Previous Year Question
Given below are two statements, one is labelled as Assertion (A) and the other is Reason (R)—
Assertion (A): The Tamil Nadu coast remains dry during South-West monsoon season.
Reason (R): The Tamil Nadu coast is situated parallel to the Bay of Bengal branch of South-West monsoon and it lies in the rain shadow area of the Arabian Sea branch of the South-West monsoon during monsoon season.
Select the correct answer using the code given below—
(A) is true but (R) is false
Both (A) and (R) are true and (R) is correct explanation of (A)
Both (A) and (R) are true but (R) is not correct explanation of (A)
(A) is false but (R) is true
Correct Answer: B
Detailed Solution
During the South-West Monsoon, most parts of India receive their principal seasonal rainfall, but the Tamil Nadu coast receives comparatively less rainfall during this season. Here, “dry” does not imply a complete absence of rainfall; it means relatively low rainfall compared with many other monsoon regions of India.
The first reason is that the Tamil Nadu coast lies approximately parallel to the Bay of Bengal branch of the South-West Monsoon. Since the winds move broadly parallel to the coast, they do not encounter an effective orographic barrier that would force strong uplift and produce heavy rainfall.
The second reason is the Western Ghats. The Arabian Sea branch produces heavy rainfall on the western slopes of the Western Ghats. After crossing the mountains, the winds lose much of their moisture, while a large part of Tamil Nadu lies on the leeward or rain-shadow side. Therefore, the Arabian Sea branch also gives relatively little rainfall to Tamil Nadu.
NCERT gives these same two factors for the relative dryness of the Tamil Nadu coast during the South-West Monsoon—the coast lies parallel to the Bay of Bengal branch and in the rain-shadow area of the Arabian Sea branch.
In contrast, an important share of Tamil Nadu's rainfall occurs during the October–December North-East/Retreating Monsoon, when north-easterly winds pick up moisture over the Bay of Bengal and bring rainfall to the Coromandel Coast.