面向事件过程的长江流域极端降水时空变化特征

Spatiotemporal Variability of Event-Based Extreme Precipitation over Yangtze River Basin During 1961-2019

基于1961~2019年逐日降水格点数据,对长江流域偏前型、偏后型、均衡型和单日型极端降水时空变化特征进行分析。结果表明:(1)在变化过程上,1961~2019年,长江流域偏前型极端降水先增加后下降,偏后型、均衡型极端降水变化以平稳波动为主,单日型极端降水持续上升;(2)在空间格局上,长江流域偏前型、偏后型极端降水量呈现“东南高—西北低”的分布格局,均衡型极端降水高值区分布于金沙江、鄱阳湖流域,单日型极端降水空间特征表现为“中间高、两侧低”;(3)在影响因素上,长江流域及其子流域不同类型极端降水与两类厄尔尼诺(东部型-Ni1o 1+2区和中部型-Ni1o 3.4区)正相关占比为79.2%,且与Ni1o 1+2区的相关性高于Ni1o 3.4区;(4)1998年长江流域极端降水以偏前型为主导,7月20~26日偏前型极端降水事件为1998年夏季洪涝灾害的核心致灾因子。

Existing observational evidence has revealed the characteristics of low probability and high risk in event-based extreme precipitation(EEP), which means that the occurrence of an EEP is uncertain. We identified the pattern of extreme precipitation in the Yangtze River Basin, i.e. early, after, balance-phase, and 1-day EEP. Based on the high-resolution(0.5°×0.5°) gridded daily precipitation dataset(V2.0) in 1961-2019 obtained from Chinese Meteorological Administration, we investigated the spatiotemporal variation of extreme precipitation in the Yangtze River Basin. Meanwhile, the response of EEP to ENSO(El Ni1 o-Southern Oscillation) events during recent 59 years was analyzed by using correlation analysis. The results are as follows:(1) the early EEP in the Yangtze River Basin showed increasing and then decreasing trends, while the EEP in the after and balance-phase experienced a stable fluctuation over the past 59 years, and 1-day EEP kept growing.(2) Spatially, the pattern of early, after EEP increased from northwest to southeast across the Yangtze River Basin, and 1-day EEP shows the ‘center-periphery’ structure, which has a higher frequency in middle areas and lower in periphery areas. For the balance-phase EEP, the high-value areas are distributed in the Jinsha River and Poyang Lake Basin.(3) The EEP in the Yangtze River Basin and its subregions is positively correlated with El Ni1 o, and the proportion is 79.2%. That is to say, while the sea surface temperature of Ni1 o 1+2 or Ni1 o 3.4 is abnormally high in the preceding winter, the volume of extreme precipitation for the four types in the Yangtze River basin will be increased. Moreover, EEP in the Yangtze River Basin and its subregions show a more positive correlation with Ni1 o 1+2 than Ni1 o 3.4.(4) For the flood induced by EEP over Yangtze River Basin in 1998, the dominant type is the early EEP. Specifically, the early EEP between July 20 th to 26 th was the core cause of the 1998 summer flood over Yangtze River Basin. This study can provide a reference to understand the lasting extreme precipitation of the monsoon region in China.