Conquering the Mysteries of Hail: Hailstone-Shaped Sensors to Study Storms

Inspired by the 1996 blockbuster movie Twister, new hailstone-shaped sensors can now travel within the eye of a storm to shed light on the mysteries of hail growth.

Powerful storms known as severe convective storms cost $35 billion US, or nearly 70% of all insured natural disaster losses worldwide in the first half of 2023, according to global insurance company Swiss Re. Approximately 60 to 80% of insured losses from these powerful storms are caused by hail, according to the National Association of Insurance Commissioners.

The new sensors, called "hailsondes," are designed to fly freely within storms and behave like real hailstones.

However, among all types of precipitation related to these violent storms, hail is the least understood. This is because much remains unknown about how these ice balls move and grow in different parts of each storm.

In the movie Twister, researchers sought to deploy weather sensors into the heart of a tornado to learn more about these disasters. In real life, scientists have deployed a wide variety of sensors to analyze storms, including drones and high-speed cameras, on the ground or up to a few hundred meters in height, explains Joshua Soderholm, a storm scientist at the Australian Bureau of Meteorology in Melbourne, who helped develop the new sensor.

However, collecting data within storm clouds "becomes much more difficult due to incredible winds, large hail, and extreme icing conditions," says Soderholm. Two previous attempts to deploy sensors within storms included an armored T-28 aircraft now retired from the South Dakota School of Mines and Technology and balloon-mounted sensors called "swarmsondes," he says.

In contrast, the new sensors, nicknamed "hailsondes," are designed to fly freely within storms and behave like real hailstones. Each probe is shaped like a hailstone - a 24-gram sphere 6.5 centimeters wide, a modified version of the Windsond S1 from Sparv Embedded in Linköping, Sweden. Although they are launched via balloons, the hailsondes are released once the updrafts within storms are strong enough to keep the sensors airborne.

The hailsondes don't measure actual hailstone trajectories or conditions. Instead, they behave much like real hailstones within a storm, "gathering information about how hail grows, is moved by winds and falls," explains Soderholm. "The careful design of the hailsonde shell and optimization of sensors has allowed not only survival in these conditions but also collection of valuable measurements."

Soderholm got the idea for the hailsonde because he says he loves studying how new technologies could benefit his storm science research field, "particularly for measuring processes that people previously thought impossible due to technological barriers," he notes. This includes 3D scanning of hailstones to illuminate their evolution within storms and their appearance on radar; using computer vision to analyze hailstone cross-sections to deduce their growth; and using drones to examine hailstone shapes in flight.

"The hailsonde idea started after seeing new work on hailstone trajectory simulation from my colleague Matt Kumjian," explains Soderholm. "I really wanted to know if the simulations were realistic, but we had no idea, so I started thinking about a way to collect measurements."

"I think my research highlights the incredible potential of observations to fill data gaps we previously thought impossible... Modern tools like 3D printing, Python, IoT, single-board computers enable rapid prototyping without needing a PhD in engineering" concludes Soderholm.

The fact that scientists know the exact size and shape of a hailsonde "is very useful for simulating its behavior after a hail event," explains Soderholm. However, "hail can develop in many different regions of the parent storm, under different conditions and is moved by different winds, often resulting in a wide variety of sizes and shapes seen on the ground" he specifies. Many hailsonde launches in different storm regions are therefore needed before scientists can draw more robust conclusions about how hail forms and evolves, he says.

Researchers now plan to expand their work from two probes in a single storm region to multiple probes in different storm regions, notes Soderholm. They also want to prioritize storms with the best weather radar coverage, "as this will allow us to test new ideas for better simulating hail trajectories," he notes. This could be done through Canada's Northern Hail project, Germany's LIFT project, and the proposed ICECHIP project in the United States, he adds.

"Once we have a large sample of hail trajectories, we expect to develop new insights about hail growth relative to weather radar observations, which will enable the development of new, more accurate tools for hail nowcasting and alert provision" concludes Soderholm.

This article comes from the source: Hailsondes Launch Into Thunderstorms to Sound Them Out Hollywood inspires new tech to probe hail, cloudbursts, and devastation
author: CHARLES Q. CHOI