RAS question
Westerlies blow between which latitudes?
Correct answer: (B) 30-60 degrees.
Westerlies blow in the mid-latitude belt between 30 degrees and 60 degrees in both hemispheres.
Explanation
Westerlies occupy the circulation belt between the subtropical high-pressure zone near 30 degrees and the sub-polar low-pressure zone near 60 degrees. The cited Weather.gov training page explains that air linked with the 30 degrees high-pressure area becomes part of a circulation cell extending towards 60 degrees, and that this 60 degrees to 30 degrees cell produces the prevailing westerlies. Their name comes from their general west-to-east flow: in the Northern Hemisphere they blow from south-west to north-east, while in the Southern Hemisphere they blow from north-west to south-east. In temperate zones, these winds are also associated with rainfall along the western margins of continents.
Why the other options are wrong
- (A) 0-30 degrees belongs to the trade-wind belt, not the mid-latitude westerly belt.
- (C) 60-90 degrees is the polar-easterly zone, so it lies poleward of the westerlies.
- (D) 0-23.5 degrees marks the tropical zone, whereas westerlies are a temperate mid-latitude wind system.
Concept
This tests the global pressure belts and planetary wind system, especially the link between latitude, pressure belts and prevailing wind direction. It recurs in RAS because climate, rainfall distribution and temperate western-margin climates depend on these wind belts.