Wednesday, May 24, 2006

Surface currents from AVHRR image sequences

The vectors plotted above show surface velocity computed from AVHRR imagery by the method of Maximum Cross Correlations for a 2-day period centered on May 18, 2006.

The MCC surface velocities show strong flow of warm water into the big warm core ring due south of Cape Cod. The flow appears to diverge and pass either side of the feature. Flow is consistently southwestward in the shelf/slope front throughout the Mid-Atlantic Bight, and also southwestward further offshore over much of the Slope Sea.

The MCC method objectively tracks the displacement of small scale anomalies in sequential infrared imagery, and composites these after a series of consistency and significance checks (Bowen et al., 2002). Here we use all possible AVHRR channel-4 image pairs separated by 3 to 13 hours. Where vectors are absent there were insufficient clear image pairs or statistically significant displacement estimates to derive a useful current vector. These results were computed from imagery acquired by the HRPT receiver at IMCS, Rutgers University (courtesy of Jen Bosch), with MCC processing by Ian Crocker at the University of Colorado. This MCC analysis is experimental but shows promise in this test as a tool for visualizing surface current trajectories through much of the MAB shelf and slope.


Bowen, M., W. J. Emery, J. Wilkin, P. Tildesley, I. Barton and R. Knewtson (2002), Extracting multi-year surface currents from sequential thermal imagery using the Maximum Cross Correlation technique, Journal of Atmospheric and Oceanic Technology, 19, 1665-1676.


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