When Super Typhoon Sinlaku crossed the North Pacific Ocean in April 2026, it did something that most tropical cyclones never do, it sent visible waves not only over the ocean surface, but through the sky, into the upper layers of the Earth’s atmosphere. The typhoon reached “violent typhoon” status, the highest category used by the Japan Meteorological Agency and roughly equivalent to a Category 5 typhoon on the Saffir–Simpson scale, making it one of a handful of typhoons to reach such intensity so early in the year in the region. As Sinalaku rapidly strengthened, satellites captured atmospheric gravity waves propagating outward from the storm in concentric ring patterns that resembled the ripples that spread across a pond after a stone is dropped.The images, captured by instruments aboard NOAA-20 and NASA’s Aqua satellites, offered scientists a rare, detailed look at how the most violent weather on Earth can perturb the atmosphere to the edge of space.
What are atmospheric gravity waves and why Super Typhoon Sinlaku matters
Atmospheric gravity waves are not the same as gravity waves in the physics sense. They are oscillations in the atmosphere that occur when air is displaced vertically and then pushed back by buoyancy, the same restoring force that creates waves on water. When something powerful 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.Tropical cyclones generate these waves through the intense emission of latent heat near their eyewalls. This drives huge 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 Hoffman, Wu, and Alexander, based on 13.5 years of satellite data from an atmospheric infrared sounder, found statistical evidence that stratospheric gravity wave activity is closely linked with the intensity of tropical cyclones and that the intensity of those waves can serve as a proxy for how fast a storm is strengthening.Sinlaku fits that pattern perfectly. 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 matched exactly with the wave signatures detected above it.
How NASA and NOAA satellites captured mesospheric airglow rings
The gravity waves generated by Sinalaku became visible through a phenomenon called airglow, a faint glow produced in the mesosphere about 80 to 100 kilometers above Earth’s surface when atoms and molecules that absorb solar energy during the day release that energy as light at night. This pattern is too faint to be seen with the naked eye under normal conditions, but the VIIRS (Visible Infrared Imaging Radiometer Suite) day-night band on the NOAA-20 satellite is sensitive enough to detect it.The image, taken on April 12, 2026, showed almost perfect concentric rings of gravity waves extending outward from the storm’s center, which surprised researchers. According to Joan Alexander, senior research fellow 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 almost intact at mesospheric altitudes. Normally, winds in the upper atmosphere scatter or weaken gravity waves before they reach that high. It appears that relatively weak stratospheric winds at the latitude of Sinalaku during April 2026 have created an unusually clear path for waves to reach the mesosphere.Imaging conditions also played a role. That night the moon was only 25 percent illuminated, keeping moonlight reflected from cloud tops at low enough levels that very little airglow signal could be resolved without interference.
Stratospheric signatures confirmed by NASA’s Aqua satellite
The gravitational wave signal was not limited to the mesosphere. NASA’s Aqua satellite, using the AIRS (Atmospheric Infrared Sounder) instrument, detected thermal emission from gravity waves in the stratosphere on April 13, and the same wavy structures appeared again in observations on April 14, confirming that the storm’s effects on the upper atmosphere persisted for several days after initial detection.NASA Earth Observatory’s original report on Sinalaku states that this type of multi-scale atmospheric observation capturing the same gravity wave event in both the stratosphere via AIRS and the mesosphere via VIIRS Airglow is rare and scientifically valuable because it allows researchers to explore how energy moves vertically through the atmosphere from a single storm source.A 2026 study in the Journal of Geophysical Research that tracked gravity waves from tropical cyclones in the atmosphere using multiple low-light satellite systems found that multi-satellite joint observations could resolve the continuous evolution of cyclone-generated gravity waves in a way that single-instrument data could not, reinforcing the value of the coordinated NOAA-20 and Aqua observations made during Sinalaku.
Why might gravity waves change tropical cyclone forecasts?
The practical implications of Sinalaku’s gravitational wave signature extend far 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 traditional 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 are particularly dangerous because they can endanger coastal populations.Alexander said 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. He and his 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 hurricane development in the most isolated parts of the Pacific and Indian Oceans.