Atmospheric Chemistry and Physics Discussions
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2006
10.5194/acpd-6-10063-2006
http://www.atmos-chem-phys-discuss.net/6/10063/2006/
http://www.atmos-chem-phys-discuss.net/6/10063/2006/acpd-6-10063-2006.html
http://www.atmos-chem-phys-discuss.net/6/10063/2006/acpd-6-10063-2006.pdf
10063
10086
2006-10-11
Lightning-produced NO<sub>2</sub> observed by two ground-based UV-visible spectrometers at Vanscoy, Saskatchewan in August 2004
A. Fraser
F. Goutail
C. A. McLinden
S. M. L. Melo
K. Strong
Department of Physics, University of Toronto, Toronto, Ontario, Canada
Service d’Aéronomie du Centre Nationale de la Recherche Scientifique, Verrières le Buisson, France
Environment Canada, Downsview, Ontario, Canada
Space Science, Canadian Space Agency, Saint-Hubert, Québec, Canada
Ground-based measurements of ozone and NO<sub>2</sub> slant columns by the SAOZ
(Système d'Analyse par Observations Zénithales) and UT-GBS (University of
Toronto Ground-Based Spectrometer) instruments during the MANTRA 2004 field
campaign are presented herein. During the afternoon of 28 August, a
thunderstorm passed over the instruments, which were installed at Vanscoy,
Saskatchewan (52° N, 107° W). Enhanced slant columns of ozone and
NO<sub>2</sub> were observed by both instruments during the storm, with maximum
values of two and 25 times the expected columns, respectively. The enhanced
ozone slant columns are primarily due to the longer path traversed by the
solar radiation caused by multiple scattering inside the thick cloud layer
associated with the thunderstorm. The enhanced NO<sub>2</sub> columns are attributed
to NO<sub>x</sub> production by lightning. Two different methods are used to separate
the NO<sub>2</sub> enhancements into contributions from the longer path length and
production by lightning. Combining the observed excess NO<sub>2</sub> with lightning
flash data from the Canadian Lightning Detection Network and Environment
Canada Doppler radar measurements, the production of NO<sub>2</sub> molecules per
lightning flash is determined. Using these two methods, the best estimate of
the production rate is found to be (7.45±1.38)×10<sup>26</sup> molecules
NO<sub>2</sub>/flash from the UT-GBS and (6.58±1.21)×10<sup>26</sup> molecules
NO<sub>2</sub>/flash from SAOZ. These results are consistent with previous estimates
which range from 10<sup>26</sup> molecules NO<sub>2</sub>/flash (Noxon, 1976) to (7±3)×10<sup>26</sup> molecules NO<sub>2</sub>/flash (Franzblau and Popp, 1989).