EarthCARE. Credit: ESA/ JAXA/ ECMWF. CC BY.

World first as the European Centre for Medium-Range Weather Forecast brings cloud radar data into its global forecasting system.

New cloud radar data from the ESA–JAXA EarthCARE space mission is being assimilated into the ECMWF’s global forecasting system for the first time.

Clouds are a key source of uncertainty in weather forecasting, so being able to observe both their location at the time of measurement and simulate how they will evolve over time, has a significant impact on the overall accuracy of a forecast.

New EarthCARE cloud observations being assimilated into ECMWF’s Integrated Forecasting System (IFS) enable this, providing a unique view of the vertical structure of clouds across the globe, helping to improve forecasting.

Some information on the structure of clouds has been included within IFS for several years, from microwave imagers and sounders, but as ECMWF director-general Florian Pappenberger explained, for radar data, this goes further: “This is the first operational assimilation of cloud radar observations by any weather forecasting centre. 

“The new data from the Cloud Profiling Radar on the joint ESA-JAXA EarthCARE mission is a crucial step for reducing uncertainties in how clouds influence the weather, and as ever, international collaboration has been at the heart of EarthCARE.

“Scientists at ECMWF have been working with ESA and JAXA engineers to ensure the best data quality and we also have our partners at the Dutch national meteorological service KNMI and McGill University, Canada to thank, along with the many others involved in bringing EarthCARE to fruition.”

Simonetta Cheli ESA’s director of Earth Observation Programmes, added: “This is the result of years of dedication, expertise and collaboration from the many scientists, engineers and mission teams across the world.

“It is also thanks to JAXA, whose contribution of the cloud profiling radar has been key to the mission’s success.

“Our thanks go to ECMWF and all who have worked tirelessly to ensure that data from the cloud profiling radar can be assimilated into their forecasting system – a huge amount of consideration and preparation has led to this important milestone.”

‘Best estimate’

The observations of a wide range of clouds are taken from every 90-minute orbit made by EarthCARE and combined with a previous model forecast through data assimilation.

This ‘best estimate’ of the current weather is then input into the IFS. 

Mark Fielding, who leads the EarthCARE assimilation project at ECMWF, said: “Bringing cloud radar observations that reveal the vertical profiles of cloud and rain into the IFS is an exciting new development for weather forecasting. 

“EarthCARE was not originally designed for operational forecasting, so realising this additional benefit is a real bonus on top of the scientific understanding that the new observations are giving us.”

EarthCARE observations are especially valuable because of the new constraints on the physical processes within clouds they provide. 

For example, the new observations make it possible to detect if a cloud is composed of ice or liquid, and the mass of water it contains, its average particle size and even how fast the particles are falling.  

One recent example is when EarthCARE flew directly over the eye of Hurricane Humberto in September 2025 and captured a never seen before from space observation of the vertical motion of wind, rain and snow within a hurricane eyewall. 

These insights are helping ECMWF scientists to improve how cloud processes are represented in our weather model and ultimately how realistic weather forecasts are.

Rebecca Murray-Watson, a scientist at ECMWF who works with the EarthCARE data in the IFS, said: “As a cloud physicist, what excites me the most about EarthCARE is the Doppler radar – for the first time we have a satellite that can tell us not just where the ice is, but how fast it’s falling.

“That kind of information is exactly what drives improvements in the next generation of weather models. 

“Being able to sit down with the EarthCARE data and compare it directly against our model simulations tells us where we’re getting things right, and where there’s still work to do.

“Furthermore, improved understanding of physical processes can also ultimately help to inform climate projections carried out by the wider weather and climate community.”

Improving accuracy

Having the capability to simulate EarthCARE within the ECMWF model also allows the data quality of EarthCARE’s observations to be monitored. 

Within days of the instruments being switched on, ECMWF began monitoring EarthCARE’s radar and lidar performance in near-real time to provide rapid feedback to teams at ESA and JAXA. 

JAXA and ESA have then been able to take this into account and recalibrate as necessary.

Takuji Kubota, JAXA’s EarthCARE mission scientist, concluded: “ECMWF’s initiatives in collaboration with the ESA are expected to improve the accuracy of forecasts for extreme weather events such as typhoons and heavy rainfall, and to strengthen early warning capabilities for floods and landslides.

“Through these disaster prevention and mitigation efforts, we greatly welcome their contribution to building a safer and more secure society – not only in Europe, but also in Japan.”