the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 09 Jan 2024
Understanding the variation of Reflected Solar Radiation: A Latitude- and month-based Perspective
Abstract. The hemispheric symmetry of planetary albedo (PA) is crucial for the Earth's energy budget. However, our understanding of hemispheric albedo is still limited, particularly regarding its variations at finer spatial and temporal scales. Using 21 years of radiation data from CERES-EBAF, this study quantifies the contribution rates of different latitudes to the hemispheric reflected solar radiation and examines their seasonal variations. Statistical results show that the northern latitudinal zones of 0° to 40° contribute more reflected radiation than the corresponding southern latitudes, but the southern latitudinal zones of 50° to 90° compensate for this. From the equator to 40°, the latitudinal contribution to the hemisphere is high in autumn and winter and low in spring and summer; however, after 50°, the situation is reversed. And even during extreme cases, anomalies of the cloud component contribution play a dominant role in anomalies of the total reflected radiation contribution of the latitudinal zone in most latitudinal zones. Additionally, this study evaluates the performance of four radiation data (including: satellite and reanalysis data) in reproducing hemisphere albedo and its hemispheric symmetry compared to CERES-EBAF data. Under different symmetry criteria, the applicability of different datasets to hemispheric symmetry of PA studies varies. Note that the Cloud_cci AVHRR performs better in capturing hemispheric symmetry. However, none of these datasets can decompose the different components of reflected radiation well. These results contribute to advancing our understanding of hemispheric symmetry variations and compensation mechanisms, reducing the uncertainty of model simulations, and improving algorithms for different radiation datasets.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Journal article(s) based on this preprint
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-2882', Anonymous Referee #1, 05 Feb 2024
The authors use Edition 4.2 CERES EBAF product and analyze top-of-atmosphere albedo separated by northern and southern hemisphere. They show that albedos are decreasing about the same rate for both hemispheres. They also separate the contribution by atmosphere, surface, and clear- and cloudy-sky using the method used in Stephens et al. They also separate by 10-degree zones and analyze annual contributions by 10-degree zone. In addition, they analyze 10-degree zonal contributions separated by climatological month. Furthermore, they use AVHRR, MERRA-2, ERA5, and ISCCP data and compare correlation coefficient, mean and RMS difference of hemispherical with the albedo derived form EBAF.
The authors cite large amounts of published studies on hemispherical albedo symmetry. The authors analyze southern and northern hemispheres’ surface and atmosphere contributions. However, the result of the zonal analysis is mainly that higher land albedo in the northern hemisphere present in the midlatitude is compensated by clouds over southern ocean, which was pointed out in earlier studies (e.g. Stephens et al. 2015). Hemispherical albedo trends were analyzed by Datseries and Stevens (2021). Therefore, most of their results are reproduction of the results of earlier studies. Among three main results discussed in the discussion and summary session, only 3), which is the result of the comparison of different products, might be new. But the result is not essential in understanding the hemispherical albedo symmetry. In addition, as far as I know, AVHRR and ISCCP data products were not used in analyzing hemispherical albedo symmetry in earlier studies. Therefore, the motivation of the comparison is not clear. New knowledge added by this study is not significant enough to worth publication. However, because the extensive coverage of earlier studies, there might be a path forward. Because of the good coverage of earlier studies on this subject, I suggest converting this manuscript to a review paper.
My further comments follow.
Line 69-70. The location of ITCZ shifting with season is known before 2007.
Line 70-71 There are many places that sentences are either awkward or do not make sense. In addition to this sentence, the sentence on line 84-85, line 290 “contribution rate”, line 294 “molecular part of Eq. (14), line 360 (10a)-1 awkward units, for example.
Line 80 the authors used “oblique pressure activity” several places in the manuscript. I think what they mean is mid-latitude baroclinic low pressure systems or synoptic systems, but I am not sure.
Line 88-90. If the authors are telling that aerosols increase deep convective clouds, could you cite papers?
Line 97-98. I do not think that available data limit studying hemispherical albedo symmetry. The authors might mean studying how the symmetry changes with time?
Line 139 Why do the authors mention filtered radiance here?
Section 2.2.1 is largely the reproduction of earlier study.
Equation (12) Weighting by clear and cloud fraction is missing in the equation.
Equation (14) area weighted mean is probably sufficient instead of introducing the equation.
Equation (20). Generally, we do not put variables with different units in an equation. Correlation coefficient is a non-dimensional number while mean and RMS have units.
Figures are generally too small to see the details.
References
Datseris, G., & Stevens, B. (2021). Earth’s albedo and its symmetry. AGU Advances, 2, e2021AV000440. https:// doi.org/10.1029/2021AV000440
Stephens, G. L., D. O’Brien, P. J. Webster, P. Pilewski, S. Kato, and J.-l. Li (2015), The albedo of Earth, Rev. Geophys., 53, 141–163, doi:10.1002/2014RG000449.
