title: Observational Constraints on the Oxidation of NOx in the Upper Troposphere.
abstract: NOx (NOx ≡ NO + NO2) regulates O3 and HOx (HOx ≡ OH + HO2) concentrations in the upper troposphere. In the laboratory, it is difficult to measure rates and branching ratios of the chemical reactions affecting NOx at the low temperatures and pressures characteristic of the upper troposphere, making direct measurements in the atmosphere especially useful. We report quasi-Lagrangian observations of the chemical evolution of an air parcel following a lightning event that results in high NOx concentrations. These quasi-Lagrangian measurements obtained during the Deep Convective Clouds and Chemistry experiment are used to characterize the daytime rates for conversion of NOx to different peroxy nitrates, the sum of alkyl and multifunctional nitrates, and HNO3. We infer the following production rate constants [in (cm(3)/molecule)/s] at 225 K and 230 hPa: 7.2(±5.7) × 10(-12) (CH3O2NO2), 5.1(±3.1) × 10(-13) (HO2NO2), 1.3(±0.8) × 10(-11) (PAN), 7.3(±3.4) × 10(-12) (PPN), and 6.2(±2.9) × 10(-12) (HNO3). The HNO3 and HO2NO2 rates are ∼ 30-50% lower than currently recommended whereas the other rates are consistent with current recommendations to within ±30%. The analysis indicates that HNO3 production from the HO2 and NO reaction (if any) must be accompanied by a slower rate for the reaction of OH with NO2, keeping the total combined rate for the two processes at the rate reported for HNO3 production above.
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Nault
authors.forename: Charity
authors.initials: C
authors.lastname: Garland
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Wooldridge
authors.affiliation: Department of Meteorology, Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: William H
authors.initials: WH
authors.lastname: Brune
authors.affiliation: Cooperative Institute for Research in the Environmental Sciences and Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Pedro
authors.initials: P
authors.lastname: Campuzano-Jost
authors.forename: John D
authors.initials: JD
authors.lastname: Crounse
authors.affiliation: Cooperative Institute for Research in the Environmental Sciences and Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Day
authors.affiliation: Earth Systems Research Center, Institute for the Study of Earth Oceans and Space, University of New Hampshire , Durham, New Hampshire 03824, United States.
authors.forename: Jack
authors.initials: J
authors.lastname: Dibb
authors.affiliation: Atmospheric Chemistry Division, National Center for Atmospheric Research (NCAR) , Boulder, Colorado 80307, United States.
authors.forename: Samuel R
authors.initials: SR
authors.lastname: Hall
authors.affiliation: School of Earth and Atmospheric Sciences, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
authors.forename: L Gregory
authors.initials: LG
authors.lastname: Huey
authors.affiliation: Cooperative Institute for Research in the Environmental Sciences and Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: José L
authors.initials: JL
authors.lastname: Jimenez
authors.affiliation: School of Earth and Atmospheric Sciences, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
authors.forename: Xiaoxi
authors.initials: X
authors.lastname: Liu
authors.affiliation: Geophyiscal Fluid Dynamics Laboratory, National Oceanic and Atmospheric Administration , Princeton, New Jersey 08540, United States.
authors.forename: Jingqiu
authors.initials: J
authors.lastname: Mao
authors.affiliation: Oak Ridge Associated Universities , Oak Ridge, Tennessee 37831, United States.
authors.forename: Tomas
authors.initials: T
authors.lastname: Mikoviny
authors.affiliation: Chemical Sciences Division, Earth System Research Lab, National Oceanic and Atmospheric Administration , Boulder, Colorado 80305, United States.
authors.forename: Jeff
authors.initials: J
authors.lastname: Peischl
authors.affiliation: Chemical Sciences Division, Earth System Research Lab, National Oceanic and Atmospheric Administration , Boulder, Colorado 80305, United States.
authors.forename: Ilana B
authors.initials: IB
authors.lastname: Pollack
authors.affiliation: Air Resources Laboratory, National Oceanic and Atmospheric Administration , College Park, Maryland 20740, United States.
authors.forename: Xinrong
authors.initials: X
authors.lastname: Ren
authors.affiliation: Chemical Sciences Division, Earth System Research Lab, National Oceanic and Atmospheric Administration , Boulder, Colorado 80305, United States.
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Ryerson
authors.affiliation: Earth Systems Research Center, Institute for the Study of Earth Oceans and Space, University of New Hampshire , Durham, New Hampshire 03824, United States.
authors.forename: Eric
authors.initials: E
authors.lastname: Scheuer
authors.affiliation: Atmospheric Chemistry Division, National Center for Atmospheric Research (NCAR) , Boulder, Colorado 80307, United States.
authors.forename: Kirk
authors.initials: K
authors.lastname: Ullmann
authors.forename: Paul O
authors.initials: PO
authors.lastname: Wennberg
authors.affiliation: Institute of Ion Physics and Applied Physics, University of Innsbruck , 6020 Innsbruck, Austria.
authors.forename: Armin
authors.initials: A
authors.lastname: Wisthaler
authors.affiliation: Department of Meteorology, Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Cohen