Variability of compound drought and heatwave events over the Mediterranean and their large-scale atmospheric circulation drivers

Abstract

<p><span lang="EN-US">Current research has shown that extreme events can be interrelated and can trigger cascading impacts.</span> <span lang="EN-US">Traditional climate risk and impact assessments typically consider a single extreme event, a fact that leads to the underestimation of risks, as such events are often interdependent. This work </span><span lang="EN-GB">will address the field of extreme climate and weather through the assessment of compound drought and heatwave (CDHW) events. The principal aim of this study is to evaluate the current state of climate over </span><span lang="EN-US">the Mediterranean in</span><span lang="EN-GB"> terms of droughts and heatwaves, focusing on their compound effects, and identifying their large-scale atmospheric circulation drivers. The identification of the CDHW climatology is carried out through the improvement of a novel index tailored to the Mediterranean region. Multiple combinations are examined according to the generic definition of CDHW events (i.e., heatwaves that occur during the period of drought events) and an optimum compound index is developed </span><span lang="EN-US">that successfully quantifies the interrelations of droughts and heatwaves</span><span lang="EN-GB">. Extensive statistical analysis is carried out to evaluate their frequency, duration, intensity, and trends. The analysis is based on the </span><span lang="EN-US">high-resolution state-of-the-art ERA5-Land reanalysis product at a </span>0.1° x 0.1°<span lang="EN-US"> horizontal resolution. </span><span lang="EN-GB">Following a data-driven methodology, the role of large-scale atmospheric circulation drivers on the onset, duration, and intensity of the CDHW events is examined using the synoptic climatology approach. The ‘environment-to-circulation’ approach is selected that employs the Self-Organizing Map (SOM) artificial neural networks for clustering and mapping the atmospheric circulation for enabling the understanding of the large-scale drivers responsible for CDHW events. The analysis provides the hot-spot regions of CDHW high-impact phenomena over the </span><span lang="EN-US">Mediterranean</span><span lang="EN-GB"> region and their association with large-scale circulation is established.</span></p>