Annual Dynamics of Shortwave Radiation as Consequence of Smoothing Previously Plowed Bare Arable Land Surface in Europe
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsChanges in the area, water content and irregularities in the soil surface layer affect the surface albedo and energy balance. This paper addresses the problem of annual variation of shortwave radiation, reflected under clear-sky conditions from air-dried, previously deeply plowed arable land surfaces, as a consequence of its smoothing, using a smoothing harrow by using Sentinel 2 images to ensure the higher accuracy of such parameters estimation for the European Union and its associated countries. And the results of the study basically answer the above questions. My questions focused on the research methodology and the analysis of the results, and I hope that the authors will clarify the questions and add to the analysis.
About the research methodology, I have three main questions.
1) the period of analysis was set from December 23, 2020 to December 22, 2021, and 119 divided into decades. How do it divide a year's data into decades?
2) Surfaces were shaped by plow (Pd) and smoothing harrow (Hs) to predict their mean diurnal albedo values using custom SALBEC software. What are the criteria under which it is implemented? Is it possible to explain the specific method?
3) the increase of the reflected radiation resulting from the smoothing, by Hs, of the surfaces previously treated by Pd, was the difference between the radiation reflected from those surfaces. If we consider the solar altitude angle which has an effect on solar radiation, and the time interval from previously Plowed Bare Arable Land Surface to its smoothing, does this method of finding the difference include the effect of time? And Is it possible to know from Sentinel 2 images how long the time interval will take?
About the results, the paper mainly analyzes the total amounts of shortwave radiation and the reflected amount under clear-sky conditions from air-dried surfaces of the land shaped by a Pd and Hs. But there is a lack of in-depth analysis, such as, how the bare arable land in extremely different roughness states within the EU and its associated countries lead to the regional change? How does the soil texture, SOC and CaCO3 content affect albedo in different regions?
Author Response
Dear Mr. Travičić,
Thank you very much for the valuable comments on our manuscript with the manuscript ID: remotesensing-3034289, entitled "Annual Dynamics of Shortwave Radiation as Consequence of Smoothing Previously Plowed Bare Arable Land Surface in Europe”. Preparing its improved version, we referred to all the comments as shown below. In each case the original comments are shown in Italic and our responses are in regular font. We have also attached a file showing the differences between the improved manuscript and the previously submitted one.
Yours sincerely,
Jerzy Cierniewski
Reply for Reviewer #1
Thank you very much for the valuable comments on our manuscript with the manuscript ID: remotesensing-3034289, entitled "Annual Dynamics of Shortwave Radiation as Consequence of Smoothing Previously Plowed Bare Arable Land Surface in Europe”. Preparing its improved version, we referred to all the comments as shown below. In each case the original comments are shown in Italic and our responses are in regular font. We have also attached a file showing the differences between the improved manuscript and the previously submitted one.
“1) the period of analysis was set from December 23, 2020 to December 22, 2021, and 119 divided into decades. How do it divide a year's data into decades?”
Our naming convention was indeed confusing, as by the decades we meant periods of ten days, essentially this year`s period was split into ten days chunks. So, accordingly we changed the manuscript to replace mentions of decades with periods of ten days to avoid confusion.
“2) Surfaces were shaped by plow (Pd) and smoothing harrow (Hs) to predict their mean diurnal albedo values using custom SALBEC software. What are the criteria under which it is implemented? Is it possible to explain the specific method?”
Following the above suggestion, the text of 2.3. subsection of the revised manuscript was improved and supplemented with the following fragments:
“Additionally, the following data, defined as input data:
- location of the studied surfaces (latitude and longitude in decimal degree format),
- the date range for which it is intended to calculate the ad values.of the studied surface, and
- two roughness indices, namely the standard deviation of their surface height (HSD) and the index, defined as the ratio of the actual surface within the basic unit to its flat horizontal surface (T3D),
were used for each tested surface.”
“The SALBEC uses four equations to calculate the diurnal variation in the α value of a soil surface with a specific roughness. The first equation [16]:
(1)
computes the overall a level of the surface at θs= 45° (a45), where d, together with its associated number relates to the soil reflectance data transformed to the second derivative for a specified wavelength in nm. The second equation [16]:
, (2)
computes the αvalues of the tested surface (aθs) under θs < 75°, where sa is the slope of the a rise. The third equation [16]:
(3)
enable to fit the course of the relations between á of the soil surface and the θs for the θs range from 0° to 90°. This relationship is complemented by α = 1 when θs = 90° and when symbols a, b, c, and d denote the fitted parameters of the equation.
