On the basis of origin, rainfall may be classified into three main types – the convectional, orographic or relief and the cyclonic or frontal.

Convectional Rainfall

The, air on being heated, becomes light and rises up in convection currents.

As it rises, it expands and loses heat and consequently, condensation takes place and cumulous clouds are formed.

With thunder and lightening, heavy rainfall takes place but this does not last long.

Such rain is common in the summer or in the hotter part of the day.

It is very common in the equatorial regions and interior parts of the continents, particularly in the northern hemisphere.

Orographic Rainfall

When the saturated air mass comes across a mountain, it is forced to ascend and as it rises, it expands; the temperature falls, and the moisture is condensed.

The chief characteristic of this sort of rain is that the windward slopes receive greater rainfall.

After giving rain on the windward side, when these winds reach the other slope, they descend, and their temperature rises. Then their capacity to take in moisture increases and hence, these leeward slopes remain rainless and dry.

The area situated on the leeward side, which gets less rainfall is known as the rain-shadow area.

It is also known as the relief rain.

Cyclonic and Frontal Rainfall

This type of precipitation is associated with a cyclonic activity (Tropical and Temperate) and also occurs along the frontal zone.

Cyclonic rainfall is associated with Cumulo Nimbus (CuNi) clouds.

The rainfall is very heavy and accompanied with lightning and thunder and high speed winds which has the potential to cause damage.

‘Frontal rainfall’ is associated with fronts which form due to collision of different air masses.

Warm front is formed due to advent of warm air masses which leads to moderate rainfall.

In the same way cold front is formed due to advent of cold air mass which leads to heavy rainfall with
lightning and thunder.