![\"NOAA\u2019s](\"https:\/\/media.nature.com\/lw800\/magazine-assets\/d41586-022-00127-1\/d41586-022-00127-1_20043630.gif\")
<\/p>\n The US National Oceanic and Atmospheric Administration\u2019s GOES-West satellite captured the explosive eruption of Hunga Tonga\u2013Hunga Ha\u02bbapai.<\/span>Credit: NOAA<\/span><\/p>\n<\/figcaption><\/div>\n<\/figure>\n Scientists are racing to understand a puzzling series of massive ripples in Earth\u2019s atmosphere triggered by the eruption of the Tongan volcano at the weekend. Satellite data shows that the event \u2014 which some fear might have devastated the Pacific-island nation \u2014 provoked an unusual pattern of atmospheric gravity waves. Previous volcanic eruptions have not produced such a signal, leaving experts stumped.<\/p>\n \u201cIt\u2019s really unique. We have never seen anything like this in the data before,\u201d says Lars Hoffmann, an atmospheric scientist at the J\u00fclich Supercomputing Centre in Germany.<\/p>\n The discovery was made in images collected by the Atmospheric Infrared Sounder (AIRS), mounted on Nasa\u2019s Aqua satellite, in the hours after the eruption of the Hunga Tonga\u2013Hunga Ha\u02bbapai volcano on 14 January.<\/p>\n They show dozens of concentric circles, each representing a fast-moving wave in the gases of the atmosphere, stretching for more than 16,000 kilometres. The waves reached from the ocean surface to the ionosphere, and researchers think that they probably passed around the globe several times.<\/p>\n \u201cThis instrument has been operating for something like 20 years now and we have never seen such nice concentric wave patterns,\u201d Hoffmann adds.<\/p>\n Atmospheric gravity waves occur when air molecules in the atmosphere are vertically, rather than horizontally, disturbed in the air column. This can happen as wind picks up speed as it rises over a mountaintop, or as a result of convection in local weather systems.<\/p>\n The up-and-down waves transfer energy and momentum through the atmosphere, and often show their effects in the way in which they cause high clouds to form in a series of ripples.<\/p>\n Images from the Atmospheric Infrared Sounder on NASA\u2019s Aqua satellite show dozens of concentric circles, which are fast-moving atmospheric waves.<\/span>Credit: Lars Hoffmann, J\u00fclich Supercomputing Centre. AIRS Level-1 data by NASA DES DISC<\/span><\/p>\n<\/figcaption><\/div>\n<\/figure>\n In theory, the rapid updraft of hot air and ash from an erupting volcano into the upper atmosphere could trigger gravity waves on a much larger scale. But nothing like this has been observed with previous eruptions analysed since the AIRS instrument was launched in May 2002.<\/p>\n \u201cThat\u2019s what\u2019s really puzzling us,\u201d says Corwin Wright, an atmospheric physicist at the University of Bath, UK. \u201cIt must have something to do with the physics of what\u2019s going on, but we don\u2019t know what yet.\u201d<\/p>\n He and his co-workers suspect that a \u201cgreat big, messy pile of hot gases\u201d in the upper atmosphere might be what kicks the waves off. The hot gas is \u201cgoing up high into the stratosphere and knocking the air around\u201d, he says. <\/p>\n The eruption of the Hunga Tonga-Hunga Ha\u02bbapai volcano was heard across the South Pacific, and even in parts of the United States. Ash has covered many regions of Tonga, but a loss of power, phone lines and Internet connectivity has made it difficult for aid agencies to assess the extent of injuries, fatalities and damage.<\/p>\n Wright, who was the first to spot the wave patterns in data supplied by Hoffmann, says that the images show what looks like a mixture of wave sizes and types.<\/p>\n The convection in the atmosphere seems to be \u201cvery complicated and bumpy, and it\u2019s generating a whole family of things at the same time\u201d, he says. \u201cThat is what we currently think is going on, but we\u2019ve only been looking at it for a few hours.\u201d<\/p>\n\u2018Nice concentric wave patterns\u2019<\/h2>\n
![\"Hunga-Tonga-Hunga](\"https:\/\/media.nature.com\/lw800\/magazine-assets\/d41586-022-00127-1\/d41586-022-00127-1_20043652.jpg\")
<\/p>\nEruption heard across the planet<\/h2>\n