PYREX OBSERVATION AND MODEL DIAGNOSIS OF THE TRAMONTANE WIND

The horizontal and vertical structure of the Tramontane wind is analyz ed in this paper using the PYREX Data Base. Important aspects of the T ramontane description known or assumed by previous climatological stud ies are confirmed or modified from this analysis. However the main aim of this paper is to establish the importance of the Pyrenean orograph ic forcing as the main factor driving the intensity and distribution o f the Tramontane wind. We do this in two ways: (1) computing the corre lation between the surface and upper level winds and the orographic fo rcing, measured by the pressure drag, (2) comparing the tangential acc eleration (obtained from two versions of a numerical model with differ ent orography) to the acceleration derived from observations. We think we can confirm the orographic origin of the Tramontane wind.