Geography Optional Paper II – Page 5
Indian Climate & Monsoon System: Origin, Mechanism and Variability
1. Introduction
India experiences a tropical monsoon climate, dominated by seasonal reversal of winds. The monsoon plays a decisive role in agriculture, water resources, economy, and overall livelihood of the Indian population. Hence, Indian climate and monsoon are core topics in UPSC Geography Optional Paper II.
2. Factors Influencing Indian Climate
- Latitude: Tropical location with subtropical influences
- Altitude: Himalayas block cold continental winds
- Distance from Sea: Controls continentality
- Pressure & Wind Systems: Seasonal shift of ITCZ
- Ocean Currents: ENSO, IOD influence rainfall
3. Origin of Indian Monsoon – Major Theories
🔹 Thermal Theory
- Developed by Halley
- Based on differential heating of land and sea
- Explains seasonal wind reversal
🔹 Dynamic Theory
- Focuses on global pressure belts
- Shifting of ITCZ towards north in summer
- Monsoon as part of planetary wind system
🔹 Jet Stream Theory
- Role of Subtropical Westerly Jet (STWJ)
- Tibetan Plateau heating weakens STWJ
- Onset of southwest monsoon linked to jet shift
🔹 ENSO & IOD Influence
- El Niño leads to weak monsoon
- La Niña strengthens rainfall
- Positive IOD can offset El Niño impact
4. Mechanism of Indian Monsoon
- Formation of low pressure over NW India
- Cross-equatorial flow from Southern Hemisphere
- Coriolis force causes southwest direction
- Orographic rainfall along Western Ghats & Himalayas
5. Branches of Southwest Monsoon
- Arabian Sea Branch: Heavy rainfall on west coast
- Bay of Bengal Branch: Rainfall over eastern & northeastern India
6. Retreating (Northeast) Monsoon
- Occurs from October to December
- Affects Tamil Nadu, Andhra coast
- Associated with tropical cyclones
7. Monsoon Variability
- Temporal variability (onset & withdrawal)
- Spatial variability (regional rainfall differences)
- Break monsoon conditions
- Increasing impact of climate change
8. Impact of Monsoon on Indian Economy
- Agricultural productivity
- Hydropower generation
- Floods and droughts
- Food security and inflation
9. Previous Year Question (Model)
“Explain the mechanism of Indian monsoon and examine the causes of its variability.”
10. Answer Writing Tips
- Draw monsoon wind diagram
- Link theory with current climate events
- Use subheadings and flowcharts
- Conclude with climate change dimension
📘 Shaktimatha Learning | Geography Optional – Climate Made Scorable
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