Causal networks and spatiotemporal patterns of different droughts from the perspective of hydrological cycle - a case study of the Nenjiang River Basin, China

Different drought types exhibit propagation phenomena and feedback through the hydrological cycle. Therefore, this study utilized the convergent cross mapping to identify the causality among meteorological drought(MD), agricultural drought(AD), hydrological drought(HD), and ecological drought(ED) in the Nenjiang River Basin from 1980 to 2020, constructing a causal relationship network. The results indicate that different types of droughts are more prone to spread and influence each other at shorter time scales. Although there exist bidirectional causality between MD and other droughts at the monthly scale, no clear causal relationship is observed between AD and ED. Contrasting the direction and strength of causality, presenting the order MD-AD-HD-ED. This finding is consistent with the hydrological cycle pattern. The intensity of drought causality varies significantly across different regions spatially. This study delves into the mechanisms and intensities of mutual influence among different types of droughts by establishing the causal relationship network, offering essential scientific basis for drought monitoring, early warning, and emergency response.