What you are describing is more commonly called "mirage." High magnification scopes and situations where there exists high temperature differnetial between the ground and the ambient air (cold night, followed by bright sunny day; deserts; etc.) could produce pronounced mirage.
In the book "The Ultimate Sniper" (I will put info at bottom of the post) goes into great detail on how to handle and reduce the effects of mirage. The easiest thing to do is reduce your scope magnification.
Here is the book info from
www.paladinpress.com
ULTIMATE SNIPER
An Advanced Training Manual for Military and Police Snipers
by Maj. John L. Plaster, USAR (Ret.)
This highly readable and extremely valuable training book covers the practical, field-tested details of sniping's three great skill areas - marksmanship, fieldcraft and tactics. Rifles, scopes, ballistics, target detection, stalking, hides, cammo, countersniping, special ops, police vs. military and much more. 8 1/2 x 11, softcover, photos, illus. 464 pp.
ISBN: 0873647041
Publisher code: ULTI
Price: $42.95
Hope this helps!
