 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.


 Angle of Repose for Graupel

   January 28, 2021

    Image

    Graupel4a

   Photographer:  Roger Hopkins
   Summary Author:  Roger Hopkins

   The  Nor’easter that visited the northeast U.S. on December 16-17,
   2020, brought 13 inches (33 cm) of fine-grained  graupel to Lansing,
   New York, and an amazing 40 plus inches (100 cm) of  snow and
   graupel to Binghamton, about 40-miles (64 km) to the southeast. The
   above photos show the  angle of repose of these small uniform
   graupel pellets as they accumulated on horizontal surfaces. Graupel
   pellets bounce on impact and roll like tiny BBs off the edges of the
   pile. After a few hours, the pellets within the pile can weld together
   and as the height of the pile increases, fewer will land on the top,
   creating  a pointed witches hat shape. My measurements show an angle
   of approximately 65 degrees. Note that the  Avalanche Handbook and
   other sources show values that range from 35 degrees to as high as 80
   degrees.

   The top photo (at left, courtesy of Scott Geiger of Binghamton) shows
   his car with piled-up graupel that was still growing when the storm
   abated, while the fence posts (at top right in Lansing) could only
   sustain 3 inches (8 cm) high caps. The bottom photo illustrates the
   interesting effect on a round rotating surface; two soda bottles
   forming my squirrel barrier that will henceforth be called my snow
   accumulation rotisserie.
     * Lansing, New York Coordinates:  42.4842, -76.4799

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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

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

https://epod.usra.edu
 
