[ncl-talk] Missing values after ESMF regridding

[Bian Qingyun]

Hello,

I'm regridding AMSR-E L3 daily snow following the examples on NCL website http://www.ncl.ucar.edu/Applications/Scripts/ESMF_regrid_13.ncl and hdf website http://hdfeos.org/zoo/index_openNSIDC_Examples.php#AMSR_E.

All is fine,but there are missing values along 90°E and 90°W after regridding while there are no missing values in original data along and near 90°E and 90°W 。

Followed is my script.

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load "$NCARG_ROOT/lib/ncarg/nclscripts/esmf/ESMF_regridding.ncl"

begin
;-----read data
    srcFileName = "AMSR_E_L3_DailySnow_V09_20100311.hdf"                   ; Source file
    eos_file   = addfile(srcFileName + ".he2","r")
    lon2d       = eos_file->GridLon_Northern_Hemisphere
    lat2d       = eos_file->GridLat_Northern_Hemisphere
  ; Process NAN (1e51) fillValue for LAMAZ geolocation.
    lon2d=where(lon2d .gt. 1000, -999.0, lon2d)
    lat2d=where(lat2d .gt. 1000, -999.0, lat2d)
    lon2d at _FillValue = -999.0
    lat2d at _FillValue = -999.0


    hdf_file = addfile(srcFileName, "r")
  ; Read the dataset.
    hdf_data = hdf_file->SWE_NorthernDaily

  ; Filter out invalid range values.
  ; See "Table 2. Pixel Values ofr the SWE Feids" from [2].
    hdf_data = where(hdf_data .gt. 240, hdf_data at _FillValue, hdf_data)

  ; Prepare data for plotting by converting type.
    swe2d = tofloat(hdf_data)
    swe2d at _FillValue = tofloat(hdf_data at _FillValue)

  ; Multiply by two according to data spec [2].
    swe2d = 2 * swe2d

  ; You can get the description of data set from the data spec [2].
    swe2d at long_name = "Northern Hemisphere 5-day Snow Water Equivalent ~C~ (" + hdf_data at hdf_name + ")"
    swe2d at units = "mm"
  ; Associate data with lat/lon.
    swe2d at lon2d = lon2d
    swe2d at lat2d = lat2d

;-----ESMF regridding
    Opt                   = True            ; Options for regridding

    Opt at SrcFileName       = "EASE_SCRIP.nc"  ; Output files
    Opt at DstFileName       = "NH_SCRIP.nc"
    Opt at WgtFileName       = "EASE_2_NH_patch.nc"
    Opt at ForceOverwrite    = True
    Opt at SrcMask2D         = where(ismissing(lat2d),0,1)
    Opt at SrcGridLat        = lat2d
    Opt at SrcGridLon        = lon2d

    Opt at DstGridType       = "0.25deg"       ; Destination grid
    Opt at DstTitle          = "Northern Hemisphere 0.25 resolution"
    Opt at DstLLCorner       = (/ 0.25d,   0.25d/)
    Opt at DstURCorner       = (/89.75d, 179.75d/)

    Opt at InterpMethod      = "bilinear"   ; Careful! Patch method takes a long time

    Opt at Debug           = True

    swe_regrid = ESMF_regrid(swe2d,Opt)    ; Regrid swe
    printVarSummary(swe_regrid)

;----------------------------------------------------------------------
; Plotting section
;----------------------------------------------------------------------
    wks = gsn_open_wks("x11","ESMF_regrid")     ; send graphics to PNG file

    res                     = True              ; Plot mods desired.
    res at gsnMaximize         = True              ; Maximize plot

    res at gsnDraw             = False
    res at gsnFrame            = False

    res at cnFillOn            = True              ; color plot desired
    res at cnFillPalette       = "amwg"            ; set color map
    res at cnLinesOn           = False             ; turn off contour lines
    res at cnLineLabelsOn      = False             ; turn off contour labels
    res at cnFillMode          = "RasterFill"      ; turn raster on

    res at cnLevelSelectionMode= "ExplicitLevels" ; set explicit contour levels
    res at cnLevels            = (/-300,-250,-200,-150,-100,   \
                                0,1,5,10,25,100,200,300,400/)

    res at lbLabelBarOn        = False              ; turn on in panel

    res at trGridType          = "TriangularMesh"   ; allow missing coordinates


    res at gsnPolar            = "NH"               ; specify the hemisphere
    res at mpMinLatF           = 35

;---Plot original data.
    res at gsnAddCyclic = False
    res at sfXArray     = lon2d
    res at sfYArray     = lat2d
    res at tiMainString = "Original EASE grid (" + str_join(dimsizes(lat2d),",") + ")"
    res at trGridType = "TriangularMesh"
    res at cnFillMode = "RasterFill"

    plot_orig   = gsn_csm_contour_map_polar(wks,swe2d,res)

    delete(res at sfXArray)
    delete(res at sfYArray)

;---Plot regridded data.
    res at gsnAddCyclic = True

    dims = tostring(dimsizes(swe_regrid))
    res at tiMainString = "Regridded to 0.25 degree grid (" + \
                       str_join(dims," x ") + ")"

    plot_regrid = gsn_csm_contour_map_polar(wks,swe_regrid,res)

;---Compare the plots in a panel
    pres                    = True
    pres at gsnMaximize        = True
    pres at gsnPanelLabelBar   = True
    pres at lbLabelFontHeightF = 0.01
    pres at pmLabelBarWidthF   = 0.8

    gsn_panel(wks,(/plot_orig,plot_regrid/),(/1,2/),pres)
end

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Any suggestions are appreciated! Thank you!

Best,

Qingyun


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