Cloud is a mass of minute water droplets or tiny crystals of ice formed by the condensation of the water vapour in free air at considerable elevations.

●  As the clouds are formed at some height over the surface of the earth, they take various shapes.

Types of Clouds

●  According to their height, expanse, density and transparency or opaqueness clouds are grouped under four types.

●  The four types of clouds are: 

(i) cirrus

(ii) cumulus

(iii) stratus

(iv) nimbus

Cirrus

●  Cirrus clouds are formed at high altitudes (8,000 – 12,000m).

●  They are thin and detached clouds having a feathery appearance.

●  They are always white in colour.

Cumulus

●  Cumulus clouds look like cotton wool.

●  They are generally formed at a height of 4,000- 7,000 m.

●  They exist in patches and can be seen scattered here and there.

●  They have a flat base.

Stratus

●  These are layered clouds covering large portions of the sky.

●  These clouds are generally formed either due to loss of heat or the mixing of air masses with different temperatures.

Nimbus

●  Nimbus clouds are black or dark gray.

●  They form at middle levels or very near to the surface of the earth.

●  These are extremely dense and opaque to the rays of the sun.

●  Sometimes, the clouds are so low that they seem to touch the ground.

●  Nimbus clouds are shapeless masses of thick vapour

●  A combination of these four basic types can give rise to the following types of clouds:

➔ high clouds – cirrus, cirrostratus, cirrocumulus

➔ middle clouds – altostratus and altocumulus

➔ low clouds – stratocumulus and nimbostratus

➔ clouds with extensive vertical development – cumulus and cumulonimbus.