Geoscience Reference
In-Depth Information
VISUAL CONCEPT CHECK
5.1
1.
An airliner in the midlatitudes takes off and climbs through
the troposphere to its cruising altitude. As it rises through
the troposphere, does the outside temperature (a) increase,
(b) decrease, or (c) remain the same?
2.
The pilot informs you that the plane's cruising altitude is
36,000 ft. Is this in the (a) troposphere, (b) stratosphere, or
(c) mesosphere?
3.
The pilot decides to avoid some turbulence by having the
plane climb to 40,000 ft. At this new altitude, is the outside
temperature (a) higher, (b) lower, or (c) the same?
George Hall/Corbis Images
The name of this atmospheric layer is derived from the Greek
thermo
, which implies “heat”; this term makes perfect sense if
you look at the temperature patterns of the thermosphere in Fig-
ure 5.1b. Notice that they increase drastically about 10 km (6
mi) above the mesopause, ultimately reaching 1200°C (2200°F)
and higher. These high temperatures occur because intense solar
radiation interacts with the upper part of the atmosphere, caus-
ing the few oxygen molecules present to vibrate at tremendously
high speeds, which creates
kinetic energy
. This form of energy
is specifically contained within the molecules by virtue of their
spatial relationship to other oxygen molecules. The thermosphere
is important for human communications because it enables ra-
diowaves from one location at the surface to bounce off and be
received at locations beyond the horizon.
Despite the very high temperatures of the thermosphere, this
atmospheric layer does not feel “hot” in the same way you feel
heat on the Earth's surface. The reason for this oddity is that in-
dividual oxygen molecules in the thermosphere are so far apart
from one another. Because of these great distances, the molecules
hardly ever come into contact with each other, which means that
very little heat is transferred from one to another. At lower levels
of the atmosphere, in contrast, temperatures are genuinely higher
because trillions of molecules are constantly colliding and a great
deal of heat is exchanged.
2.
The troposphere lies closest to the Earth's surface and
typically has a positive lapse rate of 6.4°C per 1000 m
or 3.5°F per 1000 ft.
3.
The next lowest layer is the stratosphere, which con-
tains the ozone layer and thus warms with increasing
altitude.
4.
Immediately above the stratosphere is the mesosphere,
which cools with increasing altitude and is the part of
the atmosphere where solar radiation reduces individual
molecules to ions.
5.
The uppermost layer of the atmosphere is the thermo-
sphere. Although the temperature in this part of the at-
mosphere is very high, it does not feel hot because the
individual air molecules are very far apart.
Surface and Air Temperatures
Most of the atmospheric behavior of interest to geographers
occurs near the Earth's surface. Of particular significance are
global surface and air temperatures, which measure the amount
of sensible heat at the surface or in the atmosphere. Atmospheric
temperature is a measure of the kinetic energy contained within
a unit of geographical space within the air. Surface temperature,
in contrast, is a measure of the kinetic energy contained in a re-
gion very close to the Earth's surface. Thus, changes in surface
temperature measure the ebb and flow of energy at ground level.
As noted in Chapter 4, this variation in energy on Earth depends
largely on net radiation. When a net surplus of radiation occurs,
temperature increases because the surface absorbs more radi-
ant energy than it is emitting in longwave form. Conversely,
temperature decreases with a net deficit of radiation because
the surface emits more energy than it absorbs. Recall from
Chapter 4 that surface temperature can also change through the
KEY CONCEPTS TO REMEMBER ABOUT
THE STRUCTURE OF THE ATMOSPHERE
1.
The atmosphere consists of four major layers, each with
distinct temperature characteristics.
The energy of motion in a body, measured as
temperature, that is derived from movement of molecules within
Kinetic energy
