| Abstract: |
Eyjafjallajökull, a volcano in southern Iceland, erupted explosively in April and May
2010 depositing ash over a region of more than 3000 km2 to the east and southeast of the
volcano. This deposited ash has been frequently remobilized by the wind causing concern
for the health of Icelanders living in the region. An investigation was carried out to
determine whether it would be possible to produce forecasts of days when high airborne
ash concentrations were likely to occur. Information about the spatially varying surface
characteristics of the region of deposited ash is not available so in the modeling approach
adopted here ash is released from the surface at a rate proportional to the cube of the excess
friction velocity (local friction velocity minus a threshold) only when the friction velocity
exceeds a threshold. Movement of the resuspended ash is then modeled in a Lagrangian
dispersion model. Modeled ash concentrations are compared to observed concentrations
from two periods; PM10 observations between 23 May and 2 July 2010 and airborne
particle counts between 21 September 2010 and 16 February 2011. More than 66% of the
resuspension episodes between May and July are captured by the model and the relative
magnitudes of the modeled episodes in this period are in good agreement with the
observations. 66% of episodes between October and February are also captured by the
model although there is an increase in the false alarm rate which appears to be due to the
influence of precipitation.
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