Twenty-Year Climatology of Solar UV and PAR in Cyprus: Integrating Satellite Earth Observations with Radiative Transfer Modeling

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Review of the manuscript "Twenty-Year Climatology of Solar UV and PAR in Cyprus: Integrating Satellite Earth Observations with Radiative Transfer Modeling" written by Fragkos et al.

The manuscript describes the evaluation of climatologies of effective UV quantities and photosynthetically active radiation (PAR) over Cyprus for the period 2004 to 2023. In addition, trends were calculated for the study period. Radiative transfer model simulations were performed and they were validated against ground-based and satellite retrievals. The manuscript is relevant for e.g., public health, agriculture, and biological and multidisciplinary studies. It demonstrates in a nice way the variations in UVI and PAR, the annual cycle, seasonal differences, and trends. The reasons for the trends were investigated, but unfortunately, the methodology was not clearly explained. Before acceptance for publication, the manuscript should be revised according to the comments here below. The English should be checked, especially in the Results section. The introduction was very well written, easy to follow, and gave a very good overview of the effects of solar radiation and its importance.


Main comments:

The manuscript lacks information on ground-based instruments and measurements.

The manuscript lacks a description of the trend analysis. For example, how was the effect of clouds determined for UVI and DLI trends?

I liked the use of CMF comparison when you compared your model results with satellite and TEMIS results. Please explain more about the choice of CMF comparison. And the fact that you actually compare model calculations with each other, so that actually what matters is how good/comparable the model inputs are.

I don't think you can really compare noon UVI and DLI as you have done in the results because they are completely different quantities: one is an instantaneous value (in your case noon UVI) and the other is an integrated value (DLI). It's fine to discuss the effect of TOC, cloudiness and aerosols in both, but the expectation is not that they should be comparable.

The figures should be cited in the correct order in the text.


Specific comments:
line 47: "About half of the total solar radiation is in the visible spectral region." -> Half of the total solar radiation energy? Please specify.

lines 170-175: Please write explicitly that you used those parameters/measurements as input to the model. That's maybe not clear for a ready who is not familiar with look-up tables.

line 180: "a correction for the effect of height on solar radiation" -> a correction for the ALTITUDE of the location?

lines 184-186: It's not completely clear if you calculated the CMF yourself or if you retrieved it from CAMS.

lines 200-203: DLI is the PAR in μmol⋅m⁻²⋅s⁻¹ integrated over the day, isn't it? ). If yes, please add that you integrate over all the simulations of the day to get the DLI.

lines 189-190: "Then, the CMF for UV (UV_CMF) was calculated from CMF using the methodology suggested by Staiger et al. [74]." Please open this a little bit more. Did you use Eq.(2) in Staiger et al., if yes, how did you define "p" in that equation?

line 211: "Daylight integrals were computed using the described methodology, akin to that applied for the model outputs." -> You did not really explain any methodology for daily integral calculation.

line 235: Please describe in more detail the ground-based measurements and what variable they measure: UV? PAR? What is the instrument? How are they calibrated?

lines 241-247: Please represent the statistics using equations.

lines 266-269: "The histogram on the right shows that the differences between the model and TEMIS values are almost
symmetrically distributed around zero." -> not really. To me, it looks like the model tends to underestimate, as there are more negative values.

lines 279-281: It's unclear how the CMF was calculated from ground-based measurements. Please add a description in the Method section. What was used as clear sky ground-based GHI? Modelled GHI? How it was done?

Figure 1: Is this for all common TEMIS + model pixels? For which time period?  Please clarify in the text and figure caption.

Figure 2: For which locations are these results? For the three ground-based stations? For which time period? Please specify in the text and figure caption.

line 291-298: To me, both the model and Temis seem to overestimate the cloudiness. Not much, but a little. And TEMIS more than the model. -> TEMIS sees less clouds -> explanation for Figure 1 model<TEMIS ?

line 320: Here also, where does the measured CMF come from?

Figure 4: See comments for Figures 2 and 3.

