The Indian Monsoon

The Climate of India is described as the ‘Monsoon’ type which refers to the seasonal reversal in the wind direction during a year. In Asia, this kind of climate is found substantially in the south and the southeast.  

The Indian Monsoon

• This phenomenon was first noticed by the sailors who came to India in historic times and benefited from the reversal of the wind system as they came by sailing ships at the mercy of the winds
• It was named ‘monsoon’ by the Arab traders
• It’s experienced in the tropical zone around between 20 ° N and 20 °S
• Its duration is between 100- 120 days from early June to mid-September
• Unlike the Indian summer monsoon, the northeast monsoon spans for 3 months (between October to December) and covers five divisions of India, namely Kerala and Mahe, Tamil Nadu, Karaikal and Puducherry, Yanam and coastal Andhra Pradesh and south interior Karnataka

Factors affecting the Mechanism of Monsoon

• Differential heating and cooling of land and water create a low pressure on land in India and relatively high pressure on seas
• The shift of the Inter-Tropical Convergence Zone (ITCZ) in Summer, over the Ganga plains (this is the equatorial channel usually positioned about 5 ° N of the Equator. It’s also known as the Monsoon channel during the Monsoon season)
• The sight of the high-pressure region, east of Madagascar, around 20 ° S over the Indian Ocean. Its power and position influence the Indian Monsoon
• During Summer, the Tibetan level gets seriously warmed which brings about solid vertical air flows and the arrangement of low tension over the level at around 9 km above ocean level
• The movement of the westerly fly stream toward the North of the Himalayas and the presence of the tropical easterly fly stream over the Indian promontory during Summer
• The southwest monsoon arrives in two branches: the Bay of Bengal branch and the Arabian Sea branch
• During the monsoon season, the unbroken western ghats act as a barrier to the moisture-filled clouds. The heavy eastward-moving rain-bearing clouds are forced to rise and deposit most of their rain on the side of the wind
• The monsoon is also affected by the pressure conditions over the southern oceans
• Usually, when the tropical eastern south Pacific Ocean experiences high pressure, the tropical eastern Indian Ocean experiences low pressure. But in some years, there’s a reversal in the pressure conditions and the eastern Pacific has lower pressure in comparison to the eastern Indian Ocean. This is known as the Southern Oscillation or SO
• The unlikeness in pressure over Tahiti (Pacific Ocean) and Darwin in northern Australia (Indian Ocean) is computed to forecast the intensity of the monsoons
• In India, crops depend on rain and monsoon occurs during the summer period supplying water to the crops. Crops that are monsoon friendly and require a huge amount of water like paddy and jute can be easily grown during the southwest monsoon. 

El Niño Southern Oscillations (ENSO)

• It relates to the SO in which a warm ocean current flows past the Peruvian Coast, in place of the cold Peruvian current, every 2 to 5 years
•  The inconsistencies in pressure conditions are connected to the El Nino
• The phenomenon is known as ENSO (El Nino Southern Oscillations).

Mechanism of Monsoon

Onset of Monsoon

• The Monsoon, unlike the trade winds, is not steady in nature and is affected by dissimilar atmospheric conditions on its way over the warm tropical sea
• The continuance of the monsoon is between 100-120 days from early June to mid-September
• The burst of Monsoon: Around the occasion of its arrival, the normal rainfall increases suddenly and continues constantly for several days
• The islands take the very earliest monsoon showers, progressively from South to North
• It arrives at the southern tip of the Indian peninsula and proceeds into two – the Arabian Sea branch and the Bay of Bengal branch. Both branches combine over the north-western part of the Ganga plains
• Delhi usually receives the monsoon showers from the Bay of Bengal branch
• Different regions or states welcome the monsoon on different dates. By Mid-July, the monsoon reaches Himachal Pradesh and the rest of India. 

Withdrawal of Monsoon

• It is a more gradual process that begins in the North-Western part of India by early September and withdraws completely from the northern half of the Peninsula by mid-October
• The withdrawal from the southern half of the peninsula is enough rapid-fire. By early December, the monsoon usually withdraws from the rest of India
• The rainfall during the months of October to December is the northeast monsoon which is confined to the states like Tamil Nadu, Puducherry, Andhra Pradesh, Kerala. 

Conclusion

Monsoon is the seasonal reversal in the wind direction during a year. This phenomenon was first noticed by the sailors who came to India, and it was named ‘monsoon’ by the Arab traders. It’s sustained in the zone between 20 ° N and 20 °S. Its duration is between 100- 120 days from early June to mid-September. When the monsoon trough passes over plains, it results in good rainfall, but when the monsoon trough passes closer to the Himalayas, the rainfall is poor and plains experience longer dry spells while mountainous catchment areas of the Himalayan Rivers experience widespread rain. When there is a difference in the temperature of the land and water, it creates low pressure on land and relatively high pressure on seas. 

El Niño refers to the large-scale Ocean atmosphere climate interaction and is linked to warming which is periodic in the surface of the sea and is across the central and East-Central equatorial  Pacific.