scholarly journals Tracking isotopic signatures of CO<sub>2</sub> at the high altitude site Jungfraujoch with laser spectroscopy: analytical improvements and representative results

2013 ◽  
Vol 6 (7) ◽  
pp. 1659-1671 ◽  
Author(s):  
P. Sturm ◽  
B. Tuzson ◽  
S. Henne ◽  
L. Emmenegger
Keyword(s):  
High Altitude ◽  
Isotope Ratios ◽  
Particle Dispersion ◽  
High Temporal Resolution ◽  
Research Station ◽  
Close Link ◽  
Diurnal Variability ◽  
Air Masses ◽  
The Mean ◽  
Δ13c And Δ18o

Abstract. We present the continuous data record of atmospheric CO2 isotopes measured by laser absorption spectroscopy for an almost four year period at the High Altitude Research Station Jungfraujoch (3580 m a.s.l.), Switzerland. The mean annual cycles derived from data of December 2008 to September 2012 exhibit peak-to-peak amplitudes of 11.0 μmol mol−1 for CO2, 0.60‰ for δ13C and 0.81‰ for δ18O. The high temporal resolution of the measurements also allow us to capture variations on hourly and diurnal timescales. For CO2 the mean diurnal peak-to-peak amplitude is about 1 μmol mol−1 in spring, autumn and winter and about 2 μmol mol−1 in summer. The mean diurnal variability in the isotope ratios is largest during the summer months too, with an amplitude of about 0.1‰ both in the δ13C and δ18O, and a smaller or no discernible diurnal cycle during the other seasons. The day-to-day variability, however, is much larger and depends on the origin of the air masses arriving at Jungfraujoch. Backward Lagrangian particle dispersion model simulations revealed a close link between air composition and prevailing transport regimes and could be used to explain part of the observed variability in terms of transport history and influence region. A footprint clustering showed significantly different wintertime CO2, δ13C and δ18O values depending on the origin and surface residence times of the air masses. Several major updates on the instrument and the calibration procedures were performed in order to further improve the data quality. We describe the new measurement and calibration setup in detail and demonstrate the enhanced performance of the analyzer. A measurement precision of about 0.02‰ for both isotope ratios has been obtained for an averaging time of 10 min, while the accuracy was estimated to be 0.1‰, including the uncertainty of the calibration gases.

scholarly journals Tracking isotopic signatures of CO<sub>2</sub> at Jungfraujoch with laser spectroscopy: analytical improvements and exemplary results

2013 ◽  
Vol 6 (1) ◽  
pp. 423-459 ◽  
Author(s):  
P. Sturm ◽  
B. Tuzson ◽  
S. Henne ◽  
L. Emmenegger
Keyword(s):  
Dispersion Model ◽  
Isotope Ratios ◽  
Particle Dispersion ◽  
High Temporal Resolution ◽  
Research Station ◽  
Close Link ◽  
Diurnal Variability ◽  
Air Masses ◽  
The Mean ◽  
Δ13c And Δ18o

Abstract. We present the continuous data record of atmospheric CO2 isotopes measured by laser absorption spectroscopy for an almost four year period at the High Altitude Research Station Jungfraujoch (3580 m a.s.l.), Switzerland. The mean annual cycles derived from data of December 2008 to September 2012 exhibit peak-to-peak amplitudes of 11.0 μmol mol−1 for CO2, 0.60‰ for δ13C and 0.81‰ for δ18O. The high temporal resolution of the measurements also allow to capture variations on hourly and diurnal time scales. For CO2 the mean diurnal peak-to-peak amplitude is about 1 μmol mol−1 in spring, autumn and winter and about 2 μmol mol−1 in summer. The mean diurnal variability in the isotope ratios is largest during the summer months too, with an amplitude of about 0.1‰ both in the δ13C and δ18O, and a smaller or no discernible diurnal cycle during the other seasons. The day-to-day variability, however, is much larger and depends on the origin of the air masses arriving at Jungfraujoch. Backward Lagrangian particle dispersion model simulations revealed a close link between air composition and prevailing transport regimes and could be used to explain part of the observed variability in terms of transport history and influence region. A footprint clustering showed significantly different wintertime CO2, δ13C and δ18O values depending on the origin and surface residence times of the air masses. Based on the experiences gained from our measurements, several major updates on the instrument and the calibration procedures were performed in order to further improve the data quality. We describe the new measurement and calibration setup in detail and demonstrate the enhanced performance of the analyser. A precision of about 0.02‰ for both isotope ratios has been obtained for an averaging time of 10 min.

