Climatological study reveals large-scale atmospheric and oceanic drivers governing severe hail seasons across the Alps, highlighting key precursors for seasonal storm prediction.
Key Points
Identify the large-scale atmospheric, oceanic, and land-surface patterns driving the interannual variability of hail seasons north and south of the Swiss Alps.
Analyzed a 64-year historical reconstruction of hail days spanning 1959 to 2022.
Evaluated atmospheric circulation patterns, sea-surface temperatures, and thermodynamic environmental profiles using ERA5 reanalysis data.
Active hail seasons correlate with recurrent Euro-Atlantic wave trains, warm and moist boundary layers, high instability, and moderate convective inhibition.
Regional mechanisms diverge, with northern hail activity limited primarily by temperature and continental/Atlantic moisture, whereas southern activity depends on Mediterranean moisture and elevated dry layers.
Identified winter precursor signals including continental cooling and Pacific sea-surface temperature anomalies matching a positive Pacific Decadal Oscillation phase.