UPSC CIVIL SERVICES EXAMINATION

PRELIMS SPECIAL

1995 - 2018

PREVIOUS YEAR QUESTIONS

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Climatology

(Pressure Belts & Wind System)

CHAPTER LISTING

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Unit Chapter

World Geography

Physical Geography

Geomorphology

Climatology

Oceanography

Biogeography

Social Geography

Economic Geography

Indian Geography

Physical Geography

Basics of India

Physical features

River systems

Climate

Agriculture

Vegetation and Fauna

Social Geography

Economic Geography

L4

L1 – L3

CHAPTER LISTING

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L4

Chapter Topics

Climatology

Atmosphere

Temperaure & Insolation

Pressure Belts & Wind Systems

Humidity & Precipitation

Cyclones & Anti Cyclones

Major Climatic Types

Q 44-53

Q. Consider the following statements: [2007]

1. Either of the two belts over the oceans at about 30° to 35° N and S Latitudes is known as Horse

latitude.

2. Horse latitudes are low pressure belts.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

QUESTION 44

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QUESTION 44

• The weight of a column of air contained ina unit area from the mean sea level to thetop of the atmosphere is called theatmospheric pressure.

• It is measured by means of an instrumentcalled barometer. The units used bymeteorologists for this purpose arecalled millibars (mb).

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The Atmospheric Pressure

QUESTION 44

• Run in East – West direction along certainspecific latitudes

• Total seven pressure belts.• Thermally induced belts:

Equatorial low North Polar high South Polar High

• Dynamically induced belts: Sub-Tropical high (north) Sub-Tropical High (south) Sub-Polar Low (north) Sub-Polar Low (south)

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Pressure Belts

QUESTION 44

• Due to intense heating, air gets warmed up and risesover the equatorial region (convection).

• Whenever there is vertically upward movement ofair, the region at the surface will be at low pressure.Thus the belt along the equator is called equatoriallow pressure belt.

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Equatorial Low Pressure Belt

Formation

• This belt is characterized by extremely low pressure with calm conditions.• As the larger part of the low pressure belt passes along the oceans, the winds obtain huge amount of

moisture.• Vertical winds (convection) carrying moisture form cumulonimbus clouds and lead to thunderstorms

(convectional rainfall).• Inspite of high temperatures, cyclones are not formed at the equator because of ‘zero’ Coriolis force.

Climate

QUESTION 44

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QUESTION 44

• The air moving away from equatorial low pressure belt in the upper troposphere becomes dry and cold.This dry and cold wind subsides at 30°N and S.

• So the high pressure along this belt is due to subsidence of air coming from the equatorial region whichdescends after becoming heavy.

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Subtropical High Pressure Belt

Formation

• The subsiding air is warm and dry, therefore, most of the deserts are present along this belt, in bothhemispheres.

• A calm condition (anticyclonic) with feeble winds is created in this high pressure belt.• The descending air currents feed the winds blowing towards adjoining low pressure belts.• This belt is frequently invaded by tropical and extra-tropical disturbances.

Climate

QUESTION 44

• They lie around poles between 80 – 90° N and S latitudes.• Extremely cold temperatures at the poles result in high pressure at the surface and cold air from the

upper atmosphere subsides

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Polar High Pressure Belt

Formation

• The lowest temperatures are found over the poles.• There is very little moisture in the air. Polar air is as dry as the air over driest deserts.

Climate

QUESTION 44

• Located between 45°N and S latitudes and the Arctic and the Antarctic circles (66.5° N and S latitudes).• These are dynamically produced due to Coriolis Force produced by rotation of the earth on its axis, and

ascent of air as a result of convergence of winds coming from polar and sub tropical high.• Owning to low temperatures in these latitudes the sub polar low pressure belts are not very well

pronounced year long. Such belts in the southern hemisphere are not as well differentiated.• On long-term mean climatic maps, the sub polar low-pressure belts of the northern hemisphere are

grouped into two centers of atmospheric activity: the Iceland low and the Aleutian depression (Aleutianlow).

