Decadal Variation of Summer Precipitation over China and Associated Atmospheric Circulation after the Late 1990s

摘要

In this study, the authors found that the summer precipitation over China experienced different decadal variation features from north to south after the late 1990s. In northeastern and North China and the lower-middle reaches of the Yangtze River, precipitation decreased after 1999, while precipitation experienced a significant reduction over South and southwestern China and a significant increase over the southern parts of Hetao region and Huaihe River valley after 2003. The authors next analyzed the associated decadal variation of the atmospheric circulation and attempted to identify the mechanisms causing the two decadal variations of precipitation. The wind anomalies for the former exhibit a barotropic meridional dipole pattern, with anticyclonic anomalies over Mongolia to northern China and cyclonic anomalies over the southeastern Chinese coast to the northwestern Pacific. For the latter, there is a southeast-northwest-oriented dipole pattern in the middle and lower troposphere, with cyclonic anomalies over the northern parts of the Tibetan Plateau and anticyclonic anomalies over the lower-middle reaches of the Yangtze River to southern Japan. An anomalous anticyclone dominates the upper troposphere over China south of 40 degrees N. The authors further found that the summer sea surface temperature (SST) warming over the tropical Atlantic played an important role in the decadal variation around 2003 via inducing teleconnections over Eurasia. In contrast, the decadal variation around 1999 may be caused by the phase shift of the Pacific decadal oscillation (PDO), as has previously been indicated.