;*************************************************
; mask_3.ncl
;************************************************
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"  
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"  
;************************************************
begin
;************************************************
; read in netCDF file
;************************************************
  in = addfile("atmos.nc","r")
  ts = in->TS(0,:,:)
;************************************************
; use mask function to mask out a range of the data 
;************************************************
  range_only  = ts                               ; trick to keep cv's and atts
  range_only  = mask(ts,(ts.ge.279),True)
;************************************************
; common resources
;************************************************
  wks = gsn_open_wks("ps","mask")                   ; open a ps file
  gsn_define_colormap(wks,"BlAqGrYeOrRe")           ; choose colormap


  res                      = True     ; plot mods desired
  res@cnFillOn             = True     ; turn on color fill
  res@cnLinesOn            = False    ; turn of contour lines

  res@gsnSpreadColors      = True     ; use full colormap
  res@gsnSpreadColorStart  = 10       ; start at color 10
  res@gsnSpreadColorEnd    = 96       ; end at color 96

  res@cnLevelSelectionMode    = "ManualLevels"   ; manual levels
  res@cnMinLevelValF          = 219              ; min level
  res@cnMaxLevelValF          = 310              ; max level
  res@cnLevelSpacingF         = 3                ; interval

  res@lbLabelStride           = 4                ; every 4th label
  res@tiMainString            = "Range Only"     ; title
  plot = gsn_csm_contour_map_ce(wks,range_only,res)

 
end