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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 11 | Copyright
Atmos. Chem. Phys., 18, 8249-8264, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 13 Jun 2018

Research article | 13 Jun 2018

Airborne observations of newly formed boundary layer aerosol particles under cloudy conditions

Barbara Altstädter1, Andreas Platis2, Michael Jähn3,a, Holger Baars3, Janine Lückerath4, Andreas Held4,b, Astrid Lampert1, Jens Bange2, Markus Hermann3, and Birgit Wehner3 Barbara Altstädter et al.
  • 1Institute of Flight Guidance, Technische Universität Braunschweig, Braunschweig, Germany
  • 2Center for Applied Geosciences, Eberhard Karls University Tübingen, Tübingen, Germany
  • 3Leibniz Institute for Tropospheric Research, Leipzig, Germany
  • 4Atmospheric Chemistry, University of Bayreuth, Bayreuth, Germany
  • anow at: Laboratory for Air Pollution/Environmental Technology, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
  • bnow at: Environmental Chemistry and Air Research, Technical University of Berlin, Berlin, Germany

Abstract. This study describes the appearance of ultrafine boundary layer aerosol particles under classical non-favourable conditions at the research site of TROPOS (Leibniz Institute for Tropospheric Research). Airborne measurements of meteorological and aerosol properties of the atmospheric boundary layer (ABL) were repeatedly performed with the unmanned aerial system ALADINA (Application of Light-weight Aircraft for Detecting IN-situ Aerosol) during three seasons between October 2013 and July 2015. More than 100 measurement flights were conducted on 23 different days with a total flight duration of 53h. In 26% of the cases, maxima of ultrafine particles were observed close to the inversion layer at altitudes between 400 and 600m and the particles were rapidly mixed vertically and mainly transported downwards during short time intervals of cloud gaps. This study focuses on two measurement days affected by low-level stratocumulus clouds, but different wind directions (NE, SW) and minimal concentrations (<4.6µgm−3) of SO2, as a common indicator for precursor gases at ground. Taken from vertical profiles, the onset of clouds led to a non-linearity of humidity that resulted in an increased turbulence at the local-scale and caused fast nucleation e.g., but in relation to rapid dilution of surrounding air, seen in sporadic clusters of ground data, so that ultrafine particles disappeared in the verticality. The typical banana shape of new particle formation (NPF) and growth was not seen at ground and thus these days might not have been classified as NPF event days by pure surface studies.

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This article describes the appearance of ultrafine aerosol particles (size < 12 nm) within the atmospheric boundary layer under cloudy conditions. New particle formation (NPF) was observed with the ALADINA unmanned aerial system in relation to increased turbulence near the inversion layer. Fast mixing processes and rapid dilution of surrounding air led to an insufficient particle growth rate, seen in sporadic clusters at ground. These events might not have been classified as NPF by surface data.
This article describes the appearance of ultrafine aerosol particles (size  12 nm) within the...