Iceland Volcano Ash Plume Electrified

Shortly after the volcano's active eruption phase began in mid-April, the U.K. Met Office contacted Joseph Ulanowski from the Science and Technology Research Institute at the University of Hertfordshire, who last year, together with Giles Harrison from the Department of Meteorology at the University of Reading, had developed a specialized weather balloon that could assess the location and composition of the volcanic ash clouds.

Their balloons, originally designed and used to study the properties of desert dust clouds, are able to assess not only the size of particles suspended in the atmosphere — such as volcanic ash — but also the electric charge present, which can be important to know when evaluating a plume's threat to aircraft.

"Detailed volcanic plume properties, such as the particle size, concentration and charge found by our weather balloon are important in predicting the impact on aircraft," Harrison said.

Lightning seen in the plume from Eyjafjallajökull is also attributed to electrical charges generated in the plume from particles rubbing together.

Measurements made last year with the balloons in Kuwait and off the west coast of Africa showed clearly that desert dust could become strongly electrified aloft.

When particles in the atmosphere become charged, it can change how effectively they grow in size or are washed out by rain.

When Eyjafjallajökull erupted, a team of scientists was quickly assembled and travelled to a site near Stranraer in Scotland where a balloon was launched. The balloon detected a layer of volcanic ash about 2.5 miles (4 kilometers) above the ground, about 1,970 feet (600 meters) thick, with very abrupt upper and lower edges.

The charge detected by the balloon was deep inside the plume, not along the edges. This is contradictory to what would be expected from the normal weather-induced charging of cloud layers.

From their measurements, the researchers conclude that neither energy from the volcanic source — more than 745 miles (1,200 km) away — nor weather conditions could have been responsible for the position of the charge found by the balloon.

The team's observations are detailed in the May 27 issue of the journal Environmental Research Letters.

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