Cloud has been defined as a visible aggregation of minute water droplets or ice particles in the air, usually above the general ground level. Clouds are the most important forms of suspended water droplets caused by condensation.
Divisions of cloud-based on their appearance and height are as follows:
A. High ( mean Heights 5to 13km)
1. Cirrus: It is in the form of white or mostly white patches or narrow bands. They are composed of ice crystals. These clouds do not give precipitation.
2. Cirrocumulus: It is thin, white patch, sheet or layer of the cloud without shading, composed of very small elements in the form of grains, ripples etc. This type of cloud is not common.
3. Cirrostratus: This cloud is transparent, whitish cloud veil of fibrous or smooth appearance, totally or partly covering the sky. This type of cloud gives the sky a milky appearance.
B. Middle(mean Heights 2to7km)
4. Alto-cumulus: This cloud is white or Grey, or both white and Grey, patch, sheet or layer of cloud, generally with shading, composed of laminar, rounded masses, rolls etc. They generally found in wavy or parallel bands.
5. Alto-stratus: This is grayish or bluish cloud sheet or layer of striated, fibrous or uniform appearance, totally or partly covering the sky. It causes precipitation as drizzle or snow.
6. Nimbostratus: It is Grey cloud layer, often dark, the appearance of which is rendered diffuse by more or less continuously falling rain or snow.
C: Low (mean height 0to2km)
7. Strato-cumulus: This cloud is found in a low cloud layer consisting of large lumpy masses or rolls of dull Grey colour with bright interestices.
8. Stratus: These clouds are without any particular form or structure. Sky may be completely covered by this type of cloud. They are frequently broken.
9. Cumulus: These clouds are generally detached clouds with sharp outlines. They generally found in the daytime and disappears at night.
10. Cumulo-nimbus: This is a heavy and dense cloud, with considerable vertical extent, in the form of a mountain or huge tower. This type of cloud is associated with heavy rainfall, Thunder, lightning, hail, and tornadoes.