Evaluation of ERA5-Land Against Ground-Based Precipitation Observations in Supporting Landslide Analysis in Pannonian Croatia

Due to its global coverage, high temporal and enhanced spatial resolution (compared with the ERA5 product), and open availability, the ERA5-Land global atmospheric reanalysis dataset offers a promising framework for various applications in environmental modeling. In this study, the ERA5-Land post-processed daily precipitation product was compared against ground-based observations to evaluate its reliability in representing regional precipitation patterns and its capacity to reproduce landslide-triggering rainfall conditions. The investigation was conducted across five landslide locations in Pannonian Croatia over a 35-year period (1990–2024). It encompassed a comparative statistical analysis of daily and monthly precipitation, an evaluation of rainfall day and event frequency distributions, and a reconstruction of specific historical landslide-triggering events. The results confirm that ERA5-Land exhibits a systematic dual bias, overestimating low-intensity precipitation frequencies while underestimating high-intensity rainfall peaks. Concurrently, the pronounced drizzle effect directly increases the duration of rainfall events, altering landslide-triggering rainfall conditions. The findings align with previous research, confirming that ERA5-Land data can effectively capture broad, long-term regional climate trends and track antecedent rainfall indices. However, its integration into operational landslide early warning systems would benefit from statistical bias-correction or localized calibration to reduce systematic errors.