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How Earth Works > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

The electromagnetic spectrum

A
  • the radiant energy produced by the sun that is measured in progressive wavelengths
  • the entire wavelength range of electromagnetic energy
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2
Q

Wavelength

A
  • the distance between adjacent wave crests or wave troughs
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3
Q

Wave amplitude

A
  • 1/2 the height between the wave crest and wave trough
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4
Q

Crests and troughs

A
  • crests, the top of the wave

- trough, the bottom of the wave

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5
Q

Shortwave radiation and Longwave radiation

A
  • shortwave radiation, the portion of the electromagnetic spectrum that includes gamma rays, x-rays, ultraviolet radiation, visible light, and near-infrared radiation
  • sun emits shortwave radiaition
  • longwave radiation, the portion of the electromagnetic spectrum that includes thermal infrared radiation
  • Earth emits longwave radiation
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6
Q

2 important principles of electromagnetic radiation

A
  1. an inverse relationship exists between the temperature of an object and the wavelength of the electromagnetic radiation it emits (hotter objects emit radiation with shorter wavelengths)
  2. a direct relationship exists between the absolute temperature of the object and the radiation it emits (hotter objects emit more radiation) - therefore earth emits less radiation than the sun
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7
Q

Radiation to and from Earth

A
  • earth receives shortwave radiation from the sun, some of this radiation reaches the surface of Earth where it is absorbed and then re-emitted as longwave energy
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8
Q

Solar energy and the solar constant

A
  • solar energy created in vast quantities by nuclear fusion within the sun, works its way to the surface and is emitted as electromagnetic radiation
  • then they rays travel at the speed of light through space toward Earth
  • rays become spread out/less concentrated, intensity is inversley proportional to the square of distance travelled (inverse square law- energy travelling twice the distance will have 1/4 the intensity)
  • output of solar radiation is nearly constant
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9
Q

Solar constant

A
  • the average amount of solar radiation (1,367W/m2) received at the top of the atmosphere
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10
Q

Composition of the atmosphere

A
  • supports life by providing oxygen & carbon dioxide
  • shields the planet from UV radiation from the sun, allowing mostly visible and infared wavelengths to reach Earth
  • fundmental components of the atmosphere:
    1. constant gases
    2. variable gases
    3. particulates
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11
Q

Constant gases

A
  • atmospheric gases such as nitrogen, oxygen and argon that remain relatively consistent levels in space/time
  • nitrogen (78%), derived from the decay/burning of organic material, volcanic eruptions, chemical breakdown of specific rocks, critical to plant life because it can be transformed/fixed into chemical compounds in the soil, maintains a constant proportion because it’s balanced by precipitation and various biological processes
  • oxygen (21%), by-product of photosynthesis, very active & can combine with other elements through the process of oxidation, essential to animal respiration bc it is required to convert food into energy, constant gas bc the amount produced by plants balances the amount absorbed by various organisms through respiration
  • argon (1%), chemically inactive, of little importance in natural processes
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12
Q

Variable gases

A
  • variable gases differ in their proportion of the atmosphere over time/space, depending on environmental conditions
  • important to life, but make up less than 1% of the atmosphere

Water Vapour

  • 3 states: liquid, solid, gas
  • amount in the atmosphere near Earth’s surface is about 2% but may range to less than 1% over deserts and 4% over tropical zones (depend on proximity to a large body of water or the air temperature)
  • direct relationship between the temp of air and the amount of water vapour it can hold (warmer holds more), which directly influences the process of precipitation
  • water vapour is vital bc it absorbs and stores heat energy from the sun
  • water vapour moderates temperature and transports energy around Earth by airflow

Carbon Dioxide

  • about 0.04 percent of the atmosphere
  • CO2 is critical for 2 reasons: (1) plants absorb CO2 and release oxygen as a byproduct, (2) atmospheric CO2 contributes significantly to the greenhouse effect

