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By simulating Eyjafjallajokull for various eruption dates, I sought to investigate how the circulation patterns changed both seasonally and weekly and whether the seasonal versus weakly variations dominated the ash dispersal patterns. Simulations showed that the weekly changes in atmospheric circulation patterns dominated any seasonal trends. Eyjafjallajokull sits at the boundary between two different air masses (between the polar and Eddy regimes); --air nearer to the poles is generally cold and dry whereas at mid-latitudes it is warmer and also influenced by the tropics). This region is influenced by the North Atlantic Oscillation (NAO) phenomenon in which the circulation patterns vary dramatically.
The pronounced weekly variation in the ash dispersal may result from the varying Eddies that pass by the region of the volcano. The Eddies are mesoscale (order of 1000 km), and thus which Eddy occupies the region during the eruption would serve as the main determinant of the ashes' dispersal.
April 14-16, 2010
Image 3: 3-day ash dispersal simulation for Eyjafjallajokull for actual eruption date of April 14, 2010. The plume initially moves north-eastward and then south-westard. As the plume moves northward it deflects to the east and as it moves southward it deflects to the west as predicted by the rightward deflection of the coriolis force in the northern hemisphere. The two layers closest to the Earth's surface spread the furthest.
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