Temporal and spatial propagation characteristics of meteorological drought to hydrological drought and influencing factors

Meteorological drought, characterized by a decrease in precipitation, leads to hydrological drought, characterized by a decrease in runoff through the water cycle. Currently, research on drought propagation primarily considers the entire region as the research object, which cannot effectively reflect the difference in propagation characteristics within the region. Therefore, this study analyzed the propagation time, probability, and threshold of meteorological to hydrological drought based on precipitation and runoff data with 0.25(degrees) spatial resolution. The propagation time was primarily determined according to the correlation coefficients of the standard precipitation index and standard streamflow index sequences at different timescales. To calculate the propagation probability and propagation threshold, this study proposes a novel method based on Bayesian conditional probabilities to calculate the propagation characteristics that embody the internal mechanism of propagation effectively by fitting the marginal and joint distributions. Otherwise, based on the 20-year moving average and Mann-Kendall trend test to analyze the dynamic changing trends of propagation probability and propagation threshold during the study period (1961-2015). In addition, the influences on the propagation threshold were analyzed from the perspectives of meteorology (precipitation, temperature, and evaporation) and the underlying surface (elevation, slope, and soil moisture). The analysis of drought propagation characteristics can deepen the understanding of the propagation process, which also provides guidance for the timely formulation of drought control measures in the future.