Development and testing of a new whole air sampler for use on the NASA Global Hawk aircraft during the Airborne Tropical Tropopause Experiment (ATTREX)

A new whole air sampler was developed to study trace gas chemistry in the upper troposphere and lower stratosphere for the Airborne Tropical Tropopause Experiment (ATTREX). The sampler collects up to 90 samples per flight for measurement of a range of hydrocarbons, halocarbons, organic nitrates and solvents. Hydrocarbons and short-lived organic halogen gases play an important role in the chemistry of the of the upper troposphere/lower stratosphere (UT/LS) region. The characterization of these gases not only provides information on air mass sources and transport time scale, but also defines the reactive halogen budget and the conditions for the stratospheric chemistry that affects ozone depletion rates. As part of the transition between troposphere and stratosphere, nonmethane hydrocarbons (NMHC) and halocarbons reach the Tropical Tropopause Layer (TTL) where chemical and physical processes determine their fate. However, very limited data are available regarding composition, seasonality and variability of these gases, since only high altitude aircraft can reach this region of the atmosphere (>13-14 Km). In November 2011, we flew the new whole air sampling system on 2 research flights. A total of 173 samples were collected during flights of approximately 16-24 hours long, which sampled air in the upper troposphere over the tropical Pacific Ocean at altitudes from 14 - 19 km. Measurements of trace gases were done in the University of Miami (UM) laboratory using a combination of gas chromatography with mass spectrometric, flame ionization, and electron capture detectors. This presentation focuses on the design of the new University of Miami-Advanced Whole Air Sample (UM_AWAS), describes the operation of the instrument components, and shows preliminary results of selected hydrocarbon and halogen concentrations in the TTL region.