Python script: 3D variables

On pressure levels and a Gaussian grid (N 128):

#!/usr/bin/env python
from ecmwfapi import ECMWFDataServer
import calendar

server = ECMWFDataServer()

for year in range(1979, 2005):
 print 'YEAR ',year
 for month in range(03,13):
  lastday1=calendar.monthrange(year,month)
  lastday=lastday1[1]
  bdate="%s%02d01"%(year,month)
  edate="%s%02d%s"%(year,month,lastday)
  print "######### ERA-interim  #########"
  print 'get data from ', bdate,' to ',edate,' (YYYYMMDD)'
  print "################################"
  server.retrieve({
    'dataset'  : "interim",
    'date'     : "%s/to/%s"%(bdate,edate),
    'time'     : "00/06/12/18",
    'step'     : "0",
    'stream'   : "oper",
    'levtype'  : "pl",
    'levelist' : "all",
    'type'     : "an",
    'class'    : "ei",
    'grid'     : "128",
    'param'    : "129/130/131/132/133/157",
    'target'   : "ERA-Int_pl_%s_%s.grb"%(bdate,edate),
    })

Each file will have a size between 6.1 and 6.8GB.