UPSC Prelims 2015 · Question 66 of 98
UPSC Prelims 2015 question on Westerlies and Winter Rain
- ExamUPSC CSE
- Year2015
- PaperGeneral Studies Paper I
- SubjectGeography
- TopicClimatology
- DifficultyMedium
- TypeStatement
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?
Show answer
Answer: B. 2 only
Verdict
The answer is 2 only. Winter rain in north-western India does come from the westerlies, but the latitude range given in the first statement is wrong.
Analysis
Statement 2 is CORRECT. Western disturbances are extratropical storms originating over the Mediterranean and steered eastward by the westerlies, and they bring winter rain and snow to the north-western subcontinent, a non monsoonal precipitation pattern. Statement 1 is INCORRECT as written. The westerlies blow between roughly 30 and 60 degrees latitude in each hemisphere, so the correct description is between 30 and 60 degrees North and separately between 30 and 60 degrees South. The statement's mixed range from 30 degrees North to 60 degrees South is not the westerly belt.
Source
NCERT Class XI, India: Physical Environment, pages 35 to 36.
How to crack it
Read latitude ranges character by character, because a single swapped hemisphere letter is enough to falsify an otherwise textbook sentence, and it is easy to skim past. Then sanity check against the general circulation: planetary wind belts are symmetrical about the equator, so any belt described as running from a northern latitude to a southern one across the equator is suspect by construction. The physical model is your check on the printed number.