About

The Cloud_cci project covers the cloud component in the European Space Agency’s (ESA) Climate Change Initiative (CCI) programme.

Background

In the Cloud_cci project, long-term and coherent cloud property datasets have been generated for which the synergistic capabilities of different Earth observation missions (European and non-European) were exploited. A centrepiece of this activity has been the development and application of two state-of-the-art physical retrieval systems that use the optimal estimation technique for a simultaneous, spectrally consistent retrieval of cloud properties including pixel-based uncertainty measures:

• The Community Cloud retrieval for Climate (CC4CL) which has been applied to AVHRR and AVHRR-heritage channels of MODIS, (A)ATSR and SLSTR (Sus et a., 2018; McGarragh et al., 2018)
• The Freie Universität Berlin AATSR-MERIS Cloud retrieval (FAME-C, Henken et al., 2014) applied to synergistic MERIS and AATSR measurements on-board ENVISAT

After producing prototype datasets (version 1), a series of multi-annual, global datasets were generated using the passive imager satellite sensors listed above. These datasets (version 2 hereafter, Stengel et al., 2017) were comprehensively evaluated and documented. Updates of a subset of these datasets (version 3, Stengel et al., 2020; Poulsen et al., 2020) benefited from retrieval improvements, were characterised by extended temporal coverage and included consistently derived radiation properties in addition to the cloud properties.

Next steps

In Cloud_cci+ project phase 1 the focus was put on the European sensors SEVIRI and SLSTR that provide higher spatial and/or temporal resolution than the previously used sensors. Additionally, the full spectral information of these sensors for the retrieval of cloud and radiation properties has been being exploited.

The objectives of the current Cloud_cci+ Phase 2

The ESA Cloud_cci+ Phase 2 started in April 2025 aiming at the following five goals:

Firstly, the preparation of demonstrator data jointly based on polar-orbiting and geostationary satellite observation, capitalising on the complementarity of geostationary and polar-orbiting information in the high latitudes.

Secondly, the implementation of further CC4CL retrieval improvements targeting the retrieval of cloud properties in high latitudes.

Thirdly, the comprehensive utilization of EarthCARE data for evaluation of Cloud_cci data and the contribution to EarthCARE cal/val activities.

Fourthly, demonstrating the beneficial impact of Cloud_cci+ data products for climate science, i.e. by using Cloud_cci data in a use case study on Tropical convective clouds associated with the EarthCARE ORCESTRA field campaign.

Fifthly, developing cloud retrievals and generating cloud products from the Arctic Weather Satellite, specifically focussing on ice clouds in the high latitudes.

As in previous project phases, the implemented developments will be provided to operational entities such as the EUMETSAT SAF network and the Copernicus Climate Change Service. Furthermore, the work undertaken in this project phase will continue to contribute to the international climate research activities, e.g. by providing observational constraints to climate model and process studies and as input to climate analyses in general.