ATS 351, Spring 2010
Lab #2
Energy & Radiation – 60 points
Please show your work for calculations
Question #1: Energy (11 points)
Heat is a measure of the transfer of energy from a body with a higher temperature to a
body with a lower temperature. There are three types of heat transfer:
1. Conduction
2. Convection
3. Radiation
The formation of a thunderstorm on a hot, sunny summer day is a great way to illustrate
the transfer of heat by all three mechanisms:
1. First, electromagnetic waves from the sun travel through the atmosphere and heat
the soil and vegetation molecules at the surface of the earth.
2. The excited molecules at the surface then transfer their energy to adjacent air
molecules in the atmosphere, thus heating the lower atmosphere.
3. Since warm air is LESS dense than cold air, the warm air parcel at the surface will
rise to replace colder air aloft.
A.(3 pts) On the diagram below, please fill in the blanks with Conduction, Convection, or
Radiation, corresponding to the descriptions of how heat is transferred at points 1, 2 & 3.
B. (4 pts) Warm air rises because it is less dense than cold air. As this warm air rises, the
water vapor it contains condenses, forming liquid cloud droplets and eventually rain.
Warm air that rises establishes updrafts, which sustain thunderstorms. Recalling your
knowledge of latent heat from the lab presentation, why does the air within the storm
cloud remain warm, sustaining updrafts?
C. (4 pts.) Often, if a storm cloud begins to rain, the storm will die. Again, recalling your
knowledge of latent heat, explain why the evaporation of rain below the cloud would
suppress the storm? (Hint: What drives updrafts that sustain thunderstorms?)
Question #2: Blackbody Temperature (10 points)
All things emit radiation. As the temperature of an object increases, more total radiation
is emitted each second. The Stefan-Boltzmann Law expresses this mathematically:
E = σ · T4
…where σ = 5.67x10-8 Watts/(m2K4), E = Maximum rate of radiation emitted by
each square meter of surface area, and T is the object’s ‘blackbody’ temperature
in degrees Kelvin.
If some imaginary planet were to emit 500 Watts/ m2 of radiant energy, what would its
blackbody temperature be?
Question #3: Electromagnetic Spectrum (14 points)
Pictured below is the electromagnetic spectrum.
The electromagnetic spectrum characterizes radiation by wavelength. As the wavelength
of light decreases, the energy carried per wave increases.
The sun radiates light in the shortwave (SW) part of the spectrum, at wavelengths
between 0.4 and 0.7 μm, while the earth radiates light in the longwave (LW), between 5
and 25 μm.
A.
(3 pts.) Recalling that 1 micron (μm) = 1.0 * 10-6 meters (m), and using both
of the above diagrams, what type (i.e. visible, infrared, ultraviolet, microwave)
of shortwave radiation does the sun emit?
B.
(3 pts.) What type of longwave radiation does the earth emit?
C.
(3 pts.) Does radiation emitted from the sun or the earth carry more energy per
wave? Why?
D.
(5 pts.) Wien’s Law relates the peak wavelength of emitted light of an object
to that object’s temperature:
λmax = 2897 / T
…where the numerator has units of μm · K and T is in degrees Kelvin.
Using your answer from Question 1, what would you expect the peak wavelength of
light (in microns) of radiation emitted by this imaginary planet to be?
Question #4: Short Answers (15 points)
Using the information provided in our first lecture and in Appendix B in the book, look at
the surface plot image below and state what conditions (temp, dewpoint, wind, pressure,
weather) are indicated at stations marked CAO, ALS and COS.
Question #5: Surface Analysis (10 points)
Draw temperature contours (isotherms) on the surface analysis maps with the specified
contour interval.
Wyoming (in class – no points): every 5C
Nebraska (for homework – 10 points): every 2C