Correct Option (b):
The intense heating of the Indian subcontinent, particularly the northwestern plains, during the summer months (May-June) creates a significant low-pressure area. Concurrently, a high-pressure region prevails over the southern Indian Ocean. This pressure gradient draws moisture-laden winds from the Indian Ocean towards the landmass. These winds originate as south-east trade winds in the Southern Hemisphere. Upon crossing the equator, they are deflected to the southwest due to the Coriolis effect, becoming the South-West Monsoon winds. These winds are crucial for the Indian climate and agriculture, typically splitting into two main branches:
- The Arabian Sea branch, which impacts the Western Ghats and parts of northwest India.
- The Bay of Bengal branch, which influences northeastern India and the Indo-Gangetic plains.
Incorrect Options:
The South-east monsoon refers to the south-east trade winds of the Southern Hemisphere before they cross the equator. Upon crossing the equator, these winds are deflected by the Coriolis force and transform into the South-west Monsoon winds.
Trade winds are a system of permanent or prevailing winds that blow from the subtropical high-pressure belts towards the equatorial low-pressure belt. While they are a component of the atmospheric circulation that gives rise to monsoons, the term 'trade winds' itself does not describe the seasonal reversal of winds characteristic of the monsoon phenomenon over India.
Westerlies are prevailing winds that blow from west to east in the mid-latitudes (between 30 and 60 degrees latitude) in both the Northern and Southern Hemispheres. In the context of India, the Westerly Jet Stream influences the winter weather, bringing western disturbances, and is not associated with the summer monsoon circulation.