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Instrument: TOTCAP : Tropospheric Ozone and Tracers from Commercial Aircraft Platforms
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NASA's Atmospheric Effects of Aviation Program (AEAP) is charged
with the effects of aircraft on climate and on the chemistry of
the atmosphere. Much of this effort has been dedicated to
interpretation of atmospheric observations and prediction of
the impact of future aircraft fleets using two-and
three-dimensional models. However, some of the information
needed to assess aircraft impacts is lacking. In response, the
Tropospheric Ozone and Tracers from Commercial Aircraft
Platforms (TOTCAP) project was conceived as a means to gather a
long-term data set that would address transport in the
tropopause region. Students in Linnea Avallone's group and LASP
technical staff have designed and tested a suite of instruments
that measures several trace gases. Although ultimately this
instrument package will be flown on commercial (revenue)
aircraft, it was initially deployed on NASA's DC-8 flying
laboratory during the SOLVE campaign to study ozone loss in the
northern hemisphere. Four i ndependent chemical sensors are
packaged into a single unit that operates autonomously.

Measurements of ozone (by ultraviolet absorption), water vapor
(by near-infrared tunable diode laser spectroscopy), carbon
dioxide (by near-infrared absorption), and short-lived
halocarbons (by gas chromatography) are made continuously
during aircraft flight, every second for O3, H2O and CO2, and
every four minutes for halocarbons. The wide range of lifetimes
and source/sink processes for these compounds provide the means
to assess the relative importance of various transport
processes in determining the chemical composition of the
tropopause region. A more complete understanding of these
processes (e.g., convection, stratosphere-troposphere exchange)
is essential to the construction of realistic atmospheric
models that are used to assess the impact of aviation. Until
applications on commercial aircraft become a reality, the
instruments will be used in other projects to study chemistry
and transport in the troposphere.

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[Summary provided by University of Colorado]