The Inversion Of The Gravity Anomalies And The Assessment Of Its Accuracy Based On Multi-satellite Altimeter Data In China Sea And Its Vicinity

Satellite altimetry can provide a long time series of sea surface observations with widerange and high-precision, and the results of its research explain geoid and gravity anomalybetter than ever before. So satellite altimetry gradually becomes the primary means ofaccessing the data of marine gravity field. Based on studying the methods of the satellitealtimeter data processing and the inversion of the marine deflection of vertical and gravityanomaly, this article combined Geosat/GM, Geosat/ERM, ERS-1/ERM, ERS-1/GM,ERS-2/ERM, Envisat, T/P, Jason-1and Jason-2satellite altimeter data, computed the northand east component of the deflections of vertical and the gravity anomalies gridding at2′×2′over China Sea and its vicinity based on the EGM2008earth gravity field model and theDOT2008A sea surface topography model, and compared the results respectively with thedata of the gravity field model and shipborne gravity anomalies. The achievements are got asfollows:1. The analysis of the sea surface heights from different satellite altimeters after unifying thereference ellipsoid and the reference frame showed that small difference between the seasurface height corrections of two adjacent measurement points.99.47%of points are less than1mm, and only0.05%of points are more than2mm. So the sea surface height differencecaused by the different reference ellipsoid and frame can be ignored when the marinedeflections of vertical and gravity anomalies are computing from the along track gradients ofaltimeter observations.2. Using the remove-restore technology based on the EGM2008gravity field model andDOT2008A sea surface topography model, along with multi-satellite altimeter data, the resultof the residual along-track deflections of vertical was obtained by the slope of two successive geoidal heights. Then based on the least squares principle, the deflections of vertical griddedat2′×2′in China sea and its vicinity were determined using the along-track deflections ofvertical and its azimuth. This paper used the method of computing minimum norm inverseduring the calculation which solved the problem of rank defect successfully. The result wascompared with the data of EGM2008model, the corresponding RMS of the difference is0.91″in meridian and0.27″in prime vertical, and compared with the data of EIGEN_CG01Cmodel, the corresponding RMS of the difference is6.99″in meridian and7.48″in primevertical.3. By the inverse Vening-Meinesz formula, the gravity anomalies over China sea and itsvicinity were computed using the residual deflections of vertical in different range andintegral radius and compared with the shipborne gravity anomalies respectively. The accuracyof residual deflections of vertical in the range of0~3″is best, and if the data resolution is highenough, the optimal integral radius is15′~45′. Based on the above conclusions, the gravityanomalies gridding at2′×2′over China sea and its vicinity were determined with45′integralradius, removing the points that absolute value of the residual deflections of vertical was lagerthan3″. Comparing the results with shipborne data, the corresponding RMS is between3.388mGal and6.197mGal, and the total accuracy is5.251mGal.