Aerosol climatology at the high‐alpine site Jungfraujoch, Switzerland

Abstract

Abstract. Continuous aerosol measurements have been performed at the high-alpine site Jungfraujoch (3450 m above sea level) since 1988 by means of an epiphaniometer. The instrument, which determines the Fuchs surface area of the aerosol particles, was operated with a time resolution of 30 min. High correlation coefficients (r > 0.8) were found between the epiphaniometer signal and other aerosol parameters, which could be attributed to a rather constant size distribution of the Jungfraujoch aerosol in the accumulation range (0.1 < d < 1 /.tm). Well-defined diurnal variations with a peak in the late afternoon were observed on many days during summer, which was not the case during winter. Comparison with black carbon and radon daughter measurements revealed that these diurnal variations are due to vertical transport processes. A statistical analysis showed that the fraction of days with a well-defined diurnal pattern increased with decreasing stability of the atmosphere; however, late afternoon peaks also occurred during days when the potential temperature profile indicated a stable atmosphere. First simulations with ALPTHERM, a new convection model which takes topography into account, were able to explain the observed aerosol patterns. This indicates that slope winds over a certain catchment area are responsible for the transport to this highelevation site. The distinct seasonal variation with summer values, which are about a factor of 10 higher than winter values, could therefore be attributed to seasonally varying transport processes, due to the seasonal variation of radiation. The data show that even sites at very high elevation cannot be assumed to be in the free troposphere all the time.

Saharan dust events at the Jungfraujoch: detection by wavelength dependence of the single scattering albedo and first climatology analysis

“…The JFJ is prevalently situated in the free troposphere, but is influenced by convection of planetary boundary layer air during the warmer months (Baltensperger et al, 1997;Lugauer et al, 1998). Consequently all the measured aerosol parameters show a clear annual cycle with maximum values in July and August and minimum values in the NovemberJanuary period.…”

Long‐term trend analysis of aerosol variables at the high‐alpine site Jungfraujoch

“…The JFJ site (3580 m asl) is prevalently situated in the lower FT, but is often influenced by thermal convection of PBL air during the warmer months [Baltensperger et al, 1997;Lugauer et al, 1998]. All measured aerosol variables show a clear annual cycle (Figure 1) with maximum values between June and August and minimum values around the winter solstice [Nyeki et al, 1998;M.…”

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

“…From 06:00 LT, the concentration of both polarities increase until reaching a maximum of 825 # cm −3 and 875 # cm −3 respectively for negative and positive ions at 13:00 LT. Then the concentrations decrease rapidly from 15:00 to 18:00 LT to reach the level of night time. Baltensperger et al (1997) showed that diurnal variations of aerosol parameters such as surface area are due to thermally driven vertical exchange. In their article, Lugauer et al (2000) have demonstrated that during winter the Jungfraujoch is most of time decoupled from the PBL and, during the summer, air from the PBL is transported to the site by thermally driven convection.…”