Accelerated western European heatwave trends linked to more-persistent double jets over Eurasia

Abstract

Persistent heat extremes can have severe impacts on ecosystems and societies, including excess mortality, wildfires, and harvest failures. Here we identify Europe as a heatwave hotspot, exhibiting upward trends that are three-to-four times faster compared to the rest of the northern midlatitudes over the past 42 years. This accelerated trend is linked to atmospheric dynamical changes via an increase in the frequency and persistence of double jet stream states over Eurasia. We find that double jet occurrences are particularly important for western European heatwaves, explaining up to 35% of temperature variability. The upward trend in the persistence of double jet events explains almost all of the accelerated heatwave trend in western Europe, and about 30% of it over the extended European region. Those findings provide evidence that in addition to thermodynamical drivers, atmospheric dynamical changes have contributed to the increased rate of European heatwaves, with implications for risk management and potential adaptation strategies.

Large‐Scale Drivers of Persistent Extreme Weather During Early Summer 2021 in Europe

“…In keeping with Rousi et al. (2022), the heatwave in Eastern Europe was associated with a double jet. Our results shed some light on causality by showing that the double jet and the heatwave both resulted from the recurrent amplification of the flow manifested by the blocks and RWB episodes.…”

“…The blocks and RWB episodes also sustained each other, notably through diabatic feedbacks, and contributed to maintaining the large-scale circulation anomalies. In keeping with Rousi et al (2022), the heatwave in Eastern Europe was associated with a double jet. Our results shed some light on causality by showing that the double jet and the heatwave both resulted from the recurrent amplification of the flow manifested by the blocks and RWB episodes.…”

North-West Europe hottest summer temperatures rising much faster than the mean

“…Hence, if the enhanced temperature gradient mechanism is correct, the jet shift will be related to the max/mean trend difference. The southward jet shift could be related to the increase in double jet regimes found by Rousi et al (2022), as a mean southward jet will likely project onto a 'split' or double jet configuration. Intriguingly, the observed jet trend lies outside the range of model trends and the multi-model mean shows no overall trend (figure 5d).…”

Increasing risk from landfalling tropical cyclone-heatwave compound events to coastal and inland China

“…The response of the mode to warming and its implications on future TC-heatwave compound events remains to be explored. Additionally, there is emerging evidence on that as the climate warms, Rossby waves at mid-high latitudes would become increasingly wavy (Sussman et al 2020), in favor of more frequent, hotter and longer-lasting heatwaves across broad swathes of mid-latitudes including eastern China (Mann et al 2018, Rousi et al 2022. This changing dynamic could also promote the sequencing of TCs and heatwaves, even if TCs change little.…”