The relationship between heavy precipitation in the eastern region of China and atmospheric heating anomalies over the Tibetan Plateau and its surrounding areas

Abstract

The relationships among heavy precipitation in the eastern region of China, the atmospheric heat source over the Tibetan Plateau and its surrounding areas, and atmospheric circulation in East Asia were investigated using the multi-variate empirical orthogonal function (MV-EOF) method and synthetic analysis on daily meteorological data from May through August 2010, which were compared with data from 2013. The MV-EOF decomposition results revealed that the atmospheric heating over the eastern region of the Tibetan Plateau and the Bay of Bengal exhibited opposite trends when heavy precipitation events occurred in South China, West China, and the middle and lower reaches of the Yangtze River. These results indicated that the land–sea thermal contrast between the eastern region of the Tibetan Plateau and the Bay of Bengal was likely one of the key factors leading to the occurrence of heavy precipitation events in the eastern region of China. The results of the synthetic analysis revealed a possible physical mechanism: When the atmospheric heating was weak over the Tibetan Plateau and strong over the Bay of Bengal, there was a strong ascending motion over the Bay of Bengal and its surrounding areas, which was conducive to maintaining the South Asian high and the western Pacific subtropical high (WPSH) in southerly positions. This also resulted in weak water vapor transport in the southwest, thus forming continuous heavy precipitation in South China. After the increase in atmospheric heating over the Tibetan Plateau, the convergence and ascending motion of the lower atmosphere were strengthened, and the South Asian high moved northward to the plateau, with a strengthened eastward extension. The WPSH then lifted northward, and the airflow around it conveyed more water vapor to West China and the middle and lower reaches of the Yangtze River, resulting in heavy precipitation in these regions.