the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 28 Mar 2023
Examining cloud vertical structure and radiative effects from satellite retrievals and evaluation of CMIP6 scenarios
Johannes Quaas
Yong Han
Abstract. Clouds exhibit a wide range of vertical morphologies that are regulated by distinct atmospheric dynamics/thermodynamics and are related to a diversity of microphysical properties and radiative effects. In this study, the new CERES-CloudSat-CALIPSO-MODIS (CCCM) RelD1 dataset is used to investigate the morphology and spatial distribution of different CVS types during 2007–2010. The combined active and passive satellites provide a more precise CVS than only based on passive imagers or microwave radiometers. We group the clouds into 12 CVS classes based on how they are located or overlapping in three standard atmospheric layers with pressure thresholds of 440 and 680 hPa. For each of the 12 CVS types, the global average cloud radiative effects (CREs) at the top of the atmosphere, within the atmosphere and at the surface, as well as the cloud heating rate (CHR) profiles are examined. The observations are subsequently used to evaluate the variations in total, high-, middle- and low-level cloud fractions in CMIP6 models. The ‘historical’ experiment during 1850–2014 and two scenarios (ssp245 and ssp585) during 2015–2100 are analysed. The observational results show a substantial variance in the spatial pattern among different CVS types, with the greatest contrast between high and low clouds. Single-layer cloud fraction is almost four times larger on average than multi-layer cloud, with significant geographic differences associated with clearly distinguishable regimes, showing that overlapping clouds are regionally confined. The global average CREs reveal that four types of CVS warm the planet while eight of them cool it. The longwave component drives the net CHR profile, and the CHR profiles of multi-layer clouds are more curved and intricate than those of single-layer clouds, resulting in complex thermal stratifications. According to the long-term analysis from CMIP6, the projected total cloud fraction decreases faster over land than over the ocean. The high clouds over the ocean increase significantly, but other types of clouds over land and ocean continue to decrease, helping to offset the decrease in oceanic total cloud fraction. Moreover, it is concluded that the spatial pattern of CVS types may not be significantly altered by climate change, and only the cloud fraction is influenced. Our findings suggest that long-term observed CVS should be emphasized in the future to better understand CVS responses to anthropogenic forcing and climate change.
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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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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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Supplement
(48079 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Hao Luo et al.
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-453', Anonymous Referee #1, 18 Apr 2023
Review of “Examining cloud vertical structure and radiative effects from satellite retrievals and evaluation of CMIP6 scenarios” by Luo et al.
This study investigates the global scale spatial pattern and vertical extent of cloud vertical structure using the new CCCM dataset. The cloud radiative effect for each classified cloud vertical structure type is quantified. In addition, long-term changes in cloud vertical structure are explored in the context of climate change using CMIP6 models. Valuable conclusions have been achieved, which can improve our understanding of cloud vertical structure, its long-term trends, and radiative effects from the perspective of satellite observations and climate models. Overall, this work addresses relevant scientific questions within the scope of ACP and presents interesting ideas using the new data and solid methods. Also, the paper is well written and the figures are displayed in a good manner. For these reasons, I would recommend its acceptance for publication in ACP after minor revisions.
Detail comments:
Line 13, the full name should be stated on the first occurrence in the Abstract. It seems that CVS stands for cloud vertical structure after reading the entire text.
Line 58, “…from ground-based remote sensors and from radiosonde measurements”, please strike out the second “from” in this sentence.
Line 89-90, in the introduction, the authors state that “Due to the interference with solar and terrestrial radiation, changes in CVS can strongly affect the Earth’s energy budget, even when the total cloud fraction remains constant”. How to understand “strongly”? since the authors did not make an explanation or cite any references. I would recommend omitting this word unless a reasonable explanation is provided by referring to relevant literature.
Line 90-91, “Satellite observations are insufficient for examining long-term trends in CVS, not only because of the limited time records…”. In my opinion, satellites have decades of records so far, and satellite-based long-term trend analyses have been conducted in previous literature. The authors could say, compared to ground-based observations and models, the satellite time records are limited. So, the expression here is not accurate, and should be rephrased.
Line 148, one concern here is that the authors did not claim the cloud pressure boundary of the layered clouds in the CMIP6 models.
Line 276, “the SW CREs further increases as the…”, change “increases” to “increase”.
Line 327-330, this sentence depicts two figures including Figs. S3 and S4, to avoid misunderstanding, should be split into two sentences.
Line 420, why do the authors think the trends in Fig. 9 is “nonlinear”? I personally cannot see a noticeable non-linearity, and suggest removing this word and only saying “noticeable”.
