Questions:

（ 1 ） How many kinds of clouds are there? What are they?

（ 2 ） How does the cloud appear?

 Rain

A cloud is a visible aggregate of tiny water droplets and/or ice crystals suspended in the atmosphere and can exist in a variety of shapes and sizes. Some clouds are accompanied by precipitation; rain, snow, hail or sleet.

All clouds form as a consequence of rising air. Sometimes air is forced to rise over mountains. More usually, warm air, being less dense, will rise above cold air. At fronts for example, warm air masses rise over cold air masses when they converge. At much smaller scales, columns of rising warm air may be generated by daytime heat from the Sun.

When air rises, it expands, causing cooling and a drop in temperature. As the temperature falls, the humidity (or water vapour content) of air increases towards 100%. Finally, after sufficient cooling, the air becomes saturated, and water vapour begins to condense out as tiny water droplets, forming cloud.

There are four principal classes of cloud:

Cirrus clouds are the highest of all clouds, and are sometimes a foreteller of bad weather to come.

Stratus clouds usually cover the whole sky and make for a grey, dreary day.

Cumulus clouds look like fluffy balls of cotton wool, and generally only develop during the daytime.

Cumulonimbus clouds can be beautiful but often bring with them heavy rain, hail and lightning. They are much larger and vertically developed than cirrus clouds which forms a more stable atmosphere