Prelims 2015 · archive
EasyConsider 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?
Answer & explanation
Answer: (b) 2 only
Westerlies are a mid-latitude wind belt in each hemisphere, roughly 30°–60° N and 30°–60° S. A belt running from 30° N to 60° S would cross the equator and the trade-wind zone, so statement 1 is wrong. The winter rain in north-west India comes from western disturbances. These travel in the westerly wind regime, so statement 2 is correct.
- ✗ 1. Westerlies occupy about 30°–60° in each hemisphere, that is 30° N–60° N and 30° S–60° S. The stated span of 30° N to 60° S would include the equatorial and trade-wind regions, where surface winds are not westerly.
- ✓ 2. Western disturbances are low-pressure troughs or weak temperate cyclones in the westerly wind regime. They originate over the Mediterranean region and move east. They bring winter rain to Punjab, Haryana, Delhi and western Uttar Pradesh. The amount is small, but it is highly beneficial for rabi crops.
Remember · Westerlies blow in mid-latitudes, about 30°–60° in both hemispheres. Western disturbances ride on them and bring winter rain to north-west India. This rain is good for rabi crops such as wheat.
📘 Read it in NCERT: Class 11 India: Physical Environment, Ch 4 (practise this chapter)
Sources
- NCERT Class 11 · India: Physical Environment, Chapter 4 “In northwestern India, some weak temperate cyclones from the Mediterranean sea cause rainfall in Punjab, Haryana, Delhi and western Uttar Pradesh. Although the amount is meagre, it is highly beneficial for rabi crops.”
- India Meteorological Department, Forecasting Manual: Western Disturbances ↗ “At present the term "western disturbance" is applied to low or trough either at surface or in upper air in the region of westerly wind regime (north of 20°N)”
- US National Weather Service (NOAA), Prevailing Winds ↗ “In the circulation cell that exists between 60° and 30° north, the movement of air produces the prevailing westerlies.”
Question: UPSC Civil Services (Preliminary) 2015, General Studies paper. Explanation: Minimalist IAS, checked 25 Oct 2026 (how we verify). ·