next up previous
Next: spm.F Up: The Proudman Oceanographic Laboratory Previous: setopenbc.F

Subsections


sigmaset.F


subroutine sigmaset

Description

This subroutine calculates the vertical coordinate sigma defined by $\sigma=(z-\zeta)/(d+\zeta)$, where $d$ is the equilibrium water depth, $\zeta$ is the sea surface elevation and $z$ is the cartesian vertical coordinate. The water column at each grid point is divided into $n-1$ equally-spaced $\sigma $-levels between the sea bed ($\sigma = -1$) and the sea surface ($\sigma = 0$). On these levels, the vertical velocity, eddy viscosity and diffusivity and turbulent kinetic energy are defined ($\Omega $ points in the figure). The horizontal u and v currents and scalars, such as temperature and salinity, are defined at the midpoints of these $\sigma $-levels (u points in the figure) and have indices $k=0,\ldots,n-1$, where levels $k=0$ and $k=n-1$ lie below the sea bed and above the sea surface, respectively, to facilitate the use of flux boundary conditions.

Figure 5: Positions of $\sigma $-levels for $\Omega $ and u points.
\includegraphics[scale=0.9]{sigma_levels.ps}

Subroutine Arguments

none

Local variables

k index of vertical level.
dsc, sds variables for use in calculating the sigma levels.

Global variables changed

sigo, sig, ds, dsu, dsup

Logical units

none

Order of Things

  1. Calculate $\sigma $ values at levels where the vertical velocity, eddy viscosity and diffusivity and turbulent kinetic energy are defined - array sigo.
  2. Calculate $\sigma $ values at levels where the horizontal u and v currents and scalars such as temperature and salinity are defined - array sig - midway between the sigo levels.

Calls

none

Called By

b3dgrid

Options - Logical

lpgrad - true if using pressure gradient calculations on a horizontal plane.
zvarybc - true if using depth-varying boundary condition.

Options - Compiler

SCOORD - use horizontally varying vertical coordinate.
DEBUG, DEBUG_B3DRUN, DEBUG_MODEL - output variables for debugging.

Known Issues

none


next up previous
Next: spm.F Up: The Proudman Oceanographic Laboratory Previous: setopenbc.F
The AMMP Project 2005-04-20