In general, the static sample dataset is not suitable for initialising an NWP model. Although encoding examples of all parameters at all forecast steps are provided, for those parameters on constant pressure levels, for example, only the 1hPa level is provided. However, users that use initial and lateral boundary conditions (LBCs) from ECMWF data to initialise and update their NWP models should note the change in the way the parameters on soil levels are provided as this may require changes to your code. Instead of having four separate parameters at each soil layer (level), in GRIB2 there will be one parameter available at each of the four layers - see Soil temperature, volumetric soil moisture and sea-ice temperature, below, for details.

Other sources of ECMWF GRIB2 data that can be used for testing

...

The encoding of the ecCodes paramId, shortName, name and units have changed for some surface parameters from the analysis and forecast. Users may need to adapt their workflows in order to process these parameters successfully. The main changes affecting parameters provided in the static sample dataset are summarised belowin Migration to GRIB2 - changes to encoding of parameters. For a list of all changes to parameter encoding made at each ecCodes version, see Migration to GRIB2 - new in ecCodes.

...

In GRIB1, soil temperature, volumetric soil moisture and sea-ice temperature have different paramIds for each of the 4 soil layers. In GRIB2, only a single paramId is used with the layer indicated by the level key.

For example, in GRIB1, there is a paramId for Volumetric soil water layer 1 and a different paramId for Volumetric soil water layer 2, etc. In GRIB2, only a single paramId is used for Volumetric soil water, with the layer 1 having level=1 and layer 2 having level=2.

Old paramId	Old shortName	Old name	Old units	New paramId	New shortName	New name	New units	level
139	stl1	Soil temperature level 1	K	260360	sot	Soil temperature	K	1
170	stl2	Soil temperature level 2	K	260360	sot	Soil temperature	K	2
183	stl3	Soil temperature level 3	K	260360	sot	Soil temperature	K	3
236	stl4	Soil temperature level 4	K	260360	sot	Soil temperature	K	4
39	swvl1	Volumetric soil water layer 1	m3 m-3	260199	vsw	Volumetric soil moisture	m3 m-3	1
40	swvl2	Volumetric soil water layer 2	m3 m-3	260199	vsw	Volumetric soil moisture	m3 m-3	2
41	swvl3	Volumetric soil water layer 3	m3 m-3	260199	vsw	Volumetric soil moisture	m3 m-3	3
42	swvl4	Volumetric soil water layer 4	m3 m-3	260199	vsw	Volumetric soil moisture	m3 m-3	4
35	istl1	Ice temperature layer 1	K	262024	sit	Sea ice temperature	K	1
36	istl2	Ice temperature layer 2	K	262024	sit	Sea ice temperature	K	2
37	istl3	Ice temperature layer 3	K	262024	sit	Sea ice temperature	K	3
38	istl4	Ice temperature layer 4	K	262024	sit	Sea ice temperature	K	4

These parameters will be archived in MARS with levtype=sol (surface other levels). To retrieve these parameters in GRIB2, users will need to change their MARS requests to specify levtype=sol,levelist=1/2/3/4.

Parameters statistically processed over a time window

In GRIB1, parameters that are statistically processed over a time window, such and maximum, minimum and average values over the last 3 or 6 hours, have different paramIds for each time window available. In GRIB2, there is a unique paramId indicating the parameter and type of statistical processing, e.g., paramId=237167, shortName=max_2t for maximum temperature at 2 metres. A separate key, called statisticalwindow, is then used to specify the time window. For example, paramId=237167, statisticalwindow=3h identifies maximum temperature at 2 metres during the last 3 hours.

This change applies to:

Maximum 10 metre wind gust.
Maximum and minimum temperature at 2 metres.
Maximum and minimum total precipitation rate.
Maximum CAPE and CAPE shear.
Average lightning flash density.
Most severe and most frequent precipitation type.

To retrieve these parameters in GRIB2 from MARS, users will need to use the new paramId and also specify the statistical processing time window using a new MARS keyword - timespan - that is to be introduced.