Figure 4: What is the reason for the positive outliers in the model and SAF?

line 325: "The model demonstrates a stronger correlation with the measured data, suggesting it may offer a more accurate representa-
tion of PAR CMF under varying sky conditions." -> but with a positive bias?

line 361: "the overall means"-> it's not clear what overall means. Is it in terms of space (whole Cyprus) or time (time period)? Or both?

lines 371-381: how about differences in local cloudiness conditions, e.g. in coastal areas compared to inland?

line 406: "the trend" -> this is not the proper English term here. Please correct.

line 411: "variability in total ozone concentration during spring". To me, it sounds strange that there are local differences in total ozone column, as Cyprus is relatively small in area.

line 437: "UVI is measured around noon.." -> I understood that you modeled the UVI, not measured. If this is not correct, please introduce the UVI measurements. And why AROUND noon? Isn't it the noon UVI? If it is an average value around noon, please explain it in the method.

line 439: "UVI may not be as sensitive to changes in cloud cover outside of midday" -> is not sensitive at all if you have simulated the noon UVI.

line 440: "Thus, the effects of altitude and clouds are canceled out for the UVI." -> a strange sentence. I think altitude and clouds affect UVI as well. Please rephrase.

Is there any regular diurnal cycle in the cloudiness of Agros/mountain region? Something like cloudiness every morning/evening in some season?

line 473: Can trends be based on climatology? Or do you mean that they are calculated using the same data set that you used previously for climatology?

Figures 10-> You should put the figures in the right order 10, 11,12 etc. not 10,12,11, as you have done in the text.

Figure 12: You have not explained how you calculate the UVI trends due to cloudiness changes. Please add a section in Methods.

line 525: "Autumn reveals a complex pattern for DLI, contrasting with the more uniform and statistically significant positivity noted in UVI trends"-> Isn't it a negative trend in UVI in Figure 10, SON months?

line 578: "The presence of significant positive trends in TOC during autumn affecting UVI levels was also noted" -> explain how it affected the UVI levels, decrease in UVI?

Author Response

We would like to thank the reviewer for his constructive comments. Please see the attached document for detailed replies.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

Grammatical and expression errors:

l  Original: "The UV index (UVI) [27] is a common metric used to quantify the potential of UV radiation to cause erythema on human skin."

Correction: "The UV Index (UVI) [27] is a common metric used to quantify the potential of UV radiation to cause erythema on human skin."

Note: UV Index should be capitalized as it is a standardized measurement.

l  Original: "Another important metric is the effective dose to produce vitamin D (VID) [28], which measures the potential of solar UV radiation to stimulate vitamin D production in the human skin [29]."

Correction: "Another important metric is the effective dose for producing vitamin D (VID) [28], which measures the potential of solar UV radiation to stimulate vitamin D production in human skin [29]."

Note: "to produce" should be "for producing" for grammatical parallelism and "the" before "human skin" is unnecessary.

l  Original: "UV-A radiation, on the other hand, enters the troposphere, where it is strongly scattered by air molecules and aerosols."

Correction: "UV-A radiation, on the other hand, enters the troposphere, where it is strongly scattered by air molecules and aerosols."

Note: The original is correct; this is a reiteration for clarity.

l  Original: "Most UV-B is also absorbed by molecular oxygen and stratospheric ozone, with only photons having wavelengths longer than 295 nm reaching the Earth's surface."

Correction: "Most UV-B radiation is also absorbed by molecular oxygen and stratospheric ozone, with only photons with wavelengths longer than 295 nm reaching the Earth's surface."

Note: "UV-B" should be followed by "radiation" for consistency; "having" should be "with" for conciseness.

l  Original: "Systematic overexposure to UV stands as a primary environmental risk factor for non-melanoma skin cancer and is among the key contributors to melanoma skin cancer [20,21], along with eye cataract [22]."

Correction: "Systematic overexposure to UV stands as a primary environmental risk factor for non-melanoma skin cancer and is among the key contributors to melanoma and cataracts [20–22]."

Note: Streamline the sentence by combining the diseases and references.

l  Original: "This radiation covers a wide spectral range, ranging from about 2 nm (x-rays) to up to 10 meters (radio waves), with its peak emission at approximately 550 nm."

