Clouds are visible aggregates of water droplets, ice particles, or a mixture of both along with varying amounts of dust particles.

Clouds are generally classified on the basis of their general form or appearance and altitude.

Combining both these characteristics, clouds may be grouped as under.

Low clouds

The base level of low clouds varies from very near the ground to about 2000m.

The basic type of this family is the status, a low, uniform layer resembling fog but not resting on the ground.

Stratocumulus clouds form a low, gray layer composed of globular masses or rolls which are usually arranged in groups, lines, or waves.

Clouds with vertical development fall into two principal CategoriesCumulus and Cumulonimbus.

Cumulus clouds are dense, dome-shaped and have flat bases.

They may grow to become cumulonimbus, the extent of vertical development depending upon the force of vertical currents below the clouds as well as upon the amount of latent heat of condensation liberated in the clouds as they form.

To an observer directly beneath, a cumulonimbus cloud may cover the whole sky and have the appearance of Nimbostratus, The word nimbus (or prefix nimbo) applies to a cloud from which rain is falling.


Medium clouds

These clouds are formed at altitudes between 2000 to 6000 metres.

This group of clouds includes altocumulus and altostratus.


High clouds

These clouds are formed above the altitude of 6000 metres and include cirrus, cirrostratus and cirrocumulus.