Goddard Cumulus Ensemble (Gce) Model: Application for Understanding Preciptation Processes

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). The 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 (size about 2–200 km). The CRMs also allow explicit interaction between outgoing longwave (cooling) and incoming solar (heating) radiation with clouds. Observations can provide the initial conditions and validation for CRM results.

[1]  G. E. Hill.  Factors Controlling the Size and Spacing of Cumulus Clouds as Revealed by Numerical Experiments , 1974 .

[2]  M. Moncrieff,et al.  A Numerical Study of the Diurnal Cycle of Tropical Oceanic Convection , 1998 .

[3]  Joanne Simpson,et al.  A Double-Moment Multiple-Phase Four-Class Bulk Ice Scheme. Part II: Simulations of Convective Storms in Different Large-Scale Environments and Comparisons with other Bulk Parameterizations , 1995 .

[4]  Joanne Simpson,et al.  An Ice-Water Saturation Adjustment , 1989 .

[5]  Joanne Simpson,et al.  Goddard Cumulus Enble Model. Part II: Applications for Studying Cloud Precipitating Processes and for NASA TRMM , 1993 .

[6]  Robert F. Adler,et al.  Microwave simulations of a tropical rainfall system with a three-dimensional cloud model , 1991 .

[7]  J. Elsner,et al.  Large-scale circulation departures related to wet episodes in north-east Brazil , 2007 .

[8]  Ka-Ming Lau,et al.  The Tropical Water and Energy Cycles in a Cumulus Ensemble Model. Part I: Equilibrium Climate , 1994 .

[9]  Alexander Khain,et al.  Simulation of precipitation formation in the Eastern Mediterranean coastal zone using a spectral microphysics cloud ensemble model , 1996 .

[10]  G. Holland,et al.  Cumulus mergers in the maritime continent region , 1993 .

[11]  J. Gamache,et al.  Water Budget of a Mesoscale Convective System in the Tropics , 1983 .

[12]  J. Molinari,et al.  Parameterization of Convective Precipitation in Mesoscale Numerical Models: A Critical Review , 1992 .

[13]  Peter V. Hobbs,et al.  The Mesoscale and Microscale Structure and Organization of Clouds and Precipitation in Midlatitude Cyclones. XII: A Diagnostic Modeling Study of Precipitation Development in Narrow Cold-Frontal Rainbands , 1984 .

[14]  M. Lemone,et al.  Cumulonimbus vertical velocity events in GATE. Part I: Diameter, intensity and mass flux , 1980 .

[15]  R. P. Pearce,et al.  A three‐dimensional primitive equation model of cumulonimbus convection , 1974 .

[16]  Steven K. Krueger,et al.  SUMMARY OF PROGRESS AND MAIN ACTIONS / RECOMMENDATIONS FROM THE NINTH MEETING OF THE GEWEX CLOUD SYSTEM STUDY ( GCSS , 2001 .

[17]  H. Chin.  The impact of the ice phase and radiation on a midlatitude squall line system , 1994 .

[18]  B. Ferrier,et al.  Shipboard Radar Rainfall Patterns within the TOGA COARE IFA , 1997 .

[19]  Chung-Hsiung Sui,et al.  A preliminary study of the tropical water cycle and its sensitivity to surface warming , 1993 .

[20]  Smoothing of the Intensity Curve Obtained from a Solution of the Spherical Harmonics Approximation to the Transfer Equation , 1974 .

[21]  Shuyi S. Chen,et al.  Three-Dimensional Week-Long Simulations of TOGA COARE Convective Systems Using the MM5 Mesoscale Model , 1999 .

[22]  J. Malkus.  SOME RESULTS OF A TRADE-CUMULUS CLOUD INVESTIGATION , 1953 .

[23]  J. Warner.  Observations Relating to Theoretical Models of a Thermal , 1963 .

[24]  K. Emanuel,et al.  The Representation of Cumulus Convection in Numerical Models , 1993 .

[25]  Wei-Kuo Tao,et al.  A Parameterization for the Triggering of Landscape-Generated Moist Convection. Part I: Analysis of High-Resolution Model Results , 2001 .

[26]  B. Ferrier,et al.  A Double-Moment Multiple-Phase Four-Class Bulk Ice Scheme. Part I: Description , 1994 .

