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Q66 (IAS/2015) Geography › World Physical Geography › Atmospheric pressure winds Official Key

Consider the following statements : 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?

Result
Your answer: —  ·  Correct: B
Explanation

**Statement 1 is incorrect.** Westerlies are prevailing winds that blow from the west at midlatitudes.[1] The statement claims westerlies blow between 30° N and 60° S, which is geographically impossible as it spans both hemispheres. Westerlies typically blow between approximately 30° and 60° latitude in *each* hemisphere (30°-60° N and 30°-60° S separately), not across hemispheres.

**Statement 2 is correct.** In north-western region of the subcontinent, winter precipitation is caused by the depressions that are associated with the westerly disturbances moving out from the Mediterranean Sea.[2] The western disturbances are the low pressure depressions which originate from the Mediterranean Sea and enter India after crossing Turkey, Syria, Iraq, Iran, Afghanistan and Pakistan. The jet streams plays an important role in bringing the western disturbances to India.[3] These disturbances are indeed part of the westerly wind system that brings winter rainfall to northwestern India.

Therefore, only statement 2 is correct, making option B the right answer.

Sources
  1. [1] https://education.nationalgeographic.org/resource/wind/
  2. [2] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 4: Climate of India > 1. The Cold Weather Season > p. 18
  3. [3] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 8: Natural Hazards and Disaster Management > Western Disturbances > p. 52
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PROVENANCE & STUDY PATTERN
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Don’t just practise – reverse-engineer the question. This panel shows where this PYQ came from (books / web), how the examiner broke it into hidden statements, and which nearby micro-concepts you were supposed to learn from it. Treat it like an autopsy of the question: what might have triggered it, which exact lines in the book matter, and what linked ideas you should carry forward to future questions.
Q. Consider the following statements : 1. The winds which blow between 30° N and 60° S latitudes throughout the year are known as westerlie…
At a glance
Origin: Books + Current Affairs Fairness: Moderate fairness Books / CA: 5/10 · 5/10

Statement 1 is a classic 'Coordinate Trap'—the numbers (30, 60) are correct, but the span (N to S) implies a wind blowing across the Equator, which defies physics (Trade Winds exist there). Statement 2 is a direct lift from NCERT Class XI (Indian Physical Environment). Strategy: Visualize the globe, don't just read the text.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
Do westerlies refer to the prevailing winds that blow between 30° N and 60° S latitudes throughout the year?
Origin: Web / Current Affairs Fairness: CA heavy Web-answerable

Web source
Presence: 5/5
"Westerlies are prevailing winds that blow from the west at midlatitudes."
Why this source?
  • Defines westerlies as prevailing winds that blow from the west at midlatitudes, indicating a latitude-band location rather than a single hemisphere-spanning band.
  • Implies westerlies occupy the midlatitude zones (between horse latitudes and polar easterlies), not specifically a continuous band from 30° N to 60° S.
Web source
Presence: 4/5
"Horse latitudes are about 30 and 35 degrees north and south."
Why this source?
  • Gives the approximate latitude of the horse latitudes (~30–35° N and S), which serve as the equatorward boundary for midlatitude wind zones.
  • Shows westerlies lie poleward of roughly 30° (not extending as a single band from 30° N across the equator to 60° S).
Web source
Presence: 3/5
"The Falklands have a cold maritime climate with strong westerly winds."
Why this source?
  • Provides an example of strong westerly winds affecting the Falkland Islands (a Southern Hemisphere midlatitude location), supporting that westerlies occur in midlatitudes of both hemispheres.
  • Implies westerlies are characteristic of midlatitude regions (e.g., around 50°S), not a continuous 30°N–60°S band throughout the year.

Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Primary winds or Prevailing Winds or Planetary Winds > p. 318
Strength: 5/5
“• The winds blowing almost in the same direction throughout the year are called prevailing or permanent winds. These are also called invariable or planetary winds because they involve larger areas of the globe. The two most significant winds for climate and human activities are trade winds and westerly winds.”
Why relevant

Defines 'prevailing winds' as winds that blow almost in the same direction throughout the year and explicitly lists westerly winds as one of the major prevailing/planetary winds.

How to extend

A student can combine this with latitude bands for 'prevailing' cells (e.g., Ferrel cell) to judge whether westerlies should be year-round in a given latitude band.

Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Ferrel Cell > p. 317
Strength: 5/5
“• In the middle latitudes, the circulation is that of sinking cold air that comes from the poles and the rising warm air that blows from the subtropical high. At the surface, these winds are called westerlies, and the cell is known as the Ferrel cell.”
Why relevant

Links westerlies to the Ferrel cell and places them in the 'middle latitudes' (the circulation between subtropical highs and polar lows).

