Correlation pattern between effective radius and optical thickness of water clouds simulated by a spectral bin microphysics cloud model

The cloud particle size distribution of water clouds was simulated by a non-hydrostatic spectral bin microphysics cloud model. The result shows two different correlation patterns in the simulated optical thickness and effective radius; positive and negative correlations for non-drizzling and drizzling clouds, respectively, similar to the observed features reported by past remote sensing works. The correlation pattern in a pristine condition is mainly composed by negative correlation with small fragment of positive correlation, similar to the satellite-observed characteristics over the FIRE region offCalifornia. In the case of polluted condition, on the contrary, only a positive correlation is simulated, similar to the satellite observation over the ASTEX region of North Atlantic Ocean. Satelliteobserved contrast of correlation patterns between FIRE and ASTEX regions can be explained by the difference in the aerosol burden of airmasses over the two regions.