Snow day!

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0:42Eligible students get a year of Microsoft 365 Premium and a year of Xbox Game Pass Ultimate with a custom color Xbox wireless controller. Learn more at windows.com slash student offer. While supplies last, ends June 30th. Terms at aka.ms slash college PC. All right. It is a day after a very intense snowstorm here in New York City. And my editor, Joanna, came up with the idea that I should go outside and talk to people about the snow. So I am looking out at what can only be described as a winter wonderland. everything is truly covered it's like not a blanket it's covered in a quilt of snow it's like fluffy and white and charming and cold I don't want to go outside oh it's so windy do you hear that?

1:42alright let's go a few weeks ago I had an extremely nice time wandering around the streets of Brooklyn in Prospect Park and talking to people about the snow. I can say this park, it's beautiful. It has a lot of trees and all of the trees are really snowy. I can see a lot of snowmen. There's a huge snowman over there. Like, I don't know how to say it in feet, but I can say it's at least 160 centimeters. We realized this morning that this was the best snowman-making snow that I've ever seen. And so we made this snowman this morning. Now we're back to give it a personality. Is that about summing up?

2:31Help. Help what? You're about to slip? Well, we already built a snowman and we frolicked in the park. So now we're going to go get some hot cocoa. I talked to people who were shoveling their walkways, going sledding, going skiing. I am wearing my cross-country skis from high school. How are you fitting cross-country skis in your New York apartment? It's a great question. I talk to people with lots of thoughts on snow. I love working out. I love shoveling it. I cross-country ski. I just love it. Pro snow. Love it. Except a month from now and we still have it and it's black. Yeah. Like once it gets disgusting like the last snow did, then I'm over it.

3:09But I like this snow for right now. I love it from a distance. Only because he's small. We out here other than that, I'd have been in my house. But I do love it from a distance though. And I also asked people if they had questions about snow. Well, I know that it makes things very quiet because it absorbs sound. But I don't understand, I guess I don't know the science behind why. I did it here. I'm not sure if it's true that every snowflake is different. I guess one question would be, sometimes when snow falls, you can't really make snowballs out of it. And then sometimes it's perfect like this where you can grab it and make a snowball.

3:47Yeah, just kind of what determines that. because this feels like a totally different ballgame. So not everyone had questions for me. Not really. I kind of like not knowing. Like not knowing how things... Yeah, you know what I mean.

4:03Okay, great. I'll go home. That's not what I meant.

4:12I did get enough questions that I decided to call up a snow scientist in search of some answers. So I am Bird Pinkerton, and today on the show, I'm talking to Jessica Lundquist. She's a professor of civil and environmental engineering, and she's going to answer a whole bunch of questions about snow for us. Of course, this is unexplainable, though. So a little later in the show, she's also going to tell us some things about snow that she does not yet know and is still trying to figure out.

4:55All right, well, I have a bunch of questions for you as our resident snow expert. Let's go. So the first question I got from a few people is actually about the shape of snowflakes. How was it formed? How did the design come about? Like, is there anything that makes it have a different shape, the snowflake? Why are snowflakes all different shapes?

5:19Jessica Lundquist:So snowflakes will form around a tiny speck of dust called a condensation nuclei. Okay. But now it can grow in different ways. So you can grow out to make what we call a dendrite shape. So that's your postcard snowflake. But it could also grow down, right? So you could also get a column. which one of these you get will depend actually on the temperature and water vapor content in the atmosphere where the snowflake is being formed depending on the conditions in the atmosphere it will grow in a certain way and then it's not sitting at just one point in the atmosphere it's often like being blown up and down to different points with different amounts of water vapor different temperatures and so it's often like growing differently throughout its lifetime and then has to fall from that cloud down to where we are at the surface.

6:13Jessica Lundquist:And it will often like hit different snowflakes and then they can aggregate and you can get these sort of messy big things. Wait, so what you're saying to me is like the snowflake's shape is like a record of the life it's lived almost, like where it's been? Yes. So it's telling you about where it's been in the cloud and what it's fallen through and whether it hit another snowflake and how it grew. And if you really want to know about snowflakes, I recommend checking out Ken Liebrich, who grows them in his lab at Caltech. He can make designer snowflakes. Every day I learn about a job that I wish I had.

6:52Okay, so the answer to this first question of sort of like, why is every snowflake different, is like every snowflake has its own little individual path through the atmosphere that shapes how it grows. And then also go check out this guy's designer snowflake lab. Yes. Question two is I got a question kind of about not how it looks, but how it sounds. So one of the people I met did sort of like an ASMR demonstration of the snow crunching.

7:32and then was asking, like, why does it crunch like that?

