Oligarch, here's what I found in one of the original missions (3.1):
function SetLight( level, time )
SetAmbientLight( GROUND, "fog_light_level"..level, true, time);
end;
The call is quite simple in one of the functions:
function IsOrnellaMeetArantir()
SetLight(2, 3);
end;
startThread(IsOrnellaMeetArantir);
The script location: Maps/scenario/A2C1M4
Maybe this will help ;)
But does it need to be applied to one of the regions, for example?