May 6, 2010

Better Satellite Technology Needed For Tracking Ash

The volcanic activity that has recently happened in Iceland is making the case for a new satellite tracking instruments.

As ash from Eyjafjallajokull grounded more flights this week, Dr. Fred Prata, a remote sensing expert, told an Earth sciences meeting in Vienna that current monitoring from space was good but not good enough.

"Of the present suite of satellite instruments, none were developed for the volcanic ash problem," he said.

"Therefore, they are sub-optimal for detecting and determining quantities of volcanic ash."

Prata has been speaking at the European Geosciences Union (EGU) conference in the Austrian capital.

He leads a group called Support to Aviation for Volcanic Ash Avoidance (SAVAA) and is a senior scientist at the Norwegian Institute for Air Research.

The team hopes to improve the way satellite data is collected for use in the dispersion models that help airlines and the FDA, along with other airline authorities, decide whether or not it is safe to fly planes.

BBC News reports that Prata said several space instruments currently in operation had been critical to the current monitoring efforts.

He used the Seviri instrument on Europe's Meteosat 8 and 9 spacecraft as an example.  Seviri returns images of the Earth every 15 minutes and has helped distinguish the volcanic ash from other clouds, determining its extent in two dimensions.

He said the lidar on the U.S. Calipso spacecraft brought a unique and extremely valuable capability.

"Because it's an active instrument that fires pulses of light down to the Earth and gets the backscatter radiation, it gives us height-resolved information. You can see the top of the cloud and its bottom, so that means you get the thickness," Prata told BBC News.

"Once we get the thickness, combining that with our two-dimensional picture of the mass loading we can get the concentration; and that's the number that the airlines would like to have."

At this time, the airlines are working only at a safe limit of two micrograms of ash per 35 cubic feet of air.

The third instrument noted by Prata is Iasi, which is an infrared sounding interferometer on Europe's polar orbiting Metop platform.  He said it sends back data on the presence of ash, sulphur dioxide (SO2), ice, and even the conversion of SO2 to sulphuric acid.

Metop and Calipso's downside is that they circle the Earth and do not have permanent vision over Iceland and the rest of Europe.  A version of Iasi is supposed to go on the next generation of Meteosats, however these platforms will not fly until 2018.

According to what Prata told BBC, there was a case now for fast-tracking the launch of this instrument.

"Everyone's looking at what the best solutions might be. Nobody wants to spend lots of money so fast-tracking an existing program would be a good solution," he said.

"Another possibility is to have a scanning lidar in space. Calypso looks straight down. If it's scanning, you'd get a lot more information."

EGU has also heard of the latest science being done in the volcanologist and seismologist department at Eyjafjoll.

Dr. Thor Thordarson of Edinburgh University, U.K. works with a team that collects large numbers of samples of the ash that fall on Iceland and beyond.

The team is trying to determine why the volcano ejected so much fine material in sizes that could be transported great distances.

This ash ranged in size from about 30-40 microns down to even the sub-micron scale.

Thordarson said it was clear that melt waters getting into the vent from the glacier on the volcano helped to contribute to the explosive fragmentation of rock.  However, he said that exact reasons are still unknown.

"Why this event disintegrated the magma so intensely, we don't know; and it's something we desperately want to find out," he told BBC News.

"If we get enough observations from a good number of sites then we can reconstruct the total grain-size distribution that was coming out of the vent. And when you have that information, then you can start looking at models to explain the fragmentation processes involved and why they were so intense."


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