How to Measure Rainfall? Video Lecture | Class 7 Oxford Science: Chapter Notes, Worksheets & Tests

hello friends this video on whether
climate and adaptations part six is
brought to you by example Oh calm no
more pure from exam so let us now talk
about another element of weather which
is a very important element and that is
rainfall now we often talk of rainy days
we often the school our schools gets
shut down if it is raining very heavily
so what is this rainfall and how do we
measure how much rainfall is taking
place at a particular place so for
measuring rainfall we have something
called as rain watch so this rain gosh
helps to measure the amount of rainfall
at a particular place now you would have
learned it in your GPA that general
knowledge that which please receives
highest rainfall in India and you would
have learned it that challenges the
things now how do we know that which
place receives more rainfall and which
place receives less rainfall so there
has to be something which can measure
with actually how much rain is happening
at a particular place so that is why
this rain watch has been designed so
here in this picture you can actually
see how the rain goes looks like it is
it looks like a cylinder but to write
one smaller cylinder inside the bigger
cylinder that is how it is appearing to
me so let us now try to see what is the
rain gods and how does it measure rain
so let us look at a bigger picture of a
rain garden so there are three important
parts in a rain god so the first
important part is a funnel as you can
see here you have a funnel like
structure here so that funnel is one
important fact because funnel is that
part which actually helps to collect the
rain so that's the funnel inside you
have a tube that is the inner measuring
tube so that is the tube which actually
measures the amount of rainfall so
therefore it is the measuring tube and
outside you have a cylindrical structure
right so this one is the outer cylinder
so these are the three important parts
again gotcha now how do we measure rain
now when it rains now this upper part is
open so that's how the funnel is so to
collect the rainfall so when it rains
the funnel will collect the rainfall
anchoring and then the rain will get
collected in the inner cylinder you see
the funnel is actually linked to the
inner measuring tube so the rain will
come into the inner measuring tube and
the inner measuring tube is actually
graduated with values which it can
actually measure how much water is
coming to this tube now this tube can
measure up to 25 millimetre of rainfall
so 25 millimetre is nothing but the
height of this tube so the measurements
which I mentioned in now the question is
let's suppose if it is raining very
heavily so the inner tube will get
immediately filled up so how are we
going to measure the excess amount of
rain that is coming in so any excess
amount of rain is captured in the outer
cylinder and that is why we have and a
big outer cylinder so look at this
picture it will give it is giving you a
better view so the inner cylinder is
only up to this much but the thickness
of the outer cylinder is much more so it
can actually accommodate a lot of water
so all the excess water will get
collected in this outer cylinder and
then how are we going to measure it and
then what we will do is first we will
measure the water that is there in the
inner cylinder we will pour the water
outside and we will again take the water
from the outer cylinder and put it into
the inner cylinder and then again
measure it so using the inner cylinders
calibration rainfall as low as 0.1 inch
can also be measured so
the calibration is done in such a way
that even a small amount of rain for
even a few drops of rainfall can also be
measured so that's how we can decide
where we are
less than four and where we are having
more than one so and quickly repeats the
process how we actually measure it so
let us suppose it is raining very
heavily so what happen will happen when
it is raining very heavily so very soon
that in the measuring tube will be full
so when it is fun so you already know
what is the maximum capacity of the
inner tube so that is let us say in this
case that is 25 millimeters so 25
millimeter do you have already measured
so now what you do this 25 milliliter
you take out from this to end you just
keep it somewhere else
outside you pour that water outside so
now you have this inner cylinder envy
now all that excess water has been
connected in the outer cylinder so from
outer cylinder you pour it into the
inner cylinder and again you measure it
so let's say again it became completely
full so again you have 25 millimeter
right and now let us say whatever you
put it is maybe 2 or 3 millimeters okay
so you just write it 2 millimeter and
now you add this all up to get the
rainfall or to measure the rainfall so
in fact this is how 10 fault
is measured now how do we determine
whether this much rainfall is less
rainfall or heavy rainfall or moderate
rainfall so for that purpose we have
decided arrange that okay if the
rainfall nature it comes to be in this
range then it is moderate rainfall if it
comes in this range then it is heavy
rainfall so what is that range so any
rainfall so less rainfall or low
rainfall low rainfall or less rainfall
would be less than 0.1
puch so inch per hour so that is because
time plays a very important role
maybe you just kept it like this for 10
to 12 hours so obviously it will get
filled up so you have to specify a fixed
angle baby in 1 hour how much
ability will get filled that will decide
the measurement of rainfall so if the
amount of water corrected is less than
0.1 inch in one hour then we will see it
as the plate that location got too low
rainfall what would be moderate rainfall
so moderate rainfall would be anything
in the range of 0.1 zero two zero point
three zero inches per hour so this would
be the range for moderate rainfall and
when you talk about heavy rainfall so
here if it rains one would be anything
more than zero point three zero inches
per hour so that would be heavy rainfall
so basically with rain watch rainfall
amount is described as the depth of the
water which is reaching the ground in
inches so you we are actually trying to
measure the depth of the water which is
reaching inside this - so that's what we
are trying to do so this is how they
important is measured and that is now
you got an idea that why do we see that
okay check when she gets maximum
rainfall because when you were trying to
measure rainfall of different locations
you can actually get the values and
those values will be able to tell you
which place gets how much rainfall thank
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