vapour amount, can be divided by processes into an exponential adjustment to the new balanced state on a long time-scale (15 days), superimposed by short time-scale variability (<4 days) that is governed almost solely by the convective mass-flux. The determination of the long time-scale trend to equilibrium is then investigated with further numerical experiments, which demonstrate that radiation determines the adjustment time-scale via its control of the subsidence velocities in the clear-sky regions surrounding convection. Some implications of the results for cumulus parametrization are discussed."
"23486505900;35578543700;7006184606;","Thermodynamic control of tropical cyclogenesis in environments of radiative-convective equilibrium with shear",2010,"10.1002/qj.706","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650050885&doi=10.1002%2fqj.706&partnerID=40&md5=5f5433c33a533ef7af2f1ef319200c5e","The potential for tropical cyclone formation from a pre-existing disturbance is further explored with high-resolution simulations of cyclogenesis in idealized, tropical environments. These idealized environments are generated from simulations of radiative-convective equilibrium with fixed sea-surface temperatures (SSTs), imposed mean surface winds, and an imposed profile of vertical wind shear. The propensity for tropical cyclogenesis in these environments is measured in two ways: first, in the period of time required for a weak, mid-level circulation to transition to a developing tropical cyclone; and second, from the value of an incubation parameter that incorporates environmental measures of mid-level saturation deficit and thermodynamic disequilibrium between the atmosphere and ocean. Conditions of tropospheric warming can be produced from increased SSTs or from increased mean surface winds; in either case, the time to genesis increases with atmospheric warming. As these parameters are varied, the incubation parameter is found to be highly correlated with changes in the time to genesis.The high resolution (3 km) of these simulations permits analysis of changes in tropical cyclogenesis under warming conditions at the vortex scale. For increasing SST, increased mid-level saturation deficits (dryness) are the primary reason for slowing or preventing genesis. For environments with increased surface wind, it is the decreased thermodynamic disequilibrium between the atmosphere and ocean that delays or prevents development. An additional effect in both cases is a decoupling of the low-level and mid-level vortices, primarily as a result of increased advecting flow at the altitude of the mid-level vortex, which is linked to the height of the freezing level. © 2010 Royal Meteorological Society."
"56942309200;35321650700;55967916100;33367455100;16022263500;55383456100;57191576880;","The effects of consistent chemical kinetics calculations on the pressure-temperature profiles and emission spectra of hot Jupiters",2016,"10.1051/0004-6361/201628799","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84991687203&doi=10.1051%2f0004-6361%2f201628799&partnerID=40&md5=1664128b294b8dd591adfb7357c25764","In this work we investigate the impact of calculating non-equilibrium chemical abundances consistently with the temperature structure for the atmospheres of highly-irradiated, close-in gas giant exoplanets. Chemical kinetics models have been widely used in the literature to investigate the chemical compositions of hot Jupiter atmospheres which are expected to be driven away from chemical equilibrium via processes such as vertical mixing and photochemistry. All of these models have so far used pressure-temperature (P-T) profiles as fixed model input. This results in a decoupling of the chemistry from the radiative and thermal properties of the atmosphere, despite the fact that in nature they are intricately linked. We use a one-dimensional radiative-convective equilibrium model, ATMO, which includes a sophisticated chemistry scheme to calculate P-T profiles which are fully consistent with non-equilibrium chemical abundances, including vertical mixing and photochemistry. Our primary conclusion is that, in cases of strong chemical disequilibrium, consistent calculations can lead to differences in the P-T profile of up to 100 K compared to the P-T profile derived assuming chemical equilibrium. This temperature change can, in turn, have important consequences for the chemical abundances themselves as well as for the simulated emission spectra. In particular, we find that performing the chemical kinetics calculation consistently can reduce the overall impact of non-equilibrium chemistry on the observable emission spectrum of hot Jupiters. Simulated observations derived from non-consistent models could thus yield the wrong interpretation. We show that this behaviour is due to the non-consistent models violating the energy budget balance of the atmosphere. © ESO, 2016."
"13411455700;6507112497;","The sensitivity of convective aggregation to diabatic processes in idealized radiative-convective equilibrium simulations",2016,"10.1002/2015MS000511","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956867468&doi=10.1002%2f2015MS000511&partnerID=40&md5=1e3bddafb28c271e8b3440a1f358d4ae","Idealized explicit convection simulations of the Met Office Unified Model exhibit spontaneous self-aggregation in radiative-convective equilibrium, as seen in other models in previous studies. This self-aggregation is linked to feedbacks between radiation, surface fluxes, and convection, and the organization is intimately related to the evolution of the column water vapor field. Analysis of the budget of the spatial variance of column-integrated frozen moist static energy (MSE), following Wing and Emanuel (2014), reveals that the direct radiative feedback (including significant cloud longwave effects) is dominant in both the initial development of self-aggregation and the maintenance of an aggregated state. A low-level circulation at intermediate stages of aggregation does appear to transport MSE from drier to moister regions, but this circulation is mostly balanced by other advective effects of opposite sign and is forced by horizontal anomalies of convective heating (not radiation). Sensitivity studies with either fixed prescribed radiative cooling, fixed prescribed surface fluxes, or both do not show full self-aggregation from homogeneous initial conditions, though fixed surface fluxes do not disaggregate an initialized aggregated state. A sensitivity study in which rain evaporation is turned off shows more rapid self-aggregation, while a run with this change plus fixed radiative cooling still shows strong self-aggregation, supporting a ""moisture-memory"" effect found in Muller and Bony (2015). Interestingly, self-aggregation occurs even in simulations with sea surface temperatures (SSTs) of 295 and 290 K, with direct radiative feedbacks dominating the budget of MSE variance, in contrast to results in some previous studies. © 2016. The Authors."
"35568218100;7006184606;","A theory for buoyancy and velocity scales in deep moist convection",2009,"10.1175/2009JAS3103.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73549125262&doi=10.1175%2f2009JAS3103.1&partnerID=40&md5=bcfb21f627f1f65f0072cb5c7acfa512","Buoyancy and velocity scales for dry convection in statistical equilibrium were derived in the early twentieth century by Prandtl, but the scaling of convective velocity and buoyancy, as well as the fractional area coverage of convective clouds, is still unresolved for moist convection. In this paper, high-resolution simulations of an atmosphere in radiative-convective equilibrium are performed using the Weather Research and Forecasting (WRF) model, a three-dimensional, nonhydrostatic, convection-resolving, limited-area model. The velocity and buoyancy scales for moist convection in statistical equilibrium are characterized by prescribing different constant cooling rates to the system. It is shown that the spatiotemporal properties of deep moist convection and buoyancy and velocity scales at equilibrium depend on the terminal velocity of raindrops and a hypothesis is developed to explain this behavior. This hypothesis is evaluated and discussed in the context of the numerical results provided by the WRF model. The influence of domain size on radiative-convective equilibrium statistics is also assessed. The dependence of finescale spatiotemporal properties of convective structures on numerical and physical details is investigated. © 2009 American Meteorological Society."
"7003406400;7006184606;","The vertical resolution sensitivity of simulated equilibrium temperature and water-vapour profiles",2000,"10.1002/qj.49712656502","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034130313&doi=10.1002%2fqj.49712656502&partnerID=40&md5=76b2c9adb5dd8a0dd7feee50abb107f3","Variability of atmospheric water vapour is the most important climate feedback in present climate models. Thus, it is of crucial importance to understand the sensitivity of water vapour to model attributes, such as physical parametrizations and resolution. Here we attempt to determine the minimum vertical resolution necessary for accurate prediction of water vapour. To address this issue, we have run two single-column models to tropical radiative-convective equilibrium states and have examined the sensitivity of the equilibrium profiles to vertical resolution. Both column models produce reasonable equilibrium states of temperature and moisture. Convergence of the profiles was achieved in both models using a uniform vertical resolution of around 25 hPa. Coarser resolution leads to significant errors in both the water vapour and temperature profiles, with a resolution of 100 hPa proving completely inadequate. However, fixing the boundary-layer resolution and altering only the free-tropospheric resolution significantly reduces sensitivity to vertical resolution in one of the column models, in both water and temperature, highlighting the importance of resolving boundary-layer processes. Additional experiments show that the height of the simulated tropopause is sensitive to upper-tropospheric vertical resolution. At resolutions higher than 33 hPa, one of the models developed a high degree of vertical structure in the vapour profile, resulting directly from the complex array of microphysical processes included in the stratiform cloud parametrization, some of which were only resolved at high resolutions. This structure was completely absent at lower resolutions, casting some doubt on the approach of using relatively complicated cloud schemes at low vertical resolutions."
"7103074130;","Radiative-convective equilibrium models of Uranus and Neptune",1986,"10.1016/0019-1035(86)90145-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38249042675&doi=10.1016%2f0019-1035%2886%2990145-4&partnerID=40&md5=8311bab118771474e2bdd4a332611015","A study of radiative-convective equilibrium models for Uranus and Neptune is presented, with particular emphasis on the stratospheric energy balance, including the influence of aerosol heating and convective penetration. A straightforward numerical method is employed (J. F. Appleby and J. S. Hogan (1984). Icarus 59, 336-366) along with standard opacity formulations and the assumption of local thermodynamic equilibrium. A range of models was considered for Uranus, reflecting uncertainties in observational constraints on the middle stratospheric temperatures. The results indicate that a ""continuum absorber"" could be significant in the stratosphere, despite Uranus' great distance from the Sun. Also, test runs are presented to illustrate the influence of uncertainties in the gas composition and changes in the effective mean insolation. A long-standing theoretical problem for Neptune has been to explain the unexpectedly high stratospheric temperatures without invoking supersaturation of CH4. The results show that a ""continuum absorber"" could contribute significantly to the energy balance within a localized stratospheric region; however, it probably cannot provide enough power to explain the observed infrared spectrum, regardless of its vertical distribution. One alternative is ""convective penetration"" which could arise if, for example, vertical mixing is so rapid that CH4 condensation cannot occur before the gas is swept upward, above the condensation region. In the example considered here, the CH4 mixing ratio in the middle and upper stratosphere is equal to that below the condensation region in the troposphere. The infrared emission from this model was found to be in generally good agreement with the observations. Such a model could also apply to Uranus, in lieu of aerosol or other ""additional"" heating mechanisms, to an extent that is commensurate with weaker convective uplifting. © 1986."
"35321650700;33367455100;56743128100;55967916100;55665248300;56942309200;22134847000;55383456100;","Fingering convection and cloudless models for cool brown dwarf atmospheres",2015,"10.1088/2041-8205/804/1/L17","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938226595&doi=10.1088%2f2041-8205%2f804%2f1%2fL17&partnerID=40&md5=1e1e7c91254ba325fd8c76486e46bd51","This work aims to improve the current understanding of the atmospheres of brown dwarfs, especially cold ones with spectral types T and Y, whose modeling is a current challenge. Silicate and iron clouds are believed to disappear at the photosphere at the L/T transition, but cloudless models fail to reproduce correctly the spectra of T dwarfs, advocating for the addition of more physics, e.g., other types of clouds or internal energy transport mechanisms. We use a one-dimensional radiative/convective equilibrium code ATMO to investigate this issue. This code includes both equilibrium and out-of-equilibrium chemistry and solves consistently the PT structure. Included opacity sources are H2-H2, H2-He, H2O, CO, CO2, CH4, NH3, K, Na, and TiO, VO if they are present in the atmosphere. We show that the spectra of Y dwarfs can be accurately reproduced with a cloudless model if vertical mixing and NH3 quenching are taken into account. T dwarf spectra still have some reddening in, e.g., J-H, compared to cloudless models. This reddening can be reproduced by slightly reducing the temperature gradient in the atmosphere. We propose that this reduction of the stabilizing temperature gradient in these layers, leading to cooler structures, is due to the onset of fingering convection, triggered by the destabilizing impact of condensation of very thin dust. © 2015. The American Astronomical Society. All rights reserved."
"36992744000;8866821900;6701431208;13406399300;","Global radiative-convective equilibrium in the community atmosphere model, version 5",2015,"10.1175/JAS-D-14-0268.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943780744&doi=10.1175%2fJAS-D-14-0268.1&partnerID=40&md5=b1caebeeb1da43b155080226d51adf78","In the continued effort to understand the climate system and improve its representation in atmospheric general circulation models (AGCMs), it is crucial to develop reduced-complexity frameworks to evaluate these models. This is especially true as the AGCM community advances toward high horizontal resolutions (i.e., grid spacing less than 50 km), which will require interpreting and improving the performance of many model components.A simplified global radiative-convective equilibrium (RCE) configuration is proposed to explore the implication of horizontal resolution on equilibrium climate. RCE is the statistical equilibrium in which the radiative cooling of the atmosphere is balanced by heating due to convection. In this work, the Community Atmosphere Model, version 5 (CAM5), is configured in RCE to better understand tropical climate and extremes. The RCE setup consists of an ocean-covered Earth with diurnally varying, spatially uniform insolation and no rotation effects. CAM5 is run at two horizontal resolutions: a standard resolution of approximately 100-km grid spacing and a high resolution of approximately 25-km spacing. Surface temperature effects are considered by comparing simulations using fixed, uniform sea surface temperature with simulations using an interactive slab-ocean model. The various CAM5 configurations provide useful insights into the simulation of tropical climate as well as the model's ability to simulate extreme precipitation events. In particular, the manner in which convection organizes is shown to be dependent on model resolution and the surface configuration (including surface temperature), as evident by differences in cloud structure, circulation, and precipitation intensity. © 2015 American Meteorological Society."
"56575724100;","Role of cumulus congestus in tropical cyclone formation in a high-resolution numerical model simulation",2014,"10.1175/JAS-D-13-0257.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896773101&doi=10.1175%2fJAS-D-13-0257.1&partnerID=40&md5=8353558921e52d6b33e1cdc8df9c6bb3","The role of cumulus congestus (shallow and congestus convection) in tropical cyclone (TC) formation is examined in a high-resolution simulation of Tropical Cyclone Fay (2008). It is found that cumulus congestus plays a dominant role in moistening the lower to middle troposphere and spinning up the near-surface circulation prior to genesis, while deep convection plays a key role in moistening the upper troposphere and intensifying the cyclonic circulation over a deep layer. The transition from the tropical wave stage to the TC stage is marked by a substantial increase in net condensation and potential vorticity generation by deep convection in the inner wave pouch region. This study suggests that TC formation can be regarded as a two-stage process. The first stage is a gradual process of moisture preconditioning and low-level spinup, in which cumulus congestus plays a dominant role. The second stage commences with the rapid development of deep convection in the inner pouch region after the air column is moistened sufficiently, whereupon the concentrated convective heating near the pouch center strengthens the transverse circulation and leads to the amplification of the cyclonic circulation over a deep layer. The rapid development of deep convection can be explained by the power-law increase of precipitation rate with column water vapor (CWV) above a critical value. The high CWV near the pouch center thus plays an important role in convective organization. It is also shown that cumulus congestus can effectively drive the low-level convergence and provides a direct and simple pathway for the development of the TC protovortex near the surface. © 2014 American Meteorological Society."
"7006095466;","The Multiscale Organization of Moist Convection and the Intersection of Weather and Climate",2013,"10.1029/2008GM000838","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84951267523&doi=10.1029%2f2008GM000838&partnerID=40&md5=1135d7bc724e4429bce4f6ba0cbad04b","Moist convection organizes into cloud systems of various sizes and kinds, a process with a dynamical basis and upscale connotations. Although organized precipitation systems have been extensively observed, numerically simulated, and dynamically modeled, our knowledge of their effects on weather and climate is far from complete. Convective organization is absent de facto from contemporary climate models because the salient dynamics are not represented by parameterizations and the model resolution is insufficient to represent them explicitly. Highresolution weather prediction models, fine-resolution cloud system models, and dynamical models address moist convective organization explicitly. As a key element in the seamless prediction of weather and climate on timescales up to seasonal, organized convection is the focus of the Year of Tropical Convection, an international collaborative project coordinated by the World Meteorological Organisation. This paper reviews the scientific basis of convective organization and progress toward comprehending its large-scale effects and representing them in global models. © 2010 by the American Geophysical Union. All rights reserved."
"7003718864;","The mean State of axisymmetric hurricanes in statistical equilibrium",2011,"10.1175/2010JAS3644.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959669273&doi=10.1175%2f2010JAS3644.1&partnerID=40&md5=8dd57fb44c3337220f0b40def553910e","Numerical experiments are performed to determine the mean state of an axisymmetric hurricane in statistical equilibrium. Most earlier studies used a damping scheme on the temperature field as a parameterization of radiative cooling, which the authors demonstrate yields storms that have little convection outside the eyewall and do not achieve statistical equilibrium. Here the effects of infrared radiation are explicitly simulated, which permits the storm to achieve radiative-convective equilibrium. Beginning from a state of rest, a storm spontaneously develops with maximum surface wind speeds in excess of 100 m s-1 by day 10. This transient ""superintense"" storm weakens and is replaced by an equilibrium storm that lasts over 400 days with a time-mean maximum wind speed that compares closely with a diagnostic estimate of potential intensity (PI). The main assumptions of PI theory are found to be consistent with the properties of the equilibrium storm, but the thermodynamic cycle does not resemble a Carnot cycle, with an implied efficiency of about half that of the Carnot limit. Maximum radiative cooling is found in the midtroposphere outside the storm, where convective clouds detrain into the dry layer of storm-outflow subsidence, producing a large vertical gradient in water vapor and cloud water. Sensitivity experiments reveal that the results are robust to changes in the prestorm thermodynamic sounding, ambient rotation, horizontal turbulent mixing, and details in the radiative heating field. Subject to the assumptions in this study, it can be concluded that 1) the undisturbed tropical atmosphere is unstable to axisymmetric hurricanes, 2) PI theory accurately bounds time-mean storm intensity (but not transient fluctuations), and 3) equilibrium storm intensity is insensitive to turbulent mixing in the radial direction. © 2011 American Meteorological Society."
"7202154330;7006186794;","Towards understanding the unusual indian monsoon in 2009",2010,"10.1007/s12040-010-0033-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955626654&doi=10.1007%2fs12040-010-0033-6&partnerID=40&md5=e92e140603e9c80a0b3252bcdd12e889","The Indian summer monsoon season of 2009 commenced with a massive deficit in all-India rainfall of 48% of the average rainfall in June. The all-India rainfall in July was close to the normal but that in August was deficit by 27%. In this paper, we first focus on June 2009, elucidating the special features and attempting to identify the factors that could have led to the large deficit in rainfall. In June 2009, the phase of the two important modes, viz., El Niño and Southern Oscillation (ENSO) and the equatorial Indian Ocean Oscillation (EQUINOO) was unfavourable. Also, the eastern equatorial Indian Ocean (EEIO) was warmer than in other years and much warmer than the Bay. In almost all the years, the opposite is true, i.e., the Bay is warmer than EEIO in June. It appears that this SST gradient gave an edge to the tropical convergence zone over the eastern equatorial Indian Ocean, in competition with the organized convection over the Bay. Thus, convection was not sustained for more than three or four days over the Bay and no northward propagations occurred. We suggest that the reversal of the sea surface temperature (SST) gradient between the Bay of Bengal and EEIO, played a critical role in the rainfall deficit over the Bay and hence the Indian region. We also suggest that suppression of convection over EEIO in association with the El Niño led to a positive phase of EQUINOO in July and hence revival of the monsoon despite the El Niño. It appears that the transition to a negative phase of EQUINOO in August and the associated large deficit in monsoon rainfall can also be attributed to the El Niño. © Indian Academy of Sciences."
"6602729726;7005461477;","Surface fluxes and boundary layer recovery in TOGA COARE: Sensitivity to convective organization",1998,"10.1175/1520-0469(1998)055<2763:SFABLR>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032467676&doi=10.1175%2f1520-0469%281998%29055%3c2763%3aSFABLR%3e2.0.CO%3b2&partnerID=40&md5=9601c93a2d3864b2eb40e9da2b0be205","Shipboard radar data collected during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) are used in conjunction with surface meteorological data from the Woods Hole Oceanographic Institute's IMET buoy to describe in detail how three classifications of convective systems modify the surface fluxes of heat, moisture, and momentum. The classifications of convection were based on spatial-scale [sub-mesoscale convective system (MCS) vs MCS scale], horizontal morphology (nonlinear vs linear organization), and the presence of stratiform precipitation as determined by quantitative radar data. Three types of convective organization were examined; sub-MCS-scale nonlinear events and MCS-scale linear events with and without significant stratiform precipitation. These three classifications were present about 90% of the time and produced over 90% of the rainfall during TOGA COARE. as determined by shipboard radar. Composite analyses of the surface fluxes along with the pertinent bulk variables have been constructed for each of these classes of convective organization. During the compositing process, the convectively active and recovery periods were separated, allowing these distinctly different phases to both be represented in the final composite analyses. The sensible and latent heat flux enhancements were decomposed through perturbation analyses and the relative importance of each term during the convectively active and recovery phases was also assessed. All three types of convective organization altered the surface fluxes in a similar manner, producing greatly enhanced surface fluxes during the convectively active phase with weaker enhancements during the recovery. However, the duration of the convectively active and recovery phases were highly dependent on the type of convective organization that was present. The average length of the convectively active phase ranged from approximately 45 min for MCS-scale linear events that had little stratiform precipitation to about 1.5 h for MCS-scale linear events with extensive stratiform regions. The average length of the recovery phase was approximately 3.5 h for sub-MCS-scale nonlinear events, 2.5 h for MCS-scale linear events with little stratiform precipitation, and nearly 9.5 h for the MCS-scale linear events with extensive stratiform areas. The magnitudes of the surface fluxes were also highly dependent on the mode of convective organization. The MCS-scale linear systems that had extensive stratiform precipitation were indicative of highly organized and mature squall line systems and hence produced the greatest modulations of the surface fluxes. These events produced peak sensible and latent heat fluxes of about 60 W m-2 and 250 W m-2, respectively. The sub-MCS-scale nonlinear events and the MCS-scale linear events with little stratiform precipitation produced much weaker peak sensible and latent heat fluxes (about 20 W m-2 and 150 W m-2, respectively). For all three types of convective organization the enhanced sensible heat fluxes were due primarily to increased air-sea temperature differences (i.e., decreased air temperature) and increased wind speeds. Approximately two-thirds of the total enhanced sensible heat transfer occurred during the recovery phase for each type of convective organization. For the sub-MCS-scale nonlinear events and MCS-scale linear events with little stratiform precipitation, the latent heat flux enhancements were due primarily to increased wind speeds. Increased wind speeds were also the primary contributor to the enhanced latent heat fluxes for the MCS-scale linear events with extensive stratiform precipitation, but increases in the air-sea humidity difference and the transfer coefficient for moisture also contributed. For the MCS-scale events, the enhanced latent heat transfer was split nearly evenly between the convectively active and recovery phases, whereas for the sub-MCS-scale nonlinear event, nearly 60% of the enhanced latent heat transfer occurred during the convectively active phase compared to about 40% during the recovery phase."
"6701540733;","Multiple equilibria in radiative-convective atmospheres",1997,"10.3402/tellusa.v49i4.14681","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031399189&doi=10.3402%2ftellusa.v49i4.14681&partnerID=40&md5=37e032921d5f1834fdd30206c03ff206","A one-dimensional, radiative-convective model is used to study the equilibria conditions of moist atmospheres. We show that when the hydrologic cycle is included in the model a subcritical bifurcation occurs, leading to 2 linearly stable solutions to the radiative-convective equilibria. In this case, when the net forcing is larger than a critical value, two equilibria are possible. Furthermore, a finite amplitude instability can lead to a runaway greenhouse regime when the solar forcing is larger than a second critical value. In general, previous climate studies with radiative-convective models did not include a hydrologic cycle. Instead, the atmosphere's water vapor mixing ratio was diagnosed based on the climatological profile of relative humidity. We show that fixing the water vapor relative humidity profile at the climatological value (in the computation of the radiation fluxes only) leads to a unique stable solution to the radiative-convective equilibria. Thus, the crucial part of the hydrologic cycle which allows multiple solutions is the relaxation of the assumption of a climatological relative humidity profile. Our results do not apply directly to any real planet because of large uncertainties in our calculation due to the absence of clouds and the use of a one-dimensional model. The 1st equilibrium corresponds to an optically thin atmosphere. In this regime, the system is nearly linear and is in a state of small dissipation. The 2nd equilibrium corresponds to an optically thick atmosphere. In this 2nd regime, the system is highly nonlinear and is in a state of large dissipation."
"57210687618;7006184606;7103372949;","Island precipitation enhancement and the diurnal cycle in radiative-convective equilibrium",2015,"10.1002/qj.2443","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927623600&doi=10.1002%2fqj.2443&partnerID=40&md5=a2de1047a0ee08255e27d9cb7678101e","To understand why tropical islands are rainier than nearby ocean areas, we explore how a highly idealized island, which differs from the surrounding ocean only in heat capacity, might respond to the diurnal cycle and influence the tropical climate, especially the spatial distribution of rainfall and the thermal structure of the troposphere. We perform simulations of three-dimensional radiative-convective equilibrium with the System for Atmospheric Modeling (SAM) cloud-system-resolving model, with interactive surface temperature, where a highly idealized, low heat capacity circular island is embedded in a slab-ocean domain. The calculated precipitation rate over the island can be more than double the domain average value, with island rainfall occurring primarily in an intense, regular thunderstorm system that forms in the afternoon to early evening each day. Island size affects the magnitude of simulated island rainfall enhancement, the intensity of the convection, and the timing of the rainfall maximum relative to solar noon. A combination of dynamic and thermodynamic mechanisms leads to a monotonic enhancement of domain-averaged tropospheric temperature with increasing fraction of island surface, which may contribute to localization of ascent over the Maritime Continent and its relationship to the Walker Circulation. © 2014 Royal Meteorological Society."
"36054921000;7003648299;7102567936;7004060399;","Impact of the tropopause temperature on the intensity of tropical cyclones: An idealized study using a mesoscale model",2014,"10.1175/JAS-D-14-0029.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910135163&doi=10.1175%2fJAS-D-14-0029.1&partnerID=40&md5=23adeb2ca21c6e9d0fe524fd908fcef8","This study investigates the impact of the tropopause temperature on the intensity of idealized tropical cyclones (TCs) superimposed on background states of radiative-convective equilibrium (RCE) in a threedimensional (3D) mesoscale model. Simulations are performed with constant sea surface temperature and an isothermal stratosphere with constant tropopause temperature. The potential intensity (PI) computed from the thermodynamic profiles of theRCE state (before the TCs are superimposed on it) increases by 0.4-1ms-1 for each 1 K of tropopause temperature reduction. The 3D TC experiments yield intense tropical cyclones whose intensities exceed the PI value substantially. It is further shown that the discrepancy may be largely explained by the supergradient wind in the 3D simulations. The intensities of these 3D TCs increase by ~0.4ms-1 per 1 K of cooling in the tropopause temperature in RCE, on the low end of the PI dependence on the tropopause temperature. Sensitivity experiments with a larger horizontal grid spacing of 8 kmproduce less intense TCs, as expected, but similar dependence (~-0.5ms-1K-1) on tropopause temperature. Equilibrium TC solutions are further obtained in 200-day experiments with different values of constant stratospheric temperature. Similar relationships between TC intensity and tropopause temperature are also found in these equilibrium TC solutions. © 2014 American Meteorological Society."
"34976226000;7101714349;7403058740;7403134439;","Diurnal variation of rainfall in the Yangtze River Valley during the spring-summer transition from TRMM measurements",2012,"10.1029/2011JD017056","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859467045&doi=10.1029%2f2011JD017056&partnerID=40&md5=beeb61816873cbf1eee33de5e3f0fc95","A 12 year archive of the Tropical Rainfall Measuring Mission (TRMM) rain rate is used to document the regionality of diurnal rainfall cycle in the Yangtze River Valley (YRV). The regional rain peaks, local phase shifts, rain event's behavior, and related seasonal change from March to August are examined. In the middle reach of YRV, rainfall appears mainly in early morning and displays a distinct local shift of diurnal phase. Such features are well established at each presummer (from May to June) and result from the eastward migrating events with a late night growth in size. They are supported by the low-level convergence that moves from the east slope of the Tibetan Plateau to the middle reach of YRV, as the deviated wind vector rotates clockwise to enhance southerlies at late night and southwesterlies in the morning. In the lower reach of YRV, however, one observes an eruption of morning rainfall with less local difference in diurnal phase. Morning rainfall is active in presummers of some years but suppressed in some others, contributing greatly to the variance of rainfall budget and resulting in anomalous wet/dry seasons. It is found to arise from a local growth of rain events rather than the migrating events from the middle reach. A majority of these organized convections prefer to form and develop in a belt-shaped zone where the nocturnal southwesterlies of warm/moist air impinge on the Meiyu front in the lower troposphere. © 2012 by the American Geophysical Union."
"7402977304;7101867299;","The response time of a convective cloud ensemble to a change in forcing",2004,"10.1256/qj.02.218","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2142757324&doi=10.1256%2fqj.02.218&partnerID=40&md5=f03224ccdd5e2863d5819bba626e0ba5","In this paper, the timescale of the convective mass-flux response to step-function changes in external forcing conditions is measured directly using idealized cloud-resolving model simulations of unorganized convection in radiative-convective equilibrium. Many parametrization schemes require an estimate of this response time in the form of a fixed adjustment timescale, but the physical mechanism which sets its value is currently unknown. These experiments confirm the existence of a unique timescale, for given initial forcing conditions, of the order of one hour. The hypothesized role of gravity waves in effecting the convective adjustment is tested by changing the mean cloud spacing of the initial state. This reveals a linear dependence of the response time on the cloud spacing, in agreement with the theory. Meanwhile, similar experiments to investigate the sensitivity of the timescale to changes in gravity-wave speed reveal a remarkable robustness of the average wave speed over a range of stratifications and tropospheric depths. © Royal Meteorological Society, 2004."
"6701764745;7401921174;7004187536;","A polar-low development over the Bering sea: Analysis, numerical simulation, and sensitivity experiments",1997,"10.1175/1520-0493(1997)125<3109:APLDOT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0000180121&doi=10.1175%2f1520-0493%281997%29125%3c3109%3aAPLDOT%3e2.0.CO%3b2&partnerID=40&md5=19d36b7cd27fa2b4ee76c3eaef4219ea","A polar low that developed over the westeren Bering Sea on 7 March 1977 and tracked across St. Paul Island is investigated using observations and the Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model Version 5 (MM5). A series of fine-mesh (20 km) simulations are performed in order to examine the structure of the cyclone and the airflow within it and to determine the physical processes important for its development. Observations show that the low formed near the ice edge in a region of moderate low-level baroclinicity and cold-air advection when an upper-level trough, or lobe of anomalously large potential vorticity (PV), broke off from a migratory, upper-level cold low over Siberia and advanced into the region. A full physics model experiment, initialized 24 h prior to the appearance of the polar low, produced a small, intense cyclone having charcteristics similar to the observed low. The simulated low more closely resembled an extratropical cyclone than a typical circularly symmertric hurricane, possessing a thermal structure with frontlike features and an asymmetric precipitation shield. Although the simulated low developed southeast of, and earlier than, the observed low, the basic similarity of the observed and modeled systems was revealed by a comparison of the sequence of weather elements at a point in the path of the simulated low with the sequence of observations from nearby St. Paul Island, Alaska. A series of experiments was performed to test the sensitivity of the simulated polar low development to various physical processes. Four experiments of 48-h duration each were initialized 24 h before the low appeared. In the first experiment, in which surface fluxes were turned off, the low failed to develop. In the second experiment, in which the fluxes were switched on after a 24-h delay, only a weak low formed. In the third experiment, in which the ice edge was shifted a degree of latitude to the north, thus increasing the overwater fetch of the cold air, the low's evolution was slightly altered but the final outcome was little changed. A fourth high-horizontal resolution experiment (6.67-km spacing) displayed more plentiful and sharper mesoscale features but on the storm scale yielded results that were similar to those of the full-physics run. A full-physics experiment initialized 24 h later, at the time the low first appeared, and run for 24 h, produced a system of similar intensity to that in the 48-h full-physics run but somewhat better positioned. Corresponding sensitivity experiments showed that with both surface fluxes and latent heating-omitted, the low weakened and nearly died away. Experiments retaining only surface fluxes in one case and only latent heating in the other, produced similar cyclones of moderate depth. The results suggest that the development of some, if not most, polar lows can be regarded as fundamentally similar to that of midlatitude ocean cyclones. In both cases a mobile upper-level PV anomaly interacts with a low-level thermal or PV anomaly produced by thermal advection and/or diabatic heating. The polar low lies at the end of the spectrum of extratropical cyclogenesis in which concurrent surface fluxes of sensible and latent heat and the immediately ensuing condensation heating in organized convection dominate the development of the low-level anomaly."
"7004188723;7101630970;","On the derivation of the divergent flow from the rotational flow: The χ problem",1987,"10.1002/qj.49711347519","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0023524143&doi=10.1002%2fqj.49711347519&partnerID=40&md5=2efc2696083f18f31ee9bac6a6097473","The vertical component of the vorticity equation in pressure coordinates involves only the divergent and rotational components of the horizontal motion. Taking the dominant rotational component as specified, the equation may be considered as an equation for the velocity potential, χ, of the divergent motion. Solving this χ problem yields a divergence pattern which is dynamically consistent with the generally much better observed rotational flow (provided, of course, that the vorticity dynamics is represented correctly). A simple way of doing this is described, and applied to seasonally averaged and instantaneous winds analysed at the European Centre for Medium Range Weather Forecasts (ECMWF). In view of the delicate nature of the vorticity balance, a comparison of δ, the horizontal divergence obtained in this manner, with D, derived directly from the analysed winds, provides a stringent test for the data assimilation system. For seasonal averages, D̃ based on an inviscid vorticity equation in the upper troposphere is generally found to agree well with D, even in the deep tropics. However, some features achieve a more interesting and believable structure than in the analyses. Allowing for a vorticity sink in regions of strong organized convection changes this estimate of δ only slightly, well within the range of observational uncertainty, and not always in the sense of improving the agreement with D. It is therefore possible that on the large scale, ‘cumulus friction’ is only important in areas of strong convection, and if so, is not large enough to be determined unambiguously from existing data sets. Solution of the χ problem at a particular initial time requires an additional piece of information, the vorticity tendency, which could be obtained operationally using a suitable backward time‐differencing scheme. This contrasts with the use of the usual balance procedures, which require a knowledge of the less readily accessible diabatic heating rate. Copyright © 1987 Royal 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)."
"16644246500;7003648299;7102567936;","Role of radiative-convective feedbacks in spontaneous tropical cyclogenesis in idealized numerical simulations",2016,"10.1175/JAS-D-15-0380.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977469568&doi=10.1175%2fJAS-D-15-0380.1&partnerID=40&md5=b1efa66c01fb3d3c94d940efd79e0b9e","The authors perform 3D cloud-resolving simulations of radiative-convective equilibrium (RCE) in a rotating framework, with interactive radiation and surface fluxes and fixed sea surface temperature. A tropical cyclone is allowed to develop spontaneously from a homogeneous environment, rather than initializing the circulation with a weak vortex or moist bubble (as is often done in numerical simulations of tropical cyclones). The resulting tropical cyclogenesis is compared to the self-aggregation of convection that occurs in nonrotating RCE simulations. The feedbacks leading to cyclogenesis are quantified using a variance budget equation for the column-integrated frozen moist static energy. In the initial development of a broad circulation, feedbacks involving longwave radiation and surface enthalpy fluxes dominate, which is similar to the initial phase of nonrotating self-aggregation. Mechanism denial experiments are also performed to determine the extent to which the radiative feedbacks that are essential to nonrotating self-aggregation are important for tropical cyclogenesis. Results show that radiative feedbacks aid cyclogenesis but are not strictly necessary. © 2016 American Meteorological Society."
"56417341400;26536569500;","Why does tropical convective available potential energy (CAPE) increase with warming?",2015,"10.1002/2015GL066199","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84953449543&doi=10.1002%2f2015GL066199&partnerID=40&md5=c0d8897dc41de335aed72e9b2555d2ba","Recent work has produced a theory for tropical convective available potential energy (CAPE) that highlights the Clausius-Clapeyron (CC) scaling of the atmosphere's saturation deficit as a driver of increases in CAPE with warming. Here we test this so-called ""zero-buoyancy"" theory for CAPE by modulating the saturation deficit of cloud-resolving simulations of radiative-convective equilibrium in two ways: changing the sea surface temperature (SST) and changing the environmental relative humidity (RH). For earthlike and warmer SSTs, undilute parcel buoyancy in the lower troposphere is insensitive to increasing SST because of a countervailing CC scaling that balances the increase in the saturation deficit; however, buoyancy increases dramatically with SST in the upper troposphere. Conversely, in the RH experiment, undilute buoyancy throughout the troposphere increases monotonically with decreasing RH. We show that the zero-buoyancy theory successfully predicts these contrasting behaviors, building confidence that it describes the fundamental physics of CAPE and its response to warming. © 2015. American Geophysical Union. All Rights Reserved."
"7401538490;7402593184;","Heat fluxes and roll circulations over the western Gulf Stream during an intense cold-air outbreak",1991,"10.1007/BF00122580","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026306395&doi=10.1007%2fBF00122580&partnerID=40&md5=c5f0e3ab6a98601660deaa5b3675d39f","Turbulence and heat fluxes in the marine atmospheric boundary layer (MABL) for the roll vortex regime, observed during the Genesis of Atlantic Lows Experiment (GALE) over the western Gulf Stream, have been studied. The spectral analysis suggests that cloud streets (roll vortices) are vertically organized convection in the MABL having the same roll scale for both the cloud layer and subcloud layer, and that the roll spacing is about three times the MABL depth. The roll circulations contribute significantly to the sensible (temperature) and latent heat (moisture) fluxes with importance increasing upward. Near the MABL top, these fluxes are primarily due to roll vortices which transfer both sensible heat and moisture upward in the lower half of the convective MABL. Near the MABL top, the roll circulations transfer sensible heat downward and moisture upward in the clear thermal-street region, but roll vortices influenced by evaporative cooling can transfer sensible heat upward and moisture downward in the cloud-street region. Near the cloud-top, the upward buoyancy flux due to evaporative cooling is highly related to the roll circulations near the inversion. For the lower half of the MABL, the normalized temperature flux decreases upward more rapidly than the humidity flux, which is mainly because potential temperature (θ) increases slightly upward while humidity (q) decreases slightly upward above the unstable surface layer. The gradient production (associated with the θ gradient) is a source for the temperature flux in the unstable surface layer but changes to a sink in the mixed layer, while the gradient production (associated with the q gradient) acts as a source for the humidity flux in both the unstable surface and mixed layers. The results suggest that the entrainment at the MABL top might affect the budgets of temperature and humidity fluxes in the lower MABL, but not in the unstable surface layer. © 1991 Kluwer Academic Publishers."
"7401945370;7201504886;36646089600;6701346974;57208455668;8687063000;54879515900;","Global Cloud-Resolving Models",2019,"10.1007/s40641-019-00131-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85066108278&doi=10.1007%2fs40641-019-00131-0&partnerID=40&md5=293f1c4b2b8ce22f4552b3c953d69036","Purpose of Review: Global cloud-resolving models (GCRMs) are a new type of atmospheric model which resolve nonhydrostatic accelerations globally with kilometer-scale resolution. This review explains what distinguishes GCRMs from other types of models, the problems they solve, and the questions their more commonplace use is raising. Recent Findings: GCRMs require high-resolution discretization over the sphere but can differ in many other respects. They are beginning to be used as a main stream research tool. The first GCRM intercomparison studies are being coordinated, raising new questions as to how best to exploit their advantages. Summary: GCRMs are designed to resolve the multiscale nature of moist convection in the global dynamics context, without using cumulus parameterization. Clouds are simulated with cloud microphysical schemes in ways more comparable to observations. Because they do not suffer from ambiguity arising from cumulus parameterization, as computational resources increase, GCRMs are the promise of a new generation of global weather and climate simulations. © 2019, The Author(s)."
"6701538799;7003885275;7101661890;","Influences of moist convection on a cold-season outbreak of clear-air turbulence (CAT)",2012,"10.1175/MWR-D-11-00353.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862890437&doi=10.1175%2fMWR-D-11-00353.1&partnerID=40&md5=6ee2ad4ff27b41aff7d9099c5d931540","The 9-10 March 2006 aviation turbulence outbreak over the central United States is examined using observations and numerical simulations. Though the turbulence occurs withina deep synoptic cyclone with widespread precipitation, comparison of reports from commercial aircraft with radar and satellite data reveals the majority of the turbulence to be in clear air. This clear-air turbulence (CAT) is located above a strong upper-level jet, where vertical shear rangedbetween 20 and 30 m s -1 km -1. Comparison of a moist simulation with a dry simulation reveals that simulated vertical shear and subgrid turbulence kinetic energy is significantly enhanced by the anticyclonic upper-level flow perturbation associated with the organized convection in regions of observed CAT. A higher-resolution simulation is used to examine turbulence mechanisms in two primary clusters of reported moderate and severe turbulence. In the northern cluster where vertical shear is strongest, the simulated turbulence arises from Kelvin-Helmholtz (KH) instability. The turbulence farther south occurs several kilometers above shallow, but vigorous, moist convection. There, the simulated turbulence is influenced by vertically propagating gravity waves initiated when the convection impingeson a lowered tropopause. In some locations these gravity waves amplify and break leading directly to turbulence, while in others they aid turbulence development by helping excite KH instability within the layers of strongest vertical shear above them. Although both clusters of turbulence occur either above or laterally displaced from cloud, a shared characteristic is their owed existence to moist convection within the wintertime cyclone, which distinguishes them from traditional CAT. © 2012 American Meteorological Society."
"35767566800;7202208382;","Impacts of idealized air-Sea coupling on Madden-Julian oscillation structure in the superparameterized CAM",2011,"10.1175/JAS-D-11-04.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053215574&doi=10.1175%2fJAS-D-11-04.1&partnerID=40&md5=ce6f5684e9205a57c9d08dfc5c6389cd","Air-sea interactions and their impact on intraseasonal convective organization are investigated by comparing two 5-yr simulations from the superparameterized Community Atmosphere Model version 3.0 (SP-CAM). The first is forced using prescribed sea surface temperatures (SSTs). The second is identical except that a simplified oceanic mixed-layer model is used to predict tropical SST anomalies that are coupled to the atmosphere. This partially coupled simulation allows SSTs to respond to anomalous surface fluxes. Implementation of the idealized slab ocean model in the SP-CAM results in significant changes to intraseasonal convective variability and organization. The more realistic treatment of air-sea interactions in the coupled simulation improves many aspects of tropical convection on intraseasonal scales, from the relationships between precipitation and SSTs to the space-time structure and propagation of the Madden-Julian oscillation (MJO). This improvement is associated with a more realistic convergence structure and longitudinal gradient of SST relative to MJO deep convection. In the uncoupled SP-CAM, SST is roughly in phase with the MJO convective center and the development of the Kelvin wave response and boundary layer convergence east of the convective center is relatively weak. In the coupled SP-CAM, maxima in SST lead maxima in MJO convection by 1/4 cycle. Coupling produces warmer SSTs, a stronger Kelvin wave response, enhanced low-level convergence, and increased convective heating ahead (east) of the MJO convective center. Convective development east of the MJO precipitation center is more favorable in the coupled versus the uncoupled version, resulting in more realistic organization and clearer eastward propagation of the MJO in the coupled SP-CAM. © 2011 American Meteorological Society."
"57199689992;6507400558;","Convectively coupled waves in a sheared environment",2010,"10.1175/2010JAS3335.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958587987&doi=10.1175%2f2010JAS3335.1&partnerID=40&md5=10e2ff881b0bb4bf950540efe4c2f7ee","A linear stability analysis, about a radiative-convective equilibrium in a sheared environment, on an equatorial beta plane, for a simple multicloud model for organized tropical convection is presented here. Both vertical/baroclinic and meridional/barotropic zonal wind shears are considered separately in a parameter regime for which the shear-free multicloud model exhibits synoptic-scale instability of Kelvin and n = 0 eastward inertio-gravity [eastward mixed Rossby-gravity (MRG)] waves only, with moderate growth rates. The maximum growth rates appear to increase significantly with the strength of the background wind shear, and new wave instabilities appear and/or disappear depending on the strength and type of the wind shear. It is found here that both high-and low-level vertical shears have a strong impact on the stability of convectively coupled waves (CCWs), consistent with the fact that the multicloud instability mechanism is controlled by both stratiform heating and low-level moisture and congestus heating. Typically, vertical shears with high-level easterly wind destabilize westward moving waves and stabilize eastward waves, whereas westerly winds aloft and on bottom tend to destabilize eastward moving and stabilize westward moving waves. In the mixed situation of high-level easterlies and low-level westerlies both eastward and westward waves are unstable, while in the case of high-level westerlies and low-level easterlies only eastward waves are unstable. In the presence of a barotropic/meridional shear, synoptic-scale convectively coupled westward MRG and Rossby waves emerge, when the shear strength is large enough, due essentially to pure shear instability of the dry dynamics. The meridional shear has also an important impact on the horizontal structure of the waves. Owing to the meridional shear, the Kelvin wave displays a nonzero meridional velocity that induces a significant contribution toward the horizontal convergence. The two-day waves adopt a crescentlike shape while the westward MRG, and somewhat the Rossby waves, become less trapped in the vicinity of the equator. © 2010 American Meteorological Society."
"55763471100;","Radiative constraints on the hydrological cycle in an idealized radiative-convective equilibrium model",2009,"10.1175/2008JAS2797.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549088071&doi=10.1175%2f2008JAS2797.1&partnerID=40&md5=e4d250cce43c62cb667bee78eadf7cf6","The radiative constraints on the partitioning of the surface energy budget and, hence, on the strength of the hydrological cycle are analyzed in an idealized one-dimensional radiative-convective equilibrium model formulated in terms of the energy budgets at the top of the atmosphere, the subcloud layer, and the free atmosphere, which enables it to predict both surface relative humidity and the air-sea temperature difference. Using semigray radiative transfer, a semianalytical solution was obtained that explicitly shows how the surface latent heat flux (LHF) is related to the radiative properties of the atmosphere. This solution was also used in conjunction with a full radiative transfer code and was found to provide reasonably realistic quantitative estimates. In the model the LHF is fundamentally constrained by the net longwave flux divergence above the level of condensation by lifting (LCL) and by the atmospheric absorption of shortwave radiation, with only a weak indirect control by near-surface moisture. The latter implies that the Clausius-Clapeyron relation does not directly constrain the strength of the hydrological cycle. Under radiative perturbations, the changes in LHF are determined by the changes in the net longwave fluxes at the LCL, associated mainly with the changes in the longwave transmissivity, and by the changes in shortwave absorption by the atmosphere (e.g., by increased water vapor). Using a full radiative transfer model with interactive water vapor feedback with the semianalytical solution indicates a rate of change in LHF with greenhouse forcing of around 2 W m-2 K-1 of surface warming, which corresponds to the Planck feedback (∼3.2 W m-2 K-1) multiplied by a coefficient of order one that, to first approximation, depends only on the relative magnitudes of the net longwave radiation fluxes at the LCL and the top of the atmosphere (i.e., on the shape of the vertical profile of the net long-wave flux). © 2009 American Meteorological Society."
"6701538799;7404361000;","Influence of balanced motions on heavy precipitation within a long-lived convectively generated vortex",2002,"10.1175/1520-0493(2002)130<0877:IOBMOH>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036538212&doi=10.1175%2f1520-0493%282002%29130%3c0877%3aIOBMOH%3e2.0.CO%3b2&partnerID=40&md5=5ff725cfc4f13b5b1907d0819312f057","The forcing of heavy precipitation within a long-lived convectively generated mesoscale vortex (MCV) is investigated with the aid of diagnoses from Rapid Update Cycle gridded analyses. Organized convection within the MCV followed a distinct diurnal cycle, which featured organized mesoscale convective systems (MCSs) that matured overnight near the MCV center on successive days. The MCV was typically most intense in the middle troposphere, but intensified within the lower troposphere during the episodes of organized nocturnal convection. The lower-tropospheric vertical shear was an important organizing factor in MCS development and sustenance, in the sense that its interaction with the cold temperature anomaly beneath the MCV center determined where balanced lower-tropospheric ascent occurred. From trajectory analyses, we estimate that balanced ascent accounted for approximately half of the total vertical displacement of the thermodynamically unstable air that eventually composed elevated saturated layers immediately upstream of areas of active deep convection within the MCS. Flooding occurred overnight during a portion of the MCV life cycle when the balanced ascent became located toward the rear flank of the MCS (i.e., opposite to the orientation of the mean flow). This evolution served to focus the propagation of the region of intense convection toward a direction opposite to the overall MCS movement, thereby slowing the envelope of heavy precipitation."
"35584010200;7006432091;","The 1997 Pan American Climate Studies Tropical Eastern Pacific Process Study. Part I: ITCZ region",2000,"10.1175/1520-0477(2000)081<0451:TPACST>2.3.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0000725846&doi=10.1175%2f1520-0477%282000%29081%3c0451%3aTPACST%3e2.3.CO%3b2&partnerID=40&md5=2d22283f39a727031e628a6c05d969da","The Pan American Climate Studies Tropical Eastern Pacific Process Study (TEPPS) obtained a comprehensive set of observations of the structure of clouds and precipitating storms over the eastern tropical Pacific from 28 July to 6 September 1997. The TEPPS data can address a wide range of problems involving tropical oceanic clouds and precipitation. The main goal of the project was to understand why passive microwave satellite algorithms indicate an E-W gradient in the precipitation pattern in the tropical Pacific with heavier rainfall in the east while infrared satellite algorithms indicate heavier rainfall in the west. Satellite-derived precipitation estimates are based on characteristics of the vertical structure of precipitating clouds: in the case of infrared methods, cloud-top temperature, and in the case of microwave methods, the vertically integrated ice scattering and/or water absorption determined by the vertical profile of hydrometeors. The premise of the expedition was that by obtaining surface-based radar measurements of the vertical structure of precipitation where and when the differences between the infrared and microwave precipitation estimates were large, it could be determined which satellite method yielded a more accurate pattern of precipitation in the Pacific. This paper describes the types of observations obtained during TEPPS and some preliminary results. A single, well-equipped vessel on its maiden voyage, the National Oceanic and Atmospheric Administration ship Ronald H. Brown, was the base for all observations. Scanning C-band Doppler radar and cloud photography documented the three-dimensional structure of clouds and precipitation in the vicinity of the ship. Upper-air soundings were obtained at ≤ 4 h intervals. Surface meteorological and oceanographic instruments and vertically pointing 915-MHz and S-band profilers characterized conditions at the ship itself. During 28.5 days in the eastern Pacific ITCZ, the shipborne radar observed echoes larger than 50 km in maximum horizontal dimension within 100-km radius of the ship 71% of the time and larger than 100 km 55% of the time. The ship spent 16 days on station at 7.8°N, 125°W and 4 days in the vicinity of Hurricane Guillermo. Samples of surface atmospheric and oceanic data collected during the cruise illustrate the difficulty of interpreting short timescale buoy data time series in the absence of the mesoscale context provided by radar data. The ship sounding data show that the larger-scale, longer-lived convective precipitation activity and organization on timescales of days in the eastern Pacific ITCZ is closely associated with the presence of stronger southerly winds, which in turn suggests that large-scale atmospheric processes such as easterly waves or inertial stability oscillations are a regulating mechanism. Comparison of the ship radar data, satellite IR data, and satellite microwave data shows that part of the reason why the IR and microwave-derived precipitation maps differ is that in the eastern Pacific ITCZ IR cold cloudiness resolves only a subset of the precipitation detected by microwave data. Large precipitating systems (> 100 km scale) of long duration (> 24 h; i.e., the mesoscale organized systems) were reliably associated with cold cloudiness < 235 K. Precipitating systems of shorter duration and/or smaller scale (i.e., the less-organized convection) sometimes reached 235 K and sometimes did not. Satellite microwave data generally agreed with the radar data regarding the location and areal coverage of precipitating regions larger than ∼10 km in horizontal scale. However, the microwave algorithm examined in this study had varying degrees of skill in locating the heavier rainfall areas within rainy regions."
"56971606900;7006198994;6701835010;","Vertically resolved weak temperature gradient analysis of the Madden-Julian Oscillation in SP-CESM",2016,"10.1002/2016MS000724","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84991063306&doi=10.1002%2f2016MS000724&partnerID=40&md5=cfc3c7d0920a78dd456d1061076d56e4","The collective effects of convection can influence large-scale circulations that, in turn, act to organize convective activity. Such scale interactions may play an important role in moisture-convection feedbacks thought to be important to both convective aggregation and the Madden-Julian Oscillation, yet such interactions are not fully understood. New diagnostics based on tropical weak temperature gradient (WTG) theory have begun to make this problem more tractable, and are leveraged in this study to analyze the relationship between various apparent heating processes and large-scale vertical moisture advection in SP-CESM. WTG theory provides a framework for accurately diagnosing intraseasonal variations in large-scale vertical motion from apparent heating, allowing large-scale vertical moisture advection to be decomposed into contributions from microphysical processes, subgrid scale eddy fluxes, and radiative heating. This approach is consistent with the column moist static energy (MSE) budget approach, and has the added benefit of allowing the vertical advection term of the column MSE budget to be quantitatively partitioned into contributions from the aforementioned apparent heating processes. This decomposition is used to show that the MJO is an instability strongly supported by radiative feedbacks and damped by horizontal advection, consistent with the findings of previous studies. Periods of low, moderate, and high MJO amplitude are compared, and it is shown that changes in the vertical structure of apparent heating do not play a dominant role in limiting the amplitude of the MJO in SP-CESM. Finally, a diagnostic approach to scale analysis of tropical dynamics is used to investigate how the governing dynamics of various phenomena differ throughout wavenumber-frequency space. Findings support previous studies that suggest the governing dynamics of the MJO differ from those of strongly divergent convectively coupled equatorial waves. © 2016. The Authors."
"6602240529;55567317300;16307052600;","Synergism between the low-level jet and organized convection at its exit region",2007,"10.1175/MWR3317.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34248366970&doi=10.1175%2fMWR3317.1&partnerID=40&md5=afc64c34ef0374c19fa76ec5173595d5","Previous studies suggest that the enhanced meridional extent of some South American low-level jet events (known as Chaco jets) is a consequence of a positive feedback between the low-level wind and strong convection that is usually observed at their exit region. To assess how this interaction takes place, a Chaco low-level jet event observed between 18 and 19 December 2002 (i.e., during the South America Low-Level Jet Experiment) and the associated mesoscale convective system that evolved at its exit region have been selected to perform numerical experiments where diabatic heating effects associated with phase changes can be quantified. This case study has also been used to analyze the diurnal oscillations related to planetary boundary layer (PBL) mechanisms in order to describe whether the observed evolution of the low-level wind can be explained either by PBL-related forcing or by the interaction with convection. The sensitivity experiments confirm that there is a positive feedback at low levels between convection and the northerly wind flow that becomes accelerated and also aids in the identification of a strong coupling between organized convection and the upper-level circulation, resulting in an increase of the upper-level jet strength downstream of the simulated precipitation area. A conceptual model of how these systems (i.e., convection, low- and upper-level jets) mutually interact is proposed, which differs from coupling mechanisms documented for the Great Plains low-level jet. © 2007 American Meteorological Society."
"8539422800;57211224269;6603412788;","South and East Asian summer monsoon climate and variation in the MRI coupled model (MRI-CGCM2)",2004,"10.1175/1520-0442(2004)017<0763:SAEASM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842533238&doi=10.1175%2f1520-0442%282004%29017%3c0763%3aSAEASM%3e2.0.CO%3b2&partnerID=40&md5=cdfc0272f54e63ac75666fce43c0ef0a","Simulations of the major characteristics of the summer monsoon climate over South Asia, East Asia, and the western North Pacific by the new version of the Meteorological Research Institute coupled GCM (MRI-CGCM2) are analyzed. In addition to assessing the simulation of mean summer monsoon rainfall and its association with SST and basic circulation parameters, the model's performance in reproducing the seasonal variation, climatological onset, peak, withdrawal, and subseasonal variation of the monsoon is also studied. The mean rainfall distribution and the maximum rainfall centers over South Asia and the western North Pacific, including the monsoon rainbelt over central India, though shifted southward of its observed position by about 5°, and the baiu rainband across Japan, are well simulated. However, the model underestimates the monsoon rainfall over southeast China. The biases in model mean rainfall are found to be associated with biases in wind, moisture convergence, and vertical stability of the atmosphere. The relationship between mean SST and organized convection in the model is close to the observations, with a propensity for deep convection increasing with an increase in SST above the threshold value. The simulated summer anomalies of SST and surface fluxes imply the dominance of the SST-wind-evaporation feedback system over most of the Indian and western Pacific Oceans on intraseasonal time scales. In addition, in the model, equatorial eastern Pacific SST anomalies strongly influence the Indian summer monsoon predominantly on biennial time scales. The model captures the basic monsoon seasonal cycle, onset, peak, and withdrawal over India and the western North Pacific across Japan. However, the simulation shows an early onset of the monsoon over mainland China and the early occurrence of peak rainfall over southeast China. The active-break spells in Indian monsoon rainfall and meridional propagations of rainbelts over India and the western North Pacific are realistically simulated. But, over southeastern China, the model is unable to simulate northward propagation of rainbelts, which contributes to the poor simulation of seasonal mean rainfall. © 2004 American Meteorological Society."
"55808016000;57034458200;","Subkilometer simulation of a torrential-rain-producing mesoscale convective system in East China. Part I: Model verification and convective organization",2012,"10.1175/MWR-D-11-00029.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862918824&doi=10.1175%2fMWR-D-11-00029.1&partnerID=40&md5=dafde84f8da4029414e2201b4c0e9fe2","A nocturnal torrential-rain-producing mesoscale convective system (MCS) occurring during the mei-yu season of July 2003 in east China is studied using conventional observations, surface mesoanalysis, satellite and radar data, and a 24-h multinested model simulation with the finest grid spacing of 444 m. Observational analyses reveal the presence of several larger-scale conditions that were favorable for the development of the MCS, including mei-yu frontal lifting, moderate cold advection aloft and a moist monsoonal flow below, and an elongated old cold dome left behind by a previously dissipated MCS. Results show that themodel could reproduce the evolution of the dissipatingMCS and its associated cold outflows, the triggering of three separate convective storms over the remnant cold dome and the subsequent organization into a large MCS, and the convective generation of an intense surface meso-high and meso-β-scale radar reflectivity morphologies. In particular, the model reproduces the passage of several heavy-rain-producing convective bands at the leading convective line and the trailing stratiform region, leading to the torrential rainfall at nearly the right location. However, many of the above features are poorly simulated or missed when the finest model grid uses either 1.33- or 4-km grid spacing. Results indicate the important roles of isentropic lifting of moist monsoonal air over the cold dome in triggering deep convection, a low-level jet within an elevated moist layer in maintaining conditional instability, and the repeated formation and movement of convective cells along the same path in producing the torrential rainfall. © 2012 American Meteorological Society."
"7801642934;7004978125;","Gravity waves in shear and implications for organized convection",2009,"10.1175/2009JAS2976.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73549100885&doi=10.1175%2f2009JAS2976.1&partnerID=40&md5=fb837bd7e1a4dcd5047ad0ca547cacef","It is known that gravity waves in the troposphere, which are often excited by preexisting convection, can favor or suppress the formation of new convection. Here it is shown that in the presence of wind shear or barotropic wind, the gravity waves can create a more favorable environment on one side of preexisting convection than the other side. Both the nonlinear and linear analytic models developed here show that the greatest difference in favorability between the two sides is created by jet shears, and little or no difference in favorability is created by wind profiles with shear at low levels and no shear in the upper troposphere. A nonzero barotropic wind (or, equivalently, a propagating heat source) is shown to also affect the favorability on each side of the preexisting convection. It is shown that these main features are captured by linear theory, and advection by the background wind is the main physical mechanism at work. These processes should play an important role in the organization of wave trains of convective systems (i.e., convectively coupled waves); if one side of preexisting convection is repeatedly more favorable in a particular background wind shear, then this should determine the preferred propagation direction of convectively coupled waves in this wind shear. In addition, these processes are also relevant to individual convective systems: it is shown that a barotropic wind can lead to near-resonant forcing that amplifies the strength of upstream gravity waves, which are known to trigger new convective cells within a single convective system. The barotropic wind is also important in confining the upstreamwaves to the vicinity of the source, which can help ensure that any new convective cells triggered by the upstream waves are able to merge with the convective system. All of these effects are captured in a two-dimensional model that is further simplified by including only the first two vertical baroclinic modes. Numerical results are shown with a nonlinear model, and linear theory results are in good agreement with the nonlinear model for most cases. © 2009 American Meteorological Society."
"7101661890;7006095466;","Stratospheric gravity waves generated by multiscale tropical convection",2008,"10.1175/2007JAS2601.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51749106111&doi=10.1175%2f2007JAS2601.1&partnerID=40&md5=e7b1ad6957129801044e5ae423f67b66","The generation of gravity waves by multiscale cloud systems evolving in an initially motionless and thermodynamically uniform environment is explored using a two-dimensional cloud-system-resolving model. The simulated convection has similar depth and intensity to observed tropical oceanic systems. The convection self-organizes into preferred horizontal and temporal scales involving weakly organized propagating cloud clusters. The multiscale systems generate a broad spectrum of gravity waves with horizontal scales that range from the cloud-system scale up to the cloud-cluster scale. The gravity waves with the largest horizontal scale play an important role in modifying layered tropospheric inflow and outflow to the cloud systems, which in turn influence the multiscale convective organization. Slower-moving short-scale gravity waves make the strongest individual contribution to the vertical flux of horizontal momentum and cause a robust peak in the momentum flux spectrum that corresponds to the lifetime and spatial scale of the individual cloud systems. © 2008 American Meteorological Society."
"6701718281;6505932008;7202899330;","Trimodal cloudiness and tropical stable layers in simulations of radiative convective equilibrium",2008,"10.1029/2007GL033029","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48249151841&doi=10.1029%2f2007GL033029&partnerID=40&md5=566f78b725f856836cc06344563b2e79","In this paper, we examine the tropical environment at radiative convective equilibrium using a large-domain cloud system resolving numerical model. As in observed studies of convectively active periods over warm tropical oceans (in particular the tropical western Pacific), we find a trimodal cloud structure that is closely associated with the presence of three distinct stable layers, including a prominent stable layer located near the zero-degree Celsius level. In addition, the simulation exhibits three separate large scale zonal overturning circulations, with two of these circulations located above the trade wind inversion and separated by the freezing level stable layer. At equilibrium, latent heat release associated with freezing and melting processes is dwarfed by that of vapor transitions, and simulation results suggest that this stable layer can be maintained by subsidence in the presence of longwave radiative cooling above the zero-degree level. Copyright 2008 by the American Geophysical Union."
"8382949200;25953950400;","Observational analysis of the predictability of mesoscale convective systems",2007,"10.1175/WAF1012.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38849085762&doi=10.1175%2fWAF1012.1&partnerID=40&md5=bfaea87f25a50d850a9a6db9f344d88a","Mesoscale convective systems (MCSs) have a large influence on the weather over the central United States during the warm season by generating essential rainfall and severe weather. To gain insight into the predictability of these systems, the precursor environments of several hundred MCSs across the United States were reviewed during the warm seasons of 1996-98. Surface analyses were used to identify initiating mechanisms for each system, and North American Regional Reanalysis (NARR) data were used to examine the environment prior to MCS development. Similarly, environments unable to support organized convective systems were also investigated for comparison with MCS precursor environments. Significant differences were found between environments that support MCS development and those that do not support convective organization. MCSs were most commonly initiated by frontal boundaries; however, features that enhance convective initiation are often not sufficient for MCS development, as the environment needs also to be supportive for the development and organization of long-lived convective systems. Low-level warm air advection, low-level vertical wind shear, and convective instability were found to be the most important parameters in determining whether concentrated convection would undergo upscale growth into an MCS. Based on these results, an index was developed for use in forecasting MCSs. The MCS index assigns a likelihood of MCS development based on three terms: 700-hPa temperature advection, 0-3-km vertical wind shear, and the lifted index. An evaluation of the MCS index revealed that it exhibits features consistent with common MCS characteristics and is reasonably accurate in forecasting MCSs, especially given that convective initiation has occurred, offering the possibility of usefulness in operational forecasting. © 2007 American Meteorological Society."
"56014511300;8728190500;","The general circulation and robust relative humidity",2006,"10.1175/JCLI3979.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845662910&doi=10.1175%2fJCLI3979.1&partnerID=40&md5=45fce21841a4cd3dba8973871e94dd92","The sensitivity of free-tropospheric relative humidity to cloud microphysics and dynamics is explored using a simple 2D humidity model and various configurations of the National Center for Atmospheric Research (NCAR) Community Atmosphere Model version 3 (CAM3) atmospheric general circulation model (AGCM). In one configuration the imposed surface temperatures and radiative perturbations effectively eliminated the Hadley and Walker circulations and the main westerly jet, creating instead a homogeneous ""boiling kettle"" world in low and midlatitudes. A similarly homogeneous state was created in the 2D model by rapid horizontal mixing. Relative humidity R simulated by the AGCM was insensitive to surface warming. Doubling a parameter governing cloud water reevaporation increased tropical mean R near the midtroposphere by about 4% with a realistic circulation, but by more than 10% in the horizontally homogeneous states. This was consistent in both models. AGCM microphysical sensitivity decreased in the upper troposphere, and vanished outside the Tropics. Convective organization by the general circulation evidently makes relative humidity much more robust to microphysical details by concentrating the rainfall in moist environments. Models that fail to capture this will overestimate the microphysical sensitivity of humidity. Based on these results. the uncertainty in the strength of the water vapor feedback associated with cloud microphysical processes seems unlikely to exceed a few percent. This does not include uncertainties associated with large-scale dynamics or cloud radiative effects, which cannot be quantified, although radical CAM3 circulation changes reported here had surprisingly little impact on simulated relative humidity. © 2006 American Meteorological Society."
"7403968239;55729083100;7403646891;","The effect of subtropical cooling on the amplitude of ENSO: A numerical study",2004,"10.1175/1520-0442(2004)017<3786:TEOSCO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8644277129&doi=10.1175%2f1520-0442%282004%29017%3c3786%3aTEOSCO%3e2.0.CO%3b2&partnerID=40&md5=d4ef737e79095c26567d3869d7471762","The effect of an enhanced subtropical surface cooling on El Niño-Southern Oscillation (ENSO) through the ""ocean tunnel"" is investigated using a coupled model. Here, the term "" ocean tunnel"" refers to the water pathway that connects the equatorial upwelling water to the subtropical/extratropical surface water. The subtropical cooling is introduced through a reduction of the radiative-convective equilibrium SST (SSTp) in that region. The SSTp for the equatorial region is kept fixed. It is found that an enhanced cooling in the subtropics results in a regime with stronger ENSO. This is because an enhanced subtropical cooling reduces the temperature of the water feeding the equatorial undercurrent through the ocean tunnel. The resulting larger difference between the warm-pool SST and the temperature of the equatorial thermocline water-the source water for the equatorial upwelling-tends to increase the equatorial zonal SST contrast between the western and the eastern Pacific. In response to this destabilizing forcing to the coupled equatorial ocean-atmosphere, a stronger ENSO develops. ENSO is found to regulate the time-mean difference between the warm-pool SST and the temperature of the equatorial undercurrent. The findings provide further support for the ""heat pump"" hypothesis for ENSO, which states that ENSO is an instability driven by the meridional differential heating over the Pacific Ocean and that ENSO regulates the long-term stability of the coupled equatorial Pacific climate. The results also substantiate the notion that surface variability from higher latitudes may influence equatorial SST variability through the ocean tunnel. © 2004 American Meteorological Society."
"7102875645;","Early development in the study of greenhouse warming: The emergence of climate models",1997,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030616779&partnerID=40&md5=994e8f9e567ab5fdbb603037e4799357","Following the pioneering contributions of Arrhenius, Callendar and others, climate models emerged as a very promising tool for the study of greenhouse warming. In the early 1960s, a one-dimensional, radiative-convective equilibrium model was developed as the first step towards the development of a three-dimensional model of climate. Incorporating not only the radiative but also the convective heat exchange between the earth's surface and the atmosphere, the model overcame the difficulty encountered by the earlier approach of surface radiative heat balance in estimating the magnitude of greenhouse warming. By the 1970s, a three-dimensional, general circulation model (GCM) of the atmosphere, coupled to a very idealized ocean of swamp-like wet surface, had been used for studies of greenhouse warming. Despite many drastic simplifications, the GCM was very effective for elucidating the physical mechanisms that control global warming and served as a stepping stone towards the use of more comprehensive, coupled ocean-atmosphere GCMs for the study of this problem."
"57203012011;7006095466;","Collective effects of organized convection and their approximation in general circulation models",1996,"10.1175/1520-0469(1996)053<1477:CEOOCA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030468908&doi=10.1175%2f1520-0469%281996%29053%3c1477%3aCEOOCA%3e2.0.CO%3b2&partnerID=40&md5=c0818efc74a1f5cbb0a682815cf77dde","The collective effects of organized convection on the environment were estimated using a two-dimensional, two-way nested cloud-resolving numerical model with a large outer domain (4500 km). As initial conditions, the authors used an idealized environment of the onset stage of the December 1992 westerly wind burst that occurred during the Tropical Oceans Global Atmosphere Coupled Ocean-Atmosphere Response Experiment. Two key aspects relating to convective parameterization were examined. First, the transports, sources, and sinks of heat, moisture, and momentum were derived using the model-produced dataset. In particular, the total momentum flux compares well with Moncrieff's dynamical theory. Second, the bulk energetics of the cloud system were examined using the model-produced dataset. The authors found that the shear generation of kinetic energy is comparable to the buoyancy generation and dominates the sum of the buoyancy and water-loading generation. This means that, in addition to the thermodynamic generation of kinetic energy, shear generation should be included in the closure condition for the parameterization of organized convection in large-scale models. A simple mass-flux-based parameterization scheme is outlined for organized convection that consistently treats dynamical and thermodynamical fluxes."
"7401559815;7006329926;7202772927;","A preliminary study of the tropical water cycle and its sensitivity to surface warming",1993,"10.1175/1520-0477(1993)074<1313:APSOTT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027881086&doi=10.1175%2f1520-0477%281993%29074%3c1313%3aAPSOTT%3e2.0.CO%3b2&partnerID=40&md5=d162580536e88b604dd77b9c9704fde1","This paper presents the preliminary findings of an investigation of the water budget of tropical cumulus convection using the Goddard Cumulus Ensemble Model (GCEM). Results of an experiment designed to obtain a ""fingerprint' in the tropical hydrologic cycle in response to surface warming are also presented. The ensemble mean water budget shows that the distribution of water vapor and cloud water in the tropical atmosphere is maintained as a result of a balance between moisture convergence (including cloud scale and large scale) and condensation and reevaporation by various microphysical species within the cumulus clusters. Under radiative convective equilibrium conditions, 66% of the precipitation reaching the ground comes from the convective region and 34% from the stratiform region. In a climate with above-normal sea surface temperature but fixed large-scale vertical velocity, tropical convection is enhanced with more abundant moisture sources. -from Authors"
"7103074130;57197606165;","Radiative-convective equilibrium models of Jupiter and Saturn",1984,"10.1016/0019-1035(84)90106-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0001603120&doi=10.1016%2f0019-1035%2884%2990106-4&partnerID=40&md5=1b1f401858ede9199d73a15397987c3e","Radiative-convective equilibrium models for Jupiter and Saturn have been produced in a study centered primarily on the stratospheric energy balance and the possible role of aerosol heating. These models are compared directly to the thermal structure profiles obtained from Voyager radio occultation measurements. The method is based on a straightforward flux divergence formulation derived from earlier work (J. S. Hogan, S. I. Rasool, and T. Encrenaz 1969, J. Atmos. Sci.26, 898-905). The balance between absorbed and emitted energies is computed iteratively at each level in the atmosphere, assuming local thermodynamic equilibrium and employing a standard treatment of opacities. Results for Jupiter indicate that a dust-free model (no aerosol heating) furnishes a good mean thermal profile for the stratosphere when compared with the Voyager 1 radio occultation (RSS) measurements. These observations of the equatorial region (0° and 12°S, respectively) exhibit periodic vertical structure. Of course, among many possible complications, the Voyager profiles may not represent typical excursions from the mean. The aerosol heat depositions required to match these profiles exactly, relative to the nominal dust-free model, are reasonably consistent with independent estimates for ""continuum"" absorbers. Other interpretations are discussed, along with a survey of problems encountered in intercomparing the lower portions (P ≳ 300 mb) of the models, the RSS profiles, and a recent IRIS equatorial profile. Although aerosol heating cannot be ruled out at low latitudes on Jupiter, our results indicate that it may not be required to reproduce the Voyager 1 RSS profiles. On the other hand, heating by aerosols or some other absorber seems necessary in order to match the high-latitude Voyager 2 RSS temperature profile. The Saturn models are relatively simple and in good-to-excellent agreement with the Voyager 2 RSS profiles at all levels. Our comparisons indicate that aerosol heating played a minor role in Saturn's midlatitude stratospheric energy balance at the time of the Voyager 2 encounter. These models, however, may need to be reassessed once the hydrocarbon concentrations have been more precisely determined. © 1984."
"56450100300;7201504886;11939918300;","Imprint of the convective parameterization and sea-surface temperature on large-scale convective self-aggregation",2017,"10.1002/2016MS000865","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021211205&doi=10.1002%2f2016MS000865&partnerID=40&md5=22b34cc639cc582d5c0bf9927dc959a4","Radiative-convective equilibrium simulations with the general circulation model ECHAM6 are used to explore to what extent the dependence of large-scale convective self-aggregation on sea-surface temperature (SST) is driven by the convective parameterization. Within the convective parameterization, we concentrate on the entrainment parameter and show that large-scale convective self-aggregation is independent of SST when the entrainment rate for deep convection is set to zero or when the convective parameterization is removed from the model. In the former case, convection always aggregates very weakly, whereas in the latter case, convection always aggregates very strongly. With a nontrivial representation of convective entrainment, large-scale convective self-aggregation depends nonmonotonically on SST. For SSTs below 295 K, convection is more aggregated the smaller the SST because large-scale moisture convergence is relatively small, constraining convective activity to regions with high wind-induced surface moisture fluxes. For SSTs above 295 K, convection is more aggregated the higher the SST because entrainment is most efficient in decreasing updraft buoyancy at high SSTs, amplifying the moisture-convection feedback. When halving the entrainment rate, convection is less efficient in reducing updraft buoyancy, and convection is less aggregated, in particular at high SSTs. Despite most early work on self-aggregation highlighted the role of nonconvective processes, we conclude that convective self-aggregation and the global climate state are sensitive to the convective parameterization. © 2017. The Authors."
"7101867299;55914316600;","A coarsening model for self-organization of tropical convection",2013,"10.1002/jgrd.50674","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885096245&doi=10.1002%2fjgrd.50674&partnerID=40&md5=14c49b1e02ee59fc73c02b84ab4d9aab","If the influence of humidity on cumulus convection causes moist regions of the tropical troposphere to become moister and dry regions to become drier, and if horizontal mixing of moisture is not rapid enough to overcome this tendency, then the atmosphere will tend to separate into increasingly large moist and dry regions through a process of coarsening. We present a simple model for the moisture budget of the free troposphere, including subsidence drying, convective moistening, and horizontal mixing, and a constraint on total precipitation representing radiative-convective equilibrium. When initialized with a spatially uncorrelated moisture distribution, the model shows self-organization of precipitation with two main stages: A coarsening stage where the correlation length grows proportional to time to the power 1/2 and a droplet stage where precipitation is confined to a decreasing number of circular moist regions. A potential function is introduced to characterize the tendency for self-organization, which could be a useful diagnostic for analyzing cloud-resolving model simulations. © 2013. Her Majesty the Queen in Right of Canada. American Geophysical Union."
"7103372949;7006184606;","Temperature profiles in radiative-convective equilibrium above surfaces at different heights",1999,"10.1029/1999JD900485","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033610367&doi=10.1029%2f1999JD900485&partnerID=40&md5=9feeaa1d2fa924158a5454a430ced62d","Soundings of temperature and specific humidity calculated assuming radiative-convective equilibrium over surfaces at different heights show only small variations in surface temperature and specific humidity with surface height. Calculated surface temperatures decrease at ∼2°C km-1, with all other parameters held fixed. Calculated temperatures aloft in the upper troposphere above surfaces at different heights differ by 10°-20°C; those above surfaces at 3000-5000 m are significantly warmer. These differences support the contention that an elevated terrain can force significant atmospheric circulation through its effect on equilibrium temperatures, as occurs in the case of the Tibetan Plateau forcing the south Asian monsoon. Copyright by the American Geophysical Union."
"56014511300;","Maintenance of the free-tropospheric tropical water vapor distribution. Part I: Clear regime budget",1996,"10.1175/1520-0442(1996)009<2903:MOTFTT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030357115&doi=10.1175%2f1520-0442%281996%29009%3c2903%3aMOTFTT%3e2.0.CO%3b2&partnerID=40&md5=8aaf65260db973bddef555afb571858e","The water vapor budget of the free troposphere of the maritime Tropics is investigated using radiosonde observations, analyzed fields, and satellite observations, with particular attention paid to regions free of organized convection. In these arid regions, time-average drying by subsidence must be balanced by moistening via horizontal advection from convective areas and via vertical turbulent transport from below. It is found that for at least 25% of the maritime Tropics, 80% ± 10% of this source above 700 mb is by horizontal advection. The remainder comes from vertical convective transport (scales &lt; 250 km), with a pronounced local maximum at 500 mb. The regions for which this is true are characterized by pentad outgoing longwave radiation &gt; 270 W m-2 and may be said to exist out of equilibrium with the surface as regards moisture. Transport from below makes a significant contribution between 700 and 800 mb, despite the usual presence of an inversion below these levels, but is difficult to quantify accurately. The convective transport convergence is estimated as a residual from large-scale budgets and directly from sounding time series by an independent method, which shows a narrow maximum at 500 mb. Half of the paper addresses the question of data accuracy, including sounding and analyzed data, as it pertains to the question at hand. It is concluded that the moisture budgets from the European Centre for Medium-Range Weather Forecasts (ECMWF) analyses are of useful accuracy despite some significant mean descrepancies between the analyses and sounding observations in convective areas. The budget is found to be similar to that of a general circulation model based on the ECMWF forecasting model. Humidity measurements from operational soundings appear responsive below 300 mb, but then abruptly become unresponsive."
"7004427298;7006729638;","Atmospheric circulation controls and characteristics of a flood event in central South Africa",1991,"10.1002/joc.3370110604","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026289974&doi=10.1002%2fjoc.3370110604&partnerID=40&md5=222417c91420cd151b5f95a24d1fdd2d","Factors contributing to the synoptic‐scale forcing of flood‐producing rainfall over central South Africa in February 1988 are identified as tropical convection over southern Africa, easterly waves and an anticyclone over the south‐west Indian Ocean and Mozambique Channel, and mid‐latitude westerly wave disturbances to the south of Africa. Tropical moisture was advected over southern Africa during this period by barotropic perturbations that originated over the south‐west Indian Ocean as easterly waves. The area of tropical convection was linked to a mid‐latitude westerly wave to the south of the subcontinent by a tropical‐temperate trough and attendant cloud band during the flood episode. The development and persistence of a lower tropospheric anticyclone over the Mozambique Channel during the rainfall event slowed the progress of westerly troughs across the region and contributed to the increased residence time of strong, organized convection over central South Africa. The thermodynamic and kinematic characteristics of the atmosphere over the subcontinent in the presence of the tropical‐temperate trough are typical of enhanced convection in a tropical environment. Distinctive features associated with the presence of the well‐developed tropical‐temperate trough during the flood event are increased westerly relative angular momentum generation around 20°S, the forcing of an anomalous Hadley‐type circulation over eastern southern Africa, strong poleward fluxes of momentum in the upper troposphere, and poleward displacement of the subtropical jet in the region of Marion Island. Copyright © 1991 John Wiley & Sons, Ltd"
"7003527377;7407016988;6701432911;","The wake low in a midlatitude mesoscale convective system having complex convective organization",1991,"10.1175/1520-0493(1991)119<0134:TWUIAM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026273436&doi=10.1175%2f1520-0493%281991%29119%3c0134%3aTWUIAM%3e2.0.CO%3b2&partnerID=40&md5=dbe007b9e43d593e919eccce541db8c3","Although the organization of the storm was complex, the surface pressure field resembled those associated with simpler, quasi-linear squall systems containing trailing stratiform regions: a mesohigh existed near the convective line and a wake low was observed to the rear of the stratiform region. A strong system-relative descending rear inflow jet was observed in the northern part of the storm near the wake low. These findings indicate that the trailing stratiform precipitation regions of mesoscale convectve systems can be dynamically significant phenomena, generating rapidly descending inflow jets at their back edges and, consequently, producing pronounced lower-tropospheric warming, intense surface pressure gradients and strong low-level winds. -from Authors"
"7006095466;7409792174;6506848305;","Simulation, modeling, and dynamically based parameterization of organized tropical convection for global climate models",2017,"10.1175/JAS-D-16-0166.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018379930&doi=10.1175%2fJAS-D-16-0166.1&partnerID=40&md5=c033d7f278553cbda70a652788c128b7","A new approach for treating organized convection in global climate models (GCMs) referred to as multiscale coherent structure parameterization (MCSP) introduces physical and dynamical effects of organized convection that are missing from contemporary parameterizations. The effects of vertical shear are approximated by a nonlinear slantwise overturning model based on Lagrangian conservation principles. Simulation of the April 2009 Madden-Julian oscillation event during the Year of Tropical Convection (YOTC) over the Indian Ocean using the Weather Research and Forecasting (WRF) Model at 1.3-km grid spacing identifies self-similar properties for squall lines, MCSs, and superclusters embedded in equatorial waves. The slantwise overturning model approximates this observed self-similarity. The large-scale effects of MCSP are examined in two categories of GCM. First, large-scale convective systems simulated in an aquaplanet model are approximated by slantwise overturning with attention to convective momentum transport. Second, MCSP is utilized in the Community Atmosphere Model, version 5.5 (CAM5.5), as tendency equations for second-baroclinic heating and convective momentum transport. The difference between MCSP and CAM5.5 is a direct measure of the global effects of organized convection. Consistent with TRMM measurements, the MCSP generates large-scale precipitation patterns in the tropical warm pool and the adjoining locale; improves precipitation in the intertropical convergence zone (ITCZ), South Pacific convergence zone (SPCZ), and Maritime Continent regions; and affects tropical wave modes. In conclusion, the treatment of organized convection by MCSP is salient for the next generation of GCMs. © 2017 American Meteorological Society."
"7005808242;57218978981;","Horizontally homogeneous rotating radiative-convective equilibria at GCM resolution",2008,"10.1175/2007JAS2604.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45849088853&doi=10.1175%2f2007JAS2604.1&partnerID=40&md5=aab08d32cb21738bcca42aad0eef0eaf","Rotating radiative-convective equilibrium, using the column physics and resolution of GCMs, is proposed as a useful framework for studying the tropical storm-like vortices produced by global models. These equilibria are illustrated using the column physics and dynamics of a version of the GFDL Atmospheric Model 2 (AM2) at resolutions of 220, 110, and 55 km in a large 2 × 104 km horizontally homogeneous domain with fixed sea surface temperature and uniform Coriolis parameter. The large domain allows a number of tropical storms to exist simultaneously. Once equilibrium is attained, storms often persist for hundreds of days. The number of storms decreases as sea surface temperature increase, while the average intensity increases. As the background rotation is decreased, the number of storms a so decreases. At these resolutions and with this parameterization of convection, a dense collectior of tropical storms is always the end state of moist convection in the cases examined. © 2008 American Meteorological Society."
"7004868129;7103269306;6701561763;6506067014;","A numerical case study of a polar low in the Labrador Sea",1996,"10.3402/tellusa.v48i3.12067","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029828193&doi=10.3402%2ftellusa.v48i3.12067&partnerID=40&md5=5b0c2a7d7000107b42392712baea5dce","A mesoscale (15 km) version of the Canadian regional finite-element model is used to study a polar low that developed in the Labrador Sea on 11 January 1989, in the wake of an intense cold air outbreak associated with a major synoptic-scale system located to the east of Greenland. The rapid evolution of the polar low is well revealed from satellite imagery showing a complex structure with strong surface winds near the vortex and deep convection nearby during the mature stage. The simulated structure of the polar low agrees quite well with observed features. Based on the detailed mesoscale model outputs, the evolution of the Labrador Sea polar low is discussed at the initiation and mature stages. The polar low developed under a combination of baroclinic and convective processes. At an early stage, barochnic development takes place in conditions of reversed shear flow, marked by low-level baroclinicity near the ice edge and a mobile upper-level short wave. Rapid modification of the Arctic boundary layer by strong surface heat fluxes is similar to that observed in other areas. Sensitivity experiments indicate that the mutual interaction between the upper-level potential vorticity anomaly and the low-level baroclinicity at the Arctic front, favored by the deep convective boundary layer, appears to trigger the polar low. At the onset of the mature stage, the approach of a cold air dome favors the outbreak of deep convection, in agreement with satellite imagery. As shown by sensitivity experiments, latent heat release from organized convection contributes to the major part of the rapid deepening of the polar low in its mature stage, and sea surface evaporation is the primary feeding mechanism for condensation processes. The structure of the polar low is characterized by a warm core due to the combined effects of warm air seclusion and diabatic heating. Comparisons with previously studied polar lows developing in similar conditions of reversed shear at other locations are discussed."
"57195998621;15124325100;","Retrieval of exoplanet emission spectra with HyDRA",2018,"10.1093/mnras/stx2748","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045735688&doi=10.1093%2fmnras%2fstx2748&partnerID=40&md5=d1579d6a2974c52054852551bf309e21","Thermal emission spectra of exoplanets provide constraints on the chemical compositions, pressure-temperature (P-T) profiles, and energy transport in exoplanetary atmospheres. Accurate inferences of these properties rely on the robustness of the atmospheric retrieval methods employed. While extant retrieval codes have provided significant constraints on molecular abundances and temperature profiles in several exoplanetary atmospheres, the constraints on their deviations from thermal and chemical equilibria have yet to be fully explored. Our present work is a step in this direction. We report HyDRA, a disequilibrium retrieval framework for thermal emission spectra of exoplanetary atmospheres. The retrieval code uses the standard architecture of a parametric atmospheric model coupled with Bayesian statistical inference using the nested sampling algorithm. For a given data set, the retrieved compositions and P-T profiles are used in tandem with the GENESIS self-consistent atmospheric model to constrain layer-by-layer deviations from chemical and radiative-convective equilibrium in the observable atmosphere. We demonstrate HyDRA on the hot JupiterWASP-43b with a high-precision emission spectrum. We retrieve an H2O mixing ratio of log (H2O) = -3.54-0.52+0.82, consistent with previous studies. We detect H2O and a combined CO/CO2 at 8s significance. We find the dayside P-T profile to be consistent with radiative-convective equilibrium within the 1s limits and with low day-night redistribution, consistent with previous studies. The derived compositions are also consistent with thermochemical equilibrium for the corresponding distribution of P-T profiles. In the era of high-precision and high-resolution emission spectroscopy, HyDRA provides a path to retrieve disequilibrium phenomena in exoplanetary atmospheres. © 2017 The Author(s)."
"55628587967;6507400558;55550388400;34870277200;7004978125;","Improving synoptic and intraseasonal variability in CFSv2 via stochastic representation of organized convection",2017,"10.1002/2016GL071542","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85013054762&doi=10.1002%2f2016GL071542&partnerID=40&md5=3383e893a16bced05ba84ec2b3560ba7","To better represent organized convection in the Climate Forecast System version 2 (CFSv2), a stochastic multicloud model (SMCM) parameterization is adopted and a 15 year climate run is made. The last 10 years of simulations are analyzed here. While retaining an equally good mean state (if not better) as the parent model, the CFS-SMCM simulation shows significant improvement in the synoptic and intraseasonal variability. The CFS-SMCM provides a better account of convectively coupled equatorial waves and the Madden-Julian oscillation. The CFS-SMCM exhibits improvements in northward and eastward propagation of intraseasonal oscillation of convection including the MJO propagation beyond the maritime continent barrier, which is the Achilles Heel for coarse-resolution global climate models (GCMs). The distribution of precipitation events is better simulated in CFSsmcm and spreads naturally toward high-precipitation events. Deterministic GCMs tend to simulate a narrow distribution with too much drizzling precipitation and too little high-precipitation events. ©2016. American Geophysical Union. All Rights Reserved."
"57195998621;15124325100;","GENESIS: New self-consistent models of exoplanetary spectra",2017,"10.1093/MNRAS/STX1601","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85035362901&doi=10.1093%2fMNRAS%2fSTX1601&partnerID=40&md5=d505019bdf3bdc5e15d11565fd61c9b2","We are entering the era of high-precision and high-resolution spectroscopy of exoplanets. Such observations herald the need for robust self-consistent spectral models of exoplanetary atmospheres to investigate intricate atmospheric processes and to make observable predictions. Spectral models of plane-parallel exoplanetary atmospheres exist, mostly adapted from other astrophysical applications, with different levels of sophistication and accuracy. There is a growing need for a new generation of models custom-built for exoplanets and incorporating state-of-the-art numerical methods and opacities. The present work is a step in this direction. Here we introduce GENESIS, a plane-parallel, self-consistent, line-by-line exoplanetary atmospheric modelling code that includes (a) formal solution of radiative transfer using the Feautrier method, (b) radiative-convective equilibrium with temperature correction based on the Rybicki linearization scheme, (c) latest absorption cross-sections, and (d) internal flux and external irradiation, under the assumptions of hydrostatic equilibrium, local thermodynamic equilibrium and thermochemical equilibrium. We demonstrate the code here with cloud-free models of giant exoplanetary atmospheres over a range of equilibrium temperatures, metallicities, C/O ratios and spanning non-irradiated and irradiated planets, with and without thermal inversions. We provide the community with theoretical emergent spectra and pressure-temperature profiles over this range, along with those for several known hot Jupiters. The code can generate self-consistent spectra at high resolution and has the potential to be integrated into general circulation and non-equilibrium chemistry models as it is optimized for efficiency and convergence. GENESIS paves the way for high-fidelity remote sensing of exoplanetary atmospheres at high resolution with current and upcoming observations. © 2018 The Author(s)."
"16636807900;26536569500;","Effective buoyancy, inertial pressure, and the mechanical generation of boundary layer mass flux by cold pools",2015,"10.1175/JAS-D-14-0349.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943404745&doi=10.1175%2fJAS-D-14-0349.1&partnerID=40&md5=1f9f707af355016c4a43894cc6579305","The Davies-Jones formulation of effective buoyancy is used to define inertial and buoyant components of vertical force and to develop an intuition for these components by considering simple cases. This decomposition is applied to the triggering of new boundary layer mass flux by cold pools in a cloud-resolving simulation of radiative-convective equilibrium (RCE). The triggering is found to be dominated by inertial forces, and this is explained by estimating the ratio of the inertial forcing to the buoyancy forcing, which scales as H/h, where H is the characteristic height of the initial downdraft and h is the characteristic height of the mature cold pool's gust front. In a simulation of the transition from shallow to deep convection, the buoyancy forcing plays a dominant role in triggering mass flux in the shallow regime, but the force balance tips in favor of inertial forcing just as precipitation sets in, consistent with the RCE results. © 2015 American Meteorological Society."
"56282825100;35619212800;8502619500;7005804830;","The dominant synoptic-scale modes of North American monsoon precipitation",2015,"10.1002/joc.4104","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939467560&doi=10.1002%2fjoc.4104&partnerID=40&md5=1047a918de543a9a3361cddd3e2b448d","In this study, we explore the mechanisms of synoptic rainfall variability using observations from the Tropical Rainfall Measuring Mission satellite. Although previously shown to have an important impact on North American monsoon rainfall, tropical cyclones are excluded from this analysis, in order to focus on more frequent synoptic disturbances within the region. A rotated empirical orthogonal function (EOF) analysis of North American monsoon rainfall during June to September 2002-2009 suggests that low-level tropical disturbances contribute to the leading two modes of precipitation variability within this region. These disturbances result in gulf surges or low-level surges of moisture up the Gulf of California, and provide a key moisture source to facilitate the development of organized convection. In the first mode, the low-level trough brings precipitation to lower elevations along the western slopes of the Sierra Madre Occidental south of Hermosillo, Mexico and over the southern Baja Peninsula. In the second mode, the low-level trough interacts with an upper-level inverted trough enhancing precipitation into the southwestern United States and northwest Mexico. In particular, the upper-level trough contributes to the easterly to northeasterly shear across the region, favouring mesoscale convective organization and enhanced deep convection over the Sierra Madre Occidental and higher elevations in southeast Arizona. The EOF methodology offers an objective approach for determining the dominant modes of precipitation for the monsoon region useful for identifying past and monitoring future low-frequency impacts on these modes. © 2015 Royal Meteorological Society."
"55775119300;7102019758;","Wet and dry spell characteristics of global tropical rainfall",2013,"10.1002/wrcr.20275","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879424593&doi=10.1002%2fwrcr.20275&partnerID=40&md5=0fde9f42136186f4e804ecbb1884a253","In this study, we analyze satellite-based daily rainfall observations to compare and contrast the wet and dry spell characteristics of tropical rainfall. Defining a wet (dry) spell as the number of consecutive rainy (nonrainy) days, we find that the distributions of wet spells appear to exhibit universality in the following sense. While both ocean and land regions with high seasonal rainfall accumulation (humid regions; e.g., India, Amazon, Pacific Ocean) show a predominance of 2-4 day wet spells, those regions with low seasonal rainfall accumulation (arid regions; e.g., South Atlantic, South Australia) exhibit a wet spell duration distribution that is essentially exponential in nature, with a peak at 1 day. The behavior that we observed for wet spells is reversed for the dry spell characteristics. In other words, the main contribution to the dry part of the season, in terms of the number of nonrainy days, appears to come from 3-4 day dry spells in the arid regions, as opposed to 1 day dry spells in the humid regions. The total rainfall accumulated in each wet spell has also been analyzed, and we find that the major contribution to seasonal rainfall for arid regions comes from 1-5 day wet spells; however, for humid regions, this contribution comes from wet spells of duration as long as 30 days. We also explore the role of chance as well as the influence of organized convection in determining some of the observed features. ©2013. American Geophysical Union. All Rights Reserved."
"57210719777;","Spurious convective organization in simulated squall lines owing to moist absolutely unstable layers",2005,"10.1175/MWR2952.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-24144463812&doi=10.1175%2fMWR2952.1&partnerID=40&md5=b8b51c2c7e46ebdd498bef7c5f0e9237","A spurious updraft pattern has been documented in some numerical simulations of squall lines. The pattern is notable because of a regular, repeating pattern of updrafts and downdrafts that are three-six grid lengths wide. This study examines the environmental and numerical conditions that lead to this problem. The spurious pattern is found only in simulations of upshear-tilted convective systems. Furthermore, the pattern coincides with deep (2-3 km) and wide (5-20 km) moist absolutely unstable layers (MAULs) - saturated layers of air that are statically unstable. In this physical environment, small-scale perturbations grow rapidly. The necessarily imperfect numerical schemes of the model introduce spurious small-scale perturbations into the MAULs, and these perturbations amplify owing to the unstable stratification. Some techniques are investigated that diffuse the perturbations or minimize their introduction in the statically unstable flow. © 2005 American Meteorological Society."
"57201177267;7102643810;6603137309;7006874359;7103246957;13408501200;55946190800;7005206400;35450918400;56350164900;13408938100;","A case study of convective organization into precipitating lines in the Southwest Amazon during the WETAMC and TRMM-LBA",2002,"10.1029/2001JD000375","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36448950225&doi=10.1029%2f2001JD000375&partnerID=40&md5=1b54764ef4d97d20d3d2a91c611c39c0","A case study of convective development in the Southwest Amazon region during the Wet Season Atmospheric Mesoscale Campaign (WETAMC) and Tropical Rainfall Measuring Mission (TRMM)/Large-Scale Biosphere-Atmosphere (LBA) Experiment in Amazonia is presented. The convective development during 7 February 1999 is shown to occur during a period of very weak large-scale forcing in the presence of topography and deforestation. The available data include dual Doppler radar analysis, radiosonde launches, and surface and boundary layer observations. The observational analysis is complemented with a series of model simulations using the RAMS with 2-km resolution over a 300 km × 300 km area forced by a morning radiosonde profile. A comparison of the observed and simulated thermodynamic transformation of the boundary layer and of the formation of convective lines, and of their kinematic and microphysical properties is presented. It is shown that only a few very deep and intense convective cells are necessary to explain the overall precipitating line formation and that discrete propagation and coupling with upper atmosphere circulations may explain the appearance of several lines. The numerical simulation indicates that topography may be the cause of initial convective development, although later on the convective line is parallel to the midlevel shear. There are indications that small-scale deforestation may have an effect on increasing rainfall in the wet season when the large-scale forcing is very weak. Copyright 2002 by the American Geophysical Union."
"7404361000;6602645956;6701538799;","Detection and prediction of warm season midtropospheric vortices by the Rapid Update Cycle",2002,"10.1175/1520-0493(2002)130<0024:DAPOWS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036326739&doi=10.1175%2f1520-0493%282002%29130%3c0024%3aDAPOWS%3e2.0.CO%3b2&partnerID=40&md5=6c8dd67fa529591d89e9a36eed063557","The authors perform a statistical and dynamical analysis of midtropospheric mesoscale vortices captured by analyses from the Rapid Update Cycle, version 2 (RUC-2), during the period 1 May to 31 August 1999. A total of 203 vortices meeting conditions of an automated algorithm were found. Of these, 86 were observed to form within organized convection and were termed mesoscale convective vortices (MCVs). MCVs were favored over a broad area from eastern Colorado and western Nebraska to the Mississippi River valley, essentially collocated with the loci of organized convection. The remaining 117 vortices (termed dry vortices) clustered in the immediate lee of the Rocky Mountains and over the southeastern United States. Vortices arising from convection had considerably greater intensity and longevity than dry vortices. They were roughly five times more likely to be involved with the triggering of new convection. A relationship was found between intensity and longevity such that there appears to be a maximum vortex lifetime that can be estimated from its maximum intensity. Vortices arising from convection had markedly greater humidity and water vapor mixing ratio underneath their centers compared to dry vortices, consistent with many dry vortices having a topographic origin and MCVs arising from organized convection. Parameters such as horizontal scale, background vertical wind shear, and horizontal deformation were not systematically related to intensity or longevity. Prediction of mesoscale vortices by the RUC-2 was examined for a subsample of all cases. In general, the RUC-2 was able to predict the evolution of vortices once analyzed, but had virtually no skill at predicting (12 h in advance) the formation of the vortices. However, forecasts of organized convection should still benefit from accurate predictions of long-lived vortex tracks."
"57217451702;7005045912;35467186900;","Development and structure of a maritime continent thunderstorm",1994,"10.1007/BF01029612","https://www.scopus.com/inward/record.uri?eid=2-s2.0-21344493864&doi=10.1007%2fBF01029612&partnerID=40&md5=7a66308390ce60088df23a083851ece9","The evaluation of a maritime continent thunderstorm complex (Hector) occurring over Bathurst and Melville Islands north of Darwin, Australia (12° S, 131° E) is investigated primarily using Doppler radar data. Thunderstorm formation follows the development of sea breeze circulations and a period of shallow non-precipitating convection. Evidence exists for initiation of long-lived and organised convection on the sea breeze fronts, although short-lived, scattered convection is apparent earlier in the day. Merging of the convective systems is observed in regions of enhanced low-level convergence related to sea breeze circulations. The merged convective complex is initially aligned in an almost east-west direction consistent with the low-level forcing. The merged complex results in rapid vertical development with updraughts reaching 40 m s- and echo tops reaching 20 km height. Maximum precipitation production occurs during this merger phase. On the perimeter of the merged convective complex, evidence exists for front-to-rear updraughts sloped over lower-level downdraughts with rear-to-front relative flow and forward propagating cold pools. The mature phase is dominated by this convection and the complex re-orientates in the prevailing easterly vertical shear to an approximate north-south direction, then moves westward off the islands with the classic multicellular squall-like structure. The one-dimensional cloud model of Ferrier and Houze (1989) used with a four class ice formulation reproduced the cloud top height, updraught structure and echo profile very well. To test the importance of ice physics upon thunderstorm development, several sensitivity tests were made removing the effects of the ice phase. All of these model clouds reached nearly 20 km, although simulations without the effects of ice had updraughts reduced from about 40 m s-1 to 30 m s-1. The simulated convection was more sensitive to changes in environmental conditions and parameterised cloud dynamics. The strong intensity of the convection was largely accounted for by increasing equivalent potential temperatures due to diurnal heating of the surface layer. The vertical velocity and radar structure of the island thunderstorm has more similarity with continental rather than oceanic convection. Maximum vertical velocities, in particular are almost an order of magnitude greater than typical of oceanic convection. With the intense updraughts, even in the low shear environment, there is evidence for mesoscale circulations within the convection. © 1994 Springer-Verlag."
