📌 Topic 01 of 6 · Chapter 03 · Climate of India
Factors Controlling India’s Climate
Latitude, altitude, distance from sea, monsoon winds, jet streams, Western Ghats — complete notes for UPSC & PSC exams.
🌡️ Factors Controlling India’s Climate
| Factor | Effect on Climate |
|---|---|
| Latitude | Tropic of Cancer divides India into tropical (south) and sub-tropical (north). Southern India has high temperatures year-round; northern India has extreme seasons. |
| Altitude | Temperature decreases ~6.5°C per 1,000m rise. Himalayas are cold; Deccan Plateau is cooler than coastal plains at same latitude. |
| Distance from Sea | Coastal areas (Mumbai, Chennai) have moderate climate (equable). Interior areas (Delhi, Nagpur) have extreme climate (continental). |
| Himalayas | Act as a barrier — block cold Central Asian winds in winter; force monsoon winds to rise and cause heavy rainfall on windward side. |
| Western Ghats | Windward side (west) gets heavy rainfall; leeward side (east) is in rain shadow — dry (Deccan Plateau). |
| Monsoon Winds | SW monsoon (June–Sept) brings most of India’s rainfall. NE monsoon (Oct–Dec) brings rain to Tamil Nadu coast. |
| Jet Streams | Sub-tropical westerly jet stream controls winter weather; Tropical easterly jet stream triggers SW monsoon onset. |
| Ocean Currents | Warm Indian Ocean moderates coastal temperatures; no cold currents near India’s coast. |
🌬️ Jet Streams & Indian Climate
- Sub-tropical Westerly Jet Stream: Flows at ~12 km altitude; splits around Himalayas in summer — one branch north, one south; controls western disturbances in winter
- Western Disturbances: Extra-tropical cyclones from Mediterranean Sea; bring winter rainfall to NW India (Punjab, Haryana, UP) — important for rabi crops
- Tropical Easterly Jet Stream: Develops over India in summer (June); its establishment triggers the onset of SW monsoon
- ITCZ (Inter-Tropical Convergence Zone): Shifts northward in summer over India — draws in SW monsoon winds
⭐ Rain Shadow Effect — Western Ghats:
• Windward side (west coast — Mumbai, Mangaluru, Kochi) = very heavy rainfall (200–400 cm/year)
• Leeward side (Deccan Plateau — Pune, Bengaluru, Hyderabad) = much less rainfall (50–75 cm/year)
• This is why Cherrapunji (Meghalaya) gets very heavy rain — windward side of Khasi Hills
• Windward side (west coast — Mumbai, Mangaluru, Kochi) = very heavy rainfall (200–400 cm/year)
• Leeward side (Deccan Plateau — Pune, Bengaluru, Hyderabad) = much less rainfall (50–75 cm/year)
• This is why Cherrapunji (Meghalaya) gets very heavy rain — windward side of Khasi Hills
📌 Equable vs Continental Climate:
• Equable (Maritime) climate = coastal areas = small temperature range = Mumbai, Chennai, Kochi
• Continental (Extreme) climate = interior areas = large temperature range = Delhi, Nagpur, Jodhpur
• Reason: Sea has high specific heat — moderates temperature of nearby areas
• Equable (Maritime) climate = coastal areas = small temperature range = Mumbai, Chennai, Kochi
• Continental (Extreme) climate = interior areas = large temperature range = Delhi, Nagpur, Jodhpur
• Reason: Sea has high specific heat — moderates temperature of nearby areas