Re: Another dumb "dewpoint on tephigram" question (picture included)

On Fri, 16 Dec 2005 17:46:55 GMT,
wxforecaster <wxforecaster@xxxxxxxxx>, in
<j4Dof.4246$7S.304@xxxxxxxxxxxxxxxxxxxxx> wrote:

>+ Furthermore, whoever posed this problem needs to check his/her own
>+ work. How can fog, a ground based phenomenon, occur at 660mb in this
>+ scenario?

Well, let's just abstract to more general terms and say "reaches
saturation". Now, whether that actually condenses into a visible
object is another question.

Of course, you're correct in noting that fog is nothing more than a
cloud in contact with the ground. Fog can indeed occur at 660mb, if
you're in the right location:

http://www.peakware.com/highest.html?list=8000

That's at the "Roof of the World". So possible, if not particularly
likely.

>+ Honestly have never heard of a "Tephigram" before

Tephigram: derives its name from its coordinates of temperature and
entropy (T, phi). It was introduced by Sir Napier Shaw ("Manual of
Meteorology," vol. 2, p. 36; vol. 3, pp. 223-224, Cambridge University
Press, London 1926, 1930). [1]

Goodness. They're old, and not particularly well-liked by us moderns,
but where used prior to the introduction of the skew-t. One major
drawback of the tephigram is that it's difficult to estimate the
potential energy (CAPE) from a plot.

Nowadays, that's not really an issue, as we'd just use a computer to
compute all the relevant derived quantities for us. But we still plot
up soundings on the skew-t 'cause that's what we're used to.

If you're more interested, you might want to reference Byers (page 129).

[1] Byers, Horace "General Meteorology" 1959, ISBN 0-07-009500-0.

James
--
Consulting Minister for Consultants, DNRC
I can please only one person per day. Today is not your day. Tomorrow
isn't looking good, either.
I am BOFH. Resistance is futile. Your network will be assimilated.
.