Evolution Characteristics of Meteorological Drought under Future Climate Change in the Middle Reaches of the Yellow River Basin Based on the Copula Function

Abstract

Against the background of global warming and frequent extreme precipitation events, the changes in drought characteristics in the middle reaches of the Yellow River Basin (YRMB) have been particularly pronounced in recent years. Under the new situation, it is necessary to further our understanding of drought risk in the basin and its response mechanisms to climate change. In this study, YRMB was utilized as the research area. Based on the precipitation (P) and potential evapotranspiration (PET) data under four emission scenarios (historical and future), five timescales (SPEI-1, SPEI-3, SPEI-6, SPEI-9, and SPEI-12) of SPEI drought indices were estimated in this study. Drought events were identified using the run-length theory, and the spatial distribution values of drought frequency, duration, intensity, and severity were also examined. Based on the preferred copula function, the two-dimensional joint distribution of drought variables was established, and the two-dimensional return period of drought indices in the historical (1901–2014) and future (2022–2100 under SSP245 and SSP585 emission scenarios) periods were calculated. The results show that the SPEI index in the middle reaches of the YRMB is increasing in the future period and the basin tends to be more humid. Under the SSP245 and SSP585 scenarios, the frequency of long drought durations, high drought intensities, or severe drought events in the basin may be higher. The univariate return period is always higher than the joint return period, but lower than the co-occurrence return period, and both types of return periods can be used to assess range estimations in the future. The research results can provide support for understanding the spatiotemporal distribution characteristics of drought in the YRMB and improving the accuracy of drought decision making.