Estimates of Tropospheric Ozone from Nimbus 7 LIMS and TOMS Datasets

Remsberg, Ellis

doi:10.5194/egusphere-2026-3796

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https://doi.org/10.5194/egusphere-2026-3796

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07 Jul 2026

| 07 Jul 2026

Status: this preprint is open for discussion and under review for Atmospheric Measurement Techniques (AMT).

Estimates of Tropospheric Ozone from Nimbus 7 LIMS and TOMS Datasets

Ellis Remsberg

Abstract. This work is a diagnostic study of distributions of tropical tropospheric column ozone (TRCO) based on subtracting Limb Infrared Monitor of the Stratosphere (LIMS) Version 6 (V6) Level 3 stratospheric column ozone (SCO) values from Total Ozone Mapping Spectrometer (TOMS) total ozone for several selected days of 1978–1979. The focus of this study is the low latitudes, where the tropopause is near 100 hPa and zonal wave activity is weak. TRCO exhibits a zonal wave-1 feature in the southern tropics with maximum values near 0° longitude during November 1978. Its zonal variation is 70 to 30 Dobson units (DU) and agrees with that of other similar analysis studies. V6 estimates of SCO and calculated TRCO are less reliable in March and May 1979 because those data are affected by temperature biases of order -1.0 to -2.0 K at 30 and 50 hPa; retrieved ozone at those levels may be too large by ~20 % as a result. The LIMS Level 3 sequential estimation algorithm provides smoothed zonal wave ozone amplitudes and reduced zonal variations of SCO. The corresponding calculated TRCO amplitudes are enhanced and not quantitative in those instances. The findings herein should be helpful to others, as they analyze infrared limb measurements of ozone and subtract their stratospheric column amounts from coincident total ozone to obtain accurate zonal variations of tropospheric ozone.

Received: 26 Jun 2026 – Discussion started: 07 Jul 2026

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Ellis Remsberg

Status: open (until 14 Oct 2026)

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RC1:
'Comment on egusphere-2026-3796', Anonymous Referee #1, 29 Sep 2026 reply
This manuscript presents an exploratory attempt to combine LIMS and TOMS stratospheric and total ozone columns, respectively, to obtain tropospheric ozone column (TRCO) data. The LIMS observations are among the first limb measurements ever performed from a satellite platform, and this study investigates the application of a residual technique to these very early observations. This aspect makes the study interesting; however, the scientific value of the resulting data is quite limited, both because of the short time span covered by the data set and because of the sub-optimal quality of the available observations: as the author states at the end, reasonable values of TRCO are possible to obtain only for November 1978. The author provides quite extensive explanations of possible causes for the obtained unrealistic TRCO values in the other analyzed periods. However, TRCO values are not directly inter-compared with other observations or a climatology: is there any profile data that can be integrated and used for comparison in the troposphere? No ozonesonde available at that time? Comments are detailed in the following.
Major comments
A wish that I think would improve the paper, is about the comparison with tropospheric other ozone values, if available. Is there any ozonesonde available for November 1978 that can be used for comparison? If not available, I suggest to state it in the paper. Alternatively, the good results obtained in Nov 1978 could be compared with a November climatology to have an impression on how the retrieved results compare.

In the abstract the author says that the focus of the study is in the tropics, but then he provides the TRCO results on global maps (Fig.5, 9, 12) even though for March and May 1979 especially the outer tropical values are clearly nonphysical. I suggest to limit the latitude span of these plots, especially Fig. 9 and 12 to ±30°. I am also wondering if it would be better to show first Nov 1978 that works nicely and afterwards the cases that are not working and discuss the possible causes.

A methodological question: the paper presents a L3 residual approach, would it be possible or has it been tested a residual calculation for collocated TOMS/LIMS observations? Even a few cases could give a hint if this way gives useful information or the discussed biases prevent getting reasonable results.

