GRACE大气与海洋去混频模型计算及其应用

Gravity Recovery and Climate Experiment (GRACE) satellites can detect the change of Earth gravity field with microwave ranging observations of high precision in the form of remote sensing, which is not influenced by atmospheric troposphere and ionosphere. So GRACE has important applications to extract Earth mass transport signal, but the precision of state-of-the-art temporal gravity field models still cannot reach the simulated precision before launch. This project will analyze all kinds of impacts that restrict the precision improvement of GRACE temporal gravity field models, and set the atmospheric and oceanic de-aliasing models as the primary impact. According to the spurious jumps and insufficient spatial resolution of atmosphere data used for present models, we will combine global atmospheric data with consistent character and regional atmospheric data with high spatial resolution, and use posterior variance component estimation method to compute a new generation of atmospheric and oceanic de-aliasing models which consider the errors of different atmospheric data. Using the new atmospheric and oceanic de-aliasing models we can reconstruct GRACE monthly temporal gravity field models and assess the ability of these new models to extract Earth mass transport signal with all kinds of other data. Moreover, we will evaluate the impacts of atmospheric and oceanic de-aliasing models to GRACE Follow-on (GFO) satellite gravity recovery. At last we will develop a complete software system which has the function to compute atmospheric and oceanic de-aliasing models and temporal gravity field models, thus making a preparation for the gravity measurement data adjustment of GFO and our Chinese gravity satellite missions.

GRACE卫星通过高精度微波测距观测值以无接触的方式感应地球重力场的变化，不受大气对流层和电离层影响，在提取地球质量迁移信号方面具有重要应用，但现有GRACE时变地球重力场模型的精度仍然达不到发射前的模拟精度。本项目紧密分析制约GRACE时变地球重力场模型精度提高的各项因素，以大气与海洋去混频模型为突破口，针对现有模型所采用大气数据存在跳跃和空间分辨率不足的缺陷，结合全球稳定分布和局部区域高空间分辨率大气数据，考虑不同类大气数据的误差，利用验后方差分量估计计算新一代大气与海洋去混频模型，重新构建GRACE月时变地球重力场模型，通过各种外部数据全面检核其在提取地球质量变化信号的能力，并评估大气与海洋去混频模型对GFO卫星重力反演的影响。最终开发出一套集大气与海洋去混频模型计算和时变地球重力场模型计算的软件系统，为GFO及我国未来卫星重力测量数据处理做准备。

卫星重力测量为全球重力场的探测提供了一种连续大尺度的手段，本项目开展GRACE卫星重力反演计算及其应用研究，为GRACE-FO和我国卫星重力任务的实施提供技术保障。本项目基于改进动力学法计算了GRACE时变地球重力场模型，其精度与国际官方机构相当；利用ERA-Interim数据计算了GRACE大气去混频模型，计算结果与GFZ的AOD1B精度相当，同时基于局部高空间分辨率的大气数据，计算了更高精度的大气去混频模型；利用GRACE时变地球重力场模型计算了地表垂直位移负荷形变，与GNSS直接量测的地表负荷形变和模型计算的负荷形变进行了详细的比较和讨论，得出了一些有意义的结论；提出了一种三维点质量法来计算GRACE探测的全球质量变化，比较了其相对传统球谐系数方法的优越性；利用ICA或EICA方法来提取GRACE时变地球重力场的同震重力变化信号，可以分离几次连续大地震的信号。上述研究内容和成果为卫星重力测量的相关研究提供了重要的依据和参考，也为GRACE Follow-on或NGGM重力卫星的计算及其应用提供一些有益的尝试。