the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 26 May 2025
Giant Cloud Condensation Nuclei enhanced Ice Sublimation Process: A potential mechanism in mixed phase clouds
Abstract. The Wegener-Bergeron-Findeisen (WBF) process describes the growth of ice crystals at the expense of supercooled liquid droplets in mixed-phase clouds, driven by phase transitions at temperatures below 0 °C. In this study, we introduce a potential mechanism involving the transfer of water vapor from ice to cloud droplets formed on Giant Cloud Condensation Nuclei (GCCN). This process occurs under specific atmospheric conditions influenced by temperature and CCN size, particularly for CCN with diameters exceeding 1 μm. We term this mechanism the Giant Cloud Condensation Nuclei-Enhanced Ice Sublimation Process (GCCN-ISP). We first conduct a theoretical analysis to develop a physical model for determining these specific atmospheric conditions, followed by validation through observations. Model simulations informed by observational data from aircraft indicate that when CCNs are sufficiently large and cold, the water vapor partial pressure over droplets formed on these CCNs can be lower than that over ice. Consequently, water vapor can transfer from ice to supercooled droplets, causing the droplets to grow. Eventually, the water vapor pressures of both reach equilibrium, resulting in their coexistence.
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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
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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-2025-1932', Anonymous Referee #2, 12 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1932/egusphere-2025-1932-RC1-supplement.pdfCitation: https://doi.org/
10.5194/egusphere-2025-1932-RC1 -
AC1: 'Reply on RC1', Denghui Ji, 05 Aug 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1932/egusphere-2025-1932-AC1-supplement.pdf
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AC1: 'Reply on RC1', Denghui Ji, 05 Aug 2025
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RC2: 'Comment on egusphere-2025-1932', Anonymous Referee #1, 15 Jun 2025
This study presents a novel and compelling mechanism—the Giant Cloud Condensation Nuclei-enhanced Ice Sublimation Process (GCCN-ISP)—that challenges the traditional Wegener-Bergeron-Findeisen (WBF) paradigm in mixed-phase clouds. The key innovation lies in demonstrating how large CCN can alter the direction of vapor transfer, enabling supercooled droplets to coexist with ice crystals under specific conditions. The theoretical framework, combining Köhler theory with solute effects, is well-constructed and supported by observational data from the AFLUX campaign. The identification of a "balanced diameter" for droplet-ice equilibrium provides a valuable conceptual advance, with potential implications for improving cloud microphysics in climate models. I recommend acceptance after minor revisions, contingent on a more comprehensive discussion of uncertainties and broader impacts.
- The reliance on a single case study (AFLUX campaign) limits the generalizability of GCCN-ISP. Expanding validation to diverse geographic regions (e.g., mid-latitude mixed-phase clouds) and seasons would strengthen the conclusions. Direct measurements of CCN size/composition (e.g., via aerosol mass spectrometers)，if available, can be used to corroborate inferred CCN properties.
- The assumption of pure NaCl CCN (κ=1.4) oversimplifies real-world aerosol diversity. Incorporating mixed CCN types (e.g., organics, sulfates) and non-spherical shapes would enhance realism. Additionally, the model neglects dynamic processes like turbulence and entrainment, which could modulate GCCN-ISP efficiency.
- While the mechanism’s microphysical basis is plausible, its broader climatic impacts (e.g., on cloud radiative forcing or Arctic amplification) remain unquantified. Some words on coupling the framework with large-scale models and further study on the climate effect of this mechanism can be added.
- The study does not explore how GCCN-ISP competes or synergizes with other ice nucleation pathways (e.g., secondary ice production) or collision-coalescence. A discussion of these interactions would contextualize the mechanism’s relative importance
- Controlled laboratory experiments (e.g., cloud chamber studies) are critical to isolate GCCN-ISP under varying temperature, humidity, and CCN conditions. Such experiments could validate the theoretical "balanced diameter" and vapor transfer dynamics .
Citation: https://doi.org/10.5194/egusphere-2025-1932-RC2 -
AC2: 'Reply on RC2', Denghui Ji, 05 Aug 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1932/egusphere-2025-1932-AC2-supplement.pdf
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2025-1932', Anonymous Referee #2, 12 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1932/egusphere-2025-1932-RC1-supplement.pdf
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AC1: 'Reply on RC1', Denghui Ji, 05 Aug 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1932/egusphere-2025-1932-AC1-supplement.pdf
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AC1: 'Reply on RC1', Denghui Ji, 05 Aug 2025
-
RC2: 'Comment on egusphere-2025-1932', Anonymous Referee #1, 15 Jun 2025
This study presents a novel and compelling mechanism—the Giant Cloud Condensation Nuclei-enhanced Ice Sublimation Process (GCCN-ISP)—that challenges the traditional Wegener-Bergeron-Findeisen (WBF) paradigm in mixed-phase clouds. The key innovation lies in demonstrating how large CCN can alter the direction of vapor transfer, enabling supercooled droplets to coexist with ice crystals under specific conditions. The theoretical framework, combining Köhler theory with solute effects, is well-constructed and supported by observational data from the AFLUX campaign. The identification of a "balanced diameter" for droplet-ice equilibrium provides a valuable conceptual advance, with potential implications for improving cloud microphysics in climate models. I recommend acceptance after minor revisions, contingent on a more comprehensive discussion of uncertainties and broader impacts.
- The reliance on a single case study (AFLUX campaign) limits the generalizability of GCCN-ISP. Expanding validation to diverse geographic regions (e.g., mid-latitude mixed-phase clouds) and seasons would strengthen the conclusions. Direct measurements of CCN size/composition (e.g., via aerosol mass spectrometers)，if available, can be used to corroborate inferred CCN properties.
- The assumption of pure NaCl CCN (κ=1.4) oversimplifies real-world aerosol diversity. Incorporating mixed CCN types (e.g., organics, sulfates) and non-spherical shapes would enhance realism. Additionally, the model neglects dynamic processes like turbulence and entrainment, which could modulate GCCN-ISP efficiency.
- While the mechanism’s microphysical basis is plausible, its broader climatic impacts (e.g., on cloud radiative forcing or Arctic amplification) remain unquantified. Some words on coupling the framework with large-scale models and further study on the climate effect of this mechanism can be added.
- The study does not explore how GCCN-ISP competes or synergizes with other ice nucleation pathways (e.g., secondary ice production) or collision-coalescence. A discussion of these interactions would contextualize the mechanism’s relative importance
- Controlled laboratory experiments (e.g., cloud chamber studies) are critical to isolate GCCN-ISP under varying temperature, humidity, and CCN conditions. Such experiments could validate the theoretical "balanced diameter" and vapor transfer dynamics .
Citation: https://doi.org/10.5194/egusphere-2025-1932-RC2 -
AC2: 'Reply on RC2', Denghui Ji, 05 Aug 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1932/egusphere-2025-1932-AC2-supplement.pdf
Peer review completion
Journal article(s) based on this preprint
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Denghui Ji
Christoph Ritter
Xiaoyu Sun
Manuel Moser
Christiane Voigt
Mathias Palm
Justus Notholt
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(3012 KB) - Metadata XML