[AZ-Observing] Re: Seeing Conditions During Monsoon

In my earlier note, the humidity I have observed under may be a by-product
of other atmospheric phenomena that affect seeing. (Brain Skiff suggests
that humidity is not a factor; he may be right, so I surmise that the
humidity/haziness may be a byproduct of other forces.)  Most of the
turbulence cells that affect seeing occur fairly high up.  I don't know
whether winds aloft smash these cells out and produce uniformity in the
air's gasses, or whether other things are at work.  The turbulence caused by
local thermals diminishes with altitude.  (Anyone here fly light airplanes
and can vouch for ground-produced thermals and how high they can be felt?)

With an atmosphere that extends upwards many miles, the relatively "thin"
layer of ground level turbulence may be a minor element in overall seeing.
Aperture also plays a role-- a smaller scope must look through fewer
turbulence cells than a larger one, which is why small scopes often show
sharper images (but with less magnification and resolution than larger
ones). 

Dick


-----Original Message-----
From: az-observing-bounce@xxxxxxxxxxxxx
[mailto:az-observing-bounce@xxxxxxxxxxxxx] On Behalf Of Derrick Lim
Sent: Monday, July 23, 2007 2:36 PM
To: az-observing@xxxxxxxxxxxxx
Subject: [AZ-Observing] Re: Seeing Conditions During Monsoon

So the question seems to be why is there no effect on the seeing conditions
from the breezes right? What if the surrounding air is sufficiently humid,
and the air from the storms do not offer much of a temperature gradient?
Also, is it possible that most of the hot/cold air mixing happens near the
outskirts of the city (at the boundary of the heat island) and by the time
the breezes get to "smack dab in the middle of Tempe" (as Tom and Jenn P.
put it :) ), the air temperature difference is much less due to this "heat
island"? I'm imagining this heat island as a bubble of hot air surrounding
the city.
PS: Please pardon my ignorance or lack of knowledge (if any at all) on this.
:)

Regards,

Derrick

On 7/23/07, Brian Skiff <bas@xxxxxxxxxx> wrote:
>
>      I think Tom P was expressing puzzlement about the seeing
> more than any specific effect.  The "lore" is that if there are
> storms in the region pushing various parcels of hot/cold air
> around, then the resulting mixing ought to make the seeing rather
> poor, or perhaps greatly variable but mostly lousy.  I'm pretty sure
> humidity per se has little to do with it.
>
> \Brian
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