I had to fly up to Anchorage for a 3 weeklong work stint. I was able to upgrade to 1st class getting a window on both the Orange County to Seattle leg and the Seattle to Anchorage leg.
Taking off from Orange County we had a thick cloud cover. We rose above it, but it seemed to be very thick. We were cruising well over 30,000 feet, but the clouds seemed to be just below us. I napped, then woke up just before crossing the Columbia River into Washington State. The clouds were still thick, but the layer was much lower.
I looked for Mt. St. Helens and Mt. Ranier, but these were on the opposite side of the jet. Instead I found a rare and seldom seen sight, a rainbow.
A rainbow is not a physical object, but an ephemeral optical phenomenon only seen when conditions are right. Lots of things have to come together at one time to see one. You need moisture in the air, you need the sun shining on the moisture, and the reflection of the sun from the moisture must find your eye. As the sun moves in the sky so does the rainbow. As you move so does the rainbow. Of course you have to be looking in the right place. There are other conditions, but basically you have to be in the right place at the right time to see it.
Complicating this the correct conditions may exist for only a short time & be confined to a small place, for instance a few minutes and a few hundred yards in any direction. Or the conditions may be good for tens of minutes and tens of miles in any direction.
The center of the rainbow is always at the anti solar point in the sky. This means the center is 180 degrees from the sun. This rule never varies. And a rainbow is always a circle. That is another rule that never varies. From the ground it looks like an arch or semi circle because the ground or horizon breaks up half of the reflected light of the rainbow. Looking down from the sky a rainbow shows the full circle.
Seen from the ground the main arch is always 42 degrees from the center of the rainbow. In clear air you may see a fainter secondary arch farther out, and in perfect conditions you may see a very faint third arch even farther from the center.
Seeing a rainbow from the air is much more rare than seeing one from the ground. You still need the sun, which from above the clouds is easy enough. You still need moisture, which in this instance seems to have been supplied by the clouds. And you still need to be in a position where you are between the sun and the moisture so the sunlight reflects the spectral light into your eye.
My seat was facing the anti solar point of the sky. It was about 10 am and sun was high above us. As it shone down I could see the rainbow in clouds below. Above the jet the sun was free of all clouds. The sunlight reflected off of the cloud layer below making the clouds look like a bright white carpet. The rainbow was there not quite drowned out by the bright sun.
The rainbow seemed smaller than the 42 degree ground arc, but there was definitely a secondary arc and the second photo hints at a third arc.
At first I thought the rainbow might have been an artifact of the plastic portholes, but it showed in another window next to mine. Then I calculated where the sun was. It was above and behind me so I realized I was looking down at the anti solar point of the sky. I moved my head up and down, right and left & the rainbow moved. After a while the plane began to turn toward the rainbow. The rainbow moved forward in my windows until the fuselage covered the display. So a rainbow it was.
As we left the Seattle-Tacoma airport we circled around and came very close to some of the rugged mountains on the Olympic Peninsula. These are not very good, but give you an idea. These places are maybe 30-40 miles east of Seattle.
Just after this next photo the clouds obscured all view of the land below. This shot shows the Makah area, the most westerly part of Washington State. The jet airplane is flying in a north west direction and is over Vancouver Island of British Columbia, Canada, which barely shows at the bottom of the frame.
The large body of water covered mostly by clouds is the Strait of Juan de Fuca, part of the Salish Sea. The very small island at the far right of the frame is Tatoosh Island, home to the Cape Flattery Lighthouse. The lake at the far right of the frame is Ozette Lake. That far shore heads north & south.
As we approached Anchorage we dropped below the clouds. I got a few photos of the approach. The iced over water is part of the Cook Inlet, or perhaps the Knik arm of the inlet. In the last photo the tide is low showing the mud flats. The slight band of light is a distant mountain range reflecting the afternoon sunlight.