Inversion of Temperature

●  The normal lapse rate is the decrease in temperature with an increase in elevation.

●  Sometimes, 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.

●  There are six favorable conditions producing surface inversion they are:

1.             long nights,

2.             clear skies or high clouds

3.             relatively dry air

4.             slight air movement

5.             snow-covered surface

6.             flattish surfaces with a few topographic depressions.

●  Surface inversion promotes stability in the lower layers of the atmosphere. This inversion commonly lasts for a few hours until the sun comes up and begins to warm the earth.

Air drainage

●  The inversion takes place in 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. It protects plants from frost damages.

Temperature Anomaly

●  The difference between the mean temperature of any place and the mean temperature of its parallel is defined as the temperature anomaly or thermal anomaly.

●  It expresses the deviation from the normal. This deviation is caused by the land and water contrasts, ocean currents, and prevailing winds.

●  Isanomal is lines joining the places of equal thermal anomalies. The distribution of anomalies is studied on the maps showing isanomal.

●  The largest anomalies occur in the Northern and the smallest in the Southern Hemisphere.