Table D, proposal for an new BUFR template dedicated to drifting balloon platforms: 3 11 013

[adoerenbecher]

Initial request

Rationale:
Field campaigns with long duration drifting balloons are quite common/frequent. Sometimes high-value data are available in real-time and could be used in numerical weather prediction applications (e.g. data assimilation).

Drifting balloons are a world unto themselves and a very wide variety of measurements can be collected using them (both in-situ and remotely sensed data, e.g. radio-occultation) because these are primarily vectors. These vectors are chosen for their ability to transport sensors to atmospheric regions that would otherwise be difficult to access.

These drifting systems are very often fitted with sensors to measure the close environment of the balloon, and these are the data of interest here.

With this issue we propose to set up a new BUFR template to allow the dissemination of in-situ data (at the flight level) to the meteorological community. Such a BUFR template would be a trade-off between aircraft or radiosonde messages, involving the definition of new tables as a few novel concepts should be defined.

Purpose:
The requestor (Météo-France Research Department, aka CNRM) has some experience in using observations collected by balloons operated par CNES (French National Space Agency) in various field campaigns such as CONCORDIASI, Stratéole-2 (stratospheric data in the global model) or HyMeX (marine boundary layer above the Mediterranean in the regional model). During these campaigns the data were made available using FTP repositories. Having an official BUFR template dedicated to these balloons data would also help in the dissemination of the data to the community.

The Stratéole-2 is not over and a last (third) campaign will take place at the end of 2026 with flights circumnavigating the tropical tropopause layer (TTL) for months with a flotilla of about 20 balloons drifting at either 18 or 20km of altitude. Many experimental systems will collect research data, but the TSEN system (IPSL/LMD, France) is able to collect high quality data and send them in real-time through satellite link.
Météo-France participates in the Stratéole-2 effort and is ready to disseminate the data on the global telecommunication system if WMO allows it, and having a proper BUFR template is part of it.

At CNRM, we have designed a preliminary local version of a BUFR template to make tests with the data of the two first campaigns of the Stratéole-2 project. This dedicated BUFR format allow both the IT system and data assimilation systems to handle balloon data properly. For these data which are neither radiosonde, neither aircraft data, it is crucial to properly control black or whitelisting, observation uncertainties or thinning procedures.

Implementation plan:
Here we simply submit our attempts to build a sensible template (3 11 012) to your expertise.
We have used new code for descriptors corresponding to the quantities that were not already defined in the BUFR documentation. We hope that these do not clash with recent descriptors.
Depending on the decisions of the WMO experts, we can adjust the preliminary template we have build and provide WMO with a sample of real data collected during the past Stratéole-2 data.
As soon as the BUFR template is validated we will ask WMO for an authorization to disseminate the Stratéole-2 data.
If authorized, we will prepare the data flow in order to be ready in September 2026.

Amendment details

The tables below describe the descriptors we are proposing for the new BUFR message model for data from drifting balloons. We have tried to follow the format used in the official BUFR documentation. The last column gives examples of values for data from the Stratéole-2 campaign.

Most of the descriptors used here already exist.

However, new descriptors need to be created, in particular for metadata describing the balloons and also how the data is collected. In the case of Stratéole-2, the measurement station is not compact like a radiosonde and the measurement points are distributed vertically: it is therefore necessary to be able to describe this staggering in relation to the point where the altitude is measured (GNSS).
We have put a ‘new’ label next to the descriptors to be created.

We include the necessary structure for humidity information, even though Stratéole-2/TSEN data do not have humidity.
But in case it may happen with other balloons (e.g. encoding for Windborne data) the structure is already there.

The following section (publication) lists the descriptors to be created.

