Mesoscale transport of atmospheric trace constituents across the central Alps: Transalp tracer experiments

This paper summarizes the goals, the experimental setup and the main phenomenological findings of the TRACT sub-project TRANSALP. TRANSALP consisted of three tracer field experiments carried out in the Ticino area of southern Switzerland in the years 1989, 1990 and 1991. The experiments were designed to study the transport and diffusion of trace gases over the very complex Alpine topography. The results and knowledge gained from each experiment were used for the design of the next experiment and to improve the logistics. All the data collected were stored in a well organized data bank, which can be made available to the scientific community interested in evaluating mesoscale atmospheric transport and dispersion models for complex terrain. All these experiments contributed to the understanding of the flow and dispersion characteristics in very complex terrain. Specifically, under particular meteorological conditions, these experiments gave evidence of the occurrence of a transalpine exchange of air constituents, both in north-to-south and south-to-north directions.