Simulations of atmospheric CO2 and δ13C-CO2 compared to real-time observations at the high altitude station Jungfraujoch

2020 ◽  
Author(s):  
Simone M. Pieber ◽  
Béla Tuzson ◽  
Stephan Henne ◽  
Ute Karstens ◽  
Dominik Brunner ◽  
...  
Keyword(s):  
Stable Isotope ◽  
High Altitude ◽  
Time Resolution ◽  
Experimental Studies ◽  
Isotope Ratios ◽  
Particle Dispersion ◽  
Stable Isotope Ratios ◽  
Research Station ◽  
Data Set ◽  
Model Simulations

&lt;p&gt;Evaluating atmospheric transport simulations against observations helps refining bottom-up estimates of greenhouse gas fluxes and identifying gaps in our understanding of regional and category-specific contributions to atmospheric mole fractions. This insight is critical in the efforts to mitigate anthropogenic environmental impact. Beside total mole fractions, stable isotope ratios provide further constraints on source-sink processes [1-3].&lt;/p&gt;&lt;p&gt;Here, we present two receptor-oriented model simulations for carbon dioxide (CO&lt;sub&gt;2&lt;/sub&gt;) mole fraction and &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C-CO&lt;sub&gt;2&lt;/sub&gt; stable isotope ratios for a nine year period (2009-2017) at the High Altitude Research Station Jungfraujoch (Switzerland, 3580 m asl). The model simulations of CO&lt;sub&gt;2&lt;/sub&gt; were performed on a 3-hourly time-resolution with two backward Lagrangian particle dispersion models driven by two different numerical weather forecast fields: FLEXPART-COSMO and STILT-ECMWF. Anthropogenic CO&lt;sub&gt;2&lt;/sub&gt; fluxes were based on the EDGAR v4.3 emissions inventory aggregated into 14 source categories representing fossil and biogenic fuel uses as well as emissions from cement production. Biospheric CO&lt;sub&gt;2&lt;/sub&gt; fluxes representing the photosynthetic uptake and respiration of 8 plant functional types were based on the Vegetation Photosynthesis and Respiration Model (VPRM). The simulated CO&lt;sub&gt;2&lt;/sub&gt; emissions per source and sink category were weighted with category-specific &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C-CO&lt;sub&gt;2&lt;/sub&gt; signatures from published experimental studies. Background CO&lt;sub&gt;2&lt;/sub&gt; values at the boundaries of both model domains were taken from global model simulations and the corresponding &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C-CO&lt;sub&gt;2&lt;/sub&gt; values were constructed as suggested in Ref. [3]. We compare the simulations to a unique data set of continuous in-situ observations of CO&lt;sub&gt;2&lt;/sub&gt; mole fractions and &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C-CO&lt;sub&gt;2&lt;/sub&gt; stable isotope ratios by quantum cascade laser absorption spectroscopy as described in previous work [1, 4-5], available for the whole nine year period at the site.&lt;/p&gt;&lt;p&gt;The simulated atmospheric CO&lt;sub&gt;2&lt;/sub&gt; and &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C-CO&lt;sub&gt;2&lt;/sub&gt; time-series are in good agreement with the observations and capture the observed variability at the models' 3-hourly time-resolution. This allows for an in-depth evaluation of the contribution of different CO&lt;sub&gt;2&lt;/sub&gt; emission sources and for an allocation of source regions when Jungfraujoch is influenced by air masses from the planetary boundary layer. In brief, the receptor-oriented model simulations suggest that anthropogenic CO&lt;sub&gt;2&lt;/sub&gt; contributions are primarily of fossil origin (90%). Anthropogenic emissions contribute between 60% in February, and 20% in July/August, to the CO&lt;sub&gt;2&lt;/sub&gt; enhancements observed at Jungfraujoch. The remaining fraction is due to biosphere respiration, which thus largely dominates emissions during the summer season. However, intense photosynthetic CO&lt;sub&gt;2&lt;/sub&gt; uptake during June, July and August roughly outweighs CO&lt;sub&gt;2&lt;/sub&gt; contributions from anthropogenic activities and biosphere respiration at JFJ.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;REFERENCES&lt;/p&gt;&lt;p&gt;[1] Tuzson et al., 2011. ACP, 11, 1685&lt;/p&gt;&lt;p&gt;[2] R&amp;#246;ckmann et al., 2016. ACP, 16, 10469&lt;/p&gt;&lt;p&gt;[3] Vardag et al., 2016. Biogeosciences, 13, 4237&lt;/p&gt;&lt;p&gt;[4] Tuzson et al., 2008. Appl. Phys. B, 92, 451&lt;/p&gt;&lt;p&gt;[5] Sturm et al., 2013. AMT 6, 1659&lt;/p&gt;

scholarly journals Atmospheric mercury observations from Antarctica: seasonal variation and source and sink region calculations

