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> One article and/or pictures I have waited. There have been
> some discussion last year about publishing text and photos
> about coronae caused by pollen grains. I think it was Mr.
> Parviainen who talked with Mr. O'Meara or someone else about
> the phenomenon. We heard that also some others have detected
> 'clear sky coronae' and there was plan to publish something
> about these in this Spring.
Of course! Pollen. Never crossed my mind. I have a few pictures of a clear
sky corona while I was in Arizona back in January 1987. I had assumed it
must have been volcanic aerosols, but Stephen O'Meara assured me that the
aerosol counts were quite low at that time. Then I figured it was dust,
since I photographed a strong white (not brown) haze layer as I landed at
Phoenix. having just come from Alberta (54 degrees N) and -25C pollen was
not on my mind.
On the other hand, the pollen have to be remarkably uniform to produce
nice coronae. My shot is on the pale side, but definitely colored, and
smaller than the usual cloud droplet corona, implying a larger diameter.
I thought that pollen was smaller than a cloud drop? Correct me here if I
am wrong. It's been too long since I was at University and could rattle
off various size of atmospheric particles, including industrial smog. I
thought smog and not pollen, because I have never seen a pollen corona in
Alberta, and we have lots of pollen, but little trapped industrial
pollutants. Then again, I've lived in Montreal and Toronto and surely
would have seen industrial coronae.
Interesting! Thanks for the discussion,
Alister.
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