On the role of antecedent meteorological conditions on flash drought initialization in Europe

Abstract

The fast depletion of soil moisture in the top soil layers characterizes flash drought events. Due to their rapid onset and intensification, flash droughts severely impact ecosystem productivity. Thus understanding their initialization mechanisms is essential for improving the skill of drought forecasting systems. Here, we examine the role of antecedent meteorological conditions that lead to flash droughts across Europe over the last 70 years (1950--2020) using ERA5 dataset. We find two major flash-drought types based on a sequence of development of antecedent hydro-meteorological conditions. The first type is characterized by a joint occurrence of two mechanisms, a decline of precipitation in conjunction with an increase of the evaporative demand, both occurring before the onset of a flash drought event. The second type, on the contrary, is characterized by high precipitation preceding the event's start, followed by a sudden precipitation deficit combined with an increase in evaporative demand at the onset of the drought. Both drought types showed increased occurrence and higher spatial coverage over the last 70 years; the second drought type has increased at a much faster rate compared to the first one specifically, over Central Europe and the Mediterranean region. Overall our study highlights the differences between the two types of flash droughts, related to varying antecedent meteorological conditions, and their changes under recent climate warming.

Viewing Soil Moisture Flash Drought Onset Mechanism and Their Changes Through XAI Lens: A Case Study in Eastern China

“…Notably, the majority of events were associated with the Antecedent-concurrent Prec type (Cluster 2), the Antecedent Tem-concurrent Prec type (Cluster 3), or the Antecedent Tran-concurrent Prec type (Cluster 4). This emphasizes the pronounced influence of antecedent conditions in shaping the dynamics of flash drought occurrences (Shah et al, 2023). In addition, some flash drought events were only driven by the Concurrent Prec type (Cluster 1), indicating the crucial role of concurrent Prec deficit in flash drought occurrences (Koster et al, 2019).…”

“…This trend implies a potential amplification of vegetation water consumption's role in influencing the occurrence of flash droughts (Guo et al, 2023). These results imply a growing influence of antecedent conditions, particularly antecedent temperature and transpiration (Shah et al, 2023). Subsequently, we analyzed the spatial patterns of trends for each identified cluster with a 15-year moving window (Figure 9).…”

Disparities and similarities in the spatiotemporal dynamics of flash and slow droughts in China

“…In addition, we used 0-1 m soil moisture, which is critical for both surface evaporation and root zone vegetation transpiration, to identify grids under drought conditions. However, the definition is not sensitive to the choice of 0-1 m soil moisture or total column soil moisture according to previous work (Shah et al 2023. Finally, this study includes small to large scale drought events to provide a comprehensive comparison across spatial scales and between 1D and 3D methods.…”

Flash drought: A state of the science review

“…These studies found that flash droughts occur most frequently in central and eastern Europe (Shah et al, 2022;Sungmin & Park, 2023) and have become more common across all of Europe, with many areas experiencing at least an 80% increase in flash drought frequency from 1950-1984(Shah et al, 2022. Shah et al (2023) also identified two types of flash drought development across Europe. The first is associated with a decline in precipitation combined with increased evaporative demand, while the second type is associated with high precipitation preceding the event start, followed by an immediate precipitation deficit.…”