[ncl-talk] Error when using center_finite_diff_n

[Lyndz]

Dear Sir Dennis,

Thank you for this.
My data has missing values, that's why  I used cfd.

Sincerely,

On Thu, Mar 4, 2021 at 7:28 AM Dennis Shea <shea at ucar.edu> wrote:

>
> Given the dimension sizes (73x144), I am sure the data are global.
> In fact, a 2.5 degree grid. I speculate, it is ordered North-to-South.
>
> I am not sure why you used centered finite differences (cfd).
> Of course, it can be done. However, it is recommended to use the "highly"
> accurate spherical harmonic functions.
> ===
> Based on your script, try the following. **If ** your source grid is
> ordered South-to-North, no reordering is needed. Skip that part.
> ====
>
>   ufile  = addfile("uwnd_2008.nc","r")       ; open netcdf file
>   u   = short2flt(ufile->uwnd(:,{925},:,:))                             ;
> pull u off file
>
>   vfile  = addfile("vwnd_2008.nc","r")
>   v   = short2flt(vfile->vwnd(:,{925},:,:))                             ;
> pull v off file
>
> ;*******************************************************************
> ; Spherical harmonics require the data to be South-to-North
> ; Skip this step if source data are already South-to-North
> ;******************************************************************
>
>   u = u(:,::-1,:)                  ; make grid South-to-North
>   printVarSummary(u)
>   printMinMax(u,0)
>   print("-------------")
>
>   v = v(:,::-1,:)                  ; make grid South-to-North
>   printVarSummary(v)
>   printMinMax(v,0)
>
> ;*******************************************************************
> ; calculate vorticity on a Global Fixed Grid via spherical harmonics
> ;*******************************************************************
>
>   vr = uv2vrF_Wrap (u,v)
>   printVarSummary(vr)
>   printMinMax(vr,0)
>   print("-------------")
>
>
> ;**********************************************************************************
> ; calculate wind component gradients on a Global Fixed Grid via spherical
> harmonics
>
> ;**********************************************************************************
>
>   u_grad_lon = u                ; create arrays to hold output, same size
> and type as input
>   u_grad_lat = u
>   gradsf (u, u_grad_lon, u_grad_lat)
>   u_grad_lon at long_name = "U longitudinal gradient: dUdX"
>   u_grad_lon at units     = "1/m"
>   u_grad_lat at long_name = "U latitudinal gradient: dUdY"
>   u_grad_lat at units     = "1/m"                        ; (m/s)*(1/m) = 1/m
>   printVarSummary(u_grad_lon)
>   printMinMax(u_grad_lon,0)
>   print("-------------")
>   printVarSummary(u_grad_lat)
>   printMinMax(u_grad_lat,0)
>   print("-------------")
>
>   v_grad_lon = v                ; create arrays to hold output, same size
> and type as input
>   v_grad_lat = v
>   gradsf (v, v_grad_lon, v_grad_lat)
>   v_grad_lon at long_name = "V longitudinal gradient: dVdX"
>   v_grad_lon at units     = "1/m"
>   v_grad_lat at long_name = "V latitudinal gradient: dVdY"
>   v_grad_lat at units     = "1/m"
>   printVarSummary(v_grad_lon)
>   printMinMax(v_grad_lon,0)
>   print("-------------")
>   printVarSummary(v_grad_lat)
>   printMinMax(v_grad_lat,0)
>   print("-------------")
>
>
> On Wed, Mar 3, 2021 at 10:35 AM Lyndz via ncl-talk <
> ncl-talk at mailman.ucar.edu> wrote:
>
>> Dear. NCL-experts,
>>
>> I want to get the dV/dx and dU/dy when calculating the relative vorticity.
>>
>> I tried using the *center_finite_diff_n* but encountered this error:
>>
>> *fatal:center_finite_diff_n: r must either be a scalar, a 1D array the
>> same length as the dim-th dimemsion of q, or the same size as q*
>>
>> *fatal:["Execute.c":8637]:Execute: Error occurred at or near line 39 in
>> file orig_vort.ncl*
>>
>>
>> Attached file is the script that I am using.
>>
>> The input file has the following dimension:
>>
>> *Dimensions and sizes: [time | 4] x [lat | 73] x [lon | 144]*
>>
>>
>>
>> I am using the lat and lon for dY and dX, respectively.
>>
>> I'll appreciate any help on this matter.
>>
>>
>> Sincerely,
>> Lyndz
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>
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