Review of “Influences of sudden stratospheric warmings on the ionosphere above Okinawa” by Hocke et al.

The manuscript presents results of the impact of sudden stratospheric warmings (SSWs) on the ionosphere based on a long-term observational record. The observations are based on the ionosonde at Okinawa, and cover the time period from 1972-2023, encompassing 29 SSW events. The ionosonde observations are used to determine the influence of SSWs on the solar semidiurnal tide. The authors additionally find enhancements in the diurnal, semidiurnal, and terdiurnal lunar tides. Although a number of previous studies have investigated the influence of SSWs on the ionosphere, they have primarily focused on case studies. The present study is based on 29 SSW events, and thus provides a statistical view of how SSWs impact the ionosphere. The results are therefore new and would be suitable for publication. However, prior to publication I believe that several aspects of the manuscript need to be clarified. Specific detailed comments are provided below.

1. In order to understand variability that is not related to SSWs, the authors perform a composite analysis of the variability in years without SSWs. Though I agree with the approach that the authors have taken, I believe that they should provide additional details about the no SSW events. The no SSW years are referenced to a central date (e.g., Figures 3 and 4); however, in the absence of a SSW it is not clear how the central date is determined. The authors should provide additional details on how the central date is defined for the no SSW cases. Additionally, for scientific reproducibility, I suggest that the authors include a listing of the years that are used for the no SSW cases.

2. In lines 123-124, the authors state that “we start with foF2 since the composite shows a clearer effect than for NmF2”. Since foF2 and NmF2 are directly related to each other, one would expect that the results for foF2 and NmF2 are also similar, though perhaps scaled differently since NmF2 ~ foF2^2. Furthermore, it is unclear to the reviewer why having foF2 being the original measurement (lines 124-125) would impact the results since the conversion from foF2 to NmF2 does not introduce additional errors. The authors should provide additional explanation as to why the conversion from foF2 to NmF2 influences the results.

3. The authors state that “the SSW effect [in NmF2] is not so obvious as for foF2” (line 142). However, Figure 3 shows the absolute values of foF2 and Figure 4 shows the relative values for NmF2. It is therefore difficult to directly compare the results. Would the enhancements be similar if both are shown in either absolute or percentage variations?

4. In determining the results for Figure 5, do the authors consider the effects of geomagnetic activity? Although such effects may be small in the composite analysis, for any individual event it is possible that geomagnetic effects could large. It is recommended that the authors consider only using geomagnetically quiet days when determining the maximum amplitude in any given year.

The manuscript titled 'Influences of sudden stratospheric warmings on the ionosphere above Okinawa' by Hocke et al. provides a fresh take on the impact of SSWs on the ionosphere. The past 15 years of research on this topic has mostly focused on the SSW effects at low-latitudes, with few studies reporting on the effects at mid- and high-latitudes. This observational work is noteworthy in the sense that it is analyzing multiple SSW events and provides statistical results of the SSW effects at Okinawa through composite analysis of NmF2 and foF2. The authors have made a dexterous use of the long-term  NmF2 and foF2 observations at Okinawa in this study and that should be commended. Of particular interest, is the analysis of the lunar tides in NmF2 and the new discovery of terdiurnal lunar tidal enhancement during SSWs is particularly a novel finding. This manuscript provides a lot of new results that will be of great interest to the aeronomy community. I recommend that the paper should be accepted after a minor revision mainly due to its novel findings.

Minor comments:

Line 18: Please be more specific with regards to the reversal of the zonal mean zonal wind of the stratospheric polar vortex.

Line 43: ‘latitudes’

Line 56: ‘whether’

Line 82: bracket is missing in the citation of McInturff (1978)

Line 141: The authors mention that the effect of SSW is not so obvious in NmF2 as for fof2. It will be better if the authors could elaborate on the reason behind this statement as it is not discussed anywhere later in the manuscript.