A hybrid method for reconstructing the historical evolution of aerosol optical depth from sunshine duration measurements

Wandji Nyamsi, William; Lipponen, Antti; Sanchez-Lorenzo, Arturo; Wild, Martin; Arola, Antti

doi:https://doi.org/10.5194/amt-13-3061-2020

Articles | Volume 13, issue 6

https://doi.org/10.5194/amt-13-3061-2020

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

https://doi.org/10.5194/amt-13-3061-2020

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

Articles | Volume 13, issue 6

Research article

|

11 Jun 2020

Research article |

| 11 Jun 2020

A hybrid method for reconstructing the historical evolution of aerosol optical depth from sunshine duration measurements

William Wandji Nyamsi, Antti Lipponen, Arturo Sanchez-Lorenzo, Martin Wild, and Antti Arola

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Final revised paper (published on 11 Jun 2020)
Supplement to the final revised paper
Preprint (discussion started on 06 Jan 2020)

Interactive discussion

Status: closed

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

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RC1: 'review of William Wandji Nyamsi et al.', Anonymous Referee #1, 18 Jan 2020
- AC1: 'ANSWERS TO REFEREE #1', William Wandji, 31 Mar 2020
RC2: 'Review of "A hybrid method for reconstructing the historical evolution of aerosol optical depth from sunshine duration measurements"', Anonymous Referee #2, 24 Feb 2020
- AC2: 'ANSWERS TO REFEREE #2', William Wandji, 31 Mar 2020

Peer-review completion

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

AR by William Wandji on behalf of the Authors (31 Mar 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (02 Apr 2020) by Andrew Sayer

RR by Anonymous Referee #1 (03 Apr 2020)

RR by Anonymous Referee #2 (26 Apr 2020)

ED: Publish subject to minor revisions (review by editor) (27 Apr 2020) by Andrew Sayer

Dear authors,

I have now received two reviews of your revised manuscript. Both authors feel, and I agree, that the revision addresses many of the comments raised in the main peer review. However, both reviewers have a few remaining comments, reproduced below:

Reviewer 1
1. Authors dealing with the uncertainty analysis would be complete if you cold add the figure from wich the (new) equation 8 has been extracted.

2. concerning cloud cover, the 3 points per day availability is the best existing. So I understand the limitations. However, it is quite simple to think that during all days with 0 cloud cover over these 3 measurements during the day there will be a number of days with some (e.g. cirrus) clouds in between. That will systematically bias the AOD retrieval to higher values. I guess authors just have to mention this possibility ?

Reviewer 2

1. It is not clear if the authors investigated the possibility of using remote sensing cloud cover products in the study. The authors must mention in the manuscript if it is feasible or not to use this type of data in the reconstruction of AOD.

2. Although the authors mention in the answer to my main comment that: "In this study, a cloud-free day is assumed when the mean daily value of TCC is rounded to 0 okta. That average value is computed from three-daily observations, typically at 06:00, 12:00 and 18:00 UTC.", the ATB of the ECAD daily data reveals that "Daily mean cloud cover CC: Whenever synoptical cloud cover data is available at 00, 06, 12 and/or 18 UT, mean daily cloud cover is calculated as the average of the available values" (in document https://eca.knmi.nl//documents/atbd.pdf, page 9). The authors must clarify this aspect.

3. The authors must verify the link which points to the ECAD dataset (Section 2.2); the link assigned belongs to the Finish Met. Institute.

4. Apparently, there is a typo in the caption of figure 5.

I would appreciate if you could further revise the manuscript with attention to the above comments. As they are fairly minor, I expect to accept the paper for publication following these revisions without need for a further round of peer review.

Please let me know if you have any questions.

Best wishes,

Andrew

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AR by William Wandji on behalf of the Authors (30 Apr 2020) Author's response Manuscript

ED: Publish as is (05 May 2020) by Andrew Sayer

AR by William Wandji on behalf of the Authors (06 May 2020)

Short summary

This paper proposes a novel and accurate method for estimating and reconstructing aerosol optical depth from sunshine duration measurements under cloud-free conditions at any place and time since the late 19th century. The method performs very well when compared to AErosol RObotic NETwork measurements and operates an efficient detection of signals from massive volcanic eruptions. Reconstructed long-term aerosol optical depths are in agreement with the dimming/brightening phenomenon.