« Chicago Public Library "Best of the Best - 2010" ListThree From This Evening »


Comment from: [Member]

I have a hard time taking my eyes off the first crystal - such a clean and sharp image!

So, I came up with a few different ones than you. One difficulty is in choosing the underlying pattern. For example, is the underlying pattern in #1 dendritic or stellar? You thought the former, I thought the latter.And then there is a grey zone between ordinary dendrite and fern-like. Another difficulty is distinguishing sectorlike from plate extension.

As I read things, a dendrite should have some significant sidebranches, whereas a stellar should have no major sidebranch.

About sectors, I’ve never seen anyone really clarify the meaning, so I’ve taken it to mean segments that have almost a pie-slice shape. I didn’t see this in #1, so I voted for P2a, stellar with plates at the end. It is true that the plates have some small sidebranches at the ends, but they seem like small additions at the end of growth so I ignored them. (Stunning though!)

On #2, I also went with plates at the end, calling it P2c - dendrite with plate ends.

On 3,4,5&6, I got the same as you: R1d, P4a, P1e, and P1e.

#7 seemed close to fern-like, so I voted for P1f. But it is a tough call.

#8 is a toss. I figured it could be either R2b or R1d. I leaned towards the former though, and you picked the latter.

#9 & 10 I got the same as you: R2b.

Interesting view about the classification with all the rime. They must explain the choices in their 1966 article. I have the article somewhere in my collection, but can’t find it.

I suppose though that they wanted the classification to give useful knowledge about the cloud conditions. Rime is a very useful observation because it tells us that the cloud had a lot of liquid water (i.e., many drops). The underlying shape is important too, but harder to interpret, even now. Presently, we don’t have enough knowledge to be able to infer the humidity and temperature except in special cases, like the fern-like form. For example, broad-branches can form at two temperature zones.


02/18/10 @ 19:02
Comment from: [Member]

Your interpretations of how to classify the snow crystals make a lot of sense, Jon. And thanks for the kind words about the first image in the post –the snow can fall in beautiful crystals when conditions are right, but more often than not I see rime cover and fluffy white, opaque crystals. The clean and translucent ones are a rarity.

- Mark

02/20/10 @ 17:55

Form is loading...