Different Ice Patterns Inside a Hailstone
January 19, 2023
Photographer: Mario Freitas
Summary Author: Mario Freitas
The photo above was taken just after a violent spring storm in Curitiba, Brazil. The collected 1-inch diameter (2.54 cm) hailstone fragment shows a milky nucleus surrounded by alternating rings of transparent and translucent ice.
Hail can be formed when thunderstorm drafts carry up raindrops into higher freezing layers of the atmosphere. A hailstone grows inside a cloud each time it collides with water drops making them freeze onto its surface, until an upper limit is reached when the updraft can no longer support its weight, causing it to fall and impacting the ground. Microphysical processes determine density, structure, and sizes of hailstones. At very high altitudes, temperature can be so low that few liquid water drops remain, so hailstones don’t reach significative sizes.
The structure of a cloudy ice layer scatters light in all directions because specific temperature conditions cause supercooled liquid water to freeze instantaneously on hailstone surfaces, resulting in cracked ice with trapped air bubbles (dry growth). Light is otherwise refracted leading to the hailstones' transparency if the water freezes slowly enough, permitting penetration into the gaps before freezing and thus allowing air bubbles to escape (wet growth). Photo taken on November 23, 2022.
Curitiba, Brazil Coordinates: -25.4372, -49.2700
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