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Remote Sens. 2013, 5(11), 6096-6115; doi:10.3390/rs5116096
Article

Spectral Properties of ENVISAT ASAR and QuikSCAT Surface Winds in the North Sea

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DTU Wind Energy, Technical University of Denmark, Risø Campus, Building 118, Frederiksborgvej 399, Roskilde 4000, Denmark
* Author to whom correspondence should be addressed.
Received: 30 September 2013 / Revised: 25 October 2013 / Accepted: 8 November 2013 / Published: 18 November 2013
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Abstract

Spectra derived from ENVISAT Advanced Synthetic Aperture Radar (ASAR) and QuikSCAT near-surface ocean winds are investigated over the North Sea. The two sensors offer a wide range of spatial resolutions, from 600 m to 25 km, with different spatial coverage over the area of interest. This provides a unique opportunity to study the impact of the spatial resolution on the spectral properties of the wind over a wide range of length scales. Initially, a sub-domain in the North Sea is chosen, due to the overlap of 87 wind scenes from both sensors. The impact of the spatial resolution is manifested as an increase in spectral density over similar wavenumber ranges as the spatial resolution increases. The 600-m SAR wind product reveals a range of wavenumbers in which the exchange processes between micro- and meso-scales occur; this range is not captured by the wind products with a resolution of 1.5 km or lower. The lower power levels of coarser resolution wind products, particularly when comparing QuikSCAT to ENVISAT ASAR, strongly suggest that the effective resolution of the wind products should be high enough to resolve the spectral properties. Spectra computed from 87 wind maps are consistent with those obtained from several thousands of samples. Long-term spectra from QuikSCAT show that during the winter, slightly higher energy content is identified compared to the other seasons.
Keywords: SAR; QuikSCAT; wind spectra; spatial resolution SAR; QuikSCAT; wind spectra; spatial resolution
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Karagali, I.; Larsén, X.G.; Badger, M.; Peña, A.; Hasager, C.B. Spectral Properties of ENVISAT ASAR and QuikSCAT Surface Winds in the North Sea. Remote Sens. 2013, 5, 6096-6115.

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