IWXXM 2025-2RC1 Comment 1 - QVA concentration category

[blchoy]

Larry Burch [email protected]

to tt-avdata, Karen

Dear members of the WMO Task Team on Aviation Data

I have concerns with the threshold descriptors in the QVA schema (shown below), as these differ from the descriptors used in the QVA information flyer (see Table 1 in the attached).

The code list for volcanic ash concentrations: - >= 0.2 mg/m3 "Low and possibly higher" - >= 2 mg/m3 "Medium and possibly higher" - >= 5 mg/m3 "High and possibly higher" - >= 10 mg/m3 "Very High”

The inclusion of the words "and possibility higher" should be removed as they may be misinterpreted by users and could negatively impact the operational use of the QVA forecasts.

Regards, Larry

Larry Burch Owner Flying and Weather, LLC Florida, U.S.A.

Mobile: +1-816-582-1904 Email: [email protected]

QVA Concentration Information Flyer 1stEd - rev21JUN2024.pdf

[amilan17]

https://github.com/wmo-im/iwxxm/wiki/TT-AvData-Discussion-2025-Jan-22 notes:

• The team discussed and agreed that "and higher" is correct.
• Team decided to bring this request back to Karen, who introduced QVA

[blchoy]

Right. Table 1 in the Flyer Larry posted defines the descriptors as follow:

Each of these descriptors refers to a range, and the highest and lowest ones are open ended.

In QVACI spatial variation of concentration of volcanic ash is represented by iwxxm:ElevatedVolume in which the boundary surface equals to the indicated value (e.g. 0.2 mg/m3) and the inside of the surface is greater than the indicated value. For such a volume a description combining "Low" (i.e. 0.2 <= x < 2 mg/m3) and "and possibly higher" (i.e. x > 2 mg/m3) is a logical choice but the whole phrase "Low and possibily higher" could be confusing to those who have no idea that "Low" is a defined range.

I am not a language expert and as discussed we will bring this back to the ICAO team for their advise.

[blchoy]

Karen Shorey reminded us that only when the whole range of polygons are present, viz:

should the verbose descriptions "Very low", "Low", "Medium", etc. be meaningful because they are describing the concentration in the space between adjacent polygons. In other words, textual description for individual code list entry cannot use any of these terms. We may simply present the symbolic range in text form in the description:

>= 0.2 mg/m3    "Greater than or equal to 0.2 mg/m3"
>= 2 mg/m3      "Greater than or equal to 2 mg/m3"
>= 5 mg/m3      "Greater than or equal to 5 mg/m3"
>= 10 mg/m3     "Greater than or equal to 10 mg/m3”

[mgoberfield]

@blchoy to make sure I understand correctly: The ash concentration code list may have concepts like "Low", "High", "Very high" but the description of each concept should not include the adjectives. If this is correct, then the schema documentation should just match the table you've shown. Shall I make the changes to the QVACI documentation in the UML model or will you do it?

[blchoy]

Thanks @mgoberfield. However, not only the description of each entity needs to be changed, but the notation itself too. Currently for category >= 0.2 mg/m3, the codelist entry is:

http://codes.wmo.int/iwxxm/VolcanicAshConcentrations/LOW_AND_POSSIBLY_HIGHER

Since we can only use LOW to represent a range, viz 0.2 <= x < 2 mg/m3, we need a name for the category >= 0.2 mg/m3. If we follow what the BUFR Code and Flag Tables are doing (i.e. using numbers to represent each category):

For x >= 0.2 mg/m3

http://codes.wmo.int/iwxxm/VolcanicAshConcentrations/1

For x >= 2 mg/m3

http://codes.wmo.int/iwxxm/VolcanicAshConcentrations/2

For x >= 5 mg/m3

http://codes.wmo.int/iwxxm/VolcanicAshConcentrations/3

For x >= 10 mg/m3

http://codes.wmo.int/iwxxm/VolcanicAshConcentrations/4

Until someone can think of more verbose categories, I think that is the way to go.

[amilan17]

https://github.com/wmo-im/iwxxm/wiki/TT-AvData-Discussion-2025-Jun-13 notes: ask WG-MIE if needed, might not need to have descriptive thresholds for the ranges included in the report

[blchoy]

Just confirmed with Karen that there is no textual descriptions for the thresholds, and there is no point to describe >= 0.2 mg/m3 in textual form "Greater than or equal to 0.2 mg/m3". In that case, there is no need to use a code list and it will be removed in 2025-2RC2.

[blchoy]

Implemented in IWXXM 2025-2.