Q 1 – How does the unequal distribution of heat over the planet earth in space and time cause variations in weather and climate?
Ans. Weather and climate gets affected by the unequal distribution of temperature on the earth. The areas where there is high temperature, wind blows from low temperature areas. Therefore, wind move upward from equatorial regions and blow towards two poles.
Due to this wind, pressure on both the poles increases. In winter season, wind blows from land regions to oceanic regions. Therefore these wind are dry. On the other hand, during summers, wind blow from ocean towards land. Therefore, these winds are humid. Unequal distribution of temperature is main case of blowing of wind. Rainfall and cyclone also arise due to unequal distribution of temperature. In this way, unequal distribution of temperature affects climate and weather.
Q 2 – What are the factors that control temperature distribution on the surface of the earth?
Ans. Factors controlling temperature distribution: The temperature of air at any place is influenced by
- the latitude of the place;
- the altitude of the place;
- distance from the sea, the air- mass circulation;
- the presence of warm and cold ocean currents;
- local aspects.
1. The latitude: The temperature of a place depends on the insolation received. It has been explained earlier that the insolation varies according to the latitude hence the temperature also varies.
2. The altitude: The atmosphere is indirectly heated by terrestrial radiation from below. Therefore, the places near the sea-level record higher temperature than the places situated at higher elevations.
3. Distance from the sea: Another factor is the location of a place with respect to the sea. Compared to land, the sea gets heated slowly and loses heat slowly. Land heats up and cools down quickly. Therefore, the differences in the temperature over the sea is less compared to land. And this places near the sea has a moderate temperature.
4. Air-mass and ocean currents: Air- masses affects the temperature. The places which come under the influence of warm air- masses experience higher temperature and the place that comes under the influence of cold air-masses experience low temperature.
Q 3 – In India, why is the day temperature maximum in May and why not after the summer solstice?
Ans. The main cause behind temperature being highest in May is due to summer solstice. At that time sun shines on the Tropic of Capricorn. Tropic of Capricorn passes through middle of India. But it remains till end of May in India. It is because rain starts on Malabar coast at the end of the May. Due to this, temperature does not increase in South India. Although increase in temperature continues in India till 21 June and we find highest temperature in first week of June in India.
Q 4 – Why is the annual range of temperature high in the Siberian plains?
Ans. Siberian plains are quite far off from sea. Uneven climate is found in areas located away from oceans and seas. The mean monthly temperature for January is between -18° C to -48° C in the Siberian plains. In summers, it is up to 20°celcius. Therefore, the annual range of temperature is -68 (-48-20) which is extremely high. The pressure of warm ocean currents, Gulf Stream and north Atlantic drift, make the northern Atlantic Ocean warmer and the isotherms bend towards the north. Over the land, the temperature decreases sharply and the isotherms bend towards south in Europe.
Q 5 – How do the latitude and the tilt in the axis of rotation of the earth affect the amount of radiation received at the earth’s surface?
Ans. Sunrays fall vertical on equator through the year. From 0° to 23.5° north and south, the sun keeps fluctuating. From 1st march to 21st march, the sun is southern and sunrays fall vertical on tropic of cancer. This time there is summer in northern hemisphere. From 23rd September to 22nd December, the sun is southern. During this time, the sunrays fall vertical on tropic of capricorn. On 21st march and 23rd September, sunrays fall vertical on equator. As we move towards poles from tropic of cancer and tropic of Capricorn, temperature keeps on decreasing. Therefore, after 6614 degree north and south there is cold zone. Throughout the year, the temperature remains low here. In this region, throughout the year, there is frigid snow. It is because the sun’s rays fall tilted on it. In this way, the latitude and the tilt in the axis of rotation of the earth affect the amount of radiation received at the earth’s surface.
Q 6 – Discuss the processes through which the earth-atmosphere system maintains heat balance.
Ans.
1. Conduction:
- The earth after being heated by insolation transmits the heat to the atmospheric layers near to the earth in long wave form. The air in contact with the land gets heated slowly and the upper layers in contact with the lower layers also get heated.
- It takes place when two bodies of unequal temperature are in contact with one another, there is a flow of energy from the warmer to cooler body. The transfer of heat continues until both the bodies attain the same temperature or the contact is broken. Conduction is important in heating the lower layers of the atmosphere.
