 Hello everyone from wherever you're joining. Thank you so much for being here today for this NCAR Explorer series lecture. What can satellites tell us about the quality of the air we breathe with Dr. Helen Warden and Dr. David Edwards? My name is Dr. Dan Ziello and I'm an education specialist here at the National Center for Atmospheric Research or NCARC, which is a world-leading organization dedicated to understanding our system science and that includes our atmosphere, climate, weather, the sun, and the importance of all of these systems to our society. I'm really glad y'all could be here today to learn more about how scientists like Helen and David use satellites to study air quality and the air that we breathe. So for this event we'll be taking questions at the end of the lecture, but please definitely submit any questions you might have throughout the talk using the Slido platform. So if you scroll down the webpage just a little bit you can see the Slido window just below where you were seeing the live stream video of this event. Go ahead and click the green join event button if you haven't already and that way you can ask questions on the Q&A tab and answer poll questions on the polls tab. And definitely be sure to join Slido to add your thoughts to our word cloud question that's going on right now. What do you think contributes to our air quality? Because we're going to get to that really soon. This lecture is also going to be recorded and will be available on the NCAR Explorer series website. So with us today we have NCAR scientists Dr. Helen Warden and Dr. David Edwards. Dr. Warden is a scientist in the Atmospheric Chemistry Observations and Modeling Lab or ACOM. And since 2016 she has led the team for the NASA U.S. Terra satellite instrument called MOPET which has been observing global distributions of carbon monoxide for 21 years. The program provides a fully characterized long-term archive of satellite observations of atmospheric carbon monoxide that can be used to study changes in atmosphere chemistry and emissions of pollution. Dr. Edwards is also a scientist in ACOM and he has 30 years of experience working on satellite mission design and development to investigate pollutant, trace gas and aerosol seasonal variations and global distributions. A particular interest is the integration of measurements from different observational platforms using chemical transport models. And Dr. Edwards has worked on the development of the new international satellite constellation whose goal of achieving continuous observational coverage of atmosphere composition is about to be realized. And so with that Helen and David could you give a quick hello and then maybe we'll check out the answers to our world cloud. Hi everyone I'm Helen. I'm David. Awesome so Paula can you throw up that word cloud for us? Cool so right away I'm seeing cars, planes, fires, smoke, wildfires, air pollution, climate change, unclear policy, PM or particulate matter, VOCs or volatile organic compounds, airplanes, human activity. So I'm seeing a lot of general themes on our word cloud Helen and David do you have any thoughts on that before you dive into your lecture? I think it's great this is some of the things that we're going to talk about so hopefully the folks who put these words up there they're going to hear some answers. Yeah and I think just looking out the window we can see some effect from fires so that's obviously on everyone's mind right now. Awesome thanks Paul and I'm stoked to hear y'all's talk. All right okay are we sharing uh is everything good? We're trying something a little new today so it's to bear with us if you're sitting at home. Yeah just um I think it's yeah that button didn't pop up like it should have. There we go we're going to go and present. There we are. Awesome thank you very much for our technical support so our talk today we're going to for this Encore Explorer series we're going to talk about what air what can satellites tell us about the quality of the air we breathe. I'm David I'm Helen and we can jump straight in here for this talk we're going to cover a number of different topics which I hope are going to be interesting to everybody. The problem we'll try and define this air pollution and what how it affects us. We'll talk about some of the tools we have such as computer models observations and then describe the role of satellites. We'll then go on to talk about some of the air pollution sources that we see how this pollution gets moved around in the atmosphere and how we miss estimate emissions of pollution. And so when one tiny silver lining of the COVID-19 lockdowns were um was the reduction in air pollution so we're going to talk about what we saw from space in that and then obviously fires in their effect on air quality is a big issue um and how air pollution has changed over time and then finally uh what future satellite observations will tell us about uh air quality and how we can improve air quality forecasts. So the first of these topics is air pollution and air quality and how this affects us and we'll jump straight into a very dramatic video. This was taken by a journalist in Beijing back in 2017 and it just shows how quickly pollution can change our environment and really affect our air quality so you can go from very clean skies one moment to very very uh polluted atmosphere the next moment and this can happen really very quickly and you go from this to the the pollution and suddenly you can't see the next uh you can't see the next building over and that depends a lot on the weather too so yeah so now we're to our first uh quiz in Slido um which was what which risk risk factors cause about the same global mortality for women as poor air quality and so if we can bring up that response from Slido yes every a lot of people got that get that right it was uh one of those all of these combined um but those other ones are also very important and if we go to the next slide um just up to um we can see that for both men and women uh the next um it contributes globally to 6.7 million premature deaths per year and about 100,000 or more in the U.S. and it also causes crop damage which has a significant impact on food security so that's over one billion per year but going back to the global burden of disease this is the most recent assessment of risk factors for women and you can see that air pollution is the fourth highest uh risk if you go to there and um with the different colors on there showing the resulting diseases so the the highest one is cardiovascular disease um and that's really the highest for a lot of those risk factors um but also important for air pollution is chronic respiratory disease so those all um are important uh health effects from air pollution so how do we understand and predict air quality? Helen's described how uh this is definitely important for our health and the scientists some of the questions that we're wanting to ask are relatively straightforward what are the sources and processes that emit pollution? What are the chemical and physical transformations that take place in the atmosphere and how does this pollution move around in the atmosphere and now how does it affect air we breathe? However although these are fairly straightforward questions getting the answers as you might guess it's a little more evolved and also we have some challenges some particular questions that we're interested in answering for instance observing modeling and predicting air composition in both the developed and the developing world understanding the interactions between natural and also human driven emissions and quantifying the impacts of extreme fires such as extreme events such as fires uh and and heat waves obviously a topic of great interest right now. So what do we need to measure to understand air quality? So we have a list here of the EPA criteria pollutants and these are from primary production so they're produced directly from uh sources on the on the ground and the pollutants in yellow are the ones that we can measure from space. So we have sulfur dioxide which is from burning of coal and oil nitrogen oxides which come from high temperature combustion, carbon monoxide from incomplete combustion and that's something David and I have studied a lot so we'll be talking about that a lot but it's um just so you know it's the same toxic carbon monoxide that you would monitor in your home but not at such high concentrations outside um but it's very important for atmospheric chemistry and then there's particulate matter that you've probably heard about in especially PM 2.5 is dangerous to human health and they're direct sources from smoke and dust but then there's the things that are made from secondary production in the atmosphere and those are like ground level ozone which is very toxic to humans um and then also more particulate matter from sulfates sulfate and nitrate and organic aerosols. So to put a little bit more detail on this we can talk about the complex chemistry of air pollution in not too much detail but we'll just see if you have a flavor here. So Helen talked about some of the emissions and from especially from cities and urban activity we might have SO2 and nitrogen oxide which we call NOx these come from as Helen mentioned a high combustion high temperature combustion sources. Then there are some pollutants that we get from a mixture of sources there could be ammonia which comes from agricultural processes as well as uh uh industrial emissions and methane which comes from uh potentially