Onset of flash drought based on the WRF in the Poyang Lake Basin of China

The occurrence of flash droughts rapidly triggers soil water deficits, easily causing significant impacts on agricultural production, water resources, and ecosystems. As a critical phase in the formation and widespread outbreaks of flash drought, the rapid onset increases the difficulty of monitoring and forecasting. However, the evolutionary mechanisms of flash drought have not been given sufficient attention. In this study, we identified flash drought based on soil moisture from 1993 to 2022 to deepen the understanding of flash drought and presented simulations of three typical flash drought events (occurring in 2019, 2021, and 2022) to explore drought processes by the Weather Research and Forecasting (WRF) model over the largest flesh lake basin of China, Poyang Lake Basin (PLB). The driving factors and short-term atmospheric characteristics of flash drought were used to illustrate the rapid onset. The results show that (1) the PLB experienced increasements in flash drought. The frequency of flash droughts was approximately 4-10 times per decade, with more flash droughts occurring in the northern part of the PLB than in the south. The average duration of flash drought onset was between 9 and 13 days. The types of flash drought onset with two pentads had the highest ratio (70%). (2) The meteorological drivers (precipitation, temperature, evapotranspiration) had strong impacts on the soil evolution in the central and northern parts of the PLB. Precipitation always appeared before or at the very beginning of onset and almost disappeared during the onset of flash drought. (3) The atmosphere over the PLB was relatively dry during the onset. Different atmospheric conditions were observed to follow flash drought onset, which were likely to result in different recovery periods.