WBBSE Chapter 2 Atmosphere Long Question And Answers

Question 1. Discuss the influence of the various components of the atmosphere.
Answer:

The influence of the various components of the atmosphere:

The different components of the atmosphere influence the environment in many ways.

1. Nitrogen (78.08%):

1.  Leguminous plants fix atmospheric nitrogen into the soil with the help of bacteria like Rhizobium, making the soil fertile.
2.  Atmospheric nitrogen is extracted to manufacture chemical fertilizers.
3.  The atmospheric nitrogen meets the demand for nitrogen from plants and animals directly or indirectly.

2. Oxygen (20.94%):

1.  Oxygen helps in respiration, without which no life on earth can survive.
2.  Oxygen causes weathering of rocks containing iron, by the process of oxidation.
3.  Combustion is possible only in the presence of oxygen.

3. Carbon dioxide (0.03%):

1. Carbon dioxide helps plants conduct photosynthesis, which produces food or glucose. All animals are directly or indirectly dependent on plants for food.
2.  t influences the temperature of the atmosphere.
3. The rocks rich in calcium carbonate are weathered by carbon dioxide and water through the process of carbonation.
4. Several landforms like stalactites and stalagmites are formed in limestone regions due to reactions with carbon dioxide.

4. Ozone:

The ozone layer lies within the stratosphere at an altitude of 20-40km above the earth’s surface. It prevents the harmful ultraviolet radiation from reaching the earth’s surface and causing severe diseases like skin cancer, eye problems, infertility, wilting of leaves of plants, etc.

5. Water vapor:

1. Water vapor leads to the formation of clouds and rainfall.
2. Life on the earth would have been impossible without the presence of water. All plants and animals need water to survive.
3. Precipitation occurs due to the presence of water vapor in the atmosphere.

6. Dust particles:

1. The dust particles act as the medium of condensation of water vapor in order to create clouds and fog.
2. The dust particles absorb heat directly from solar radiation and warm the atmosphere.
3. The dust particles act as prisms and cause the refraction of light. Thus, the earth appears so bright and beautiful.
4. Dawn and dusk are created in the sky due to the presence of dust particles in the atmosphere of the atmosphere according to temperature.

Question 2. Classify the layers of the atmosphere according to temperature.
Answer:

The atmosphere can be classified into six prominent layers according to the distribution of temperature—

The different layers of the atmosphere are discussed in a tabular form:

The different layers of the atmosphere are discussed in a tabular form.

Question 3. Classify the atmosphere into layers according to differences in temperature. Discuss any one layer of the atmosphere.
Answer:

The atmosphere into layers according to differences in temperature:

The atmosphere can be classified into six For the second part, stratosphere (12-50 km), mesosphere (50-80 km), thermosphere (80-640 km), exosphere (600-1500 km), and magnetosphere (150010000 km).

2. Oxygen (20.94%):

• Oxygen helps in respiration, without which no life on earth can survive.
• Oxygen causes weathering of rocks containing iron, by the process of oxidation.
• Combustion is possible only in the presence of oxygen.

3. Carbon dioxide (0.03%):

• Carbon dioxide helps to conduct photosynthesis in plants to produce food or glucose.
• All animals are directly or indirectly dependent on plants for food.
•  It influences the temperature of the atmosphere.
• The rocks rich in calcium carbonate are weathered by carbon dioxide and water through the process of carbonation.
• Several landforms like stalactites and stalagmites are formed in limestone regions due to reactions with carbon dioxide.

4. Ozone:

• The ozone layer lies within the stratosphere at an altitude of 20-40km above the earth’s surface.
• It prevents the harmful ultraviolet radiation from reaching the earth’s surface and causing severe diseases like skin cancer, eye problems, infertility, wilting of leaves of plants, etc.

5. Water vapor:

• Water vapor leads to the formation of clouds and rainfall.
• Life on the earth would have been impossible without the presence of water. All plants and animals need water to survive.
• Precipitation occurs due to the presence of water vapor in the atmosphere.

6. Dust particles:

• The dust particles act as the medium of condensation of water vapor in order to create clouds and fog.
• The dust particles absorb heat directly from solar radiation and make the atmosphere warm.
• The dust particles act as prisms and cause refraction of light. Thus, the earth appears so bright and beautiful.
•  Dawn and dusk are created in the sky due to the presence of dust particles in the atmosphere of the atmosphere according to temperature.

Question 4. Name the components of the atmosphere.
Answer:

The atmosphere is made up of three types of components—

1. Gases,
2. Water vapor and
3. Dust particles.

 

Troposphere Characteristics

1. Gases:

The atmosphere mostly contains nitrogen (78.08%) and oxygen (20.94%) gases. Other gases present in the atmosphere are—argon (0.93%), carbon dioxide (0.03%), helium, hydrogen, krypton, methane, neon, ozone, xenon, etc.

 

2. Water vapor:

Water vapor is an important component of the atmosphere.

3. Dust particles:

Dust particles, ash particles, sea salt nuclei, etc. are present in the lower layers of the atmosphere, and play a vital role in heat absorption, condensation of water vapor, and occurrence of rainfall.

Question 5. Discuss the importance of nitrogen gas in the atmosphere.
Answer:

The importance of nitrogen gas in the atmosphere:

By volume, nitrogen constitutes about 78.08% of atmospheric gases.

The importance of nitrogen is—

1. Nitrogen requirement of plants and animals:

• Animals do not use nitrogen directly. Some pulses fix the atmospheric nitrogen in their root legumes with the help of some bacteria like Rhizobium.
• Animals take in these leguminous plants as their food and meet their demand for nitrogen.

2. Increase in soil fertility:

• Leguminous plants like pulses, peas, etc. fix the atmospheric nitrogen with the help of bacteria like Rhizobium in the soil.
• This helps to increase soil fertility. During agriculture, the fertility of soil can be brought back by cultivating such leguminous plants in between other crops.

3. Fertilisers: Nitrogen compounds are often used to produce fertilizers that enhance plant growth.

Question 6. Discuss the importance of oxygen in the atmosphere.
Answer:

The importance of oxygen in the atmosphere:

By volume, the atmosphere contains about 20.94% of oxygen.

