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

KSEC1 element	Contents	GRIB octet	Recommended GRIB_API keys	Coded GRIB_API keys
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