The document discusses key concepts about Earth's atmosphere including: 1. The atmosphere is composed primarily of nitrogen and oxygen gases. It also contains variable amounts of gases like carbon dioxide and ozone that influence climate. 2. Solar radiation is processed as it passes through the atmosphere, being scattered, absorbed, or transmitted. Particulates play an important role by reflecting or absorbing sunlight. 3. Temperature varies with altitude, decreasing in the troposphere due to conduction and the environmental lapse rate, and increasing in the stratosphere due to ozone absorption of UV light.

1. Physical Geography
Lecture 4.5
EARTH’S ATMOSPHERE

2. Ready for a quick review?
1.What’s the difference between shortwave
and longwave electromagnetic radiation?
Which of these does Earth predominantly
radiate?
2.What are the two important principles of
EMR emissions?
3.What is the solar constant? Why do we
care?
4.The amount of insolation received by an
area on Earth’s surface depends on what?

3. 5.How are the Tropics of Cancer and
Capricorn related to Earth’s axial tilt?
6.How are the Arctic and Antarctic Circles
related to Earth’s axial tilt?
7.What are aphelion and perihelion? On
about what date do they occur?
8.True or false? Earth’s axial tilt shifts over
time. By 2015, it will be 25°.
9.What causes Earth’s seasons?
10. What is the subsolar point? How is it
related to the solstices and equinoxes?

4. How is insolation “processed” by
Earth’s atmosphere?

5. First, we need to ask:
What is the make-up of Earth’s
atmosphere?

6. Air is...where?
 Air has weight, it has
mass
 Air is attracted by
Earth’s gravity

7. Composition of the Atmosphere
 The atmosphere is composed of two
types of gases:
1. Those which generally do not change their
concentrations from place to place
2. Those which do

9. Proportional Volume of Atmospheric Gases

10. Particulates in the Atmosphere

11. The Importance of Particulates
 Absorb and reflect sunlight
 This reduces the amount of sunlight that
reaches Earth’s surface
 Scatter sunlight
 Mostly in the blue range of the spectrum,
giving the sky its blue color
 At sunrise and sunset, most of the blue has
been scattered in the upper atmosphere,
leaving red and yellow

13. The Importance of Particulates
 They also act as condensation nuclei...

14. Condensation Nuclei
 Condensation nuclei are
necessary elements for the
formation of cloud droplets
 Without them, conditions may
be perfect for the formation of
clouds or fog, yet condensation
does not occur
 Excess condensation nucleii also
may cause condensation before
the saturation point has been
reached
 Some particles are
hygroscopic—they attract and
absorb water (salt)

15. Vertical Structure of the Atmosphere

16. Thermal Structure of the Atmosphere
 Troposphere
 Temp. decreases with
increasing altitude (surface
warmed by the sun is its heat
source)

17. Conduction
 Conduction is the
passing of heat from
molecule to molecule
by touch

18. Conduction
 Temperature is an expression
of molecular motion
 As one molecule bangs into
another, it makes the next one
vibrate, as well—thus passing
on its molecular motion and
increasing the temperature of
the molecule it just “sped up”
 Thus the heat passes up the
metal bar until it reaches the
hand holding it…

19. Conduction in the Troposphere
 The sun’s radiation is absorbed at Earth’s
surface and reradiated upward as heat
 But air is a poor conductor of heat (the
molecules are too far apart and move
around too much)
 So heat is not transferred upward very far
 This is why the Troposphere is warmest at
the surface and gets colder as you rise
upward

20. ELR
 The rate at which air temperature drops as
you rise through the Troposphere can be
roughly estimated:
 6.5ºC/1000 m or 3.5ºF/1000 ft
 This rate is called the Environmental
Temperature Lapse Rate, or ELR

21. Thermal Structure of the Atmosphere
 Troposphere
 Temp. decreases with
increasing altitude (surface
warmed by the sun is its heat
source)
 Stratosphere
 Temp. increases as ozone
absorbs UV light

22. A Little Bit About the
Importance of Ozone…

23. The Ozone Hole

24. Thermal Structure of the Atmosphere
 Troposphere
 Temp. decreases with
increasing altitude (surface
warmed by the sun is its heat
source)
 Stratosphere
 Temp. increases as ozone
absorbs UV light
 Mesosphere
 Temp. decreases (no heat
source)
 Thermosphere
 Temp. increases as stratified
layers of gases absorb high-
intensity ultraviolet radiation
and are split apart
 Exosphere
 Merging into space
 So few molecules of gas in this
layer that “temperature” really
doesn’t apply

25. Vertical Structure of the Atmosphere
 Ionosphere—begins in the
Mesosphere
 blocks extremely harmful short
wave radiation (UV-B and UV-C),
some cosmic rays, and high
energy particles from the sun
 reflects radio waves back to the
surface, aiding long-distance
communications
 source of the arorae (borealis
and australis), a.k.a. the
Northern and Southern Lights
 Homosphere
 Mixed gases in roughly equal
concentrations
 Heterosphere
 Gases so far from Earth’s
surface that the effect of gravity
is minimized—gases are
stratified (layered) by molecular
weight

26. A little more review:
1.Why are most of Earth’s atmospheric
gases found near the surface?
2.Name 3 important variable-amount gases
found in Earth’s atmosphere. Why is each
one important?
3.Why are atmospheric particulates
important?
4.What would happen if there were no
condensation nuclei in the atmosphere?
What happens when there is an abundance
of nuclei?

27. 5.What is ozone? In which thermal layer of the
atmosphere is it found? How does it affect
temperatures within that layer?
6.What generally happens to the surrounding air
temperature as you rise through the troposphere?
7.What happens in the -pauses?
8.What is conduction? Is air a good conductor of
heat?
9.What is the ELR? What is the rate of change of the
ELR? To which thermallayer of the atmosphere
does it apply?
10.What is the homosphere? What is the
heterosphere? What does the ionosphere do?

28. Practice drawing the vertical structure of the
atmosphere diagram in a notebook
Watch a Khan Academy video (see the post
on Oct. 5 for links, about mid-way down the
post)
Finish reading Chapter 3. Take notes.
Write questions in the margins.
Review the class slides
Study the chapter review questions
To Work On: