[ncl-talk] ESMF regrid for large array data

[Dennis Shea]

Given no responses, I speculate no user knows how to generate the edge
vertices.

*https://www.ncl.ucar.edu/Applications/ESMF.shtml*
<https://www.ncl.ucar.edu/Applications/ESMF.shtml>

Example 6 reads the vertices from a file.

ESMF_regrid_6.ncl:    Opt at SrcGridCornerLat = sfile->lat_vertices    ;
corners are necessary
ESMF_regrid_6.ncl:    Opt at SrcGridCornerLon = sfile->lon_vertices    ; for
"conserve" method

===
The text above the examples contains:

" You can (and are highly recommended to) provide your own grid corners via
the special Src/Dst/GridCornerLat/Lon resources. They must be provided as
an *N* x 4 array, where *N* represents the dimensionality of the center
lat/lon grid. For example, if the center lat/lon grid is dimensioned 256 x
220, then the corner arrays must be 256 x 220 x 4. Sometimes the corner
grids are provided on the file along with the center grids, with names like
"lat_vertices"/"lon_vertices" or "lat_bounds"/"lon_bounds"."

Good Luck

On Wed, Mar 23, 2022 at 7:17 AM Anil Kumar - NOAA Affiliate via ncl-talk <
ncl-talk at mailman.ucar.edu> wrote:

> Hi All,
> I am using ncl script for esmf regrid and converting unstructured onto WRF
> grid.
> There is nothing wrong with the script, it was working fine with the
> previous unstructured grid nodes ( node = 1813443).
> Now I am facing issues running these scripts for new unstructured data
> nodes ( node = 6057307). It is taking a long time and CPU time terminates
> the script and even job_script takes more than 8 hours and time limitation
> issues with job_scripts.
> Any suggestions to resolve this issue? Below is my script
>
> However, when I run script, it says
>  This can be VERY slow if you have a large array.
> (0)                           To speed up code, provide your own edge
> vertices via the
> (0)                           'ElementVertices' option.
> How to use ElementVertices?
>
> *******************************************************
>  src_file = "../fort.63.nc"
>  sfile = addfile(src_file,"r")
>  lat1D = sfile->y
>  lon1D = sfile->x
>  var = sfile->zeta(89,:)
>
>  dst_file = "../geo_em.d01.nc"
>  dfile    = addfile(dst_file,"r")
>   Opt                = True
>
> ;---"bilinear" is the default. "patch" and "conserve" are other options.
>     Opt at InterpMethod     = "neareststod"        ;;---Change (maybe)
>     Opt at WgtFileName      = "unstruct_to_rect_2906_D1.nc"
>     Opt at SrcGridLat       = lat1D
>    Opt at SrcGridLon       = lon1D
>     Opt at SrcRegional      = False            ;;--Change (maybe)
>     Opt at SrcInputFileName = src_file          ; optional, but good idea
>
>     Opt at SrcMask2D        = where(.not.ismissing(var),1,0) ; Necessary if
> has
>                                                           ; missing values.
>
>     dst_lat              = dfile->XLAT_M(0,:,:)    ; Be sure to use
> appropriate names
>     dst_lon              = dfile->XLONG_M(0,:,:)   ; here.
>     Opt at DstGridLon       = dst_lon
>     Opt at DstGridLat       = dst_lat
>     Opt at DstRegional      = True            ;;--Change (maybe)
>     Opt at ForceOverwrite   = True
>     Opt at Debug            = True
>     Opt at PrintTimings     = True
>     var_regrid = ESMF_regrid(var,Opt)     ; Do the regridding
>     printVarSummary(var_regrid)
>
> --
> Dr. Anil Kumar
> Environmental Modeling Center/NCEP/NWS/NOAA
> College Park, MD, USA
>
>
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