How to extend

Knowing Ferrel cell occupies mid-latitudes, a student can map the Ferrel cell approximate limits against 30°–60° to assess the statement's latitudinal claim.

Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > The Westerlies > p. 319
Strength: 4/5
“• The westerlies are the winds blowing from the sub-tropical high-pressure belts towards the sub-polar low-pressure belts. They blow from southwest to northeast in the northern hemisphere and northwest to southeast in the southern hemisphere. They produce wet spells and variability in weather.• The westerlies are best developed between 40° and 65° S latitudes. These latitudes are often called Roaring Forties, Furious Fifties, and Shrieking Sixties – dreaded terms for sailors. The poleward boundary of the westerlies is highly fluctuating.• 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.”
Why relevant

Gives a best-developed latitude range for southern hemisphere westerlies (40°–65° S) and notes the poleward boundary is highly fluctuating; contrasts stronger southern vs irregular northern westerlies.

How to extend

Using these ranges and the noted fluctuation, a student could question the uniform 30°–60° N/S band and year-round persistence implied by the statement.

Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 14: Climate > Pressure and Planetary Winds > p. 140
Strength: 5/5
“They are more variable in the northern hemisphere, but they play a valuable role in carrying warm equatorial waters and winds to western coasts of temperate lands. weather is damp and cloudy and the seas are violent and stormy. It is thus usual for seafarers to refer to the Westerlies as the Roaring Forties, Furious Fifties and Shrieking or Stormy Sixties, according to the varying degree of storminess in the latitudes in which they blow. It must be pointed out that not all the western coasts of the temperate zone receive Westerlies throughout the year. Some of them, like California, Iberia, central Chile, southern Africa and southwestern Australia, receive Westerlies only in winter.”
Why relevant

States that not all western coasts of the temperate zone receive Westerlies throughout the year, and gives examples where westerlies are seasonal.

How to extend

A student could use these examples to infer that westerlies are not uniformly year-round everywhere within a broad latitude belt, challenging the 'throughout the year' claim.

Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Upper Tropospheric Westerlies > p. 385
Strength: 3/5
“So, at the surface the winds flow from the pole towards the equator whereas at an altitude the winds flow from the equator towards poles). The high-pressure gradient force is directed from south to north. • Anything moving from tropics towards poles deflects towards their right in the northern hemisphere and towards their left in the southern hemisphere due to the Coriolis effect. Thus, jet streams flow from west to east in both the hemispheres and hence they are called westerlies or upper-level westerlies.”
Why relevant

Explains that upper-level jet streams are 'westerlies' flowing west to east in both hemispheres, indicating a vertical/altitude component and hemispheric symmetry.

How to extend

A student might combine surface vs upper-level distinctions with latitude info to test whether the term 'westerlies' uniformly applies at surface across the stated band year-round.

