1981－2020年沂沭河流域极端降水事件特征及环流背景

利用1981—2020年沂沭河流域内12个气象台站逐日降水观测资料，西太平洋副热带高压（西太副高）指数、太平洋年代际振荡指数（PDO）等资料以及NCEP/NCAR逐日再分析资料，采用线性趋势分析、累积距平法联合滑动t检验、morlet小波分析、相关性分析、合成分析等方法，研究近40 a沂沭河流域极端降水事件的时空变化特征，并进一步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：沂沭河流域极端降水事件具有整体上增多且强度增强的特征，且近年来在频次和年极端降水量上波动峰间值增大，分别为6.2 d/a、538.2 mm/a，极端降水事件日趋严重。空间分布上南多北少，中部、北部较南部增速更明显。极端降水频次和年极端降水量均在1989年和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 a、10 a和22 a的周期波动为主。西太副高的脊线位置跟频次和年极端降水量具有正相关性，PDO与频次和年极端降水量具有负相关性。东亚夏季风强度和西太副高的位置是影响沂沭河流域极端降水事件多寡的重要因子，在预测该流域的极端降水情况时可做参考依据。

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

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 (the WPSH) index, Pacific Decadal Oscillation (PDO) data and the NCEP/NCAR daily reanalysis data, the spatial and temporal variation characteristics of the extreme precipitation events in the Yishuhe River basin in recent 40 years are studied by using linear trend analysis, cumulative anomaly, combined moving-t-test, morlet wavelet analysis, correlation analysis, composite analysis and other methods. The correlation between extreme precipitation index and climate factors, and the abnormal circulation background of extreme precipitation events are further studied. The results show that the extreme precipitation events in the Yishuhe River basin increased in frequency and intensity. Moreover, the peak-to-peak fluctuations of the frequency and amount of the annual extreme precipitation increased by 6.2 d/a and 538.2 mm/a, respectively, in recent years. Extreme precipitation events are increasingly serious. Spatial distributions are displayed more in the south and less in the north, and the growth rate in the central and northern regions is higher than that in the south. There was a sudden increase in the frequency and amount of the annual extreme precipitation in 1989 and 2002, and an increase in 1989 and an obvious decrease around 2000 in the extreme participation intensity. The frequency, intensity, and amount of the annual extreme precipitation are mainly fluctuating in the quasi-period of 22 a, 10 a, and 22 a. The WPSH is positively while PDO is negatively correlated with the frequency and amount of the annual extreme precipitation. The intensity of the East Asian summer monsoon and the anomalous position of the WPSH are important factors affecting the frequency of the extreme precipitation events in the Yishuhe River basin, which can be used as a reference forecasting extreme precipitation in the basin.