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john65pennington's avatar

Why do the clouds appear to have a pink color, just before a snowfall?

Asked by john65pennington (29057 points ) January 10th, 2011

My wife has brought this question up to me on several occasions, just before the snow begins. Question: to you, just before the snow falls, do the clouds appear to have a pink cast to them? If so, why is this and what is your opinion?

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9 Answers

JLeslie's avatar

I think of pink at sundown, when the next day will be dry and clear. I will have to look for pink before a snowfall. I am interested to see the answers.

Meego's avatar

I always went by red sky at night sailors delight, red sky in the morning sailors warning, otherwise I have no clue but wiki says this:

Cloud iridescence occurring in clouds

Sunset reflecting shades of grey and pink in clouds.
The color of a cloud, as seen from the Earth, tells much about what is going on inside the cloud. Dense deep tropospheric clouds exhibit a high reflectance (70% to 95%) throughout the visible spectrum. Tiny particles of water are densely packed and sunlight cannot penetrate far into the cloud before it is reflected out, giving a cloud its characteristic white color, especially when viewed from the top. Cloud droplets tend to scatter light efficiently, so that the intensity of the solar radiation decreases with depth into the gases. As a result, the cloud base can vary from a very light to very dark grey depending on the cloud’s thickness and how much light is being reflected or transmitted back to the observer. Thin clouds may look white or appear to have acquired the color of their environment or background. High tropospheric and non-tropospheric clouds appear mostly white if composed entirely of ice crystals and/or supercooled water droplets.

As a tropospheric cloud matures, the dense water droplets may combine to produce larger droplets, which may combine to form droplets large enough to fall as rain. By this process of accumulation, the space between droplets becomes increasingly larger, permitting light to penetrate farther into the cloud. If the cloud is sufficiently large and the droplets within are spaced far enough apart, it may be that a percentage of the light which enters the cloud is not reflected back out before it is absorbed. A simple example of this is being able to see farther in heavy rain than in heavy fog. This process of reflection/absorption is what causes the range of cloud color from white to black.

Other colors occur naturally in clouds. Bluish-grey is the result of light scattering within the cloud. In the visible spectrum, blue and green are at the short end of light’s visible wavelengths, while red and yellow are at the long end. The short rays are more easily scattered by water droplets, and the long rays are more likely to be absorbed. The bluish color is evidence that such scattering is being produced by rain-sized droplets in the cloud.

A greenish tinge to a cloud is produced when sunlight is scattered by ice. A cumulonimbus cloud emitting green is an imminent sign of heavy rain, hail, strong winds and possible tornadoes.

Yellowish clouds are rare but may occur in the late spring through early fall months during forest fire season. The yellow color is due to the presence of pollutants in the smoke.

Red, orange and pink clouds occur almost entirely at sunrise/sunset and are the result of the scattering of sunlight by the atmosphere. The clouds do not become that color; they are reflecting long and unscattered rays of sunlight, which are predominant at those hours. The effect is much like if one were to shine a red spotlight on a white sheet. In combination with large, mature thunderheads this can produce blood-red clouds.

Clouds look darker in the near-infrared because water absorbs solar radiation at those wavelengths.

Baddreamer27's avatar

“Red sky at night-a sailors delight. Red sky in morning-sailors warning” This was passed on to me by my grandfather. He said if the sky is red in the morning the weather will be good, but red in the morning and look for the weather to turn. I looked it up and found that when the sun is low in the sky as it is in morning and evening it’s light is shining through the thickest part of the atmosphere. When the sky at night is red it is the light coming through a heavy concentration of dust and high pressure coming in from the west…meaning good weather should follow. When the sun rises in the east and is red, the light is shining through a weather system that just passed and a fiery red could mean alot of moisture meaning rain is coming. Dont know if it is related to snowing, but I would guess that its just the moisture in the clouds reflecting the light.

Baddreamer27's avatar

Meego beat me to it! But very well answered!

gailcalled's avatar

@Meegol Very good answer but do you have a source?

Meego's avatar

Oh ya my source was Wikipedia.

gailcalled's avatar

Here we get a lot of snow. The cloud cover always seems to be gunmetal grey. I do not recall seeing a pink cast, but I will have a chance tomorrow night and Wed. morning to check yet again.

Adirondackwannabe's avatar

Get a glass prism, hold it in sunlight and look at the colors. Same principle applies with clouds and light refraction.

gailcalled's avatar

Snow flurries here. I would be thrilled to see some pinkish streaks above but it is a 1984 grey, from horizon to horizon.

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