University Place Wednesday Nite at the Lab  
Mike Pavolonis: 
"The Role of Satellite Data in Preventing Aircraft Encounters with Volcanic Ash"  
September 15, 2010 

>> Tom Zinnen: Welcome, everybody, to Wednesday Nite at the Lab. I'm Tom Zinnen. I work here at the UW Biotechnology Center. I also work for UW Extension. And on behalf of the Wisconsin Alumni Association and Wisconsin Public Television, welcome to Wednesday Nite at the Lab. We do this every Wednesday night, 50 times a year. Tonight I'm delighted to be able to introduce Mike Pavolonis to us. He's a physical scientist for the National Oceanic and Atmospheric Administration. One of the great acronyms out of Washington, DC, otherwise known as... >> Mike Pavolonis: NOAA. 

>> Zinnen: NOAA, as in "know a lot" and "Noah the ark." Mike's a member of the Advanced Satellite Products Branch of NOAA which is located at the Cooperative Institute for Meteorological Satellite Studies here at the University of Wisconsin-Madison. He specializes in satellite cloud remote sensing and infrared radiative transfer. Mike has developed several satellite-based tools for tracking dangerous volcanic ash clouds, and works with the international, operational and research community to improve volcanic cloud monitoring and forecasting. Mike received his BS in meteorology from the Pennsylvania State University in 2000 and his MS in atmospheric and oceanic sciences from the University of Wisconsin-Madison in 2002. Prior to joining NOAA in September of 2005, Mike worked as a researcher in the Cooperative Institute for Meteorological Satellite Studies, otherwise known as CIMSS, here at UW-Madison from May of 2002 to August of 2005. As many of you read about this spring, that wonderful little volcano, which no one has yet pronounced correctly, in Iceland did a major job of disrupting international travel. We get to hear about how Mike's work helps us deal with that kind of issue. Please join me in welcoming Mike to Wednesday Nite at the Lab. [APPLAUSE] >> Pavolonis: Thanks, Tom. It's great to be here to talk about this. 

This is something that we've all become more aware of now since the eruption of that unpronounceable volcano in Iceland-- I will try to pronounce it in a little bit-- in April. One of the major missions of NOAA is to support the nation's commerce by providing information for safe transportation, including air travel. So it's no surprise that NOAA is very, very interested in keeping aircraft out of volcanic ash clouds which are very dangerous to aircraft, and I'll explain why during the course of this talk. Of course, in April Eyjafjallajokull in Iceland erupted and wreaked all sorts of havoc with air travel across the north Atlantic and Europe, having incredible impacts on the economy and really disrupting people's travels. But this is an issue that we at NOAA and a lot of people outside of NOAA have actually been working for over 20 years now in terms of using satellite assets to try to keep aircraft out of volcanic ash clouds. I've been working on this issue myself for about eight years. But we've come a long way in that 20-some years but we still have a little bit further to go yet, but it's an exciting time for sure. Just to give you an idea of where I'm going, I'll just say a few words about volcanoes and volcanic eruptions. I'll warn that I'm not a geologist or a volcanologist. I'm an atmospheric scientist so my understanding is very basic. 

I'll also talk about what volcanic ash actually is and how does it damage aircrafts, and then I'll get into how we use satellites to track these clouds. First thing, just a little bit of volcano 101. A volcano is a vent or a fissure or a large crack through which molten rock, which is basically melted rock, and associated gases can be expelled. A volcanic eruption will occur when magma reaches the surface through one of these vents. Now what determines whether or not it's an explosive eruption that will actually produce a volcanic ash cloud or to the extent that it will produce a violent explosion that produces a huge volcanic ash cloud really depends on the viscosity of the magma. In other words, is it runny or is it very resistant to flow? If it's highly viscous or resistant to flow, a lot of these volatile gases can be trapped within the magma building up, building up, building up until finally a threshold is reached and a big explosion happens and you get a large ash cloud. Magma that is a little bit more runny, gases can escape a little bit more easily, and you don't tend to get these very large eruptions. So the consistency of the magma plays a large role in determining what kind of eruption you get. Groundwater also plays a role, but that's sort of the basics. There are two eruption types, really. 

There's effusive and explosive. Now effusive, think Volcanoes National Park on the big island in Hawaii, Kilauea, rarely produce ash clouds or if they do they're very, very low level. Not really a threat to aviation. They're actually a tourist attraction. But then you get eruptions that actually do produce ash clouds, sometimes quite violently and these are explosive eruptions. These are the ones that we're most concerned about from an aviation perspective. Just to give you a sense for how often eruptions occur. On average, about 60 different volcanoes per year erupt. And you get about 10 eruptions per year, on average, that will ascend a volcanic ash cloud up to about 35,000 feet or so, airline cruising altitudes. But every day you get at least one or two little eruptions. 

