load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl" 
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"   

begin
  a       = addfile("pop.nc","r")     ; Read in POP data.
  t       = a->t
  t@lat2d = a->lat2d
  t@lon2d = a->lon2d

  wks = gsn_open_wks("ps", "contour4b")  ; Open a PS file called "contour4b.ps"

  res              = True
  res@gsnAddCyclic = True    ; By default, this is False for 2D lat/lon coords

  plot = gsn_csm_contour_map(wks,t,res)   ; Call the gsn_csm function for
                                          ; drawing contours over a map.
end