Project overview

AIRSENSE’s main objective is to enhance the understanding of aerosol and aerosol-cloud interactions. This activity is part of Atmosphere Science Cluster of ESA’s EO Science for Society programme, an element of the ESA FutureEO programme, which aims at boosting Europe’s excellence in EO science and its applications.

One of the goals of this programme is to establish a strong coordinated scientific effort in Europe on Aerosol and Aerosol/Cloud interaction research by promoting a cooperation between activities launched by ESA and the European Commission (EC), in particular with CLEANCLOUD  and CERTAINTY projects that were selected under the EC Horizon Europe Call “Improved knowledge in cloud-aerosol interaction” (HORIZON-CL5-2023-D1-01-04).

AIRSENSE objectives
  1. Support algorithms development for multi-mission approach promoting synergies between different space-borne instruments to compensate for individual weaknesses allowing the creation of long Aerosol Optical properties (e.g., AOD, AE) time series (i.e., Aerosol_CCI) combining mid resolution satellite such as Sentinel5-p and CO2M with high resolution sensors such as PRISMA and Sentinel-3.
  2. Explore the capability of new aerosol and cloud products from existing (e.g. POLDER) or upcoming (CO2M, PACE, MAIA) Multi Angle Polarimeters (MAP) to infer aerosol characterization and absorption properties developing products such as Angstrom Exponent (AE), Single Scattering Albedo (SSA), Absorbing Aerosol Optical Depth (AAOD) and Fine mode Aerosol Optical Depth (AODF) but also Cloud Condensation Nuclei (CCN) and their role in climate and radiative forcing of the Earth system.
  3. Maximize the scientific impact of EarthCARE (in combination with additional EO missions and ground observations) in terms of novel observations and enhance scientific understanding of cloud, aerosol properties and their interactions: e.g., Long-term assessments in combination with Aeolus and CALIPSO data; aerosol-cloud interactions from the synergy between space- and ground-based instruments, study of precipitation initiation processes, characterisation of convection with synergistic GEO and LEO satellite observations, light precipitation and low-level oceanic clouds, global estimates of hydrometeors sedimentation rates, etc.
  4. Study the effects of cloud screening and aerosol retrievals in partly cloudy scenes, develop and improve the capabilities to detect aerosol above clouds and over challenging scenarios such as snow, ice shelves and in low illumination conditions such as the Arctic.
  5. Study cloud height, aerosol-cloud interactions and chemistry to understand the processes that can lead to cloud formation and to infer radiative properties of different cloud and aerosol types.
  6. Improve the quantification of the impact of 3D cloud shape and cloud shadow on cloud retrievals and for the impact of 3D cloud effects and apply this to aerosol retrievals close to clouds edges.
  7. Investigate the aerosol influence on the hydrological cycle fostering the use of aerosols products in combination with water vapour and water vapour isotopologues satellite observations. 
  8. Investigate aerosol and cloud observations from Aeolus and extend this into the use of ATLID on EarthCARE with respect to humidity-growth effects in different areas of the world and for different aerosol types by comparing them with ground-based measurements during nearby overpasses; Make use of multiwavelength polarization Raman lidars that comprise also water-vapour channels are best suited for the detection of changes in scattering properties at high relative humidity.
  9. Improve the capabilities to detect stratospheric aerosol with a classification scheme allowing their separation by sources. Build on existing work and enhance the generation of stratospheric aerosol CDRs.
  10. Advance the retrieval of aerosol vertical profiles fostering the simultaneous use of active and passive satellite instruments considering lessons learnt from Aeolus, but mainly novel EarthCARE products and validation activities.
  11. Support (coordinated) activities on the radiative forcing due to aerosol-cloud interactions and the anthropogenic contribution on it considering lessons learnt from Aeolus and the future availability of EarthCARE mission products that will provide vertical information about aerosol particles and clouds (e.g., shape, size, type, amount).
  12. Support (coordinated) activities on the effect of climate and air quality on cloud properties, relevance for extreme events such as heavy rainfall, hailstorm, etc.
  13. Support (coordinated) activities to quantify the improvement of the numerical weather predictions (NWP), Earth System Models (ESM), and for the understanding of atmospheric dynamics and its interaction with the water cycle related to the development of novel aerosol products.
  14. Capitalise on novel EO-based capabilities, in particular EarthCARE observations, to advance our understanding and characterisation, including uncertainty reduction, of radiative forcing due to aerosol-cloud interactions and the anthropogenic contribution on it considering lessons learnt from Aeolus and the future availability of EarthCARE mission products that will provide vertical information about aerosol particles and clouds.
  15. Capitalise on novel EO-based capabilities, in particular EarthCARE observations, to advance understanding of atmospheric dynamics and its interaction with the water cycle related to the development of novel aerosol products and potentially numerical weather predictions (NWP).
Outline of the AIRSENSE activities

