Exploring the sensitivity of mineral dust aging to parameters of aerosol size distribution in the ICON-ART model

<p>Mineral dust is known to play an important role in weather and climate through its interactions with clouds, radiation, and nutrient cycles. Dust aerosols are emitted as water-insoluble particles which experience chemical aging (conversion to water-soluble mixtures) through the accumulation of soluble materials like sulfate and nitrate. This aging process affects the chemical composition and size distribution of the dust particles as well as their optical properties. Within the context of the dust aging mechanism, different approaches are applied in atmospheric models regarding the representation of the aerosol size distribution (bin or modal representation) and the number of microphysical processes included. The ICOsahedral Nonhydrostatic model with Aerosols and Reactive Trace gases (ICON-ART) and the new AERODYN aerosol dynamic module consider the nucleation and condensation of sulfuric acid gas, coagulation and aging of aerosols, size-dependent wet and dry deposition, and sedimentation. The aerosol size distribution in the model is represented by eight unimodal lognormal distributions (also called modes) with constant width. These modes describe four different size groups, two in the submicron range (typically <1 &#956;m) and two in the coarse range (>1 &#956;m), and two hygroscopic classes in a homogeneous or core-shell mixture (insoluble, soluble, and mixed). This approach is a common technique in global aerosol simulations yet implies simplifications of complex aerosol size distributions. It may cause uncertainties in simulating the aging processes of dust aerosols and inaccuracies in representing their observed size distributions. We conduct global simulations using ICON-ART to analyze the sensitivity of simulated dust to parameters representing properties of the modes, namely initial geometric median diameter and standard deviations, and threshold diameters for shifting between modes. We also aim to explore the impact of the mineral dust aging process on the range of dust direct radiative feedback.&#160; This study will show the importance of aerosol size distribution parameter combinations for representing the chemical aging of mineral dust and its climate impacts.</p>