This document provides an overview of Earth's atmosphere and its layers. It begins by defining an atmosphere and noting that Earth's protects the planet from extreme temperatures and harmful solar radiation. The five main layers of Earth's atmosphere are then described in more detail, including the gases present and how temperature varies with altitude. Key functions of the atmosphere such as the greenhouse effect and atmospheric circulation driven by uneven solar heating are also summarized.

1. Atmosphere
& Air Review
Earth’s Pr
o
tective Bla
nket

2. Earth's Atmosphere
What's an atmosphere?
 Air surrounding a planet
 Earth's atmosphere has 5 layers
 Different planets have different
layers and different gases in their
atmospheres
What does it do?
 Protects from Sun's heat (and space's
cold)

day/night temps would be
extreme without blanket of gases
 Protects from Sun's harmful rays

solar (ultraviolet) radiation would
destroy all life if not filtered out
Exosphere
Thermosphere
Mesosphere
Stratosphere
Troposphere

3. Layers Identified by Temperature
Temperature changes
determine layers
Top region and
transition to next
layer called:
 Tropopause
Mesopause
 Stratopause
 Mesopause
Stratopause
Tropopause

4. Earth's atmosphere, a mixture of gases:
• N2, O2, Ar, CO2, and others gases plus water vapor, dust, etc.
•Earth's gravity holds more air molecules near it's surface than in
the upper atmosphere where gravitational forces are weaker

5. Atmospheric
Pressure
Higher altitudes=
 Fewer molecules
pushing on each other
and their surroundings
 Lower pressure
 Less concentrated
oxygen levels

6. Density
Amount of matter
within a specific
volume


# of atoms
occupying a
particular space
how close
together the
atoms are packed
SI base units = g/cm3
or g/ml

7. Altitude & Density
 As air pressure decreases,
density of air also
decreases
 Air particles are not
squashed together as
tightly the higher one
goes (because of gravity)
Air at sea level and 8km
both have 21% oxygen
 But 21% of 100 = 21,
while 21% of 10 is only 2!
 At 8km there are fewer
molecules per cubic cm,
so you take in less
oxygen with each

8. Evaporative Cooling
When droplets
of sweat
evaporate from
your skin, they
take a lot of heat
with them, and
your body is thus
colder because it
has lost heat
energy.

9. Layers of Earth’s Atmosphere
 Troposphere
 Where we live
 Stratosphere
 Ozone layer
 Mesosphere
 Meteors burn up
 Thermosphere
 Space shuttle
 Aurora Borealis
 Exosphere
 Thin, outer layer
 Beginning of
outer space
Exosphere

10. Troposphere
 Thinnest layer (4 to 12 miles thick)
 Thickness depends on terrain, season, time
of day & latitude
 Holds ~80% of Earth's atmospheric mass
 Highest pressure at lowest levels
 Most weather occurs here
 Water vapor (& clouds), wind, lightning
 Jet stream (river of 250 mph winds) is just
below the Tropopause (upper boundary)
or in the lowest parts of the stratosphere
 Temperature cools as you go up
 Sun heats ground, which radiates warmth
to air above it
 Air is warmest near the ground
 Air cools ~6.4oC

14oC (57oF)
every 1 km you go up
Top of Troposphere is -50oC (-58o F)

11. Greenhouse Effect
 Solar radiation that reaches earth is absorbed by:
 Earth's surface (50%)


land heats quicker and radiates sooner
bodies of water heat slower and hold onto heat longer
 Earth's atmosphere (15%)
 35% of Solar radiation
is reflected from
 Earth's
atmosphere
 Clouds
 Earth's surface
(i.e. snow, sand)
 Some of the heat
absorbed by Earth's
surface is released
into the atmosphere

12. Air Pollution
 Nitrogen Oxides
 Damage lung tissue
 Sources:


car, plane, mower engines
lightening burning N2 in air
 Sulfur Oxides
 Damage lung tissue
 Sources:


burning coal
volcanic eruptions
 Carbon Monoxide
 Causes asphyxiation
 Sources:


gasoline engines (automobiles, chainsaws, trains, etc.)
forest fires, woodstoves, cigarettes
 Airborne Lead
 Destroys brain tissue
 Source: leaded gasoline
 Particulates