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Subpolar Low Pressure Belt

Formation

• The area of contrast between cold and warm air masses produces polar jet streams which encircles theearth at 60 degrees latitudes and is focused in these low pressure areas.

• Due to a great contrast between the temperatures of the winds from sub-tropical and polar sourceregions, extra tropical cyclonic storms or lows’ (temperate cyclones or frontal cyclones) are produced inthis region.

Climate

QUESTION 44

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Q. Consider the following statements: [2007]

1. Either of the two belts over the oceans at about 30° to 35° N and S Latitudes is known as Horse

latitude.

2. Horse latitudes are low pressure belts.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: a

QUESTION 44

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Q. Consider the following statements. [2015 - I]

1. The winds which blow between 30° N and 60° S latitudes throughout the year are known as

westerlies.

2. The moist air masses that cause winter rains in North-Western region of India are part of westerlies.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

QUESTION 45

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QUESTION 45

• Winds blow in the same directionthroughout the year covering the wholeglobe.

• These flow from high pressure belts to lowpressure belts.

• They are classified into: The Trade Winds The Westerlies The Polar Easterlies

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Planetary Winds

Formation

QUESTION 45

• These blow from the sub-tropical high pressure areas towards the equatorial low pressure belt, confinedto a region between 30°N and 30°S throughout the earth’s surface.

• They flow as the north-eastern trades in the northern hemisphere and the south-eastern trades in thesouthern hemisphere.

• The trade winds from two hemispheres meet at the equator, and due to convergence they rise and causeheavy rainfall.

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Trade Winds (Tropical Easterlies)

• The westerlies are the winds blowing from the sub-tropical high pressure belts towards the sub polar lowpressure belts.

• They blow from southwest to north-east in the northern hemisphere and north-west to south-east in thesouthern hemisphere.

• The westerlies of the southern hemisphere are stronger and persistent due to the vast expanse of water,while those of the northern hemisphere are irregular because of uneven relief of vast land-masses.

• The westerlies are best developed between 40° and 65° S latitudes. These latitudes are oftencalled Roaring Forties, Furious Fifties, and Shrieking Sixties – dreaded terms for sailors.

Westerlies

QUESTION 45

• The Polar easterlies are dry, cold prevailing winds blowing from north-east to south-west direction inNorthern Hemisphere and south-east to north-west in Southern Hemisphere.

• They blow from the polar high-pressure areas of the sub-polar lows.• These winds give birth to cyclones when they come in contact with westerlies

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Polar Easterlies

Western Disturbance

Q. Consider the following statements. [2015 - I]

1. The winds which blow between 30° N and 60° S latitudes throughout the year are known as

westerlies.

2. The moist air masses that cause winter rains in North-Western region of India are part of westerlies.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: b

QUESTION 45

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Q. What causes wind to deflect toward left in the Southern Hemisphere? [2010]

(a) Temperature

(b) Magnetic field

(c) Rotation of the earth

(d) Pressure

Answer: c

QUESTION 46

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QUESTION 46

• Due to this effect, winds in the northern hemisphere getdeflected to the right of their path and those in the southernhemisphere to their left, following Farrell’s Law .

• This deflection force does not seem to exist until the air is setin motion and increases with wind velocity, air mass andan increase in latitude.

• The Coriolis force acts perpendicular to the pressure gradientforce (pressure gradient force is perpendicular to an isobar).

• The Coriolis force is directly proportional to the angle oflatitude. It is maximum at the poles and is absent at theequator.

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Coriolis Force

Q. Westerlies in southern hemisphere are stronger and persistent than in northern hemisphere.

Why ? [2011 - I]

1. Southern hemisphere has less landmass as compared to northern hemisphere.

2. Coriolis force is higher in southern hemisphere as compared to northern hemisphere.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: a

QUESTION 47

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Q. Consider the following statements about the 'Roaring Forties': [2000]

1. They blow uninterrupted in the northern and Southern Hemispheres

2. They blow with great strength and constancy

3. Their direction is generally from north-west to east in the Southern Hemisphere

4. Overcast skies, rain and raw weather are generally associated with them

Which of these statements are correct?