"7403232646;7005281574;","Mesoscale budgets of heat and moisture in a convective system over the central United States.",1984,"10.1175/1520-0493(1984)112<1482:MBOHAM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021560362&doi=10.1175%2f1520-0493%281984%29112%3c1482%3aMBOHAM%3e2.0.CO%3b2&partnerID=40&md5=bfe7a371a1018a4e9419d99d307c7ec6","The effect of midlatitude organized convection on its environment is diagnosed through the calculation of mesoscale heat and moisture budgets over a region during the 10-11 April 1979 AVE-SESAME case. The noise level or error at individual points is about 5oC day-1 for the heat budget and 2 g kg-1 day-1 for the moisture budget, consistent with the sensitivity tests discussed by Kuo and Anthes in a related paper. However, when averaged over an area bigger than the observational scale, the noise level is considerably reduced. -from Authors"
"19639722300;57115138000;35105747400;57214772271;56562594400;7005702722;","Role of surface heat fluxes underneath cold pools",2016,"10.1002/2015GL067262","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84958074598&doi=10.1002%2f2015GL067262&partnerID=40&md5=32dca1037782bf8d679ef65ae2611dc8","The role of surface heat fluxes underneath cold pools is investigated using cloud-resolving simulations with either interactive or horizontally homogenous surface heat fluxes over an ocean and a simplified land surface. Over the ocean, there are limited changes in the distribution of the cold pool temperature, humidity, and gust front velocity, yet interactive heat fluxes induce more cold pools, which are smaller, and convection is then less organized. Correspondingly, the updraft mass flux and lateral entrainment are modified. Over the land surface, the heat fluxes underneath cold pools drastically impact the cold pool characteristics with more numerous and smaller pools, which are warmer and more humid and accompanied by smaller gust front velocities. The interactive fluxes also modify the updraft mass flux and reduce convective organization. These results emphasize the importance of interactive surface fluxes instead of prescribed flux boundary conditions, as well as the formulation of surface heat fluxes, when studying convection. © 2016. American Geophysical Union. All Rights Reserved."
"55993535000;7003345391;6701567335;55036442600;7007155308;8362283200;","Interpreting the photometry and spectroscopy of directly imaged planets: A new atmospheric model applied to β Pictoris b and SPHERE observations",2015,"10.1051/0004-6361/201526332","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945197149&doi=10.1051%2f0004-6361%2f201526332&partnerID=40&md5=d912ca60ab2e05c98033e5e0dff8864e","Context. Since the end of 2013 a new generation of instruments optimized to image young giant planets around nearby stars directly is becoming available on 8-m class telescopes, both at Very Large Telescope and Gemini in the southern hemisphere. Beyond the achievement of high contrast and the discovery capability, these instruments are designed to obtain photometric and spectral information to characterize the atmospheres of these planets. Aims. We aim to interpret future photometric and spectral measurements from these instruments, in terms of physical parameters of the planets, with an atmospheric model using a minimal number of assumptions and parameters. Methods. We developed the Exoplanet Radiative-convective Equilibrium Model (Exo-REM) to analyze the photometric and spectroscopic data of directly imaged planets. The input parameters are a planet's surface gravity (g), effective temperature (Teff), and elemental composition. The model predicts the equilibrium temperature profile and mixing ratio profiles of the most important gases. Opacity sources include the H2-He collision-induced absorption and molecular lines from eight compounds (including CH4 updated with the Exomol line list). Absorption by iron and silicate cloud particles is added above the expected condensation levels with a fixed scale height and a given optical depth at some reference wavelength. Scattering was not included at this stage. Results. We applied Exo-REM to photometric and spectral observations of the planet β Pictoris b obtained in a series of near-infrared filters. We derived Teff = 1550 ± 150 K, log (g) = 3.5 ± 1, and radius R = 1.76 ± 0.24 RJup (2σ error bars from photometric measurements). These values are comparable to those found in the literature, although with more conservative error bars, consistent with the model accuracy. We were able to reproduce, within error bars, the J- and H-band spectra of β Pictoris b. We finally investigated the precision to which the above parameters can be constrained from SPHERE measurements using different sets of near-infrared filters as well as low-resolution spectroscopy. © ESO, 2015."
"7006614696;","Short-term versus climatological relationship between precipitation and tropospheric humidity",2012,"10.1175/JCLI-D-12-00037.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84869755994&doi=10.1175%2fJCLI-D-12-00037.1&partnerID=40&md5=b87fd3e6abc439a26379808c8a7172c0","In this study the observed relationship of precipitation with column relative humidity (CRH), a metric of tropospheric humidity, is examined in order to address a known discrepancy inherent to past studies. A composite analysis of satellite data is carried out to explore the short-term (i.e., from hourly to daily) atmospheric variability for comparison with the climatology, hypothesizing that a primary cause for the discrepancy arises from a difference in the time scale of interest. The analysis is broken down into four classes on the basis of the degree of convective organization, ranging from unorganized shallow cumuli to highly organized convective systems. The CRH-precipitation relationship is found to be extremely nonlinear for the shortterm variability, while the nonlinearity weakens to some degree when different convective systems in diverse humidity environments are averaged together into climatology. The weak exponential rise in the climatological CRH-precipitation curve occurs because highly organized convective systems become more frequent and intense and thus receive increasing weight in the climatological mean as the environment moistens. © 2012 American Meteorological Society."
"7202899330;7202962414;8266109300;","On the radiative effects of dust on tropical convection",2004,"10.1029/2004GL021342","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16644403082&doi=10.1029%2f2004GL021342&partnerID=40&md5=badcf828971eed6291588820834c6e13","Radiative-convective equilibrium experiments with a two-dimensional cloud resolving model illustrate the influence of a lofted absorbing dust layer on the organization of tropical convection. At quasi-equilibrium, the dust-covered region of the model exhibits increased occurrence of deep convection compared to the dust-free region but with reduced convection in the dust-free region controlled in part by a large-scale monsoon-like circulation forced by the aerosol radiative heating. The dry air associated with the dust layer inhibits convection initially over most of the dust-covered region with convection occurring predominantly at the lateral boundaries of the layer. This behavior reproduces features which have been observed in cases of Saharan dust transport over the tropical Atlantic. Copyright 2004 by the American Geophysical Union."
"7202899330;7102389805;","Cloud decoupling of the surface and planetary radiative budgets.",1984,"10.1175/1520-0469(1984)041<0681:CDOTSA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021639716&doi=10.1175%2f1520-0469%281984%29041%3c0681%3aCDOTSA%3e2.0.CO%3b2&partnerID=40&md5=508a9c9e584e8a9be6967dcdb0c492c1","Employs a one-dimensional radiative-convective equilibrium model with multiple cloud layers to demonstrate that the surface equilibrium temperature is highly sensitive to the vertical distribution of effective cloud base heights. It is also demonstrated that the reflected solar flux from an ensemble of cloud layers is independent of the vertical distribution of these cloud layers and is a function only of the total water path integrated in the vertical, a property which also determines the solar radiation reaching the surface. -from Author"
"42262516200;6506642126;57195881858;","An ensemble approach to investigate tropical cyclone intensification in sheared environments. Part I: Katia (2011)",2016,"10.1175/JAS-D-15-0052.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957663106&doi=10.1175%2fJAS-D-15-0052.1&partnerID=40&md5=ac46f3565ffe39699307e864ded67292","The mechanisms responsible for tropical cyclone (TC) intensification in the presence of moderate vertical shear magnitudes are not well understood. To investigate how TCs intensify in spite of moderate shear, this study employed a 96-member ensemble generated with the Advanced Hurricane Weather Research and Forecasting (AHW) Model. In this first part, AHW ensemble forecasts for TC Katia (2011) were evaluated when Katia was a weak tropical storm in an environment of 12 ms-1 easterly shear. The 5-dayAHWforecasts for Katia were characterized by large variability in the intensity, presenting an opportunity to compare the underlying mechanisms between two subsets of members that predicted different intensity scenarios: intensification and weakening. The key difference between these two subsets was found in the lower-tropospheric moisture north of Katia (i.e., right-of-shear quadrant). With more water vapor in the lower troposphere, buoyant updrafts helped to moisten the midtroposphere and enhanced the likelihood of deep and organized convection in the subset that predicted intensification. This finding was validated with a vorticity budget, which showed that deep cyclonic vortex stretching and tilting contributed to spinning up the circulation after the midtroposphere had moistened. Sensitivity experiments, in which the initial conditions were perturbed, also demonstrated the importance of lower-tropospheric moisture, which suggests that moisture observations may help reduce uncertainty in forecasts of weak, sheared tropical storms. © 2016 American Meteorological Society."
"12144041700;","The effects of imposed stratospheric cooling on the maximum intensity of tropical cyclones in axisymmetric radiative-convective equilibrium",2013,"10.1175/JCLI-D-13-00195.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890211818&doi=10.1175%2fJCLI-D-13-00195.1&partnerID=40&md5=f638d6fff26e7e952406dc8423af4e0f","The effects of stratospheric cooling and sea surface warming on tropical cyclone (TC) potential intensity (PI) are explored using an axisymmetric cloud-resolving model run to radiative-convective equilibrium (RCE). Almost all observationally constrained datasets show that the tropical lower stratosphere has cooled over the past few decades. Such cooling may affect PI by modifying the storm's outflow temperature, which together with the sea surface temperature (SST) determines the thermal efficiency in PI theory. Results show that cooling near and above the model tropopause (̃90 hPa), with fixed SST, increases the PI at a rate of 1ms-1 per degree of cooling. Most of this trend comes from a large increase in the thermal efficiency component of PI as the stratosphere cools. Sea surface warming (with fixed stratospheric temperature) increases the PI by roughly twice as much per degree, at a rate of about 2ms-1K-1. Under increasing SST, most of the PI trend comes from large changes in the air-sea thermodynamic disequilibrium. The predicted outflow temperature shows no trend in response to SST increase; However, the outflow height increases substantially. Under stratospheric cooling, the outflow temperature decreases and at the same rate as the imposed cooling. These results have considerable implications for global PI trends in response to climate change. Tropical oceans have warmed by about 0.15Kdecade-1 since the 1970s, but the stratosphere has cooled anywhere from 0.3 to over 1Kdecade-1, depending on the dataset. Therefore, global PI trends in recent decades appear to have been driven more by stratospheric cooling than by surface warming. © 2013 American Meteorological Society."
"34979145900;","The moisture mode in the quasi-equilibrium tropical circulation model. Part II: Nonlinear behavior on an equatorial β plane",2009,"10.1175/2008JAS2691.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69849111669&doi=10.1175%2f2008JAS2691.1&partnerID=40&md5=1d6c71fa93c4cbaa47510d28cfe47716","Numerical calculations of a simplified quasi-equilibrium tropical circulation model (QTCM) on the equatorial β plane have been performed to explore the nonlinear regime of the moisture mode. Sensitivity tests have examined the effects of nonlinear advection and nonlinear wind-induced surface heat exchange (WISHE). Starting from a spatially homogeneous radiative-convective equilibrium with some background gustiness, the model develops quasi-stationary moisture modes, as expected from linear analysis. Upon nonlinear saturation due to thermodynamic limiting processes, a different regime emerges. A classical Gill model augmented with a prognostic humidity variable is found to be able to capture the nonlinear dynamics of the moisture mode; the time evolution solely resides in the humidity variable, and it is possible to understand its dynamics by examining the humidity budget. A scaling analysis shows that the approximation with a Gill model is valid for disturbances whose time scale is much longer than the damping time scale of equatorial waves. When nonlinear WISHE is included, a large-scale disturbance of wavenumber 1 grows and moves westward because evaporation is enhanced to the west of increased convection. Turning on nonlinear advection leads to disturbances of wavenumber 10 that translate eastward via advection of dry air by Rossby gyres. Combining nonlinear WISHE and nonlinear advection leads to gross moist instability and prohibits long-term numerical integration, which suggests that QTCM must be refined to fully describe the nonlinear dynamics of the moisture mode. © 2009 American Meteorological Society."
"45661986200;13411455700;55418382000;35509639400;","Observed relationships between cloud vertical structure and convective aggregation over tropical ocean",2017,"10.1175/JCLI-D-16-0125.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85014523830&doi=10.1175%2fJCLI-D-16-0125.1&partnerID=40&md5=899d159e265b696b9afedb60df57ef19","Using the satellite-infrared-based Simple Convective Aggregation Index (SCAI) to determine the degree of aggregation, 5 years of CloudSat-CALIPSO cloud profiles are composited at a spatial scale of 10 degrees to study the relationship between cloud vertical structure and aggregation. For a given large-scale vertical motion and domain-averaged precipitation rate, there is a large decrease in anvil cloud (and in cloudiness as a whole) and an increase in clear sky and low cloud as aggregation increases. The changes in thick anvil cloud are proportional to the changes in total areal cover of brightness temperatures below 240 K [cold cloud area (CCA)], which is negatively correlated with SCAI. Optically thin anvil cover decreases significantly when aggregation increases, even for a fixed CCA, supporting previous findings of a higher precipitation efficiency for aggregated convection. Cirrus, congestus, and midlevel clouds do not display a consistent relationship with the degree of aggregation. Lidar-observed low-level cloud cover (where the lidar is not attenuated) is presented herein as the best estimate of the true low-level cloud cover, and it is shown that it increases as aggregation increases. Qualitatively, the relationships between cloud distribution and SCAI do not change with sea surface temperature, while cirrus clouds are more abundant and low-level clouds less at higher sea surface temperatures. For the observed regimes, the vertical cloud profile varies more evidently with SCAI than with mean precipitation rate. These results confirm that convective scenes with similar vertical motion and rainfall can be associated with vastly different cloudiness (both high and low cloud) and humidity depending on the degree of convective aggregation. © 2017 American Meteorological Society."
"56567409000;23492864500;7201504886;","The role of precipitation and spatial organization in the response of trade-wind clouds to warming",2016,"10.1002/2015MS000568","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84973596894&doi=10.1002%2f2015MS000568&partnerID=40&md5=303428d89742eb71514ba2b52edd4300","Using highly resolved large-eddy simulations on two different domain sizes, we investigate the influence of precipitation and spatial organization on the thermodynamic structure of the trade-wind layer, under a uniform 4 K warming at constant relative humidity. In nonprecipitating simulations, the increased surface latent heat flux in the warmer climate produces a deeper and drier cloud layer with reduced cloud fractions between 1.5 and 4 km. Precipitation prevents the deepening and drying of the cloud layer in response to warming. Cloud fractions still decrease in the upper cloud layer, because stratiform outflow layers near cloud tops are less pronounced and because the larger liquid water contents are confined to narrower updrafts. Simulations on a 16-fold larger domain lead to the spatial organization of clouds into larger and deeper cloud clusters. The presence of deeper clouds results in a shallower, warmer, and drier trade-wind layer, with strongly reduced cloud cover. The warming response in the precipitating large-domain simulation nevertheless remains similar to the small-domain precipitating simulation. On the large domain, deeper clouds can also develop without precipitation, because moisture-convection feedbacks strengthen in the absence of cold-pool dynamics. Overall, total cloud cover and albedo decrease only slightly with warming in all cases. This demonstrates the robustness of shallow cumuli—in particular of cloud fraction near the lifting condensation level—to changes in the large-scale environment. © 2016. The Authors."
"55469523400;15124698700;","Increases in moist-convective updraught velocities with warming in radiative-convective equilibrium",2015,"10.1002/qj.2567","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946481565&doi=10.1002%2fqj.2567&partnerID=40&md5=83372d07eefe03c0d969806e198ce0d0","The scaling of updraught velocities over a wide range of surface temperatures is investigated in simulations of radiative-convective equilibrium with a cloud-system resolving model. The updraught velocities increase with warming, with the largest fractional increases occurring in the upper troposphere and for the highest percentile updraughts. A plume model approximately reproduces the increases in updraught velocities if the plume environment is prescribed as the mean profile in each simulation while holding the entrainment and microphysical assumptions fixed. Convective available potential energy (CAPE) also increases with warming in the simulations but at a much faster fractional rate when compared with the square of the updraught velocities. This discrepancy is investigated with a two-plume model in which a weakly entraining plume represents the most intense updraughts, and the environment is assumed to adjust so that a more strongly entraining plume has negligible buoyancy. The two-plume model suggests that updraught velocities increase with warming at a lower fractional rate than implied by the CAPE because of the influence of entrainment on both the mean stratification and the updraughts themselves. © 2015 Royal Meteorological Society."
"55037642100;56575724100;","Water vapor budget in a developing tropical cyclone and its implication for tropical cyclone formation",2014,"10.1175/JAS-D-13-0378.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910140468&doi=10.1175%2fJAS-D-13-0378.1&partnerID=40&md5=b54a34bc09dcf8de9bb321d6c20f879f","Evolution of the water vapor budget from the tropical wave stage to the tropical cyclone stage is examined using a high-resolution numericalmodel simulation. The focus is on a time window from 27 h prior to genesis to 9 h after genesis, and the diagnoses are carried out in the framework of themarsupial paradigm. Analysis shows that the vertically integrated inward moisture flux accounts for a majority of the total condensation and that its fractional contribution increases from the tropical wave stage to the tropical cyclone stage. The fractional contribution of the local evaporation ismuch smaller and decreases from the tropical wave stage to the tropical cyclone stage. It is also shown that the radial moisture flux above 850 hPa is rather weak prior to genesis but increases significantly after genesis because of the deepening of the inflow layer. The decrease in the fractional contribution of the local evaporation, or the increase in the fractional contribution of the vertically integrated inward moisture flux, is due to the strengthening of the low-level convergence associated with the secondary circulation. The intensification of the secondary circulation can be attributed to the organized convection and concentrated diabatic heating near the circulation center. The results suggest that the local evaporation and its positive interaction with the primary circulation may not be as important as generally appreciated for tropical cyclone development. By contrast, the increase in the fractional contribution by the inward moisture flux with the storm intensification implies the importance of the positive feedback among the primary circulation, the secondary circulation, and convection for tropical cyclone development. © 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."
"57193882808;7006095466;","Large-scale organization of tropical convection in two-dimensional explicit numerical simulations: Effects of interactive radiation",2002,"10.1256/qj.01.104","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036774875&doi=10.1256%2fqj.01.104&partnerID=40&md5=e304007a014e164349c0013d8a5fec06","We examine interactions among radiative processes, water vapour, clouds, and the multi-scale organization of tropical convection in two-dimensional idealized cloud-resolving simulations using planetary-scale horizontal domains. We extend our earlier study where radiative cooling was prescribed. Therein, deep convection spontaneously organized into two primary scales: westward travelling mesoscale convective systems on a scale of a few hundred kilometres and the eastward-propagating envelopes of convection spanning thousands of kilometres. These envelopes represented large-scale convectively coupled gravity waves, two-dimensional non-rotating analogues of equatorially trapped Kelvin waves. Interactive radiation introduces a new mechanism of large-scale convective organization. Weak overturning circulations, steered by the mean wind and of a few thousand kilometres in scale, gradually develop. This overturning is a manifestation of the baroclinic response to horizontal gradients of radiative heating established between the moist and dry regions, which causes a spontaneous positive feedback among large-scale dynamics, water vapour, clouds, and radiation. The mechanism is as follows: the convective systems maintain the humidity (vapour and cloud) in the ascending branch which, in turn, maintains the differential radiative heating. Conversely, the large-scale overturning provides the large-scale dynamical forcing that maintains the deep convection. This quantifies recent idealized studies that applied convective parametrizations. The radiatively driven overturning and the deep convection are modulated by large-scale convectively coupled gravity waves responsible for the large-scale envelopes reported earlier. A series of sensitivity tests, including the effects of environmental shear, demonstrate the robustness of these results."
"36992744000;36961988200;","Uniformly rotating global radiative-convective equilibrium in the Community Atmosphere Model, version 5",2015,"10.1002/2015MS000519","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959488002&doi=10.1002%2f2015MS000519&partnerID=40&md5=07baf0b9bfcd5581de60fc96d86e9f4b","A standard atmospheric general circulation model is run in a uniformly rotating global radiative-convective equilibrium configuration to explore the equilibrium state, including the statistics of its constituent tropical cyclones, and its sensitivity to horizontal resolution. The Community Atmosphere Model 5 (CAM5) is run at the conventional resolution of approximately 100 km grid spacing and a high resolution of 25 km grid spacing globally. The setup uses an aqua-planet configuration with spatially uniform, diurnally varying insolation, uniform fixed sea surface temperatures, and a uniform rotation rate equal to that at 10?N. The resulting state is one in which tropical cyclones fill the global domain, such that storm count and outer storm size covary strongly. At higher resolution, the storm inner core is more intense and compact but the size of the outer circulation decreases only marginally, and storm count increases in a manner consistent with this decrease in size. Furthermore, the size of the wind field and precipitation fields are highly correlated. A simple analytical model is found to robustly reproduce the radial structure of the broad outer storm circulation. Finally, the minimum central pressure is demonstrated to be an exclusive function of peak azimuthal-mean wind speed and outer storm size. Despite significant changes in the statistics of storm count, intensity, and structure, the mean environment, including the potential intensity, is nearly identical for both simulations. Results are compared with the nonrotating case from a prior study, and a generalized conceptual framework for the interpretation of aggregation with or without rotation is proposed. © 2015. The Authors."
"56272964700;","Impact of convective organization on the response of tropical precipitation extremes to warming",2013,"10.1175/JCLI-D-12-00655.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880663322&doi=10.1175%2fJCLI-D-12-00655.1&partnerID=40&md5=caf831ea786a67399a8b4efb8a40dce2","In this study the response of tropical precipitation extremes to warming in organized convection is examined using a cloud-resolving model. Vertical shear is imposed to organize the convection into squall lines. Earlier studies show that in disorganized convection, the fractional increase of precipitation extremes is similar to that of surface water vapor, which is substantially smaller than the increase in column water vapor. It has been suggested that organized convection could lead to stronger amplifications. Regardless of the strength of the shear, amplifications of precipitation extremes in the cloud-resolving simulations are comparable to those of surface water vapor and are substantially less than increases in column water vapor. The results without shear and with critical shear, for which the squall lines are perpendicular to the shear, are surprisingly similar with a fractional rate of increase of precipitation extremes slightly smaller than that of surface water vapor. Interestingly, the dependence on shear is nonmonotonic, and stronger supercritical shear yields larger rates, close to or slightly larger than surface humidity. A scaling is used to evaluate the thermodynamic and dynamic contributions to precipitation extreme changes. To first order, they are dominated by the thermodynamic component, which has the same magnitude for all shears, close to the change in surface water vapor. The dynamic contribution plays a secondary role and tends to weaken extremes without shear and with critical shear, while it strengthens extremes with supercritical shear. These different dynamic contributions for different shears are due to different responses of convective mass fluxes in individual updrafts to warming. ©2013 American Meteorological Society."
"37162559400;7003656857;","Convective boundary layers driven by nonstationary surface heat fluxes",2011,"10.1175/2010JAS3643.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954999128&doi=10.1175%2f2010JAS3643.1&partnerID=40&md5=d936fe471c809c922c731ce9ef3fc5de","In this study the response of dry convective boundary layers to nonstationary surface heat fluxes is systematically investigated. This is relevant not only during sunset and sunrise but also, for example, when clouds modulate incoming solar radiation. Because the time scale of the associated change in surface heat fluxes may differ from case to case, the authors consider the generic situation of oscillatory surface heat fluxes with different frequencies and amplitudes and study the response of the boundary layer in terms of transfer functions. To this end both a mixed layer model (MLM) and a large-eddy simulation (LES) model are used; the latter is used to evaluate the predictive quality of the mixed layer model. The mixed layer model performs generally quite well for slow changes in the surface heat flux and provides analytical understanding of the transfer characteristics of the boundary layer such as amplitude and phase lag. For rapidly changing surface fluxes (i.e., changes within a time frame comparable to the large eddy turnover time), it proves important to account for the time it takes for the information to travel from the surface to higher levels of the boundary layer such as the inversion zone. As a follow-up to a 1997 study by Sorbjan, who showed that the conventional convective velocity scale is inadequate as a scaling quantity during the decay phase, this paper addresses the issue of defining, in (generic) transitional situations, a velocity scale that is solely based on the surface heat flux and its history. © 2011 American Meteorological Society."
"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."
"36054921000;7102567936;","Factors controlling rain on small tropical Islands: Diurnal cycle, large-scale wind speed, and topography",2017,"10.1175/JAS-D-16-0344.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029111050&doi=10.1175%2fJAS-D-16-0344.1&partnerID=40&md5=c7bd40c681d6a21f763ac9ea00e33e48","A set of idealized cloud-permitting simulations is performed to explore the influence of small islands on precipitating convection as a function of large-scale wind speed. The islands are situated in a long narrow ocean domain that is in radiative-convective equilibrium (RCE) as a whole, constraining the domain-average precipitation. The island occupies a small part of the domain, so that significant precipitation variations over the island can occur, compensated by smaller variations over the larger surrounding oceanic area. While the prevailing wind speeds vary over flat islands, three distinct flow regimes occur. Rainfall is greatly enhanced, and a local symmetric circulation is formed in the time mean around the island, when the prevailing large-scale wind speed is small. The rainfall enhancement over the island is much reduced when the wind speed is increased to a moderate value. This difference is characterized by a change in the mechanisms by which convection is forced. A thermally forced sea breeze due to surface heating dominates when the large-scale wind is weak. Mechanically forced convection, on the other hand, is favored when the large-scale wind is moderately strong, and horizontal advection of temperature reduces the land-sea thermal contrast that drives the sea breeze. Further increases of the prevailing wind speed lead to strong asymmetry between the windward and leeward sides of the island, owing to gravity waves that result from the land-sea contrast in surface roughness as well as upward deflection of the horizontal flow by elevated diurnal heating. Small-amplitude topography (up to 800-m elevation is considered) has a quantitative impact but does not qualitatively alter the flow regimes or their dependence on wind speed. © 2017 American Meteorological Society."
"6602826286;7404029779;6602887222;8650145400;26644701600;57200884451;57197451381;36597856600;","Sahel decadal rainfall variability and the role of model horizontal resolution",2016,"10.1002/2015GL066690","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956587213&doi=10.1002%2f2015GL066690&partnerID=40&md5=c2a6dc10ea3c9fe1312a19565ba02603","Substantial low-frequency rainfall fluctuations occurred in the Sahel throughout the twentieth century, causing devastating drought. Modeling these low-frequency rainfall fluctuations has remained problematic for climate models for many years. Here we show using a combination of state-of-the-art rainfall observations and high-resolution global climate models that changes in organized heavy rainfall events carry most of the rainfall variability in the Sahel at multiannual to decadal time scales. Ability to produce intense, organized convection allows climate models to correctly simulate the magnitude of late-twentieth century rainfall change, underlining the importance of model resolution. Increasing model resolution allows a better coupling between large-scale circulation changes and regional rainfall processes over the Sahel. These results provide a strong basis for developing more reliable and skilful long-term predictions of rainfall (seasons to years) which could benefit many sectors in the region by allowing early adaptation to impending extremes. ©2015 American Geophysical Union. This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland."
"34972803800;23485958100;14920137300;7003408439;","How systematic is organized tropical convection within the MJO?",2013,"10.1002/grl.50308","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876943484&doi=10.1002%2fgrl.50308&partnerID=40&md5=8a80cbef07e2fb3032fcff883866b562","Recent theories of the dynamics of the Madden-Julian Oscillation (MJO) have been building on its multiscale structure. While it is observed that much of the convection within the MJO envelope is related to higher frequency equatorial waves, it is not known to what extent this organization is systematic from one MJO event to another. For instance, it is of interest to know whether MJO favors waves of particular types and propagation direction, and how this variability changes seasonally. This work presents a wavenumber-frequency spectral analysis of the MJO convective envelope, which indicates that there is no strong preferred scale of high frequency organization that is ubiquitous to the MJO. This null finding supports the use of convective parametrizations in modeling the MJO since, while moist convection is likely critical to its initiation and maintenance, the particular details of that organization may not be critical for its prediction and simulation. Key Points Documentation of convective organization within the MJO's convective envelope The MJO does not seem to favor certain specific convective equatorial waves This observational finding supports the use of convective parametrizations ©2013. American Geophysical Union. All Rights Reserved."
"11940701600;7003926380;","Regional variation of morphology of organized convection in the tropics and subtropics",2013,"10.1029/2012JD018409","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884832808&doi=10.1029%2f2012JD018409&partnerID=40&md5=815d5739f510bd438bcad131e77fcec3","Properties of organized convection with large horizontal area (> 1000 km2) and with different horizontal structures in the tropics and subtropics are investigated by using 14 years of Tropical Rainfall Measuring Mission observations. First, the convective features (CFs) are defined as contiguous areas of convective precipitation detected by the Tropical Rainfall Measuring Mission precipitation radar. Using the minor and major axes of fitted ellipses, the morphology of the CFs are described as closer to a circular or a line shape. Regional variations and the properties of organized convection are examined with CFs with area>1000 km2 after categorizing them by their shapes. Organized convection tends to have larger extent and a higher fraction of near-circular shapes over land than over ocean. Shallow organized convection with maximum radar echo top height below 4.5 km is found mainly over ocean and some coastal regions. Of all tropical oceans, most shallow organized convection is found over the east Pacific. The fraction of line shaped organized convection is higher over the ocean than over land, and is higher in the subtropics than in the tropics. More convective lines are found in winter than in summer over oceans, but more in summer over land. Organized convective lines are slightly less convectively intense indicated by lower 30 dBZ echo top heights and warmer 37 GHz brightness temperatures than those with near-circular shapes. Orientations of organized convective lines are often aligned with fronts, dry lines, warm ocean currents, coastlines, and mountain slopes. Over the subtropics, organized convective lines are tilted more east-west over land, and more north-south over oceans. The largest and the most intense convective lines are found over central Africa, Argentina, and southeast U.S. over land, and over several warm currents in subtropical oceans. © 2012. American Geophysical Union."
"7005702722;","Weakly forced mock walker cells",2012,"10.1175/JAS-D-11-0307.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867940075&doi=10.1175%2fJAS-D-11-0307.1&partnerID=40&md5=4e50737f6f15d494cd27d6a885118c2a","Mock Walker cells driven by weak sea surface temperature (SST) forcing are studied using planetary-scale cloud system-resolving simulations and a simplified framework that represents convection with its linear response functions and parameterizes the large-scale flow based on the gravity wave equation. For sinusoidal SST forcings of the same amplitude, as the horizontal domain size increases, the mock Walker cells strengthen substantially and shorter vertical scales in the vertical velocity profile diminish. This is explained by the fact that temperature anomalies required to sustain a vertical velocity profile of given amplitude are stronger in cases of larger horizontal and smaller vertical scales. Such temperature anomalies become significant at planetary scales so that properly accounting for the horizontal momentum balance, including convective momentum transport (CMT), becomes necessary, while a weak temperature gradient approach that neglects horizontal momentum balance is no longer adequate. The downward advection component of the CMT in particular is important for capturing a number of features of the mock Walker cells. The extent of convective organization also affects the mock Walker cell through its effects on the sensitivities of convective heating and moistening to temperature and moisture anomalies. For strongly organized convection with deep inflows, these sensitivities are consistent with a layer mode of convective overturning, instead of the parcel mode as in unorganized convection, resulting in a weaker second baroclinic component in the mock Walker cells. © 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."
"55576500100;57201725986;7202772927;56227660900;","Effects of vertical wind shear on convective development during a landfall of severe tropical storm Bilis (2006)",2009,"10.1016/j.atmosres.2009.06.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68949148777&doi=10.1016%2fj.atmosres.2009.06.004&partnerID=40&md5=215dd15e359d0ad74afd106910ceb975","Effects of vertical wind shear on convective development during the landfall of tropical storm Bilis (2006) are investigated with a pair of sensitivity experiments using a two-dimensional cloud-resolving model. The validated simulation data from Wang et al. [Wang, D., Li, X., Tao, W.-K., Liu, Y., Zhou, H., 2009: Torrential rainfall processes associated with a landfall of severe tropical storm Bilis (2006): A two-dimensional cloud-resolving modeling study. Atmos. Res., 91, 94-104.] are used as the control experiment. The difference between the control and sensitivity experiments is that vertically varying zonal winds in the control experiment are replaced by their mass-weighted means in the sensitivity experiment. The imposed vertical velocity with ascending motion in the upper troposphere and descending motion in the lower troposphere is responsible for dominant stratiform rainfall on 15 July. The vertical wind shear does not have important impacts on development of stratiform rainfall. One day later, imposed upward motion extends to the lower troposphere. The inclusion of negative vertical wind shear produces well-organized convection and strong convective rainfall because it causes kinetic energy transfer from large-scale forcing to perturbation circulations. © 2009 Elsevier B.V."
"57193882808;","Impact of ice microphysics on multiscale organization of tropical convection in two-dimensional cloud-resolving simulations",2003,"10.1256/qj.02.110","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037286738&doi=10.1256%2fqj.02.110&partnerID=40&md5=a8f67d350708e1101be7f2b139c5fe68","This paper documents the impact of ice microphysics on the multiscale organization of tropical convection as simulated in two-dimensional cloud-resolving model simulations. Results from simulations which apply warm-rain microphysics are compared with results from a simulation which includes ice processes presented previously in this journal. In these simulations, moist convection and large-scale dynamics interact on an unprecedented range of spatial and temporal scales, albeit within a limited two-dimensional dynamical framework. In general, the large-scale organization of convection is similar in all simulations, although the scale and propagation speed of convectively-coupled gravity waves are different between the warm-rain and ice simulations. The most striking differences are on the mesoscale. The warm-rain simulations feature mesoscale convective systems with a reduced stratiform component and shorter life cycle than mesoscale systems in the simulation with ice microphysics. These impacts are consistent with previous modelling studies of the impact of ice microphysics on organized convection. It is hypothesized that the shorter life cycle of mesoscale convective systems in warm-rain simulations influences scale selection of the large-scale convectively-coupled gravity waves. Moreover, the vertical transport of horizontal momentum is affected as well. To the author's knowledge this is the first time the impact of cloud microphysics on mesoscale convective systems is shown to affect the coupling between deep convection and large-scale perturbations in the tropics."
"7102567936;7004479957;","Large-scale waves interacting with deep convection in idealized mesoscale model simulations",2003,"10.1034/j.1600-0870.2003.201421.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037269775&doi=10.1034%2fj.1600-0870.2003.201421.x&partnerID=40&md5=ea2465c2df18b891f7dea2e2483e7e35","The authors study the interaction of large-scale waves with deep convection in nonrotating mesoscale model simulations, without mean vertical shear, under idealized boundary conditions (doubly periodic, fixed uniform sea surface temperature). Radiative cooling is fixed, so radiative-convective feedbacks are not considered. The model is initialized with random thermal perturbations near the surface and then run for 16 days to a state of approximate radiative-convective equilibrium. At this point, a wave-like heating is imposed for one day in order to create a wave. The heating is uniform in the meridional direction, sinusoidal with a wavelength equal to the domain size (4500 km) in the zonal direction, and has a roughly ""first baroclinic mode"" structure in the vertical. After this single day of forcing, the heating is turned off and the wave is allowed to evolve freely for seven more days. A range of forcing phase speeds and amplitudes are used, but two simulations are presented in detail. One has a flow-relative forcing phase speed of 55 m s-1 and the other of zero, and both have maximum forcing amplitude of 10 K d-1. Both of these forcings produce waves which are initially rapidly damped, but then settle in to quasi-steadily propagating, coherent configurations which are weakly decaying or neutral. The authors focus on this latter period. The faster forcing produces a convectively coupled gravity wave qualitatively similar to those predicted by strict quasi-equilibrium (SQE) theory, but whose interaction with convection is weaker than that theory predicts. The adiabatic cooling is considerably larger than the diabatic heating, and consequently the phase speed is roughly 30 m s-1 rather than the 10-15 m s-1 typically predicted by SQE for waves of this vertical structure. Sensitivity studies show that this wave, when propagating eastward against a mean westward flow, is destabilized by linear evaporation-wind feedback. The slower forcing produces a wave which is stationary in the mean flow frame and does not have the structure of a gravity wave. This wave has a much larger signal in the moisture field than does the faster wave, and much closer cancellation between adiabatic cooling and diabatic heating. This wave appears similar to ones appearing in some recent theoretical studies and cloud-resolving simulations."
"56125751300;7201424715;","Radiative forcing of simulated tropical cloud clusters",1993,"10.1175/1520-0493(1993)121<0482:RFOSTC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027839240&doi=10.1175%2f1520-0493%281993%29121%3c0482%3aRFOSTC%3e2.0.CO%3b2&partnerID=40&md5=c9f398743aa957427f39aa927684cc73","In this study, an interactive radiative transfer scheme is incorporated into a two-dimensional version of the Pennsylvania State University-NCAR Mesoscale Model to simulate the evolution of these systems within a large-scale environment under a diurnally varying radiative influence. Simulations of individual MCSs with radiation produced more rainfall than those without it. While runs with forced background ascent all peaked after the same elapsed time regardless of diurnal initialization time, the peak rainfall rates that occurred at night were greater than those occurring during daytime hours. Initialized deep stratiform and cirriform clouds developed mesoscale, edge-oriented convective organization due to the lateral gradients of radiative forcing at the cloud edges. Convective overturning within these mesoscale systems' own trailing anvil clouds was insignificant, and there was no evidence of active latent heating in the clouds great distances away from the convection. Although horizontally varying radiative processes appear to play some role in determining the location of convection, they do not appear to have major effects upon either the total amount of or the diurnal variations in tropical rainfall. -from Authors"
"7402786837;35605362100;7006698304;55521517400;","Improved MJO-simulation in ECHAM6.3 by coupling a Stochastic Multicloud Model to the convection scheme",2017,"10.1002/2016MS000809","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018484190&doi=10.1002%2f2016MS000809&partnerID=40&md5=3b7540770e1d51b6bbadb51fa3f7a473","We implement a Stochastic Multicloud Model (SMCM) in an observation-informed configuration into the convection scheme of the state-of-the-art GCM ECHAM6.3. The SMCM configuration we use here has been tuned to represent observed tropical convection by associating the occurrence and strength of deep convection to midtropospheric vertical velocity and relative humidity. We show that compared to the ECHAM6.3 standard model, the SMCM-modified version shows improved capacity to simulate features of tropical intraseasonal variability, including MJO-like disturbances, without significantly distorting the mean model climate. This improvement goes in hand with ameliorated coupling of atmospheric convection to tropospheric moisture and spatiotemporal coherence of tropical convection compared to reanalysis and observations. We attribute these effects to (i) improved coupling of triggering and suppression of deep convective events to the model's large-scale environment and (ii) the observations-informed closure formulation which leads to an overall reduction of deep convective mass fluxes. Sensitivity tests show that while (ii) improves the convection-moisture relationship, it is (i) which improves the spatiotemporal coherence of tropical rainfall and is important for MJO simulation. Further, the simulated spatiotemporal coherence of tropical rainfall is an intrinsic property of the convection schemes themselves and not of their parameters. We stress that this study serves as a proof-of-concept and motivates further efforts towards building a novel convection parameterization with the SMCM as a central element. © 2016. The Authors."
"23393212200;57171236300;7005808242;55286185400;","Surface temperature dependence of tropical cyclone-permitting simulations in a spherical model with uniform thermal forcing",2016,"10.1002/2016GL067730","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977950735&doi=10.1002%2f2016GL067730&partnerID=40&md5=89a9215e3f1168510ce34c6ed83a5bff","Tropical cyclone (TC)-permitting general circulation model simulations are performed with spherical geometry and uniform thermal forcing, including uniform sea surface temperature (SST) and insolation. The dependence of the TC number and TC intensity on SST is examined in a series of simulations with varied SST. The results are compared to corresponding simulations with doubly periodic f-plane geometry, rotating radiative convective equilibrium. The turbulent equilibria in simulations with spherical geometry have an inhomogenous distribution of TCs with the density of TCs increasing from low to high latitudes. The preferred region of TC genesis is the subtropics, but genesis shifts poleward and becomes less frequent with increasing SST. Both rotating radiative convective equilibrium and spherical geometry simulations have decreasing TC number and increasing TC intensity as SST is increased. ©2016. American Geophysical Union. All Rights Reserved."
"56194231200;7004479957;","Large-scale character of an atmosphere in rotating radiative-convective equilibrium",2014,"10.1002/2014MS000342","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937203439&doi=10.1002%2f2014MS000342&partnerID=40&md5=cab965480fa7a52b27e8943d87ec48da","A rotating radiative-convective equilibrium on a sphere is reached using a global atmospheric model with prescribed globally uniform sea surface temperature and no insolation. In such an equilibrium state, multiple tropical cyclone-like vortices coexist in the extratropics, moving slowly poleward and westward. Many vortices have a lifetime longer than 2 months and travel from the tropics to the polar regions. The typical spacing of simulated tropical cyclone-like vortices is comparable to the deformation radius, while the production of available potential energy is at a scale slightly smaller than those vortices. It is hypothesized that the growth of tropical cyclone-like vortices is driven by the self-aggregation of convection, while baroclinic instability destabilizes any vortices that grow significantly larger than the deformation radius. A weak Hadley circulation dominates in the deep tropics, and an eastward propagating wave number 1 Kelvin-like mode having a period of 30-40 days develops at the equator. The weak Hadley circulation is found to emerge from an initially quiescent atmosphere due to poleward momentum transport by the vortices. Key Points Multiple tropical cyclone-like vortices coexist in rotating RCE on a sphere Self-aggregation and baroclinic instability limit the spacing of vortices The tropics is dominated by a Hadley circulation driven by eddy momentum flux © 2014. The Authors."
"7101661890;7006095466;","Characterization of momentum transport associated with organized moist convection and gravity waves",2010,"10.1175/2010JAS3418.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958583383&doi=10.1175%2f2010JAS3418.1&partnerID=40&md5=d181bf4d8c62ed42df1d7b5cfd52e534","Tropical convection is inherently multiscalar, involving complex fields of clouds and various regimes of convective organization ranging from small disorganized cumulus up to large organized convective clusters. In addition to being a crucial component of the atmospheric water cycle and the global heat budget, tropical convection induces vertical fluxes of horizontal momentum. There are two main contributions to the momentum transport. The first resides entirely in the troposphere and is due to ascent, descent, and organized circulations associated with precipitating convective systems. The second resides in the troposphere, stratosphere, and farther aloft and is caused by vertically propagating gravity waves. Both the convective momentum transport and the gravity wave momentum flux must be parameterized in general circulation models; yet in existing parameterizations, these two processes are treated independently. This paper examines the relationship between the convective momentum transport and convectively generated gravity wave momentum flux by utilizing idealized simulations of multiscale tropical convection in different wind shear conditions. The simulations produce convective systems with a variety of regimes of convective organization and therefore different convective momentum transport properties and gravity wave spectra. A number of important connections are identified, including a consistency in the sign of the momentum transports in the lower troposphere and stratosphere that is linked to the generation of gravity waves by tilted convective structures. These results elucidate important relationships between the convective momentum transport and the gravity wave momentum flux that will be useful for interlinking their parameterization in the future. © 2010 American Meteorological Society."
"6701670597;57203012011;","Notes and correspondence convective eddy momentum tendencies in long cloud-resolving model simulations",2001,"10.1175/1520-0469(2001)058<0517:NACCEM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035279551&doi=10.1175%2f1520-0469%282001%29058%3c0517%3aNACCEM%3e2.0.CO%3b2&partnerID=40&md5=274882ed3219bdcc1af45195e82c450c","Domain-average momentum budgets are examined in several multiday cloud-resolving model simulations of deep tropical convection in realistic shears. The convective eddy momentum tendency F, neglected in many global circulation models, looks broadly similar in two-and three-dimensional simulations. It has a large component in quadrature with the mean wind profile, tending to cause momentum profile features to descend. This component opposes, and exceeds in magnitude, the corresponding large-scale vertical advective tendency, which would tend to make features ascend in convecting regions. The portion of F in phase with the mean wind is isolated by vertically integrating F u, yielding a kinetic energy tendency that is overwhelmingly negative. The variation of this energy damping with shear flow kinetic energy and convection intensity (measured by rain rate) gives a ""cumulus friction"" coefficient around - 40% to -80% per centimeter of rain in 3D runs. Large scatter reflects the effects of varying convective organization. Two-dimensional runs overestimate this friction coefficient for the υ (out of plane) wind component and underestimate it for the υ (in plane) component. Another 2D artifact is that 460-hPa-wavelength shear is essentially undamped, consistent with the descending jets reported by Held et. al. in a free-running 2D cloud model."
"55619308081;7006380976;7102609291;7102746335;","Tropical island convection in the absence of significant topography. Part II: Nowcasting storm evolution",2001,"10.1175/1520-0493(2001)129<1637:TICITA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035390975&doi=10.1175%2f1520-0493%282001%29129%3c1637%3aTICITA%3e2.0.CO%3b2&partnerID=40&md5=6703ac8f9172faee33a9f188f4e1b8e2","This paper examines influences on the short-range prediction of organized convection under conditions of strong diurnal forcing. The analyses are based on data provided by the Maritime Continent Thunderstorm Experiment, which was conducted in 1995 over the Tiwi Islands (11°S) 50-100 km north of the Australian continent. Organized convection over the Tiwi Islands is often dubbed ""Hector"" by residents and researchers alike. The authors' purpose is to utilize results from these analyses, to improve convective storm ""nowcast"" systems and their associated forecast and warning products. The environmental near-surface wind direction is shown to be singularly influential in statistically predicting the location of convection and its time of occurrence over the Tiwi Islands. This finding is robust, despite the fact that mean wind speeds were merely 1-4 m s-1. The island boundary layer water vapor mixing ratio, derived from a morning sounding and inland surface stations, is shown to be correlated with measures of overall convective activity. Mesonet inferences of ambient water vapor anomalies, together with geostationary satellite cloud imagery and radar data, point to favored locations for individual thunderstorm initiation nowcasts. The detailed evolution of Hector thunderstorms on any given day is dependent upon the location and movement of quasi-chaotic interactions among sea breezes, gust fronts, cumulus clouds, and existing storms. The primary mechanism for increasing the size of Hector was an excitation of new convection and merging with existing storms in response to forcing by a westward-propagating gust front. This is fully consistent with previous works, which have examined the effects of convergence lines, cold pools, shear, and the merging of radar echoes. Dissipation of Hector may be predicted as it moves westward from land to ocean and, occasionally, when it moves over land to areas that have been cooled by earlier storms. The results of this study have important implications for expert and numerically based forecasting methods concerned with thunderstorm prediction in the 0-6-h range. A twofold approach exhibits promise in the Tiwi Islands: 1) use of statistical information provided by a dynamically based climatology (∼6 h forecast) and 2) monitoring and extrapolation of existing convergence lines, storms, and cumulus clouds for individual thunderstorm predictions (0-2 h). Variational assimilation of such information into high-resolution forecast models should lead to improved dynamical predictions in the 2-6-h range."
"6603301294;7101780145;6602846660;6602514573;55666972000;6603801190;","A climatological study of thunderstorm activity in the Po Valley",1995,"10.1007/BF00866116","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029535425&doi=10.1007%2fBF00866116&partnerID=40&md5=20bb34ee8408e93727148ffd3e08fdb4","After a description of the monthly distribution of thunderstorm occurrence in the Po Valley and in the Northern Adriatic region and an identification of the homogeneous areas in terms of the contemporary occurrence of the phenomenon, this study examines the dynamic and thermodynamic characteristics of the atmosphere that are conducive to the development of thunderstorms. The study was carried out using ground-level and radiosonde observed data, as well as objective analyses of mean sea level pressure, geopotential height and vertical velocity at different upper-air levels. The period considered, not always homogeneous for the different types of data, refers to the years 1985-1988. The main result that emerges from this study is that thunderstorms are, in the majority of cases, associated with synoptic-scale dynamical forcing, as for example the passage of fronts (generally cold) in the Po Valley, which are also almost invariably connected with depressions affecting the entire Northern Italy. Only a small number of thunderstorms can be attributed to pure local thermodynamic causes, such as for example moist-static instability due intense heating. An analysis of the thermodynamic indices indicates that a suitable vertical distribution of humidity, temperature and static stability can certainly favour thunderstorm activity, but only when the larger scale dynamical forcing is favourable (from the subsynoptic scale to the mesoscale) will the organized convection develop in a sustained manner. © 1995 Springer-Verlag."
"7004187536;7401921174;6506634734;","Origin and structure of a numerically simulated polar low over Hudson Bay",1995,"10.3402/tellusa.v47i5.11578","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029477154&doi=10.3402%2ftellusa.v47i5.11578&partnerID=40&md5=de2d658077fd646331df0f72c309c9c6","The PSU-NCAR mesoscale model (MM4) is used to simulate a polar low that developed over Hudson Bay in December 1988. The structure and characteristics of the simulated low are documented, and results are presented of sensitivity experiments aimed at elucidating the physical mechanisms involved in the cyclogenesis. The low formed over an ice-free region in the eastern bay as an amplifying upper-level cold trough advanced into the region. The model depicted the polar low as a small, relatively shallow system embedded within the larger cold low. The sensitivity experiments revealed that fluxes of heat and moisture from the region of open water and the associated condensation heating in deep organized convection were essential to the development. -from Authors"
"6701537458;","A model-based diagnostic study of the development and maintenance mechanism of two polar lows",1990,"10.3402/tellusa.v42i1.11863","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025235831&doi=10.3402%2ftellusa.v42i1.11863&partnerID=40&md5=ddf1b5fd4bed22c19983fe36caf4f79b","The life cycles of two polar lows in the Norwegian Sea have been studied. Both lows were observed, analysed and forecast by the Norwegian mesoscale model system. The system is run operationally 4 times a day and provides high spatial and temporal resolution data for diagnostics in addition to daily forecasts. Both lows start developing as upper level vorticity maxima approach low-level baroclinic zones. One of the lows decays after the initial baroclinic intensification phase, while the other develops further. This second phase, the maintenance phase, seems to be related to organized convection. The possibility for air-sea interaction instability is discussed. -from Author"
"7005035762;56562594400;56272964700;36634069800;","A Survey of Precipitation-Induced Atmospheric Cold Pools over Oceans and Their Interactions with the Larger-Scale Environment",2017,"10.1007/s10712-017-9447-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85033722298&doi=10.1007%2fs10712-017-9447-x&partnerID=40&md5=596ff8138cf962b85ec1e06e597b45b1","Pools of air cooled by partial rain evaporation span up to several hundreds of kilometers in nature and typically last less than 1 day, ultimately losing their identity to the large-scale flow. These fundamentally differ in character from the radiatively-driven dry pools defining convective aggregation. Advancement in remote sensing and in computer capabilities has promoted exploration of how precipitation-induced cold pool processes modify the convective spectrum and life cycle. This contribution surveys current understanding of such cold pools over the tropical and subtropical oceans. In shallow convection with low rain rates, the cold pools moisten, preserving the near-surface equivalent potential temperature or increasing it if the surface moisture fluxes cannot ventilate beyond the new surface layer; both conditions indicate downdraft origin air from within the boundary layer. When rain rates exceed ∼ 2 mm h- 1, convective-scale downdrafts can bring down drier air of lower equivalent potential temperature from above the boundary layer. The resulting density currents facilitate the lifting of locally thermodynamically favorable air and can impose an arc-shaped mesoscale cloud organization. This organization allows clouds capable of reaching 4–5 km within otherwise dry environments. These are more commonly observed in the northern hemisphere trade wind regime, where the flow to the intertropical convergence zone is unimpeded by the equator. Their near-surface air properties share much with those shown from cold pools sampled in the equatorial Indian Ocean. Cold pools are most effective at influencing the mesoscale organization when the atmosphere is moist in the lower free troposphere and dry above, suggesting an optimal range of water vapor paths. Outstanding questions on the relationship between cold pools, their accompanying moisture distribution and cloud cover are detailed further. Near-surface water vapor rings are documented in one model inside but near the cold pool edge; these are not consistent with observations, but do improve with smaller horizontal grid spacings. © 2017, The Author(s)."
"56294114300;55716319700;","Arctic warming induced by tropically forced tapping of available potential energy and the role of the planetary-scale waves",2015,"10.1175/JAS-D-14-0334.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942156675&doi=10.1175%2fJAS-D-14-0334.1&partnerID=40&md5=7105a897bdbfc1c1489e681e99f8711f","One of the challenging tasks in climate science is to understand the equator-to-pole temperature gradient. The poleward heat flux generated by baroclinic waves is known to be central in reducing the equator-to-pole temperature gradient from a state of radiative-convective equilibrium. However, invoking this relationship to explain the wide range of equator-to-pole temperature gradients observed in past climates is challenging because baroclinic waves tend to follow the flux-gradient relationship such that their poleward heat flux is proportional to the equator-to-pole temperature gradient and zonal available potential energy (ZAPE). With reanalysis data, the authors show the existence of poleward heat transport by planetary-scale waves that are independent of the flux-gradient relationship and baroclinic instability. This process arises from a forced tapping of atmospheric ZAPE by planetary-scale waves that are triggered by enhanced tropical convection over the Pacific warm pool region. The Rossby waves excited by this tropical convection propagate northeastward over the Pacific Ocean and constructively interfere with the climatological stationary waves at higher latitudes. During polar night, when the current warming is most rapid, the forced tapping of ZAPE by planetary-scale waves produces a substantially greater warming than that by the synoptic-scale eddy fluxes that presumably arise from baroclinic instability. © 2015 American Meteorological Society."
"57200926820;7005874614;","A theory of the MJO horizontal scale",2014,"10.1002/2013GL058542","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893662670&doi=10.1002%2f2013GL058542&partnerID=40&md5=618fc9c55cc6e4bc73b86d18a8df4a36","Here we ask, what controls the horizontal scale of the Madden-Julian Oscillation, i.e., what controls its zonal wave number k? We present a new one-dimensional (1D) β-plane model that successfully simulates the MJO with the same governing mechanism as the 2D shallow water model of Yang and Ingersoll (2013). Convection is parameterized as a short-duration localized mass source that is triggered when the layer thickness falls below a critical value. Radiation is parameterized as a steady uniform mass sink. Both models tend toward a statistically steady state - a state of radiative-convective equilibrium, not just on a global scale but also on the scale of each MJO event. This gives k ~ (Sc/c)1/2, where Sc is the spatial-temporal frequency of convection events and c is the Kelvin wave speed. We offer this scaling as a prediction of how the MJO would respond to climate change. Key Points Triggered convection is essential for simulating the MJO Interaction of convection with gravity waves is the other essential element The scale of the MJO is controlled by the number density of convective events ©2014. American Geophysical Union. All Rights Reserved."
"25823818000;7410255460;","Cloud clusters and tropical cyclogenesis: Developing and nondeveloping systems and their large-scale environment",2013,"10.1175/MWR-D-11-00239.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874897902&doi=10.1175%2fMWR-D-11-00239.1&partnerID=40&md5=c414961f93766d3aba4d43d76a5aa7d0","Tropical cyclone (TC) genesis occurs only when there is persistent, organized convection. The question of why some cloud clusters develop into a TC and others do not remains unresolved. This question cannot be addressed adequately without studying nondeveloping systems in a consistent manner together with developing systems. This study presents a systematic approach in classifying developing and nondeveloping cloud clusters based on their large-scale environments. Eight years of hourly satellite IR data and global model analysis over the western North Pacific are used.A cloud cluster is defined as an area of≤ 208-K cloud-top temperature, generally mesoscale in size. Based on the overlapping area between successive hourly images, they are then tracked in time as time clusters. The initial formations of nearly all TCs during July-October 2003-10 were associated with time clusters lasting at least 8 h (8-h clusters). The occurrence of an 8-h cluster is considered to indicate the minimum degree of convective organization needed for TC genesis. A nondeveloping system is defined as an 8-h cluster that is considered to be a viable candidate for TC genesis, but was not associated with the TC genesis. The large-scale environmental conditions of cyclonic low-level vorticity, low vertical wind shear, low-level convergence, and elevated tropospheric water vapor are statistically more favorable for developing systems. Generally, the environment became more (less) favorable with time for the developing (nondeveloping) systems. Nevertheless, many developing (nondeveloping) systems formed (dissipated) in seemingly unfavorable (favorable) environments within a lead time of < 24 h. © 2013 American Meteorological Society."
"37093971200;13605965600;","A climatology of fatal convective wind events by storm type",2011,"10.1175/2010WAF2222428.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953222260&doi=10.1175%2f2010WAF2222428.1&partnerID=40&md5=0aebc9dd1e572fac9249f610a1d104ff","There are still hundreds of casualties produced by thunderstorm hazards each year in the United States despite the many recent advances in prediction and mitigation of the effects of convective storms. Of the four most common thunderstorm hazards (wind, hail, flooding, and lightning), convective winds (tornadic and nontornadic) remain one of the most dangerous threats to life and property. Using thunderstorm fatality and Weather Surveillance Radar-1988 Doppler (WSR-88D) data, this research illustrates a spatial and temporal analysis of the storm morphological characteristics, or convective mode, of all fatal tornadic and nontornadic convective wind events from 1998 to 2007. The investigation employs a radar-based morphology classification system that delineates storm type based on an organizational continuum, including unorganized cellular, quasi-organized cellular (either a cluster of cells or a broken line of cells), organized cellular (supercells and supercells embedded in an organized linear system), and organized linear (either squall lines or bow echoes). Results illustrate that over 90% of the 634 recorded tornado deaths were associated with supercells, with 78% of the deaths due to isolated tornadic supercells and 12% linked to tornadic supercells embedded within an organized linear convective system. The morphologies responsible for the 191 nontornadic convective wind fatalities vary substantially, with bow echoes (24%), squall lines (19%), and clusters of cells (19%) the most prominent convective modes producing fatalities. Unorganized and quasi-organized convection accounted for nearly half (45%) of all nontornadic convective wind fatalities. Over half of all fatal tornadoes (53%) occurred between 0000 and 0600 UTC, and most (59%) fatalities from nontornadic convective winds occurred in the afternoon between 1800 and 0000 UTC. Two corridors of nontornadic convective wind fatalities were present: the lower Great Lakes region and the mid-South. Tornado fatalities were greatest in a zone extending from southeastern Missouri, through western Tennessee, northeastern Arkansas, Mississippi, Alabama, and Georgia. The methods employed and results found in this study are directly applicable in the further development of storm classification schemes and provide forecasters and emergency managers with information to assist in the creation and implementation of new convective wind mitigation strategies. © 2011 American Meteorological Society."
"30967646900;36992744000;8866821900;","The link between extreme precipitation and convective organization in a warming climate: Global radiative-convective equilibrium simulations",2016,"10.1002/2016GL071285","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84998577610&doi=10.1002%2f2016GL071285&partnerID=40&md5=db4e5520dddcd519ad53ad60721de7a8","The rate of increase of extreme precipitation in response to global warming varies dramatically across climate model simulations, particularly over the tropics, for reasons that have yet to be established. Here we propose one potential mechanism: changing organization of convection with climate. We analyze a set of simulations with the Community Atmosphere Model version 5 with an idealized global radiative-convective equilibrium configuration forced by fixed sea surface temperatures varying in 2° increments from 285 to 307 K. In these simulations, convective organization varies from semiorganized in cold simulations, disorganized in warm simulations, and abruptly becomes highly organized at just over 300 K. The change in extreme precipitation with warming also varies across these simulations, including a large increase at the transition from disorganized to organized convection. We develop an extreme precipitation-focused metric for convective organization and use this to explore their connection. ©2016. American Geophysical Union. All Rights Reserved."
"24070588000;56014511300;","A numerical investigation of cumulus thermals",2016,"10.1175/JAS-D-15-0385.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84994162830&doi=10.1175%2fJAS-D-15-0385.1&partnerID=40&md5=4afbf8a760aa3eec169017ca69a3f64d","Although the steady, entraining, updraft plume is widely taken as the foundational concept of cumulus convection, past studies show that convection is typically dominated by thermals that are transient, more isotropic in shape, and possess interior vortical circulations. Here, several thousand such thermals are tracked in cloud-resolving simulations of transient growing convective events. Most tracked thermals are small (with radius R &lt; 300 m), ascend at moderate rates (~ 2-4 m s-1), maintain an approximately constant size as they rise, and have brief (4-5 min) lifetimes, although a few are much larger, faster, and/or longer lived. They show slight vertical elongation, but few, if any, would be described as plumes. As convection deepens, thermals originate higher up, are larger, and rise faster, although radius and ascent rate are only weakly correlated among individual thermals. The main force opposing buoyancy is a nonhydrostatic pressure drag, not mixing of momentum. This drag can be expressed in terms of a drag coefficient cd that decreases as convection intensifies: deep convective thermals are less damped, with cd ~ 0.2, while shallow convective thermals are more damped, with cd ~ 0.6. The expected dependence of cd based on theoretical form and wave drag coefficients for a solid sphere is inconsistent with these results, since it predicts the opposite dependence on the Froude number. Thus, a theory for drag on cumulus thermals is not straightforward. Overall, it is argued that thermals are a more realistic prototype for atmospheric deep convection than plumes, at least for the less organized convection types simulated here. © 2016 American Meteorological Society."
"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."
"55683400000;6602805147;6505932008;","Aerosol-induced mechanisms for cumulus congestus growth",2015,"10.1002/2015JD023743","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943456833&doi=10.1002%2f2015JD023743&partnerID=40&md5=a9fe908dd473501ccd51a62e5b910f7c","Tropical convection has been observed to contain three cloud modes, the middle of which is cumulus congestus clouds. Congestus clouds act to moisten the tropical atmosphere, may be mixed-phase, and on occasion surpass the freezing level inversion from where they may develop into deeper convection. This study investigates the impacts of enhanced aerosol concentrations on the growth of congestus clouds produced in idealized cloud-resolving model simulations run under a state of radiative convective equilibrium (RCE). High-resolution, long-duration simulations were completed using the Regional Atmospheric Modeling System (RAMS). Aerosol concentrations between 2 and 4km above ground level were varied from clean to polluted conditions in order to represent the advection of Saharan dust over the Atlantic Ocean. The congestus populations within each aerosol simulation are statistically analyzed using 10 days of model output after the simulation reaches RCE. Results indicate that congestus in more polluted conditions produce greater amounts of cloud water and ice mass, enhanced updraft strengths, and an increase in the number of congestus cloud tops that extend above the freezing level. Enhanced vapor depositional growth on the populations of more numerous, smaller cloud droplets in the polluted conditions, and the subsequent increase in latent heat release in the warm phase regions of the cloud, is found to be important factors in convective invigoration of these cloud systems. Aerosol feedbacks associatedwith cold pools and condensate loading also influence the updraft strength and act in opposition to the warm phase invigoration processes. © 2015. American Geophysical Union. All Rights Reserved."
"35572026100;7409792174;7006095466;","Self-organized criticality and homeostasis in atmospheric convective organization",2012,"10.1175/JAS-D-12-069.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871969125&doi=10.1175%2fJAS-D-12-069.1&partnerID=40&md5=8681d76c1193b0e696b32c1c22e951d9","Atmospheric convection has a tendency to organize on a hierarchy of scales ranging from the mesoscale to the planetary scales, with the latter especially manifested by the Madden-Julian oscillation. The present paper examines two major competing mechanisms of self-organization in a cloud-resolving model (CRM)simulation from a phenomenological thermodynamic point of view. The first mechanism is self-organized criticality.A saturation tendency of precipitation rate with increasing column-integrated water, reminiscent of critical phenomena, indicates self-organized criticality. The second is a self-regulation mechanism that is known as homeostasis in biology. A thermodynamic argument suggests that such self-regulation maintains the column-integrated water below a threshold by increasing the precipitation rate. Previous analyses of both observational data as well as CRMexperiments give mixed results. In this study, a CRM experiment over a large-scale domain with a constant sea surface temperature is analyzed. This analysis shows that the relation between the column-integrated total water and precipitation suggests self-organized criticality, whereas the one between the column-integrated water vapor and precipitation suggests homeostasis. Theconcurrent presence of these two mechanisms is further elaborated by detailed statistical and budget analyses. These statistics are scale invariant, reflecting a spatial scaling of precipitation processes.©2012 American Meteorological Society."
"7006095466;","The multiscale organization of moist convection and the intersection of weather and climate",2010,"10.1029/2008GM000838","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051806765&doi=10.1029%2f2008GM000838&partnerID=40&md5=b91b7904bb50eba22cfb08e8a825ec94","Moist convection organizes into cloud systems of various sizes and kinds, a process with a dynamical basis and upscale connotations. Although organized precipitation systems have been extensively observed, numerically simulated, and dynamically modeled, our knowledge of their effects on weather and climate is far from complete. Convective organization is absent de facto from contemporary climate models because the salient dynamics are not represented by parameterizations and the model resolution is insufficient to represent them explicitly. Highresolution weather prediction models, fine-resolution cloud system models, and dynamical models address moist convective organization explicitly. As a key element in the seamless prediction of weather and climate on timescales up to seasonal, organized convection is the focus of the Year of Tropical Convection, an international collaborative project coordinated by the World Meteorological Organisation. This paper reviews the scientific basis of convective organization and progress toward comprehending its large-scale effects and representing them in global models. Copyright © 2010 by the American Geophysical Union."
"7202772927;","Cloud resolving modeling",2007,"10.2151/jmsj.85B.305","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34948905301&doi=10.2151%2fjmsj.85B.305&partnerID=40&md5=2f5a18d4006a6ae718cf06fef514d27a","One of the most promising methods to test the representation of cloud processes used in climate models is to use observations together with cloud resolving models (CRMs). CRMs use more sophisticated and realistic representations of cloud microphysical processes, and they can reasonably well resolve the time evolution, structure, and life cycles of clouds and cloud systems (with sizes ranging from about 2-200 km). CRMs also allow for explicit interaction between clouds, outgoing longwave (cooling) and incoming solar (heating) radiation, and ocean and land surface processes. Observations are required to initialize CRMs and to validate their results. This paper provides a brief discussion and review of the main characteristics of CRMs as well as some of their major applications. These include the use of CRMs to improve our understanding of: (1) convective organization, (2) cloud temperature and water vapor budgets, and convective momentum transport, (3) diurnal variation of precipitation processes, (4) radiative-convective quasi-equilibrium states, (5) cloud-chemistry interaction, (6) aerosol-precipitation interaction, and (7) improving moist processes in large-scale models. In addition, current and future developments and applications of CRMs will be presented. © 2007, Meteorological Society of Japan."
"7005051641;6603543777;7006450978;","Comparison of lightning activity and radar-retrieved microphysical properties in EULINOX storms",2005,"10.1016/j.atmosres.2004.11.027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23144451687&doi=10.1016%2fj.atmosres.2004.11.027&partnerID=40&md5=34a994c497c86671bebf583d2af3392e","A combined analysis of microphysical thunderstorm properties derived by C-band polarimetric Doppler radar measurements and lightning observations from two ground-based systems are presented. Three types of storms, a multicell, a supercell, and a squall line, that were observed during the European Lightning Nitrogen Oxides project (EULINOX) are investigated. Correlations are sought between the mass of rain, graupel, hail, and snow derived form radar observations at different height levels and the electrical activity, represented either by cloud-to-ground or intracloud flashes. These relationships are explained by connecting the radar-derived properties with the non-inductive charging process. For the multicell and the supercell storm, the lightning activity can be linearly correlated to both the hydrometeor total mass and class specific mass in the upper part of the storm. It is shown that the fractions of graupel and hail above the -20 °C-level in these storms positively correlate with the intracloud flash activity in the supercell, and negatively for the cloud-to-ground lightning frequency in the multicell. No such relation can be established for the squall line, indicating that the convective organization plays a crucial role in the lightning development. The analysis of the masses in the different storms shows that lightning activity cannot be parameterized by total mass alone, other parameters have to be identified. The results provide important information for all lightning studies that rely on bulk properties of thunderstorms, e.g., the parameterization of lightning in mesoscale models or the nowcasting of lightning by radar. © 2005 Elsevier B.V. All rights reserved."
"7403282069;7202208382;","A sensitivity study of radiative-convective equilibrium in the tropics with a convection-resolving model",1999,"10.1175/1520-0469(1999)056<3385:assorc>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033208554&doi=10.1175%2f1520-0469%281999%29056%3c3385%3aassorc%3e2.0.co%3b2&partnerID=40&md5=a701c4cc54da9ff272574286e1cca2a2","Statistical-equilibrium (SE) states of radiative-convective systems in tropical oceanic conditions are simulated with a cloud ensemble model (CEM) in this study. Typical large-scale conditions from the Marshall Islands and the eastern tropical Atlantic regions are used to drive the CEM. The simulated SE precipitable water, column temperature, and relative humidity are only slightly higher than those of the observed mean states in both regions when time-invariant large-scale total advective cooling and moistening effects are imposed from observations. They are much higher than the observed if time-invariant observed large-scale ascent is imposed for the Marshall Islands region (i.e., ignoring horizontal advective effects). Compared with results from two similar studies, this SE state is somewhere between the cold/dry regime by Sui et al. and the warm/humid regime by Grabowski et al. Temporal variations of the imposed large-scale vertical motion that allows for subsidence make the SE state colder and drier. It remains about the same, however, if the magnitude of the imposed large-scale vertical motion is halved. The SE state is also colder and drier if solar radiation is absent. In general, all the SE states show that wet columns are thermally more stable (unstable) and dry columns are thermally more unstable (stable) in the lower (upper) troposphere. Column budget analyses are performed to explore the differences among the simulations performed in this study and among the different studies. © 1999 American Meteorological Society."
"7004157687;7401584839;","Numerical simulations of convective equilibrium under prescribed forcing",1999,"10.1256/smsqj.55920","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033402216&doi=10.1256%2fsmsqj.55920&partnerID=40&md5=a9fe045e8e6c537e61b7ddc01a06b089","Some characteristic properties of simulated moist convective equilibria are examined for different imposed cooling rates. These numerical simulations extend the work of Vallis et al. and were motivated by the need to show that their conclusions (concerning the upscale energy cascade) were not sensitive to vertical resolution. Although kinetic energy does cascade to large scales, much of the large-scale motion in the model is associated with horizontally-divergent winds, and the energy spectra may be better explained as a direct consequence of the generation of convective lines. These lines have a typical spacing of about 60 km which leads to a local maximum in the kinetic-energy spectrum. In addition, the design of our experiments was found to match that envisaged in recent idealized 'heat-engine theories' of radiative-convective equilibria, thereby providing an opportunity to evaluate their utility. It is shown that a variant of these scaling theories appears to fit the statistical properties of our simulations quite well and provides expressions for the convective available potential energy, cloud mass flux and the fractional area occupied by convective updraughts. Scaling arguments also suggest that the convective line separation is of the order of the convecting layer depth divided by the square root of the updraught fractional area-consistent with the wavelength of the local maximum in the energy spectrum."
"7406363479;7004479957;","Tropical wave instabilities: convective interaction with dynamics using the Emanuel convective parameterization",1995,"10.1175/1520-0469(1995)052<0067:TWICIW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028975184&doi=10.1175%2f1520-0469%281995%29052%3c0067%3aTWICIW%3e2.0.CO%3b2&partnerID=40&md5=cfd66db9a58d987f4e8eaa3c68ad6b71","Wave-CISK and evaporation-wind feedback modes, also known as WISHE (wind-induced surface heat exchange) modes, are investigated using a two-dimensional (x-p), hydrostatic, nonrotational model linearized about a basic state in radiative-convective equilibrium with no vertical shear. Cumulus convection is parameterized using version 1.22 of the Emanuel convective parameterization scheme, a mass flux scheme that includes the effects of evaporatively driven unsaturated downdrafts. It is found that the only unstable modes are long-wavelength WISHE modes. All wave-CISK modes are damped, though the longest-wavelength modes have nearly netural growth rates. It is demonstrated that the presence of evaporatively driven unsaturated downdrafts plays a major role in damping both short-wave WISHE and wave-CISK modes in the model. The model favors approximately the same horizontal scale as observed for the Madden-Julian oscillation (40-60 day wave) but the phase speed is too large by a factor of ~4-5. -from Authors"
"6701540733;57206416522;7006184606;","Radiative-convective model with an explicit hydrologic cycle 2. Sensitivity to large changes in solar forcing",1994,"10.1029/94jd01332","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028586331&doi=10.1029%2f94jd01332&partnerID=40&md5=b6f10fab4c8800fe0b259929469d9232","For fixed cloud conditions, the critical solar forcing for a runaway greenhouse to occur is between approximately 1.22 and 1.49 times the global mean value for the Earth, and for clear sky conditions, it is a few percent lower. The runaway greenhouse in the experiments with the mass flux schemes generally occurs more rapidly than in the experiments with the adjustment schemes. In addition, the inability of the hard convective adjustment scheme to produce an efficient vertical transport of moisture, together with the saturation requirement for convection to occur, leads to the breakdown of the radiative-convective equilibria when other processes are not available to provide the necessary vertical transport of water vapor. -from Authors"
"26536569500;","Clausius-clapeyron scaling of CAPE from analytical solutions to RCE",2016,"10.1175/JAS-D-15-0327.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84988353511&doi=10.1175%2fJAS-D-15-0327.1&partnerID=40&md5=1456c692c836328a623c49ddfa1bd340","By deriving analytical solutions to radiative-convective equilibrium (RCE), it is shown mathematically that convective available potential energy (CAPE) exhibits Clausius-Clapeyron (CC) scaling over a wide range of surface temperatures up to 310 K. Above 310 K, CAPE deviates from CC scaling and even decreases with warming at very high surface temperatures. At the surface temperature of the current tropics, the analytical solutions predict that CAPE increases at a rate of about 6%-7% per kelvin of surface warming. The analytical solutions also provide insight on how the tropopause height and stratospheric humidity change with warming. Changes in the tropopause height exhibit CC scaling, with the tropopause rising by about 400 m per kelvin of surface warming at current tropical temperatures and by about 1-2 km K-1 at surface temperatures in the range of 320-340 K. The specific humidity of the stratosphere exhibits super-CC scaling at temperatures moderately warmer than the current tropics. With a surface temperature of the current tropics, the stratospheric specific humidity increases by about 6% per kelvin of surface warming, but the rate of increase is as high as 30% K-1 at warmer surface temperatures. © 2016 American Meteorological Society."
"23991212200;57200926820;","Response of the superparameterized Madden-Julian oscillation to extreme climate and basic-state variation challenges a moisture mode view",2016,"10.1175/JCLI-D-15-0790.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977558915&doi=10.1175%2fJCLI-D-15-0790.1&partnerID=40&md5=3ae029591fe321d8bb36082908d43720","The climate sensitivity of the Madden-Julian oscillation (MJO) is measured across a broad range of temperatures (1°-35°C) using a convection-permitting global climate model with homogenous sea surface temperatures. An MJO-like signal is found to be resilient in all simulations. These results are used to investigate two ideas related to the modern ""moisture mode"" view of MJO dynamics. The first hypothesis is that the MJO has dynamics analogous to a form of radiative convective self-aggregation in which longwave energy maintenance mechanisms shut down for SST ≪ 25°C. Inconsistent with this hypothesis, the explicitly simulated MJO survives cooling and retains leading moist static energy (MSE) budget terms associated with longwave destabilization even at SST < 10°C. Thus, if the MJO is a form of longwave-assisted self-aggregation, it is not one that is temperature critical, as is observed in some cases of radiative-convective equilibrium (RCE) self-aggregation. The second hypothesis is that the MJO is propagated by horizontal advection of column MSE. Inconsistent with this view, the simulated MJO survives reversal of meridional moisture gradients in the basic state and a striking role for horizontal MSE advection in its propagation energy budget cannot be detected. Rather, its eastward motion is balanced by vertical MSE advection reminiscent of gravity or Kelvin wave dynamics. These findings could suggest a tight relation between the MJO and classic equatorial waves, which would tend to challenge moisture mode views of MJO dynamics that assume horizontal moisture advection as the MJO's propagator. The simulation suite provides new opportunities for testing predictions from MJO theory across a broad climate regime. © 2016 American Meteorological Society."
"55717881500;7003545639;","Role of large-scale moisture advection for simulation of the MJO with increased entrainment",2015,"10.1002/qj.2510","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937065690&doi=10.1002%2fqj.2510&partnerID=40&md5=673a662264e3b09462248d51f7df0c16","The intraseasonal moisture budget is analyzed in simulations with the UK Met Office climate model, which produces a reasonable representation of the Madden-Julian Oscillation (MJO) when the entrainment rate in the convective parametrization is increased by 50%. Analysis of the moisture budget shows that parametrized convection tends to dry the troposphere and that large-scale vertical advection moistens the troposphere. These two tendencies mostly balance each other. However, the total moisture tendency is asymmetric relative to the maximum precipitation, corresponding to the recharge and discharge process of organized convection in the Tropics. This moistening before and drying after the maximum precipitation is largely due to large-scale horizontal advection of moisture. By comparing to the control run that does not simulate a realistic MJO, we find that increasing the entrainment acts to reduce deep convection in the relatively dry environment by increasing the mixing of the dry air. As a result, large-scale convection and large-scale advective processes play a stronger role during the development stage, which implies that convection is necessarily better organized. © 2015 Royal Meteorological Society."
"7004870145;6603812137;8210567900;15833802900;25638488000;6506013168;15833947900;21739916500;36833399300;","A Mediterranean nocturnal heavy rainfall and tornadic event. Part I: Overview, damage survey and radar analysis",2011,"10.1016/j.atmosres.2010.12.024","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955672223&doi=10.1016%2fj.atmosres.2010.12.024&partnerID=40&md5=60f6a9c7703fa7dd161de5640fa10d5c","This study presents an analysis of a severe weather case that took place during the early morning of the 2nd of November 2008, when intense convective activity associated with a rapidly evolving low pressure system affected the southern coast of Catalonia (NE Spain). The synoptic framework was dominated by an upper level trough and an associated cold front extending from Gibraltar along the Mediterranean coast of the Iberian Peninsula to SE France, which moved north-eastward. South easterly winds in the north of the Balearic Islands and the coast of Catalonia favoured high values of 0-3. km storm relative helicity which combined with moderate MLCAPE values and high shear favoured the conditions for organized convection. A number of multicell storms and others exhibiting supercell features, as indicated by Doppler radar observations, clustered later in a mesoscale convective system, and moved north-eastwards across Catalonia. They produced ground-level strong damaging wind gusts, an F2 tornado, hail and heavy rainfall. Total lightning activity (intra-cloud and cloud to ground flashes) was also relevant, exhibiting several classical features such as a sudden increased rate before ground level severe damage, as discussed in a companion study. Remarkable surface observations of this event include 24. h precipitation accumulations exceeding 100. mm in four different observatories and 30. minute rainfall amounts up to 40. mm which caused local flash floods. As the convective system evolved northward later that day it also affected SE France causing large hail, ground level damaging wind gusts and heavy rainfall. © 2010 Elsevier B.V."
"55739579300;55716319700;","Hadley cell dynamics in a primitive equation model. Part I: Axisymmetric flow",2001,"10.1175/1520-0469(2001)058<2845:HCDIAP>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035482947&doi=10.1175%2f1520-0469%282001%29058%3c2845%3aHCDIAP%3e2.0.CO%3b2&partnerID=40&md5=c7557138c6872d3cb68fa7701a8cce5e","A strategy is adopted that applies the mean meridional circulation (MMC) equation to two different steady states of a primitive equation model. This allows for the investigation of the mechanisms behind the sensitivity of the Hadley cell structure to individual source terms in an axisymmetric circulation. Specifically, the strategy allows the MMC response to the individual source terms to be partitioned into direct and indirect components. The model's Hadley cell strengthens and broadens as the viscosity of the model is increased. It is found that a substantial portion of this sensitivity is attributable to diabatic heating and surface friction changes, which are ultimately induced by changes in viscosity. Similar behavior is found as the meridional gradient of the radiative-convective equilibrium temperature is increased, except that in this case the indirect response arises through the viscosity and surface friction change. In both cases, the changes in the static stability change are found to be of secondary importance. It is found that the latitudinal extent of the Hadley cell is more sensitive to the meridional temperature gradient than to the static stability. However, when the static stability is decreased (increased) by a sufficient amount, the Hadley cell becomes narrower (broader). Additional analyses indicate that the change in Hadley cell width is a response to the change in Hadley cell strength."
"7409792174;7006095466;57193882808;","Hierarchical modelling of tropical convective systems using explicit and parametrized approaches",2001,"10.1256/smsqj.57212","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035079387&doi=10.1256%2fsmsqj.57212&partnerID=40&md5=28421d874d02b978f31ed27ccd50da4c","Cloud systems observed during 1-7 September of GATE are examined in a hierarchical approach, namely: a two-dimensional cloud-resolving simulation using a 2 km grid length; two- and three-dimensional simulations using the Kain-Fritsch convective parametrization and 10, 15 and 25 km grid lengths; and coarse-grid simulations without any convective parametrization. All simulations are forced by the same objectively analysed time-varying large-scale advection of temperature and moisture. The domain-mean winds are relaxed to the observed wind profiles. Both the cloud-resolving modelling and the lower-resolution modelling with parametrized convection realize the three observed cloud system categories (squall line, non-squall cluster and scattered convection) and transitions among them. In particular, the well-organized fast-moving squall-type cloud system observed on 4 September is realized in a three-dimensional experiment with parametrized convection. In contrast, the lower-resolution modelling without any convective parametrization fails to produce the squall-type convective system during the weakly forced period but successfully represents the non-squall cluster during strong forcing. This lack of success is mostly attributed to convective triggering and the absence of resolved downdraught-enhanced surface fluxes. These issues are not as critical during strong large-scale forcing. The observed evolutions of temperature, water vapour mixing ratio, precipitation and surface moisture flux are realized in all simulations. A common deficiency is the overprediction of upper-level relative humidity. The simulation with parametrized convection features a comparatively large low-level water vapour mixing ratio, a surface and upper-level cold temperature bias and a mid-tropospheric warm bias. This is mainly attributed to deficiencies in how the Kain-Fritsch scheme represents convective mass flux, detrainment and entrainment by cumulus congestus."
"7407663727;6506865841;","A procedure for automated satellite-based identification and climatology development of various classes of organized convection",1996,"10.1175/1520-0450(1996)035<0638:APFASB>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030464123&doi=10.1175%2f1520-0450%281996%29035%3c0638%3aAPFASB%3e2.0.CO%3b2&partnerID=40&md5=1ea68dabd4c411064a17ee0c2769c848","A fully automated, objective classification system has been developed to analyze infrared satellite imagery. This automated system facilitates tracking and categorization of convective weather systems into various classes. The classes chosen reflect the maximum degree of organization attained by each weather system. Four classes of convective weather system are defined: tropical cyclones (TS; including prestorm clusters through to decaying storms), mesoscale convective complexes (MCC), convective cloud clusters (CCC), and disorganized short-lived convection (DSL). Systems are identified, tracked, and then classified. If a system satisfies the criteria for any of the organized convection classes (TS, MCC, or CCC) for at least two time periods, the entire track is allocated to that class. In cases where a system satisfies the criteria for more than one type of organized convection (commonly MCC and CCC), it is assigned to the ""most organized"" class (in this case, MCC). Thus, the characteristics of each class incorporate the life cycles of systems that satisfy the imposed criteria for at least a 6-h period. Two satellite infrared-based (IR) rain-rate algorithms are applied to the convective areas in order to obtain precipitation amounts for the various classes of convection. The domain of interest extends from the eastern Pacific margin to the African coast (15°W) and 40°N-40°S. In addition to the IR data, rain rates derived from Special Sensor Microwave/Imager data are compared with the infrared retrieved rain rates at available times for a subset of each of the three organized convection classes. Rainfall amounts obtained from these infrared algorithms are also compared with ground-based station observations over Florida. Comparison of the inferred rainfall with station data reveals that the TS precipitation is in approximate agreement (in the mean), whereas the precipitation contributions from the other forms of convection are somewhat overestimated. DSL is overestimated the most and CCCs are overestimated the least. According to the infrared-based rain-rate algorithms, DSLs (short-lived systems) contribute the most total (basinwide, annual) precipitation, CCCs contribute the second largest amount, MCCs are third in the contribution of precipitation, and TSs contribute the least to the total precipitation."
"7006095466;","Mesoscale convection from a large-scale perspective",1995,"10.1016/0169-8095(94)00012-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028976988&doi=10.1016%2f0169-8095%2894%2900012-3&partnerID=40&md5=32c47764dfa4328216ed88fbc532594f","This essay concerns precipitating convective cloud systems and convectively-driven mesoscale circulations (""mesoscale convection"") and their role in the large-scale structure of the atmosphere. Mesoscale convection is an important and ubiquitous process on scales of motion spanning a few kilometers to many hundreds of kilometers. It plays a role in the input of energy to the climate system through the radiative effect of upper-tropospheric cloud and water vapor, and enhanced surface fluxes. This is in addition to its important effect on energy, heat and momentum transport within the atmosphere. However, mesoscale convection is neither parameterized nor adequately resolved in atmospheric general circulation models. Its representation in mean-flow terms raises issues that are quite distinct from classical approaches to sub-grid scale convection parameterization. Cloud-resolving modeling and theoretical concepts pertinent to the transport properties and mean-flow effects of organized convection are summarized, as are the main convective parameterization techniques used in global models. Two principal themes that are relevant to the representation of organized mesoscale systems are discussed. First, mesoscale transports and their sub-grid scale approximation with emphasis on dynamical approaches. Second, long time-scale modeling of mesoscale cloud systems that involves the collective effect of convection, boundary and surface layers, radiation, microphysics acting under the influence of large-scale forcing. Finally, major research programs that address the role of precipitating convection and mesoscale processes in global models are summarized. © 1995."
"6601987737;6603801190;35566896300;16423154100;","High-resolution numerical modelling of convective precipitation over Northern Italy",1992,"10.1007/BF01025510","https://www.scopus.com/inward/record.uri?eid=2-s2.0-21144474139&doi=10.1007%2fBF01025510&partnerID=40&md5=af7cc4268f45e3ad6627fc5ffdc46b9b","A number of forecast experiments were performed in order to assess the capability of reproducing, by means of a limited-area numerical model, the highly structured mesoscale circulations occurring in the Po Valley of Northern Italy during a north-westerly cold front passage across the Alpine chain, with particular attention to the modelling of the effects of organized convection. The case-study occurred during summer 1987 and the model used throughout was the 1989 version of the UB/NMC Limited Area Model (University of Belgrade, National Meteorological Centre of Washington). The model was integrated both with eta, η, and sigma, θ{symbol}, as vertical coordinates and ECMWF initialized analyses were always used as initial conditions. ECMWF initialized analysis or operational forecast fields were also used for updating in time the lateral boundary conditions. Experiments show qualitative and quantitative agreement with observations, both in upper-air geopotential height fields, in MSLP and in cumulated precipitation. Several modelling issues were also investigated, e.g. sensitivity of the results to horizontal and vertical model resolution and to the influence of the lateral boundaries poitioning, finding large effects of the latter on quantitative precipitation fields. Difficulties in modelling very localized mesoscale phenomena, e.g. organized convective thunderstorms in the Po Valley and Alpine North Foehn in the Milan area, were generally encounted. © 1992 Springer-Verlag."
"7409838605;","Effects of downdrafts and mesoscale convective organization on the heat and moisture budgets of tropical cloud clusters. Part II: effects of convective-scale downdrafts",1989,"10.1175/1520-0469(1989)046<1540:eodamc>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024837276&doi=10.1175%2f1520-0469%281989%29046%3c1540%3aeodamc%3e2.0.co%3b2&partnerID=40&md5=f47f14c94152ae2a6b7a75d8d6703f06","The diagnostic cumulus ensemble model presented in Part I of this paper is applied to the data taken during Phase III of the GARP Tropical Atlantic Experiment (GATE). The model is used to diagnose the mass fluxes of cumulus updrafts and downdrafts using the observed values of Q1 - Q2 - QR, where Q1, Q2 and QR are the apparent heat source, the apparent moisture sink and radiative heating rate, respectively. We demonstrate that the inclusion of convective-scale downdrafts is essential to obtain accurately the cumulus contributions to the budget residuals. In the lower troposphere the contributions of downdrafts to Q1 - QR and Q2 are comparable to the contributions of updrafts. Convective-scale updrafts tend to warm and dry the cumulus environment, while convective-scale downdrafts tend to cool and moisten the lower cloud layer. We find that significant downdraft activity is usually associated with organized convection. -from Author"
"57210687618;16644246500;","Clouds, Circulation, and Climate Sensitivity in a Radiative-Convective Equilibrium Channel Model",2017,"10.1002/2017MS001111","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040726266&doi=10.1002%2f2017MS001111&partnerID=40&md5=3a49224d3d1b31f31cb6d8de66870849","Tropical cloud and circulation changes are large sources of uncertainty in future climate change. This problem owes partly to the scale separation between large-scale tropical dynamics (~104 km) and convective dynamics (~7 km), which generally requires parameterizing convection in models that resolve large-scale dynamics, or parameterizing (or omitting) large-scale dynamics in models that permit convection. Here we discuss simulations of radiative-convective equilibrium (RCE) across a wide range of surface temperatures in long-channel geometry—where the domain size and resolution marginally resolve both large-scale dynamics and convection. Self-aggregation of convection in these simulations spontaneously produces realistic dynamical regimes of large-scale vertical motion. The circulation weakens with surface warming but changes in the degree of self-aggregation depend on the metric that is used; there is no obvious trend in aggregation with warming. Surface warming causes an upward shift and decrease in area of high clouds, and a sharp decline in midlevel clouds, but no systematic trend in low cloud cover. We introduce a method for approximate radiative kernel feedback analysis in RCE, and apply it to both simulations in long-channel geometry and in a smaller square domain. The kernel-corrected cloud feedback is positive but its magnitude varies across temperatures. Compared to simulations that do not have aggregation, there is a more negative net feedback due to the effects of aggregation on relative humidity and cloud cover. These results are consistent with the hypothesis that self-aggregation moderately reduces climate sensitivity. © 2017. The Authors."
"57171236300;7005808242;7103242280;","Parameter study of tropical cyclones in rotating radiative-convective equilibrium with column physics and resolution of a 25-km GCM",2014,"10.1175/JAS-D-13-0190.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896795041&doi=10.1175%2fJAS-D-13-0190.1&partnerID=40&md5=384738a6942d25a07f4dfd0567d515e6","Rotating radiative-convective equilibrium is studied by extracting the column physics of a mesoscaleresolution global atmospheric model that simulates realistic hurricane frequency statistics and then coupling it to rotating hydrostatic dynamics in doubly periodic domains. The parameter study helps in understanding the tropical cyclones simulated in the global model and also provides a reference point for analogous studies with cloud-resolving models. The authors first examine the sensitivity of the equilibrium achieved in a large square domain (2 3 104km on a side) to sea surface temperature, ambient rotation rate, and surface drag coefficient. In such a large domain, multiple tropical cyclones exist simultaneously. The size and intensity of these tropical cyclones are investigated. The variation of rotating radiative-convective equilibrium with domain size is also studied. As domain size increases, the equilibrium evolves through four regimes: a single tropical depression, an intermittent tropical cyclone with widely varying intensity, a single sustained storm, and finally multiple storms. As SST increases or ambient rotation rate f decreases, the sustained storm regime shifts toward larger domain size. The storm's natural extent in large domains can be understood from this regime behavior. The radius of maximum surface wind, although only marginally resolved, increases with SST and increases with f for small f when the domain is large enough. These parameter dependencies can be modified or even reversed if the domain is smaller than the storm's natural extent. © 2014 American Meteorological Society."
"56450100300;7201504886;","Climate and climate sensitivity to changing CO2 on an idealized land planet",2014,"10.1002/2014MS000369","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027939481&doi=10.1002%2f2014MS000369&partnerID=40&md5=47d46b7709de128768f2c825bdb3b92d","The comprehensive general circulation model ECHAM6 is used in a radiative-convective equilibrium configuration. It is coupled to a perfectly conducting slab. To understand the local impact of thermodynamic surface properties on the land-ocean warming contrast, the surface latent heat flux and surface heat capacity are reduced stepwise, aiming for a land-like climate. Both ocean-like and land-like RCE simulation reproduce the tropical atmosphere over ocean and land in a satisfactory manner and lead to reasonable land-ocean warming ratios. A small surface heat capacity induces a high diurnal surface temperature range which triggers precipitation during the day and decouples the free troposphere from the diurnal mean temperature. With increasing evaporation resistance, the net atmospheric cooling rate decreases because cloud base height rises, causing a reduction of precipitation. Climate sensitivity depends more on changes in evaporation resistance than on changes in surface heat capacity. A feedback analysis with the partial radiation perturbation method shows that amplified warming over idealized land can be associated with disproportional changes in the lapse rate versus the water vapor feedback. Cloud feedbacks, convective aggregation, and changes in global mean surface temperature confuse the picture. © 2014. The Authors."
"35619212800;24485218400;8525144100;56387632200;7006198994;7003408439;","Tropical intraseasonal modes of the atmosphere",2014,"10.1146/annurev-environ-020413-134219","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908023020&doi=10.1146%2fannurev-environ-020413-134219&partnerID=40&md5=02ab2219b8c2375488605bcb1c429328","Tropical intraseasonal variability (TISV) of the atmosphere describes the coherent variability in basic state variables, including pressure, wind, temperature, and humidity, as well as in the physical phenomena associated with the covariability of these parameters, such as rainfall and cloudiness, over synoptic (∼1,000 km, ∼1-10 days) to planetary (∼10,000 km, ∼10-100 days) scales. In the past, the characteristics of individual TISV modes were studied separately, and much has been learned from this approach. More recent studies have increasingly focused on the multiscale nature of these modes, leading to exciting new developments in our understanding of tropical meteorology. This article reviews the most recent observations of TISV and its associated impacts on regional weather, short-term climate patterns, and atmospheric chemical transports, as well as the ability of numerical models to capture these interacting modes of variability. We also suggest where the field might focus its efforts in the future. Copyright © 2014 by Annual Reviews. All rights reserved."
"7102080550;57205302128;7402627827;57205303892;7601508123;57205299261;57207592379;","Prediction of convective storms at convection-resolving 1 km resolution over continental united states with radar data assimilation: An example case of 26 May 2008 and precipitation forecasts from spring 2009",2013,"10.1155/2013/259052","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893781619&doi=10.1155%2f2013%2f259052&partnerID=40&md5=45e72e79a00fe29c0303c441e697550b","For the first time ever, convection-resolving forecasts at 1 km grid spacing were produced in realtime in spring 2009 by the Center for Analysis and Prediction of Storms (CAPS) at the University of Oklahoma. The forecasts assimilated both radial velocity and reflectivity data from all operational WSR-88D radars within a domain covering most of the continental United States. In preparation for the realtime forecasts, 1 km forecast tests were carried out using a case from spring 2008 and the forecasts with and without assimilating radar data are compared with corresponding 4 km forecasts produced in realtime. Significant positive impact of radar data assimilation is found to last at least 24 hours. The 1 km grid produced a more accurate forecast of organized convection, especially in structure and intensity details. It successfully predicted an isolated severe-weather-producing storm nearly 24 hours into the forecast, which all ten members of the 4 km real time ensemble forecasts failed to predict. This case, together with all available forecasts from 2009 CAPS realtime forecasts, provides evidence of the value of both convection-resolving 1 km grid and radar data assimilation for severe weather prediction for up to 24 hours. © 2013 Ming Xue et al."
"6701782816;6701773705;55712683400;55712772000;","A numerical study on appearance of the runaway greenhouse state of a three-dimensional gray atmosphere",2002,"10.1175/1520-0469(2002)059<3223:ANSOAO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037113331&doi=10.1175%2f1520-0469%282002%29059%3c3223%3aANSOAO%3e2.0.CO%3b2&partnerID=40&md5=e2ae539c5353be634e10c37a0b4c9b3b","A numerical study on the runaway greenhouse state is performed by using a general circulation model (GCM) with simplified hydrologic and radiative processes. Except for the inclusion of three-dimensional atmospheric motion, the system utilized is basically equivalent to the one-dimensional radiative-convective equilibrium model of Nakajima et al, in which the runaway greenhouse state is defined. The results of integrations with various values of solar constant show that there exists an upper limit of the solar constant with which the atmosphere can reach a statistical equilibrium state. When the value of solar constant exceeds the limit, 1600 W m-2, the atmosphere sets in a ""thermally runaway"" state. It is characterized by continuous increase of the amount of water vapor, continuous decrease of the outgoing longwave radiation, and continuous warming of the atmosphere and the ground surface. The upper-limit value of the solar constant obtained by the GCM experiments corresponds to the upper limit of outgoing longwave radiation determined by the one-dimensional model of Nakajima et al, with a fixed value of relative humidity, 60%, which is a typical value obtained by the GCM. The thermally runaway states realized in the GCM are caused by the radiation structure found by Nakajima et al. that prohibits the existence of thermal equilibrium states. The calculated values of the upper limit of radiation and water vapor content cannot be directly applied to describing real planetary atmospheres, since the model physical processes are quite simple-gray radiation scheme without clouds. However, because of this simplification, the GCM gives deeper insight into the structure of a runaway atmosphere."
"6506537159;7006432091;7410255460;","Layer inflow into precipitating convection over the western tropical Pacific",2002,"10.1256/003590002320603502","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036630184&doi=10.1256%2f003590002320603502&partnerID=40&md5=74d6fe5d02b49dbfe86f35a2d3efc8b2","A conceptual model of tropical convection frequently used in convective parametrization schemes is that of a parcel process in which boundary-layer air, characterized by high equivalent potential temperature, ascends to great heights in convective updraughts, while air above the planetary boundary layer with lower equivalent potential temperature mixes into convective downdraughts and sinks. However, airborne Doppler-radar data show that organized deep convective systems over the western tropical Pacific warm pool are often characterized by layers of ascending inflow ∼0.5-4 km in depth. These inflow layers do not consist merely of boundary-layer air. In this study a high-resolution numerical cloud model is employed to investigate these inflow layers. Input data are from the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). Two time periods are selected in December 1992, which represent the onset and peak of a strong westerly phase of the intraseasonal oscillation. Model simulations for 14 December, representative of westerly onset conditions and the beginning of a convectively active period, and 23 December, representative of strong low-level westerlies and extremely widespread convection, are conducted. To bridge the coarse resolution of the global-model analysis fields and the fine resolution of the cloud model, hourly output from a mesoscale model is used to supply initial and lateral boundary conditions for the cloud model. Control simulations of 14 and 23 December reveal distinct convective organizations and, specifically, inflow characteristics for the two systems embedded in different large-scale environmental conditions. In the case of 23 December, convection simulated under conditions of the strong westerly wind and near-saturated low-mid troposphere exhibits deep inflow layers. Trajectories computed from the simulation of 23 December under these conditions show a strong layer-lifting inflow signal. In contrast, the control simulation of 14 December shows a parcel-like inflow with only the air in the lower part of the inflow actually rising in the deep convective updraughts. One of the main differences between the two simulations is the lack of a deep environmental moist layer in the 14 December case. The control simulation did not capture well the extent of precipitating mesoscale stratiform clouds that developed from earlier convection in the vicinity of the deep convective cells as indicated in the COARE observations. Previous studies have shown that spatially extensive convection is correlated with enhanced mid-level humidity. To isolate the effect of the mid-level moist layer on the characteristics of inflow of convective systems, a numerical experiment based on the control simulation of 14 December was conducted. The relative humidity of environment air in the low-mid troposphere (1.7-6 km layer) was increased to 95%. Trajectory statistics calculated for this sensitivity experiment show increased layer lifting, with a significant amount of air from the upper part of the inflow layer rising in the updraught along with air from just above the surface. Moistening the inflow layer in this sensitivity experiment allows it to saturate more quickly when it encounters the mesoscale cold pool. Once saturated, the relevant static stability is the moist rather than dry static stability, and the whole layer more easily rises over the cold pool. Moistening the inflow layer also modifies the nature of the simulated cold pool itself, which seems to promote layer lifting in the simulation. Possible mechanisms for moistening the mid-levels are briefly discussed."
"7103246957;7006783796;56216966700;7404150761;","Integration of satellite and surface data using a radiative- convective oceanic boundary-layer model",1992,"10.1175/1520-0450(1992)031<0340:IOSASD>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026613579&doi=10.1175%2f1520-0450%281992%29031%3c0340%3aIOSASD%3e2.0.CO%3b2&partnerID=40&md5=3cb352ce1bb87224470b943579b14a79","A mixing-line boundary-layer model is used to retreive cloud-top height from satellite-derived cloud-top temperatures, using 700-hPa National Meteorological Center (NMC) analyses and the Comprehensive Ocean and Atmosphere Data Set (COADS) surface data as supporting datasets. Results are compared with the fixed-lapse-rate method of retrieving boundary-layer depth from sea surface temperatures (SST) and cloud-top temperatures. A radiative-convective equilibrium boundary-layer model is used to retrieve boundary-layer structure given SST and surface wind, satellite cloud-top temperatures and cloud fraction, and the 700-hPa NMC thermodynamic analyses. -from Authors"
"7103242280;7102836087;","The Development of Organized Convection In A Simplified Squall‐Line Model",1992,"10.1002/qj.49711850306","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026613198&doi=10.1002%2fqj.49711850306&partnerID=40&md5=6562b15473e00c22cd13f5334142fac9","Squall lines stand out from ordinary cumulonimbus convection because of a special structure that dramatically extends their duration, precipitation output and area of influence. Time‐dependent models have identified surface outflow boundaries and low‐level environmental wind shear as the crucial elements in squall‐line formation and/or maintenance. Steady‐state models have shown how properties of the downdraught reservoir, or ‘cold pool’, must be matched to the far‐field wind and thermodynamic profiles to sustain the convection. However, the dynamical role of the environmental shear and the nature of the interaction between the positively and negatively buoyant air have remained uncertain. For help with these issues, a time‐dependent numerical model is developed with all moist processes either parametrized or based on ad hoc assumptions. the simplifications make it possible to distinguish more clearly than in the past between the formation and maintenance of squall lines and between the initial and disturbed far‐field environments. The convective updraught forms within an expanding region of disturbed flow separated from the undisturbed environment by ‘storm fronts’. Forced (or neutral) ascent occurs at a surface ‘gust front’ on the upwind side of the cold pool. We distinguish squall lines from ordinary convection by looking at the coherence between the forced and convective updraughts. It is found that subsidence over the cold pool disorganizes the updraughts, whereas a deep overturning circulation downshear from the gust front has an organizing effect. Hence, factors which allow the initial subsidence to occur ahead of the gust front, namely contrasting lower‐and upper‐level winds and large potential buoyancy, favour squall‐line development. It is argued that, in cases with large convective potential energy, the deep mesoscale circulation is more important in the formation and maintenance of the line than either the vertical shear of the air reaching the cold pool or the strength of the forced updraught. Copyright © 1992 Royal Meteorological Society"
"55194361500;7003869059;","Thermal equilibration of planetary waves",1990,"10.1175/1520-0469(1990)047<0963:TEOPW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025691047&doi=10.1175%2f1520-0469%281990%29047%3c0963%3aTEOPW%3e2.0.CO%3b2&partnerID=40&md5=1bcb05a68bbe71dce0d93f899b899986","Equilibration of planetary waves toward free-mode forms, steady solutions of the unforced, undamped equations of motion, is studied in a three-level quasi-geostrophic model on the hemisphere. A thermal mechanism is invoked, parameterized as a Newtonian process Q=-γ(T-T*), relaxing the atmosphere toward a radiative-convective equilibrium temperature T* on γ-1 time scales. If T* is chosen to project onto the class of finite-amplitude stationary Rossby waves, T can closely approach T* if, simultaneously, the surface winds vanish switching off the Ekman layers at the surface. The equilibrated state is characterized by vertical phase lines, zero surface winds, vanishing diabatic heating rates and a temperature field that is phase-locked with T* corresponding to ridges over the oceans and troughs over the land. -from Authors"
"56971606900;7006198994;57189202421;6701835010;","Climate change and the Madden-Julian Oscillation: A vertically resolved weak temperature gradient analysis",2017,"10.1002/2016MS000843","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85011268676&doi=10.1002%2f2016MS000843&partnerID=40&md5=25881b0a8a2018e07fdd9fb1504ff1ee","WTG balance is used to examine how changes in the moist thermodynamic structure of the tropics affect the MJO in two simulations of the Superparameterized Community Earth System Model (SP-CESM), one at preindustrial (PI) levels of CO2 and one where CO2 levels have been quadrupled (4×CO2). While MJO convective variability increases considerably in the 4×CO2 simulation, the dynamical response to this convective variability decreases. Increased MJO convective variability is shown to be a robust response to the steepening vertical moisture gradient, consistent with the findings of previous studies. The steepened vertical moisture gradient allows MJO convective heating to drive stronger variations in large-scale vertical moisture advection, supporting destabilization of the MJO. The decreased dynamical response to MJO convective variability is shown to be a consequence of increased static stability, which allows weaker variations in large-scale vertical velocity to produce sufficient adiabatic cooling to balance variations in MJO convective heating. This weakened dynamical response results in a considerable reduction of the MJO's ability to influence the extratropics, which is closely tied to the strength of its associated divergence. A composite lifecycle of the MJO was used to show that northern hemisphere extratropical 525 hPa geopotential height anomalies decreased by 27% in the 4×CO2 simulation, despite a 22% increase in tropical convective heating associated with the MJO. Results of this study suggest that while MJO convective variability may increase in a warming climate, the MJO's role in “bridging weather and climate” in the extratropics may not. © 2017. The Authors."
