西南地区极端降水时空变化特征及其与强ENSO事件的关系

Spatiotemporal Change Characteristics of Extreme Precipitation in Southwestern China and its Relationship with Intense ENSO Events

西南地区因紧邻青藏高原,地形地貌复杂,由于受南亚季风、东亚季风和高原季风的共同影响,其气候呈现出独特性,是我国气候变化的敏感区和脆弱区,也是极端天气气候事件发生最为频繁的地区之一。本文利用1969-2020年93个气象站的逐日气温和降水数据,通过选取11个极端降水指数,采用线性回归分析、M-K突变检验、EOF分析等方法,不仅对西南地区52年极端降水的时空变化特征进行了分析,而且通过计算复合比率对其与强ENSO事件的关系进行了探讨。研究表明:(1)西南地区在1969-2020年整体呈现降水频率和强度增大,极端降水增多的趋势,按地形划分的四个区域也呈现出不同程度的降水特征;(2)在52年各站点空间平均变化率分布上,西南地区各站点的整体连续干旱日增多,连续降水日减少,降水量呈现由西北向东南递减的趋势,但极端降水事件增多,其中横断山脉地区的极端降水事件增加幅度最为明显;(3)极端降水指数的突变年代主要分布在20世纪80年代中期和21世纪前期,EOF分析表明,极强降水量R99p的增长趋势是由西向东减少,5日最大降水量RX5的增长趋势呈现中间减少、两边增多的分布型式;(4)西南地区的极端降水指数与强ENSO事件关系密切,主要表现为在强厄尔尼诺年降水总量多,降水持续时间长且极端降水事件多,在强拉尼娜年则降水总量少,但降水强度大,极端降水事件少的特点,其极端降水事件会受强ENSO事件的影响而发展。该研究结果能为相关部门在全球变暖背景下更全面了解和应对西南地区极端降水事件以及防洪减灾措施制定提供重要的科学参考依据。

Under the background of global warming,it is of great application value to study extreme precipitation events in four southwestern provinces and cities in China,which are vulnerable to the ecological environment and sensitive to climate change.Based on the daily temperature and precipitation data of 93 weather stations from 1969 to 2020,by selecting 11 extreme precipitation indices,using linear regression analysis,M-K mutation test,EOF analysis,and other methods,this paper not only analyzed the spatiotemporal variation characteristics of extreme precipitation events in Southwestern China in 52 years,but discussed the relationship between extreme precipitation indices and intense ENSO events by calculating the composite ratio.The results showed that:(1)The overall frequency and intensity of precipitation in Southwestern China increased from 1969 to 2020,and extreme precipitation trend increased.The four regions divided by topography also showed precipitation characteristics of different degrees;(2)In terms of the distribution of the average spatial variation rate at each station in 52 years,the overall number of consecutive dry days at all stations in Southwestern China increased,and the number of consecutive wet days decreased.The precipitation decreased from northwest to southeast,but extreme precipitation events increased.The increase of extreme precipitation events in Hengduan Mountain was the most obvious;(3)The abrupt change age of the extreme precipitation indices was mainly distributed in the mid-1980s and early 21st century.The EOF analysis showed that the growth trend of R99p was decreasing from west to east,and the growth trend of RX5 showed a distribution pattern of decreasing in the middle and increasing on both sides;(4)The extreme precipitation indices in Southwestern China were closely related to intense ENSO events,mainly characterized by more total precipitation,longer precipitation duration and more extreme precipitation events in robust El Niño years,and less total precipitation but higher precipitation intensity and fewer extreme precipitation events in robust La Niña years.The extreme precipitation events would be affected by intense ENSO events.The study results can provide an important scientific reference for relevant departments to more comprehensively understand and deal with extreme precipitation events in Southwestern China and formulate flood control and disaster reduction measures under the background of global warming.