Hygroscopicity and cloud droplet activation of mineral dust aerosol

Abstract

Hygroscopicity and cloud condensation nucleus (CCN) activity were measured for three mineral dust samples: one from the Canary Islands, representing North African dust transported across the Atlantic; one from outside Cairo, representing North African dust transported to the eastern Mediterranean; and Arizona Test Dust, representing dust in the southwestern United States. To reaerosolize bulk samples, dust samples were either suspended in high purity water and particles generated by atomization, or samples were resuspended in dry air using a fluidized bed. Only the Canary Island sample generated from aqueous suspension showed appreciable hygroscopic growth at subsaturated conditions; all other samples exhibited diameter growth factors of less than 1.1 for relative humidities ≤90%. Despite their low hygroscopicities at subsaturated conditions, all samples activated as cloud droplets at supersaturations lower than required for insoluble particles. We suggest that the CCN activity of these mineral dusts are well‐represented using the hygroscopicity parameter 0.01 ≤ κ ≤ 0.08.

Aerosol indirect effect on the grid-scale clouds in the two-way coupled WRF–CMAQ: model description, development, evaluation and regional analysis

“…Note that the single parameter κ value in Petters and Kreidenweis (2007) is practically equivalent to the hygroscopicity B value here (Liu and Wang, 2010). Koehler et al (2009) estimated that the hygroscopicity B values for (NH 4 ) 2 SO 4 and NaCl ranged from 0.33 to 0.72 and 0.91 to 1.33, respectively. The hygroscopicity values for anthropogenic SOA range from 0.06 to 0.14 (Prenni et al, 2007), and for biogenic SOA, they range from 0.06 to 0.23 (Prenni et al, 2007;King et al, 2010).…”

“…Jimenez et al (2009) showed that the hygroscopicity of SOA changes from 0 to 0.2 because of its aging in the atmosphere. On the basis of the measurements for three mineral dust samples (dust from the Canary Islands, outside of Cairo, and Arizona Test Dust), Koehler et al (2009) reported that the hygroscopicity values for the minimally processed dust particles vary from 0.01 to 0.08, with a suggested median value of 0.03. In this study, the hygroscopicity B values for ASO4, ANO3, ANH4 and AORGC are assumed to be 0.5.…”

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

“…Neglecting sea salt particles with a high hygroscopicity growth (κ NaCl = 1.12 at 90 %, Petters and Kreidenweis, 2007) may cause an underestimation of particle hygroscopicity. Inversely, neglecting mineral dust with less hygroscopicity (mineral dust κ = 0.01-0.08, Koehler et al, 2009) may cause an overestimation of particle hygroscopicity. The statistical analyses on the basis of a long-term observation showed that the dust storm events typically take place in the spring in Beijing .…”

Cloud condensation nucleus activity comparison of dry- and wet-generated mineral dust aerosol: the significance of soluble material

“…Among the individual types of aerosol particles previously investigated, mineral dust is of particular importance because of its high abundance in the atmosphere (Ganor and Mamane, 1982;Gano and Foner, 1996;Chou et al, 2008;Coz et al, 2009) and its demonstrated ability to nucleate cloud droplets (Ma et al, 2004;Furutani et al, 2008;Herich et al, 2009;Koehler et al, 2009;Sullivan et al, 2009Sullivan et al, , 2010Lee et al, 2010;Kumar et al, 2011a, b). It is also important for primary production in oceans and rainforests because air masses laden with crustal material often transport limiting nutrients like iron and phosphorus (Duce et al, 1991;Jickells et al, 2005;Pett-Ridge, 2009).…”

“…Therefore, laboratory studies of aerosol particles are necessary for determining how their various physical and chemical properties affect their ability to act as CCN in the atmosphere. Many previous studies investigated the nucleation potential both of individual types of aerosol particles Pandis, 2002, 2003;Petters and Kreidenweis, 2007a;Koehler et al, 2009;Sullivan et al, 2009Sullivan et al, , 2010aKumar et al, 2011a, b), and of simple mixtures Pandis, 2002, 2003;Bilde and Svenningsson, 2004;Abbatt et al, 2005). Observations indicate that the size of an aerosol particle is the primary factor in determining its efficiency as a CCN (Dusek et al, 2006); but its composition, though a secondary factor, should also be considered because it can affect how the particle will change due to the chemical interactions with its surroundings (Petters and Kreidenweis, 2007a;Rudich et al, 2007).…”