Atmosphere and Climate

The atmosphere is a mixture of different gases, water vapour, and dust particles. The two most important gases are nitrogen and oxygen. Composition of the atmosphere:

Nitrogen

78%

Oxygen

21%

Argon

0.93%

Carbon dioxide

0.04%

Other gases

0.03%

Other gases include helium, neon, krypton, xenon, ozone, and hydrogen. The atmosphere also contains water vapour and tiny dust particles. Water vapour helps in cloud formation and rainfall. Dust particles help water vapour condense into droplets.

The atmosphere is divided into five main layers

troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

Troposphere

This is the lowest and most important layer. The air we breathe, most water vapour, clouds, rainfall, fog, and storms are found here. Almost all weather phenomena occur in this layer.

Stratosphere

This layer contains the ozone layer, which protects life on Earth by filtering harmful ultraviolet rays from the Sun. Aeroplanes usually fly in this layer because it is mostly free from clouds and weather disturbances.

Mesosphere

Most meteors burn up in this layer before reaching the Earth’s surface. This protects the Earth from many small space objects.

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.

Monsoon means the seasonal reversal of wind direction during a year. The word comes from the Arabic word mausim, meaning season. The monsoon mainly occurs because of the unequal heating of land and sea. During summer, the Indian landmass heats up faster than the surrounding seas. This creates a low-pressure area over land. The sea remains comparatively cooler and has high pressure. Since winds blow from high pressure to low pressure, moist winds blow from the Indian Ocean, Arabian Sea, and Bay of Bengal towards India. These are called south-west monsoon winds. They bring heavy rainfall from June to September. During winter, the Indian landmass cools faster than the sea. A high-pressure area develops over land and low pressure develops over the sea. So, winds blow from land to sea. These are called north-east monsoon winds. They are mostly dry, but when they pass over the Bay of Bengal, they pick up moisture and give rainfall to Tamil Nadu, Andhra Pradesh, and parts of Karnataka.

A carbon footprint is the total amount of greenhouse gases released into the atmosphere due to human activities such as transport, electricity use, water use, and waste production. We can reduce our carbon footprint in the following ways: Walk or use a bicycle for short distances. Use public transport or carpool. Switch off lights, fans, and appliances when not in use. Save water and avoid wasting it. Avoid single-use plastic. Reuse and recycle materials. Plant more trees. Use renewable energy wherever possible. Follow an eco-friendly and sustainable lifestyle. Small steps by every person can help reduce climate change and protect the environment.

If there were no atmosphere, life on Earth would not be possible. There would be no oxygen for humans and animals to breathe. Plants would also not get carbon dioxide for photosynthesis. The atmosphere protects us from harmful ultraviolet radiation from the Sun. Without it, harmful rays would directly reach the Earth’s surface and harm living beings. There would also be no clouds, rainfall, wind, or weather. The water cycle would stop. The atmosphere also controls the Earth’s temperature by trapping some of the Sun’s heat. Without it, days would become extremely hot and nights would become extremely cold. Meteors would not burn up in the atmosphere and could directly hit the Earth. Therefore, the atmosphere is essential for life, weather, rainfall, and protection.

Nitrogen is very useful for plants because plants need it to make proteins, chlorophyll, and other important substances required for growth. However, plants cannot directly use nitrogen gas from the air. Certain bacteria present in the soil and in the root nodules of leguminous plants convert atmospheric nitrogen into usable nitrogen compounds. This process is called nitrogen fixation. Plants absorb these nitrogen compounds from the soil through their roots. Nitrogen helps plants grow healthy leaves, stems, and seeds. It also improves soil fertility.

Strong winds can cause many problems in daily life. During storms, strong winds may uproot trees, break branches, damage roofs, and disturb electricity lines. They can blow dust into our eyes and make it difficult to see clearly. Strong winds can also create problems for cyclists, two-wheeler riders, and pedestrians. Umbrellas become difficult to use during strong winds. In coastal areas, strong winds can create high waves and disturb fishing activities. Sometimes, strong winds may delay flights, trains, and road transport. Thus, strong winds can affect transport, safety, houses, trees, electricity supply, and daily activities.

The chapter gives examples such as calm, light breeze, strong breeze, and storm. Some other categories of wind based on speed are: Wind speed helps us understand whether the wind will be harmless, uncomfortable, or dangerous.

