It’s been implemented successfully in another engine here:
I think atmospheric scattering integration could only serve to improve the quality of outdoor environments with a fairly high degree of autonomy.
This would make outdoor more realistic.
Would anyone be interested in pursuing this feature as a community contribution?
Happy to supply any art and content necessary to kick this off.
Object lighting part was my favorite.
We do have atmospheric fog:
https://docs.unrealengine.com/latest/INT/Engine/Actors/FogEffects/AtmosphericFog/index.html
Is that not what you are looking for?
Hey there . 
Unfortunately, the current feature is an approximation, such that I cannot recreate the level of accuracy and depth in UE4 that I see above.
For example, the mountains do not appear to be occluded in any truly volumetric way by the atmospheric ‘fog’. It seems the current implementation does not fully or accurately take geometry into account when scattering the light throughout the world. I think it could and should be taken the full 9 yards.
Another strong indication for me is the colors of the sky sphere in the unreal docs. They appear false, over-saturated and unnatural as opposed to the pastel subtlety one can expect in the natural world. The example I shown above appears to approximate Mie and Rayleigh scattering in a more natural way.
So, better atmospheric scattering? Stuff that takes into account actual volumetric shadowing and global illumination, along with anistropic participating media is doable today at the high end. Up to how important the devs at Epic feel it is.
Indeed. Certainly worth adding onto the roadmap?
Hi everyone -
I have entered a feature request to add improvements to the Atmospheric Fog currently in the engine based on your suggestions above. (UE-15979, for reference)
Thank You