Validation of an Empirical Subwaveform Retracking Strategy for SAR Altimetry

• Published in: Remote Sensing
• Main Authors: Marcello Passaro, Laura Rautiainen, Denise Dettmering, Marco Restano, Michael G. Hart-Davis, Florian Schlembach, Jani Särkkä, Felix L. Müller, Christian Schwatke, Jérôme Benveniste
• Format: Text
• Language: English
• Published: Multidisciplinary Digital Publishing Institute 2022
• Subjects: sea level; retracking; satellite altimetry; tide gauge; Baltic Sea; Jagged; Sea ice
• Online Access: https://doi.org/10.3390/rs14164122

The sea level retrievals from the latest generation of radar altimeters (the SAR altimeters) are still challenging in the coastal zone and areas covered by sea ice and require a dedicated fitting (retracking) strategy for the waveforms. In the framework of the European Space Agency’s Baltic + Sea Level (ESA Baltic SEAL) project, an empirical retracking strategy (ALES + SAR), including a dedicated sea state bias correction, has been designed to improve the sea level observations in the Baltic Sea, characterised by a jagged coastline and seasonal sea ice coverage, without compromising the quality of open ocean data. In this work, the performances of ALES + SAR are validated against in-situ data in the Baltic Sea. Moreover, variance, crossover differences and power spectral density of the open ocean data are evaluated on a global scale. The results show that ALES + SAR performances are of comparable quality to the ones obtained using physical-based retrackers, with relevant advantages in coastal and sea ice areas in terms of quality and quantity of the sea level data.