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meteoptic-l [ät] ursa.fi
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> In addition to halos the past few days, I noticed that during our
> summer or dry season, as we call it in the tropics, there is an
> increased incidence of pearlescent clouds (those cloud patches
> which appear very highly colored with mint green, baby pink, lilac,
> baby blue, and the like) which readily capture my attention since
> their color is so demanding of attention compared to the usual
> color of the clouds and the sky.
> Would their mechanism be similar to that of halos? I've noticed
> that they normally occur together with dark cloud bands, probably a
> precursor to rainclouds or incoming fronts.
I guess you seen iridescent clouds. Those are seen here quite
often, but usually with pale and faint color and those are very
never the Sun. As bright and colorful those are more rare.
The mechanism is not the same as in halos. Halos are formed
refraction/reflection in ice crystals, but iridescent clouds
are formed in uniform sized water droplets in clouds. There
could be regions in clouds where droplets have same diameter
with each other. The diffraction from these droplets and
interference between light rays from two different drops
make those pure colors.
Iridescence have the same mechanism like in coronas and it have
some relationship also to rainbows (interference).
-VeikkoM-
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