How many types of rainfall are there?

Sometimes rain falls softly and sometimes it rains heavily and there are times when rain falls like a blanket of wrathful force. So we can say not all rain looks the same. The three ways by which air is induced to rise produce three different types of rainfall.

 

3 Types of Rainfall

 

1. Convectional rainfall

 

Alternatively, it is called the 4 o�clock shower

 

� This type of rainfall is caused by the process of convection.

 

� The two factors necessary to cause this type of precipitation are Intense heating of the surface and abundant supply of moisture.

 

� Due to intense heating of the surface, the surface air gets heated expands, and rises up conventionally holding moisture. After getting cooled adiabatically, its temperature falls below dew point and clouds are formed.

 

� The resultant clouds are of Cumulonimbus formed at about 10 km height which gives heavy rains. This type of Rain mostly occurs in the Equatorial zone which experiences direct rays of the Sun almost throughout the year and hence receives more than 200 cm of annual rainfall.

 

� Such rainfall is also accompanied by thunder and lightning.

 

But why it is called the 4 o�clock shower? This type of rain mostly occurs at 4 o�clock in the afternoon and is always torrentially accompanied by lightning and thunder.

Let us learn about 2 more types of rainfall.

 

2. Orographic Rainfall

 

Its alternate name is Relief Rainfall.

 

� The word Orographic is derived from the Greek word �Oros� meaning a mountain. When moisture-laden winds are unable to cross the mountains, they are forced to rise along with it. They mostly rise along the windward slopes of the mountains due to which their pressure decreases and the air expands and gets cooled adiabatically and if sufficient water vapor is present, rain or snow occurs on the windward slopes. This type of rainfall is called Orographic rainfall.

 

� While windward sides receive most of the rainfall, on the leeward sides the dry air descends the mountain slopes so the pressure and temperature both increase, leading the air to get compressed and warm. Hence they receive quite less rainfall. On the leeward slopes of mountains, there always exists a relatively dry area called a rain shadow.

 

� Since it is caused by the relief of the land, it is called relief rainfall. For example, in India, the Western Ghats on the windward side get maximum moisture from monsoons whereas on the leeward side there is a rain shadow area receiving very little rainfall.

 

� Some other areas receiving orographic rainfall include eastern Brazil, East China, South-Eastern United Nations.

 

3. Cyclonic Rainfall

 

Alternate name: Frontal Rainfall

 

� In Tropical Latitudes this type of rainfall is due to cyclones and in Temperate latitudes it is due to depressions. Cyclonic rain occurs when a mass of warm air (Warm front) meets a mass of cold air (Cold front). The warm air is forced up above the cooler air as it is lighter. Condensation takes place and clouds are formed, followed by rains.

 

� The boundary zones of these air masses are called fronts and the rising air is cooled while undergoing frontal lift, hence the name frontal rainfall.

 

� In Temperate depressions, it is much lighter, but lasts for many days.

 

� Since the lifting of warm air along the warm front of the temperate cyclone is slow and gradual, the condensation is slow and gradual. Hence Cyclonic rains are usually in the form of a drizzle.

 

� Cyclonic rain is common throughout Doldrums where the Trade Winds meet. Winter Rainfall in Northwest India is a typical example of cyclonic rainfall.

 

� The tropical cyclones are regionally known as typhoons, hurricanes, and tornadoes that yield heavy rainfall in China, Japan, Southeast Asia, India, the USA, etc.

Types of Rainfall Questions:

 

1. Which rain is common throughout Doldrums?
(i) Orographic
(ii) 4 o�clock shower
(iii) Convectional Rainfall
(iv) Cyclonic rainfall

 

2. Which type of rainfall occurs on the Western coast of India?
(i) Convectional rainfall
(ii) Cyclonic rainfall
(iii) 4 o�clock shower
(iv) Orographic rainfall

 

3. The boundary zones of cold mass of wind and hot mass of wind is known as
(i) Zone
(ii) Boundary
(iii) Joint
(iv) Front

 

4. Which is the alternate name for cyclonic rainfall?
(i) 4 o�clock shower
(ii) Orographic Rainfall
(iii) Conventional Rainfall
(iv) Frontal Rainfall

 

5. Orographic rainfall is also known as _____.
(i) Frontal rainfall
(ii) 4 o�clock shower
(iii) convectional rainfall
(iv) Relief rainfall