I have now 100 hours in Animal Crossing New Horizons so I am going to give you a town tour and a house tour so you know all sorts of tours this is my house I think I have to upgrade it one more time and I have a little flower garden and I love it outside I have you know roads actually I have a garden gnome and my laundry I have all the different bushes of fruit as well it is still Easter time in the game here we have the barbecue station that is pretty cute it is done with simply pathways and fences over here we have my town hall some public benches and some flowers and some trees this is my one of my beach areas I like that oh there's a bubble over here I have my museum I'm gonna do some more funny stuff around the museum shortly so over here we have the residence of Renee one of my first villagers so I made it sort of cozy and pretty now we can run over to the other side so here I have a bridge that is under construction I actually had my bridge over here then I had to demolish it and build it again here's a new town person, Claudia she is okay I don't know her much yet okay one of my prettiest places that I'm most happy about is the residence of Bangal this place so cozy I like what I did there actually and next to him lives Ruald and he is a sports person so he has his bike outside so I try to match the homes of the residence with their personality also if you didn't know this you can give them decorations for their doors and they will actually hang that stuff up here we have a money tree with 99 bells on it times three three in the tree the turnip person cat and nick lol okay here is my first bridge which I'm gonna demolish and do some you know do a stone bridge instead this is something I came up with placing the pathways in this way so that it is more like circles on the ground it's a cozy sort of look to it I think ooh a bottle so here we have the residence of I don't know can't read the nameplate but I know who lives here wick lives there here I have my campsite a little popcorn machine a little toilet and a stall and a microphone I don't know what I was thinking we can go further this way as you can see I have the placements of the logs you know the the sitting things so that I can do this every day I can also do that here with the placement of the table so the bridge is coming here across the town hall and then we get up here where I have my shopping district nooks cranny of course can't wait for that to be upgraded and my abel sister store now here we are back at my house so I am actually really close to the shops over here we are coming over to a really cozy area residential area with a waterfall and all of that and here lives Lionel I gave him that door plate because it suits him and here we have stitches home I like that too over here we have this guy sly so he is a crocodile I think or alligator so he has more of a jungle theme outside of his and he lives next to a pond and he likes fishing here I have a well and I have my stone path-ish thing going down here here lives Claudia the pink tiger so I made it sort of cozy there as well here's my first place on the beach that I talked about in my review video and I I'm really happy with my review video of Animal Crossing so let's go up here again to the residential district do you come to the cloud district very often no over here I have the eggs are everywhere literally and here lives Philbert yes yes correct Philbert so he is a squirrel and he can fish here and he needs more furniture definitely outside his home this is what I recently made just a you know pretty sort of waterfall area and here I have my bigger flower garden so where I tried to crossbreed some some stuff it got away over here another waterfall and over this bridge over here we have Gladys home it is cozy kind of looks like a cemetery it's sort of style with this sort of fence but it's okay and there he is sitting in his Easter outfit enjoying his day I think and here I have a little sitting area and another pond have I shown you my entire town already well this is basically my town after 105 hours playtime you know what on the switch you cannot see how much you have played a game up until you have played it for 10 days so when 10 days passed it said 85 hours and I didn't think I had played this game that much to be honest so that was kind of shocking time flies by so fast when you're playing Animal Crossing so it's like I feel like I just started the game and just now started to get to know the residents and the people I feel like I haven't even scratched the surface of what this game has and that is after 100 hours okay I totally forgot to show you my house Jesus Christ okay I'm actually recording two videos in one day so that is why you see me in this outfit all of a sudden lulvatt here is my main room nothing fancy going on I am not happy with this room it is under construction okay so never mind this room here is my kitchen so far well I am collecting kitchen furniture and I am definitely missing a kitchen sink which is the main thing to have in a kitchen so I am not done with my kitchen but I like the vibe so far I guess well over here we have my bathroom and it's just bathroom me what can I say collecting bathroom things also on the floor here I have a just a you know you can see that clearly that it is just a custom design that is my bathroom it's gonna be way more fancy later I want another sink that's one thing if we go up to the upper room I have not completed this room either it's not gonna look like this at all it's basically a place where I just dump all my items and you know for hope for the best but it's not gonna go into look like that and I don't have any plans for that room I'm not sure yet now I have one more room to show you and that is upstairs which is basically just my master bedroom with a lot of bunny things going on that was my fantastic room tour so terraforming is definitely a thing that I enjoyed unlocking and it took literally 90 hours of playtime to unlock that so this is a long game it is the best game I have played this year so far now I haven't played a lot of games this year so far but this is the best I enjoy logging on Animal Crossing every day because there's something new there are new fossils new stuff going on well one thing is that the random encounters random encounters of Animal Crossing in my experience I have met the ghost I think five times already so there's not much variety in random encounters so far Gulliver has washed a shore twice so I feel like this is only the beginning so this is looking really good this is a 10 out of 10 solid Nintendo game and a bunch of people I know are also playing this game sick much I don't even feel like I have played it that much if you know what I mean so I hope you enjoy my videos and if you have not watched all of my previous videos I want you to be up to date on the channel and you know watch the ones that you haven't seen yet also another thing is that I like it when people go back to my not necessarily really old videos but older-ish videos and look around or even just rewatch some of my older videos all right that was my Animal Crossing 100 point video I hope you enjoyed it so thank you so much for watching and I will see you later


Alright, welcome back. So, in the previous session we dealt with concentrations and perception and what is the way that you can say how bad is bad in terms of pollution, etc., etc. But then just before that we actually stopped and then talked a little bit about what assignments can do in terms of the development. Ultimately for me teaching is about human resource development and so there are different ways that one can do it. So, I was just sharing one of the ways I have been using this assignment. So, to have students step into adulthood and step into some aspects of what they would have to deal with in taking a stand of them for themselves. So, back now to the channel where you are the collector of your city and I hope that during the tea break you actually got a chance to say hello to the other collectors of your city and also made some new friends. I do not know the composition of each of the centers but some of you might know each other and some of you may be meeting each other for the first time. So, I do in the background also have this commitment that those of you who are participating from a particular center that you form a group of your own and be there as a support structure for each other because geographically you close by and anytime there is a project to be done in that region, live project to be done in that region then we can consider that group to be working together. So, it is one of those courses where you come meet but I do not want it to be a course where you come meet and then go away. If you are looking at a five year time frame for relationships I think it is important to get to know people around you and appreciate each other's strengths and be able to then bring that to the table. So, back to the channel now with you as a collector of the city we somewhere