(meteorobs) on the subject of clouds

[arlene]

Bruce, you're great...Alister is great.
It's great to be able to 'connect' to
such a wealth of knowledge, even here, in the
middle of nowhere!

He may be right about this cloud. The area
it hung above was on the Asian side of Istanbul
very close to the mouth of the Black Sea. It
meets the criteria as described.

I'm just sorry I didn't own a digital at that point.
It would have been quite a photo for the album!

I thank you sincerely.

Arlene
south of Troy

----- Original Message ----- 
From: "Bruce McCurdy" <bmccurdy at telusplanet.net>
To: "Global Meteor Observing Forum" <meteorobs at meteorobs.org>
Sent: Thursday, September 02, 2004 6:31 AM
Subject: (meteorobs) on the subject of clouds


>
> To Arlene south of Troy, I sent your cloud question to Alister Ling,
> astronomer, meteorologist, and skywatcher extraordinaire. His response
> follows. regards, Bruce
>
> > Arlene, it's not easy to be sure from your description. Stationary
clouds
> > are quite common in hilly terrain. As long as the atmosphere is moist
> enough
> > at the right altitude for a prolonged time, the cloud will form above a
> peak
> > or range of hills. The basics of it is that a non-saturated airmass is
> > forced to rise over terrain, and cools because it ascends into lower
> > pressure and expands. If there is sufficient moisture in the original
> > parcel, the cooling will eventually hit the parcel's dewpoint and become
> > saturated and a cloud forms. As the parcel goes back down on the other
> side
> > of the hill, it is compressed by the higher pressure below and warms up
> > above the dewpoint and the cloud evaporates.
> >
> > The odd thing, at first glance, is that the cloud is stationary, but the
> air
> > is constantly moving through it. In some ways, it is like a breaking
wave
> in
> > a river, attached by a rock in the stream. The wave is stationary but
the
> > water moves through it.
> >
> > The shape you describe is fairly unusual for an "orographic cloud".
> > Otherwise, I can't think of much else it could be.
> >
> > Good observing,
> > Alister.
> > (meteorologist)
>
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