Quantifying the Effect of Building Shadowing and Cloudiness on Mean Radiant Temperature in Singapore
Round 1
Reviewer 1 Report
The submitted manuscript is a study about mean radiant temperature (Tmrt) measurements conducted in Singapore and dependencies of Tmrt with cloudiness. Although stated otherwise, I do not find a clear analysis of the dependency of Tmrt on the sky view factor (SVF). Furthermore, a negative correlation between Tmrt and diffuse radiation is stated (Section 4.2.1, Fig. 9). It is unclear how diffuse radiation was quantified and – more importantly - the negative correlation is inconsistent with the diurnal variation of Tmrt on a cloudy day shown in Fig. 10 in which it is clearly shown that Tmrt increases with global radiation (=diffuse radiation on an overcast day), which indicates a positive correlation. Furthermore, the novelty and original aspects of this study are not clearly stated.
For these reasons, I do not recommend the manuscript for publication in Atmosphere.
Author Response
[Reviewer]: The submitted manuscript is a study about mean radiant temperature (Tmrt) measurements conducted in Singapore and dependencies of Tmrt with cloudiness. Although stated otherwise, I do not find a clear analysis of the dependency of Tmrt on the sky view factor (SVF).
[Authors]: The work does not want to focus uniquely in the dependency of Tmrt on SVF. Actually, the abstract states: "Tmrt difference between sites is analyzed based on the weather conditions, the sky view factor (SVF) and the type of surrounding urban elements". This is, we analyze the measurements in each site based on the characteristcis of the site as well as the weather conditions, and thus, do not focus on a dependency of Tmrt on SVF.
[Reviewer]: Furthermore, a negative correlation between Tmrt and diffuse radiation is stated (Section 4.2.1, Fig. 9). It is unclear how diffuse radiation was quantified and – more importantly - the negative correlation is inconsistent with the diurnal variation of Tmrt on a cloudy day shown in Fig. 10 in which it is clearly shown that Tmrt increases with global radiation (=diffuse radiation on an overcast day), which indicates a positive correlation.
[Authors]: The negative correlation presented in Figure 9 corresponds ONLY to Duxton3. This is because at the time considered (5pm) this site (Duxton3) was not under building shadow influence, whereas the other 2 sites (Pinnacle 1 and Pinnacle2) where shadowed by the building. In this situation, sites under the shadow of the building showed no relation between Tmrt and diffuse radiation, which looking at Figure 9 suggested the influence of other radiation components different to diffuse solar radiation. In the case of non-shaded sites (Duxton3), the negative correlation could be explained since higher diffuse radiation is associated with lower global solar radiation, which was seen to govern the variability of Tmrt levels in non-shaded sites.
Diffuse radiation was measured in a nearby station located on a roof, above the urban canopy. The records of this variable correspond to the incoming diffuse solar radiation (influenced by the state of the atmosphere) and not by reflections inside the urban canopy. Although in section 4.2.3 we highlighted that the measurement were above the urban canopy, we have further commented it in the methodology (Section 3.1)
Regarding the statement of the reviewer: "the negative correlation of (Figure 9) is inconsistent with the diurnal variation of Tmrt on a cloudy day shown in Fig. 10 in which it is clearly shown that Tmrt increases with global radiation (=diffuse radiation on an overcast day), which indicates a positive correlation." we have further clarified the type of day we are presenting in Figure 10. The term overcast day was misleading, confusing and incorrect. Regarding cloud cover the 25th July 2010 should be defined as 'partly cloudy' and not 'overcast'. We have changed this in the text. In this context, on a partly cloudy day, certain fraction of direct solar radiation are expected in a way that global radiaton reach the levels presented in Figure 10. Additionally, records confirm that diffuse radiation is different to global radiation that day (at midday and in the afternoon Rad_diffuse / Rad_global is 0.75 and thus there is direct radiation influencing non shaded sites). Thus, we agree that the term overcast was not accurate for the type of day represented on Figure 10.