Objective 1 of AIRSENSE project aims to enhance global aerosol characterization by synergistically combining observations from various Earth observation satellites, such as Sentinel-3, TROPOMI/S-5P, PRISMA, EarthCARE, SPEXone, HARP-2, CO2M, and 3MI. The goal is to address the limitations of individual sensors by creating joint retrieval products, utilizing the strengths of each instrument, and therefore to improve the understanding of complex atmospheric processes, including aerosol-cloud interaction, diurnal and vertical changes in aerosol properties, aerosol transport, and more, at a fine spatial-temporal resolution.

Objective 2 of the project aims to focus on the NASA PACE mission, scheduled for launch in January 2024, which will provide valuable Multi-Angular Polarimeter (MAP) observations. The objective is to develop advanced MAP products and explore the capabilities of MAP observations for detailed characterization of atmospheric aerosol and clouds. The advancements made will also be applicable to future MAP instruments such as 3MI and CO2M-MAP, contributing crucial information on aerosol particle sizes, types, composition, and absorption for accurate climate effect estimation.

Objective 3 targets improving the characterization of aerosol and clouds and enhancing our understanding of their interactions by utilising space lidar data unique sensitivity to aerosol and cloud vertical variability. Provided by CALIOP, ALADIN and ATLID instruments, these data in synergy with passive observations should be beneficial for tackling aerosol-cloud interactions, precipitation initiation processes, convection, light precipitation and low-level oceanic clouds, global estimates of hydrometeors, sedimentation rates and other challenging scientific questions (Objectives 3 and 10). Similarly, there is potential in the synergy of aerosol satellites with water vapour satellite observations for investigating the aerosol influence on the hydrological cycle fostering (Objective 7). The developed enhanced synergy approaches can also be very beneficial for processing observations in near cloud edges and in broken-cloud environments (Objectives 4 and 6), improving screening of aerosol products from cloud contaminations, cloud shadows and 3D effects, and providing more information about aerosol and cloud properties in partly cloudy scenes. Similarly, these synergy approaches should improve the capabilities to detect aerosols above clouds and over challenging scenarios such as snow, ice shelves and in low illumination conditions found in the Arctic environment (Objective 4). 

Ground-based networks such as AERONET and EARLINET, ACTRIS research infrastructure and field campaigns implementing sensor synergies from ground and air are planned to be used for the validation of AIRSENSE advanced aerosol and cloud products, as well as for studying aerosol-cloud interactions, humidity-growth effects and other complex processes (Objectives 2, 3 and 8) utilising diverse instrumentation including sun/sky-scanning radiometers and advanced multiwavelength polarization Raman lidars with water-vapour channels. The unique data synergy from space, air and ground, along with the new products and data assimilation techniques can be utilised for (i) understanding the processes that can lead to cloud formation (Objectives 2, 3, 7 and 8); (ii) inferring radiative properties of different cloud and aerosol types (Objective 5); (iii) studying humidity-growth effects (Objective 8) and detection, classification and source separation of stratospheric aerosol for generating a unique Climate Data Records (CDRs) (Objective 9).

A number of activities are planned by cooperating with the teams of CleanCloud and CERTAINTY participating in the EC Horizon Europe (HE) project and the ESA Atmosphere Science Cluster. AIRSENSE aims to provide to the HE projects enhanced data products, and support the utilisation of the newly generated products for activities planned in their projects, including demonstration studies. Specifically, support is planned for studies of the radiative forcing due to ACI and the anthropogenic impact relying on Aeolus and the future availability of EarthCARE data (Objective 11) and for studies of the effect of climate and air quality on cloud properties and relevance for extreme events (Objective 12). Also, support is planned for activities on the improvement of the Numerical Weather Predictions (NWP) and Earth System Models (ESM), and the understanding of atmospheric dynamics and its interaction with the water cycle (Objective 13). 

Building on the results and insights gained through the AIRSENSE project, there is a plan to prioritize the exploration of novel EO capabilities, with a special focus on EarthCARE. This emphasis aims to enhance our comprehension and characterization of radiative forcing caused by aerosol-cloud interactions, including the anthropogenic impact. Additionally, the goal is to further our understanding of atmospheric dynamics and its interplay with the water cycle, aligning with Objectives 14 and 15.

