2-DIMENSIONAL STRUCTURE OF MOUNTAIN WAVE OBSERVED BY AIRCRAFT DURING THE PYREX EXPERIMENT

This study presents an experimental analysis from aircraft measurement s above the Pyrenees chain during the PYREX experiment. The Pyrenees c hain, roughly WE oriented, is a major barrier for northerly and southe rly airflows. We present a case of southerly flow (15 October 1990) an d three successive cases of northerly flows above the Pyrenees (14, 15 and 16 November 1990) documented by two aircraft. The aircraft have d escribed a vertical cross section perpendicular to the Pyrenean ridge. This area is described via the thermodynamical and dynamical fields w hich have a horizontal resolution of 10 km. Three methods for computin g the vertical velocity of the air are presented. The horizontal advec tion terms which play a role in the budget equations are also evaluate d. The altitude turbulence zone of 15 October are shown via turbulent fluxes, turbulent kinetic energy (TKE), dissipation rate of TKE and in ertial length-scale. A comparison of results obtained by eddy-correlat ion and inertial-dissipation method is presented. The experimental res ults show a warm and dry downdraft for the southerly flow with large v alues for advection terms. All the mountain wave cases are also shown to present an important dynamical perturbation just above the Pyrenees at upper altitudes.