About this exercise type...

There are several reasons why an improved knowledge of the global stratospheric and especially tropospheric distribution of NO_x is important:

• NO_xand _ are emitted in large quantities from human activities such as traffic and industry. In the summer months this mixture can produce smog.
• The chemical budget of _ in the _ is largely determined by the concentration of NO_x.
• Our knowledge of the distribution of _ is severely limited by a lack of information about the concentrations of NO and NO₂ in the _.
• NO_x contributes to _, and with decreasing SO₂ emissions its role in causing acidity is increasing.
• In the _, NO_x has a large impact on _ levels. On the one hand it can destroy _ catalytically, but on the other hand it also forms stable reservoir species with _, thereby reducing _ depletion.