Atmosphere and Climate

The atmosphere is a blanket of air that surrounds the Earth. It is held around the Earth by gravity . It is made up of different gases, water vapour, and dust particles. The atmosphere is very important because it: provides oxygen for breathing, protects us from harmful solar radiation, especially ultraviolet rays, helps in cloud formation and rainfall, controls temperature by trapping some heat, makes weather and climate possible. Without the atmosphere, life on Earth would not be possible. The Earth would become extremely hot during the day and extremely cold at night.

The atmosphere has two important aspects: Composition – what gases and particles it contains. Structure – how it is divided into different layers.

The Earth’s atmosphere is a mixture of gases. The two main gases are nitrogen and oxygen . Main gases in the atmosphere Nitrogen – 78% It is the most abundant gas. It is important for plant growth because plants need nitrogen to make proteins. Oxygen – 21% It is necessary for breathing and burning. Argon – 0.93% It is present in small quantity. Carbon dioxide – 0.04% Plants use carbon dioxide for photosynthesis. It also helps in maintaining Earth’s temperature. Other gases – very small amount These include helium, neon, krypton, xenon, ozone, hydrogen, etc. The atmosphere also contains water vapour and dust particles . Water vapour helps in the formation of clouds and rainfall. Dust particles help water vapour to condense into tiny droplets.

The atmosphere is divided into different layers on the basis of changes in temperature and density with height. The main layers are: Troposphere Stratosphere Mesosphere Thermosphere Exosphere

The troposphere is the lowest and most important layer of the atmosphere. Its average height is about 12 km . Most of the air we breathe is found in this layer. Most weather activities such as clouds, rainfall, fog, storms, and hail occur here. In this layer, temperature decreases as altitude increases. The upper boundary of the troposphere is called the tropopause .

The stratosphere lies above the troposphere and extends up to about 50 km . This layer is suitable for flying aeroplanes because it is mostly free from clouds and weather disturbances. The important feature of this layer is the presence of the ozone layer . The ozone layer protects us from harmful ultraviolet radiation from the Sun. The upper boundary of the stratosphere is called the stratopause .

The mesosphere lies above the stratosphere and extends up to about 80 km . In this layer, temperature again decreases with increasing height. Most meteors burn up in this layer before reaching the Earth’s surface.

The thermosphere lies above the mesosphere and extends from about 80 km to 700 km . In this layer, temperature increases very rapidly with height because gas molecules absorb X-rays and ultraviolet radiation from the Sun. The ionosphere is a part of the thermosphere. It helps in radio communication by reflecting radio waves back to Earth. Auroras, also called northern and southern lights, occur in this layer.

The exosphere is the uppermost layer of the atmosphere. The air is extremely thin here. Light gases like hydrogen and helium may escape into space from this layer. This layer gradually merges with outer space.

In this chapter, auroras are mentioned in the thermosphere . They occur when charged particles from the Sun, called solar wind , enter the Earth’s atmosphere and move towards the magnetic poles. When these particles interact with atmospheric gases, the gases glow in different colours. There are two main types: Aurora Borealis – seen in the Northern Hemisphere. Aurora Australis – seen in the Southern Hemisphere. The word aurora comes from Latin and means “dawn” or “morning light.”

Weather Weather refers to the day-to-day and hour-to-hour condition of the atmosphere. For example, today may be sunny, tomorrow may be cloudy, and the next day may be rainy. Weather changes quickly. Climate Climate refers to the average weather conditions of a place over a long period of time, usually 30 years or more . For example, Rajasthan has a hot and dry climate, while Kerala has a warm and wet climate. Difference between Weather and Climate Weather changes quickly, but climate changes slowly over a long period. Weather is short-term, while climate is long-term.

The major elements of weather and climate are: Temperature Humidity Precipitation Atmospheric pressure Wind

Temperature means the degree of hotness or coldness of the air. The main source of heat is the Sun. The incoming solar energy received by the Earth is called insolation . Temperature decreases from the equator towards the poles because the Sun’s rays fall directly near the equator and slantingly near the poles.

