Quantifying hazard of drought and heat compound extreme events during maize (Zea mays L.) growing season using Magnitude Index and Copula

Hazard assessment is the basic work in the field of disaster risk. For the agricultural field which is seriously affected by extreme events, it is necessary to carry out hazard assessment of compound extreme events (CEEs) to increase the accuracy of risk assessment. First, in this study, the SMDI and TCI were used to characterize the spatial and temporal distribution patterns of agricultural drought and heat, respectively, and the drought and heat compound extreme events (DHCEEs) were identified by characterizing the drought and heat events based on runs theory. Then, the compound event magnitude index (CEMI) was constructed by fitting the non-transcendent probabilities. next, the optimal copula function of severity and duration of DHCEEs was screened, and the fitted probabilities were used in the hazard assessment. The hazard assessment model of DHCEEs is constructed by considering the occurrence probability, severity, and duration. We evaluated the hazard of all DHCEEs identified in the Songliao Plain from 1990 to 2020. The results show that the whole study area is affected by agricultural drought, and heat mainly affects the western region. CEMI can effectively determine the severity of DHCEEs. In the study area, 46.51% of the DHCEEs have a hazard less than 0.1, and 2.71% have a hazard greater than 0.5. The event that had the biggest hazard occurred in 2001, and the proportion of high hazard compound events gradually increased after 2000. Similar compound extreme events are gaining attention in important food-producing regions around the world, and the hazard assessment model constructed in this study can be used to assess crop damage from compound extreme events in real-time, increasing the relevance and accuracy of risk assessment.