 Explorer series lecture, atmospheric rivers in a changing climate, how rivers in the sky could change with Christine Shields. My name is Dan Zietlow, and I'm an educational designer here with the National Center for Atmospheric Research or NCAR, which is a world-leading organization dedicated to understanding our system science. So that includes our climate, weather, the atmosphere, the sun, and how all these systems interact together to impact society. I'm really glad y'all could be with us today to learn more about these rivers in the sky. I'm also really excited to be here with y'all since this is our first in-person Explorer series event since the end of 2019. I'm really psyched to be piloting the foundation for hybrid events going forward in 2023. So please give us a little leeway as we figure out that this new space. For this event, you'll be able to ask Christine questions following her lecture, and I'll help moderate that. So that way we can share time between both the in-person audience and our virtual audience. If you're in-person, you can simply just raise your hand and ask your question. The room microphones will pick you up. If you're in our virtual audience, you can ask your questions using Slido. So if you scroll down the web page just a little bit from where you're seeing the live stream, you'll see the Slido window. If you haven't already, go ahead and click the screen join event button, and then you can ask questions on the Q&A tab. Christine also has a few poll questions for us. So for both of our in-person and our virtual audience, you can also respond on Slido. For those in-person, you can use your phone or a laptop to go to slido.com and type in the code NCARMSR. Definitely be sure to add your answers because we're going to be getting to our word cloud question pretty soon. That's what do you think of when you hear the phrase atmospheric rivers? This lecture is also being recorded and will be available on our NCAR Explorer Series website. So with us today, we have NCAR scientists Christine Shields from NCAR's Climate and Global Dynamics Lab. Christine is a project scientist with expertise in simulating Earth's past, present, and future climate with the Community Earth System or CESM. She earned her Master's of Science in Meteorology from the Pennsylvania State University, and has focused her research towards understanding Earth's hydrological cycle in the context of climate change with particular emphasis on atmospheric rivers, monsoons, moisture transport, cyclones, and weather extremes. Christine is also involved in a community-driven effort to define the uncertainty surrounding the various definitions of atmospheric rivers, and is particularly interested in how this uncertainty shapes our understanding of atmospheric rivers in a warmer world. Now before I turn it over to Christine, let's check out y'all's thoughts on our word cloud question. So Paul, Brett, or Nick, would you be able to share Slido for us? Awesome. So I'm seeing lots of great answers up here. So lots of rain seems to be the biggest one, and they definitely do produce lots of rains, and we'll hear from Christine a little bit more about that. I'm seeing moisture, water, a river in the atmosphere, air currents, ocean, intense rainfall, wind, temperature, pressure, gradients, precipitation, river, the Pacific Ocean. Yeah, so I'm seeing lots of great themes up here. So maybe as we transition over to Christine, I'd love to hear some of your thoughts as I welcome you up here about our word cloud. Hi, Dan. Great, thanks. Yeah, these are all great responses to the word cloud, and I think they're all pretty applicable as well. So yeah, lots of rain. That's like the big thing with atmospheric rivers, they bring a ton of rain. So I guess, shall we just proceed on to the presentation? Okay. Okay. All right, well, can we get the, here we go. All right, so thank you all for coming here to my presentation, both online and in person. So let's get started. Oops, oops, here we go. So what, here's my outline, what are atmospheric rivers? I'm gonna talk a little bit about what atmospheric rivers are, I'm using the acronym AR a lot in my presentation, so when you see AR, it means atmospheric rivers. Then I'm gonna tell you a little bit about where they occur and why they're important for climate, and then I will finish with what happens to atmospheric rivers in a warmer world. All right, so the first question, what are atmospheric rivers? Well, one of the things that we say a lot as atmospheric scientists, my fellow atmospheric river researchers is, well, we'll know them when we see them. And so this isn't really a scientific explanation for what atmospheric rivers is, but it actually just helps to explain it a little bit when you look at pictures of atmospheric rivers. So here what I'm showing you are two satellite photographs from the NASA Earth Observatory. These were taken in October of 2017, this first one was October 14th, and this one down below, if you can follow my cursor, October 17th. And in these, you can really just see this beautiful long banded structure, weather structure that's crossing the entire Pacific thousands of miles long and several hundred miles wide, and this is typically how we define an atmospheric river. Incidentally, I grabbed these images from the NASA Earth Observatory, but you can also find them on the Wikipedia page, which actually isn't too bad for atmospheric river stuff. All right, so let's, here we go. So how do we actually identify them? Well, we identify them often by their water content. And so this is what you're looking at is a looped image of an atmospheric river that's making landfall in the Pacific Northwest, right around here. And it's a different type of satellite that you're looking at here. This is called a water vapor imagery, and it's created from the Corruptive Institute for Meteorology of Satellite Studies, that's based at a university of Wisconsin and Madison. And what you're looking at, it's labeled up there, total precipitable water. And what that means is if you take all the water vapor that's in the atmosphere, and then you all of a sudden just precipitated out how much water comes out of the atmosphere, that's what we're actually looking at. And these colors down here, this red and orange colors, show where there's the most precipitable water in the atmosphere in this shot. And this is typical because it's the tropical bands and you have a lot of water vapor down there. But what you do see is this, the scooping of this tropical moisture into the mid-latitudes, into these long, striated streams, which actually eventually make landfall in the, in this case, the West Coast of the US or the West Coast of Canada. And this is really what we're talking about and we're talking about atmospheric rivers. Incidentally, this particular atmospheric river that's making landfall in the Pacific Northwest there produced about two to five inches of rain in the Seattle area. Oh, okay, so before we move to the next slide, do we have the answers for our first poll question because I'm gonna answer it in the next slide. So I thought we might actually answer the first question. We can. All right, yeah, so actually this is really good. The answer, believe it or not, is similar to two Amazon rivers. So most of you were actually really close, but it's similar to actually like double, a typical Amasberg river is similar to double the Amazon. So if I, we go back to the slide and I forward advance my slide, I can show you just give a second here, I guess. Here we go. Amasberg rivers are actually, believe it or not, the largest freshwater river on earth, but we're not talking on the land, we're talking in the skies. Freshwater is actually in the atmosphere. Double the Amazon river and for those of you who would like to think in Mississippi instead of Amazon, it's about five, seven to 15 Mississippi rivers. This schematic I took from the NOAA website and it's a really nice schematic that shows you what sort of happens mechanistically. You have warm moist atmospheric moisture from the tropics that just sort of gets pushed along in the atmosphere until it hits the land mass and then it interacts with that the mountain ranges and the air gets sort of pushed up and then as it gets pushed up, it cools, it condenses, clouds form, those clouds get heavy and then you have this precipitation and heavy rain and heavy snow is the result. So