"6507400558;7006095466;","Organized convection parameterization for the ITCZ",2015,"10.1175/JAS-D-15-0006.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943413782&doi=10.1175%2fJAS-D-15-0006.1&partnerID=40&md5=d86ad59013f3890445b6f4f42d476e55","Mesoscale convective systems (MCSs) are of fundamental importance in the dynamics of the atmospheric circulation and the climate system. They are often observed to develop over significant terrain in ambient shear flows in midlatitudes and embedded within the Madden-Julian oscillation (MJO) and convectively coupled equatorial wave (CCEW) envelopes, as well as in the intertropical convergence zone (ITCZ). Yet general circulation models (GCMs) fail to resolve these systems, and their underlying convective parameterizations are not directed to represent organized circulations. Shear-parallel MCSs, which are common in the ITCZ, have a three-dimensional structure and, as such, present a serious modeling challenge. Here, a previously developed multicloud model (MCM) is modified to parameterize MCSs. One of the main modifications is the parameterization of stratiform condensation to capture extended stratiform outflows, which characterize MCSs, resulting from strong upper-level jets. Linear analysis shows that, under the influence of a typical double African and equatorial jet shear flow, this modification results in an additional new scale-selective instability peaking at the mesoalpha scale of roughly 400 km. Nonlinear simulations conducted with the modified MCM on a 400 km × 400 km doubly periodic domain, without rotation, resulted in the spontaneous transition from a quasi-two-dimensional shear-perpendicular convective system, consistent with linear theory, to a fully three-dimensional flow structure. The simulation is characterized by shear-parallel bands of convection, moving slowly eastward, embedded in stratiform systems that expand perpendicularly and propagate westward with the upper-level jet. The mean circulation and the implications for the domain-averaged vertical transport of momentum and potential temperature are discussed. © 2015 American Meteorological Society."
"7403326970;7402331557;6507305095;6603261861;","Adjoint sensitivity and predictability of tropical cyclogenesis",2012,"10.1175/JAS-D-12-0110.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84872004151&doi=10.1175%2fJAS-D-12-0110.1&partnerID=40&md5=e8b2b495e6d284000c0692849db9d971","The sensitivity of tropical cyclogenesis and subsequent intensification is explored by applying small perturbations to the initial state in the presence of organized mesoscale convection and synoptic-scale forcing using the adjoint and tangent linear models for the Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS). The forward, adjoint, and tangent linear models are used to compare and contrast predictability characteristics for the disturbance that became Typhoon Nuri and a nondeveloping organized convective cluster in the western Pacific during The Observing System Research and Predictability Experiment (THORPEX) Pacific Asian Regional Campaign (T-PARC) and the Tropical Cyclone Structure-2008 (TCS-08) experiments. The adjoint diagnostics indicate that the intensity (e.g., maximum surface wind speed, minimum surface pressure) of a tropical disturbance is very sensitive to perturbations in the moisture and temperature fields and to a lesser degree the wind fields. The highest-resolution adjoint simulations (grid increment of 13 km) indicate that themost efficient intensification is throughmoistening in the lower andmiddle levels and heating in banded regions that are coincident with vorticitymaxima in the initial state. Optimal adjoint perturbations exhibit rapid growth for the Nuri case and onlymodest growth for the nondeveloping system. The adjoint results suggest that Nuri was near the threshold for development, indicative of low predictability. The low-level sensitivity maximumand tendency for optimal perturbation growth to extend vertically through the troposphere are consistent with a ""bottom up"" development process of TC genesis, although a secondary midlevel sensitivity maximum is present as well. Growth originates at small scales and projects onto the scale of the vortex, a manifestation of perturbations that project onto organized convection embedded in regions of cyclonic vorticity."
"36868795400;7005461477;7202119915;","Investigation of microphysical processes occurring in organized convection during name",2012,"10.1175/MWR-D-11-00124.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864859092&doi=10.1175%2fMWR-D-11-00124.1&partnerID=40&md5=0cc6b7ce02bd9ba4ca9e3466f0e666c9","A major objective of the North American Monsoon Experiment (NAME) was to quantify microphysical processes within convection occurring near the steep topography of northwestern Mexico. A previous study compared examples of isolated convection using polarimetric radar data and noted a dependence on mixed-phase processes via drop freezing and subsequent riming growth along the coastal plain and western slopes, with an even greater role of melting ice in rainfall production over the highest terrain. Despite the higher frequency of these isolated cells compared to organized convective systems, the latter were responsible for 75% of rainfall. Therefore, this study seeks to evaluate the role of mesoscale organization on microphysical processes and describes the evolution of these systems as a function of topography. Similar to isolated convection, both warm-rain and ice-based processes played important roles in producing intense rainfall in organized convection. Although similarities existed between cell types, organized con-vection was typically deeper and contained greater ice mass, which melted and contributed to the de-velopment of outowboundaries. As convection organized along the slopes, these boundaries spread over the lower terrain, converging with diurnally driven upslope ow, thus allowing for the generation of new con-vection and propagation toward the coast. Once over lower elevations, additional warm-cloud depth con-tributed to intense rainfall and allowed for continued ice production. This, along with the development of rear inow in the trailing stratiform region, led to further development of convective outow, similar to organized systems in the tropics and midlatitudes. © 2012 American Meteorological Society."
"7102340415;6507400558;","Boundary layer dynamics in a simple model for convectively coupled gravity waves",2009,"10.1175/2009JAS2871.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73549088967&doi=10.1175%2f2009JAS2871.1&partnerID=40&md5=c3cb40fe9708ac927b3c25d5f3c9ded9","A simplified model of intermediate complexity for convectively coupled gravity waves that incorporates the bulk dynamics of the atmospheric boundary layer is developed and analyzed. The model comprises equations for velocity, potential temperature, and moist entropy in the boundary layer as well as equations for the free tropospheric barotropic (vertically uniform) velocity and first two baroclinic modes of vertical structure. It is based on the multicloud model of Khouider and Majda coupled to the bulk boundary layer-shallow cumulus model of Stevens. The original multicloud model has a purely thermodynamic boundary layer and no barotropic velocity mode. Here, boundary layer horizontal velocity divergence is matched with barotropic convergence in the free troposphere and yields environmental downdrafts. Both environmental and convective downdrafts act to transport dry midtropospheric air into the boundary layer. Basic states in radiative-convective equilibrium are found and are shown to be consistent with observations of boundary layer and free troposphere climatology. The linear stability of these basic states, in the case without rotation, is then analyzed for a variety of tropospheric regimes. The inclusion of boundary layer dynamics-specifically, environmental downdrafts and entrainment of free tropospheric air-enhances the instability of both the synoptic-scale moist gravity waves and nonpropagating congestus modes in the multicloud model. The congestus mode has a preferred synoptic-scale wavelength, which is absent when a purely thermodynamic boundary layer is employed. The weak destabilization of a fast mesoscale wave, with a phase speed of 26 m s-1 and coupling to deep convection, is also discussed. © 2009 American Meteorological Society."
"7004014731;7103342287;","Interaction between the Brewer-Dobson circulation and the Hadley circulation",2005,"10.1175/JCLI3509.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28244480368&doi=10.1175%2fJCLI3509.1&partnerID=40&md5=74fb1d95802d70d01f3b866247c8b24d","Interannual changes of the stratospheric circulation are studied in relation to coherent changes of the tropospheric circulation. Emerging over the winter pole is a clear signature of adiabatic warming and anomalous downwelling. Reflecting an intensification of the Brewer-Dobson circulation, the signature of anomalous downwelling extends from stratospheric levels into the troposphere. Compensating for it at subpolar latitudes is a signature of adiabatic cooling and anomalous upwelling. Equally coherent, the signature of anomalous upwelling occupies the same levels as the signature of anomalous downwelling. Inside the tropical troposphere, anomalous cooling is replaced by anomalous warming. It reflects an intensification of organized convection and the Hadley circulation, one that accompanies the intensification of the Brewer-Dobson circulation. These signatures of anomalous vertical motion represent changes that operate coherently in the stratosphere and troposphere. They share major features with the Arctic Oscillation. Extending across the tropopause, they couple the stratosphere and troposphere through a transfer of mass. By modifying vertical motion inside the Tropics, anomalous upwelling influences organized convection. Support for this interpretation comes from anomalous divergence in the tropical upper troposphere; it is shown to vary coherently with anomalous downwelling in the Arctic stratosphere. Exhibiting analogous behavior are changes of the tropical tropopause. Coupled to stratospheric changes, these variations of the tropical circulation act to organize convection about the equator, favoring a split ITCZ. They reflect as much as 40% of the interannual variance of tropical divergence, representing an important complement to ENSO. Much of the covariance between the polar stratosphere and the tropical troposphere is concentrated at periods shorter than 5 yr. Included is variability that is associated with the quasi-biennial oscillation (QBO) in the tropical stratosphere. Also included is biennial variability, which accompanies the QBO in the polar stratosphere. These stratospheric variations involve the same time scales as biennial variability in the tropical troposphere, which likewise influences convection. © 2005 American Meteorological Society."
"8911587200;6701557528;","Roll convection during a cold air outbreak: A large eddy simulation with stationary model domain",2005,"10.1029/2005GL022872","https://www.scopus.com/inward/record.uri?eid=2-s2.0-25444436748&doi=10.1029%2f2005GL022872&partnerID=40&md5=3c7112772600e67efb4d1b2908fe96ed","A large eddy simulation (LES) of a cold air outbreak along with organized convection is presented. The computational grid was chosen to be fine enough to explicitly resolve small scale unorganized turbulence, while the size of the model domain was large enough to include the evolution of large scale organized convection. For the first time such an LES was performed with a stationary model domain, being one of the most extensive LES in meteorology so far. During the simulation, convective rolls were formed which showed typical characteristics as observed in nature, such as significantly increasing aspect ratios with increasing distance from the ice edge and orientation of the roll axes in direction of the mean wind shear vector. Copyright 2005 by the American Geophysical Union."
"6506553288;7407663727;","Global and regional diurnal variations of organized convection",2003,"10.1175/1520-0442-16.10.1562","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037929480&doi=10.1175%2f1520-0442-16.10.1562&partnerID=40&md5=0f36b668b66cccc13fb8fce579a4b293","An automated objective classification procedure, the Convection Classification and Automated Tracking System (CCATS), is used to analyze the mean life cycles of organized convection in the global Tropics and midlatitudes (40°N-40°S). Five years (1989-93) of infrared satellite imagery are examined for the Pacific and Atlantic basins and one year (April 1988-March 1989) is studied for the Indian basin. Two main classes of organized convection (lifetime of 6 h or more) are tracked: MCT and CCC. MCT represent a combined dataset of tropical cyclones and mesoscale convective complexes (MCC). Convective cloud clusters (CCC) meet the same cold cloud-top temperature, time, and size criteria used to distinguish MCC, but fail to sustain the same high degree of symmetry for at least 6 h. That is, CCC represent more elongated systems, such as squall lines. The frequency of CCC exceeds that of MCT by a factor of 30 over both land and sea. MCT and CCC are each stratified to into 12 continental and oceanic regions and the diurnal variation of system characteristics in each geographic region are studied, leading to composite life cycle descriptions for each region. Oceanic CCC formed overnight and the shorter-lived, land-based CCC formed in the afternoon; apart from this time offset, oceanic and land-based CCC were found to have very similar life cycle evolution patterns. Continental MCT exhibit a rapid size expansion early: this is not part of the oceanic system life cycle. Apart from this growth spurt, the evolution of land and ocean MCT follows the same pattern of CCC with early symmetry, then size expansion until just before termination. Land-based MCT are longer lived and more symmetric than oceanic MCT."
"7004201807;6701549604;16185051500;","A new look at the super outbreak of tornadoes on 3-4 April 1974",2002,"10.1175/1520-0493(2002)130<1633:ANLATS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036612299&doi=10.1175%2f1520-0493%282002%29130%3c1633%3aANLATS%3e2.0.CO%3b2&partnerID=40&md5=0e3b6b4e28c7511eed5648f3136c14fd","The outbreak of tornadoes from the Mississippi River to just east of the Appalachian Mountains on 2-5 April 1974 is analyzed using conventional techniques and the Pennsylvania State University-National Center for Atmospheric Research fifth-generation Mesoscale Model (MM5). The MM5 was run for 48 h using the NCEP-NCAR reanalysis dataset for initial conditions. It is suggested that the first damaging squall line within the storm of 2-5 April 1974 (herein referred to as the Super Outbreak storm) was initiated by updrafts associated with an undular bore. The bore resulted from the forward advance of a Pacific cold front into a stable air mass. The second major squall line within the Super Outbreak storm, which produced the strongest and most numerous tornadoes, was directly connected with the lifting associated with a cold front aloft. This second squall line was located along the farthest forward protrusion of a Pacific cold front as it occluded with a lee trough/dryline. An important factor in the formation of this occluded structure was the diabatic effects of evaporative cooling ahead of the Pacific cold front and daytime surface heating behind the Pacific cold front. These effects combined to lessen the horizontal temperature gradient across the cold front within the boundary layer. Although daytime surface heating and evaporative cooling are considered to be essential ingredients in the formation and maintenance of organized convection, the MM5 produced a strong squall line along the leading edge of the Pacific cold front even with the effects of surface heating and evaporational cooling removed from the model simulations."
"35572026100;7006095466;57203012011;55578808274;","Wavelet analysis of simulated tropical convective cloud systems. Part I: Basic analysis",2001,"10.1175/1520-0469(2001)058<0850:WAOSTC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035870803&doi=10.1175%2f1520-0469%282001%29058%3c0850%3aWAOSTC%3e2.0.CO%3b2&partnerID=40&md5=bc8f82f28589a952d532762dbacb82d2","A wavelet analysis of a three-dimensional 7-day explicit simulation of the tropical cloud systems in the Global Atmosphere Research Programme (GARP) Atlantic Tropical Experiment Phase III is performed. Three physically distinct regimes (squall line, nonsquall cloud cluster, and scattered convection) in a doubly periodic domain are analyzed using discrete Meyer wavelets. These wavelets are complete and facilitate the inversion of the decomposed modes. The full wavelet spectra well characterize the spatial localization of each physical variable, in particular, the vertical velocity and the condensate fields. The probability distribution of the wavelet coefficients is non-Gaussian despite the horizontal winds, the temperature, and humidity being closely Gaussian in physical space. This demonstrates the effectiveness of the wavelet basis for analyzing cloud system organization. The full wavelet spectrum also selects a preferred spatial orientation of the convective organization in physical space. A pseudospectrum is defined by taking the maximum absolute value of the wavelet coefficients for a given horizontal wavenumber vector as the spectrum coefficient. Unlike the conventional spectrum, this pseudospectrum objectively selects the observed convective-scale and mesoscale structure characteristic of observed mesoscale convective systems. The results demonstrate the broad utility of discrete Meyer wavelet analysis for objectively characterizing the structure and organization of multiscale convective cloud systems in an objective way."
"56537463000;7004479957;7410255460;","Self-aggregation and large-scale control of tropical deep convection: A modeling study",2000,"10.1175/1520-0469(2000)057<1797:SAALSC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034210360&doi=10.1175%2f1520-0469%282000%29057%3c1797%3aSAALSC%3e2.0.CO%3b2&partnerID=40&md5=9d6a1a9975b427eedbe9b4eff20d6c2a","The Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model version 5 (MM5) is used to investigate whether superclusters represent a mode of self-aggregation of tropical deep convection that occurs spontaneously under horizontally uniform boundary conditions and large-scale forcings. The nonhydrostatic version of MM5 is run with prescribed domain-averaged vertical velocity and periodic boundary conditions in both east-west and north-south directions. Domain-averaged horizontal winds are relaxed to a specified reference wind profile. Two vertical profiles of mean ascent are used. One has an elevated maximum at the upper troposphere and near-zero vertical velocity in the lower troposphere. The other peaks at the midtroposphere representing the vertical velocity distribution of convective towers only. Simulations with the same initial conditions but two different forcings show significant differences in convective organization. The run with elevated forcing develops larger cloud clusters than the run with midtropospheric forcing, suggesting some degree of self-aggregation under favorable large-scale forcings. A Fourier analysis of the precipitation organization in the elevated forcing run indicates considerable variance in propagating waves of wavelength 1000-2000 km in which convective heating is positively correlated with temperature and moisture anomalies. Sensitivity tests show that the long-wavelength organization does not require horizontal variability of surface fluxes and so cannot be explained by wind-induced surface heat exchange (WISHE)-type mechanisms. Sensitivity tests of model results to magnitude and vertical distribution of forcings, cloud-radiation feedbacks, reference wind profiles, and grid resolution are also conducted.The Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model version 5 (MM5) is used to investigate whether superclusters represent a mode of self-aggregation of tropical deep convection that occurs spontaneously under horizontally uniform boundary conditions and large-scale forcings. The nonhydrostatic version of MM5 is run with prescribed domain-averaged vertical velocity and periodic boundary conditions in both east-west and north-south directions. Domain-averaged horizontal winds are relaxed to a specified reference wind profile. Two vertical profiles of mean ascent are used. One has an elevated maximum at the upper troposphere and near-zero vertical velocity in the lower troposphere. The other peaks at the midtroposphere, representing the vertical velocity distribution of convective towers only. Simulations with the same initial conditions but two different forcings show significant differences in convective organization. The run with elevated forcing develops larger cloud clusters than the run with midtropospheric forcing, suggesting some degree of self-aggregation under favorable large-scale forcings. A Fourier analysis of the precipitation organization in the elevated forcing run indicates considerable variance in propagating waves of wavelength 1000-2000 km in which convective heating is positively correlated with temperature and moisture anomalies. Sensitivity tests show that the long-wavelength organization does not require horizontal variability of surface fluxes and so cannot be explained by wind-induced surface heat exchange (WISHE)-type mechanisms. Sensitivity tests of model results to magnitude and vertical distribution of forcings, cloud-radiation feedbacks, reference wind profiles, and grid resolution are also conducted."
"57195673296;56522444900;6602999057;","Rainfall types over southern West Africa: Objective identification, climatology and synoptic environment",2018,"10.1002/qj.3345","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053343108&doi=10.1002%2fqj.3345&partnerID=40&md5=daae70cd003e69cb40a2e4d5e3d18e70","Southern West Africa (SWA) is characterised by a wide range of rainfall types, the relative importance of which have never been quantified on a regional level. Here, we use 16 years of three-dimensional reflectivity data from the Tropical Rainfall Measuring Mission–Precipitation Radar (TRMM-PR) to objectively distinguish between seven different rainfall types in three subregions of SWA. Highly organized Mesoscale Convective System (MCS) events are the dominating rain-bearing systems in SWA. They tend to occur in highly sheared environments as a result of mid-level northeasterlies ahead of a cyclonic vortex. Their contribution to annual rainfall decreases from 71% in the Soudanian to 56% in the coastal zone. MCSs in SWA also propagate slower than their Sahelian counterparts and occur predominantly at the start of the first coastal rainy season. However, in terms of numbers, about 90% of rainfall systems are weakly organized classes, particularly small-sized, highly reflective and moderately deep (40 dBZ at altitude <10 km) systems. Contrary to MCSs, less organized convection typically occurs during and after the passage of a cyclonic vortex within a regime of deep westerly anomalies, low wind shear and low to moderate CAPE (convective available potential energy), bearing some resemblance to what has been termed “monsoon” or “vortex rainfall”. Combining TRMM-PR rainfall system identification with infrared-based cloud tracking reveals that organized convection over SWA typically lasts for more than >9 h, whereas less intense rainfall types tend to be short-lived, diurnal phenomena. This novel approach stresses the relevance of mid-level (wave) disturbances on the type and lifetime of convective systems and thereby their regionally, seasonally and diurnally varying contribution to rainfall amount. The present study suggests further investigations into the character of the disturbances as well as possible implications for operational forecasting and the understanding of rainfall variability in SWA. © 2018 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"55437450100;7201504886;8696069500;6603247427;","Radiative convective equilibrium as a framework for studying the interaction between convection and its large-scale environment",2016,"10.1002/2016MS000629","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983485991&doi=10.1002%2f2016MS000629&partnerID=40&md5=44ee641ec13077ca2401ea4e533a94d7","An uncertain representation of convective clouds has emerged as one of the key barriers to our understanding of climate sensitivity. The large gap in resolved spatial scales between General Circulation Models (GCMs) and high resolution models has made a systematic study of convective clouds across model configurations difficult. It is shown here that the simulated atmosphere of a GCM in Radiative Convective Equilibrium (RCE) is sufficiently similar across a range of domain sizes to justify the use of RCE to study both a GCM and a high resolution model on the same domain with the goal of improved constraints on the parameterized clouds. Simulations of RCE with parameterized convection have been analyzed on domains with areas spanning more than two orders of magnitude (0.80-204X106km2), all having the same grid spacing of 13km. The simulated climates on different domains are qualitatively similar in their degree of convective organization, the precipitation rates, and the vertical structure of the clouds and water vapor, with the similarity increasing as the domain size increases. Sea surface temperature perturbation experiments are used to estimate the climate feedback parameter for the differently configured experiments, and the cloud radiative effect is computed to examine the role which clouds play in the response. Despite the similar climate states between the domains the feedback parameter varies by more than a factor of two; the hydrological sensitivity parameter is better behaved, varying by a factor of 1.4. The sensitivity of the climate feedback parameter to domain size is related foremost to a nonsystematic response of low-level clouds as well as an increasingly negative longwave feedback on larger domains. © 2016. The Authors."
"56471241700;6507400558;7004978125;6504750541;","Effect of stratiform heating on the planetary-scale organization of tropical convection",2016,"10.1175/JAS-D-15-0178.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957641898&doi=10.1175%2fJAS-D-15-0178.1&partnerID=40&md5=c07fa832635c1b0721cb3f2cfb983017","It is widely recognized that stratiform heating contributes significantly to tropical rainfall and to the dynamics of tropical convective systems by inducing a front-to-rear tilt in the heating profile. Precipitating stratiform anvils that form from deep convection play a central role in the dynamics of tropical mesoscale convective systems. The wide spreading of downdrafts that are induced by the evaporation of stratiform rain and originate from in the lower troposphere strengthens the recirculation of subsiding air in the neighborhood of the convection center and triggers cold pools and gravity currents in the boundary layer, leading to further lifting. Here, aquaplanet simulations with a warm pool-like surface forcing, based on a coarse-resolution GCM of approximately 170-km grid mesh, coupled with a stochastic multicloud parameterization, are used to demonstrate the importance of stratiform heating for the organization of convection on planetary and intraseasonal scales. When the model parameters, which control the heating fraction and decay time scale of the stratiform clouds, are set to produce higher stratiform heating, the model produces low-frequency and planetary-scale MJO-like wave disturbances, while parameters associated with lower-to-moderate stratiform heating yield mainly synoptic-scale convectively coupled Kelvin-like waves. Furthermore, it is shown that, when the effect of stratiform downdrafts is reduced in the model, the MJO-scale organization is weakened, and a transition to synoptic-scale organization appears despite the use of larger stratiform heating parameters. Rooted in the stratiform instability, it is conjectured here that the strength and extent of stratiform downdrafts are key contributors to the scale selection of convective organizations, perhaps with mechanisms that are, in essence, similar to those of mesoscale convective systems. © 2016 American Meteorological Society."
"23991212200;7004479957;6507017020;","Restricting 32-128 km horizontal scales hardly affects the MJO in the Superparameterized Community Atmosphere Model v.3.0 but the number of cloud-resolving grid columns constrains vertical mixing",2014,"10.1002/2014MS000340","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84932199444&doi=10.1002%2f2014MS000340&partnerID=40&md5=4b5ba6f0720cd6fd63979db9a1efdea3","The effects of artificially restricting the 32-128 km horizontal scale regime on MJO dynamics in the Superparameterized Community Atmosphere Model v.3.0 have been explored through reducing the extent of its embedded cloud resolving model (CRM) arrays. Two and four-fold reductions in CRM extent (from 128 to 64 km and 32 km) produce statistical composite MJO signatures with spatial scale, zonal phase speed, and intrinsic wind-convection anomaly structure that are all remarkably similar to the standard SPCAM's MJO. This suggests that the physics of mesoscale convective organization on 32-128 km scales are not critical to MJO dynamics in SPCAM and that reducing CRM extent may be a viable strategy for 400% more computationally efficient analysis of superparameterized MJO dynamics. However several unexpected basic state responses caution that extreme CRM domain reduction can lead to systematic mean state issues in superparameterized models. We hypothesize that an artificial limit on the efficiency of vertical updraft mixing is set by the number of grid columns available for compensating subsidence in the embedded CRM arrays. This can lead to reduced moisture ventilation supporting too much liquid cloud and thus an overly strong cloud shortwave radiative forcing, particularly in regions of deep convection. Key Points Physics of MMF MJO are insensitive to near elimination of meso-beta-scale The efficiency of deep convective mixing in MMFs is limited by CRM extent 4x speedup of superparameterized models possible for MJO analysis © 2014. The Authors."
"16309604700;34770884300;7402330357;38461378900;35407865200;10038888600;7201926991;55691665700;24399716000;","Effects of large-scale moisture transport and mesoscale processes on precipitation isotope ratios observed at Sumatera, Indonesia",2011,"10.2151/jmsj.2011-A03","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79957675606&doi=10.2151%2fjmsj.2011-A03&partnerID=40&md5=ce9a31a0e9f160607d7ff89d2da64553","Isotopic and meteorological observations in November 2006 on the west coast of Sumatera, Indonesia during the intense observation period of the Hydrometeorological ARray for Intraseasonal Variation-Monsoon AUtomonitoring (HARIMAU2006), revealed the impacts of large-scale moisture transport and mesoscale processes on precipitation isotope ratios. Intraseasonal changes in the precipitation d2H in November had large variability ranging from +10 to -65 per mil, as a result of the changes in the large-scale moisture transport associated with the intraseasonal oscillation with a time-scale of 10-15 day over Sumatera. The isotopic composition of precipitation was independent from di{currency sign}erence in precipitation type (convective or stratiform precipitation). An isotope circulation model reproduced the observed isotopic changes, supporting that the isotopic effect of large-scale moisture transport was the main contributor to intraseasonal isotopic changes. In high-frequency samples taken over a shorter time scale, isotopic variability was related to event type classified by the analysis of radar observations, although the isotopic effects of mesoscale processes on the isotopic averages of each precipitation event were almost masked by the isotopic effect of large-scale moisture transport. The precipitation δ2H accompanying the well-organized convection type decreased significantly by about 20 per mil. Drastic changes in isotope ratios could be described by the Rayleigh distillation process. Isotope ratios of precipitation gently decreased and subsequently increased in the unorganized convection type since the water vapor in surrounding convectively rising air isotopically enriched the remaining low-isotope water vapor advected from the precedent clouds. Isotope ratios in the strati form precipitation remained steady, possibly attributable to the homogeneous moisture of strati form clouds. © 2011, Meteorological Society of Japan."
"8255473900;7004279605;","A nonlinear perspective on the dynamics of the MJO: Idealized large-eddy simulations",2010,"10.1175/2009JAS3160.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953339027&doi=10.1175%2f2009JAS3160.1&partnerID=40&md5=d99a1a7c556ed455007b0793496062f3","The 30-60-day intraseasonal atmospheric oscillation in the equatorial atmosphere, the Madden-Julian oscillation (MJO), is most visible in its signature of outgoing longwave radiation and associated convective centers. Diabatic processes related to tropical convection and two-way atmosphere-ocean interaction are hence generally believed to be crucial in explaining the origin of the MJO phenomenon. However, reliable deterministic forecasting of the MJO in global circulation models and understanding its mechanism remains unsatisfactory. Here a different approach is taken, where the hypothesis is tested that eastward-propagating MJO-like structures originate fundamentally as a result of nonlinear (dry)Rossbywave dynamics. Alaboratoryscale numerical model is constructed, where the generation of solitary structures is excited and maintained via zonally propagating meanders of the meridional boundaries of a zonally periodic b plane. The large-eddy simulations capture details of the formation of solitary structures and of their impact on the convective organization. The horizontal structure and the propagation of anomalous streamfunction patterns, a diagnostic typically used in tracing the equatorial MJO, are similar to archetype solutions of the Korteweg-deVries equation, which extends the linear shallow water theory-commonly used to explain equatorial wave motions- to a weakly nonlinear regime for small Rossby numbers. Furthermore, the characteristics of the threedimensional laboratory-scale numerical results compare well with observed features of the equatorial MJO and thus the study provides indirect evidence of the basic principles underlying the wave-driven eastward propagation of the MJO. © 2010 American Meteorological Society."
"7409792174;7006095466;7102609291;","A note on propagating rainfall episodes over the Bay of Bengal",2008,"10.1002/qj.246","https://www.scopus.com/inward/record.uri?eid=2-s2.0-55349095481&doi=10.1002%2fqj.246&partnerID=40&md5=9a0ce7039297ebdeec5006ffb38a4020","An observational analysis of precipitation episodes over the Bay of Bengal and the adjacent coastal region is conducted using the TRMM Real-Time Multi-Satellite Precipitation Analysis (MPA-RT) products for three warm seasons (i.e. May to September for 2002-2004). Time-distance diagrams (Hovmüller diagrams) of rainfall episodes reveal frequent travelling precipitation episodes having lifetimes greatly exceeding those of individual convective systems. The majority of the episodes translate southward and many do not appear to have a steering level (i.e. they propagate in a hydraulic-like manner), unlike those previously documented over midlatitude and tropical continents which usually have a steering level. On average, the coherent systems have a latitudinal span of 5 degrees and a 1-day duration and a meridional propagation speed of 8 m s-1, approximately. The episodes mostly initiate over the coastal land around midday and offshore around midnight. Copyright © 2008 Royal Meteorological Society."
"16445293700;6701744275;6603432436;","Boreal summer intraseasonal variability in coupled seasonal hindcasts",2008,"10.1175/2008JCLI2216.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-53649105590&doi=10.1175%2f2008JCLI2216.1&partnerID=40&md5=c92e629f32d4528b6c983afad7ab2957","The intraseasonal variability (ISV) of the Asian summer monsoon represented in seven coupled general circulation models (CGCMs) as part of the Development of a European Multimodel Ensemble System for Seasonal-to-Interannual Prediction (DEMETER) project is analyzed and evaluated against observations. The focus is on the spatial and seasonal variations of ISV of outgoing longwave radiation (OLR). The large-scale organization of convection, the propagation characteristics, and the air-sea coupling related to the monsoon ISV are also evaluated. A multivariate local mode analysis (LMA) reveals that most models produce less organized convection and ISV events of shorter duration than observed. Compared to the real atmosphere, these simulated patterns of perturbations are poorly reproducible from one event to the other. Most models simulate too weak sea surface temperature (SST) perturbations and systematic phase quadrature between OLR, surface winds, and SST - indicative of a slab-ocean-like response of the SST to surface flux perturbations. The relatively coarse vertical resolution of the different ocean GCMs (OGCMs) limits their ability to represent intraseasonal processes, such as diurnal warm layer formation, which are important for realistic simulation of the SST perturbations at intraseasonal time scales. Models with the same atmospheric GCM (AGCM) and different OGCMs tend to have similar biases of the simulated ISV, indicating the dominant role of atmospheric models in fixing the nature of the intraseasonal variability. It is, therefore, implied that improvements in the representation of ISV in coupled models have to fundamentally arise from fixing problems in the large-scale organization of convection in AGCMs. © 2008 American Meteorological Society."
"6603263640;","Sources and sinks of available potential energy in a moist atmosphere",2007,"10.1175/JAS3937.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547725599&doi=10.1175%2fJAS3937.1&partnerID=40&md5=d93edb96ec477c32f63f500cc857daf8","Available potential energy (APE) is defined as the difference between the total static energy of the atmosphere and that of a reference state that minimizes the total static energy after a sequence of reversible adiabatic transformations. Determining the rate at which APE is generated in the atmosphere allows one to estimate the amount of kinetic energy that can be generated by atmosphere flows. Previous expressions for the sources and sinks of APE rely on a dry framework and are limited by the fact that they require prior knowledge of the distribution of latent heat release by atmospheric motion. In contrast, this paper uses a moist APE framework to derive a general formula for the sources and sinks of APE that can be equally applied to dry and moist circulations. Two key problems are addressed here. First, it is shown that any reorganization of the reference state due to diabatic heating or addition of water does not change its total static energy. This property makes it possible to determine the rate of change in APE even in the absence of an analytic formula for the reference state, as is the case in a moist atmosphere. Second, the effects of changing the total water content of an air parcel are also considered in order to evaluate the changes of APE due to precipitation, evaporation, and diffusion of water vapor. Based on these new findings, one can obtain the rate of change of APE from that of atmospheric entropy, water content, and pressure. This result is used to determine the sources and sinks of APE due to different processes such as external energy sources, frictional dissipation, diffusion of sensible heat and water vapor, surface evaporation, precipitation, and reevaporation. These sources and sinks are then discussed in the context of an idealized atmosphere in radiative-convective equilibrium. For a moist atmosphere, the production of APE by the surface energy flux is much larger than any observational or theoretical estimates of frictional dissipation, and, as is argued here, must be balanced by a comparable sink of APE due to the diffusion of water vapor from unstable to stable air parcels. © 2007 American Meteorological Society."
"6506537159;7410255460;7006432091;","Momentum transport processes in the stratiform regions of mesoscale convective systems over the western Pacific warm pool",2006,"10.1256/qj.04.141","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745010419&doi=10.1256%2fqj.04.141&partnerID=40&md5=60db5838296dc63ea5d9d822cb9f6da2","Momentum transport by the stratiform components of mesoscale convective systems (MCSs) during the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment in December 1992 is investigated using a cloud-resolving model. The mesoscale momentum transport by the stratiform regions of MCSs is examined in two distinct large-scale flow regimes associated with the intraseasonal oscillation over the western Pacific warm pool. Model simulations for 14 December 1992 characterize the 'westerly onset' period, which has relatively weak low-level westerlies with easterlies above. Simulations for 23-24 December represent the 'strong westerly' regime, when westerlies extend from the upper troposphere to the surface, with a jet 2-3 km above the surface. In the westerly onset simulation, the extensive stratiform region of a MCS contained a broad region of descent that transported easterly momentum associated with the mid-level easterly jet downward. Thus, the stratiform regions acted as a negative feedback to decrease the large-scale mean westerly momentum developing at low levels. In the strong westerly regime, the mesoscale downward air motion in the stratiform regions of large MCSs transported westerly momentum downward and thus acted as a positive feedback, strengthening the already strong westerly momentum at low levels. Momentum fluxes by the mesoscale stratiform region downdraughts are shown to have a systematic and measurable impact on the large-scale momentum budget. © Royal Meteorological Society, 2006."
"7005706662;","Spatial and temporal scales of precipitating tropical cloud systems in satellite imagery and the NCAR CCM3",2003,"10.1175/1520-0442(2003)016<3545:SATSOP>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141804864&doi=10.1175%2f1520-0442%282003%29016%3c3545%3aSATSOP%3e2.0.CO%3b2&partnerID=40&md5=83104fbeb9fe24e71c82fe81c7794a60","Testing general circulation model parameterizations against observations is traditionally done by comparing simulated and observed, time-averaged quantities, such as monthly mean cloud cover, evaluated on a stationary grid. This approach ignores the dynamical aspects of clouds, such as their life cycle characteristics, spatial coverage, temporal duration, and internal variability. In this study, a complementary Lagrangian approach to the validation of modeled tropical cloudiness is explored. An automated cloud detection and tracking algorithm is used to observe and track overcast decks of cloud in a consecutive set of hourly Meteosat-5 images and the National Center for Atmospheric Research Community Climate Model version 3 (NCAR CCM3). The algorithm is applied to the deep convective cloud systems of the tropical Indian Ocean region during a 49-day period of the 1999 winter monsoon season. Observations of precipitation are taken from the Tropical Rainfall Measuring Mission (TRMM) satellite in addition to a Meteosat-5 infrared rainfall technique that is calibrated using the TRMM data. Clouds, defined as overcast decks, are observed spanning spatial scales from 25 km2 to greater than 107 km2, as well as temporal scales from 1 h to greater than 100 h. Semipermanent decks of anvil and cirrus cloud, with numerous regions of deep convection embedded within, dominate total cloud cover. Bridging between convective centers within the deck by cirrus clouds, particularly during the suppressed portion of the diurnal cycle of convection, may help to maintain the integrity of semipermanent overcast decks over long timescales. At scales greater than 10° km2 the size distribution of simulated clouds is biased such that the dominant scale of clouds is several million square kilometers larger than the dominant scale of observed clouds. Virtually all of the simulated precipitation occurs at rain rates lower than 2 mm h-1, while as much as 25% of observed precipitation occurs at rain rates higher than 2 mm h-1, Precipitation associated with deep convection in observed semipermanent cloud systems is organized into more localized mesoscale structures of adjacent convective cells attached to stratiform precipitation regions. A separate analysis of TRMM data by Wilcox and Ramanathan determined that such structures can exceed the size of grid cells in coarse-grid global models and have area-averaged rain rates up to and exceeding 2 mm h-1. These mesoscale convective systems are responsible for the extreme, episodic precipitation events that are not parameterized in the model. The simulated cloud systems gently precipitate throughout their duration and everywhere within their boundaries. The model lacks a process that acts to organize the convective cells within fewer grid cells, in addition to a representation of the observed stratiform precipitation structures. A modification to CCM3 is tested that is intended to account for the evaporation of upper-level precipitation in midlevel mesoscale downdrafts. The modification results in only a slight change in domain-averaged precipitation. However, it causes a significant shift in the distribution of precipitation toward higher rain rates that is more consistent with the distribution of TRMM observed rain rates. The modification demonstrates the sensitivity of the model to one important component of mesoscale organized convection."
"7401945370;55712772000;","Simple cumulus models in one-dimensional radiative convective equilibrium problems",1992,"10.1175/1520-0469(1992)049<1202:SCMIOD>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027063974&doi=10.1175%2f1520-0469%281992%29049%3c1202%3aSCMIOD%3e2.0.CO%3b2&partnerID=40&md5=a2f23b7a896211191d80f331bbdc7719","The cumulus model presented by Lindzen et al. for calculating one-dimensional radiative convective equilibria is examined. When only the balance of moist static energy is considered, the value of the convective mass flux Mc is required to be externally specified. In order to obtain an appropriate equilibrium solution where the buoyancy is positive, the balance of kinetic energy, especially the dissipative process, should be considered. It is found that the value of Mc, which gives a realistic value of the dissipative process, is close to the upper limit. In order to have a solution with a more realistic temperature profile, the model assumption that Mc is independent of time and height should be released. -from Authors"
"55417497600;57205863266;34976155900;57208121852;7102227540;","Quantifying the effects of horizontal grid length and parameterized convection on the degree of convective organization using a metric of the potential for convective interaction",2018,"10.1175/JAS-D-16-0307.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042224670&doi=10.1175%2fJAS-D-16-0307.1&partnerID=40&md5=a04e687ebf2d39a88e719a5feb7ee48f","The organization of deep convection and its misrepresentation in many global models is the focus of much current interest. A new method is presented for quantifying convective organization based on the identification of convective objects and subsequent derivation of object numbers, areas, and separation distances to describe the degree of convective organization. These parameters are combined into a ""convection organization potential"" based on the physical principle of an interaction potential between pairs of convective objects. This technique is applied to simulated and observed fields of outgoing longwave radiation (OLR) over the West African monsoon region using data from Met Office Unified Model simulations and satellite observations made by the Geostationary Earth Radiation Budget (GERB) instrument. The method is evaluated by using it to quantify differences between models with different horizontal grid lengths and representations of convection. Distributions of OLR, precipitation and organization parameters, the diurnal cycle of convection, and relationships between the meteorology in different states of organization are compared. Switching from a configuration with parameterized convection to one that allows the model to resolve convective processes at the model grid scale is the leading-order factor improving some aspects of model performance, while increased model resolution is the dominant factor for others. However, no single model configuration performs best compared to observations, indicating underlying deficiencies in both model scaling and process understanding. © 2018 American Meteorological Society."
"57034069700;35509639400;","Internal variability in a coupled general circulation model in radiative-convective equilibrium",2017,"10.1002/2017GL073658","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019691726&doi=10.1002%2f2017GL073658&partnerID=40&md5=b52d5af7ace1200ac0f077bbf623b540","Numerical models run in non-rotating radiative-convective equilibrium (RCE) using prescribed sea surface temperatures (SSTs) show that convection can spontaneously aggregate into dry and moist areas, and that convective aggregation tends to increase with temperature. Using a general circulation model coupled to an ocean mixed layer, we show that in RCE the coupled ocean-atmosphere system exhibits some internal variability. This variability arises from the interplay between mean surface temperature, SST gradients and convective aggregation, and its timescale is proportional to the depth of the ocean mixed layer. For an ocean layer deeper than 10 m, the variability occurs at the interannual timescale, and variations of convective aggregation are almost out of phase with those of surface temperature. The coupled RCE framework might be relevant to understand some internal modes of variability of the tropical ocean-atmosphere system such as El Niño Southern Oscillation. ©2017. The Authors."
"57190300360;6505932008;6602805147;7005968859;","The microphysical contributions to and evolution of latent heating profiles in two MC3E MCSs",2016,"10.1002/2016JD024762","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84979079595&doi=10.1002%2f2016JD024762&partnerID=40&md5=fab5560ef9b2aeb3fa2d56c73fb15351","The shapes and magnitudes of latent heating profiles have been shown to be different within the convective and stratiform regions of mesoscale convective systems (MCSs). Properly representing these distinctions has significant implications for the atmospheric responses to latent heating on various scales. This study details (1) the microphysical process contributions to latent heating profiles within MCS convective, stratiform, and anvil regions and (2) the time evolution of these profiles throughout the MCS lifetime, using cloud-resolving model simulations. Simulations of two MCS events that occurred during the Midlatitude Continental Convective Clouds Experiment (MC3E) are conducted. Several features of the simulated MCSs are compared to a suite of observations obtained during the MC3E field campaign, and it is concluded that the simulations reasonably reproduce the MCS events. The simulations show that condensation and deposition are the primary contributors to MCS latent warming, as compared to riming and nucleation processes. In terms of MCS latent cooling, sublimation, melting, and evaporation all play significant roles. It is evident that throughout the MCS lifecycle, convective regions demonstrate an approximately linear decrease in the magnitudes of latent heating rates, while latent heating within stratiform regions is associated with transitions between MCS flow regimes. Such information regarding the temporal evolution of latent heating within convective and stratiform MCS regions could be useful in developing parameterizations representing convective organization. © 2016. American Geophysical Union. All Rights Reserved."
"56402758400;7102322882;7404894686;22962457400;","A new, fast and flexible radiative transfer method for Venus general circulation models",2015,"10.1016/j.pss.2014.11.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920528418&doi=10.1016%2fj.pss.2014.11.008&partnerID=40&md5=50197408b4e6d55a9ed752161071d0d9","We present a new radiation scheme for the Oxford Planetary Unified Model System for Venus, suitable for the solar and thermal bands. This new and fast radiative parameterization uses a different approach in the two main radiative wavelength bands: solar radiation (0.1-5.5μm) and thermal radiation (1.7-260μm). The solar radiation calculation is based on the δ-Eddington approximation (two-stream-type) with an adding layer method. For the thermal radiation case, a code based on an absorptivity/emissivity formulation is used. The new radiative transfer formulation implemented is intended to be computationally light, to allow its incorporation in 3D global circulation models, but still allowing for the calculation of the effect of atmospheric conditions on radiative fluxes. This will allow us to investigate the dynamical-radiative-microphysical feedbacks. The model flexibility can be also used to explore the uncertainties in the Venus atmosphere such as the optical properties in the deep atmosphere or cloud amount. The results of radiative cooling and heating rates and the global-mean radiative-convective equilibrium temperature profiles for different atmospheric conditions are presented and discussed. This new scheme works in an atmospheric column and can be easily implemented in 3D Venus global circulation models. © 2014 Elsevier Ltd. All rights reserved."
"6701368631;24173681800;13405658600;","A simple way to improve the diurnal cycle in convective rainfall over land in climate models",2014,"10.1002/2013JD020149","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898475785&doi=10.1002%2f2013JD020149&partnerID=40&md5=6bbac06d45acc6649e67986750eb1159","Within the tropics, and during the summer months in midlatitudes, most of the rainfall reaching the surface is generated by moist convection. Over land, the diurnal cycle in moist convective rainfall usually peaks in the late afternoon. In most climate models, the diurnal peak in convective rainfall occurs several hours too early and is often near local solar noon. We argue that this bias partly originates from the methods used in convective parameterizations to calculate the cloud base mass flux. In most convective parameterizations, the initial convective mass flux is determined from the convective available potential energy (CAPE) of an updraft parcel originating from the model layer closest to the surface. In models, the rapid increase in the CAPE of this near-surface layer following sunrise contributes to a rapid increase in convective precipitation. However, the mass-weighted CAPE of the boundary layer as a whole responds much more slowly to the increase in downward solar radiation at the surface. Using a recently developed convective parameterization in version 4 of the Community Atmosphere Model (CAM4), we show that the overall accuracy in the diurnal simulation of convective precipitation increases as the number of near-surface layers from which convective air parcels are permitted to originate increases from one to four. We also show that the simulation of the diurnal cycle in convective precipitation over land can be improved through the introduction of variables which attempt to represent the persistence of subgrid-scale convective organization within a grid column across model time steps. © 2014. American Geophysical Union. All rights reserved."
"22134910200;55716319700;15026371500;","Tropopause structure and the role of eddies",2011,"10.1175/JAS-D-11-087.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862907539&doi=10.1175%2fJAS-D-11-087.1&partnerID=40&md5=fff8f00a8ae7e8cc187f2de7631568d0","This paper presents a series of dynamical states using an idealized three-dimensional general circulation model with gray radiation and latent heat release. Beginning with the case of radiative-convective equilibrium, an eddy-free two-dimensional state with zonally symmetric flow is developed, followed by a threedimensional state that includes baroclinic eddy fluxes. In both dry and moist cases, it is found that the deepening of the tropical tropospheric layer and the shape of the extratropical tropopause can be understood through eddy-driven processes such as the stratospheric Brewer-Dobson circulation. These results suggest that eddies alone can generate a realistic tropopause profile in the absence of moist convection and that stratospheric circulation is an important contributor to tropopause structure. © 2011 American Meteorological Society."
"12144461400;7103201242;7801600522;24075934200;6602908667;55262957100;8986820300;6701670597;","Characteristics of 3-4- and 6-8-day period disturbances observed over the tropical Indian ocean",2010,"10.1175/2010MWR3469.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650198704&doi=10.1175%2f2010MWR3469.1&partnerID=40&md5=06954f5d7bed797e10213b3ce379a27b","A field observational campaign [i.e., the Mirai Indian Ocean cruise for the Study of the MJO-convection Onset (MISMO)] was conducted over the central equatorial Indian Ocean in October-December 2006. During MISMO, large-scale organized convection associated with a weak Madden-Julian oscillation (MJO) broke out, and some other notable variations were observed. Water vapor and precipitation data show a prominent 3-4-day-period cycle associated with meridional wind y variations. Filtered y anomalies at midlevels in reanalysis data [i.e., the Japan Meteorological Agency (JMA) Climate Data Assimilation System (JCDAS)] show westward phase velocities, and the structure is consistent with mixed Rossby-gravity waves. Estimated equivalent depths are a few tens of meters, typical of convectively coupled waves. In the more rainy part of MISMO (16-26 November), the 3-4-day waves were coherent through the lower and midtroposphere, while in the less active early November period midlevel y fluctuations appear less connected to those at the surface. SST diurnal variations were enhanced in light-wind and clear conditions. These coincided with westerly anomalies in prominent 6-8-day zonal wind variations with a deep nearly barotropic structure through the troposphere. Westward propagation and structure of time-filtered winds suggest n = 1 equatorial Rossby waves, but with estimated equivalent depth greater than is common for convectively coupled waves, although sheared background flow complicates the estimation somewhat. An ensemble reanalysis [i.e., the AGCM for the Earth Simulator (AFES) Local Ensemble Transform Kalman Filter (LETKF) Experimental Reanalysis (ALERA)] shows enhanced spread among the ensemble members in the zonal confluence phase of these deep Rossby waves, suggesting that assimilating them excites rapidly growing differences among ensemble members. © 2010 American Meteorological Society."
"55202929100;7003507545;","Intraseasonal variability of the summer monsoon over the north Indian ocean as revealed by the BOBMEX and ARMEX field programs",2005,"10.1007/s00024-005-2680-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-22144499180&doi=10.1007%2fs00024-005-2680-0&partnerID=40&md5=15ad161a7eac95fd4e5be22fdfeb2631","During the summer monsoon season over India a range of intraseasonal modulations of the monsoon rains occur due to genesis of weather disturbances over the Bay of Bengal (BOB) and the east Arabian Sea. The amplitudes of the fluctuations in the surface state of the ocean (sea-surface temperature and salinity) and atmosphere are quite large due to these monsoonal modulations on the intraseasonal scale as shown by the data collected during the field programs under Bay of Bengal Monsoon Experiment (BOBMEX) and Arabian Sea Monsoon Experiments (ARMEX). The focus of BOBMEX was to understand the role of ocean-atmospheric processes in organizing convection over the BOB on intra-seasonal scale. ARMEX-I was aimed at understanding the coupled processes in the development of deep convection off the West Coast of India. ARMEX-II was focused on the formation of the mini-warm pool across the southeast Arabian Sea in April-May and its role in the abrupt onset of the monsoon along the Southwest Coast of India and its further progress along the West Coast of India. The paper attempts to integrate the results of the observational studies and brings out an important finding that atmospheric instability is prominently responsible for convective organization whereas the upper ocean parameters regulate the episodes of the intraseasonal oscillations. © Birkhäuser Verlag, Basel, 2005."
"7003728653;23049355400;","The 21 June 1997 flood: Storm-scale simulations and implications for operational forecasting",2001,"10.1175/1520-0434(2001)016<0197:TJFSSS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035298066&doi=10.1175%2f1520-0434%282001%29016%3c0197%3aTJFSSS%3e2.0.CO%3b2&partnerID=40&md5=caea13d02ac6b61434259a6e742f7b5d","On 20-21 June 1997, a convective outbreak in Nebraska. Iowa, Illinois, and Wisconsin resulted in two fatalities, eight injuries, and approximately $104 million in damage. The majority of the damage ($92 million) was the result of flooding in southeastern Wisconsin owing to nearly 250 mm of rain produced by training convection and to a lesser extent the passage of a persistent, elongated convective system. The flood event is analyzed and storm-scale (5- and 1.67-km grid spacing) resolution model simulations at 0-24-, 12-36-, and 24-48-h ranges are produced to study the evolution and predictability of the rainfall. Synoptic conditions corresponded closely to the mesohigh pattern frequently associated with heavy rainfall events. Despite the recognition by National Weather Service forecasters of the potential for heavy rainfall, uncertainty concerning event magnitude and affected areas, exacerbated by poor operational model guidance, resulted in a failure to issue flash flood watches prior to the onset of flooding. Simulations of the event using 5-km grid spacing show that short-range forecasts (0-24 h) are able to suggest focused precipitation in southeastern Wisconsin. Initiation of the convection is tied to lift at the leading edge of a low-level jet (LLJ), with a focus along a weak frontogenetic boundary. A rapid loss of predictability at the 12-36- and 24-48-h ranges results in part from poorer representations of the LLJ. Increased resolution (1.67-km grid spacing) is necessary to capture the magnitude of the event. The increased resolution led to little change in available moisture or lift, but substantial increases in precipitation efficiency, arising from the capability to resolve the details of convective organization in an aggregate, time-averaged sense. With 1.67-km grid spacing, the probability of detection (false alarm ratio) for critical precipitation thresholds of 25, 50, 75, and 125 mm in the heavy rainfall region are 0.79 (0.01), 0.60 (0.21), 0.51 (0.23), and 0.36 (0.32), respectively. Precipitation forecast skill as measured by the Kuiper skill score for these same threshold os 0.30, 0.36, 0.39, and 0.33. However, on a county warning area basis for flash flooding, these same forecasts yield probability of detection (false alarm ratio) of 0.71 (0.55). The results of this study suggest that the consistent use of storm-scale model output in conjunction with observations in such events will likely lead to improved forecasts and greater forecast value, although significant constraints related to real-world application of such models and procedures would still remain. In order to firmly establish these points, it is necessary to analyze a number of such cases within an operational context."
"6701346974;7006184606;","Intraseasonal variability in a cloud-permitting near-global equatorial aquaplanet model",2018,"10.1175/JAS-D-18-0152.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059253113&doi=10.1175%2fJAS-D-18-0152.1&partnerID=40&md5=49568b2b0331865ab7625998596f3cba","Recent studies have suggested that the Madden-Julian oscillation is a result of an instability driven mainly by cloud-radiation feedbacks, similar in character to self-aggregation of convection in nonrotating, cloud-permitting simulations of radiative-convective equilibrium (RCE). Here we bolster that inference by simulating radiative-convective equilibrium states on a rotating sphere with constant sea surface temperature, using the cloud-permitting System for Atmospheric Modeling (SAM) with 20-km grid spacing and extending to walls at 46° latitude in each hemisphere. Mechanism-denial experiments reveal that cloud-radiation interaction is the quintessential driving mechanism of the simulated MJO-like disturbances, but wind-induced surface heat exchange (WISHE) feedbacks are the primary driver of its eastward propagation. WISHE may also explain the faster Kelvin-like modes in the simulations. These conclusions are supported by a linear stability analysis of RCE states on an equatorial beta plane. © 2018 American Meteorological Society."
"13411455700;","Convective aggregation in realistic convective-scale simulations",2017,"10.1002/2017MS000980","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020442803&doi=10.1002%2f2017MS000980&partnerID=40&md5=0e1beefc5258b4619fe7b354fd9e2b53","To investigate the real-world relevance of idealized-model convective self-aggregation, five 15 day cases of real organized convection in the tropics are simulated. These include multiple simulations of each case to test sensitivities of the convective organization and mean states to interactive radiation, interactive surface fluxes, and evaporation of rain. These simulations are compared to self-aggregation seen in the same model configured to run in idealized radiative-convective equilibrium. Analysis of the budget of the spatial variance of column-integrated frozen moist static energy shows that control runs have significant positive contributions to organization from radiation and negative contributions from surface fluxes and transport, similar to idealized runs once they become aggregated. Despite identical lateral boundary conditions for all experiments in each case, systematic differences in mean column water vapor (CWV), CWV distribution shape, and CWV autocorrelation length scale are found between the different sensitivity runs, particularly for those without interactive radiation, showing that there are at least some similarities in sensitivities to these feedbacks in both idealized and realistic simulations (although the organization of precipitation shows less sensitivity to interactive radiation). The magnitudes and signs of these systematic differences are consistent with a rough equilibrium between (1) equalization due to advection from the lateral boundaries and (2) disaggregation due to the absence of interactive radiation, implying disaggregation rates comparable to those in idealized runs with aggregated initial conditions and noninteractive radiation. This points to a plausible similarity in the way that radiation feedbacks maintain aggregated convection in both idealized simulations and the real world. © 2017. The Authors."
"57193882808;","Towards global large eddy simulation: Super-parameterization revisited",2016,"10.2151/jmsj.2016-017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84988382933&doi=10.2151%2fjmsj.2016-017&partnerID=40&md5=2844d8207bea1fe693d2afae738ba2a0","This paper argues that a global large eddy simulation can be achieved through the application of the superparametrization (SP) methodology on massively parallel computers. SP was proposed over 15 years ago to improve the representation of deep convection and accompanying small-scale processes in large-scale models for the weather and climate. The main idea was to embed in all columns of the large-scale model (featuring horizontal grid lengths of the order of 100 km) a two-dimensional (2D) convection-permitting small-scale model with approximately a 1-km horizontal grid length and periodic lateral boundaries. We propose to expand this methodology by applying a high-spatial-resolution three-dimensional (3D) large-eddy simulation (LES) model as the SP model and by embedding it in all columns of a large-scale model with a horizontal grid length in the range of 10 to 50 km. The outer model can apply hydrostatic equations as typical global numerical weather prediction and climate models today and can simulate atmospheric processes down to the mesoscale, including organized convection. Small-scale processes, such as boundary-layer turbulence and convective drafts, can be simulated by embedded nonhydrostatic (e.g., anelastic) LES models. Although significantly more expensive than the traditional SP, SP LES is ideally suited to take advantage of parallel computation because of the minimal communication between LES models when compared to traditional domain-decomposition methodologies in parallel simulation. Moreover, as illustrated through the idealized 2D mock-Hadley cell simulations, LES models can feature different horizontal and vertical grids in various columns of the large-scale model, and thus target dominant cloud regimes in various geographical regions. Such a system allows an unstructured grid simulation with no additional model development. © 2016, Meteorological Society of Japan."
"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."
"22962457400;7401977103;","A discrete ordinate, multiple scattering, radiative transfer model of the venus atmosphere from 0.1 to 260 μm",2011,"10.1175/2011JAS3703.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959627524&doi=10.1175%2f2011JAS3703.1&partnerID=40&md5=0391f129eca492eb2e7ffc060aea73da","The authors describe a new radiative transfer model of the Venus atmosphere (RTM) that includes optical properties from nine gases and four cloud modes between 0.1 and 260 μm. A multiple-stream discrete ordinate flux solver is used to calculate solar and atmospheric infrared fluxes with a prescribed temperature profiles and calculate radiative-convective equilibrium temperatures using the model. Components of the RTM are validated using observations from Pioneer Venus and Venus Express. A visible bond albedo of 0.74 and subsolar surface visible flux of 50 W m-2 [4.0% of the top-of-atmosphere (TOA) insolation] are calculated for a suitable temperature and composition profile derived from the Venus International Reference Atmosphere. Solar fluxes are simulated over a range of latitudes and good agreement is found with results from the Pioneer Venus probes and Venera landers. TOA infrared fluxes are compared with Venus Express observations and found to compare well at all observed wavelengths. The RTM is used to calculate radiative heating rates and these calculated heating rates are compared with those prescribed in a modern Venus GCM. Modifications are suggested to improve the prescribed thermal forcing used in recent GCMs. Using a small family of numerical and physical configurations, little sensitivity to vertical resolution is found in the model. For suitable global mean solar forcing a surface temperature of 750 K at radiative-convective equilibrium is calculated, in good agreement with observations and other recent modeling efforts. © 2011 American Meteorological Society."
"14044750400;6701469150;7006728825;6701590980;8363135900;12766815800;","Observations of the evolution of the nocturnal and convective boundary layers and the structure of open-celled convection on 14 June 2002",2010,"10.1175/2010MWR3200.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958482949&doi=10.1175%2f2010MWR3200.1&partnerID=40&md5=9faf8e651f43618a24fbaaa5e61a55c4","The Boundary Layer Evolution (BLE) missions of the International H2O Project (IHOP_2002) were designed to provide comprehensive observations of the distribution of water vapor in the quiescent boundary layer and its evolution during the early morning. The case study discussed in this paper presents detailed observations of the development of the boundary layer from before sunrise through to the period of growth of the mature convective boundary layer (CBL) during the 14 June 2002 BLE mission. The large number of remote sensing platforms, including the multiple instruments collocated at the Homestead Profiling Site, provided a detailed set of measurements of the growth and structure of the CBL. The observations describe the classic evolution of a daytime CBL, beginning with a shallow nocturnal boundary layer (NBL) below the remnants of the previous day's mixed layer, or residual layer. The vertical distribution of humidity in these layers during the early morning was affected by advection of dry air and by gravity waves. About an hour after sunrise a CBL developed, and gradually deepened with time as it mixed out the NBL and residual layer. The growth of the top of the CBL was particularly well observed because of the strong vertical gradients in temperature, humidity, and aerosol concentration. As the CBL deepened and the average CBL wind speed decreased, the mode of convective organization evolved from horizontal convective rolls to open-celled convection. A unique set of detailed measurements of the structure of the open cells was obtained from multiple instruments including the Doppler-on-Wheels radar, the Mobile Integrated Profiling System wind profiler, and the Scanning Raman lidar. They showed the relationship between open cells, thermals, mantle echoes, and the CBL top. © 2010 American Meteorological Society."
"6508080531;7402750556;","Small-scale rainfall mechanisms for an idealized convective southerly flow over the Alps",2003,"10.1256/qj.02.85","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038684935&doi=10.1256%2fqj.02.85&partnerID=40&md5=df16b2bb0691a619f719c284a6770afa","Rain-producing flows over the south side of the Alps are investigated with an idealized high-resolution (2.5 km) numerical configuration where only three basic ingredients of typical heavy-precipitation situations have been retained: (1) a uniform and stationary southerly flow far upstream from the Alps, which drives (2) a conditionally unstable atmosphere towards (3) the real topography of the Alps and the surrounding secondary mountains. Attention is given to small-scale mechanisms of rainfall over the Po Plain and the Alpine slopes. These are linked with two orographically induced low-level wind jets: the easterly barrier-wind jet along the southern flank of the Alps and a south-easterly jet formed over the sea along the south-western flank of the Apennines and continuing over land up to the Alps. The specific role of the secondary relief upstream from the Alps in inducing or influencing these low-level flow features, and also in triggering organized convection, is studied by means of experiments on the sensitivity to topography. The idealized configuration also allows the advantages of a convection-resolving model for modelling precipitation distributions at the Alpine valley scale to be considered."
"7006422084;6602836578;","Analysis and numerical modelling of a frontal passage associated with thunderstorm development over the Po valley and the Adriatic sea",1992,"10.1007/BF01029569","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0000479493&doi=10.1007%2fBF01029569&partnerID=40&md5=af900ecc9f6a9ba6cffeb89ba96156ca","A case study is presented of the meteorological situation of 26 July 1987, when a moderate lee cyclone formed south of the Alps associated with a cold front moving from the northwest. A convective line developed over the Po valley and the northern Adriatic sea, slightly in advance of the position of the cold front which, over that area, was associated with a north-easterly low-level flow. The mesoscale situation over the Po valley before and after the frontal passage was complex, with different flow configurations and weather phenomena affecting the eastern and western portions of the region. The analysis of observations has been complemented by the results of numerical experiments run with a limited area, high resolution model, initialized using interpolated ECMWF analyses. Sensitivity experiments show the important roles played by the orography and by the condensation-evaporation processes in determining the mesoscale field environment favourable for the development of the organized convection. © 1992 Springer-Verlag."
"6701377983;8847661900;6603618743;7006076277;6602303799;23080482300;9536879500;6506471425;24502309100;","Variations of the stratospheric temperature along the limb of Uranus: Results of the 22 April 1982 stellar occultation",1985,"10.1016/0019-1035(85)90040-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0006762224&doi=10.1016%2f0019-1035%2885%2990040-5&partnerID=40&md5=d114553dbe6dbad61a96d2f3623a26f4","Stratospheric temperature profiles of Uranus were derived from the stellar occultation of 22 April 1982 in the pressure range 5-30 μbar. The observations were made at the European Southern Observatory, Chile, and at the Observatoire du Pic du Midi et de Toulouse, France with two telescopes in both sites. The study of these profiles confirms that Uranus' stratosphere is warmer than had been expected from radiative models (J. F. Appleby, 1980, Atmospheric Structures of the Giant Planets from Radiative-Convective Equilibrium Models. PhD. Thesis, State University of New York at Stony Brook) and that there has been a general increase of temperature since 1977 (R. G. French, J. L. Elliot, E. W. Dunham, D. A. Allen, J. H. Elias, J. A. Frogel, and W. Liller, 1983, Icarus 53, 399-414). Furthermore, the profiles exhibit a nonisothermal feature with a maximum temperature around the 8-μbar pressure level. The amplitude of this feature increases linearly with the diurnally averaged insolation 〈D〉 up to the observed value 〈D〉 ∼ 0.15. Moreover, the temperature at 8 μbar, as well as the mean stratospheric temperature, reaches a plateau around the equator of the planet which is far from maximum insolation. For a nominal abundance of methane ηCH4 ∼ 3 × 10-5 and normal incidence, the UV absorption could compete with the IR methane absorption bands at the pressure level 8 μbar. However, the high temperatures observed even at grazing incidence imply important circulation phenomena to isothermalize distant regions of the planet. Alternatively, the observed profiles may suggest that an optically thin aerosol layer distributed over one scale height is responsible for the temperature maximum at 8 μbar. The total mass of dust necessary to heat this region up significantly would be a small fraction (6 × 1010 g vs 5 × 1018 g) of the Uranian ring system, which appears then as a possible reservoir of dust. However, a falling rate of ∼1 msec-1 would deplete the rings in a short time (≈2 × 105 years) so that a dynamical process is needed to sustain the aerosol layer. © 1985."
"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."
"56450100300;7004479957;11939918300;7201504886;","Estimating Bulk Entrainment With Unaggregated and Aggregated Convection",2018,"10.1002/2017GL076640","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040573078&doi=10.1002%2f2017GL076640&partnerID=40&md5=c6bf7122ca59408e204e30a6a648a924","To investigate how entrainment is influenced by convective organization, we use the ICON (ICOsahedral Nonhydrostatic) model in a radiative-convective equilibrium framework, with a 1 km spatial grid mesh covering a 600 by 520 km2 domain. We analyze two simulations, with unaggregated and aggregated convection, and find that, in the lower free troposphere, the bulk entrainment rate increases when convection aggregates. The increase of entrainment rate with aggregation is caused by a strong increase of turbulence in the close environment of updrafts, masking other effects like the increase of updraft size and of static stability with aggregation. Even though entrainment rate increases with aggregation, updraft buoyancy reduction through entrainment decreases because aggregated updrafts are protected by a moist shell. Parameterizations that wish to represent mesoscale convective organization would need to model this moist shell. ©2017. American Geophysical Union. All Rights Reserved."
"56447483100;35209683700;7402324853;","A dynamical and statistical characterization of U.S. extreme precipitation events and their associated large-scale meteorological patterns",2017,"10.1175/JCLI-D-15-0910.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85012273892&doi=10.1175%2fJCLI-D-15-0910.1&partnerID=40&md5=22ea6de26be720553b73da74e85f103f","Regional patterns of extreme precipitation events occurring over the continental United States are identified via hierarchical cluster analysis of observed daily precipitation for the period 1950-2005. Six canonical extreme precipitation patterns (EPPs) are isolated for the boreal warm season and five for the cool season. The large-scale meteorological pattern (LMP) inducing each EPP is identified and used to create a ""base function"" for evaluating a climate model's potential for accurately representing the different patterns of precipitation extremes. A parallel analysis of the Community Climate System Model, version 4 (CCSM4), reveals that the CCSM4 successfully captures the main U.S. EPPs for both the warm and cool seasons, albeit with varying degrees of accuracy. The model's skill in simulating each EPP tends to be positively correlated with its capability in representing the associated LMP. Model bias in the occurrence frequency of a governing LMP is directly related to the frequency bias in the corresponding EPP. In addition, however, discrepancies are found between the CCSM4's representation of LMPs and EPPs over regions such as the western United States and Midwest, where topographic precipitation influences and organized convection are prominent, respectively. In these cases, the model representation of finer-scale physical processes appears to be at least equally important compared to the LMPs in driving the occurrence of extreme precipitation. © 2017 American Meteorological Society."
"54397273100;8502619500;35228711600;35619212800;56082285300;57190859090;","Long-term changes in the climatology of transient inverted troughs over the North American monsoon region and their effects on precipitation",2016,"10.1175/JCLI-D-15-0726.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983488694&doi=10.1175%2fJCLI-D-15-0726.1&partnerID=40&md5=f46b4f4690365b80ac50086a56cd2cc8","Transient inverted troughs (IVs) are a trigger for severeweather during theNorthAmericanmonsoon (NAM) in the southwest contiguous United States (CONUS) and northwest Mexico. These upper-tropospheric disturbances enhance the synoptic-scale and mesoscale environment for organized convection, increasing the chances for microbursts, straight-line winds, blowing dust, and flash flooding. This work considers changes in the track density climatology of IVs between 1951 and 2010. IVs are tracked as potential vorticity (PV) anomalies on the 250-hPa surface from a regional climate model that dynamically downscales the NCEP- NCAR Reanalysis 1. Late in the NAM season, a significant increase in IV track density over the 60-yr period is observed over Southern California and western Arizona, coupled with a slight decrease over northwest Mexico. Changes in precipitation are evaluated on days when an IV is observed and days without an IV, using high-resolution model-simulated precipitation estimates and CPC gridded precipitation observations. Because of changes in the spatial distribution of IVs during the 1951-2010 analysis period, which are associated with a strengthening of the monsoon ridge, it is suggested that IVs have played a lesser role in the initiation and organization of monsoon convection in the southwest CONUS during recent warm seasons."
"56562594400;7005702722;","A Lagrangian study of precipitation-driven downdrafts",2016,"10.1175/JAS-D-15-0222.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84958602366&doi=10.1175%2fJAS-D-15-0222.1&partnerID=40&md5=1791118a1a88b26949c3242af74a5fd6","Precipitation-driven downdrafts are an important component of deep convective systems. They stabilize the atmosphere by injecting relatively cold and dry air into the boundary layer. They have also been invoked as responsible for balancing surface latent and sensible heat fluxes in the heat and moisture budget of tropical boundary layers. This study is focused on precipitation-driven downdrafts and basic aspects of their dynamics in a case of radiative-convective equilibrium. Using Lagrangian particle tracking, it is shown that such downdrafts have very low initial heights, with most parcels originating within 1.5 km from the surface. The tracking is also used to compute the contribution of downdrafts to the flux of moist static energy at the top of the boundary layer, and it is found that this is on the same order of magnitude as the contribution due to convective updrafts, but much smaller than that due to turbulent mixing across the boundary layer top in the environment. Furthermore, considering the mechanisms driving the downdrafts, it is shown that the work done by rain evaporation is less than half that done by condensate loading. © 2016 American Meteorological Society."
"55807154400;8958009400;7006432091;","Latent heating characteristics of the MJO computed from TRMM Observations",2015,"10.1002/2014JD022530","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925014733&doi=10.1002%2f2014JD022530&partnerID=40&md5=2508985359f2d43b382aec7942015f77","The Tropical Rainfall Measurement Mission’s (TRMM) Spectral Latent Heating algorithm shows the contributions of different forms of convection to the latent heating profiles of the Madden-Julian Oscillation over the central Indian and West Pacific Oceans. In both oceanic regions, storms containing broad stratiform regions produce increased upper level heating during active Madden-Julian Oscillation (MJO) phases. The largest differences between the central Indian and West Pacific Ocean heating are associated with heating produced by convective elements. Examination of the most extreme forms of convection shows that mesoscale organized convection often produces at least as much latent heat as young vigorous deep convection. Heating from nonextreme (often midlevel-topped) convection is an important component of the MJO heating in both regions in all stages of the MJO. Over the central Indian Ocean the heating profile changes from having a maximum at 2 km due to nonextreme convection to a profile during the active stage that has two maxima:one at 3 km due to nonextreme convection and 6 km owing to numerous mature mesoscale storms with broad stratiform precipitation components. Over the West Pacific, the maxima at 3 and 6 km are present in all MJO stages, but the magnitude of the 6 km maximum sharply increases in the active MJO stage due to an increase in the number of storms with broad stratiform precipitation areas. © 2015. American Geophysical Union. All Rights Reserved."
"8658853400;6701538799;57195881858;","Numerical simulation of episodes of organized convection in tropical Northern Africa",2012,"10.1175/MWR-D-11-00330.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867976222&doi=10.1175%2fMWR-D-11-00330.1&partnerID=40&md5=66409c32f4cc5ef535613e0c36d72327","A large-domain convection-permitting numerical model is used to simulate episodes of deep convection, which are generated during the day over the Ethiopian Highlands and then propagate westward over the eastern and central Sahel region (5°-20°N) of northern Africa. The simulation comprises 12.5 days within the African Monsoon Multidisciplinary Analysis (AMMA) field campaign in 2006. During this period, long-lived precipitation episodes that survived beyond a single diurnal cycle occurred in the lee of the Ethiopian Highlands only every 2-3 days in both the simulation and observations. This contrasts with some other latitudinal corridors in the lee of major topography, such as the central United States, where long-lived heavy precipitation episodes frequently occur on successive nights. The intermittency of long-lived events for the current case occurs despite regular daily triggering of convection along the upstream orography, and is linked to strong lower-tropospheric stabilization and reduction of daytime surface sensible heat flux due to residual cloudiness in the wake of long-lived precipitation events during the previous diurnal cycle. The vertical shear that helps organize deep convection is also weakened in the wake of the long-lived events by temporary disruptions of the midtropospheric African easterly jet. The environments of mesoscale convection are presented for the eastern Sahel, a region where most Sahelian convection originates, but about which little is known at the mesoscale. The study describes the potential for early identification of long-lived convection episodes that are likely to have high impact on the central Sahel and West Africa. © 2012 American Meteorological Society."
"7006874359;7202119915;7005461477;57194974100;7003926380;23494417700;7004452985;","Characteristics of an African easterly wave observed during NAMMA",2010,"10.1175/2009JAS3141.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953280457&doi=10.1175%2f2009JAS3141.1&partnerID=40&md5=26a31b9f1d6d3d3b9d221d776d60b49c","The evolution of an African easterly wave is described using ground-based radar and ancillary datasets from three locations inWest Africa: Niamey, Niger (continental), Dakar, Senegal (coastal), and Praia, Republic of Cape Verde (oceanic). The data were collected during the combined African Monsoon Multidisciplinary Analyses (AMMA) and NASA AMMA (NAMMA) campaigns in August-September 2006. Two precipitation events originated within the wave circulation and propagated with the wave across West Africa. Mesoscale convective systems (MCSs) associated with these events were identified at all three sites ahead of, within, and behind the 700-mb wave trough. An additional propagating event was indentified that originated east of the wave and moved through the wave circulation. The MCS activity associated with this event did not show any appreciable change resulting from its interaction with the wave. The MCS characteristics at each site were different, likely due to a combination of life cycle effects and changes in relative phasing between the propagating systems and the position of low-level convergence and thermodynamic instability associated with the wave. At the ocean and coastal sites, the most intense convection occurred ahead of the wave trough where both high CAPE and low-level convergence were concentrated. At the continental site, convection was relatively weak owing to the fact that the wave dynamics and thermodynamics were not in sync when the systems passed through Niamey. The only apparent effect of the wave on MCS activity at the continental site was to extend the period of precipitation activity during one of the events that passed through coincident with the 700-mb wave trough. Convective organization at the land sites was primarily in the form of squall lines and linear MCSs oriented perpendicular to the low-level shear. The organization at the oceanic site was more complicated, transitioning from linear MCSs to widespread stratiform cloud with embedded convection. The precipitation activity was also much longer lived at the oceanic site due to the wave becoming nearly stationary near the Cape Verdes, providing an environment supportive of deep convection for an extended period. © 2010 American Meteorological Society."
"6506723397;7005120823;57195881858;6602351024;","Baroclinic transition of a long-lived mesoscale convective vortex",2009,"10.1175/2008MWR2651.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68249150802&doi=10.1175%2f2008MWR2651.1&partnerID=40&md5=901121da4c1fcbce8683e3670f38bb4a","The period 5-15 June 2003, during the field phase of the Bow Echo and Mesoscale Convective Vortex (MCV) Experiment (BAMEX), was noteworthy for the wide variety of mesoscale convective systems (MCSs) that occurred. Of particular interest was a long-lived MCV that formed in the trailing stratiform region of an MCS over west Texas at 0600 UTC 10 June. This MCV was noteworthy for its (i) longevity as it can be tracked from 0600 UTC 10 June to 1200 UTC 14 June, (ii) development of a surface cyclonic circulation and attendant -22- to -24-hPa sea level pressure perturbation, (iii) ability to retrigger convection and produce widespread rains over several diurnal heating cycles, and (iv) transition into a baroclinic surface cyclone with distinct frontal features. Baroclinic transition, defined here as the acquisition of surface fronts, occurred as the MCV interacted with a remnant cold front, left behind by a predecessor extratropical cyclone, over the Great Lakes region. Although the MCV developed well-defined frontal structure, which helped to focus heavy precipitation, weakening occurred throughout the baroclinic transition process. Energetics calculations indicated that weakening occurred as the diabatic and baroclinic energy conversion terms approached zero just prior and during baroclinic transition. This weakening can be attributed to (i) an increase in environmental wind shear, (ii) the development of a downshear tilt and associated anticyclonic vorticity advection over the surface low center, and (iii) the eastward relative movement of organized convection away from the MCV center. © 2009 American Meteorological Society."
"7003962569;7006514964;7006970286;6701540733;12805239400;6604017334;","Radiation in the atmosphere of venus",2007,"10.1029/176GM08","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880598913&doi=10.1029%2f176GM08&partnerID=40&md5=7804832728a765a4d322794f24e4efd8","This chapter reviews the observations of the radiative fluxes inside and outside the Venusian atmosphere, along with the available data about the planetary energy balance and the distribution of sources and sinks of radiative energy. We also briefly address the role of the heat budget on the atmospheric temperature structure, global circulation, thermodynamics, climate and evolution. We compare the main features of radiative balance on the terrestrial planets, and provide a general description of the radiative-convective equilibrium models used to study their atmospheres. We describe the physics of the greenhouse effect as it applies to the evolution of the Venusian climate, concluding with a summary of outstanding open issues. © 2007 by the American Geophysical Union."
"7402358349;7006095466;7005685786;7409792174;","Multiscale temporal variability of warm-season precipitation over North America: Statistical analysis of Radar measurements",2006,"10.1175/JAS3752.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749249605&doi=10.1175%2fJAS3752.1&partnerID=40&md5=d4faaf9b115d86f81c33898739742698","Directionally averaged time series of precipitation rates for eight warm seasons (1996-2003) over the continental United States derived from Next Generation Weather Radar (NEXRAD) measurements are analyzed using spectral decomposition methods. For the latitudinally average data, in addition to previously identified diurnal and semidiurnal cycles, the temporal spectra show cross-scale self-similarity and periodicity. This property is revealed by a power-law scaling with an exponent of -4/3 for the frequency band higher than semidiurnal and -3/4 for the 1-3-day band. For the longitudinally averaged series the scaling exponent for the frequency band higher than semidiurnal changes from -4/3 to 5/3 revealing anisotropic properties. The dominant periods and propagation speeds display temporal variability on about 1/2, 1, 4, 11, and 25 days. Composite patterns describing periods of <5 days display the eastward propagation characteristic of classical mesoscale convective organization. The tower-frequency (>5 days) patterns propagate westward suggesting the influence of large-scale waves, and both dominant periods and propagation speeds show marked interannual variability. The implied dependence between propagation and mean-flow <5 days is consistent with the macrophysics of warm-season convective organization, and extends known dynamical mechanisms to a statistical framework. © 2006 American Meteorological Society."
"7409838605;","Effects of downdrafts and mesoscale convective organization on the heat and moisture budgets of tropical cloud clusters. Part I: a diagnostic cumulus ensemble model",1989,"10.1175/1520-0469(1989)046<1517:eodamc>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024813972&doi=10.1175%2f1520-0469%281989%29046%3c1517%3aeodamc%3e2.0.co%3b2&partnerID=40&md5=46a521b8b0503b0e99bb41b107eefd01","The model adopts the spectral representation of a cumulus ensemble and includes the vertical momentum budgets for both convective-scale updrafts and downdrafts. The downdrafts are initiated and maintained by the loading and evaporation cooling effects of rainwater which is generated in the updrafts tilting from the vertical. A theory for determining the updraft tilting angle based on the stability analysis of the rainwater budget equation is presented. We find a remarkable correlation between the diagnosed updraft tilting angle and the degree of mesoscale convective organization observed by radar. -from Author"
"7409838605;7409598352;","Effects of downdrafts and mesoscale convective organization on the heat and moisture budgets of tropical cloud clusters. Part III: effects of mesoscale convective organization",1989,"10.1175/1520-0469(1989)046<1566:eodamc>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024784920&doi=10.1175%2f1520-0469%281989%29046%3c1566%3aeodamc%3e2.0.co%3b2&partnerID=40&md5=99367cd1c8abe1897cb1d16fb9b87453","The contributions from mesoscale circulations to the observed heat and moisture budget residuals are identified by eliminating the effects of the subsidence compensating the cumulus mass flux from these quantities. Then, the mesoscale contributions are objectively isolated from the observed budget residuals with the aid of a diagnostic cumulus ensemble model developed in Part I of this paper. The isolated mesoscale contributions clearly show warming and drying in the upper troposphere and cooling and moistening in the lower troposphere, indicating the condensation within the anvil cloud and evaporation of rainwater beneath the anvil. Large values of the thermodynamically diagnosed tilting angle of deep cumulus clouds appear well before the mesoscale convective organization is detected by radar, suggesting that there are thermodynamically preferred regions for the formation of organized cumulus convection. The tilting angle further increases as squall clusters develop. -from Authors"
"7103194443;","Cumulus dynamics: Local compensating subsidence and its implications for cumulus parameterization",1975,"10.1007/BF01592963","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0010133477&doi=10.1007%2fBF01592963&partnerID=40&md5=b9b9145697a9ed8a8e657c80fe1bbcc0","Observations of air flow in and around convective clouds are summarized and discussed in light of the requirements for parameterization of midlatitude convection. Both theory and observation indicate that a substantial portion of the compensating subsidence occurs as dry downdrafts in the immediate vicinity of convective clouds, which suggests that an additional physical mechanism is necessary in linking convection to the large scale. A conceptual three-dimensional model of midlatitude organized convection along with its implications for parameterization, particularly in mesoscale modeling, is presented. The effects of moist downdrafts are also considered and some differences between midlatitude and tropical convection are discussed. © 1975 Birkhäuser Verlag."
"55628587967;6507400558;55550388400;34870277200;7004978125;","Implementation and calibration of a stochastic multicloud convective parameterization in the NCEP Climate Forecast System (CFSv2)",2017,"10.1002/2017MS001014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027844288&doi=10.1002%2f2017MS001014&partnerID=40&md5=414d675bd1f64cbb042920104bc80295","A comparative analysis of fourteen 5 year long climate simulations produced by the National Centers for Environmental Predictions (NCEP) Climate Forecast System version 2 (CFSv2), in which a stochastic multicloud (SMCM) cumulus parameterization is implemented, is presented here. These 5 year runs are made with different sets of parameters in order to figure out the best model configuration based on a suite of state-of-the-art metrics. This analysis is also a systematic attempt to understand the model sensitivity to the SMCM parameters. The model is found to be resilient to minor changes in the parameters used implying robustness of the SMCM formulation. The model is found to be most sensitive to the midtropospheric dryness parameter (MTD) and to the stratiform cloud decay timescale (τ30). MTD is more effective in controlling the global mean precipitation and its distribution while τ30 has more effect on the organization of convection as noticed in the simulation of the Madden-Julian oscillation (MJO). This is consistent with the fact that in the SMCM formulation, midtropospheric humidity controls the deepening of convection and stratiform clouds control the backward tilt of tropospheric heating and the strength of unsaturated downdrafts which cool and dry the boundary layer and trigger the propagation of organized convection. Many other studies have also found midtropospheric humidity to be a key factor in the capacity of a global climate model to simulate organized convection on the synoptic and intraseasonal scales. © 2017. The Authors."
"55589313600;10042470700;6603581315;","Impact of deep convection on the isotopic amount effect in tropical precipitation",2017,"10.1002/2016JD025555","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85013220247&doi=10.1002%2f2016JD025555&partnerID=40&md5=f0a36b99b84b860f83dc33b535682cb8","The empirical “amount effect” observed in the distribution of stable water isotope ratios in tropical precipitation is used in several studies to reconstruct past precipitation. Recent observations suggest the importance of large-scale organized convection systems on amount effect. With a series of experiments with Community Atmospheric Model version 3.0 with water isotope tracers, we quantify the sensitivity of amount effect to changes in modeled deep convection. The magnitude of the regression slope between long-term monthly precipitation amount and isotope ratios in precipitation over tropical ocean reduces by more than 20% with a reduction in mean deep convective precipitation by about 60%, indicating a decline in fractionation efficiency. Reduced condensation in deep convective updrafts results in enrichment of lower level vapor with heavier isotope that causes enrichment in total precipitation. However, consequent increases in stratiform and shallow convective precipitation partially offset the reduction in the slope of amount effect. The net result is a reduced slope of amount effect in tropical regions except the tropical western Pacific, where the effects of enhanced large-scale ascent and increased stratiform precipitation prevail over the influence of reduced deep convection. We also find that the isotope ratios in precipitation are improved over certain regions in the tropics with reduced deep convection, showing that analyses of isotope ratios in precipitation and water vapor are powerful tools to improve precipitation processes in convective parameterization schemes in climate models. Further, our study suggests that the precipitation types over a region can alter the fractionation efficiency of isotopes with implications for the reconstructions of past precipitation. © 2017. American Geophysical Union. All rights reserved."
"14020255000;57192945770;56893431700;13204740600;","Sensitivity of supercell simulations to initial-condition resolution",2017,"10.1175/JAS-D-16-0098.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85009387040&doi=10.1175%2fJAS-D-16-0098.1&partnerID=40&md5=38620097f358242076c589303feb59a0","Observational and model resolution limitations currently preclude analysis of the smallest scales important to numerical prediction of convective storms. These missing scales can be recovered if the forecast model is integrated on a sufficiently fine grid, but not before errors are introduced that subsequently grow in scale and magnitude. This study is the first to systematically evaluate the impact of these initial-condition (IC) resolution errors on high-resolution forecasts of organized convection. This is done by comparing high-resolution supercell simulations generated using identical model settings but successively coarsened ICs. Consistent with the Warn-on-Forecast paradigm, the simulations are initialized with ongoing storms and integrated for 2 h. Both idealized and full-physics experiments are performed in order to examine how more realistic model settings modulate the error evolution. In all experiments, scales removed from the IC (wavelengths < 2, 4, 8, or 16 km) regenerate within 10-20 min of model integration. While the forecast errors arising from the initial absence of these scales become quantitatively large in many instances, the qualitative storm evolution is relatively insensitive to the IC resolution. It therefore appears that adopting much finer forecast (e.g., 250 m) than analysis (e.g., 3 km) grids for data assimilation and prediction would improve supercell forecasts given limited computational resources. This motivates continued development of mixed-resolution systems. The relative insensitivity to IC resolution further suggests that convective forecasting can be more readily advanced by improving model physics and numerics and expanding extrastorm observational coverage than by increasing intrastorm observational density. © 2017 American Meteorological Society."
"55519994900;23991212200;56297863500;6701835010;7202208382;","Impacts of cloud superparameterization on projected daily rainfall intensity climate changes in multiple versions of the Community Earth System Model",2016,"10.1002/2016MS000715","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84995687626&doi=10.1002%2f2016MS000715&partnerID=40&md5=a98ac573b26cb3dade27b11fd749e462","Changes in the character of rainfall are assessed using a holistic set of statistics based on rainfall frequency and amount distributions in climate change experiments with three conventional and superparameterized versions of the Community Atmosphere Model (CAM and SPCAM). Previous work has shown that high-order statistics of present-day rainfall intensity are significantly improved with superparameterization, especially in regions of tropical convection. Globally, the two modeling approaches project a similar future increase in mean rainfall, especially across the Inter-Tropical Convergence Zone (ITCZ) and at high latitudes, but over land, SPCAM predicts a smaller mean change than CAM. Changes in high-order statistics are similar at high latitudes in the two models but diverge at lower latitudes. In the tropics, SPCAM projects a large intensification of moderate and extreme rain rates in regions of organized convection associated with the Madden Julian Oscillation, ITCZ, monsoons, and tropical waves. In contrast, this signal is missing in all versions of CAM, which are found to be prone to predicting increases in the amount but not intensity of moderate rates. Predictions from SPCAM exhibit a scale-insensitive behavior with little dependence on horizontal resolution for extreme rates, while lower resolution (∼2°) versions of CAM are not able to capture the response simulated with higher resolution (∼1°). Moderate rain rates analyzed by the “amount mode” and “amount median” are found to be especially telling as a diagnostic for evaluating climate model performance and tracing future changes in rainfall statistics to tropical wave modes in SPCAM. © 2016. The Authors."
"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."
"54406513400;47861975900;35555506600;55078250400;54406790400;57189692419;55409862900;55486654300;55861537900;","Maritime Continent rainfall variability during the TRMM era: The role of monsoon, topography and El Niño Modoki",2016,"10.1016/j.dynatmoce.2016.05.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84974653316&doi=10.1016%2fj.dynatmoce.2016.05.004&partnerID=40&md5=4647742f8bdc07d7e559dae6c2577a0d","Rainfall is among the most important climatic elements of the Maritime Continent. The Maritime Continent rainfall climate is uniquely located in the world's most active convective area. Satellite data measured by the Tropical Rainfall Measuring Mission (TRMM) 3B43 based high-resolution rainfall products represent monthly Maritime Continent rainfall characteristics over 16 years. Several statistical scores were employed to analyse annual means, linear trends, seasonal means, and anomalous Maritime Continent rainfall characteristic percentages. The effects of land and topography on rainfall quantities were also studied and compared with the Global Precipitation Climatology Project (GPCP) gridded precipitation estimates which has low-resolution. Comparison also applied on linear correlation and partial correlation techniques to determine the relationship between rainfall and the El Niño Modoki and El Niño-Southern Oscillation (ENSO; hereafter conventional El Niño). The results show that north-south Maritime Continent precipitation is associated with and generated by the northwest and southeast monsoon patterns. In addition, the large-scale circulations are linked with heavy rainfall over this land-ocean region due to large-scale island-topography-induced convective organization. The rainfall responses to El Niño Modoki and conventional El Niño clearly indicated the times at which the conventional El Niño had a higher impact than El Niño Modoki, especially during northern winter and spring, and vice versa during northern fall, and similarly affect during northern summer. Furthermore, the dynamic movements of rainfall anomaly that are caused by El Niño Modoki and the conventional El Niño events spanned from the southwest during June-July-August (JJA) to throughout the northeast ending in March-April-May (MAM). © 2016 Elsevier B.V."
"7102875645;","Study of global warming by GFDL climate models",1998,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031803794&partnerID=40&md5=25348fee97bfa2ecc83ddc5359eaa17c","This paper is based on the commemorative lecture which was delivered at the award ceremony of the Volvo Environmental Prize. The author describes his early attempt to study the greenhouse effect using a one-dimensional model of radiative, convective equilibrium of the atmosphere. This is followed by the description of a recent study of global warming which employs a general circulation model of the coupled atmosphere-ocean-land surface system developed at the Geophysical Fluid Dynamics Laboratory (GFDL). In particular, the study attempts to elucidate the role of oceanic and land surface processes in shaping the response of surface air temperature to a gradual increase in atmospheric carbon dioxide (CO2)."
"6603263640;","The mean air flow as lagrangian dynamics approximation and its application to moist convection",2016,"10.1175/JAS-D-15-0284.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84994142371&doi=10.1175%2fJAS-D-15-0284.1&partnerID=40&md5=c39fdb8bf7bc556b98881c4017f9201a","This paper introduces the Mean Airflow as Lagrangian Dynamics Approximation (MAFALDA), a new method designed to extract thermodynamic cycles from numerical simulations of turbulent atmospheric flows. This approach relies on two key steps. First, mean trajectories are obtained by computing the mean circulation using height and equivalent potential temperature as coordinates. Second, thermodynamic properties along these trajectories are approximated by using their conditionally averaged values at the same height and θe. This yields a complete description of the properties of air parcels that undergo a set of idealized thermodynamic cycles. MAFALDA is applied to analyze the behavior of an atmosphere in radiative-convective equilibrium. The convective overturning is decomposed into 20 thermodynamic cycles, each accounting for 5% of the total mass transport. The work done by each cycle can be expressed as the difference between the maximum work that would have been done by an equivalent Carnot cycle and a penalty that arises from the injection and removal of water at different values of its Gibbs free energy. The analysis indicates that the Gibbs penalty reduces the work done by all thermodynamic cycles by about 55%. The cycles are also compared with those obtained for doubling the atmospheric carbon dioxide, which in the model used here leads to an increase in surface temperature of about 3.4 K. It is shown that warming greatly increases both the energy transport and work done per unit mass of air circulated. As a result, the ratio of the kinetic energy generation to the convective mass flux increases by about 20% in the simulations. © 2016 American Meteorological Society."
"56033418400;6505932008;","Latent heating and mixing due to entrainment in tropical deep convection",2014,"10.1175/JAS-D-13-0140.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893857538&doi=10.1175%2fJAS-D-13-0140.1&partnerID=40&md5=09ffd35d7619297bd9c87a4100c80ddb","Recent studies have noted the role of latent heating above the freezing level in reconciling Riehl and Malkus' hot tower hypothesis (HTH) with evidence of diluted tropical deep convective cores. This study evaluates recent modifications to theHTHthrough Lagrangian trajectory analysis of deep convective cores in an idealized, high-resolution cloud-resolving model (CRM) simulation that uses a sophisticated two-moment microphysical scheme. A line of tropical convective cells develops within a finer nested grid whose boundary conditions are obtained from a large-domain CRM simulation approaching radiative convective equilibrium (RCE). Microphysical impacts on latent heating and equivalent potential temperature (θe) are analyzed along trajectories ascending within convective regions of the high-resolution nested grid. Changes in θe along backward trajectories are partitioned into contributions from latent heating due to ice processes and a residual term that is shown to be an approximate representation of mixing. The simulations demonstrate that mixing with dry environmental air decreases θe along ascending trajectories below the freezing level, while latent heating due to freezing and vapor deposition increase θe above the freezing level. Latent heating contributions along trajectories from cloud nucleation, condensation, evaporation, freezing, deposition, and sublimation are also quantified. Finally, the source regions of trajectories reaching the upper troposphere are identified. Much of the air ascending within convective updrafts originates from above the lowest 2 km AGL, but the strongest updrafts are composed of air from closer to the surface. The importance of both boundary layer and midlevel inflow in moist environments is underscored in this study. © 2014 American Meteorological Society."
"57195556064;7101867299;","A simple dynamical model of cumulus convection for data assimilation research",2014,"10.1127/0941-2948/2014/0492","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924748440&doi=10.1127%2f0941-2948%2f2014%2f0492&partnerID=40&md5=63bf38a2ff0eb96b6aa019bb1a78694d","A simplified model for cumulus convection has been developed, with the aim of providing a computationally inexpensive, but physically plausible, environment for developing methods for convective-scale data assimilation. Key processes, including gravity waves, conditional instability and precipitation formation, are represented, and parameter values are chosen to reproduce the most important space and time scales of cumulus clouds. The model is shown to reproduce the classic life cycle of an isolated convective storm. When provided with a low amplitude noise source to trigger convection, the model produces a statistically steady state with cloud size and cloud spacing distributions similar to those found in radiative-convective equilibrium simulations using a cloud resolving model. Results are also shown for convection triggered by flow over an orgraphic obstacle, where depending on the wind speed two regimes are found with convection trapped over the mountain, or propagating downstream. The model features prognostic variables for wind and rain that can be used to compute synthetic observations for data assimilation experiments. © 2014 The authors."
"36015299300;7203025162;","Understanding ENSO regime behavior upon an increase in the warm-pool temperature using a simple ENSO model",2011,"10.1175/2010JCLI3635.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955022776&doi=10.1175%2f2010JCLI3635.1&partnerID=40&md5=12f09e368ff09816749102737423ed93","The regime behavior of the low-order El Niño-Southern Oscillation (ENSO) model, according to an increase in the radiative-convective equilibrium sea surface temperature (SST; Tr), is studied to provide a possible explanation for the observed increase in ENSO irregularity characterized by decadal modulation. During recent decades, a clear increasing trend of the warm-pool SST has been observed. In this study, the increase in the warm-pool maximum SST is interpreted as an increase in Tr following previous studies. A bifurcation analysis with Tr as a control parameter is conducted to reveal that the degree of ENSO irregularity in the model is effectively controlled by the equilibrium states of the model. At a critical value of Tr, bifurcation analysis reveals that period-doubling bifurcation occurs and an amplitude-modulated ENSO emerges. At this point, a subcycle appears within the preexisting ENSO cycle, which initiates decadal modulation of ENSO. As Tr increases further, nested oscillations are successively generated, illustrating clear decadal modulation of ENSO. The qualitative regime changes revealed in this study are supported by the observation of regime shifts in the 1970s. With increasing Tr, the mean zonal SST gradient increases, and the model adjusts toward a ""La Niña-like"" mean state. Further constraint with shoaling of the mean thermocline depth and increasing stratification causes ENSO to exhibit stronger amplitude modulation. Furthermore, the timing of the period-doubling bifurcation advances with these two effects. © 2011 American Meteorological Society."
"36449157300;36449278400;6603480361;7006532784;","Modelling deep convection and its impacts on the tropical tropopause layer",2010,"10.5194/acp-10-11175-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649603126&doi=10.5194%2facp-10-11175-2010&partnerID=40&md5=05b9a97ec57d0f0e006bc2d10e8c1038","The UK Met Office's Unified Model is used at a climate resolution (N216, ∼0.83°×∼0.56°, ∼60 km) to assess the impact of deep tropical convection on the structure of the tropical tropopause layer (TTL). We focus on the potential for rapid transport of short-lived ozone depleting species to the stratosphere by rapid convective uplift. The modelled horizontal structure of organised convection is shown to match closely with signatures found in the OLR satellite data. In the model, deep convective elevators rapidly lift air from 4-5 km up to 12-14 km. The influx of tropospheric air entering the TTL (11-12 km) is similar for all tropical regions with most convection stopping below ∼14 km. The tropical tropopause is coldest and driest between November and February, coinciding with the greatest upwelling over the tropical warm pool. As this deep convection is co-located with bromine-rich biogenic coastal emissions, this period and location could potentially be the preferential gateway for stratospheric bromine. © Author(s) 2010."
"35619212800;","Atmospheric boundary layer over the central and western equatorial Pacific Ocean observed during COARE and CEPEX",1997,"10.1029/97JC01191","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031414992&doi=10.1029%2f97JC01191&partnerID=40&md5=ec293937e40603baf79655d641f03986","The present study is based on aircraft data collected in the western and central equatorial Pacific as a part of the Coupled Ocean-Atmosphere Response Experiment (COARE) and the Central Equatorial Pacific Experiment (CEPEX). The purpose of this discussion is to provide some insight into the coupling of the atmosphere to the ocean in regions of light winds and high humidity, as well as near deep organized convection, and to compare and contrast these climatically important tropical regions. The results presented use both the aerial extent of cold cloud top temperatures and surface layer similarity to highlight the variation of the surface fluxes as a function of convective regimes. A wide range of convective conditions were encountered during the 5 months of COARE and CEPEX, ranging from deep, towering anvils to shallow trade cumuli. The variety of conditions sampled has provided a unique set of turbulence data over open ocean, which are compared to fundamental spectral forms. Results suggest that assumptions regarding surface layer processes based on a large-scale assessment of the convective conditions are likely to be inaccurate. For example, during free convective conditions, where buoyancy production dominates over mechanical production of turbulence in the boundary layer, surface heat and buoyancy fluxes are enhanced for the given wind conditions, compared to those observed for forced convection, due to transport by buoyant plumes. This highlights the importance of considering the effect of the buoyancy flux on the vertical velocity variance in light winds in the parameterization of the surface fluxes. For forced convective conditions, where cloud circulations cause enhanced mechanical turbulence and reduced buoyancy in the boundary layer, surface fluxes are enhanced, as are the scales of turbulent eddies, drawing surface heat and moisture away from the surface. As with buoyant plumes, this process needs to be considered by surface flux parameterizations early enough in the convective process in order to accurately represent the role of the surface in the development of convection. While the temperature of the warm pool region in COARE is found to be largely independent of local conditions measured by the aircraft, we observe that the warmest temperatures (>30°C) coincide exclusively with the lightest winds, which highlights the importance of wind-driven mixing in determining the thermal structure of the upper ocean. Copyright 1997 by the American Geophysical Union."
