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11 Wonderful Winter Weather Terms

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When winter bears down, it can be hard to think of anything outside of how much you hate (or love!) the snow and ice. But there’s more to winter weather than you might think! Here are a few of the words and phenomena that could define this season.

1. Hoarfrost

John Primm

One of the first signs of winter is the hoarfrost of late autumn. Deriving its name from an Old English word (hoar), meaning “to appear old,” this is the thin, crisp coating of ice that often forms on objects during cool nights with clear skies. The clear skies allow the ground to lose heat more quickly than the surrounding air, and the humidity in the atmosphere condenses and freezes solid. This frost can occur even when the air a few feet above ground is well above freezing, and usually melts within an hour or two of sunrise.

2. Frost Flower

Wikimedia Commons

Frost flowers (and the related “ice ribbons” and “ice beards”) are very thin, spindly, unique formations of ice, seen in late autumn or early winter, when plants are first freezing.

When the water in the plant stem freezes, it expands to the point where the plant splits open along the side, and the frozen water is extruded from the split. More water is then drawn up from the ground via capillary action, and the flower continues to grow all night long.

Because of this water requirement, the ground must be damp, but not frozen, and because the frost flower splits the stem open, they only form once a year from any individual plant. These beautiful formations generally form during the first hoarfrosts, and are best found in unmowed areas with lots of weeds and brambles. Though not uncommon in certain areas, this ephemeral event is rarely seen before it sublimates or evaporates. 

3. Glaze Ice

When falling rain hits a roadway or surface that’s below freezing, it instantly forms what’s known as “glaze ice,” a buildup of transparent ice that is an extreme danger to drivers. This is also one of the causes of black ice, which is actually clear, and thin enough that it appears to be the same color and texture as the asphalt and macadam it has accumulated on. (Black ice can also be caused by the freezing of standing water or compacted snow, in which case, it's not glaze ice.) Glaze ice has contributed to some of the costliest ice storms in history, such as the 1998 North American ice storm, and the 2010 New Year's storm in the United Kingdom.

4. Hard Rime

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As the weather cools further, freezing fogs can occur, and when that fog is combined with wind, hard rime can form on windward (wind-facing) surfaces. “Rime” literally means “hoarfrost,” and while slightly different on a meteorological level, “soft rime” is very similar to a thick hoarfrost. Hard rime, on the other hand, is much thicker and harder to remove, and consists of fairly dense pellets of irregular ice crystals.

Though it’s generally seen at high elevations (mountain-based weather observatories often have serious problems with hard rime coating their instruments), this icy coating can form anywhere that a freezing fog and wind occur simultaneously. It’s rarely seen below -8 C (17.6 F), because colder air cannot hold enough moisture to create freezing fogs.

5. Thundersnow

The conditions required to create thundersnow are most common around lakes (it occasionally accompanies “lake-effect snow”) and coastal areas. In these places, the sun is able to heat the ground and cause (relatively) warm and humid columns of unstable air to rise up, and form turbulent clouds.

But clouds alone don’t make thundersnow. Only if the layer of air between the clouds and the ground is warmer than the cloud cover, but still cold enough to create snow, and the wind shear is pushing the warmer air slightly upwards, does thundersnow form. (In lake-effect thundersnow, the temperature has to be at least 45 degrees Fahrenheit higher below the clouds than at the cloud top for the phenomenon to occur.)

Most instances of thundersnow occur during extreme storms, with high-intensity wind and accumulations of between 2 and 6 inches of snow per hour. The lightning bolts are rarely visible as they are in summer thunderstorms, and the snow can often muffle the thunderclap, meaning that many instances of thundersnow go unnoticed.

6. Snowpack

Gallatin National Forest Avalanche Center

When a place has an extended cold season—like the majority of Canada, for example—snow rarely melts between each subsequent snowfall. Some of it will sublimate—or transition directly from a solid to a gas—especially in areas with lots of sunlight and dry wind, but the majority of it will stay present on the ground. When fresh snow falls on top of the old snow, the crystals of the old snow get packed down under the weight of the new cover. Depending on the length of time, snowflake types, and weather conditions between snowfalls, each layer of the snowpack may have a different thickness and density; heavy snow on top of a loose, unstable layer is one of the ways avalanches form.

By the end of the season, the snow in undisturbed areas will be many layers thick, and the melting of this accumulated water is an important source of fresh water for streams and rivers in the spring. In some places, though, the snow doesn’t melt completely, and another year’s snow accumulates on top of the old snowpack.

7. Firn

When years and years of snowpack accumulate in an area, that buildup is called “firn.” It’s much denser than regular snowpack, because of two factors: the partial melting during warmer seasons creates smaller crystals, packed closer together; and the new snow falling on top of the ultra-condensed pack pushes the crystals together without melting during the cold season.

