From MSG SEVIRI to MTG FCI: Extending All-Sky IR radiance assimilation in the regional high-resolution ensemble prediction system of GeoSphere Austria

The transition from Meteosat Second Generation (MSG) to Meteosat Third Generation (MTG) represents a major step forward in European geostationary satellite observing capability. This work presents preparatory and preliminary results from extending the established all-sky radiance assimilation framework, originally developed for MSG SEVIRI to MTG FCI. The study emphasizes methodological continuity to ensure a seamless evolution of satellite data assimilation practices within convective-scale numerical weather prediction. 

Earlier all-sky assimilation experiments with SEVIRI water vapour channels established a robust framework for handling cloud-affected radiances through dynamically adaptive, cloud-dependent observation error modelling. Here, the same principles are applied to FCI water vapour channels, enabling a consistent assessment of how these observations interact with existing assimilation systems. FCI’s enhanced spatial resolution, improved radiometric accuracy, and expanded spectral sampling promise greater information content, but also introduce increased representativeness and cloud-related uncertainties, reinforcing the value of adaptive error characterisation. 

Preliminary 3D-EnVar experiments within the pre-operational regional high resolution ensemble prediction system of GeoSphere Austria compare the all-sky assimilation approaches for both SEVIRI and FCI radiances. Results show that the cloud-dependent observation error model previously validated with SEVIRI yields a neutral to positive impact on the short-range forecast. This demonstrates a structured pathway toward the operational exploitation of FCI observations, supporting improved short-range forecasts of high-impact weather. Progress on assimilation of visible channels from SEVIRI and FCI are also foreseen.