"7005814217;7202741460;","Some dynamical properties of idealized thermally-forced meridional circulations in the tropics",1990,"10.1007/BF01026813","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025590320&doi=10.1007%2fBF01026813&partnerID=40&md5=d7bc276a9f81ca24916d3f226f6c01d0","Through the use of a zonal balance model we investigate the properties of the tropical meridional circulation to a range of specified diabatic forcing fields for climatologically observed zonal winds. As in earlier studies, the solutions show that latent heat release away from the equator forces an asymmetric meridional circulation in response the anisotropy in the inertial stability parameter with respect to the meridional location of the forcing. The presence of strong zonal flows appears to play a relatively minor role in determining the magnitude and asymmetry of the meridional circulation, whereas the structure of the diabatic heating, particularly the meridional breadth, proves to be of much greater importance. A dynamic efficiency factor, which provides an analytic measure of the efficacy of diabatic heating at generating zonal kinetic energy, generally exhibits a meridionally symmetric structure except during Northern Hemisphere summer. This asymmetry gives rise to a pronounced sensitivity of zonal kinetic energy generation to the meridional location of ITCZ convection. Further examination of the flow pattern suggests that for zonal flows representative of those over the Indian Ocean during the Northern Hemisphere summer months, meridional displacements of the heating of less than 20° latitude can result in as much as an order of magnitude difference in the rate of kinetic energy generation. Solution of the balance system also implies the existence of a feedback mechanism, between zonally-organized convection and the energetics properties of the large-scale flow, that is highly sensitive to the meridional location of the convection. © 1990 Springer-Verlag."
"7202910232;","Satellite observations of the Southern Hemisphere monsoon during winter MONEX.",1983,"10.3402/tellusa.v35i3.11432","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021092007&doi=10.3402%2ftellusa.v35i3.11432&partnerID=40&md5=93eedfdc74f2bb2a63b0d228f984af28","Time-longitude strips of infrared GMS satellite imagery have been used to study the Southern Hemisphere summer monsoon during winter MONEX. This representation reveals a sudden monsoon onset in late December characterized by a transition to spatially organized convection. Active and break regions of the monsoon show a strong coherence in time but are very longitudinally dependent. -from Author"
"57198373559;","The roles of mean meridional motions and large-scale eddies in zonally averaged circulations.",1980,"10.1175/1520-0469(1980)037<0001:TROMMM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0018924517&doi=10.1175%2f1520-0469%281980%29037%3c0001%3aTROMMM%3e2.0.CO%3b2&partnerID=40&md5=5a56edbfe667f7585951ed66bf8a6331","A hierarchy of zonally averaged atmospheric models is used to study the role of mean meridional motions and large-scale eddies in determining the zonal climate. Five models are developed: a radiative-convective equilibrium model (no large-scale motion), a zonally uniform model(no longitudinal asymmetries), an energy balance model (parameterized energy transport), a model that combines the physics of the two previous models, and a full statistical-dynamic model (with parameterizations of eddy momentum transport as well as eddy sensible heat transport). -from Authors"
"15724418700;57194698592;","On the relative importance of radiative and dynamical heating for tropical tropopause temperatures",2017,"10.1002/2016JD026445","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021741468&doi=10.1002%2f2016JD026445&partnerID=40&md5=4f81381895ef3d2619925cd45cf4b001","The tropical tropopause layer (TTL) shows a curious stratification structure: temperature continues to decrease beyond the level of main convective outflow (~200 hPa) up to the cold point tropopause (~100 hPa), but the TTL is more stably stratified than the upper troposphere. A cold point tropopause well separated from the level of main convective outflow has previously been shown to be consistent with the detailed radiative balance in the TTL even without dynamical effects. However, the TTL is also controlled by adiabatic cooling due to large-scale upwelling within the Brewer-Dobson circulation, which creates the extremely low stratospheric water vapor content via freeze drying. Here we study the role of water vapor and ozone radiative heating on the detailed temperature structure of the TTL based on idealized single-column radiative-convective equilibrium simulations. An atmosphere without adiabatic cooling due to upwelling results in much higher stratospheric water vapor content; the resulting altered radiative heating structure is shown to push the TTL in a regime of radiative control by water vapor. The TTL structure is furthermore shown to be strongly sensitive to the altitude where ozone sharply transitions from tropospheric to stratospheric values. Adiabatic cooling due to upwelling is found to reduce the radiative control by water vapor, resulting primarily in a negative transport-radiation feedback. Conversely, the radiative control by ozone is enhanced due to upwelling-a positive transport-radiation feedback. The particularly strong ozone radiative effect may explain about half of the reported spread in cold point ~10 K) in current climate models. © 2017. American Geophysical Union. All rights reserved."
"6701670597;","Gregarious convection and radiative feedbacks in idealized worlds",2016,"10.1002/2016MS000651","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84971449687&doi=10.1002%2f2016MS000651&partnerID=40&md5=26a717e0aa0096898ff0612f50ac1bba","What role does convection play in cloud feedbacks? What role does convective aggregation play in climate? A flurry of recent studies explores “self-aggregation” of moist convection in diverse simulations using explicit convection and interactive radiation. The implications involve upper level dry areas acting as infrared windows—the climate system's “radiator fins.” A positive feedback maintains these: dry columns undergo radiative cooling which drives descent and further drying. If the resulting clumpiness of vapor and cloud fields depends systematically on global temperature, then convective organization could be a climate system feedback. How reconcilable and how relevant are these interesting but idealized studies?. © 2016. The Authors."
"36992744000;8866821900;","A reduced complexity framework to bridge the gap between AGCMs and cloud-resolving models",2016,"10.1002/2015GL066713","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84958061555&doi=10.1002%2f2015GL066713&partnerID=40&md5=881dc61b30d086241ff155e8a2670cf0","The role of convective parameterizations at high horizontal resolution and their impacts on clouds, circulation, and precipitation processes represent large uncertainties in atmospheric general circulation models (AGCMs). As the statistical equilibrium in which radiative cooling is balanced by convective heating, radiative-convective equilibrium (RCE) offers a simplified framework to investigate such uncertainties. The Community Atmosphere Model 5 is configured in a RCE setup that consists of an ocean-covered planet with diurnally varying, spatially uniform insolation with no rotation effects. A series of simulations are performed in which the planetary radius is incrementally reduced. Because of the homogeneity of the setup, the effect is to reduce grid spacing, mimicking increased resolution without increasing the number of grid points. The results suggest that the reduced planet approach is able to reproduce the behavior of convection from full high-resolution simulations. At grid spacing less than 20 km, convective motions are predominantly produced by resolved scales. © 2016. American Geophysical Union. All Rights Reserved."
"57189634238;8511991900;6506328135;8922308700;7102266120;","Roles of wind shear at different vertical levels: Cloud system organization and properties",2015,"10.1002/2015JD023253","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938208199&doi=10.1002%2f2015JD023253&partnerID=40&md5=ab0156397a52488dd521e3bc2a528196","Understanding critical processes that contribute to the organization of mesoscale convective systems (MCSs) is important for accurate weather forecasts and climate predictions. In this study, we investigate the effects of wind shear at different vertical levels on the organization and properties of convective systems using the Weather Research and Forecasting model with spectral bin microphysics. Based on a control run for a MCS with weak wind shear (Ctrl), we find that increasing wind shear at the lower troposphere (L-shear) leads to a more organized quasi-line convective system. Strong wind shear in the middle troposphere (M-shear) tends to produce large vorticity and form a mesocyclone circulation and an isolated strong storm that leans toward supercellular structure. By increasing wind shear at the upper vertical levels only (U-shear), the organization of the convection is not changed much, but the convective intensity is weakened. Increasing wind shear in the middle troposphere for the selected case results in a significant drying, and the drying is more significant when conserving moisture advection at the lateral boundaries, contributing to the suppressed convective strength and precipitation relative to Ctrl. Precipitation in the L-shear and U-shear does not change much from Ctrl. Evident changes of cloud macrophysical and microphysical properties in the strong wind shear cases are mainly due to large changes in convective organization and water vapor. The insights obtained from this study help us better understand the major factors contributing to convective organization and precipitation. © 2015. American Geophysical Union. All Rights Reserved."
"26536569500;","On the equivalence of two schemes for convective momentum transport",2012,"10.1175/JAS-D-12-068.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871952962&doi=10.1175%2fJAS-D-12-068.1&partnerID=40&md5=677624469da33f3c3fd47f4646393ebe","The Gregory-Kershaw-Inness (GKI) parameterization of convective momentum transport, which has a tunable parameter C, is shown to be identical to a parameterization with no pressure gradient force and a mass flux smaller by a factor of 1 2 C. Usingcloud-resolving simulations, the transilient matrix for momentum is diagnosed for deep convection in radiative-convective equilibrium. Using this transilient matrix, it is shown that the GKI scheme underestimates the compensating subsidence of momentumby a factor of 1 2 C, as predicted. This result is confirmed using a large-eddy simulation.©2012 American Meteorological Society."
"35435487400;7005446873;","Large-scale length and time-scales for use with stochastic convective parametrization",2012,"10.1002/qj.992","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864282046&doi=10.1002%2fqj.992&partnerID=40&md5=b23a6710d1dbdcbc9515e5ba77ecde06","Many numerical models for weather prediction and climate studies are run at resolutions that are too coarse to resolve convection explicitly, but too fine to justify the local equilibrium assumed by conventional convective parametrizations. The Plant-Craig (PC) stochastic convective parametrization scheme, developed in this paper, solves this problem by removing the assumption that a given grid-scale situation must always produce the same sub-grid-scale convective response. Instead, for each time step and grid point, one of the many possible convective responses consistent with the large-scale situation is randomly selected. The scheme requires as input the large-scale state as opposed to the instantaneous grid-scale state, but must nonetheless be able to account for genuine variations in the large-scale situation. Here we investigate the behaviour of the PC scheme in three-dimensional simulations of radiative-convective equilibrium, demonstrating in particular that the necessary space-time averaging required to produce a good representation of the input large-scale state is not in conflict with the requirement to capture large-scale variations. The resulting equilibrium profiles agree well with those obtained from established deterministic schemes, and with corresponding cloud-resolving model simulations. Unlike the conventional schemes, the statistics for mass flux and rainfall variability from the PC scheme also agree well with relevant theory and vary appropriately with spatial scale. The scheme is further shown to adapt automatically to changes in grid length and in forcing strength. © 2011 Royal Meteorological Society."
"25823623500;15132236700;6701346187;7102495313;","Large-scale dynamical response to subgrid-scale organization provided by cellular automata",2011,"10.1175/JAS-D-10-05028.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855838601&doi=10.1175%2fJAS-D-10-05028.1&partnerID=40&md5=caf63697532e3b58de1f3f88efb54b85","Because of the limited resolution of numerical weather prediction (NWP) models, subgrid-scale physical processes are parameterized and represented by gridbox means. However, some physical processes are better represented by amean and its variance; a typical example is deep convection, with scales varying fromindividual updrafts to organized mesoscale systems. This study investigates, in an idealized setting, whether a cellular automaton (CA) can be used to enhance subgrid-scale organization by forming clusters representative of the convective scales and thus yield a stochastic representation of subgrid-scale variability. The authors study the transfer of energy from the convective to the larger atmospheric scales through nonlinear wave interactions. This is done using a shallow water (SW) model initialized with equatorial wave modes. By letting a CA act on a finer resolution than that of the SWmodel, it can be expected tomimic the effect of, for instance, gravity wave propagation on convective organization. Employing the CA scheme permits the reproduction of the observed behavior of slowing down equatorial Kelvin modes in convectively active regions, while random perturbations fail to feed back on the large-scale flow. The analysis of kinetic energy spectra demonstrates that the CAsubgrid scheme introduces energy backscatter from the smallest model scales to medium scales. However, the amount of energy backscattered depends almost solely on the memory time scale introduced to the subgrid scheme, whereas any variation in spatial scales generated does not influence the energy spectra markedly. © 2011 American Meteorological Society."
"22954465900;6602908667;7402397262;14020534200;35103573800;7103201242;15726586900;","Westerly wind bursts and their relationship with ENSO in CMIP3 models",2011,"10.1029/2010JD015039","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951483207&doi=10.1029%2f2010JD015039&partnerID=40&md5=f01e4289b09662e6ce70cf9be13479ef","Equatorial westerly wind bursts (WWBs) and their relationship with El Niño-Southern Oscillation (ENSO) in the 18 climate models presented in the World Climate Research Programme's Coupled Model Intercomparison Project phase 3 (CMIP3) are examined. Some models depict a realistic eastward shift of collective occurrences of WWBs over the Pacific as the warm pool expands eastward. These models that depict the frequent western Pacific WWBs preceding El Niño peak, known to trigger or enhance El Niño, tend to reproduce westerly background states and ENSO more accurately. Thus the reproducibility of the westerly background states is suggested to be fundamental for WWB occurrences as well as the following El Niño. Although WWBs generate with active convection in most of the models as observations, various kinds of intraseasonal disturbances that cause the active convection are found. It is suggested that organized convection is essential for the WWB generation but is prepared by each model's own dominant mode in the tropics. Under global warming, WWBs tend to increase over the eastern Pacific and decrease over the Indian Ocean whereas the total number of WWBs does not change consistently. This might arise from an increase of short-period convective disturbances over the eastern Pacific due to a sea surface temperature increase. Although there is a weak relationship between changes in the ENSO amplitude and the eastern Pacific WWBs in general, good models reproducing the WWB-ENSO relationship in the current climate tend to show consistent changes, suggesting the possibility of the eastern Pacific WWBs to intensify ENSO. Copyright 2011 by the American Geophysical Union."
"6602729726;7005461477;","Surface rainfall-cold cloud fractional coverage relationship in TOGA COARE: A function of vertical wind shear",2000,"10.1175/1520-0493(2000)128<0407:SRCCFC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034112396&doi=10.1175%2f1520-0493%282000%29128%3c0407%3aSRCCFC%3e2.0.CO%3b2&partnerID=40&md5=8f139b2517da587f9fba42e9b8301432","Shipboard radar-derived rain rates and satellite-observed IR brightness temperatures have been used to examine the relationship between cold cloud fractional coverage for brightness temperatures &lt;235 K and areally averaged surface rainfall during the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). A nearly linear relationship was observed with a ratio of mean rain rate to fraction cold cloud coverage of approximately 1 mm h-1. This is in contrast to the GOES precipitation index (GPI) methodology, which assumes a proportionality (GPI slope coefficient) of 3 mm h-1. It was also observed that when considering 5-day timescales. the relationship between the cold cloud fractional coverage and surface rainfall exhibited considerable variability. This variability was in phase with the interseasonal oscillations (ISOs). During the convectively active phase of the ISOs, the deep vertical wind shear (700-150 mb) was strong and the convective organization was dominated by squall line type systems. Hence, the cold cloud fractional coverage tended to be greater than the area of rainfall, a large fraction of which was stratiform in nature. The GPI slope coefficient was typically less than 1 mm h-1 during these periods. During the suppressed phase of the ISOs, tropospheric shear was much weaker and the convective organization consisted primarily of isolated convective cells. The cold cloud fractional coverage was typically about equal to the raining area, which was split nearly evenly between convective and stratiform precipitation. This resulted in a significant increase in the GPI slope coefficient, typically greater than 2 mm h-1 during these suppressed phases. It is also shown that during COARE, the variability in the GPI slope coefficient can to a large extent be explained by variations in tropospheric wind shear."
"57192667753;15725353500;42662159500;7003855401;","A Uniform Retrieval Analysis of Ultra-cool Dwarfs. III. Properties of y Dwarfs",2019,"10.3847/1538-4357/ab16db","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068690170&doi=10.3847%2f1538-4357%2fab16db&partnerID=40&md5=f077d479c2b02bdad98fb483a03e8ff8","Ultra-cool brown dwarfs offer a unique window into understanding substellar atmospheric physics and chemistry. Their strong molecular absorption bands at infrared wavelengths, Jupiter-like radii, cool temperatures, and lack of complicating stellar irradiation make them ideal test beds for understanding Jovian-like atmospheres. Here, we report the findings of a uniform atmospheric retrieval analysis on a set of 14 Y- and T-type dwarfs observed with the Hubble Space Telescope Wide Field Camera 3 instrument. From our retrieval analysis, we find the temperature structures to be largely consistent with radiative-convective equilibrium in most objects. We also determine the abundances of water, methane, and ammonia, as well as upper limits on the alkali metals sodium and potassium. The constraints on water and methane are consistent with predictions from chemical equilibrium models, while those of ammonia may be affected by vertical disequilibrium mixing, consistent with previous works. Our key result stems from the constraints on the alkali metal abundances where we find their continued depletion with decreasing effective temperature, consistent with the trend identified in a previous retrieval analysis on a sample of slightly warmer late T-dwarfs in Line et al. (2017). These constraints show that the previously observed Y-J color trend across the T/Y transition is most likely due to the depletion of these metals, in accordance with predictions from equilibrium condensate rainout chemistry. Finally, we simulate future James Webb Space Telescope observations of ultra-cool dwarfs and find that the Near Infrared Spectrometer (NIRSpec) PRISM offers the best chance at developing high-precision constraints on fundamental atmospheric characteristics. © 2019. The American Astronomical Society. All rights reserved.."
"55778380300;36627288300;56402758400;56414357900;54979231000;57189220200;57061487100;23989037500;","Self-luminous and Irradiated Exoplanetary Atmospheres Explored with HELIOS",2019,"10.3847/1538-3881/ab1084","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067349514&doi=10.3847%2f1538-3881%2fab1084&partnerID=40&md5=3504fbb0903cc97867fc33f8b2b13cd4","We present new methodological features and physical ingredients included in the one-dimensional radiative transfer code HELIOS, improving the hemispheric two-stream formalism. We conduct a thorough intercomparison survey with several established forward models, including COOLTLUSTY and PHOENIX, and find satisfactory consistency with their results. Then, we explore the impact of (i) different groups of opacity sources, (ii) a stellar path length adjustment, and (iii) a scattering correction on self-consistently calculated atmospheric temperatures and planetary emission spectra. First, we observe that temperature-pressure (T-P) profiles are very sensitive to the opacities included, with metal oxides, hydrides, and alkali atoms (and ionized hydrogen) playing an important role in the absorption of shortwave radiation (in very hot surroundings). Moreover, if these species are sufficiently abundant, they are likely to induce nonmonotonic T-P profiles. Second, without the stellar path length adjustment, the incoming stellar flux is significantly underestimated for zenith angles above 80, which somewhat affects the upper atmospheric temperatures and the planetary emission. Third, the scattering correction improves the accuracy of the computation of the reflected stellar light by ∼10%. We use HELIOS to calculate a grid of cloud-free atmospheres in radiative-convective equilibrium for self-luminous planets for a range of effective temperatures, surface gravities, metallicities, and C/O ratios to be used by planetary evolution studies. Furthermore, we calculate dayside temperatures and secondary eclipse spectra for a sample of exoplanets for varying chemistry and heat redistribution. These results may be used to make predictions on the feasibility of atmospheric characterizations with future observations. © 2019. The American Astronomical Society. All rights reserved."
"55838270500;36810780500;56183114900;7402944490;55437594700;22235186000;","Diversity of the Pacific-Japan Pattern among CMIP5 Models: Role of SST Anomalies and Atmospheric Mean Flow",2018,"10.1175/JCLI-D-17-0541.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052791648&doi=10.1175%2fJCLI-D-17-0541.1&partnerID=40&md5=0b9b7bd851c6c44ab094638b09346932","This study investigates the reproducibility of the spatial structure and amplitude of the observed Pacific- Japan (PJ) pattern in the phase 5 of the Coupled Model Intercomparison Project (CMIP5) models. In particular, the role of sea surface temperature anomalies (SSTAs) and atmospheric mean flow in the diverse reproducibility of the PJ pattern among models is investigated. Based on the pattern correlation between simulated and observed PJ patterns, models are categorized into high and low correlation groups, referred to asHCGand LCG, respectively. The observed cold SSTAs in the western North Pacific (WNP) and equatorial central Pacific, organized convection and precipitation anomalies, and Rossby wave response are reproduced well in HCG models, whereas these features are not present in LCG models. The summer SSTAs are closely tied to the preceding El Niño-Southern Oscillation and its temporal evolution in the tropical Indo-Pacific Ocean in both observations and models, but the SSTAs in the Indian Ocean are weak in bothHCG and LCG, implying a weak Indian Ocean capacitor effect. As a result, the reproducibility of the amplitude of the WNP center of the PJ pattern is mainly modulated by the SSTAs and local air-sea feedback over the WNP in the models. On the other hand, a model with stronger climatological southerly along the coast of East Asia tends to produce more realistic amplitude of the midlatitude center of the PJ pattern with clearer poleward waveactivity fluxes due to more efficient local barotropic energy conversion from the mean flow. © 2018 American Meteorological Society."
"55949041700;12446578100;7004462660;57075093400;35413974900;","Stable Isotopes of Precipitation During Tropical Sumatra Squalls in Singapore",2018,"10.1002/2017JD027829","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045833938&doi=10.1002%2f2017JD027829&partnerID=40&md5=a4e17539781e33a5c5e9b3b1b33c817d","Sumatra Squalls, organized bands of thunderstorms, are the dominant mesoscale convective systems during the intermonsoon and southwest monsoon seasons in Singapore. To understand how they affect precipitation isotopes, we monitored the δ value of precipitation daily and continuously (every second and integrated over 30 s) during all squalls in 2015. We found that precipitation δ18O values mainly exhibit a “V”-shape pattern and less commonly a “W”-shape pattern. Variation in δ18O values during a single event is about 1 to 6‰ with the lowest values mostly observed in the stratiform zone, which agrees with previous observations and modeling simulations. Reevaporation can significantly affect δ values, especially in the last stage of the stratiform zone. Daily precipitation is characterized by periodic negative shifts in δ value, largely associated with the squalls rather than moisture source change. The shifts can be more than 10‰, larger than intraevent variation. Initial δ18O values of events are highly variable, and those with the lowest values also have the lowest initial values. Therefore, past convective activities in the upwind area can significantly affect the δ18O, and convection at the sampling site has limited contribution to isotopic variability. A significant correlation between precipitation δ18O value and regional outgoing longwave radiation and rainfall in the Asian monsoon region and western Pacific suggests that regional organized convection probably drives stable isotopic compositions of precipitation. A drop in the frequency of the squalls in 2015 is related to weak organized convection in the region caused by El Niño. ©2018. The Authors."
"56865242700;56014511300;57213995653;38561188200;","The Robust Relationship Between Extreme Precipitation and Convective Organization in Idealized Numerical Modeling Simulations",2017,"10.1002/2017MS001125","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85031431728&doi=10.1002%2f2017MS001125&partnerID=40&md5=7fe7583b7a693ab7edb20a419218f003","The behavior of tropical extreme precipitation under changes in sea surface temperatures (SSTs) is investigated with the Weather Research and Forecasting Model (WRF) in three sets of idealized simulations: small-domain tropical radiative-convective equilibrium (RCE), quasi-global “aquapatch”, and RCE with prescribed mean ascent from the tropical band in the aquapatch. We find that, across the variations introduced including SST, large-scale circulation, domain size, horizontal resolution, and convective parameterization, the change in the degree of convective organization emerges as a robust mechanism affecting extreme precipitation. Higher ratios of change in extreme precipitation to change in mean surface water vapor are associated with increases in the degree of organization, while lower ratios correspond to decreases in the degree of organization. The spread of such changes is much larger in RCE than aquapatch tropics, suggesting that small RCE domains may be unreliable for assessing the temperature-dependence of extreme precipitation or convective organization. When the degree of organization does not change, simulated extreme precipitation scales with surface water vapor. This slightly exceeds Clausius-Clapeyron (CC) scaling, because the near-surface air warms 10–25% faster than the SST in all experiments. Also for simulations analyzed here with convective parameterizations, there is an increasing trend of organization with SST. © 2017. The Authors."
"6701622352;8247122100;","Cloud-resolving large-eddy simulation of tropical convective development and surface fluxes",2015,"10.1175/MWR-D-14-00247.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943388786&doi=10.1175%2fMWR-D-14-00247.1&partnerID=40&md5=da94c842c793b1def84e5789b5e5a2c4","Cloud-resolving large-eddy simulations (LES) on a 500 km × 500 km periodic domain coupled to a thermodynamic ocean mixed layer are used to study the effect of large-scale moisture convergence M on the convective population and heat and moisture budgets of the tropical atmosphere, for several simulations with M representative of the suppressed, transitional, and active phases of the Madden-Julian oscillation (MJO). For a limited-area model without an imposed vertical velocity, M controls the overall vertical temperature structure. Moisture convergence equivalent to ~200 W m-2 (9 mm day-1) maintains the observed temperature profile above 5 km. Increased convective heating for simulations with higher M is partially offset by greater infrared cooling, suggesting a potential negative feedback that helps maintain the weak temperature gradient conditions observed in the tropics. Surface evaporation decreases as large-scale moisture convergence increases, and is only a minor component of the overall water budget for convective conditions representing the active phase of the MJO. Cold pools generated by evaporation of precipitation under convective conditions are gusty, with roughly double the wind stress of their surroundings. Consistent with observations, enhanced surface evaporation due to cold pool gusts is up to 40% of the mean, but has a small effect on the total moisture budget compared to the imposed large-scale moisture convergence."
"6507400558;57199689992;6603169474;","Convective momentum transport in a simple multicloud model for organized convection",2012,"10.1175/JAS-D-11-042.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863393334&doi=10.1175%2fJAS-D-11-042.1&partnerID=40&md5=b6a5e3fa9934e6472800f7c692d6b01e","Convective momentum transport (CMT) is the process of vertical transport of horizontal momentum by convection onto the environmental flow. The significance of CMT from mesoscale to synoptic- and planetaryscale organized cumulus convection has been established by various theoretical and observational studies. A new strategy mimicking the effect of unresolved mesoscale circulation based on the weak temperature gradient (WTG) approximation with a Gaussian profile to redistribute the heating due to parameterized cumulus convection at the subgrid scale is adopted here to construct a CMT parameterization for general circulation models (GCMs). Two main regimes of CMT are considered: an upscale squall-line regime and a downscale non-squall-line regime. An exponential probability distribution is used to select which of these two effects is active, conditional on the state of the large-scale shear. The shear itself is used as a measure of the persistence of mesoscale organized circulation due to the presence or not of tilted deep convective heating with lagged stratiform anvils. TheCMTmodel is tested in the simple case of the multicloud model of Khouider and Majda, used here as a toy GCM. Numerical simulations are performed here for the simple case without rotation, in a parameter regime where the multicloud model exhibits packets of convectively coupled gravity waves moving in one direction, at 17 m s -1, and planetary-scale wave envelopes moving in the opposite direction, at 4-6 m s -1, reminiscent of the Madden-Julian oscillation (MJO) and the associated embedded synopticscale superclusters. The results herein show that the inclusion of CMT intensifies both the synoptic-scale convectively coupled waves and the manifestation of planetary-scale waves in the multicloud model. This provides evidence that the present CMT model captures the essence of the physical mechanism through which kinetic energy is transferred from the subgrid-scale mesoscale circulation to the large-scale/resolved motion. Sensitivity simulations showed that two key parameters for the CMT parameterization are the relative strength of the parameterized stratiform anvils and the dimensional threshold used in the exponential distribution for the cumulus friction and the upscale CMT forcing resulting from organized subgrid mesoscale circulation. © 2012 American Meteorological Society."
"35568218100;7006621313;7006184606;","Signature of microphysics on spatial rainfall statistics",2011,"10.1029/2010JD015124","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960910834&doi=10.1029%2f2010JD015124&partnerID=40&md5=ccb940c3752d4872c4d68d86ed0141de","Previous studies have suggested that the statistical multiscale structure of rainfall can be parameterized in terms of thermodynamic descriptors of the storm environment, and such dependence has been successfully implemented in downscaling applications. In this paper we suggest that it is possible to adopt the raindrop terminal velocity as a physical parameter to explain to a large degree the statistical variability of convective rainfall over a range of scales. We examine this assertion by analysis of high-resolution simulations of an atmosphere in radiative-convective equilibrium performed using the Weather Research and Forecasting (WRF) model and prescribing different rain terminal velocity settings corresponding to small, slowly falling drops and large, quickly falling drops, respectively. The analysis has focused on the study of the dependence of some basic statistics of rainfall fields (probability distribution of convective rain cell areas, power spectra, and multiscale statistics of rainfall intensity) on the raindrop terminal velocity by using a well-documented and widely used atmospheric model. Possible applications of our results include downscaling of rainfall satellite measurements, conditional on limited microphysical information from dual-frequency spaceborne radars, and conversion of radar reflectivity to rain rate, conditional on drop size distribution inferred from the scaling parameters of the reflectivity fields. Copyright 2011 by the American Geophysical Union."
"57201810978;36705143500;","Abrupt seasonal migration of the ITCZ into the summer hemisphere",2008,"10.1175/2007JAS2367.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45849083197&doi=10.1175%2f2007JAS2367.1&partnerID=40&md5=542755998379f2f069c6c4809c7fbf48","Although the maximum of solar radiation at the top of the atmosphere moves gradually from one hemisphere to the other as part of the seasonal cycle, the intertropical convergence zone (ITCZ) moves abruptly into the summer hemisphere. An axisymmetric circulation model is developed to study this rapid transition. The model consists of an upper and lower layer of the Hadley circulation (HC), with the surface layer attached to a slab ocean and the lower layer connected to the upper layer by a constant lapse rate. The model is forced by solar heating, and the ITCZ is prescribed to coincide with the warmest sea surface temperature (SST). The collocation of tropical rainfall with warm SST allows the model ITCZ migration to be understood in terms of the relative influence of solar heating and atmospheric dynamics upon ocean temperature. Atmospheric dynamics allow the ITCZ to move off the equator by flattening the meridional temperature gradient that would exist in radiative-convective equilibrium. For the present-day tropical oceanic mixed layer depth and ITCZ width, the model exhibits an abrupt seasonal transition of the ITCZ across the equator. It is found that there are two determinative factors on the abrupt transition of the ITCZ: the nonlinear meridional advection of angular momentum by the circulation and ocean thermal inertia. As a result of nonlinear dynamics, angular momentum is well mixed, resulting in minimum atmospheric temperature at the equator and a similar equatorial minimum in SST. This inhibits convection over the equator while favoring a rapid seasonal transition of the ITCZ between the warmer surface water on either side of this latitude."
"15030854100;7006184606;56279190400;","Orographic effects on convective precipitation and space-time rainfall variability: Preliminary results",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-27644566441&partnerID=40&md5=a2d085943f4f726af441f59db3b662be","In the EFFS Project, an attempt has been made to develop a general framework to study the predictability of severe convective rainfall events in the presence of orography. Convective activity is embedded in orographic rainfall and can be thought as the result of several physical mechanisms. Quantifying its variability on selected area and time scales requires choosing the best physical representation of the rainfall variability on these scales. The main goal was (i) to formulate a meaningful set of experiments to compute the oscillation of variance due to convection inside model forecasts in the presence of orography and (ii) to give a statistical measure of it that might be of value in the operational use of atmospheric data. The study has been limited to atmospheric scales that span the atmosphere from 2 to 200 km and has been focused on extreme events with deep convection. Suitable measures of the changing of convection in the presence of orography have been related to the physical properties of the rainfall environment. Preliminary results for the statistical variability of the convective field are presented. © EGU."
"6701382162;7003553324;","Influence of upper-tropospheric inertial stability on the convective transport of momentum",2003,"10.1256/qj.00.08","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037880670&doi=10.1256%2fqj.00.08&partnerID=40&md5=641e2f2dd1ecf00884c3d55bd2bad29c","This study verifies the apparent high positive correlation between environmental and convection-relative inertial stability, and the transport of momentum by deep convection. We evaluate the hypothesis that convection structural aligns itself to best access the region of lowest upper-tropospheric inertial stability, while forming the lowest convective updraught-relative inertial stability. A numerical experiment evaluates variations in the structure, behaviour and momentum-transport characteristics of deep convection across the tropical-plume genesis region in the eastern Pacific. This unique region forms as a precursor to tropical-plume genesis, and possesses spatially varying very-low upper-tropospheric inertial stability (the potential vorticity locally reaches zero, or becomes slightly negative, in the northern hemisphere). Our results show that the vertical transport of horizontal momentum is predictable, given knowledge of the inertial-stability fields immediately surrounding the convection. It is conjectured that the preferred mode of convective organization (squall-line dominated versus more three-dimensional) near the intertropical convergence zone is a function of the ambient inertial stability. Therefore, as the convection organizes itself, it selects the most efficient access to regions of lowest inertial stability to enable its upper-tropospheric outflow."
"6701540733;7006184606;57206416522;","Radiative-convective model with an explicit hydrologic cycle - 1. Formulation and sensitivity to model parameters",1994,"10.1029/94jd00020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027949811&doi=10.1029%2f94jd00020&partnerID=40&md5=17005ff5f07008137e81a040d67768ef","A hydrological cycle is explicitly included in a one-dimensional radiative-convective equilibrium model which is coupled to a 'swamp' surface and tested with various cumulus convection schemes: the hard and soft convective adjustment schemes, the Kuo scheme, the Goddard Institute for Space Studies (GISS) (1974) model 1 scheme, the GISS (1983) model 2 scheme, and the Emanuel scheme. The essential difference between our model and other radiative-convective models is that in our model the moisture profile (but not cloudiness) is interactively computed by the cumulus convection scheme. (from Authors)"
"24485834000;57203492395;7005167347;36597856600;7004764167;8982748700;","The interaction between moist diabatic processes and the atmospheric circulation in African Easterly Wave propagation",2017,"10.1002/qj.3173","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85039412759&doi=10.1002%2fqj.3173&partnerID=40&md5=3827d146cfb32d10ed6b1dd7a550237c","An objective tracking algorithm is used to characterize the three-dimensional structure of African Easterly Waves (AEWs) in ERA-Interim reanalysis and a Met Office Unified Model (UM) simulation. A special focus is dedicated to the coupling of dynamical aspects of the wave and moist convection. The relation between baroclinic features of the wave and latent heating is explored. Latent heating at and slightly ahead of the wave trough is found to reinforce and sustain the anomalous wave circulation through potential vorticity (PV) generation and vortex stretching. The coupling of moist processes and the circulation takes place mainly through moisture convergence at lower mid-tropospheric levels, between 850 and 500 hPa. These findings are confirmed and examined in more detail in a case-study of a strong AEW based on high-resolution UM simulations. PV tracers are used to investigate how different moist diabatic processes invigorate the wave. Again moisture anomalies are found to be the main contributors to generating small-scale convergence centres and updraughts ahead of the trough at mid-tropospheric levels. Although buoyancy effects are ultimately responsible for the convective uplift, the results suggest that mesoscale circulations associated with the AEW dynamics are crucial in creating the small-scale moist static instabilities and vortices which are essential for the AEW maintenance. Boundarylayer mixing and advection from the northern Sahel may create pockets of high-PV air around the trough in some instances, but this mechanism of wave sustainment needs further investigation. © 2017 Crown Copyright. Quarterly Journal of the Royal Meteorological Society © 2017 Royal Meteorological Society"
"6504750541;6507400558;7004978125;56471241700;","Role of stratiform heating on the organization of convection over the monsoon trough",2016,"10.1007/s00382-016-3033-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84975704352&doi=10.1007%2fs00382-016-3033-7&partnerID=40&md5=e18d02df6b9b471c612688ef5f21a389","It has been recently demonstrated that stratiform heating plays a critical role in the scale-selection of organized tropical convection, in an aquaplanet version of a coarse-resolution atmospheric general circulation model coupled to a stochastic multicloud cumulus parameterization scheme. It is shown that Madden–Julian oscillation-like organization dominates when the model is tuned to produce strong and long lived stratiform heating while it gives rise to mostly convectively coupled waves in the case of weak and short lived stratiform clouds. The study is extended here to the case of an asymmetric forcing mimicking the migration of the intertropical convergence zone (ITCZ) during summer to understand the impact of changes in stratiform heating on the monsoon dynamics. Consistent with the equatorial ITCZ case, strong and long lived stratiform heating promotes northward and eastward moving intraseasonal disturbances while weak and short lived stratiform heating yields mostly westward propgating synoptic scale low pressure systems. Moreover, the underlying intraseasonal versus low pressure system activity seems to impact the strength and extend of the monsoon trough (MT). In the regime with intraseasonal activity the MT is much stronger and extends northward while in the low pressure system case MT is some what weaker in strength but extends further westward. In the low pressure dominated regime, the background vorticity and zonal wind profiles over the monsoon trough are consistent with the observations. © 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."
"56951139400;56520921400;","Origins of climate model discrepancies in atmospheric shortwave absorption and global precipitation changes",2015,"10.1002/2015GL065931","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946601041&doi=10.1002%2f2015GL065931&partnerID=40&md5=257015a6f676de49864d038116a1e9da","Projected increases in mean precipitation are constrained by the atmospheric energy budget through radiative-convective equilibrium. However, significant differences persist between climate models on the rate of increase in precipitation per unit warming, mostly arising from the clear-sky radiative response. While the intermodel spread in clear-sky longwave cooling has been explained by climate feedbacks, the sources of spread in clear-sky shortwave heating are still unclear. This article focuses on the latter. Since water vapor contributes most of the atmospheric shortwave absorption, both intermodel differences in its spatial distribution and in radiative transfer parameterizations are plausible hypotheses for the spread. This work reestablishes the primary contribution from water vapor relative to other shortwave-absorbing species and evaluates the validity of both hypotheses. It is found that the intermodel spread in shortwave absorption change most likely originates from the radiation schemes, possibly because of simplifications induced by their low spectral resolutions. Key Points Water vapor appears as the main cause of intermodel differences in atmospheric shortwave absorption Such discrepancies seem to come from the shortwave radiative transfer formulation for water vapor Errors arising from the coarse spectral resolution in radiation schemes could explain this spread © 2015. American Geophysical Union. All Rights Reserved."
"54881950900;35612769500;6603275645;7102567936;19639722300;","Radiative-convective equilibrium over a land surface",2014,"10.1175/JCLI-D-13-00654.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919683157&doi=10.1175%2fJCLI-D-13-00654.1&partnerID=40&md5=53f2e12f25f32f292289eb0417d89938","Radiative-convective equilibrium (RCE) describes an idealized state of the atmosphere in which the vertical temperature profile is determined by a balance between radiative and convective fluxes. While RCE has been applied extensively over oceans, its application over the land surface has been limited. The present study explores the properties of RCE over land using an atmospheric single-column model (SCM) from the Laboratoire de Météorologie Dynamique-Zoom, version 5B (LMDZ5B) general circulation model coupled in temperature and moisture to a land surface model using a simplified bucket model with finite moisture capacity. Given the presence of a large-amplitude diurnal heat flux cycle, the resultant RCE exhibits multiple equilibria when conditions are neither strictly water nor energy limited. By varying top-of-atmosphere insolation (through changes in latitude), total system water content, and initial temperature conditions the sensitivity of the land RCE states is assessed, with particular emphasis on the role of clouds. Based on this analysis, it appears that a necessary condition for the model to exhibit multiple equilibria is the presence of low-level clouds coupled to the diurnal cycle of radiation. In addition the simulated surface precipitation rate varies nonmonotonically with latitude as a result of a tradeoff between in-cloud rain rate and subcloud rain reevaporation, thus underscoring the importance of subcloud layer processes and unsaturated downdrafts. It is shown that clouds, especially at low levels, are key elements of the internal variability of the coupled land-atmosphere system through their feedback on radiation. © 2014 American Meteorological Society."
"36660830300;7102745183;","A Study of the role of daytime land-atmosphere interactions on nocturnal convective activity in the southern great plains during CLASIC",2014,"10.1175/JHM-D-14-0016.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907450700&doi=10.1175%2fJHM-D-14-0016.1&partnerID=40&md5=80cea4a5a3005e291cf860defc922806","This study examines whether and how land-atmosphere interactions can have an impact on nocturnal convection over the southern Great Plains (SGP) through numerical simulations of an intense nocturnal mesoscale convective system (MCS) on 19-20 June 2007 with the Weather Research and Forecasting (WRF) Model. High-resolution nested simulations were conducted using realistic and idealized land surfaces and two planetary boundary layer (PBL) parameterizations (PBLp): Yonsei University (YSU) and Mellor-Yamada-Janjić (MYJ). Differences in timing and amount of MCS precipitation among observations and model results were examined in the light of daytime land-atmosphere interactions, nocturnal prestorm environment, and cold pool strength. At the meso-γ scale, land cover and soil type have as much of an effect on the simulated prestorm environment as the choice of PBLp: MYJ simulations exhibit strong sensitivity to changes in the land surface in contrast to negligible impact in the case of YSU. At the end of the afternoon, as the boundary layer collapses, a more homogeneous and deeper PBL (and stronger low-level shear) is evident for YSU as compared to MYJ when initial conditions and land surface properties are the same. At the meso-β scale, propagation speed is faster and organization (bow echo morphology) and cold pool strength are enhanced when nocturnal PBL heights are higher, and there is stronger low-level shear in the prestorm environment independent of the boundary layer parameterization for different land surface conditions. A comparison of one- and two-way nested MYJ results demonstrates how daytime land-atmosphere interactions modify the prestorm environment remotely through advection of low-level thermodynamic features. This remote feedback strongly impacts the MCS development phase as well as its spatial organization and propagation velocity and, consequently, nocturnal rainfall. These results indicate that synoptic- and meso-α-scale dynamics can play an important role in determining the spatial and temporal scales over which precipitation feedbacks of land-atmosphere interactions emerge regionally. Finally, this study demonstrates the high degree of uncertainty in defining the spatial and temporal scales of land-atmosphere interactions where and when organized convection is dominant. © 2014 American Meteorological Society."
"54585176800;6507400558;7004978125;","Simple multicloud models for the diurnal cycle of tropical precipitation. Part I: Formulation and the case of the tropical oceans",2011,"10.1175/2011JAS3568.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81555213085&doi=10.1175%2f2011JAS3568.1&partnerID=40&md5=72b9f00b299f9d80f201504b66076192","The variation of tropical precipitation due to the diurnal cycle of solar heating is examined here in the context of two simple models for tropical convection. The models utilize three cloud types-congestus, deep, and stratiform-that are believed to characterize organized tropical convection and are based on the two first baroclinic modes of vertical structure plus a boundary layermode. The twomodels differ mainly in the way they treat the boundary layer dynamics. The first one is purely thermodynamical and is reduced to a single equation for the equivalent potential temperature θe connecting the boundary layer to the upper troposphere through downdrafts and to the surface through evaporation while the second uses full bulk boundary layer (FBBL) dynamics with a careful separation between sensible and latent heat fluxes and parameterization of nonprecipitating shallow cumulus. It turns out that in the case of the precipitation over the ocean where the Bowen ratio is small, both models yield a qualitatively similar solution, characterized by an overnight initiation and early morning peak in precipitation consistent with observations. The modeled diurnal cycle of precipitation over the ocean is divided into four cyclic phases: 1) a CAPE (re)- generation phase characterized by the enhancement of the boundary layer θe and moisture fluxes during midday and early afternoon that is followed by 2) a (re)moistening phase dominated by congestus heating during the late afternoon and moistening from downdrafts (due to detrainment of shallow cumulus, specifically in the FBBL model) and radiative cooling that lasts until midnight. 3) Deep convection is initiated around midnight when the midtroposphere is sufficiently moist and cool and (re)establishes the precipitation level near its radiative convective equilibrium (1 K day-1) and then 4) peaks with sunrise at 0600 LST to yield a precipitation maximum of roughly 2 K day-1 at around 0900 LST that dries the troposphere and consumes CAPE and closes the cycle. © 2011 American Meteorological Society."
"35460698500;24741232500;24740735800;7102981983;16643314500;7102001105;35477562700;","Influence of CO2 line profiles on radiative and radiative-convective equilibrium states of the Venus lower atmosphere",2010,"10.1029/2009JE003488","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954482032&doi=10.1029%2f2009JE003488&partnerID=40&md5=e79182600b7a0bb53792fefee895c25a","Influence of CO2 line profiles on vertical temperature distributions in the radiative and radiative-convective equilibria is examined in the Venus atmosphere. The CO2 opacity obtained by the Voigt (Lorentz) profile without the line cutoff is shown to be excessive since this opacity gives surface temperatures of about 860-1020 K in the radiative-convective equilibrium. On the other hand, the opacity obtained by the extremely sub-Lorentzian profiles of Pollack et al. (1993) and Tonkov et al. (1996) are underestimated; the surface temperature obtained with this opacity remains 600 K even in the radiative equilibrium. In this case, convection does not take place below the cloud layer because of the cloud opacity. It is also shown that Fukabori et al.'s (1986) and Meadows and Crisp's (1996) profiles, both of which have intermediate absorption coefficients, give temperature distributions close to the observed one in the radiative-convective equilibrium. In these cases, the convection layer extends from the surface to 30-50 km altitudes. Then, the temperature distribution below the cloud layer is determined by a dry adiabatic lapse rate and the temperature near the cloud bottom. The surface temperature in the radiative-convective equilibrium is strongly affected by the temperature near the cloud bottom in this situation. The detailed structure of the H2SO4 cloud must be taken into account to construct a realistic radiative transfer model. © 2010 by the American Geophysical Union."
"8229909000;","Prediction of monsoon rainfall with a nested grid mesoscale limited area model",2003,"10.1007/BF02709776","https://www.scopus.com/inward/record.uri?eid=2-s2.0-30244563069&doi=10.1007%2fBF02709776&partnerID=40&md5=31d946cbd5fcda60c893c5038da25d18","At the India Meteorological Department (IMD), New Delhi, a 12-level limited area model with 100 km horizontal resolution has been in use for weather forecasting. The present study uses this model together with a higher horizontal resolution (50 km) and vertical resolution (16-levels) model to examine the impact of increased resolution to simulate mesoscale features of rainfall during monsoon disturbances. The model was run for 22 days in the month of August 1997 and one week in September 1997 during three monsoon depressions and one cyclonic storm in the Bay of Bengal. The model results are compared with observations. The study shows that the model can capture mesoscale convective organization associated with monsoon depression."
"6603513407;7007177353;7005144444;","Detection and characterization of mesoscale cyclones in RADARSAT synthetic aperture radar images of the Labrador Sea",2000,"10.1080/07038992.2000.10874771","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034197078&doi=10.1080%2f07038992.2000.10874771&partnerID=40&md5=e415adf0a44cb07344e9aecf4b58888a","We consider RADARSAT synthetic aperture radar (SAR) ScanSAR wide mode images of several mesoscale cyclones that developed over the Labrador Sea during the winter of 1997/98. The three case studies demonstrate RADARSAT ScanSAR's capability to provide detailed information on the near surface wind field structure associated with these intense storms. The SAR images, along with accompanying meteorological conditions and thermal infrared images of the associated cloud patterns, show the spiral-form shear zones of the cyclones as well as nearby organized convection during various stages of cyclone development. In future, ocean wind fields retrieved from RADARSAT ScanSAR images could help to improve simulation models for polar and other mesoscale cyclones and could have a role in operational marine meteorology."
"57209147154;7102301816;","Comparison of the Madden-Julian oscillation (MJO) during the TOGA COARE IOP with a 15-year climatology",2000,"10.1029/1999JD901045","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033753557&doi=10.1029%2f1999JD901045&partnerID=40&md5=e6d77dbcfd7d36ed760c279646f3463e","During the Tropical Ocean-Global Atmosphere (TOGA) Coupled Ocean-Atmosphere Response Experiment (COARE) intensive observing period (IOP) (November 1992 to February 1993), two pronounced Madden-Julian oscillation (MJO) events were observed and have been intensively studied. To provide a necessary climatological basis for the case study as well as to evaluate how typical the COARE MJO cases are and to what degree conclusions made from these cases can be generalized, we compare the MJOs that occurred during the COARE IOP with a 15-year climatology. In this paper, along with a description of the characteristics of large-scale background including flow patterns, OLR and SST, the emphasis is placed on the intensity and propagation of the oscillations exhibited in organized convection and atmospheric circulation. Moreover, the maintenance of perturbation kinetic energy (PKE) associated with 30- to 60-day variability containing the MJOs is compared as well. The COARE IOP occurred in a lingering period between the persistence and the rejuvenation of the warm ENSO episode of 1992-1993. The intraseasonal oscillations in the convective activity and large-scale circulation are intensified during the IOP, and the maximum intensification is located in the region of central Pacific. Two MJO events in the COARE IOP are typical in terms of phase propagation. The major features of the energy transformation processes, such as the predominant role of the generation of the perturbation available potential energy (PAPE) by convective heating and its conversion into the PKE in the maintenance of the MJOs, found in the COARE IOP, are also displayed in the climatology indicating the generality of the results obtained from the COARE case study. Copyright 2000 by the American Geophysical Union."
"57199000416;7202208382;7202899330;","A simple radiative-convective model with a hydrological cycle and interactive clouds",1999,"10.1002/qj.49712555505","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032765966&doi=10.1002%2fqj.49712555505&partnerID=40&md5=d5d37eea5db64ce1bca4ac08e71baff0","We have developed a simple, analytically tractable radiative-convective model of the tropical climate system that includes an explicit moisture budget, a simple convection parametrization, a simple but physically based radiation parametrization, and interactive clouds. The underlying surface is assumed to be ocean. The model includes prognostic equations for the sea surface temperature and the vertically integrated water vapour content. A stratosphere in radiative equilibrium limits the depth of the convective layer. The lower-tropospheric lapse rate, surface evaporation rate, and clear-sky long-wave and short-wave radiative fluxes at the surface and the top of the atmosphere are determined as functions of the sea surface temperature and precipitable water only. The radiative-convective equilibria of the model atmosphere resemble the observed tropical climate, if realistic sea surface temperatures are prescribed. However, cloud-free radiative-convective equilibria of the tropical atmosphere-ocean system do not occur for realistic values of the surface albedo. When cloud radiative effects are included, the model produces radiative-convective equilibria that are unrealistically warm. With prescribed realistic lateral energy and moisture transports, however, the equilibria of the model are realistic."
"7402755025;7408612236;","Variability of radiative cooling during the Asian summer monsoon and its influence on intraseasonal waves",1997,"10.1175/1520-0469(1997)054<0941:VORCDT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031444329&doi=10.1175%2f1520-0469%281997%29054%3c0941%3aVORCDT%3e2.0.CO%3b2&partnerID=40&md5=cf355f9b18656ac4d39432b7405a5496","Infrared radiative cooling rates are calculated over the Asian summer monsoon between 5°S-20°N and 40°-135°E at a spatial resolution of 5° × 5° for the summer seasons of 1984 and 1987. A medium spectral resolution infrared radiative transfer model with specified temperature, moisture, clouds, and trace gas distributions is used to obtain the cooling rate profiles. Cloud distributions for the two summers are obtained from Indian National Satellite measurements. Seasonal mean and intraseasonal variations of clouds and radiative cooling rates over a 21-76-day range of periods are examined. The analysis identifies centers over the central and eastern Indian Ocean, and western Pacific Ocean, along the equator, and along 15°N, where seasonal mean cloud amounts range from 40% to 80% with cloud tops mostly in the middle and upper troposphere. Intraseasonal variability of clouds is also large over these centers (% variances &gt;25%). Consistently, seasonal mean cooling rates are at a maximum (3°-5°C day-1) in the upper troposphere between 300 and 400 mb, related to cloud-top cooling. The cooling rates below 400 mb are between 1° and 3°C day-1. The cooling rates exhibit intraseasonal amplitudes of 1.0°-1.50C day-1. The largest amplitudes are found between 300 and 500 mb, indicating that cooling rate variability is directly related to intraseasonal variability of convective clouds. Spatial distributions of clouds and cooling rates remain similar during the 1984 and 1987 summer seasons. However, during 1987, intraseasonal amplitudes of deep convective cloud amount and cooling rate over the Indian Ocean are 10%-15% larger than in 1984. It is shown that intraseasonal variability of cooling rates over the Indian Ocean can perturb convective heating by 10%-30% in the upper and lower troposphere. Based on a one-dimensional radiative-convective equilibrium model, it is estimated that the radiative damping timescale over the Indian Ocean region is ∼3 days. Based on this damping timescale and in conjunction with a model of equatorial Kelvin waves with first baroclinic mode, it is hypothesized that the variable cloud-radiative cooling rates can alter phase speeds of Kelvin waves by up to 60%. This helps explain why the frequency range of intraseasonal oscillations is so broad."
"7006698304;55469523400;57205096472;","Radiative Convective Equilibrium and Organized Convection: An Observational Perspective",2019,"10.1029/2018JD030092","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85066501388&doi=10.1029%2f2018JD030092&partnerID=40&md5=a70230217fef381450ec05081a14eb0a","Radiative convective equilibrium (RCE) describes a balance between the cooling of the atmosphere by radiation and the heating through latent heat release and surface heat fluxes. While RCE is known to provide an energetic constraint on the atmosphere at the global scale, little is known about the proximity of the atmosphere to RCE at smaller spatial and temporal scales, despite the common use of RCE in idealized modeling studies. Here we provide the first observational evaluation of the scales at which the atmosphere is near RCE. We further use observations of cloud characteristics to investigate the role played by organized convection in the RCE state. While the tropical atmosphere as a whole is near RCE on daily time scales and longer, this is not the case for any given location. Rather, areas in excess of 5,000 × 5,000 km2 must be considered to ensure the atmosphere remains near RCE at least 80% of the time, even for monthly averaged conditions. We confirm that RCE is established through the interplay of regions of active deep convection with high precipitation and weak radiative cooling and regions of subsiding motions leading to shallow cloud states that allow strong radiative cooling with no precipitation. The asymmetry in the maximum amount of radiative cooling and latent heating leads to the well-known ratio of small areas of precipitation and large regions of subsidence observed in the tropics. Finally, we show that organized deep convection does not occur when regions smaller than 1,000 × 1,000 km2 are near RCE. ©2019. American Geophysical Union. All Rights Reserved."
"56417341400;16636807900;26536569500;","FAT or FiTT: Are Anvil Clouds or the Tropopause Temperature Invariant?",2019,"10.1029/2018GL080096","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061436550&doi=10.1029%2f2018GL080096&partnerID=40&md5=fbbc9d185b1bc30a5fbab2c10fb77fdd","The Fixed Anvil Temperature (FAT) hypothesis proposes that upper tropospheric cloud fraction peaks at a special isotherm that is independent of surface temperature. It has been argued that a FAT should result from simple ingredients: Clausius-Clapeyron, longwave emission from water vapor, and tropospheric energy and mass balance. Here the first cloud-resolving simulations of radiative-convective equilibrium designed to contain only these basic ingredients are presented. This setup does not produce a FAT: the anvil temperature varies by about 40% of the surface temperature range. However, the tropopause temperature varies by only 4% of the surface temperature range, which supports the existence of a Fixed Tropopause Temperature (FiTT). In full-complexity radiative-convective equilibrium simulations, the spread in anvil temperature is smaller by about a factor of 2, but the tropopause temperature remains more invariant than the anvil temperature by an order of magnitude. In other words, our simulations have a FiTT, not a FAT. ©2019. American Geophysical Union. All Rights Reserved."
"55531609200;7006417494;","Deep convective organization, moisture vertical structure, and convective transition using deep-inflow mixing",2019,"10.1175/JAS-D-18-0122.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065041936&doi=10.1175%2fJAS-D-18-0122.1&partnerID=40&md5=2fb14cfb0e8f9e6cccd37f6dfbe4dce2","It is an open question whether an integrated measure of buoyancy can yield a strong relation to precipitation across tropical land and ocean, across the seasonal and diurnal cycles, and for varying degrees of convective organization. Building on previous work, entraining plume buoyancy calculations reveal that differences in convective onset as a function of column water vapor (CWV) over land and ocean, as well as seasonally and diurnally over land, are largely due to variability in the contribution of lower-tropospheric humidity to the total column moisture. Over land, the relationship between deep convection and lower-freetropospheric moisture is robust across all seasons and times of day, whereas the relation to boundary layer moisture is robust for the daytime only. Using S-band radar, these transition statistics are examined separately for mesoscale and smaller-scale convection. The probability of observing mesoscale convective systems sharply increases as a function of lower-free-tropospheric humidity. The consistency of this with buoyancybased parameterization is examined for several mixing formulations. Mixing corresponding to deep inflow of environmental air into a plume that grows with height, which incorporates nearly equal weighting of boundary layer and free-tropospheric air, yields buoyancies consistent with the observed onset of deep convection across the seasonal and diurnal cycles in the Amazon. Furthermore, it provides relationships that are as strong or stronger for mesoscale-organized convection as for smaller-scale convection. © 2019 American Meteorological Society."
"56520853700;7401945370;","Roles of Cloud Microphysics on Cloud Responses to Sea Surface Temperatures in Radiative-Convective Equilibrium Experiments Using a High-Resolution Global Nonhydrostatic Model",2018,"10.1029/2018MS001386","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052625880&doi=10.1029%2f2018MS001386&partnerID=40&md5=06de60c519fecbb68ad27026c0210d7a","The high-cloud amount responses to sea surface temperature (SST) changes were investigated based on simulations with radiative-convective equilibrium configuration using a high-resolution nonhydrostatic icosahedral atmospheric model. The radiative-convective equilibrium was calculated using a nonrotating sphere with Earth radius and a 14-km horizontal mesh with uniform SSTs of 300 and 304 K. Two types of cloud microphysics schemes (single- and double-moment bulk schemes) and two types of vertical layer configurations (38 and 78 layers) were tested. The radiatively driven circulation weakens with increasing SST in all simulation pairs due to the increase in the static stability, as suggested in previous studies. In contrast, the high-cloud amount increases in three simulation pairs and decreases in one pair. These indicate that the weakening of radiatively driven circulation with increasing SST does not always accompany the high-cloud amount decrease. We determined that the tropopause layer was wet (dry) in simulations that showed positive (negative) high-cloud cover responses. The radiatively driven upward moisture transport just below the wet tropopause layer increases with increasing SST in the simulation pairs with positive high-cloud amount responses, and this causes the supply of ice condensate to the lower layer through the sedimentation process, while this feedback was not observed in the simulation pair with the negative response. These indicate that the high-cloud cover response depends on the occurrence of the feedback and there is a feedback threshold among the variety of simulations. And furthermore, these speculate that whether the feedback mechanism is effective or not has the large impact on high-cloud responses in the real atmosphere. ©2018. The Authors."
"57212215393;8687063000;","Nonrotating Convective Self-Aggregation in a Limited Area AGCM",2018,"10.1002/2017MS001218","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045299854&doi=10.1002%2f2017MS001218&partnerID=40&md5=4ce1f57bb08fa91f0b9dcfd678653a90","We present nonrotating simulations with the Goddard Earth Observing System (GEOS) atmospheric general circulation model (AGCM) in a square limited area domain over uniform sea surface temperature. As in previous studies, convection spontaneously aggregates into humid clusters, driven by a combination of radiative and moisture-convective feedbacks. The aggregation is qualitatively independent of resolution, with horizontal grid spacing from 3 to 110 km, with both explicit and parameterized deep convection. A budget for the spatial variance of column moist static energy suggests that longwave radiative and surface flux feedbacks help establish aggregation, while the shortwave feedback contributes to its maintenance. Mechanism-denial experiments confirm that aggregation does not occur without interactive longwave radiation. Ice cloud radiative effects help support the humid convecting regions but are not essential for aggregation, while liquid clouds have a negligible effect. Removing the dependence of parameterized convection on tropospheric humidity reduces the intensity of aggregation but does not prevent the formation of dry regions. In domain sizes less than (5,000 km)2, the aggregation forms a single cluster, while larger domains develop multiple clusters. Larger domains initialized with a single large cluster are unable to maintain them, suggesting an upper size limit. Surface wind speed increases with domain size, implying that maintenance of the boundary layer winds may limit cluster size. As cluster size increases, large boundary layer temperature anomalies develop to maintain the surface pressure gradient, leading to an increase in the depth of parameterized convective heating and an increase in gross moist stability. © 2018. The Authors."
"26656668800;7004003763;6701546267;7004242319;7201888941;14018610000;7409792174;7403077486;","Dynamics of cloud-top generating cells in winter cyclones. Part III: Shear and convective organization",2017,"10.1175/JAS-D-16-0314.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029074521&doi=10.1175%2fJAS-D-16-0314.1&partnerID=40&md5=a5eb21674e536c2bf17c44e571e4a25e","Cloud-top generating cells (GCs) are a common feature atop stratiform clouds within the comma head of winter cyclones. The dynamics of cloud-top GCs are investigated using very high-resolution idealized WRF Model simulations to examine the role of shear in modulating the structure and intensity of GCs. Simulations were run for the same combinations of radiative forcing and instability as in Part II of this series, but with six different shear profiles ranging from 0 to 10 m s-1 km-1 within the layer encompassing the GCs. The primary role of shear was to modulate the organization of GCs, which organized as closed convective cells in simulations with radiative forcing and no shear. In simulations with shear and radiative forcing, GCs organized in linear streets parallel to the wind. No GCs developed in the initially stable simulations with no radiative forcing. In the initially unstable and neutral simulations with no radiative forcing or shear, GCs were exceptionally weak, with no clear organization. In moderate-shear (Δu/Δz = 2, 4 m s-1 km-1) simulations with no radiative forcing, linear organization of the weak cells was apparent, but this organization was less coherent in simulations with high shear (Δu/Δz = 6, 8, 10 m s-1 km-1). The intensity of the updrafts was primarily related to the mode of radiative forcing but was modulated by shear. The more intense GCs in nighttime simulations were either associated with no shear (closed convective cells) or strong shear (linear streets). Updrafts within GCs under conditions with radiative forcing were typically ~1-2 m s-1 with maximum values &lt; 4 m s-1. © 2017 American Meteorological Society."
"57195559046;55713076400;","The environment of aggregated deep convection",2017,"10.1002/2017MS000967","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028775543&doi=10.1002%2f2017MS000967&partnerID=40&md5=18763d2a019be768ef14e007e3722269","In this study, the environment of aggregated deep convection is investigated using a vector vorticity equation cloud-resolving model (VVM). Idealized experiments are performed under various environmental moisture with or without imposed vertical wind shear. Convective aggregation is then evaluated through diagnosing the 3-D size of an individual cloud from the model output using a six-connected segmentation method. The aggregated convection is recognized by a distinct mode with larger size in the cloud-size distribution. The results suggest that aggregated convection tends to develop when column relative humidity (CRH) is larger than 80% (67%) in nonshear (shear) cases. In addition, the degree of aggregation further increases with the increase of CRH. This aggregation process may be caused by an increasing probability of multicellular cloud structure under a moister environment. The results also suggest that there are at least five convective cores of such system. Analyses of precipitation distribution suggest that the most extreme instantaneous grid point precipitation mainly occurs within the largest convective clusters. © 2017. The Authors."
"57194201247;7004479957;6701346974;","Cloud and circulation feedbacks in a near-global aquaplanet cloud-resolving model",2017,"10.1002/2016MS000872","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019111827&doi=10.1002%2f2016MS000872&partnerID=40&md5=f56da88225433e8775d2af74657d3a3b","A near-global aquaplanet cloud-resolving model (NGAqua) with fixed meridionally varying sea-surface temperature (SST) is used to investigate cloud feedbacks due to three climate perturbations: a uniform 4 K SST increase, a quadrupled-CO2 concentration, and both combined. NGAqua has a horizontal resolution of 4 km with no cumulus parameterization. Its domain is a zonally periodic 20,480 km-long tropical channel, spanning 46°S–N. It produces plausible mean distributions of clouds, rainfall, and winds. After spin-up, 80 days are analyzed for the control and increased-SST simulations, and 40 days for those with quadrupled CO2. The Intertropical Convergence Zone width and tropical cloud cover are not strongly affected by SST warming or CO2 increase, except for the expected upward shift in high clouds with warming, but both perturbations weaken the Hadley circulation. Increased SST induces a statistically significant increase in subtropical low cloud fraction and in-cloud liquid water content but decreases midlatitude cloud, yielding slightly positive domain-mean shortwave cloud feedbacks. CO2 quadrupling causes a slight shallowing and a statistically insignificant reduction of subtropical low cloud fraction. Warming-induced low cloud changes are strongly correlated with changes in estimated inversion strength, which increases modestly in the subtropics but decreases in the midlatitudes. Enhanced clear-sky boundary layer radiative cooling in the warmer climate accompanies the robust subtropical low cloud increase. The probability distribution of column relative humidity across the tropics and subtropics is compared between the control and increased-SST simulations. It shows no evidence of bimodality or increased convective aggregation in a warmer climate. © 2017. The Authors."
"8538154900;6507113463;","Sensitivity of different convective parameterization schemes on tropical cyclone prediction using a mesoscale model",2014,"10.1007/s11069-013-0824-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905373212&doi=10.1007%2fs11069-013-0824-6&partnerID=40&md5=4c728273df4a47010b34f25d0b907214","Abstact: This study presents an intercomparison of four cumulus parameterization schemes (CPS) in the prediction of three cases of tropical cyclones in the north Indian Ocean. The study makes use of the Weather Research and Forecasting model of Non-hydrostatic Mesoscale Model version with a horizontal resolution of 27 km. The four deep cumulus schemes studied are (a) modified Kain-Fritsch (KF), (b) Betts-Miller-Janjic, (c) Simplified Arakawa-Schubert and (d) Grell-Devenyi Ensemble (GD) schemes. Three cases chosen for the study are unique cases with entirely different characteristics, synoptic/convective conditions and with varying levels of performance of the driving global model forecasts. The objective of the current study is to report the relative performance of the CPSs rather than the accuracy of the forecasts, under different convective conditions as reflected in the initial and boundary conditions. The study shows that generally KF scheme produced near-realistic track, intensification and the associated rainfall patterns and GD performed worst in terms of convective organisation and the sustained intensity. The impact of cumulus parameterization schemes and its performance vary widely among the three cases studied. The standard verification scores and the contribution of grid-scale precipitation towards the total rainfall by the mesoscale model are also compared between the different cases as well as the different cumulus parameterization schemes. The performance evaluation of the tropical cyclone predictions by the mesoscale model is influenced by not only the model physics but also the convective conditions as input into the model. © 2014 Springer Science+Business Media Dordrecht."
"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."
"8621896800;7004462778;6701674358;","Simulation of a serial upstream-propagating mesoscale convective system event over Southeastern South America using composite initial conditions",2009,"10.1175/2008MWR2617.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350337823&doi=10.1175%2f2008MWR2617.1&partnerID=40&md5=649b51ea6e1534433e979c24b83f7b38","Serial upstream-propagating mesoscale convective system (MCS) events over southeastern South America are important contributors to the local hydrologic cycle as they can provide roughly half of the total monthly summer precipitation. However, the mechanisms of upstream propagation for these events have not been explored. To remedy this situation, a numerical simulation of the composite environmental conditions from 10 observed serial MCS events is conducted. Results indicate that the 3-day simulation from the composite yields a reasonable evolution of the large-scale environment and produces a large region of organized convection in the warm sector over an extended period as seen in observations. Upstream propagation of the convective region is produced and is tied initially to the development and evolution of untrapped internal gravity waves. However, as convective downdrafts develop and begin to merge and form a surface cold pool in the simulation, the cold pool and its interaction with the environmental low-level flow also begins to play a role in convective evolution. While the internal gravity waves and cold pool interact over a several hour period to control the convective development, the cold pool eventually dominates and determines the propagation of the convective region by the end of the simulation. This upstream propagation of a South American convective region resembles the southward burst convective events described over the United States and highlights the complex interactions and feedbacks that challenge accurate forecasts of convective system evolution. © 2009 American Meteorological Society."
"7201605742;","A study of cloud clusters associated with a Baiu front by use of a mesoscale-convection-resolving model",2002,"10.2151/jmsj.80.595","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036703523&doi=10.2151%2fjmsj.80.595&partnerID=40&md5=29661b3a9a912f09945dc13236fc3515","Numerical experiments are performed to simulate and understand cloud clusters associated with a Baiu front observed over Kyushu and the East China Sea on 16 July 1993. The clusters treated in this study are those that are not associated with any synoptic-scale low. A numerical model used is a mesoscale-convection-resolving model (MCRM) that resolves mesoscale organized convection by a grid, and treats cumulus convection as the subgrid-scale (Yamasaki 2001). The primary objective of this study is to investigate to what degree the MCRM can describe cloud clusters, and mesoscale organized convection that constitutes the clusters. In this study the grid size is taken to be 5/36 degrees (about 15 km) in the finest grid area of the triply-nested grid model. A global objective analysis data of JMA is used as the initial condition (00UTC, 16 July). A numerical experiment is performed by use of the MCRM reffered above. For comparison, an old version of the MCRM (Yamasaki 1986) is also used, and an additional experiment is made for the case without parameterization of cumulus convection. The rainfall distributions at 12 hours after the initial time are compared with AMeDAS data, and with those from Peng and Tsuboki (1997) in which four cloud parameterization schemes are used. It is emphasized that the most important factor to prediction and understanding of the cloud cluster and rainfall over Kyushu at 12 hours is the eastward movement of a latently unstable area that exists at the initial time. A comparison of the results from the MCRM with those from the case without cumulus-scale parameterization shows that the effects of cumulus convection are not essential to the eastward movement of the unstable area and rainfall over Kyushu at 12 hours, but time evolution (behavior) of mesoscale organized convection and cloud clusters are quite different, depending on the inclusion of the cumulus-scale effects. The performance of the model as to how cloud clusters and mesoscale organized convection behave realistically under the given initial condition is discussed, based on the studies in the past and physical considerations."
"7201783608;7004854393;","Aspects of the parametrization of organized convection: Contrasting cloud-resolving model and single-column model realizations",2002,"10.1256/003590002321042126","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036127249&doi=10.1256%2f003590002321042126&partnerID=40&md5=1fb62483d4935e1eed0310b93602af8a","Cloud-resolving model (CRM) simulations of organized tropical convection observed in the Tropical Ocean/Global Atmosphere Coupled Ocean-Atmosphere Response Experiment are used to evaluate versions of the European Centre for Medium-Range Weather Forecasts convection and cloud schemes in single-column model simulations. Emphasis is placed upon the ability of the convection scheme to represent 'convective-scale' processes with typically mode-1 heating structures through the troposphere, together with a cloud scheme representing the 'stratiform (mesoscale) component' with upper-level heating and low-level cooling due to the evaporation of precipitation. While diagnosis of convective and stratiform precipitation is sensitive to the sampling criteria applied to the CRM, vertical structures of the mass and heat budgets are robust. Using diagnostics from the CRM simulations as a guide, revisions to the convection and cloud schemes are suggested in order to enable the parametrization to represent the two scales. The study suggests that a mass-flux convection scheme linked via detrainment to a prognostic treatment of cloud can represent organized convection, provided that the upward motion in the upper-level stratiform cloud is considered."
"7406671641;","Oceanic Regulation of the Atmospheric Walker Circulation",1997,"10.1175/1520-0477(1997)078<0407:OROTAW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030722081&doi=10.1175%2f1520-0477%281997%29078%3c0407%3aOROTAW%3e2.0.CO%3b2&partnerID=40&md5=31500d5422784a99c78ca5d83ed30d67","A coupled theory is proposed to account for the magnitude of the Walker circulation in the tropical Pacific. It is suggested that the Pacific Walker circulation is at a saturation state, at which the zonal sea surface temperature difference is bounded by about a quarter of the latitudinal difference of the radiative-convective equilibrium sea surface temperature."
"7403544649;","An economical scheme for the vertical integral of atmospheric emission in longwave radiative transfer",1989,"10.2151/jmsj1965.67.6_1047","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0009607139&doi=10.2151%2fjmsj1965.67.6_1047&partnerID=40&md5=405676f30653904643dc36a33cac58e3","A computationally fast scheme has been developed which accurately evaluates the vertical integral of the transmission function for longwave radiative transfer, incorporating with the multi-parameter random model. In this scheme transmittances are calculated only between the half-levels of the vertical coordinate, while the Planck fluxes are evaluated at both the half- and full-levels. The vertical integral in one layer can be represented with two terms; one is for a temperature profile with no inversion and the other for a profile with inversion. The validity of this scheme has been investigated by calculating temperature profiles in radiative and radiative-convective equilibria. It has been found that this scheme can accurately evaluate the cooling rates at levels with extreme temperatures near the tropopause and stratopause, and that the temperature profiles contain no fluctuation due to two-grid noise. © 1989, Meteorological Society of Japan."
"6602286842;","Heating by organized convection as a source of polar low intensification",1987,"10.1111/j.1600-0870.1987.tb00317.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981671409&doi=10.1111%2fj.1600-0870.1987.tb00317.x&partnerID=40&md5=68c4a544695297cd1058492eefd3a544","The paper discusses some observed characteristics which have not been taken into account in previous theoretical studies. For instance, a well‐mixed convective boundary layer is a common feature of the synoptic situation when polar lows are observed. However, in the polar lows themselves, the convection seems to reach much higher levels. Also, many polar lows have a characteristic central domain with especially strong winds and large vorticity. A simple linear CISK model is used to estimate the intensification caused by the convection. The model is based on constraints imposed by the assumption of a well‐mixed convective layer. Elements of the cloud physics are used to explain observed characteristics of clouds and precipitation. Finally, it is shown that additional growth rate may be expected if CISK is present in an environment of large relative vorticity. An observed case is studied in the light of the general ideas set forth in this paper. 1987 Blackwell Munksgaard"
"35203870600;36705265400;55614754800;23970271800;6506594339;11939918300;","How organized is deep convection over Germany?",2019,"10.1002/qj.3552","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85069891620&doi=10.1002%2fqj.3552&partnerID=40&md5=444e1cbe7e636956991305d4652f6be2","Deep moist convection shows a tendency to organize into mesoscale structures. To be able to understand the potential effect of convective organization on the climate, one needs first to characterize organization. In this study, we systematically characterize the organizational state of convection over Germany based on two years of cloud-top observations derived from the Meteosat Second Generation satellite and of precipitation cores detected by the German C-band radar network. The organizational state of convection is characterized by commonly employed organization indices, which are mostly based on the object numbers, sizes and nearest-neighbour distances. According to the organization index Iorg, cloud tops and precipitation cores are found to be in an organized state for 69% and 92% of the time, respectively. There is an increase in rainfall when the number of objects and their sizes increase, independently of the organizational state. Case-studies of specific days suggest that convectively organized states correspond to either local multi-cell clusters, with less numerous, larger objects close to each other, or to scattered clusters, with more numerous, smaller organized objects spread out over the domain. For those days, simulations are performed with the large-eddy model ICON with grid spacings of 625, 312 and 156 m. Although the model underestimates rainfall and shows a too large cold cloud coverage, the organizational state is reasonably well represented without significant differences between the grid spacings. © 2019 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"55823467500;57204886915;55717244800;8971211200;","Do We Need to Parameterize Mesoscale Convective Organization to Mitigate the MJO-Mean State Trade-Off?",2019,"10.1029/2018GL080314","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062321359&doi=10.1029%2f2018GL080314&partnerID=40&md5=b438be8dc95369d2be89be0f612b07a7","Modifications in cumulus parameterizations that improve Madden-Julian oscillation (MJO) simulation tend to degrade the mean state—known as the MJO-mean state trade-off. The impacts of parameterizing mesoscale convective organization on the relationship between the MJO and the mean state simulation fidelity are examined. A series of experiments are made with a general circulation model that parameterizes the mesoscale convective organization and simulates well both the MJO and the mean state. In the control simulation, a prognostic nondimensional variable (Ω) represents the degree of convective organization. In order to examine the effect of the parameterized convective organization, fixed Ω values are imposed in a series of constrained experiments. The fixed-Ω simulations show a negative relationship between the MJO and the mean state simulation fidelity. The control simulation is deviated from the negative relationship, suggesting the parameterized mesoscale convective organization helps general circulation models to mitigate the MJO-mean state trade-off. ©2019. American Geophysical Union. All Rights Reserved."
"7006184606;","Inferences from simple models of slow, convectively coupled processes",2019,"10.1175/JAS-D-18-0090.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060033497&doi=10.1175%2fJAS-D-18-0090.1&partnerID=40&md5=bbce613dab42e9a7a6eedc065ce8baa5","A framework for conceptual understanding of slow, convectively coupled disturbances is developed and applied to several canonical tropical problems, including the water vapor content of an atmosphere in radiative-convective equilibrium, the relationship between convective precipitation and column water vapor, Walker-like circulations, self-aggregation of convection, and the Madden-Julian oscillation. The framework is a synthesis of previous work that developed four key approximations: boundary layer energy quasi equilibrium, conservation of free-tropospheric moist and dry static energies, and the weak temperature gradient approximation. It is demonstrated that essential features of slow, convectively coupled processes can be understood without reference to complex turbulent and microphysical processes, even though accounting for such complexity is essential to quantitatively accurate modeling. In particular, we demonstrate that the robust relationship between column water vapor and precipitation observed over tropical oceans does not necessarily imply direct sensitivity of convection to free-tropospheric moisture. We also show that to destabilize the radiative-convective equilibrium state, feedbacks between radiation and clouds and water vapor must be sufficiently strong relative to the gross moist stability. © 2019 American Meteorological Society."
"57034069700;35509639400;","On the Interplay Between Convective Aggregation, Surface Temperature Gradients, and Climate Sensitivity",2018,"10.1029/2018MS001406","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058690710&doi=10.1029%2f2018MS001406&partnerID=40&md5=22e521dae65d78317cb87a9ba0c433ad","This study explores the extent to which convective aggregation interacts with sea surface temperature (SST) and affects climate sensitivity. For this purpose, radiative-convective equilibrium simulations are run with a general circulation model coupled to an ocean mixed layer, and several types of perturbations are imposed to the ocean-atmosphere system. Convective aggregation turns out to be much more sensitive to temperature in coupled experiments than in prescribed SST experiments. But changes in convective aggregation induced by a doubling of the CO 2 concentration are always smaller than changes associated with the transition from a non-aggregated to an aggregated state. If aggregation changes were acting alone, they would exert a strong negative feedback on global mean surface temperature. However, in a coupled framework, aggregation changes interact with the SST and generate SST gradients that strengthen the positive low-cloud feedback associated with changes in SST pattern. This overcompensates the negative feedback due to aggregation changes and leads to a larger equilibrium climate sensitivity than in the absence of SST gradients. Although this effect might be model specific, interactions between convective aggregation and the spatial distribution of SST appear crucial to assess the impact of convective aggregation on climate sensitivity. ©2018. The Authors."
"55622802000;57205257707;6603499076;","A wavelet-based analysis of convective organization in ICON large-eddy simulations",2018,"10.1002/qj.3409","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058052877&doi=10.1002%2fqj.3409&partnerID=40&md5=8f0ac29750a19d753b26d0f3adb911de","Wavelet spectra of rain rates are used to characterize convective organization in high-resolution simulations (horizontal grid spacing 156 m) with the large-eddy model ICON-LEM over Germany. Scattered convection takes place on scales between 1.2 and 4.8 km, while organized structures like supercells or mesoscale convective systems act on scales above 4.8 km. Organization of convection within squall lines is visible in the spectra as spectral energy is increased in certain directions. We further investigate the dynamical properties that relate to convective organization, and highlight the role of parameters such as CAPE and wind shear. Preferred spatial scale, average convective rain rate and anisotropy as inferred from the wavelet spectra are important characteristics to quantify convective organization. They are used to introduce a wavelet-based organization index (WOI). Compared with other indices for convective organization, WOI does not require the definition of objects. Using the WOI we are able to distinguish organized from non-organized convection. © 2018 Royal Meteorological Society"
"56951139400;51864663400;56520921400;","Simultaneous characterization of mesoscale and convective-scale tropical rainfall extremes and their dynamical and thermodynamic modes of change",2017,"10.1002/2017MS001033","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028930026&doi=10.1002%2f2017MS001033&partnerID=40&md5=1aca73ffd89116727c4e553af2304a7a","The Superparameterized Community Atmosphere Model (SPCAM) is used to identify the dynamical and organizational properties of tropical extreme rainfall events on two scales. We compare the mesoscales resolved by General Circulation Models (GCMs) and the convective scales resolved by Cloud-Resolving Models (CRMs) to reassess and extend on previous results from GCMs and CRMs in radiative-convective equilibrium. We first show that the improved representation of subgridscale dynamics in SPCAM allows for a close agreement with the 7%/K Clausius-Clapeyron rate of increase in mesoscale extremes rainfall rates. Three contributions to changes in extremes are quantified and appear consistent in sign and relative magnitude with previous results. On mesoscales, the thermodynamic contribution (5.8%/K) and the contribution from mass flux increases (2%/K) enhance precipitation rates, while the upward displacement of the mass flux profile (-1.1%/K) offsets this increase. Convective-scale extremes behave similarly except that changes in mass flux are negligible due to a balance between greater numbers of strong updrafts and downdrafts and lesser numbers of weak updrafts. Extremes defined on these two scales behave as two independent sets of rainfall events, with different dynamics, geometries, and responses to climate change. In particular, dynamic changes in mesoscale extremes appear primarily sensitive to changes in the large-scale mass flux, while the intensity of convective-scale extremes is not. In particular, the increases in mesoscale mass flux directly contribute to the intensification of mesoscale extreme rain, but do not seem to affect the increase in convective-scale rainfall intensities. These results motivate the need for better understanding the role of the large-scale forcing on the formation and intensification of heavy convective rainfall. © 2017. The Authors."
"7003523768;6603381853;6701434176;","CHROMOSPHERIC MODELS AND THE OXYGEN ABUNDANCE IN GIANT STARS",2016,"10.3847/2041-8205/821/1/L7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84964203124&doi=10.3847%2f2041-8205%2f821%2f1%2fL7&partnerID=40&md5=8d06fdc08ca3021e5f072dc641238e1e","Realistic stellar atmospheric models of two typical metal-poor giant stars in Omega Centauri, which include a chromosphere (CHR), influence the formation of optical lines of O I: the forbidden lines (λ6300, λ6363) and the infrared triplet (λλ7771-7775). One-dimensional semi-empirical non-local thermodynamic equilibrium (LTE) models are constructed based on observed Balmer lines. A full non-LTE formulation is applied for evaluating the line strengths of O I, including photoionization by the Lyman continuum and photoexcitation by Lyα and Lyβ. Chromospheric models (CHR) yield forbidden oxygen transitions that are stronger than those in radiative/convective equilibrium (RCE) models. The triplet oxygen lines from high levels also appear stronger than those produced in an RCE model. The inferred oxygen abundance from realistic CHR models for these two stars is decreased by factors of ∼3 as compared to values derived from RCE models. A lower oxygen abundance suggests that intermediate-mass AGB stars contribute to the observed abundance pattern in globular clusters. A change in the oxygen abundance of metal-poor field giants could affect models of deep mixing episodes on the red giant branch. Changes in the oxygen abundance can impact other abundance determinations that are critical to astrophysics, including chemical tagging techniques and galactic chemical evolution. © 2016. The American Astronomical Society. All rights reserved."
"16426378500;44161353800;55324953800;","The role of radiation in organizing convection in weak temperature gradient simulations",2016,"10.1002/2015MS000587","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84960145936&doi=10.1002%2f2015MS000587&partnerID=40&md5=b8a9bd39fc6c0465df1ac61c18f9b1ce","Using a cloud system resolving model with the large scale parameterized by the weak temperature gradient approximation, we investigated the influence of interactive versus noninteractive radiation on the characteristics of convection and convective organization. The characteristics of convecting environments are insensitive to whether radiation is interactive compared to when it is not. This is not the case for nonconvecting environments; interactive radiative cooling profiles show strong cooling at the top of the boundary layer which induces a boundary layer circulation that ultimately exports moist entropy (or analogously moist static energy) from dry domains. This upgradient transport is associated with a negative gross moist stability, and it is analogous to boundary layer circulations in radiative convective equilibrium simulations of convective self-aggregation. This only occurs when radiation cools interactively. Whether radiation is static or interactive also affects the existence of multiple equilibria-steady states which either support precipitating convection or which remain completely dry depending on the initial moisture profile. Interactive radiation drastically increases the range of parameters which permit multiple equilibria compared to static radiation; this is consistent with the observation that self-aggregation in radiative-convective equilibrium simulations is more readily attained with interactive radiation. However, the existence of multiple equilibria in absence of interactive radiation suggests that other mechanisms may result in organization. © 2016 The Authors."
"16475714800;57203053066;36671874400;","Convective self-aggregation and tropical cyclogenesis under the hypohydrostatic rescaling",2016,"10.1175/JAS-D-15-0049.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84958611898&doi=10.1175%2fJAS-D-15-0049.1&partnerID=40&md5=25cde9c33ae961b51a2c8e973d63cbb0","The behavior of rotating and nonrotating aggregated convection is examined at various horizontal resolutions using the hypohydrostatic, or reduced acceleration in the vertical (RAVE), rescaling. This modification of the equations of motion reduces the scale separation between convective- and larger-scale motions, enabling the simultaneous and explicit representation of both types of flow in a single model without convective parameterization. Without the RAVE rescaling, a dry bias develops when simulations of nonrotating radiative-convective equilibrium are integrated at coarse resolution in domains large enough to permit convective self-aggregation. The rescaling reduces this dry bias, and here it is suggested that the rescaling moistens the troposphere by weakening the amplitude and slowing the group velocity of gravity waves, thus reducing the subsidence drying around aggregated convection. Separate simulations of rotating radiative-convective equilibrium exhibit tropical cyclogenesis; as horizontal resolution is coarsened without the rescaling, the resulting storms intensify more slowly and achieve lower peak intensities. At a given horizontal resolution, using RAVE increases peak storm intensity and reduces the time needed for tropical cyclogenesis-effects here suggested to be caused at least in part by the environmental moistening produced by RAVE. Consequently, the RAVE rescaling has the potential to improve simulations of tropical cyclones and other aggregated convection in models with horizontal resolutions of order 10-100 km. © 2016 American Meteorological Society."
"57208702763;7202004261;6701768500;","Parameterization of radiative heating and cooling rates in the stratosphere of jupiter",2014,"10.1016/j.icarus.2014.08.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907618383&doi=10.1016%2fj.icarus.2014.08.001&partnerID=40&md5=df37659d11b6ead3eb0263fce4e46703","We present a newly developed parameterization of radiative heating and cooling for Jupiter's upper troposphere and stratosphere (103 to 10-3hPa) suitable for general circulation models. The scheme is based on the correlated k-distribution approach, and accounts for all the major radiative mechanisms in the jovian atmosphere: heating due to absorption of solar radiation by methane, cooling in the infrared by methane, acetylene, ethane, and collisionally-induced molecular hydrogen-hydrogen, and molecular hydrogen-helium transitions. The results with the scheme are compared with line-by-line calculations to demonstrate that the accuracy of the scheme is within 10%. The parameterization was applied to study the sensitivity of the heating/cooling rates due to variations of mixing ratios of hydrocarbon molecules. It was also used for calculating the radiative-convective equilibrium temperature, which is in agreement with observations in the equatorial region. In midlatitudes, the equilibrium temperature is approximately 10K colder. Our results suggest that the radiative forcing in the upper stratosphere is much stronger than it was thought before. In particular, the characteristic radiative relaxation time decreases exponentially with height from 108s near the tropopause to 105s in the upper stratosphere. © 2014 Elsevier Inc."
"7408519295;14031427400;7202201947;","The improved NRL tropical cyclone monitoring system with a unified microwave brightness temperature calibration scheme",2014,"10.3390/rs6054563","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901490405&doi=10.3390%2frs6054563&partnerID=40&md5=fcb41490995bf3fcb26df6db40386687","The near real-time NRL global tropical cyclone (TC) monitoring system based on multiple satellite passive microwave (PMW) sensors is improved with a new inter-sensor calibration scheme to correct the biases caused by differences in these sensor's high frequency channels. Since the PMW sensor 89 GHz channel is used in multiple current and near future operational and research satellites, a unified scheme to calibrate all satellite PMW sensor's ice scattering channels to a common 89 GHz is created so that their brightness temperatures (TBs) will be consistent and permit more accurate manual and automated analyses. In order to develop a physically consistent calibration scheme, cloud resolving model simulations of a squall line system over the west Pacific coast and hurricane Bonnie in the Atlantic Ocean are applied to simulate the views from different PMW sensors. To clarify the complicated TB biases due to the competing nature of scattering and emission effects, a four-cloud based calibration scheme is developed (rain, non-rain, light rain, and cloudy). This new physically consistent inter-sensor calibration scheme is then evaluated with the synthetic TBs of hurricane Bonnie and a squall line as well as observed TCs. Results demonstrate the large TB biases up to 13 K for heavy rain situations before calibration between TMI and AMSR-E are reduced to less than 3 K after calibration. The comparison stats show that the overall bias and RMSE are reduced by 74% and 66% for hurricane Bonnie, and 98% and 85% for squall lines, respectively. For the observed hurricane Igor, the bias and RMSE decrease 41% and 25% respectively. This study demonstrates the importance of TB calibrations between PMW sensors in order to systematically monitor the global TC life cycles in terms of intensity, inner core structure and convective organization. A physics-based calibration scheme on TC's TB corrections developed in this study is able to significantly reduce the biases between different PMW sensors. © 2014 by the authors."
"6506961196;6602667252;35555971200;23989995400;8116763300;55999772700;","Rainfall variability associated with the summer African monsoon: A satellite study",2010,"10.1016/j.atmosres.2010.05.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955769072&doi=10.1016%2fj.atmosres.2010.05.004&partnerID=40&md5=94f3bdd6ca6f643e86555e3c37cdd3fe","Instantaneous rainfall intensities retrieved by a multi-sensor precipitation estimation algorithm based on the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) onboard Meteosat and on the Special Sensor Microwave Imager (SSM/I) data are used to investigate the dynamics and phenomenology associated with the African monsoon regime. A 5-year (2004-2008) climatology during the warm season (June-August) of coherent precipitation patterns is presented with emphasis on the intraseasonal and interannual variability of the tropical northern African Monsoon for the investigation of the longitudinal distribution of rainfall and the zonal component of motion. The coherence and phase speed of rain streaks are also quantified by means of a two-dimensional autocorrelation analysis to derive the zonal-span and the duration properties of the identified rain systems. The periodicity of the precipitating episodes is finally investigated through harmonic analysis performed in different longitudinal bands of the studied domain.Rainfall episodes tend to initiate in the lee of steep topography (maxima in correspondence of the Ethiopian highlands), consistently with the thermal heating forcing from elevated terrain. Such an organized convection consists of coherent sequences of precipitation episodes, which span an average distance of about 460. km and last about 10. h. The diurnal cycle of summer precipitation is characterised by afternoon and early evening maxima located mainly downwind of the major mountain chains, as also the spectral analysis has clearly highlighted. © 2010 Elsevier B.V."
"8688004400;57193882808;7103158465;","The impact of atmospheric aerosols on precipitation from deep organized convection: A prescribed-flow model study using double-moment bulk microphysics",2009,"10.1002/qj.450","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350624537&doi=10.1002%2fqj.450&partnerID=40&md5=b7949d9088f235b2e7f4dfffddacedc0","This note discusses the results of numerical simulations in which a prescribed-flow model is merged with a double-moment warm-rain and ice microphysics scheme to investigate the impact of microphysical processes on precipitation from deep organized convection. The prescribed two-dimensional flow mimics an idealized squall line, with a narrow region of strong convective updraft and much wider region of weak stratiform updraft overlaying a stratiform downdraft. To cover the broad range of conditions that are possible for a squall line as well as to explore precipitation dependence on different parameters, 25 pairs of simulations are performed. Simulated cases differ in the dynamics (e.g. changing the updraft strength or large-scale shear), thermodynamics (e.g. changing the inflow sounding) or microphysics (e.g. changing the collision efficiencies). Each pair features cloud condensation nuclei (CCN) in either a pristine or polluted environment. Total surface precipitation and partitioning between convective and stratiform precipitation in each pair appears to be almost the same, with the difference being typically a few tenths of 1%. However, the dynamical and thermodynamical parameters do affect the precipitation significantly. It follows that the surface precipitation from organized convection can differ between pristine and polluted environments only through the feedback of CCN on cloud dynamics. In this feedback, small differences in the latent heating for the same flow pattern lead to different flow patterns in subsequent squall-line evolution. Details of this feedback need to be investigated using a dynamical model. © 2009 Royal Meteorological Society."
"7201605742;","A view on tropical cyclones as CISK",2007,"10.2151/jmsj.85B.145","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34848884234&doi=10.2151%2fjmsj.85B.145&partnerID=40&md5=4f4afd77635d94f75c20f7e253d2496c","The author's view on tropical cyclones as the conditional instability of the second kind (CISK) is presented. Many theoretical and numerical studies of tropical cyclones have discussed the original CISK of Ooyama (1964, 1969) and Charney and Eliassen (1964) in which frictional convergence plays an important role. In this paper, the author emphasizes that this CISK is applied primarily to the eyewall circulation in intense tropical cyclones, and describes other types of CISK, which are appropriate to explain many of tropical disturbances and tropical depressions, and the formation and early development stages of tropical cyclones. In addition, the importance of resolving mesoscale organized convection in coarse-resolution numerical models is emphasized. © 2007, the Meteorological Society of Japan."
"34979145900;57206416522;7006184606;","The role of relative humidity in radiative-convective equilibrium",2005,"10.1175/JAS3434.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23744472822&doi=10.1175%2fJAS3434.1&partnerID=40&md5=f73f86c04845a63133d3f2907917a189","The following conditions are derived for the existence of a radiation limit of tropospheric origin in a nongray atmosphere, extending the work on a gray atmosphere by Nakajima et al.: 1) the atmosphere must become sufficiently optically thick, and 2) the temperature must become only a function of optical depth at each frequency, independent of surface temperature. The first condition is satisfied at high temperatures even in a window region as long as there is weak but nonzero absorption, because the optical depth of the entire atmosphere roughly scales as saturation vapor pressure. At high temperatures, the pseudoadiabatic temperature structure asymptotes to the saturation vapor pressure curve, satisfying the second condition at each frequency. A rapidly decreasing vertical gradient of water vapor mixing ratio allows temperature to asymptote faster in optical depth coordinates than in pressure coordinates. Analyses using a radiative-convective model show that inte ractive relative humidity can give rise to a different kind of runaway greenhouse effect and multiple equilibria, if the strength of relative humidity feedback exceeds a critical value. The results suggest that this mechanism may be able to explain the runaway greenhouse effect found by Rennó et al. and radiative-convective multiple equilibria by Rennó. The framework employed in this study will serve as a diagnostic tool for further research on the runaway greenhouse effect and radiative-convective multiple equilibria. © 2005 American Meteorological Society."
"56245933700;6701873414;","Observations of transient linear oraganization and nonlinear scale interactions in lake-effect clouds. Part I: Transient linear organization",2005,"10.1175/MWR-2879.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17044400131&doi=10.1175%2fMWR-2879.1&partnerID=40&md5=246a3cc22e87d1376b1d1d645b76bbc7","The cold-air outbreak of 13-14 January 1998 during the Lake-Induced Convection Experiment was characterized by large positive buoyancy flux and moderate wind shear. Although theory predicts only cellular organization in these conditions, transient linear organization was observed. Time series of vertical velocity obtained with the Pennsylvania State University 94-GHz vertically pointing cloud radar, which is sensitive to cloud droplets and ice crystals, were used to document the changes in organization that occurred during this wintertime lake-effect event. The cloud radar was deployed on the downwind shore of southern Lake Michigan and measured high-temporal-resolution vertical velocity data at several in-cloud heights. The duration of the event was 18 h, encompassing three cycles of linear organization switching to cellular organization. In Part I of this two-part series the authors document the transient nature of the linearly organized convection and evaluate the role of atmospheric conditions in the mode switching between linear and cellular organization. Within the limits of the available measurements, no correlation was found with mean or low-level shear, surface fluxes, or stability parameters. The mode switching in this case does not appear to be controlled by the atmospheric indicators typically associated with linearly organized convection, suggesting that other factors must have played an important role. © 2005 American Meteorological Society."
"7006184606;","Chapter 8 Quasi-equilibrium thinking",2000,"10.1016/S0074-6142(00)80056-X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956774037&doi=10.1016%2fS0074-6142%2800%2980056-X&partnerID=40&md5=2df257e64e70c445f95a1b9ba22cd6b5","Until quite recently, quasi-equilibrium has been thought of primarily as a closure for convective parameterizations; its effect on the way we think about convection has been relatively slow to come about. In this paper I have reviewed and in some small ways extended Emanuel et al.'s (1994) exploration of the full implications of quasi-equilibrium. The main structure of quasi-equilibrium thinking emphasizes the following points:u• Latent heating is a concept that applies to the dynamics of individual clouds. In contrast, it plays no role in the energetics of cumulus ensembles.• The state of radiative-convective equilibrium serves as the basic equilibrium state for quasi-equilibrium thinking in the same way that an east-west baroclinic flow serves as the basic state for quasi-geostrophic thinking about many midlatitude flows.• Disturbances with space and time scales much larger than convective overturning time scales, and intercloud spacing characterizing the radiative-convective equilibrium state may be considered to be in quasi-equilibrium with the convective clouds.• Such disturbances ""feel"" an effective stratification that, while positive, is much less than typical dry stratifications. The stratification may also be related physically to drying of the subcloud layer by convective downdrafts. The effective stratification vanishes when the large scale becomes saturated, as happens in the core of tropical cyclones.• Such disturbances are also damped in proportion to their frequency. This tends to filter high-frequency disturbances and to damp most nascent tropical depressions.• Convection that is not close to being in equilibrium with explicitly simulated flows cannot be parameterized as a function of the explicitly resolved variables. A full appreciation of the consequences of quasi-equilibrium will no doubt lead to important advances in understanding and predicting large-scale disturbances in convecting atmospheres. © 2001 Elsevier Inc. All rights reserved."
"7006422084;7006236576;57215790062;","Quasi-stationary organized convection in the presence of an inversion near the surface: Experiments with a 2-D numerical model",1991,"10.1007/BF01027476","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0043015104&doi=10.1007%2fBF01027476&partnerID=40&md5=eedaadc67ec3b8d074f3bb68599d24e0","Quasi-steady states of organized convection are studied in a two-dimensional nonhydrostatic primitive-equation numerical model. Uni-and multi-cellular patterns are identified in the presence of a low-level inversion, and discussed in relation to those obtained, by various authors, in the more traditional monotonic-sounding case. The stable layer near the ground is shown to be responsible for a configuration of flow normally not observed in cases of monotonic sounding and reminiscent of an orographically generated wave. Exploring the conditions conducive to quasi-steady convection it is found that in the presence of a low-level inversion, a strong shear of the wind component perpendicular to the squall line is required near the surface, deeper than that required in the absence of the inversion. © 1991 Springer-Verlag."
"7101673388;7003935733;","A numerical method for determining the temperature structure of planetary atmospheres",1973,"10.1016/0019-1035(73)90137-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-21344467051&doi=10.1016%2f0019-1035%2873%2990137-1&partnerID=40&md5=628b186e7ca7b7f2dbf4ef38d3100394","A numerical method for calculating the time-average, vertical temperature structure of planetary atmospheres is presented. It is assumed that the atmospheres are in radiative-convective equilibrium, which is a good first approximation to many situations. Numerical tests of the rate of convergence and accuracy of the answer are presented. The method can readily handle molecular sources of opacity. Accurate results can be obtained with a minimum of computer time, because the number of iterations needed (∼ 4) is small and the number of pressure levels at which the net flux needs to be evaluated (∼ 10) is small. As an application of this procedure, we have calculated some model atmospheres of Jupiter. © 1973."
"26649925100;55436842300;57191498195;57192591629;","Circling in on Convective Organization",2019,"10.1029/2019GL082092","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068159036&doi=10.1029%2f2019GL082092&partnerID=40&md5=5f97db968689283d7f2c72f6911628dd","Cold pools (CPs) contribute to convective organization. However, it is unclear by which mechanisms organization occurs. By using a particle method to track CP gust fronts in large eddy simulations, we characterize the basic collision modes between CPs. Our results show that CP interactions, where three expanding gust fronts force an updraft, are key at triggering new convection. Using this, we conceptualize CP dynamics into a parameter-free mathematical model: circles expand from initially random points in space. Where two expanding circles collide, a stationary front is formed. However, where three expanding circles enclose a single point, a new expanding circle is seeded. This simple model supports three fundamental features of CP dynamics: precipitation cells constitute a spatially interacting system, CPs come in generations, and scales steadily increase throughout the diurnal cycle. Finally, this model provides a framework for how CPs act to cause convective self-organization, clustering, and extremes. ©2019. American Geophysical Union. All Rights Reserved."
"55344397300;6602761005;55260519600;","Axisymmetric constraints on cross-equatorial hadley cell extent",2019,"10.1175/JAS-D-18-0306.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067175755&doi=10.1175%2fJAS-D-18-0306.1&partnerID=40&md5=008b9fd6d64ec970c776d877b938c7db","We consider the relevance of known constraints from each of Hide's theorem, the angular momentum- conserving (AMC) model, and the equal-area model on the extent of cross-equatorial Hadley cells. These theories respectively posit that a Hadley circulation must span all latitudes where the radiative-convective equilibrium (RCE) absolute angular momentum Mrce satisfies Mrce &gt; Ωa2 or Mrce &lt; 0 or where the RCE absolute vorticity hrce satisfies fηrce &lt; 0; all latitudes where the RCE zonal wind exceeds theAMCzonal wind; and over a range such that depth-averaged potential temperature is continuous and that energy is conserved. The AMC model requires knowledge of the ascent latitude ϕa, which needs not equal the RCE forcing maximum latitude ϕm.Whatever the value of ϕa, we demonstrate that anAMCcell must extend at least as far into the winter hemisphere as the summer hemisphere. The equal-area model predicts ϕa, always placing it poleward of ϕm. As ϕm is moved poleward (at a given thermal Rossby number), the equal-area-predicted Hadley circulation becomes implausibly large, while both ϕm and ϕa become increasingly displaced poleward of the minimal cell extent based on Hide's theorem (i.e., of supercritical forcing). In an idealized dry general circulation model, cross-equatorial Hadley cells are generated, some spanning nearly pole to pole. All homogenize angular momentum imperfectly, are roughly symmetric in extent about the equator, and appear in extent controlled by the span of supercritical forcing. © 2019 American Meteorological Society."
