THE OIL SPILL RECOVERY INSTITUTE: PAST, PRESENT, AND FUTURE DIRECTIONS by National Research Council of the National Academies

Author:National Research Council of the National Academies
Language: eng
Format: epub
Tags: Environment and Environmental Studies : Policy, Reviews and Evaluations
Publisher: NATIONAL ACADEMY PRESS
Published: 2003-03-14T00:00:00+00:00

STATUS OF NOWCAST/FORECAST MODEL COMPONENTS

Below is a summary of capabilities of the PWS NC/FC model components, the scientific validity and accuracy of the model simulations, and the degree to which the models represent or are pushing forward the state of the art.

Hydrodynamics Model

The hydrodynamic model in the SEA program (Mooers and Wang, 1998; Wang, 2001) was designed to be run as a hindcast for specific periods of time in order to evaluate physical-biological coupling and ecosystem dynamics. The model was forced with observational wind data from several stations, tidal data from three tidal stations, and freshwater runoff calculated from annual rainfall uniformly spread along the shoreline. The boundary was defined at Hinchinbrook Entrance (HE) and Montague Strait (MS) and forced with measured data at those locations. This implementation provided considerable understanding of the circulation dynamics within PWS.

The POM implementation under the OSRI program has been expanded to include the Alaskan Shelf from Yakatat Bay to Kennedy Entrance in Shelikof Strait. Earlier modeling and measurements at HE and MS showed inflow/outflow to be complex. GLOBEC investigations have identified eddies (20-200 km) that come up against the continental margin and onto the shelf, which have a role in exchanging waters in and out of PWS. There is large variability from year to year, and it is not always clear what is upstream or downstream on the shelf. On-shelf exchange between the coastal shelf current and PWS is complex and seasonally dependent.

As the nontidal circulation is driven by shelf processes, moving the boundary out to sea allows the longer-term circulation to be addressed. This approach makes sense, as the only alternative is to force the model with high-resolution (vertically and temporally) measurement data at the entrances, and only one acoustic doppler current profiler is available at HE. However, intensive measurements could be made at the two entrances for specific events, which could be used to verify the dynamics within PWS. While efforts at validation have been made, there are still considerable differences and unknowns in the dynamics within PWS that should be addressed (such as circulation driven by freshwater inflow and local wind dynamics).

Only one wind station in central PWS is online in the NC/FC system at present (although other wind stations have existed and will be coming online), and any hydrodynamic model needs better forcing, particularly for winds. Winds vary tremendously across PWS because of orographic steering. There are important mesoscale features in the winds (gap winds, barrier jets) that will influence circulation and oil transport. The plan is to drive the hydrodynamic and oil models with gridded winds produced by a mesoscale atmospheric model.

Freshwater inflow also has an influence on circulation (Mooers and Wang, 1998), however including this forcing appears not to be in plans for immediate future for lack of sufficient data. A sensitivity analysis could be performed to determine how sensitive the model is to this forcing.

The recent hydrodynamic model validation (Bang et al., submitted) is comprehensive and is to be commended. Given the complexities in the underlying physical

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