Vertical velocity(W) in vtable

dakyoung

New member
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

New member
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

Moderator
Staff member
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

New member
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

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

dakyoung

New member
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

New member
Is there anyone who can help me?

Ming Chen

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

dakyoung

New member
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.