Radar surface signatures based on the two-dimensional tidal circulation of Phelps Bank

Numerical results for the M/sub 2/ tidal currents over Phelps Bank, Nantucket Shoals, Massachusetts, with 1/8*1/8 min arc resolution are used to predict the radar surface signatures (cross sections sigma ) of Phelps Bank using the first-order relaxation model of W. Alpers and I. Hennings (1984). The numerical predictions of sigma incorporate all two-dimensional contributions from the tidal currents and include both the residual and first-harmonic term. Strong correlation between spatially resolved contour plots of sigma over a wide range of directions and time intervals within the tidal cycle, with variations in the bottom topography of the Phelps Bank, is obtained even when Bragg wave scattering alone is included. The predictions for sigma are contrasted with previous measurements in the Phelps Bank by the US Naval Research Laboratory, and the importance of including the off-diagonal elements from the current stress tensor in the evaluation of sigma is discussed.<
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