The aerosol indirect effects examined by numerically calculated aerosols and satellite derived clouds

We discussed the relationships between anthropogenic aerosols and low-level water clouds to better understand the aerosol indirect effect over East Asia. Results from numerical simulations yielded the anthropogenic aerosol concentration Ma. Satellite-derived products yielded information on low-level water cloud properties (cloud optical depth t, effective particle radius re, vertically integrated cloud droplet number Nc). Comparisons of monthly means for aerosols and clouds showed that t increased and re decreased as Ma increased. Such tendencies were consistent with the Twomey effect, which describes how aerosols affect cloud properties. Nevertheless, comparisons of Ma with t in April and October would suggest the importance of dynamic effects on cloud formation and maintaining processes. Values of Nc that were calculated from t and re also increased as Ma increased. This result also agreed with the Twomey effect by indicating that additional aerosols generated more cloud droplets. A comparison of Ma with lower and middle clouds revealed similar tendencies to the previous case (i.e., total water cloud case), but differences in re (i.e., larger for middle and smaller for lower clouds) reflected the vertical profile of aerosol numbers. However, differences in t (i.e., thicker for middle and thinner for lower clouds) might have been influenced by the vertical extent.