[27]  R. Houze.  Observed structure of mesoscale convective systems and implications for large-scale heating , 1989 .

[28]  Isaac M. Held,et al.  Radiative-convective equilibrium with explicit two-dimensional moist convection , 1993 .

[29]  Jean-Luc Redelsperger,et al.  Comparison between a Three-Dimensional Simulation and Doppler Radar Data of a Tropical Squall Line: Transports of Mass, Momentum, Heat, and Moisture , 1988 .

[30]  D. Randall,et al.  Liquid and Ice Cloud Microphysics in the CSU General Circulation Model. Part 1: Model Description and Simulated Microphysical Processes , 1996 .

[31]  M. Lemone,et al.  Perturbation Pressure Fields Measured by Aircraft around the Cloud-Base Updraft of Deep Convective Clouds , 1988 .

[32]  W. Grabowski,et al.  The multidimensional positive definite advection transport algorithm: nonoscillatory option , 1990 .

[33]  Robert F. Adler,et al.  An algorithm to estimate the heating budget from vertical hydrometeor profiles , 1990 .

[34]  Anne M. Thompson,et al.  Free tropospheric ozone production following entrainment of urban plumes into deep convection , 1992 .

[35]  Harry H. Hendon,et al.  Some Implications of the Mesoscale Circulations in Tropical Cloud Clusters for Large-Scale Dynamics and Climate , 1984 .

[36]  W. Tao,et al.  The Sensitivity of Tropical Squall Lines (GATE and TOGA COARE) to Surface Fluxes: Cloud Resolving Model Simulations , 1999 .

[37]  Edward J. Zipser,et al.  Cumulonimbus Vertical Velocity Events in GATE. Part II: Synthesis and Model Core Structure , 1980 .

[38]  W. Collins,et al.  Long-Term Behavior of Cloud Systems in TOGA COARE and Their Interactions with Radiative and Surface Processes. Part II: Effects of Ice Microphysics on Cloud–Radiation Interaction , 1999 .

[39]  Wei-Kuo Tao.  A Numerical Study of the Structure and Vertical Transport Properties of A Tropical Convective System , 1983 .

[40]  K. E. Moore,et al.  Daytime turbulent exchange between the Amazon forest and the atmosphere , 1990 .

[41]  W. Tao,et al.  Factors Responsible for Precipitation Efficiencies in Midlatitude and Tropical Squall Simulations , 1996 .

[42]  M. Lemone.  The influence of vertical wind shear on the diameter of cumulus clouds in CCOPE , 1989 .

[43]  Robert F. Adler,et al.  On the Tropical Rainfall Measuring Mission (TRMM) , 1996 .

[44]  H. D. Orville,et al.  Bulk Parameterization of the Snow Field in a Cloud Model , 1983 .

[45]  W. Cotton,et al.  Numerical Study of an Observed Orogenic Mesoscale Convective System. Part 2: Analysis of Governing Dynamics , 1989 .

[46]  S. Rutledge,et al.  A Diagnostic Modelling Study of the Trailing Stratiform Region of a Midlatitude Squall Line. , 1987 .

[47]  M. Bader,et al.  Convective cloud merging and its effect on rainfall , 1982, Nature.

[48]  Roscoe R. Braham,et al.  The thunderstorm : report of the thunderstorm project , 1949 .

[49]  Robert B. Wilhelmson,et al.  A Numerical Study of Storm Splitting that Leads to Long-Lived Storms , 1978 .

[50]  Internal Structure and Development Processes of C-Scale Aggregates of Cumulus Clouds , 1978 .

[51]  W. Tao,et al.  A Study of Landscape-Generated Deep Moist Convection , 1998 .

[52]  S. Changnon.  Effects of Urban Areas and Echo Merging on Radar Echo Behavior , 1976 .

[53]  K. Lau,et al.  Radiative–Convective Processes in Simulated Diurnal Variations ofTropical Oceanic Convection , 1998 .

[54]  An Investigation of the Development of Cumulonimbus Systems over South Florida. Part I: Boundary Layer Interactions , 1986 .

[55]  Eric A. Smith,et al.  Retrieved Vertical Profiles of Latent Heat Release Using TRMM Rainfall Products for February 1998 , 2000 .

