Sea‐ice detection from near‐nadir Ku‐band echoes from CFOSAT/SWIM scatterometer

Type Article
Date 2022-06
Language English
Author(s) Peureux CharlesORCID1, Longépé Nicolas2, Mouche AlexisORCID3, Tison Céline4, Tourain Cédric4, Lachiver Jean‐michel4, Hauser DanièleORCID5
Affiliation(s) 1 : Collecte Localisation Satellites, 45 avenue La Pérouse, 29 280 Plouzané, France
2 : Φ‐lab Explore Office ESRIN ,European Space Agency (ESA) Frascati ,Italy
3 : Ifremer, Univ. Brest CNRS IRD Laboratoire d’Océanographie Physique et Spatiale IUEM, 29 280 Brest , France
4 : Centre National d’Études Spatiales, Toulouse ,France
5 : Université Versailles Saint‐Quentin en Yvelines ,Sorbonne Université CNRS LATMOS Guyancourt, france
Source Earth And Space Science (2333-5084) (American Geophysical Union (AGU)), 2022-06 , Vol. 9 , N. 6 , P. e2021EA002046 (20p.)
DOI 10.1029/2021EA002046
WOS© Times Cited 2
Keyword(s) SWIM, CFOSAT, sea-ice, Geophysical Model Function
Abstract

SWIM on board CFOSAT is the first spaceborne, low incidence, rotating scatterometer, aiming at measuring in near-real time ocean waves spectra. With 5 off-nadir beams at incidences between 2° and 10° plus one nadir beam, it covers the Earth in 13 days, including polar regions thanks to its polar orbit. This work aims at exploiting the SWIM data over ice regions with two objectives. An off-nadir data-based sea-ice flag is here proposed that allows, first, to eliminate sea-ice polluted echoes for improving the wave spectrum retrieval, and second, to open perspectives for application of sea-ice monitoring with near nadir Ku-band active sensors. To this end, the signature of both open water and sea-ice radar backscatter is parameterized into Geophysical Model Functions. Then, comparisons with observed profiles through a Bayesian scheme provide a probability of sea-ice presence. After comparison with both model (ECMWF-IFS) and radiometer (SSMI) derived reference data sets, the proposed flag is found to be ready for operational use. At latitudes greater than 40° in absolute value, the proposed flagging algorithm exhibits accuracies of approximately 98% for all beams compared to SSMI data. Beam to beam performances are characterized and show potential for the characterization of sea-ice at Ku band.

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Peureux Charles, Longépé Nicolas, Mouche Alexis, Tison Céline, Tourain Cédric, Lachiver Jean‐michel, Hauser Danièle (2022). Sea‐ice detection from near‐nadir Ku‐band echoes from CFOSAT/SWIM scatterometer. Earth And Space Science, 9(6), e2021EA002046 (20p.). Publisher's official version : https://doi.org/10.1029/2021EA002046 , Open Access version : https://archimer.ifremer.fr/doc/00745/85673/