this is sort of the mechanistically what happens with atmospheric rivers. All right. So when we think of atmospheric rivers are actually, it's not just all water, they're actually two different things. You have the water part and then you have the transport part. So atmospheric rivers are comprised of both water and when integrated vapor transport, this is another acronym, IVT, is a variable that we use as a typical way we measure the intensity of an atmospheric river and it's comprised of both water and wind. So from a practical sense, when we forecast these things, we look at IVT and so these series of images, I sort of grabbed from an operational center that's centered in Scripps, the Center for Western Weather and Water Extremes and I have that website up there for those who wanna take a look at it. This is an operational center that forecasts atmospheric rivers and this is a typical product that comes out of it. They run this model and they show this integrated vapor transport intensity which is these really dark, dark colors. It shows you how strong that atmospheric river is and in some cases they do what we call reconnaissance missions where they put airplanes into the sky and they crisscross the atmospheric river to take measurements so we can understand them better. Sort of like hurricane hunters putting flying airplanes into the eye of a hurricane, these guys fly their airplanes into atmospheric rivers. So that's sort of a really fun thing that they do that gives us a lot of good data. So atmospheric rivers are actually often attached to winter time low pressure systems. So I've taken here on the left, this is a schematic from the glossary of meteorology which is produced by the American Meteorological Society and it's just sort of like a, we call a plain view way of looking what's happening with the atmospheric river compared to the low pressure systems in the area. So here's your low pressure system and you have these frontal boundaries and the atmospheric river, the moisture piece just sort of gets scooped up by this trailing front and this moisture transport here, this is really what we're talking about when we're talking about the atmospheric river, this long, narrow piece. I've tried to superimpose that onto a real world picture which is this picture over here on the lead, the satellite picture from NOAA. We have this, the atmospheric river is this sort of piece underneath the front I've drawn and the green circle is really the, this is what I'm talking about, we're talking about the atmospheric river. This is where the water is being transported. All right, so what is actually pushing these atmospheric rivers along? So this loop that I'm showing you is another example of these water vapor satellite pictures of different examples of atmospheric rivers. This one I'm talking about is actually called the pineapple express. I saw that in the word clouds as some of you know what the pineapple express is, it's just a flavor of a type of an atmospheric river and it's called pineapple express because you can see the Hawaiian islands here and the moisture is sort of being transported from the Hawaiian island region all the way into the west coast and so hence pineapple and Hawaii, pineapple express. But what is pushing these things along? Well, the jet streams, so jet streams are narrow and fast moving streams of air that blow from west to east in the same direction of the rotation of the earth and so I've grabbed this nice schematic from the Science Photo Library and it shows you sort of how the earth rotates over here in those little arrows up above and then we have the globe, we have two different types of jet streams that I'd like to highlight are important for atmospheric rivers. So the blue one is what we're calling a polar jet and this separates the polar regions from the mid-latitude band which is sort of where we live. The red one is the subtropical jet and that separates the mid-latitude band sort of from the equator. So it's these two types of jets that interact with our weather to produce and move the atmospheric rivers to where they're going. All right, so this is just sort of like a pause for a second. So to give you a couple of tools that you can do on your own after the lecture, in your own time I've put the web link here for this water vapor imagery website. It's really downloadable data so you can take a look at this sort of stuff and this is a great tool to use to try to just if you care about, if you like to looking at weather maps and stuff. And so this atmospheric river was just last week or so, like a week and a half ago and it made impact or it made landfall in the Pacific Northwest and there's sort of two pieces to this. The first piece was this moisture that was sort of scooping up from the subtropical band and the second piece was what actually got pushed into the Pacific Northwest. So let's just jump over to this other tool called earth.nullschool.net and this is something that you could go on the web and it's an interactive tool. You click on it and you can move the globes around and you can pick all sorts of things like look at winds or you can even look at clouds and a bunch of different stuff and it'll let you play with that on your own. But I wanted to show it to show you this was the time, the same time that this is what the jets looked like at this time where these atmospheric rivers were happening. So if I can draw your attention to this piece here, this is part of the subtropical jet is grabbing this sort of, the United States is sort of right here, it's sort of hard to see but the white line is sort of the outline here. So this is the West Coast. So the subtropical jet is sort of pulling up moisture and that's this piece right here and then it gets into the polar driven jet region and so that moisture gets scooped up into the polar jet and then the polar jet just pushes it into the Pacific Northwest and that was our atmospheric river transport that happened just a week and a half ago. So if there's an atmosphere river that's forecast to happen, you can go to these different tools and you can see and play with what's happening on your own. All right, so how do we measure the strength of an AR? So there's a new scale that came out, this was developed by the CW3 crew over at Scripps and it uses two different quantities. The first is IVT, which is our integrated vapor transport which incorporates both wind and water and then the second is the duration meaning how long it's gonna last and so like the category scale you have for hurricanes this is a category scale we have for atmospheric rivers and over here on the left is sort of like a diagram that shows you what's going on here. So on the X axis is the duration, so how long it lasts, the Y axis is the maximum strength of IVT so this is how strong it is in terms of water and wind and then we can calculate these two things or grab them from our observations and put a category onto that atmospheric river. So for example, if atmospheric river is 550 kilogram per meter per second and this is the unit we use kilogram per meter per second which is mass and speed and it lasts only for 24 hours it's considered a category one which is sort of a moderate and that's beneficial, it just gives rain, it's not too intense and it just replenishes water sources and then however if it's long, too long or quite intense then it's a category five which means it's primarily hazardous and it's probably gonna cause floods. All right so that's sort of the atmospheric 101 of what atmospheric rivers are. So where do atmospheric rivers occur? Well they typically occur in mid latitudes because this is where the interaction with the jets happen and the most common locations is the west coast of continents. So you've seen this one, this was our pineapple express that was in making impact around California. However they're very common also in Europe and so here this is the US here and this is the European continent here in Africa right here and this is the Atlantic Ocean and you can see the moisture that's just being pushed from the Caribbean area all the way up into Europe. Other regions that are common is in Southern Hemisphere. We have the western South America. The country of Chile is very commonly influenced by atmospheric rivers and so this is an example of an atmospheric river making impact in that on the coastlines of Chile. South Africa is another place where