Regional differentiation and decadal change of precipitation in China in 1960-2010

Based on precipitation data from 1840 meteorological stations in China in 1960-2010, this study examines the regional differentiation of precipitation and characteristics of its change in the recent 50 years. Using the empirical orthogonal function(EOF) and rotated EOF(REOF) methods, precipitation in China is divided into 11 regions, which are grouped into four areas according to their geographic locations: East China area(North China,Huanghuai and Jianghuai, the middle and lower reaches of the Yangtze River, and Jiangnan and South China regions), Northwest China area(Midwest Inner Mongolia, western part of the Northwest China, and eastern part of the Northwest China regions), Southwest China area(southeastern part of the Southwest China, western part of the Southwest China, and northeastern part of the Southwest China regions), and Northeast China. Compared with the results of previous studies, precipitation regions derived with the REOF method in combination with detailed long time series precipitation data are consistent with the regional differentiation of actual precipitation and the climate division of China. The analysis shows that precipitation in the East China area changed in the late 1970 s, from the late 1980 s to the early 1990 s, and in the beginning of the 21 st century respectively, featuring recurrent south-north shifts of the rain belt in both directions, which were mainly influenced by the interdecadal variability of the East Asian summer monsoon and atmospheric circulation. Precipitation in the Northwest China area experienced a major change in the mid-1980 s. The western part of the Northwest China area became wet compared to the dry period in the previous years, whereas the eastern part of the area became dry compared to the previous wet years. The decreasing precipitation in the eastern Northwest China area was related to the continually weakening of the East Asia summer monsoon, while the increasing precipitation in the western Northwest China area were mainly due to the anomalous high moisture transport from the Arabia Sea and the Caspian Sea. Precipitation in the Northeast China area underwent similar abrupt changes in the early 1980 s and the late1990 s respectively-it changed from the previous near normal level to high in the early 1980 s, and from high to low in the late 1990 s. The changes were influenced by the East Asian summer monsoon on the one hand, and related to the anomalous moisture transport form the Northwest Pacific Ocean on the other. Evident changes in precipitation have been detected over each region in the Southwest China area-precipitation changes over the western and northeastern parts of this region were in opposite directions before 2000. Precipitation in the Southwest China area is not only influenced by the terrain of the Tibetan Plateau, but also affected by the East Asian monsoon and the subtropical high, which cause complicated changes in precipitation of the area.