Obs3RvE - Optimising 3D RT EarthCARE product using geostationary observations and AI

Home

Obs3RvE (Optimising 3D RT EarthCARE product using geostationary observations and AI) is a project funded by ESA, in the framework of EC-ESA Earth System Science Initiative, that aims to produce ground-breaking scientific results through the exploitation of the EarthCARE mission.

Obs3RvE proposes an innovative approach towards more accurate quantification of the 3D radiative effects of clouds and their impact on climate, utilising the observations of EarthCARE and MTG missions with AI tools. The results of Obs3RvE will also aim to extend the contribution of the EarthCARE data on solar energy applications, a scientific domain beyond the mission primary objectives.

Project overview

EarthCARE mission provides 3D radiative transfer (RT) calculations to address the 3D radiative effects of clouds, which is already a big step beyond the state-of-the-art for Earth Observation. These products utilize constructed 3D cloud scenes, combining top-of-the-atmosphere (TOA) 2D observations with vertical profiles of aerosols and clouds along the satellite track. The vertical information of the off-track pixels is deduced from the nadir pixel profiles that present similar radiative properties. Although the uncertainties introduced by this approximation have not been extensively tested yet, this technique may fail when e.g. the off-track clouds are not observed in the nadir profiles (Qu et al., 2023).

Obs3RvE proposes a different methodology for constructing the 3D scenes of EarthCARE, where the missing vertical information of the off-nadir pixels is provided by a Machine Learning (ML) algorithm, trained to derive the vertical structure for all the pixels in the 3D atmospheric scene, using the corresponding 2D radiances at the top of the scene, combined with the vertical structure provided for the nadir track.

The ML algorithm will use the 2D observations from the MultiSpectral Imager (MSI), and the vertical structure of cloud properties provided by EarthCARE (Irbah et al., 2023; Mason et al., 2023). Its output will be 3D scenes of cloud types and cloud microphysical properties (i.e., water content, effective radius of cloud particles), which may be then utilized by 3D RT models to assess the radiative impact of clouds on climate.

Part of the training of the ML algorithm will utilize geostationary observations from the Flexible Combined Imager (FCI) of the MTG mission of EUMETSAT, since the number of available EarthCARE observations will not be enough to do so. This pre-training with MTG observations will also generate a second product of 3D constructed scenes, with high temporal resolution for MTG observations, that may be utilized for solar energy applications.

The proposed study will produce two innovative 3D products:

EarthCARE 3D product: 3D scenes of cloud types and cloud microphysical properties along the EarthCARE swath
MTG 3D product: high-temporal-resolution 3D scenes of cloud types and cloud microphysical properties for the MTG observations

The EarthCARE 3D product is expected to have a high impact on decreasing the uncertainty of the cloud radiative impact on climate, (also) due to its global coverage. The MTG 3D product will be used for assessing the cloud impact on solar energy applications, due to its high-temporal resolution.

Outline of Obs3RvE activities

Development of the EarthCARE 3D product, providing realistic 3D atmospheric scenes of cloud types and cloud microphysical properties, for 3D RT calculations. The development will utilize ML techniques, combining geostationary MTG with EarthCARE data. The output will be validated with ground-based and airborne observations of cloud properties, as well as with radiation measurements at aircraft level, in Europe and in the Atlantic Ocean.
Development of the MTG 3D product, providing 3D scenes of cloud types and cloud microphysical properties in high temporal resolution. The development will utilize ML techniques, using collocated MTG and EarthCARE observations. The product will be validated with ground-based and airborne observations of cloud properties, along with radiation measurements at aircraft level, in Europe and in the Atlantic Ocean.
Improvement of the quantification of cloud radiative effect. Quantify the cloud radiative effect on selected case studies, using the EarthCARE 3D product and 3D RT calculations performed with the Monte Carlo Code for the phYSically correct Tracing of photons in Cloudy atmospheres (MYSTIC)/libRadtran RT software (Mayer, 2009). The calculations will be compared with the state-of-the art 3D RT products of EarthCARE.
Assessment of the impact of clouds on solar energy applications. Use the MTG 3D product and 3D RT calculations with MYSTIC/libRadtran RT software, to provide surface radiation calculations in high temporal resolution, enabling its utilisation for solar energy applications.
Synergy with projects of ESA/ EC Earth System Science initiative and ESA Atmosphere Science Cluster, along with the management activities of ESA EarthCARE mission: Obs3RvE will be coordinated with the projects ESA/EU-CERTAINTY, ESA-AIRSENSE and EarthCARE DISC, through the participation of the Obs3RvE team members in the activities of the respective projects.

Project consortium and people

National Observatory of Athens (NOA)

NOA is a pioneering research institution with over 170 years of international presence in science and education. NOA excels in observing the atmospheric environment, focusing on physical processes, interactions, and extreme events. NOA participates in the project with researchers from the Institute of Astronomy, Astrophysics, Space Applications & Remote Sensing (IAASARS) under the Remote sensing of Aerosols, Clouds and Trace gases (ReACT) Unit and the BEYOND EO Centre.

