8th Standard, Social, Geography, CHAPTER – 13
ATMOSPHERE
Exercises
I Fill in the blanks with suitable words:
1. The two major gases of the atmosphere are Nitrogen and Oxygen.
2. The lowest layer of the atmosphere is Troposphere.
3. The average air pressure of the atmosphere at the sea level is
1013.25 mb.
4. Westerlies is also known as Anti-trade Winds.
5. The scientific study of weather is ‘Meteorology’.
II Answer the following questions briefly:
6. What is atmosphere?
Answer: Atmosphere is a thin layer of gases, dust particles and water vapour surrounding the Earth.
7. Name the important layers of the atmosphere.
Answer: The important layers of the atmosphere are as follows.
1. Troposphere,
2. Stratosphere,
3. Mesosphere,
4. Thermosphere (Ionosphere)
5. Exosphere.
8. What is the significance of ozone layer?
Answer: Stratosphere is the second layer of the atmosphere. This layer extends up to 50 km’s from the surface. It lies between troposphere and mesosphere. In this layer Ozone is the most important gas which absorbs ‘ultraviolet rays’ of the sun and protect all forms of life on the Earth. This layer is free from clouds and other important weather phenomenon and provides ideal flying conditions for jet aircrafts
9. What is Doldrum? Where is it found?
Answer: The equatorial low pressure belt is a zone of high temperature and low pressure. This region is called ‘Doldrum. This region gets direct rays of the Sun almost throughout the year. Hence air is always very warm and hot. This is a calm region with very little wind. So it is known as ‘Doldrum’ means ‘belt of calm’ (equatorial calm). Doldrum found between 0° to 5° North and South of the equator.
10. Name the different types of planetary winds.
Answer: Winds are classified into 4 major types. They are Planetary winds, Seasonal winds, Local winds, Cyclones and Anti cyclones
1. Planetary winds: Planetary Winds are also called ‘Permanent winds’ or ‘Prevailing winds’ or ‘Regular winds’. They classified into 3 types. They are,
a) Trade Winds b) Westerlies or Anti-trade Winds c) Polar winds
2. Seasonal winds
3. Local winds
4. Cyclones and Anti cyclones:
a) Cyclones: They are divided into Tropical cyclones, Temperate cyclones.
b) Anti Cyclones.
11. What are local winds? Give any two examples.
Answer: Local winds also known as periodic winds are the result of variation in local temperature, pressure, humidity which in turn are attributed to the formation of air currents, crossing mountain ranges, valleys and other relief barriers.
Two common examples are,
1. Sea Breeze: A cool wind then blows from the high-pressure area over the water to the low-pressure area over the land.
2. Land Breeze: A wind blows from the cooler land towards the warmer sea.
The other local winds are Mountain breeze (Katabatic winds),Valley breeze (Anabatic winds) and other few winds are Loo (India), Chinook or Snow eater (USA), Fohn (Alps region), Mistral (France), Sirocco (Sahara region), Brick Fielder (Australia), Blizzard (Antarctica) etc.
12. Mention the different types of clouds.
Answer: Clouds are classified in to 4 types on the basis of their shapes and heights at which they occur. The important types of clouds are as follows.
1. Stratus
2. Cumulus,
3. Cirrus
4. Nimbus
These are further categorized into ten main types, such as
- Cirrus (Ci)
- Cirrocumulus (Cc)
- Cirrostratus (Cs)
- Altocumulus (Ac)
- Altostratus (As)
- Nimbostratus (Ns)
- Cumulus (Cu)
- Cumulonimbus (Cb)
- Stratocumulus (Sc)
- Stratus (St)
13. Distinguish between weather and climate.
Answer: The main differences between weather and climate as follows.
1. Weather: The day-to-day or even hour-to-hour state of the atmosphere at a specific location.
Climate: The average weather conditions and variations over a large area for a long period.
2. Weather: Short-term, from minutes to days or weeks.
Climate: Long-term, typically observed over decades, such as 30 years or more.
