2-DIMENSIONAL SIMULATIONS OF MOUNTAIN WAVES OBSERVED DURING THE PYREXEXPERIMENT

Two-dimensional numerical simulations of mountain waves observed durin g 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-de pendent boundary conditions that were updated using the closest upwind sounding. The numerically simulated mountain waves agree well with th e available aircraft observations. Good agreement is also obtained bet ween the simulated and observed vertical momentum flux profiles. In ad dition, the model-generated cross-mountain pressure drag accurately fo llows the time evolution of the observed drag. To get such a good agre ement between observations and computations, it has been necessary to take into account in the model surface layer the effects of subgrid-sc ale orographic elements.