TEMPO, A New Era of Air Quality Monitoring Over North America: 2026 Ozone Garden Summer Webinar

All right. And I believe now we are recording. Okay. Hello everyone. Welcome to our third webinar of the summer. Today we have Dr. Caroline Nolan who is the deputy PI for the Tempo Science team and she's here today to talk about updates with the Tempo mission and how Tempo is helping us better understand our air quality. So I'm going to go ahead and pass it to Caroline. >> Hey, thanks. Can you hear me? >> Yes. Okay, great. Um, I can't see the results of the poll. Are those available? >> I can send those to you after the meeting. I'm curious because then it depend that that that will make me either go through my introductory slides very slowly or very quickly. >> Why don't you show them to the crew for a quick second? >> Yeah, let me let me show them. Give me one sec. Can I share results? Here you go. Can you see them now? >> Yes. Okay, great. Okay, so most people actually are familiar with tempo. And I think I'm probably not I I I put crystal clear, but maybe someone else did as well. Um as in they could brief NASA on it. That might be Erica. Uh all right. Um so thanks for joining us today. Um I'll be talking about Tempo um a new era of air quality monitoring over North America. All right. So I think now knowing the familiarity of people with tempo, I maybe don't need to explain all of this. Uh but this is a little bit of the justification for why we need an instrument like Tempo. So um the groundbased uh air pollution monitoring is really the gold standard. Um this is used for regulatory purposes by the EPA. And here's a map of EPA air quality system um AQS NO2 monitors. Oh, sorry. I have NO2, but it's also actually ozone on this map as well. I guess I added it later. Uh so NO2 is in blue and ozone is in pink. Um, and you can see there's there's quite a lot of them, but if you zoom in, you'll see in some states, uh, for instance, I think in Idaho here, we have some ozone monitors. We don't have any NO2 monitors on this particular year of data. Um, and some areas are monitored quite uh quite well like Los Angeles and New York. But even there um for a a short-lived uh molecule or gas like nitrogen dioxide which is only in the atmosphere for a few hours um we we also we still don't have enough monitors to really capture the variability of that gas. So for instance um this is Indiana because the last talk I gave to was to the department of environment in Indiana. Um, but you can see the NO2 NO2 monitors in blue here. Um, and the ozone monitors in pink. Um, in Indianapolis, there's two NO2 monitors. Um, up near Chicago, there's only a couple in Indiana as well, even though there's, um, a lot of industry and power plants up there. Uh, on the other hand, we have satellite monitoring, which we've been doing for about 30 years now from low Earth orbit. So lower earth orbit is where the um satellite is monitor or sorry orbiting the earth about um 700 km above the surface. Uh and these kind of instruments um look down at reflected sunlight off the surface of the earth and clouds and we can estimate how much pollution is in the swath under the satellite. But to get uh coverage we uh have to go around the planet about 15 times a day um in this orbit and we only get measurements once a day. So for instance, this is a um NO2 data from the Tropomi uh satellite which is a European Space Agency uh instrument and we collect data from that instrument at 1:30 about 1:30 local time every day. So we know what the pollution looks like at 1:30 but we don't have that um uh frequent time temporal monitoring. So tempo is um the answer to this and instruments like it and tempo is very similar to this last instrument I just talked about tropomi but it's been put into a geostationary orbit. So the the technology is actually really similar but the orbit is what's really different and so that orbit instead of being 700 km above the surface of the earth is about 35,000 km um and it sits over the equator. So it it um orbits the earth with the same period of rotation of the earth 24 hours and so it's always essentially in the same place at the same time. The difference here is that we don't get global measurements but we do get by scanning the continent continuously. We can get um high time measurements. So we can do this um typically we do it every hour, 40 minutes in the morning and evening um and we can even go down to as short as 5 minute periods um just scanning a limited region of the continent. So, TEMPO stands for tropospheric emissions monitoring pollution and it was launched in 2023 in April. Um, it's led by our group at the Smithsonian Astrophys Physical Observatory in partnership with NASA and it's uh provides the first and only um hourly high spatial resolution measurements over North America of um four of the six EPA criteria air pollutants. So those are air pollutants regulated by law. And the ones that we measure are NO2, ozone, particulate matter and SO2. And we also measure for maldahhide as well. Uh and these on the this on the right this animation is the very first measurements that were collected from tempo of NO2 on the 2nd of August in 2023. And so you can see here um we scan the continent from east to west and