Ozone

  • a form of oxygen that has 3 oxygen atoms (O3)
  • atmospheric ozone forms when gaseous chemicals react in the upper atmosphere with light energy
  • in the formation process, O2 absorbs UV energy which causes the oxygen molecule to split into 2 oxygen atoms, one of which combines with O2 to form ozone
  • ozone naturally destroyed when it absorbs UV energy and splits from O3 to O2+O, but the single atom can then recombine with O2 to form ozone
  • O3 and O2 atoms are repeatedly formed, destroyed and reformed in the ozone layer in a way that absorbs UV radiation every time a transformation takes place
  • ozone in 2 layers of the atmosphere: (1) ground level, (2) the stratosphere
  • ground level ozone: form of pollution created when nitrogen and organic gases emitted by automobiles and industrial sources react
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13
Q

The formation of rainbows

A
  • water vapour is linked to the formation of rainbows
  • a rainbow develops when white light from the sun peeks through the clouds and strikes water droplets in the air from a rainstorm, water droplets bend the light rays, but by a different amount for each colour, resulting in white light spread out into a continuous spectrum of colours, reflected to earth at an avg. angle of 42 degrees
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14
Q

Greenhouse effect

A

-the process through which the lower part of the atmosphere is warmed because long-wave radiation from Earth is trapped by CO2 and other greenhouse gases

  1. Earth receives shortwave radiation from the sun
  2. Earth releases energy as longwave radiation
  3. Longwave radiation absorbed by greenhouse gases
  4. Longwave radiation absorbed by greenhouse gases escapes to scape
  5. Longwave radiation absorbed by greenhouse gases heats Earth’s surface (counter-radiation)
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15
Q

Counter radiation

A
  • longwave radiation that is emitted toward the Earth’s surface from the atmosphere
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16
Q

Formation of atmospheric ozone

A
  • O2 absorbs UV energy which causes the oxygen molecule to split into 2 oxygen atoms, one of which combines with O2 to form ozone
  • ozone naturally destroyed when it absorbs UV energy and splits from O3 to O2+O, but the single atom can then recombine with O2 to form ozone
  • O3 and O2 atoms are repeatedly formed, destroyed and reformed in the ozone layer in a way that absorbs UV radiation every time a transformation takes place
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17
Q

Ozone concentration in the atmosphere

A
  • one layer of ozone is at high altitudes and absorbs UV radiation from the sun
  • second concentration occurs in the lower part of the atmosphere and is associated with pollution, particularly chemical smog in cities
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18
Q

Ozone layer

A
  • the layer of the atmosphere that contains high concentrations of ozone, which protect the Earth from UV radiation
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19
Q

Ozone hole

A
  • the decrease in stratospheric ozone observed on a seasonal basis over Antarctica, and to a lesser extent over the Arctic
  • ozone hole caused by ozone layer being depleted: some occurs naturally by volcanic aerosols, but most of the reduction due to industrial CFC production
  • Antarctic ozone hole forms every spring in the Southern Hemisphere because a polar vortex develops during the previous winter, trapping the air within it
  • resulted in average amount of annual exposure to UV radiation at 55 degrees S increased about 10% per decade since late 1970s
  • similar but weaker hole exists in over the Arctic region in the Northern Hemisphere winter
  • resulted in average amount of annual exposure to UV radiation at 55 degrees N increased about 7% per decade since late 1970s
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20
Q

Destruction of the ozone layer

A
  1. CFC molecule absorbs Uv radiation and chlorine atom breaks away
  2. Chlorine atom reacts with ozone molecule
  3. Reaction products are chlorine oxide (ClO) and oxygen molecules
  4. Oxygen atom is pulled of ClO molecule by another oxygen atom, forming another oxygen molecule
  5. Molecule breaks up into oxygen molecule and chlorine atom, which is free to react again with another ozone molecule
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21
Q

Particulates

A
  • microscopic bodies carried in the air (both liquid and solid form)
  • less than 1% of atmosphere
  • liquid: clouds and rain, develop when water vapour changes its physical state due to temperature changes in the atmosphere
  • solid: snow, hail, pollutants, wind-blown soil, smoke from wildfires, volcanic ash, pollen grains, salt spray
  • particulates usually densest near place of origin
  • important role in weather & climate: precipitation occurs because dust particles provide a nucleus around which water condenses in the 1st step of cloud formation, smoke/volcanic ash absorb or reflect solar energy, combined processes influence local weather and regional climate by moderating temp of the atmosphere
  • also neg. consequences of particulates - toxic air pollutants
22
Q

