Retreating monsoon and North-East winds
Explanation
The rainfall pattern of the Tamil Nadu coast (Coromandel Coast) is distinct from the rest of the Indian subcontinent. While most of India receives rainfall during the summer (South-West Monsoon), Tamil Nadu remains largely dry during that period and receives its primary precipitation during the transition and winter seasons due to specific wind systems.
Option Analysis:
- South-West Monsoon winds South-West Monsoon winds (Incorrect): During the South-West Monsoon (June to September), the Tamil Nadu coast lies in the rain-shadow region of the Western Ghats regarding the Arabian Sea branch. Additionally, the Bay of Bengal branch of the monsoon flows parallel to this coast, resulting in very little rainfall during this season.
- Retreating monsoon and North-East winds Retreating monsoon and North-East winds (Correct): During October and November, the South-West Monsoon winds retreat from Northern India. This period marks the transition to the North-East Monsoon. The winds reverse direction, blowing from the land towards the sea (North-East to South-West). As these winds cross the Bay of Bengal, they pick up abundant moisture. When they strike the Coromandel Coast, they cause heavy rainfall.
- Western Cyclonic Disturbances Western Cyclonic Disturbances (Incorrect): These are shallow cyclonic depressions originating over the Mediterranean Sea. They travel eastwards and are responsible for winter rainfall in North-Western India (Punjab, Haryana, Western Uttar Pradesh), not the southern peninsula.
- Intense heating of the landmass Intense heating of the landmass (Incorrect): Intense heating of the landmass creates the low-pressure system that attracts the South-West Monsoon in early summer. In contrast, the October–November period is characterized by the cooling of the landmass and the establishment of high pressure over the subcontinent.
Key Takeaway:
The Tamil Nadu coast receives the bulk of its annual rainfall during the Retreating Monsoon (North-East Monsoon) season because the North-East trade winds pick up moisture from the Bay of Bengal and blow onshore.