[APML] Fw: WX-TALK Digest - 11 Jan 2002 to 13 Jan 2002 (#2002-12)]

["Fred & Liz Lusen" <fl.lusen@verizon.net>]

Hi all,

This was forwarded to me by a good friend Sam Barricklow, all around ham
radio operator and good weather guy http://www.k5kj.net/home.htm  I think
this will be of interest to everyone if you have not already seen it.

Regards,

Fred Lusen W5CWO
fl.lusen@verizon.net

> >   1. Weather and astronomy viewing conditions
> >
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> > ----------------------------------------------------------------------
> >
> > Date:    Sun, 13 Jan 2002 08:57:04 -0600
> > From:    Tim Vasquez <tim@WEATHERGRAPHICS.COM>
> > Subject: Weather and astronomy viewing conditions
> >
> > Are there any amateur astronomers here?  If anyone hasn't
> > seen it, I recommend checking out the Clear Sky Clock at:
> >     http://cleardarksky.com/csk/
> > It's a cool interface that assimilates opacity and transparency
> > data from the Canadian GEM output at:
> >     http://www.cmc.ec.gc.ca/cmc/htmls/transparence_e.html
> > to show the amount of cloud cover and transparency that will
> > affect night viewing.  Of course I advise all the usual caveats
> > and cautions about modelcasting.
> >
> > One issue I am having trouble with is that CMC bases the
> > transparency off of humidity, assuming the drier the air, the
> > more transparent it is.  They cite the example of clear blue
> > skies that occur in desert regions.  This isn't necessarily true
> > as I've seen deep, crisp night skies in moist, dewpoint-laden
> > tropical patterns.
> >
> > Water vapor is a GAS, so how can water vapor alone cut
> > down on transparency without condensating?  If water vapor
> > indeed causes some sort of opacity effect (Rayleigh scattering?)
> > I assume we should be looking at absolute humidity values rather
> > than relative ones.  I'm assuming that's what CMC is doing.  I'll
> > ask them this once I get an idea of the physics involved.
> >
> > Tim Vasquez
> >
> > ------------------------------
> >
> > End of WX-TALK Digest - 11 Jan 2002 to 13 Jan 2002 (#2002-12)
> > *************************************************************
>


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