Oral

IAMAS

JMP03 - High-impact Weather and Climate Extremes

Different roles of land-atmosphere coupling in compound drought-heatwave events

Droughts and heatwaves are interlinked through different land-atmosphere coupling pathways. Identifying these coupling behaviors and understanding their roles are essential. However, how each coupling behavior spatiotemporally varies in compound drought-heatwave events and influences predictability remains unclear. We suggest a quantitative framework to represent the spatiotemporal variability of land-atmosphere coupling behaviors during compound drought-heatwave events. Six extreme cases were targeted, and the temporal coupling patterns between latent heat flux (LHF) and the co-evolution of drought and heatwave were classified on a grid-by-grid basis. In the 2022 (2023) East Asia (Central America) case, LHF was strongly coupled with heatwaves (droughts) over 64.77% (45.42%) of the region. In other cases, more spatiotemporally inhomogeneous coupling behaviors were observed. Differences in coupling behavior within a case were significantly correlated with the partitioning of surface fluxes, governed by critical soil moisture. These distinct coupling behaviors were also reproduced in medium-range forecasts for drought-heatwave events, leading to higher forecast skill for the 2023 case compared to the 2022 case. Consequently, the dynamics shaping compound drought-heatwaves can vary depending on land-atmosphere coupling behaviors, which also affect their predictability.