Western disturbances that bring winter rainfall to northern India originate from:
Correct answer: (D) Mediterranean Sea region.
Western disturbances that bring winter rainfall to northern India originate in the Mediterranean Sea region as extratropical cyclones.
Explanation
Western disturbances are extratropical cyclones that originate in the Mediterranean Sea region and then move eastwards towards the Indian subcontinent. The IMD source describes them as non-monsoonal systems driven by the westerlies, carrying moisture in the upper layers of the atmosphere. When such a system reaches the Himalayas or the Himalayan region, that moisture can be shed as rain or snow. This is why north-western India receives winter and early spring precipitation from western disturbances rather than from the summer monsoon. The rainfall is especially important for rabi crops such as wheat, which depend on cool-season moisture.
Why the other options are wrong
- (A) The Pacific Ocean is linked with ENSO influences, whereas western disturbances affecting India are extratropical systems originating to India's west.
- (B) The Bay of Bengal is associated with the northeast monsoon, not with the westerly, non-monsoonal systems called western disturbances.
- (C) The Arabian Sea supplies moisture to the southwest monsoon, but western disturbances are defined by their origin in the Mediterranean region.
Concept
This tests the Indian climatology concept of non-monsoonal winter rainfall. It recurs in RAS because western disturbances link atmospheric circulation, Himalayan precipitation and rabi agriculture in north-western India.