Meteorological Technology International finds out what action is being undertaken to reduce the environmental impact of the hundreds of weather balloons and radiosondes being released into the atmosphere daily.
Radiosonde observations continue to be one of the primary in-situ measurements relied on by atmospheric modelers. Coordinating them is a global initiative and the profiles they provide support – among other things – the validation of Earth-observing satellite observations, aviation industry planning (to optimize operations and potentially reduce fuel consumption) and the characterization of air masses that enable utility companies to plan for surge demands.
The industry is aware, however, of the environmental impact. Hundreds of radiosondes containing electronics, plastics and other environmentally hazardous materials are attached to weather balloons and released every day, many of which are discarded and forgotten about. But to their credit, manufacturers have begun taking action to improve the environmental sustainability of their products.
“Industry has stepped up to the challenge in the past two years, since this topic was openly discussed at events like Meteorological Technology World Expo (MTWE),” explains Shannon Kaya, director of transformation, innovation and engineering at the Meteorological Service of Canada, Environment and Climate Change Canada.
“Manufacturers have been making steady progress, implementing innovations such as biotwine, esondes and other biodegradable parts. However, the criticality of radiosonde observations has challenged the ability of manufacturers to make wholesale changes to their approach while ensuring support for the continuity of global operational air monitoring programs,” she adds.
Kaya notes that the Ecodesign Directive and Digital Product Passport are also helping to drive the radiosonde industry toward more sustainable, transparent and environmentally conscious designs. These regulations encourage the development of products that minimize environmental impact and enable circular economy principles.
Recover and reuse?
Generally, radiosonde recovery takes place only when there’s a need to reuse specific instruments or gather additional data from the device. In most instances, they’re not recovered due to their low cost and the difficulty of retrieval – accessing some of the landing locations, for example, could actually have a greater environmental impact than abandoning the equipment.
“Meteorological services don’t have the human resources to do this, and the carbon footprint of such an operation is also questionable,” explains Bruno Piguet, head of the upper-air observation department in Météo France’s directorate of observation systems.
“Due to the critical importance of the radiosonde data, it’s better to use recycled materials and manufacture a new radiosonde than collect, transport and reuse,” adds Aki Lilja, director of infrastructure devices and systems at instrument producer Vaisala. “Transportation to Vaisala would cause additional CO2 footprint with no guarantee of the possibility of reuse.”
“Manufacturers have been making steady progress, implementing innovations such as biotwine, esondes and other biodegradable parts”
Shannon Kaya, Meteorological Service of Canada, Environment and Climate Change Canada
There is a view, however, that recovery could help reduce the environmental impact as components could either be recycled or reused – but not the unit as a whole because the quality of the observations may be compromised by the environment, meaning a recovered radiosonde may not perform in the same way as a new one.
There are several potential solutions to aid the recovery of old radiosondes, including radio tracking, where the radiosonde emits a signal that can be tracked; balloon recovery systems such as parachutes and buoyancy controls that ensure the radiosonde lands in a specific, recoverable location; and automatic locator systems (GPS). The latter bring up another concern, however: a tracking system will limit the battery’s life, but replacing it with a larger battery would increase the impact on environmental sustainability.
Organizations are also turning to the general public for support. Many agencies mark radiosondes with information on how to return or recycle them, and there are also community retrieval initiatives. “We partner with Australian non-profit SondeHub, which tracks global radiosonde launches to enable hobbyists and researchers to recover payloads,” says Johannes Frielingsdorf, head of R&D (sounding systems) at radiosonde manufacturer Graw. “We believe that enabling the recovery of any radiosonde, independent of vendor, should be supported.”
Alternatives to radiosondes
Research also continues into technologies that could supplement or possibly replace radiosonde observations. For example Graw recently announced the world’s first operational lidar that can measure wind and temperature profiles from the ground up to above the stratosphere.
