Microphysical analysis on the impacts of reduced aerosol concentrations on tropical cyclone precipitation in South China Area

Abstract

Previous studies have discovered that an increase in aerosol concentration could affect the development of precipitation and tropical cyclones. However, with increasing efforts to mitigate climate change, the amount of anthropogenic aerosols in the atmosphere is expected to decrease in the future. This study aims at understanding how such a reduction in aerosol number concentration could affect the precipitation pattern of tropical cyclones through case studies of Typhoon Haikui and Koinu. The Thompson aerosol-aware microphysics scheme in the Weather Research and Forecast (WRF) model is used, and the water-friendly aerosol number concentration is reduced by a factor of 100. For both tropical cyclones, a reduction in aerosol results in consistent expansion of precipitation area due to the enhanced warm rain process. However, the total precipitation of Koinu decreases while that of Haikui increases, depending on whether warm-rain or ice-phase processes dominate and whether upper-level convection is altered.