Cross‐polarization geophysical model function for C‐band radar backscattering from the ocean surface and wind speed retrieval

Hwang, Paul A.; Stoffelen, Ad; Zadelhoff, Gerd-Jan van; Perrie, William; Zhang, Biao; Li, Haiyan; Shen, Hui

doi:10.1002/2014jc010439

Cited by 83 publications

(86 citation statements)

References 31 publications

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“…The void fraction f a is 0.98, the foam bubble radius r s is 2 mm, and ΔT = 3 • C. Four incidence angles are analyzed: 22.5 • (blue), 27.5 • (green), 32.5 • (red), and 37.5 • (cyan). These angles are consistent with the mean incidence angles of [7], [10], and [30], where RADARSAT-2 data (covering the range 20 • -40 • ) were sorted into incidence angle bins, with 5 • bin width. Fig.…”

Section: A Wind Speed Dependencesupporting

confidence: 67%

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

Fois¹,

Hoogeboom

Chevalier³

et al. 2015

IEEE Trans. Geosci. Remote Sensing

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This paper investigates the potential of cross polarization (VH) to extend the upper dynamic range of the wind measurements from ocean scatterometry. An analytical model for the VH polar scattering of the microwave radiation from ocean is proposed. The model combines the second-order smallslope approximation theory with the vector radiative transfer theory to obtain a statistical expression of the ocean scattering in presence of foam. Cross-polarized backscatter signals from RADARSAT-2 C-band synthetic aperture radar imagery, which were acquired during severe weather events, and collocated/ time-coincident stepped-frequency microwave radiometer wind measurements by the National Oceanic and Atmospheric Administration's hurricane-hunter aircraft are used to verify the model. The validity of the model has been also proven against European Centre for Medium-Range Weather Forecasts forecasted winds. The results suggest that the present scattering model can be a valuable tool for understanding VH at very high wind speeds and for interpreting the data collected by the future dual polarimetric wind scatterometer (SCA), which will be flown on the Second Generation Meteorological Operational satellite program (MetOp-SG) as an evolution of the Advanced Scatterometer instrument on board MetOp.Index Terms-Cross-polar scattering, foam, normalized radar cross section (NRCS), ocean scatterometry, ocean wave height spectrum.

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Section: A Wind Speed Dependencesupporting

confidence: 67%

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

Fois¹,

Hoogeboom

Chevalier³

et al. 2015

IEEE Trans. Geosci. Remote Sensing

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“…Based on this linear relationship, some VH GMFs have been proposed using RS-2 data. Here, we compare the VH NRCS dependence with the proposed models by Vachon et al [13] and Zhang et al [18], and two models (H14S and H14E) by Hwang et al [20]. These comparisons show that the model in Vachon et al [13] is relatively close to GF-3.…”

Section: Wind Sensitivity For Nrcsmentioning

confidence: 74%

“…This unique sensitivity for cross-polarization data is mainly attributed to the contribution of breaking waves [15,16]. Some cross-polarization GMFs have been developed based on this sensitivity [13][14][15][16][17][18][19][20]. These models are simple and considered more suitable for high wind conditions.…”

Section: Introductionmentioning

confidence: 99%

Preliminary Analysis of Chinese GF-3 SAR Quad-Polarization Measurements to Extract Winds in Each Polarization

et al. 2017

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This study analyzed the noise equivalent sigma zero (NESZ) and ocean wind sensitivity for Chinese C-band Gaofen-3 (GF-3) quad-polarization synthetic aperture radar (SAR) measurements to facilitate further operational wind extraction from GF-3 data. Data from the GF-3 quad-polarization SAR and collocated winds from both NOAA/NCEP Global Forecast System (GFS) atmospheric model and National Data Buoy Center (NDBC) buoys were used in the analysis. For NESZ, the co-polarization was slightly higher compared to the cross-polarization. Regarding co-polarization and cross-polarization, NESZ was close to RadarSAT-2 and Sentinel-1 A. Wind sensitivity was analyzed by evaluating the dependence on winds in terms of normalized radar cross-sections (NRCS) and polarization combinations. The closest geophysical model function (GMF) and the polarization ratio (PR) model to GF-3 data were determined by comparing data and the model results. The dependence of co-polarized NRCS on wind speed and azimuth angle was consistent with the proposed GMF models. The combination of CMOD5 and CMOD5.N was considered to be the closest GMF in co-polarization. The cross-polarized NRCS exhibited a strong linear relationship with moderate wind speeds higher than 4 m·s −1 , but a weak correlation with the azimuth angle. The proposed model was considered as the closest GMF in cross-polarization. For polarization combinations, PR and polarization difference (PD) were considered. PR increased only with the incidence angle, whereas PD increased with wind speed and varied with azimuth angle. There were three very close PR models and each can be considered as the closest. Preliminary results indicate that GF-3 quad-polarization data are valid and have the ability to extract winds in each polarization.

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“…Presently, there are many GMFs for several microwave frequency bands: Ku, X, C, and L. Most of them are for copolarized returns VV and HH . Only the L and C bands offer several versions of the VH GMF [ Meissner et al ., ; van Zadelhoff et al ., ; Zhang et al ., ; Hwang et al ., ]. In principle, they can all be used for our task of inferring the surface roughness and wave breaking properties.…”

Section: Introductionmentioning

confidence: 99%

Surface roughness and breaking wave properties retrieved from polarimetric microwave radar backscattering

Hwang

Fois

2015

JGR Oceans

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Ocean surface roughness and wave breaking are the two main contributors of radar backscattering from the ocean surface. The relative weightings of the two contributions vary with the microwave polarization: the VV (vertical transmit vertical receive) is dominated by the Bragg resonance scattering mechanism, and the HH (horizontal transmit horizontal receive) and VH (horizontal transmit vertical receive or vertical transmit horizontal receive) contain nontrivial non‐Bragg contributions mainly produced by breaking features. A method is developed to obtain the short‐scale properties of ocean surface roughness and wave breaking from Ku, C, and L band polarimetric sea returns. The results are used for quantitative evaluation of the ocean surface roughness spectral models and for deriving understanding of the breaking contribution important to microwave ocean remote sensing, in particular its dependence on wind speed, microwave frequency, and incidence angle. Implications of the results to air‐sea interaction applications are discussed.

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Cross‐polarization geophysical model function for C‐band radar backscattering from the ocean surface and wind speed retrieval

Cited by 83 publications

References 31 publications

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

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

Preliminary Analysis of Chinese GF-3 SAR Quad-Polarization Measurements to Extract Winds in Each Polarization

Surface roughness and breaking wave properties retrieved from polarimetric microwave radar backscattering

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