HoloGondel: in situ cloud observations on a cable car in the Swiss Alps using a holographic imager
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 profil...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-02-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/10/459/2017/amt-10-459-2017.pdf |
| Summary: | 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<sup>−1</sup> 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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| ISSN: | 1867-1381 1867-8548 |