 So, first thing I tell the students is, what are they going to learn today? I think the learning objective, if you define the learning objective, it kind of makes it easier to say, then they know okay, if they could deal with this by the end of this particular lecture, then they would have done the job, okay? There is to learn today in this one particular lecture is, everybody, you appreciate right that I am not really teaching here? Everybody with me, I am not teaching here, right? I am just sharing with you what we do in class, okay? So estimate pollutant concentration related to exposure, okay? So that's what there is to learn today. And then, by the, another thing that we will do is you'll be able to explain the effects of meteorology and the physics of dispersion of pollutants in the atmosphere. Those are the two things that we will learn today. So we will spend an hour or so working on that, fair enough? Okay, good. So, begin with what is air pollution? So, what they are going to learn is this, but then, this is the first lecture. They haven't come, they haven't done, by the way, I do a similar pre-course quiz with them, like what you just did. I have a pre-course quiz in which I ask some of the questions which will get answered. The ODs in that will get converted to people knowing the answer by the end of the seven lectures, right? So, in some sense, if at the end of it I gave the same pre-course quiz as a post-course quiz, they should be able to answer everything, okay? So in some sense, that's a learning objective. So what is air pollution? You can do how it is perception. You can smell it. You can, you know, see it. A lot of times you can't smell it. You can't see it. That doesn't mean it's not there. For example, is this room polluted right now? With what? Why? Carbon dioxide is not a pollutant. What? Are you... What are you talking about? The pollution is increasing. There is no limit to it. There is limit for carbon dioxide. But you get, right? This is the kind of conversation I have with students. You understand, right? That's the kind of conversation I have. And now, of course, I tell them we conducted a study in IIT and different halls, different sizes of halls, etc., with, you know, air conditioned and with ventilated, you know, rooms, etc., etc. And we found out the carbon dioxide levels can go very high as much as 1200, 1300 ppm, okay? And we've very, very... There's a very high correlation between people going to sleep and carbon dioxide concentrations. And by now it is well established that it is the carbon dioxide in the room and not the boring lecture that would be able to sleep. All right. So, you know, just get them the sense of visible what is, you know, when they see it's order, etc., etc., sometimes order, a lot of time, you know, some railway stations on central line, you have to be asleep and you can actually smell, ha, station agya, all right? So that is there. And then, you know, I also tell them when is the last time that they actually experienced air pollution, okay? And typically I, you know, tell them from here you go down, the closest railway station is Kanjurmark. So if you go down in an auto to Kanjurmark and as you're sitting over there, the light turns red and right next to you, there's a truck standing here. And the truck, you know, the diesel exhaust, the pipe, it is designed just so that it goes into the auto, right? So you're sitting over there and, you know, you just, you know, chit-chatting whatever you're doing and suddenly the light now is going to turn green. That's how it goes, you know? So the person actually pushes the accelerator and the moment you push the accelerator, you know, the whole thing comes in you and you go, you do all of that stuff, right? And then you are out to say some bad words, right? And then you actually look out and right there it says, Jai Bhavani. That's it. You know, that's all you can do about it. So you actually get them to experience, where is it that the last experience pollution, okay? So another example I give them usually is, you know, I ask them, do they know Saif Ali Khan? Saif Ali Khan? Karina Kapoor's husband? You know, okay. So Saif Ali Khan's mother, Sharmila Tagore? Ah, so everybody knows Sharmila Tagore. Very good, very good. So Sharmila Tagore, you know, some of the movies, they would actually show that there is this, you know, the large part of the suffering and all that stuff, right? That there'll be the kajal and the kajal, the tear is coming. Why? The chula is burning and you go into the chula and all the smoke is coming. You remember some movies like that? Yeah, okay. So that whole perspective of indoor air quality, that while we think that it's an urban phenomena, actually it's not that there's a large part of the issues with, so recently a report came from Yale. Yale comes up with these environmental reports. And air quality in India was rated somewhere in the 170th, somewhere pretty low down on a list of 200. We're pretty low down. So there's a question on the Lok Sabha and they said, hey, you know, is this any good? Is this report any good? Is the assertion that India's air quality is very bad? Is it really, you know, valid? So the report came to us, we