Resonant Waves Play an Important Role in the Increasing Heat Waves in Northern Hemisphere Mid-Latitudes Under Global Warming

Extreme events have become more frequent in the Northern Hemisphere mid-latitudes in recent decades, hugely impacting the ecosystem and society. The quasi-resonance amplification (QRA) of planetary waves is considered one of the dynamic mechanisms leading to extreme weather. However, the specific impact of resonant waves caused by QRA on surface heat extremes is still an open issue. Here we show that the QRA of planetary waves leading to heat extremes is closely related to double jets, accompanied by the enhancement of atmospheric blocking and the weakening of planetary wave escaping into the stratosphere. Our results illustrate the important role of mid-latitude planetary waves with zonal wavenumber m = 6-8 caused by QRA in the increasingly frequent heat waves in recent years, as it can increase the coverage area and occurrence frequency of heat extremes in mid-latitudes and show a significant impact on preferred regions, especially in Eurasia.