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Solar Energy to Earth and the Seasons

Solar Energy to Earth and the Seasons. Monitoring the Climate System Electromagnetic Spectrum   Radiation Laws Greenhouse Effect Seasonality Solar Elevation at Noon For Wednesday: Read Christopherson Ch. 3 available on AsUlearn.

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Solar Energy to Earth and the Seasons

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  1. Solar Energy to Earth and the Seasons • Monitoring the Climate System • Electromagnetic Spectrum   • Radiation Laws • Greenhouse Effect • Seasonality • Solar Elevation at Noon • For Wednesday: Read Christopherson Ch. 3 available on AsUlearn

  2. 2014 Peru Summer Study Abroad: Andean Societies and Environments July 15 to July 31, 2014 GHY 4530/5530: Andean Mountain Geography (3 hrs) GHY 4531/5531: Climate and Tropical Glaciers (3 hrs) This 17-day intensive program introduces students to AndeanMountain Geography and Climate and Tropical Glaciers through direct field experience and research activities, readings, discussions, and meetings with guest speakers. Field excursions to Machu Picchu and other locations in the Sacred Valley and an 8-day trek in the Cordillera Vilcanota (with strenuous ascents to over 17,000 ft) will provide an outstanding setting for the study of Andean human-environment interactions and the impacts of climate variability and change on tropical glaciers, ecosystems, and human populations. Program Leaders: Dr. Baker Perry, Mrs. Patience Perry, and Dr. Anton Seimon Interested? Contact Dr. Perry (perrylb@appstate.edu) to apply or for more information.

  3. Observing the Climate System • Remote Sensing by Satellite • Sensors observing Earth from orbiting spacecraft measure selected wavelengths of the electromagnetic radiation reflected or emitted by the Earth’s climate system

  4. Observing the Climate System • Remote Sensing by Satellite • Satellites fly in either geostationary or polar orbits Geostationary orbit Polar orbit

  5. Observing the Climate System Visible Satellite Image

  6. Observing the Climate System Infrared Satellite Image

  7. Observing the Climate System Water Vapor Satellite Image

  8. International Cooperation inUnderstanding Earth’s Climate System • Intergovernmental Panel on Climate Change (IPCC) • Formed in 1988 by the World Meteorological Organization (WMO) and the United Nations Environmental Programme (UNEP) • Evaluates the state of climate science • Composed of three working groups and a task force

  9. The Electromagnetic Spectrum Figure 2.6

  10. Wavelength and Frequency Figure 2.5

  11. Wave Model of Electromagnetic Energy The relationship between the wavelength, , and frequency, , of electromagnetic radiation is based on the following formula, where c is the speed of light: Note that frequency,  (nu), is inversely proportional to wavelength,  (lambda). The longer the wavelength, the lower the frequency, and vice-versa.

  12. Stefan Boltzmann Law The total emitted radiation (Ml) from a blackbody is proportional to the fourth power of its absolute temperature. This is known as the Stefan-Boltzmann lawand is expressed as: where s is the Stefan-Boltzmann constant, 5.6697 x 10 -8 W m-2 K -4. Thus, the amount of energy emitted by an object such as the Sun or the Earth is a function of its temperature.

  13. Wien’s Displacement Law • In addition to computing the total amount of energy exiting a theoretical blackbody such as the Sun, we can determine its dominant wavelength (lmax) based on Wien's displacement law: • where k is a constant equaling 2898 mm K, and T is the absolute temperature in kelvin. Therefore, as the Sun approximates a 6000 K blackbody, its dominant wavelength (lmax) is 0.48 mm:

  14. Solar vs. Terrestrial Radiation • Solar Radiation (Insolation): Short-wave, high intensity, mostly in the visible portion of the EM spectrum. • Source is the Sun. • Terrestrial Radiation: Long-wave, lower intensity. • Source is the Earth and Atmosphere (or Earth-Atmosphere System)

  15. Solar and Terrestrial Energy Figure 2.7

  16. Group Exercise • What is the Greenhouse Effect and why is it important?

  17. Figure 2.9

  18. Outgoing Infrared Radiation • Greenhouse Effect • Heating of Earth’s surface and lower atmosphere caused by strong absorption and emission of infrared radiation (IR) by certain atmospheric gases • known as greenhouse gases • Similarity in radiational properties between atmospheric gases and the glass or plastic glazing of a greenhouse is the origin of the term greenhouse effect

  19. Greenhouse Effect Responsible for considerable warming of Earth’s surface and lower atmosphere Earth would be too cold without it to support most forms of plant and animal life Outgoing Infrared Radiation

  20. Outgoing Infrared Radiation • Greenhouse Gases • Water Vapor is the principal greenhouse gas • Clear-sky contribution of 60% • Other contributing gases: • carbon dioxide (26%) • ozone (8%) • methane plus nitrous oxide (6%)

  21. Greenhouse Gases Atmospheric window: range of wavelengths over which little or no radiation is absorbed Visible atmospheric window extends from about 0.3 to 0.7 micrometers Infrared atmospheric window from about 8 to 13 micrometers Outgoing Infrared Radiation

  22. Outgoing Infrared Radiation • Greenhouse Gases • Water vapor strongly absorbs outgoing IR and emits IR back towards Earth’s surface • Does not instigate warming or cooling trends in climate • Role in climate change is to amplify rather than to trigger temperature trends • Clouds affect climate in two ways: • Warm Earth’s surface by absorbing and emitting IR • Cool Earth’s surface by reflecting solar radiation

  23. Seasonality • Why is seasonality important?

  24. Seasonality • Two important seasonal changes • Sun’s altitude – angle above horizon or Solar Elevation at Noon (SEN) • Day length

  25. Reasons for Seasons  • Revolution • Earth revolves around the Sun • Voyage takes one year • Earth’s speed is 107,280 kmph (66,660 mph) • Rotation • Earth rotates on its axis once every 24 hours • Rotational velocity at equator is 1674 kmph (1041 mph)

  26. Revolution and Rotation Figure2.13

  27. Annual March of the Seasons • Winter solstice – December 21 or 22 • Subsolar point Tropic of Capricorn • Spring equinox – March 20 or 21 • Subsolar point Equator • Summer solstice – June 20 or 21 • Subsolar point Tropic of Cancer • Fall equinox – September 22 or 23 • Subsolar point Equator

  28. Annual March of the Seasons Figure 2.15

  29. 11:30 P.M. in the Antarctic Figure 2.16

  30. Midnight Sun Figure 2.17

  31. Insolation at Top of Atmosphere Figure 2.10

  32. Solar Elevation at Noon Figure 2.18

  33. Solar Elevation at Noon (SEN) • SEN is the angle of the noon sun above the horizon • SEN = 90˚ - ArcDistance • ArcDistance = number of degrees of latitude between location of interest and sun’s noontime vertical rays • If the latitude of location of interest and sun are in opposite hemispheres, add to get ArcDistance • If they are in the same hemisphere, subtract from the larger of the two values

  34. SEN Example • What is the SEN on June 21 for Boone (36 N) • SEN = 90 – ArcDistance • Where are the sun’s noontime vertical rays? • ArcDistance = 36 – 23.5 • ArcDistance = 12.5 • SEN = 90 – 12.5 • SEN = 77.5˚

  35. Analemma

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