Aerosol relationships to warm season clouds and rainfall at monthly scales over east China: Urban land versus ocean

Abstract

This paper provides a prototype study on combining the advanced satellite observations of rainfall, clouds, and aerosols to examine their interrelationships. Monthly satellite observations from the Tropical Rainfall Measuring Mission (TRMM) and Moderate Resolution Imaging Spectroradiometer (MODIS) for July (2000-2005) were analyzed to assess how urban aerosols affect cloud droplet size and cumulative rainfall over the eastern China mainland and the China Sea, respectively. It seems that aerosol effects may be more evident on clouds than on convective rainfall: high correlation coefficients between aerosol optical thickness (AOT) and water cloud drople size are observed, while only a weak aerosol-rainfall relationship is detectable during light rainfall cases (i.e., rainfall rate < 2.5 mm/d) and that is most likely for warm rain clouds only. In addition, aerosols affect clouds more significantly over ocean than over land. Over the ocean, at the monthly scale, the aerosol-cloud relationship is evident: the cloud effective radius decreases as aerosol optical thickness (AOT) increases However, over land, cloud effective radius does not show an apparent relationship with aerosol processes, which indicates that aerosols are not the only physical process affecting clouds. Dynamic processes related to factors like urban land cover may play at least an equally critical role in cloud formation. Copyright 2008 by the American Geophysical Union.