Compound dry and hot extremes: A review and future research pathways for India

Compound Dry and Hot Extremes (CDHEs) is gaining attention compared to individual dry or hot extremes, due to their amplified impacts on both the population and ecosystems in India. This underscores the importance of transitioning from studying individual extremes to adopting a compound perspective. Despite this, investigation of CDHEs during the Indian summer monsoon remain limited, and a comprehensive review of methodologies for the investigation of CDHE is absent. This review systematically synthesizes recent literature, covering concepts of CDHE with illustrative examples, including identification, characterization, drivers, and prediction. It illustrates three widely used methods for the identification of CDHEs along with their advantages and disadvantages. Furthermore, it describes concepts with illustrative examples to investigate the characteristics (frequency, spatial extent, timing, duration, severity, and likelihood), explores drivers using event coincidence analysis and a complexity-based framework, and discusses the strengths and weaknesses of a logistic regression model for predicting the occurrence of CDHE. In light of the growing significance of CDHEs, we suggest future directions for Indian CDHE research, including an improved characterization of CDHEs across multiple temporal and spatial scales, a deep understanding of the physical mechanism, a robust evaluation of climate models, attribution and projection, and a comprehensive impact assessment. CDHEs are the new normal, and there is an urgent need to advance research on CDHEs in vulnerable regions like India to combat and mitigate their effects.