Just what is Alpenglow?

Discussion in 'Nature' started by kerry_grim, Feb 27, 2006.

  1. Just what is Alpenglow? I do know that it is the pink light you see
    on the mountain peaks. Galen Rowell had many great photos like that.
    What I am wondering is the pink or red showing on lower non-snow
    covered mountain at a lower elevation, say 1400 feet also Alpenglow?
    What about the pink light on clouds. Is this also Alpenglow? I am
    referring to this pink coloration under a clear sky with high
    visibility and the sun not shining through clouds.

    I do not see this term used in meteorology which I find somewhat
    puzzling. Perhaps the term is only used by nature photographers and
    artists. Dictionary.com mentions it as a rosy glow on snow-covered
    peaks at dusk or dawn on a clear day. Is this definition correct?
     
  2. alpenglow \AL-puhn-gloh\, noun:

    A reddish glow seen near sunset or sunrise on the summits of mountains.

    You might also try clicking here
     
  3. SCL

    SCL

    I think the German term is Abend Sonnenschein, or evening sunshine...which I interpret as dusk. IMHO alpenglow is the reddish spectrum of sunlight reflected by an object arising from the surface of the earth (like a mountainous peak, rock outcrop, etc) shortly before sunset, the reddish color caused by absorption or scatter of the blue spectrum due to the light passing through more atmosphere. Why would it be puzzling that meterology doesn't use the term? Science doesn't necessarily follow the vernacular idiom.
     
  4. The defining quality of alpenglow isn't the result (beautiful, reddish light) or locale (mountainous environs) so much as the cause. In the strictest sense it is a diffused and indirect illumination (via refraction due to moisture and reddish-colored from pollutants in the atmosphere) rather than DIRECT light from an almost-set or just-risen sun. It often occurs just before sunrise or just after sunset, thus precluding direct light. Consider the word 'glow' for a moment, which denotes 'light being emanated from' rather than 'illuminated by' an external source. Without direct light from the sun that is below the horizon, the mountain seems to be inexpliably 'glowing from within'.

    The word has a romantic flavor, thus encouraging its misuse to refer to any reddish/golden light as alpenglow. It's not an everyday occurrence (whereas the direct, golden light at sunrise / sunset is) and is reliant on proper atmospheric conditions. German origin: alpen + glühen.
     
  5. Alpenglow; it wouldn't surprise me a bit if it was Galen Rowell's use of the term that popularized the word among photographers, namely to describe the reddish glow that would appear on the snow-crested Alps. Taken in a more common context, I describe alpenglow to people as the red and pink colored light that appears at either sunrise or sunset.

    The reddish color lightwaves are the longest in the visible spectrum of electromagnetic energy. Of all the visible lightwaves, they also move the slowest. Light that has to travel through more atmosphere has most of the blue absorbed, so the slower red waves of color are actually the only ones that make it through to our eyeballs. As the sun sets (or rises; reverse the process) you can see a gradation of color rise in the eastern sky, pinkish red onto of blueish purple. As I actually once explained to Galen - this transition of color is really our horizontal view of the Terminator Line, which is the line between day and night that the space shuttle astronauts would see when looking down (vertical) on the planet. (It was a big deal to be able to know that I taught him something, however small, albeit thanks to my interest in astronomy.) The pinkish red light is actually sunset light that continues to rise in the sky as the sun dips below the horizon. The blue purple light is actually the shadow of the earth also rising into the sky. Mountains get the most red light since they are higher, but that same ligh can also light the underside of clouds after the sun has already dipped below the horizon.

    Yes, you can see alpenglow at lower elevations including sea level. The primary difference is the amount of time that red light will be distinctly visible, before transitioning to a warm golden, or yellow light. When I did my book on San Francisco, I purposely shot the TransAmerica Pyramid as if it was a mountain peak. The red light did show on the building, but it didn't last for more that 2 minutes. In the Eastern Sierra, you can watch the transition form pink to red to gold take over ten minutes or more. Again, the differnce in time that the effect lasts is totally related to the amount of atmosphere the light needs to travel through.

    The San Francisco image is Here.

    One of my favorite Yosemite alpenglow images is Here.

    Finally, I hate to dispute with Lilly, but Alpenglow is still very much a form of Direct light. If you stood on a moutaintop bathed in alpenglow, you would see the sun.

