Sierra Bullets Ballistic Software used to calculate the following for a .300 Win. Mag. cartridge:
Drift at 900 yards for wind only in the last 300-yard segment's about 1/3rd of what wind only in the first 300-yard segment.
For wind only in the middle 300-yard segment, drift at 900 yards is a little more than twice what wind only in the last 300-yard segment has at 900 yards.
The bullet's drift rate increases with range but the distance to the target gets less with each range band further down range.
Reading the mirage through a spotting scope will reveal the wind at the top of the bullet's trajectory moves at the same speed as it does in the line of sight. The wrinkles high and low all have the same speed; they move together. If the wrinkles at the high point of the trajectory did move faster than the lower ones, it would be easily seen.
Normal come up on M1 and M14 sights going from 600 to 1000 yards is about 23 clicks/MOA for .308 Win. ammo. At 600 yards, that moves the bullet trajectory up about 12 feet at 600 yards; the average high point in its trajectory to 1000 yards. The wind atop a 30 foot pole is over 15 feet higher than the bullet's path; it doesn't effect the bullet at all.