There's a little ash cloud somewhere in the world just about every day. Those clouds are less of a threat to commercial aviation, but they're a threat to local and regional aviation, especially in places like Mexico City where you have a volcano just outside the city, and it produces these little ash clouds. But the volcano is very high so the ash gets blown off the volcano and it's already pretty high and the airport's close by so even very minor eruptions like that sometimes cause a problem for aviation. But you can see here that based on this very qualitative scale here and these numbers here on the diagonal indicate how many eruptions are in the Smithsonian database for this type of event with this qualitative description. See most of them fall into the category of gentle, effusive or explosive. And it's really when you start getting into where this blue line is where you get ash clouds that go five kilometers or more above the crater that it becomes a more significant threat to aviation. And just to give you some sense, Mount St. Helens, when that erupted in 1980, fell about right here on this scale. That actually put a cloud above 25 kilometers so we're talking it was above 40,000 feet, 50,000 feet. Mount Pinatubo is the largest eruption in recent history, that was in 1991 in the Philippines. That actually was large enough to actually influence climate slightly for the next year or two after the eruption. 

And then, of course, the granddaddy of them all, Yellowstone. That happened several hundred thousand years ago. And those events, thankfully, are very, very rare. We probably have more things to worry about than aviation when an event like that happens. So where are the world's volcanoes? Well, they tend to be located at the boundaries of tectonic plates. And there are a lot of boundaries here out rimming the Pacific. And this chain of volcanoes that goes all the way around here throughout the Pacific basin is known as the ring of fire. But you have volcanoes elsewhere. There are volcanoes on Africa. There are volcanoes in Europe, Asia, even Antarctica. 

So there are volcanoes basically everywhere. Now, where are volcanoes relative to major international air routes? That's a major question here. And so what this map shows, although not quite as colorful, in red here you have the location of volcanoes, in blue are major international flight routes. You can see these blue lines intersect or go over these red dots quite often, and so you do have a lot of air routes that go over regions where there's a lot of active volcanoes. Let's just zoom in on one particular region. Take the north Pacific. This is a region that has hundreds of volcanoes along the Kuril Islands and the Kamchatka Peninsula of Russia, the Aleutian Islands of Alaska and even in southern mainland Alaska here, there are plenty of volcanoes, and then superimposed on this are some of the major flight routes that go through this region. On average, you have 10,000 passengers riding these air routes per day, and you have millions of dollars in cargo going from Asia to North America along these routes every day. On a yearly basis you get about four days per year in this region where you have a volcanic ash cloud at cruising altitude. Some years it's more, some years a little less, but on average about four. 

So that's a major deal considering the volume of air traffic that goes here and the number of active volcanoes. There are actually volcanoes on Kamchatka Peninsula that basically erupt every day. Some days they're just small eruptions below the cruising altitudes, another day it will get a little bit higher. And so this is a region where we really watch it very, very closely from satellite. So what is volcanic ash? Simply put, it's extremely fine particles of pulverized rock and glass. Now, it's mainly composed of silicates, but you do get some oxides in there like sodium, aluminum, iron and calcium. That's important because these can dissolve in water and when they do they can be corrosive. So that's just an additional effect here. Volcanic ash is a very hard material. It's very similar to quartz. 

So it's extremely hard and it's extremely abrasive. And perhaps the most important fact here is that it has a melting temperature that is lower than the temperature at which the combustion chambers within jet aircraft operate, meaning it can be melted when ingested into jet engines. And I'll show you in a little bit what that means. This is just sort of a closer look at what magnified particles of volcanic ash look like. You can clearly see these things are very rough, very jagged looking, very abrasive looking. It's not soft at all. You don't want to breathe this in. The particle sizes can range from something that's really, really tiny, almost invisible to the naked eye, to things that are the size of big boulders or cars. But those things usually fall out right next to the volcano after an explosive eruption. But it's the smaller particles that can actually remain suspended in the atmosphere and be transported by the winds away from the volcano. 

And those are the ones that really wreak havoc with aviation. So how does volcanic ash affect aircraft? Well, the primary thing is it can damage jet engines. And actually can lead to, and has in the past led to, complete engine failure. Being that it's so abrasive, it basically sand blasts the entire exterior of the plane. I was up in Alaska for a meeting last year, and I got to see the wind screen or the cockpit windshield of a plane that flew through an ash cloud. It was totally opaque because it was just sand blasted by volcanic ash. You could not see through it. And it will not only damage the windows but the whole air frame and all the flight surfaces. Another thing it does, is it really messes with your air speed instrument. And so the readings from it are no longer reliable. 