The importance of oxygen is:

• Survival of life: Life cannot be survived without oxygen for both plants and animals. Thus, if there would have been no oxygen in the atmosphere, there would have been no life.
•  Atmospheric balance: An increase or decrease in the amount of oxygen in the atmosphere may disturb the atmospheric balance
• Weathering: Rocks containing iron are weathered by the oxygen present in the atmosphere through the process of oxidation.
• Combustion: Oxygen helps in the combustion and burning of fire. Thus, without oxygen, no fire could have been lit.

Question 7. Discuss the importance of dioxide in the atmosphere.
Answer:

The importance of water vapor in the atmosphere is :

• Influences on rainfall: The presence of water vapor in the atmosphere leads to precipitation of different forms (such as rainfall, snowfall, fog, dew, hailstorm, etc.). The amount of precipitation is directly proportional to the amount of water vapor present in the atmosphere.
• Sustaining life: Life is impossible without water. The presence of water vapor in the atmosphere helps to cause rainfall and hence, helps to sustain life on the earth.
• Control of climate: The climate of a region is dependent on the amount of rainfall, snowfall, drizzle, fog, cloud, dew, or hailstorm occurring in the region. The climate is humid in regions that receive heavy rainfall, the climate is dry desert type in regions that receive scanty rainfall.

Stratosphere and Ozone Layer

Question 8. Discuss the importance of dust particles in the atmosphere.
Answer:

The importance of dust particles in the atmosphere is—

1. Cloud formation: The water vapor condenses around the dust particles to form clouds and different forms of precipitation occur from them.
2. Distribution: The dust particles get heated directly by the insolation, hence making the atmosphere warm. Thus, the presence of dust particles influences the distribution of solar heat in the atmosphere.
3. Colour of the sky: The dust particles act as prisms and cause refraction of light. Thus, the sky appears colorful at times. The excess of blue light in the color spectrum makes the sky appear blue.

Question 9. How is the ozone layer being depleted?
Answer:

The ozone gas is concentrated in the stratosphere. It is being depleted fast by photochemical reactions.

The causes of the depletion of the ozone layer are as follows—

1. Influence of CFCs:

• The chloroform carbons in refrigerators, air conditioners, body sprays, cosmetics, hair sprays, insecticides, and pesticides are responsible for the depletion of the ozone layer.
• The ultraviolet rays of the sun release the chlorine molecules from the CFCs which react with the ozone and deplete it.

2. Sulphate compounds:

• The chimneys of various factories emit huge quantities of sulfur dioxide.
• These are converted to sulfate compounds by sunlight and harm the ozone layer.

3. Aeroplanes:

• The jet planes that fly through the stratosphere emit a lot of nitrogen oxide.
• This is harmful to the ozone layer.

Question 10.  Mention the general characteristics of air.
Answer:

The general characteristics of air are—

1. Air becomes heavy and dense if temperature decreases.
2. The rise in temperature expands the air, makes it light, and causes it to rise.
3. Warm air has more moisture-holding capacity than cool air.
4. An increase in the amount of water vapor in the air reduces air pressure.
5. Moist air is lighter than dry air.
6. Warm air is lighter and rises upward, while cool air is heavier and sinks downward.
7.  The density of air is maximum near the earth’s surface and goes on decreasing with an increase in height.

Question 11.  Why would life not have been created if the atmosphere was absent?
Answer:

Life would not have been created in the absence of atmosphere because:

•  In the absence of the atmosphere, the day temperature of the earth would have been 70’C and the night temperature would have been- 145°C. Life cannot survive in such extreme temperature conditions.
• Oxygen and carbon dioxide present in the atmosphere are indispensable for sustaining life.
• Water vapor present in the atmosphere condenses to give rainfall. The first proof of life originated in water. Hence, if there would have been no rainfall, there would have been no life.
• The ozone gas present in the atmosphere protects 1 the earth from the harmful ultraviolet rays of the sun, thus saving life on the earth.

Question 12.  Differentiate between the homosphere and the heterosphere.
Answer:

The Differences between the homosphere and the heterosphere are-

Question 13. Differentiate between the troposphere and stratosphere
Answer:

The Differences between the troposphere and stratosphere

Question 14.  Why does temperature decrease with an increase in altitude in the Troposphere?
Answer:

Temperature decreases with the increase of altitude in the Troposphere at the rate of 6.4° C with every 1000 m altitude. This is known as a normal lapse of temperature.

This happens because of the following reasons:

• Less radiation received: The atmosphere does not get heated directly. It gets heated up by the radiation received from the surface of the earth. Thus, the lower part of the atmosphere coming in direct contact with the surface of the earth gets more heat than the portion lying above.
• Less dense air: The layers of air are denser near the earth’s surface and become lighter with increasing altitude. Hence, the upper layers receive less heat.
• Less heat absorbing capacity: The lower layer of the atmosphere contains more water vapor, dust particles, and sea salt nuclei than the layers above and hence heat retentive and heat absorbing capacity considerably decrease with the increase of altitude.
• Thin layer of air: The atmosphere gradually thins out with an increase in altitude. For this reason, the air in the upper layers expands quickly and cools rapidly by the release of radiation.

Question 15. Discuss the causes of differences in temperature in the air in different parts of the earth. OR, Explain the causes of the difference in air temperature in the atmosphere. OR, How is the temperature of the atmosphere influenced by different factors?
Answer:

The various causes of the difference in the air temperature in different parts of the earth are as follows—

Mesosphere Facts for Student

1. Latitude: The angle of incidence of the sun’s rays is different in different latitudes. The sun’s rays fall almost vertically over the equator and go on becoming tangent over the higher latitudes towards the poles.

• The tangent rays give less amount of heat for the following reasons

1. Tangent rays have to cross a larger distance through the atmosphere than vertical rays.
2. Tangent rays spread over a larger area on the earth’s surface and distribute the heat. Thus, the temperature is highest at the equator and goes on decreasing towards the poles.

2. Altitude:

• By the normal lapse rate, temperature decreases by 6.4°C for every 1000 m rise in altitude. Hence, two places located on the same latitude but different altitudes will have different temperature conditions.
• The eg-Average temperature of the capital of Uganda, Kampala (0°21’N, altitude-1190 m) is 22.7°C, while that of the capital of Ecuador, Quito (1°08’N, altitude- 2850 m) is 15.6°C.

