基于FFT与小波变换的SOI与GNSS ZTD的周期变化影响研究

Study on the Periodic Variation of SOI and GNSS ZTDBased on FFT and Wavelet Transform

为探究ENSO事件对GNSS ZTD(水汽)周期变化的影响及其相互关系,以河北省为例开展ENSO事件对GNSS ZTD及其周期变化的影响研究。首先利用快速傅里叶变换方法筛选出南方涛动指数(SOI)与GNSS水汽的共同周期,再利用小波变换提取GNSS水汽与SOI共同周期所在的高频项,并将重构的高频项与SOI进行相关性分析。结果表明,SOI与GNSS ZTD存在负相关性,由此推断ENSO事件与GNSS ZTD的周期变化存在一定关联。利用快速傅里叶变换方法分别提取ENSO事件和正常气候下GNSS ZTD的变化周期,分析ENSO事件对GNSS ZTD周期变化的影响,结果表明,ENSO暖事件(厄尔尼诺事件)对GNSS ZTD的最长显著周期存在显著影响;ENSO冷事件(拉尼娜事件)对GNSS ZTD的最长显著周期影响较弱。

In order to explore the influence of ENSO events on GNSS ZTD(PWV)and their relationship,this paper takes Hebei province as an example to conduct a study on the influence of ENSO events on GNSS ZTD and its periodic variation.Firstly,using the method of fast Fourier transform to select the common cycle of southern oscillation index(SOI)and GNSS water vapor,and we use the wavelet transform to extract the common cycle of SOI and GNSS water vapor in high frequency.We analyze the correlation between the reconstructed high frequency term and SOI,finding that the negative correlation between SOI and GNSS ZTD in Hebei province.We conclude that the ENSO event is related to the periodic variation of GNSS ZTD.Then,using the method of fast Fourier transform to extract the GNSS ZTD change cycles under ENSO events and normal climate and analyze the influence of ENSO events on the change of GNSS ZTD cycle.The result shows that ENSO warm event(El Nino event)has a significant influence on the longest significant cycle of GNSS ZTD.The longest significant cycle of GNSS ZTD is slightly affected by ENSO cold event(La Nina event).