Georgelin, Marc (Laboratoire d'Aerologie, Toulouse, France)
The case of January 12, 1996, has been selected for pre-MAP studies devoted to foehn and mountain wave.
This day, a south foehn was observed with a significant warming in the Bavarian lowland. Clear air turbulence was reported by pilots over the Innsbruck-Salzburg area, indicating a possible overturning of the mountain wave.
This case study has been simulated with the Meso-NH model, recently developed at Laboratoire d'Aerologie and Meteo-France. The model did predict overturning of the wave. Wave breaking appears mainly at low-levels (3-4 km) and some severe turbulence is found above the Innsbruck area. Results are compared with the available observations.
Several sensitivity experiments to the roughness definition have been conducted. The modifications due to roughness change were found confined between ground and the critical level associated with the wave breaking.
When roughness is enhanced, the wave intensity is reduced, confirming in that way the PYREX results, but in the case of the Alpes, this enhancement is accompanied by tri-dimensional effects that modify the spatial location of wave breaking areas.