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United States Department of Agriculture

Agricultural Research Service

Title: The Structure and Metamorphism of Snow Crystals As Revealed by Low Temperature Scanning Electron Microscopy

Authors
item Wergin, William
item Rango, Albert
item Erbe, Eric

Submitted to: Proceedings of the Eastern Snow Conference
Publication Type: Abstract Only
Publication Acceptance Date: March 2, 1996
Publication Date: N/A

Technical Abstract: Low temperature scanning electron microscopy (LTSEM) was used to observe precipitated and metamorphosed snow crystals commonly known as "snowflakes". Snow was collected from sites in Maryland, West Virginia, Colorado and Alaska. The samples consisted of freshly precipitated snowflakes as well as snow collected from snowpits measuring up to 1m in depth. The samples were frozen in LN2 and then transferred either to a cryosystem mounted on an SEM or to a storage dewar. LTSEM observations revealed that precipitated snowflakes, consisting of plates, columns, needles and dendrites, did not appear to be affected by storage. Snowpacks that had been exposed to temperature gradients contained crystals with unique structural features and bonding patterns that resulted from variations in temperature and pressure. Melt-freeze cycles were also associated with the appearance of "red snow" resulting from the presence of cells believed to be an alga. This study indicates that LTSEM is a feasible technique for observing snow that was sampled at remote locations and determining the shapes of precipitated and metamorphosed snow crystals. The results assist research activities that forecast water in the winter snowpack and predict the amount that will be available for agriculture.

Last Modified: 11/21/2014
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