Spatial and compound dependencies in drought and heatwaves in the climate of South-Western Europe

Abstract

The South-Western Europe (Iberian Peninsula) has been highlighted for the escalating occurrence and severity of droughts and heatwaves during the last decades. However, the statistical interdependencies between these extremes remain largely understudied, which makes effective climate adaptation and mitigation strategies compromised as a result. In this study, ERA5 reanalysis of daily mean temperature and accumulated precipitation data is used to examine the statistical interdependencies that exist between drought conditions and heatwaves in the Iberian Peninsula from 1950 to 2022. Markov chain models are applied to establish the probability of transitions among the four states monthly, event-free, drought, heatwave and compound states. The connection of these extremes between pairs of grid points by the use Hamming distance technique is also explored by analysing the similarities in decades and seasons. The results confirm that there is a rise in extreme events in the Iberian Peninsula, the magnitude is increasing and the connections of occurrences of extreme events between grid points are gradually becoming weaker which shows that the statistical similarities are changing significantly in time.