Study Notes on Concept of Inversion of Temperature

Concept of Inversion of Temperature

The temperature decreases with the altitudes in the troposphere at an average rate of 6.5 °C per 1000 m, this is known as normal lapse rate. But sometimes the temperature increases upward upto a few kilometers from the earth's surface. This is known as inversion of temperature i.e. presence of warm layer of air above the cold layer of air.

Types of inversion of temperature:

1. Ground surface inversion:

The most common condition for inversion of temperature is through the cooling of the air near the ground at night. Once the sun goes down, the ground loses heat very quickly, and this cools the air that is in contact with the ground. However, since air is a very poor conductor of heat, the air just above the surface remains warm. Conditions that favour the development of a strong surface inversion are calm winds, clear skies, and long nights. Calm winds prevent warmer air above the surface from mixing down to the ground, and clear skies increase the rate of cooling at the Earth's surface. Long nights allow for the cooling of the ground to continue over a longer period of time, resulting in a greater temperature decrease at the surface. Since the nights in the winter time are much longer than nights during the summer time, surface inversions are stronger and more common during the winter months. During the daylight hours, surface inversions normally weaken and disappear as the sun warms the Earth's surface.

2. Upper air inversion:

 The thermal upper air inversion is caused by the presence of ozone layer in the stratosphere. The ozone layer absorbs most of the ultraviolet rays radiated from the sun  thus the temperature of this layer becomes  higher than the other layers.

Consequences of Temperature Inversions

a) Fog is formed due to the presence of warm air above the cold air. The cold air cools the warm air from below thus forms the tiny droplets around dust particles and smokes during winter season that result in formation of fog.

b) The urban smog is formed by the intensification of fog by pollution. When smog gets mixed with sulphur dioxide it becomes poisonous and deadly for human beings.

c) Inversion of temperature leads to formation of frost. Frost is economically unfavourable weather phenomenon as it damages fruit orchids and crops.

d) The inversion of temperatures creates anticyclonic conditions thus inhibits rainfall and encourages dry conditions.