Change in amount of vertical levels in the the metgrid files with newer a WPS version

[Bas Cammeraat]

Good afternoon,

Recently I switched from WRFV/WPS version 3.9.1 to 4.2. I found out that with the same initial data (latest GFS forecast data with 42 vertical levels) in WPS3.9.1 the amount of vertical levels also is 42 in met_em files, but when I execute the metgrid.exe with the newer WPS4.2 version the amount of vertical levels apparently is reduced to 34 levels. Is this just something that cannot be adjusted or is this adjustable?

I tried both

1. Use the &mod_levs command in the namelist.wps file.

This command allows you to specify which vertical levels are to be kept or removed from the original input dataset. To increase the number of vertical levels, simply add more levels to the keep list.

For example, the following namelist.wps commands would increase the number of vertical levels in metgrid to 34:

&mod_levs
keep = 1,42
end

and

1. Use the -v option on the metgrid command line.

This option allows you to specify the number of vertical levels to use in metgrid. To increase the number of vertical levels, simply pass a higher number to the -v option.

For example, the following command would increase the number of vertical levels in metgrid to 34:

./metgrid.exe -v 42



But still the the amount of Vertical levels remains the same. Does anyone know how to adjust it? Many thanks in advance!

Bas

 

[kwerner]

Hi Bas,
Are you using GFS data newer than June 2019? If so, take a look at this post that discusses the changes to GFS files and what that means for using WPS.

 

[Bas Cammeraat]

Thank you, I do. So according to that message the vertical levels in this case just automatically goes from 42 to 34 without any adjustments? But then the question is, how to I maintain the 42 vertical levels that I previously had? What do you actually mean with "If you do not use the supplementary pressure level data"?

 

[kwerner]

What do you actually mean with "If you do not use the supplementary pressure level data"?

I believe the wording was incorrect in that sentence, and should have been "If you do not use any supplementary pressure level data," meaning as long as you're only using GFS data, and no additional data, then...

It looks like if you use the "pmin" namelist variable in the ungrib section (prior to running ungrib and metgrid), you can adjust how many levels you get. I played around with this and found that setting it to 0 gave me 42 levels. Give that a try and let me know if it works.

 

[Bas Cammeraat]

I believe the wording was incorrect in that sentence, and should have been "If you do not use any supplementary pressure level data," meaning as long as you're only using GFS data, and no additional data, then...

It looks like if you use the "pmin" namelist variable in the ungrib section (prior to running ungrib and metgrid), you can adjust how many levels you get. I played around with this and found that setting it to 0 gave me 42 levels. Give that a try and let me know if it works.

This is indeed working for me as well. Thank you a lot!

 

[kwerner]

Great! Thank you so much for the update.