Tag: temperature inversion layer

4 TYPES OF TEMPERATURE INVERSION




Temperature inversion is a condition in which the temperature of the atmosphere increases with altitude in contrast to the normal decrease with altitude.

When temperature inversion occurs, cold air underlies warmer air at higher altitudes.

There are four kinds of temperature inversions: ground, turbulence, subsidence, and frontal.




A ground inversion

develops when air is cooled by contact with a colder surface until it becomes cooler than the overlying atmosphere; this occurs most often on clear nights, when the ground cools off rapidly by radiation.

If the temperature of surface air drops below its dew point, fog may result. Topography greatly affects the magnitude of ground inversions.




If the land is rolling or hilly, the cold air formed on the higher land surfaces tends to drain into the hollows, producing a larger and thicker inversion above low ground and little or none above higher elevations.




A turbulence inversion

often forms when quiescent air overlies turbulent air.

Within the turbulent layer, vertical mixing carries heat downward and cools the upper part of the layer.

The unmixed air above is not cooled and eventually is warmer than the air below; an inversion then exists.




A subsidence inversion

develops when a widespread layer of air descends.

The layer is compressed and heated by the resulting increase in atmospheric pressure, and as a result, the lapse rate of temperature is reduced.

If the air mass sinks low enough, the air at higher altitudes becomes warmer than at lower altitudes, producing a temperature inversion.




Subsidence inversions are common over the northern continents in winter and over the subtropical oceans; these regions generally have subsiding air because they are located under large high-pressure centres.

A frontal inversion

occurs when a cold air mass undercuts a warm air mass and lifts it aloft; the front between the two air masses then has warm air above and cold air below.

This kind of inversion has considerable slope, whereas other inversions are nearly horizontal.




In addition, humidity may be high, and clouds may be present immediately above it.

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7 CAUSES OF TEMPERATURE INVERSION




Temperature inversion is a condition in which the temperature of the atmosphere increases with altitude in contrast to the normal decrease with altitude.

When temperature inversion occurs, cold air underlies warmer air at higher altitudes.




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    Normally, temperature decreases with an increase in elevation. It is called the normal lapse rate.

At times, the situation is reversed and the normal lapse rate is inverted. It is called Inversion of temperature.

Inversion is usually of short duration but quite common nonetheless. A long winter night with clear skies and still air is an ideal situation for inversion.

The heat of the day is radiated off during the night, and by early morning hours, the earth is cooler than the air above.

Over polar areas, a temperature inversion is normal throughout the year. Surface inversion promotes stability in the lower layers of the atmosphere.




Smoke and dust particles get collected beneath the inversion layer and spread horizontally to fill the lower strata of the atmosphere.

Dense fogs in the mornings are common occurrences, especially during winter season. This inversion commonly lasts for few hours until the sun comes up and beings to warm the earth.

The inversion takes place in hills and mountains due to air drainage. Cold air at the hills and mountains, produced during night, flows under the influence of gravity.




Being heavy and dense, the cold air acts almost like water and moves down the slope to pile up deeply in pockets and valley bottoms with warm air above.

This is called air drainage. It protects plants from frost damages.

Causes of Temperature Inversions

Normally, air temperature decreases at a rate of 3.5°F for every 1000 feet (or roughly 6.4°C for every kilometer) you climb into the atmosphere.




When this normal cycle is present, it is considered an unstable air mass and air constantly flows between the warm and cool areas.

As such the air is better able to mix and spread around pollutants.During an inversion episode, temperatures increase with increasing altitude. The warm inversion layer then acts as a cap and stops atmospheric mixing.




This is why inversion layers are called stable air masses.
Temperature inversions are a result of other weather conditions in an area.

They occur most often when a warm, less dense air mass moves over a dense, cold air mass.

This can happen for example, when the air near the ground rapidly loses its heat on a clear night. In this situation, the ground becomes cooled quickly while the air above it retains the heat the ground was holding during the day.




Additionally, temperature inversions occur in some coastal areas because upwelling of cold water can decrease surface air temperature and the cold air mass stays under warmer ones.

Topography can also play a role in creating a temperature inversion since it can sometimes cause cold air to flow from mountain peaks down into valleys.




This cold air then pushes under the warmer air rising from the valley, creating the inversion.

In addition, inversions can also form in areas with significant snow cover because the snow at ground level is cold and its white color reflects almost all heat coming in.

Thus, the air above the snow is often warmer because it holds the reflected energy.




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