Tuesday 23 August 2005

G2
1330-1525 hours

169
Improved sea surface height and marine gravity in the Chinese coastal regions from post-retracked altimeter data
Bao, Lifeng¹, Yang, Lu¹, Houtze, Hsu¹
1 Institute Of Geodesy and Geophysics, Chinese Academy Of Sciences, Wuhan, PR China
Author email: baolifeng@asch.whigg.ac.cn
Re-tracking satellite altimeter waveform data has been used as one of the ways to improve the precision of sea surface height data in the coastal regions, where the altimeter data are most probably in error. Based on a linear re-tracking algorithm having five unknown parameters, the improved sea surface height in Chinese coastal regions is achieved by re-tracking the 20 Hz waveform data of ERS-1 from 1993 to 1996 and more than 300 repeated cycles T/P waveform data. Re-tracking is defined as a waveform post-processing algorithm, which computes the departure of the mid-point on the waveform's leading edge from the altimeter tracking gate and the corresponding change in range measurements accordingly. The results show that re-tracking can improve the precision of altimeter measurements and improve the ocean coverage, especially near coastlines and on the shallow continental margins. Then, the marine gravity anomalies over shall waters are derived from post-processing sea surface height and the new Earth gravity model from GRACE mission with remove-recovering method. Comparison between shipborne gravity anomalies with gravity anomalies from post-retracked and non-retracked altimeter data are 11.6 and 14.8 mgal, indicating that waveform retracking can improve the accuracy of gravity anomalies near the coastal regions.

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