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Indian Geography : भारत की जलवायु & वर्षा | Climate | Lecture #09 | Part-1
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Overview
This video explains the climate of India, differentiating between weather and climate, and defining India's climate as tropical monsoon. It details the formation of monsoons based on the thermal theory, explaining how temperature differences create pressure gradients that drive wind. The video elaborates on the two main branches of the Southwest Monsoon (Arabian Sea and Bay of Bengal) and their impact on rainfall across different regions of India. It also touches upon the Northeast Monsoon, Western Disturbances, and their effects on agriculture, concluding with a discussion of rainfall distribution across India and specific regional phenomena like 'Amr Varsa'.
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Chapters
- Climate is the long-term average of atmospheric conditions (temperature, pressure, wind, precipitation) over decades, while weather is the short-term state of the atmosphere.
- India's climate is classified as 'Tropical Monsoon Climate'.
- The term 'monsoon' originates from the Arabic word 'Mausam', meaning seasonal wind shift.
- Factors influencing a region's climate include latitude, altitude, distance from the sea, and topography.
Distinguishing between climate and weather is crucial for understanding long-term environmental patterns and their impact on human activities and ecosystems.
Shimla and Amritsar are at the same latitude, but their climates differ due to Shimla's higher altitude.
- Monsoon formation is primarily driven by seasonal temperature variations, leading to pressure differences.
- During summer, the Indian subcontinent heats up, creating a low-pressure area.
- Conversely, the Indian Ocean remains cooler, maintaining a high-pressure area.
- Winds naturally flow from high-pressure areas (Indian Ocean) to low-pressure areas (Indian subcontinent), bringing moisture and causing rainfall.
Understanding the thermal theory explains the fundamental mechanism behind the seasonal reversal of winds that characterize monsoons, impacting agriculture and water resources.
In summer, the landmass of India heats up more than the surrounding oceans, creating a low-pressure zone that draws moisture-laden winds from the high-pressure Indian Ocean.
- The Southwest Monsoon has two main branches: the Arabian Sea branch and the Bay of Bengal branch.
- The Arabian Sea branch first hits the Kerala coast around June 1st.
- It then divides into three sub-branches: one causing heavy rainfall along the Western Ghats, another entering through the Narmada-Tapti valleys, and a third moving towards Gujarat and Rajasthan.
- The eastern slopes of the Western Ghats experience less rainfall due to the 'rain shadow effect'.
This branch is responsible for the majority of India's annual rainfall, significantly impacting agriculture and water availability in western and central India.
The Western Ghats receive heavy rainfall, while the leeward side (eastern slopes) forms a rain shadow region affecting states like Tamil Nadu, Karnataka, and Andhra Pradesh.
- The Bay of Bengal branch first strikes the coast of Myanmar and Bangladesh.
- It then splits, with one part moving into West Bengal and the Ganga plains, and another entering the Brahmaputra valley.
- This branch causes significant rainfall in Northeast India, including Meghalaya, where Mawsynram receives the world's highest average annual rainfall.
- The 'U'-shaped Garo hills funnel clouds, leading to extreme rainfall in Mawsynram.
This branch is vital for rainfall in eastern and northeastern India, supporting agriculture in the fertile plains and contributing to the unique high-rainfall zone in Meghalaya.
Mawsynram in Meghalaya, situated within the Garo hills, receives exceptionally high rainfall due to the funneling effect of the mountains.
- The Northeast Monsoon occurs during winter, with winds blowing from land to the Indian Ocean.
- A portion of these winds picks up moisture from the Bay of Bengal, causing rainfall in Tamil Nadu, Andhra Pradesh, and Odisha in October-November.
- Western Disturbances are extra-tropical storms originating from the Mediterranean Sea and Atlantic Ocean.
- These disturbances bring winter rainfall and snowfall to northwestern India, crucial for Rabi crops like wheat.
These phenomena provide essential rainfall during the dry winter months, supporting specific crops and influencing the climate of northwestern India.
Western Disturbances cause snowfall in Jammu and Kashmir and rain in the plains of Punjab, benefiting the winter wheat crop.
- India's average annual rainfall is about 125 cm, but distribution is uneven.
- Areas receiving over 100 cm rainfall are suitable for rice cultivation (Kharif crops).
- Regions with less than 100 cm rainfall are generally suited for wheat cultivation (Rabi crops).
- 'Amr Varsa' (Mango Showers) are pre-monsoon showers in Bihar and Bengal that benefit mango crops.
Understanding rainfall patterns is fundamental to agricultural planning, crop selection, and water management across different regions of India.
Eastern India, with higher rainfall, predominantly cultivates rice, while northwestern India, with lower rainfall, focuses on wheat cultivation.
Key takeaways
- India's climate is uniquely tropical monsoon, characterized by seasonal wind shifts that dictate rainfall patterns.
- The thermal contrast between land and sea during summer is the primary driver for the onset of the Southwest Monsoon.
- The Southwest Monsoon's two branches (Arabian Sea and Bay of Bengal) bring most of India's annual rainfall, with regional variations.
- Rainfall distribution is uneven, with some areas receiving extreme rainfall (Mawsynram) and others experiencing drought conditions (Western Rajasthan).
- Winter precipitation from the Northeast Monsoon and Western Disturbances is vital for specific regions and crops like wheat.
- Climate directly influences agricultural practices, dictating suitable crops for different rainfall regimes.
- Phenomena like the 'rain shadow effect' and 'Amr Varsa' highlight localized climatic influences on geography and agriculture.
Key terms
ClimateWeatherTropical Monsoon ClimateThermal TheorySouthwest MonsoonArabian Sea BranchBay of Bengal BranchNortheast MonsoonWestern DisturbancesRain Shadow EffectAmr VarsaLatitudeAltitude
Test your understanding
- What is the fundamental difference between climate and weather, and why is India's climate classified as 'Tropical Monsoon'?
- How does the thermal theory explain the formation and direction of the Southwest Monsoon winds?
- Describe the two main branches of the Southwest Monsoon and explain how their paths lead to varied rainfall patterns across India, including the concept of a rain shadow.
- What are Western Disturbances, and why are they significant for the climate and agriculture of northwestern India during winter?
- How does the uneven distribution of rainfall across India influence agricultural practices and crop choices in different regions?