The effect of physical and chemical aerosol properties on warm cloud droplet activation

Abstract

Abstract. The effects of atmospheric aerosol on climate forcing may be very substantial but are quantified poorly at present; in particular, the effects of aerosols on cloud radiative properties, or the "indirect effects" are credited with the greatest range of uncertainty amongst the known causes of radiative forcing. This manuscript explores the effects that the composition and properties of atmospheric aerosol can have on the activation of droplets in warm clouds, so potentially influencing the magnitude of the indirect effect. The effects of size, composition, mixing state and various derived properties are assessed and a range of these properties provided by atmospheric measurements in a variety of locations is briefly reviewed. The suitability of a range of process-level descriptions to capture these aerosol effects is investigated by assessment of their sensitivities to uncertainties in aerosol properties and by their performance in closure studies. The treatment of these effects within global models is reviewed and suggestions for future investigations are made.

Relating hygroscopicity and optical properties to chemical composition and structure of secondary organic aerosol particles generated from the ozonolysis of α-pinene

“…-O : C, the oxygen-to-carbon ratio, for both the bulk and the surface composition of the SOA; it is well known that particle composition, in particular that of the surface, strongly influences the water uptake ability of the particle and its CCN potential (McFiggans et al, 2006;Dusek et al, 2006;Hatch et al, 2008;Moussa et al, 2009;McIntire et al, 2010;Semeniuk et al, 2007; C. Denjean Lamb Wong et al, 2011;Mei et al, 2013;Rickards et al, 2013). To encompass the difficulty of representing the full molecular composition, the O : C of SOA has been included in global climate models to provide a description of the aerosol aging (Tost and Pringle, 2012).…”

Metrics to quantify the importance of mixing state for CCN activity

“…In this study we focus on CCN activity, and indeed, many CCN closure studies show that the quality of the closure depends crucially on the assumptions about aerosol mixing state (McFiggans et al, 2006;Wang et al, 2010;Bhattu and Tripathi, 2015;Ervens et al, 2010). Based on these observational findings, it is commonly assumed that the internal mixture assumption works well for regions that are not directly influenced by fresh emission sources.…”

Particle hygroscopicity and its link to chemical composition in the urban atmosphere of Beijing, China, during summertime

“…Particle hygroscopicity is one of the important parameters controlling direct and indirect climate effects of atmospheric particles (McFiggans et al, 2006;Haywood and Boucher, 2000). Due to water uptake, hydrophilic particles grow significantly in size at high relative humidity (RH), which influences the particle light scattering and extinction coefficients, thereby impairing visibility (Sloane and Wolff, 1985).…”