Chemical Meters/Analyzers
type: Concept

TOTCAP
type: Concept
definition: 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 t…
in scheme: instruments