Water, earth and air

[Jorge_Stolfi]

I'm a little confused with the different terminology being thrown around here

Again, the confusion is only that there is a heraldry element called "nebuly" that is a simple line with "bulbous" undulations and apparently referred to clouds, without any cosmic connections.   It seems to be totally unrelated to the "cloud-band" ("wolkenband") we are discussing and which is used in your examples. 

but these "undulations" patterns [are indeed]used to depict - I think - a seperation between the earth and other planes of existence (heaven, the sky etc).

Yes, the "cloud-band" seems to be a conventional graphical device used specifically for that purpose.   In the same class as the halos used to identify saints, or the pointy things used to represent stars, or the disk with fiery frame representing the the sun.

More precisely, the cloud-band seems to represent the "vault of the sky" -- that, in medieval cosmology, lies above the stars and planets, and holds up the vast ocean of the "waters above".

examples of a non-frilly line ... There is an example of this in You are not allowed to view links. Register or Login to view.  Here is saturn: So I think it is possible that the pattern does not always require the exact frilly pattern, it just matters that the reader understands that the pattern represents a cosmic boundary of sorts.

Good point.  Perhaps the inspiration of the VMS artist was a diagram with a non-frilled but still 3D cloud-band, like that in this example.

However, just after the section on 53v (You are not allowed to view links. Register or Login to view.) a frilly undulation-like pattern is used to depict the 10th heaven.

Interesting.  I suppose that was part of the standard "cosmology" of the times.  (IIRC, the vision of Paradise in the Divina Commedia had several levels.  I am not sure because I read only the Hell part -- the other two were too boring...) 

There is also use of frilly wolkenbands for what seem to be actual clouds, immediately after a non frilly pattern used as a boundary, on folios 108-110. So it's clear that the meanings of each style were flexible, at least.

I think that the cloud-band in that example still represents the "vault of the sky".  At that time, people did not know that rain came from water evaporated from the seas and other water bodies.  In their view (based on the Bible, which in turn was based in Sumerian cosmology) the rains came from the "waters above", percolating through the "vault of the sky".  The Biblical Flood, in particular, came from that source as well as from the "waters below":

11 In the six hundredth year of Noah’s life, on the seventeenth day of the second month—on that day all the springs of the great deep burst forth, and the floodgates of the heavens were opened.

I suppose that people knew that clouds were somehow associated with rain, but did not realize that rain came from the clouds.

All the best, --stolfi