begin 

dir="/Users/nuovoaccount/Documents/PYTHON/"
fil="geop_500_975_89_20.nc"
f = addfile(dir+fil,"r")
z = f->z
time = f->time
lat = f->latitude
lon = f->longitude
date = tointeger(cd_calendar(time, -1))
print(date)
expver=f->expver
print(expver)
level=f->level
print(level)

Z=z/9.81
copy_VarMeta(z,Z)

z975=Z(:,1,1,:,:)    ; 975 hPa
z975@longname="Geopotential height(m)"


;------- Plotting ------------------------------------------------------

 wks = gsn_open_wks("x11","polar")              ; send graphics to PNG file

  res            =  True                          ; plot mods desired
  res@gsnPolar   =  "NH"                          ; specify the hemisphere
  res@mpMinLatF  =  60
  res@mpPerimOn  = False 
 
  res@cnFillOn   =  True                          ; color fill
  res@cnLinesOn  =  False
  ;res@gsnAddCyclic              = True         ; add a cyclic longitude point
  
  res@gsnLeftString = "Geopotential Height"
  res@gsnRightString = "m"


  plot = gsn_csm_contour_map_polar(wks,z975(0,:,:),res)    ; create the plot

end