That's a very, very bad thing. And then it can get into the air conditioning, the cooling systems and then this leads to contamination of the electrical and avionic units. And another thing is it gets into the cargo hold and the cargo hold smoke detection systems will constantly go off because of the ash in there. Just a little bit more specific information on what volcanic ash does to jet engines. These are very abrasive particles, as I said, so they enter the engine and as they're entering they actually erode away at the compressor blades. This greatly reduces their performance. Then the glass particles of the ash will actually melt within the combustion chamber because it's much hotter than the melting point of the ash. This is especially true if you're at a higher thrust on the engine. And then this melted material will cool down in the turbine and actually deposit on the veins, and it will actually restrict the flow of the high pressure combustion gasses that make the aircraft move. And if enough of this happens, it can actually lead to complete engine failure. 

And this has happened. And so there was an event in 1982 where we really first became aware of how dangerous volcanic ash is for jet aircraft. Prior to 1982 there weren't a whole lot of jet aircraft out in our commercial fleets, and so this is really was the beginning of the jet aircraft days. So this is the first real incident. So on June 24, 1982, a British Airways flight, it was a 747, accidentally flew into a volcanic ash cloud from Mount Galunggung in Indonesia. It flew into this cloud and it lost power in all four engines. And so it's now the world's largest glider. And so it basically dropped from 37,000 feet to 12,000 feet. And then at about 12,000 feet, and as they descended, they actually got out of the ash cloud. Which was very, very fortunate. 

And then some of the ash that had piled up on the turbines had broken off during their descent down. Enough of it broke off, they were able to re-start three engines and make an emergency landing in Jakarta. This is what some of the engine looked like. You can see the melted and cooled stuck-on volcanic ash here. And what I'm going to play for you next, you're not going be able to hear the sound, but the words are scrolled across the screen. If you can't see them, I can summarize. But it's actually a recording of the cockpit talking to the tower after the plane lost all four engines.  So you're not going to hear the sound, but if you can read the bottom. And so this is the cockpit talking to the Jakarta tower and telling them they've lost all four engines. Also in a very calm voice. 

Very calm. The tower misunderstands and thinks they said we only lost number four engine. No, they clarify, we lost all four engines. And then he very calmly says that, he clarifies, and there's a possibility we may have to ditch. And, fortunately, they did not have to. But if you could hear the sound on this, the calm and it was probably a first officer radioing in, but it was incredible. >> Where was the plane destined for? >> It was destined for Perth, Australia. It was coming from, I think Kuala Lumpur and going to Perth. Okay, that was the first major incident where a jet lost all four engines. The second one occurred in 1989 in Alaska when a KLM flight, another 747, encountered an ash cloud from eruption from Mount Redoubt which is just outside of Anchorage. 

And here's an actual picture of what the eruption looked like. It was a pretty big eruption. The ash got to airline cruising altitudes in less than five minutes. So they were descending to land in Anchorage. I actually don't recall, I think they were coming from Europe. And they were at 25,000 feet when they encountered the ash cloud. And they encountered this and they wanted to get out of it. At this point they knew that ash clouds were bad so they decided to try to climb to 27,000 feet. When we were climbing to 27,000 feet they increased their engine thrust and you ended up increasing the temperature of the combustion chamber and ingesting additional ash and melting more. Don't know if that caused it for sure but that might not have helped. 

And on their way up to 27,000 feet they lost all four engines. And they ended up gliding down to 17,000 feet, frantically trying to restart an engine or two, and finally at 17,000 feet they restarted engines one and two, and then at 13,000 feet engines three and four. Now, this is not over the ocean like the British Airways flight was. This was over mountainous area where the ground can be at 11,000 feet. So this was mighty close. The plane was heavily damaged. I actually saw the windshield from this. That was what I was referring to earlier, totally opaque. So when they landed in Anchorage, it was a blind landing, they could not see out of the cockpit at all. Totally sandblasted. 

So what I'll show you next is a computer simulation using the actual coordinates of where the flight was and a simulation of the ash cloud to show you kind of what the path of the aircraft looked like here. So there it is, encounters the ash, tries to climb, stalls, and then it's not long before they get close to these mountain tops that they're able to restart engines and made an emergency landing. This was a brand new plane at the time. This plane is actually still in service, but it's not used for passengers anymore. They completely refurbished it. $80 million worth of damage but it's used to haul cargo now. >> What's the minimum number of engines they need to be able to stay up? >> I think you need at least two, probably. Yeah, I don't know what you can do with one. It might be better than none. Okay, just to give you some visual perspective, how much volcanic ash is too much volcanic ash for an aircraft. 

