1-01-01 Addition of variable definitions (part 1: clouds)

[fstuerzl]

Initial Request

This proposal intends to review and revise several cloud variables in WMDR: 182, 183, 507, 508, 533, 551, 552, and 553.
Here is a summary of the issues:
• 551, 552, and 553’s descriptions need to be revised

Amendment Details

• Description for 551, 552, and 553 are revised and ready for next level review

notation	path	name	description
551	\Atmosphere\Clouds\Type\Type of high clouds	Type of high clouds	Type of clouds of genera Cirrus, Cirrocumulus, or Cirrostratus. These occur between 3-8 km (polar regions), 5-13 km (temperate regions) and 6-18 km (tropics) above ground [ref: WMO, International Cloud Atlas, 2017 ed.]
552	\Atmosphere\Clouds\Type\Type of low clouds	Type of low clouds	Type of clouds of genera Stratus, Stratocumulus, Cumulus, or Cumulonimbus. These occur between 0-2 km above ground [ref: WMO, International Cloud Atlas, 2017 ed.]
553	\Atmosphere\Clouds\Type\Type of middle clouds	Type of middle clouds	Type of clouds of genera Altocumulus, Altostratus, or Nimbostratus. These occur between 2-4 km (polar regions), 2-7 km (temperate regions) and 2-8 km (tropics) above ground [ref: WMO, International Cloud Atlas, 2017 ed.]

Add definitions to cloud variables.

Comments

Every entry in the WMDR code lists should have a useful definition.

Requestor(s)

• Franziska Stuerzl

Stakeholder(s)

• WIGOS Community

Publication(s)

Manual on Codes vI.3, WMDS Table 1-01-01

Expected Impact of Change

LOW

Collaborators

References

https://cloudatlas.wmo.int

Validation

[gaochen-larc]

I think we should add description to each variable to ensure these codes will be properly used. Also, we need to do a comparison with the other cloud variables to understand if there is any significant overlap. I cannot help wonder if "Height of inversion" belong to the cloud category. I understand the presence of cloud has impact on the inversion height, but the inversion height itself is a property of the lower atmospheric structure...

[gaochen-larc]

"type of high clouds", "type of middle clouds", and "type of low clouds" definitely need description for how high, middle, and low are defined...

[fstuerzl]

"type of high clouds", "type of middle clouds", and "type of low clouds" definitely need description for how high, middle, and low are defined...

The levels high/middle/low are described in the cloud atlas: https://cloudatlas.wmo.int/en/useful-concepts.html#levels

Based on this reference, I propose to use the following description (analog for the 2 other variables):
Type of low clouds = "Result of cloud type classification in the lower level of the troposphere at 3 – 8 km altitude in polar regions, 5 – 13 km in temperate regions and 6 –18 km in tropical regions (https://cloudatlas.wmo.int/en/useful-concepts.html#levels)."

@gaochen-larc, do you agree with that?

[gaochen-larc]

"type of high clouds", "type of middle clouds", and "type of low clouds" definitely need description for how high, middle, and low are defined...

The levels high/middle/low are described in the cloud atlas: https://cloudatlas.wmo.int/en/useful-concepts.html#levels

Based on this reference, I propose to use the following description (analog for the 2 other variables): Type of low clouds = "Result of cloud type classification in the lower level of the troposphere at 3 – 8 km altitude in polar regions, 5 – 13 km in temperate regions and 6 –18 km in tropical regions (https://cloudatlas.wmo.int/en/useful-concepts.html#levels)."

@gaochen-larc, do you agree with that?

I think the "low clouds" are clear, i.e., clouds between the surface and 2 km. I think the key difference between middle and high clouds is: water clouds vs. ice clouds... I need to look into this a little more. The table you referred to lists the types of high, middle, and low clouds.