saw the report, they've done two, three things in that. They looked at the ambient air quality, okay? They looked at the ambient air quality. And then they said, look, the air quality in India is at a certain level, but there are two factors that you now have to take care of. One is, what is the size of the population being exposed? Okay, so the size of the population being exposed being larger gets multiplied by a factor, okay? And then second thing is, how much of solid fuel is being used? Okay, another factor. So while it may have been all right in terms of ambient, but because of these two factors, it comes down. Okay, so one of the assignments for students now is to read the Yale report, okay? So there is interest now because it is directly, and this is real actually, it's coming directly from the Lok Sabha. The minister over there is actually standing and defending why India's air quality is not as bad as what Yale is making out to be, okay? So right there, there's an assignment, okay? What is clean air? I think this is one of those questions. If I woke you up in the middle of the night from class six or seven, you've memorized it, committed to memory like that, right? If I wake you up in the middle of the night and say, hey, what is the nitrogen concentration? 78, doesn't matter where you are, what you do, but 78 will come out of your mouth, right? So this one is known, this one I think right now is requires which year? Which year, so that is changing every year. See what you did in class five or six, and what is being done in class five and six, that number is changed, and it's changing every year. So carbon dioxide levels are changing, you know that, right? Okay, so this is where the whole idea of global warming gets introduced. Now they'll have to go look at the two movies and then figure out this whole business about global warming, all right? Okay, then we go into some of these details about Earth as a sink system, etc., etc., we have this concept that no matter how much junk you put into River Ganga, it has a self, what is it called? Self healing by nonsense. Just go look at the trash we've turned Ganga into, right? And there's also this concept that the blue sky, the Neel Gagan, it's wow, infinite, no it's not infinite, yeah. You can't keep dumping into it and then hope that it'll remain blue, yeah. By the way, sky is an illusion, everybody know? There's no sky, really, it disappears at night, right? Everybody? It disappears at night, so it's only an illusion. If you see blue, you see blue because it scatters light. Molecules are scattering blue light, therefore you see it. If you don't see blue, that means it must be some pollutants. Okay, so the whole idea is just looking at the sky, you can actually say whether it is polluted or not based on the aerosols, the particulate matter that are out there, okay? If it is black smoke or there is white smoke, okay? Just by looking at that, you'll be able to say what is the quality of emissions that are coming out, black is carbonaceous, white may be just steam, which is condensing because it's now in a cooler environment, all right? Okay, good, all kinds of stuff like that. Then scales, etc, we go into and say, okay, if we say it is infinite, it's really not, if Earth were an apple, then the thickness of the atmosphere was only the thickness of the skin of an apple. And you might want to find out your own ways to be able to illustrate that it's really not infinite, it's not, it's very poetic in all to say that, Neil Gagan and all that stuff, but hey, there's finite depth over there, okay? First 10, 12 kilometers is all there is, okay? Okay, then you get into this whole business of national ambient air quality standards, the concentration, the exposure, there is the, I'll give this to you later, everybody familiar with this, right? There are some national ambient air quality, it's on the Gazette, so you can actually see how much of concentration has to be below a certain limit, etc, etc. Okay, so let's, then we get into a class exercise, okay? And the class exercise is pretty straightforward. We actually say, okay, given regulatory limit for sulfur dioxide in ambient air is 80 micrograms of meter cube for annual average. So if you and I were exposed to 80 micrograms of meter cube for the whole year, 24 hours a day, we'd still be okay. Above 80, there may be some health concerns. As long as it is below 80, you're in compliance, okay? So as a city, as a city, as your home city, if you are, suddenly now you're in charge of your city, okay? You're in charge of city, so your concern would be, hey, what is the air quality in my city? So I'll have to go to the regulations to see, okay, if 80 is the requirement, what is the actual level in my city? Okay, so we get into that and then, if you were exposed for three hours, then 1300 and then we actually say, we actually do an exercise in which we say how many grams of sulfur, if burnt in this lecture hall, would pose a health risk to you, given that you're going to be here for three hours, okay? So you don't have to get into the details of what the emission levels are, and etc, etc, etc. You, they actually need to get a hands-on calculation of how do I