What is inversion of temperature? Under what conditions does it apply?

The temperature decreases at the rate of about 1°C per 166 m or 6°C per 1,000 metres of altitude. There are, however some places where certain special conditions in the lower atmosphere produce a reversal of the normal lapse rate so that temperature actually increases with an increase in altitude. This is known as temperature inversion.

It is generally experienced in hollows and valleys on calm clear nights when radiation has caused cooling and cold air has sunk down. At the same time on the mountain slopes the air is warmer. Temperature inversion is normally found in the middle latitude and for this reason fruit growers in these regions prefer gentle slopes to valley bottom for orchard sites.