Understanding the Indian South West Monsoon

The monsoon season in India is a crucial part of the country's climate, bringing much-needed rainfall. The primary monsoon system that affects India during the summer months (June to September) is known as the 'South West Monsoon'. This name is not arbitrary; it directly relates to the direction from which the monsoon winds originate and travel across the Indian subcontinent.

Why is it Called the South West Monsoon?

The name 'South West Monsoon' is derived from the prevailing direction of the winds associated with this weather phenomenon. These winds blow predominantly from the South-West direction towards the North-East.

• During the summer, due to intense heating, the landmass of the Indian subcontinent becomes significantly warmer than the surrounding seas.
• This temperature difference creates a low-pressure area over the land, particularly over the North Indian plains and the Tibetan Plateau.
• The relatively cooler and higher-pressure air over the Indian Ocean is drawn towards this low-pressure area over the land.
• As the Earth rotates (Coriolis effect), these winds are deflected towards the right in the Northern Hemisphere.
• Consequently, the moisture-laden winds blow from a South-Westerly direction across the Arabian Sea and the Bay of Bengal towards the Indian landmass.

These South-Westerly winds carry vast amounts of moisture from the ocean. As they hit the Western Ghats and the Himalayan ranges, they are forced to rise, leading to condensation and heavy rainfall over large parts of India.

Analyzing the Options

Let's look at the given options in light of this understanding:

• Option 1: Monsoon winds run through North-East to South-West direction. This is incorrect. The direction is primarily from South-West to North-East during the summer monsoon.
• Option 2: Monsoon winds run through South-West to North-East direction. This statement accurately describes the direction of the prevailing winds that define the South West Monsoon.
• Option 3: Monsoon hits South-West part of India in the beginning. While it is true that the monsoon typically arrives first in the South-Western state of Kerala, the name "South West Monsoon" is derived from the direction of the winds themselves, not solely the first point of landfall. The winds originate from the south-west and blow inland.
• Option 4: None of the above. This is incorrect as Option 2 correctly identifies the wind direction.

Therefore, the primary reason the Indian Monsoon is called the 'South West Monsoon' is the direction of the monsoon winds.