Numerical Simulation of Tehran Dust Storm on 2 June 2014: A Case Study of Agricultural Abandoned Lands as Emission Sources

Round 1

Reviewer 1 Report

This study showcased the ability of a numerical model, DREAM, for early warning of dust storms by simulating (hindcasting) a severe dust event in Tehran, Iran as an example. The study claimed that this is the first numerical model of its kind developed for Tehran. The analysis has an acceptable quality, and the manuscript is relatively clear. With minor revisions, I would recommend the work to be published. Please find my suggestions below:

 

1. It is not very clear to me about the advantages/disadvantages of WRF-Chem compared to DREAM. In the Discussion section, the authors suggested that both models provided simulations with good quality, and the key advantage of DREAM seemed to be a more accurate dust source mask. Therefore, can the WRF-Chem model also use the same dust source mask, and is the quality of WRF-Chem expected to improve when using the same dust source mask? If the WRF-Chem could have a similar quality as DREAM when using the same mask, what were the remaining advantages of DREAM (i.e., would there still be a strong reason to use DREAM over WRF-Chem)? As DREAM plays a fundamental role to achieve the claimed goal (early warning of dust events), I would like to see more discussions about these questions.

 

2. I am interested to see a more comprehensive comparison between the ground PM10 observations and PM10 simulations during the dust event at the monitoring locations. The observations are “gold-standard”, so they should be good independent reference data to evaluate the quality of simulations even though the monitoring locations were mostly in urban areas. However, this critical comparison was not properly conducted and described.

 

3. Line 59, pg. 2: Is there any reference to support that the PM10 values could be as high as 10000 ug/m3 during a severe dust event?

 

4. Line 206, pg. 6: A more detailed introduction to DREAM with necessary references is needed. It is important to clarify what type of model it is (e.g., whether it is a physical transport-dispersion model or a chemical model) and what the major characteristics of the model are (e.g., how it is designed to simulate dust events).

 

5. Figure 9: The figure captions should be standalone with necessary information to explain the details of the figures. In this case, it should be added to the caption that what colors stand for what features (e.g., red means high convective activity).

 

6. Figure 11: In the subfigure of 13UTC, there are some redundant dots around the dashed line.

 

7. I would recommend unifying the geographical ranges of the figures. Some figures showed the range of the “case study area” but others showed a substantially larger domain without identification of the “case area” (e.g., Figure 3 and Figure 4). Even for the figures supposed to show the “case area”, the geographical ranges were not exactly the same, which was very confusing.

 

8. I would also recommend the authors thoroughly examine the potential grammar issues (there are some obvious ones) with the help of an English native speaker.

Author Response

Please see the attachment. 

Author Response File: Author Response.pdf

Reviewer 2 Report

General comments:

This manuscript contains too many grammar errors needed to be checked. The template of writings should also be modified (for example, the layout of the subtitles of Figures, etc.).  The grammar errors made the text difficult to follow. In this case, I suggest the authors rephrase the text before further reviewing of this article. 

 

Other comments:

L132-136: This section is more like an introduction of the usage of the data, not analysis of the data. Should be rephrase to something like: “Data used in this study include meteorological and air quality observations, as well as numerical simulations.”

L138: “In Figure 1 is presented models’ domain of the numerical simulation…” grammar error.

Figure1: Domains of …

L153-154: “Stations from which were collected meteorological data are presented in Table 1 and Figure 2a.” Writing style needs to check. Not the general style of scientific writing. Should be changed as something like: “Table 1 and Figure 2a show stations with meteorological observations used in this study.”, or “Data are collected from thirteen meteorological stations as in Table 1 and Figure 2a.”

L162: “…, which is the observational proof, …” not sure what it means.

L164-165: “Both locations are listed in the list of meteorological stations, but METAR data will provide added values for this analysis.” What do you mean “added” values? additional values?

L168-171: “They include all airborne particles, but in case of severe local dust storms immediate significant increase in PM10 happens (up to several 1000 μm/m3 or 10000 μm/m3 near sources), and it can be assumed it is actually the PM10 concentration of the dust particles.” Not sure what is means.

L176: Figure 2b for PM10 measurements, not Figure 1b.

Table 2: Why are there four sites with “no data”? if there are no data then the authors should not show it. Or the authors need to explain why to show them without available data.

