Sea Wind Extraction From RADARSAT-2 and Scatterometer Data Over the Gulf of Mexico

Rodrigues, Douglas Fraga; Landau, Luiz; Torres, Audálio Rebelo; Lanzillotti, Regina; Miranda, Fernando

doi:10.1109/lgrs.2017.2692044

Cited by 3 publications

(2 citation statements)

References 21 publications

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“…These GMFs relate the NRCS to the incidence angle, wind speed at a height of 10 m above sea level, and azimuth angle (radar look angle with respect to wind direction). Not only from scatterometers, such as QuickSCAT [ 16 , 17 ] and ASCAT [ 18 ], they can also accurately retrieve the wind speed from SAR images (within about 2 m/s), e.g., ENVISAT [ 19 ], RADARSAT-1/2 [ 20 , 21 , 22 ] and Sentinel-1A/B [ 23 ]. However, such GMFs are only suitable for VV-polarized NRCS, and no similar models exist to retrieve wind speed from images in HH-polarization.…”

Section: Introductionmentioning

confidence: 99%

A Preliminary Analysis of Wind Retrieval, Based on GF-3 Wave Mode Data

Wang

Han

Yuan

et al. 2018

Sensors

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This paper presents an analysis of measurements of the normalized radar cross-(NRCS) in Wave Mode for Chinese C-band Gaofen-3(GF-3) synthetic aperture radar (SAR). Based on 2779 images from GF-3 quad-polarization SAR in Wave Mode and collocated wind vectors from ERA-Interim, this experiment verifies the feasibility of using ocean surface wind fields and VV-polarized NRCS to perform normalized calibration. The method uses well-validated empirical C-band geophysical model function (CMOD4) to estimate the calibration constant for each beam. In addition, the relationship between cross-pol NRCS and wind vectors is discussed. The cross-pol NRCS increases linearly with wind speed and it is obviously modulated by the wind direction when the wind speed is greater than 8 m/s. Furthermore, the properties of the polarization ratio, denoted PR, are also investigated. The PR is dependent on incidence angle and azimuth angle. Two empirical models of the PR are fitted, one as a function of incidence angle only, the other with additional dependence on azimuth angle. Assessments show that the σVV0 retrieved from new PR models as well as σHH0 is in good agreement with σVV0 extracted from SAR images directly.

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Section: Introductionmentioning

confidence: 99%

A Preliminary Analysis of Wind Retrieval, Based on GF-3 Wave Mode Data

Wang

Han

Yuan

et al. 2018

Sensors

View full text Add to dashboard Cite

show abstract

“…These GMFs relate the NRCS to the incidence angle, wind speed at a height of 10m above sea level, and azimuth angle (radar look angle with respect to wind direction). Not only scatterometer, such as QuickSCAT [16,17] and ASCAT [18], they can also accurately retrieve the wind speed from SAR image (within about 2m/s), e.g., ENVISAT [19], RADARSAT-1/2 [20][21][22] and Sentinel-1A/B [23]. However, such GMFs are only suitable for VV-polarized NRCS, no similar models exist to retrieve wind speed from images in HH-polarization.…”

Section: Introductionmentioning

confidence: 99%

Preliminary Analysis of Wind Retrieval Based on GF-3 Wave Mode Images

Wang¹,

Han²,

Yuan³

et al. 2018

Preprint

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In this paper, we analyze the measurements of the normalized radar cross-section(NRCS) in Wave Mode for Chinese C-band Gaofen-3(GF-3) synthetic aperture radar (SAR). Based on 2779 images from GF-3 quad-polarization SAR in Wave Mode and collocated wind vectors from ERA-Interim, we verify the feasibility of using ocean surface wind fields and VV-polarized NRCS to perform normalized calibration. The method uses well-validated empirical C-band geophysical model function (CMOD4) to estimate the calibration constant for each beam. The Amazon rainforest experiment results show that the accuracy of obtained calibration constant meets the requirements. In addition, the relationship between cross-pol NRCS and wind vectors is discussed. The cross-pol NRCS increases linearly with wind speed and it has an approximate cosine modulation with the wind direction when the wind speed is greater than 8m/s. The cross-polarized system noise floor is low enough to ignore it in wind retrieval. Furthermore, we also investigate the properties of the polarization ratio, denoted PR, and show that it is dependent on incidence angle and azimuth angle. Two empirical models of the PR are fitted, one as a function of incidence angle only, the other with additional dependence on azimuth angle. Assessments show that the σ_VV^0 retrieved from new PR models as well as σ_HH^0 is in good agreement with σ_VV^0 extracted from SAR images directly. And it is also shown that considering the azimuth angle can improve polarization conversion accuracy.

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