Okay, so, good morning. Welcome to this course!
ME-5530, Introduction to Atmospheric Science, I introduced this course in the year April-2008
because I have been working in this area for last 12 years or so and we wanted to give
a general introduction to this subject to all branches, right. So, it is basically a
3 credit course, three lectures, no tutorial, no practical and three credits, the 3 meetings
per week.But, of course, I will, will solve a lot of problems during this course. So, the lectures will be interspersed with
problems, okay. So, all the quizzes and exams will be open notes, not open book, open your
notes without photocopying, okay. So, your notes and there is no tension, there is no
need to memorize formulae and all that. And questions like with the need sketch you explained
all this will not come in the exam basically you have to crack problems. So, it is a typical
math oriented course, right. I have given you the course content. Let us quickly go
through this. The first few lectures we look at introduction,
where we look at the various components of the climate system. Here we look not only
at the atmosphere; we look at the oceans, okay. Why do you think the oceans are very
important in the climate system of the earth? There is a big heat sync, right. The mass
of the ocean is so much, the mass and the specific heat is so much that they can act
as a thermal reservoir, okay. So, they will and therefore their response to any thermal
disturbance will be accentuated or will be slowed down because of the high mass into
specific into the oceans. So, they are like a thermal buffer, okay.
So, they are an important, oceans are an important actor in this whole drama of the climate and
we are not going to study more about the oceans because it is not an Ocean Engineering it
is not OE course but we will have to, we will have to look at it 2, 3 hours. So, that will
be the perspective. So, all this will consider in the first chapter; then, the Cryosphere.
The Cryosphere is that part of the earth system where everything is in the form of ice, right.
So, Antarctica ice, Arctic ice and then subsurface ice and so on. Terrestrial biosphere, vegetation and all
this; Vegetation also controls evaporation, transpiration, temperature control. For example,
you get into our campus is a distinct difference from Sardar Patel Road, you get in there is
a 2 degree drop rate, is much better, right because of the vegetation, right. So, we look
at this then the Earth's crust and mantle. The Earth's crust and mantle are also important.
So, plate tectonics continental drift and all that there are many issues involved in
that. But this I will be able to look at will be
looking at them as an overview kind of thing because the course is not on the earth system,
right. It is not a geology course it is an atmospheric science but this is an important
aspect so that will be covered in the first chapter. Role of all these various components
the climate hydrological cycle is you have studied from basic geography. So, evaporation,
then, this thing convection, rainfall, then, glaciers melting, rivers flowing down and
all this; Then, the carbon cycle is very important and
then we will also look at the brief history of the Earth's climate and the earth system.
For example, the ice age and all this and then, what about the changes in the solar
radiation, how they affect the climate and all that and why the earth temperature is
increasing now the average temperature is, is climate change real? Or this climate change
is a very nee-jerk response; is it, is it scientific? All those issues we look at it we look at
them from we will try to put the whole thing down as a simple first order equation and
okay or a 0 order equation and try to find out, okay; we will take a inertia or time
constant of the system, we will see how long it will take for the earth to respond based
on various what we call as force syncs, that is wave various forcing vectors these forcing
vectors may be increase in carbon dioxide or this may be increase in carbon dioxide
and this and many other things like that, okay. And after going through the introduction we
spend a considerable time on this atmospheric thermodynamics this is a very important part
of the course, where we start from the basic, ME-1100 which all of you have undergone, all
of you have taken this course, that is thermodynamics other colleges also they would have studied
this thermodynamics. We start with gas laws hydrostatic equation. Then, we look at the
first law of thermodynamics applicable to an atmosphere. Then, the adiabatic process is a big deal,
okay. Adiabatic process that is where there is no heat transfer adiabatic process is a
big deal in the atmosphere and what is the difference, if you already thermodynamics
is known to you, what is it big deal in studying thermodynamics again in this course. So, what
is special in Atmospheric Thermo dynamics? You, that is okay, but looks beyond. We are interested in thermodynamics of dry
air or moist air? We are always interesting thermodynamics of moist air. There you did
create cylinder and piston is always dry here. P is = Rho RT UD you did not worry much about
the moisture content and all this excepting one course if you are mechanical student,
refrigeration air conditioning where you looked at cyclone-metric chart, right where you looked
at dry bulb temperature, wet bulb temperature and otherwise we have never studied moisture
thermodynamics. Moisture thermodynamics is very important,
why moisture thermodynamics is very important because, let us take an air parcel, it is
going up after sometime it will reach a temperature at which water will become ice. Okay. At that
time, there is a chance that you can fall as rain or it can be a super saturated liquid,
okay. So, there is something called lifting condensation level there are various terminologies
which you have to understand, right. How this rising air parcel finally becomes precipitate
sheds its moisture as precipitation and so on. All these atmospheric processes will consider.