you see a lot of atmospheric rivers and incidentally interspersed in a lot of my slides I have citations for scientific publications where I've grabbed this information from and so if people are interested and are able you can grab on you can look up those citations if you like but I just need to credit whoever I'm getting the information from. So for the South Africa one these colors show the strength of IVT and so you can see it this is South America right over here and this is Africa right here so you can see the atmospheric rivers sort of cross over the South Atlantic and hit the tip of South Africa. Also interestingly we see them in Australia quite a bit. This is a satellite picture that's actually taking a moisture stream from the tropical deep in the tropic band and it's being pushed along into across Australia into the eastern Australia region and western New Zealand so there's quite a few Australian atmospheric rivers as well. All right so less typical but also other regions that atmospheric rivers have impact northeastern North America believe or not so even though it's not a west coast of the US there's the east coast there are times where moisture from the deep in the Caribbean gets pushed up along the Atlantic and here in this particular example is impacting Newfoundland and beyond. Here we have East Asian examples with the Caribbean peninsula and believe it or not actually the Middle East sometimes experiences atmospheric rivers are quite rare here but they still happen so this is an atmospheric river that's streaming across Africa and impacting the Arabian peninsula. Also we have atmospheric rivers that influence the polar regions Antarctica and the Arctic. This is an Antarctica example so this happened just earlier this year there was an extreme event that was coupled with an extreme heat that produced an atmospheric river that made an impact in East Antarctica so this little bit is East Antarctica over here is Australia just to orient you everything is sort of flipped because it's upside down and then so this atmospheric river actually was the last straw and the collapse of the Congo ice shelf. Congo ice shelf was actually stressed before this and this was just sort of the last straw but this is sort of the piece that actually contributed to that collapse. This image in the middle is a satellite photograph that shows you this like the rough looking white stuff those are the clouds in the atmosphere river and the smoother white is Antarctica and this image over here is just shows you how anomalous or how the departure from what normally is in terms of temperature how strangely warm temperatures they actually occur during that period during this warm, this bullet that you see right here that actually Antarctica is actually flipped in terms of rotation here this area here sort of corresponds to this area here this area here we had temperatures that were over 70 degrees Fahrenheit above normal so this was a really profound extreme event that was closely tied to an atmospheric river and then we also have them in the Arctic and I like this example because this is sort of fun this happened just last month where we have Hurricane Fiona that influenced the Eastern seaboard we have the remnants of Hurricane Fiona you can totally see right here as it spins up they get scooped into a different moisture stream and then eventually cuts across the tip of Greenland and that was an atmospheric river that occurred in Greenland just last month all right so now we're onto why are atmospheric rivers important for climate and I think it's time for our second poll question so yeah and actually everyone got this one the majority of the people got this one correct the answer is yes 10% there are very long and narrow types of features and so even though they transport most of the moisture that we see from the tropics since the mid-latitudes they actually only account for a really small surface area so good job everyone all right okay and so here we go here's the sort of explanatory slide that I have for this but I don't yeah so anyway I hear I've just sort of written out what I just said even though airs move about 90% of the poleward water vapor outside of the tropics which I have grayed out here they only occupy 10% of the space and this is that you can visually see this by just looking at this map you can see just how there's very the different atmospheric rivers that really take up only a small space so this is why they're really important for climate because they really are one of the primary movers of moisture from the tropics into the extra tropics aside from tropical cyclones of course they're also very important all right so another reason why they're important for climate is that what we can call them drought busters this term was actually coined by Mike Denger who I'm crediting with this series of images here he is a retired USGS person he did a study where he looked at atmospheric river the drought severity in the western California, Nevada, Oregon areas before and after a series of atmospheric rivers so this panel on the left is from a period in January in 2010 where we had anywhere between abnormally dry to severe drought and then this middle panel here is the precipitation that occurred during a series of atmospheric rivers that week and so where the darkest blues are sort of correspond to this next image the grays here where these regions in the west are no longer under drought because those atmospheric rivers basically provided enough moisture to lift those localized regions out of drought so they're very important to sources of moisture for these regions especially winter time precipitation which is the primary time where atmospheric rivers occur October through March so this is also, I like to throw this example up here just to show you what water managers might use in terms of trying to understand and prepare for future or for their near future climate and water resources this is an example I grabbed from the California website for water managers you have, you can, I don't expect everyone to actually, this is pretty small to see but you can click different years to see what years with the amount of water that was accumulated that years and you can compare it to what's average so to explain the figure a little bit on the X axis is the water what I'm saying by water year so this starts in October first and it goes for a full year and it basically just accumulates all the precipitation or all the water that eventually falls into the basins that for these particular basins that we're looking at in California and you can see by the time you hit by the end of March or April which is sort of the atmospheric river season season you can see that most of the precipitation and most of the water that is used by these regions has fallen by that time so without the atmospheric rivers there you would have a year that might have a very low water year which would be one of these two years or if you have a lot of atmospheric rivers you would have, it would be way up here above normal and this is exactly what this figure is meant to communicate to you ARs either make or break water years for many locations and so this was 2017 which was a record year for California in terms of water and this was also not coincidentally the reason why is because it had this year just had a ton of atmospheric rivers or many, many atmospheric rivers of all sorts of intensities that fell during this year and this was really the primary reason why this year was a record water year another important piece to climate are extreme events and so atmospheric rivers often especially if they're in their category four and five those high really intense ones they can contribute to severe flooding and so this is just sort of an example of a series of atmospheric rivers that happened that caused the Orville Dam to collapse back in February of 2017 so this was, if you are from California or follow California news you probably have remembered this incident it was a pretty major deal with this dam that collapsed and here's sort of a picture of it this is the atmospheric river that sort of was the final straw to that collapse and I've shown you this a couple different times already this was the Pineapple Express that grabbed and sucked all that moisture into the Feather River basin here and I put a star where the basin is but yeah, 13 inches of rain fell in a very very short