New section 4 templates to encode optical products at a particular wavelength or for a particular wavelength range

[sebvi]

Initial request

There has been considerable interest in ECMWF's true colour imagery of the IFS (see AMETSOC paper) but it requires offline processing of model fields to generate reflectance fields in the Red (600-700nm), Green(500-600nm) and Blue(400-500nm) parts of the spectrum (coded in RGB). ECMWF expect to be using a new version of the radiation scheme with bands coinciding with these three parts of the spectrum. We are also collaborating with the University of Massachusetts to obtain a new MODIS land-surface albedo climatology with 7 channels including these three bands in the visible. Therefore it will be possible to compute RGB imagery of the Earth online as three grib fields, which can be used immediately for visualisation with minimal post processing.

We would like to produce the following accumulated fluxes (J/m2) for these parts of the spectrum:

1. Incoming top shortwave radiation
2. Net top shortwave radiation
3. Net surface shortwave radiation
4. Downwelling surface shortwave radiation
5. Direct part of the downwelling surface shortwave radiation
6. Net top shortwave radiation for clear skies
7. Net surface shortwave radiation for clear skies
8. Downwelling surface shortwave radiation for clear skies
9. Direct part of the downwelling surface shortwave radiation for clear skies

We are also planning to produce the following parameters for other specific part of the spectrum:

1. Photosynthetically active radiation at surface (total 400-700nm)
2. Photosynthetically active radiation at surface for clear skies (total 400-700nm)
3. UV spectral flux by band of 5mn between 200 and 440nm

The Copernicus Marine Service is interested in getting hold of surface downwelling shortwave in 12 bands between 400 and 700 nm at 25 nm intervals.

Amendment details

ADD the following templates entries in code table 4.0

Code	Description
108	Analysis or forecast at a horizontal level or in a horizontal layer at a point in time for generic optical products
109	Individual ensemble forecast, control and perturbed, at a horizontal level or in a horizontal layer at a point in time for generic optical products
110	Average, accumulation, extreme values or other statistically processed values at a horizontal level or in a horizontal layer in a continuous or non-continuous time interval for generic optical products
111	Individual ensemble forecast, control and perturbed, at a horizontal level or in a horizontal layer, in a continuous or non-continuous interval for generic optical products

ADD template 4.108 - Analysis or forecast at a horizontal level or in a horizontal layer at a point in time for generic optical products

Octet	Content
10	Parameter category
11	Parameter number
12	Type of interval (for wavelength)( code table 4.91)
13	Scale factor of first wavelength
14-17	Scaled value of first wavelength
18	Scale factor of second wavelength
19-22	Scaled value of second wavelength
23	Type of generating process
24	Background generating process identifier (defined by originating centre)
25	Forecast generating process identifier (defined by originating centre)
26-27	Hours after reference time of data cut-off
28	Minutes after reference time of data cut-off
29	Indicator of unit of time range
30-33	Forecast time in units defined by octet 29
34	Type of first fixed surface
35	Scale factor of first fixed surface
36-39	Scaled value of first fixed surface
40	Type of second fixed surface
41	Scale factor of second fixed surface
42-45	Scaled value of second fixed surface

ADD template 4.109 - Individual ensemble forecast, control and perturbed, at a horizontal level or in a horizontal layer at a point in time for generic optical products

Octet	Content
10	Parameter category
11	Parameter number
12	Type interval (for wavelength) (code Table 4.91)
13	Scale factor of first wavelength
14-17	Scaled value of first wavelength
18	Scale factor of second wavelength
19-22	Scaled value of second wavelength
23	Type of generating process
24	Background generating process identifier (defined by originating centre)
25	Forecast generating process identifier (defined by originating centre)
26-27	Hours after reference time of data cut-off
28	Minutes after reference time of data cut-off
29	Indicator of unit of time range
30-33	Forecast time in units defined by octet 29
34	Type of first fixed surface
35	Scale factor of first fixed surface
36-39	Scaled value of first fixed surface
40	Type of second fixed surface
41	Scale factor of second fixed surface
42-45	Scaled value of second fixed surface
46	Type of ensemble forecast
47	Perturbation number
48	Number of forecasts in ensemble

ADD template 4.110 - Average, accumulation, extreme values or other statistically processed values at a horizontal level or in a horizontal layer in a continuous or non-continuous time interval for generic optical products

Octet	Content
10	Parameter category
11	Parameter number
12	Type of interval (for wavelength) (code Table 4.91)
13	Scale factor of first wavelength
14-17	Scaled value of first wavelength
18	Scale factor of second wavelength
19-22	Scaled value of second wavelength
23	Type of generating process
24	Background generating process identifier (defined by originating centre)
25	Forecast generating process identifier (defined by originating centre)
26-27	Hours after reference time of data cut-off
28	Minutes after reference time of data cut-off
29	Indicator of unit of time range
30-33	Forecast time in units defined by octet 29
34	Type of first fixed surface
35	Scale factor of first fixed surface
36-39	Scaled value of first fixed surface
40	Type of second fixed surface
41	Scale factor of second fixed surface
42-45	Scaled value of second fixed surface
46-47	Year of end of overall time interval
48	Month of end of overall time interval
49	Day of end of overall time interval
50	Hour of end of overall time interval
51	Minute of end of overall time interval
52	Second of end of overall time interval
53	n - number of time range specifications describing the time intervals used to calculate the statistically processed field
54-57	Total number of data values missing in statistical process
	58-69 Specification of the outermost (or only) time range over which statistical processing is done
58	Statistical process used to calculate the processed field from the field at each time increment during the time range
59	Type of time increment between successive fields used in the statistical processing
60	Indicator of unit of time for time range over which statistical processing is done
61-64	Length of the time range over which statistical processing is done, in units defined by the previous octet
65	Indicator of unit of time for the increment between the successive fields used
66-69	Time increment between successive fields, in units defined by the previous octet
	70-nn These octets are included only if n > 1, where nn = 57 + 12 x n
70-71	As octets 58 to 69, next innermost step of processing
72-nn	Additional time range specifications, included in accordance with the value of n. Contents as octets 58 to 69, repeated as necessary

