CBSE Class 11 Geography Chapter 10: Atmospheric Circulation and Weather Systems NCERT Solutions

Reviewed by NCERT Help Editorial Team · Updated on 29 Jul 2026

NCERT Solutions PDF Class 11 PDF

This chapter, "Atmospheric Circulation and Weather Systems," delves into the fundamental forces that drive atmospheric movements and shape weather patterns. It explains concepts like air pressure, pressure gradients, and the Coriolis effect, which influence wind direction and speed. The solutions cover various aspects, including the formation and characteristics of air masses, the mechanisms behind land and sea breezes, and the factors determining wind speed and direction. Understanding these principles is crucial for comprehending global weather phenomena and climate. These NCERT Solutions provide clear, step-by-step explanations and answers to help students grasp complex meteorological concepts, aiding in effective exam preparation and revision.

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Board	CBSE
Class	Class 11
Subject	Geography
Session	2026
Language	English
Type	NCERT Solutions
Chapter	10. Atmospheric Circulation and Weather Systems

Chapter summary

Chapter 10 of the Class 11 Geography syllabus focuses on Atmospheric Circulation and Weather Systems. The NCERT Solutions provided here explain the measurement of atmospheric pressure, the reasons for pressure reduction to sea level, and the influence of the Coriolis force on wind direction. It also defines geostrophic winds and elaborates on the formation and working of land and sea breezes, along with a detailed discussion on factors affecting wind speed and direction. These solutions aim to build a strong foundation in understanding atmospheric dynamics.

Learning outcomes

Understand the units of atmospheric pressure and the necessity of reducing pressure to sea level.
Explain the influence of the Coriolis force on wind deflection in different hemispheres.
Define geostrophic winds and the forces that balance to create them.
Describe the formation and daily cycle of land and sea breezes.
Analyze the various factors that determine the speed and direction of wind.

Topics covered

Paper topics

Atmospheric Pressure Measurement
Pressure Reduction to Sea Level
Wind Formation and Movement
Coriolis Force
Geostrophic Winds
Air Mass Source Regions
Land Breezes
Sea Breezes
Factors Affecting Wind Speed
Factors Affecting Wind Direction

Important topics

Atmospheric Circulation
Coriolis Force and its effect on winds
Pressure Gradient Force
Geostrophic Winds
Land and Sea Breezes
Factors affecting wind speed and direction

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Questions and Solutions

1. Multiple choice questions

(i) If the surface air pressure is 1,000 mb, the air pressure at 1 km above the surface will be:

(a) 700 mb

(b) 1,100 mb

(d) 1,300 mb

Solution: The correct answer is (c) 900 mb. Air pressure decreases with an increase in altitude because the density of air decreases. As you move higher up in the atmosphere, there is less air above pushing down. Therefore, the pressure at 1 km above the surface will be lower than the surface pressure of 1,000 mb. Approximately, for every 100 meters increase in altitude, the pressure drops by about 10 mb, so at 1 km (1000 meters), the pressure would be around 900 mb.

(ii) The Inter Tropical Convergence Zone normally occurs:

(a) near the Equator

(b) near the Tropic of Cancer

(d) near the Arctic Circle

Solution: The correct answer is (a) near the Equator. The Inter Tropical Convergence Zone (ITCZ) is a low-pressure belt located near the Equator. It is characterized by the convergence of the northeast and southeast trade winds, leading to rising air, cloud formation, and precipitation.

(iii) The direction of wind around a low pressure in northern hemisphere is:

(a) clockwise

(b) perpendicular to isobars

(d) parallel to isobars

Solution: The correct answer is (c) anti-clock wise. In the Northern Hemisphere, the Coriolis force deflects moving air to its right. Around a low-pressure system, air flows inwards towards the center. Due to the Coriolis effect, this inward-moving air is deflected to its right, resulting in an anti-clockwise circulation pattern around the low-pressure center.

(iv) Which one of the following is the source region for the formation of air masses?

(a) the Equatorial forest

(b) the Himalayas

(d) the Deccan Plateau

Solution: The correct answer is (c) the Siberian Plain. Air masses form over large, homogeneous areas with stable atmospheric conditions, known as source regions. The Siberian Plain, with its vast, flat, and cold expanse, is an ideal source region for the formation of cold, dry continental polar air masses.