near the half way mark on slide number 41. So, we set two learning objectives for today. The first one was estimate pollutant concentration related to our exposure and the second one we are saying is you will be able to explain the effects of meteorology and the physics of dispersion of pollutants in the atmosphere. So, that is the second learning objective which connects up with the place where we had stopped we had said carrying capacity what is the carrying capacity? I think we understand carrying capacity from the perspective of let us say a river. We say how much can we dump into the river but you know rivers have a way of rejuvenating themselves and we have had this myth fictitious belief for the longest time that even a sacred river like Ganga is self purifying no matter how much you dump into it it you know cleanses itself because it is sacred. You know for a fact now that there are long stretches of Ganga where the water may not even be drinkable and the amount of untreated sewage and industrial effluence that goes into the river is just mind boggling. So, we clearly know over there that the carrying capacity has been exceeded we cannot add more pollutants without treatment. So, carrying capacity you know has that kind of a connotation for rivers and water systems but if for air it is difficult more difficult because there is no boundary to it. There is no place where we can define that there is a ground and there are these vertical walls and then there is a ceiling on top. You do not know you emit a pollutant how and where it is going to go. So, to some extent I will give you an example for one of the decisions that was made. Delhi at some point in time was switching over from diesel to CNG and the reason was that it is a landlocked area and the flushing out of that region totally depended on the winds. So, if the winds were not there then pollutants would tend to accumulate in that area making the air quality bad. So, it made sense to actually have switching over from diesel to CNG so that we could actually have lesser amount of pollutants being added to that air shed they actually then made a proposal that we should do something similar for Mumbai. Now people in Mumbai felt that it was not quite necessary here because we are right at the coast and the land sea breezes on a 24 hour basis are adequate to flush out most of the pollutants from Mumbai. So, that argument was accepted and then later we did not convert to CNG at the same rate or the same scale as we converted to CNG in Delhi. So, those are issues of how flushed or how let me put it crudely how ventilated is your city. So, as a collector you want to know if I were to add a pollutant in my air space in my air shed in my city how long will it be before it gets flushed out by winds or some other vertical mixing. That is a question it is a very valid question you would have that question if you are in a flat land which is close to the ocean the flushing time is you know sometimes even minutes. But if you are in a valley then depending on the temperatures depending on the weather conditions you could actually have pollutants accumulate in the valley and which may not get flushed for many days and weeks. So, some places any time I am traveling you go through some hills and you suddenly find a lovely valley and that in that valley you actually see some industry and you can see this thick layer of smoke and pollutants that are sitting over there which you know are not going to get flushed out for the next few days because just the way the temperature in the mixing takes place that it will not. So, it is important for you therefore as a collector as a somebody who is accountable for your city to know what is the relationship that your topography your geography your location has with the winds of this area etcetera. So, that is why we are looking at carrying capacity if it is well flushed then the carrying capacity is high you can probably have more industry and the pollutants would get flushed out. But if your carrying capacity if the amount of wind that is there which is available to you on an annual basis is low then it is not such a good idea to have too much industry in where you are located ok. So, carrying capacity and this is not just a conceptual term it is actually quantified and some of the things we will talk about, but we will not necessarily get to the point because it goes beyond the scope of this course to actually be telling students about how to do some of this modeling. But you know you need to introduce them and some of the advanced learners can actually then step into it. So, carrying capacity ok how do the sources affect the ambient air quality. So, side of that question immediate question is what are the different sources or what are the different types of sources ok. So, when you are looking at different types of sources we will say let us say an industry ok. Industry if they are polluting then they will be required to have some kind of a chimney ok. So, chimney of a certain height the higher the chimney the more the dispersion, but the capital investment is high. So, what should be the right height of the chimney it gets decided by some of the modeling work that is done in terms of the impact analysis environmental impact analysis work that gets done. So, industry typically you would expect it to be a point source if there are any pollutants coming from the industry then you expect that the process would ultimately lead up to a particular point source which is the chimney. So, this is a point which is now throwing out air throwing out polluted air pollution pollutants into the air. Industry does not necessarily mean just a point source they could have some operations for example, in a coal plant they would have handling of coal for example. So, it also becomes some kind of an area source, but by and large when you are identifying industry you would say point source and you know how much is the emission coming out from there. The license to an industry is given for the point source as well as some of the other operations those are details that we do not have to get into right now. Okay, I like vehicles being called a line source because they are longer road, but at any point in time it is a point source which is moving. So, when a point moves it actually makes a line. So, therefore it is a line source. Famous artist Paul Klee once described he used a lot of lines. He says for me a line is a point taking a walk kind of nice description. So, vehicles are line sources any kind of movement that happens which with the polluting source is a line source. Dust, big problem in India is an area source. So, if you go to Rajasthan if you go to the Thar desert and anytime there is a dust storm the wind picks up some of the dust and brings it to other parts of India. They could even be dust during agricultural operations. I also put dust as a line source because especially in India invariably the roads have dust. So, every time a vehicle passes by the pollutants coming from the exhaust of the vehicle may not be as much. They are there, but they are not as much they may not be as much as the amount of dust that actually gets resuspended from the road. So, therefore dust also could be associated with the line source otherwise line sources are typically vehicles. Home cooking again it is a point source, but if it is a collection of houses then instead of taking each individual source you can say okay there are 30 houses over here all of them are using cold cook stoves. So, I can broadly group them together as an area source. The other thing about the source sources is this is again at a XY level at this plane of the ground. The height at which these are getting emitted has a lot to do with how much of an influence they would have on us. So, if a chimney is emitting at the height of 200 meters then at least people who are within and around the chimney for at least 100-200 meters then are going to get affected because this plume by and large will take the pollutants away with the wind and the pollutants will hit somewhere else, but not necessarily in the shadow area of the chimney. So, the height at which it is getting released into the atmosphere is something that you know is important. A vehicle or an area source is ground level it affects you and me directly. So, there's the vertical component also in that consideration. Now, how much are these industries, these vehicles, these areas, the home cooking, how much are they emitting? Is there some way to estimate how much is being emitted from here? The exact design criteria that you were to go for every industry you of course can get that from Maharashtra Pollution Control Board or any state pollution control board you can get that information, but it takes effort and sometimes there are a lot of sources which may not be known etc. So, they go and do these surveys to develop the inventory like you would find out want to go into your kitchen and find out how much flour and how much sugar and how much oil is in the