Re: subtracting vectors from a netcdf file

Dear All,

Thanks for the reply. That works.

It is interesting that before going to the nc-talk I tried a similar way,
but it didn't work.

I tried:

u_pl14 = u(95,14,:,:)
u_pl09 = u(95,9,:,:)

v_pl14 = v(95,14,:,:)
v_pl09 = v(95,9,:,:)

delta_u = u_pl14 - u_pl09
delta_v = v_pl14 - v_pl09

plot = gsn_csm_vector_map_polar(wks,delta_u,delta_v,res)

I guess I didn't preserve the metadata?

Thanks!
Mariangel

On Thu, Sep 6, 2012 at 1:01 PM, David Brown <dbrown@ucar.edu> wrote:

> ; preserve the metadata
> usub = u(95,14,:,:)
> vsub = v(95,14,:,:)
> ; do the subtraction
> usub = u(95,9,:,:) - u(95,14,:,:)
> vsub = v(95,9,:,:) - v(95,14,:,:)
> plot = gsn_csm_vector_map_polar(wks,usub,vsub,res)
>
> I think that is all there is to it.
> -dave
>
>
> On Sep 6, 2012, at 12:55 PM, Mariangel Fedrizzi wrote:
>
> Hi,
>
> Is there an easy way to subtract winds at two different pressure levels
> from a netcdf file, in the ncl script?
>
> I have:
>
> Dimensions and sizes for a: [time | 96] x [plev | 15] x [lat | 90] x
> [lon | 20]
> a = addfile("file.nc","r")
> t = a->time
> u = a->zonal_wind
> v = a->meridional_wind
>
> I need to subtract:
>
> u(95,14,:,:) from u(95,9,:,:)
>
> and
>
> v(95,14,:,:) from v(95,9,:,:)
>
> and plot the resultant vector on a stereographic polar projection, which
> is already working for any given pressure level using:
> plot = gsn_csm_vector_map_polar(wks,u(95,9,:,:),v(95,9,:,:),res)
>
> In summary, I need to plot the resulting wind vector from the subtraction
> between values at two different pressure levels, but same time, lat, lon.
> These numbers are in the same netcdf file.
>
> Thanks.
>
> Best,
> Mariangel.
>
>
>
>
>
>
>
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>
>

-- 
===============================================
Mariangel Fedrizzi, Ph.D.
NOAA/SWPC - University of Colorado/CIRES
325 Broadway
Boulder, CO 80305
Tel: 1-303-497-3833
Fax: 1-303-497-3645
E-mail: Mariangel.Fedrizzi@noaa.gov
===============================================

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Received on Thu Sep 6 14:04:49 2012