Citation: https://doi.org/10.5194/egusphere-2023-2882-RC1 - AC1: 'Reply on RC1', Ruixue Li, 08 Apr 2024
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RC2: 'Comment on egusphere-2023-2882', Anonymous Referee #2, 14 Feb 2024
This manuscript analyzes the spatiotemporal variability of planetary albedo (PA), particularly on a monthly scale for each latitudinal zone. It focuses on the hemispheric symmetry of PA and separates contributions from different components (surface, atmosphere, and cloud). The asymmetry issue of current model data is also analyzed, providing insights for improving PA modeling within the community. Overall, the analysis is comprehensive, and sufficient evidence has been cited to support this work. However, I suggest the authors emphasize the key contributions of this work compared to previous studies. Additionally, the manuscript's structure may need refinement as the model data comparison appears independent from the previous analysis. Furthermore, certain analyses and discussions require revision before publication.
Major
- In Section 3.3, rather than simply comparing with CERES for the asymmetry issue in modeled PA, the analysis should be integrated more cohesively with key findings from previous sections. This integration is essential for establishing a stronger motivation and relevance for the comparison. For instance, it would be valuable to assess whether the model data captures the interannual anomaly of the contribution rate of different components to total reflected radiation, thus linking the analysis with earlier sections and enhancing the manuscript's continuity and depth of analysis.
- Simulated Snow uncertainty has been suggested to introduce substantial bias of surface albedo among reanalysis data, especially at mid and high latitudes [1]. Are there any influences for the TOA asymmetry issue in simulations?
- Line 546: despite including various driving factors (e.g., NDVI, snow cover) for anomaly attribution, their corresponding radiative forcings differ significantly. Consequently, even if two factors exhibit similar anomaly magnitudes in a given year, the importance of NDVI may not be comparable to snow cover changes, rendering the anomaly analysis less meaningful. Therefore, I recommend converting the anomaly analysis to a corresponding radiative forcing analysis to better capture the relative importance of different factors in driving changes in radiative forcing over time.
- The difference of r in Eqs. 4 and 5: r in Eq.4 represents blue-sky reflectance, where the solar beam reflects from the surface, whereas the r in eq5 is black-sky reflectance and the incoming radiation is from space. Does this difference in physics have any impact, particularly at high latitudes where the SZA is large?
Minor
Suggest introducing parameters with 0 in Eq. 20
Figure 2a: I suggest changing the color bar because the conventional association of 'blue & red' typically implies negative and positive directions, whereas the result here is uni-directional.
Line 437: The dominant component in the NH?
Line 438: 0°-70°? Why does it have some overlaps with the following ones?
The figures should be enlarged.
[1] Jia, Aolin, et al. "Global daily actual and snow‐free blue‐sky land surface albedo climatology from 20‐year MODIS products." Journal of Geophysical Research: Atmospheres 127.8 (2022): e2021JD035987.
Citation: https://doi.org/10.5194/egusphere-2023-2882-RC2 - AC2: 'Reply on RC2', Ruixue Li, 08 Apr 2024
- AC3: 'Comment on egusphere-2023-2882', Ruixue Li, 08 Apr 2024
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-2882', Anonymous Referee #1, 05 Feb 2024
The authors use Edition 4.2 CERES EBAF product and analyze top-of-atmosphere albedo separated by northern and southern hemisphere. They show that albedos are decreasing about the same rate for both hemispheres. They also separate the contribution by atmosphere, surface, and clear- and cloudy-sky using the method used in Stephens et al. They also separate by 10-degree zones and analyze annual contributions by 10-degree zone. In addition, they analyze 10-degree zonal contributions separated by climatological month. Furthermore, they use AVHRR, MERRA-2, ERA5, and ISCCP data and compare correlation coefficient, mean and RMS difference of hemispherical with the albedo derived form EBAF.
The authors cite large amounts of published studies on hemispherical albedo symmetry. The authors analyze southern and northern hemispheres’ surface and atmosphere contributions. However, the result of the zonal analysis is mainly that higher land albedo in the northern hemisphere present in the midlatitude is compensated by clouds over southern ocean, which was pointed out in earlier studies (e.g. Stephens et al. 2015). Hemispherical albedo trends were analyzed by Datseries and Stevens (2021). Therefore, most of their results are reproduction of the results of earlier studies. Among three main results discussed in the discussion and summary session, only 3), which is the result of the comparison of different products, might be new. But the result is not essential in understanding the hemispherical albedo symmetry. In addition, as far as I know, AVHRR and ISCCP data products were not used in analyzing hemispherical albedo symmetry in earlier studies. Therefore, the motivation of the comparison is not clear. New knowledge added by this study is not significant enough to worth publication. However, because the extensive coverage of earlier studies, there might be a path forward. Because of the good coverage of earlier studies on this subject, I suggest converting this manuscript to a review paper.
My further comments follow.
