Local mechanisms for global daytime, nighttime, and compound heatwaves

Abstract Heatwaves impose serious impacts on ecosystems, human health, agriculture, and energy consumption. Previous studies have classified heatwaves into independent daytime, nighttime, compound daytime-nighttime types, examined the long-term changes in three types. However, underlying mechanisms associated with variations different heatwave types remain poorly understood. Here we present first investigation of local physical processes over global land during 1979–2020. The results show that occur frequently increasingly most regions worldwide. Nighttime exhibit stronger increases both frequency (the yearly number events) fraction ratio one type to total all types) than daytime heatwaves. Composite diagnostic analyses meteorological variables suggest are increased solar radiation under dry conditions reduced cloud cover humidity a clear sky. In contrast, nighttime typically accompanied by moist fraction, humidity, longwave at night. These synoptic for combined contribute Local divergences moisture fluxes responsible further revealed. Positive divergence anomalies seen areas heatwaves, while they mainly appear low latitudes Our research provides comprehensive understanding informing future risks impact assessments.