A011-0007
Understanding Microphysical Processes in Arctic Mixed-Phase Clouds from Balloon-Borne Holographic Instrument

Monday, 7 December 2020
Poster
Julie Pasquier1, Jan Henneberger1, Jörg Wieder1, Robert David2, Guangyu Li1, Tim Carlsen2, Rosa Gierens3, Kerstin Ebell3, Marion Maturilli4, Christoph Ritter5, Roland Neuber, Paul Zieger7 and Ulrike Lohmann8, (1)ETH Swiss Federal Institute of Technology Zurich, Institute for Atmospheric and Climate Science, Zurich, Switzerland, (2)University of Oslo, Department of Geosciences, Oslo, Norway, (3)University of Cologne, Institute of Geophysics and Meteorology, Cologne, Germany, (4)Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Potsdam, Potsdam, Germany, (5)Alfred Wegener Institute Helmholtz- Center for Polar and Marine Research, Climate Sciences, Atmospheric circulations, Potsdam, Germany, (6)Stockholm University, ACES, Stockholm, Sweden, (7)ETH Zurich, Zurich, Switzerland
Abstract:
The Arctic is warming faster than the rest of the world. Clouds have been associated with this Arctic Amplification as they influence downwelling solar and upwelling terrestrial radiative fluxes, which determine the surface radiative energy budget. Mixed-phase clouds (MPCs), which contain both cloud droplets and ice crystals, are highly abundant in the Arctic. The cloud phase partitioning within MPCs especially influences the atmospheric radiation balance due to the different scattering properties between liquid droplets and ice crystals. Additionally, the lifetime of MPCs depends on the spatial distribution of cloud droplets and ice crystals. However, the cloud phase partitioning in Arctic clouds is poorly understood due to the limited availability of in-situ measurements.

Measurements were conducted in Ny-Ålesund, Svalbard, Norway, during October and November 2019. The main instrument used was a tethered balloon system called HoloBalloon. HoloBalloon consists of a holographic cloud probe, a 3D sonic anemometer, four radiation sensors (up- and downward looking solar and terrestrial broadband irradiance), and two optical particle counters mounted on a 175 m3 tethered balloon system which can fly up to 1000 m above ground. Additionally, ice nucleating particles (INP) and cloud condensation nuclei were quantified at the measurement site. The in-situ cloud measurements were complemented by a comprehensive set of remote sensing instruments deployed at the AWIPEV Observatory that profile the entire troposphere and additional radiosondes were launched.

Here we will present the observed microphysical properties of precipitating MPCs that were measured during five consecutive days from November 8 to 12, 2019. During the two first days, an occluded front influenced the formation of the MPCs. On the third day, despite ground temperatures below -10°C, the limited ambient INP concentration inhibited the glaciation of the clouds. Additionally, the entire cloud layer was probed and the cloud top radiative properties analysed. During the two last days, the MPCs were characterised by the collocated occurrence of large supercooled droplets up to 200 µm and high concentrations of pristine ice crystals. This suggests secondary ice formation through droplet shattering and rime splintering.

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