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More Snowflake Photographs with Classifications
I found Jon's post regarding the Magono-Lee Snow Crystal classification system to be quite interesting. Here are some more shots from Monday night - I'll see if I can classify them... something tells me that will be more difficult than it sounds.
Let's start with something simple. My first guess is that the two crystals that follow would be classified as P2d - Dendrite with Sector-like ends:
It looks like that crystal bumped into a couple of simple plates along the way, and they are stuck to it in the lower right quadrant.
The one below has one spot of rime on it - which I assume is not enough to knock it into the rimey category, so it too is a P2d:
This one is similar in general form to the one above, but has a bit of rime spotting it up. I guess it would fall under rimed stellar R1d under Magono-Lee's system. Personally, I think it would make more sense to have rime as a qualifier of the basic shape, so if I was cooking up a classification scheme I'd call this a Dendrite with Sector-like ends with moderate rime. Maybe P2d-r2.
The next one is a 12 branched crystal without rime, so it is either a P4a (broad branched with 12 branches) or a P4b (dendrite with 12 branches.) Personally, I'd call it a 12 branched variant of the P2d formation, which we just saw above. Maybe P2d-2x? Well - under the existing system it is either a P4a or P4b...
You may have noticed what looks like a sectored plate emerging from one arm at about the 8 o'clock position - that appears to be a growth at the end of that arm.
OK - let's get back to something simple. I think the following are all ordinary dendrites - P1e.
This first one has a 'crack' in the center plate - something I've seen several times. I'm not sure what causes it.
And I'll close out with three rimey subjects, the first two would be R1d - Rimed Stellar and, I think, the last one would be R2b - Densely Rimed Stellar. Though one might think it was a densely rimed fernlike stellar dendrite - maybe P1f-r3, eh?
Magono-Lee is an interesting classification system. I don't understand exactly why it places such an emphasis on rime at the expense of the core structure of the crystal. It seems to me that rime is an incidental condition independent of the core structure of the crystal. Classifying rimey crystals as a distinct group is sort of like lumping all molting birds into a distinct group. But just as Nietzsche observed that histories reveal almost as much about the historians who wote them as about actual past events, I'd speculate that classification systems tell us a bit about the people who developed them as well as the subjects being classified. Maybe rime was important to Magono or Lee...
So - how many did I get right, Jon?
- Mark
mark This entry was posted on February 17th, 2010 at 10:56:32 pm by Mark and is filed under Photos, Snow Science.
2 comments
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.
Jon
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