What Formed the North-South Contrasting Pattern of Summer Rainfall Changes over Eastern China?

Abstract

The south-flood-north-drought pattern of summer rainfall change over eastern China has been attributed to external forcing (greenhouse gas concentration and aerosol emission changes) and a coupled ocean-atmosphere mode (the Pacific Decadal Oscillation; PDO). Here, we investigate the possibility whether the north-south contrasting pattern of summer rainfall change may occur without external forcing and the PDO effect. Analysis of preindustrial and historical climate model simulations and climatological sea surface temperature–forced atmospheric model simulations identified the north-south pattern of summer rainfall changes under constant external forcing and without the PDO signal. This suggests a possible role of atmospheric internal variability. The decadal rainfall change pattern appears as a manifestation of change in the frequency of occurrence of rainfall anomaly distribution from one specific pattern to the other between two neighboring periods. The external forcing and the ocean-atmosphere coupled mode are not necessary conditions for the occurrence of the north-south pattern of summer rainfall changes over eastern China.