Class 9 Social Science: ATMOSPHERE AND CLIMATE — Chapter Question Set

(b) Blanket of air surrounding Earth

(b) Nitrogen and Oxygen

(b) 0.1-0.4%

(b) 12 km

(b) Stratosphere

(c) Mesosphere

(d) Thermosphere

(b) Day-to-day atmospheric conditions

(c) Average weather over 30+ years

(b) Incoming solar energy

(b) Presence of water vapour in air

(c) Fog

(b) Sea level

(b) High to low pressure

(b) Arabic

(b) Sea to land

(b) Eastern coast

(b) December to early April

(b) April to June/July

(c) June to September

(d) October to December

(b) Stratosphere

(b) Very thin air

(b) Solar wind interacting with gases

(b) Northern Hemisphere

(a) Southern Hemisphere

(b) Troposphere and Mesosphere

(c) Thermosphere

(d) Thermosphere

(b) Greenhouse gases released by humans

(b) Ministry of Earth Sciences

(a) Weather Ready and Climate Smart

(c) December and January

(b) May

(b) Shillong

(b) Leh

(b) Clear and sunny skies

(b) Cloudy and wet weather

(a) March-April

(c) July-August

(b) Meghadutam

(b) Varahamihira

(b) Human activities mainly

(c) Carbon dioxide

(a) Tropopause

(b) Stratopause

(b) Rises rapidly

(d) Exosphere

(a) Kallanai

(b) Earthen bunds on hillslopes

The atmosphere is composed of nitrogen and oxygen as primary gases, along with carbon dioxide, argon, helium, neon, krypton, xenon, ozone, hydrogen, water vapour, and dust particles.

The atmosphere has five major layers extending from Earth's surface to outer space: Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere.

The major elements impacting human life are temperature, precipitation, humidity, wind, and atmospheric pressure. These elements can change under varying conditions.

The amount of insolation decreases from the equator towards the poles. Hence, temperature decreases from the equator towards the poles.

Sea breeze blows from sea to land during daytime when land becomes warmer. Land breeze blows from land to sea at night when land cools faster than sea.

The Indian Meteorological Department recognizes Winter, Summer (pre-monsoon), Monsoon (rainy/advancing monsoon), and Post-monsoon (retreating monsoon) seasons.

Southwest monsoon (summer) blows from sea to land bringing most rainfall. Northeast monsoon (winter) blows from land to sea, bringing rainfall to southeastern regions.

Climate change refers to long-term changes in weather patterns caused mainly by human activities like burning of fossil fuels and deforestation that release greenhouse gases.

We can reduce carbon footprint by walking, cycling, using public transport, switching off electrical appliances, using water judiciously, and avoiding single-use plastics.

The National Monsoon Mission under the Ministry of Earth Sciences aims to enhance monsoon predictions for India over all time frames using state-of-the-art models.

Traditional seasons are Vasanta (March-April), Grishma (May-June), Varsha (July-August), Sharad (September-October), Hemanta (November-December), and Shishira (January-February).

Weather refers to hour-to-hour and day-to-day conditions of the atmosphere. Climate refers to the sum total of weather conditions over a large area for an extended period.

Air always moves from high-pressure areas to low-pressure areas. This movement of air from high-pressure to low-pressure areas is called wind.

The troposphere contains the air we breathe, most water vapour and clouds, and nearly all weather phenomena like rainfall, fog, and hail occur in this layer.

The ozone layer in the stratosphere shields us by filtering the Sun's harmful radiation, including ultraviolet radiation that can damage life on Earth.

Most meteorites entering from space burn up in the mesosphere due to friction with atmospheric gases at high altitudes.

The thermosphere contains the ionosphere which helps with radio transmission by reflecting radio waves transmitted from the Earth back towards it.

On humid days, clothes take longer to dry, and sweat evaporates more slowly, leaving us feeling very uncomfortable due to high moisture levels in the air.

Precipitation includes drizzle, rain, snow, sleet, and hail. Rain is the most common form and lowers the temperature of a place.

In areas with high temperatures, air heats up and rises creating low-pressure. In areas with lower temperatures, air sinks creating high-pressure.

High pressure is associated with clear and sunny skies. Low pressure is associated with cloudy skies and wet weather.

Mission Mausam is designed to position India as a global leader in weather and climate sciences, making the nation 'Weather Ready' and 'Climate Smart'.

Kalidas in Meghadutam mentions monsoon onset. Krishna'shara and Brihatsamhita describe rainfall prediction methods based on Moon, Sun positions, and nakshatras.

Coastal regions have moderate climate because local winds like sea breeze and land breeze create moderate climatic conditions, preventing extreme temperatures.

Temperature decreases with increasing altitude in the troposphere and mesosphere. As we go higher, air becomes thinner and temperature drops.

Shillong receives more rainfall than Kolkata due to its higher altitude and location, which causes more condensation and precipitation from monsoon winds.

Delhi receives more rainfall than Jodhpur because it is closer to the monsoon wind path and has more favorable conditions for precipitation.

The Punjab Floods 2025 case study demonstrates how natural factors (heavy monsoon rains) and human-made factors (weak embankments) together cause devastating floods.

Climate change causes more frequent floods, droughts, melting of glaciers, rising sea levels, loss of biodiversity, and impacts on agriculture, health, and livelihoods.

