Analysis of a southern sub-polar short-term ozone variation event using a millimetre-wave radiometer

Orte, Pablo Facundo; Wolfram, Elian; Salvador, Jacobo; Mizuno, Akira; Bègue, Nelson; Bencherif, Hassan; Bali, Juan Lucas; D'Elia, Raúl; Pazmiño, Andrea; Godin-Beekmann, Sophie; Ohyama, Hirofumi; Quiroga, Jonathan

doi:https://doi.org/10.5194/angeo-37-613-2019

Articles | Volume 37, issue 4

https://doi.org/10.5194/angeo-37-613-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/angeo-37-613-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 37, issue 4

Regular paper

|

24 Jul 2019

Regular paper |

| 24 Jul 2019

Analysis of a southern sub-polar short-term ozone variation event using a millimetre-wave radiometer

Pablo Facundo Orte, Elian Wolfram, Jacobo Salvador, Akira Mizuno, Nelson Bègue, Hassan Bencherif, Juan Lucas Bali, Raúl D'Elia, Andrea Pazmiño, Sophie Godin-Beekmann, Hirofumi Ohyama, and Jonathan Quiroga

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Final revised paper (published on 24 Jul 2019)
Preprint (discussion started on 18 Feb 2019)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Analysis of an event of short term ozone variation using a Millimiter - Wave Radiometer installed in subpolar region', Lucas Vaz Peres, 23 Mar 2019
- AC1: 'Author's comments: Analysis of a southern sub-polar short-term ozone variation event using a Millimeter-Wave Radiometer', Pablo Facundo Orte, 25 Apr 2019
RC2: 'Referee's comments', Anonymous Referee #2, 01 Apr 2019
- AC2: 'Author's comments: Analysis of a southern sub-polar short-term ozone variation event using a Millimeter-Wave Radiometer', Pablo Facundo Orte, 25 Apr 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Publish subject to revisions (further review by editor and referees) (29 Apr 2019) by Petr Pisoft

AR by Pablo Facundo Orte on behalf of the Authors (02 May 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (03 May 2019) by Petr Pisoft

RR by Lucas Vaz Peres (04 Jun 2019)

Suggestions for revision or reasons for rejection

Orte et al., 2019:

“Analysis of a southern sub-polar short-term ozone variation event using a Millimeter-Wave Radiometer”.

General comments:

The authors present a study about an atypical event of polar vortex and ozone hole influence over Río Gallegos during November of 2014. This event was detected from the Millimeter Wave Radiometer (MWR) measurements at 27 and 37 km and the advected potential vorticity (APV) was calculated from the high-resolution advection model MIMOSA (Modélisation Isentrope du transport Mésoéchelle de l’Ozone Stratosphérique par Advection) at 675 and 950 K to understand and explain the atmospheric dynamic related to ozone rapid variation during the passage of the polar vortex. In addition, the MWR dataset were compared for first time with Microwave Limb Sounder (MLS) to 27 km, 37 km and 65 km and with the Differential Absorption Lidar (DIAL) installed in Observatorio Atmosférico de la Patagonia Austral (OAPA) between October 2014 and 2015.
This work is a useful representation of the important contribution made by the Millimeter Wave Radiometer (MWR) at Río Gallegos and certainly, understand the ozone hole influence over Río Gallegos is of fundamental importance in many environmental processes which can lead to increases in the UV radiation on the surface. This increase in the UV radiation related to ozone reductions can be dangerous to life on earth and it represents a significant scientific advance.
After the first review, major corrections were suggested and in general the authors were able to remedy the main failures observed. The Point-by-point response to the referee comment’s was very clear and precise in most points, however small details can still be improved especially in discussing results in the literature, although this has already been greatly improved.
Because of these I would recommend to accept with Minor Revisions this manuscript. Also, because I am not a English language native speaker, I suggest to the editor to check if the English is proper for publication.

Specific comments:

* In the abstract: Requested modifications are made.

