There are many different flavors of HIBAL projects (high altitude balloons). Unless you can find the specific reference to a specific project, it seems difficult to track down what the purpose of the balloon is. I've seen them a couple of times in the NM deserts. Sometimes you can find a HIBAL NOTAM about them if you catch them when they are flying.
Here is the Wikipedia page for the Google Project Loon. At the bottom of the article there are links to other uses of high altitude balloons and tons of references.https://en.wikipedia.org/wiki/Project_Loon
And, great pictures, by the way!