    Gary Crabbe
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  6. Here is one.
    00FS7X-28495184.jpg
     
  7. This one too.
    00FS7t-28495284.jpg
     
  8. ...and this is my favorite. The original slide looks a lot better than this scan.

    Mary
     
  9. It's one of those things I can't define, but this thread gives me the opportunity to shamelessly post one of my favorite examples of it.
    00FSJg-28501284.jpg
     
  10. Silly me I thought it was a breakfast cereal :) ( Sorry I could not resist. )

    However I have learnt something but have a question - does atmospheric pollution not have an effect sometimes ?

    Impressed by the images.
     
  11. Actually it is Alpengluehn (i think the rest of the world cannot display the single letter for "ue" we have here in Germany, it is a u with 2 dots on top) which means the same as Alpenglow.
     
  12. Of all the visible lightwaves, they also move the slowest.
    Don't think so -- unless you're trying to tell us that the speed of light varies with wavelength.
     
  13. Perhaps he meant "vibrates" the slowest - longer wavelength/lower freq -> lower energy? (not sure if this is directly related to the described phenomenon - I had thought it was more a prism-esque scattering). Last time I checked, you had to do something more impressive than put a red gel over your flashlight to slow the light down. ;-) Nice site/blog though Gary and pictures all.
     
  14. you had to do something more impressive than put a red gel over your flashlight to slow the light down
    The speed of light does vary with the medium through which it is traveling -- the well- known value of ~ 300,000 km/sec is what occurs in a vacuum. In denser media (such as air, water, glass lenses, etc.), it does slow down relative to vacuum speed.
    I'm no atmospheric physicist but I think the usual explanation of the red color shift in sunrises and sunsets is 'simply' a filtration effect -- shorter wavelengths (blues, etc) are more scattered, absorbed, etc. when passing through a thick layer of atmosphere than are long wavelengths (reds). It's not a function of different wavelengths traveling at different speeds.
     
  15. >Alpenglow is still very much a form of Direct light. If you stood on a moutaintop bathed in alpenglow, you would see the sun<

    Gary, are you sure this is true? I've made many photographs with the sun long gone. I can recall memorable sunsets a few weeks after the eruption of Mt. Pinatubo, when a red glow suffused the high country well into twilight; in fact, the effect was visible on film, even though the human eye could no longer discern the warm color.

    Is is possible Alpenglow can occur in both direct and indirect light?
    Or is the faded light something different from classic Alpenglow?
     
  16. Just FYI: The OED defines alpenglow:
    The rosy light of the setting or rising sun seen on high mountains.
    It gives the earliest use to John Tyndall's Fragments of science for unscientific people from
    1871: "On August 23, 1869, the evening Alpenglow was very fine."
     
  17. Technically, alpenglow is a very specific thing: shortly after the sun has set, sunlight may reflect from a bright reflective surface such as snow or ice (and sometimes water or sand) which is beyond the horizon, back up into the atmosphere.
    Searching on google images, I found a perfect example. Note that there is no direct sunlight in this photo, not even lighting the clouds.
    It appears that the term is being aggressively redefined to mean merely: low angle, reddish direct sunlight. This is unfortunate, as true alpenglow is a somewhat rare and unique form of light.
     
  18. OK: I'm Busted. Yes, I meant red light was of lower frequency wavelength. Not Slower than the speed of light. When I meant slow, I was referring to the timing interval between wavelength peaks.

    But, yes, I am also sure that Alpenglow is a form of direct light. Even though the sun has set from YOUR vantage point the light of the sunset continues up into the sky. Imagine watching a shadow move up a mountain. The line where the shadow starts has direct light above it. Once the shadow reaches the top of the mountain, the light just doesn't "Turn Off" like a light switch. The sun and shadow continue to move upwards into the sky. You can mimic the effect with a penlight, tennis ball, and your finger to represent the sun, (Curved) earth, and a mountain.

    Michael: I wish I could see your perfect example, as all I got was bear eyes. What you are referring to may happen, but I don't think it is alpenglow. Esp. since it sounds like you'd have to be facing the setting sun, looking toward that direction of where something bright is below the western horizon. Alpenglow is usually seen when facing away from the rising or setting sun. Frankly, I think you have it a bit backwards, in that Alpenglow is relatively common, but what you describe is more like a rare phenomenon. Just like a Specter of the Brocken is a type of rainbow, it is very rare and requires specific conditions. It wouldn't typically be referred to as an ordinary or common rainbow. But please, if you do find more info, post away. I really want to see that picture.

