Chapter 9: Atmospheric Circulation and Weather Systems
Geography - Fundamental of Physical Geography • Class 11
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Chapter Analysis
Intermediate10 pages • EnglishQuick Summary
The chapter 'Atmospheric Circulation and Weather Systems' explores the fundamental concepts of atmospheric pressure, wind patterns, and their implications on weather systems. It discusses the movement of air due to pressure variations and the interaction between different air masses that result in various weather phenomena like cyclones, anticyclones, and local winds such as land and sea breezes. Additionally, it highlights the role of forces such as the Coriolis effect and friction in influencing wind direction and velocity.
Key Topics
- •Atmospheric Pressure
- •Coriolis Effect
- •Wind Circulation Patterns
- •Cyclones and Anticyclones
- •Air Masses and Fronts
- •Tropical Cyclones
- •General Circulation of the Atmosphere
- •Local Winds and Breezes
Learning Objectives
- ✓Understand the concept of atmospheric pressure and its measurement.
- ✓Analyze how temperature and pressure gradients influence wind patterns.
- ✓Discuss the formation and characteristics of different air masses and fronts.
- ✓Identify the factors that lead to cyclonic and anticyclonic activity.
- ✓Explain the Coriolis Effect and its role in global wind circulation.
- ✓Examine the impact of global atmospheric circulation on climate and weather systems.
Questions in Chapter
If the surface air pressure is 1,000 mb, the air pressure at 1 km above the surface will be:
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The Inter Tropical Convergence Zone normally occurs:
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The direction of wind around a low pressure in northern hemisphere is:
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Which one of the following is the source region for the formation of air masses?
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What is the unit used in measuring pressure? Why is the pressure measured at station level reduced to the sea level in preparation of weather maps?
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While the pressure gradient force is from north to south, i.e. from the subtropical high pressure to the equator in the northern hemisphere, why are the winds north easterlies in the tropics?
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What are the geotrophic winds?
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Explain the land and sea breezes.
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Discuss the factors affecting the speed and direction of wind.
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Draw a simplified diagram to show the general circulation of the atmosphere over the globe. What are the possible reasons for the formation of subtropical high pressure over 30o N and S latitudes?
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Why does tropical cyclone originate over the seas? In which part of the tropical cyclone do torrential rains and high velocity winds blow and why?
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Additional Practice Questions
What are the major forces affecting wind circulation on Earth?
mediumAnswer: The major forces affecting wind circulation are the pressure gradient force, Coriolis force, and frictional force. The pressure gradient force initiates wind movement from high-pressure to low-pressure areas. The Coriolis force, due to Earth’s rotation, deflects winds to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Frictional force, significant near the Earth's surface, slows down wind speed.
Explain the process and significance of the Hadley Cell.
hardAnswer: The Hadley Cell is a large-scale tropical atmospheric circulation pattern that starts at the equator with the rising of warm, moist air. As it rises, it cools and moves poleward at high altitudes. When it sinks at around 30 degrees latitude, it creates dry, high-pressure areas that are major desert regions. This circulation pattern helps to distribute thermal energy from the equator towards the poles.
Define and differentiate between cyclones and anticyclones.
mediumAnswer: Cyclones are low-pressure systems characterized by inward spiraling winds that rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Anticyclones are high-pressure systems with winds spiraling outward, rotating clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. Cyclones typically bring stormy weather, whereas anticyclones are associated with calm and clear conditions.
What is the Coriolis effect and how does it impact weather systems?
mediumAnswer: The Coriolis effect is the deflection of moving objects, such as winds, caused by Earth's rotation. This effect causes winds to turn to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, influencing the direction of wind systems and ocean currents, and playing a crucial role in the formation of cyclones and anticyclones.
How do seasonal changes affect atmospheric circulation patterns?
hardAnswer: Seasonal changes affect atmospheric circulation through the shifting of pressure belts and temperature gradients, altering wind patterns. During summer, warmer temperatures can strengthen and shift the subtropical high-pressure zones poleward, changing monsoon patterns and affecting trade winds. In winter, cooling intensifies polar high-pressure zones, which can enhance westerlies and impact storm tracks.