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Last evening (Thursday, March 13, 1997) on my way home from work I
observed
a wonderful halo display on the ground.
On Tuesday and Wednesday of this week we received 20 cm of fine
snow (on
top of the 130+ that we still have) in Red Deer, Alberta, Canada.
Yesterday, the
weather cleared and the sun shone brightly on the fresh covering of snow.
At about
5 pm (Mountain Standard Time) I was walking home across a field on my well
packed
trail. The sun was about 15° above the horizon and shining brightly on
the snow.
As is my habit, I looked around for interesting things to see. "On" the
snow, I
observed a very nice 22° halo. The air was very clear so there was none
in the air
around the sun. As I looked more closely and looked towards my feet, I
could very
plainly distinguish a 40° halo as well. The colouration of the 40° halo
was not as
distinct as the 22° halo, as I could see individual snow crystals
glistening, but
was none-the-less quite impressive. I attempted to take some photos of
the event
and hope they will turn out. The temperature at the time was about -15°C.
This morning on my way to work, the sun was again at an elevation
of about
15°. Now, looking towards the other side of the field, was a very
distinct and
colourful 22° halo "on" the snow. This was especially impressive because
the halo
extended across the snow approximately 500 m along both arms. Again,
clear air so
no halo around the sun. Temperature is -25°C.
I have observed the 22° ground halo many times (I actively look
for it) on
snow and frost. I have never before seen the 40° ground halo nor have I
heard of
any observations of it. Does anyone know how common it is? Have I just
been
missing it or is this a relatively rare observation? Any comments would
be
appreciated.
By the way, the crescent moon and comet Hale-Bopp were both
beautifully
visible last night as well.
Paul Williams
Red Deer College
Red Deer, Alberta
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