The results of laboratory measurements described in the previous
section, combined with simple chemical/dynamical models, reveal
which chemical constituents should be measured and what
atmospheric/photochemical conditions are likely to be the most
important ones to consider. The task then becomes to devise
experimental methods suitable for the analysis of the atoms,
molecules and radicals of interest. Often, laboratory parameters
such as the absorption cross section provide a basis for the
analytical technique. Thus, lab measurements serve the needs of
both the modeling and the observational communities in
atmospheric science.
This section will survey a few important experimental approaches to making ambient measurements of the atmosphere's chemical composition. We begin with satellite approaches, which are used at the largest possible spatial scales to give global distributions of gases in the middle and lower atmosphere. We proceed to techniques that are applied at smaller and smaller spatial scales, concluding with the case in which small volumes of air are retrieved in containers and taken to the laboratory for analysis.