Street-Level Sensing for Assessing Urban Microclimate (UMC) and Urban Heat Island (UHI) Effects on Air Quality

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The reviewed manuscript presents the results of measurements and modeling of the variability of selected meteorological parameters (including temperature) and ambient air quality measurements for streets lined with buildings of varying heights relative to the street width. Despite the significant workload involved in this study, certain aspects reveal serious methodological errors in the organization of the measurement experiment, particularly concerning nitrogen dioxide (NO₂) and ozone (O₃), which prevent me from giving it a positive assessment. Below, I provide several comments that should be considered for future improvements.

Major comments

1. The phrase "high H/W ratios 2.5–3.0, significantly increased temperatures 30.12–32.10°C and reduced wind speeds 0.02–3.20 m/s" used in the Abstract (lines 6-7) requires correction, as it is incomprehensible in the context of the changes caused ("increase in temperature to a level of approximately...", ""reduction of wind speed to approximately..." or "increase in temperature from .. to ...", "reduction in wind speed from ... to ...", or "increase in temperature by ...", "reduction in wind speed by ..."). Furthermore, it is not entirely clear whether "high H/W ratios 2.5–3.0" is intended to be a distinction of the range of data averaging or their range of variability to compare data obtained for H/W = 2.5 and H/W = 3.0. If the former, then the sentence proposes to provide the values ​​"2.5–3.0" in brackets. Why is the H/W ratio given in the Abstract different from the H/W described in Section 2.1 and Section 2.4.2?
2. The review of previous works on this topic could be more detailed. On the other hand, some doubts are raised about the justification for citing too many publications published 40-60 years ago, especially if they concern methodological issues and are reflected in newer works.
3. In the sentence "For example, elevated temperatures induced by UHI accelerate chemical reactions that increase nitrogen oxide (NOx) emissions by up to 25% and tropospheric ozone concentrations by 15% during heat events" (lines 28-30) it is necessary to add a missing reference to the literature. Furthermore, should it really be "increase nitrogen oxide (NOx) emissions"? It is likely that the emission of pollutants into the air from some sources was confused with their levels recorded in the air. Heat does not usually cause an increase in NOx emissions (from what sources?). On the other hand, the chemistry of nitrogen oxide transformations in the ground-level atmosphere is quite strongly related to the chemistry of ozone formation and destruction. Undoubtedly, these chemistries are correlated with temperature and insolation, but also with other factors, including the presence of other substances in the air.
4. Section 2 requires supplementation with missing references to source materials, as well as to the guidelines and data services used.
5. The use of the term "mobile sensing" in the work seems to be inappropriate. The description of the methodology indicates that sensors installed in a fixed location were used.
6. In scientific terms, calibration is defined as the process of configuring an instrument to provide a result for a sample within an acceptable range. The description of calibration for individual sensors (especially gas sensors) given in Section 2.2.3 (Sensor Calibration Methods) is imprecise and requires further detail. It does not indicate how to perform this calibration enabling the creation of a calibration curve. Was zero and spam calibration performed? The calibration results given in Section 3.1 use and refer to "respective reference instruments". What respective reference instruments were used in the case of gas sensors?
7. In line 266 it is stated that "for NO2 raw readings ranged from 1.92 to 2.42 ppm, while the reference values ​​ranged from 1.94 ppm to 2.45 ppm". What caused such high NO₂ concentration values ​​(2 ppm = 2 000 ppb, i.e. 3.825 mg/m³ or 3825 µg/m³ at normal pressure and temperature 20^oC)? Even at traffic stations, 1-hour NO₂ concentrations in the air rarely exceed 200 µg/m³. The use of low-precision NO₂ sensors (resolution 0.1 ppm) requires special caution. This remark also applies to the results of NO₂ concentration measurements in the air presented in Section 3.
8. Ozone concentrations ranged from 0.2 to 0.3 ppm (Figure 12, line 392) are also very high and unlikely for points located near streets, which indicates the use of an inaccurate sensor. Were the results obtained compared with reference methods used in professional air quality monitoring for analyzed pollutants, if such monitoring stations were located nearby? See also e.g. https://doi.org/10.1016/j.atmosenv.2022.119239.
9. The accuracy of reporting temperature measurement results and even average modeling results in degrees Celsius to two decimal places is rather unjustified.
10. The discussion of results should refer to previously published works in a similar field. It also lacks a more detailed commentary on the results obtained, especially in the case of the range of variability of air pollutant concentrations.

Minor comments

The name "Washington DC." used in the Abstract (line 6) should be corrected (changed to "Washington DC", "Washington D.C.", "Washington, DC," or "Washington, D.C.,").

In the expression "1 ° C" and "7 ° C" (line 21) it is proposed to remove unnecessary spaces before and after the degree symbol.

Instead of "Sensor.Commumity" (line 63) it should be "Sensor.Community". It is also suggested to verify whether the source materials given in line 64 are appropriate.

In the symbols NO2, NH3, and O3 (Sections 2 and 3), the numbers 2 or 3 should be placed in subscript. Incorrect symbol of O₃ in the description of Figure 8 (given in brackets).

When referring to figures in the text, there is no need to use a period after the figure number (lines 84, 86, 90, etc.).

The description of Figure 1 should be supplemented with missing punctuation marks {e.g.: "Figure 1. Experimental sites: (a) Veazey St NW; (b) Connecticut Ave NW; (c) Van Ness St NW."}. Descriptions of Figures 2, 5, 6 and 10-16 require a similar correction, which should also be supplemented with a general title if it is missing. Descriptions of most figures need to be corrected for unnecessary use of capital letters and the occasional double use of the colon, as well.

