I`m looking for the best way to simulate the heat coming off the desert floor. It lasts a certain distance and has a very distinct ripple to it. I was thinking an adjustment layer with a gradient matte on it...but what to apply to make the 'heat displacement'. Turbulent displace goes in noticeable loops, not sure what else to try

I'm working on this effect as well. I need to try a 'practical' element: film the shadow of a charcoal fire and use that as the displacement map. I'll get to it eventually, let me know if you get any play from that idea.

I was just going to suggest using fire as a displacement map. The turbulance you're talking about should be the same air displacement regardless the source of the heat. You could potentially shoot a tight grid placed behind the fire as well and shoot over the flames where the heat displacement would be hitting the most and use the resulting distortions as a map for the displacement map... or a medium gray which you could then push to the extreme black and white with a color corrector to make the displacement more effective.

Found this in about 10 seconds with a Google search (what would we do without Google?)
http://creativemac.digitalmedianet.com/articles/viewarticle.jsp?id=34773

And if you have the ability to do it during acquisition... shooting over the hood of a hot car can get the heat wave effect for you. An old trick.

-gb-

You shouldn't need an effect this time of year. But you can film with a tota light in front and below the camera.

Thanks for the tutorial, looks like it should do the trick.