Linking High-Amplitude Quasi-Stationary Waves With Concurrent Humid-Heat Extremes in a Warming World

Abstract

Humid-heat extremes pose serious risks to human health. When occurring simultaneously across different regions, they can lead to widespread exposure and substantial economic loss. Previous studies have linked concurrent humid-heat extremes in the Northern Hemisphere midlatitudes to high-amplitude quasi-stationary waves (QSWs). However, how these waves respond to climate warming remains unclear, limiting our ability to assess future risks quantitatively. Using a single model initial-condition large ensemble, we find that the climatological-mean amplitude of wavenumbers 3 and 7 QSWs increases in late summer as the climate warms, along with more frequent high-amplitude Wave-3 and Wave-7 events. These changes are associated with increased regional frequencies of humid-heat extremes, particularly in regions with strong historical connections between humid-heat extremes and high-amplitude QSWs. Our findings help identify regions characterized by high-impact concurrent humid-heat extremes and improve understanding of spatially heterogeneous changes in humid-heat extremes in a warming climate.