3. Presence of mountains:

• The presence of mountains across the direction of hot or cold winds influence the temperature of the region.
• Example: The Himalayan mountains prevent the chilling cold polar winds coming from Siberia from entering India and making it chilled.

4. Distance from the sea:

• The regions close to the sea enjoy a moderate maritime climate, while the places far away from the sea experience harsh, extreme continental climates.
  • Example: Mumbai lying on the coast of the Arabian Sea has an average summer temperature of 33°C and winter temperature of 21°C.
• On the other hand, Delhi lying far away from the sea has an average summer temperature of 47°C and winter temperature of 12°C.

5. Slope of land:

• The slope which faces the sun receives more solar radiation than the opposite slope, thus they are warmer.
  • Example:  The southern slope of the Himalayas receives direct rays and the northern slope receives tangent rays.
• Thus, the southern slope is warmer than the northern slope.

6. Length of day and night:

• The length of day and night influences the temperature of the places.
• If the length of the day is smaller than the night, the insolation can be totally radiated back during the night, thus making the nights cooler.
• But if the length of the day is greater than the night, the total insolation cannot be radiated back within the smaller length of the night.
• Some heat remains in the atmosphere and raises the average temperature of the place.

7. Cloud cover:

• The cloud cover prevents solar energy from reaching the earth’s surface during the daytime.
• It also prevents solar radiation from escaping from the earth’s atmosphere into outer space.

8. Ocean currents:

• If warm and cold ocean currents flow along either side of a continent at the same latitudes, the warm current makes the coastal region warm and raises the temperature.
• The cold current makes the coastal region cooler and drops the temperature. Thus, along the same latitudes, one side of the continent remains warmer than the other side.

9. Winds:

Prevailing winds influence the temperature conditions of the regions.

Example: 

• The cold winds from the Arctic region reach far into North America and make the climate of the USA chill during winter and during the night.
• Thus, cloudy nights are warmer than cloudy days, and the temperature of the atmosphere causes heavy snowfall.
• On the other hand, the warm Chinook wind makes the Prairies warm and causes the snow to melt.

10. Forest:

• The canopy of leaves and branches in forests prevent solar radiation from reaching the earth’s surface easily.
• Thus, forested regions are cooler than barren regions.

11. Soils:

• Different types of soils absorb heat differently. Moist clayey soils like alluvium absorb lesser heat than dry sandy soils.
• Hence, places comprising sandy soil are warm in the daytime and cool after the radiation of heat at night.
• The places comprising moist alluvial soil are moderately warm and cool during the day and night respectively.

12. Urbanisation and industrialization:

• The smoke emitted by vehicles in cities and towns and the chimneys of industries increase the general temperature of the environment.
• Thus, urbanization and industrialization tend to increase the average temperature of the regions.

Example:  The average temperature of Kolkata always remains 2-3°C higher than the vacant region near the Dum Dum airport.

Question 16.  Discuss the influence of latitude and altitude on air temperature.
Answer:

The influence of latitude and altitude on air temperature

1. Latitude:

• The angle of incidence of the sun’s rays is different in different latitudes. The sun’s rays fall almost vertically over the equator and go on becoming tangent over the higher latitudes towards the poles.
• The tangent rays give less amount of heat for the following reasons
• Tangent rays have to cross a larger distance through the atmosphere than vertical rays.
• Tangent rays spread over a larger area on the earth’s surface and distribute the heat. Thus, the temperature is highest at the equator and goes on decreasing towards the poles.

2. Altitude:

• By the normal lapse rate, temperature decreases by 6.4°C for every 1000 m rise in altitude. Hence, two places located on the same latitude but different altitudes will have different temperature conditions.
• The eg-Average temperature of the capital of Uganda, Kampala (0°21’N, altitude-1190 m) is 22.7°C, while that of the capital of Ecuador, Quito (1°08’N, altitude- 2850 m) is 15.6°C.

Question 17.  Discuss the characteristics of the temperature zones of the world.
Answer:

The earth is divided into five temperature zones according to the difference in temperature. They are as follows—

1. Torrid zone

Location: The Torrid zone lies between the Tropic of Cancer (231/4°N) and the Tropic of Capricorn (23°S) across the equator (0°). The region is the warmest on the earth as it receives the direct rays of the sun. Sometimes the 30°N and 30°S latitudes are considered the limits of the Torrid zone.

Characteristics:

1. The Torrid zone receives vertical rays of the sun almost throughout the year.
2. The average temperature remains around 27°C.
3. The length of day and night remain equal throughout the year.
4. This zone does not experience any climatic change during different times of the year. Summer is the only season prevailing here.

2. Northern Temperate zone and Southern Temperate zone

Location:

The northern temperate zone lies between the Tropic of Cancer (23340N) and the Arctic Circle (661/i°N) and the southern temperate zone lies between the Tropic of Capricorn (231/4°S) and Antarctic Circle (6634°S). The average temperatures of these zones vary between 0°C-27°C.

Characteristics:

1. The angle of incidence of sun’s rays is medium in the temperate zones.
2. The length of day and night is variable but medium.
   
3. The region closer to the tropics is known as the warm temperate zone, while the region closer to the polar regions is known as the cool temperate zone.

3. Northern Frigid zone and Southern Frigid zone

Location: The northern Frigid zone extends from the Arctic Circle (66>20N) to the North Pole (90°N). The sun’s rays are extremely inclined or tangent in this region. Hence, the region is extremely cold.

Characteristics:

1. The difference between the length of day and night is extreme in this region. The polar regions experience six months of continuous day and six months of continuous night.
2. The extremely inclined rays of the sun do not provide much heat to the region. The continuous daylight for six months is also not sufficient to raise the temperature of the place.
3.  During the continuous six months of night, some bright lights can be seen in the sky. These are called Aurora Borealis in the northern hemisphere and Aurora Australis in the southern hemisphere.

Question 18. Discuss the effects of global warming.
Answer:

The effects of global warming on the earth are as follows—

1. Melting of polar and glacial ice:

The gradual increase in atmospheric temperature is causing the ice of the South Pole and the glaciers of Greenland, and the Atmosphere of other mountain glaciers like Gangotri, Yamunotri, etc to melt.