Humidity means the amount of water vapour present in the air. When water evaporates from oceans, rivers, lakes, and land, it becomes water vapour. Warm air can hold more water vapour than cold air. High humidity makes us feel uncomfortable because sweat does not evaporate quickly. Clothes also take longer to dry on humid days.

Precipitation means the falling of water from the atmosphere to the Earth. It may occur in the form of: rain, drizzle, snow, sleet, hail. Rain is the most common form of precipitation. It helps in agriculture, fills rivers and reservoirs, and recharges groundwater. Long absence of rainfall may lead to drought.

Atmospheric pressure is the pressure exerted by the weight of air on the Earth’s surface. Air pressure is highest at sea level and decreases with height. Warm air rises and creates low pressure. Cold air sinks and creates high pressure. Low pressure is usually linked with cloudy and wet weather. High pressure is usually linked with clear and sunny weather.

Wind is the movement of air from a high-pressure area to a low-pressure area. Winds may be gentle or very strong. Strong winds can uproot trees, damage houses, and disturb transport. Winds are named after the direction from which they blow. For example, a wind blowing from the west is called a westerly wind .

Land and sea breeze are local winds that affect coastal areas. Sea Breeze Sea breeze blows from sea to land during the day. During the day, land heats up faster than the sea. The air over land becomes warm and rises, creating low pressure. The sea remains cooler and has relatively high pressure. So, cool air from the sea moves towards the land. Sea breeze makes coastal areas cooler during the day.

Land breeze blows from land to sea during the night. At night, land cools faster than the sea. The sea remains warmer. So, air moves from the cooler land towards the warmer sea. Land breeze is usually weaker than sea breeze.

India has a tropical monsoon climate . The Indian Meteorological Department divides the year into four main seasons. 1. Winter Season The winter season generally lasts from December to early April . December and January are the coldest months. Northern India experiences lower temperatures, while southern India remains comparatively warmer. 2. Summer or Pre-Monsoon Season This season lasts from April to June , and sometimes up to July in north-western India. Temperatures are very high during this season. In northern India, May is usually the hottest month. In many inland regions, temperatures may range between 32°C and 40°C . 8.3 Monsoon or Rainy Season The monsoon season generally lasts from June to September . During this season, the south-west monsoon winds bring rainfall to most parts of India. Agriculture in India depends heavily on this rainfall.

The monsoon season generally lasts from June to September . During this season, the south-west monsoon winds bring rainfall to most parts of India. Agriculture in India depends heavily on this rainfall. 4. Post-Monsoon or Retreating Monsoon Season This season lasts from October to December . During this period, the monsoon begins to withdraw from India. North-western India usually has clear skies in October and November. South-eastern India, especially Tamil Nadu and parts of Andhra Pradesh, receives rainfall from the north-east monsoon.

Traditionally, India has six seasons: Vasanta – Spring Grīṣhma – Summer Varṣhā – Rainy season Śharad – Early autumn Hemanta – Late autumn Śhiśhira – Winter

The word monsoon comes from the Arabic word mausim , which means season. Monsoon means the seasonal reversal of wind direction during a year. India’s climate is strongly influenced by monsoon winds. Monsoon winds are divided into two types: South-west monsoon North-east monsoon

The south-west monsoon is also called the summer monsoon. It occurs from June to September . During summer, the Indian landmass heats up faster than the surrounding seas. This creates a low-pressure area over land and high pressure over the sea. Moist winds blow from the Indian Ocean, Arabian Sea, and Bay of Bengal towards India. These winds bring heavy rainfall. The south-west monsoon gives most of the annual rainfall to India.

The north-east monsoon is also called the winter monsoon. It occurs from October to February . During winter, the Indian landmass cools faster than the surrounding seas. This creates high pressure over land and low pressure over the sea. Dry winds blow from land to sea. These winds do not bring much rainfall to most parts of India. However, when they pass over the Bay of Bengal, they collect moisture and give rainfall to the eastern coast, especially Tamil Nadu, Andhra Pradesh, and parts of Karnataka.

