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This revised chapter on NCERT Class 11 Geography India Physical Environment Chapter 4: Climate Notes provides a clear overview of India’s climatic conditions, factors influencing it, the mechanism of monsoons, seasonal rhythms, and spatial variations in temperature and rainfall. These notes simplify complex concepts into easy-to-understand pointers. They are basically designed for exam preparation and quick revision of monsoon dynamics, seasonal weather patterns, and climatic diversity across regions. You can also download a free PDF for effective exam preparation.
Contents
Explore Notes of Class 11 India Physical Environment
Introduction
‘Climate’ refers to the average weather conditions of a place over a long period, usually 30-35 years. India’s climate is described as monsoon type because of the dominant influence of monsoon winds. While there is broad unity in the monsoon climate across the country, linking it to Southeast Asia, there are also significant regional variations in temperature, rainfall, and seasonal patterns.
Factors Influencing India’s Climate
Several factors control the climate of India. These include latitude, altitude, pressure and wind systems, distance from the sea, and relief features. The Himalayas act as a barrier protecting northern India from cold winds and influencing monsoon rains. The tropical location near the equator ensures high temperatures, while the vast size of the country creates diverse climatic conditions.
The Mechanism of the Indian Monsoon
The Indian monsoon is driven by differential heating of land and sea. In summer, low pressure develops over northwest India, attracting moisture-laden winds from the southwest. The upper air circulation, including jet streams, plays a key role. The western jet stream shifts north in summer, allowing the easterly tropical jet to bring the monsoon burst. Inter-Tropical Convergence Zone (ITCZ) movement and phenomena like El-Nino and Southern Oscillation also affect monsoon variability.
Unity and Diversity in the Monsoon Climate
The monsoon provides a rhythmic seasonal pattern uniting the country, but regional differences exist due to topography and location. For example, rainfall is heavy on windward slopes but scanty in rain-shadow areas.
The Rhythm of Seasons
India experiences four main seasons based on monsoon cycles:
- The Cold Weather Season (Winter: December to February): High pressure over north India leads to clear skies and low temperatures. Nights are cold, days pleasant. Western cyclonic disturbances bring light rainfall in northwest India and snow in the Himalayas. Frost occurs in the northern plains.
- The Hot Weather Season (Summer: March to May): Temperatures rise sharply, especially in the northwest. Hot dry winds like ‘Loo’ blow. Dust storms and thunderstorms (Kal Baisakhi in West Bengal, Mango showers in Kerala) provide relief.
- The Southwest Monsoon Season (Advancing Monsoon: June to September): Monsoon arrives in early June, covering the country by mid-July. The Arabian Sea branch brings heavy rain to the western coast and Ghats; the Bay of Bengal branch to the northeast and plains. Rainfall decreases westward. Breaks in the monsoon occur due to shifting pressure.
- The Season of Retreating Monsoon (October to November): Monsoon withdraws, bringing clear skies and rising temperatures initially. Retreating winds pick up moisture from the Bay of Bengal, causing rainfall on the Tamil Nadu coast.
Spatial Distribution of Temperature and Rainfall
Temperature is high throughout the year in coastal and southern areas, with low annual and diurnal ranges. Northern plains have a continental climate with extreme temperatures. Rainfall varies greatly: highest in Meghalaya hills (Mawsynram), heavy on Western Ghats, moderate in plains, low in Rajasthan and Ladakh.
Traditional Indian Seasons
Ancient texts describe six seasons: Vasanta (spring), Grishma (summer), Varsha (monsoon), Sharad (autumn), Hemanta (pre-winter), and Shishira (winter).
Climatic Variations and Global Warming
Despite monsoonal unity, India shows diverse climatic regions. Global warming may alter monsoon patterns, increasing variability and extreme events.
Important Definitions in NCERT Notes Class 11 Geography India Physical Environment Chapter 4: Climate
Here we have explained the key concepts and terms of this chapter to make it easy for you to understand.
- Monsoon: Seasonal reversal of wind direction bringing heavy rainfall in summer.
- Burst of Monsoon: Sudden onset of heavy rainfall with thunder and lightning.
- Western Disturbances: Temperate cyclones from the Mediterranean bring winter rain to northwest India.
- Octroi: Rain during the retreating monsoon in coastal Tamil Nadu.
- Mango Showers: Pre-monsoon rains in Kerala are helping mango fruiting.
- Kal Baisakhi: Violent thunderstorms in West Bengal during summer.
- Loo: Hot, dry winds in the northern plains during summer.
- El Niño: Warming of Pacific Ocean waters affects monsoon strength.
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FAQs
The four seasons are cold weather (winter), hot weather (summer), southwest monsoon (rainy), and retreating monsoon (transition).
It is due to the seasonal reversal of winds that bring heavy rainfall in summer and dry conditions in winter.
Mawsynram in Meghalaya receives the highest rainfall due to the orographic effect.
Western cyclonic disturbances originating from the Mediterranean Sea cause this rainfall.
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