Overall, I find that the different parts of the paper are not well connected. Questions are posed to guide the reader in the investigations but I suggest a revision of the paper including some more connections between the paragraphs within sections and between sections. For example,

Minor comments
L18-21: I find this sentence a bit confusing here, is it related to the previous sentence on the temperature bias? As a reader of the abstract, it is not clear if this is happening only for March and May 1979 or is overall the case?

L99: It is not clear to me which pattern the author is referring to, as a function of latitude or across the three pictures? In addition, the quality of Fig.1 is poor; can it be improved? Is this taken from an older paper?

L110-112: Are these errors random or systematic? You mention ±1.2 K, random, shouldn’t this be reduced in magnitude with averaging on a monthly basis?

L139: In the Supplements there is only a plot with the SH profiles, can you add the figure number you are referring to? It is also not clear at which altitude the author is referring to. Do you have the tropical tropopause height for that day that you could include?

L161: Can you be more specific about the tropopause? Which definition are you using? This information could also be used in Fig.1 to visualize the lower bottom of SCO on average.

L172-Table 1: Would it be possible to add an estimated uncertainty to these values? For example in terms of combined std of the monthly SCO and TCO used to compute the residual, to have an idea of the variability of the used quantities. Alternatively, could you add a typical range of zonal TRCO, for example from Ziemke et al., at least for the tropics?

Paragraph L193-L205: You say that TRCO data from Ziemke’s papers show a decrease of ~20 DU from Nov to May, this justifies the decrease of 30 DU (or 20 DU after the adjustment) you see at 5° S. I would remove the Dobson observation from this reasoning as it might be related to the specific day considered, whereas satellite data are monthly averages, so not directly comparable.

L252: “or where there are decreases…” not clear, do you mean that you selected location where the TRCO is lower due to orography? Why is this choice made?

L255: Nonphysical values are found not only at 70° W but overall in the SH.

L255-258: Can you please state from the beginning that the temperature bias can explain only partially the negative values, not only at the very end?

L277-279: The author writes that “that zonal variations of TRCO are qualitative at best”. Do you then expect that once zonally averaged the TRCO results should be more realistic, taking into account the instrumental biases you mention? It seems to me that zonal averages in SH tropics are also generally negative for this day, regardless of their longitude variations.

Paragraph L281-L288: The author seems to suggest the extension of the dataset at lower levels but then concludes that it is not reliable, so that “TRCO distributions are only evaluated for the tropics and subtropics”. However the next pictures are still showing mid-latitude regions.

6 May 1979 paragraph. In the tropics (20°S to 20°N) I see values between 80 and -40 DU, not from 0 to

L305: I don’t see deep blue areas in Fig.10 at northern high latitudes.

I would state also in the conclusion that this is the first case of application of a residual technique to satellite observations, which make this study interesting.

Technical comments
L43: Please add “In the following,” at the beginning of the new sentence.

L120: What do you mean with “a vertical layering of the ozone profiles near the tropopause”?

L131: “bottom left” → “top left”.

L137: “or” → “i.e.,”

L178-179: I suggest to rewrite the last sentence like “Possible causes of these unrealistic features in March and May are discussed in the next paragraphs.”

L215: “20° W” → “50° W”.

L218: I would remove “from west to east longitude”.

L219: “Poona” → “Pune”.

L220: Please add “Collocated” before “Dobson/TOMS tropical total ozone”.

L236: I would put this details in a footnote.

L361: “not as reliable” → “not reliable”.

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Citation: https://doi.org/10.5194/egusphere-2026-3796-RC1

Ellis Remsberg

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https://doi.org/10.5194/egusphere-2026-3796-supplement

Ellis Remsberg

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Short summary

This study considers several sample days of tropospheric column ozone (TRCO) obtained by subtracting LIMS stratosphere column ozone (SCO) from TOMS total ozone. TRCO is elevated in the southern hemisphere tropics near west Africa during November 1978. Conversely, there are small biases in the LIMS ozone of the lower stratosphere that affect the accuracy of its SCO values in March and in May 1979; calculated zonal variations of TRCO are spurious on those days.


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