Fig. 1: Illustration of the proposed agricultural flash drought definition.
From: The prevalent life cycle of agricultural flash droughts
a Scatterplot of evaporative fraction (EF) vs. volumetric soil moisture (\({\rm{\theta }}\)) at the grid point corresponding to the agricultural flash drought case presented in b (adapted from refs. 10,32). The blue dots represent the pentad values from 1 Aug–20 Sep during the 1960–2020 period. The black line represents the average EF-\({\rm{\theta }}\) relationship computed by binning the data within \({\rm{\theta }}\) ranges close to 0.01 m3 m−3. Soil moisture (dry, transitional, and wet) and evapotranspiration (water- and energy-limited) regimes are highlighted with colors. The solid vertical lines indicate the soil property values, namely permanent wilting point (\({{\rm{\theta }}}_{{\rm{WP}}}\)), soil moisture critical value (\({{\rm{\theta }}}_{{\rm{CRIT}}}\)), and field capacity (\({{\rm{\theta }}}_{{\rm{FC}}}\)) with their corresponding soil water deficit index (SWDI) values. The dashed vertical lines highlight the SWDI thresholds. The upper SWDI threshold (SWDI = −3) is at the beginning of the transitional regime and the lower SWDI threshold (SWDI = −5) ensures that several crops begin to experience water stress. b Representative example of an agricultural flash drought case experienced in southern China (112°E, 28°N) during the summer of 2020. The solid black line shows the pentads (5-day means) for the SWDI (left axis) and \({\rm{\theta }}\) (right axis) during the flash drought event. The upper and lower SWDI thresholds are shown as dashed lines, while \({{\rm{\theta }}}_{{\rm{FC}}}\) and \({{\rm{\theta }}}_{{\rm{WP}}}\) are presented as solid lines.
