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HoloGondel: in situ cloud observations on a cable car in the Swiss Alps using a holographic imager

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Beck Alexander, Henneberger Jan, Schöpfer Sarah, Fugal Jacob, Lohmann Ulrike,
Project Beitrag an den Unterhalt und Betrieb der Hochalpinen Forschungsstationen Jungfraujoch und Gornergrat, 2015-2017
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Original article (peer-reviewed)

Journal Atmospheric Measurement Techniques
Volume (Issue) 10(2)
Page(s) 459 - 476
Title of proceedings Atmospheric Measurement Techniques
DOI 10.5194/amt-10-459-2017

Open Access

URL http://doi.org/10.5194/amt-10-459-2017
Type of Open Access Publisher (Gold Open Access)

Abstract

In situ observations of cloud properties in complex alpine terrain where research aircraft cannot sample are commonly conducted at mountain-top research stations and limited to single-point measurements. The HoloGondel platform overcomes this limitation by using a cable car to obtain vertical profiles of the microphysical and meteorological cloud parameters. The main component of the HoloGondel platform is the HOLographic Imager for Microscopic Objects (HOLIMO 3G), which uses digital in-line holography to image cloud particles. Based on two-dimensional images the microphysical cloud parameters for the size range from small cloud particles to large precipitation particles are obtained for the liquid and ice phase. The low traveling velocity of a cable car on the order of 10 m s −1 allows measurements with high spatial resolution; however, at the same time it leads to an unstable air speed towards the HoloGondel platform. Holographic cloud imagers, which have a sample volume that is independent of the air speed, are therefore well suited for measurements on a cable car. Example measurements of the vertical profiles observed in a liquid cloud and a mixed-phase cloud at the Eggishorn in the Swiss Alps in the winters 2015 and 2016 are presented. The HoloGondel platform reliably observes cloud droplets larger than 6.5 µm, partitions between cloud droplets and ice crystals for a size larger than 25 µm and obtains a statistically significantly size distribution for every 5 m in vertical ascent.
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