. Compendium of meteorology. Meteorology. VALLEY WIND -⦠MOUNTAIN WIND SYSTEM => GENERAL WIND SYSTEM NEUTRAL LAYER Fig. 7.âSchematic illustration of the air circulation dur- ing daytime in a cross section through the Alps. [After Burger and Ekhart [12].) reach their greatest intensity at the time of maximum insolation and reverse their direction in the evening (about one fourth to three fourths of an hour after sun- set). Because of the stronger insolation, they are es- pecially well developed on the southern slopes and are weaker or almost nonexistent on the northern slopes. This wind pre
. Compendium of meteorology. Meteorology. VALLEY WIND -⦠MOUNTAIN WIND SYSTEM => GENERAL WIND SYSTEM NEUTRAL LAYER Fig. 7.âSchematic illustration of the air circulation dur- ing daytime in a cross section through the Alps. [After Burger and Ekhart [12].) reach their greatest intensity at the time of maximum insolation and reverse their direction in the evening (about one fourth to three fourths of an hour after sun- set). Because of the stronger insolation, they are es- pecially well developed on the southern slopes and are weaker or almost nonexistent on the northern slopes. This wind prefers the ravines and gullies of the usually eroded slopes and is hardly noticeable on the projecting ridges. Numerous pilot-balloon observations in the up- and-down drafts on the slopes of the mountains north of the Inn valley near Innsbruck [43-45, 65] have clearly demonstrated the existence of such currents. Here the thickness of the slope wind layer, as meas- ured perpendicular to the slope, varies periodically with the wind intensity. Maximum values up to 260 m have been measured. However, as a rule, the thickness of the layer lies between 100 and 200 m. The thickness is less for the nocturnal downslope wind. The uphill wind continuously entrains, along its path, air from the space over the valley, so that the thickness of the affected layer is steadily increased in the direction of the uphill flow, and the layer becomes wedge-shaped. Naturally, the intensity of these slope winds varies greatly with the local differences in the slope and its exposure. Also, these winds can seldom be observed in their pure form and are often weakened or strengthened by extraneous wind conditions. On the average, the slope-wind speeds in the direction of the slope amount to about 2-4 m sec~\ according to measurements. Projecting parts of the slope cause a detachment of this current from the slope and thereby an increased vertical movement which can be utilized by soaring pilots to gain alt
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