How ground effect works?
For an article I'm doing for Aviation History Magazine on Soviet ekranoplans, I'm trying to come up with a simple but complete explanation of how ground effect works. It's not as easy as it was back when the old "cushion of air" theory held sway. (As an aerodynamicist friend wrote to me recently, "You're right that 'cushion of air' has gone out the window, which is too bad in a way, because like creation myths it offered a simple, easily memorized way to get people to stop asking unanswerable questions...")
Question: can anybody help me out by suggesting a brief explanation that will be understandable to people who are familiar with aircraft (though they aren't necessarily pilots) but who -aren't- aerodynamicists?