Middleham, Yorkshire, UK. 11th December 2013. Early morning Weather at Dawn with mist, Fog & Inversion Layer. Sunrise over moorland in the North Yorkshire Dales. A temperature inversion is a meteorological phenomenon in which air temperature increases with height for some distance above the ground, as opposed to the normal decrease in temperature with height.
There are several reasons why an inversion might develop. One situation in which a low level, or surface inversion, might take place is on a clear night, when the earth's surface radiates heat away rapidly. If the air is clear, the ground, and the air directly above it, can be cooler than the air at higher altitudes. Another type of inversion, called an advectional inversion, involves a horizontal inflow of cold air. This might be air blowing in from cold water to a coastal area. Along the coast, winds frequently blow onshore, passing over the cold ocean waters before reaching land. When this occurs, the air at ground level may be colder than the air above it, and the air is stable. A third type of surface inversion takes place at night in valleys, when cold, dense air flows downslope under the influence of gravity, draining off the slopes and uplands, and into the valleys. The air in the valley bottoms is colder than the air above. Other types of inversions may also develop under various conditions. This high pressure cell develops in response to global patterns of atmospheric pressure and circulation, rather than local conditions. The presence of high pressure means that the air in the region is subsiding from high altitudes in the atmosphere. Subsiding air is compressed by the increasing pressure of the surrounding air as it descends, so the air warms up as it subsides. So not only is there cool air at ground level (from onshore flow of cool air), there is also a general subsidence of warm air aloft. The inversion layer acts as a lid to prevent air at ground level from rising and dispersing. If there are mountains inland, the mountains can also help trap the air. This means that any pollutants emitted accumulate in the trapped air.
Size: 3600px × 2400px
Location: Middleham, Yorkshire, UK.
Photo credit: © MediaWorldImages / Alamy / Afripics
License: Licensed
Model Released: No
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