[ncl-talk] height issue

[ali mughal]

Dear Everyone

I guess the differences in the plots were because elevation from wrfout is
extracted by the following equation

*ELEVATION_THETA(i,j,k) =0.5*(PHB(i,j,k) + PH(i,j,k) + PHB(i,j,k+1) +
PH(i,j,k+1))/9.81*


Further information is provided in the following threads.

https://forum.mmm.ucar.edu/phpBB3/viewtopic.php?f=39&t=9831
https://wiki.openwfm.org/wiki/How_to_interpret_WRF_variables


Let me know if this is the correct reason for the differences I observe in
the plots.


On Mon, Jan 24, 2022 at 6:59 PM ali mughal <mughalali655 at gmail.com> wrote:

> Dear NCL users
>
> I reported this issue a few days ago.
>
> if I subtract the terrain height from the code by adding the following step
>
>
>
> ter=  wrf_user_getvar(a, "ter",-1)
> nheight = conform(z,ter,(/0,2,3/))
> z_agl = z-nheight
>
> do level=0, nlevels-1
>
>  height=levels(level)
>
>
> u_plane = wrf_user_intrp3d( u,z_agl,"h",height,0.,False)
> v_plane = wrf_user_intrp3d( v,z_agl,"h",height,0.,False)
> ta_mean_plane = wrf_user_intrp3d(ta_mean_a ,z_agl,"h",height,0.,False)
>
> I get the following plot
>
> [image: image.png]
>
>
> As you can see there is change in the field compared to the plots I shared
> earlier but white spaces are removed.
>
> Now I am not able to understand what is causing the white spaces earlier
> and why they are removed when I subtract the terrain height.
>
> In the following example, a similar procedure is followed, however, the
> only difference between my code and the one in the example is the wrf file
> used in the example is for multiple time steps while I am using a file
> which is generated with cdo as an hourly average.
>
>
> https://www2.mmm.ucar.edu/wrf/OnLineTutorial/Graphics/NCL/Examples/LEVELS_INTERP/wrf_Height.ncl
>
>
>
>
>
>
>
>
> On Fri, Jan 21, 2022 at 6:58 PM ali mughal <mughalali655 at gmail.com> wrote:
>
>> Dear NCL community
>>
>> I attach the output from two ncl scripts. The first one
>> (Seabreeze_hourly_Ind_avg.png)  interpolates temperature and wind field to
>> the first pressure level from WRF out file. If I convert the pressure level
>> to the height in m it comes out to be 10 m. The 2nd output I obtain by
>> using the following method instead of using the first pressure level
>>
>> levels = (/30.,35.,40.,45.,50.,55.,60.,65.,70.,75.,80.,85.,90./)
>> nlevels=dimsizes(levels)
>>
>> do level=0, nlevels-1
>>
>>   height=levels(level)
>>   u_plane = wrf_user_intrp3d( u,z,"h",height,0.,False)
>>   v_plane = wrf_user_intrp3d( v,z,"h",height,0.,False)
>>   ta_mean_plane = wrf_user_intrp3d(ta_mean ,z,"h",height,0.,False)
>>   U_1=u_plane(0,:,:)
>>   V_1=v_plane(0,:,:)
>>  ta_mean_1=ta_mean_plane(0,:,:)
>>  tc2=ta_mean_1-273
>>
>> As you can see that the first level is 30m, considerably higher than the
>> first pressure level but in the first plot, there are no white spaces which
>> mean every thing is plotted above the terrain while in the second plot
>> there are white spaces meaning these are points below the terrain.
>> Can someone kindly let me know how I can remove this difference ?
>>
>> Regards
>>
>> Ali
>>
>>
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