Validation results for the 2 km ICON-reanalysis based on conventional observations for climate applications in Central Europe

Reanalysis data sets are becoming increasingly popular for a broad spectrum of applications such as climate adaptation and mitigation, renewable energy, agriculture, or hydrology, including the assessment of meteorological hazards and extremes. Recently, the high relevance of reanalysis data sets has increased further due to their value as a basis for training AI-based NWP model emulators such as AICON or AIFS. Most of these applications require much finer grid spacing compared to ERA5 (31 km), ERA6 (14 km), or even ICON-DREAM (dual resolution reanalysis for emulators, applications, and monitoring, 13 and 6.5 km). Therefore, regional reanalysis is designed and produced for limited geographical regions, allowing for the provision of high-quality and high-resolution data sets.

The 2 km ICON-reanalysis based on conventional observations for climate applications in Central Europe (ICON-FORCE-c) has been produced adapting the operational 2 km ICON-RUC (Rapid Update Cycle) numerical weather prediction (NWP) model framework, which uses the 2-moment microphysics parameterization to better represent precipitation processes. Its operational data assimilation cycle comprises the KENDA LETKF-based data assimilation scheme at hourly intervals, complemented by a snow analysis every 6 hours, and T2M, SST and soil moisture analysis every 24 hours (at 00 UTC). The background error covariances are provided by a 20 member ensemble at the same 2.1 km resolution of the deterministic run. The boundary conditions come from the ICON-DREAM European nest domain. The next version of ICON-FORCE-c will also include SEVIRI radiometer satellite data to better constrain the upper atmosphere.

This presentation is a companion work with colleagues from the research and development department of DWD, jointly comparing and evaluating our product with their reanalysis products ICON-FORCE and ICON-DREAM. While the full-input ICON-FORCE regional reanalysis aims to provide the best description of the Earth system, with the modern regional observational network, the sparse input ICON-FORCE-c reanalysis aims to provide the best possible climate state for the area, thus focusing on climate trends and its consistency. We aim to present first evaluation results by comparing ICON-FORCE-c with ICON-FORCE, ICON-DREAM and ERA5.