Correction: "This radiation spans a wide spectral range, from about 2 nm (x-rays) to up to 10 meters (radio waves), with its peak emission at approximately 550 nm."

Note: Avoid redundancy by replacing "covers a wide spectral range, ranging from" with "spans a wide spectral range, from."

l  Original: "PAR controls biomass productivity through photosynthesis and plays a vital role in carbon and water cycles (e.g., [7])."

Correction: "PAR controls biomass productivity through photosynthesis and plays a vital role in the carbon and water cycles (e.g., [7])."

Note: Add "the" before "carbon and water cycles" for proper noun agreement.

l  Original: "The EO dataset, encompassing satellite and re-analysis data for aerosols, total ozone column, and water vapor, alongside cloud modification factors, to capture the nuanced dynamics of Cyprus's atmospheric conditions."

Correction: "The EO dataset encompasses satellite and re-analysis data for aerosols, total ozone column, and water vapor, along with cloud modification factors, capturing the nuanced dynamics of Cyprus's atmospheric conditions."

Note: Change to active voice for clarity and correct sentence structure.

l  Original: "Significant decreasing trends in the noon ultraviolet index (UVI), of -2 to -4% per decade have been found in Autumn, especially marked on the island’s Northeastern part, mainly originating from the (significant) positive trends in TOC."

Correction: "Significant decreasing trends in the noon ultraviolet index (UVI), ranging from -2 to -4% per decade, have been found in autumn, especially marked in the island’s northeastern part, mainly originating from significant positive trends in TOC."

Note: "of" should be "ranging from"; "Autumn" should be lowercased; "on" should be "in" for location accuracy.

l  Original: "Nevertheless, ground-based PAR measurements are sparse and thus it is commonly estimated either from measurements of the SSR using empirical equations (e.g., [9–11]) or from satellite observations (e.g.,[12])."

Correction: "Nevertheless, ground-based PAR measurements are sparse, and thus PAR is commonly estimated either from measurements of SSR using empirical equations (e.g., [9–11]) or from satellite observations (e.g., [12])."

Note: Add a comma after "sparse" for correct punctuation; clarify what "it" refers to by replacing with "PAR."

l  Original: "These findings are align with those from other studies in the Mediterranean region, which report similar trends."

Correction: "These findings align with those from other studies in the Mediterranean region, which report similar trends."

Note: Remove "are" to correct verb tense agreement and streamline the sentence.

l  Original: "The use of UV data, PAR data and their implications has significantly advanced our understanding of climate impact on human health."

Correction: "The use of UV data, PAR data, and their implications has significantly advanced our understanding of the climate's impact on human health."

Note: Add a comma before "and" in a list for clarity; include "the" before "climate" to specify the subject.

l  Original: "These datas are crucial for developing effective public health policies and preventive measures."

Correction: "This data is crucial for developing effective public health policies and preventive measures."

Note: "Data" is treated as a singular noun in formal English.

l  Original: "It was observed that there was an increase in the average annual UV exposure particularly during the summer months."

Correction: "An increase in the average annual UV exposure was observed, particularly during the summer months."

Note: Use passive voice more effectively by restructuring the sentence for clarity and conciseness.

l  Original: "Different methodologies has been applied to quantify the various effects of solar radiation."

Correction: "Different methodologies have been applied to quantify the various effects of solar radiation."

Note: Correct subject-verb agreement from "has" to "have" for the plural noun "methodologies."

l  Original: "The model's accuracy are validated by comparing the satellite-derived estimations with ground-based measurements."

Correction: "The model's accuracy is validated by comparing the satellite-derived estimations with ground-based measurements."

Note: Change "are" to "is" to match the singular noun "accuracy."

l  Original: "These result provides an in-depth analysis of how climate variability affects UV exposure levels."

Correction: "These results provide an in-depth analysis of how climate variability affects UV exposure levels."