2. Convection:
- The air in contact with the earth rises vertically on heating in the form of currents and further transmits the heat
of the atmosphere. This vertical heating of atmosphere is known as convection. - The convection transfer of energy is confined only to the troposphere
3. Advection:
- The transfer of heat through horizontal movement of air is called advection. Horizontal movement of the air is relatively more important than the vertical movement.
- In tropical regions particularly in northern India during summer season local winds called ‘loo’ is the outcome of advection process.
Q 7 – Compare the global distribution of temperature in January over the northern and the southern hemisphere of the earth.
Ans. In January, there is summer in southern hemisphere and winter in northern hemisphere. The main reason behind it is that sun has northern face and sunrays fall vertical in northern hemisphere. The areas which are closer to equator have temperature up to 27°C and over the land the temperature decreases sharply and the isotherms bend towards south in Europe. It is much pronounced in the Siberian plain. The mean January temperature along 60° E longitude is minus 20° C both at 80° N and 50° N latitudes. The mean monthly temperature for January is over 27° C, in equatorial oceans over 24° C in the tropics and 2° C – 0° C in the middle latitudes and -18° C to -48° C in the Eurasian continental interior.
Q 8 – What factors cause variation in insolation?
Ans. The factors that cause these variations in insolation are :
- the rotation of earth on its axis;
- the angle of inclination of the sun’s rays;
- the length of the day;
- the transparency of the atmosphere;
- the configuration of land in terms of its aspect.
Q 9 – What is aphelion?
Ans. During its revolution around the sun, the earth is farthest from the sun (152 million km) on 4th July. This position of the earth is called aphelion.
Q 10 – What is perihelion?
Ans. On 3rd January, the earth is the nearest to the sun (147 million km). This position is called perihelion.
Q 11 – What does Plank’s law state?
Ans. Plank’s law states that hotter a body, the more energy it will radiate and shorter the wavelength of that radiation.
Q 12 – What factors affect the temperature of a place?
Ans. The temperature of air at any place is influenced by
- the latituae of the place;
- the altitude of the place;
- distance from the sea, the air- mass circulation;
- the presence of warm and cold ocean currents;
- local aspects.
Q 13 – What is terrestrial radiation?
Ans. The insolation received by the earth is in short wave orms and heats up its surface. The i arth after being heated itself becomes a radiating body and it radiates energy to the atmosphere in long wave form. This energy heats up the atmosphere from below. This process is known as terrestrial radiatio”
Q 14 – What are the causes behind loo in tropical regions?
Ans. In tropical regions particularly in northern India during summer season local winds called ‘loo’ is the outcome of advection process.
Q 15 – Why does sun look red during rising and setting and why does sky look blue?
Ans. Within the troposphere water vapour, ozone and other gases absorb much of the near infrared radiation. Very small- suspended particles in the troposphere scatter visible spectrum both to the space and towards the earth surface.
This process adds colour to the sky. The red colour of the rising and the setting sun and the blue colour of the sky are the result of scattering light of the atmosphere.
Q 16 – How does some amount of energy is reflected to the atmosphere? or what is albedo?
Ans. While passing through the atmosphere some amount of energy is reflected, scattered and absorbed. Only the remaining part reaches the earth surface. The reflected amount of radiation is called the albedo of the earth.
Q 17 – How do sunrays while passing through atmosphere gets absorbed?
Ans. Out of 100% received, 65 units are absorbed, 14 units within the atmosphere and 51 units by the earth’s surface. The earth radiates back 51 units in the form of terrestrial radiation. Of these, 17 units are radiated to space directly and the remaining 34 units are absorbed by the atmosphere (6 units absorbed directly by the atmosphere, 9 units through convection and turbulence and 19 units through latent heat of condensation).
Q 18 – Atmosphere gets heated up indirectly by terrestrial radiation and not directly by s nrays. Explain.
Ans. Tne long wave radiation is absorbed by the atmospheric gases particularly by carbon dioxide and the other green house gases. Thus, the atmosphere is indirectly b ^ated by the earth’s radiation. The atmosphere in turn radiates and transmits heat to the space. Finally, the amount of heat received from the sun is returned to space, thereby maintaining constant temperature at the earth’s surface and in the atmosphere.
