So what's the difference between this very fine volcanic dust and the very fine sand which gets blown in from the sahara after sand storms? Presumably both are equally as abrasive and judging by the quantities accreting on my car in the past, in probably just as high a concentration.
Having flown through a lot of Sahara Dust, and a small amount of volcanic dust, the most noticeable difference is the abrasion of windshield glass. It becomes micro-pitted, almost looks frosted, after volcanic dust. No effect noticed after Sahara dust.
And forecasting where the effects will be noticed is not easy either.
I remember during an eruption of St Vincent, that we all went out east to avoid the obvious plume that was being carried off to the west of St Vincent on the southeast trades. Imagine the headscratching that took place when volcanic dust came floating into Barbados, over 100 miles east of St Vincent, on the southeast trades.
What had happened is that the dust had left westbound, and risen through a masking layer of cirrus, to pick up the upper level westerlies, ride several hundred miles eastward whilst drifting back down, to hitch a ride back into Barbados on the southeast trades. So here came volcanic dust from the east with the nearest volcano on that side being several thousand miles away.
Go figure.
