Abstract: Understanding “energy drought” and its impact on system performance is a key challenge under changing environments.This study extends our previously proposed data assimilation-driven adaptive operation framework to re-evaluate system performance from an energy drought perspective.A comprehensive “resource drought-energy drought” assessment framework is established,defining the extreme low value of potential power generation capacity before operation (resource drought) and that of constrained output after operation (energy drought).Furthermore,non-stationary stress scenarios characterized by variations in mean level,variation coefficient,and seasonal distribution are constructed using stochastic simulation,identifying how different variation types influence drought propagation from resources to energy outputs.A case study on the hydro-wind-solar integrated system in the upper Yellow River basin reveals:(1)The periods with high incidence of hydropower,wind,and solar resource droughts exhibit clear seasonal misalignment (winter,winter,and summer,respectively),whereas drought intensity increases with resource stochasticity (hydropower