What you see here on the vial on the left-hand side of the screen is the amount of ash that was estimated to be present per cubic meter of air, a cubic meter of air is like a 35 cubed foot volume, this is the amount of volcanic ash that was present when this occurred. So the amount in this vial here. So you spread this amongst 35 cubic feet. That's not a huge area. So it's a decent amount of volcanic ash. The vial on the right is a thousand times less volcanic ash. This is the amount of ash that was over Europe in the spring this year. That being said, there were Finnish F-18s that encountered this much ash and actually had damage. They had to refurbish some engines. And so it does not take much. 

While the amount in this vial is a big threat to stall out engines, the amount in this vial is also a major threat because it really, really decreases the lifetime of engine parts big time. But you can see the difference in the magnitude of what was there. It's quite striking when you look at it that way. This is sort of another story about an aircraft encountering a volcanic ash cloud. But this time it's a very, very diffuse cloud. So probably more like this amount of ash than the amount the KLM jet encountered. But this time it was a NASA research aircraft. And this was an accident. They were flying from Edwards Air Force Base in California to Kiruna, Sweden, for a field experiment where they had the aircraft instrumented with all sorts of things to measure particles in the atmosphere and do atmospheric chemistry experiments up in the stratosphere to study ozone loss and things like that at high latitudes. And this was in 2000. 

And another volcano in Iceland erupted called Hekla, a lot easier to pronounce. We thought we knew where all the volcanic ash was, and so the NASA aircraft was instructed to stay out of a certain area. So they flew a hundred miles north outside of the area where there was thought to be ash. But as they were flying along, they're looking at their instruments, these special instruments that measure particles in the atmosphere, and all the sudden they start seeing spikes. What the heck is this? And so it wasn't until after they landed in Kiruna, Sweden, they looked at these measurements again and said could this be ash from Hekla. And they started looking at the engine closely, started taking it apart a little bit and there was damage throughout the entire engine. Nothing that was going to lead to immediate engine failure but if they had not noticed this and this they ran this aircraft for another hundred hours of flight time, it could have been a major issue. These parts are supposed to last for at least a thousand hours of flight time, but after a 10-minute encounter with a very, very diffuse volcanic ash cloud that was 35 hours old, damage like this was done. So large amounts of volcanic ash can certainly stall aircraft, but small amounts do a load of damage. By the way, the total bill to repair this aircraft was $3.2 million. 

But we did get some nice measurements. To put this in more of a local perspective, in 1992 there was an eruption in Alaska at Mount Spurr. Mount Spurr, if you're in Anchorage on a clear day you can actually see it. It was a fairly sizable eruption, and the wind patterns were such that the volcanic ash was dispersed down to the south and east and over down into the lower 48. So this is the only time I'm aware of that air traffic in Milwaukee and Chicago were impacted by a volcanic ash cloud. But it has happened. In 1991 when Mount Pinatubo erupted, a much larger eruption, there were 20 aircraft encounters with that cloud. Most of the encounters took place 600 miles from the volcano. So it's not just near the volcano, it can be quite a distance as this also shows. There are 500 airports around the world that are within 62 miles of an active volcano. 

So you not only can disable and damage aircraft while they're in flight, but you can also disrupt air traffic by shutting down airports. Volcanic ash can damage all the instruments needed to track flights and for airports to run. They can also, if there's a lot of it, get on the runways and make them to the point where you can't land on them. This is an example of a fairly light event, but it still closed this airport. This is in Guatemala City in May of this year from an eruption of Pacaya, which is a volcano not far from there. The ash cloud itself didn't cause much of a problem for actual air traffic. It was more the disruption at the airport. Here's a little bit more of a severe case. This is in 1981, this is again after the eruption of Pinatubo in the Philippines. This was at a naval base. 

This is a big 747. There was heavy ash fallout here. And then to boot, there was a typhoon, or remnants of a typhoon, that came in afterwards and rained on top of this volcanic ash making it even more dense and heavy, and it actually collapsed the tail end of this 747. So imagine what this does to houses and other parts of the infrastructure. It's a multifaceted problem. There's a lot of motivation to understand where ash clouds are going and to warn people and aircraft about this. The economic impacts are pretty significant. In the last 35 years, there's been about 120 aircraft encounters with volcanic ash clouds. The repair costs alone is over $300 million at this point. That number is small compared to the impact of grounding and rerouting passenger and cargo planes. 

