kwinter
Contributor
M-values are chosen, not measured or calculated.
You may want to rethink this. Gradient factors are chosen. M-values are most definitely calculated. They may be calculated differently by different models, but that doesn't alter what they represent. The maximum supersaturation level, essentially the line (if you agree they are linear) that represents the maximum safe differential. Rather than making blanket statements, I would rather refer the OP to read Erik Baker's classic "Understanding M-values."