7:36Jessica Lundquist:So we talked about the snowflakes' history in the atmosphere, right? But then the snow also falls on the ground and has a history on the ground. So your snowflakes start accumulating on the ground, and you have all these, you know, little individual snowflakes that fall on top of each other, and they have air in between them. It's not ice. It's a pile of little snow crystals with air in between it. Like a fluffy pillow almost. The way that your pillow is like a bunch of feathers. Except this is cooler than feathers because snow is always close to its melting point. So if you think about some arterial science, if you have like metal and you heat it up so you can weld it and center it, if you get your metal really close to its melting point, you can like make two points of metal actually attached to each other.

8:23Jessica Lundquist:So snowflakes will do something we call sintering. So you also center things with metal. But snow will center by itself just sitting there. So your snowflakes fell down. They made, you know, kind of like your feather pillow with air inside. And then your little crystals start attaching themselves to each other. So now you have this matrix of snowflakes that are attached to each other. And then underneath it, they have air. You could also have right at the surface, it might melt and refreeze a little bit. So they'll often be, you know, attached at the surface with air underneath. Now, your crunchy sound, you're breaking that.

8:55Oh, you're breaking the connections that they formed.

8:58Jessica Lundquist:Yeah. But it's only sometimes. Your snow won't always make a crunchy noise. Okay? So basically, like, because snow is slightly melted almost, but it has the power to stick together, it's forming all these sort of fragile bridges. Yes. And when you crunch it, you're just demolishing a lot of bridges all at the same time. Great. Another sound question. This is question three. Why does snow absorb sound? Okay. And this, it doesn't always do that either. So one thing is snowflakes are all different. The snow on the ground is also all different. So sometimes it might make a crunching sound and sometimes it might absorb sound.

9:40Jessica Lundquist:So when it most absorbs sound is right after new snowfall. So it hasn't yet a time to make all these centering connections. You just have a whole bunch of little snowflakes just loosely lying at surface. So think of kind of like your feather pillow, not yet attached, but lots of air in between it. So the sound gets kind of muffled by going into all those air pockets in the snow and doesn't get reflected back to your ear. So it ends up sort of being a sound absorber because it's just loosely connected a whole bunch of air pockets. Delightful. Okay. So then I got a lot of questions about why the snow is the way that it is.

10:19So people were talking about sort of like the texture of the snow in this storm versus the one two weeks ago. It seems like thicker and stickier. And like the fluffiness, what makes it so fluffy? One person got really descriptive. It's like AI snow. What do you mean? Like I feel like it was 3D printed. Yeah. Like Tempur-Pedic snow. But it was apparently, like, better for snowballs, better for snowbuilding. Yes. And people wanted to know, like, what was going on there, essentially, like, physically, chemically, whatever, to make different snows after different storms. Yes.

10:57Jessica Lundquist:So, again, we talk about the history, right? It starts with their falling through the atmosphere. They fell through different atmospheres. Warmer storms, cooler storms, depending on the conditions in the atmosphere. Snow crystals grow differently. and they also have different amounts of liquid water inside of them. So if you get a colder storm, you have a lot less liquid water and you end up with dry snow. It won't make a snowball, right? So as you get warmer and you get the biggest change above negative three degrees C, so as you get between, again, when we talked about snow being really close to its melting point, Right.

11:34Jessica Lundquist:So snow is multipoints at about zero degrees C. And as you get really close to that, you actually get more molecules that actually are liquid. And that makes it really sticky. You can build good snowballs with warmer snow. One person asked how it accumulates on surfaces. And so specifically, we were talking about tree branches. And then I was thinking about wires. And I was curious if there's any interesting physics or whatever going on structurally there. So there are actually these amazing studies done both in Japan and in Switzerland, where they put out all these boards of different widths and different sizes, and then they just measured how much snow accumulated on all of them.

12:12Jessica Lundquist:The pictures in their papers are really cool. And they also did studies where they tried to see how tall could you stack snow and what was the angle of repose of just a stack of snow. So these are questions that lots of people have. Well, maybe not lots of people, but it's definitely been studied quite a bit. It goes back to some of the things we talked about before. So how much snow you can stack up actually depends on the temperature of the snow. So again, we got back to that snow being really close to its melting point, particularly if you have a warmer snowstorm, right? And the fact that the snowflakes can center and stick to each other.

12:52Jessica Lundquist:So they will actually attach themselves to each other. Also, the stickiness, per se, of snow goes up hugely between negative three degrees C and zero degrees C. And if you think about like little bits of it will like melt to be liquid and then refreeze again, that it will sort of freeze itself onto your tree branches and your different things. And then it will attach itself by centering to each other. And so it can stack up amazingly. Wow. Okay. I'm learning a lot. But unrelated to structure of things, one person asked what the benefits of snow are for the environment. So like for trees or for parks, etc.

