OPERA5 – the renewal of the production lines

For over 20 years, the Operational Programme on the Exchange of Weather Radar Information (OPERA) has been coordinating radar cooperation among national weather services in Europe, operating under the umbrella of the European Meteorological Services Network, EIG EUMETNET. More information on this programme can be found at www.eumetnet.eu/opera [Saltikoff et al. 2019].

Since 2011, the OPERA data center (ODC), also known as Odyssey, has been producing three Pan-European radar composite products, with spatial resolution of 2 km and 15-minute update cycle. The composite products are:  maximum reflectivity, rain rate, and 1-hour accumulation. Additionally, Odyssey provides the quality-controlled (QC) single-site volume radar data for the numerical weather prediction (NWP) consortia to be used for assimilation. OPERA data are utilized for a variety of applications, including nowcasting, NWP assimilation, and flood warnings. As the OPERA data archive has grown to over ten years, also the creation of climatological applications is possible based on OPERA data. Different user groups have various needs for the data, with some requiring advanced QC and production of complex products, while others prioritize timely access to the data.

During the current OPERA phase 5 (2019-2023), the programme's main focus is to gradually replace the ODC with three new production lines:

• The CUMULUS/STRATUS line is responsible for gathering incoming radar data and forwarding it to other production lines.
• The CIRRUS line generates a high-resolution maximum reflectivity composite (updated every 5 minutes with 1 km horizontal resolution).
• The NIMBUS line produces precipitation composites and provides quality-controlled volume radar data for the purpose of NWP assimilation.

Additionally, OPERA centrally monitors the network's performance, including the level of radio frequency interference and the antenna pointing using methods such as solar monitoring [Huuskonen and Holleman, 2007].

During the conference, we will present the updated production lines and preliminary results of their performance compared to the ODC. The CIRRUS represents an updated version of the ODC software, but due to the different spatial and temporal resolutions, the CIRRUS maximum reflectivity product is inherently different from the ODC equivalent composite. The methodology used to compare these two products is based on the SAL method [Wernli et al. 2008], which not only compares the amplitude but also the structural differences of the two products. The NIMBUS production is based on the BALTRAD open radar software, and its performance for the rain accumulation composite product is compared to gauge observations, similar as in the study by [Park et al. 2019].

We will also provide insights for data sharing in OPERA. The EU Implementing Regulation has defined weather radar data as High-Value Datasets (HVD) that should be shared free of charge, openly accessible via Application Programming Interfaces (APIs), machine-readable, and bulk downloadable in the coming years.