Mountain breeze and valley breeze

The mountain and valley wind circulation is occurring on a clear day in the mountains daily periodic wind system. The daytime occurring valley wind is driven by the stronger as a result of solar radiation compared to the free atmosphere warming the suspension. The engine of the late evening waving until morning mountain wind is opposite to the valley stronger charisma and cooling of air over the plateaus and slopes. The mountain and Talwindzirkulation similar to the daily cycle of land and sea breeze, but because of the diversity of the relief and the overlay with the Hangauf and downdraft complicated.

Valley wind

On a sunlit hillside sets after sunrise a strong warming of the soil, thus increasing the surface air warms faster than the slope distant air. By reducing the air density (thermal buoyancy) is a first in the morning a ridge lift. Its maximum speed is usually 2 to 3 km / h The rising air cools over the mountain ridge and drops to the original or an adjacent valley or over the foreshore again into deeper layers. To replace the Ascended air masses, arises gradually a from the foreland up the valleys flowing compensating flow, the valley wind. During the afternoon the wind exceeds about 20 km / h upwind from strength to strength. Around noon, can form cumulus clouds over the mountain slopes depending on the weather conditions ( stratification stability and humidity). About the valleys of the sky because of the decreasing tendency of the air, however, remains cloudless. The valley wind can be enhanced or reduced by about regional wind as a result of pressure equalization between high and low pressure areas.

Mountain Wind

After sunset slope and valley wind slowly come to a halt. After a short halt the wind system is reversed. The air above the high plains and the mountain slopes cools down by the stronger radiance faster than the air above the valley at a comparable level. The now cooler, denser and therefore heavier air flows down the slopes and provides fresh air on the valley floor. Normally, the nocturnal mountain wind is weaker than the valley wind during the day. Since forming a pool of cold air at night in the valley, barely over it you can feel the sweeping mountain wind. In middle of the valley, a reversal thermals can form and sometimes it comes through the flow convergence means that the air rises to the level of condensation and clouds form, in this case, mostly smaller, shallow cumulus clouds ( stratocumuli ).