Types Of Rainfall

Posted on Posted in Geography

Introduction

As monsoon has arrived in India and is on its peak, we are bringing to you a brief explanation about the types of rainfall and their carriers, i.e. the clouds.

Hope you all would find it useful. 

Types of Clouds

Before discussing about the types of rainfall, its our obligation to know about their carriers. 

 

 

  • The highest clouds in the atmosphere are cirrocumulus, cirrus, and cirrostratus. Cumulonimbus clouds can also grow to be very high.
  • Mid-level clouds include altocumulus and altostratus.
  • The lowest clouds in the atmosphere are stratus, cumulus, and stratocumulus.

 

Stratus/strato = flat/layered and smooth

Cumulus/cumulo = heaped up/puffy, like cauliflower

Cirrus/cirro = High up/wispy

Alto = Medium level

Nimbus/Nimbo = Rain-bearing cloud

Convectional Rainfall

It is typical of warm moist air by heating from the ground surface and phenomenon called thermal convection . As a result of heating of the surface air, the air expands and forced to rise to great height. As the air rises, it cools and becomes saturated and dew point temperature(the temperature at which water vapour in the air condense(gas-liquid)) is attained and then clouds will form. By further cooling, precipitation takes place. The rain bearing clouds in the convectional rainfall are cumulonimbus clouds. 

 

 

 

cumulonimbus Cloud

 

 

In the equatorial regions, the precipitation due to convectional rainfall occurs in the afternoon. The rainfall is of very short duration but in the form of heavy showers.

Cyclonic / Frontal Rainfall

Cyclonic rainfall occurs due to the upward movement of the air caused by the convergence of different air masses with different temperatures. The warm air rises over the cold air and cyclonic rain occurs. The cold air pushes up the warm air and sky gets clear again.

 

 

These fronts and associated weather phenomenon are best developed in the middle latitudes, most of the winter precipitation of low lands in the middle latitudes is cyclonic or frontal is origin.

 

In India the phenomenon of cyclonic rainfall could be seen profoundly in the region of West Bengal and Assam as every year the cyclonic rainfall brings about a lot of damage in these states as the rains are very heavy. In the states of Punjab and Punjab, these rainfalls occur mainly in the winters and is generally mild.

Orographic/Relief rainfall

Orographic rainfall occurs in the mountainous regions near the coastal lines in general. Conditions favoring orographic rainfall in India is seen only over the Western ghats during monsoon period. Monsoon winds from Arabian sea gets blocked by Western ghats and gets lifted over the ranges and precipitates leaving dry winds to blow over Peninsular India.

 

 

Orographic rainfall results in heavier rainfall along the western side of Western ghats leading to more than 250cm rainfall per year.

 

Dominance of orographic rainfall in the western coastline of India.

 

If you will observe closely in the above given illustrations, you all will find that the eastern part of the Western Ghats are having a minimal amount of rainfall. This phenomenon is called the 'rain shadow effect'. 

This phenomenon is seen in the orographic rainfall. Under this phenomenon the moment of the rain-bearing clouds due to the winds is hampered by the collision with western ghats which results in precipitation. On the contrary the part which is on the other side of the western ghats(eastern) go through a dry spell when the western part is having monsoon showers.

Some of the places worth mentioning which face this effect are- Satara, Kolhapur, Marathwada, Nanded etc

The primary source of rainfall in this region limits to the convectional rainfall.

 

Similarly Himalayas blocks the monsoon winds and precipitates rain over the ranges of Himalayas. Cherrapunji and Mawsynram are the wettest place in the world due to its location in the windward side of Himalayas and Tibet remains dry being in the leeward side and experience the rain shadow effect. 

 

 

During winter, Western Himalayas block the warm moist air from Mediterranean sea and results in orographic precipitation. This results in snow over the higher reaches of Himalayas in Himachal and Jammu and Kashmir.

Tell Us Your Views

Please tell us in the comment section your views about these geographical phenomenons. 

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