Preliminary marine gravity field from HY-2A/GM altimeter data
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Preliminary marine gravity field from HY-2A/GM altimeter data Qiankun Liu1, 2, Ke Xu1*, Maofei Jiang1, Jiaming Wang1, 2 1 The CAS Key Laboratory of Microwave Remote Sensing, National Space Science Center, Chinese Academy of
Sciences (CAS), Beijing 100190, China 2 University of Chinese Academy of Sciences, Beijing 100049, China
Received 22 October 2019; accepted 13 January 2020 © Chinese Society for Oceanography and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract
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°–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-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. Key words: HY-2A, radar altimeter, geodetic mission, marine gravity anomaly, inversion Citation: Liu Qiankun, Xu Ke, Jiang Maofei, Wang Jiaming. 2020. Preliminary marine gravity field from HY-2A/GM altimeter data. Acta Oceanologica Sinica, 39(7): 127–134, doi: 10.1007/s13131-020-1610-4
1 Introduction The satellite radar altimeter is an important microwave remote sensor. The radar altimeter loaded on the satellite sends radar pulse signals to the sea surface and receives echo signals. Through ground data processing, the sea surface height (SSH), significant wave height and wind speed measurements can be obtained. Retrieving the ocean gravity field using altimeter SSH data is one of the main applications of satellite altimeters. This work was first demonstrated with GEO-3 data by Rapp (1979). Marine gravity fields and geoids obtained from GEO-3, Seasat and GEOSAT exact repetitive mission (ERM) data were given (Haxby et al., 1983; Rapp, 1986; Sandwell and McAdoo, 1988). Due to the sparse ground track of ERM data, these inversion results were limited to spatial resolutions with wavelengths longer than 50–100 km. The emergence of GEOS
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