China's emission control strategies have suppressed unfavorable influences of climate on wintertime PM<sub>2.5</sub> concentrations in Beijing since 2002

Gao, Meng; Liu, Zirui; Zheng, Bo; Ji, Dongsheng; Sherman, Peter; Song, Shaojie; Xin, Jinyuan; Liu, Cheng; Wang, Yuesi; Zhang, Qiang; Xing, Jia; Jiang, Jingkun; Wang, Zifa; Carmichael, Gregory R.; McElroy, Michael B.

doi:https://doi.org/10.5194/acp-20-1497-2020

Articles | Volume 20, issue 3

https://doi.org/10.5194/acp-20-1497-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-20-1497-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 20, issue 3

Research article

|

07 Feb 2020

Research article |

| 07 Feb 2020

China's emission control strategies have suppressed unfavorable influences of climate on wintertime PM_2.5 concentrations in Beijing since 2002

Meng Gao, Zirui Liu, Bo Zheng, Dongsheng Ji, Peter Sherman, Shaojie Song, Jinyuan Xin, Cheng Liu, Yuesi Wang, Qiang Zhang, Jia Xing, Jingkun Jiang, Zifa Wang, Gregory R. Carmichael, and Michael B. McElroy

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Final revised paper (published on 07 Feb 2020)
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Preprint (discussion started on 23 May 2019)
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Interactive discussion

Status: closed

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

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RC1: 'Suggestions', Bin Zhu, 16 Jun 2019
RC2: 'Comments', Anonymous Referee #3, 16 Sep 2019
AC1: 'Response to reviewers', Meng Gao, 29 Oct 2019

Peer-review completion

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

AR by Meng Gao on behalf of the Authors (29 Oct 2019) Manuscript

ED: Referee Nomination & Report Request started (18 Nov 2019) by Xiaohong Liu

RR by Anonymous Referee #4 (23 Dec 2019)

Suggestions for revision or reasons for rejection

The revised manuscript and response letter have fairly addressed the reviewers’ comments. Now following the reviewer 2’s discussion, I have one more concern that I hope the authors can address to improve the manuscript.

The key message of this study is as claimed by the title, “China’s Clean Air Action has suppressed unfavorable influences of climate on wintertime PM2.5 concentrations in Beijing since 2002”. The Clean Air Action were enforced during the period of 2013-2017, while it was used by the authors to explain the trends of PM2.5 levels and haze days in Beijing over winters 2002-2016. The inconsistency between the two time periods needs caution. Based on the two sensitivity experiments (CTL: varying emissions, and MET: 2002 fixed emissions), the study did only separate the role of varying anthropogenic emissions over the whole period of 2002-2016, and did not separate the role of emission reductions due to the Clean Air Action alone over 2013-2017. Thus, attributing the trends over 2002-2016 to the Clean Air Action may not fully correct based the current model experiments. One evidence to support this argument is in Fig 4, the turning points driven the trend of PM2.5 were in 2010 and 2011, these were before the Clean Air Action. Therefore, I think what suppressed the unfavorable climate influences is not the Clean Air Action alone, but all emission control strategies over 2002-2016, based on the analyses in the present manuscript.

Other Comments:
Page 8, Line 241:
The two sentences here “there is no notable declining trend in number of haze days inferred from observations over 2005-2016” and “it is consistent that both model and observations indicate rapid declines in number of haze days (-4.8 days and -3.0 days per winter, respectively)” are inconsistent. Was the second sentence for the period of 2011-2016?

Page 9, Line 275:
What is the difference of RH and RH2? Please clarify.

Page 10, Figure 5:
What is a blue y-axis “wind speed” in Fig 5 panel (c)for? Is it the same as panel (b) and why not merge panel (b) and panel (c)?

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ED: Publish subject to technical corrections (24 Dec 2019) by Xiaohong Liu

AR by Meng Gao on behalf of the Authors (27 Dec 2019) Author's response Manuscript

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Short summary

We quantified the relative influences of anthropogenic emissions and meteorological conditions on PM_2.5 concentrations in Beijing over the winters of 2002–2016. Meteorological conditions over the study period would have led to an increase of haze in Beijing, but the strict emission control measures have suppressed the unfavorable influences of the recent climate.

China's emission control strategies have suppressed unfavorable influences of climate on wintertime PM2.5 concentrations in Beijing since 2002

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Interactive discussion

Peer-review completion

China's emission control strategies have suppressed unfavorable influences of climate on wintertime PM_2.5 concentrations in Beijing since 2002