Impact of summer Tibetan Plateau snow cover on the variability of concurrent compound heatwaves in the Northern Hemisphere

Abstract

Abstract Concurrent compound heatwaves (CCHWs) occurring simultaneously in multiple regions in the Northern Hemisphere (NH) pose high-end risks to human health and global supply chains. Over the past decade, CCHWs related to human health have substantially increased in occurrence. However, the mechanisms of the CCHWs remain uncertain. This work has revealed a significant relationship between the variability of summer CCHWs in the NH and changes in quasi-stationary waves during 1979–2021, which can be attributed to the variation of summer snow cover over the western Tibetan Plateau (SC_WTP). Excessive SC_WTP causes diabatic cooling by modulating the surface energy budget and stimulating a tripolar Rossby wave source. The atmospheric response to the SC_WTP-driven disturbance manifests as a circumglobal circulation pattern, weakening the meridional temperature gradients and causing a ‘double jet stream’ in the NH. These changes modulate the phase, amplitude and proportion of quasi-stationary waves with wavenumbers 4–6, leading to an increase in CCHWs in the NH. In addition, population exposure to CCHWs reaches 4.91 billion person-day when the SC_WTP increases by one standard deviation. Our study highlights the significance of early warning and forecasting implications related to SC_WTP for CCHWs that impact human health within the context of climate change.