Q 19 – What is meant by insolation?
Ans. The earth’s surface receives most of its energy in short wavelengths. The energy received by the earth’s is known as incoming solar radiation which in short is termed as insolation.
Q 20 – Differentiate between Perihelion and Aphelion.
Ans. During its revolution around the sun, tho earth is farthest from the sun, on 4th July. This position of earth is called Aphelion.
And on 3rd January, the earth is the nearest to the sun. This position is called Perihelion.
Q 21 – Why the annual insolation received by the earth on 3rd January is more than that of 4th July?
Ans. The solar output received at the top of atmosphere varies slightly in a year due to the variations in the distance between the earth and the sun. Therefore, the annual insolation received by the earth on 3rd January is more than the amount received on 4th July.
Q 22 – What is inversion of temperature? When | and in what regions does it take place?
Ans. At times, the situations are reversed and the normal lapse rate is inverted. It is called Inversion of temperature. Inversion is usually of short duration but quite common nonetheless. A long winter night with clear skies and still air is ideal situation for inversion. The heat of the day is radiated off during the night, and by early morning hours, the earth is’ cooler than the air above. Over polar areas, temperature inversion is normal throughout the year. Surface inversion promotes stability in the lower layers of the atmosphere.
Smoke and dust particles get collected beneath the inversion layer and spread horizontally to fill the lower strata of the atmosphere. Dense fogs in mornings are common occurrences especially during winter season. This inversion commonly lasts for few7 hours until the sun comes up and beings to warm the earth. The inversion takes place in hills and mountains due to air drainage.
Q 23 – How does the energy received in upper layer of the atmosphere keep changing at different times of the year?
Ans. The solar output received at the top of the atmosphere varies slightly in a year due to the variations in the distance between the earth and the sun. During its revolution around the sun, the earth is farthest from the sun (152 million km) on 4th July. This position of the earth is called aphelion.On 3rd January, the earth is the nearest to the sun (147 million km). This position is called perihelion. Therefore, the annual insolation received by the earth on 3rd January is slightly more than the amount received on 4th July.
However, the effect of this variation in the solar output is masked by other factors like the distribution of land and sea, and the atmospheric circulation. Hence, this variation in the solar output does not have great effect on daily weather changes on the surface of the earth.
Q 24 – How does the amount of insolation received depends on the angle of inclination of the rays?
Ans. The amount of insolation received depends on the angle of inclination of the rays. It depends on the latitude of a place. The higher the latitude the less is the angle they make with the surface of the earth resulting in slant sunrays. The area covered by vertical rays is always less than the slant rays. If more area is covered, the energy gets distributed and the net energy received per unit area decreases. Moreover, the slant rays are required to pass through greater depth of the atmosphere resulting in more absorption, scattering and diffusion.
Q 25 – Explain about spatial distribution of insolation on the earth’s surface.
Ans. The insolation received at the surface varies from about 320 Watt/m2 in the tropics to about 70 Watt/m2 in the poles. Maximum latitude insolation is received over the subtropical deserts, where the cloudiness is the least. Equator receives comparatively less insolation than the tropics. Generally, at the same latitude the insolation is more over the continent than over the oceans. In winter, the middle and higher latitudes receive less radiation than in summer.
Q 26 – Explain the distribution of temperature in July.
Ans. Distribution of temperature in July
- During this period the sun shines vertically over head near the tropic of cancer. It is summer for the northern hemisphere and winters for the southern hemisphere.
- In the northern hemisphere the isotherm bends equator wards while crossing the oceans and pole wards ‘while crossing the landmass. In the southern hemisphere it is vice-versa.
- The isotherms are most irregular and zig-zig in northern hemisphere on the other hand the isotherms are relatively more regular and straight in southern hemisphere.
- Maximum temperature of about 30 degree centigrade occurs entirely in the northern hemisphere between 10° and 40° north latitude however the lowest temperature below 0° C is recorded over northern hemisphere in the central parts of green land.
Q 27 – Explain the factors affecting insolation at the surface of earth.