amount of time to cause this collapse so yeah, so not only are they beneficial they can also be quite destructive but the West Coast is not the only place that gets extreme events there are many other places just like we saw where they occur this study was done by David Lavers he's over in Europe at the ECMWF facility he looked at the top 10 UK flooding events and all top 10 flooding events for all these locations that I've labeled A, B, C and D which correspond to A, B, C and D all of these events were atmospheric rivers and you can see the trajectories of each of these so again, very important in terms of climate so I wanted to throw this in here for Antarctica because they're also very important in terms of the snow accumulation that happens on the ice sheets in Anorca this is work that Michelle McLennan who is the PhD student at University of Colorado has been doing, she cares about what's going on with Earthweights Glacier this is a picture of the different of the actual instrumentation that they used to capture this data and this figure in the middle is the graph of the snow accumulation during the several months from January to March or April during these two different camps and I can't remember, I think this might be cavity camp but I might be wrong, which one is which but the point I'm making is that this circle, event that have circle was an atmospheric river that happened over Earthweights Glacier and it bumped the accumulation in a massive amount just by that one atmospheric rivers and if we take a look at that from a climatological perspective which is this figure on the far right this little red point here this is the event that we're talking about and we compare to climatology which is this gray curve area we can see that this atmospheric river would far surpass what the climatological snow accumulation is for these events and this year was also a big year for Antarctica atmospheric rivers we had two more during the course of the year. On the flip side it can also account for weakening ice shelf stability this has happened in Greenland as well as Antarctica but I'm using this Antarctica example because this is a really nice paper by Jonathan Willie he's a researcher in Switzerland at the moment and he did this nice study analyzing that this ice shelf weakening in the Antarctic Peninsula which is this little point right here this is South America here's Antarctica sort of rotated so you can see the Antarctic Peninsula. These colors are these warm colors are the departures from normal in terms of sea surface temperatures so the yellow and the orange show you a really warm sea surface temperature and these black lines are the trajectory so you see the atmosphere river sort of moving over the warm area and then eventually making impact on the Antarctic Peninsula this figure here that's labeled D it shows you the actual integrated vapor transport with that particular event and then we move up here to this image this photograph this satellite photograph that shows you what the Larson A and B ice sheets look like before the event and then this middle figure is what was happening in terms of the atmosphere river during the event you can see the atmosphere river right here in that striated cloud looking area and then after the event you can see the disintegration of the ice sheet so again very very important for climate for not only mid latitudes but for high latitudes as well okay so that brings us to the final piece of the talk which was the title what happens atmospheric rivers in a warmer world okay so now that we have all this background let's actually talk about what happens to atmospheric rivers in a warmer world alright so to talk about what happens with atmospheric rivers in a warmer world we need to talk a little bit about climate models or system models the models are a glorified computer program that actually compute fields like temperature and precipitation and wind on a gridded data set and when I mean by gridded data set I sort of put this little image here where you can see the globe and that mesh that looks over that's wrapped around the globe so you wrap this mesh around the globe and the intersection of all these intersection points we call those grid points and at each of these grid points we do these calculations which actually then tell us then we can analyze it help us to understand what's happening with temperature what's happening with winds what's happening with precipitation so all of these things that are calculated are actually listed or some of them are listed here in this schematic things like ocean currents and sea ice and wind and precipitation evaporation all this stuff is calculated on these grid points and then we look at the as scientists we look at this data and then we you know if we simulate a period of time with enhanced greenhouse gases we can try to understand what happens to the climate with a warming world and then the step beyond that for us is what do atmospheric rivers do on these but we're looking at them in these models and gridded data sets okay so let's go back to this basic figure AR for ARs we need to consider both water and wind for climate change so warmer air means more water is available to ARs in the atmosphere and so this is simulations by the community air system model CESM for two different periods this period on the in the middle here this the leftmost blue-red figure is we call this an historical period and this means like you know it's already happened or it's happening it's sort of like modern times and so this sort of figure you can trip in is this is sort of what the atmosphere looks like now in terms of precipitable water remember this is the variable where if you take it all and you precipitate it out that's how much water is in the atmosphere this figure on the right is a future climate so this is what the world looks like under future greenhouse gases more that are elevated and then this figure on the bottom is the difference and so you can see everything is red which means that pretty much when we warm our atmosphere we have more water that's available into the atmosphere so there's just more water that's that exists it's a water vapor in the atmosphere so that's our water piece and we know we're gonna have a lot more water the second piece is winds so winds are what we call dynamic they move around and this is actually a little bit more complicated and it's very very active area of research so if we go back to our figure of the globe where we're looking at our jet streams we have our polar jet stream which is projected to move forward with enhanced greenhouse gas warming for the sub-tropical jet which is this red one this is projected to sort of expand and intensify and so these two things will interact with our daily weather and how they interact is actually a little bit tricky to try to diagnose and understand but this is what we need to do when we wanna try to figure out what's happening with atmospheric rivers so this is a figure that is looking at the difference in what's happening with just the wind component so AR's track with jet streams as I've mentioned so where the jets move so will the atmospheric rivers so this figure is actually looking at the difference between like a business as usual scenario what the worst amount of you know the warmest we could project the world to be in terms of no stops on emissions and then we subtract that from what's happening now and then we can see what the difference is and so this is the west coast of the US zero means the equator and we'll just take a look at these enhanced oranges so this tells us that the jet streams will strengthen in this sub-tropical region and for the polar region the blues tell us that for this particular simulation so that we expect the jets to decrease and so this has implications for where AR's are going to be so if we look at that from different regions around the world and this is work that I have collaborated with and taken with from Ashley Payne she has this, this is the citation for where this work has been published to nature review journals in terms of atmospheric rivers and climate change it's a very nice diagnosis of what the state of the literature as it is right now in terms of what we know in terms of atmospheric rivers and climate change she's produced this really nice pot that we're breaking it up in between the water piece and the wind piece and so the water piece