Set the aerosol asymmetry parameter for all wavelengths and altitudes to a constant value between -1.0 and 1.0. Please note that this option is only applied if a Henyey-Greenstein phase function is used but not if an explicit phase function is defined e.g. with a aerosol_files. It doesn't make sense to modify only the first moment of an explicit phase function.  

aerosol_set_gg value