[ncl-talk] interpolation

[Ehsan Taghizadeh]

 Thank you so much for your help.The script works now, correctly.1- However could I ask what the main reason(s) for the difference between "linint2_points" and "bilinear" in "ESMF_regrid" is(are)? I mean why the outputs of these two methods are different?I took a glance on these pages: "http://www.ncl.ucar.edu/Applications/ESMF.shtml", "http://earthsystemmodeling.org/esmf_releases/non_public/ESMF_6_1_1/ESMF_refdoc/node5.html#SECTION05012600000000000000", "http://earthsystemmodeling.org/esmf_releases/non_public/ESMF_6_1_1/ESMF_refdoc/node5.html#SECTION05012600000000000000" and they help me a lot.
2- Beside that why the following two lines have to be commented?";    setfileoption("nc", "FileStructure", "Advanced");    setfileoption("nc", "Format",  "NetCDF4Classic")
"
Albeit there isn't setfileoption in examples like this "http://www.ncl.ucar.edu/Applications/Scripts/ESMF_regrid_13.ncl".
SincerelyEhsan    On Tuesday, July 24, 2018, 4:27:49 AM GMT+4:30, Dennis Shea <shea at ucar.edu> wrote:  
 
 I modified your script.

Use only "bilinear" and/or "nearest neighbor' . 

"patch" is *NOT* appropriate. I was/is for highly accurate derivatives. as needed for say ocean curl.

Please read all ESMF documentation.

On Sat, Jul 21, 2018 at 5:43 AM, Ehsan Taghizadeh <ehsantaghizadeh at yahoo.com> wrote:

 Thank you for your help.I'd used ncl scrip which was written by ncl-talk group, to interpolate GPM data to station points, in ASCII format.After finishing work, and sending paper to journal, referee wants to know the effect of other interpolating methods. So I decided to use some other methods to interpolate GPM data on station points.I've tried ESMF regridding library as you suggested. However I faced the error:"ESMF_regrid_gen_weights: 'ESMF_RegridWeightGen' was not successful."Beside that I have to write output file in ASCII format.I've attached first script (Interpolating_bilinear.ncl) which works correctly via bilinear method, and second script (Interpolating_ESMF.ncl) which uses ESMF regridding. Also input data are attached (GPM_IMERGV04DE_20160401_ 20170228 directory and stations_NW.csv file which contains destination lat/lon).Could I have your help to modify "Interpolating_ESMF.ncl" to use different interpolating methods (bilinear", "neareststod", "patch")?Also could I have your opinion to answer the referee about using different interpolating methods? Is it necessary to use different interpolating methods and comparing them?
;;;;;;;;;;;;;;;;;;;;;;;;;;;;$ ncl -V    6.5.0$ uname -a    Linux localhost.localdomain 3.10.0-514.2.2.el7.x86_64 #1 SMP Tue Dec 6 23:06:41 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux$ gcc --version    gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-28)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;

SincerelyEhsan
    On Thursday, July 19, 2018, 10:22:38 PM GMT+4:30, Dennis Shea <shea at ucar.edu> wrote:  
 
 Without the printVarSummary() of your 'z' variable, it is hard to tell what the problem might be:

function dspnt2 (
                x  [*] : numeric,  
                y  [*] : numeric,
                z      : numeric,  
                xo [*] : numeric,  
                yo [*] : numeric
        )

This assumes a cartesian grid. Still: lon[*] and lat[*] are commonly input to the function as x[*] and y[*]

=====
However, I am not evne going to deall with the 'dspnt2. Please use the ESMF regridding library.


  http://www.ncl.ucar.edu/ Applications/ESMF.shtml

Something like:

    var = f->FOO    
    printVarSummary(var)
    printMinMax(var,0)

    interp_method = "bilinear"   ; "neareststod", "patch"
    wgt_file_name = "wgt.ESHAN_"+interp_method+". nc"   Opt                 = True
  Opt at SrcGridLat      = lat     ; rectilinear lat[*]
  Opt at SrcGridLon      = lon     ;      "      lon[*]

  Opt at DstGridLat      = ulat    ; unstructured latitudes  
  Opt at DstGridLon      = ulon    ;      "       longitudes
 
  Opt at InterpMethod    = interp_method

  Opt at WgtFileName     = wgt_file_name

  
  var_regrid = ESMF_regrid(var,Opt)     ; Do the regridding    printVarSummary(var_regrid))
    printMinMax(var_regrid,0)

PLEASE *CAREFULLY* READ the documentation and examples.


On Thu, Jul 19, 2018 at 2:04 AM, Ehsan Taghizadeh <ehsantaghizadeh at yahoo.com> wrote:

Hi,Is there any interpolation method from rectilinear grid to an unstructured grid other than bilinear interpolation in NCL, like kriging, nearest point, etc? However I found this link (https://www.ncl.ucar.edu/ Support/talk_archives/2011/ 0595.html) which states "There is no kriging interpolation function in NCL".Beside that could "dspnt2" be used to interpolate from rectilinear grid to an unstructured grid? However it seems it couldn't and following error is the subject "fatal:dspnt2: the rightmost dimension of z must be the same as the dimension of x and y".
I'll be thankful for any help.
SincerelyEhsan

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