solar energy to earth and the seasons finish numerical modeling electromagnetic spectrum radiation...
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Solar Energy to Earth and the Seasons
Finish Numerical Modeling
Electromagnetic Spectrum
Radiation Laws
Greenhouse Effect
Seasonality
Solar Elevation at Noon
For Wednesday: Read Ch. 4 (pp. 101-116)
2015 Peru Summer Study Abroad: Andean Societies and Environments
July 6 to July 26, 2015GHY 1011: Global Climate Change (4 hrs)
GHY 3140: Andean Mountain Geography (3 hrs) This 20-day intensive program introduces students to Andean Mountain 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.
Numerical Weather Prediction
We will keep a close eye on the numerical forecast models, including the Global Forecast System (GFS) model run by the National Centers for Environmental Prediction (NCEP):• http://mag.ncep.noaa.gov/• Specifically, we will look at the 850 mb temperature
(equivalent to ~4750 ft asl or the top of Rich Mountain), mean sea level pressure, and quantitative precipitation forecast (850temp_mslp_precip).
© AMS 4
Modeling Earth’s Climate System
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
© AMS 6
Modeling Earth’s Climate System
Long-Term Climate Forecasting• Global Climate Model (GCM): simulates Earth’s climate
system Numerical models Boundary conditions can be changed to determine how
Earth adjusts to new conditions
The relationship between the wavelength, , and frequency, , of electromagnetic radiation is based on the following formula, where c is the speed of light:
The relationship between the wavelength, , and frequency, , of electromagnetic radiation is based on the following formula, where c is the speed of light:
Wave Model of Electromagnetic EnergyWave Model of Electromagnetic Energy
vc
Note that frequency, (nu), is inversely proportional to wavelength, (lambda).The longer the wavelength, the lower the frequency, and vice-versa.
Note that frequency, (nu), is inversely proportional to wavelength, (lambda).The longer the wavelength, the lower the frequency, and vice-versa.
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 law and 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.
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 law and 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.
Stefan Boltzmann LawStefan Boltzmann Law
4TM
Wien’s Displacement LawWien’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:
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:
T
kmax
K
Kmm
6000
2898483.0
Solar vs. Terrestrial RadiationSolar 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)
© AMS 15
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
© AMS 16
Outgoing Infrared Radiation
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
© AMS 17
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%)
© AMS 18
Outgoing Infrared Radiation
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
© AMS 19
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
SeasonalityTwo important seasonal changes
Sun’s altitude – angle above horizon or Solar Elevation at Noon (SEN)
Day length
Reasons for Seasons Revolution
Earth revolves around the Sun
Voyage takes one year
Earth’s speed is 107,280 kmph (66,660 mph)
RotationEarth rotates on its axis once every 24 hours
Rotational velocity at equator is 1674 kmph (1041 mph)
Annual March of the SeasonsWinter solstice – December 21 or 22
Subsolar point Tropic of Capricorn
Spring equinox – March 20 or 21Subsolar point Equator
Summer solstice – June 20 or 21Subsolar point Tropic of Cancer
Fall equinox – September 22 or 23Subsolar point Equator
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˚
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