Download Ch01 Earth Atmosphere

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.
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.
Overview of the Earth’s
Atmosphere
• Composition
– Water a variable gas following the hydrologic
cycle.
– Carbon dioxide has risen in recent years and
is an important greenhouse gas.
– Other greenhouse gases exist beyond carbon
dioxide.
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
(a) The solid blue line shows the average yearly measurements of CO2 in parts per million (ppm) at Mauna Loa Observatory, Hawaii,
from 1958 to 2011. The jagged dark line illustrates how higher readings occur in winter where plants die and release CO2 to the
atmosphere, and how lower readings occur in summer when more abundant vegetation absorbs CO2 from the atmosphere.
(b) The insert shows CO2 values in ppm during the past 1000 years from ice cores in Antarctica (orange line) and from Mauna Loa Observatory (blue line). (Mauna Loa data NOAA-Ice Core data courtesy of Carbon Dioxide Information Analysis Center, Oak Ridge National
Laboratory
The darkest color represents the area of lowest ozone concentration, or ozone hole,
over the Southern Hemisphere on September 25, 2010. Notice that the hole is larger
than the continent of Antarctica. A Dobson unit (DU) is the physical thickness of the
ozone layer if it were brought to the earth’s surface, where 500 DU equals 5
millimeters.
• Variable components of air
– Ozone
• Three atoms of oxygen (O3)
• Distribution not uniform
• Concentrated between 10 and 50 km above the
surface
• Absorbs harmful UV radiation
• Human activity is depleting ozone by adding
• Chlorofluorocarbons (CFCs)
Ozone Depletion
Variable components of air
• Water vapor
– Up to 4% of air’s volume
– Forms clouds and precipitation
– It is also a greenhouse gas
– Important role in absorbing and releasing latent
heat during phase change
• Aerosols
– Tiny solid and liquid particles
– Water vapor can condense on solids
– Reflect sunlight
– Color sunrise and sunset
Overview of the Earth’s
Atmosphere
• The Early Atmosphere
– The Earth’s first atmosphere was composed
mostly of hydrogen and helium.
– 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.
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 is1013.25 mb =
1013.25 hPa = 29.92 in Hg
– Atmospheric pressure decreases with an increase
in height.
Both air pressure and air density decrease with
increasing altitude. The weight of all the air molecules above the earth’s
surface produces an average pressure near 14.7 lbs/in.2
Atmospheric pressure decreases rapidly with
height. Climbing to an altitude of only 5.5 km, where the pressure is
500 mb, would put you above one-half of the atmosphere’s molecules.
Vertical Structure 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
Near the earth’s surface the air temperature lapse rate is often close to 3.5F per 1000 ft. If this
temperature lapse rate is present and the air temperature at the surface (0 ft) is 46F, the air temperature
about 4000 ft above the surface would be at freezing, and snow and ice might be on the ground.
Vertical Structure of the
Atmosphere
• Layers of the Atmosphere
– 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
• Troposphere
– Bottom layer
– Temperature decreases
with altitude
–Environmental lapse
rate
• Average 6.5˚C per km
or 3.5˚F per 1000 feet
– Thickness varies
• Average height is
about 12 km
– Outer boundary is the
tropopause
– Where weather
happens!
• Stratosphere
– 12 to 50 km
– Temperature increases
at top
– Outer boundary is the
stratopause
• Mesosphere
– 50 to 80 km
– Temperature decreases
– Outer boundary is the
mesopause
• Thermosphere
– No well-defined upper
limit
– Fraction of atmosphere’s
mass
– Gases moving at high
speeds
Layers of the
atmosphere as
related to the
average profile of
air temperature
above the earth’s
surface.
The red line
illustrates how the
average
temperature
varies in each
layer.
Stepped Art
• Special Topic: The Atmospheres of Other
Planets
– Each planet’s atmosphere is unique in terms of temperature and
composition.
– Earth: N2, O2
– Venus: 95% CO2, thick
– Mars: 95% CO2, thin
– Jupiter: H2, He, Red Spot
Vertical Structure of the
Atmosphere
• Observation: Radiosonde
– Weather balloon
– Instrument and transmitter
– Air temperature, humidity,
pressure
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.
At night, the higher region of the ionosphere (F region) strongly reflects AM radio waves, allowing
them to be sent over great distances. During the day, the lower D region strongly absorbs and
weakens AM radio waves, preventing them from being picked up by distant receivers.
(left) Layers of the atmosphere based on temperature (red line), composition (green line), and
electrical properties (dark blue line). (An active sun is associated with large numbers of solar
eruptions.)
Weather and Climate
• Weather: short term
– Air temperature
– Air pressure
– Humidity
– Clouds
– Precipitation
– Visibility
– Wind
• Climate: long term patterns and average
weather; not just magnitude but also
frequency
Weather & Climate
• Meteorology – brief history
– Study of the atmosphere and its phenomena
– Aristotle 340 B.C. Meterologica, meteoros:
high in air
– 1843 telegraph
– 1920s air masses
– 1940s upper air
– 1950s radar and computers
– 1960s satellite
Doppler radar has the capacity of estimating
rainfall intensity. In this composite image, the areas
shaded green and blue indicate where light-tomoderate rain is falling.
Yellow indicates heavier rainfall. The red-shaded
area represents the heaviest rainfall and the
possibility of intense thunderstorms.
(Notice that a thunderstorm is approaching
Chicago from the west.)
Weather & Climate
• Satellite’s View
– Geostationary satellite 22,300 mi above equator
– Meridians measure longitude (W-E)
– Parallels measure latitude (N-S)
– Weather maps: pressure cells, fronts, surface
stations
This satellite image (taken in visible reflected light) shows a variety of cloud patterns and storms in the earth’s
atmosphere.
• Simplified surface
weather map that
correlates with the
satellite image
shown in Fig. 1.15.
The shaded green
area represents
precipitation. The
numbers on the
map represent air
temperatures in oF.
Weather & Climate
• Weather and Climate in Our Lives
– Two general reasons for studying how
weather and climate impacts our lives:
economic efficiency and public safety.
– Clothing
– Crops
– Utilities
– Extreme cold and heat
– Tornados and hurricanes
Ice storm near Oswego, New York, caused utility poles and power lines to be weighed down, forcing road closur
A tornado and a rainbow form over south-central Kansas during June, 2004. White streaks in the sky are descending hailstones.
Flooding during April, 1997, inundates Grand Forks, North Dakota, as flood waters of the Red River extend over much of the city.
Estimates are that lightning strikes the earth about 100 times every second. About 25 million lightning strikes hit the United States
each year. Consequently, lightning is a very common, and sometimes deadly, weather phenomenon.