NCERT Class 11 Geography Chapter 9 : ATMOSPHERIC CIRCULATION AND WEATHER SYSTEMS | Line-by-Line MCQs & Mains Questions for UPSC

Chapter Insights: Chapter -9- ATMOSPHERIC CIRCULATION AND WEATHER SYSTEMS

This chapter explains the dynamic forces that drive the Earth's weather and climate. It begins by defining atmospheric pressure—the weight of the air column above a point—and how its uneven horizontal distribution, depicted by isobars, creates the primary force for wind (Pressure Gradient Force).

The chapter details the major global pressure belts (Equatorial Low, Subtropical Highs, etc.) and their seasonal oscillations. The core of atmospheric motion is explained through the interplay of three key forces acting on wind: the Pressure Gradient Force, the Frictional Force, and the Coriolis Force (due to Earth's rotation).

This interaction leads to phenomena like the geostrophic wind (where pressure gradient and Coriolis forces balance) and distinct circulation patterns around highs (anticyclonic) and lows (cyclonic).

The chapter elaborates on the General Circulation of the Atmosphere, comprising the Hadley, Ferrel, and Polar cells, which redistribute heat globally. This large-scale circulation interacts with oceans, influencing events like ENSO (El Niño-Southern Oscillation).

Finally, the chapter categorizes various weather systems. It explains local winds like land/sea breezes and mountain/valley winds, the formation and classification of air masses, and the weather disturbances at their boundaries called fronts.

It contrasts the formation, structure, and impact of massive storm systems: Extra-Tropical Cyclones (with clear frontal systems in mid-latitudes) and more intense Tropical Cyclones (driven by latent heat over warm oceans). It concludes with violent, localized storms such as thunderstorms and tornadoes.

Note on Coverage: These questions are developed through a line-by-line analysis of the textbook. This ensures that even the smaller details and nuanced concepts often overlooked are covered for comprehensive exam preparation.

Preparation Method

We recommend reading the NCERT chapter thoroughly before attempting these questions. The page numbers provided correspond to the actual textbook pages to help you locate the source material quickly.

Section A: Descriptive Questions

  1. What is atmospheric pressure? How is it defined and what is its average value at sea level? (Pg. 1) Page 76
  2. Describe the vertical variation of atmospheric pressure. What is the standard rate of decrease? (Pg. 1) Page 76
  3. What is represented by a low-pressure system and a high-pressure system on a weather map? (Pg. 2) Page 77
  4. Name and describe the major pressure belts of the world. Are they permanent? (Pg. 2-3) Page 77-78
  5. Explain the Pressure Gradient Force. When is it strong or weak? (Pg. 3) Page 78
  6. Explain how the Coriolis force affects wind direction in both hemispheres. Why are tropical cyclones not formed near the equator? (Pg. 3-4) Page 78-79
  7. Using Table 9.2, describe the pattern of wind direction in cyclones and anticyclones in both hemispheres. (Pg. 4) Page 79
  8. Describe the Hadley cell circulation in the tropics. (Pg. 5) Page 80
  9. What are land and sea breezes? Explain their formation. (Pg. 6) Page 81
  10. What is an air mass? Name the five major source regions and the corresponding air mass types. (Pg. 6) Page 81
  11. What are extra-tropical cyclones? Describe their formation and characteristics. (Pg. 7) Page 82
  12. List the conditions favourable for the formation and intensification of tropical cyclones. (Pg. 8) Page 83
  13. Describe the structure of a mature tropical cyclone, including the eye and eye wall. (Pg. 8) Page 83

Section B1: Multiple Choice Questions

Page 76

What is the primary cause of air motion (wind)? (Pg. 1)

A) Variation in temperatureB) Variation in atmospheric pressureC) Rotation of the EarthD) Frictional force
View Answer
Answer: B
Source Reference: Page 76
Page 76

What is the approximate decrease in pressure for every 10m increase in elevation in the lower atmosphere? (Pg. 1)

A) 0.1 mbB) 1 mbC) 10 mbD) 100 mb
View Answer
Answer: B
Source Reference: Page 76
Page 77

Near the equator, the sea level pressure zone is known as: (Pg. 2)

A) Subtropical HighB) Subpolar LowC) Equatorial LowD) Polar High
View Answer
Answer: C
Source Reference: Page 77
Page 78

What is the combined effect that horizontal winds near the Earth's surface respond to? (Pg. 3)

A) Pressure gradient and Coriolis forceB) Pressure gradient, frictional and Coriolis forceC) Gravitational and Coriolis forceD) Pressure gradient and gravitational force
View Answer
Answer: B
Source Reference: Page 78
Page 78

The frictional force affecting wind speed is greatest: (Pg. 3)

A) In the upper atmosphereB) At the surfaceC) Over the seaD) At the poles
View Answer
Answer: B
Source Reference: Page 78
Page 79

