Dynamic analysis of drought propagation in the context of climate change and watershed characterization: a quantitative study based on GAMLSS and Copula models

Abstract. The analysis of the law of drought propagation under a changing environment is of great significance for drought early warning and reducing social and economic losses. Currently, few studies have analyzed the effects of meteorological factor and watershed characteristics on drought propagation based on non-stationary drought indices. In this paper, the probabilities and thresholds of meteorological drought to hydrological drought propagation were calculated using the non-stationary drought index constructed using the Generalized Additive Model for Location, Scale, and Shape (GAMLSS) model and the Copula function to assess the influence of large-scale climatic indices, meteorological elements, and watershed characteristics on the propagation characteristics of seasonal droughts. The results showed that non-stationary drought indices that incorporate meteorological factors tended to have better performance than standardized drought indices. Under the combined influence of large-scale climatic indices, temperature, specific humidity, and wind speed, the propagation probabilities became larger especially during spring and winter in the upstream and midstream regions, with the propagation thresholds in winter significantly increasing by 0.1–0.2. These mean that hydrologic droughts are more likely to be triggered. Furthermore, watershed characteristics also be factors influencing spatial differences in drought propagation.