Aerosol transport to the high Alpine sites Jungfraujoch (3454 m asl) and Colle Gnifetti (4452 m asl)

Abstract

Atmospheric transport processes, relevant to high Alpine sites, were deduced from 2 sets of aerosol records: a 9-year record from the Jungfraujoch (3454 m) on the northern side of the Swiss Alps and a 2.5-year record from Colle Gnifetti (4452 m) on the southern side. A classification scheme for synoptic weather types was applied to separate the aerosol data into groups corresponding to different atmospheric transport conditions. For both sites, vertical aerosol transport by thermally driven convection, acting between late spring and late summer, was found to be the dominant transport process. In summer, the thermally-driven aerosol transport to both sites caused an increase of the seasonally averaged aerosol concentration between 0800 and 1800 local standard time by a factor of two. Under anticyclonic conditions, when subsidence on a synoptic scale is present, the thermally driven aerosol transport is most pronounced. Therefore, the aerosol determining thermal transport takes place within a synoptic scale vertical motion of opposite direction. Under cyclonic conditions, when lifting on a synoptic scale is present, the thermally driven aerosol transport is nearly absent. In winter, thermally driven convection does not contribute to the aerosol concentrations at both sites. Nevertheless, also in winter statistically significant differences in aerosol concentration were found between cyclonic and anticyclonic weather conditions, which can be attributed to the vertical transport acting on the synoptic scale. These differences in aerosol concentration were small compared to the corresponding differences in summer. Within the weather types, which are dominated by horizontal advection in the Alpine region, the aerosol concentrations are more difficult to interpret with respect to the effective transport process.

PathfinderTURB: an automatic boundary layer algorithm. Development, validation and application to study the impact on in situ measurements at the Jungfraujoch

“…In autumn (September-November), the LCBLH shows a less pronounced daily cycle than in spring and summer, this is probably due to the fact that the vertical transport of aerosol-rich air is reduced by the stabilization within the lower troposphere during this period (Lugauer et al, 1998).…”

“…Different sources and transport regimes towards the JFJ have been studied by many authors (e.g. Lugauer et al, 1998;Zellweger et al, 2003;Balzani Lööv et al, 2008;Henne et al, 2010;Collaud Coen et al, 2011Herrmann et al, 2015), showing that the JFJ resides most of the time in the undisturbed ("clean") lower FT. Nevertheless and especially in summer, the JFJ is influenced by thermally induced uplifted CBL air, and it is also influenced by additional lifting processes such as frontal passages and Föhn flows (Zellweger et al, 2003;Ketterer et al, 2014).…”

“…Ketterer et al, 2014). Lugauer et al (1998) provide a 9-year climatological analysis of the vertical transport of aerosols to the JFJ and the corresponding synoptic conditions. The thermally induced transport is nearly absent in winter or under cyclonic conditions and it is strongest in summer under anticyclonic periods.…”

A review of atmospheric chemistry observations at mountain sites

“…Transport of anthropogenic emissions in Europe to the high-altitude Alpine stations have been observed at SNB (Gros et al 2001;Jabbar et al 2012;Kaiser 2009;Kaiser et al 2007;Karl et al 2001a, b;Seibert et al 1998), ZUG/ZSF (Jabbar et al 2012;Kaiser et al 2007), CMN (Bonasoni et al 1997;Bonason 2009, 2013), KVV (Kaiser et al 2007), ARO Pochanart et al 2001), and JFJ Forrer et al 2000;Kaiser et al 2007;Kuebler et al 2001;Lanz et al 2009;Legreid et al 2008;Lugauer et al 1998;Pandey Deolal et al 2013;Seibert et al 1998;Tuzson et al 2011). The Po Basin is a densely populated and highly industrialized region located immediately adjacent to the Alps that is known to have a relatively high level of air pollution.…”

“…Thermally induced processes were observed mainly in spring and summer, and processes at the regional and synoptic scales were observed during the entire year. Continuous measurements of the total and backward scattering coefficients, absorption coefficient, condensation nuclei concentrations, epiphaniometer signals, total suspended particulate matter (TSP) mass concentrations, and major PM 1 and TSP compounds at JFJ have shown distinct seasonal cycles with a summer maximum and a winter minimum (Baltensperger et al 1997;Cozic et al 2008;Henning et al 2003;Lugauer et al 1998;Nyeki et al 1998a, b). The seasonal cycles of SO 4 2− , NO 3 − , and NH 4 + of aerosols at SNB also showed a summer maximum and a winter minimum .…”