Shallow and deep low-wind events in Europe: an ERA5-based event dataset (1979–2024)

Abstract. Persistent low-wind events (LWEs), often referred to as wind droughts, pose a growing challenge to power systems with high shares of wind energy. Existing assessments typically identify LWEs using wind speed at a single height, implicitly treating wind droughts as vertically homogeneous. However, weak-wind conditions can exhibit different vertical structures within the atmospheric boundary layer, leading to different wind conditions at turbine height. We present an event-based dataset of European LWEs derived from hourly ERA5 reanalysis for 1979–2024. The dataset introduces a two-height classification based on 10 and 100 m wind speeds. Events lasting at least 48 h are classified as shallow LWEs when wind speed is below 3 m s^-1 at 10 m but above this threshold at 100 m, and as deep LWEs when wind speed remains below the threshold at both heights. Corresponding shallow-LWE-like and deep-LWE-like events are also identified for durations shorter than 48 h. The principal novelty of the dataset is that it adds a previously neglected vertical dimension to wind-drought climatology by distinguishing between weak-wind conditions confined near the surface and those that extend to turbine height. The physical plausibility of the classification is supported by distinct spatial and seasonal distributions and contrasting boundary-layer characteristics. Shallow LWEs are associated with stronger 10–100 m wind contrasts and more stable surface conditions, whereas deep LWEs represent more vertically coherent weak-wind states. The dataset contains event timing, duration, location, and classification, providing a resource for investigating European wind-drought climatology, boundary-layer controls, and land–sea contrasts. It also supports separate assessment of near-surface and turbine-height low-wind exposure in future renewable-energy systems. The dataset is available at https://doi.org/10.5281/zenodo.20748499 (Zhou and Esau, 2026).