[ncl-talk] A Chinese Student Has Some Questions about ORCA.

[Mary Haley]

Dear Yidi Xue,

Unfortunately, I do not have these data files. The examples you reference
were for an NCL workshop we conducted at CERFACS, and these scripts were
for those students to use on their own datasets.

NCL cannot generate vectors from triangular meshes (yet).  Do you have the
data in any other format, like two-dimensional lat/lon arrays?

One possible idea is to regrid your data, but you have to be careful with
regridding vector data.  You can read about vector regridding in the
Climate Data Guide, https://climatedataguide.ucar.edu (search on
"regridding overview"):

Vector interpolation (eg, U, V) should be performed on the vector pair
simultaneously. Interpolating U, then separately, interpolating V may be
adequate for some purposes, but not if the interpolated vector components
were subsequently used to derive (say) divergence. An indirect approach
would be to (a) calculate the scalar quantities vorticity and divergence on
the source grid; (b) interpolate these scalar quantities to the destination
grid using standard methods; and then, (c) derive the U and V from the
rotational and divergent wind components.



--Mary


On Wed, Nov 4, 2015 at 7:40 PM, 薛一迪 <1027958839 at qq.com> wrote:

> Dear the NCL webmaster,
>
>      Hello, I am a Chinese student, and I feel very sorry about that I
> will take your valuable time. I want to use NCL to treat the files which
> the grid is ORCA025. I find some examples in the website, such as
> http://www.ncl.ucar.edu/Training/Workshops/CERFACS/Scripts/ORCA/ and
> http://www.ncl.ucar.edu/Applications/orca.shtml. I need the datasets in
> these examples because my files are different from them and I want to know
> the information of them. The datasets are
> PSY4V2R1_1dAV_20110531_20110601_gridU_R20110601.nc and
>  PSY4V2R1_1dAV_20110531_20110601_gridV_R20110601.nc . I do not find them in
> the website. What’s more, I have attached the information and a script in a
> word. I want to draw a picture of the vector of the sea surface current
> velocity. But I fail to do that. This is my first time to treat ORCA
> dataset. It is a triangular grid. I do not know how to read them. Can you
> give me some suggestions?
>
>    Thanks for your time and attention. I would appreciate it very much if
> you give me a reply.
>
> Best regards,
>
> Yidi Xue from China
>
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