crab,
" DJ - I want to know how the ground effect increases lift and decreases drag without altering the pressure below the wing."
I don't think it does. I suspect that hover in ground effect and that hover in an updraft are similar, and they both differ from hover OGE because their collectives are lower. In other words, the lift and the drag of the first two are less while all three are maintaining a constant elevation.
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vorticey,
I agree with most of your comments and concur with the rest.
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Nick,
" Look at a heavy bomber moving across the water at 100 knots, its wing within 1/3 of a span of the water, using much less power due to ground effect. Its wake is hundreds of feet behind it."
Perhaps this distant wake is from the more powerful and 'horizontal' propwash and not from the wings.
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A pictorial thought, supporting the 'bubble of air' ;
Envision a tube that has diaphragms covering the openings at both ends. If one diaphragm is flicked, then the other diaphragm will experience roughly the same displacement, but with a small delay cause by the time it takes the wave to travel down the tube, at the speed of sound.
Now envision the tube where one diaphragm is replaced by a solid plug and the other diaphragm is replaced by a plunger. If the plunger is pushed in an inch and held in, a wave will be produced. This wave will travel at the speed of sound down the tube. When it hits the plug at the other end, it will bounce back. It will continue bouncing back and forth between the plug and the plunger. Segments of the wave will be traveling in both directions. These interacting segments will quickly neutralize each other, and after a very short period of time there will be an increased but consistent pressure through the whole tube.