The flow of solar radiation on Earth

A
  • when solar radiation reaches earth, it flows along several pathways within the atmosphere to the surface of earth
  • some radiation flows straight from Earth as insolation
  • but most radiation follows a very indirect path
23
Q

Insolation

A
  • amount of solar radiation, measured in watts per square metre (w/m2) that strikes a surface perpendicular to the sun’s incoming rays
24
Q

Heat transfer

A
  • first law of thermodynamics: energy cannot be created or destroyed, it can only change form
  • second law of thermodynamics: heat can spontaneously flow from a region of higher temperature to an area of colder temperature, but not the reverse
  • heat is transferred through radiation(1), a process that involves the creation of electromagnetic waves, either visible or invisible, this radiation exists in wave form, it carries energy and can move
  • radiation(1) is the process of electromagnetic energy being emitted from objects, the hotter the object the more intense the radiation and the shorter the wavelength, when this radiation reaches you, part of the energy of the wave is converted to heat
  • conduction(2) involves the diffusion of energy through molecules that are in contact with one another, the diffusion occurs because as temperature increases, they begin to vibrate more rapidly, causing collisions that produce similar motions in adjacent molecules
  • convection (3) involves the upward movement of heat, an important mechanism of heat transfer on Earth and is associated with atmospheric circulation and precipitation
25
Q

Radiation

A
  • energy that is transmitted in the form of rays or waves
26
Q

Conduction

A
  • the transfer of heat energy from one substance to another by direct physical contact
27
Q

Sensible heat

A
  • heat that can be felt and measured with a thermometer
28
Q

Convection

A

-a circular cell of moving matter that contains warm material moving up and cooler material moving down

29
Q

Mechanism of heat transfer

A

(a) conduction - transfer of heat by collision of atoms or molecules
(b) convection - transfer of heat by movement of fluids in semicircular pattern
(c) radiation - transfer of heat by electromagnetic radiation

30
Q

The flow of solar radiation in the atmosphere

A
  • of incoming radiation that reaches earth, 25% flows uninterrupted as direct radiation (varies depending on local geographical variables such as cloud cover, or density of atmospheric dust)
  • remaining 75% of incoming insolation is either absorbed or redirected in the atmosphere
  • absorption occurs when variable gases and particulates in the atmosphere interrupt the flow of solar radiation by absorbing specific wavelengths (almost all UV wavelengths are absorbed by oxygen and ozone)
  • approx 24% of incoming solar radiation is absorbed, 18% by atmospheric water vapour and dust, 3% by ozone, and 3% by clouds
  • absorption important because it helps to moderate the temperature in the atmosphere
  • some incoming solar radiation is redirected by reflection, the amount depending on the albedo (the amount of reflection it can cause) of the surface
  • approx 21% of radiation is reflected back to space in this manner, clouds being the most important reflector
  • some incoming radiation is redirected through scattering, the indirect effects of which can be seen in the sky (oxygen & nitrogen molecules cause solar radiation to bounce around in the air, the sky appears blue because the blue wavelength is more easily scattered)
  • non-selective scattering, when the atmosphere contains large particulates such as water droplets the wavelengths will be scattered evenly, responsible for white clouds and fog
  • some reflected/scattered radiation is redirected downward to the surface of Earth as indirect radiation, approx 20% of solar radiation that reaches earth is indirect
31
Q

Direct radiation

A
  • solar radiation that flows directly to the surface of Earth and is absorbed
32
Q

Absorption

A
  • the assimilation and conversion of solar radiation into another form of energy by a medium such as water vapour, in this process, the temperature of absorbing medium is raised
33
Q

Reflection

A
  • the process through which solar radiation “bounces off” an object
  • in terms of the energy balance, it refers to the solar radiation that is returned directly to space without being absorbed by Earth
34
Q

Albedo

A
  • the reflectivity of features on the Earth’s surface or in the atmosphere
35
Q

Scattering

A
  • the redirection and deflection of solar radiation by atmospheric gases or particulates
36
Q

