Estimating vehicle carbon dioxide emissions from Boulder, Colorado, using horizontal path-integrated column measurements

Waxman, Eleanor M.; Cossel, Kevin C.; Giorgetta, Fabrizio; Truong, Gar-Wing; Swann, William C.; Coddington, Ian; Newbury, Nathan R.

doi:https://doi.org/10.5194/acp-19-4177-2019

Articles | Volume 19, issue 7

https://doi.org/10.5194/acp-19-4177-2019

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

https://doi.org/10.5194/acp-19-4177-2019

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

Articles | Volume 19, issue 7

Research article

|

03 Apr 2019

Research article |

| 03 Apr 2019

Estimating vehicle carbon dioxide emissions from Boulder, Colorado, using horizontal path-integrated column measurements

Eleanor M. Waxman, Kevin C. Cossel, Fabrizio Giorgetta, Gar-Wing Truong, William C. Swann, Ian Coddington, and Nathan R. Newbury

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Final revised paper (published on 03 Apr 2019)
Preprint (discussion started on 03 Sep 2018)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review of acp-2018-796: Estimating vehicle carbon dioxide emissions from Boulder, Colorado using horizontal path-integrated column measurements', Anonymous Referee #1, 05 Oct 2018
RC2: 'A review of Waxmann et al. "Estimating vehicle carbon dioxide emissions from Boulder, Colorado using horizontal path-integrated column measurements"', Anonymous Referee #2, 14 Oct 2018
AC1: 'Response to Reviewer Comments', Eleanor Waxman, 09 Feb 2019

Peer-review completion

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

AR by Eleanor Waxman on behalf of the Authors (09 Feb 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (11 Feb 2019) by Ronald Cohen

RR by Anonymous Referee #3 (09 Mar 2019)

Suggestions for revision or reasons for rejection

To preface this, I was not one of the original reviewers of this manuscript. In contrast to the rather negative first round of reviews, I quite like this manuscript. I think Waxman et al. do a nice job of presenting an (albeit uncertain) CO2 emissions estimate for Boulder using a novel instrument (dual frequency comb spectrometer). The authors have been quite diligent in their analyses over the years including direct comparisons with a CRDS from NOAA on a tower along their beam in previous work. I think this work should be published in ACP with minor corrections. It is well-written, the figures are high quality, and the analysis is quite novel. In my opinion, the only real short-comings are the lack of a high-quality bottom-up inventory and the fairly simplistic atmospheric modeling. I only have one substantial comment below (and a few editorial comments):

* Comparison of the Gaussian plume with Footprints:
It seems that the Gaussian plume analysis was carried over from the original manuscript and the footprint analysis was conducted in response to the first round of reviewers. However the Gaussian plume setup is fairly simplistic in that it assumes a set of point sources and uniform winds. The authors now have footprints for their time period. It would nice to see a comparison between the concentrations simulated with the Gaussian plume and the footprints. That is to say, could the authors 1) compute the concentrations with their Gaussian plume and 2) run those same emission point sources through their footprints to get the concentrations? Large differences would imply that their Gaussian plume calculation is missing something, if the results are similar then it would give me more confidence in their emissions estimates.

Line 46: Previous OSSE work has actually shown that the low-cost sensors are less sensitive to systematic biases at individual sites (Turner et al., ACP, 2016) because 1) you have an abundance of sites and 2) because you're putting less weight on any given site since the error is larger.

Lines 74-80: It would be good to list the specific papers that show these because the measurements are novel to most atmospheric chemists.

Line 86: Which figure? The diurnal cycle is more consistent with a morning-build up from traffic, than a mid-day decline due to the rising PBL. I'd say the diurnal cycle is more consistent with meteorology than anthropogenic sources.

Lines 246-254: This discussion of CH4 seemed a bit out of place since the rest of the paper is on CO2, not sure if it adds that much or distracts from the message.

Line 277: Why use NARR? Isn't HRRR available? That would be much higher resolution and is easy to use with the new STILT

Eq 4: Writing out the steps in a supplement would be useful. I had to look at this equation a few times before it made sense.

Line 380: I think this should be "These non-traffic sources", not "source"

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ED: Publish subject to technical corrections (12 Mar 2019) by Ronald Cohen

AR by Eleanor Waxman on behalf of the Authors (21 Mar 2019) Author's response Manuscript

Short summary

In this work we measure carbon dioxide for the city of Boulder, Colorado, using a novel laser-based instrument. We then use a model to determine the strength of the emissions from the city. Based on our measurement location, we attribute the majority of these emissions to vehicles. We compare our emissions to the city vehicle emissions inventory with good agreement.