CATEGORY	ELEMENT NAME	TABLE REFERENCE	UNIT	SCALE	REF. VALUE	DATA WIDTH	STATUS	COMMENTS	EXAMPLE (case of TSEN Strateole-2)
WIGOS	Wigos Identifier Series	0-01-125	Numeric	0	0	4	existing		0
WIGOS	Wigos Issuer Of Identifier	0-01-126	Numeric	0	0	16	existing		250 (France in ISO-3166)
WIGOS	Wigos Issue Number	0-01-127	Numeric	0	0	16	existing		0
WIGOS	Wigos Local Identifier Character	0-01-128	CCITT IA4	0	0	128	existing		"STR2C201"
Carrier	Balloon flight number	0-01-156 (new)	CCITT IA4	0	0	64	to be proposed	curr. vacant	"STR2C201"
Carrier	Balloon Registration number or other identification	0-01-157 (new)	CCITT IA4	0	0	64	to be proposed	curr. vacant	"Stratéole-2"
Carrier	Originating centre	0-01-035	Common Code Table C-11	0	0	8	existing		85 (Météo-France, Toulouse)
Carrier	Identification of originating/generating sub-centre	0-01-034	Common Code Table C-12	0	0	16	to be proposed	curr. vacant	205 (CNES)
Carrier	Type of balloon envelope	0-01-158 (new)	Code Table	0	0	16	to be proposed	curr. vacant	0 (SPB)
Carrier	Typical size of balloon enveloppe	0-01-159 (new)	m	0	0	12	existing		12 (ballon diameter)
Carrier	Phase of balloon flight	0-08-100 (new)	Code Table	0	0	4	to be proposed	curr. vacant	ascent, ceiling, descent, drop, unsteady
Sonde	Type of station	0-02-001	Code Table	0	0	2	existing		0 (Automatic)
Sonde	Radiosonde type	0-02-011	Code Table	0	0	8	to be proposed	curr. vacant	136 (TSEN)
Sonde	Precision of temperature observation	0-02-005	K	2	0	7	existing		0.05 (values for TSEN)
Sonde	Precision of pressure observation	0-02-192 (new)	Pa	-1	0	14	to be proposed	curr. vacant	10 (values for TSEN)
Sonde	Precision of mixing ratio observation	0-02-193 (new)	kg/kg	-1	0	14	to be proposed	curr. vacant	missing (no value for TSEN)
Sonde	Tracking technique/status of system used	0-02-014	Code Table	0	0	7	existing		8 (Automatic satellite navigation)
Sonde	Type of measuring equipment used	0-02-003	Code Table	0	0	4	existing		7 (satellite navigation)
Sonde	pressureSensorType	0-02-095	Code Table	0	0	5	existing		30 (other: piezo-electric transducer)
Sonde	temperatureSensorType	0-02-096	Code Table	0	0	5	existing		1 (bead thermistor)
Sonde	humiditySensorType	0-02-097	Code Table	0	0	5	existing		31 (missing)
Sonde	Sample averaging period	0-25-171	s	0	0	10	existing		900
Sonde	Sample size	0-25-172 (?)	Numeric	0	0	10	existing		30
Date/Time	Time significance	0-08-021	Code Table	0	0	6	existing		26 (Time of last known position)
Date/Time	Year	0-04-001	a	0	0	12	existing		2018
Date/Time	Month	0-04-002	mon	0	0	4	existing		12
Date/Time	Day	0-04-003	d	0	0	6	existing		1
Date/Time	Hour	0-04-004	h	0	0	5	existing		0
Date/Time	Minute	0-04-005	min	0	0	6	existing		0
Date/Time	Second	0-04-006	s	0	0	6	existing		0
Positionning	Latitude	0-05-001	degree	5	-9000000	25	existing	high accuracy
Positionning	Longitude	0-06-001	degree	5	-18000000	26	existing	high accuracy
Positionning	Height	0-07-007	m	0	-1000	17	existing	at GPS rec.
Positionning	Station elevation quality mark (for mobile stations)	0-33-024	Code Table	0	0	4	existing		2 or 1 (values for TSEN system)

Here follow the descriptors for the data :