kitchen that way you want to know how much of pollutants are being added to your air shed as a collector you want to know what are the sources that are there. So, you say okay how many vehicles in this particular city and you say I'll go to the RTO I can get you that information okay get me the information of how many petrol cars, how many diesel cars, how many trucks, how many of them are five years young, how many of them are between five and ten years old how many of them are greater than ten years old. So, these are information that will tell you what is the standard that a manufacturer had made a vehicle to and what is the level of maintenance that might be required or carried out or not carried out, but an older vehicle is likely to be polluting more. So, that information you get okay you get all the numbers now what do you do with these numbers these are just numbers of vehicles right. So, what you then do is you go to a book which is considered in some way the Bible in the area of emission inventory it's called AP 42 air pollution 42 it's a big thick document which actually tells you that for a particular activity this is the amount of pollutant that is expected. So, for example, if you were to look at power generation from a cold plant and you say the plant is 1000 megawatts. So, for every megawatt you are allowed to emit a certain amount of sulfur dioxide okay. So, that is an estimate that is made and it's an average. So, you say okay if I have a 1000 megawatt plant I multiply that emission factor with 1000 to say okay this is the amount of sulfur dioxide being added in my air shed every year. So, there will be some tons of sulfur dioxide being added every year. So, that's how you develop an inventory. If that is being emitted in a year then you can go to a 24 hour resolution or an hourly resolution all of that stuff can be done. But the important thing over here is how do we manage air quality we start looking at the sources the kind of sources we start looking at the height at which these emissions will be released we also look at the level of emissions that might be coming from a particular operation. Now once it is out from the chimney once it is out of the car once it is resuspended in back into the atmosphere from the movement of traffic as road dust when the smoke has left the house never mind if you have to look at the indoor air quality then you will actually go into the house and do the measurements. But once that cooking stove has left the smoke and this smoke is now out left the house and it's out in the atmosphere at that point in time now it's all open system till it left the chimney top of the chimney it was still a closed system most of the time before it is left into the chimney they do everything they can they put all the control devices before it is let into the chimney so that the best available control technology has been used to be able to remove as much particulate matter as much gaseous pollutants as possible as thermodynamically possible before it is getting released into the chimney once it goes into the chimney it actually now is up in an open system now same thing for a car till the time that it is actually in the exhaust fan you may have still some engineering solutions to be able to control it once it has the left the exhaust pipe there's no more control on it it's now into the atmosphere so then we are going to depend on the dispersion of these pollutants and the mixing of these pollutants with clean air such that it gets diluted this is where that whole question of carrying capacity again comes so I know that there are many sources that are in my city I know how much of a particular source is there in the city I know the emission factors and therefore I can multiply the emission factor with the number to be able to say what is the total amount that is coming from a particular source that much pollutant is being added on an hourly basis or a daily basis or a yearly basis in my airshed and now I have to make an estimate of will the air that gets flushed out will the air that accumulates on a daily basis will that be sufficient to flush out to dilute these pollutants to take these pollutants away such that I have an air which is not unhealthy to breathe or I have an quality of air which is breathable okay so that's the connect over there with meteorology okay so mixing and dispersion we now begin to enter a domain which I had not been introduced to in all of my chemical engineering or in any of the sciences meteorology is a science is a discipline by itself most of us don't get exposed to it but you know it's an important when it comes down to air pollution meteorology is a extremely important component and you really want to look at it as a partner while pollution control boards are dealing with control of pollutants you also be want to be looking at meteorology in the department of meteorology as a partner to provide you information to be able to deal with the air quality in your city as a collector okay so the some of the obvious things around meteorology are that there's when and when there's when there'll be you know the wind will have a certain speed a certain direction and frequency that's important all those three important and so this is the horizontal domain but then there's also in the vertical domain by and large our perception tells us when okay you see trees moving and I don't know as a boy I used to fly kites I don't know how many of you have flown kites so I never learned how to fly a kite but I was the youngest and the most qualified meteorologists that other children could use to look at which way the wind direction was so the way we used to do it is we would go pick up a certain amount of dust and put it in the air and depending on the wind direction the dust would go in that direction and you'd say yes that is the direction of the wind and that's the direction in which the kite needs to be taken for flying and then of course as I grew up I became more of a chemical engineer and I believe there is another way of dealing with how to find out the wind direction is so everybody ready for this one okay this is a very important demonstration I think you should all see it so what you do is you take this finger and you put it in your mouth and you wet it so you do this okay now the finger is wet from all sides now whichever side is cooling more is the side from which wind is coming okay what a lovely demonstration so you can have your students do this demonstration also but the point is that while our association with meteorology is related with kite flying we are bringing that same concept now to the area of management of air quality for you now as a older child who is now the collector okay so we want to study a little bit of meteorology horizontal we understand vertical it's a little not intuitive so I'll talk about that vertical mixing is very critical so we will talk about that okay so just to explain you know how a particular pollutant will get dissipated okay so this is some industry over here this is the industry this is the chimney this is the chimney over here some of you it is a little faint so if it's not visible you should know the chimney over here and the outlet of the chimney is right here okay and there's a wind in this direction oh by the way this is some trees over here some other houses this is some smoke coming from one of one of the houses where cooking is happening and this oh this is a car it's a very polluting car it's got black smoke coming out from it okay some trees over here they still look a little green maybe it's just after the rain because a little while after the rains these begin to look like dark green almost black in color because of deposits coming from all this smoke and dust and oh by the way this is you and me over here this is you and me by now you should have probably figured out that I am very good at drawing so this is human beings over here okay and that's it so that is a scenario oh by the way there is also a little it's not a flat land there's a little hill over here also a little hill over here also okay so the smoke from here which comes out or the emissions from the chimney rise up over here and notice this red spot over here this red actually is representing the high concentration of the pollutants that are coming out this is even after the best available control technology okay this is even after the best available this is the best that the industry could do and by the way let's get this sorted out this is the amount that the industry is allowed to pollute okay they have permission they have permission to pollute this much because it is well established technically that you may not be able to control better than this for this size of power plant okay or this side of some other industry so this is the amount now what one is hoping to do is by having a high chimney a tall chimney and by having the winds help us we actually want to go ahead and disperse this polluted parcel of air which of gases which is coming out we want to have it