Semi-Lagrangian shallow water modeling on the CM-5

Publisher Summary This chapter discusses the parallel implementation of a semi-Lagrangian Shallow-Water Model on the massively parallel connection machine CM-5. It models the wind-driven circulation in a closed rectangular mid-latitude ocean basin. The model consists of a dynamically active shallow surface layer overlying an infinitely deep lower layer and the chosen wind forcing, acting on the surface layer, results in the formation of a double gyre. The vertically-averaged circulation of the surface layer can then be modeled using the hydrostatic shallow water equations. The chapter addresses two alternative formulations of the elliptic problem and their relative efficiencies. It examines the performance of two successive orders of a generalized conjugate residual elliptic solver, and the time spent in unstructured communication, which is an unavoidable feature of semi-Lagrangian schemes. The chapter also discusses the scalability of the algorithm. The available software utilities on the CM-5 allow significant improvement in the computational efficiency of the model.