A coastal retracking system for satellite radar altimeter waveforms: Application to ERS‐2 around Australia

Abstract

[1] Satellite radar altimeter-derived sea surface heights (SSH) are in error in coastal regions due, in part, to the complex nature of echoes returned from rapidly varying land and sea surfaces. This paper presents improved altimeter-derived SSH results in Australian coastal regions using the waveform retracking technique, which reprocesses the waveform data through a ''coastal retracking system''. The system, based upon a systematic analysis of satellite radar altimeter waveforms around Australia, improves SSH data from several retrackers depending on the waveforms' characteristics. Central to the system is the use of two techniques: the least squares fitting and the threshold retracking algorithms. To overcome the problem of fading noise, the fitting algorithm has been developed to include a weighted iterative scheme. The retrackers include five fitting models and the threshold method with varying threshold levels. A waveform classification procedure has also been developed, which enables the waveforms to be sorted and then retracked by an appropriate retracker. Two cycles of 20-Hz waveform data from ERS-2 have been reprocessed using this system to obtain the improved SSH estimates. Using the AUSGeoid98 gravimetric geoid model as a quasi-independent reference, the system improves SSH estimates from beyond $22 km to beyond $5 km from the coastline.Citation: Deng, X., and W. E. Featherstone (2006), A coastal retracking system for satellite radar altimeter waveforms: Application

Vertical Motion Determined Using Satellite Altimetry and Tide Gauges

“…A detailed analysis of the correlations between the tide gauge data and altimeter data will be conducted to enhance the error model. Waveform retracking techniques could also be employed to provide additional and more reliable altimeter sea surface height data closer to tide gauge stations (Deng and Featherstone 2006). Overall, the improvement of vertical motion estimates at global tide gauge sites caused by GIA and other phenomena, should improve the accuracy of global sea level change measurements.…”

Improving Jason-2 Sea Surface Heights within 10 km Offshore by Retracking Decontaminated Waveforms

“…Some other approaches that use refined model-based retrackers, such as Brown plus specular peak model [39] and the Brown with asymmetric Gaussian peak (BAGP) model [6], were developed to conform peaky altimetric waveforms that occupy a large percentage of coastal areas. In addition, some researchers developed adaptive retracking systems by applying an optimal retracker for various characteristic shapes, on the basis of waveform classification [36,38,[40][41][42]. Although these retrackers contribute enormously to coastal SSH retrievals with better accuracy and shortened coastal gaps, handling coastal waveforms within 10 km of the shore is still a thorny issue [2,38,43].…”

Near‐coastal satellite altimetry: Sea surface height variability in the North Sea–Baltic Sea area

“…For other purposes, interpolation of the valid radiometer wet tropospheric correction estimations is possible [Vignudelli et al, 2005]. To obtain altimetric data even closer to the coast, retracking is necessary [e.g., Deng and Featherstone, 2006].…”