This study aims to analyze the impact of climate change and watershed characteristics on the spread of drought. Based on the GAMLSS (Generalized Additive Model for Location, Scale, and Shape) framework and Copula model, the probability and threshold of drought spread in different seasons were calculated without being affected by climate factors. The results show that: the spatiotemporal variability of drought spread is influenced by climate change and watershed characteristics

This study tests 36 combinations of microphysics and boundary layer schemes in the Weather Research and Forecasting model for extreme rainfall over Saudi Arabia. Using the Kling–Gupta Efficiency, the Yonsei University boundary layer with the Thompson microphysics performs best; the Morrison microphysics with the Mellor–Yamada–Nakanishi–Niino boundary layer ranks lowest. Mean temporal efficiency is 0.37, spatial efficiency is 0.26, revealing spatial prediction challenges in arid regions.