Second law and entropy and we will also look at atmospheric dispersion, okay. Atmospheric
dispersion is basically winds are carrying these aerosols and other things get dust for
example there is something called the Asian brown cloud they are saying that we are pumping
lot of gases from our power plants and all this; this is causing Asian Brown cloud over
the whole. This thing and if somebody is seeing from the top using a satellite every, everything
it is brown and they are saying that India is the culprit and all that. But other people have already grown. We also
have to grow, right so, right and our growth cannot be started stop this just because the
others have achieved the growth but these are these are geopolitical consequences. So,
let us not go into that. This, these are all policy issues, okay then, Radiative transfer
the atmosphere, we look at the electromagnetic spectrum, radiation laws, then, physics of
absorption, emission and scattering. This is very important, okay because the climate
of the earth is controlled by the radiation balance. The weather is mostly, the weather is mostly
controlled by winds and other things, right. The climate, the climate is governed by the
radiation balance now you have to understand the difference between weather and climate.
Weather is basically, maximum up to one or 2 weeks. Climate is a long term you are looking
at long term changes. So, if you have to so the frequently they will say why are you talking
big about the supercomputers atmospheric science and modeling and all that. You can't even predict tomorrow's weather,
how can you predict the Earth's climate after 30 years? This is a genuine question many
people ask, right. You don't even tomorrow you say it rains, it doesn't rain. You can't
even predict tomorrow why are you staring at after 30 years this will be like that,
all glaciers will melt, what do you think will be an appropriate response to that question
or that criticism? Climate is an average quantity and climate is a mathematically prediction
of climate is a boundary value problem, where the boundaries we know the conditions exactly. The prediction of weather is an initial value
problem in maths. So, it strongly depends on your initial condition. Suppose I have
to forecast the weather tomorrow morning 8 o'clock in Chennai, I will use the present
conditions as initial conditions and then, I will solve some non-linear governing equations,
these are the laws of conservation of mass momentum energy or navier-stokes equation,
equation of energy, equation of continuity and so on. But if I have a problem with my initial conditions
as you know nonlinear dynamics problem if there are any errors in the initial condition,
the errors will propagate with time. So, if you predict for 24 hours, if you get some
error, if you predict for 48 hours I will get even more error. If you predict for 72
hours even more error if you predict for one week it will be totally so what I predict
will be completely, completely different from the truth. But climate is lot easier to predict because
it is average and climate is a boundary value problem, right because the solar suppose you,
you are calculating the Earth's average temperature based on the solar radiation solar constant
which is 1353 watts per meter square for example, amount of radiation per meter square falling
on the earth it is not going to change from Monday to Tuesday to Wednesday, it will change
but its time constant is so high. It is not going to change tomorrow or July or August
or September. So, it is it is easier to track the problem
therefore when scientifically we study climate changes we are able to predict scenarios.
Our confidence level is much more than the confidence level which we have in predicting
weather events in 72 hours or 96 hours. So, regardless of our ability or the absence of
ability to accurately predict weather, here we have to, we have, we we have to we have
to give, we have to give it, we have to give it to the community, the atmospheric and climate
modulus, that it is possible to predict the Earth's climate reasonably well, okay. So, Radiative transfer in the atmosphere,
planetary radiation budget, this is very very important. So, so many watts per meter square
is entering, how many watts per meter square are going out as a reflection from the clouds,
reflection from the surface, how many watts per meter square is going as evaporation,
transpiration. So, if you do this energy balance then, we will work out quantities like how
much is reflected that is called as a planetary albedo. How much is reflected as a percentage of incoming.
