Intensified atmospheric aridity in East Africa under future climate change

Vapor pressure deficit (VPD) plays a critical role in regulating water and CO₂ exchanges between land and atmosphere, particularly in climate-vulnerable regions. This study investigated historical and future patterns of VPD using state-of-the-art datasets, including ERA5, CRU TS, MERRA2, and five general circulation models (GCMs) from the Inter-Sectoral Impact Model Inter-comparison Project (ISIMIP) over East Africa. Trends were analyzed annually and seasonally for the historical period (1981–2022), near future (2023–2061), and distant future (2063–2100), along with contributions from temperature, relative humidity, and air pressure to future VPD changes. Results showed that VPD increased annually by 0.04 hPa year⁻¹ from 1981 to 2022, with the most significant rise in dry regions. Future projections indicate continued VPD increases at both annual and seasonal scales, intensifying in accordance with the magnitude of CO₂ emission scenarios (SSP126, SSP370, and SSP585, respectively). Under SSP585 and SSP370 the annual VPD is projected to increase by 0.06 and 0.05 hPa year⁻¹, respectively from 2023 to 2100. The summer season exhibits the highest rate of increase, followed by spring, across all scenarios. This substantial change in VPD during the summer season will significantly impact the agricultural sector of the region. Furthermore, the contribution of temperature increase (148 %–162 %) to the projected increase in VPD outweighs that of relative humidity (−99 % to −117 %) and air pressure (51 %–55 %) changes across the scenarios. Thus, the increasing VPD is expected to have a significant impact on the ecosystems of the East Africa by exacerbating drought conditions.