the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 29 Aug 2025
Validation of SNPP OMPS limb profiler version 2.6 ozone profile retrievals against correlative satellite and ground based measurements
Abstract. The Ozone Mapping and Profiler Suite Limb Profiler (OMPS LP) was launched onboard the Suomi National Polar-orbiting Partnership (SNPP) satellite in 2011 and began routine science operations in April 2012. The OMPS LP uses measurements of scattered solar radiation in the ultraviolet, visible and near infrared wavelengths to retrieve high vertical resolution profiles of ozone from 12 km (or cloud tops) up to 57 km. In mid-2023, version 2.6 of the OMPS LP ozone profile retrievals was released, featuring improvements in calibration, the retrieval algorithm, and data quality. We evaluate OMPS LP version 2.6 ozone retrievals using correlative data from other satellite instruments and ground based data for the period April 2012 to April 2024. Our results show agreement between OMPS LP and all correlative data sources between 20 and 50 km at all latitudes with differences of less than 10 %, with OMPS generally exhibiting a negative bias, except between 32 and 38 km in the tropics and southern mid-latitudes, where the bias is positive. In the tropics and southern mid-latitudes the differences between OMPS LP and MLS, and OMPS LP and SAGE III/ISS are less than ±5 % between 20 and 45 km. Above 50 km, the agreement with MLS is still on the order of -5 % or better. Larger positive biases, up to ~35 %, are seen in the upper troposphere lower stratosphere layer (~15 to 20 km) between approximately 40° South and 40° North. We find that OMPS version 2.6 ozone exhibits the same seasonal cycle as compared to all correlative measurement sources and our analysis shows that there is no significant seasonal bias in the OMPS LP. We find small drifts relative to correlative observations at all latitude bands of less than ±0.2 %/yr (±0.1 %/yr) between 25 and 50 km for the 2012–2024 period, with larger drifts above 50 km and below 20 km. These small drifts vary between correlative measurements and straddle the zero line, we therefore conclude that there is no significant systematic drift in OMPS LP version 2.6 ozone for the period 2012 to 2024. The drift results represent an improvement in the long term stability of version 2.6 ozone over that of version 2.5.
Competing interests: Some authors are members of the editorial board of Atmospheric Measurement Techniques.
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2025-4117', Anonymous Referee #1, 22 Sep 2025
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RC2: 'Comment on egusphere-2025-4117', Anonymous Referee #2, 22 Sep 2025
The manuscript provides a validation of the SNPP OMPS-LP v2.6 ozone dataset. Validation is done primarily with comparisons to MLS/ACE/SAGE III/ISS, but also other data sources like ozonesondes, lidar, and OMPS-NP. It is an important paper to be in the literature since OMPS-LP is poised to become the backbone of vertically resolved global ozone measurements in the near future. Overall the flow is easy to follow, presents useful information, and should be published subject to some revisions. My main suggestion is that the information could be summarized better for data users, specifically the estimated drift levels for the dataset.
General Comments
The choice to not degrade SAGE III/ISS to a similar resolution I don't think has a justification other than convenience. While it doesn't change any of the main conclusions of the paper in my opinion, various statements in the discussion are likely because of this choice. For example, the significantly degraded correlation with SAGE at high altitudes, or some of the increased oscillations noted in the drift analysis. I would suggest the SAGE III/ISS data be smoothed to approximately the same resolution as OMPS-LP and the analysis repeated.
The paper is long, I don't believe it is too long, but there is a lot of information. What might be useful is to provide a summary table (something akin to the MLS data quality document tables) of observed drifts/estimated accuracy for the v2.6 data products based on the analysis done here to better provide easy to digest recommendations to users of the data.
I find the stability discussion not to be wrong, but maybe is too optimistic in some places. Specifically the statement "We therefore conclude that there is no significant systematic drift in OMPS LP version 2.6 ozone for the period 2012 to 2024 and that it is suitable for use in ozone trend studies." which may not technically be incorrect, but the numbers presented are 2%/decade from 20-50 km and becoming larger outside. Statements like "We find small drifts ... of less than 2%/decade ..." may not that be useful to potential users of the data trying to attribute changes of 1%/decade, which is the level that most trend studies would be looking at. I think this is solved if a summary table is included with estimated drift levels so the user can decide if it is useful for their application, as well as maybe a softening of the blanket statement that the dataset is suitable for ozone trend studies.
Specific Comments
l. 98. There should be a more detailed explanation of how this study differs from the v2.6 validation already done by Kramarova et al. (2024)
l. 102. The motivation/wording here seems like a repeat of what is at the start of Sec. 6, and the Sec. 6 wording does a better job of motivating how OMPS-LP could be validated going forward. On the same topic, I know it is outside the scope of the paper, but there is no mention anywhere (that I could find) of the potential of validating/cross-calibrating OMPS-LP based on the overlap between NPP and N21 or future satellites.
l. 112. Here the evaluation period is stated as ending June 2024, but earlier it was April 2024?
l. 130. At this point the co-location criteria has not been stated, but there are figures showing coincidences which is slightly confusing.
l. 150. I believe SAGE III/ISS does extend to +/- 70 degrees latitude? albeit for a very limited time of the year
l. 180. I know in previous studies since Aura and NPP are in similar orbits you can get almost perfect coincidences between MLS and OMPS-LP. Is that is what is done here? Or is the same criteria applied to MLS?