2. Rise in sea level:

• The melting of ice caps is raising the level of water in the seas. The sea level rises by 10-12 cm for every 1°C rise in temperature
• . This leads to the submergence of coastal lowlands, change in the direction of ocean currents, increase in salinity of groundwater, etc.

3. Change in the type of precipitation:

• A rise in temperature increases the level of evaporation and the moisture-holding capacity of the atmosphere.
• This increases the occurrence of rainfall, hailstorms, snowfall, etc.
• Some regions may be affected by floods, while some regions may face droughts due to uneven distribution of rainfall.

4. Crop production:

An increase in the general temperature of the environment may reduce the production of food crops by 10-70%. Production of crops like rice, oats, tobacco, cotton, and jute may decline, while production of sugarcane, jowar, bajra, etc. may increase.

Example:  In Kullu Valley, the cultivation of onions and others has taken up the place of apples in many areas.

5. Cropping methods:

• The cropping patterns will change all over the world due to the rise in atmospheric temperature.
• The agricultural lands dependent on irrigation will transform into pastures for grazing.
• Crops like rice, jute, and cotton will be grown in the temperate zone instead of the tropical zone.
• Methods of cultivation will also change all over the world.

6. Effects of El Nino:

• In the southern hemisphere along the coast of Peru and Ecuador of South America a warm current is suddenly generated in the Pacific Ocean, which raises the temperature of the ocean by 1.5-2.5°C.
• This is known as El Nino. This causes heavy rainfall in Peru and Ecuador but may cause droughts in India.

Question 19.  How does altitude influence air, Why are places in high altitudes cooler, Why are the mountains cooler than the low plains?
Answer:

Temperature decreases by 6.4°C for every 1000 m rise in altitude by the normal lapse rate. Thus, places lying on the same latitude but at different altitudes record different temperatures.

Example: The capital of Uganda, Kampala (1192 m) is about 7°C warmer than the capital of Ecuador, Quito (2819 m), although they are located almost on the same latitude.

This difference in temperature occurs because of the following reasons:

1. Radiation in higher altitudes: In the lower altitudes, the combined effect of incoming solar radiation and outgoing terrestrial radiation makes the place warmer as compared to the higher latitudinal locations. Most of the heat is absorbed in the lower layers of the atmosphere closer to the earth’s surface. Thus, the temperature goes on decreasing at the upper levels or higher altitudes.

2. Less density of air: The density of air decreases as altitude increases. Less dense air has less temperature.

3. Less absorption of heat: The lack of dust particles and water vapor in higher altitudes lead to less absorption and retention of heat in the air present there.

4. Thin layers of air: The air becomes thinner with the rise in altitude. It radiates heat and becomes cool very fast.

Composition of Atmospheric Gases

Question 20.  Describe the Six’s maximum and minimum thermometer and discuss its uses.
Answer:

The Six’s maximum and minimum thermometer and discuss its uses:

The Six’s maximum and the minimum thermometer is an instrument used to measure the maximum and minimum temperatures of a day. It is also used to calculate the diurnal, monthly, and annual ranges of temperatures of a place. The Instrument was invented by James Six in 1782.

Six’s maximum and minimum  The instrument:

• The thermometer looks like the alphabet ‘U’, fixed in a frame.
• It is made up of very thin tubes of glass.
• There are two bulbs on the two limbs of the thermometer.
• The limbs remain filled with mercury up to a certain level, and the rest is filled with alcohol.
• Two indicators are placed just above the mercury level, which floats above the mercury for being lighter in weight.
• The indicators are pushed upwards through the glass tube to measure the level of temperatures.
• The instrument is graduated in Celsius and Fahrenheit scales for easy calculation of temperature.

Six’s maximum and minimum  Use:

• The thermometer is installed in a shady place where the direct sunlight does not reach, but the heat reaches.
• The indicators are placed touching the mercury level with the help of magnets.
• When temperature increases, the alcohol expands and pushes the mercury and the indicator through the tube to record the highest temperature.
• When the temperature decreases, the alcohol contracts and pulls the mercury and the indicator toward the other limb to record the lowest temperature.
• The indicators do not move from their positions, hence maximum and minimum temperatures are easily recorded.
• The lower tips of the indicators point out the temperature of the atmosphere.

Question 21.  Divide the earth into different temperature zones.
Answer:

The earth can be divided into three parts or temperature zones, according to a latitudinal extent—

1. Torrid zone:

• The region extending between the Tropic of Cancer (231/2°N) and the Tropic of Capricorn (231/2°S) across the equator (0°) is known as the Torrid zone.
• The average temperature of this region is around 27°C. This zone does not experience many climatic changes throughout the year. Hence, summer persists around the year.

2. Temperate zone:

• The region lies between 231/z° and 661/2° latitudes in both hemispheres and is known as the temperate zone.
• It stretches from the Tropic of Cancer to the Arctic Circle in the northern hemisphere and the Tropic of Capricorn to the Antarctic Circle in the southern hemisphere. Here, the average temperature varies between 0° and 27°C.

3. Frigid zone:

• The region extending between 661/2° latitudes and the Poles in both hemispheres is known as the Frigid zone.
• It stretches from the Arctic Circle to the North Pole in the northern hemisphere and from the Antarctic Circle to the South Pole in the southern hemisphere.
• The average temperature is around 0°C.

Question 22.  Discuss the processes by which the atmosphere gets heated.
Answer:

The processes by which the atmosphere gets heated:

The atmosphere is heated by the processes of conduction, convection, and radiation.

1. Conduction:

• Conduction is the method of transfer of heat from one part to another of a substance or to a different substance that is in physical contact with the first substance.
• There is no noticeable movement of molecules. Energy is transferred by the movement of free electrons through vibrations between atoms and molecules.

2. Convection:

• The cyclical movement of warm air upwards and cooler air downwards and sidewards to fill up the gap is known as convection.
• In the equatorial region, excessive heating of the earth’s surface leads to heating of the adjacent air molecules, which rise upwards creating convection currents.

3. Radiation: The method of transfer of heat from one place to another without the help of any medium, or without heating the medium present in between, is called radiation.

 

Question 23.  What do you mean by inversion of temperature?
Answer:

Inversion of temperature:

• By the normal Lapse rate, the air temperature decreases by 6.4°C for every 1000 m rise in altitude.
• But in certain cases, it is seen that temperature increases with an increase in altitude. This phenomenon is known as the ‘inversion of temperature’.

