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(ii) coNvEctioNal raiNfall
Convectional rain is caused when the sun heats up the ground and the air above it. This then rises
and the water vapour condenses into water droplets, forming clouds. As the clouds grow heavier
it starts to rain. Convectional rain can also be found year round in regions near the equator.

(iii) cycloNic raiNfall

When a warm air mass and a cold air mass meet, the warm air being lighter climbs over
the cold air mass and cools and condenses. This causes rainfall along the path and is called
‘cyclonic’ rainfall. It is generally associated with cyclones.

Relief Rainfall Convectional Rainfall Cyclonic Rainfall

BENEfits of raiNfall
• Most of the ground water comes from rain water.

• If rainfall is less, water scarcity and drought occur.
• It is very important for the survival of plants and animals.
• It provides fresh water to the earth’s surface.

air pollutioN

Any change in the composition of air is termed as air pollution.
It results from release of certain gaseous, solid or liquid agents
in the atmosphere. The obvious causes of air pollution are,
growing industrial activity, excessive burning of fossil fuels,
rising numbers of automobiles, fires and burning of solid wastes.
The chief air pollutants are carbon dioxide, carbon monoxide,

chlorofluoro carbons, suspended particulate matter, sulphur
dioxide, nitrogen oxide and lead.
Air pollution leads to serious health problems, loss of biodiversity and damage to historical

monuments. It is a serious environmental problem and must be tackled urgently.

Now I Know :

ƒ Our earth is surrounded by a huge blanket of air called atmosphere. Air is the gas all around us. It is a mixture of
several different gases, mainly nitrogen and oxygen.
ƒ Our atmosphere is divided into five layers starting from the earth’s surface. These are Troposphere, Stratosphere,
Mesosphere, Thermosphere and Exosphere.
ƒ The elements of weather and climate are temperature, pressure, winds, humidity, precipitation, sunshine and cloudiness.
ƒ Various factors influencing weather and our climate are temperature, air or atmospheric pressure, wind and moisture.

Social Studies
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