Closed sebvi closed 1 year ago
This proposal is particularly long, I could split it into smaller chunks.
https://github.com/wmo-im/CCT/wiki/Teleconference-1-and-2.11.2022 notes:
@SibylleK provided comments. Add notes for sunshine duration fraction, duct base and trapping layer. Add hypen to high/low vegetation. Rephrase 'Charnock' to something more meaningful. Add note for normalized * (normalized by what?). Clarify meaning of 'over the oceans' or is it needed?
https://github.com/wmo-im/CCT/wiki/Teleconference-21.11.2022 notes: (@sebvi) reviewing comments and will update issue and branch
!!! REMOVED. the following parameters from the proposal: !!! Mean wave period based on first moment 10 0 74 s Mean wave period based on first moment for swell 10 0 75 s Mean wave period based on first moment for wind waves 10 0 76 s Mean wave period based on second moment for swell 10 0 77 s Mean wave period based on second moment for wind waves 10 0 78 s
"Mean wave period based on first moment" is already defined as "inverse mean wave frequency" "Mean wave period based on second moment" is already defined as "mean zero-crossing period" These are alternative naming definitions that make sense if you are dealing with waves according to our in-house expert so the parameters we were proposing are already defined in
Inverse mean wave frequency 10 0 25 s Inverse mean frequency of wind waves 10 0 26 s Inverse mean frequency of total swell 10 0 27 s Mean zero-crossing period of wind waves 10 0 29 s Mean zero-crossing period of total swell 10 0 30 s
Response to comments formulated by @SibylleK and DWD:
could be already existing:
“Geometric height 0 3 6 m” and a new entry in Code Table 4.5 – Fixed surface types and units: “Level of specified web-bulb temperature K (or °C instead?)”
After discussing with our expert, it does not seem that we will ever produce this with other values of wet bulb temperature so it feels a bit overkill to create a new type of Fixed surface for this purpose. Instead of 2 parameters in code tables, we would have 1 parameter in it and 1 entry in Code table 4.5 .
-Regarding New entry: “Sunshine duration fraction 0 6 51 Proportion” The following entries do already exist: “Sunshine 0 6 24 Numeric” “Sunshine duration 0 6 33 s”
Maybe one could add a Note for the new entry to explain: “fraction” of what? For instance: “Note xyz: Sunshine duration fraction of local length of day(?)“.
This sunshine concept is tricky. Strictly speaking the sunshine duration parameter in seconds is the amount of seconds over a period of time when the radiation intensity is above 120 W/m2 . My understanding is that 0/6/24 is the instantaneous radiation: at a given time t, if the downward radiation is above 120 W/m-2 then the parameter is 1 otherwise it is 0. Then if you accumulate this over a period a time, and your delta t is 1 seconds, it is the number of seconds in the time interval where radiation is over or equal to 120 W/m-2. Strictly speaking 0/6/33 could be encoded as 0/6/24 + accum key and should then be deprecated. Now our new parameter is different, it is a fraction so in a sense it is the accumulation in seconds I just described divided by the overall size of the accumulation window in seconds. For instance 2468 seconds of sunshine during the last hour is 2468/3600 = 0.6855555 . Does it makes sense?
A duct layer is an atmospheric layer with a refractivity which leads to a trapping of electromagnetic waves. In a trapping layer the refractivity leads to a bending of EM waves, which is stronger than the earth’s curvature.
"Water runoff and drainage rate” includes the drainage rate while “surface runoff rate” does not.
Not sure I understand the comment. Charnock is roughness over water, what else should be specify?
Parameters containing "over the oceans" are only calculated over water bodies represented in the ocean wave model. It is interpolated from the atmospheric model horizontal grid onto the horizontal grid used by the ocean wave model.
Parameters are normalised by being divided by the product of air density and the square of the friction velocity.
https://github.com/wmo-im/CCT/wiki/Teleconference-12-and-13.12.2022 notes:
sebastien posted answers to questions (in comment above), updated the proproposal to indicate changes. @sebvi will add notes to the issue summary and add note for Charnock. @SibylleK will review the feedback and updated proposal.
branch updated with new wave parameter numbering, added a parameter that was missing (last one of the list) and added all the notes we discussed
https://github.com/wmo-im/CCT/wiki/Teleconference-10.01.2023 notes:
@SibylleK double check the changes and then tag @amilan17 or @marijanacrepulja when complete
Initial request
[to be added]
Amendment details
ADD in Code Table 4.2, in the correct disciplines and categories:
Note: This parameter is the amount of sunshine in seconds over a given length of time in seconds. Sunshine is defined as a radiation intensity above 120 W m-2
Note 1: A duct layer is an atmospheric layer with a refractivity which leads to a trapping of electromagnetic waves. In a trapping layer the refractivity leads to a bending of EM waves, which is stronger than the earth’s curvature.
Note 1: This parameter can be used with templates for chemical constituents to specify a chemical species if needed, for instance: Net ecosystem CO2 exchange flux or Net ecosystem CH4 exchange flux
Mean wave period based on first moment10074sMean wave period based on first moment for swell10075sMean wave period based on first moment for wind waves10076sMean wave period based on second moment for swell10077Mean wave period based on second moment for wind waves10078s7974807581768277837884798580868187828883898490859186Note 1: The Charnock parameter accounts for increased aerodynamic roughness as wave heights grow due to increasing surface stress. It depends on the wind speed, wave age and other aspects of the sea state and is used to calculate how much the waves slow down the wind. Note 2: Parameters are normalised by being divided by the product of air density and the square of the friction velocity.
Comments
No response
Requestor(s)
Matthew Griffith, Robert Osinski and Sebastien Villaume (all ECMWF)
Stakeholder(s)
ECMWF Copernicus program Destination Earth program
Publication(s)
Manual on Codes (WMO-No. 306), Volume I.2, GRIB code table 4.2
Expected impact of change
No response
Collaborators
No response
References
No response
Validation
No response