Urban canopy parameters for BEP

[NinglvLi]

Hello ,


I’m running WRF-Urban with the BEP multilayer UCM for 1 km urban microclimate simulations. I noticed that even for BEP, different papers/documentation list different “urban morphology/canopy parameters”: some describe BEP inputs in street-canyon/building-scale terms (e.g., road width, building width, street direction, building height distribution as in URBPARM.TBL), while others provide grid-scale gridded UCPs via the URB_PARAM array (e.g., plan area fraction λp, area-weighted mean building height, building surface density/ratio λb, and height distribution).


Since my simulations are at 1 km resolution, I would like to use grid-scale (gridded) morphology inputs rather than LCZ-based lookup tables. However, I cannot find a clear “minimum required” list of parameters that BEP actually reads/needs in this gridded-input configuration.


Could you please clarify for WRF version [your WRF version]:

1. When BEP is enabled, what is the minimum set of gridded urban morphology fields that must be provided (e.g., FRC_URB2D and specific URB_PARAM indices)?
2. If certain fields are missing, does BEP fall back to URBPARM.TBL defaults, or will it fail?
3. Is there an official document (users guide/tech note) that explicitly maps BEP-required fields between URBPARM.TBL and URB_PARAM (especially for street parameters and building height distribution)?

Any pointers to the relevant documentation or code references would be greatly appreciated.


Best regards,

 

[Ming Chen]

Please see my answers below:

Hello ,


I’m running WRF-Urban with the BEP multilayer UCM for 1 km urban microclimate simulations. I noticed that even for BEP, different papers/documentation list different “urban morphology/canopy parameters”: some describe BEP inputs in street-canyon/building-scale terms (e.g., road width, building width, street direction, building height distribution as in URBPARM.TBL), while others provide grid-scale gridded UCPs via the URB_PARAM array (e.g., plan area fraction λp, area-weighted mean building height, building surface density/ratio λb, and height distribution).


Since my simulations are at 1 km resolution, I would like to use grid-scale (gridded) morphology inputs rather than LCZ-based lookup tables. However, I cannot find a clear “minimum required” list of parameters that BEP actually reads/needs in this gridded-input configuration.


Could you please clarify for WRF version [your WRF version]:

1. When BEP is enabled, what is the minimum set of gridded urban morphology fields that must be provided (e.g., FRC_URB2D and specific URB_PARAM indices)?

• FRC_URB2D and parameters from URBPARM.TBL are required to run BEP.

1. If certain fields are missing, does BEP fall back to URBPARM.TBL defaults, or will it fail?

Can you specify what fields might be missing? Generally, BEP will use default values (mainly from URBPARM.TBL).

1. Is there an official document (users guide/tech note) that explicitly maps BEP-required fields between URBPARM.TBL and URB_PARAM (especially for street parameters and building height distribution)?

I am not aware of such documents specifically maps BEP-required fields between URBPARM.TBL and URB_PARAM. But the two papers below may provide some helpful information:

Salamanca, F., and A. Martilli, 2010: A new building energy model coupled with an urban canopy parameterization for urban climate simulations––part II. Validation with one dimension off–line simulations. Theor. Appl. Climatol., 99, 345–356.
doi:10.1007/s00704-009-0143-8


Martilli A, Clappier A, and Rotach M.W., 2002: An urban surface exchange parameterization for mesoscale models. Bound.-Layer Meteorol., 104, 261–304.
doi:10.1023/A:1016099921195

Any pointers to the relevant documentation or code references would be greatly appreciated.


Best regards,

 

[QiSun]

May i consult you a technical question, in your wrfinput, the variable FRC_URB2D is all 0 or have some values? and for BUILD_HEIGHT, in my wrfinput. after incorporating LCZ map, the values are all 0, i am wondering if it is correct or not.

 

[Ming Chen]

FRC_URB2D is only available over CONUS. It is zero in other areas.

BUILD_HEIGHT should be read from URBPARM.

May i consult you a technical question, in your wrfinput, the variable FRC_URB2D is all 0 or have some values? and for BUILD_HEIGHT, in my wrfinput. after incorporating LCZ map, the values are all 0, i am wondering if it is correct or not.

 

[QiSun]

Thanks for the answer, may i consult how can i figure out if the LCZ map read properly in wrf, except changes of LU_INDEX from 21 to 60.

 

[Ming Chen]

LCZ has been introduced to WPS since WRFv4.3. Since then its application has been evolved quite a bit with several bug fixes.

I would recommend you run WPSV4.6, with the option below in namelist.wps:

geog_data_res = 'lcz_new+default','lcz_new+default'

Also remember that you should use

GEOGRID.TBL.ARW_LCZ as GEOGRID.TBL

This will ensure that you process LCZ correctly.

Please elt me know if you have any issues regarding LCZ.