* In the 1. Introduction: Requested modifications are ok.

* In the 2. Materials and methods: Requested modifications are ok. However, a subsection should be created describing the UV radiation data used in this new version of the manuscript.

* 2.3
Why the comparison of the MWR with DIAL occurs only for the 27 km height. It could also occur for 37 km. Or is there any impediment?

* In the 3. Results: Requested modifications are ok.

* Y axis of figure 7a (top) should contain values throughout the graph and contemplate values close to 230 DU observed.

* In the 4. Discussion

Creating a discussion section instead of discussing the results as they occur in the text is always a dilemma. You can make the mistake of not discussing some results in the literature. Comparing the results with what was discussed. It is observed that not all results were properly discussed as listed below:

- In Pg 11, line 5: “The difference between measurements can be attributed to the typical uncertainties of each instrument, although another source of difference is introduced due to the non-collocated measurements inter-compared”. This affirmation was discussed but not referenced.

- Discussion on results related to UV radiation should be attached.

- Discussion on results related to AOH influences should be improved, mainly in relation to the advection of potential vorticity process which caused the observed ozone reduction.

- The first paragraph of the discussion has affirmations without reference.

- The present affirmation was not discussed: “When we compare the MWR with the MLS, it is considered that both instruments are measuring the same air masses, although the location of the satellite measurements differs from the location of the MWR measurements, which can introduce a difference in the ozone mixing ratio measured.”

- The present affirmation was not discussed: “One reason why the correspondence between the MWR and the DIAL is greater with respect to the MLS may be that the two instruments installed on the ground (MWR and DIAL) are monitoring the same air mass, while the distance with the location of the MLS observations could be introducing differences in the comparison”.

- The present affirmation was not discussed: “It is important to note that the MWR and DIAL instruments retrieve ozone in different fundamental units. While the MWR 30 provides the ozone mixing ratio, the DIAL provides the ozone number density as a function of altitude. The DIAL unit was converted to the MWR unit for the inter-comparison using the temperature and pressure retrieved from the DIAL. Thus, uncertainties in these parameters could be adding uncertainties in the ozone amount in ppm from the DIAL”.

* Conclusions
- Requested modifications are ok.

Referee Report: PDF

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RR by Anonymous Referee #2 (07 Jun 2019)

Suggestions for revision or reasons for rejection

Journal: Annales Geophysicae

Revision of MS No.: angeo-2019-17-R1

Title: Analysis of a southern sub-polar short-term ozone variation event using a Millimeter-Wave Radiometer.

Authors: Pablo Facundo Orte, Elian Wolfram, Jacobo Salvador, Akira Mizuno, Nelson Bègue, Hassan Bencherif, Juan Lucas Bali, Raúl D’Elia, Andrea Pazmiño, Sophie Godin-Beekmann, Hirofumi Ohyama, Jonathan Quiroga.

Overall evaluation:

The manuscript has definitely improved. However, this second revision evidences still several necessary corrections. Again, these comments may be considered as relatively “minor changes”, but in my opinion they are mandatories to consider the manuscript as acceptable for publication:

Specific comments:

- Abstract: sentence “The measurement shows a very short-term recovery in the middle of ozone mixing ratio decrease that could be detected by the MWR” is confuse. Please clarify.

- The concepts of potential temperature, isentropic surface, isentropic level, are introduced after temperatures 675 K and 950 K are mentioned, starting with the Abstract. Please define the concept as at the beginning as possible and unify terminology. In my opinion, the denomination of “isentropic level” is the most appropriate and should be used to avoid different denominations for the same concept.

- In the same aspect, the fact that isentropic levels 675 K and 950 K correspond to approximately ~27km and ~37km is explained too late in the text (page 12). Please clarify this fact as at the beginning as possible in the text.