2012 ◽  
Vol 12 (7) ◽  
pp. 3241-3251 ◽  
Author(s):  
K. A. Pfaffhuber ◽  
T. Berg ◽  
D. Hirdman ◽  
A. Stohl
Keyword(s):  
Southern Hemisphere ◽  
Dispersion Model ◽  
Particle Dispersion ◽  
Atmospheric Mercury ◽  
The Arctic ◽  
Research Station ◽  
The Mean ◽  
The Antarctic ◽  
Source And Sink

Abstract. Long term atmospheric mercury measurements in the Southern Hemisphere are scarce and in Antarctica completely absent. Recent studies have shown that the Antarctic continent plays an important role in the global mercury cycle. Therefore, long term measurements of gaseous elemental mercury (GEM) were initiated at the Norwegian Antarctic Research Station, Troll (TRS) in order to improve our understanding of atmospheric transport, transformation and removal processes of GEM. GEM measurements started in February 2007 and are still ongoing, and this paper presents results from the first four years. The mean annual GEM concentration of 0.93 ± 0.19 ng m−3 is in good agreement with other recent southern-hemispheric measurements. Measurements of GEM were combined with the output of the Lagrangian particle dispersion model FLEXPART, for a statistical analysis of GEM source and sink regions. It was found that the ocean is a source of GEM to TRS year round, especially in summer and fall. On time scales of up to 20 days, there is little direct transport of GEM to TRS from Southern Hemisphere continents, but sources there are important for determining the overall GEM load in the Southern Hemisphere and for the mean GEM concentration at TRS. Further, the sea ice and marginal ice zones are GEM sinks in spring as also seen in the Arctic, but the Antarctic oceanic sink seems weaker. Contrary to the Arctic, a strong summer time GEM sink was found, when air originates from the Antarctic plateau, which shows that the summertime removal mechanism of GEM is completely different and is caused by other chemical processes than the springtime atmospheric mercury depletion events. The results were corroborated by an analysis of ozone source and sink regions.

scholarly journals Continuous isotopic composition measurements of tropospheric CO<sub>2</sub> at Jungfraujoch (3580 m a.s.l.), Switzerland: real-time observation of regional pollution events

2010 ◽  
Vol 10 (10) ◽  
pp. 24563-24593 ◽  
Author(s):  
B. Tuzson ◽  
S. Henne ◽  
D. Brunner ◽  
M. Steinbacher ◽  
J. Mohn ◽  
...  
Keyword(s):  
Particle Dispersion ◽  
Integration Time ◽  
High Temporal Resolution ◽  
Research Station ◽  
Mixing Ratios ◽  
Keeling Plot ◽  
Time Observation ◽  
First Time ◽  
Pollution Events

Abstract. A quantum cascade laser based absorption spectrometer (QCLAS) is applied for the first time to perform in situ, continuous and high precision isotope ratio measurements of CO2 in the free troposphere. Time series of the three main CO2 isotopologue mixing ratios (12C16O2, 12C16O2 and 12C18O16O) have simultaneously been measured at one second time resolution over two years (from August 2008 to present) at the High Altitude Research Station Jungfraujoch (3580 m a.s.l., Switzerland). This work focuses on periods in February 2009 only, when sudden and pronounced enhancements in the tropospheric CO2 were observed. These short-term changes were closely correlated with variations in CO mixing ratios measured at the same site, indicating combustion related emissions as potential source. The analytical precision of 0.046‰ (at 50 s integration time) for both δ13C and δ18O and the high temporal resolution allowed the application of the Keeling plot method for source signature identification. The spatial origin of these CO2 emission sources was then determined by backward Lagrangian particle dispersion simulations.