Note: Correct "result" to plural "results" and adjust "provides" to "provide" for agreement.

l  Original: "The studies focus were mainly on the seasonal variations and their correlation with atmospheric conditions."

Correction: "The study's focus was mainly on the seasonal variations and their correlation with atmospheric conditions."

Note: Correct "studies focus were" to "study's focus was" for grammatical accuracy and clarity.

l  Original: "This technique enable us to predict changes in UV radiation with reasonable accuracy."

Correction: "This technique enables us to predict changes in UV radiation with reasonable accuracy."

Note: Change "enable" to "enables" to match the singular subject "technique."

l  Original: "In conclusion, the integration of satellite data with ground observations have provided new insights."

Correction: "In conclusion, the integration of satellite data with ground observations has provided new insights."

Note: Change "have" to "has" to correctly agree with the singular subject phrase "the integration."

 

Detailed Review Comments

1.        Introduction: The introduction effectively sets the context for the research but could benefit from a clearer statement of the study's novelty, especially how it differs from or builds upon previous work in the field.

2.        Methodology: The methodology section is detailed and well-structured, providing a good understanding of how the data was collected and analyzed. However, it would be enhanced by a more explicit discussion of any limitations associated with the data sources or models used.

3.        Discussion: The discussion effectively ties the findings to broader climatic and health implications. Expanding on how these trends might affect future public health policies or agricultural practices in Cyprus and similar environments would add value.

4.        Conclusion: The conclusion succinctly summarizes the findings and their implications. It could be strengthened by explicitly linking back to the research objectives stated in the introduction, to reinforce how the study addresses these aims.

5.        Figures and Tables: While the graphical representations are generally clear, some figures could be improved with higher resolution or better labeling to enhance clarity and impact. Such as Figure 10 and Figure 11.

6.        Literature Review: The review of existing literature is comprehensive; however, more recent studies could be included to ensure the research context is up-to-date.

7.        Data Presentation: In some instances, the presentation of complex data could be simplified or summarized in a more reader-friendly format, potentially through the use of additional charts or tables.

8.        Technical Language: The paper occasionally uses technical jargon that might not be accessible to all readers in the broader scientific community. Simplifying some of the more complex terminology or providing definitions could widen the audience reach.

9.        Statistical Methods: While adequate, the explanation of the statistical methods used could be more detailed to aid in reproducibility and transparency of the analysis.

10.     Model Validation: The validation of the modeling approaches used is crucial and well-addressed, but further details on the specific validation metrics and their thresholds would provide additional assurance of the model's reliability.

11.     Environmental Impact Discussion: Discussing the potential environmental impacts of changes in UV and PAR in more detail would be beneficial, especially in terms of ecological changes and biodiversity.

12.     Future Research Directions: The section on future research is insightful. Detailing more specific follow-up studies or potential collaborative projects could inspire subsequent research initiatives.

13.     References: The references are appropriate and relevant, but ensuring that all sources are current and from peer-reviewed journals would strengthen the paper's credibility.

14.     Accessibility of Data: Mentioning the availability of the data used for analysis, either through a public repository or upon request, would enhance the paper's transparency and allow for independent verification of the results by other researchers.

15.     Implications for Policy Making: Elaborating on how these findings can directly inform policy decisions, particularly in public health and urban planning, would make the implications more tangible.

16.     Comparative Analysis: Adding a comparative analysis with other regions that have undergone similar studies could highlight unique or common trends that could be crucial for a broader understanding.

Comments on the Quality of English Language

it is generally ok

Author Response

We would like to thank the reviewer for his constructive comments. Please see the attached document for detailed replies.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for the replies to my previous comments. I think the manuscript was well improved and I suggest it be published after a small minor revision: Please check that the reference in line 279 is the right one. Now it is the number 74, but I think it should be number 75. If so, please change it.

I leave the Editor to decide about referencing figures in a non-general order.

Author Response

We would like to once again thank the anonymous reviewer for their careful review. We have now corrected the incorrect citation number.

Reviewer 2 Report

Comments and Suggestions for Authors

I  suggest to accept it

Author Response

We would like to thank the anonymous reviewer for his careful review.