Inversion of Temperature, also called thermal inversion, is a reversal of the normal behaviour of temperature in the troposphere (the region of the atmosphere nearest Earths surface), in which a layer of cool air at the surface is overlain by a layer of warmer air. This is one of the crucial topics in geography. The Heat Budget and insulation is very important concept in the syllabus of the UPSC examination.

Inversion of Temperature - Concept

• 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 normal lapse rate.
• However, in rare cases, the situation is reversed, and the temperature rises rather than falls with height. Temperature inversion is the term for this phenomenon.

Temperature inversion

Mechanism

• In this meteorological occurrence, a layer of warm air sits on top of the cold air layer.
• It is caused by static atmospheric conditions, but it can also be induced by horizontal or vertical air movement.
• Temperature inversions are usually short-lived, but they are quite common.

Mechanism

Suitable Conditions for Temperature Inversion

1. Long winter nights: During the night, heat loss from the earth surface due to terrestrial radiation may exceed the amount of incoming solar radiation.
2. Dry air near the surface of the ground: It prevents radiating heat from the Earth's surface from being absorbed.
3. The slow movement of air: There is no heat transfer or mixing in the lower layers of the atmosphere as a result.
4. Snow-covered the surface of the ground: It causes the greatest amount of heat loss by reflecting incoming solar light.
5. Clear and cloudless sky: Heat loss by terrestrial radiation is more rapid when there is no impediment.

Suitable Conditions

Types

• Temperature inversion can occur in a variety of situations, from the ground to considerable heights. As a result, there are various types of temperature inversions.
• The following are classified according to their relative heights above the earth's surface and the sort of air circulation they use:

1. Non-Advectional

Radiation Inversion (Surface Temperature Inversion):

• When air is cooled by contact with a colder surface, it becomes cooler than the surrounding atmosphere.
• This happens most often on clear nights, when the ground cools off quickly due to radiation.
• Fog can form when the temperature of the surface air falls below the dew point. In the higher latitudes, it is fairly prevalent.
• It occurs during chilly nights in lower and medium latitudes and is destroyed throughout the day.

Radiation Inversion

Subsidence Inversion (Upper Surface Temperature Inversion):

• When a spreading layer of air falls, the resulting increase in atmospheric pressure compresses and heats it, reducing the lapse rate of temperature.
• A temperature inversion occurs when the air at higher altitudes gets warmer than the air at lower altitudes. Subsidence inversion is the name for this sort of temperature inversion.
• It is especially common in the winter (dry atmosphere) over the northern continents and over the subtropical oceans; these places generally have sinking air because they are positioned under massive high-pressure centres.
• Because it occurs in the highest reaches of the atmosphere, it is also known as upper surface temperature inversion.

Subsidence Inversion

2. Advection

Valley inversion in the intermontane valley:

• The temperature of the lowest layers of air can sometimes increase rather than decrease with elevation along a sloping surface in high mountains or deep valleys.
• 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.
• Because of the sloping surface underneath them, they gravitate to the bottom, where the cold layer settles as a low-temperature zone, while the top layers are somewhat warmer.
• Temperature Inversion is a circumstance in which the vertical distribution of temperature is the polar opposite of the typical vertical distribution.

Valley inversion

Frontal or Cyclonic inversion:

• When the warm and cold fronts collide, the warm front rises, while the cold front lowers due to its weight. Frontal Inversion develops as a result.
• Other inversions are essentially horizontal, however this one has a significant slope. It frequently occurs in the temperate zone, causing cyclonic conditions that produce various types of precipitation.
• When the weather changes, a frontal inversion becomes unstable and is eliminated.

Frontal Inversion

Effects of Temperature Inversion

• It determines the precipitation, clouds form, and also causes frost due to condensation of warm air due to its cooling.
• It causes the stability of the atmosphere that stops the downward and upward movement of air.
• Furthermore, temperature inversion effects diurnal variations.
• Moreover, it limits the diffusion of air pollutants and hence stagnation in weather is witnessed for some periods.
• Also, convection clouds can’t rise upwards so there is less rainfall and no showers. So, it causes a problem for agricultural productivity.
• Besides, they also disturb the radio signals which get reflected from the layer above cold air.
• Most noteworthy, if the temperature inversion is broken then it can cause a violent thunderstorm.
• Due to the formation of cumulus clouds sometimes sunlight is unable to reach the ground.

Significance

• Cloud formation, precipitation, and visibility 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.

Conclusion

Temperature inversion can at times result in freezing rain in cold climates. Thus temperature inversion is a major phenomenon that has a deep impact on various happenings.