Citation: https://doi.org/10.5194/egusphere-2023-453-RC1 -
RC2: 'Comment on egusphere-2023-453', Anonymous Referee #2, 20 Apr 2023
Review of "Examining cloud vertical structure and radiative effects from satellite retrievals and evaluation of CMIP6 scenarios" by Luo et al.
This study aims to investigate cloud morphologies and their radiative effect on the global scale. The authors use and present the new product CCCM RelD1 and compare it with 2B-GEOPROF-LIDAR, proving the reliability of the new dataset. The CCCM dataset is used to classify the clouds into 12 classes as a function of their vertical structure. The spatial distribution and the radiative effect of each class are studied in detail and presented in a clear and complete manner.
In the second part of the paper, the authors use CMIP6 models to investigate cloud amount trends during both the historical period and future projections. A comparison between models and observation is given in order to evaluate the reliability of the time series obtained from the models.This work addresses relevant scientific questions within the scope of ACP using clear and valid methods. Moreover, the paper is well written, it is easy to follow and the figures are very clear. Overall, I find this work to be very valuable and interesting, and I recommend its acceptance for publication in ACP after minor revisions.
Specific comments:
Line 20: The word "variance" is generally used to indicate the square of the standard deviation. I suggest replacing it.
Section 2.1: The authors mentioned the horizontal resolution of all the relevant instruments. However, I would recommend mentioning also the horizontal resolutions of the two final products 2B GEOPROF-LIDAR and CCCM.
Lines 131, 147, 196: Could the authors clarify the meaning of the word "interpolation"? Does it mean "average in the 2x2 gridbox"? If so, I would suggest to substitute it with the word "average", if not, I would suggest explaining the meaning.
Lines 245-247: The negative correlation between the low cloud tops and the distance between low and upper clouds looks like an artifact coming from the definitions (e.g. given X,Y uncorrelated, then R(X,Y-X) is negative). I suggest removing these lines.
If instead, this is not the case, and if the negative correlation is significant, I suggest explaining better why.Line 312: it is not clear if "high-, middle- and low-level" are identified from cloud top of the highest cloud or not. For example, are clouds of HMxL labeled high-level? Or they are included also in middle- and low-level classes?
Lines 325-330: Figures S3 and S4 are shown to compare the MME mean and the two models available for the future period. I suggest adding in the supplement material a figure similar to Figure 8, but using only GFDL-CM4 and IPSL-CM6A-LR, in order to compare them with the data in the period 2007-2010.
Line 380: The "CSV" identifies just low-, middle-, and high-cloud in this line, while it identifies the 12 classes of vertical structure in the rest of the paper. Could the authors substitute "CSV" with "low-, middle-, and high-level cloud amounts"?
Figures 5 & 6: Figure 6 shows that all the CSV classes have a net cooling effect on the surface, while Figure 5 shows that there are some regions where the net CRE on the surface is positive. Could the author comment on this?
Technical corrections:
Line 13: Please write CVS as full name before using the acronym in the abstract.
Line 154: SSP245 and SSP585 are capitalized in this line, while they are lower letters in the rest of the paper.
Lines 178, 185, 191: equation numbers are not correctly written.
Citation: https://doi.org/10.5194/egusphere-2023-453-RC2 -
AC1: 'Comment on egusphere-2023-453', Hao Luo, 06 Jun 2023
We would like to thank the reviewers for giving constructive criticisms and comments. We have made the point-by-point response to the comments and revised the manuscript accordingly. Attached please find the detailed response.
Hao Luo and co-authors
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-453', Anonymous Referee #1, 18 Apr 2023
Review of “Examining cloud vertical structure and radiative effects from satellite retrievals and evaluation of CMIP6 scenarios” by Luo et al.
This study investigates the global scale spatial pattern and vertical extent of cloud vertical structure using the new CCCM dataset. The cloud radiative effect for each classified cloud vertical structure type is quantified. In addition, long-term changes in cloud vertical structure are explored in the context of climate change using CMIP6 models. Valuable conclusions have been achieved, which can improve our understanding of cloud vertical structure, its long-term trends, and radiative effects from the perspective of satellite observations and climate models. Overall, this work addresses relevant scientific questions within the scope of ACP and presents interesting ideas using the new data and solid methods. Also, the paper is well written and the figures are displayed in a good manner. For these reasons, I would recommend its acceptance for publication in ACP after minor revisions.
Detail comments:
Line 13, the full name should be stated on the first occurrence in the Abstract. It seems that CVS stands for cloud vertical structure after reading the entire text.
Line 58, “…from ground-based remote sensors and from radiosonde measurements”, please strike out the second “from” in this sentence.