[56]  David A. Randall,et al.  Explicit Simulation of Cumulus Ensembles with the GATE Phase III Data: Comparison with Observations , 1996 .

[57]  Tetsuo Nakazawa,et al.  Tropical Super Clusters within Intraseasonal Variations over the Western Pacific , 1988 .

[58]  Sensitivity of a simulated tropical squall line to long‐wave radiation , 1997 .

[59]  C. W. Newton.  Circulations in large sheared cumulonimbus , 1966 .

[60]  R. A. Pielke,et al.  On cumulus mergers , 1980 .

[61]  Robert F. Adler,et al.  A Satellite Infrared Technique to Estimate Tropical Convective and Stratiform Rainfall , 1988 .

[62]  D. Churchill,et al.  Development and Structure of Winter Monsoon Cloud Clusters On 10 December 1978 , 1984 .

[63]  Kensuke Nakajima,et al.  Numerical Experiments Concerning the Origin of Cloud Clusters in the Tropical Atmosphere , 1988 .

[64]  Robert F. Adler,et al.  A Proposed Tropical Rainfall Measuring Mission (TRMM) Satellite , 1988 .

[65]  Joanne Simpson,et al.  Statistical properties of a cloud ensemble - A numerical study , 1987 .

[66]  W. Tao,et al.  Comments on "The Sensitivity Study of Radiative-Convective Equilibrium in the Tropics with a Convective Resolving Model" , 2000 .

[67]  Q. Fu,et al.  Interactions of Radiation and Convection in Simulated Tropical Cloud Clusters , 1995 .

[68]  Leo J. Donner,et al.  Three-Dimensional Cloud-System Modeling of GATE Convection , 1999 .

[69]  W. Tao,et al.  A regional estimate of convective transport of CO from biomass burning , 1992 .

[70]  W. Tao,et al.  A parameterization for the triggering of landscape-generated moist convection. Part II: Zero-order and first-order closure , 2001 .

[71]  C. W. Newton,et al.  Dynamics of Severe Convective Storms , 1963 .

[72]  W. Tao,et al.  Response of Deep Tropical Cumulus Clouds to Mesoscale Processes , 1980 .

[73]  William R. Cotton,et al.  Cumulus Convection in Shear Flow—Three-Dimensional Numerical Experiments , 1978 .

[74]  R. Rotunno,et al.  A Theory for Strong, Long-Lived Squall Lines , 1988 .

[75]  Richard H. Johnson,et al.  Heating, Moistening, and Rainfall over the Western Pacific Warm Pool during TOGA COARE. , 1996 .

[76]  J. Dudhia.  Numerical Study of Convection Observed during the Winter Monsoon Experiment Using a Mesoscale Two-Dimensional Model , 1989 .

[77]  John M. Brown.  Mesoscale Unsaturated Downdrafts Driven by Rainfall Evaporation: A Numerical Study , 1979 .

[78]  Kuan-Man Xu,et al.  Evaluation of cloudiness parameterizations using a cumulus ensemble model , 1991 .

[79]  William A. Gallus,et al.  Heat and Moisture Budgets of an Intense Midlatitude Squall Line , 1991 .

[80]  Joanne Simpson,et al.  Goddard Cumulus Ensemble Model. Part I: Model Description , 1993 .

[81]  Y. Ogura,et al.  Response of Tradewind Cumuli to Large-Scale Processes , 1980 .

[82]  C. Sui,et al.  Heating, Moisture, and Water Budgets of Tropical and Midlatitude Squall Lines: Comparisons and Sensitivity to Longwave Radiation , 1993 .

[83]  W. M. Gray,et al.  Diurnal Variation of Deep Cumulus Convection , 1977 .

[84]  Wojciech W. Grabowski,et al.  Cloud Resolving Modeling of Tropical Cloud Systems during Phase III of GATE. Part III: Effects of Cloud Microphysics , 1999 .

[85]  E. Rappaport,et al.  Air Motions and Precipitation Structure of an Early Summer Squall Line over the Eastern Tropical Atlantic , 1984 .

[86]  K. Lau,et al.  Origin of Low-Frequency (Intraseasonal) Oscilliations in the Tropical Atmosphere. Part II: Structure and Propagation of Mobile Wave-CISK Modes and Their Modification by Lower Boundary Forcings. , 1989 .

