Download Sparse Hydrodynamic Ocean Code V5199 User Manual

SHOC User Manual
Physical constants
Values must be provided for a number of physical constants. Most are rarely changed far
from the values shown below. An exception is the Coriolis parameter, which is latitude
dependent.
# Acceleration due to gravity (m s-2)
G
9.81
# Air density - note that it might be better to calculate this
# internally in the model code, based on the air temperature.
# For the moment, however, it is specified in the parameter file
# as a constant value (kg m-3).
AIRDENS
1.225
# Specific heat of water. Again, the model could calculate this
# based on salinity, temperature, etc. For now, however, this
# is specified as a constant (J C-1 kg-1) - FIX - CHECK THIS
SPECHEAT
3990
# The Coriolis parameter value for the area of interest.
# This is an NCE1*NCE2 floating point array, so that it is
# possible to set a different value in every grid cell. However,
# for most applications where the grid geographical extent is not
# large, a uniform value can be used, as shown here, for a
# hypothetical 40*50.
# The CORIOLIS parameter will be automatically computed if not
# supplied, but the PROJECTION parameter is.
CORIOLIS
2000
-0.000019
4.5
Horizontal coordinate system
SHOC uses a sparse, or compressed, array configuration (Herzfeld, 2006) which represents a
three dimensional region as a one dimensional vector in computer memory. One of the
advantages of this approach is that all non-wet land cells may be omitted from the grid in
memory. This means that when constructing a grid there is no computational penalty when
large amounts of land are included in the grid. This approach requires, however, that at least
one land cell must be adjacent to wet cells at coastal boundaries (i.e. a solid boundary is
not allowed to be adjacent to a cell containing water; land cells only must be adjacent to wet
cells).
A unique feature of SHOC is not only its ability to support a myriad of different horizontal grid
geometries, but also its ability to handle different coordinate systems. Currently SHOC
supports three coordinate systems:
•
•
•
Arbitrary Cartesian
Geographic - Latitude/Longitude
Geographic - Map projected
The Cartesian system defines the coordinates on a rectangular plane with no physical
association to real locations on the Earth. The geographic based coordinate systems
however, map directly to real-world locations. For a Latitude/Longitude coordinate system all
grid metrics are computed on the spheroid, while for the map projected coordinate system the
metrics are computed on the projected plane.
The coordinate system is defined using the PROJECTION parameter and applies to ALL
windows.
20/08/2015
Page 19 of 185
Version: 1.00