When water vapor in the atmosphere changes through condensation to liquid or solid state and falls on the earth’s surface, it is called precipitation. It can be in a liquid or solid state. It involves water drops falling as snow, hail due to formation of clouds. When the precipitation occurs in the form of water, it is called rain and when the temperature is below 0°, the precipitation occurs in the form of snowflakes, it is called snow fall. Hail, snow and water are included in precipitation.
Types of Rainfall:
Rainfall on the earth is divided into three types on the basis of origin:
1. Convectional Rainfall: This rain occurs primarily in the equatorial linear regions after noon, because due to excessive heat, the air rises above and simultaneously the water of the ocean becomes rapidly transformed into vapor and rises up, and the process is called convection. This process of convection results in convectional rainfall.
2. Orographic Rainfall: It can also be called surfacial rainfall. Mountain rains take place in the highest amount in the world, in which the air denser than vapor has to get cooled up while rising along the mountain. By cooling, the air becomes condensed and it causes rainfall. This wind rises due to the obstruction of the mountains and causes rainfall. In the mountainous rain, there is more rainfall towards the windward side on the mountains, but on the other hand, the rainfall is very low on the other side (leeward side) and this side is called Rain Shadow region.
3. Cyclonic Rainfall: This rain occurs in the mid-latitudinal and sub – tropical countries. It is caused due to the cyclones. In the cyclones, the wind blows rapidly towards the center and begins to rise. Due to coming through the sea, this air is denser than water vapor. So when the cold polar air comes in contact with it, a kind of front region develops in the middle and the warm air containing water vapor cools down, which is called cyclonic rain. This rainfall is not rapid, instead, it is in the form of drizzling. This type of rainfall occurs in regions of temperate cyclones. In the north-west India also in the winter, there is rainfall caused by cyclones.