taking these measurements. And uh you'll notice the um big gaps in the data. That's where there's clouds. So, we actually make measurements there, but we don't um typically put them in a plot because we can't see very well below the cloud and so we're not seeing any NO2 below the cloud there. So, uh the instrument went up in 2023. Um we had a period of commissioning that lasted for a few months and then we went into what we call nominal operations. That was an 18month um mission. That was what the funding was originally for. Uh we are now in uh what's called extended operations. So NASA um provided funding for Tempo to extend past that date up until the end of this September. And after that we enter um what is called the senior review extension provided we pass the senior review. So the senior review for those who aren't aware um every 3 years NASA operating missions are reviewed um and uh depending on budget and performance of the instrument and the use of the data those missions can be chosen to be extended for an additional three years in and onward in three-year increments. So we just did that senior review proposal in April um and we're hopeful that uh tempo will be extended um past uh September of this year. The initial feedback we have is um positive and we have a lot of data users. So the tempo instrument um at its core is a grading spectrometer and um this is the Intel SAT satellite that it flies on. It's a commercial geostationary satellite. Um so providing satellite internet to cruise ships, airlines, um remote areas and tempo is this uh box on the end that's looking at the earth and it is about the size of a dishwasher um in real life and inside its core. It has a diffraction grading uh and that grading splits the um back scattered sunlight from the earth into different wavelengths or colors and we get these spectra that look like this. So these are wavelengths of light um and if you think about like colors this is ultraviolet light here um down lower than 400 nmters and we have like blue light, green light, red light and we're into the infrared near infrared here and the the kind of broad features are representative of the reflectance of the surface. So if you have a cloud for instance this bright blue is um bright because clouds are bright. Um and uh when you start looking into like um say uh desert for instance, we get more red light down here. Um the squiggles are uh molecular absorption of gases in the atmosphere. And so this is actually what we use to retrieve the amounts of the gases in the atmosphere. And tempo measures a very high spatial resolution for a satellite instrument of this kind. Um it's the first before it was launched tropomy had the highest spatial resolution. You can see this box here is Washington DC of what a single measurement of tropomy could resolve. Um and tempo is this little red box. These bigger ones are our older instruments. So it's about 2x 5 km. So the observations that we have now that are publicly available that anyone can download and use are of nitrogen dioxide, formaldahhide, ozone, we have total ozone. Um and so uh that that includes a lot of stratospheric ozone. It's typically dominated by that. But also we have an ozone profile product which um has some information on ozone in the lower atmosphere under the surface and particulate matter is also available that's um produced by our colleagues at Noah using the tempo spectra. We also recently have uh got funding to develop a lot more products. Um these include sulfur dioxide. So um that's mostly coming these days from volcanoes but also from burning coal. uh water vapor um surface ozone and NO2 concentrations. So we actually measure the column amount in uh in tempo data. That's the total amount between the surface and the top of the atmosphere typically. Um but what people are really interested in is what they're breathing at the surface. [clears throat] Tempo can also measure ocean color. Um and so uh there's ocean chlorophyll and ocean color products under development. Nighttime lighting is something you might not expect, but we can do measurements at night and derive um observations of lighting types. I'll show a bit about that later. And UVB radiation, which is um useful for um skin and and ecosystem UV exposure studies. Here's a couple of uh plots just showing the kind of uh temporal um changes and that we can measure in NO2. This first one, this is New York City. This is the very first measurements again made by Tempo. Um New York, uh Washington DC, Philadelphia, and you can really see here the NO2 in the I95 corridor. So NO2 is mostly produced by burning fossil fuels um with small amount smaller amounts from lightning and um soil emissions. But here you can see the the basically the effects of traffic in the um around noon time. Um and as we enter the later afternoon uh further away from the morning rush hour, these amounts have diminished um and you actually can see them in the next subsequent scans going up again. This is showing um a nitrogen dioxide and formaldahhide over Houston, Texas um from some uh observations in I think May of 2024, March, I can't remember which date exactly. Oh, here it is, August of 2024. And you'll note here um there's so we're moving through the day