be disperse such that it gets diluted so by the time it comes over here if you took a cross section of the pollutant over here it is turned pink so this red I've made it into pink which means that the concentration is much lower okay the concentration is much lower and by the time by the way this these people are not experiencing that pollution at all these people over here this habitation is in the shadow area so they're not establishing they're not experiencing any pollutants effect at all so what is happening then is that this bloom over here which is an approximate boundary will at some point in time over here hit the ground level so somewhere here if I were to extend this plane over here somewhere here never mind this hill for now never mind this hill for now this over here will go and hit the ground level now when it hits the ground level it is very very diluted so therefore it is safe for you and me to breathe okay so that is the rationale behind tall chimneys and using meteorology now the concern here is if this is a hillock and there are several hillocks in Mumbai and there are several slum areas in Mumbai which are actually sitting on top of these hills so if you don't take into account the topography then these people will get really exposed to a higher level of concentration okay so if there is terrain over here and you know it just doesn't have to be slums it could be you know normal middle class upper class upper class you know different economic groups that are settled in different parts of the city which has a certain topography that you actually can have pollutant levels be varying depending on whether you're at ground level or whether you're at a higher level so you would design for the worst case scenario and make sure that your chimney is high enough that in the worst possible case that these people don't get exposed to the concentration which is above the standard okay another issue that's coming up this is natural okay this is natural but in a lot of places there was this industry which got established in 1960 okay but in 2014 2012 a skyscraper came up which is much taller than the hillock and it is right into the path of the plume okay so up to here there was no problem suddenly this particular high rise of 30 stories or 40 stories has come up and so the plume is now going to hit so somebody who invested in this lovely view of you know the entire ocean etc etc and they've opened the window in the morning and said they would do yoga early in the morning they're sitting over there in their balcony over there and they so pranayama and all the pollutants from the plume straight into the lungs okay so that problem we now need to deal with now industry has been there industry was designed in 1960s it is doing whatever it was doing for the last 40 50 years suddenly the new construction has come up and that which was not a problem is now a problem okay so you know people are being asked to go for better even better control technologies some people are even saying you should raise the size of the chimney in all kinds of crazy things are being suggested but now there is a problem okay okay anything else about this I think that's it oh one last thing just to be clear okay while this pink over here which will get pinker and pinker lighter and lighter pink by the time it gets to ground level to the point that it is breathable this is not breathable okay you can't expect somebody to go on top of the chimney look into the chimney and say lovely no no it's not you will die okay so this is definitely not at a level which is breathable we are banking on dispersion we are banking on vertical mixing to be able to disperse it to a certain concentration which is now breathable okay so that's the that's the way the thinking is okay now I just want you to know that when we are talking about wind over here when you're talking about the wind over here as a person who's accountable for the air quality in your city you need to know what the wind conditions are not just for today not just for this hour but you want to know throughout the year what is the wind condition and not just for this year you want to know for the last 10 years what is the average wind conditions typically what is the direction from which wind is coming what is the speed of the wind and for how many months or how many days does it last in that direction with that speed so during monsoons you can have high winds coming from a particular direction during summertime you may be winds from a different direction altogether at different speeds and during winter it may be very calm so you need to be able to take into account all different scenarios of wind conditions how do you do that meteorologists are very creative people they've actually come up with this very nice representation of what they lovely it's a lovely thing to call it's called a wind rose it doesn't look like a rose but it's poetic enough for it to be called a rose okay so this is a complicated but very elegant representation of three things one is the wind direction I always used to get confused what is wind direction is it the direction in which the wind is going or is it the direction in which the wind is coming so professor Rashmi Patel she settled it for me she says look she's my guru I mentioned about her in the morning she said to me she said look you can only say where the wind is coming from where it is going you have no idea so that makes it very easy for me to remember that when you're giving wind direction you only give the direction from which the wind is coming okay so this is now a wind rose it's a representation of wind direction okay so wind direction you've got north you got south you got east you got west so if you see this particular petal rose petal okay so if you see this particular rose petal you know that it is coming in this direction for a certain amount of time what is that time and what is the speed is now given by the colors okay so the color over here the legend for the color is given over here so the particular speed is given by that particular color okay and the last thing over there is is it for one day is it for five days is it for one percent of the time is it for 30 percent of the time that is determined by these equally spaced circles each circle represents in this particular case I think two percent so two percent four percent six percent eight percent so depending on the length of the petal not the width is radially so it'll keep expanding so don't worry about the radial expansion that look at the length of the radius that will give you the frequency and of course as it is going outwards it'll keep expanding as a petal so don't worry about the expansion of the petal okay so coming back to this this particular wind rose I don't know if it is easily readable over there it's legible this is for grand rapids in Michigan United States is for a period of April 1 to September 30th which is for a particular six month season it also it's given in knots which is the unit of speed but it's about approximately 1.8 kilometers per hour okay so those are some of the features of a wind rose and I asked the students typically in an exam I asked them what are the three key features of a of a wind rose so the three key features are wind direction wind speed and the frequency okay those are the three things as a collector of the city you need to know as an average for the entire year I'll give you an example there are places in India and in other countries which are cities where parts of the city where they have a lot of VIPs so for example in Delhi all the people all the elected members of the parliament would probably be living in a certain region okay so one of the questions that comes up is that when they are locating some hazardous materials let's say some gases let's say chlorine they want a place to store a go down for storing chlorine they want to know where to locate this go down should it be north should it be south should it be east should it be west or where the VIPs live because it you don't want to create a situation in which there is some kind of an accident or not just VIPs actually it could be large population also but sometimes the consideration comes from VIPs as well so they would look to see during six months the wind is coming in this direction so if the wind is coming in this direction then the VIPs or the habitation is over here and the go down is kept downstream of the wind so that even if there is an accident the emissions will get taken away from the population okay and the other six months they shift the go down storage on the other side because the wind is in the opposite direction okay so those are some of the considerations that come in for some scale of planning for pollutants that are spread across the city like line sources or area sources it doesn't matter you just have to make sure that you know the worst case scenario or when the wind conditions are worst so that there's no movement at all of the pollutants and therefore that is the worst case scenario