Sea Surface KA-BAND Doppler Scatterometry at High Wind Speed: a Field Experiment

Type Proceedings paper
Date 2021
Language English
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Author(s) Yurovsky Yury Yu1, Kudryavtsev Vladimir N.1, 2, Grodsky Semyon A.3, Chapron Bertrand4
Affiliation(s) 1 : FSBSI FRC Marine Hydrophysical Institute RAS, 2, Kapitanskaya, Sevastopol 299011, Russia
2 : Russian State Hydrometeorological University, 98, Malookhtinskiy, Saint-Petersburg 195916, Russia
3 : University of Maryland, Dept. of Atmospheric and Oceanic Sciences, College Park, MD 20742, USA
4 : Institut Français de Recherche pour l'Exploitation de la Mer, Pointe du Diable, Plouzane 29280, France
Meeting The 42nd Asian Conference on Remote Sensing (ACRS2021) 22-24th November, 2021 in Can Tho University, Can Tho city, Vietnam
Source ACRS2021 Proceedings. n°15, 226 (9p.)
Keyword(s) radar, scatterometer, Ka-band, ocean, Doppler

Measuring sea surface winds and currents from space may become possible using a Doppler scatterometer. Dedicated missions are planned in the Ka-band to improve the data resolution and accuracy. However, the knowledge of the Ka-band backscattering from the real sea surface is still poor. Particularly, the behavior of the Ka-band backscattered signal is less known for high wind conditions (>20m/s). The Ka-band crosssection, in contrast to the lower frequency Ku/X/C/L-bands, is more sensitive to small-scale particles, e.g. droplets separated from wave crests at high winds. In this message, we report the results of a tower-based field experiment conducted using a continuous wave dual-co-polarized Ka-band radar during strong, up to 33 m/s, offshore wind events. In addition to the radar, this strong offshore katabatic wind event, about 12 hours long, was also recorded by supplementary wave, wind, and current sensors. At the wave fetch about 1 km, the maximum wavelength was about 10 m. At such extremely young wind-sea conditions, an apparent droplet generation was observed during wind gusts. The radar measurements were performed at 10, 20, and 45-degree incidence angles mostly at cross-wind and up-wind look geometry. Based on these measurements, we refine the previously developed Ka-band geophysical model function for high wind conditions. The droplet cloud radar signatures are apparent in the Doppler spectrum tails, but their overall contribution is rather weak. Thanks to this fact, the standard modulation transfer function (MTF) approach works well to evaluate the wave-induced Doppler velocity contribution and thus estimate the sea surface current. These results can be useful for the interpretation of tropical cyclone observation using Doppler radar techniques.

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Yurovsky Yury Yu, Kudryavtsev Vladimir N., Grodsky Semyon A., Chapron Bertrand (2021). Sea Surface KA-BAND Doppler Scatterometry at High Wind Speed: a Field Experiment. ACRS2021 Proceedings. n°15, 226 (9p.).