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

Abstract

Atmospheric Chemistry and PhysicsNew particle formation and ultrafine charged aerosol climatology at a high altitude site in the Alps (Jungfraujoch, 3580 m a.s.l., Switzerland) Abstract. We investigate the formation and growth of charged aerosols clusters at Jungfraujoch, in the Swiss Alps (3580 m a.s.l.), the highest altitude site of the European EU-CAARI project intensive campaign. Charged particles and clusters (0.5 − 1.8 nm) were measured from April 2008 to April 2009 and allowed the detection of nucleation events in this very specific environment (presence of free tropospheric air and clouds). We found that the naturally charged aerosol concentrations, which are dominated by the cluster size class, shows a strong diurnal pattern likely linked to valley breezes transporting surface layer ion precursors, presumably radon. Cosmic rays were found not to be the major ion source at the measurement site. However, at night, when air masses are more representative of free tropospheric conditions, we found that the cluster concentrations are still high. The charged aerosol size distribution and concentration are strongly influenced by the presence of clouds at the station. Clouds should be taken into account when deriving high altitude nucleation statistics. New particle formation occurs on average 17.5% of the measurement period and shows a weak seasonality with a minimum of frequency during winter, but this seasonality is enhanced when the data set is screened forCorrespondence to: J. Boulon (j.boulon@opgc.univ-bpclermont.fr) periods when the atmospheric station is out of clouds. The role of ions in the nucleation process was investigated and we found that the ion-mediated nucleation explains 22.3% of the particle formation. The NPF events frequency is correlated with UV radiation but not with calculated H 2 SO 4 concentrations, suggesting that other compounds such as organic vapors are involved in the nucleation and subsequently growth process. In fact, NPF events frequency also surprisingly increases with the condensational sink (CS), suggesting that at Jungfraujoch, the presence of condensing vapours probably coupled with high CS are driving the occurrence of NPF events. A strong link to the air mass path was also pointed out and events were observed to be frequently occurring in Eastern European air masses, which present the highest condensational sink. In these air masses, pre-existing cluster concentrations are more than three time larger than in other air masses during event days, and no new clusters formation is observed, contrarily to what is happening in other air mass types.

Long-term analysis of clear-sky new particle formation events and nonevents in Hyytiälä

“…In particular, Baranizadeh et al (2014) studied the effect of cloudiness on NPF events observed at SMEAR II in Hyytiälä. They concluded, in agreement with some other studies, that clouds tend to attenuate or interrupt NPF events Boulon et al, 2010;Baranizadeh et al, 2014;Nieminen et al, 2015). In this study, we eliminated one variable that limits NPF (cloudiness) in order to provide a better insight into the other quantities related to atmospheric NPF.…”

General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) – integrating aerosol research from nano to global scales

“…Hõrrak et al, 2008;Hirsikko et al, 2011 and the references therein). The aircraft measurements made during the LONGREX experiment as well as the ground based-measurements at high elevation sites revealed that this cluster ion mode can be seen in the free troposphere Boulon et al, 2010). The first quantitative estimates on the concentrations of neutral sub-3 nm particles were obtained for both the continental boundary layer Lehtipalo et al, 2009) and the free troposphere .…”

“…The field measurements brought plenty of new insight into the role of ions in atmospheric nucleation Kerminen et al, 2007;Gagné et al, 2008Gagné et al, , 2010Manninen et al, 2010;Mirme et al, 2010;Boulon et al, 2010). The contribution of charged particles to the total formation rate of 2-nm particles was usually found to be well below 10 %, but it showed substantial temporal variability both during a nucleation event and between the different event days.…”

Growth rates of nucleation mode particles in Hyytiälä during 2003−2009: variation with particle size, season, data analysis method and ambient conditions

“…However, Boulon et al (2010) and Manninen et al (2010) obtained yearly averages of 5.1 nm h −1 and 3.7 nm h −1 , respectively, for sub-3 nm particles from the same one year data set measured at high altitude site Jungfraujoch, Switzerland. These two studies used a maximum concentration method but with different modifications: Manninen et al (2010) used the method described in this paper whereas Boulon et al (2010) considered the time lag between the maximum concentrations of particles in two size classes. Additionally, Manninen et al (2010) determined the GR for particle size range of 1.5-3 nm whereas Boulon et al (2010) considered size range of 1.3-3 nm.…”

“…These two studies used a maximum concentration method but with different modifications: Manninen et al (2010) used the method described in this paper whereas Boulon et al (2010) considered the time lag between the maximum concentrations of particles in two size classes. Additionally, Manninen et al (2010) determined the GR for particle size range of 1.5-3 nm whereas Boulon et al (2010) considered size range of 1.3-3 nm. The variation between the GR values obtained in these two studies is likely due to these differences.…”