Geoscience Reference
In-Depth Information
• Seasonality is much more pronounced in the Northern Hemisphere than
in the Southern Hemisphere in association with the distribution of the
continents, except over Antarctica.
• Air temperatures over land are warmer than temperatures over the oceans
in the summer hemisphere, and generally cooler in the winter hemisphere.
Recall from
Figure 2.6
that the annual mean air temperature is warmer over
land than over oceans.
• The east-west temperature gradients over the tropical oceans are in place
throughout the year.
Temperature profiles provide more detail about the vertical structure of
the atmosphere.
Figure 2.8
shows the globally and annually averaged tem-
perature profile through the height of the earth's atmosphere. The region
of the atmosphere from the surface to roughly 12 km is termed the
tropo-
sphere
, which is derived from the Greek root meaning “the turning or chang-
ing sphere.” This region is where weather systems exist and is the focus of
our study of climate dynamics. Temperature decreases with height,
z
, in the
troposphere, from a globally averaged surface air temperature of 287.5 K to
about 218 K at the top of the troposphere, which is known as the
tropopause
.
Pressure decreases from about 1000 hPa at the surface (the globally averaged
value is generally taken as 1013 hPa) to about 200 hPa at the tropopause.
Almost all the atmosphere's water resides in the troposphere, as does about
80% of its mass.
The
stratosphere
lies above the tropopause, extending to about 48 km or 1
hPa, and is capped by the
stratopause
. It is a vertically stable, stratified region—
hence its name—in which temperature increases with altitude. The
mesosphere
(“middle sphere”) stretches from the stratopause to about 80 km, with temper-
ature again decreasing with height. The region of transition to interplanetary
space, above 80 km, is the
thermosphere
.
100
0.001
Thermosphere
90
80
0.01
Mesopause
70
0.1
60
Mesosphere
50
1
Stratopause
40
Stratosphere
10
30
20
100
Figure 2.8 Globally
and annually averaged
atmospheric temperature
as a function of height and
pressure.
10
Tropopause
Troposphere
1000
160
180
200
220 240 260
Temperature (K)
280
300
