Cosmic rays used to track and visualize tropical cyclones offer new perspectives

It’s hard to overlook the many stories in the news of severe storms in different parts of the world, often attributed to climate change. Weather forecasting and early warning systems have always been important, but with increased storm activity, this seems particularly important these days. A team of researchers led by Professor Hiroyuki Tanaka of Muographix at the University of Tokyo is offering the meteorological world a novel way to detect and study tropical cyclones, using a quirk of particle physics that constantly plays out over our heads.

“You’ve probably seen photos of cyclones taken from above showing swirling cloud vortices. But I doubt you’ve ever seen a cyclone from the side, maybe as computer graphics but never as actual captured sensor data,” Tanaka said. “What we are offering to the world is the ability to visualize large scale weather phenomena like hurricanes from a 3D perspective, including in real time. We’re doing this with a technique called muography, which you can think of like an X-ray, but for really seeing enormous things inside.”

Muography creates X-ray-like images of large objects, including volcanoes, pyramids, bodies of water, and now, for the first time, atmospheric weather systems. Special sensors called scintillators are assembled into a grid, similar to the pixels on your smartphone’s camera sensor. However, these scintillators do not see optical light, but rather particles called muons, which are created in the atmosphere when cosmic rays from outer space collide with atoms in the air. Muons are special because they can easily pass through matter without being scattered as much as other types of particles. But the small amount they deviate when passing through solid, liquid, or even gaseous matter can reveal details of their journey between the atmosphere and the sensors. By capturing a large number of muons traversing something, an image of it can be reconstructed.

“We successfully imaged the vertical profile of a cyclone, and this revealed density variations that are essential for understanding how cyclones work,” Tanaka said. “The images show cross-sections of the cyclone that swept through Kagoshima Prefecture in western Japan. I was surprised to see clearly that it had a warm, low-density core that contrasted dramatically with the cold, high-pressure exterior. There is absolutely no way to capture such data with traditional pressure sensors and photography.”

The detector used by the researchers has a 90-degree viewing angle, but Tanaka plans to combine similar sensors to create hemispherical, and therefore omnidirectional, observing stations that could be deployed along a coastline. These could potentially see hurricanes up to 300 kilometers away. Although satellites are already tracking these storms, the additional detail the muography offers could improve predictions of approaching storms.

“One of the next steps for us now will be to refine this technique to detect and visualize storms of different magnitudes,” Tanaka said. “This could mean better modeling and forecasting not only for larger storm systems, but also for more local weather conditions.”

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Materials provided by University of Tokyo. Note: Content can be edited for style and length.