I've noticed that snow seems to reflect red light more than any other wavelength at night. It's seen in the sky, as well as the snow itself, both of which take on a reddish tint. Why exactly does it do this? Additionally, why is this only noticeable under moonlight? If it's the moonlight that's tinted red, then alternatively, why is that? My apologies for the rather basic question, but I can't seem to find information on the matter elsewhere.
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1$\begingroup$ We don't get snow that much in the UK, but my memory of the last major snowfall was that everything looked bluish rather than reddish. This was during the day, but moonlight is also bluish provided the Moon isn't near the horizon. Was the Moon low in the sky when you saw the reddish colour? $\endgroup$– John RennieFeb 14, 2014 at 10:44
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$\begingroup$ I believe it was around 30 degrees from the horizon, so it could have been atmospheric interference. I actually hadn't thought about that. $\endgroup$– caseifFeb 14, 2014 at 21:11
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$\begingroup$ During winter nights I observed reddish lighed snow below streetlights (sodium-vapor lamp which has amber/yellow light) while the areas that were lighted by the moon looked blueish. This makes sense. Since you mentioned moonlight, I guess you've observed the same like me? $\endgroup$– try-catch-finallyJun 15, 2014 at 8:15
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2 Answers
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According to most sources such as this university page on albedo and this modeling paper on albedo versus wavelength, the typical albedo of snow is virtually 1 throughout the visible region, so it seems unlikely that it is the snow itself which is causing this effect.
Also, I've never personally observed this as John Rennie stated, so perhaps it's caused by something else in your case, such as an atypical source of illumination.
answered Feb 14, 2014 at 15:09
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Since red is on the opposite spectrum of blue, I would assume we perceive the reflection of red in greater concentration because the blue sky is reflected on the neutral(white) snow. This is more intuition based however. A good experiment would be to test different colors in pitch darkness to see if red still is the dominant reflected color.
