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Hygroscopic growth and cloud forming potential of Arctic aerosol based on observed chemical and physical characteristics (a 1 year study 2007–2008)
Author(s) -
Silvergren S.,
Wideqvist U.,
Ström J.,
Sjogren S.,
Svenningsson B.
Publication year - 2014
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2014jd021657
Subject(s) - aerosol , cloud condensation nuclei , supersaturation , relative humidity , sulfate , sea salt aerosol , particle size distribution , particle (ecology) , chemistry , scanning mobility particle sizer , sea salt , particle size , atmospheric sciences , environmental science , environmental chemistry , meteorology , oceanography , geography , organic chemistry , geology
Aerosol particle samples were collected, and the particle size distribution was measured during 1 year at the Zeppelin station (474 m asl) on Svalbard. The chemical constituents, hygroscopicity, and cloud forming properties of the aerosol were analyzed. The aerosol contained mostly sulfate and nitrate during the summer, whereas from September to February the main components were sodium and chloride. The highest concentration (20%) of water‐soluble organic matter was sampled in December. The hygroscopic growth factors for the water‐soluble fraction were 1.56–2.01 at 90% relative humidity, peaking in October, when the measured supersaturations needed for cloud drop formation were also the lowest. Sea‐salt components showed a positive correlation with the cloud forming capability, whereas the organic content had no correlation. The hygroscopicity factors, or κ values, were determined in three ways for each month: (1) κ H‐TDMA from measurements of the hygroscopic growth of particles produced from atomization of the filter extracts, (2) κ CCNC from measurements of the critical supersaturation as a function of size for these particles, and (3) κ chem was modeled based on the organic and inorganic composition of the filter samples. Using the measured particle size distributions and the critical activation diameters from the Cloud Condensation Nuclei Counter (CCNC) measurements, it was found that the number of CCN varied more with supersaturation during the summer months. The best agreement between all three κ values was in December and January. Comparisons with earlier studies do not suggest any trend in the Arctic aerosol seasonal variability over the last decade.