RAS question
Indian monsoon is primarily driven by:
Correct answer: (D) Differential heating of land and sea creating pressure gradient.
The Indian monsoon is primarily driven by differential heating of land and sea, which creates a pressure gradient between the heated subcontinent and the surrounding ocean.
Explanation
NCERT explains the core mechanism through the distribution of land and water: land heats and cools faster than the sea, so different air-pressure zones form around the Indian subcontinent in different seasons. In summer, the large landmass north of the Indian Ocean heats intensely, producing low pressure over the north-western subcontinent, while the ocean to the south remains relatively higher pressure because water heats slowly. This pressure contrast draws winds towards the subcontinent and sets the stage for the southwest monsoon. Monsoon formation is not limited to heating alone: the northward shift of the ITCZ, the Somali Jet and El Nino effects, Tibetan Plateau heating, and withdrawal of the subtropical jet also shape the monsoon. The primary driver remains the land-sea thermal contrast and resulting pressure gradient.
Why the other options are wrong
- (A) Volcanic activity is not a driver of the Indian monsoon mechanism in the NCERT account.
- (B) Ocean currents alone cannot explain the monsoon because the mechanism depends on contrasting heating of land and sea and the pressure gradient that follows.
- (C) Earth's revolution alone is too narrow because the monsoon is shaped by several atmospheric factors, with land-sea differential heating as the primary trigger.
Concept
The mechanism of the Indian monsoon belongs to Indian physical geography. It recurs in RAS because monsoon behaviour connects climate, agriculture, rainfall distribution, and Rajasthan's seasonal weather patterns.