Brian Sandle wrote:

No-one has commented on polar stratospheric cloud. Grant pointed out how
thin the atmosphere is there. They occur in the winter. Maybe conditions
are sufficient to make clouds of water from cometary fragments. Can any
large fragments get through?

We touched on vortices. Vortex theory was advanced by Kelvin and Thomson,
but superceded by the particle theory, though particles were found to have
spin. Maybe spin can have a laser effect. Sorry about the dreaming. The
simple wind vortices would seem to produce too irregular a form to be
recognised as a crop circle.

Is there any theory of how smoke rings can bounce off one another, and can
that happen with any atmospheric clouds?

Grant said that if vortices were present which could form ice meteors then
there would be clouds, too. But is it possible to have in the upper
atmosphere a wind sort of like the Antarctic katabatic, 350 km/hr with a
clear sky?

What is the velocity of wind in the clear air turbulence which affects
aircraft?