Sorry, I realize I should have been more clear.
Tilting the camera down would bring the horizon up, but that is not the problem. The reason the horizon is at the bottom of the frame is so that I can have as much sky and clouds at the top of frame and I don't want to render any of the ground plane.
What I really need to do is extend the brighter gradient that makes up the horizon higher in the frame. Maybe not quite as much as I indicated in my image but at least double what it is now. Sort of like if I brought the image into Photoshop and warped that part up the image up in frame.
I thought the Atmosphere > Height Controls panel would be the place to start but I could not see any changes in my test renders.
Thanks for your help.
Kevin