calculate, what is it that I'm going to get exposed to which can get dangerous, based on the standard. Fair enough, and then, of course, this is where the fun begins, ready? This is the hall, this is the hall. So now you've got to figure out the volume of the hall, because sulfur plus oxygen is equal to sulfur dioxide, 32 grams of sulfur, so you know, that's straightforward over there, that chemistry is straightforward, right? That's not a problem. The real question is, what is the volume of the room, right? That's the real question, what's the volume of this hall? So there you go, ready? Prices to be one, double-dhamaka, okay? So the point is, there is double prices, so closest to the actual volume. Now people are estimating this, okay, on the little attendance slip. They will write the name, they will write the roll number, and they'll also write the volume of this room in meter cube. Because this is a, what do we win here, one over here, right? Okay, so you go double-dhamaka, so for, of course, somebody who's closest to the actual volume gets a five-star chocolate. Not bad at all, right? And just to be fair, because actual, I don't really know what actual is, there's a second prize, which is closest to the average. So I take everybody's, average it, whoever is closest to the average, gets a chocolate, how about that? Not bad, okay, very good. There's a problem though, and the problem is this. That previous year, I'm not telling you this auditorium, okay? I'm talking about another auditorium, FC Coley auditorium, otherwise it'd be cheating, I'll give you the answer. No, no, no, no, no, no, I'm not giving you the answer, okay? So what you've got over here is, this is the volume, this is the students. This is the volume that was reported, by the way, this is log scale, right? Y-axis is log scale. So some students have even said, I don't even know how many zeros there are. Hello, what are the number of zeros here? One, two, three, four, five, six, seven, or three, six, eight. I don't know, how many zeros, seven or eight over here? Okay, and this one is saying over thousand, so it's like a five order of magnitude difference. This is intelligent, BTEC students sitting in this class. Five orders of magnitude, the volume difference. Now, it's okay, people have the creative self-expression so they can give whatever they want, but there are implications here. What is the implication? The implications are this, in one case it is saying, even if you burnt only 20 milligrams of sulfur in this room, you'll be dead. That's one extreme, which extreme is that? This extreme, right? And the other extreme says that even if you burnt 8 kgs of sulfur, suddenly you're interested in the volume of the room, aren't you? All right, so some of these things you do because you are, everybody understand this double dhammaka, this, that, and the other is required for what? Because by this time students are already going to sleep. All right, so if I don't, every seven minutes or so, every six minutes or so, if I don't introduce a double dhammaka, I've lost my audience, all right? So, hey, everybody with me? It's okay thing to do, right? Okay, double dhammaka, yeah. And actually give them chocolates, by the way. The problem though is that this particular, I don't know how to find the average here. This is another assignment, by the way. Because in environmental systems, you will have variations like this. And when you have variations like this, how do you deal with the average? So the whole aspect of statistical methods that are required for environmental work, right here from this room, I generated the data to be able to now work with it. You understand, right? If I take the average of this, it'll be weighted totally by this, right? Because it's five orders of magnitude. This will all disappear inside of just one factor over here, all right? Okay, good. Low self-adhesive, there are issues about that, it's to ships, etc., etc. So how many of you weren't in this lecture hall, we'll write the estimate on the attendance slip, this is what they do. You take that back, and then of course you give them the homework. At this point in time, they're ready for a homework. So here's the homework, okay? Now you give them a deadline, they need to see it by a certain date, which is three days from the day of the lecture, okay? All right, then you get into air quality, all right? So can we stop for a moment? By the way, another thing I do very regularly is people will do their estimate and all that stuff, right? People will do that. What I would do is I would lead this up and have people talk to each other. So whatever we discuss, people talk to each other. Invariably, when they talk to each other, some things become to become unclear, okay? While some things get cleared, there are some things begin to get unclear, no? I didn't really understand that. So they raise their hand and then you answer that question, okay? So I always give this opportunity for people to talk to each other in the class, because that's another way. I don't do it as a technique of keeping them awake, okay? It's just that most of them are shy. They will not raise their hand and ask the question. So if they're still not clear to