The formation of clouds has always been very important to man. You must be curious to know how the clouds are formed and how many kinds of clouds are there.
We know that the water of rivers, ponds, lakes and seas is converted into vapour by the solar heat and this vapour moves in air. Hot air, mixed with water vapour, being lighter, goes up high in the sky. When the air mixed with water vapour accumulates at one place, it gives the appearance of smoke. We call it a cloud.
On the basis of their different shapes and sizes, clouds have been divided into mainly four kinds:
1. Cirrus clouds: Cirrus clouds are formed at great heights. They are white in colour and look like birds’ feathers. Their height ranges from 8,000 to 11,000 metres. They are made up of small ice particles.
2. Stratus clouds: Stratus clouds are formed at a height of about 2,438 metres. They look like layers of fog. They foretell bad weather and drizzle.
3. Cumulus clouds: Cumulus clouds are formed at a height of 1,219 to 1,524 metres. They are dome-shaped at the top and flat at the bottom. They look like White Mountains in the sky.
4. Nimbostratus clouds: Nimbostratus clouds are formed at the lowest heights. They are deep brown or black in colour. These are the clouds which rain.
There are ten different types of clouds. But the four discussed above are the main kinds.
If the air below clouds carrying condensed water vapour is cool, the size of the water droplets present in the clouds will go on increasing and when they attain an optimum size, they fall down on the Earth in the form of rain.
Similarly, if the air below these clouds is not cold, the water droplets present in the clouds will be reconverted into vapour. Consequently the clouds will disappear without raining. That is why some clouds disappear without raining.
