Limitation in Road Width Parameter on the Urban Canopy Model

[geraldogomes]

I'm trying to run the WRF coupled to the Urban Canopy Model (Initially, with the SLUCM and later with the BEP and BEP+BEM) on the metropolitan region of São Paulo with LCZ, however the WRF stops without giving an error warning.

# ZR: Roof level (building height) [ m ] (sf_urban_physics=1)
ZR: 45.0, 15.0, 5.0, 40.0, 15.0, 5.0, 3.0, 7.0, 5.0, 8.5, 0.5

# SIGMA_ZED: Standard Deviation of roof height [ m ](sf_urban_physics=1)
SIGMA_ZED: 5.0, 3.0, 1.0, 4.0, 3.0, 1.0, 0.5, 1.5, 1.0, 2.5, 0.2

# ROOF_WIDTH: Roof (i.e., building) width [ m ] (sf_urban_physics=1)
ROOF_WIDTH: 10.0, 5.1, 4.3, 8.0, 5.3, 3.2, 3.0, 5.5, 2.9, 10.0, 0.2

# ROAD_WIDTH: road width [ m ] (sf_urban_physics=1)
ROAD_WIDTH: 10.0, 5.1, 4.3, 8.0, 5.3, 3.2, 3.0, 5.5, 2.9, 10.0, 10.0

I saw that there was a similar discussion here on the forum where it looks like I would have to increase the road width a lot (ROAD_WIDTH > 90 m) especially for the LCZ1 and LCZ4, and indeed the WRF manages to run but this value is unrealistic. I took a measurement and the average street width for the LCZ1 and LCZ4 is a maximum of 10-20 meters.

How do I run WRF-UCM (Single-layer and Multi-layer) with the values I initially chose?

 

[kwerner]

Hi,
I contacted one of the developers of the UCM to ask them this question. They responded that they don't know the exact answer. Their best guess is that what matters is not the value of road width, but the relative ratio of road width and building height, which determines the street canyon geometry parameters used for urban radiation and turbulence calculations. This is done in the urban_param_init subroutine in module_sf_urban.F. So if you want to keep a relatively realistic road width, but this is causing the model to crash, you'll need to also modify the building heights to allow WRF to run. The model likely crashes because the street canyon geometry causes some weird values in the urban radiation and turbulence calculations.

 

[jolasie]

Hi! I am curious if anyone has deal with the error thrown by WRF simulation with SLUCM and LCZ, which occurs after changing default values of URBPARM_LCZ.TBL (ZR,SIGMA_ZED, ROOF_WIDTH, ROAD_WIDTH) on more adequate for particular city. In my case simulations on the default table (URBPARM_LCZ.TBL) works fine, but after modifying values of urban canopy parameters the model receive SEGMENTATION FAULT error. Now I am testing which exactyl parameter (ZR,SIGMA_ZED, ROOF_WIDTH, ROAD_WIDTH) make an error in my case.