Trough (meteorology)

A trough is a large area relatively low atmospheric pressure. In the trough weather conditions there are two versions: the upper level trough and the surface trough.

• 2.1
• 2.2 Effects

Surface trough / rear trough

The bottom tray or backing tray designated areas low air pressure at the back of a strong, an aging lows behind the cold front or occlusion. In these areas, there is a re- depression of the cyclones due to strong Aufgleitvorgänge of air masses, which are formed when the amount of hot air is entrained on the front side of the low anti-clockwise around the center of the low and reaches the rear side in the region of the cold air.

Floor troughs are not completely surrounded by higher pressure, which distinguishes them from lows. Furthermore, they have no closed cyclonic circulation.

Isobars bumps from the core of the low wedge or trough-shaped from said bottom tray other than a front separates any air masses different from each other. One speaks of as long as a trough, as the circulation is not complete. Once it comes to a closed circulation in the trough region and thereby forms a closed core, one speaks of a deep trough.

Determination

A surface trough is heralded by the fact that after passage of the front is not as usual an air pressure increase occurs and the wind after previous strong clockwise rotation turns back, but the air pressure again falls on quickly after a short rise. The surface trough follows a cold front or occlusion usually at a distance of about 15 to 20 hours, and then brings a new, significant weather change, which is usually accompanied by very strong wind gusts.

The clouds at trough layers may differ in principle. Sometimes a closed Nimbostratusbewölkung may predominate, falls out of the prolonged showery precipitation. But usually there is extensive Kumulusbildung with showers and thunderstorms due to the unstable air stratification.

Level trough

The upper level trough caused by meandering of the jet streams. It consists of the upper level trough of highly polar air, mostly polar origin. Bulges of the jet stream to the south of, the result is an upper level trough. Bulges of the jet stream to the north of, the result is a height wedge or back.

Upper Troughs are usually found in layers of air above 4000m.

On a trough front side of the high-altitude wind has a southwestern or southern flow. This warm air is transported to the northeast or north. On the back of the trough level wind, however, has a northwest or north flow, and there is cold air transported to the southeast or south.

Troughs and ridges are effects of the Rossby waves.

Determination

Level troughs can be identified by the strong cyclonic curved contour lines of elevation weather map. The default card is usually the map of the 500 -hPa pressure surface which lies in the middle in 5500 meters altitude, used.

Effects

The high and low formation at ground level depends very closely with the level troughs and closer together.

In an upper level trough the flow lines ( contour lines ) have a strong curvature in the region of the trough axis. Prior to the trough axis, the flow lines run closer together, they converge. This takes the wind speed in the area of the trough axis. Because of the strong curvature of the flow lines in the area of the tray axis, the air mass is slowed down, which causes an accumulation of air masses from the curvature. The be astonished air masses are mainly transported down because upwards the end of the troposphere prevents removal. Descending air mass means at the bottom of a rise in pressure, thereby providing a high-pressure area is created on the back of a trough.

Behind the trough axis, the curvature of the flow lines rapidly, and the flow lines diverge diverge. This more air masses are transported at the output of the upper trough, resulting in a mass deficiency. As compensation flock to air masses from below. Ascending air masses leave the pressure at ground level fall, and there is at the bottom of a low pressure area. Thus, areas of low pressure at the bottom on the front of troughs by the air masses very active weather here and delve strong. For fronts, the same applies.

Even after the high and low education level control troughs the shift of ground-based printing systems. For example, ground-level lows, depending on the inclination of the upper-level trough axis shift to low: A vertical axis inclination leads to a stationary depth, an eastward inclined axis leads to the development of a low or relocated an existing deep eastward. A backward inclination of the axis leads analogously to shift westward or weakening of the lows.

Shortwave trough

At the border of warm air caused short-wave troughs than smaller bulges at the edge of the large-scale bulge. As a small-scale low-pressure systems pull in rapid succession along the jet stream to the north- east. They are harder to detect. They are usually quite weatherproof effective, they can cause rain, snow, severe thunderstorms and tornadoes.

Swell

• Karl -Heinz Bock, Ralf Brown, Frank -Ulrich Dentler: marine weather, DSV -Verlag GmbH, German Sailing Association -Verlag GmbH, 2009, ISBN 978-3884123676
• Trough in the weather glossary of weather online
• Trough at wissen.de

• Pressure areas and fronts