13. Stratosphere
 Thickness from 33 to 40 km (20-25 miles)
 Depends on Troposphere's thickness
 Top boundary (Stratopause) at 50km
above sea level
 Contains the Ozone Layer
 Earth's "sunscreen"
 Temperatures rise as you go up
 Heat trapped by ozone warms layer
 -50oC to -3oC to (-58o to 27o Fahrenheit)
 Very stable/stagnant layer
 Little to no wind (not much mixing)

Jet aircraft fly lower stratosphere
 No water vapor/clouds (very dry)

14. Ozone Layer
O3 Molecules
Absorbs UV light which cause skin cancer & cataract
Absorbs heat
Toxic to breathe

15. "Hole" in the Ozone Layer
Chlorine & Bromine bind to
oxygen & deplete ozone
Mostly at the south pole where
Artic winds carry Cl & Br up into
the Stratosphere
Localized & seasonal "thinning"
- not a complete "hole"
CFCs in refrigerants
Montreal Protocol
Studies now show reversal
Some models predict reversal
will increase global warming

16. Global Warming
Average global
temperatures
have increased
by about 1oC
over the past 150
years.
How do we
know this?

17. The Big Picture

18. Causes of Global Climate Change
Greenhouse gases
 Carbon Dioxide
 Methane
 Nitrous Oxide
 Water Vapor
Solar activity
Earth's elliptical orbit
Volcanic Eruptions

19. Transfer of Heat Energy

20. Conduction
Heat moving through molecules
Molecules bumping into each other transfers heat
What make good conductors?
gases are poor conductors
metals are good conductors
Animation

21. Convection
 Heat moves with the
molecules as they flow
- Warmer
molecules move faster
and push each other
apart
- Less dense particle masses
rise up, leaving space
- As molecules lose heat,
they sink back down,
creating a circular flow
 Gas and liquids only
 Animation

22. Radiation
 Does not involve
matter (atoms)
 Can travel through
space (vacuum)
 Electromagnetic
waves carry heat
 Different
wavelengths
 visible light
 infrared light
 ultraviolet light
 Sun, flame, light
bulb or other heat
source

24. Atmospheric Convection
Concentrated solar radiation at equator = hotter air (re-
radiation)
 Rising heated air masses creates low pressure areas (L)
Cold air from poles sinks down
 Denser (colder) air molecules results in high pressure areas (H)
H
L

25. Convection Cells
Sinking polar air reaches warmer 60o latitudes and rises
 Poles are high pressure areas (90o N & S)
Rising equatorial air reaches cooler 30o latitudes and sinks
 Equator is low pressure area
L
In between (temperate latitudes)
 Airflow in reverse directions
H
because of H's & L's
Ultimate source of air
L
movement (wind) on Earth:
 Uneven heating of earth’s surface
H

26. Coriolis Effect
The perceived curving of global winds due to Earth's
rotation
Video Illustration
 Each cell curves (seemingly)
 N. hemisphere curves right (clockwise)
 S. hemisphere curves left (counter-clockwise)
 Polar matter rotates slower than equatorial matter:
greater effect near equator

27. Global Winds
Trade Winds
North & South of the
Equator
Blow from East to West
Prevailing Westerlies
Latitudes 30 to 60
Named for the direction
from which they blow
Polar Easterlies
North & South Poles
Weak & irregular

28. Sea and Land Breezes
Sea Breeze
 Daytime:
 Land heats up faster than water
 Hot air over land rises (L)
 Cool air over water pushes onto
land (H)
Land Breeze
 Nighttime:
 Land cools faster than water
 Warm air over water rises
(leaving a low pressure area)
 Cool air over land pushes into
low pressure area over water

29. Jet Streams
High up in
atmosphere
Upper Troposphere
Lower Stratosphere
Form between cold &
warm air masses
bigger temperature
difference = faster jet
stream winds
Flow west to east
around the globe