How to get hourly snowfall?

[hss816]

Hi all,

I'm trying to get the hourly snowfall (in terms of equivalent water, mm) from WRF model. However, I'm confused about SNOWNC and ACSNOW.

I found the following information in the Registry.EM_COMMON
SNOWNC - "ACCUMULATED TOTAL GRID SCALE SNOW AND ICE" "mm"
ACSNOW - "ACCUMULATED SNOW" "kg m-2"

My question is:
1. SNOWNC only represents grid-scale snow and ice. I think it can't be used as it doesn't include snow from the unresolved scale. Is this Right?
2. Does ACSNOW represent accumulated snowfall? Does it melt during the simulation process?

Thank you very much!

 

[kwerner]

Hi,
If you're looking at a case that only had snowfall (no liquid precipitation), then you can use the value of RAINC + RAINNC because these equal total convective and non-convective precipitation (including snow and ice). Otherwise, yes, I believe ACSNOW would be the way to go. It is initialized to zero at the model initial time and then accumulates over time. Regarding melting, this variable is handled differently in various surface physics schemes. For whichever surface scheme you're using, you can take a look at specific code in the WRF/phys/module_sf_<scheme>.F file (for e.g., if you're using Noah, look in module_sf_noahdrv.F). Another option would be the SNOWH variable, which is the physical snow depth. You would need to subtract the depth at the previous hour so determine the hourly rate.

 

[hss816]

Hi,
If you're looking at a case that only had snowfall (no liquid precipitation), then you can use the value of RAINC + RAINNC because these equal total convective and non-convective precipitation (including snow and ice). Otherwise, yes, I believe ACSNOW would be the way to go. It is initialized to zero at the model initial time and then accumulates over time. Regarding melting, this variable is handled differently in various surface physics schemes. For whichever surface scheme you're using, you can take a look at specific code in the WRF/phys/module_sf_<scheme>.F file (for e.g., if you're using Noah, look in module_sf_noahdrv.F). Another option would be the SNOWH variable, which is the physical snow depth. You would need to subtract the depth at the previous hour so determine the hourly rate.

Thanks for your reply. It really helps.