Rainbows and Green Flashes

I've seen the "green flash" three times--all at sunset, from west coast beaches:  Once from Cannon Beach, in Oregon, Twice from Pajaro Dunes, in California, all in the winter.  There's a reason for this, as I'll get into later.  Many people are skeptical that it's a real thing.  It is, but things have to line up just exactly right to be able to see it:

You need to have clear viewing all the way to the horizon and past it--no clouds, no haze, especially no mountains.  Typically these conditions happen only when it's been raining and it's cleared up just an hour or two before sunset.  it helps if there's a little bit of haze right at the horizon, but not much.

The water needs to be warmer than the air.  This is why it tends to be a winter phenomenon.  The green flash is a member of the broad class of optical phenomena called "mirage", which results from layers of air being heated differently, resulting in them refracting different colors differently.  The bottom level of air needs to be quite a bit warmer than the air at eye level, which really can only happen if it's being heated by water.  Because blue and green are scattered more than red, sunsets tend to look red.  But there's a moment that the red light is all passing above your eye while green is coming your way.

The reason I think rainbows are similar is because they take a combination of several things to make them happen:  it needs to be clear enough that the water vapor is well lit.  But rainbows aren't very bright and it's hard to see them against a clear blue sky: there needs to be something behind.  it's usually in front of clouds or something else that's darker than the sky.  The primary rainbow is about 2 degrees thick and it's about 80 to 84 degrees wide.  Rainbows are the result different colors of light being refracted differently by water, but all being reflected together inside drops of water.   (To see all of it with a 35mm camera, you need a 19mm lens.  usually you can't see all of it.  to see all of a double rainbow, you need a 13mm lens.)

My favorite rainbow was when I was driving almost due north late on a winter afternoon.  I was at the southern edge of a storm--behind me was well lit, but the hood of my car was in light rain.  the rainbow appeared to be around the hood of my car.  Todd Newman was with me and we both saw it, but we didn't have a camera convenient and it didn't last long.