Monsoon – large scale seasonal rains that dramatically alter the landscape, life of the India. While the arrival of monsoon brings a huge cheer and respite from the hot and humid summer, it unleashes utter chaos and brings life to a halt in many areas before departing. Below are few facts that helps us understand the nature of monsoon and the role it plays in Indian subcontinent.
What is Monsoon and where they occur?
Monsoon winds are large scale winds that flow from oceans to the lands and vice-versa. Monsoon winds occur in regions adjoining seas and oceans and areas that receive intense solar radiations.
How does Monsoon happen?
1) Monsoon happens due to the contrasting styles of heat absorbed by land and oceans (water) causing temperature imbalance between the two bodies.
2) Water having a higher heat capacity, by convection (transfer of heat by movement of fluids) and conduction (movement of heat inside and over the surface) stabilize the heat absorbed whereas land (consisting of sand, stone etc.) with a lower heat capacity and only by conduction heats up faster.
3) As a result of land heating quickly the air above the land dries, expands and creates a low-pressure region. By contrast, Oceans maintains a stable temperature thereby allowing creation of a high-pressure region with moisture.
4) With air flowing from high pressure to low pressure, the moist air from oceans flows towards land.
5) On reaching land the winds move higher resulting the incoming winds becoming cooler. The cooler winds unable to hold moisture(water vapor) results in large-scale precipitation (rain).
What are South-West Monsoons?
South-West Monsoon occurs in the Indian subcontinent during the months of July-September. The Indian subcontinent experiences extreme heat during the April-June causing the land to heat more than oceans. This creates a temperature imbalance between the land and seas.
By the end of June, the moist air from the Indian Ocean enters the Indian subcontinent. The moist air first passes through the state of Kerala initiating the South-West Monsoon.
On entering the Indian state of Kerala, the winds encounter the Western Ghats causing them to branch into two.
1) Arabian Sea branch
2) Bay of Bengal branch
The Arabian Sea branch starting from Kerala proceeds towards the coast of Karnataka, Maharashtra, Goa, Mumbai.
The Bay of Bengal branch picks more moisture from Bay of Bengal arriving at North-East India (the major reason why Assam receives the highest rainfall). It further moves northwards to Eastern Himalayas which blocks the winds moving further northwards, from there it proceeds westwards towards the states of Bihar, Uttar Pradesh, and Delhi.
Northern, North-East and South-West India receive greater share of the rainfall during the South-West Monsoon.
What are North-East Monsoons?
Also known as retreating monsoon this occurs during the months of November-January. By the end of September, due to the tilting of earth(23 & 1/2 degrees) the Sun beings to move towards the Southern hemisphere causing North, North-East India to cool more rapidly.
As result of temperature imbalance, the cool winds flows towards the Indian Ocean passing through the Bay of Bengal picking up moisture and pouring it over the peninsular India(mainly TamilNadu) and parts of SriLanka. Ironically the Indian state of Kerala gets good rainfall during both the monsoons.
How Monsoon impacts India?
Monsoon brings 80% rains in India. Indian agriculture which employs 80% of the population and contributes 25% of India’s GDP is very much dependent on Monsoon. Delay of monsoon by a few days adversely affects agricultural process in turn impacting the economy to a large extent.
Cities, Towns completely come to a standstill as the roads, sewage and drainage supply takes a heavy beating pushing life into chaos.