Ans. The factors affecting insolation at the surface of earth are:-
1. The rotation of earth on its axis: The fact that the earth on its axis makes an angle of 6614 with the plane of it’s orbit round the sun has a greater influence on the amount of insolation received at different latitudes.
2. The angle of inclination of the sunrays: The higher the latitude the greater is the angle they make with the surface of the’earth resulting in slant sunrays. The areas covered by vertical rays is always less than the slant rays. If more areas is covered the energy gets distributed and the net energy received per unit area decreases. Thus, the slant rays are required to pass through greater depth of the atmosphere resulting in more absorption, scattering and diffusion.
3. The transparency of the atmosphere: The atmosphere is largely transparent to the short wave solar radiation. The incoming solar radiation passes through the atmosphere before striking the earth’s surface. Within the troposphere water vapour, ozone and other gases absorb much of the near infrared radiation.
4. The configuration of land in terms of its aspect: The insolation received at the surface varies from about 320 watt/ m2 in the poles. Maximum insolation is received over the subtropical deserts, when the cfoudness is the least. Equator receives less rainfall as compared to tropics
Q 28 – Distribution of temperature in the month of July.
Ans.
- During this period the sun shines vertically over head near tropic of cancer it is the summer for northern hemisphere and winter for southern hemisphere.
- The isotherms are relatively more regular and straight in southern hemisphere.
- Maximum temperature of over 30°C occurs entirely in northern hemisphere between 10° and 40° temperature below 0° C is recorded over northern hemisphere in the central parts of Greenland.
Q 29 – Explain the distribution of temperature in January.
Ans.
1. In January the isotherms deviate to north over the ocean and to the south over the continent. This can be seen on the North Atlantic Ocean.
2. The pressure of warm ocean currents, Gulf Stream and north Atlantic drift, make the northern Atlantic Ocean warmer and the isotherms bend towards the north.
3. Over the land the temperature decreases sharply and the isotherms bend towards south in Europe.
4. It is much pronounced in the Siberian plan. The mean January temperature along 60° E longitude is minus 20° both at 80° N and 50° N latitude. The mean monthly temperature for January is over 27° C in equatorial oceans over 24°C in the tropics and 2° C- 0° C in middle latitudes and -18° C to -48° C in Eurasian continental interior.
5. The effect of the ocean in well pronounced in southern hemisphere. Here, the isotherms are more or less parallel to latitudes and the variations in temperature is more gradual than in the northern hemisphere. The isotherm of 20°C, 10°C, and 0°C run parallel to 35°S, 45° and 60°S latitudes respectively
Q 30 – Explain about inversion of temperature.
Ans. At times, the situations are reversed and the normal lapse rate is inverted. It is called inversion of temperature. Inversion is usually of short duration but quite common nonetheless. A long winter night with clear skies and still air is ideal situation for inversion. The heat of the day is radiated off during the night, and by early morning hours, the earth is cooler than the air above.
Over polar areas, temperature inversion is normal throughout the year. Surface inversion promotes stability in the lower layers of the atmosphere. Smoke and dust particles get collected beneath the inversion layer and spread horizontally to fill the lower strata of the atmosphere. Dense fogs in mornings are common occurrences especially during winter season. This inversion commonly lasts for few hours until the sun comes up and beings to warm the earth. The inversion takes place in hills and mountains due to air drainage.
Q 31 – Explain the heating and the cooling mechanism of atmosphere.
Or
Discuss the process through which earth and the atmosphere system maintain heat balance.
Ans.
(a) Conduction:
- The earth after being heated by insolation transmits the heat to the atmospheric layers near to the earth in long wave form. The air in contact with the land gets heated slowly and the upper layers in contact with the lower layers also get heated.
- Conduction takes place when two bodies of unequal temperature are in contact with one another, there is a flow of energy from the warmer to cooler body. The transfer of heat continues until both the bodies attain the same temperature or the contact is broken. Conduction is important in heating the lower layers of the atmosphere.
(b) Convection
- The air in contact with the earth rises vertically on heating in the form of currents and further transmits the heat of the atmosphere. This vertical heating of atmosphere is known as convection.
- The convection transfer of energy is confined only to the troposphere.
