New Particle Formation (NPF) strongly influences the number of atmospheric aerosol particles and the number of cloud condensation nuclei, thus influencing weather and climate. It is of great interest to increase the understanding of the processes leading to NPF in different environments, as well as the meteorological factors influencing NPF.
This master thesis investigates the seasonality of New Particle Formation (NPF) frequency as well as other factors influencing NPF at the Sonnblick Observatory (SBO), a measurement station at an altitude of 3106 m at the top of ”Hoher Sonnblick” in Austria. The study analyzes three years - January 2019 to December 2021 - of aerosol number size distribution data to identify NPF events. The NPF event frequency is calculated for each month and season and analyzed in combination with meteorological variables and trace gas concentrations.
Overall, 132 NPF events were registered during the measurement period, resulting in a total NPF frequency of 14%. The highest NPF frequency occurred in autumn (SON) with 17%, followed by winter (DJF) with 16.7% and spring (MAM) with 15.9%, so no clear difference could be found among these seasons.
In contrast, the clearly lowest NPF frequency was observed during the summer months (JJA), where values dropped to 7.2%, which is about half of the other seasons’ values.
Comparing the seasonality of NPF frequency at SBO with values found in other studies investigating NPF at high altitude stations, no regular seasonal pattern for NPF frequency could be found. The influence of various factors on NPF events at SBO was investigated in four case studies and radiation input, relative humidity, wind direction - providing the transport of precursor rich air masses to the station - were found to influence NPF.
The study concludes that NPF events occur least frequently in summer, while the frequencies in autumn, winter, and spring are comparable. Additional research including the analysis of a longer time series is necessary to confirm this observation. Furthermore, the inclusion of measurements of VOCs, basic compounds and ions as well as the investigation of the growth rate, formation rate and condensation and coagulation sinks would provide better understanding of the observed seasonality .