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Posts tagged ‘weather’

Hoar Frost and Rime Ice: What’s the Difference?

The New Year dawned cold in the badlands of South Dakota.  Temperatures in the low single digits at sunrise on January 1 warmed to a balmy 30°F by midday.  The sunny, calm conditions were perfect for my first hike of 2013.  I hadn’t walked fifty feet from the trailhead, however, before the sun glinting off the surface of the snow captured my attention.  I commonly see delicate sparkles on the snow in the morning sun, but these were bold flashes coming from platy ice crystals the size of my thumbnail.

I knelt to see better, and exclaimed in delight.  Even with my naked eye, I could see fine growth ridges running parallel to the edges of each plate, forming beautiful facets.  My first thought was surprise that such big, perfectly hexagonal snowflakes could have persisted since the last snowfall, several days ago.  But then I realized that the ice crystals weren’t old snowflakes at all: they were a beautiful example of surface hoar. Read more

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