Q. Westerlies in southern hemisphere are stronger and persistent than in northern hemisphere. Why?
- Southern hemisphere has less landmass as compared to northern hemisphere.
- Coriolis force is higher in southern hemisphere as compared to northern hemisphere.
Which of the statements given above is/are correct? (UPSC Prelims 2011)
Answer:
1 only
Notes: The correct answer is
1 only. The Westerlies are the prevailing winds that blow from the high-pressure area in the horse latitudes (30 to 35 degrees) toward the poles. While they exist in both hemispheres, they are famously more powerful and consistent in the South.
- Landmass and Friction (Statement 1 is Correct): The Northern Hemisphere is "land-heavy," containing large continents with mountain ranges, forests, and urban centers. These physical features act as barriers and create friction, which breaks up the wind flow and slows it down. In contrast, the Southern Hemisphere is dominated by vast, open oceans. With very little land to obstruct them, the Westerlies can build up incredible speed and remain remarkably persistent. This is why sailors refer to these latitudes as the "Roaring Forties," "Furious Fifties," and "Shrieking Sixties."
- Coriolis Force (Statement 2 is Incorrect): The Coriolis force is a result of the Earth's rotation. Its strength depends entirely on the latitude and the velocity of the moving object (the wind). It is not inherently "higher" in one hemisphere over the other at the same latitude. At 40 degrees North and 40 degrees South, the Coriolis parameter is identical in magnitude (though it deflects wind in opposite directions).