[Music]
PAUL NEWMAN: The Earth's atmosphere is divided into layers.
The lowest layer is what we call the troposphere.
And temperatures decrease
as you go upward into the troposphere.
You eventually reach a point where it's incredibly cold.
In fact, interestingly enough,
some of the warmest temperatures that we see at the ground
are in the tropics.
Where this might be 80 to 90 degrees.
But also. some of the coldest temperatures
that we see in the world
are found about 50,000 feet above the ground
in the tropics.
So here it's getting down to temperatures
of about -110 degrees below zero.
So there's a huge decrease in temperature
and this is all occurring in the troposphere.
And the troposphere is where we find most of our weather,
all the cloud systems are down here in the troposphere.
Now you get to the stratosphere, that's this layer,
and temperatures begin to increase.
This cold point is called the tropopause.
The tropopause separates
the troposphere from the stratosphere.
Most of the ozone in our atmosphere is found
up here in the stratosphere.
We call this the ozone layer.
Now, the Sun's radiation, as it comes down,
it comes down in a couple of different forms.
One we call ultraviolet radiation.
Now this is an invisible form of light.
It can't be seen.
And this is a very damaging form of light,
it can cause skin cancer, for example,
But it's mainly absorbed here by the ozone layer.
So we see this stuff coming down,
but we don't see much of it get through the ozone layer.
So about 90% of what we call UV-B
90% is absorbed by the ozone layer.
There's another class, called UV-C.
100% of the UV-C,
this is a very dangerous form of solar radiation,
is completely absorbed by the ozone layer.
[Music]
PAUL NEWMAN: The interesting thing is, the reason the stratosphere
begins to warm up
is because all of this radiation from the Sun
is being absorbed in the ozone layer up here.
So the atmosphere is a bit warmer down here.
There's almost no UV radiation that gets down here
and so it gets pretty cold
because there's no absorption of solar radiation here.
Now you go down all the way to the surface,
and you get down here,
and all of the visible radiation gets to the surface.
So the visible radiation, getting to the surface,
makes the surface warm.
So you have a lot of absorption of solar energy down here,
visible radiation,
and you have a lot of absorption of solar energy up here,
that's the UV.
And because you have very little absorption of UV here,
it just gets cold.
So that's why you have a tropopause
between the stratosphere and the troposphere,
because here's where you absorb energy
and up here is where you absorb energy.
[Music] [Radio Chatter]