Planetary Energy Budget Current News and Weather Electromagnetic Spectrum Insolation (Short-Wave Energy) Terrestrial Radiation (Long-Wave Energy) Greenhouse Effect For Next Class: Read Ch. 4 (pp ) The Electromagnetic Spectrum Figure 2.6 Wavelength and Frequency Figure 2.5 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) Solar and Terrestrial Energy Figure 2.7 Figure 2.9 Insolation What factors influence the average values of insolation (incoming solar radiation)? Seasonality Two important seasonal changes Suns altitude angle above horizon or Solar Elevation at Noon (SEN) Day length 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 Annual March of the Seasons Figure 2.15 11:30 P.M. in the Antarctic Figure 2.16 Insolation at Top of Atmosphere Figure 2.10 Solar Elevation at Noon Figure 2.18 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 suns 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 SEN Example What is the SEN on June 21 for Boone (36 N) SEN = 90 ArcDistance Where are the suns noontime vertical rays? ArcDistance = 36 23.5 ArcDistance = 12.5 SEN = 90 12.5 SEN = 77.5 Group Exercise What is the Greenhouse Effect and why is it important? What are the dominant greenhouse gases? AMS21 Terrestrial Radiation Greenhouse Effect Heating of Earths surface and lower atmosphere caused by strong absorption and emission of infrared radiation (IR) by certain atmospheric gases Heating of Earths surface and lower atmosphere caused by strong absorption and emission of infrared radiation (IR) by certain atmospheric gases known as greenhouse gasesknown 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 Similarity in radiational properties between atmospheric gases and the glass or plastic glazing of a greenhouse is the origin of the term greenhouse effect AMS22 Terrestrial Radiation Greenhouse Effect Responsible for considerable warming of Earths surface and lower atmosphere Responsible for considerable warming of Earths surface and lower atmosphere Earth would be too cold without it to support most forms of plant and animal life Earth would be too cold without it to support most forms of plant and animal life AMS23 Terrestrial Radiation Greenhouse Gases Water Vapor is the principal greenhouse gas Water Vapor is the principal greenhouse gas Clear-sky contribution of 60%Clear-sky contribution of 60% Other contributing gases: Other contributing gases: carbon dioxide (26%)carbon dioxide (26%) ozone (8%)ozone (8%) methane plus nitrous oxide (6%)methane plus nitrous oxide (6%) AMS24 Terrestrial Radiation Greenhouse Gases Atmospheric window: range of wavelengths over which little or no radiation is absorbed Atmospheric window: range of wavelengths over which little or no radiation is absorbed Visible atmospheric window extendsVisible atmospheric window extends from about 0.3 to 0.7 micrometers from about 0.3 to 0.7 micrometers Infrared atmospheric window fromInfrared atmospheric window from about 8 to 13 micrometers about 8 to 13 micrometers AMS25 Terrestrial Radiation Greenhouse Gases Water vapor strongly absorbs outgoing IR and emits IR back towards Earths surface Water vapor strongly absorbs outgoing IR and emits IR back towards Earths surface Does not instigate warming or cooling trends in climateDoes not instigate warming or cooling trends in climate Role in climate change is to amplify rather than to trigger temperature trendsRole in climate change is to amplify rather than to trigger temperature trends Clouds affect climate in two ways: Clouds affect climate in two ways: Warm Earths surface by absorbing and emitting IRWarm Earths surface by absorbing and emitting IR Cool Earths surface by reflecting solar radiationCool Earths surface by reflecting solar radiation