In the first two years, CERISE established key methodological and infrastructure developments. WP1 advanced ensemble and unified land data assimilation and developed machine-learning observation operators. WP2 implemented outer-loop coupling infrastructure in ECMWF IFS and weakly coupled systems in HARMONIE-AROME. WP3 improved land surface initial conditions for seasonal forecast demonstrators, and WP4 delivered the first ERA6-Land and Arctic CARRA-Land-Pv1 prototypes. WP5 completed Phase 0 and most Phase 1 seasonal forecast demonstrators, with the SUNSET app deployed for preliminary analysis. WP6 developed land-surface diagnostics and evaluation tools, while WP7 established a centralised data archive and generated time-varying lake and land cover datasets, with vegetation data in preparation.
By month 34, CERISE further developed methodologies to enhance the use of surface-sensitive observations. WP1 advanced land data assimilation in both the ECMWF and HARMONIE-AROME systems through methodological, technical, and machine-learning developments that improved ensemble performance, surface–soil coupling, and use of satellite observations. WP2 advanced regional and global coupled data assimilation by testing land–atmosphere coupling strategies, skin-temperature coupling, and passive microwave coupled data assimilation. These developments demonstrated clear near-surface forecast improvements and confirming strong performance of outer-loop coupling in the IFS, reaching TRL7. WP3 completed the preparation and delivery of seasonal forecast initialisation datasets for both Phase 1 and Phase 2 demonstrators, with most Phase 2 datasets archived on MARS. In addition, monthly mean land surface data were provided to support intercomparison and further assessment.WP4 had largely progressed as planned, with most deliverables met and the milestone on coupled global reanalysis achieved ahead of schedule. Key achievements include the successful delivery of the ERA6-Land-Pv2 global reanalysis, the production of the first coupled ERA7 prototype, and substantial progress on regional reanalysis demonstrators across pan-Arctic and pan-European domains, with CARRA-Land-Pv2 completed in November. WP5 focused on producing seasonal forecast demonstrators using initial conditions from WP3 and WP4, with all Phase 1 demonstrators successfully archived. Phase 2 demonstrators progressed well toward completion, alongside continued development of collective assessment activities and forecast evaluation tools. WP6 completed the development of its analysis tools and initiated their application to key CERISE outputs. Progress was made on assessing prototype reanalyses and seasonal forecasts, preparing for results and recommendations due in M48. WP7 finalized long-term databases of land surface characteristics (lake cover, land cover, LAI) spanning 1925–2020, which were used in the ERA6-Land-Pv2 reanalysis.
