Aerosol processes in the Planetary Boundary Layer: High resolution Aerosol Mass Spectrometry on a Zeppelin NT Airship

Beschreibung

Atmospheric aerosol plays an ambivalent role for mankind. On the one hand, aerosol is known to have adverse health effects and even increase mortality. On the other hand, a raised aerosol concentration in the atmosphere is the only anthropogenic contribution to the Earth’s climate known to have a net cooling effect by scattering light and acting as cloud condensation nuclei (CCN). Among other things, the magnitude of these effects depend on the chemical composition of the aerosol. In this work, an Aerosol Mass Spectrometer (AMS) was adapted for airborne aerosol chemical composition measurements on a Zeppelin NT airship. The Zeppelin platform allows for measurements with high spatial resolution throughout the entire planetary boundary layer (PBL). The new instrument was successfully operated aboard the Zeppelin NT on nine out of ten flight days of a seven week campaign in two countries in the context of the European project PEGASOS. The mass concentrations of the measured aerosol chemical species are presented for these days. The campaign observations revealed a higher relative concentration of nitrate aerosol in the Netherlands compared to the Po Valley in northern Italy. For sulfate aerosol, the situation was opposite. Furthermore, the organic aerosol was more aged in the Po Valley than in the Netherlands. The influence of the aerosol chemical composition on the cloud droplet activation was studied by computation of the critical activation diameter and comparing to aerosol number size distribution measurements. In some situations, the chemical composition was the driving force behind changes in CCN concentration, in other situations its effect was overshadowed by changes in the size distribution. Differences between the individual layers of the PBL were identified in the mass concentrations of the aerosol chemical species and the organic aerosol age. A backward trajectory analysis was used in conjunction with the obtained data to estimate the aerosol production rate of the Po Valley to 0.60 (µg/m3)/h for organic aerosol, 0.88 (µg/m3)/h for nitrate aerosol, and 0.15 (µg/m3)/h for sulfate aerosol. The aerosol ion balance was used to gain insights into organic aerosol functionalization patterns

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Florian Rubach

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