Ash radar proves useful

Posted: Tuesday, March 31, 2009

Although the Mount Redoubt volcano color code was lowered from orange to yellow a few weeks ago, about the time scientists brought a volcanic ash radar dish to Kenai, it didn't take long for the new device to prove its worth.

All set up and ready to go, the radar went to work tracking ash from several Redoubt eruptions last week.

"We've been using it; it's working really well," said geophysicist David Schneider with the U.S. Geological Survey's Alaska Volcano Observatory in Anchorage, on Friday.

"It's been a nice tool," he said.

The radar, erected March 12 at Kenai Municipal Airport, measures the amount of ash emitted and the velocity of the erupting plume, giving geophysicists and other volcanologists a sound idea of where the ash cloud will head presenting a severe navigational hazard to aviators and a potential health hazard to beings on the ground.

The equipment consists of a 20-foot conex trailer converted into an office and an 8-foot radar dish on a pedestal inside a 14-foot diameter golf ball-shaped dome. The radar is set up near the airport operations building and is operated remotely from the AVO in Anchorage.

By measuring reflectives in the ash cloud, the Doppler radar can detect the velocity of things coming out of the volcano -- how fast the particles are moving -- so scientists can determine the amount of turbulence generated by an eruption, Schneider said earlier.

This is the first time this system has been deployed to look at a volcano. It was originally purchased in 2004 around the time of the most recent Mount St. Helens eruption and was shipped to Kenai from the Cascades Volcano Observatory in Vancouver, Wash.

"It's giving us more confidence in interpreting data," Schneider said. "To be able to see the particles over the mountain is helpful."

The National Weather Service has another weather radar -- NEXRAD -- based in Nikiski, and Schneider said readings from the ash radar can be compared with readings from that one.

Other equipment deployed by the vulcanologists includes pressure sensors that can detect pressure waves coming off the volcano's explosive events, Schneider said.

Some episodes also are seen seismically.

"The radar allows us to see the ash at altitude to determine the magnitude of the eruption," he said.

Studying the data from all sources allows AVO to provide as accurate a forecast product as possible.

"We try to be 100 percent all the time," Schneider said. "That's a pretty high standard."

During last week's eruptions, views of Mount Redoubt from the Kenai Peninsula were obscured by clouds much of the time, but Schneider said the volcanic ash radar can see through the clouds.

"When the ash cloud appears (on the radar) we can track it instantly," he said.

When asked why central Kenai Peninsula residents are not feeling or hearing anything from the recent eruptions, especially when links from the AVO Web site report such facts as the 1980 Mount St. Helens eruption being 500 times as strong as the nuclear bomb blast at Hiroshima, Schneider said comparing last week's eruptions to the Mount St. Helens eruption is like apples to oranges.

"These eruptions are orders of magnitude smaller than the May 18, 1980, Mount St. Helens eruption," he said. "If we had anything like that, you'd feel it."

Schneider again thanked the city of Kenai and the airport for allowing AVO to park the equipment there and provide electrical power.

"I can't say enough how helpful the airport has been to us," he said.

On Friday, airport Manager Mary Bondurant said the morning eruptions caused Grant Aviation and Era to once again suspend all flights from Kenai at least through late afternoon. The Anchorage airport was shut down from Saturday to Sunday afternoon and some flights were cancelled following ash fall events Monday.

"The best advice for travelers is still to call their airline first, before heading to the airport," Bondurant said.

Phil Hermanek can be reached at phillip.hermanek@peninsulaclarion.com.



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