Inversion of temperature Process:

• In mountainous regions on clear nights, the air radiates back to heat and cools down fast. This cool air becomes heavy and slips down along the sides of the valleys due to gravitational pull.
• This air is known as a katabatic wind. On the other hand, the heating up of the lower regions of valley walls causes air to rise upwards. This air is called anabatic wind. As a result, the cooler air lies below the warmer air. This condition is known as the inversion of temperature.

Inversion of temperature Effect:

Due to the inversion of temperature, in many places in Europe, settlements and agricultural activity are found on the upper parts of mountain slopes than the valleys.

Question 24.  Why is Delhi warmer than Mumbai during the summer season?
Answer:

• Average annual temperature Total of the average monthly temperature of 12 months Ansi Delhi is situated almost at the center of the northern part of India.
• It is far away from the influence of the sea. Hence, it experiences extreme or continental climates where summers are hot and winters are very cold.
• Mumbai is situated on the coast of the Arabian Sea and enjoys a maritime or moderate climate. The difference in temperature between summers and winters is not very large.
• Hence, Delhi remains warmer than Mumbai during the summer seasons conditions of the earth’s surface and maintains its uniformity.

Question 25. What is the main characteristic of the horizontal distribution of the temperature on the earth’s surface?
Answer:

The main characteristic of the horizontal distribution of the temperature on the earth’s surface

The horizontal distribution of temperature on the earth’s surface is influenced by the latitude and the angle of incidence of the sun’s rays.

The temperature conditions of January and July are drastically opposite all over the world. The weather maps of these two months give an idea of the distribution of temperature on the earth’s surface throughout the world.

Question 26.  Describe the pressure belts of the world along with a diagram, How many pressure belts are there in the world?
Answer:

 

The pressure belts of the world are described below-

Question 27. What are the causes of differences in pressure conditions in the atmosphere?
Answer:

The causes of the difference in air pressure in the atmosphere are—

1. Temperature:

1. Air expands when heated and rises upwards.
2. As a result, both density and pressure decrease.
3. This is why a low-pressure belt exists in the equatorial region.
4. Air contracts when cooled, and descends.
5. This increases both density and pressure.

2. Water vapor:

Air filled with water vapor is lighter than dry air. Thus, the regions where the water vapor content in the air is high, experience low pressure and vice versa.

3. Altitude:

The atmosphere becomes lighter and its mass decreases with an increase in altitude. This results in low pressure in higher altitudes. Thus, Darjeeling experiences lower pressure than Siliguri due to its higher altitude even though both of them are located on more or less the same latitude.

4. Rotation of the earth:

The rotation of the earth deflects the air from the sub-polar region towards the sub-tropical and polar regions. Thus, the sub-polar region has low pressure while the sub-tropical and polar regions have high pressure.

5. Distribution of landmass and water bodies:

The opposite characteristics of land and water also cause differences in atmospheric pressure. The land gets heated faster than water during the daytime.

The air adjacent to the landmasses also gets heated, becomes light and rises. This creates low pressure over land and high pressure over water bodies.

During the night, land radiates heat faster than the water bodies and gets cooled. The adjacent air also cools, gets heavier, and descends, thus increasing pressure over land than water bodies.

Question 28.  Explain the relation between temperature and pressure of the atmosphere.
Answer:

The relation between temperature and pressure of the atmosphere.

The temperature of the atmosphere is inversely related to the pressure conditions. This can be explained in the following ways-

Air expands, becomes lighter, and rises when temperature increases. This causes low-pressure conditions. E.g- The equatorial region receives almost vertical rays of the sun throughout the year. Thus, the air in this region remains warm, and light and tends to rise upwards throughout the year.

This creates low-pressure conditions in the equatorial region.  Air pressure increases when air is cooled or temperature is lowered. Cool air becomes heavier and tends to descend downwards.

This makes the air dense and increases pressure. E.g – The air around the polar region remains chilled throughout the year due to severe cold conditions prevailing over there. Thus, air pressure remains high throughout the year. The water vapor content of the air also influences air pressure. Warm air can hold much more water vapor than cool air.

Question 29. What Is the relation between monsoon winds and the jet stream?
Answer:

The sub-tropical jet stream and the tropical easterly jet stream have a great influence on the climate of India.

1. Monsoon season: The tropical easterly jet stream blows over India in the month of June. The onset of the southwest monsoon winds is influenced to a great extent by the easterly jet stream.

2. Winter season: The sub-tropical westerly jet stream blows over India during October-November as the southwest monsoon winds start retreating. It continues to blow over India till the month of May. As the jet stream moves southwards than its original position, the severity of cold increases in the country.

It reaches its maximum southern limit in February, after which it starts moving northwards till May. During the winter season, as the jet stream blows over India from the west to the east, it collides with the mighty Himalayas and gets bifurcated into two branches.

These branches blow over the northern and southern slopes of the Himalayas, where their speed gets reduced. Once they cross the Himalayas, they unite and gain speed like before.

The climate of India is much dependent on the jet streams. The duration of the seasons, the intensity of the heat and cold, the amount of rainfall, cyclones and storms, etc. are all influenced by the jet streams.

Question 30. Describe the planetary wind with the help of a diagram. Or, Explain with sketches the origin and direction of planetary winds of the world.

1. Trade winds: The winds that blow from the sub-tropical high-pressure belts in either hemisphere towards the equatorial low-pressure belt throughout the year, are called trade winds.

Trade winds are of two types—

1. North-east trade winds: These winds blow from the sub-tropical high-pressure belt of the northern hemisphere near the Tropic of Cancer, towards the equatorial low-pressure belt. The winds are deflected to the right according to Ferret’s law. Thus, they blow from the northeastern direction.
2. South-east trade winds: These winds blow from the sub-tropical high-pressure belt of the southern hemisphere near the Tropic of Capricorn, towards the equatorial low-pressure belt. The winds are deflected towards the left according to Ferrel’s law, and thus they blow from the south-eastern direction.

Characteristics:

1. The speed of trade winds is slower in the northern hemisphere (15-25 km/hr) due to the presence of more landmasses.
2. The speed of these winds is greater in the southern hemisphere (25-35 km/hr) due to the presence of more water bodies,
3. The winds blow between 0°and 30° N and S latitudes throughout the year, [iv] A number of deserts have been formed in the path of the trade winds. Examples— Sahara, Thar, Kalahari, Atacama, etc.