(c) Advection:
- The transfer of heat through horizontal movement of air is called advection. Horizontal movement of the air is relatively more important than the vertical movement.
- In tropical regions particularly in northern India during summer season local winds called ‘loo’ is the outcome of advection process.
Q 32 – Explain about heat budget of the earth.
Ans. The earth receives almost all of its energy from the sun. The earth in turn radiates back to space the energy received from the sun. As a result, the earth neither warms up nor does it get cooled over a period of time. Thus, the amount of heat received by different parts of the earth is not the same. This variation causes pressure differences in the atmosphere. This leads to transfer of heat from one region to the other by winds. The insolation received at the top of the atmosphere is 100 per cent. While passing through the atmosphere some amount of energy is reflected, scattered and absorbed. Only the remaining part reaches the earth surface.
Roughly 35 units are reflected back to space even before reaching the earth’s surface. Of these, 27 units are reflected back from the top of the clouds and 2 units from the snow and ice- covered areas of the earth. The reflected amount of radiation is called the albedo of the earth. The remaining 65 units are absorbed, 14 units within the atmosphere and 51 units by the earth’s surface. The earth radiates back 51 units in the form of terrestrial radiation. Of these, 17 units are radiated to space directly and the remaining 34 units are absorbed by the atmosphere (6 units absorbed directly by the atmosphere, 9 units through convection and turbulence and 19 units through latent heat of condensation). 48 units absorbed by the atmosphere (14 units from insolation +34 emits from terrestrial radiation) are radiated back into space.
Q 33 – What is insolation?
Ans. The incoming solar radiation is called insolation.
Q 34 – How much energy radiated by the sun is intercepted by the earth?
Ans. Only A of the billionth fraction of the energy radiated from the sun is intercepted by the earth.
Q 35 – What is isotherm?
Ans. Isotherms are imaginary lines joining places having equal temperatures.
Q 36 – Where does the energy radiate from the sun come from?
Ans. The energy radiated from the sun comes from nuclear reactions in its core.
Q 37 – What is the temperature at the core of the sun?
Ans. The temperature at the core of sun-is about 15,000,000°C.
Q 38 – What is the radiant energy of sun commonly known as?
Ans. The radiant energy of the sun is commonly known as short waves or electromagnetic waves.
Q 39 – At what speed the short waves travel?
Ans. The short waves travel at a speed of light, i.e., about 2,98,000 km. per second.
Q 40 – What is terrestrial radiation?
Ans. The longwave radiation, i.e., re-emittance of the energy received from the earth’s surface, is terrestrial radiation.
Q 41 – Name the processes which control the heat budget of the earth ., and the atmosphere.
Ans. They are the processes of absorption, reflection and scattering.
Q 42 – Define heat budget.
Ans. The gains and losses in heat by incoming and outgoing radiation is known as heat budget.
Q 43 – What is advection?
Ans. Transfer of heat through the horizontal movement of the air is called advection.
Q 44 – What is meant by temperature gradient?
Ans. The rate of change of temperature is called the temperature gradient.
Q 45 – Name two months of the year which represent the seasonal extremes of temperature
Ans. January and July months represent the seasonal extreme of temperature.
Q 46 – Define Planck’s law.
Ans. Planck’s law states that hotter a body, the more energy it will ‘ radiate and shorter is the wavelength of that radiation.
Q 47 – What is specific heat?
Ans. Specific heat is the energy needed to raise the temperature of one grain of a substance by one degree Celsius.
Q 48 – What is insolation?
Ans. The incoming solar radiation is termed as insolation. It comes in the form of short waves.
Q 49 – What are the methods by which the atmosphere is heated?
Ans. The atmosphere gets heated in the following ways:
(a) Radiation,
(b) Conduction,
(c) Convection,
(d) Advection.
Q 50 – Why do isotherms bend while crossing the continents and oceans?
Ans. Due to differential heating and cooling of land and sea water.
Q 51 – How much energy radiated by the sun is intercepted by the earth?
Ans. 1/2000 million part of the total energy radiated by the sun is intercepted by the earth.
Q 52 – Which is the most important process of heating the atmosphere?
Ans. Terrestrial radiation.
Q 53 – What is the temperature?
Ans. Warmth or coolness of the air is called its temperature.
