A Comparison of Radiation Variables Calculated in the UCLA General Circulation Model to Observations

Abstract

Comparisons are made between the spatial patterns of solar and thermal fluxes of radiation calculated by the UCLA general circulation model and observations. The latter include estimates at the Pacific Ocean surface of the climatological averages of net solar and thermal radiation, satellite observations of the climatological averages of planetary albedo and outgoing longwave radiation and satellite observation of the anomalies of albedo and outgoing longwave, for the December?February period of the 1982/83 El Niño. The results show differences between model and observed climatological net solar radiation at the surface, and planetary albedo are up to about 25% of the mean with these differences closely tied to errors in the specification of model cloudiness. Model climatological net longwave radiation at the surface is systematically larger than the estimates of the observations by up to about 50% of the mean. The differences seem to he relatively unrelated to errors in model generated total cloudiness Systematic differences of around 5% of the mean are also evident between model climatological outgoing longwave at the top of the atmosphere and satellite observation. Model generated El Niño anomalies of planetary albedo and outgoing longwave radiation generally agree with observations as to position but underestimate magnitudes by up to a factor of 4. The potential causes and significance of them results are briefly discussed.