# [ncl-talk] plotting spatial average of wind vector from wrf output

Dennis Shea shea at ucar.edu
Sun Dec 26 17:05:28 MST 2021

```I have no idea what *wrf_vector *is doing within the function. That
function was written by WRF developers.
Maybe, you could look

%> less .../.../WRFUserARW.ncl                    search for *wrf_vector*
-------------------------------------
NCL's *wind_direction *will return meteorological direction

*dir10_avg = wind_direction
<http://www.ncl.ucar.edu/Document/Functions/Contributed/wind_direction.shtml>(u10_avg,
v10_avg, 1) ; meteorological wind direction*

On Sun, Dec 26, 2021 at 12:28 AM sangeeta maharjan via ncl-talk <
ncl-talk at mailman.ucar.edu> wrote:

> Hi,
>
> I have been using  " vector = wrf_vector(a,wks,u10,v10,opts)" for
> plotting wind vector distribution from wrf output.
>
> Inorder to plot the monthly average spatial wind vector distribution , I
> computed the average of u10_avg and v10_avg .
>
> On using the same function, " vector =
> wrf_vector(a,wks,u10_avg,v10_avg,opts)", I got a very odd plot
> distribution.
>
> As mentioned in "Technical note of  averaging wind speed and direction" by
> Stuart K. Grange , average wind direction  is arctan(u10_avg/v10_avg)+flow
>
> where flow =+ 180  for arctan (u10_avg/v10_avg) < 180
>                   =- + 180  for arctan (u10_avg/v10_avg) >180
>
> Could you kindly suggest how to plot wind vectors from averaged u and v
> components.
>
> Any help is appreciated.
>
> Kind regards,
> Sang
> _______________________________________________
> ncl-talk mailing list
> ncl-talk at mailman.ucar.edu
> List instructions, subscriber options, unsubscribe:
> https://mailman.ucar.edu/mailman/listinfo/ncl-talk
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.ucar.edu/pipermail/ncl-talk/attachments/20211226/0d9b06f4/attachment.html>
```