Best practice for adding high-resolution urban morphology data into WRF (UCM/BEP) via WPS

[sarah.navin]

Hi everyone,

I’m working with WRF v4.6.0 + WPS 4.6 and running simulations with SLUCM / BEP over a metropolitan area.

I have high-resolution urban morphology data (building height, plan area fraction, street width) derived from GIS sources.

My main confusion is about the correct workflow to ingest custom urban parameters into WRF, specifically:

1. Should custom urban fields (e.g., mean building height, PAF, FRC_URB2D) be introduced through WPS geogrid tables, or is modifying URB_PARAM.nc the recommended approach?
2. If using geogrid, which urban fields are actually read by SLUCM vs BEP in WRF 4.6, and which are ignored?
3. Is there an example of a minimal but complete set of urban canopy variables required for BEP to function correctly?

I’m aiming for a physically consistent setup rather than trial-and-error tuning.

Any guidance, documentation pointers, or real-world examples would be highly appreciated.

Thanks in advance.

 

[cenlinhe]

Hi, to answer your questions:
1. to ingest your customized data into WRF/WPS, you could either do it by adding it directly to the default geo_em.d01 file you generated to modify those fields (e.g., building height, PAF, FRC_URB2D) if you have the spatially-varying 2D fields for those urban parameters. If you only have a mean value for the entire urban region, the easiest way is to modify the URB_PARAM.TBL (text look-up table).
2. For geo_em file, the urban field used is FRC_URB2D and URBPARM variables. Both are used by SLUCM and BEP. The URBPARM variable is a 3-D matrix, with a middle dimension of 132 elements:
Based on the NUDAPT-44 packing used by WPS, the 132 indices are grouped like this (index ranges are 1-based as documented):

• 1–15: Frontal Area Density at 0° (15 vertical bins, 0–75 m in 5 m bins)
• 16–30: Frontal Area Density at 135°
• 31–45: Frontal Area Density at 45°
• 46–60: Frontal Area Density at 90°
• 61–75: Plan Area Density (15 vertical bins)
• 76–90: Roof Area Density (15 vertical bins)
• 91: Plan Area Fraction
• 92: Mean Building Height
• 93: Std Dev of Building Height
• 94: Area-weighted Mean Building Height
• 95: Building Surface-to-Plan Area Ratio
• 96–99: Frontal Area Index (4 directions)
• 100: Complete Aspect Ratio
• 101: Height-to-Width Ratio
• 102: Sky View Factor
• 103–104: Roughness length / displacement (Grimmond & Oke 1999)
• 105–112: Roughness length / displacement (Raupach 1994; 4 directions)
• 113–117: Roughness length / displacement (Macdonald et al. 1998; 4 directions + displacement)
• 118–132: Distribution of Building Heights (15 bins)

3. For BEP, you can take a look at the run/URBPARM.TBL look-up table which indicates what are the urban parameters needed for BEP (sf_urban_physics = 2).