Coastal altimetry products in the strait of Gibraltar

TL;DR

This study evaluates the accuracy of coastal altimetry sea level products in the Strait of Gibraltar, comparing different data sources and retrackers, and validating results with tide gauges to improve understanding of measurement precision.

Contribution

It provides a comparative analysis of Envisat and AltiKa altimetry data, highlighting improvements from using the ALES retracker and validating accuracy with tide gauge data.

Findings

ALES retracker improves Envisat SLA accuracy by 20%.

AltiKa shows higher overall accuracy with no significant difference between data sources.

Validation with tide gauges confirms the reliability of the improved altimetry products.

Abstract

This paper analyzes the availability and accuracy of coastal altimetry sea level products in the Strait of Gibraltar. All possible repeats of two sections of the Envisat and AltiKa ground-tracks were used in the eastern and western portions of the strait. For Envisat, along-track sea level anomalies (SLAs) at 18-Hz posting rate were computed using ranges from two sources, namely, the official SGDRs and the outputs of a coastal waveform retracker, the ALES retracker; in addition, SLAs at 1 Hz were obtained from CTOH, France. For AltiKa, along-track SLA at 40 Hz was also computed both from SGDR and ALES ranges. The quality of these altimeter products was validated using two tide gauges located on the southern coast of Spain. We observed an improvement of about 20% in the accuracy of the Envisat SLAs from ALES compared to the standard (SGDR) and the reprocessed CTOH data sets. AltiKa shows higher accuracy, with no significant differences between SGDR and ALES.