Accession Number:

AD1099079

Title:

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

Descriptive Note:

Journal Article - Open Access

Corporate Author:

NAVAL RESEARCH LAB WASHINGTON DC WASHINGTON United States

Personal Author(s):

• Marmorino,George
• Chen,Wei

Report Date:

2019-04-10

Pagination or Media Count:

9.0

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.

Descriptors:

• remote sensing
• satellite imaging
• Baltic sea
• algae
• image processing
• cyanobacteria
• convergence
• high resolution

Subject Categories:

• Miscellaneous Detection and Detectors
• Biology

Distribution Statement:

APPROVED FOR PUBLIC RELEASE