Two-dimensional monitoring of air pollution in Madrid using a Multi-AXis Differential Optical Absorption Spectroscopy two-dimensional (MAXDOAS-2D) instrument

Garcia-Nieto, David; Benavent, Nuria; Borge, Rafael; Saiz-Lopez, Alfonso

doi:https://doi.org/10.5194/amt-14-2941-2021

Articles | Volume 14, issue 4

https://doi.org/10.5194/amt-14-2941-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/amt-14-2941-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 14, issue 4

Research article

|

17 Apr 2021

Research article |

| 17 Apr 2021

Two-dimensional monitoring of air pollution in Madrid using a Multi-AXis Differential Optical Absorption Spectroscopy two-dimensional (MAXDOAS-2D) instrument

David Garcia-Nieto, Nuria Benavent, Rafael Borge, and Alfonso Saiz-Lopez

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Final revised paper (published on 17 Apr 2021)
Preprint (discussion started on 15 Jul 2020)

Interactive discussion

Status: closed

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

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RC1: 'Review', Anonymous Referee #1, 24 Jul 2020
- AC1: 'Anonymous Referee 1 Answer', David Garcia-Nieto, 30 Oct 2020
RC2: 'Review', Anonymous Referee #2, 17 Aug 2020
- AC2: 'Anonymous Referee 2 Answer', David Garcia-Nieto, 30 Oct 2020

Peer-review completion

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

AR by David Garcia-Nieto on behalf of the Authors (30 Oct 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (30 Oct 2020) by Daniel Perez-Ramirez

RR by Anonymous Referee #1 (03 Nov 2020)

RR by Anonymous Referee #2 (09 Nov 2020)

RR by Anonymous Referee #3 (24 Nov 2020)

Suggestions for revision or reasons for rejection

This paper presents nitrogen dioxide and nitrous acid observations over Madrid obtained using a new 2D MAXDOAS instrument. The reported observations show good agreement with mesoscale observations and in-situ measurements provided by Madrid air quality monitoring stations. The capacity of this 2D MAXDOAS instrument to infer horizontal gradients and vertical distribution is discussed as well as future strategies to improve retrievals. The paper is clearly written and the MAXDOAS-2D datasets presented here are a valuable addition to understand air quality in Madrid. For those reasons the paper is worth publication.
However, before publication this paper would benefit of more specific descriptions of technical aspects of RTM calculations and inversion methods. Large extensions of the text are devoted to general descriptions of the theory and methods employed by the authors but if provides insufficient details about the specifics of RTM calculations, inversion algorithms, and protocols used to compare in-situ and MAXDOAS-2D observations. Someone trying to reproduce the results presented here will have a very hard time given the lack of specific details. The minor comments section below specifies some of the sections where further details will be useful.
Minor comments:
Cloud screening algorithm: How is AERONET information combined with the photos taken by the camera. AERONET observations follow the Sun so how they do contribute to other azimuth angles. It may help to understand better this step and increase confidence in its efficacy to include a plot or a discussion of the cloud screening statistics.
Section 4.2 provides a nice description of the general aspects of profile inversion in MAX-DOAS retrievals but is probably not necessary in a research paper. Particularly if we consider that details about the forward model and the inversion algorithms are limited to one single sentence referencing Clémer et al., 2010. Further technical details would be more helpful to the specialized reader than the general description provided.
Since the retrieval is using US Standard atmosphere as unique source of p/T profiles it will be interesting to know how different it is from the typical p/T profiles in Madrid during the observation campaign.
The RTM calculations in the estimation of NO2 horizontal gradients are performed for each VEA or only for VEA = 0. If so, the onion peeling approach is only applied to surface layer mixing ratios?
Section 5.4 compares in-situ and MAXDOAS-2D NO2 observations looking at the correlation between surface layer retrievals and in-situ observations. While the results here show good correlation they bring little confirmation about the 2D capabilities of the instrument (which is the novel capacity that is presented in the paper) because the comparison is done averaging results over an hour. Would it be possible to analyze qualitative agreement between in-situ and MAXDOAS-2D as function of VAA? How many in-situ stations are finally considered in the comparisons out of the 24 available? Do correlations shown in figure 10 increase or decrease when MAXDOAS VAA is considered in the analysis.
Technical comments:
Line 24: south-pointing geometry is meaningless without providing an origin. Is this looking towards Madrid’s outskirts or towards downtown?
Line 61: add dimensions after “both in horizontal and vertical “
Line 68: remove comma after monitored
Line 99: remove “will”
Table 1 and table 2: Most likely due to my lack of knowledge but I wonder if Serdyuchenko et al., at 223K was fitted twice or it is a typo.
Figure 3: Would it be possible to include the viewing geometries corresponding to the shown DSCDs fits?
Figure 4: It seems that the results presented here are for the whole campaign. Please clarify? How is surface extinction coefficient defined? It would be helpful to illustrate in some way the vertical grid of the retrievals.
Figure 5: I guess is also for the whole period of time.
Line 495: Missing “T” at the end of the line.
Line 536. Vertical profiles are retrieve not only using the RTM explained in section 4. That is one of the components of the inversion algorithm. Besides, details of the RTM are not provided in section 4.
Figure 6 caption can be expanded to provide further details. What do the red dots represent? It must be some kind of average over the campaign. Besides that, red dots are not simulated or otherwise the x-axes labels “DSCD measured” don’t make much sense.
Figure 10: What represents the radial dimension of the polar plot. The estimated distance from the measurement center? If so, is it the mean distance of each layer with respect to the center?

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ED: Reconsider after major revisions (10 Dec 2020) by Daniel Perez-Ramirez

AR by David Garcia-Nieto on behalf of the Authors (12 Feb 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (15 Feb 2021) by Daniel Perez-Ramirez

AR by David Garcia-Nieto on behalf of the Authors (24 Feb 2021) Author's response Manuscript

Short summary

Trace gases play a key role in the chemistry of urban atmospheres. Therefore, knowledge about their spatial distribution is needed to fully characterize the air quality in urban areas. Using a new Multi-AXis Differential Optical Absorption Spectroscopy two-dimensional (MAXDOAS-2D) instrument, along with inversion algorithms, we report for the first time two-dimensional maps of NO₂ concentrations in the city of Madrid, Spain.