A New Retracking Technique for Brown Peaky Altimetric Waveforms

ABSTRACT

A new Brown-Peaky (BP) retracker has been developed for peaky waveforms that usually appear within ∼10 km to the coastline. The main feature of the BP is that it fits peaky waveforms using the Brown model without introducing a peak function. The retracking strategy first detects the peak location and width of a waveform using an adaptive peak detection method, and then estimates retracking parameters using a weighted least squares (WLS) estimator. The WLS assigns a downsized weight to corrupted waveform gates, but an equal weight to other normal waveform gates. The BP retracker has been applied to 4-year Jason-1 waveform (2002–2006) in two Australian coastal zones. The results retracked by BP, MLE4 and ALES retrackers have been validated against tide-gauge observations located at Burnie, Lorne and Broome. The comparison results show that three retrackers have similar performance over open oceans with the correlation coefficient (∼0.7) and RMSE (∼13 cm) between altimetric and tide-gauge sea levels for distance >7 km offshore. The main improvement of BP retracker occurs for distance ≤7 km to the coastline, where validation results indicate that data retracked by BP are more accurate (15–21 cm) than those by ALES (16–24 cm) and MLE4 (19–37 cm).

KEYWORDS:

• Brown-peaky waveform
• coastal satellite altimetry
• peak detection
• sea level anomaly
• tide gauge
• weighed least squares estimator
• validation

Acknowledgements

The authors thank Archiving, Validation, and Interpretation of Satellite Oceanography (AVISO) for providing the latest Jason-1 SGDR data, Dan Codiga for providing utide MATLAB code, Yongchun Cheng for sharing response method program, and Marcello Passaro for communications about the ALES.

Additional information

Funding

This research is supported by the Australian Research Council's Discovery Project funding scheme (project number DP150100615, 2015-2017).