The possible influence of tropical Pacific subsurface temperature anomalies on summer precipitation in eastern China

摘要

Using NCEP (National Centers for Environmental Prediction) GODAS (Global Ocean Data Assimilation System) monthly subsurface temperature (SsT) from 1980 to 2009, a 3-D four-step model was established to categorize the SsT interannual variations in the tropical Pacific. In combination with NCEP/National Center for Atmospheric Research (NCAR) reanalysis 850-hPa wind field and 160 stations' precipitation data in China, an intimate connection between the tropical Pacific SsT and eastern China summer precipitation anomalies is discovered by examining the time-lagged and simultaneous correlations among the interannual anomalies of SsT in the tropical Pacific, the 850-hPa wind pattern and summer rainfall in China. In previous winter, if the SsT in the tropical Pacific indicates an El Nino-type anomaly, an anticyclonic circulation anomaly over the East Asian coast, South China Sea and east of Taiwan along with a cyclonic circulation anomaly over the Japanese archipelago emerges in following summer. At the same time, a cyclonic circulation and an anticyclonic circulation prevail over the Lake Baikal and Kuril Islands in the high latitude. These combined circulation patterns facilitate the southward transport of cold air from high latitude and northward transport of warm and moist air through the western edge of the subtropical high. The meet between two air masses results in significantly abundant anomalous precipitation in the Sichuan Basin, Dongting and Poyang Lake Basin, and possibly deficit precipitation occurs over the Hetao region and lower Yellow River Basin, northern Zhejiang, as well as the coastal region of southern China and southern Yunnan. These findings offer a very useful predictive power for eastern China summer precipitation based on tropical Pacific SsT status in previous winter and subsequent developments of SsT and East Asian large-scale circulations.