Set the water cloud asymmetry factor for all wavelengths and altitudes to a float 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 wc_files. It doesn't make sense to modify only the first moment of an explicit phase function.  

wc_set_gg value

 
This option is useful only for monochromatic calculations or in wavelength regions where the optical properties of water clouds can be considered constant, e.g. the ultraviolet range.