Variation in Summer Rainfall over the Yangtze River Region during Warming and Hiatus Periods

Abstract

Variation in summer precipitation over the Yangtze River region during a global warming period (1976−1997) and a hiatus period (1998−2013) are investigated in this study. The results show that during the warming period, precipitation over both the Yangtze River region and South China shows an increasing trend, attributable to increasing ascending motion, a decreasing East Asian westerly jet (EAWJ), and a decreasing temperature gradient. During the hiatus period, the rainfall belt moves from the Yangtze River region to the Huang-Huai River region in association with the northward displacement of the EAWJ, attributable to the increasing trend in the temperature gradient at high latitudes. Empirical orthogonal function (EOF) analysis is one of the widely used methods in atmospheric science. It is also known as principal component analysis (PCA). The second EOF mode of summer precipitation can represent the variation in rainfall over the Yangtze River region. During the warming period, rainfall over the Yangtze River region is controlled by a dipole mode of water vapor transport, induced by SST cooling in the Maritime Continent, which can lead to a strong Pacific–Japan teleconnection; warming SST in the east-central tropical Pacific can also strengthen this pattern. During the hiatus period, the Pacific–Japan pattern is weak, and the water vapor transport pattern over the western subtropical Pacific changes from a dipole structure to a weak monopole structure.