Formation of clouds can be understand by the concept:-
Air contains moisture and this is extremely important to the formation of clouds. Cloud is formed around microscopic particles such as dust, smoke, salt crystals and other materials that are present in the atmosphere. These materials are called “Cloud Condensation Nucleus” (CCN). Without these, no cloud formation will take place. Certain special types known as “ice nucleus” on which cloud droplets freeze or ice crystals form directly for water vapour.
Generally, condensation nuclei are present in plenty in air. But there is scarcity for special ice forming nuclei. Generally, clouds are made up of billions of these tiny water droplets or ice crystals or combination of both. There are two rain forming process, viz.,
1. Warm rain process (rain fall process in the tropics), and
2. Cold rain process.
Warm rain – Rain occurs when the temp is above 0°C never colder than 0°C and when larger droplets collide and absorb smaller cloud droplets. They grow larger and larger and become raindrops. This process is known as “Coalescence cold rain process”.
Cold rain – It occurs when the cloud temperature is colder than 0°C. Clouds are usually with ice crystals and liquid water droplets. These crystals grow rapidly drawing moisture from the surrounding cloud droplets until their weight-causes them to fall. Falling ice crystals may melt and join with smaller liquid cloud droplets. Resulting in raindrops if ice crystals do not melt, they may grow into large snowflakes and reach the ground as snow.