We recommend that you get familiar with the data and its availability using MARS Catalogue

You can also get the request syntax using " View MARS request " feature.

verb,
 keyword1 = value1,
      ... = value2,
 keywordN = valueN

retrieve,
 class=ei,
 stream=oper,
 expver=1,
 levtype=sfc,
 param=165.128/41.128,
 step=0,
 grid=0.75/0.75,
 time=00,
 date=2013-09-01/to/2013-09-30,
 area=75/-15/30/42.5, 
 type=an,
 target="ei_sfc_165_41.grib"

#Specifies the ECMWF classification given to the data
  class=ei,

#Identifies the forecasting system used to generated the data when the same meteorological types are archived
  stream=oper,

#Is the version of the data, 1 is OPERATIONAL
  expver=1,

#Denotes type of level
  levtype=sfc,

#Meteorological parameter
  param=165.128/41.128,

#Determines the type of field to be retrieved:
  type=an,

#Specifies the forecast time step from forecast base time
  step=0,

#Base time
  time=00,

#Specifies the Analysis date, the Forecast base date or Observations date
  date=2013-09-01/to/2013-09-30,

#Output grid mesh
  grid=0.75/0.75,

#Area
  area=75/-15/30/42.5,

#specifies a Unix file into which data is to be written after retrieval
    target="ei_sfc_165_41.grib",

##OPTIONAL MARS SERVICE KEYWORD
   #(Optional) argument to retrieve NetCDF format
     format=netcdf,