CATEGORY	ELEMENT NAME	TABLE REFRENCE	UNIT	SCALE	REF. VALUE	DATA WIDTH	STATUS	COMMENTS	EXAMPLE
Measurements	Pressure	0-07-004	Pa	-1	0	14	existing
Measurements	Height of pressure sensor wrt station	0-07-077 (new)	m	0	-400	12	to be proposed		0
Measurements	Geopotential height	0-10-009	gpm	0	-1000	17	existing
Measurements	Temperature/air temperature	0-12-001	K	1	0	12	existing
Measurements	Height of temperature sensor wrt station	0-07-079 (new)	m	0	-400	12	to be proposed		-10
Measurements	Standard deviation of temperature	0-12-051	K	0	0	10	existing
Measurements	Water vapour mixing ratio	0-13-002	kg/kg	5	0	14	existing		missing
Measurements	Height of humidity sensor wrt station	0-07-080 (new)	m	0	-400	12	to be proposed		missing
Measurements	Standard deviation of mixing ratio	0-13-165 (new)	kg/kg	5	0	14	to be proposed	curr. vacant	missing
Measurements	Wind direction	0-11-001	degree true	0	0	9	existing
Measurements	Wind speed	0-11-002	m/s	1	0	12	existing
Measurements	Height of wind sensor wrt station	0-07-078 (new)	m	0	-400	12	to be proposed		10
Measurements	Standard deviation of wind direction	0-11-049	degree true	0	0	9	existing
Measurements	Standard deviation of wind speed	0-11-050	m/s	1	0	12	existing

As we introduce new Code tables... Here are the information for the code figures to be used.

Descriptor 0-01-158 for "Type of balloon envelope"

Code figure	Meaning
0	Reserved
1	SPB (Super-Pressurized Balloon) without altitude control
2	SPB (Super-Pressurized Balloon) with altitude control
3	ZPB (Zero-Pressure Balloon)
4	IRM (Infra-Red Montgolfier)
5	Airship (Airship-shaped Balloon)
6	Tetrodon (NOAA tetraedric Balloon)
15	Missing value

Descriptor 0-02-011 for "Sonde type" : add a new entry

Code figure	Meaning
136	TSEN

Descriptor 0-08-100 for "Phase of balloon flight"

Code figure	Meaning
0	Reserved
1	Ascent
2	Ceiling
3	Descent
4	Drop (falling station)
5	Unsteady (during manoeuvres)
15	Missing value

Comments

We have a PDF document about this BUFR template proposal.
It is available on demand.

Requestor(s)

DOERENBECHER Alexis, Météo-France, Reaserche Center (CNRM) and Stratéole-2 project ([email protected])
POURRET Vivien, Météo-France, Reaserche Center (CNRM) and Stratéole-2 project ([email protected])

Stakeholder(s)

The amendment has been designed to not change (hopefully) the existing BUFR matter, but only to add new features to the BUFR system.
All the research and operational numerical weather prediction centers might be impacted as soon as they try to decode balloon data that would have been disseminated by the Météo-France/Stratéole-2 project on the global telecommunication system by the end of 2026 (see "initial request" section for more details on the implementation plan).

Publication(s)

