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Modulation of Mid‐Holocene African Rainfall by Dust Aerosol Direct and Indirect Effects
Author(s) -
Thompson Alexander J.,
Skinner Christopher B.,
Poulsen Christopher J.,
Zhu Jiang
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl081225
Subject(s) - aerosol , environmental science , atmospheric sciences , radiative forcing , precipitation , anomaly (physics) , mineral dust , climatology , vegetation (pathology) , holocene , climate model , forcing (mathematics) , climate change , geology , meteorology , oceanography , geography , physics , medicine , condensed matter physics , pathology
Climate model simulations of the mid‐Holocene (MH) consistently underestimate northern African rainfall for reasons not fully understood. While most models incorporate orbital forcing and vegetation feedbacks, they neglect dust reductions associated with greater vegetation cover. Here we simulate the MH climate response to reduced Saharan dust using CESM CAM5‐chem, which resolves direct and indirect dust aerosol effects. Direct aerosol effects increase Saharan and Sahel convective rainfall by ~16% and 8%. In contrast, indirect aerosol effects decrease stratiform rainfall, damping the dust‐induced total rainfall increase by ~13% in the Sahara and ~59% in the Sahel. Sensitivity experiments indicate the dust‐induced precipitation anomaly in the Sahara and Sahel (0.27 and 0.18 mm/day) is smaller than the anomaly from MH vegetation cover (1.19 and 1.08 mm/day). Although sensitive to dust radiative properties, sea surface temperatures, and indirect aerosol effect parameterization, our results suggest that dust reductions had competing effects on MH African rainfall.