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Terminology definition needed

post #1 of 22
Thread Starter 
Hi all,

 I just joined the forum and am looking for a bit of information.  I skied Saddleback Maine today and took a bunch of pictures of frozen snow and ice built up on trees, poles, towers, etc.......Anyone know what the proper term for this is? 
 I used to know it but spacing it right now.
 Here is a picture of what I am talking about......there are actually trees under there.

post #2 of 22
That is called Rime, and it forms on the upwind side of objects exposed to super-cooled moisture.
post #3 of 22
Quote:
Originally Posted by Cirquerider View Post

That is called Rime, and it forms on the upwind side of objects exposed to super-cooled moisture.

 

Pretty much a dictionary definition right here.
post #4 of 22
I've seen a lot of it.  Just remember, rime doesn't grow on a rolling stone.
post #5 of 22
Quote:
Originally Posted by Nomad72 View Post

Hi all,

 I just joined the forum and am looking for a bit of information.  I skied Saddleback Maine today and took a bunch of pictures of frozen snow and ice built up on trees, poles, towers, etc.......Anyone know what the proper term for this is? 
 I used to know it but spacing it right now.
 Here is a picture of what I am talking about......there are actually trees under there.


ummm never seen the top of mansfield eh?

post #6 of 22
Seems that hoarfrost is a better fit in this case than rime ice.  The former is more associated with vegetation and the latter with super cooled droplets ... and you could make an arguement that you may have to observe the process since both may fit.

I associate rime more of a problem with aircraft surfaces .... super cooled suspended droplets that collide with the wing until that compression in or near the surface in the pressure systems that develop at varying points..
post #7 of 22
Quote:
Originally Posted by Yuki View Post

Seems that hoarfrost is a better fit in this case than rime ice.  The former is more associated with vegetation and the latter with super cooled droplets ... and you could make an arguement that you may have to observe the process since both may fit.

I associate rime more of a problem with aircraft surfaces .... super cooled suspended droplets that collide with the wing until that compression in or near the surface in the pressure systems that develop at varying points..
no


http://www.avalanche.org/~uac/encyclopedia/rime.htm
post #8 of 22
Well, that depends on what site you go to and if you want to get into a  cat fight, never  get between two geologists arguing about schist.  It's kind of the same thing.

Your site calls rime kind of crumbly and crunchy .... however

A UK site (WeatherOnline.co) cautions the reader not to confuse hoar frost (not one word) with rime ice which is a hard glaze.

Now, I tend to agree with you in this case and stand corrected but I have seen in varied flying journals these two terms confused.
post #9 of 22
post #10 of 22
I'll bet the folks in AK know what they are talking about:

http://www.gi.alaska.edu/ScienceForum/ASF3/300.html

Like everything Epic, different words can mean the same thing and the same word can mean different things. Its all about who is righter and who is wronger. Am I right?

post #11 of 22
I always thought that stuff was rime, but I had never heard of "hoarfrost" until just now.  I was skiing Cannon this weekend and the trees looked like the OP's photo -- just buried under several inches of the stuff.

How do the trees survive with that much weight on them?  It would seem like that much weight would just snap the limbs right off.
post #12 of 22
They are often stubby little trees used to being blasted by winds up to 200+ mph. The rime is like a cast and is to an extent self supporting. Have you tried to break off a piece of rime? Or worse yet run into a tree covered in it? It gets hard and thick over time. It isn't all feather and soft throughout.
post #13 of 22

ski this!

post #14 of 22
Slider, that is a perfect textbook example of "chicken-heads"




The authoritative all-time thread by Physicsman for Names for Different Types of Snow was  made into a Wik for Snow Types and Namesi.  It would be great if members would edit that  with pictures
post #15 of 22
Truly beautiful with the sun shinning through the trees,but dangerous when Ice began to melt and fall. I will add some different Met. snow pics this PM to the wiki.
post #16 of 22

I'm sure these links cover it, but it's not that complicated. Rhime will always build up toward the wind. never down wind. That's what distinguishes it from other ice formations. If you see it on a chair that was stationary over night, all the pipe will have ice built up toward where the wind came from. Northerly wind, rhime on the north surface of things, chairs, trees, etc. I'll get a photo next time it takes a classic form.

That's the cutest little chicken (head) I've seen, or is it a diminutive penguin. penguins know a thing about ice.

post #17 of 22
MastersRacer, well, you have been righter !!   

And, it looks like the stuff in (Schtuff in German, highly technical), Sliders pics was caused by sublimation. 

How much of this do you think is caused by the "ice fog" of snowmaking (Schnowmaking in German) ... I think some of what has been depicted is "natural" and some is .. academic ... er ,,, incuced ???
.
post #18 of 22

There's a slim chance it's RIME, but a fat chance it's HOARFROST

post #19 of 22
Quote:
Originally Posted by Yuki View Post

MastersRacer, well, you have been righter !!   

Thank you!



It doesn't really matter to me who's right as long as we are learning. I was being facetious about definitions and their varied usage on Epic.

And, it looks like the stuff in (Schtuff in German, highly technical), Sliders pics was caused by sublimation. 

It is ice on the chairs; don't know what other form it may have had. It looks typical of what would happen if the chairs were near snow making ops. In the ground images its surface hoar created by sublimation. On the last tree shot, it is presently mostly ice, although it could have been rime or hoar to start. It has melted and lost its original identity.

How much of this do you think is caused by the "ice fog" of snowmaking (Schnowmaking in German) ... I think some of what has been depicted is "natural" and some is .. academic ... er ,,, incuced ???
.
 
post #20 of 22
I love learning new things every day, this is some great stuff! All very interesting.
post #21 of 22
Hoar frost has significant implications to snow layer bonding and snow pack analysis. It makes a poor bond between layers when present.

Rime doesn't exist without the effects of wind. Rime will not be found hanging down, dripping down, frozen down. And never in the lee of the wind.
post #22 of 22
Hoar frost and rime are very different animals and as Dave said above, its really important to be able to recognize hoar frost.  Hoar tends to be delicate large crystals.  It breaks apart easily and if it becomes trapped in a layer of snow, it will lubricate the slab above and can cause very dangerous conditions.  Hoar forms in calm conditions and grows in elaborate well-formed translucent crystals up from the surface of objects or the snow surface.  The crystals are often clear enough to separate light like a prism and this shimmering appearance in sunlight is very different from the dense white coating of rime.  Hoar cannot form or exist in strong winds.  Another term for hoar is radiation frost. 

Rime is a form of advection frost.  Advection frosts form into the wind but it occurs under slower crystalizing conditions and can look a lot like hoar.  Rime occurs rapidly.  It is harder smaller crystals.  The formation is very dense and individual crystals are very tiny and will be more opaque (white) than hoar frost, and it usually shows the opposite of a "flag" as it grows into the wind.

So they are both frozen water that condenses and forms on objects, but they have very different characteristics.  For me, when you hit a tree laden with rime, it hits back hard and breaks in chunks.  Hoar explodes into a shower of ice particles that go down your neck and into your goggles.  Next time you see frost and want to identify it just hit it.  The answer will come.
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