10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Free Tropospheric New Particle Formation Observation from High Altitude Sites around the Globe
FEDERICO BIANCHI, Claudia Mohr, Diego Aliaga, Qiaozhi Zha, Xuemeng Chen, Otso Peräkyla, Joonas Enroth, Yee Jun Tham, Liine Heikkinen, Fernando Velarde, Juha Kangasluoma, Angela Marinoni, Stefania Gilardoni, Mikael Ehn, Katrianne Lehtipalo, Paulo Artaxo, Mikko Sipilä, Marcos Andrade, Radek Krejci, Armin Hansel, Paolo Laj, Tuukka Petäjä, Neil Donahue, Douglas Worsnop, Markku Kulmala, University of Helsinki
Abstract Number: 1146 Working Group: Aerosol Chemistry
Abstract Atmospheric aerosols affect the climate directly by interacting with the incoming solar radiation and also indirectly via acting as cloud condensation nuclei (CCN) and thus impacting the cloud albedo and lifetime. A significant fraction of atmospheric CCN arises from new particle formation (NPF) of which 35% are directly formed in the free troposphere. During the last decade, several nucleation studies have been published based on field observations. However most of the studies are conducted within the planetary boundary layer (PBL), and only little information is available of NPF in the free troposphere (FT). The aim of this presentation is to elucidate the chemical fingerprints of the species involved in the NPF in the upper troposphere.
In the last years, we have used a number of state-of-the-art instruments to retrieve chemical information about the vapours involved in NPF in the FT: First at the Swiss high alpine research station Jungfraujoch (3580 m asl), then at the Himalayan Nepal Climate Observatory Pyramid (NCO-P) site on the southern slope of the Himalayas (5079 m asl), not far from Everest base camp and currently (December 2017 – May 2018) at the Chacaltaya station (5300 m asl) located in Bolivia. Previous studies have already shown that in all of these locations NPF takes place frequently, albeit without chemically specifying the involved vapours.
We deployed the most advanced instrumentation for studying new particle formation in all of the three locations. The basic set of instruments consists of an atmospheric pressure interface time-of-flight mass spectrometer (APi-TOF), a particle size magnifier (PSM) and a neutral cluster and air ion spectrometer (NAIS). The APi-TOF measured the chemical composition of either the positive or negative gas phase ions and ion clusters throughout many NPF events, and when equipped with a chemical ionization source (CI-APi-TOF) it also provided information on the chemical composition of the neutral species. Additional important instrumentation added in the latest measurement at the Chacaltaya station are a CI-APi-TOF equipped with a FIGAERO (Filter Inlet for Gases and AEROsols), and two ACSMs (Aerosol Chemical Speciation Monitor) for chemical composition measurements of larger atmospheric particles; and a proton transfer reaction time-of-flight mass spectrometers (PTR3TOF) to gain information on volatile organic compounds and their oxidation products, which are important precursors of organic aerosol.
In this presentation, we will focus on the results collected during the latest measurement campaign at Chacaltaya station, Bolivia, and compare them against the findings from previous high-altitude measurement campaigns from Jungfraujoch and Himalaya. We will present a detailed analysis of the evolution of the newly formed particles during NPF as well as the chemical composition of the small clusters measured with the (CI-)APi-TOFs. Finally, we will highlight the importance of these processes in order to understand the aerosol conditions in the pre-industrial era where information is really scarce.