the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 25 Jan 2024
Relations between cyclones and ozone changes in the Arctic using data from satellite instruments and the MOSAiC ship campaign
Abstract. Large-scale meteorologic events (e.g. cyclones), referred to as synoptic events, strongly influence weather predictability but still cannot be fully characterised in the Arctic region because of the sparse coverage of measurements. Due to the fact that atmospheric dynamics in the lower stratosphere and troposphere influence the ozone field, an approach to analyse these events further is the use of space-borne measurements of ozone vertical distributions and total columns. In this study we investigate the link between cyclones and changes in stratospheric ozone by using a combination of unique measurements during the MOSAiC ship expedition, ozone profile and total column observations by satellite instruments (OMPS-LP, TROPOMI), and ERA5 reanalysis data. Three special cases during the MOSAiC expedition were selected and classified for the analysis. They consist of one 'normal' cyclone, where a low surface pressure coincides with a minimum in tropopause height, and two 'untypical' cyclones, where this is not observed. The influence of cyclone events on ozone in the upper-troposphere lower-stratosphere (UTLS) region was investigated, using the fact that both are correlated with tropopause height changes. The negative correlation between tropopause height from ERA5 and ozone columns was investigated in the Arctic region for the three-month period from June to August 2020. This was done using total ozone columns and subcolumns from TROPOMI, OMPS-LP and MOSAiC ozonesonde data. The greatest influence of tropopause height changes on ozone contour levels occurs at an altitude between 10 and 20 km. Moreover, the lowering of the 250 ppb ozonopause (about 11 km altitude) below 9 km was used to identify and track cyclones using OMPS-LP ozone observations. The potential of this approach was demonstrated in two case studies where the boundaries of cyclones could be determined using ozone observations. The results of this study can help improve our understanding of the relationship between cyclones, tropopause height, and ozone in the Arctic and demonstrate the usability of satellite ozone data for investigating cyclones in the Arctic.
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Status: final response (author comments only)
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RC1: 'Nice work showing Arctic connections between ozone and tropopause', Anonymous Referee #1, 15 Feb 2024
This paper nicely shows that well known connections between ozone, potential vorticity, tropopause height, and, more generally, tropospheric weather also work in the Arctic. I think the paper is well written and well illustrated and deserves publication in ACP.
I have only few suggestions for changes.
The color scale for ozone seems unfortunate in Figs. 1, 2, 3, 11. Especially in Figs. 1 to 3 everything is just dark blue and there is very little to see. Maybe a logarithmic color scale, say from 50 to 1000 ppb , would work much better. It would expand variations at low ppb, and compress variations at high ppb. I strongly suggest that the authors test this.
Also in Figs. 1 to 3: I am missing/ not seeing the red line for the tropopause. Please add.
2.2 Vertical resolution of 3 to 10 meters. While ozone sondes may give data points every few meters, the time constant of the ozone reaction cell is about 20 seconds - which corresponds to a vertical resolution of about 100m for ozone. This is still much finer than OMPS Limb profiles, which also integrate over a few hundred kilometers horizontally. The finer structures seen by the sonde, and their intrinsic measurement noise may well explain another good part of the lower correlations mentioned later in 4.2.3.
Citation: https://doi.org/10.5194/egusphere-2023-3036-RC1 - AC1: 'Reply on RC1', Falco Monsees, 19 Apr 2024
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RC2: 'Comment on egusphere-2023-3036', Anonymous Referee #2, 25 Feb 2024
This manuscript outlined a method to identify cyclone passage using ozone and tropopause height measurements. Satellite, ERA5, and ozonesonde launch data during the MOSAiC expedition were used to both identify cyclones and evaluate the relationship between ozone levels, tropopause height, and cyclone passage. The authors found the 250ppb ozone level can best be used to identify cyclone passage.
This is an interesting additional way by which cyclones can be identified. The figures are clean and concise, and the writing is mostly clear with the exception noted below. There are places where clarification is needed, so the recommendation is major revisions. The following should be addressed/answered before publication.
- What value does this type of analysis bring in cyclone identification beyond using minima in sea level pressure/geopotential height or maxima in vorticity? I am not suggesting there is not value, just that it would strengthen the paper to highlight what value this brings beyond the cyclone tracking methods already available.
- A big question I had is – what is the large takeaway from this work? Verifying ERA5 ozone data so a gap-free, long term ozone dataset can be used for this type of analysis? A method for using ozone to identify cyclones? There was a lot of discontinuity in the description of the work, and how it all tied together. It would be helpful to be clearer as to why you did each step and better organize the analysis so that each step flows into the next. For example, there was the initial analysis for the 3 cyclones shown in figures 1-3, then different cyclones in Figures 11-15. There was the analysis looking at the relationship between tropopause height and total column ozone. And then the analysis comparing all of the ozone data to each other. There needs to be a bit more verbiage and reorganization to tie all of these analyses together. There are interesting results from this work - putting everything into context in a cohesive manner would really strengthen the paper.
- I’m not clear as to why the analysis using the S5P data is done. Is this done to validate ERA5 ozone data? If so, why was there not more analysis done with ERA5? For example, how come you did not identify the cyclone borders with the ERA5 data as well? As you state, the reanalysis data has the benefit of being gap-free and covers a long time period.
- For Figure 4, is there a relationship between what you are showing here and the cyclones? Meaning you are showing the relationship between total column ozone and tropopause height, which makes sense, but how does this tie back into the results from Figures 1-3?
- Why do you show the order of Figures 13 and 14 the way you do? The time stamp for the cross section in Figure 14 is 2 hours earlier than Figure 13.
- Figures 1-3:
- The red curve indicating the 4-PVU tropopause height is missing.
- Add a bit more detail to the X-axis (i.e., in the text you reference very specific times that would be easier to locate in these figures with additional labeling on the X-axis).
- What do the vertical black dashed lines represent?
- Sections 2 and 3 could be combined into a ‘Data and Methods’ section.
- Line 48: East coast of where?
- Line 79: for a multidisciplinary -> for multidisciplinary
- Lines 155-156: ‘Due to the smaller scale of the tropopause height’, what does this mean?
- Lines 284-285: Which figure showed this?
Citation: https://doi.org/10.5194/egusphere-2023-3036-RC2 - AC2: 'Reply on RC2', Falco Monsees, 19 Apr 2024
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