The fourth equation [34]:
(4)
by transforming equation (3) into the integral, allows to calculation of the ad value, where L denotes the length of the aθs list.”
3) the increase of the reflected radiation resulting from the smoothing, by Hs, of the surfaces previously treated by Pd, was the difference between the radiation reflected from those surfaces. If we consider the solar altitude angle which has an effect on solar radiation, and the time interval from previously Plowed Bare Arable Land Surface to its smoothing, does this method of finding the difference include the effect of time? And is it possible to know from Sentinel 2 images how long the time interval will take?”
The procedure used in this study does not allow the detection of the roughness state of bare arable land, those shaped by Pd and those smoothed by Hs, based on satellite imagery. Using the relationship between individual bands of the Sentinel 2 satellite, only fragments of arable land not covered with vegetation were detected and the annual variation in their areas in three EU subregions was determined. It is only assumed that all this bare land after deep plowing (using Pd) could be smoothed after some time.
Clarification of this issue has been included at the beginning of the "Discussion" section of the improved manuscript.
“About the results, the paper mainly analyzes the total amounts of shortwave radiation and the reflected amount under clear-sky conditions from air-dried surfaces of the land shaped by a Pd and Hs. But there is a lack of in-depth analysis, such as, how the bare arable land in extremely different roughness states within the EU and its associated countries lead to the regional change? How does the soil texture, SOC and CaCO3 content affect albedo in different regions?”
These subregions were distinguished primarily for phenological reasons, assuming that they would be characterized by different patterns of bare soil surface variation throughout the year. The results obtained actually confirmed this. The influence of soil texture, SOC and CaCO3 contents was not discussed separately in specific subregions. This was not done because, after appropriately weighted averaging of the spectra representing individual soil units, it turned out that these averaged spectra (which were the basis for calculating the annual variability of mean diurnal albedo values) in all subregions differed very little from each other (Fig. 2). It was therefore difficult to discuss the influence of soil texture, SOC and CaCO3 on the pattern of such averaged spectra characterizing all analyzed soil units within the studied subregions. However, recognizing the above remark as creating an innovative and most justified view of the results of these studies, the "Results" part of the revised manuscript was supplemented with a fragment discussing the impact of the above soil properties on the diversity of patterns of selected averaged soil units spectra in the S and W subregions. In the improved Figure 2, added also charts that clearly illustrate this.
These two fragments of the text below provide clarification on the comment above. This first fragment was placed in the "3. Results" section and the second fragment in the "4. Discussion" section of the improved manuscript.
“The greatest diversity of the reflectance spectra of soil samples for soil units collected within the studied subregions was found in the S subregion. The lowest reflectance was determined for the dark-colored Phaeozems and Chernozems, developed there from SICL and SIL, with a relatively high average contents of SOC (about 2%) and CaCO3 (4-5%), which in this amount contributes to increasing the roughness of their surfaces (Fig. 2). Meanwhile, a very high reflectance was determined for light-colored Cambisols, developed from CL, covering almost 1/3 of the surface of this subregion, with a low average SOC content (about 1.5%), but the highest average CaCO3 content (over 9%) among the analyzed soil units, which, however, should not increase the reflectance of these soils (Table 2). While, the Leptosols in the W subregion, with the enough content of the CaCO3 (over 20%) to brighten the soil surface have one of the highest reflectances. The spectra of two large-area soil units (Cambisols and Luvisols) are characterized by similar average (approximately 1.5%) SOC content.”
“The influence of soil texture, SOC and CaCO3 content was not discussed separately in specific subregions. This was not done because, after appropriately weighted averaging of the spectra representing individual soil units, it turned out that these averaged spectra (which were the basis for calculating the annual variability of mean diurnal albedo values) in all subregions differed very little from each other (Fig. 2). It was therefore difficult to discuss the influence of soil texture, SOC and CaCO3 on the pattern of such averaged spectra characterizing all analyzed soil units within the studied subregions. Even on the example of the S subregion, where the diversity of the analyzed spectra in relation to the corresponding soil units is the clearest, it was not possible to formulate sufficiently clear correlations between them, probably due to the averages made.”
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe manuscript investigated the annual dynamics of shortwave radiation reflected from bare arable land as a result of smoothing previously plowed land located in three different agricultural subregions of the Europe. The manuscript falls into the scope of RS and the theme is quite interesting, but there remained some critical questions. I am afraid the manuscript can not be accepted.
Major:
1. Two-part results were presented in the manuscript: ‘the soil units’ and ‘the shortwave radiation’. The authors simply presented the results, yet no further analysis between soil units (e.g. CaCO3) and the shortwave radiation were conducted. what is the correlation between soil units and shortwave radiation? Does the Pd Hs influence the soil units as well??
