The atmosphere is concentrated at the Earth's surface and rapidly thins as you move upward, blending with space at about 100 miles above sea level
Most of the stratosphere, which extends to about 50 kilometers above the surface, is cold and free of clouds Figure 8 12 Structure of Earth's Atmosphere
TROPOSPHERE (up to 10 miles above Earth's surface): The lowest region of the atmosphere, where weather and clouds are formed STRATOSPHERE (10-30 miles above
The thermosphere is the layer of the Earth's atmosphere directly above the mesopause and below the exosphere It varies from 90 km to about 500 km
Since collisions are negligible above the exobase, the molecules in this region, called the exosphere, move along ballistic trajectories under the action of the
Air molecules are held near the earth by gravity • This strong, invisible force pulling down by the air above compresses air molecules closer together, which
above the earth The temperature here decreases with altitude I • The strato~phere is the layer above the troposphere extending from 16 km to 50 km (9 I
9 oct 2018 · At this extreme altitude gas molecules are widely separated Above (100 km) from Earth's surface the chemical composition of air becomes
atmosphere This picture was taken from a weather balloon at about 30km above the Earth's surface In contrast to the troposphere, the temperature in the
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Atmosphere Page 1
Atmosphere
Oǀerǀiew of Earth͛s Atmosphere
The atmosphere is comprised of of gases, consisting mostly of nitrogen and oxygen. It also contains lesser amounts of argon, carbon dioxide, and many other trace gases.
The different layers of the atmosphere have
contrasting characteristics, the most fundamental of which is pressure, which decreases with altitude.
Each layer has distinct qualities in terms of
temperature.
From bottom to top, the layers are:
The troposphere The stratosphere The mesosphere The thermosphere The exosphere
Atmosphere Page 2
Layer 1: Troposphere
The lowermost of the atmosphere, in contact with the ground is called the troposphere. Temperature decreases with altitude
In the troposphere.
We live and breathe in the troposphere,
which extends from the ground to about 10 km elevation. What you see from an airplane window is the troposphere.
80% of the mass of the atmosphere is in
the troposphere, as the weight of the overlying atmospheric layers compresses the air near the ground.
Most weather is confined to the
troposphere as well (although some cumulonibmus clouds reach the stratosphere).
Atmosphere Page 3
Layer 2: Stratosphere
The second layer of the atmosphere is called the stratosphere. This layer is between approximately 10 km and 50 km above the surface.
Compared to the troposphere,
the stratosphere has very little water vapor. This layer contains most (19.9% of the remaining 20%) of the remaining of the mass of the atmosphere. This picture was taken from a weather balloon at about 30km above the
Earth͛s surface.
In contrast to the
troposphere, the temperature in the stratosphere rises with elevation because. radiation from the sunͶor heat energyͶ is absorbed by ozone molecules in this layer.
Because the air is so
thin at that altitude, it requires very little heat to raise the temperature compared to what occurs near the ground.
An important aspect of the
stratosphere is that there is a key layer of high concentrations of ozone, a molecule consisting of 3 oxygen atoms.
Atmosphere Page 4
Layer 3: Mesosphere
The third layer, or middle layer, of the atmosphere is called the mesosphere. This layer is between approximately 50 km and 80-85 km above the surface.
This layer contains gases
including oxygen molecules but they become less abundant as the distance from
Earth increases. This picture
shows mesospheric clouds; it was taken by an astronaut.
In contrast to the
stratosphere, the temperatures in the mesosphere are colder at higher altitudes and warmer at lower altitudes.
Temperatures
decrease with height because the gases become less abundant with height and thus absorb less radiation at higher altitudes.
An interesting aspect of the
mesosphere is that the gases are thick enough to slow down meteorites. As the meteorite slows down it burns up leaving a fiery trail.
Atmosphere Page 5
Layer 4: Thermosphere
The fourth layer of the atmosphere, or upper atmosphere, is called the thermosphere. This layer is between approximately 80 km and 500 km above the surface.
Like the mesosphere, this
layer also contains gases including oxygen molecules but here they become even rarer as the distance from
Earth increases. The
International Space Station
orbits in the thermosphere.
In contrast to the
mesosphere, the temperatures in the thermosphere are higher and increase with altitude.
Temperatures increase
with height becauseͶ although molecules are rare they are moving very rapidly.
Temperature is a
measure of molecular motion.
An interesting aspect of the
thermosphere is that radiation cause particles to become electrically charged, or ionized. The thermosphere is where auroras occur.
Atmosphere Page 6
Layer 5: Exosphere
The fifth layer of the atmosphere, or outmost layer, is called the exosphere. This layer is between approximately 600 km to 10,000km above the surface. This layer contains the fewest molecules within the Earth͛s atmosphere. From the exosphere, molecules can escape into outer space. NASA͛s Mercury MESSENGER spacecraft took this photo on a mission to obserǀe the Earth͛s edžosphere.