The ENSO's Effect on Eastern China Rainfall in the Following Early Summer

摘要

ENSO’s effect on the rainfall in eastern China in the following early summer is investigated by using station precipitation data and the ERA-40 reanalysis data from 1958 to 2002. In June, after the El Nino peak, the precipitation is significantly enhanced in the Yangtze River valley while suppressed in the Huaihe River-Yellow River valleys. This relationship between ENSO and the rainfall in eastern China is established possibly through two teleconnections: One is related to the western North Pacific (WNP) anticyclonic anomaly in the lower troposphere leading to enhanced precipitation in the Yangtze River valley, and the other is related to the southward displacement of the Asian jet stream (AJS) in the upper troposphere resulting in suppressed precipitation in the Huaihe River-Yellow River valleys. This southward displacement of the AJS is one part of ENSO’s effect on the zonal flow in the whole Northern Hemisphere. After the El Nino peak, the ENSO-related warming in the tropical troposphere persists into the following early summer, increasing the meridional temperature gradient and through the thermal wind balance, leads to the enhancement of westerly flow in the subtropics south of the westerly jet stream and results in a southward displacement of the westerly jet stream.