Manual on Codes (WMO-No. 306), Volume I.2, BUFR, Table D, Class/Category 11, add BUFR descriptor 3 11 013 (template)
Manual on Codes (WMO-No. 306), Volume I.2, BUFR, Class 01, code table 0 02 011: add TSEN station
Manual on Codes (WMO-No. 306), Volume I.2, BUFR, Class 01, add BUFR descriptor 0 01 156
Manual on Codes (WMO-No. 306), Volume I.2, BUFR, Class 01, add BUFR descriptor 0 01 157
Manual on Codes (WMO-No. 306), Volume I.2, BUFR, Class 01, add BUFR descriptor 0 01 158
Manual on Codes (WMO-No. 306), Volume I.2, BUFR, Class 01, add BUFR descriptor 0 01 159
Manual on Codes (WMO-No. 306), Volume I.2, BUFR, Class 02, add BUFR descriptor 0 02 192
Manual on Codes (WMO-No. 306), Volume I.2, BUFR, Class 02, add BUFR descriptor 0 02 193
Manual on Codes (WMO-No. 306), Volume I.2, BUFR, Class 07, add BUFR descriptor 0 07 077
Manual on Codes (WMO-No. 306), Volume I.2, BUFR, Class 07, add BUFR descriptor 0 07 078
Manual on Codes (WMO-No. 306), Volume I.2, BUFR, Class 07, add BUFR descriptor 0 07 079
Manual on Codes (WMO-No. 306), Volume I.2, BUFR, Class 07, add BUFR descriptor 0 07 080
Manual on Codes (WMO-No. 306), Volume I.2, BUFR, Class 08, add BUFR descriptor 0 08 100
Manual on Codes (WMO-No. 306), Volume I.2, BUFR, Class 13, add BUFR descriptor 0 13 165

Expected impact of change

MEDIUM

Collaborators

Collaborators are the principal investigators (PI) in the Stratéole-2 project.
Stratéole-2 project is a French-American project to better understand atmospheric mechanisms at stake in the Earth climate system, focusing on the Tropical Tropopause Layer and hydration processes in relation with deep convection.
Stratéole-2 has 2 field campaigns involving instrumented stratospheric balloons operated by CNES (plus a test campaign). Scientific payloads may vary from one balloon to another and most of these are cutting edge systems to collect unprecedented dataset. However, all balloons are fitted with high quality instrumentation to measure pressure and temperature at flight level and also estimate horizontal wind (TSEN system, IPSL/LMD). The data collect by the latter are available at high-frequency and in near-real-time.
These data are of high value global numerical weather prediction activities. All other data are available on open database after the campaigns.
The PI for the TSEN system is Albert Hertzog (IPSL/LMD). He is responsible for the raw data collection and preprocessing.
The CNES chief manager of the balloon operations is Stephanie Venel.

References

Here follow a few references about Stratéole-2.
TSEN website: https://www.lmd.ipsl.fr/en/instruments-lmd/tsen-2/
Stratéole-2 in EOS: https://eos.org/science-updates/around-the-world-in-84-days
Stratéole-2 white paper: https://www.lmd.polytechnique.fr/VORCORE/Documents/US%20Involvement%20in%20the%20Strateole%202%20Balloon%20Campaign.pdf

Validation

A prototype of this BUFR template for balloons has been built at Météo-France (research center) on the basis of local tables that can be used with EcCodes.

Data assimilation experiments in the ARPEGE global model have thus been carried out and the impact of TSEN data from the 2 Stratéole-2 campaigns that have already taken place (test campaign and campaign n°1) has been measured. A scientific article on the results is being prepared and is not yet ready for distribution.

The results were presented at the Stratéole-2 conference in Boulder (USA) in June 2023. The presentation is available on request.

[adoerenbecher]

Sorry, I've forgotten to include a diagram that shows how the TSEN system is built - especially the vertical distance between the sensors. Here is the picture. !

strateole_balloon_parameters

[amilan17]

https://github.com/wmo-im/tt-tdcf/wiki/2024.10.16.tt.tdcf notes:

• Alexis presented the proposal
• Marijana and Sibylle provided feedback on details (@marijanacrepulja @SibylleK please add comments below as needed)
• @SibylleK will consult with colleaugues
• next campaign will start in October 2026, but it would be better to have this template available in advance
• discussion about whether this template also be used for WindBorne observations;
• after updates to the proposal based on feedback -- @adoerenbecher to provide sample BUFR files

[adoerenbecher]

Following the meeting on Oct. 16, I formalised the sequence of this proposed template. The description above is more or less a list of content. Colleagues explained to me how e well-defined sequence limits the number of new entries/descriptors to be created.

