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Study of Polarization Differences in Ku-Band Ocean Radar Imagery

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  • 1 Cooperative Institute for Research in Environmental Sciences, University of Colorado/N0AA, Boulder, Colorado
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Abstract

Radar returns from the sea surface can be represented as the sum of two contributions from Bragg scattering and from individual breaking events. This representation is used to analyze polarimetric radar images of ocean areas obtained at grazing angles 6°<ψ<18° with the airborne Ku-band radar in the New York Bight. All images were obtained for light and moderate winds and can be divided into three types according to texture differences. Images obtained confirm that there are differences between returns for horizontal/horizontal (HH) and vertical/vertical (VV) polarizations for the three types. The first type agrees qualitatively with predictions of the two-scale Bragg model, whereas the other two do not. The second and third types have a significant spike contribution from breaking events at both polarizations. The last type reveals drastic differences between images obtained using HH and VV polarizations. The polarization dissimilarity is a result of a low correlation between the spike clusters in HH-polarized images and the variations of continuous background in VV-polarized images. The role of atmospheric stability in processes responsible for spatial decorrelation of the different scatterers is also examined.

Abstract

Radar returns from the sea surface can be represented as the sum of two contributions from Bragg scattering and from individual breaking events. This representation is used to analyze polarimetric radar images of ocean areas obtained at grazing angles 6°<ψ<18° with the airborne Ku-band radar in the New York Bight. All images were obtained for light and moderate winds and can be divided into three types according to texture differences. Images obtained confirm that there are differences between returns for horizontal/horizontal (HH) and vertical/vertical (VV) polarizations for the three types. The first type agrees qualitatively with predictions of the two-scale Bragg model, whereas the other two do not. The second and third types have a significant spike contribution from breaking events at both polarizations. The last type reveals drastic differences between images obtained using HH and VV polarizations. The polarization dissimilarity is a result of a low correlation between the spike clusters in HH-polarized images and the variations of continuous background in VV-polarized images. The role of atmospheric stability in processes responsible for spatial decorrelation of the different scatterers is also examined.

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