A cross-scale model for 3D baroclinic circulation in estuary–plume–shelf systems: I. Formulation and skill assessment

Challenges posed by the Columbia River estuary–plume–shelf system have led to the development of ELCIRC, a model designed for the effective simulation of 3D baroclinic circulation across river-to-ocean scales. ELCIRC uses a finite-volume/finite-difference Eulerian–Lagrangian algorithm to solve the shallow water equations, written to realistically address a wide range of physical processes and of atmospheric, ocean and river forcings. The numerical algorithm is volume conservative, stable and computationally efficient, and it naturally incorporates wetting and drying of tidal flats. ELCIRC has been subject to systematic benchmarking, and applied to the description of the Columbia River circulation. This paper motivates and describes the formulation, presents and critically analyzes the results of selected benchmarks, and introduces ELCIRC as an open-source code available for community use and enhancement. A companion paper describes the application of ELCIRC to the Columbia River.