"55469523400;","Limits on the extent of the solsticial Hadley cell: The role of planetary rotation",2019,"10.1175/JAS-D-18-0341.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067176671&doi=10.1175%2fJAS-D-18-0341.1&partnerID=40&md5=0b5751cd7ffb3b2de2e3ece20d9d1eae","The role of planetary rotation in limiting the extent of the cross-equatorial solsticial Hadley cell (SHC) is investigated using idealized simulations with an aquaplanet general circulation model run under perpetualsolstice conditions. Consistent with previous studies that include a seasonal cycle, the SHC extent increases with decreasing rotation rate, and it occupies the entire globe for sufficiently low planetary rotation rates. A simple theory for the summer-hemisphere extent of the SHC is constructed in which it is assumed that the SHC occupies regions for which a hypothetical radiative-convective equilibrium state is physically unattainable. The theory predicts that the SHC extends farther into the summer hemisphere as the rotation rate is decreased, qualitatively reproducing the behavior of the simulations, but it generally underestimates the simulated SHC extent. A diagnostic theory for the summer-hemisphere SHC extent is then developed based on the assumptions of slantwise convective neutrality and conservation of angular momentum within the Hadley cell. The theory relates the structure of the SHC in the summer hemisphere to the distribution of boundary layer entropy in the dynamically equilibrated simulations. The resultant diagnostic for the SHC extent generalizes the convective quasi-equilibrium-based constraint of Privé and Plumb, in which the position of rain belts is related to maxima in the low-level entropy distribution. © 2019 American Meteorological Society."
"55979043800;7006614696;","Origins of heavy precipitation biases in the TRMM PR and TMI products assessed with cloudsat and reanalysis data",2019,"10.1175/JAMC-D-18-0011.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060915134&doi=10.1175%2fJAMC-D-18-0011.1&partnerID=40&md5=661943f9fcdb82c282dc2140a0640d68","This study aims to characterize the background physical processes in the development of those heavy precipitation clouds that contribute to the Tropical Rainfall Measuring Mission (TRMM) active and passive sensor differences. The combined global observation data from TRMM, CloudSat, and European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim) from 2006 to 2014 were utilized to address this issue. Heavy rainfall events were extracted from the top 10% of the rain events from the Precipitation Radar (PR) and TRMM Microwave Imager (TMI) rain-rate climatology. Composite analyses of CloudSat and ERA-Interim were conducted to identify the detailed cloud structures and the background environmental conditions. Over tropical land, TMI tends to preferentially detect deep isolated precipitation clouds for relatively drier and unstable environments, while PR identifies more organized systems. Over the tropical ocean, TMI identifies heavy rainfall events with notable convective organization and clear regional gradients between the western and eastern Pacific Ocean, while PR fails to capture the eastward shallowing of convective systems. The PR-TMI differences for the moist and stable environments are reversed over tropical land. © 2019 American Meteorological Society."
"56893786200;57210687618;","Increase in Precipitation Efficiency With Surface Warming in Radiative-Convective Equilibrium",2018,"10.1029/2018MS001482","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85057465995&doi=10.1029%2f2018MS001482&partnerID=40&md5=44db350955df840d2b5bdf8d4ab13a78","The precipitation efficiency of convection (ε) plays an important role in simple models of the tropical atmosphere as well as in global climate models' projections of future climate changes, but remains poorly understood and poorly constrained. A particularly urgent question is how ε will change in warmer climates. To address these issues, this study investigates the precipitation efficiency in simulations of radiative-convective equilibrium with a cloud-resolving model forced by a wide range of sea surface temperatures (SSTs). Two different domains are considered: a small, doubly periodic domain, and a 2-D (x-z) “mock-Walker” domain with a sinusoidal SST profile that resembles the equatorial Pacific, and the sensitivities of the results to the microphysical scheme and to the horizontal resolution are also explored. It is found that ε generally increases with warming in the small domain simulations because of increases in the efficiency with which cloud condensate is converted into precipitation, with changes in the re-evaporation of falling precipitation playing a secondary role. This picture is complicated in the 2-D simulations by substantial changes in the degree of convective organization as the underlying SSTs are varied. ε is found to decrease as convection becomes more organized, because convective organization results in relatively more low clouds, which have small (≤0.1) precipitation efficiencies, and relatively less high clouds, which have larger (∼0.4) precipitation efficiencies. ©2018. The Authors."
"6701670597;36634069800;7005702722;7005035762;","Importance Profiles for Water Vapor",2017,"10.1007/s10712-017-9427-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030721046&doi=10.1007%2fs10712-017-9427-1&partnerID=40&md5=842b9397f74025a9fa9d2171cd05fbca","Motivated by the scientific desire to align observations with quantities of physical interest, we survey how scalar importance functions depend on vertically resolved water vapor. Definitions of importance begin from familiar examples of water mass Im and TOA clear-sky outgoing longwave flux IOLR, in order to establish notation and illustrate graphically how the sensitivity profile or “kernel” depends on whether specific humidity S, relative humidity R, or ln(R) are used as measures of vapor. Then, new results on the sensitivity of convective activity Icon to vapor (with implied knock-on effects such as weather prediction skill) are presented. In radiative-convective equilibrium, organized (line-like) convection is much more sensitive to moisture than scattered isotropic convection, but it exists in a drier mean state. The lesson for natural convection may be that organized convection is less susceptible to dryness and can survive and propagate into regions unfavorable for disorganized convection. This counterintuitive interpretive conclusion, with respect to the narrow numerical result behind it, highlights the importance of clarity about what is held constant at what values in sensitivity or susceptibility kernels. Finally, the sensitivities of observable radiance signals Isig for passive remote sensing are considered. While the accuracy of R in the lower free troposphere is crucial for the physical importance scalars, this layer is unfortunately the most difficult to isolate with passive remote sensing: In high emissivity channels, water vapor signals come from too high in the atmosphere (for satellites) or too low (for surface radiometers), while low emissivity channels have poor altitude discrimination and (in the case of satellites) are contaminated by surface emissions. For these reasons, active ranging (LiDAR) is the preferred observing strategy. © 2017, Springer Science+Business Media B.V."
"25941200000;57195576398;56009810800;35317714900;9239331500;7003557662;","Scaling properties of observed and simulated satellite visible radiances",2017,"10.1002/2017JD027146","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028937797&doi=10.1002%2f2017JD027146&partnerID=40&md5=ada80f879f83479097e98195312f394c","Structure functions Sq, which are related to power spectra and used to study turbulence, were computed for GOES-13 visible radiances measured on 16 May 2015 over French Guiana and adjacent Atlantic Ocean. The nested Global Environmental Multiscale (GEM) numerical weather prediction (NWP) model was run for the same time and area. Cloud data generated by GEM over (300 km)2 domains, with one-way nesting ending at horizontal grid-spacing of 0.25 km, were operated on by a 3-D solar radiative transfer model with resulting radiances degraded to GOES-13 resolution (~1 km) and Sq computed for them, too. For GOES-13 radiances, scaling exponents ζ(2) associated with S2, for separation distances between 5 km and 25 km, were typically &gt;0.6 for deep convective and marine boundary layer clouds and &lt;0.4 for shallow cumuli over land. ζ(2) for GEM agreed well with GOES-13 for deep convective clouds. This suggests that the self-organizing properties of deep convection in GEM exhibit realistic geometric features, a potentially important point given the link between cloud structure and precipitation, with the latter being much more difficult to measure and assess than visible radiances. Regarding radiances for GEM's marine boundary layer clouds, their Sq differed markedly from GOES-13's; better resembling fair-weather cumulus. Likewise, GEM's shallow cumuli over land appear to have bypassed the “scattered” fair-weather stage and went straight into more organized convection. Thus, it appears that comparing time series of Sq for geostationary satellite data and corresponding modeled radiances has the potential to benefit assessment of cloud system-resolving models. ©2017 Her Majesty the Queen in Right of Canada. Reproduced with the permission of the Minister of Environment."
"34972803800;41662112800;7003408439;24492188100;","Influences of the MJO on the space-time organization of tropical convection",2017,"10.1002/2017JD026526","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028058765&doi=10.1002%2f2017JD026526&partnerID=40&md5=4b308b13c48c94861f036ca86e5dd2a7","The fact that the Madden-Julian Oscillation (MJO) is characterized by large-scale patterns of enhanced tropical rainfall has been widely recognized for decades. However, the precise nature of any two-way feedback between the MJO and the properties of smaller-scale organization that makes up its convective envelope is not well understood. Satellite estimates of brightness temperature are used here as a proxy for tropical rainfall, and a variety of diagnostics are applied to determine the degree to which tropical convection is affected either locally or globally by the MJO. To address the multiscale nature of tropical convective organization, the approach ranges from space-time spectral analysis to an object-tracking algorithm. In addition to the intensity and distribution of global tropical rainfall, the relationship between the MJO and other tropical processes such as convectively coupled equatorial waves, mesoscale convective systems, and the diurnal cycle of tropical convection is also analyzed. The main findings of this paper are that, aside from the well-known increase in rainfall activity across scales within the MJO convective envelope, the MJO does not favor any particular scale or type of organization, and there is no clear signature of the MJO in terms of the globally integrated distribution of brightness temperature or rainfall. © 2017. American Geophysical Union. All Rights Reserved."
"54585541100;55714142500;7203055935;57190839123;","Rapid weakening of Typhoon Chan-Hom (2015) in a monsoon gyre",2016,"10.1002/2016JD025214","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983394271&doi=10.1002%2f2016JD025214&partnerID=40&md5=e8bd2a90235831d0e8d3e566560c7e36","A monsoon gyre is a low-frequency cyclonic circulation over the western North Pacific, which plays important roles in tropical cyclone formation and motion. This study shows that the interaction between a monsoon gyre and a tropical cyclone can lead to a sudden weakening of the tropical cyclone through an observational analysis of Typhoon Chan-Hom (2015). Typhoon Chan-Hom (2015) initially moved westward along ~10°N and sharply turned northeastward in the Philippine Sea at 0000 UTC 3 July. Its intensity decreased by 10.3ms-1 within 12 h during the sudden northward turn. Such a rapid weakening event was failed to predict in all of the operational forecasts. It is found that Chan-Hom was coalescing with a large-scale monsoon gyre on the intraseasonal (15-30 day) timescale, while it experienced the sudden track change and rapid intensity weakening. The weak and loosely organized convection on the eastern side of the monsoon gyre at 1200 UTC 2 July rapidly enhanced into the well-organized convection within 6 h. The strong convection maintaining from 1800 UTC 2 July to 0600 UTC 3 July enhanced inflows outside the radius of 500 km from the tropical cyclone center, which prevented the inward transportation of mass and moisture into Chan-Hom, leading to the collapsing of the eastern part of the eyewall. As a result, Chan-Hom underwent the rapid weakening even under a large-scale environment favorable for intensification. The study suggests that the rapid weakening of a tropical cyclone can result from its interaction with a monsoon gyre. © 2016. American Geophysical Union. All Rights Reserved."
"36240879400;56308982600;16202470400;","Meteorological aspects of mud bank formation along south west coast of India",2013,"10.1016/j.csr.2013.05.016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880149501&doi=10.1016%2fj.csr.2013.05.016&partnerID=40&md5=6197ef431115d4ffa17b63fc9fdfce25","The study mainly intends to investigate the meteorological aspects associated with the formation of mud banks along southwest coast of India. During the formation of mud bank, the prominent monsoon organized convection is located in the equatorial region and relatively low clouding over Indian mainland. The wind core of the low level jet stream passes through the monsoon organized convection. When the monsoon organized convection is in the equatorial region, the low level wind over the southwest coast of India is parallel to the coastline and toward south. This wind along the coast gives rise to Ekman mass transport away from the coastline and subsequently formation of mud bank, if the high wind stress persists continuously for three or more days. As a result of the increased alongshore wind stress, the coastal upwelling increases. An increase in chlorophyll-a concentration and total chlorophyll can also be seen associated with mudbank formation. © 2013."
"7006331431;55419044600;","Intraseasonal variability in MERRA energy fluxes over the tropical oceans",2012,"10.1175/JCLI-D-11-00428.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867664999&doi=10.1175%2fJCLI-D-11-00428.1&partnerID=40&md5=e0517d4151727605523aec5a9cff35f6","This paper investigates intraseasonal variability as represented by the recent NASA Global Modeling and Assimilation Office (GMAO) reanalysis, the Modern-Era Retrospective analysis for Research and Applications (MERRA). The authors examine the behavior of heat, moisture, and radiative fluxes emphasizing their contribution to intraseasonal variations in heat and moisture balance integrated over the tropical oceans. MERRA successfully captures intraseasonal signals in both state variables and fluxes, though it depends heavily on the analysis increment update terms that constrain the reanalysis to be near the observations. Precipitation anomaly patterns evolve in close agreement with those from the Tropical Rainfall Measuring Mission (TRMM) though locally MERRA may occasionally be smaller by up to 20%. As in the TRMM observations, tropical convection increases lead tropospheric warming by approximately 7 days. Radiative flux anomalies are dominated by cloud forcing and are found to replicate the top-of-the-atmosphere (TOA) energy loss associated with increased convection found by other observationally based studies. However, MERRA's convectively produced clouds appear to deepen too soon as precipitation increases. Total fractional cloud cover variations appear somewhat weak compared to observations from the Moderate Resolution Imaging Spectroradiometer (MODIS). Evolution of the surface fluxes, convection, and TOA radiation is consistent with the ""discharge-recharge""paradigm that posits the importance of lower-tropospheric moisture accumulation prior to the expansion of organized deep convection. The authors conclude that MERRA constitutes a very useful representation of intraseasonal variability that will support a variety of studies concerning radiative-convective-dynamical processes and will help identify pathways for improved moist physical parameterization in global models. © 2012 American Meteorological Society."
"6603145318;7004470971;","Simulating convectively coupled Kelvin waves using Lagrangian overturning for a convective parametrization",2010,"10.1002/qj.666","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954358075&doi=10.1002%2fqj.666&partnerID=40&md5=a211549048111977b787d2c64f694c13","The first tests of a new Lagrangian atmospheric model (LAM) focus on its representation of moist convective processes. The LAMis constructed bymodifying a Lagrangian ocean model to accommodate compressible fluid parcels. The model includes a simple convective parametrization referred to as 'Lagrangian Overturning (LO)', in which air parcels exchange vertical positions in convectively unstable regions. Radiative convective equilibrium experiments conducted with a single-column version of the LAM show that combining LO with simple parametrizations for surface fluxes, radiation and the evaporation of rain produces realistic temperature and moisture profiles for the Tropics. When LO is used in a tropical aquaplanet model, convectively coupled Kelvin waves spontaneously develop that have realistic temperature and zonal wind perturbations. These results have implications both for the potential usefulness of Lagrangian models for simulating moist convective processes, and for the mechanism of convectively coupled equatorial waves. © 2010 Royal Meteorological Society."
"7005446873;","Statistical properties of cloud lifecycles in cloud-resolving models",2009,"10.5194/acp-9-2195-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-63049105610&doi=10.5194%2facp-9-2195-2009&partnerID=40&md5=efc21da49d7786c5636dc707ee06d61e","A new technique is described for the analysis of cloud-resolving model simulations, which allows one to investigate the statistics of the lifecycles of cumulus clouds. Clouds are tracked from timestep to timestep within the model run. This allows for a very simple method of tracking, but one which is both comprehensive and robust. An approach for handling cloud splits and mergers is described which allows clouds with simple and complicated time histories to be compared within a single framework. This is found to be important for the analysis of an idealized simulation of radiative-convective equilibrium, in which the moist, buoyant updrafts (i.e., the convective cores) were tracked. Around half of all such cores were subject to splits and mergers during their lifecycles. For cores without any such events, the average lifetime is 30 min, but events can lengthen the typical lifetime considerably."
"7004014731;7103342287;","Evidence of the solar cycle in the tropical troposphere",2006,"10.1029/2006JD007133","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250814709&doi=10.1029%2f2006JD007133&partnerID=40&md5=46a4067e24c7147f56ed91a346969fb3","An analysis of low-frequency variability in the National Centers for Environmental Prediction record reveals a decadal oscillation inside the tropical troposphere, one that operates coherently and in phase with the 11-year variation of solar irradiance. The oscillation represents a robust signature of solar variability, achieving higher levels of significance than have previously been required. Characterized by symmetric latitudinal structure, the oscillation involves anomalous temperature that maximizes over the equator and anomalous zonal wind that maximizes in the tropics of each hemisphere. Its deep vertical structure, in concert with the horizontal distribution of anomalous temperature, suggests the involvement of organized convection, as well as a direct radiative influence at upper levels, inside the tropical tropopause layer. Copyright 2006 by the American Geophysical Union."
"6701606453;7006614696;7004114883;","Variability in the characteristics of precipitation systems in the tropical Pacific. Part II: Implications for atmospheric heating",2006,"10.1175/JCLI3698.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646809014&doi=10.1175%2fJCLI3698.1&partnerID=40&md5=46fdebb8e4108e3ff8524db0519b0b78","This paper explores changes in the principal components of observed energy budgets across the tropical Pacific in response to the strong 1998 El Niño event. Multisensor observations from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), Visible and Infrared Scanner (VIRS), and precipitation radar (PR) instruments aboard TRMM are used to quantify changes in radiative and latent heating in the east and west Pacific in response to the different phases of the El Niño-Southern Oscillation. In periods of normal east-west SST gradients there is substantial heating in the west Pacific and cooling in the east, implying strong eastward atmospheric energy transport. During the active phase of the El Niño, both the east and west Pacific tend toward local radiative-convective equilibrium resulting in their temporary energetic decoupling. It is further demonstrated that the response of these regions to ENSO-induced SST variability is directly related to changes in the characteristics of clouds and precipitation in each region. Through quantitative analysis of the radiative and latent heating properties of shallow, midlevel, and deep precipitation events and an equivalent set of nonprecipitating cloud systems, times of reduced atmospheric heating are found to be associated with a shift toward shallow and midlevel precipitation systems and associated low-level cloudiness. The precipitation from such systems is typically less intense, and they do not trap outgoing longwave radiation as efficiently as their deeper counterparts, resulting in reduced radiative and latent heating of the atmosphere. The results also suggest that the net effect of precipitating systems on top-of-the-atmosphere (TOA) fluxes and the efficiency with which they heat the atmosphere and cool the surface exhibit strong dependence on their surroundings. The sensitivity of cloud radiative impacts to the atmospheric and surface properties they act to modify implies the existence of strong feedbacks whose representation may pose a significant challenge to the climate modeling community. © 2006 American Meteorological Society."
"7201605742;","A study of the mesoscale structure of Typhoon Flo (T9019): A case of COMPARE model intercomparison",2005,"10.2151/jmsj.83.1057","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33344459901&doi=10.2151%2fjmsj.83.1057&partnerID=40&md5=ef9d5e7fdf0ffc5c92b3255448df1321","Numerical experiments are performed for Typhoon Flo (T9019), which was the subject of an international model intercomparison (COMPARE III). The model used is a mesoscale-convection-resolving model. A global objective analysis (GANAL) data produced by JMA is used as an initial condition, and the initial time is 00 UTC 14 September 1990. The horizontal grid size is taken to be 5/36 degrees (about 15 km) in the fine-mesh area of a triply-nested grid model. Mesoscale structure of the simulated typhoon is studied in detail. Cloud water and rainwater fields are compared with satellite images. In the first 12 hours, the predicted rainwater field is quite different from that suggested from satellite images, mainly because the initial field is latently stable in the typhoon area. Latent instability is created by strong surface winds. Later in the integration, the rainfall patterns exhibit several important features in the satellite images. The simulated 6-hour accumulated rainfall between 48 and 54 hours is compared with some simulations from COMPARE. Rainfall amounts in the inner area of the typhoon, and in the tropics, appear to be better simulated. It is also shown that the time change of latent instability distribution is an important measure to explain how the rainfall distribution during this period is realized. Comparison of the wind fields at 200 hPa indicates great differences among the models. The structure of simulated rainbands is examined in some detail. It is shown that the model simulates rainbands of four types, with respect to locations of updraft/downdraft and the cold pool relative to the rainwater field, and whether the inflow into the rainband is on the concave edge or the convex edge. Behavior of mesoscale organized convection, which constitutes the rainband, is also examined. These res ults suggest that even a model with a coarse grid size of about 15 km can describe important features of the mesoscale structure of tropical cyclones. © 2005, Meterological Society of Japan."
"7201605742;","A numerical study of cloud clusters and a meso-α-scale low associated with a Meiyu front",2005,"10.2151/jmsj.83.305","https://www.scopus.com/inward/record.uri?eid=2-s2.0-24144437765&doi=10.2151%2fjmsj.83.305&partnerID=40&md5=85625fca7cfbd2d236b6cedf8cf38bc3","In order to understand cloud clusters and a meso-α-scale low, which were observed on the China Continent on 29 June 1998, numerical experiments are performed with a model which intends to resolve mesoscale organized convection, the effects of cumulus convection being incorporated as the subgrid-scale. The horizontal grid size is taken to be about 5 km for the fine grid area of the triply-nested grid model. The initial time for the numerical experiments is 00 UTC 29 June. Global analysis data (GANAL) of JMA is used as an initial condition, but two numerical experiments are performed, without and with slight reduction of low-level relative humidity of GANAL data. Results from numerical experiments indicate that in both cases, convective clouds are formed in a banded form, and a front that can be called a Meiyu front is also produced. On this front, a meso-α-scale low is also formed. The positions of the mesoscale lows predicted at 24 hours after the initial time in both cases, are almost the same. These are roughly in agreement with the position from GANAL data. Significant differences are found in the evolution stage for a period of 24 hours. In the original case, strong convective activity creates a mesoscale low at an earlier time (12 hours), and it is probably somewhat too intense compared with that observed. On the contrary, in the less humid case, three mesoscale convective systems and vortices (or closed isobars) are found at 12 hours. The easternmost vortex develops, and it becomes a mesoscale low at 18 hours. Discussions in this paper are made with an emphasis on the relation among latent instability, mesoscale convective systems, vortices, a mesoscale low and a Meiyu front. One of the significant features of the present case is that convective activity takes a banded form in a relatively large area of latent instability, and a Meiyu front is produced and intensified for the given initial conditions. As expected, latent instability becomes weaker, owing to convective activities. Eventually a latently stable area appears first around and just to the north of the convective area, and it expands northward. It is important to remark that the latently stable area to the north of the Meiyu front in the later stages is created by convective activities (not by synoptic-scale motions). In an area to the south of the front, latent instability becomes weaker gradually. However, continual rainfalls are maintained in the trailing portion of the mesoscale low till 00 UTC 30 June. This is in agreement with the observations. The relative importance of the effects of subgrid-scale cumulus convection and the grid-resolved condensation is also discussed. The importance of the latter increases with time; it contributes particularly to the development of the mesoscale low. © 2005, Meteorological Society of Japan."
"56245933700;6701873414;","Observations of transient linear organization and nonlinear scale interactions in lake-effect clouds: Part II: Nonlinear scale interactions",2005,"10.1175/MWR-2880.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17044372323&doi=10.1175%2fMWR-2880.1&partnerID=40&md5=e1ee982cf8419ac05c8f5b8b20db32ee","Linearly organized convection and associated horizontal roll vortices occasionally occur in atmospheric conditions in which theory predicts only cellular organization. One possible contributor to the occurrence of rolls in such conditions is nonlinear interactions between different scales of motion. In the winter of 1997/98, the Lake-Induced Convection Experiment (Lake-ICE) was conducted in part to investigate scale interactions in linearly organized convection. As discussed in Part I of this series, transient linear organization was observed during a wintertime lake-effect event during Lake-ICE. In Part II two-part nonlinear scale interactions and their possible role in the occurrence of linear organization in an unfavorable environment are investigated. Turbulence-scale vertical velocity variance peaks were consistently observed during roll strengthening and decay, suggesting a link between the scales. Composites of the nonlinear interaction terms in the roll-scale vertical turbulent kinetic energy (TKE) budget revealed that nonlinear interactions between the roll and turbulence scales were large compared to the observed change in roll-scale TKE, but do not coincide in time. © 2005 American Meteorological Society."
"7201926991;","Formation of multiple tropopause and stratospheric inertio-gravity waves",1992,"10.1016/0273-1177(92)90464-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026491917&doi=10.1016%2f0273-1177%2892%2990464-9&partnerID=40&md5=a4b8084a46ac79f62bf8cd7ac8dd5242","Lower-stratospheric layered structures of a few kilometers in thickness observed mainly by rawinsondes and MST radars are reviewed. Multiple tropopauses and temperature significant levels are found in the data of rawinsonde observations, whereas wind fluctuations associated with quasi-monochromatic internal inertio-gravity waves are analyzed from the MST radar observations. These two features are identified by several case studies, and a preliminary theoretical approach to explain the origin and role of them is presented. A poleward flow is induced and maintained by this structure, which is considered to compensate a vertical velocity field induced by an imbalance of the radiative-convective equilibrium in the troposphere. © 1992."
"7202910232;","Satellite observations of the southern hemisphere monsoon during Winter MONEX",1983,"10.1111/j.1600-0870.1983.tb00196.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977713954&doi=10.1111%2fj.1600-0870.1983.tb00196.x&partnerID=40&md5=c3fdab7c3808fb26c59b95185b2f87dd","Time‐longitude strips of infrared GMS satellite imagery have been used to study the southern hemisphere summer monsoon during Winter MONEX. This representation reveals a sudden monsoon onset in late December characterized by a transition to spatially organized convection. Active and break regions of the monsoon show a strong coherence in time but are very longitudinally dependent. The latitudinal dependence, on the other hand, is quite weak. The dominant spatial scale over which changes in convection take place is of order 35 degrees longitude by 15 degrees latitude. These synoptic scale convective regions can move in either the eastward or westward direction. Typical phase speeds of movement range between 3 and 8 degrees longitude per day. Tropical cyclones in the region are revealed to be embedded in the large‐scale monsoon circulation. 1983 Blackwell Munksgaard"
"56724696200;36724322000;7404678955;57203492395;57217271893;24554420100;21935606200;8982748700;57188570624;56317558800;54789101600;7006422317;7003745084;55341341000;57214537462;36134488100;25640569400;57189492881;57104577500;9536598800;57190120326;25721586700;57200650233;57209115087;56989640500;6507719789;35490341500;8946494600;7101874266;55554531900;55752760600;7005203586;7006151934;55345946200;55436842300;57203635779;57218874034;7201594914;55338801300;55458732800;9244954000;57214343044;57218873996;6507848228;57212198554;34968437900;57212198838;57212200093;57198459732;57211031187;6506746457;57218874058;57218874154;6504043008;57218874119;55658058500;55001699000;57204531461;55390690800;57218874005;57218874176;41361927700;25523100000;57203544786;57218873997;","Interaction of convective organization with monsoon precipitation, atmosphere, surface and sea: The 2016 INCOMPASS field campaign in India",2020,"10.1002/qj.3633","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068147381&doi=10.1002%2fqj.3633&partnerID=40&md5=34574f9caff6fa391937b39792a41943","The INCOMPASS field campaign combines airborne and ground measurements of the 2016 Indian monsoon, towards the ultimate goal of better predicting monsoon rainfall. The monsoon supplies the majority of water in South Asia, but forecasting from days to the season ahead is limited by large, rapidly developing errors in model parametrizations. The lack of detailed observations prevents thorough understanding of the monsoon circulation and its interaction with the land surface: a process governed by boundary-layer and convective-cloud dynamics. INCOMPASS used the UK Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 aircraft for the first project of this scale in India, to accrue almost 100 h of observations in June and July 2016. Flights from Lucknow in the northern plains sampled the dramatic contrast in surface and boundary-layer structures between dry desert air in the west and the humid environment over the northern Bay of Bengal. These flights were repeated in pre-monsoon and monsoon conditions. Flights from a second base at Bengaluru in southern India measured atmospheric contrasts from the Arabian Sea, over the Western Ghats mountains, to the rain shadow of southeast India and the south Bay of Bengal. Flight planning was aided by forecasts from bespoke 4 km convection-permitting limited-area models at the Met Office and India's NCMRWF. On the ground, INCOMPASS installed eddy-covariance flux towers on a range of surface types, to provide detailed measurements of surface fluxes and their modulation by diurnal and seasonal cycles. These data will be used to better quantify the impacts of the atmosphere on the land surface, and vice versa. INCOMPASS also installed ground instrumentation supersites at Kanpur and Bhubaneswar. Here we motivate and describe the INCOMPASS field campaign. We use examples from two flights to illustrate contrasts in atmospheric structure, in particular the retreating mid-level dry intrusion during the monsoon onset. © 2019 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"55845531400;36663291700;","Deflating Super-puffs: Impact of Photochemical Hazes on the Observed Mass-Radius Relationship of Low-mass Planets",2020,"10.3847/1538-4357/ab6a9b","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081622335&doi=10.3847%2f1538-4357%2fab6a9b&partnerID=40&md5=bbfe11dea5a576c9e2ed6b4edd7a59cf","The observed mass-radius relationship of low-mass planets informs our understanding of their composition and evolution. Recent discoveries of low-mass, large-radius objects (""super-puffs"") have challenged theories of planet formation and atmospheric loss, as their high inferred gas masses make them vulnerable to runaway accretion and hydrodynamic escape. Here we propose that high-altitude photochemical hazes could enhance the observed radii of low-mass planets and explain the nature of super-puffs. We construct model atmospheres in radiative-convective equilibrium and compute rates of atmospheric escape and haze distributions, taking into account haze coagulation, sedimentation, diffusion, and advection by an outflow wind. We develop mass-radius diagrams that include atmospheric lifetimes and haze opacity, which is enhanced by the outflow, such that young (∼0.1-1 Gyr), warm (T eq ≥ 500 K), low-mass objects (M c &lt; 4 M ⊕) should experience the most apparent radius enhancement due to hazes, reaching factors of three. This reconciles the densities and ages of the most extreme super-puffs. For Kepler-51b, the inclusion of hazes reduces its inferred gas mass fraction to &lt;10%, similar to that of planets on the large-radius side of the sub-Neptune radius gap. This suggests that Kepler-51b may be evolving toward that population and that some warm sub-Neptunes may have evolved from super-puffs. Hazes also render transmission spectra of super-puffs and sub-Neptunes featureless, consistent with recent measurements. Our hypothesis can be tested by future observations of super-puffs' transmission spectra at mid-infrared wavelengths, where we predict that the planet radius will be half of that observed in the near-infrared. © 2020. The American Astronomical Society. All rights reserved."
"7006095466;","Toward a Dynamical Foundation for Organized Convection Parameterization in GCMs",2019,"10.1029/2019GL085316","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076216991&doi=10.1029%2f2019GL085316&partnerID=40&md5=70d64bf79ad4b94d8d0bb8112c7aae57","A dynamically based parameterization of organized moist convection in the form of multiscale coherent structures and slantwise layer overturning principles provides upscale heat and counter-gradient momentum transports distinct from diffusive down-gradient mixing by unorganized cumulus. Implementation of a minimalist version of this new parameterization in a state-of-the-art global climate model (GCM) improves the Madden-Julian Oscillation and convectively coupled waves and generates large-scale patterns of tropical precipitation consistent with Tropical Rainfall Measuring Mission satellite measurements. A question on the need to parameterize mesoscale convective organization to mitigate mean state biases is addressed. ©2019. American Geophysical Union. All Rights Reserved."
"57213995653;56014511300;57112070700;35509639400;56471281900;","Identifying the sources of convective memory in cloud-resolving simulations",2019,"10.1175/JAS-D-18-0036.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059549670&doi=10.1175%2fJAS-D-18-0036.1&partnerID=40&md5=2eaafa189bcd477de0e2551445b65f16","Convection is often assumed to be controlled by the simultaneous environmental fields.But to what extent does it also remember its past behavior? This study proposes a new framework in which the memory of previous convective-scale behavior, ''microstate memory,'' is distinguished from macrostate memory, and conducts numerical experiments to reveal these memory types. A suite of idealized, cloud-resolving radiative-convective equilibrium simulations in a 200-km square domain is performed with the Weather Research and Forecasting (WRF)Model. Three deep convective cases are analyzed: unorganized, organized by low-levelwind shear, and selfaggregated. The systematic responses to sudden horizontal homogenization of various fields, in various atmospheric layers, designed to eliminate their specific microstructure, are compared in terms of precipitation change and time of recovery to equilibrium. Results imply a substantial role for microstate memory. Across organization types, microstructure in water vapor and temperature has a larger and longer-lasting effect on convection than in winds or hydrometeors. Microstructure in the subcloud layer or the shallow cloud layer has more impact than in the free troposphere. The recovery time scale dramatically increases from unorganized (2-3 h) to organized cases (24 h or more). Longer-time-scale adjustments also occur and appear to involve both small-scale structures and domainmean fields. These results indicate that most convective microstate memory is stored in low-level thermodynamic structures, potentially involving cold pools and hot thermals.This memory appears strongly enhanced by convective organization. Implications of these results for parameterizing convection are discussed. © 2019 American Meteorological Society."
"55944765000;57192468922;","Simulating Nonhydrostatic Atmospheres on Planets (SNAP): Formulation, Validation, and Application to the Jovian Atmosphere",2019,"10.3847/1538-4365/aafdaa","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062603506&doi=10.3847%2f1538-4365%2faafdaa&partnerID=40&md5=25069f4c33cd17a371f43e882031597c","A new nonhydrostatic and cloud-resolving atmospheric model is developed for studying moist convection and cloud formation in planetary atmospheres. It is built on top of the Athena++ framework, utilizing its static/adaptive mesh-refinement, parallelization, curvilinear geometry, and dynamic task scheduling. We extend the original hydrodynamic solver to vapors, clouds, and precipitation. Microphysics is formulated generically so that it can be applied to both Earth and Jovian planets. We implemented the Low Mach number Approximate Riemann Solver for simulating low-speed atmospheric flows in addition to the usual Roe and Harten-Lax-van Leer-Contact (HLLC) Riemann solvers. Coupled with a fifth-order weighted essentially nonoscillatory subgrid-reconstruction method, the sharpness of critical fields such as clouds is well-preserved, and no extra hyperviscosity or spatial filter is needed to stabilize the model. Unlike many atmospheric models, total energy is used as the prognostic variable of the thermodynamic equation. One significant advantage of using total energy as a prognostic variable is that the entropy production due to irreversible mixing processes can be properly captured. The model is designed to provide a unified framework for exploring planetary atmospheres across various conditions, both terrestrial and Jovian. First, a series of standard numerical tests for Earth's atmosphere is performed to demonstrate the performance and robustness of the new model. Second, simulation of an idealized Jovian atmosphere in radiative-convective equilibrium shows that (1) the temperature gradient is superadiabatic near the water condensation level because of the changing of the mean molecular weight, and (2) the mean profile of ammonia gas shows a depletion in the subcloud layer down to nearly 10 bars. Relevance to the recent Juno observations is discussed. © 2019. The American Astronomical Society. All rights reserved."
"57210687618;36961988200;","Dry and semidry tropical cyclones",2019,"10.1175/JAS-D-18-0357.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075573988&doi=10.1175%2fJAS-D-18-0357.1&partnerID=40&md5=53e4e699956b3d6f425133fa68f8cea8","It is widely believed that tropical cyclones are an intrinsically moist phenomenon, requiring evaporation and latent heat release in cumulus convection. Recent numerical modeling by Mrowiec et al., however, challenged this conventional wisdom by finding the formation of axisymmetric dry tropical cyclones in dry radiative–convective equilibrium (RCE). This paper addresses ensuing questions about the stability of dry tropical cyclones in 3D, the moist–dry vortex transition, and whether existing theories for intensity, size, and structure apply to dry cyclones. A convection-permitting model is used to simulate rotating 3D RCE, with surface wetness (0–1) and surface temperature (240–300 K) smoothly varying between dry and moist states. Tropical cyclones spontaneously form and persist for tens of days in both moist and dry/cold states, as well as part of the relatively moist/warm intermediate parameter space. As the surface is dried or cooled, cyclones weaken, both in absolute terms and relative to their potential intensities. Dry and semidry cyclones have smaller outer radii but similar-sized or larger convective centers compared to moist cyclones, consistent with existing structural theory. Strikingly, spontaneous cyclogenesis fails to occur at moderately low surface wetness values and intermediate surface temperatures of 250–270 K. Simulations with time-varying surface moisture and sea surface temperatures indicate this range of parameter space is a barrier to spontaneous genesis but not cyclone existence. Dry and semidry tropical cyclones in rotating RCE provide a compelling model system to further our understanding of real moist tropical cyclones. © 2019 American Meteorological Society."
"55682851300;7101661890;6505932008;","The role of cold pools in tropical oceanic convective systems",2018,"10.1175/JAS-D-17-0352.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050964198&doi=10.1175%2fJAS-D-17-0352.1&partnerID=40&md5=b6672d5b98b7825c5c037c97af18ff35","The processes governing organized tropical convective systems are not completely understood despite their important influences on the tropical atmosphere and global circulation. In particular, cold pools are known to influence the structure and maintenance of midlatitude systems via Rotunno-Klemp-Weisman (RKW) theory, but cold pools may interact differently with tropical convection because of differences in cold pool strength and environmental shear. In this study, the role of cold pools in organized oceanic tropical convective systems is investigated, including their influence on system intensity, mesoscale structure, and propagation. To accomplish this goal, high-resolution idealized simulations are performed for two different systems that are embedded within a weakly sheared cloud population approaching radiative-convective equilibrium. The cold pools are altered by changing evaporation rates below cloud base in a series of sensitivity tests. The simulations demonstrate surprising findings: when cold pools are weakened, the convective systems become more intense. However, their propagation speeds and mesoscale structure are largely unaffected by the cold pool changes. Passive tracers introduced into the cold pools indicate that the convection intensifies when cold pools are weakened because cold pool air is entrained into updrafts, thereby reducing updraft intensity via the cold pools' initial negative buoyancy. Gravity waves, rather than cold pools, appear to be the important modulators of system propagation and mesoscale structure. These results reconfirm that RKW theory does not fully explain the behavior of tropical oceanic convective systems, even those that otherwise appear consistent with RKW thinking. © 2018 American Meteorological Society."
"57204833386;7201504886;","Observing the tropical atmosphere in moisture space",2018,"10.1175/JAS-D-17-0375.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85057355483&doi=10.1175%2fJAS-D-17-0375.1&partnerID=40&md5=88d557495b6c0f122056c9903d2bd9d9","Measurements from the Barbados Cloud Observatory are analyzed to identify the processes influencing the distribution of moist static energy and the large-scale organization of tropical convection. Five years of water vapor and cloud profiles from a Raman lidar and cloud radar are composed to construct the structure of the observed atmosphere in moisture space. The large-scale structure of the atmosphere is similar to that now familiar from idealized studies of convective self-aggregation, with shallow clouds prevailing over a moist marine layer in regions of low-rank humidity, and deep convection in a nearly saturated atmosphere in regions of high-rank humidity. With supplementary reanalysis datasets the overall circulation pattern is reconstructed in moisture space, and shows evidence of a substantial lower-tropospheric component to the circulation. This shallow component of the circulation helps support the differentiation between the moist and dry columns, similar to what is found in simulations of convective self-aggregation. Radiative calculations show that clearsky radiative differences can explain a substantial part of this circulation, with further contributions expected from cloud radiative effects. The shallow component appears to be important for maintaining the low gross moist stability of the convecting column. A positive feedback between a shallow circulation driven by differential radiative cooling and the low-level moisture gradients that help support it is hypothesized to play an important role in conditioning the atmosphere for deep convection. The analysis suggests that the radiatively driven shallow circulations identified by modeling studies as contributing to the self-aggregation of convection in radiative-convective equilibrium similarly play a role in shaping the intertropical convergence zone and, hence, the large-scale structure of the tropical atmosphere. © 2018 American Meteorological Society."
"7409792174;7006095466;","Shear-parallel mesoscale convective systems in a moist low-inhibition mei-yu front environment",2017,"10.1175/JAS-D-17-0121.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040350350&doi=10.1175%2fJAS-D-17-0121.1&partnerID=40&md5=d001c8cb2c582b8cefaece2d41a5836e","Numerical simulations are performed to investigate organized convection observed in the Asian summer monsoon and documented as a category of mesoscale convective systems (MCSs) over the U.S. continent during the warm season. In an idealized low-inhibition and unidirectional shear environment of the mei-yu moisture front, the structure of the simulated organized convection is distinct from that occurring in the classical quasi-two-dimensional, shear-perpendicular, and trailing stratiform (TS) MCS. Consisting of four airflow branches, a three-dimensional, eastward-propagating, downshear-tilted, shear-parallel MCS builds upshear by initiating new convection at its upstream end. The weak cold pool in the low-inhibition environment negligibly affects convection initiation, whereas convectively generated gravity waves are vital. Upstream-propagating gravity waves form a saturated or near-saturated moist tongue, and downstream-propagating waves control the initiation and growth of convection within a preexisting cloud layer. A sensitivity experiment wherein the weak cold pool is removed entirely intensifies the MCS and its interaction with the environment. The horizontal scale, rainfall rate, convective momentum transport, and transverse circulation are about double the respective value in the control simulation. The positive sign of the convective momentum transport contrasts with the negative sign for an eastward-propagating TS MCS. The structure of the simulated convective systems resembles shear-parallel organization in the intertropical convergence zone (ITCZ). © 2017 American Meteorological Society."
"56089348800;16475714800;","The physics of orographic elevated heating in radiative-convective equilibrium",2017,"10.1175/JAS-D-16-0312.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85026291548&doi=10.1175%2fJAS-D-16-0312.1&partnerID=40&md5=2b33c63f5ea17e115afc0160d9d9d613","Elevated heating of the atmosphere by large plateaus has been argued to influence regional climate in Asia and other regions, but the mechanisms that cause the troposphere to equilibrate at warmer temperatures over elevated terrain are not well understood. This paper quantitatively describes the physics that controls temperatures over elevated terrain in radiative-convective equilibrium (RCE). First, a cloud-system-resolving model (CSRM) is used to simulate RCE states over surfaces with various elevations. Then, a theory for the influence of surface elevation on temperatures in RCE is presented. Together with offline radiative transfer calculations, this theory is used to quantitatively attribute the magnitude of the elevated heating effect to topof- atmosphere radiative flux changes caused by decreases in longwave absorption, shortwave scattering, and the moist lapse rate that occur as surface pressure drops. Sensitivity functions obtained through these offline calculations suggest that elevated heating is weaker in warmer climates, and additional CSRM simulations support this hypothesis. Under certain circumstances, even the sign of the elevated heating effect can change to produce cooler temperatures at a given pressure level as the surface is lifted in RCE. © 2017 American Meteorological Society."
"56127067100;7103119050;","Connections matter: Updraft merging in organized tropical deep convection",2017,"10.1002/2017GL074162","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85023636294&doi=10.1002%2f2017GL074162&partnerID=40&md5=c1c8cd8dfc923da00f8e22d8885dedf0","When tropical cumulus convection is organized, the spacing between updrafts is reduced, and deep convective cloud tops are higher. The relative importance of various processes through which organization increases cloud top heights is not well understood. It is likely that decreased spacing between updrafts in organized convection increases the frequency of convective updraft merging. What is the relative importance of merging in determining an updraft parcel's detrainment height? We investigated updraft parcel merging in organized deep convection using results from a large eddy simulation. We used Lagrangian parcel trajectories (LPTs) to locate merging events. LPTs that merge reach detrainment heights 1.5 km higher on average than LPTs which do not merge. Merged LPTs are more buoyant than nonmerged LPTs, implying less dilution due to entrainment. Using mutual information analysis, we found that merging, cloud base vertical velocity, and cloud base area are about equally important in determining parcel detrainment height. ©2017. American Geophysical Union. All Rights Reserved."
"16834715500;55740123300;23491820700;6701744275;35325977100;56186932200;7102609908;","Tropospheric turbulence over the tropical open Ocean: Role of gravity waves",2017,"10.1175/JAS-D-16-0135.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016762417&doi=10.1175%2fJAS-D-16-0135.1&partnerID=40&md5=b17514a9a1985944a965f7e75628699a","A large set of soundings obtained in the Indian Ocean during three field campaigns is used to provide statistical characteristics of tropospheric turbulence and its link with gravity wave (GW) activity. The Thorpe method is used to diagnose turbulent regions of a few hundred meters depth. Above the mixed layer, turbulence frequency varies from ~10% in the lower troposphere up to ~30% around 12-km height. GWs are captured by their signature in horizontal wind, normalized temperature, and balloon vertical ascent rate. These parameters emphasize different parts of the wave spectrum from longer to shorter vertical wavelengths. Composites are constructed in order to reveal the vertical structure of the waves and their link with turbulence. The relatively longer-wavelength GWs described by their signature in temperature (GWTs) are more active in the lower troposphere, where they are associated with clear variations in moisture. Turbulence is then associated with minimum static stability and vertical shear, stressing the importance of the former and the possibility of convective instability. Conversely, the short waves described by their signature in balloon ascent rate (GWws) are detected primarily in the upper troposphere, and their turbulence is associated with a vertical shear maximum, suggesting the importance of dynamic instability. Furthermore, GWws appear to be linked with local convection, whereas GWTs are more active in suppressed and dry phases in particular of the Madden-Julian oscillation. These waves may be associated with remote sources, such as organized convection or local fronts, such as those associated with dry-air intrusions. © 2017 American Meteorological Society."
"54983414800;56192746700;6602805147;","The tropical precipitation pickup threshold and clouds in a radiative convective equilibrium model: 1. Column moisture",2017,"10.1002/2016JD025907","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021336818&doi=10.1002%2f2016JD025907&partnerID=40&md5=fa694d0214eea314a13c428871628b3a","A survey of published results indicates that a column relative humidity near 77% is consistently observed to separate raining and nonraining columns in a time and space mean in the tropics, but why this approximate value of humidity should initiate such a statistical state transition is not readily apparent. An investigation is conducted of the submesoscale cloud processes that link column relative humidity to this abrupt pickup in heavy precipitation and of the magnitude of humidity at which this transition occurs. A cloud system resolving model in radiative convective equilibrium is used. Precipitation statistics from this simulation indicate a switch in mean precipitation state at 77% relative humidity with infrequent heavy rainfall at lower humidity. These statistics are broadly insensitive to spatial scaling. Low-level cloud fraction and convergent flux of moisture are shown to be sensitive to column humidity near 77%, while upper level cloud fraction is markedly less sensitive. Mean updraft mass flux increases with increasing humidity but only at values of humidity well above the pickup. Both warm rain processes and melting are shown to depend strongly on column humidity near the pickup but in different circumstances. No single process is determined to result in a pickup in precipitation. It is suggested that column humidity temporally leads precipitation and therefore causes its intensity. © 2017. American Geophysical Union. All Rights Reserved."
"56487672200;8684508300;57201725986;57189466749;56593857400;","Kinetic energy budget during the genesis period of tropical cyclone durian (2001) in the South China Sea",2016,"10.1175/MWR-D-15-0042.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981294584&doi=10.1175%2fMWR-D-15-0042.1&partnerID=40&md5=8e75cd829dafb6b1c86a208425896de3","Aset of kinetic energy (KE) budget equations associated with four horizontal flow components was derived to study the KE characteristics during the genesis of Tropical Cyclone (TC) Durian (2001) in the South China Sea using numerical simulation data. The genesis process was divided into three stages: the monsoon trough stage (stage 1), the midlevel mesoscale convective vortex (MCV) stage (stage 2), and the establishment stage of the TC vortex (stage 3). Analysis showed that the KE of the symmetric rotational flow (SRF) was the largest and kept increasing, especially in stages 2 and 3, representing the symmetrization process during TC genesis. TheKEof the SRF was mainly converted from theKEof the symmetric divergent flow (SDF), largely transformed from the available potential energy (APE). It was found that vortical hot towers (VHTs) emerged abundantly, aggregated, and merged within the MCV region in stages 1 and 2. From the energy budget perspective, massive moist-convection-produced latent heat was concentrated and accumulated within the MCV region, especially in stage 2, and further warmed the atmosphere, benefiting the accumulation of APE and the transformation from APE to KE. As a result, the midlevel circulation (or MCV) grew strong rapidly. In stage 3, the intensity and number of VHTs both decreased. However, affected by increasing lower-level inward radial wind, latent heat released by the organized convection, instead of disorganized VHTs in the first two stages, continuously contributed to the strengthening of the surface TC circulation as well as the warm core. © 2016 American Meteorological Society."
"55270376800;26536569500;","Self-consistency tests of large-scale dynamics parameterizations for single-column modeling",2015,"10.1002/2014MS000378","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027917856&doi=10.1002%2f2014MS000378&partnerID=40&md5=b41193754afb61062e235477f0c05082","Large-scale dynamics parameterizations are tested numerically in cloud-resolving simulations, including a new version of the weak-pressure-gradient approximation (WPG) introduced by Edman and Romps (2014), the weak-temperature-gradient approximation (WTG), and a prior implementation of WPG. We perform a series of self-consistency tests with each large-scale dynamics parameterization, in which we compare the result of a cloud-resolving simulation coupled to WTG or WPG with an otherwise identical simulation with prescribed large-scale convergence. In self-consistency tests based on radiative-convective equilibrium (RCE; i.e., no large-scale convergence), we find that simulations either weakly coupled or strongly coupled to either WPG or WTG are self-consistent, but WPG-coupled simulations exhibit a nonmonotonic behavior as the strength of the coupling to WPG is varied. We also perform self-consistency tests based on observed forcings from two observational campaigns: the Tropical Warm Pool International Cloud Experiment (TWP-ICE) and the ARM Southern Great Plains (SGP) Summer 1995 IOP. In these tests, we show that the new version of WPG improves upon prior versions of WPG by eliminating a potentially troublesome gravity-wave resonance. © 2015. The Authors."
"55351496300;55510783800;7501630594;55751472800;55817283000;55510690200;","Structure and evolution of line-shaped convective systems associated with Changma front during GRL PHONE-09: 6 July 2009 case",2014,"10.1002/met.1418","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904739695&doi=10.1002%2fmet.1418&partnerID=40&md5=d0d86e62be09730c1ae410b775d5d84d","This study investigates the structure and evolution of line-shaped convective systems (LCSs) associated with the Changma front observed over Chujado in the southwestern Korean Peninsula by using intensive observational data from upper-air sounding and Doppler radars. LCSs embedded as a multicellular precipitation system developed north of the warm front and persisted for 4 h. With continuous new cells development, the convective cells gradually strengthened and merged into the LCSs and exhibited a high low-level mixing ratio, weak vertical wind shear, and negligible instability. A rear-to-front jet corresponding to a low-level jet (LLJ) was concurrent with a high equivalent potential temperature (θe) environmental inflow over the warm front, which suggests that the rear-to-front jet with moist air induced destabilization. Three-dimensional kinematic and reflectivity structures of the LCSs exhibited homogeneous southerly and southwesterly winds with height, small horizontal wind shear, and convergence. Transfer of positive u and v momentum upward by convective eddies into the LCSs and of horizontal momentum occurred through organized convection; both these transfers acted to intensify the LLJ. © 2014 Royal Meteorological Society."
"7402346120;7801485866;","Indian ocean near-equatorial symmetric stability from satellite observations: An elusive connection to atmospheric convection",2010,"10.1080/01431161.2010.485153","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957697675&doi=10.1080%2f01431161.2010.485153&partnerID=40&md5=3f45a50107a556abdda651ae53d9c1de","The north-south symmetry of the low level near-equatorial atmospheric flow is examined in relation to the position of the Intertropical Convergence Zone (ITCZ) over the Indian Ocean with the aid of satellite and reanalysis data. Absolute vorticity (AV) and convergence fields on temporal scales of 10 days are derived from 7 years of Quick Scatterometer (QuikSCAT) observations and related statistically to organized convection deduced from outgoing longwave radiation (OLR) measured by the National Oceanic and AtmosphericAdministration (NOAA)polar-orbiting satellites. The AV observations reveal a belt of symmetric instability on the summer side of the equator. The evolution of this symmetric instability with respect to the crossequatorial flow (CEF), the location of the ITCZ, and monsoonal forcing is investigated. We identify three distinct dominant convective regimes. We show that during the active Indian monsoon season, symmetric instability and the displacement of the zero-AV line off the equator are directly linked to organized convection and the offequatorial location of the ITCZ. The advective (inertial) regime interacts with and is controlled bymonsoon andCEF. In periods of transition between summer and winter monsoon, the lower atmosphere is symmetrically stable and two other convective regimes can be identified: a double ITCZ, and localized convection near the equator. © 2010 Taylor & Francis."
"8266109300;7202899330;","The role of radiation in influencing tropical cloud distributions in a radiative-convective equilibrium cloud-resolving model",2009,"10.1175/2008JAS2738.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549155388&doi=10.1175%2f2008JAS2738.1&partnerID=40&md5=2a34a44aa201ee92720a16f9e7415635","Observations by Johnson et al. depict regions of active tropical convection as possessing increased relative humidity through a deep layer and reduced low-level static stability when compared to nonconvecting regions. Shallow cumulus clouds, congestus clouds, and deep convection all coexist within these convecting regions. This investigation explores the effect that radiation might have on the tropical cloud distributions by using large-domain (20 000 km) radiative - convective equilibrium cloud-resolving model (RCE-CRM) experiments that reproduce similar moisture, stability, and cloud structures to those observed. Radiation is found to significantly increase the amount of shallow and intermediate-level clouds (tops between 1.5 and 5 km) by increasing low-level stability and thus promoting additional low-level cloud detrainment. The mechanism by which radiation stabilizes the low levels is found to differ between convectively suppressed and active regions. In convectively suppressed regions, strong relative humidity gradients within the trade inversion layer produce a low-level cooling maximum that further stabilizes the stable layer, much as proposed by Mapes and Zuidema. In convectively active regions, sufficiently moist columns with no relative humidity gradients are also found to produce a low-level cooling maximum that stabilizes the lower levels. This cooling maximum is due to the complicated effects of the water vapor continuum and is sensitive to the absolute moisture path. Because of the dependence on absolute moisture, the radiative enhancement of shallow and intermediate-level clouds in convectively active regions is potentially sensitive to SSTs. © 2009 American Meteorological Society."
"13605965600;6603667298;7101787483;","The extensive episode of derecho-producing convective systems in the United States during May and June 1998: A multi-scale analysis and review",2007,"10.1002/met.23","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548752957&doi=10.1002%2fmet.23&partnerID=40&md5=a02b350cff625e730c14b307c625f832","A multi-scale analysis is presented on widespread and long-lived convectively generated windstorms, known as derechos. Analyses of the derecho-producing environments during 15 May-30 June 1998 indicate that this exceptional episode of derechos and derecho groupings (or series) was supported by ingredients (i.e. moisture, instability, and wind shear) that were supplied by the large-scale setting. In particular, the semi-stagnant subtropical ridge and associated capping inversion across the southern tier of the U.S. were important in supplying amplified moisture and instability to derecho-genesis regions through an underrunning process. Regions of preferred derecho formation appeared to correspond to shifts in the overall strength and position of the ridge, illustrating the importance of the ridge in focusing successive organized convection. Initiating mechanisms varied widely and were not restricted to warm-air advection regimes along quasi-stationary boundaries that forecasters often associate with warm-season derecho environments. In several cases, derecho-producing convective systems were generated by tropospheric features not consistent with common conceptual models of derecho environments such as closed lows and strong vorticity maxima. Further, three distinct series types were identified and classified based on their initiating mechanisms. Copyright © 2007 Royal Meteorological Society."
"6602418877;57193882808;7006095466;","Explicit convection over the Western Pacific warm pool in the community atmospheric model",2005,"10.1175/JCLI3345.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20544469956&doi=10.1175%2fJCLI3345.1&partnerID=40&md5=0439b0acfd8d0b702b85071fa789a7d8","This paper reports on the application of the cloud-resolving convection parameterization (CRCP) to the Community Atmospheric Model (CAM), the atmospheric component of the Community Climate System Model (CCSM). The cornerstone of CRCP is the use of a two-dimensional zonally oriented cloud-system resolving model to represent processes on mesoscales at the subgrid scale of a climate model. Herein, CRCP is applied at each climate model column over the tropical western Pacific warm pool, in a domain spanning 10°S-10°N, 150°-170°E. Results from the CRCP simulation are compared with CAM in its standard configuration. The CRCP simulation shows significant improvements of the warm pool climate. The cloud condensate distribution is much improved as well as the bias of the tropopause height. More realistic structure of the intertropical convergence zone (ITCZ) during the boreal winter and better representation of the variability of convection are evident. In particular, the diurnal cycle of precipitation has phase and amplitude in good agreement with observations. Also improved is the large-scale organization of the tropical convection, especially superclusters associated with Madden-Julian oscillation (MJO)-like systems. Location and propagation characteristics, as well as lower-tropospheric cyclonic and upper-tropospheric anticyclonic gyres, are more realistic than in the standard CAM. Finally, the simulations support an analytic theory of dynamical coupling between organized convection and equatorial beta-plane vorticity dynamics associated with MJO-like systems. © 2005 American Meteorological Society."
"7006453728;56353724900;","Characteristic scale of convective organization and monsoon intensity",2004,"10.1029/2004GL020268","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14544307423&doi=10.1029%2f2004GL020268&partnerID=40&md5=6f3ae310dec836f95bf4f0d26eac4312","Many aspects of the inter-annual variability of the Indian summer monsoon (ISM) remain unexplained. While boundary forcing like SST, snow cover and land surface processes are known to play significant roles, they cannot explain all of the inter-annual variability of ISM. We identify and show that nature and organization of dynamics play a critical role in the intensity, and hence the variability of ISM. Investigation using a 55-year dataset from NCEP at different scales and locations clearly shows a sharp contrast in organized convergence at a scale of 20° between excess and deficit monsoon years; the deficit monsoon years, including 2002, are marked by suppressed organized convergence. The general conclusions are valid even in presence of moist convergence, indicating that it is the efficient organization through convergence that plays a critical role in monsoon intensity. The results thus provide new insight into the dynamics and simulation of monsoon. Copyright 2004 by the American Geophysical Union."
"7003406400;8551194800;","Solar radiative biases in deep convective regimes: Possible implications for dynamical feedback",2003,"10.1256/qj.02.105","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038556967&doi=10.1256%2fqj.02.105&partnerID=40&md5=997a23d397027670709229bafb8dc3ac","There is increasing evidence that interactions between radiation and convectively determined water vapour and cloud fields can have a significant dynamical impact on the tropical circulation. However, the use of a one-dimensional (1D) independent column method for the calculation of solar fluxes in cloud-resolving or mesoscale models could possibly misrepresent this feedback. This is investigated by calculating 1D and full three-dimensional (3D) solar fluxes through a 3D field of deep convective clouds generated using a high-resolution cloud-resolving model, and diagnosing the clear-sky subsidence velocities required to balance this if a state of radiative convective equilibrium were to exist. The mean clear-sky solar radiative heating rate is found to change by up to 15%. At low sun angles the shading of the clear-sky regions implies a reduction of net clear-sky heating rates. In contrast, at higher solar elevations the scattering effect dominates shading and the clear-sky heating rates are enhanced, implying an enhancement of the diurnal cycle. However, since the 1D/3D heating-rate differences in the clear sky increase smoothly from zero at the tropopause to their maximum value near the surface, the vertical gradient and thus the impact on the vertical profile of entrainment and detrainment into the convective regions is negligibly small. This implies that the strong radiative dynamical feedbacks so far documented in cloud-ensemble models cannot be discounted on the grounds of their use of an independent column calculation for the solar radiative transfer. That said, the substantial bias noted in surface downward solar fluxes could result in a substantial impact in convective organization if an interactive land surface were used as a lower boundary condition."
"7409792174;7006095466;","Mass and momentum transports by organized convection: Effects of shear and buoyancy",1996,"10.1175/1520-0469(1996)053<0964:MAMTBO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029729565&doi=10.1175%2f1520-0469%281996%29053%3c0964%3aMAMTBO%3e2.0.CO%3b2&partnerID=40&md5=1da580c467523379342f54a0102bb1dd","The dynamical theory of mass and momentum transport by organized convection, produced by Moncrieff, is extended using a hydrodynamical model, a two-dimensional buoyant model, and a quasi-three-dimensional buoyant model. Each is characterized by three relative flow branches that idealize the structure of squall-line cloud systems. Despite the physical and structural diversity, a clear similarity in mass and momentum transports holds for the entire hierarchy, such as the negative-dominant momentum flux by systems propagating in the positive x-direction. Shear and buoyancy are shown to alter the details but not the overall nature of the dynamical transports. In particular, both mass and momentum fluxes are insensitive to the Froude numbers in the hydrodynamical model. The two-dimensional buoyant model enhances the momentum flux amplitude but has a much less noticeable impact on mass fluxes. In contrast, the three-dimensional buoyant model has a larger mass flux and raises the heights of the mass and momentum flux extrema. The low-level inflow shear has a similar effect in these models by increasing both mass and momentum fluxes. Buoyancy affects transports largely through modifying the flow field while the inflow shear influences transports by strengthening the low-level convergence."
"55456758000;7003625261;57201235812;","Upper ocean dynamics",1987,"10.1029/RG025i002p00193","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84995064183&doi=10.1029%2fRG025i002p00193&partnerID=40&md5=96ad266d838d1030692e33380a65e847","Research on upper ocean dynamics has contributed steady progress towards a more complete and useful understanding of the ocean's role in air/sea interaction and climate. High resolution models of the upper ocean thermal structure are now quite realistic, and in some applications are limited as much by uncertainties in the surface heat flux as by uncertainties in model physics. Low resolution upper ocean thermal models are routinely included in most climate models, and have been shown to give far better simulations than do simple slab or heat conduction models. Some of these climate models have provided important new insights into the mechanisms by which the ocean may respond to a future greenhouse‐imposed surface heating anomaly. In contrast, the structure of the upper ocean wind‐driven velocity is not so well understood. Some models and high quality field data show significant sustained vertical shears within the temperature mixed‐layer, while other data sets show organized, energetic, three‐dimensional flow structures. Still other field data appear to reveal a velocity mixed‐layer very much like the thermal mixed‐layer. Thus the structure of the upper ocean velocity is an important and still open issue for dynamics and models, and also for the interpretation of the large and rapidly growing drifting buoy data base. The role of surface waves in generating and maintaining this current structure also remains poorly understood. Waves certainly play a central role in the mechanics of momentum transfer across the air‐sea interface, both through surface roughness and more directly as a consequence of breaking. The combined system of waves and wind‐driven currents is also known to be unstable, and their interaction may be an important mechanism for producing certain types of organized convection in the mixed‐layer. Copyright 1987 by the American Geophysical Union."
"6602286842;","Heating by organized convection as a source of polar low intensification.",1987,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0023490672&partnerID=40&md5=3eb3c997ec40607fa71a2e4f7e8046a4","A well-mixed convective boundary layr is a common feature of the synoptic situation when polar lows are observed. However, in the polar lows themselves, the convection seems to reach much higher levels. Also, many polar lows have a characteristic central domain with especially strong winds and large vorticity. A simpel linear CISK model is used to estimate the intensification caused by the convection. The model is based on constraints imposed by the assumption of a well-mixed convective layer. Elements of the cloud physics are used to explain observed characteristics of clouds and precipitation. Finally, it is shown that additional growth rate may be expected if CISK is present in an environment of large relative vorticity. -from Author"
"25640569400;57203492395;56724696200;57104577500;7404678955;34976155900;24554420100;6505835093;57190120326;57217271893;7006432091;6507809414;36724322000;","The dynamic and thermodynamic structure of the monsoon over southern India: New observations from the INCOMPASS IOP",2020,"10.1002/qj.3439","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064069522&doi=10.1002%2fqj.3439&partnerID=40&md5=cb7e2a5dd36f61f26131c709d2001b70","Some of the highest summer monsoon rainfall in South Asia falls on the windward slopes of the Western Ghats mountains on India's west coast and offshore over the eastern Arabian Sea. Understanding of the processes determining the spatial distribution and temporal variability of this region remains incomplete. In this paper, new Interaction of Convective Organization and Monsoon Precipitation, Atmosphere, Surface and Sea (INCOMPASS) aircraft and ground-based measurements of the summer monsoon over the Western Ghats and upstream of them are presented and placed within the context of remote-sensing observations and reanalysis. The transition from widespread rainfall over the eastern Arabian Sea to rainfall over the Western Ghats is documented in high spatial and temporal resolution. Heavy rainfall offshore during the campaign was associated primarily with mid-tropospheric humidity, secondarily with sea surface temperature, and only weakly with orographic blocking. A mid-tropospheric dry intrusion suppressed deep convection offshore in the latter half of the campaign, allowing the build-up of low-level humidity in the onshore flow and enhancing rainfall over the mountains. Rainfall on the lee side of the Western Ghats occurred during the latter half of the campaign in association with enhanced mesoscale easterly upslope flow. Diurnal cycles in rainfall offshore (maximum in the morning) and on the mountains (maximum in the afternoon) were observed. Considerable zonal and temporal variability was seen in the offshore boundary layer, suggesting the presence of convective downdraughts and cold pools. Persistent drying of the subcloud mixed layer several hundred kilometres off the coast was observed, suggesting strong mixing between the boundary layer and the free troposphere. These observations provide quantitative targets to test models and suggest hypotheses on the physical mechanisms determining the distribution and variability in rainfall in the Western Ghats region. © 2018 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"55778380300;37000037400;37861539400;57194594341;7102286699;23090619000;","Analyzing Atmospheric Temperature Profiles and Spectra of M Dwarf Rocky Planets",2019,"10.3847/1538-4357/ab4a05","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077268767&doi=10.3847%2f1538-4357%2fab4a05&partnerID=40&md5=36a099879272f770b6fe9d5a0d668b4a","The James Webb Space Telescope (JWST) will make it possible to comprehensively measure the thermal emission spectra of rocky exoplanets orbiting M dwarfs and thus characterize their atmospheres. In preparation for this opportunity, we present model atmospheres for three M-dwarf planets particularly amenable to secondary eclipse spectroscopy - TRAPPIST-1b, GJ 1132b, and LHS 3844b. Using three limiting cases of candidate atmospheric compositions (pure H2O, pure CO2, and solar abundances) we calculate temperature-pressure profiles and emission spectra in radiative-convective equilibrium, including the effects of a solid surface. We find that the atmospheric radiative transfer is significantly influenced by the cool M-star irradiation; H2O and CO2 absorption bands in the near-infrared are strong enough to absorb a sizeable fraction of the incoming stellar light at low pressures, which leads to temperature inversions in the upper atmosphere. The non-gray band structure of gaseous opacities in the infrared is hereby an important factor. Opacity windows are muted at higher atmospheric temperatures, so we expect temperature inversions to be common only for sufficiently cool planets. We also find that pure CO2 atmospheres exhibit lower overall temperatures and stronger reflection spectra compared to models of the other compositions. We estimate that for GJ 1132b and LHS 3844b we should be able to distinguish between different atmospheric compositions with JWST. The emission lines from the predicted temperature inversions are currently hard to measure, but high-resolution spectroscopy with future extremely large telescopes may be able to detect them. © 2019. The American Astronomical Society. All rights reserved."
"56520853700;7401945370;57212988186;","Fine Vertical Resolution Radiative-Convective Equilibrium Experiments: Roles of Turbulent Mixing on the High-Cloud Response to Sea Surface Temperatures",2019,"10.1029/2019MS001704","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067498398&doi=10.1029%2f2019MS001704&partnerID=40&md5=52abca8b15fd26ff0378a40e6004f6ac","In this study, the vertical resolution dependency of the high-cloud fraction response on the increase in sea surface temperature was investigated via radiative-convective equilibrium simulations. We performed radiative-convective equilibrium simulations for configurations with a wide range of vertical resolutions using a global nonhydrostatic model including explicit cloud microphysics. It was found that the high-cloud cover almost monotonically decreased as the vertical resolution increased. We also found that the high-cloud cover increased (decreased) as the sea surface temperature increased for higher (lower) vertical resolutions. Budget analyses of ice water condensate in transition states to equilibria were performed using the binned vertical profile method and revealed that the tendencies due to the turbulent mixing near convective cores were strongly dependent on the vertical resolution. Analyses of turbulent diffusivity profiles showed that the diffusivity tended to decrease as the vertical resolution increased. The vertical resolution dependency of turbulent mixing was related to frequently occurring weak stratification near the convective cores. We verified these findings via sensitivity experiments and determined that the contribution of the vertical resolution dependency of other processes was secondary. As substantial variability in vertical diffusivity has been reported in both models and observations, these results suggest that a more thorough understanding of turbulent mixing is needed to comprehend high-cloud changes in warming climates better. ©2019. The Authors."
"16644246500;","Self-Aggregation of Deep Convection and its Implications for Climate",2019,"10.1007/s40641-019-00120-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060695648&doi=10.1007%2fs40641-019-00120-3&partnerID=40&md5=a20cc50d867fcad0ffd5509247a9a4b8","Purpose of Review: This paper reviews the self-aggregation of deep convection, its impact on the large-scale environment, its dependence on surface temperature, and its implications for climate. Recent Findings: Self-aggregation generates significant humidity variability, dries the mean state, reduces high cloud cover, and increases the ability of the atmosphere to cool to space. Some studies find that convection is more self-aggregated at warmer temperatures but other studies, or other ways of measuring the degree of self-aggregation, disagree. There is not a simple, monotonic relationship between self-aggregation and surface temperature. Summary: Self-aggregation, through its effect on the humidity distribution and radiative budget, can affect climate. However, there is uncertainty over how strong the modulation of climate by self-aggregation is, in part because of the ambiguity over its temperature dependence. There are some indications that self-aggregation may modestly reduce climate sensitivity even without a dramatic temperature dependence, but more research is needed to understand this behavior. © 2019, Springer Nature Switzerland AG."
"57208242863;55542320000;8502619500;8603242500;","Credibility of convection-permitting modeling to improve seasonal precipitation forecasting in the southwestern United States",2019,"10.3389/feart.2019.00011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064212870&doi=10.3389%2ffeart.2019.00011&partnerID=40&md5=36601d0c7ceb816aa494e8be5869ec3e","Sub-seasonal to seasonal (S2S) forecasts are critical for planning and management decisions in multiple sectors. This study shows results from dynamical downscaling using a regional climate model at a convection-permitting scale driven by boundary conditions from the global reanalysis of the Climate Forecast System Model (CFSR). Convection-permitting modeling (CPM) enhances the representation of regional climate by better resolving the regional forcings and processes, associated with topography and land cover, in response to variability in the large-scale atmospheric circulation. We performed dynamically downscaled simulations with the Weather Research and Forecasting (WRF) model over the Upper and Lower Colorado basin at 12 km and 3 km grid spacing from 2000 to 2010 to investigate the potential of dynamical downscaling to improved the modeled representation of precipitation the Southwestern United States. Employing a convection-permitting nested domain of 3 km resolution significantly reduces the bias in mean (∼2 mm/day) and extreme (∼4 mm/day) summer precipitation when compared to coarser domain of 12 km resolution and coarse resolution CFSR products. The convection-permitting modeling product also better represents eastward propagation of organized convection due to mesoscale convective systems at a sub-daily scale, which largely account for extreme summer rainfall during the North American monsoon. In the cool season both coarse and high-resolution simulations perform well with limited bias of ∼1 mm/day for the mean and ∼2 mm/day for the extreme precipitation. Significant correlation was found (∼0.85 for summer and ∼0.65 for winter) for both coarse and high-resolution model with observed regionally and seasonally averaged precipitation. Our findings suggest that the use of CPM is necessary in a dynamical modeling system for S2S prediction in this region, especially during the warm season when precipitation is mostly convectively driven. © 2019 Pal, Chang, Castro and Dominguez."
"56562594400;7005702722;","On Cold Pool Collisions in Tropical Boundary Layers",2019,"10.1029/2018GL080501","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059581001&doi=10.1029%2f2018GL080501&partnerID=40&md5=4f2d547dc739711b750feb7f64474dbf","Collisions between cold pools are generally acknowledged to be important processes through which new convective cells are triggered. Yet relatively little has been done to characterize these processes in detail, quantify their impact on the life cycle of cold pools, and include them in convective parameterizations. We use a combination of Eulerian and Lagrangian models to investigate how much cold pools are affected by collisions. Results from simulations in radiative-convective equilibrium suggest that collisions represent a first-order process in the dynamics of cold pools, the median time of first collision being under 10 min since cold pool birth. Through a Lagrangian tracking algorithm, it is also shown that cold pools are significantly deformed by collisions and lose the circular shapes they would have if in isolation only a few minutes after birth. Finally, it is suggested that cold pools happen in clusters, and associated spatial and temporal scales are presented. ©2018. American Geophysical Union. All Rights Reserved."
"56865242700;56014511300;","The Role of Convective Self-Aggregation in Extreme Instantaneous Versus Daily Precipitation",2019,"10.1029/2018MS001503","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059582776&doi=10.1029%2f2018MS001503&partnerID=40&md5=263ad30e2ff17b155dd1e0e335198251","The impacts of convective self-aggregation on extreme precipitation and updraft velocity are investigated by using the Weather Research and Forecasting Model in the idealized setting of radiative-convective equilibrium with a 3-km horizontal resolution. Aggregated and unaggregated states are achieved by conducting simulations with fully interactive and fixed radiation, respectively. We find that convective self-aggregation has a negligible impact on extreme instantaneous precipitation but weakens the extreme updrafts and condensation, indicating a negative dynamical contribution from aggregation to extreme instantaneous precipitation. However, this is balanced by higher precipitation efficiency to maintain the same extreme instantaneous precipitation. This balance occurs because updrafts decrease mainly above the freezing level, suppressing graupel production. As graupel has a longer residence time than rain, less graupel formation with aggregation implies enhanced instantaneous local precipitation efficiency. Peak updraft velocity scales with the vertical integral of buoyancy, measured with respect to the local prestorm environment. This local environment is warmer and moister at middle and high levels when convection is aggregated compared to when it is unaggregated, reducing the buoyancy and updraft velocity. Unlike extreme instantaneous precipitation, extreme daily precipitation is stronger in aggregated states, as self-aggregation localizes and sustains updrafts and condensation in relatively fixed locations. Our results imply that extreme instantaneous precipitation is more sensitive to microphysical processes while extreme daily precipitation is more linked to the degree of aggregation. ©2018. The Authors."
"6602835531;7402717381;36544881500;36343109300;55438286600;57191504846;36139445300;7004233804;7006865796;","The June 2013 Alberta catastrophic flooding event – part 2: fine-scale precipitation and associated features",2016,"10.1002/hyp.10855","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84991795076&doi=10.1002%2fhyp.10855&partnerID=40&md5=da397215fc77678289f3faf83057e77a","Data obtained from a variety of sources including the Canadian Lightning Detection Network, weather radars, weather stations and operational numerical weather model analyses were used to address the evolution of precipitation during the June 2013 southern Alberta flood. The event was linked to a mid-level closed low pressure system to the west of the region and a surface low pressure region initially to its south. This configuration brought warm, moist unstable air into the region that led to dramatic, organized convection with an abundance of lightning and some hail. Such conditions occurred in the southern parts of the region whereas the northern parts were devoid of lightning. Initially, precipitation rates were high (extreme 15-min rainfall rates up to 102 mm h−1 were measured) but decreased to lower values as the precipitation shifted to long-lived stratiform conditions. Both the convective and stratiform precipitation components were affected by the topography. Similar flooding events, such as June 2002, have occurred over this region although the 2002 event was colder and precipitation was not associated with substantial convection over southwest Alberta. Copyright © 2016 Her Majesty the Queen in Right of Canada. Hydrological Processes. © John Wiley &amp; Sons, Ltd. Copyright © 2016 Her Majesty the Queen in Right of Canada. Hydrological Processes. © John Wiley & Sons, Ltd."
"6507905797;56308982600;23569021500;55556257300;57189357863;","Thermodynamic and dynamic structure of atmosphere over the east coast of Peninsular Malaysia during the passage of a cold surge",2016,"10.1016/j.jastp.2016.05.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84969771757&doi=10.1016%2fj.jastp.2016.05.011&partnerID=40&md5=f095e836cd7b8a9e12cf02d37def6bfe","An intense field observation was carried out for a better understanding of cold surge features over Peninsular Malaysia during the winter monsoon season. The study utilizes vertical profiles of temperature, humidity and wind at high vertical and temporal resolution over Kota Bharu, situated in the east coast of Peninsular Malaysia. LCL were elevated during the passage of the cold surge as the relative humidity values decreased during the passage of cold surge. Level of Free Convection were below 800 hPa and equilibrium levels were close to the LFC in most of the cases. Convective available potential energy and convection inhibition energy values were small during most of the observations. Absence of local heating and instability mechanism are responsible for the peculiar thermodynamic structure during the passage of the cold surge. The wind in the lower atmosphere became northeasterly and was strong during the entire cold surge period. A slight increase in temperature near the surface and a drop in temperature just above the surface were marked by the passage of the cold surge. A remarkable increase in specific humidity was observed between 970 and 900 hPa during the cold surge period. Further, synoptic scale features were analyzed to identify the mechanism responsible for heavy rainfall. Low level convergence, upper level divergence and cyclonic vorticity prevailed over the region during the heavy rainfall event. Dynamic structure of the atmosphere as part of the organized convection associated with the winter monsoon was responsible for the vertical lifting and subsequent rainfall. © 2016 Elsevier Ltd."
"56417341400;26536569500;","Tropical cloud buoyancy is the same in a world with or without ice",2016,"10.1002/2016GL068583","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84979493636&doi=10.1002%2f2016GL068583&partnerID=40&md5=72f41d6a7646d165ff9a2fdb6700b13a","When convective clouds grow above the melting line, where temperatures fall below 0°C, condensed water begins to freeze and water vapor is deposited. These processes release the latent heat of fusion, which warms cloud air, and many previous studies have suggested that this heating from fusion increases cloud buoyancy in the upper troposphere. Here we use numerical simulations of radiative-convective equilibrium with and without ice processes to argue that tropical cloud buoyancy is not systematically higher in a world with fusion than in a world without it. This insensitivity results from the fact that the environmental temperature profile encountered by developing tropical clouds is itself determined by convection. We also offer a simple explanation for the large reservoir of convective available potential energy in the tropical upper troposphere that does not invoke ice. © 2016. American Geophysical Union. All Rights Reserved."
"56308982600;55556257300;23569021500;","Characteristics of precipitation pattern in the Arabian Peninsula and its variability associated with ENSO",2016,"10.1007/s12517-015-2265-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84961136519&doi=10.1007%2fs12517-015-2265-x&partnerID=40&md5=ad06fe1bd40267e60230dba3a8f72979","A detailed analysis of the precipitation pattern of the Arabian Peninsula and its temporal and spatial variability were investigated in connection with ENSO. Also, the variability of precipitable water and circulation characteristics was examined for a better understanding. The study was carried out utilizing TRMM rainfall, NOAA OLR, precipitable water, wind, and humidity data sets. It is evident that Northern Arabian Peninsula receives high amount of rainfall mainly during winter and early summer (November to April) in connection with the passage of mid tropospheric westerly troughs and Mediterranean low-pressure systems. But the precipitation pattern over the Southern Arabian Peninsula reveals that it is mainly during summer (May to October) due to the Arabian Sea branch of monsoon and moisture laden cross equatorial LLJ flow. Further, analysis was carried out to assess the influence of ENSO on the precipitation pattern. Thorough analysis was carried out on the circulation pattern using velocity potential in the lower troposphere to understand the features of variability on Hadley/Walker circulation in relation with organized convection. El Nino and La Nina have profound influence on the rainfall pattern in a different manner in the Northern and Southern Arabian Peninsula. Large-scale circulation pattern as derived from velocity potential indicates that shifting of the rising/sinking limb of Hadley/Walker circulation associated with the ENSO causes variability in precipitation. © 2016, Saudi Society for Geosciences."
"7401945370;57192718630;57211976266;","Structure of tropical convective systems in aqua-planet experiments: Radiative-convective equilibrium versus the earth-like experiment",2016,"10.2151/sola.2016-044","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007524082&doi=10.2151%2fsola.2016-044&partnerID=40&md5=847a9c3b54eafd6a0e12e7f211d83e1e","A previous study shows that tropical convective systems share a similar structure regardless of horizontal scale: lower-level horizontal convergence precedes maximum precipitation and this convergence rises and tilts over time. We conduct a series of aqua-planet experiments (APE) using the Non-hydrostatic Icosahedral Atmospheric Model (NICAM) to investigate whether this structure is maintained under different conditions with an Earthlike APE (CTL-exp) and a radiative convective equilibrium (RCEexp) where sea surface temperature is uniform and no planetary rotation is applied. The experiments are conducted with the 56 km mesh size with explicit convective calculation without a cumulus parameterization scheme. CTL-exp shows a well-known multiscale convective structure where a smaller convective system propagates westward along the equator whereas a larger convective system propagates eastward. In RCE-exp, the simulation also has a multi-scale structure but the larger-scale convective system no longer propagates in a preferred direction. The convective systems in CTL-exp have a similar tilting structure to tropical convective systems regardless of horizontal scale, while the larger scale convective system in RCE-exp show a smaller tilting structure. We speculate that the difference in CTL-exp and RCE-exp structures comes from the propagation speed of the convective systems. © 2016, the Meteorological Society of Japan."
"35572026100;7006095466;","Numerical archetypal parameterization for mesoscale convective systems",2016,"10.1175/JAS-D-15-0207.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84975039951&doi=10.1175%2fJAS-D-15-0207.1&partnerID=40&md5=930988a37f953fc4cd0fb8b45c98fb0a","Vertical shear commonly organizes atmospheric convection into coherent multiscale structures. The associated countergradient vertical transport of horizontal momentum by organized convection can enhance the wind shear and transport kinetic energy upscale. However, organized convection and its upscale effects are not represented by traditional mass-flux-based parameterizations. The present paper sets the archetypal dynamical models, originally formulated by the second author, into a parameterization context by utilizing a nonhydrostatic anelastic model with segmentally constant approximation (NAM-SCA). Using a twodimensional framework as a starting point, NAM-SCA spontaneously generates propagating tropical squall lines in a sheared environment. High numerical efficiency is achieved through a novel compression methodology. The numerically generated archetypes produce vertical profiles of convective momentum transport that are consistent with the analytic archetype. © 2016 American Meteorological Society."
"57009165600;8043701900;","Higher surface Bowen ratios ineffective at increasing updraft intensity",2015,"10.1002/2015GL066878","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84953639236&doi=10.1002%2f2015GL066878&partnerID=40&md5=76279b609f84a043ebf70248fadc9f7e","The sensitivity of various metrics of convective intensity to changes in boundary layer depth via changes in the surface Bowen ratio is explored with radiative-convective equilibrium (RCE) and initial condition simulations in the System for Atmospheric Modeling, a cloud-resolving model. In the RCE simulations, high-percentile updrafts showed little change in response to changes in the surface Bowen ratio. Initial condition simulations showed low surface Bowen ratios having stronger updrafts than high surface Bowen ratios. A parcel model was used to explore whether RCE results could be explained with an entrainment parameter independent of boundary layer depth. It was found that for every set of simulations in RCE, entrainment rates independent of boundary layer depth could explain the lack of change in updraft velocities with boundary layer depth. Given the indifference of high-percentile updraft velocities in our simulations to changes in the surface Bowen ratio, we conclude that convective intensity as measured by this quantity in the cloud-resolving model is not sensitive to this forcing. © 2015. American Geophysical Union. All Rights Reserved."
"57008570500;7004114883;6505932008;54983414800;","Observed and modeled warm rainfall occurrence and its relationships with cloud macrophysical properties",2015,"10.1175/JAS-D-14-0368.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950349728&doi=10.1175%2fJAS-D-14-0368.1&partnerID=40&md5=450b95731a3819f827beec466a104701","Observed and modeled rainfall occurrence from shallow (warm) maritime clouds and their composite statistical relationships with cloud macrophysical properties are analyzed and directly compared. Rain falls from ~25% of warm, single-layered, maritime clouds observed by CloudSat and from ~27% of the analogous warm clouds simulated within a large-domain, fine-resolution radiative-convective equilibrium experiment performed using the Regional Atmospheric Modeling System (RAMS), with its sophisticated bin-emulating bulk microphysical scheme. While the fractional occurrence of observed and simulated warm rainfall is found to increase with both increasing column-integrated liquid water and cloud depth, calculations of rainfall occurrence as a joint function of these two macrophysical quantities suggest that the modeled bulk cloud-to-rainwater conversion process is more efficient than observations indicate-in agreement with previous research. Unexpectedly and in opposition to the model-derived relationship, deeper CloudSat-observed warm clouds with little column water mass are more likely to rain than their corresponding shallow counterparts, despite having lower cloud-mean water contents. Given that these composite relationships were derived from statically identified warm clouds, an attempt is made to quantitatively explore rainfall occurrence within the context of the warm cloud life cycle. Extending a previously established cloud-top buoyancy analysis technique, it is shown that rainfall likelihoods from positively buoyant RAMS-simulated clouds more closely resemble the surprising observed relationships than do those derived from negatively buoyant simulated clouds. This suggests that relative to the depiction of warm clouds within the RAMS output, CloudSat observes higher proportions of positively buoyant, developing warm clouds. © 2015 American Meteorological Society."
"7006060300;","Entropy production and climate efficiency",2015,"10.1175/JAS-D-14-0361.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943376907&doi=10.1175%2fJAS-D-14-0361.1&partnerID=40&md5=d8e2c6466ad7193ece9c85c52466efff","Earth's climate system is a heat engine, absorbing solar radiation at a mean input temperature Tin and emitting terrestrial radiation at a lower, mean output temperature Tout &lt; Tin. These mean temperatures, defined as the ratio of the energy to entropy input or output, determine the Carnot efficiency of the system. The climate system, however, does no external work, and hence its work efficiency is zero. The system does produce entropy and exports it to space. The efficiency associated with this entropy production is defined for two distinct representations of the climate system. The first defines the system as the sum of the various material subsystems, with the solar and terrestrial radiation fields constituting the surroundings. The second defines the system as a control volume that includes the material and radiation systems below the top of the atmosphere. These two complementary representations are contrasted using a radiative-convective equilibrium model of the climate system. The efficiency of Earth's climate system based on its material entropy production is estimated using the two representations. © 2015 American Meteorological Society."
"56308982600;55078057600;","Variability and mechanisms of vertical distribution of aerosols over the Indian region",2014,"10.1080/01431161.2014.975379","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84911478095&doi=10.1080%2f01431161.2014.975379&partnerID=40&md5=d8c15eae3fc6aeecdb7bab7e3d1ff084","The present study investigates the seasonal variability in the vertical distribution of aerosol over the Indian region and its surroundings, and the possible mechanisms in the atmosphere that give rise to vertical transport of the aerosols. During boreal summer months, the aerosols reach a higher altitude of above 5 km over the Indian region. In the winter season, especially during December, January, and February, the aerosols remain at low levels of the atmosphere, extending to about 3 km. The low-level atmospheric conditions are favourable for lifting of aerosols associated with the organized convection in the atmosphere during the months from May to September. The shifting of the Inter Tropical Convergence Zone (ITCZ) towards the northern hemisphere and the monsoon activity associated with it makes the atmosphere turbulent over the region during the period. The vorticity and convergence patterns are favourable for the vertical transport of aerosols during the period from May to November. High vertical wind shear, which leads to the generation of turbulence during the monsoon season, enhances the mixing of aerosols in the atmosphere and supports the lifting motion. Over the Arabian Sea, during the summer months, the aerosols reach a higher altitude of about 6 km. The production of marine aerosols is increased by the monsoon winds over the sea, and the turbulent atmosphere lifts the particles to high altitudes. The transportation of dust aerosols from west and northwest parts is found at high altitudes towards the destination regions in north and south India. This also dominates the total aerosol content over the region. © 2014, Taylor & Francis."
"56073532500;7102866124;7004864963;","Droplet Size Distributions as a function of rainy system type and Cloud Condensation Nuclei concentrations",2014,"10.1016/j.atmosres.2014.02.022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896481498&doi=10.1016%2fj.atmosres.2014.02.022&partnerID=40&md5=9c95dcbd487e6146c90f57d0f51f80b1","This work aims to study typical Droplet Size Distributions (DSDs) for different types of precipitation systems and Cloud Condensation Nuclei concentrations over the Vale do Paraíba region in southeastern Brazil. Numerous instruments were deployed during the CHUVA (Cloud processes of tHe main precipitation systems in Brazil: a contribUtion to cloud resolVing modeling and to the GPM) Project in Vale do Paraíba campaign, from November 22, 2011 through January 10, 2012. Measurements of CCN (Cloud Condensation Nuclei) and total particle concentrations, along with measurements of rain DSDs and standard atmospheric properties, including temperature, pressure and wind intensity and direction, were specifically made in this study. The measured DSDs were parameterized with a gamma function using the moment method. The three gamma parameters were disposed in a 3-dimensional space, and subclasses were classified using cluster analysis. Seven DSD categories were chosen to represent the different types of DSDs. The DSD classes were useful in characterizing precipitation events both individually and as a group of systems with similar properties. The rainfall regime classification system was employed to categorize rainy events as local convective rainfall, organized convection rainfall and stratiform rainfall. Furthermore, the frequencies of the seven DSD classes were associated to each type of rainy event. The rainfall categories were also employed to evaluate the impact of the CCN concentration on the DSDs. In the stratiform rain events, the polluted cases had a statistically significant increase in the total rain droplet concentrations (TDCs) compared to cleaner events. An average concentration increase from 668cm-3 to 2012cm-3 for CCN at 1% supersaturation was found to be associated with an increase of approximately 87m-3 in TDC for those events. For the local convection cases, polluted events presented a 10% higher mass weighted mean diameter (Dm) on average. For the organized convection events, no significant results were found. © 2014 Elsevier B.V."
"7004978125;6507400558;54585176800;","Effects of rotation and mid-troposphere moisture on organized convection and convectively coupled gravity waves",2014,"10.1007/s00382-014-2222-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939890232&doi=10.1007%2fs00382-014-2222-5&partnerID=40&md5=f3f7446413bba9c929beb08c67a361e6","Atmospheric convection has the striking capability to organize itself into a hierarchy of cloud clusters and super-clusters on scales ranging from the convective cell of a few kilometres to planetary scale disturbances such as the Madden–Julian oscillation. It is widely accepted that this phenomenon is due in large part to the two-way coupling between convective processes and equatorially trapped waves and planetary scale flows in general. However, the physical mechanisms responsible for this multiscale organization and the associated across-scale interactions are poorly understood. The two main peculiarities of the tropics are the vanishing of the Coriolis force at the equator and the abundance of mid-level moisture. Here we test the effect of these two physical properties on the organization of convection and its interaction with gravity waves in a simplified primitive equation model for flows parallel to the equator. Convection is represented by deterministic as well as stochastic multicloud models that are known to represent organized convection and convectively coupled waves quite well. It is found here that both planetary rotation and mid-troposphere moisture are important players in the diminishing of organized convection and convectively coupled gravity wave activity in the subtropics and mid-latitudes. The meridional mean circulation increases with latitude while the mean zonal circulation is much shallower and is dominated by mid-level jets, reminiscent of a second baroclinic mode circulation associated with a congestus mode instability in the model. This is consistent with the observed shallow Hadley and Walker circulations accompanied by congestus cloud decks in the higher latitude tropics and sub-tropics. Moreover, deep convection activity in the stochastic model simulations becomes very patchy and unorganized as the computational domain is pushed towards the subtropics and mid-latitudes. This is consistent with previous work based on cloud resolving modeling simulations on smaller domains. © 2014, Springer-Verlag Berlin Heidelberg."
"54983414800;6505932008;7202899330;6701718281;","Convective-scale responses of a large-domain, modelled tropical environment to surface warming",2014,"10.1002/qj.2230","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902247274&doi=10.1002%2fqj.2230&partnerID=40&md5=59099410db4272a028cbb16d05bc63db","This article explores the response of convective-scale atmospheric characteristics to surface temperature through the lens of large-domain, cloud-system-resolving model experiments run at radiative convective equilibrium. We note several features reminiscent of the response to surface warming in atmospheric general circulation models. These include an increase in the rain rate that is smaller than the modelled increase in precipitable water, a systematic decrease in sensible heating and an increase in clear-sky cooling. However, in contrast to climate models, we note that tropospheric relative humidity increases and column-integrated water vapour increases at the rate anticipated from the Clausius-Clapeyron relationship, but only when compared with the troposphere mean temperature rather than surface temperature. Also shown are results elucidating the changes in the vertically integrated water budget and the distribution of high precipitation rates shifting toward higher rates. Moist static energy distributions are analyzed and, from these, clouds are implicated in effecting the final equilibrium state of the atmosphere. The results indicate that, while there are aspects of the tropical equilibrium that are represented realistically in current general circulation model climate-change experiments, there are potentially influential local interactions that are sufficiently important as to alter the mean response of the tropical water and energy balance to changes in sea-surface temperature. Convection is shown to dictate the equilibrium state across all scales, including those unresolved in climate models, rather than only responding to surface-induced changes. © 2013 Royal Meteorological Society."
"7201784177;7101661890;","Toward an understanding of vertical momentum transports in cloud-system-resolving model simulations of multiscale tropical convection",2013,"10.1175/JAS-D-13-068.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885943760&doi=10.1175%2fJAS-D-13-068.1&partnerID=40&md5=ff818a7a404b22dd884777a7961b471f","This study examines the characteristics of convective momentum transport (CMT) and gravity wave momentum transport (GWMT) in two-dimensional cloud-system-resolving model simulations, including the relationships between the two transports. A linear group velocity criterion is shown to objectively separate CMT and GWMT. TheGWMTcontribution is mostly consistent with upward-propagating gravity waves and is present in the troposphere and the stratosphere. The CMT contribution forms a large part of the residual (nonupward-propagating contribution) and dominates the fluxes in the troposphere. Additional analysis of the vertical sensible heat flux supports the physical interpretation of the two contributions, further isolating the effects of unstable convection from vertically propagating gravity waves. The role of transient and nonconservative (friction and diabatic heating) processes in generating momentum flux and their dependence on changes in convective organization was assessed using a pseudomomentum budget analysis. Nonconservative effects were found to dominate the transports; the GWMT contribution involved a diabatic source region in the troposphere and a dissipative sink region in the stratosphere. The CMT contribution was consistent with transport between the boundary layer and free troposphere via tilted convection. Transient buoyancy-vorticity correlations highlighted wave sources in the region of convective outflow and the boundary layer. These sources were akin to the previously described ''mechanical oscillator'' mechanism. Fluxes associated with this upper-level source were most sensitive to convective organization, highlighting the mechanism by which changes in organization are communicated to GWMT. The results elucidate important interactions between CMT and GWMT, adding further weight to suggestions that the two transports should be linked in parameterizations. © 2013 American Meteorological Society."
"35572026100;35592560600;55988223200;","Theoretical and operational implications of atmospheric convective organization",2012,"10.1175/BAMS-D-11-00178.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860691996&doi=10.1175%2fBAMS-D-11-00178.1&partnerID=40&md5=48b5cf3194c47b758abab0571c16806e","Despite its potential importance, we are still far from including convective organization explicitly within parameterization algorithms. As one participant from Météo-France remarked, the operational priorities always remain the closure and entrainment-detrainment problems. No one objected to this remark, except for possibly regarding downdrafts as another priority. The effects of organization may somehow be implicitly taken into account within our current frameworks, but no specific proposal from participants was heard. © 2012 American Meteorological Society."
"54585176800;6507400558;7004978125;","Simple multicloud models for the diurnal cycle of tropical precipitation. Part II: The continental regime",2011,"10.1175/2011JAS3600.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81555213082&doi=10.1175%2f2011JAS3600.1&partnerID=40&md5=0b069af5b0c527e0e08db1adc71380d0","The variation of precipitation over land due to the diurnal cycle of solar heating is examined here in the context of a simple multicloud model for tropical convection with bulk atmospheric boundary layer (ABL) dynamics. The model utilizes three cloud types (congestus, deep, and stratiform) that are believed to characterize organized tropical convection based on the first two baroclinic modes of vertical structure in the free troposphere, coupled to the ABL through full bulk boundary layer (FBBL) dynamics, that allow a careful separation between sensible and latent heat surface fluxes. In a land parameter regime, characterized by a strong inversion profile, a large Bowen ratio of 0.4, and active mixing of sensible heat due to cumulus entrainment and downdraft fluxes at the top of the ABL, the model supports a stable 1-day periodic solution that is characterized by a pronounced (7 K day-1) afternoon peak in precipitation consistent with observations of tropical precipitation over continental regions. The current study suggests a division of the diurnal cycle of precipitation over land into a cycle of five phases: 1) an overnight phase of a radiative-convective equilibrium (RCE) state between 2000 and 0600 LST; 2) an early morning CAPE buildup accompanied by a sudden rise in precipitation that quickly dries the middle troposphere occurs between 0600 and roughly 1000 LST; 3) a moistening phase between roughly 1000 and 1600 LST; 4) a phase of maximum precipitation between 1600 and 1800 LST that dries the middle troposphere and quickly consumes CAPE; and 5) a rapid remoistening phase that restores the moisture level to sustain the overnight RCE precipitation and connects to phase 1 in the cycle. Sensitivity tests in the model confirm that the late afternoon precipitation maximum over land depends crucially on a strong inversion, the large Bowen ratio, and the active mixing of sensible heat due to cumulus entrainment and downdraft fluxes at the top of the ABL. © 2011 American Meteorological Society."
"6603458452;7005453346;15724418700;","Fluctuation of mass flux in a cloud-resolving simulation with interactive radiation",2010,"10.1175/2009JAS3215.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953250384&doi=10.1175%2f2009JAS3215.1&partnerID=40&md5=8b705ff25a31346a6cbaa3daea45082f","It was shown by Craig and Cohen that fluctuations of cumulus clouds under homogeneous large-scale forcing satisfy the Gibbs canonical ensemble in a strict radiative-convective equilibrium (RCE). In the limit of random noninteracting convective cells, an analytical expression for the distribution function of total mass flux over a region of given size was derived. The authors examine the consistency of the Gibbs canonical ensemble as a representation for the mass flux fluctuations when the large-scale forcing is time dependent. A cloud-resolving simulation (CRM) with interactive radiation, fixed imposed surface temperature, and diurnally varying solar forcing to mimic the diurnal cycle over the tropical ocean is used. As a necessary condition for the existence of a state of quasi-equilibrium, the time-scale separation between convective processes and forcing is studied. Detailed evaluation of time scales of convective adjustment and memory in a three-month run confirms the hypothesis of time-scale separation. The Craig and Cohen theory, in a varying range of heights between the cloud base up to the level of neutral buoyancy (LNB), is tested. It is shown that, although the theory is capable of reproducing the qualitative features of the variability, systematic deviations are detected. By quantifying the spatial distribution of the clouds, the authors suggest that deviations are associated with clustering effects. © 2010 American Meteorological Society."
"36008544500;7402469637;9535769800;7401945370;","Analysis of the tropical tropopause layer using the Nonhydrostatic Icosahedral Atmospheric Model (NICAM): Aqua planet experiments",2010,"10.1029/2009JD012686","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951801844&doi=10.1029%2f2009JD012686&partnerID=40&md5=c2d193c408713bb24e7125a5b1be4a05","The dynamical characteristics of the tropical tropopause layer (TTL) are investigated using the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) run on the Earth Simulator under an aqua planet condition. Two experiments are performed: one with a 3.5 km horizontal spacing and a three-dimensional snapshot output and another with a 7 km horizontal spacing and 3-hourly averages for 1 month. The number of vertical levels is 54 and the model top is at 40 km; the vertical spacing in and around the TTL is ̃700 m. Large-scale organized convection associated with convectively coupled equatorial Kelvin waves prevails around the equator. The zonal mean vertical distribution of cloud top height near the equator shows a realistic trimodal structure. The simulation results reveal that cumulus clouds penetrate the lapse-rate tropopause and the bottom boundary of the TTL (defined as the lapse rate minimum) for ̃0.1% and ̃25%, respectively, in the equatorial area. The frequency distribution of vertical wind may provide a good indicator of the TTL bottom boundary. A significant reduction in the speed of strong vertical winds is observed at ̃16 km. High variability in temperature and the water vapor mixing ratio observed around the tropopause is mainly caused by equatorial Kelvin waves generated by the organized convection in these experiments. Horizontal variability in tropopause height over a large-scale convective system is much smaller than that in the area of Kelvin waves. The gravity waves generated by this large-scale convective system locally control the temperature around the tropopause. In addition, large-amplitude gravity waves with a scale of 600 km are superimposed on the cold phase of Kelvin waves, producing one of the coldest regions around the tropopause. It is suggested that the combination of Kelvin waves and gravity waves may be one of the most effective dehydration processes in the TTL. Copyright 2010 by the American Geophysical Union."