them, they'll ask the person next to get you something, how do you deal with it, what is this? And some of them will even raise their hand and say, sir, we didn't understand, let's go over it again, okay? Yes? Okay, excellent. So then you take this and actually do the attendance and also the meter detector, air quality, okay? So how do we manage air quality? Interested, given that you are in charge of your city? Given that you're in charge of the air quality in your city, this would be of interest to you, yes? Yes? Okay, good. So we look at how do we manage, so at the source itself, okay? Industry, if you can control in the industry itself, if you can take care of vehicles which are not polluting. Dust, India, dust is a big problem, okay? I'll talk a lot about Chandrapur a little later. And the issue in Chandrapur, let me just give you the story of Chandrapur. How many people close to Chandrapur from Chandrapur? Nagpur, Kachiroli, Yawatmal, yeah, where are you from? Nagpur, okay, good. Chandrapur is well established, right, polluted, huh? Nagpur, yeah, okay, very good. So Chandrapur is known to be polluted, right? And Nagpur is affected by it also? Very heavily, yeah, very bad, yeah, it's quite bad. So we've been working there, okay? For the last two years, we've been working in Chandrapur. And there was this index called CEPI, Comprehensive Environmental Pollution Index, which got developed at MOEF. This is at the time of Jai Ram Ramesh. And based on that, there were some 88 clusters, industrial clusters that got declared as critically polluted. Okay? People have, anytime there's an index like that that comes up, people usually question it because they say, hey, this is not done right, that's not done right, et cetera, et cetera. So there was a lot of doubt around the CEPI. And what we did is we went to the satellite data, okay? We went to the satellite data and looked to see which are the hotspots in the country. You can figure out from the satellite, I'll talk about that also a little later. From the satellite data, you can figure out what are the hotspots. And it turns out to be that all 88 were identified as the hotspots even from satellite data. So any concern that you might have that somebody's doing mischiefs and somebody's being political, et cetera, et cetera, that gets taken care of because satellite can actually tell you from one instrument, it's not even an issue of two instruments being compared because the same instrument, same instruments that are going over the country again and again and in all parts of the world you can actually compare it with one location from another. It turns out that Chandrapur is very polluted. It was the fourth most polluted city in 2010, okay? So they spent about 400, 500 crores, I believe, the industry was asked to spend money because it's like, hey, you guys are polluting so you better take care of it, right? So they spent 400, 500 crores and after three years it became from fourth most polluted to second most polluted, okay? So now immediate doubt begins to come as to where did the money go? No, the money went to the right place. The industry did the work that was required for it to improve its control systems, et cetera, et cetera. What was not dealt with was that industry was not the one that was not the main source of pollution. So then at some point in time, Maharashtra Pollution Control Board invited Neery and IIT Bombay to start working with them and so it was very obvious that it's the dust and more importantly, the coal chulas, coal cookstuffs. Coal is, there are a lot of coal mines over there. So coal is quote-unquote freely available, okay? So coal, people use coal for cooking. So every day in the morning and every day in the evening, they put out the chula, burn it, all of Chandrapura is being given this gift of the smoke and not just from one household, 50,000 households, right? And then once in the morning and once in the evening and that's it. The entire, when I was a kid, that time they were just introducing the diesel locomotives. So holidays, vacation, I used to go to my grandmother's place. We would go in this howler express which used to have the steam engine. So when you're in a steam engine, you smell the smoke which is coming from coal. So the railway station used to smell, has to, used to have a particular smell. You know, you understand, right? Particular activity has porotas, dosas have a particular smell. So similarly, coal burning has a certain smell which for me was associated with railway station. All of Chandrapur, no matter where you go, there's a railway station. Again, the perception comes from smell. Now the other thing I realized was every time I go to Chandrapur, by evening I would have a mild headache. And the moment I came back to Mumbai, that headache would disappear. So people in Chandrapur do not know that they're suffering from a headache on a daily basis. They don't even know that they have a headache. Okay, so point, are you convinced or should I keep talking? Convinced, sources? Okay, different kinds of sources, different places, home cooking, people think home cooking is a big issue. As long as you've controlled the pollutants at the source itself, okay, you're