[87]  E. B. Kraus,et al.  The Diurnal Precipitation Change over the Sea , 1963 .

[88]  M. Chou,et al.  A Solar Radiation Model for Use in Climate Studies , 1992 .

[89]  E. Zipser.  The Role of Organized Unsaturated Convective Downdrafts in the Structure and Rapid Decay of an Equatorial Disturbance , 1969 .

[90]  Wojciech W. Grabowski,et al.  Cloud-resolving modeling of cloud systems during Phase III of GATE. Part II: Effects of resolution and the third spatial dimension , 1998 .

[91]  J. McBride,et al.  The Vertical Distribution of Heating in AMEX and GATE Cloud Clusters. , 1989 .

[92]  Xiaoqing Wu,et al.  Long-Term Behavior of Cloud Systems in TOGA COARE and Their Interactions with Radiative and Surface Processes. Part I: Two-Dimensional Modeling Study , 1998 .

[93]  C. W. Newton.  Structure and mechanism of the prefrontal squall line. , 1950 .

[94]  Edward J. Zipser,et al.  Mesoscale and convective-scale downdrafts as distinct components of squall-line structure , 1977 .

[95]  Wojciech W. Grabowski,et al.  Cloud-Resolving Modeling of Tropical Cloud Systems during Phase III of GATE. Part I: Two-Dimensional Experiments. , 1996 .

[96]  K. Lau,et al.  Equilibrium States Simulated by Cloud-Resolving Models , 1999 .

[97]  Joseph B. Klemp,et al.  The structure and classification of numerically simulated convective storms in directionally varying wind shears , 1984 .

[98]  Roland List,et al.  Free-Fall Behavior of Planar Snow Crystals, Conical Graupel and Small Hail , 1971 .

[99]  Wei-Kuo Tao,et al.  A Study of the Response of Deep Tropical Clouds to Mesoscale Processes: Three-Dimensional Numerical Experiments , 1986 .

[100]  W. Frank,et al.  Radiative forcing of simulated tropical cloud clusters , 1993 .

[101]  W. Tao,et al.  The Influence of Soil Moisture, Coastline Curvature, and Land-Breeze Circulations on Sea-Breeze Initiated Precipitation , 2013 .

[102]  M. Chong,et al.  A Tropical Squall Line Observed during the COPT 81 Experiment in West Africa. Part II: Water Budget , 1989 .

[103]  R. J. Reed,et al.  Structure and Properties of Synoptic-Scale Wave Disturbances in the Intertropical Convergence Zone of the Eastern Atlantic. , 1979 .

[104]  Mitchell W. Moncrieff,et al.  Organized convective systems : archetypal dynamical models, mass and momentum flux theory, and parametrization , 1992 .

[105]  Robert A. Houze,et al.  Radar Characteristics of Tropical Convection Observed During GATE: Mean Properties and Trends Over the Summer Season , 1977 .

[106]  R. Wilhelmson,et al.  Evolution and Structure of Tropical Squall Line Elements within a Moderate CAPE and Strong Low-Level Jet Environment , 1998 .

[107]  W. Tao,et al.  Microwave and infrared simulations of an intense convective system and comparison with aircraft observations , 1995 .

[108]  Joanne Simpson,et al.  Cloud interactions and merging - Numerical simulations , 1984 .

[109]  J. Dudhia,et al.  A numerical simulation of quasi-stationary tropical convective bands , 2007 .

[110]  W. Frank.  A Hybrid Parameterization with Multiple Closures , 1993 .

[111]  William R. Cotton,et al.  The Sensitivity of a Simulated Extratropical Mesoscale Convective System to Longwave Radiation and Ice-Phase Microphysics , 1988 .

[112]  Robert F. Adler,et al.  Retrieval Algorithms for Estimating the Vertical Profiles of Latent Heat Release: Their Applications for TRMM@@@TRMMへの応用 , 1993 .

[113]  W. Tao,et al.  The Impact of Ocean Surface Fluxes on a TOGA COARE Convective System , 1996 .

[114]  Edward J. Zipser,et al.  The Role of Environmental Shear and Thermodynamic Conditions in Determining the Structure and Evolution of Mesoscale Convective Systems during TOGA COARE , 1998 .

