ANNALES GEOPHYSICAE, VOL. 26, 1255-1268, 2008
Parameterisation of the chemical effect of sprites in the middle atmosphere
1Sodankylä Geophysical Observatory, Sodankylä,
2Dept of Physics and Astronomy, Leicester University, UK,
3Dept of Geophysics, Tohoku University, Sendai, Japan,
4Danish National Space Center, Technical University of Denmark, Copenhagen, Denmark,
5Earth Observation Unit, Finnish Meteorological Institute, Helsinki, Finland,
6Dept of Physics, National Cheng Kung University, Tainan, Taiwan.
Transient luminous events, such as red sprites, occur in the middle atmosphere in the electric field above thunderstorms. We here address the question whether these processes may be a significant source of odd nitrogen and affect ozone or other important trace species. A well-established coupled ion-neutral chemical model has been extended for this purpose and applied together with estimated rates of ionisation, excitation and dissociation based on spectroscopic ratios from ISUAL on FORMOSAT-2. This approach is used to estimate the NOx and ozone changes for two type cases.
The NOx enhancements are at most one order of magnitude in the streamers, which means a production of at most 10 mol per event, or (given a global rate of occurrence of three events per minute) some 150-1500 kg per day. The present study therefore indicates that sprites are insignificant as a global source of NOx. Local effects on ozone are also negligible, but the local enhancement of NOx may be significant, up to 5 times the minimum background at 70 km in extraordinary cases.
© 2008 by the European Geosciences Union. Further electronic publication not allowed.
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