Monsoon is very important for India because: agriculture depends on monsoon rainfall, crops need rainwater for sowing and growth, rivers, wells, and reservoirs are filled by monsoon rain, it affects drinking water supply, it influences transport, festivals, employment, and rural life. A good monsoon brings prosperity, while weak monsoon may cause drought. Excessive rainfall may cause floods. The chapter also mentions India’s official efforts to improve monsoon prediction through the National Monsoon Mission , whose objective is to improve monsoon forecasts over different time scales. Mission Mausam was launched to strengthen India’s weather and climate prediction systems and make the country more resilient to weather-related hazards.

Climate change means long-term changes in weather patterns such as temperature, rainfall, and wind. The main causes of climate change are human activities such as: burning fossil fuels, deforestation, industrial pollution, excessive use of vehicles, wastage of energy and resources. These activities increase greenhouse gases such as carbon dioxide, methane, nitrous oxide, and water vapour. These gases trap heat in the atmosphere and cause global warming.

Climate change causes: rise in global temperature, more frequent floods, droughts, melting of glaciers, rise in sea level, loss of biodiversity, health problems, damage to agriculture, loss of livelihoods.

A carbon footprint is the total amount of greenhouse gases released due to human activities. We can reduce our carbon footprint by: walking or cycling for short distances, using public transport, switching off lights and fans when not in use, saving water, avoiding single-use plastic, reusing and recycling materials, planting trees, using renewable energy, following a sustainable lifestyle.

In 2025, Punjab experienced severe floods due to heavy monsoon rains and swelling of major rivers such as the Satluj , Beas, Ravi, and Ghaggar. The floods damaged villages, agricultural fields, houses, roads, bridges, and public infrastructure. Reports also linked the disaster to extreme rainfall, weak embankments, floodplain encroachment, and poor drainage conditions. News reports described the 2025 Punjab floods as one of the worst floods in decades, causing serious losses to lives, homes, crops, and livestock.

The causes can be divided into two parts: Natural Causes Very heavy monsoon rainfall occurred in Punjab. Western disturbances brought additional moisture and rain. Heavy rainfall also occurred in Himachal Pradesh and Jammu & Kashmir. Rivers like Satluj , Beas, Ravi, and Ghaggar were already flowing high. Additional rainwater from hills and local rainfall caused rivers to overflow. Human-Made Causes Weak and old embankments could not stop the rising water. Houses and farms were built too close to rivers. Floodplains were encroached. Silt and mud reduced the capacity of rivers and dams. Flood warnings were delayed or not clearly communicated in some areas. Poor planning increased the damage.

The floods had serious effects on human life, agriculture, animals, and infrastructure. Major effects were: Many people lost their lives. Thousands of people had to leave their homes. People were shifted to relief camps. Large areas of farmland were submerged. Paddy and other crops were badly damaged. Poultry and dairy farms were destroyed. Animals such as cows, buffaloes, and chickens became sick or died. Roads, bridges, border fences, and public buildings were damaged. Standing dirty water caused health problems and waterborne diseases. The state suffered economic loss and social disruption.

Atmosphere – The blanket of air surrounding the Earth. Gravity – The force that pulls objects towards the Earth. Altitude – Height of a place above mean sea level. Weather – Day-to-day condition of the atmosphere. Climate – Average weather condition of a place over a long period. Insolation – Incoming solar energy received by the Earth. Humidity – Amount of water vapour present in the air. Precipitation – Falling of water from the atmosphere in the form of rain, snow, hail, etc. Atmospheric Pressure – Pressure exerted by the weight of air. Wind – Movement of air from high-pressure area to low-pressure area. Monsoon – Seasonal reversal of wind direction. Carbon Footprint – Total greenhouse gases released due to human activities. Climate Change – Long-term change in weather patterns caused mainly by human activities. Aurora – Colourful lights seen near the poles in the sky.

