Interdecadal Change of Spring Rainfall over Southern China and The Physical Factors

Spring rainfall over southern China experiences both strong interannual variability and interdecadal variability. Employing the monthly precipitation data from 1901-2010, this research examines the interdecadal change of spring rainfall over southern China. Based on the Empirical Orthogonal Function (EOF) analysis, four distinctive precipitation periods (epochs) have been identified: 1901-1937, 1938-1958, 1959-1994 and 1995-2010. During the first and third epochs, the center of the interannual variation of spring rainfall was located in the South China (SC) region. Low-latitude climate forcing played an important role in the interannual variation of the spring rainfall anomaly over the SC region within these epochs. During typical eastern-Pacific El Niño conditions, the western Pacific subtropical high (WPSH) was stronger, driving a warm, moist southeasterly air mass across the South China Sea and onto the SC region. During the second and the fourth epochs, the maximum of the leading mode of the spring precipitation anomaly was located in the mid-lower reaches of the Yangtze River (MLYR) region. Counter to the analysis of the first and third epochs, the leading mode of the spring rainfall anomaly was mainly attributed to mid- and high-latitude forcing during the second epoch. In the wet years a negative Eurasian teleconnection (EU) wave train was observed with a positive anomaly in 500 hPa geopotential height located over the southern Japan. The WPSH was located farther to the north, bringing water vapor into the MLYR region from the northwestern Pacific. During the fourth epoch, these factors were similar to those of the second epoch.