143 OPERA5 – Updates of the European Operational Radar Exchange

Thursday, 31 August 2023
Boundary Waters (Hyatt Regency Minneapolis)
Annakaisa von Lerber, Finnish Meteorological Institute, Helsinki, Finland; and M. Goreta, G. Haase, M. Jurašek, P. Karsisto, S. Klink, M. Koutek, H. Leijnse, V. Meyer, C. Mueller, T. Nicolau, S. Park, M. Peura, M. Radojevic, K. Stephan, L. Tuechler, and B. Vodaric Surija

Operational Programme on the Exchange of Weather Radar Information, OPERA, is the weather radar programme operating under the European Meteorological Services Network, EIG EUMETNET. The programme has been coordinating radar collaboration between the national weather services (NMSs) in Europe for more than two decades [Saltikoff et al. 2019]. To learn more about this initiative, visit www.eumetnet.eu/opera.

Starting in 2011, the OPERA data center (ODC), also known as Odyssey, has been generating three Pan-European radar composite products. These products, the maximum reflectivity, rain rate, and 1-hour accumulation, have a spatial resolution of 2 km and an update cycle of 15 minutes. Additionally, Odyssey produces quality-controlled (QC) single-site volume radar data to the numerical weather prediction (NWP) consortia for assimilation purposes. The applications of OPERA data, in addition to NWP assimilation, encompass for example nowcasting and flood warnings. Due to the archive's growth to over a decade, it is now also possible to create climatological applications using OPERA data. As various user groups have distinct needs for the data, some require sophisticated QC and the creation 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].

In the conference, we will be presenting updated production lines and preliminary results regarding their performance in comparison to ODC. CIRRUS is an updated version of the ODC software, but due to the differences in spatial and temporal resolutions, the maximum reflectivity product of CIRRUS is inherently different from the ODC equivalent composite. The methodology used to compare the two maximum reflectivity 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 comparison is performed in terms of precipitation rates. The preliminary results indicate that the composites are very similar in terms of amplitude (A) and location (L), with CIRRUS showing slightly higher values in rain intensity. However, the computed structure (S) parameter suggests that CIRRUS produces lower precipitation rates, which may be more widely spread compared to the ODYSSEY products.

The production of NIMBUS is based on the BALTRAD open radar software, and we have compared its performance for the rain accumulation composite product to gauge observations, similar to the study by [Park et al. 2019]. Park et al. have developed a daily real-time gauge adjustment method, which has been applied to the OPERA rainfall estimates since 2013. This methodology has provided useful statistics regarding the quality of the OPERA precipitation estimates.

In our presentation, we will also provide insights regarding data sharing in OPERA. In December 2022, the European Union (EU) Implementing Regulation defined weather radar data as a High-Value Dataset (HVD). This means that these datasets should be made available free of charge, openly accessible via Application Programming Interfaces (APIs), and machine-readable in the coming years. This regulation aims to make important datasets available to the public and enable their reuse, promoting innovation and creating economic and social benefits. Additionally, the datasets should be available for bulk download, which allows users to obtain a large amount of data quickly and easily. OPERA, within EUMETNET, is part of the EU-funded RODEO project, which is designing and developing interfaces for sharing meteorological data as HVDs.

[1] Saltikoff et al. OPERA the radar project, Atmosphere 2019, 10(6), 320.
[2] Huuskonen, A., and I. Holleman, determining weather radar antenna pointing using signals detected from the sun at low antenna elevations., J. Atmos. Oceanic Technol., 2007, 24, 476–483.
[3] Wernli, H. et al. (2008). SAL—A Novel Quality Measure for the Verification of Quantitative Precipitation Forecasts, Monthly Weather Review, 136(11), 4470-4487.
[4] Park S., Berenguer M., Sempere-Torres D., Long-term analysis of gauge-adjusted radar rainfall accumulations at European scale, Journal of Hydrology, 2019, 573, 768-777.
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