13:37Jessica Lundquist:Snow insulates things really well. Just like in your house, the insulation is, you know, a lot of pockets of air in between two walls, right? Your snow builds up with a lot of trapped pockets of air that insulate the temperature. So it turns out that in most cold regions, the temperature at the top of the snowpack above the snow is significantly colder than the temperature at the base of the snow. So if you go to the Arctic, it's often like more than 20 degrees Celsius different between the top and the bottom of the snow. So it'll be, you know, like can get negative 40 in the air. And if you're under the snow, you're super warm.

14:14Jessica Lundquist:So if you're out in a really cold storm, you could dig yourself a snow fort, bury yourself under the snow. you'll be warmer, right? So a lot of animals live under the snow. Some hibernate under the snow. Many build their dens under the snow, right? It's a warm, safe place through the winter. And is it just animals or are there other things kind of taking advantage of this warm blanket effect? Plants, microbes, you know, things in the soil that are using that same insulation to survive. Like plants with shallow roots in cold regions will often have root damage if there's not a good snow year. It's kind of counterintuitive that often in years with less snow, it's colder for a lot of plants and animals because they can't hide under that blanket.

15:04So clearly there is a lot about snow that's no mystery to Jessica. But there are some things Jessica does not know about snow. So after the break, it's Snow Mysteries with Jessica.

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18:30All schools are officially closed for a snow day.

18:38All right. Jessica Lundquist was patiently answering all our questions about snow. But I also had some questions about Jessica. Like, what got her into studying snow to begin with? She told me she grew up in California, and her favorite thing to do was to go to Yosemite.

18:54Jessica Lundquist:I just like going in the mountains and going hiking. And I went in the summer, which, you know, generally there's no snow. But then quickly realized that the amount of water in the river that I like to jump in and go swimming was completely related to the amount of snow in the mountains. So you were like, I'm going to spend a great deal of my career studying this question? No, of course not. I said, I want to be a park ranger and just go hiking in the mountains. She did wind up becoming a researcher, though, not a park ranger. And she began tackling this big question related to snow. How much snow is there actually in the mountains?

19:29It turns out that on the west coast of the U.S., snow melt can be an important source of water.

19:34Jessica Lundquist:So basically, in the western U.S., we don't have enough water for all the things we want to use water for. There's a lot of people living in the west. There's a lot of crops grown in the West. All of these need water to grow. And basically, the water is allocated to people through this water rate system. So in terms of like, what is the value of snow? It's like free reservoirs, right? It's storing that water in the winter for the summer. So people always want to know how much water exactly do we have in the snowpack? because it's actually so dry out here that people will be told don't plant, right?

20:14Jessica Lundquist:We can't give you water this year. You can't plant your crops. You need to furlough your fields. You need to do something else. So a lot of what I try to do is figure out how much snow there is in the mountains at any given point in time. I mean, the job is often to predict the future, right? Can you predict how much water we'll have in the future? But this is easier said than done, because it's tricky to measure how much snow there is in the mountains. A lot of snow falls in places that don't have roads, that don't have infrastructure. They're rugged, steep terrain without, you know, a lot of access.

20:48Jessica Lundquist:So a lot of it fell in place you can't go. But it also, like, it's extremely variable. So if you put out a measurement site, so the National Resource Conservation Service, or NRCS, has something that's called a snow pillow. Okay. So it's basically, you have like two metal plates, you fill it with antifreeze, you put it right by the surface of the ground, you bury it slightly so bears can't find it. The snow falls on it, squeezes the water, the antifreeze, which then creates a pressure gradient. And it tells you how much, what is the weight of the snow resting on this snow pillow. So basically that weight tells you what we call the snow water equivalent.

21:25Jessica Lundquist:Like for basically for water resources, if all that snow melts, how much water do we get out of it? This is the snow water equivalent. Or you may hear the term SWE. S-W-E. Snow water equivalent. I have not heard the term SWE, but I like the term SWE quite a bit. Okay. That sounds great. That sounds like we have a measurement. Fantastic. Exactly. But if you walk 10 steps to the left, you're going to measure something completely different. Oh, right. Okay. This is somewhat less sweet.

21:59The same problem exists for other measurements, and satellite images can be tricky. And so Jessica and researchers like her may never be able to work out a perfect measurement of the snow in the mountains on any given year. What they can work out, though, is patterns. So for many decades now, people have been taking measurements of snow in the mountains at certain spots and then seeing how much water there ends up being in the following warm season. And that means that they can say, you know, when our measurements look like this in these various spots, there will probably be this amount of water.