Code Table 4.2 and new code table: add code table entry for character of precipitation

[tomkralidis]

Branch

https://github.com/wmo-im/GRIB2/tree/issue81

Summary and purpose

This document proposes a new GRIB2 Code Table 4.2 parameter as well as a new table (4.249).

Action proposed

The @wmo-im/tt-tdcf team is requested to approve the content of this proposal for inclusion with the next update of the WMO Manual on Codes.

Discussions

The tables contain a proposed addition to Table 4.2 as well as a new Table 4.248 within the GRIB2 section of the Manual on Codes. These are necessary to reflect new post-processing diagnostics and Nowcasting forecasts being implemented at the Meteorological Service of Canada. The additions further qualify the character of precipitation to reflect how information is transmitted to users in the context of a fully automated forecast. It is hoped that they are also sufficient for use by other Centers.

Detailed proposal

Addition to 4.2

Parameter	Product Discipline	Parameter Category	Parameter number	Units
Character of precipitation	0	1 (moisture)	147	(Code table 4.249)

New code table 4.249 (Character of precipitation)

Title_en	SubTitle_en	CodeFlag	Value	MeaningParameterDescription_en	Note_en	UnitComments_en	Status
Character of precipitation		0		None			Operational
Character of precipitation		1		Showers			Operational
Character of precipitation		2		Intermittent			Operational
Character of precipitation		3		Continuous			Operational

[sebvi]

I like and support this proposal. I only have 2 comments:

• When we create a parameters that is essentially a bitmap and refers to a table to decode the meaning of the integers we usually have "code table 4.XXX" in the units column so I would recommend to do this for this one (although I am not a huge fan of this practice!).
• In GRIB3, I hope that all these parameters that are essential quality/property flags would go as "overlays" in the newly created overlay section :)

[tomkralidis]

Merci @sebvi. Proposal updated :)

[sebvi]

looks good to me, I support this proposal

[tomkralidis]

Update (2021-05-18):

• updated branch https://github.com/wmo-im/GRIB2/tree/issue81
• bumped code flag and code table entry numbers accordingly given they were taken at the time

[jitsukoh]

@tomkralidis @amilan17 I confirm that this proposal is finalized and the branch is updated, and move this issue to "Validated" status.