AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Ground Based Observations of New Particle Formation during the PEGASOS - SUPERSITO Joint Campaign in the Po Valley
STEFANO DECESARI, M. Cristina Facchini, Claudio Carbone, Stefania Gilardoni, Angela Marinoni, Paolo Cristofanelli, Gian Paolo Gobbi, Amar Hamed, Ari Laaksonen, Hanna Manninen, Tuukka Petäjä, Johannes Groess, Laurent Poulain, Michela Maione, Vanes Poluzzi, CNR-ISAC
Abstract Number: 99 Working Group: Remote and Regional Atmospheric Aerosols
Abstract During the PEGASOS-SUPERSITO field campaign held in the Po Valley (Italy) in June-July 2012, new particle formation (NPF) was observed on 87.5% of the days at the rural station of San Pietro Capofiume (SPC), which is consistent with the observed climatology for this site. On average, the formation and growth rates estimated by the DMPS were also high: 6 cm3 s-1 and 7 nm/h, respectively. The fast particle growth from 2 to 3 nm made the DMPS and ion spectrometers (NAIS) record the start of nucleation nearly simultaneously. This happened in the first two hours following sunrise, before the mixing layer development, in an atmospheric layer characterized by reduced ozone concentrations, high NOx and relatively high anthropogenic VOC levels (200 ppt of toluene). Nucleation rate (J3) peaked in windy, dry days and showed a negative correlation with condensation sink (CS). Accurate calculations of ambient (humid) CS were performed based on aerosol chemical composition and hygroscopicity measurements. The comparison of nucleation events in SPC with those recorded at other Po Valley stations distant 40 – 100 km indicates that NPF occurred over vast sectors of the plain, although the events did not start always simultaneously, probably because of differences in CS levels or in the local boundary layer meteorology. New particle formation was also observed at a nearby mountain station (Monte Cimone, 2165 m a.s.l), where a much lower frequency (35 %) occurred in comparison with the low-altitude stations. This was unexpected because, even if anthropogenic VOC concentrations are much lower in Monte Cimone than in San Pietro Capofiume, the emissions of biogenic VOCs are higher over the Apennines and temperature and CS lower. The experiment provides a nice opportunity to investigate NPF in contrasting environments in respect to anthropization level and emission patterns.