[115]  Robert A. Houze,et al.  The Contribution of Mesoscale Motions to the Mass and Heat Fluxes of an Intense Tropical Convective System , 1980 .

[116]  S. Esbensen,et al.  Determination of Bulk Properties of Tropical Cloud Clusters from Large-Scale Heat and Moisture Budgets , 1973 .

[117]  Robert B. Wilhelmson,et al.  Simulations of Right- and Left-Moving Storms Produced Through Storm Splitting , 1978 .

[118]  Joanne Simpson,et al.  Numerical Simulation of a Subtropical Squall Line over the Taiwan Strait , 1991 .

[119]  Margaret A. LeMone,et al.  Momentum and Mass Transport by Convective Bands: Comparisons of Highly Idealized Dynamical Models to Observations. , 1994 .

[120]  R. S. Scorer,et al.  Bubble theory of penetrative convection , 1953 .

[121]  G. Stephens.  The Influence of Radiative Transfer on the Mass and Heat Budgets of Ice Crystals Failing in the Atmosphere , 1983 .

[122]  K. Lau,et al.  An inquiry into the cirrus-cloud thermostat effect for tropical sea surface temperature , 1994 .

[123]  R. Hemler,et al.  Numerical simulation of deep tropical convection associated with large-scale convergence , 1986 .

[124]  C. Sui,et al.  Mechanisms of Cloud-radiation interaction in the tropics and midlatitudes , 1996 .

[125]  M. Chou,et al.  Technical report series on global modeling and data assimilation. Volume 3: An efficient thermal infrared radiation parameterization for use in general circulation models , 1994 .

[126]  W. Tao,et al.  The Effect of Melting Processes on the Development of a Tropical and a Midlatitude Squall Line , 1995 .

[127]  S. K. Cox,et al.  Estimates of Radiative Divergence during Phase III of the GARP Atlantic Tropical Experiment: Part II. Analysis of Phase III Results , 1979 .

[128]  M. Garstang,et al.  Amazon Coastal Squall Lines. Part II: Heat and Moisture Transports , 1994 .

[129]  J. McBride,et al.  Rawinsonde Budget Analyses during the TOGA COARE IOP , 1996 .

[130]  R. Holle,et al.  Tornado Formation from Downdraft Interaction In the FACE Mesonetwork , 1980 .

[131]  R. Houze.  Stratiform precipitation in regions of convection : A meteorological paradox ? , 1997 .

[132]  J. T. Steiner.  A Three-Dimensional Model of Cumulus Cloud Development , 1973 .

[133]  P. Webster,et al.  Tropical Upper-Tropospheric Extended Clouds: Inferences from Winter MONEX , 1980 .

[134]  Joanne Simpson,et al.  Comparison of Ice-Phase Microphysical Parameterization Schemes Using Numerical Simulations of Tropical Convection , 1991 .

[135]  W. Tao,et al.  Modeling Study of a Tropical Squall-Type Convective Line , 1989 .

[136]  D. Churchill,et al.  Effects of Radiation and Turbulence on the Diabatic Heating and Water Budget of the Stratiform Region of a Tropical Cloud Cluster , 1991 .

[137]  Steven K. Krueger,et al.  Numerical simulation of tropical cumulus clouds and their interaction with the subcloud layer , 1988 .

[138]  Edward V. Browell,et al.  Cloud draft structure and trace gas transport , 1990 .

[139]  Richard H. Johnson,et al.  Rainfall and Radiative Heating Rates from TOGA COARE Atmospheric Budgets , 2000 .

[140]  Akio Arakawa,et al.  Semiprognostic Tests of the Arakawa-Schubert Cumulus Parameterization Using Simulated Data , 1992 .

[141]  R. Rauber,et al.  Numerical Simulation of the Effects of Varying Ice Crystal Nucleation Rates and Aggregation Processes on Orographic Snowfall , 1986 .

[142]  J. Dudhia,et al.  The two‐dimensional dynamics of West African squall lines , 2007 .

[143]  J. Charney,et al.  A Numerical Model for Thermal Convection in the Atmosphere , 1960 .

[144]  Robert E. Schlesinger,et al.  A Three-Dimensional Numerical Model of an Isolated Thunderstorm: Part I. Comparative Experiments for Variable Ambient Wind Shear , 1978 .