(a) 1, 2 and 3

(b) 2, 3 and 4

(c) 1, 3 and 4

(d) 1, 2 and 4

Answer: b

QUESTION 48

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Q. Assertion (A) : 60° - 65º latitudes in both the hemispheres have a low pressure belt instead of high

pressure.

Reason (R) : The low pressure areas are permanent over oceans rather than on land.

Select the correct code. [2002]

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is NOT a correct explanation of A

(c) A is true but R is false

(d) A is false but R is true

Answer: b

QUESTION 49

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Q. Assertion (A) : Areas near the equator receive rainfall throughout the year.

Reason (R) : High temperatures and high humidity cause convectional rain in most afternoons near

the equator.

In the context of the above two statements, which one of the following is correct? 1996]

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R true but R is not a correct explanation of A

(c) A is true but R is false

(d) A is false but R is true

Answer: a

QUESTION 50

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Q. Which one of the following weather conditions is indicated by a sudden fall in barometer

reading? [2001]

(a) Stormy

(b) Calm weather

(c) Cold and dry weather

(d) Hot and sunny weather

Answer: a

QUESTION 51

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QUESTION 51

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Q. Match List-I with List-II and select the correct answer using the codes given below the lists: [2001]

List-I (Local Wind) List-II (Region)

A. Fohn 1. Argentina

B. Sarmun 2. Kurdistan

C. Santa Ana 3. California

D. Zonda 4. Alps

Codes:

(a) A-2; B-4; C-1; D-3

(b) A-4; B-2; C-3; D-1

(c) A-2; B-4; C-3; D-1

(d) A-4; B-2; C-1; D-3

QUESTION 52

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QUESTION 52

• Local differences of temperature and pressure produce local winds.• Such winds are local in extent and are confined to the lowest levels of the troposphere.

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Local Winds

QUESTION 52

• Foehn like winds in USA and Canada move down the west slopes of the Rockies and are known as• It is beneficial to ranchers east of the Rockies as it keeps the grasslands clear of snow during much of

the winter.

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Chinook

• Foehn is a hot wind of local importance in the Alps. It is a strong, gusty, dry and warm wind whichdevelops on the leeward side of a mountain range. As the windward side takes away whatever moisturethere is in the incoming wind in the form of orographic precipitation, the air that descends on theleeward side is dry and warm.

• The temperature of the wind varies between 15°C and 20°C. The wind helps animal grazing by meltingsnow and aids the ripening of grapes.

Foehn or Fohn

Q. Match List-I with List-II and select the correct answer using the codes given below the lists: [2001]

List-I (Local Wind) List-II (Region)

A. Fohn 1. Argentina

B. Sarmun 2. Kurdistan

C. Santa Ana 3. California

D. Zonda 4. Alps

Codes:

(a) A-2; B-4; C-1; D-3

(b) A-4; B-2; C-3; D-1

(c) A-2; B-4; C-3; D-1

(d) A-4; B-2; C-1; D-3

Answer: b

QUESTION 52

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Q. Assertion (A) : Cyclones spin clockwise in the Northern Hemisphere and anti-clockwise in the Southern

Hemisphere.

Reason (R) : The directions of wind patterns in the Northern and the Southern Hemisphere are governed by the

Coriolis effect.

In the context of the above two statements, which one of the following is correct? [2005]

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is NOT a correct explanation of A

(c) A is true but R is false

(d) A is false but R is true

QUESTION 53

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QUESTION 52

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Q. Assertion (A) : Cyclones spin clockwise in the Northern Hemisphere and anti-clockwise in the Southern

Hemisphere.

Reason (R) : The directions of wind patterns in the Northern and the Southern Hemisphere are governed by the

Coriolis effect.

In the context of the above two statements, which one of the following is correct? [2005]

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is NOT a correct explanation of A

(c) A is true but R is false

(d) A is false but R is true

Answer: d

QUESTION 53

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