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Understanding wind

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J

janac4

Member
Hello,
I'm daily running a 96h WRF with the attached namelist.input file.
To represent wind properly I need to understand bottom-top levels related to real height in meters, but I don't know how to do it.
I have never changed ztop variable and I'm not sure if it is related somehow.
Also with the representations I have made, I found that U and V variables barely change during in magnitude and direction neither in vertical levels or during time evolution, which doesn't seem real.
Thanks for your help,
Jana.
 

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Jana,
I looked at your namelist.input and I have a few concerns:
(1) For real-data case, you should specify p_top_requested instead of ztop
(2) parent_grid_ratio = 1, 5,
parent_time_step_ratio = 1, 5,
These two option should be consistent
(3) radt had better be the same for all domains
(4) delx = 5km is a typical grey-zone resolution, at which cumulus scheme emery not work well. Yet it is also not cloud-resolving.

For the model level height, you can get geopotential at each level by PH + PHB. PH and PHB are standard output variables in wrfout files.
 
Hello Ming Chen,
Thanks for your reply. About ztop variable, how much trouble could it cause using ztop=2000? Could we divide ztop/e_vert to get difference height in meters between bottom-top levels?
Also, which p_top_requested value would you suggest? (We are using GFS files as input data).
Geopotential height would be great but it is time dependent, is there a way to get estationary height differences in bottom-top levels (for example ztop/e_vert or p_top_requestes/e_vert?).
Jana.
 
Jana,
I often set p_top_requested - 3000 if any study is focused on thee troposphere. Using GFS with this p_top value should be fine.
As for geopotential height, it is a time-varying variable and I don't think you can stay with a fixed value.
 
Hello again, thanks for your explanation. I am gonna try to run the model with your suggestion instead of using ztop=2000. Do you think results will be very different? I have always tested and configured the model without changing ztop and don't wanna lose all the work done.
Regarding bottom-top levels, is there a way to associate for example bottom_top index = 10 to a height of 500hPa or similar?
Thanks again,
Jana
 
Janase za,
I am not sure of your first question. We never really run real data case with specification of ztop.
For your second question, you need to try different settings and manage to make vertical level 10 located at around 500 hpa. It is practical but needs some work to make it.
 
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