SDUST2023VGGA: a global ocean vertical gradient of gravity anomaly model determined from multidirectional data from mean sea surface

Abstract. Satellite altimetry is a vital tool for global ocean observation, providing critical insights into ocean gravity and its gradients. Over the past 6 years, satellite data from various space agencies have nearly tripled, facilitating the development of high-precision ocean gravity anomaly and ocean vertical gradient of gravity anomaly (VGGA) models. This study constructs a global ocean VGGA model named SDUST2023VGGA using multidirectional mean sea surface (MSS). To address computational limitations, the global ocean is divided into 72 sub-regions. In each sub-region, the DTU21 MSS model and the CNES-CLS22 mean dynamic topography (MDT) model are used to derive the geoid. To mitigate the influence of long-wavelength signals on the calculations, the study subtracts the long-wavelength geoid derived from the XGM2019e_2190 gravity field model from the (full-wavelength) geoid, resulting in a residual (short-wavelength) geoid. To ensure the accuracy of the VGGA calculations, a weighted least-squares method is employed using residual geoid data from a 17′×17′ area surrounding the computation point. This approach effectively accounts for the real ocean environment, thereby enhancing