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

HY-2 A(Haiyang-2 A),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-2 A 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-2 A/GM data from March 2016 to December 2017 near Taiwan(21°–26°N,119°–123°E).The gravity anomaly is computed by Inverse Vening Meinesz(IVM)formula with a onedimensional 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-2 A/GM data.The evaluations show that HY-2 A and CryoSat-2 are at the same level in terms of gravity field recovery and the HY-2 A/GM altimeter-derived gravity field has an accuracy of 2.922 mGal.Therefore,we can believe that HY-2 A 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.