for different regions I'll just say this is the west Pacific so this is like Japan Australia is right here the South Pacific and South America this is South America and this is the South Pacific and then here the South Atlantic and South Africa so for all of these regions the water is just going to increase and so this is something we understand from that earlier plot we saw with the community earth system model these black contour lines are meant to represent what the core of the IVT this integrated vapor transport or the strength of where the ARs are where the core, average core is actually going to live so this, these little black enhanced lines with this concentric circles tells you this is where we expect the atmospheric rivers sort of to be at the current times and then the colors in the background is what's projected in the future so if we look at the wind piece on the right here this hopefully this explanation will make start to make a little more sense where the colors are blue is where IVT is decreasing and the reds are where IVT is increasing and so if we take a look at these same black lines where we expect the core of the IVT going to be so for example in the South Africa piece we see that the IVT is projected to decrease and then the IVT is projected to increase a little bit to the north of that and so what this type of figure tells us is that that core of the IVT is sort of expected to shift equatorward and so that would draw atmospheric rivers away from the tip of South Africa and potentially decrease the amount of water that's available to them and so if we look at different regions you can see all of these different blues and reds and you know where things are shifting is different for each region so the lesson to be learned from a figure like this is that regionally atmospheric rivers are gonna do something different depending on where you are, what region you are and where the winds are gonna do in the particular region that you are that you're looking at so it's a very regional specific thing unlike the water piece where it's just gonna get wetter everywhere all right so let's just step back to the water piece because this is even though we know that there's gonna be more water what does it actually mean? Well what it means that we're probably gonna have more intense precipitation so this is work that was led by Alan Rhodes and if you're interested there's the citation right there and he ran the community air system model for recalling historical simulations and future climate simulations so 1985 to 2015 was what we call our historical period and our 2070 to 2100 is what we're calling our future period and we're looking at the amount of water or amount of precipitation that was produced from ARs by category so the x-axis is the month of the year October through August and the y-axis is the amount of precipitation where there is no color means the precipitation that fell in this for these months and these ranges it was not an AR but for the ARs are colored by category so here we have for example here can't reach that the 46% means that 46% of the precipitation for January for the historical period was due to an AR so that's how you interpret this sort of figure so the figure on the far right is the difference between the two and so the one thing that does pop out to everyone's eyes you see a lot of red so the red is telling us that in the future simulate in a future type of climate we expect more precipitation from these category five these most intense and extreme types of atmospheric rivers so that is what we expect in the future depends so we don't know where they're necessarily going to land because that depends on where the wind is gonna go but where they do land they will whatever precipitation is in there will be more extreme all right so this is sort of like a summary figure and again this is out of Ashley's paper The Pain at All in 2020 and so you can spend a lot of time with this figure but it's a great summary figure so this is why I like to sort of choose it so here we, the pink here is the just represent what we expect atmospheric rivers to do in terms of frequency and counts just due to more water availability just these are just basically where the storm tracks are these different icons are very specific metrics this metric over here is what we call in frequency this is simply just the AR counts the little locator symbol here is location where the atmospheric rivers are going to fall so this is where the winds are gonna do this is the wind piece how those winds move back and forth we have precipitation and precipitation extreme icons and we have a melt icon and then a flooding icon so let's just take a look at the western US for example we see that most of these things are red which means we expect increases in all of these things but the locator icon is part red and part blue and this has to do with the red is that polar jet that's being pushed forward and the red is where the sub-tropical genth is intensifying so ARs that are influenced by the sub-tropical jet are going may increase and those are influenced by the polar jet for the western or the America are expected to decrease depending on where the jets go for example another example here would be in the South Africa piece we saw this in the previous two slides ago where I was showing you the different the IBT cores and where the winds are expected to go for different regions we have an expected decrease in precipitation and the location but a lot of this other stuff is grayed out and the gray sort of means it's not really resolved yet there's still a lot of uncertainty and so if you just take a look at a lot of these different icons you can see there's a lot of gray here which means there's still a lot of work to be done and a lot of understanding that has to happen before we really understand what atmospheric rivers are gonna do from region to region. Okay so I often also get asked what does the shape of AR change with warming and this is sort of hard to answer because this also depends on how you define an AR in models or maybe I should rather have said gridded data sets because we actually look at these things in gridded data sets we have to have an algorithm that says okay so for these great gridded data sets here and here this is what the spatial footprint looks like so depending on what research group and what research question you're doing you may have a slightly different way of defining the spatial footprint on a gridded data set than the next person and so that's sort of what happened in the community we have and which is this figure right here that shows all these different color outlines show you all the different ways that are now currently in the community which people define a particular atmospheric river there is this purple one that's like a sort of a broad spatial footprint and then we have this green one which is sort of a narrow spatial footprint so what do we do to try to understand what's happening when there's so many different ways of actually defining it on a gridded data set? Well there is an effort out there called ARTMIP and this is something I'm heavily involved in called the atmospheric river tracking method in our comparison project and one of the things that we wanna do is we wanna try to understand what's gonna happen what are the differences just due to this these different definitions and how we can take that information and then say something about climate change so what we need to do is we actually need to look at all of these different types of ways of defining them and then we need to look at the range of answers before we can actually say something and so this is what this plot is trying to do it's taking this range of different ways of defining an atmospheric river on a gridded data set and it's applying it to a model and then we're looking at the historical period which is the black and the future period which is the red and we're looking at the climatology so the x-axis is the month of the year and the y-axis is labeled as percent of AR condition at coastline but that's just sort of fancy for saying how many counts, how many ARs hit the coast okay so at first glance you can see oh well for the northern American west coast it seems like there's gonna be an increase and yeah that's what the literature sort of tells us but if you look closely you can see the range of answers sometimes overlap each