Intercomparison of cloud condensation nuclei and hygroscopicfraction measurements: Coated soot particles investigatedduring the LACIS Experiment in November (LExNo)

摘要

Four cloud condensation nuclei (CCN) instruments were used to sample size-selectedparticles prepared at the Leipzig Aerosol Cloud Interaction Simulator facility. Includedwere two Wyoming static diffusion CCN instruments, the continuous flow instrument builtby Droplet Measurement Technologies, and the continuous flow Leipzig instrument.The aerosols were composed of ammonium sulfate, levoglucosan, levoglucosan and soot,and ammonium hydrogen sulfate and soot. Comparisons are made among criticalsupersaturation values from the CCN instruments and derived from measurements madewith a humidified tandem differential mobility system. The comparison is quiteencouraging: with few exceptions the reported critical supersaturations agree within knownexperimental uncertainty limits. Also reported are CCN- and hygroscopicity-basedestimates of the soot particles' solute fraction. Relative differences between these are as largeas 40%, but an error analysis demonstrates that agreement within experimental uncertainty isachieved. We also analyze data from the Droplet Measurement Technologies and the twoWyoming static diffusion instruments for evidence of size distribution broadening andinvestigate levoglucosan particle growth kinetics in the Wyoming CCN instrument.