When Super Typhoon Sinlaku tore across the North Pacific in April 2026, it did something that most tropical cyclones never do it sent visible ripples not just across the ocean surface but through the sky itself, all the way into the upper layers of Earth’s atmosphere. The storm reached “violent typhoon” status, the highest category used by the Japan Meteorological Agency and roughly equivalent to a Category 5 hurricane on the Saffir-Simpson scale, making it one of only a handful of storms in the region to reach such intensity so early in the year. As Sinlaku rapidly strengthened, satellites captured atmospheric gravity waves spreading outward from the storm in concentric ring patterns resembling ripples expanding across a pond after a stone is dropped in.The images, captured by instruments aboard the NOAA-20 and NASA‘s Aqua satellites, offered scientists a rare, detailed look at how the most violent weather on Earth can disturb the atmosphere all the way to the edge of space.
What are atmospheric gravity waves and why does Super Typhoon Sinlaku matter
Atmospheric gravity waves are not the same as gravitational waves in the physics sense. They are oscillations in the atmosphere caused when air is displaced vertically and then pushed back by buoyancy, the same restoring force that makes a wave on water. When something powerful enough disturbs the lower atmosphere, those oscillations can travel upward through layer after layer of air, carrying energy from the storm far above the weather system itself.Tropical cyclones generate these waves through the intense release of latent heat near their eyewalls. This drives towering convective clouds known as hot towers that can punch through the troposphere and inject energy directly into the stratosphere. A peer-reviewed study in Geophysical Research Letters by Hoffmann, Wu, and Alexander, drawing on 13.5 years of satellite data from the Atmospheric Infrared Sounder, found statistical evidence that stratospheric gravity wave activity is closely associated with the intensification of tropical cyclones and that the intensity of those waves can serve as a proxy for how rapidly a storm is strengthening.Sinlaku fit that pattern precisely. In the 24 hours before the satellite image was captured, the storm had strengthened from a Category 2 system to the equivalent of a Category 5, a dramatic, rapid intensification event that coincided exactly with the wave signatures detected above it.
How NASA and NOAA satellites captured the mesospheric airglow rings
The gravity waves Sinlaku generated became visible through a phenomenon called airglow a faint luminescence produced in the mesosphere, roughly 80 to 100 kilometres above Earth’s surface, when atoms and molecules that absorbed solar energy during the day release that energy as light at night. The pattern is too faint to be seen by the naked eye under ordinary circumstances, but the VIIRS (Visible Infrared Imaging Radiometer Suite) day-night band aboard the NOAA-20 satellite is sensitive enough to detect it.The image captured on 12 April 2026 showed near-complete concentric rings of gravitational waves spreading outward from the storm’s centre a pattern that surprised researchers. According to Joan Alexander, senior research at NorthWest Research Associates, the waves were propagating radially and upward in a cone-like shape. What made the observation unusual was that the rings remained nearly intact at mesospheric altitudes. Normally, winds in the upper atmosphere disperse or weaken gravity waves before they can travel that high. The relatively weak stratospheric winds at Sinlaku’s latitude during April 2026 appear to have created an unusually clear passage for the waves to reach the mesosphere.The imaging conditions also played a role. The Moon was only about 25 per cent illuminated on the night in question, keeping reflected moonlight from the cloud tops below at low enough levels that the much fainter airglow signal could be resolved without interference.
Stratospheric signatures confirmed by NASA’s Aqua satellite
The gravity wave signal was not limited to the mesosphere. NASA’s Aqua satellite, using the AIRS (Atmospheric Infrared Sounder) instrument, detected thermal emissions from gravity waves in the stratosphere on 13 April, and the same rippling structures appeared again in observations on 14 April, confirming that the storm’s influence on the upper atmosphere persisted for multiple days after the initial detection.The original NASA Earth Observatory report on Sinlaku noted that this kind of multi-level atmospheric observation capturing the same gravity wave event simultaneously in both the stratosphere via AIRS and the mesosphere via VIIRS airglow is rare and scientifically valuable because it allows researchers to trace how energy moves vertically through the atmosphere from a single storm source.A 22026 study in the Journal of Geophysical Research: Atmospheres tracking gravity waves from tropical cyclones using multiple low-light satellite systems found that multi-satellite joint observation can resolve the continuous evolution of cyclone-generated gravity waves in ways that single-instrument data cannot, reinforcing the value of the coordinated NOAA-20 and Aqua observations made during Sinlaku.
Why gravity waves could transform tropical cyclone forecasting
The practical implications of Sinlaku’s gravity wave signature extend well beyond the visual drama of airglow rings. One of the most persistent challenges in tropical cyclone forecasting is monitoring storm intensity over the open ocean, where conventional weather station data is sparse or absent. Rapid intensification events in which a storm strengthens dramatically within 24 hours are particularly difficult to predict and particularly dangerous because they can catch coastal populations off guard.Alexander noted that gravity waves could eventually allow researchers to track whether a storm is intensifying even from remote sensing data alone, by treating the wave signature as an indicator of convective activity near the eyewall. She and her colleagues have suggested that future geostationary satellites equipped with suitable infrared instruments could provide continuous gravity wave monitoring, giving forecasters a real-time window into storm development over the most isolated parts of the Pacific and Indian oceans.
