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View Full Version : I saw the Green Flash this morning.



Hornblower
2014-Nov-19, 01:14 PM
As I watched the first speck of the rising Sun appear on the horizon, it was distinctly greenish yellow before becoming the usual yellowish orange in uncommonly clear air over northern Virginia this morning. The view was not as good as at sea because of trees, but it was there, about a degree and a half above where a true horizon would have been. My table in Norton's Star Atlas shows about half the refraction we would have had at a true horizon, which was plenty for the effect. It is caused by dispersion of the refracted light, with the shorter wavelengths being elevated the most.

KaiYeves
2014-Nov-19, 03:33 PM
Wow! Jealous!

Swift
2014-Nov-19, 06:20 PM
Wow! Jealous!
What she said. I've looked for years but never seen it.

Mr Q
2014-Nov-19, 06:22 PM
Yes, Wow, since most observations occur over a large body of water (water reaching the visible horizon). First time hearing about it being seen over a land horizon and if as rare as this is (over land), it would be a great observation indeed.

Has anyone else seen or heard of the green flash being seen over a distant land horizon?

Hornblower
2014-Nov-20, 03:06 AM
Yes, Wow, since most observations occur over a large body of water (water reaching the visible horizon). First time hearing about it being seen over a land horizon and if as rare as this is (over land), it would be a great observation indeed.

Has anyone else seen or heard of the green flash being seen over a distant land horizon?
My guess is that it is rarer over even a low and unobstructed land horizon because of more dust in the air, which blocks the shorter wavelengths strongly at that low elevation.

Jerry
2014-Nov-20, 03:50 AM
I have seen it four to six times, but I live on a spit in the Pacific, and see sunrises and sunsets many days every month. I have not seen it during a sunrise, which is over distal land. I have only seen it on days when it is quite cold relative to the seasonal high; so I think they are more likely to occur when there are clear inversion layers. Also; I am not certain every occurrence has been a 'real' green flash. It is normal to see inverted colored spots when a strong source of light is removed - sudden loss of red leads to the appearance of a green spot. I have tried to catch one on a camera, as proof positive, but I haven't been successful.

George
2014-Nov-20, 02:27 PM
Congrats on seeing a green Sun (tip)! I was surprised you saw it ~ 1.5 deg. above the horizon. That is about 1/2 the air mass as the horizon and I thought extra air mass was more important for the effect.

Hornblower
2014-Nov-20, 02:59 PM
Congrats on seeing a green Sun (tip)! I was surprised you saw it ~ 1.5 deg. above the horizon. That is about 1/2 the air mass as the horizon and I thought extra air mass was more important for the effect.

Yes, the dispersion would have been about twice as much at the true horizon, making the effect last longer, but the greater mass of air and haze in the optical path could have dimmed it more and made it harder to see.

My first glimpse was through the lowest hole in the superimposed crowns of many trees. After it had brightened and become yellowish orange a second speck appeared just to the right and initially looked greenish yellow. Each time that tint lasted about a second at the most. This morning I looked again, and with some thin clouds I saw only orange.

Mr Q
2014-Nov-20, 04:23 PM
As I understand the conditions for a green flash is the Sun rising or setting over a far horizon (i.e. the ocean horizon). The refraction of the Sun's light through the thickest part of the atmosphere above this great distance and the presence of a calm, stable air mass between the visible horizon and the observer is a must for the flash to occur. This is why lots of people try to see it but can't. The conditions along the line of sight have to be near perfect for the flash to occur. I have tried many times and one morning the conditions were perfect, looking across the Atlantic Ocean from a beach, and it was easily seen, lasting for about a second. So keep trying - sooner or later you will get to see it with patience.

George
2014-Nov-21, 06:38 PM
Yes, the dispersion would have been about twice as much at the true horizon, making the effect last longer, but the greater mass of air and haze in the optical path could have dimmed it more and made it harder to see.
That's a good point. Your reduction of about 20 air masses at 1.5 degrees would give green a greater chance.

Is there a weather site, I wonder, that shows the atmospheric inversion regions, or whatever, necessary to favor a flash?

tony873004
2014-Nov-24, 10:57 PM
As a child I read about the green flash. For years, I looked for it but couldn't see it. Then I finally saw it, and have seen it countless of times since. I think the problem is with the way it was described to me as a child. I expected the sky to flash green, rather than the almost point-like upper edge of the Sun turning a very distinctive green for less than 1 second. I think that's why most people have never seen it. They don't know what they're looking for.

My bedroom window has a view of the Pacific Ocean to the west. So if the sunset is not obscured by trees, its easy to see from my house, and hence I've seen it many times since.