other and so that means there's still some uncertainty and what we really need to say about what's gonna happen with atmospheric rivers just based on how we're defining it on these gridded data sets so we wanna look at the full range before we actually give an answer like yes atmospheric rivers are gonna increase we can say well yeah they're gonna increase but there's this range of possibilities and so this is another way of looking at the different range of possibilities but also with precipitation this is actually a little bit more robust there's less, there's more agreement here and so I'll step you through these figures this figure cause it's a little complicated the x-axis is the, we're calling the rain rate so this is the intensity this is, these are precipitation distributions and the distribution is basically we're looking at different intensities and how much rain falls for a given intensity so for this three to five degree or three to five bin of rain rate that is sort of like a moderate or a drizzle and 150 to 200 millimeter per day is like it's pouring so the bins on the left are less or light precipitation the bins on the right are intense precipitation so for example for the SWUS at Southwest US we take a look at these moderate rates the grays are the historical and the reds are the future and so with this figure is telling us is that we expect in the future there to be less precipitation falling in this moderate rate but if we move over to the extreme rates we see that the red is now more over the ray line so that tells us that we expect more precipitation to occur in these extreme rates and this is robust and pretty consistent across all these methods all right so another thing is there are climate change fingerprint already and there are people that are thinking about this and so this was a study led by Allison McCallis and this was looking at that Orville Dam event and so this little icon that showed to remind you what the or which is the series of atmospheric rivers that causes the dam collapse so what they did is they ran this regional climate model called model for prediction across scales that's MPASS and they ran this model to simulate what the storm would have been like in the past which is the blue line and then they simulated it to what it actually happened in current times which is the black line and then near future and present and then far future with conditions so the past means there's less greenhouse gases and the far future means there's more greenhouse gases so as you go from the past to the future you see that the intensity of this storm would have been much less in the past and much more in the future and so if we look at this in terms of precipitation during the course of the storm there were two pulses one between February 7th and 8th and one another one between February 9th and 10th and you can see again this progression of what the storm would have been like in the past in the blue and would have been like more in the future in the far red and you do see that one there is a small climate change signal that's already happened because what would have happened the current simulation shows more precipitation than it would have been in the past but we also see that in the far future the precipitation would be much more severe so there's other people that are doing these types of things and this is a study by Hwang and Swain this was actually just published this is the arc storm scenario where they're trying to figure out okay what's the worst storm that happened in the historical past I mean call that arcist and that's what these two bands and then what's the worst storm that happened could happen in the future with enhanced greenhouse gases and this is arc future these upper panels show these departures from sea surface temperature so these are where there's reds and oranges where the sea surface temperatures are warm and these bottom panels are showing you the integrated vapor transport by now everyone is familiar with the IVT and the integrated vapor transport and how these look so you can just sort of see that the arc future just looks pretty devastating so but what do we do with this information this is a super high resolution I mean there's like all the fidelity is really high and those red points are very close together so that way we can resolve what's happening on a local scale much better than we could if it was a global model we take that information and then we produce metrics that water managers can use such as what is the hourly precipitation rate or what's the hourly runoff rate and once we have this information and then the water managers can take this information and then plan for what we need to do in the future so we are trying to prepare for any type of megastorm that might happen in the future all right so I think that's all I really had to present to you so let me just sort of give you a summary the atmospheric rivers are important for earth's water cycle and local climate and hopefully I've convinced you of this they are comprised of water and wind water availability will increase in future climate and will more likely have intense precipitation associated with that the changes in the winds and the jets will be regionally dependent and then finally by setting errors in the future we can prepare for any changes and be prepared here's the final slide I have with just a bunch of resources and tools with different websites that I've mentioned for those of people who wanna go and play with stuff on their own and here's also a list of operational centers that I talked about that produce actual atmospheric forecasts and other products there's also one here I wanted to highlight in Chile, South America which is sort of the counterpart to the one that scripts for South America as well so with that I'll stop awesome thank you Christine so we have just over 20 ish minutes for questions so as a reminder for folks that are in person you can just simply raise your hand and ask your question and the room microphones will pick up your sound and then for folks that are online you can just ask your questions through the Slido platform and then for these links as well I can also point folks to Slido if you click on that hamburger menu the three horizontal lines there's a drop down there that'll also summarize all of these links and some other websites that Christine shared throughout her presentation and so as we collect our thoughts maybe in person for some questions there's already a couple online the first was from AJ who was wondering how El Niño and La Niña might impact atmospheric rivers? Yeah that's a really good question with El Niño and La Niña tend to for West Coast and like the West yeah the West Coast of the U.S. and California that has a really big impact because El Niño will create warmer SSTs or cooler SSTs depending what phase you're on and so with the warmer SSTs there is some correlation to increased atmospheric river activity and so one of the things that we that just preliminarily have found is that with the El Niño you do see more of atmospheric river coming into Southern California but as I said like not all El Niño flavors are the same and so you can have an El Niño that may actually produce less precipitation on California than on La Niña for example so yeah I feel like these modes of variability need to be investigated a lot more deeply before we can actually say anything for sure but that is definitely an active area of research Any impressed questions? We can also end the fire season and really wrap up bring a lot of moisture to our fields Can you talk a little bit about how they might how ARs might shift in seasonality particularly maybe for the West Coast? Yeah so I don't from what we've seen before seen in like some of these simulations that I could go back to the slide that sort of showed the seasonality a little bit Don't see like because there's a depending on where you are in California or even like Northern California, Southern California it matters it's not clear what month is going to be the most active for atmospheric river so it really is going to follow the seasonal flow of the jet so you don't see a big change in seasonality for the future climate but there is some hint that October might be a little bit more active just because the warm season is sort of expanding a little bit but as I said I'm very hesitant to actually give you a firm answer just