Скачать или смотреть The Science of Snow Formation: From Vapor to Crystal

Snow is a solid form of precipitation that crystallizes within the Earth's atmosphere. The process begins when the atmospheric temperature is at or below freezing (0°C or 32°F) and there is a sufficient amount of moisture in the air.

Nucleation: The formation starts when water vapor in the clouds turns directly into ice. This process requires a "nucleus," such as a microscopic dust particle or pollen, around which the water vapor can freeze.

Deposition: Unlike rain, which freezes into sleet, snow is formed through a process called deposition. In this stage, water vapor changes from a gas directly into a solid (ice) without becoming a liquid first.

Crystal Growth: As the ice crystal moves through the cloud, it attracts more water vapor molecules. These molecules arrange themselves in a precise hexagonal (six-sided) lattice structure, dictated by the molecular bonds of water. This is why almost all snowflakes have six arms.

Temperature and Shape: The specific shape of a snowflake—whether it looks like a needle, a plate, or a complex dendrite—is determined by the exact temperature and humidity levels it encounters as it falls toward the ground.

Reaching the Surface: For snow to reach the ground without melting, the entire column of air from the cloud to the surface must be near or below freezing. If the air near the ground is slightly above freezing, the flakes may partially melt, resulting in "wet snow" or "slush."