Environmental Engineering Reference
In-Depth Information
Figure 6.21
Classification of atmospheric layers depending on their altitude [135].
values. In particular, the tropopause temperature is higher near the equator and
lower at the poles. The stratosphere lies above the tropopause up to the stratopause
at an altitude of (50
5) km, and the temperature of the stratosphere increases
with altitude and reaches 270
˙
20 K in the stratopause. In the mesosphere, which
starts from the stratopause, the temperature drops up to 160-190 K at an altitude of
85-100 km. At higher altitudes the temperature of the atmosphere increases with
increasing altitude. Figure 6.21 gives definitions of some atmospheric layers de-
pending on their altitude [135].
This behavior of the temperature of the atmosphere results from the heat bal-
ance of the atmosphere at these altitudes. In particular, most of the ozone is in the
stratosphere, and absorption of VUV solar radiation by ozone leads to an increase
of the temperature of the stratosphere compared with neighboring regions. On the
basis of the temperature gradient at low altitudes near the Earth's surface one can
find the contribution of the heat flux
q
due to the thermal conductivity of air to the
Earth's heat balance. Our estimate for the heat flux resulting from thermal con-
ductivity is
q
˙
10
8
W/cm
2
, whereas according to the data in
Table 6.7, convection is responsible for an average heat flux of 2
D j
dT
/
dz
jD
3
10
3
W/cm
2
,
which is significantly more.
