That Snow Joke

November 17th, 2017

A variation on a joke I heard from the UK Laugh Lab, customized for you snow-blog readers:

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Sherlock Holmes and Dr Watson go snow camping. After a day snowshoeing around the forest, they return to their camp, have some wine, and crawl into their sleeping bags.

Some snow flurries drift down.

Sherlock says to his friend "Watson, the snow is falling on us, what does that tell you."

Watson gazes up at the drifting flakes, thinks for a moment, then replies:
"Well, first off, I'd say that the forecast was wrong, but snow is notoriously difficult to predict so I won't disparage the meteorologist. About this particular snow, it appears to be nicely branched dendrites, so I'd deduce then that they formed near negative fifteen degrees, surrounded by small droplets. Furthermore, I'd...Er, what are you doing?"

Sherlock was out of his bag, looking around the camp.
"Watson, Someone has stolen our tent!"
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- JN

Grain boundaries between crystals in big ice

November 6th, 2017

Most snow crystals are single crystals. Being single is an outcome of their growth process and small size. On the other hand, most larger ice formations are not single crystals. These latter types are called "polycrystals". A polycrystal usually appears the same as any other type of ice -- smooth, uniform, clear or white -- just as if it were also single crystal. But the poly nature can be revealed when the ice warms to the melting temperature. At melting temperature, the boundaries between the separate crystals become visible. As an example, note the white lines in the ice in the inset in the image below.

Grain boundaries between crystals in big ice


(This image is from the ice drip complex in the previous post.) We call each individual crystal a "grain", and the boundaries between grains as "grain boundaries". The grain boundaries show up because the region has disordered ice that will melt at a lower temperature than regular ice. Thus, the light, upon passing through a grain boundary, will scatter more, making a whiter region, as shown in the image.

The ice is thus weaker on a grain boundary and has a tendency to break along these boundaries. On the surface of ponds and lakes, the grains (individual crystals) can be several inches or more across. So, if you get a sheet of such ice, and let it warm up to melting, you will find it easy to break the ice sheet along a grain boundary and thus isolate a large single crystal.

The size and pattern of the grains affect the mechanical properties of the ice. So, glaciologists, who want to know how a given glacier or ice sheet moves, are very interested in such patterns. They call this pattern the "ice fabric".

-JN

Sheet icicles

November 6th, 2017

On a bitter cold day in 2013, I was at a familiar cliff, climbing under a large rock ceiling. A little water had been seeping down through the crack above, forming an ice-filled crack that I had to dig out with my hammer to proceed. In a few spots, the water drips had detoured, meandering along the granite ceiling and freezing into very thin s-curved ribbons of ice. I'd never seen any drip formation so bizarre, or even seen a picture of anything like them. But my camera was far below, and I had to regretfully blast through the ice to proceed.



Recently I came across another thin, sheet-like ice formation on a small tree under a drip. In this case, the sheets followed a twig, and thus did not meander in s-curves. But they were similarly thin and sheet-like. Call them "sheet icicles". This time I had my camera handy.



Here's an overview of the drip formation.

Sheet icicles


And a close-up of one of the sheet icicles.
Sheet icicles


Full story »

The "Snow Candle"

November 6th, 2017

If you go about 50-km northwest of Sapporo, Japan, aiming to stay on the coast, you will land in the port city of Otaru. Like Sapporo and the rest of Hokkaido, this is snow and ice country. Here in Otaru, they have a "snow candle" festival every winter. The snow candles are just partly scooped out, upside down, packed lumps of snow with a lit candle inside. (Perhaps a better name would be "snow lantern".) They make them in quantity by packing a standard-sized plastic bucket with snow, scooping out part of the center and side, then turning them upside down and removing the bucket moulding. Then they put a standard, short candle inside and light it. When they are all lit, they appear like small glowing igloos along various walkways and attract large crowds at night.


Yasuko made a mini version recently, and brought it indoors. Instead of using a bucket and standard-sized candle, she used a coffee mug and snipped birthday-cake candle.

