Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Periodic Report Summary 1 - NACRE (Impact of Nitrate on Aerosol Composition and Radiative Effects)

During the first period of the project the researcher assessed the chemical composition and global aerosol load of the major inorganic aerosol components, focusing on aerosol nitrate. The mineral dust aerosol components (i.e., Ca2+, Mg2+, K+, Na+) and their emissions were included in EMAC chemistry climate model (CCM). Gas/aerosol partitioning was simulated using the ISORROPIA-II thermodynamic equilibrium model. Emissions of mineral dust were calculated online by taking into account the soil size distribution and chemical composition. The model simulates high fine aerosol nitrate concentrations over urban and industrialized areas while coarse aerosol nitrate is highest close to deserts. The presence of metallic ions substantially affected the nitrate partitioning into the aerosol resulting in an increase of its tropospheric burden by 44%. Sensitivity tests show that nitrate is most sensitive to the chemical composition of mineral dust, followed by the dust aerosol size distribution, the dust emission load, and the aerosol state assumption.
In addition, The researcher has implemented into EMAC a new cloud droplet formation parameterization, the “unified dust activation framework”, to account for both the hygroscopicity from the solute and the hydrophilicity from adsorption. The activation of freshly emitted dust particles through water adsorption resulted in an increase of cloud droplet number concentration (CDNC) over the deserts. On the contrary, over polluted regions, dust particles strongly compete for water reducing the supersaturation and therefore the CDNC from the smaller in size anthropogenic aerosols. Considering the interactions of inorganic anions with mineral cations resulted in an increase of CDNC over biomass burning and urban areas. However, CDNC over the deserts decreased since the consideration of crustal cations significantly increased its solubility and atmospheric removal.
Overall, the research undertaken so far enhanced the state of the art in nitrate aerosol modeling by improving its representation in a CCM. The developed modeling framework takes into account the nitrate thermodynamic interactions with crustal species and accurately predicts the aerosol size distribution by considering the kinetic limitations of the gas/aerosol partitioning in the coarse mode. Furthermore, by using an explicit geographical representation of the emitted soil particle size distribution and chemical composition the researcher created a novel representation of the emissions of mineral dust and the individual crustal species which is beyond the state of the art used currently in CCMs. In addition, a novel approach was used to account for the CCN activity of mineral dust coated with soluble aerosols (like nitrates) by considering both the water adsorption and absorption effects. The developed modeling framework will serve as an ideal tool for providing unprecedented understanding of the increased role of nitrate on the future global climate and air quality.
The excellent profile of the researcher and his expertise in aerosol modeling and cloud microphysics makes him a natural favorite for recruitment as a senior researcher at the host institute. Provided the successful completion of the NACRE project, the researcher will have the opportunity to pursue a position as a leader of the Atmospheric Aerosol Modeling group under the Atmospheric Chemistry Department.

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Life Sciences
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