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Andre V. Smirnov

Abstract

Both natural and artificial (ship induced) features of atmospheric motions can be seen in ocean radar imagery. Observations of a surface wake extending downstream from the atmospheric vortices in a thermal ship plume are described. To demonstrate the usefulness of radar systems in observing the ocean surface, the authors studied hot ship exhaust using a 2.25-cm-wavelength airborne radar. The ship-induced feature in the polarimetric radar images was observed in the ocean surface cold environment with moderate horizontal ambient winds. The smokelike feature appears only in the vertically polarized images, not in the horizontally polarized images.

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Andre V. Smirnov and Valery U. Zavorotny

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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