There is a hailstone behind this colorfully patterned image: its unique internal crystal structure has been made visible using the latest technology. It shows that this hailstone has gone through four stages of growth.
Hailstones arise from raindrops that are transported by updrafts in thunderclouds to great heights of over 12,000 meters and freeze there. If they fall down, they continue to grow – depending on the temperature and humidity – by freezing new layers of crystals. This process can be repeated several times.
The more violent a thunderstorm, the higher the probability that large hailstones will end up on the earth. This was particularly severe, for example, during a devastating storm in 2013 in southern Germany. At that time, damage worth billions was caused in Baden-Württemberg, for example.
An international team of researchers led by Maurine Montagnat from the French University of Grenoble collected a few grains in Tübingen and in southern France in order to investigate their internal, so far hardly explored crystal structure. To do this, the researchers analyzed the grains using the most modern methods and made their texture visible with an “Automated Ice Texture Analyzer”.
The result: The fascinating patterns of the hailstone structures could be seen in different colors in the resulting images – as with the grain in our photo. The inner structure of each hailstone is individual, as the scientists discovered. This shows the stage of growth in which the grain is. “In this way we can better understand how hailstones are formed and perhaps better predict the damage they can cause,” concludes Paul Bons from the University of Tübingen.