The atmosphere regulates Earth's temperature by trapping some of the Sun's energy and preventing it from escaping back into space through the greenhouse effect. 5-MARK QUESTIONS (100 Words with Intro - Points - Conclusion)

Introduction: The Earth's atmosphere is a mixture of gases in various proportions, vital for survival, pulled down by gravity, and shielding us from harmful radiation.
Points:
• Composition: Nitrogen and oxygen are primary gases. Others include carbon dioxide, argon, helium, neon, krypton, xenon, ozone, hydrogen, water vapour (0.1-0.4%), and dust particles.
• Troposphere: Most important layer up to 12 km. Temperature decreases with altitude. Contains air, water vapour, clouds, and all weather phenomena.
• Stratosphere: Extends up to 50 km. Contains ozone layer filtering UV radiation. Ideal for aeroplanes as it is free of weather disturbances.
• Mesosphere: Extends up to 80 km. Temperature decreases with altitude. Most meteorites burn up here.
• Thermosphere: Extends from 80 to 700 km. Temperature rises rapidly as gas molecules absorb X-rays and short-wave UV. Contains ionosphere for radio transmission and auroras occur here.
• Exosphere: Uppermost layer with very thin air. Light gases like helium and hydrogen escape into space due to weak gravity.
Conclusion: Each layer plays a vital role in atmospheric processes affecting weather and climate.

Introduction: Monsoon refers to the seasonal reversal in wind direction during a year, derived from the Arabic word 'mausim' meaning season.
Points:
• Southwest Monsoon (Summer Monsoon - June to September): Caused by unequal heating of land and sea. During summer, landmass heats faster creating low pressure over India, while ocean remains cooler with high pressure. Moist winds blow from sea to land bringing rainfall. Accounts for most of India's rainfall.
• Northeast Monsoon (Winter Monsoon - October to February): During winter, land cools faster creating high pressure over land and low pressure over seas. Cold dry winds blow from land to sea. Generally no rainfall except when winds pass over Bay of Bengal, picking up moisture and causing rainfall in Tamil Nadu, Andhra Pradesh, and parts of Karnataka.
• Effects: Monsoon plays vital role in agriculture, economy, daily life, festivals, and employment. Good monsoon ensures food production and water supply. Weak monsoon causes droughts; excessive rainfall causes floods.
Conclusion: Monsoon greatly influences the economy, lifestyle, and livelihoods of people in India.

Introduction: Weather refers to day-to-day conditions while climate is the average weather over a long period, usually thirty years or more.
Points:
• Weather vs Climate: Weather is hour-to-hour and day-to-day conditions (e.g., today's rain). Climate is sum total of weather conditions over large areas for extended periods (e.g., tropical monsoon climate of India).
• Elements of Weather/Climate: Temperature (varies with insolation), Precipitation (rain, snow, sleet, hail), Humidity (water vapour in air), Wind (air movement), Atmospheric Pressure (weight of air).
• Atmospheric Pressure: Pressure exerted by weight of air. Highest at sea level, decreases with altitude. Distribution influenced by air temperature.
• Pressure and Wind: In high temperature areas, air heats up and rises creating low-pressure (cloudy, wet). In low temperature areas, air sinks creating high-pressure (clear, sunny). Air moves from high to low pressure creating wind.
• Wind Naming: Winds are named after the direction they blow from (e.g., westerly blows from west).
Conclusion: Weather and climate elements are interconnected and shape human life on Earth.

Introduction: The Indian Meteorological Department recognizes four distinct seasons in India, reflecting the tropical monsoon climate.
Points:
• Winter (December to early April): Coldest months December-January. Temperature 10-15°C in northwest, 20-25°C in southeast.
• Summer/Pre-monsoon (April to June/July): Hottest month April in west/south, May in north. Temperature 32-40°C across most inland areas.
• Monsoon/Rainy (June to September): Humid southwest summer monsoon sweeping across country. Most rainfall occurs during this period.
• Post-monsoon/Retreating (October to December): Cloudless in northwest. South India receives more rainfall.
• Climate Change: Long-term changes in weather patterns caused by human activities - burning fossil fuels, deforestation, industrial pollution releasing greenhouse gases (carbon dioxide, methane, nitrous oxide).
• Effects: Global warming, frequent floods and droughts, melting glaciers, rising sea levels, loss of biodiversity, impacts on health, agriculture, livelihoods.
• Mitigation: Reduce carbon footprints, use renewable energy, protect forests, adopt sustainable lifestyles, switch off appliances, use water judiciously, recycle and avoid single-use plastics.
Conclusion: Every small step counts in shaping a healthier and greener future.

Introduction: Monsoon plays a vital role in India as most agriculture depends on monsoon rainfall, affecting economy, lifestyle, and livelihoods.
Points on Monsoon Role:
• Agriculture: Farmers rely on rain for sowing and growing crops. Good monsoon ensures food production.
• Water Supply: Recharges rivers, reservoirs, and wells.
• Daily Life: Affects transport, festivals, and employment, especially in rural areas.
• Economic Impact: Influences economy, lifestyle, and livelihoods of people.
• Challenges: Excessive rainfall causes floods, while weak monsoons lead to droughts.
Punjab Floods 2025 Case Study:
Natural Causes:
• Very heavy monsoon rains intensified by western disturbances
• Rains in Punjab, Himachal Pradesh, and Jammu & Kashmir
• Major rivers (Satluj, Beas, Ravi, Ghaggar) already flowing high
• Water from hills and local rainfall caused rivers to overflow
Human-made Causes:
• Weak and old river embankments (dhasi bandh) unable to stop rising water
• Houses and farms built too close to rivers, reducing natural flood spread space
• Silt and mud collected in rivers and dams reducing capacity
• Late or unclearly communicated flood warnings
Effects:
• Many lives lost
• Thousands displaced to relief camps
• Large areas of farmland damaged; paddy crops severely affected
• Poultry and dairy farms destroyed; animals sick or died
• Roads, bridges, border fences, and public buildings damaged
• Health problems due to murky standing water
Conclusion: The floods underscore the urgent need for improved flood management and preparedness through better planning and infrastructure.