Solar radiation 2: The earth's atmosphere.
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- 16mm Film, Educational Film, Solar radiation, Space (Astronomy), Energy and matter, Astronomy
- Rochester, N.Y. : Released by Modern Learning Aids and Universal Education and Visual Arts
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Describes the spectral distribution of incoming solar radiation, the outgoing infrared terrestrial radiation, and the interactions of these two types of radiant energies with atmospheric gases
Examines the effects of solar radiation on the earth. Uses instruments to study the light spectrum and light absorption.
- 2014-11-06 21:36:33
- It's from. A. Song. A constant stream of radiant energy pours down through the atmosphere at the Earth's surface. That's radiant energy is converted into heat energy. This heat energy melt snow. And evaporates water. Informs quote and drives the wind. It can reappear and electrical energy and sound energy the. Solar radiation is absorbed by Badger Taishan which converted to chemical energy. Each year we watch the ever repeated cycle of plant growth. The human race. Indeed the rest of life honor the pens on the energy stored by plants for its very existence. You'll. How does this radiant energy produced so many affects to answer this question we must learn more about its nature. When light from the sun passes through raindrops are the separated into the many colors of the rainbow. Similarly one light from a lamp is passed through slit. Our limbs. And then a prism the spectrum produced shows the colors present in the light. When this red liquid is placed in the path of the light the blue and green colors in the spectrum are removed. This part of the light has been selectively absorbed by the liquid. But moving green light absorbed by the liquid is converted into heat. The movement starting to appear. Our convection currents caused by heating. If we could see the individual molecules in a liquid we would find that they move more quickly as the light is absorbed and the temperature rises. Selective absorption very similar divide which we're just observed also occurs in the atmosphere. And in this film we will explore some of it's the facts then play influence not only the entire atmosphere but also the surface of the earth and the life which exists here. We begin our story with the white light spectrum know how one color merges imperceptibly into the next at each end red and violet fade gradually into black although the screen appears dark Those does not mean there was no energy or writing. On the contrary there are considerable amounts of energy both beyond the violet in the ultraviolet and be on the red and the Emperor red regions of the spectrum. In a classic experiment carried out by Sir William Herschel over one hundred fifty years ago there are mothers were placed in the spectrum of sunlight the temperature readings traced out a smooth curve across the spectrum. These ratings are a measure of the radiant energy in different parts of the spectrum. Notice there is energy in both the ultra violet and the Emperor red. How does this radiant energy travel from the sun to the earth. In one description the energy is carried by smaller particles called photon let us consider a light of a single color produced by identical photons as the number of photons increases the light becomes brighter. These photons can pass through transparent substances such as glass they can be scattered all over they can be absorbed when they are absorbed the photons disappear but their energy is given to the observer. We can describe the radiation and different parts of the spectrum by the energy carried by single photons. Sense photons of the same color all carry the same energy. For example. Protons of while it light happy about twice the energy of photons of red light ultraviolet photons are much more energetic than infrared photons. Each photon has a characteristic wavelength associated with it these wavelengths are very short and a special unit of Micron one millionth of a metre is used to measure them. Red light has a wavelength of about points. Seven microns and a vial of light a wavelength of about point of four microns. They're very energetic ultraviolet photons have much shorter wavelengths than the last energetic and for red photons. Today we can repeat Hershel's experiment and measure the amount of solar radiation at each wing feeling this curve measured at the bottom of the atmosphere extends into both the are provided and the Emperor read might it be possible that in space the spectrum would extend even further. Today we can measure solar radiation far above the ground with instruments carried by by loans rockets and satellites. The measurements of shown that the solar spectrum outside the atmosphere doesn't extend to much shorter and longer wavelengths. However ninety nine percent of the energy lies between fifteen hundred and three and a half microns. About fifteen percent. Isn't the ultraviolet thirty five percent is I'm a visible and forty nine percent isn't the Emperor read. Part of the ultraviolet and in Parade radiation from the sun is selectively absorbed as it passes through certain regions of the atmosphere what causes this absorption. Why does it occur in certain levels in the regions. To understand the nature of this. Absorption we must first understand the composition of our atmosphere. Almost four fifths of our atmosphere is nitrogen one fifth is oxygen in addition there are small amounts of water vapor and other gases some of great importance but use ozone and carbon dioxide. If we could look closely we would see the error of my. Like you're traveling quickly in all directions and getting fewer as we go higher in the atmosphere. When energy is added the average speed of the molecules increases and the temperature of the air rises. One way of adding energy is by the absorption of photons. Even if only one of the gases in the atmosphere absorbs photons the energy added will be shared with the other gases because of the collisions which are continually occurring and does raises the temperature of the entire region. Oxygen in the high atmosphere absorbs many of the and coming older Violet photons from the sun in fact radiation of wave lengths shorter than point one five microns does not penetrate below about eighty kilometers. When these four times are absorbed they not only make the molecules move more quickly but some have sufficient energy to separate dissociate oxygen molecules into two oxygen atoms. Other ultra violet photons can detach and electronic from the oxygen molecule and leave it. Ionized. That's the nature of the high atmosphere through which Earth orbiting satellites travel is very different from lap near the surface. Because there are free electrons and ions present this region can readily conduct electricity and there are so few atoms and molecules that are behaves as if it were a very good vacuum of the Adams and molecules present travels so quickly that the temperature is high. Lower down near a fifty kilometers the atmosphere is heated by ultraviolet photons of longer wavelengths. These last energetic ultraviolet photons are absorbed by own zone owns on his forearm and bought a combination of oxygen molecules and free oxygen atoms. To discover what determines