Cold front

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Representation of a cold front passage of the first kind (ana front)

The cold front is how the warm front , a weather phenomenon associated with a low pressure area . The cold air moves here in the direction of the warm air. The cold front normally results in cooling at all levels of the air layers. A distinction is also made between fronts where cooling only occurs in higher layers of air. One speaks here of an altitude cold front . Furthermore, in winter it can happen that the cooled air mass close to the ground is replaced by somewhat milder maritime cold air. Thus it becomes even warmer in the layers close to the ground. One speaks here of a masked cold front .

Furthermore, a distinction is made between the cold fronts according to the flow behavior of cold air compared to warm air. In the case of the cold front of the first type ( Anafront ), the cold air is pushed under the warm air and in the case of the cold front of the second type ( Katafront ), the cold air is pushed over the warm air; further explanation see below.

Cold fronts are characterized by increased vertical air movements . Thereby occurring convective cloud cover often leads to enhanced showery precipitation or thunderstorms . The arrival of a stronger cold front can often be observed very well: quite strong, somewhat cooled wind, cumulative clouds (possibly already a few cumulonimbus clouds) announce it. The temperature drops by several degrees during the passage, it can even happen that after a beautiful spring day with 16 ° C there is snow the next day after the passage of the cold front.

On the back of the cold front ( cold sector ), the atmosphere is usually unstably stratified. Together with the soil, which is still damp from the rain, this leads to cumulus clouds and showers under the sun's rays, the so-called reverse weather . Furthermore, the air pressure increases again after passing the front. Because the air is absolutely and relatively less humid than before the precipitation, the air becomes clear and visibility is good. If the cold front has caught up with the warm front, an occlusion is formed .

Cold front symbol on weather maps

On a weather map , cold fronts are marked by blue triangles that point in the direction of the migration.

Anacal front

In summer, a cold front passage is often accompanied by thunderstorms

According to the classical theory, cold air comes under warm air, whereby convergence occurs at the air mass limit . Here, the warm, moist air is forced to rise. The result is cloud formation and precipitation behind the cold front.

In the illustration, the cold air advance is from the right; In contrast, the pressure and temperature curves are mirror-inverted.

Catacalt front

In the case of the catacal front, the cold air gets over the warm air. The rise of the warm air is prevented by the sinking of the dry air. Thus the cloud development that takes place in front of the cold front is kept small.

Web links

Commons : Kaltfront  - Album with pictures, videos and audio files