Influence of mountain waves downwind of the Pyrenees

Mountain waves are generated when a flow is displaced vertically after crossing a mountain barrier within a stably stratified atmosphere. These gravity waves are manifested as fluctuations in velocity, pressure and temperature fields. They significantly influence the dynamics of the atmosphere and they can be a source of turbulence. In this study we focus on mountain waves generated over the Pyrenees, a complex terrain area in southwest Europe.

To investigate this phenomenon and its consequences, Weather Research and Forecasting (WRF) model simulations are performed for certain mountain-wave events detected with satellite imagery observations and soundings. Results show that the model is able to capture the mean wave motions leeward of the mountain range. In addition, different model configurations are used to explore the numerical issues relevant to the prediction of mountain waves over complex terrain. The influence of the lee waves within the boundary layer, with the possible flow separation, is explored including the lee-wave rotor formation with the associated enhanced turbulence.