中国西北汛期极端降水事件分析

 利用中国西北五省（区）1960—2004年125个台站汛期（5—9月）逐日降水资料,首先定义了不同台站的极端降水阈值,然后统计出了不同台站近45 a逐年汛期发生极端降水事件的发生频次,并进行了时空分布特征分析,结果表明:中国西北汛期极端降水事件发生频次同降水量的空间分布有很大的差异;一致性异常分布特征是中国西北汛期极端降水事件发生频次的最主要空间模态;中国西北汛期极端降水事件发生频次的空间分布可分为以下6个分区:高原东部区、南疆区、北疆区、西北东部区、青海高原区及河套区;从长期变化趋势来看,高原东部区近45 a来汛期极端降水事件发生频次没有明显的变化趋势,北疆区、南疆区、青海高原区及河套区表现为较明显的的增长趋势,而西北东部区表现为较明显的减少趋势;中国西北汛期极端降水事件发生频次的各主要空间分区中,近45 a来13 a左右的周期振荡表现得比较显著。

Anlysis on Extreme Precipitation Envent over the Northwest China in Flood Season

Based on the daily precipitation data of flood season(Mar to September) in 1960-2004 from 125 stations in Northwest China,we firstly determined the extreme precipitation threshold values for every station,then counted the extreme precipitation event frequency in flood season and analyzed their temporal and spatial characteristics.The results show that the spatial distribution of extreme precipitation event frequency in flood season is remarkably different from the distribution of precipitation,and the consistent anomaly distribution is the main spatial model of extreme precipitation event frequency in Northwest China.The spatial distribution of extreme precipitation event frequency in Northwest China can be divided into six regions: east of Qinghai-Xizang Plateau,south of Xinjiang,north of Xinjiang,east of Northwest China,Qinghai Plateau,and Hetao area.Seen from long-term changing trend,the extreme precipitation event frequency in flood season from 1960 to 2004 appeared no obvious changing trend in the east of Qinghai-Xizang Plateau,remarkable increasing trend in the north of Xinjiang,the south of Xinjiang,Qinghai Plateau,and Hetao area,but a clear decreasing trend in the east of Northwest China.The periods of 45-year and 13-year were relatively outstanding in variation of the extreme precipitation event frequency in Northwest China.