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

Abstract

Purpose of Review: 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. Recent Findings: 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. Summary: 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.