The "Snow Candle"




It lasted only about 15 minutes. But if you make it like they do in Otaru and keep it outside, it may last much of the evening or night.



- JN

A Fogbow

October 25th, 2017

A fogbow, or cloudbow (fog is a type of cloud), is a special type of rainbow. It is just white, and so not as often photographed as the full-spectrum rainbow, but it can be exciting to see nevertheless.

A Fogbow


The reason the fogbow is white is because the water droplets in fog are much smaller than raindrops. Fog droplets may vary in diameter roughly between 1 and 20 millionths of a meter (i.e., 1-20 microns), whereas raindrops are typically 1-3 thousandths of a meter, or about 500 times larger. The wavelength of visible light is only about a half a micron, so the light rays inside a fog droplet are still fairly well defined, but there is simply not enough room to separate out the colors, to state things simply.

Upon approaching a fog in the morning, look towards, but above your shadow. About 50-60 degrees from the shadow of your head is where the fogbow will sit, just as it would for a rainbow. Evenings will work too. But midday, the angles 50-60 degrees above your shadow will have you looking at the ground, so you probably won't see a fogbow there. (If you are in an outdoor shower, you might see a rainbow though.)

The above photograph shows the fogbow I saw yesterday morning, about 8:30 am, biking into a nearby park.

-- JN

New paperback edition out, Sept. 2017

October 25th, 2017

After eight years, several translated editions, a teacher's guide, and a Scholastic edition, The Story of Snow had a paperback edition, also from Chronicle books. The size is the same, and the content is the same except for one thing. This version lists some of the glowing reviews and accolades on the inside cover (click on image to read):

New paperback edition out, Sept. 2017



- JN

Concentric Film Frost

October 25th, 2017

October 16, 2017, the first frost of the 2017-18 winter as far as I know. Frost in Eastern Washington anyway, those of us on the west side of the Cascade Mts have not gotten any yet. Marc Fairbanks, an avid nature observer from the mountains near Cle Elum, sent me the following shot (click on the image to fully appreciate the pattern).

Concentric Film Frost


This is primarily film-frost, that is, is based on ice that formed when liquid film froze. But as I discussed in a previous post, some important growth processes here also occur through the vapor phase:

http://www.storyofsnow.com/blog1.php/crystal-to-crystal-communication-through-vapor-and-heat

I had even earlier noted some "ripple" patterns on a windshield and mused about their formation:

http://www.storyofsnow.com/blog1.php/ripples


As I'll discuss next, there are some other illuminating observations here.

Full story »

A complete picture book of all (known) snow types

February 24th, 2017

Prof. Katsuhiro Kikuchi, a highly regarded ice and snow researcher from Hokkaido, Japan, kindly mailed me a copy of his wonderful new book (coauthored with Dr. Masahiro Kajikawa). Never before has there been anything nearly as complete as this book in describing and showing all known types of falling snow. It is called "Picture Book of Natural Snow Crystals” and published by the Hokkaido Shinbun News Paper Co., Sapporo. 

A complete picture book of all (known) snow types

The only issue for most of the readers here is the fact that it is written in Japanese. This issue though does not mean one cannot learn a lot from the pictures. Here are a few sample pages: 

First, the broad-branch planar crystals P4d, P4e, and P4f: 

A complete picture book of all (known) snow types

Next, some basic combination forms (columnar and planar), specifically CP1a and CP1b: 

A complete picture book of all (known) snow types

A few of the above have been named after the Japanese-type drum "tsuzumi" due to their resemblance to this drum. Next, a type named for its resemblance to a flying seagull, the CP9a and CP9b: 

A complete picture book of all (known) snow types

Finally, a sample of the many explanatory diagrams: 

A complete picture book of all (known) snow types

The above diagrams explain how some crystals transform from a frozen sphere ("droxtal"), which all snow-crystals begin as (excluding broken fragments), to the larger forms we see on the pages. About these crystal images, Prof. Kikuchi collected them from a range of locations he visited including his nearby area of Hokkaido and Honshu, and further north and south, to the Arctic, Greenland, and the South Pole. So, though it may be possible, don't expect to see all these forms in your neighborhood. 

