京津冀地区GNSS ZTD时序分析及对厄尔尼诺事件的响应

京津冀地区夏季暴雨频发，水汽是影响暴雨形成的关键要素之一.本文利用中国大陆构造环境监测网络（CMONOC）京津冀地区GNSS（全球导航卫星系统）观测资料，开展GNSS天顶对流层总延迟（ZTD）时序分析及对厄尔尼诺事件的响应研究.利用快速傅里叶变换与小波变换方法从频域和时域开展GNSS ZTD时序分析，并对GNSS ZTD不同周期时序与东部型指数（I_EP）、中部型指数（I_CP）进行比较，分析I_EP、I_CP对GNSS ZTD周期变化的影响.研究发现：GNSS ZTD异常时段与厄尔尼诺事件存在对应关系.东部型指数（I_EP）与GNSS ZTD呈正相关；中部型指数（I_CP）与GNSS ZTD呈显著负相关.在东部型厄尔尼诺事件的影响下，GNSS ZTD的季节性周期增大，月周期和半月周期减小；在中部型厄尔尼诺事件的影响下，GNSS ZTD的季节性周期、月周期、半月周期都减小.研究结果可为掌握区域GNSS ZTD预测变化规律提供参考，并为利用水汽感知厄尔尼诺事件提供可行性基础.

GNSS ZTD time series in Beijing-Tianjin-Hebei region and their response to El Niño events

Summer rainstorms occur frequently in Beijing-Tianjin-Hebei region.As one of the key factors affecting the formation of heavy rain,precipitable water vapor has been recognized as highly correlated with the Global Navigation Satellite Systems Zenith Tropospheric Delay(GNSS ZTD).In this study,the time series of GNSS ZTD and their response to El Niño events were analyzed based on GNSS observations in Beijing-Tianjin-Hebei region.Fast Fourier transform and wavelet transform were used to carry out GNSS ZTD timing sequence analysis from frequency domain and time domain,and the time sequence of GNSS ZTD with different periodicity was compared with the Eastern-Pacific types of El Niño index(I_EP) and the Central-Pacific types of El Niño index(I_CP).The results showed that there was a corresponding relationship between the abnormal period of GNSS ZTD and El Niño events.Specifically,the GNSS ZTD was positively correlated with I_EP,and significantly negatively correlated with I_CP.Under the influence of I_EP,the GNSS ZTD increased in seasonal cycle,but decreased in monthly cycle and half-monthly cycle.While under the influence of I_CP,the GNSS ZTD decreased in seasonal cycle,monthly cycle,and half-monthly cycle.The above results can provide reference for regional GNSS ZTD variation analysis,and provide a reliable basis for sensing El Niño events with precipitable water vapor.