Temperature Inversion, Causes, Types, Diagram, Effects, Examples

Temperature Inversion Meaning

Temperature inversion is a reversal of temperature behaviour in the troposphere. A layer of warm air lies over the layer of cold air in this meteorological phenomenon.

In normal conditions, as we go up, the temperature drops as per the normal lapse rate. It is 6.5 ° C per 1,000 m. Contrary to this general rule, the temperature may sometimes rise with height instead of decreasing. Cool air is closer to the ground and warmer air is higher. This increase in temperature with height is known as Temperature Inversion.

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Temperature Inversion Conditions

There are certain conditions under which Temperature Inversion occurs:

• Long Winter Nights: when the sky is clear during the long night in winter, the terrestrial radiation is faster. The reason is that the earth is cooling off faster. The lower layer of the earth-bound atmosphere is also cooled, and the upper layer remains warm.
• Clear, Cloudless Sky: Clouds block the earth’s terrestrial radiation. But this radiation pass unobstructed on cloudless days. So the soil is cooled faster and so is the air that comes into contact.
• Dry Air: Moist air absorbs the earth’s radiation, but dry air does not block radiation and allows radiation to escape into the atmosphere.
• Ice-covered Area: In ice-covered areas due to high albedo less sunlight is received. At night due to the earth’s radiation, most of the heat is lost in the atmosphere and the surface is cooled. The contact air is also cooled but the upper layer remains warm.
• Calm Atmosphere: the blowing of winds brings warm and cold air into contact. Under conditions of a calm atmosphere, the cold air stays put near the ground.

Read More: Heat Transfer

Temperature Inversion Types

There are mainly two types of Temperature Inversion namely Surface Inversion and Upper-air Inversion.

Surface Inversions

Also called surface temperature inversions. This is a phenomenon that occurs when the air is cooled by coming in contact with a colder surface until the air becomes cooler than the overlying atmosphere. This surface temperature inversion occurs mostly on clear nights when the ground cools rapidly by radiation. In case the temperature of the surface air drops below its dew point, this may result in fog. The most visible inversions are those found at ground level. These are of the following types:

• Radiational Inversion: These can develop on a long, cold winter night when a land surface rapidly emits longwave radiation into a clear, calm sky. Conduction cools the air above as a result of the cold ground. In a relatively short time, the lowest few hundred meters of the troposphere become colder than the air above, and a temperature inversion is in effect. Radiational inversions primarily occur in the winter because there is only a short daylight period for incoming solar heating and a long night for radiational cooling. They are therefore much more prevalent in high latitudes than elsewhere.
• Advection Inversions: They develop when there is a horizontal inflow of cold air into an area. This is common to cool maritime air blowing into a coastal locale. Advection inversions are usually short-lived (typically overnight) and shallow. They can happen at any time of year, depending on the location of the relatively cold surface and the direction of the wind.
• Drainage Inversion: Another type of surface inversion results when cooler air slides down a slope into a valley, thereby displacing slightly warmer air. During winter, this fairly common occurrence in some midlatitude regions is called a cold-air drainage inversion.

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Upper-air Inversions

Temperature inversions in the upper air are nearly always the result of air descending from above and are hence called as subsidence inversions. Subsidence inversions are usually associated with high-pressure conditions, which are particularly characteristic of subtropical latitudes throughout the year and of Northern Hemisphere continents in winter. A subsidence inversion can be fairly deep (sometimes several thousand meters), and its base is usually a few hundred meters above the ground, as low-level turbulence prevents the warmer air from sinking lower.

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The stability of the nighttime temperature inversion is usually destroyed soon after sunrise as the sun’s energy warms the ground, which warms the air in the inversion layer. The stability that distinguishes the nightly inversion is subsequently destroyed when the warmer, less dense air rises. Temperature inversion is a phenomenon that is most frequently seen in valleys.

During winter, the mountain slopes cool very rapidly due to the quick radiation of heat. The air resting above them also becomes cold and its density increases. Hence, it moves down the slopes and settles down in the valleys. This air pushes the comparatively warmer air of valleys upwards, resulting in a temperature inversion. That is why apple orchids in the Himalayan region, the tea garden of Darjeeling, are found on the upper slopes of the valleys.

Read More: Structure of the Atmosphere

Temperature Inversion Diagram

Inversions play an important role in determining cloud forms, precipitation, and visibility. The diagram of Temperature Inversion is below:

Read More: Heat Waves

Temperature Inversion Effects

• The temperature inversion helps in precipitation, forming clouds, and frost.
• The inversion of temperature leads to the floating of dust particles in the air, thus, checking dust particles and smoke from dispersing on the surface.
• Temperature inversion brings stability to the atmosphere by checking the downward and upward movement of the air.
• At times the temperature inversion can become a matter of concern. It checks the convection clouds from rising higher, thus, pouring less rainfall.
• Fog formed due to temperature inversion reduces visibility and is a concern for transportation.
• Intense thunderstorms and tornadoes are associated with temperature inversions.

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Temperature Anomaly

The temperature of a region varies along the same parallel of latitudes. The temperature also varies due to land and water contrasts, due to the prevailing winds and also due to ocean currents. Thus, the temperature anomaly can be defined as the difference between the mean temperature of any place and the mean temperature of its parallel is known as a temperature anomaly. The temperature anomaly is also known as a thermal anomaly.

Temperature anomalies could be positive or negative. An anomaly is said to be a negative anomaly when the temperature of a place is less than the expected temperature of the latitude. The anomaly is a positive anomaly when the temperature of a place is more than the expected temperature of the latitude.

Due to the uneven distribution of land and water, the maximum temperature anomalies are found in the Northern Hemisphere and the minimum in the Southern Hemisphere.

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Temperature Inversion UPSC

At times, the temperature at the valley bottom drops below freezing, while the air at higher altitudes remains relatively warm. As a result, the trees on the lower slopes are frost-bitten, whereas those on higher levels are not.

Because of the temperature inversion, air pollutants such as dust particles and smoke do not disperse in the valley bottoms. Because of these factors, houses and farms in intermountain valleys are typically located on the upper slopes, away from the cold and foggy valley bottoms. For example, coffee farmers in Brazil and apple farmers and hoteliers in India’s Himalayan mountain states avoid lower slopes.

This article will discuss an important phenomenon known as temperature inversion in the context of the UPSC IAS Exam.

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