the temperature of the lower atmosphere where airplanes travel and where temperatures are often measured by a balloon borne radio silence we must find out what happens to the rest of the solar radiation. On a clear day eighty percent of the incident solar radiation reaches the earth surface primarily in the form of visible and improve red radiation even on a cloudy day fifty percent can reach the surface after being scattered by clouds. A small part of the radiation is used by plans but most of it is going to voted to heat energy some of those heat energy evaporates water and melt snow the larger portion However eats the surface. The air molecules collide with the service and are heated the air becomes more brilliant and it is pushed up by cooler less buoyant air which in turn is heated. In this manner. Heat energy is added to the lower atmosphere and convection currents are formed. The one I'm writing error Kerry's molecules of water vapor as it rises the air expands and cools eventually the rotter vapor condenses to form clouds the clouds there all day arises until it cools to the same temperature as the air around it. Bus service heating by solar radiation causes rising air over Rome services and descending air over cool services. The resulting weapons carry energy from the lamb or to the cooler parts of the world and from the surface to as high as twelve kilometers this part of the atmosphere is called the troposphere. So far we have seen how the atmosphere gains energy. There must be some way for the earth atmosphere system to lose energy. Otherwise it would continue to become hotter and hotter this Istomin loses energy by itself radiating to space. All bodies radiate the amount and nature of the method radiation depends on both their temperature and their composition. The hot Sun emits a large amounts of ultraviolet visible and Emperor red radiation per unit area. Objects near room temperature events much less radiation per unit area and those are lies in the infrared. Most of the solar radiation lies near the visible part of the spectrum. But that arrest real radiation rise of much longer wavelengths. If we consider the total amount of solar radiation which falls upon the earth and the total amount of terrestrial radiation emitted in all directions out to space we know that on the average these must be the same than the earth's temperature does not change from year to year. Thus the two curves are drawn the same size. Part of the solar energy absorbed by the sunlit surface of the earth is lost by infrared radiation this is an addition to that last by convection. At night the earth's surface continues to radiate since no solar radiation is received the surface cools and convection is greatly reduced. Some of the Emperor red photons emitted by the earth servos pass directly into space. Others are selectively absorbed by the atmosphere. These photons are an additional source of the energy to the atmosphere. Our over the gas molecules which selectively absorb. Also all selectively emit and for red photons in this way the atmosphere loses energy. This exchange of energy between photons and molecules is complex but since it influences the temperature of most of the lower atmosphere and also the earth's surface itself we must look in more detail at some of the processes which can occur. The important molecules which absorb improve red photons are water vapor owns on and carbon dioxide. And in parental taught me is absorbed by a carbon dioxide molecule and its energy is increased the energy and shared with the Emperor red in active molecules such as oxygen or nitrogen. Eventually another and bread. Active molecule gains energy which is lost as a photon is emitted. Algal many different types of interaction are occurring we nevertheless find that when infrared photons for all on an error Southall the rate of absorption is not very dependent on the air temperature. But the number of photons Emad and depends very strongly on the air temperature and decreases very rapidly as the air cools. Ross epicenter of air is receiving energy only from incoming photons it will absorb them at a constant rate causing a steady increase in temperature. The number of photons emitted will depend on the temperature of the air sample. And equilibrium temperature is reached when the rate of the mission of energy is equal to the rate of absorption. In this condition the errors in radiative equilibrium. Now we can describe the temperature structure of the atmosphere in the troposphere. The transfer of heat from the surface by convection is much more rapid than the transfer of heat by radiation the average temperature decreases with height up to about twelve kilometers. Above the troposphere temperatures are primarily determined by radiative processes from twelve to eighty to one meters. Infrared photons from the earth than lower atmosphere are absorbed and the entire region loses heat by radiating. The absorption of solar ultraviolet radiation by owns all and near fifty kilometers adds additional energy. The air temperature rises so that this energy can be removed by him parade radiation. Above eighty kilometers the atmosphere is also heated by the absorption of solar ultraviolet radiation. Since there are no molecules to email him for red photons the temperature is high over one thousand degrees Kelvin I brought one hundred fifty kilometers. Returning from behind them hot happiness fair to the surface we find that the temperatures there are determined not only by the amounts of radiation being received any method but also by the composition and density of the apples fair which is present after dawn the surface is heated by the sun but the temperature increases often moderated by convection currents which carry large amounts of energy from the surface. On the moon there is no atmosphere and there are no convection currents to carry energy from the surface. Bus daytime temperatures are very high. At night. The lunar surface radiates in cooled rapidly to very low temperatures. The earth's surface also cools at night. However the atmosphere returned some of the energy it received during the daytime. The surface cooling does not progress as rapidly as on the moon. Nighttime temperatures are much lower when the air is Carmine dry and there are no clouds. The atmosphere returns most energy to the service when it was cloudy and Wendy. Because of the presence of the atmosphere and because much of the earth is covered by clouds. It is estimated that the average surface temperature is thirty degrees Kelvin warmer than the average lunar surface. Besides moderating the temperature extremes we would otherwise experience at the service the atmosphere also protects living things from harmful short wave length radiation from the sun. Looking down on the Earth we see by its appearance were clouds and oceans occur. Similarly by observing the outgoing radiation from the earth in the ultraviolet and infrared it is possible to estimate the temperature of the app and spear the heights of cloud and the amounts of temporary active gases present. Today. Satellites circle the earth carry an instrument for making these measures which well ventilated doubles better weather forecasts and perhaps show us how to harness the weather. Amanda.
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