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Warm Up 3/6/09
More solar energy reaches the equatorial regions than
the polar regions because the equatorial regions
a. are covered by a greater area of land.
b. have more vegetation to absorb sunlight.
c. receive sun rays closest to vertical.
d. have days with more hours of sunlight.
2) Most important weather phenomena occur in the ____.
a. stratosphere
c. mesosphere
b. thermosphere
d. troposphere
3) The form of oxygen that combines three oxygen atoms
into each molecule is called ____.
a. ozone
c. thermopause
b. argon
d. chlorofluorocarbon
Answers: 1) c. 2) d. 3) a.
1)
Heating the Atmosphere
Chapter 17, Section 2
Energy Transfer as Heat
Heat – the energy transferred from one
object to another because of a difference
in their temperatures
 Temperature – measure of the kinetic
energy (energy of motion) of the
individual atoms or molecules in a
substance
 Three mechanisms of energy transfer as
heat are conduction, convection, and
radiation
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Heat Transfer
Conduction
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Conduction – the transfer of heat through
matter by molecular activity
The energy of molecules is transferred by
collisions from one molecule to another
Heat flows from the higher temperature matter
to the lower temperature matter
Different materials conduct heat better than
others
Metals are good conductors, while air is a poor
conductor of heat
Conduction is only important between Earth’s
surface and the air directly in contact with the
surface
Conduction
Convection
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Much of the heat transfer that occurs in the
atmosphere is carried on by convection
Convection – the transfer of heat by mass
movement or circulation within a substance
Convection takes place in fluids, like the ocean
and air, where the atoms and molecules are free
to move about
Convection also takes place in solids, such as
Earth’s mantle, which behave as fluids over long
periods of time
Most of the heat acquired by radiation and
conduction in the lowest layer of the atmosphere
is transferred by convective flow
Convection
Concept Check
What is convection?
 Convection is the transfer of heat by mass
movement or circulation within a
substance.
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Electromagnetic Waves
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The sun is the ultimate source of energy that
creates our weather
All radiation from the sun (electromagnetic waves),
whether X-rays, radio waves, or heat waves, travel
through the vacuum of space at 300,000 km/s
(only slightly slower through our atmosphere)
Electromagnetic waves move outward from their
source and come in a variety of sizes
The most important difference between types is
their wavelength (Radio waves have the longest,
and Gamma waves have the shortest)
Visible light is a small part of this electromagnetic
spectrum (each color corresponds to a specific
wavelength of visible light), the combination of
which is white light
Electromagnetic Spectrum
Concept Check
Which electromagnetic wave has the
longest wavelength?
 Radio Waves
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Radiation
Radiation – the transfer of energy (heat)
through space by electromagnetic waves
 Unlike conduction and convection, radiant
energy can travel through the vacuum of space
The four laws governing radiation
1. All objects, at any temperature, emit radiant
energy
2. Hotter objects radiate more total energy per
unit area than colder objects do
3. The hottest radiating bodies produce the
shortest wavelengths of maximum radiation
4. Objects that are good absorbers of radiation
are good emitters as well
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Three Mechanisms of Heat Transfer
What Happens to Solar Radiation?
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When radiation strikes an object, there
usually are three different results
Some energy is absorbed by the object
Substances such as water and air are
transparent to certain wavelengths of
radiation
Some radiation may bounce off the
object without being absorbed or
transmitted
Reflection and Scattering
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Reflection – occurs when light bounces off an
object
The reflected radiation has the same intensity as
the incident (coming in) radiation
Scattering – produces a larger number of
weaker rays that travel in different directions
About 30 % of solar energy is reflected back
into space, this energy is lost and doesn’t go
into heating the atmosphere
Small particles in the atmosphere also help
scatter solar radiation
About half of the solar radiation that is absorbed
at Earth’s surface arrives as scattered light
Reflection and Scattering
Concept Check
How much solar energy is reflected back
to space?
 30%
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Absorption
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About 50 % of the solar energy that strikes the top of
the atmosphere reaches Earth’s surface and is
absorbed, then is redirected skyward
Earth’s surface is continually supplied with heat from
the atmosphere as well as from the sun
Greenhouse Effect – the heating of Earth’s surface
and atmosphere from solar radiation being absorbed
and emitted by the atmosphere, mainly by water
vapor and carbon dioxide
Some incoming solar radiation is not absorbed and
reradiated, but instead is used by plants for
photosynthesis
Solar energy is the main energy source for virtually all
life on Earth
Heating of the Atmosphere
Distribution of Incoming Solar
Radiation
Assignment
Read Chapter 17, Section 2 (pg. 483-487)
 Do Chapter 17 Assessment #1-30 (pg. 499500)
 For Section 2: #’s 5, 6, 13, 16, 20, 30
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