Interaction of solar radiation with various components of the atmosphere

A
  • direct radiation reaching earth = 25%
  • indirect radiation reflected down to earth = 20%
  • absorbed directly by atmospheric water vapour & dust = 18%
  • absorbed by ozone = 3%
  • absorbed by clouds = 3%
  • scattered to space by dust = 7%
  • reflected to space by clouds = 21%
  • reflected to space by surface = 3%
37
Q

Variation of the receipt of solar radiation based on cloud cover

A

Cloudy sky:

  • reflection by clouds 30%-60%
  • absorption in the clouds 5-20%
  • reaches the ground 10-45%

Clear sky:

  • absorption by air & dust 16%
  • reflection from air and dust 4%
  • reaches ground 80%
38
Q

Interaction of solar radiation and the earth’s surface

A
  • approx 45% of all solar solar energy strikes earth directly or indirectly
  • this influences variables such as temperature, atmospheric circulation, density & type of vegetation in a region, soils, and where glaciers occur
  • either of 2 things happens when solar radiation strikes the ground 1. absorbed 2. reflected
39
Q

Absorbed radiation

A
  • 96% of solar energy that reaches the ground is absorbed, by land & water bodies, which heats earth
  • can be stored as sensible heat: heat that can be sensed by touching or feeling and measured by a thermometer
  • can be stored as latent heat, when water is transformed into water vapour within the atmosphere through evaporation, cannot be measured by thermometer
  • stored energy can be lost in several ways: sensible heat can be transferred from the surface if earth to the atmosphere through convection (warm air rises up and cool air replaces it), or heat can be removed through evaporation, the change of liquid water to water vapour by absorption of heat, or radiation can be re-radiated back into space as longwave radiation (escapes directly back into space or absorbed by atmospheric CO2 and water vapour, or backscattered by dust particles)
40
Q

Reflected radiation

A
  • energy that bounces off the earths surface
41
Q

Latent heat

A
  • heat stored in molecular bonds that cannot be measured
42
Q

Evaporation

A
  • the process by which atoms and molecules of liquid water gain sufficient energy to enter the gaseous phase
43
Q

Indirect radiation

A
  • radiation that reaches Earth after it has been scattered or reflected and does not supply heat
  • 3% of incoming radiation is reflected this way
  • amount of incoming radiation reflected is dependant on the albedo (dark objects absorb and increase in temperature, bright objects reflect and gain little heat)
  • amount of incoming radiation reflected is dependant also on the angle of incidence (high angle of sun interacts directly with earth and sun rays more intense, low angle of sun results in more radiation being reflected and radiation spread further, therefore less intense)
  • sun directly overhead: albedo value of 5% (almost all is absorbed)
  • sun near horizon: albedo value of 65%, radiation reflecting more readily (oceans at higher latitudes have higher albedos)
44
Q

Variation of surface albedo

A
  • snow 80-95%
  • forest 10-20%
  • grass 25-30%
  • blacktop highway 5-10%
  • crops, fields 10-25%
  • dark roof 10-15%
  • concrete, city streets 5-15%
  • dark roof, 10-15%
  • lakes, oceans 5-65% (depending on sun angle)
45
Q

