Satellite Radar Altimetry shows how Water Surface Smoothness varies in the Salar de Uyuni (Bolivia)
Stefano Vignudelli (1), Ron Abileah (2), Paula Pacheco (3) and Francesco De Biasio (4)

1 National Research Council of Italy,Institute of Biophysics, Pisa, Italy

2 jOmegak, San Carlos, CA, USA

3 University Montpellier, France

4 National Research Council of Italy, Institute of Polar Sciences, Venice, Italy

Abstract

Salar de Uyuni is a salt desert in Bolivia, situated at an altitude of 3,600 meters and spanning approximately 10,000 square kilometers. It holds the record as the ^world^s largest natural mirror^ when the surface is covered with a thin layer of water. However, that statement has never been scientifically proved. There is only evidence from photographs that tourists take along the border as the interior area is not easily accessible during the wet season.
In this study, we use new observations from Sentinel-3 satellites to show that the Salar de Uyuni is not the vast uniform mirror on a year-to-year basis as believed. The confidence in our observations is corroborated from the optical measurements taken during the field survey (16th - 20th of February 2024), never conducted before in the interior of the Salar de Uyuni in presence of water and in coincidence with a satellite passage on 20th February 2024. Radar altimetry is a remote sensing technique that is primarily designed to measure heights. However, Abileah and Vignudelli (2021) using radar echoes developed a metrics to identify how water surface is reflecting radar waves. The idea was to use the Radar Cross Section (RCS). The smoother is the surface the higher is the RCS. Initially, we used a very basic formulation that sufficed the unknown design parameters of the radar. In this study, RCS values are now more accurately estimated using an enhanced method based on the inversion of the radar equation provided by EUMETSAT.

REFERENCE

R. Abileah, S. Vignudelli. Precise inland surface altimetry (PISA) with nadir specular echoes from Sentinel-3: algorithm and performance assessment. Remote Sensing of Environment, 264, 112580, 2021 https://doi.org/10.1016/j.rse.2021.112580

Keywords: Satellite radar altimetry, Salar de Uyuni, water smoothness

Topic: Topic A: General Remote Sensing