I was on holiday last week, hence the lack of posts. Like many other web-loggers, I'm going to post a few holiday photos, but by using them to point out an interesting meteorological phenomenon, I'll pretend that this post actually has content:
These were taken at an altitude of about 2,000 meters above sea level, near Alpbach in Austria. The brown colour in the clouds is caused by Saharan dust, blown north across the Mediterranean. The visual effect was really striking, especially since we had, at the time, no idea what caused it. It's a cliché to call such things `apocalyptic', but that's really how it looked. One person (not me, before you ask) half-jokingly suggested that a nuclear war had destroyed everything outside the valley we were in, and that (a) what we were seeing was the smoke; and (b) we should enjoy ourselves while we still could.
I've white-balanced the pictures above to make the snow look white, which is more-or-less how it seemed to the eye; the pictures come out of the camera looking even more freaky:
The clouds are also mentioned in this Reuters piece, which points out their effects on glacial melting: the dust is dark, and when it settles on the glaciers, it decreases their albedo and makes them melt faster in the summer. As one of my companions said, now is the time to go skiing in the Alps -- while you still can....