that people would get exposed to and you got to be ready for that kind of a situation the worst case scenario okay so that's a win rose for everybody let's get into vertical mixing okay vertical mixing is something which is not so intuitive when we had discussed the pollutant being released in this closed room we just assumed that there are four walls ground and a ceiling and it's a well defined volume okay but if I were to go back to one of my previous slides you know there are two boundaries of this particular plume the bottom boundary and the upper boundary the volume that's available is going to be determined by the definition of the two boundaries so if there is vertical mixing then this particular plume would be very wide if vertical mixing is not there then this plume will tend to remain as a narrow plume that remains concentrated so if it is mixing over a larger volume that is good from the perspective of air pollution because the pollutant is getting mixed in a larger volume and therefore getting easily diluted by the way one of the things we say about solution to pollution is dilution okay that used to be the thumb rule for the longest time but it still is used but it's not such a good idea solution to pollution is dilution okay so that's exactly what we're doing here actually we are banking on the dilution as a solution to the pollution okay so our concern is what is this height does that get affected somehow by the meteorological conditions that is our concern so if this vertical mixing is there then we have a solution if the vertical mixing is not there then we don't have a solution we're stuck okay so that's something to be keeping into mind and keeping in mind so this is now I'm going to begin to start dealing with vertical mixing and this is a graph of earth's atmospheric profile where you have temperature on the x-axis and you have height on the vertical axis and what you see over here is the temperature profile in the troposphere so above the troposphere there is a stratosphere and all that stuff but we're not dealing with that we're just going to be dealing with the first 10 11 kilometers of the the troposphere I'm not talking about this we'll talk about it if you have time we'll talk about it a little later our concern really is in this first 10 kilometers or so after the 10 kilometers there's this ozone layer which we have a concern about but we're not going to be dealing with it in air pollution okay so let's take a look at this graph in 10 kilometers we have gone from about 280 to about 220 the temperature has dropped by that much so about 65 degree Celsius in 10 kilometers which means every kilometer we have dropped by about six and a half degree Celsius okay so about six and a half degree Celsius for every kilometer so you should just commit to memory six and a half degree Celsius per kilometer if I wake you up in the middle of the night and ask you what is the temperature drop rate on planet you should be able to tell me 6.5 degrees Celsius for every kilometer okay then all right good so that's what I wanted to emphasize over there and that's how I do it for the students so just for you to be able to share that with your students this over here is what's called the lapse rate or the reduction of temperature as we go with height it's called the lapse rate okay so the way we define lapse rate is the atmosphere is cooling with height we want to know at what rate it is cooling okay so you see 10 degree Celsius here per kilometer and you see 6 degree Celsius here per kilometer you don't see 6.5 6.5 is somewhere in between two extreme conditions one condition is when the humidity is 100% which means that the atmosphere is fully saturated with water vapor another case is where there is no water vapor and it is completely dry okay so we're looking at atmospheric lapse rate completely dry would be 10 degree Celsius per kilometer completely wet which means 100% humidity would be about 6 degree Celsius this these are the two extremes so what you will actually experience in the atmosphere would be somewhere between 6 and 10 okay but for the sake of this argument over here we will talk about two different conditions and we will only deal with the first one by the way I think it should be clear why when it is fully humid that the rate of cooling is lesser is because of the release of heat of condensation so the temperature the atmosphere is not cooling as fast as it would if it was completely dry because it is humid as you're going up there will be some condensation which would release the heat and therefore the temperature will not go down as much as it would go under a dry condition okay so these are the so we're going to look at oh by the way adiabatic everybody heard of adiabatic adiabatic adiabatic adiabatic what is adiabatic I mean my thermodynamics are the hardest time dealing with adiabatic okay but here's what adiabatic here means adiabatic means that if you take a parcel of air okay a volume of air a balloon of air without the boundary without the rubber on it if you took this parcel of air and you moved it let's say to a slightly higher level say you moved it by 100 meters but you moved it quickly enough fast enough that heat transfer between the outside air and this parcel of air didn't take place that's what adiabatic means here it means that if you take a parcel of air and you move it up or you move it down quickly enough that the exchange of heat between the parcel and the ambient air doesn't take place then it is adiabatic okay so that's a condition we're going to assume and we're going to compare our tendency for vertical mixing against this adiabatic lapse rate okay so if you were to look at the lapse rate adiabatic lapse rate this is the dry adiabatic lapse rate this is the wet adiabatic lapse rate this is 10 degree Celsius for every kilometer this is 6 degree Celsius for every kilometer in reality you will be somewhere in between these two okay this is the adiabatic lapse rate okay one more time this is the adiabatic lapse rate this is what is defined by physics on the planet this has got nothing to do with what's actually out there this is defined by the physics if I took a parcel of air and I raised it fast enough and moved it from 100 meters to 200 meters to 300 meters to 400 meters this is the rate at which that parcel of air would change temperature okay all right now this parcel of air is in the middle of a larger envelope of air outside and it is going to depend the buoyancy of this particular parcel is going to depend on the relative temperature of this parcel of air and the surrounding air okay that's what we are dealing with in terms of vertical mixing so when I look at the next slide the dashed line over here is the adiabatic lapse rate if I were to take a parcel of air and take it up adiabatically then this is the path it would follow in terms of the temperature of cooling okay so this is the adiabatic lapse rate this dark line the black line is the actual temperature in the atmosphere it's got nothing to do with the adiabatic lapse rate it is a lapse rate but it is the actual lapse rate of the air in the atmosphere so let me give an example if you were to take a balloon okay some kind of a balloon which is filled with helium which will rise in the air if I put a temperature sensor on it and I release the balloon every 100 meters or so the balloon is transmitting data and telling me what is the temperature what is the temperature what is the temperature what is the temperature and I record that temperature then this black line is representing that balloon data okay so I got the balloon data for temperature which is the actual temperature or the environmental temperature and I am now going to compare it with the adiabatic lapse rate or the adiabatic temperature change okay so I am now going to take this particular height this is a height of let's say 1 kilometer at 1 kilometer height if there is a parcel of air which I want to raise by 100 meters adiabatically then it would follow this path because it's adiabatic I'm taking it quickly enough it will cool but it will cool as an adiabatic parcel of air and therefore the temperature at a height of 1100 meters would be 19 degree Celsius we started with 20 degree Celsius now it is 19 degree Celsius okay very good good job well done so what this is where now we're going to start dealing with vertical mixing or not vertical mixing okay now this parcel of air which is now at a height of 1.1 kilometers is surrounded by air which is at a temperature of 18 degree Celsius see this is the actual temperature at this height this is the actual temperature which is 18 degree Celsius so now I have a parcel of air which I raised from 20 degree Celsius brought it to a height of 1.1 kilometers adiabatically now the temperature of this parcel of air is 19 degree Celsius but around it is air of temperature 18 degree Celsius which is cooler so this parcel of air is lighter than the air around it so it will continue to rise so what happened what happened is that