What can be seen?
Generally, ProcEarl will spit out several graphs that help the user know several different parameters. There is a graph that charts the laser power over time to see how it fluctuates, a graph that shows the backscattered light that has been corrected for the distance to an object, and a graph that shows the depolarized light that is backscattered. If the light is depolarized, then that means that the laser light hit a non-spherical molecule like dust, pollen, ash, ice, etc. Dust, pollen, and ash are referred to as "aerosols," a category which also includes ozone and other non-spherical molecules that exist in the atmosphere. Generally, though, most of the molecules that the laser hits are spherical molecules. Specifically, water droplets are the most numerous. At heights below 6 kilometers, most clouds contain purely water droplets. At heights 7 kilometers and above, these water droplets freeze into ice due to the decreased temperature.
The graph in the upper left corner is what is referred to as the "Range Corrected Backscatter" graph. Basically, it shows all the molecules that scattered back light into EARL. When nothing discernable can be distinguished from the graph, like in the upper left hand corner of the graph where it just seems like a colorful blob, that means that EARL collected too much noise in the data. In other words, there was a lot of varying amounts of light recieved for one location. Think of white noise and how it is difficult to pick ouit a single pitch of sound since white noise is all over the place. This part of the graph is basically the same. Generally, nothing can be said about this region unless some of the noise is removed.
At the bottom, you can see that the data looks blue at first and, as one looks more toward the right (which suggests that time has moved forward), the color seems to become more turquoise and slope upwards. This means that more light was being scattered back at this point in time. This area that gradually seems to grow at the bottom of the graph is what atmospheric physicists refer to as the "boundary layer." This is the area where everyone lives and breathes, where the sun warms up the atmosphere, caused all the dust and pollen on the ground to rise as heat rises. This is why the turquoise area slopes upward: the ground is heating up, and whatever is in the atmosphere is heating up and moving upward with the heat. This is called the "mixing layer" because everything is mixing together before rising.
Also on the graph, if you look very closely and zoom in to the photo, are what seem to be weird blips above the rising turquoise area. These are clouds. Generally, clouds that form at altitudes below 6,000 meters are full of spherical water droplets, which bounce back light in the same direction that the light came to them. The laser light bounces off all of these small water droplets in the clouds in such an amount that the graph of the backscattered light is able to show that something was in that area, something that reflects more light than what is in the atmosphere around it.
The graph in the upper left corner is what is referred to as the "Range Corrected Backscatter" graph. Basically, it shows all the molecules that scattered back light into EARL. When nothing discernable can be distinguished from the graph, like in the upper left hand corner of the graph where it just seems like a colorful blob, that means that EARL collected too much noise in the data. In other words, there was a lot of varying amounts of light recieved for one location. Think of white noise and how it is difficult to pick ouit a single pitch of sound since white noise is all over the place. This part of the graph is basically the same. Generally, nothing can be said about this region unless some of the noise is removed.
At the bottom, you can see that the data looks blue at first and, as one looks more toward the right (which suggests that time has moved forward), the color seems to become more turquoise and slope upwards. This means that more light was being scattered back at this point in time. This area that gradually seems to grow at the bottom of the graph is what atmospheric physicists refer to as the "boundary layer." This is the area where everyone lives and breathes, where the sun warms up the atmosphere, caused all the dust and pollen on the ground to rise as heat rises. This is why the turquoise area slopes upward: the ground is heating up, and whatever is in the atmosphere is heating up and moving upward with the heat. This is called the "mixing layer" because everything is mixing together before rising.
Also on the graph, if you look very closely and zoom in to the photo, are what seem to be weird blips above the rising turquoise area. These are clouds. Generally, clouds that form at altitudes below 6,000 meters are full of spherical water droplets, which bounce back light in the same direction that the light came to them. The laser light bounces off all of these small water droplets in the clouds in such an amount that the graph of the backscattered light is able to show that something was in that area, something that reflects more light than what is in the atmosphere around it.
The other important graph that ProcEarl gives us is the "Depolarization Ratio" graph. It shows the amount of depolarized light that EARL collects. As mentioned before, this light is usually bouncing off of non-spherical particles like ice, dust, pollen, ash, etc. Ice generally forms from water that exists in clumps in the upper atmosphere above 7 kilometers. Usually, ice at these high levels indicates cirrus clouds, which contain heavy amounts of ice and exist in the upper troposphere. However, ice at these high levels can also indicate contrails, which form from the exhaust of a plane that flies through the upper atmosphere. This exhaust condenses into ice and can show up on a graph like the one above. Generally, if something shows up on the "Depolarization Ratio" graph, then it also shows up on the graph of "Range Corrected Backscatter" discussed above.
With the EARL, we can track how pollen rises during the day, how the temperature varies at differing levels of the atmosphere, what type of objects are in the sky, and more. If volcanic ash was moving through the upper atmosphere within our range, then we would be able to see it.
With the EARL, we can track how pollen rises during the day, how the temperature varies at differing levels of the atmosphere, what type of objects are in the sky, and more. If volcanic ash was moving through the upper atmosphere within our range, then we would be able to see it.