Proposed Approach

AIRSENSE focuses on using cutting-edge capabilities of novel observations and on the use of advanced products from multi-instrument synergy processing for conducting studies of aerosol, aerosol-cloud interactions or other science questions. Based on data availability and maturity, it is planned to gradually, as shown in the diagram of Fig. 1, generate and enrich the novel products starting from (i) synergy and combined products of passive instruments (for example, Sentinel-3, S-5P, PRISMA (or Sentinel-2), etc.), then (ii) adding advanced active remote sensing products (Aeolus, EarthCARE) followed by (iii) products from MAP observations and synergy of MAP and single viewing instruments (Sentinel-3, S-5P, with PACE or GAPMAP). Such a multi-sensor retrieval approach concludes with advanced aerosol products and cloud-relevant aerosol properties, which will be validated with ground-based observations and data from field campaigns. 

Once new products are validated, they are planned for exploitation in science studies to address the project objectives towards better understanding the aerosol effects on Earth climate, aerosol-cloud interactions, and physical processes in the atmosphere. These products will be examined on their impact on data assimilation and high-resolution modelling over different aerosol regimes (domains in the Atlantic Ocean and the Mediterranean, following the ESA field campaigns for Aeolus and EarthCARE Cal/Val), and observational aerosol-cloud relationships. This is considered as a crucial step towards science exploitation by bridging the AIRSENSE efforts with the EC HE ACI projects. 

Figure 1: Illustration of the proposed approach


Fig.2 AIRSENSE sensors
* (provisional) ESA-JATAC, NASA-CPEX, ACROSS, MOSAiC, COALA, DACAPO-PESO, Research cruises with RV Polarstern and RV Sonne, PACE-PAX, EC-TOOC, AERO-HDF, AEROCLO-SA
Fig.3 Deliverables (products intended for delivery in the AIRSENSE project)*
 * Exact instrument selection is subject to change
**Following the data availability, the best (coverage, resolution, accuracy and information content) combination will be selected
Members of consortium

The teams participating in AIRSENSE are involved in multiple ESA studies and proposals submitted to the ESA Atmosphere Science Cluster (ASC) activities (e.g., LIVAS, DEDICAtE, eVe, ASKOS, NEWTON, DOMOS, L2A+, ACPV, CARDINAL). In addition, several members of the AIRSENSE consortium are key partners in theCleanCloud (TROPOS and SRON) and CERTAINTY (NOA and KNMI) projects, launched by European Commision in the Horizon Europe Call on improved knowledge in cloud-aerosol interaction (HORIZON-CL5-2023-D1-01-04).

Together, AIRSENSE and CleanCloud/CERTAINTY partners will ensure a strong coordination of activities between the ESA and HE projects, with focus on the scientific exploitation of the newly developed products of AIRSENSE and collaborate towards maximising the impact of the parallel studies. Additionally, AIRSENSE aims to design further studies towards maximising the scientific impact of new spaceborne products in collaboration with CleanCloud and CERTAINTY, including key partners, in particular from the modelling community (e.g. ECMWF for operational assimilation of the AIRSENSE products). 

GRASP SAS shorten from ‘Generalized Retrieval of Atmosphere and Surface Properties” is a company that was founded in February 2015 with the main goal of development of remote sensing algorithms and scientific methods for environment studies of atmosphere and surface of the Earth.

The initial idea of GRASP has been developed by the efforts of CNRS and University of Lille. Then this base scientific concept has been realized in open-source GRASP-OPEN software adapted to diverse remote sensing applications. The main GRASP SAS activities cover a wide range of remote sensing topics:

  • Developments of algorithms for advanced atmosphere and surface characterization from passive and active ground based and spaceborne remote sensing.
  • Scientific consulting in environmental studies.
  • Distribution and support of GRASP open source code.

Since its creation, GRASP SAS has been involved in collaboration with world-wide environmental public organizations and private companies, universities and the largest space agencies (ESA, EUMETSAT, NASA, JAXA) with the goal to improve the scientific knowledge of the atmosphere and surface properties, which have an essential impact on Earth climate, and tightly interconnected with human activities.

The GRASP code was developed for advanced aerosol and surface retrieval from remote sensing measurements. GRASP-SAS is composed by a unique team with full understanding of all aspects of the code: physical and mathematical basis, software optimization etc. GRASP team has led several projects to retrieve atmosphere and surface parameters from different satellite sensors (PARASOL, MERIS, Sentinel 3 and 4, 3MI).

