Recent studies have analyzed satellite data in terms of the relationship of cloud albedo with droplet size for warm clouds. It was found that for optically thick marine clouds (&tgr;>15) the cloud albedo increases with decreasing cloud droplet effective radius (re). For optically thinner marine clouds (&tgr;<15) cloud albedo increases with increasing re as to be expected if the liquid water content is adiabatic. Hypotheses for the change in sign in the &tgr;-re relationship are deviations from an adiabatic liquid water content or the presence of single layer versus multi layer clouds. In this study, the ECHAM model, which exhibits this sign change in the &tgr;-re correlation for optically thin and thick marine clouds, is used to test these hypotheses. Probability density functions of &tgr;-re show that the change in sign of the correlation can be attributed to precipitating versus non-precipitating clouds, but not to the difference in single layer versus multi-layer clouds. ¿ 2000 American Geophysical Union