Lightning Disaster Risk Zoning In Hangzhou City

Thunderstreak disaster is the global high frequent and serious influence. Thunderstreak often causes casualties, farmland disaster and the loss of fishery. Hence, it seriously restricts the development of social economy and the protection of environmental resources. Hangzhou which is located in the northeast coast of Zhejiang is one of the most serious thunderstreak disaster areas in China. According to Hangzhou meteorological related data and statistical analysis, in one year, there are40.6thunderstorms days on average in Hangzhou. Hangzhou belongs to high thunder area based on the thunderstorm standard, which causes serious losses on social economic development in Hangzhou.According to the2000-2008thunderstreak disaster data, this paper assesses the thunderstreak disasters caused loss through the selection of three indexes which are the number of death, the number of injury and the direct economic losses. It shows a quantitative evaluation on the situation of thunderstreak disaster damage and space losses based on the grey relation model. In this paper, it uses the GIS spatial analysis technique to study space laminated analysis of the index and uses the fuzzy comprehensive evaluation method to analyze thunderstreak disaster risk situation in the selected area on the base of theory of thunderstreak disaster formation, thunderstreak disaster development and the spread of the disaster and proper disaster risk evaluation index. The author produces the Hangzhou municipal thunderstreak disaster risk diagram with the1km*1km grid for basic evaluation unit and divides Hangzhou into five risk categories which are high, secondary high, medium, secondary low and low respectively.(1) Through the analysis of thunder climate characteristic in Hangzhou, there is consistence between the analysis results of the number of thunderstorm days coming from each weather station from1966to2010and observation data from2008to2010on lightning location system. It shows that the thunderstorm weather breaks out frequently in June, July and August. Lightning mainly concentrates in the period between12a.m. and11p.m. It bursts most frequently and arrives on peak from3p.m. to6p.m., but it occurs rarely from2a.m. to10a.m..(2) Based on the history of Hangzhou lightning disaster data, this paper divides all previous lightning damage situations into different grades. The disaster in Hangzhou, Jianggan District and Xiaoshan district are relatively heavy.(3) The statistical results of thunder and lightning parameters in Hangzhou show that there is an inversely proportional relationship between ground flash density and maximum ground flash intensity. Based on the typical regression analysis of Hangzhou city ground flash density spatial distribution and the maximum ground flash intensity spatial distribution, it finds that the maximum ground flash intensity contributes more than ground flash density for lightening disaster.(4) Division results show that there is an increasing trend from southwest to northeast on the risk situation of Hangzhou thunderstreak disaster. Coastal plains for example Xiaoshan district, Yuhang district and main urban areas in Hangzhou show relatively higher risk level. However, midwest hilly areas such as Jiande and Chunan show slightly lower risk level. Finally, according to nearly nine years of thunderstreak disaster data in Hangzhou, the verified evidence shows that the risk division results are in accordance with the regional disaster distribution.