[ncl-talk] regridding CMIP5 coarse resolution output to high resolution (0.5 x 0.5) using area_conserve_remap_Wrap

[Dennis Shea]

Of course you can interpolate a coarse grid to a high resolution grid.
However, the high-resolution grid *does not contain any additional
information" then the original grid. Just more values.

ncl-talk is not going to tell you what method to use. You should try both
bilinear and conservative
and compare ... do difference plots. This is how you learn.

Generally, for the tyoe of varuiable you are interpolating ... conservative
is the better approach.

==

If you are new to NCL, ***please read the documentation***

http://test.www.ncl.ucar.edu/Document/Manuals/

http://test.www.ncl.ucar.edu/Document/Manuals/language_man.pdf

An excellent tutorial by DKRZ is here

https://dl.dropboxusercontent.com/u/8357888/homepage/tutoriais/ncl/NCL_Tutorial_V1.1.pdf
https://dl.dropboxusercontent.com/u/8357888/homepage/tutoriais/ncl/NCL_Exercises_and_Tasks_all.pdf

It is your responsibility to put forth the effort to learn the language.

Good Luck





On Fri, Jun 10, 2016 at 8:45 AM, Mary Haley <haley at ucar.edu> wrote:

> Samy,
>
> I'm not sure what you mean by your question.  Are you asking how to
> compare whether the regridding is correct or not?
>
> If you use ESMF regridding, and you have NCL V6.3.0, then you can set
>
>  Opt at Check = True
>
> This turns on the "--check" option in the regridding, which the ESMF folks
> describe as:
>
>  "This option performs a regridding operation on an analytic field using
> the weights and computes both the interpolation error and the conservation
> error (if used with a conservative interpolation method). These errors are
> then output to the user. "
>
> The output will look like this:
>
>       Grid 1 min:    1.0001662906361517          Grid 1 max:
>  2.9998337097885632
>       Grid 2 min:    1.0004992779714816          Grid 2 max:
>  2.9995007220286158
>
>       Maximum negative weight =    0.0000000000000000
>       Maximum positive weight =   0.74984053650072569
>
>       Mean relative error     =    1.9234096383084854E-004
>       Maximum relative error  =    4.4673574673482763E-003
>       Least squares error     =    2.4340317596281900E-004
>
>       Grid 1 area =    0.0000000000000000
>       Grid 2 area =    0.0000000000000000
>       Conservation error =    0.0000000000000000
>
> --Mary
>
>
> On Thu, Jun 9, 2016 at 7:36 AM, <ratebsamy at yahoo.com> wrote:
>
>> Hello NCL Team,
>>
>> Good afternoon. I am samy ashraf a phd student in ICTP institute and have
>> the output for carbon cycle parameters from CMIP5 on coarse resolution
>> (3.75 x 2.5 degree for example) and I want to regrid it to high resolution
>> (0.5 x 0.5) degrees using *area_conserve_remap_Wrap*
>> <http://www.ncl.ucar.edu/Document/Functions/Contributed/area_conserve_remap_Wrap.shtml>
>> in order to compare it with gridded observation data on 0.5 x 0.5, so my
>> question is the regridding is correct or not?
>>
>> Thanks in advance
>>
>> Best
>>
>> Samy
>>
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