RAS question
The Malabar Coast receives heavy rainfall because:
Correct answer: (D) The Western Ghats force the moisture-laden SW monsoon winds to rise (orographic rainfall).
The Malabar Coast receives heavy rainfall because the Western Ghats force moisture-laden south-west monsoon winds from the Arabian Sea to rise, cool and shed rain on the windward coast.
Explanation
The key factor is relief, not simply coastal location. During the south-west monsoon season, winds reach the Kerala coast and move inland from the Arabian Sea side. The Western Ghats stand close to this coast, so the moist air is forced upward along the windward western slopes. As the air rises, it cools and condenses, producing heavy orographic rainfall over the Malabar Coast. The same barrier also explains the contrast across the Ghats: the southern plateau to the east lies on the leeward side and remains much drier. NCERT states this general pattern clearly, noting high rainfall on the windward sides of the Western Ghats during June-September and drier conditions over the southern plateau because of its leeward situation.
Why the other options are wrong
- (A) Nearness to the equator helps explain generally high tropical temperatures, but it does not explain the sharp windward-leeward rainfall contrast across the Western Ghats.
- (B) Volcanic activity is not part of the monsoon rainfall mechanism described here; the rain comes from uplift of moist south-west monsoon winds by relief.
- (C) Warm oceanic influence alone cannot account for the heavy rainfall pattern, because the decisive process is moist monsoon air being forced up the Western Ghats.
Concept
This tests the Indian monsoon and orographic rainfall under physical geography. RAS repeatedly asks it because Rajasthan's climate questions often compare windward rainfall, rain-shadow areas and the role of relief in monsoon distribution.