Preprints
https://doi.org/10.5194/acp-2020-1228
https://doi.org/10.5194/acp-2020-1228

  05 Jan 2021

05 Jan 2021

Review status: this preprint is currently under review for the journal ACP.

Model simulations of chemical effects of sprites in relation with satellite observations

Holger Winkler1, Takayoshi Yamada2, Yasuko Kasai2,3, Uwe Berger, and Justus Notholt1 Holger Winkler et al.
  • 1Institute of Environmental Physics, University of Bremen, Germany
  • 2Terahertz Technology Research Center, National Institute of Information and Communications Technology, Japan
  • 3Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, Japan
  • deceased, 4 April 2019 (Leibniz-Institute of Atmospheric Physics, Kühlungsborn, Germany)

Abstract. Recently, measurements by the Superconducting Submillimeter-Wave Limb Emission Sounder (SMILES) satellite instrument have been presented which indicate an increase of mesospheric HO2 above sprite producing thunderstorms. These are the first direct observations of chemical sprite effects, and provide an opportunity to test our understanding of the chemical processes in sprites. In the present paper, results of numerical model simulations are presented. A plasma chemistry model in combination with a vertical transport module was used to simulate the impact of a streamer discharge in the altitude range 70–80 km, corresponding to one of the observed sprite events. Additionally, a horizontal transport and dispersion model was used to simulate advection and expansion of the sprite volumes. The model simulations predict a production of hydrogen radicals mainly due to reactions of proton hydrates formed after the electrical discharge. The net effect is a conversion of water molecules into H + OH. This leads to increasing HO2 concentrations a few hours after the electric breakdown. According to the model simulations, the HO2 enhancements above sprite producing thunderstorms observed by the SMILES instrument can not solely be attributed to the detected one sprite event for each thunderstorm. The main reason is that the estimated amount of HO2 released by a sprite is much smaller than the observed increase. Furthermore, the advection and dispersion simulations of the observed sprites reveal that in most cases only little overlap of the expanded sprite volumes and the field of view of the SMILES measurements is expected.

Holger Winkler et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2020-1228', Anonymous Referee #1, 18 Jan 2021
  • RC2: 'Comment on acp-2020-1228', Anonymous Referee #2, 09 Feb 2021

Holger Winkler et al.

Holger Winkler et al.

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Short summary
Sprites are electrical discharges above thunderstorms. In recent years, model simulations of chemical effects of sprites have been presented but no measurements were available. For the first time we were able to compare model results with satellite observations which show an increase of reactive hydrogen due to sprites. According to our simulations, sprites lead to a conversion of water molecules in hydrogen radicals. This can serve as an explanation for the observed enhancements of hydrogen.
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