Previous Year Question
Consider the following statements:
The winds which blow between 30° N and 60° S latitudes throughout the year are known as westerlies.
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?
1 only
2 only
Both 1 and 2
Neither 1 nor 2
Correct Answer: B
Detailed Solution
Statement 1—Incorrect
The westerlies blow in the middle latitudes of both hemispheres:
In the Northern Hemisphere, approximately between 30° N and 60° N.
In the Southern Hemisphere, approximately between 30° S and 60° S.
They blow from the subtropical high-pressure belts towards the subpolar low-pressure belts.
Due to the Earth’s rotation, they are deflected towards the right in the Northern Hemisphere and towards the left in the Southern Hemisphere.
Their general movement is from west to east; hence, they are called the westerlies.
The statement places them between 30° N and 60° S. This range would also include the trade-wind belts of both hemispheres and the equatorial region. It is therefore not the correct latitudinal extent of the westerlies.
Statement 2—Correct
Winter precipitation in north-western India is primarily associated with Western Disturbances.
Western Disturbances are extratropical weather systems that travel from west to east with the mid-latitude westerly circulation.
They generally acquire moisture from the Mediterranean and West Asian regions and reach India through Iran, Afghanistan and Pakistan.
They produce snowfall over Jammu and Kashmir, Himachal Pradesh and Uttarakhand, and winter rainfall over Punjab, Haryana, Rajasthan, Delhi and western Uttar Pradesh.
This rainfall benefits rabi crops such as wheat, although excessive rain, hailstorms and strong winds can also damage crops.