A Study On Methods Of Short-Medium-Range Prediction Of Thunderstorm Along The BoHai Rim

As an extreme weather event usually accompanying with heavy precipitation, destructive gale, hail and lightning stroke, thunderstorm can bring harm to industry, agriculture, transportation and people’s treasure. Therefore it is veay essential to study early-warning methods for thunderstorm. By using observing data of thunderstorm from2000to2009along BoHai rim, the climatic character of spatial and temporal distribution including inter-annual, annual and daily variation of thunderstorm is analyzed in detail. Based on synoptic map data, synoptic type has been identified in three areas (Liao-xi corridor, Shandong Peninsula, Liaodong peninsula) along BoHai rim. On the basis of synoptic type classification and subsequent diagnosis of physical quanitity, short-medium forcasting methods of thunderstorm has been established in these three regions. The main results are as follows:(1) The annual thundery days are increased from land ring to land center, and then decreaed grually to the coastal area. The mean annual thundery day is16d, the most thundery days is located in Chengde (30d/a). The highest frquency of thunderstorm is11.8d in the summer, which accounts74.2%of the total; secondly,13.8%thunderstorm happens in spring, with frequency of2.2d; average thunderstorm day of1.9d happens in autumn, accounting12.0%; there is hardly none thunderstorm happening in winter. Thunderstorm mainly occurred from14:00to23.00in a day.(2) The synoptic situation can be classified into five kinds:upper-level trough, upper-level cold vortex, northwest airflow, edge of subtropical high and outer of Typhoon. The most common synoptic type of thunderstorm is synopitic situation with upper-level trough and upper-level cold vortex, which account50.2%and33.8%, and mainly happen during May-August.the second is synopitic situation with northwest airflow. thunderstorm synopitic situation with edge of subtropical high and outer of Typhoon is rally to seen, which only happens during July-September.(3) The synoptic modles are quantified. a preliminary prediction of thunderstorm has been obtained by stepwise discriminant analysis. the slake vacancy rate of BoHai Rim is above40%, the threat score is above32.2%. The results show that the quantitative method can be able to indentify five thunderstorm synoptic situation and corresponding weather system.(4) They have good indicative function for thunderstorm, which are A, K, SI, T500-850, Δθse58, TTd850and ΔT850hpa in discrimination Process of physical diagnosis, it is deeply distinguished by the physical quanitity, to forecast with or without thunderstorm.(5) The forcasting results are as follows:. regional forcasting in Liao-xi corridor:the threat score is between39.13%and88.89%, the wrong report rate is below52.38%, the missing report rate is below37.50%; Regional forcasting in Shandong Peninsula: the threat score is between12.50%and88.89%, the wrong report rate is below75.00%, the missing report rate is below80.00%; Regional forcasting in Liaodong peninsula:the threat score is between20.00%and83.33%, the wrong report rate is below75.00%, the missing report rate is below50.00%. The results show the method has good forecasting effect for thunderstorm during April, May, September and October, but was worse during July and Aguest in regions along Bohai rim.