Wednesday, 9 July 2014
Deep convective clouds can produce significant amount of precipitation. Previous studies have shown that, serving as both cloud condensation nuclei (CCN) and ice nuclei (IN), aerosol can make influences on deep convective clouds and precipitation through microphysical processes. However, as a result of the complexity of the microphysical processes in mixed-phase clouds, the effects of aerosol on the precipitation of deep convective clouds are still unclear. This study uses the mesoscale WRF model with a double-moment microphysics scheme to simulate a deep convective system in Southern China. We discover that in the polluted case that has more CCN (ammonium sulfate), precipitation is suppressed, and to some degree, delayed. We also discover that the impact of the concentration of IN (dust) on precipitation is obviously non-monotonic. At lower IN concentration, the increasing of IN may increase precipitation; however, when IN concentration is high enough, the increasing of IN will suppress precipitation. In other words, if dust aerosol concentration is too low or too high, the precipitation will be both suppressed. The change of precipitation due to the increases of CCN and IN are related with the changes of the mass and number concentrations of cloud water, cloud ice, rain, snow and graupel in deep convective clouds. The mechanisms of the interaction of aerosol and deep convective precipitation are being investigated.
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