On the influence of the Alps on a cold front

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Abstract
This paper discusses the synoptic- scale environment and the scale dependent features of a cold front which crossed southern Bavaria on 8 October 1987. The analysis is based on rawinsonde, Doppler radar, aircraft and surface data. The observations reveal that the front was of the ana-type in the synoptic-scale. Its leading edge exhibited small-scale, bore-like characteristics which are typical for an atmospheric gravity current interacting with a stable layer at the ground. The leading edge was marked by several spectacular roll clouds; their generation was favored by south-foehn in the pre-frontal area and by post-frontal precipitation. The low-level front was retarded by the Alps whereas the upper level front crossed the Alps without being distorted. The analysis shows that the cross-frontal gradients in pressure and temperature were stronger close to the Alps than at a greater distance from the obstacle. The data suggest that the middle tropospheric extrusion of cold air towards the front in a downward direction and from behind, which is a characteristic synoptic-scale feature of an ana-front, is weakened in the vicinity of the orography. DOI: 10.1034/j.1600-0870.1990.00013.x

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