Decadal variability in summer precipitation over eastern China and its response to sensible heat over the Tibetan Plateau since the early 2000s

摘要

This study investigates the decadal variations in summer precipitation over eastern China (SPEC) and its response to the decadal change of sensible heat (SH) flux over the Tibetan Plateau (TP). The results show that SPEC experiences a significant decadal change in approximate 2003, demonstrating positive rainfall anomalies over central China and negative anomalies over northeast, north, and south China. Meanwhile, a noticeable increase in SH over the TP occurs in the early 2000s at the decadal time scale. Further analysis reveals that when spring SH over the TP is abnormally strong, there will be a stronger atmospheric heat source and development of deep convection over the TP in the forthcoming summer. The positive thermal forcing induces an abnormal anticyclonic circulation and airflow divergence in the upper layer and cyclonic circulation and airflow convergence in the mid-layer over the TP. And the negative vorticity and positive geopotential height anomalies in the upper layer over the TP and south China leads to the strengthening of the South Asian High (SAH) and the northwestern Pacific subtropical high (NWPSH). As a result, cold and dry air from higher latitudes and warm and humid air from the tropics converge over central China and diverge over north and south China. In addition, there exist a strong ascending motion over central China and an anomalous descending motion over south China due to the positive diabatic heating and horizontal temperature advection anomalies over central China and negative anomalies over south China. On the other hand, the circulation conditions strengthen the East Asian summer monsoon and weaken the South China Sea summer monsoon. Ultimately, more moisture is transported into central China, but less into south China, which give rise to positive and negative rainfall amounts in the corresponding areas, respectively.