GRACE和SLR观测的地球动力学扁率最大熵谱及小波相关分析

Maximum entropy spectral analysis and wavelet coherence analysis of the dynamic ellipticity of the earth from GRACE and SLR measurements

卫星重力测量技术的实现为测定地球动力学扁率提供了新的方式和途径，GRACE卫星是目前最新的重力测量卫星，据其恢复的低阶重力场较以往精度得到大大提高，然而其观测地球动力学扁率（二阶项）却与卫星激光测距（SLR）结果相差较大.本文采用最大熵谱和小波分析方法对GRACE和SLR观测的地球动力学扁率时间序列信号进行定量比较分析，结果表明：GRACE观测的地球动力学扁率年际周期变化振幅仅为SLR观测结果的25%，并且目前GRACE观测的地球动力学扁率数据中含有系统输入信息和相位差，但前者较后者包含有较强的短周期（2-6月）信息.造成这种差异的主要原因可能来自于GRACE与SLR全球观测数据时空分布不同.

With the advent of the satellite gravity measurements, this new technique which is different from Satellite Laser Ranging （SLR） provides a new approach to determine the Earth＇s Dynamic Ellipticity （EDE）. The Gravity Recovery and Climate Experiment （GRACE） is the latest satellite gravity mission, the accuracy of low degree Stokes coefficients of the gravity field models derived from GRACE has been greatly improved. However, the results of EDE from GRACE do not agree well with that from SLR measurements. In this paper, the maximum entropy spectral analysis and wavelet analysis are used to assess the data sets EDE from GRACE and SLR. The results show that the interannual amplitude of the EDE signal from GRACE is only 25 % of that from SLR, and GRACE EDE signals contain inputted system information and great phase difference, but the former reveals stronger short-term （2 - 6 months） signals than the later. These differences might be caused by the un-synchronism of the global measurements from GRACE and SLR.