Atmospheric aerosols, notably those from anthropogenic sources, adversely affect human health and play an important role in changing the Earth’s climate. The scientific interest in these effects of anthropogenic aerosols initially focused on sulfate and to a lesser extent on other low-volatile inorganic species, and subsequently on carbonaceous compounds. Inorganic particulate nitrate constituents also contribute significantly to the total aerosol mass, especially in urban areas and industrialized regions. However, only a limited number of global models have been used to predict particulate nitrate concentrations and their regional distributions, while even fewer studies have addressed the direct and indirect effects of aerosol nitrate. The scope of the proposed work is to improve the representation of nitrate aerosol formation and size distribution in a climate chemistry model to accurately predict their global concentration fields and their effects on global air quality and climate. Improvements will include i) nitrate interactions with mineral dust and sea salt, using the thermodynamic equilibrium models EQSAM and ISORROPIA-II, ii) increase on the accuracy of the predicted nitrate aerosol size distribution by using the hybrid approach for aerosol dynamics, iii) explicit calculation of nitrate aerosol formation using the comprehensive aerosol chemistry model MECCA-AERO, iii) the use of a “unified dust activation framework” to account for the CCN activity of mineral dust coated with soluble aerosols (like nitrates) and iv) the use of the adjoint sensitivity technique to investigate the uncertainty of the CDNC predictions to aerosol number and hygroscopicity. The new modeling framework will be used to accurately predict i) the nitrate formation and growth, its interactions with mineral dust and sea salt, as well as the radiative forcing of nitrate, its effects on mineral dust and sea salt CCN activity and its impact on future aerosol radiative effects and clouds.
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