For example, it is not necessary to define a height in relation to the station for each parameter/sensor; it is sufficient to use a generic descriptor and to use the sequence "pressure", "temperature", "humidity" and "winds" to specify the vertical positioning of each sensor under the balloon.

The same logic applies to the sampling description. In the case of Stratéole 2, some raw data are acquired at high frequency and are averaged subsequently. The descriptors 0-25-170 and 0-25-171 are used to give this information. It is updated for each sensor, as each sensor may have its own acquisition protocol.

As a consequence, the measurement section should better read as follows.

CATEGORY	ELEMENT NAME	TABLE REFRENCE	UNIT	SCALE	REF. VALUE	DATA WIDTH	STATUS	COMMENTS	EXAMPLE
	Time significance	0-08-021	Code Table	0	0	6	existing		2
	Height of sensor wrt station	0-07-077 (new)	m	0	-400	12	to be proposed		0
	Sampling interval	0-25-170	s	0	0	10	existing		2
	Sample averaging period	0-25-171	s	0	0	10	existing		600
	Pressure	0-07-004	Pa	-1	0	14	existing
	Geopotential height	0-10-009	gpm	0	-1000	17	existing
	Height of sensor wrt station	0-07-077 (new)	m	0	-400	12	to be proposed		-10
	Sampling interval	0-25-170	s	0	0	10	existing		2
	Sample averaging period	0-25-171	s	0	0	10	existing		600
	Temperature/air temperature	0-12-001	K	1	0	12	existing
	Standard deviation of temperature	0-12-051	K	0	0	10	existing
	Height of sensor wrt station	0-07-077 (new)	m	0	-400	12	to be proposed		missing
	Sampling interval	0-25-170	s	0	0	10	existing		missing
	Sample averaging period	0-25-171	s	0	0	10	existing		missing
	Water vapour mixing ratio	0-13-002	kg/kg	5	0	14	existing		missing
	Standard deviation of mixing ratio	0-13-165 (new)	kg/kg	5	0	14	to be proposed	curr. vacant	missing
	Height of sensor wrt station	0-07-077 (new)	m	0	-400	12	to be proposed		10
	Sampling interval	0-25-170	s	0	0	10	existing		60
	Sample averaging period	0-25-171	s	0	0	10	existing		600
	Wind direction	0-11-001	degree true	0	0	9	existing
	Wind speed	0-11-002	m/s	1	0	12	existing
	Standard deviation of wind direction	0-11-049	degree true	0	0	9	existing
	Standard deviation of wind speed	0-11-050	m/s	1	0	12	existing

The template is open to the introduction of other parameters in relation with e.g. atmospheric chemistry.

[adoerenbecher]

I attach here a PDF document to better show the clarified sequence for this template.

BUFR_proposal_sequence_v2.pdf

[jbathegit]

As noted by a colleague within DMI, the data width for the proposed new 0-01-158 ("Type of balloon envelope") descriptor appears to be incorrect. It is listed as 16, when a look at the corresponding proposed code table indicates the data width should be 4 instead.

[amilan17]

https://github.com/wmo-im/tt-tdcf/wiki/2024.11.12.tt.tdcf notes:

• Alexis provided an update (see PDF );
• team asked questions about the various details
• Sibylle recommended adding time period and significance
• add (008021) time significance and (004026) time period or displacement (for the parameters)
• remove line 28 for time significance
• spell out wrt
• @adoerenbecher update proposal and provide sample data
• Jeff expressed concern about pushing the template before real data is available; Alexis noted that there is real data from 2019 and 2021, but the intent is to use this for the 2026 data.
• Jeff has shared this effort with WindBorne and others for their awareness; Marijana noted that we think that the WindBorne data is not averaged
• Target fast-track is 2025-2

[amilan17]

https://github.com/wmo-im/et-data/wiki/2024.12.04.et.data notes:
still waiting for feedback and there is time before FT2025-2