基于小波变换的苏州暴雨前GNSS水汽异常变化分析

Anomaly analysis of GNSS water vapor before rainstorms based on wavelet transform

为研究暴雨前的大气水汽异常变化,该文基于2022年苏州市全球卫星导航系统(GNSS)数据和邻近气象站的逐小时降水量观测数据,利用小波变换方法分解重构GNSS大气可降水量(PWV)时序,分析暴雨前的GNSS PWV时序变化特征和异常信号。研究结果表明:2022年苏州暴雨发生前PWV普遍有1~3日内的明显上升期,夏季暴雨的PWV最大峰值可达72.4 mm,秋季暴雨PWV的最大峰值可达68.3 mm,春季暴雨的PWV峰值最大可达46.3 mm;突发性极端暴雨与PWV增幅关系密切,增幅越快,降水量越大;PWV经小波分解重构后,第四层高频系数(d4)的峰值或谷值往往早于暴雨发生时刻1~3 d,PWV增幅越快,PWV的d4高频系数振幅越大。本方法可探测出暴雨发生前的PWV时序异常变化,为暴雨短临预报提供一定参考依据。

In order to explore the abnormal changes in atmospheric water vapor before rainstorms,this paper is based on the ground-based global navigation satellite system(GNSS)data and hourly precipitation observation data of adjacent meteorological stations at Suzhou in 2022,the GNSS atmospheric precipitable water vapor(PWV)was decomposed and reconstructed using wavelet transform to analyze the abnormal change characteristics of GNSS PWV time series before and after rainstorms.The research results show that there is generally a significant increase in 1-3 days before the occurrence of rainstorms in 2022.The maximum peak value of PWV for summer rainstorm can reach 72.4 mm,the maximum peak value of PWV for autumn rainstorms can reach 68.3 mm,and the maximum peak value of PWV for spring rainstorms can reach 46.3 mm.The relationship between sudden extreme rainstorms and PWV amplification is related,and the faster the amplification,the greater the precipitation of rainstorms.The peak or valley value of the fourth layer high-frequency coefficient(d4)of PWV after wavelet decomposition and reconstruction is earlier than that of rainstorms occurrence by 1-3 days,and the faster the amplification,the greater amplitude of high-frequency coefficient of PWV d4 after wavelet transform.This method can detect the abnormal changes in the PWV time series before rainstorms and provide a certain reference basis for a short-term forecast of rainstorms.