WMO UAS Demonstration Campaign Description

Background

The WMO Uncrewed Aircraft Systems Demonstration Campaign (UAS-DC) was an eight-month programme of meteorological observations made by UAS. It ran from 1 March to 31 October 2024. Participant operators contributed on a voluntary basis and at their own cost. Contributors came from the public, governmental, academic and private sectors and worked with researchers and developers of UAS for meteorological research and operational forecasting.

The campaign was set up following Decision 18 (INFCOM-1), by which the Commission endorsed the further development and scoping of a WMO-coordinated global demonstration project on UAS. It also built on the recommendations of the WMO Workshop on the Use of Unmanned Aerial Vehicles for Operational Meteorology (Toulouse, July 2019). The UAS-DC Plan (Version 1.2, September 2022) was endorsed by the INFCOM Management Group in March 2022 and presented to INFCOM-2.

Aims

1. To demonstrate current capabilities of a range of UAS and to measure their capacity to contribute to meeting operational requirements for upper-air observations and the filling of observational gaps of the WIGOS GBON and/or RBON.
2. To demonstrate the capacity of UAS and their data processing systems to provide data in an interoperable format ready for use by relevant applications and forecast systems.
3. To measure, analyse and report on the impacts of UAS observations on relevant WMO application areas and forecast systems.
4. To determine more generally and report on areas of development needed for UAS to adequately meet requirements to efficiently, economically and environmentally responsibly contribute operationally to WIGOS.
5. To determine and make recommendations relating to regulatory conditions imposed on UAS that impact their ability to contribute to WIGOS.

Coordination and Planning

The UAS-DC was planned and coordinated under the WMO Commission for Observation, Infrastructure and Information Systems (INFCOM). The Joint Expert Team on Aircraft-Based Observing Systems (JET-ABO) and its Subgroup on UAS were mainly responsible for coordination until INFCOM 3, when the coordination was taken by Expert Team on Aircraft-Based Observing Systems (ET-ABO)

In 2022, JET-ABO set up a Scoping, Planning and Organizing Committee (SPOC), which:

• oversaw the development and approval of the campaign plan, including its scope and the requirements of participants;
• developed a communications plan;
• coordinated the external approvals needed, for example with regulators;
• oversaw and coordinated the campaign before, during and after the observing period.

The SPOC and the UAS-DC Core Coordination Group held regular online meetings with participants during the preparatory phase and throughout the campaign.

Scope and Participation

Observing period and Special Observing Periods (SOPs). The campaign ran from 1 March to 31 October 2024 and included three SOPs. During the SOPs, participants were encouraged to fly more often and from more sites:

1. April 2024, with priority on the week of the total solar eclipse of 8 April;
2. 28 July – 14 August 2024, overlapping with the Paris 2024 Olympic Games;
3. 8–13 September 2024, alongside the ISARRA 2024 flight week and the SCALES campaign in Tulsa, Oklahoma, USA.

Participants. There were two groups of participants:

• Participant UAS Operators: 44 operators from 13 countries, including national meteorological and hydrological services, research institutions and commercial companies.
• Participant Data Users: NWP centres (including ECMWF, DWD, MeteoSwiss and NOAA GSL), meteorological services and research organizations.

Platforms. The campaign used a wide range of platforms:

• multirotor UAS, about 82 % of logged flights;
• fixed-wing UAS, about 10 %;
• VTOL UAS, about 2 %;
• dropsondes released from balloons, about 5 %;
• balloon-launched gliders and long-duration high-altitude balloons.

Most flights sampled the lowest 1.5 km of the atmosphere. Some UAS reached 9,000 m above mean sea level (MSL), and balloon-based platforms reached up to 23,177 m MSL. All observations were made in the Northern Hemisphere, mostly in Europe and the United States, with additional sites in Asia.

Observed variables. The campaign focused on near-real-time provision of the variables needed for data assimilation in numerical weather prediction (NWP):

• Nearly all data files contained air temperature, air pressure and relative humidity.
• More than 90 % also contained horizontal wind.
• A small fraction contained vertical wind, aerosols, trace gases (O₃, NH₃, CO, NO₂, H₂S, SO₂, VOCs) and turbulence parameters.

Data provision. Operators were asked to provide routine observations (at least once a day, on at least four days per week) for at least one month and during at least one SOP. They were asked to deliver data in near-real time, preferably within 30 minutes and no later than 3 hours after the observation.

Data were submitted in the WMO-CF UAS Trajectory (CF-NetCDF) format to a central repository operated by Synoptic Data PBC. They were converted automatically to BUFR and distributed through the WIS 2.0 UAS DC Global Broker. In total, the campaign produced more than 13,000 flights and 13,100 data files, and more than 80 % of files were uploaded within one hour of acquisition. All participants were required to adhere to the UAS-DC Data Policy.

Reporting. Operators recorded their flights in the Daily Operator Log and summarized their experience in the Post-Campaign Report, which 27 operators completed. These reports, together with assessments by data users, are the basis of the Final Report of the WMO UAS-DC.

Outcomes

The campaign delivered or contributed to the following outcomes, reported in detail in the Final Report:

1. Assessment of the capabilities of UAS to contribute to WIGOS and GBON.
   • The campaign was the first globally coordinated WxUAS observing exercise and showed that it is feasible at this scale.
   • Routine profiling with a low rate of technical failures was demonstrated.
   • Validations of individual platforms indicate boundary-layer data quality comparable to ground-based remote sensing.
   • A systematic, campaign-wide validation against reference instruments remains to be done.
2. Understanding of the technical and operational improvements needed for transition to operations. These include:
   • standardized calibration and uncertainty estimation;
   • better resilience to wind, precipitation and icing;
   • extended metadata in data files;
   • refinement of the data format and conversion tools.
3. Improved understanding of the impact of UAS on NWP and other forecast systems.
   • Comparisons with the NWP background fields of DWD and NOAA show few outliers, indicating that the data are suitable for data assimilation.
   • Observing system experiments using campaign data are ongoing.
4. Improved understanding of the limitations imposed by airspace regulations.
   • Approval processes for flights beyond visual line of sight (BVLOS) and above 120 m, and the requirement for a pilot and an observer for each UAS, were identified as the main constraints on routine operations.
   • The report includes recommendations for ICAO, civil aviation authorities and air navigation service providers.

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