Hygroscopic growth and activation of HULIS particles: experimental data and a new iterative parameterization scheme for complex aerosol particles

[摘要] The hygroscopic growth and activation of two HULIS (HUmic LIkeSubstance) and one Aerosol-Water-Extract sample, prepared fromurban-type aerosol, were investigated. All samples were extractedfrom filters, redissolved in water and atomized for theinvestigations presented here. The hygroscopic growth measurementswere done using LACIS (Leipzig Aerosol Cloud InteractionSimulator) together with a HH-TDMA (High Humidity TandemDifferential Mobility Analyzer). Hygroscopic growth was determinedfor relative humidities (RHs) up to 99.75%. The criticaldiameters for activation were measured for supersaturationsbetween 0.2 and 1%.All three samples showed a similarhygroscopic growth behavior, and the two HULIS samples also weresimilar in their activation behavior, while theAerosol-Water-Extract turned out to be more CCN active than theHULIS samples. The experimental data was used to deriveparameterizations for the hygroscopic growth and activation ofHULIS particles. The concept of ρ_ion (Wex et al., 2007a)and the Szyszkowski-equation (Szyszkowski, 1908; Facchini, 1999)were used for parameterizing the Raoult and the Kelvin (surfacetension) terms of the Köhler equation, respectively. Thisconcept proved to be very successful for the HULIS samples in thesaturation range from RHs larger than 98% up to activation. Itwas also shown to work well with data on HULIS taken fromliterature. Here, different atmospheric life-times and/ordifferent sources for the different samples showed up in differentcoefficients for the parameterization. However, theparameterization did not work out well for the Aerosol-Water-Extract.

[学科分类] 大气科学