By Stephen Beech via SWNS
Hailstones could help forecast future storms, suggests a new study.
Spanish scientists used state-of-the-art CT scanning technology to learn more about the hidden anatomy of giant hailstones.
They believe the insights they gained can provide new information that may help mitigate damage as more giant hail storms are expected in the future.
The research team explained that the stones are formed during thunderstorms when raindrops are propelled into very cold parts of a cloud, where they freeze.
Once the particles are heavy enough, gravity pulls them back towards Earth.
As they plummet, they ‘grow’ into hailstones, which can cause significant damage to homes and cars and can cause injury to people and animals.
Scientists have been studying how hailstones grow since the 1960s, but doing so meant breaking them in the process.
To better understand the anatomy and growth of hailstones, the Spanish team used computed tomography (CT) scans to examine giant hailstones that hit the north-east of the Iberian Peninsula during an exceptionally strong thunderstorm in the summer of 2022.
Study lead author Dr. Carme Farnell Barqué, of the Meteorological Service of Catalonia, said: “We show that the CT scanning technique enables the observation of the internal structure of the hailstones without breaking the samples.
“It is the first time that we have a direct observation of the entire internal structure of hailstones, which can provide clues to improve hail formation forecasting.”
After the storm hit Catalonia on August 30, 2022, the research team tracked the storm path with the help of local witnesses and collected hailstones from observers who saved them in their freezers.
Some of the stones measured up to 12 cm (4.7 inches) in diameter.
Back in the lab, three randomly selected hailstones were scanned, using equipment from a dental clinic.
Study senior author Professor Xavier Úbeda, of the University of Barcelona, said: “We wanted to use a technique that would provide more information regarding the internal layers of the hailstones, but without breaking the samples.
“We didn’t expect to obtain as clear imagery as we got.”
By way of CT scanning, a technology that uses a rotating X-ray machine to create 3D images, the researchers learned much about the external and internal structure of hailstones.
A total of 512 images – known as ‘slices’ – of each hailstone showed the location of the core and different layers.
Study co-author Professor Javier Martin-Vide, also of the University of Barcelona, said: “CT scans provide information related to the density, which allows us to identify the different stones’ layers associated with the growth stages of the hailstorm.
“They also help us understand the processes that contributed to its formation.”
The research team found that axes and planes can be irregular on the inside, even when from the outside, stones look like near-perfect spheres.
They also discovered that the stones’ cores were not located in the centers, especially in spherical stones.
Co-author Dr. Tomeu Rigo Ribas,of the Meteorologic Service of Catalonia, said: “We show that the embryo can be located far from the center.
“This fact implies that the stones can grow heterogeneously in three directions.”
The findings, published in the journal Frontiers in Environmental Science, also showed that different layers had different density levels, and two of the samples had thicker parts, which indicates that was the side of the stone facing downwards as it fell.
The insights gained regarding the insides of hailstones overturned previous assumptions.
Dr Farnell Barqué said: “Until now, it was believed that very large hailstones could only have irregular shapes.
“However, we observed that the external and internal shapes can differ.
“In one case, we have demonstrated that the sample exhibited heterogeneous growth but had a regular external shape.
“Conversely, stones with irregular external shapes showed homogeneous growth.”
She added that making CT scans is expensive, and some of the resulting images show anomalies the research team has yet to understand.