I took a parcel of air here which was at 20 degree Celsius which is a surrounding air I'm just taking a parcel of air which is at 20 degree Celsius and I raise it up somehow by some turbulence by some disturbance I raise it the moment I raise it it cools adiabatically but when it is cooling adiabatically the surrounding temperature is such that this continues to be buoyant more buoyant than the surrounding air so it continues to rise so this is a very good scenario this particular temperature this particular temperature over here is very good for vertical mixing to take place so if a parcel of air is released and there's a little bit of disturbance and it has a lot of pollutants in it this particular pollutant air will quickly get dispersed in a vertical higher volume okay so I'm going to now switch the scenario and instead of raising the parcel of air I will push it down same I'm not changing anything I'm keeping the environmental the real lapse rate there I'm leaving the adiabatic lapse rate I'm not changing the meteorological conditions at all all I'm doing is taking the parcel of air and instead of raising it this time I'm going to go ahead and push it down okay and if it is good condition then it will continue to go down that means that vertically if I take it up it continues to go up if vertically I take it down it continues to go down so I'm left with a very large volume in which this parcel of pollutants can get mixed okay so I'm going to go to the next slide where we are trying to push this parcel of air okay here we go so we take the same parcel of air I push it down the moment I push it down it will follow this dashed line it will come to a new temperature which is 21 degrees Celsius the actual temperature around it is 22 degrees Celsius so it is cooler than the surrounding air so therefore it is less buoyant so it will continue to sink good scenario very good scenario now I'm going to switch the scenario okay when I'm switching the scenario just watch what I'm going to do is I'm going to change the two slopes I don't know how this slope is going to show up on the screen but let's say okay this is one slope this is another slope okay what I'm going to do is let me hold something okay this bottle slope all right this bottle slope is the can you see the bottle yeah okay this bottle slope is the adiabatic lapse rate in one case I have the slopes like this in the other case I'm going to switch the slopes okay instead of the slope being like this sorry instead of it being like this now it is like this so I've changed the slopes watch okay I'm going to go back and forth on this slide so notice that I have not changed the adiabatic slope I'm only changing the environmental lapse rate the solid line will change positions watch okay watch carefully see so this particular solid line is now above the dashed line okay so now we are comparing this environmental lapse rate against the same adiabatic lapse rate but the condition is different at that time it was an unstable condition where vertical mixing was being promoted by the environmental condition but in this particular case look what will happen if we try and take this parcel of air and push it up it'll get pushed down if you push it down it'll get pushed up okay watch what's what's going to happen so you take this parcel of air here okay and let's say you what do you want to do with it we want to take this parcel of air and take it to the new height of 1.1 meters 1.1 kilometers okay we raise it up it'll come here it is 20 degrees Celsius which will become 19 degrees Celsius okay it becomes 19 degrees Celsius because adiabatically that's what's going to happen it'll cool by 1 degree Celsius the surrounding temperature is 19.5 so this parcel of air over here is now cooler than the surrounding air therefore more dense so it'll try to come down you try to push it up somehow okay by some turbulence by some disturbance there was a tendency it was pushed up but the tendency in the atmosphere right now the environmental lapse rate is such that it will not allow to continue to go up it'll push it down because the buoyancy is such okay so I'm going to pause for a second and let you discuss this particular case in which the condition is unstable that means if you push it down it will tend to continue to go down in this particular case if you push it up it'll actually get pushed down okay so actually let me do it slightly differently I'm going to do both cases I'll show you both cases for being pushed up in one case the tendency will be to continue to go up and the other case the tendency will not to be pushed up but do be pushed down okay so here we go so please discuss with your partner convince yourself that in this case if you take the parcel of up it'll continue to go up I'll stop for about one minute you should talk to each other in your centers okay so now I'm going to go to the condition of stability where I have interchanged the slopes okay so notice the change of the slopes and then discuss if you were to take this parcel of air up that it will actually have a tendency of coming down here we go please discuss with your partner give you half a minute okay all right so you know if this is if there are questions about this you know you welcome to give it on a piece of paper to your coordinator and they can communicate it to us all right that otherwise you know there's also some reading material that's available I can send to you I just want you to know this is not intuitive okay it is it takes a little bit of work to get an appreciation by the students so I spent quite a bit of time on this actually let them talk to each other I give them in fact I'm going to show you a particular example of I give this as a class quiz so then they have option a b c or d and then they give that answer and based on that answer then we this time we don't give chocolates though okay all right I'll move on to the next slide so here the implications okay the implications are that this is the adiabatic lapse rate this is the adiabatic lapse rate this is the actual lapse rate up to a certain height and after a certain height the the environmental lapse rate changes so if this particular lapse rate had continued then I would probably have this amount of pollutant over here diluted to this large volume but because there is inversion because this particular slope has turned around I do not have volume available above this for mixing there is a false ceiling that has become available now which does not allow me to penetrate the pollutant beyond a certain level so pollutants will get mixed below that level but not above that level so this is what we refer to as what's called the mixing height there's a certain mixing height in which the pollutants of the air shed will get mixed and that sets the limit to the volume that's available for mixing and it changes the carrying capacity of your location now these are different scenarios so this is a scenario which is basically this one okay the next scenario is that of stability the next scenario is that of neutral this is just to commit to memory if you are if your slope if your slope is on this side then it is a condition of stability if your slope is on this side of the adiabatic this is adiabatic okay this is adiabatic region so if you're on this side it is stable if you're on this side it is unstable unstable in our context means good unstable means more mixing unstable means better dispersion of the pollution okay and stable means it's not going anywhere it is going to stay here it's not a good thing okay unstable is good for us okay this is the class exercise I give in the class so there are two chimneys here okay one is a small chimney and the other one is a tall chimney okay small chimney tall chimney in the small chimney if you notice the plume seems to be well behaved it is not going up and down it seems to have a very narrow definition this is a condition of stability by the way I tell my students that after this class they will not see chimneys the same way they'll have a whole new viewpoint of how they see the chimneys the chimneys the smoke coming out of it how the smoke is going is going to have them think what is the actual environmental lapse rate in this particular is it stable or is it unstable that's how you start looking at chimneys after this particular lecture okay so this is a chimney in which the smoke is coming out and it is stable it's not moving up and down it's in some sense behaving itself the pollutants are restricted to a very narrow band in the other case this chimney is taller and it has this plume which is you know kind of going all over the place so which means large wide volume over which it is expanding so this is a condition of stable this is a question this is a situation of unstable now this particular situation would correspondingly have some temperature profile in the atmosphere so the question is looking at the two chimneys can you predict can you make an estimate can you make a guess as to what would be the actual temperature