Waves propelled through the air by distant thunderstorms produced glowing bands in the sky during a 2016 “bright night” event, when the atmosphere was illuminated by a green glow visible to the naked eye. The ripples disturbed an atmospheric layer nearly 90 kilometers (56 miles) above El Leoncito Astronomical Complex in Argentina, at an altitude where reactions between oxygen molecules produce the brilliant airglow of a bright night; solar energy hitting Earth’s magnetic field excites the same molecules to create aurorae. The new observations suggest that gravity waves from storms have bigger impacts on global and space weather than expected.
The energy and momentum transported by these thunderstorms were much larger than expected, said Steve Smith, a space physicist at Boston University and lead author of a new study presenting these findings, which was published in AGU’s Journal of Geophysical Research: Atmospheres.
Gravity waves occur in a variety of ways, from the wind producing waves on an ocean surface to storms producing atmospheric waves that ripple through the air. Atmospheric gravity waves can affect weather by reorienting wind and producing air turbulence.
Although there have been previous observations of gravity waves affecting airglow at such high altitudes, the newly described event was remarkable for its brightness and persistence. By combining satellite imagery and data captured by an all-sky imager, Smith and colleagues determined that the gravity wave ripples originated from a thunderstorm complex several hundred kilometers away. These measurements also enabled the calculation of the wave’s momentum flux, or how much “push” a wave has, which was several times larger than previously observed.
“That’s going to have an impact on how we model the effect of gravity waves,” Smith said, for both global wind circulation and radio wave propagation through the ionosphere. (Journal of Geophysical Research: Atmospheres, https://doi.org/10.1029/2020JD033381, 2020)
—Jack Lee (@jackjlee), Science Writer