1981-2020年沂沭河流域极端降水事件特征及环流背景OACSTPCD

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.