from oil and gas exploration but also from livestock. Then we have a whole set of different chemicals called volatile organic compounds and these are often big molecules that are emitted could be from industrial processes or from urban processes but also from natural vegetation. Then we have the carbon monoxide that we get from in complete combustion and also primary air assault these are the little particles that come come out of fires for instance often carbon based. These things all get into the atmosphere and they all mix together and give a good dose of sunlight which drives a lot of the chemical reactions that we get and we get some cooking of other chemicals. Most notably amongst these is ozone the lobe this is ozone down in towards the surface of the atmosphere to be distinguished from the ozone high up in the stratosphere that protects protects us from the sun's UV radiation and we also get secondary aerosol this sulfodi oxide for instance can get oxidized in the atmosphere and it produces sulfate particles which have a big impact both on the chemistry and health but also on climate. So observations can help if we can observations of a lot of these different compounds we can get a handle on where they are and where they're coming from and this helps us to understand some of these processes that we talked about before the emissions the chemical and physical transformations and the transport that we're interested in. So that brings us to our second quiz and that was a two-parter which is which air pollutant has decreased the most since 1990 in the US in which has it decreased the least and so if we can bring up the responses for those so we have decreased the most in fact it was sulfur dioxide and I don't know if anyone remembers acid rain but it's that was a big problem in the 90s and we still a problem in other places but not really in the US and then if you go to the next one that also yeah so so ozone is the one that has decreased the least so sulfur dioxide has decreased the most and ozone has decreased the least and we'll see that in the next graph of trends from the EPA. So this is a EPA air pollution trend since 1990 and you can see the green line there's I'm sorry for all the lines on there but the the dark blue line is sulfur dioxide so that's gone down a lot and then the dark the lighter green line is ozone and so it's all compared to this national standard which is the dashed line on there and that's based on health outcomes and that gets revised as we learn more about pollution sources and attribution and regulations depend on whether the sources are local or from other states and other countries so although we are mostly below that national standard level ozone is still often an exceedance and you can see from the next map here that Denver has a high ozone event on this day this is from the EPA's air now site and Denver in the front range have a mix of pollution sources from urban oil and gas and agriculture along with a lot of sunshine and that can cause these ozone exceedances along with wildfire smokers so. So now we're going to talk a little bit about the different tools that we have and these basically come down to two categories the first of these is models these are computer models that can simulate the atmosphere and pretty much encompass all of our knowledge of what's happening and they range in in scale from process models which really look in the fine detail of what might be happening say what what chemicals are coming out of a particular fire for instance and they range up then to regional models which are high resolution models over a particular area that can give us some really fine scale information about the chemistry and the weather and then all the way up to global models which are the way in which we can add our knowledge of chemistry into the big global simulation models that are used for climate and we can it's a way in which we can understand the impact of chemistry on climate. Corresponding to all these different models we also have observations and it and for the questions that we want to ask about air quality there's no single observation can give us all the answers so again we have to go through observations at different scales and this ranges all the way from lab studies and this is where we do observations in a laboratory this is a traditional idea that you might have of some person in a white coat with a test tube all the way up to then we have in situ observations where we go out into the environment and take some samples of air and if we put some of our chemistry instruments on an aircraft and fly it around we can get a larger scale context of some of the local observations we make but then in this I know the right way in this talk we're going to be particularly concentrated on satellite, satellite remote sensing and I'll explain later what that means but we're looking at the role of satellites and what they can provide this mix of information they provide us with the long-term observations, large-scale context for the process observations and modeling that we make and a regional to global scale coverage. So here's a great example of a high resolution NASA model that shows the complexities of sources and transport for different aerosol types so in the northern hemisphere you have a lot of sulfate and nitrate aerosols from human activity but then you also have some carbonaceous aerosols coming off of the burning in Africa and South America and some dust coming off of the Sahara so this model includes everything we know about sources chemistry and transport so if we see large discrepancies with observations we use that information to improve the model and now we're going to get into the more specific role of satellites in all of this so we've now benefited from more than two decades of a golden age of observations from satellites of atmospheric composition and David and I have both benefited from our careers in that we've really had a lot of good data to look at and these satellite instruments have characterized pollution sources transport and variability on weekly to monthly and regional to global scales the instruments have lasted way past their design lifetimes which are usually like five to six years and now give insight into atmospheric composition trends and the long-term records have also allowed new analysis techniques to detect small signals but we're entering now a new era of higher spatial and temporal resolution observations that will let us access local regional and hourly scales so in addition to some of the planetary probes you've heard about like the missions to Mars NASA also has a lot of satellites that observe different aspects of the earth system so the atmosphere the surface oceans ice and on the bottom you can see the the missions that are in orbit now and then the ones in yellow are being formulated so the questioner is on your mind is probably how from satellite do we look at the atmosphere and how do we measure pollution in the atmosphere when we're some 600 kilometers above the earth's surface but we're not driving the satellite through the atmosphere and getting out and actually taking a sample of the air what we use is a technique out of physics called spectroscopy and I'm just going to walk you through this hopefully not too in a too complicated manner so coming out of the sun we have radiation and as everybody probably knows we have the radiation that we see the white light that coming from from the sun is actually made up of all the colors of the rainbow and a few more on the longest wavelength side we have infrared radiation on the short wavelength side we have the ultraviolet radiation which we have to protect ourselves from in the case of sunburn for instance this comes down into the atmosphere and the atmospheric gas molecules absorb this radiation at very specific signature wavelengths and you might ask well why why specific wavelengths well this is quantum mechanics and are these wavelengths correspond to the same energy that is needed to make the bonds that exist between the atoms of the molecule vibrate and so here's an example is a little picture here of a CO2 molecule and the atoms are vibrating so we take the radiation after that we observe it with a satellite and the satellite instrument that is capable of separating out all the different radiation wavelengths now this is shown schematically here by a prism separating out the white light into all its components but we have lots of different instrumentation that can perform essentially the same function of separate separating out the different wavelengths and what we end up after that is a transmission spectrum which shows the absorption of the signature wavelengths of each particular gas so in this particular figure we can see water vapor ozone carbon monoxide and carbon dioxide and the particular absorption features that they produce and so what we can do is to look at the amount of absorption of each of these gases and it gives us an indication of how much of the different gases were actually present so how do we make a measurement well as I said we are often using radiation from the sun and it comes down through the atmosphere and as it does that it passes through the atmosphere and absorption takes place by these molecules at these signature wavelengths I talked about before we get a reflection at the earth's surface and it bounces back up to the satellite but as it does so it passes through the atmosphere once again and we have more radiation absorbed again at these