Westerlies in the southern hemisphere are stronger and persistent than in the northern hemisphere. W

Q: What is UPSC Prelims?

UPSC Prelims is a competitive examination conducted in India. This question is from the 2011 UPSC Prelims Geography paper.

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To prepare for UPSC Prelims Geography, practice previous year questions (PYQs), understand concepts thoroughly, and solve mock tests regularly. This 2011 question covers Wind Systems, Pressure Belts & Jet Streams topic.

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This UPSC Prelims 2011 Geography question has a easy difficulty level and is marked as an important question.

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Question

Westerlies in the southern hemisphere are stronger and persistent than in the northern hemisphere. Why?Southern hemisphere has less landmass as compared to northern hemisphere.Coriolis force is higher in southern hemisphere as compared to northern hemisphereWhich of the statements given above is/are correct?

Accepted Answer

Correct Answer: A — 1 onlyStep-by-step Solution:The Westerlies (also called the Prevailing Westerlies or Roaring Forties/Furious Fifties/Screaming Sixties) are the dominant wind systems in the mid-latitudes (approximately 40°–60° latitude) of both hemispheres, blowing from west to east. However, they are significantly stronger and more consistent in the Southern Hemisphere — a fact well-known to sailors (these winds were critical in the Age of Sail for circumnavigating the globe).Statement 1 — Less landmass in the Southern Hemisphere: This is correct and is the PRIMARY reason for stronger Southern Hemisphere westerlies. The Southern Hemisphere between 40°S and 70°S is almost entirely ocean (the Southern Ocean) — there are virtually no landmasses to interrupt the wind flow. Land surfaces create much greater friction than ocean surfaces — they also create pressure variations (thermal highs and lows over continents) that disrupt the smooth, zonal wind flow. In the Northern Hemisphere, the westerlies at these latitudes must navigate over North America, Europe, and Asia — creating friction, disruption, and meanders (the Rossby waves/jet stream configurations). The unobstructed ocean in the Southern Hemisphere allows winds to blow freely and build up tremendous speed. ✓Statement 2 — Coriolis force is higher in Southern Hemisphere: This is incorrect. The Coriolis force at a given latitude is IDENTICAL in both hemispheres (it depends on latitude and Earth's angular velocity — the same in both hemispheres). At 45°S and 45°N, the Coriolis force magnitude is exactly the same; only its direction differs (rightward in Northern Hemisphere, leftward in Southern Hemisphere). Therefore, Coriolis force cannot explain the stronger westerlies in the Southern Hemisphere. ✗Key Concept: Southern Hemisphere westerlies: Called 'Roaring Forties' (40°–50°S), 'Furious Fifties' (50°–60°S), 'Screaming Sixties' (60°–70°S) — based on the intensity of winds; The unobstructed Southern Ocean allows these winds to encircle the globe completely — they are the strongest sustained winds on Earth; Important for: Sailing routes (clipper ships), ocean currents (Antarctic Circumpolar Current), climate patterns. The jet stream in the Northern Hemisphere is more variable and meandering due to land-ocean contrasts — causing more extreme weather variability.

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