The measurements presented in this study (when comparing building shaded areas and none shaded areas) want to reflect that the direct solar radiation has a relevant importance to govern variability of Tmrt levels in Singapore during midday and afternoon period. Thus, there is no contradiction between Fig 9 and Fig 10. Higher levels of Global radiation produce higher Tmrt, although during midday and afternoon direct solar radiation has an important role in Tmrt variability in Singapore (as discussed in Fig.8 and presented in section 4.21.)
[Reviewer]: Furthermore, the novelty and original aspects of this study are not clearly stated.
[Authors]: At the end of the introduction, we have further included the concepts of: 1) extensive measurement campaigns (since it is not a common practice to measure simultaneously in 5 sites more than 3.5 months in an area of 3 hectares), and 2) include specifically the analysis of the influence of incoming solar radiation
The novelty and value of the results derived from this measurement campaign could be used for futher reference in literature
Reviewer 2 Report
Comments
This is a very interesting study. As a case study, it can be accepted with the minor corrections pointed out below.
L129-133 (1)
It is better to write the sensitivity to the input data of Tmrt.
In particular, ΔTmrt/Tmrt) / (ΔA/A)
Where A is Tg, Ta or WS.
The meaning of this formula is the effect of the rate of change of A on the rate of change of Tmrt.
After L139
The observation of the amount of diffuse solar radiation described in L412-413 is moved here.
L198, L200, Table 3
"11th July" to "13th July"
Table 3
Please write the unit as WS (ms-1), Ta (° C) and e (hPa).
It is better to add a new column in the table to show the GHI value (720 W m-2 and 1002 W m-2).
L208-210
Is "θz" the solar zenith angle?
Table 4
What is the time of Morning, Midday/Afternoon and Evening?
Is “Max” an average time of 10 minutes?
Please write a numeric unit (W m-2).
Fig 5
It is better that the title of the table "Mean Tmrt (SW Monsoon)" is changed "Mean Tmrt (1st to 31st Aug.)" as in Fig. 6. "Mean Tmrt (Wet Inter-Monsoon)" is changed the same way.
Is the plotted data a period average of 10 minutes? Specify clearly.
Figures of other time series are specified in the same way.
Fig 7 and Fig 10 are time series of GHI and Tmrt for a specific day.
Is it possible to draw a thick line of Tmri at the time when the direct solar radiation is expected to reach the black globe?
Fig 5, Fig 6 and Fig 11
They are time series of Tmrt of the period average. Is it possible to draw a thick line of Tmri at the time when the direct solar radiation is expected to reach the black globe?
Even in cloudy conditions, the sky around the sun is bright, so it may correspond to the peak of Tmrt.
L289
"Table 4" to "Table 3"
Fig 8
The plot data are hourly average (L201).
Does "10:30" in the title of the figure represent the hourly average of "09:30-10:30", "10:00-11:00" or "" 10:30-11:30 "?
It is better to write "Clearness Index: Kt" on the x-axis.
L330-333
Reviewer thinks that the reason why the difference between Tmrt of "Pinnacle 1" and "Pinnacle 2" in Fig. 9 is several degrees Celsius is "long wave radiation", but he thinks it is better to write it more clearly.
Fig 9 Bottom figure
The number of data is different from the upper right figure of Fig. 8. Why is the data for "Tmrt <45 ° C" not plotted?
Fig 12
The number of data of "BoonTat711" and "BoonTatSt" is different. Why is the number of data in "BoonTat711" so small?
Author Response
[Reviewer]: This is a very interesting study. As a case study, it can be accepted with the minor corrections pointed out below.
[Authors]: Happy to know
[Reviewer]: L129-133 (1)
It is better to write the sensitivity to the input data of Tmrt. In particular, ΔTmrt/Tmrt) / (ΔA/A). Where A is Tg, Ta or WS. The meaning of this formula is the effect of the rate of change of A on the rate of change of Tmrt.
