Ice crystals in clouds form when temperatures drop below freezing. This process involves water vapor or liquid droplets transforming into ice.
The Formation of Ice Crystals
The referenced video, "How Ice Crystals in Clouds form and why the Math doesn't add up," highlights that ice crystals form from:
- Water Vapor: When temperatures are sufficiently cold, water vapor can directly deposit onto a surface and form ice without going through a liquid phase.
- Liquid Droplets: Supercooled water droplets (liquid water below 0°C) in clouds can also freeze and turn into ice crystals if they encounter a tiny particle called an ice nucleus or when the temperature drops low enough.
Key Factors
Here's a breakdown of the key factors involved in ice crystal formation in clouds:
| Factor | Description |
|---|---|
| Temperature | Temperatures must be below freezing (0°C or 32°F) for ice crystals to form. Often significantly below. |
| Water Vapor | Water vapor needs to be present in the air for deposition to occur. |
| Liquid Droplets | Clouds often contain supercooled water droplets, which can freeze when nucleation occurs. |
| Ice Nuclei | Small particles, called ice nuclei, provide a surface for ice to form and grow. |
How it all Comes Together
- Cooling: As air rises in the atmosphere, it expands and cools.
- Condensation and Droplet Formation: Water vapor in the air condenses into tiny droplets.
- Supercooling: These droplets can remain liquid even when cooled below freezing, becoming supercooled.
- Ice Nucleation: Ice nuclei come into play as these particles allow for ice crystals to start growing, by causing the supercooled water droplets to freeze, or by providing a place for water vapor to deposit as ice directly.
- Crystal Growth: Once ice crystals form, they attract more water vapor, causing them to grow larger and potentially form snowflakes.
In summary, ice crystals in clouds are the result of water vapor or liquid droplets freezing at temperatures below freezing. This is often due to deposition or the presence of ice nuclei that help the process of ice formation to begin.