ReACT/NOA

The experimental and theoretical work of the ReACT/ΝΟΑ group, is dedicated to the application of measuring methodologies for the remote sensing of aerosol and clouds, along with their interactions, processes and their radiative impacts. ReACT/NOA activities are targeted towards understanding physical and chemical processes in the atmosphere, seizing the opportunity provided by the complex and vulnerable Mediterranean environment, utilising advanced ground-based and space-borne remote sensing observations and theoretical models.

BEYOND/NOA

The BEYOND Center of Excellence for Earth Observation Research & Satellite Remote Sensing was established through competitive European Union funding. BEYOND focuses on developing innovative, integrated solutions using big Earth Observation data and cutting-edge AI to address societal and environmental challenges. The centre’s efforts are directed toward enhancing resilience and response capabilities in natural disaster management, assessing and mitigating climatic risks, supporting sustainable agricultural practices, advancing public health applications, and optimising renewable energy solutions.

Ludwig Maximilian University of Munich (LMU)

The Meteorological Institute of the Faculty of Physics at the Ludwig-Maximilians-University (LMU) in Munich includes the Chair of Experimental Meteorology (Prof. Bernhard Mayer) and the Chair of Theoretical Meteorology (Prof. George Craig). The latter performs research in atmospheric dynamics, predictability, and data assimilation. The experimental meteorology section performs radiative transfer modelling, cloud and aerosol physics, and active and passive remote sensing of clouds, aerosols and trace gases.
The strength of the Chair of Experimental Meteorology is the combination of experimental, technological, and theoretical experience over many years, which allows innovative process development and scientific assessment of new measurement technologies. The group has been developing the publicly available libRadtran RT package which is one of the most common RT models and has been used for more than 1000 publications, in numerous projects including a number of ESA studies. The Monte Carlo Code for the phYSically correct Tracing of photons in Cloudy atmospheres (MYSTIC), also developed by the group, is one of the most advanced 3D RT solvers, which allows handling 3D clouds as well as inhomogeneous surface albedo and structured terrain.

Physikalisch-Meteorologisches Observatorium Davos / World Radiation Center (PMOD/WRC)

Radiation measurements are a fundamental part of meteorological observation and climate monitoring. Research has been conducted on solar irradiance at the PMOD since 1907. In 1971, the World Meteorological Organization (WMO) gave the PMOD the additional mandate of serving as the World Radiation Center (WRC). The WRC plays a crucial role in maintaining quality standards in global climate monitoring programmes. The WRC fields of activity are divided into four Sections in which the measurement of solar radiation is the central focus of each one. While the PMOD/WRC develops new techniques and instruments to measure solar radiation, measured data is analysed and used for instance to investigate Climate Change. PMOD/WRC is the World meteorological Organization global solar radiation and aerosol optical depth center providing the global solar irradiance “scale”.

Team

National Observatory of Athens - ReACT

Alexandra Tsekeri

Alexandra Tsekeri received her Ph.D. in Earth and Environmental Sciences from the Graduate School and University Center, The City University of New York (CUNY), USA, in 2011. Since 2012, she works for the National Observatory of Athens, focusing on (a) the remote sensing of the atmosphere, using passive and active remote sensing methods, as well as their combination with airborne and ground-based in-situ measurements, (b) inversion techniques using also machine learning techniques to derive the microphysical properties of aerosols in the atmosphere, (c) development of aerosol models, focusing on desert dust, using scattering calculations, ground-based and satellite active and passive remote sensing measurements, (d) design, optimization and operation of remote sensing instruments with emphasis on polarimetric measurements, for monitoring atmospheric aerosols, (f) optimize dust optical properties in transport models and assimilation techniques, (e) assessing aerosol and cloud radiative effects, along with the corresponding effects on weather and climate.

Eleni Marinou

Eleni Marinou is an associate scientist of the National Observatory of Athens in Greece. She is an atmospheric researcher focusing on the characterization of aerosols, clouds, and their interactions, along with their impact on radiation and atmospheric dynamics. Her research is mainly based on observations from remote sensing instruments (ground-based and space-borne passive and active lidars and radars) and synergies with Earth System Models.

Dimitra Kouklaki

Dimitra Kouklaki is a PhD student at the National and Kapodistrian University of Athens (NKUA). Her research focuses on assessing the impact of atmospheric composition on solar irradiance and solar energy. As a scientific member of the National Observatory of Athens (NOA) in Greece, her work is focused on the impact of aerosols and clouds on solar radiation, by employing synergistic atmospheric measurements, combining ground-based, airborne and spaceborne observations along with modeling techniques. Her work aims to enrich understanding and existing knowledge on Earth’s radiation budget, contributing to solar energy applications, weather prediction and climate projections.

Ioanna Tsikoudi

Ioanna Tsikoudi completed her PhD at the National and Kapodistrian University of Athens (NKUA), in close collaboration with the National Observatory of Athens (NOA), Greece. Her doctoral research focused on investigating the dynamics of the atmospheric boundary layer using a combination of remote sensing observations (ground-based and satellite), radiosondes, and model data. Since 2022, she has been working with cloud remote sensing datasets to study cloud microphysics and contribute to the validation of the EarthCARE satellite mission.