"7202650266;36098762900;55740245100;","Global warming of the atmosphere in radiative-convective equilibrium",2004,"10.1175/1520-0469(2004)061<1894:GWOTAI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4344713278&doi=10.1175%2f1520-0469%282004%29061%3c1894%3aGWOTAI%3e2.0.CO%3b2&partnerID=40&md5=fdcff35ddf118552e712edf8183fa639","Many studies of global warming have commonly reported positive warming feedback by water vapor, exhibiting relative humidity in the atmosphere unchanged for different warming conditions. However, this is not self-evident, since water vapor content in the atmosphere may be significantly affected by atmospheric convections, such as cumulus convection, which involve strong vertical motions of air. To find an explanation, global warming experiments were run in this study that included atmospheres at radiative-convective equilibrium with differing amounts of a noncondensable greenhouse gas. The models used were the dynamical convection model (DCM) and kinematic circulation model (KCM). When the noncondensable greenhouse gas is increased in the models, the free atmosphere in both the DCM and KCM show similar increases in air temperature and water vapor content. Changes in temperature and water vapor occur such that the relative humidity remains mostly constant. As Iwasa et al. show, water vapor distribution is controlled by a net circulation that is driven by radiative cooling. It is not convectively forced. Relative humidity is unchanged because the net circulation that increases temperature leaves the subsidence flow pattern similar. The DCM reveals a new aspect of global warming. The vertical temperature profile in the dry convective boundary layer (CBL) becomes dry adiabatic, a lapse rate larger than the moist adiabatic lapse rate in the free troposphere. Both the depth of the CBL and tropospheric temperatures increase. The development of the CBL accompanies an additional temperature increase in the bottom atmosphere and at the surface, in contrast to temperature profiles predicted from models without such CBL structures. © 2004 American Meteorological Society."
"7202650266;36098762900;55740245100;","Structure of the atmosphere in radiative-convective equilibrium",2002,"10.1175/1520-0469(2002)059<2197:SOTAIR>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037099120&doi=10.1175%2f1520-0469%282002%29059%3c2197%3aSOTAIR%3e2.0.CO%3b2&partnerID=40&md5=d297718b84f5a13d8c061c31c4866305","To investigate water vapor transport in an atmosphere in radiative-convective equilibrium, a simplified dynamical convection model (DCM) was constructed that explicity models moist convection and longwave radiation in a gray atmosphere. In the subsidence region of the equilibrium, atmosphere is predicted by the DCM. dynamical heating, and radiative cooling balance. Subsidence that satisfies local thermodynamical balance includes detrainment from adjacent cumulus updraft at all levels in the free troposphere, from high levels with a small absolute humidity to low levels with a large absolute humidity. In this subsidence region, absolute humidity increase downward, but relative humidity is approximately constant with height. This contrasts sharply with results from a cumulus chimney model (CCM) that limits detrainment to near the tropopause and produces drying in the free troposphere. To demonstrate the accuracy of the transport mechanism implied by the DCM, results from a kinematic circulation model (KCM) were examined. The DCM and the KCM both produced an atmosphere far moister than predicted by the CCM. The feature of the detrainment at all levels of the free troposphere under a normal atmospheric situation does not depend on the radiation schemes used in the models. Furthermore, an analytic solution of the humidity fields, obtained using a few additional assumptions on atmospheric properties, agrees with the humidity fields in the DCM and KCM. The relative humidity in the subsidence region in the free troposphere has a mostly uniform vertical profile and the mean value in the horizontal is independent of the horizontal scale. Water vapor transport moistens the atmosphere, preventing the excess drying that occurs in the CCM."
"9535769800;7201605742;","A representation of cumulus-scale effects in a mesoscale-convection-resolving model for tropical cyclones",2001,"10.2151/jmsj.79.1035","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23044530415&doi=10.2151%2fjmsj.79.1035&partnerID=40&md5=d0c632a3f5a3834db4d69c4deebd06bc","A new mesoscale-convection-resolving model (MCRM) for tropical cyclones (TCs) is proposed along a line of Yamasaki's (1986) model in which mesoscale organized convection (MC) is resolved by the grid, but cumulus-scale convection (CC) is treated as the subgrid-scale. The most significant difference from Yamasaki's model is that Kuo's (1965) formulation is used to represent the CC-effects. Some important modifications from Kuo are made: (1) it is assumed that part of moisture converged in an air column is used for CC and that the ratio depends on low-level convergence and the degree of latent instability; (2) the ratio of moisture consumed for heating to moisture redistributed by CC is assumed to be significantly larger than that given by Kuo; (3) turbulent and dynamic entrainment and detrainment are taken into account so that the vertical profile of heating, which is crucial to MC, may be effectively controlled; (4) cloud water and rainwater of the subgrid-scale are treated with prognostic equations. Numerical experiments are performed with an axisymmetric model having a horizontal grid size of 10 km. The results are discussed compared with those from a 1 km grid model that can resolve CC. It is shown that the new model can simulate important features of MC and a TC, provided that the values of model parameters are specified properly. The CC-effects are made clear by comparison with a case that does not include them. It is shown that CC has two different effects, depending on the low-level relative humidity. One is to give realistic growth of MC through the upward transports of heat and moisture under a very humid condition, and the other is to enhance the formation and growth of MC when the air is not very humid. This study suggests that though Kuo's parameterization was not proposed as that representing the CC-effects, a reasonable model can be developed when Kuo's formulation is adopted in the framework of the MCRM. Important aspects of the model that contribute to realistic simulation of MC and a TC are discussed in comparison with those of Yamasaki's model. ©2001, Meteorological Society of Japan."
"7004534048;","Radiative-Convective Latitudinal Gradients for Jupiter and Saturn Models with a Radiative Zone",1999,"10.1006/icar.1999.6193","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346542866&doi=10.1006%2ficar.1999.6193&partnerID=40&md5=4a1b9a377b0c8d5088e17395a2d9ab06","Local radiative-convective thermal structure is calculated on Jupiter and Saturn under the assumption that a low opacity zone exists near the 2000-K depth, as suggested by T. Guillot et al. (1994a, Icarus112, 337-353). The opacity is uncertain, and a simple but qualitatively accurate model is used to explore a range of opacities. Under the assumption of local radiative-convective equilibrium, insolation gradients lead to latitudinal temperature gradients in the shell outside the stably stratified radiative zone near 2000 K, and to a latitudinal variation in the emission to space. Measurements of the net heat balance (solar and planetary radiation) do not yet extend to high enough latitudes to test these predictions. On Jupiter and especially Saturn, the preference for westerly surface motion may be due to equator-to-pole temperature gradients in this shell. It is speculated that the dynamical response to radiative forcing due to low opacity near the 2000-K level may limit latitudinal temperature gradients and may be an important drive for meteorology on the outer planets. © 1999 Academic Press."
"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."
"57213656510;7004972676;","Dual Doppler radar investigation of the tropical convective boundary layer",1988,"10.1175/1520-0469(1988)045<0853:DDRIOT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024255317&doi=10.1175%2f1520-0469%281988%29045%3c0853%3aDDRIOT%3e2.0.CO%3b2&partnerID=40&md5=5733725410c04ee28b1160958e6ca0bf","Radar observations of the convective boundary layer were made during the ""COPT81' experiment in May-June 1981 over western Africa. The lower atmosphere was characterized by the interaction between the southerly monsoon and the African easterly jet above it. The mean wind shear between both flows is found to organize convective elements along preferred directions and to transfer energy to the perturbed field (velocity variances, momentum fluxes). However, the convective organization is also the cause of increasing horizontal variance and in some cases of a negative shear stress production. The global behavior of the convective boundary layer in the four observed situations appeared similar to those observed in middle latitudes, but the strong wind shear is an important feature of the layer. -Authors"
"16441664100;7006095466;","The dynamics and simulation of organized deep convection.",1983,"10.1007/978-94-017-2241-4_25","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020924103&doi=10.1007%2f978-94-017-2241-4_25&partnerID=40&md5=2b39ec23a673e5f586bf1e7ab0e3400e","The dynamical implications of certain observational models of deep convection are discussed. Various approximations to equations representing the macroscale dynamics of deep, organised convection are presented and compared, and distinctive finite difference techniques are discussed.-from Authors"
"7404678955;8946494600;7404747615;8982748700;7101874266;55345946200;24554420100;7005909380;57190120326;","Forecasting the monsoon on daily to seasonal time-scales in support of a field campaign",2020,"10.1002/qj.3620","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074520196&doi=10.1002%2fqj.3620&partnerID=40&md5=2a90bc5b6a5f707e716a50125e015431","The successful planning and execution of a major field campaign relies on the availability and reliability of weather forecasts on a range of time-scales. Here, we describe the wide range of forecast products generated in support of a field campaign that took place in India in 2016 as part of the Interaction of Convective Organization with Monsoon Precipitation, Atmosphere, Surface and Sea (INCOMPASS) project. We show examples of the suite of plots generated every day from the forecasts and supplied to the mission scientists, and describe how these were used to plan the flights. We highlight the benefits of having access to forecasts from a range of model resolutions and configurations; these allowed judgements to be made about uncertainty, particularly in the amount and location of deep convective rainfall, which is an important consideration for flight planning. Finally, we discuss the legacy of the forecasting activity, which has not only advanced our understanding of monsoon forecasting but also created a large database of targeted model forecast products for the whole of the 2016 monsoon season. These can be used by researchers for comparisons with in situ observations as well as future modelling studies. © 2019 The Authors and Crown Copyright, Met Office. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society"
"57211623938;57195065818;7404732357;7201504886;7003696273;56592876500;25649175400;35775264900;15724418700;","A 1D RCE study of factors affecting the tropical tropopause layer and surface climate",2019,"10.1175/JCLI-D-18-0778.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074668680&doi=10.1175%2fJCLI-D-18-0778.1&partnerID=40&md5=e5c5345c0ed6b60cf6166580a1d86d6c","There are discrepancies between global climate models regarding the evolution of the tropical tropopause layer (TTL) and also whether changes in ozone impact the surface under climate change. We use a 1D clear-sky radiative–convective equilibrium model to determine how a variety of factors can affect the TTL and how they influence surface climate. We develop a new method of convective adjustment, which relaxes the temperature profile toward the moist adiabat and allows for cooling above the level of neutral buoyancy. The TTL temperatures in our model are sensitive to CO2 concentration, ozone profile, the method of convective adjustment, and the upwelling velocity, which is used to calculate a dynamical cooling rate in the stratosphere. Moreover, the temperature response of the TTL to changes in each of the above factors sometimes depends on the others. The surface temperature response to changes in ozone and upwelling at and above the TTL is also strongly amplified by both stratospheric and tropospheric water vapor changes. With all these influencing factors, it is not surprising that global models disagree with regard to TTL structure and evolution and the influence of ozone changes on surface temperatures. On the other hand, the effect of doubling CO2 on the surface, including just radiative, water vapor, and lapse-rate feedbacks, is relatively robust to changes in convection, upwelling, or the applied ozone profile. © 2019 American Meteorological Society."
"23393212200;7005808242;","Aquaplanet Simulations of Tropical Cyclones",2019,"10.1007/s40641-019-00133-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067264129&doi=10.1007%2fs40641-019-00133-y&partnerID=40&md5=4ab51d684d7adbcd939dc3c0d014f619","Purpose of Review: Tropical cyclones (TCs) are strongly influenced by the large-scale environment of the tropics and will, therefore, be modified by climate changes. Numerical simulations designed to understand the sensitivities of TCs to environmental changes have typically followed one of two approaches: single-storm domain sizes with convection-permitting resolution and uniform thermal boundary conditions or comprehensive global high-resolution (about 50 km in the horizontal) atmospheric general circulation model (GCM) simulations. The approaches reviewed here rest between these two and are an important component of hierarchical modelling of the atmosphere: aquaplanet TC simulations. Recent Findings: Idealized model configurations have revealed controls on equilibrium TC size in large-domain simulations of rotating radiative-convective equilibrium. Simulations that include differential rotation (spherical geometry) but retain uniform thermal forcing have revealed a new mechanism of TC propagation change via storm-scale dynamics and show a poleward shift in genesis in response to warming. Simulations with Earth-like meridional thermal forcing gradients have isolated competing influences on TC genesis via shifts in the atmospheric general circulation and the temperature dependence of TC genesis in the absence of mean circulation changes. Summary: Aquaplanet simulations of TCs with variants that include or inhibit certain processes have recently emerged as a research methodology that has advanced the understanding of the climatic controls on TC activity. Looking forward, idealized boundary condition model configurations can be used as a bridge between GCM resolution and convection-permitting resolution models and as a tool for identifying additional mechanisms through which climate changes influence TC activity. © 2019, The Author(s)."
"26649925100;","Convective Self-Aggregation As a Cold Pool-Driven Critical Phenomenon",2019,"10.1029/2018GL081817","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064069250&doi=10.1029%2f2018GL081817&partnerID=40&md5=20d5c53e09bbe93f7c283ea7fc3dfc65","Convective self-aggregation is when thunderstorm clouds cluster over a constant temperature surface in radiative convective equilibrium. Self-aggregation was implicated in the Madden-Julian Oscillation and hurricanes. Yet, numerical simulations succeed or fail at producing self-aggregation, depending on modeling choices. Common explanations for self-aggregation invoke radiative effects, acting to concentrate moisture in a subdomain. Interaction between cold pools, caused by rain evaporation, drives reorganization of boundary layer moisture and triggers new updrafts. We propose a simple model for aggregation by cold pool interaction, assuming a local number density ρ(r) of precipitation cells, and that interaction scales quadratically with ρ(r). Our model mimics global energy constraints by limiting further cell production when many cells are present. The phase diagram shows a continuous phase transition between a continuum and an aggregated state. Strong cold pool-cold pool interaction gives a uniform convective phase, while weak interaction yields few and independent cells. Segregation results for intermediate interaction strength. ©2019. American Geophysical Union. All Rights Reserved."
"57209713643;7202208382;","Sensitivity of Convective Self-Aggregation to Domain Size",2019,"10.1029/2019MS001672","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068524766&doi=10.1029%2f2019MS001672&partnerID=40&md5=07799523871c580fb3e9146ea0e2c954","A 3-D cloud-resolving model has been used to investigate the domain size dependence of simulations of convective self-aggregation (CSA) in radiative-convective equilibrium. We investigate how large a domain is needed to allow multiple convective clusters and also how the properties equilibrated CSA depend on domain size. We used doubly periodic square domains of widths 768, 1,536, 3,072, and 6,144 km, over 350 simulated days. In the 768-, 1,536-, and 3,072-km domains, the simulations produced circular convective clusters surrounded by broader regions of dry, subsiding air. In the 6,144-km domain, the convection ultimately forms two semiconnected bands. As the domain size increases, equilibrated CSA moistens in two ways. First, as the circulation widens, this leads to stronger boundary layer winds and a more humid boundary layer. Second, the stronger inflow into the convective region boundary layer is associated with a warmer convective region boundary layer, which leads to intensified deep convection, more melting and freezing near the freezing level, enhanced midlevel stability, increased congestus activity, and detrainment of moist air into the dry region. In the larger domains, the deep convection and congestus slowly oscillate out of phase with each other with a time period of about 25 to 30 days. We hypothesize that other important domain size sensitivities, including a decrease in net moist static energy export from the convective region, are fundamentally linked to the increasing relationship between domain size and boundary layer wind speed. Our results suggest that the statistics of CSA converge only for domains wider than about 3,000 km. © 2019. The Authors."
"24485834000;","Mesoscale circulations and organized convection in African easterly waves",2018,"10.1175/JAS-D-18-0183.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059265515&doi=10.1175%2fJAS-D-18-0183.1&partnerID=40&md5=7a2abfc9f94df95be2b3aef724f675ff","Global convection-permitting model simulations and remote sensing observations are used to investigate the interaction between organized convection, both moist and dry, and the atmospheric circulation in the case of an African easterly wave (AEW). The wave disturbance is associated with a quadrupole structure of divergence, with two convergence centers slightly ahead of the trough. Moisture transport from southeast of the trough to the area in front and lower midtropospheric moisture convergence precondition and organize convection. The main inflow into the squall-line cluster is from behind. The moisture-abundant inflow collides at the low level with monsoon air with high moist static energy and establishes a frontal line of updrafts at the leading edge of the propagating mesoscale convective system.Amantle of moisture surrounds the convective core.Apotential vorticity budget analysis reveals that convective latent heating is driving the evolution of the wave but not in a quasi-steady way. The wave propagation includes a succession of convective bursts and subsequent dynamic adjustment processes. Dry convection associated with the Saharan air layer (SAL) and SAL intrusions into the wave trough together with vorticity advection can play a role in intensifying AEWs dynamically as they move from the West African coast across the Atlantic Ocean. Our analysis demonstrates that the synoptic-scale wave and convection are interlinked through mesoscale circulations on a continuum of scales. This implies that the relation between organized convection and the atmospheric circulation is intrinsically dynamic, which poses a particular challenge to subgrid convection parameterizations in numerical models. © 2018 American Meteorological Society."
"55176818100;7004978125;56434851400;","The Multiscale Impacts of Organized Convection in Global 2-D Cloud-Resolving Models",2018,"10.1029/2018MS001335","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052407037&doi=10.1029%2f2018MS001335&partnerID=40&md5=c0470fa6efa53581962a71d1b0e6ee66","This paper studies the mechanisms behind the multiscale organization of tropical moist convection using a trio of cloud-resolving atmospheric simulations performed in a periodic two-dimensional 32,000-km domain. A simulation with interactive surface fluxes and long-wave radiation over a constant sea surface temperature of 300.15 K produces a planetary-scale self-aggregated patch of convection after 80 days of simulation. Fixing the surface fluxes and radiative cooling at a constant value suppresses this planetary-scale organization. However, increasing the stability at the tropopause by adding stratospheric heating produces a simulation, which generates a planetary-scale wave after just 30 days. This planetary-scale wave modulates eastward propagating synoptic-scale waves, which in turn modulate westward propagating mesoscale convective system. Low-pass filters are used to diagnose the feedbacks, which produce large-scale variance of zonal velocity, buoyancy, and humidity. The planetary-scale buoyancy variance and zonal velocity variance are related to the available potential energy (APE) and kinetic energy (KE) budgets, respectively. In the simulation with stratospheric heating, planetary-scale KE is created by vertical fluxes of zonal momentum, converted to APE, and then dissipated by latent heating, mixing, and other buoyancy sources. Without stratospheric heating, the KE produced by these feedbacks is strongly damped in the stratosphere. The mesoscale eddy flux convergence of zonal momentum dominates the total vertical flux feedback on the planetary-scale KE, and its vertical structure is consistent with the westward propagating mesoscale convective systems. Overall, these results demonstrate that these eddy fluxes can organize two-dimensional deep convection on planetary scales in the absence of other diabatic feedbacks. ©2018. American Geophysical Union. All Rights Reserved."
"56575724100;","What is the key feature of convection leading up to tropical cyclone formation?",2018,"10.1175/JAS-D-17-0131.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047195939&doi=10.1175%2fJAS-D-17-0131.1&partnerID=40&md5=593592fb3e6be39264c29508533c4641","Infrared brightness temperature data are used to investigate convective evolution during tropical cyclone (TC) formation in a quasi-Lagrangian framework. More than 150 named Atlantic storms during 1989-2010 were examined. It is found that both convective intensity and convective frequency increase with time in the inner pouch region but change little, or even weaken slightly, in the outer pouch region. Convection thus appears to concentrate toward the circulation center as genesis is approached. However, large variability is found from storm to storm in convective intensity, area, and duration, and the convective evolution of individual storms does not resemble the composite mean. Further analysis suggests that the composite mean or the median represents the probability of occurrence of convection instead of a recurrent pattern. Three distinct spatial patterns of convection are identified using cluster analysis. Substantial differences in convection intensity and area are found among the clusters and can be attributed to the impacts of environmental conditions. These differences suggest that convection intensity or area is not a key feature of convection for tropical cyclogenesis. In particular, a small and weak convective system is not necessarily associated with a weak vortex. A simple proxy of the radial gradient of convection is found to be similar among the clusters. Furthermore, convection is most effective in strengthening the TC protovortex when its maximum occurs near the pouch center. These findings suggest that organized convection near the pouch center is a key feature of convection for tropical cyclogenesis and that emphasizing convective intensity or frequency without considering the spatial pattern may be misleading. © 2018 American Meteorological Society."
"55718206700;22234129400;36054921000;7202772927;36868795400;35325977100;57196115458;7403577184;7405489798;","Evolution of Precipitation Structure During the November DYNAMO MJO Event: Cloud-Resolving Model Intercomparison and Cross Validation Using Radar Observations",2018,"10.1002/2017JD027775","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045835676&doi=10.1002%2f2017JD027775&partnerID=40&md5=ca545b4ade160956d9948c262548969f","Evolution of precipitation structures are simulated and compared with radar observations for the November Madden-Julian Oscillation (MJO) event during the DYNAmics of the MJO (DYNAMO) field campaign. Three ground-based, ship-borne, and spaceborne precipitation radars and three cloud-resolving models (CRMs) driven by observed large-scale forcing are used to study precipitation structures at different locations over the central equatorial Indian Ocean. Convective strength is represented by 0-dBZ echo-top heights, and convective organization by contiguous 17-dBZ areas. The multi-radar and multi-model framework allows for more stringent model validations. The emphasis is on testing models' ability to simulate subtle differences observed at different radar sites when the MJO event passed through. The results show that CRMs forced by site-specific large-scale forcing can reproduce not only common features in cloud populations but also subtle variations observed by different radars. The comparisons also revealed common deficiencies in CRM simulations where they underestimate radar echo-top heights for the strongest convection within large, organized precipitation features. Cross validations with multiple radars and models also enable quantitative comparisons in CRM sensitivity studies using different large-scale forcing, microphysical schemes and parameters, resolutions, and domain sizes. In terms of radar echo-top height temporal variations, many model sensitivity tests have better correlations than radar/model comparisons, indicating robustness in model performance on this aspect. It is further shown that well-validated model simulations could be used to constrain uncertainties in observed echo-top heights when the low-resolution surveillance scanning strategy is used. ©2018. American Geophysical Union. All Rights Reserved."
"57198803827;7401945370;25924499900;25647939800;","Initiation Processes of the Tropical Intraseasonal Variability Simulated in an Aqua-Planet Experiment: What is the Intrinsic Mechanism for MJO Onset?",2018,"10.1002/2017MS001243","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046996322&doi=10.1002%2f2017MS001243&partnerID=40&md5=c96d22fd8961446e751e3dd96692924f","To understand the intrinsic onset mechanism of the Madden-Julian Oscillation (MJO), we simulated a set of initiation processes of MJO-like disturbances in 10 year aqua-planet experiments using a global atmospheric model with a 56 km horizontal mesh and an explicit cloud scheme. Under a condition with a zonally nonuniform sea surface temperature (SST) in the tropics, we reproduced MJO-like disturbances over the western warm pool region. The lagged-composite analysis of detected MJO-like disturbances clarifies the time sequence of three-dimensional dynamic and moisture fields prior to the onset. We found that midtropospheric moistening, a condition that is favorable for deep convection, is particularly obvious in the initiation region 5–9 days before onset. The moistening is caused by two-dimensional horizontal advection due to cross-equatorial shallow circulations associated with mixed Rossby-gravity waves, as well as anomalous poleward flows of a negative Rossby response to suppressed convection. When the midtroposphere is sufficiently moistened, lower tropospheric signals of circumnavigating Kelvin waves trigger active convection. The surface latent heat flux (LHF) feedback contributes to the initial stages of convective organization, while the cloud-radiation feedback contributes to later stages. Sensitivity experiments suggest that circumnavigating Kelvin waves regulate the period of MJO-like disturbances because of efficient convective triggering and that the LHF feedback contributes to rapid convective organization. However, the experiments also reveal that both conditions are not necessary for the existence of MJO-like disturbances. Implications for the relevance of these mechanisms for MJO onset are also discussed. © 2018. The Authors."
"57189213948;6701670597;","Effects of a Simple Convective Organization Scheme in a Two-Plume GCM",2018,"10.1002/2017MS001106","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044512565&doi=10.1002%2f2017MS001106&partnerID=40&md5=377a5a220071a45d5973a5bd413c457f","A set of experiments is described with the Community Atmosphere Model (CAM5) using a two-plume convection scheme. To represent the differences of organized convection from General Circulation Model (GCM) assumptions of isolated plumes in uniform environments, a dimensionless prognostic “organization” tracer Ω is invoked to lend the second plume a buoyancy advantage relative to the first, as described in Mapes and Neale (2016). When low-entrainment plumes are unconditionally available (Ω = 1 everywhere), deep convection occurs too easily, with consequences including premature (upstream) rainfall in inflows to the deep tropics, excessive convective versus large-scale rainfall, poor relationships to the vapor field, stable bias in the mean state, weak and poor tropical variability, and midday peak in diurnal rainfall over land. Some of these are shown to also be characteristic of CAM4 with its separated deep and shallow convection schemes. When low-entrainment plumes are forbidden by setting Ω = 0 everywhere, some opposite problems can be discerned. In between those extreme cases, an interactive Ω driven by the evaporation of precipitation acts as a local positive feedback loop, concentrating deep convection: In areas of little recent rain, only highly entraining plumes can occur, unfavorable for rain production. This tunable mechanism steadily increases precipitation variance in both space and time, as illustrated here with maps, time-longitude series, and spectra, while avoiding some mean state biases as illustrated with process-oriented diagnostics such as conserved variable profiles and vapor-binned precipitation curves. © 2017. The Authors."
"57200650233;56989640500;21935606200;25721586700;56724696200;","Vertical Structure and Radiative Forcing of Monsoon Clouds Over Kanpur During the 2016 INCOMPASS Field Campaign",2018,"10.1002/2017JD027759","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042074383&doi=10.1002%2f2017JD027759&partnerID=40&md5=c45fc3b104635566caa5528353010f34","An overview of cloud vertical structure (CVS) and cloud radiative forcing (CRF) during Indian summer monsoon is obtained over Kanpur, through observations made during the Interaction of Convective Organisation and Monsoon Precipitation, Atmosphere, Surface and Sea field campaign of 2016. Associations of CVS parameters with CRF at surface and top of atmosphere (TOA) are also investigated. One hundred thirty-seven radiosondes were launched at Indian Institute of Technology Kanpur, between 5 and 28 July 2016. CVS is determined using an algorithm that identifies cloud layers from vertical profiles of relative humidity, with altitude-dependent relative humidity thresholds. CVS is analyzed by separating the campaign period on the basis of presence and absence of depressions/low-pressure systems. Compared to nondepression periods, low-pressure events showed significant difference in all CVS and CRF parameters except cloud top height. CVS was multilayered in ∼75% launches, with deep, mixed-phase clouds being present in ∼70% launches. CRF was calculated from clear-sky measurements and TOA observations from Clouds and the Earth's Radiant Energy System satellite retrievals, and surface measurements. A net cooling effect was found overall, with instantaneous shortwave CRF (mean values of −95.92 and −101.89 W/m2 at surface and TOA, respectively) dominating longwave cloud radiative forcing (LWCRF) (mean values of 15.33 and 66.55 W/m2 at surface and TOA, respectively). Results suggest that shortwave CRF depends on total depth of cloud layers and is independent of cloud altitude, whereas LWCRF depends on both depth and vertical location of cloud layers, with base and top heights regulating LWCRF at surface and TOA, respectively. ©2018. American Geophysical Union. All Rights Reserved."
"55958422800;42262516200;","Factors leading to extreme precipitation on dominica from Tropical Storm Erika (2015)",2018,"10.1175/MWR-D-17-0242.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042418683&doi=10.1175%2fMWR-D-17-0242.1&partnerID=40&md5=6d36b4426a08a61fc45a7043297fe034","Tropical cyclones are generally characterized by strong rotating winds, and yet, the associated rainfall can be equally destructive. Tropical Storm Erika (2015) is an example of such a cyclone whose heavy rainfall south of the storm center was responsible for significant loss of life and property. Tropical Storm Erika was a weak tropical storm in a sheared environment that passed through the Lesser Antilles on 27 August 2015. Radar and rain gauges measured at least a half meter of rainfall on the Commonwealth of Dominica in about 5 h. In this study, an analysis of several observational datasets showed that the combination of a sheared environment, dry northern sector, and mesovortex contributed to the significant storm precipitation. The sheared environment affected the storm structure, causing it to weaken, but also organized convection and precipitation in the region that passed over Dominica. Furthermore, a mesovortex embedded within the storm persisted over Dominica, leading to enhanced rainfall totals. Understanding the factors leading to heavy rainfall for this case is important for future prediction of similar weak, sheared tropical storms passing near mountainous islands. © 2018 American Meteorological Society."
"14325218600;7005449794;","Simulations of the observed ‘jump’ in the West African monsoon and its underlying dynamics using the MIT regional climate model",2018,"10.1002/joc.5214","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041448152&doi=10.1002%2fjoc.5214&partnerID=40&md5=318a9c8e1d9e67f6b795dc65ed0658e3","The observed seasonal migration of rainfall associated with the West African monsoon (WAM) is characterized by two regimes of relatively intense rainfall: an early, intense peak over the Guinean Coast during late May to early July; and a late, less-intense peak over the Sahel during mid-July to mid-September. The transition between these two rainfall regimes occurs relatively quickly around the beginning of July. This quick transition can be described as a ‘jump’ of the WAM into the continent. Eltahir and Gong (1996) proposed a theory for the WAM whereby the solar radiation forcing during the summer shapes a distribution of boundary-layer entropy that peaks over the continent. By assuming a quasi-equilibrium balance between moist convection and the large-scale radiative forcing, the distribution of boundary-layer entropy can be linked to the absolute vorticity at the tropopause. According to this analytical theory, the onset of the monsoon, characterized by the ‘jump’, reflects of a nonlinear shift from a radiative-convective equilibrium regime to an angular momentum conserving regime that would only occur when the value of absolute vorticity in the upper troposphere approaches a threshold of zero. It is because, when the absolute vorticity is significantly different from zero, then the air as a rotating fluid is too rigid to exhibit a meridional overturning. Here, we use the MIT regional climate model (MRCM) to test this theory further and reach a couple of conclusions. First, MRCM succeeds in reproducing the main features of the observed rainfall distribution, including the ‘jump’. Second, analysis of the rainfall, vorticity, entropy, and wind fields simulated by the model reveals a dynamical picture consistent with the proposed theory. © 2017 The Authors. International Journal of Climatology published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"57201877896;57034458200;","On the extraordinary intensification of Hurricane Patricia (2015). Part I: Numerical experiments",2018,"10.1175/WAF-D-18-0045.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062150109&doi=10.1175%2fWAF-D-18-0045.1&partnerID=40&md5=2d78b48ab0c8a1896fc6f08efd00f514","Hurricane Patricia (2015) broke records in both peak intensity and rapid intensification (RI) rate over the eastern Pacific basin. All of the then-operational models predicted less than half of its extraordinary intensity and RI rate, leaving a challenge for numerical modeling studies. In this study, a successful 42-h simulation of Patricia is obtained using a quintuply nested-grid version of the Weather Research and Forecast (WRF) Model with the finest grid size of 333 m. Results show that the WRF Model, initialized with the Global Forecast System Final Analysis data only, could reproduce the track, peak intensity, and many inner-core features, as verified against various observations. In particular, its simulated maximum surface wind of 92ms -1 is close to the observed 95ms -1 , capturing the unprecedented RI rate of 54ms -1 (24 h)21. In addition, the model reproduces an intense warm-cored eye, a small-sized eyewall with a radius of maximum wind of less than 10 km, and the distribution of narrow spiral rainbands.Aseries of sensitivity simulations is performed to help understand which model configurations are essential to reproducing the extraordinary intensity of the storm. Results reveal that Patricia's extraordinary development and its many inner-core structures could be reasonably well simulated if ultrahigh horizontal resolution, appropriate model physics, and realistic initial vortex intensity are incorporated. It is concluded that the large-scale conditions (e.g., warm sea surface temperature, weak vertical wind shear, and the moist intertropical convergence zone) and convective organization play important roles in determining the predictability of Patricia's extraordinary RI and peak intensity. © 2018 American Meteorological Society."
"56089348800;16475714800;","Competing effects of surface albedo and orographic elevated heating on regional climate",2017,"10.1002/2016GL072441","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021897313&doi=10.1002%2f2016GL072441&partnerID=40&md5=0b794147e856c9b0ba060bcae379cb14","All else being equal, a given atmospheric pressure level is thought to be warmer over a plateau than over surrounding nonelevated terrain because of orographic “elevated heating.” However, elevated surfaces are also typically brighter due to reduced vegetation and increased ice cover. Here we assess the degree to which surface albedo compensates for orographic elevated heating. We confirm that land surface albedo generally increases with surface elevation in observations. Using a cloud system-resolving model, we show that increased surface albedo strongly compensates for orographic elevated heating in radiative-convective equilibrium. A nonelevated surface with the albedo of modern India would enter a runaway greenhouse regime without ventilation by monsoonal winds, while a surface with the albedo and elevation of Tibet would achieve a cooler radiative-convective equilibrium. Surface albedo changes may thus be just as important as surface elevation changes for the evolution of low-latitude regional climate throughout Earth's history. ©2017. American Geophysical Union. All Rights Reserved."
"7005485117;56021872900;56391331800;16202411300;57189644727;","Scale interaction during an extreme rain event over southeast India",2017,"10.1002/qj.3016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019612230&doi=10.1002%2fqj.3016&partnerID=40&md5=441f35298f7ae23bf54b0a6fdd196d6c","The major rains and floods over southeast India (during October through to December 2015) are addressed in the context of atmospheric scale interactions in the frequency domain. Some of the salient observational features of this period include: (i) the major El Niño of 2015, (ii) the stretch of lower tropospheric easterlies from the region of the warm sea-surface temperature anomalies westwards to the east coast of India, (iii) presence of shear flow instability, in the presence of convection, along a long stretch of the easterly wind belt from the eastern Pacific Ocean to the eastern Bay of Bengal, (iv) large conversions of horizontal shear vorticity to curvature vorticity along this stretch of easterly trades, where these rain-producing storms were forming, (v) an active IntraSeasonal Oscillation (ISO) time-scale oscillation in the wind field that alternated between cyclonic and anticyclonic phases over southeast India during this period of heavy rains, and (vi) an active quasi-biweekly oscillation that provides alternating onshore and offshore winds during this same period. The ISO and the quasi-biweekly components contribute to the enhancement of the moisture supply from the Bay of Bengal during the extreme rain events. The synoptic scale receives its energy largely from organized convection within these disturbances on horizontal scales of the order of 2500 km. Other aspects such as the role of the sea-surface temperatures of the Bay of Bengal and the role of Gill's antisymmetric heat source of the El Niño are also examined in this study. © 2017 Royal Meteorological Society"
"54983414800;","The tropical precipitation pickup threshold and clouds in a radiative convective equilibrium model: 2. Two-layer moisture",2017,"10.1002/2016JD025908","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021382423&doi=10.1002%2f2016JD025908&partnerID=40&md5=00f9c149a7320aedc0378dce6a459258","This paper complements Part 1 in which cloud processes of aggregated convection are examined in a large-domain radiative convective equilibrium simulation in order to uncover those responsible for a consistently observed, abrupt increase in mean precipitation at a column relative humidity value of approximately 77%. In Part 2, the focus is on how the transition is affected independently by total moisture above and below the base of the melting layer. When mean precipitation rates are examined as simultaneous functions of these two moisture layers, four distinct behaviors are observed. These four behaviors suggest unique, yet familiar, physical regimes in which (i) little rain is produced by infrequent clouds, (ii) shallow convection produces increasing warm rain with increasing low-level moisture, (iii) deep convection produces progressively heavier rain above the transition point with increasing total moisture, and (iv) deep stratiform cloud produces increasingly intense precipitation from melting for increasing upper level moisture. The independent thresholds separating regimes in upper and lower layer humidity are shown to result in the value of total column humidity at which a transition between clear air and deep convection, and therefore a pickup in precipitation, is possible. All four regimes force atmospheric columns toward the pickup value at 77% column humidity, but each does so through a unique set of physical processes. Layer moisture and microphysical budgets are analyzed and contrasted with column budgets. © 2017. American Geophysical Union. All Rights Reserved."
"57188594058;35578543700;6701670597;","Convectively coupled Kelvin waves in aquachannel simulations: 2. Life cycle and dynamicalconvective coupling",2016,"10.1002/2016JD025022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84991067535&doi=10.1002%2f2016JD025022&partnerID=40&md5=6913197dc3f6d4a604167ecfebe01120","This second part of a two-part study uses Weather Research and Forecasting simulations with aquachannel and aquapatch domains to investigate the time evolution of convectively coupled Kelvin waves (CCKWs). Power spectra, filtering, and compositing are combined with object-tracking methods to assess the structure and phase speed propagation of CCKWs during their strengthening, mature, and decaying phases. In this regard, we introduce an innovative approach to more closely investigate the wave (Kelvin) versus entity (super cloud cluster or “SCC”) dualism. In general, the composite CCKW structures represent a dynamical response to the organized convective activity. However, pressure and thermodynamic fields in the boundary layer behave differently. Further analysis of the time evolution of pressure and low-level moist static energy finds that these fields propagate eastward as a “moist” Kelvin wave (MKW), faster than the envelope of organized convection or SCC. When the separation is sufficiently large the SCC dissipates, and a newSCC generates to the east, in the region of strongest negative pressure perturbations. We revisit the concept itself of the “coupling” between convection and dynamics, and we also propose a conceptual model for CCKWs, with a clear distinction between the SCC and the MKW components. © 2016. American Geophysical Union. All Rights Reserved."
"55469523400;15124698700;","Scaling of the entropy budget with surface temperature in radiative-convective equilibrium",2016,"10.1002/2016MS000673","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84979735717&doi=10.1002%2f2016MS000673&partnerID=40&md5=0c627f56c07fe9e7ce9ba554fe545afb","The entropy budget of the atmosphere is examined in simulations of radiative-convective equilibrium with a cloud-system resolving model over a wide range of surface temperatures from 281 to 311 K. Irreversible phase changes and the diffusion of water vapor account for more than half of the irreversible entropy production within the atmosphere, even in the coldest simulation. As the surface temperature is increased, the atmospheric radiative cooling rate increases, driving a greater entropy sink that must be matched by greater irreversible entropy production. The entropy production resulting from irreversible moist processes increases at a similar fractional rate as the entropy sink and at a lower rate than that implied by Clausius-Clapeyron scaling. This allows the entropy production from frictional drag on hydrometeors and on the atmospheric flow to also increase with warming, in contrast to recent results for simulations with global climate models in which the work output decreases with warming. A set of approximate scaling relations is introduced for the terms in the entropy budget as the surface temperature is varied, and many of the terms are found to scale with the mean surface precipitation rate. The entropy budget provides some insight into changes in frictional dissipation in response to warming or changes in model resolution, but it is argued that frictional dissipation is not closely linked to other measures of convective vigor. © 2016. The Authors."
"36458171200;36890184300;","Cold-air outbreaks over the ocean at high latitudes and associated mesoscale atmospheric circulations: Problems of numerical modelling",2015,"10.1134/S0001433815090078","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84954327578&doi=10.1134%2fS0001433815090078&partnerID=40&md5=249a037a6c0e81441af4d2f5d279446e","A review of the current state of research in the field of numerical modelling and forecasting of cold-air outbreaks over the ocean at high latitudes and associated mesoscale circulations is presented. It is shown that the most relevant tasks are as follows: (1) the improvement of predictability and the adequacy of reproduction of polar mesocyclones, (2) a more adequate representation of the marginal sea-ice zone in the numerical models, and (3) solving problems of the parametrization and explicit reproduction of organized convection and orographic jets in numerical atmosphere models. It is demonstrated that these tasks only can be accomplished as a result of a comprehensive development of different components of the climatic system models and technology of the numerical weather prediction (NWP). One of the most promising approaches to overcome the identified problems is to develop and use methods of satellite remote sensing of the atmosphere and underlying surface in NWP technology. The high potential of analyzing the satellite multisensor data for quantifying parameters of different-scale atmospheric circulations is demonstrated using the example of cold-air outbreaks over the seas of the Far East. © 2015, Pleiades Publishing, Ltd."
"56770222600;55881511800;57204256646;","Distinguishing between unorganized and organized convection when examining land-atmosphere relationships",2015,"10.1175/JAMC-D-15-0086.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939855993&doi=10.1175%2fJAMC-D-15-0086.1&partnerID=40&md5=a6fc22ad4b9440a4324125658d6a49d1","In this study, the robustness of a previously developed classification system that categorizes convective thunderstorm events initiated during various synoptic and dynamic conditions is analyzed. This classification system was used to distinguish between organized and unorganized convection and then used to determine whether unorganized convection occurs preferentially over wet or dry soils. The focus is on 12 events that occurred in synoptically benign (SB) environments where the Great Plains low-level jet was not present (noLLJ), and whether these events were accurately classified as unorganized convection is evaluated. Although there is a small sample size, the results show that the classification system fails to differentiate between local unorganized convection and large-scale organized convection under SB-noLLJ conditions. The authors conclude that past studies that have used this classification to study how soil moisture influences unorganized convection should be revisited. Additional variables and/or alternative precipitation datasets should be employed to enhance the robustness of the classification system. © 2015 American Meteorological Society."
"57195549023;","Microscale simulations of Venus' convective adjustment and mixing near the surface: Thermal and material transport processes",2011,"10.1016/j.icarus.2010.11.019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79151472092&doi=10.1016%2fj.icarus.2010.11.019&partnerID=40&md5=0593ac2e070d94b81cba09eb0bf2e04f","Heat and material transport processes caused by convective adjustment and mixing are important in modeling of Venus' atmosphere. In the present study, microscale atmospheric simulations near the venusian surface were conducted using a Weather Research and Forecasting model to elucidate the thermal and material transport processes of convective adjustment and mixing. When convective adjustment occurs, the heat and passive tracer are rapidly mixed into the upper stable layer with convective penetration. The convective adjustment produces large eddy diffusions of heat and passive tracer, which may explain the large eddy diffusions estimated in the radiative-convective equilibrium model.For values of surface heat flux Q greater than a threshold (=0.064Kms-1 in the present study), the convectively mixed layer with high eddy diffusion coefficients grows with time. In contrast, the mixed layer decays with time for Q values smaller than the threshold. The thermal structure near the surface is controlled not only by extremely long-term radiative processes, but also by microscale dynamics with time scales of several hours. A mixed layer with high eddy diffusion coefficients may be maintained or grow with time if the surface heat flux is high in the volcanic hotspot and adjacent areas. © 2010 Elsevier Inc."
"6603713237;","Effects of bias in solar radiative transfer codes on global climate model simulations",2005,"10.1029/2005GL023644","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28944445997&doi=10.1029%2f2005GL023644&partnerID=40&md5=db1efa32390d73769912e6ec52385757","Codes commonly used in climate and weather preliction models for calculating the transfer of solar radiation in the atmosphere show systematic differences amongst each other, and even the best of codes show systematic differences with respect to observations. A 1-dimensional radiative-convective equilibrium model is used to show the effects of such bias on the global energy balance and on the global response to a doubling of CO2. We find the main impact is in the energy exchange terms between the surface and atmosphere and in the convective transport in the lower troposphere, where it exceeds 10 W m-2. The impact on model response to doubling of CO2, on the other hand, is quite small and in most cases negligible. Copyright 2005 by the American Geophysical Union."
"6506761906;","Development of convective systems over Baja California during Tropical Cyclone Linda (2003)",2005,"10.1175/WAF879.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-28144440150&doi=10.1175%2fWAF879.1&partnerID=40&md5=bef988190a5a5700cd45e67bce489fc9","Characteristics of the life cycle and motion of convective systems that occurred over the Baja California Peninsula were determined from a case study in September of 2003. This note applies data from satellite imagery, regular observations from upper-air and surface networks, and operational analyses. Changes in environmental conditions over northwestern Mexico are documented and these are associated with the development of Tropical Cyclone Linda in the eastern Pacific Ocean. When Linda became a tropical storm and was located several hundred kilometers away to the southwest, a convective outbreak occurred over land. An examination of large-scale conditions indicated that flow from the eastern flank of Linda supplied low-to midlevel moisture. Significant convection is associated with specific thresholds for precipitable water, CAPE, and lifted index. Convective systems initiated in the early afternoon remained active for several hours and provided localized areas of precipitation along the western side of the peninsular mountains. An assessment of all the available surface data was performed to determine regional elements that played a role in the development of these systems. Results include documentation of a sea breeze from the Gulf of California onto the mountain slopes when organized convection was first detected. © 2005 American Meteorological Society."
"7407663727;57213941968;","Satellite-based monitoring of intraseasonal variations in tropical Pacific and Atlantic convection",2001,"10.1029/1999GL011259","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035870337&doi=10.1029%2f1999GL011259&partnerID=40&md5=a04dfc312552fb010a08f26884e857f8","An automated Convection Classification, Analysis and Tracking Scheme (CCATS) is used to diagnose spatial and temporal variability of convection in the tropical western Pacific and Atlantic Oceans. Three organized convection classes are differentiated; degree of organization is related to lifetime, symmetry and peak system size. A fourth category of short-lived thunderstorms is also detected. Two cycles of the Madden Julian Oscillation (MJO) are tracked across the Pacific basin. The degree of organization of the convective systems increases as the MJO progresses through the region, preconditioning the environment for tropical cyclogenesis. Satellite-inferred rainfall budgets reveal that tropical western Pacific and Atlantic rainfall is dominated by organized convection. This has potentially important implications for representation of the hydrologic cycle in numerical simulations of the tropics, particularly for models that do not explicitly resolve the mesoscales."
"7201605742;","A tropical cyclone model resolving mesoscale organized convection with prognostic treatment of subgrid-scale cloud water",2001,"10.2151/jmsj.79.637","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23044525322&doi=10.2151%2fjmsj.79.637&partnerID=40&md5=84c7b45ea8c49831a3eda8f3e78702f5","A new version of a tropical cyclone model is presented as an extension of Yamasaki's (1986) model that intended to resolve mesoscale organized convection by a grid and treat the cumulus-scale motion as the subgrid-scale. Two important improvements are made in this study. One is a prognostic treatment of cumulus-scale cloud water, which was treated diagnostically in the old version. The other is that the ratio of the cumulus-scale ascending area is not assumed to be sufficiently small compared to unity. Results from numerical experiments indicate that the features of tropical cyclones (including rainwater distribution) simulated by the new and old versions are essentially similar, but the cloud water distribution is simulated more realistically by the new version, as evident from the model formulation. Clarification of the impact of the finite area ratio and an improvement of its assumption remain to be studied. ©2001, Meteorological Society of Japan."
"7801604237;","A case study of Rayleigh-Benard convection with clouds",1998,"10.1023/A:1001145803614","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032462694&doi=10.1023%2fA%3a1001145803614&partnerID=40&md5=5bba4d7fa2de3bad758691256625a193","A turbulence data set collected by the research aircraft Hercules and Falcon in the planetary boundary layer (PBL) over the North Sea during Rayleigh-Benard convection (RBC) is analysed. Altogether nearly three hundred cell passages at different levels and in two different flight directions were sampled. The convective boundary-layer height (H) was about 1 km, and the RBC cells had a diameter D of roughly 2-3 km, resulting in an aspect ratio A = D/H ~ 2-3. This value is also found in the case of RBC in laboratory-scale flows, whereas most of the recent PBL experimental work reports convection PBL rolls with A ~ 3 and mesoscale cellular convection (MCC) with A ~ 10-40 over the oceans. The large number of RBC cell passages made it possible to composite their average structure. Due to the more complex three-dimensional structure and the importance of thermals to the RBC dynamics, spectral, temporal and spatial decompositions and model calculations were necessary to illuminate structure, dynamics, energetics and organisation. The final impression is that the structure of RBC in the PBL is given by a honeycomb-like arrangement of short-lived mixed-layer thermals with more passive downward motions in between. The regularity of the Cu-cloud cover results partly from the more stationary flow in the cloud-free cell centres. On the other hand it is shown that active as well as inactive clouds contribute to the cloud cover. Thus, the PBL flow and the cloud cover are decoupled, at least temporarily and locally. Due to sparse observational and measured information about RBC occurrence and structure in the PBL, additional material was gathered, resulting in the impression that RBC is one additional realised mode of organised convection in the PBL, as has already been clarified for PBL rolls and MCC by recent investigations."
"6701669750;","Angular momentum and temperature homogenization in the symmetric circulation of the atmosphere",1998,"10.1175/1520-0469(1998)055<1997:AMATHI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031851302&doi=10.1175%2f1520-0469%281998%29055%3c1997%3aAMATHI%3e2.0.CO%3b2&partnerID=40&md5=35630061a9657c72ac503fb5eb8e33ac","The axisymmetric model of the Hadley circulation can be systematically reduced in the limit of small Rossby number to a simpler one-dimensional system. The reduced system governs the nonlinear evolution of the surface angular momentum and the vertically averaged potential temperature. The meridional transports of heat and angular momentum take the form of downgradient nonlinear diffusion, which acts to homogenize laterally the angular momentum and the potential temperature within the meridional Hadley cells. The diffusivities for both quantities are proportional to the square of the latitudinal gradient of potential temperature. The reduced system is amenable to analytic exploration and allows the explicit determination of the extent and strength of the meridional circulation in terms of the parameters of the problem, such as the Rossby number, the stratification imposed by the radiative-convective equilibrium, and the surface drag. The reduced system also shows that surface easterlies at the equator are possible even when the heating distribution is latitudinally symmetric, as long as the surface drag or the imposed stratification are small."
"57213656510;","Convective organization in a tropical boundary layer: an interpretation of Doppler radar observations using Asai's model.",1985,"10.1175/1520-0469(1985)042<2844:COIATB>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022266371&doi=10.1175%2f1520-0469%281985%29042%3c2844%3aCOIATB%3e2.0.CO%3b2&partnerID=40&md5=42c6f1d8e8cdac32f2e3d97ae25c0a99","Convective structures in a tropical boundary layer were analyzed using two Doppler radars. Their spatial organization is examined, revealing favored directions of alignment of cells in the four cases studied. The effect of the wind shear on the organization of these cells is studied using Asai's model and taking into account the thermal stratification. The results are in agreement with observations, showing longitudinal or transverse modes of alignment, depending on the stratification. However some observed modes of large wavelength could not be simulated by the model. -Author"
"6603297364;","Numerical simulation of organized convection. Part I: model description and preliminary comparisons with squall line observations.",1985,"10.1175/1520-0469(1985)042<0155:NSOOCP>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022266213&doi=10.1175%2f1520-0469%281985%29042%3c0155%3aNSOOCP%3e2.0.CO%3b2&partnerID=40&md5=a58ca379ccfd6c1932ed302e87d51ca2","A numerical model designed for the simulations of mesoscale flows perturbed by deep convective clouds is discussed. It is based on the time dependent coupling between a three-dimensional nonhydrostatic mesoscale model and a quasi-one-dimensional cloud model. A particular simulation is analyzed. Analysis reveals that the main characteristics of the flow perturbed by the convective cells are similar to those of a squall line deduced from ground station measurements. -from Author mesoscale flows gust front time dependent coupling"
"57213656510;","Radar analysis of a tropical convective boundary layer with shallow cumulus clouds.",1984,"10.1175/1520-0469(1984)041<1380:RAOATC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021554806&doi=10.1175%2f1520-0469%281984%29041%3c1380%3aRAOATC%3e2.0.CO%3b2&partnerID=40&md5=fd17eb22bb45fe9e5103e48056d844f6","A situation of fair weather cloud convection is examined using a dual Doppler radar, environmental measurements and cloud photogrammetry. The convective layer is characterized by the interaction between the northward monsoon wind at low levels and the easterly wind above; a convective organization is found to be related to the shear between both flows. Moreover, at the convective scale, properties of the convective layer below clouds and in clear air ar considered.-from Author"
"6603833748;","Information theory lateral density distribution for earth inferred from global gravity field.",1982,"10.1029/JB087iB07p05541","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020398543&doi=10.1029%2fJB087iB07p05541&partnerID=40&md5=3bd4415a8ffded51712078fa2f52406a","Information theory inference, better known as the maximum entropy method, is used to infer the lateral density distribution inside the earth. The approach assumes that the earth consists of indistinguishable Maxwell - Boltzmann particles populating infinitesimal volume elements and follows the standard methods of statistical mechanics (maximizing the entropy function). The GEM 10B spherical harmonic gravity field coefficients, complete to degree and order 36, are used as constraints on the lateral density distribution. The spherically symmetric part of the density distribution is assumed to be known. The lateral density variation is assumed to be small in comparison with the spherically symmetric part. The resulting information theory density distribution for the cases of no crust removed, 30km of compensated crust removed, and 30km of uncompensated crust removed all give broad density anomalies extending deep into the mantle, but with the density contrasts being the greatest toward the surface (typically + or -0.004g cm-3 in the first two cases and + or -0.04g cm-3 in the third). None of the density distributions resemble classical organized convection cells. The information theory approach may have use in choosing standard earth models, but the inclusion of seismic data into the approach appears difficult.-Author"
"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."
"57188866963;57192156759;57210687618;23991212200;","Comparing Convective Self-Aggregation in Idealized Models to Observed Moist Static Energy Variability Near the Equator",2019,"10.1029/2019GL084130","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85071749544&doi=10.1029%2f2019GL084130&partnerID=40&md5=947a6b25a6b7dd3fddf9defcfebe4555","Idealized convection-permitting simulations of radiative-convective equilibrium have become a popular tool for understanding the physical processes leading to horizontal variability of tropical water vapor and rainfall. However, the applicability of idealized simulations to nature is still unclear given that important processes are typically neglected, such as lateral water vapor advection by extratropical intrusions, or interactive ocean coupling. Here, we exploit spectral analysis to compactly summarize the multiscale processes supporting convective aggregation. By applying this framework to high-resolution reanalysis data and satellite observations in addition to idealized simulations, we compare convective-aggregation processes across horizontal scales and data sets. The results affirm the validity of the radiative-convective equilibrium simulations as an analogy to the real world. Column moist static energy tendencies share similar signs and scale selectivity in convection-permitting models and observations: Radiation increases variance at wavelengths above 1,000 km, while advection damps variance across wavelengths, and surface fluxes mostly reduce variance between 1,000 and 10,000 km. ©2019. American Geophysical Union. All Rights Reserved."
"57209286045;7101867299;","Universality in the spatial evolution of self-aggregation of tropical convection",2019,"10.1175/JAS-D-18-0129.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067181847&doi=10.1175%2fJAS-D-18-0129.1&partnerID=40&md5=bf3b884587a43df69ff627022a454590","Self-aggregation in numerical simulations of tropical convection is described by an upscale growth and intensification of dry and moist regions. Previous work has focused on determining the relevant mechanism that induces moist regions to get moister and dry regions to get drier. Though different mechanisms have been identified, the spatial evolution of self-aggregation is remarkably universal. The first part of this study shows that different mechanisms can lead to a similar evolution of self-aggregation, if self-aggregation is described by a phase separation of moist and dry regions, through a process called coarsening. Though it was previously introduced based on a convection-humidity feedback, coarsening, importantly, is not tied to a specific feedback process but only requires an intensification of local humidity perturbations. Based on different feedback loops, three simple models of the evolution of the humidity field are introduced, all of which lead to coarsening. In each model, diffusive transport of humidity is assumed, which approximates a humidity increase due to convection, within a finite region around convective cores. In the second part, predictions made by coarsening are compared with atmospheric model simulations. Analyzing a set of radiative-convective equilibrium simulations shows that coarsening correctly predicts the upscale growth of the moist and dry regions in the early stages of self-aggregation. In addition, coarsening can explain why self-aggregation is not observed for small domains and why the shape of the final moist region changes with the shape of the domain. © 2019 American Meteorological Society."
"7006788343;57194051517;7401796996;7103119050;","Sensitivity of Numerical Simulations of a Mesoscale Convective System to Ice Hydrometeors in Bulk Microphysical Parameterization",2019,"10.1007/s00024-018-1787-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065747265&doi=10.1007%2fs00024-018-1787-z&partnerID=40&md5=e9ba7677ad7b4397034c4e4390cedce7","Mesoscale convective systems (MCSs) and their associated cloud properties are the important factors that influence the aviation activities, yet they present a forecasting challenge in numerical weather prediction. In this study, the sensitivity of numerical simulations of an MCS over the US Southern Great Plains to ice hydrometeors in bulk microphysics (MP) schemes has been investigated using the Weather Research and Forecasting (WRF) model. It is found that the simulated structure, life cycle, cloud coverage, and precipitation of the convective system as well as its associated cold pools are sensitive to three selected MP schemes, namely, the WRF single-moment 6-class (WSM6), WRF double-moment 6-class (WDM6, with the double-moment treatment of warm-rain only), and Morrison double-moment (MORR, with the double-moment representation of both warm-rain and ice) schemes. Compared with observations, the WRF simulation with WSM6 only produces a less organized convection structure with a short lifetime, while WDM6 can produce the structure and length of the MCS very well. Both simulations heavily underestimate the precipitation amount, the height of the radar echo top, and stratiform cloud fractions. With MORR, the model performs well in predicting the lifetime, cloud coverage, echo top, and precipitation amount of the convection. Overall results demonstrate the importance of including double-moment representation of ice hydrometeors along with warm-rain. Additional experiments are performed to further examine the role of ice hydrometeors in numerical simulations of the MCS. Results indicate that replacing graupel with hail in the MORR scheme improves the prediction of the convective structure, especially in the convective core region. © 2018, Springer International Publishing AG, part of Springer Nature."
"57188866963;57210687618;","A budget for the size of convective self-aggregation",2019,"10.1002/qj.3468","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062308611&doi=10.1002%2fqj.3468&partnerID=40&md5=3dc0626f42da479a5e9d06830b34d037","There is no consensus on the physical mechanisms controlling the scale at which convective activity organizes near the Equator. Here, we introduce a diagnostic framework relating the evolution of the length-scale of convective aggregation to the net radiative heating, the surface enthalpy flux, and horizontal energy transport. We evaluate these expansion tendencies of convective aggregation in 20 high-resolution cloud-permitting simulations of radiative-convective equilibrium. While both radiative fluxes contribute to convective aggregation, the net long-wave radiative flux operates at large scales (1,000–5,000 km) and stretches the size of moist and dry regions, while the net short-wave flux operates at smaller scales (500–2,000 km) and shrinks it. The surface flux expansion tendency is dominated by convective gustiness, which acts to aggregate convective activity at smaller scales (500–3,000 km). © 2018 Royal Meteorological Society"
"55670345400;6603081424;","Subgrid precipitation properties of mesoscale atmospheric systems represented by modis cloud regimes",2019,"10.1175/JCLI-D-18-0570.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062995204&doi=10.1175%2fJCLI-D-18-0570.1&partnerID=40&md5=baefb44a9ddf2644e5339e992774cac0","The distribution of mesoscale precipitation exhibits diverse patterns: precipitation can be intense but sporadic, or it can be light but widespread. This range of behaviors is a reflection of the different weather systems in the global atmosphere. Using MODIS global cloud regimes as proxies for different atmospheric systems, this study investigates the subgrid precipitation properties within these systems. Taking advantage of the high resolution of Integrated Multisatellite Retrievals for GPM (IMERG; GPM is the Global Precipitation Measurement mission), precipitation values at 0.1° are composited with each cloud regime at 1° grid cells to characterize the regime's spatial subgrid precipitation properties. The results reveal the diversity of the subgrid precipitation behavior of the atmospheric systems. Organized convection is associated with the highest grid-mean precipitation rates and precipitating fraction, although on average only half the grid is precipitating and there is substantial variability between different occurrences. Summer extratropical storms have the next highest precipitation, driven mainly by moderate precipitation rates over large areas. These systems produce more precipitation than isolated convective systems, for which the lower precipitating fractions balance out the high intensities. Most systems produce heavier precipitation in the afternoon than in the morning. The grid-mean precipitation rate is also found to scale with the fraction of precipitation within the grid in a faster-than-linear relationship for most systems. This study elucidates the precipitation properties within cloud regimes, thus advancing our understanding of the precipitation structures of these atmospheric systems. © 2019 American Meteorological Society."
"57192700976;57204886915;36868795400;","Objective Quantification of Convective Clustering Observed During the AMIE/DYNAMO Two-Day Rain Episodes",2018,"10.1029/2018JD028497","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054006279&doi=10.1029%2f2018JD028497&partnerID=40&md5=653d2a12a90dee77d837d4554bb797dc","One critical bottleneck in developing and evaluating ways to represent the mesoscale organization of convection in cumulus parameterization schemes is that there is no single accepted method of objectively quantifying the degree of convective organization or clustering from observations. This study addresses this need using high-quality S-PolKa radar data from the Atmospheric Radiation Measurement Madden-Julian Oscillation Investigation Experiment/Dynamics of the Madden-Julian Oscillation (AMIE/DYNAMO) field campaign. We first identify convective elements (contiguous convective echoes [CCEs]) from radar reflectivity observations using the rain type classification algorithm of Powell et al. (2016, https://doi.org/10.1175/JTECH-D-15-0135.1). Then we apply scalar clustering metrics, including the organization index (Iorg) of Tompkins and Semie, to the radar CCEs to test their ability of quantifying convective clustering during the observed two-day rain episodes. Our results show two distinct phases of convective clustering during the two-day rain episodes, with each phase covering about 10 hr before (Phase 1) and after (Phase 2) the time of peak rain rate. In Phase 1 clustering, the number of CCEs increases and convective cells cluster as new cells form preferentially near existing convective entities. The number of CCEs decreases as the environment stabilizes in Phase 2 clustering, during which already clustered cells with associated stratiform clouds are preferred over the isolated ones. Iorg is capable of capturing convective clustering in both phases. The possible mechanisms for convective clustering are discussed, including cold pool-updraft feedback, moisture-convection interaction, and mesoscale circulations. Our results suggest that parameterizations of convective organization should represent the feedback processes that are responsible for the convective clustering during both phases. ©2018. American Geophysical Union. All Rights Reserved."
"57188866963;57210687618;7006184606;","A Linear Response Framework for Radiative-Convective Instability",2018,"10.1029/2018MS001280","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052615953&doi=10.1029%2f2018MS001280&partnerID=40&md5=affa952eb0262dfe651c5b0a17411190","Radiative-convective equilibrium is a simple paradigm for the tropical climate, in which radiative cooling balances convective heating in the absence of lateral energy transport. Recent studies have shown that a large-scale circulation may spontaneously develop from radiative-convective equilibrium through the interactions among water vapor, radiation, and convection. This potential instability, referred to as radiative-convective instability, may be posed as a linear stability problem for the water vapor profile by combining a linear response framework with the weak temperature gradient approximation. We design two analytic models of convective linear response to moisture perturbations, which are similar to Betts-Miller and bulk-plume convection schemes. We combine these convective responses with either clear-sky gray or real-gas radiative responses. In all cases, despite consistent radiative feedbacks, the characteristics of convection dominate the vertical structure of the most unstable linear mode of water vapor perturbations. For Betts-Miller convection, the stability critically depend on a key parameter: the heating to advection of moisture conversion rate (HAM); warmer atmospheres with higher HAM exhibit more linear instability. In contrast, bulk-plume convection is stable across temperatures but becomes linearly unstable with a moisture mode peaking in the midtroposphere once combined to radiation, with approximate growth rates of 10 days. ©2018. The Authors."
"56789223800;7007010459;","Reduced Sensitivity of Tropical Cyclone Intensity and Size to Sea Surface Temperature in a Radiative-Convective Equilibrium Environment",2018,"10.1007/s00376-018-7277-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048197068&doi=10.1007%2fs00376-018-7277-5&partnerID=40&md5=1621275bbde494a6e7981af56ee694e7","It has been challenging to project the tropical cyclone (TC) intensity, structure and destructive potential changes in a warming climate. Here, we compare the sensitivities of TC intensity, size and destructive potential to sea surface warming with and without a pre-storm atmospheric adjustment to an idealized state of Radiative-Convective Equilibrium (RCE). Without RCE, we find large responses of TC intensity, size and destructive potential to sea surface temperature (SST) changes, which is in line with some previous studies. However, in an environment under RCE, the TC size is almost insensitive to SST changes, and the sensitivity of intensity is also much reduced to 3% °C−1–4% °C−1. Without the pre-storm RCE adjustment, the mean destructive potential measured by the integrated power dissipation increases by about 25% °C−1 during the mature stage. However, in an environment under RCE, the sensitivity of destructive potential to sea surface warming does not change significantly. Further analyses show that the reduced response of TC intensity and size to sea surface warming under RCE can be explained by the reduced thermodynamic disequilibrium between the air boundary layer and the sea surface due to the RCE adjustment. When conducting regional-scale sea surface warming experiments for TC case studies, without any RCE adjustment the TC response is likely to be unrealistically exaggerated. The TC intensity–temperature sensitivity under RCE is very similar to those found in coupled climate model simulations. This suggests global mean intensity projections under climate change can be understood in terms of a thermodynamic response to temperature with only a minor contribution from any changes in large-scale dynamics. © 2018, The Authors."
"6602871700;","A wave-number frequency wavelet analysis of convectively coupled equatorial waves and the MJO over the Indian Ocean",2018,"10.1002/qj.3207","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042803843&doi=10.1002%2fqj.3207&partnerID=40&md5=5fccda574aede7e0b554d3486771f647","Convectively coupled equatorial waves and the Madden–Julian Oscillation (MJO) constitute the dominant coherent modes of planetary- to synoptic-scale organized convection in the Tropics. This work presents a space–time wavelet analysis of outgoing long-wave radiation (OLR) data globally at wave-numbers 0–1 and isolated more closely about the Indian Ocean at higher wave numbers. The mean power spectrum shows broad similarity to Fourier power spectra in previous works after normalization by a red background. The seasonal cycle of the power spectrum is analysed, along with its association with the phases of an index of the MJO and background-state zonal winds at a variety of pressure levels over the Indian Ocean. Results show substantial variability across the seasonal cycle and the MJO in the distribution of power above the background. Results also show that the spectral peaks associated with the MJO and Kelvin and equatorial Rossby waves lose 20–50% of their normal variance during periods of strong easterly wind in the upper troposphere over the Indian Ocean, while at the same time, fast westward-moving waves increase between wave-numbers 7 and 14 and periods of 2–6 days. © 2017 Royal Meteorological Society"
"12645767500;36161790500;57205867148;","An Observational View of Relationships Between Moisture Aggregation, Cloud, and Radiative Heating Profiles",2017,"10.1007/s10712-017-9443-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032698723&doi=10.1007%2fs10712-017-9443-1&partnerID=40&md5=ca782711f63e6bbea3eab00f888602ef","Data from several coincident satellite sensors are analyzed to determine the dependence of cloud and precipitation characteristics of tropical regions on the variance in the water vapor field. Increased vapor variance is associated with decreased high cloud fraction and an enhancement of low-level radiative cooling in dry regions of the domain. The result is found across a range of sea surface temperatures and rain rates. This suggests the possibility of an enhanced low-level circulation feeding the moist convecting areas when vapor variance is large. These findings are consistent with idealized models of self-aggregation, in which the aggregation of convection is maintained by a combination of low-level radiative cooling in dry regions and mid-to-upper-level radiative warming in cloudy regions. © 2017, The Author(s)."
"55547451000;7101661890;7006095466;7006698304;","Insights into convective momentum transport and its parametrization from idealized simulations of organized convection",2017,"10.1002/qj.3118","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85034641641&doi=10.1002%2fqj.3118&partnerID=40&md5=f76a3711ff534b691d7c5255eedda65c","Deep convection is a multiscale process that influences the budgets of heat, moisture and momentum significantly. In global climate models, the thermodynamic effects of convection are normally treated by parametrization schemes, with a separate formulation for convective momentum transport (CMT). The schemes for current thermodynamic and momentum parametrizations are based on upright entraining plume models that do not account for vertically tilted mesoscale circulations, which characterize organized convection in sheared environments. The associated countergradient vertical transport of horizontal momentum fundamentally affects dynamical interactions between the convection and the mean flow. This study examines the CMT properties of simulated idealized mesoscale convective systems, including their sensitivity to horizontal resolution, domain size and lateral boundary conditions. It is found that, even for large domains, the horizontal gradient terms are important, especially the mesoscale pressure gradients, which are neglected in CMT parametrizations. A nonlinear analytic model provides a dynamical foundation for the effects of convective organization, including the role of the horizontal pressure gradient. It is found that a small computational domain affects the convective organization adversely by generating artificially large compensating subsidence and an unrealistic evolution of CMT. Finally, analyses of the cross-updraught/downdraught pressure gradients expose significant uncertainties in their representation in contemporary CMT parametrization schemes. © 2017 Royal Meteorological Society"
"8688004400;6603263640;7004978125;57193882808;","Multiscale interactions in an idealized walker cell: Analysis with isentropic streamfunctions",2016,"10.1175/JAS-D-15-0070.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84962214158&doi=10.1175%2fJAS-D-15-0070.1&partnerID=40&md5=435e8c0cd9e6afdb6d153b173bf65e44","A new approach for analyzing multiscale properties of the atmospheric flow is proposed in this study. For that, the recently introduced isentropic streamfunctions are employed here for scale decomposition with Haar wavelets. This method is applied subsequently to a cloud-resolving simulation of a planetary Walker cell characterized by pronounced multiscale flow. The resulting set of isentropic streamfunctions-obtained at the convective, meso-, synoptic, and planetary scales-capture many important features of the across-scale interactions within an idealized Walker circulation. The convective scale is associated with the shallow, congestus, and deep clouds, which jointly dominate the upward mass flux in the lower troposphere. The synoptic and planetary scales play important roles in extending mass transport to the upper troposphere, where the corresponding streamfunctions mainly capture the first baroclinic mode associated with large-scale overturning circulation. The intermediate-scale features of the flow, such as anvil clouds associated with organized convective systems, are extracted with the mesoscale and synoptic-scale isentropic streamfunctions. Multiscale isentropic streamfunctions are also used to extract salient mechanisms that underlie the low-frequency variability of the Walker cell. In particular, the lag of a few days of the planetary scale behind the convective scale indicates the importance of the convective scale in moistening the atmosphere and strengthening the planetary-scale overturning circulation. Furthermore, the mesoscale and synoptic scale lags behind the planetary scale reflect the strong dependence of convective organization on the background shear. © 2016 American Meteorological Society."
"56919065500;7005685786;","Case study of moisture and heat budgets within atmospheric rivers",2015,"10.1175/MWR-D-15-0006.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945151645&doi=10.1175%2fMWR-D-15-0006.1&partnerID=40&md5=116df6ecf1aea23b29c8de118cd42f9b","This work studies moisture and heat budgets within two atmospheric rivers (ARs) that made landfall on the west coast of North America during January 2009. Three-dimensional kinematic and thermodynamic fields were constructed using ECMWF Year of Tropical Convection data and global gridded precipitation datasets. Differences between the two ARs are observed, even though both had embedded precipitating convective organizations of the same spatial scale. AR1 extended from 20� to 50�N in an almost west-east orientation. It had excessive warm and moist near-surface conditions. Its precipitating systems were mainly distributed on the southwest and northeast sides of the AR, and tended to exhibit stratiform-type vertical heat and moisture transports. In contrast, AR2 spanned latitudes between 20� and 60�N in a north-south orientation. It was narrower and shorter than AR1, and was mostly covered by pronounced precipitating systems, dominated by a deep convection type of heating throughout the troposphere. In association with these distinctions, the atmosphere over the northeastern Pacific on average experienced episodic cooling and drying despite the occurrence of AR1, yet underwent heating and drying during AR2, when latent heating was strong. Downward sensible heat flux and weak upward surface latent heat flux were observed particularly in AR1. In addition, cloud radiative forcing (CRF) was very weak in AR1, whereas it was strongly negative in AR2. In short, it is found that the oceanic convection in ARs both impacts the moisture transport of ARs, as well as modifies the heat balance in the midlatitudes through latent heat release, convective heat transport, surface heat fluxes, and CRF. � 2015 American Meteorological Society."
"8953038700;36672729600;7003266014;16645127300;6604098421;7006306835;56744278700;","A radiative-convective equilibrium perspective of weakening of the tropical walker circulation in response to global warming",2013,"10.1175/JCLI-D-12-00288.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874803357&doi=10.1175%2fJCLI-D-12-00288.1&partnerID=40&md5=067483aed5dcb30dba33055e2b1fef03","Both observational analysis andGCMsimulations indicate that the tropical Walker circulation is becoming weaker and may continue to weaken as a consequence of climate change. Here, the authors use a conceptual radiative-convective equilibrium (RCE) framework to interpret the weakening of the Walker circulation as simulated by the GFDL coupled GCM. Based on the modeled lapse rate and clear-sky cooling rate profiles, the RCE framework can directly compute the change of vertical velocity in the descending branch of the Walker circulation, which agrees with the counterpart simulated by the GFDL model. The results show that the vertical structure of clear-sky radiative cooling rate QR will change in response to the increased water vapor as the globe warms. The authors explain why the change of QR is positive in the uppermost part of the troposphere (&lt;300 hPa) and is negative for the rest of the troposphere. As a result, both the change of clearsky cooling rate and the change of tropospheric lapse rate contribute to the weakening of circulation. The vertical velocity changes due to the two factors are comparable to each other from the top of the planetary boundary layer to 600 hPa. From 600 to 300 hPa lapse rate changes are the dominant cause of the weakening circulation. Above 300 hPa, the change due to QR is opposite to the change due to lapse rate, which forces a slight increase in vertical velocity that is seen in the model simulation. © 2013 American Meteorological Society."
"55717881500;7102567936;","Comparison of a single-column model in weak temperature gradient mode to its parent AGCM",2012,"10.1002/qj.967","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84862199361&doi=10.1002%2fqj.967&partnerID=40&md5=b92c2ae55880c4e23c4d2c1d8650707b","A single-column model (SCM) version of the HadGEM1 is run in weak temperature gradient (WTG) mode, assuming a free-tropospheric temperature profile obtained from the same single-column model in radiative-convective equilibrium (RCE) over a sea-surface temperature (SST) of 301 K. The resulting quasi-steady solutions are compared with climate statistics from time-dependent solutions of the full three-dimensional (3D) Atmospheric General Circulation Model (AGCM) sharing the same physics, with the aim of evaluating the strengths and weaknesses of the WTG parametrization of large-scale dynamics. Making some allowance for unavoidable differences between quasi-steady 1D solutions and more fully transient 3D solutions, the two models produce grossly similar sensitivities of precipitation and relative humidity to local SST. The greatest differences arise from the relatively sharp transition in the SCM between very dry and rainy states as SST is varied, while the GCM statistics vary more smoothly with SST. When a relaxation on the moisture field towards a target profile-a crude parametrization of horizontal moisture advection-is included in the SCM, this difference is reduced. The SCM is then able to produce some convection at low SST, and the increases in humidity and precipitation with SST become more gradual, as in the GCM. The RCE temperature profile used to obtain these results is colder in the upper troposphere and thus more unstable to deep convection than is the climatological tropical profile from the GCM. When the latter is used in the SCM, the precipitation as a function of SST does not change greatly, but the convection becomes considerably shallower than that in either the GCM, or the SCM with the RCE temperature profile. We speculate that some of these differences may be due to the much greater transience in the GCM solutions compared to the SCM's quasi-steady states. © 2011 Royal Meteorological Society."
"37111149200;7004504559;","A column model of moist convection: Some exact equilibrium solutions",2011,"10.1002/qj.820","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79957894775&doi=10.1002%2fqj.820&partnerID=40&md5=b692e102264f82c4d1ee6d2139e2eafb","A radiative-convective model for a moist single-column atmosphere is presented. A test problem is considered in which exact, explicit analytical solutions are found by using a form for the saturation specific humidity that closely models that for Earth's atmosphere. Simple equations for the conservation of mass, energy, and moisture are solved with a new type of weak solution, where the fluid satisfies Lagrangian versions of these equations. A numerical method using a Lagrangian-based hard convective adjustment step calculates solutions which converge to the analytical solutions as the vertical mesh size decreases, and is stable in time. When the thermodynamic paths followed by an ascending and descending parcel do not overlap in a potential temperature-pressure diagram, steady equilibrium solutions are found; otherwise, non-equilibrium behaviour of the numerical solution occurs. This work suggests that it is useful to interpret column models in a Lagrangian sense as weak solutions of systems of partial differential equations. Copyright © 2011 Royal Meteorological Society."
"55309118800;7006069664;55441669800;35503593800;7003937114;","Circulation characteristics of a monsoon depression during BOBMEX-99 using high-resolution analysis",2003,"10.1007/BF02701985","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038375422&doi=10.1007%2fBF02701985&partnerID=40&md5=42236edac96145dc903baa1641693d22","The skill and efficiency of a numerical model mostly varies with the quality of initial values, accuracy on parameterization of physical processes and horizontal and vertical resolution of the model. Commonly used low-resolution reanalyses are hardly able to capture the prominent features associated with organized convective processes in a monsoon depression. The objective is to prepare improved high-resolution analysis by the use of MM5 modelling system developed by the Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR). It requires the objective comparison of high and low-resolution analysis datasets in assessing the specific convective features of a monsoon depression. For this purpose, reanalysis datasets of NCAR/NCEP (National Center for Atmospheric Research/National Centers for Environmental Prediction) at a horizontal resolution of 2.5° (latitude/longitude) have been used as first guess in the objective analysis scheme. The additional asynoptic datasets obtained during BOBMEX-99 are utilized within the assimilation process. Cloud Motion Wind (CMW) data of METEOSAT satellite and SSM/I surface wind data are included for the improvement of derived analysis. The multiquadric (MQD) interpolation technique is selected and applied for meteorological objective analysis at a horizontal resolution of 30 km. After a successful inclusion of additional data, the resulting reanalysis is able to produce the structure of convective organization as well as prominent synoptic features associated with monsoon depression. Comparison and error verifications have been done with the help of available upper-air station data. The objective verification reveals the efficiency of the analysis scheme."
"7202772927;6701681018;35467186900;","Comments on ""A sensitivity study of radiative-convective equilibrium in the tropics with a convection-resolving model""",2001,"10.1175/1520-0469(2001)058<1328:COASSO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035872739&doi=10.1175%2f1520-0469%282001%29058%3c1328%3aCOASSO%3e2.0.CO%3b2&partnerID=40&md5=3531f85f4cdc2e672e64c367fee23826",[No abstract available]
"24778565600;","Mesoscale spatial and temporal variability of meteorological observations from an array of buoys in JASIN-1978",1986,"10.1007/BF00122761","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022857320&doi=10.1007%2fBF00122761&partnerID=40&md5=d3fd56a75f61d9253ec15669884c2f66","Observations of wind speed and direction, air and sea temperatures and solar radiation were obtained from an array of buoys in JASIN-1978 conducted in the area northwest of Scotland in the summer of 1978. The observations were analyzed to show spatial and temporal variability in the mesoscale fields. Spectra of wind speed and air and sea temperatures were computed to illustrate the distribution of variance over periods ranging from 3.5 min to 40 days. When plotted on log-log graphs, the spectral estimates generally decreased with slopes between -3/2 and -2 with increasing frequency. Spectra of air and sea temperatures had a peak at the diurnal period but not the wind speed spectrum. When plotted in variance-preserving form, the spectrum of wind speed was consistent with a spectral gap and was qualitatively similar to other observations of low-frequency spectra. On the basis of auto- and cross-correlation analyses, it appeared that mesoscale eddies propagated through the array of buoys with the mean wind speed except during times of frontal passages. The cross-correlation between wind speed and air temperature showed evidence of horizontal roll vortices or some other forms of organized convection. © 1986 D. Reidel Publishing Company."
"7202500058;6506034344;","Structure of a Tropical Squall Line Observed in the Western Tropical Pacific during MONEX",1982,"10.2467/mripapers.33.117","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85004570401&doi=10.2467%2fmripapers.33.117&partnerID=40&md5=9bc3e597b13d83c19bff6f1aec348f4d","This paper describes an analysis of the structure of a tropical squall line by the use of radar, satellite, and upper air sounding data. The observation was made in the west of the western tropical Pacific during Summer MONEX in 1979. The results of the analysis were compared with the structure of tropical squall lines observed by other authors. The squall line in this study showed a significantly organized mesoscale structure; that is, cumulus-scale convections and organized convections were combined within it. The existence of organized convection was the particular feature of this squall line. Anvil clouds covered these convectoins and extended back from the leading edge for more than 200 km. The line-shaped leading edge of the squall line propagated at a speed larger than that of ambient winds. Some portions of the leading edge were not dissipated and grew into organized convections, which maintained size and intensity for several hours. The squall line was formed in the boundary region between the monsoon southwesterly and the trade wind easterly in the lower troposphere. Just before the squall line was formed, a relatively large positive vorticity had existed in the middle and lower troposphere, and a large divergence of air above 400 mb and moderate convergence below 400 mb. The overturning of the atomosphere was found by upper sounding data, and the moist static energy located in the lower troposphere ahead of the squall line was thought to be an energy source of the formation of the squall line. Several common properties were seen in tropical squall lines in our case and in other tropical regions, but the cloud structure of the squll line in our case should be discussed three-dimensionally because of the existence of the organized convections. © 1982, Japan Meteorological Agency/Meteorological Research Institute. All rights reserved."
"57201492011;55897783400;12801073500;8934032500;24460577700;57201132165;6701607011;6602783179;6603886699;26424614800;57190489343;","Identification of processes that control the stable isotope composition of rainwater in the humid tropical West-Central Africa",2020,"10.1016/j.jhydrol.2020.124650","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079135936&doi=10.1016%2fj.jhydrol.2020.124650&partnerID=40&md5=396314e239935f7892e196f7f60b5cf9","This study interprets 11 years (2006 to 2016) and 6 months (March to August in 2017) of respectively monthly and daily isotopic (δD and δ18O) monitoring of rain at Douala (Cameroon), a humid tropical station in Western Africa. The main scope is to analyze the climate controls on precipitation isotopes at different timescales. Firstly, we examine the annual cycles of δ18O. Over the 11 years of survey, the annual cycle exhibits a W shape that is quite reproducible from year to year, with two minima in spring and autumn periods. Based on back trajectory calculations and remote sensing observations of water vapor isotopic composition, we show that the observed depletion in spring and autumn is due to strong convective activity along air mass trajectories. The same effect of convective activity can be observed at the daily timescale. At seasonal and daily time scales, the isotopic composition is also strongly tied to the convective organization and cloud types. More depleted precipitation is associated with larger areas of high clouds. Very low to low clouds are observed in July-August, mid-level to high clouds are dominant in June and high to very high clouds characterize March-April-May, thus explaining the enriched (depleted) values in summer (spring). Finally, this paper highlights the importance of large scale meteorological conditions controls on precipitation stable isotope composition in the Gulf of Guinea. © 2020 Elsevier B.V."
"57195349030;11939918300;","Self-Aggregation of Convection in Spatially Varying Sea Surface Temperatures",2020,"10.1029/2019MS001698","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078783700&doi=10.1029%2f2019MS001698&partnerID=40&md5=e6f6944c0c217a22d083ef66762be4a8","The phenomenon of self-aggregation of convection was first identified in convection-permitting simulations of radiative convective equilibrium, characterized by homogeneous boundary conditions and in the absence of planetary rotation. In this study, we expose self-aggregation of convection to more complex, nonhomogeneous boundary conditions and investigate its interaction with convective aggregation, as forced by large-scale variations in sea surface temperatures (SSTs). We do this by conducting radiative convective equilibrium simulations on a spherical domain, with SST patterns that are zonally homogeneous but meridionally varying. Due to the meridional contrast in SST, a convergence line first forms, mimicking the Intertropical Convergence Zone. We nevertheless find that the convergence line breaks up and contracts zonally as a result of the self-aggregation of convection. The contraction is significant, being here more than 50% of the original extent. The stability of the convergence line is controlled by the strength of the meridional circulation, which depends upon the imposed SST contrast. However, the process of self-aggregation, once it is initiated, is insensitive to the strength of the SST contrast. The zonal contraction is accompanied by a slight meridional expansion and a moistening of the high latitudes, where SSTs are low. The moistening of the high latitudes can be understood from the fact that the convective cluster intensifies and expands its moist meridional low-level outflow when it self-aggregates zonally. Overall, our results suggest that the Intertropical Convergence Zone may be unstable to the self-aggregation of convection, that self-aggregation may serve as a precursor to the formation of atmospheric rivers, and that longer convergence lines are more likely to exist in regimes with strong SST gradients. ©2019. The Authors."
"56567409000;23492864500;7201504886;","Influence of deepening and mesoscale organization of shallow convection on stratiform cloudiness in the downstream trades",2020,"10.1002/qj.3664","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075463687&doi=10.1002%2fqj.3664&partnerID=40&md5=d44a3ec04872549e0a5b0f5b9f86c14a","In this study we use large-eddy simulation to explore the factors controlling stratiform cloudiness in the downstream trades. We perform sensitivity experiments with different large-scale forcings, radiation specifications and domain sizes, which isolate the influence of convective deepening, moisture–radiation interactions and mesoscale organization, respectively. Across the simulations with different large-scale forcings, we find that the deepening of the cloud layer and the associated increase in precipitation strongly correlate with decreasing inversion strength and stratiform cloudiness. The relationship between cloud-layer depth and cloud amount is largely independent of the way a specific change in the large-scale forcing induces the deepening. The interaction of radiation with the domain-averaged humidity and cloud profile is necessary for stratiform cloudiness to form. Strong radiative cooling experienced by updraughts overshooting a strong inversion induces the formation of detrained stratiform layers, and strong long-wave cooling associated with the stratiform layers stabilizes the inversion. Interactive radiation is also important for exposing differences in shallow convection under different free-tropospheric humidities. A drier initial free troposphere leads to both increased cloud-layer and free-tropospheric radiative cooling and increased surface evaporation, which forces deeper convection and more precipitation compared to a moister initial free troposphere. The simulations with a drier initial free troposphere thus have weaker inversions and less stratiform cloud. The organization of convection into larger clusters in large-domain simulations increases precipitation and weakens the inversion compared to a simulation on a 16-fold smaller domain, which does not support convective organization. Organized updraught clusters carry more moisture and liquid to the inversion, so that the same amount of stratiform cloudiness forms, despite the inversion being weaker. The simulations presented here suggest that the deepening and organization of shallow convection plays an important role in regulating stratiform cloudiness and thus total cloud cover in the downstream trades. © 2019 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"26536569500;","Evaluating the Future of Lightning in Cloud-Resolving Models",2019,"10.1029/2019GL085748","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077078517&doi=10.1029%2f2019GL085748&partnerID=40&md5=f105974fdc10c0a17a10853a78a873d7","Two proxies for lightning predict very different responses to global warming: the CAPE times precipitation proxy predicts a large increase in lightning over both the continental United States and the tropical oceans, while the ice flux proxy predicts a small increase over the United States and a decrease over the tropical oceans. To date, however, these proxies have been studied only in global climate models with parameterized convection. Here, cloud-resolving simulations are used to assess their predictions of future lightning rates. Over the United States, all proxies predict a large increase in the lightning rate in the range of 8–16%/K. On the other hand, in the tropics as modeled by radiative convective equilibrium, half of the proxies predict an increase (of 5–12%/K), while the other half predict a decrease (of 1–4%/K). The reasons for the different responses of these proxies is explored, but it remains unclear which proxy is best suited to predicting future lightning rates. ©2019. American Geophysical Union. All Rights Reserved."
"57195065818;57211623938;7003696273;7404732357;7201504886;","Re-examining the first climate models: Climate sensitivity of a modern radiative–convective equilibrium model",2019,"10.1175/JCLI-D-18-0774.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074671889&doi=10.1175%2fJCLI-D-18-0774.1&partnerID=40&md5=7958c88ebd07d4a2de1faf4689f5c314","We revisit clear-sky one-dimensional radiative–convective equilibrium (1D-RCE) and determine its equilibrium climate sensitivity to a CO2 doubling (ECS) and associated uncertainty. Our 1D-RCE model, named konrad, uses the Rapid Radiative Transfer Model for GCMs (RRTMG) to calculate radiative fluxes in the same way as in comprehensive climate models. The simulated radiative feedbacks are verified by a line-by-line radiative transfer model, with which we also investigate their spectral distribution. Changing the model configuration of konrad enables a clear separation between the water vapor and the lapse rate feedbacks, as well as the interaction between the two. We find that the radiative feedback and ECS are sensitive to the chosen relative humidity profile, resulting in an ECS range of 2.09–2.40 K. Using larger CO2 forcings we find that the radiative feedback changes up to 10% for surface temperatures of 291–299 K. Although the ECS is similar to previous studies, it arises from the compensation of a larger clear-sky forcing (4.7 W m22) and more strongly negative feedbacks (22.3 W m22 K21). The lapse rate feedback and the feedback from the interaction of lapse rate and humidity compensate each other, but the degree of compensation depends on the relative humidity profile. Additionally, the temperature profile is investigated in a warming climate. The temperature change at the convective top is half as large as at the surface, consistent with the proportionally higher anvil temperature hypothesis, as long as the humidity is consistently coupled to the temperature profile. Ó 2019 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"57211713918;26649925100;","Tracking the Gust Fronts of Convective Cold Pools",2019,"10.1029/2019JD030980","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074878715&doi=10.1029%2f2019JD030980&partnerID=40&md5=966991909aec3390393d807acb0b74c6","It is increasingly acknowledged that cold pools can influence the initiation of new convective cells. Yet the full complexity of convective organization through cold pool interaction is poorly understood. This lack of understanding may partially be due to the intricacy of the dynamical pattern formed by precipitation cells and their cold pools. Additionally, how exactly cold pools interact is insufficiently known. To better understand this dynamics, we develop a tracking algorithm for cold pool gust fronts. Rather than tracking thermodynamic anomalies, which do not generally coincide with the gust front boundaries, our approach tracks the dynamical cold pool outflow. Our algorithm first determines the locus of the precipitation event. Second, relative to this origin and for each azimuthal bin, the steepest gradient in the near-surface horizontal radial velocity vr is employed to determine the respective locus of the cold pool gust front edge. Steepest vr gradients imply largest updraft velocities, hence strongest dynamical triggering. Results are compared to a previous algorithm based on the steepest gradient in temperature—highlighting the benefit of the method described here in determining dynamically active gust front regions. Applying the method to a range of numerical experiments, the algorithm successfully tracks an ensemble of cold pools. A linear relation emerges between the peak rain intensity of a given event and maximal vr for its associated cold pool gust front—a relation found to be nearly independent of the specific sensitivity experiment. ©2019. American Geophysical Union. All Rights Reserved."
"7202145115;8882641700;57209244069;","Convection and Climate: What Have We Learned from Simple Models and Simplified Settings?",2019,"10.1007/s40641-019-00136-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067030032&doi=10.1007%2fs40641-019-00136-9&partnerID=40&md5=c43d81c70ad49a8c250270e2129a708c","Purpose of Review: We ask what fundamental insights about the relationship of tropical convection to climate have arisen from recent investigations using simplified models. Recent Findings: The vertical distribution of relative humidity should remain approximately constant in a changed climate. The temperature of clouds in the upper troposphere should also remain effectively constant for climate changes likely to occur in response to human-induced warming. The fractional coverage of convective clouds will likely decrease slightly with warming, but it is not known how the albedo and net radiative effect of tropical convective clouds will change. The areal extent and net radiative effect of tropical convective clouds depend on the interactions of radiation, cloud physics, and turbulence within the extended upper-level ice clouds. SST gradients develop naturally as a result of the aggregation of convection and large-scale thermodynamics and circulation act to couple the cloud properties and the SST. Summary: Radiative-convective equilibrium continues to provide insight into the structure and energy balance of the atmosphere by incorporating the interactions among radiation, cloud physics, and atmospheric motion. © 2019, Springer Nature Switzerland AG."
"57202789763;7006422317;57193886077;36724322000;56724696200;","Simulation of location-specific severe thunderstorm events using high resolution land data assimilation",2019,"10.1016/j.dynatmoce.2019.101098","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068146593&doi=10.1016%2fj.dynatmoce.2019.101098&partnerID=40&md5=379016ea019d12be4b2ebebfd92ce08c","In this study, the impact of different land initial conditions on the simulation of thunderstorms and monsoon depressions is investigated using the Weather Research and Forecasting (WRF) model. A control run (CNTL) and a simulation with an improved land state (soil moisture and temperature) using the High Resolution Land Data Assimilation System (HRLDAS, experiment name: EHRLDAS) are compared for three different rainfall cases in order to examine the robustness of the assimilation system. The study comprises two thunderstorm cases (one in the pre-monsoon and one during the monsoon) and one monsoon depression case that occurred during the Interaction of Convective Organisation, Atmosphere, Surface and Sea (INCOMPASS) field campaign of the 2016 Indian monsoon. EHRLDAS is shown to yield improvements in the representation of location-specific rainfall, particularly over land. Further, it is found that surface fluxes as well as convective indices are better captured for the pre-monsoon thunderstorm case in EHRLDAS. By analysing components of the vorticity tendency equation, it is found that the vertical advection term is the major contributor towards the positive vorticity tendency in EHRLDAS compared to CNTL, hence improving localised convection and consequently facilitating rainfall. Significant improvements in the simulation of the pre-monsoon thunderstorm are noted, as seen using Automatic Weather Station (AWS) validation, whereas improvements in the monsoon depression are minimal. Further, it is found that vertical advection (moisture flux convergence) is the major driver modulating the convective circulation in localised thunderstorm (monsoon depression) cases and these dynamics are better represented by EHRLDAS compared to CNTL. These findings underline the importance of accurate and high resolution land-state conditions in model initial conditions for forecasting severe weather systems, particularly the simulation of localised thunderstorms over India. © 2019 Elsevier B.V."
"55880478000;6507400558;57204253860;56242059600;","Using Radar Data to Calibrate a Stochastic Parametrization of Organized Convection",2019,"10.1029/2018MS001537","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067459521&doi=10.1029%2f2018MS001537&partnerID=40&md5=61e590c4d3821a4e51e28cc929a5a1c2","Stochastic parameterizations are increasingly becoming skillful in representing unresolved atmospheric processes for global climate models. The stochastic multicloud model, used to simulate the life cycle of the three most common cloud types (cumulus congestus, deep convective, and stratiform) in tropical convective systems, is one example. In this model, these clouds interact with each other and with their environment according to intuitive-probabilistic rules determined by a set of predictors, depending on the large-scale atmospheric state and a set of transition time scale parameters. Here we use a Bayesian statistical method to infer these parameters from radar data. The Bayesian approach is applied to precipitation data collected by the Shared Mobile Atmospheric Research and Teaching Radar truck-mounted C-band radar located in the Maldives archipelago, while the corresponding large-scale predictors were derived from meteorological soundings taken during the Dynamics of the Madden-Julian Oscillation field campaign. The transition time scales were inferred from three different phases of the Madden-Julian Oscillation (suppressed, initiation, and active) and compared with previous studies. The performance of the stochastic multicloud model is also assessed, in a stand-alone mode, where the cloud model is forced directly by the observed predictors without feedback into the environmental variables. The results showed a wide spread in the inferred parameter values due in part to the lack of the desired sensitivity of the model to the predictors and the shortness of the training periods that did not include both active and suppressed convection phases simultaneously. Nonetheless, the resemblance of the stand-alone simulated cloud fraction time series to the radar data is encouraging. ©2019. The Authors."
"6701670597;36634069800;7005702722;55683526900;7005035762;","Estimating convection's moisture sensitivity: An observation-model synthesis using AMIE-DYNAMO field data",2019,"10.1175/JAS-D-18-0127.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85067187437&doi=10.1175%2fJAS-D-18-0127.1&partnerID=40&md5=439a2df2be0fafb52c3de1e83daecdfc","We seek to use ARM MJO Investigation Experiment (AMIE)-DYNAMO field campaign observations to significantly constrain height-resolved estimates of the parameterization-relevant, causal sensitivity of convective heating Q to water vapor q. In field data, Q profiles are detected via Doppler radar wind divergence D while balloon soundings give q. Univariate regressions of D on q summarize the information from a 10-layer time-pressure series from Gan Island (0°, 90°E) as a 10 × 10 matrix.Despite the right shape and units, this is not the desired causal quantity because observations reflect confounding effects of additional q-correlated casual mechanisms. We seek to use this matrix to adjudicate among candidate estimates of the desired causal quantity: Kuang's matrix M of the linear responses of a cyclic convectionpermitting model (CCPM) at equilibrium. Transforming M to more observation-comparable forms by accounting for observed autocorrelations, the comparisons are still poor, because (we hypothesize) largerscale vertical velocity, forbidden by CCPM methodology, is another confounding cause that must be permitted to covary with q. By embedding Mandmodified candidates in an idealized GCM, and treating its outputs as virtual field campaign data, we find that observations favor a factor of 2 (rather than 0 or 1) to small-domain M's free-tropospheric causal q sensitivity of about 25% rain-rate increment over 3 subsequent hours per +1 gkg-1 q impulse in a 100-hPa layer. Doubling this sensitivity lies partway toward Kuang's Mfor a long domain that organizes convection into squall lines, a weak but sign-consistent hint of a detectable parameterization-relevant (causal) role for convective organization in nature. Caveats and implications for field campaign proposers are discussed. © 2019 American Meteorological Society."
"55716092000;55713076400;22635190100;","Evaluating the bias of South China Sea summer monsoon precipitation associated with fast physical processes using a climate model hindcast approach",2019,"10.1175/JCLI-D-18-0660.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068087889&doi=10.1175%2fJCLI-D-18-0660.1&partnerID=40&md5=3a88cd6f3a1300343324b988c08dd7af","The present study aims to identify the precipitation bias associated with the interactions among fast physical processes in the Community Atmospheric Model, version 5 (CAM5), during the abrupt onset of the South China Sea (SCS) summer monsoon, a key precursor of the overall East Asia summer monsoon (EASM). The multiyear hindcast approach is utilized to obtain the well-constrained synoptic-scale horizontal circulation each year during the onset period from the years 1998 to 2012. In the pre-onset period, the ocean precipitation over the SCS is insufficiently suppressed in CAM5 hindcasts and thus weaker land-ocean precipitation contrasts. This is associated with the weaker and shallower convection simulated over the surrounding land, producing weaker local circulation within the SCS basin. In the post-onset period, rainfall of the organized convection over the Philippine coastal ocean is underestimated in the hindcasts, with overestimated upperlevel heating. These biases are further elaborated as the underrepresentation of the convection diurnal cycle and coastal convection systems, as well as the issue of precipitation sensitivity to environmental moisture during the SCS onset period. The biases identified in hindcasts are consistent with the general bias of the EASM in the climate simulation of CAM5. The current results highlight that the appropriate representation of land-ocean-convection interactions over coastal areas can potentially improve the simulation of seasonal transition over the monsoon regions. © 2019 American Meteorological Society."
"6506756436;7003554893;","The coupling of deep convection with the resolved flow via the divergence of mass flux in the IFS",2019,"10.1002/qj.3528","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064715568&doi=10.1002%2fqj.3528&partnerID=40&md5=b3d7e4841404fb2404d95cc2182d7c6d","The resolution of the European Centre for Medium-range Weather Forecast (ECMWF) integrated forecast system (IFS) is expected to reach 5 km in the coming decade. Assumptions in the parametrization of deep convection, such as that all of the compensating environmental flow occurs in the grid column, i.e. the convective and environmental mass fluxes cancel each other in term of mass transport, have to be challenged. In this paper, we further develop the original concept of separating the convective updraught from the subsiding branch of the overturning convective circulation and apply it to the global hydrostatic equations of the IFS. In practice, this constitutes a revised convection–dynamics coupling where the mass flux subsidence of the dynamical variables is not computed locally by the convection scheme, but instead is recomputed from the revised continuity equation and is effective through the semi-Lagrangian advection of the dynamical core. Therefore horizontal divergence/convergence is also generated in the dynamics at the top/bottom of the convective columns, thus adding to the representation of deep convection a three-dimensional character which is not present in traditional schemes. The proposed physics–dynamics coupling is intended to be applicable to any mass flux convection scheme and within any regional or global model. We first demonstrate the accuracy of the revised physics–dynamics coupling in terms of global temperature and moisture budgets. The potential impact of the coupling on the convective organization is demonstrated for an idealized squall line case at high horizontal resolution using the small planet testbed. Model reforecasts at 9 km and 5 km resolution confirm the viability of the method in terms of forecast skill and model climate. However, the model impacts are limited as the main factor that still determines the convective stabilization and organization is the current conceptual model of subgrid mass flux which, actually, remains unchanged. © 2019 Royal Meteorological Society"
"57207932352;7006614696;","New observational metrics of convective self-aggregation: Methodology and a case study",2018,"10.2151/jmsj.2018-054","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063289262&doi=10.2151%2fjmsj.2018-054&partnerID=40&md5=677309bd0259a2aeecc1096d27c6f3bb","A new observational measure, the Morphological Index of Convective Aggregation (MICA), is developed to objectively detect the signs of convective self-aggregation on the basis of a simple morphological diagnosis of convective clouds in satellite imagery. The proposed index is applied to infrared imagery from the Meteosat-7 satellite and is assessed with sounding-array measurements in the tropics from Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011 (CINDY2011)/Dynamics of the Madden Julian Oscillation (MJO) (DYNAMO)/Atmospheric Radiation Measurement (ARM) MJO Investigation Experiment (AMIE). The precipitation events during the observational period are first classified by MICA into “aggregation events” and “nonaggregation events”. The large-scale thermodynamics implied from the sounding-array data are then examined, with a focus on the difference between the two classes. The composite time series show that drying proceeds over 6 – 12 has precipitation intensifies in the aggregation events. Such drying is unclear in the nonaggregation events. The moisture budget balance is maintained in very different manners between the two adjacent sounding arrays for the aggregation events, in contrast to the nonaggregation events that lack such apparent asymmetry. These results imply the potential utility of the proposed metrics for future studies in search of convective self-aggregation in the real atmosphere. © The Author(s) 2018."
"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."
"57206511020;7004540083;","The interaction between deep convection and easterly wave activity over Africa: Convective transitions and mechanisms",2018,"10.1175/MWR-D-17-0217.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063010664&doi=10.1175%2fMWR-D-17-0217.1&partnerID=40&md5=d919fed2aeb0701a48946095b2ad5954","Recent work using observational data from the International Satellite Cloud Climatology Project (ISCCP) and reanalysis products suggests that African easterly waves (AEWs) form in association with a ''transition'' process from smaller and scattered convection into larger and organized mesoscale convective activity. However, the transition process is unclear and how mesoscale convection initiates AEWs is not well understood. Analysis based on 25 years of ISCCP and reanalysis datasets show that increasing intradiurnal activity, atmospheric instability, and specific humidity precede the development of well-organized convection over the Ethiopian highlands. Atmospheric instability favors a high frequency of scattered, isolated convection to the east of the Ethiopian highlands, first, followed by a continuing and large increase in instability and increasing humidity, which supports well-organized larger-scale convection. The timing of the changes of thermodynamic variables shows that the dominant transition process is scattered, with weakly organized convection transitioning into the well-organized mesoscale convection, and this initiates the AEWs. Slightly before the mesoscale convection peaks over the Ethiopian highlands, low-level moist westerlies, low- to midlevel wind shear, and positive relative vorticity increase over the region. Evidence shows that the largescale and local environment enables the scattered and less well-organized convection to merge and form larger and well-organized convection. The dynamic processes suggest that the dominant pathway for AEW initiation is scattered convection transitioning to large and well-organized convection over the Ethiopian highlands and this initiates AEWs westward of the Ethiopian highlands. © 2018 American Meteorological Society."