[Authors]: We do not see the purpose of the reviewer in changing this. At this point what we want to show how the Tg measurements are transformed to Tmrt. This is a formula adapted to Singapore. The sensitivity proposed by the reviewer could be valid, but in another context.
[Reviewer]: After L139
The observation of the amount of diffuse solar radiation described in L412-413 is moved here.
[Authors]: we have changed slightly the sentence and included what components of solar radiation are measured in 322: '.... it is considered that measured global and diffuse solar radiation in station 322...'
[Reviewer]: L198, L200, Table 3
"11th July" to "13th July"
[Authors]: Thank you. It has been changed
[Reviewer]: Table 3
Please write the unit as WS (ms-1), Ta (° C) and e (hPa). It is better to add a new column in the table to show the GHI value (720 W m-2 and 1002 W m-2).
[Authors]: We have included the units of the variables, but we prefer not to include a new column because on the table we are presenting afternoon mean values (in the period 11 to 16 LT), while the radiation values mentioned by the reviewer represent measurements just before the shadow of building started to affect the sites.
[Reviewer]: L208-210
Is "θz" the solar zenith angle?
[Authors]: Correct. We have included it in the text
Table 4
What is the time of Morning, Midday/Afternoon and Evening?
Is “Max” an average time of 10 minutes?
Please write a numeric unit (W m-2).
[Authors]: We have included the time period of morning, afternoon and evening. We have included the variable unit in the caption (Watt/m2). The values in Table 4 are extracted from 10-min irradiance values and "max." is the maximum of those 10-min records in each period (morning, midday/afternoon, evening)
[Reviewer]: Fig 5
It is better that the title of the table "Mean Tmrt (SW Monsoon)" is changed "Mean Tmrt (1st to 31st Aug.)" as in Fig. 6. "Mean Tmrt (Wet Inter-Monsoon)" is changed the same way.
Is the plotted data a period average of 10 minutes? Specify clearly.
Figures of other time series are specified in the same way.
[Authors]: Changes in the titles of the graphs have been made. We have specify that the data plotted are 10-min averaged data in the time series plots
[Reviewer]: Fig 7 and Fig 10 are time series of GHI and Tmrt for a specific day.
Is it possible to draw a thick line of Tmri at the time when the direct solar radiation is expected to reach the black globe?
[Authors]: We do not understand what the reviewer mean with Tmri (it should be Tmrt, right?) and what kind of line/region of direct solar solar radiation is expected. We would prefer to draw a line where the shadow of the building starts affecting the black globe (i.e. at a certain time). But we haven't done so since in the text we already state the time when this appens. Also it has to be taken into consideration that Pinnacle 1 and Pinncale 2 might difer slightly since the buildings have slight different orientation with respect to the North. This will cause slight difference in the shadow reaching the black globe. This aspect is commented in 4.1.1
[Reviewer]: Fig 5, Fig 6 and Fig 11
They are time series of Tmrt of the period average. Is it possible to draw a thick line of Tmri at the time when the direct solar radiation is expected to reach the black globe?
Even in cloudy conditions, the sky around the sun is bright, so it may correspond to the peak of Tmrt.
[Authors]: For the same reason that in Figure 7 and 10 we prefer not to include this line inside the figure. Adittionally, in Figure 5,6,11 the position of the sun is not fixed (and neither the shadow produced) since they correspond to period of time (several days). In any case, the aim was not precisely to know the hour, but the differences in peaks and the effect of shadowing for simulatenous measurements in different sites. This aspect has been attained in the manuscript
[Reviewer]: L289
"Table 4" to "Table 3"
[Authors]: Thanks. Corrected
[Reviewer]: Fig 8
The plot data are hourly average (L201).
Does "10:30" in the title of the figure represent the hourly average of "09:30-10:30", "10:00-11:00" or "" 10:30-11:30 "?
It is better to write "Clearness Index: Kt" on the x-axis.
