This may be overtaken by later postings, but a couple of reasons why n5692s's explanation might not work:-
Most of the lift is generated on the upper surface and is dominated by the vortex lift which is a product of vortex strength and airspeed. The vortex strength depends on the local aoa at the leading edge. As the aircraft enters ground effect the passage of air under the wing is restricted so more has to go over the top and the local LE aoa is increased along with vortex strength. The important bit of the wing for this bit of lift increase is the front half which is in the higher part of the wind profile. But in any case, following our old friend Bernoulli, the upper surface suction will depend on the resultant circumferential velocity as the vortex scrubs its way across the wing upper surface, and I can't see a knot or two of wind making a big difference to the circumferential velocities under those vortices.
The undersurface flow is of course restricted. and the lift is more Newtonian in character. A reduction in local airspeed because of the wind height profile could give a reduction in lift due to ground effect near the TE. However, in the normal course of events this additional lift is accompanied by a nose down pitch which is countered by a steadily increasing back stick movement as the pilor maintains the more or less constant pitch attitude "flare" manoeuvre. This up elevator gives an increasing negative lift to maintain pitch control which, since the effective cop of the elevator lift is at the elevon hinge line means that the net gain in overall lift from this part of the ground effect is quite small. If this undersurface TE lift were to be reduced by the wind gradient the effect would. be that the nose down pitch would be smaller than usual and the pilot would have to apply less back stick, but I doubt he would notice this in a dynamic situation (remembering that strong winds are usually accompanied by turbulence).
So I can't identify any gremlin job specification that might support n5296s's argument.
Kaypam: Remember the Concotrde was certificated to TSS Standards not JAR25. The certificated approach speed is Vref, Vref plus 7 if memory serves, was introduced as an approach noise reduction and became anaccepted norm so Vrefplus 10 should be OK for 20 kt winds?
Last edited by CliveL; 4th Feb 2017 at 08:30.