Anna Gialitaki

Anna Gialitaki received her Ph.D. in Atmospheric Physics and Remote Sensing from the Aristotle University of Thessaloniki in 2023. Since 2017, she works for the National Observatory of Athens, focusing on aerosol optical and microphysical properties retrievals using synergies of active and passive remote sensing sensors. She has worked on the development of a novel airborne polarimeter (2021–2023). She has participated in 9 European research projects, and large measurement campaigns. Her publication record includes >20 peer-reviewed articles and >75 peer-reviewed conference proceedings and presentations (h-index = 11, 355 citations). She is an active member of ACTRIS, EARLINET, AERONET and acts as a reviewer for leading atmospheric science journals.

Dimitra Karkani

Dimitra Karkani is a graduate from the school of Electrical and Computer Engineering of NTUA with a Master’s degree in Data Science and Machine Learning. She is a member of ReACT-NOA focusing on applied data science and machine learning for atmospheric studies.

National Observatory of Athens - BEYOND

Stella Girtsou

Stella Girtsou is a Machine Learning Research Scientist at the Operational Unit BEYOND Centre of the National Observatory of Athens, and a PhD candidate at the National Technical University of Athens, focusing on Deep Learning methodologies for Earth Observation. She holds an MSc in Space Technologies and Applications (NOA & University of Peloponnese) and a BSc in GIS and Remote Sensing (NTUA). With over five years of experience in applying Deep Learning to EO data, she has developed and operationalized end-to-end ML pipelines for data collection, preprocessing, model optimization, and forecasting. Her research expertise lies in wildfire risk forecasting, self-supervised learning, and 3D scene reconstruction. Recently, she contributed to Frontier Development Lab Europe (ESA, University of Oxford, Google, NVIDIA, Trillium Technologies), where she worked on self-supervised learning for 3D cloud mapping and the study of tropical cyclones through the integration of active and passive satellite sensors.

Giorgos Giannopoulos

Giorgos Giannopoulos received his Diploma and PhD in Computer Science from the National Technical University of Athens, Greece, in 2006 and in 2013. He is currently a Scientific Associate at the Operational Unit BEYOND Centre of the National Observatory of Athens, while he also collaborates with Athena Research and Innovation Center. His research interests focus on the adaptation and extension of Machine/Deep Learning methods in various disciplines, including: fairness and explainability of ML algorithms; Deep Learning methods and Foundation models for fire risk prediction and fire detection; pattern recognition and event detection on timeseries; explanation and prediction of Solar events; ML-driven data integration and annotation. He has published more than 60 papers in the above areas. Google Scholar Citations reports more than 2000 citations to his work and h-index 18.

LMU MUENCHEN

Bernhard Mayer

Bernhard Mayer is full professor for Experimental Meteorology at Ludwig-Maximilians-University Munich. He has more than 25 years' experience in 1D and 3D Radiative transfer model development (libRadtran, MYSTIC). He has used the model to develop cloud remote sensing techniques, and to study the impact of clouds on radiation in the context of numerical weather prediction and climate. He is member of the International Radiation Commission (IRC) and has been PI in various national and international projects. He has 163 peer-reviewed publications and an h-index of 44 (Web of Science).

PMOD-WRC

Stelios Kazadzis

Stelios Kazadzis has 25 years of experience in basic and applied research in Atmospheric Physics. He studied Physics at the Department of Physics, Aristotle University of Thessaloniki, Greece (Physics Degree, MSc in Environmental Physics and PhD in Atmospheric Physics). He is currently a senior researcher and head of the World aerosol optical depth research and calibration center at the PMODWRC, Switzerland. He is also part of various World Meteorological Organization units (Scientific advisory group of aerosols, Expert teams on network evolution and data quality), member of the International Radiation Commission, chair of the COST action Harmonia on sun-photometry and deputy PI on the Expert team of satellite validation for ACTRIS. He is also a lecturer at ETH Zurich teaching atmospheric remote sensing.

Kyriaki Papachristopoulou

Kyriaki Papachristopoulou received her Ph.D. in the Section of Geography and Climatology, Department of Geology and Geoenvironment, NKUA, Athens, Greece, in 2023. She currently works as a Postdoctoral researcher at Physics and Meteorological Observatory Davos, World Radiation Center (PMOD/WRC),Switzerland. Her research interests focus on (a) the estimation of solar/thermal radiation fields within Earth’s atmosphere, as well as aerosol-cloud-radiation interactions, using radiative transfer modelling and earth observation (satellite and model based) and ground-based data. She was part of the team that developed and assessed the solar energy nowcasting and short-term forecasting system NextSENSE2 and a long-term solar forecasting system for two days ahead.

News

20/06/2025

Obs3RvE kick off!

The Kickoff Meeting of Obs3RvE project took place on June, 20th, 2025. The meeting was held in an online format, with a total of 17 participants. This successful kick-off meeting is a strong start of our challenging project!

Publications

Obs3RvE publications in peer-reviewed journals and conferences will be available soon.

Data

The Obs3RvE data will be available soon.