📍 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.
🌏 Why Monsoon Occurs in India?
🌡️ Main Causes:
- Differential Heating of Land & Sea
- Land heats up faster → low pressure over land
- Sea remains cooler → high pressure
- Seasonal Shift of Inter Tropical Convergence Zone
- ITCZ shifts northward in summer → pulls winds toward India
- Effect of Himalayas
- Blocks cold winds from Central Asia
- Forces monsoon winds to rise → rainfall
- Jet Streams
- Subtropical jet shifts → allows monsoon winds to enter India
- Surrounding Water Bodies
- Arabian Sea & Bay of Bengal provide moisture
🌦️ Types of Monsoon in India
☀️ 1. Southwest Monsoon (Summer Monsoon)
📅 Period:
June to September
🌬️ Direction:
From sea → land
🌊 Two Branches:
🌴 (A) Arabian Sea Branch
- Hits Western Ghats
- Causes heavy rainfall in:
- Kerala
- Karnataka
- Maharashtra
🌾 (B) Bay of Bengal Branch
- Moves towards Northeast India
- Heavy rainfall in:
- Meghalaya (e.g., Mawsynram – highest rainfall)
- Then moves westward along the Himalayas
🌧️ Key Features:
- Provides ~75% of India’s rainfall
- Sudden start → called “Burst of Monsoon”
- Uneven distribution → floods & droughts
🍂 2. Northeast Monsoon (Retreating Monsoon)
📅 Period:
October to December
🌬️ Direction:
From land → sea
🌧️ 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
🔄 Mechanism of Monsoon
- Summer:
- Low pressure over North India
- Winds from sea bring moisture → rainfall
- Winter:
- High pressure over land
- Winds reverse → dry conditions
⚠️ 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
📊 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 |
🎯 Easy Trick to Remember
👉 “SW = Summer Wet, NE = Not Everywhere”
⭐ Importance of Monsoon in India
- Backbone of Indian agriculture
- Affects economy & GDP
- Controls water supply
- Impacts food production