Interactive comment on “ Diurnal variations of stratospheric ozone measured by ground-based microwave remote sensing at the Mauna Loa NDACC site : measurement validation and GEOSCCM model comparison ” by

The diurnal variation of ozone in the stratosphere and lower mesosphere is analyzed using data from a ground-based microwave radiometer operating at the Mauna Loa NDACC station since the 1990s. Presented are considerations concerning the internal quality of the measurements, a verification study of the quality of the observed diurnal variability in comparison with external data sets obtained from different satellite instruments, and model comparisons aiming at testing the modelled ozone diurnal variation in a chemistry-climate model.

lieve much in the TIMED/SABER results on the diurnal ozone variation at stratospheric altitudes.They look quite shaky and seem to be not consistent.Actually the present Parrish et al. study is most convincing since their radiometer measures the complete daily cycle at an high-altitude station.The observational results of Haefele et al. and Studer et al. (2013) are also good and in agreement with Parrish et al. but a rest risk remains in the data retrieval of Haefele and Studer because of the high tropospheric opacity at a low altitude station such as Bern or Payerne.Thus the main point seems to be that Parrish et al. give for the first time a really clear observational evidence of the daily cycle of stratospheric ozone.I would suggest that the authors communicate this crucial point in a clear manner in the revised version.
Response: We would make this point by comparing the typical tropospheric opacity value at Mauna Loa to the value it would have at a low altitude midlatitude station in the instrument description section in a revised manuscript.
Comment: p.31858, line 6, the equation for photolysis of O2 is missing Response: Thanks for noticing this.We would add it in a revised manuscript.
Comment: p.31878, last sentence: "The good agreement between MWR, Aura-MLS, UARS-MLS, and SMILES suggests that the last three, together with the model, can be used to estimate such adjustments over a wider range of latitudes."I disagree with this statement.The authors did not make a model validation at polar latitudes where model simulations of ozone photochemistry, polar vortex variations and tides are much more difficult than at mid-latitudes.
Response: We agree that this is an overstatement and would remove it in a revised manuscript.
Comment: Acknowledgments: I am missing an acknowledgment to the ISSI ozone team where most of the authors participated.
Response: Thanks for noticing this.We would add the acknowledgement in a revised C12844 manuscript.

Referee 2:
Comment: Analyzing the magnitude of the diurnal variation of stratospheric and mesospheric ozone is nothing really new.In the introduction I would have expected to see a more comprehensive summary of previous work (historical and recent) on the subject.Whilst most of the early work focussed on the mesosphere, some of these studies contain also results for the mid to upper stratosphere and at different latitudes.In order to place the new work in an appropriate (historical) context, I suggest that the authors amend this part and refer the interested reader to relevant earlier work addressing ozone diurnal variation.
Response: We would do this in a revised manuscript, referring to the measurements by Haefele et al. (2008), Connor, et al. (1994), Ogawa, et al. (1996), and Studer et al. (2013), and discuss some differences between these results.We chose these papers because they report results from the stratosphere as well as the mesosphere.Because the focus of this work is on the afternoon enhancement in the stratosphere, we don't plan to include results from papers that present only results in the mesosphere.We would add this material at line 19 on page 31860.
Comment: Results obtained in this study on the magnitude of the ozone diurnal variation in the stratosphere (Sections 3 and 4) should then also be compared with results from previous studies by different authors.What is consistent with earlier work and what is new in this study?
Response: As we remarked in response to a comment by referee #1, it is difficult to know how meaningful direct comparisons between measurements made at tropical and midlatitude locations will be, but we would comment on shared features between the present and previously published results iin a revised manuscript, noting the point that there could be differences between tropical and midlatitude results.
our resolution is about at the limit of that obtainable with a fixed, ground-based, remote sensing instrument that is capable of observations over the complete diurnal cycle.Higher resolution is available with satellite-borne limb sounding instruments.We commented on issues with satellite measurements in section 1.We would clarify language in a revised manuscript to make these points.

Anonymous Referee #3
Comment: This paper presents an intercomparison of ozone datasets with the aim to tease out small diurnal variations in stratospheric ozone.The comparisons are thorough, convincing and certainly merit publication.While this is a potentially very good paper, I did feel, however, that they didn't go quite far enough.As the authors do note, there is a rich literature on this from Huang et al and also Haefele and yet the authors do not adequately place their results in context with these earlier studies.Do they agree?For example for Day 85, Huang et al (2010) (their Figure 5) show a decrease in the afternoon at 30 hPa which they believe to be real.It appears, based upon the comments at the very end of Section 4, that the present authors disagree.If so, they should say so.
Response: We do not agree with the 10% decrease at 16h that Huang et al. ( 2010) reported.We see a 2% decrease at that time and altitude.We would discuss this issue in a revised manuscript.
Comment: The final comparison of the present paper is limited to March.One wonders if another figure for a solstice case would be any different For example, Huang et al [2010] show both day 85 and day 180 analyses and Haefele et al have a section on seasonal variations.Perhaps at the relatively low latitudes of Hawaii, seasonal variations are less important.But this would be good to clarify.I do not think the above comments would require much work to address; however, I certainly would suggest adding another figure, for a different season, to complement Figure 8 and another couple of paragraphs of discussion where they put their results in context.

C12848
Response: Model results for March were the only ones available at the time our paper was submitted.Results for other months only became available in January 2014.We propose to replace Figure 8 with two similar figures showing results for winter and summer, because the contrast between these two seasons is the largest.Results for spring and autumn are nearly identical and generally lie between the winter and summer results.
Comment: Since the existence of the afternoon stratospheric ozone enhancement is not a new result, their results are more of a confirmation (albeit the most comprehensive that has been presented) rather than a discovery and this should be explicitly stated.
Response: We would replace the sentence "However, ground-based microwave measurements by Haefele. .."beginning on page 31860 line 14 with "Haefele et al. ( 2008) also reported the afternoon enhancement based on their ground-based microwave measurements and attributed it to continuing ozone formation during the day through reaction (2) and the relatively high density and consequent low O/O3 ratio" in a revised manuscript.
Very minor comment: For Figure 3, I was a bit confused (line 15 of text) Which of the colored curves is the best?Is it the black curve?Is this what is used to create the bottom panel?
Response: The black curve is best, and it was used to make the lower panel.We will clarify the caption.