Temperature Inversion

Under normal circumstances, the temperature in the troposphere declines at a rate of 1 degree per 165 metres as height rises. This is referred to as the usual lapse rate. However, in rare circumstances, the scenario is reversed, and the temperature rises rather than falls with height. Temperature inversion is the term for this. 

Temperature inversion refers to a reverse of the troposphere's typical temperature pattern. A warm air's layer sits over the cold air layer in this meteorological occurrence.

After understanding what is temperature inversion, let us move further to what causes temperature inversion and temperature inversion diagram. Here is the temperature inversion diagram:

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But what Causes Temperature Inversion?

It is caused by static atmospheric conditions, although it can also be caused by horizontal or vertical air movement. Temperature inversions are usually short-lived, but they are pretty common.

Favourable Conditions for Temperature Inversion

• Long winter nights: Heat loss from the earth’s surface due to terrestrial radiation may exceed the amount of incoming solar radiation during the night.

• When the sky is clear and there are no clouds, heat is lost more quickly through terrestrial radiation.

• Dry air near the ground surface: It prevents radiated heat from the Earth's surface from being absorbed.

• Slow air movement: There is no heat transmission or mixing in the lower levels of the atmosphere due to this.

• Snow-covered ground surfaces result in the most significant heat loss due to the reflection of incoming solar energy.

Temperature Inversion Effects

Here are some common temperature inversion effects:

• Cloud formation, visibility, and precipitation are all influenced by inversions.

• The upward movement of air from the layers below is slowed by an inversion. As a result, convection caused by below-inversion heating is limited to levels below the inversion. Dust, smoke, and other air pollutants are also limited in their spread.

• Convective clouds cannot develop high enough to produce showers in areas where there is a strong low-level inversion.

• Due to the accumulation of dust and smoke particles below the inversion, visibility may be considerably decreased. Fog is typically prevalent towards the base of an inversion because the air is cold.

• Temperature diurnal variations are also affected by inversions. The difference between the hours of the day and the hours of the night is usually relatively minor.

Types of Temperature Inversion

Here are the common types of temperature inversion:

1. Intermountain Valley temperature inversion (Air Drainage Type of Inversion)

With elevation, the temperature in the lower layers of the air can sometimes rise rather than fall. This is a common occurrence on a sloping surface. The surface here rapidly radiates heat back to space and cools down faster than the top layers. The lower cold layers condense and become heavier as a result.

They travel towards the bottom of the sloping surface, where the cold layer settles as a zone of low temperature, while the top layers are somewhat warmer. Temperature Inversion is a circumstance in which the vertical temperature distribution is the polar opposite of the typical vertical distribution. 

In other words, during a temperature inversion, the vertical temperature is inverted. In the middle and upper latitudes, this type of temperature inversion is particularly strong. It can also be influential in areas with steep mountains or deep valleys.

2. Ground Inversion (Surface Temperature Inversion)

A ground inversion occurs when the air gets chilled by contact with a colder surface until it is cooler in comparison to the overlying atmosphere; this happens most often during clear nights when the ground cools very quickly due to radiation. Fog may also form as the temperature of the surface air falls below the level of the dew point. 

This type of temperature inversion is prevalent at higher latitudes. In the lower and medium altitudes, a surface temperature inversion occurs during cold nights and is removed throughout the day.

3. Subsidence Inversion (Upper Surface Temperature Inversion)

When a significant layer of air falls, a subsidence inversion occurs. As a result of the increased atmospheric pressure, the layer is compressed and heated, lowering the temperature lapse rate. When the air mass decreases, higher altitude air becomes warmer than lower altitude air, resulting in a temperature inversion.

In winter (dry atmosphere), subsidence inversions are widespread over the subtropical oceans and the northern continents; these locations generally contain subsiding air due to their location under massive high-pressure centres. Because it occurs in the upper atmosphere, this temperature inversion is known as upper surface temperature inversion.

4. Frontal Inversion (Advectional type of Inversion of Temperature)

A frontal inversion happens when a cold air mass undercuts a warm air mass and raises it aloft (Cold and Warm Fronts: we'll go over that later); a front between the two air masses then has hot air above it and cold air beneath.

This type of inversion has a steeper slope than others, which are virtually level. Furthermore, humidity levels may be high, and clouds may be present just above it. This form of inversion is unstable, and as the weather changes, it disintegrates.

Economic Implications of Temperature Inversion

• The air temperature near the valley bottom can drop below freezing at times, while the air at higher altitudes remains quite warm. As a result, the trees on the lower slopes are frost-bitten, while those on the higher slopes are unaffected.

• Air contaminants such as dust particles and smoke do not disperse in the valley bottoms due to temperature inversion. Houses and farms in intermountain valleys are located along the upper slopes, avoiding the cold and foggy valley bottoms because of these conditions. Coffee growers in Brazil and apple growers and hoteliers in India's Himalayan mountain states shun lower slopes.

• Fog reduces visibility, which has an impact on plants and human settlements.

• Less rain as a result of the stable weather.

• Above, we discussed what temperature inversion is and the types of temperature inversion. You can check more details and definitions on temperature inversion pdf versions too.