N₂O Temporal Variability from the Middle Troposphere to the Middle Stratosphere Based on Airborne and Balloon-Borne Observations during the Period 1987–2018

Round 1

Reviewer 1 Report

It is a well-prepared, highly informative study that I recommend for publication. My minor comments do not touch the overall merit of the paper.

Introduction: Part of the citation can/should be replaced by more recent ones. For example, the WMO publishes the latest N₂O trend annually in its Greenhouse Gas Bulletin, which can be downloaded from the WMO website. The reference to the ’State of Climate 2008’ is a bit strange in 2023 given our rapidly changing world. IPCC also published an updated report in 2021.

Figure 2: Will you give the chosen arbitrary amplitude?

Line 238: 45 pressure levels?

Figure 4: A more traditional scale (1, 2, 5, 10, 20, 50, 100,... or something similar) might be nicer but it is a matter of taste.

Lines 298-299: Is the difference in the trends statistically significant (also the difference from the trend at the surface)? If yes, it would need a short discussion in Section 4.

Line 334: The sources of N₂O are not in the troposphere, they are at the surface, in the soil, and in the ocean. A minor rewording of the sentence is desirable.

Lines 410-411 and Fig. 8: I recommend using a decimal period instead of a comma following the IPCC convention (RCP 6.0).

Line 427: It seems as if a different font size was used for “Minganti” than for the rest of the text. At least in the PDF file, I review.

Reference [58]: The correct page numbers are 11309-11317.

Author Response

We sincerely thank the reviewers for their comments and questions, which improve the quality of the paper. We have made numerous changes to make the paper read better and show the paper in revision mode to highlight the changes. 

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper is focused on the time evolution of N₂O from the middle troposphere (600 hPa) to the middle stratosphere (5 hPa). The period analysed extended from 1987 to 2018 and observations came from aircraft and balloon campaigns. The areas covered include North America, Europe, North Atlantic, Western North Pacific and East Asia. N₂O mixing ratio is modelled as a pressure function with two modes whose corresponding amplitudes depend on the latitude. Three latitude intervals are considered where the N₂O trend is calculated. Moreover, latitudes where the N₂O upwelling is favoured are suggested. The global scope of this research together with the time interval analysed are key points to the publication of this research. However, some minor changes should be introduced prior to its acceptance.

Although the analysis presents the results on a latitudinal basis, some noticeable areas are outside this study due to the lack of observations. Perhaps emissions may be important in China and South America and low in Africa. The authors should stress the limits of their analysis.

L. 209-229 and Figure 4. The authors present the procedure to avoid the outliers and graph the number of observations for each latitude sector. They should indicate if this number is an average for the period analysed or the global number in the period used. Since this number is low in many of the intervals used, the authors should introduce a comment about the representativeness of this number and the results obtained with these observations.

Minor remarks

Along the paper. Is the uncertainty the standard deviation?

Figure 7. Magnitude and unit should be introduced in the Y axis.

All the acronyms, such as the Representative Concentration Pathways, should be introduced the first time that they are used.

Reference 107. This reference should be revised since “Jégou, F” is repeated.

Author Response

We sincerely thank the reviewers for their comments and questions, which improve the quality of the paper. We have made numerous changes to make the paper read better and show the paper in revision mode to highlight the changes. 

Author Response File: Author Response.pdf