signature wavelengths of each particular gas in the atmosphere now at the same time the shortwave radiation that I talked about from the sun is joined by longwave radiation that's emitted from the earth's surface and this passes also up through the atmosphere we're joined by some emission from the atmosphere again at these specific wavelengths characteristic of the particular gases that we have it reaches the satellite and the satellite instrument detects the radiation spreads it out separates the wavelengths and then looks at the amount of absorption in each of each of these spectral signatures in order to come up with an idea of how much gas there was so now once we have this spectrum measured by the satellite we have a process where we want to infer the amount of gas in the atmosphere and that's what we call the retrieval so what we want is the information about the distribution of the gas and what we have is this satellite observation and as well as some other important information about meteorology and surface properties that affect the measurements and what we think we know are the factors that determine the signal that reaches the satellite so the gas and the particle absorption the emission and scattering and the effective clouds the surface properties for emission and reflection and then how the instrument processes that and that gives us this forward model which is basically another spectrum of the absorption in the atmosphere but we also need to have prior information or first guess about what we think is in the atmosphere and that's like the average gas distribution so you can see a picture of that which varies with latitude and then what we do is an inverse process to obtain the optimal estimate of the gas amount and the distribution that's consistent with the new measurement in our prior knowledge of the atmosphere and that gives us the picture there on the bottom which is a new estimate of the gas amount in the distribution and this was for a day with fires last last year so you can see a pretty spectacular signature from those fires that was not there in the prior and that information on the also gives us some uncertainties of the estimate and the measurement of the vertical sensitivity so we promise the physics lesson is over now and everything from here on out will be a little easier but we want to talk about especially about this instrument called Mopit this is stands for it's a funny name it stands for measurement of pollution in the troposphere and it was launched back in 1999 so it's on the Terra satellite and now we have over 20 years of observations from this satellite now I was lucky enough to be the one to make the very first global retrieval of carbon monoxide in the in the atmosphere as shown in this newspaper cutting from back in 2000 it was very exciting for myself as a young scientist at the time having worked on the design of this instrument to see something that no one had ever seen before from space it was kind of a eureka moment for me in my career and back then we didn't exactly understand all these pollution patterns that you can see in this we didn't know what quite what those red marks were and I remember bringing together a lot of observationalists and models here at Encarta try and make sure we understood exactly what it was and come to the conclusion that it was due to vegetation burning in Africa and it's something that's something we'll talk about later so these are some of the other a few of the other missions and measurements that we've been involved with so you have Terra aquanora which are the eos missions from NASA and then some of the European missions and we set metope and sentinel 5p so and and this shows the ultraviolet the shortwave and the thermal molecules that are are detected from these and then along with that we use some other earth system remote sensing information to make our observations so tropomy on sentinel 5p is a relatively new satellite instrument and is a follow-on from omie on aura and it has very good spatial resolution and that that allows us to see finer details than before so on the on the left of that picture you have the omie NO2 observations at about 13 times 24 kilometers spatial resolution and you can see things are sort of blobby but then on the right you have tropomy which now has 3.5 by 7 kilometer spatial resolution and you can really see that we can pinpoint pollution sources a lot better so this was built by our Dutch colleagues and launched by the European Space Agency and now to continue with tropomy we're now looking at tropomy carbon monoxide observations and this is a good example of validation and validation is how we determine the accuracy of our observations from space tropomy was able to make useful observations right after launch and part because of existing satellite instruments like mop it that it could compare to so we make comparisons with known measurements such as those on at aircraft and this global map shows the tropomy CO data for the 24th of April to 21st of May the year after uh tropomy launched the circles show aircraft profiles that are converted to total columns that are then compared to tropomy and these are from the atom for field campaign and you can see that the circles really match the map pretty well the differences is hard to see sometimes because the agreement is very good so now we get into the sorts of orbits that we're going to talk about we have the low earth orbit these are polar orbits shown on the left and they're at about 800 kilometers or about with about 100 minutes per orbit and around 14 orbits a day so these give you a day and night view but always a snapshot at the same time of day for any one location and then in the animation on the right we have a geostationary orbit which is around 36,000 kilometers and rotates with the earth so that it stares at the full disk centered on the same location all the time so we need observations from both of these orbit types for understanding weather and air quality since these are all transported globally as we see by the polar orbits on the left but also change over the day like a good example is rush hour traffic and that you can see from the geostationary orbits on the right so the geostationary perspective has already made huge improvements to weather forecasts and we've gone from like a skill of three to four days to about 10 days out because of that so the next part of this talk we're going to talk about we're going to do a little survey about some of the different pollution sources that we expect to be able to measure and also look at the transport of some of this pollution in the atmosphere and what I mean by that is you've often seen we've all seen areas say over a city where the air quality is really bad you can't see the buildings in front of you it's really not pleasant to be out and trying to breathe that and we can see this from space here's an example of a picture from from Mopit and you can see over China very high levels of carbon monoxide pollution which is characteristic of this whenever we have this incomplete combustion taking place but what I want to point out here is that this doesn't stay over China it then gets moved by the prevailing meteorology by the winds it gets blown out into the Pacific Ocean and crosses the Pacific Ocean and includes that we can detect from space before we get reaching as far away as the next continent over in this case the United States now looking at these newer observations of carbon monoxide from trope oh me we can see every frame here is a is a day and you can see that the pollution transport that David was talking about so we have the sources from African biomass burning in South American biomass burning that are are transported mostly mostly eastward then there's pollution from China and also fires in Siberia and that gets transported all around all across the globe another thing that we can do is to monitor and detect different pollutants from space and here's an example for ash detection and there was a volcano erupted in Iceland back in 2010 and this resulted in so much pollution taking place and coming down ash pollution coming down over Europe that because there's a lot of fear about the effect of ash in jet engines all the planes were grounded during this this time now our colleagues in our colleagues in France and Belgium came up with a way in which they could monitor and detect and track this pollution as it as it came down and this this figure here shows the distribution of the ash at different times during the day and since that time this capability has been developed even further to produce an early warning system that can be accessed by air traffic control by airlines etc so that it can avoid these plumes or not decide to not fly all together and so next we're going to talk about ammonia the sources of ammonia which has a weak spectral signature in the infrared and ammonia is produced from agricultural domestic and industrial activities for human produced ammonia and it's important because it not only impacts air quality but it also affects lakes and oceans through acidification and nutrification and nutrification is the lack of oxygen and water from too many nutrients that is sometimes caused by fertilizer runoff and you can see the the primary sources for human activities are agriculture which is fertilization mostly livestock and then industry and fires are also important so as Helen has mentioned this is a very important very important pollutant for us to be able to measure but it's also