Abstract
This chapter provides a report on how the fluxes of trace gases can be validated among different scales. A variety of techniques determine the trace gas fluxes, including chamber, micrometeorological, and airborne methods. Micrometeorological measurements of oceanic fluxes pose additional problems. For many trace gases, the fluxes between the ocean and the atmosphere are small compared to fluxes between terrestrial ecosystems and the atmosphere. This causes technical problems related to the detection limits of instruments. Two distinct methods exist to derive fluxes using atmospheric models—that is, forward simulations and inverse methods. In forward atmospheric modeling, emissions are used to drive the atmospheric model to predict concentrations and fluxes. Inverse methods use observations of atmospheric concentrations to derive flux estimates. Both methods can be applied at all scale levels. In many cases, fluxes can be determined with different techniques, used simultaneously. Inverse methods use observations of atmospheric concentrations to derive flux estimates.