new probability templates for large ensemble

[sebvi]

Initial request

This proposal extends the existing templates 4.5 and 4.9 for probability forecasts by additional keys which allow to encode the ensemble size of large ensembles and the type of ensemble forecast from which the probabilities are derived.

A branch with an implementation of this template is accessible under: https://github.com/ecmwf/eccodes/tree/feature/ECC-1705-probabilitiesWithFocalStats

Amendment details

ADD the following templates entries in code table 4.0.

Code	Name
119	Probability forecasts from large ensembles at a horizontal level or in a horizontal layer at a point in time
120	Probability forecasts from large ensembles at a horizontal level or in a horizontal layer in a continuous or non-continuous time interval

ADD Template 4.119 - Probability forecasts from large ensembles at a horizontal level or in a horizontal layer at a point in time.

Octet	Number of octets	Description
10	1	Parameter Category (see code table 4.1)
11	1	Parameter Number (see code table 4.2)
12	1	Type of Generating Process (see code table 4.3)
13	1	Background Process
14	1	Generating Process Identifier
15-16	2	Hours After Data Cut-off
17	1	Minutes After Data Cut-off
18	1	Indicator of Unit of Time Range (see code table 4.4)
19-22	4	Forecast Time
23	1	Type of First Fixed Surface (see code table 4.5)
24	1	Scale Factor of First Fixed Surface
25-28	4	Scaled Value of First Fixed Surface
29	1	Type of Second Fixed Surface (see code table 4.5)
30	1	Scale Factor of Second Fixed Surface
31-34	4	Scaled Value of Second Fixed Surface
35	1	Type of ensemble forecast (see Code table 4.6)
36-39	4	Number of forecasts in ensemble
40	1	Forecast Probability Number
41	1	Total Number of Forecast Probabilities
42	1	Probability Type (see code table 4.9)
43	1	Scale Factor of Lower Limit
44-47	4	Scaled Value of Lower Limit
48	1	Scale Factor of Upper Limit
49-52	4	Scaled Value of Upper Limit

ADD Template 4.120 - Probability forecasts from large ensembles at a horizontal level or in a horizontal layer in a continuous or non-continuous time interval.

Octet	Number of octets	Description
10	1	Parameter Category (see code table 4.1)
11	1	Parameter Number (see code table 4.2)
12	1	Type of Generating Process (see code table 4.3)
13	1	Background Process
14	1	Generating Process Identifier
15-16	2	Hours After Data Cut-off
17	1	Minutes After Data Cut-off
18	1	Indicator of Unit of Time Range (see code table 4.4)
19-22	4	Forecast Time
23	1	Type of First Fixed Surface (see code table 4.5)
24	1	Scale Factor of First Fixed Surface
25-28	4	Scaled Value of First Fixed Surface
29	1	Type of Second Fixed Surface (see code table 4.5)
30	1	Scale Factor of Second Fixed Surface
31-34	4	Scaled Value of Second Fixed Surface
35	1	Type of ensemble forecast (see Code table 4.6)
36-39	4	Number of forecasts in ensemble
40	1	Forecast Probability Number
41	1	Total Number of Forecast Probabilities
42	1	Probability Type (see code table 4.9)
43	1	Scale Factor of Lower Limit
44-47	4	Scaled Value of Lower Limit
48	1	Scale Factor of Upper Limit
49-52	4	Scaled Value of Upper Limit
53-54	2	Year of end of overall time interval
55	1	Month of end of overall time interval
56	1	Day of end of overall time interval
57	1	Hour of end of overall time interval
58	1	Minute of end of overall time interval
59	1	Second of end of overall time interval
60	1	n - number of time range specifications describing the time intervals used to calculate the statistically processed field
61-64	4	Total number of data values missing in statistical process
		65 - 76 Specification of the outermost (or only) time range over which statistical processing is done
65	1	Statistical process used to calculate the processed field from the field at each time increment during the time range (see code table 4.10)
66	1	Type of time increment between successive fields used in the statistical processing (see code table 4.11)
67	1	Indicator of unit of time for time range over which statistical processing is done (see code table 4.4)
68-71	4	Length of the time range over which statistical processing is done, in units defined by the previous octet
72	1	Indicator of unit of time for the increment between the successive fields used (see code table 4.4)
73-76	4	Time increment between successive fields, in units defined by the previous octet
		77 - nn These octets are included only if n > 1, where nn = 65+ 12 x n
77-88	12	As octets 65 to 76, next innermost step of processing
89-nn	n/a	Additional time range specifications, included in accordance with the value of n. Contents as octets 65 to 76, repeated as necessary

Add to table 4.7: Derived forecast

Code	name
10	Variance of all ensemble members

Comments

No response

Requestor(s)

Robert Osinski (ECMWF) Sebastien Villaume (ECMWF)

Stakeholder(s)

ECMWF + member states

Publication(s)

Example: Manual on Codes (WMO-No. 306), Volume I.2, GRIB templates in section 4

Expected impact of change

None

Collaborators

No response

References

No response

Validation

No response

[amilan17]

https://github.com/wmo-im/CCT/wiki/Teleconference.17.18.October.2023 notes: Sebastien introduced the proposal; team agrees to proposal; there are samples in the eccodes branch linked to in the issue summary;

[sebvi]

we need a branch for this proposal

[amilan17]

done

[amilan17]

https://github.com/wmo-im/CCT/wiki/Teleconference.21.22.November.2023 notes: Sebastien copied the previous templates and increased the number of octets and will have a branch ready for tomorrow;

[sebvi]

branch updated

[amilan17]

https://github.com/wmo-im/CCT/wiki/Teleconference.21.29.November.2023 notes:

Sebastien will add samples;

[sebvi]

I am adding a sample for template 4.120

GRIB2_224.zip

[amilan17]

https://github.com/wmo-im/CCT/wiki/Teleconference.10.January.2024 notes:

Anna provided an editorial review; @SibylleK to validate samples

[SibylleK]

For a pure technical validation, I was able to read the entries in section 4 of the GRIB example file PDTN_120.grib2 with a DWD GRIB reader software. The entries were the same as in an output of eccodes grib_dump. This means that the proposal has been validated.