Expert: Tom Whiting - 4/6/2009

Question
My niece majored in astrology; she said turbulence like that of a tornado is one cause of violent color changes and violent flickering from stars;what's your opinion?
Darlene

Answer
Hi Darlene,
I didn't know any college had a major in astrology (fortune telling)
...because that's all astrology is...like numerology,
ouiga boards, gypsy fortune telling, palm reading...they are all
in the same catagory....ie.  junky trash not to be believed in.
OR, perhaps you meant something completely different....astronomy;
the scientific study of the heavens.  That's completely different
than the pseudo-religion of astrology.  They are completely different
so you have to keep them straight, and completely apart.

Well, it's not "my opinion"....it's factual.
Ahhh, yes, she is right.  She is correct in that atmospheric turbulence is the main cause of twinkling and apparent color changes in the stars, but it doesn't take tornadic jet stream violence to do it....even the excess heat coming off a tarred black "neighbor's roof" is enough (heat waves) to cause the background stars to sintillate wildly...(the real scientific word for 'twinkling'). Astronomers refer it to the "seeing" conditions.  It can be perfectly clear, but IF there is the jet stream core right overhead, some astronomers put their equipment away for the night because the "seeing" is very bad....and that means poor resolution of all the objects.  For instance, instead of superb 0.5 arc-second resolution, you might only have 4 to 5 arc-second resolution due to atmospheric turbulence, so the clear night is a complete waste of time....a real waste of a beautiful moonless, clear night.  It happens more often than one thinks.  On the Earth's surface, we
reside as if at the bottom of a 'swimming pool'...the atmosphere.
If someone is 'swimming' in the pool, then that affects our looking
up thru the atmosphere, so we need a 'calm swimming pool' above us
to see the heavens....as they are. That was why we put the Hubble
Space Telescope up in orbit, so it is not affected by the atmosphere,
so we can achieve very high resolution (definition) of the heavenly
objects. And it's well worth it, if you've viewed any of the Hubble
Telescope pictures.

If we didn't have an atmosphere, then the stars would remain bright
steady pin-points all the way down to the horizon, (like on the lunar surface)...and they would immediately disappear behind the horizon unaffected. There would be no horizon haze to dim them down, no twinkling, no violent color changes....in addition, no rainbows, no haloes, no circumzenithal arcs, no corona's....none of that atmospheric stuff. In effect, anything you see from the ordinary and steady pin-points of starlight, you can be assured that it's the atmosphere interfering with our view of the heavens.

Hope this helps,
Clear Skies,
Tom Whiting
Erie, PA

FOLLOW UP:
Most common cause of bad "seeing" is the jet stream up at altitude overhead, followed by an unstable lower atmosphere (approaching or receding low pressure system), immediately before cold front passage, high horizontal winds, and lastly, observing around a lot of buildings that give off heat waves at night, but these settle down around midnight local time. That's why we astronomers with
portable telescopes prefer to set up on a rural flat grassy area as opposed to a cement or asphalt parking lot which is radiating heat waves from the daytime sun exposure.

 Best seeing conditions are usually with a high pressure system directly overhead, then the upper air is slowly descending overhead with relatively stable, clear sky conditions. And some nights, a
slightly hazy sky means very stable conditions, and therefore
excellent "seeing" at the sacrifice of a very slight haze layer above you.
Clear skies,
Tom

ADDITIONAL FOLLOW UP;
Oh, and if your question was meant as a "tornado" forecaster just using 'astronomical seeing'... you can forget about that.  Tornadoes require a thunderstorm (first requirement) and anytime conditions are ripe for thunderstorm formation, you're going to have a very unstable atmosphere and subsequent bad seeing all around the area
of thunderstorm formation; irrespective of whether a tornado forms,
or not.  And as you know, not every thunderstorm produces a tornado.
Clear skies,
Tom