The global radiation budget

A
  • the global radiation budget refers to the balance between incoming (shortwave) radiation and outgoing radiation, which is either re-radiated through reflecting & scattering, or released from earth in long-wave form
  • difference between incoming and outgoing radiation is the net radiation
  • for earth as a whole, the longterm radiation budget must be balanced, otherwise earth would become progressively hotter or cooler, the balance is achieved by incoming radiation flows matching the outgoing flows
  • 69% of solar radiation (shortwave) is absorbed by earth, by clouds, water, or the surface
  • direct radiation absorption 25%
  • indirect radiation absorption 20%
  • atmosphere absorption 18%
  • ozone absorption 3%
  • cloud absorption 3%
  • 31% remaining of solar radiation (shortwave) is reflected directly back into space due to albedo or scattering
  • cloud reflection 21%
  • surface reflection 3%
  • dust reflection 7%
  • for the global radiation budget to stay in balance, earth must emit all the absorbed energy back to space (in longwave form)
  • this release, plus the 31% of reflected shortwave radiation keeps the system balanced
  • Earth’s temperature is moderated because greenhouse gases such as CO2 and water vapour trap a small amount of longwave radiation
  • most of the longwave radiation is lost in different ways to balance the global radiation budget
  • longwave energy lost to space by direct radiation to the surface 45% (does not happen evenly across the earth, lower latitudes emit more energy than higher latitudes because low latitudes receive more shortwave radiation)
  • long wave energy lost directly by radiation 21%
  • emitted by ozone 3%
  • long-term energy budget balances on a global scale, however may vary over short term in different regions due to environmental factors, so certain locations have net surplus at one point of the year and net deficit at another
  • primary factors that influence net radiation around the globe:
    1. the sun’s angle of incidence (directly affects absorption and reflection)
    2. latitude (low latitudes have low sun angles & receive high amounts of radiation and have a net surplus, whereas high latitudes have a net deficit and receive less direct radiation)
    3. seasonality (seasonal effect is a result of the geometric relationship between the earth and sun, resulting in changes to the angle of incidence over the year, position of sun at solar noon migrates over the year bc of axial tilt and orbital position, causing the subsolar point to change position with respect to latitude, from 23.5N in June to 23.5S in Decemeber, this shift has a major influence on seasonal distribution of net radiation)
    4. length of day
  • secondary factors that influence net radiation around the globe:
    1. varying output of sun due to sun spots & solar flares
    2. elliptical nature of the earths orbit
    3. changes in thickness and properties of the atmosphere
    4. variability in length of day
  • ** focus on the 4 primary factors as they work in a holistic way
  • when the 4 variables are considered together (angle of incidence, latitude, seasonality, and length of day):
    • Equator (0): receives consistently high amounts of radiation all year, 2 peaks in daily insolation over the year as the sun is directly over the equator twice during the year (at each equinox), day length is always about 12 hours
    • 45N: moderate range of daily insolation, peak during summer months and lower values during winter
    • North Pole (90N): greatest annual range of daily insolation with distinct peak at the summer solstice and no radiation received in winter, receives more insolation around the summer solstice than the equator because latitudes above the arctic circle receive radiation for 24h as the sun doesn’t set
46
Q

Radiation budget

A
  • the overall balance between incoming and outgoing radiation on Earth
47
Q

Net radiation

A
  • the difference between incoming and outgoing flows of radiation
48
Q

Mean annual net radiation at the top of the atmosphere on Earth

A
  • low to middle latitudes have a net surplus of radiation, whereas high latitudes have a net deficit
  • due to the relationship between latitude and angle of incidence (low latitude areas experience a high angle of incidence and a net surplus of radiation)
49
Q

Net radiation and the transfer of heat energy on Earth

A
  • energy surplus at equatorial/tropical regions

- energy deficit at the poles

50
Q

Average seasonal changes in net radiation on Earth

A
  • in January, where the subsolar point is at the topic of capricorn (23.5N), the highest net radiation is in the southern hemisphere across the band of the south pacific and south atlantic oceans, this is the SH’s summer and the NH’s winter
  • in July, the subsolar point is now at the tropic of cancer and the NH is experiencing its summer
51
Q

Human Interactions: Solar Energy Production

A
  • office buildings and homes built with windows that face the sun when it is at a low angle of incidence during the winter months, allows the sun to shine directly into the building and enables heat to be trapped by the glass (passive solar heating)
  • further developing of active solar systems, ex. photovoltaic systems (solar cells) change sunlight directly into electricity
  • solar power plants contain a number of mirrors (heliostats) to indirectly produce electricity by redirecting sunlight into fluid that warms and produces steam, used to power generators, they are designed to follow the sun over the course of the day constantly collecting energy
  • pros of solar energy: clean, sustainable, doesn’t produce greenhouse gas emissions, doesn’t contribute to global warming, can produce electricity wherever the sun shines
  • cons of solar energy: current technology is inefficient in producing an adequate supply, the sun doesn’t shine everywhere on a constant basis (Great Lakes region of Canada is too cloudy, the best place in Canada for solar energy production is the prairies), supplementary supply when compared to energy produced by fossil fuels
52
Q

Solar energy potential in Canada

A
  • western BC and Northern Canada are poor places for solar energy production because of cloudy weather and low angles of insolation
  • prairie region has very high potential for producing solar energy because it is a sunny environment

How Earth Works (7 decks)

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