Types of Rainfall: When the air rises it expands and gets cooled.
When the air is cooled beyond the dew point, condensation takes place and
results in rainfall. Rainfall occurs in three different ways and as such it is
known by three different names, i.e.. the relief rainfall, the convectional
rainfall and the cyclonic rainfall.
1. Relief Rainfall — Air is forced to rise, when it meets a
mountain and is therefore cooled. If enough water vapour is present it is
deposited on the windward side of the mountains. This is the most widespread
form of rainfall. When the moisture-laden winds strike against the mountain
ranges, they rise up. expand and down and bring heavy rainfall on the wind-ward
side. Such a rain by the uprising winds striking against the mountains is
called the Relief Rainfall.
Example of Relief Rainfall in India: The rain on the Western Ghats of India or on
the southern slopes of the Himalayas is the relief rainfall. As winds cross
over to the other side (leeward side) they lose most of their moisture. While
descending they become warm and dry and hence there is less rain on the leeward
side. The rainless area on the leeward side of a mountain is called the Rain
Shadow Area. The Deccan region in India lies in the rain shadow of the Western
Ghats.