Development and application of a United States-wide correction for PM<sub>2.5</sub> data collected with the PurpleAir sensor

Barkjohn, Karoline K.; Gantt, Brett; Clements, Andrea L.

doi:https://doi.org/10.5194/amt-14-4617-2021

Articles | Volume 14, issue 6

https://doi.org/10.5194/amt-14-4617-2021

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

https://doi.org/10.5194/amt-14-4617-2021

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

Articles | Volume 14, issue 6

Research article

|

22 Jun 2021

Research article |

| 22 Jun 2021

Development and application of a United States-wide correction for PM_2.5 data collected with the PurpleAir sensor

Karoline K. Barkjohn, Brett Gantt, and Andrea L. Clements

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Final revised paper (published on 22 Jun 2021)
Supplement to the final revised paper
Preprint (discussion started on 02 Dec 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', Anonymous Referee #3, 09 Dec 2020
- AC1: 'Reply on RC1', Karoline Johnson Barkjohn, 12 Mar 2021
RC2: 'Review', Anonymous Referee #1, 27 Dec 2020
- AC2: 'Reply on RC2', Karoline Johnson Barkjohn, 12 Mar 2021
RC3: 'Review of ATM-2020-413', Anonymous Referee #2, 27 Dec 2020
- AC3: 'Reply on RC3', Karoline Johnson Barkjohn, 12 Mar 2021

Peer-review completion

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

AR by Karoline Barkjohn on behalf of the Authors (12 Mar 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (14 Mar 2021) by Pierre Herckes

RR by Anonymous Referee #3 (18 Mar 2021)

RR by Anonymous Referee #2 (21 Mar 2021)

Suggestions for revision or reasons for rejection

GENERAL COMMENTS

I appreciate the authors’ careful consideration of my previous comments! I’ve listed a few minor concerns below. All line numbers correspond to the revised manuscript.

SPECIFIC COMMENTS

1. Lines 199–204: “…occasionally, an extremely high temperature (i.e., 2147483447) or an extremely low temperature (i.e., -224 or -223) was reported…Temperature values above 540 C (1000 F) were excluded before calculating daily averages…” All temperatures between -224 and 1000 F were included? Why not use stricter criteria for excluding erroneous temperature measurements? The results of a quick web search suggest that temperatures in the U.S. have historically ranged from -80 to 135 F. I suspect that many other groups will adopt the quality assurance criteria proposed here, so I think it’s worth scrutinizing those criteria.

2. Lines 521–522: “Applying this correction to our dataset results in an underestimate of PM2.5 by 3 ug/m3 (34%) on average…” Does this mean that MBE = -3 ug/m3? If so, can you please be more specific? This comment also applies to lines 529 and 534.

3. Figures 5, 6, and S10: Were the corrected PurpleAir PM2.5 values plotted in these figures calculated using the coefficients shown in Equation 10 (which were obtained using the full dataset), or were they calculated using one of the withholding methods? I’m assuming the former, but it’s not clear. Can the authors please clarify in the captions?

TECHNICAL CORRECTIONS

1. Line 105: “cited” should be “sited”
2. Lines 263–264: I think this should just say “(Figure 2, Table 1)” but the entire Figure 2 caption seems to have been inserted by mistake.
3. Lines 272–274: Now that the manuscript has been reorganized, the inaccuracies associated with PurpleAir temperature and relative humidity measurements have not been discussed yet. The authors could revise this sentence to something like “There were limited data above 80% RH as measured by the PurpleAir sensor, which, as discussed in the following section, is known to consistently report RH lower than ambient.”
4. Line 302: “was” should be “were,” since it refers to “equations”
5. Line 325: Delete the comma after “sensors”
6. Lines 401–403: The entire Figure 4 caption seems to have been inserted by mistake.
7. Line 480: Delete “Lastly,”. Sections 5.3.3 and 5.3.4 both start with “Lastly,”.
8. Line 583: “Norther” should be “Northern”
9. Table S9 caption: Should “(as summarized in Table A5)” say “(as summarized in Table S8)”?
10. Figure S2: Do the authors want to remove the x-axis label [“xlab(NULL)”] or add one that isn’t just their internal variable name?

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RR by Anonymous Referee #1 (04 Apr 2021)

ED: Publish subject to minor revisions (review by editor) (07 Apr 2021) by Pierre Herckes

AR by Karoline Barkjohn on behalf of the Authors (27 Apr 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (29 Apr 2021) by Pierre Herckes

AR by Karoline Barkjohn on behalf of the Authors (21 May 2021) Manuscript

Short summary

Although widely used, air sensor measurements are often biased. In this work we develop a correction with a relative humidity term that reduces the bias and improves consistency between different United States regions. This correction equation, along with proposed data cleaning criteria, has been applied to PurpleAir PM_2.5 measurements across the US on the AirNow Fire and Smoke Map and has the potential to be successfully used in other air quality and public health applications.

Development and application of a United States-wide correction for PM2.5 data collected with the PurpleAir sensor

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Interactive discussion

Peer-review completion

Development and application of a United States-wide correction for PM_2.5 data collected with the PurpleAir sensor