Temperature Inversion- Normally, temperature decreases with an increase in elevation. It is called the normal lapse rate. At times, the situation is reversed and the normal lapse rate is inverted. It is called Inversion of temperature. Inversion is usually of short duration but quite common nonetheless.
Ideal Conditions for Temperature Inversion
The heat of the day is radiated off during the night, and by early morning hours, the earth is cooler than the air above. Over polar areas, a temperature inversion is normal throughout the year.
Types of Temperature Inversion
1. Air Drainage (Inversion in hills and mountains)
The inversion takes place in the hills and mountains due to air drainage. Cold air at the hills and mountains, produced during the night, flows under the influence of gravity. Being heavy and dense, the cold air acts almost like water and moves down the slope to pile up deeply in pockets and valley bottoms with warm air above. This is called air drainage.
2. Ground Inversion (Surface Temperature Inversion)
A ground inversion develops when air is cooled by contact with a colder surface until it becomes cooler than the overlying atmosphere; this occurs most often on clear nights when the ground cools off rapidly by radiation. If the temperature of surface air drops below its dew point, fog may result.
3. Subsidence Inversion (Upper Surface Temperature Inversion)
A subsidence inversion develops when a widespread layer of air descends. The layer is compressed and heated by the resulting increase in atmospheric pressure, and as a result, the lapse rate of temperature is reduced. If the air mass sinks low enough, the air at higher altitudes becomes warmer than at lower altitudes, producing a temperature inversion. Subsidence inversions are common over the northern continents in winter and over the subtropical oceans; these regions generally have subsiding air because they are located under large high-pressure centres.
4. Frontal Inversion
A frontal inversion occurs when a cold air mass undercuts a warm air mass and lifts it aloft; the front between the two air masses then has warm air above and cold air below. This kind of inversion has a considerable slope, whereas other inversions are nearly horizontal. In addition, humidity may be high, and clouds may be present immediately above it.
Economic Implication of Temperature Inversion