Analysis of vertical deflections determined from one cycle of simulated SWOT wide-swath altimeter data

The marine gravity field model is mainly derived from nadir satellite altimetry measurements. However, the accuracy of the east component of the vertical deflection is significantly lower than that of the north component in most areas due to the orbital inclination of altimetry satellites. As a novel altimetry technique, wide-swath altimeters are expected to simultaneously obtain high-precision and high-resolution two-dimensional sea surface height measurements and hence to improve the accuracy and resolution of the recovered marine gravity field model. Here, taking the Surface Water and Ocean Topography (SWOT) wide-swath altimeter mission as an example, based on the proposed nadir ground tracks and swath width, one cycle of SWOT sea surface height measurements is simulated and compared with one year of the simulated sea surface height measurements from the nadir altimeter missions of Jason-1/GM (Geodetic Mission), Cryosat-2/LRM (Low Rate Mode) and SARAL/GM. Then, the vertical deflections are determined in the South China Sea and part of the Indian Ocean. Compared with the EGM2008 gravity field model, the vertical deflections determined by one cycle of SWOT data are better than the results determined by the combined dataset of Jason-1/GM, Cryosat-2/LRM and SARAL/GM data and can significantly improve the accuracy of east vertical deflection. It is determined that the SWOT random and systematic errors have certain effects on the accuracy of the vertical deflection, but these can be reduced by filtering. In addition, under the premise of the expected accuracy and spatial resolution of the SWOT mission, vertical deflections with grid spacing smaller than 1 arcmin and comparable accuracy could be derived.