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. In the summer of 2022, the Northern Hemisphere mid‐latitudes were affected by widespread, intense heat waves that developed more quickly than climatologists had expected, hugely impacting the ecosystem and society. Understanding the extent and causes of extreme heat can help local authorities better prepare for the extreme weather that may occur in the near future. Planetary wave, also known as Rossby wave, manifested as a large‐scale oscillation of the midlatitude atmospheric flow, usually forms a snaking shape over the Earth, leading to persistent surface weather systems and often resulting in extreme events. Existing studies have shown that, planetary wave is one of the important dynamic mechanism behind heat waves. At certain frequencies and wavelengths (short‐wavelength), this circumglobal waves disturbance can be significantly amplified through resonance, resulting in heat extremes. Our work indicates that resonant wave plays an increasingly important role in heat events over Northern Hemisphere mid‐latitudes. The long‐term changes in resonant wave trend deserve continuous attention, because an improved understanding of planetary waves behind extreme events can help assess future wave activity's potential social and economic effects. The influence of resonant waves on heat extremes in the Northern Hemisphere mid‐latitude summer is increasing, especially in EurasiThe occurrence of resonant waves is closely related to double jets, accompanied by the enhancement of atmospheric blockingThe occurrence of resonant waves is accompanied by the weakening of the upward‐propagating planetary waves The influence of resonant waves on heat extremes in the Northern Hemisphere mid‐latitude summer is increasing, especially in Eurasi The occurrence of resonant waves is closely related to double jets, accompanied by the enhancement of atmospheric blocking The occurrence of resonant waves is accompanied by the weakening of the upward‐propagating planetary waves