Contrasting impacts of two types of El Niño events on winter haze days in China's Jing-Jin-Ji region

Yu, Xiaochao; Wang, Zhili; Zhang, Hua; He, Jianjun; Li, Ying

doi:https://doi.org/10.5194/acp-20-10279-2020

Articles | Volume 20, issue 17

https://doi.org/10.5194/acp-20-10279-2020

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

https://doi.org/10.5194/acp-20-10279-2020

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

Articles | Volume 20, issue 17

Research article

|

04 Sep 2020

Research article |

| 04 Sep 2020

Contrasting impacts of two types of El Niño events on winter haze days in China's Jing-Jin-Ji region

Xiaochao Yu, Zhili Wang, Hua Zhang, Jianjun He, and Ying Li

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Final revised paper (published on 04 Sep 2020)
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Preprint (discussion started on 17 Mar 2020)
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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: 'Review for “Contrasting impacts of two types of El Niño events on winter haze days in China’s Jing-Jin-Ji region” by Yu et al.', Anonymous Referee #1, 13 Apr 2020
- AC1: 'Response to Referee 1', Xiaochao Yu, 09 Jun 2020
RC2: 'review', Anonymous Referee #2, 15 Apr 2020
- AC2: 'Response to Referee 2', Xiaochao Yu, 09 Jun 2020

Peer-review completion

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

AR by Xiaochao Yu on behalf of the Authors (10 Jun 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (19 Jun 2020) by Patrick Jöckel

RR by Anonymous Referee #2 (02 Jul 2020)

RR by Anonymous Referee #1 (03 Jul 2020)

Suggestions for revision or reasons for rejection

Review for revised version of “Contrasting impacts of two types of El Niño events on winter haze days in China’s Jing-Jin-Ji region” by Yu et al.

The authors have adequately addressed most of my concerns with the previous version of their manuscript. I recommend publication with some minor additional changes listed below.

Regarding the statistical significance of the correlations shown in Fig. 1 and Table 2, it is stated in the response to the review that the degrees of freedom were determined from the number of months taken into account (DJF from 1961 to 2012).
Are the three consecutive winter months independent of each other? Otherwise the degrees of freedom would reduce to 50 and the threshold for significance would increase to something like 0.25.

However, I think the paper would benefit from not putting too much emphasis on these numbers anyway. As the authors elude to in the revised version, there are a number of local factors complicating the relationship between El Niño events and WHD. I think it would thus be more instructive to focus on the consistent responses found and formulate them in terms of tendencies rather than first stating that some very low correlations are significant and then admitting that they are weak.
To give an example, instead of writing “ As seen in Figure 1, the absolute values of the correlation coefficients at some stations exceed 0.4. There are statistically significant correlations between the site averaged WHD in the JJJ region and the Iep and Icp indices (p 0.05), with correlation coefficients of 0.16 and 0.2, respectively (Table 2). These low correlation values likely imply a mild impact of ENSO on WHD. However, the corresponding correlation coefficients reach 0.31 and 0.43, respectively, with a confidence level of 99%, when only considering the stations at which the correlations pass a significance level of 90%” (lines 154 to 159) one could say something like “Even though the correlations are rather low with values hardly exceeding at 0.4 at individual stations and correlations of WHD averaged over the JJJ region and Iep and Icp of only 0.16 and -0.2, respectively, a pattern emerges with central Pacific El Niños being associated with less WHD and a tendency for more WHD during eastern Pacific El Niños. This is corroborated by the composite analysis…”

Specific comments:
Line 9: I would suggest “El Niño events differ widely in their patterns and intensities”
Line 10; “events” instead of “event”
Line 17: “obvious” or “clear instead of “obviously”
Line 39: “As the strongest” instead of “As a strongest”
Line 106: What is meant by “smoothing average”? A running mean?

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ED: Publish subject to minor revisions (review by editor) (14 Jul 2020) by Patrick Jöckel

AR by Xiaochao Yu on behalf of the Authors (20 Jul 2020) Author's response Manuscript

ED: Publish as is (23 Jul 2020) by Patrick Jöckel

AR by Xiaochao Yu on behalf of the Authors (25 Jul 2020) Author's response Manuscript

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Short summary

There are statistically significant positive and negative correlations, respectively, between winter haze days (WHDs) in China's Jing-Jin-Ji region and eastern Pacific and central Pacific El Niño events. These opposite changes in WHDs are attributable to the anomalies of both large-scale circulation and local synoptic conditions corresponding to two types of El Niño. Our study highlights the importance of distinguishing the impacts of two types of El Niño on winter haze pollution in this region.