The chemical ageing of aeolian dust, through interactions with air pollution, affects the optical and hygroscopic properties of the mineral particles and hence their atmospheric residence time and climate forcing. Conversely, the chemical composition of the dust particles and their role as coagulation partners impact the abundance of particulate air pollution. This results in a change in the aerosol direct radiative effect that we interpret as an anthropogenic radiative forcing associated with mineral dust–pollution interactions. Using the ECHAM/MESSy atmospheric chemistry climate model (EMAC), which combines the Modular Earth Submodel System (MESSy) with the European Centre Hamburg (ECHAM) climate model, including a detailed parametrisation of ageing processes and an emission scheme accounting for the chemical composition of desert soils, we study the direct radiative forcing globally and regionally, considering solar and terrestrial radiation. Our results indicate positive and negative forcings, depending on the region. The predominantly negative forcing at the top of the atmosphere over large parts of the dust belt, from West Africa to East Asia, attains a maximum of about −2 W m−2 south of the Sahel, in contrast to a positive forcing over India. Globally averaged, these forcings partially counterbalance, resulting in a net negative forcing of −0.05 W m−2, which nevertheless represents a considerable fraction (40 %) of the total dust forcing.
|Original language||English (US)|
|Number of pages||12|
|Journal||Atmospheric Chemistry and Physics|
|State||Published - Jun 4 2019|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): URF/1/2180-01
Acknowledgements: The research reported in this publication has received funding from the King Abdullah University of Science and Technology (KAUST) CRG3 grant URF/1/2180-01 “Combined Radiative and Air Quality Effects of Anthropogenic Air Pollution and Dust over the Arabian Peninsula”.