Clarification on AHE Data Selection in WRF-SLUCM with Custom Grid-Based Inputs

[ZHOU Wan]

Dear WRF Support Team,
I am running WRF version 4.6 with the Single-Layer Urban Canopy Model (SLUCM, sf_urban_physics=1) and have incorporated custom grid-based anthropogenic heat emission (AHE) data as well as Local Climate Zone (LCZ) data into the simulation. My question pertains to how WRF determines whether to use the input grid-based AHE data or the LCZ-based urban grid values from URBANPARAM_LCZ.TBL for calculating anthropogenic heat effects.

Key details of my setup:​

1. Custom AHE Input: I have provided externally derived spatially varying AHE data as an additional input in wrfinput (following the distributed_ahe_opt option).
2. LCZ Data: I have also modified the land use data to incorporate LCZ classifications, which correspond to predefined urban parameters, including AHE values, specified in URBANPARAM_LCZ.TBL.
3. WRF Physics Setting:
   • sf_urban_physics = 1 (SLUCM)
   • distributed_ahe_opt = 1 or 2 (to add AHE to temperature tendency or surface sensible heat flux)

Question:​

When WRF simulates the effect of anthropogenic heat emissions under this configuration, how does it determine whether to use the grid-based custom AHE data from wrfinput or the LCZ-based AHE values from URBANPARAM_LCZ.TBL? Specifically:

• Does enabling distributed_ahe_opt override the LCZ-based AHE values?
• If both inputs are present, does WRF combine them or prioritize one over the other?
• Is there a way to confirm in the model output which AHE data source is being used for urban grid cells?

I appreciate your guidance on how WRF selects and applies AHE data in SLUCM with LCZ integration. Wish your early answer, thanks!

 

[htan2013]

This is very interesting. I am also looking forward to some answers here.

 

[Ming Chen]

Please see my answers below:

Dear WRF Support Team,
I am running WRF version 4.6 with the Single-Layer Urban Canopy Model (SLUCM, sf_urban_physics=1) and have incorporated custom grid-based anthropogenic heat emission (AHE) data as well as Local Climate Zone (LCZ) data into the simulation. My question pertains to how WRF determines whether to use the input grid-based AHE data or the LCZ-based urban grid values from URBANPARAM_LCZ.TBL for calculating anthropogenic heat effects.

Key details of my setup:​

1. Custom AHE Input: I have provided externally derived spatially varying AHE data as an additional input in wrfinput (following the distributed_ahe_opt option).
2. LCZ Data: I have also modified the land use data to incorporate LCZ classifications, which correspond to predefined urban parameters, including AHE values, specified in URBANPARAM_LCZ.TBL.
3. WRF Physics Setting:
   • sf_urban_physics = 1 (SLUCM)
   • distributed_ahe_opt = 1 or 2 (to add AHE to temperature tendency or surface sensible heat flux)

Question:​

When WRF simulates the effect of anthropogenic heat emissions under this configuration, how does it determine whether to use the grid-based custom AHE data from wrfinput or the LCZ-based AHE values from URBANPARAM_LCZ.TBL? Specifically:

• Does enabling distributed_ahe_opt override the LCZ-based AHE values?

No, it doesn't. AH is still read into WRF from URBANPARAM_LCZ. TBL

• If both inputs are present, does WRF combine them or prioritize one over the other?

My understanding is that WRF uses values from both sources.

• Is there a way to confirm in the model output which AHE data source is being used for urban grid cells?

No, WRF doesn't provide this capability. However, one can always develop a post process utility to do so.

I appreciate your guidance on how WRF selects and applies AHE data in SLUCM with LCZ integration. Wish your early answer, thanks!

I will talk to our expert and he may provide more insights regarding this issue.

 

[cenlinhe]

1. The "distributed_ahe_opt" namelist option controls a specific AHE data that has been implemented into WPS. If you want to use this option to read in your own data, you could use your own AHE data/map to replace the one generated by default WPS in geo_em file.
2. The "distributed_ahe_opt" overlaps with the AHE specified from the urban parameter table, so if you use the "distributed_ahe_opt" option, please make sure you turn off the AHE in the urban parameter table for your simulation.
3. The "distributed_ahe_opt" directly adds the AHE to the temperature tendency or surface sensible heat flux after the land and urban model processes are done (i.e., outside urban code), while the AHE specified in urban parameter table adds AHE to the urban flux within the urban code. This is the key difference.
Here is the main code changes related to "distributed_ahe_opt" capabilities: [Resubmit for PR #1881] New option for SLUCM to use global distribute… · wrf-model/WRF@3cadf04