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The Indian Monsoon

…How & Why

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Etymology :

Portuguese -> monção

Dutch -> monsun

Arabic -> mawsim (season)

Used by ancient Arabic sailors

A global phenomenon

Strengthened 8 mya by Tibetan plateau formation

The real finance minister of India

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The Definition:

IMD -> “… seasonal reversals of the wind direction along the shores of the Indian Ocean, especially in the Arabian Sea, that blow from the southwest during one half of the year and from the northeast during the other half …”

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Some Prerequisites…

• The Inter Tropical Convergence Zone ( ITCZ )

• The Coriolis Effect

• India : The geophysical features

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The ITCZArea of maximum insolationConvergence of trade winds

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The Coriolis Force• Apparent force due to earth’s rotation• Movement to the right in NH and to the

left in SH• Affects Wind movements• coriolis effect (2-11).mp4

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Where does it start…

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• The Macarena's High

• The Coriolis Force

• The Somali Jet Stream

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The Classification Based on their spatial spread

Arabian Sea Branch

Bay of Bengal Branch

Based on the direction of rain bearing winds

South-West Monsoon (SW Monsoon)

North-East Monsoon (NE Monsoon)

Based on the time of the year

the Summer monsoon (May to September)

the Winter monsoon, (October to November)

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The Vagaries of Monsoon

• The Jet Stream Effect

• ENSO/La Nina

• The Indian ocean Dipole

• EQINOO

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El-Nino/La-Nina/ENSO Abnormal warming/cooling of tropical eastern

pacific

Combines with surface air pressure oscillations

Fall in air pressure over Tahiti – drives the warm Indian Ocean water towards eastern pacific – weakens the trade winds and draws the rain along with it

Southern Oscillation Index (SOI)

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Indian Ocean Dipole : Variations in sea surface temperatures b/w western and eastern Indian Ocean

+ve IOD index : Western Indian Ocean warmer than Eastern

Equatorial Indian Ocean Oscillation : Atmospheric component of Indian Ocean Dipole

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• Thank you …..