very difficult because it has a very very weak spectral signature one of those characteristics in spectral signatures I was talking about before and so again our friends in France and Belgium have developed a techniques using their yasi instrument where they can average over very long periods of time and gradually build up enough information so they can get a handle on where the sources are and what emissions are taking place so in this figure I'm showing an example from the Nile Valley in Egypt and this is a build up over a long period of time a very difficult measurements to make that's one day two days three days a week a month a year and by the time you get to 10 years we cannot start to see exactly where the emissions are taking place we can go on to derive these emissions and it gives us a handle on what pollution the sources are taking place and just an example of another valley but one close to home here's the San Joaquin Valley in California and as you know this is where a lot of our fruits and vegetables are grown but it's also where a lot of fertilizer is used and so we can see large amounts of ammonia accumulating over this over this area and this is important for air quality and also has climate effects all right so now we're going to talk about nitrogen dioxide NO2 and if you remember recall that nitrogen dioxide is produced from high temperature combustion so it provides a very good indication of industry and transportation activity and this is an annual 2019 annual average from Tropomy and so these observations you can see all the major urban areas but you can also see some of the transportation corridors so this is a highway map and you can see on the west coast especially that a lot of the features match exactly the highway map and now we've been talking about sources and concentrations but we need to estimate emissions so something like tons per day because these are the things we can actually regulate and control and so if you look at the sources of some of the pollutants we've been talking about you have biomass birding fossil fuel combustion and then some of the natural sources and we have to be able to separate all of those so we do that with a process called inverse another inverse algorithm and this is with a chemical transport model so we start with prior emissions and those are things like inventories from the EPA we have our concentration observations from satellite and then we could also use aircraft and surface and that gets combined with meteorology so we have to know how the winds and everything moved around and so if you go with a forward model you go from emissions to concentrations but for an inverse algorithm you go from concentrations back to emissions and those estimate emissions are an update that give us the best fit to the data so this is an example for nitrogen that nitrogen oxide emissions and it's using data from the omie instrument and on the left you have prior emissions and on the right you have the updated emissions and then the bottom shows the change from the prior so if it's red it means that it's increased with respect to the prior and if it's blue it's decreased and a good example of that that you can see right off the bat is some of the shipping tracks so there were actually more shipping emissions than in the updated emissions than we expected from the original inventory and so now what do we see from space during the COVID lockdowns? Well this was a really, obviously it wasn't very pleasant to have lockdowns etc but for chemists it gave a natural experiment out in the atmosphere in order to see what happens when reduced activity, human activity results in less emissions into the atmosphere and what it does to affect this has on our air quality. Here's a striking picture this is from New Delhi showing the India Gate and normally Delhi is one of the most polluted cities in the world in fact but you can see in November the 3rd of 2019 the picture on the left there shows a very polluted atmosphere with very low visibility but during the lockdown period you can start to see very blue skies and much improved visibility. Now during this time the particular matter, the fine mode particular matter decreased some 60% in Delhi however it was very complicated in terms of chemistry because the changes in ozone which has produced this secondary cooked chemical after it's gone into the atmosphere, after the primary emissions have gone into the atmosphere are very difficult to predict and in fact the reductions in the NOx cannot of the chemical regime and ozone actually decreased in some of the cities during the lockdown and of course if we're going to look at differences year to year we also have to account for changing metrology between one year and the next. So these are some views of East Asia and we point out some of the major cities in China on there and this is Tropomy NO2 again and you can see on the left 2019 as compared to 2020 and then the difference is on the right so you can see for this pollutant really it reduced quite a bit because of the lockdown and it's a little more subtle to see in carbon monoxide you can see some differences especially in the cities but then in Southeast Asia you can see a little bit of an increase and that was from some of the fires that were larger actually in 2020 and that also makes sense in terms of aerosol optical depth so in the cities again this is from MODIS the MODIS instrument on Terra and the cities again had some some lower values for aerosols but fires actually were increased in 2020 in Southeast Asia. So if we look at the US we saw again this same mix of effects due to the lockdown and reductions in emissions due to reduced human activity and also the mix the way that this mix is then with emissions from fires and how complicated this can be. So what these two plots show they show the US and they show carbon monoxide measurements as observed by MODIS and they in both cases we're contrasting the years 2020 with the Covid year with 2019 and we're doing this with two different periods March and April and August and September. Now in March and April this was the beginning of the lockdown you can see this quite dramatic where is blue here it shows a reduction in pollution and we see this rather dramatic decrease in pollution just as Helen was mentioning before for the NOx emissions but if we look at August and September we actually see an increase and this was a gain due to the impact of fires because although human activity had decreased and emissions from this activity had decreased we had very large fires especially in California which produced more pollution than the year before and so that's why we're seeing this difference shown up as red here and these satellite measurements actually agreed with what was mentioned what was observed on the surface this this map here is showing pollution levels on the surface of surface particulate matter fine-scale particulate matter and if you look to the east coast of the US you can see things are shown in blue there that means that this a reduction in the pollution between 2020 and 2019 and that's in general as a result of this decreased human activity and decreased emissions as a result however if we look over towards California and to the west coast you can see the large spikes there of more blue to there as a resulting from this these fires and so this is an interesting thing that we are interested in looking at from space can we separate the influences of fires from the influences of some of these industrial emissions and so this takes us into our next section where we're going to talk about fires because I'm sure everyone is interested in some of the pictures that we can see from space as a result of the fires that we've had just recently. So first some some quick facts about fires every year there's approximately 1.2 billion acres of natural and human induced burning and that has of course a large environmental impact in the tropical regions biomass burning occurs annually and that's for cultivation deforestation in savanna grazing in the northern hemisphere we have burning but there's a lot of variability from year to year fires are major pollutant sources they affect atmospheric chemistry and air quality and they also have a climate impact and satellites can help detect the fires and track the smoke plumes as they are transported in the atmosphere so this picture shows again the modus instrument on terra and it's fire counts and these are use observations of long wave heat energy from fires and so when you see yellow that's really where the most intense burning is happening but you can see that it's especially strong in in african in this may 2003 but but there's really fires everywhere that modus can detect. So Helen mentioned these fires in Africa and this is a thing that we see every year every year in the southern hemisphere there are fires in Africa and they gradually move south towards the continent during the year and also we have indications of fires also in South America and you can see this the sources of the fires very this is showing hub and monoxide again from tropomy and the high high values indicate the fire regions but not only do we see the pollution over the regions of burning themselves but we see these plumes that will find their way out into the Atlantic Indian oceans from the fires. Now this particular year was this was in August 2019 and it was a year when there was particularly large fires in South America and in the Amazon and these were due to intense