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How to use urb_param morphology parameters instead of urbparm_lcz morphology paramaters


New member

I am using WRF 4.4. I use wudapt (w2w) to generate a geogrid file and I implemented the urb_param index in the geogrid file. I would like to simulate UHI with bep+bem scheme (sf_urban_physics = 3). I set surface_input_source to 3 and use_wudapt_LCZ to 1 in the namelist.

There are values in my geogrid and met.em files but it seems they are no urb_param in wrf.input when i run ./real.exe.

How does WRF use urb_param index info instead of urbparm_lcz parameters? I am not sure WRF uses urb_param index instead of urbparam_lcz ?

How can I assure that WRF use urb_param morphology parameters in wrfinput files with urbparam_lcz.tbl implemented for thermal and building characteristics ?

Thank you for your help.

The URBPARM table used during the model run is dependent on your namelist option "use_wudapt_lcz".

For use_wudapt_lcz = 0, you will run with URBPARM.TBL

For use_wudapt_lcz = 1, you will run with URBPARM_LCZ.TBL

If you run WPS with LCZ data included, then you must run with use_wudapt_lcz = 1. Otherwise the model will crash.
Hi thank you for your answer.
I understand that and already set use_wufapt_lcz to 1 to use urbparm_lcz.tbl, everything runs right.

I choose to define urban parameters in urb_param index in geogrid file (with ncdump/ncgen) for use in BEP+BEM scheme like Plan Area Fraction (91), Building Surface to Plan Area Ratio (95) etc to have a definition of urban parameters for each cell of the grid. These urb_param data appear also in my metgrib file after run.

I used LCZ Land use data, so I had to define urbparm_lcz.tbl for thermal and building caracteristics but at the end there are also some street (width) and building (width and heights) parameters for each LCZ classes.

Wen i run .real.exe in my wrfinput_d there are some parameters : Build Area Fraction, Distribution of Building Heights, etc., which seems to correspond to the urb_param data set in my geogrid file.

I would like to know how WRF knows how to use urb_param data for each cell in geogrid and metgrid files instead of urbparm_lcz street and building data for each LCZ class. I want to assure that WRF uses urban parameters for each cells (with urb_param) and not average values obtained for each LCZ class (with urbparam_lcz). I am working in UHI simulation in my PhD and would like to understand it correctly.

Thanks to you again.

I think you can try to first read and understand the subroutine code in read_param, urban_param_init, and urban_var_init in the phys/module_sf_urban.F
Each grid cell has its landuse type (including urban type), and the characteristic urban parameters at each grid cell are determined based on landuse type at this cell and corresponding values in "urbparam_lcz".

I agree that you may need to read the related codes listed by tslin2 (thank you, tslin2 ! ) to fully understand how the model works.