The science of atmospheric chemistry measurement is continuing its evolution
towards more selective, sensitive and robust techniques. The increasing
level of sophistication is also making possible the measurement of new
species. For example, there have been recent advances in the determination
of the OH radical, the species which is so crucial to the chemistry
of the lower atmosphere. Going beyond the measurement of concentration,
many field campaigns now incorporate the measurement of fluxes (exchanges)
of trace gases, such as O3, CO, CH4,
and H2O. The advance of chemical instrumentation,
combined with increasingly sophisticated techniques of modeling the chemistry
and dynamics of the atmosphere, will continue to enhance our understanding
of atmospheric chemistry. The advances are urgently needed as we strive
to find solutions for several problems which humans have posed for our
planet's atmosphere.