iNRACM: incorporating 15N into the Regional Atmospheric Chemistry Mechanism (RACM) for assessing the role photochemistry plays in controlling the isotopic composition of NOx, NOy, and atmospheric nitrate

Fang, Huan; Walters, Wendell W.; Mase, David; Michalski, Greg

doi:https://doi.org/10.5194/gmd-14-5001-2021

Articles | Volume 14, issue 8

https://doi.org/10.5194/gmd-14-5001-2021

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

https://doi.org/10.5194/gmd-14-5001-2021

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

Articles | Volume 14, issue 8

Model description paper

|

12 Aug 2021

Model description paper |

| 12 Aug 2021

i_NRACM: incorporating ¹⁵N into the Regional Atmospheric Chemistry Mechanism (RACM) for assessing the role photochemistry plays in controlling the isotopic composition of NO_x, NO_y, and atmospheric nitrate

Huan Fang, Wendell W. Walters, David Mase, and Greg Michalski

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Final revised paper (published on 12 Aug 2021)
Supplement to the final revised paper
Preprint (discussion started on 22 Jun 2020)
Supplement to the preprint

Interactive discussion

Status: closed

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

- Printer-friendly version

- Supplement

RC1: 'Review of the isotope incorporated model', Lei Geng, 08 Aug 2020
- AC1: 'Reply on RC1', Greg Michalski, 30 Mar 2021
RC2: 'Anonymous Review', Anonymous Referee #2, 20 Aug 2020
- AC2: 'Reply on RC2', Greg Michalski, 30 Mar 2021

Peer-review completion

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

AR by Greg Michalski on behalf of the Authors (07 Apr 2021) Author's response Author's tracked changes

ED: Referee Nomination & Report Request started (13 Apr 2021) by Christoph Knote

RR by Anonymous Referee #1 (30 Apr 2021)

Suggestions for revision or reasons for rejection

The constructed model frame work represents an important step forward regarding the studies of isotope effects during atmospheric transformations of oxidized reactive nitrogen. The authors made substantial changes in the revised manuscript that helps a lot to clarify the calculations and model setup, as well as discussion of the model outputs. But it is my opinion that in order to validate the model, it should be the chemistry be validated or compared first, i.e., would the model be able to reproduce the production of nitrate first (or the consumption of NOx), including its day vs. night and seasonal variations. Overall the key idea here is that chemistry leads to isotope variations, so if the model can't reproduce the production of nitrate, a question mark would be placed on the isotopes even that show consistence with observations. I think two things added would provide additional validation to the model and strengthen the result: 1) whether the model predicts nitrate qualitatively consistent with observations, e.g., in the model, how much daytime nitrate production vs how much night time production, and is the relative importance the same as observations? 2) in the Tuson validation case, how is nitrate concentration in the model compared to the observations? the model reproduced the observed d15N very well, indicating nitrate in the city (observations) were mainly from local conversion of NOx to nitrate. It would be simply pull out the model predicted nitrate mass (seasonal pattern if it is difficult to convert the modeled nitrate production to air concentration and compare with the observations directly) and compare with observations. In other words, if the model can't produce the mass right (it is often the case even for a chemical transport model), something strange may happen and need to be clarified.

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ED: Publish subject to minor revisions (review by editor) (03 May 2021) by Christoph Knote

AR by Greg Michalski on behalf of the Authors (11 May 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (14 May 2021) by Christoph Knote

Short summary

A new photochemical reaction scheme that incorporates nitrogen isotopes has been developed to simulate isotope tracers in air pollution. The model contains 16 N compounds, and 96 reactions involving N used in the Regional Atmospheric Chemistry Mechanism (RACM) were replicated using ¹⁵N in a new mechanism called i_NRACM. The model is able to predict d¹⁵N variations in NO_x, HONO, and HNO₃ that are similar to those observed in aerosol and gases in the troposphere.