Copernicus European Regional ReAnalysis (CERRA): Towards Near Real-Time Production and Extended Climate Records

In this presentation, we will present the Copernicus European Regional ReAnalysis (CERRA, https://climate.copernicus.eu/regional-reanalysis-europe). This dataset is produced by the Swedish Meteorological and Hydrological Institute (SMHI) within the Copernicus Climate Change Service (C3S). The system consists of three main components: the ensemble data assimilation component, CERRA TU, and the CERRA-Land component. The data assimilation system is based on the HARMONIE-ALADIN numerical weather prediction system, using 3DVAR for upper-air observations and an optimal interpolation approach for surface observations. The system uses ERA5 as boundary conditions, additional local observations, and provides reanalysis at 5.5 km horizontal resolution, with 3-hourly analysis fields and hourly forecast fields. The CERRA dataset includes more than 50 parameters, covering both surface and atmospheric variables, and is archived on the CDS from 1984 to the latest month with a latency of 3.5 months. The ensemble data assimilation component of the system consists of a 10-member ensemble for generating the B-matrix and uncertainty estimates at 11 km horizontal resolution.

Besides near-real-time production, climate records extending from 1961 to 1984 are also being produced using six parallel streams for the back extension. These data are planned to be made available to users in 2027.

In the current project, daily and monthly means from CERRA, along with ensemble statistics from EDA, are being produced and archived on the CDS.

The presentation will describe the CERRA system and the performance of CERRA in comparison to ERA5. The presentation will also address the challenges related to real-time CERRA production, ensuring data quality, and carrying out the back-extension runs.