Transcript Fig. 18-CO, p.428

Chapter 18: Energy Balance in the
Atmosphere
Fig. 18-CO, p.428
Incoming Solar Radiation
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Almost all surface events are driven by solar energy.
Weather: state of the atmosphere at a given place and
time
Climate: characteristic weather of a region
(particularly temp and precipitation) averaged over
several decades.
Earth receives one two-billionth of the total solar
output! Light behaves as a particle (Newton) and
wave (Hooke and Huygens) at the same time.
Photons travel at the speed of light (through the
vacuum of space at 300,000 km/sec) from Sun to
Earth (150 million km) in how many minutes?
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Visible light is a tiny portion of the electromagnetic
spectrum. The terms used to describe a light wave
are identical to those used for water, sound and other
types of waves.
Fig. 18-1, p.429
Fig. 18-2, p.430
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Absorption and Emission:
Absorption of a photon causes
suntan or sunburn (for example).
Emission occurs when the photon
hooks up with an electron and
falls to a lower energy state. An
iron bar (at room temp) emits
infrared radiation. If heated it
emits red progressing to white:
temp of source determines
wavelength and color emitted.
The Sun (very hot) emits highenergy (low wavelength)
radiation…rocks and soil re-emit
it as low-energy (invisible)
infrared radiation.
Fig. 18-3, p.431
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Albedo: the
proportional
reflectance of
a surface.
The albedo
of common
Earth
surfaces vary
greatly.
What would
happen to
the surface
of our planet
if glaciers
and cloud
cover grew?
Fig. 18-4, p.431
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Scattering: inversely proportional to the wavelength of light. Short
wavelength (blue light) scatters more than long wavelength (red light). So,
sky is blue…Sun is yellow because this is color of white light with most of
the blue light removed…what color would the Sun be if viewed above our
atmosphere?
Fig. 18-5, p.432
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The Radiation Balance: one-half of the incoming solar radiation
reaches the Earth’s surface. The atmosphere scatters, reflects
and absorbs the other half. All of the radiation absorbed by the
Earth’s surface is re-radiated as long-wavelength heat radiation.
Fig. 18-6, p.432
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Greenhouse Effect: 1.
rocks, soil and water
absorb short-wavelength
solar radiation and
become warmer. 2. the
Earth re-radiates the
energy as longwavelength infrared heat
rays. 3. molecules in the
atmosphere absorb some
of the heat, and the
atmosphere becomes
warmer. What are the
main greenhouse gases?
Fig. 18-7, p.433
Energy Storage and Transfer: the
driving mechanisms for weather and
climate
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Heat and Temperature: temperature is
proportional to the avg. speed of atoms
or molecules in a sample (cup of boiling
water and bathtub full of ice
water)…heat is total energy in a sample
(many more molecules, so total heat
energy is greater).
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Heat transport by conduction and convection (and
advection).
Fig. 18-8, p.434
Fig. 18-8a, p.434
Fig. 18-8b, p.434
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Changes of State: at Earth’s surface, water commonly exists in
all three states (ice, liquid and water vapor)…Latent heat
(stored heat) is the energy released or absorbed when a
substance changes from one state to another.
Fig. 18-9, p.435
Heat Storage
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Place a pan of water and a rock outside on a hot
summer day, which becomes hotter and why?
Specific Heat: amount of energy needed to raise
the temperature of 1 gram of material by 1
degree C. Water has very high specific
heat…what are the implications?
Why are coastal areas are cooler in the summer
and warmer in the winter than continental
interiors.
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Temperature changes with
latitude and season: Before
seasons, do you understand
Latitude and Longitude
(see Focus On, page 459)
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How to locate a place on
Earth.
*Earth has natural points of
reference (the North and
South geographic poles lie
on Earth’s spin axis).
*Lines of Latitude form
imaginary horizontal rings
around the spin axis.
Equator at 0 degrees
latitude. What about North
and South Poles?
*Lines of Longitude also in
degrees, beginning at
Greenwich, England
(arbitrarily chosen, 0
degrees longitude).
p.436
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If light shines directly overhead, the radiation is
concentrated on a small area. However, if the light
shines at an angle, or if the surface is tilted, the
radiant energy is dispersed over a larger area. How
does this apply to the Equator and Polar regions of the
Earth?
Fig. 18-10, p.437
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Where does
the most
intense solar
radiation strike
Earth?
Equator
receives the
most concentrated solar
radiation
Temps cooler
toward poles
Fig. 18-11, p.437
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Weather changes with the seasons because the Earth’s axis is tilted relative
to the plane of its orbit around the Sun. The Northern Hemisphere receives
more direct sunlight during summer, but less during winter. Tilt is 23.5
degrees; tropic of Cancer (23.5 degrees north latitude); tropic of Capricorn
(23.5 degrees south latitude).
Fig. 18-12, p.438
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Canadian
Arctic,
midnight
during
July…location
is 70 degrees
north latitude
(Beaufort
Sea).
Fig. 18-13, p.438
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During equinoxes (equal nights) all areas on the Earth
receive about 12 hours of daylight and darkness. Poles not
tilted toward or away from the Sun.
In fact, all areas of the Earth receive the same total number
of hours of sunlight every year, so why is there such a
variation in climates?
Table 18-1, p.439
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Temperature
changes with
geography. Lines
of avg.
temperature
(isotherms) show
global
temperature
distributions in
January and July.
Changes with
altitude.
Fig. 18-14, p.440
Fig. 18-14a, p.440
Fig. 18-14b, p.440
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Ocean Effects: continental St. Louis (red line) is colder
in the winter and warmer in the summer than coastal
San Francisco.
Fig. 18-15, p.441
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Paris is warmed by the Gulf Stream and the North Atlantic Drift.
St. John’s is alternately warmed by the Gulf Stream and cooled
by the Labrador Current. This cooling effect depresses the
temperature of St. John’s year round.
Fig. 18-16, p.441
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Wind Direction: during the summer, temperatures in
Vladivostok and Portland are nearly the same. In the winter,
cold Arctic winds cool Vladivostok to temps much lower than
Fig. 18-17, p.442
Portland.
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Cloud cover and Albedo. Clouds cool the Earth’s
surface during the day, but warm is during the night.
Fig. 18-18, p.443
p.444