Q 54 – What is the extent of the Torrid Zone?
Ans. 23’/2°N to 23’/2°S.
Q 55 – What is the extent of the Frigid Zone?
Ans. 66V20 to poles.
Q 56 – Name the type of climate found in coastal areas.
Ans. Maritime (moderate).
Q 57 – Why is the temperature of the earth increasing?
Ans. Due to the increase in carbon dioxide
Q 58 – What is insolation?
Ans. The incoming solar radiation is termed as insolation.
Q 59 – What is air drainage?
Ans. The cold air acts almost like water and moves down the slope to pile up deeply in pockets and valley bottoms with warm air above. This is called air drainage. It protects plants from frost damages.
Q 60 – What are the characteristics of isotherms?
Ans. Main characteristics of isotherms are:
- Isotherms run along the latitudes.
- Isotherms take sudden bends at the land-water edge because of land-water contact.
- They are drawn at equal space which indicates the latitudinal thermal gradient.
- Isotherms change their positions.
Q 61 – Discuss the variation in the distribution of insolation over the earth’s surface.
Ans The incoming solar radiation is called insolation. Insolation is * greatest at the equator. It decreases polewards. The total amount of insolation received at the equator is roughly about 4 times of that received at the poles. In tropical regions, the amount of insolation is only large but there is also little seasonal variation. It is because all their places between Tropic of Cancer and Capricorn experience overhead sun twice during the course of a year. Insolation is maximum twice in a belt between 23°30’ and 66°30′.
Q 62 – What are the effects of the atmosphere on insolation?
Ans. The energy from the sun passes through different layers of the atmosphere before it reaches the ground. Atmospheric gases are essentially transparent to visible light, but suspended particles of liquid or solid material can absorb or reflect light. A thick cloud may allow less than 10% of sunlight to reach the earth’s surface. Clouds generally behave like mirrors. They reflect sunlight off in different directions rather than absorbing. Reflected sunlight is permanently lost from the earth. The blue colour of the daytime sky is due to the scattering of sunlight.
Q 63 – Define temperature.
Ans. The temperature is the measurement of available or sensible heat energy in a system. It is a measure of hotness or coldness of the body. Such property determines whether the heat will flow out or into an object when it comes in contact with other objects.
Q 64 – Explain why the angle of the sun’s rays falls variably on different latitudes.
Ans. The earth revolves around the sun once in a year in an elliptical path called the ‘plane of ecliptic’. At the same time, the earth rotates on its axis in 24 hours. The earth’s axis is tilted making an angle of 66°30′ from the plane. Due to inclination of the earth’s axis, the angle of the sun’s rays falling on the earth’s surface varies from vertical on the equator to more and more slanting as one moves towards the poles.
Q 65 – Explain how the ocean currents influence the temperature distribution over the earth surface.
Ans. Ocean currents are large movements of ocean water from places of warm temperature to colder temperature or vice-versa. Their movement affects the temperature of the adjacent areas. The warm currents raise the temperature of adjoining colder landmasses. The climate of north-western Europe is modified to a large extent by ocean currents of the North Atlantic Ocean. The cold currents of the western coast of South Africa or South America lower the temperature of adjacent warmer lands.
Q 66 – What is the role played by prevailing winds in temperature modification?
Ans. Prevailing winds also affect the temperature conditions of the areas. The moderating effects of oceans are brought to the adjacent lands through winds. On the contrary, off-shore winds take the effects of warm or cold currents away from the land.
Q 67 – What is the difference between direct radiation and diffused radiation?
Ans. The sun emits short wave radiation to space and the earth’s surface. The solar energy strikes the upper limits of the atmosphere and it gradually reaches the earth’s surface directly or indirectly (scattered) and is absorbed. It is estimated that out of 100 units of incoming solar energy, 22 units travel directly to the earth’s surface. This energy flow is called direct radiation. Some of the scattered rays eventually also find their way down indirectly to the earth’s surface. They are collectively called diffused radiation.
Q 68 – What is global warming? What are its causes?
Ans. The burning of fossil fuels, the cultivation of the soil, industrialisation of land on a large scale, rapid means of transport and deforestation have caused an imbalance in the atmosphere. These activities are increasing the amount of carbon dioxide. Thus, the greenhouse effect has raised the average temperature of the earth by 0,5°C. By the year 2000, the earth’s average temperature will go up by 2°C.
