Extracting wind speed at 100-meter height.

[shahbaz757]

Hi, I want to ask how can I get the wind speed at my desired height (10m, 50m, 100m and 200m).

In the wrfout netcdf file, I get wind speed at 45 pressure levels but I don't know how to interpret these pressure levels at meters. can you please tell me how to understand pressure levels?

I am attaching my namelist file which I am using currently please check it out. I am also defining the z_levels in my namelist file, but I am not sure which output variables gives me values at that defined z_levels.

Can you please tell me what is the best practice and method to get the wind speed at my desired height in meters from the wrfout file?

Thank you so much
Shahbaz Khan

 

[Ming Chen]

Shahbaz,
Vertical interpolation is required to put wrfout data from eta levels to either pressure level or height level. NCL and Python both have the capability of vertical interpolation. Please take a look at the documents;
For NCL:

wrf_interp_3d_z

NCL built-in functions (interpolation)

www.ncl.ucar.edu

For Python:

wrf.vertcross — wrf-python 1.3.4.1 documentation

 

[shahbaz757]

Hi,

Thanks for your reply, I understood the method to vertical interpolate and get wind speed in meters.

Is the eta levels like vertical grid points? how to interpret the eta levels?
If my model output has 45 eta levels then what is it comparable to in-meter height?

 

[Ming Chen]

If I understand your question correctly,
(1) eta levels are vertical levels and they correspond to vertical grid points
(2) to understand eta levels , please see this document
https://www2.mmm.ucar.edu/wrf/users/docs/technote/v4_technote.pdf

 

[shahbaz757]

Thank you so much, Ming you gave a clear explanation.
I understood

 

[HARISH]

Hello.
There is an option in WRF namelist.input to obtain the common variables at pressure or vertical levels.
Take a look at the following in the namelist.input
&diags:
p_lev_diags = 1, ! Vertically interpolate diagnostics to p-levels
0=NO, 1=YES
num_press_levels = 0, ! Number of pressure levels to interpolate to, for example,
could be 2
press_levels = 0, ! Which pressure levels (Pa) to interpolate to, for example
could be 85000, 70000
use_tot_or_hyd_p = 2 ! Which half level pressure to use: 1=total (p+pb); 2=hydrostatic
(p_hyd). The p_hyd option is the default and less noisy. Total
pressure is consistent with what is done in various post-proc
packages.
z_lev_diags = 0, ! Vertically interpolate diagnostics to z-levels
0=NO, 1=YES
num_z_levels = 2, ! Number of height levels to interpolate to
z_levels = 0, ! List of height values (m) to interpolate data to.
Positive numbers are for height above mean sea level (i.e. a flight level)
Negative numbers are for levels above ground