may I ask for what purpose you are asking that question? It could help to understand what you are aiming at.
"patchy fog"....modern visual renderings attempt to model clouds and fog as particle masses, generated from a database of different cloud types, with some added pseudo-random "growth", and then calculate the interaction with light sources, light absorption, scattering, shadows; and occlusion of objects behind as seen from point of view
blowing snow or sand can be modeled in the same way, but to make a wild guess (because I didnt pay attention to that), accurate generation of blowing sand visuals is a less common feature in certified flight simulators , than clouds/fog/rain/snow, but sandstorms are commercially available.
depending on your needs, you can go about the modeling of underlying physics for volumetric cloud visuals in very complex ways, including modelling fluid motions, thermodynamic processes, buoyant forces, and water phase transitioning. Yet cloud visuals are "fluff", to a degree, not on the top of the list of requirements, appendix H to FAR 121 lists few requirements for visuals (the closest you get to clouds is that they mention proximity of a thunderstorm):
https://www.law.cornell.edu/cfr/text...121/appendix-H
I once did some work for a system integrator who built various simulators, in the last millenium. Entire books were devoted only to 3D clouds, and complexity of visuals and simulations has increased a lot since then, is all I know
maybe ask your training dept, or friendly sim instructors, if they have any tech specs lying around?
I can't answer how many simulators are equipped with what technology, vendors would be the best source for that information, they usually visit know their (potential) customers, and get a birds-eye view I don't have now.
here are some pointers, not sure if they help:
Clouds
https://www.metavr.com/products/vrsg...ml#Environment
SilverLining 3D Clouds and Skies for OpenGL and DirectX