A Mixed Spectral Finite-Difference 3D Model of Neutral Planetary Boundary-Layer Flow over Topography

Abstract

A simple three-dimensional linear model of planetary boundary-layer flow is developed based on the Mixed Spectral Finite-Difference model of Beljaars et al. using the full second-order turbulence closure of Launder et al. The model uses a steady-state solution to the fully nonlinear model equations over a horizontally homogeneous surface to specify the zero-order, upwind profiles of mean and turbulent quantities. Due to the complexity of the closure and linearization of the model equations, the authors use an automated method of source code generation to produce both the time-dependent model used to generate the zero-order solution and the 3D model. Model results are presented for flow over a simple isolated hill.