Download 411 Notes Atmosphere Structure

I.
Lecture Notes - Atmospheric Structure & Composition 2016
Atmospheric Structure - Layers of the Atmosphere
A.
Troposphere - (0 - 12 km (38 000 feet)) is the home of almost all of our
weather . Most cloud activity is limited to the troposphere, where the low-lying
stratus and fluffy white cumulus clouds are found.
The troposphere is thicker at the equator than at the poles.
A2.
Jet Stream - (12 km (38 000 feet)) Flowing along the top of the
troposphere are the river-like jet streams. These upper level winds travel
in a generally west to east direction at speeds of up to 190 miles per hour!
The jet streams are “sandwiched” between the troposphere and the stratosphere.
There are two main jet streams in North America:
1) The polar jet stream rides along the southern edge of the polar air mass,
which means it usually travels across the United States in a swooping line from
the Pacific Northwest down to the Gulf Coast and back up to New England.
 In the summer, the jet stream usually weakens and flows across Canada.
 In the winter, the jet stream intensifies and heads south! As it bends and
twists, the jet stream drives and profoundly changes our weather!
2) The sub - tropical jet stream is a little less changeable and usually flows from
west to east across Mexico and the southern United States.
 Sometimes, the two jet streams merge. When that happens - look out!
The result will be severe supercell thunderstorms or even tornadoes.
B.
Stratosphere - (12 km - 47 km (150 000 feet)) is the calm, clear layer
directly above the troposphere. The stratosphere primarily contains cirrus
clouds, which are made of tiny ice crystals.
Towering cumulonimbus thunderheads start out in the troposphere, but can
grow quickly upwards and punch a hole into the stratosphere.
B2.
Ozone Layer (20 km - 47 km ) - The stratosphere is also home to the
ozone layer. The ozone layer gets depleted more during some years than it does
during others. In 2003, the second worst “ozone hole” ever recorded was
measured. The ozone layer also causes the surprising warming of the air that
occurs while rising through the upper stratosphere.
C.
Mesosphere - ( 47 km - 80 km (250,000 ft ) is the middle layer; air
temperature starts to get colder again - drops to - 90 C at top of the mesosphere.
D.
Thermosphere/Ionosphere (80 km - 350 km) The ionosphere is full of
charged particles (ions) and is found in the lower part of the thermosphere.
The ionosphere is the layer of the atmosphere which interacts with the solar wind to
create the Northern Lights (Aurora borealis).
E. Exosphere - Beyond the thermosphere is the exosphere, which continues
until it merges with the interplanetary gases of outer space. The exosphere is
primarily made of Hydrogen and Helium like most of the rest of the universe!
E2. Extending far above earth is the invisible magnetosphere, or magnetic field
of the earth. While it is not part of Earth’s atmosphere, it connects and interacts
with the sun’s magnetic field and deflects the powerful ionized radiation of the
solar wind towards the magnetic north and south poles. That is why the auroras
are usually found up near the Arctic Circle in North America and Europe. P.S. - the
aurora near the South Pole is called the Aurora australis: the Southern Lights”.
II.
Composition - % by Volume of Gases in the Atmosphere
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#1. Nitrogen (N2) - 78.08%
#7. Methane (CH4) - 0.00014 %
#2. Oxygen (O2) - 20.95 %
#8. Krypton (Kr) - 0.00010 %
#3. Argon (Ar) - 0.93 %
#9. Nitrous oxide (NO2) = 0.00005 %
#4. Carbon dioxide (CO2) - 0.035 %
#10. Hydrogen (H2) = 0.00005 % (5 ppm)
#5. Neon (Ne) - 0.0018 %
#11. Ozone (O3) - 0.000007 % (0.07 ppm)
#6. Helium (He) - 0.00052 %
#12. Xenon (Xe) - 0.000009 % (0.09 ppm)
*** Variable Gases - Water Vapor - 0 - 4% / Volcanic Ash/Dust - trace
Although CO2, CH4 and O3 are only present in tiny amounts, they play a huge role in the
atmosphere:
 #4: CO2 (Carbon dioxide) and #7: CH4 (Methane) are the two most common
greenhouse gases warm and may eventually overheat our planet.
 #11: Ozone (O3) is considered a pollutant here at the surface, but 30 km up in the
stratosphere, it forms the thin ozone layer which is crucial in protecting life on
land from the sun’s harmful ultra-violet radiation.
The %s are based on dry air (no water vapor). Although there is always some water
present in air, the % of atmospheric water vapor never gets higher than 4 %.
#3 Ar, #5 Ne, #6 He, #8 Kr, and #12 Xe are all inert gases. These gases do
not chemically react with the other gases or with the rocks or life forms on the surface.
Nitrogen (N2) is also nearly inert, which is why it has accumulated to the #1 spot.
Earth actually has far more Oxygen (O2) than Nitrogen! However, Oxygen (#2)
is highly reactive, so much of Earth’s Oxygen is tied up in its rocks and ocean water.