GRASP SAS is fully privately owned, and employs more than 15 researchers in different fields.

LOA — Laboratoire d’Optique Atmosphérique is a research laboratory with about 50 members. Its main areas of research are atmospheric radiative transfer, aerosol and cloud remote sensing, and climate. In the past decades, one major activity of the LOA has been the development of the POLDER missions, starting with the development of an airborne sensor, to the analysis of the POLDER-1 (onboard ADEOS-1), POLDER-2 (onboard ADEOS-2) and PARASOL-3 (onboard PARASOL -a microsatellite that flies within the A-Train). LOA is also closely involved in development of the 3MI, which is a POLDER like satellite polarimeter jointly developed by ESA and EUMETSAT and planned to be launched on a Post-EPS platform of the European EUMETSAT agency. LOA is also in charge of the PHOTONS component of the AERONET program that includes more than 60 sites AERONET sites in France and Africa, as such it is a mirror-site of the GSFC/NASA data archive, which facilitates access to the corresponding validation data set. For several years, PHOTONS supported the “supersite approach” involving both lidars and sun-photometers. In addition, researchers of LOA made a key contribution in the development of the aerosol retrieval algorithm used by the AERONET program in operational data processing. Finally, the base of GRASP algorithm was developed by LOA scientists, and later GRASP SAS was stated as University Spin-off with the objective of valorizing scientific developments and specifically GRASP algorithm.

NOA — The National Observatory of Athens 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. Housed within the Institute of Astronomy, Astrophysics, Space Applications & Remote Sensing (IAASARS) of NOA, the Remote sensing of Aerosols, Clouds and Trace gases group (ReACT) is dedicated to remote sensing methodologies for aerosols, clouds, and trace gases. Leveraging complex Mediterranean conditions, they use advanced ground-based and spaceborne observations and models to comprehend atmospheric and chemical processes.

ReACT/NOA’s expertise spans aerosol remote sensing, in-situ techniques, multi-instrument remote sensing Research Infrastructure (RI), intensive campaigns, theoretical research, lidar system design, aerosol transport modeling, and data assimilation techniques. They developed reference lidar systems for ESA missions like eVe and are actively engaged in the Cal/Val of the Aeolus ESA mission. They’ve played roles in various ESA studies and projects such as LIVAS, DEDICAtE, A-CARE, NEWTON, L2A+, CORAL, and DOMOS, focusing on aerosol characterization, data assimilation, and product derivation.

ReACT/NOA has organized ESA campaigns like Charadmexp, Pre-TECT, and ASKOS, assessing aerosol mixtures, product quality, and cloud data. They manage the PollyXT lidar system in Greece and operate the Remote Sensing National Facility of the PANGEA Research Infrastructure. The group is an active member of EARLINET and ACTRIS.

SRON Netherlands Institute for Space Research is the expert space research institute for the Netherlands. The Earth-group within SRON is an expert group in atmospheric satellite remote sensing focusing on long lived greenhouse gases (CO2 and CH4) and aerosols. Target research areas are the carbon cycle, aerosol effects on climate including aerosol cloud interaction, and the water cycle. The group has strong expertise in hardware technology development, radiation transfer modelling, retrieval techniques and data analysis and assimilation. SRON co-initiated the development of the TROPOMI instrument and is the co-PI institute for TROPOMI responsible for safeguarding the scientific performance of TROPOMI with respect to the SWIR channel measuring CH4, CO and water vapour. The team is also responsible for the development of the algorithms and codes for the operational products CO and CH4. SRON also initiated the SPEXone instrument development for the NASA PACE mission focusing on the characterisation of aerosol, and is the PI institute for this instrument. As such, SRON is responsible for the operational algorithm development for the full data processing chain (L0-L2).

TROPOS – The Leibniz Institute for Tropospheric Research is a renowned institute focused on aerosol and cloud research, boasting around 150 staff members. It excels in cutting-edge observational techniques and modeling for climate system processes. TROPOS has led various global projects on cloud, aerosol, air pollution, and climate research, offering guidance to national and international policymakers. TROPOS Remote Sensing Department (RSD) emphasizes satellite and ground-based remote sensing.

The RSD team has pioneered aerosol and cloud lidar advancements, developed inversion techniques, and conducted international field campaigns. They specialize in long-term studies using lidar, radar, microwave radiometer, and sun photometer measurements. Their expertise spans aerosol transport, cloud interactions, ice formation, wave-induced cloud creation, and more. The PollyNet network employs portable lidars for global aerosol, cloud, and water-vapor profiling. The department contributes to ACTRIS with permanent observatories in Germany and Cabo Verde, as well as mobile platforms like LACROS and OCEANET for diverse missions.