This is called global warming. It is causing a rise in the sea level due to melting of glaciers. It is threatening to submerge many coastal areas.
Q 69 – How does the angle of the sun’s rays falling on the ground affect the amount of insolation?
Ans. The amount of insolation reaching the earth’s surface depends largely on the inclination or angle of the sun’s rays. Vertical rays and those nearly 80 in the lower latitudes are more effective in increasing temperature than the oblique rays in the higher latitudes, although the duration of sunshine may be much longer in the latter case. Moreover, the oblique rays spread over a larger area on the earth’s surface whereas the vertical rays are concentrated over a smaller area, the intensity of heat being lighter in the area insolated by vertical rays.
Q 70 – Differentiate between advection and convection.
Ans. Transfer of heat through the horizontal movement of the air is called advection, whereas the vertical mixing of the air is termed as convection. Convection is caused by the circulatory movement of the air itself and the pull of gravity.
Q 71 – Isotherms do not show the correct temperature of a place. Discuss.
Ans., sotherms show the temperature of a place supposing it to be at sea level. The temperature is reduced to sea level to avoid the effect of relief. Thus, isotherms do not show the actual temperature of a place.
Q 72 – Discuss the impact of altitude on temperature over the atmosphere.
Ans. Altitude is the height of a point above mean sea level, measured vertically. The temperature decreases with increasing height and latitude from the earth’s surface. This vertical decrease in temperature takes place at the rate of 0.65° per 100 metres or 165 metres per 1°C. These variations are normal throughout the troposphere and are termed as normal lapse rate. The atmosphere near the surface is denser and contains a large amount of water vapour and dust particles. Being closer to the land surface, it absorbs more terrestrial heat than that of the upper air. Hence, the temperature is higher in the lower part of the atmosphere than in the upper part, where the air is cleaner. That is why the higher we go, the cooler it is. Ootacamund, Mount Abu, Panchmarhi are cooler in summer than plains.
Q 73 – What are the basic mechanisms of heat transfer? Discuss the importance of these mechanisms with reference to the atmosphere.
Ans. There are three basic mechanisms of heat transfer:
- Radiation,
- Conduction, and
- Convection.
1. Radiation: Radiation is the act of transmitting energy in the form of particles of electromagnetic waves. The process is similar to that of transmission of light from an electric bulb. There are two forms of radiations: solar radiation and terrestrial radiation. The atmosphere gets heated up, in fact, through terrestrial radiation and not by solar radiation.
2. Conduction: When two bodies of unequal temperatures are in contact with one another, there is a flow of energy in the form of heat from warmer to cooler body. The layer of air resting upon the warmer earth becomes heated by the process of conduction. The actual conduction during the course of the day affects only the lowest layer of the atmosphere.
3. Convection: Convection is the process of heat transfer caused by the dying circulatory movement of the fluid itself. It takes place due to difference in temperature, and hence in density, and the pull of gravity. Convection produces vertical movement. The horizontal movement of a similar nature is called advection.
A cyclic circulation helps in transforming the heat of lower layers to the upper layers of the atmosphere. This process of heating is convection.
Q 74 – How many shapes the sun has? Describe photosphere.
Ans. The sun has three shapes: the core and the interior. The innermost portion of the sun is extremely hot and hence here hydrogen atoms combine to form a smaller number of heavier helium atoms. In this process, certain mass is converted into energy.
The Photosphere: Photosphere is the solar surface. The energy produced in the core reaches to this surface. Most of the sun’s energy comes from the photosphere and we see it as a solar disc. In the photosphere, there are granules that transport energy from the base of the photosphere to its surface. Sunspots are dark regions on the photospheres. They are formed due to strong magnetic fields. The energy is released in the form of x-ray and ultra-violet radiations from the sunspots.
Above the photosphere occurs the sun’s atmosphere. The lower part is chromosphere and the upper is the corona. They are visible only during solar eclipses. Corona exudes electromagnetic energy. These energy particles can be captured by earth’s magnetic field in the ionosphere and their interaction with gases produce the aurora.