Overall, it is an amazing book, and I wish we had something like it in English. 

 

- JN

 

 

Columns!

January 18th, 2017

The poor columns get left out of nearly all snow-crystal discussions, but they are an interesting type. So, to help them out a bit, here's my first column appreciation post. 

Let's start with perhaps the most extreme column of all, the Shimizu prism*: 

Columns!

I say 'extreme' because they are so long and thin--sometimes over 1-mm long yet just 0.01-0.02 mm in diameter. These types have so far been found to fall only on the Antarctic Plateau. But in theory, they should be able to form elsewhere. It is like a "whisker" crystal, which Teisaku Kobayashi grew below -50 C on a surface in the lab.  The image above shows many other crystals as well, including another solid column crossing the Shimizu prism.

Next, the bullet rosette: 

Columns!

The bullet rosette is most often found below -25 C in high cirrus clouds. It is an example of a polycrystal; in this case, a frozen droplet that froze into several distinct crystals (one for each "bullet"). 

Next, one of my favorites, the scroll column (though the picture doesn't quite do it justice): 

Columns!

In this form, the sides of the crystal seem to fold inward, like a scroll. 

Finally (for now, anyway), the ubiquitous hollow column: 

Columns!

 The funny banding you see (horizontal lines inside the 'hollow') is a mystery. 

There are many other columnar forms, many of which are in the following diagram (as with all images here, click on it to see it enlarged)**: 

Columns!

 One neat thing about the columnar forms is that you can see roughly exact replicas of them in hoarfrost. The Shimizu prism may be hard to find, but the others are common if you look closely. 

 

-JN 

 

* Images are from the Magono & Lee collection, used in their paper: Meteorological classification of natural snow crystals. J. Fac. Sci., Hokkaido Univ., Ser. VII 4, 321335.

 

**Drawings are based on those in Kikuchi, Kameda, Higuchi, and Yamashita: A global classification of snow crystals, ice crystals, and solid precipitation based on observations from middle latitudes to polar regions. Atmos. Res. 132-133 (2013) 460-472. 

 

 

How clouds form snow

January 14th, 2017

To understand snow formation, one must know a little about clouds. 

Q: What is in a cloud?

A: Air, dust, vapor, droplets, and often, ice. 

Q: How much air? How much liquid water? How much ice?

A: The answers will probably surprise you. See my short 20-min presentation below. I gave this recently to the Bellingham, WA Snow School. (23 slides, but due to file-upload-size restrictions, I had to put them into three parts below, 10 slides, 6 slides, 7 slides.)

Snow, rain, and weather affect everybody, yet how many of us learned in school even the most basic facts about precipitation in school?

Q: Who first realized how ice grew in a cloud?

How clouds form snow

As described in my presentation, he realized this by observing frost on the ground. 

Q: Who first realized how Alfred's theory was intimately connected with rainfall? 

How clouds form snow

Tor discovered this by observing fog in a mountain forest, and like Alfred, applied some of his physics knowledge. 

In my presentation, I discussed Alfred Wegener, the roles of the different cloud components, and briefly how the ice, once formed, takes on its strange shapes: 

 

First 10 slides (with blue text added to account for the things I said during the talk):

http://www.storyofsnow.com/media/blogs/a/Jan2017/snowschool_annotated1t10.pdf?mtime=1484585328

 

Next 6 slides:

http://www.storyofsnow.com/media/blogs/a/Jan2017/snowschool_annotated11t16.pdf?mtime=1484585328

 

Last 7 slides:

http://www.storyofsnow.com/media/blogs/a/Jan2017/snowschool_annotated17t23.pdf?mtime=1484585309

 

 

Later, I will show specifically how the ice gets arranged into all these strange shapes. 

- JN