varname  = "TREFHT"
 varname  = "CLDTOT"
 varname  = "PHIS"
 datafile = "./aerosol_F2010.eam.h0.2014-12.nc"

 ; Open data file and read data

 File = addfile(datafile,"r")
 var  = File->$varname$(0,:)   ; get the whole globe, but only time step 0
 lat  = File->lat
 lon  = File->lon

 ; create an NCL workspace and "resources" variable 

 wks = gsn_open_wks("png",varname+"_NCL")

 res = True

 ; The two lines below are needed when plotting unstructured data.
 ; They tell NCL how to overlay the data on the globe.

 res@sfXArray = lon
 res@sfYArray = lat

 ; Misc. plot settings

 res@cnFillOn            = True                 ; Turn on contour fill
 res@cnFillPalette       = "BlAqGrYeOrReVi200"  ; set color map
 res@cnLinesOn           = False                ; Turn off contour lines
 res@cnLineLabelsOn      = False                ; Turn off contour line labels
 res@tiMainString        = varname              ; Title of plot

 ; Create the plot

 plot = gsn_csm_contour_map(wks,var,res)