The National Oceanic and Atmospheric Administration (NOAA) continues to evaluate everything from satellite soundings and aircraft observations through to drones and ground-based remote sensing (lidars). However, although each of these observation methods provides excellent data in its own right, they all have limitations that render them insufficient to fully replace the traditional upper-air radiosonde observations, notes NOAA spokesperson Marissa Anderson.
“There’s a lot of potential in some of these technologies and as advances continue to be made, they’ll be evaluated,” she says. “It’s worth noting that even if a technology comes along that gives the accuracy and vertical coverage of a traditional sounding, radiosondes may still be needed in a limited capacity for calibration.”
New developments and designs
Researchers and manufacturers are now looking for new ways to reduce the environmental impact of their radiosondes. At the UK’s National Centre for Atmospheric Science (NCAS), researchers have begun using radiosondes that can be reused. Currently they cannot fly as high or as long as standard radiosondes, but they use less helium gas, have tracking software and land closer to the launch site, so they’re more likely to be recovered.
“Atmospheric observation scientists have also recently helped with testing experimental sustainable radiosondes that are made from small biodegradable balloons and lightweight electronics, which is a step in the right direction,” says David Hooper, an instrument scientist at NCAS and deputy head of the Atmospheric Measurement and Observation Facility (AMOF).
A typical radiosonde model lifespan is 10 to 15 years, and manufacturers are now incorporating changes mid-lifecycle. Frielingsdorf notes that this was unheard of previously and “is a clear sign of how important this issue is to the community”.
Batteries, circuit boards, gas, plastics and packaging are all important factors to consider when developing more sustainable radiosondes, as well as how appropriate they are for making atmospheric measurements. As far as waste is concerned, the two main areas of action are material substitution and mass reduction, notes Piguet. For the latter, the radiosondes used today are much lighter and require fewer batteries.
“In recent years, there’s been an increased focus on reducing the environmental impact of the instruments themselves, but changes to material design take a long time to develop and test,” explains David Edwards, a radiosonde network specialist at the UK Met Office.
“Radiosondes operate in a very challenging environment, enduring extremes of temperature, humidity, wind and pressure,” Edwards adds. “Therefore, the materials chosen need to be suitable for the job, which adds complexity. The impact of the materials on the quality of measurements also needs to be considered, as does the cost of any changes to the design.”
The hardest component to decarbonize
Manufacturers are improving the sustainability of their products. For example, in 2018 Vaisala decreased the amount of plastic in radiosonde covers by 47% and changed the supporting material inside each package to biodegradable paper-based material. “In 2023 we introduced Vaisala BioCover to get rid of expanded polystyrene and fiberglass-reinforced plastics in cover mechanics, and BioTwine to replace polypropylene with cellulose-based fiber as unwinder string material,” Lilja notes. “These new materials represent an overall reduction of 82% in plastics for the RS41 E-models compared with the original RS41 introduced in 2013.”
However, although other components of the radiosonde, such as plastics, PCBs and packaging, can be decarbonized using existing or emerging technologies, industry experts agree that the battery remains the hardest component to address. This is due to its reliance on carbon-intensive materials, energy storage limitations and the need for high reliability in challenging conditions.
Most batteries are lithium-based or other types that rely on rare and finite resources, which have significant carbon footprints from mining and processing. More sustainable battery technologies, such as solid-state, zinc-air or biodegradable, are still in the research and development phase and may not yet meet the strict requirements for energy density, reliability and operational lifespan in harsh weather conditions, notes Kaya.
“In addition, battery production is highly energy-intensive, contributing significantly to the carbon footprint,” she explains. “Creating battery cells requires large amounts of electricity, often sourced from fossil fuels, especially in countries where renewable energy is less common in industrial processes. This manufacturing process emits a substantial amount of carbon dioxide even before the battery is used.
“Batteries often contain toxic or harmful chemicals such as lithium, cadmium and cobalt,” she continues, “making disposal challenging and potentially harmful to the environment if they are not properly managed. Devising sustainable biodegradable or easily recyclable batteries is a technical challenge that hasn’t yet been fully resolved,” Kaya continues.
