Comment on acp-2021-224

The paper compares, among four high-altitude analyses, the representation of the zonalmean temperature and wind and the amplitudes of planetary and tidal waves. The result serves as an initial estimate of uncertainty of the high-altitude analyses. The analysis period is not long but benefits such an estimate by including an important phenomenon of wintertime variations, the sudden stratospheric warming. Although this is an initial analysis (based on the authors' statements), the result already contains plenty of information, and I believe that it will provide a useful insight that can contribute to the future improvement of the middle-atmosphere assimilation and to the whole-atmosphere modeling.

The paper compares, among four high-altitude analyses, the representation of the zonalmean temperature and wind and the amplitudes of planetary and tidal waves. The result serves as an initial estimate of uncertainty of the high-altitude analyses. The analysis period is not long but benefits such an estimate by including an important phenomenon of wintertime variations, the sudden stratospheric warming. Although this is an initial analysis (based on the authors' statements), the result already contains plenty of information, and I believe that it will provide a useful insight that can contribute to the future improvement of the middle-atmosphere assimilation and to the whole-atmosphere modeling.
The paper is written in a logical manner, and the quality of presentation of the results is good. I recommend this paper for publication with technical corrections. Please check the below.
[ Specific comments ] (mostly technical) L19 : "can" consistently represent ? If you would mean that they are currently consistent, it seems to be contradictory to the "large discrepancies" in L29. L64 : I would suggest removing "(non-orographic)" because this could be misleading (as there exist primary orographic waves in general).
L96 : "in the equatorial region the lack of wind measurements …" L100 : "that" to "than" L117 : Maybe one of the two "constrained" might be removable.
L159 : "horizontal and vertical" or "zonal and meridional" ? (By the way, has there been a place where v or w is used for this intercomparison ?) L183 : "produces global synoptic gridded atmospheric data sets" : repetitive (L159) Section 2.1-2.4 : Horizontal and vertical resolutions of the four models : Would these be easier to read from a table rather than from the text in each section ?
L226 : "for the surface" to "from the surface" L227-228 : Maybe the second "system" (L228) should be removed. L384-385 (also in L464 and L495) : "suggesting that differences in the treatment of gravity wave drag may be a primary factor explaining the large differences among the analyses above 80 km" : Provided the existence of the difference in parameterized GW processes between models (which I fully agree), what would be the role of the differences in the data assimilation methods ? Would the larger difference between WACCMX+DART and the others than the difference among the latter three (shown in Figs. 2 and 3) mean that the difference in GW parameterization is also larger for WACCMX+DART from the others ? L420 : "eastward" : Would it be "westward" ? L500 : I would suggest changing "Difference among ... in the analyses" to "The spread of ... among the analyses".
L516 : "addition" L521 : "in daily-mean temperature at …" L548 : "in each hemisphere during summer" : It was not clear to me. Is it mean the northern summer ? Or, the solstices ?
L554 : "4-6 days" ? (or 0.24 cpd ?) L555 : "high-altitude" to "high-latitude" ? L599 : "seasonal" to "altitude" ? L601-609 and L639-641 : In these lines, the day-to-day variations of tides associated with SSWs in previous studies are being discussed. I would suggest moving this content to L653 where I see it is more relevant , as the current paragraphs are explaining the monthly mean amplitudes of tides.) L611-612 : "latitude and ... January 2010" : repetitive (L599-600) L620-622 : The peak amplitude of the tide seems to appear slightly (5-10 km) below the top of each model. Would it be related to some damping mechanisms near the model top ? L717 : I would suggest adding "at the equator" after "50 km altitude".