- Usually as we move up in troposphere from the surface, the temperature decreases with increase in altitude.
- But sometimes due to local conditions, the temperature, instead of decreasing, increases with height.
- This phenomenon is called temperature inversion.
- This is also known as negative lapse rate.
- The different types of inversions may be classified as –
Low level or ground surface inversion:
- this is the condition where temperature near the ground increases, rather than decreasing with elevation.
- This type of inversion occurs generally in tropical and sub- tropical regions during the period of long winter nights.
- This inversion however, disappears with sunrise.
- The duration and height of surface inversion increases pole wards.
- Following conditions are required for ground surface inversion:
Long winter nights Cloudless calm skies
Dry air and low relative humidity
Calm atmosphere or slow movement of air Snow covered surface
Upper air inversion:
it occurs when the warm air is transported upwards into the cold air due to eddies.
It may be caused due to compression of the descending air as it happens in the case of subtropical high pressure belts.
it is caused by horizontal and vertical movement of air.
The temperate cyclones are formed by convergence of warm westerlies and cold polar air, and thus the warm air overlies the cold air.
The presence of warm air above and cold air below reverses the normal lapse rate and inversion of temperature occurs.
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