Eddy generation in the tidal Potomac River |
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| Authors: | Richard P Mied Timothy F Donato Carl T Friedrichs |
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| Institution: | 1. Naval Research laboratory, Remote Sensing Division, Code 7200, 20375, Washington, D.C.
2. College of William and Mary, Virginia Institute of Marine Science, 23062, Gloucester Point, Virginia
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| Abstract: | This paper deals with eddies generated by a shear flow instability in the tidal Potomac River, Maryland-Virginia, USA. An
evolution sequence of this robust phenomenon is synthesized using ASTER and Landsat visible imagery, and its growth from small-amplitude
waves into mature eddies is shown. Using feature tracking between two nearly contemporaneous ASTER and Landsat images, an,
along-river surface velocity profile is computed. Archived velocity and density profiles, taken during accelerating ebb at
locations up-river and down-river of the study area indicate the water column is relatively homogenous up-river, but resembles
a two-layer fluid down-river where estuarine stratification is present in the lower water column. Velocity variation with
depth in the upper water column is relatively small, deviating at mid depth from the near-surface value by only 9–15% at both
sites. We examined the horizontal stability properties of this flow by modeling it as inviscid and barotropic., and predicted
rapidly growing unstable waves with wavelengths close to the observed ones. Their proximity to the coast, as well as the precise
details of the coastline configuration, are shown to have a negligible effect in determining the observed unstable wavelengths. |
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