[ncl-talk] convert png to nc file after plot command

[zoe jacobs]

Dear all NCL users,
I have a script (attached) which gives me  monthly averages of
precipitation and plots the result as png files. I wonder if there is any
command in NCL which could   convert the png file to nc file after plot
command?
Please kindly advise me in this regard,
Many thanks in advance,
Best wishes,
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 fils = systemfunc ("ls precip.*.nc") ; file paths
 a    = addfiles (fils, "r")   
 printVarSummary (a)
 ListSetType (a, "cat")        ; concatenate (=default)

;************************************************
; Read the file
;************************************************
 
  ymdStrt = 19790101                            ; climatology start year/month
  ymdLast = 19801231                             ;      "      last  year/month  a  time   = f->time 
  time    = a[:]->time            
  yyyymmdd= cd_calendar(time, -2)
  print(yyyymmdd)

  ntStrt = ind(yyyymmdd.eq.ymdStrt)                ; start time index
  ntLast = ind(yyyymmdd.eq.ymdLast)                ; last  time index
  print("ntStrt="+ntStrt+"  ntLast="+ntLast)

  prc   = a[:]->precip(ntStrt:ntLast,:,:)               ; read T from all files
  printVarSummary (prc)
  printMinMax (prc,0)

;************************************************
; Compute Year-month means or totals
;************************************************

;;prcMonth = calculate_monthly_values(prc, "avg", 0, False)   ; mm/day
;;prcMonth at units = "mm/day"
  prcMonth = calculate_monthly_values(prc, "sum", 0, False)   ; mm/month
  prcMonth at units = "mm/month"                                 ; monthly total
  printVarSummary (prcMonth)   
  printMinMax (prcMonth,0)

;************************************************
; Compute monthly climatology from all year-month means
;************************************************
  prcClm   = clmMonTLL(prcMonth)
  printVarSummary (prcClm)           ; (12,lat,lon)
  printMinMax (prcClm,0)

;************************************************
; Explore [statistical dispersion] the monthly climatology 
;************************************************
  opt_sd = True
  opt_sd at PrintStat = True
  stat_prc = stat_dispersion(prcClm, opt_sd )

;************************************************
; Plot
;*************************************************
  months = (/"January", "February", "March", "April" \
            ,"May", "June", "July", "August"         \
            ,"September", "October", "November"      \
            ,"December" /)
  nmos   = dimsizes(months)

  wks = gsn_open_wks("png","climo_prc_ghcn")    ; send graphics to PNG file
  plot   = new (nmos, graphic)                  ; create graphical array

  res                      = True               ; plot options desired
  res at gsnDraw              = False
  res at gsnFrame             = False
  res at cnFillOn             = True               ; turn on color fill
  
  res at cnInfoLabelOn        = False              ; turn off contour info label
  res at cnLinesOn            = False              ; turn off contour lines
  res at cnLineLabelsOn       = False              ; turn off line labels
  res at cnFillMode           = "RasterFill"       ; Raster Mode

;;res at cnFillPalette        = "????" ; set color map
;;res at cnLevelSelectionMode = "ManualLevels"     ; set manual contour levels
;;res at cnMinLevelValF       = 0                  ; set min contour level
;;res at cnMaxLevelValF       = 300                ; set max contour level
;;res at cnLevelSpacingF      = 20.0               ; set contour spacing

  res at cnLevelSelectionMode = "ExplicitLevels"
;;res at cnLevels             = (/ 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300/) ; 12 contour values
;;res at cnLevels             = (/ 10, 20, 30, 40, 50, 75,100,125,150, 200, 300, 400/) ; 12 contour values
  res at cnLevels             = (/ 10, 20, 30, 40, 50, 75,100,150,200, 300, 400, 500/) ; 12 contour values
  res at cnFillPalette        = (/"WhiteSmoke"  \                                      ; 13 colors          
                              ,"PaleTurquoise","PaleGreen","SeaGreen3" ,"Yellow"  \
                              ,"Orange","HotPink","Red","Violet", "Purple"        \
                              ,"burlywood3",  "Brown", "Black"/) 

  res at mpFillOn             = False              ; turn off gray continents
  res at mpCenterLonF         = 0                  ; Centers the plot at 0 
  res at lbLabelBarOn         = False              ; No single label bar

  do nmo=0,nmos-1                               ; loop over the months
     res at gsnLeftString     = months(nmo)
     plot(nmo) = gsn_csm_contour_map(wks,prcClm(nmo,:,:), res)  ; create plot
  end do
  
;************************************************
; create panel plots
;*************************************************
  
  resP                     = True               ; panel options
  resP at gsnPanelMainString  = "GHCN: Precipitation: "+(ymdStrt/10000)+"-"+(ymdLast/10000)
  resP at gsnMaximize         = True               ; maximize image
  resP at gsnPanelLabelBar    = True               ; Add common label bar 
  gsn_panel(wks,plot,(/4,3/),resP)