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I know that contrails are not part of the natural atmosphere, but
they are ice clouds (of sorts) and I have noted two phenomena that I
don't understand the basis for and hope that someone has the answers.
They may be related, then again, maybe not.
- The first was observed several years ago in San Diego, CA,
USA. There was a thin (but quite visible with some structure) Cirrus
cloud deck with a long (essentially horizon to horizon) contrail under
the cirrus (this was obvious from the structure). The sun was
essentially directly behind contrail from my viewing point. I was in an
automobile driving along and as I drove, the sun's position changed from
slightly to the left of the contrail to slightly to the right of the
contrail. The phenomena observed was a "shadow" on the cirrus that was
on the side of the contrail opposite from the sun (i.e., it was on the
right of the contrail when the sun was on the left of the contrail).
None of this is especially strange except (as I noted above), the
contrail was BELOW the cirrus deck (hence the quotes around the term
shadow, since it seemed to be reflected back onto the cirrus deck).
- Just the other day, while driving southe near Portland, OR,
USA, I saw a long contrail toward the west. It was approximately 2 pm
local standard time, and although I couldn't see the sun (the car's roof
was in the way), they must have been fairly close. The contrail was
essentially north-south, as was the direction of the aircraft, which was
visible near the head of the contrail in the south. There was cirrus
present, although none was visible in the vicinity of the contrail
(although there could have been thin, non-visible cirrus). A thin
darkening appeared as a thin straight line, essentially co-located with
the contrail (perhaps slightly offset, but if so not by much). This
darkening of the sky extended along the contrail and in front of the
contrail all the way to the horizon.
Does anyone have any explanations for these observations?
Thanks.
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William M. Cornette Photon Research Associates, Inc.
(619) 455-9741 10350 N. Torrey Pines Road, Suite 300
FAX (619) 455-0658 La Jolla, California 92037
wmc_at_photon.com
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T.A.N.S.T.A.A.F.L.
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