Atmospheric Circulation and Weather Systems Short and Long Important Question Class 11 Geography Chapter-9 Book-Fundamental of Physical Geography

 

1. What is atmospheric pressure?

Answer: 

Atmospheric pressure is the force exerted on the Earth's surface due to the weight of the air. It is measured in millibars (mb) and its average value at sea level is 1,013.2 mb.

2. Which instruments are used to measure air pressure?

Answer:

• Mercury Barometer: A column of mercury is used in this.

• Aneroid Barometer: It measures air pressure without liquid.

3. How does air pressure change with altitude?

Answer:

• As altitude increases, air becomes rarefied, which reduces air pressure.

• For every 10 metres of height the air pressure decreases by approximately 1 millibar.

4. Why is the horizontal distribution of air pressure studied?

Answer: 

The horizontal distribution of air pressure is used to understand the speed and direction of winds. It is represented through isobars.

5. What are the main air pressure belts on Earth?

Answer:

• Equatorial Low Pressure Belt – 0°-10° latitude

• Subtropical High Pressure Belt - 30°N and 30°S

• Subpolar Low Pressure Belt - 60°N and 60°S

• Polar High Pressure Belt - 90°N and 90°S

6. How does air pressure affect winds?

Answer: 

Air always flows from high pressure to low pressure. This flow is due to the pressure gradient force.

7. What are the main forces affecting the speed and direction of winds?

Answer:

• Pressure Gradient Force: It causes air to flow from high pressure to low pressure.

• Coriolis Force: Due to the rotation of the Earth, the wind direction turns to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

• Frictional Force: Slows down the speed of winds near the surface.

• Gravitational Force: Keeps the air close to the earth.

8. Where is the effect of Coriolis Force the highest and the lowest?

Answer:

• Most common: at the poles.

• Lowest: At the Equator, where its effect is zero.

9. What is Geostrophic Wind?

Answer: 

When the pressure gradient force and Coriolis force come into balance, the winds blow parallel to the isobar lines, this is called geostrophic wind.

10. What are the three main chambers of Earth's atmospheric circulation?

Answer:

• Hadley Cell: From the Equator to 30°N/S.

• Ferrel Cell: Between 30°-60°N/S.

• Polar Cell: Between 60°-90°N/S.

11. What are seasonal winds?

Answer: 

Seasonal winds are those winds which change their direction according to the season. Example: Indian Monsoon.

12. What are the local winds?

Answer:

• Cold winds: Mistral, Bora, Blizzard.

• Hot winds: Foehn, Chinook, Sirocco, Harmattan.

13. How do Land and Sea Breeze work?

Answer:

• During the day: The land warms up quickly, causing a breeze to blow from the sea towards the land (sea breeze).

• At night: The land cools quickly, causing a breeze to blow from the land towards the sea (land breeze).

14. What is the difference between a tornado and a thunderstorm?

Answer:

• Tornado: A concentrated column of extremely fast rotating air, with speeds reaching up to 300–500 km/h.

• Thunderstorm: Stormy weather associated with thunder, lightning, and heavy rain.

15. What is the difference between Tropical Cyclone and Extra-Tropical Cyclone?

Answer:

16. What are the different names of tropical cyclones?

Answer:

• Cyclone: ​​Indian Ocean.

• Hurricane: Atlantic Ocean.

• Typhoon: Western Pacific.

• Willy-Willy: Around Australia.

17. What are fronts? Explain their types.

Answer: 

Front is the area where two different air masses meet. Its types are:

• Cold Front: Cold air displaces warm air.

• Warm Front: Warm air rises over cold air.

• Stationary Front: Both air masses remain stationary.

• Occluded Front: The cold front completely covers the warm front.

18. What is air mass?

Answer: 

Air mass is a large volume of air that has uniform temperature and humidity.

19. What is the difference between cyclone and anticyclone?

Answer:

• Cyclone: ​​A low pressure centre in which air rotates inwards.

• Anticyclone: ​​A high pressure centre in which air rotates outward.

20. What is the importance of the study of air pressure?

Answer: 

Air pressure plays an important role in understanding weather, wind systems, cyclones and global climate.