Align definitions for cloud drop effective radius (table 1-01-01)

[amilan17]

Initial request

The OSCAR/Requirement for Cloud drop effective radius was updated in summer of 2024. The purpose of this issue is to align the definition with the equivalent WIGOS Metadata code.

• The definition in OSCAR/Requirements is: Ratio of integral of water droplets size distribution in volume divided by integral in area.
• The definition in the Codes Registry is: The area weighted mean radius of liquid water drops, assimilated to spheres of the same volume.
• The OLD definition the Codes Registry was amended in 2021: Size distribution of liquid water drops, assimilated to spheres of the same volume. Considered as both a 3D field throughout the troposphere and a 2D field at the top of cloud surface.

Amendment details

TBD

Requestor(s)

GCOS, OSCAR Requirements, @kpremec

Stakeholder(s)

Enter list of stakeholder(s).

Applications or Systems

• OSCAR/Surface
• OSCAR/requirements
• Radar/DB
• OceanOPS
• WHOS
• WDQMS
• GBON Compliance Monitor
• Other

Expected impact of change

None

Collaborators

No response

References

No response

Comments

No response

Publication(s)

Manual on Codes (WMO-No. 306), Volume I.3, WMO Codes Registry - WMDR

Validation

No response

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/Meeting.2024.10.24 notes:
@gaochen-larc taking responsiblity

[gaochen-larc]

Both OSCAR/Requirements and WMDR code recognize cloud drop as liquid cloud drop. The OSCAR definition can be interpreted as the ratio of integrated volume over surface area, which is incorrect. The current WDMR code definition is correct. Recommend to adopt the WMDR code definition.

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/Meeting.2024.11.21 notes:
@kpremec it is recommended to update the OSCAR/Requirements to reflect the definition that was approved through the fast-track procedure in 2021. "The area weighted mean radius of liquid water drops, assimilated to spheres of the same volume."

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/Meeting.2024.12.13 notes:
@amilan17 to coordinate feedback with GCOS

[amilan17]

not a fast-track amendment.

[amilan17]

The change in OSCAR/Requirements was introduced by a joint proposal between GCOS/GAW.
@kpremec will bring this to the attention.

[joergklausen]

not a fast-track amendment.

Why not?

[gaochen-larc]

not a fast-track amendment.

Why not?

I recall we conclude to ask them just use the existing WMDR code and description.