A C-Band Geophysical Model Function for Determining Coastal Wind Speed Using Synthetic Aperture Radar

Type Article
Date 2018-07
Language English
Author(s) Lu Yiru1, Zhang Biao1, Perrie William2, Mouche AlexisORCID3, Li Xiaofeng4, Wang He5
Affiliation(s) 1 : Nanjing Univ Informat Sci & Technol, Sch Marine Sci, Nanjing 210044, Jiangsu, Peoples R China.
2 : Fisheries & Oceans Canada, Bedford Inst Oceanog, Dartmouth, NS B2Y 4A2, Canada.
3 : Inst Francais Rech Exploitat Mer, Lab Oceanog Phys Spatiale, F-29280 Plouzane, France.
4 : NOAA, Global Sci & Technol Inc, Natl Environm Satellite Data & Informat Serv, College Pk, MD 20746 USA.
5 : State Ocean Adm, Natl Ocean Technol, Tianjin 300171, Peoples R China.
Source Ieee Journal Of Selected Topics In Applied Earth Observations And Remote Sensing (1939-1404) (Ieee-inst Electrical Electronics Engineers Inc), 2018-07 , Vol. 11 , N. 7 , P. 2417-2428
DOI 10.1109/JSTARS.2018.2836661
WOS© Times Cited 52
Keyword(s) Coastal wind speed, geophysical model function (GMF), synthetic aperture radar (SAR)

A new geophysical model function (GMF), called C_SARMOD2, has been developed to relate high-resolution C-band normalized radar cross section (NRCS), acquired in VV polarization over the ocean, to the 10-m height wind speed. A total of 3078 RADARSAT-2 and Sentinel-1A VV-polarized synthetic aperture radar (SAR) images, acquired under different wind speed conditions, were collocated with in situ buoy measurements. The paired dataset was used to derive transfer functions and coefficients of C_SARMOD2, and then to validate the wind speed retrievals. The comparison between SAR-retrieved wind speeds and buoy measurements show almost no bias and a root mean square error of 1.84 m/s. Two representative quad-and dual-polarization SAR images, acquired from coastal regions, are used as case studies to examine C_SARMOD2 performances. The case study and statistical validation results suggest that the proposed C_SARMOD2 has the potential to measure coastal wind speeds at subkilometer resolutions. Although derived from low resolution NRCS measurements, this study also confirms the great robustness of CMOD5.N and recent CMOD7 when applied to SAR data. In addition, it shows that with the new generation of SAR satellite-borne sensors, it is no longer mandatory to rely on scatterometers in order to build a GMF, which will be used for SAR applications. Such an approach is particularly important in view of the upcoming RADARSAT Constellation Mission with new polarization configurations. Moreover, it also opens new perspectives on the derivation of GMFs in HH-polarization. However, these results also suggest that for coastal areas, the increase of the resolution to define the GMF is less important than adding other geophysical parameters to improve wind retrieval performance. This advocates for the necessity of revisiting the methodologies for ocean surface wind speed measurements in coastal areas.

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Lu Yiru, Zhang Biao, Perrie William, Mouche Alexis, Li Xiaofeng, Wang He (2018). A C-Band Geophysical Model Function for Determining Coastal Wind Speed Using Synthetic Aperture Radar. Ieee Journal Of Selected Topics In Applied Earth Observations And Remote Sensing, 11(7), 2417-2428. Publisher's official version : https://doi.org/10.1109/JSTARS.2018.2836661 , Open Access version : https://archimer.ifremer.fr/doc/00452/56390/