Evidence for preferred propagating terrestrial heatwave pathways due to Rossby wave activity.

Terrestrial heatwaves are prolonged hot weather events often resulting in widespread socioeconomic impacts. Predicting heatwaves remains challenging, partly due to limited understanding of the events' spatial evolution and underlying mechanisms. Heatwaves were mainly examined at fixed stations, with little attention given to the fact that the center of a heatwave can move a long distance. Here, we examine the spatial propagation of terrestrial heatwaves using a complex network algorithm, and find four preferred propagation pathways of terrestrial heatwaves in the northern hemisphere. Along each preferred pathway, heatwaves evolve in two ways: propagating along the pathway or being stationary. We show that the propagating heatwave pathways are consistent with the movement of Rossby wave trains, and that both are guided by enhanced Rossby wave flux activities. The detected propagation pathways are found to provide prior knowledge for occurrences of downstream heatwaves that can be used for identifying associated precursor signals. The results shed light on the mechanisms responsible for preferred propagating heatwave pathways and provide potential predictability of terrestrial heatwaves.