Monsoon System (Especially Indian Monsoon)
Delhi Police & SSC Exams
1. Introduction: What is a Monsoon?
Definition & Origin:
- Origin: Arabic word "Mausim" meaning season
- Definition: Seasonal reversal of winds
- Main Cause: Differential heating of land and water
- Key Areas: Indian subcontinent and surrounding seas
Heating Pattern:
Uneven heating between land (Indian subcontinent) and surrounding seas (Indian Ocean, Arabian Sea, Bay of Bengal)
Exam Trick: "Monsoon = Seasonal Swap of Winds"
2. Types of Monsoon Winds
Southwest Monsoon (Summer Monsoon)
- Duration: June to September
- Direction: From sea to land
- Effect: Heavy rainfall across most parts of India
- Branches:
- Arabian Sea Branch: Hits Western Ghats
- Bay of Bengal Branch: Moves towards Northeast India
Northeast Monsoon (Winter Monsoon)
- Duration: October to December
- Direction: From land to sea
- Effect: Rainfall mainly over Tamil Nadu, Andhra Pradesh
- Nature: Dry winds picking moisture from Bay of Bengal
- Special: Causes rainfall in Tamil Nadu coast
Exam Trick: "SW → Sea to Land (Rainy) | NE → Land to Sea (Dry)"
3. Mechanism of Indian Monsoon
Key Factors:
- Differential Heating: Land heats faster → Low pressure on land, High pressure on sea
- ITCZ Shift: Moves northward in summer → pulls trade winds
- Tibetan Plateau: Heating affects jet stream movement
- Western Disturbances: Influence winter rainfall in northwest India
Pacific Ocean Effects:
El Niño Effect
Warm Pacific waters → weak monsoon, drought conditions
La Niña Effect
Cold Pacific waters → stronger monsoon, excess rainfall
Exam Trick: "LITEJ = Land heating + ITCZ + Tibetan Plateau + El Niño + Jet stream"
4. Onset and Retreat of Monsoon
Monsoon Onset:
- Kerala: Reaches around 1st June (official start)
- Northward Advance: Covers entire India by mid-July
- Progression: Moves from south to north gradually
- Significance: Marks beginning of rainy season
Monsoon Retreat:
- Starts From: Northwest India in September
- Complete Withdrawal: From south by December
- Tamil Nadu: Receives rainfall during retreating monsoon
- Pattern: Withdraws from north to south
5. Regional Distribution of Rainfall
| Region | Rainfall (Approx.) | Remarks |
|---|---|---|
| Western Coast (Konkan, Malabar) | Heavy (200–400 cm) | Arabian Sea branch impact |
| Northeast India (Meghalaya, Assam) | Very heavy (>400 cm) | Bay of Bengal branch impact |
| North India (Punjab, Haryana, Rajasthan) | Low (50–100 cm) | Monsoon weakens |
| Tamil Nadu Coast | Moderate (100–150 cm) | Winter monsoon rainfall |
Exam Trick: "Wettest Place = Mawsynram (Meghalaya)"
6. Importance of Monsoon in India
Positive Impacts:
- Supports agriculture (about 70% of annual rainfall)
- Recharges rivers, lakes, groundwater
- Controls crop cycles (Kharif & Rabi seasons)
- Essential for drinking water supply
Economic Significance:
Affects economy, transport, and industry
Weak monsoon = Drought conditions
Excess monsoon = Flood situations
PYQs (Delhi Police Exam)
The word "Monsoon" is derived from which language?
Options: A) Greek B) Arabic C) Latin D) Persian
Category: Origin & Definition
Show Answer
B) Arabic
The Southwest monsoon in India blows from:
Options: A) Land to Sea B) Sea to Land C) North to South D) West to East
Category: Wind Direction
Show Answer
B) Sea to Land
The Bay of Bengal branch of monsoon causes rainfall in:
Options: A) Gujarat B) Punjab C) West Bengal and Assam D) Rajasthan
Category: Regional Impact
Show Answer
C) West Bengal and Assam
Tamil Nadu receives rainfall mainly from:
Options: A) Southwest Monsoon B) Northeast Monsoon C) Westerlies D) Cyclones
Category: Regional Rainfall
Show Answer
B) Northeast Monsoon
7. Quick Revision Notes
Monsoon Types & Timing:
- Southwest Monsoon: June–Sept → Sea → Land → Rainy
- Northeast Monsoon: Oct–Dec → Land → Sea → Dry (except Tamil Nadu)
- Onset: Kerala – June 1
- Retreat: From NW India – Sept onward
Key Facts:
- Wettest place: Mawsynram (Meghalaya)
- Weak Monsoon: El Niño year
- Strong Monsoon: La Niña year
- Tamil Nadu: Rainfall from retreating monsoon
8. Exam Tricks & Memory Aids
"SW – Sea Wins, NE – No Effect (Dry)"
"Mausim = Season" → Monsoon = Seasonal Wind
El Niño = Drought | La Niña = Rain
Kerala – Gateway of Monsoon (1st June)
Final Exam Tip
For Delhi Police Geography paper, monsoon-related questions often ask about direction, timing, and effects of winds, Tamil Nadu rainfall, and El Niño concept. Revise SW & NE differences, ITCZ, and rainfall regions map for full marks. Remember the key dates and regional variations for scoring high.
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