Calibration of LACIS as a CCN detector and its use in measuring activation and hygroscopic growth of atmospheric aerosol particles

[摘要] A calibration for LACIS (Leipzig Aerosol Cloud InteractionSimulator) for its use as a CCN (cloud condensation nuclei)detector has been developed. For this purpose, sodium chloride andammonium sulfate particles of known sizes were generated and theirgrown sizes were detected at the LACIS outlet. From these signals,the effective critical super-saturation was derived as a functionof the LACIS wall temperature. With this, LACIS is calibrated forits use as a CCN detector. The applicability of LACIS formeasurements of the droplet activation, and also of thehygroscopic growth of atmospheric aerosol particles was tested.The activation of the urban aerosol particles used in themeasurements was found to occur at a critical super-saturation of0.46% for particles with a dry diameter of 75 nm, and at 0.42%for 85 nm, respectively. Hygroscopic growth was measured foratmospheric aerosol particles with dry diameters of 150, 300 and350 nm at relative humidities of 98 and 99%, and it was foundthat the larger dry particles contained a larger soluble volumefraction of about 0.85, compared to about 0.6 for the 150 nmparticles.

[学科分类] 大气科学