in good shape. Once it has left the source, then you're pretty much leaving it to the meteorology. You're leaving it to the wind conditions, you're leaving it to the temperature conditions. You're pretty much depending on the god of winds to now take care of your pollutants, okay? What is the impact of a particular pollutant, et cetera, et cetera. Familiar? So I just show some images now. Looks familiar? Middle of the night somewhere, but you know, looks like a pretty sight. By the way, these are also called plumes. Plumes, feather plumes, there was a time when if you had a plume in your cap, it would be a mark of credibility, yes? So if you go to the laboratory and you look at some of the books from the 1960s, okay? The cover would have chimneys with smoke coming out of it. 30 years later, same books, cover has chimneys, but no smoke on it. It's politically, there was a time when having those smoke was a sign of, was a symbol of, was a representation of industrial progress and development, et cetera. Now you have to have chimneys, but no smoke, okay? All right, very good. Typical, Delhi morning. There's a bus there, can you see the bus? Oh, okay. Just checking if you could see the bus, because the first time I saw it, I said, where is the bus? Somewhat, somewhat. Somewhat, somewhat, yeah, you're sure. Familiar? Looks familiar, right? Anybody can identify your city here? Everybody should raise their hand. Your city? This is your city, yeah. Pretty bad, yeah? Now this is dust and smoke, okay? And that's a big issue in India, yes? All right, all images from Google. And what we will do is we will give you a lot of the resources, a lot of the links, and you can share them with the students, all right? Okay, now let's get into this business of meteorology, okay? So if I'm a chimney, everybody, it's not so difficult to imagine me as a chimney, right? Can you? So this chimney is throwing out, throwing out smoke, right? I smoke, and there was a smaller chimney, and they said, you're too small to smoke, all right? So I smoke, everybody? Okay, so I smoke. So things are coming out of my top over here. By the way, industry is allowed to pollute a certain level, you know this? Okay, so it's not that they have a chimney, but nothing should come out of it, okay? They may have issues about visibility, because the moment people can see the smoke, they say it is polluting, but if it is white smoke, somebody might even say it's steam, but if it's black smoke, clearly there's an issue, all right? So there's a certain amount of emission that I'm allowed. Everybody with me? We're allowed, and how that is determined is what's called an emission factor. We'll come to that a little later, but let's first deal with if I'm a chimney, and this is coming out from here, if there's wind coming in this direction, if there's wind coming in this direction, then this entire pollutant gets thrown away, okay? Now I'll introduce you to the best artist in the world, all right, very good. So you will see that there is a chimney here, there's some industry here. The industry has best available control technologies that were put in place when the plant was set up, okay? So they are using control devices, but then there is a thermodynamic limit, there's a commercial limit as to how much can be controlled from here, okay? So some amount will come. This is a regular house, this is a hut, some cooking happening over here. Again, I'm hungry, so be thinking of food, okay? All right, some smoke coming out from here. Oh, there's a little car also over here, and there's some smoke coming from here. This is you and me, by the way, right? Over here, if you missed me, there you go, that's you and me, right? Okay, so smoke is coming out from here, and there's wind, and notice that little red spot over there, okay? That red spot is the concentrated pollutant that is being thrown from the chimney, okay? And that is not at a concentration which you can go on top of the chimney, stand like this and say, pranayama. You'll die, you can't do that, okay? So they're fairly concentrated, but again, allowed based on the size of the plant and the activity that they have. So you're allowed to emit that, but not allowed to breathe that, you understand? You're not allowed to breathe that. Now, the size or the height of this chimney, in some sense, is going to tell you how I'm going to have this small parcel of concentrated pollutant in the air be dispersed and diluted. So what's gonna happen is, when the wind comes, it's gonna get dispersed into a larger volume. So this small volume, this small volume, got mixed with the larger volume, and therefore has become diluted, okay? So it is still not breathable, though. It is still not breathable. It has to be breathable when this particular plume hits the ground level sometime. This is still in the air. At some point in time, this edge will hit the ground level. When it hits the ground level, the concentration at that ground level should be breathable. Fair enough, this is from one source, by the way. If there are other sources whose plume also touches the ground, then it is additive. That pollutant from here, pollutant from here, pollutant here put together, it should be less