INTERDECADAL CHANGE OF THE SEASONAL EVOLUTION OF RAINFALL OVER SOUTH CHINA

ZHAO En-rong; JIAN Mao-qiu; LI Chun-hui

doi:10.16032/j.issn.1004-4965.2018.03.010

Abstract：This paper studies the interdecadal change of the seasonal evolution of rainfall over South China and its atmospheric circulation anomalies in the recent 35 years, based on the observed daily precipitation data from 1979 to 2013 provided by China Meteorological Administration and the reanalysis data of NCEP/NCAR. The seasonality of rainfall evolution in South China experienced an interdecadal change in the early 1990s. However, the interdecadal changes of rainfall seasonality in the eastern and western South China are different to each other. The precipitation pattern of seasonal distribution in the western South China changed from a bimodal pattern to an unimodal pattern with a peak in June around 1990, while in the eastern South China the weak bimodal precipitation pattern with two peaks in May and August, respectively, turned into a significant bimodal pattern with two peaks appearing in June and August, respectively, around 1990. The study also shows that the interdecadal changes of the seasonal precipitation pattern in both eastern and western South China are closely related to the interdecadal increase of precipitation in June in South China and the significant inverse interdecadal change in the east and the west of South China (less rainfall in the west part and more rainfall in the east part) in August, which are directly contributed by the significant interdecadal change of heavy precipitation frequency around 1990. The increase of precipitation over South China in June is caused by the interdecadal southward advancement of the western Pacific subtropical high after 1990, while the interdecadal increase of precipitation over South China in July results from the interdecadal eastward withdrawal of the western Pacific subtropical high, and the interdecadal increase of tropical cyclones affecting South China. The significant out-of-phase interdecadal change in both the east and west part of South China in August is associated with the interdecadal weakening of South tropical Asian summer monsoon, which leads to a weak transport of water vapor to the western South China, and the interdecadal intensification of the western Pacific Subtropical high and its westward extension forced by the interdecadal warming of sea surface temperature in the subtropical northwestern Pacific, which results in intensified water vapor transport to the eastern South China from the southwestern flank of the western Pacific subtropical high. Meanwhile, the interdecadal change of tropical cyclones affecting South China has direct impact on the interdecadal change of precipitation over South China in August.