L199-200: “Start of the forecast was 12 UTC 1 June and ended on the 00 UTC 3 June 2014 (forecast time 36h).” Not the general style of scientific writing. Should be change to “The forecast started at 12 UTC on June 1, 2014 and ended at 00 UTC on June 3, 2014 (the forecast time is 36 hours).”

L210: “in further text “dust source mask – DSM” better to rephrase as “i.e., the dust source mask, dotted as DSM”.

L214: NDVI in long name for the first time in the text. Same case for STATSGO-FAO.

L216-217: “Soil texture is information already included in numerical 216 weather prediction models (in this case from STATSGO-FAO database) and gives an in- 217 formation about soil particles size distribution.” The word “information” is not the right word for usage.

L218-220: “In this case study forecast of PM10 is presented, meaning that clay and silt size particles are contributors to the PM10 concentration.” Please rephrase this sentence. There are lots of factors contributing PM10, not just clay and silt size particles.

L221-222: “…, also dust emission rates depend on the clay and silt content in the soil.”  Please rephrase this sentence.

Figure 3. Over the model domain are … -> grammar error.

Figure 4. the (a), (b), and (c) should be in front of source mask, DSM2, and DSM3, individually. Also to be easily inter-comparison, original source mask should be using the same protocols for plotting as same as (b) and (c).

L227: The spatial resolution for DREAM is 0.1 degree. What’s the resolution of 0.025 degree in L204?

L246: “Forecast done for case study of Tehran dust storm was done with the same model set-up as DREAM… ” The forecast was done for the case study of …

L174-175: “Averaging the values for one hour does not represent peaking PM10 values during the dust storm passing, which lasts about 10 minutes.” This conflicts Figure 10 for the peak of PM10 while dust storm passing by.

Figure 14 and 16: where is the geolocation of the cross section?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Overview and General Impression
The described in the manuscript (MS) study is dedicated on hindcast/numerical simulation of Tehran dust storm in 2014. The subject of the MS relevant and well argued from the authors. It fits also good in the scope of ‘Atmosphere’.
As main strength of the work, alongside the in-depth ‘synergistic’ (i.e. based on the combined and skillful use of practically all available data) analysis, I would outline the focus on the dust source and, subsequently, the use of different dust source masks. valuable are also the key messages, titled ‘learned lessons’ and presented as a list. 
During my review I have not detected any principal flaws or main caveats that makes the MS not publishable or requires major revision and thus I have not included ‘Major Remarks’ section in this review.
I have, however, some proposals from which, according my opinion, the MS could benefit.

- The relevance of the question of the over exploited/abandoned agricultural lands as potential dust sources, respectively airborne dust hazards, deserves a little more attention. Shortly to mention probably the most recognizable example (if possible – with reference) the American Dust Bowl during the 1930s could be good idea. The literature for such ‘non-desert’ cases is also scarce, but the motivation could be supported with citation of previous works. A good description of such event can be find in the articles with followingDOIs:
10.5194/acp-8-997-2008 
and numerical hindcast of the same case in:
10.1016/j.atmosenv.2011.04.061
- Hence the vertical atmospheric movements are considered in the study, it is good to emphasize that the both models are non-hydrostatic.
- The selected dust activation scheme (it is possible to select among listed options) in WRF-Chem have to be stated and motivated.

specific remarks
- r60: ...magnitude ~1000s μg/m^3 →  1000 μg/m^3 (as the above notation)
- r94: remove (Iran) - it is already explained where the domain is.
- r164: The notations of the both airports are the same.
- r190: T-difference ()+()+() is cryptic. Reformulate if possible.
- r286-289: It is not clear what is placed on the radii of the polar diagrams. Speed? Units? On figure 8 is correct.
-r295: The list contains five items instead of four (funny!). It will be good to note  the horizontal resolution in the list again.
- r459: 20 m/2 → 20 m/s
 -r483: The caption of Figure 15 could be shortened as: ‘Same as a) and b) respectively, but for 13 UTC.
- Figures 16 and 18: The notation of the ordinate and the vertical levels are not stated in the captions; you can refer to Figure 14 for sake of brevity.
 - Due to their importance, the learned lessons in the ‘Conclusion’ could be outlined as separate paragraphs.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The authors have made all changes, suggested by me in my first review and thus I have no more remarks, except two (one of them considers a new text)

r254: "...of dust particle sizes (radii of 0.15, 0.25, 0.45, 0.78, 1..." - radii or aerodynamic diameter?, Check, please!

r453,r457, r458, r566, r615, r680: The units of the concentration: μm/m³ -->μg/m³