So, if you can work out a planetary albedo for Mars, Jupiter, this thing and all that,
and you can see whether the planetary albedo is changing and what is its influence on the
Earth's climate, for example you can do calculations where if planetary albedo changes by one percent,
2 percent, five percent, what will be its effect on the Earth's average temperature
in the five years, 10 years, 50 years, whatever, all right. Then, this radiation is also important because
the radiation can be used to the radiation of the Earth's surface can be used to remotely
measure several things. For example if I keep, if I keep a sensor on the top of a satellite
and this sensor is a microwave sensor, the microwave sensor is capable, the microwave
is capable of penetrating clouds, okay. So, if you look at the ocean from the top, even
if there are heavy clouds the signature or the output which you are seeing at the top
of the atmosphere gives a lot of information about the cloud structure and the water and
the water vapor and ice, if any in the atmosphere. Therefore it is possible for you to write
down the radiative transfer equations assume some distribution of moisture and water and
ice in the atmosphere and solve the radiative transfer equation and actually calculate what
will be the theoretically measured radiance or radiation at the top of the satellite.
But the satellite at that point is measuring something. These 2 will not match. Therefore,
assuming that the measurement is correct I have to correct my assumption of the distribution
of water, ice and all that. I will keep on correcting till I get very
good agreement between measurements and simulation. If there these 2 match, then, whatever I have
got, the profiles I have got are the correct profiles. So, this is basically a 2 minute
course on remote sensing. This can be done using the infrared part of the spectrum. This
can be done using the microwave part of the spectrum. Infrared cannot penetrate the clouds
but infrared can give good information in partly cloudy situations and clear case situations.
Microwave can good, good can give good information in rainy situations. This remote sensing originally in the 70s
when people launched satellite, it was, it was considered great to just look at pictures
in the visible part of the spectrum. If you put images in newspapers and media and all
that it was considered a great achievement, if I am able to see clouds from the top. But
what is the difficulty with the visible imager? Just think. It is 2-dimensional is alright
with all the things are 2 dimensional, that is correct. It is that's a good point. All
are only 2D, any simple? you just see one layer may be the top. Third night times you can't see. Night them
you can't see. Infrared we will give 24 hours but infrared it cannot penetrate the clouds
so infrared also we will see one top layer whatever is a top layer so we can get the
temperature at the top layer if it is cloudy I can get the temperature at the top most
cloud. Then I can from the topmost cloud, what can I do now? If I know the temperature
at the topmost cloud now you think? Use a model what model yes it's not so difficult,
totally good okay. It is too early I will for you because you
are not exposed to this. Assume that the surface of the earth is at 30 degrees okay you know
there is called atmospheric lapse rate I will discuss this in later classes. That means
in how many degrees centigrade per kilometer the temperature will fall. If it is known
in that place, from the infrared, if you know the cloud top temperature that is the top
of the cloud temperature, you know the surface temperature, you can actually work out the
distance, based on this distance, you can find out whether it is high cloud, medium
cloud or low cloud. If it is a high cloud there is a chance that
a lot of moisture will be there and therefore it is it there is a chance it will be a Thunder
cloud or cumulonimbus or really heavily convecting precipitating cloud. If the top layer temperature
is very high that means the cloud is very close to the earth then it may not rain so
indirectly you can, you can figure out. So, like this and there are other things like
invisible part of the spectrum also you can look at the same, you can look at for example the Western Ghats, and last 10
years you can find out whether vegetation has increased or decreased. You can spot forest fires, okay. So, you can
do lot of things with satellite technology, okay to understand satellite technology and
use it in remote sensing you have to, you have to know get your basics and atmospheric
science, right, All right. Then, Atmospheric dynamics. Dynamics means how thunderstorm evolves? How
does a tropical cyclone evolve, a typhoon, okay. Those kinds of things first you will
have to find out. What are the governing equations what governs the dynamics of the atmosphere
it is basically the fluid dynamic loss laws of conservation of mass momentum and energy
then we briefly go through that. There is something called geostrophic approximation
and then cyclostrophic approximation. We are in this big navier-stokes equation some inertia
term some terms, you can omit. And then make it simple and lead it lead to
an approximation wherein first cut you can get how many meters per second will be the
wind speed and all that, okay. If you are a, if you are very rich and if you have supercomputers,
you can, you can, solve the problem in its full string. But sometimes wait take a ak-47
to kill a mosquito, right. So, if it is required, if it is required, you will have to solve
it on the supercomputer. Otherwise can you do some intelligent back-of-the-envelope
calculations at approximately first-order can you say whether it is 10 meters per second
100meters per second, ok. So, we need to get our fundas right in atmospheric dynamics.
