(Issued Monday, Jan. 29 for classes starting Friday, Feb. 9 and for several more weeks thereafter)
Supplemental Reading (previously assigned)
- Basic background on electromagnetic radiation, provided as a handout
(from Danielson, Levin and Abrams, Meteorology, 1998, pp. 80-87).
A note on the questions ("Reading Questions") below: You should use these questions (1) to help guide you to the points
the text that we regard as the most important; and (2) to give you something
to look for as you read, thereby making your reading more active and directed.
We do not expect you to submit written answers to these questions, though either
recording your answers in writing or highlighting/annotating the portions
the text containing the answers should help you retain the information better.
At least two, and possibly three, pre-class quizzes based on these reading
questions will be posted on iLearn. Consult
the course schedule on the class
Web site for more information.
From The Earth System, 3rd Ed., Chapter 3:
"Global Energy Balance: The Greenhouse Effect" (pp. 36-48)
- Key Questions: #'s 1 and 2.
- Chapter Overview
- How is the Earth heated and how does it cool? [Note that the text is
only partly correct about what heats the Earth; the sun emits more than
just visible radiation (light), and the other wavelengths of radiation
that the sun emits also heat the Earth, though it is true that these other
wavelengths do little to heat the Earth's surface directly.]
- What determines the (global average) surface temperature of the Earth?
- How does the global average surface temperature of the Earth compare
to that of Mars and of Venus?
- What is the "Goldilocks Problem" of comparative
- Electromagnetic Radiation
- What proportion of the radiation emitted by the sun consists of visible
Properties of Electromagnetic Radiation
- What is electromagnetic radiation?
- What properties of electromagnetic characterize it? Are they independent of each other?
Photons and Photon Energy
The Electromagnetic Spectrum
- What is the electromagnetic spectrum?
- What distinguishes visible light, infrared (IR) radiation, and ultraviolet
(UV) radiation? What proportion of the energy emitted by the sun is IR
radiation? UV radiation?
- What types of radiation are the most important to climate?
- What type(s) of radiation does the Earth emit, mostly?
- How is a flux defined? In particular, how is radiative flux
defined? In the metric system, what are the units of radiative
- Why does the radiative flux, or intensity of radiation, that
strikes a piece of paper vary when the angle between the paper and the
radiation striking it varies?
The Inverse-Square Law
- How does the radiative flux, or radiative intensity,
vary with distance from a "point source" of radiation such
as a light bulb or the sun (or the Earth)?
- In the mathematical expression for the inverse-square law, what does
each symbol represent, and what are its units (in the metric system)?
- What is an "astronomical unit" (AU)? What
is the flux of solar radiation at a distance of 1 AU from the sun (in
- What is the authors' reason for asserting that the inverse-square law
is fundamentally important to the study of planetary climates?
- Temperature Scales
- What is temperature? What is heat energy (also
sometimes called "sensible heat" or "internal energy")?
- What physically significant events define the Fahrenheit temperature
scale? The Celsius scale? The Kelvin scale?
- How is a temperature in degrees Celsius converted to Kelvins (and vice-versa)?
How does this compare to converting a change in temperature
expressed in °C to the equivalent change in temperature expressed
- Blackbody Radiation
- What is a blackbody?
- What determines how the radiative energy emitted by
a blackbody is distributed over different wavelengths? What is a "blackbody radiation curve"?
- Blackbodies emit more radiative energy at one wavelength (the wavelength
of peak emission) than any other wavelength. How does the wavelength of
peak emission vary with absolute temperature? (That is, what is Wien's
- According to Wien's Law, what is the wavelength peak emission of the
sun? The Earth? Why can't we see the radiation emitted by the Earth?
The Stefan-Boltzmann Law
- The radiative energy emitted by a blackbody at different wavelengths
can be summed to give a total radiative emission intensity. How does the
total radiative emission intensity of a blackbody vary with absolute temperature?
(That is, what is the Stefan-Boltzmann Law?)
- Planetary Energy Balance
- In the context of a whole planet in space, what is meant by energy
balance? Is the Earth in energy balance? What happens to the average
planetary temperature when the planet achieves energy balance?
- What three factors determine the Earth's global average surface
- About what proportion of the solar energy arriving at the top of the
Earth's atmosphere is reflected back to space? What does most of the reflecting?
What is meant by a planet's albedo? How is it defined quantitatively?
- How is the effective radiating temperature of a planet defined?
Magnitude of the Greenhouse Effect
- How can we interpret the meaning of a planet's effective radiating temperature?
- What two factors determine a planet's effective radiating temperature?
Where does the factor of 4 come from in the expression for a planet's
effective radiating temperature?
- What is the effective radiating temperature of the Earth? What is the
magnitude of the greenhouse effect on the Earth?
- Atmospheric Composition and Structure
Chapter Summary: Item #1
Review Questions: #'s 3-8
Critical Thinking Problems: #'s 1-5
(Recommended unless explicitly assigned.)
- Of gases does air consist, mostly? Do these gases contribute to the greenhouse
- What proportion of the atmosphere does water vapor compose? Carbon dioxide?
- What are the two most important greenhouse gases? What are some other
important greenhouse gases, although they are merely trace gases in the
- What is atmospheric pressure? How does it vary with altitude
in the atmosphere? What is the Earth's average sea-level pressure (expressed
- How does atmospheric temperature vary with altitude (on the average)?
What atmospheric layers are defined, based on this behavior?
- In which atmospheric layer does most of what we regard as "weather" occur?
What is convection? How does it differ from conduction?
Which plays the more important role in heat transfer within the atmosphere
- Why is the lowest atmospheric layer (the troposphere) convective?
- What is latent heat?
- How does the stratosphere differ from the troposphere?
- Why is the atmosphere warmest near the Earth's surface? What accounts
for the increase in temperature with altitude in the stratosphere?
- Why isn't the stratosphere convective? Why are clouds almost nonexistent
in the stratosphere?
Assignments, Handouts, etc.