Spatio-Temporal Dynamics of Rapid Drought-to-Wet Transitions in Thessaly, Greece (1990–2024)

This study fills a significant knowledge gap in hydroclimatic studies by exploring rapid transition from droughts to wet conditions—an influential yet incompletely known process. Instead of viewing wet events and droughts as separate extremes, it highlights the shift dynamics that characterize hydroclimatic variability in Thessaly, Greece, a significant cropland region. Using ERA5-Land soil moisture data at 0.1° (~9 km) spatial resolution and pentad (five-day) time resolution for the period of 1990–2024 this analysis focuses on developing the temporal and geographical pattern of shift from droughts to wet events. Four diagnostic indexes were used: duration (length of transition), change (magnitude of increase of soil moisture), intensity (rate of change per pentad), and peak (maximum soil moisture reached during transition). Spatially, the longest transitions, up to 17 pentads (~85 days), are located in central and east Thessaly, while the strongest moisture recoveries (change up to 72%) and greatest intensities remain mostly in the west and north. Seasonally, the majority of the transitions occur from late spring to mid-summer, and with May to July being the period of peak events, marking the usual end of drought events in the region. The statistical analysis also shows a strong significant negative correlation between duration and intensity (r = –0.82), implying that shorter-length transitions are more intense and abrupt. In contrast, the positive correlation between change and peak (r = 0.53) associates larger moisture recoveries correspond to greater wet extremes. These findings provide an integrated view of the temporal and spatial development of sudden hydroclimatic shifts and potential practical applications for optimizing irrigation scheduling, creating early warning systems, and improving adaptive water management strategies in Mediterranean farming conditions with respect to climate change.