Notes Chapter 3 Climates of India Class 7 Social Science

Introduction

• Weather: Day-to-day conditions like rain, sunshine, or wind.
• Climate: Long-term weather patterns in a region (over decades).
• Seasons: Recurring periods in a year (e.g., spring, summer, monsoon, autumn, winter).
• In India, traditionally six seasons (ṛitus): vasanta (spring), grīṣhma (summer), varṣhā (rainy), śharad (autumn), hemanta (pre-winter), śhiśhir (winter).
• Seasons influence crops, food, clothing, and festivals, aligning human, plant, and animal life with nature.

Weather, Seasons, and Climate

• Weather: Short-term, changes hourly or daily (e.g., rainy, sunny, windy).
• Seasons: Annual cycles tied to Earth’s revolution around the Sun.
• In India: Spring, summer, monsoon, autumn, winter, plus the rainy season.
• Seasons affect weather (e.g., hot and dry in summer, rainy in monsoon).
• Climate: Long-term weather pattern of a region, stable over decades but changing recently due to human activities.

Activities

• Write an essay on favorite seasons.
• Discuss seasonal events (songs, feasts, practices) in groups and document them.
• Identify trees that change color or shed leaves before winter and document their local names.

Types of Climates in India

India’s diverse geography leads to varied climates:

• Alpine (Himalayas): Cold, snowy winters, cool summers; thick clothing used.
• Temperate (Lower Himalayas, hilly areas): Moderately cold winters, mild summers; popular hill stations.
• Subtropical (Northern Plains): Very hot summers, cold winters; major wheat-growing region.
• Arid (Thar Desert): Hot days, cool nights, minimal rainfall; unique water conservation methods.
• Tropical Wet (Western Coastal Strip): Heavy monsoon rainfall, ideal for rice and spices.
• Semi-Arid (Deccan Plateau): Hot summers, mild winters, moderate rainfall.
• Tropical (Eastern India, Southern Peninsula): Mild winters, distinct wet and dry periods due to monsoons.

Factors Determining Climate

Latitude:

• Near Equator (low latitudes): Warmer due to direct sunlight (e.g., Kanniyakumari).
• Near poles (high latitudes): Colder due to oblique sunlight (e.g., Srinagar).
• Sun’s rays at Equator are perpendicular, concentrating energy; at poles, they are spread out.

Altitude:

• Higher altitudes are cooler due to lower air density and distance from Earth’s heated surface.
• Hill stations (e.g., Ooty, Shimla) are cooler than nearby plains (e.g., Coimbatore).
• Himalayas’ high peaks remain snow-covered year-round.

Proximity to the Sea:

• Coastal areas have milder temperatures (e.g., Mumbai: 32°C summer, 18°C winter).
• Inland areas have extreme temperatures (e.g., Nagpur: 44°C summer, 10°C winter).
• Sea moderates temperature as it absorbs and loses heat slowly.

Winds:

• Hot, dry winds from deserts (e.g., Arabia) cause heatwaves in summer (e.g., Punjab, Rajasthan).
• Cold winds from Himalayas cause cold waves in winter.
• Sea winds bring moisture, leading to rainfall.

Topography:

• Himalayas shield India from cold Central Asian winds.
• Flat Thar Desert is exposed to hot, dry winds.
• Western Ghats influence monsoon rainfall distribution.

Microclimates

• Small areas with unique climates (e.g., enclosed valleys, forests, urban heat islands).
• Urban heat islands: Cities with concrete structures trap heat, making them warmer than surroundings.
• Microclimates affect local flora, fauna, crops, and human health.

Activities

• Compare temperatures of Ooty (10–25°C) and Coimbatore (25–38°C) despite similar latitude, explaining altitude’s role.

The Monsoons

Monsoon: Seasonal winds (from Arabic “mausim” = season) bringing heavy rains, vital for agriculture.

