Copernicus European Regional ReAnalysis (CERRA)

The Copernicus European Regional ReAnalysis (CERRA, https://climate.copernicus.eu/regional-reanalysis-europe) is produced by the Swedish Meteorological and Hydrological Institute (SMHI) as part of the Copernicus Climate Change Service (C3S). The CERRA model system is based on a setup of HARMONIE-ALADIN, including a 3D-Var data assimilation scheme for upper-air observations and an Optimal Interpolation scheme for surface observations. The model domain covers the entirety of Europe at a horizontal resolution of 5.5 km. The system provides eight analyses per day – from 00 UTC to 21 UTC. Between the analyses, data are available at hourly resolution from the forecast model. More than fifty parameters are available on various level types.

Uncertainty estimates for reanalysis variables are provided by CERRA-EDA, a 10-member ensemble data assimilation system. This ensemble system is run at a horizontal resolution of 11 km.

From a previous contract, CERRA is available for the period September 1984 – June 2021 through the Copernicus Climate Data Store (CDS). Under the new contract, production has continued from July 2021 onwards. The data produced under this new contract are available on the CDS until the end of September 2022. The CDS is updated monthly with two months of CERRA and CERRA-EDA outputs. However, we aim to update the series operationally in near real-time.

In addition, a back extension covering the period 1961–1984 is in development and is scheduled to begin production in summer 2025.

We will present the data assimilation system and the performance of CERRA in comparison to ERA5. The challenges involved in the real-time production of CERRA, quality control of the output, and running the back extension will also be discussed.