With Europe's airport staffers scrambling to send tens of thousands of flights into the air to make up for a week's worth of halted traffic and stranded travelers thanks to Iceland's Eyjafjallajökull volcano, researchers at the U.K.'s University of Reading are taking the first direct measurements of the ash plume parked over Scotland.

The researchers are using a newly developed weather balloon, a miniature laser system and a measurement technique originally developed to study the properties of Saharan dust clouds for climate models to gather detailed information on the ash plume's position, extent and structure.

Measurements taken thus far have shown a 500-meter-thick layer of volcanic dust at 4,000 kilometers overhead, with most particles about one millionth of a meter (one micron) in diameter, according to Giles Harrison, a professor of atmospheric physics in Reading's Meteorology Department, and fellow researcher Keri Nicoll. Another plume from Eyjafjallajökull is due to sweep across the U.K. in the next few days.

Reading researchers, of course, aren't the only ones with high-tech ash-plume observations under way. Scientists at Denmark's Risø DTU National Laboratory for Sustainable Energy are using LiDAR (lIght detection and ranging) technology to follow the progress of the ash cloud from Eyjafjallajökull across their country. LiDAR systems, which can shoot a laser beam up into the air to strike particles and then reflect back, are expected to provide more details about the actual height and development of the ash cloud as well as qualitative measurements of the volcanic ash concentrations in the cloud.

Officials have broken the affected areas of airspace around Europe into three tiers: normal flight zones where ash no longer poses a risk, no-fly zones where ash remains in high concentrations, and intermediate, potentially hazardous zones where flights can proceed with caution, subject to route restrictions and other limitations.

To draw those boundaries, flight controllers were forced to determine what constitutes an acceptable level of volcanic ash, despite a lack of data to inform their assessment. With the help of the experiments under way, hopefully future assessments will be based on stronger knowledge of the shape and activity of volcanic ash plumes.

A 2006 view of Eyjafjallajökull from a recreation area on the Sólheimajökull, a glacier on the nearby Katla Volcano, courtesy of Advanstra via Wikimedia Commons