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Location: UFOUpDatesList.Com > 2007 > Jan > Jan 7

Re: O'Hare Sighting Cloud Hole Effect - Tarbell

From: Michael Tarbell <mtarbell.nul>
Date: Sat, 06 Jan 2007 13:38:44 -0700
Fwd Date: Sun, 07 Jan 2007 11:25:44 -0500
Subject: Re: O'Hare Sighting Cloud Hole Effect - Tarbell


>From: Martin Shough <parcellular.nul>
>To: <ufoupdates.nul>
>Date: Thu, 4 Jan 2007 16:13:15 -0000
>Subject: Re: Holes In The Cloud Deck

>>From: Jim Deardorff <deardorj.nul>
>>To: ufoupdates.nul,
>>Date: Wed, 03 Jan 2007 09:44:16 -0800
>>Subject: Holes In The Cloud Deck [was: In the sky! A bird? A
>>plane? A... UFO?]

>>>From: Michael Tarbell <mtarbell.nul>
>>>To: ufoupdates.nul
>>>Date: Tue, 02 Jan 2007 10:39:55 -0700
>>>Subject: Re: In the sky! A bird? A plane? A... UFO?

>>A similar phenomenon are the large, very circular holes very
>>infrequently observed in an alto-cumulus layer. There, cloud
>>physicists could assume that the cloud was composed of
>>supercooled droplets into which ice crystals had somehow formed
>>at one spot, which then rapidly spread out laterally to form a
>>circle of increasing diameter, with trails of ice crystals
>>falling out. (I can't find my files on this at the momemnt).
>>Trouble is, no such circles have ever been observed in their
>>initial phases, no substantial ring of falling ice-crystal
>>trails was observed, and the holes were very large (1/2 mile or
>>so in diameter) yet had a well defined circular edge despite
>>local variations in cloud-droplet density, temperature, wind
>>shear, etc.

>There's a slightly unusual cloud hole shown at:

>http://epod.usra.edu/archive/epodviewer.php3?oid=99360

>"...the centerpiece of the photo is the donut-shaped
>altocumulus cloud. Note the iridescent nature of this cloud,
>which means that it's likely less than about 40 degrees away from
>the Sun. Iridescence results from diffraction - deflection of
>light around objects, water droplets for instance. For a hole to
>occur in a cloud, some process must be at work to remove the
>cloud droplets or crystals. For example, if a cloud is seeded
>with silver iodine or carbon dioxide, a hole could occur in a
>portion of the cloud deck. In this case thought, the hole is more
>perpendicular than parallel to the ground surface, so it's
>unlikely that it results from seeding. Also, note the jet
>contrail and its shadow to the left of the donut cloud. Although,
>it appears the jet pierced the hole, it couldn't have caused the
>hole to form in a fraction of a second."

>Terrific photo of the more usual type of hole in stratified cloud
>(over Mobile, Alabama, I think) at this blog:

>http://rustybucket.blogspot.com/2004_09_01_rustybucket_archive.html

>Another beautiful example from the UK is here:

>http://tinyurl.com/yexmxf

<snip>

Great images Martin. It would seem your first example is most
analagous to the O'Hare phenomenon, aside from size and
orientation.

I must admit some puzzlement if the mechanism here is the sudden
transformation of supercooled water droplets into ice crystals.
Such crystals would be less dense and have a higher drag
coefficient than water droplets, so there's no obvious reason
why they should "rain out", indeed one would guess quite the
opposite. If the effect derives from the differing light
transmitting properties of ice and water (their indices of
refraction are very similar), why do we commonly see high
altitude clouds composed entirely of ice crystals that have the
same basic appearance as clouds of water droplets?

Still hoping for a cloud physics guru to jump in.

>A different angle, if we're looking at technology, is the
>following patent for a cloud-punching laser device for military
>surveillance. CO2 lasers of the type mentioned work in the
>infrared:

>http://www.freepatentsonline.com/4411487.html

>-----

<snip>

>I suppose in an O'Hare type situation a downward-directed maser
>beam beneath an ascending object might keep a relatively
>well-defined cloud hole open for some time after it had passed
>though. The directionality and various possible pulse v. cw
>characteristics of such a coherent emission would obviously make
>a big difference to any calculation of power generated from pwer
>density "on target".

This calculation becomes more intimidating upon further
inspection. The medium is optically thick and dynamic (the
fluence at any given depth is evolving with time as upstream
droplets evaporate). Neverthelss, I would speculate that the
result will show that the power requirements are not
astronomical (i.e., earth-based technology not ruled out in
principle). Again, a critical ingredient is the thickness of the
cloud layer, which has not been forthcoming. I've emailed both
Peter Davenport and Jon Hilkevitch for any clues to where I
might even start looking, nothing so far. Do I dare simply
contact the FAA or the O'Hare airport administrators? Nothing to
lose I guess.


Mike






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