Download The Earth and Its Atmosphere

Chapter 1
Overview of the Earth’s
Atmosphere
The atmosphere is a delicate life-giving
blanket of air surrounding the Earth.
 Without the atmosphere the Earth would
not have lakes or oceans.
 Radiant energy from the sun energizes
the atmosphere driving day to day
weather.

Fig. 1-1, p. 5
Overview of the Earth’s
Atmosphere

Composition
 99% of the atmosphere is within 30km of the
Earth’s surface.
 N2 78% and O2 21%
 The percentages represent a constant
amount of gas but cycles of destruction and
production are constantly maintaining this
amount.
Table 1-1, p. 5
Overview of the Earth’s Atmosphere

Composition
 Water is a variable gas following the
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hydrologic cycle.
Carbon dioxide has risen in recent years
and is an important greenhouse gas.
Other greenhouse gases exist beyond
carbon dioxide.
Ozone – surface, upper, hole
Aerosols
Fig. 1-3, p. 7
FIGURE 1.3 The main
components of the
atmospheric carbon
dioxide cycle. The gray
lines show processes
that put carbon dioxide
into the atmosphere,
whereas the red lines
show processes that
remove carbon dioxide
from the atmosphere.
Stepped Art
Fig. 1-3, p. 7
Fig. 1-4, p. 7
Fig. 1-5, p. 8
Fig. 1-6, p. 8
Overview of the Earth’s
Atmosphere

The Early Atmosphere
 The Earth’s first atmosphere was composed
mostly of hydrogen and helium (most abundant
gases in the universe).
 The atmosphere evolved due to outgassing of
CO2 and H2O from the cooling center of the
Earth causing rain and eventually lakes and
oceans.
 Lakes and oceans acted as a sink, absorbing
CO2 from atmosphere.
 Plants evolved producing oxygen to form our
current atmosphere several 100 million ybp.
Overview of the Earth’s
Atmosphere
This video shows someone’s overview
of the change in composition of earth’s
atmosphere through time.
 The presenter shows what changed and
lists reasons why it changed.
 Is it successful?
 Is it fun?

http://www.youtube.com/watch?v=UpvsUwxJgYY&feature=pla
yer_detailpage
Vertical Structure of the
Atmosphere

Air Pressure and Air Density
 Weight = mass x gravity
 Density = mass/volume
 Pressure = force/area
 At the Earth’s surface the pressure of the
atmosphere is 14.7 lbs/in2 .
 Standard sea level pressure is 1013.25 mb
= 1013.25 hPa = 29.92 in Hg
 Atmospheric pressure decreases with an
increase in height.
Fig. 1-7, p. 10
Fig. 1-8, p. 10
Vertical Structure of the
Atmosphere
This video describes why it is colder on
top of mountains and warmer closer to
sea level.
 Is it successful?
 Is it fun?

http://www.youtube.com/watch?v=gGNxYtT_36I&list=
FLA8rzatZrvuFZS5jkp0XvIg&index=3&feature=plpp_
video
Class Exercise 1
Complete Table 1-1 and then plot the
data on the graph.
 Here is the “rule of thumb” you can use
to complete the table:

 “For every 5.6 km you ascend, there is half
the atmospheric mass above you as when
you started.”
Class Exercise 1
X
X
X
X
Vertical Structure of
the Atmosphere

Observation: Radiosonde
 Weather balloon
 Instrument and transmitter
 Air temperature, humidity, pressure
Vertical Structure of the
Atmosphere

Layers of the Atmosphere
 Lapse rate = change in temperature with a
change in height
 Isothermal environment = no change in
temperature with height
 Inversion layer = change in the sign of the
lapse rate
Vertical Structure of the
Atmosphere

Layers of the Atmosphere
http://www.youtube.com/watch?v=nOvcz3nHuzo&list=UU7SQV7CGSJfLDRIJmutuDQ&index=63&feature=plpp_video
 Troposphere: decrease in temperature, day
to day weather, tropopause
 Stratosphere: increase in temperature,
ozone, stratopause
 Mesosphere: decrease in temperature,
mesopause
 Thermosphere: increase in temperature,
suns strongest radiation
Fig. 1-9, p. 11
Stepped Art
Fig. 1-9, p. 11
Class Exercise 2
Complete Table 1-2 and then plot the
data on the graph.
 Here is the “rule of thumb” you can use
to complete the table:

 “When averaged over all seasons, air
temperature is 15 deg C at the earth’s
surface and decreases by 6.5 deg C per
kilometer in the lowest 11 km. Consequently,
this decrease is often referred to as the
average lapse rate – the average for all
locations and seasons”
Class Exercise 2
Fig. 1-10, p. 13
Vertical Structure of the
Atmosphere

The Ionosphere
 Not a true layer but an electrified region
 Ions = molecule with an additional or minus
an electron
 Exists at the top of the atmosphere in the
thermosphere
 F,E,D layer
 Sun light creates layers, D disappears at
night and less interference with AM radio
transmissions
Fig. 1-11, p. 14
BREAK TIME!, then….
Weather and Climate
Weather: short term air temperature, air
pressure, humidity, clouds, precipitation,
visibility, and wind
 Climate: long term patterns and average
weather; not just magnitude but also
frequency

Weather and Climate

Satellite’s View
 Geostationary satellite
 Meridians measure longitude (W-E)
 Parallels measure latitude (N-S)
 Weather maps: pressure cells, fronts,
surface stations
Fig. 1-16, p. 21
Weather and Climate

Storms of All Sizes
 Middle-latitude cyclone
 Hurricane
 Thunderstorms
 Tornadoes
Weather and Climate

A Look at the Weather Map
 Wind
 Wind direction
 Wind speed
 Front
Fig. 1-12, p. 16

“Fronts”
 A cold front is defined as the leading edge of
a cooler mass of air, replacing (at ground
level) a warmer mass of air, which lies within
a fairly sharp surface trough of low pressure.
Fig. 1-13, p. 17
Fig. 1-15, p. 20
Fig. 2, p. 18
Weather and Climate

Meteorology
 Study of the atmosphere and its phenomena
 Aristotle 340 B.C. Meterologica, meteoros:
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high in air
1843 telegraph
1920s air masses
1940s upper air
1950s radar and computers
1960s satellite
Weather and Climate

Weather and Climate in Our Lives
 Two general reasons for studying how
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weather and climate impacts our lives:
economic efficiency and public safety.
Clothing
Crops
Utilities
Extreme cold and heat
Tornados and hurricanes
Fig. 1-17, p. 21
Fig. 1-18, p. 21
Fig. 1-19, p. 22
Fig. 1-20, p. 22
Fig. 3, p. 23
Weather and Climate

Career: Meteorologist
 Any person with a college degree in
meteorology or atmospheric science; not
just the TV weather person
 Half of 9000 meteorologists employed by the
US National Weather Service
 Researchers and operational meteorologists

What is happening today in the
southeastern United States?
 http://weather.gov