Abstract
Two-dimensional numerical simulations of mountain waves observed during the Pyrenees Experiment have been performed. Two intensive observing periods (IOP) have been simulated, IOP 3, which lasted less than one day, and IOP 9, which lasted two and one-half days. The time evolution of the large-scale flow was incorporated in the model through time-dependent boundary conditions that were updated using the closet upwind sounding. The numerically simulated mountain waves agree well with the available aircraft observations. Good agreement is also obtained between the simulated and observed vertical momentum flux profiles. In addition, the model-generated cross-mountain pressure drag accurately follows the time evolution of the observed drag. To get such a good agreement between observations and computations, it has been necessary to take into account in the model surface layer the effects of subgrid-scale orographic elements.
