Microphysical properties and fall speed measurements of snow ice crystals using the Dual Ice Crystal Imager (D-ICI)

Accurate predictions of snowfall require good knowledge of the microphysical properties of the snow ice crystals and particles. Shape is an important parameter as it strongly influences the scattering properties of the ice particles, and thus their response to remote sensing techniques such as radar...

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Published in:Atmospheric Measurement Techniques
Main Authors: Kuhn, Thomas, Vázquez-Martín, Sandra
Format: Text
Language:English
Published: 2020
Subjects:
Online Access:https://doi.org/10.5194/amt-13-1273-2020
https://amt.copernicus.org/articles/13/1273/2020/
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spelling ftcopernicus:oai:publications.copernicus.org:amt80275 2023-05-15T17:04:21+02:00 Microphysical properties and fall speed measurements of snow ice crystals using the Dual Ice Crystal Imager (D-ICI) Kuhn, Thomas Vázquez-Martín, Sandra 2020-03-16 application/pdf https://doi.org/10.5194/amt-13-1273-2020 https://amt.copernicus.org/articles/13/1273/2020/ eng eng doi:10.5194/amt-13-1273-2020 https://amt.copernicus.org/articles/13/1273/2020/ eISSN: 1867-8548 Text 2020 ftcopernicus https://doi.org/10.5194/amt-13-1273-2020 2020-07-20T16:22:21Z Accurate predictions of snowfall require good knowledge of the microphysical properties of the snow ice crystals and particles. Shape is an important parameter as it strongly influences the scattering properties of the ice particles, and thus their response to remote sensing techniques such as radar measurements. The fall speed of ice particles is another important parameter for both numerical forecast models as well as representation of ice clouds and snow in climate models, as it is responsible for the rate of removal of ice from these models. We describe a new ground-based in situ instrument, the Dual Ice Crystal Imager (D-ICI), to determine snow ice crystal properties and fall speed simultaneously. The instrument takes two high-resolution pictures of the same falling ice particle from two different viewing directions. Both cameras use a microscope-like setup resulting in an image pixel resolution of approximately 4 µ m pixel −1 . One viewing direction is horizontal and is used to determine fall speed by means of a double exposure. For this purpose, two bright flashes of a light-emitting diode behind the camera illuminate the falling ice particle and create this double exposure, and the vertical displacement of the particle provides its fall speed. The other viewing direction is close-to-vertical and is used to provide size and shape information from single-exposure images. This viewing geometry is chosen instead of a horizontal one because shape and size of ice particles as viewed in the vertical direction are more relevant than these properties viewed horizontally, as the vertical fall speed is more strongly influenced by the vertically viewed properties. In addition, a comparison with remote sensing instruments that mostly have a vertical or close-to-vertical viewing geometry is favoured when the particle properties are measured in the same direction. The instrument has been tested in Kiruna, northern Sweden (67.8 ∘ N, 20.4 ∘ E). Measurements are demonstrated with images from different snow events, and the determined snow ice crystal properties are presented. Text Kiruna Northern Sweden Copernicus Publications: E-Journals Kiruna New Ground ENVELOPE(-55.215,-55.215,49.567,49.567) Atmospheric Measurement Techniques 13 3 1273 1285
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collection Copernicus Publications: E-Journals
op_collection_id ftcopernicus
language English
description Accurate predictions of snowfall require good knowledge of the microphysical properties of the snow ice crystals and particles. Shape is an important parameter as it strongly influences the scattering properties of the ice particles, and thus their response to remote sensing techniques such as radar measurements. The fall speed of ice particles is another important parameter for both numerical forecast models as well as representation of ice clouds and snow in climate models, as it is responsible for the rate of removal of ice from these models. We describe a new ground-based in situ instrument, the Dual Ice Crystal Imager (D-ICI), to determine snow ice crystal properties and fall speed simultaneously. The instrument takes two high-resolution pictures of the same falling ice particle from two different viewing directions. Both cameras use a microscope-like setup resulting in an image pixel resolution of approximately 4 µ m pixel −1 . One viewing direction is horizontal and is used to determine fall speed by means of a double exposure. For this purpose, two bright flashes of a light-emitting diode behind the camera illuminate the falling ice particle and create this double exposure, and the vertical displacement of the particle provides its fall speed. The other viewing direction is close-to-vertical and is used to provide size and shape information from single-exposure images. This viewing geometry is chosen instead of a horizontal one because shape and size of ice particles as viewed in the vertical direction are more relevant than these properties viewed horizontally, as the vertical fall speed is more strongly influenced by the vertically viewed properties. In addition, a comparison with remote sensing instruments that mostly have a vertical or close-to-vertical viewing geometry is favoured when the particle properties are measured in the same direction. The instrument has been tested in Kiruna, northern Sweden (67.8 ∘ N, 20.4 ∘ E). Measurements are demonstrated with images from different snow events, and the determined snow ice crystal properties are presented.
format Text
author Kuhn, Thomas
Vázquez-Martín, Sandra
spellingShingle Kuhn, Thomas
Vázquez-Martín, Sandra
Microphysical properties and fall speed measurements of snow ice crystals using the Dual Ice Crystal Imager (D-ICI)
author_facet Kuhn, Thomas
Vázquez-Martín, Sandra
author_sort Kuhn, Thomas
title Microphysical properties and fall speed measurements of snow ice crystals using the Dual Ice Crystal Imager (D-ICI)
title_short Microphysical properties and fall speed measurements of snow ice crystals using the Dual Ice Crystal Imager (D-ICI)
title_full Microphysical properties and fall speed measurements of snow ice crystals using the Dual Ice Crystal Imager (D-ICI)
title_fullStr Microphysical properties and fall speed measurements of snow ice crystals using the Dual Ice Crystal Imager (D-ICI)
title_full_unstemmed Microphysical properties and fall speed measurements of snow ice crystals using the Dual Ice Crystal Imager (D-ICI)
title_sort microphysical properties and fall speed measurements of snow ice crystals using the dual ice crystal imager (d-ici)
publishDate 2020
url https://doi.org/10.5194/amt-13-1273-2020
https://amt.copernicus.org/articles/13/1273/2020/
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geographic Kiruna
New Ground
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New Ground
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Northern Sweden
genre_facet Kiruna
Northern Sweden
op_source eISSN: 1867-8548
op_relation doi:10.5194/amt-13-1273-2020
https://amt.copernicus.org/articles/13/1273/2020/
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container_title Atmospheric Measurement Techniques
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