[Author]: The hourly average corresponds to the previous hour. i.e. the timestamp for the hourly average is at the end of period considered 10:30 corresponds to 9:30 to 10:30. We have written Clearness Index (Kt) in Figure 8
[Reviewer]: L330-333
Reviewer thinks that the reason why the difference between Tmrt of "Pinnacle 1" and "Pinnacle 2" in Fig. 9 is several degrees Celsius is "long wave radiation", but he thinks it is better to write it more clearly.
[Authors]: Instead of '(e.g. longwave radiation); we have now written ('i.e. longwave radiation'). We consider that the influence of this radiation component is clear. Additionally, references are included
[Reviewer]: Fig 9 Bottom figure
The number of data is different from the upper right figure of Fig. 8. Why is the data for "Tmrt <45 ° C" not plotted?
[Authors]: The reviewer is right. The reason for this is that we removed the days when there was precipitation before 17:00. We wanted an homogeneous dataset with similar surface temperatures influencing Tmrt. We have included in the caption of Figure 9: "days with precipitation before 17:00 are not considered"
[Reviewer]: Fig 12
The number of data of "BoonTat711" and "BoonTatSt" is different. Why is the number of data in "BoonTat711" so small?
[Authors]: The number of points are the same. It is just that the values are overlaping
Reviewer 3 Report
This is an interesting paper and the result is clear. I have only a few comments.
- The author should describe the application of the data in urban temperature, otherwise, it is just measurements.
- What is the meaning of “site” in Table 4?
- The units should be described to all measurements in both tables and figures.
- I suggested that the authors should update the references, because the percentage of references before 2015 accounts for > 60%.
- The conclusion is too long. I suggested that the authors should focus on the major findings.
Author Response
[Reviewer] This is an interesting paper and the result is clear. I have only a few comments.
[Authors]: Happy to know. See below our comments
[Reviewer]: 1. The author should describe the application of the data in urban temperature, otherwise, it is just measurements.
[Authors]: The last sentence of the abstract refers to the benefits on the defintion of thermal comfort strategies. Also at the end of the conclusions, the impact of these analysis on urban planning is reflected
[Reviewer]: 2. What is the meaning of “site” in Table 4?
[Authors]: The term 'site' has been removed. Thanks. It was an mistake
[Reviewer]: 3. The units should be described to all measurements in both tables and figures.
[Authors]: All measurements have now units either on the figure itself or in the caption
[Reviewer]: 4. I suggested that the authors should update the references, because the percentage of references before 2015 accounts for > 60%.
[Authors]: We have included more references to the work done in Hong-kong for vegetation and in Greece related for urban design (morphology)
[Reviewer]: 5. The conclusion is too long. I suggested that the authors should focus on the major findings.
[Authors]: We do not see a way to shorten the conclusion. Different topics are analyzed (weather conditions, SVF, radiation, street orientation...) and somehow they have to be mentioned in the conclusions.
Round 2
Reviewer 1 Report
Thank you for your detailed reply to my first review and improvements made to the manuscript. I still have a few remarks (see below).
For this reason the study is suitable for publication in Atmosphere after minor revisions.
Remarks:
A space between numbers and units is missing in many instances.
I suggest writing “W” instead of “Watt”.
Introduction:
How does this study go beyond an earlier study by Tan et al. 2013, which also studied mean radiant temperatures in Singapore?
Methods:
Please provide more information on the diffuse and direct solar radiation sensors (model, accuracy) used.
Results:
Boxplots of Tmrt (in the same season) for each site sorted by SVF would be a valuable addition so that readers can see what range of Tmrt can be expected in different urban environments in Singapore.
Detailed remarks:
l. 107: full stop missing at end of sentence
l. 114-115: I suggest changing the sentence to:” For the first five variables the Weather Transmitter WXT520 of Vaisala was used.”.
l. 138: I suggest changing “in a roof” to “on a roof”
l. 141: please add information about the instruments used to measure global and diffuse radiation
Table 1: “were” should be “where”
l. 175: “were” should be “where”
l. 267-271: I think whether this is due to diffuse shortwave or longwave radiation cannot be decided since these variables were not measured at this site.
l. 314: “h.” -> “h”
l. 329: change “effect of cloudiness in Tmrt” to “effect of cloudiness on Tmrt”
l. 354: typo
Figure 12: I suggest changing “anomaly” to “difference”, since this is not unexpected.
