MELISSA BLOCK, host:
The volcanic eruption in Iceland has triggered an intense effort by scientists to do two things. One, improve our ability to detect volcanic ash clouds. And two, forecast their movement in the atmosphere.
Eruptions are surprisingly common, and as NPR's Richard Harris reports, more precise information about them could ultimately make air travel safer.
RICHARD HARRIS: In the past decade or so, scientists around the world have actually gotten a lot better at detecting and tracking dangerous ash clouds.
Mike Pavolonis at the National Oceanic and Atmospheric Administration says it wasn't so long ago that forecasters just eyeballed weather satellite photographs to track plumes.
Dr. MIKE PAVOLONIS (National Oceanic and Atmospheric Administration): What we've gone to now more is turning that satellite data into quantitative information, on not just is the ash cloud there but how high is it? How much ash is there? What are its physical properties? Are they large particles, which fall out quicker than small particles?
HARRIS: The satellites now use infrared data, which means they can track clouds even in the dark. Satellites do a pretty good job mapping the size and shape of a cloud, and they can even determine its height within a mile or so. But seeing inside the clouds or below them is still a big challenge.
Pavolonis says airlines would ideally like to know how clean the air is below the bulk of the cloud, but that's tricky.
Dr. PAVOLONIS: Gravity is always working on it and so it's always falling. And so you may always have some ash falling out, so flying under may never be the best option anyhow.
HARRIS: Research flights occasionally go up and sample air to get a better sense of how much ash is up there, and to get a better idea of its composition.
Dr. PAVOLONIS: It doesn't happen very often because it is dangerous and it is expensive to repair the plane after you go through it.
HARRIS: There is another way to get at this information though. Dave Winker is in charge of NASA's CALIPSO satellite, which can measure particles in the atmosphere using a technology called LIDAR.
Dr. DAVE WINKER (Principal Investigator, CALIPSO, NASA): We send out pulses of laser light and that lets us measure the altitudes where aerosol and cloud layers are located.
HARRIS: Including volcanic ash.
Dr. WINDER: Including volcanic ash, yes.
HARRIS: LIDAR provides very detailed information, but it can only look straight down, so it can only see thin slices of an ash cloud, and only during the brief periods when the satellite is directly overhead. Still, the information can help flesh out the expansive satellite pictures.
Dr. WINDER: This volcano in Iceland has kind of emphasized that we have a lot of capabilities we could bring to bear on an issue like this. But everything needs to be organized a little better than it is currently.
HARRIS: Part of the challenge is pulling information together from weather satellites, volcano observatories on the ground and science instruments in orbit.
Ms. MARIANNE GUFFANTI (Volcanologist, US Geological Survey): So we need to get kind of Star-Treky, where you can, like, move your hands over the keyboard and see the little puff on the planet's surface. And we're moving in that direction but we're not there yet.
HARRIS: Marianne Guffanti is a volcano specialist at the US Geological Survey. She says we'd benefit from improvements across the board.
Ms. GUFFANTI: Volcanologists need to really focus on giving the best description possible of what the emission is like. And we have groups working on that, believe me. Then you have to have really good wind data, and around the world, that quality varies. And you have to have good forecasts of what the winds are because that's what's going to disperse the cloud.
HARRIS: Wind and forecasts are critical. After all, it's not enough to know where the cloud is at any given instant. If you've taken off from San Francisco bound for London, you want to know where the cloud will be many hours later. And winds blow in different directions at different altitudes, so forecasters need to know a plume's exact altitude in order to predict its movement.
Finally, Mike Pavolonis from NOAA says airlines would ultimately like to know what a safe concentration of ash is for a jet airliner. And we simply don't know.
Dr. PAVOLONIS: And so, right now the policy is zero tolerance. And that is the best policy, not knowing anything else. If we can determine if there is a safe concentration, that will help us more than anything, especially if its a concentration we can observe from satellite.
HARRIS: And they're working on all that right now.
Richard Harris, NPR News.