Unformatted text preview: ncentration is low. In this chapter we will
review the effects of air pollutants on the ozone layer, on the Earth's temperature, and on other phenomena
related to the atmosphere. Regions of the Atmosphere. For convenience the atmosphere is divided into four regions with respect
to altitude. The lowest region is the troposphere. This region extends up to about 10 km. The temperature
decreases with altitude in the troposphere from about 25°C at sea level to –55°C at 10 km. The troposphere
contains about 80% of the mass of the atmosphere and virtually all the precipitation, clouds, and water vapor.
All the weather occurs in the troposphere. Remember that the atmosphere gradually thins out as the altitude
increases. The atmospheric pressure at 10 km is about 230 mm Hg. 3 56
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Above 10 km we enter the stratosphere which extends upward to 50 km. In the stratosphere the temperature
increases with altitude from about –55°C at 10 km to –10°C at 50 km. The atmospheric pressure at 50 km is
only 0.5 mm Hg. For the most part there is very little mixing of the contents of the troposphere and the
Above the stratosphere we enter the mesosphere. As in the troposphere, the temperature decreases with
altitude, falling to –90°C at 80 km. From 80 km to 100 km we find the ionosphere (also called the
thermosphere). In this region, the temperature increases slightly with increasing altitude. The region gets its
name from the ions that are produced there by high energy solar radiation. The temperatures associated with the
different regions of the atmosphere are shown in Figure 17.3 of the text. Auroral Displays. Chemical processes in the ionosphere produce the phenomena called "northern lights,"
or aurora borealis in the Northern hemisphere and aurora australis in the Southern hemisphere. In Chapter 7 you
learned that excited atoms emit light when electrons ju...
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This note was uploaded on 09/15/2009 for the course CHEM 102 taught by Professor Bastos during the Spring '08 term at Adelphi.
- Spring '08