1/3/2024 0 Comments Deep contour definitionIn regions where there is upward movement near the ground and divergence at altitude, there is a loss of mass. In the absence of a wind shift, the region is designated a col, akin to a geographic saddle between two mountain peaks.Ī trough is the result of the movements of the air in the atmosphere. Sometimes the region between two high pressure centers may also assume the character of a trough when there is a detectable wind shift noted at the surface. Inversely, sometimes collapsed frontal systems will degenerate into troughs. However, such a weather front is usually less convective than a trough in the tropics or subtropics (such as a tropical wave). If a trough forms in the mid-latitudes, a temperature difference at some distance between the two sides of the trough usually exists and the trough might become a weather front at some point. Since pressure is closely linked to wind, there are often changes in wind direction across a trough. The elongated cloud is surrounded by two big areas of higher atmospheric pressure, clearly shown with no clouds at all.Ī trough is an elongated area of lower air pressure. If they are not marked, troughs may still be identified as an extension of isobars away from a low pressure center.Ī very large trough (about 8000 km or more) crosses the North Atlantic Ocean from north east to south west. In the UK, Hong Kong and Fiji, it is represented by a bold line extended from a low pressure center or between two low pressure centers in Macau and Australia, it is a dashed line. In the United States, a trough may be marked as a dashed line or bold line. The weather charts in some countries or regions mark troughs by a line. Unlike fronts, there is not a universal symbol for a trough on a surface weather analysis chart. Their motion induces upper-level wind divergence, lifting and cooling the air ahead (downstream) of the trough and helping to produce cloudy and rain conditions there. Upper-level troughs in the jet stream (as shown in diagram) reflect cyclonic filaments of vorticity. Near-surface troughs sometimes mark a weather front associated with clouds, showers, and a wind direction shift. Since low pressure implies a low height on a pressure surface, troughs and ridges refer to features in an identical sense as those on a topographic map. Representation of alternating troughs and ridges in upper-level westerlies for the Northern Hemisphere, with regions of convergence and divergence labeled.Ī trough is an elongated region of relatively low atmospheric pressure without a closed isobaric contour that would define it as a low pressure area.
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