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   Car headlamp fogbows - Simulation 

  Fogbow supernumeraries and glory rings are rich material for comparisons with simulations although the divergence of the headlamp beam introduces some uncertainty in the derived droplet sizes.   The lower section is an IRIS calculation for droplets of mean diameter 9.6 micron and a narrow size distribution (6% std.dev).   Droplets of greater size variation give supernumerary rings which are too diffuse.   

Marko Riikonen says, "Fog with uniformly sized droplets is always fresh, just formed. On that night we found a place where fog formed and disappeared continuosly. So it was very interesting...     ...usually fog stays where it's formed and you do not then get a full set of arcs all the way from glory to fogbow because the droplet distribution is uneven. On the other hand, I think the places where fog comes and goes are not that rare. "

Car fogbow from "older" fog.