Modeling Envisat RA-2 waveforms in the coastal zone: Case study of calm water contamination

TL;DR

This paper models Envisat RA-2 waveforms over a coastal island to explore waveform variations and demonstrates potential for improved sea surface height measurements near the coast, aiding coastal studies.

Contribution

It introduces a waveform modeling approach for complex land/sea environments, showing potential for enhanced coastal sea surface height retrievals from satellite altimetry.

Findings

Waveform reductions over land observed in most passes.

Anomalously bright hyperbolic features linked to calm waters.

Modeling indicates improved coastal sea surface height measurements.

Abstract

This letter examines waveform data from the Envisat RA-2 as it passes regularly over Pianosa (a 10-km 2 island in the northwestern Mediterranean). Forty-six repeat passes were analyzed, with most showing a reduction in signal upon passing over the island, with weak early returns corresponding to the reflections from land. Intriguingly, one third of cases showed an anomalously bright hyperbolic feature. This feature may be due to extremely calm waters in the Golfo della Botte (northern side of the island), but the cause of its intermittency is not clear. The modeling of waveforms in such a complex land/sea environment demonstrates the potential for sea surface height retrievals much closer to the coast than is achieved by routine processing. The long-term development of altimetric records in the coastal zone will not only improve the calibration of altimetric data with coastal tide gauges but also greatly enhance the study of storm surges and other coastal phenomena.