Research News
First stages of the eruption of the Grímsvötn volcano on 21 May 2011. Photo: Ólafur Sigurjónsson/en.vedur.is
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Helmholtz Experts Comment the Ash Cloud after Grímsvötn Erruption
On 21 May, the volcano Grímsvötn in Iceland erupted, three days later it arrived over Northern Germany: The ash cloud. And as a precaution, several airports in the north of Germany were closed for a short period of time. After all, ash particles can damage the turbines of aeroplanes and thereby interfere with safety. Once more, several Helmholtz centres contributed to representing the expansion of the ash cloud in a model and to measure the concentration of ash in the air.
After the Eyjafjallajökull Eruption 2010: Threshold Values and Improved Models
Only after the eruption of the Eyjafjallajökull volcano in April 2010, a threshold value of two milligramme ash per cubic metre was defined. At levels below flights can be permitted. The measuring flights conducted by the Falcon 20E from the German Aerospace Centre significantly contributed to this ascertainment. Moreover, scientists have considerably improved the procedures for forecasting the expansion of ash clouds since that time: For instance, the simulation model COSMO-ART*, which was developed by researchers at the KIT Institute for Meteorology and Climate Research, Atmospheric Environmental Research – Division Troposphere in cooperation with the Deutscher Wetterdienst (DWD - German Weather Service), now is a standard method in use. With this model, the DWD calculates the expansion of ash clouds – and thus their impact on aviation – over a period of 72 hours.
First Measurements
However, the concentration of ash in the air had to be assessed first also in this case: During a measuring flight on Wednesday 25 May 2011, scientists from the Research Centre Jülich gathered data and samples directly from within the ash cloud. The LIDAR measurements conducted by the Jülich researchers revealed, that the ash concentration had remained roughly one order of magnitude below the threshold value of 2 milligramme volcanic ash per cubic metre of air. Thomas Walter, volcano expert at the GFZ, writes with regard to this: Over the course of the past 200 years, Europe experienced volcanic eruptions of a height of more than 5 kilometres and thus of potential impact on air transport in intervals of four years. Consequently, it is not so much the volcanic activity that has increased but airborne traffic, so that now we feel the consequences more poignantly.
