[ncl-talk] Problem with interpolation

[张 南水]

Dear Sir,
   I have a problem to interpolate potential vorticity to isentropic levels. All the data is derived from NCEP-DOE Reanalysis 2. The potential vorticity is obtained via the function "pot_vort_isobaric", and so as to the potential temperature. And the interpolation is done by the function "int2p_n". However, plenty of undefined grids appear in the the potential vorticity field at an isentropic level, see 350K. And the undefined grids, which locate at the same position for all time, are not coherent with the topography. I have no idea that how does those undefined grids appear and how to deal with it? Thank you for your attention to this matter.
The version of NCL I used is 6.4. And my system is Ubuntu 16.0 on windows 10. My script is as following and the image is attached.
;==========================================================================
  begin
  f1 = addfile("/mnt/e/NCEP/NCEP-R2/Daily/pv/pv.2010.nc<http://pv.2010.nc>","r")
  f2 = addfile("/mnt/e/NCEP/NCEP-R2/Daily/pt/pt.2010.nc<http://pt.2010.nc>","r")

  pv = f1->pv
  time = f1->time
  theta = f2->pt

  ; lvl = ispan(270,400,10)*1.
  lvl  = (/ 300, 350, 400/)                              ; user specified inentropic levels
  lvl at description = "isentropic level"           ; add meta data
  lvl at units       = theta at units
  lvl!0           = "lvl"
  lvl&lvl         =  lvl



  ; pv2 = int2p(theta(time|:,lat|:,lon|:,level|:), \
  ;             pv(time|:,lat|:,lon|:,level|:), lvl, 1)
  pv2 = int2p_n(theta, pv, lvl, 1, 1)

  pv2!0    = "time"                      ; name dimensions
  pv2!2    = "lat"
  pv2!3    = "lon"
  pv2!1    = "lvl"
  pv2&time =  time                    ; assign coordinates
  pv2&lvl  =  lvl                          ; isentropic levels
  pv2&lat  =  pv&lat
  pv2&lon  =  pv&lon
  pv2 at long_name = pv at long_name           ; attributes
  pv2 at units     = pv at units

 ;------output
  fNameo = "/mnt/e/NCEP/NCEP-R2/Daily/pv_pt/pv.2010.nc<http://pv.2010.nc>"
  system("/bin/rm -f " + fNameo)
  fout = addfile(fNameo,"c")
  fout at title = " potential vorticity"
  fout at creation_date = systemfunc("date")
  filedimdef(fout,"time",-1,True)
  fout->pv = pv2

end

;==========================================================================


Yours,
Nanshui


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