Page 123 - SST Class 07

3. Sea breeze is an example of which wind?
4. In which zone the polar wind blows?
5. What is the process of descending down of moisture from clouds called?
6. What type of rainfall do you find in equatorial regions?

F. Answer the questions in brief :
1. What do you mean by atmosphere?
2. Why is atmosphere important for us?
3. What do you mean by weather and climate?
4. What is atmospheric temperature? Which factors influence it?
5. Define atmospheric pressure.
6. What is precipitation?

G. Answer the questions in detail :
1. What is the composition of the atmosphere?
2. What is known as stratosphere? State its importance.
3. Why does the amount of insolation decrease from Equator towards poles?
4. What are the different types of winds? Describe each.

5. Write a short note on three major zones based on the temperature.
6. Describe the different types of rainfalls with the help of a diagram.

1. What is the importance of weather forecasts for a farmer, a fisherman, an engineer working on a
dam, a captain of a ship and a pilot?
2. What is the importance of water vapour in the atmosphere? What happens to water vapour in the
air?

Global Warming

The earth’s atmosphere acts like the glass walls and the roof of a
greenhouse. Gases such as carbon dioxide, methane, nitrogen oxide and
the water vapour present in the atmosphere are transparent to sunlight as
the glass. These gases freely allow sunlight to pass through and reach the
earth’s surface. But when the surface gets heated by the sun, these gases
do not allow the radiated heat rays to escape into space. As a result, heat
remains trapped in the atmosphere and helps to keep the earth’s
temperature at a comfortable level. Since the gases, carbon dioxide,
methane, nitrogen oxide as well as water vapour in the atmosphere acts in a manner similar to a
greenhouse, these are known as greenhouse gases. So if there was no atmosphere, the average
temperature on the earth would have been a frigid –15°C.
But due to human activities, the amount of CO in the atmosphere is continuously increasing. Excess of
2
CO traps a lot of heat and leads to warming of the earth’s surface. This would make the earth warmer
2
than usual. This condition is called global warming. Global warming can cause melting of ice at poles.
Because of this, the sea level can rise and leads to the floods.
The Atmosphere
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