1972—2005年大兴安岭林区雷击火特征及其与干旱指数的关系

Characteristics of Lightning Fire in Daxing'anling Forest Region from 1972 to 2005 and Its Relationships with Drought Index

对1972—2005年大兴安岭林区雷击火特征及其与Palmer干旱指数(PDSI)和Keetch-Byram干旱指数(KBDI)的关系分析表明:雷击火主要发生在5—9月,峰值出现在6月,约占全年雷击火次数的42%;雷击火的最大过火面积出现在5月和6月,约占全年过火总面积的85%。雷击火发生次数和面积的月动态均呈单峰型曲线变化,不同干旱指数的动态不同,其中KBDI的月动态呈单峰型曲线变化,5,6,7月最干旱;而PDSI则呈弱单峰型曲线变化,5月较干旱,6月和7月则较湿润。雷击火的年发生次数与9月的PDSI(R2=0.47,P<0.01)或6月和8月的KBDI(R2=0.57,P<0.01)关系密切,年过火总面积则与8月的PDSI(R2=0.20,P<0.01)或6月的KBDI(R2=0.40,P<0.01)有一定的关系。KBDI更适于描述大兴安岭林区的雷击火特征。

The characteristics of lightning fires from 1972 to 2005 and its relationships with Palmer drought severity index （PDSI） and Keetch-Byram drought index （KBDI） in Daxing’anling forest region were analyzed in this paper. The results showed that the lightning fire mainly happened from May to September. A peak of the lightning fires occurred in June, accounting for about 42% of the annual numbers. The maximum burned area happened in May and June, accounting for about 85% of the annual burned areas. Monthly dynamics of numbers and burned area of lightning fires could be expressed as one-humped curves. The monthly dynamics varied with drought indexes. A typical one-humped curve presented with KBDI and the driest months were from May to July, while a weak one-humped curve presented with PDSI, with May drier and June and July wetter. Annual numbers of lightning fires could be closely correlated with PDSI in September （R2=0.47, P0.01） or KBDI in June and August（R2=0.57,P0.01）, and annual burned areas of lightning fires with PDSI in August（R2=0.20, P0.01） or KBDI in June（R2=0.40,P0.01）. It was indicated that KBDI was more suitable for simulating the characteristics of lightning fires in Daxing’anling forest region than PDSI.