Time-varying Earth's Gravity Field Inversion And GNSS Observation For Solid Earth's Surface Responses To Environmental Loading

The Solid Earth's surface has significant load response to environmental load changes(mainly including the mass changes of surface fluids such as atmosphere,ocean,land water and ice and snow circle),including the changes of the shape of Earth's surface,Earth's gravity field and geoid.Accurate inversion of surface load deformation is of great significance for the interpretation of geophysical phenomena and the study of dynamic process.Global Navigation Satellite System(GNSS)can obtain high-precision deformation of Earth's surface,while Gravity Recovery and Climate Experiment(GRACE)can obtain high-resolution Earth's gravity field dynamically and continuously in temporal and spatial.In this paper,GRACE and GNSS were used to inverse the load deformation of Earth's surface to study the influence of environmental load on GNSS coordinate time series.The main works and results are as follows:(1)DDK5 de-correlation and smoothing filter and adverse Gaussian filter were used to process monthly GRACE time-varying Earth's gravity field data,the high-frequency noise,strip noise and signal leakage can be solved effectively.The non-tidal load deformation and the formula of its accuracy can be inversed and deduced,and the accuracy of the four products is GFZ>CSR>ITSG>JPL from high to low.The non-tidal load deformation derived by GRACE was compared with GNSS,and the correlation and consistency were calculated.The results show that more than 64% of IGS stations have correlation coefficients over 0.5,and the highest is 0.9,which are BRAZ and HYDE stations;more than 84% of IGS stations have consistency.Thus,it is feasible to use GRACE to inverse the non-tidal load deformation caused by the change of surface mass continuously in temporal and spatial,and has a certain scientific significance for explaining the fluctuation of GNSS time series and its precise positioning.(2)DDK3 de-correlation and smoothing filter was used to process daily GRACE time-varying Earth's gravity field data,the residual stripe noise can be suppressed effectively.Comparing GRACE with GNSS coordinate time series,the amplitude and phase of GRACE and GNSS annual term and semi-annual term as well as the correlation and consistency were calculated.The results show that the amplitude and phase of GRACE and GNSS time series are in good agreement;more than 53% of GNSS stations have correlation coefficient higher than 0.5,the highest is 0.88,which is novm station;more than 63% of GNSS stations have consistency.In addition,this paper also compared the four periods of GRACE load deformation in 2016 with IMLS and GFZ mass load deformation,and used four schemes to study the impact of load deformation on China and its surrounding areas in spatial and temporal.The results show that: 1)different schemes show differences in surface load deformation in space,which can be roughly divided into six regions,and in the process of transition from spring to summer,autumn and winter,there is a trend of up,down,down,which is supported by CMONOC results;2)compared with scheme 1,scheme 2 is closer to IMLS scheme in numerical results,but there are still differences.For China and its surrounding areas,the magnitude of surface load deformation varies with seasons.The maximum value is 19.1 mm in summer,and the minimum value is-19.0 mm in spring.