FN Archimer Export Format PT J TI Ku-Band Sea Surface Radar Backscatter at Low Incidence Angles under Extreme Wind Conditions BT AF LI, Xiuzhong ZHANG, Biao MOUCHE, Alexis HE, Yijun PERRIE, William AS 1:1,2;2:1,2;3:1,3;4:1,2;5:1,4; FF 1:;2:;3:PDG-ODE-LOPS-SIAM;4:;5:; C1 Nanjing Univ Informat Sci & Technol, Sch Marine Sci, Nanjing 210044, Jiangsu, Peoples R China. Jiangsu Res Ctr Ocean Survey & Technol, Nanjing 210044, Jiangsu, Peoples R China. IFREMER, Ctr Brest, Lab Oceanog Spatiale, F-29280 Plouzane, France. Fisheries & Oceans Canada, Bedford Inst Oceanog, Dartmouth, NS B2Y 4A2, Canada. C2 NUIST, CHINA UNIV NANJING, CHINA IFREMER, FRANCE MPO BEDFORD INST OCEANOG, CANADA SI BREST SE PDG-ODE-LOPS-SIAM UM LOPS IN WOS Ifremer jusqu'en 2018 DOAJ copubli-int-hors-europe copubli-sud IF 3.406 TC 12 UR https://archimer.ifremer.fr/doc/00385/49659/50197.pdf LA English DT Article DE ;NRCS;extreme wind conditions;low incidence angles AB This paper reports Ku-band normalized radar cross section (NRCS) at low incidence angles ranging from 0° to 18° and in the wind speed range from 6 to 70 m/s. The precipitation radar onboard the tropical rainfall measuring mission and Jason-1 and 2 have provided 152 hurricanes observations between 2008 and 2013 that were collocated with stepped-frequency microwave radiometer measurements. It is found that the NRCS decreases with increasing incidence angle. The decrease is more dramatic in the 40–70 m/s range of wind speeds than in the 6–20 m/s range, indicating that the NRCS is very sensitive to low incidence angles under extreme wind conditions and insensitive to the extreme wind speed. Consequently, the sea surface appears relatively “smooth” to Ku-band electromagnetic microwaves. This phenomenon validates the observed drag coefficient reduction under extreme wind conditions, from a remote sensing viewpoint. Using the NRCS dependence on incidence angle under extreme wind conditions, we also present an empirical linear relationship between NRCS and incidence angles, which may assist future-satellites missions operating at small incidence angles to measure sea surface wind and wave field. PY 2017 PD MAY SO Remote Sensing SN 2072-4292 PU Mdpi Ag VL 9 IS 5 UT 000402573700077 DI 10.3390/rs9050474 ID 49659 ER EF