3
Eastcoast 2001 Grid
Development
The domain used to develop the Eastcoast 2001 tidal database remains essen-
tially the same as for the Eastcoast 1991 and Eastcoast 1995 databases. The land
boundary definition has been improved due to increased grid resolution near the
coast. The grid has been improved by increasing the total number of nodes by a
factor of four and by placing these nodes in a more strategic manner due to the
use of both the wavelength to grid size ratio and the topographic length scale
(TLS) criteria. Further significant improvements were derived from the use of an
additional bathymetric database, which drastically redefined depths in critical
regions.
Domain Definition
The WNAT domain used in these computations covers the deep Atlantic
Ocean westward from the 60W meridian and encompasses the western North
Atlantic Ocean, the Gulf of Mexico, and the Caribbean Sea. The 60W meridian
open-ocean boundary runs from the vicinity of Glace Bay in Nova Scotia,
Canada, to the vicinity of Corocora Island in eastern Venezuela. This boundary
lies almost entirely in the deep Atlantic Ocean and has the following advantages:
(a) It is geometrically simple and includes no corners, (b) the tidal signal gen-
erally varies slowly in space since the boundary includes only a small portion of
the continental shelf and is positioned well away from any amphidromes, and (c)
nonlinear tidal constituents are not significant in the deep ocean, since they are
generated on the continental shelf and are largely trapped there due to the out-of-
phase reflective character of the continental slope.
An updated land boundary for the WNAT domain, shown in Figure 6, was
necessary to improve the accuracy of its placement and inclusion of details
neglected in the prior WNAT grids. Grid size at the shoreline was targeted to be
half the size of that in the Eastcoast 1995 grid or less. The Defense Mapping
Agency's (DMA) World Vector Shoreline (WVS) coastal database was utilized
data points approximately every 100 m and has a stated accuracy that 90 percent
of the points are within 500 m of the actual feature. The Eastcoast 2001
1
Data obtained from National Geophysical Data Center, World Wide Web page accessed on
25 February 2000, http://rimmer.ngdc.noaa.gov/coast.
9
Chapter 3 Eastcoast 2001 Grid Development
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