Towards the combination of in-situ and satellite-based solar radiation data in near-realtime – the project DUETT at DWD

As the production of the current solar radiation sensor systems ceased and changes due to automation of the measuring network were necessary, a new concept of solar radiation measurements in Germany was established by Deutscher Wetterdienst (DWD). Aiming at an efficient network with high-quality data, it was decided to enhance the coverage of high-quality pyranometers that measure global and diffuse solar radiation, herewith also allowing the calculation of sunshine duration via the pyranometric method. The use of low to moderate quality instruments to measure solar radiation and sunshine duration will be discontinued in the future. To compensate for the reduction of the number of in-situ measurements and with solar radiation products from satellite data continuously improving in quality, the integration of both data sources was planned within the project DUETT at DWD.  

The project DUETT focuses on the development of merging algorithms for the parameters global radiation and sunshine duration and therefore uses data from the (future) 42 pyranometer stations as well as near-real-time satellite data based on measurements of the METEOSAT SEVIRI instrument with a latency of only a few minutes. Preoperational, merged DUETT products are processed on an hourly basis with a spatial resolution of 2x2 km for Germany and a time delay of 15 minutes after each full (synoptic) hour for both parameters. Here, validation results of the latest version of the merging procedure, based on independent in-situ data, are presented for both parameters for a validation period of one full year; possible future improvements are also discussed.