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Abstract:
Aerosol effects on convective clouds remain an important open-ended question in climate research. This paper reports on the climatological effects of anthropogenic aerosols on the convections during Mei-yu season by means of long-term simulations with the Weather Research and Forecasting with Chemistry (WRF/Chem) model. Sensitivity experiments indicate that increased aerosols reduce the total rainfall and convection occurrences by 9.00% and 7.17% over the Yangtze–Huai River Valley during Mei-yu season due to the suppression of shallow convections with cloud geometrical thickness (CGT) less than 4 km. Aerosol radiation effect plays a dominant role in shallow convections suppression by cooling the surface air and increasing regional atmospheric stability. On the contrary, deep convections are invigorated under polluted conditions with a stronger updraft and more latent heating release, which can be explained by the interactions between aerosol-induced microphysical effects and the dynamical response. Due to the shorter distances that the downdrafts accelerate to the surface in shallow convections, the interaction between dynamics and microphysics is reduced comparing to the deep convections, leading to suppression of shallow convections at high aerosols. In addition, relative humidity which controls the balance between the net generation and loss of condensate mass is an important meteorological factor in regulating the net influence of aerosols on convections. These findings provide us insight into the competing mechanism between aerosol radiative and microphysical effects on convections during Mei-yu season, which can aid in better parameterizing aerosol effects in climate models.
