Northward Dust-Induced Shift of Tropical Atlantic Precipitation in CMIP6 Models

Precious Ebiendele, Adeyemi A Adebiyi , John Abatzoglou, Ryan J. Kramer, Akintomide A. Akinsanola, Paul Adigun, Ian Chang

Mineral dust has substantially increased since the pre-industrial period, particularly over North Africa and the Atlantic Ocean. However, the impacts of increased dust burden over the tropical Atlantic Ocean on the position of the Intertropical Convergence Zone (ITCZ) and regional precipitation remain poorly resolved. Here, we analyze seven CMIP6 models participating in the Aerosol Chemistry Model Intercomparison Project (AerChemMIP) piClim-2xdust experiment to quantify the changes in precipitation and the ITCZ and isolate the doubling of dust concentration over the tropical Atlantic. We find a robust northward shift of the ITCZ, with corresponding increased precipitation on its northern flank and suppressed precipitation to the south, consistent across five of seven models and strongest in boreal spring and summer. This precipitation dipole is driven by a coherent radiative–dynamical mechanism whereby asymmetric dust absorption and rapid cloud adjustments warm the northern tropical Atlantic troposphere and cool the southern side, thereby strengthening the interhemispheric energy gradient. This heating enhances vertical moisture transport northward – controlled primarily by dynamic rather than thermodynamic adjustments – producing a convective dipole that tracks the precipitation response. Two models representing dust as cloud condensation nuclei and ice-nucleating particles deviate from this response, underscoring the sensitivity of precipitation responses to aerosol-cloud microphysical representation. Overall, our findings suggest that if dust over North Africa continues to increase in the future, the associated radiative and dynamical adjustments identified here could significantly influence tropical Atlantic precipitation, with consequences for the West African monsoon.