Comment on acp-2020-1228

This is an interesting paper showing the efforts made by the authors to model the SMILES measured HO2 chemical signature associated to sprite streamer chemical activity in the mesosphere (70 80 km). What is the final cause of the measured HO2 increase?. There are no clear conclusions in the paper since available measurements and model results do not completely match. There is not a clear causal link between the enhanced HO2 observations and the sprite streamer + transport modeling described in this paper. The paper is mostly clear and well written. There are, however, some comments I would like to make.

This is an interesting paper showing the efforts made by the authors to model the SMILES measured HO 2 chemical signature associated to sprite streamer chemical activity in the mesosphere (70 -80 km). What is the final cause of the measured HO 2 increase?. There are no clear conclusions in the paper since available measurements and model results do not completely match. There is not a clear causal link between the enhanced HO 2 observations and the sprite streamer + transport modeling described in this paper. The paper is mostly clear and well written. There are, however, some comments I would like to make.

Satellite observations
This section is devoted to briefly explain SMILES measurements from the ISS of enhanced mesospheric HO 2 over sprite-producing thunderstorms.
Already here the authors indicate that ISUAL detected three thunderstorm systems producing sprites prior to SMILES observations. Authors also highlight that WWLLN indicated strong lightning activity in these 3 thunderstorms systems and that more sprites than those detected by ISUAL could have been occurred.
I miss here a thorough discussion about the 3 thunderstorms systems producing the sprites that seem to have triggered HO 2 detections by SMILES. In particular, how many positive and negative lightning occurred?. What were their corresponding charge moment change (CMC)?. Where (and when) did they occur?. It is known (see Qin et al. GRL 2013) that lightning CMC values can largely determine the type/morphology of sprite (columnar or carrot-like). In particular, CMCs > 500 C km favor carrot sprites, while column sprites (with less streamers) are usually associated to lightning with CMCs lower than ~ 500 C km. I think that an exhaustive analysis of those 3 thunderstorm systems is crucial here because they critically condition the frequency and type of sprites produced.
At least one carrot sprite (associated to event A) was reported in Yamada et al. GRL 2020 (see Figure 1d). A sprite halo with downward many propagating streamers looking like the onset of a carrot sprite (event B, see Figure 1e in Yamada et al. GRL 2020) was also detected by ISUAL prior to measurements by SMILES. The image shown in figure 1f of Yamada et al. GRL 2020 also seems to be a carrot-like sprite.

Sprite chemistry and vertical transport simulations
Line 147: I would replace "afterglow region" by streamer glow or streamer trailing glow region. The word "afterglow" somehow indicates chemical delayed reactions, but the chemistry in sprite glows are driven by an active electric field (~Ek).
In a time-integrated image of a sprite, the image is mostly dominated by the sprite glows (see Stenbaek-Nielsen and McHarg, JPD-AP 2008). Streamers only leave relatively faint traces in long exposure images. Thus, if we consider optical emissions as a driver for energy input into the mesosphere, this implies that the main local energy dissipation is in the sprite streamer trailing glows and beads, as studied by Parra-Rojas et al. JGR-Space Physics (2015). Line 232: Suggest to replace: "... the concentration of HO 2 increases." by "... the concentration of HO 2 slightly increases above ambient values." Line 235-236: The red dashed line is missing in Fig. 10.
Line 255-260: What types of sprites are reported by Heavner et al. (2000), Kuo et al. 2008 andTakahashi et al. 2010?. The ~10e22 photons per sprite streamer is a reasonble number that agrees with available detailed simulations. The 10e24 photons per sprite could be typical of column-like sprites (with some tens to a few hundreds of streamers).
I agree in that it is unlikely that the measured HO 2 enhancenment is only due to 3 sprites.
As said above, a careful analysis of the the 3 thunderstorms and the produced types (lightning polarities, CMCs, ...) of sprites (column/carrot, producing infrasound?, ...) would be important to advance in the understanding of the underlying reasons leading to HO 2 enhancements in the mesosphere.
Finally, it would also be interesting if the authors could show a plot of the model predicted ozone (O 3 ) density, whether it is predicted to stay the same, increase or decrease at 75 km, 77 km and 80 km. SMILES did not measure a clear change of O 3 due to sprite chemical activity.

Recommendation:
I think this paper could be published in ACP. However, before final acceptance, the authors should try to appropiately address the comments / questions stated above.