RSD collaborates with ESA on spaceborne lidar projects (Aeolus, EarthCARE), engaging in Cal/Val activities for CALIPSO and Aeolus. They’ve pioneered aerosol algorithms and contributed to EarthCARE with ATLID and MSI developments, along with synergistic algorithms. RSD leads Aeolus aerosol algorithm development since 2023. They also manage a satellite receiving station and data archive for METEOSAT and maintain an operational METEOSAT SEVIRI data product chain.

UW – The University of Warsaw established in 1816, is Poland’s largest public nonprofit university, ranked in the top 3% globally. UW holds an endowment of ~€300 million and a research budget of ~€100 million, funded mainly by the Polish government and international bodies. With 50,000+ annual students and ~3,500 teaching/research staff, UW hots 50,000+ annual students and ~3,500 teaching/research staff and excels across diverse disciplines, participating in ~300 European research projects, including EU initiatives like ERC grants, FP(5-7), REGPOT, and CIP projects.

The Institute of Geophysics within the Faculty of Physics at UW will take part in AIRSENSE. It collaborates closely with global research institutions (e.g., NCAR, TROPOS, AWI, INOE, NILU), and has engaged in 3 ESA projects. The Institute focuses on aerosol optical, radiative, and microphysical properties, cloud modeling, and microphysics research. It boasts unique research infrastructure: the Radiative Transfer Laboratory (RT-Lab, since 2008), Remote Sensing Laboratory (RS-Lab, since 2015), and in-situ observation vans. The Institute is progressing toward being designated a National Facility with ACTRIS-ERIC for aerosol and cloud remote sensing. It actively contributes to national/international aerosol networks, research alliances (EARLINET, CLOUDNET, AERONET), and global climatological databases.

KNMI is the National Meteorological Service of the Netherlands operating under the responsibility of the Ministry of Infrastructure and Water Management. It is composed of both a research division and an operation meteorological service providing weather observations, weather forecasts, and vital weather information and warnings 24/7 all year round. The R&D departments are covering the areas of Weather and Climate modelling, Seismology and Acoustics, Ground-based Observations and Data Technology, and Satellite Observations. It employs approximately 370 FTE staff. 

Climate research is amongst one of the key research topics of the KNMI, which has recognized the importance of an accurate description of clouds and cloud-radiation interactions in climate models. Thus, KNMI has been active in terms of modeling and observational studies related to cloud-aerosol-radiation interactions, including the development of new multi-sensor cloud retrieval algorithms.

Relevant to this proposal is KNMI’s R&D Satellite Observations department. In this department the themes are: Atmospheric Dynamics, using wind scatterometer missions and the Aeolus wind lidar; Clouds, aerosols, and solar radiation using Meteosat/SEVIRI, NOAA/AVHRR, and preparing for EarthCARE; and Atmospheric Composition, using the UV-visible-near-infrared spectrometers GOME, SCIAMACHY, GOME-2, OMI, and TROPOMI. The department holds the Principal Investigator role for OMI and TROPOMI and leads the EarthCARE L2 ESA CARDINAL project.

KNMI has worked on a large number of ESA projects related to spaceborne lidar operational processor developments for both the Aeolus and EarthCARE missions, where it is involved in both the level 1 and level 2 processor developments as well as the EarthCARE simulator (ECSIM). 

THALES Services Numériques (Thales) is a French company within Thales Group, specializing in critical information systems and secure communications. With 5000 employees, Thales ensures customers’ system performance and security, integrating innovations while guarding against cyber threats. With 40+ years in space systems engineering, Thales excels in software development, particularly for Earth Observation and Algorithm Expertise Domains. Expertise covers geophysical parameter retrieval from sounders like IASI, MTG-IRS, and OCO-2, utilizing radiative transfer codes (RTTOV, 4A/OP, LIDORT/VLIDORT) and inversion codes (4ARTIC). Thales also maintains the Lidar simulator BLISS. It’s adept at spectroscopy, scattering, polarization, BRDF, and comparing retrieved quantities to in-situ profiles, models, and other data. Notably, Thales develops C2IMES software for Cal/Val and GHG monitoring in missions like MicroCarb and Merlin. C2IMES facilitates intercomparisons of gas measurements from various instruments and models, considering system differences. It’s employed by CNES Technical Expertise Centre.


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The data will be available soon.