Impacts of Anthropogenic Aerosols on Springtime Mesoscale Convective Systems over Southern China

We simulated the mesoscale convective systems (MCSs) in Southern China in April 2009 and 2010 with and without anthropogenic aerosol and precursor emissions, with the goal of evaluating the impacts of anthropogenic aerosols on the springtime MCSs. During the study period, the domain-average aerosol number concentrations at the surface over Southern China were 4 Relative to the clean simulations, the April domain-total rainfall in the polluted simulations decreased by 15% and 6.4% in 2009 and 2010, respectively. This simulated change of precipitation in response to increased aerosol concentration was consistent with the observations, which showed a 17% decrease in precipitation over Southern China in April during the years 2001-2011 relative to the years 1979-1989. The probability distribution functions of the simulated rainfall intensities in the polluted simulations shifted toward smaller values relative to the clean simulations. In addition, the numbers of developed MCSs in the polluted simulations decreased by 39% and 24% relative to the clean simulations in 2009 and 2010, respectively, due to lower surface temperatures and less convective available potential energy. The structure of the MCSs also changed in the presence of more anthropogenic aerosols, developing deeper convection core due to changes in cloud microphysics and regional atmospheric thermodynamic condition.