How do the clear layers in hailstones form?

The formation of clear layers in hailstones primarily occurs through the process involving larger droplets colliding with the hailstone. When hailstones ascend and descend within a thunderstorm, they pass through various layers of differing moisture and temperature. In the upper regions of the storm, they encounter supercooled water droplets, which are liquid water that remains unfrozen under cold conditions.

As these droplets collide with the hailstone, they freeze upon contact, contributing to the hailstone's mass and creating a clear, glossy layer. This process is crucial as it allows for the accumulation of clear ice layers that are characteristic of a hailstone’s structure. The transparent appearance of these layers is a result of the rapid freezing of the larger droplets, which prevents the formation of air bubbles typically found in softer layers of hail.

Overall, the interaction between the hailstone and larger supercooled droplets is what determines the clarity and density of the layers as they are trapped in the ice. Other scenarios, such as altitude conditions, melting of ice layers, or exposure to sunlight during descent, do not accurately describe the specific formation mechanism behind the clear layers observed in hailstones.