[145]  K. Lau,et al.  Large-Scale Forcing and Cloud–Radiation Interaction in the Tropical Deep Convective Regime , 1999 .

[146]  J. Klemp,et al.  The Simulation of Three-Dimensional Convective Storm Dynamics , 1978 .

[147]  D. Randall,et al.  Impact of Interactive Radiative Transfer on the Macroscopic Behavior of Cumulus Ensembles. Part II: Mechanisms for Cloud-Radiation Interactions , 1995 .

[148]  Robert A. Houze,et al.  Structure and Dynamics of a Tropical Squall–Line System , 1977 .

[149]  Mesoscale Motion Fields Associated with a Slowly Moving GATE Convective Band , 1981 .

[150]  A Quasi-One-Dimensional Cumulus Cloud Model and Parameterization of Cumulus Heating and Mixing Effects. , 1980 .

[151]  N. Phillips,et al.  Scale Analysis of Deep and Shallow Convection in the Atmosphere , 1962 .

[152]  G. Sommeria,et al.  Three-Dimensional Simulation of Turbulent Processes in an Undisturbed Trade Wind Boundary Layer , 1976 .

[153]  Richard H. Johnson.  Heat and moisture sources and sinks of Asian monsoon precipitating systems , 1992 .

[154]  W. Tao,et al.  GEWEX Cloud System Study (GCSS) Working Group 4: Precipitating Convective Cloud Systems , 1997 .

[155]  Terry L. Clark,et al.  Numerical simulations with a three-dimensional cloud model: Lateral boundary condition experiments and multicellular severe storm simulations , 1979 .

[156]  Richard H. Johnson,et al.  The Relationship of Surface Pressure Features to the Precipitation and Airflow Structure of an Intense Midlatitude Squall Line , 1988 .

[157]  Anthony D. Del Genio,et al.  A Prognostic Cloud Water Parameterization for Global Climate Models , 1996 .

[158]  A. Robert,et al.  Cloud Clusters and Large-Scale Vertical Motions in the Tropics , 1982 .

[159]  D. Randall,et al.  A Semiempirical Cloudiness Parameterization for Use in Climate Models , 1996 .

[160]  M. Chong,et al.  A Tropical Squall Line Observed during the COPT 81 Experiment in West Africa. Part III: Heat and Moisture Budgets , 1990 .

[161]  D. Gregory,et al.  A numerical study of the parametrization of deep tropical convection , 1989 .

[162]  W. Tao,et al.  Vertical Profiles of Latent Heat Release and Their Retrieval for TOGA COARE Convective Systems Using a Cloud Resolving Model, SSM/I, and Ship-borne Radar Data , 2000 .

[163]  N. Westcott.  A Historical Perspective on Cloud Mergers , 1984 .

[164]  Harshvardhan,et al.  Diurnal Variability of the Hydrologic Cycle in a General Circulation Model , 1991 .

[165]  Robert B. Wilhelmson.  The Life Cycle of a Thunderstorm in Three Dimensions , 1974 .

[166]  Wei-Kuo Tao,et al.  A numerical study of the vertical transport of momentum in a tropical rainband , 1984 .

[167]  Richard H. Johnson.  Partitioning tropical heat and moisture budgets into cumulus and mesoscale components: implications for cumulus parameterization , 1984 .

[168]  Joanne Simpson,et al.  A Further Study of Cumulus Interactions and Mergers: Three-Dimensional Simulations with Trajectory Analyses , 1989 .

[169]  Robert E. Schlesinger,et al.  A Three-Dimensional Numerical Model of an Isolated Deep Convective Cloud: Preliminary Results , 1975 .

[170]  R. Houze,et al.  Rear Inflow in Squall Lines with Trailing Stratiform Precipitation , 1987 .

[171]  K. Lau,et al.  Genesis and Evolution of Hierarchical Cloud Clusters in a Two-Dimensional Cumulus-Resolving Model , 2001 .

[172]  J. Simpson.  Downdrafts as Linkages in Dynamic Cumulus Seeding Effects , 1980 .

[173]  W. Tao,et al.  Tropical Deep Convection and Ozone Formation , 1997 .

[174]  G. Caniaux,et al.  A Numerical Study of the Stratiform Region of a Fast-Moving Squall Line. Part I: General Description and Water and Heat Budgets , 1994 .