Flash drought characteristics based on three identification methods in the North China Plain, China

Abstract Flash drought (FD) is a rapid onset and intense drought threatening ecology, economy, and agriculture. The North China Plain (NCP) suffers from frequent droughts and limited water resources. This study proposed a new FD identification method, termed mean-scaled evaporative stress ratio (MESR), to identify FD events in the NCP from 1981 to 2022. This method applied an improved standardized evaporative stress ratio (SESR) framework to identify FD by atmospheric evaporative demand. Combining root zone soil moisture (RZSM), SESR, and MESR, FD spatiotemporal characteristics were explored from agricultural and land-atmosphere perspectives. A percentile-based FD hotspot indicator integrating FD characteristics was introduced to identify FD hotspots. The threshold sensitivity for FD identification was evaluated across different FD methods. Results show that FD frequency is high in north-central NCP and low in southern NCP. The onset and recovery stages, total duration, and severity all increase with RZSM-based FD intensity grades. However, FDs based on SESR and MESR have shorter onset stages but longer recovery stages as FD intensity grade increases. By the joint influence of climate factors and human activities, FD characteristics show a decreasing trend temporally and spatially. Two FD hotspots with frequent, severe, and intense FDs are in northeastern and southwestern NCP. Furthermore, FD frequency is significantly influenced by thresholds, RZSM-based FD frequency decreases with increasing soil depth. Besides, compared to thresholds on decreasing indices, thresholds about pentads are sensitive to FD identification. This study improves the FD understanding in the NCP, providing valuable insights for regional FD adaptation.