What is Adiabatic change of temperature?
The change in temperature of any parcel of air due to change in pressure is called adiabatic change in temperature. This change in temperature happens without exchange of heat of a given parcel of rising air with the surrounding air.
Let’s disaggregate this concept
- First, Earth surface gets heated from solar radiation. Then the air near earth surface gets hot.
- Heated air becomes lighter than upper air. Hence, hot air rises towards higher altitude.
- The atmospheric pressure decreases with increase in altitude above sea level or earth surface.
- Decrease in pressure causes any parcel of rising hot air to expand.
- Expansion of air or any fluid causes it to cool.
- Similarly, when a parcel of cold air from higher altitude starts to subside, it experiences increase in pressure.
- Increase in pressure causes the air to contract.
- Contraction of air leads to heating of air.
For detail, read laws of therodynamics.
Summary
The rise and decline in temperature of air due to expansion and contraction of air is called adiabatic change of temperature. The decline in temperature i.e. cooling of rising parcel of air due to expansion is called adiabatic lapse rate. The increase in temperature i.e. heating of subsiding parcel of air due to contraction is called adiabatic heating of air. There are two types of adiabatic lapse rate i.e. Dry Adiabatic Lapse Rate and Wet Adiabatic Lapse Rate.
Dr. Nisha is an Assistant Professor of Geography at Kamala Nehru College, University of Delhi.