A first: EarthCARE cloud data sharpen weather forecasts

Launched in May 2024, EarthCARE carries four instruments that work in synergy to provide unprecedented insights into the complex interactions between clouds, aerosols and radiation to understand exactly how clouds and aerosols influence our climate through the heating and cooling of the atmosphere – an interplay that is extremely complex, and still not fully understood.

While EarthCARE continues its bold scientific mission, its cloud profiling radar is already proving its value beyond climate research.

EarthCARE is a joint venture between ESA and the Japan Aerospace Exploration Agency (JAXA), which provided one of the satellite’s instruments: the cloud profiling radar – and it’s the data from this instrument that are now, for the first time, ultimately leading to improved weather forecasts.

The cloud profiling radar is essential for studying cloud processes, such as their formation and dissipation.

It penetrates through clouds – providing detailed information on location, vertical structure, particle fall velocity, particle size and distribution, and water content.

For climate research, EarthCARE observations are helping to reduce scientific uncertainty on how clouds and aerosols influence Earth’s energy balance, crucial for future climate projections.

The same observations are also highly relevant for weather forecasting, where clouds are one of the biggest challenges to accurate predictions.

EarthCARE’s observations can improve weather forecasting in two ways: by helping scientists better understand and represent cloud processes in forecast models, and by providing detailed measurements that can be assimilated into forecasting systems to improve the description of current atmospheric conditions from which forecasts begin.

The quality of EarthCARE’s cloud profiling radar observations has led the European Centre for Medium-Range Weather Forecasts (ECMWF) to assimilate them into its Integrated Forecasting System (IFS) starting on 10 June 2026 – the first time that spaceborne cloud radar observations have been assimilated operationally into a global weather forecasting system.

This infographic below highlights the main steps involved in assimilating the radar data into the ECMWF numerical weather predication model to update the current state of the atmosphere, providing initial conditions which ultimately improve the forecast of future weather.

EarthCARE’s radar data are used to nudge the IFS model-simulated atmosphere to the actual observations.

This is illustrated in the plots below by the vertical cross-sections through cloud systems along an orbit segment – shown here for the Tropics where heavy storm clouds are especially prominent.

The plots show ‘radar reflectivity’ along the satellite track before and after EarthCARE data were assimilated into the model, in comparison to EarthCARE’s original observations shown on top. Lower reflectivity values indicate ice clouds and light rain, while higher values indicate heavy rain and snow.

A particularly intense thunderstorm near 27°N, with cloud tops extending above 18 km, is represented much more accurately after EarthCARE’s radar data had been assimilated, both horizontally and vertically. In other areas, the model was already in good agreement with the observations, so the impact of assimilation is less noticeable.

Some information on the structure of clouds has been assimilated into the IFS for several years, from microwave imagers and sounders, but as ECMWF Director-General Florian Pappenberger explains, 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 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.” 

ESA’s Director of Earth Observation Programmes, Simonetta Cheli, added, “EarthCARE is an Earth Explorer mission – research missions that are at the cornerstone of ESA’s FutureEO programme.

“These missions have an extraordinary track record in exceeding expectations, delivering scientific breakthroughs, advancing technological innovation and generating lasting benefits for society – and we are very proud to see EarthCARE going above and beyond its original scientific objectives.

“This achievement is the result of years of dedication, expertise and collaboration from the many scientists, engineers and mission teams involved across the world. It is also thanks to the strength of our international partnership with JAXA, whose contribution of the cloud profiling radar has been key to the mission’s success.

“Our thanks go to ECMWF and all the teams who have worked tirelessly to ensure that data from the cloud profiling radar can be assimilated into their forecasting system – this is not something that is done lightly and a huge amount of consideration and preparation has led to this important milestone.”

JAXA’s EarthCARE Mission Scientist, Takuji Kubota commented, “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.”

Preparation for using cloud profiling radar data operationally began years ago, but since EarthCARE launched ECMWF has been able to compare how closely their model matches with what the satellite is seeing.

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

With EarthCARE now leading to more accurate weather forecasts, enhancing public awareness and supporting earlier and more reliable warnings of hazardous weather, it demonstrates how investments in cutting-edge Earth observation science can deliver tangible benefits for society while advancing our understanding of the changing climate.

Read news from ECMWF: World first as ECMWF brings cloud radar data into its global forecasting system

Read news from JAXA: EarthCARE satellite data begins use by ECMWF, boasting world-class meteorological forecast accuracy (in Japanese)