Oral

IAMAS

JMP03 - High-impact Weather and Climate Extremes

Exploring Multi-year Predictability of Terrestrial Heatwaves in Global Hotspot Regions

Terrestrial heatwaves (THWs) pose significant risks to ecosystems, human health, and socio-economies. However, predicting THW statistics (e.g., frequency) over practical multi-year time scales remains challenging due to the complex interactions between internal climate variability, large-scale climate drivers, and local processes. Using a large ensemble of uninitialized simulations, assimilations, and hindcasts from the Community Earth System Model version 2, we assess the predictability and prediction skill of THWs in global hotspot regions with lead times of up to 5 years initiated every January from 1981 to 2020. Our results show distinct differences in THWs predictability between El Ni?o and Southern Oscillation (ENSO)-dominant and ENSO-independent regions. ENSO strongly influences THWs in South America, Alaska?Northwest Canada, and Central Africa, particularly in improving short-term predictability. In contrast, the Atlantic Multidecadal Oscillation has a stronger influence along the subtropical Gulf Coast, suggesting that THWs in this region are more externally driven. This effect is even more pronounced over Greenland, where heatwaves are highly predictable due to strong external forcing, and only moderately modulated by Atlantic and Arctic oscillations. The Arabian Peninsula and Southeast Asia also show high short-term predictability, but their long-term forecasting skill is lower. These findings emphasize the pivotal role of both external forcing and internal climate variability in global heatwave predictability. Improving our understanding of the underlying mechanisms can enhance long-term heatwave forecasts, guide climate adaptation strategies, and inform proactive measures to mitigate risks in vulnerable regions.