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> > Marko,
> >
> > Your skies in the north might be more conducive to more colorful
> > displays since ice crystals should be (?) more common in your
area -
> > the mere fact that ice crystals exist here in the tropics raises
more
> > than a few eyebrows when I relate it to my officemates.
>
> Actually, the tropical tropopause is colder than polar tropopause.
This
> can be explained by the fact that the tropical tropopause is in
much
> higher altitude, near 15 kilometers, compared to about 8 kilometer
of
> polar tropopause.
>
> - Timo
But actually the answer must be more complicated than this, I think:
first,
does sufficient water vapor for ice-xtal formation more often reach into
the polar upper atmosphere than into the tropical? Colder may not be
relevant if there is not enough water to form clouds.
Second, tropical conditions may more often result in extensive
lower-atmosphere cloud development, which may then tend to obscure upper
atmosphere halo-generating clouds.
I am just speculating: I myself do not know whether haloes are more
frequent
in higher latitudes or in lower. I do however think the question is much
more complicated than simply the temperature of the tropopause.
The accumulating data on halo occurrences that is being accumulated might
be helpful in this regard, though the important information about the
visibility of upper clouds / obscuration by lower clouds is not easy to
account for.
Chris
Christian B. Luginbuhl
U.S. Naval Observatory Flagstaff Station
Flagstaff, Arizona USA
cbl_at_nofs.navy.mil
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