RAS question
Cold waves in India are caused by:
Correct answer: (D) Outflow of cold air from Central Asia and western disturbances.
Cold waves in India are mainly caused by the inflow of cold, dry air from Central Asian and Siberian anticyclones into the Indo-Gangetic plains, with western disturbances often intensifying the cold conditions.
Explanation
Cold waves in India are a winter phenomenon, mainly during December to February, when very cold, dry air from Central Asian and Siberian anticyclones reaches the Indo-Gangetic plains. The IMD monograph frames the same mechanism in operational terms: cold waves usually occur when cold air from higher or northern latitudes is transported into northwestern India, often along with eastward-moving westerly disturbances. Western disturbances matter because their upper-air troughs can carry a pool of cold air; after their passage, cold and dry air can flow into northwest and central India, triggering or intensifying a cold wave. For plains, the IMD criterion is minimum temperature at or below 10°C with a departure of at least -4.5°C from normal; severe cold wave begins at -6.5°C departure.
Why the other options are wrong
- (A) Volcanic eruptions are not the regular synoptic cause of Indian cold waves; they are caused by cold-air inflow and western disturbances.
- (B) Deforestation may affect local climate in other contexts, but it is not the direct winter-weather mechanism that produces cold waves over north and central India.
- (C) El Nino is not the direct cause asked here; cold-air outflow from Central Asia and Siberia, strengthened by western disturbances, causes Indian cold waves.
Concept
This tests the Indian climatology portion of Geography: winter weather systems, western disturbances and regional temperature extremes. It recurs in RAS because cold waves directly affect Rajasthan and other north Indian states, making the mechanism and IMD criteria exam-relevant.