Statement 2
Are the moist air masses (western disturbances) that cause winter rains in the North-Western region of India part of the westerlies?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 4: Climate of India > 1. The Cold Weather Season > p. 18
Presence: 5/5
“In north-western region of the subcontinent, winter precipitation is caused by the depressions that are associated with the westerly disturbances moving out from the Mediterranean Sea (Fig. 4.14A). The cold weather precipitation, though small, is highly beneficial to Rabi crops. Besides, snowfall from the western disturbances feed the glaciers of the Western Himalayas.”
Why this source?
  • Explicitly identifies winter precipitation in NW India as caused by depressions associated with 'westerly disturbances'.
  • States these disturbances move out from the Mediterranean Sea toward India, linking their origin and path to mid-latitude westerly systems.
CONTEMPORARY INDIA-I ,Geography, Class IX . NCERT(Revised ed 2025) > Chapter 4: Climate > The Cold Weather Season (Winter) > p. 28
Presence: 5/5
“Some amount of rainfall occurs on the Tamil Nadu coast from these winds as, here they blow from sea to land. In the northern part of the country, a feeble high-pressure region develops, with light winds moving outwards from this area. Influenced by the relief, these winds blow through the Ganga valley from the west and the northwest. The weather is normally marked by clear sky, low temperatures and low humidity and feeble, variable winds. A characteristic feature of the cold weather season over the northern plains is the inflow of cyclonic disturbances from the west and the northwest. These low-pressure systems, originate over the Mediterranean Sea and western Asia and move into India, along with the westerly flow.”
Why this source?
  • Describes the low-pressure systems (western disturbances) originating over the Mediterranean/western Asia and moving into India 'along with the westerly flow'.
  • Directly connects these depressions' movement into India with the westerly circulation.
Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 8: Natural Hazards and Disaster Management > Western Disturbances > p. 52
Presence: 5/5
“Te western disturbances are the low pressure depressions which originate from the Mediterranean Sea and enter India after crossing Turkey, Syria, Iraq, Iran, Afghanistan and Pakistan. Te jet streams plays an important role in bringing the western disturbances to India. Teir frequency is high between November and May. Te average frequency of these western disturbances is 2 in November and May, and 4 or 5 from December to April. Tese disturbances result in light rains that are benefcial to Rabi crops. Te human efciency also increases at the arrival of western disturbances. In winter months, the disturbances are also followed by cold waves over northern and central India.”
Why this source?
  • Defines western disturbances as low-pressure depressions originating in the Mediterranean and notes the jet stream's role in bringing them to India.
  • Links these disturbances to light winter rains beneficial to Rabi crops, reinforcing their climatic impact as part of the westerly-related systems.
Pattern takeaway: UPSC frequently tests 'Coordinate Blindness'. They provide familiar numbers (30, 60) but scramble the hemispheres or directions to trap speed-readers. Always verify the spatial span on a mental map.
How you should have studied
  1. [THE VERDICT]: Mixed Bag. Statement 1 is a 'Geography Logic Trap' (GC Leong Ch 14). Statement 2 is a 'Sitter' (NCERT Class XI, Ch 4).
  2. [THE CONCEPTUAL TRIGGER]: Planetary Wind Systems (General Geography) intersecting with Indian Climate (Winter Season).
  3. [THE HORIZONTAL EXPANSION]: Memorize the specific belts: Doldrums (5°N-5°S), Trade Winds (5°-30°), Horse Latitudes (30°-35°), Westerlies (35°-60°), Polar Easterlies (65°-90°). Also, link 'Western Disturbances' to the Subtropical Westerly Jet Stream (STWJ).
  4. [THE STRATEGIC METACOGNITION]: When you see coordinates like '30° N to 60° S', pause and draw a mental line. Does one wind system cover the Northern Hemisphere, Equator, and Southern Hemisphere? Impossible due to Coriolis force and pressure belts. This was a test of visualization, not just definition.
Concept hooks from this question
📌 Adjacent topic to master
S1
👉 Westerlies as prevailing (planetary) winds and the Ferrel cell
💡 The insight

References identify westerlies as one of the major prevailing/planetary winds and associate them with mid‑latitude (Ferrel) circulation.

High-yield for UPSC geography: questions often ask definitions of planetary wind systems and their relation to atmospheric cells. Mastering this links to pressure belts, mid‑latitude climate, and jet stream dynamics; learn definitions and Ferrel cell mechanics with diagrammatic revision.

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Primary winds or Prevailing Winds or Planetary Winds > p. 318
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Ferrel Cell > p. 317
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Upper Tropospheric Westerlies > p. 385
🔗 Anchor: "Do westerlies refer to the prevailing winds that blow between 30° N and 60° S la..."
📌 Adjacent topic to master
S1
👉 Latitudinal distribution and Southern Hemisphere intensity (Roaring Forties etc.)
💡 The insight

Evidence highlights the westerlies' prominent band (e.g., 40°–65° S) and the nomenclature Roaring Forties/Furious Fifties used for southern latitudes.

Frequently tested: UPSC often asks latitude ranges and hemisphere contrasts. Knowing the typical latitudinal bands and stronger southern persistence helps eliminate wrong options in MCQs and supports answers on oceanic/storm patterns; memorise ranges from sources and note exceptions.

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > The Westerlies > p. 319
  • Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 14: Climate > Pressure and Planetary Winds > p. 140
🔗 Anchor: "Do westerlies refer to the prevailing winds that blow between 30° N and 60° S la..."
📌 Adjacent topic to master
S1
👉 Seasonal and regional variability of westerlies
💡 The insight

References show westerlies vary by hemisphere and region (southern stronger/persistent, northern more irregular) and that some coasts receive westerlies only seasonally (e.g., winter).

Important for applied questions on regional climates, coastal rainfall and cyclone behaviour. UPSC may ask about seasonal influence on western coasts or interaction with tropical cyclones; study regional examples and seasonal shifts rather than assuming year‑round uniformity.

