Validation of an Empirical Subwaveform Retracking Strategy for SAR Altimetry

• Published in: Remote sensing (Basel, Switzerland) Vol. 14; no. 16; p. 4122
• Main Authors: Passaro, Marcello, Rautiainen, Laura, Dettmering, Denise, Restano, Marco, Hart-Davis, Michael G., Schlembach, Florian, Särkkä, Jani, Müller, Felix L., Schwatke, Christian, Benveniste, Jérôme
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.08.2022
• Subjects: Algorithms; Altimeters; Altimetry; Baltic Sea; Coastal zone; Datasets; Ice cover; Power spectral density; Radio altimeters; Remote sensing; retracking; satellite altimetry; Satellites; Sea ice; Sea level; Sea states; Synthetic aperture radar; tide gauge; Waveforms; Baltic Sea
• ISSN: 2072-4292; 2072-4292
• DOI: 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.