When firn becomes dense enough, it’s considered to be ice, and the buildup of firn at a glacial head, high up in the mountains or near the poles, is what makes glaciers able to maintain their size (assuming a stable climate) despite constant melting and breaking at the glacier foot. The density of firn is between 550 kg/m³ and 830 kg/m³. To put that in perspective, the density of freshly-fallen “powder” snow is around 50-70 kg/m³, and the snow at the bottom of a seasonal snowpack is generally no more than 300 kg/m³.

8. Albedo

The fraction of the sun’s radiation reflected from the earth’s surface is known as the “albedo,” from the Latin albus, or “whiteness.” This is particularly relevant during winter snowfalls, since fresh, clean snow has an albedo of up to 0.7-0.85, meaning up to 85 percent of the radiation from the sun (including the radiant heat) is reflected back into the atmosphere. This can create local cooling effects after a new snowfall, even on a very bright, sunny day. The temperature depression from the albedo can actually cause more snow to fall in an area, if there are other, slightly warmer areas nearby.

On a very small scale, albedo can be experienced just by changing your shirt from black to white. The darker colors absorb much more of the radiation from the sun, and are much better at keeping you warm, while bright whites can reflect almost all of the heat, and can help keep you cool in the summer.

9. Gloriole

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Also known as a “halo” or “icebow,” this optical phenomenon causes a bright circle or rainbow around the sun or moon, 22 degrees away from the center of the object. To differentiate between a gloriole and the related “corona” phenomenon (caused by water droplets, and much closer to the sun or moon), if you put your palm over the sun and extend your fingers, they should reach about 20 degrees from the center.

Glorioles can be seen year-round, but are always caused by ice crystals suspended in the atmosphere. When a gloriole is seen in Tallahassee, Florida, in the middle of June, that simply means that the ice crystals are suspended very high up in the atmosphere, where the temperature is much lower. However, during the coldest parts of winter, the ice crystals can be suspended throughout most of the atmosphere, creating glorioles on most bright, sunny days, or when the moon is full and bright.

10. Parhelia


Sometimes accompanying glorioles are the “sun dogs”—more technically known as parhelia (meaning “beside the sun”). These are bright spots occurring 22 degrees away and the same distance above the horizon as the sun. This phenomenon has been known since ancient times, and was sometimes thought to be “multiple suns” in the sky. When the ice crystals that form glorioles are oriented randomly, they act as prisms in all directions, and the rainbow halo is what becomes visible. As these ice crystals sink through the atmosphere, they tend to fall into a vertical alignment, which reflects the light horizontally, and the sun dogs are formed. While parhelia can potentially be created while the sun is at any position in the sky, they’re most often seen when it’s just above the horizon.

11. Paraselene


The night-time equivalent of the parhelia, “moondogs” are exactly analogous to the “sun dogs.” They’re bright spots on a moon ring (a night-time gloriole), caused by vertically-aligned ice crystals in the atmosphere refracting light horizontally. In folklore, moon rings are said to predict storms, and when moondogs are present, the storm is said to be even stronger. While the predictive power of the 22 degree rings is limited in the winter (as there are often ice crystals in the air that are unrelated to upper-atmosphere changes), the moon rings in warmer months are usually caused by the thin cirrus clouds that often precede a storm front by a few days.

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iStock // Ekaterina Minaeva
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Here's How to Change Your Name on Facebook
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Whether you want to change your legal name, adopt a new nickname, or simply reinvent your online persona, it's helpful to know the process of resetting your name on Facebook. The social media site isn't a fan of fake accounts, and as a result changing your name is a little more complicated than updating your profile picture or relationship status. Luckily, Daily Dot laid out the steps.

Start by going to the blue bar at the top of the page in desktop view and clicking the down arrow to the far right. From here, go to Settings. This should take you to the General Account Settings page. Find your name as it appears on your profile and click the Edit link to the right of it. Now, you can input your preferred first and last name, and if you’d like, your middle name.

The steps are similar in Facebook mobile. To find Settings, tap the More option in the bottom right corner. Go to Account Settings, then General, then hit your name to change it.

Whatever you type should adhere to Facebook's guidelines, which prohibit symbols, numbers, unusual capitalization, and honorifics like Mr., Ms., and Dr. Before landing on a name, make sure you’re ready to commit to it: Facebook won’t let you update it again for 60 days. If you aren’t happy with these restrictions, adding a secondary name or a name pronunciation might better suit your needs. You can do this by going to the Details About You heading under the About page of your profile.

[h/t Daily Dot]