Invisible forces: Through the cloud of atmospheric aerosols

If you’re a scientist in an oceanography department, you’re probably studying the ocean, right? Well, part of your job might be studying things like phytoplankton, the tiny oceanic powerhouses that play a crucial role in our planet’s ecosystem. But how about clouds? Oh, and the properties of light, too?

Wait a minute…

Atmospheric scientist Kirk Knobelspiesse sat down with us to talk about how atmospheric aerosols interact with clouds, the intricate dance of light and its polarization, and what it’s like to look up when everyone else is looking down.

This episode was produced by Shane M Hanlon, and mixed by Collin Warren. Artwork by Karen Romano Young. Interviews conducted by Jason Rodriguez.


Shane:                          00:00                Hi, Vicki.

Vicki:                            00:01                Hi, Shane.

Shane:                          00:03                Were you ever a hairspray person? Not the musical, but I guess also the musical. Have you seen the musical?

Vicki:                            00:09                I’ve seen the musical.

Shane:                          00:10                It’s really fun. It’s weird.

Vicki:                            00:12                It’s fun and weird, yes.

Shane:                          00:13                Yeah, but were you ever a Hairspray product person?

Vicki:                            00:18                No, never. I have this one-

Shane:                          00:21                Literally never?

Vicki:                            00:22                Never. No.

Shane:                          00:22                No?

Vicki:                            00:24                I’m too lazy. Even when, first of all, we missed the big hair time.

Shane:                          00:29                Sure, right.

Vicki:                            00:32                We missed the big hair time, and I just never had a hairstyle. My hair was just always down. Sometimes when I was little, I would do curlers-

Shane:                          00:41                Okay, sure.

Vicki:                            00:42                Which was always ridiculous, but no, I never had a hairspray phase, or mousse phase.

Shane:                          00:49                Or any sort of product?

Vicki:                            00:51                No, I can’t say that I did.

Shane:                          00:53                Interesting.

Vicki:                            00:54                I can’t think of anything. I could think of one picture of me at my confirmation, maybe, with a French braid that was plastered to my head.

Shane:                          01:07                That’s amazing.

Vicki:                            01:07                Besides that, I can’t think of anything.

Shane:                          01:10                Yeah. As anyone who has listened to this for more than maybe two or three episodes, where you are consistently commenting on my hair-

Vicki:                            01:19                Yes, always.

Shane:                          01:19                Things go in my hair, but these days-

Vicki:                            01:23                Thanks.

Shane:                          01:24                … I switch all the time. Hairspray was never really one of them, except for in the very beginning when I started actually trying to do something with my hair when I was in late middle school, early high school, and people, kids, boys in particular started doing things with their hair, and I was like, “I want to do a thing.” We didn’t have anything. There was no mousse at the house. There was no gel, none of that stuff. There was hairspray, because my mom and maybe my dad used hairspray.

                                    01:51                There’s this very vivid memory of, I went to a birthday party of some sort at a batting cage arcade type thing in our hometown, and I changed many big things about me. I had glasses at the time. I didn’t wear glasses that day and I couldn’t see anything. That was thing one. That was fun. Then two is I tried to do something with my hair, and instead of it doing anything, it just ended up sticking straight out and being hard as a rock because we just added a boatload of hairspray to it. That was a bad look, let’s say.

Vicki:                            02:30                No, I love it, but I love it so much. Also, wait, you said you changed a few things about yourself all at once. It was a big reveal, or it was-

Shane:                          02:38                It was a big reveal, and then I went completely backwards the next day.

Vicki:                            02:41                I want to imagine you coming into the party, what’s that Sixpence None the Richer song? There She Goes.

Shane:                          02:48                There she goes again.

Vicki:                            02:48                She goes again, yeah, just you walking into the party.

Shane:                          03:01                Science is fascinating, but don’t just take my word for it. Join us as we hear stories from scientists for everyone. I’m Shane Hanlon.

Vicki:                            03:11                I’m Vicki Thompson.

