Geoscience Reference
In-Depth Information
100
Thermosphere
0.0001
0.0005
80
Mesopause
0.001
0.005
Mesosphere
0.01
60
0.05
Stratopause
0.1
40
0.5
1
Stratosphere
5
20
10
Figure 1.2
Idealized vertical
temperature profile for the
US Standard Atmosphere
showing the most important
layers, 'spheres, and the
'pauses' that separate them.
Tropopause
Troposphere
50
0
160
100
180
200
220
Temperature (K)
240
260
280
300
The relative concentration of atmospheric nitrogen, oxygen and other inert
gases is uniform with height, but most ozone is found in the middle atmosphere
where it absorbs ultraviolet radiation to warm the air. The concentration of carbon
dioxide falls away in the mesosphere and the vast majority of atmospheric water
vapor is found within 10 km of the ground, mainly in the lower levels of the
troposphere. The fact that water vapor content falls quickly with height is strongly
related to the fall in temperature with height. The amount of water vapor that air
can hold before becoming saturated is less at lower temperatures and water is
precipitated out as water droplets or ice particles in clouds. The concentrations of
liquid and solid water in clouds and that of other atmospheric constituents,
including solid particles such as dust particles, sulfate aerosols, and volcanic ash,
all vary substantially both in space and with time.
As previously mentioned, the residence time for water in the atmosphere is
short, about 10 days. In fact, a comparatively short response time is a general
feature of the atmosphere that distinguishes it from the other components of the
climatic system. Air has a relatively large compressibility and low specific heat and
density compared to the fluids and solids that make up the hydrosphere,
cryosphere, lithosphere and biosphere. Because air is more fluid and unstable, any
