📍 What is Monsoon?

The word monsoon is derived from the Arabic word “Mausim”, meaning season.
It refers to seasonal reversal of winds, especially associated with rainfall.

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🌏 Why Monsoon Occurs in India?

🌡️ Main Causes:

1. Differential Heating of Land & Sea
   • Land heats up faster → low pressure over land
   • Sea remains cooler → high pressure
2. Seasonal Shift of Inter Tropical Convergence Zone
   • ITCZ shifts northward in summer → pulls winds toward India
3. Effect of Himalayas
   • Blocks cold winds from Central Asia
   • Forces monsoon winds to rise → rainfall
4. Jet Streams
   • Subtropical jet shifts → allows monsoon winds to enter India
5. Surrounding Water Bodies
   • Arabian Sea & Bay of Bengal provide moisture

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🌦️ Types of Monsoon in India

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☀️ 1. Southwest Monsoon (Summer Monsoon)

📅 Period:

June to September

🌬️ Direction:

From sea → land

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🌊 Two Branches:

🌴 (A) Arabian Sea Branch

• Hits Western Ghats
• Causes heavy rainfall in:
  • Kerala
  • Karnataka
  • Maharashtra

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🌾 (B) Bay of Bengal Branch

• Moves towards Northeast India
• Heavy rainfall in:
  • Meghalaya (e.g., Mawsynram – highest rainfall)
• Then moves westward along the Himalayas

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🌧️ Key Features:

• Provides ~75% of India’s rainfall
• Sudden start → called “Burst of Monsoon”
• Uneven distribution → floods & droughts

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🍂 2. Northeast Monsoon (Retreating Monsoon)

📅 Period:

October to December

🌬️ Direction:

From land → sea

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🌧️ Key Features:

• Dry winds generally
• Picks moisture from Bay of Bengal → gives rain to:
  • Tamil Nadu
  • Coastal Andhra Pradesh

👉 Important because Tamil Nadu gets major rainfall in this season

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🔄 Mechanism of Monsoon

1. Summer:
   • Low pressure over North India
   • Winds from sea bring moisture → rainfall
2. Winter:
   • High pressure over land
   • Winds reverse → dry conditions

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⚠️ Important Terms

🌩️ Burst of Monsoon

• Sudden heavy rainfall at beginning

🌦️ Break in Monsoon

• Temporary dry period during monsoon

🌊 Monsoon Trough

• Low-pressure region attracting rainfall

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📊 Summary Table

Feature	Southwest Monsoon	Northeast Monsoon
Season	June–Sept	Oct–Dec
Wind Direction	Sea → Land	Land → Sea
Rainfall	Heavy	Limited
Important Areas	Most of India	Tamil Nadu

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🎯 Easy Trick to Remember

👉 “SW = Summer Wet, NE = Not Everywhere”

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⭐ Importance of Monsoon in India

• Backbone of Indian agriculture
• Affects economy & GDP
• Controls water supply
• Impacts food production