[ncl-talk] Clarification in velocity potential (fixed grid) calculations

[Dennis Shea]

attached a 'my' calculation script and figure.

On Wed, Apr 26, 2017 at 10:14 PM, Lyndon Mark Olaguera <
olagueralyndonmark429 at gmail.com> wrote:

> Dear all,
>
> I am trying to plot the divergent winds and velocity potential using a
> modified version of wind_3.ncl (https://www.ncl.ucar.edu/
> Applications/wind.shtml) in the NCL page. I am doing the calculation for
> a fixed grid.
>
> *I am not sure if I'm doing the calculations correctly.*
>
> I have some problems with the velocity potential calculation. The results
> do not agree with the divergent winds (e.g. divergent winds at 200hPa
> should correspond to negative velocity potential).
>
> I think I am missing something in the script or I am incorrectly doing the
> calculations.
>
>
> I am calculating the divergent winds and velocity potential like this:
>
>  * ;Divergence*
>   div = uv2dvF_Wrap(u,v)
>
>   chi = uv2sfvpF(u,v)
>   chi := chi(1,:,:,:)                     ; 1 for velocity potential
>   chi = (/chi/1e6/)                     ; arbitrary scale
>   chi at long_name = "velocity potential"
>   chi at units     = "m/s"
>   printVarSummary(chi)
>
>
> *;Divergent wind components*
>
>   ud    = new ( dimsizes(u), typeof(u), u at _FillValue )
>   vd    = new ( dimsizes(v), typeof(v), v at _FillValue )
>   dv2uvf(div,ud,vd) ; div  ==> divergent  wind components
>
> *;Plotting*
> plot=gsn_csm_vector_scalar_map(wks,ud(0,:,:),vd(0,:,:),chi(0,:,:),res)
>
>
> Here are the data files that I am using.I am also attaching the sample
> image and script here.
>
> [VWIND] https://drive.google.com/file/d/0B9faET7Bc2o8MzlGVUZsMjdHa28/
> view?usp=sharing
>
> [UWIND]
> https://drive.google.com/file/d/0B9faET7Bc2o8QTh1OG4zOVYtVlU/
> view?usp=sharing
>
>
> I'll appreciate if anyone can suggest any way to improve this.
>
>
> Sincerely,
>
> Lyndz
>
> _______________________________________________
> ncl-talk mailing list
> ncl-talk at ucar.edu
> List instructions, subscriber options, unsubscribe:
> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20170428/6b5e4654/attachment-0001.html 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: lyndon.ncl
Type: text/x-ncl
Size: 5248 bytes
Desc: not available
Url : http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20170428/6b5e4654/attachment-0001.bin 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: lyndon.png
Type: image/png
Size: 429163 bytes
Desc: not available
Url : http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20170428/6b5e4654/attachment-0001.png