These two amazing photographies were taken in the Melchsee-Frutt region of Switzerland by Max Emerson. They are showing most of the known halos and
arcs, including the rarest, like the "Parry supralateral arc" and the "suncave Parry arc"...
Atoptics had made a beautiful and realistic composition of both photography visible in the website
HERE, as well as a HaloSim ray tracing simulation showing all of these arcs and their names as well.
....captured by Doug Short. "These clouds were changing fast and within 10 minutes were overtaken by a solid layer of clouds. The cloud layer showed some iridescence on its
leading edge for a few minutes as it merged with the first clouds."
Why would clouds appear to be different colors?
A relatively rare phenomenon known as iridescent clouds can show unusual colors vividly or a whole spectrum of colors simultaneously. These clouds are
formed of small water droplets of nearly uniform size.
When the Sun is in the right position and mostly hidden by thick clouds, these thinner clouds significantly diffract sunlight in a nearly coherent
manner, with different colors being deflected by different amounts. Therefore, different colors will come to the observer from slightly different
Many clouds start with uniform regions that could show iridescence but quickly become too thick, too mixed, or too far from the Sun to exhibit
Light Pillars, Calgary, Alberta Imaged by Larry McNish (Calgary center RASC).
"Calgary has been experiencing one of the coldest run of February and March temperatures in recent memory. After midnight on March 5 at -20 C, with a
light shower of fine falling ice crystals (needle-like) in the air and almost no wind, we spotted these light pillars on just about every sodium and
mercury vapour light in the area.
The top is a tripod shot, 1.3 second, f/5.6, ISO 800, 42mm lens.
Sodium streetlights on Sunvalley Blvd. [Canon EOS Digital Rebel XSi]."
Light pillars are usually produced by hexagonal plate-shaped ice crystals in low cloud or in ice fogs at ground level.
The crystals drift very slowly downwards (only a few mm/s) relative to the direction of local air currents. They are not necessarily falling towards
The drift motion sets up an aerodynamic drag that aligns them with their large hexagonal faces nearly horizontal.
The large faces act as mirrors and glint light from lamps on the ground back downwards.
Sun pillars need crystals that wobble from the horizontal orientation. They can also form light pillars at night but tilted crystals are not
Other crystals sometimes form pillars - sometimes with odd effects.
Credits due to:
Larry McNish (Calgary Center RASC). Atoptics
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