Performance of Jason-2/GM altimeter in deriving marine gravity with the waveform derivative retracking method: a case st
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ORIGINAL PAPER
Performance of Jason-2/GM altimeter in deriving marine gravity with the waveform derivative retracking method: a case study in the South China Sea Zhen Li 1 & Xin Liu 1 & Jinyun Guo 1 & Chengcheng Zhu 1 & Jiajia Yuan 1 & Jinyao Gao 2 & Yonggang Gao 3 & Bing Ji 4 Received: 19 February 2020 / Accepted: 2 September 2020 # Saudi Society for Geosciences 2020
Abstract Deriving marine gravity is one of the important applications of satellite altimetry in earth science. The quality of marine gravity derived from each altimeter data always is limited by the range measurement on the certain ground track spacing. We assess the performance of Jason-2/geodetic-mission (GM) altimeter in deriving marine gravity by the improved range from waveform retracking. The singular value decomposition was applied to denoise waveforms, and the waveform derivative retracking was employed to improve the sea surface heights (SSHs). Finally, Jason-2/GM-derived gravity anomalies on 1′ × 1′ grids were determined by the least-squares collocation method based on the resample 5 Hz SSHs around the South China Sea (SCS). Assessed by ship-borne data from different institutions, the accuracy of Jason-2/GM-derived gravity is consistent with that of the V27.1 and DTU13 models. Moreover, with the application of waveform derivative retracking, the accuracy of gravity anomalies has improved from 6.6 mGal before retracking to 5.5 mGal after retracking over the open ocean, and from 8.9 to 7.4 mGal over the coastal area. It is better than the results obtained by traditional retracking methods, including off-center of gravity (OCOG), 5-β, threshold, Ice-1, and maximum likelihood estimator-4 (MLE4). Furthermore, evaluated by V27.1 and DTU13, the result shows root mean square (RMS) difference of 2.0 mGal and 3.0 mGal, respectively. Therefore, the waveform derivative retracking is an effective method for altimeter data, and the accuracy of derived gravity is an improvement by retracked SSHs. Keywords Marine gravity . Satellite altimetry . Waveform retracking . Waveform derivative . Jason-2/geodetic mission . Ship-borne gravimetry
Introduction Satellite altimetry has wide applications in earth science, where it provides precise sea surface heights (SSHs) all over Responsible Editor: Biswajeet Pradhan * Xin Liu [email protected] 1
College of Geodesy and Geomatics, Shandong University of Science and Technology, Qingdao 266590, China
2
Second Institute of Oceanography of MNR, Hangzhou 310012, China
3
College of Environment and Resources, Fuzhou University, Fuzhou 350108, China
4
Department of Navigation Engineering, Naval University of Engineering, Wuhan 430033, China
the world (Shum et al. 1995; Guo et al. 2016; Stammer and Cazenave 2017; Yuan et al. 2020a). The SSHs are used to derive global and regional marine gravity (Hwang et al. 2006; Sandwell et al. 2013; Khaki et al. 2015). Marine gravity derived from satellite altimeter data can reveal more localized information than that provided by satellite gravity missions (Sandwell et al. 2014; Z
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