资源环境科技发展态势分析平台

Observations have suggested that the 550-nm aerosol optical depth (AOD) decreases over East Asia (EA) but increases over eastern United States (EUS) in boreal spring. Based on the NCEP CFSR reanalysis and TRMM 3A25 data set, the present work indicates that this asymmetry can be ascribed to the distinct feedback of general circulation and atmospheric heat source (AHS) between the two regions. In April and May, condensation heating becomes dominant in the AHS over EA and leads to low-level southerly and upper-tropospheric northerly flow in response. Subsequently, deep convection with strong ascending motion is generated, which reduces AOD over EA via the effect of vertical ventilation and rainfall-related washout. Meanwhile, the AHS over EUS is induced by circulation originating from the Tropics and mid-high latitudes. Thus, AOD further increases over EUS due to the absence of vertical ventilation and the import of dust aerosols from EA in the upper troposphere during late spring. Also discussed is the role played by the Tibetan Plateau in this distinct AHS-circulation relationship between EA and EUS.