HR: 1400h
AN: A33A-16    [Abstracts]
TI: Peroxy Radical Behavior During MIRAGE and INTEX-B as Measured Aboard the NSF/NCAR C- 130
AU: * Anderson, R S
EM: rsa@ucar.edu
AF: NCAR, P.O. Box 3000, Boulder, CO 80307-3000, United States
AU: Cantrell, C A
EM: cantrell@ucar.edu
AF: NCAR, P.O. Box 3000, Boulder, CO 80307-3000, United States
AU: Eisele, F
EM: eisele@ucar.edu
AF: NCAR, P.O. Box 3000, Boulder, CO 80307-3000, United States
AU: Kosciuch, E
EM: kosciuch@ucar.edu
AF: NCAR, P.O. Box 3000, Boulder, CO 80307-3000, United States
AU: Mauldin, R L
EM: mauldin@ucar.edu
AF: NCAR, P.O. Box 3000, Boulder, CO 80307-3000, United States
AU: McCoy, J
AF: NCAR, P.O. Box 3000, Boulder, CO 80307-3000, United States
AB: We report measurements of HO₂ and HO₂+RO₂ made onboard the NSF/NCAR C-130 using our Peroxy Radical Chemical Ionization Mass Spectrometer (PeRCIMS) during the MIRAGE-Mex and INTEX-B field campaigns in the spring of 2006. Separation of HO₂ and HO₂+RO₂ was achieved by varying the [NO]/[O₂] ratio in the PeRCIMS inlet. At small ratios, most RO₂ radicals are measured efficiently, while at larger ratios the measurement efficiency of most RO₂ radicals is reduced to less than 0.15 of the HO₂ measurement. The O₂ concentration is changed by diluting the air sample containing the radicals by half with either O₂ or N₂. Likewise, the reagent gas concentrations are varied by a factor of 10. Comparisons between observations and box model calculations show relatively good agreement for NO mixing ratios below 1 ppb. As NO mixing ratios increase, the box model predicts decreases for both hydroperoxy and organic peroxy radicals, with values nearing zero in air masses where NO exceeds 5 ppbV while our measurements show little change compared to those at lower NO values. We also present comparisons of the ratios of HO₂ to HO₂+RO₂ in urban air masses, air masses heavily influenced by fires, and air masses in the marine boundary layers of the Pacific Ocean and the Gulf of Mexico. We compare these ratios with ratios predicted from box models.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly