Flow Over Complex Terrain, Numerical Modeling of

Abstract

Abstract This article provides a general description of numerical modeling over complex terrain, including both diagnostic and prognostic approaches and their associated advantages and limitations. Diagnostic models solve simplified versions of the equations of motion and are widely used in the engineering community for simulations of flow over complex terrain. These models produce a description of the steady‐state flow, while requiring few inputs and being computationally efficient. Diagnostic models do not predict time evolution of flow, and are often only appropriate for terrain with small slopes. Prognostic models solve the full equations of motion and are used for both engineering and numerical weather prediction applications. Details of the implementation of prognostic models vary widely, but they are capable of producing time‐varying descriptions of the flow and handling very complex terrain with no limitations on terrain slope. These models can require detailed three‐dimensional inputs and large computational resources. Additional simplifications can reduce these requirements, but generally at the expense of functionality, such as producing a steady‐state solution or the inability to handle arbitrarily complex terrain.