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How to classify snow crystals
According to Edward LaChapelle’s Field Guide to Snow Crystals (1969), the most widely used classification for falling ice is a system of 10 types from the International Commission on Snow and Ice, which came out in 1951. A few years later, ice researcher Ukichiro Nakaya published a new system with four times the number of ice types. The number doubled 12 years later in 1966 when Magono and Lee published an extension of Nakaya’s system. Of all systems, I think Magono and Lee’s classification of 80 types gets the most use nowadays, so I show it here to help make more people aware of it.
To classify a crystal, you simply look at the table below and find the example that most nearly resembles your crystal. This table is a scanned copy of the one in LaChapelle’s book, with some markings cleaned up and a little color added. Click on it to enlarge.
For example, the crystal in Mark's Feb. 14 posting is P1c, a broad-branch crystal.
The number 80 seems large, but even this system has notable omissions. Magono and Lee include graupel (R4a, R4b), which are crystals that collided with many supercooled droplets, but they exclude crystals that collided with and adhered to other crystals. That is, they exclude snowflakes. Other omissions include distinct forms like the spearhead and seagull types as well as sub-divisions of forms they do include; for example, plates like P1a except with unequal sides such as the oft-sited trigonal forms (alternating prism faces are shorter/longer), and hollow columns like C1f except with hollows on all faces. And although they include 12-branched crystals, they don’t include 18 and 24-branched forms. They probably had a good reason for excluding these forms, but it would be nice to have a more complete table for the avid naturalist to refer to.
Choji Magono was a professor of geophysics at Hokkaido University in Sapporo Japan, and C. W. Lee was his student. I’ve known about other work by Magono for some time, but I’ve never found any other publications by Lee. I recently asked about Lee to someone who once was a student there, and he told me that Lee returned to North Korea soon after getting the PhD, apparently never to be heard from again. It sounds like a sad ending for a once very promising young researcher. If you can read this Lee, here’s a big thanks for your great dissertation work.