HOLIMO II: a digital holographic instrument for ground-based in situ observations of microphysical properties of mixed-phase clouds

Henneberger, Jan; Fugal, Jacob P.; Stetzer, O.; Lohmann, Ulrike

doi:10.5194/amt-6-2975-2013

Cited by 68 publications

(86 citation statements)

References 29 publications

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“…Stratiform MPCs are prevalent in the Arctic [67,89] and in orographic terrain [28,50,57]. In situ observations and surface remote sensing suggest that clouds in the mixedphase temperature range in mid-latitudes tend to consist almost entirely of ice or of liquid water [10,11,48].…”

Section: Aerosol Effects On Stratiform and Shallow Convective Mpcsmentioning

confidence: 99%

Anthropogenic Aerosol Influences on Mixed-Phase Clouds

Lohmann

2017

Curr Clim Change Rep

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Aerosol effects on mixed-phase clouds (MPCs) are more complex than in warm clouds because aerosol particles can act both as cloud condensation nuclei and as ice nucleating particles and more microphysical pathways exist. Stratiform MPCs are most prevalent in the Arctic where cloud top cooling enables heterogeneous ice formation and in orographic terrain where large updrafts prevail. Recently, aerosol effects on stratiform MPCs have also been considered in global climate models. The estimated effective aerosol radiative forcing due to aerosol-cloud and aerosol-radiation interactions (ERFaci+ari) at the top-ofthe-atmosphere (TOA) in stratiform warm and MPCs, which is an update of the estimate given in the fifth assessment report (AR5) of the Intergovernmental Panel of Climate Change, is −1.2 W m −2 with a 5-95 % range between −0.8 and −2.0 W m −2 . Since AR5, only one new estimate of ERFaci+ari including aerosol effects on both stratiform and convective clouds of −1.4 W m −2 has been published. In all cases, ERFaci+ari is dominated by changes in the shortwave TOA radiation with changes in the longwave TOA radiation amounting to 0.15 W m −2 .

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Section: Aerosol Effects On Stratiform and Shallow Convective Mpcsmentioning

confidence: 99%

Anthropogenic Aerosol Influences on Mixed-Phase Clouds

Lohmann

2017

Curr Clim Change Rep

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“…Henneberger et al (2013) made measurements with a holographic instrument and also observed a transition from mixed-phase to glaciated cloud over a larger temporal scale of 8 h. Choularton et al (2008) showed that strongly glaciated cloud periods at JFJ were linked to polluted air masses, characterised by higher loadings of sulphate, arriving at the site. Clouds were found to contain variable ice number concentrations measured by various cloud imaging probes, often in the range 1-1000 L −1 .…”

Section: G Lloyd Et Al: the Origins Of Ice Crystals Measured In MIXmentioning

confidence: 99%

“…No shattering event was detected in the case study presented in this paper. A digital holographic imager HOLIMO II (Henneberger et al, 2013) was also used to make in-situ image ensembles of cloud particles within a well-defined sample volume that yields single particle size and shadowgraph information for particles between 6 and 250 µm. Advancements in data processing software now offer phase-resolved size distributions, concentrations, and water contents for cloud particles larger than 20 µm.…”

Section: Jungfraujochmentioning

confidence: 99%

The origins of ice crystals measured in mixed-phase clouds at the high-alpine site Jungfraujoch

et al. 2015

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Abstract. During the winter of 2013 and 2014 measurements of cloud microphysical properties over a 5-week period at the high-alpine site Jungfraujoch, Switzerland, were carried out as part of the Cloud Aerosol Characterisation Experiments (CLACE) and the Ice Nucleation Process Investigation and Quantification project (INUPIAQ). Measurements of aerosol properties at a second, lower site, Schilthorn, Switzerland, were used as input for a primary ice nucleation scheme to predict ice nuclei concentrations at Jungfraujoch. Frequent, rapid transitions in the ice and liquid properties of the clouds at Jungfraujoch were identified that led to large fluctuations in ice mass fractions over temporal scales of seconds to hours. During the measurement period we observed high concentrations of ice particles that exceeded 1000 L −1 at temperatures around −15 • C, verified by multiple instruments. These concentrations could not be explained using the usual primary ice nucleation schemes, which predicted ice nucleus concentrations several orders of magnitude smaller than the peak ice crystal number concentrations. Secondary ice production through the Hallett-Mossop process as a possible explanation was ruled out, as the cloud was rarely within the active temperature range for this process. It is shown that other mechanisms of secondary ice particle production cannot explain the highest ice particle concentrations. We describe four possible mechanisms that could lead to high cloud ice concentrations generated from the snowcovered surfaces surrounding the measurement site. Of these we show that hoar frost crystals generated at the cloud enveloped snow surface could be the most important source of cloud ice concentrations. Blowing snow was also observed to make significant contributions at higher wind speeds when ice crystal concentrations were < 100 L −1 .

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“…As described in Henneberger et al (2013) the resolution of a holographic system is limited by three constraints. One limitation is imposed by the pixel size of the camera (D pixel ) and the magnification of the lens system (M):…”

Section: Resolution Measurementsmentioning

confidence: 99%

“…Digital in-line holography has been previously used in a series of airborne (Conway et al, 1982;Beals et al, 2015) and ground-based field instruments (Thompson, 1964;Kozikowska et al, 1984;Borrmann and Jaenicke, 1993;Raupach et al, 2006;Henneberger et al, 2013). In comparison to other in situ cloud probes, holographic imagers have specific advantages and disadvantages (see Baumgardner et al, 2011).…”

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confidence: 99%

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

et al. 2017

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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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HOLIMO II: a digital holographic instrument for ground-based in situ observations of microphysical properties of mixed-phase clouds

Cited by 68 publications

References 29 publications

Anthropogenic Aerosol Influences on Mixed-Phase Clouds

Anthropogenic Aerosol Influences on Mixed-Phase Clouds

The origins of ice crystals measured in mixed-phase clouds at the high-alpine site Jungfraujoch

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

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