Satellite data shows that the event — which some fear might have devastated the Pacific-island nation — provoked an unusual pattern of atmospheric gravity waves. Previous volcanic eruptions have not produced such a signal, leaving experts stumped.
“It’s really unique. We have never seen anything like this in the data before,” says Lars Hoffmann, an atmospheric scientist at the Jülich Supercomputing Centre in Germany.
The discovery was made in images collected by the Atmospheric Infrared Sounder (AIRS), mounted on Nasa’s Aqua satellite, in the hours after the eruption of the Hunga Tonga-Hunga Haʻapai volcano on 14 January.
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.
“This instrument has been operating for something like 20 years now and we have never seen such nice concentric wave patterns,” Hoffmann adds.
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.
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.
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.
“That’s what’s really puzzling us,” says Corwin Wright, an atmospheric physicist at the University of Bath, UK. “It must have something to do with the physics of what’s going on, but we don’t know what yet.”
He and his co-workers suspect that a “great big, messy pile of hot gases” in the upper atmosphere might be what kicks the waves off. The hot gas is “going up high into the stratosphere and knocking the air around,” he says.
Tsunami waves up to 10 m (33 feet) high hit Ha'apai Islands, Tonga
The Tongan Navy has reported major damage in the Ha’apai Islands after the major eruption at Hunga Tonga-Hunga Ha'apai volcano on January 15, 2022.
Waves that hit Ha'apai Islands were estimated to be 5 - 10 meters (16 - 33 feet) in height, reaching 500 meters (1 640 feet) inland. Ha'apai is a group of islands, islets, reefs, and shoals in the central part of Tonga. Their combined population is 5 419.
Electricity and local mobile phone networks have been restored on the main island of Tongatapu but the power connection is not yet stable, the Council for International Development (CID) reports.1
International and inter-island calls are still not possible due to the damage to the undersea cable. Tonga Cable and other entities are actively working to repair the damage, CID said, adding that there is still no timeframe available for when communications will be restored.
Tonga’s main airport Fua’amotu International Airport is undamaged but heavy ashfall is being cleared and inhibits the airport from being fully operational. The Director of Civil aviation in Tonga advises that the airport runway clearance will take days to complete as this is being conducted manually. The earliest possible clearance is Wednesday, January 19.
Western Tongatapu suffered significant damage and the government has evacuated people from that part of the island.
1 comment:
Tantamount to an atmospheric nuclear explosion.
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