How to change the number of vertical layers?

[lo-y-wni]

Hello all UFS users and developers,

Does anyone know how to change the number of vertical layers?
The default number seems to be 65, however, I want to compare the results of UFS with WRF, so I need to set their coordination as the same as possible. Currently my ptop of WRF is 50 hPa and number of vertical layers is 51.
Because there is no any information of changing vertical coordination on web document, please teach me if you know how to do it. Besides, also tell me what should be changed if the number of vertical layers changed, please. (sponge layers for example)
Thanks a lot!.

Yi-Chuan

[ShawnCebulaNOAA]

Hello Yi-Chuan!

Thanks for the question. Are you talking about configuring the grid you're using in the SRW App? It looks like you should be able to set this up by creating a new grid and cloning the settings from an existing grid and changing that file. You can find this in the SRW documentation here. If you're talking about in the Weather Model, this is currently unsupported, but may be added in later versions.

[lo-y-wni]

Hello Shawn:

Thanks your response. Yes, I'm talking about the Weather Model and I have been able to customize the horizontal domain.
Look forward to see the changing of vertical resolution in later versions. The fixed vertical layer is really hard to compare with WRF fairly.

[gspetro-NOAA]

Hi Yi-Chuan,

Shawn is right that changing the levels is an unsupported feature in the UFS WM, but I was able to get some guidance from @BenjaminBlake-NOAA and @JiliDong-NOAA about how it could be done, and I have provided their answers below.

To start, you would have to create the text file global_hyblev_fcst.txt, containing ak/bk, to define the levels. You can use the vcoord_gen tool from UFS_UTILS or another tool of your choice to generate ak/bk.

The npz and levp variables also need to be reset in FV3 namelist file (input.nml). For 51 vertical layers, those numbers would be npz=50 and levp=51. But levels and layers are not the same, so if you are actually interested in having 51 vertical levels, then you should use npz=51 and levp=52:

&fv_core_nml
   npz = 50

&external_ic_nml
   levp = 51

The approaches for applying the new vertical coordinate in chgres_cube or in FV3 are also different. If the vertical level conversion is done in chgres_cube, as we are currently doing in the SRW App, the new text file will be specified in fort.41 when executing chgres_cube. You would need to make sure to set external_eta = .true. in input.nml.

Hope this helps!

Best,
Gillian Petro, EPIC Advanced User Support (AUS) Team

[gspetro-NOAA]

Hi Yi-Chuan,

I'm back with more information! @JiliDong-NOAA has kindly provided a file with the ak/bk of 51 layers in HRRR as an example:
HRRR_op_51.txt
If using chgres_cube, the first line needs to be changed to:

2     52

and one more line needs to be added at the bottom of the text file as:

0   0

These changes are not necessary when using FV3 for the vertical coordinate conversion.

@JeffBeck-NOAA suggested that you take a look at the technical documentation for for the FV3 dycore if you haven't already, since it may clarify what the different variables do and help you with any further trouble-shooting.

Best of luck!
Gillian

[lo-y-wni]

ohhhh! Many thanks your respond, Gillian.

The information really help me a lot and very thanks @JiliDong-NOAA provided HRRR file as an example. I'll take a look in it.
And may ask one more question? when you make the ak/bk file, how do you set pressure needed by vcoord_gen.exe?

!!   Example: Create the operational GFS 64-level hybrid coordinate.
!!     real(8) pmin,ak(0:64),bk(0:64)
!!     call vcoord_gen(64,64,100000.,99400.,7000.,0.,0.,500.,1200.,18000.,60.,60.,&
!!                  pmin,ak,bk)
!!     print '(2i6)',2,64
!!     print '(f12.3,f12.8)',(ak(k),bk(k),k=0,64)
!!     end
!!
!!   Graphical description of parameters and zones:
!!     ptop  ---  -----  ----------------------
!!           ...  dptop
!!           ---         zone U (upper atmos)
!!           ...
!!     pupp  ---  -----  ----------------------
!!           ...  dpupp
!!           ---  -----
!!           ...         zone P (pure pressure)
!!           ---
!!           ...
!!     ppre  ---  -----  ----------------------
!!           ...
!!           ---  dppre  zone T1 (transition 1)
!!           ...
!!           ---  -----  ----------------------
!!           ...
!!           ---
!!           ...         zone T2 (transition 2)
!!           ---
!!           ...
!!           ---  -----  ----------------------
!!           ...
!!           ---  dpsig  zone T3 (transition 3)
!!           ...
!!     psig  ---  -----  ----------------------
!!           ...
!!           ---  -----  zone S (pure sigma)
!!           ...  dpbot
!!     pbot  ---  -----  ----------------------
!! </pre>

There're lots of parameters needed in the program, and I heard that if I set something wrong, FV3 easily goes unstable. Is there any key points in it?

Yi-Chuan

[JeffBeck-NOAA]

Hi Yi-Chuan, Please see the UFS_UTILS repository documentation on vcoord_gen here <https://noaa-emcufs-utils.readthedocs.io/en/latest/ufs_utils.html#vcoord-gen>. Hopefully that will help. - Jeff

…

On Thu, Apr 6, 2023 at 7:12 PM lo-y-wni ***@***.***> wrote: ohhhh! Many thanks your respond, Gillian. The information really help me a lot and very thanks @JiliDong-NOAA <https://github.com/JiliDong-NOAA> provided HRRR file as an example. I'll take a look in it. And may ask one more question? when you make the ak/bk file, how do you set pressure needed by vcoord_gen.exe? !! Example: Create the operational GFS 64-level hybrid coordinate. !! real(8) pmin,ak(0:64),bk(0:64) !! call vcoord_gen(64,64,100000.,99400.,7000.,0.,0.,500.,1200.,18000.,60.,60.,& !! pmin,ak,bk) !! print '(2i6)',2,64 !! print '(f12.3,f12.8)',(ak(k),bk(k),k=0,64) !! end !! !! Graphical description of parameters and zones: !! ptop --- ----- ---------------------- !! ... dptop !! --- zone U (upper atmos) !! ... !! pupp --- ----- ---------------------- !! ... dpupp !! --- ----- !! ... zone P (pure pressure) !! --- !! ... !! ppre --- ----- ---------------------- !! ... !! --- dppre zone T1 (transition 1) !! ... !! --- ----- ---------------------- !! ... !! --- !! ... zone T2 (transition 2) !! --- !! ... !! --- ----- ---------------------- !! ... !! --- dpsig zone T3 (transition 3) !! ... !! psig --- ----- ---------------------- !! ... !! --- ----- zone S (pure sigma) !! ... dpbot !! pbot --- ----- ---------------------- !! </pre> There're lots of parameters needed in the program, and I heard that if I set something wrong, FV3 easily goes unstable. Is there any key points in it? Yi-Chuan — Reply to this email directly, view it on GitHub <#10 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ANFE566SLVRP6RUUMBB4KW3W75SW5ANCNFSM6AAAAAAWM3DVTE> . You are receiving this because you were mentioned.Message ID: ***@***.***>