the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 25 Nov 2022
Cloud mask algorithm from the EarthCARE multi-spectral imager: the M-CM products
Abstract. The EarthCARE satellite mission will provide new insights into aerosol-cloud and radiation interactions by means of synergistic observations of the Earth's atmosphere from a collection of active and passive remote sensing instruments, flying on a single satellite platform. The Multi-Spectral Imager (MSI) will provide visible and infrared images in the cross-track direction with a 150 km swath and a pixel sampling at 500 m. The suite of MSI cloud algorithms will deliver cloud macro- and micro-physical properties complementary to the vertical profiles measured from the ATmospheric LIDar (ATLID) and the Cloud Profiling Radar (CPR) instruments. The MSI cloud mask algorithm (M-CM) provides a cloud flag, cloud phase and cloud type product which are essential parameters for the cloud optical and physical properties (M-COP) as well as for the aerosol optical properties (M-AOT). Synthetic test scenes from the EarthCARE end-to-end simulator provide a first overview of the expected performance of the M-CM products before launch. Validation of the MSI cloud mask algorithm against satellite products from MSG SEVIRI and MODIS demonstrates a good performance of the algorithm. The MSI cloud detection performance is not completely aligned with that from MODIS, which is however not surprising when considering the rather limited number of spectral channels of MSI in comparison to MODIS. The direct comparison to MODIS shows that some threshold tuning should be done especially over desert or sun glint regions once real observations are available. However the MSI bands are less affected by sun glint because of the asymmetric view of the imager.
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Notice on discussion status
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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Preprint
(10557 KB)
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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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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2022-1240', Anonymous Referee #1, 11 Jan 2023
In the study “Cloud mask algorithm from the EarthCARE multi-spectral imager:
the M-CM products” by Hünerbein et al. the MSI cloud mask algorithm is described and its performance compared to selected test scenes of the EarthCARE simulator. A first validation shows a good agreement of the M-CM algorithm with 45 MODIS scenes as well as 12 MSG SEVIRI cloud mask algorithms of one selected scene.
A description and first tests of the M-CM algorithm is very valuable for the cloud community and on time before the launch of EarthCARE that will provide simultaneous measurements of clouds and aerosol properties as well as radiation fluxes.
The paper is written in a clear and concise way. Some minor deficits are noted in the abstract and conveyed messages of the paper. It is recommended for publication after minor revisions.
Minor comments:
The abstract needs modification as the study’s purpose is not clearly stated. What is the study’s motivation, goal, result and outlook?
From my perspective a description of the M-CM algorithm is provided together with a first validation.The terms “validation” and “verification” should not be used interchangeably as they describe different things. Verification determines if the algorithm developed is suited to the specified requirements. This can be done by testing selected scenes. However, a profound validation should contain a quantitative analysis of a larger and well suited test data set that will follow after the launch as explained in the conclusion. Please check and correct the appropriate usage of these terms throughout the manuscript.
l.14 Comma is missing after “However”. Please check this throughout the manuscript.l.34 “a a decision tree”. Delete "a"
l.122 "makes no sense" Please be more specific. Why does it make no sense? Is a probability more useful for the user's applications as it provides a confidence measure or is there another reason? Please rephrase l.121-124 for clarity.
l.130 How are these surface dependent thresholds derived?
l.180 Please rephrase the sentence for clarity. Is the following correct?
The same applies for the tri-spectral brightness temperature difference test. Further investigation is needed to define the base threshold, which is strongly dependent on surface and water vapor.
l.190 “probabilities that the pixel is clear” --> probabilities of a pixel being clearl.237 "the the" --> that the
l. 269 “synthetic atmospheric test scenes created with” atmospheric test scenes created synthetically with …
Fig. 6 Figure subtitle >0.1 disagrees with caption and text (≥ 0.1)
l. 303 “difference” is not true.The term “confusion matrix” would be more appropriate.
l. 307 "while the true cloud flag". This may be misleading as the 3D simulations are not ground truth and are highly dependent on the assumptions (l. 276). Might be better to use the word test or simulated cloud flag instead.
l. 315 “data form the Copernicus” –> data from the Copernicus
l. 351 "Twelve groups" what is meant by this? Where do the 12 algorithms originate from?
Citation: https://doi.org/10.5194/egusphere-2022-1240-RC1 -
AC1: 'Reply on RC1', Anja Hünerbein, 20 Mar 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1240/egusphere-2022-1240-AC1-supplement.pdf
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AC1: 'Reply on RC1', Anja Hünerbein, 20 Mar 2023
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RC2: 'Comment on egusphere-2022-1240', Anonymous Referee #2, 31 Jan 2023
This paper describes the EarthCARE MSI cloud mask (M-CM) algorithms, showing algorithm descriptions and validations. Validations has been performed by using, synthetic dataset, versus MODIS, versus SEVIRI. This paper is well organized and reliable. However, some minor improvements will be needed before accepting this paper. Reviewer recommends that this paper to be accepted with some minor modifications.
(1) Line 27.
Could you please mention about how large of uncertainties can be lead. Please add some reference papers?(2)Line 77.
What is "a histgram-based scene analysis"? Please clarify this point.(3) From Line 111 to 115.
Please unify the symbol that means "phi".(4) Line 138.
Please define "the sun glint angle" by schematic figure or formulation.(5) Equation (3) and (4)
Why multiply 100?(6) Line 253, and 254.
Please write formulations of the NDVI and the NDSI.(7) Line 299.
That does a sentence "The M-CF algorithm yields a cloud fraction of 50%" mean? Please clarify this point.(8) Line 329.