here from morning to um evening and you can see the NO2 and formaldahhide developing in this time period and they have very different sources in Houston. So in NO2 you have a lot coming from traffic and there's also industry. This little blob down on the left is power plant. Um and with I'll just show it again. Formaldahhide um typically there's some direct production from petrochemical facilities in Houston but it also there's hardly any in the morning. You can see um it's also produced as a secondary pollutant from um uh chemical reactions in the atmosphere of other volatile like volatile organic compounds. And formaldihide's interesting because we can't measure most VOCC's from space. There's thousands of them. But uh in their chemical breakdown they all eventually um produce formaldahhide at some point. And so we use formaldahhide as a proxy of total VOCC's in the atmosphere. Uh we now have ozone. This is um new as of um last [clears throat] excuse me last fall. Um it's quite a difficult product to retrieve. Um I should say ozone profile. It's quite a difficult difficult and time consuming and computationally intensive product to retrieve. Um and so it came a little bit later than the other ones. Uh but we can see here um this is a feature on the NASA Earth Observatory web page from um a month or so ago. Uh NO2 changes in New York City on May 18th in the morning. We have lots of NO2 less again in the evening kind of like what I showed before. Um and then sorry mid-after afternoon and then into the early evening we now start to see um formation of ozone because o o o o o o o o o o o o o o o o o o o o ozone is a secondary um product formed um from the reaction of of nitrogen oxides and VOCC's. So this is I don't have too many images from the wildfires that are happening but this I just made this quickly. This is obviously um probably of interest right now, timely interest. So Noah is producing aerosol products from Tempo. One of the products that they produce is smoke detection. So uh they basically are differentiating between smoke and dust. You can see here um this is uh almost all categorized as smoke. There's a little bit of dust down there. I'm guessing that's some kind of retrieval artifact um in aged old smoke. Um probably not actually dust here. Uh but you can see clearly um the these are some major fires uh near Thunder Bay in Ontario uh that grow and grow and grow throughout the day. And there's also some smaller ones up here. I think that's in Saskatchewan um possibly. And we can see the smoke being transported down. It's actually really hard to do the retrieval when there's clouds uh that just get gets mixed up with all the um uh smoke as well. It looks a lot like smoke. So sometimes we retrieve smoke as clouds but um it it is obviously detecting a lot of smoke here. Um tempo can do something that most instruments um cannot do in space. So Noah uh usually is using an instrument on their weather satellites um called ABI for looking at aerosols. Um but it is an imager. So it measures very discreet wavelengths of light. Uh tempo on the other hand has that complete spectrum and ABI does high resolution measurements on the ground spatial resolution but tempo is not as high but it has a lot of information in the wavelengths and so um we can retrieve or Noah retrieves uh other other um parameters from tempo that they're not able to easily do with AI. This is the aerosol optical depth which they um can do from ABI. This is the total um basically represents the total amount of aerosols essentially. This is the layer height which is an interesting product from tempo. Um so they can use additional information in tempo to get the the layer height of the aerosol and that's important for say forecasting aerosols. Um and also important to know where the plume is. So if the smoke plume is in this case purple means 5 km high. If the smoke plume is 5 km high, that's a lot different um you know from what people are breathing uh at 0 to 1 kilometers which is the the kind of lighter um orange and yellow. So now uh I'll get into some science highlights uh from Tempose and just go through a few of the interesting papers that have been published in the last year. Uh the first one and I think um pretty relevant for the ozone gardens is excuse me um observing the dal variations in ozone production from space. So as I'm sure many of you know um you need VOCC's and and nitrogen oxides and the presence of sunlight can react to form ozone. Um and so what uh this paper has done, this is Xiaomang Jen at Ruckers University wrote this uh paper. Um and she looked at the um ratio of formaldahhide to NO2 from the instrument. Um and what this is used as an indicator basically of whether a um chemical regime is NOx saturated or NOx limited. So um if you have a lot of I always get confused explaining this even to myself. If you have a lot of NO2 and a little bit of formaldahhide all the formaldahhide will react with some of the NO2 and then changing that NO2 um is not going to have the same effect it would have if you change the formaldahhide. And so it's important to know um the the ratio of those two to understand policywise is it should the emphasis be put on reducing the VOCC's or the emphasis be put more on reducing