So, these ambitious I don't know how much we can cover in this 40 or 42 hours but this
at least what should be taught in an atmospheric introduction to atmospheric science course. Then an atmospheric boundary layer, you know
that there is a boundary layer but the boundary layer the atmosphere. Any guess, what will
be the height of the boundary layer? Normal boundary layer what will be the thickness
10 millimeter, 20 millimeter to the atmospheric boundary layer but 1 to 2 kilometers, ok.
So, in that we will see we will kilometers, right in that boundary layer we love to look
at various approximate formula which can be used in the dynamics. Then the last chapter is very important. The
climate dynamics or the climate science or climate change, ok. First you have to look
at what are the factors governing the present climate, what is climate variability and the
sensitivity and feedback. That is what are the factors on which the climate is very sensitive
to if we change these factors the climate will change, ok. So, we look at finally of
course we will have to look at global warming; Global warming and then climate monitoring
and prediction, all right. So, I have given this to you and I also sent
it as email to the people who already registered, right. So, at the end of the, at the end of
today's class I will note down names of people who have just joined. So, the references are: It is a very good book Wallace and Hobbs.
It is like a Bible. I don't know whether enough copies are there in the library. So, if you
get one just latch onto this any of these books, very good book. Then, the Physics of
Atmospheres, John Houghton is also very respected meteorologist Introduction to Atmospheric
Thermodynamics by Tsonis, any book on atmospheric physics of thermodynamics, we get it in the
library just take it on long term. Introduction to Dynamic Meteorology where
he looks at dynamics J R Holton, A Climate modeling primer. This will be, the last 2
books will be for the last chapter, okay. Then, there is something called the IPCC right
Intergovernmental Panel on Climate Change IPCC. They give this assessment reports about
climate prediction, climate change and all that. So, this 2007 climate change, 2007 the
physical science basis book is also available I have one copy if somebody wants you just
you can take it for one or 2 weeks and return it back to me so that your other friends can
use it. So, this climate change 2007 you can borrow
it from me, if you want, okay. So, the classroom is basically studio one
so Tuesday 11:00 to 11:50, Wednesday 10:00 to 1050 Thursday 8:00 to 8:50, Friday 9:00
to 9:50 is the reserved, okay. Don't give it to anybody else because of travel and other
things if you miss classes we have to make it, make up okay but I will give you at least
2 three days notice I won't tell on a Thursday that tomorrow please come, alright. Generally,
it is three lecture meetings per week. So, the grading policy for this course will
be the first quiz will be 20% the second quiz will be 20% we you will all present a term
paper I'll divide it into groups of 2 or three I will select some topics I will give you
some topics then you choose among the one among this and then you'll have to present
you'll have to give a term paper and also give a presentation. And everybody else will
be there so we will evaluate you and that will be for 15% and End semester will be 45,
okay. All quizzes and end semester will be open notes, okay. Now let's get into this Atmospheric science.
I am using the PowerPoint basically today to cover ground introductory material, material
otherwise I have to write a lot. We will quickly switch to chalk and talk so that is my preferred
mode and then please bring calculators to every class mostly we every class will be
working on problems, all right. So, atmospheric science is a relatively new applied discipline.
