The influence of the Alps on structure and behaviour of cold fronts over southern Germany

Summary In the paper results of investigations of the first two front events of the German Front Experiment 1987/88 are presented. In both cases a frontogenesis took place in the lower troposphere north of the Alps—in the first case directly at the cold front, in the second case ahead of it. The main reason for that was the incorporation of warm and dry air produced by foehn or advected along the Alps into the frontal zone of the approaching front. In the second case the cooling through evaporation of falling rain was an additional important factor for the increase of the temperature gradient. The computation of kinematic parameters yields as an interesting result the proof of areas with absolute vorticity near or below zero within the southwesterly current at the northwestern flank of the Alps.With 6 Figures