Impact of the spring sensible heat flux over the Tibetan Plateau on summer rainfall over East China and its role in rainfall prediction

By using observational data from 71 stations over the central and eastern Tibetan Plateau, monthly rainfall data from 756 rain gauges throughout China, HadISST v1.1 and ERA-Interim reanalysis data, impacts of the spring sensible heat flux over the Tibetan Plateau along with the global SST on rainfall over East China were investigated. The present study aims to improve the prediction skill of summer rainfall over China by using the sensible heat observations over the Tibetan Plateau in the preceding spring. Results show that there is a close relationship between the spring sensible heat flux over the Tibetan Plateau and rainfall over East China. When the upward sensible heat flux over the Tibetan Plateau increases in the spring, rainfall increases over the middle and lower Yangtze River valley in the spring and throughout the Yangtze River valley in the subsequent summer, whereas rainfall over Southeast China decreases. The increase of the sensible heat flux over the Tibetan Plateau concurs with a Rossby wave train along the middle-high latitudes of the northern hemisphere. The anticyclone robe over the North Pacific extends southwestward to the western North Pacific and transports abundant moisture to the Yangtze River valley. In the subsequent summer, the South Asian high shifts eastward and the western Pacific subtropical high shifts westward in the lower and middle troposphere, while a cyclonic anomaly occurs to the north. Under the control of the subtropical high, rainfall over Southeast China is inhibited; however, rainfall over the Yangtze River valley increases as abundant moisture is transported to this region by southerly flow to the west of the subtropical high. The southerly flow converges with the northerly flow to west of the cyclonic anomaly over the Yangtze River valley. The sensible heat flux over the Tibetan Plateau in the spring could be a key precursor of summer rainfall over Southeast China and the Yangtze River valley. With its impact considered, the rainfall predictions are highly consistent with observations, and the prediction skill of the summer rainfall increases by nearly 15%.