Line 89-90, in the introduction, the authors state that “Due to the interference with solar and terrestrial radiation, changes in CVS can strongly affect the Earth’s energy budget, even when the total cloud fraction remains constant”. How to understand “strongly”? since the authors did not make an explanation or cite any references. I would recommend omitting this word unless a reasonable explanation is provided by referring to relevant literature.
Line 90-91, “Satellite observations are insufficient for examining long-term trends in CVS, not only because of the limited time records…”. In my opinion, satellites have decades of records so far, and satellite-based long-term trend analyses have been conducted in previous literature. The authors could say, compared to ground-based observations and models, the satellite time records are limited. So, the expression here is not accurate, and should be rephrased.
Line 148, one concern here is that the authors did not claim the cloud pressure boundary of the layered clouds in the CMIP6 models.
Line 276, “the SW CREs further increases as the…”, change “increases” to “increase”.
Line 327-330, this sentence depicts two figures including Figs. S3 and S4, to avoid misunderstanding, should be split into two sentences.
Line 420, why do the authors think the trends in Fig. 9 is “nonlinear”? I personally cannot see a noticeable non-linearity, and suggest removing this word and only saying “noticeable”.
Citation: https://doi.org/10.5194/egusphere-2023-453-RC1 -
RC2: 'Comment on egusphere-2023-453', Anonymous Referee #2, 20 Apr 2023
Review of "Examining cloud vertical structure and radiative effects from satellite retrievals and evaluation of CMIP6 scenarios" by Luo et al.
This study aims to investigate cloud morphologies and their radiative effect on the global scale. The authors use and present the new product CCCM RelD1 and compare it with 2B-GEOPROF-LIDAR, proving the reliability of the new dataset. The CCCM dataset is used to classify the clouds into 12 classes as a function of their vertical structure. The spatial distribution and the radiative effect of each class are studied in detail and presented in a clear and complete manner.
In the second part of the paper, the authors use CMIP6 models to investigate cloud amount trends during both the historical period and future projections. A comparison between models and observation is given in order to evaluate the reliability of the time series obtained from the models.This work addresses relevant scientific questions within the scope of ACP using clear and valid methods. Moreover, the paper is well written, it is easy to follow and the figures are very clear. Overall, I find this work to be very valuable and interesting, and I recommend its acceptance for publication in ACP after minor revisions.
Specific comments:
Line 20: The word "variance" is generally used to indicate the square of the standard deviation. I suggest replacing it.
Section 2.1: The authors mentioned the horizontal resolution of all the relevant instruments. However, I would recommend mentioning also the horizontal resolutions of the two final products 2B GEOPROF-LIDAR and CCCM.
Lines 131, 147, 196: Could the authors clarify the meaning of the word "interpolation"? Does it mean "average in the 2x2 gridbox"? If so, I would suggest to substitute it with the word "average", if not, I would suggest explaining the meaning.
Lines 245-247: The negative correlation between the low cloud tops and the distance between low and upper clouds looks like an artifact coming from the definitions (e.g. given X,Y uncorrelated, then R(X,Y-X) is negative). I suggest removing these lines.
If instead, this is not the case, and if the negative correlation is significant, I suggest explaining better why.Line 312: it is not clear if "high-, middle- and low-level" are identified from cloud top of the highest cloud or not. For example, are clouds of HMxL labeled high-level? Or they are included also in middle- and low-level classes?
Lines 325-330: Figures S3 and S4 are shown to compare the MME mean and the two models available for the future period. I suggest adding in the supplement material a figure similar to Figure 8, but using only GFDL-CM4 and IPSL-CM6A-LR, in order to compare them with the data in the period 2007-2010.
Line 380: The "CSV" identifies just low-, middle-, and high-cloud in this line, while it identifies the 12 classes of vertical structure in the rest of the paper. Could the authors substitute "CSV" with "low-, middle-, and high-level cloud amounts"?
Figures 5 & 6: Figure 6 shows that all the CSV classes have a net cooling effect on the surface, while Figure 5 shows that there are some regions where the net CRE on the surface is positive. Could the author comment on this?
Technical corrections:
Line 13: Please write CVS as full name before using the acronym in the abstract.
Line 154: SSP245 and SSP585 are capitalized in this line, while they are lower letters in the rest of the paper.
Lines 178, 185, 191: equation numbers are not correctly written.
Citation: https://doi.org/10.5194/egusphere-2023-453-RC2 -
AC1: 'Comment on egusphere-2023-453', Hao Luo, 06 Jun 2023
We would like to thank the reviewers for giving constructive criticisms and comments. We have made the point-by-point response to the comments and revised the manuscript accordingly. Attached please find the detailed response.
Hao Luo and co-authors
Peer review completion
Journal article(s) based on this preprint
Hao Luo et al.
Hao Luo et al.
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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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Supplement
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