deforestation activities at that time and it came to the national news if you remember due to the fact that in some of these cities such as South Paulo shown here day turned to night as a result of these the emissions and the smoke coming from these fires. Moving now closer to home we have western wildfires and here's a quite dramatic photograph which I actually took last year in left hand canyon here in Boulder and it shows the smoke that this was after the fire had just started. So our western fire season are at least a couple of months longer than they used to be in the 1970s according to the forest surface. The Californian fire agency Cal Fire actually no longer consider those to be a fire season at all because it's an all year round event. The large the number of large fires in the western United States doubled between 1984 and 2015 and the fires are increasing in intensity the nine largest fires in record have burned since 2005 and as we'll talk about this the air quality is severely affected close to the fires as shown by that huge plume of smoke on the on the photograph but also far downwind. Why are we having more fires this is a result essentially of drought we're having climate change is causing warmer winters less snowpack lower precipitation and generally drier conditions. Warmer air temperatures tend to soak up moisture from the surface and the heat waves and drought result in more stressed vegetation which then dies and dries and it's been noted that the same forests are not growing back after the fires as they used to just because these fires are so large and so intense now that burned areas are very very large indeed and you've probably read about the effect of fire suppression the fire management over the last few years not burning so much of the undergrowth in in the forests resulting in the availability of a lot of fuel. So if we look at the statistics so far for this year 2021 total fires have been about 41 000 an area burned is about 4.5 million acres so far and if you can compare that to the statistics for last year it's quite scary to see that we're on track to be meeting statistics for last year and we're only in August and if you remember last year in 2020 the biggest fires were in California but they also took place in the fall season. So now we're getting to this year's fires and we're going to talk first about the Oregon bootleg fire so this was a fire so intense it produced its own weather and it burned 646 square miles and we can see what this looked like from space so this is a satellite view of the bootleg fire burning in Oregon on July 13th and you can see the flames and the smoke and fire agencies use imagery like this to help in fire management and also firefighting decisions and satellites can observe that in detail and then track those plumes as they develop to impact air quality far downwind so this is looking on July 20th at the fires that there's the California Dixie fire and the Oregon bootleg fire you can see some of the smoke coming off of them in this image but we also can look at the carbon monoxide that comes from them and then then is transported away and then the aerosol optical depth and in the blue arrows there show the prevailing transport patterns so this is what it actually looked like on the ground from those on that day so we have Denver, New York City and Washington DC and New York City had the worst air quality in 14 years and you really shouldn't be able to take a picture of the sun at that height it's only because of the smoke that they could do that so now we're getting into how air pollution is changing. And one thing that we're able to do now as Helen mentioned right at the start we've had satellite missions we've had some instruments that have lasted way past their design lifetime Moffitt was supposed to last for about five years and is now running on 21 years of data and we have in other cases we have measurements of other gases such as nitrogen dioxide N02 which have been measured by a number of instruments each one following on from the last and this has allowed us to produce very long-term satellite data sets spanning these multiple missions. This plot here shows trends in tropospheric nitrogen dioxide as measured over a couple of decades from 1996 through to 2017 and where it's shown in blue this means that pollution has gone down where it's shown in red this means we've had increases in pollution at those times and as Helen mentioned before this is nitrogen nitrogen dioxide is produced where we have high temperature combustion taking place and so this is a regular indication of human activity and where human activity admissions have either gone up or gone down so you can see that in Europe and Japan and the US we've got significant reductions during this time whereas in some of the developing regions such as China and India there have been significant increases and these pollution amounts and also these trends are very sensitive to environmental policies and so one of the reasons why for instance in the US we have such significant reductions are the result of the Clean Air Act and the similar policies and we also were able to see reductions in recessions etc. Another gas that we're interested in is sulfur dioxide I mentioned before volcanoes but sulfur dioxide comes from volcanoes but it's also produced whenever we have fossil fuel burning especially from coal for instance it's a precursor of secondary sulfate aerosol in the atmosphere which is important with health and also has a significant climate effect and what we have now are long-term records of measurements from the only satellite shown here which are contrast the distributions of sulfur dioxide between 2005 and 2016 and so you can see some significant changes in this back in 2005 there were large amounts of sulfur dioxide over China indicating the use of a large energy production from coal fire power stations this has been reduced by 2016 as a result of some improvements in air quality as a result of policy regulations in China during the same period however you can see in India that we've gone from not very high emissions in 2005 to high emissions in 2016 as a result of the rapid industrialization and growth of that economy there and at the time coal fire power stations accounted for about three quarters of the energy production in India and although there has been a move to cleaner energy in India coal fire still power stations still are being built although there is a move to improve the quality of the the scrubbing of the pollutants from these emissions moving having a look what we can see now with tropomy and when it's very high spatial resolution observations we can zoom in on particular power stations and so this gives us a way that we can see exactly where particular emissions are taking place and this is very useful for working out the efficiency of these power stations and also for regulation so now we're going to talk about the trend in carbon monoxide as observed from from Moppet Moppet has the longest record of carbon monoxide from space and this is a convenient way to look at this so it's there's year on the x-axis and latitude on the y-axis and then amount on the z-axis and so we have the red colors indicate more carbon monoxide and you can see this gradient from the southern hemisphere to the northern hemisphere as well as the seasonal variation in carbon monoxide and that's determined by emission sources and photochemistry and then on the bottom we have the anomaly and that's taken you take the top part and you subtract out the record monthly mean and that lets us see some of these big events that we've been talking about so that in that anomaly you can clearly see these indonesian fires that were driven by the 2015 aluminium conditions which cause a lot of huge drop in precipitation so everything dries out and this map on the left shows Moppet observations of the surface and those are some of the highest ones we've ever seen with Moppet um you can also see these Australian fires that were really large in the winter of 2019 to 20 uh should say summer for them and then uh and then also some of the 2020 fires that we talked about and there were also some really large Siberian fires in 2020 so the other thing you can see there is that over the over the record we've gone from sort of green colors in that bottom plot to blue colors and that shows that globally carbon monoxide is declining and that's primarily due to improved combustion efficiency we remember that carbon monoxide is from incomplete combustion and so as you make things more efficient then you produce less carbon monoxide and it's also because of some reduction in the tropical biomass burning which um until recently was going down but as David talked about in 2019 there were some large fires again so we hope that that trend continues with a reduced biomass burning as well. So we can focus in on a number of regions and showing some of this same data that Helen was talking about but this time just showing a plot of the seasonal variation of not only the moped carbon monoxide measurements but also the modus aerosol measurements and modus is an instrument that flies alongside the moped on the terra satellite and so we have measurements at the same place and at the same time and we can look we can compare and contrast these two pollutants during this this time and we can see that the moped is moped co is shown there in red and we have decreasing co trends for all regions across these two decades and in the eastern part of the