How is radiation in snow calculated in CLM4 with -snicar_frc=off?

[wadewei]

I understand that -snicar_frc is off by default in CLM4 or CLM4.5. Can somebody kindly explain how radiation in snow is calculated when SNICAR is off?
For what it's worth, I am running CESM1.2.2 with -phys cam4 -prog_species DST, i.e. prognostic dust, and would like to examine the effect of a larger-than-PI dust loading on the climate.

 

[slevis]

Other community members are encouraged to respond.

Meanwhile though I wanted to mention that you are working with unsupported versions of the model; however, you can always look at the code to answer your question.