This is a long paper, and it seems to border somewhere between comprehensive and tedious.  It would be nice for the science issues to be separated from the listing of values for each and every model for each and every variable.  Perhaps the paper could be made quite a bit shorter, with many of the details moved to the appendix, for those interested in them.  The conclusions are that models are different from each other and different from the available observations.  But what now?  Why is this?  What specifically has to be addressed to improve them?  And how important are these climatologies for non-volcanic periods?  How much do these differences affect their responses to volcanic eruptions or potentially to climate intervention?

There are problems with several of the plots.  The complete seasonal cycle is not plotted, with the variations from December to January missing.  Italics should not be used for units.  Many of the contour labels cannot be read with a background very similar to the text.  Units for pressure should be hPa, and not Pa.

In many places, “notably” or “It should be noted” are used, and all should be deleted.  Every sentence in the paper should be noted or it should not be in the paper. 

Several acronyms, including SAOD and UTLS are not defined.  And for SAOD, at what wavelength?  And SAD is defined multiple times.

Northern Hemisphere and Southern Hemisphere are names and should be capitalized.  And it would be better to use NH and SH as acronyms for them throughout the paper rather than just occasionally.

The 56 comments in the attached manuscript all have to be addressed.

General comments

The paper presents a comparison of time-slice simulations by 9 chemistry climate models for a volcanically quiet situation. The idea goes back to a SSIRC (Stratospheric Sulfur and its Role in Climate) meeting in 2013 and a paper in 2018. The results show that the outliers are models with inappropriate horizontal resolution (e.g. Lofverstrom and Liakka, 2018) or with lack of important parts of sulfur chemistry. This should be addressed also in the conclusions.

A problem in the generally well written paper is that available satellite observations of OCS and middle atmospheric SO₂ and the reanalysis data (ERA5 or ERA-I) are not used in the comparisons but only multi-model averages instead (except for the tropopause height). This should be improved before publication.

Specific comments

Line 30: A reference to Watts (2000) would be useful here too (also in line 324).

Line 243ff: Which sulfur species are included? This model is the only one where this information is missing.

Line 263 or 282: Two important datasets are missing: MIPAS OCS by Glatthor et al. (2017) and MIPAS SO₂ up to 45 km (Höpfner et al., 2013). This should be also included in Figure 1 and later.

Line 392: Add: "and missing OCS, see later".

Line 550: This is in contradiction to MIPAS data.

Figure 6: Please include MIPAS data (caution with averaging kernel effect, Glatthor et al., 2017).

Line 584: Replace "polar" by "Antarctic".

Figure 7: Fill in MIPAS data in panel k. Here it might be useful to display only the ones of Höpfner et al. (2013) which show the secondary maximum due to OCS photolysis and also the increase in the middle stratosphere simulated e.g. by WACCM. 

Line 628ff: Modify corresponding text. 

Figure A1: Please comment on outgassing volcanoes in caption. Compared to standard references some important ones appear to be missing in scenario NAT.

Figure A3: Why is there no comparison with ERA-I?

Technical corrections

Figure 1: Some fonts too small.

Figure 3: Please include more ticks at the abscissa in panels a-e. List the peak values of ULAQ in panels s,t in the caption. Include a remark there that panel u-y include only a subset of models (?).

Line 348: Include "e.g.".

Line 548: Typo in volcano name.

Figure 5 and 6: Is there a gap between Dec 15 and Jan 15? This looks odd, please improve that.

Line 656: Typo or grammar problem.

Figure A2-A4: Consider superscripts for the units in the captions.

Please correct several typos in author names and missing subscripts in the reference list. There are also wrong links (lines 1065 and 1114). Don't repeat identifiers several times (line 816f).

References

  Glatthor, N., M. Höpfner, A. Leyser, G. P. Stiller, T. von Clarmann, U. Grabowski, S. Kellmann, A. Linden, B.-M. Sinnhuber, G. Krysztofiak, and K.A. Walker: Global carbonyl sulfide (OCS) measured by MIPAS/Envisat during 2002–2012,  Atmos. Chem. Phys., 17, 2631–2652, doi:10.5194/acp-17-2631-2017, 2017.

  Höpfner, M., N. Glatthor, U. Grabowski, S. Kellmann, M. Kiefer, A. Linden, J. Orphal, G. Stiller, T. von Clarmann, B. Funke, and C. D. Boone: Sulphur dioxide (SO₂) as observed by MIPAS/Envisat: Temporal development and spatial distribution at 15–45 km altitude, Atmos. Chem. Phys., 13, 10,405–10,423, doi:10.5194/acp-13-10405-2013, 2013.

  Lofverstrom, M. and J. Liakka: The influence of atmospheric grid resolution in a climate model-forced ice sheet simulation, The Cryosphere, 12, 1499–1510, doi:10.5194/tc-12-1499-2018, 2018.

  Watts, S.F.: The mass budgets of carbonyl sulfide, dimethyl sulfide, carbon disulfide and hydrogen sulfide, Atmos. Environ., 34, 761–779, 2000.