1961—2008年内蒙古降水极端事件分析

Extreme Precipitation Events in Inner Mongolia in 1961-2008

利用内蒙古自治区116个气象站1961—2008年逐日降水量资料,以年序列的第90和95个百分位,分别建立了单站日降水量极端气候事件的阈值,检测了近48年来内蒙古逐日降水量极端事件的出现频率,分析了极端事件阈值、频数及降水量的空间分布和年际、年代际及季节变化的差异,对比分析了1987年前后极端事件频次和降水量的变化。结果显示:1)内蒙古日降水极端事件的阈值普遍较小,在2.1～23.8 mm之间;全年极端事件出现的频次在2.4～20.9 d之间;降水极端事件的阈值、频次、降水量等空间差异十分明显。2)近48年来内蒙古区域平均的夏季和全年降水极端事件没有显著的增减变化趋势,但进入21世纪后,7—8月内蒙古极端降水事件和极端事件的降水量明显减少。3)1987年气温显著升高以后,中部大部地区和东南部降水极端事件减少,东北部大部和西部增加。

Threshold values of extreme precipitation events were determined individually according to the 90th and 95th percentile values of annual daily precipitation series at the 116 meteorological stations of Inner Mongolia during the period 1961-2008.The frequencies,distributive and change characters of extreme precipitation events were examined in recent 48 years.Changes in the frequency and rainfall of extreme precipitation events after the temperature abrupt change in about 1987 were also analyzed.The results show that 1） the threshold values of extreme precipitation events were generally small,within 2.1 and 23.8 mm,the extreme precipitation events occurred 2.4 to 20.9 days in a year,and there were distinctive spatial differences in the distributive character and change of the threshold values,frequencies,and rainfall of extreme precipitation events.2） Extreme precipitation events in Inner Mongolia whether for summer or for the whole year both showed no obvious trend in recent 48 years.3） The rainfall of extreme precipitation events decreased in the middle and southeast of Inner Mongolia,but increased in the northeast and west,after the temperature abrupt increase in 1987.