CB,
2000 ft has no relevance to the near surface drop off in free stream wind velocity. The effect is only noticeable at heights sensibly relevant to the landing. Centaurus, while confusing two different effects is, I suggest, bang on target.
CB, you might like to play with the model generally used to get a feel for the effect.
speed(1)/speed(2) = (height(1)/height(2))^(1/7)
As a for instance ...for those of you who flew F27 in Oz, you would recall the crosswind limit of 22 knots. The RLD AFM limit was, if my memory serves me, 30 knots measured at 50 feet (and that document contained a very nice picture of the above equation). The then DCA, when the aircraft was first introduced, decided that this fire-breathing monster was too much of a handful for mere mortals so the relevant flight standards chap in Melbourne HO (whom many of the older brethren will recall with mixed feelings - including Centaurus - however I must admit that I learnt quite a few things from him in my early years) decided that a limit related to a lower height would be more appropriate. The formula will show that the height chosen approximated the height of a hand held anemometer.
How do I know this ? In another life, I argued until I was blue in the face to have this unnecessary conservatism removed (in fact, Centaurus will recall this as we were, at the time, working for the same operator). The aforementioned chap, however, was not to be denied his view .. so I lost ... and Centaurus continued to have to observe a 22 knot limit instead of the 30 knots which Fokker intended.
[ 08 October 2001: Message edited by: john_tullamarine ]