Chapter 11 from text.

1. Chapter 14 – The Atmosphere

2. Weather and Climate
• The average weather
conditions over the
year in a particular
location determine its
climate.
• “Climate is what you
expect, but weather
is what you get.”

3. The modern atmosphere
• Two most abundant gases: 78% N2 and 21% O2
– Neither of these gases influence weather phenomena
• Argon (< 1%) inert gas
• Water vapor (varies from 1 to 4%)
– Source of all clouds and precipitation
– Absorbs and releases latent heat during phase change
– Greenhouse gas (traps atmospheric heat)
• CO2 (.039% or 39 ppm) – Greenhouse gas
• Non-gaseous components: water droplets, dust,
pollen, soot and other particulates
– Act as condensation surfaces for water in atmosphere
– Block sunlight and act as a cooling agent.

4. Fig. 17.6, p.437

5. Solar radiation and the atmosphere
• Much of the highest
frequencies (x-rays,
gamma rays) are
absorbed by oxygen
atoms in the
thermosphere and O2 gas
in the mesosphere.
• Much ultraviolet (uv)
absorbed by the ozone in
the stratosphere.
• Visible light waves (still
considered shortwave)
pass through atmosphere
and are absorbed by
earth.

6. Ozone formation in stratosphere

7. Depletion of the ozone layer
• Ozone – O3 forms in the stratosphere and
absorbs UV energy, which can be harmful
• Halons and Chlorofluorocarbons (CFCs), – are
organic compounds that destroy ozone in the
ozone layer

8. Depletion of the ozone layer
• Ozone hole – reported in
1985 and linked to CFCs
in Antarctic ice clouds
• Many nations of the world
agreed to reduce or stop
use of these CFCs and
halons
• Most industrial countries
no longer produce CFCs.
• Since banning CFCs, the
hole may be decreasing

9. Ozone high and low
• The ozone layer in
the stratosphere is a
good thing because it
protects life on Earth
from harmful UV rays
• The Ozone in the
troposphere is a bad
thing because it
damages hearts and
lungs.

10. Thermal Structure of Atmosphere: Troposphere
• Extends to about 12 km
(40,000 ft) elevation
• All clouds & water vapor
and most weather
• Temperature decreases as
elevation increases,
because chief source of
heat is radiated heat from
the earth’s surface
• Tropopause: boundary
between troposphere and
stratosphere.

11. Environmental Lapse Rate
• Lapse rate: the rate at which air
temperature decreases with
altitude.
•The environmental lapse rate is the
overall temperature decrease in the
troposphere with altitude
•The normal environmental lapse
rate is 6.5°C/1000m, however
various factors can change this.
•The illustration shows an
environmental lapse rate of
0.5°C/100m, which equates to
5°C/1000m.
•Question 7, in the homework, uses
this concept.

12. Example problem using normal lapse
rate
It is 25 C at the surface. Under normal̊
conditions, what is the air temperature at 4
kilometers (4000 meters) above the surface.
The normal lapse rate is 6.5 C/1000m̊
a.21 C̊
b.19.5 C̊
c.Still 25 C̊
d.-1 C̊

13. Example problem using normal lapse
rate
It is 25 C at the surface. Under normal̊
conditions, what is the air temperature at 4
kilometers (4000 meters) above the surface.
The normal lapse rate is 6.5 C/1000m̊
a.21 C̊
b.19.5 C̊
c.Still 25 C̊
d.-1 C̊ (this is about 30 degrees F)

14. Thermal Structure of Atmosphere: Upper Layers
• Stratosphere – heated
primarily by solar radiation
– Ozone (O3) layer
absorbs UV energy,
causing temperatures
to rise
– Above 55km
(stratopause) temps
fall again
• Mesosphere – thin air
(can’t absorb energy), very
cold up to 80km
• Thermosphere – above
80km, temps rise rapidly
(to just below freezing!)

15. Earth rotates around an axis from the
North to South Pole
• Lines of latitude:
imaginary horizontal
rings around the axis
– Equator is at 00
latitude
– Geographic poles at 900
latitude
– Arctic and Antarctic
circles at 66.50
latitude
– Tropic of Cancer (N),
Capricorn (S) at 23.50
latitude, define tropics

16. Earth rotates around an axis from the
North to South Pole
• Lines of longitude (meridians):
imaginary vertical lines that run
north to south.
• Line through Greenwich,
England (Prime Meridian) at 00
longitude.
• Longitude increases both east
and west of Prime Meridian and
meets at 1800
longitude, the
International Date Line.

17. The Earth’s axis is tilted 23.50
from the
perpendicular to the orbital plane.
AXIS
Perpendicular to
orbital plane
In this picture, the northern hemisphere is tilted away from the
Sun. In 6 months, when the earth has orbited to the other
side of the Sun, the northern hemisphere will be tilted towards
the Sun.

