Good question. This number does not have any intrinsic units. Here are the notes from the code (the person who wrote it is not here today):

"Several constants control the look of the plume. I was not sure how big to make a plume. The parameters are the Amount and ElapsedTime. I just multiply the amount and time together. That did not seem big enough so I added a WeightingFactor of 10. Nothing special about the value. I just picked it because it made the plume big enough.

Wind stretches the plume circle into a ellipse. The amount of stretch is determined by the WindRatio constant. When the wind speed reaches the WindRatio constant of 20, then the ellipse is twice as long as the original circle. The width of the ellipse is reduced so the total area of the plume is the same."

This built-in model is quite simplistic. Depiction is a platform where experts can write addins that provide higher fidelity models, or completely different models. We are working on an publishing an SDK to make this easier. In the meantime, if you are interested in doing this, please send email to info@depiction.com.

 Have you considered having Depiction interface with CAMEO in lieu of using MARPLOT?

A LOT of EM folks are trained on CAMEO, so it was seem to me that this would be a useful capability.