PEroxy rAdicals measured by OF-Cavity Enhanced spectroscopy in the free troposphere with a focus on the upper troposphere / lower stratosphere (PEACE)
Final Report Abstract
Accurate knowledge of the amount and distribution of tropospheric peroxy radicals is necessary and essential to test our understanding of the chemistry of the troposphere. The production and loss of these short lived species which comprise the hydroperoxyl (HO2) and the organic peroxy radicals (RO2; R = organic chain), are intrinsically linked to the majority of the oxidative processes occurring in the troposphere. The airborne measurement of peroxy radicals is challenging because of their small concentrations and mixing ratios, and results in a limited number of unequivocal measurements. The DFG project PEACE (PEroxy rAdicals measured by OF-Cavity Enhanced spectroscopy in the free troposphere with a focus on the upper troposphere/lower stratosphere), proposed the development of a new airborne instrument with suitable accuracy and sensitivity for the sampling and detection of atmospheric peroxy radicals. on the research HALO platform (High altitude and long range research aircraft). As a resulf of the above, the PEACE project was a strongly experimental driven project, which necessitated the delivery of a system able to measure the sum of HO2 and RO2* from the fast flying airborne platform HALO, the first of its kind. Within PEACE the Institute of Environmental Physics of the University of Bremen (IUP-UB) continued the development of the PeRCEAS (Peroxy Radical Cavity Enhanced Absorption Spectrometer) instrument, by optimally combining the PeRCA (Peroxy Radical Chemical Amplification) and the CEAS (Cavity Enhanced Absorption Spectroscopy) / CRDS (Cavity Ring Down Spectroscopy) measurement techniques, for its deployment in HALO missions. The HALO flight mission OMO: Oxidation Mechanism Observations, proposed to study and assess our understanding of the oxidation mechanisms and radical chemistry in the free troposphere, provided a first opportunity to exploit the novel and unique capability offered by the HALO aircraft for the deployment of PeRCEAS. For a variety of organisational technical reasons, associated with bringing the HALO platform into routine service, the start of the OMO mission was delayed. Additional support of the DFG enabled the successful participation of the PeRCEAS instrument in the reschedule OMO campaign in summer 2015 and the first observations of peroxy radicals form this platform in different tropospheric air masses. Therefore one important achievement of PEACE was the development optimisation and characterisation of an instrument which was deployed not only within OMO on HALO but also in test campaigns on other aircraft and in a ground based study. This instrument, its design and validation has been published. PEACE also improved our knowledge of proposed approaches to make speciated measurements of HO2 and RO2. Apart from the development of the state of the art instrument, its use to observe peroxy radical mixing ratios during OMO was a particular highlight of PEACE. The highest mixing ratios of the peroxy radicals were measured in the range 80-100 pptv in photochemically active air masses at 5-6 km altitudes over the Arabian Peninsula, North Africa and the eastern Mediterranean region. The interpretation of these results is in preparation for publications. At altitudes above 10-12 km the concentration of peroxy radicals yielded upper limits. Finally the experience gained during OMO allowed for further improvements of the instrument technique concerning stability and detection limits which enables the altitude range of the measurements in the troposphere to be extended.
Publications
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Peroxy radical observations over West Africa AMMA 2006: Photochemical activity in the outflow of convective systems, ACP, 9, 3681- 3695, 2009
Andrés- Hernández, M.D., Kartal, D., Reichert, L., and Burrows, J.P., Meyer Arnek, J., Lichtenstern, M., Stock, P., Schlager, H.
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Atmospheric composition of West Africa: highlights from the AMMA international program. Atmospheric Science Letters
Mari, C. H., Reeves, C. E., Law, K. S., Ancellet, G., Andrés-Hernández, M. D., Barret, B., Bechara, J., Borbon, A., Bouarar, I., Cairo, F., Commane, R., Delon, C., Evans, M. J., Fierli, F., Floquet, C., Galy-Lacaux, C., Heard, D. E., Homan, C. D., Ingham, T., Larsen, N., Lewis, A. C., Liousse, C., Murphy, J. G., Orlandi, E., Oram, D. E., Saunois, M., Serça, D., Stewart, D. J., Stone, D., Thouret, V., Velthoven, P. v. and Williams, J. E.
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Peroxy radical partitioning during the AMMA radical intercomparison exercise, Atmos. Chem. Phys., 10, 10621-10638
Andrés-Hernández, M. D., Stone, D., Brookes, D. M., Commane, R., Reeves, C. E., Huntrieser, H., Heard, D. E., Monks, P. S., Burrows, J. P., Schlager, H., Kartal, D., Evans, M. J., Floquet, C. F. A., Ingham, T., Methven, J., and Parker, A. E.
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Technical Note: Characterisation of a DUALER instrument for the airborne measurement of peroxy radicals during AMMA 2006, ACP, 10, 3047-3062, 2010
Kartal, D., Andrés- Hernández, M.D., Reichert, L., Schlager H., and Burrows, J.P.
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Frequency stabilization of blue extended cavity diode lasers by external cavity optical feedback, Applied Physics B - Lasers & Optics
Horstjann, M., Nenakhov, V., and Burrows, J.P.
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In situ trace gas measurements. In: Wendisch, M. and J.L. Brenguier (Eds.), Airborne Measurements for Environmental research: methods and instruments, Wiley–Blackwell, 2013, ISBN 978-3-527-40996-9
M.D. Andrés Hernández
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Peroxy radical detection for airborne atmospheric measurements using absorption spectroscopy of NO2, Atmos. Meas. Tech. 7, 1245-1257
Horstjann, M., Andrés Hernández, M. D. , Nenakhov, V., Chrobry, A., and Burrows, J. P.
