Cooperative effects of tropical Pacific and Atlantic SST forcing in southern China winter precipitation variability

Abstract

This study investigates the variability of winter precipitation over southern China (SC) and the impacts of sea surface temperature (SST) forcing in the tropical Pacific and Atlantic Oceans. The SC winter precipitation displays two major spatial modes: a same-sign mode with the maximum center located in southeastern China, and a north–south dipole mode with opposite variations between the lower reach of the Yangtze River and the southeastern coast of China. Both modes are associated with the variation of the western North Pacific (WNP) anticyclone. The same-sign mode is associated with canonical El Nino through the Pacific-East Asian teleconnection in the lower troposphere. The north–south dipole mode is subject to the impact of the western Pacific warm pool associated with the central Pacific El Nino and equatorial Atlantic forcing. The influence of equatorial Atlantic warming is through an upper-tropospheric zonal wave pattern from the tropical Atlantic to the mid-latitudes of East Asia. Both the tropical Pacific and Atlantic oceanic forcing induce a north–south dipole pattern of winter precipitation anomalies over SC by affecting the northward extension of the WNP anticyclone. Moreover, the observed statistical relationship between the dipole mode and the equatorial Atlantic SST anomalies is present in hindcasts/forecasts of the NCEP Climate Forecast System version 2 (CFSv2), confirming a potential source of the predictability of the north–south dipole-like variation of the winter precipitation in SC.