Shane:                          03:12                This is Third Pod from the Sun. We’re talking about hairspray today. Well, we’re not, actually. We’re going to stop talking about hairspray, but I was reminded of the old aerosol can, the cans that were just absolutely terrible for the environment, releasing all sorts of stuff, CFCs, whatever, before we switched over to something safer. I think that’s right. If I’m remembering that correctly.

Vicki:                            03:40                Have we switched enough to say we’ve switched?

Shane:                          03:46                See, that’s a great question. I do not know. I actually did a little bit of digging before this, because I wanted to make sure when I wrote this that it was correct. Better, I think, not perfect. Let’s just leave it there.

Vicki:                            04:01                We’re not getting worse.

Shane:                          04:03                Yeah, yeah. Well, today, we are talking about aerosols in the environment, among a slew of other things. We spoke with a NASA researcher who studies them. Our interviewer was Jason Rodriguez.

Kirk Knobelspie…:         04:18                My name is Kirk Knobelspiesse. I work at the NASA Goddard Space Flight Center in the Ocean Ecology lab. I’m actually an atmospheric scientist. I’m not an oceanographer, but the act of studying the oceans in the atmosphere is inherently multidisciplinary. I work on two different missions right now. The one that’s closest to launch is called PACE. PACE stands for the Plankton, Aerosol, Cloud, and Ocean Ecosystem Mission. That’s something that will be launched very soon in January of 2024.

                                    04:55                PACE started as primarily an ocean color instrument. That’s using very fine measurements of the color of the oceans to understand what’s living in them. These are important, because they’re essentially plants that are photosynthesizing. They’re plants, so they’re part of the carbon cycle. They breathe carbon dioxide, they exhale oxygen. In fact, about half of the oxygen that we’re breathing, every other breath is not made by plants on land. It’s made by phytoplankton in the oceans, and so they’re part of the carbon cycle.

                                    05:38                Carbon dioxide is in the atmosphere, but part of that carbon dioxide is taken it by the oceans, and depending on how it interacts with the biology in the oceans is potentially removed from the system in a short-term basis. That’s one component of it. From that, you can understand the types of plankton in the oceans, or phytoplankton in the oceans, and making distinctions between different parts. The atmosphere is also very important. My particular background has to do with the study of aerosols.

                                    06:09                Aerosols are a… Well, I guess it’s a term that scientists use to describe any sort of suspended particle in the atmosphere. Aerosols have a number of different sources. Some of them are natural, some of them are anthropogenic, some of them are made by humans. I live in Washington DC, and this has been an unusual summer in that we have bad air quality from forest fire emissions from up in Canada. Of course, this is something that affects people in the western part of the US more frequently. It’s just very unusual for us.

                                    06:45                Smoke is a type of aerosol. It’s particles that are a result of combustion. They can travel for a long distance. They can go much farther than people would expect. The fires in Canada were thousands of miles away from here, but they don’t live for decades in the atmosphere or anything like that. Unlike greenhouse gases, aerosols live for a little while in the atmosphere, but they settle out pretty quickly after a week or two or three. That’s opposed to carbon dioxide and methane, which stay up for decades or centuries.

Vicki:                            07:29                Aerosols aren’t that bad, right?

Shane:                          07:32                Yeah. Compared to some other stuff, sure, but still probably not great.

Vicki:                            07:37                Oh, yeah. For sure. I was wondering, can Kirk do this work from anywhere, or does he have to get to travel to different places to do some research?

Kirk Knobelspie…:         07:48                One of my specific roles is to plan a field campaign that will happen about nine months after the launch. This field campaign will fly two different airplanes, and the airplanes will have various instruments measuring the atmosphere. We’ll have a ship in the ocean and various other things on the grounds, and a whole team of people making measurements that we compare to the satellite. We do a lot of planning before we go into the field. I mentioned earlier a field campaign I’m planning for the fall of 2024. We first started thinking about this maybe two or three years ago.

