Transcript Terrestrial Radiation

Planetary Energy Budget
Current News and Weather
Finish Chapter 2
Electromagnetic Spectrum
Insolation (Short-Wave Energy)
Terrestrial Radiation (Long-Wave Energy)
Greenhouse Effect
For Next Class: Read Ch. 3 (pp. 80-100)
International Cooperation in
Understanding Earth’s Climate System
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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
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Modeling Earth’s Climate System
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Model: an approximate representation or simulation
of a real system, incorporating only the essential
features of a system while omitting details
considered non-essential or non-predictable
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Modeling Earth’s Climate System
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Numerical Model: consists of many mathematical
equations that simulate the processes under study
• Numerical weather and climate forecasting done at
National Centers for Environmental Prediction (NCEP)
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Modeling Earth’s Climate System
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Modeling Earth’s Climate System
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Short-Term Climate Forecasting
• NCEP’s Climate Prediction Center
• 30-day (monthly), 90-day (seasonal), and multi-seasonal
climate outlooks prepared
• Outlooks issued two weeks to 12.5 months in advance for
the coterminous U.S., Hawaii, and other Pacific islands
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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 EarthAtmosphere 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
Sun’s 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 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
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˚
Group Exercise
What is the Greenhouse Effect and why is it
important?
What are the dominant greenhouse gases?
Terrestrial Radiation
 Greenhouse
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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
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Similarity in radiational properties between
atmospheric gases and the glass or plastic
glazing of a greenhouse is the origin of the
term greenhouse effect
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Terrestrial Radiation
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Greenhouse Effect
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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
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Terrestrial Radiation
 Greenhouse
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Gases
Water Vapor is the principal greenhouse gas
• Clear-sky contribution of 60%
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Other contributing gases:
• carbon dioxide (26%)
• ozone (8%)
• methane plus nitrous oxide (6%)
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Terrestrial Radiation

Greenhouse Gases
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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
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Terrestrial Radiation
 Greenhouse
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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
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Clouds affect climate in two ways:
• Warm Earth’s surface by absorbing and emitting IR
• Cool Earth’s surface by reflecting solar radiation
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Questions?
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Take out a sheet of paper and write down any
questions about the material we covered in lecture
today.