I observed the weather report of my locality for two weeks. During the first few days, the weather was mostly sunny and warm. The temperature was high during the afternoon. After some days, clouds appeared in the sky and the humidity increased. On two days, light rainfall occurred, which reduced the temperature for a short time. During the second week, the mornings were pleasant, but afternoons were warmer. On some days, winds were stronger than usual. After rainfall, the air felt cooler and cleaner. On humid days, clothes took longer to dry and people felt uncomfortable. Main observations: Weather can change even within a single day.

Cloudy days are usually cooler than bright sunny days. Rainfall lowers the temperature. Humidity makes the weather uncomfortable. Wind direction and wind speed affect the feeling of heat or coolness. Weather reports help us plan our daily activities. This activity shows that weather is the short-term condition of the atmosphere and keeps changing from day to day.

In Hindustani Classical music, many rāgas are traditionally connected with particular seasons. These associations may vary slightly according to different traditions and teachers. Some examples are:

Rāgas such as Basant, Bahar, and Hindol are widely associated with spring, while Megh and Malhar are strongly associated with the rainy or monsoon season.

Monsoon affects the lives of people in many ways. In India, farmers depend heavily on monsoon rainfall for sowing and growing crops. A good monsoon helps in better crop production and improves the supply of food grains. Monsoon rain fills rivers, ponds, wells, and reservoirs. This helps in drinking water supply, irrigation, and groundwater recharge. It also gives relief from the summer heat. However, monsoon can also create problems. Heavy rainfall may cause waterlogging, floods, traffic jams, damage to roads, and spread of diseases. Weak monsoon can cause drought, crop failure, and water shortage. Thus, monsoon affects agriculture, water supply, transport, health, employment, and daily life. A good monsoon brings happiness and prosperity, but excessive or weak monsoon can create difficulties.

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.

LET’S EXPLORE

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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.

The atmosphere is the blanket of air that surrounds the Earth. It is held around the Earth by gravity. It is very important for life because it provides air for breathing, protects us from harmful solar radiation, helps in cloud formation and rainfall, and controls the Earth’s temperature. The atmosphere is made up of different gases, water vapour, and dust particles. The two main gases are nitrogen and oxygen. Composition of the atmosphere:

Nitrogen

78%

Oxygen

21%

Argon

0.93%

Carbon dioxide

0.04%

Other gases

0.03%

Other gases include helium, neon, krypton, xenon, ozone, and hydrogen. Water vapour helps in cloud formation and precipitation.

The atmosphere has five main layers. These layers are divided on the basis of changes in temperature and density with increasing height. Explanation: The troposphere is the most important layer for weather. The stratosphere contains the ozone layer. The mesosphere burns most meteors. The thermosphere helps in radio communication and contains auroras. The exosphere is the outermost layer.

According to the Indian Meteorological Department, India has four main seasons:

• Winter season – December to early April
• Summer or pre-monsoon season – April to June
• Monsoon or rainy season – June to September
• Post-monsoon or retreating monsoon season – October to December
• India’s climate is broadly classified as a tropical monsoon climate.

We do not feel the pressure of the atmosphere because air presses on our body from all sides. At the same time, the pressure inside our body balances the pressure from outside. So, the atmospheric pressure and the internal pressure of our body cancel each other. That is why we do not feel the heavy pressure of the air above us.

Aeroplanes usually fly in the stratosphere. The stratosphere is suitable for flying aeroplanes because it is mostly free from clouds and weather disturbances. This makes the flight smoother and safer. The stratosphere also contains the ozone layer, which protects the Earth from harmful ultraviolet radiation.

Distinguish between the following

6(a). The troposphere and stratosphere

Distinguish between the following

To complete this activity, students should draw temperature and rainfall graphs for the 10 stations given in Table 3.3. How to draw the graph: Take months from January to December on the horizontal axis. Show temperature on one vertical axis. Show rainfall on the other vertical axis. Use a line graph for temperature. Use bars for rainfall. Compare the graphs of different stations.

Broad generalisations about India’s climate: 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.