18. On Earth, heat energy comes from light energy
• One energy “unit” can be concentrated in a relatively
small surface, or spread out over a large surface,
depending on the angle of incidence.
• The more the energy is spread out, the less heat it
generates.
Warmest (Direct) Less Warm Least Warm

19. The Seasons (N. Hemisphere)
• Summer is warm
– Sun is higher in the sky
so solar energy is more
concentrated.
– North Pole receives sun
all day long.
– Days are longer than
nights.
• Winter is cold
– Sun is lower in the sky.
– North Pole receives no
sunlight.
– Nights are longer than
days.

20. The Seasons (N. Hemisphere)
• Fall and Spring –
Vernal and Autumnal
Equinox
– Poles not tilted away
or towards the Sun.
– Both hemispheres
receive equal amounts
of solar energy.
– Days and nights are
the same length (12
hours).

21. Heat, Temperature, and Thermal Energy
•Thermal energy is an energy of the system due to the
motion of its atoms and molecules. Any system has
thermal energy even if it is isolated and not interacting
with its environment.
•Heat is energy transferred between the system and the
environment as they interact due to a difference in
temperature.
• Temperature quantifies the “hotness” or “coldness” of a
system. Although proportional to the thermal energy of a
system, it is not the same thing! A temperature difference
is required in order for heat to be transferred between the
system and the environment.

22. Methods of Heat Transfer
• Radiation is the heat-
transfer mechanism by
which solar energy
reaches our planet.
• Energy transferred by
radiation is called
electromagnetic
radiation and can travel
through a vacuum. This
radiation is NOT
radioactive!
• All radiation travels at
the speed of light in a
vacuum.

23. Electromagnetic Spectrum
Note the distinction between short-wave and long-
wave radiation.

24. Laws Governing Radiation
1. All objects emit radiant energy. This
includes the Earth, and its polar ice caps.
2. For a given size, hot object emit more
energy than cold objects
3. The hotter the radiating body, the shorter
the maximum wavelength. Solar
radiation is called short-wave radiation
and Earth’s radiation is called long-wave
radiation .

25. Laws Governing Radiation
4. Objects that are good absorbers of
radiation are good emitters as well. The
Earth and the Sun absorb and radiate
with nearly 100% efficiency for their
respective temperatures
5. The gases of the atmosphere are not so
good. They absorb some wavelengths
and then re-emit it. They let other
wavelengths pass through with no
absorption.

26. When radiation strikes an Object
• Transmission (no change in direction or temperature)
• Scattering and Reflection (transmission in another
direction)
• Absorption, which is accompanied by change of
temperature for object absorbing the radiation.

27. Solar Radiation in the Atmosphere

28. Reflection and Albedo
• Reflection–electromagnetic radiation bouncing of
from a surface without absorption or emission, no
change in material or energy wavelength
• Albedo – proportional reflectance of a surface
– a perfect mirror has an albedo of 100%
– Glaciers & snowfields approach 80-90%
– Clouds – 50-55%
– Pavement and some buildings – only 10-15%
– Ocean only 5%! Water absorbs energy.

29. Typical Albedos of Materials on the Earth

30. Absorption and Emission
• Absorption of radiation – electrons of absorbing
material are “excited” by increase in energy
– Increase in temperature; physical/chemical change
– Examples: sunburn, cancer
• Emission of radiation – excited electrons return
to original state; radiation emitted as light or heat
– Example: earth absorbs short wave radiation from
sun (i.e. visible light) and emits longwave (infrared or
heat) into the atmosphere

31. Fig. 18-6, p.432

32. the Radiation Balance
• Sun emits EM radiation of all wavelengths, but
primarily shortwave (i.e. light).
– Earth’s surface absorbs this energy
– Most is re-emitted upward, as heat (longwave)
• Greenhouse Effect
– “greenhouse gases” (water vapor, carbon dioxide,
methane, etc.) let shortwave energy pass, but absorb
and longwave energy radiated upward by the Earth.
– this longwave energy is re-radiated in all directions,
some of it returning to the Earth’s surface. This is
what keeps our atmosphere at a livable temperature
of about 15 degrees C (59 degrees F).

34. Controlling Factors of Temperature
• Latitude: tropics are warmer and higher
latitudes are colder temperature due to
differences in the Sun’s angle and the
length of the day in these locations.
• Land and Water
• Altitude (troposphere temperature
decreases with altitude)
• Geographic position (windward coast vs.
leeward coast
• Cloud cover and albedo

35. Continental Climate vs Marine
Climate: Moderating influence of a
large body of water

36. Effect of the Gulfstream on Climate

37. Effect of westerlies carrying marine
air mass vs a continental air mass
Siberia (cold
arctic wind)
Pacific (moderate
ocean wind)

38. Effect of Clouds on Temperature;
cooling effect during the day,
warming effect at night

39. Global temperature distribution in January
• Red-warmer, blue-cooler
• Northern hemisphere colder than southern
• Coldest/warmest places are on continents
• Isotherms bend southward on land in northern
hemisphere – means inland is colder than ocean

40. Global temperature distribution in July
• red-warmer, blue-cooler
• Southern hemisphere colder than northern
• Coldest place Antarctic continent /warmest places are
continental deserts in the northern hemisphere
• Isotherms bend northward on land in northern
hemisphere, means inland is warmer than ocean