2. In the abstract, the authors stated:
‘This estimate takes into account: the annual variation of the bare arable land area, the spatial variability of soil units within croplands, and the laboratory spectral reflectance characteristics of these units’
However, only the conclusions of shortwave radiation were presented in the abstract, as well as in the conclusion part.
The readers can acquire little information through the abstract
3. the bare arable land area, maybe the results (Table 1) should be presented in the Result part?
4. In the introduction, the authors stated ‘These properties depend primarily on the content of soil organic carbon (SOC), iron oxides (Fe2O3) and calcium carbonate (CaCO3). The higher the content of SOC and Fe2O3, the higher XXXXX’.
The reader may wonder since Fe2O3 is an important factors, why no Fe2O3 data was included in the manuscript.
5. The conclusion was too simple, for the most important part, the shortwave radiation, only the highest and lowest values were drawn. What is the annual variation? spatial variation? the difference caused by Pd and Hs?
Author Response
Thank you very much for the valuable comments on our manuscript with the manuscript ID: remotesensing-3034289, entitled "Annual Dynamics of Shortwave Radiation as Consequence of Smoothing Previously Plowed Bare Arable Land Surface in Europe”. Preparing its improved version, we referred to all the comments as shown below. In each case the original comments are shown in Italic and our responses are in regular font. We have also attached a file showing the differences between the improved manuscript and the previously submitted one.
“Major:”
“1. Two-part results were presented in the manuscript: ‘the soil units’ and ‘the shortwave radiation’. The authors simply presented the results, yet no further analysis between soil units (e.g. CaCO3) and the shortwave radiation were conducted. what is the correlation between soil units and shortwave radiation? Does the Pd Hs influence the soil units as well??”
By devoting so much space to the description of soils within the EU and associated countries in the results of this study, the intention was only to emphasize their great diversity there. The purpose of this study was not to present the differences in these soils, but only to quantify the annual dynamics of the amount of shortwave radiation reflected from bare arable land in extremely different roughness states within the study area. However, it turned out that the averaged reflectance spectra of all these soils within the distinguished subregions (used to calculate the amount of shortwave radiation reflected from bare arable land in these regions) do not differ much from each other.
“2. In the abstract, the authors stated:
‘This estimate takes into account: the annual variation of the bare arable land area, the spatial variability of soil units within croplands, and the laboratory spectral reflectance characteristics of these units” However, only the conclusions of shortwave radiation were presented in the abstract, as well as in the conclusion part.
The readers can acquire little information through the abstract.”
I agree with this comment, but due to the clearly limited size of the "Abstract", this part of the improved manuscript has been supplemented only with the following sentence:
“The properties of soil units that cover the area of at least 4% of each subregion were characterized here.”
“3. the bare arable land area, maybe the results (Table 1) should be presented in the Result part?”
I agree with this suggestion, although the reference to Table 1 is already mentioned in Section 2.1, where it is written that only soil units that "cover an area of at least 4% of each subregion" were included in this study.
“4. In the introduction, the authors stated ‘These properties depend primarily on the content of soil organic carbon (SOC), iron oxides (Fe2O3) and calcium carbonate (CaCO3). The higher the content of SOC and Fe2O3, the higher XXXXX’.
The reader may wonder since Fe2O3 is an important factors, why no Fe2O3 data was included in the manuscript.”
Table 2 does not include data on Fe2O3 content for the tested soil units because this data was not found for all these units in the LUCAS system used here.
“5. The conclusion was too simple, for the most important part, the shortwave radiation, only the highest and lowest values were drawn. What is the annual variation? spatial variation? the difference caused by Pd and Hs?”
In agreement with this comment, section "5. Conclusions" of the revised manuscript has been supplemented with the following two passages:
“Also in summer, around the 225th DOY (August 13), similar amounts of this radiation were predicted for such lands in S, i.e. about 800 PJ day-1 for those shaped by Pd and about 1.0 EJ day-1 for those treated by Hs. Also in summer, around (August 18) these amounts for C were significantly lower, reaching only approximately 400 PJ day-1 and 520 PJ day-1 for the land treated by Pd and Hs, respectively.”
“Whereas in S at the turn of winter and spring, around the 80th DOY (March 21), amounts of this radiation were higher – approximately 400 PJ day-1 and 520 PJ day-1 for the land treated by Pd and Hs, respectively.”
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for Authorsall revelant questions were solved
Author Response
Dear Sir,
thank you for your valuable comments and suggestions to improve our manuscript.
Yours faithfully,
Jerzy Cierniewski
