The Surface Downward Longwave Radiation in the ECMWF Forecast System

The surface downward longwave radiation, computed by the European Centre for Medium-Range Weather Forecasts (ECMWF) forecast system used for the ECMWF 40-yr reanalysis, is compared with surface radiation measurements for the April‐May 1999 period, available as part of the Baseline Surface Radiation Network (BSRN), Surface Radiation (SURFRAD), and Atmospheric Radiation Measurement (ARM) programs. Emphasis is put on comparisons on a 1-h basis, as this allows discrepancies to be more easily linked to differences between model description and observations of temperature, humidity, and clouds. It is also possible to compare the model and observed temporal variability in the surface radiation fluxes. Comparisons are first carried out at locations for which the spectral model orography differs from the actual station height. Sensitivity of the model fluxes to various algorithms to correct for this discrepancy is explored. A simple interpolation‐extrapolation scheme for pressure, temperature, and specific humidity allows the improvement of model calculations of the longwave surface fluxes in most cases. Intercomparisons of surface longwave radiation are presented for the various longwave radiation schemes operational since the 15-yr ECMWF Re-Analysis (ERA-15) was performed. The Rapid Radiation Transfer Model of Mlawer et al., now operational at ECMWF, is shown to correct for the major underestimation in clear-sky downward longwave radiation seen in ERA-15. Sensitivity calculations are also carried out to explore the role of the cloud optical properties, cloud effective particle size, and aerosols in the representation of the surface downward longwave radiation.

[1]  W. F. Staylor,et al.  Downward longwave radiation at the surface from satellite measurements , 1983 .

[2]  Jean-Jacques Morcrette,et al.  Pressure and temperature dependence of the absorption in longwave radiation parameterizations , 1986 .

[3]  A Goldman,et al.  The HITRAN database: 1986 edition. , 1987, Applied optics.

[4]  Y. Fouquart.  Radiative Transfer in Climate Models , 1988 .

[5]  Andrew J. Heymsfield,et al.  A scheme for parameterizing ice cloud water content in general circulation models , 1990 .

[6]  Adrian Simmons,et al.  Use of Reduced Gaussian Grids in Spectral Models , 1991 .

[7]  J. Morcrette.  Radiation and cloud radiative properties in the European Centre for Medium Range Weather Forecasts forecasting system , 1991 .

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

[9]  V. M. Devi,et al.  THE HITRAN MOLECULAR DATABASE: EDITIONS OF 1991 AND 1992 , 1992 .

[10]  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 .

[11]  Nancy A. Ritchey,et al.  Seasonal variation of surface radiation budget derived from International Satellite Cloud Climatology Project C1 data , 1992 .

[12]  Q. Fu,et al.  Parameterization of the Radiative Properties of Cirrus Clouds , 1993 .

[13]  E. Kowalczyk,et al.  The Surface Energy Balance at Local and Regional Scales-A Comparison of General Circulation Model Results with Observations , 1993 .

[14]  J. T. Suttles,et al.  Longwave surface radiation over the globe from satellite data - An error analysis , 1993 .

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

[16]  S. Schwartz,et al.  The Atmospheric Radiation Measurement (ARM) Program: Programmatic Background and Design of the Cloud and Radiation Test Bed , 1994 .

[17]  D. W. Johnson,et al.  The Measurement and Parameterization of Effective Radius of Droplets in Warm Stratocumulus Clouds , 1994 .

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

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

[20]  William B. Rossow,et al.  Calculation of surface and top of atmosphere radiative fluxes from physical quantities based on ISCCP data sets: 2. Validation and first results , 1995 .

[21]  Martin Wild,et al.  Validation of general circulation model radiative fluxes using surface observations , 1995 .

[22]  E. Roeckner,et al.  Regional climate simulation with a high resolution GCM: surface radiative fluxes , 1995 .

[23]  Q. Fu.  An Accurate Parameterization of the Infrared Radiative Properties of Cirrus Clouds for Climate Models , 1996 .

[24]  J. R. Garratt,et al.  Downwelling Longwave Fluxes at Continental Surfaces-A Comparison of Observations with GCM Simulations and Implications for the Global Land-Surface Radiation Budget , 1996 .

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

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

[27]  Steven P. Love,et al.  The Baseline Surface Radiation Network Pyrgeometer Round-Robin Calibration Experiment , 1998 .

[28]  Long-wave optical properties of water clouds and rain , 1998 .

[29]  J. R. Garratt,et al.  The Surface Radiation Budget over Oceans and Continents , 1998 .

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

[31]  P. Koepke,et al.  Optical Properties of Aerosols and Clouds: The Software Package OPAC , 1998 .

[32]  Laurence S. Rothman,et al.  Reprint of: The HITRAN molecular spectroscopic database and HAWKS (HITRAN Atmospheric Workstation): 1996 edition , 1998 .

[33]  B. McArthur,et al.  Baseline surface radiation network (BSRN/WCRP) New precision radiometry for climate research , 1998 .

[34]  L. Rikus,et al.  Parametrization of effective sizes of cirrus‐cloud particles and its verification against observations , 1999 .

[35]  Gary G. Gibson,et al.  A Climatology of Surface Radiation Budget Derived from Satellite Data , 1999 .

[36]  M. Wild.  Discrepancies between model-calculated and observed shortwave atmospheric absorption in areas with high aerosol loadings , 1999 .

[37]  C. Long,et al.  SURFRAD—A National Surface Radiation Budget Network for Atmospheric Research , 2000 .

[38]  Parameterization of the Optical Properties for Water Clouds in the Infrared , 2000 .

[39]  J. Morcrette,et al.  Comparison of Model Fluxes with Surface and Top-of-the-Atmosphere Observations , 2000 .

[40]  Stephen A. Klein,et al.  A parametrization of the effects of cloud and precipitation overlap for use in general‐circulation models , 2000 .

[41]  Martin Wild,et al.  Evaluation of Downward Longwave Radiation in General Circulation Models , 2001 .

[42]  Clive Temperton,et al.  A two‐time‐level semi‐Lagrangian global spectral model , 2001 .

[43]  Zhian Sun.  Reply to comments by Greg M. McFarquhar on ‘Parametrization of effective sizes of cirrus‐cloud particles and its verification against observations’. (October B, 1999, 125, 3037–3055) , 2001 .

[44]  Mariano Hortal,et al.  The development and testing of a new two‐time‐level semi‐Lagrangian scheme (SETTLS) in the ECMWF forecast model , 2002 .

[45]  Jean-Jacques Morcrette,et al.  Assessment of the ECMWF Model Cloudiness and Surface Radiation Fields at the ARM SGP Site , 2002 .