Comparisons of Three Inversion Approaches for Recovering Gravity Anomalies From Altimeter Data

One of the major applications of satellite altimetry is to recover gravity information. In this paper, three methods (i.e., analytical and numerical inversion of the stokes formula, and the inverse Vening Meinesz formula) for deriving gravity anomalies from altimeter data are developed and studied in detail. The three formulae are implemented using fast Fourier transform (FFT) technique. And a series of modified spherical 2D FFT formula for the computation of gravity anomaly have been proposed in this step. Then they are compared and tested using synthetic data from an ultra high degree geopotential model MOD99c to degree and order 1440. The stability of the three approaches is investigated using simulated data, and many numerical tests are done to quantify the feature of the three approaches. Finally, the three formulae are employed to compute gravity anomalies over the South China Sea using geoidal undulations and deflections from Seasat, Geosat, ERS-1 and TOPEX/POSEIDON (T/P) satellite altimetry. And the estimated gravity anomalies are compared to marine gravity data from shipboard measurements in the studied area.