LAUSR

Abstract Here, we examine the aerosol - cloud relations over three major urban clusters of China, representative of three different climatic regimes, under different water vapor conditions and cloud heights, using Aerosol Optical Depth at 550 nm (AOD), Cloud Fraction (CC), Cloud Optical Depth (COD), Water Vapor (WV) and Cloud Top Pressure (CTP) data from the MODIS instrument. Over all regions and for all seasons, CC is found to increase with increasing AOD, WV and cloud height. Aerosols, at low WV environments and under constant CTP, have less impact on CC than at high WV environments. Furthermore, AOD has a varying influence on COD depending on CTP. Finally, COD is found to increase with height for low and middle height clouds, and with increasing AOD, especially at low AOD. Our results demonstrate that the role of WV in the observed satellite-based aerosol - cloud relations is significant for all cloud heights.