3. Weather: A sudden rain shower, a very hot afternoon, or a strong gust of wind are all examples of weather.
Climate: A tropical climate with warm temperatures year-round, or a desert climate characterized by very little rainfall, describe climate.
4. Weather: Affects daily activities, such as what to wear, whether to carry an umbrella, or if you can play outside.
Climate: Influences major aspects of life in a region, such as the types of crops that can be grown, the kind of industries, and the overall lifestyle of the inhabitants.
III Define the following:
14. Ionosphere: Thermosphere layer lies next to Mesosphere. In this layer temperature rises drastically. It is also called ‘Ionosphere’ as the gaseous atoms are ionized due to very high temperature.
15. Normal lapse rate: Normal lapse rate is the decreasing rate of temperature with the increase of altitude. The rate of decrease is 10 C for every 165 meters or 6.40 C for every 1000 meters of height (1 km).
16. Torrid zone: This is the zone of high temperature. This region is found between 0° or Equator and Tropic of Cancer in the north (23°.30l N) and the Equator and Tropic of Capricorn (23°.30l S) in the south. This region receives direct rays of the Sun.
17. Orographic rainfall: Orographic rainfall is also called ‘Mountain rainfall’ or ‘Relief rainfall’. When moisture laden air is obstructed by a mountain barrier, the air is forced to rise up. As the air rises upwards, it cools and gets saturated. Further cooling of this air causes condensation resulting in orographic or mountain rainfall.
18. Climatology: The scientific study of climate is called ‘Climatology’.
IV Terms to remember:
1. Insolation: The Sun is the main source of energy to the Earth which supplies heat through insolation. Insolation means incoming solar radiation from the sun to the Earth.
2. Inversion of temperature: In some situations temperature also increase with increasing height. This takes place in mountain valleys during long winter nights with clear sky, dry air, no wind and snow covered surface.
3. Anemometer: ‘Anemometer’ is used to measure the speed of the wind.
4. Roaring forties: The westerlies of southern hemisphere are very strong over the oceans. Hence they are called ‘Roaring Forties’ (40° south latitude),
5. Nimbus clouds: Nimbus clouds are rain clouds which occur at low levels. These clouds have the shape of stratus or cumulus.
6. Meteorology: The scientific study of weather is called ‘Meteorology’.
Additional Questions:
1 . Which are the various elements influences the Weather condition?
Answer: Weather condition of a place is influenced by various elements are as follows.
- Temperature
- Pressure
- Wind
- Humidity
- Clouds
- Rainfall
2. Name the important factors which influence atmospheric temperature.
Answer: The important factors which influence atmospheric temperature are latitude, altitude or height, distance from the sea, wind, ocean currents, relief, clouds, rainfall etc.
3. What is atmospheric pressure? Name the instrument used by measuring atmospheric pressure.
Answer: Air has weight and it exerts pressure. This is called atmospheric pressure. Air pressure is measured by an instrument called Barometer.
4. What is pressure belt? Name the Major pressure belts of the Earth.
Answer: The pressure on the earth is distributed in the form of belts. There are seven pressure belts. They are,
1. The Equatorial low pressure belt
2. North Sub- tropical high pressure belt
3. South Sub-tropical high pressure belt
4. North -Sub- Polar low pressure belt
5. South Sub-polar low pressure belt
6. North Polar high pressure belt
7. South Polar High pressure belt
5. What is Humidity? Name the instrument used by measuring Humidity?
Answer: Humidity is the amount of water vapour or moisture present in the air. Humidity is measured by using an instrument called Hygrometer or Psychrometer.
6 . What are the different types of Humidity?
Answer: The different types of Humidity are as follows.
- Absolute humidity
- Relative humidity
- Specific humidity
7. What is rainfall? Name the types of rainfall.
Answer: Precipitation in the form of water droplets is called rainfall. The types of rainfall are as follows.
- Convectional rainfall
- Orographic rainfall
- Cyclonic rainfall.
V Activity:
1. Draw a diagram showing different temperature zones on the basis of latitudes.
