Preliminary marine gravity field from HY-2A/GM altimeter data

HY-2A (Haiyang-2A), launched in 2011, is the first ocean dynamic environment satellite of China and is equipped with a radar altimeter as one of the primary payloads. HY-2A shifted the drift orbit in March 2016 and has been accumulating geodetic mission (GM) data for more than three years with 168-day cycle. In this paper, we present the preliminary gravity field inverted by the HY-2A/GM data from March 2016 to December 2017 near Taiwan (21 degrees-26 degrees N, 119 degrees-123 degrees E). The gravity anomaly is computed by Inverse Vening Meinesz (IVM) formula with a one-dimensional FFT method during remove-restore procedure with the EGM2008 gravity model as the reference field. For comparison, CryoSat-2 altimeter data are used to inverse the gravity field near Taiwan Island by the same method. Comparing with the gravity field derived from CryoSat-2, a good agreement between the two data sets is found. The global ocean gravity models and National Geophysical Data Center (NGDC) shipboard gravity data also are used to assess the performance of HY-2A/GM data. The evaluations show that HY-2A and CryoSat-2 are at the same level in terms of gravity field recovery and the HY-2A/GM altimeter-derived gravity field has an accuracy of 2.922 mGal. Therefore, we can believe that HY-2A will be a new reliable data source for marine gravity field inversion and has the potentiality to improve the accuracy and resolution of the global marine gravity field.