Abstract:

Based on the daily precipitation，maximum temperature，relative humidity and wind speed at 34 weather stations in Chongqing during 1961－2007，the homochronous monthly reanalysis data from NECP/NCAR and forest fire data from the Headquarter of Chongqing Forest Fire Prevention during 1970－1998，the variation characteristics of forest fire was investigated by defining the meteorological environment index of the forest fire danger．And on this basis the atmospheric circulation features of the typical years with high forest fire danger were analyzed further in spring and hot summer．The results displayed that the temporal and spatial characteristics of the forest fire in Chongqing was obvious．The peak periods of forest fire occurred in hot summer ( from August to September) and spring ( from February to April) ，which accounted for 78% of the annual fire．The number of forest fires was the most in August，which accounted for 18% of the annual total number．The forest fires occurred mostly at afternoon when temperature is higher．The atmospheric circulation anomaly of the 500 hPa geopotential height field in typical years of high forest fire danger in spring was negative in Ural Mountains，Lake Baikal and Okhotsk Sea，and that was positive in Sichuan Basin．Thus the cold air was accumulated in the middle and high latitudes，which resulted in the location of the main frontal zone of weather system to northward． In hot summer，the large－scale circulation pattern of the 500 hPa geopotential height anomaly field in typical years of high forest fire danger was negative in Lake Baikal and Okhotsk region，and that was positive in Korean Peninsula which indicated location of the western Pacific subtropical high was to the north．The high forest fire danger was easy to happen．

Key words:
Chongqing, forest fire danger, high summer, fire danger rating

摘要：

利用重庆市34个气象站1961～2007年逐日气象观测资料以及同期NECP/NCAR逐月再分析数据，根据森林火险环境气象指数的定义，研究了重庆市森林火灾变化特征，并对春季和盛夏高森林火险等级下的典型年份的大气环流特征进行了分析。结果表明：重庆林火次数具有明显的年季月日变化特征，盛夏(7～9月)和春季(2～4月)为2个高峰期，其林火次数占全年林火总数的78%，其中8月最多(占全年林火总数的18%)，午后是森林火灾多发时段；春季重庆市高森林火险的大气环流特征表现为：乌拉尔山贝加湖和鄂霍茨克海地区500 hPa位势高度偏低，四川盆地高度场偏高，冷空气在中高纬地区堆积，天气活动主锋区偏北;盛夏重庆市高森林火险的环流特征为:巴尔喀什湖和鄂霍茨克海地区500 hPa位势高度显著偏低，朝鲜半岛位势高度显著偏高，西太平洋副热带高压位置偏北。

关键词: 重庆市, 森林火险, 盛夏, 春季:火险等级