2. Westerly winds:

The winds blowing from the sub-tropical high-pressure belts towards the sub-polar low-pressure belts in both the northern and southern hemispheres throughout the year are called westerly winds, or westerlies.

The westerlies are of two types—

1. South-west westerlies:

The winds blowing from the sub-tropical high-pressure belt near the Tropic of Cancer towards the subpolar low-pressure belt near the Arctic Circle in the northern hemisphere throughout the year, are called southwest westerlies. According to Ferrel’s law, they are deflected toward the right.

North-west westerlies:
The winds blowing from the sub-tropical high-pressure belt near the Tropic of Capricorn towards the sub-polar low-pressure belt near the Antarctic Circle in the southern hemisphere throughout the year, are called north-west westerlies. According to Ferrel’s law, these winds are deflected toward the left.

Characteristics:

1. The winds are named westerlies as they blow from the west,
2. They blow between 30° and 60°N and S latitudes in both hemispheres,
3. The westerlies cause more rainfall on the western margins of the continents than the east,
4. Less rainfall on the eastern margins of the continents has led to the formation of vast grasslands in the temperate region.

E.g.—Prairies in North America, Pampas in South America, Steppe in Russia and Europe, Downs in Australia, and Veld in South Africa.

3. Polar winds: The winds that blow from the high-pressure belts around the poles towards the sub-polar low-pressure belts in both hemispheres are called polar winds. The polar winds are of two types—

North-east polar winds: The winds that blow from the polar high-pressure belt around the North Pole towards the sub-polar low-pressure belt near the Arctic in the northern hemisphere are called northeast polar winds. They are deflected towards the right according to Ferrel’s law.

South-east polar winds: The winds that blow from the high-pressure belt around the South Pole towards the sub-polar low-pressure belt near the Antarctic Circle in the southern hemisphere are called southeast polar winds. They are deflected towards the left according to Ferrel’s law.

Characteristics:

1. Polar winds are extremely cold and dry.
2. The influence of these winds is more actively felt during the winter,
3. Polar winds cause snowfall and a little rainfall on the eastern margins of the continents. They cause severe blizzards near the Arctic and Antarctic Circles.

Question 31. Describe the various periodic winds
Answer:

Periodic winds: The winds that blow regularly for a certain period of time over a certain region due to differences in pressure conditions are called periodic winds.

Periodic winds are of three types—

1. Sea breeze,
2. Land breeze and
3. Seasonal winds.

1. Sea breeze: In the coastal regions during Seabreeze Land breeze; Seasonal winds daytime, the land gets heated faster than the sea.

Thus, the air adjacent to the land also gets heated, expands, becomes light, and tends to rise upwards, This creates a vacuum on the land, leading to low-pressure conditions.

The air over the sea Is comparatively cooler and denser, Hence, a high-pressure condition prevails over the sea. Winds rush from this high-pressure region towards the low-pressure region on the land. This is known as the sea breeze.

2. Land breeze: In the coastal regions during the night, the land radiates the heat very fast and cools down. The sea remains warmer, and the air over the sea also becomes warmer, and lighter and tends to rise upwards. Thus, low-pressure conditions are created over the sea.

The land is comparatively cooler, and the air adjacent to it is cool and heavy. This air rushes towards the low-pressure region over the land. This is known as the land breeze

3. Seasonal winds: Seasonal winds are caused due to differential heating of the land and water bodies in different seasons, During summers, low-pressure cells are created over the land surface, which draws winds from the sea.

During winter, high-pressure conditions are created over land, from where winds blow toward the sea. In India, the periodic seasonal winds are known as monsoon winds. The southwest monsoon winds blow during summer and the northeast monsoon winds blow during winter.

Question 32. Discuss the occasional winds. OR, What are cyclones and anticyclones? Discuss them briefly.
Answer:
Occasional winds: The winds that occur suddenly due to sudden differences caused by atmospheric pressure conditions are called occasional winds. There is no regularity of their occurrence.

They may last for a few hours or a few days They are classified into two types—

1.  Cyclones and
2.  Anticyclones.

1. Cyclones: If a low-pressure cell is created suddenly due to some reason, the cool and heavy winds around the low-pressure cell rush in to balance the pressure conditions in circular motions with great speed. These are called cyclones.

The direction of winds: The cyclones blow in the anti-clockwise direction in the northern hemisphere and in the clockwise direction in the southern hemisphere.

Classification: Cyclones can be classified into two types—

1. Tropical cyclones: In both the northern and southern hemispheres, especially between 16° and 24° latitudes, the temperatures over the sea may rise so much during summers that the adjacent air masses get hot, become lighter, expand, and tend to rise upwards. This creates a deep low-pressure cell.

Cooler and heavier winds from the surrounding regions rush at high speeds towards this center of low pressure in circular motions. These are called tropical cyclones.

Cyclones are known by different names in different countries. E.g.—typhoons in the East and South China sea; hurricanes in the Caribbean sea; Tornado or Twister in the central USA.

2. Temperate cyclones: In the northern and southern hemispheres between 35° and 65° latitudes, two contrasting air masses of different physical properties meet with each other.

The line along which warm sub-tropical air mass and cold polar air mass meet with each other is called a front. The cold air tends to move downwards and the warm air tries to move upwards.

As the warm air enters the cold air, it gains speed and rises upwards in a circular motion. In this way a temperate cyclone forms.

2. Anticyclones: In the temperate and frigid zones in both northern and southern hemispheres, sometimes a high-pressure cell is created due to severe cold and concentration of air.

Cold and dry winds blow out from the high-pressure cell towards the surrounding low-pressure regions in circular motions.

These are called anticyclones. In the northern hemisphere, the anticyclones move in a clockwise direction, and in the southern hemisphere, it moves in an anticlockwise direction. The winds move from the center outwards and descend downwards.

Question 33.  What are planetary winds? Describe the trade winds.
Answer:

Planetary winds: The winds blowing from the high-pressure belts towards the low-pressure belts of the earth throughout the year in a fixed direction, are called planetary winds.

