Revision of convection, radiation and cloud schemes in the ECMWF integrated forecasting system

Revisions to the convection, radiation and cloud schemes recently introduced into the European Centre for Medium‐Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS) are described, together with discussion of their impact upon model performance. Seasonal simulations with observed sea surface temperatures (SSTs) for June/July/August 1987 and December/January/February 1987/88 with a low‐resolution (T63) version of the model are used to assess the impact of the revised schemes, concentrating upon tropical climate and variability. While the revisions improve the physical basis of the schemes, and each improves aspects of the seasonal climate, overall improvement does not result until the changes are combined. Biases in simulated temperature and top‐of‐atmosphere and surface energy budgets are reduced, leading to a substantial decrease of an equatorial SST cold bias in coupled ocean‐atmosphere simulations used in seasonal forecasting. At higher resolution (T213) changes to temperature and wind fields are similar to those found in seasonal simulations, with little impact upon medium‐range forecast performance in mid latitudes, although these forecasts proved a more critical test of the impact of the schemes upon mid‐latitude flows. The paper demonstrates the methodology used in the development of parametrizations of physical processes at ECMWF, and points to the need to balance parametrization improvements especially between schemes which are highly interactive.

[1]  F. Guichard,et al.  A gcss model intercomparison for a tropical squall line observed during toga‐coare. I: Cloud‐resolving models , 2000 .

[2]  Jean-François Mahfouf,et al.  The representation of soil moisture freezing and its impact on the stable boundary layer , 1999 .

[3]  P. Courtier,et al.  Extended assimilation and forecast experiments with a four‐dimensional variational assimilation system , 1998 .

[4]  E. Mlawer,et al.  Radiative transfer for inhomogeneous atmospheres: RRTM, a validated correlated-k model for the longwave , 1997 .

[5]  D. Gregory,et al.  Parametrization of momentum transport by convection. II: Tests in single‐column and general circulation models , 1997 .

[6]  D. Gregory,et al.  Parametrization of momentum transport by convection. I: Theory and cloud modelling results , 1997 .

[7]  T. Stockdale.  Coupled Ocean–Atmosphere Forecasts in the Presence of Climate Drift , 1997 .

[8]  David A. Randall,et al.  A university perspective on global climate modeling , 1996 .

[9]  Bing Lin,et al.  Seasonal Variation of Liquid and Ice Water Path in Nonprecipitating Clouds over Oceans , 1996 .

[10]  M. Tiedtke.  An Extension of Cloud-Radiation Parameterization in the ECMWF Model: The Representation of Subgrid-Scale Variations of Optical Depth , 1996 .

[11]  A. Slingo,et al.  Studies with a flexible new radiation code. I: Choosing a configuration for a large-scale model , 1996 .

[12]  David J. Raymond,et al.  Regulation of moist convection over the West Pacific warm pool , 1995 .

[13]  Pedro Viterbo,et al.  An Improved Land Surface Parameterization Scheme in the ECMWF Model and Its Validation. , 1995 .

[14]  A. Simmons,et al.  Implementation of the Semi-Lagrangian Method in a High-Resolution Version of the ECMWF Forecast Model , 1995 .

[15]  M. Blackburn,et al.  Mean climate and transience in the tropics of the UGAMP GCM: Sensitivity to convective parametrization , 1994 .

[16]  M. Tiedtke,et al.  Representation of Clouds in Large-Scale Models , 1993 .

[17]  Lei Shi,et al.  Surface Forcing of the Infrared Cooling Profile over the Tibetan Plateau. Part I: Influence of Relative Longwave Radiative Heating at High Altitude. , 1992 .

[18]  J. Curry,et al.  A parameterization of ice cloud optical properties for climate models , 1992 .

[19]  Manfred Owe,et al.  Measurement and spatial variation of thermal infrared surface emissivity in a savanna environment , 1991 .

[20]  M. Morassutti.  Climate model sensitivity to sea ice albedo parameterization , 1991 .

[21]  Albert A. M. Holtslag,et al.  Flux Parameterization over Land Surfaces for Atmospheric Models , 1991 .

[22]  J. Morcrette.  Impact of changes to the radiation transfer parameterizations plus cloud optical properties in the ECMWF model , 1990 .

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

[24]  M. Tiedtke.  A Comprehensive Mass Flux Scheme for Cumulus Parameterization in Large-Scale Models , 1989 .

[25]  A. Slingo,et al.  The response of a general circulation model to cloud longwave radiative forcing. I: Introduction and initial experiments , 1988 .

[26]  K. Masuda,et al.  Emissivity of pure and sea waters for the model sea surface in the infrared window regions , 1988 .

[27]  J. Fritsch,et al.  Numerical Prediction of Convectively Driven Mesoscale Pressure Systems. Part I: Convective Parameterization , 1980 .

[28]  S. E. Taylor,et al.  Measured Emissivity of Soils in the Southeast United States , 1979 .

[29]  D. Murcray.  Optical Properties of the Atmosphere , 1968 .

[30]  J. Janowiak,et al.  The Global Precipitation Climatology Project (GPCP) combined precipitation dataset , 1997 .

[31]  F. Lott,et al.  A new subgrid‐scale orographic drag parametrization: Its formulation and testing , 1997 .

[32]  Da‐Lin Zhang,et al.  Summary of a mini-workshop on cumulus parameterization for mesoscale models , 1997 .

[33]  J. D. Haigh,et al.  Improved Broadband Emissivity Parameterization for Water Vapor Cooling Rate Calculations , 1995 .

[34]  Kuo-Nan Liou,et al.  Ice microphysics and climatic temperature feedback , 1995 .

[35]  John S. Kain,et al.  Convective parameterization for mesoscale models : The Kain-Fritsch Scheme , 1993 .

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