Suppose a seamount located inside a periodic f-plane ( 
s
) channel with two solid, free-slip boundaries along constant y.
Unforced flow over seamount in the presence of resting, level isopycnals is an
idea test case for the assessment of pressure gradient errors in simulating
stratified flow over topography. The flow is assumed to be reentrant
(periodic) in the along channel coordinate (i.e., x-axis). We use this
seamount case of the Semi-spectral Primitive Equation Model (SPEM) version 3.9
to test the new difference scheme. The reader is referred to the original
reference (Haidvogel et al., 1991) and the SPEM 3.9 User's Manuel (Hedstrom,
1995) for detail information. In the horizontal directions the model uses the
C-grid and the second-order finite difference discretization except for the
horizontal pressure gradient, which the user has choice of either second-order
or fourth-order difference discretization (McCalpin, 1994). In the vertical
direction the model uses a boundary fitted 
-coordinate system. The
discretization is by spectral collocation using Chebyshev polynomials. Our
model configuration is similar to that of Beckmann and Haidvogel (1993),
McCalpin (1994), and Chu and Fan (1997). The time step and grid size used here are,
