长沙地区干旱时空分布特征及其对森林火灾的影响

利用1971—2016年长沙市常规气象资料,计算综合气象干旱指数,分析长沙地区干旱的时空分布特征及气象成因,并利用2003—2015年森林火灾资料进一步研究干旱对森林火灾的影响。结果表明,近46年来长沙地区干旱频率有所下降,干旱的年代际变化明显,呈三峰型。最长干旱持续天数和干旱总日数的年变化对应较好,长沙、浏阳、宁乡3站年际变化基本一致,且3站干旱分级特征具有较高的空间一致性。长沙地区以夏秋干旱最为常见,持续时间最长,最主要的气象原因为大气环流的影响。干旱情况下,森林等植被含水率下降,下降到一定程度,森林火灾容易发生。最长干旱持续日数和森林火灾发生次数、受灾面积的相关系数超过0.05信度水平。2007年的火灾情况分析表明,森林火灾多发生在干旱条件下的连晴时段内。

Spatial and Temporal Distribution of Drought and Its Impact on Forest Fire in Changsha Area

Based on the conventional meteorological data of Changsha City from 1971 to 2016, the comprehensive meteorological drought index was calculated, and the temporal and spatial distribution characteristics of drought in Changsha area and meteorological factors were analyzed .The effects of drought on forest fires were further studied by using forest fires data from 2003 to 2015 .The results showed that the frequency of drought in Changsha area decreased in the past 46 years, and it had a obvious decadal variation of triple peak type .The annual variation of the longest consecutive dry days quite matches with the total dry days , the decadal variations of the longest annual consecutive dry days and the total annual dry days of Changsha, Ningxiang and Liuyang stations were consistent, and the consistency was found in hierarchical drought characteristics of the three stations.Drought of Changsha area occured mostly in summer and autumn,and lasted for a long time on account of atmospheric circulation. Under drought conditions,the forest vegetation water content decreased down to a certain extent, which was beneficial to forest fire.The correla-tion coefficient of the longest annual consecutive dry days and the numbers of forest fires and the affected area exceeded the reliability level of 0.05.Analysis of forest fire in 2007 showed that forest fire easily occured in a period of consecutive sunny days during a drought.