Effects of Key Regional SST Inter-decadal Anomaly on Summer Precipitation in Eastern China

By the influence of the summer wind, the summer rain-band in Eastern China advances gradually from the south to the north in China, but under the influence of a variety of complicated factors, the rain-band propulsion speeds up or delays in a certain area, finally forms the different rain-band distribution types. First, four rain-band patterns are defined in summer precipitation in Eastern China and then four sea surface temperature (SST) modes which lead to summer precipitation anomaly are found using singular value decomposition (SVD) method, from which four key sea regions related significantly with summer rain-band patterns in Eastern China are selected, and characteristics of summer precipitation distribution in Eastern China and atmospheric circulation in East Asia are analyzed with composite analysis in the background of key sea regional winter sea surface temperature anomaly (SSTA) in terms of NOAA Twentieth Century reanalysis data, UKMO HADISST1 global monthly SST and monthly precipitation of 96 stations in Eastern China during 1931—2010.When the winter Kuroshio SST inter-decadal anomaly is positive phase, 500 hPa geopotential height field in summer shows that the blocking highs develop in the mid-high latitudes of Eurasia, the meridional circulation in westerlies are intensified, the cold forces are strong and the western Pacific subtropical high strengthens and shifts westwards. 850 hPa wind field anomaly in summer shows that the north of China is governed by anomalous anticyclone, over the South China Sea is southerly winds anomalies, and the East Asian summer monsoon is weak. The circulations are useful for Pattern Ⅲ in summer precipitation in Eastern China where the rain belt is located in the mid-lower reaches of the Yangtze. When the winter Southern Indian Ocean Dipole inter-decadal anomaly is positive phase, 500 hPa geopotential height field in summer shows that a positive anomaly distribution develops in the mid-high latitudes, the blocking highs develop, meridional circulation are intensified, cold forces are strong and the western Pacific high becomes strong and shifts southward and westwards. 850 hPa wind field anomaly in summer shows that north China is controlled by anti-cyclonic anomaly, the anomaly north airflow extends to Southern China region and the Somalia cross-equatorial flow strengthens, which bring more rainfall in the Southern China region.