    Gary Crabbe
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  19. Micheal: Blame the lack of caffine, but I did see the photo, not by clicking the link, but by copy & pasting the URL. Weird. Anyway, Your picture is a classic example of what I said in my first post. That's the horizontal view of the vertical terminator line, or in simple terms, the earth shadow. The blue light is the earths shadow rising up into the sky as the sun sets. The upper (red / pink / purple) sky is NOT light reflected off anything, but is 100 driect sunlight, passing through so much atmosphere that it's color has shifted dramatically. If you stood on a ladder high enough to be above that blue line, you would see the sun. Guarenteed.

    I gotta admit, I was a tad let down seeing this photo. I was all set to see some totally cool and rare optical phenomenon, and instead wat I got was the most common thing of all, happening twice a day for the last 4 billion years. The earth shadow rises in the east at sunset, and sets in the west at sunrise. If you don't believe me, go out any clear morning 40 minutes before sunrise, face west, and watch what happens. You'll see exactly the same light in the sky, minus the mountains.

    Gary Crabbe
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  20. Dave: Yes I'm sure. Imagine the sky at sunset is a two-toned umbrella. The half that is pink / red is direct sunlight, then below that is a blue half in shadow. When the sun sets, all the umbrella (sky) is pink. As the sun sets further below the horizon, imagine tilting the umbrella tip toward the setting sun, moving up and west at the same rate the sun sinks in the west (because the earth spins east). The blue part of the umbrella rises in the east, and the pink part moves higher in the sky, up and over the zeinith, until the last remanents of direct sunlight (glow) sets in the west.

    You are also right that film is more attuned to rendering that than our eyes, especially saturated films like velvia. But it is the light from the pink part of the umbrella that is still providing the light on the landscape. This picture shows a perfect example of the glow 20 minutes after sunset still providing a good deal of light, but it also required a 30 second exposure to get it all on film. With Mt. Pinatubo, the ash helped make the red light more intense, by scattering and absorbing more of the blue. But the red was still direct light. Just picture a straight line from the red glow on the bottom of a cloud after sunset (or before sunrise) to the sun below the horizon. There's no snow or water or ice in my photo, so the red light has to be coming from somewhere; there's no relection, so by default the that bright red light must be coming directly from sun. And again, if you were on a ladder at the same level as those clouds, you would see the sun. Guarenteed. It takes a much greater mass than the earth to warp gravitational space enough to bend lightwaves.

    Hope that all helps everyonne.

    Gary Crabbe
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  21. . This picture shows a perfect example of the glow 20 minutes after sunset still providing a good deal of light, but it also required a 30 second exposure to get it all on film. With Mt. Pinatubo, the ash helped make the red light more intense, by scattering and absorbing more of the blue. But the red was still direct light. Just picture a straight line from the red glow on the bottom of a cloud after sunset (or before sunrise) to the sun below the horizon. There's no snow or water or ice in my photo, so the red light has to be coming from somewhere; there's no relection, so by default the that bright red light must be coming directly from sun.
    I don't think this example shows direct sunlight, if by 'direct' you mean a photon traveling in a straight line from sun to Earth would hit Checkerboard Mesa, or that someone sitting on top of Checkerboard Mesa could still see the sun. If you took the photo 20 minutes after sunset, the sun was about 5 degrees below the horizon (the sun "moves" through the sky at 15 degrees per hour). That's ten solar diameters below the horizon. Put it another way, at that time the sun would be setting about 300 miles to the west (sunset moves west at about 1,000 miles per hour at the equator, and at decreasing 'speed' as you go to higher latitudes).
    I can't do the math in my head, but you would need to be many tens of miles above the Earth's surface to get direct sunlight at that time. The red light in your image was coming from the sun, but not directly; it was scattered through the atmosphere "around" the horizon; so much of that light is lost that you needed an extremely long exposure to record the scene.
     
  22. Mark:

    Sorry, I may not have been clear. The checkerboard mesa shot was lit by the
    reflected glow of the pink umbrella of light high in the sky after sunset. The pink glow is caused by direct light, but it is acting just like an umbrella that you would see in a photo studio.

