Analysis on the Ability of Marine Gravity Inversion from the SWOT Wide-swath Altimeter Mission

Marine gravity is mainly inversed by the nadir satellite altimetry observations. By combing with multi-satellite nadir altimeter, the spatial resolution of marine gravity has reached 1'×1'. However, due to the nadir altimeter data distributed only along the orbit track, the accuracy of the east-west component of vertical deflection is significantly lower than the north-south component for some particular satellite. The wide-swath altimeter is one of the main altimetry missions in the future. Its two-dimensional design is expected to obtain high-precision and high-resolution sea surface height observations simultaneously, and improve the quality of the marine gravity inversion. Taking the SWOT (Surface Water and Ocean Topography) wide-swath altimeter mission as an example, based on the designed parameters including the nadir observations, the width of swath and the spatial resolution, the static sea surface height observations of SWOT, as well as the nadir altimeter missions Jason-1/GM, Sentinal-3A and Cryosat-2/LRM, are simulated. Then, the vertical deflections are calculated from above observations to analyze the ability of marine gravity inversion in the South China Sea and part of the Indian Ocean. Compared with EGM2008 model, the vertical deflections determined by SWOT are comparable to that determined by combing Jason-1/GM, Sentinel-3A, and Cryosat-2/LRM. And the results determined by SWOT significantly improve the accuracy of the east-west component of vertical deflection. And then, several specific errors of SWOT satellite are simulated using the PSD provided by the official handbook, and their influence on the determination of the vertical deflection is analyzed. It is noted that these errors have certain influence on the accuracy, but can be weakened by using a simple Gaussian filter. As a result, under the premise of the designed accuracy and resolution of the SWOT wide-swath altimeter, its observations can effectively improve the inversion quality of marine gravity.