Transcript Atmospheric Layers - Earth Geography

Atmospheric Layers
McLayer
“McAtmosphere”
Illustrate the layers of the atmosphere and label each correctly. Include subtext & miles.
Exosphere
238,900 mi
Occasional molecules, gradually escaping Earth’s gravity field
Thermosphere
320/500-120,000 mi
Fewer molecules, large temperature fluctuations
Mesosphere
52-220/500 mi
Cold, a few molecules, meteorites burn up here
31-52 mi
Stratosphere
Contains Ozone layer, 24% of atmosphere
7-32 mi
9-20 mi
0-8 mi
Ozone
layer
Troposphere
Life forms, weather, 75% of atmosphere
Earth
Troposphere
The troposphere begins at the surface and extends to
between 0 to 8 miles, with some variation due to
weather. The troposphere is mostly heated by transfer of
energy from the surface, so on average the lowest part of
the troposphere is warmest and temperature decreases
with altitude. This promotes vertical mixing (hence the
origin of its name in the Greek word, tropos, meaning
"turn"). The troposphere contains roughly 80% of the
mass of the atmosphere and basically all the weatherassociated cloud genus types (very tall cumulonimbus
thunder clouds can penetrate the stratosphere from
below). The tropopause is the boundary between the
troposphere and stratosphere.
Stratosphere
The stratosphere extends from the tropopause at
about 7.5 mi to about 32 mi. Temperature increases
with height due to increased absorption of ultraviolet
radiation by the ozone layer, which restricts
turbulence and mixing. While the temperature may
be −60 °C (−76 °F; 210 K) at the tropopause, the top of
the stratosphere is much warmer, and may be near
freezing. Polar stratospheric or nacreous clouds are
occasionally seen in this layer of the atmosphere. The
stratopause, which is the boundary between the
stratosphere and mesosphere, typically is at 31 to 34
mi. The pressure here is 1/1000 sea level.
Mesosphere
• The mesosphere extends from the stratopause at about
31 mi to 50–53 mi. It is the layer where most meteors
burn up upon entering the atmosphere. Temperature
decreases with height in the mesosphere. The
mesopause, the temperature minimum that marks the
top of the mesosphere, is the coldest place on Earth
and has an average temperature around −85 °C (−120
°F; 190 K). At this altitude, temperatures may drop to
−100 °C (−150 °F). Due to the cold temperature of this
layer, water vapor is frozen, occasionally forming polarmesospheric noctilucent clouds which are the highest
water-based aerosols in the atmosphere. A type of
lightning referred to as either sprites or ELVES,
occasionally form far above tropospheric
thunderclouds.
Thermosphere
• Temperature increases with height in the thermosphere from
the mesopause up to the thermopause, then is constant with
height. Unlike in the stratosphere, where a temperature
inversion is caused by absorption of radiation by ozone, in the
thermosphere the inversion is a result of the extremely low
density of molecules. The temperature of this layer can rise to
1,500 °C (2,700 °F), though the gas molecules are so far apart
that temperature in the usual sense is not well defined. The
air is so rarefied that an individual molecule (of oxygen, for
example) travels an average of 1 kilometer between collisions
with other molecules. The International Space Station orbits
in this layer, between 200 and 240 mi. The aurora borealis
and aurora australis are occasionally seen in the
thermosphere and the lower part of the exosphere. The top
of this layer is also the bottom of the exosphere, and is called
the exobase. Its height varies with solar activity and ranges
from about 220–500 mi.
Exosphere
The exosphere is the outermost layer of Earth's
atmosphere, extending beyond the exobase at an
altitude of about 372 mi. It is mainly composed of
hydrogen, helium and some heavier molecules such
as nitrogen, oxygen and carbon dioxide closer to the
exobase. The atoms and molecules are so far apart
that they can travel hundreds of kilometers without
colliding with one another, so the atmosphere no
longer behaves like a gas. These free-moving particles
follow ballistic trajectories and may migrate in and
out of the magnetosphere or the solar wind.
Ozone (O ) Layers
3
90% of the ozone layer is contained within the lower
stratosphere, about 9.3–22 mi; the thickness varies
seasonally and geographically.
In this layer ozone concentrations are about 2 to 8 parts
per million, which is much higher than in the lower
atmosphere but still very small compared to the main
components of the atmosphere.
Air pollution is the introduction into the atmosphere of
chemicals, particulate matter, or biological materials that
cause harm or discomfort to organisms. Stratospheric
ozone depletion is believed to be caused by air pollution
(chiefly from chlorofluorocarbons).
Build up of CO2
Pressure and thickness
The average atmospheric pressure at sea level is 1
standard atmosphere (atm)=14.7 psi (pounds per
square inch).
Atmospheric pressure is the total weight of the air
above unit area at the point where the pressure is
measured. Thus, air pressure varies with location and
weather.
If the atmosphere had a uniform density, it would
terminate abruptly at an altitude of 5.2 miles.
However, the atmosphere is modeled according to
gradients of temperature, molecular composition,
solar radiation and gravity.
Oh yeah, there are more layers in the layers
;-)
• ionosphere – between the mesosphere &
thermosphere, it is a region that is ionized by solar
radiation. This zone creates auroras (Northern
Lights).
• Magnetosphere-part of the ionosphere, allows
radio propagation on Earth.
• Homosphere-involves well mixed gasses, due to
turbulance, in the first three layers of the
Atmosphere.
• Heterosphere-in the areas of the exosphere &
themosphere, where great distance seperates
particals, and molecular weight creates more layers.
…and another…
• planetary boundary layer— part of the troposphere
closest to Earth's surface and directly affected by it,
through turbulent diffusion. During the day the
planetary boundary layer is well-mixed, but at night
it becomes stably stratified with weak or
intermittent mixing. The depth of the planetary
boundary layer ranges from as little as about 100
meters on clear, calm nights to 3000 m or more
during the afternoon in dry regions.