There are three main types of rainfall — convectional rainfall, orographic rainfall, and cyclonic rainfall.
Types of Rainfall #1
- Convectional rainfall mostly occurs in the equatorial regions. High temperature in the equatorial regions results in a high rate of evaporation.
- When the temperatures are high, the air gets heated. Warm air rises higher in the atmosphere; it then expands and spreads at the top. Ascending currents of hot and humid air result in condensation and the formation of cumulonimbus clouds of a great vertical extent.
- Such clouds give heavy rainfall. This rainfall is associated with thunder and lightning.
- The Amazon river basin lies in the equatorial region, and hence, it rains almost every day.
Types of Rainfall #2
Orographic or Relief Rainfall
- Relief rainfall is called so because it is affected by the relief or physical features of a place, i.e. mountains.
- This type of rainfall is also known as relief rainfall. When the moisture-bearing winds strike a mountain range, it is forced to ascend.
- Because the wind rises up the mountains, it cools down to its saturation point bringing rainfall on the windward side of the mountains. These winds are devoid of moisture when they reach the leeward side of mountains. Hence, places located on the leeward side of mountains get scanty rainfall.
- For example, Mumbai which lies on the windward side of the Western Ghats receives heavy rainfall, while Pune which lies on the leeward side receives scanty rainfall.
Types of Rainfall #3
Cyclonic or Frontal Rainfall
- This type of rainfall occurs when the warm and the cold air meet each other. Because the warm air is lighter, it rises above the cold air. The rising air is then cooled beyond the saturation point resulting in heavy rainfall.
- Such rainfall lasts only for few hours. It is very heavy during tropical cyclones.
Thunderstorms are associated with heavy rainfall and lightning
- Lightning is caused when raindrops move up and down because of convectional air currents.
- Because the temperature above the clouds is extremely low, small ice particles are formed.
- When these ice particles move against each other, they become electrically charged. While positively charged ions (which are lighter) settle at the top of the cloud, the negatively charged ions settle at the bottom of the clouds.
- When positively and negatively charged ions are attracted towards each other, a flash of lightning takes place.
Also, Read Types of Clouds