Inter-seasonal connection of typical European heatwave patterns to soil moisture

Although prolonged heat periods have become a recurring feature of European climate, little knowledge is available on dominant spatial patterns of heatwaves and their influence on moisture-related processes. Increased knowledge will help to improve heatwave and drought prediction and mitigation. This study uses hierarchical agglomerative clustering to derive nine dominating spatial heatwave patterns from a 50-member regional climate model (Canadian Regional Climate Model version 5, CRCM5-LE). The heatwave patterns correspond well with clusters derived from an observational data set (E-OBS) and with extreme historical heatwave events. Moreover, we analyse the occurrence of heatwaves in the identified spatial patterns regarding a soil moisture deficit present before and after the event. We show that negative soil moisture anomalies in the preceding winter/spring (JFMA) can serve as a predictor for heatwaves in South Europe. For North Europe, we find a negative correlation between the number of heatwave days in summer and autumn (OND) soil moisture content.

Automated summary

This study uses hierarchical agglomerative clustering to derive nine dominating spatial heatwave patterns from a 50-member regional climate model. The heatwave patterns correspond well with clusters derived from an observational dataset and with extreme historical heatwave events. Moreover, the occurrence of heatwaves in the identified spatial patterns is analyzed regarding soil moisture deficit before and after the event. Negative soil moisture anomalies in the preceding winter/spring can serve as a predictor for heatwaves in South Europe. For North Europe, there is a negative correlation between the number of heatwave days in summer and autumn and soil moisture content.