profile of the atmosphere and the options are four a b c and d the dashed lines are the adiabatic lapse rates okay they are parallel they remain same it's like a mini drafter no matter where you take this line it will always be parallel because parcel of air taken at any height raised adiabatic will always follow this path so it is a comparison that you have to make to say whether the condition is stable or unstable so in this particular case let's say we know that this is adiabatic this one is on this side therefore we will be able to say that it is stable so this is definitely a condition of stable which corresponds to the height of the small chimney so a is possible okay a is possible from the limited data that I am using for the small chimney if it is only the small chimney I could say okay a is the correct answer but there's another chimney here a taller chimney which is behaving differently so I look to see what is the behavior above and let's see that the slope above here is also greater is also on the other side so that is also stable so which means if this was the actual condition then even this plume should have been stable which is not the condition so a cannot be the correct answer so let's take a look at b in b this is stable okay correct but this one is unstable so b is also not the correct answer now I'm going to let you work with your partner and decide whether c is the correct answer or d is the correct answer and then I'll take maybe a raise of hands to say how many people said c and how many people said d okay so talk to your partner and tell me whether the right answer is c or the right answer is d take a one take one minute to do this so we have response from 98 centers uh we need another 54 responses please so for the coordinators who have not sent in the response please send in the response as c or d from your center okay 122 now so 30 more please 30 more coordinators to please send the responses so I think four centers are offline so we should stop at 148 145 now okay so I think three more centers would give in the response but let me give you the statistics here this is exciting okay so 146 about 62 are saying c and 54 are saying b okay so that is the result okay this is the result of the poll so poll result I do not it's pretty close actually okay it's pretty close so I think it may be a good idea to discuss the options c and d so that we bring clarity I'm sure the people who are saying c have their reasons for it but the correct answer is d okay so let me just go over it so that we are clear so let's go to c okay if you look at c this is clearly a situation of unstable okay because the slope is on this side slope is below the idea and in this case above for the higher chimney the slope is on the stable so this is actually a situation which is complete reverse of this if this was unstable and this was stable then c would be the correct answer but that's not the case let's take a look at d okay d is stable over here and unstable over here so d is the correct answer okay so for those of you who said d congratulations for those of you who said c if it is still not clear please send in a question and then I'll be able to explain it okay okay thank you for participating in that exercise we'll move on to the next slide now let's review so what we're saying is that pollutants are going to once they have left the source whether it is from a chimney whether it is from a car whether it is from a house whether it's from agricultural burning once it has left the source it is out in the atmosphere and how much of that will influence the concentration is going to get determined by the dispersion and mixing and we depend on the meteorological conditions of wind and vertical temperature profiles to be able to say how well the mixing will take place for windrows we have three parameters speed direction and frequency that is captured by windrows that's the win quantification and for temperature lapse rate we will actually look at the dry lapse rate which is constant for planet earth wet adiabatic rate and then the stability okay so that's what we have done you as a collector now have a sense of what are the wind conditions and what are the vertical mixing conditions based on the temperature profiles that would be there which are available from the meteorological department okay so that is what you know now as a collector of the city oh why are we doing all of this comes back to the same question why are we doing all of this why are we doing vertical mixing why are we doing adiabatic lapse rate why are we trying to understand the physics of the atmosphere because you're accountable for the quality of air in your city you are the collector you need to know what is the carrying capacity of your region you need to know whether a new industry can be added or some industry has to be shut down okay so that is something that you need to answer therefore you need to have this question answered if you want to set up a new industry it implies adding a new source of pollutants this source is permitted it is permitted by the state pollution control board to emit after it has applied the best available control technology on their processes after leaving the chimney the concentrations on ground is determined by the meteorology okay that is said again and again but it's good to reemphasize so if you want to know where to put the new industry if you want to know the pollution levels under the worst case scenario of stable conditions and low wind conditions if you want to know what height does the chimney need to be then quantification quantification quantification quantification of horizontal movement and vertical mixing is absolutely essential okay we now introduce the students to what's called the Gaussian plume or dispersion model also called gpm it is used to estimate the ground level concentrations for pollutants coming from a chimney this is chimney but you also can add line sources and area sources to this what are the inputs that go into a Gaussian plume model height of chimney and the source strength that is an input wind rose data is an input atmospheric stability of the region is the other input so these are the three inputs that are required for you to be able to estimate how much of an influence a source would have on the air quality in and around the region okay that you need to know and then isopleths maps can be made etc etc for the particular region this plume okay the word plume it's actually means a feather and I think at some point in time a feather it looked like a feather it's not a good feather but it's a feather all the same it looks like a feather and if you went into a library and you looked at some of the books from 1960s even up to 70s they would invariably have the cover which would have chimneys with these with smoke coming out of it okay that was actually a symbol of industrialization and progress but if you look at the covers of books that are now available in the 80s and 90s and 2000s they still have the chimneys but this time the chimney does not have the smoke coming out of it so politically it is incorrect to show smoke coming out of the chimneys so if you see a chimney and nothing come coming out of it that means you have a sense of satisfaction that there's no pollution being caused however the restriction is perception if you can't see it you can't smell it doesn't mean that pollution is not there so a lot of times when you see chimney and you see white smoke coming out of it maybe that smoke is only water droplets so you're not too concerned but if you see black smoke coming out of a chimney you'll be concerned you'll be worried that there is pollution okay so that's what a plume means and that's the political correctness around it these days okay I'm just giving you example of Mumbai I think it'd be great if you can take up your region your local region and look to see what is the predominant wind direction for that region depending on different times of the year and how location of certain industries might be there so because this thinking would have actually gone in when they do the permit process of an industry the pollution control board actually has to go through a process of environmental impact assessment okay they actually have to determine whether a location of industry in a particular region will influence the air quality of population in that area okay so this is for example in Mumbai this part of Mumbai this is the Arabian Sea this is the creek the Thane Creek this is predominantly where the industry is located now there was a time and it was also in this part of Mumbai some of the mills were here but not anymore you have malls over here now but not the mills so next time you're in Mumbai you should definitely visit this particular mall I went there a couple of weeks lot of bollywood actors and actresses come to this mall so in case there's an interest in visiting some of these you know you may want to come to this mall all I want to tell you is that this industry has moved out so