wrf albedo data interpolation from 12month to 6hours

[Pinto]

Dear WRF modelers,

I have a question regarding the usage of the sst_update option to read-in the time-varying data. Twelve monthly values of albedo are available from the geogrid program.
The question is how are the 12 monthly values interpolated into 6h time steps when one runs real.exe?

Thanks in advance
Pinto