Abstract
Between November 15 and 30, 1985, an international mesoscale transport experiment was performed on the Swiss Plain. Seven meteorological groups from Denmark, Germany, Italy and Switzerland measured diffusion properties of near neutral planetary boundary layers during six completely overcast days: four “Bise” (north-east wind) situations, one transitional situation and one west-wind situation. Diffusion was measured using SF6 as tracer, which was released at the meteotower of the Gösgen nuclear power plant at 6 m above ground level. One hundred automatic samplers plus a mobile gas chromatograph were used to measure the concentration fields at distances up to 90 km downwind. Meteorological parameters were observed using radar-tracked constant-level balloons, tethered balloon soundings, sonic anemometers, an acoustic sounder and several meteorological ground stations, including a 110 m mast. All data were collected on a magnetic tape with free access to interested persons.
The aim of the experiments was to obtain knowledge about the general nature of the turbulence, advection and atmospheric dispersion during neutral weak-wind situations over complex terrain. The collected data set will be useful for testing mesoscale transport and diffusion models. The results clearly show the channelling effect of the Jura mountains and the hilly prealpine region. An interesting result is that the SF6 plumes showed intensive horizontal spread but only limited diffusion in the vertical direction.
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References
Gassmann, F. et al, 1986: Investigation of Atmospheric Dispersion over Complex Terrain in a Prealpine Region (Experiment SIESTA), EIR-Bericht Nr. 604.
Pasquill, F., 1961: The estimation of the dispersion of windborne material, Met. Mag., 90, No. 1063, 33–49.
Weil, J.C., 1985: Updating Applied Diffusion Models, J.Clim. Appl. Met., 24, No. 11, 1111–1130.
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Gassmann, F., Bürki, D. Experimental investigation of atmospheric dispersion over the Swiss Plain — Experiment “SIESTA”. Boundary-Layer Meteorol 41, 295–307 (1987). https://doi.org/10.1007/BF00120446
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DOI: https://doi.org/10.1007/BF00120446