I don't have a number for that because that's very hard to come by. It's proprietary information. But this number is very significant. And I could tell you I could just give you one example where we do have some numbers and it's just for one event and that was for Eyjafjallajokull. In April and May there were nearly 100,000 canceled flights. Airlines were losing something like $200 million a day, that was their estimate. Total economic impact all around the board was in the billions likely. This panel down here, this is the number of the flights, these little streaks represent planes, little flight tracks. This is what a normal day looks like in Europe. This is what it looked like when the volcanic ash warnings are there. 

So quite a bit different. Quite striking. Okay, logistically, how do we deal with tracking volcanic ash cloud? Who's responsible for issuing warnings to the aviation community and air traffic controllers? Well, in 1998 the International Civil Aviation Organization formed Volcanic Ash Advisory Centers around the world. And each Volcanic Ash Advisory Center is responsible for a certain area. And within that area it's their responsibility to, 24/7, monitor for volcanic ash clouds and get warnings out. NOAA operates two of these Volcanic Ash Advisory Centers. They operate one that's based in Washington, DC, and has a large area to cover that is all of the continental United States, down through Central America, the Caribbean, out into the central Atlantic down into South America and then way out into the central and western Pacific. The Alaska Volcanic Ash Advisory Center has all of Alaska, and then it stretches westward toward Russia and the Kamchatka Peninsula where there's a lot of volcanoes. And then you see there are other VAACs operated by other meteorological organizations in those respective countries. So these are the centers. 

This is where the information flows. So my job is to use science to better use satellite information so that these Volcanic Ash Advisory Centers can issue more timely and more accurate volcanic ash cloud warnings. >> What's the shaded area? >> Those are regions, those are dead zones. Nobody really covers those. They are regions where you really don't see volcanic ash, and so they're still kind of up in the air who's going to take care of those. But we haven't seen volcanic ash in those areas. They're relatively safe zones, but it can happen for sure. So what I do is I work very closely, especially with the Washington and Anchorage Volcanic Ash Advisory Centers to get them the tools they need to issue more accurate and timely alerts. And I also work with other VAACs. For instance, I have a good relationship with the VAAC in Darwin, Australia. 

Okay, so the VAACs rely heavily on satellite-based tools for them to do their job, for them to identify volcanic ash clouds, track them and then initialize their models to predict, in the short-term, where these clouds with going to go. And so there's really two types of satellite orbits of interest to us when we're doing volcanic ash monitoring from satellites. One is the low earth orbit and the next one is the geostationary. So just a little bit of satellite 101 here. First, the low earth orbit. The orbit is such is that, as you can see in this animation, that the satellite moves from pole to pole and progresses from east to west as time goes on, eventually covering the entire globe. So because just the nature of this orbit you get basically two looks at a given point on earth per day. That's not a lot. But the nice thing is it is in a relatively low orbit. It's only about 500 miles above the ground. 

As such, it's capable of providing very detailed images because it has that low orbit. And the two overpasses that you get tend to happen at the same local solar time every day. So low earth orbiting satellites are great for very detailed images. But if we want to have frequent images, which is very important because we want to get aviation, actually the aviation community has asked for a five-minute warning criteria. They want to know within five minutes if there's airborne volcanic ash at cruising attitudes. So we need satellites that take frequent measurements. So we use geostationary satellite orbits for that. Geostationary satellites are located above the equator about 22,000 miles. And that position is very, very special because at that position the force of gravity and then the opposite-directed centrifugal force exactly cancel and the satellite stays put above a given location on the equator. So it basically images the same disk-like area over and over and over and over again. 

It's not orbiting around the earth like lower earth orbiters. As such, we can get high, very frequent images, in some cases up to every one minute. And this is really the source of satellite data. If you watch the weather on the news, this is what they show. More often than not, they show movies of clouds moving in and stuff. That's from a geostationary satellite. It's a very important tool. The one down side is that because it's in a higher orbit it's more difficult to get very, very detailed images compared to the low earth orbit. You need very, very special optics to do that. >> Is there one on the other side of the earth? >> Yes. 

There are geostationary satellites located all around the equatorial belt, and so you basically end up with full global coverage. NOAA operates two geostationary satellites for weather purposes. This is one of them and there's another one that's positioned further west that provides better coverage of Hawaii and points westward like that. Okay, so how do satellites work? Satellites work a lot like human vision. Okay? The human eye senses light or visible radiation, light and visible radiation are the same thing, that's reflected from a distant source like that screen right there. The light is reflected off it and your eyes sense it and then your brain turns it into an image and information. That's similar to what a satellite does. A satellite senses radiation that's reflected or emitted from a distant object like, say, earth, and then the electronics in the satellite and the optics turn that information into radiant energy at desired wavelengths. And from that radiant energy, we can then gain information about things like clouds. For volcanic ash remote sensing there are two different wavelength regions that we use, primarily. 