When isobars are straight and friction is absent, the wind blowing parallel to the isobars is called: (Pg. 4)

A) Valley breezeB) Geostrophic windC) Trade windD) Katabatic wind
View Answer
Answer: B
Source Reference: Page 79
Page 79

Over a low-pressure area at the surface, the air generally: (Pg. 4)

A) Diverges and sinksB) Converges and risesC) Remains stationaryD) Moves parallel to isobars
View Answer
Answer: B
Source Reference: Page 79
Page 80

The combined phenomenon of Southern Oscillation and El Nino is known as: (Pg. 5)

A) ITCZB) ENSOC) Ferrel CellD) Katabatic Wind
View Answer
Answer: B
Source Reference: Page 80
Page 81

During the day, the wind blows from: (Pg. 6)

A) Land to sea (Land breeze)B) Sea to land (Sea breeze)C) Valley to mountainD) Mountain to valley
View Answer
Answer: B
Source Reference: Page 81
Page 81

Which of the following is a warm air mass? (Pg. 6)

A) Continental Polar (cP)B) Maritime Polar (mP)C) Maritime Tropical (mT)D) Continental Arctic (cA)
View Answer
Answer: C
Source Reference: Page 81
Page 82-83

Extra-tropical cyclones have a clear: (Pg. 7-8)

A) Eye wallB) Frontal systemC) Calm centreD) Uniform temperature
View Answer
Answer: B
Source Reference: Page 82-83
Page 83

What is the calm centre of a mature tropical cyclone called? (Pg. 8)

A) Eye wallB) VortexC) EyeD) Core
View Answer
Answer: C
Source Reference: Page 83
Page 84

Thunderstorms are caused by: (Pg. 9)

A) Intense convectionB) Coriolis forceC) Frontal upliftD) Divergence in upper air
View Answer
Answer: A
Source Reference: Page 84
Page 84

(Exercise) If the surface air pressure is 1,000 mb, the air pressure at 1 km above the surface will be: (Pg. 9)

A) 700 mbB) 1100 mbC) 900 mbD) 1300 mb
View Answer
Answer: C
Source Reference: Page 84
Page 84

(Exercise) The Inter Tropical Convergence Zone normally occurs: (Pg. 9)

A) near the EquatorB) near the Tropic of CancerC) near the Tropic of CapricornD) near the Arctic Circle
View Answer
Answer: A
Source Reference: Page 84
Page 84

(Exercise) The direction of wind around a low pressure in northern hemisphere is: (Pg. 9)

A) clockwiseB) perpendicular to isobarsC) anti-clockwiseD) parallel to isobars
View Answer
Answer: C
Source Reference: Page 84
Page 84

(Exercise) Which one is the source region for the formation of air masses? (Pg. 9)

A) the Equatorial forestB) the HimalayasC) the Siberian PlainD) the Deccan Plateau
View Answer
Answer: C
Source Reference: Page 84

Section B2: One-Word / Factual Check

The instrument used to measure air pressure is a ______. (Pg. 1) Page 76

Show Answer
barometer (Reference: Page 76)

Lines connecting places having equal pressure are called ______. (Pg. 2) Page 77

Show Answer
isobars (Reference: Page 77)

The high-pressure areas found along 30° N and 30° S are called ______ highs. (Pg. 2) Page 77

Show Answer
subtropical (Reference: Page 77)

The force exerted by the rotation of the Earth which affects wind direction is the ______ force. (Pg. 3) Page 78

Show Answer
Coriolis (Reference: Page 78)

The Coriolis force is maximum at the ______ and absent at the equator. (Pg. 3-4) Page 78-79

Show Answer
poles (Reference: Page 78-79)

The wind circulation around a low-pressure area is called ______ circulation. (Pg. 4) Page 79

Show Answer
cyclonic (Reference: Page 79)

The pattern of the movement of the planetary winds is called the ______ of the atmosphere. (Pg. 4) Page 79

Show Answer
general circulation (Reference: Page 79)

The easterlies from either side of the equator converge in the ______. (Pg. 5) Page 80

Show Answer
Inter Tropical Convergence Zone (ITCZ) (Reference: Page 80)

The cool air draining from high plateaus into valleys is called ______ wind. (Pg. 6) Page 81

Show Answer
katabatic (Reference: Page 81)

The boundary zone where two different air masses meet is called a ______. (Pg. 6) Page 81

Show Answer
front (Reference: Page 81)

Extra-tropical cyclones generally move from ______ to east. (Pg. 8) Page 83

Show Answer
west (Reference: Page 83)

Tropical cyclones in the Indian Ocean are known as ______. (Pg. 8) Page 83

Show Answer
cyclones (Reference: Page 83)

A tornado over the sea is called a ______. (Pg. 9) Page 84

Show Answer
water spout (Reference: Page 84)

(Exercise) The pressure is measured in units of ______. (Pg. 9) Page 84

Show Answer
millibar (Reference: Page 84)

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