New insights into the vertical structure of the September 2015 dust storm employing eight ceilometers and auxiliary measurements over Israel

Uzan, Leenes; Egert, Smadar; Alpert, Pinhas

doi:https://doi.org/10.5194/acp-18-3203-2018

Articles | Volume 18, issue 5

https://doi.org/10.5194/acp-18-3203-2018

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

Special issue:

Environmental changes and hazards in the Dead Sea region (NHESS/ACP/HESS/SE...

https://doi.org/10.5194/acp-18-3203-2018

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

Articles | Volume 18, issue 5

Research article

|

06 Mar 2018

Research article |

| 06 Mar 2018

New insights into the vertical structure of the September 2015 dust storm employing eight ceilometers and auxiliary measurements over Israel

Leenes Uzan, Smadar Egert, and Pinhas Alpert

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Final revised paper (published on 06 Mar 2018)
Preprint (discussion started on 24 Aug 2017)

Interactive discussion

Status: closed

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

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RC1: 'review of Uzan et al.', Anonymous Referee #1, 21 Sep 2017
RC2: 'review and recommendations', Anonymous Referee #2, 17 Oct 2017
AC1: 'Point to point response to referees', Leenes Uzan, 30 Nov 2017
AC2: 'Summarized file: point to point response to both referees', Leenes Uzan, 04 Dec 2017

Peer-review completion

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

AR by Leenes Uzan on behalf of the Authors (01 Jan 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (03 Jan 2018) by Hailong Wang

RR by Anonymous Referee #2 (08 Jan 2018)

Suggestions for revision or reasons for rejection

The revised version is significantly improved, more than I expected. The authors did a rather good job. Thank you for this!

The Introduction now provides a very nice overview!

But I still have problems with the ceilometer observations….

P10, L286: you state: …. we refer to the ceilometer signal count profiles between 100-1000m. This statement is good, but I am afraid that non-lidar dust-interested readers will not remember that statement when they see Figures 6-12. I will come to this point again, below.

P13, L355: Global radiation measured … Table 6. …. ? In Table 6, I find PM10 for 31 stations only. Do you mean Table 7 (but I do not have Table 7?)

P13, L378: I have generally my problems with the uncertainty statements (here MSG, somewhere else MODIS). I think in the paper of Mamouri they compared MODIS with AERONET for these very large AODs and gave some uncertainty statements. At least, 15% uncertainty appears to me rather low… for these extreme dust conditions with AOD probably even larger than 3… , I think the AOD uncertainty is of the order of 1.0 or even more.

P14, L395: Again, an uncertainty of 0.1 is probably ok for AOD< 1.0, but what about cases with >2.5? Then the error is certainly much larger, of the order of 0.5 to 1.0.

Section 3, I would introduce subsections! … with head lines (titles): 3.1 7 September 2015, 3.2 8 September 2015 etc. That would make the full and very complex discussion section easier to read.

P15, L426: Now the ceilometer observations are introduced….

P23, L557: .. and now, the discussion of the 8 September starts. As mentioned above, we need a clear statement that the colored areas in Figs 6-12 only show the lowest few hundred meters of the dust layer (which actually reached up to 4-5 km according to all the articles published before: Mamouri, Solomos, Gasch, and all the CALIOP observations, including the one shown in Fig 21, and Fig.21 comes much too late, to my opinion). Without such a clear remark (and this remark is definitely not given), most readers will intuitively think, the ceilometers show the entire dust layer.

If I compare Fig 9 with Fig 16 (the radiosonde profiles are very nice now!), then my opinion is confirmed that the ceilometers see only the lowest few hundred meters of the dust layer because the top height of the colored ceilometer backscatter areas coincide with the temperature inversion height (the base of the main dust layer, higher up…).

Fig 13: This plots shows nothing? Clear skies? Or just overloaded by heavy dust? The plot is almost entirely deep blue! But there should be a lot of dust according to all the satellite observations presented. So, maybe an APD, PMT overloading effect. The ceilometer detectors were just overloaded because of the huge amount of dust around? Please clarify.

Fig 17: Now the quantitative analysis is much improved. But I want to say, just that you think about it….: An attenuated backscatter coefficient of 10-4 m-1 sr-1 is equivalent to 4 km-1 extinction coefficient (for a lidar ratio of 40sr), and thus 2x10-4 means 8 km-1 extinction. Do you have the feeling, this is correct? I just ask you! Do you believe in your numbers?

The other point: Fig 17 nicely shows that backscatter signals (from five of the seven ceilometers) which are backscattered from heights above 500-700m were completely attenuated so that the attenuated backscatter coefficient is simply zero. That does not mean that the backscatter coefficient was zero…… The backscatter coefficient was probably even larger than at ground. So, attenuated backscatter is a very ‘dangerous’ parameter.

P23, L571: … reveal a two-layer shape …. How do you know, there may have been even 4 or 5 distinct layers up to 4-5 km height.

P24, L590: … which may indicate the dust plume base height….. Again this statement is confusing when having the colored areas observed with ceilometers in mind, which suggest--- TOP HEIGHT. Non-lidar people will not understand what you want to say… without these explanations I suggested above.

Fig.20: Black numbers on dark blue or dark brownish background… any idea to improve that?

P26, L625: The dust top height of 2-4 km is mentioned here for the first time (if I read the paper carefully enough). This is simply much too late. And the overall context given by the papers of Mamouri et al., Solomos et al. (presenting CALIOP obs.), Gasch et al. (also presenting CALIOP obs.) clearly shows that the top height was always and everywhere at 4-5km height, in full agreement with your Fig 21 for 10 September. So, please improve…. Not 2-4 km, it was 4-5 km …

All in all, the paper is already in a good shape, very much improved, well done! But some additional work would make the article even more clear and straight forward!

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RR by Anonymous Referee #1 (10 Jan 2018)

ED: Publish subject to minor revisions (review by editor) (10 Jan 2018) by Hailong Wang

AR by Leenes Uzan on behalf of the Authors (19 Jan 2018) Author's response Manuscript

ED: Publish as is (24 Jan 2018) by Hailong Wang

Short summary

The extraordinarily extreme dust storm of September 2015 is analyzed using an array of eight ceilometers and auxiliary measurements, revealing the dust plume penetration, ground coverage and gradual dispersion in the first kilometer above Israel. This research emphasized the importance of ceilometer networks as an essential tool in the analysis of meteorological phenomena and aerosol transport as being the most valuable in the mesoscale.