Mechanism:

Summer (Southwest Monsoon):

• Land heats up, creating low pressure.
• Winds blow from high-pressure ocean to land, carrying moisture.
• Moisture condenses over land, causing heavy rains.
• Starts in southern India (early June), covers subcontinent by mid-July.
• Western Ghats cause heavy rain on western slopes, less on Deccan Plateau.

Winter (Northeast Monsoon):

• Land cools faster, creating high pressure.
• Winds blow from land to ocean, bringing dry conditions.
• Some winds over Bay of Bengal bring rain to east and south India.

Facts:

• Mawsynram (Meghalaya) receives the world’s highest rainfall (~11,000 mm annually).
• Monsoons inspire classical music ragas (e.g., Meghamalhar, Amruthavarshini).

Traditional Knowledge:

• Fishermen predict monsoons when fish surface (Konkan coast).
• Golden Shower tree blooming indicates monsoon in ~50 days (southern India).
• Crow nests: High = less rain, low = heavy rain.

Activities

• List local traditional knowledge about rain, fog, snow, or hail.
• Organize a cultural fest showcasing traditional festivals, dances, and songs linked to agriculture and rain.

Climate and Our Lives

Culture: Festivals like Baisakhi, Pongal, and Onam are tied to seasons and agriculture.

Economy:

• Monsoon failure (poor rainfall) leads to:
• Reduced agricultural output.
• Water scarcity, forcing women to travel for water.
• Migration of laborers to cities.
• Higher food prices, causing inflation.
• Industries rely on predictable weather and water availability.

Socioeconomic Impact: Climate affects livelihoods, food security, and economic stability.

Climates and Disasters

India’s diverse climates cause extreme weather events:

Cyclones:

• Common on eastern coast, causing destruction (e.g., loss of life, property damage).
• Formed by low-pressure systems over seas, drawing moist air that forms clouds and rotates.
• “Eye of the cyclone”: Calm, cloudless center.
• Monitored by India Meteorological Department (IMD).
• National Disaster Response Force (NDRF) aids rescue during cyclones.

Floods:

• Caused by heavy rainfall or overflowing rivers/lakes.
• Common in Uttar Pradesh, Bihar, Kerala, Andhra Pradesh, Assam.
• Himalayan glacial lake bursts (e.g., 2013 Uttarakhand flood) cause devastation.
• Urban flooding due to poor drainage and concrete surfaces.

Landslides:

• Sudden collapse of rock/soil in hilly areas (e.g., Himachal Pradesh, Uttarakhand).
• Triggered by heavy rain, earthquakes, or human activities (deforestation, poor construction).

Forest Fires:

• Spread rapidly in dry conditions, fueled by drought or human carelessness.
• Common in Uttarakhand, Himachal Pradesh, Western Ghats.
• Harm wildlife, ecosystems, air quality, and displace communities.

Activities

• Describe effects of cyclones, floods, landslides, and forest fires on people, plants, animals, and economy.
• In groups, identify natural vs. human causes of disasters and suggest preventive measures.

Climate Change

Definition: Long-term changes in climate (temperature, precipitation, weather events) on global or regional scales.

Causes:

• Historically natural, but since the 19th century, driven by human activities:
• Burning fossil fuels (coal, oil, gas) releases greenhouse gases (e.g., CO2).
• Deforestation, harmful industrial practices, excessive consumption.
• Greenhouse gases trap extra heat, causing global warming and disrupting climate patterns.

Impact in India:

• 2025: Average temperatures 1–3°C above normal, shorter/milder winters.
• Affects agriculture and small-scale industries.

Consequences:

• Extreme weather (floods, cyclones).
• Challenges to food security, health, and infrastructure.

Solutions:

• Mitigation: Reduce greenhouse gas emissions, plant trees, use renewable energy, promote sustainable lifestyles.
• Resilience: Build community adaptation to climate challenges.
• Governments promote mitigation, but economic growth often conflicts with sustainability.