Chapter 4 – Climate
What type of climate does India have?
India has a monsoon-type climate characterized by seasonal reversal of winds, hot summers, and wet monsoon seasons. It varies from tropical in the south to temperate in the north.
What is the southwest monsoon?
It is the seasonal wind that brings heavy rainfall to most of India from June to September, originating from the Indian Ocean and Arabian Sea.
What causes the southwest monsoon?
It is caused by intense heating of the Indian subcontinent, low-pressure formation, and the southeast trade winds being deflected as southwest winds due to the Coriolis force.
What is the retreating monsoon?
From October to December, monsoon winds start retreating as the landmass cools. It brings rainfall mainly to southeastern India (especially Tamil Nadu).
What is the cold weather season in India?
From December to February, the northern parts experience cold weather due to the movement of western disturbances and dry continental winds.
What are western disturbances?
They are temperate cyclones originating over the Mediterranean Sea. In winters, they bring rain and snow to north and northwest India.
What is the hot weather season?
From March to May, high temperatures prevail, particularly in north India. Heat waves, dust storms, and local winds like loo occur during this time.
What is loo?
Loo is a hot, dry, and dusty wind that blows over the northern plains during summer. It causes heatstrokes and dehydration.
What are local winds?
Winds specific to a region, such as loo in north India and kalbaisakhi in eastern India, that affect weather locally during summer months.
What is kalbaisakhi?
Also called Nor’westers, they are violent thunderstorms in eastern India during pre-monsoon months, bringing rain, lightning, and damage to crops.
What is mango shower?
Pre-monsoon showers in Kerala and Karnataka, locally known as mango showers because they help in the ripening of mangoes.
What is the role of ITCZ in India’s climate?
The Inter-Tropical Convergence Zone (ITCZ) shifts northward in summer, causing low pressure over India and drawing in moisture-laden monsoon winds.
What are jet streams?
High-altitude fast-flowing winds that influence monsoon development and movement, especially subtropical westerly and easterly jet streams.
What is El Niño?
A warming of Pacific Ocean waters that affects global weather, including weakening of Indian monsoon, leading to droughts in India.
What is La Niña?
It is the cooling phase of Pacific Ocean temperatures, often associated with stronger monsoons and higher rainfall in India.
Why is monsoon called a unifying bond?
Despite regional differences, monsoon influences the economy, agriculture, festivals, and social life across all parts of India, creating a common seasonal experience.
What is the average annual rainfall in India?
India receives an average of about 1,180 mm of rainfall annually, with regional variations ranging from 100 mm in Rajasthan to over 11,000 mm in Mawsynram.
Which is the wettest place in India?
Mawsynram in Meghalaya receives the highest annual rainfall in the world, over 11,800 mm, due to orographic lift caused by Khasi Hills.
What is the driest place in India?
Jaisalmer in Rajasthan is one of the driest places, receiving less than 120 mm of rainfall annually due to desert conditions.
How does the Himalayas affect India’s climate?
The Himalayas block cold Siberian winds, keeping northern India warmer in winter. They also force monsoon winds to rise and bring rain.
Why does Tamil Nadu receive winter rainfall?
Due to retreating northeast monsoon winds that blow over the Bay of Bengal, pick up moisture, and cause rain on Tamil Nadu’s coast.
What causes rainfall during summer in India?
Intense surface heating creates low pressure, drawing in moisture-rich winds from the sea, which rise, cool, and condense to form rain.
Why does rainfall vary in India?
Rainfall distribution is affected by topography, wind direction, monsoon strength, and distance from the sea. Coastal and hill areas receive more rain than interiors.
What is the significance of monsoon rainfall?
Monsoon rain supports agriculture, water supply, hydroelectricity, and replenishes rivers. A weak monsoon can cause drought and food scarcity.
What are rain shadow areas?
Regions on the leeward side of mountains receive little rain because winds lose moisture on the windward side. Example: Eastern Maharashtra behind Western Ghats.
What is the role of the Thar Desert in the monsoon?
Intense heating over the Thar Desert creates low pressure, drawing in monsoon winds from oceans and enhancing summer rainfall.
What are the effects of monsoon failure?
Failure leads to crop loss, drought, famine, water shortages, and impacts the economy, especially in agriculture-dependent regions.
How does climate affect Indian agriculture?
Climatic factors like rainfall and temperature determine crop types, sowing/harvest times, and yield. Monsoon timing is critical for kharif crops.
What is climate variability?
It refers to short-term changes in climate patterns. In India, variability in monsoon onset, duration, and intensity leads to unpredictable weather and agriculture challenges.