GENERAL COMMENTS

This paper addresses the response of noctilucent clouds (NLCs) to solar cycle variations in Lyman alpha irradiance. A combination of two 3-D atmospheric models is used to fully capture both background atmosphere variations and ice particle microphysics. H2O response to Lyman alpha variations is shown to have a clear altitude dependence, with positive correlation above 83 km (due to temperature increase) and negative correlation below 83 km (due to photolysis). Increasing the abundance of greenhouse gases (CO2, CH4) amplifies the H2O response. The apparent lack of H2O and NLC solar cycle variation after 2005 (noted by previous authors) is attributed to the reduced amplitude of Lyman alpha variations and the cancellation of H2O effects caused by averaging vertically over the 80-85 km region.

This paper is well written. The background discussion is comprehensive, the modeling studies follow a logical progression, and the identification of relevant mechanisms is presented very nicely. I have only a few minor comments.

SPECIFIC ITEMS

1. p. 2, lines 27-28: This sentence partially duplicates the sentence on lines 22-24.

1. p. 2, lines 32-34: This sentence partially duplicates the statements on lines 17-20.

1. p. 6, line 135: Are these data taken from the LASP Interactive Solar Irradiance Data Center (LISIRD)?

1. p. 14, lines 335-338: The current solar cycle (Cycle 25) has already reached higher Lyman alpha irradiance values than the peak of Cycle 24, and is not expected to reach its maximum until 2025. You may wish to comment briefly on possible NLC and H2O behavior during the next few years compared to previous solar cycles, since greenhouse gas concentrations continue to increase.

1. p. 17, line 435: There are no locations listed for data availability.

TYPOGRAPHICAL AND GRAMMATICAL CHANGES

p. 1, line 17: “correlate” should be “correlates”

p. 5, line 106: “calculate” should be “calculates”

p. 6, line 136: I would say “other spectral bands” for clarity

p. 6, line 139: “continiums” should be “continuums”

p. 10, line 234: I would write “this change affects” or “these changes affect”, depending on whether you are referring to temperature only or both temperature and solar irradiance

p. 15, line 375: “solarcycle” should be “solar cycle”

The manuscript describes the response of water vapor (H2O) and noctilucent clouds (NLC) to solar variability. To explain this process the authors applied two models (LIMA and MIMAS) because they can simulate the behavior of H2O and temperature (which are responsible for NLC formation) during different solar activity states. The idea of the manuscript is interesting and original. The manuscript will be of interest to the community. I support publication with minor corrections described below.   

Minor issues:

Lines 14-16: Potentially solar activity can also affect the circulation and transport of the H2O and CH4 from the troposphere.

Lines 27-28: In absolute or relative values? 

Lines 33-34: Little explanation of the mechanism would be nice. 

Lines 50: Which trends? Any trends?

Lines 72-78: Has it been already performed and described somewhere, or it is planned for the current manuscript? These lines are confusing because after that they mentioned the goals of the paper.  Some rewriting would be nice to distinguish between the introduction and motivation. 

Lines 101: What is the lower atmosphere here?

Lines 103: Does it mean that GWD forcing is fixed and does not depend on the solar cycle?  

Figure 1: CH4 looks strange. It has no source, no effects. 

Lines 115-116: But there is H2O photolysis. Why only CH4?

Lines 118: 40 million is enough? Any justification? What is the source and properties of the dust particles? 

Lines 137: Only H2O? CH4 is not photolyzed?

Lines 139-140: HAMMONIA is not the original source for the photolysis code. Would it be TUV or something else?  What is taken from Lean et al. (1997)? The description of the used spectral solar irradiance is not clear. Obviously, there is an inconsistency between H2O photolysis in the two used models.   

Lines 157-159: Maybe it depends on the location. Some anti-correlation for the ‘late’ period is visible in satellite data (see 10.5194/acp-21-201-2021).

Lines 161-162: Do the authors mean temperature effect from solar variability or from GHG or from GWD via circulation?  

Line 223: It is important to emphasize the novelty of the results in Fig.4 compared to the mentioned literature.  

Lines 253: to atmospheric absorption by which species. Should be another maximum lower down due to ozone absorption. 

Lines 275: ‘increase’ or ‘production’ is missing

Lines 390-391: Is LIMA really an atmospheric transport model? In lines 97-98, I see ‘which calculates winds and temperature’.

Lines 423-425: Why is this not the case for HALOE data?

Conclusions: It would be nice to discuss limitations (e.g., fixed GWD) and uncertainties in the applied models. I would also expect some discussion about the statistical significance of the results related to the internal variability of the model based on first principles.