A PARAMETERIZATION OF WARM CLOUDS FOR USE IN ATMOSPHERIC GENERAL-CIRCULATION MODELS

Simple parameterizations of droplet effective radius in stratiform and convective clouds are presented for use in global climate models. Dat asets from subtropical marine stratocumulus, continental and maritime convective clouds, and hill cap clouds in middle latitudes and a small amount of data from stratocumulus clouds in middle latitudes have bee n examined. The results suggest strongly that a simple relationship ex ists between droplet effective radius and liquid water content in laye r clouds with the droplet effective radius proportional to the cube ro ot of the liquid water content. The constant of proportionality is dif ferent over oceans and continents. In current global climate models li quid water content is not a predicted variable in convective clouds, a nd the data strongly suggest that a fixed value of droplet effective r adius between 9 and 10 mum should be used for continental clouds more than 500 m deep and 16 mum for maritime cumulus more than 1.5 km deep.