Assessment of DUACS Sentinel-3A Altimetry Data in the Coastal Band of the European Seas: Comparison with Tide Gauge Measurements

Antonio Sánchez-Román,Marie-Isabelle Pujol,Marta Marcos,Yannice Faugère,Ananda Pascual,Guillaume Taburet

doi:10.3390/rs12233970

Abstract

The quality of the Data Unification and Altimeter Combination System (DUACS) Sentinel-3A altimeter data in the coastal area of the European seas is investigated through a comparison with in situ tide gauge measurements. The comparison was also conducted using altimetry data from Jason-3 for inter-comparison purposes. We found that Sentinel-3A improved the root mean square differences (RMSD) by 13% with respect to the Jason-3 mission. In addition, the variance in the differences between the two datasets was reduced by 25%. To explain the improved capture of Sea Level Anomaly by Sentinel-3A in the coastal band, the impact of the measurement noise on the synthetic aperture radar altimeter, the distance to the coast, and Long Wave Error correction applied on altimetry data were checked. The results confirmed that the synthetic aperture radar altimeter instrument onboard the Sentinel-3A mission better solves the signal in the coastal band. Moreover, the Long Wave Error processing contributes to reduce the errors in altimetry, enhancing the consistency between the altimeter and in situ datasets.

Highlights

Since 1992, altimeter missions have been providing accurate measurements of sea surface height (SSH) [1]
The Permanent Service for Mean Sea Level (PSMSL) repository presents a dense tide gauge network in the European coasts similar to that found in the cmEMS repository, but it is based on monthly average sea level records. [41,42] conducted a regional calibration of the Sentinel-3A data at higher temporal scales by using tide gauge measurements included in the cmEMS repository, but it was focused on the German coasts of the German Bight and of the Baltic Sea
This validation was conducted by comparing the equivalent Sea Level Anomaly (SLA) derived from 6-h sampled tide gauges over the same period in the whole domain and the following sub-regions: the Mediterranean and Baltic Seas and the IBI and North-West Shelves (NWS) regions

Summary

Introduction

Since 1992, altimeter missions have been providing accurate measurements of sea surface height (SSH) [1]. There is still a degree of uncertainty in altimeter measurements and in the geophysical corrections applied in the SSH computation [2,3,4,5]. Efforts have aimed at extending the capabilities of current altimeters closer to the coastal zone. This includes the application of improved geophysical corrections, data recovery strategies near the coast using new editing criteria, and high-frequency along-track sampling associated with updated quality control procedures [6,7,8,9]. Concerning the geophysical corrections, one of the major improvements is in the tide models where the tidal component is not part of the observed signal [10] and needs to be removed [7]

Methods

Results

Discussion

Conclusion