Author Response
[reviewer]: Thank you for your detailed reply to my first review and improvements made to the manuscript. I still have a few remarks (see below).
For this reason the study is suitable for publication in Atmosphere after minor revisions.
[authors]: Thank you. Happy to know the reviewer's possitive perspective. We have answered all your remarks and comments.
[reviewer]: Remarks:
A space between numbers and units is missing in many instances.
I suggest writing “W” instead of “Watt”.
[authors]: We have added an space, specially in the '°C'. As commented by reviewer there was no space between number and units. On the other hand, we prefer to leave Watt/m2 instead of w/m2. This is commonly used in climatology
[reviewer]: Introduction:
How does this study go beyond an earlier study by Tan et al. 2013, which also studied mean radiant temperatures in Singapore?
[authors]: In the study of Tan et al. 2013 the measurements were conducted during a period of 2 months in each area and only clear sunny skies days were considered. This is, measurements considered were approximately only 10 days per site, which is less than our study that extended during different climatic seasons. Additionally, we analyzed clear, partly cloudy and overcast days together of each season, and looked at the influence of cloudiness in Tmrt in Singapore. In the text, we have added that the study of Tan (2013) was for ' clear and sunny days'.
[reviewer]: Methods:
Please provide more information on the diffuse and direct solar radiation sensors (model, accuracy) used.
[authors]: We are unable to know the model of the pyranomenter but we found a conference paper of the uncenrtainty of the sensor. We have included: "The uncertainty of the irradiance sensors is 5% [47]"
[reviewer]: Results:
Boxplots of Tmrt (in the same season) for each site sorted by SVF would be a valuable addition so that readers can see what range of Tmrt can be expected in different urban environments in Singapore.
[authors]: The authors are not against this, but consider could require a relevant restructuration of the paper. The authors consider that with the plots provided now the aim of the paper is covered, i.e. mean values in different seasons and evaluation of different season and cloudiness in Singapore.
[reviewer]: Detailed remarks:
l. 107: full stop missing at end of sentence
[authors]: done
[reviewer]: l. 114-115: I suggest changing the sentence to:” For the first five variables the Weather Transmitter WXT520 of Vaisala was used.”.
[authors]: done. thanks
[reviewer]: l. 138: I suggest changing “in a roof” to “on a roof”
[authors]: done.
[reviewer]: l. 141: please add information about the instruments used to measure global and diffuse radiation
[authors]. as mentioned before we have included the uncertainty of the sensors found in a publication of the owners of the sensors. We could not find any reference to the model of the instrumentation
[reviewer]: Table 1: “were” should be “where”
[authors]: done
[reviewer]: l. 175: “were” should be “where”
[authors]: done
[reviewer]: l. 267-271: I think whether this is due to diffuse shortwave or longwave radiation cannot be decided since these variables were not measured at this site.
[authors]: thank you. Yes we have slightly reestructrure thse sentence. It can now be readen as: "Tmrt difference is due to lower levels of radiation in Pinnacle1. As commented previously, the latter is partly covered by trees that limit the access of diffuse solar radiation, but also the surrounding surfaces are colder (e.g. leaves) reducing longwave irradiance in the Pinnacle1."
[reviewer]: l. 314: “h.” -> “h”
[authors]: done
[reviewer]: l. 329: change “effect of cloudiness in Tmrt” to “effect of cloudiness on Tmrt”
[authors]: done
[reviewer]: l. 354: typo
[authors]: change from 'Monsson' to 'Monsoon'
[reviewer]: Figure 12: I suggest changing “anomaly” to “difference”, since this is not unexpected.
[authors]: done