[gaochen-larc]

I think the "Cloud Hydrometeors" term is vague. We should consider use "Cloud Particles" instead. AMS uses the term "hydrometeors" for "any product of condensation or deposition of atmospheric water vapor", which is too broad. WMO has a very similar definition.

https://glossary.ametsoc.org/wiki/Hydrometeor

[amilan17]

subset of issue #190

[joergklausen]

Please consult WMO 182 and update the proposal with definitions. Also, the International Cloud Atlas may be a valuable resource. Who are the specific stakeholders, and who will be consulted for input? We need names there. @RMaerz Could you provide names from DWD? @ferrighi from metno? @JohnEyre from UKMO? @meulenvd from KNMI? We don't need representation from all of them, but a few statements would be helpful. We have only 2 weeks left ...

[meulenvd]

I recommed to contact the experts who worked on the publication of the digital ICA in 2017. You can find them in the foreword of the iCA, see https://cloudatlas.wmo.int/en/foreword-to-the-2017-edition.html - not only for clouds, but also for weather phenomena

[joergklausen]

notation	path	name	description
551	\Atmosphere\Clouds\Type\Type of high clouds	Type of high clouds	Type of clouds of genera Cirrus, Cirrocumulus, or Cirrostratus. These occur between 3-8 km (polar regions), 5-13 km (temperate regions) and 6-18 km (tropics) above ground [ref: WMO, International Cloud Atlas, 2017 ed.]
552	\Atmosphere\Clouds\Type\Type of middle clouds	Type of middle clouds	Type of clouds of genera Altocumulus, Altostratus, or Nimbostratus. These occur between 2-4 km (polar regions), 2-7 km (temperate regions) and 2-8 km (tropics) above ground [ref: WMO, International Cloud Atlas, 2017 ed.]
553	\Atmosphere\Clouds\Type\Type of low clouds	Type of low clouds	Type of clouds of genera Stratus, Stratocumulus, Cumulus, or Cumulonimbus. These occur between 0-2 km above ground [ref: WMO, International Cloud Atlas, 2017 ed.]

@gaochen-larc @fstuerzl Please update the proposal if you believe suggestions make sense. Then we can ask experts to confirm.

george.anderson@metoffice.gov.uk was suggested as an expert to consult for confirmation.

Error identified (low vs middle) corrected.

[gaochen-larc]

Michael (Shook, Michael A. (LARC-E303) michael.a.shook@nasa.gov) helped me identified a few issues: 1) definition for low clouds and middle clouds are switched, i.e., the description for 552 should be for middle clouds, not the low clouds as shown in the "name" column, and the description for 553 should be for low clouds; 2) we probably should add altostratus as one of the possible high cloud type. The nimbostratus may also be a low cloud type. Since there are overlaps in the middle and high altitude ranges, we may want to change the description text from "These occur between..." to "These usually occur between".

We may look at the AMS cloud classification: https://glossary.ametsoc.org/wiki/Cloud_classification

[JohnEyre]

This list of cloud variables seems rather arbitrary. If the full list of cloud variables in /wmdr is much longer than this, and if the aim of this proposal is only to add definitions for those variables currently lacking them, then this is OK. However, at some point, it may be good to review the full list of cloud variables for coherence and completeness.

[joergklausen]

@gaochen-larc I am not a cloud specialist, but these altitude ranges are the ones specified in the international cloud atlas. I don't know if they are really part of the definition, or if the word 'usually' can be added. You're assigned to the issue, it's your call what to push ;-)
@JohnEyre Yes, the intention was to advance what we can and I simply added definitions where I could. I agree that a more hoistic review at a later stage would be useful.

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/Meeting-2022.09.22 notes:

@gaochen-larc to follow up

[gaochen-larc]

If we change "These occur" to "These usually occur", can we move forward? agree with @JohnEyre, we should look at the full cloud list at some point

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/2022.10.06-TT-WIGOSMD meeting notes:

@gaochen-larc to update the summary with proposal as it stands now to determine what we can update in this fast-track or not

[fstuerzl]

Cloud hydrometeor concentration is currently used at one station in OSCAR/Surface: https://oscar.wmo.int/surface/#/search/station/stationReportDetails/0-242-3-7765C

[gaochen-larc]

After today's lively discussion, I believe we have reached the conclusion on 551, 552, and 553. While "hydrometeor" is an outdated term, there are two codes for "cloud hydrometeor concentration" in the table: 132 and 182. We need to look into this further to see if this variable can be substituted by "Number density of cloud droplets". Similarly, "Effective radius of cloud hydrometeors" (131 and 183) may be substituted by "Cloud drop effective radius" (181) and "Cloud ice effective radius" (329). We don't have sufficient information to properly add definitions for 501, 502, and 533. We should find out if these variables are actively used and what data they represent...

