When I was at Sonora Pass with Lon back in July, we were camped below some nice granite crags. Soon after sunset, we observed some nice alpenglow on the peaks.
There seems to be some confusion among photographers as to what the phenomenon of alpenglow really is. I had a pretty good idea, but wanted to be certain, so I did a little research and found the following definition in the American Meteorological Society Glossary.
"Alpenglow—The occasional reappearance of sunset colors on a (snow-covered) mountaintop soon after sunset and a similar phenomenon before sunrise.
Alpenglow has three phases. During evening twilight, the first stage is the mountain peak's usual coloration seen at low sun elevations h(sub)0 (h(sub)0 < 2°). Second is the alpenglow proper that occurs a few minutes after the first color has faded (h(sub)0 slightly less than 0°). The peaks are still in direct sunlight, and their colors are purer and often pinker than before. The alpenglow boundary may first occur hundreds of meters below the summit, then moves upward, and finally fades as the atmosphere's dark segment rises. Third is the afterglow, which occurs nearly simultaneously with the first purple light. The peaks are no longer in direct sunlight; the illumination is more diffuse and its boundary vaguer than in the earlier stages. The third stage lasts longer than the other two (−5° < h(sub)0 < −9°), and its color varies from yellow to purple. A faint second afterglow has been reported and is associated with the rare occurrence of a second purple light. The alpenglow appears to be much less common at sunrise than at sunset. The morning colors are more pink and purple, while those of evening are more orange and red."
The light and color we see on the peaks is caused by sunlight being backscattered by dust, snow or ice particles, or water droplets in the atmosphere.
So, there you have it. I hope you find this enlightening, and possibly helpful in your photography efforts.
-P
Posted by Steve Sieren on August 26, 2009 at 3:33 AM
just followed the trail from CANP
This is really good to know especially since since it's less likely at sunrise. Need to head on over to the other side of the Sierra now.
Posted by Mark Caton on August 26, 2009 at 6:23 PM
Preston,
Thanks for the explanation.
The following shot was taken at Sunrise, nr. Banff Canada.
Since I was there in advance, I took a few before, during and after the event, but this was about the best of the lot. In the morning, at this site anyway, there was an added morning mist over the lake, which added to the atmosphere.
Mark
Posted by Paul Duval on August 27, 2009 at 12:30 AM
In Galen Rowell's excellent book Mountain Light there is a less scientific explanation for Alpenglow . The low angle light passing through so much atmosphere completely filters out the blue spectrum leaving only the orange red. While the most intense color at sunrise and sunset can be where the sun in rising or setting, the Alpenglow is opposite the sun. It is most bright and colorful on the high mountains. Mt. Whitney, Lone Pine Peak and Mt. Willamson are great for sunrise in the Eastern Sierra. However Thunderstorms which punch as high as 50,000 ft also show very colorful Alpenglow. The post is an evening Thunderstorm over the Inyo Mountains taken from old 395 near Aberdeen resort.
Posted by Jack Brauer on August 31, 2009 at 9:21 PM
I'm not so sure about the reasoning that sunset alpenglow is more frequent. Here in Colorado at least, I'd claim the opposite, but maybe that's just been my experience (or maybe because of dust and haze to the west).
One tangent question I have is whether or not the alpenglow is enhanced by cloud cover (with a gap at the horizon). Or is it just an optical perception that the alpenglow is more brilliant in contrast to the dark cloudy skies? I tend to think that a cloud cover actually does enhance the light, perhaps by focusing the red wavelengths somehow. All I know is that the most incredible alpenglow lighting I've seen has always occurred through a cloud gap at the horizon.
I would submit that you are correct in your thinking that the intensity of alpenglow would increase when there is an opening between a cloud deck and the horizon. Two things would likely contribute to this. There would be a greater density of water molecules and second, the clouds would reflect some light.
In October of 2005, a group of us were photographing the sunset on Bishop Creek on the Sierra East Side. There was a huge Sierra Wave cloud present. As the sun set, the cloud turned a nice purple color. When the sun went below the horizon, and below a cloud deck to the west, the cloud, the mountains, and us were bathed in a yellow glow. It was one of the finest sunsets I have ever seen.
Discussion
5 repliesThere seems to be some confusion among photographers as to what the phenomenon of alpenglow really is. I had a pretty good idea, but wanted to be certain, so I did a little research and found the following definition in the American Meteorological Society Glossary.
"Alpenglow—The occasional reappearance of sunset colors on a (snow-covered) mountaintop soon after sunset and a similar phenomenon before sunrise.
Alpenglow has three phases. During evening twilight, the first stage is the mountain peak's usual coloration seen at low sun elevations h(sub)0 (h(sub)0 < 2°). Second is the alpenglow proper that occurs a few minutes after the first color has faded (h(sub)0 slightly less than 0°). The peaks are still in direct sunlight, and their colors are purer and often pinker than before. The alpenglow boundary may first occur hundreds of meters below the summit, then moves upward, and finally fades as the atmosphere's dark segment rises. Third is the afterglow, which occurs nearly simultaneously with the first purple light. The peaks are no longer in direct sunlight; the illumination is more diffuse and its boundary vaguer than in the earlier stages. The third stage lasts longer than the other two (−5° < h(sub)0 < −9°), and its color varies from yellow to purple. A faint second afterglow has been reported and is associated with the rare occurrence of a second purple light. The alpenglow appears to be much less common at sunrise than at sunset. The morning colors are more pink and purple, while those of evening are more orange and red."
The light and color we see on the peaks is caused by sunlight being backscattered by dust, snow or ice particles, or water droplets in the atmosphere.
So, there you have it.
-P
This is really good to know especially since since it's less likely at sunrise. Need to head on over to the other side of the Sierra now.
Thanks for the explanation.
The following shot was taken at Sunrise, nr. Banff Canada.
Since I was there in advance, I took a few before, during and after the event, but this was about the best of the lot. In the morning, at this site anyway, there was an added morning mist over the lake, which added to the atmosphere.
Mark
One tangent question I have is whether or not the alpenglow is enhanced by cloud cover (with a gap at the horizon). Or is it just an optical perception that the alpenglow is more brilliant in contrast to the dark cloudy skies? I tend to think that a cloud cover actually does enhance the light, perhaps by focusing the red wavelengths somehow. All I know is that the most incredible alpenglow lighting I've seen has always occurred through a cloud gap at the horizon.
I would submit that you are correct in your thinking that the intensity of alpenglow would increase when there is an opening between a cloud deck and the horizon. Two things would likely contribute to this. There would be a greater density of water molecules and second, the clouds would reflect some light.
In October of 2005, a group of us were photographing the sunset on Bishop Creek on the Sierra East Side. There was a huge Sierra Wave cloud present. As the sun set, the cloud turned a nice purple color. When the sun went below the horizon, and below a cloud deck to the west, the cloud, the mountains, and us were bathed in a yellow glow. It was one of the finest sunsets I have ever seen.
-P