Variations of cloud condensation nuclei (CCN) and aerosol activity during fog–haze episode: a case study from Shanghai

Leng, C.; Zhang, Q.; Zhang, D.; Xu, C.; Cheng, T.; Zhang, R.; Tao, J.; Chen, J.; Zha, S.; Zhang, Y.; Li, X.; Kong, L.; Gao, W.

doi:https://doi.org/10.5194/acp-14-12499-2014

Articles | Volume 14, issue 22

https://doi.org/10.5194/acp-14-12499-2014

© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-14-12499-2014

© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 14, issue 22

Research article

|

27 Nov 2014

Research article |

| 27 Nov 2014

Variations of cloud condensation nuclei (CCN) and aerosol activity during fog–haze episode: a case study from Shanghai

C. Leng, Q. Zhang, D. Zhang, C. Xu, T. Cheng, R. Zhang, J. Tao, J. Chen, S. Zha, Y. Zhang, X. Li, L. Kong, and W. Gao

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Final revised paper (published on 27 Nov 2014)
Preprint (discussion started on 26 Jun 2014)

Interactive discussion

Status: closed

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

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- Supplement

RC C4338: 'comments to acp-2014-269', Anonymous Referee #1, 01 Jul 2014
- AC C6215: 'Response to anonymous referee #1's comments and the related information', Tiantao Cheng, 26 Aug 2014
RC C5919: 'Review of Leng et al., acp-2014-269', Anonymous Referee #2, 15 Aug 2014
- AC C6241: 'Response to anonymous referee #2's comments and the related information', Tiantao Cheng, 27 Aug 2014

Peer-review completion

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

AR by Tiantao Cheng on behalf of the Authors (27 Aug 2014) Author's response Manuscript

ED: Referee Nomination & Report Request started (27 Aug 2014) by Veli-Matti Kerminen

RR by Anonymous Referee #2 (02 Oct 2014)

Suggestions for revision or reasons for rejection

General comments

This is the second round review of the paper "Variations of cloud condensation nuclei (CCN) and aerosol activity during fog-haze episode: a case study from Shanghai" by Leng et al. The paper has improved from the previous version. I have still few concerns about the paper. The dataset is short which somewhat weakens the general value of the conclusions. The measurements have been going on for four years and the conclusions would be much stronger if more cases would be used. With additional data there would be a possibility to find a solid fog-case too. There are some technical and scientific issues, some of which remain from the previous version, which should be considered and explained in more detail before publication. Detailed comments are listed below.

Specific comments

- The diurnal variation has some effect on the results (e.g. foggy-haze case at night/in the morning other during the day).
- The lidar data analysis in general needs polishing and more explanation. The PBL top heights are not realistic for some periods (see detailed comments below). This will affect the analysis and results related to PBL heights and mixing.

Methods
- Section 2.2, lidar methods: What is the full overlap of the system (i.e. from what altitude above ground the data is reliable)? The upper detection limits are mentioned but the lower limit is missing. What is the effect of the overlap on the comparison to ground-based measurements, if any?
- Section 2.3, line 254-256: “... without anthropogenic particulate pollutants... “. Maybe “with less anthropogenic...” would be a better. There is always some anthropogenic influence.

Results
- Section 3.1., line 292: “clear episode”, maybe clear “case” instead of episode.
- Section 3.3.1, line 408 & Conclusions line 545-546: Is the great influence of wind direction and temperature shown somewhere?
- Section 3.3.2, line 447-448: “...significant enchancement of aerosol extinction coefficient on 7 and 8 Nov (Fig3)”. This is difficult to state based on the figure. Maybe some values of extinction coefficients would give more information. Or plotting some hourly profiles in a figure for comparison.

Conclusions
- Lines 558-559: “BC was correlated well with N(CCN) in the foggy-hazy and hazy cases but the clear case, as not N(CCN)/N(CN) did.” Check this sentence.

Tables
- Table 1: The PBL values should be re-checked after proper calculation/cleaning of the PBL-top data. Does the PBL detection suffer from the fog to that extent that the PBL values would not be valid for that period? Where are the extinction values from? From certain altitude or averaged over the boundary layer or for the whole profile? Please add a unit for the extinction. I suggest decreasing the number of decimals to one in the weather parameters, due to the measurement accuracies of the instruments (I doubt that the accuracy is this good).

Figures
- Please mention the meaning of the red and black boxes of the plots in the Figure captions. Now this is in the text but it would help the reader if the figures would explain themselves.
- Figure 3: I assume the orange triangles in the upper figure are the PBL top values which come from some automatic routine. These values are in many parts unrealistic and the plot needs some polishing. For example on 6th Oct there are values from 300m to almost 2 km at the same time. Also the missing data on 7th Oct 5:00-9:00 and the PBL top points around the period seem odd and unrealistic. Further on there are many PBL top points that need to be re-checked in the Figure. What do the two subplots actually show? Check the z-labels of the colorbars and Figure caption. Now they do not match.
- Figure 5: This shows the distribution to some extent. Even more clear presentation would be a plot with just three curves, size on the x-axis, number concentration in some format on y-axis (e.g. dN/dDp, depending how the instrument size bins are distributed).
- Figure 10 & 11: These figures present nearly the same results. Are both needed as figures?

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ED: Reconsider after minor revisions (Editor review) (03 Oct 2014) by Veli-Matti Kerminen

AR by Tiantao Cheng on behalf of the Authors (06 Oct 2014) Author's response Manuscript

ED: Publish subject to technical corrections (09 Oct 2014) by Veli-Matti Kerminen

The authors have made the necessary changes based on the reviewer comments. Minor technical/grammatical corrections need to be still made before uploading the final files into the system.

Abstract. line 34: should be “…were usually higher in the hazy case”; line 36: “…in the foggy-hazy and clear cases. The BC…”; line 37: ”..in the foggy-..”, line 38: ”…in the clear…”; line 39: “..in both foggy-hazy and hazy cases.”

Lines 57-61: should be something like “Elevated CCN loadings… Feichter, 2005), in addition to which they can promote…”

Line 86: “…the aerosol mass concentration consists of carbonaceous…”

Line 132: start: “The CCN number concentration (NCCN) was…”

Line 272: maybe a new paragraph could be started from “Fog can..”

Lines 280-281: “A fog or …and high (>90%) relative humidity (RH). When…”

Line 283: ”Figures 2 and 3…”, the same in other places where more than 1 figure is referred to.

Line 314: “A similar classification was applied to the measurements…”

Lines 317-320 and elsewhere: do not use comma (,) in the middle of numbers. You may use space when having more than 5 digits, e.g. “10 500”

Lines 322-324: There is something wrong in this sentence. Do you mean “In general, 20-100 nm (Aitken mode) particles dominated the particle number size distribution, probably due to…”?

Lines 342-344: The concentratoins appear to be too accurate, maybe 54.2 or 54 etc.

Lines 356-357: The reader may confuse this to aerosol mass burden. Maybe better to say “..to the global burden of aerosol number than…”

Figure 5: Usually particle size is plotted in a logaritmic scale in these kind of plots. Is the linear scale meant to highlight the size distribution above 100 nm?

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AR by Tiantao Cheng on behalf of the Authors (10 Oct 2014) Manuscript