Radiosondes have strict weight limits to reduce balloon size and gas use, and reducing the carbon footprint of the battery while maintaining adequate power capacity in a lightweight form is a major challenge, Kaya notes. “Any increase in battery size or weight would necessitate a larger balloon, more gas and a higher overall environmental impact.”
“Radiosondes operate in a very challenging environment, enduring extremes of temperature, humidity, wind and pressure”
David Edwards, UK Met Office
Creating sustainable solutions
Work has begun and will be ongoing for many years to find a viable full solution to radiosondes. Although there are promising alternatives, there’s nothing currently that can fully replace this key piece of observation equipment.
As Kaya points out, “The global community needs to continue exploring alternative sources of equal-quality observations or methods of performing observations equivalent to current balloon-borne radiosondes.
“This challenge exists across many domains of the Earth systems observing community and is why WMO has placed such an emphasis on developing sustainable solutions,” she continues. “As long as we can keep this issue high on the global agenda for weather and environmental monitoring advances, a solution will eventually be developed,” Kaya concludes.
What happened to the Glidersonde project?
Back in the early 1990s, US National Center for Atmospheric Research (NCAR) engineer Dean Lauritsen proposed the concept of a recoverable/reusable sonde. His idea was the Glidersonde – a small, unpowered autonomous sailplane that would carry sensors for the collection of atmospheric data comparable to that from a radiosonde, and could be recovered, refurbished and reused.
“Now retired, Lauritsen said that NOAA’s National Severe Storms Lab was interested in the concept and may have done some tests, but the device was never put into operation in the US,” says NOAA spokesperson Marissa Anderson. “A key reason was that Federal Aviation Administration (FAA) regulations prohibited self-guided aircraft like the Glidersonde. However, the idea was picked up by a company in New Zealand called GPS Boomerang, which created an uncrewed system called the DataBird that carried a radiosonde and returned to base.”
Unfortunately, production of the radiosonde recovery system was abruptly halted by the Christchurch earthquake. Since then, attempts have been made by the company to revive the technology but it hasn’t yet been able to find a suitable market, according to its founder, Synco Reynders.
The concept of the glidersonde lives on, however, most currently in the form of R2Home’s ultralight glidersonde (see Reusable radiosondes, September 2024, p96*). “The real innovation with my glidersonde compared with previous attempts is its really low weight and small size, which makes it almost completely unregulated and thus easy to use,” notes R2Home founder Yohan Hadji.
Reynders has been mentoring Hadji since 2022, and the future is looking positive for this latest iteration of the glidersonde. R2Home is currently testing its solution with MeteoSwiss and the FAA, and the Swiss Federal Office of Civil Aviation (FOCA) has confirmed that the company’s glidersonde fits the same regulatory category as conventional models. This means R2Home requires no special authorization to operate in the skies.
In addition, R2Home recently announced its acquisition by Swiss weather forecasting company Meteomatics. “I’d love to get in touch with Lauritsen to let him know that 30 years later the dream is still on,” says Anderson. R2Home’s glidersonde concept
WMO support for sustainable observing systems
Over the past three years the Meteorological Service of Canada (MSC), in the role of focal point for environmental sustainability under the WMO, has significantly advanced work on the development and adoption of more environmentally sustainable weather observation strategies and technologies.
Work began in 2022 with a survey sent out to all WMO members, and a presentation at the TECO-2022 conference. Interest continued to grow and last year project lead Shannon Kaya held a two-day workshop for which more than 400 people registered, closely followed by a presentation at the 2023 Meteorological Technology World Expo. This year, the WMO endorsed the creation of a Study Group on Environmental Sustainability, which is being chaired by Karen Grissom, a physical scientist at the USA’s National Oceanic and Atmospheric Administration (NOAA) and National Environmental Satellite, Data and Information Service (NESDIS). The work of this study group will evolve over the coming years, with exciting opportunities and advances expected.
In the April 2024 issue of MTI, the WMO provided an update on its sustainable observing system work (see Going green, p20*).
This article originally appeared in the January 2025 issue of Meteorological Technology International. To view the magazine in full, click here.
