[ncl-talk] ESMF_regrid_24.ncl

[Sri nandini]

Hello dear NCL users,

I am trying to use the online ncl script: ESMF_regrid_24.ncl: 
https://www.ncl.ucar.edu/Applications/Scripts/ESMF_regrid_24.ncl

This example shows how to regrid data from a POP curvilinear gx1v3 grid 
(384 x 320) to a 1.0 degree world grid, which is my aim.

My modified script runs successfully with tas=(0,:,:) ====where the 
timestep is 0 and       x_regrid = ESMF_regrid(x,Opt)     does this only 
allow for latlon 2D?

At the end i wish to regrid my variable into 1X1 resolution and save it 
for future analysis, but i need the entire variable dimensions e.g. 
time, lat,lon and not just the lat,lon. When i enter the full 3D 
variable into my script, than i get an error at the x_regrid = 
ESMF_regrid(x,Opt) "fatal:Eq: Dimension size, for dimension number 0, of 
operands does not match, can't continue"

Please have a look at my script below. Would be grateful for any comments.


;----------------------------------------------------------------------
; This script regrids a POP grid to a 1.0 degree regular latlon grid and
; plots sea surface height [zos] on the new grid.
;----------------------------------------------------------------------

; This file still has to be loaded manually
load "$NCARG_ROOT/lib/ncarg/nclscripts/esmf/ESMF_regridding.ncl"

begin
ensemble=(/"r1i1p1","r2i1p1","r3i1p1","r4i1p1","r5i1p1","r6i1p1","r7i1p1","r8i1p1","r9i1p1","r10i1p1","r11i1p1","r12i1p1","r13i1p1","r14i1p1","r15i1p1","r16i1p1","r17i1p1","r18i1p1","r19i1p1","r20i1p1","r21i1p1","r22i1p1","r23i1p1","r24i1p1","r25i1p1","r26i1p1","r27i1p1","r28i1p1","r29i1p1","r30i1p1","r31i1p1","r32i1p1","r33i1p1","r34i1p1","r35i1p1","r36i1p1","r37i1p1","r38i1p1","r39i1p1","r40i1p1"/)
   do i=0,dimsizes(ensemble)-1
   region=ensemble(i)
   print(i+": "+region)

print("Starting: "+region+" now")

;---Interpolation methods
     methods        = (/"bilinear"/)     ; ,"conserve","patch"/)

;---Input file
     srcDirName     = "./"
     srcFileName    = 
"zos_Omon_CESM1-CAM5_historical_rcp85_"+region+"_192001-210012.nc"
     print(srcFileName)
     varName        = "zos"
     printVarSummary(varName)
;---Get data and lat/lon grid from source Grid; uses surface level and 
initial time
     ;ne=2172
     ;do i=0,ne-1
     sfile          = addfile(srcFileName,"r")
     x              = sfile->$varName$        ; (time,lat,lon)
     printVarSummary(x)
     dimx  = dimsizes( x )
     ntim  = dimx( 0 )

     x at lat2d        = sfile->lat                   ; Needed for plotting.
     x at lon2d        = sfile->lon
     x at time         =sfile->time

;---Specify a name for the destination regridded variable (no spaces)
   ;;DstGridDir     = "./"
     DstGridName    = "1x1"

;---Create the destination rectilinear lat/lon
     lat            = fspan(-89.5, 89.5,180)
     lon            = fspan(  0.5,359.5,360)

;---Specify name of weight file(s) to be generated; name of destination 
grid; dst directory
     WgtFileDir     = "./"
     WgtFileName    = "POP_gx1v3_to_"+DstGridName+"."+methods+".nc"

     Opt                  = True
     Opt at SrcFileName      = "POP_gx1v3_SCRIP.nc"   ; source grid 
description file name
     Opt at DstFileName      = "Globe1deg_SCRIP.nc"   ; destination grid 
description file name
     Opt at ForceOverwrite   = True

     Opt at SrcMask2D        = where(.not.ismissing(x),1,0)  ; land/ocean 
mask; Necessary if has
                                                            ; missing 
values.
     Opt at DstTitle         = "Global Grid 1-degree Resolution"
     Opt at DstGridLat       = lat
     Opt at DstGridLon       = lon

;----------------------------------------------------------------------
; Loop across each method and generate interpolation weights for
; POP Grid to regular LatLon  Grid
;----------------------------------------------------------------------
       plot_regrid = new(dimsizes(methods),graphic)

       print("Generating interpolation weights from POP to regular 
LatLon Grid")
       print("Global LatLon grid using the " +methods+" method.")

       Opt at WgtFileName  = WgtFileName

       Opt at InterpMethod = methods

       ;-- if we don't need to generate the source and destination grids 
again
;  Opt at SkipDstGrid    =  True                            ;-- if True 
skip regridding
;  Opt at SkipSrcGrid    =  True                            ;-- if True 
skip regridding
;----------------------------------------------------------------------
; Interpolate data from POP to destination grid.
;----------------------------------------------------------------------
;----------------------------------------------------------------------
; Regridding over each time independently, pass a 3D variable to 
ESMF_regrid, and it will do the
;looping under the hood. What this function does is creates the weights for
;one level, and applies them to the rest of the levels.  It assumes that the
;lat/lon grid is the same for each level.
;----------------------------------------------------------------------
       x_regrid = ESMF_regrid(x,Opt)     ;only allows for latlon 2D
       printVarSummary(x_regrid)

;----------------------------------------------------------------------
; Save the regridded data onto new netcdf file
;----------------------------------------------------------------------
     print("saving "+region+" regridded")
     system("/bin/rm -f 
zos_Omon_CESM1-CAM5_historical_rcp85_"+region+"_regridded.nc")   ; 
remove any pre-existing file
     outfile = 
addfile("zos_Omon_CESM1-CAM5_historical_rcp85_"+region+"_regridded.nc","c")
     outfile->zos = x_regrid




-- 
Dr. Sri Nandini-Weiss

Center for Earth System Research and Sustainability (CEN)
Cluster of Excellence 'Climate, Climatic Change, and Society' (CLICCS)

Universität Hamburg
Institute of Oceanography
Bundesstraße 53
20146 Hamburg
Germany