There are three kinds of planetary winds—

1. Trade winds,
2. Westerly winds and
3. Polar winds.

1. Trade winds: The planetary winds blowing from the sub-tropical high-pressure belt towards the equatorial low-pressure belt in both hemispheres are called the trade winds. These winds blow from the eastern direction and hence are also called easterly winds or easterlies. In early times, these winds helped ships to sail in the tropical regions for trade and business. Thus, they were named ‘Trade winds’.

Classification: Trade winds can be classified into two types–

1. North-east trade winds: These winds blow from the sub-tropical high-pressure belt near the Tropic and Cancer in the northern hemisphere towards the equatorial low-pressure belt. The winds are deflected and Scanned towards the right according to Ferrel’s Law and blow from the northeast.

2. South-east trade winds: These winds blow from the subtropical high-pressure belt near the Tropic of Capricorn in the southern hemisphere towards the equatorial low-pressure belt. The winds are deflected towards the left according to Ferrel’s Law, and blow from the southeast.

Characteristics:

1. The speed of the trade winds is less in the northern hemisphere due to the presence of more landmasses (15-25 km/hr),
2. In the southern hemisphere, the speed of the trade winds is more (25-35 km/ hr) due to the presence of more water bodies,
   
3. The trade winds blow between 0° and 30° latitudes in both the northern and southern hemispheres,
   
4. The winds blow from the tropical to the equatorial region. Thus, the winds become warm, and their moisture-holding capacity increase.

Influence on climate:

1. In the northern hemisphere, the trade winds fail to provide enough rainfall,
2. In the southern hemisphere, the winds gather moisture from the sea (due to evaporation) and cause rainfall,
3. The trade winds cause rainfall along the eastern margin of the continents and become dry as they move westwards. Thus, several hot deserts have been formed on the western
4. side of the continents in the tropical region. E.g.— Sahara, Kalahari, Thar, Atacama, etc.

Question 34. What are Local winds? Describe some of them.
Answer:

Local winds:

Local winds: The winds that are generated over a region due to local geographical and environmental factors that create a difference in temperature and pressure conditions of the atmosphere are called local winds. The local winds are broadly classified as hot winds and cold winds.

1. Loo: In India, during summer, the northwestern region becomes too hot in the daytime. The air adjacent to this region also gets heated and starts blowing parallel to the earth’s surface at great speed. This very hot and dry wind is called Loo. Loo commonly blows over Delhi, Rajasthan, western Uttar Pradesh, etc.

The velocity of the wind decreases during the evening. The wind is so hot that the heat often kills people and cattle.

2. Foehn: The Foehn blows along the northern slopes of the Alps mountains in Europe and enters the valley of the river Rhine. Warm and dry air follows the down-slope of the Alps mountains and starts descending with speed. The temperature of the wind increases with the downward movement.

This warm, dry wind is known as Foehn. This wind can raise temperatures by as much as 15°C in just a matter of minutes and cause the snow to melt. The snow meltwater helps in the growth of vast grasslands in the valleys of the Alps mountains.

3. Chinook: In North America, the warm and dry wind descending along the eastern slopes of the Rocky Mountains is known as Chinook. ‘Chinook’ means snow-eater. This warm and dry wind melts the snow lying in the foothill regions of the Prairies in winter.

4. Sirocco and Khamsin: In Africa, during the summer, very hot, dry, dusty winds generate over the Sahara desert and blow towards the Mediterranean Sea in the north. Such winds are called Sirocco in Sicily and Khamsin in Egypt.

5. Nor’westers: This is a hot, humid local wind blowing over eastern India (Jharkhand, Odisha, Bihar, West Bengal and Assam) and Bangladesh during the summer season in the months of April-May. The wind generates from the Chotanagpur plateau region of Jharkhand. It causes thunderstorms, lightning, and little rainfall.

6. Aandhi: In the plains of north-western India, a hot dry dusty storm blows during the summer due to sudden pressure changes caused by extreme heating. This dust storm is known as ‘Gandhi’. The wind may blow at a speed of 70-100 km/hr and reduces visibility due to the huge amount of dust present in the air.

7. Mistral: This is a cold local wind. This wind generates in the Alps and blows over the valley of river Rhone in France. This wind causes the temperature of the Rhone valley to drop considerably.

8. Pampero: The cold dry wind blowing over the Pampas grasslands from the Andes mountains in South America, is called Pampero.

9. Bora: In Europe, during the winter, a cold dry wind blows from the Alps mountains towards the Adriatic sea coast. This is known as Bora. This wind decreases the temperature of the Adriatic coast considerably.

Question 35.  Describe the westerly winds.
Answer:

Westerlies:

The planetary winds blowing from the sub-tropical high-pressure belts towards the sub-polar low-pressure belts In both hemispheres are called westerly winds.

1. South-west westerlies:

• In the northern hemisphere, the wind blowing from the sub-tropical high-pressure belt near the Tropic of Cancer towards the sub-polar low-pressure belt near the Arctic Circle is known as the southwest westerlies.
• According to Ferrel’s law, these winds are deflected towards the right.

2. North-west westerlies:

• In the southern hemisphere, the wind blowing from the sub-tropical high-pressure belt near the Tropic of
• Capricorn towards the sub-polar low-pressure belt near the Antarctic Circle is known as the north-west westerlies.

According to Ferrel’s law, these winds are deflected toward the left.

Characteristics:

• The winds are called westerlies as they blow from the west.
• The winds blow between 30° and 60° latitudes in both hemispheres.
• The winds are stronger in the southern hemisphere than in the northern hemisphere. Due to the tremendous speed of the winds, the latitudes have been named as ‘Roaring Forties’, ‘Furious Fifties’ and ‘Shrieking Sixties’

Influence on climate:

• Cyclones and anticyclones occur in regions influenced by westerlies.
• The winds are more active in winter than in summer.
• The westerlies cause rainfall on the western margin of the continents.
• Rainfall reduces as the winds none towards the east. Thus vast grasslands are created in the temperate region.

Example:

Prairies in North America Pampas in South America, Steppes in Russia and Europe, Downs in Australia and Veld in South Africa.

Question 36. Differentiate between temperate and tropical cyclones.
Answer:

The differences between temperate and tropical cyclones are-

Question 37.  Discuss the relationship of the planetary winds with the pressure belts of the world. OR, Classify the planetary winds based on the relation with the pressure belts of the world. OR, Why are the planetary winds related to the pressure belts of the world?
Answer:

Relation of planetary winds with world pressure belts: They are seven pressure belts found on the earth’s surface.