the knocks and you know maybe both would be useful but um it's uh if you're going to focus on something you want to know um what kind of u what those ratios are for ozone production. And so this we've um she's been able to do for the first time actually use satellite data to look at how that changes over a day. And you can see for instance an example like Atlanta in the early morning it's actually NOX saturated in the this is I think just in the summer in the um afternoon where there's a lot of VOCC's it's actually um NOX limited. Uh the next I'm going to talk about is lightning contributions to atmospheric NOx. So um Roy Jan Dang who's a was a grad student at Harvard um used a cloud slicing technique where she um looked at how much NO2 was above a cloud and um below a cloud to estimate upper tropospheric NO2 from tempo. So that's um NO2 like in the sort of 3 to 10 km range above the surface and uh in the summer at least um concluded that lightning is responsible for the dominant or is a dominant source of free tropospheric 2. She also um showed some interesting results uh showing how tempo the tempo observations do not agree well with this uh the results from the GSCF model which is a big global model of chemical model of the atmosphere atmosphere. Um and so if you look at the spatial distributions for instance tempo sees lots of um NO2 being produced down in the Caribbean uh whereas this is in June July August whereas um the GCF model is not seeing here that indicates there's some um uh issues in the parameterization of lightning in um the chemical transport models. This is uh rocket launches observed by tempo. Uh so this is a study done by Joe Palmo who's a graduate student at MIT and this paper is currently um under review at geophysical research letters and uh this image here shows um a tempo scan of the Aremis 2 launch that happened on April 1st of this year and uh this is Cape Canaveral right here this little star um the launch pad I think is just a little bit to the north um east and these are actually six minute scans done by Tempo. So, like I mentioned before, we usually do these hourly scans, but uh with special commanding, if we know there's like something interesting happening, and if you actually know if there's something interesting happen happening, you can talk to us um with strong scientific justification can actually command the instrument to do much faster scans. So, in this case, we just scanned Florida um in the evening during the temp the sorry the Artemis 2 launch window. And so, we were able to make these six minute scans. Um this NO2 is coming from Orlando, by the way, over here. Um and you can see just this is right next scan right now. Yeah, you can see the NO2 plume. Um and so um he's used that and I think 18 other launches that have been observed with Tempo to estimate um uh rocket uh launch NO2. Um and this u there's a lot of launches that are coming up in the next few years like thousands and thousands of them. um they're growing exponentially with uh networks like Starlink and so um it's important to start to to understand um how these uh these kind of emissions are going to affect the atmosphere particularly stratosphere. Uh and he can then um derive the total NO2 produced of the evolution and its decay in the rocket launch plumes. Uh next up is measurements of nighttime lighting. So now we'll get into a couple of um things that Tempo can measure that are not in the original baseline plan. And this one is uh nighttime lights. So we can do observations um early in the morning um before the sun rises of uh of the dark uh continent. And this is a composite um from a couple of weeks in February of 2024. This is work done by Jim Carr um from car astronautics who uh also was responsible for the developing the algorithm to geollocate tempo data on the ground but he was interested in trying this as well and it's become a this is kind of now um becoming a a really interesting collaboration with other groups um who study nighttime lighting from space. So here we have uh the composite of the whole continent and then over on the right we have just this is just Miami right here. So that's a blowing up Miami. Um because Tempo measures these uh full spectra of lights, we can actually fit um the known spectra of different kinds of lighting like fluorescent lighting or LEDs to those spectra. So other instruments do this from space uh like ve um is a instrument on the Noah satellites that makes very high spatial resolution observations of nighttime lighting. um but they can't get the type of lighting because they only measure a few wavelengths, not this whole full spectrum of of a thousand 2,000 wavelengths actually that we measure. And so in this case uh he's then used this information over Miami to um partition the kinds of uh or the radiances into different kinds of lighting. So you can see in this case LED lighting is dominating and this has a lot of um interesting applications in um health and sleep and uh energy use and ecosystems. Tempo can also measure ocean color. Um this is also not a baseline product but we're hoping at some point this will become publicly available on um NASA's data um data archive like our other data. Uh so this also can be done by instrument other