- Page 2, line 32: sentence “Ground and space-based observations and models have shown an increase of the total ozone since 2000” is incoherent with the two following sentences: “Nevertheless, this increase is not significant for the period 2000-2013 (WMO, 2014). Ball et al. (2018) extended this period from 1998 to 2016 and concluded that there are non-significant changes in the total amount of ozone from merged ozone datasets”. Please clarify.

- Page 3, line 20: Bresciani et al. (2018) named this phenomenon “secondary effect of the Antarctic ozone hole”, concluding that “Data revealed the poor ozone air mass trajectory from some days before arriving in southern Brazil and Uruguay to some days after its passage, and confirmed its polar origin”, but… could this sentence be interpreted as the authors refers to?: an actual pass of the polar vortex over Uruguay and Southern Brazil?.

- Page 11, line 13: R=0.68 is mentioned for altitude 27 km, but in item 3.1.1, table 1 and figure 5 it is referred to as R=0.65.

- Page 12, paragraph starting in line 15: an adaptation of the phrase from the answers to referee “We decided to present the daily maximum UVI due to the fact that most of the analysed days were partially cloudy with broken clouds, and the maximum UVI were measured near to the noon” must be included in the text of the manuscript.

- Figure 8: plots on the left (675 K) and on the right (950 K) look too similar given that the same colour scale is used in both, but in fact the actual values of APV are totally different. I suggest unify the scale of colours using the same scale on both sides with the total range APV (0-900), but still highlighting with colours and tones the features you want emphasize: for instance the same present colours in the range 0-200 (blue to yellow) but then passing to (red to pink) in the range 200-900.

Minor comments:

- Page 2, line 5: Add comma: “It acts as an absorber of harmful solar UVB radiation, …”.

- Page 2, line 7: please change “Although most production takes place in the equatorial region” by “Although most production takes place in the mesospheric-stratospheric equatorial region”.

- Page 2, line 21: Please revise sentence “the total ozone column (TOC) and vertical reduction”, it could be better simply “ozone reduction at different height levels”.

- Page 2, line 25: “More recent study reported reduction of 40-45% in TOC over Río Gallegos”, please specify the date of the reported TOC reduction.

- Page 3, line 15: change by “The passage of the AOH is identified using the TOC threshold of 220 DU”.

- Page 4, line 27: change by “and the unique installed in subpolar region”.

- Page 4, line 31: Did you mean “improving the validation of the dynamical models”?.

- Page 10, line 4: remove word “system”: 3.1 Inter-comparison of MWR with DIAL and MLS observations.

- Page 10, line 10: change by “campaigns become”.

- Page 12, line 27: change “at both potential temperatures” by “at both isentropic levels”.

English must be still revised in many sentences throughout the text, only for example:

- Page 1, line 30: “explain the dynamics”.

- Page 2, line 20: “and they will remain for decades”.

- Page 2, line 25: “A more recent study reported a reduction of 40-45% in TOC over Río Gallegos”.

- Page 2, line 27: “respect to normal”.

- Page 3, line 26: “… reaches mid-latitudes and produces”.

- Page 4, line 31: “at these latitudes”.

- Page 11, line 26: Remove word “on”: “during November 2014”.

- Page 12, line 15: change by “daily maximum Ultraviolet Index (UVI)”.

- Page 13, line 15: remove “from”: “suffers sudden”.

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ED: Publish subject to minor revisions (review by editor) (07 Jun 2019) by Petr Pisoft

AR by Pablo Facundo Orte on behalf of the Authors (26 Jun 2019) Author's response Manuscript

ED: Publish as is (01 Jul 2019) by Petr Pisoft

AR by Pablo Facundo Orte on behalf of the Authors (03 Jul 2019) Manuscript

Short summary

We analysed an event of short-term ozone variability due to the passage of the polar vortex over Río Gallegos (southern Argentina) with the aim of highlighting the capability of a millimetre-wave radiometer to observe ozone in the stratosphere and the low mesosphere with a high temporal resolution. It is particularly important in this subpolar region due to the high variation that this gas can suffer as a consequence of the passage of the polar vortex and the ozone hole during spring.