北京地区雷电灾害风险评估方法与应用

Lightning Risk Assessment and Zoning in Beijing Based on the Technology of Spatial Grids

首先选用北京地区1961—2008年的气候站点资料分析闪电活动的气候背景特征,用2007—2008年的闪电定位资料统计各评估网格单元的地闪密度,得到北京地区网格化地闪密度分布,评估网格单元大小为1km×1km。研究发现北京地区平均地闪密度大致在1.6～2.4次·km^(-2)·a^(-1)之间,有三处地闪密度的高值分布区,分别是西南部房山的拒马河流域地区,北京城中心偏北—昌平—顺义一带以及平谷一密云一带。借助空间网格技术,根据下垫面承灾体的雷电防护及规避特征,将评估区域划分成建筑物、室外建筑物遮挡部分及空旷地带三种空间类型。然后依据不同空间类型区域的地闪密度、闪电有效截收面积、雷电防护能力和位置参数等因素,分别核算评估网格单元内的雷击危险事件次数,作为雷电灾害风险评估的主要致灾因子指标。最后以人作为雷电灾害的首要承灾体,按"风险=雷击危险事件次数×暴露人口"的概念模型方法,测算北京地区雷电灾害风险指数。风险评估结果认为北京城市地区由于人口及经济实体密集分布,雷电灾害风险普遍较高,城市地区的雷电灾害风险具可规避性;农村及城市远近郊区,人口稀少,尽管闪电活动会比城市地区活跃,雷电灾害风险不是太高。

The study primarily depends upon the climate data to analyze the climatic characteristics related to lightning activity, and the data collected by the lightning location finder is also required to denote the cloud to ground lightning density of each grid cell. According to its degree of exposure to lightning and the characteristics of lightning protection and avoidance, the potential lightning-striking areas are classified as the building, the outdoor area under the building canopy and the open field area. The expected lightning stroke times （frequency） on each class of lightning-striking area have been worked out properly with the parameters of CG flash density, equivalent intercepting area to lightning, lightning protecting capability and position factor in these areas. Eventually the risk assessment has been carried with the formula of risk = frequency × population. The assessment reveals that with dense population and aggregated belongings, the central urban district is the highest risk zoning of lightning, as well as its high flash density, while the risk of the suburbs and rural areas are not high. The conclusion is demonstrated by the distribution of lightning disaster event occurring in Beijing from 2004 to 2008, and the result of the risk assessment iscorrespondent to the actual trend and situation.