than the compliance requirement of 80 micrograms for meter cube. Fair enough? Talk to each other. Talk to each other about this. There's a comment about the planning. So if you are in charge of your city, and somebody says, I want to put up a new power plant. Power plants are important, okay? Their power and energy is required. So you want to set up a new power plant, and they come to you and say, hey, we would like to set up, it'll really change the entire phase, progress will be much higher, electricity will be available 24 by seven. It's a good idea, we need your approval. So you will say, that is a good idea, but I'd like to know what is the impact that this particular new source would have on the air quality of the air shed? That's a valid question to ask, right? So it is very much a part of, so if you are in charge of your city, it is very much a part of your thinking. It's required, and that's what we're leading up to. All right, anybody else? You had a question? Nowadays we have the industries are asked to move out from the city. We don't have such kind of problem. Mostly it is a problem due to the transportation, automobile vehicles. We have to do something. Yeah, sure. Now the point is well taken. In fact, vehicular pollution is huge. Sure. So at this point in time, you should also, I'm going to touch upon it, but I'm also looking at from the perspective of, these are students who are getting exposed for the first time. Everybody with me, you can appreciate that. Yes? Question there? Yeah. You have said that as a fume touches the ground, there's a concentration of air to breathe. Yeah, so it shouldn't harm you, yeah. But that depends on the height of the chimney. Excellent, excellent. That is my next slide now. Okay, fine. Sir, the derivation of Gaussian blue model is sweet, lot of assumptions and also limitations. Yes. Then why still we are following the very old traditional... There are other ways that we're looking at now, we're looking satellite data, we're looking at some re-analysis data, IMD data, we're doing a lot of stuff. At this point in time, for me to be able to explain to students as to what is the fate of the pollutants, that's what I've used. Okay, thank you. That's what we've been using. I'm trying to introduce satellite but then they don't have enough tools available on the satellite right now to be able to appreciate. All right, very good. So this is meteorology. How many of you heard of meteorologists? I used to be the best meteorologist when I was a kid, you know this? You know, the meteorology used to come in handy when you had to fly kites, right? So other people knew how to fly kites. I only knew how to give the kani. You understand what kani is? You actually, your job as a kani giver, right? Your job as a kani giver, I don't know if there's such a word but I call myself the kani giver. The kani giver's job was to make sure to look to see where the wind is going. So you look at the trees and you see leaves going this way, aha, like that. But on some days the leaves were not moving or something so you actually had to pick up the dust and you throw like this and then you see, oh, it's going this way. So the dust must be going this way. But the highly, most sophisticated, most technical, most chemical engineering, which is my undergraduate by the way, chemical engineering, most profound chemical engineering way of dealing with it is you take a finger and you put it up. Whichever side is cooling, by now you must have figured out that to teach this class you need to do a lot of drama. So I'm sharing this because meteorologists are a strange breed of people. Any meteorologists here? Then I can say it. Okay. The most romantic thing that they could come up with was a wind rose. Tell me, where does it look like a rose? Doesn't, but you know what? Hats off to them. They're such phenomenal people. This is such a beautiful representation of three things. Wind direction, wind speed, and the frequency. The number of times or the percentage of time that the wind is blowing from a particular direction. As the person who's in charge of your city, you need to know this about your city. You need to know this about your city. You need to figure out what is the predominant direction of the wind. And so the description of what a wind rose is, et cetera, that is there. Up to this point, we were dealing with winds. It is intuitive. We know, chimney, everybody? Hello, chimney, hello, chimney, yeah, chimney. So you got this smoke coming out and it's going in this direction because wind is coming from this direction, right? So the faster the wind, more the dispersion. Pretty intuitive, clear, okay, good. So let's move on. So I'm assuming everybody would understand Hindi. Earth ki kahaani, the story of earth. Naam to suna hoga means you must have heard of it. By the way, this is from some movie, right? So the point is this, I'm not going to talk about this part over here. I'm only talking about the first 10, 11 kilometers of the earth's atmosphere. Just the first 10, 11 kilometers of earth's atmosphere. Now if you look at the temperature, if you look at the temperature over there, it's about, what, 285 or something over here. And at 10 kilometer, if