Uploaded May 2026 | Updated September 2026, 2 weeks ago
Cloud Thinning: Observation and Inference from the Micro to the Macro Scale
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Cloud thinning is proposed as a technique where the optical depth of clouds with a warming climate effect is reduced, or their formation is suppressed by cloud seeding interventions. Seeding can be applicable to high altitude cirrus clouds or polar wintertime mixed-phase clouds. In both cloud cases, effective aerosol seeds are necessary to form ice at conditions relevant for the respective clouds. In the case of cirrus cloud thinning (CCT,) aerosol seeds that form ice at saturation (Si) conditions much lower than natural cirrus clouds are desirable so that clouds form at lower altitude, with large ice crystal size and shorter lifetime, therefore dehydrating the upper troposphere to curb natural cirrus cloud formation which requires significantly higher Si than required for seeding. In this work, we present ice nucleation threshold conditions for feldspar and silica particles (hollow and porous), demonstrating how the chosen morphology and composition can drive ice crystal formation conditions at temperatures below -40 º C, close to Si = 1 (the minimum possible Si for bulk ice crystals to form and grow). A newly developed cold cell is used to represent longer nucleation exposure times more similar to those in the atmosphere. Furthermore, we present observations on how the ice crystal seeding efficiency can deteriorate depending on the type of dispersion techniques (water versus air) and from atmospheric aging resulting in organic coatings. Future experiments are to explore inorganic coatings, and the fate of the seeding particles that remain in the troposphere with respect to oxidation processes and second cloud formation cycles.
For more information please visit: simonsfoundation.org/event/solar-radiation-management-annual-meeting-2026
Cloud Thinning: Observation and Inference from the Micro to the Macro Scale
~
Cloud thinning is proposed as a technique where the optical depth of clouds with a warming climate effect is reduced, or their formation is suppressed by cloud seeding interventions. Seeding can be applicable to high altitude cirrus clouds or polar wintertime mixed-phase clouds. In both cloud cases, effective aerosol seeds are necessary to form ice at conditions relevant for the respective clouds. In the case of cirrus cloud thinning (CCT,) aerosol seeds that form ice at saturation (Si) conditions much lower than natural cirrus clouds are desirable so that clouds form at lower altitude, with large ice crystal size and shorter lifetime, therefore dehydrating the upper troposphere to curb natural cirrus cloud formation which requires significantly higher Si than required for seeding. In this work, we present ice nucleation threshold conditions for feldspar and silica particles (hollow and porous), demonstrating how the chosen morphology and composition can drive ice crystal formation conditions at temperatures below -40 º C, close to Si = 1 (the minimum possible Si for bulk ice crystals to form and grow). A newly developed cold cell is used to represent longer nucleation exposure times more similar to those in the atmosphere. Furthermore, we present observations on how the ice crystal seeding efficiency can deteriorate depending on the type of dispersion techniques (water versus air) and from atmospheric aging resulting in organic coatings. Future experiments are to explore inorganic coatings, and the fate of the seeding particles that remain in the troposphere with respect to oxidation processes and second cloud formation cycles.
For more information please visit: simonsfoundation.org/event/solar-radiation-management-annual-meeting-2026