low earth orbiting instruments but tempo has this high time resolution um and so this is a study done by Zach Fastnak who's at NASA Gddard um who's used machine learning um and tempo to derive ocean color and so this is a map of ocean chlorophyll in the Gulf um on March 16th but we can um this is actually a movie I should probably play that and uh tempo is really useful for a couple reasons it has the dial um uh DAL cycle, but also um the clouds move during the day and so you can actually if you just want a daily average for instance of it, you get a lot more coverage than you might get from one overpass on the other instruments. Now, um I'll just get into some um applications of tempo data um in the way that um a few different organizations are using tempo data. So Erica made this image um a while ago, but there's a lot of uh wide variety of applications um possible with tempo data and some of these are are just starting to be realized and kind of an early use. Um but some of our big uh users are um the Environmental Protection Agency and state agencies. Um so the EPA has been very involved with Tempo. They coordinated the Tempo ground and airborne validation effort. So there were several campaigns that were run by NASA and Noah, NSF. Um but uh EPA scientists um basically coordinated a lot of other scientists who were on those campaigns um or who worked with groundbased data to uh validate the tempo instrument. Um they provide data access through the remote sensing information gateway which is um used by states, state and local air quality agencies. um they provide training to those agencies and they also partner with states to use tempo data to analyze um air quality basins in several non-attainment areas um where they are out of attainment of national air quality standards. This is an example um that uh of some work done in collaboration with the EPA and NASA to look at how to use tempo to assess surface network placement. So uh temple formaldahhide they found is very highly correlated with surface particulate matter. So if you want to look at surface PM2.5 um you can see here this is Los Angeles and and similar results are found in other cities. If you look at the average formaldahhide column this is on the um x-axis and the average PM you get quite a nice correlation um and these are where those various PM sites are located and then with tempo formaldahhide overlaid on top. So for instance, if you um know that these are correlated well, you might be able to say like, oh well, look at these areas, you know, with lots of formaldahhide and they're not monitored very well. So that may help in sight selection of surface monitors. um the G uh different states like the Georgia um environmental protection division are using uh tempo data in various ways in um forecasting or um retroactively in this case for um looking at uh exceedence events. So um the state of Georgia uh has been using tempo vertical columns as proxies for surface concentrations um for when they uh have to produce exceedence reports or to demonstrate an exceptional event. So in this case we can see um exceed these these are exceedence days on the left where the ozone uh was in exceedence of national air quality standards um and on the uh the right this is non-existence days and the top is NO2 and the bottom is fromaldahhide. So you can see this is plus or minus one day in the middle um from the exceedence. So you can clearly see that on the days where um Atlanta in this case exceeded air quality standards um there was a lot of NO2 there was also a lot of formaldahhide um and formaldahhide in Atlanta is often dominated by um biogenic formaldahhide so it's produced from the oxidation of isoprne um in the southeastern US in the summer so uh in that case um you know you might be able to say like well actually we exceeded this because we had so much biogenic um VOCC's and so that that can help to explain why in a particular day you have an ozone exceedence. This is an example of looking at a um a major pollution event. Um in this case uh this was a barge fire in Mobile, Alabama that um burned on um January 12th to 13th. And uh you can see here this is before the fire. This is J. This is um 2026. This is before the fire um in early January. This is Mobile um down here. And uh you can see clearly that the NO2 is um very high during the active fire. This is from um Aaron Nagger at NASA Marshall. And there's been tempo's been used for a to demonstrate um observations of uh some major events like that on occasion. So um now using tempo data and I think Eric has probably talked about this before um so I'm just so I'm sure everybody knows about this um this uh interface but uh for this is actually I think one of the the cosmic data stories tempo light viewer in my opinion is like the easiest way to look at tempo data. In fact I use it all the time um despite the fact I have access to like eight different kinds of viewers. Um I really like this one. Um so uh and and she's she and the cosmic data stories team are working on a um tempo lab which will include other molecules in addition to NO2 that's currently available. Uh I'm not entirely sure of all of the backgrounds of the people here, but um for those people who are kind of working in air