"57190859090;8502619500;57200315890;57200317029;55542320000;","Improvement in the modeled representation of North American monsoon precipitation using a modified Kain-Fritsch convective parameterization scheme",2018,"10.3390/atmos9010031","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040786181&doi=10.3390%2fatmos9010031&partnerID=40&md5=b56fd1401ac633616033e36f3b8d976b","A commonly noted problem in the simulation of warm season convection in the North American monsoon region has been the inability of atmospheric models at the meso-β scales (10 s to 100 s of kilometers) to simulate organized convection, principally mesoscale convective systems. With the use of convective parameterization, high precipitation biases in model simulations are typically observed over the peaks of mountain ranges. To address this issue, the Kain-Fritsch (KF) cumulus parameterization scheme has been modified with new diagnostic equations to compute the updraft velocity, the convective available potential energy closure assumption, and the convective trigger function. The scheme has been adapted for use in the Weather Research and Forecasting (WRF). A numerical weather prediction-type simulation is conducted for the North American Monsoon Experiment Intensive Observing Period 2 and a regional climate simulation is performed, by dynamically downscaling. In both of these applications, there are notable improvements in the WRF model-simulated precipitation due to the better representation of organized, propagating convection. The use of the modified KF scheme for atmospheric model simulations may provide a more computationally economical alternative to improve the representation of organized convection, as compared to convective-permitting simulations at the kilometer scale or a super-parameterization approach. © 2018 by the authors."
"57200334425;7006198994;6505932008;","Wind-flux feedbacks and convective organization during the november 2011 MJO event in a high-resolution model",2018,"10.1175/JAS-D-16-0346.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040953661&doi=10.1175%2fJAS-D-16-0346.1&partnerID=40&md5=636b0cc761d88c17d9f9dec6bef909fc","The November 2011 Madden-Julian oscillation (MJO) event during the Dynamics of the MJO (DYNAMO) field campaign is simulated with the Regional Atmospheric Modeling System (RAMS) cloud-resolving model to examine the relationship between precipitation and surface latent heat flux (LHFLX) for deep convective clusters within the MJO and to discern the importance of surface LHFLX for organizing MJO convection. First, a simulation similar in size to the DYNAMO northern sounding array was run with interactive surface fluxes. Composites for precipitation, surface LHFLX, wind speed, wind vectors, and near-surface specific humidity are described for various-sized convective clusters during different MJO regimes. The precipitation-LHFLX relationship generally evolves as follows for an individual cluster. About 2 h before cluster identification, the maximum LHFLX occurs upwind of maximum precipitation. As cluster identification time is approached, LHFLX and precipitation maxima become coincident. At and after the cluster is identified, maximum LHFLXs move downwind of the precipitation maximum with a local minimum in LHFLXs behind the precipitation maximum. Sensitivity simulations with spatially homogenized LHFLXs were then run to determine the impacts of local LHFLX feedbacks on convective organization. Using area-averaged convective versus stratiform precipitation fraction and a simple convective aggregation index to quantify organization, no systematic difference in convective organization was detected between the control and sensitivity simulations, suggesting that local LHFLX variability is not important to convective organization in this model. Implications of these results are discussed. © 2018 American Meteorological Society."
"6701573532;8549221700;","Forecasting tropical cyclone eye formation and dissipation in infrared imagery",2017,"10.1175/WAF-D-17-0037.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040364120&doi=10.1175%2fWAF-D-17-0037.1&partnerID=40&md5=70ae58b668dc6fdf3219dba08cde33c0","The development of an infrared (IR; specifically near 11 μm) eye probability forecast scheme for tropical cyclones is described. The scheme was developed from an eye detection algorithm that used a linear discriminant analysis technique to determine the probability of an eye existing in any given IR image given information about the storm center, motion, and latitude. Logistic regression is used for the model development and predictors were selected from routine information about the current storm (e.g., current intensity), forecast environmental factors (e.g., wind shear, oceanic heat content), and patterns/information (e.g., convective organization, tropical cyclone size) extracted from the current IR image. Forecasts were created for 6-, 12-, 18-, 24-, and 36-h forecast leads. Forecasts were developed using eye existence probabilities from North Atlantic tropical cyclone cases (1996-2014) and a combined North Atlantic and North Pacific (i.e., Northern Hemisphere) sample. The performance of North Atlantic-based forecasts, tested using independent eastern Pacific tropical cyclone cases (1996-2014), shows that the forecasts are skillful versus persistence at 12-36 h, and skillful versus climatology at 6-36 h. Examining the reliability and calibration of those forecasts shows that calibration and reliability of the forecasts is good for 6-18 h, but forecasts become a little overconfident at longer lead times. The forecasts also appear unbiased. The small differences between the Atlantic and Northern Hemisphere formulations are discussed. Finally, and remarkably, there are indications that smaller TCs are more prone to form eye features in all of the TC areas examined. © 2017 American Meteorological Society."
"55170496500;7004114883;7202504983;","Sensitivity of rain-rate estimates related to convective organization: Observations from the Kwajalein, RMI, Radar",2017,"10.1175/JAMC-D-16-0218.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85017520481&doi=10.1175%2fJAMC-D-16-0218.1&partnerID=40&md5=161354c85bd63bdbbbdddd36c1641988","Ground radar rainfall, necessary for satellite rainfall product (e.g., TRMM and GPM) ground validation (GV) studies, is often retrieved using annual or climatological convective/stratiform Z-R relationships. Using the Kwajalein, Republic of the Marshall Islands (RMI), polarimetric S-band weather radar (KPOL) and gauge network during the 2009 and 2011 wet seasons, the robustness of such rain-rate relationships is assessed through comparisons with rainfall retrieved using relationships that vary as a function of precipitation regime, defined as shallow convection, isolated deep convection, and deep organized convection. It is found that the TRMM-GV 2A53 rainfall product underestimated rain gauges by -8.3% in 2009 and -13.1% in 2011, where biases are attributed to rainfall in organized precipitation regimes. To further examine these biases, 2A53 GV rain rates are compared with polarimetrically tuned rain rates, in which GV biases are found to be minimized when rain relationships are developed for each precipitation regime, where, for example, during the 2009 wet-season biases in isolated deep precipitation regimes were reduced from -16.3% to -4.7%. The regime-based improvements also exist when specific convective and stratiform Z-R relationships are developed as a function of precipitation regime, where negative biases in organized convective events (-8.7%) are reduced to -1.6% when a regime-based Z-R is implemented. Negative GV biases during the wet seasons lead to an underestimation in accumulated rainfall when compared with ground gauges, suggesting that satellite-related bias estimates could be underestimated more than originally described. Such results encourage the use of the large-scale precipitation regime along with their respective locally characterized convective or stratiform classes in precipitation validation endeavors and in development of Z-R rainfall relationships. © 2017 American Meteorological Society."
"57203474131;57193990211;35768178600;","The role of land surface processes on tropical cyclones: Introduction to land surface models",2016,"10.5822/978-94-024-0896-6_8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018052066&doi=10.5822%2f978-94-024-0896-6_8&partnerID=40&md5=57cf35c7ec6f73e2858992bd662bd30c","The role of land surface processes in land falling tropical cyclones is an area of emerging interest. Tropical cyclones are formed as organized convection over warm water (typically 26.5 °C, Gray, 1968) packing tremendous amounts of energy. Tropical cyclones have a typical size of 200-2000 km with a life span of about one to two weeks. The cyclone and its environment are interlinked. There are a number of environmental factors that are important for sustaining and intensifying a tropical cyclone including low humidity, cooler sea surface temperature (SST), or higher tropopause temperatures, dry air intrusion from land masses, and large vertical wind shear (Gray, 1968; McBride and Zehr, 1981). However a number of environmental conditions can change the evolution of a landfalling storm. © 2016 Capital Publishing Company."
"37124192900;6603805587;7003584509;","Vertical temperature profiles at maximum entropy production with a net exchange radiative formulation",2013,"10.1175/JCLI-D-13-00060.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880963476&doi=10.1175%2fJCLI-D-13-00060.1&partnerID=40&md5=edb8979cf85f3f29a463ee9375af53df","Like any fluid heated from below, the atmosphere is subject to vertical instability that triggers convection. Convection occurs on small time and space scales, which makes it a challenging feature to include in climate models. Usually subgrid parameterizations are required. Here, an alternative view based on a global thermodynamic variational principle is developed. Convective flux profiles and temperature profiles at steady state are computed in an implicit way by maximizing the associated entropy production rate. Two settings are examined, corresponding respectively to an idealized case of a gray atmosphere and a realistic case based on a net exchange formulation radiative scheme. In the second case, the effect of variations of the atmospheric composition, such as a doubling of the carbon dioxide concentration, is also discussed. © 2013 American Meteorological Society."
"55628570879;7004696243;","Theoretical estimation of the superrotation strength in an idealized quasi-axisymmetric model of planetary atmospheres",2013,"10.2151/jmsj.2013-203","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878205518&doi=10.2151%2fjmsj.2013-203&partnerID=40&md5=9c1042511e4fa535d7cad2a232375720","This paper presents a theoretical estimation of the strength of equatorial superrotation in planetary atmospheres by exploring a quasi-axisymmetric system that is zonally averaged primitive equations for a dry Boussinesqfluid on a rotating hemisphere with the effects of nonaxisymmetric eddies parameterized by eddy diffusion. The fluid is forced by Newtonian heating and cooling, and the horizontal eddy diffusion of momentum is assumed to be much stronger than the vertical one. In this system, the superrotation is maintained by the Gierasch mechanism, which possibly explains the superrotation of the Venus atmosphere by angular momentum transport due to the mean meridional circulation and horizontal diffusion. For the estimation, a quintic equation for a scalar measure of the superrotation strength is developed from the primitive equations. The quintic equation estimates the superrotation strength by its unique positive solution, which depends only on three nondimensional parameters: the external thermal Rossby number, the ratio of the radiative relaxation time to the timescale for the vertical diffusion, and the ratio of the planetary rotation period to the geometric mean of the timescales for the horizontal and vertical diffusion. The parameter dependence of the dominant dynamical balance is also investigated. The balance is a cyclostrophic, geostrophic, or horizontal diffusion balance, and in each balance, the equator-to-pole temperature difference is either nearly equal to that in the radiative-convective equilibrium state or signifficantly reduced by thermal advection. Steady-state or statistically steady-state solutions of the primitive equations are obtained by numerical timeintegrations for a wide parameter range covering many orders of magnitude. The numerical solutions show that the theoretical estimates have a relative error of less than 50%, which is very small compared with the superrotation strength varying five orders depending on the external parameters, and show that the estimation is valid. © 2013, Meteorological Society of Japan."
"34978268900;6602872956;","Idealized annually averaged macroturbulent hadley circulation in a shallow-water model",2013,"10.1175/JAS-D-12-072.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871905215&doi=10.1175%2fJAS-D-12-072.1&partnerID=40&md5=7be3b16498648216a5c7e97d4f598a8c","The interaction of midlatitude eddies and the thermally driven Hadley circulation is studied using an idealized shallow-water model on the rotating sphere. The contributions of the annually averaged differential heating, vertical advection of momentum from a stationary boundary layer, and the gross effect of eddies, parameterized by Rayleigh damping, including a hemispherically asymmetric damping, are examined at steady state. The study finds that the relative dominance of eddies, as quantified by the local Rossby number, is predicted by an effective macroturbulent Hadley circulation Prandtl number Pr. In addition, viscous solutions of the Hadley circulation width and strength, subtropical jet amplitude, and equator-to-pole temperature difference scale as deviations from the respective inviscid solutions. Semianalytic solutions for the steady circulation are derived in the limit of weak eddy dominance (small Pr) as deviations from the respective inviscid solutions. These solutions follow a three-region paradigm: weak temperature gradient at the ascending branch of the Hadley circulation, monotonically decreasing angular momentum at the descending branch, and modified radiative-convective equilibrium at the extratropics. Using the three-region solutions, scaling relations found in the full solutions are reproduced analytically. The weak eddy-dominance solutions diverge from the full solutions as Pr increases and may become invalid for Pr&gt;1 due to the breakdown of the three-region global circulation structure. The qualitative predictions of the response of the Hadley circulation to heating based on the weak eddydominance solutions and Pr are in agreement with the findings of more complex models and the observed atmosphere. © 2013 American Meteorological Society."
"7201605742;","Development of a nonhydrostatic version of the mesoscale-convection-resolving model and its application to the eyewall and spiral rainbands of tropical cyclones",2010,"10.2151/jmsj.2010-407","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958122058&doi=10.2151%2fjmsj.2010-407&partnerID=40&md5=06b014246c59de265e1ed38561b21ae9","A numerical model in which the effects of cumulus convection are incorporated as the subgrid-scale and mesoscale organized convection is resolved by the grid (mesoscale-convection-resolving model, MCRM) was developed in the 1980s with an intention of improving the parameterization schemes for moist convection, which had been used since the 1960s. As in many numerical models with parameterization in the 1980s, hydrostatic equilibrium was assumed. The present paper describes a nonhydrostatic version of the MCRM, with some modifications of the subgrid-scale effect formulation used in the hydrostatic MCRM. Numerical experiments are performed to get some evaluation of the performance of the nonhydrostatic version of the MCRM through the comparison of the results in two cases with and without the effects of the subgrid-scale cumulus convection. Although the most efficient horizontal grid size of the MCRM ranges from about 20 km to 5 km, only the results of a 15-km grid case are presented in this paper. The initial condition used in the numerical experiments is idealized (simplified). However, such numerical experiments can be considered useful to understand the behavior of spiral rainbands and eyewall convection in well-developed tropical cyclones and to evaluate the model validity. The subgrid-scale effects in the nonhydrostatic MCRM are not so important as those in the hydrostatic MCRM. However, it is shown that the eyewall and spiral rainbands are not simulated well unless the subgrid-scale effects are incorporated. © Meteorological Society of Japan."
"56355073800;56691869300;7004884101;7003408439;","Wind profiler observations over the central equatorial Pacific: Optimizing processing to improve quality and height coverage",2007,"10.1175/JTECH2072.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35548940663&doi=10.1175%2fJTECH2072.1&partnerID=40&md5=3a46ee1e396726b1748bd42aa2ad37b6","UHF (boundary layer) and VHF (troposphere-stratosphere) wind profilers have operated at Christmas Island (2°N, 157°W) in the central equatorial Pacific from 1986 to 2002. Observed profiles of winds are sparse over the tropical oceans, but these are critical for understanding convective organization and the interaction of convection and waves. While the zonal winds below about 10 km have previously shown good agreement with the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis (RI), significant differences were found above a height of 10 km that were attributed to the low detectability of the wind signal in the profiler observations. Meridional winds at all levels show less agreement, with differences attributed to errors of representativeness and the sparseness of observations in the region. This paper builds on previous work using the Christmas Island wind profilers and presents the results of reprocessing the 17-yr profiler record with techniques that enhance the detectability of the signal at upper heights. The results are compared with nearby rawinsonde soundings obtained during a special campaign at Christmas Island and the RI, NCEP-Department of Energy (DOE) reanalysis (RII), and the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40). The newly processed profiler zonal and meridional wind observations show good agreement with rawinsonde observations from 0.5 to 19 km above sea level, with difference statistics similar to other studies. There is also significant improvement in the agreement of RI and RII reanalysis and profiler upper-level zonal and meridional winds from previous studies. A comparison of RII and ERA-40 reanalysis shows that difference statistics between the reanalyses are similar in magnitude to differences between the profiler and the individual reanalyses. © 2007 American Meteorological Society."
"35572026100;7006095466;","Impact of mesoscale momentum transport on large-scale tropical dynamics: Linear analysis of the shallow-water analog",1998,"10.1175/1520-0469(1998)055<1038:IOMMTO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031833192&doi=10.1175%2f1520-0469%281998%29055%3c1038%3aIOMMTO%3e2.0.CO%3b2&partnerID=40&md5=5d363d31230c0c8734df7594f3c697e5","The vertical transport of horizontal momentum by organized convection is a prominent process, yet its impact on the large-scale atmospheric circulation has not even been qualitatively assessed. In order to examine this problem in a simple framework the authors incorporate a nonlinear dynamical model of convective momentum flux into a linear model of the large-scale tropical atmosphere. This model has previously been used to investigate the WISHE (wind-induced surface-heat exchange) instability. In order to implement the dynamically determined fluxes as a parameterization, a closure assumption is required to relate the relevant mesoscale parameters to the large-scale variables. The most straightforward method is to relate the low-level large-scale pressure (pL) to the mesoscale pressure perturbation (pM), which is linked to the mesoscale momentum flux by the dynamical model. The mesoscale momentum transport under this closure reduces the effective pressure gradient in the large-scale momentum equation and, consequently the effective stratification. A sufficiently large pM may even cause an effectively unstable stratification (convective instability by mesoscale momentum transport), which is marginally realizable according to a scale analysis. In general, the WISHE instability is suppressed by the mesoscale momentum flux under this closure because a larger effective stratification can provide a more efficient mass redistribution and, in turn, a larger potential energy for WISHE. This demonstrates that momentum transport by mesoscale convective systems can substantially modify the large-scale tropical dynamics through the WISHE mechanism."
"7004187536;7401921174;6506634734;","Origin and structure of a numerically simulated polar low over Hudson Bay",1995,"10.1034/j.1600-0870.1995.00123.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981567364&doi=10.1034%2fj.1600-0870.1995.00123.x&partnerID=40&md5=7e548d725c357c924d7fae98b0d83048","The PSU‐NCAR mesoscale model (MM4) is used to simulate a polar low that developed over Hudson Bay in December 1988. The structure and characteristics of the simulated low are documented, and results are presented of sensitivity experiments aimed at elucidating the physical mechanisms involved in the cyclogenesis. The low formed over an ice‐free region in the eastern bay as an amplifying upper‐level cold trough advanced into the region. The model depicted the polar low as a small, relatively shallow system embedded within the larger cold low. It resembled a miniature hurricane in structure but lacked hurricane‐force winds. The lapse rate near its center was moist neutral to 550 mb (4 km); anticyclonic outlow occurred at and immediately below that level. The sensitivity experiments revealed that fluxes of heat and moisture from the region of open water and the associated condensation heating in deep organized convection were essential to the development. Sensible heating alone produced a relatively weak low and no low formed in an experiment with a completely ice‐covered bay. The feedback between the surface fluxes and wind speed enhanced the intensification, especially in an experiment with the sea surface temperature raised by 8 °C. Winds of minimal hurricane intensity were attained in the latter experiment when the feedback effect was included but not when it was disallowed. A sizable impact of the ice‐edge configuration was found. It is concluded that the Hudson Bay polar low formed as a consequence of latent heat release in deep organized convection that formed when an upper‐level cold low moved over a relatively warm body of open water from which large fluxes of heat and moisture took place. Baroclinic forcing appeared to play little direct role in the low development. Instead, the configuration of the upstream ice boundary provided an important initiating and organizing mechanism. Copyright © 1995, Wiley Blackwell. All rights reserved"
"6701537458;","A model‐based diagnostic study of the development and maintenance mechanism of two polar lows",1990,"10.1034/j.1600-0870.1990.00009.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981641824&doi=10.1034%2fj.1600-0870.1990.00009.x&partnerID=40&md5=8eb4b6f3cdf13110a354cf597ed3aa67","The life cycles of two polar lows in the Norwegian Sea have been studied. Both lows were observed, analysed and forecast by the Norwegian mesoscale model system. The system is run operationally 4 times a day and provides high spatial and temporal resolution data for diagnostics in addition to daily forecasts. Both lows start developing as upper level vorticity maxima approach low‐level baroclinic zones. One of the lows decays after the initial baroclinic intensification phase, while the other develops further. This second phase, the maintenance phase, seems to be related to organized convection. The possibility for air‐sea interaction instability is discussed. The role of the underlying surface in creating conditions favourable for polar low developments is addressed as is the predictability of these mesoscale cyclones. Copyright © 1990, Wiley Blackwell. All rights reserved"
"7003703412;6506918018;6505737760;","Remote sensing of water vapor convergence, deep convection, and precipitation over the tropical pacific ocean during the 1982-1983 E1 Niño",1987,"10.1029/JC092iC13p14204","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0002843814&doi=10.1029%2fJC092iC13p14204&partnerID=40&md5=f6f9ef2677850056807f989a4f79ae24","Deep tropospheric warming and mass flux, produced by the convection associated with organized tropical precipitation, is responsible on monthly and seasonal time scales for the presence of the Hadley and Walker circulations. In El Nifio-Southern Oscillation (ENSO) event years such as 1982-1983, in response to a perturbed sea surface temperature (SST) field in the equatorial Pacific Ocean, a major displacement in the ascending branch of these thermally direct, planetary-scale cells occurs. As the northern winter monsoonal rainfall develops over the tropical Pacific Ocean near the date line, normal precipitation over Indonesia and the Amazon and Congo river valleys is suppressedL. ater, as the SST maximum approaches the coast of South America, flooding occurs over Ecuador. As a direct result of the induced anomalies in the general circulation, droughts are caused not only in Indonesia but also in northern Australia and in the northern subtropical Pacific Ocean along an axis from the Phillipines to Hawaii. The scanning multichannel microwave radiometer (SMMR) on board the Nimbus 7 spacecraft has been used to derive estimates of atmospheric water vapor. The correlation between the satellite and verifying radiosonde data is better than 0.83 at all stations considered. The Earth radiation budget experiment flown on the same satellite observes the terrestrial net radiation, albedo, and outgoing longwave radiation (OLR). The OLR fields have been related to the 200-mbar divergence fields in the tropics during the First GARP Global Experiment with a correlation of 0.8. The derived relationship has been successfullye xtended to realistically map the irrotational flow and divergent circulation present in the troposphere both prior to and during the 1982-1983 ENSO event. Together, the two data sets yield a joint estimate of the convergent flux of water vapor, a critical controlling parameter for organized convection.T he derived water vapor flux convergencesa re analyzed during the recent El Nifio episodet o map the evolution of the parameter, inferred deep convection, and estimated rainfall over regions impacted by the event. The inferred monthly rainfall amounts are compared with observations for 14 island and coastal stations in the Pacific Ocean. For the stations, linear models are developed that explain up to 71% of the variance of the signal. For a rainfall model developed using the ensemble of stations, skill is demonstrated in describing the temporal and spatial evolution of the drought and flood anomalies present during 1982 and 1983. Over an equatorial belt extending from Indonesia to the coast of South America,p ositiver ainfall anomaliesr eaching4 0 cm month- are presentD. ue to changesin the Hadley and Walker circulations, these flood regions are bordered on all sides by rainfall deficits which are in excess of - 20 cm month-. Copyright 1987 by the American Geophysical Union."
"16644246500;57219201388;56450100300;36992744000;55823467500;57212215393;35509639400;6701835010;57210719777;6602176524;6603606681;56925245400;11939918300;57194693620;24335361400;37107744600;6701346974;57204886915;57208054058;57218450611;8866821900;25647939800;22954298000;57195349030;56520853700;56471429200;57192174561;7202208382;42262516200;54881950900;36187387300;26536569500;55940978200;7401945370;55437450100;55469523400;7201504886;24485834000;25645385100;36054921000;55286185400;","Clouds and Convective Self-Aggregation in a Multimodel Ensemble of Radiative-Convective Equilibrium Simulations",2020,"10.1029/2020MS002138","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086879900&doi=10.1029%2f2020MS002138&partnerID=40&md5=a471402d55ec9d5e9e85478030e3d140","The Radiative-Convective Equilibrium Model Intercomparison Project (RCEMIP) is an intercomparison of multiple types of numerical models configured in radiative-convective equilibrium (RCE). RCE is an idealization of the tropical atmosphere that has long been used to study basic questions in climate science. Here, we employ RCE to investigate the role that clouds and convective activity play in determining cloud feedbacks, climate sensitivity, the state of convective aggregation, and the equilibrium climate. RCEMIP is unique among intercomparisons in its inclusion of a wide range of model types, including atmospheric general circulation models (GCMs), single column models (SCMs), cloud-resolving models (CRMs), large eddy simulations (LES), and global cloud-resolving models (GCRMs). The first results are presented from the RCEMIP ensemble of more than 30 models. While there are large differences across the RCEMIP ensemble in the representation of mean profiles of temperature, humidity, and cloudiness, in a majority of models anvil clouds rise, warm, and decrease in area coverage in response to an increase in sea surface temperature (SST). Nearly all models exhibit self-aggregation in large domains and agree that self-aggregation acts to dry and warm the troposphere, reduce high cloudiness, and increase cooling to space. The degree of self-aggregation exhibits no clear tendency with warming. There is a wide range of climate sensitivities, but models with parameterized convection tend to have lower climate sensitivities than models with explicit convection. In models with parameterized convection, aggregated simulations have lower climate sensitivities than unaggregated simulations. ©2020. The Authors."
"20435708300;7403232646;8597673800;","The impact of GPS ro data on the prediction of tropical cyclogenesis using a nonlocal observation operator: An initial assessment",2020,"10.1175/MWR-D-19-0286.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088230218&doi=10.1175%2fMWR-D-19-0286.1&partnerID=40&md5=a72aa1560bbd0ce70e29d5bd8641ad03","In this study, the impact of global positioning system (GPS) radio occultation (RO) data on the prediction of the genesis of 10 tropical cyclones over the western North Pacific Ocean is assessed. With the use of a nonlocal excess phase observation operator in cycling data assimilation, the probability of detection for tropical cyclogenesis is increased from 30% to 70% for the cases considered, all of which developed into typhoons. However, the probability of detection is only increased to 40% when a local observation operator is used, indicating that the observation operator can significantly influence the performance of RO data assimilation in capturing tropical cyclogenesis. A nonlocal excess phase operator, which considers the atmospheric horizontal gradients by integrating the refractivity along a ray path, gives superior performance over the local observation operator. Additional sensitivity experiments on 3 of the 10 typhoon cases show that the RO data in the vicinity of the incipient cyclones (within 500 km of the cyclone center) are most critical to successful cyclogenesis prediction. This reflects the fact that having good RO observations at the right time and place is critical for RO to have beneficial impacts on tropical cyclogenesis. Further analyses for Typhoon Nuri (2008) show that assimilation of RO data using the nonlocal operator leads to moistening of the lower and middle troposphere, organized convection, robust grid-scale vertical motions, and the development of midlevel relative vorticity, all of which are favorable for tropical cyclogenesis. © 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"7003991093;57194637327;","Convective organization and eastward propagating equatorial disturbances in a simple excitable system",2020,"10.1002/qj.3792","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084139452&doi=10.1002%2fqj.3792&partnerID=40&md5=de7b0f8db3c440c0dbb680cd92b6c037","We describe and illustrate a mechanism whereby convective aggregation and eastward propagating equatorial disturbances, which are similar in some respects to the Madden–Julian Oscillation (MJO), arise. We construct a simple explicit system consisting only of the shallow-water equations plus a humidity variable; moisture enters via evaporation from a wet surface, is transported by the flow and removed by condensation, thus producing an anomaly in the height field. For a broad range of parameters the system is excitable even when linearly stable, with condensation producing convergence and gravity waves that, acting together, trigger more condensation. On the equatorial β-plane the convection first aggregates near the Equator, generating patterns related to those encountered in the Matsuno–Gill problem. However, the pattern is unstable and more convection is triggered on its eastern edge, leading to a self-sustaining precipitating disturbance that progresses eastward. The propagation is eastward because the warm, moist converging air from the east induced by the Matsuno–Gill pattern is more convectively unstable than the converging air from the west. The pattern is confined to a region within a few deformation radii of the Equator, as here the convection can create the convergence needed to organize itself into a self-sustaining pattern; thus, smaller values of the beta parameter give rise to a wider disturbance. Formation of the disturbance preferentially occurs where the surface is warmer, and sufficient time (typically a few tens of days) must pass before conditions arise that enable the disturbance to reform, a well-known characteristic of the MJO. The speed of the disturbance depends on the efficiency of evaporation and the heat released by condensation, and is typically a few metres per second, much less than the Kelvin wave speed. © 2020 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"57194110694;35509639400;","Relationship Between Precipitation Extremes and Convective Organization Inferred From Satellite Observations",2020,"10.1029/2019GL086927","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084434550&doi=10.1029%2f2019GL086927&partnerID=40&md5=28053f0c4cd5f3d03cbab7a84b424e5b","Convective organization has the potential to impact the strength of precipitation extremes, but numerical models disagree about this influence. This study uses satellite observations to investigate the link between the mesoscale organization of deep convection and precipitation extremes in the Tropics. Extremes in domain-averaged precipitation are found mostly over the western Pacific and Indian Ocean warm pools, and they primarily depend on the number of deep convective entities within the domain. On the other hand, extremes in local precipitation are found primarily over land, and they increase with the degree of convective organization. Therefore, this observational study shows evidence for a modulation of the strength of tropical precipitation extremes by the spatial organization of deep convection, especially over land. ©2020. The Authors."
"57209312587;35321650700;55967916100;55665248300;7004241402;6602806483;57191576880;56942309200;15033163800;","A new set of atmosphere and evolution models for cool T-Y brown dwarfs and giant exoplanets",2020,"10.1051/0004-6361/201937381","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089032079&doi=10.1051%2f0004-6361%2f201937381&partnerID=40&md5=c1b376b70542abbfc6b52e75e0d4ca94","We present a new set of solar metallicity atmosphere and evolutionary models for very cool brown dwarfs and self-luminous giant exoplanets, which we term ATMO 2020. Atmosphere models are generated with our state-of-the-art 1D radiative-convective equilibrium code ATMO, and are used as surface boundary conditions to calculate the interior structure and evolution of 0.001-0.075 M∗ objects. Our models include several key improvements to the input physics used in previous models available in the literature. Most notably, the use of a new H-He equation of state including ab initio quantum molecular dynamics calculations has raised the mass by ∼1-2% at the stellar-substellar boundary and has altered the cooling tracks around the hydrogen and deuterium burning minimum masses. A second key improvement concerns updated molecular opacities in our atmosphere model ATMO, which now contains significantly more line transitions required to accurately capture the opacity in these hot atmospheres. This leads to warmer atmospheric temperature structures, further changing the cooling curves and predicted emission spectra of substellar objects. We present significant improvement for the treatment of the collisionally broadened potassium resonance doublet, and highlight the importance of these lines in shaping the red-optical and near-infrared spectrum of brown dwarfs. We generate three different grids of model simulations, one using equilibrium chemistry and two using non-equilibrium chemistry due to vertical mixing, all three computed self-consistently with the pressure-temperature structure of the atmosphere. We show the impact of vertical mixing on emission spectra and in colour-magnitude diagrams, highlighting how the 3.5-5.5 μm flux window can be used to calibrate vertical mixing in cool T-Y spectral type objects. © ESO 2020."
"56533742600;11939918300;7201504886;","Mesoscale marine tropical precipitation varies independently from the spatial arrangement of its convective cells",2020,"10.1002/qj.3742","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079468135&doi=10.1002%2fqj.3742&partnerID=40&md5=08ad453fe449e63339e2174d6e447bb2","The relationship between mesoscale convective organization, quantified by the spatial arrangement of convection, and oceanic precipitation in the tropical belt is examined using the output of a global storm-resolving simulation. The analysis uses a 2D watershed segmentation algorithm based on local precipitation maxima to isolate individual precipitation cells and derive their properties. 10° by 10° scenes are analyzed using a phase-space representation made of the number of cells per scene and the mean area of the cells per scene to understand the controls on the spatial arrangement of convection and its precipitation. The presence of few and large cells in a scene indicates the presence of a more clustered distribution of cells, whereas many small cells in a scene tend to be randomly distributed. In general, the degree of clustering of a scene (Iorg) is positively correlated to the mean area of the cells and negatively correlated to the number of cells. Strikingly, the degree of clustering, whether the cells are randomly distributed or closely spaced, to a first order does not matter for the precipitation amounts produced. Scenes of similar precipitation amounts appear as hyperbolae in our phase-space representation, hyperbolae that follow the contours of the precipitating area fraction. Finally, including the scene-averaged water vapour path (WVP) in our phase-space analysis reveals that scenes with larger WVP contain more cells than drier scenes, whereas the mean area of the cells only weakly varies with WVP. Dry scenes can contain both small and large cells, but they can contain only few cells of each category. © 2020 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"47861021500;56450100300;8696069500;7201504886;","Global variability in radiative-convective equilibrium with a slab ocean under a wide range of CO2 concentrations",2020,"10.1080/16000870.2019.1699387","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077586059&doi=10.1080%2f16000870.2019.1699387&partnerID=40&md5=3c91f2adf1b8a8f05adab29bcf1341ca","In radiative-convective equilibrium (RCE), radiative cooling of the troposphere is roughly balanced by the vaporization enthalpy set free by precipitating moist convection. Many earlier studies restricted the investigation of RCE to the dynamics of the atmosphere with constant boundary conditions including prescribed surface temperature. We investigate a GCM setup where a slab ocean is coupled to the atmosphere, and we explore a wide range of CO2 concentrations. We obtain reliable statistical quantities from thousand-year-long simulations. For moderate CO2 concentrations, we find unskewed temporal variations of 1–2 K in global mean surface temperature, with an almost constant climate sensitivity of 2 K. At CO2 concentrations beyond four times the preindustrial value, the climate sensitivity decreases to nearly zero as a result of episodic global cooling events as large as 10 K. The dynamics of these cooling events are investigated in detail and shown to be associated with an increase in large-scale low-level stratiform cloudiness in the subsiding region, which is a result of penetrative shallow convection being capped by an inversion and thus not ventilating the lower troposphere. These dynamics depend on the CO2 concentration: both through the effect of temperature on stratification and through the changing spatial scale of organization of the flow, which determines the spatial scale and temporal coherence of the stratiform cloud sheets. © 2020, © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group."
"57092467500;7409322518;7101801476;7202772927;7202048112;","Structural changes and variability of the ITCZ induced by radiation–cloud–convection–circulation interactions: inferences from the Goddard Multi-scale Modeling Framework (GMMF) experiments",2020,"10.1007/s00382-019-05000-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074472344&doi=10.1007%2fs00382-019-05000-y&partnerID=40&md5=2dcecaa28da0c0d96bf44608c2947415","In this paper, we have investigated the impact of radiation–cloud–convection–circulation interaction (RC3I) on structural changes and variability of the Inter-tropical Convergence Zone (ITCZ) using the Goddard Multi-scale Modeling Framework, where cloud processes are super-parameterized, i.e., explicitly resolved with 2-D cloud resolving models embedded in each coarse grid of the host Goddard Earth Observing System-Version 5 global climate model. Experiments have been conducted under prescribed sea surface temperature conditions for 10 years (2007–2016), with and without cloud radiation feedback in the atmosphere, respectively. Diagnostic analyses separately for January and July show that RC3I leads to an enhanced and expanded Hadley Circulation characterized by (1) a quasi-uniform warming and moistening of the tropical atmosphere and a sharpening of the ITCZ with enhanced deep convection, more intense precipitation and higher clouds, (2) extended drying of the tropical marginal convective zones, and extratropical mid- to lower troposphere, and (3) a cooling of the polar regions, with increased baroclinicity and midlatitude storm track activities. Computations based on the zonal mean thermodynamic energy balance equation show that the radiative warming and cooling are strongly balanced by local adiabatic processes associated with changes in large-scale vertical motions, as well as horizontal atmospheric heat transport. In the tropics, enhanced short-wave absorption and longwave water vapor greenhouse effects by high clouds play key roles in providing strong positive feedback to the tropospheric warming. In the extratropics, increased atmospheric heat transport associated with changes in the Hadley circulation is balanced by strong longwave cooling above, and warming below due to increased high clouds. We also find a strong positive correlation between daily and pentad heavy rain in the ITCZ core, and expansion of the drier zones coupled to a contraction of the highly convective zones in the ITCZ, indicating a strong tendency RC3I-induced convective aggregation in tropical clouds i.e., wet-regions-get-wetter and contracted, and dry-areas-get-drier and expanded. © 2019, The Author(s)."
"57205541625;36676894700;7006206130;","Convective shower characteristics simulated with the convection-permitting climate model COSMO-CLM",2019,"10.3390/ATMOS10120810","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079786649&doi=10.3390%2fATMOS10120810&partnerID=40&md5=c0bede729e9bd91e6bbf7e2a86d2f346","This paper evaluates convective precipitation as simulated by the convection-permitting climate model (CPM) Consortium for Small-Scale Modeling in climate mode (COSMO-CLM) (with 2.8 km grid-spacing) over Germany in the period 2001-2015. Characteristics of simulated convective precipitation objects like lifetime, area, mean intensity, and total precipitation are compared to characteristics observed by weather radar. For this purpose, a tracking algorithm was applied to simulated and observed precipitation with 5-min temporal resolution. The total amount of convective precipitation is well simulated, with a small overestimation of 2%. However, the simulation underestimates convective activity, represented by the number of convective objects, by 33%. This underestimation is especially pronounced in the lowlands of Northern Germany, whereas the simulation matches observations well in the mountainous areas of Southern Germany. The underestimation of activity is compensated by an overestimation of the simulated lifetime of convective objects. The observed mean intensity, maximum intensity, and area of precipitation objects increase with their lifetime showing the spectrum of convective storms ranging from short-living single-cell storms to long-living organized convection like supercells or squall lines. The CPM is capable of reproducing the lifetime dependence of these characteristics but shows a weaker increase in mean intensity with lifetime resulting in an especially pronounced underestimation (up to 25%) of mean precipitation intensity of long-living, extreme events. This limitation of the CPM is not identifiable by classical evaluation techniques using rain gauges. The simulation can reproduce the general increase of the highest percentiles of cell area, total precipitation, and mean intensity with temperature but fails to reproduce the increase of lifetime. The scaling rates of mean intensity and total precipitation resemble observed rates only in parts of the temperature range. The results suggest that the evaluation of coarse-grained (e.g., hourly) precipitation fields is insufficient for revealing challenges in convection-permitting simulations. © 2019 by the authors. Licensee MDPI, Basel, Switzerland."
"57033686900;7202145115;7401776640;","Is the Net Cloud Radiative Effect Constrained to be Uniform Over the Tropical Warm Pools?",2019,"10.1029/2019GL083642","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074866926&doi=10.1029%2f2019GL083642&partnerID=40&md5=c944bcb76d7286c88910735fd5f7e49f","Global radiative-convective equilibrium simulations are used to investigate the hypothesis that mutual interactions among cloud albedo, sea surface temperature gradients, and atmospheric circulation constrain the net cloud radiative effect (CRE) to be similar in convective and nonconvective regions over the tropical warm pools. We perform an experiment in which convective clouds interact naturally with the ocean and atmosphere by forming over the warmest water and shading it and an experiment in which this interaction is removed by randomizing cloud shading of the ocean. Removing the cloud shading interaction enhances sea surface temperature gradients, lateral atmospheric heat transport, and large-scale convective aggregation and produces convective clouds with much more negative net CRE. These findings support the hypothesis that feedbacks between sea surface temperature and convection are critical to obtaining similar net CRE in convective and nonconvective regions over the tropical warm pools. ©2019. American Geophysical Union. All Rights Reserved."
"55819549500;57188837293;","On the connection between remote dust aerosol and Indian summer monsoon",2019,"10.1007/s00704-018-2647-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068756616&doi=10.1007%2fs00704-018-2647-6&partnerID=40&md5=777d539d2b568a7b7ada25784f27ebc1","Understanding of interaction between remote dust aerosol and Indian summer monsoon (ISM) remains dubious in literature because of wide disagreement among previous studies. This problem is revisited using version-2 of Modern-Era Retrospective Analysis for Research and Applications (MERRA-2) datasets. ISM variability at intraseasonal timescale is not constrained by the changes in dust aerosols over the most parts of West Asia and North Africa. A new hypothesis is proposed to explain covariability of dust over the Arabian Sea and ISM circulation. Large-scale forcing modulates monsoon intraseasonal oscillations (ISOs) and creates active-like condition over the Indian landmass extending up to the Arabian Sea and the Arabian Peninsula. Organized convection induces anomalous southwesterly and northwesterly circulation as a response to enhanced latent heating. Enhanced northwesterly winds strengthen transport of dust over the Arabian Sea. Augmented dust forcing and associated warming over the Arabian Sea is unlikely to create a positive feedback because of its limited spatial extent. Findings of the present study provide a new insight into remote dust-ISM connection problem and the hypothesis proposed differs considerably from the previously proposed hypotheses. © 2018, Springer-Verlag GmbH Austria, part of Springer Nature."
"56487672200;57195881858;56593857400;","Dynamics of lower-tropospheric vorticity in idealized simulations of tropical cyclone formation",2019,"10.1175/JAS-D-18-0219.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063659162&doi=10.1175%2fJAS-D-18-0219.1&partnerID=40&md5=4629c2f441c275ab78a62e34a2d8c331","Idealized simulations are conducted using the Cloud Model version 1 (CM1) to explore themechanism of tropical cyclone (TC) genesis from a preexistingmidtropospheric vortex that forms in radiative-convective equilibrium. With lower-tropospheric air approaching near saturation during TC genesis, convective cells become stronger, along with the intensifying updrafts and downdrafts and the larger area coverage of updrafts relative to downdrafts. Consequently, the low-level vertical mass flux increases, inducing vorticity amplification above the boundary layer. Of interest is that while surface cold pools help organize lowertropospheric updrafts, genesis still proceeds, only slightly delayed, if subcloud evaporation cooling and cold pool intensity are drastically reduced. More detrimental is the disruption of near saturation through the introduction of weak vertical wind shear. The lower-tropospheric dry air suppresses the strengthening of convection, leading to weaker upward mass flux and much slower near-surface vortex spinup. We also find that surface spinup is similarly inhibited by decreasing surface drag despite the existence of a nearly saturated column, whereas larger drag accelerates spinup. Increased vorticity above the boundary layer is followed by the emergence of a horizontal pressure gradient through the depth of the boundary layer. Then the corresponding convergence resulting from the gradient imbalance in the frictional boundary layer causes vorticity amplification near the surface. It is suggested that near saturation in the lower troposphere is critical for increasing the mass flux and vorticity just above the boundary layer, but it is necessary yet insufficient because the spinup is strongly governed by boundary layer dynamics. © 2019 American Meteorological Society."
"57200211495;56308982600;","Organized convection over southwest peninsular India during the pre-monsoon season",2019,"10.1007/s00704-018-2446-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064180371&doi=10.1007%2fs00704-018-2446-0&partnerID=40&md5=010d84576a223fd96b49b5d7be8bfec4","The paper addresses observational aspects of widespread rain associated with the organized convection that forms over the southwest peninsular India during the pre-monsoon season. The evolution of the cloud band over the equatorial region, its northward propagation, development of cross equatorial flow near the Somalia coast, and appearance of equatorial westerly wind resemble closely to that of the monsoon organized convection. Low-level convergence, cyclonic vorticity, and ascending motion are other major characteristics of the cloud bands associated with the pre-monsoon organized convection which exhibits similarity with that of monsoon. The ascending motion plays vital role on the formation of cloud band that produces widespread rainfall persisting for more than a week. The vertical shear of meridional winds is found to co-exist with precipitation over the Arabian Sea off the southwest peninsular India. The velocity potential values derived from the winds at 850 and 200 hPa levels confirm the rising motion on the basis of low-level convergence and upper level divergence. Also, shifting of ascending limb of the local Hadley circulation to the north of the equator is observed during the days of the presence of organized convection over the southwest peninsular region. Noticeable shift in the Walker circulation rising limb is also identified during the same time. © 2018, Springer-Verlag GmbH Austria, part of Springer Nature."
"57205587578;7202208382;","Geographical and Seasonal Variability of Cloud-Radiative Feedbacks on Precipitation",2019,"10.1029/2018JD029186","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060597967&doi=10.1029%2f2018JD029186&partnerID=40&md5=438eee26259c5f1fe327079d9dc95e18","We have used observations to study the temporal covariability of precipitation and atmospheric radiative cooling (ARC, defined as positive when the atmosphere is radiatively cooled) on seasonal and longer time scales. Clouds act to decrease the globally averaged ARC, but their radiative effect on the ARC varies with latitude. Clouds decrease the ARC in the tropics, mainly by reducing the outgoing longwave radiation, but they increase the ARC in higher latitudes, primarily by increasing the downwelling longwave radiation at the surface. The temporal correlation of the zonally averaged precipitation rate and the zonally averaged ARC is about −0.7 in the tropics and +0.5 in higher latitudes, and it changes sign almost discontinuously toward the poles at approximately 30°N and 30°S. This suggests that changes in the ARC feed back negatively on precipitating tropical systems and positively on precipitating systems at higher latitudes. ©2019. American Geophysical Union. All Rights Reserved."
"55227473700;57034458200;","An observational analysis of three extreme rainfall episodes of 19–20 July 2016 along the Taihang Mountains in North China",2019,"10.1175/MWR-D-18-0402.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075635563&doi=10.1175%2fMWR-D-18-0402.1&partnerID=40&md5=c86f6f45671d280a7504b82d647ee7b2","This study examines the synoptic- and mesoscale processes leading to the generation of three extreme rainfall episodes with hourly rates of greater than 100 mm h21 over the southern, middle, and northern portions of the eastern foothills of Mt. Taihang in North China on 19–20 July 2016. The extreme rainfall episodes took place over the 200–600-m elevation zones in the southern and northern portions but also over the lower elevations in the middle portion of the target region, sequentially during late morning, early evening, and midnight hours. Echo training accounted for the development of a linear convective system in the southern region after the warm and moist air carried by a southeasterly low-level jet (LLJ) was lifted to condensation as moving across Mt. Yuntai. In contrast, two isolated circular-shaped convective clusters, with more robust convective cores in its leading segment, developed in the northern region through steep topographical lifting of moist northeasterly airflow, albeit conditionally less unstable. Extreme rainfall in the middle region developed from the convergence of a moist easterly LLJ with a northerly colder airflow associated with an extratropical cyclogenesis. Results reveal that the LLJs and associated moisture transport, the intensifying cyclone interacting with a southwest vortex and its subsequent northeastward movement, and the slope and orientation of local topography with respect to and the stability of the approaching airflows played different roles in determining the timing and location, the extreme rainfall rates, and convective organizations along the eastern foothills of Mt. Taihang. © 2019 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy."
"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."
"57207042957;35572026100;25823927100;","Is atmospheric convection organised?: information entropy analysis",2019,"10.1080/03091929.2018.1506449","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053539407&doi=10.1080%2f03091929.2018.1506449&partnerID=40&md5=88da391d403d2f1547d4c9f803205bff","In order to quantify the degree of organisation of atmospheric convection, an analysis based on the information entropy, which is widely considered a measure of organisation in information science, is performed. Here, the information entropy is defined in terms of the spectrum of the empirical orthogonal functions (EOFs). Satellite-based brightness temperature data from CLAUS (Cloud Archive User Service) is used over the domain covering the Indian Ocean and the Western Pacific with a spatial resolution of 2/3° from January 1985 to June 2009. The information entropy remains close to a mean value of 0.899 with a very small standard deviation of 2.7 × 10−3, suggesting that the atmospheric convection is always disorganised under a measure of the information entropy, which is against our common understanding. To better interpret this result, some basic theoretical analyses are performed, and the values of the information entropy for different systems (English literature texts, turbulent flows) from previous studies are reviewed. The same analysis is further performed on the Ising model, which is characterised by a clustering tendency of spin distribution, akin to convective organisation morphologically, at the critical temperature. The study suggests a need for a careful use of the term “organised”. Atmospheric convection represents a tendency for clustering up to the planetary scale in analogous manner as the critical-point behaviour of the Ising model. However, neither is considered an “ordered” state under a measure of the information entropy. © 2018, © 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group."
"57200131336;56308982600;23569021500;","Characteristics of surface boundary layer during active and weak phases of southwest monsoon over Kochi: A tropical station",2018,"10.1016/j.jastp.2018.07.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050073940&doi=10.1016%2fj.jastp.2018.07.005&partnerID=40&md5=511168f0cbb9662fca080063c1dc81ba","This study explores the features of atmospheric surface layer over Kochi during active and weak phases of the southwest monsoon season. The classification of active and weak phases of monsoon is made on the basis of monsoon organized convection over the region. When the monsoon organized convection is over (away from) Kochi, considered it as an active (weak) phase. The study primarily utilizes sonic anemometer data. The diurnal variation of surface fluxes and turbulent kinetic energy (TKE) during active and weak conditions are examined in addition to surface wind and temperatures. It is found that monsoon clouds spread extensively over large area stabilizes the surface layer and a drastic decrease in sensible heat flux is observed during the active monsoon conditions. The average value of momentum flux and TKE decreases, surface layer becomes stable, and Atmospheric Boundary Layer (ABL) height lowers during active monsoon phase. A significant oscillation of 3.5 h periodicity is found to be embedded in the momentum flux and in the wind speed which is attributed to the penetration of the low level monsoon circulation. Weak monsoon phase is characterized by higher value of fluxes and TKE with higher amplitude of diurnal variation due to local heating and sea breeze circulation. Unstable condition between 00:00 IST and 01:00 IST and stable conditions in the early morning is observed during both active and weak phases. It is observed that there are two different relations for the growth and dissipation of fluxes and TKE. The dissipation is faster than growth in the case of surface fluxes with temperature. The sensible heat flux, momentum flux and TKE are logarithmically related with wind speed. Sensible heat flux has logarithmic relation with temperature, whereas momentum flux and TKE have exponential relation. © 2018 Elsevier Ltd"
"23492864500;7006184606;","Congestus modes in circulating equilibria of the tropical atmosphere in a two-column model",2018,"10.1002/qj.3385","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056101036&doi=10.1002%2fqj.3385&partnerID=40&md5=1e985e62effe14475fe043fa72e7d7bd","A two-column radiative–convective equilibrium (RCE) model is used to study the depth of convection that develops in the subsiding branch of a Walker-like overturning circulation. The model numerically solves for two-dimensional non-rotating hydrostatic flow, which is damped by momentum diffusion in the boundary layer and model interior, and by convective momentum transport. Convection, clouds and radiative transfer are parametrized, and the convection scheme does not include explicit freezing or melting. While integrating the model towards local RCE, the level of neutral buoyancy (LNB) fluctuates between mid- and high levels. Evaporation of detrained moisture at the LNB locally cools the environment, so that the final RCE state has a stable layer at mid-levels (550 hPa ≈ 50–100 hPa below 0 °C), which is unrelated to melting of ice. Preferred detrainment at mid- and high levels leaves the middle-to-upper troposphere relatively dry. A circulation is introduced by incrementally lowering the sea-surface temperature in one column, which collapses convection: first to a congestus mode with tops near 550 hPa, below the dry layer created in RCE; then to congestus with tops near 650 hPa; and finally to shallow cumulus with tops near 850 hPa. Critical to stabilizing congestus near 650 hPa is large radiative cooling near moist cumulus tops under a dry upper atmosphere. This congestus mode is very sensitive, and only develops when horizontal temperature gradients created by evaporative and radiative cooling can persist against the work of gravity waves. This only happens in runs with ample momentum diffusion, which are those with convective momentum transport or large domains. Compared to the shallow mode, the congestus mode produces a deep moist layer and more precipitation. This reduces radiative cooling in the cloud layer and enhances stability near the cloud base, which weakens the circulation, and leads to less precipitation over the warm ocean. © 2018 Royal Meteorological Society"
"8882641700;7004479957;7402781278;23013520400;","Locally Enhanced Aerosols Over a Shipping Lane Produce Convective Invigoration but Weak Overall Indirect Effects in Cloud-Resolving Simulations",2018,"10.1029/2018GL078682","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053454765&doi=10.1029%2f2018GL078682&partnerID=40&md5=63a7a2eec0558fcd3d6952b2c171aa05","The effect of aerosol emissions from an active shipping lane in the Indian Ocean is simulated using an idealized framework in a cloud-resolving model. Increased aerosol concentrations over the modeled shipping lane lead to increased cloud droplet number, cloud liquid mass, ice hydrometeor mass, and simulated radar reflectivity. The invigoration of deep convection induces mesoscale uplift and increased precipitation over the shipping lane. A predicted increase in the prevalence of both strong updrafts and radar echoes aloft is suggestive of enhanced lightning activity over the shipping lane, as observed in a recent study. Cloud radiative effects, both shortwave and longwave, are intensified over the shipping lane, but the change in the net radiative flux at top of atmosphere is not significantly different from zero. ©2018. American Geophysical Union. All Rights Reserved."
"56587020100;7006256622;","Long-Lived Mesoscale Convective Systems of Superparameterized CAM and the Response of CAM",2018,"10.1029/2018MS001339","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053461778&doi=10.1029%2f2018MS001339&partnerID=40&md5=a87407a35a3c885145a317a552fa1b12","Mesoscale organized convection is generally misrepresented in the large-scale convective parameterizations used in contemporary climate models. This impacts extreme weather events (e.g., Madden-Jullian Oscillation) and the general circulation driven by the significant amount of latent heat released from mesoscale organized convection. Studies show that the missing processes could be partially recovered by embedding a 2-D cloud-resolving model in each general circulation model columns, that is, superparameterization. To enable analysis of mesoscale convective systems (MCSs) in the multiscale modeling framework, we apply a detection and hierarchical clustering algorithm on the 3-hourly 2-D cloud-resolving model embedded in the superparameterized Community Atmosphere Model (SPCAM) 5.2. We then examine the fields of a long-lived and large MCS cluster at the central Pacific. The MCS cluster shows a squall line-like circulation throughout the life cycle in SPCAM. We simultaneously obtain the 3-hourly CAM parameterized convection outputs based on the time step-wise perfect initial conditions given by SPCAM. This allows pure model physics comparison without introducing initial condition errors. The results show that CAM has a systematically biased stratiform cooling and moistening response below 3 km to the given SPCAM deep convection favoring conditions. We show that this bias is mainly due to the CAM's stratiform microphysics scheme. The mesoscale organization in SPCAM thus provides a baseline for improvements of convective parameterization of CAM. ©2018. The Authors."
"7005702722;","Linear stability of moist convecting Atmospheres. Part I: From linear response functions to a simple model and applications to convectively coupled waves",2018,"10.1175/JAS-D-18-0092.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052628578&doi=10.1175%2fJAS-D-18-0092.1&partnerID=40&md5=d8daf954a7d7859a4e02fe845fb2b339","A procedure is presented to systematically construct simple models for the linear stability of moist convecting atmospheres. First, linear response functions of a cumulus ensemble constructed from cloud-system-resolving models are coupled with matrices expressing two-dimensional large-scale linear wave dynamics. For a radiative-convective equilibrium reference state, this model gives two branches of unstable modes: a propagating convectively coupled wave branch and a stationary branch related to storage of column-integrated moist static energy (MSE). The stationary branch is unstable only when radiative feedback is included, while the convectively coupled wave branch is less affected by radiative feedback. With a modular order-reduction procedure from control theory, the linear-response-function-based model is reduced to a system of six ordinary differential equations while still capturing the essential features of the unstable modes (eigenvalues and structures). The six-dimensional system is then split into a slow and a fast manifold. The slow manifold (again, reflecting column MSE storage) is essential for the stationary mode but not for the convectively coupled waves. The fast manifold is then transformed into a form similar to that of prior simple models of convectively coupled waves, thus placing those models and the insights derived from them on a firmer footing. The procedure also better quantifies the parameters of such simple models and allows the stability difference between different reference states to be better understood. © 2018 American Meteorological Society."
"6602305510;6601963192;6603091453;37081953300;7201799893;","Buildup of Abiotic Oxygen and Ozone in Moist Atmospheres of Temperate Terrestrial Exoplanets and Its Impact on the Spectral Fingerprint in Transit Observations",2018,"10.3847/1538-4357/aaca36","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85051522316&doi=10.3847%2f1538-4357%2faaca36&partnerID=40&md5=6389c870c68c2c45759a45cd4d62205d","We investigate the abiotic production of oxygen and its photochemical byproduct ozone through water vapor photolysis in moist atmospheres of temperate terrestrial exoplanets. The amount of water vapor available for photolysis in the middle atmosphere of a planet can be limited by an atmospheric cold-trap, the formation of which largely depends on the amount of noncondensable gases. We study this effect using a photochemical model coupled to a 1D radiative-convective equilibrium model in atmospheres with N2, CO2, and H2O as the main constituents. We find that in atmospheres with a low N2 inventory, water vapor mixing ratios in the middle atmosphere can be more than two orders of magnitude higher compared to atmospheres with an Earth-like N2 inventory. Without a strong surface sink, the noncondensable oxygen can build up rapidly, drying out the upper atmosphere. With a moderate surface sink, the planet can approach a steady state with significant oxygen mixing ratios in which oxygen production is balanced by surface uptake. We use a radiative transfer model to study the spectroscopic fingerprint of these atmospheres in transit observations. Spectral signatures of abiotic oxygen and ozone can be of comparable magnitude as in spectra of Earth seen as an exoplanet. Middle atmospheric water vapor is unlikely to be a usable indicator of the abiotic origin of oxygen because of the influence of oxygen on the water vapor distribution. This suggests that atmospheric oxygen and ozone cannot be used as binary bioindicators and that their interpretation will likely require atmospheric and planetary models. © 2018. The American Astronomical Society. All rights reserved."
"56293796000;16636807900;11939929300;7005808242;","Sensitivity of Radiative-Convection Equilibrium to Divergence Damping in GFDL-FV3-Based Cloud-Resolving Model Simulations",2018,"10.1029/2017MS001225","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050931187&doi=10.1029%2f2017MS001225&partnerID=40&md5=74ac62e131175619909f001bdcb709c6","Using a nonhydrostatic model based on a version of Geophysical Fluid Dynamics Laboratory's FV3 dynamical core at a cloud-resolving resolution in radiative-convective equilibrium (RCE) configuration, the sensitivity of the mean RCE climate to the magnitude and scale-selectivity of the divergence damping is explored. Divergence damping is used to reduce small-scale noise in more realistic configurations of this model. This sensitivity is tied to the strength (and width) of the convective updrafts, which decreases (increases) with increased damping and acts to organize the convection, dramatically drying out the troposphere and increasing the outgoing longwave radiation. Increased damping also results in a much-broadened precipitation probability distribution and larger extreme values, as well as reduction in cloud fraction, which correspondingly decreases the magnitude of shortwave and longwave cloud radiative effects. Solutions exhibit a monotonic dependence on the strength of the damping and asymptotically converge to the inviscid limit. While the potential dependence of RCE simulations on resolution and microphysical assumptions are generally appreciated, these results highlight the potential significance of the choice of subgrid numerical diffusion in the dynamical core. ©2018. The Authors."
"56123453900;6603667298;","Variability in warm-season atmospheric circulation and precipitation patterns over subtropical South America: relationships between the South Atlantic convergence zone and large-scale organized convection over the La Plata basin",2017,"10.1007/s00382-016-3072-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84960368719&doi=10.1007%2fs00382-016-3072-0&partnerID=40&md5=09c931d28d6558b3fb0902a1cf026ddd","Warm-season precipitation variability over subtropical South America is characterized by an inverse relationship between the South Atlantic convergence zone (SACZ) and precipitation over the central and western La Plata basin of southeastern South America. This study extends the analysis of this “South American Seesaw” precipitation dipole to relationships between the SACZ and large, long-lived mesoscale convective systems (LLCSs) over the La Plata basin. By classifying SACZ events into distinct continental and oceanic categories and building a logistic regression model that relates LLCS activity across the region to continental and oceanic SACZ precipitation, a detailed account of spatial variability in the out-of-phase coupling between the SACZ and large-scale organized convection over the La Plata basin is provided. Enhanced precipitation in the continental SACZ is found to result in increased LLCS activity over northern, northeastern, and western sections of the La Plata basin, in association with poleward atmospheric moisture flux from the Amazon basin toward these regions, and a decrease in the probability of LLCS occurrence over the southeastern La Plata basin. Increased oceanic SACZ precipitation, however, was strongly related to reduced atmospheric moisture and decreased probability of LLCS occurrence over nearly the entire La Plata basin. These results suggest that continental SACZ activity and large-scale organized convection over the northern and eastern sections of the La Plata basin are closely tied to atmospheric moisture transport from the Amazon basin, while the warm coastal Brazil Current may also play an important role as an evaporative moisture source for LLCSs over the central and western La Plata basin. © 2016, Springer-Verlag Berlin Heidelberg."
"6701538799;","Modeling studies of turbulence mechanisms associated with mesoscale convective systems",2016,"10.1007/978-3-319-23630-8_17","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85017076884&doi=10.1007%2f978-3-319-23630-8_17&partnerID=40&md5=a66532f00d26bb84594e4d997cf44a2c","High-resolution numerical simulations have aided recent understanding of mechanisms responsible for convectively induced aviation turbulence (CIT) spatially removed from its parent moist convection. Anticyclonic jets occurring near the tropopause, which are often significantly enhanced by mesoscale convective systems or other forms of organized convection, influence a variety of different mechanisms of turbulence at commercial aviation cruising altitudes. Herein, we describe different CIT mechanisms that are possible near these anticyclonic outflow jets and illustrate them with examples from recent simulations. © Springer International Publishing Switzerland 2016."
"57015826100;23991212200;","The effect of large-scale model time step and multiscale coupling frequency on cloud climatology, vertical structure, and rainfall extremes in a superparameterized GCM",2015,"10.1002/2015MS000493","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959536194&doi=10.1002%2f2015MS000493&partnerID=40&md5=d315f1dcaa4ecf6aea4d3ab402f7eed7","The effect of global climate model (GCM) time step-which also controls how frequently global and embedded cloud resolving scales are coupled-is examined in the Superparameterized Community Atmosphere Model ver 3.0. Systematic bias reductions of time-mean shortwave cloud forcing (-10 W/m2) and longwave cloud forcing (-5 W/m2) occur as scale coupling frequency increases, but with systematically increasing rainfall variance and extremes throughout the tropics. An overarching change in the vertical structure of deep tropical convection, favoring more bottom-heavy deep convection as a global model time step is reduced may help orchestrate these responses. The weak temperature gradient approximation is more faithfully satisfied when a high scale coupling frequency (a short global model time step) is used. These findings are distinct from the global model time step sensitivities of conventionally parameterized GCMs and have implications for understanding emergent behaviors of multiscale deep convective organization in superparameterized GCMs. The results may also be useful for helping to tune them. © 2015. The Authors."
"7409792174;7006095466;7402358349;56228672600;","Effects of dimensionality on simulated large-scale convective organization and coupled waves",2012,"10.2151/jmsj.2012-104","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863251901&doi=10.2151%2fjmsj.2012-104&partnerID=40&md5=73f90ad551cf1fca7e80891657c1de75","Tropical multi-scale convective organization of the super-cluster kind and convectively coupled gravity waves are investigated by both two and three-dimensional cloud-system-resolving simulations. The experimental setup includes a constant-temperature ocean surface, constant and horizontally-uniform radiative cooling in the troposphere, and a uniform easterly background wind. The objective of this study is to quantify the impacts of dimensionality on the simulated large-scale convective patterns and associated gravity waves. Eastward propagating large-scale coherent precipitating convection occurs regardless of the spatial dimension. The convective organization has a horizontal wavenumber-one structure in the computational domain and travels at about 1317 m s -1 relative to the ground, equivalent to 19-23 m s -1 relative to the environmental flow. However, the convectively-induced wave signature is much weaker in three dimensions than in two dimensions, as well as a faster translation and a smaller tilt of the vertical. Moreover, a two-dimensional framework generates additional organizational modes compared to the three-dimensional results, including a fast westward-moving system with a mean-flow-relative speed comparable to the eastward-moving wavenumber-1 counterpart and the quasi-stationary (relative to the background flow) higher wavenumber precipitating system. This does not necessarily imply that these additional modes are artifacts of two dimensionality. © 2012, Meteorological Society of Japan."
"36676883100;56349032700;36645990400;13403895300;36678135100;6603566959;","Performance of multi-model AEMET-SREPS precipitation probabilistic forecasts over Mediterranean area",2011,"10.5194/adgeo-26-133-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79251520298&doi=10.5194%2fadgeo-26-133-2011&partnerID=40&md5=70beba4e188e57de088c14ff603d13a1","Spanish Meteorological Agency (AEMET) runs a daily experimental multi-model Short-Range Ensemble Prediction System (AEMET-SREPS). The role of the system horizontal resolution (0.25 degrees) on the performance of 24-h precipitation probabilistic forecasts, and its relation with mesoscale events, are assessed comparing the performance over the Mediterranean area and over an European Atlantic area. Gridded high resolution rain observations and standard verification measures have been used at different precipitation thresholds, while studying the dependency on seasons for a one year period (May 2007 to June 2008). As a general result, performance over the Mediterranean area is higher than over the Atlantic one, albeit some relative loss of skill is found in autumn, when mesoscale convective organization is assumed to play a more important role. So it is suggested that AEMET-SREPS system precipitation predictability over the Mediterranean in autumn could be expected to improve if the horizontal and vertical resolution is increased in order to take into account the effect of meso-beta scale, especially important for convective organization. © Author(s) 2011."
"7402346120;55293560600;6602971470;","Near-equatorial convective regimes over the Indian ocean as revealed by synergistic analysis of satellite observations",2011,"10.1142/9789814355315_0008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84973437275&doi=10.1142%2f9789814355315_0008&partnerID=40&md5=bf0c6f89dabf5ad6194372115e96bd8f","We examine the organization and temporal evolution of deep convection in relation to the low level flow over the Indian Ocean by a synergistic analysis of several satellite datasets for wind, rainfall, Outgoing Longwave Radiation (OLR) and cloud liquid water. We show that during the active Indian monsoon season, symmetric instability is present and is directly linked to organized convection and the off-equatorial location of the InterTropical Convergence Zone (ITCZ). The inertial regime interacts with and is controlled by monsoon and cross-equatorial flow. We characterize the dominant regimes of deep convective organization and the possible ocean-atmosphere mechanisms that control them at different phases of the Indian Monsoon. Ongoing work on development of algorithms for automated identification of convective regimes in climate data and their application and testing on 30 years of OLR data are discussed, and preliminary results of the double ITCZ organization in climate data are presented. © 2011 by World Scientific Publishing Co. Pte. Ltd. All rights reserved."
"7102594787;","Entropy sources in equilibrium conditions over a tropical ocean",2005,"10.1175/JAS3422.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20444485099&doi=10.1175%2fJAS3422.1&partnerID=40&md5=8e17d153e42fbcb3ca22ed9640a586bc","Confusion has existed as to sources of entropy due to irreversible processes in the atmosphere, the total of which matches the export of entropy by radiation. What is the mechanical efficiency of convection? For an ideal tropical oceanic system in radiative-convective equilibrium, relative magnitudes of sources of entropy are reviewed - from both observations and numerical model results. Recycling of moisture is shown to be important. Leading terms are those relating to evaporation of precipitation, water loading by falling precipitation, and mixing of unsaturated parcels of air, contributing roughly 37%, 30%, and 15% of the total irreversible production of entropy, respectively. Evaporation from the surface accounts for 11%. The remaining 7% is due to turbulent kinetic energy, generation of gravity waves, and sensible heating at the surface. A mechanical efficiency of conversion of heat s upply at the surface into kinetic energy of the direct circulation, ≈2.0%, is obtained after the budget study. The leading contribution to the conversion is due to the effect of hydrometeors. Drag of hydrometeors is split into two components based on relative contributions of form drag plus water loading (50%) and frictional drag (50%); however, only the former contributes to the direct circulation. The contribution of turbulent kinetic energy is found to be small. Results from the budget study are found to correspond with the finding of a threshold in values of convective available potential energy by Roff and Yano, and with numerical results from a three-dimensional model of convective equilibrium by Shutts and Gray. © 2005 American Meteorological Society."
"6602445893;55798412800;6603271938;","A study of non-forecasted cyclogenesis in a polar air mass over the Baltic Sea",1990,"10.3402/tellusa.v42i1.11868","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025257705&doi=10.3402%2ftellusa.v42i1.11868&partnerID=40&md5=dcf3e88f638a66bbd50be0aa6a62c5f4","We present a case study of a developing meso-scale low in a cold air mass where baroclinicity was weak. Both mid-trophospheric vorticity advection and enhanced organized convection over the Baltic Sea seem to have caused the initial development. Later, baroclinic instability took over the dominating role in the development. The low studied exhibited properties of both polar lows and comma clouds. The case was simulated by a high-resolution limited area numerical model, which failed to develop the intense meso-scale part of the surface cyclone, probably because of too coarse a resolution. -Authors"
"7407043017;6602910772;6701570637;","Impact of missing wind observations on the simulation of a severe storm environment.",1986,"10.1175/1520-0493(1986)114<1278:IOMWOO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022825113&doi=10.1175%2f1520-0493%281986%29114%3c1278%3aIOMWOO%3e2.0.CO%3b2&partnerID=40&md5=4220ba12047a73db3f663ddc9a541282","The sensitivity of a numerical simulation of a severe storm environment in the southwestern US to a missing wind sounding is investigated. The case is the AVE-SESAME '79 storm of 10 April 1979. On that day a major outbreak of severe local storms took place in Oklahoma and Texas. Two 24 h fine-mesh forecasts were conducted using the Drexel Limited Area Mesoscale Prediction System (LAMPS). The initial wind fields of these two forecasts were significantly different in the speed and structure of the upper-level jet around the base of a sharp trough over northwestern Mexico.This difference was caused by the deletion of one wind sounding located at the base of the trough from the initial observations used by the analysis scheme. Numerical results show profound impact of such changes on the 24 h simulations. Detailed comparisons between the experiments based on the simulation motion fields are made to provide physical understanding of the impact. The numerical experiments underline the seriousness of uncertainty in wind analyses. In particular, due to missing or inadequate observations, the consequential errors in portraying the jet streak can result in the generation of spurious vorticity in the upper troposphere. This spurious vorticity, as it moves toward warm, moist air over the Gulf States, can cause erroneous prediction of the circulation and of the organized convection. This case shows clearly that sensitivity to sparse data is a strong function of the gradients that exist at observation time and other factors such as the associated topographic features and moisture patterns.-Authors"
"6701652286;7102875645;","Sensitivity studies of climate involving changes in CO2 concentration",1979,"10.1016/B978-0-444-41766-4.50012-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84915133672&doi=10.1016%2fB978-0-444-41766-4.50012-6&partnerID=40&md5=87a9b56ce6046f7f6e77db2a8eedccf2","Attempts are made to estimate the temperature changes resulting from increasing the present CO2 concentration by the use of: (a) a one-dimensional radiative convective equilibrium model and, (b) a simplified three-dimensional general circulation model. The following assumptions are made in the 3-D model: a limited computational domain, an idealized topography, zero surface heat capacity, no heat transport by ocean currents and an annual mean insolation. In general, the CO2 increase raises the temperature of the model troposphere, whereas, it lowers that of the model stratosphere for both the 1-D and 3-D models. It is found that the tropospheric warming is somewhat larger for the 3-D model as compared with that obtained from the 1-D radiative convective equilibrium model. In particular, the increase of surface temperature in the 3-D model in high latitudes is magnified due to the recession of the snow boundary and the thermal stability of the lower troposphere which limits convective heating to the lowest layer. It is also found that increasing the CO2 concentration significantly increases the overall intensity of the hydrologic cycle of the 3-D model. However, this does not necessarily imply the increase of wetness everywhere in the model region. In particular, the sign of wetness change depends upon the geographical location within the model domain. © 1979, Elsevier Scientific Publishing Company."
"6506994719;7004534048;","The vertical thermal structure of the Martian atmosphere: Modification by motions",1973,"10.1016/0019-1035(73)90179-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-49549169214&doi=10.1016%2f0019-1035%2873%2990179-6&partnerID=40&md5=92841b25459b98c051d3d464b6a05a88","The discrepancy between observations of the Martian atmospheric thermal structure and the radiative-convective equilibrium theory is considered and three processes that could account for this difference are analyzed. Baroclinic waves tend to redistribute heat in the atmosphere in such a way as to raise the temperature in the middle portion while lowering the temperature above and below. A further drop in the mean temperature high up in the atmosphere (above about 25km) may result from the existence of vertical motions due to the nonlinear nature of the cooling law. Finally, heat can be redistributed on the average when the amplitude of vertical motions varies with altitude.,. © 1973."
"26649925100;57158381300;57192591629;","Diurnal self-aggregation",2020,"10.1038/s41612-020-00132-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088789558&doi=10.1038%2fs41612-020-00132-z&partnerID=40&md5=eb6df21f68653e4cde0c137faa1111a7","Convective self-aggregation is a modelling paradigm for convective rain cell organisation over a constant-temperature tropical sea surface. This set-up can give rise to cloud clusters developing over timescales of weeks. In reality, sea-surface temperatures do oscillate diurnally, affecting the atmospheric state and influencing rain rates significantly. Over land, surface temperatures vary more strongly. Here, we carry out a suite of cloud-resolving numerical experiments, and find that qualitatively different dynamics emerge from modest surface temperature oscillations: while the spatial distribution of rainfall is homogeneous during the first day, already on the second day, the rain field is firmly structured. In later days, this clustering becomes stronger and alternates from day to day. We show that these features are robust to changes in resolution, domain size and mean surface temperature, but can be removed by a reduction of the amplitude of diurnal surface temperature oscillation, suggesting a transition from a random to a clustered state. Maximal clustering occurs at a scale of lmax≈180km, which we relate to the emergence of mesoscale convective systems. At lmax, rainfall is strongly enhanced and far exceeds the rainfall expected at random. Simple conceptual modelling helps interpret the transition to clustering, which is driven by the formation of mesoscale convective systems, and brings about day-to-day moisture oscillations. Our results may help clarify how continental extremes build up, and how cloud clustering over the tropical ocean could emerge as an instance of spontaneous symmetry breaking at timescales much faster than in conventional radiative–convective equilibrium self-aggregation. © 2020, The Author(s)."
"57204951554;8678477400;57204956184;57204954945;8879755400;","Assessment of MPAS variable resolution simulations in the grey-zone of convection against WRF model results and observations: An MPAS feasibility study of three extreme weather events in Europe",2020,"10.1007/s00382-018-4562-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058074324&doi=10.1007%2fs00382-018-4562-z&partnerID=40&md5=fa7fdf06a66920f0a78a4daa034c8151","Regional weather forecasting models like the Weather Research and Forecasting (WRF) model allow for nested domains to save computational effort and provide detailed results for mesoscale weather phenomena. The sudden resolution change by nesting may cause artefacts in the model results. On the contrary, the novel global Model for Prediction Across Scales (MPAS) runs on Voronoi meshes that allow for smooth resolution transition towards the desired high resolution in the region of interest. This minimises the resolution-related artefacts, while still saving computational effort. We evaluate the MPAS model over Europe focussing on three mesoscale weather events: a synoptic gale over the North Sea, a föhn effect in Switzerland, and a case of organised convection with hail over the Netherlands. We use four different MPAS meshes (60 km global refined to-3 km (60– 3 km), analogous 30–3 km, 15–3 km, global 3 km) and compare their results to routine observations and a WRF setup with a single domain of 3 km grid spacing. We also discuss the computational requirements for the different MPAS meshes and the operational WRF setup. In general, the MPAS 3 km and WRF model results correspond to the observations. However, a global model at 3 km resolution as a replacement for WRF is not feasible for operational use. More importantly, all variable-resolution meshes employed in this study show comparable skills in short-term forecasting within the high-resolution area at considerably lower computational costs. © 2018, The Author(s)."
"57217222742;26649925100;","Cold Pools as Conveyor Belts of Moisture",2020,"10.1029/2020GL087319","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086801132&doi=10.1029%2f2020GL087319&partnerID=40&md5=4e91ca86d18c4666f8df0f1f8627526a","Observations and simulations have found convective cold pools to trigger and organize subsequent updrafts by modifying boundary layer temperature and moisture as well as by lifting air parcels at the outflow boundaries. We study the causality between cold pools and subsequent deep convection in idealized large-eddy simulations by tracking colliding outflow boundaries preceding hundreds of deep convection events. When outflow boundaries collide, their common front position remains immobile, whereas the internal cold pool dynamics continues for hours. We analyze how this dynamics “funnels” moisture from a relatively large volume into a narrow convergence zone. We quantify moisture convergence and separate the contribution from surface fluxes, which we find to play a secondary role. Our results highlight that dynamical effects are crucial in triggering convection, even in radiative-convective equilibrium. However, it is the low-level convergence resulting from this dynamics that removes inhibition, moistens the atmosphere aloft, and ultimately permits deep convection. ©2020. American Geophysical Union. All Rights Reserved."
"57217417712;55717244800;57208660400;","Lagrangian Analysis of Tropical Cyclone Genesis Simulated by General Circulation Models Compared with Observations",2020,"10.1175/JCLI-D-19-0586.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087200604&doi=10.1175%2fJCLI-D-19-0586.1&partnerID=40&md5=9bfa64c41e569a79c1be5741391ef6a6","As a contribution to understanding the genesis of tropical cyclones (TCs), we compared TC genesis processes simulated by the Seoul National University Atmosphere Model version 0 with a Unified Convection Scheme (SAM0) and the Community Atmosphere Model version 5 (CAM5) with those from the ERA-Interim reanalysis (ERA-Interim, hereafter ERAI) and best track observations. In contrast to previous studies that estimated the TC genesis potential using the Eulerian mean environmental conditions, we calculated the probability of a pre-existing weak cyclonic embryo vortex (EV) developing into a TC by analyzing changes in the environmental conditions along the EV trajectories. Our analysis indicates that the spatial distribution and annual cycles of TCs obtained from the SAM0 and ERAI are similar to those obtained from the best track observation data. With the exception of the mesoscale convective organization and associated variables, most environmental variables along the trajectories of DEVs (EVs developing into TCs) showed monotonic variations. When EVs were born, environmental conditions of DEVs were significantly different from those of nondeveloping EVs, allowing for the prediction of TC genesis. In general, TC genesis probability increased as the environment became more cyclonic, moist, unstable, and with a weaker wind shear. Rapidly strengthening EVs were more likely to develop into TCs. SAM0 and ERAI have the same combination of environmental variables with the best prediction skill for TC genesis-absolute vorticity at 850 hPa, column saturation deficit, sea surface temperature, vertical shear of horizontal winds between 200 and 850 hPa, and latitude-with similar sensitivities to individual environmental variables, indicating that SAM0 well simulates the observed TC genesis processes. © 2020 American Meteorological Society. All rights reserved."
"57216924311;16644246500;","Tropical Cyclogenesis From Self-Aggregated Convection in Numerical Simulations of Rotating Radiative-Convective Equilibrium",2020,"10.1029/2019MS002020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085304153&doi=10.1029%2f2019MS002020&partnerID=40&md5=433d983db63f0273c16cb7658456234a","In a modeled environment of rotating radiative-convective equilibrium (RCE), convective self-aggregation may take the form of spontaneous tropical cyclogenesis. We investigate the processes leading to tropical cyclogenesis in idealized simulations with a three-dimensional cloud-permitting model configured in rotating RCE, in which the background planetary vorticity is varied across f-plane cases to represent a range of deep tropical and near-equatorial environments. Convection is initialized randomly in an otherwise homogeneous environment, with no background wind, precursor disturbance, or other synoptic-scale forcing. We examine the dynamic and thermodynamic evolution of cyclogenesis in these experiments and compare the physical mechanisms to current theories. All simulations with planetary vorticity corresponding to latitudes from 10°–20° generate intense tropical cyclones, with maximum wind speeds of 80 m s−1 or above. Time to genesis varies widely, even within a five-member ensemble of 20° simulations, indicating large stochastic variability. Shared across the 10°–20° group is the emergence of a midlevel vortex in the days leading to genesis, which has dynamic and thermodynamic implications on its environment that facilitate the spin-up of a low-level vortex. Tropical cyclogenesis is possible in this model at values of Coriolis parameter as low as that representative of 1°. In these experiments, convection self-aggregates into a quasicircular cluster, which then begins to rotate and gradually strengthen into a tropical storm, aided by strong near-surface inflow that is already established days prior. Other experiments at these lower Coriolis parameters instead self-aggregate into a nonrotating elongated band and fail to undergo cyclogenesis over the 100-day simulation. ©2020. The Authors."
"35509639400;57204833386;49664027700;7201504886;","Sugar, Gravel, Fish, and Flowers: Dependence of Mesoscale Patterns of Trade-Wind Clouds on Environmental Conditions",2020,"10.1029/2019GL085988","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083484048&doi=10.1029%2f2019GL085988&partnerID=40&md5=ff264d32716d7a34346cadf0bb8893dc","Trade-wind clouds exhibit a large diversity of spatial organizations at the mesoscale. Over the tropical western Atlantic, a recent study has visually identified four prominent mesoscale patterns of shallow convection, referred to as flowers, fish, gravel, and sugar. We show that these four patterns can be identified objectively from satellite observations by analyzing the spatial distribution of infrared brightness temperatures. By applying this analysis to 19 years of data, we examine relationships between cloud patterns and large-scale environmental conditions. This investigation reveals that on daily and interannual timescales, the near-surface wind speed and the strength of the lower-tropospheric stability discriminate the occurrence of the different organization patterns. These results, combined with the tight relationship between cloud patterns, low-level cloud amount, and cloud-radiative effects, suggest that the mesoscale organization of shallow clouds might change under global warming. The role of shallow convective organization in determining low-cloud feedback should thus be investigated. ©2020. The Authors."
"57196437869;7006698304;55469523400;","Assessing Convective Organization in Tropical Radar Observations",2020,"10.1029/2019JD031801","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083382183&doi=10.1029%2f2019JD031801&partnerID=40&md5=950b35c9df10aca29f7402b3439021ac","The spatial organization of deep moist convection is known to be an important determinant of the impacts of severe weather, while future changes to convective organization have been linked to various radiative feedbacks under climate warming. Yet there is no unanimously agreed upon definition of convective organization and so there is also no obvious way to objectively define it. In this work, we set out to define a metric for convective organization based on the size and proximity of convectively active regions. The metric is developed based upon tropical radar observations and takes two-dimensional convective objects, which are predefined in a horizontal plane, as input. We call the metric Radar Organization Metric (ROME). In addition to the proximity of different convective objects, which is used in other organization metrics, ROME is also sensitive to object size. As a result, ROME is also defined for the case of only one convective object. Thus, ROME provides a smoothly evolving measure of the degree of convective organization, which compares well to a visual assessment of the convective objects. ROME is found to be sensitive to different regimes of the North Australian monsoon, and its average diurnal cycle is coherent with the daily evolution of tropical rainfall. Through its dependence on area, ROME adds new capabilities that other metrics lack in measuring the degree of convective organization. In particular, ROME permits quantification of the individual contributions of the object size distribution and the spatial clustering of objects to the overall degree of convective organization. ©2020. The Authors."
"34976226000;","Diurnal cycle of the Asian summer monsoon: Air pump of the second kind",2020,"10.1175/JCLI-D-19-0210.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081170952&doi=10.1175%2fJCLI-D-19-0210.1&partnerID=40&md5=db73558f39eb9c31840b67aaa4848b49","Diurnal variations of rainfall and winds are pronounced over the Asian summer monsoon region, but their activities under different monsoon conditions are not clarified. Here, the diurnal cycle of monsoon flow and its influence are examined using 20-yr satellite rainfall and reanalysis data. A total of 1840 summer days are partitioned into four dynamic groups of strong or weak background flows with large or small diurnal amplitudes of low-level meridional wind. Large-scale southerly wind is found to be strongest after midnight, with a large diurnal amplitude on strong monsoon days over central-north India and southeast China. Such a nocturnal speed-up is closely associated with the Blackadar boundary layer inertial oscillation due to the diurnal heating over low-lying landmass. It acts like a large air pump that injects moisture poleward at night and strengthens monsoonal circulation with anomalous rising motion at the northern rainband of the Asian monsoon. In particular, monsoon southerlies with large nighttime speed-up converge with downslope winds from the Himalayas or northerly anomaly from midlatitudes. Enhanced water vapor convergence facilitates the growth of organized convection, producing substantial rainfall at the Himalayan foothills in predawn hours and at the mei-yu–baiu zone from predawn to noon. When monsoon flow undergoes a small diurnal cycle, rainfall is instead displaced south and mostly recorded in daytime. Both the daily mean and morning peak of rainfall are suppressed on land under weak monsoon southerlies. Moreover, the monsoon diurnal cycle exhibits evident intraseasonal/interannual variations and contributes to rainfall variability. The results highlight that monsoon flow couples with subdaily forcings to strongly regulate the detailed patterns of rainfall and moisture budget over the Asian monsoon regions. © 2020 American Meteorological Society."
"7201431739;","Shallow convective closure in a spectral cumulus parameterization",2020,"10.1016/j.atmosres.2019.104707","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85073634708&doi=10.1016%2fj.atmosres.2019.104707&partnerID=40&md5=cf9fa3cc4f4991b2c111ac2a3309f9e3","A shallow convective closure (shallow closure) was introduced in a spectral cumulus parameterization (spectral scheme), and the validity was evaluated using an atmospheric general circulation model (AGCM) and Atmospheric Model Intercomparison Project (AMIP) experiments. The spectral scheme with shallow closure improved model simulated climatology and variability as compared with the spectral scheme only. The shallow closure enhanced shallow convection, leading to an improvements in dry bias in the tropics and cold bias in the extratropics. The simulated interannual variabilities were comparable regardless of the shallow closure; however, intraseasonal variability was greatly improved with the shallow closure. This is because detrainment from shallow convection during development of the Madden-Julian oscillation (MJO) contributes to supplying moisture in organized convection, and the spectral scheme with shallow closure was able to simulate this contribution well. © 2019 The Author"
"16636807900;6506539438;","On the cooling-to-space approximation",2020,"10.1175/JAS-D-18-0352.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082883555&doi=10.1175%2fJAS-D-18-0352.1&partnerID=40&md5=f7161ffd58379128b85b16bef25934d9","The cooling-to-space (CTS) approximation says that the radiative cooling of an atmospheric layer is dominated by that layer’s emission to space, while radiative exchange with layers above and below largely cancel. Though the CTS approximation has been demonstrated empirically and is thus fairly well accepted, a theoretical justification is lacking. Furthermore, the intuition behind the CTS approximation cannot be universally valid, as the CTS approximation fails in the case of pure radiative equilibrium. Motivated by this, we investigate the CTS approximation in detail. We frame the CTS approximation in terms of a novel decomposition of radiative flux divergence, which better captures the cancellation of exchange terms. We also derive validity criteria for the CTS approximation, using simple analytical theory. We apply these criteria in the context of both gray gas pure radiative equilibrium (PRE) and radiative–convective equilibrium (RCE) to understand how the CTS approximation arises and why it fails in PRE. When applied to realistic gases in RCE, these criteria predict that the CTS approximation should hold well for H2O but less so for CO2, a conclusion we verify with line-by-line radiative transfer calculations. Along the way we also discuss the well-known ‘‘t 5 1 law,’’ and its dependence on the choice of vertical coordinate. © 2020 American Meteorological Society."
"56272964700;6602908667;","Response of precipitation extremes to warming: what have we learned from theory and idealized cloud-resolving simulations, and what remains to be learned?",2020,"10.1088/1748-9326/ab7130","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082671320&doi=10.1088%2f1748-9326%2fab7130&partnerID=40&md5=f838420f560e0ba88f1fb6c8bed45542","This paper reviews recent important advances in our understanding of the response of precipitation extremes to warming from theory and from idealized cloud-resolving simulations. A theoretical scaling for precipitation extremes has been proposed and refined in the past decades, allowing to address separately the contributions from the thermodynamics, the dynamics and the microphysics. Theoretical constraints, as well as remaining uncertainties, associated with each of these three contributions to precipitation extremes, are discussed. Notably, although to leading order precipitation extremes seem to follow the thermodynamic theoretical expectation in idealized simulations, considerable uncertainty remains regarding the response of the dynamics and of the microphysics to warming, and considerable departure from this theoretical expectation is found in observations and in more realistic simulations. We also emphasize key outstanding questions, in particular the response of mesoscale convective organization to warming. Observations suggest that extreme rainfall often comes from an organized system in very moist environments. Improved understanding of the physical processes behind convective organization is needed in order to achieve accurate extreme rainfall prediction in our current, and in a warming climate. © 2020 The Author(s). Published by IOP Publishing Ltd."
"7403282069;7407116104;7403531523;","Convective Aggregation and Indices Examined from CERES Cloud Object Data",2019,"10.1029/2019JD030816","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076753083&doi=10.1029%2f2019JD030816&partnerID=40&md5=a15237fdfe42d3e54c2c84f0e1ee922e","Convective aggregation is a self-aggregation phenomenon appearing in idealized radiative-convective equilibrium simulations under constant, uniform sea surface temperature (SST). To gain an understanding of observed convective aggregation or organization, three metrics, i.e., simple convective aggregation index (SCAI), modified SCAI (MCAI), and convective organization potential (COP), are evaluated with cloud object data from CERES. MCAI is related to object sizes through a modified inter-object distance (IOD). It is found that large-size object groups are less aggregated according to SCAI but more organized according to COP, compared to small-size object groups. The opposite sensitivities to object-group size can be explained by the dominant roles of the IOD in SCAI and the sum of object radii in COP as object-group sizes increase. However, large-size object groups are slightly more aggregated than small-size ones according to MCAI. Both SCAI and MCAI increase with the number of cloud objects (N) in an object group but COP has a weak dependency on N. Further sorting by object-group total area shows that sensitivity of MCAI to object-group area agrees with that of SCAI for small-area ranges but with that of COP for large-area ranges, which is related to the weak sensitivity of the modified IOD to object-group area, as compared to that of the original IOD. Finally, the three metrics show the similar contrasts between continental and oceanic convection and the same weak sensitivity to SST. The latter suggests that self-aggregation is weaker at higher SSTs than at lower SSTs, in contrast to the findings of many simulations. Published 2019. This article is a U.S. Government work and is in the public domain in the USA."
"57194698592;15724418700;43860918700;","Ozone Transport-Radiation Feedbacks in the Tropical Tropopause Layer",2019,"10.1029/2019GL084679","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076834069&doi=10.1029%2f2019GL084679&partnerID=40&md5=b98d718490c2c28336bde69038fd9ca8","The tropical tropopause layer (TTL) temperature balance is of considerable interest for its control over the amount of water entering the stratosphere. The upwelling branch of the Brewer-Dobson circulation (BDC) directly affects these temperatures through adiabatic cooling. BDC upwelling also indirectly affects TTL temperatures through the influence of ozone transport on radiative heating. We investigate this latter feedback using a single-column radiative-convective equilibrium model coupled with a model of simplified stratospheric ozone chemistry and vertical transport. We find that BDC ozone transport is of first-order importance for TTL temperatures. Additionally, we estimate the effect of ozone transport on cold point tropopause temperature responses to changes in upwelling. We find that the feedback is responsible for approximately 20% of the response to perturbations on time scales longer than about half a year but that this contribution can be neglected for time scales shorter than about a week. ©2019. American Geophysical Union. All Rights Reserved."
"57209286045;11939918300;","Convection On the Edge",2019,"10.1029/2019MS001820","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076366489&doi=10.1029%2f2019MS001820&partnerID=40&md5=4f9e837dae0720fcf313601ba07f2517","Deep convection over tropical oceans often appears intensified at the edge of convectively active regions, both in idealized studies and in observations. This edge intensification of convection is studied in detail here, using the steady state of a radiative-convective equilibrium study, marked by a single convective cluster with deep convection intensified at the edge of this cluster. The cause for edge intensification and its dependence on the cluster area is investigated by comparing the spatial distribution of deep convection to different variables known to be important for convection. Analysis of the simulation suggests that the edge is marked by an increased probability for the triggering of convection rather than by stronger updrafts. In particular, while the edge of the moist region is not thermodynamically more favorable, we find strong surface convergence and therefore dynamical lifting at this edge. The surface convergence is shown to result from two opposing flows. On the one hand, there is, as expected from previous radiative-convective equilibrium simulations, a low-level inflow directed toward the moist region. On the other hand, there is a positive density anomaly at the surface which is the result of continuously forming cold pools within the convectively active region, creating a super-cold-pool. As the velocity of the low-level inflow approximately matches the potential propagation speed of the super-cold-pool boundary, these opposing flows explain the presence of strong convergence at the edge of this region. Whether the resulting lifting induces the formation of deep convection is shown to depend on the large-scale instability. ©2019. The Authors."
"57196195795;23096635200;","Collapse of the General Circulation in Shortwave-Absorbing Atmospheres: An Idealized Model Study",2019,"10.3847/2041-8213/ab4c43","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075312895&doi=10.3847%2f2041-8213%2fab4c43&partnerID=40&md5=6929b0f54c69c4aaf8542291bd4c977a","The response of the general circulation in a dry atmosphere to various atmospheric shortwave absorptivities is investigated in a three-dimensional general circulation model with gray radiation. Shortwave absorption in the atmosphere reduces the incoming radiation reaching the surface but warms the upper atmosphere, significantly shifting the habitable zone toward the star. The strong stratification under high shortwave absorptivity suppresses the Hadley cell in a manner that matches previous Hadley cell scalings. General circulation changes may be observable through cloud coverage and superrotation. The equatorial superrotation in the upper atmosphere strengthens with the shortwave opacity, as predicted based on the gradient wind of the radiative-convective equilibrium profile. There is a sudden drop of equatorial superrotation at very low shortwave opacity. This is because the Hadley cell in those cases are strong enough to fill the entire troposphere with zero momentum air from the surface. A diurnal cycle (westward motion of substellar point relative to the planet) leads to acceleration of the equatorial westerlies in general, through the enhancement of the equatorward eddy momentum transport, but the response is not completely monotonic, perhaps due to the resonance of tropical waves and the diurnal forcing. © 2019. The American Astronomical Society. All rights reserved."
"57211602898;55713076400;","The Role of Interactive SST in the Cloud-Resolving Simulations of Aggregated Convection",2019,"10.1029/2019MS001762","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074557734&doi=10.1029%2f2019MS001762&partnerID=40&md5=9553e137916373f207a7ba5e1c44c784","This study investigates the role of interactive sea surface temperature (SST) in the early development of aggregated convection using a vector vorticity equation cloud-resolving model coupled to a slab ocean. The simulations are initialized by a mock Walker circulation driven by initial SST gradient in the elongated x axis, with an average of 300 K and sinusoidal variation of amplitude ranging from 1.5 to 3 K. According to large-scale perturbation strength, which is caused by SST variation, the results can be divided into two groups. Under weak perturbation, convection-SST feedback efficiently eliminates SST gradient and moisture anomaly. The large-scale environment is homogenized within 2 days. Even though SST in the group with stronger perturbation undergoes a similar process, significant moist static energy (MSE) advection in the boundary produces enough moisture difference to introduce virtual temperature effect and aggregation is triggered. Once dry zone starts to expand, radiative and convective effects regenerate SST gradient, which intensifies circulation and accelerates the process. We further show that the evolution of aggregation or not is captured by the trend of MSE-EIS (estimated inversion strength) variance. The results highlight the boundary layer processes on the formation of aggregated convection in the tropics. © 2019. The Authors."
"57208394173;24398842400;","Aerosol-Cloud-Precipitation Interactions in the Context of Convective Self-Aggregation",2019,"10.1029/2018MS001523","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064667146&doi=10.1029%2f2018MS001523&partnerID=40&md5=f109b1a6953190bb624601fcd5a9ece9","We investigate the sensitivity of self-aggregated radiative-convective-equilibrium cloud-resolving model simulations to the cloud condensation nuclei (CCN) concentration. Experiments were conducted on a long (2,000-km × 120-km) channel domain, allowing the emergence of multiple convective clusters and dry regions of subsidence. Increasing the CCN concentration leads to increased moisture in the dry regions, increased midlevel and upper level clouds, decreased radiative cooling, and decreased precipitation. We find that these trends follow from a decrease in the strength of the self-aggregation as measured by the moist static energy (MSE) variance. In our simulations, precipitation is correlated, both locally and in total, with the distribution of MSE anomalies. We thus quantify changes in the adiabatic/diabatic contributions to MSE anomalies (Wing & Emanuel, 2014, https://doi.org/10.1002/2013MS000269) and relate those changes to changes in precipitation. Through a simple two-column conceptual model, we argue that the reduction in precipitation can be explained thermodynamically by the reduction in mean net radiative cooling and mechanistically by the weakening of the area-weighted radiatively driven subsidence velocity—defined as the ratio of the total radiative cooling over the dry regions and the static stability. We interpret the system's response to increasing CCN as a thermodynamically constrained realization of an aerosol indirect effect on clouds and precipitation. ©2019. The Authors."
"56810508600;7003926380;","Tropical Oceanic Thunderstorms Near Kwajalein and the Roles of Evolution, Organization, and Forcing in Their Electrification",2019,"10.1029/2018JD029320","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060207702&doi=10.1029%2f2018JD029320&partnerID=40&md5=12de8ea0271ad837b9d2c9d2fc66481a","We explore the physical reasons behind the pronounced contrast in the probability of lightning over land and ocean. For decades, from a multitude of platforms, it has been observed that lightning is much rarer over the ocean, and throughout the literature, many have offered physical and environmental hypotheses to explain this dichotomy. Focusing on the tropical oceans, we apply a new ground-based approach using feature tracking software to radar data from the Kwajalein atoll in the tropical west Pacific Ocean. As seen in satellite-based approaches in the same region, features with lightning tend to be much larger and persist much longer than those without. Lightning occurs on average 40 min into the tracked life cycle of the features. Within those 40 min, features with lightning exhibit rapid development of layers of high radar reflectivity at and above the freezing level, as would be consistent with electrification. Traditional environmental parameters, such as convective available potential energy or total column water vapor, show only weak relationships to the probability of the features to develop lightning or to grow to large sizes, until the probabilities are examined on daily time scales and on larger (synoptic) spatial scales. We present an environmental and evolutionary case study over Kwajalein, and within a longer time frame and within a synoptic forcing context, convective organization appears to play a role in the development of deep oceanic precipitating features and their tendency to become sufficiently strong as to develop lightning. ©2019. American Geophysical Union. All Rights Reserved."
"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."
"57171236300;57202301596;","A conceptual spectral plume model for understanding tropical temperature profile and convective updraft velocities",2019,"10.1175/JAS-D-18-0330.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075636173&doi=10.1175%2fJAS-D-18-0330.1&partnerID=40&md5=cbc89d00f85425439326b74b0b427812","The tropical tropospheric temperature is close to but typically cooler than that of the moist adiabat. The negative temperature deviation from the moist adiabat manifests a C-shape profile and is projected to increase and stretch upward under warming in both comprehensive climate models and idealized radiative–convective equilibrium (RCE) simulations. The increased temperature deviation corresponds to a larger convective available potential energy (CAPE) under warming. The extreme convective updraft velocity in RCE increases correspondingly but at a smaller fractional rate than that of CAPE. A conceptual model for the tropical temperature deviation and convective updraft velocities is formulated to understand these features. The model builds on the previous zero-buoyancy model but replaces the bulk zero-buoyancy plume by a spectrum of entraining plumes that have distinct entrainment rates and are positively buoyant until their levels of neutral buoyancy. Besides the negative temperature deviation and its increasing magnitude with warming, this allows the spectral plume model to further predict the C-shape profile as well as its upward stretch with warming. By representing extreme convective updrafts as weakly entraining plumes, the model is able to reproduce the smaller fractional increase in convective velocities with warming as compared to that of CAPE. The smaller fractional increase is mainly caused by the upward stretch in the temperature deviation profile with warming, which reduces the ratio between the integrated plume buoyancy and CAPE. The model thus provides a useful tool for understanding the tropical temperature profile and convective updraft velocities. © 2019 American Meteorological Society."
"25823623500;34972803800;55332289000;7003554893;7202748672;7201398636;55311451800;7005868133;6505903827;14920137300;7003408439;","Convectively coupled equatorial wave simulations using the ECMWF IFS and the NOAA GFS cumulus convection schemes in the NOAA GFS model",2019,"10.1175/MWR-D-19-0195.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075635856&doi=10.1175%2fMWR-D-19-0195.1&partnerID=40&md5=490b69a5357b6f697df0000217f46262","There is a longstanding challenge in numerical weather and climate prediction to accurately model tropical wave variability, including convectively coupled equatorial waves (CCEWs) and the Madden–Julian oscillation. For subseasonal prediction, the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS) has been shown to be superior to the NOAA Global Forecast System (GFS) in simulating tropical variability, suggesting that the ECMWF model is better at simulating the interaction between cumulus convection and the large-scale tropical circulation. In this study, we experiment with the cumulus convection scheme of the ECMWF IFS in a research version of the GFS to understand which aspects of the IFS cumulus convection scheme outperform those of the GFS convection scheme in the tropics. We show that the IFS cumulus convection scheme produces significantly different tropical moisture and temperature tendency profiles from those simulated by the GFS convection scheme when it is coupled with other physics schemes in the GFS physics package. We show that a consistent treatment of the interaction between parameterized convective plumes in the GFS planetary boundary layer (PBL) and the IFS convection scheme is required for the GFS to replicate the tropical temperature and moisture profiles simulated by the IFS model. The GFS model with the IFS convection scheme, and the consistent treatment between the convection and PBL schemes, produces much more organized convection in the tropics, and generates tropical waves that propagate more coherently than the GFS in its default configuration due to better simulated interaction between low-level convergence and precipitation. © 2019 American Meteorological Society."
