Experts gather as volcanic dust settles

Following the eruption of Iceland’s Eyjafjallajoekull volcano that spewed huge amounts of ash and grounded numerous flights, more than 50 experts from around the world gathered at a workshop organized by ESA and EUMETSAT to discuss what has been learned and identify future opportunities for volcanic ash monitoring.

The experts included meteorologists, ground-based, air-borne and Earth-observation specialists and modelers. While scientists and researchers shared information about the unique eruption, monitoring capabilities, modeling and validation techniques, the Volcanic Ash Advisory Centres (VAAC) explained their role and expectations of the scientific community.

Fred Prata, Senior Scientist for Atmosphere and Climate Change at the Norwegian Institute for Air Research, said: “Satellite data are extremely important for volcanic eruptions because they can occur anywhere, anytime, so you need a measurement system that can see the entire globe all the time.

“One missing part of the story is the vertical profile, which lidars in space can provide. ESA will launch a couple of scientific lidar missions in the future, ADM-Aeolus and EarthCARE.”

The crucial role of infrared instruments was emphasized in several talks, highlighting and EUMETSAT’s upcoming Meteosat Third Generation satellites, being developed by ESA.

“Infrared instruments are absolutely vital because they do not require sunlight so we can see volcanic emissions day or night. They also use a band between 8 and 12 microns, which is key because the particles that cause aviation problems are micron-sized,” Prata said.

The presentations on ground-based observations and modeling showed very good consistency, also with satellite observations, and it was well recognized all data and information needs to be combined for the best result.

“There has been an unprecedented amount of ground data collected by the European community on this ash cloud, providing a great opportunity to learn more about data-collection processes,” said David Schneider, Research Geophysicist at the US Geological Survey, Alaska Volcano Observatory.

Philippe Husson, Aviation Weather Forecast Deputy and the Toulouse VAAC Manager for Meteo France, explained that observation requirements of volcanic ash evolved during the eruption to include numbers and expressed the impact this will have on VAACS.

“In the past, we used qualitative results to depict hazards, but now that we have been provided with ash threshold values we will probably be required to provide concentration maps with absolute numbers. As we must go from qualitative to quantitative information about ash concentrations and the distribution and size of particles, we need satellites to provide numbers,” he said.

Husson said the threshold figures are not definitive and are being reassessed by aviation authorities. Several factors will be considered, including trial results of real ash in real engines, engine types and rates of ingestion, as flying 10 minutes in high concentration could be equivalent to six hours in weak concentration.

“As the decision was taken quickly there was not a lot of input from scientists, but now there is time to consult them to find out what confidence we can have in the numbers,” he added.

A set of recommendations were outlined at the workshop. These will be documented in a joint ESA-EUMETSAT publication and made available online.

“I’m looking forward to the recommendations because the things being discussed here are essential for doing our job,” said Jean-Paul Malingreau, Head of Unit Work Programme and Strategy of the Joint Research Centre of the European Commission.

“We also need to assess whether the available and future satellite instruments are sufficient, so recommendations on this can be made available to policymakers to decide what to finance.”

Envisat captures renewed volcanic activity

New eruptions from Iceland's Eyjafjallajoekull volcano have produced a 1600 km-wide ash cloud over the Atlantic. The brownish plume, traveling east and then south, is clearly visible in stark contrast to white clouds framing this Envisat image from May 6, 2010. -  ESA
New eruptions from Iceland’s Eyjafjallajoekull volcano have produced a 1600 km-wide ash cloud over the Atlantic. The brownish plume, traveling east and then south, is clearly visible in stark contrast to white clouds framing this Envisat image from May 6, 2010. – ESA

New eruptions from Iceland’s Eyjafjallajoekull volcano have produced a 1600 km-wide ash cloud over the Atlantic. The brownish plume, travelling east and then south, is clearly visible in stark contrast to white clouds framing this Envisat image from 6 May.

The volcano began emitting steam and ash on 20 March, wreaking havoc on European aviation last month. Renewed activity earlier this week caused some flights to be suspended to and from Ireland, Northern Ireland and Scotland.

Authorities are monitoring the position and height of the ash cloud as well as the direction of prevailing Atlantic winds, which pose a problem when they blow south towards Ireland, located 1500 km southeast of the volcano.

Envisat’s Medium Resolution Imaging Spectrometer (MERIS) acquired this image. To see the latest MERIS images of the ash cloud, visit our MIRAVI website. MIRAVI, which is free and requires no registration, generates images from the raw data collected by MERIS and provides them online quickly after acquisition.

Envisat keeping an eye on the Eyjafjallajoekull volcano

The development of the ash plume from Iceland's Eyjafjallajoekull volcano between April 17-20, 2010, is tracked in this series of Envisat images. On April 17 and 19, the brown-colored ash plume is visible traveling in a roughly southeasterly direction over the Atlantic Ocean by the prevailing western air current. By April 20, much less ash is visible spewing from the volcano. -  ESA
The development of the ash plume from Iceland’s Eyjafjallajoekull volcano between April 17-20, 2010, is tracked in this series of Envisat images. On April 17 and 19, the brown-colored ash plume is visible traveling in a roughly southeasterly direction over the Atlantic Ocean by the prevailing western air current. By April 20, much less ash is visible spewing from the volcano. – ESA

The development of the ash plume from Iceland’s Eyjafjallajoekull volcano between 17-20 April is tracked in this series of Envisat images.

On 17 and 19 April, the brown-colored ash plume is visible traveling in a roughly southeasterly direction over the Atlantic Ocean by the prevailing western air current. By 20 April, much less ash is visible spewing from the volcano.


In the latest Envisat image acquired on 21 April at 13:36 CEST, even less ash is visible. Envisat has been monitoring the volcano since its recent eruptions began on 20 March. To see the latest Envisat satellite images over the area, simply visit our MIRAVI website. MIRAVI, which is free and requires no registration, generates images from the raw data collected by Envisat’s Medium Resolution Imaging Spectrometer (MERIS) instrument and provides them online quickly after acquisition.

MERIS images provide visual clues of what is happening over the volcano and, furthermore, can provide information on the height of the ash plume in the atmosphere.

Scientists from the Free University of Berlin have developed an experimental algorithm for the retrieval of cloud-top height from measurements taken by MERIS between 17 – 19 April from 14:00 and 15:00 CEST.

The algorithm, which is operationally applied within the MERIS ground segment, is normally used to determine the height of clouds to support weather and precipitation forecasts. A similar algorithm, based on the exploitation of the height dependent oxygen absorption (~ 0.76 microns), is now being experimentally applied to determine the height of the ash cloud spewing from the volcanic eruption.

“We normally apply this method to clouds to determine their heights over ground. We have now applied the same technique to the ash plume from Iceland’s volcano. The results show that the method works, and we can now provide the ‘starting height’ of the ash cloud and hope to be able to better predict the ash distribution in the future,” said Prof. Juergen Fischer from the Free University of Berlin, who provided the height maps.

On 17 April, the ash plume reached a top height of more than 5 km close to its origin over the southern coast of Iceland with its top height dropping below 2 km as it travelled. On 19 April, the massive, wide-spread ash plume resided in the lower atmosphere close to the volcano with top heights below 2 km.

According to Prof. Fischer, these preliminary results agree with the volcanic plume heights established by research flights and forecasts by volcanic plume models. A more detailed algorithm dedicated to the height of volcanic ash clouds is currently under development.

Other satellite datasets as well as ground measurements are being used to measure the evolution of the ash cloud. To learn more about these, visit the links on the right.