U.S. we also get reductions in both the aerosol and the carbon monoxide at this time and this again is a very good indicator of the impact of the strong air quality and climate related policies that we had in in the U.S. Things that are a little different in China again there's a decrease in the amount of carbon monoxide during this time and it's interesting to see that in the first decade here shown here 2000 to 2010 the initial decline in carbon monoxide was not accompanied by a decline in aerosol in fact the aerosol increased during this period and this reflected a move to a central energy production that actually improved the combustion efficiency as Helen was talking about and reduced the carbon monoxide but not necessarily the particulate pollution back in 2010 China implemented a clean air policy and the aerosol after that point started to decrease as well and accompanied the CO in decrease in decreased amount of pollution in for both of these species. So now we get to how satellite observations inform our daily decisions for example should I go outside and exercise today. And some of the some of the most impactful work on this has been done in Europe and we're showing on this slide is some results from the Copernicus atmospheric modeling service or CAMHS and this is located at the European Center for Medium-Wage Weather Forecast and what this project has done is to take satellite observations from all the different satellites across the world including Moppet and along with in situ observations that's ground-based monitoring of pollutants in different places and they've integrated these observations in their big weather forecasting model and this is allowed to then drive some regional scale models over specific regions and this allows these regional scale models to provide forecasts of air quality and you can download an app for your phone for instance this is an example from the Weather Underground app showing for instance in this case moderate air quality over boulder and this is driven by the information provided by this Copernicus system so when you look at these apps you're actually having the benefit of some of these satellite measurements informing your decisions. So this is an example of how satellite data is used in that used for forecasting so you have Moppet observations on the left and those were from during these fires last summer and you can see on the right of the forecast that use those observations this is for surface level carbon monoxide and so this is a process called data assimilation data assimilation and in the in the case of Moppet you have some gaps in the data but what that the model does is fill in those gaps but it's informed by the data that it does have so now we're getting into we're almost to the end and we want to tell you about what comes next. So before we actually do that we also thought it would be interesting to tell you a little bit about how we developed the new satellite mission this is an activity that both Helen and I have been involved in during our careers and we've always just stepped through some of the some of the steps that we go through to produce these rather expensive satellites to fly and tell us about our air quality. So to start off with the first part is that we need to motivate we need a science question or an application need and that might be a question like we need to be able to make better health advisories for air quality and it's based on community input and that comes from often convening expert panels or going out into the community and asking particular stakeholders what do they need what observations do they need and this helps us come up with the observables that have to be measured what exactly are they are they where are we going to measure them when and how well do we need to measure them in order to be able to answer the questions we want to answer. So then we get to the design phase and there you have to identify candidate technologies to make the measurement and you have to make some requirements and you come up with an engineering design to meet those requirements which in this case we're showing a CAD drawing for the PRONOS instrument that David and I both worked on and you also have to consider the data processing approach. The next stage is to go build something and often before we actually start on building the satellite instrument we could be building an aircraft instrument that's going to be able to act as a demonstrate a proof of concept for what the satellite observation might look like and here's just a shot showing the retrievals from Ben02 over the Colorado Front Range you can see Denver pollution from Denver there going towards the mountains and this was a demonstration instrument called GeoTasso which was built by Ball Aerospace here in Boulder which flew on aircraft as a trying to demonstrate the kind of coverage and seamless coverage that we were going to get from the geostationary satellites that we're going to talk about next and the good thing about this is although Helen and I are unlikely to be astronauts we can sometimes fly on the aircraft when these instruments are flying so that we can check out the performance and see if we think that they're going to be suitable for the and have the same performance that we need for the satellites. After the aircraft instruments the next stage is to build a satellite instrument to the required specifications and here's a photograph of the tropomy instrument in the clean room before launch these instruments then have to go through a very intensive calibration and testing they get shaken around to make sure that they're not going to fall apart on launch and we also have to develop the data processing infrastructure that's going to deal with all the data download and also the processing of the data and all the things that Helen talked about in doing retrievals and the like. Finally the instrument is integrated on the satellite bus. Then finally we get to launch and after launch you have to do a check out of the instrument I'll make sure that the data and the performance are good and then we get to what we what I talked about before with data validation and checking out the accuracy of your observations and at that point you can then distribute the the data and it's good for the science and applications that we've been talking about here. So in this slide we're going to talk about a few of the trends if you like in how instruments are being developed and what missions are going forward. So in the in addition to our US satellite missions investigating air quality we also have programs in Europe and Asia that we work with as well. We've built satellite constellations and there's just many satellites all flying at the same time to help provide comprehensive information on many different atmospheric properties. Now these constellations can be built through an international cooperation with different countries providing different satellites all to make become members of a constellation or they might be multiple copies of a small satellite that they're all launched together but they can by working together they can achieve greater spatial and temporal coverage. Commercial initiatives are becoming much more important it's not just the big space agencies anymore but we have partnerships with the private sector for mission development and also for access to space and just over there on on the right is just an example of one of these small sats this is methane sat which is actually being built right now in Boulder by Ball Aerospace. This is funded by the Environmental Defense Fund and it's a spectrometer planned for launch next year and what methane sat is going to do is to measure methane in the atmosphere at a very high spatial resolution. Now we haven't talked that much about methane but it's a very important gas because it has consequences for air quality it's involved in a lot of air quality and atmospheric pollution chemistry but it's also a very important climate gas as well and so the goal one of the goals of methane sat is to target the main sites around the globe that are responsible for the majority of the oil and gas production. Tropomy was a really big leap forward for us and our Dutch colleagues deserve a huge amount of congratulation for producing an instrument that has really revolutionised the way we look at pollution in the atmosphere at such high resolution and which is such great coverage but the next step is the upcoming geostationary geomissions and we're really looking forward to this. Here's a picture of what it's going to look like we're going to have geostationary emissions and if you remember Helen talked about geostationary emissions as looking down over a particular part of the earth and they orbit at such an altitude of 36 000 kilometers that they rotate with the earth's surface and look down continually over the same area and so we have measurements every hour and so they can show these variations during the day we're going to have tempo looking down over the United States Sentinel-4 looking down over Europe and the GEMS instrument looking down over Asia and GEMS in fact was already been launched. Now these geostationary satellites are going to be in constellation again with the low earth orbit instruments that we've got such as tropomy and these are going to have the capability of tying the measurements if you like between the two between the three geostationary areas because these missions all have common objectives and they're working in this constellation