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How to produce HFX and LH at different heights?

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Z

Z_wendy

New member
Hi all,
I am studying the urban physics, especially BEM. Some experiments were finished these days, but I am not sure if the parameters in URBPARM.TBL are set correctly. And how to output sensible heat flux and latent heat flux at different heights? i know the symbols "HFX" and "LH" mean sensible heat flux and latent heat flux respectively. Here are the files (attached).

Thank you!
 

Attachments

  • namelist input.txt
    5 KB · Views: 68
  • URBPARM TBL.txt
    11.9 KB · Views: 83
When we talk of sensible and latent heat fluxes in WRF, we refer to the fluxes at the surface (i.e., HFX and LE). These fluxes are then distributed within PBL with boundary layer eddy fluxes and allow for PBL growth by entrainment. RTHBLTEN and RQVBLTEN are temperature and water vapor tendencies in the PBL, which are directly linked to surface fluxes. WRF doesn't output heat fluxes at each model levels.
Parameters in URBPARM.TBL may not be accurate because they are determined based on specific cases/locations.You can always modify the values based on the specific case your are studying.
 
Thank you for your reply. I still have some doubt about the parameter settings in URBPARM.TBL. 1. How can I choose the specific urban type, such as the second one (Hi-dens Res)? I am not sure if it is right to alter only the second column parameters.
2. If I want to modify albedo or emissity of buildings, is it okay to change the values of roof, wall and ground in URBPARM.TBL? I have tried this method but the results do not seem to have changed. I notice that the files, LANDUSE.TBL and VEGPARM.TBL, both have the corresponding parameters. So I‘d like to know if I should set the corresponding parameters in the three files at the same time.
 
Please see my answers below:

1. How can I choose the specific urban type, such as the second one (Hi-dens Res)? I am not sure if it is right to alter only the second column parameters.

These urban type are only roughly defined. I don't think they are accurate. You definitely can make changes based on your case.

2. If I want to modify albedo or emissity of buildings, is it okay to change the values of roof, wall and ground in URBPARM.TBL? I have tried this method but the results do not seem to have changed. I notice that the files, LANDUSE.TBL and VEGPARM.TBL, both have the corresponding parameters. So I‘d like to know if I should set the corresponding parameters in the three files at the same time.

If you run with urban scheme activated, then thee values from URBPARM.TBL are used for those grid points defined as urban landuse type. So changing the values in this TBL file should lead to changes in the simulation.
 
Thank you for the reply.I am clear about the parameters in URBPARM.TBL.

I'll be grateful if you can give further guidance on the output variables. I have learned that the sensible heat ejected into the atmosphere by an air conditiong system (△Hs) , sensible heat pumped out for cooling (Hsout) and latent heat pumped out for cooling (Hlout) can be calculated when sf_urban_physics = 3. I looked through the file "Registry.EM_COMMON", and noticed some relevant variables, "SF_AC_URB3D", "LF_AC_URB3D", and "CM_AC_URB3D" that can be obtained from wrfout files.

I think the variables, △Hs, Hsout and Hlout can't be generated directly. Maybe they are derived from the above two variables, "SF_AC_URB3D" and "LF_AC_URB3D", like the following relationships?
Hsout = SF_AC_URB3D * Area_building
Hlout = LF_AC_URB3D * Area_building

Thanks for any suggestion.
 
Please change the lines below in Registry.EM_COMMON:

state real SF_AC_URB3D ij misc 1 - r "SF_AC_URB3D" "SENSIBLE HEAT FLUX FROM THE AIR COND." "W m{-2}"
state real LF_AC_URB3D ij misc 1 - r "LF_AC_URB3D" "LATENT HEAT FLUX FROM THE AIR COND." "W m{-2}"
state real CM_AC_URB3D ij misc 1 - r "CM_AC_URB3D" "CONSUMPTION OF THE AIR COND." "W m{-2}"

Change them to
state real SF_AC_URB3D ij misc 1 - rh "SF_AC_URB3D" "SENSIBLE HEAT FLUX FROM THE AIR COND." "W m{-2}"
state real LF_AC_URB3D ij misc 1 - rh "LF_AC_URB3D" "LATENT HEAT FLUX FROM THE AIR COND." "W m{-2}"
state real CM_AC_URB3D ij misc 1 - rh "CM_AC_URB3D" "CONSUMPTION OF THE AIR COND." "W m{-2}"

Then type ./clean -a and recompile WRF

With the above changes, these variables will be included in wrfout files.
 
Thank you for the reply.

I have tried the method and it works. Now I'm doing some urban cases to analyze the local climate change with air conditioners on. And I notice that there is another output variable, GRDFLX (ground heat flux). I'm confused about the relationship among GRDFLX, HFX (upward sensible heat flux at the surface) and LH (latent heat flux at the surface). I wonder if the surface refers to the ground. If so, GRDFLX should be equal to the sum of HFX and LH at the same time，right? Actually, I can't find the above relationship among the three variables in my case.


Thanks for your advice.
 
GRDFLX is the heat flux that goes into the ground. It is one term in the surface energy budget equation:
HFX + LH + Radiation + GRDFLX = 0
 
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