Vertical velocity(W) in vtable

[dakyoung]

Hi,
Why doesn't metgrid name have vertical velocity(W) in Vtable.GFS, Vtable.ECMWF?
The reason why only U and V are included except for W is that WPS and WRF basically only consider horizontal direction?

Thank you!

 

[dakyoung]

And I have another question. How does W exist in the "wrfout_* " file when W (vertical velocity) is not included in the Vtable? I don't understand how it's calculated.

 

[Ming Chen]

Vtable only provide GRIB parameters for variables required to run WRF. 'w' is not a variable required, and thus it is not included in Vtable.
"W' is a pronostic variable, which is calculated in WRF based on the equation:

∂tW +(∇·Vw)−g[(α/αd)∂ηp−μd]=FW

Detailed description can be found in https://www2.mmm.ucar.edu/wrf/users/docs/technote/v4_technote.pdf

 

[dakyoung]

When I printed out W(vertical velocity), it came out as attached csv file.
However, at certain parts of all levels, the value appears to be zero as if it were missing.
Can I know why or how to solve it?

 

[Ming Chen]

w =0 at some poins is physically reasonable. If something went Wong, w will be NaN.

 

[dakyoung]

If W=0 is a valid value, why does W get 0 at the same position at all levels? (1000mb,950mb... 70mb)
My guess is that the more oceans are included in the nesting area, the more this happens. Can you tell me why? Thank you.

 

[dakyoung]

Is there anyone who can help me?

 

[Ming Chen]

I suppose w==0 is from your forcing data, not from wrfout. Please let me know if I am wrong.

 

[dakyoung]

Please provide information on the files or relevant settings that can handle the vertical velocity(W) high-resolution processing in WRF.

• Note that high-resolution processing of vertical velocity refers to an increase in the number of vertical velocity points at specific isobaric surfaces.