Interannual Variations of Regional Summer Precipitation in Mainland China and their Possible Relationships with Different Teleconnections in the Past Five Decades

Abstract

  Interannual variations of regional mean summer precipitation, especially its extremes have high impacts on the agriculture, water resources, and ecosystem and environment in Mainland China. Using observational rainfall data at 596 meteorological stations in China from 1961 to 2008, we investigated the features of regional mean summer rainfall variations based on rotated empirical orthogonal function (REOF) decompositions. Moreover, we found that there are 21 regions where variations of summer seasonal mean rainfall are very regional. These 21 regions cover most of the territory of China except for some parts in west and southwest China. The time series of coefficients of the leading REOF mode for a particular region explains a large part of variance of the summer rainfall in that region, ranging from 40 % to 90 %. The periodicities and extreme years of precipitation in the 21 regions are notably different, thus suggesting a statistically independent feature of the summer mean rainfall variations among different regions. A survey has been conducted for correlations of regional mean June-August rainfall with indices including El Nino and the Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), and several atmospheric teleconnections. Outcomes of this survey suggest that the rainfall variations in 21 regions in mainland China are possibly influenced by signals from both tropical and mid-latitudes. The results of the present work provide a base for further investigation on the possible mechanisms of regional summer rainfall variations; moreover, the present work is helpful for policy making in meteorological disaster prevention and mitigations in China.