AIR MONITORING


ABB to supply interferometer for Himawari-10 Japanese geostationary meteorological satellite


ABB has been awarded a contract by L3Harris Technologies, a leading US defense company, to develop and build a high-resolution infrared interferometer system to power the next generation of L3Harris hyperspectral infrared (IR) sounder. The system onboard the Himawari-10 satellite built by Mitsubishi Electric in Japan, will map in 3D the earth’s atmosphere over the Asia- Pacifi c region for 10 years.


TALKINGPOINT


CLOUDS: ARE WE IGNORING A CRUCIAL DRIVER OF RECENT GLOBAL WARMING?


Clouds play a crucial role in regulating Earth’s climate by infl uencing both incoming solar radiation and outgoing infrared radiation. Their effects, however, depend heavily on cloud type, altitude, and coverage. As global temperatures rise, changes in cloud behaviour can either amplify or dampen warming—a process known as cloud feedback. Most evidence suggests that cloud feedback is a net positive feedback, meaning it accelerates climate change rather than counteracting it.


Clouds impact Earth’s energy balance in two key ways. Firstly, by refl ecting sunlight, or shortwave cooling. Low-altitude clouds, especially stratocumulus and stratus, have high albedo (refl ectivity) and effi ciently refl ect sunlight back into space, cooling the surface. Secondly, by trapping heat, or longwave warming. High-altitude clouds, such as cirrus, allow sunlight to pass through but trap outgoing infrared radiation, acting like a greenhouse gas and warming the Earth.


One of the most concerning cloud feedback mechanisms is the potential decrease in low-altitude clouds as temperatures rise. Several factors contribute to this reduction. As greenhouse gases trap more heat, the upper troposphere warms more than the surface. This suppresses convective mixing, making it harder for low clouds to form. A warmer atmosphere requires rising air to travel farther before it cools enough to condense into clouds. This reduces the formation of low clouds.


Warming intensifi es large-scale atmospheric circulation patterns, increasing the downward movement of dry air, which suppresses low cloud formation, particularly over oceans. More longwave radiation from the surface heats and evaporates low clouds, thinning them out and reducing their coverage.


Since low clouds are highly refl ective, their loss means more sunlight reaches the surface, causing further warming—a classic positive feedback loop.


While low clouds tend to decrease, high clouds are expected to increase in a warming world. This also creates a positive feedback effect. More water vapor in a warmer atmosphere, so high-altitude cloud formation increases. High clouds are poor at refl ecting sunlight but excellent at trapping heat.


Human activities have historically released aerosols (tiny particles) into the atmosphere, which help form low clouds by providing cloud condensation nuclei (CCN). However, as air pollution controls reduce


aerosol emissions, fewer CCN are available, leading to larger but fewer cloud droplets, which make clouds less refl ective; faster cloud dissipation, reducing low cloud coverage; and a decrease in the overall cooling effect of low clouds, amplifying warming.


This means that as pollution declines, an unintended side effect may be less cloud cooling, allowing warming to accelerate. Current climate models


suggest that cloud feedback is predominantly positive, meaning it amplifi es rather than mitigates climate change. Observational studies, satellite data, and high-resolution models increasingly show low cloud coverage declining in key regions (e.g., subtropical oceans), reducing refl ection of solar radiation, whilst high cloud coverage increases, enhancing the greenhouse effect.


Similarly, reductions in aerosols will decrease the formation of low- altitude clouds and there will be fewer refl ective particulates in the atmosphere, too.


Some researchers, including James Hansen and colleagues, argue that climate sensitivity—how much warming results from a given CO₂ increase—may be higher than previously estimated due to underestimated cloud feedback strength.


Despite strong evidence for positive cloud feedback, signifi cant uncertainties remain. Cloud formation and behaviour are highly complex, and smallscale cloud processes are diffi cult to model with precision.


The key areas of uncertainty include the exact magnitude of low cloud reduction and its impact on future warming; regional variations in cloud feedback effects, particularly in the tropics and mid-latitudes; and how cloud-aerosol interactions will evolve as air pollution declines globally. However, given the mounting observational evidence and improved climate models, it is increasingly clear that cloud feedback is not just a secondary factor but a major amplifi er of climate change.


According to Hansen et al, cloud feedback is responsible for almost two thirds of the reduction in Earth’s albedo, which they believe has been occurring since 2000.1


gather more observational data, there have been calls for higher climate sensitivity estimates, suggesting that future warming could be more severe than previously anticipated.


1 The Acid Test: Global Temperature in 2025. James Hansen and Pushker Kharecha. 2025.


The L3Harris sounder will be deployed at an altitude of 36 000 km in geostationary orbit, helping the Japan Meteorological Agency to improve predictions of the trajectory and intensity of extreme weather events as well as extend its long-term forecast. It will offer 30-minute revisit capability, considerably augmenting the quality and quantity of information feeding the weather prediction models over what is currently available.


Atmospheric sounders are high-end optical instruments able to probe the air mass’s physical properties driving weather such as temperature, humidity and movement. The bulk of the digital information ingested by supercomputers calculating today’s daily and hourly forecasts comes from infrared and microwave sounders. While Low Earth Orbit (LEO) weather satellites can map the whole globe, they can only refresh the data twice daily which creates an important temporal coverage shortage. Geostationary (GEO) weather satellites on the other hand ‘stand still’ in the sky over the equator and can track weather pattern evolution with a much-improved refresh rate.


However, Geostationary orbits are too distant for companion microwave sounders to operate making the IR sounders the sole instruments able to capture a time-lapsed digitised 3D view of the weather below.


“Hyperspectral IR sounders, introduced for the fi rst time in 2011 on the joint NASA/NOAA polar- orbiting NPP satellite, led to a transformation in the fi eld of weather forecasting,” said Dr Frederic Grandmont, Space Technology and Business Development Manager, ABB Measurement & Analytics. “Himawari-10 is expected to bring another level of improvement in weather forecasting accuracy for Japan and the Asia Pacifi c region, and the rest of the globe as long- term 14-day forecasts have global dependencies.”


As scientists refi ne climate models and


This contract follows a separate supply agreement between ABB and L3Harris, under which ABB has provided six interferometers for the Cross-track Infrared Sounder for the US low earth polar orbiting weather satellites series launched since 2011.


More information online: ilmt.co/PL/BNDm For More Info, EMAIL:


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ENVIROTECH-ONLINE.COM | AET MAY 2025 | 17


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