Dispersal of volcanic ash after the eruption of Eyjafjallajökull

Researchers develop a model for the prediction of the dispersal of volcanic ash.

The eruption of the Eyjafjallajökull volcano on Iceland in April 2010 caused a ban of flights above Europe for several days and produced considerable economic damage. The Forschungszentrum Jülich (Jülich Research Centre) expanded a the chemistry transport model EURAD-IM (EURopean Air pollution Dispersion – Inverse Model) transport model so as to be able to promptly cal­culate predictions about the dispersal of ash in the event of a further volcano eruption within Europe.

Due to the series of eruptions of Eyjafjallajökull from April to May 2010, volcanic ash transported by northwesterly winds across the North Sea and northwestern Europe within a few days.  Later on, areas as far as Central Russia and Spain and Por­tugal.

The volcanic ash finally enforced  the closure of large areas of European airspace for air traffic for safety reasons for several days. More than 100,000 flights were cancelled between April 15 and 21. The resulting total economic damage was 2.5 billion euro (Oxford-Economics, 2010).

To assess the risk for air traffic, sophisticated aerosol dispersion models together with aerosol obser­vations and measurements are required and evaluated. When the Icelandic volcano erupted, predic­tions of the official NAME (Numerical Atmospheric-dispersion Modeling Environment) dispersion model were used by the London VAAC (Volcanic Ash Advisory Center) as a basis for decisions on flying bans applying a zero tolerance criterium. Further simulations were provided by models from other VAACs and various aerosol dispersion models.

Prompt predictions of dispersion of ash clouds possible

During the Eyjafjallajökull eruption, the EURAD-IM chemical and aerosol transport model (Elbern et al., 2007) was extended to include a volcano aero­sol module at the Rheinisches Institut für Umweltforschung (Rhenish Institute for Environmental Research - RIU) at the University of Cologne. With this model, predictions of ash dispersion over Europe have been calculated (see animation ). The film shows the ash distribution over Europe calculated with this model at a height of three kilometres for the first (and in some cases second) eruption phase from April 14 to 18, 2010. A comparison with satellite and ceilometer data shows that the horizontal dispersion of the ash is well represented by the simulation (Fig. 1).

There are however uncertainties in the calculation of aerosol dispersion, mainly due to inadequate information about source strengths. This includes for example eruption height and emission strengths and vertical distribution of ash emissions. Inverse modelling and data assimilation methods can be used to obtain more exact information about source strengths (Elbern et al., 2010). With the inverse modelling method the input values of the model (here: the source strengths of the volcano eruption) are adjusted until the best possible agreement with observation data is obtained. EURAD-IM is able to implement this advanced method, which serves to calculate the source terms in the event of volcano eruptions.

In the meantime the EURAD-IM model has been expanded at the Forschungszentrum Jülich so as to be able to calculate predictions of ash dispersion as promptly as possible in the event of a further volcano eruption within Europe. These predictions are automatically graphically displayed and linked to the homepage.

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