2. Answer the following questions in about 30 words.

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?

Solution: Atmospheric pressure is measured in units of millibars (mb). Pressure measured at station level is reduced to sea level on weather maps to eliminate the effect of altitude. This standardization allows for accurate comparison of pressure conditions across different locations, regardless of their elevation.

(ii) 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.

Solution: Although the pressure gradient force in the tropics of the Northern Hemisphere directs winds from north (subtropical high) to south (equator), the Earth's rotation introduces the Coriolis force. This force deflects moving air to the right in the Northern Hemisphere. Consequently, the winds are deflected from their initial path and become north-easterlies, blowing from the northeast towards the southwest.

(iii) What are the geotrophic winds?

Solution: Geostrophic winds are theoretical winds that result from a perfect balance between the pressure gradient force and the Coriolis force. In this state, the wind blows parallel to the isobars (lines of equal pressure) at a constant speed, without any acceleration.

(iv) Explain the land and sea breezes.

Solution: Sea breezes occur during the day when land heats up faster than the sea. This causes air over the land to rise, creating lower pressure. Cooler air from the sea then flows inland to replace it. Land breezes occur at night when the land cools faster than the sea. The air over the sea is now warmer, creating lower pressure there, and air flows from the cooler land towards the sea.

3. Answer the following questions in about 150 words

(i) Discuss the factors affecting the speed and direction of wind.

Solution: The speed and direction of wind are primarily influenced by three main forces: the pressure gradient force, the Coriolis force, and friction. The pressure gradient force is the initial force that causes air to move from an area of high pressure to an area of low pressure. The greater the pressure difference over a given distance, the stronger this force and the higher the wind speed. The Coriolis force, due to the Earth's rotation, deflects winds to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This force affects the direction of the wind, causing it to curve. Friction, particularly near the Earth's surface, opposes wind motion and reduces its speed, especially in rough terrain. In the upper atmosphere, where friction is minimal, winds tend to blow more parallel to isobars (geostrophic winds). Near the surface, friction causes winds to blow at a lower speed and at an angle across the isobars towards the low-pressure area.

Common mistakes

Confusing the direction of wind around low-pressure systems in different hemispheres.
Not fully understanding the role of the Coriolis force in deflecting winds.
Incomplete explanation of why pressure is reduced to sea level for weather maps.
Failing to explain both the daytime (sea breeze) and nighttime (land breeze) conditions accurately.

Revision tips

Focus on understanding the interplay between pressure gradient force and Coriolis force for wind movement.
Draw diagrams to visualize the formation of land and sea breezes.
Memorize the units of pressure and the standard sea-level pressure value.
Review the definition and conditions for geostrophic winds.
Pay attention to the specific deflection of winds in the Northern Hemisphere as mentioned in the solutions.

Practice MCQs

Q1. What is the approximate air pressure at 1 km above the surface if the surface pressure is 1,000 mb?

Q2. Where is the Inter Tropical Convergence Zone (ITCZ) normally located?

Q3. What is the direction of wind circulation around a low-pressure system in the Northern Hemisphere?

Q4. Which of the following regions is a common source region for the formation of air masses?

Q5. What unit is commonly used to measure atmospheric pressure?

Frequently asked questions

What is atmospheric pressure and how is it measured?

Atmospheric pressure is the force exerted by the weight of the atmosphere above a given point. It is commonly measured in units called millibars (mb).

Why is atmospheric pressure reduced to sea level for weather maps?

Pressure measured at a station is reduced to sea level to eliminate the effect of altitude. This allows for accurate comparison of pressure conditions across different locations, regardless of their elevation.

What is the Coriolis force and how does it affect winds?

The Coriolis force is an apparent force caused by the Earth's rotation. It deflects winds to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, influencing their direction.

What are geostrophic winds?

Geostrophic winds are theoretical winds that occur when the pressure gradient force is exactly balanced by the Coriolis force. They blow parallel to the isobars.

How do land and sea breezes form?

Sea breezes form during the day when land heats up faster than the sea, causing air to flow from the cooler sea to the warmer land. Land breezes form at night when the land cools faster than the sea, and air flows from the land to the sea.

What factors influence the speed and direction of wind?

The speed and direction of wind are influenced by the pressure gradient force, the Coriolis force, friction, and local factors like topography.

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