📚 Reading List :
  • Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 14: Climate > Pressure and Planetary Winds > p. 140
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > The Westerlies > p. 319
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 26: Tropical Cyclones > 26.4. Path of Tropical Cyclones > p. 371
🔗 Anchor: "Do westerlies refer to the prevailing winds that blow between 30° N and 60° S la..."
📌 Adjacent topic to master
S2
👉 Western disturbances: origin, path and impacts
💡 The insight

The references repeatedly identify western disturbances as temperate depressions originating over the Mediterranean and causing NW India's winter rains.

High-yield for climate questions: explains a major source of winter precipitation in India and links to agriculture (Rabi crops) and Himalayan snowfall. Master by mapping origin → path → surface impacts and practising linked MCQs and diagram-based questions.

📚 Reading List :
  • Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 4: Climate of India > 1. The Cold Weather Season > p. 18
  • Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 8: Natural Hazards and Disaster Management > Western Disturbances > p. 52
🔗 Anchor: "Are the moist air masses (western disturbances) that cause winter rains in the N..."
📌 Adjacent topic to master
S2
👉 Westerly jet streams and steering of temperate cyclones
💡 The insight

Several references state that upper-air westerly jet streams steer these depressions into India.

Important for understanding dynamic causes of weather systems and seasonality; connects to atmospheric circulation, cyclone tracks and seasonal rainfall patterns. Learn by studying jet stream location/seasonal shifts and their effects on surface weather.

📚 Reading List :
  • Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 4: Climate of India > JET STREAM AND INDIAN MONSOON > p. 8
  • INDIA PHYSICAL ENVIRONMENT, Geography Class XI (NCERT 2025 ed.) > Chapter 4: Climate > Understanding the Monsoon > p. 33
🔗 Anchor: "Are the moist air masses (western disturbances) that cause winter rains in the N..."
📌 Adjacent topic to master
S2
👉 Middle-latitude westerly flow reaching northern India
💡 The insight

Evidence notes that the middle-latitude westerlies (westerly flow) extend southward and carry depressions into north India causing winter precipitation.

Useful for questions contrasting monsoon (tropical) systems with temperate westerlies; helps answer why NW India gets winter rains while most of India is dry. Prepare by comparing latitude-linked wind belts and their seasonal shifts.

📚 Reading List :
  • Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 4: Climate of India > 1. The Cold Weather Season > p. 17
  • CONTEMPORARY INDIA-I ,Geography, Class IX . NCERT(Revised ed 2025) > Chapter 4: Climate > The Cold Weather Season (Winter) > p. 28
🔗 Anchor: "Are the moist air masses (western disturbances) that cause winter rains in the N..."
🌑 The Hidden Trap

The 'Easterly Jet Stream'. While the Westerly Jet brings winter rain (Western Disturbances), the Tropical Easterly Jet (TEJ) is unique to the Asian Summer Monsoon and is crucial for the onset of the South-West Monsoon. UPSC loves contrasting these two jets.

⚡ Elimination Cheat Code

Apply the 'Equator Test'. Statement 1 says Westerlies blow from 30°N to 60°S. This range includes the Equator (0°). You know Trade Winds blow near the equator. Therefore, a single wind system cannot span this entire range. Statement 1 is physically impossible. Eliminate A and C immediately.

🔗 Mains Connection

Food Security & Economy: Western Disturbances are critical for India's 'Rabi' crop (Wheat). A failure of these westerlies leads to wheat inflation, linking physical geography directly to GS-3 Agriculture and Inflation dynamics.

✓ Thank you! We'll review this.

SIMILAR QUESTIONS

NDA-I · 2018 · Q27 Relevance score: 1.34

Consider the following statements : 1. The doldrums is a low pressure area around Equator where the prevailing winds are calm. 2. Chinook is a hot and dry wind that blows in winter and therefore raises the temperature in a short time. Which of the statements given above is/are correct?

CAPF · 2014 · Q7 Relevance score: 1.32

Statement I : Roaring Forties are strong Westerly winds found in the Southern Hemisphere, generally between the latitudes of 40° and 50° Statement I : The strong East to West air currents are caused by the combination of air being displaced from the Equator towards the South Pole and the Earth’s rotation and there are few landmasses to serve as wind breaks

IAS · 2007 · Q93 Relevance score: 1.29

Consider the following statements: 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?

NDA-I · 2018 · Q26 Relevance score: 0.76

Consider the following statements about Roaring Forties : 1. They are strong Westerly winds found in the oceans of Southern Hemisphere. 2. The strong east to west air cuirents are caused by the combination of air being displaced from the Equator towards the South Pole and the earth’s rotation and abundance of landmasses to serve as wind breaks. Which of the statements given above is/are correct ?