quality or environmental science as um a profession, uh there are several ways to get involved to learn how to use tempo data. So if you know something about air quality already but you don't know how to use satellite data for instance um or even if you're an expert on uh air quality and satellite data the tempo early adopters and now the name is changing I think to community of practitioners or something like that um because it was called early adopters before the mission even went up um they have a a program for um finding out about tempo data for updates um for trainings in person and online there's 650 regist users from a diverse array of um organizations um including all levels of government and uh and they do again in-person trainings and online ones. This one I think is from the Western States Air Resources Council organized this last year this training and um before there were 30 people and before that only two of them had ever used tempo data. So they do a lot of engagement with like state users and local air quality um air man air um air quality managers as well. And just um I wanted to end by pointing out that we're not actually the only geostationary satellite up there. Um we measure uh North America, but there's also a recently launched mission um over Europe and North Africa called Sentinel 4. And the gems uh mission is run by um the South Korean uh government and Jonzai University and that's measuring most parts of Asia. Uh in the future ideally we would actually start to get some geostationary coverage of the southern hemisphere. Um but uh but for now what we have is um this northern hemisphere coverage and we combine that um to really understand global air quality also with the low earth orbiters that are already in space. And with that, I'll end um my tempo update and I guess take any questions. >> Thank you so much, Caroline. And actually, before we go into Q&A, I just have one closing poll as well. Um so we can we can start Q&A, but um if participants could please answer this question as well, that would be fantastic. And for Q&A, you can just kind of unmute and ask a question. You don't have to raise your hand or anything. Um, hey, I have a question. Yep. um with the public publicly available data. I was trying to figure out how to look at um ozone, but am [clears throat] I correct that you can just see the NO2 on the publicly available site? >> So there's a lot of ways to visualize um tempo data. So, the cosmic uh data stories tempo light viewer that um has been developed at um the Smithsonian is kind of like I don't know Erica maybe I'm totally I'll explain it wrong but it's kind of it's really um aimed at public engagement and K to2 students teachers there are a several other ways to visualize tempo data so there's NASA worldview is a um I think a a very thorough way to look at data. Um it's pretty busy though because it's also got like 5,000 other data sets on it. So you have to type in tempo ozone and things will come up. But you may depending on your level of expertise may need to like look around a bit to find out which is right. Like I know that you probably want level three tropospheric ozone or something. But you you know there may be like eight options that come up. There's also um uh ArcGIS uh viewers for tempo ozone. Um but right now in that like more simple tempo um viewer that I put on the screen, you can't see ozone. So Erica, you might want to give an update there. Yeah. Uh by this fall we will be launching the Tempo Lab uh which is the next round of kind of a deeper dive into Tempo data that is still geared towards learners uh and public audiences as opposed to kind of already the science deep science audiences. Um, and so that will certainly be communicated to this network when when that [clears throat] tool is available. And that does have one of the ozone data products, not all of the ozone data products. Um, as well as formaldahhide and potentially [clears throat] a few others over time. >> All right. Hi, this is Jennifer. Um, can you go back to Atlanta and explain a little bit more about the natural um systems that that take place to produce the increased ozone? >> Sure. Um, I'll preface this by saying I have not been to Atlanta. don't know exactly all of the different kinds of sources um that we have here, but um so first of all, there's lots of um like any big city in the US, there's lots of um fossil fuel burning uh and so that produces NO2. So on some days, you're going to have a lot of NO2. Um there's, you know, a big airport that I think we can see, I can't remember exactly where it is, but I know it's been seen in the in the tempo data. There's power plants nearby. Um but one of the main um uh air quality issues in the southeastern United States in the summer is that we have a lot of natural VOC. So those are things that you really can't control. So um because of the um forest types in the southeastern US, I think it's a lot of elms. Um but someone maybe someone else here could correct me if I'm wrong. Um uh we there's a certain certain trees produce a lot of isoprene which is a VOCC as well um when they're heat stressed and so you don't get that issue in the winter but in the summer you have a lot of isoprene produced and isoprne uh in these