Low-level stratiform clouds and dynamical features observed within the southern West African monsoon

Dione, Cheikh; Lohou, Fabienne; Lothon, Marie; Adler, Bianca; Babić, Karmen; Kalthoff, Norbert; Pedruzo-Bagazgoitia, Xabier; Bezombes, Yannick; Gabella, Omar

doi:https://doi.org/10.5194/acp-19-8979-2019

Articles | Volume 19, issue 13

Atmos. Chem. Phys., 19, 8979–8997, 2019

https://doi.org/10.5194/acp-19-8979-2019

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

Special issue: Results of the project "Dynamics–aerosol–chemistry–cloud...

Atmos. Chem. Phys., 19, 8979–8997, 2019

https://doi.org/10.5194/acp-19-8979-2019

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

Articles | Volume 19, issue 13

Research article 16 Jul 2019

Research article | 16 Jul 2019

Low-level stratiform clouds and dynamical features observed within the southern West African monsoon

Cheikh Dione et al.

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Final revised paper (published on 16 Jul 2019)
Preprint (discussion started on 05 Dec 2018)

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 Jan 2019
- AC1: 'AC', Cheikh Dione, 27 Apr 2019
RC2: 'Review of Dione et al.', Anonymous Referee #2, 08 Jan 2019
- AC2: 'AC', Cheikh Dione, 27 Apr 2019
RC3: 'Review of “Low-level cloud and dynamical features within the southern West African monsoon” by Cheikh Dione et al.', Anonymous Referee #3, 21 Jan 2019
- AC3: 'AC', Cheikh Dione, 27 Apr 2019
- AC4: 'AC', Cheikh Dione, 27 Apr 2019

Peer-review completion

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

AR by Cheikh Dione on behalf of the Authors (27 Apr 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (03 May 2019) by Susan van den Heever

RR by Michael Diamond (08 May 2019)

RR by Christophe Lavaysse (15 May 2019)

RR by Anonymous Referee #3 (19 May 2019)

Suggestions for revision or reasons for rejection

Review for “Low level stratiform clouds and dynamical features observed within the Southern West African Monsoon” by Cheikh Dione et al.

The authors have engaged very well with the reviewers’ comments and the manuscript is now in a state that is nearly ready for publication. Two figures should still be adjusted to improve legibility, but these are minor (technical) corrections.

Figure 4:
Considering this figure in the context of the manuscript, the barbs are not essential to this figure. It appears that wind direction is relevant for the identification of the NLLJ, as described on page 9 lines 17-18, but this is not referred to again when discussing figure 4. The barbs therefore clutter the figure while their information is summarized by the black vertical line for NLLJ onset.
The panels also contain an unnecessary dashed line at zero height, to separate the coloured figure from the line plot below. I propose the following improvements:
1. Remove the wind barbs. If the authors believe this is essential information for the paper (which is possible, given the barbs inform the NLLJ detection), then they can be included as a separate, supplementary figure. To reiterate, the authors do not mention wind direction in their discussion of Figure 4, so it does not appear essential for this figure.
2. Slightly detach the coloured figure from the line plot below, so that the need for the dashed line is removed. It will allow the y-axis label (Height) to be centered on the coloured figure and allow a separate y-axis (FLF?) for the line graph below.

Figure 10:
This figure does not require “the mean color of the IR cloud sky camera image” to be included. It is clear from Figure 9 how LLC onset and break are determined from the IR imagery, so the key point of Figure 10 is to show how LLC onset and break vary with NLLJ onset and break. The colours distract from this information.
Also, the black stars are difficult to discern, partly because of the colours, but also because markers are used for the four lines. Please remove the markers (currently squares) for those lines, so that the black starts stand out as the only markers of interest.

Minor comments:
Page 4, line 1-2: Please include the Dee et al. (2011) reference for ERA-Interim:
Dee, D.P., Uppala, S.M., Simmons, A.J., Berrisford, P., Poli, P., Kobayashi, S., Andrae, U., Balmaseda, M.A., Balsamo, G., Bauer, D.P. and Bechtold, P., 2011. The ERA‐Interim reanalysis: Configuration and performance of the data assimilation system. Quarterly Journal of the royal meteorological society, 137(656), pp.553-597.
Page 8, line 1: “3th” Should this be “1.5 UHF wind profiler gates”?
Page 9, line 21: “satisfied for at least two hours” – this part of the NLLJ onset criterion is not reflected in Figure 4 and the discussion, e.g. page 11, line 3-4: “the wind vertical profile reaches the threshold of 5 m/s at 2100 UTC, which is the onset time of the NLLJ”. Should the onset time be 2300 UTC, or does the two-hour criterion only apply to wind direction and/or surface sensible heat flux?

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ED: Publish subject to minor revisions (review by editor) (06 Jun 2019) by Susan van den Heever

AR by Anna Wenzel on behalf of the Authors (17 Jun 2019) Author's response

ED: Publish as is (19 Jun 2019) by Susan van den Heever

Short summary

Low atmospheric dynamics and low-level cloud (LLC) macrophysical properties are analyzed using in situ and remote sensing data collected from 20 June to 30 July at Savè, Benin, during the DACCIWA field campaign in 2016. We find that the low-level jet (LLJ), LLCs, monsoon flow, and maritime inflow reveal a day-to-day variability. LLCs form at the same level as the jet core height. The cloud base height is stationary at night and remains below the jet. The cloud top height is found above the jet.