Effect of Increasing Anthropogenic Sulfate Aerosols Concentration on the Decadal Shift of Summer Precipitation in the Middle and Lower Reaches of the Yangtze River

To explore the impact of the increasing anthropogenic sulfate aerosol concentration on the decadal shift of summer precipitation in the middle and lower reaches of the Yangtze River valley since the late-1970s,a global climate model(GFDL-AM2) is employed to conduct ensemble sensitive experiments.The modeled results display that the spatial-temporal structure shift of summer rainfall bear a big similarity to the observed.In particular,the shift characteristics in several East Asian Summer Monsoon subsystems,including the southward and westward stretch of the western Pacific subtropical high and the anomalous northerly along the east coast of East China as well as those in the vertical distribution of air temperature and vertical velocity,can be captured.Mechanisticly,the increasing sulfate aerosols causes intensified negative radiative forcing,results in cooling in much of east China from the surface to the middle troposphere.Subsequently,this weakens the land-sea thermal contrast and East Asian Summer Monsoon,and favors the rainband staying in the Yangtze River basin rather than moving northward to North China and Northeast China in middle summer(July-August).Thus,it is concluded that the increased anthropogenic sulfate aerosols have contributed substantially to the decadal shift of summer precipitation in the middle and lower reaches of the Yangtze River since the late-1970s.