Nitrogen dioxide, tropospheric sources

Ozone forms in the upper stratosphere from molecular oxygen under the influence of UV solar radiation. In the lower stratosphere and troposphere, the source of ozone is the decomposition of nitrogen dioxide under the influence of UV and visible radiation. The formation of the vertical profile of ozone concentration is connected with its meridional and vertical transport. The general characteristic of this profile is the total amount of ozone measured by the thickness of its layer given in Dobson units (1 DU = 0.001 cm). 

The source of nitric oxide in the unpolluted troposphere is the photodissociation of nitrogen dioxide, which leads to the reactions... 

Nitrogen oxides play an important role in the photochemistry of the troposphere, controlling the formation of tropospheric O3, affecting the concentration of the hydroxyl radical, and contributing to acid precipitation. Nitrogen dioxide (NO2) is one of the most important reactive nitrogen species its photolysis is the primary source of O3 in the troposphere (see Section 28.6 for further details on the actual chemical processes and rates). 

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