It is not as old as civil engineering or mechanical engineering or so on. So, atmospheric science
courses might have started out maybe last 50, 60, 70 years. It is not even a century
old, right. So, where for example the Guindy Engineering
College is 250 years old, you know, right across the Civil engineering in Anna University
is about 250 years old, okay. So, they read rain it started as a survey school by the
British, alright. So what is the atmospheric science? You can take down this if you want.
Atmospheric science is concerned with the structure and evolutionary and evolution,
evolution of planetary atmosphere, where is this delete now. yeah where we are concerned
with the structure and evolution of planetary atmosphere and the phenomena associated with
them, okay. So, you can do atmospheric science of Mars,
Venus, Neptune, Pluto, whatever. But in this course, we are looking at the atmosphere of
the earth okay. So, so that is interplanetary science
or planetary science, that is beyond the if you want to do that, you have to go to some
other place. We can't do that in India. If you want to if you want to research an atmosphere
of the Mars, of Jupiter you have to go to Oxford or Cambridge or some of these schools,
all right. So, the main focus is usually on the Earth's
atmosphere. In atmospheric science is also a subset of Earth or geosciences. Earth science
is a much broader term because the earth science will include several things, okay. Geology,
geochemistry, geophysics, atmospheric science, ocean engineering, ocean sciences, atmosphere,
ocean coupling, all this, right; Why did the atmospheric science, why did that matter how
did the atmospheric science develop as a separate subject? The answer is already there. There was a requirement
of reliable and accurate weather prediction may be over cricket matches or something,
I don't know. Our agricultural production, monsoon whatever but that is Indian but West
I don't know why they wanted it. So, but people wanted to know about the weather, okay. So,
the demand started, the study started with the demand for a knowledge or need for reliable
weather prediction. So, weather prediction has hopefully evolved
from an art into a science, okay. Now, weather prediction is based heavily on mathematical
models it is not just based on some instruments and charts and it is not an extrapolation
of the previous years this thing. Are you getting the point? There is one way of for
example I'll give you another 2 minute course on statistical forecasting, okay. Now, let
us say we want to there is a cyclone which is formed in the Bay of Bengal. There is a
satellite which is seeing this. So the eye of the cyclone is the place in
at the center, the eye of the storm is the place of the lowest pressure, where all the
winds are converging so, right so that from where you can you have seen satellite pictures
of what disease and all the what X and all that. Now let us say that every 6 hours or
every 4 hours you are seeing the satellite picture and then in 24 hours you are actually
recording, ok. T so this is the position of the eye, at time
T. T plus 6, T plus 12. Then, they are joint base straight line. Like 2 points and you
don't paint me that serve you can join the best straight line right otherwise 2 points
are in straight line. Now statistical forecasting is, if you have these points, last hundred
years you looked at cyclones and if you look at the average and then in 12 hours if something
has gone like this then they will extrapolate this and say that T plus 18 T plus 24 it will
be like that based on an ensemble average of already available data. This, that is brute force statistics. That
is a statistical forecasting but suppose you have this you have this position you ingest
this position and then let us say you take this domain on solve CFD equations on your
supercomputer then you are doing mathematical modeling and weather forecasting, okay. So,
this is a quick fix. This is a crossing for every figure this is this little more there
is a antibiotic and even more deeper I think you find out what is this. But even then here
also there are lots of approximations okay. And the whole idea of suppose there is a,
there is a satellite overpass, microwave satellite so in this region it is giving good information
right on microwave. Suppose you incorporate this information into the model then you are
doing even better. That is called a simulation. You assimilate or ingest or inject observations
whenever you have whenever you inject observations which are closer to truth or the truth itself. When you are into a mathematical model, generally,
it is it is expected to improve things, okay. So, weather forecasting has now evolved from
an art into a science that relies on mathematical models based on conservation laws of mass
momentum and energy. A very important slide: This is from Wallace
and Hobbs the level of skill is the level of skill is determined by how accurately are
able to predict it even. How will you measure quantify this level of skill? They usually
done by something called not forecast, Hindcast. Last 10 years you look at all tropical cyclones
use your models and predict actual truth will be there after the cyclone has crossed. So,
this can be your variable can be the quantity you are using may be where the cyclone hits
the Indian coast? What is the error in the geographical location of the okay? This is
called landfall. That means where it hits the land so you can take the error so in the
kilometers, okay. So then, if you see error in kilometer by this thing that will be this
percent that will be the skill. One hundred percent skill will represent 0
error, okay. So, you can see that the day three forecast it can be for a precipitating
system, monsoon or average climate or average weather whatever. So, day 3 forecast has increased
like this. Day 5 is increased like this. Day 7 is increased like this from the 80s to the
data is up to 2007 or 08. Now, a couple of quick questions: What do you think it is like
this? Why is day seven lower? Error propagates with time, very good right. Now, northern hemisphere is more southern
hemisphere is less with the within the day 3, day 5 and this Babu is there any pointer?
