I'm Bruce Bugbee president of Apogee Instruments,
and in this video I'd like to show you how we used Apogee instruments to monitor
the radiation characteristics that occurred during the solar eclipse, which happened a few days ago.
As everybody knows it went across the United States, didn't quite go across
Apogee Instruments headquarters here in Logan, Utah so a couple of colleagues and I went to
Rexburg, Idaho where it was right close to the very middle of the of totality.
I'd like to show you how close the Eclipse was to the Apogee headquarters.
We went up to Rexburg, Idaho right here on the map.
Logan, Utah is right below Franklin County it's about right here.
We just drove up to Rexburg right near the center line so we got an excellent viewing angle for the Eclipse.
We had a camera running the whole time to record how dark it got and
for people that were in 96, 97 percent totality that's not nearly the same as
being in 100% of totality. This is the video we ran.
Here's the apogee setup here and I'm going to talk about these in a minute.
We had three laptops recording this. We all had our solar glasses.
This is just a 30 second video to give you a sense of how dark it is. Here we go it is.
This a colleague Tyler Volk from New York University that's written like seven books now on
mega patterns and he was with us. Right here is when it's close to totality.
You can see it's not quite as dark as a full moon. It lasted two minutes and 20 seconds in Rexburg.
We're not gonna show the entire two minutes. We sped it up here
starting to get light, I'm getting pictures, the street lights came on, it's dark,
and now that Sun comes out just to crack and it very quickly became light out.
This is in a rural area, not rural sorry, it's in Rexburg, Idaho but it was not near downtown.
We had a lot of neighbors coming by all kinds of neighbors, and we took a picture with the
neighborhood kids, which was especially interested in the whole thing right
after the Sun started to come back out. Here's the instruments we used.
We used an Apogee net radiometer here. We used an Apogee quantum sensor here,
three spectroradiometers to look at color changes during the Eclipse, and an up and
down infrared sensors to do sky temperature and ground temperature.
Then of course an Apogee aspirated shield for precision measurements of air temperature.
These next several slides now show you the changes that occurred during the Eclipse.
This is not what we might call rocket science, NASA measures this stuff as well.
It's just that here we were measuring it ourselves not relying on NASA's data.
This is the picture I took of the Eclipse as it looked in Rexburg and it looks like other people's pictures.
Its just with the standard camera. Eclipses are really a unique event they don't occur
on other planets in our solar system. Let me see if I can show you how unique they are.
Here's the Sun and in fact I want to show you the Sun in yellow to get it anatomically correct.
The Sun is 400 times bigger than the moon.
Over here is the earth and we're gonna put the earth right there on this side of the screen.
The moon as everybody knows is just a little dot right there.
The Sun is 400 times farther from the earth than the moon is from the earth, but the Sun is also 400 times
bigger than the moon.
So the moon cast just enough shadow right there to give us a total solar eclipse.
It's a remarkable thing just happens in a small area. What happened to the environmental conditions?
The first one is photosynthetic radiation and it's closely related to visible light. Here's the morning.
Here's the sensor, an Apogee full-spectrum quantum sensor, the morning here.
We moved the table just a tiny bit there's a little hiccup.
This is going up, up, up, up, up until the Eclipse starts right there and as soon as the moon started to move in
front of the Sun it started a curve down.
We really had an hour, over an hour, of watching the moon get closer and closer to the Sun.
It goes down. We get totality right here and finally it starts to come back up.
Everybody said let's go we're done, let's go and I said oh no, no we gotta wait to keep the instruments here
till this levels out to complete the study.
This point right here is when it's a total eclipse it is about as dark as a night with a full moon,
and the interesting part of that is the full moon takes a long gradual time this
happens just very quickly.
Even five minutes before totality it's still as bright as a cloudy day. It is just as that moment right here.
Full moon we usually consider to be 0.05 micromoles per meter squared per second.
Now we didn't have the adequate resolution to document this, but I know
it didn't quite go down to this dark. You could see that in the video.
It was brighter than it would have been on a full moon but still really dark as indicated by going to zero.
What happened to the other radiation characteristics?
Here's the Apogee net radiometer. Here's the actual instrument right here.
Remember that this has shortwave on one side and long-wave on the other.
Here's the incoming and outgoing shortwave. The incoming shortwave looks just like photosynthetic.
The outgoing also decreased because there was less light to reflect.
This was over a grassy surface and grass reflects about 20 to 25 percent of the solar radiation.
Let's look at the ratio of these two during the Eclipse. The ratio of these two has a special name albedo.
This graph shows the albedo. It's a flat line and right here we got division by
zero because the numbers were so close to zero. It gets really noisy right in
the middle of the Eclipse, but the Eclipse did very little to the albedo,
the reflectance of the shortwave.That shows how well the Apogee instrument
worked because it's very flat through all of this.
The other side of this does long wave radiation. You can see the blacktop.
Here's the long wave. Look at these lines very flat.
The incoming long wave right through here is just remarkably flat.
Overall the sky temperature changed very little during the Eclipse.
The outgoing longwave dipped a little bit because the surface of the ground got colder without the radiation.
Let's look at in detail at the surface temperature.
Here's the net, all four components added together.
It dips below zero like it does at night so the earth is cooling because it's a negative net radiation.
The sum of these four numbers is the net and it's negative.
The negative radiation meant much cooler surface temperatures and much cooler air temperatures.
Let's start with air temperature. The line curves down here.
The air temperature dropped from aout 20 to about 17, but look at what happened to the surface temperature.
That went from about 23 down to about 12 during the eclipse. This is the temperature of the ground.
Ground temperature is measured with the Apogee infrared sensor. We had one up and one down.
I'll show you that up in a second. Notice that the air temperature and the ground temperature took a while
to recover after this radiation came back up, it took a while to warm back up.
This was very noticeable. We were putting on coats in preparation for the cold temperature.
Typically the ground temperature is far more responsive to solar radiation than the air as indicated here.
This is the sky temperature as measured with an upward facing infrared sensor, and look very
cold minus 50 Celsius and a flat line because the Apogee infrared sensor is
designed to see through the atmosphere, close to seeing the infinity of space.
So it gets very cold and that temperature changed very little during the eclipse.
We didn't expect that it would change and it didn't it stayed cold.
A tiny bit of warming later in the day when the temperature came back up but minimal effect on sky temperature.
The biggest change was the colors of light.
This is our spectroradiometers measuring from 350 to 1000 nanometers, and measuring from
during the Eclipse to just after the Eclipse. What we predicted was by blocking the direct shortwave radiation
the blue component of radiation would increase because of Rayleigh scattering.
That's why the sky looks blue. The shorter wavelengths are reflected more
and increase.It happens at different Sun angles. We've blocked the direct
radiation and sure enough during the Eclipse
we got a higher fraction of blue light. Now keep in mind that during the Eclipse
these lines were way down here the radiometers picked up the blue shift
even though the intensity was many times less. That's because of auto integration
and the analyzers that we're able to do this. This is all normalized
out here so we can look at the relative spectral changes. This was a great fun
study to quantify these changes. We measured all the data some of it was on
the screen real time. People were coming by to watch it and it is a fun
documentation of the kinds of things Apogee radiometers can do during a solar
eclipse. Thanks for watching we'll look for you again in another video.