In this study, the parameterization for the cloud fraction and the cloud optical properties in the Center for Ocean-Land-Atmosphere Studies (COLA) atmospheric general circulation model (GCM) are replaced. The new parameterization for cloud fraction is based on the National Center for Atmoshperic Research (NCAR) Community Climate Model (CCM2). The new cloud optical properties are from the NCAR CCM3. The top of the atmosphere radiation budget from the GCM is compared with that from the Earth Radiation Budget Experiment (ERBE) data. Longwave and shortwave cloud forcings are also evaluated and compared with the ERBE data. The GCM simulates the annual mean and seasonal variations of these quantities quite well with some noticeable biases. The most obvious deficiency of the GCM simulation is that the longwave cloud forcing is not strong enough in the precipitating regions of the tropical continents. There is also an underestimate of the shortwave cloud forcing in the precipitating regions over the tropical oceans. Speculation about the cause of these errors and possible solutions is given.
Complete copies of this report are available from:
Center for Ocean-Land-Atmosphere Studies
last update: 1 July 1996
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