Open-path measurement of stable water isotopologues using mid-infrared dual-comb spectroscopy

Herman, Daniel I.; Mead, Griffin; Giorgetta, Fabrizio R.; Baumann, Esther; Malarich, Nathan A.; Washburn, Brian R.; Newbury, Nathan R.; Coddington, Ian; Cossel, Kevin C.

doi:https://doi.org/10.5194/amt-16-4053-2023

Articles | Volume 16, issue 17

https://doi.org/10.5194/amt-16-4053-2023

© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/amt-16-4053-2023

© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 16, issue 17

Research article

|

08 Sep 2023

Research article |

| 08 Sep 2023

Open-path measurement of stable water isotopologues using mid-infrared dual-comb spectroscopy

Daniel I. Herman, Griffin Mead, Fabrizio R. Giorgetta, Esther Baumann, Nathan A. Malarich, Brian R. Washburn, Nathan R. Newbury, Ian Coddington, and Kevin C. Cossel

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Final revised paper (published on 08 Sep 2023)
Preprint (discussion started on 31 Jan 2023)

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2022-1263', Anonymous Referee #2, 16 Feb 2023

This paper describes a novel technique for open path measurement of water vapor isotopologues and makes some preliminary analysis of measurements acquired during a 3 month period in the Denver, Colorado area. The measurements are compared to point measurements acquired 70 km away and show both similarities and differences that can be interpreted.
The paper is extrmely clear, the figures are of high quality, and all discussions make sense. The abstract is a fair summary of what has been achieved in the study.
This paper should be accepted as is.

Citation: https://doi.org/10.5194/egusphere-2022-1263-RC1
- AC1: 'Reply on RC2', Kevin Cossel, 06 Apr 2023
  
  We thank the reviewers for their time and for the kind remarks.
  We agree with reviewer 2 that the discrepancies between HITRAN and VSMOW are indeed negligible for this work and appreciate the careful checking of the math. The 1 permil number given was intended to be an upper limit depending on the exact isotope ratio used (for example, the numbers in Griffith 2018 differ slightly from that IUPAC technical report), but it was also indeed too large. Instead, we have changed that sentence to read: "Finally, we note that there are slight differences between isotopologue ratios determined using HITRAN and ratios in the VSMOW scale; however, these differences are negligible here (Griffith, 2018)."
  We have also corrected Line 31 to say isotopologue ratio instead of isotope ratio.
  
  Citation: https://doi.org/10.5194/egusphere-2022-1263-AC1
RC2:
'Comment on egusphere-2022-1263', Ivan Prokhorov, 20 Feb 2023

Herman and his colleagues present a truly impressive accomplishment in measuring the water D/H ratio using DCS in an open path configuration. The methodology is explained in details and supported by preliminary field measurements. The obtained data is interpreted in a coinsice manner.
I would like to bring authors' attention to descripancies between isotopologue ratios reported in HITRAN and those in VSMOV material. Following IUPAC technical report https://doi.org/10.1351/pac200274101987, rD_VSMOW = 15574/99984426, it gives HDO/HHO = 3.115285e-04 in agreement with the value reported in Line 30. HITRAN2020 has HDO/HHO = 3.106930e-4/0.997317 = 3.115288e-04. The difference is <1e-3 permil, which is much less than 1 permil reported in Line 265. Hence, it is insignificant to be included in the interpretation of the results. Another minor remark to Line 31, R_VSMOW = 0.0003115 is the isotopologue ratio in VSMOW material, not the isotope ratio, please correct the text accordingly.
The paper is very well written, it is certainly within the scope of AMT, and deserves to be published.

Citation: https://doi.org/10.5194/egusphere-2022-1263-RC2
- AC1: 'Reply on RC2', Kevin Cossel, 06 Apr 2023
  
  We thank the reviewers for their time and for the kind remarks.
  We agree with reviewer 2 that the discrepancies between HITRAN and VSMOW are indeed negligible for this work and appreciate the careful checking of the math. The 1 permil number given was intended to be an upper limit depending on the exact isotope ratio used (for example, the numbers in Griffith 2018 differ slightly from that IUPAC technical report), but it was also indeed too large. Instead, we have changed that sentence to read: "Finally, we note that there are slight differences between isotopologue ratios determined using HITRAN and ratios in the VSMOW scale; however, these differences are negligible here (Griffith, 2018)."
  We have also corrected Line 31 to say isotopologue ratio instead of isotope ratio.
  
  Citation: https://doi.org/10.5194/egusphere-2022-1263-AC1

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Kevin Cossel on behalf of the Authors (07 Apr 2023) Author's response Author's tracked changes Manuscript

ED: Publish subject to technical corrections (14 May 2023) by Christof Janssen

AR by Kevin Cossel on behalf of the Authors (26 May 2023) Manuscript

Post-review adjustments

AA: Author's adjustment | EA: Editor approval

AA by Kevin Cossel on behalf of the Authors (29 Aug 2023) Author's adjustment Manuscript

EA: Adjustments approved (30 Aug 2023) by Christof Janssen

Short summary

Measurements of the isotope ratio of water vapor provide information about the sources and history of water vapor at a given location, which can be used to understand the impacts of climate change on global water use. Here, we demonstrate a new method for measuring isotope ratios over long open-air paths, which can reduce sampling bias and provide more spatial averaging than standard point sensor methods. We show that this new technique has high sensitivity and accuracy.