The first one is the visible. Our eyes see visible radiation. It's the same radiation our eyes see. And so during the day that's a very nice source for detecting volcanic ash clouds and satellite imagery. Because what it does is it relies on solar radiation or sunlight that's reflected by the earth, the atmosphere and the clouds back out to space. So that's what you're sensing there. The second region that we use is the infrared. Now we cannot see in the infrared with our eyes, but every object on this planet emits infrared radiation that can be detected because we all have a temperature. The amount of infrared radiation emitted is directly proportional to the temperature of the object doing the emitting. And so the nice thing about the infrared, it doesn't rely on reflected sunlight, and so it works at all times of day. 

So first, and actually I should mention that when you watch your local newscast and they show satellite imagery, sometimes if it's daytime the images that you're seeing are from the visible region, if it's nighttime you're seeing images from the infrared region. >> What's on the far left of the spectrum? What kind of rays are those? >> Gamma rays. Those are the highest energy radiation. That's the really bad stuff. So you can see this with nuclear reactions and explosions. So just to give you a perspective of how far we've come with satellite imagery, these are visible satellite images, so what the satellite is measuring is sunlight that's reflected by the ground, the atmosphere and the clouds, of the Mount St. Helens volcanic ash cloud from 1980. And because we know where Mount St. Helens is, and it was well instrumented, so we knew an eruption was eminent, the USGS did, it was easy to pick this, and it's a big eruption, so it's easy to pick out in this fairly coarse resolution rough satellite imagery. But as this cloud thinned out and spread out, the imagery we're getting at this time in 1980 wasn't of the highest quality, and it was very hard to track volcanic ash clouds for the most part. You can only see this one because it's very, very prominent volcanic ash cloud. So since that time, both satellite technology and our ability to turn the data measured, gathered by the satellites into information has improved considerably. 

So for instance, we have satellites now in low earth orbit that can measure reflected sunlight in the blue, green, and red parts of the visible spectrum. And then you can use some imaging techniques to actually combine those three measurements  such that the satellite data can be constructed to look like a photograph from space. So let's take a closer look at this. And so this is basically how our human eyes would see this. Clouds are white. The land is kind of brown from that height. This is ice over Iceland. Ice is white. The ocean is blue and look what's here. What's brown is the volcanic ash. 

It contrasts quite well with the white clouds. And so identifying a volcanic ash cloud in this imagery is a heck of a lot easier than back in the days when we had things like this. So very useful. Here's another example to really highlight the usefulness of these types of measurements. Of course, these are only good during the day. At night you don't have sunlight and you don't have images like this. This is an ash cloud from an eruption from Kasatochi in the Aleutian Islands of Alaska in 2008. And so here you have this brown volcanic ash cloud, and it basically overlies a whole bunch of weather clouds. So if you were looking at just a standard visible satellite image where you're only looking at one wavelength of the reflective radiation like this, because that volcanic ash cloud lies on top of the white background, which is the weather clouds, you would never see it. But when you combine these three different wavelengths of radiation, you can see it. 

So that's very helpful. So of course we can only do this during the day. So what we use more often than not to monitor volcanic ash clouds is measurements of infrared radiation. Now, when you take measurements of infrared radiation, you can actually convert the radiant energy that you measure using a very fundamental physical relationship into an infrared temperature. Now this temperature is not the same thing as the temperature you'd measure with a standard thermometer, but it has similarities in that lower values mean colder, higher values mean warmer, so it's a very comfortable set of units to work with. And so imagine here you have an atmosphere where you have the ground and you're going up in the atmosphere and so, as you probably realize, near the ground, the temperatures are higher, and as you increase in height the temperature decreases with height. And recall that the measured infrared radiation is directly proportional to the temperature. So the greater the temperature, the greater the infrared radiation that you measure. So the infrared radiation that is coming from lower in the atmosphere where it's warmer is greater than the infrared radiation coming from higher up in the atmosphere where it's colder. So you put a cloud in here and this cloud has properties such that it can allow some of the radiation, infrared radiation that's coming from the lower levels down here where it's warmer through up where the satellite can detect it. 