I've seen a blue flash and a red flash too.
I was once driving east on a highway in Arizona. Through my side mirror, I could see that the Sun was about to set behind a flat spot on distant mountains. So I pulled over and saw a beautiful green flash. Got back on the road, and through my mirror I watched the Sun rise again as I outraced the mountain's shadow. As it did, I saw a blue flash followed by a green flash. Pulled over again, and saw another green flash. Got back on the road again, but couldn't outrace the mountains' shadow again.

Another time, the sky was overcast except for a clearing at the horizon. It was night. Minutes before the Moon was about to set, it emerged from the overcast, into the clearing. Its lower limb was briefly a very distinctive red color for just under 1 second, before becoming bright orange as it was close to the horizon.

DaveC426913
2014-Nov-25, 12:19 AM
:envy: looked for years, never saw it.

NEOWatcher
2014-Nov-25, 12:36 AM
:envy: looked for years, never saw it.
Green with envy?

DaveC426913
2014-Nov-25, 12:55 AM
D'oh! Perfectly good pun and I let it slip right past.

George
2014-Nov-25, 08:59 PM
D'oh! Perfectly good pun and I let it slip right past. Yep, they can come and go in a flash.

Hornblower, I meant to ask why the Sun's higher altitude did not cause too much glare for your flash observation. Were the tree leaves that effective, and you that patient?

Hornblower
2014-Nov-26, 03:22 AM
Yep, they can come and go in a flash.

Hornblower, I meant to ask why the Sun's higher altitude did not cause too much glare for your flash observation. Were the tree leaves that effective, and you that patient?
The first thing I saw was a tiny speck through the superimposed crowns of many trees. I think it would have been much brighter in an unobstructed view of the upper limb emerging from behind distant terrain.

I was not looking for anything special. I just get a primal fascination out of watching the Sun come up.

George
2014-Nov-26, 02:33 PM
The first thing I saw was a tiny speck through the superimposed crowns of many trees. I think it would have been much brighter in an unobstructed view of the upper limb emerging from behind distant terrain. You may have some sort of flash altitude record. :)


I was not looking for anything special. I just get a primal fascination out of watching the Sun come up.I enjoy every morning at my father's small ranch as we bundle-up, drink coffee (his with Irish Whiskey), and sit on his trailer home's front porch.

Trebuchet
2014-Nov-26, 03:37 PM
You may have some sort of flash altitude record. :)

The best green flash I've seen was when the sun was dropping behind a distant cloud deck. Took me by surprise, that did. (Probably described somewhere upthread as well.)

George
2014-Nov-28, 07:28 PM
The best green flash I've seen was when the sun was dropping behind a distant cloud deck. Took me by surprise, that did. (Probably described somewhere upthread as well.)Ok, you may have some sort of flash altitude record. :) I have assumed that the green flash required low altitude atmospherics (inversion layers or something).

Mr Q
2014-Nov-30, 07:20 AM
Ok, you may have some sort of flash altitude record. :) I have assumed that the green flash required low altitude atmospherics (inversion layers or something).

You are correct. It does take an inversion layer to refract the tiny spot of sunlight as the sun comes into view and this happens mostly over a large span of sea water where the very small spot of light (the edge of the Sun instantly becoming visible) gets refracted like in a prism. As long as a stable layer of inversion air is present (even across land with a very distant horizon), the flash should be seen but this condition is much rarer than over a large body of water where the inversion is easier to form but I would think it would be possible over a distant land horizon where inversions take place more often.

Hornblower
2014-Nov-30, 02:55 PM
Yes, inversion layers strengthen the refraction and dispersion. I think the conditions were favorable for an inversion that morning I saw it, but I did not think to go outdoors to check up. I can tell by listening whether or not there is an inversion. When there is one, I can hear the dull roar of traffic on the Capital Beltway, a busy interstate highway two miles away. The warmer air aloft transmits the sound faster than at the ground and focuses it toward the ground. Without the inversion the sound is much fainter and often inaudible at that distance. Of course I could not hear that from in the kitchen with the exhaust fan going and the double glazed windows closed.

Trebuchet
2014-Nov-30, 04:13 PM
I may, of course, have seen some other phenomenon entirely. Whatever it was, it was pretty cool.

Hornblower
2014-Nov-30, 06:32 PM
I may, of course, have seen some other phenomenon entirely. Whatever it was, it was pretty cool.

If you saw green, it was from dispersion of the Sun's light by the atmosphere, regardless of what the occulting object was or whether or not there was any inversion layer to increase the magnitude of it. If you were lucky, the motion of the cloud top could have been enough to prolong it somewhat.