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Sound and Fury, Lightning and Ash

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Created on Friday, 17 December 2010 16:29
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Lightning Offers Early Warnings Of Volcanic Ash
by Emilie Lorditch l Inside Science News Service
We all know that lightning comes before thunder. But it also comes during a volcanic eruption -- and two teams of scientists are building early-warning systems that use lightning to tell pilots when and where ash clouds may be hovering in the sky.

Pilots receive first successful warning of volcanic activity based on lightning
photo: Harald Edens

Volcanic lightning experts gathered to discuss the state-of-the-art in spotting volcanic lightning and to present the first successful eruption warnings based on these detections during a meeting of the American Geophysical Union in San Francisco this week.

When Stephen McNutt, a volcano seismologist at the University of Alaska's Fairbanks' Geophysical Institute teamed up with New Mexico Tech physicist and electrical engineer Ronald Thomas in Sorroco, their collaboration sparked new insights into volcanic lightning.

Using Lightning Map Array, the LMA stations placed on or near a volcano to measure an eruption's electrical activity, Thomas and his team of atmospheric physicists examined the data from the St. Augustine volcanic eruption in January of 2006.
 
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They discovered a new kind of lightning called explosive phase lightning, which they spotted again and recorded in 3-D during the Alaska's Mount Redoubt eruption in March of 2009 and Iceland's Eyjafjallajökull eruption in April of 2010. "Looking at the volcanic lighting in 3-D, we can see the pockets of positive and negative charges within the ash plume," said Thomas.  "Plus, we can also see how high the lightning extends vertically."


"The explosive phase lightning happens when the volcano is erupting," said Sonja A. Behnke, a Ph.D. candidate in atmospheric physics at New Mexico Tech. "This lighting looks like little small sparks [a few hundred meters long], but it indicates that an eruption is happening; it's a unique signal we can use to detect and confirm volcanic activity."

This means that LMA stations on remote volcanoes could confirm a volcanic eruption and ash cloud before the ash cloud is seen in the sky or by satellites.  

While LMA stations take onsite measurements of eruption activity, the World Wide Lightning Location Network, or WWLLN,  uses 40 sensors in cities such as Osaka,  Budapest, and Seattle, to monitor over 1,500 volcanoes to look for ash cloud lightning. The WWLLN is updated every minute.  

Because the WWLLN monitors such a wide area, the scientists first need to identify whether the lighting is from a volcanic eruption or from a thunderstorm.

"A lightning strike is the first alarm that tells us to take a closer look at the data," said Robert Holzworth, an earth and space scientist at the University of Washington in Seattle. "If we see a lot of strikes close to the volcano, that lightning is more likely coming from a volcanic eruption."

Once lightning is identified as coming from a volcanic eruption, the WWLLN sends out automatic alerts to the United States Geological Survey and the University of Washington, usually before the volcanic ash cloud is even visible.  The WWLLN had their first success in giving advanced warning of an explosive volcanic eruption during Russia's Shiveluch volcano eruption in October 2010. The WWLLN system sent automatic alert e-mails about one hour before the ash cloud was visible to weather satellites.

"The problem is that a volcanic eruption can eject volcanic ash to aircraft cruising altitude in about five minutes," said John Ewert, a volcanologist with the USGS Cascade Volcano Observatory in Vancouver.  "So we want to distribute this information as quickly as possible."

The WWLLN automatic alert system has been up and running for about two and half months now, the group of scientists plan to keep fine-tuning the system in order to find more ways to provide early warnings for volcanic ash hazards.