When Hurricane Helene hit the southeastern United States last month, it caused widespread power outages and devastating flooding on the ground. But as revealed in new NOAA data, the superstorm also generated shockwaves in Earth’s atmosphere.
The Atmospheric Waves Experiment (or AWE) aboard the International Space Station captured images of Hurricane Helene’s gravity waves, showcasing both the instrument’s capabilities and the hurricane’s intensity.
Gravity waves are ripples in the air caused many of Earth’s natural—and often violent—phenomena. Everything from thunderstorms and tornadoes to tsunamis and volcanoes can generate atmospheric waves, and studying the atmosphere’s gravity waves can help scientists determine terrestrial weather’s effects on space weather, which can disrupt instruments in low-Earth orbit and communications beyond.
Hurricane Helene offered an ideal opportunity for interrogating AWE’s ability to spot atmospheric gravity waves. The hurricane smashed into Florida’s Big Bend in late September as a Category 4 storm with winds exceeding 140 miles per hour (225 kilometers per hour). Helene wiped out power for millions of people across the southeastern United States and devastated inland areas with flooding, especially in parts of Tennessee and western North Carolina. Satellite imagery released in the immediate aftermath of the storm revealed the communities that lost power and the storm’s intense lightning from the air.
The newly released data shows that the hurricane generated gravity waves high in the atmosphere, far above the storm clouds. To be perfectly clear, gravity waves are not the same as gravitational waves, perturbations in spacetime that are measured by interferometers and pulsar timing arrays. Gravitational waves do pass through Earth (and everything on it, including you and me), but they are far subtler than ripples in the atmosphere and are generated by sources much, much larger than hurricanes.
The waves are artificially colored in the data—visualized below—red, yellow, and green, to reflect differences in radiance of infrared wavelengths produced by airglow in Earth’s mesosphere, the layer of the planet’s atmosphere that stretches 31 to 53 miles (50 to 85 kms) above its surface. The AWE views of gravity waves are some of the first publicly released images from the instrument, which launched in November last year and is mounted on the International Space Station. The images confirm AWE’s ability to study how hurricanes affect Earth’s atmosphere.
“Like rings of water spreading from a drop in a pond, circular waves from Helene are seen billowing westward from Florida’s northwest coast,” said Ludger Scherliess, AWE’s principal investigator at Utah State University, in a NASA release.
AWE data showing Hurricane Helene’s atmospheric waves above the southeastern U.S. Image: Utah State UniversityNatural disasters produce devastating effects, many of which are plain to see. But they also produce some effects which fly under the radar. For example, the huge Hunga Tonga-Hunga Ha’apai eruption of 2022 produced a kind of air pressure wave that was theorized in 1937 but not proven to exist until two years ago. Just last week, a team of researchers found that the eruption was preceded by a previously undetected seismic wave which was detected at stations hundreds of miles away, a reminder that emergency preparedness systems can still be more ready for these cataclysmic events.
Even ordinary thunderstorms—that is, not just the extreme weather associated with hurricanes and volcanic eruptions—harbor secrets. Last month, a team of scientists found that thunderstorms in the tropics were emitting a newly identified kind of gamma radiation, establishing a potential link between glows and flashes associated with the storms.
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