Distance from the equator increases as latitude increases. Therefore, the stations can be arranged from nearest to farthest from the equator as follows:

• Thiruvananthapuram – 8°29'N
• Bengaluru – 12°58'N
• Chennai – 13°4'N
• Mumbai – 19°N
• Nagpur – 21°9'N
• Kolkata – 22°34'N
• Shillong – 24°34'N
• Jodhpur – 26°18'N
• Delhi – 29°N
• Leh – 34°N

The two stations with the most extreme climate are: Leh

Jodhpur

Reason: Leh has very cold winters and mild summers. Its annual temperature range is very high. Jodhpur also has hot summers and comparatively cool winters because it is located in the dry desert region of Rajasthan. Delhi also shows an extreme climate, but from the given table, Leh and Jodhpur show very high variation.

The two stations influenced by retreating monsoons are: Chennai

Thiruvananthapuram

Reason: Chennai receives heavy rainfall in October and November due to the north-east or retreating monsoon. Thiruvananthapuram also receives rainfall during the post-monsoon period.

The two hottest stations in February are:

The two hottest stations in June are:

• Jodhpur – 33.9°C
• Delhi – 33.3°C

Shillong receives more rainfall than Kolkata because Shillong is located in the hills of Meghalaya. Moist winds from the Bay of Bengal are forced to rise when they strike the Meghalaya hills. As the air rises, it cools and causes heavy rainfall. This is called orographic rainfall. Kolkata is located in the plains of West Bengal. It receives rainfall from the monsoon winds, but it does not get as much orographic rainfall as Shillong. Therefore, Shillong receives more rainfall than Kolkata.

Delhi receives more rainfall than Jodhpur because Delhi is more influenced by the monsoon winds, especially the Bay of Bengal branch of the south-west monsoon. Jodhpur is located in western Rajasthan, near the Thar Desert. This region is dry and receives less rainfall. The Aravalli hills are almost parallel to the direction of the monsoon winds, so they do not block the winds effectively to cause heavy rainfall. Therefore, Jodhpur receives less rainfall than Delhi.

Thiruvananthapuram has an equable climate because it is located near the sea. The sea heats and cools slowly, so it moderates the temperature of nearby coastal areas. Due to the influence of the sea breeze and land breeze, Thiruvananthapuram does not become extremely hot in summer or very cold in winter. Its temperature remains almost uniform throughout the year.

Chennai receives more rainfall after the main south-west monsoon season because it lies on the Coromandel Coast. During the south-west monsoon, Chennai receives less rainfall because it lies in the rain-shadow region of the Western Ghats and the monsoon winds blow mostly parallel to the coast. When the monsoon retreats, the north-east monsoon winds pass over the Bay of Bengal. These winds pick up moisture and bring rainfall to Tamil Nadu, including Chennai. That is why Chennai receives heavy rainfall in October and November, when the monsoon has already weakened in many other parts of India.

Leh receives very little precipitation throughout the year because it lies in a cold desert region. It is located in the rain-shadow area of the Himalayas. The high mountains block the moisture-laden monsoon winds from reaching Leh. However, Leh receives small amounts of precipitation in different months, mostly in the form of light rain or snow. Some precipitation also occurs due to western disturbances. Therefore, Leh has low but fairly spread-out precipitation during the year.

Yes, the monsoons provide a strong framework and bring climatic unity to India. Although India has great climatic differences due to relief, latitude, altitude, distance from the sea, and local conditions, the monsoon affects almost the whole country. Most parts of India receive the major part of their rainfall during the monsoon season. The south-west monsoon brings rainfall to large parts of India from June to September. The retreating or north-east monsoon gives rainfall to the south-eastern coast, especially Tamil Nadu. Thus, the timing, amount, and distribution of rainfall in India are mainly controlled by the monsoon system.

Agriculture, water supply, festivals, transport, and daily life in many regions depend on the monsoon. Therefore, the monsoon gives India an overall climatic unity despite regional diversity.

Yes, the houses and clothing of people in different regions of India clearly show a relationship with the climate and relief of those regions. In Rajasthan, the climate is hot and dry. People often wear loose cotton clothes, turbans, and long dresses to protect themselves from heat, dust, and strong sunlight. Houses usually have thick walls and small windows to keep the interior cool. In cold mountain regions such as Ladakh, Himachal Pradesh, and Kashmir, people wear woollen clothes, jackets, caps, and boots to protect themselves from cold. Houses often have sloping roofs so that snow can slide down easily. Thick walls help in keeping the house warm.

In coastal areas such as Kerala, Goa, and Tamil Nadu, the climate is hot and humid. People usually wear light cotton clothes. Houses often have sloping roofs because these areas receive heavy rainfall. In some coastal areas, houses are well ventilated to allow air circulation. 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.