                                    08:22                Once I’m in the field, it’s actually quite a different experience. We’ll wake up real early, and as part of our team, we will have a group of meteorologists. We’ll sit down and have a briefing with the pilots, and we’ll plan where the plane is going to fly for the day. We have a very specific schedule. In some field campaigns I’ve been involved with, we fly on the plane, and so that involves going very early to the airfield, type of airplanes that we fly on look very different inside than what you would expect from, say, a commercial plane. They’re a lot less pretty.

                                    09:00                They have racks full of equipment everywhere, and some of it’s covered up with padding, I guess, but it’s different. I’ve flown on a plane called the P3, the NASA P3, and so that is a four engine turboprop. I believe it’s a Lockheed Orion P3, and that’s a plane that’s designed for sub-hunting. It’s designed to fly over the oceans at low altitudes. It’s not a particularly comfortable plane. It’s very noisy inside. We’re always wearing headsets with noise-canceling and talking with each other.

                                    09:35                It is kind of amazing. I get very tired by a long commercial flight, an eight-hour commercial flight, but you’ll do a 10-hour experience on one of these planes, and it’s of course tiring, but not boring in the same way.

Shane:                          09:35                Yeah, I can imagine.

Kirk Knobelspie…:         09:50                Yeah. Everyone’s looking at their instruments or they’re talking about what they’re seeing, and it’s like, “Oh, this is a very interesting phenomena that we’re flying through right now,” or whatever. It’s different. You get to travel to places that you would not go otherwise. I did a field campaign once. This was a multi-year campaign. The first year we went to Namibia in Southern Africa, and the second year, we went to a small country called Sao Teme in Principe. The main island is called Sao Teme, that’s sort of south of Nigeria off the coast of Africa.

                                    10:24                What we are interested in was the relationship between aerosols and clouds. There’s some interesting things that happen in the Southeast Atlantic Ocean. For one, there’s persistent clouds, so there’s something called the marine shredded cumulus cloud deck. That’s a very particular type of cloud that is created with cold water. This happens off the coast of California, happens off the western coast of South America, and also the southwest coast of Africa.

                                    10:54                What’s interesting about Africa is that there’s a lot of biomass burning, so creation of dark smoke aerosols, over the South African continent that is carried out over those clouds. A lot of smoke also in North America, but usually the smoke blows east. In this case, the smoke blows west, so those aerosols get above clouds. What the aerosols do is if the cloud is real bright and the aerosol is dark, it absorbs some energy. If the aerosols sink into the clouds, they can change the properties of the clouds.

                                    11:24                They can also change the meteorological conditions. If you have an absorbing amount of aerosols, they’ll change the temperature profile in the atmosphere. The temperature profile is what drives formation of clouds. All these complicated things happen, and so it’s a phenomena that happens out over the oceans. What we did in our research was not much on the location itself we were flying. I can claim to fame that I was within 200 meters of the zero-zero point, so 200 meters from the equator and the prime meridian.

Shane:                          11:57                Oh, wow.

Kirk Knobelspie…:         11:57                Latitude, longitude, zero-zero. I was very happy. We had a little monitor of where exactly we were, and I was like, “Oh, we’re almost there.” I was like, “Can we turn a little bit left so we can go exactly over?” Of course, it messes up everyone’s data processing because you have a latitude and longitude associated with things, and often, if that goes wrong…

Shane:                          12:21                Vicki, have you ever been to Four Corners? The place in the US where Colorado, Utah, Arizona, and New Mexico meet?

Vicki:                            12:31                Never, but I have been-

Shane:                          12:33                Oh goodness.

Vicki:                            12:34                … To three corners, I will call it now, where Pennsylvania, New York, and New Jersey meet.

Shane:                          12:39                Oh, interesting. I feel like I’ve-

Vicki:                            12:42                Maybe not corners.

Shane:                          12:43                Yeah, Three Points? I feel like I had to have been there, considering where in the country I’m from. Yeah, well, regardless, okay. I’ve been to Four Corners. It’s fine. Maybe I’ve been to Three Corners. I feel like it’s a much less cool version of what Kirk experienced.

Vicki:                            13:03                We’re much less cool.

Shane:                          13:05                True. I appreciate you including yourself in that.

