1981-2020年沂沭河流域极端降水事件特征及环流背景

Characteristics of Extreme Precipitation Events and Circulation Background in the Yishuhe River Basin from 1981 to 2020

利用1981-2020年沂沭河流域12个气象台站逐日降水观测资料,西太平洋副热带高压(WPSH)指数、太平洋年代际振荡指数(PDO)以及NCEP/NCAR逐日再分析资料,采用统计分析、合成分析等方法,研究沂沭河流域极端降水事件的时空变化特征,研究极端降水指数与气候因子之间的相关性以及极端降水事件的异常环流背景。结果表明:沂沭河流域的极端降水事件整体上呈增多且强度增强的趋势,空间分布上南多北少,中部和北部的增速明显高于南部。极端降水频次和年极端降水量均在1989和2002年左右突增;极端降水强度在1989年突增,2000年左右突减。极端降水的频次、强度和年极端降水量分别以22、10、22 a的周期波动为主。西太平洋副热带高压的脊线位置与频次和年极端降水量呈正相关,PDO与频次和年极端降水量呈负相关。东亚夏季风强度和西太平洋副热带高压的位置是影响沂沭河流域极端降水事件的重要因素,可为预测该流域极端降水提供参考。

Based on the observed daily precipitation data of 12 meteorological stations in the Yishuhe River Basin from 1981 to 2020,the Western Pacific subtropical high(WPSH)index,Pacific Decadal Oscillation(PDO)data,and NCEP/NCAR daily reanalysis data,the spatial and temporal variation characteristics of the extreme precipitation events in the Yishuhe River Basin were studied by using statistical analysis,composite analysis,and other methods.The correlation between the extreme precipitation index and climate factors,and the abnormal circulation background of extreme precipitation events were further studied.The results show as follows:The extreme precipitation events in the Yishuhe River Basin have shown an overall increasing trend in frequency and intensity,becoming more severe over time.Spatially,these events are more frequent in the southern region compared to the northern region,with the central and northern regions experiencing a higher growth rate than the south.The frequency and annual amount of extreme precipitation exhibit abrupt increases around 1989 and 2002,while the intensity of extreme precipitation increases in 1989 and decreases around 2000.The frequency,intensity,and annual amount of extreme precipitation are mainly fluctuating in the quasi-period of 22,10,and 22 years.The WPSH ridge line is positively correlated with the frequency and annual amount of extreme precipitation,while PDO is negatively correlated.The intensity of the East Asian summer monsoon and the anomalous position of the WPSH are important factors influencing extreme precipitation events in the Yishuhe River Basin,which can be used as references for forecasting extreme precipitation in the region.