framework they're going to provide us with this brand new global perspective and a non-precedented capability to meet the needs of air quality research and applications. So this animation of tropospheric ozone shows how the constellation of geostationary and low earth polar orbit satellites that David just described will work together we have the view over the USA from tempo which used to be called geocape with pollution changing from day into night and then we have the Sentinel-4 view over Europe with a polar orbiter is zipping around that can observe the pollution that's transported all around the globe tying those observations from st. North America to Europe and then to Asia and that's the GEMS view over Asia that we're going to talk a little bit more about. So the GEMS spectrometer was launched by South Korea in February 2020 from the Guyana Space Center and that shows a nice launch there the instrument was built by Ball and Boulder by Ball Aerospace which is also building its sister instrument tempo and GEMS is the first satellite instrument in the geoconsolation that David was talking about and it's already producing some exciting results so this is a picture an animation of aerosol optical depth from GEMS and this shows hourly views over two days so each frame there is an hourly observation and GEMS requires sunlight for the measurements so the progression is westward and you can see the higher particulate pollution in Beijing and then also in northwest India over those two days. And so now we've arrived at our last slide and before we put down a few final thoughts we hope we've explained enough about air quality in the atmosphere and the role of satellites to convince you that air quality is an important topic for us to study. The process is emitting the pollution, how these move around in the atmosphere and what chemical and physical transformations take place and how it finally affects the air we breathe and our health. Definitely over the last couple of decades we've been provided with some amazing satellite measurements of pollutants in the atmosphere and this has really improved our understanding and these satellite data are routinely now compared and integrated in atmospheric models to improve the models themselves, improve our representation of our understanding and also to make predictions. So these advances have been made using low earth orbit measurements mostly and they've they take measurements on the sort of continental to global and the weekly to seasonal scales but the new geostationary perspective with high spatial resolution and hourly measurements will be a big leap forward and it's essential for understanding processes at the local scale so like an urban area and also for providing input to air quality forecasts and management and we are hoping that the measurements from geostationary will be as revolutionary as for air quality as they have been for improving weather forecasts. And with that it just remains for us to thank you very much, I hope you found this interesting and we would also like to thank NCAR and also our funding agencies at the National Science Foundation and NASA and definitely thank all our US and international collaborators and partners for their contributions and one way or another the material that we're presented in the store. They stole a lot of stuff. This is great, thank you so much Helen and David for for sharing all this knowledge with us. A couple quick quick updates so again if you have any questions from the audience definitely join the Slido platform so you can ask Helen and David your questions and to Karen's quick question yes the the recording of this presentation will be available shortly hopefully within the next couple of weeks. So giving right to the questions maybe starting first with Alyssa's and this builds nicely off of your discussion about the methane sat instrument. Can you detect methane links leaks from satellites so you talked a little bit about oil and gas infrastructure but maybe can you detect methane leaks from like a home or a business like a smaller scalar one and then also who decides what to name the satellites? It depends on the size of the leak I mean what was the resolution for methane set? It's sub kilometer. There are there are some satellites flying at the moment there's the greenhouse gas that which is a commercial venture and they're going to be they're providing that's 15 years right they're providing information to oil and gas concerns so that they can detect leaks and make sure that they're not leaking methane from these oil and gas from these gas particularly gas extraction facilities because if we're losing methane from the from the extraction itself then obviously this is not only a waste of money for the oil from the oil for the gas company but also this is contributing to climate change as well because methane is a very strong greenhouse gas. And I should point out that the one that David was just describing yeah has to be pointed and so it has to know where to look and one of the roles of Trobomi has been to figure out if it does see a big methane signature that's not expected it can sort of direct where to point these other ones so that's a good example of how satellites can work together for this. And who decides what to name the satellites? You probably noticed during this talk that there are a huge number of acronyms floating around and we often have second order acronyms acronyms of acronyms but people spend quite some time trying to come up with a catchy name for satellite and we've been involved in this it's often it's just trying to get build an acronym that describes really what you want to do but usually the person who gets to name it is the principal investigator who who proposes the satellite in the first place. Great and our next question is from Peter now who's asking did you consider using the cross-track infrared sounder for NH3 or ammonia? So speaking of satellites that work together you know these satellites fly in close formation with Trobomi. Yes and in fact we didn't we didn't include Chris because we just had so much material but I actually do work on Chris and Chris does observe ammonia and so we are looking at ammonia from fires for example and we're also looking at how to take the observations so like Peter now is saying they're within about five minutes of each other and how you might combine those observations to give you even more information. And just for everyone's information Peter now happens to be the principal investigator of the Omi instrument and a co-in principal investigator of the Trobomi instrument and has recently joined NCAR as the new director of the atmospheric chemistry lab. Hi Peter now. Thanks for being here. Great so our next question comes from Ben and this this builds off of those photos you are showing right of you know New York City with horrible air pollution from fires thousands of miles away so what approximately what proportion of pollution in the US and Canada carries over from China and India? So yeah that's good. Well it depends on which it really depends on what what pollutant we're talking about because different pollutants have different lifetimes in the atmosphere. Some of them like carbon monoxide can last for weeks and so we can often see a build-up if if there's a lot of sources of say carbon monoxide it can build up especially during the winter months and it can a lot of it can pass from one continent to another continent just because it has a long lifetime in the atmosphere. Aerosols often have a lifetime of days to a week or something and so it depends on the transport times. How long is it going to take the particular pollutant to get from one continent to the next continent and how does that relate to the lifetime of the of the particular pollutant we're interested in. So it depends. Yeah but whether or not it gets to the surface depends on the weather so it's usually transported higher in the troposphere and a lot of times it just stays there and then eventually is chemically destroyed but if the weather conditions are such that it'll bring air down from that part of the troposphere then you can get it at the surface and that's what we saw on that day this summer July 20th that those fire plumes really did come back down to the surface that day. Great and our next question comes from Curious and this is a great question because it really gets at kind of the interconnectedness of all of our earth systems so does wildfire smoke affect plant growth? That's a very interesting question and I can't say I know off the top but we do know that pollution does affect plant growth in general and especially ozone as we saw earlier has a big effect on crops and to the extent that wildfire smoke does contribute to ozone along with everything else locally you know it could but I'm not really sure about smoke itself I know that it's going to affect sunlight for example so that's one thing but I'm not sure about you know whether it will cause harm to the plants. Yeah definitely and this also kind of ties in with our you know our ozone garden up at the the Mesa lab for anybody that is ever able to you know visit our our buildings which unfortunately are currently still close to the public but the garden's outside at least so as we wait for some more questions to pop in I'm curious how did the two of you become interested in this line of work? Well my background is actually high energy physics and I guess I started counting photons then so still doing that now I I guess I