[meulenvd]

Cloud hydrometeor concentration is currently used at one station in OSCAR/Surface: https://oscar.wmo.int/surface/#/search/station/stationReportDetails/0-242-3-7765C

Interesting, observations started in 1983 with automatic observations (?). It looks like precipitation in clouds or drizzle detection, but it is not explaned how. May be we should contact the OSCAR/Surface contacts, mentioned on the site and ask for details.

[joergklausen]

After today's lively discussion, I believe we have reached the conclusion on 551, 552, and 553. While "hydrometeor" is an outdated term, there are two codes for "cloud hydrometeor concentration" in the table: 132 and 182. We need to look into this further to see if this variable can be substituted by "Number density of cloud droplets". Similarly, "Effective radius of cloud hydrometeors" (131 and 183) may be substituted by "Cloud drop effective radius" (181) and "Cloud ice effective radius" (329). We don't have sufficient information to properly add definitions for 501, 502, and 533. We should find out if these variables are actively used and what data they represent...

Makes sense to me. I have added the definitions to 551, 552, 553. Branch should be created; elements 132, 182 should be superseded.

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/2022.11.03-TT-WISOSMD notes:
@gaochen-larc update proposal in the issue summary with exact details of what we are proposing
@amilan17 will update the issue summary template

[amilan17]

I updated the proposal template, but I didn't check the values in the amendment details

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/2022.11.22-TT-WIGOSMD notes:

@gaochen-larc do you have a proposals for the missing descriptions?

@fstuerzl reach out to colleague (Eliane Thürig) at MeteoSwiss.

[fstuerzl]

I've checked the Int. Cloud Aatlas again and received the comments or proposals for definitions from my colleage Eliane, which I'd like to put up for discussion:

• 182, Cloud hydrometeor concentration: Concentration of liquid or solid water particles, which may be suspended in the atmosphere, fall through the atmosphere, be blown by the wind from the Earth’s surface or be deposited on other objects. Snow or water on the ground is, by convention, not considered a hydrometeor. (https://cloudatlas.wmo.int/en/general-classification-of-meteors-hydrometeors.html) Comment: Humidity close to or at 100% in order to make the waterdroplets or ice particles visible.
• 183, Effective radius of cloud hydrometeors: Link, that may be helpful: https://acp.copernicus.org/preprints/acp-2021-295/acp-2021-295.pdf
• 507, Optical depth of fog: The term “fog” is used when microscopic droplets reduce horizontal visibility at the Earth’s surface to less than 1 km, while the term “mist” is used when the droplets do not reduce horizontal visibility to less than 1 km. In practice, mist is considered synonymous with “light fog”. (https://cloudatlas.wmo.int/en/fog-compared-with-mist.html)
• 508, Optical depth within each cloud layer: Should be the same than Cloud optical depth. A cloud layer is a group of clouds, that have the same height of their base.
• 533, Height of inversion: An increase of temperature with height. Inversions and stable layers inhibit vertical motion, often limiting the vertical extent of cumuliform clouds. If the air below an inversion is relatively moist, the inversion often caps a layer of stratiform cloud. (https://cloudatlas.wmo.int/en/glossary.html#I)

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/2022.12.08-TT-WIGOSMD notes: @fstuerzl posted some review comments (see just above). @gaochen-larc will provide an update on 508. @fstuerzl will ask data provider for their definition.

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/2023.01.12-TT-WIGOSMD notes:

• still under discussion
• @fstuerzl move more controversial variables into new issue and update proposal

[amilan17]

@fstuerzl when the branch is ready, please open a PR to merge it into the FT2023-1 branch.

[fstuerzl]

@amilan17, the only uncontroversial changes are the new definitions for variables 551-553, which I've included in the branch for this issue. All other changes are moved to issue #443.