PYREX OBSERVATION AND MODEL DIAGNOSIS OF THE TRAMONTANE WIND

The horizontal and vertical structure of the Tramontane wind is analyzed in this paper using the PYREX Data Base. Important aspects of the Tramontane description known or assumed by previous climatological studies are confirmed or modified from this analysis. However the main aim of this paper is to establish the importance of the Pyrenean orographic forcing as the main factor driving the intensity and distribution of the Tramontane wind. We do this in two ways: (1) computing the correlation between the surface and upper level winds and the orographic forcing, measured by the pressure drag, (2) comparing the tangential acceleration (obtained from two versions of a numerical model with different orography) to the acceleration derived from observations. We think we can confirm the orographic origin of the Tramontane wind.