Aerosol Effects on the Summer Precipitation over the Tibet Plateau and East Asia: The quasi-biweekly intraseasonal variation

Wednesday, December 16, 2015 - 17:30
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Recent studies have shown that the quasi-biweekly (QBW) intraseasonal variation (ISV) is the dominating ISV over the Tibet Plateau (TP) during the summer season, and is associated with the formation of TP vortices, many of which eventually develop into synoptic systems that produce precipitation over the East Asia. Given the rapid increase of aerosol loading over China and India, this study is motivated to investigate whether and how the aerosol loading affects the QBW ISV over the TP and subsequently the downstream precipitation. A combination of the MODIS AOD data and the multi-component aerosol data simulated by the CAM-CHEM model was employed to simulate direct and indirect effects of aerosols in WRF simulations. Results show that the increase of the aerosol loading with respect to that of 1970 cools the surface over the East Asia, which weakens the summer monsoon and reduces precipitation over most regions, except the North India and the eastern TP, where the surface is warmed due to more solar radiation as the increase of absorbing aerosols reduce the cloud cover. The surface warming of the eastern TP with respect to its north enhances the QBW ISV, and tends to facilitate stronger low-level vortices and increase the precipitation along the vortex main propagating path. Further research is needed to sort out the mechanism in which the QBW ISV modulates the TP vortices and subsequently the downstream synoptic systems.