Business India - the magazine of the corporate world, July 2-15, 2018
Talking To
“Instead of monsoon India followed the
fashions of the West”
Prof Roddam Narasimha
(Courtesy ICTS)
Prof Roddam Narasimha, (84), FRS, is a
distinguished aerospace
scientist, and among the first few Indian
engineers to be elected to
several prestigious international academies
like the Royal Society,
UK; the US National Academy of Sciences, US;
National Academy of
Engineering, US and the American Academy of
Arts and Sciences.
He has contributed enormously to the
development of aeronautical
and space sciences in India. He is presently
at the Jawaharlal Nehru
Centre for Advanced Scientific Research,
Bengaluru. One of his
major areas of research today is cloud
evolution and dynamics, a
subject of great relevance to the Indian
monsoons and global climate
change. These are excerpts of a conversation
between Shivanand
Kanavi and Roddam Narasimha
In the U.S., every tv channel will
tell you weather predictions
for
the next 24, 48, 72-hours and
they are fairly accurate. What
is
it that makes weather
prediction
complicated in India?
The dynamics at higher latitudes of
Europe and North America are simpler
than the dynamics in the tropics.
It is not that the British and Americans
are better at predicting the monsoons
than us. Of course we make mistakes
but so have they.
We have to be the foremost experts
in the world on monsoon. But the best
minds in India have not devoted their
time to the study of monsoon and they
have followed the fashions of the West.
And the West will study what is important
to them. We can say with the state
of knowledge existing in the world
today, not just in India, predicting the
monsoon is a tough job. The Indian
response has been to borrow unknown
American computer codes and so on,
but our experience with them is not
any better. Americans themselves say,
“We can’t predict monsoons”.
Can we compare the actual
weather
data with traditional
Panchanga
predictions and see any
correlation
and how accurate the
predictions
are?
If we are talking about rainfall, the
correlations
are poor. Panchanga depends
on the longitude, etc. So, there is
no way that it can be precise for the
whole of India or even a large region
of India. Nakshatras for rains are basically
empirical and those are correct
but they vary from region to region.
What about El Nino and so on?
El Nino was first discovered by a British
head of the India Meteorological
Department (imd) around 1915-1920.
Sir Gilbert Walker was a very bright
man. When he came here he didn’t
know any meteorology but he was
fascinated by it. But after a while
he decided that the monsoon was
too erratic – and he didn’t see how
one could understand the dynamics
completely. He said, “I will try and
do statistical predictions” and introduced
statistical predictions to the
Met department.
Till today, Walker’s philosophy, not
precisely his formula but his philosophy,
is what governs predictions in
our imd. It is based on some correlations.
There is Vasant Gowarikar’s
model that took many more parameters
than Walker’s did, but the philosophy
was exactly the same. One
of the things that Walker found was
that monsoon rainfall in India had a
link with what happened in Australia
– which is ironic. Walker didn’t live
to see that a couple of years after he
died, the connection was established
by much better measurements. It left
no doubt. That phenomenon is what
has grown into El Nino. The connection
that Walker saw between Indian
monsoon rainfall and what happened
in Northern Australia is one signal of
El Nino.
ISRO
has
launched many
meteorological satellites,
have they
helped in any way?
Yes, in a big way. To give you a striking
example, look at our cyclone predictions
now. In fact our Met department
had also predicted the cloud burst that
happened in Kedarnath, Uttarakhand.
But no government department took it
seriously. And it led to a major disaster.
So, we are getting better at that
kind of relatively short-term prediction.
Doppler radar too helps a great
deal in short-term predictions whereas
our satellites help a great deal over the
life cycle of a cyclone.
Has computer modelling helped?
Is
it easier in upper latitudes?
Computer modelling has helped, but
not as much as one would have liked.
By and large it is easier in the upper
lattitudes. The clouds are
what stump us in the computer models
of the tropics. Northern latitudes
do not have these kinds of cumulus
clouds. They are largely static clouds,
spread clouds. So that is why clouds
are very important to India and that is
how my interest in clouds started.
Is global warming a certain
thing now?
