[AZ-Observing] Re: Seeing Conditions During Monsoon

Trying to put this all together to solve this puzzle of good seeing around
the monsoon season.
1. Fundamentally, it is the mixing of hot and cold air that creates
turbulence that creates bad seeing. Humidity plays a very small role in
terms of stabilizing local temperature.
2. Thermals from the ground reaches the base of the cumulus clouds (10,000ft
+??)
3. Effect of "heat island" over Phoenix: A Thermal "Pillbox"/Cylinder/dome?
(Cylindrical region which ends at area above city where temperature gradient
is indiscernible) (Any different viewpoints? Descriptions?)
4. Height of this Thermal "Pillbox": Depends on atmospheric conditions? (air
pressure, temperature, humidity...?)
5. Distortion of this Thermal "Pillbox" by winds?

A wild idea: It would be an interesting project to have people from
different points in the Phoenix metro area record the seeing conditions
together with weather/geographical conditions (wind speed/direction,
temperature, humidity, surrounding buildings, elevation...etc.) and put this
data together for a few nights during this monsoon season (and maybe even
other times of the year) and see how the good and bad seeing conditions are
distributed throughout the valley. Have this ever been done before?

Derrick

On 7/23/07, Richard Harshaw <rharshaw2@xxxxxxx> wrote:
>
> 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?)



Rick Tejera:

>About as high as the base of Cumulus Clouds. Since cumuloform clouds are
> convective in origin the height at which they form is typical the height
> of
> convective turbulence. That being said, upslope turbulence near mountains
> can be felt for quite a ways above the tops of the mountains  (or hills)
> that form them. Also can be felt for quite a ways downrange.
>
> Since most of my flying was done along the relatively flat east coast. I
> didn't have much experience with Upslope turbulence, although I do
> remember
> a bumpy ride home to Long Island from Albany at 10,500'. I was picking up
> turbulence from the Catskill Mountains about 50 miles to the west. The
> highest peak there is about 3500'. Fortunately I had an 80 knot tailwind,
> so
> the bumps were endured for a pretty short time.


Tom Polakis:

>One thing is certain.  If you're observing on the desert or Valley floor on
> a calm night during our other nine months of dry weather and a breeze comes
> along, you can bet the seeing will degrade quickly.  I have recently
> observed on two breezy Monsoon nights that have been steady.  Were these
> conditions both rare exceptions or the rule?  The only way to find out is to
> set up the scope and look, which was the reason for my original post.
>
> Last but not Least! Brian Skiff:
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.


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