Articles | Volume 18, issue 3
https://doi.org/10.5194/essd-18-1813-2026
© Author(s) 2026. This work is distributed under the Creative Commons Attribution 4.0 License.
All-day global cloud physical properties products with 0.07° resolution retrieved from geostationary satellite imagers covering the period from 2000 to 2022
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- Final revised paper (published on 10 Mar 2026)
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Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor
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RC1: 'Comment on essd-2025-425', Anonymous Referee #1, 03 Oct 2025
- AC1: 'Reply on RC1', Feng Zhang, 15 Jan 2026
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RC2: 'Comment on essd-2025-425', Anonymous Referee #2, 22 Oct 2025
- AC2: 'Reply on RC2', Feng Zhang, 15 Jan 2026
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AR – Author's response | RR – Referee report | ED – Editor decision | EF – Editorial file upload
AR by Feng Zhang on behalf of the Authors (15 Jan 2026)
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ED: Referee Nomination & Report Request started (19 Jan 2026) by Jing Wei
RR by Anonymous Referee #2 (05 Feb 2026)
RR by Anonymous Referee #1 (16 Feb 2026)
ED: Publish subject to minor revisions (review by editor) (17 Feb 2026) by Jing Wei
AR by Feng Zhang on behalf of the Authors (21 Feb 2026)
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ED: Publish as is (28 Feb 2026) by Jing Wei
AR by Feng Zhang on behalf of the Authors (03 Mar 2026)
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This study develops an AI algorithm for cloud-top phase, altitude, and particle size, and cloud optical thickness based on the infrared window band (~11 μm) and infrared water vapor band (~6.7 μm) from geostationary satellite observations, alongside temperature & humidity profile products from reanalysis data. The research topic is interesting. However, all of the input variables of the deep learning model are solely correlated with cloud-top height, the inversion of other cloud properties lacking physically explainability (see below for details). Numerous technical details remain underspecified. At minimum, a major revision is required before consideration for acceptance.
Major Comments:
1. Physical explainability:
Fundamentally, neither the ~11 μm infrared window band nor the numerical ERA-5 temperature -humidity profiles provide direct information about cloud-top phase, particle size, or cloud optical thickness—they primarily constrain cloud-top height. While incorporating the ~6.7 μm infrared water vapor band may marginally improve cirrus cloud-top height retrieval, these parameters inherently lack sensitivity to phase/microphysics. Consequently, the inversion model lacks robustness. For instance, although cloud-top temperatures (brightness temperatures) above 0°C typically indicate liquid phase and below -40°C suggest ice phase, values between -40°C and 0°C can represent supercooled liquid, ice, or mixed-phase conditions. The proposed empirical relationships, trained on large datasets, constitute merely statistical correlations—analogous to predicting human height from tree height—with tenuous physical connections. This limitation explains the significant performance drop observed when validating the phase classification algorithm independently on 2022 data. Further independent testing (exposing unseen scenarios) would likely yield even lower metrics. Authors must establish stronger physical justification for their methodology to convince reviewers and readers.
2. Data matching
Considering the disparate spatial resolutions—8 km for geostationary satellite products, 0.25° for reanalysis data, versus 1 km for polar-orbiting MODIS/CALIOP—how are these multi-source datasets temporally and spatially matched? Has horizontal Homogeneity been addressed?
How does the vertical cloud-phase profiling capability of CALIOP map onto the single-layer cloud-top phase retrieved from geostationary imagery? Given CALIOP’s inability to penetrate optically thick clouds, is its reported optical thickness suitable as a ‘truth’ reference for evaluating your algorithm’s performance?
Minor Comments:
1. When first introducing “cloud effective radius” in the abstract and main text, use the precise term“ cloud-top particle effective radius” or “cloud-top particle size” .
2. Spell out the full names upon first occurrence for acronyms like CARE, CLARA.
3. 2.1.2: Specify the exact MODIS product ID(s) and version(s) used. Note that MODIS offers three types of cloud-top particle effective radius at 1.6 μm, 2.1 μm, and 3.9 μm, please clarify which one was selected.
4. Table 4 & Fig. 4: Compared to prior studies, the reported accuracies are relatively low. Particularly, the coefficient of determination (R²) for cloud optical thickness is notably poor.