No, a cloud is not generally considered a sublimation process, but sublimation can contribute to cloud formation and, more commonly, cloud dissipation.
Here's a breakdown:
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Cloud Formation: Clouds primarily form through condensation. Water vapor in the air cools and condenses into liquid water droplets or ice crystals around tiny particles called condensation or sublimation nuclei.
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Condensation Nuclei vs. Sublimation Nuclei: The reference mentions both "condensation nuclei" and "sublimation nuclei." While condensation is the more common process, sublimation nuclei can directly transform water vapor into ice crystals in very cold conditions.
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Sublimation: Sublimation is the process where a solid (like ice) directly changes into a gas (water vapor) without passing through the liquid phase.
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Sublimation's Role in Clouds: Sublimation is more often associated with cloud dissipation. If the air surrounding a cloud is dry and relatively warm, ice crystals within the cloud can sublimate directly into water vapor, causing the cloud to shrink or disappear. This is more common in high-altitude cirrus clouds.
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Deposition: The opposite of sublimation is deposition. Deposition involves water vapor changing directly into ice crystals, which can also contribute to cloud formation, especially cirrus cloud formation.
In summary, while sublimation isn't the primary formation process for most clouds (condensation is), it plays a role, especially in very cold environments or in the dissipation of ice crystal clouds. Deposition, the reverse of sublimation, is more directly related to cloud formation.
