Future Ocean Scatterometry: On the Use of Cross-Polar Scattering to Observe Very High Winds

Fois, F.; Hoogeboom, P.; Chevalier, François Le; Stoffelen, Ad

doi:10.1109/tgrs.2015.2416203

Cited by 50 publications

(22 citation statements)

References 33 publications

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“…It is seen, that V Dopmax increase with increasing u * and U 10 . Note that these dependencies differ from the prediction of small-scale approximation that the peak velocity of the Doppler spectra of cross-polarized backscatter does not depend on wind velocity in (Fois et al, 2015b). It means that apparently at high winds, there is an additional mechanism responsible for radar backscattering at both polarizations.…”

Section: 1029/2018jc014090contrasting

confidence: 70%

Cross‐Polarization GMF for High Wind Speed and Surface Stress Retrieval

et al. 2018

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This paper describes the construction of geophysical model function (GMF) for wind speed and surface stress retrieval at high winds from cross‐polarized radar backscatter at the water surface. The starting point is the laboratory experiment designed for the study of X‐band backscattering from water surface. In particular, it was shown that cross‐polarized normalized radar cross section (NRCS) keeps sensitivity to wind friction velocity at high winds alternatively to co‐polarized radar return. Basing on the analysis of the Doppler spectra and simultaneous measurements of parameters of surface waves, we suggest a hypothesis that at high winds the cross‐polarized backscattered signal is formed mainly due to scattering from wave breakers. The hypothesis is supported by the experimentally detected proportionality between the power of the scattered signal at cross polarization and the area swept by wave breakers. These results obtained in the laboratory environment are applied for constructing the similar dependencies for field conditions. Using the phenomenological statistical physics approach, a parameterization of active whitecap coverage fraction dependence on wind friction velocity is suggested. With the use of this parameterization, the empirical function expressing the cross‐polarized NRCS by u* is derived. Using the surface drag parameterization applicable at strong winds, this dependence is verified on the base of available data sets containing collocated satellite measurements of cross‐polarized C‐band NRCS and ground measurements of wind speed. GMFs for u* and U10 retrieval are suggested. Analysis shows that taking into account the angular dependence of cross‐polarized radar backscattered power improves the accuracy of wind speed and wind friction velocity retrieval.

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Section: 1029/2018jc014090contrasting

confidence: 70%

Cross‐Polarization GMF for High Wind Speed and Surface Stress Retrieval

et al. 2018

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“…In all of these reports, the co-polarization (VV) NRCS saturated at high wind speeds up to 25 m/s. Non-saturated cross-polarization (HV or VH) NRCS variation at high wind speeds has also been reported [10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 85%

Ku-Band Sea Surface Radar Backscatter at Low Incidence Angles under Extreme Wind Conditions

Zhang

Mouche

et al. 2017

Remote Sensing

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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.

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“…Future scatterometer systems will include polarimetric capability, such as that proposed for the C-band dual polarimetric wind scatterometer to be flown on the second generation meteorological operation satellite program (MetOp-SG) [127]. SAR studies have shown that polarimetric backscatter measurements are effective in extending the number of ice classes that can be differentiated [1], which suggests that polarimetric scatterometers will enable improved sea-ice classification and mapping.…”

Section: Future Directionsmentioning

confidence: 99%

Polar Applications of Spaceborne Scatterometers

Long

2017

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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Wind scatterometers were originally developed for observation of near-surface winds over the ocean. They retrieve wind indirectly by measuring the normalized radar cross section (σ o ) of the surface, and estimating the wind via a geophysical model function relating σ o to the vector wind. The σ o measurements have proven to be remarkably capable in studies of the polar regions where they can map snow cover; detect the freeze/thaw state of forest, tundra, and ice; map and classify sea ice; and track icebergs. Further, a long time series of scatterometer σ o observations is available to support climate studies. In addition to fundamental scientific research, scatterometer data are operationally used for sea-ice mapping to support navigation. Scatterometers are, thus, invaluable tools for monitoring the polar regions. In this paper, a brief review of some of the polar applications of spaceborne wind scatterometer data is provided. The paper considers both C-band and Ku-band scatterometers, and the relative merits of fan-beam and pencil-beam scatterometers in polar remote sensing are discussed.

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Future Ocean Scatterometry: On the Use of Cross-Polar Scattering to Observe Very High Winds

Cited by 50 publications

References 33 publications

Cross‐Polarization GMF for High Wind Speed and Surface Stress Retrieval

Cross‐Polarization GMF for High Wind Speed and Surface Stress Retrieval

Ku-Band Sea Surface Radar Backscatter at Low Incidence Angles under Extreme Wind Conditions

Polar Applications of Spaceborne Scatterometers

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