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

• Published in: Earth and Space Science
• Main Authors: Peureux, Charles, Longépé, Nicolas, Mouche, Alexis, Tison, Céline, Tourain, Cédric, Lachiver, Jean‐michel, Hauser, Danièle
• Other Authors: Collecte Localisation Satellites (CLS), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National d'Études Spatiales Toulouse (CNES), European Space Research Institute (ESRIN), European Space Agency (ESA), Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales Toulouse (CNES), Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: SWIM Radar; CFOSAT Mission; Ocean Surface Wind; Ocean Surface Waves; Scatterometer; Sea Ice; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Sea ice
• Online Access: https://hal.archives-ouvertes.fr/hal-03543717; https://hal.archives-ouvertes.fr/hal-03543717/document; https://hal.archives-ouvertes.fr/hal-03543717/file/Peureux_etal_accepted_tablescorrected.pdf; https://doi.org/10.1029/2021ea002046

International audience 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.