Question about Noah-MP vegetation parameters and LAI source

[seti]

Dear WRF Support Team,

I am currently using WRF v4.6.0 with the Noah-MP land surface model (sf_surface_physics = 4) for winter simulations (January) over a complex mountainous region.

As part of a sensitivity study, I would like to modify several vegetation-related parameters in MPTABLE.TBL, including:

• Leaf Area Index (LAI)
• Stem Area Index (SAI)
• Roughness length (Z0MVT)
• Vegetation height (HVT)
• Other vegetation parameters available in Noah-MP

However, I am uncertain about how Noah-MP determines which vegetation parameters are actually used during the simulation.

I understand that WRF also generates vegetation-related fields (such as LAI and vegetation fraction) through the WPS/geogrid preprocessing system (geo_em, met_em, and wrfinput). At the same time, Noah-MP contains monthly vegetation parameters in MPTABLE.TBL.

My objective is to perform sensitivity experiments by modifying the values in MPTABLE.TBL. Therefore, I would like Noah-MP to use these modified values instead of the vegetation fields provided by the geogrid input.

Could you please clarify the following questions?

1. When using Noah-MP (sf_surface_physics = 4), under what conditions does the model read LAI, SAI, roughness length, vegetation height, and other vegetation parameters from MPTABLE.TBL, and under what conditions does it use the corresponding fields from geo_em/met_em/wrfinput?
2. Is there a namelist option (for example, dveg or any other option) that explicitly controls whether LAI comes from MPTABLE.TBL or from the input geogrid files?
3. If I modify LAI_JAN, SAI_JAN, Z0MVT, HVT, and other vegetation parameters in MPTABLE.TBL, what additional steps are required to ensure that Noah-MP actually uses these modified values during the simulation? For example, do I need to regenerate geo_em, met_em, or wrfinput, or is rerunning real.exe sufficient?
4. Is there any recommended way to verify from the WRF output or log files that Noah-MP is indeed using the modified values from MPTABLE.TBL rather than the vegetation information contained in the input files?

Thank you very much for your time and assistance.

Best regards,

 

[BHajni]

Hi,

There are options in the namelist with which you can adjust the Noah-MP settings (in noah_mp section, take a look at the README.namelist)
the dveg option is what you're looking for, but it only controls LAI and FVEG.

HVT and Z0MVT are not in the geo_em files I think, so they are read from the MPTABLE. Since the noah_mp options are in the namelist.input you only need to rerun real.exe (just in case, because real.exe is a menace).

To verify the application use outrageous but realistic numbers for one vegetation type, start your run at local noon, and stop after 1 hour, you should be able to see large differences in latent heat flux over the gridpoints of your chosen extreme vegetation.

&noah_mp
dveg = 4, ! Noah-MP Dynamic Vegetation option:
1 = Off (LAI from table; FVEG = shdfac)
2 = On (LAI predicted; FVEG calculated)
3 = Off (LAI from table; FVEG calculated)
4 = Off (LAI from table; FVEG = maximum veg. fraction)
5 = On (LAI predicted; FVEG = maximum veg. fraction)
6 = On (use FVEG = SHDFAC from input)
7 = Off (use input LAI; use FVEG = SHDFAC from input)
8 = Off (use input LAI; calculate FVEG)
9 = Off (use input LAI; use maximum vegetation fraction)

Cheers