Vicki:                            13:08                Yeah.

Shane:                          13:09                Beyond Kirk getting to do some amazing field experiences, we wanted to dig into the actual research he’s doing and the data he was collecting.

Kirk Knobelspie…:         13:19                We can all imagine an imager from space, a camera, and that camera might have multiple colors: red, green, and blue that it’s sensitive to. One of the instruments on PACE is what we call hyperspectral. Instead of having three color channels, it will have… I forget exactly the number, but more than 30, so lots and lots of colors to work with to understand what’s going on in the scene. That’s one dimension you can work with is color of light.

                                    13:43                Another dimension you can work with is the polarization state. Polarization is the direction in which light waves oscillate. Coming from the sun, that direction is just randomized. Some light waves are in one direction, some are in another. When that light interacts with, say, the surface of the ocean, what’s reflected might have a preference. If you saw the world through polarization-sensitive eyes, every time you flew in an airplane, you’d see rainbows everywhere.

                                    14:13                We know rainbows is light interacting with rain droplets. There’s something else that’s very similar that we call a cloud bow. This is light interacting with smaller cloud droplets. There are certain situations where you can see little bits of cloud bows. I think if you’re in an airplane, if you really look out the window and look, you might see, in some situations, if you’re looking down in a cloud and the sun is behind you. It’s harder, it’s not very distinct. In polarization, it is.

                                    14:38                We can look out, we can look at clouds with polarization and look for rainbows. It’s not just because it’s cool to see a rainbow. The location and the type of that rainbow tells us about the cloud droplets themself. The specific angle with respect to the sun that the rainbow occurs at tells us, is the droplet large or small? If there’s secondary rainbows or what we call supernumerary bows, those tell us about the distribution of sizes. Is everything one size, or is it like a dispersion of a whole bunch of different sizes together?

                                    15:19                All these things we can use to understand clouds. If you want to look at the role between aerosols and clouds, you have a good instrument for studying aerosols, but you also have a good way of understanding what the clouds are doing from that type of instrument.

Vicki:                            15:43                Okay. Do you feel like you now know more about clouds than you ever really wanted to?

Shane:                          15:49                I honestly don’t think about cloud composition very often, but yeah. Yeah, this is cool stuff. What about you?

Vicki:                            15:57                Yeah, I think about clouds. I think about clouds a lot. I feel like you just hurt clouds’ feelings. I don’t think about clouds.

Shane:                          15:57                We’re not going there.

Vicki:                            15:57                Sorry, clouds.

Shane:                          16:09                Oh, my gosh. I’m just picturing an illustration of a cloud, like an anthropomorphized cloud with, what is that from? It’s from a show or a movie. This is a great story and I’m going to stop talking about it, but Kirk is obviously very into this, but I don’t know that he always wanted to be a kind of capital S scientist.

Kirk Knobelspie…:         16:34                I think I always wanted to be a scientist, but at some point in maybe high school, I changed my mind on that. I got into the arts. I went to art school. I have a degree in photography, and then throughout the rest of my adulthood, I sort of slowly shifted a little bit closer, and a little bit closer, and a little bit closer to doing science.

                                    16:57                After photo school, I kind of was trying to decide if I wanted to move in the more artsy direction or the more techy direction. I received some advice from an advisor that it was usually a little bit easier to do arts in your own time than it is to do science or technology in your own time. It’s okay to like both things.

Shane:                          17:20                I was really struck by this thought from Kirk, because I had to make that decision actually pretty early on too. I am a musician. There’s a drum set literally right behind me, but also liked science. I had to choose which was going to be, which way my main passion was going to go, and I went with science.

Vicki:                            17:47                Yeah. I feel like a lot of people make that choice, even just from a money standpoint. What can I do with my passion? Right?

Shane:                          17:56                Yeah, that was part of it. I have a minor in music. I didn’t… What is that?

Vicki:                            18:06                No, you kept it, you made it, it’s still a serious… You still have it as a serious enough thing. It’s like you didn’t just designate it to a hobby. You kept learning-

Shane:                          18:18                Sure, yeah.

