Physical modelling of baroclinic development in the lee of the Alps

A. Longhetto, L. Briatore, G. Chabert d'Hieres, H. Didelle, E. Ferrero, C. Giraud

Abstract


When baroclinic development is triggered by an obstacle, like an extended mountain range, the so-called lee, or secondary cyclogenesis can develop. The presence of the obstacle exerts a blocking effect on the lower layers of the impinging airflow, forcing them to go round its borders and reach the lee region with a delay. Blocking and delay are both responsible for the initial pressure decrease downwind of the mountain and for the subsequent proper downstream baroclinic development. According to this rather simple scheme, a cyclogenesis episode in the lee of the Alps was simulated in a hydraulic turntable. The results of these experiments showed a good agreement, both from a qualitative and quantitative point of view, with the analysis of an episode of lee cyclogenesis coupled to a cold outbreak in the Mediterranean, which actually occured in Southern Europe downstream of the Alps.

Keywords


baroclinic intability;orographic cyclogenesis;laboratory modelling

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References


DOI: https://doi.org/10.4401/ag-3861
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X