Monday, December 29, 2014

Skiing :) New Snow and Rime

Before Christmas I went on a ski trip with my cousins to Brundage Mountain. Brundage is a ski resort near McCall, Idaho. They claim to have the "Best Snow in Idaho." The days we skied didn't have the best snow, but I'd say the view is one of the best!

The day before skiing the mountain received about of foot of new snow. After the first ride up the Bluebird lift it was apparent there was a lot more weather going on the night before than just snow. Everything at the top of the mountain was covered in thick rime. The wind sensor on top of the ski patrol hut was surely not working properly.

Ski Patrol at the top of the mountain.
Rime is caused when the temperatures are below freezing, but the cloud droplets aren't quite frozen--the cloud is still liquid. Water doesn't necessarily freeze at 0 degrees Celsius. It needs something to freeze onto. For example, water will freeze onto dust particles (I suppose this is why as a kid I was always told that snow is dirty when it falls from the sky).

Liquid cloud droplets below freezing are called supercooled. Riming occurs when supercooled droplets hit something they can freeze onto. The droplets then freeze on contact. From all the riming on all the trees, chairlifts, towers, and buildings, it is apparent that the clouds last night were supercooled.

A general wind direction can also be inferred based on the side of the object the rime is located. You can see in the picture below that most of the rime is on one side of the post. That is the direction the wind was blowing. The wind blew the supercooled droplets onto one side of the post.

Also notice the detail in the rime. This isn't the same thing as snow. It's not made of flakes. Instead, it looks a lot like the frost build up you would see in an old freezer.
Snow flakes can also be rimed. Since the top parts of a cloud are much colder than the bottom, ice crystals are common at the top of a cloud while the bottom of the cloud can be made of supercooled droplets. As the snowflake falls through the cloud it collides with the supercooled droplets and we get graupel! Those soft, hail-like snow pellets.

Below are pictures of snow flakes taken by a multi-angle snow flake camera. On the left is a normal snowflake, the middle is a flake that is lightly covered in rime, and the right picture is a flake completely covered by rime, otherwise known as graupel.

More pictures of skiing:

On the way home from Idaho my cousin and I had to rent a car in Boise to drive to Salt Lake. We took rode the Frontrunner the rest of the way home. We looked like a pair of ski bums carrying all our gear and Christmas packages.

And just a few days after Christmas I took my younger brothers skiing at Sundance. It was the first time for two of them, and they caught on quick. I'll have to take them up again. Hopefully we'll have better snow this week. It was a really icy. 

This is what it looked like on the University of Utah campus Monday morning. Probably wont get much more between now and next ski trip.

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