Environmental Engineering Reference
In-Depth Information
2.1.2
Atmosphere
The atmosphere of the earth is defined as the gaseous atmosphere held by the
gravitational force of the earth. It is divided into different "layers" (Fig. 2.4). Only
the lower layers are of particular interest for the use of renewable energies on the
surface of the earth. For the use of wind power, the atmosphere up to an altitude
of, at most, several 100 m is significant.
The lower section of the atmosphere is called the troposphere. It is the atmos-
pheric layer that influences the weather and where formation of clouds and pre-
cipitation mainly takes place. In a timely and spatial average, it is characterised by
a temperature decrease with increasing altitude. The extent of this temperature
change depends on location and time. The temperature gradient can fluctuate
within relatively large boundaries around a mean value of 0.65 K/100 m. Under
certain meteorological circumstances, vertically sharply defined layers occur
where the temperature does not decrease with increasing altitude, but increases
instead. Such inversions occur particularly often at altitudes between 1,000 and
2,000 m at the planetary boundary layer (Chapter 2.3.1) as well as immediately
above the surface of the earth ("soil inversions") and at the tropopause.
The boundary of the troposphere is the tropopause connected to the strato-
sphere. Within the stratosphere, a temperature maximum is reached at an altitude
of 40 to 50 km. The next atmospheric layer is the mesosphere; it reaches the next
temperature extreme, a minimum at an altitude of approximately 80 km. Above it,
demarcated by the mesopause, is located the thermosphere.
Air pressure in mbar
-6
-5
-4
-3
-2
-1
0
1
2
3
-7
10
10
10
10
10
10
10
10
10
10
10
160
Temperature
140
Thermosphere
Polar lights
120
100
Mesopause
80
Air pressure
Meteors
Mesosphere
Stratopause
60
40
Stratosphere
20
Clouds
Tropopause
Troposphere
Mount Everest
0
-200
-100
0
100
200
300
400
500
600
700
Temperature in °C
Fig. 2.4
Cross-section through the atmosphere (see /2-2/)
Up to an altitude of around 100 km, the atmosphere consists of a mixture of
different gases (Table 2.1). The proportion of its ingredients is as defined as a
chemical compound. This gaseous mix is - especially in the troposphere - mixed
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