The more radiation that this cloud lets through from below, the greater the infrared temperature. Okay? So this is the physical basis for how we differentiate between ash clouds and weather clouds using infrared radiation. So this is just a plot of the infrared temperature as a function of wavelength in the 10- to 13-micron region of the infrared spectrum. So the brown line here is volcanic ash. The red line is liquid water clouds, clouds that you'd see lower in the atmosphere. And the blue line is ice clouds, clouds you typically see in the middle and upper atmosphere, troposphere. What you see here is that as wavelength increases for volcanic ash, the infrared temperature that you would measure increases, because at increasing wavelengths more and more radiation from below the cloud is allowed to pass through. Now what you see for weather clouds is the opposite effect. As the infrared wavelength increases, the infrared temperature that you measure decreases. So what this means is that if we can take measurements at two different wavelengths in this region, and in this case 11 microns and 12 microns, if we were to take the difference between the infrared temperature measured at 11 microns, minus the infrared temperature measured at 12 microns, for volcanic ash it would be negative. 

Whereas for weather clouds it would be positive. Totally different sign. So this is very, very good information for sorting out in a satellite image what is volcanic ash and what is weather clouds, because at night we can't make images like that. So here's just a standard black and white infrared image like you've seen on the newscasts probably. This is Iceland. So there's lots of clouds in this scene and here's the ash cloud. You know it's there so it's easier to pick out, but there's not a lot of contrast between the ash cloud and the other clouds. And if you knew nothing about this eruption or any background details about this image, you would not necessarily say that's a volcanic ash cloud. But now, what we make an image of the difference in the infrared temperature between 11 and 12 microns, and we colorize in non-gray colors where you get a negative difference, you see that the volcanic ash cloud pops out and separates itself quite well from the weather clouds. One thing to point out, though, is it's not totally perfect. 

This relationship I showed you is very ideal. Unfortunately mother nature does not always cooperate and there are exceptions. And so you see here these are actually weather clouds in this region right here, and they show up with a small negative difference as well. So this image is a lot better than this previous one but we can do better. So if we can take the difference in the infrared temperature between two wavelengths, why can't we add in a third? A fourth? Gain additional information? And so we can actually do that, and we can actually use imaging techniques to combine these all into one image where, in this case, the volcanic ash will appear this reddish color and the weather clouds will appear, liquid water clouds will appear light brown, ice clouds will appear barker brown. But you see here you get a very clear distinction as to what is volcanic ash without these sort of false alarms over here. So we add additional piece of information from the infrared measurements, we get better. Now just to give you some sense, this is how it compares to that daytime imagery that looks like a photograph. You see that the red matches up very, very nicely with where you see the brown for the ash cloud. And the nice thing about this image is we can do it 24/7. 

We're not limited by having to measure reflected sunlight. So making satellite images is great. It's very useful. Forecasters look at them. They can identify ash clouds. They can block off areas where there is volcanic ash. It's very useful. But the thing that we've been personally working on in my research group is how do we turn that satellite data into more quantitative information. For instance, can we use satellite data to build a computer algorithm that will automatically tell us where there is volcanic ash as opposed to always relying on the human manually analyzing these images like this and this. Because these images can come in fast and furious and it's very manually intensive to just go through these by hand and you can't keep up with the data that comes in. 

So it's not practical. Another thing is can we use a satellite data to tell us how much volcanic ash is there? Do we have what's in the vial on the left, or do we have what's in the vial on the right? Also, how high is the volcanic ash cloud and what are the size of the particles. And so we've actually built computer algorithms to tell us these things. Just to go through these panels one by one. We have a computer algorithm that will actually automatically tell us where volcanic ash is located. So we display this by taking this image that I showed you earlier and then contouring in white the outlines of the ash cloud that the computer automatically generated. So everything inside this white contour we detected as volcanic ash, the computer did. Notice that it's very, very similar to what you would draw by hand based on knowing that volcanic ash appears red in these images. And we have a good degree of skill of doing this. We also can estimate the concentration. 

So, again, this speaks to, is it the vial on the left or the vial on the right. And also this information is very, very useful for, and we're working more and more towards this, is to initialize models that can forecast where a cloud is going to go, we can actually use this information to initialize those models. So you get a more accurate result. Knowing where the top of the ash cloud to a first order is critical because you want to know is volcanic ash at airline cruising altitudes. That's question number one. The next thing is that the winds in the atmosphere, generally the wind, both the speed and the direction, vary with height. And so where the volcanic ash cloud is in the atmosphere highly influences where it's going to go in the future. And so models that predict where it's going to go really need to know is this cloud at eight kilometers or is that 10 kilometers. Because you can have a big difference in the wind speed and/or the direction between those two levels. Another one, this one might not be so obvious why you want to know things about the particle size, but we can retrieve this information, and the physical basis is that larger particles, all else being equal, because of gravity will fall out quicker than smaller particles. 

