山东半岛东海岸一次台风暴雨的成因研究

Study on the Causes for a Typhoon Torrential Rain over the East Coast of Shandong Peninsular

利用NCEP 1°×1°再分析资料、FY-2E卫星云图资料和山东省123个国家气象站资料和雷达产品,对2015年7月12日台风"灿鸿"给山东半岛东部海岸带来的暴雨天气过程进行分析。结果表明:中高纬环流与台风环流相互作用是这次台风暴雨形成的主要成因。主要表现为,中高纬度东移高空槽携带的干冷空气与台风西侧外围暖湿气流在山东半岛交汇,地面"鞍型场"诱发的冷锋侵入山东半岛,为山东东部海岸暴雨发生提供了有利的天气尺度环流背景条件;高低空急流"耦合"为暴雨的发生提供了强烈的动力条件;台风北侧不断发展的TBB低于-40℃对流云团长时间维持以及低空急流风速脉动是暴雨过程中强降水持续出现的重要因素。另外,山东半岛东侧海岸线的海陆差异造成的摩擦辐合也是造成强降水的原因之一。暴雨个例对比可知,高低空急流"耦合"的区域是决定暴雨落区位于台风移动方向左前方或右前方的预报着眼点之一。

As one of the regions with high frequent typhoon and heavy rain in China, Shandong Peninsula annually has July, August and September as its peak season of typhoons. Based on the data from the NCEP reanalysis (1°×1°), the FY-2E satellite cloud pictures and the data from 123 automatic meteorological stations in Shandong province, the rainstorm process of Typhoon "Chan-hom" over the east coast of Shandong Peninsula in mid July 2015 is analyzed. The research shows that the high latitude circulation interaction with typhoon circulation is the main cause of the typhoon heavy rain. To be specific, after the dry cold air in the east upper trough of high latitudes meets the warm humid air outside the west of the typhoon over the Shandong Peninsula, the surface cold pressure field there comes across a cold front invasion, resulting in favorable synoptic-scale atmospheric circulation conditions for the rainstorm over the east coast of the Peninsula. In the early period of precipitation, the water vapor source is abundant, but its transportation condition is poor. This condition improves with typhoon circulation, and so makes it possible to maintain heavy precipitation in the rainfall area. In the course of Typhoon Chan-hom moving northward, high energy tongue extends to the north and interacts with the dry and cold air in the north, leading to a large pseudo-equivalent potential temperature gradient. This large gradient area just covers the east side of the coastline of the Shandong Peninsula, which favors the generation of heavy rain. Moreover, the high and low air jet coupling as a strong dynamic condition accounts for the rainstorm occurrence. Moreover, on the north of the typhoon the convective cloud with its TBB under -40℃ develops but maintains for a long time, and the wind speed pulsates in the low-level jet. These phenomenon are crucial causes for the continuous heavy rainfall during the storm. Another reason for this heavy rain fall lies in the friction convergence caused by the sea-land difference on the east coast of the Peninsula. In this paper, the cases of typhoon "Muifa" No. 9 in 2011 and typhoon "Matmo" No. 10 in 2014 were compared with the case of typhoon "Chan-hom". Based on the study of rainstorm cases, it can be concluded that the coupling area of upper and lower-level jets can assist in predicting whether the heavy rainfall area is on the left front or the right front in the typhoon moving direction.