Structural and Transient Compoundness in Natural Systems

In recent years, compound events, i.e., events resulting from the interaction between multiple physical drivers, have gained great attention in the scientific community especially as they can lead to greater impacts than events controlled by a main single physical driver. The majority of the studies relied on the use of statistical measures of dependence and multivariate analyses to show potential for compound events across diverse climatic and geographical regions. However, these approaches provide limited insights into the system being investigated and its behavior.

Here, we propose an approach to characterize the 'compoundness' of a system in terms of two components: structural compoundness, which refers to the overall tendency of physical drivers to jointly occur and interact, and transient compoundness, which refers to the specific occurrence or manifestation of interacting physical drivers. We provide example applications of the proposed characterization and discuss their implications for developing climate-resilient adaptation strategies.