I'm confusing. My understanding is that, Fig.8 MODIS cloud flag was generated by using MODIS-Level1b data with use of the M-CLD processor as noted Line around 315. So, spectral channels used in both MODIS cloud flag and MSI cloud flag is the same (is it true?). However, this sentence mentioned that "the MODIS cloud tests are based on much more spectral channels". I imagine that two examinations are mixed in this topic. Please explain more.That's all of reviewer's comments, questions, and suggestions for improvement.
Citation: https://doi.org/10.5194/egusphere-2022-1240-RC2 -
AC2: 'Reply on RC2', Anja Hünerbein, 20 Mar 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1240/egusphere-2022-1240-AC2-supplement.pdf
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AC2: 'Reply on RC2', Anja Hünerbein, 20 Mar 2023
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2022-1240', Anonymous Referee #1, 11 Jan 2023
In the study “Cloud mask algorithm from the EarthCARE multi-spectral imager:
the M-CM products” by Hünerbein et al. the MSI cloud mask algorithm is described and its performance compared to selected test scenes of the EarthCARE simulator. A first validation shows a good agreement of the M-CM algorithm with 45 MODIS scenes as well as 12 MSG SEVIRI cloud mask algorithms of one selected scene.
A description and first tests of the M-CM algorithm is very valuable for the cloud community and on time before the launch of EarthCARE that will provide simultaneous measurements of clouds and aerosol properties as well as radiation fluxes.
The paper is written in a clear and concise way. Some minor deficits are noted in the abstract and conveyed messages of the paper. It is recommended for publication after minor revisions.
Minor comments:
The abstract needs modification as the study’s purpose is not clearly stated. What is the study’s motivation, goal, result and outlook?
From my perspective a description of the M-CM algorithm is provided together with a first validation.The terms “validation” and “verification” should not be used interchangeably as they describe different things. Verification determines if the algorithm developed is suited to the specified requirements. This can be done by testing selected scenes. However, a profound validation should contain a quantitative analysis of a larger and well suited test data set that will follow after the launch as explained in the conclusion. Please check and correct the appropriate usage of these terms throughout the manuscript.
l.14 Comma is missing after “However”. Please check this throughout the manuscript.l.34 “a a decision tree”. Delete "a"
l.122 "makes no sense" Please be more specific. Why does it make no sense? Is a probability more useful for the user's applications as it provides a confidence measure or is there another reason? Please rephrase l.121-124 for clarity.
l.130 How are these surface dependent thresholds derived?
l.180 Please rephrase the sentence for clarity. Is the following correct?
The same applies for the tri-spectral brightness temperature difference test. Further investigation is needed to define the base threshold, which is strongly dependent on surface and water vapor.
l.190 “probabilities that the pixel is clear” --> probabilities of a pixel being clearl.237 "the the" --> that the
l. 269 “synthetic atmospheric test scenes created with” atmospheric test scenes created synthetically with …
Fig. 6 Figure subtitle >0.1 disagrees with caption and text (≥ 0.1)
l. 303 “difference” is not true.The term “confusion matrix” would be more appropriate.
l. 307 "while the true cloud flag". This may be misleading as the 3D simulations are not ground truth and are highly dependent on the assumptions (l. 276). Might be better to use the word test or simulated cloud flag instead.
l. 315 “data form the Copernicus” –> data from the Copernicus
l. 351 "Twelve groups" what is meant by this? Where do the 12 algorithms originate from?
Citation: https://doi.org/10.5194/egusphere-2022-1240-RC1 -
AC1: 'Reply on RC1', Anja Hünerbein, 20 Mar 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1240/egusphere-2022-1240-AC1-supplement.pdf
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AC1: 'Reply on RC1', Anja Hünerbein, 20 Mar 2023
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RC2: 'Comment on egusphere-2022-1240', Anonymous Referee #2, 31 Jan 2023
This paper describes the EarthCARE MSI cloud mask (M-CM) algorithms, showing algorithm descriptions and validations. Validations has been performed by using, synthetic dataset, versus MODIS, versus SEVIRI. This paper is well organized and reliable. However, some minor improvements will be needed before accepting this paper. Reviewer recommends that this paper to be accepted with some minor modifications.
(1) Line 27.
Could you please mention about how large of uncertainties can be lead. Please add some reference papers?(2)Line 77.
What is "a histgram-based scene analysis"? Please clarify this point.(3) From Line 111 to 115.
Please unify the symbol that means "phi".(4) Line 138.
Please define "the sun glint angle" by schematic figure or formulation.(5) Equation (3) and (4)
Why multiply 100?(6) Line 253, and 254.
Please write formulations of the NDVI and the NDSI.(7) Line 299.
That does a sentence "The M-CF algorithm yields a cloud fraction of 50%" mean? Please clarify this point.(8) Line 329.
I'm confusing. My understanding is that, Fig.8 MODIS cloud flag was generated by using MODIS-Level1b data with use of the M-CLD processor as noted Line around 315. So, spectral channels used in both MODIS cloud flag and MSI cloud flag is the same (is it true?). However, this sentence mentioned that "the MODIS cloud tests are based on much more spectral channels". I imagine that two examinations are mixed in this topic. Please explain more.That's all of reviewer's comments, questions, and suggestions for improvement.
Citation: https://doi.org/10.5194/egusphere-2022-1240-RC2 -
AC2: 'Reply on RC2', Anja Hünerbein, 20 Mar 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1240/egusphere-2022-1240-AC2-supplement.pdf
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AC2: 'Reply on RC2', Anja Hünerbein, 20 Mar 2023
Peer review completion
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Cited
Sebastian Bley
Stefan Horn
Hartwig Deneke
Andi Walther
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(10557 KB) - Metadata XML