Coupled land-atmosphere processes exacerbate recent compound drought and heatwaves over Africa

Global warming has increased the likelihood of compound drought and heatwave (CDHW) events, posing profound socioeconomic risks globally, with Africa being particularly vulnerable due to its limited adaptive capacity and high exposure to climate extremes. Using ERA5 and NCEP-2 reanalysis datasets for 1980-2024, we analyze recent trends in CDHW occurrences across Africa and diagnose the underlying land-atmosphere drivers. Our results reveal a pronounced hotspot in equatorial Africa, where CDHW frequency has increased by 0.9 events season^-1 decade^-1, duration by 1.2 days season^-1 decade^-1, and magnitude by 0.4 °C season^-1 decade^-1. Change-point analysis reveals two distinct periods: P1 (1980-2003), with a modest increase of 0.4 events season^-1 decade^-1, and P2 (2005-2024), marked by rapid intensification of 1.1 events season^-1 decade^-1. The recent intensification is driven primarily by stronger land-atmosphere coupling, with higher potential evaporation due to elevated maximum temperatures and declining soil moisture from reduced precipitation. These drier and warmer surface conditions enhance the concurrent occurrence of drought and heatwaves, amplifying CDHW frequency. Furthermore, we found that the recent warming is attributable largely to increased net downward radiation, modulated by enhanced downward clear-sky longwave radiation, while decreased precipitation is linked to weakening of the vertical dynamic term associated with reduced diabatic heating. In addition, our results show an increased contribution of large-scale climate modes such as the Atlantic meridional oscillation, Indian Ocean Dipole and Pacific Decadal Oscillation to recent CDHW intensification. These findings highlight the critical role of coupled land-atmosphere processes in modulating compound extreme events in Africa.