doc2025715586701.pdf
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🔆 Monsoon: India’s Lifeline, Now More Unpredictable
📍 India’s monsoon is central to agriculture, economy, and culture — but climate change is reshaping its rhythm and risks.
✅ Monsoon rains affect over 64% of India’s population dependent on agriculture
✅ Only 55% of sown land is irrigated; rest depends on rain
✅ SW Monsoon (June–Sept) gives 75% of annual rain; essential for crops like rice, cotton
✅ NE Monsoon (Oct–Dec) benefits Tamil Nadu, SE coast
✅ Key drivers: ITCZ, El Niño (weakens rain), La Niña (boosts rain)
✅ Rain varies: Western Ghats & NE >400 cm; Rajasthan <60 cm
✅ Climate change impacts:
• 75% rise in extreme rainfall events (1950–2015)
• 27% rise in dry spells
• 50% rain now falls in just 20–30 hours
✅ IMD Accuracy: 100% accurate monsoon forecast (2021–24), ±5% of LPA
✅ Mission Mausam: 9-vertical weather upgrade mission for a “climate-smart Bharat”
✅ Lightning rising: Shift from NE to Central & Western India
📘 Source: Ministry of Earth Sciences, IMD, Economic Survey 2024-25
#GS1 #GS3 #IndianMonsoon #ClimateChange
#Geography #GS1 #prelims
Join @CSE_EXAM
@PIB_UPSC
📍 India’s monsoon is central to agriculture, economy, and culture — but climate change is reshaping its rhythm and risks.
✅ Monsoon rains affect over 64% of India’s population dependent on agriculture
✅ Only 55% of sown land is irrigated; rest depends on rain
✅ SW Monsoon (June–Sept) gives 75% of annual rain; essential for crops like rice, cotton
✅ NE Monsoon (Oct–Dec) benefits Tamil Nadu, SE coast
✅ Key drivers: ITCZ, El Niño (weakens rain), La Niña (boosts rain)
✅ Rain varies: Western Ghats & NE >400 cm; Rajasthan <60 cm
✅ Climate change impacts:
• 75% rise in extreme rainfall events (1950–2015)
• 27% rise in dry spells
• 50% rain now falls in just 20–30 hours
✅ IMD Accuracy: 100% accurate monsoon forecast (2021–24), ±5% of LPA
✅ Mission Mausam: 9-vertical weather upgrade mission for a “climate-smart Bharat”
✅ Lightning rising: Shift from NE to Central & Western India
📘 Source: Ministry of Earth Sciences, IMD, Economic Survey 2024-25
📝 Prelims MCQ:
Which of the following is true about El Niño’s impact on India?
A. It strengthens the southwest monsoon
B. It leads to above-normal winter rainfall
C. It weakens monsoon and causes droughts
D. It leads to flooding in central India
Answer: C
📝 Mains GS1/GS3 Question:
Discuss the factors affecting the variability of the Indian Monsoon. How is climate change altering its patterns and consequences?
#GS1 #GS3 #IndianMonsoon #ClimateChange
#Geography #GS1 #prelims
Join @CSE_EXAM
@PIB_UPSC
❤3
Press Release_Press Information Bureau (3).pdf
254.7 KB
🔆 Fossil Leaves & Monsoon Evolution
📍 Why in Focus?
✅ Fossil leaves (~34 million years old) found in Nagaland’s Laisong Formation reveal how Antarctic glaciation shaped the Indian monsoon.
✅ Study by Birbal Sahni Institute of Palaeosciences (Lucknow) & Wadia Institute of Himalayan Geology (Dehradun).
📍 Key Highlights
✅ Fossils show Nagaland once had a warm, wet climate with very high rainfall.
✅ Timing matched the formation of Antarctic ice sheets, which shifted global wind & rainfall patterns by moving the ITCZ (Intertropical Convergence Zone) toward the tropics.
✅ This triggered the early evolution of the Indian monsoon system.
✅ Method used: CLAMP (Climate Leaf Analysis Multivariate Program) to reconstruct past climates.
✅ Study warns: With modern Antarctic ice melt, ITCZ may shift again, disrupting tropical monsoons → major risk for agriculture & water security in India.
#IndianMonsoon #ClimateChange #Geography
📍 Why in Focus?
✅ Fossil leaves (~34 million years old) found in Nagaland’s Laisong Formation reveal how Antarctic glaciation shaped the Indian monsoon.
✅ Study by Birbal Sahni Institute of Palaeosciences (Lucknow) & Wadia Institute of Himalayan Geology (Dehradun).
📍 Key Highlights
✅ Fossils show Nagaland once had a warm, wet climate with very high rainfall.
✅ Timing matched the formation of Antarctic ice sheets, which shifted global wind & rainfall patterns by moving the ITCZ (Intertropical Convergence Zone) toward the tropics.
✅ This triggered the early evolution of the Indian monsoon system.
✅ Method used: CLAMP (Climate Leaf Analysis Multivariate Program) to reconstruct past climates.
