Effects of urbanization on regional meteorology and air quality in Southern California

Li, Yun; Zhang, Jiachen; Sailor, David J.; Ban-Weiss, George A.

doi:https://doi.org/10.5194/acp-19-4439-2019

Articles | Volume 19, issue 7

https://doi.org/10.5194/acp-19-4439-2019

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

https://doi.org/10.5194/acp-19-4439-2019

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

Articles | Volume 19, issue 7

Research article

|

05 Apr 2019

Research article |

| 05 Apr 2019

Effects of urbanization on regional meteorology and air quality in Southern California

Yun Li, Jiachen Zhang, David J. Sailor, and George A. Ban-Weiss

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Final revised paper (published on 05 Apr 2019)
Supplement to the final revised paper
Preprint (discussion started on 04 Oct 2018)
Supplement to the preprint

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review of : Effects of Urbanization on Regional Meteorology and Air Quality in Southern California.', Anonymous Referee #1, 19 Oct 2018
- AC1: 'Response to Referee #1', George Ban-Weiss, 13 Feb 2019
RC2: 'Review_Li_etal_South_California_Urbanization_AQ', Anonymous Referee #2, 05 Dec 2018
- RC3: 'Shi Zhong et al 2017', Anonymous Referee #2, 06 Dec 2018
- AC2: 'Response to Referee #2', George Ban-Weiss, 13 Feb 2019
RC4: 'Review of Manuscript: acp-2018-889', Anonymous Referee #3, 29 Dec 2018
- AC3: 'Response to Referee #3', George Ban-Weiss, 13 Feb 2019

Peer-review completion

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

AR by George Ban-Weiss on behalf of the Authors (13 Feb 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (14 Feb 2019) by Robert Harley

RR by Anonymous Referee #2 (22 Feb 2019)

RR by Anonymous Referee #3 (05 Mar 2019)

Suggestions for revision or reasons for rejection

The revised manuscript is significantly improved compared to the previous version. Many of my comments have been addressed. I have few comments and a concern regarding the interpretation of the statistical significance of the land surface changes impacts on regional meteorology and air quality; and the variable used to derive the confidence levels.

Major comment:

The authors state in many places of the manuscript “significantly differ from zero at the 95% confidence level” (i.e. line 355, 425, 435, and elsewhere). The measure used for the statistical significance is not meaningful since the differences in the fields simulated under the scenarios considered are likely expected to be different from zero. In fact, even WRF simulations using same configurations but different computer platforms or compiler options can lead to different results due to errors. I would suggest basing the statistical significance on the sign of the difference in the fields simulated. The confidence level at which the difference is positive (negative) if you are expecting increases (decreases) would be more meaningful.

Other comments:

1- Please indicate the year of the JJA observations discussed in the text (Line 180) and in the caption of Figure S8.

2- Line 310: Please use a different word for “validation”. I would suggest “verification”. A complex model like WRF cannot be validated. Verifications of WRF are always required as the WRF results give different results depending on the configurations, regions, periods and the physics parameterizations employed.

3- Line 290 and elsewhere: Please reconsider the interpretation of the statistical significance (see the comment above).

4- Line 345: I would remove the sentence “Given that the atmosphere is stratified in models”. The discrete approximation shown in Eq2 does not depend on the stratification of the atmosphere since you are not using temperature or density as an independent variable in the integral. I would remove Eq2 (or Eq1) since they are equivalent.

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ED: Publish subject to minor revisions (review by editor) (06 Mar 2019) by Robert Harley

AR by George Ban-Weiss on behalf of the Authors (10 Mar 2019) Author's response Manuscript

ED: Publish as is (11 Mar 2019) by Robert Harley

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Short summary

In this study, we find that land surface changes via urbanization have caused reductions (increases) in air temperature and ventilation during the day (night) in Southern California. Changes in meteorology have consequently caused (a) increases in PM_2.5 during the day, vice versa at night, and (b) increases in O₃ for most times of day. These results suggest that all environmental systems should be taken into account when studying the influence of policies that impact the land surface in cities.