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Jeff
Paduan, Naval Postgraduate School
Igor Shulman, University of Southern Mississippi
James McWilliams, UCLA
Background
An effort is underway to set-up and validate a high-resolution (~1
km), primitive-equation circulation model of the coastal ocean around
Monterey Bay. The initial development, testing, and data assimilation
trials of this model have been carried out using a version of the
Princeton Ocean Model (POM)
as part of the National Ocean Partnership Program's Innovative
Coastal-Ocean Observing Network (NOPP/ICON). Details of the present
model configuration can be seen under the ICON
modeling links. (An example SST map from the wind-forced spin-up runs
for the 1995 upwelling season is shown in the figure below.) As with any
ocean model, and particularly for open ocean coastal models, there are
many important issues to work out before the model can be used to simulate
important bio-chemical processes, such as upwelling-related productivity
and air-sea interactions. ICON is addressing many of these issues,
including:
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The need to obtain open boundary conditions for mass,
temperature, and salt fluxes from a regional-scale ocean model. (The
ICON model is nested within a California Current-wide version of POM
run by the Naval Research Laboratory.)
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The need to utilize accurate wind stress and surface
flux forcing. (ICON is comparing the effects of meteorological
products with 100 km [NOGAPS] and 9 km horizontal resolution [COAMPS].)
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The need to invoke data assimilation of local
mesoscale-resolving
quantities to improve real-time tracking of the upwelling filaments
and eddies that dominate bio-chemical and air-sea interactions in the
coastal zone. (ICON is testing data assimilation schemes applied to
surface velocity data from a five-site network of high frequency [HF]
radar installations.)
The next modeling-related steps beyond these
involved
tests with higher horizontal resolution to assess the effects of fronts
and the implementation of bio-chemical tracking submodels that will,
ultimately, provide for estimates of seasonally varying primary
productivity as well as the ability to study the coupling between
mesoscale circulation and bio-chemical responses.
Snapshot of model sea surface temperature from a nested
run using large-scale (~100 km), 12-hourly wind forcing showing typical
upwelling-related filaments and meanders. The modeled area includes
Monterey Bay, California and is about 80 km x 150 km with horizontal grid
resolution between 1 km and 3 km and 30 vertical levels.
MUSE Efforts
As part of MUSE, the ICON team conducted a set of special
model runs that doubled or tripled the horizontal grid resolution
during the August 2000 field campaign. This provided a set of model
outputs that can be compared with the high-resolution sampling of the
expected upwelling fronts by ships and AUVs involved in MUSE. Several
months of SST output from the initial model run illustrated above were also
used within the MUSE planning effort to develop and exercise optimal
sampling schemes.
MUSE also provided a starting point for the
implementation of bio-chemical submodels aimed at tracking primary
productivity within the Monterey Bay coastal upwelling system, which is a
system with a rich set of validation data for both physical and
bio-chemical modeling components. In this arena, ICON scientists were
joined and aided by the research team of Prof. James McWilliams of UCLA.
This team just began an effort to nest a Monterey Bay high-resolution
grid as part of a newer-generation modeling framework (ROMS).
The UCLA effort will include bio-chemical modeling and will take place in
parallel with ICON modeling while the merits of POM-based versus ROM-based
models are documented. Again, the MUSE field data provided one of the
best-ever validation opportunities for these types of comparisons.
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