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www.atmos-chem-phys-discuss.net/9/18793/2009/
doi:10.5194/acpd-9-18793-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
Peroxy radicals and ozone photochemistry in air masses undergoing long-range transport
1Department of Chemistry, University of Leicester, Leicester, LE1 7RH, UK
2School of Environmental Sciences, University of East Anglia, Norwich, UK
3Department of Chemistry, University of York, York, UK
4School of Chemistry, National Centre for Atmospheric Science (NCAS), University of Leeds, Leeds, LS2 9JT, UK
5Department of Meteorology, University of Reading, UK
6Norsk Institutt for Luftforskning, P.O. Box 100, 2027 Kjeller, Norway
*now at: PC2A, Université des Sciences et Technologies de Lille, France
**now at: MPI, Mainz, Germany
***now at: Department of Chemistry Univ of Reading, Reading, UK
Abstract. Concentrations of peroxy radicals (HO2+ΣiRiO2) in addition to other trace gases were measured onboard the UK Meteorological Office/Natural Environment Research Council British Aerospace 146-300 atmospheric research aircraft during the Intercontinental Transport of Ozone and Precursors (ITOP) campaign based at Horta Airport, Faial, Azores (38.58° N, 28.72° W) in July/August 2004. The overall peroxy radical altitude profile displays an increase with altitude that is likely to have been impacted by the effects of long-range transport. The peroxy radical altitude profile for air classified as of marine origin shows no discernable altitude profile. A range of air-masses were intercepted with varying source signatures, including those with aged American and Asian signatures, air-masses of biomass burning origin, and those that originated from the east coast of the United States. Enhanced peroxy radical concentrations have been observed within this range of air-masses indicating that long-range transported air-masses traversing the Atlantic show significant photochemical activity. The net ozone production at clear sky limit is in general negative, and as such the summer mid-Atlantic troposphere is at limit net ozone destructive. However, there is clear evidence of positive ozone production even at clear sky limit within air masses undergoing long-range transport, and during ITOP especially between 5 and 5.5 km, which in the main corresponds to a flight that extensively sampled air with a biomass burning signature. Ozone production was NOx limited throughout ITOP, as evidenced by a good correlation (r2=0.72) between P(O3) and NO. Strong positive net ozone production has also been seen in varying source signature air-masses undergoing long-range transport, including but not limited to low-level export events, and export from the east coast of the United States.
Discussion Paper (PDF, 7412 KB) Interactive Discussion (Closed, 4 Comments) Publication in ACP not foreseen
Citation: Parker, A. E., Monks, P. S., Jacob, M. J., Penkett, S. A., Lewis, A. C., Stewart, D. J., Whalley, L. K., Methven, J., and Stohl, A.: Peroxy radicals and ozone photochemistry in air masses undergoing long-range transport, Atmos. Chem. Phys. Discuss., 9, 18793-18838, doi:10.5194/acpd-9-18793-2009, 2009. Bibtex EndNote Reference Manager XML