Line 69-70. The location of ITCZ shifting with season is known before 2007.
Line 70-71 There are many places that sentences are either awkward or do not make sense. In addition to this sentence, the sentence on line 84-85, line 290 “contribution rate”, line 294 “molecular part of Eq. (14), line 360 (10a)-1 awkward units, for example.
Line 80 the authors used “oblique pressure activity” several places in the manuscript. I think what they mean is mid-latitude baroclinic low pressure systems or synoptic systems, but I am not sure.
Line 88-90. If the authors are telling that aerosols increase deep convective clouds, could you cite papers?
Line 97-98. I do not think that available data limit studying hemispherical albedo symmetry. The authors might mean studying how the symmetry changes with time?
Line 139 Why do the authors mention filtered radiance here?
Section 2.2.1 is largely the reproduction of earlier study.
Equation (12) Weighting by clear and cloud fraction is missing in the equation.
Equation (14) area weighted mean is probably sufficient instead of introducing the equation.
Equation (20). Generally, we do not put variables with different units in an equation. Correlation coefficient is a non-dimensional number while mean and RMS have units.
Figures are generally too small to see the details.
References
Datseris, G., & Stevens, B. (2021). Earth’s albedo and its symmetry. AGU Advances, 2, e2021AV000440. https:// doi.org/10.1029/2021AV000440
Stephens, G. L., D. O’Brien, P. J. Webster, P. Pilewski, S. Kato, and J.-l. Li (2015), The albedo of Earth, Rev. Geophys., 53, 141–163, doi:10.1002/2014RG000449.
Citation: https://doi.org/10.5194/egusphere-2023-2882-RC1 - AC1: 'Reply on RC1', Ruixue Li, 08 Apr 2024
-
RC2: 'Comment on egusphere-2023-2882', Anonymous Referee #2, 14 Feb 2024
This manuscript analyzes the spatiotemporal variability of planetary albedo (PA), particularly on a monthly scale for each latitudinal zone. It focuses on the hemispheric symmetry of PA and separates contributions from different components (surface, atmosphere, and cloud). The asymmetry issue of current model data is also analyzed, providing insights for improving PA modeling within the community. Overall, the analysis is comprehensive, and sufficient evidence has been cited to support this work. However, I suggest the authors emphasize the key contributions of this work compared to previous studies. Additionally, the manuscript's structure may need refinement as the model data comparison appears independent from the previous analysis. Furthermore, certain analyses and discussions require revision before publication.
Major
- In Section 3.3, rather than simply comparing with CERES for the asymmetry issue in modeled PA, the analysis should be integrated more cohesively with key findings from previous sections. This integration is essential for establishing a stronger motivation and relevance for the comparison. For instance, it would be valuable to assess whether the model data captures the interannual anomaly of the contribution rate of different components to total reflected radiation, thus linking the analysis with earlier sections and enhancing the manuscript's continuity and depth of analysis.
- Simulated Snow uncertainty has been suggested to introduce substantial bias of surface albedo among reanalysis data, especially at mid and high latitudes [1]. Are there any influences for the TOA asymmetry issue in simulations?
- Line 546: despite including various driving factors (e.g., NDVI, snow cover) for anomaly attribution, their corresponding radiative forcings differ significantly. Consequently, even if two factors exhibit similar anomaly magnitudes in a given year, the importance of NDVI may not be comparable to snow cover changes, rendering the anomaly analysis less meaningful. Therefore, I recommend converting the anomaly analysis to a corresponding radiative forcing analysis to better capture the relative importance of different factors in driving changes in radiative forcing over time.
- The difference of r in Eqs. 4 and 5: r in Eq.4 represents blue-sky reflectance, where the solar beam reflects from the surface, whereas the r in eq5 is black-sky reflectance and the incoming radiation is from space. Does this difference in physics have any impact, particularly at high latitudes where the SZA is large?
Minor
Suggest introducing parameters with 0 in Eq. 20
Figure 2a: I suggest changing the color bar because the conventional association of 'blue & red' typically implies negative and positive directions, whereas the result here is uni-directional.
Line 437: The dominant component in the NH?
Line 438: 0°-70°? Why does it have some overlaps with the following ones?
The figures should be enlarged.
[1] Jia, Aolin, et al. "Global daily actual and snow‐free blue‐sky land surface albedo climatology from 20‐year MODIS products." Journal of Geophysical Research: Atmospheres 127.8 (2022): e2021JD035987.
Citation: https://doi.org/10.5194/egusphere-2023-2882-RC2 - AC2: 'Reply on RC2', Ruixue Li, 08 Apr 2024
- AC3: 'Comment on egusphere-2023-2882', Ruixue Li, 08 Apr 2024
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Ruixue Li
Jiming Li
Deyu Wen
Lijie Zhang
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(3181 KB) - Metadata XML
-
Supplement
(3567 KB) - BibTeX
- EndNote
- Final revised paper