Vicki:                            18:19                … In a serious way.

Shane:                          18:20                At this point, it’s a hobby that every year, I think I say that I need to pick back up. Yeah, yeah, let’s go with that, that I made that dedicated decision. After Kirk chose science as his main passion, he had to do some deciding on exactly what he wanted to get into.

Jason:                           18:40                You said that you were drawn to satellite images. What drew you to those?

Kirk Knobelspie…:         18:46                They’re pretty.

Jason:                           18:47                Yeah.

Kirk Knobelspie…:         18:49                There’s a lot about the earth that you can only understand from a distance. There’s an aspect of… Just look out the window of an airplane, that you can see things that you just can’t see from the ground. There’s beauty in that. There’s an aspect of satellite remote sensing as well that is even beyond that, really. We’re making measurements all the time, every day over the course of years. There’s things, there’s phenomena that you cannot observe until you start doing that.

                                    19:23                You’re not going to see very obviously, some particular part of your climate model by just looking at one image. You need to look at 20 years of data before you can start to understand, “Oh, this thing is impacting in some way.” I guess at the core is that there are scales of human perception, and satellite imaging brings us to a different scale of human perception, both in space and in time.

Shane:                          20:01                Vicki, do you think you have the patience to work on timescales of tens of years like Kirk has to do with his work?

Vicki:                            20:09                No, absolutely not. I get frustrated or start to feel nervous if I don’t move the needle on work by the end of the day. To have something that I’m working on for that long would keep me up at night every night for tens of years.

Shane:                          20:30                Keep you up for tens of years. Yeah. I don’t either, or even I don’t think I did when I was a researcher. I was always amazed by folks who did studies that were just a couple of years. If I couldn’t answer a question in a field season, we’re talking months, I usually just wasn’t interested.

Vicki:                            20:47                Yeah, and look at you now. You’re running a weekly podcast. Multiple seasons.

Shane:                          20:53                Yeah. It’s a little bit different, but I’ll take the compliment.

Vicki:                            20:57                There was no compliment. It was just facts that I was-

Shane:                          20:59                Vicki, I’m going to cut you off for time.

Vicki:                            21:02                Time?

Shane:                          21:03                Yes, for time. We have no more time. We are over. With that, that is all from Third Pod from the Sun.

Vicki:                            21:12                Special thanks to Jason Rodriguez for conducting the interview, and to NASA for sponsoring the series.

Shane:                          21:18                This episode was produced by me, with audio engineering from Colin Warren, and artwork by Karen Romano Young.

Vicki:                            21:25                We’d love to hear your thoughts, so please rate and review us. You can find new episodes on your favorite podcasting app or at

Shane:                          21:32                Thanks all, and we’ll see you next week. Oh, all right. That’s how that’s going to go with us just singing into our title credit. Yeah, it was not a good look to say the least.

Vicki:                            21:51                That’s like you built your own baseball cap, it sounds like.

Shane:                          21:55                Oh, kind of. Yes. It was…

Vicki:                            21:57                It was themed for the party. You were just being on theme.

Shane:                          22:00                Yeah. Theme for the party, actually kind of. Then there was a moment, for a long time, I used a product that it was called Ice. It essentially was, it did the same effect of hair spray, but it made it kind of hard. Instead of going straight out, it does what it kind of does now except less natural. It went up.

Vicki:                            22:23                Oh.

Shane:                          22:24                Yeah, high school was fun. I liked high school a lot, but my look was awkward.

Vicki:                            22:32                Tragic.

Shane:                          22:34                Tragic? All right, we need to keep going.

Vicki:                            22:36                No, I’ll reveal that. I had, I think I’ve said this before. I had a full face of blue makeup phase that I went through. Blue lipstick, blue eyeshadow, blue anything I could get, blue mascara.

Shane:                          22:52                That is..

Vicki:                            22:53                You’re not alone.

Shane:                          22:54                Okay. Well, that’s good to know. I appreciate that. I would love to see those picture.


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