摘要：This work recompiles studies that have been done with respect to hygroscopic growth in
the regime of high relative humidities and with respect to activation for different kinds of
particle at LACIS (Leipzig Aerosol Cloud Interaction Simulator) during the last
few years. The particles examined consisted of a mixture of succinic acid and
ammonium sulfate, seawater samples, soot coated with an organic and/or an inorganic
substance, and two different atmospheric HULIS (HUmic LIke Substance) samples. An
influence of changing non-ideal behavior and of slightly soluble substances on the
hygroscopic growth was found in varying degrees in the subsaturation regime.
The measured hygroscopic growth was extrapolated towards supersaturation,
using a simple form of the Köhler equation, and assuming a constant number of
molecules/ions in solution for high
relative humidities (≥95% or ≥98%, depending on the particles). When the surface tension of water was used, the modeled
critical supersaturations reproduced the measured ones for the seawater samples and for
the coated soot particles. To reach agreement between measured and modeled critical
supersaturations for the HULIS particles, a concentration-dependent surface tension
had to be used, with values of the surface tension that were lower than that of
water, but larger than those that had been reported for bulk measurements in the
past.
