High Resolution Mean Sea Surface Over China Sea Derived from Multi-satellite Altimeter Data

Referenced to an earth ellipsoid,Mean Sea Surface(MSS) is made up of geoid and the dynamic ocean topography.So a high resolution and high quality MSS is a very valuable surface for geodesists and geophysicists.Because the instantaneous sea surface height(SSH) above a reference ellipsoid can be computed from satellite altimetry,MSS is derived from it.Several mean sea surfaces have been computed using satellite altimeter data and widely used.After reducing the geophysical and environment corrections,it is very important that reducing systematic biases between the missions and the residual orbit errors in the data. Based on the editions and geophysical corrections of multi-satellite altimeter data(3-year T/P data,4-year ERS-2/35 data,2-year GEOSAT/ERM data and 1-year ERS-1/168 Geodetic Mission data),the orbit accuracy of ERS-2,GEOSAT/ERM data and ERS-1/168 geodetic mission data by using combined crossover adjustment with fixing the T/P mean orbits are improved,and the 2.5'×2.5'MSS model of China sea and its adjacent sea areas(1°N~41°N,103°E~137°E) is obtained.For reducing the magnitude of the errors caused by time variations,all repeat cycles data are averaged into mean tracks respectively.After averaging,the Root Mean Square(RMS) values of the differences between the sea surface heights at the crossover points for T/P,ERS-2,and GEOSAT are from 0.099m,0.211m and 0.188m to 0.026m,0.080m and 0.099m respectively.Because of systematic biases between the missions and the residual orbit errors in the data,ERS-2,GEPSAT/ERM data and ERS-1/168 Geodetic Mission data were adjusted to the TOPEX 3-year mean tracks.After multi-mission crossover adjustment,the RMS values of the differences between the sea surface heights at the crossover points for ERS-2,GEOSAT and ERS-1 are 0.046,0.065 and 0.142 respectively.To compute the grid surfaces using the altimetric height as observations,the SHEPARD method was implemented.The MSS model is compared with the CLS-SHOM98.2,GFZ MSS95A and OSU MSS95 model respectively,the corresponding RMS of the respective difference 0.138m,0.298m and 0.120m,and the corresponding Standard Deviation(STD) of the respective difference is 0.129m,0.152m and 0.098m.