massive amounts turns into formaldahhide at some point um so it might not be like formaldahhide itself that's reacting with the NO2 but um it's some other um it could be isoprene or from aldahhide um to produce ozone. So you need for ozone production. Ozone is not emitted directly. It's produced as a secondary pollutant um from other pollutants reacting. And so you have like you have hot hot summer um lots of sun, lots of NO2 and lots of volatile organics which for which fromaldahhide is a proxy that combination is going to lead to a lot of ozone. I don't know. Is that uh >> It's very helpful. It might be oaks >> because Oh, yeah. Could be where I am. I'm on the Great Lakes. I'm Canadian. I apologize. [laughter] >> I'm sorry. I'm on the Great Lakes. So, we have the same thing with oaks. Thank you. >> Yeah. And Caroline, I will note that uh Atlanta is known as the city in a forest, I believe, is one of its nicknames or something along those lines, right? So, >> it is definitely >> That's correct. >> Yeah. [clears throat] So definitely forest coverage. >> Yeah. Yeah. I mean I think some like very detailed observations of cities have seen like increased fromaldahhide over parks for instance because you get again isoprne coming from from these green spaces. Emmy has chimed in and said oaks and pines in the southeast. Okay, I might ask you to go back a couple more slides to um when you were talking Keep going backwards was one of your early slides about ozone. That one. Go back. >> This one here. Yeah. >> Yeah. So, the dial variations. Um could you just I think dive in a little bit more to what we're seeing in the graphs in the bottom for us. Yeah, sure. So um okay, maybe we can take Atlanta as an example because um we just talked about it. Uh so this is um this is a representative of um the uh number of um so what she's done is taken a box around Atlanta and then she's done the spatial spatial at every like spatial grid or whatever inside that box she's ratioed formaldahhide to NO2 and so this is the fraction of the box that is in um this uh regime and so and how that changes over time. So there's actually a lot of spatial variability in a city on where it's no saturated or nox limited. So this is kind of like a summary of the whole city, but it's not actually really telling the whole story either. You may have like some suburbs that are say Knox limited and you may have some uh inner cores that are NOx saturated in that same city but this is taking the fraction of inside the box of um of how of that area whether it's NOx saturated or NOx limited. So um so a downtown core that like has a lot of NO2 um may be different from a suburb that doesn't have as much NO2 but maybe it has more formaldahhide for instance. So if you look at like one line um here at 1 hour of the day um if it's uh red it means that say in this case it's you know a bit more than 50% is no saturated. So th those that's the total amount of the area of that um [clears throat] that city where changing the NOX dial or the NO2 dial um I should say NOX is just a way to write NO and NO2 which cycle with each other and we measure NO2 so it's like a proxy of the whole of the total NOx um but changing that NOx dial in a NOx saturated regime is not going to actually reduce your ozone and there's some chemical reasons why actually reducing it might even increase your ozone a little bit. Um and uh there's but if your NOx limited um some small fraction of the area of that city, it's going to be opposite. So you can reduce the NOx to reduce the ozone production in that area because in that case um you uh you're limited by the volatile organics and I don't know if that makes it any more clear. So like Chicago myself like I said explain when I think about this >> in Chicago reducing NO2 pollution might not improve ozone is that what >> in these hours of the day at these hours of the day yes >> so morning reduction of ozone of NO2 isn't going to reduce >> so this is just the relative you know total amount um and then transitional is kind of like in the middle >> okay And if you know, is there a reason why that tends to lean towards the mornings? >> I suppose oops, sorry. Um, I suppose that in the morning there's a lot of NO2. So um there's a lot of NO2 in the morning for um photochemical reasons um when the sun comes up. Um and also there's maybe a lot of NO2 from rush hour pollution that um has dissipated more um in towards the uh the middle of the day as well. And fromaldahhide um and if it's biogenic um is first of all um it's produced when uh plants get hot and so in a place like Atlanta um in the summer then um as there's not as much formaldahhide in the morning as there is later in the day. It's also primarily produced as a secondary pollutant. So, it's coming from the reaction of other VOCC's in the air. And so, you don't have as much maybe earlier in the day as you would later in the day. >> Awesome. Thank you. >> That's my guess anyway. Educated guess. Any other questions? All right. I guess if we don't have any more questions then you're free to go. You're free to stay stick around and chat with us. Um completely up to you. Thank you again so much Caroline for joining us today. >> Thanks for having me. And I'm going to end the recording.