They are—

1. Equatorial low-pressure belt.
2. Sub-tropical high-pressure belt of the northern hemisphere.
3. Sub-tropical high-pressure belt of the southern hemisphere.
4. Sub-polar low-pressure belt of the
5. northern hemisphere
6. Sub-polar low-pressure belt of the southern hemisphere.
7. The polar high-pressure belt around the North Pole.
8. The polar high-pressure belt around the South Pole.

The winds always blow from the high-pressure regions toward the low-pressure regions. As these pressure belts exist on the surface of the earth permanently, they induce certain permanent winds to blow from the high-pressure belts towards the low-pressure belts permanently throughout the year.

These winds are called planetary/winds. The planetary winds are classified into three types—

1. Trade winds,
2. Westerly winds and
3. Polar winds.

1. Trade winds: The winds that blow from the sub-tropical high-pressure belts in either hemisphere towards the equatorial low-pressure belt throughout the year, are called trade winds. Trade winds are of two types—

North-east trade winds:

• These winds blow from the sub-tropical high-pressure belt of the northern hemisphere near the Tropic of Cancer, towards the equatorial low-pressure belt. The winds are deflected to the right according to Ferret’s law.
• Thus, they blow from the northeastern direction.
• South-east trade winds: These winds blow from the sub-tropical high-pressure belt of the southern hemisphere near the Tropic of Capricorn, towards the equatorial low-pressure belt.
• The winds are deflected towards the left according to Ferrel’s law, and thus they blow from the south-eastern direction.

Characteristics:

• The speed of trade winds is slower in the northern hemisphere (15-25 km/hr) due to the presence of more landmasses.
• The speed of these winds is greater in the southern hemisphere (25-35 km/hr) due to the presence of more water bodies,
• The winds blow between 0°and 30° N and S latitudes throughout the year, [iv] A number of deserts have been formed in the path of the trade winds. Example— Sahara, Thar, Kalahari, Atacama, etc.

2. Westerly winds:

The winds blowing from the sub-tropical high-pressure belts towards the sub-polar low-pressure belts in both the
northern and southern hemispheres throughout the year are called westerly winds, or westerlies.

The westerlies are of two types—

1. South-west westerlies:

• The winds blowing from the sub-tropical high-pressure belt near the Tropic of Cancer towards the subpolar low-pressure belt near the Arctic Circle in the northern hemisphere throughout the year, are called southwest westerlies.
• According to Ferrel’s law, they are deflected toward the right.

North-west westerlies:

• The winds blowing from the sub-tropical high-pressure belt near the Tropic of Capricorn towards the sub-polar low-pressure belt near the Antarctic Circle in the southern hemisphere throughout the year, are called north-west westerlies.
• According to Ferrel’s law, these winds are deflected toward the left.

North-west westerlies Characteristics:

• The winds are named westerlies as they blow from the west,
• They blow between 30° and 60°N and S latitudes in both hemispheres,
• The westerlies cause more rainfall on the western margins of the continents than the east,
• Less rainfall on the eastern margins of the continents has led to the formation of vast grasslands in the temperate region.

Example: Prairies in North America, Pampas in South America, Steppe in Russia and Europe, Downs in Australia, and Veld in South Africa.

3. Polar winds:

The winds that blow from the high-pressure belts around the poles towards the sub-polar low-pressure belts in both hemispheres are called polar winds.

The polar winds are of two types:

North-east polar winds:

• The winds that blow from the polar high-pressure belt around the North Pole towards the sub-polar low-pressure belt near the Arctic in the northern hemisphere are called northeast polar winds.
• They are deflected towards the right according to Ferrel’s law.

South-east polar winds:

• The winds that blow from the high-pressure belt around the South Pole towards the sub-polar low-pressure belt near the Antarctic Circle in the southern hemisphere are called southeast polar winds.
• They are deflected towards the left according to Ferrel’s law.

Characteristics:

1. Polar winds are extremely cold and dry.
2. The influence of these winds is more actively felt during the winter,
3. Polar winds cause snowfall and a little rainfall on the eastern margins of the continents. They cause severe blizzards near the Arctic and Antarctic Circles.

Question 38.  Differentiate between trade winds and westerly winds.
Answer:

The differences between trade winds and westerly winds are as follows:

Question 39. Classify different types of winds and give examples.
Answer:

Winds are classified as follows:

 

Question 40. What are isohyets?
Answer:

Isohyets

• The isohyets are imaginary lines drawn on maps to join places that receive equal amounts of rainfall.
• The isohyets help to understand the distribution of rainfall through the earth’s

Question 41. What is smog?
Answer:

Smog

• When the fog particles mix with the smoke of the lower atmosphere, especially in urban and industrial regions, a hazy condition is created, which affects visibility.
• This is known as smog (smoke + fog). Smog is created due to the presence of smoke, carbon particles, and dust particles in the sky. This is very harmful to health.

Question 42. What is a rain shadow area? v OR, How is a rain shadow area created?
Answer:

Rain shadow area

• The slope of the mountain that receives very less rainfall or sometimes no rainfall is called the rain shadow area. In a mountainous area, the moisture-laden winds collide against the windward slope.
• The moist air ends to rise along the slope, where it gets condensed and gives heavy amounts of orographic rainfall. As the winds become light after shedding the rainfall, they rise even more and cross the mountains.
• On the leeward slope, these winds provide very less or almost no rainfall.
• This region is called the rain shadow area.

Example: —The eastern slope of the Western Ghats.

Question 43. Why does orographic rainfall occur on the western slope of the western ghats?
Answer:

• The Arabian Sea branch of the southwest monsoon winds blow over the Arabian Sea and collide with the western slope of the Western Ghats.
• These winds tend to rise along the western slope, where they are cooled and the water vapor condenses. This causes heavy rainfall.
• As the moisture-laden winds cause rainfall after collision with the western slope of the Western Ghats, this rainfall is known as orographic rainfall.

Question 44. Differentiate between relative humidity and absolute humidity.
Answer:

The differences between relative humidity and absolute humidity are:

Question 45. Differentiate between cloud and fog.
Answer:

The difference between cloud and fog are-