Timescale dependence of the relationship between the East Asian summer monsoon strength and precipitation over eastern China in the last millennium

Shi, Jian; Yan, Qing; Wang, Huijun

doi:https://doi.org/10.5194/cp-14-577-2018

Articles | Volume 14, issue 4

https://doi.org/10.5194/cp-14-577-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/cp-14-577-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 14, issue 4

Research article

|

26 Apr 2018

Research article |

| 26 Apr 2018

Timescale dependence of the relationship between the East Asian summer monsoon strength and precipitation over eastern China in the last millennium

Jian Shi, Qing Yan, and Huijun Wang

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Final revised paper (published on 26 Apr 2018)
Supplement to the final revised paper
Preprint (discussion started on 16 Oct 2017)
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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', Anonymous Referee #1, 05 Nov 2017
- AC1: 'Responses to Reviewer#1', Jian Shi, 05 Jan 2018
RC2: 'Timescale-dependence of the relationship between the East Asian summer monsoon strength and precipitation over eastern China in the last millennium by Jian Shi, Qing Yan, and Huijun Wang', Anonymous Referee #2, 17 Nov 2017
- AC2: 'Responses to Reviewer#2', Jian Shi, 05 Jan 2018

Peer-review completion

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

ED: Reconsider after major revisions (19 Jan 2018) by Martin Claussen

AR by Jian Shi on behalf of the Authors (25 Jan 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (29 Jan 2018) by Martin Claussen

RR by Anonymous Referee #1 (11 Feb 2018)

Suggestions for revision or reasons for rejection

I thank the authors for considering my comments and for revising the manuscript accordingly. However, I still have one concern regarding the connection between the North Atlantic and the variations in the link between Monsoon and East Asia precipitation, as I explain below.

The new pieces of text that have been introduced in the revised version require copy-editing. The English is not quite correct.

The authors estimate the correlation patterns between that link and the North Atlantic SST. They found correlations of the order of 0.15, using the model ensemble mean. This means that even by strongly filtering out the noise of the individual realisation, the correlations remain rather low, although possibly significant. Therefore, there could be a link, but it is hard to believe that the North Atlantic SSTs are the main factor that explain the variability in the precipitation-Monsoon link. The explained variances are really low.

The authors do include a physical explanation to explain this link, via the modulation of temperature in East Asia by the North Atlantic SSTs. In their Fig S3 they show the composite fields of Asian temperature stratified by phases of the North Atlantic SST. Colder periods in East Asia should cause stronger precipitation-Monsoon link due to more effective condensation. In this chain of reasoning, I think there is a missing link, though. The authors should show in the first place that the air temperature in East Asia temperature is indeed the driving factor. This could be shown by calculating similar composite patterns as in Fig S3 but stratified by the precipitation-Monsoon links, i.e. constructing means of Asian temperature i periods where the precipitation-Monsoon link are weaker or stronger. Alternatively, they could show a figure similar to Fig11 but also showing the temperature over land in East Asia or over whole Asia for that matter. If the authors' hypothesis is true , we should see a clear correlation to air temperature.

Assuming this comes out as true, then the hypothesis would be more or less validated. It would remain to see that the main driver of decadal variations in East Asian temperature is the North Atlantic SST - something that I strongly doubt (there may be a link, but it is hard to believe that the North Atlantic is the main driver), but at least the manuscript could include it as a working hypothesis

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RR by Anonymous Referee #2 (02 Mar 2018)

Suggestions for revision or reasons for rejection

The authors have included more information from the CESM Last Millennium Ensemble (LME). However, this could be extended a bit in discussing the uncertainty regarding the single model results. For example, Figure 2c should be discussed further in connection with Figure S3 (which shows the same thing as far as I understood). In the LME runs, (fig. S3) the individual members show dramatic differences (3-4 with positive sign, 4-5 with negative sign. If such a distribution was representative for ensembles from the other models, one would have to conclude that the findings from individual runs (Fig. 2c) could be just by chance. I would also suggest providing a Taylor diagram figure in the supplement (as Fig. 1b) for the CESM LME.

Minor issues:
Page 3, ln 31: better: nine CESM-LME full-forcing experiment, one control experiment, and several sensitivity experiments with individual forcing (…

Page 6, ln 24ff: the “obvious” depends a bit on the view of the reader. In many simulations the 100-200 year periods are much more prominent that the 40-60 years.
The authors play the lower-frequency a bit down, put it is very prominent when looking just at the RPC time series from, e,g, MPI-ESM-P.
Page 7, ln 15ff. along the same line: the 120-150 year period is prominent both in the inforced control run and the MME. Is there any evidence from other analyses of the LME where this comes from?

Page 8, ln 1ff: The fact that AMO is more consistent among ensemble members implies that AMO is more directly influenced by external forcing. This issue is discussed in a manuscript on a recent reconstruction of the AMO (Wang et al Nature Geosciences, 2017, doi:10.1038/ngeo2962), which could be included here.

Referee Report: PDF

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ED: Publish subject to minor revisions (review by editor) (15 Mar 2018) by Martin Claussen

AR by Jian Shi on behalf of the Authors (22 Mar 2018) Author's response Manuscript

ED: Publish as is (28 Mar 2018) by Martin Claussen

Short summary

The paleo-East Asian summer monsoon (EASM) is widely reconstructed by precipitation/humidity proxies over East Asia. However, based on numerical simulations over the last millennium, we find that the multi-decadal relationship between the EASM and precipitation over eastern China is non-stationary, which may be attributed to the internal variability of the climate system rather than the external forcings. In contrast, the centennial EASM–precipitation relationship is much more close and stable.