It depends on whom you ask. The atmospheric
scientists are pretty convinced.
Just look at how the weather is changing.
The Arctic is melting, nobody
can doubt that, the evidence is very
strong. The frequency of the extremes
in weather is increasing. Basically,
the change in the extremes would be
more noticeable than the change in
the average. So, a degree or two in
mean earth’s temperature might not
change the mean rainfall very much.
But if you look at the monsoons of the
last twenty years, extremes of a certain
kind are more common.
So, atmospheric scientists say it is
dangerous to ignore that this may be
a possibility. By and large earth scientists
are more or less convinced that
this is happening.
But, as I said, there are other people,
businessmen and some pretty
well-known physicists who argue
against it. Their point may be translated
as “there is no clinching evidence
in favour of climate change”.
Which is true but the people who
look at extremes say the evidence is
getting stronger and stronger. It is
stronger than it was ten years ago.
However it is still based on only
100
years of reliable data?
Quite right. So the debate goes on.
Moreover, clouds are the greatest
uncertainty in these climate models,
particularly the interaction of clouds
with radiation. To give a simple example,
if you have an overcast sky during
the day it is a bit cooler because
the solar radiation is not coming down
to us, it is getting reflected back. But
during the night an overcast sky is
warmer. Why? The sun is not there
but the infrared from the ground gets
reflected back from the clouds. So, an
overcast day is pleasant, an overcast
night is warm. This is a spectacular
everyday example of how clouds interact
with radiation.
What fascinates you about
clouds and what are the
unsolved
issues there?
The largest uncertainty in the prediction
of climate change has to do
with clouds. In the research done by
all the different groups in the world
about which way the atmosphere may
go as you emit more greenhouse gases
and various other substances into
the atmosphere, every now and then
something happens which doesn’t
agree with what is predicted. The last
ten years is a good example. Then
there are always sceptics who say the
models are no good and that you are
just making alarmist statements. “If
you can’t explain why earth’s temperature
hasn’t gone up in the last 10 years,
how can we believe anything you say
about global warming,” they say.
Actually some physicists are also
sceptics. The general view in the
atmospheric science community is:
“We do not claim to predict every blip
that occurs in it. The blip is not going
to prevent warming of the planet on
the whole, or climate change”.
When did you switch to
studying
clouds from problems in
aerospace?
Globally, the serious study of clouds
started around the 1960s. Very simple
experiments were made. Unfortunately,
by the 1970s, it was realised
that those simple experiments were
not behaving like clouds at all. We
picked it up where they had stopped.
In the 1980s, I started an experiment
in the Indian Institute of Science, Bengaluru
which turned out to be very
revealing. And so from then on I have
been working on clouds in some form
or other. We are getting closer and
closer and we can reproduce a wide
variety of cloud types in our water
tank. Now a lot of people have started
taking notice. However, it is difficult
to reproduce all the atmospheric conditions
in the lab whereas on the computer,
I have more freedom, provided I
have access to a Supercomputer.
In England, rainfall is not the major
variable, it rains almost every day. It is
a drizzle most of the time, so they are
worried about temperature. In India,
we don’t worry about the temperature,
because it is warm most of the time.
Our variable is rainfall. Rainfall is one
of the hardest things to predict. Temperature
and wind can be predicted
more easily than rainfall. It can be
raining here in Malleshwaram, but not
on the Airport road in Bengaluru.
The last bit of physics required to
tell whether it is going to rain or not
is very hard. Most of these cumulus
clouds that you see in India during
the monsoons, are actually flow
clouds. They are bubbling up from
the ground. And therefore there is a
very complex fluid dynamics associated
with it, it is not just thermodynamics.
It comes as a surprise to
many people that these things that
we see every day, which we admire
and love are not understood. u
Shivanand Kanavi, Former VP of TCS, is Consulting
Editor at Business India and Adjunct Faculty at
NIAS. He tweets as
@shivanandkanavi and blogs at
http://reflections-shivanand.blogspot.com./
He can
be reached at
skanavi@gmail.com
The Arctic is melting,
