The spatial domain is a flat earth approximation with some
most important) earth spherical effects or consequences of geometry being
mapped. The different fields are gridded (discreteized) in a special fashion
following the work of Sielecki (1968) and Wübber and Krauss (1979).
Mapping is by stereographic
projection. Procedures are available at
The fundamental directions in a physical sense (x,y) are
the diagonals of the grids.
The grid representing the currents is given the type code M, the one for elevation the type
code Z. The Z-grid has one row and one column less than the M-grid. However, for
file reading/writing we will input/output MxN elements, though there will be M+N zeros
when we process a Z-grid.
Ocean depth, currents (and eventually surface wind) are
on the M-grid;
elevation, tidal gravity potential (and eventually air pressure) on the Z-grid.
In the scientific texts we can distinguish the two grids by
and primed index
numbers, i.e. i,j on the M-grid and i',j' on the Z-grid.
The position of a grid point from the origo (centre of the area)
kilometers e - east
and n - north is given by
e = [i-(M+1)/2]*ds, n = [j-(N+1)/2]*ds (M-grid)
e = [i'-M/2]*ds, n = [j'-N/2]*ds (Z-grid)
where ds is the grid constant. In the
is usually termed SCALE and its
numerical value is given in kilometers.
Flag values may show three things:
(1) represent a circumstance (e.g. land/sea)
(2) indicate a specific kind of boundary condition
(e.g. a straight piece of shoreline running north-south
with sea to the east)
(3) specify a storage address for memory-efficient storage of
auxiliary data (mostly the tide height along an open boundary)
Some basic facts:
Passive boundary conditions are associated with land.
Passive boundary conditions apply only to the equation of the currents.
Out-of-area nodes need only a distinction between land and sea.
An active (open) boundary is associated with sea.
Passive boundary conditions may occur on the end members of a
segment of active boundary, where it eventually touches land.
Using open boundaries a model can be driven by elevations or
currents or a combination (compatibility needs to be established though).
The boundary current case, however, is rare since such data is usually rare
or uncertain or noisy.
See more under Passive boundaries or Other flags.
Tide excitation: Recommended program has name otemt1, document names otemt1.doc and otet.doc. Code is available at geo/hgs/PC/OTEQ/EXEC/otemt1.f
Pressure and wind excitation: Recommended program has name otemw1. Code is available at geo/hgs/PC/OTEQ/EXEC/otemw1.f
Static pressure loading: Recommended
is available at geo/hgs/PC/OTEQ/EXEC/apload.f
See the pages about general aspects of files