Organic aerosol and global climate modelling: a review

Abstract

Abstract. The present paper reviews existing knowledge with regard to Organic Aerosol (OA) of importance for global climate modelling and defines critical gaps needed to reduce the involved uncertainties. All pieces required for the representation of OA in a global climate model are sketched out with special attention to Secondary Organic Aerosol (SOA): The emission estimates of primary carbonaceous particles and SOA precursor gases are summarized. The up-to-date understanding of the chemical formation and transformation of condensable organic material is outlined. Knowledge on the hygroscopicity of OA and measurements of optical properties of the organic aerosol constituents are summarized. The mechanisms of interactions of OA with clouds and dry and wet removal processes parameterisations in global models are outlined. This information is synthesized to provide a continuous analysis of the flow from the emitted material to the atmosphere up to the point of the climate impact of the produced organic aerosol. The sources of uncertainties at each step of this process are highlighted as areas that require further studies.

Gas–particle partitioning of atmospheric aerosols: interplay of physical state, non-ideal mixing and morphology

“…20,21 All these observations are consistent with the presence of low-volatility and higher molecular weight organic compounds that are known to form in organic aerosols; 22 such compounds tend to have high glass transition temperatures and may lead to semi-solid or glassy phases. 17 Traditionally, gas-particle equilibrium partitioning of organic substances is assumed to be established instantaneously 4,23,24 (''instantaneously'' being interpreted as rapid when compared to the timescales of the other major atmospheric processes associated with SOA formation); this assumption is in question if particles or certain phases therein are semi-solid or glassy. 21,25,26 Atmospheric large-scale models serve as the basis for predicting the concentration and composition of ambient aerosols associated with air quality and climate.…”

“…21,25,26 Atmospheric large-scale models serve as the basis for predicting the concentration and composition of ambient aerosols associated with air quality and climate. 23 Current large-scale models represent aerosol physicochemical processes by highly simplified schemes, inherently neglecting the actual nature and compositional complexity of aerosol particles. Many models substantially under-predict observed aerosol total mass.…”

“…The mixture of ammonium sulfate and organics from the ozone oxidation of a-pinene serves as a canonical system, for which aerosol composition is reasonably well established. 4,23 Using this system, we illustrate key aspects of the effects of physical state, non-ideal mixing, and morphology on gas-particle partitioning. 2.…”

Role of the reaction of stabilized Criegee intermediates with peroxy radicals in particle formation and growth in air

“…Organic aerosol makes up a substantial fraction (20-90%) of submicron particles in the atmosphere, [1][2][3] of which up to 90% is secondary organic aerosol (SOA). 2,4 SOA is produced by atmospheric oxidation of volatile organic compounds (VOCs) that can lead to the formation of products having sufficiently low vapor pressures to either nucleate to form new particles or condense onto pre-existing particles.…”

Molecular dynamics simulations of the water adsorption around malonic acid aerosol models

“…[5] These aerosols play a central role not only in the health effects of air pollution but also on climate evolution. [6,7] Indeed, they have both a direct effect on climate by scattering light, which results in negative radiative forcing (i.e., cooling), and an indirect effect by acting as cloud condensation (CCN) or ice nuclei (IN), thus changing cloud properties. [6] Aerosols may impact on the number, concentration, and size of cloud droplets and induce changes in the light scattering by clouds, in their lifetimes, and precipitation rates.…”