# [ncl-talk] Wind_vector_query

Kyle Griffin ksgriffin2 at wisc.edu
Fri Jun 24 06:46:15 MDT 2016

```Kunal,

The plot function you reference is labeled **vector**, thus it plots a
vector. The i (or x, or longitude) direction is independent from the j (or
y, or latitude) direction. The two combine in each of their directions to
make a vector, as a gsn_csm_vector plot would be expected to do. The
function is defined such that the first variable given is in the i
direction, and the second variable is in the j direction. So yes, changing
the ordering of the variables your provide the function is effectively
rotating your grid, and yes, that changes the direction of your vectors.

NCL has separate functions for wind speed and wind direction, if that is
all you are looking for. Neither of those quantities are vectors, however,
and would be best plotted by a regular gsn_csm_contour plot.

Kyle

On Fri, Jun 24, 2016 at 12:06 AM Kunal Bali <kunal.bali9 at gmail.com> wrote:

> The resultant vector basically represents the equation
>  sqrt [(U-wind)2  + (V-wind)2]
>
>
> So if we use the function
>
> Plot = gsn_csm_vector_map(wks,u,v,res)
>
> Is that mean it is providing resultant wind plot or resultant wind
> direction with wind speed.
>
> If it is providing resultant wind plot, then using code (wks, v,u, res)
> instead of (wks, u, v, res). It is plotting different wind plot.
>
>
> If the code
> Plot = gsn_csm_vector_map(wks,u,v,res) plotting resultant wind vector
> using equation  sqrt [(U-wind)2  + (V-wind)2], Then it should plot the
> same resut in both the cases (wks, u,v, res) and (wks, v,u, res). Right ?
>
> please provide some information on that.
>
>
>
>
> Kunal Bali
> Research Scholar
> Radio & Atmospheric Science Division
> CSIR - National Physical Laboratory
> New Delhi - 110012
> India
>
>
>
>
>
> On Fri, Jun 24, 2016 at 9:50 AM, Kunal Bali <kunal.bali9 at gmail.com> wrote:
>
>> I could not understand, what to use
>>
>>
>>
>> Kunal Bali
>> Research Scholar
>> Radio & Atmospheric Science Division
>> CSIR - National Physical Laboratory
>> New Delhi - 110012
>> India
>>
>>
>>
>>
>>
>> On Thu, Jun 23, 2016 at 9:54 PM, Dennis Shea <shea at ucar.edu> wrote:
>>
>>> The function plots the resultant vector.
>>>
>>>
>>> http://www.ncl.ucar.edu/Document/Graphics/Interfaces/gsn_csm_vector_map.shtml
>>>
>>> On Sat, Jun 18, 2016 at 8:31 AM, Kunal Bali <kunal.bali9 at gmail.com>
>>> wrote:
>>>
>>>> Dear NCL users
>>>>
>>>> Please correct me. The code given below is just for potting wind
>>>> directions but not far resultant vector.
>>>>
>>>> Plot = gsn_csm_vector_map(wks,u,v,res)
>>>>
>>>> It will provide only zonal wind direction. If we modify above code with
>>>>  (wks,v,u,res) ‎then it will provide the meridional wind direction.
>>>>
>>>> So if I want to plot the resultant vector of u and v then what should I
>>>> do?
>>>>
>>>> Regards
>>>> Kunal bali
>>>>
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>>>
>>
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