基于小波变换的长江中下游地区极端降水与大气环流响应关系研究

Response of extreme precipitation events in the middle and lower reaches of the Yangtze River Basin to the atmospheric circulation based on continuous wavelet transform

在气候变暖背景下,探讨极端降水对大气环流的响应规律,对区域洪涝灾害防护以及科学管理极为重要。基于长江中下游地区435个气象站点1980-2018年的日降水数据,以连续小波变换为基础,采用交叉小波变换与小波相干方法分析了长江中下游地区近40年来极端降水指数以及大气环流指数的振荡周期特征及其之间在时频域中的共同特征和相关关系。结果表明:极端降水指数均存在多尺度周期性震荡,这些指标的周期性震荡趋向于高时频尺度,这意味着从1980年到2018年,极端降水各个指标“增加-减少”变化更加频繁;大气环流指数在20世纪80年代中期至90年代中期均出现显著周期;大气环流指数与极端降水之间的相互影响主要体现在年际尺度上,不同时域中存在明显差异,但是EASM与PDO在高能量谱区对长江中下游地区极端降水的影响较弱,IOD在低能量谱区对极端降水指数影响较弱。

Under the background of climate warming,thoroughly understanding extreme precipitation in response to the atmospheric circulation is of great importance to the prevention and management of regional flood disasters.Based on the daily precipitation data of 435 meteorological stations in the middle and lower reaches of the Yangtze River Basin from 1980 to 2018,we analyzed the extreme precipitation indices,the characteristics of oscillation period of the atmospheric circulation indices,and their common characteristics and correlations in time and frequency using cross wavelet transform and wavelet coherence methods based on continuous wavelet transform.The results showed that each extreme precipitation index had multi-scale periodic oscillations,which mostly tended to be on high time-frequency scales.This indicates that each extreme precipitation index experienced“increase-decrease”changes frequently during 1980-2018.Furthermore,each atmospheric circulation index had significant cycles from the mid-1980s to the mid-1990s.The interactions between atmospheric circulation and extreme precipitation indices were mainly reflected on the interannual scale,but there were obvious differences in time domains.In addition,EASM and PDO had a weaker impact on the extreme precipitation in the high energy spectrum region,while IOD had a weaker impact in the low-energy spectral region.