Evaluation of the diurnal cycle of precipitation, surface thermodynamics, and surface fluxes in the ECMWF model using LBA data

Abstract

The mean diurnal cycle of precipitation, near-surface thermodynamics and surface fluxes from short-term forecasts of the ECMWF model are compared with corresponding observations from the Large-Scale Biosphere-Atmosphere Experiment in the Amazonia wet season campaign in 1999 in Rondônia. Precipitation starts about 2 hours after sunrise in the model, several hours earlier than observed, because the model does not simulate well the morning growth of the nonprecipitating convective boundary layer. However, the mean daily precipitation during the wet season compares well with observed rainfall. On most days, maximum early afternoon temperature and cloud base height are-lower in the model than observed. Maximum equivalent potential temperature is close to that observed. The model surface evaporative fraction is higher than observed and rises to near unity in the late afternoon. Work is in progress to evaluate and integrate the parameterizations for shallow and deep convection. Copyright 2002 by the American Geophysical Union.