Elucidating local pollution and site representativeness at the Jungfraujoch, Switzerland through parallel aerosol measurements at an adjacent mountain ridge

Nicolas Bukowiecki,Griša Močnik,Urs Baltensperger,Stéphane Affolter,Martine Collaud Coen,Günther Wehrle,Benjamin T Brem,Maxime Hervo,Markus Leuenberger,Martin Gysel-Beer

doi:10.1088/2515-7620/abe987

Abstract

Many long-term air pollution and climate monitoring stations face the issue of increasing anthropogenic activities in their vicinity. Furthermore, the spatial representativeness of the sites is often not entirely understood especially in mountainous terrain with complex topographic features. This study presents a 5-year comparison of parallel aerosol measurements (total particle number concentration and equivalent black carbon mass concentration) at the Jungfraujoch in the Swiss Alps (JFJ, 3580 m a.s.l.), and an adjacent mountain ridge, the Jungfrau East Ridge (JER, 3705 m a.s.l.), in 1000 m air-line distance to the main site. The parallel aerosol measurements reveal characteristic differences in the diurnal variations between the two sites under certain specific meteorological conditions. Our analysis estimates that on 20%–40% of the days local activities at the Jungfraujoch have a clear influence on the measured time series of the total aerosol number concentration and the equivalent black carbon mass concentration. This influence is mainly seen in form of strong isolated spikes rather than by an increase in the on-site background concentration. They can thus be flagged during the data quality assurance process and filtered from those measurement parameters available at high time resolution. Removing the spikes from the original time series results in daily mean values for the total aerosol number concentration and equivalent black carbon mass concentration that are 5%–10% lower compared to the original signals. During nighttime with hardly any local pollution sources that cause spikes this percentage decreases towards 0%. The signal baselines at the Jungfraujoch and Jungfrau East Ridge correlate well during more than 50% of the days.

Highlights

At the High Altitude Research Station Jungfraujoch in the Swiss Alps (Switzerland, 3580 m a.s.l., hereafter called JFJ) manifold properties of atmospheric aerosol have been continuously measured for more than 25 years
The main hypothesis is that this observed drift may be due to decreasing number concentrations at JFJ, as a result of measures that were introduced in 2017 by the railway company to protect the air quality monitoring from local pollution
Despite the progresses made in the assessment of spatial variability through instrument miniaturization and sampling/probing technology, a statistically satisfying assessment of the spatial representativeness is hard to get

Summary

Introduction

At the High Altitude Research Station Jungfraujoch in the Swiss Alps (Switzerland, 3580 m a.s.l., hereafter called JFJ) manifold properties of atmospheric aerosol have been continuously measured for more than 25 years. Injection of air parcels by thermal convection from the atmospheric boundary layer (ABL) often reaches the site in the afternoon, and for Southeast wind directions the JFJ remains in the aerosol residual layer during the night (Lugauer et al 1998). This leads to an increase in the aerosol loading of the air masses sampled at the JFJ. In a companion paper to this article, CO2 measurements made at both sites are compared and discussed (Affolter et al 2021)

Methods

Results and discussion

Conclusions

Data availability statement