For instantaneous fields, a monthly mean is the mean of the fields sampled at the specified averaging period.

For accumulated fields, a monthly mean is the mean rate of accumulation of the fields.

KSEC1 element | Contents | GRIB octet | Recommended GRIB_API keys | Coded GRIB_API keys | Comments
--- | --- | --- | --- | --- | ---
37 |
    ECMWF local GRIB use definition identifier.
    16 = ECMWF seasonal forecast monthly mean data
| 41 | localDefinitionNumber | localDefinitionNumber |
38 | Class | 42 | class | marsClass |
39 | Type | 43 | type | marsType |
40 | Stream | 44-45 | stream | marsStream |
41 |
    Version number or experiment identifier.
    (4 ASCII characters, right justified)
| 46-49 | expver | experimentVersionNumber |
42 |
    Number
      Ensemble member number.
      Control forecast is number 0,
      perturbed forecasts 1-nn.
| 50-51 | number | perturbationNumber |
43 | Zero | - |  |  |
44 |
    System number
      The "scientific version" number.
      0 = RD experiment
      1 - 65534 = operational version number
      65535 = missing
| 52-53 | system | systemNumber |
45 |
    Method number
      Distinguishes scientifically different forecast ensembles
      (eg different calibration/bias correction)
      0 = control integration (ie without data assimilation)
      1 - 65534 = operational version number
| 54-55 | method | methodNumber |
46 | Verifying month (in format YYYYMM) | 56-59 | verifyingMonth | verifyingMonth |
47 | Averaging period (eg 6-hour, 24-hour) | 60 | averagingPeriod | averagingPeriod |
48 | Forecast month | 61-62 | forecastMonth | forecastMonth |
- | Spare (set to zero) | 63-80 |  |  |