had been interested in satellite since I was an undergrad here in University of Colorado I worked at the Laboratory for Atmospheric and Space Physics and worked on a Pioneer Venus so that was a satellite that orbited Venus so I guess that was the initial start for me and for me as well I came from a different background I was a physicist working on in fact nuclear fusion but looking at how radiation passes through new nuclear fusion plasmas and I eventually ended up changing fields somewhat and getting a job looking at how radiation passes through the atmosphere and so that led on to working with different satellite programs so that was it's interesting we both came from different backgrounds and both physicists but ended up working in in this field. Physicists can do just about anything badly. It's a great point though that I think a lot of us in the earth sciences have come from other disciplines because I was also a physicist and I ended up in geophysics so great our next question is from Jane so if pollutants can be chemically destroyed in the troposphere does that mean we could potentially destroy pollutants before they return to the atmosphere? Well that's a great question I mean what comes to mind is a catalytic converters that's something that already is is doing that but yeah I think that's that's what you know new technology is is looking into how we make those better for example how you do that with diesel trucks I mean they do have a form of catalytic converter but it's something that could be improved. I think in general I mean taking the idea of catalytic converter or a scrubber that they stick on the top of emissions from a from a smoke sack is a similar similar idea that we're using chemistry to have this emission of a particular gas that we don't want to get into the atmosphere and by having that gas run over other compounds that can chemically react with it and remove it from the effluent that will find its way into the atmosphere that's why we can clean up our emissions definitely. Great and our next question comes from Curious who's interested if forest mitigation is even possible with all the forest land that's in our country? So I guess I'm not quite clear what forest mitigation that would that do you think that would be like? I'm gonna assume it's kind of the way we can you know help reduce wildfires. So like controlled burns maybe that's something that gets rid of a lot of the undergrowth in the forest without burning down the tall trees and but there's also talk of like you were saying forest mitigation is a is a aspect of climate change you know just planting more trees to uptake the carbon and maybe that's what they're talking about and that is something you'd have to consider in that is would it contribute to fires so. And following on from that I mean the deforestation that takes place in some places especially like the Amazon is doubly bad because it's not only producing a fire which is taking is a fire is releasing the carbon that is held in the trees into the atmosphere but it's also destroying those trees and their ability then to absorb the carbon that was previously in the atmosphere so it's kind of a double whammy when we burn when we deforest. And then a lot of those older trees don't ever grow back like David was saying they you know it's changed the ecosystem. Great our next question comes from Andre. Can the increase in pollution be the reason to the dramatic climate changes that have occurred in many places? I mean obviously the emissions man made emissions are contributing to climate change and so you have carbon dioxide which is not really considered an air pollutant it's not really that harmful for us to breathe of course at least not outside. But yeah you have all of the other pollution sources that go with it and they have definitely contributed I mean for example you know there's usually a complex rule like some aerosols reflect some light actually but other ones absorb it so it's a complicated climate and air quality are a complicated problem but that's why we really need to understand all the sources and emissions. But there's a lot of research that is going on in our lab as well as in Encore and other labs to look at these relationships between climate and the impact of chemistry on that climate. So it could be everything from just looking at the direct carbon emissions that Helen mentioned methane is a very good example from different it's a it's a gas that's involved in a lot of ozone chemistry can produce ozone for instance but it's also a very strong greenhouse gas and so we're looking at a lot of different processes that produce methane from both an air quality point of view and also a climate point of view. And then there are other gases that are involved in the production of ozone ozone itself can be a greenhouse gas in some parts of the atmosphere and it's that's produced as a result of different balances between different primary emissions of pollutants and so this gets really complicated pretty quickly but that's one of the reasons why we develop these big complex models that allow us such as some of the big models the big climate models that we run here at Encore for the community and we try and put chemistry within those models so that we can look at the effect of these different emissions on the climate system. So building on your physics background Alyssa's got a got a physics question for y'all. So each greenhouse gas emits energy right at different wavelengths so the satellites can distinguish different gases by their wavelength and then her follow-up question was what part of the electromagnetic spectrum do the gases fall into? Is it infrared uh near infrared etc? Great question um go ahead um so so first of all yeah so greenhouse gases absorb energy in the atmosphere and then re-emit it towards the surface and that's why we have that that um greenhouse forming um but we're we're looking at this absorption in all parts of the spectrum so uh the infrared is where the warming usually occurs um and then in the short wave you have more reflection to space um but I think can you go back to the question? Sorry that was sort of well I think the the answer as Helen says is that we we measure different gases uh have their specific spectral signatures in different parts of the of the electromagnetic spectrum. So it often depends which gas uh we want to measure is which part of the electromagnetic spectrum we choose to sample. Now the converse is also true that there are gases out there pollutant gases out there that we would love to measure that if they don't have a strong enough uh spectral signature in in some part of the uh uh the spectrum or um well they don't have a they don't have a signature at all or it's not strong enough then we can't measure it and so that's why we're limited to a particular handful of gases that we can measure from space and other ones we can't although we'd love to which comes down to another reason why we're always going to need a mix of different observational techniques not only satellites can provide one piece of the information but we're also going to need instruments that can go out and fly on fly on aircraft perhaps or people to go out and take samples of air and use different techniques that can measure the pollutants in those samples so we we can really reliant on the mix of these different uh these different techniques in order to be able to look at all the different pollutants we might be wanting to look at. Great and in the last two minutes that we have together uh for you know for maybe all of our students that are watching us today do you have any advice on maybe like coursework or folks they could be talking to or programs they could look into if they're interested in you know pursuing a career in in the research that y'all do? Um math and physics so uh but I think just in any sort of a stem field so science technology engineering and math uh uh can contribute to this sort of work. So I mean definitely environmental research is you know it's increasingly important for us as a species and for our environment and so you know we would certainly encourage any students out there or any people who are interested in the kind of work we do to concentrate on these uh perhaps hardest subjects from the school math physics chemistry biology the science subjects and then also check out uh different areas different different labs or organizations there's a host of material out on the web uh NASA for instance have some incredible websites NCARL has some incredible websites that you can go and find so lots of information and and try to get internships too internships are a good idea if you find something interesting often people have got their profiles on the on the web if anybody calls me up and wants advice on careers or anything in science Helen's exactly the same as as are most of the scientists at NCARL we're very happy to give advice and provide mentorship where we can fantastic and with that Helen and David thank you so much for being here today to really just chat with us about you know satellites and air quality and all the really really cool stuff that you do and also a big shout out to the team behind the scenes so we got Paul, Brett, Aliyah and Alyssa for supporting the event today and if you're interested in more NCAR Explorer series events definitely check out our website for upcoming lectures as well as recordings of our past events so with that I hope to see you all next time and I hope you have a great rest of your day