On the development and recovery of soil moisture deficit drought events

Soil moisture drought is one of the driving forces behind agricultural drought and disastrousness for food production, but the understanding of internal drought propagation is limited, making it difficult to track and predict drought propagation. Based on the trend analysis, Spearman correlation analyses, and the random forest model simulations, we analyzed the spatial and temporal distribution characteristics of soil moisture drought propagation globally from 1960 to 2020 and evaluated the contributions of various meteorological factors on soil moisture drought propagation. The results show that the mean drought instantaneous recovery speed (IRS) is 1.52 times greater than the instantaneous development speed (IDS) globally from 1960 to 2020. IDS (IRS) in arid region is lower (higher) by 24.9 % (11.7 %) than in humid areas. The drought IDS statistically increased 0.012 % pentad(-1) year(-1) and drought duration statistically decreased 0.020 pentad year(-1) from 1960 to 2020, especially in the mid- and high-latitudes of the Northern Hemisphere (45-67.5 degrees N). The timing of the occurrence of extreme meteorological conditions shows more significant effects on the propagation of drought than average meteorological conditions within the drought period. Since evapotranspiration (precipitation) exerts greater influences on drought development (recovery) than other meteorological variables, intensified hydrological cycle under a warming climate could possibly accelerate the drought development and recovery.