Strength of Linkages Between Dust and Circulation Over North Africa: Results From a Coupled Modeling System With Active Dust

摘要

North African dust aerosol and climate are known to covary, but modeling studies are uncertain as to whether this covariation arises from a positive feedback loop. This study aims to improve our understanding of the strength of the relationship between dust and climate over the Sahel. A fully coupled meteorology-land-aerosol model (NU-WRF) is applied to simulate mineral dust emission and transport over North Africa from prerainy season to postrainy season (March–October) for the years 2002–2016; results are compared to estimates from the MODerate Resolution Imaging Spectrometer (MODIS), the NASA Modern-Era Reanalysis for Research and Applications v2 (MERRA-2), the MERRA-2 Global Modeling Initiative (GMI), and the Aerosol Robotic Network (AERONET). Two model configurations (Dust-On and Dust-Off) are used to investigate the regional dust-atmosphere coupling during the Sahelian rainy season by assessing the influence of land surface conditions and near-surface meteorology on dust emission, and the impacts of dust on the atmospheric circulation features linked to climate and dust variability. Results show that coupling appears to be weak on interannual timescales, as interannual variability in dust load and dust impacts on atmospheric circulations is modest. NU-WRF captures the general spatial and temporal variability in dust, though it underestimates the burden during dusty months, as compared to observational and reanalysis products. Model emission and transport processes during the dustiest months are consistent with other data products, and differences appear to be wind driven. Though the impacts of mineral dust on climatological summertime atmospheric circulation patterns are small, these impacts are consistent with weakened monsoon flow and a southward narrowing of the rain belt.