because I feel like especially for West Coast ARs I feel like there's still so much uncertainty what's going to happen in the future because of what those jets are going to be doing especially with any different jet like where it's going to move and to what degree it's really hard to say that but maybe October will expand We will take another question from online and I apologize if I'm not pronouncing your name completely but from Yuanpu Li is wondering what altitude do atmospheric rivers lie in the atmosphere and does the wind in the lower atmosphere matter in transporting water That's a really good question I didn't really talk about levels of where the atmospheric river is but that matters so the jets we tend to think are in the upper level but most of the water actually lives in the bottom part of the atmosphere what we call the boundary layer so maybe the first few trying to convert millibars to thousands of feet or whatever but just the lower part of the atmosphere so often what's happening with the low level jet mirrors what's happening with the upper level jet but the atmospheric river itself is often considered a low level phenomenon just because that's where all the water is but you have the water in the bottom part but the driving piece of that is in the upper level so there is a little bit of a disconnect I'm not sure if I answered that question enough for you but you can pull up again I guess yeah following up on the fire question is there any research being done about the potential impacts of increased atmospheric rivers or increased moisture on things like debris flows post-fire debris flows in California things like that absolutely there are a number of people that are doing that research there are some people out of the Desert Research Institute in Nevada and there are some people at the Scripps Center the CW3E groups but they are definitely that's a very active area of research actually and I'm not coming up with a name off the top of my head right now but if you get back to me I can get you some names great and as we take our next online question Tim is also actually wondering if you would put up your conclusion slide again just so some folks online could get a snapshot of it yeah okay and then taking the next question from Liz is wondering do more intense atmospheric rivers travel further inland? yeah actually another really good question everyone so yeah the more intense ones will penetrate deeper into the continents just because they have more stuff and it takes longer for it to rain out but typically the inland ARs aren't quite as intense as the ones on the coast just because by the time by the time they reach inland they've rained out a lot and then as these weather systems move over the mountains like the continental divide on the other side that they tend to be more windy and less wet just because of you know that the mountains tend to squeeze all the moisture out but the more intense it is the more likely they will actually get further inland for sure it's a modeling question so I saw a whole bunch of different models that you put on top of each other and there looked to be quite a sizable difference in I know so can you expand more on the methodology and the percentage difference and then how that's looking correlating to your test data so can I go back is that alright if I move back okay are you talking about women this one right here yeah well you started talking about yeah so each of these different lines are different algorithms so we call these ARDTs atmospheric river detection tools there's too many acronyms but ARDTs detection tools it is will define the spatial footprint of an atmospheric river on a grid of data set and so different research groups will care about you know like one group I actually have a prepared slide one group cares more about impacts and so this is sort of a complicated slide so let's see if I can put it up here it's not maybe I just have to move it okay sorry give me a sec all right so method one method one cares more about the intensity and so the little bubbles are a time a place in time like a time stamp and this is over the whole course of the model so like 20 years of data that we're looking at the reds or the oranges or the climate change and the blues right and so method one if you take a look at how the shape is changing with warming it has actually the shape not changing too much because this is coverage this is like the area and then the average IBT intensity is on the x-axis and so they're becoming more intense but the shape isn't changing and so and then method two might care more about the impacts per given intensity so like so they're the intensity is sort of the same they sort of set the intensities like an atmospheric river needs to be at least 500 kilogram per meter per second so the kilogram per meter per second is the mass and the speed combined together so it has to be at least this amount in order to be called an atmospheric river and so those tend to actually not change much intensity but they change their shape like in the so in a warming role that 500 kilogram per meter per square area is just going to be bigger and so the method two people care more about what that spatial coverage is and method one people care more about maybe this one keeping the structure the same and so these are different research questions and so that's why they develop their tool to detect the atmospheric rivers to answer the question they want to but the problem with that is that it's really hard to say something collectively about atmospheric rivers and climate change we have so many different ways of defining it so one of the things that ArtMip tries to do is to say you can't just look at one way you need to look at a bunch of ways you know and then we can have a range of possibilities like the shape will be anywhere from here to here or the amount of atmospheric rivers that hits the west coast will be anywhere from here to here maybe expand into October you know maybe not depending on like you know what your methodology is so it's really sort of complicated and it's very subtle but it's something that absolutely has to be addressed and we are addressing it in the community right now in fact I feel I'm very positive because like now when I read papers people are talking about uncertainties and the limitations of when we use one method and you see more people using more than one method to say okay well this is the range of possibilities of what I think will happen you know based on my research question here so does that answer your question it does and how is that looking with actual physical test data versus the model like what's the percentage okay so for the the so this is like another tricky thing in terms of validating atmospheric that these tools so we validate them using reanalysis data and what I mean by reanalysis data this is actually it's a gridded data set but it melds observations and models so it's not pure observation and so one of the things that ARTMIF does is like we have a baseline everyone runs their code on our observational product which is model and arms and to have a baseline of what that you know what that method does compared to other methods and then and then the step 2 is this is how it changes in climate the problem is that the observational data set isn't pure observations right so when we first started in the ARTMIF program we actually had a few graduate students bless them to actually we had a test period of a month February of 2017 because I did so many atmospheric rivers and we had them count by hand you know this like looking at the satellite pictures and data like yes we counted by hand this is how many observational data sets we have there are also some of the observational data sets on the west coast the CW3E uses but those are for points not for the whole globe and so there's this there's this you know this balance we have to dance when we're trying to we're validating on a product that's actually not pure observations does that answer your question? thank you great our next online question is from Stu who is wondering if you could comment on short term atmospheric river forecasting affecting reservoir operations in other words flood pools I heard this was an issue at Orville yeah you know I don't know a lot about that there is a there is a definitely a lot of people researchers that are looking at short term forecasting and actually