Data Interpretation with a double line graph
That looks a double axis or dual axis graph but isn't well done or I don't understand clouds well enough. It is almost like a Sankey diagram. Problems:


What does the X axis convey, if anything?
It appears that the cloud types are relatively stratified but I'm not sure what causes the waviness over the X axis. Is it related to the two lines for temperature and pressure?


Compare that to a phase diagram like below. I'm not a chemist, but this is a lot easier for me to interpret. The x axis is the temperature, the y axis is pressure, and the lines clearly show where the material switches phases, similar to cloud types. There isn't ambiguity at any point about which phase would be in place. Now try figuring out what type of cloud you would have in your diagram at 30C and 8psi.