New wave and ocean parameters in Code Table 4.2 discipline 10 categories 0 and 2

[sebvi]

Initial request

This is a joint proposal with MeteoFrance to request new wave and ocean parameters in GRIB2 for which no official code table entries are available at the moment. This proposal suggests adding them to the oceanographic products tables. 

Amendment details

ADD to code table 4.2: Product discipline 10 Oceanographic products, parameter category 0: waves

Code	Description	Units
99	Benjamin-Feir index 2D (BFI2D) (Note 1)	Numeric
100	Crest-trough correlation (Note 2)	Numeric
101	X component of the wave radiative stress to sea ice	N m-2
102	Y component of the wave radiative stress to sea ice	N m-2

Note 1: BFI2D is calculated by dividing the BFI by an expression that increases with the directional spread and decreases with the peakedness. It comes from the consideration that an increase of the directional spread reduces the excess of kurtosis, which is not taken into account in the BFI alone. 
Mori, N., M. Onorato, and P. A. E. M. Janssen, 2011: On the Estimation of the Kurtosis in Directional Sea States for Freak Wave Forecasting. J. Phys. Oceanogr., 41, 1484–1497,  https://doi.org/10.1175/2011JPO4542.1. 

Note 2: Crest-trough correlation is an estimate of the auto-correlation between the crest heights and the trough depths. In narrow-banded seas this parameter is quite high, because crests and troughs are approximately the same size. 
Gemmrich, J., Cicon, L. Generation mechanism and prediction of an observed extreme rogue wave. Sci Rep 12, 1718 (2022). https://doi.org/10.1038/s41598-022-05671-4

ADD to code table 4.2: Product discipline 10 -, parameter category 2: ice

Code	Description	Unit
30	Sea ice breakup memory (Note 1)	Numeric

Note 1: This is a metric that quantifies the wave-induced mechanical fatigue on the sea-ice pack (0 means broken, 1 means solid). This metric only makes sense in the presence of sea ice.

Comments

No response

Requestor(s)

Sebastien Villaume (ECMWF) 
Robert Osinski (ECMWF) 
Josh Kousal (ECMWF) 
Alice Dalphinet (Meteo France) 

Stakeholder(s)

ECMWF, MeteoFrance

Publication(s)

Manual on Codes (WMO-No. 306), Volume I.2, GRIB code table 4.2, discipline 10, category 0 (update) 
Manual on Codes (WMO-No. 306), Volume I.2, GRIB code table 4.2, discipline 10, category 2 (update) 

Expected impact of change

None

Collaborators

No response

References

• Mori, N., M. Onorato, and P. A. E. M. Janssen, 2011: On the Estimation of the Kurtosis in Directional Sea States for Freak Wave Forecasting. J. Phys. Oceanogr., 41, 1484–1497, https://doi.org/10.1175/2011JPO4542.1.
• Gemmrich, J., Cicon, L. Generation mechanism and prediction of an observed extreme rogue wave. Sci Rep 12, 1718 (2022). https://doi.org/10.1038/s41598-022-05671-4

Validation

No response

[amilan17]

https://github.com/wmo-im/tt-tdcf/wiki/2024.11.13.tt.tdcf notes:

• Sebastien introduced the proposal
• Sibylle suggested adding a clarifying note for 101 and 102 in 4.2.10.4 (will add the comments to the issue)