In message ,
xmetman writes
On Wednesday, 26 October 2016 17:01:21 UTC+1, MartinR wrote:

When I was in the UKMO old-timers who had spent a spell in Antarctica
would mention diamond dust (ice fog) and considered it as cirrus on
the deck. Whether the sparkly ice crystals were neutrally buoyant or
fell down slowly they never said. It's true that typical mare's tails
cirrus (s****atus?) seem very often to originate from something
vaguely cumuliform and look like precipitation or virga.

MartinR

I reported diamond dust at Kinloss around 25 years ago. It was
obviously nowhere as cold as it gets in The Arctic, getting down to
-10°C with shallow mist and patches of fog on a snow surface. I
wouldn't have seen it (but I might have felt it) if ATC hadn't had
their searchlight trained on me in the Met enclosure doing the 2100
observation!

Its an effect that I suppose is very much like virga falling as ice
crystals in cirrus, and probably happens a lot more widely than we
imagine in the upper atmosphere.

I believe I once experienced diamond dust here in Cranleigh, one
exceptionally cold early morning when the temperature was -13 or so.
It's so long ago that I'm not quite sure when it was. It could have been
February 1986 or it might have been 1963.
--
John Hall
"One can certainly imagine the myriad of uses
for a hand-held iguana maker"
Hobbes (the tiger, not the philosopher!)