sub we'll call sub seasonal like one to you know one to four weeks or something like that but I don't that's not I don't know a lot about it but I know there are definitely like the the Scripps Group in that operational center they actually do produce short term forecasts for that sort of thing and they do work with water managers so if you're a water manager interested in that I would actually send you to that CW3E website because they probably have some some information but I do know the water managers care interact with the atmospheric river scientists because you know just in terms of like planning for the future for like you know or like a dam for example you know in the future we need to build up the height of the dam is like one thing that is being done in certain dams in California another thing is like increasing the integrity of the actual dam structure so there is less you know to be able to say more pressure within deep within the reservoir so there are definitely things that are being looked at to address that but I would send that this person to that website maybe yeah for more details great and I'll Patricia has a couple questions so I'll probably ask them together step by step so first are you using finite difference modeling so okay I mean the the there's a lot of there's some public questions I would have the models that we used for this climate change piece like what can we use the model and that does use finite differencing as a tool for the calculation if that was the question there are different types of dynamical cores are called ways we actually do the computation in different models and this one that for this study that I showed with the different climate change use the the finite volume it's called the finite volume dynamical core the one that I showed with Alice in the callous was with the oracle dam that one uses an unstructured that the modeling across scales is something a little bit different it's a it's called a spectral element type of a dynamical core so I'm not really sure if that was your question but that's my best attempt at answering it and the second part of that question is what type of computer do you use to solve these equations well we have super computers so the one that I the lot of the CSM actually which is done here at NCAR uses the our super computer in our facilities the art myth community use the the the facilities at the Berkeley lab so they're just like they could make their super computers they like they can handle like billions of calculations and it's like I don't I don't have this that so that could be completely wrong maybe it's millions maybe it's billions but it's a very fast machine not a laptop yeah and then part three how do you deal with nonlinear and chaotic effects well yeah okay so that's all hard hard question so yeah I mean I'm not sure how to interpret this question so I mean because nonlinear and chaotic I mean we're just talking sort of about weather and so I'm just going to bake all of this down into you know weather or climate is the average weather and so the climate model is different from a weather model a weather model will it tends to be higher resolution means higher closer together and it only runs like maybe up to 48 hours or a week or two weeks or something like that and so there's when equations are solved they're solved we don't have to solve everything because we're only looking at a short period of time we're not looking at the whole year so we don't have to care about the whole seasonal cycle where climate models are much different they tend to be coarser resolution and then they we run them for a lot longer and then there's more stuff we need to calculate because we have to account for the whole the whole you know like the whole seasonal cycle the whole year which means like how the sun changes and moves around the earth or moves around the sun so I probably didn't answer a question but I'm not really sure how else to address that part of the question is if there's a website that Patricia can go to to get more technical information on atmospheric models absolutely yes you can also feel free to contact me and then we can have a chat and maybe I can understand what your questions are after the community earth system model there's a we have an awesome website and we can talk about all the little you can see the different documentation for the different models especially for the atmosphere model that has a tutorial so if you're a graduate student or a postdoc I would highly encourage and you care about climate modeling you should apply to be part of the tutorial we'll teach you how to run the model and we'll teach you all sorts of things about what goes in the guts in the model and answer all of these questions better than I did so yeah so go to this he has a website yeah great any in person questions? not we'll take a question from Lou who's asking what operational forecast services are available to support atmospheric river so this was the the slide that I tried to think about that for you guys operational centers so yeah it might be in the slide though it was my last slide so there's the CW3 is definitely an operational center they do forecast they also do reconnaissance missions there's actually a water specific part to the national weather service website so that's water.weather.gov I think if I'm reading that right and so for the US now other operational centers around the world don't I don't particularly know of any that do AR specific stuff other than CW3 and the South America one the CR cubed in cell A CMWF does I'm sure there's probably people in that community that might have a research a research based operational center I just don't know about it so the one I do know about is CW3 e-scripts so I would definitely go there it's a great group and a great website our last online question is from Steven so arguably subtropical jets pose the greatest challenge in anticipating atmospheric river behavior especially the weaker subtropical jets so how well do models forecast subtropical jets well this actually depends on the model if you look at the different types of there's an effort called the C-MIMP the climate model intercomparison project that has a whole bunch of different climate models and so different climate models will actually have a different representation of what the subtropical jet does so it's a it's a research question for sure and it would be something that you need to look across climate models to see how the different jets behave across different instances just sort of like I was saying for the ARTMIF we want to look at what Mr. Gerber is doing across a range of possibilities we do the same thing with climate models this is what IPCC the Intergovernment Panel of Climate Change does it compares a whole bunch of different climate models to try to communicate with confidence or low confidence what's going to happen in the climate based on the climate model so you can check out the IPCC website to see the range of possibilities for different models any last in-person questions otherwise I do have one but I'll see if there's any other ones awesome so for our undergrad and grad students that might be in the room or watching online who might be interested in doing this type of work do you have any advice for them I know you talked about the CES sub workshop is any other ideas to give them well I yeah I guess you know participate in some of our the workshop or the tutorials if you're interested in getting into climate modeling I guess depending on like if you're an undergraduate or a graduate student there's different opportunities for our advanced studies program here at NCAR for both graduate students and undergrad and graduate students and postdocs I would yeah just reach out get involved we have a workshop the CESN has a workshop that is more about the modeling piece of it but in terms of atmospheric rivers themselves it's a fun community I would talk to people that's my advice great thanks and give another round of applause thanks everybody here thanks to everybody online I also want to give a shout out to the folks behind the scenes so Julia, Paul, Nick and Brett thank you so much for supporting this event so this is our last event for the 2022 Explorer series so stay tuned for our 2023 events we'll probably have that information here in the next couple of months thanks everybody and I hope you have a great rest of your day