The quality (resolution) of Figures 2a and 2b should be improved (increased) or the size of these figures should be reduced. The quality (resolution) of Figures 6 and 11 should be improved (increased) and the size of Figures 11a, 11b and 11c should be increased (poorly legible legends). The quality (resolution) of Figure 12a differs from the quality (resolution) of Figure 12b.

The missing concentration units in Figure 12 should be supplemented.

Using an additional bold font in the text is not recommended (lines 251, 255).

The time format used in the work (Section 3) should be standardized (e.g. 1pm or 1:00 pm?).

Other minor editorial errors required corrections: unnecessary space before the period ending the sentence (lines 120, 347) or before the comma (line 234); missing space before the beginning of the next sentence (line 169); double figure or table numbering in text references to Figure 6 (line 207), Table 2 (line 217), and Figure 11 (line 291); exceeding the right margin in the case of Table 2; no end bracket and unnecessary space after the phrases "(see Figure 13" in line 343 and "(see Figure 16" in line 356; minor errors in formatting and editing of the References section (including inconsistency in the capitalization of journal titles and not always complete bibliometric data).

Author Response

Please see attached the answers to comments.

 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

General Impression
The presented manuscript (MS) describes the authors' investigation—a combination of field measurement campaign and numerical experiment of the assessment of the influence of the urban morphology on the microclimate dynamics and air quality (AQ) levels of certain key pollutants during the (hot) summer-autumn 2024 in Washington DC, U.S.A.. Hence the microclimate, especially the thermal conditions, and the AQ plays a crucial role for the human health, well-being and productivity in the large cities worldwide, the importance of the subject of the MS is out of any doubt. It is also well-motivated by the authors. The urban morphology is quantified by the height-to-width (H/W) ratios, and thus, the three experimental sites considered are properly selected with discernible differences in this parameter.
Overall, the MS is very well conceptualized and, as a result, skillfully written and illustrated, with a good balance between the textual and graphical parts. This fact demonstrates the authors' high technical and scientific level of expertise. The length also seems reasonable. I have, however, some concerns about the structure (see below). I recognize the study's main strength in the central concept, i.e., combining optimal results from field measurements and CFD numerical simulation. The MS fits well in the thematic scope of 'Environments' and has a distinct potential to attract readers.
I have not detected any general flaws or principal caveats during the review, so I have not included a 'Major remarks' section. I have only some concerns/comments and suggestions that address, in my opinion, the MS that could benefit.
Remarks:
Hence, since the AQ analysis forms a significant part of the MS, it may be a good idea to extend the abstract explicitly to mention all of the considered pollutants.
About the structure: It remains unclear, at least for me, why Figure 6 (for which experimental site is it valid? It is not stated. The text near the color key appears blurry.), which is similar to Figures 13-15, is not in Subsection 3.3. Move it there or explain why it is here.
The CFD simulation: What is the driving model, i.e., where are the initial and boundary conditions for the simulation taken from? There is also no reference to the ENVI-met LITE model on row 183.
About the urban morphology: Where are the height and width data for the buildings taken from?
About the human thermal comfort indices: Explain the optimal range for each one (in order to judge the computed values as deviation from 'normality').
Figure 1b: Consider including a more meaningful photo – this one shows part of the equipment but nothing from the building environment.
- r196: AHRAE → ASHRAE
- r203: What is the blueprint model, and what is it used?
- Figure 11: Text is completely unreadable.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The authors measured and compared meteorological variables and pollution concentrations in three urban sites. The weather-sensitive pollution sensors were calibrated to improve the accuracy of the data. CFD was used to investigate the impact of urban morphology on temperature, humidity, wind, and pollution. However, the concentration levles of pollutants are more than 10 times larger than the typical ambient urban levels, and the differences in pollutant concentrations across urban morphology do not appear to be that big. I wonder whether other controlling factors besides urban morphology were controlled or not. For examples, vertical diffusion and emission amount are also important factors in determining air pollution levels.

Here are a few comments.

1) Line 82:  If the sensor is used for more than a month, won't the quality of the sensor deteriorate?

2) Line 149 : Normally, calibration curve needs at least two point.  How did the authors obtain the high value point in the calibration curve?

4) Equation 1: Does the Turban come from the single sensor data in each urban site? I wonder if a single sensor data can represent the temperature in the area. Could it be obscured by shadows from surrounding buildings or street trees?

5) Figure 6: It is not mentioned how the buildings in the Fig. 6 match the H/W ratio.

6) Figure 10: What does the red line indicate in Figure 10b? If the red line represents the mean temperature difference, why doesn't it match the H/W ratio as the author claims?

7) Figure 11: the legend is not clear visible.

8) Figure 12: The units of concentration are not specified.

9) Line 332: What about PM1 and PM10? Are there no correlations with temperature?

10) Why does Figure 13 have a different morphology than Figure 6?

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The reviewed manuscript contains many changes resulting from the review, which make it more correct (by correcting errors), up-to-date (by referring to more recent source materials) and coherent (by specifying and organizing the content). I thank the authors for taking into account the vast majority of my general and specific comments, as well as for the answers and explanations provided. I accept in particular the explanation regarding the errors made in the conversion from voltage to ppm on Arduino IDE. It should be assumed that after the correction, the results obtained are much more correct.

The manuscript still requires only minor editorial corrections, including removing the duplicate period at the end of the sentence (line 11), adding the missing reference number instead of the question mark (line 199), removing the unnecessary space before the comma (line 344), adding the missing period at the end of the table titles, etc.

It is also recommended to split the too long paragraph in lines 371-410 into at least two smaller ones.

The description of Figure 12 should also be improved due to the lack of information about what this figure represents.

In turn, adapting the References section to the guidelines for authors requires using abbreviations of journal names instead of their full names in the References section, if known. 

Author Response

Please see attachment 

Author Response File: Author Response.docx