Teleconnections link to summer heat extremes in the south-central U.S.: Insights from CMIP5 and CMIP6 simulations

This study examines the relationship between teleconnections, which represent quasiperiodic modes of largescale atmospheric and oceanic variability, and extreme heatwaves in the south-central (SC) U.S. region, aiming to understand multiyear variability in the heat extremes. Observational data and model simulations reveal that soil water has a stronger influence on surface air temperature in the SC region than individual teleconnections, though not as strong as their combined influence. Particularly, the Pacific North America (PNA), North Atlantic Oscillation (NAO), and Pacific Decadal Oscillation (PDO) teleconnections have a substantial impact on surface air temperature in the region through anomalous anticyclonic circulation, during their negative phases. The wave-activity flux analysis shows that the wave train associated with the PNA teleconnection originates from the extratropical North Pacific Ocean, likely influenced by sea surface temperature (SST) forcing. Similarly, the wave packet linked to the PDO pattern originates from the central Pacific Ocean in the middle latitudes. In contrast, the wave train related to the NAO pattern exhibits little connection to SST forcing, originating from Greenland and propagating across Europe, Russia, the North Pacific, and North America. While climate models generally capture the PNA and PDO wave trains, they struggle to accurately simulate the NAO wave train across the North Pacific Ocean towards North America. This indicates the current generation of climate models face challenges in representing the complex dynamics underlying the NAO wave train.