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Remote Sens. 2019, 11(7), 865; https://doi.org/10.3390/rs11070865

Use of WorldView-2 Along-Track Stereo Imagery to Probe a Baltic Sea Algal Spiral

Remote Sensing Division, Naval Research Laboratory, Washington, DC 20375, USA
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Received: 26 March 2019 / Revised: 5 April 2019 / Accepted: 8 April 2019 / Published: 10 April 2019
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Abstract

The general topic here is the application of very high-resolution satellite imagery to the study of ocean phenomena having horizontal spatial scales of the order of 1 kilometer, which is the realm of the ocean submesoscale. The focus of the present study is the use of WorldView-2 along-track stereo imagery to probe a submesoscale feature in the Baltic Sea that consists of an apparent inward spiraling of surface aggregations of algae. In this case, a single pair of images is analyzed using an optical-flow velocity algorithm. Because such image data generally have a much lower dynamic range than in land applications, the impact of residual instrument noise (e.g., data striping) is more severe and requires attention; we use a simple scheme to reduce the impact of such noise. The results show that the spiral feature has at its core a cyclonic vortex, about 1 km in radius and having a vertical vorticity of about three times the Coriolis frequency. Analysis also reveals that an individual algal aggregation corresponds to a velocity front having both horizontal shear and convergence, while wind-accelerated clumps of surface algae can introduce fine-scale signatures into the velocity field. Overall, the analysis supports the interpretation of algal spirals as evidence of a submesoscale eddy and of algal aggregations as indicating areas of surface convergence. View Full-Text
Keywords: High-resolution satellite imagery; submesoscale; spiral eddy; cyanobacteria; surface convergence; western Baltic Sea High-resolution satellite imagery; submesoscale; spiral eddy; cyanobacteria; surface convergence; western Baltic Sea
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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 (CC BY 4.0).

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Marmorino, G.; Chen, W. Use of WorldView-2 Along-Track Stereo Imagery to Probe a Baltic Sea Algal Spiral. Remote Sens. 2019, 11, 865.

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