Scheduled Downtime
On Friday 21 April 2023 @ 5pm MT, this website will be down for maintenance and expected to return online the morning of 24 April 2023 at the latest

ifsnow and sf_surface_physics

Hi everybody,
I am a bit confused about the ifsnow option in namelist.input. According to the WRF User's Guide, ifsnow=1 only works with sf_surface_physics=1, but I have seen some examples with ifsnow=1 and sf_surface_physics=2. For instance, the namelist.input in exercise 1 at the WRF-Chem Tutorial webpage ( has this combination.
I have the same issue with the icloud option, which is supposed to work only with ra_sw/lw_physics=1 or 4, according to the WRF User's Guide. However, in the link above, we can see icloud=1 and ra_sw_physics=2.

I would appreciate it if someone could explain this to me.
Last edited:
If you run with sf_surface_physics= 2 and you set ifsnow =1, then the model will simply ignore the option ifsnow =1, i.e., it doesn't have any impact on the model integration. The same for icloud = 1.