Originally posted by mattb123 Thanks!
Hmmm, I'd never thought about that. Do you know if the flash would be visible with an elevated horizon? All the green flash shots I have seen were over the ocean and I wonder if a horizon at 7000' above sea level would produce the same effect. I have never noticed it around here and have watched many sunsets from elevated locations.
We get green flashes occasionally on sunrises in Boulder Colorado from a vantage that is maybe 500-750 feet above the Eastern plains. The key seems to be that the sun is rising over a very flat expanse of land (or the sea) so that the sunlight is being refracted through a lot of air that is very close to the ground and that air is at a different temperature relative to the higher parts of the atmosphere. Your image #2 looks like it's pointing at some distant plains or flat-topped mountains and that coloration of the sky reminded me of what the sky looks like before a good sunrise. Even if green flashes don't occur, you might get some cool mirage and sun-disk distortions from that location at sunset on a very clear sky.
(At the very least, it's always interesting to revisit photographic viewpoints and learn how seasonal and weather patterns combine to create new photographs from old locations. It's never the same landscape twice.)