The Fast Response of the Atmospheric Water Cycle to Anthropogenic Black Carbon Aerosols during Summer in East Asia

Abstract

AbstractStudies of the climate effects of black carbon (BC) in East Asia are not abundant and the effects remain uncertain. Using the Community Earth System Model version 1 (CESM1) with Peking University’s emissions data, the fast response of the atmospheric water cycle to anthropogenic BC during summer in East Asia is investigated in this study. Results show that the CESM1-simulated BC concentration and its direct effective radiative forcing are comparable to observations. With the combination of aerosol–radiation interaction (ARI) and non-aerosol–radiation interaction (including aerosol–cloud interaction and surface albedo effects), anthropogenic BC induces a “wetter south and drier north” pattern over East Asia during summer. Also, anthropogenic BC affects the summer precipitation primarily through changing moisture transport rather than altering local evaporation over East Asia. Using the self-developed atmospheric water tracer method, the responses of dominant moisture sources [the tropical Indian Ocean (TIO) and northwest Pacific] to anthropogenic BC are investigated. Results show that the moisture originating from southwest monsoon-related sources (especially the TIO) is more responsive to anthropogenic BC effects over East Asia. In particular, differing from total precipitation, TIO-supplied precipitation shows a significant response to the ARI of anthropogenic BC over East Asia. Process analyses show that anthropogenic BC affects the southwest monsoon-related moisture supplies primarily via advection, deep convection, and cloud macrophysics. Interestingly, the anthropogenic BC-induced changes of TIO-supplied water vapor in these three processes are all dominated by the ARI over East Asia.