 EPOD - a service of USRA

The Earth Science Picture of the Day (EPOD) highlights the diverse processes
and phenomena which shape our planet and our lives. EPOD will collect and
archive photos, imagery, graphics, and artwork with short explanatory
captions and links exemplifying features within the Earth system. The
community is invited to contribute digital imagery, short captions and
relevant links.


 Archive - Blue Light From Deep Snow

   December 19, 2020

    Bluesnow

   Every weekend we present a notable item from our archives. This EPOD
   was originally published December 22, 2003.

   Provided by:  Cindy Foster
   Summary authors & editors:  Jim Foster

   After a big snowstorm, when you're shoveling your walkway or just
   measuring how much snow fell, have you ever noticed a turquoise or
   robin egg blue color? The color isn't due to blue snowflakes nor is it
   a result of the same process responsible for making the sky look blue.
   Rather it results from the optics of large, non-spherical particles. If
   new-fallen snow is more than about 10 inches (25 cm) deep, the myriad
   snow crystals both scatter and absorb sunlight (even on an overcast
   day). The longer wavelengths (red and yellow) of visible light are more
   readily absorbed than are the shorter wavelengths (greens and blues).
   Eventually, the red light is completely absorbed, and only blue light
   emerges when a hole is poked into the snow. If the hole is deep enough,
   the blue color completely disappears since all of the light will be
   absorbed.

   The photo above was taken last February in Silver Spring, Maryland the
   day after a powerful nor'easter buried portions of the Middle Atlantic
   region and New England under nearly 2 feet (60 cm) of snow. Anytime
   this thick mantle of snow was jabbed with a yardstick, blue light was
   liberated. Here's hoping that you have a nice Christmas and that no
   blue snowflakes start falling or blue memories come calling.


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    EPOD 20th - Lake Michigan Ice Balls Recurrence  EPOD 20th - Hair
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Cryosphere Links

     *  Guide to Frost
     *  What is the Cryosphere?
     *  Bentley Snow Crystals
     *  Glaciers of the World
     *  Ice, Snow, and Glaciers: The Water Cycle
     *  The National Snow and Ice Data Center Google Earth Images
     *  Snow and Ice Crystals

-
   Earth Science Picture of the Day is a service of the  Universities
   Space Research Association.

https://epod.usra.edu
 