So if you have an ash cloud that's dominated by a lot of small particles, it can be around for days. Whereas, if it's larger particles it's more like hours. >> Are the numbers lat/long? >> The numbers are lat/long on here, yes. And the colors are the measure of how big the particles are in microns. >> What's the largest size particle? >> The largest size particle that we sense away from the volcano is something like 15 microns which is, that would be not quite visible by eye unless there was a lot of them strung together. But if you had an individual particle it would be very hard to see by eye. So we're mainly tracking the small particles. The huge ones near the volcano fall out very quickly, and they tend to be, we have a hard time seeing them from satellite because there's so many particles above it we can't see radiation that's being emitted from where the large particles are. So during the eruption of Eyjafjallajokull we were running these retrievals in realtime. This is actually a 20-day loop using geostationary satellite imagery. 

It gives us frequent imaging that shows how the property of this cloud changed with time. First of all, just notice the drastic change with wind direction with time and where the plume goes. It starts off being south of Iceland. It rotates over going off towards Europe again. Then it blows off towards the north. And then as you come back later in time, it starts going back down towards the south again. So this just tells you how the atmospheric flow itself, especially at these latitudes, is highly variable. So it's hard to predict where these things are going without accurate information. Of course, this eruption became famous by invading Europe, and so our visualization lab took some of our retrievals of the concentration and put them on a sphere here to depict how the volcanic ash moved from northern toward southern Europe over the course of a day. So here's the animation here. 

There's the volcano. And so we'll pick up the ash where it was in northern and then moving towards central and then that's where it started out. And so that's what really made this eruption famous. And during this eruption, we were actually approached by the London Volcanic Ash Advisory Center. They were the ones responsible for issuing the ash advisories on this particular cloud. And they asked us if we can produce these satellite products of height and concentration and the size of the particles in realtime so they can look at them during their daily briefings. So we did that for them, and they used them throughout the eruption. One thing we're also doing working with VAACs is that we've built a system that can automatically, the computer goes into the satellite data, will look for a volcanic ash cloud, if it finds one under certain criteria, it will send an alert off to Volcanic Ash Advisory Centers saying a volcanic ash cloud has been detected, go look at this such-and-such image and decide what action to take. So this is the direction that the satellite aspect of it is really moving right now. Because remember the aviation community wants a five-minute warning criteria. 

The only way we're going to achieve that is if the computer is doing a lot of the work. >> You use the phrase the computer goes into the satellite data. >> The satellite data goes into the computer. Sorry if I said that backwards. Okay, another thing that we're doing and we're working with other research groups on this is to actually take the satellite information of height and how much volcanic ash is there, the concentration, and put it into a trajectory model so that we can predict three to six, to 12 to 18 hours where the volcanic ash cloud is going to move. And so we've done some initial work with that. And you see these dots here, that's initially where the satellite has the cloud and then these streaks are a prediction in time where the ash cloud is going to move, both in the horizontal here, in the horizontal plain, but the colors of these streaks indicate how high the volcanic ash cloud is as a function of time. So it's a three-dimensional prediction of where the ash cloud is going in time. And this is a big new area of research and we're really moving towards. And I think we're going to see big improvements in this in the next five years or so. 

I just want to end by mentioning sort of what the future holds in terms of satellite sensors and how they're going to help us do a better job at meeting that five-minute warning criteria. Currently, our geostationary satellites routinely provide imagery at 15- or 30-minute intervals. That's not good enough for the five-minute warning criteria. What we can do is, occasionally if we have an extra satellite up there, we can have over small regions imaging capabilities at one-minute intervals. We can do that only very sporadically and occasionally now with our current assets. But as we move towards the 2015 timeframe, we're going to be updating our geostationary satellites into a new system called GOES-R, and GOES-R will be able to routinely supply five-minute imagery and imagery up to 30-second intervals. So it's going to really revolutionize a lot of forecasting problems. Not only volcanic ash, but hurricane forecasting and severe weather forecasting. So just to give you a glimpse as to what one-minute sequenced satellite imaging looks like for an interesting feature, this is Hurricane Igor from the other day out in the Atlantic at one-minute time intervals. Just spectacular imagery. 

You can see even at these small time scales, you get all sorts of things bubbling up in the outer bands, all sorts of very, very micro-scale features. Just incredible detail. So we'll have this capability sort of more in a full-time mode, not just a part-time special mode like this, when we go to the next generation of satellites. And NOAA is making sure we're prepared to use these satellites because if all we're going to do is make imagery, pretty pictures, that's not quite, that's nice but that's not quite going to cut it. And so that's why we're working on computer algorithms to turn these measurements into real information for forecasting problems. And so with that, we can have a discussion and take questions. [APPLAUSE]