Pressure Forces On Small-Scale Three-Dimensional Hills In Stable Conditions

Numerical simulations are presented of flow over small-scale three-dimensional hills embedded within the stable boundary layer. Large surface forces are associated with internal gravity waves excited by Fourier modes aligned with the ridge axes closely parallel to the wind. Even moderate anisotropy of the topography may then lead to the surface forces (in a frame aligned with the wind) being strongly sensitive to wind direction. However, the impact of the waves on forces in the direction of the geostrophic wind is relatively minor.The British Crowns right to retain a non-exclusive royalty-free license in and to any copyright is acknowledged.