Atmospheric test of the J(BrONO2)/kBrO+NO2 ratio: implications for total stratospheric Bry and bromine-mediated ozone loss 1Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany
02 Jul 2013
2Laboratoire de Physique Moléculaire pour l'Atmosphère et l'Astrophysique (LPMAA), Université Pierre et Marie Curie, Paris, France
3Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, UK
4National Centre for Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, UK
5Institute for Space Sciences, Free University Berlin, Berlin, Germany
Received: 26 Sep 2012 – Published in Atmos. Chem. Phys. Discuss.: 23 Oct 2012Abstract. We report on time-dependent O3, NO2 and BrO profiles measured by limb observations of scattered skylight
in the stratosphere over Kiruna (67.9° N, 22.1° E) on
7 and 8 September 2009 during the autumn circulation turn-over. The observations are complemented by
simultaneous direct solar occultation measurements around sunset and sunrise
performed aboard the same stratospheric balloon
payload. Supporting radiative transfer and photochemical modelling indicate
that the measurements can be used to constrain
the ratio J(BrONO2)/kBrO+NO2,
for which at T = 220 ± 5 K an overall 1.7 (+0.4 −0.2) larger
ratio is found than recommended by the most recent Jet Propulsion Laboratory (JPL) compilation (Sander et al., 2011).
Sensitivity studies reveal the major reasons are likely to be (1)
a larger BrONO2 absorption cross-section σBrONO2, primarily for wavelengths larger than 300 nm,
and (2) a smaller kBrO+NO2 at 220 K
than given by Sander et al. (2011). Other factors, e.g.
the actinic flux and quantum yield for the dissociation of BrONO2, can be ruled out.
Revised: 30 Apr 2013 – Accepted: 02 Jun 2013 – Published: 02 Jul 2013
The observations also have consequences for total inorganic stratospheric bromine (Bry) estimated from stratospheric
BrO measurements at high NOx loadings, since the ratio J(BrONO2)/kBrO+NO2 largely
determines the stratospheric BrO/Bry ratio during daylight. Using the revised
J(BrONO2)/kBrO+NO2 ratio, total stratospheric Bry is likely to be 1.4 ppt smaller
than previously estimated from BrO profile measurements at high NOx loadings. This would bring estimates of Bry
inferred from organic source gas measurements (e.g. CH3Br, the halons, CH2Br2,
CHBr3, etc.) into closer agreement with estimates based on BrO observations (inorganic method). The consequences
for stratospheric ozone due to the revised J(BrONO2)/kBrO+NO2 ratio are small (maximum −0.8%),
since at high NOx (for which most Bry assessments are made) the enhanced ozone loss by overestimating Bry is
compensated for by the suppressed ozone loss due to the underestimation of BrO/Bry with a smaller
Citation: Kreycy, S., Camy-Peyret, C., Chipperfield, M. P., Dorf, M., Feng, W., Hossaini, R., Kritten, L., Werner, B., and Pfeilsticker, K.: Atmospheric test of the J(BrONO2)/kBrO+NO2 ratio: implications for total stratospheric Bry and bromine-mediated ozone loss, Atmos. Chem. Phys., 13, 6263-6274, doi:10.5194/acp-13-6263-2013, 2013.