Name ______________________________________
Period ________
Date _____________
Properties of the Earth's Atmosphere:
The atmosphere is divided into four different
zones: Troposphere, Stratosphere, Mesosphere,
and Thermosphere. Each of these zones is
separated by an interface, the tropopause,
stratopause, and mesopause. The 4 graphs here
make it possible to determine the temperature,
pressure, and water vapor content at any altitude
above the Earth in either miles or kilometers. Read
questions carefully! Are you being asked about an
altitude in miles or kilometers?
Be very careful about the altitude scales. Each
division on the miles side of the scale is 5 miles (5,
10, 15, 20 etc) but each division on the kilometer
side is 10 km (10, 20, 30, 40, etc). Be careful.
Check your work!
Notice that as altitude increases through the Troposphere, the
temperature decreases. This trend reverses through the Stratosphere
which warms with increasing altitude and again reverses through
the Mesospheres and Thermospheres.
You need to be able to find the temperature at any given altitude or
the altitude at which a given temperature occurs. For example:
1) What is the temperature at an altitude of 45 miles (72km)?
Find 45 miles. Use a straight edge to draw a line to the temperature
curve and drop straight down. The temperature is about -75°C.
2) At what altitude is the temperature -75°C?
Find -75°C on the bottom axis and draw a straight line up to the
temperature curve. Draw another line to the altitude (left) which is
45 miles (or 72km) above the Earth's surface.
Atmospheric pressure is given in units called
'atmospheres'. When you ate at sea level (0
altitude) there is one atmosphere pressing down on
you so the pressure at sea level is 1 atm. Using the
pressure chart on page 13 you can convert 1 atm to
1013.1 mb or 29.92 inches.
The higher you go the less atmosphere is pressing
down from above so the pressure decreases. By the
time you reach the Stratopause the pressure is very
close to 0 but not quite. As long as there is any air
above you there will be some slight pressure.
A typical question:
What is the atmospheric pressure at the tropopause
(7 mi or 12 km)? Draw a straight line down from
the tropopause and read the pressure. In this case,
0.25 atm.
Almost all of the water vapor is found in the troposphere. As
altitude increases, the concentration of water vapor decreases. This
is why most weather, clouds, storms, etc is located in the
troposphere and it is one reason why most commercial airliners fly
at or near the Tropopause. By flying above most of the water vapor
they avoid most of the weather. At an altitude of 12 - 13 miles or
21 - 22 km (blue line) there is no more detectable water vapor.
Some small amount of water vapor does reach the lower parts of
the Stratosphere, usually as the tops of thunderstorms.
Typical questions:
Q: In which layer of the atmosphere is most of the water vapor
found?
A: The Troposphere.
Q: What is the water vapor concentration at an altitude of 5mi (7
km)?
A: Find 5 miles and draw a straight line to the water vapor line.
Drop straight down and read the value as accurately as possible:
10g/m3.
Be able to reverse the process: At what altitude is the water vapor
content 10g/m3 ?