呼伦贝尔市汛期短时强降水特征

Characteristics analysis of short time heavy rainfall during the rainy season in Hulun Buir

基于1991—2013年呼伦贝尔市汛期(6—8月)16站逐小时降水资料,分别定义各站点小时降水量的短时强降水阈值,同时利用经验正交函数(EOF)分析方法揭示呼伦贝尔市短时强降水(强降水)变化特征。分析结果表明:强降水阈值、强降水事件以及强降水雨强均呈现自西向东部偏南方向递增的空间分布,最强中心位于东南部阿荣旗,其形成与地形关系密切。强降水占汛期总降水量百分比低于1/5,而且发生频率最低的地区出现84.2 mm/h的强降水事件。强降水事件具有明显年代际变化,21世纪10年代以来,强降水事件发生频率增加趋势明显,空间分布表现为自东北向西南方向传播。7月下旬是强降水事件频发的时段,而且有明显日变化特征,主峰出现在17时。EOF分析结果显示强降水事件在空间上表现出全市具有同步性以及南部和北部地区反相位的特征。

Base on the hourly precipitation data collected from 16 stations during the rainy reason （from June to August） over Hulun Buir city from 1991 to 2013, a threshold value was defined for each stations by the method of threshold value and characteristics of short time heavy rainfall （STHR） were analyzed by Empirical Orthogonal Function （EOF） analysis methods . The results show： The spatial distribution characteristic of the threshold value, events and rain intensity of STHR decrease from west to southeast, the strong center area is in Arongqi of the southeast of Hulun Buir and the spatial distribution characteristic of STHR is the closest relationship with the terrain. The total precipitation of STHR is lower 1/5 than the total precipitation of the rainy season. There appears maximum hourly rainfall of 84.2 mndh over the inactive areas of STHR events. STHR events experience obviously inter-decadal variation, It founds that the frequencies of STHR obviously increase and move from northeast to southwest after 2010s. STHR events frequently occur in late July and have diurnal variations, the most active diurnal peak is 17：00. The EOF analysis results indicate that STHR events consistent over the whole Hulun Buir and has opposite phases in the south and the north areas.