Analysis of the Conditions for Lightning Fire Occurrence in Daxing'anling Region | 大兴安岭雷击火发生条件分析

chinois. 根据2007―2009年大兴安岭林区闪电和林火监测结果进行分析,研究火灾发生时的火险状况和雷击火灾案例,提高对这一区域雷击火的认识。根据研究区内11个气象站定时观测数据,采用加拿大林火天气指数系统计算各站点每日火险指数,分析研究时段内火灾发生与火险和闪电分布的关系。结果表明：2007―2009年共发生野火195起,其中林火148起,主要发生在4,5和8月份。雷击天气主要出现在5―9月份,其中6,7和8月份闪电最多。闪电分布密度较高的区域主要在研究区东北部,大部分闪电活动伴随着降水,但在比较干旱的年份,容易出现干雷暴天气,易引发雷击火。根据林火及火灾发生前24h的闪电分布分析,雷击火占总火灾的5.1%,闪电活动不是影响林火发生的主要原因。雷击火主要发生在火险比较高、闪电活动频繁且无有效降雨的区域。

anglais. Lightning is a main natural fire source. Understanding the occurrence pattern of lightning fires in Daxing＇anling is a base for the effective fire management. Based on the data of flashes and fires monitored during 2007--- 2009, the fire conditions when fires broke and lightning fire cases were studied to improve our understanding of the lightning fires in this region. The daily fire danger indexes for 11 weather stations in the study area were calculated ~ith the method of Canadian fire weather index system to analysis the relationship among fires, flashes and fire danger. The results showed that there were 195 wildfires during 2007--2009, of which the 148 were forest fires. The fires mainly occurred in April, May and August and flashes occurred in a period from May to September, and mainly in June, July and August. The area with high flash density located in the northeast of the study region. Most of the lightning activity associated with rainfalls, but in drought years there were prone to dry thunderstorms, which may cause lightning fires. According to the distribution of wildfires and flashes in past 24 hours the lightning fires were identified, which accounted for 5. 1% of the total wildfires. Therefore, the lightning fire is not the main fire resources in the region. Lightning fires mainly occurred in the day with high fire danger and frequent lightning activity without any effective rainfall.