Oh mouse. So, this is the northern hemisphere, this is a southern hemisphere. Now, tell me
why is it like more landmass in northern image so what? Don't say mean land northern hemisphere is
more advanced that is correct actually. Yeah northern hemisphere is more developed that
is okay because of that they have more instruments more measuring instruments and all that and
that is one thing. Secondly, more landmass in the northern hemisphere so more weather
stations. Data is deficient in the southern hemisphere, okay. I won't talk about funda
level and all that that will again this thing we can't have convergence on that. So, generally but now that is also decreasing,
right. So, once satellite technology is coming and high hype or mathematical modeling is
coming all these differences are going down, okay right. I will send you this if you can
identify a class rep I will send you this PDF to one other persons one student in the
class then who can just send it as a group mail to all the students, right. If any PowerPoint
I'm using I will share it, alright. Weather forecasting basically you want to
know the future, forecasting is very intellectually stimulating, right. So, it gives you some
intellectual drive. And also there is an absolute need from governments and economies and this
thing policymakers. For example, India's gross domestic product is a strong function of how
good this monsoon is. So, the government wants to be ma modulus and meteorologist to accurately
predict beforehand so that they can take some emergency measures. A Food Corporation of India you can store
more grain, this thing, all this is possible. We are not talking about geoengineering where
we take planes and put silver iodide and create rain and all that. We don't know what those
solutions will work or not. But for preparedness, in the case of a drought or in the case of
a heavy rain, heavy monsoon, floods, loss of property, loss of life, in all these cases.
So, we want to, we want to be able to predict the future reasonably accurately. So to do
that, you have to develop infrastructure. What is the infrastructure which is required
for weather forecasting, weather balloons okay. The World Meteorological Organization
had set a standard. There are 2 times once in the morning and evening the same time all
over the world. The same time all over the world all weather stations will launch balloons.
This balloon will have instruments which will measure the humidity, temperature and so on. There will be error because from Chennai Meenambakkam
Airport, you send the balloon what is the problem after some height, it will drift but
we don't go to Malaysia or Singapore, right. So, it will be a few hundred meters or okay
depending upon the wind and all that. But so, so it will reach some level and you will
get those readings. And these are sent to the ground stations, okay and WMO ensures
that all weather stations in the world share this information. So, this information is available this basics,
okay. Then, radar the radar is an active instrument where you send it radiation and from the reflection,
you try to understand the situation, okay. Now, there is a, there is a radar on the marina,
next time when you go, you should see. It is on the Chennai port trust building opposite
to the Reserve Bank of India on the Marina Road. If you see there will be a white colour
spherical dome. You have seen on the Marina Beach next time you see that is the DWR Doppler
weather radar of Chennai, okay. So it will open up and then it will scan when
it scans, okay so it will send some radiation from its place to the sky. Now, if no radiation
comes back what will be what is the rain? No clouds, no rain, very simple. If there
is heavy rain it will get reflected so depending on the size of the raindrops and the thickness
of this layer so you will get a different signature of the reflected radiation. So,
radar is radar can also be used to hunt down aircrafts, this thing, missiles and all this. But for civilian for weather application this
is very useful to, very useful for short-term weather prediction called nowcasting. All
commercial airplanes have this radar okay. When they are going through turbulence, the
pilot will get an idea whether he can pass through that or he has to take a detour, okay.