"35572026100;7006095466;","Convective organization in evolving large-scale forcing represented by a highly truncated numerical archetype",2018,"10.1175/JAS-D-17-0372.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050961864&doi=10.1175%2fJAS-D-17-0372.1&partnerID=40&md5=712c13814341532c62137f3772773679","Considered as a prognostic generalization of mass-flux-based convection parameterization, the highly truncated nonhydrostatic anelastic model with segmentally constant approximation (NAM-SCA) is tested with time-evolving large-scale forcing. The 20-day GATE Phase III period is taken as a major data source. The main advantage of the NAM-SCA parameterization is consistency with subgrid-scale dynamics as represented by the nonhydrostatic anelastic formulation. The approach explicitly generates important dynamical structures of convection (e.g., mesoscale circulations, cold pools) spontaneously without further tuning or treatment as additional subcomponents. As with other convection parameterizations, the numerical simulation of the precipitation rate, the apparent heat source, and the apparent moisture sink is straightforward and reasonably insensitive to the numerical procedures. However, convective momentum transport by organized convection turns out to be difficult even with NAM-SCA, especially for the inherently three-dimensional shear-parallel systems. Modifications of NAM-SCA regarding the large-scale forcing formulation improves the mesoscale momentum transport. Simulation of the full 120-day TOGA COARE period demonstrates the performance of NAM-SCA in different meteorological conditions and its capacity to operate over a longer time period. © 2018 American Meteorological Society."
"57204430398;9249605700;","Diurnal variation of simulated cumulus convection in radiative-convective equilibrium",2018,"10.2151/SOLA.2018-020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055518401&doi=10.2151%2fSOLA.2018-020&partnerID=40&md5=ad3cc165955b2afec93aeb7f49fdc7e7","This study investigates the representation of the diurnal variation of cumulus convection in radiative-convective equilibrium states in an area of 200 km by 200 km without large-scale forcing by using a non-hydrostatic model with sub-kilometer horizontal resolutions. The experiment with the horizontal resolution of 200 m successfully reproduced the diurnal variability of the trimodal characteristics of cumulus convection. We demonstrated that the horizontal resolution dependence largely affects the trimodal structure of clouds and the characteristics of precipitation and its diurnal variation. With the coarse resolution of 1600 m, a signature of convective aggregation appeared and the diurnal variation of convection was not clearly seen. We further examined the mechanisms for the diurnal variation of cumulus convection by focusing on the temporal and vertical variations of radiative and latent heating anomalies. The diurnal variability of the static stability caused by both radiative and latent heating plays a role in characterizing the diurnal variation of the cumulus convection. © The Author(s) 2018."
"57212000722;36704804900;6508349802;6701416377;24554420100;","An investigation of long-term changes in rainfall over the equatorial Indian Ocean trough region during northern summer using multisatellite data",2016,"10.1007/s00704-015-1406-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923250599&doi=10.1007%2fs00704-015-1406-1&partnerID=40&md5=30c9b12fbddd5483f1e231b083fff754","During the Indian monsoon season, organized convection in the form of inter-tropical convergence zone (ITCZ) originates from the equatorial trough (ET) region over the equatorial Indian Ocean, propagates northward towards the heated Indian landmass at intraseasonal timescales (30–60 days). In this paper, the long-term changes in rainfall over the ET region during the northern summer season has been investigated for a 34-year (1979–2012) period using gauge-adjusted multisatellite Global Precipitation Climatology Project (GPCP) rainfall data set. Rainfall over this region shows a pronounced seasonality and the eastern ET (EET) receives higher rainfall than the western ET (WET) during the northern summer season. Moreover, the northern summer rainfall over the WET and EET are not significantly correlated with each other. Linear trend analysis of domain-mean seasonal rainfall shows a statistically significant increasing trend of 0.4 mm day−1 decade−1 during the northern summer over the WET, whereas no significant trend is observed over the EET. The long-term changes in the associated variables linked through the moisture budget equation are also examined over both regions of ET for the study period. Even though evaporation over both WET and EET shows statistically significant increasing trend associated with an increase in sea surface temperature and near-surface wind, the vertically integrated moisture convergence shows no significant change over the WET whereas it shows a decrease over the EET during the study period. These might be the possible reasons behind a significant increase in rainfall over the WET with an insignificant change in rainfall over the EET. © 2015, Springer-Verlag Wien."
"56919030400;7403128993;7101661890;","5-day-wave interactions with tropical precipitation in CMIP5 models",2016,"10.1175/JCLI-D-16-0190.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84996937963&doi=10.1175%2fJCLI-D-16-0190.1&partnerID=40&md5=7bb8de9c3b76ef98999dd8cfb67e5aec","The 5-day Rossby-Haurwitz wave is unlike other large-scale wave modes that interact with tropical rainfall in that associated rainfall presents as a modulation of localized areas of rainfall instead of propagating with the wave. This form of wave-modulated convective organization in climate models has received little attention. This study investigates the simulation of interactions between the 5-day wave and tropical convection in 30 models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) and compares these with the interaction diagnosed from ERA-Interim and TRMM precipitation data. Models simulate the dry dynamics of the 5-day wave well, with realistic coherences between upper- and lower-tropospheric winds, as well as magnitudes and geographic distribution of wave wind anomalies being close to observations. The models consistently display significant coherences between 5-day-wave zonal winds and precipitation but perform less well at simulating the spatial distribution and magnitude of precipitation anomalies. For example, a third of the models do not reproduce significant observed anomalies near the Andes, and the best-performing model simulates only 38% of the observed variance over the tropical Andes and 24% of the observed variance over the Gulf of Guinea. Models with higher resolution perform better in simulating the magnitude of the Andean rainfall anomalies, but there is no similar relationship over the Gulf of Guinea. The evidence therefore suggests that the simulated interaction is mostly one way only, with the wave dynamics forcing the precipitation variations on the 5-day time scale. © 2016 American Meteorological Society."
"55709582600;","Variability of oceanic deep convective system vertical structures observed by CloudSat in Indo-Pacific regions associated with the Madden-Julian oscillation",2016,"10.1002/2016JD025262","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84988372963&doi=10.1002%2f2016JD025262&partnerID=40&md5=fe6a5a1a4b3e3bb3ff8b7295b368256c","Vertical structures of deep convective systems during the Madden-Julian oscillation (MJO) are investigated using CloudSat radar measurements in Indo-Pacific oceanic areas. In active phases of the MJO, relatively more large systems and connected mesoscale convective systems (CMCSs) occur. The occurrence frequency of CMCSs peaks in the onset phase, a phase earlier than separated mesoscale convective systems (SMCSs). Compared with SMCSs, CMCSs of all sizes have weaker reflectivity above 8 km in their deep precipitating portions and thick anvil clouds closely linked to them, suggesting more “stratiform” physics associated with them. SMCSs and CMCSs together produce relatively the least anvil clouds in the onset phase, while their deep precipitating portions show stronger/weaker reflectivity above 8 km before/after the onset phase. Thus, after the onset phase of the MJO, mesoscale convective systems shift toward a more “convective” organization because SMCSs maximize after the onset, while their internal structures appear more stratiform because internally they have weaker reflectivity above 8 km. CMCSs coincide with a more humid middle troposphere spatially, even at the same locations a few days before they occur. Middle-tropospheric moistening peaks in the onset phase. Moistening of the free troposphere around deep convective systems shows relatively stronger moistening/drying below 700 hPa before/after the onset phase than domain-mean averages. Low-topped clouds occur most frequently around CMCSs and in active phases, consistent with the presence of a moister free troposphere. Coexistence of these phenomena suggests that the role of middle troposphere moisture in the formation of CMCSs should be better understood. © 2016. American Geophysical Union. All Rights Reserved."
"56184337800;7003718864;","Storm-centered ensemble data assimilation for tropical cyclones",2014,"10.1175/MWR-D-13-00099.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84901639705&doi=10.1175%2fMWR-D-13-00099.1&partnerID=40&md5=7f8a1065356f150a1fa119284a9d9baf","A significant challenge for tropical cyclone ensemble data assimilation is that storm-scale observations tend to make analyses that are more asymmetric than the prior forecasts. Compromised structure and intensity, such as an increase of amplitude across the azimuthal Fourier spectrum, are a routine property of ensemble-based analyses, even with accurate position observations and frequent assimilation. Storm dynamics in subsequent forecasts evolve these states toward axisymmetry, creating difficulty in distinguishing between model-induced and actual storm asymmetries for predictability studies and forecasting. To address this issue, a novel algorithm using a storm-centered approach is proposed. The method is designed for use with existing ensemble filters with little or no modification, facilitating its adoption and maintenance. The algorithm consists of 1) an analysis of the environment using conventional coordinates, 2) a storm-centered analysis using storm-relative coordinates, and 3) a merged analysis that combines the large-scale and storm-scale fields together at an updated storm location. This algorithm is evaluated in two sets of observing system simulation experiments (OSSEs): first, no-cycling tests of the update step for idealized three-dimensional storms in radiative-convective equilibrium; second, full cycling tests of data assimilation applied to a shallow-water model for a field of interacting vortices. Results are compared against a control experiment based on a conventional ensemble Kalman filter (EnKF) scheme as well as an alternative EnKF scheme proposed by Lawson and Hansen. The storm-relative method yields vortices that are more symmetric and exhibit finer inner-core structure than either approach, with errors reduced by an order of magnitude over a control case with prior spread consistent with the National Hurricane Center (NHC)'s mean 5-yr forecast track error at 12 h. Azimuthal Fourier error spectra exhibit much-reduced noise associated with data assimilation as compared to both the control and the Lawson and Hansen approach. An assessment of free-surface height tendency of model forecasts after the merge step reveals a balanced trend between the storm-centered and conventional approaches, with storm-centered values more closely resembling the reference state. © 2014 American Meteorological Society."
"55833115600;36713948500;56023426600;","A numerical study of the evolution of a mesoscale convective vortex on the Meiyu front",2013,"10.1007/s13351-013-0509-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893330378&doi=10.1007%2fs13351-013-0509-9&partnerID=40&md5=97b0b16d31303ba7fb7000e4c4acb995","The Advanced Research WRF (Weather Research and Forecasting) model is used to simulate the evolution of a mesoscale convective vortex (MCV) that formed on the Meiyu front and lasted for more than two days. The simulation is used to investigate the underlying reasons for the genesis, intensification, and vertical expansion of the MCV. This MCV is of a type of mid-level MCV that often develops in the stratiform regions of mesoscale convective systems. The vortex strengthened and reached its maximum intensity and vertical extent (from the surface to upper levels) when secondary organized convection developed within the mid-level circulation. The factors controling the evolution of the kinetic and thermal structure of the MCV are examined through an analysis of the budgets of vorticity, temperature, and energy. The evolution of the local Rossby radius of deformation reveals the interrelated nature of the MCV and its parent mesoscale convective system. © 2013 The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg."
"55993535000;7003345391;6701567335;55036442600;7007155308;","A radiative-convective equilibrium model for young giant exoplanets: Application to β Pictoris b",2013,"10.1017/S1743921313008570","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84891845653&doi=10.1017%2fS1743921313008570&partnerID=40&md5=a1aa7a5dea8d7c919d8ed050b16fa00b","We present a radiative-convective equilibrium model for young giant exoplanets. Model predictions are compared with the existing photometric measurements of the planet β Pictoris b in the J, H, Ks, L', NB 4.05, M' bands. This model will be used to interpret future photometric and spectroscopic observations of exoplanets with SPHERE, mounted at the VLT with a first light expected mid-2014. Copyright © 2013, International Astronomical Union."
"7201605742;","Toward an understanding of tropical cyclone formation with a nonhydrostatic, mesoscale-convection-resolving model",2013,"10.2174/1874282301307010037","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879149468&doi=10.2174%2f1874282301307010037&partnerID=40&md5=8193e7c3eb7de66247fd1f525434fdbd","This paper describes results from numerical experiments which have been made toward a better understanding of tropical cyclone formation. This study uses a nonhydrostatic version of the author's mesoscale-convection-resolving model that was developed in the 1980s to improve paramerization schemes of moist convection. In this study the horizontal grid size is taken to be 20 km in an area of 6,000 km x 3,000 km, and a non-uniform coarse grid is used in two areas to its north and south. Results from two numerical experiments are presented; one (case 1) without any environmental flow, and the other (case 2) with an easterly flow without low-level vertical shear. Three circular buoyancy perturbations are placed in the west-east direction at the initial time. Convection is initiated in the imposed latently unstable (positive CAPE) area. In both cases, a vortex with a pressure low is formed, and two band-shaped convective systems are formed to the north and the south of the vortex center. The vortex and two convective systems are oriented in the westsouthwest - eastnortheast direction, and their horizontal scales are nearly 2,000 km. In case 1, the band-shaped convective system on the southern side is stronger, and winds are stronger just to its south. In contrast, in case 2, the northern convective system is stronger, and winds are stronger just to its north. Therefore, the distributions of the equivalent potential temperature in the boundary layer and latent instability (positive buoyancy of the rising air) are also quite different between cases 1 and 2. The TC formation processes in these different cases are discussed, with an emphasis on the importance of examining the time change of latent instability field. © Masanori Yamasaki; Licensee Bentham Open."
"35572026100;55338948800;7003554893;7005446873;","Bells and whistles of convection parameterization",2013,"10.1175/BAMS-D-12-00118.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873468343&doi=10.1175%2fBAMS-D-12-00118.1&partnerID=40&md5=663282feaa04245a899fc377a9643bdf","The fifth annual series of workshop entitled 'Concepts for Convective Parameterizations in Large-Scale Models' was held in 2012. The purpose of the workshop series has been to discuss the fundamental theoretical issues of convection parameterization with a small number of European scientists. It was funded by the European Cooperation in Science and Technology (COST) Action ES0905. The theme of the workshop for the year 2012 was decided from a main conclusion of the earlier workshop, which focused on the convective organization problem, seeking a means for implementing such effects into convection parameterizations. The participants were informed that the inclusion of mid-troposphere humidity sensitivities into entrainment and detrainment formulations had contributed substantially to the model \improvements. It had significantly contributed to the improvement in prediction of the Madden-Julian oscillation (MJO)."
"6602734863;7003826074;","On baroclinic adjustment of a radiative convective atmosphere",1998,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032416368&partnerID=40&md5=a46d9aa98343db0f17fe7e49bce27db7","In this paper we study the implication of the hypothesis that the radiative convective equilibrium climate is neutral with respect to baroclinic eddies. If such neutral state is achieved by tropopause height readjustment, we find that the sensitivity of the climate equilibrium to baroclinic eddies is comparable to the sensitivity to water vapor profile. Multiple solutions to the readjusted tropopause are found by decreasing stratospheric static stability."
"7201480158;","Effects of physical processes of H2O on the general circulation of the atmosphere; part II",1996,"10.2151/jmsj1965.74.2_221","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038873997&doi=10.2151%2fjmsj1965.74.2_221&partnerID=40&md5=ef7c7b460354a7e520fc27b6b99447de","In Part 1 (Miyoshi and Morita, 1993), we investigated how the general circulation of the atmosphere was affected by all the physical processes of H2O. In this study, we divide all the physical processes of H2O into the radiative process of H2O and the hydrological cycle, and investigate the effect of both of the processes separately by a series of GCM experiments. Results are as follows. The north-to-south temperature gradient and the zonal wind distribution below 5 km height is strongly affected by the radiative process of H2O. The strength of the meridional circulation, the magnitude of the poleward energy transport, the magnitude of the sensible and latent heat fluxes and the magnitude of the diabatic heating rate in the atmosphere also depend on the radiative process of H2O. Thus, the differences of the general circulation between with and without all the physical processes of H2O is mostly caused by the radiative process of H2O. The zonal wind distributions above 5 km height, on the other hand, are affected by not only the radiative process of H2O but also by the hydrological cycle. Numerical experiments using a vertically one-dimensional radiative-convective equilibrium model are performed. By comparing the radiative-convective equilibrium temperature with the temperature in the GCM, the relation between the poleward heat transport by the dynamics and the physical processes of H2O is also examined. In the experiments without the radiative process of H2O, the temperature near the surface in the GCM is almost the same as the radiative-convective temperature. At low latitudes, the temperature difference between the GCM and the radiative-convective model is larger in the experiments with the radiative process of H2O than in the experiments without the radiative process of H2O."
"7403993727;6507796499;","Microphysical characteristics of monsoon clouds and cloud sublayers as revealed by the MONEX aircraft observations",1995,"10.1016/0169-8095(95)00004-B","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029528537&doi=10.1016%2f0169-8095%2895%2900004-B&partnerID=40&md5=51f9ce15578beba03a8e56eadd0c5a8b","The summer monsoon atmosphere was subjected to aerial cloud microphysical measurements by the National Center for Atmospheric Research (NCAR)'s Electra as part of the Arabian Sea component of the Summer Monsoon Experiment (SMONEX). The Particle Measuring System (PMS )'s probes were mounted on these flights. This study documents vertical profiles and concentration counts of aerosols and precipitation size particles for the flights on 20 and 24 June 1979. These flights were selected because the meteorology associated with them was analyzed in detail by several investigators who were interested in the turbulence flux measurements which were unique to these flights. The samples on 20 June were collected mostly underneath clouds except once within a cloud. In contrast, they were gathered exclusively within clouds on 24 June. The observations on these two days were collected in four different locations over the Arabian Sea when organized convection was presented. Results show that the aerosol concentration counts as measured by the ASAS-probe were higher than those expected from measurements in suppressed convective conditions. The ASAS and FSSP readings were nearly constant in the boundary layer. The FSSP readings increased more than ASAS readings with height passing them at elevations greater than 1500 m. Some young clouds with a depth of 1600 m showed maximum updraft values occurring at a certain level (e.g., 1000 m). At this level, a maximum concentration of droplets belonging to a particular size group ( ≈ 15 μm) was found. Thus a positive association was seen between these droplets and the vertical velocity distribution. © 1995."
"7101795549;","A linear stability analysis of stratocumulus convection driven by radiative cooling",1995,"10.3402/tellusa.v47i2.11504","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028812942&doi=10.3402%2ftellusa.v47i2.11504&partnerID=40&md5=449bb0c8e2447436af12b8f362bf046d","Fully cloudy stratocumulus layers sometimes exhibit convective organization at a single dominant length scale with an aspect ratio (width/height) ~ 1. We present a linear stability analysis of a radiatively-cooled cloud beneath a capping inversion and show that small aspect ratio modes are energetically favored over a broad range of inversion strengths and cooling depths. The integrated mode energy budgets indicate that, given a vertically limited region of radiative cooling, highly dissipative, localized convective modes can grow through efficient buoyancy production beneath the inversion. -from Author"
"7202142443;7006083502;","The Third Conference on Mesoscale Processes 20-26 August 1987, Vancouver, B.C., Canada.",1988,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0023798202&partnerID=40&md5=a9eb8e156796470f6fd50667e964d015","Reports on the Third Conference on Mesoscale Processes, held in conjunction with the International Union of Geodesy and Geophysics (IUGG) Meetings. Session topics were: Flow response to prescribed heating and entrainment; Organization of convection on the mesoscale; Boundary layer effects on the mesoscale; Mesoscale convective systems; Convection and mesoscale waves; Mesoscale waves and instabilities; Modelling and parameterization of mesoscale organized convection; Frontal rainbands; Thermally and topographically forced flows; Instruments and techniques for mesoscale analysis; Fronts and cyclones; Frontal circulations; Fronts interacting with topography; Cyclones; Stratiform precipitation and mesovortex development."
"7202298079;7004027377;","Meridional penetration of frontal systems in South America and its relation to organized convection in the Amazon.",1985,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040856408&partnerID=40&md5=fedce6df8a56139b725b350b0eb8891d","The penetration of mid-latitude frontal systems into the tropics and its relation to the enhancement of convective activity over the Amazon was investigated. A five year climatology of frontal activity in South America based on GOES satellite imagery was developed. It showed a large number of episodes in which NW-SE oriented convection cloud bands over the continent seemed to be associated with the front systems to the east for the crustal spring, summer, and autumn. During winter, frontal systems rarely organize convection over the Amazon. The preferred position of the frontal systems and associated convective cloud bands to the west-northwest aid in explaining the observed relative annual precipitation maximum extending from western Amazon to southeastern Brazil and into the South Atlantic. A synoptic case study of a frontal passage indicated that the strengthening and progression to the east-northeast of the upper level trough associated with the frontal system may be related to the enhancement of convective activity over central Brazil and the Amazon. -from STAR, 23(10), 1985"
"7102577095;","Cloud optical thickness feedbacks in the CO2 climate problem",1985,"10.1016/0273-1177(85)90323-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-46549103349&doi=10.1016%2f0273-1177%2885%2990323-0&partnerID=40&md5=c82cfc339ef3de92c51aca246cd1102f","A radiative-convective equilibrium model is developed and applied to study cloud optical thickness feedbacks in the CO2 climate problem. The basic hypothesis is that in the warmer and moister CO2-rich atmosphere, cloud liquid water content will generally be larger than at present, so that cloud optical thickness will be larger too. For clouds other than thin cirrus, the result is to increase the albedo more than to increase the greenhouse effect. Thus the sign of the feedback is negative: cloud optical properties alter in such a way as to reduce the surface and tropospheric warming caused by the addition of CO2. This negative feedback can be substantial. When observational estimates of the temperature dependence of cloud liquid water content are employed in the model, the surface temperature change due to doubling CO2 is reduced by about one half. © 1985."
"57201882846;6602999057;56522444900;57195675085;7003342687;","Skill of global raw and postprocessed ensemble predictions of rainfall in the tropics",2020,"10.1175/WAF-D-20-0082.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096090472&doi=10.1175%2fWAF-D-20-0082.1&partnerID=40&md5=ceaf6ca181194cb12dbad6edc2092543","Precipitation forecasts are of large societal value in the tropics. Here, we compare 1–5-day ensemble predictions from the European Centre for Medium-Range Weather Forecasts (ECMWF, 2009–17) and the Meteorological Service of Canada (MSC, 2009–16) over 30∘S–30∘N with an extended probabilistic climatology based on the Tropical Rainfall Measuring Mission 3 B42 gridded dataset. Both models predict rainfall occurrence better than the reference only over about half of all land points, with a better performance by MSC. After applying the postprocessing technique ensemble model output statistics, this fraction increases to 87% (ECMWF) and 82% (MSC). For rainfall amount there is skill in many tropical areas (about 60% of land points), which can be increased by postprocessing to 97% (ECMWF) and 88% (MSC). Forecasts for extremes (>20 mm) are only marginally worse than those of occurrence but do not improve as much through postprocessing, particularly over dry areas. Forecast performance is generally best over arid Australia and worst over oceanic deserts, the Andes and Himalayas, as well as over tropical Africa, where models misrepresent the high degree of convective organization, such that even postprocessed forecasts are hardly better than climatology. Skill of 5-day accumulated forecasts often exceeds that of shorter ranges, as timing errors matter less. An increase in resolution and major model update in 2010 has significantly improved ECMWF predictions. Especially over tropical Africa new techniques such as convection-permitting models or combined statistical-dynamical forecasts may be needed to generate skill beyond the climatological reference. © 2020 American Meteorological Society. F."
"57220008887;55231686100;6701744275;7005246023;","Self-Aggregation of Convective Clouds With Interactive Sea Surface Temperature",2020,"10.1029/2020MS002164","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096504291&doi=10.1029%2f2020MS002164&partnerID=40&md5=b3a65d46d9f5140de0041bea08d6313a","This study investigates the feedbacks between an interactive sea surface temperature (SST) and the self-aggregation of deep convective clouds, using a cloud-resolving model in nonrotating radiative-convective equilibrium. The ocean is modeled as one layer slab with a temporally fixed mean but spatially varying temperature. We find that the interactive SST decelerates the aggregation and that the deceleration is larger with a shallower slab, consistent with earlier studies. The surface temperature anomaly in dry regions is positive at first, thus opposing the diverging shallow circulation known to favor self-aggregation, consistent with the slower aggregation. But surprisingly, the driest columns then have a negative SST anomaly, thus strengthening the diverging shallow circulation and favoring aggregation. This diverging circulation out of dry regions is found to be well correlated with the aggregation speed. It can be linked to a positive surface pressure anomaly (PSFC), itself the consequence of SST anomalies and boundary layer radiative cooling. The latter cools and dries the boundary layer, thus increasing PSFC anomalies through virtual effects and hydrostasy. Sensitivity experiments confirm the key role played by boundary layer radiative cooling in determining PSFC anomalies in dry regions, and thus the shallow diverging circulation and the aggregation speed. ©2020. The Authors."
"56520853700;57212988186;7401945370;","Notes and correspondence impacts of sub-grid ice cloud physics in a turbulence scheme on high clouds and their response to global warming",2020,"10.2151/jmsj.2020-054","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85094117985&doi=10.2151%2fjmsj.2020-054&partnerID=40&md5=e451080eaaafb58355fe9d2117f40ea9","The impacts of the saturation adjustment type approach to sub-grid-scale (SGS) ice clouds in a turbulent closure scheme on the high clouds and their response to global warming were investigated based on the radiative– convective equilibrium experiments (RCEs). This was motivated by the fact that the time scale of ice condensation is several orders of magnitude longer than that for liquid water. The RCEs were conducted with uniform sea surface temper atures over the spherical domain for the Earth’s radius without rotation using an explicit cloud microphysics and a non-hydrostatic icosahedral atmospheric model. This study revealed that suppressing the phase change effect associated with the SGS ice condensation on the buoyancy of the SGS turbulence could cause approximately a 20 % reduction of the total high cloud covers and a significantly different response of high cloud amounts to global warming due to the change in static stability near high clouds, which leads to weaker vertical heat transport at a sub-grid scale there. Since the typical value of the time scale of the ice-phase cloud is much longer than that of liquid water and the ice supersaturation is in general, using the saturation adjustment type approach for SGS ice clouds could lead to an overestimation of the effect of ice condensation for the turbulent mixing and model biases in simulations with both cloud resolving and general circulation models. The pres-ent result underlines the critical nature of the treatment of SGS ice clouds in turbulence schemes which reflects a realistic ice condensation time scale not only for a better representation of high clouds in the current climate but for an improved projection of changes of high clouds due to global warming. © The Author(s) 2020."
"56450100300;16644246500;","Understanding the Extreme Spread in Climate Sensitivity within the Radiative-Convective Equilibrium Model Intercomparison Project",2020,"10.1029/2020MS002165","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85094143709&doi=10.1029%2f2020MS002165&partnerID=40&md5=9bc687eb94c47d2dd40a221d53ea105b","The Radiative-Convective Equilibrium Model Intercomparison Project (RCEMIP) consists of simulations at three fixed sea-surface temperatures (SSTs: 295, 300, and 305 K) and thus allows for a calculation of the climate feedback parameter based on the change of the top-of-atmosphere radiation imbalance. Climate feedback parameters range widely across RCEMIP, roughly from −6 to 3 W m−2 K−1, particularly across general-circulation models (GCMs) as well as global and large-domain cloud-resolving models (CRMs). Small-domain CRMs and large-eddy simulations have a smaller range of climate feedback parameters due to the absence of convective self-aggregation. More than 70–80% of the intermodel spread in the climate feedback parameter can be explained by the combined temperature dependencies of convective aggregation and shallow cloud fraction. Low climate sensitivities are associated with an increase of shallow cloud fraction (increasing the planetary albedo) and/or an increase in convective aggregation with warming. An increase in aggregation is associated with an increase in outgoing longwave radiation, caused primarily by mid-tropospheric drying, and secondarily by an expansion of subsidence regions. Climate sensitivity is neither dependent on the average amount of aggregation nor on changes in deep/anvil cloud fraction. GCMs have a lower overall climate sensitivity than CRMs because in most GCMs convective aggregation increases with warming, whereas in CRMs, convective aggregation shows no consistent temperature trend. ©2020. The Authors."
"57188866963;57191290414;57209286045;","Quantifying Convective Aggregation Using the Tropical Moist Margin's Length",2020,"10.1029/2020MS002092","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85094132224&doi=10.1029%2f2020MS002092&partnerID=40&md5=20eab11081a72f66989d245f220abb70","On small scales, the tropical atmosphere tends to be either moist or very dry. This defines two states that, on large scales, are separated by a sharp margin, well identified by the antimode of the bimodal tropical column water vapor distribution. Despite recent progress in understanding physical processes governing the spatiotemporal variability of tropical water vapor, the behavior of this margin remains elusive, and we lack a simple framework to understand the bimodality of tropical water vapor in observations. Motivated by the success of coarsening theory in explaining bimodal distributions, we leverage its methodology to relate the moisture field's spatial organization to its time evolution. This results in a new diagnostic framework for the bimodality of tropical water vapor, from which we argue that the length of the margin separating moist from dry regions should evolve toward a minimum in equilibrium. As the spatial organization of moisture is closely related to the organization of tropical convection, we hereby introduce a new convective organization index (BLW) measuring the ratio of the margin's length to the circumference of a well-defined equilibrium shape. Using BLW, we assess the evolution of self-aggregation in idealized cloud-resolving simulations of radiative-convective equilibrium and contrast it to the time evolution of the Atlantic Intertropical Convergence Zone (ITCZ) in the ERA5 meteorological reanalysis product. We find that BLW successfully captures aspects of convective organization ignored by more traditional metrics, while offering a new perspective on the seasonal cycle of convective organization in the Atlantic ITCZ. ©2020 The Authors."
"57194116803;57194113949;57205342499;57201725986;57212139354;","Initiation and organization mechanisms of mesoscale convective systems in a warm-sector torrential rainfall event over Beijing",2020,"10.3390/atmos11090946","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092361379&doi=10.3390%2fatmos11090946&partnerID=40&md5=96d7774c013a76a983292b0e93efa183","A torrential rainfall that occurred in Beijing during the period of 21-22 July 2012 is simulated by the Weather Research and Forecasting Model in order to investigate the probable mechanisms for the initiation and organization of warm-sector mesoscale convective systems (MCSs). The simulated results show that the cyclone, which formed in Hetao area, Inner Mongolia and moved eastward slowly, played a key role in the formation and development of warm-sector precipitation, although the favorable atmospheric environment and the configuration of weather systems are also important, which caused the trigger and organization of convective cells along Taihang Mountains. It is the interaction of the local terrain convergence line and the southerly airflows of Hetao cyclone that cause the continuous trigger of convective cells along Taihang Mountains. While, the triggers of convective cells in the plains are caused by the gravity waves, which is related to the development and eastward movement of Hetao cyclone. It must be pointed out that the merging and coupling between the cells that triggered in Taihang Mountains and moved southwesterly and the cells that triggered in plains and moved northeasterly are the key factors for the formation and development of MCSs during the warm-sector precipitation. In addition, the back-building processes and the cold pool forcing are also important for the formation and development of MCSs in this study. © 2020 by the authors."
"57204430398;8711852700;25647939800;9249605700;7202954964;","New Critical Length for the Onset of Self-Aggregation of Moist Convection",2020,"10.1029/2020GL088763","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089873617&doi=10.1029%2f2020GL088763&partnerID=40&md5=3bfd0d1e76154114d38b0561356e91af","Convective self-aggregation (CSA) in an idealized modeling framework is key to understanding the role of clouds. To investigate the existence of characteristic length of CSA onset, we conducted systematic cloud-resolving simulations, with a scope covering the horizontal domain size and resolution. In the high-resolution simulation, CSA can occur with a square domain larger than ~500 km. Based on the competition between two near-surface horizontal divergent flows, we discuss the characteristic length existence. While the flow induced by radiative cooling in the subsidence region acts as positive feedback for moisture perturbation and scales with the domain size, the other flow induced by evaporative cooling of falling rain in the convective region acts as negative feedback and does not scale. The study suggests characteristic length existence for the organization of moist convection, even in real-world conditions. ©2020. The Authors."
"57218512967;57212816521;7407084420;57218516790;","Polygonal Eyewall Asymmetries During the Rapid Intensification of Hurricane Michael (2018)",2020,"10.1029/2020GL087919","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089361823&doi=10.1029%2f2020GL087919&partnerID=40&md5=152ded408c840532287044dbad46d1d4","Polygonal eyewall asymmetries of Hurricane Michael (2018) during rapid intensification (RI) are analyzed from ground-based single Doppler radar. Here, we present the first observational evidence of the evolving wind field of a polygonal eyewall during RI to Category 5 intensity by deducing the axisymmetric and asymmetric winds at 5-min intervals. Spectral time decomposition of the retrieved tangential wind structure shows quantitative evidence of low (1–4) azimuthal wavenumbers with propagation speeds that are consistent with linear wave theory on a radial vorticity gradient, suggesting the presence of rapidly evolving vortex Rossby waves. Dual-Doppler winds from the NOAA P-3 Hurricane Hunter airborne radar provide further evidence of the three-dimensional vortex structure that supports growth of asymmetries during RI. Both reflectivity and tangential wind fields show polygonal structure and propagate at similar speeds, suggesting a close coupling of the dynamics and the convective organization during the intensification. © 2020. American Geophysical Union. All Rights Reserved."
"56342804700;","Seasonal modulation of trapped gravity waves and their imprints on trade wind clouds",2020,"10.1175/JAS-D-19-0325.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091637831&doi=10.1175%2fJAS-D-19-0325.1&partnerID=40&md5=6571bf48eb8da174429c14931d8a6fe8","Shallow convection over the oceans is responsible for the largest uncertainties in climate projections. Idealized simulations have shown decades ago that shallow clouds generate internal gravity waves, which under certain atmospheric background conditions become trapped inside the troposphere and influence the development of clouds. These feedbacks, which occur at horizontal scales of up to several tens of kilometers. are neither resolved nor parameterized in traditional global climate models (GCMs), while the newest generation of GCMs (grid spacings, 5 km) is starting to resolve them. The interactions between the convective boundary layer and trapped waves have almost exclusively been studied in highly idealized frameworks and it remains unclear to what degree this coupling affects the organization of clouds in the real atmosphere or in the new generation of GCMs. Here, the coupling between clouds and trapped waves is examined in 2.5-km simulations that span the entirety of the tropical Atlantic and are initialized and forced with meteorological analyses. The coupling between clouds and trapped waves is sufficiently strong to be detected in these simulations of full complexity. Stronger upper-tropospheric westerly winds are associated with a stronger cloud-wave coupling. In the simulations this results in a highly organized scattered cloud field with cloud spacings of about 19 km, matching the dominant trapped wavelength. Based on the large-scale atmospheric state, wave theory can reliably predict the regions and times where cloud-wave feedbacks become relevant to convective organization. Theory, the simulations, and satellite imagery imply a seasonal cycle in the trapping of gravity waves. © 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"57067732900;57203683339;36237869500;57201736598;7004170000;8948001200;6701697738;7004612205;","A systematic study of CO2 planetary atmospheres and their link to the stellar environment",2020,"10.1093/mnras/staa1929","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85095422297&doi=10.1093%2fmnras%2fstaa1929&partnerID=40&md5=8fc4c4d09171932291814798aeb1d4a2","The Milky Way Galaxy is literally teeming with exoplanets; thousands of planets have been discovered, with thousands more planet candidates identified. Terrestrial-like planets are quite common around other stars, and are expected to be detected in large numbers in the future. Such planets are the primary targets in the search for potentially habitable conditions outside the Solar system. Determining the atmospheric composition of exoplanets is mandatory to understand their origin and evolution, as atmospheric processes play crucial roles in many aspects of planetary architecture. In this work we construct and exploit a 1D radiative transfer model based on the discrete-ordinates method in plane-parallel geometry. Radiative results are linked to a convective flux that redistributes energy at any altitude producing atmospheric profiles in radiative-convective equilibrium. The model has been applied to a large number (6250) of closely dry synthetic CO2 atmospheres, and the resulting pressure and thermal profiles have been interpreted in terms of parameter variability. Although less accurate than 3D general circulation models, not properly accounting for e.g. clouds and atmospheric and ocean dynamics, 1D descriptions are computationally inexpensive and retain significant value by allowing multidimensional parameter sweeps with relative ease. © 2020 The Author(s)."
"57193205633;7201534142;57218625754;35569011300;","Characterizing thunderstorm gust fronts near complex terrain",2020,"10.1175/MWR-D-19-0316.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091154465&doi=10.1175%2fMWR-D-19-0316.1&partnerID=40&md5=525f2b692af3e5e235f82d49614cd77f","Fire safety, aviation, wind energy, and structural-engineering operations are impacted by thunderstorm outflow boundaries or gust fronts (GFs) particularly when they occur in mountainous terrain. For example, during the 2013 Arizona Yarnell Hill Fire, 19 firefighters were killed as a result of sudden changes in fire behavior triggered by a passing GF. Knowledge of GF behavior in complex terrain also determines departure and landing operations at nearby airports, and GFs can induce exceptional structural loads on wind turbines. While most examinations of GF characteristics focus on well-organized convection in areas such as the Great Plains, here the investigation is broadened to explore GF characteristics that evolve near the complex terrain of the Colorado Rocky Mountains. Using in situ observations from meteorological towers, as well as data from wind-profiling lidars and a microwave radiometer, 24 GF events are assessed to quantify changes in wind, temperature, humidity, and turbulence in the lowest 300m AGL as these GFs passed over the instruments. The changes in magnitude for all variables are on average weaker in the Colorado Front Range than those typically observed from organized, severe storms in flatter regions. Most events from this study experience an increase in wind speed from 1 to 8ms21, relative humidity from1%to 8%, and weak vertical motion from 0.3 to 3.6ms-1 during GF passage while temperature drops by 0.28-3°C and turbulent kinetic energy peaks at .4m2 s-2. Vertical profiles reveal that these changes vary little with height in the lowest 300m. © 2020 American Meteorological Society."
"56471429200;56893786200;35509639400;","The Relationship Between Convective Clustering and Mean Tropical Climate in Aquaplanet Simulations",2020,"10.1029/2020MS002070","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089852002&doi=10.1029%2f2020MS002070&partnerID=40&md5=49c00cc409246926be39c6be7e7f70c7","Convective clustering, the spatial organization of tropical deep convection, can manifest itself in two ways: through a decrease in the total area covered by convection and/or through a decrease in the number of convective areas. Much of our current understanding of convective clustering comes from simulations in idealized radiative convective equilibrium (RCE) configurations. In these simulations the two forms of convective clustering tend to covary, and their individual effects on the climate are thus hard to disentangle. This study shows that in aquaplanet simulations with more realistic boundary conditions, such as meridional gradients of surface temperature and rotational forces, the two aspects of convective clustering are not equivalent and are associated with different impacts on the large-scale climate. For instance, reducing the convective area in the equatorial region in the aquaplanet simulations results in broader meridional humidity and rain distributions and in lower tropospheric temperatures throughout the tropics. By contrast, the number of convective regions primarily impacts the zonal variance of humidity-related quantities in the aquaplanet simulations, as the distribution of convective regions affects the size of the subsidence regions and thereby the moistening influence of convective regions. The aquaplanet simulations confirm many other qualitative results from RCE simulations, such as a reduction of equatorial tropospheric humidity when the area covered by convection diminishes. © 2020. The Authors."
"24492504500;57208347885;57218625880;","Multifluids for Representing Subgrid-Scale Convection",2020,"10.1029/2019MS001966","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089845981&doi=10.1029%2f2019MS001966&partnerID=40&md5=a87678ba3f17bd9b48659faf24d6d47f","Traditional parameterizations of convection are a large source of error in weather and climate prediction models, and the assumptions behind them become worse as resolution increases. Multifluid modeling is a promising new method of representing subgrid-scale and near-grid-scale convection allowing for net mass transport by convection and nonequilibrium dynamics. The air is partitioned into two or more fluids, which may represent, for example, updrafts and the nonupdraft environment. Each fluid has its own velocity, temperature, and constituents with separate equations of motion. This paper presents two-fluid Boussinesq equations for representing subgrid-scale dry convection with sinking and w = 0 air in Fluid 0 and rising air in Fluid 1. Two vertical slice test cases are developed to tune parameters and to evaluate the two-fluid equations: a buoyant rising bubble and radiative convective equilibrium. These are first simulated at high resolution with a single-fluid model and conditionally averaged based on the sign of the vertical velocity. The test cases are next simulated with the two-fluid model in one column. A model for entrainment and detrainment based on divergence leads to excellent representation of the convective area fraction. Previous multifluid modeling of convection has used the same pressure for both fluids. This is shown to be a bad approximation, and a model for the pressure difference between the fluids based on divergence is presented. © 2020. The Authors."
"57205206162;55973371700;55716217300;57205212591;","The comparison of statistical features and synoptic circulations between the eastward-propagating and quasi-stationary MCSs during the warm season around the second-step terrain along the middle reaches of the Yangtze River",2020,"10.1007/s11430-018-9385-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086093698&doi=10.1007%2fs11430-018-9385-3&partnerID=40&md5=0ff6478f31931fd9ee387441ff6c66ee","Mesoscale convective systems (MCSs) around the second-step terrain (106°–113°E, 28°–35°N), along the middle reaches of the Yangtze River, were detected, tracked and classified using a black body temperature (TBB) dataset during May to August 2000–2016 (except 2005). The MCSs were divided into eastward-propagating (EP) and quasi-stationary (QS) types, to compare their spatial and temporal distributions and convective intensities, and to identify the favorable synoptic conditions for the formation and evolution of EP MCSs. The results showed that both MCS types occurred most often in July. The EP MCSs were mainly initiated over the eastern regions of the study area, while the QS type mainly originated in the western regions of the study area. Both MCS types mainly formed in the afternoon, but a second peak occurred in the early morning for QS MCSs. The EP MCSs had a larger cloud area at their mature stage and a lower cloud brightness temperature, indicating more intense convection. Additionally, the longer lifetime and further eastward propagation of the EP MCSs meant that they had a great influence on the precipitation over the middle and lower reaches of the Yangtze River. Synoptic circulation analysis demonstrated that the combination of the mid-level low trough east of the Tibetan Plateau (TP), and the western pacific subtropical high (WPSH), favored the formation and eastward propagation of EP MCSs. The positive vertical relative vorticity and stronger vertical wind shear provided dynamic conditions favorable for convective organization and development. Furthermore, a stronger low level jet imported warm and moist air to the eastern edge of, and the regions east of, the second-step terrain. The substantial convergence of water vapor promoted the development and long-lived maintenance of the EP MCSs. © 2020, Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature."
"56591585100;55531609200;57188711722;19639722300;","Changes in Tropical Precipitation Intensity With El Niño Warming",2020,"10.1029/2020GL087663","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088592231&doi=10.1029%2f2020GL087663&partnerID=40&md5=6dc488c3120c13cc961069f28c403bf4","Mesoscale convection generates the majority of extreme precipitation in tropical regions. Changes to these precipitation intensities, P, with long-term modes of climate variability have been hard to assess because they are not well represented in current climate models. Here we stratify a satellite climatology of convective systems by El Niño phase and cloud top temperature. We find that gains (losses) in high precipitation intensity ((Formula presented.) 10 mm hr−1) are largest for the deepest (least deep) systems during El Niño relative to La Niña. The surface temperature and wind changes that define El Niño manifest as surface flux changes but are not sufficient to explain these (Formula presented.) trends. We explore also the dynamical component of precipitation generation with a vertical momentum budget. Midtropospheric drying in the vicinity of the deepest systems boosts instability and ascent rates during El Niño, while the strengthened large-scale ascent minimizes the drag force on their updrafts. ©2020. American Geophysical Union. All Rights Reserved."
"56973051400;22980040900;36627560700;15838180100;7202189875;56959922400;6701916635;55660948300;57211033354;55263579600;8532017700;55887116200;15078583900;6602566553;6507571744;35748547500;25927321200;","The Hubble Space Telescope PanCET Program: An Optical to Infrared Transmission Spectrum of HAT-P-32Ab",2020,"10.3847/1538-3881/ab96cb","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088246289&doi=10.3847%2f1538-3881%2fab96cb&partnerID=40&md5=abc27161201209aab6f7c2bbad2b7b30","We present a 0.3-5 μm transmission spectrum of the hot Jupiter HAT-P-32Ab observed with the Space Telescope Imaging Spectrograph and Wide Field Camera 3 instruments mounted on the Hubble Space Telescope, combined with Spitzer Infrared Array Camera photometry. The spectrum is composed of 51 spectrophotometric bins with widths ranging between 150 and 400 Å, measured to a median precision of 215 ppm. Comparisons of the observed transmission spectrum to a grid of 1D radiative-convective equilibrium models indicate the presence of clouds/hazes, consistent with previous transit observations and secondary eclipse measurements. To provide more robust constraints on the planet's atmospheric properties, we perform the first full optical to infrared retrieval analysis for this planet. The retrieved spectrum is consistent with a limb temperature of 1248+9292 K, a thick cloud deck, enhanced Rayleigh scattering, and ∼10× solar H2O abundance. We find log(Z/Z o˙) =2.41+0.06-0.07, and compare this measurement with the mass-metallicity relation derived for the solar system. © 2020. The American Astronomical Society. All rights reserved."
"8658386900;57192820631;6506537159;","Cloud regimes over the Amazon Basin: Perspectives from the GoAmazon2014/5 campaign",2020,"10.5194/acp-20-7489-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088041134&doi=10.5194%2facp-20-7489-2020&partnerID=40&md5=5d64f3c090a6f13c63cb9c1210a062e2","Radiosonde observations collected during the GoAmazon2014/5 campaign are analyzed to identify the primary thermodynamic regimes accompanying different modes of convection over the Amazon. This analysis identifies five thermodynamic regimes that are consistent with traditional Amazon calendar definitions of seasonal shifts, which include one wet, one transitional, and three dry season regimes based on a k-means cluster analysis. A multisensor ground-based approach is used to project associated bulk cloud and precipitation properties onto these regimes. This is done to assess the propensity for each regime to be associated with different characteristic cloud frequency, cloud types, and precipitation properties. Additional emphasis is given to those regimes that promote deep convective precipitation and organized convective systems. Overall, we find reduced cloud cover and precipitation rates to be associated with the three dry regimes and those with the highest convective inhibition. While approximately 15% of the dataset is designated as organized convection, these events are predominantly contained within the transitional regime. © 2020 Author(s)."
"55682851300;7006095466;7101661890;6505932008;","Shear-Parallel Tropical Convective Systems: Importance of Cold Pools and Wind Shear",2020,"10.1029/2020GL087720","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086804943&doi=10.1029%2f2020GL087720&partnerID=40&md5=fe4be5c10e42cea3e9fde9f4d563c277","The impact of cold pools on line-orientated convective systems is assessed using idealized simulations of tropical oceanic convection under weak, moderate, and strong wind shear regimes. Cold pools are weakened by suppressing evaporation in the shallow subcloud layer. Analysis of objectively identified convective systems reveals that the convection with weaker cold pools is more often oriented parallel, rather than perpendicular, to the wind shear. The cold pool-induced orientation changes are most pronounced in the strong shear environment. Interactions between convective orientation and the tropical atmosphere are assessed. Simulations with shear-parallel convection demonstrate more top-of-atmosphere upwelling longwave radiation and less reflected shortwave radiation due to changes in convective anvils, faster-propagating larger-scale gravity waves, narrower cross-shear moisture distributions, and differences in convective momentum fluxes. The results highlight critical interactions across convective scales, mesoscales, and climate scales, as well as avenues for parameterizing structural modes of mesoscale-organized convection in global models. ©2020. American Geophysical Union. All Rights Reserved."
"30967646900;","Changing Degree of Convective Organization as a Mechanism for Dynamic Changes in Extreme Precipitation",2020,"10.1007/s40641-020-00157-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084644403&doi=10.1007%2fs40641-020-00157-9&partnerID=40&md5=8f9555bd9e7675dbcf0f3eb025cd2f5c","Purpose of Review: What does recent work say about how changes in convective organization could lead to changes in extreme precipitation? Recent Findings: Changing convective organization is one mechanism that could explain variation in extreme precipitation increase through dynamics. In models, the effects of convective self-aggregation on extreme precipitation are sensitive to parameterization, among other factors. In both models and observations, whether or not convective organization influences extreme precipitation is sensitive to the time and space scales analyzed, affecting extreme precipitation on some scales but not others. While trends in observations in convective organization associated with mean precipitation have been identified, it has not yet been established whether these trends are robust or relevant for events associated with extreme precipitation. Summary: Recent work has documented a somewhat view of how changes in convective organization could affect extreme precipitation with warming, and it remains unclear whether or not they do. © 2020, The Author(s)."
"57200131336;56308982600;23569021500;","Response of atmospheric surface layer parameters to cloudiness over a tropical coastal station",2020,"10.1016/j.jastp.2020.105260","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082771768&doi=10.1016%2fj.jastp.2020.105260&partnerID=40&md5=9e90ceafa37167b896edd96a1f69667c","This study examines the response of surface layer parameters and ABL height (ABLH) to the change in cloudiness over Kochi. Outgoing long wave radiation (OLR) is considered as a proxy for the cloudiness. Temperature, horizontal wind speed, vertical velocity variance (VVV), sensible heat flux, momentum flux, turbulent kinetic energy (TKE), drag coefficient and ABLH corresponding to each OLR bin are evaluated during different seasons. It is observed that the temperature response curve is similar for the pre-monsoon and the monsoon. Increase in cloudiness is associated with decrease in temperature during these seasons and it is attributed to the presence of organized convections. Pre-monsoon consists of organized convections as well as local convections. During post monsoon, an increase in temperature is observed in association with local convections having the OLR values less than 180 Wm−2. Horizontal wind speed response is similar during the pre-monsoon and post monsoon seasons with minimum corresponding to the bin 180–199 W m−2 and an increase in wind speed to both side of the OLR bins (cloudy and clear sky conditions). The increase in wind speed during cloudy (clear sky) conditions can be connected with strong downdraft from convective clouds (strong sea breeze). However, during monsoon and winter, the surface wind strengthens with decrease in cloudiness. Reduction in cloudiness increases the surface fluxes, TKE and ABLH during all the seasons. A drastic decrease (increase) in temperature, sensible heat flux and ABLH (horizontal wind speed, momentum flux and TKE) is observed during the passage of a depression. © 2020 Elsevier Ltd"
"57192156759;57210687618;57188866963;","Convective Dynamics and the Response of Precipitation Extremes to Warming in Radiative–Convective Equilibrium",2020,"10.1175/JAS-D-19-0197.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089816678&doi=10.1175%2fJAS-D-19-0197.1&partnerID=40&md5=a24abffbf71d1ed2af92fe438e55d3be","Tropical precipitation extremes are expected to strengthen with warming, but quantitative estimates remain uncertain because of a poor understanding of changes in convective dynamics. This uncertainty is addressed here by analyzing idealized convection-permitting simulations of radiative–convective equilibrium in long-channel geometry. Across a wide range of climates, the thermodynamic contribution to changes in instantaneous precipitation extremes follows near-surface moisture, and the dynamic contribution is positive and small but is sensitive to domain size. The shapes of mass flux profiles associated with precipitation extremes are determined by conditional sampling that favors strong vertical motion at levels where the vertical saturation specific humidity gradient is large, and mass flux profiles collapse to a common shape across climates when plotted in a moisture-based vertical coordinate. The collapse, robust to changes in microphysics and turbulence schemes, implies a thermodynamic contribution that scales with near-surface moisture despite substantial convergence aloft and allows the dynamic contribution to be defined by the pressure velocity at a single level. Linking the simplified dynamic mode to vertical velocities from entraining plume models reveals that the small dynamic mode in channel simulations (&amp;2% K21) is caused by opposing height dependences of vertical velocity and density, together with the buffering influence of cloud-base buoyancies that vary little with surface temperature. These results reinforce an emerging picture of the response of extreme tropical precipitation rates to warming: a thermodynamic mode of about 7% K21 dominates, with a minor contribution from changes in dynamics. Ó 2020 American Meteorological Society."
"55344397300;6602761005;55260519600;","Axisymmetric hadley cell theory with a fixed tropopause temperature rather than height",2020,"10.1175/JAS-D-19-0169.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091598277&doi=10.1175%2fJAS-D-19-0169.1&partnerID=40&md5=830710c48ab4e5b458b13e1f612d6b59","Axisymmetric Hadley cell theory has traditionally assumed that the tropopause height (Ht) is uniform and unchanged from its radiative-convective equilibrium (RCE) value by the cells' emergence. Recent studies suggest that the tropopause temperature (Tt), not height, is nearly invariant in RCE, which would require appreciable meridional variations in Ht. Here, we derive modified expressions of axisymmetric theory by assuming a fixed Tt and compare the results to their fixed-Ht counterparts. If Tt and the depth-averaged lapse rate are meridionally uniform, then at each latitude Ht varies linearly with the local surface temperature, altering the diagnosed gradient-balanced zonal wind at the tropopause appreciably (up to tens of meters per second) but the minimal Hadley cell extent predicted by Hide's theorem only weakly (18) under standard annual-mean and solsticial forcings. A uniform Tt alters the thermal field required to generate an angularmomentum-conserving Hadley circulation, but these changes and the resulting changes to the equal-area model solutions for the cell edges again are modest (10%). In numerical simulations of latitude-by-latitude RCE under annual-mean forcing using a single-column model, assuming a uniform Tt is reasonably accurate up to the midlatitudes, and the Hide's theorem metrics are again qualitatively insensitive to the tropopause definition. However imperfectly axisymmetric theory portrays the Hadley cells in Earth's macroturbulent atmosphere, evidently its treatment of the tropopause is not an important error source. © 2020 American Meteorological Society."
"57216225866;57207953733;57216223357;","Responses of Mean and Extreme Precipitation to Different Climate Forcing Under Radiative-Convective Equilibrium",2020,"10.1007/s00376-020-9236-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082866203&doi=10.1007%2fs00376-020-9236-1&partnerID=40&md5=d84b6ad7f6c9125f98a7157e0cf5d6b9","Understanding the responses of mean and extreme precipitation to climate change is of great importance. Previous studies have mainly focused on the responses to prescribed sea surface warming or warming due to increases of CO2. This study uses a cloud-resolving model under the idealization of radiative–convective equilibrium to examine the responses of mean and extreme precipitation to a variety of climate forcings, including changes in prescribed sea surface temperature, CO2, solar insolation, surface albedo, stratospheric volcanic aerosols, and several tropospheric aerosols. The different responses of mean precipitation are understood by examining the changes in the surface energy budget. It is found that the cancellation between shortwave scattering and longwave radiation leads to a small dependence of the mean precipitation response on forcings. The responses of extreme precipitation are decomposed into three components (thermodynamic, dynamic, and precipitation efficiency). The thermodynamic components for all climate forcings are similar. The dynamic components and the precipitation-efficiency components, which have large spreads among the cases, are negatively correlated, leading to a small dependence of the extreme precipitation response on the forcings. © 2020, Institute of Atmospheric Physics/Chinese Academy of Sciences, and Science Press and Springer-Verlag GmbH Germany, part of Springer Nature."
"55622802000;57203744168;6603499076;","Observations and high-resolution simulations of convective precipitation organization over the tropical Atlantic",2020,"10.1002/qj.3751","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079908464&doi=10.1002%2fqj.3751&partnerID=40&md5=55cd18539cc9762aeba88a74e86d4a7f","High-resolution simulations (grid spacing 2.5 km) are performed with ICON-LEM to characterize convective organization in the Tropics during August 2016 over a large domain ranging from northeastern South America, along the tropical Atlantic to Africa (8,000×3,000 km). The degree of organization is measured by a refined version of the wavelet-based organization index (WOI), which is able to characterize the scale, the intensity and anisotropy of convection based on rain rates alone. Exploiting the localization of wavelets both in space and time, we define a localized version of the convective organization index (LWOI). We compare convection observed in satellite-derived rain rates with the corresponding processes simulated by ICON-LEM. Model and observations indicate three regions with different kinds of convective organization. Continental convection over West Africa has a predominantly meridional orientation and is more organized than over South America, because it acts on larger scales and is more intense. Convection over the tropical Atlantic is zonally oriented along the ITCZ and less intense. ICON and observations agree on the number and intensity of the African easterly waves during the simulation period. The waves are associated with strong vorticity anomalies and are clearly visible in a spatiotemporal wavelet analysis. The central speed and the wavelength of the waves is simulated well. Both the scale and intensity components of LWOI in ICON are significantly correlated with environmental variables. The scale of precipitation is related to wind shear, CAPE and its tendency, while the intensity strongly correlates with column-integrated humidity, upper-level divergence and maximum vertical wind speed. This demonstrates that the LWOI components capture important characteristics of convective precipitation. © 2020 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"35932420900;35203870600;57189505139;55614754800;","Impact of resolution on large-eddy simulation of midlatitude summertime convection",2020,"10.5194/acp-20-2891-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081545265&doi=10.5194%2facp-20-2891-2020&partnerID=40&md5=fde784d897d270531cf8ceb149a86762","We analyze life cycles of summertime moist convection of a large-eddy simulation (LES) in a limited-area setup over Germany. The goal is to assess the ability of the model to represent convective organization in space and time in comparison to radar data and its sensitivity to daily mean surface air temperature. A continuous period of 36&thinsp;d in May and June 2016 is simulated with a grid spacing of 625&thinsp;m. This period was dominated by convection over large parts of the domain on most of the days. Using convective organization indices, and a tracking algorithm for convective precipitation events, we find that an LES with 625&thinsp;m grid spacing tends to underestimate the degree of convective organization and shows a weaker sensitivity of heavy convective rainfall to temperature as suggested by the radar data. An analysis of 3&thinsp;d with in this period that are simulated with a finer grid spacing of 312 and 156&thinsp;m showed that a grid spacing at the 100&thinsp;m scale has the potential to improve the simulated diurnal cycles of convection, the mean time evolution of single convective events, and the degree of convective organization. © 2020 Copernicus GmbH. All rights reserved."
"57192700976;57204886915;36868795400;22954298000;36054921000;","Mechanisms of Convective Clustering During a 2-Day Rain Event in AMIE/DYNAMO",2020,"10.1029/2019MS001907","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083278084&doi=10.1029%2f2019MS001907&partnerID=40&md5=ca78971955ee1fd4c5b6121c6a667110","Physical mechanisms that are key to observed convective clustering in 2-day rain events are examined. Previous analysis of the 2-day rain events during the Atmospheric Radiation Measurement Madden-Julian Oscillation Investigation Experiment (AMIE)/Dynamics of the Madden-Julian Oscillation (DYNAMO) field campaign data revealed two distinct phases of convective clustering. Using a cloud-system-resolving model, we perform a series of intervention experiments to investigate the underlying mechanisms for convective clustering in each phase. In the developing phase, in addition to previously emphasized processes such as the cold pool-updraft interaction and moisture-convection feedbacks, our results show that the vertical wind shear in the lower free troposphere is a critical factor for convective clustering. Stronger lower free-tropospheric wind shear increases the entrainment of environmental air into updrafts and prevents convective clouds from being omnipresent. This result suggests that stronger vertical wind shear in the lower free troposphere can help spatially organize the convection, even for non–squall-line-type convective systems. In the decaying phase, the cold pool-updraft interaction becomes less effective in aggregating convective clouds because the boundary layer is widely cooled by stratiform precipitation. Instead, the mesoscale downdraft driven by the stratiform precipitation becomes the dominant factor to maintain the relatively aggregated convection. Additionally, removing horizontal variations in radiative heating has no impact on convective clustering on this 2-day time scale, even in the decaying phase when stratiform clouds are widespread. The implication of these results for improving the representation of mesoscale convective organization in convection schemes is discussed. ©2020. The Authors."
"55427215500;55469523400;7006698304;","Simulations of Radiative-Convective-Dynamical Equilibrium",2020,"10.1029/2019MS001734","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083183713&doi=10.1029%2f2019MS001734&partnerID=40&md5=8b1df071950c4d164020e76fc6634e8a","Small-domain cloud-resolving model and single-column model simulations have historically applied one of three representations of large-scale vertical motion, (Formula presented.). In simulations of radiative-convective equilibrium, (Formula presented.), and a balance develops between convective heating and radiative cooling. Under the weak-temperature gradient approximation and related approaches, (Formula presented.) is diagnosed based on the model's thermodynamic profile. Finally, for real-case simulations, (Formula presented.) may be prescribed as a time-varying field derived from observations. Here, we propose one additional setup, namely, a prescribed but time-invariant vertical motion. In this case, the atmosphere evolves toward an equilibrium state characterized by a three-way balance between radiative and adiabatic cooling and convective heating, with the relative contribution of radiation decreasing with increasing (Formula presented.). We refer to this state as radiative-convective-dynamical equilibrium (RCDE). In this preliminary study we highlight the characteristics of the RCDE state through a suite of simulations performed with a single cloud-resolving model and single-column model. An appealing aspect of these simulations is the wide variety of equilibrium states achieved, ranging from dry and strongly unstable for small (Formula presented.) to approximately moist neutral for large (Formula presented.). This makes RCDE a propitious framework for future model intercomparisons. ©2020. The Authors."
"55796732400;7202245915;7202190200;7004859022;7404240633;57149785800;","Analysis of an Ensemble of High-Resolution WRF Simulations for the Rapid Intensification of Super Typhoon Rammasun (2014)",2020,"10.1007/s00376-019-8274-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077910184&doi=10.1007%2fs00376-019-8274-z&partnerID=40&md5=91f404b227936d408cb298163f73d639","Diagnostics are presented from an ensemble of high-resolution forecasts that differed markedly in their predictions of the rapid intensification (RI) of Typhoon Rammasun. We show that the basic difference stems from subtle differences in initializations of (a) 500–850-hPa environmental winds, and (b) midlevel moisture and ventilation. We then describe how these differences impact on the evolving convective organization, storm structure, and the timing of RI. As expected, ascent, diabatic heating and the secondary circulation near the inner-core are much stronger in the member that best forecasts the RI. The evolution of vortex cloudiness from this member is similar to the actual imagery, with the development of an inner cloud band wrapping inwards to form the eyewall. We present evidence that this structure, and hence the enhanced diabatic heating, is related to the tilt and associated dynamics of the developing inner-core in shear. For the most accurate ensemble member: (a) inhibition of ascent and a reduction in convection over the up-shear sector allow moistening of the boundary-layer air, which is transported to the down-shear sector to feed a developing convective asymmetry; (b) with minimal ventilation, undiluted clouds and moisture from the down-shear left quadrant are then wrapped inwards to the up-shear left quadrant to form the eyewall cloud; and (c) this process seems related to a critical down-shear tilt of the vortex from midlevels, and the vertical phase-locking of the circulation over up-shear quadrants. For the member that forecasts a much-delayed RI, these processes are inhibited by stronger vertical wind shear, initially resulting in poor vertical coherence of the circulation, lesser moisture and larger ventilation. Our analysis suggests that ensemble prediction is needed to account for the sensitivity of forecasts to a relatively narrow range of environmental wind shear, moisture and vortex inner-structure. © 2020, Institute of Atmospheric Physics/Chinese Academy of Sciences, and Science Press and Springer-Verlag GmbH Germany, part of Springer Nature."
"56342804700;7101661890;7006698304;","Gravity Wave Influences On Mesoscale Divergence: An Observational Case Study",2020,"10.1029/2019GL086539","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078224597&doi=10.1029%2f2019GL086539&partnerID=40&md5=84aca49053b1c42c2e9220b8f69d8d0c","Characteristics of tropospheric low-frequency gravity waves are diagnosed in radiosonde soundings from the Tropical Warm Pool-International Cloud Experiment near Darwin, Australia. The waves have typical vertical wavelengths of about 4 km, horizontal wavelengths of about 600 km, and intrinsic periods of about 12 hr. These scales match those of the vertical, horizontal, and temporal variability found in area-averaged horizontal wind divergence over the same domain. Vertical profiles of divergence show wave-like structures with variability of the order of 2 (Formula presented.) 10 (Formula presented.) s (Formula presented.) in the free troposphere. The results for Darwin are similar to previously reported observed mesoscale patterns of divergence/convergence over the tropical Atlantic. The findings imply that tropical divergence on spatial scales of a few hundred kilometers, which is known to influence the organization of convection, may be forced by gravity waves. © 2020. The Authors."
"56527094700;56014511300;57112070700;","Aerosol-induced modification of organised convection and top-of-atmosphere radiation",2019,"10.1038/s41612-019-0089-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085032723&doi=10.1038%2fs41612-019-0089-1&partnerID=40&md5=385dd337946872e114402b18aa80c308","Aerosol effects on cloud cover and precipitation could affect the global climate but have proven difficult to verify, because cloud and rain amounts are so strongly influenced by local meteorological conditions. Here model and observational evidence is presented that an increase in CCN concentration slightly invigorates mixed-phase convective clouds and narrows tropical convergence and rain bands, while expanding associated cloud cover particularly at mid-levels. A suite of model simulations with various approaches indicates a 4 ± 3.8% decrease in the rain-to-cloud area ratio per doubling of the CCN concentration, an effect also detected in satellite observations. Idealised numerical experiments suggest the area ratio change is due to the invigoration-induced static stability increase. Although the invigoration and cloud amount changes are much smaller than suggested in some studies, in simulations the latter cool the planet by 0.71 ± 0.25 W/m2 in deep convective regions, suggesting a global effect of order 0.2–0.5 W/m2, per aerosol doubling. The contribution to present-day anthropogenic forcing is even harder to quantify but could compare to that of the direct aerosol radiative forcing. These results indicate a previously unrecognised pathway for aerosols to indirectly cool the climate by altering convective clouds dynamically. © 2019, The Author(s)."
"56041803600;25645385100;36342881200;","Surface Moisture Exchange Under Vanishing Wind in Simulations of Idealized Tropical Convection",2019,"10.1029/2019GL085047","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076413275&doi=10.1029%2f2019GL085047&partnerID=40&md5=2bffba137f8ae809c5a0f8c7f3e940d4","Under radiative-convective equilibrium (RCE), surface moisture fluxes drive convection, while convection-driven winds regulate surface fluxes. Most simulations of RCE do not resolve the boundary-layer turbulence that drives near-surface winds due to too coarse grid spacing and instead parameterize its effects by enforcing a minimum wind speed in the computation of the ocean-atmosphere exchange. We show from RCE simulations with fully resolved boundary-layer turbulence that capturing wind dynamics at low speeds impacts the spatially averaged surface moisture flux, as well as its spatial distribution. A minimum wind speed constraint of only 1 m s−1 leads to ∼10% increase in spatially averaged surface flux in the evolution towards RCE and reduces the surface flux differences between windy and calm regions with more than a factor of two. Hence, the ability of simulations to let wind vanish is key in representing the wind-induced surface heat exchange feedback and is potentially important in convective self-aggregation. ©2019. The Authors."
"9245000500;7005859152;","Linear theory of shallow convection in deep, vertically sheared atmospheres",2019,"10.1002/qj.3609","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070701193&doi=10.1002%2fqj.3609&partnerID=40&md5=2ef986cc2d2ff12327cdbb28ea5babbf","The linear theory of vertically sheared convection is extended to deep-atmosphere flows with arbitrary wind, stability, and diffusion profiles. Consistent with previous findings, reference single-layer vertical channel flows show fastest growth for shear-parallel roll circulations and much weaker growth for shear-transverse circulations, causing the former to dominate. In a more realistic three-layer setting, where the cloud layer lies between a mixed layer below and a stable free troposphere aloft, shear-parallel rolls also dominate. However, shear-transverse rolls grow much faster than before, which degrades the convective organization. An analysis focused on the vertical perturbation phase tilt leads to a novel interpretation of these results. Vertical shear imparts a downshear tilt, which acts to weaken the convective growth driven by dynamic and non-hydrostatic buoyant vertical perturbation pressure gradients (VPPGs). Whether these VPPGs can maintain growth in the face of the shear depends largely on the Richardson number (Ri), with &#x01d445;&#x01d456; ≲ −2 becoming a necessary condition for (inviscid) growth of shear-perpendicular rolls in the short-wave limit. In deeper, three-layer atmospheres, longer vertical wavelengths are admitted, which fosters less tilted and faster growing perturbations. This effect, however, is partially offset by differential tilting between kinematic and thermal anomalies. Numerical simulations are used to verify the linear results and to explore the evolution of the convection into the nonlinear regime. As the nonlinearities grow, an initial preference for smaller-scale, shear-parallel circulations is ultimately overwhelmed by larger-scale perturbations with no preferred orientation. Thus, the linear findings are most applicable to the early evolution of cloud layers undergoing turbulent transition. © 2019 Royal Meteorological Society"
"57202219487;7006306835;16636807900;","Investigating the Fast Response of Precipitation Intensity and Boundary Layer Temperature to Atmospheric Heating Using a Cloud-Resolving Model",2019,"10.1029/2019GL082408","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070763088&doi=10.1029%2f2019GL082408&partnerID=40&md5=6f83fbb10b4f8bfa1d548b106e65efe1","Coarse-resolution global climate models cannot explicitly resolve the intensity distribution of tropical precipitation and how it responds to a forcing. We use a cloud-resolving model to study how imposed atmospheric radiative heating (such as that caused by greenhouse gases or absorbing aerosols) may alter precipitation intensity in the setting of radiative-convective equilibrium. It is found that the decrease in total precipitation is realized through preferentially reducing weak events. The intensity of strong precipitation events is maintained by a cancellation between the moistening of air parcels and weakening of updrafts. A boundary layer energy budget analysis suggests that free-tropospheric heating raises boundary layer temperatures mainly through a reduction in rain reevaporation. This insight leads to a predictive scaling for the surface sensible and latent flux changes. The results imply that cloud microphysical processes play a key role in shaping the temperature and precipitation responses to atmospheric heating. ©2019. The Authors."
"57191645378;56992522300;35093112400;","Synergistic Use of Satellite Active and Passive Microwave Observations to Estimate Typhoon Intensity",2019,"10.1109/IGARSS.2019.8897987","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077695423&doi=10.1109%2fIGARSS.2019.8897987&partnerID=40&md5=56b9b36cef0ef10e9e2f50cedc2e6706","Typhoon (TC) is one of the most powerful and destructive natural disasters. The analysis and determination of TC intensity is of great importance for disaster prevention [1] - [3]. Satellite remote sensing has become an effective means of monitoring TCs based on its high temporal and spatial resolution and large coverage. It is possible to estimate TC intensity using these satellite measurements when direct measurements are not available [4]. Microwave observations from polar-orbiting satellites can play a crucial role in revealing convective organization and eyewall structure that would otherwise be obscured by cloud tops [5]. Passive microwave sensors, such as SSM/I, TRMM/TMI, have been used to estimate TC intensity [6] - [10]. Besides, scatterometer also has allowed for continuous observation of ocean surface vector winds. Thus, scatterometer is a potential alternative for monitoring TCs. However, scatterometer measured wind speed range 2-24m/s, which make it very difficult to directly obtain the intensity of TCs [11]. © 2019 IEEE."
"57200211495;56308982600;","Is the negative IOD during 2016 the reason for monsoon failure over southwest peninsular India?",2019,"10.1007/s00703-017-0574-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040245442&doi=10.1007%2fs00703-017-0574-1&partnerID=40&md5=b577ce64aa2b3db34a0d4d0c5be5eb81","The study investigates the mechanism responsible for the deficit rainfall over southwest peninsular India during the 2016 monsoon season. Analysis shows that the large-scale variation in circulation pattern due to the strong, negative Indian Ocean Dipole phenomenon was the reason for the deficit rainfall. Significant reduction in the number of northward-propagating monsoon-organized convections together with fast propagation over the southwest peninsular India resulted in reduction in rainfall. On the other hand, their persistence for longer time over the central part of India resulted in normal rainfall. It was found that the strong convection over the eastern equatorial Indian Ocean creates strong convergence over that region. The combined effect of the sinking due to the well-developed Walker circulation originated over the eastern equatorial Indian Ocean and the descending limb of the monsoon Hadley cell caused strong subsidence over the western equatorial Indian Ocean. The tail of this large-scale sinking extended up to the southern parts of India. This hinders formation of monsoon-organized convections leading to a large deficiency of rainfall during monsoon 2016 over the southwest peninsular India. © 2018, Springer-Verlag GmbH Austria, part of Springer Nature."
"56919125400;36553486200;56089348800;57207953733;38863214100;54391390300;","Similarity Among Atmospheric Thermal Stratifications Over Elevated Surfaces Under Radiative-Convective Equilibrium",2019,"10.1029/2018GL081867","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063342208&doi=10.1029%2f2018GL081867&partnerID=40&md5=8822a1d83ba632338dc3ba49fca0cc13","An air column under radiative-convective equilibrium is studied here to understand equilibrium climate over different surface elevations. Cloud-resolving model (CRM) simulations show that atmospheric thermal stratifications exhibit similar structures when expressed in sigma coordinates over varying surface elevations under radiative-convective equilibrium. A zero-buoyancy plume model that reproduces CRM results is used to interpret related processes. As surface pressure decreases, decreased pressure on a certain σ level leads to decreases of moist adiabatic temperature lapse rate, which largely cancel the increases of moist adiabatic lapse rate by temperature decreases. Meanwhile, the invariance of convective entrainment/detrainment rates keeps the deviation of environmental temperature lapse rate from moist adiabat approximately invariant, result in similar thermal stratifications under varying surface pressures. A comparison of thermodynamic profiles over the Tibetan Plateau with those over plains in reanalysis confirms the similarity found in CRM simulations. This similarity provides a useful simplification for representing the effects of convection. © 2019. American Geophysical Union. All Rights Reserved."
"57188594058;35578543700;6701670597;","Nonlinear zonal propagation of organized convection in the tropics",2019,"10.1175/JAS-D-19-0082.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075635790&doi=10.1175%2fJAS-D-19-0082.1&partnerID=40&md5=6322efe62fcb64560ce3462c7bdbcd30","A wide range of the observed variability in the ITCZ is frequently explained in terms of equatorially trapped modes arising from Matsuno’s linear shallow-water model. Here, a series of zonally constant, meridionally symmetric aquachannel WRF simulations are used to study the propagation of tropical cloud clusters (CCs; patches of deep cloudiness and precipitation) in association with eastward-moving super cloud clusters (SCCs), also called convectively coupled Kelvin waves (CCKWs). Two independent but complementary methods are used: the first, from a local approach, involves a CC-tracking algorithm, while the second uses Lagrangian trajectories in a nonlocal framework. We show that the large-scale flow in low to midlevels advects the CCs either eastward or westward depending on model climatology, proximity to the CCKW axis, and latitude. Moreover, for most analyzed cases, sequences of CCs oscillate, describing qualitatively sinusoidal-like paths in longitude–time space, although with sharp transitions from westward to eastward motion due to westerly wind burst activity associated with the CCKWs. We also find that the discrete precipitation elements (CCs) are embedded in continuous tracks of positive moisture anomalies, which are parallel to the Lagrangian trajectories themselves. A conceptual model of the nonlinear SCC–CC interaction is presented. © 2019 American Meteorological Society."
"56893786200;56471429200;","The influence of meridional gradients in insolation and longwave optical depth on the climate of a gray radiation GCM",2018,"10.1175/JCLI-D-18-0103.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053071343&doi=10.1175%2fJCLI-D-18-0103.1&partnerID=40&md5=694309f4e7c3f93ef67d465f8e89653b","The relative contributions of the meridional gradients in insolation and in longwave optical depth (caused by gradients in water vapor) to the equator-to-pole temperature difference, and to Earth's climate in general, have not been quantified before. As a first step to understanding these contributions, this study investigates simulations with an idealized general circulation model in which the gradients are eliminated individually or jointly, while keeping the global means fixed. The insolation gradient has a larger influence on the model's climate than the gradient in optical depth, but both make sizeable contributions and the changes are largest when the gradients are reduced simultaneously. Removing either gradient increases global-mean surface temperature due to an increase in the tropospheric lapse rate, while the meridional surface temperature gradients are reduced. ""Global warming"" experiments with these configurations suggest similar climate sensitivities; however, the warming patterns and feedbacks are quite different. Changes in the meridional energy fluxes lead to polar amplification of the response in all but the setup in which both gradients are removed. The lapse-rate feedback acts to polar amplify the responses in the Earth-like setup, but is uniformly negative in the other setups. Simple models are used to interpret the results, including a prognostic model that can accurately predict regional surface temperatures, given the meridional distributions of insolation and longwave optical depths. © 2018 American Meteorological Society."
"54983414800;","Lagrangian cloud tracking and the precipitation-column humidity relationship",2018,"10.3390/atmos9080289","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054932697&doi=10.3390%2fatmos9080289&partnerID=40&md5=2b7632b6c58f4acf553607f549405ec4","The tropical, oceanic mean relationship between column relative humidity and precipitation is highly non-linear. Mean precipitation remains weak until it rapidly picks up and grows at high column humidity. To investigate the origin of this relationship, a Lagrangian cloud tracking code, RAMStracks, is developed, which can follow the evolution of clouds. RAMStracks can record the morphological properties of convective clouds, the meteorological environment of clouds, and their effects. RAMStracks is applied to a large-domain radiative convective equilibrium simulation, which produces a complex population of convective clouds. RAMStracks records the lifecycle of 501 clouds through growth, splits, mergers, and decay. The mean evolution of all these clouds is examined. It is shown that the column humidity evolves non-monotonically, but that lower-level and upper-level contributions to total moisture do evolve monotonically. The precipitation efficiency of tropical storms tends to increase with cloud age. This is confirmed using a prototype testing method. The same method reveals that different tracked clouds with similar initial conditions evolve in very different ways. This makes drawing general conclusions from individual storms difficult. Finally, the causality of the precipitation-column humidity relationship is examined. A Granger Causality test, as well as regressions, suggest that moisture and precipitation are causally linked, but that the direction of causality is ambiguous. Much of this link appears to come from the lower-level moisture's contribution to column humidity. © 2018 by the authors."
"44161353800;16426378500;","Idealized modeling of convective organization with changing sea surface temperatures using multiple equilibria in weak temperature gradient simulations",2017,"10.1002/2016MS000873","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021742638&doi=10.1002%2f2016MS000873&partnerID=40&md5=5c58f39605de7558b4ce7438eb0764d2","The weak temperature gradient (WTG) approximation is a method of parameterizing the influences of the large scale on local convection in limited domain simulations. WTG simulations exhibit multiple equilibria in precipitation; depending on the initial moisture content, simulations can precipitate or remain dry for otherwise identical boundary conditions. We use a hypothesized analogy between multiple equilibria in precipitation in WTG simulations, and dry and moist regions of organized convection to study tropical convective organization. We find that the range of wind speeds that support multiple equilibria depends on sea surface temperature (SST). Compared to the present SST, low SSTs support a narrower range of multiple equilibria at higher wind speeds. In contrast, high SSTs exhibit a narrower range of multiple equilibria at low wind speeds. This suggests that at high SSTs, organized convection might occur with lower surface forcing. To characterize convection at different SSTs, we analyze the change in relationships between precipitation rate, atmospheric stability, moisture content, and the large-scale transport of moist entropy and moisture with increasing SSTs. We find an increase in large-scale export of moisture and moist entropy from dry simulations with increasing SST, which is consistent with a strengthening of the up-gradient transport of moisture from dry regions to moist regions in organized convection. Furthermore, the changes in diagnostic relationships with SST are consistent with more intense convection in precipitating regions of organized convection for higher SSTs. © 2017. The Authors."
"54403961000;34871858000;","Equilibrium response to carbon dioxide and aerosol forcing changes in a 1D air–sea interactive model",2017,"10.1002/asl.733","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85012066746&doi=10.1002%2fasl.733&partnerID=40&md5=4b0bed1ea6c9a665cb35d5a5a80148fe","A 1D air–sea interactive model that couples an atmospheric column model with a slab ocean model was introduced. The model simulated an exact balance between radiative cooling and convective heating in the free troposphere. Within the planet boundary layer, the turbulent mixing produces cooling in the upper part and warming in the lower part, which is compensated by radiative and convective heating together. The model was then used to explore the equilibrium response of sea surface temperature (SST) and precipitation to carbon dioxide (CO2) and aerosol forcing changes. Results show a warming or cooling signal owning to increased CO2 or aerosols can be well captured by the ocean, leading to an increasing or decreasing of the SST, and hence the precipitation. Cutting off the interactions between atmosphere and ocean however renders different results. By applying the relaxed weak temperature gradient (WTG) approximation, the local response to aerosol forcing perturbations was investigated, which was shown to be largely different from the global response in spite of the same forcing. To understand the nonlinear interactions among different forcings, the equilibrium responses to multiple combinations of CO2 and aerosol forcings are analyzed. © 2017 The Authors. Atmospheric Science Letters published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"57201600407;54879952000;","Governing factors associated with intensification of TC-A diagnostic study of VSCS PHAILIN and LEHAR",2016,"10.1007/978-3-319-40576-6_17","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018047272&doi=10.1007%2f978-3-319-40576-6_17&partnerID=40&md5=624ffa716c3036426eccbf420b25715e","Tropical cyclones (TCs) are synoptic scale intense low pressure systems which form over the warm tropical oceans characterised by strong cyclonic winds and organised convection with heavy rainfall. The TC causes enormous damage to life and property at the time of crossing the coast and subsequent movement over the land. The TCs can impact over a wide area with its strong winds, heavy rains and storm surges. Gray (Hurricanes: their formation structure and likely role in the tropical circulation. In: Shaw DB (ed) Meteorology over the Tropical Oceans. Royal Meteorological Society, Bracknell, pp 155-218,1979) prepared a detailed climatology of the TCs in the global ocean basins. He observed that annually about 80 TCs form globally of which half to two thirds reach hurricane strength (maximum sustained winds greater than 33 m/s). East coast of India is frequently affected by TCs that form over Bay of Bengal (Tyagi et al., Inter-annual variation of frequency of cyclonic disturbances landfalling over WMO/ESCAP Panel Member Countries. WMO/TD-No. 1541 on 1st WMO International conference on Indian Ocean tropical cyclones and climate change, Muscat, Sultanate of Oman, 8-11 March 2009, WWRP-2010/2, 2010). During the period 1891-2010, about 134 severe TCs crossed the east coast of India (IMD, Cyclone e-Atlas-IMD tracks of cyclones and depressions over North Indian Ocean., 2011; Atlas of storm track). Anthes (Tropical cyclones: their evolution, structure and effects. Meteorological Monographs, American Meteorological Society, Boston, 1982) has extensively studied the three dimensional structure of TC. He observed that the surface pressure is lowest at the centre of the TC and increases outward. The wind speed reaches its maximum value at nearly 40-80 km from the centre beyond which it decreases. The central parts are warmer than the surroundings and the temperature anomaly could be more than 10° K at the upper troposphere. The TC grows upto a height of 10-15 km. Intense TCs frequently develop an eye, which is a cloud free region at the centre of the storm characterised by the presence of subsidence. © Capital Publishing Company 2017."
"56126832700;6506539438;","The role of large-scale convective organization for tropical high cloud amount",2014,"10.1002/2014GL060904","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904520513&doi=10.1002%2f2014GL060904&partnerID=40&md5=45ca55dd0e1290df5a47d5b16b1c47b3","Tropical high clouds are closely coupled to deep convection, but local cloud amount and convective mass flux are nonlinearly related. We use the Geophysical Fluid Dynamics Laboratory atmosphere-only model AM2 forced with idealized sea surface temperature (SST) perturbations to study the sensitivity of high clouds to the large-scale distribution of convection. Increasing/decreasing the SST contrast between convective and nonconvective regions decreases/increases the tropical deep convective area, and warming of convective areas decreases the tropical average convective mass flux (〈mc〉). In all experiments, fractional high cloud amount changes are less than fractional changes in 〈mc〉. High cloud amount is half as sensitive as expected from the climatological average cloud amount, as a function of convective mass flux, due to strong compensation from nonconvective high clouds. The latter results from changes in relative humidity related to the change in 〈mc〉. This effect renders high cloud amount remarkably robust to perturbations, though radiative effects of convective and nonconvective clouds will differ. © 2014. American Geophysical Union. All Rights Reserved.f."
"6603130624;","Response of the upper layers of the northern and central Bay of Bengal to the atmospheric events during summer monsoon of 1999",2014,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904500401&partnerID=40&md5=d3cc4b66bf2f0512c06c34e15c541479","Bay of Bengal Monsoon Experiment (BOBMEX-99) provided valuable information on the influence of atmospheric systems on the upper ocean thermohaline structure at 13°N, 87°E (TS1) and 17.5°N, 89°E (TS2). Two stations, separated by 545 km, were selected based on the fact that the occurrence of organized convection was high at both locations. From oceanographic point of view, TS1 and TS2 were located within anti-cyclonic and cyclonic gyres respectively, that shifted westward at a rate of 6.3 cm/sec. During the BOBMEX-99 observational period, three systems were formed over the northern BoB. Because of the proximity of TS2 to various systems, its influence was more reflected on the atmospheric and oceanic parameters at this location than at TS1. During the initial stages, atmospheric pressure at TS2 dropped by 3-6 mb and the atmosphere and the ocean surface cooled by 1.5 to 3°C and 0.35 to 0.85°C respectively. Associated with the systems, thermal inversions of 0.1°C to 0.15°C were observed at the base of isothermal layer. Surface salinity dropped by 0.8 psu and 1.2 psu with the rainfall during 31 July-1 August (70 mm) and 15-6 August (&gt;90 mm) respectively. The freshwater influx resulted in the formation of a barrier layer at TS2, which showed a positive relation thermal inversions. During BOBMEX- 99 period, the systems were formed whenever there was large positive salinity gradient; sea surface temperature exceeded 28.5°C and heat content with respect to 28.3°C exceeded ~3×107 Jm-2."
"55757850700;55758064100;","Sensitivity Of Cloud Ensembles To Variations In Microphysical Parameters. Part II - Influence Of Droplet Concentration [sensibilidade de conjuntos de nuvens a variações de parâmetros microfísicos. Parte II - Influência da concentração de gotículas]",2013,"10.1590/S0102-77862013000100003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878700856&doi=10.1590%2fS0102-77862013000100003&partnerID=40&md5=b6edac035ca28b6064c8daa729df6689","This article is the second of a series of four articles with aims in investigate the sensitivity of convective cloud systems to microphysical parameters. The tool used in this study is a cloud ensemble version of the Regional Atmospheric Modeling System (RAMS), as described in Part I. In Part II, the focus is on the influence of droplet concentrations, with the cloud ensemble model being configured with values that are typical of clean or polluted environments. Emphasis was given to the impact of those droplet concentration variations on the water partition among the different hydrometeor types, precipitation development and surface radiative budget. It was verified that the role played by droplet concentration changes over these variables might be somewhat dependent on the large-scale regime (""active"", with generalized deep convection or ""suppressed"", with inhibition of deep clouds and dominance of shallower and less organized convection)."
"7004081465;6603179076;6506482460;23012365000;57217182365;","Monitoring winter marine weather systems using satellite multisensor observations and ground-based data",2009,"10.1109/IGARSS.2009.5418047","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77950957627&doi=10.1109%2fIGARSS.2009.5418047&partnerID=40&md5=ee93bc92b0c552220e7142290e71bfea","Satellite and in situ data were examined for insights into the behavior of water vapor, cloud liquid water and wind speed during formation and evolution of synoptic-scale and mesoscale cyclones and cold air outbreaks - weather systems, which are usually accompanied by gale winds and intensive air-sea interaction. Satellite measurements carried out at visible, infrared and microwave ranges were collected over the Northern Pacific and Northern Atlantic Oceans in winter allowed investigating both the large-scale structural features (the main and the secondary fronts, etc.) and the small- and fine- scale details of the frontal boundaries, organized convection in the marine boundary layer of the atmosphere, etc. Multisatellite approach improved temporal resolution and the possibility to trace the location and characteristics of weather systems including fast moving and fast evolving systems. ©2009 IEEE."
"6507400558;7003704096;7005453346;6603561402;6603613067;","Tropical multiscale convective systems: Theory, modeling, and observations",2009,"10.1175/2008BAMS2565.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549111408&doi=10.1175%2f2008BAMS2565.1&partnerID=40&md5=fb4b1fbd4309730c1cde690e8775534e","A 5-day meeting was held at the University of Victoria in British Columbia Canada to further explain the behavior of the Madden Julian Oscillation (MJO). The MJO is poorly represented in contemporary general circulation models due to inadequacy of treatment across multiple spatial scales of the interaction of the associated hierarchy of organized structures. The event brought together 25 graduate students and post doctoral fellows from across North America with senior observationalists, theorists, and climate modelers. Topics that are included in the lecture and short course presentation are cloud microphysics, large-scale dynamics, internal waves, gravity currents and instabilities, convective organization, and global-scale dynamics."
"8658853400;7006380976;55999772700;","Propagation of convection in Africa: Implications for predictability of precipitation",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-55749095567&partnerID=40&md5=b49d9e41fa28769191dd2e80ada18ad7","Knowledge of the spatial and temporal variability of precipitation is needed for African societies to manage agriculture, water resources, public health, renewable energy, and hazard mitigation. This study examines the occurrences of organized convection in Africa using five years (1999-2003) of digital infrared imagery. Domains are: 0° to 20°N and 20°W to 40°E; 15°S to 15°N and 20°W to 45°E; 35°S to 15°S and 10°E to 45°E. Reduced-dimension techniques are used to document properties of cold clouds, proxies for precipitation. Large-scale environments are diagnosed from global analyses. A sizeable fraction of the rainfall in Africa results from long-lived ""episodes"" of deep convection. Episodes are coherent sequences of organized convection that propagate and regenerate on regional and continental scales. Most episodes have phase speeds of 10-20 m s1. A major generating factor for convection is thermal forcing associated with large elevated heat sources. Episodes occur with moderate vertical wind shear. Study results infer the potential for increased predictive skill in sub-seasonal weather prediction, which could enable substantial societal benefits. Copyright © 2007 IAHS Press."
"8986820300;15726586900;8986820700;8986820400;7103201242;7102609908;57203983376;24075934200;14020534200;57214447059;7004086472;","Diurnal variation of radar echoes and their possible role of preconditioning the atmospheric humidity",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-75149126153&partnerID=40&md5=99f242109ab5a450677c9fb53b107922","The number of convective features in three categories with their horizontal extent and their echo top height is investigated with lower tropospheric humidity. The time series of the number of convective features show clear diurnal variations in the convectively undisturbed period. The diurnal variation of isolated/slightly organized convection/congestus clouds have maximum in late midnight, and they possibly have the effect of moistening the lower troposphere. As they moisten the lower troposphere day by day, organized convections increase their number until convectively disturbed period. This diurnal variation of isolated convections is appeared to play important role for preconditioning the lower tropospheric humidity. After convective systems developed, the cycle of convective activity is delayed several hours. It is speculated that the time scale of development is getting longer from one day to one day plus several hours as they developed."
"35578543700;23486505900;7006184606;","Could random convection form hurricanes in a warmer world",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33744512943&partnerID=40&md5=8a22f45e68e5486d0eab5c39fb72f75c","The degree to which the frequency of tropical cyclogenesis depends on regional and global climate is assessed using version 2.1.2 of the Weather Research and Forecast Model (WRF). Simulations are first performed on 200-km × 200-km domains, which are too small to allow cyclogenesis during the transition to radiative-convective equilibrium (RCE). When the domain-averaged profiles of temperature and relative humidity reach a steady state, these profiles are then used as initial conditions for larger domains. These large-domain simulations are used to simulate three processes: spontaneous TC genesis from random convection; genesis (or failure) from an incipient vortex; and TC decline over cooler temperatures. Overall, results support the notion that significant changes in tropical climate, whether on geologic or anthropogenic time scales, are accompanied by significant changes in tropical cyclone activity."
"7409792174;","A numerical investigation of a slow-moving convective line in a weakly sheared environment",2005,"10.1007/BF02918706","https://www.scopus.com/inward/record.uri?eid=2-s2.0-26644447969&doi=10.1007%2fBF02918706&partnerID=40&md5=184acfa6ec25c77fc4bb9dcc45228f6b","A series of three-dimensional, cloud-resolving numerical simulations are performed to examine a slow-propagating, quasi-two-dimensional convective system in a weakly sheared environment during the Tropical Rainfall Measuring Mission Large-Scale Biosphere-Atmosphere (TRMM-LBA) field campaign. The focus is on the kinematics and thermodynamics, organization mechanisms, and dynamical effects of low-level shear, ice microphysics and tropospheric humidity. The control simulation, which is initialized with the observed sounding and includes full microphysics, successfully replicates many observed features of the convective system, such as the linear structure, spatial orientation, life cycle, and sluggish translation. The system at the mature stage displays a line-normal structure similar to that associated with squall-type convective systems, but the corresponding mesoscale circulation and thermodynamic modification are much weaker. Ice-phase microphysical processes are not necessary to the formation of the convective system, but they play a non-trivial role in the late evolution stage. In contrast, the low-level shear, albeit shallow and weak, is critical to the realistic realization of the convective line. The tropospheric moisture above the planetary boundary layer has an important impact on the behavior of convective organization. In particular, a dry layer in the lower troposphere significantly suppresses convective development and inhibits the generation of organized convection even though the convective available potential energy is substantial. The free-atmosphere humidity has received little attention in previous studies of organized convection and warrants further investigation."
"7403508241;7403531523;7004325649;7407116104;","On the relationship between tropical mean radiation and SST",2004,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-2442583277&partnerID=40&md5=a842134f472c4282978975937bb45da0","The outgoing longwave (LW) variations of tropical climate system, which shows close relationship with the blackbody emission and radiative-convective equilibrium processes in the seasonal to interannual time scales, are discussed. It is found that decadal variations of tropical mean radiation fields are much larger than expected. Theoretical calculations represent the net radiation of the system on longer time scales. On the decadal time scale, the Earth Radiation Budget Satellite (ERBS) measurements are significantly different from those of the Iris predicted tropical mean radiative flux anomalies, and do not support the strong negative feedback of the Iris effect."
"7006072255;7007099717;","Time-dependent response of the tropical atmosphere to a fixed sea surface temperature anomaly",2003,"10.1029/2003JD003524","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36549052085&doi=10.1029%2f2003JD003524&partnerID=40&md5=ba8555fcc4dba3cd83fcf4be093c3b31","The time-dependent response of the tropical atmosphere to a fixed, localized sea surface temperature (SST) anomaly is explored using a highly simplified nonlinear shallow water numerical model. The work builds on that by Webster [1972] and Gill [1980]. The present model has three layers and is formulated on an equatorial beta plane in an atmosphere initially in radiative-convective equilibrium. Observations suggest that the tropical atmosphere is only marginally unstable to moist convection. Accordingly, the convective parameterization in the model assumes that clouds consume the convective available potential energy at approximately the same rate as large-scale processes generate it. The convective parameterization allows for both shallow nonprecipitating and deep precipitating clouds. The convection scheme allows the shallow convection to condition the atmosphere for further deep convection, which is an important factor controlling deep convection in the tropics. The model calculations show that shallow convection moistens the middle troposphere, providing favorable conditions for the development of deep convection. In contrast, radiative cooling and drying of the middle troposphere act to suppress deep convection. In the model, these competing processes modulate the deep convection over the localized SST anomaly with a period of about 30 days. The convective heating also excites large-scale, equatorially trapped normal modes. The response ranges from a steady state flow similar to that by Gill to a periodic generation of Rossby-Kelvin wave couplets and finally to a transition to chaotic behavior depending on the Strength of the forcing. Copyright 2003 by the American Geophysical Union."
"7801670627;","A simplified model of quasi-organized ensembles of convection cells",1997,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031544227&partnerID=40&md5=5e930d5dacccd888c14475c0e86bc53c","The paper is devoted to theoretical study of stochastic and quasi-organized convection structures. A simplified hydrodynamic model is proposed in which the cells are either grouped into quasi-organized ensembles (hexagonal structures and cloud ridges) or located chaotically, depending on the given background fields of temperature, wind, and moisture."
"6701740416;36006968000;","Feedback between convective heating and dynamics and movements of tropical cyclones",1996,"10.1007/BF01029711","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030511413&doi=10.1007%2fBF01029711&partnerID=40&md5=450d31e7a24f7ca97ff8e350f2bec635","It is shown that there exists a mechanism that can cause north-northwest movement of tropical cyclones in addition to already recognised mechanisms such as steering current and beta drift. This mechanism depends on the interaction between organised convection and dynamics. In the initial stages of formation of a cyclone, it is assumed that the hydrodynamic instabilities result in an incipient disturbance that organises some convection giving rise to a heat source. The atmospheric response to a localized heat source located off the equator in the northern hemisphere produces a low level vorticity field with a maximum in the northwest sector of the original heat source. If the 'Ekman-CISK' which depends on the low level vorticity, was the dominating mechanism for moisture convergence, the location of the heat source would move to the new location of vorticity maximum. A repetition of this process would result in a northwest movement of the heat source and hence that of the cyclone. The movement of a tropical vortex under the influence of this mechanism which depends on asymmetries created by linear dispersion of Rossby waves is first illustrated using a linear model. It is then demonstrated that this process also enhances the motion of a tropical vortex in a nonlinear model. Importance of this feedback and the resulting movements of a tropical vortex in determining the actual track of a cyclone and in bogusing an initial vortex for prediction models are illustrated."
"7101795549;","A linear stability analysis of stratocumulus convection driven by radiative cooling",1995,"10.1034/j.1600-0870.1995.t01-1-00007.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981645310&doi=10.1034%2fj.1600-0870.1995.t01-1-00007.x&partnerID=40&md5=24236101489cd0c7a565e5b5ab2d9345","Fully cloudy stratocumulus layers sometimes exhibit convective organization at a single dominant length scale with an aspect ratio (width/height) ≈ 1. We present a linear stability analysis of a radiatively‐cooled cloud beneath a capping inversion and show that small aspect ratio modes are energetically favored over a broad range of inversion strengths and cooling depths. The integrated mode energy budgets indicate that, given a vertically limited region of radiative cooling, highly dissipative, localized convective modes can grow through efficient buoyancy production beneath the inversion. Including the effect of decoupling on the sub‐cloud layer enhances this scale selection, but as the depth of the unstable layer is increased beyond 20% of the boundary layer depth, the critical Rayleigh number and the aspect ratio of the fastest growing mode approach that of a layer capped by a no‐slip rigid lid. Copyright © 1995, Wiley Blackwell. All rights reserved"
"6602445893;55798412800;6603271938;","A study of non‐forecasted cyclogenesis in a polar air mass over the Baltic Sea",1990,"10.1034/j.1600-0889.1996.t01-1-00005.x-i1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981579217&doi=10.1034%2fj.1600-0889.1996.t01-1-00005.x-i1&partnerID=40&md5=f743910666c638976f062fa185831dc9","We present a case study of a developing meso‐scale low in a cold air mass where baroclinicity was weak. Both mid‐tropospheric vorticity advection and enhanced organized convection over the Baltic Sea seem to have caused the initial development. Later, baroclinic instability took over the dominating role in the development. The low studied exhibited properties of both polar lows and comma clouds. The case was simulated by a high‐resolution limited area numerical model, which failed to develop the intense meso‐scale part of the surface cyclone, probably because of too coarse a resolution. Copyright © 1990, Wiley Blackwell. All rights reserved"
"6602445893;55798412800;6603271938;","A study of non‐forecasted cyclogenesis in a polar air mass over the Baltic Sea",1990,"10.1034/j.1600-0870.1990.00014.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981578101&doi=10.1034%2fj.1600-0870.1990.00014.x&partnerID=40&md5=99f493f44829bf97008074f65182d60e","We present a case study of a developing meso‐scale low in a cold air mass where baroclinicity was weak. Both mid‐tropospheric vorticity advection and enhanced organized convection over the Baltic Sea seem to have caused the initial development. Later, baroclinic instability took over the dominating role in the development. The low studied exhibited properties of both polar lows and comma clouds. The case was simulated by a high‐resolution limited area numerical model, which failed to develop the intense meso‐scale part of the surface cyclone, probably because of too coarse a resolution. Copyright © 1990, Wiley Blackwell. All rights reserved"
"16197778800;7103293232;","Remote sensing of the thermal forcing on the tropical Pacific",1989,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024844833&partnerID=40&md5=c4fad73eb25a5ed127cbe85829b159e6","Monthly fields of shortwave radiation (SR) and latent heat flux (LE) over the central and eastern tropical Pacific between 1980 and 1983 have been computed using satellite data. They are the dominant variable components of surface thermal forcing on the ocean in this time scale. During the 1982-1983 El Nino Southern Oscillation (ENSO) episode, surface-wind convergence and cloudiness associated with the displacement of equatorial organized convection caused a reduction in both the SR into the ocean and the LE out of the ocean. The lag-correlation coefficients between the forcing (SR-LE) and the sea surface temperature are found to be significantly high outside the equatorial region, showing that surface thermal forcing is the dominant factor in sea surface temperature change. In the narrow equatorial wave guide, ocean dynamics play a more important role, and surface heat flux is a consequence rather than the cause of sea surface temperature change."
"7003911760;7005981420;7005941690;","LIDAR OBSERVATIONS OF PLANETARY BOUNDARY LAYER.",1985,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022286088&partnerID=40&md5=e5b7ec30bf36de706bec5bba207de5bf","It is shown that an airborne downlooking lidar is a powerful diagnostic tool for investigating the structure and dynamics of the planetary boundary layer (PBL). It is also shown that the PBL is highly variable on scales ranging from a few kilometers to several tens of kilometers and therefore conventional soundings may be inadequate in describing its structure. Finally, the presence of wind shear at the PBL top may be important both in determining entrainment rate and in controlling the horizontal size and spacings of organized convective cells."
"7801422214;7005501098;","Some aspects of post- frontal convective areas along the West Coast of the United States.",1983,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040857292&partnerID=40&md5=9c72cd7a7e0620b77493e9f98450ebee","The European Center for Medium-Range Weather Forecasts (ECMWF) Level III-b analyses are used to study cases of post-frontal convective areas that occurred off the West Coast of the United States. A five-year climatology suggests that an average of about 13 convective events occurs each winter, and that two of three cases are likely to have intense and well-organized convection. -from STAR, 23(1), 1985"
"7005485117;6602624691;","Sensitivity of the monsoon onset to differential heating ( India).",1981,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019647762&partnerID=40&md5=c05ddfa82f90ae07062ac5478acca4f2","The energetic interaction processes between stream function and velocity potential fields before, during, and after the onset of summer monsoons are examined using monsoon experiment wind data. The acceleration of low level winds at 10oN was investigated by a multilevel primitive equation model. The slow northward march of organized convection east and northeast of India is the key factor.-from STAR, 20(14), 1982"