✅ Study warns: With modern Antarctic ice melt, ITCZ may shift again, disrupting tropical monsoons → major risk for agriculture & water security in India.
✅ Prelims Question:
The CLAMP method, recently in news, is used to:
A. Estimate groundwater depletion in semi-arid zones
B. Reconstruct past climates using fossil leaves
C. Measure tectonic shifts using satellite data
D. Analyse carbon sequestration in wetlands
Ans: B
✅ Mains Question:
Discuss how paleoclimate studies using fossil evidence help us understand the evolution of the Indian monsoon system. How can such insights guide India’s response to modern climate change?
#IndianMonsoon #ClimateChange #Geography
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🔆 Indian Monsoon Mechanism – Jet Stream Theory
📍 About Jet Stream Theory
✅ Most accepted modern theory for monsoon origin.
✅ Focus on Sub-Tropical Jet Stream (STJ) in the upper troposphere.
✅ Burst & withdrawal of monsoon = linked to north-south migration of STJ.
📍 How Jet Streams Affect Weather
✅ Ridges (high pressure) → anticyclonic, clear weather.
✅ Troughs (low pressure) → cyclonic, rainfall/depressions.
✅ Jet streaks create divergence/convergence in upper air → triggers surface lows & highs.
✅ Coriolis effect → converts these surface lows/highs into cyclonic/anticyclonic systems.
🔆 Indian Monsoon Mechanism – Role of STJ
📍 Winter STJ (Hindrance Phase)
✅ STJ flows south of Himalayas → creates ridge (high pressure) over N-W India.
✅ Steers Western Disturbances into India → winter rainfall in Punjab, Haryana, snowfall in Himalayas.
✅ No South-West monsoon because:
1. ITCZ shifts south.
2. Strong divergence due to ridge over N-W India.
3. Tibet = high pressure zone.
📍 Summer STJ (Onset Phase)
✅ From March → STJ weakens & shifts northwards.
✅ By June → STJ moves north of Himalayas → removes ridge over N-W India.
✅ Low pressure over N-W India + cross-equatorial winds → sudden burst of monsoon.
✅ Easterly Jet emerges over Peninsular India → strengthens South-West monsoon.
🔆 Why No South-West Monsoon Before June?
📍 March–May Summer Period
✅ Strong heating creates low pressure in N-W India.
✅ But STJ ridge still south of Himalayas → upper divergence blocks surface convergence.
✅ Descending dry air = hot winds (loo), dry & rainless despite high temps.
📍 Key Dynamics
✅ Onset → STJ shifts north of Tibet → monsoon enters.
✅ Withdrawal → STJ shifts back south of Himalayas → monsoon retreats.
Essence:
The Sub-Tropical Jet Stream is the switch that controls India’s monsoon → its northward migration triggers onset, while southward shift causes withdrawal.
✨ #IndianMonsoon #JetStreamTheory #geography
📍 About Jet Stream Theory
✅ Most accepted modern theory for monsoon origin.
✅ Focus on Sub-Tropical Jet Stream (STJ) in the upper troposphere.
✅ Burst & withdrawal of monsoon = linked to north-south migration of STJ.
📍 How Jet Streams Affect Weather
✅ Ridges (high pressure) → anticyclonic, clear weather.
✅ Troughs (low pressure) → cyclonic, rainfall/depressions.
✅ Jet streaks create divergence/convergence in upper air → triggers surface lows & highs.
✅ Coriolis effect → converts these surface lows/highs into cyclonic/anticyclonic systems.
🔆 Indian Monsoon Mechanism – Role of STJ
📍 Winter STJ (Hindrance Phase)
✅ STJ flows south of Himalayas → creates ridge (high pressure) over N-W India.
✅ Steers Western Disturbances into India → winter rainfall in Punjab, Haryana, snowfall in Himalayas.
✅ No South-West monsoon because:
1. ITCZ shifts south.
2. Strong divergence due to ridge over N-W India.
3. Tibet = high pressure zone.
📍 Summer STJ (Onset Phase)
✅ From March → STJ weakens & shifts northwards.
✅ By June → STJ moves north of Himalayas → removes ridge over N-W India.
✅ Low pressure over N-W India + cross-equatorial winds → sudden burst of monsoon.
✅ Easterly Jet emerges over Peninsular India → strengthens South-West monsoon.
🔆 Why No South-West Monsoon Before June?
📍 March–May Summer Period
✅ Strong heating creates low pressure in N-W India.
✅ But STJ ridge still south of Himalayas → upper divergence blocks surface convergence.
✅ Descending dry air = hot winds (loo), dry & rainless despite high temps.
📍 Key Dynamics
✅ Onset → STJ shifts north of Tibet → monsoon enters.
✅ Withdrawal → STJ shifts back south of Himalayas → monsoon retreats.
Essence:
The Sub-Tropical Jet Stream is the switch that controls India’s monsoon → its northward migration triggers onset, while southward shift causes withdrawal.
✨ #IndianMonsoon #JetStreamTheory #geography
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