Source region cluster analysis in the high-altitude measuring site of Chacaltaya with WRF and FLEXPART

2020 ◽  
Author(s):  
Diego Aliaga ◽  
Victoria Sinclair ◽  
Zha Qiaozhi ◽  
Marcos Andrade ◽  
Claudia Mohr ◽  
...  
Keyword(s):  
Cluster Analysis ◽  
High Altitude ◽  
Long Range ◽  
Measurement Data ◽  
Particle Dispersion ◽  
Particle Nucleation ◽  
Free Troposphere ◽  
Data Set ◽  
Air Mass ◽  
Air Masses

&lt;p&gt;Measuring aerosol at high altitude sites is useful as it enables sampling of the free troposphere over long time frames. However, in order to draw conclusions from station measurement data, we need to determine which air mass sources are present at any given sampling time. This task is challenging at mountain sites, due to complex topography which in turn drives complex meteorology. Between December 2017 and May 2018, the Southern hemisphere high ALTitude Experiment on particle Nucleation And growth (SALTENA) campaign was conducted at Chacaltaya in Bolivia at 5240 m a.s.l. The data set obtained in this campaign contains records of nearly all relevant aerosol characteristics and aerosol precursors. To identify the source regions of the observed air masses we performed high resolution (down to 1 km) simulations with the Weather Research and Forecasting Model (WRF). The WRF model output is then used to as input to the Lagrangian particle dispersion model (FLEXPART). FLEXPART simulations are initialised every hour and 20 thousand particles are released per hour and track backwards in time for 96 hours. The FLEXPART footprint output is regridded onto a log-polar cylindrical grid where we perform a &amp;#8216;K-means&amp;#8217; cluster analysis on the 3D cells defined by the grid. The cells are clustered based on the time series of their source receptor relationship (i.e. emission sensitivities), producing regions (clusters) resolved not only in the horizontal but also the vertical domain. Our results show that regions located close to the station (&lt;100km) have a low but persistent influence with diurnal variations and close contact to the surface. Mid-range regions (100-800km) have the highest influence with a higher percentage of air masses from the free troposphere. Long-range regions (&gt;800km) have a higher influence than the short-range regions but lower than the middle-range regions. Most of the air masses from these long-range regions come from the free troposphere. With this method we have successfully resolved the various air mass influences at the measurement site. The high meteorological resolution and the stochastic nature of FLEXPART are seminal for capturing the transport pathways.&lt;/p&gt;

scholarly journals Predicting abundance and variability of ice nucleating particles in precipitation at the high-altitude observatory Jungfraujoch

2016 ◽  
Vol 16 (13) ◽  
pp. 8341-8351 ◽  
Author(s):  
Emiliano Stopelli ◽  
Franz Conen ◽  
Cindy E. Morris ◽  
Erik Herrmann ◽  
Stephan Henne ◽  
...  
Keyword(s):  
Wind Speed ◽  
High Altitude ◽  
Source Region ◽  
Environmental Parameters ◽  
Residual Fraction ◽  
First Year ◽  
Research Station ◽  
Linear Regression Models ◽  
Air Masses ◽  
Precipitation Events

Abstract. Nucleation of ice affects the properties of clouds and the formation of precipitation. Quantitative data on how ice nucleating particles (INPs) determine the distribution, occurrence and intensity of precipitation are still scarce. INPs active at −8 °C (INPs−8) were observed for 2 years in precipitation samples at the High-Altitude Research Station Jungfraujoch (Switzerland) at 3580 m a.s.l. Several environmental parameters were scanned for their capability to predict the observed abundance and variability of INPs−8. Those singularly presenting the best correlations with observed number of INPs−8 (residual fraction of water vapour, wind speed, air temperature, number of particles with diameter larger than 0.5 µm, season, and source region of particles) were implemented as potential predictor variables in statistical multiple linear regression models. These models were calibrated with 84 precipitation samples collected during the first year of observations; their predictive power was successively validated on the set of 15 precipitation samples collected during the second year. The model performing best in calibration and validation explains more than 75 % of the whole variability of INPs−8 in precipitation and indicates that a high abundance of INPs−8 is to be expected whenever high wind speed coincides with air masses having experienced little or no precipitation prior to sampling. Such conditions occur during frontal passages, often accompanied by precipitation. Therefore, the circumstances when INPs−8 could be sufficiently abundant to initiate the ice phase in clouds may frequently coincide with meteorological conditions favourable to the onset of precipitation events.

scholarly journals European source and sink areas of CO<sub>2</sub> retrieved from Lagrangian transport model interpretation of combined O<sub>2</sub> and CO<sub>2</sub> measurements at the high alpine research station Jungfraujoch

