Hi, my name is Matthew Shupe. I'm from Cooperative Institute for Research Environmental Scientists at the University of Colorado, and NOAA and Boulder. Right now I'm on an icebreaker in the Central Arctic Ocean coming back from Mosaic, the first part of Mosaic. I'm one of the co-coordinators of Mosaic. I'm pretty excited to share some information about this project with you. Arctic clouds. I want to talk about arctic clouds here. Arctic clouds are so important in the Arctic system in general. They play this really important role in terms of energy transfer in the system. They of course bring precipitation, snowfall, that determines what's happening on the surface. So clouds are really important in the overall system in the Arctic. It also turns out that clouds are a big challenge for us to model. We all rely on models of clouds for predicting the weather, for example, telling us what the temperature are going to be like tomorrow or how much snow is going to happen. For climate models as well, we really rely on understanding clouds because clouds play this huge role in the energy system of our globe, and how much that's going to change over time. So for climate models projecting the future of our Earth and for weather models that project what's going to happen tomorrow, we really have to understand clouds and represent them well. But right now, it's a huge challenge for us to do that. That's important because we haven't really made a lot of observations of clouds in the Arctic especially. We look at clouds elsewhere on the globe, and it's not clear how representative those are of the clouds we see in the Arctic. So we really need to go there and observe the clouds more in the Arctic system. There are a few details about Arctic clouds that makes them particularly interesting. One is that the Arctic is cold and these clouds are cold. They're cold cloud processes in general, but there's still liquid water in these clouds. So these are mixed-phase clouds, they have liquid water and ice together. That makes it really complicated. Also, in the Arctic, there are aerosol particles. It turns out that you need an aerosol particle a little particle in the atmosphere to form every cloud droplet. In the Arctic, those aerosol particles are unique. They're far away from a lot of sources, we don't really understand where they come from or what they're made of or how they really behave in cloud. So we really have a lot of uncertainties about the aerosol contribution to clouds in the Arctic. Also turns out that Arctic clouds are really thin. That makes them really sensitive to change. So if you have a change in a system like in a temperature, that could affect how the clouds behave. So these are some of the ways in which Arctic clouds in particular are unique relative to global clouds. Let's think about how clouds behave in the Arctic system. They play two really important roles as far as energy transport nodes. One is, they shade us. They shade the surface from the sun. So that's a cooling effect, making the surface cooler. On the other side, well, the Earth is emitting radiation and clouds can act as a blanket and they can trap the Earth's emitted radiation and send it back down to the surface. That's a warming effect. So we have this cooling effect and we have this warming effect. Those two things play out differently depending on where you are and the time of year. So if we think about, for example, the Arctic wintertime, when there is no sun, well, then clouds are just warming the surface. So it turns out in the Arctic, overall, if you average everything over the whole year, clouds warm the surface. That's pretty unique because globally, if we think about the whole globe, clouds are cooling the surface. So on the Arctic, clouds warm the surface. This other important thing is the phase of the clouds. What are the clouds composed of? Liquid and ice, sometimes together. Why does that matter? Well, it turns out that liquid and ice have different effects within a cloud system. We can all feel this and experience this in our own lives. We can look for example, at an overcast cloudy day. It's all dark out. These are liquid water clouds. They really shade us from the sun. Versus ice-water clouds, they're wispy, cirrus clouds are really high. You can often see the sun through them. You can see blue sky. So this difference between liquid clouds and ice clouds and it affects radiation. So this affects the state of the Arctic system really importantly. We could think just in the wintertime when it's dark out, the earth surface is emitting radiation to space. It's cooling and the atmosphere is not sending much radiation back down to the surface. So this is deficit, there's a loss of energy, the surface is cooling. But you bring one of these liquid water clouds in, these big blankets in, over the surface, and it's sending radiation back down. So the Earth is emitting radiation, and the cloud is sending it back down. So the balance is close to zero. It's about the same amount of radiation. So the surface is not cooling as much. We see this in the surface temperature. It turns out that on a clear day or a day without liquid water clouds, that it's really cold because that surface is cooling so much. If you add the clouds there, these liquid water blankets, then the surface is much warmer. In our observations all across the Arctic, in places like Greenland or out over the sea ice, we see differences of 10 degrees or even 20 degrees warmer when there are these liquid water clouds. So they obviously play a huge role. It also turns out that all the other energy transfer terms in the Arctic system are also dependent on these clouds. If you change the surface temperature, you're also changing how heat is moved by the winds, how it's conducted down through the sea ice and all these other energy transfer terms. So clouds play this really important role and the overall energy movement in the Arctic. So why are clouds composed of liquid water in the Arctic, or why would they be composed of ice? What makes the difference between these two things? One is those aerosol particles I was telling you about. In the Arctic, there are so few, the aerosol particles that form ice, that it turns out that the clouds form is liquid water often. That's really important in terms of finding the balance between the two phases. But there's also important drivers in the dynamics. The clouds themselves force turbulence in the atmosphere that helps to form the clouds. There's also storms that blow in from further away that bring moisture to form the clouds. That's really important in determining how the clouds live, how they develop, and the role that they play. Also, of course, the temperature is important. The Arctic is cold, and as it gets colder, and the clouds are more composed of ice. As it gets a little bit warmer, then there are more composed of liquid water. So temperature plays an important role there as well. How do we observe clouds? How do we study clouds? There are a number of different tools. I'm an observational scientist and we take things like radars, different instruments out and put them on the surface and point them up at the sky. They'll send a signal up and that signal will bounce off of the clouds and other parts of the atmosphere and come back down to our system. That returns signal tells us something about the clouds. It tells us how much water is in the clouds, how big are the particles in the clouds, and many other details. Or maybe we fly an airplane through the clouds or send a balloon through the clouds. There's lots of different ways to observe clouds to tell us about the nature of those clouds. Then we also have modeling tools. Well, we've developed models that help us to understand the formation of cloud particles or how they move around or how they interact. It turns out if we use these observations and these models together, we can understand clouds holistically. An Arctic clouds is such a complicated puzzle. We've been studying all different parts of that puzzle to try to put them together to understand them and their roles. But it's using both of these tools, these models and these observations together that's helping us to make progress and understand the clouds and ultimately to represent them better in clouds and climate models. Thank you.