High-Resolution Ocean Circulation Modeling During MUSE

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:

  • 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.)

  • 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].)

  • 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.

Data Index Aircraft AUV CODAR
Drifters Moorings Satellites Ships