2011 ◽  
Vol 11 (15) ◽  
pp. 8017-8036 ◽  
Author(s):  
C. Uglietti ◽  
M. Leuenberger ◽  
D. Brunner
Keyword(s):  
Transport Model ◽  
Dispersion Model ◽  
Seasonal Pattern ◽  
Particle Dispersion ◽  
Research Station ◽  
Co2 Uptake ◽  
Air Masses ◽  
Background Values ◽  
Co2 Concentrations ◽  
Source And Sink

Abstract. The University of Bern monitors carbon dioxide (CO2) and oxygen (O2) at the High Altitude Research Station Jungfraujoch since the year 2000 by means of flasks sampling and since 2005 using a continuous in situ measurement system. This study investigates the transport of CO2 and O2 towards Jungfraujoch using backward Lagrangian Particle Dispersion Model (LPDM) simulations and utilizes CO2 and O2 signatures to classify air masses. By investigating the simulated transport patterns associated with distinct CO2 concentrations it is possible to decipher different source and sink areas over Europe. The highest CO2 concentrations, for example, were observed in winter during pollution episodes when air was transported from Northeastern Europe towards the Alps, or during south Foehn events with rapid uplift of polluted air from Northern Italy, as demonstrated in two case studies. To study the importance of air-sea exchange for variations in O2 concentrations at Jungfraujoch the correlation between CO2 and APO (Atmospheric Potential Oxygen) deviations from a seasonally varying background was analyzed. Anomalously high APO concentrations were clearly associated with air masses originating from the Atlantic Ocean, whereas low APO concentrations were found in air masses advected either from the east from the Eurasian continent in summer, or from the Eastern Mediterranean in winter. Those air masses with low APO in summer were also strongly depleted in CO2 suggesting a combination of CO2 uptake by vegetation and O2 uptake by dry summer soils. Other subsets of points in the APO-CO2 scatter plot investigated with respect to air mass origin included CO2 and APO background values and points with regular APO but anomalous CO2 concentrations. Background values were associated with free tropospheric air masses with little contact with the boundary layer during the last few days, while high or low CO2 concentrations reflect the various levels of influence of anthropogenic emissions and the biosphere. The pronounced cycles of CO2 and O2 exchanges with the biosphere and the ocean cause clusters of points and lead to a seasonal pattern.

scholarly journals Predicting abundance and variability of ice nucleating particles in precipitation at the high-altitude observatory Jungfraujoch

2016 ◽  
Author(s):  
Emiliano Stopelli ◽  
Franz Conen ◽  
Cindy E. Morris ◽  
Erik Herrmann ◽  
Stephan Henne ◽  
...  
Keyword(s):  
Wind Speed ◽  
High Altitude ◽  
Source Region ◽  
Environmental Parameters ◽  
Residual Fraction ◽  
First Year ◽  
Research Station ◽  
Linear Regression Models ◽  
Air Masses ◽  
Precipitation Events

Abstract. Nucleation of ice affects the properties of clouds and the formation of precipitation. Quantitative data on how ice nucleating particles (INPs) determine the distribution, occurrence and intensity of precipitation are still scarce. INPs active at −8 °C (INPs−8) were observed for two years in precipitation samples at the High-Altitude Research Station Jungfraujoch (Switzerland) at 3580 m a.s.l. Several environmental parameters were scanned for their capability to predict the observed abundance and variability of INPs−8. Those singularly presenting the best correlations with observed number of INPs−8 (residual fraction of water vapour, wind speed, air temperature, number of particles with diameter larger than 0.5 μm, season and source region of particles) were implemented as potential predictor variables in statistical multiple linear regression models. These models were calibrated with 84 precipitation samples collected during the first year of observations; their predictive power was successively validated on the set of 15 precipitation samples collected during the second year. The model performing best in calibration and validation explains more than 75 % of the whole variability of INPs−8 in precipitation and indicates that a high abundance of INPs−8 is to be expected whenever high wind speed coincides with air masses having experienced little or no precipitation prior to sampling. Such conditions occur during frontal passages, often accompanied by precipitation. Therefore, the circumstances when INPs−8 could be sufficiently abundant to initiate the ice phase in clouds may frequently coincide with meteorological conditions favourable to the onset of precipitation events.

scholarly journals The diurnal and seasonal variability of ice nucleating particles at the High Altitude Station Jungfraujoch (3580 m a.s.l.), Switzerland

