Rainfall

Rainfall

Rainfall is the most predominant type of Precipitation. Moisture laden air masses raise upwards, forms clouds and bring rainfall. Based on the mechanisms of raising the air, there are three types of rainfall.

Convectional rainfall

Frontal or cyclonic rainfall

Orographic rainfall.

Convectional rainfall

Earth surface is intensely heated through solar radiation during the day time. When the air near the earth surface is heated, it rises and expands. This heating results is the formation of convectional air currents. Thus the ascending moist air cools, condenses and results in convectional rainfall. Convectional rainfall occurs regularly in the equatorial region in the evenings. It is also experienced in tropical, sub-tropical and temperate regions in the summer months and on warmer days.

Cyclonic rainfall:

Cyclonic  precipitation occurs during cyclones when air masses are made to converge and move upward so that adiabatic cooling occurs. Cyclonic rainfall occurs in tropical as well as temperate regions. When warm and cold air masses converge, condensation and precipitation takes place on the boundary between warm and cold air masses called as Frontal rainfall.

Orographic rainfall

Orographic rainfall, also called relief rainfall, is caused when air is forced to rise against a high mountain. The mountain barriers lying across the direction of air flow, force the moisture laden air rise along the mountain slope. This results in the cooling of the air, which leads to the formation of clouds and rain. 

This rainfall is called Orographic rainfall. The side of the mountain facing the wind is called the windward side and receives heavy rainfall. It is called the rainfed region. The other side of the mountain that does not face the wind is called the leeward side and receives less rainfall becomes rain shadow region.