Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Validation of Sentinel-3 SAR Level-2 and Level-3 Products in the Baltic Sea and Estonian lakes

Version 1 : Received: 25 August 2020 / Approved: 26 August 2020 / Online: 26 August 2020 (12:35:30 CEST)

How to cite: Liibusk, A.; Kall, T.; Rikka, S.; Uiboupin, R.; Suursaar, Ü.; Tseng, K. Validation of Sentinel-3 SAR Level-2 and Level-3 Products in the Baltic Sea and Estonian lakes. Preprints 2020, 2020080586 (doi: 10.20944/preprints202008.0586.v1). Liibusk, A.; Kall, T.; Rikka, S.; Uiboupin, R.; Suursaar, Ü.; Tseng, K. Validation of Sentinel-3 SAR Level-2 and Level-3 Products in the Baltic Sea and Estonian lakes. Preprints 2020, 2020080586 (doi: 10.20944/preprints202008.0586.v1).

Abstract

Multimission satellite altimetry (e.g. ERS, Envisat, TOPEX/Poseidon, Jason) data have enabled a synoptic view of ocean variations in the past decades, including sea-level rise and mesoscale circulations. Since 2016, the Sentinel-3 mission has provided better spatial and temporal sampling compared with its predecessors. The Sentinel-3 Ku/C Radar Altimeter (SRAL) is one of the synthetic aperture radar altimeters (SAR Altimeter) which is more precise in coastal and lake observations. In this study, we validate Sentinel-3 Level-2 products in Baltic Sea coastal areas and two lakes in Estonia. Moreover, the Copernicus Marine Environment Monitoring Service (CMEMS) Level-3 sea-level anomaly data and the Nucleus for European Modelling of the Ocean (NEMO) reanalysis model outcomes are compared with measurements from a tide gauge network. A dense in situ water level network deployed along the coast for geodetic observation was utilised to provide ground truths for validating altimetry results. Three validation methods were used for Level-2 data: (i) collocated Sentinel-3 and GNSS ship measurements; (ii) a national geoid model (EST-GEOID2017) with sea-level anomaly correction; (iii) collocated Sentinel-3 and buoy measurements. The validations were carried out in seven Sentinel-3A/B overpasses in 2019. Our results show that the uncertainty of the Sentinel-3 Level-2 altimetry product is below decimetre level on the Estonian coast and the targeted lakes. Results from CMEMS Level-3 showed a correlation of 0.8 (RMSE 0.19 m) and 0.91 (RMSE 0.27 m) when compared against tide gauge measurements and NEMO model, respectively.

Subject Areas

Sea level; GNSS; NEMO reanalysis; tide gauges; pressure buoys; geoid model; CMEMS; Copernicus

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