ADD template 4.111 - Individual ensemble forecast, control and perturbed, at a horizontal level or in a horizontal layer, in a continuous or non-continuous interval for generic optical products

Octet	Content
10	Parameter category
11	Parameter number
12	Type of interval (for wavelength) (code Table 4.91)
13	Scale factor of first wavelength
14-17	Scaled value of first wavelength
18	Scale factor of second wavelength
19-22	Scaled value of second wavelength
23	Type of generating process
24	Background generating process identifier (defined by originating centre)
25	Forecast generating process identifier (defined by originating centre)
26-27	Hours after reference time of data cut-off
28	Minutes after reference time of data cut-off
29	Indicator of unit of time range
30-33	Forecast time in units defined by octet 29
34	Type of first fixed surface
35	Scale factor of first fixed surface
36-39	Scaled value of first fixed surface
40	Type of second fixed surface
41	Scale factor of second fixed surface
42-45	Scaled value of second fixed surface
46	Type of ensemble forecast
47	Perturbation number
48	Number of forecasts in ensemble
49-50	Year of end of overall time interval
51	Month of end of overall time interval
52	Day of end of overall time interval
53	Hour of end of overall time interval
54	Minute of end of overall time interval
55	Second of end of overall time interval
56	n - number of time range specifications describing the time intervals used to calculate the statistically processed field
57-60	Total number of data values missing in statistical process
	61-72 Specification of the outermost (or only) time range over which statistical processing is done
61	Statistical process used to calculate the processed field from the field at each time increment during the time range
62	Type of time increment between successive fields used in the statistical processing
63	Indicator of unit of time for time range over which statistical processing is done
64-67	Length of the time range over which statistical processing is done, in units defined by the previous octet
68	Indicator of unit of time for the increment between the successive fields used
69-72	Time increment between successive fields, in units defined by the previous octet
	73-nn These octets are included only if n > 1, where nn = 60 + 12 x n
73-74	As octets 61 to 72, next innermost step of processing
75-nn	Additional time range specifications, included in accordance with the value of n. Contents as octets 61 to 72, repeated as necessary

Comments

No response

Requestor(s)

Sebastien Villaume (ECMWF representative)

Stakeholder(s)

Enter list of stakeholder(s).

Publication(s)

Manual on Codes (WMO-No. 306), Volume I.2, GRIB code table 4.0 (new entries)
Manual on Codes (WMO-No. 306), Volume I.2, GRIB templates 4.108 (new template)
Manual on Codes (WMO-No. 306), Volume I.2, GRIB templates 4.109 (new template)
Manual on Codes (WMO-No. 306), Volume I.2, GRIB templates 4.110 (new template)
Manual on Codes (WMO-No. 306), Volume I.2, GRIB templates 4.111 (new template)

Expected impact of change

MEDIUM

Collaborators

No response

References

No response

Validation

No response

[amilan17]

https://github.com/wmo-im/CCT/wiki/Teleconference-5.10.2022 meeting notes

• 4.108, octet 12: change to "type of interval (for wavelength)"
• validation will require deep review and samples

[sebvi]

Here is a link to the experimental version of ecCodes able to encode/decode the new templates: eccodes

Let me know if you do not have access.

[sebvi]

Here is a link to the experimental version of ecCodes able to encode/decode the new templates: eccodes

Let me know if you do not have access.

imagery.zip

[amilan17]

https://github.com/wmo-im/CCT/wiki/Teleconference-1-and-2.11.2022 notes:

@sebvi ready for validation; note, the template numbers that lennart is proposing are the same.

[amilan17]

https://github.com/wmo-im/CCT/wiki/Teleconference-21.11.2022 notes:
ready for validation

[sebvi]

Response to @SibylleK and DWD

• what is the difference to the existing “optical properties of aerosol”-templates 4.48, 4.49, 4.80, 4.81?
  Wouldn’t it be possible to simply set the additional entries in e.g. 4.48 to missing to meet the requirements of the generic optical products?

The templates 4.48, 4.49, 4.80, 4.81 are specific for aerosol optical properties. The proposed templates 4.108 – 4.111 are intended to be used for satellite related parameters.
In template 4.48, 6 keys would have to be set to missing to encode the desired information (Aerosol type, Type of interval for first and second size, Scale factor of first size, Scaled value of first size in metres, Scale factor of second size, Scaled value of second size in metres), containing 13 bytes (12-24). As the names of the templates are related to aerosol optical properties and several keys should be set to missing, it is probably better to have separate templates to avoid confusion.

[amilan17]

https://github.com/wmo-im/CCT/wiki/Teleconference-12-and-13.12.2022 notes:

• there was a discussion about the pros/cons of renaming existing templates to be more generic vs adding new templates
• for now, don't rename pre-existing templates, because the result would be a lot of fields set to missing

[amilan17]

https://github.com/wmo-im/CCT/wiki/Teleconference-10.01.2023 notes:

ready for final review