The Hail Risk Zoning in Beijing Integrated with the Result of Its Loss Assessment

In order to recognize the meteorological disaster risk and assess it, the task of risk zoning is started exploring the possibility and severity influenced by the disaster, and the distribution of risk area zone is determined. The study is very important for the disaster avoidance or prevention, and is widely utilized in disaster emergency and meteorological service of supporting decision regulation. Normally the risk zoning depends upon the probability of extreme weather or climate events, such as the occurrence or probability of extreme meteorological elements. However, the risk of disaster focuses on the intensity or loss of the disaster besides the probability. Moreover, the index of hail risk zoning in Beijing is carried out based on the formula that risk equals probability multiplied by loss, and it can avoid the solely doing statistics on the probability of extreme weather and climate events. The loss assessment is firstly fulfilled by the Gray-correlation Model with the data of disaster occurred in Beijing during recent 30 years. Meanwhile, the BG algorithm is introduced here for the time-series analysis on the disaster data, and it is found that the year of 1997 in the time-series is an inconsistent standpoint, which means that the data should be separated into two series for its inconsistence. Based on this judgment, the expectations of the bias from 1997 are considered to be the variation modulus. On the other hand, with the result of loss assessment, the hail occurring frequency is calculated out by 10 groups divided by average intervals form 0 to 1 of the loss index value. It can be utilized in deducing normalized hail risk index of Beijing, with which the risk zoning standards can be determined. Eventually the risk index is calculated with the risk function, and the indexes are also summed up by groups. Furthermore, the risk zonings are symbolized upon the index with its zoning standards. From the result of risk zoning, it can be concluded that the relatively higher hail risk zone mainly locate in urban area of Beijing, such as the centers of Miyun and Pinggu, while the risks of the mountain area and its piedmont, are relatively lower.