2021 ◽  
Author(s):  
Cyril Brunner ◽  
Benjamin Tobias Brem ◽  
Martine Collaud Coen ◽  
Franz Conen ◽  
Martin Steinbacher ◽  
...  
Keyword(s):  
High Altitude ◽  
Diurnal Cycle ◽  
Radiative Properties ◽  
Saharan Dust ◽  
High Time Resolution ◽  
Research Station ◽  
Data Set ◽  
Diurnal Variability ◽  
Special Events ◽  
A Minor

Abstract. Cloud radiative properties, cloud lifetime, and precipitation initiation are strongly influenced by the cloud phase. Between ~ 235 and 273 K, ice nucleating particles (INPs) are responsible for the initial phase transition from the liquid to the ice phase in cloud hydrometeors. This study analyzes immersion-mode INP concentrations measured at 243 K at the High Altitude Research Station Jungfraujoch (3580 m a.s.l.) between February 2020 and January 2021, thereby presenting the longest continuous, high-resolution (20 min) data set of online INP measurements to date. The high time resolution and continuity allow to study the seasonal and the diurnal variability of INPs. After exclusion of special events, like Saharan dust events (SDEs), we found a seasonal cycle of INPs, highest in April (median in spring 3.1 INP std L−1), followed by summer (median: 1.6 INP std L−1) and lowest in fall and winter (median: 0.5 INP std L−1 and 0.7 INP std L−1, respectively). Pollen or subpollen particles were deemed unlikely to be responsible for elevated INP concentrations in spring and summer, as periods with high pollen loads from nearby measurement stations do not coincide with the periods of high INP concentrations. Furthermore, for days when the site was purely in the free troposphere (FT), no diurnal cycle in INP concentrations was observed, while days with boundary layer intrusions (BLI) showed a diurnal cycle. The seasonal and diurnal variability of INPs during periods excluding SDEs is with a factor of 7 and 3.3, respectively, significantly lower than the overall variability observed in INP concentration including SDEs of more than three orders of magnitude, when peak values result from SDEs. The median INP concentration over the analyzed 12 months was 1.2 INP std L−1 for FT periods excluding SDEs, and 1.4 INP std L−1 for both FT and BLI, and incl. SDEs, reflecting that despite SDEs showing strong but comparatively brief INP signals, they have a minor impact on the observed annual median INP concentration.

scholarly journals Observations of fluorescent aerosol–cloud interactions in the free troposphere at the High-Altitude Research Station Jungfraujoch

2016 ◽  
Vol 16 (4) ◽  
pp. 2273-2284 ◽  
Author(s):  
I. Crawford ◽  
G. Lloyd ◽  
E. Herrmann ◽  
C. R. Hoyle ◽  
K. N. Bower ◽  
...  
Keyword(s):  
High Altitude ◽  
Pseudomonas Syringae ◽  
Wide Band ◽  
Cloud Microphysics ◽  
Research Station ◽  
Air Masses ◽  
Hierarchical Agglomerative Cluster ◽  
Aerosol Fraction ◽  
Aerosol Cloud Interactions ◽  
A Minor

Abstract. The fluorescent nature of aerosol at a high-altitude Alpine site was studied using a wide-band integrated bioaerosol (WIBS-4) single particle multi-channel ultraviolet – light-induced fluorescence (UV-LIF) spectrometer. This was supported by comprehensive cloud microphysics and meteorological measurements with the aims of cataloguing concentrations of bio-fluorescent aerosols at this high-altitude site and also investigating possible influences of UV–fluorescent particle types on cloud–aerosol processes. Analysis of background free tropospheric air masses, using a total aerosol inlet, showed there to be a minor increase in the fluorescent aerosol fraction during in-cloud cases compared to out-of-cloud cases. The size dependence of the fluorescent aerosol fraction showed the larger aerosol to be more likely to be fluorescent with 80 % of 10 μm particles being fluorescent. Whilst the fluorescent particles were in the minority (NFl∕NAll  =  0.27 &amp;pm; 0.19), a new hierarchical agglomerative cluster analysis approach, Crawford et al. (2015) revealed the majority of the fluorescent aerosols were likely to be representative of fluorescent mineral dust. A minor episodic contribution from a cluster likely to be representative of primary biological aerosol particles (PBAP) was also observed with a wintertime baseline concentration of 0.1 &amp;pm; 0.4 L−1. Given the low concentration of this cluster and the typically low ice-active fraction of studied PBAP (e.g. pseudomonas syringae), we suggest that the contribution to the observed ice crystal concentration at this location is not significant during the wintertime.

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