I cross it over here, it is about 220 or so. So 65 degrees Celsius in 10 kilometers, approximately. Approximately, right? Six and a half degrees Celsius for every kilometer. That's the drop in temperature, okay? All right? That's the actual, okay? That's the actual average drop in temperature with height. All right? Now let's take a look at something else which is called the adiabatic lapse rate. What adiabatic lapse rate is, this is a lapse rate, right? Temperature lapse rate, the rate at which the temperature is decreasing. So when I look at the adiabatic lapse rate, adiabatic lapse rate means this. If I took a parcel of air, okay? If I took a parcel of air and raised it quickly, the operator word is quickly, okay? If I raised it quickly by one kilometer, if I raised it quickly by one kilometer, which means that I didn't allow any heat exchange to take place between the parcel of air and surrounding, okay? Then the temperature of this parcel of air, one kilometer up there would be less by 10 degrees Celsius. Okay? That is if it is fully dry. If it was 100% humid, then it would be six degrees Celsius. This is for adiabatic. It's not the actual, it is not the actual, it is what is governed by the physics of a parcel of air. If it is raised by a kilometer, the temperature would drop by 10 degrees Celsius if it is adiabatic. Adiabatic means quick enough that it didn't have time to exchange heat with the surroundings, okay? My favorite slide now. This is adiabatic. One degree Celsius. For 100 meters or 10 degrees Celsius per kilometer. And assuming it's all dry. Just assume that it's dry. All right? So this is the adiabatic lapse rate. Now this dark line over here is the actual lapse rate. Actual lapse rate means if I take a balloon and I put a temperature sensor on it and I release it. And every two meters, it keeps sending me the signal of what the new temperature is, what the new temperature is, what the new temperature is, what the new temperature is. It's just giving me the actual temperature in the atmosphere, okay? That is the solid line. The rate at which it is cooling is different from an adiabatic parcel of air because the slopes are different, correct? Okay, good. Then what do I do? I took a parcel of air at a height of let's say one kilometer. At a height of one kilometer, I took a parcel of air and I raised it suddenly to a new height of 1,100 meters. If I raised it suddenly to this new height, it would have followed the adiabatic path because I did it suddenly. A parcel of air, if raised adiabatically, suddenly by 100 meters, what would be the temperature? 20 degrees temperature here. This would become 19 degrees temperature, correct? So this parcel of air is now at 19 degrees. What is the surrounding air at that height? At this height, the actual temperature is 18 degrees Celsius. So this parcel of air now is warmer than the surrounding air. It's a little warmer. So it will continue to go up. So this parcel of air, which by some freak accident got raised up, suddenly has a tendency to continue to go up, which is good from a perspective of dispersion of pollutants. That means that if I have a parcel of polluted air and there's a tendency, if it moves up, it'll continue to move up. That means there's a larger volume that it's gonna get mixed in, which is a good thing. All right, questions? By picture, what you have shown is the air parcel is having 20 degrees centigrade temperature. Yeah. Do you mean that again, environmental is also having 20 degrees centigrade? So, this is fictitious, okay? This doesn't exist. If that is the temperature or the same, then it will move up. No, no, this is the actual temperature in the ambient. You start with the parcel from here. This is the path it'll follow. Okay, sir. Because it's adiabatic. So therefore, the difference in the temperature will either make the place, so it makes it unstable. The condition of, unstable. The imbalance in that. Unstable is good, okay? Okay, good. So, now I'm gonna do something else. I'm going to now not change the slopes. I'll leave the slopes as such, but this time, instead of pushing the parcel up, I'll push it down. And you have to convince yourself that when I push it down under these conditions, it'll continue to go down. There you go. Talk to each other. Okay, let's go over it, right? Let's go over it one time. And say, okay, the parcel of air was here. And I brought it down by 100 meters. If I brought it down suddenly, it followed the adiabatic path. The temperature over here is 21 degrees Celsius. The actual temperature in the surrounding is 22. This one is cooler than this one, so it'll continue to sink. If it happened, there's a certain tendency. And there's always some movement in the atmosphere, which is of a turbulent nature. So there's got to be some random movement. The question is, is this random movement then enhanced? Or is it suppressed? So in both these conditions, what we saw is that that random movement is enhanced. If the random movement made it go up, it'll continue to go up. If it made it go down, it'll continue to go down, okay? Now that randomness, then you have to leave it to someone up there, okay? Then, okay, now I'm gonna switch the condition. I'm