About the Model

The Environmental Fluid Dynamics Code (EFDC), developed by Dr. John Hamrick (Hamrick, 1992a; 1992b), is used here to simulate the hydrodynamic circulation in the St. Johns River. The application of EFDC to the St. Johns River was developed by Sucsy and Morris (2001) of the St. Johns River Water Management District (SJRWMD). They performed a thorough calibration of the model for the period of 1/1/1995-11/30/1998. They transferred this model application to the Coast Survey Development Laboratory for development of the nowcast/forecast system.

EFDC solves finite-differenced forms of the hydrostatic Navier-Stokes equations, together with a continuity equation, and transport equations for salinity, temperature, turbulent kinetic energy and turbulent macroscale. The equations are solved horizontally on a curvilinear, orthogonal grid and vertically on a stretched, sigma-grid. Vertical diffusion coefficients for momentum, mass, and temperature are determined by the level 2.5 turbulent closure scheme of Mellor and Yamada (1982) and Galperin et al. (1988).

The model solution scheme separates the internal, baroclinic mode from the external, barotropic mode. The long-wave propagation is then treated implicitly, eliminating the long-wave celerity as a stability constraint. The model time-step is instead constrained by the explicit treatment of the advective accelerations.

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Galperin, B., L.H. Kantha, S. Hassid, and A. Rosati, 1988, A quasi-equilibrium turbulent energy model for geophysical flows, J. Atmos. Sci., 45:55-62.

Hamrick, J.M., 1992a, A three-dimensional environmental fluid dynamics compute code: Theoretical and computational aspects. Special Rept. 317. The College of William and Mary, Virginia Inst. of Marine Sciences, Virginia.

Hamrick, J.M., 1992b, Estuarine environmental impact assessment using a three-dimensional circulation and transport model. In Estuarine and Coastal Modeling, Proceedings of the 2nd International Conference, ASCE, New York.

Mellor, G.L. and T. Yamada, 1982, Development of a turbulence closure model for geophysical flows, Rev. Geophys. Space Phys., 20(6): 851-875.

Sucsy, P.V. and F.W. Morris, 2001, Calibration of a Three-dimensional Circulation and Mixing Model of the Lower St. Johns River, St. Johns River Water Management District, Palatka, Florida.