The atmosphere is a blanket of air around the Earth. It is made up mainly of nitrogen and oxygen, along with small amounts of other gases, water vapour, and dust particles. It protects life on Earth, helps in rainfall, regulates temperature, and makes weather and climate possible. The atmosphere has five main layers: troposphere, stratosphere, mesosphere, thermosphere, and exosphere. The troposphere is the most important layer for weather. The stratosphere contains the ozone layer. Meteors burn in the mesosphere. The thermosphere helps in radio communication and contains auroras. The exosphere is the outermost layer. Weather means the short-term condition of the atmosphere, while climate means the average weather of a place over a long period. The main elements of weather and climate are temperature, humidity, precipitation, atmospheric pressure, and wind. India has a tropical monsoon climate. The four main seasons are winter, summer, monsoon, and post-monsoon. The south-west monsoon brings most of India’s rainfall, while the north-east monsoon gives rainfall mainly to the south-eastern coast.

The case study of the Punjab floods of 2025 shows how heavy rainfall, overflowing rivers, weak embankments, encroachment near rivers, and poor preparedness can cause severe damage. It teaches us the importance of disaster management, better planning, early warning systems, and environmental awareness.

Atmosphere is the blanket of air around the Earth. Nitrogen is 78% and oxygen is 21% of the atmosphere. Troposphere is the layer where weather occurs. Stratosphere contains the ozone layer. Weather is short-term; climate is long-term. Wind blows from high pressure to low pressure. Sea breeze blows from sea to land during the day. Land breeze blows from land to sea at night. India has a tropical monsoon climate. South-west monsoon brings most rainfall to India. North-east monsoon gives rainfall to Tamil Nadu and nearby regions. Climate change is caused mainly by human activities. Reducing carbon footprint helps protect the environment. Punjab floods 2025 show the need for better flood management and preparedness.

Thermosphere: This layer helps in radio communication because the ionosphere, which is part of the thermosphere, reflects radio waves back to Earth. Auroras also occur in this layer. Exosphere: This is the outermost layer of the atmosphere. The air is extremely thin here, and light gases such as hydrogen and helium may escape into space. Thus, each layer protects the Earth and supports weather, communication, temperature balance, and life.

My Carbon Footprint Step 1: My Daily Habits A. Transport I use public transport/carpool. Medium impact B. Electricity Use I always switch off electrical appliances like lights and fans when not in use. Low impact C. Water Use I sometimes waste water by leaving the tap running or using extra water. Medium impact D. Waste and Plastics I reuse, recycle, and avoid single-use plastics. Low impact Step 2: Score Yourself Transport: Medium impact = 2 points Electricity use: Low impact = 1 point Water use: Medium impact = 2 points Waste and plastics: Low impact = 1 point Total score = 2 + 1 + 2 + 1 = 6 points This means my carbon footprint is not very high, but I can still improve my habits.

Step 3: My Climate Action Pledge I will make these two simple changes to reduce my score: I will save water by closing taps properly and using only the required amount of water. I will walk or cycle for short distances and avoid using private vehicles unnecessarily. By following these habits, I can reduce my carbon footprint and help protect the environment.

6(a). The troposphere and stratosphere

6(b). The south-west monsoon and north-east monsoon

After studying the table, we can make these observations: India has great climatic diversity. Coastal stations like Mumbai, Chennai, and Thiruvananthapuram have more equable climate. Inland stations like Delhi, Jodhpur, and Nagpur have more extreme temperatures. Mountain stations like Shillong and Leh are cooler because of altitude. Most stations receive maximum rainfall during the monsoon months. Chennai receives more rainfall during the retreating monsoon period. Leh receives very little rainfall because it lies in a rain-shadow region.

In north-eastern India , heavy rainfall is common. Many houses have sloping roofs and are sometimes built on raised platforms or stilts to protect them from rainwater and floods. People use raincoats, umbrellas, and light clothes suitable for a humid climate. In the Gangetic plains , summers are hot and winters are cool. People wear cotton clothes in summer and woollen clothes in winter. Houses are generally built according to both heat and winter conditions. Thus, houses and clothing are strongly influenced by climate, rainfall, temperature, and relief of a region. This shows how people adapt their lifestyle to their physical environment.