Local Enhancement of Marine Gravity Field over the Spratly Islands by Combining Satellite SAR Altimeter-Derived Gravity Data

Yihao Wu,Junjie Wang,Haihong Wang,Yuan Ding,Hongkai Shi,Adili Abulaitijiang,Xiufeng He,Zhicai Luo

doi:10.3390/rs14030474

Abstract

The marine gravity field recovery close to land/island is challenging owing to the scarcity of measured gravimetric observations and sorely contaminated satellite radar altimeter-derived data. The satellite missions that carried the synthetic aperture radar (SAR) altimeters supplied data with improved quality compared to that retrieved from the conventional radar altimeters. In this study, we combine the satellite altimeter-derived gravity data for marine gravity field augmentation over island areas; in particular, the feasibility for regional augmentation by incorporating the SAR altimeter-derived gravity data is investigated. The gravity field modeling results over the Spratly Islands demonstrate that the marine gravity field is augmented by the incorporation of newly published satellite altimeter-derived gravity data. By merging the gravity models computed with the Sentinel-3A/B SAR altimetry data, the quasi-geoid and mean dynamic topography are dramatically improved, by a magnitude larger than 4 cm around areas close to islands, in comparison with the results directly derived from a combined global geopotential model alone. Further comparison of regional solutions computed from heterogeneous gravity models shows that the ones modeled from the SAR-based gravity models have better performances, the errors of which are reduced by a magnitude of 2~4 cm over the regions close to islands, in comparison with the solutions modeled with the gravity models developed without SAR altimetry data. These results highlight the superiority of using the SAR-based gravity data in marine gravity field recovery, especially over the regions close to land/island.

Highlights

Introduction iationsHigh-resolution gravity field determination at seas is a basic task in geodesy
This study aims at strengthening the marine gravity field over regions close to land/island on a regional scale based on gravity data derived from satellite altimeters
We model the residual gravity field by using Poisson wavelets, and the long- and short-wavelength components of gravity field are recovered from the reference model and residual terrain model (RTM), respectively [48,49]

Summary

Introduction

High-resolution gravity field determination at seas is a basic task in geodesy. Thanks to the Gravity Recovery and Climate Experiment (GRACE) [1,2] and Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) missions [3,4], the global gravity field has been prominently strengthened at long wavelength up to hundreds of kilometers [5,6,7,8]. By incorporating ground-based data at short-wavelength, the derived. Global Geopotential Models (GGMs) (known as high-degree or combined GGMs) can map the gravity signals at a mean spatial resolution of 5 arc-minutes (~10 km) in global scale [9,10,11]. For regions inland, such as most areas in Asia and Africa, the Licensee MDPI, Basel, Switzerland.

Objectives

Results

Conclusion