What is PROFS?
It is a (computer) modeling
system that attempts to simulate temporal and spatial distributions of
sea-level, currents, temperature and salinity (hence density) in a specific
ocean region, such as the
The advantage of
focusing in a specific region is that one can use very high resolution, O(km)
or smaller. However, in general, the
regional model also needs to know what is going on outside its domain – this
outside information may be specified using observations, or it may be from a
larger-scale model (e.g. a global model).
In the latter case, the larger, coarser-scale model can extend its
validity to fine regional scales. May be
some day one can use a single computer model to resolve large and small
scales. However, in ocean modeling, as
in life, there are always surprises, and there are no such things as a model
that can do everything; no model is perfect.
At any rate, such an all-purpose model would be quite cumbersome to
run. A more efficient way would be to
use grid-nesting or adaptive grid. Many
PROFS simulations use grid-nesting.
PROFS uses the Princeton Ocean Model (POM) as its “core engine.”
Preparing and Running a Model:
These typically require
the following steps:
1. Choose the region of
interest and interpolate the bathymetric data to give depth values of the ocean
at gridded locations. See example grid
below (Fig.3). If you also want to
simulate inundation (wet and dry or WAD) processes, you also need to prepare
land topography near the coast – say 20km inland from the coastline;
2. Interpolate temperature
(T) and salinity (S) from climatological data [e.g. Levitus & Boyer, 1994]
onto the model grid. Typical runs use these
T/S data (which with depths or pressures also give density) as model initial
conditions, constraints to model solutions in a long-time integration, and/or
open boundary conditions. Keep in mind
though that climatology is not
observation; rather, it is an analysis of observations, and there are
limitations on its spatial and temporal scales, for example;
3. Interpolate sea-surface
fluxes (e.g. momentum – i.e. winds, heating and cooling, and evaporation and
precipitation etc.) onto the model grid.
These fluxes are used as forcing at the surface grid points of the model
ocean;
4. Obtain and specify lateral
fluxes (e.g. rivers, deep-ocean flows, heat and salt fluxes etc) at the model’s
near-coast grid points and open boundaries;
5. Obtain and specify other
forcing such as tides;
6. Run the model.
Highlights
of Recent Research with PROFS