the substance that controls the absorption of solar radiation in the earth’s atmosphere. At low altitudes, where standard conditions of pressure and temperature prevail (760 mm Hg and 0°C), the average thickness of the ozone layer is negligible, ranging from 2.5 to 3 mm. This value drops to 2 mm in equatorial regions and reaches a maximum of 4 mm at high latitudes. Most of the atmospheric ozone is distributed in a layer, the ozonosphere, at altitudes between 10 and 50 km, with maximum concentration occurring between 20 and 25 km. The ozone level in the troposphere is very low and varies with time and altitude.
The formation and distribution of atmospheric ozone at different altitudes may be explained by the photochemical theory. Since ozone readily absorbs radiation in several spectral regions, especially at wavelengths below 2,900 angstroms, the extremely biologically active segment of the solar radiation spectrum never reaches the earth’s surface. The marked increase in temperature in the ozone layer is a result of this absorption.
Atmospheric ozone is studied by analyzing samples of air from various altitudes and by optical devices, such as spectro-photometers, which can be set up on the earth’s surface or launched into the atmosphere on balloons or rockets.