Numerical simulation of atmospheric flow over an idealized mountain

The validity of linear smoothing of topography for numerical weather prediction and the variation of mountain drag with mountain height and static stability are examined in this study. In the model a constant geostrophic current is perpendicular to the mountain range and the height of the mountain is independent of y. The hydrostatic Boussinesq equations are used with motion bounded at the top by a rigid plane at z = D. A modified coordinate system similar to Phillips' sigma system was used. Solutions were obtained using a smoothed mountain profile. These solutions were compared with smoothed solutions obtained from the unsmoothed mountain, The comparison of these solutions shows that an error is introduced when non-linear terms become sufficiently large. Values of the mountain drag for differing values of mountain height at a given static stability and for differing values of static stability at a given mountain height were computed. Mountain drag was found to vary quadratically with mountain height and linearly with static stability.http://archive.org/details/numericalsimulat00deboLieutenant, United States NavyApproved for public release; distribution is unlimited