Radar weather stations, okay. There is one weather station near the stadium our stadium
IIT Stadium, okay. That now we also have what is called AWS automated weather station where
it will measure basic parameters like humidity, wind speed, temperature and so on and transmit
this data to some server, okay. Aircraft measurements, okay: You can have
you can actually go you can actually go in airplane and make measurements and actually,
you can I, you can actually open out and then take a sample, take a sample and measure,
all this, error so all this thing, in all this, there are also hurricane hunters in
the United States where they get into the storm. Indian Air Force we have not done so
far. They get into the tornado or the storm and then they collect vital measurements these
are very important to improve our models because models assume them microphysics models assume
how how these droplets are coalescing and right. How the rain starts and all these physical
processes which are represented in those equations depend on these measurements. Of course satellite
meteorology, if you are studying weather through satellites it is called satellite meteorology
so this weather forecasting has led to lot of develop, development of infrastructure
in all this. Apart from models we use all this to study weather. So, in so, if you look at a holistic picture
of a earth observation system, the weather is the weather observation system is very
very important component. But it is not the only component for the Earth's climate monitoring
system. That's climate monitoring system you have to for many many decades you have to
monitor the carbon dioxide concentration and you can also look at isotopes, okay. You can
also look at isotopes or you can go down and get samples of ice. Carbon dioxide will be trapped in that okay.
Depending upon the height, you will the height of the ice, can be correlated with the time,
okay. And then, against this time, if you measure the carbon dioxide you can see how
carbon dioxide has changed with time. So, a lot of fundas are there. Then, if you look
at isotopes and you can go back to ice age and this thing this study is called paleoclimatology. So, this is vast this thing it is not just
balloon and satellite and that is weather system. Earth observation system is much more,
okay much more detail, right. So what are these various components of this? You can
do climate monitoring that is a part of the earth observation system. You can, ecologists
are interested in studies on habitats. Habitats of light or a habitat of elephants in the
Nilgiris, there is some Professor Sukumar from IIT Bangalore. Whole life, he's studying
elephants. The professor of ecology, elephant habitat
how our human intervention, how they have been marginalized, why they are away they
are coming out and sometimes they come to the middle-of-the-road of the rain, okay.
So, studies on habitats, ecosystems, afforestation, deforestation, forest fires, how these things
are linked to rainfall or droughts and so on forest fires, right. Forest fires and all
these are part of the earth observation system. Atmospheric chemistry now if you see I am
just giving a broad overview of the various various facets of this science. Atmospheric
chemistry is also important, you must have studied in your chemistry that acid rain,
right okay. We look at what this acid rain is 50 years ago the focus was only on urban
air quality. You say, that people are int looking at respiratory diseases, okay. That
was the only concern afterwards in the 70s the discovery of acid rain the sulfur dioxide
becoming sulfuric acid and the NOx the nitrous nitric or nitrous oxide becoming the nitric
acid this was a major milestone is an important thing, okay. These reactions you know SO2 plus OH minus
gives HOSO2. HOSO2 plus O2 gives this HO2 plus SO3 and finally it becomes sulphuric
acid then NO2 plus OH gives HNO3 nitric acid. So, acid rain can cause disturbance to Regions
located thousands of kilometers upwind because there is no visa required by clouds. They
can form in Arabia come to India from India they can go to Singapore anywhere no visa
required no fly plate flight ticket is required. They just move with the winds, okay. So, therefore acid acid rain is an international
problem, okay. So, SO2, NO, NO2, N2O what we endured dissolve in why is acid rain form
because these gases which are mostly released okay which are mostly released out of power
plants and all this, they dissolve in very small cloud droplets to form weak solutions
of sulphuric and nitric acid and then when they rain along with the rain they also come
down as acid okay. Ozone destruction, all of you are aware of
this, another major discovery was that of the Antarctic ozone hole. The destruction
of ozone hole which exposes the earth because ozone protects us from the harmful ultraviolet
radiation correct from the Sun was proved to be caused by chlorofluorocarbon and then
they had an agreement and then CFCs were removed from our Refrigerators. Now, you have got
cfc-free refrigerators like R134A refrigerator is something which is new. Previously they
were using R12 or R22 after this. This is Montreal Protocol is it? I do not remember some Montreal Protocol they
all agree, everybody agree that we should have cfc-free refrigerant and the global warming
now it is making lot of noise. Global warming is caused by green house gases. Greenhouse
gases are frequently referred to as GHG greenhouse gases and group they cause global warming.
