The Time-lagged Impacts of Spring Sensible Heat over the Tibetan Plateau on the Summer Rainfall Anomaly in East China: Cases Study by Using WRF Model

Abstract:

This study explores the time-lagged impacts of the spring sensible heat (SH) source over the Tibetan Plateau (TP) on summer rainfall anomaly in east China by using the WRF model. Numerical experiments for the 2003 case indicates that spring SH anomaly over the TP can maintains its impact until summer and leads to the overall strong atmospheric heat source, which is characterized by the enhanced both SH over the western TP and condensation latent heat to the east. The wave activity diagnosis revealed that the enhanced TP heating forces a Rossby wave train to the downstream regions. The cyclonic response to the northeast TP brings about the low level northerly anomaly over the northern China, while the anticyclonic response over the western Pacific enhances the subtropical high and the low level southerly in its western flank. As a result, cold and dry airflows from mid-high latitudes and warm and wet airflows from tropical oceans converge around the Huaihe River basin. In addition, warm advection originated from the TP induces vigorous ascending motion over the convergence belt. With such a favourable circulation condition, the eastward propagating vortexes initiated over the TP intensify the torrential rainfall processes over the Huaihe River basin. Another case study of 2001 with weak spring SH over the TP and the overall southward retreat of summer rainfall belt in east China further demonstrates the role of spring SH over the TP in regulating the interannual variability of EASM in terms of wave activity and synoptic disturbance.