Notes.
Climate: Definition and Overview**
- **Weather**: The atmospheric condition of a place over a short period (e.g., a day or week).
- **Climate**: The average weather condition of a place over a long period (30 years or more).
- **India’s Climate**: India experiences a **monsoon type of climate**, characterized by
seasonal reversal of winds.
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### **Factors Influencing India’s Climate**
1. **Latitude**
- The Tropic of Cancer divides India into two climatic zones: tropical (south) and subtropical
(north).
2. **Altitude**
- Temperature decreases with an increase in altitude.
- Example: Himalayan region has a colder climate than coastal areas.
3. **Pressure and Winds**
- **Pressure Belts**: India is influenced by equatorial low pressure and subtropical high-
pressure belts.
- **Winds**: Seasonal monsoon winds affect India’s climate.
4. **Distance from the Sea**
- Coastal areas (e.g., Mumbai, Chennai) have moderate climates.
- Interior areas (e.g., Delhi, Jaipur) experience extreme temperatures.
5. **Ocean Currents**
- Warm and cold ocean currents affect coastal areas.
6. **Relief Features**
- The Himalayas block cold winds from Central Asia, protecting northern India.
- Western Ghats influence rainfall patterns.
---
### **Mechanism of Monsoons**
- Monsoons are caused by the differential heating and cooling of land and water.
- **Key Features**:
- **Low-Pressure Area**: Develops over the Indian subcontinent during summer.
- **High-Pressure Area**: Exists over the Indian Ocean.
- Winds move from high pressure (ocean) to low pressure (land), bringing rainfall.
---
### **Seasons in India**
India experiences four main seasons:
1. **Cold Weather Season (Winter)**:
- **Time**: December to February.
- **Characteristics**:
- Low temperatures.
- Northeastern trade winds prevail.
- Light rainfall in Tamil Nadu due to retreating monsoons.
2. **Hot Weather Season (Summer)**:
- **Time**: March to May.
- **Characteristics**:
- High temperatures; heatwaves (Loo).
- Low-pressure system develops over northwest India.
3. **Advancing Monsoon (Rainy Season)**:
- **Time**: June to September.
- **Characteristics**:
- Onset of southwest monsoon.
- Heavy rainfall across most parts of India.
- Uneven distribution of rainfall.
- Examples: Mawsynram in Meghalaya receives the highest rainfall in the world.
4. **Retreating Monsoon (Autumn)**:
- **Time**: October to November.
- **Characteristics**:
- Monsoons retreat as low-pressure systems weaken.
- Clear skies and warm days.
- Cyclones form over the Bay of Bengal, affecting eastern coastal states.
---
### **Distribution of Rainfall in India**
1. **Areas of Heavy Rainfall**:
- Northeastern states (e.g., Meghalaya, Assam).
- Western Ghats.
2. **Areas of Moderate Rainfall**:
- Central and northern India.
3. **Areas of Low Rainfall**:
- Rajasthan (Thar Desert).
- Gujarat.
---
### **Monsoon and Its Importance**
1. **Agriculture**
- Indian agriculture is largely dependent on monsoon rainfall.
2. **Economic Impact**
- Adequate monsoon boosts food production and GDP.
- Weak monsoon can lead to droughts and inflation.
3. **Water Resources**
- Rivers, reservoirs, and groundwater recharge depend on monsoons.
---
### **Climate Variability in India**
- **Himalayan Region**: Cold winters, moderate summers.
- **Coastal Areas**: Moderate climate with high humidity.
- **Desert Areas**: Hot summers, cold winters, very low rainfall.
---
### **Global Climatic Phenomena Influencing India**
1. **El Niño**: Warming of Pacific Ocean water; weakens monsoon winds, causing droughts.
2. **La Niña**: Cooling of Pacific Ocean water; enhances monsoon winds, leading to heavier
rainfall.
---
### **Key Terms**
- **Loo**: Hot, dry winds during summer in northern India.
- **Western Disturbances**: Weather systems bringing winter rainfall to northern India.
- **ITCZ (Inter-Tropical Convergence Zone)**: Area where northeast and southeast trade winds
converge, influencing monsoon patterns.
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These notes summarize the key points from the chapter **"Climate"** for Class 9. Let me know
if you’d like additional details on any section!
