Effect of Tibetan Plateau heating on summer extreme precipitation in eastern China

Abstract

The relationship between the Tibetan Plateau (TP) heating and summer extreme precipitation in eastern China is still unclear. This study shows that when the TP heating is stronger (weaker) than normal, summer extreme precipitation tends to be more (less) over the middle and lower reaches of the Yangtze River valley. The possible mechanisms responsible for the relationship between the TP heating and summer extreme precipitation in eastern China are revealed by investigating the effects of the upper-level South Asian High (SAH). It is found that positive and negative vorticity anomalies accompanied by an ascending motion anomaly occur over the TP regions in the lower and upper troposphere, respectively, when the TP heating is stronger, resulting in the strengthening and eastward extension of the SAH. As a result, an anomalous high-level convergence and downward movement occur over the southeastern portion of the SAH, which then diverge in the mid-lower troposphere, resulting in the formation of an anomalous negative vorticity from South China to the northern part of the South China Sea. Subsequently, the western Pacific subtropical high (WPSH) intensifies and stretches westward. Consequently, the southwestern moisture transport and moisture convergence increase over the middle and lower reaches of the Yangtze River valley, resulting in more extreme precipitation. The eastward extension of the SAH and westward stretching of the WPSH are maintained by the vertically inhomogeneous distribution of precipitation heating.