Hope you have been enjoying my posts till now. And I also hope you have given a thought to my last question in post 3, why do the winds come from south-west direction?

When we saw the definition of the word monsoon, it included major wind systems that changes direction seasonally. During summer in India, temperatures increase rapidly, especially over the north-western plains, which results in intensified low-pressure conditions. The low-pressure belt near the surface, called as ITCZ – Inter Tropical Convergence Zone – shifts northwards in a particular position near the Himalayas and this elongated low pressure monsoon trough extends from Thar desert in the north-west till Patna and even Chhota Nagpur plateau in the east-south-east.

Now, we all know, India is surrounded by ocean, which too heats up meanwhile. It creates a relatively high-pressure zone off the southern coastline. Winds always blow from high pressure area to low pressure area, so in this case, warm air moves in south-westerly direction, carrying the moisture from the sea to Indian land mass in the north and north-east direction but is deflected by Coriolis force as the Earth spins.

This air current that brings moisture is what we call as south-west monsoon.

This monsoon when it approaches the Indian landmass, it bifurcates into two branches – The Arabian Sea branch and the Bay of Bengal branch.

Let us see tomorrow how these two branches help in advance of the monsoon.

(Image credit: oneindia.com)

---- to be continued