l. 184. "The only time criterion is that the profiles be on the same day..." is this actually what is done or is it a +/- 12 hour window around the observation time?
l. 186. "... do not account for the small differences in the vertical resolution..." this is true for MLS and ACE, but the SAGE vertical resolution is significantly better than OMPS-LP
l. 203. "To the 1:30 pm local solar time ..." the measurement time is only 1:30 pm at the equator, presumably you mean to the actual measurement time of OMPS-LP?
l. 206. When I read this paragraph I thought it meant that we would only be seeing results from the wide latitude bands, but that is not the case. I would reword it or move it after the 5 degree zonal means comparisons are done
Sec 5.1: I find the systematic difference between MLS and SAGE interesting here, specifically in Figure 4 you could interpret it as MLS being ~5% higher than SAGE almost everywhere. This is quite different than say what is reported in the Wang et al. validation of SAGE. I know it's different data versions etc, and doesn't have anything to do with OMPS-LP, but I'm wondering if you noticed this and is it expected.
Fig. 4: I find it hard to quantify the differences from the color plots since the scale is so large. Perhaps some black contour lines could be added to the for example +/- 10% difference levels to guide the reader?
l. 237. Does the altitude biases correlate with the changing wavelengths used in the retrieval in altitude?
l. 250. "degraded precision and increased noise for SAGE III/ISS measurements...": yes, but a lot of this is probably because of using the raw 0.5 km SAGE measurements instead of degrading it down to the resolution of the other measurements
Fig. 5: Is there some motivation for the line at 0.75?
l. 307. "However, these biases are not seen when compared to MLS." is a possible explanation uncertainties in the diurnal scaling?
Figure 8: The scales here are really quite large, here we are extending to +/- 20%/decade, when observable ozone trends are ~1%/decade
l. 497. Here the drift is calculated until the end of 2021 at low altitudes, presumably because of the Hunga influence. But this wasn't done in comparisons with the other instruments, so it is an issue with OMPS NP? It seems odd.
l. 522. "Previously, we limited our comparisons geographically to exclude polar regions" I think some of the comparisons with MLS previously did extend to 80?
Figure 12. It is odd here to use two significantly different scales, 10% for the NP comparisons and 50% for the MLS comparisons. Also error bars are only shown for the NP comparisons?
Figure 13. Here we are also back to using the full time period with NP drift calculations instead of just to 2021
Sec 8. This section is quite short, and all of the information is in the other sections in some shape or form. I would ask the authors to consider if it could be removed.
Technical Corrections
l. 484. "OMP SNP" -> "OMPS NP"
Citation: https://doi.org/10.5194/egusphere-2025-4117-RC2
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This manuscript provides a comprehensive overview of the validation of OMPS LP v2.6 ozone profiles, discussing biases with comparative observations and the long-term stability of the SNPP dataset. This work is an extension and integration of the Kramarova et al. 2024 study, which presented the OMPS LP v2.6 retrieval. The paper is well-written and well-structured, presenting the results of the validation in a clear way. Particularly interesting is the focus provided in several parts of the paper on finding a valuable set of correlative data to be used for validation, in a future with fewer limb observations available.
I have a few minor comments to the manuscript, which are listed below and a few technical corrections.
Technical corrections
L20: I would remove “the” from “the retrieval algorithm”.
L30: Also here I would remove “the” from “the OMPS LP”.
L41-43: possible re-formulation of the sentence: “These increases are consistent with model simulation showing that they arise from a combination of ozone-depleting substances concentrations and decreasing upper-stratospheric temperatures, driven by increasing CO2”.
L48: “and so trends have large uncertainties” → “leading to large uncertainties in trends”.
L61: I would remove “when validating such data”
L85: “which is more pronounced” → ”which was more pronounced”.
L101: Possibly mention also that the altitude range over which ozonesondes can be used for validation is limited to about 30 km.
L112: Is the period until April 2024 or June? For lidar December 2024 is mentioned.
L130: “with which to compare with” → “to use for the comparison with”
L152: Since the v6 became recently available and you also mention it, I would avoid saying “the latest version”.
L175-177: I find the two sentences in these two lines very similar: isn’t the accuracy estimated by the comparison with other data sets?
L216: It is Fig. 4 not 1.
L257: The sentence is not very clear to me. Could it be that the variability of OMPS retrievals at the ozone peak is lower than for the other datasets?
L338: I think you mean between 20 and 30 km.
L379: I would add “above 20 km” at the end of the sentence.
L425: Maybe repeat the word between to make it less confusing: “and between OMPS LP and ozonesondes”.
L484: Typo in OMPS NP.
L615: Remove , after “consistent”.
References
Benito‐Barca, Samuel, et al. "Recent lower stratospheric ozone trends in CCMI‐2022 models: Role of natural variability and transport."Journal of Geophysical Research: Atmospheres 130.9 (2025): e2024JD042412.
Godin-Beekmann, Sophie, et al. "Updated trends of the stratospheric ozone vertical distribution in the 60° S–60° N latitude range based on the LOTUS regression model." Atmospheric Chemistry and Physics Discussions 2022 (2022): 1-28.
Petropavlovskikh, Irina, et al. "SPARC/IO3C/GAW report on Long-term Ozone Trends and Uncertainties in the Stratosphere." 26 Feb. 2019.