this place is not polluting anymore this place is polluting it's a chamber area people have also called it the chamber the gas chamber because the pollution levels are quite high there is the fertilizer industry chemical industry refineries Tata power plant you know so several of these plants are there Tata power plant is run very well they actually it's a matter of pride that they take that they have you know environmental stewardship and most people over here are very highly conscious of the impact that they have on the immediate surroundings are very careful very particular about the quality of air and what they're emitting so when the design of this came in over here the predominant wind direction apparently in Mumbai some people argue against it but the wind direction is in this arrow direction so which means that the pollutants of most of the population in Mumbai is in this region and if the pollutants are the source of pollutants are here then this wind with by and large take the pollutants away from Mumbai population never mind what happens to Navi Mumbai Navi Mumbai is on this side what happens to Navi Mumbai now but the distance and the height of the chimneys is such that the pollutants get sufficiently dispersed that even for people in Navi Mumbai when these were set up okay when these plants were set up there was no one Navi Mumbai okay it was some rural areas etc etc so this place got populated much later and sometimes when Navi Mumbai is being blamed for being highly polluted they're really saying look it's not I there's no industry here I'm not really the one who's polluting there's work there's pollution which might be coming from this part of Mumbai from the Chambur area which is influencing our area okay so those are some of the concerns again if you were a collector of Mumbai then you may get a call from the collector of Navi Mumbai to say hey you know you guys are sending like it would happen in Indonesia Malaysia in the Singapore area you know so it becomes a regional problem rather than a local problem okay so that's as far as that is concerned this is typically the homework exercise I give to students where I look at you know we being in Mumbai I asked them to look at the wind rows from Mumbai but you should do it for your home city your home college and we also ask whether they know whether there is a meteorological department office in your city or which is the closest one and can you you know if you want to get wind speed data to develop a wind rows can you actually get the wind speed data from the Indian meteorological department do you have to buy that data is satellite data available for wind you know to develop a wind rows so those are some of the exciting exercises that you can give to the students so they actually go and spend a little more time with the meteorological domain okay last two slides this is for advanced learners okay the advanced learners if somebody wanted to explore the Gaussian plume model then there are these software which are available in the public domain they can even look into what are the commercial models available air mod is something which we use frequently it costs about 80,000 for a for an academic license for a single computer and it costs about 1.5 lakhs if you wanted to set it for an industry so recently what we have done is we bought an individual license for a academic institute for 80,000 and our students use it you know the take turns etc to use it we don't have it in our lab because it's going to be quite expensive and we didn't want to use it that way and also some of the advanced aspects of Gaussian plume model they include the chemistry so from the time that gets emitted to the time it actually reaches the ground level there's a lot of chemistry that is happening in the atmosphere the effect of humidity the effect of other components of pollutants that are coming from other sources how that chemistry might take place etc which gives rise to a lot of times the secondary aerosols in the atmosphere which we will not touch upon in this particular course so those are some of the things that come in advance commercial models that are available okay and the last slide I think here is okay some of the exciting developments that are happening okay global circulation models you know are now available readily okay and they're already being used for weather predictions so whether it is NASA or whether it is the European Space Agency or our own ISRO okay and there's a fraternity there's a you know group of people a group of scientists across the globe who are working pretty strongly to be able to understand the global circulation model models which fits in with global warming and radiation balance and some of those other issues it's really at a global level okay however for it to be at a global level they need validation from ground level so there is on all the meteorological department offices across India are a part of the world meteorological organization and you know people from UK people from Europe people from Australia other parts of Asia they're all connected through this one organization so what they're doing is on an hourly basis or on a 24-hour basis they're actually sending the ground observation to this centralized location and this is then being used against the prediction of the global model predictions global circulation model predictions and they keep comparing and look to see what is it that might be missing that might help them through re-analysis of past data the historical data is always available you can use it against your predictions for the past and look to see how well they compare so that you can keep improving your predictions so that is something which we are seeing as a possibility of using some of the re-analysis data some of this global circulation or data to be able to instead of the 10 meter height measurements that we do for using as an input for the for the air mod we'll talk about that at some point in time if we have time okay so some of these things you know are beyond the scope of this work but you know there are always some students that will be excited about some of these things again as I said yesterday if people get excited about this and want to take it up as a career want to take it up in as an m tech want to take it up as a phd you know then there are opportunities available for that that which reminds me now okay coming back to this conversation of m tech and phd but let me just finish this and then I'll come back for those who are interested in research in this area air quality can also visit the uscpa air division website and of course I'll you know upload some of the other websites that are available there is a book which again I'll give you a reference to it's called Nathanson that has a chapter two chapters actually on air quality what I like about that book is that at the end of the chapter they give the relevant websites for that particular chapter so it's very useful because then students can actually go to the website and learn a lot about what was covered in that chapter Nathanson I'll give you the reference for that okay so that ends my lecture here today but not without an invitation okay so you should know that my lectures are always intended to end with an invitation so while we were going through the questions okay Nikhil and I we were going through these questions and we also were looking on the kind of questions and the quality of questions and some of the questions that you were asking yesterday okay now what I'm saying now is not for the students okay is for you as teachers you as partners in this entire mission okay Nikhil and I were discussing and we said you know we hear that some of you are actually saying in the unsaid that there is some more studying to be done okay so I want to open up the conversation for some of you who might be considering doing a masters or for some of you who might be considering doing a PhD to please use the Moodle I'll open it up as a conversation and in that string of kind of saying that you can add your comments or you can add if you there might be an interest or what is it that we can do through this platform to be able to encourage to be able to support you in that commitment yes so you know from a perspective of career advancement if this is an area which excites you I just want you to know that there is a lot of work going on in the area of energy environment ecology sustainability and we're always looking for committed people nationally we're looking for committed people I'll show you a video of Jairam Ramesh I promised that yesterday I'll give it to you as a link one of the things he actually is dealing with is how do we actually take our youth how do we take our young committed teachers and researchers and take them to a point where they can actually be a part of a larger resource team for you know as PhDs and as Masters and Mtex to be dealing with some of these issues so I'm opening that I will open up that conversation as a Moodle conversation for you to respond okay