gonna switch the condition. The switch in the condition is the relative slopes now. Notice I'm gonna switch the relative slopes. So right now, this one is on top. This one is at the bottom here, right? Somewhere here, like that. Now, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah. Clear? I've switched the slopes, right? I've switched the slopes, yes? Okay, now take a look and see, if you took a parcel of air over here and you raised it by 100 meters, the temperature, 20 degrees, will go to 19. It'll go here. It'll follow this path, correct? So from 20, it'll go to 19. The surrounding air is what? Is higher. So that means this parcel of air is cooler. So that means it'll try to come down because it is cooler. Talk to each other again. What we're saying is, if I took a parcel, I've changed the condition, okay? From this condition, I've come to this condition. Where this slope, the actual is now steeper, okay? So what I'm saying is, if I took a parcel of air over here and raised it suddenly to a new height, that it'll follow this particular path. So from 20 degrees Celsius, it'll become 19 degrees Celsius. The parcel of air over here is 19 degrees Celsius. But the air surrounding that parcel air is a little higher. So if the parcel of air is now cooler than the surrounding air, it'll tend to come down. Okay? So this time, under these conditions, if you try and push it up, it'll come down. If you try and push it down, it'll come back up. Not a good condition for dispersion. This is called a stable condition. Not good. It tends to restrict the pollutants in a very small volume, okay? All right, very good. So this is just an example of, we can imagine that there was, oh, by the way, when you calculate the volume of this room, you assume that there is a permanent ceiling here, right? In the atmosphere, is there a permanent ceiling? Sometimes there is. Okay, we'll just find out that sometimes there is. So what you got over here is the adiabatic lapse rate and this is the actual temperature. By the way, it can change. After certain height, it can change. Okay? So this change over here is what will cause a false ceiling. Okay? So that pollutant, which was going to get dispersed to that volume, is now going to get restricted to only this volume. Because the tendency beyond this line over here, which is referred to as the mixing height. So beyond that, it's not gonna go up. Even if it tries to go up, it'll get pushed down. So there's a smaller volume now available. This is a bad situation because you're saying that the pollutants which are coming from the industry are now going to get restricted in a smaller volume, so you and I'll have to breathe the higher concentration. Okay? All right, very good. Different scenarios. This is a scenario we just saw. This scenario, stable. This scenario, neutral. This scenario, it summarizes all the scenarios. Okay, what it's saying is that this is the dry lapse rate. This is the wet lapse rate. This is somewhere in between over here. If the slope is on this side of the actual, then you're stable. If it's on this side, then you're unstable. Unstable is good. Everybody, unstable is good. So say after me, one, two, three, you say unstable is good. One, two, three. Unstable is good. Excellent. Ah, my favorite slide. All right, yeah, this is the one which Nikhil said that I was smoking. And I said both these chimneys, even the small one is smoking here. All right, there are two chimneys. Both are smoking. One of them is smaller, but still smoking. But this one, this seems to be a stable. It seems to be pretty well confined. It seems to be restricted. Whereas this one is having a party. This one is good from the perspective of dispersion. This one is not good from the perspective of dispersion. Now, somebody, by the way, another thing about meteorology. From now on, you will not see chimneys the same way. When you look at the chimney, you'll not see what a lovely plume. You'll not see that. What you'll begin to say is, huh, what is the likely temperature profile over here? So, there are four possible conditions that could lead to these, this kind of a scenario. These are four scenarios. One of them is the correct scenario, okay? One of them is the correct scenario. You have to tell me which is the correct scenario. So, the quiz in the class is this, okay? So, this is the quiz. You can take this with you, but this is the quiz that I would ask. So, what will you do? How will you deal with this? How many of you used a mini-drafter at some point in time? Mini-drafter for making parallel lines? So, what you do is, you basically take that line, take this line, which is the adiabatic line. That slope doesn't change. 10 degrees Celsius per kilometer. That slope is not gonna change. That slope will always be the same, okay? So, what you do is, you compare the slopes against the adiabatic lapse, right? So, this is stable. This is also stable. So, it cannot be A. Let's take a look at the next one. This one is stable. Top over here is again stable. Won't work. This one, unstable. Unstable, but this is stable. So, it can't be this one. The last one, this is stable. This is unstable. D is the correct answer, okay? So, have a great lunch.