Write explanatory notes on each of the following (a) Land and sea breezes (b) Temperature inversion (c) Convectional rainfall

Answer Details

(a) Land and sea breezes

These are local winds caused by the unequal heating and cooling of land and sea. By day the land heats faster than the sea; the warm air over the land rises and the cooler, denser air from the sea blows in to replace it, giving a sea breeze (from sea to land). By night the land cools faster than the sea; the air over the sea is now warmer and rises, so cooler air from the land blows out to sea, giving a land breeze (from land to sea). They are common along coasts and moderate coastal temperatures.

(b) Temperature inversion

Normally temperature falls with height in the lower atmosphere. A temperature inversion is a reversal of this, where a layer of warm air lies above cooler air near the ground, so temperature rises with height. It occurs typically on clear, calm nights when the ground loses heat rapidly by radiation and chills the air just above it, and in valleys where cold, dense air drains down and collects at the bottom. Inversions trap smoke, fog and pollutants near the surface and prevent convection.

(c) Convectional rainfall

Convectional rainfall results from the intense heating of the ground (as in the tropics and in equatorial regions on summer afternoons). The hot surface heats the air above it, which becomes light and rises rapidly by convection. As it rises it cools, water vapour condenses to form tall cumulonimbus clouds, and heavy rain falls, usually in the afternoon and often with thunder and lightning. It is the chief rainfall type near the Equator.