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About the Circulation Model
To achieve the unique modeling requirements posed by the Columbia River estuary system, OHSU developed the CORIE modeling system (Baptista, 2006), which redundantly uses two three-dimensional numerical circulation codes: ELCIRC (Eulerian-Lagrangian Circulation) (Zhang et al., 2004) and SELFE. ELCIRC, the more mature of the two models, is the focus of this paper, although mounting evidence (Baptista, Zhang et al., private communication) suggests that SELFE will become the default model for CORIE, hence, eventually, to the NOAA operational system.
ELCIRC was developed based upon the theory and numerical derivation of the UnTRIM unstructured circulation model developed by Casulli and Zanolli (1998). ELCIRC uses a finite difference approach for the momentum equations and a finite volume approach for the continuity equation. The solution also uses an Eulerian-Lagrangian treatment of the advective terms that permits for larger time steps. This allows models that require a large degree of horizontal and vertical refinement (such as for the Columbia River) to be more computationally efficient in making forecasts and longer-term hindcast simulations.
ELCIRC has been validated using a variety of numerical benchmark scenarios (Zhang et al., 2004). It has also been extensively tested in the Columbia River to evaluate the influence of numerical parameterizations and boundary condition formulations (Baptista et al., 2005). The results of these tests were used to compose a formal set of input files and parameters to be used in transitioning the model to an experimental operational implementation at NOAA's National Ocean Service (NOS). This effort is one component of NOAA's Coastal Storms Program, a multidisciplinary effort to increase community resiliency to coastal storms by providing an integrated set of tools, data and modeling. The Columbia River model provides forecasts of water levels, velocities, salinity and temperature to the navigation, fisheries, and emergency response communities. More information is available at http://www.csc.noaa.gov/csp