    The bright red light on the clouds in the dirt road photo is direct light caused by photons travelling in a straight line from the sun.

    Richard: In reverse order, right, & wrong. The light on the cloud with the crescent moon is alpenglow, or direct light from the sun. If I assume you are facing west at sunset then your first guess was wrong. That blue line is not the earth's shadow, but rather a layer of coastal clouds (fog) hanging well offshore. The light in the sky is caused by direct light going upwards from the sun below the horizon, and hitting the dust in the atmosphere. If this had been taken not long after Pinatubo, that pink glow would have been dramatically more red.

    Gary Crabbe
    Enlightened Images
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  23. Mary:

    ** applause **

    Do you live near Denali or were you just lucky enough to get those not-a-cloud-in-the-sky shots on a short visit?

    Be well,
     
  24. >The pink glow is caused by direct light, but it is acting just like an umbrella that you would see in a photo studio. < I can buy that, Gary. But while the umbrella is being lit with direct light, Checkerboard Mesa is lit with indirect light, bouncing off the umbrella. By the same token, a landscape photographed by moonlight is using indirect light - the light reaching the moon is direct light from the sun, but the light falling on earth is indirect light, bouncing off the moon. I still think Alpenglow, as most of us understand it, can be both direct and indirect. I'm attaching a photo made a Bryce Canyon before dawn. It's obvious the upper portion of the photo is brighter than the lower portion, and not just because of the change of colors. But there are virtually no shadows, because there is no direct light, yet - the sun is bouncing off reddish clouds to the east, but not yet over the horizon.
    00FSly-28509484.jpg
     
  25. The definition of aplenglow is being over-scientificated (new word) here. Although alpenglow may be strictly defined by science, most of the posts I'm reading here are killing the magic of the moment. Does the minutiae really matter? Alpenglow is a beautiful thing that stirs my soul, and when I witness it, the very last thing I'm scrambling for is the technical definition for its occurence.
     
  26. Thank you all! What great responses. It will take a while to study all these answers. It is also great to see such fine pictures posted along with your responses.
     
  27. Words are what people use them for, and thus it this perfectly OK that Alpenglow (or more precisely the original Ladin word for it, "Enrosadira" meaning something like "getting all pink") should be universally used to describe the pretty standard phenomenon of mountain tops getting reddish at dan and sunset. However, the world was originally coined to describe a very rare phenomenon peculiar to the Dolomites (which are already reddish rocks on their own),whereby a large portion of the sky also becomes pink. I've seen it only twice in close to 40 years on mountaineering, and the attached photos (not mine) provides a very pale idea of what is happening.
    "Enrosadira" is closely linked to the legend of Laurin, King of the Dwarfs who built a splendid palace with a rose garden high on the rock face of Catenaccio (Langköfel in German). Unfortunately, the roses caught the attention of Kings Theoderich (actually a real figure, King of the Ostrogoths who invaded Italy in the 4th century)who managed to capture Laurin and had him tortured until he revealed the secret entrance to his palace, that was thus sacked and destroyed. Laurin in his torments cursed the roses and said that they should no longer be visible by day or night - but he forgot dawn and sunset.
     
  28. Mr. Ezio, wonderful story! I'm taking your account as the definitive explanation of "alpenglow."
     
  29. "Do you live near Denali or were you just lucky enough to get those not-a-cloud-in-the-sky shots on a short visit?

    Jim, glad you like the Denali shots. I was on a photo trip in which John Shaw and Jack Dykinga were two of the four leaders. Almost every morning we were fortunate enough to have witnessed moments of "alpen glow" which lingered long enough for us to capture some good shots. I have some others of the Mirror Lake with McKinley at the background with pink clouds abound. It was quite an excitiing experience.

    The fleeting moments of "alpen glow" witnessed atop Mount Whitney was quite an exhilirating experience as well.

    Mary
     
  30. I caught a good shot of the division of the last red light and the earth shadow underneath- titled "Red Band Rising" in my high desert section. A couple of other desert shots have good views of the phenomenon. Watching the liftoff of that penumbra (I think that is the correct term) is spectacular.
    00FXiR-28637684.jpg
     
  31. this was taken moments before the previous one. The edge of the red band is just visible at the far right of the picture. I then picked up the tripod and moved to the adjacent site for the previous picture. A couple of minutes delay in between.
    00FXk3-28638184.jpg
     

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