Noah-MP with new landcover category, albedo, roughness

Topics related to current and future physics in the WRF as well as any problems you may have.

Noah-MP with new landcover category, albedo, roughness

Postby emilyp » Wed Nov 27, 2019 9:38 am


Short version: Does anyone know how albedo and surface roughness are input into WRF for the Noah-MP land surface scheme?

Longer version:
I am trying to add a new landcover category into WRF, to represent debris-covered glaciers. I am using the Noah-MP land surface scheme. The process I have used is as follows:

1. Define a debris-covered glacier outline, and add this to the USGS default WRF land categories database.
2. The area that was previously "land-ice" in LU_INDEX is now split into two different categories, "land-ice" and "debris-cover". Both categories have the same soil type (of ice) in ISLTYP.
3. Change the values in the LANDUSE.TBL (not used by Noah-MP, I think), VEGPARM.TBL and MPTABLE.TBL

run WRF.

However, it seems that Noah-MP does not use the values in VEGPARM.TBL to determine albedo, surface roughness etc. Whist changing the value for albedo in these tables changes the wrfout variable "ALBBCK", this seems unrelated to "ALBEDO", at least after a few hours into the simulation (the change in albedo from albbck seems to appear once the sun rises?). I understand that it only uses these tables for vegetation parameters. Debris-cover is barren, so all the vegetation parameters have been set to the same as "barren/sparsely-vegetated".

Does anyone know how albedo and surface roughness (and other parameters such as surface heat capacity, surface emissivity etc) are calculated or input in the Noah-MP scheme? Looking at the code suggests that albedo is calculated based on short-wave radiation, but I don't see how outgoing short-wave radiation at the surface could be calculated without albedo.

I also note that vegetation parameters such as LAI are set to NaN values over ice, whereas they are 0 in the "barren/sparsely-vegetated" landcover category. Does anybody know why they are not 0 over ice?

Any help would be hugely appreciated!

Many thanks,

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