wrf.exe stops with : "Scale the dt in the model accordingly" message.

[joyeede]

GFS data : 0.25 deg, dx : 6000 m. Timestep : 24s

I followed the instructions as in the links to adjust the dx accordingly: [Wrf-users] grid ratio & map factor and
Questions about time step

Previously, with the same namelists but with GFS data having 12 km instead of 0.25deg (~27 km), the wrf run was successful.

But after using the new gfs data of 0.25 deg (met_em files, wrfbdy_d01 file, and wrfinput_d0are successfully created), the wrf run stops with "Max map factor in domain 1 = 1.52. Scale the dt in the model accordingly.
D01: Time step = 24.0000000 (s)
D01: Grid Distance = 6.00000000 (km)
D01: Grid Distance Ratio dt/dx = 4.00000000 (s/km)
D01: Ratio Including Maximum Map Factor = 6.09976149 (s/km)
D01: NML defined reasonable_time_step_ratio = 6.00000000 "

I have tried with dx :3000, 3500, 4000, 5000 m and with adjusted timesteps. But still unsuceesful while running wrf.exe.

It will be a great help if anyone would look into it.

Thanks in advance.

 

[Ming Chen]

The message "Max map factor in domain 1 = 1.52" implies that something is wrong in your domain setting. Usually maps factor should be around 1.0.

Your domain center is located at 23N, and mercator may not be an ideal projection for this domain. Can you switch to lambert, then try again?

 

[joyeede]

I tried with lambert, and this time, the run stopped with the message that the map factor was at 1.26.
What do you suggest I do next?

 

[joyeede]

Another update:
I reduced the 6km to 3km, and now the map factor is reduced to 1.06.
Yet still the wrf run gets stopped with the similar comment : "Max map factor in domain 1 = 1.06."

 

[Ming Chen]

This error message might be misleading. I don't think the map factor of 1.06 could be a trouble for the model run.

Just a quick question: why did you set etac = 0.01? Its default value should be 0.2.

 

[joyeede]

The etac value has been causing issues for some time.
For value 0.2, the ./real.exe would stop showing the message of scaling dt accordingly.
But the message disappears with successful real.exe run when the etac value is set to 0.01.

 

[Ming Chen]

I guess the high topography in your domain caused issues in this case.
etac is the eta level above which eta surfaces are isobaric. For high topography domain, etac should be a small value, However, I am suspicious that 0.01 is way too small.

Can you set hybrid_opt = 0, then rerun real.exe and wrf.exe? Please let me know whether the case can run or not. Please also set
smooth_cg_topo = .true.

 

[joyeede]

Hi,

1. I tried with the new settings, but the outcome is the same.

2. Maybe it has something to do with the input data of ~27km. Maybe something to do with the grid ratio.

3. I have a question which may or may not be related to this current issue. If hourly gfs data is available but I only pick out input data of every three hours and leave out the in-between data and put "interval_seconds=10800", will it cause any discrepancy? The met_em files are successfully created but it was something that was bugging me.

Thanks

 

[joyeede]

Just to update you, I tried by putting 6km for dx and time_step = 36 (along with the new settings that you mentioned). Same outcome, again!

1. smooth_cg_topo = .true
smooth_option = 0 #should this setting be 0?

2. epssm = 0.2 #is this setting ok?

Thanks

 

[William.Hatheway]

this is the domain you wanted correct? From your namelist.wps

 

[Ming Chen]

Hi, joyeede,

Thank you for testing the case with different options. Please see my answers below:

Hi,

1. I tried with the new settings, but the outcome is the same.

2. Maybe it has something to do with the input data of ~27km. Maybe something to do with the grid ratio.

The input data could be an issue, and I don't have concerns regarding the grid ratio.
Where did you download GFS data?

3. I have a question which may or may not be related to this current issue. If hourly gfs data is available but I only pick out input data of every three hours and leave out the in-between data and put "interval_seconds=10800", will it cause any discrepancy? The met_em files are successfully created but it was something that was bugging me.

No, I don't think you need to worry for the skipped data. 3-hr interval forcing should be fine.

Thanks

 

[Ming Chen]

Hi,
Please see my answers be;ow:

Just to update you, I tried by putting 6km for dx and time_step = 36 (along with the new settings that you mentioned). Same outcome, again!

1. smooth_cg_topo = .true
smooth_option = 0 #should this setting be 0?

smooth_option is used for for parent domain when feedback is on.

2. epssm = 0.2 #is this setting ok?

I would suggest that you set it to a larger value, e.g., 0.6 or even 0.l9, because your domain is over the Tibetan Plateau.

Thanks

 

[joyeede]

this is the domain you wanted correct? From your namelist.wps

Hi,

Since the last reply, I changed the domain size a bit. Please find the attached namelist below.

 

[joyeede]

The input data could be an issue, and I don't have concerns regarding the grid ratio.
Where did you download GFS data?

Hi,
This is the link - Index of /pub/data/nccf/com/gfs/prod/gfs.20240909/00/atmos ( I downloaded those files in three hourly manner - gfs.t00z.pgrb2.0p25.f000 , gfs.t00z.pgrb2.0p25.f003 , ........and so on)

No, I don't think you need to worry for the skipped data. 3-hr interval forcing should be fine.

Okay.

 

[joyeede]

smooth_option is used for for parent domain when feedback is on

Oh okay. So as there is no nesting in my namelist yet, I guess it doesn't matter if the feedback is on and smooth_option is 0, right? (Sorry for the silly questions but I am just few months old in all this, which included a mind-boggling installation process too)

I would suggest that you set it to a larger value, e.g., 0.6 or even 0.l9, because your domain is over the Tibetan Plateau.

Okay, I am trying that. Thanks.