Ion-mediated nucleation as an important global source of tropospheric aerosols

Abstract

Abstract. Aerosol nucleation events have been observed at a variety of locations worldwide, and may have significant climatic and health implications. While ions have long been suggested as favorable nucleation embryos, their significance as a global source of particles has remained uncertain. Here, an ion-mediated nucleation (IMN) mechanism, which incorporates new thermodynamic data and physical algorithms, has been integrated into a global chemical transport model (GEOS-Chem) to study ion-mediated particle formation in the global troposphere. The simulated annual mean results have been compared to a comprehensive set of data relevant to particle nucleation around the globe. We show that predicted annual spatial patterns of particle formation agree reasonably well with land-, ship-, and aircraft-based observations. Our simulations show that, globally, IMN in the boundary layer is largely confined to two broad latitude belts: one in the northern hemisphere (∼20 • N-70 • N), and one in the southern hemisphere (∼30 • S-90 • S). In the middle latitude boundary layer over continents, the annual mean IMN rates are generally above 10 4 cm −3 day −1 , with some hot spots reaching 10 5 cm −3 day −1 . The zonally-averaged vertical distribution of IMN rates indicates that IMN is significant in the tropical upper troposphere, the entire middle latitude troposphere, and over Antarctica. Comparing the relative strengths of particle sources due to IMN and due to primary particle emissions demonstrates that IMN is significant on a global scale. Further research is needed to reduce modeling uncertainties and to understand the ultimate contribution of freshly nucleated particles to the abundance of cloud condensation nuclei.

New particle formation and ultrafine charged aerosol climatology at a high altitude site in the Alps (Jungfraujoch, 3580 m a.s.l., Switzerland)

“…It is worth mentioning that our J 2 calculation is a higher limit, since 3 nm particles concentrations detected with the SMPS technique were measured to be lower than the 3 nm particles detected from the NAIS. According to those results, we can assume that ion-mediated nucleation is a significant source of new particle in the troposphere as previously shown by Yu et al (2008) for boundary layer conditions.…”

“…The attractive potential between ions and ions and between ions and the dipole moment (induced or not) of the condensable vapor reduces the thermodynamic barrier for nucleation and hence, enhances the condensational growth (Lovejoy et al, 2004;Nadykto and Yu, 2004). Conflicting views about the relative importance of IMN subsist between modelling studies (see for example Laakso et al, 2002;Harrisson and Carslaw, 2003;Yu et al, 2008) which assess that IMN should be an important source of atmospheric particles and field measurements (see for example Eisele et al, 2006;Manninen et al, 2009) who show that the contribution of IMN to new particle formation in planetary boundary layer (PBL) is less than 10% in average. In any case, the charged fraction of clusters and particles is a good indicator of the presence of neutral clusters and particles.…”

Impacts of new particle formation on aerosol cloud condensation nuclei (CCN) activity in Shanghai: case study

“…Kerminen et al (2012) present a synthesis of our current (end of 2012) knowledge on CCN production associated with atmospheric nucleation, and conclude that CCN production associated with atmospheric nucleation is both a frequent and widespread phenomenon in numerous types of continental boundary layers, and probably also for a large fraction of the free troposphere. The latest model results show that the NPF events contribute much more to the global aerosol number burden than primary emissions (Merikanto et al, 2009;Yu et al, 2008). Under numerous atmospheric conditions aerosol has a positive feedback to CCN number concentration (N CCN ) (Ramanathan et al, 2001;Laaksonen et al, 2005), and N CCN usually exhibits a significant increase after NPF Lihavainen et al, 2003;Kuwata et al, 2008;Yue et al, 2011).…”

EUCAARI ion spectrometer measurements at 12 European sites – analysis of new particle formation events

“…For example, while ions are known to influence both nucleation and growth (e.g. Nadykto and Yu, 2003;Winkler et al, 2008), their overall effect on atmospheric aerosol formation has remained controversial (Enghoff and Svensmar, 2008;Kazil et al, 2008;Yu et al, 2008). The ambiguities in atmospheric nucleation mechanisms make it difficult to quantify the factors governing the frequency and strength of new particle formation in different environments.…”