It is also another important issue affecting geochemistry. Emergence of new fields: Climate dynamics
is also an emerging field within the broad area of atmospheric science and availability
of realistic data and evidence is the need of the hour. I think there is a problem. Cores
and computers, we require lot of this, have all contributed to climate modeling and climate
change becoming available to real estate data and evidence. What is this? My system typed
it. I have to fix it okay. Now, let us, the last part of this lecture,
there are measurements of carbon dioxide machine continuously from 1958 by a person called
Charles Keeling okay and now because at most carbon dioxide is very dispersed in the atmosphere
it is proved that if you measure carbon dioxide at one place, in the atmosphere, it is the
same more or less anywhere in the earth. Therefore a measurement at one place can serve as a
proxy as a globally average carbon dioxide concentration. So this place is in Hawaii
called Mauna Loa. What does this say? This is from 1958, okay. So, Mauna Loa on
South Pole; both are the same and why is it fluctuating within that. This is a small fluctuation
now within a year, there is a, what is the reason for that? Not weather. The seasons;
photosynthesis and this thing some in autumn there is no there is no relation on photosynthesis
and all that so that causes the carbon dioxide within limits. But you can see the atmospheric
concentration which was 310 parts per million ppm in 1958 is now 370. So, when you are actually doing weather models,
radiative transfer modeling, now we have to use this 370 when a when you run the model
after 10 years you may use 400 or something, okay. So, this is the variation of CO2 concentration
with time, okay. So what? Okay sir let it let it increase generally
everything increases so what hmm how can you say that how can you prove it yes the answer
is here. The global increase of carbon dioxide is given
by the red line the main global temperature of the earth if you take the mean global temperature
you have some averaging procedure properly average that follows the blue line. The trouble
is they are very strongly correlated they follow a very similar trend therefore there
is enough reason to there are enough reasons to believe that there is a strong correlation
between the carbon dioxide and the global temperature increase. And this carbon dioxide concentration now
is much, much more than the last 2000 years and it is only in the last hundred years that
we have invented the IC engine, the power plants, the aircraft all of which use fossil
fuels therefore more fossil fuel burning has led to more carbon dioxide concentration more
carbon dioxide concentration has led to more absorption which we can prove from radiative
transfer principles and this causes this core so called greenhouse greenhouse effect. And therefore this is a the writing is on
the wall it is a clear message that we will have to somehow have carbon dioxide mitigating
technologies carbon dioxide sequestration whatever you should have technologies which
will limit the emission of carbon dioxide battery cars, hybrid cars whatever right.
So, foot of solar photovoltaic technology where we where we actually RG mechanical engineering
that is you bypass you bypass the heat engine okay. So, you do not burn a fossil fuel and try
to do that right. So, this is a very important this is actually a very important figure where
we are able to correlate global temperature with carbon dioxide okay thank you so we will
close. So, we will meet on Tuesday 11 o'clock any questions. So, what is so what I am saying
is the carbon dioxide concentration I can put it in the radiator transfer model in the
radiator because of carbon dioxide it will increase some property like absorptivity of
this thing emissivity whatever. Then we can show that with increase in carbon
dioxide this emissivity absorption increases with increase in absorption this it will that
we can prove okay. Any near the question okay, thank you.
