Microphysical properties and fall speed measurements of snow ice crystals using the Dual Ice Crystal Imager (D-ICI)
<p>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...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-03-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/13/1273/2020/amt-13-1273-2020.pdf |
| _version_ | 1818020361353035776 |
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| author | T. Kuhn S. Vázquez-Martín |
| author_facet | T. Kuhn S. Vázquez-Martín |
| author_sort | T. Kuhn |
| collection | DOAJ |
| description | <p>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.</p>
<p>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 <span class="inline-formula">µ</span>m pixel<span class="inline-formula"><sup>−1</sup></span>.
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.</p>
<p>The instrument has been tested in Kiruna, northern Sweden (67.8<span class="inline-formula"><sup>∘</sup></span> N, 20.4<span class="inline-formula"><sup>∘</sup></span> E). Measurements are demonstrated with
images from different snow events, and
the determined snow ice crystal properties are presented.</p> |
| first_indexed | 2024-04-14T08:05:01Z |
| format | Article |
| id | doaj.art-2a6bd5e778da4a2e855c04bebd76082e |
| institution | Directory Open Access Journal |
| issn | 1867-1381 1867-8548 |
| language | English |
| last_indexed | 2024-04-14T08:05:01Z |
| publishDate | 2020-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Measurement Techniques |
| spelling | doaj.art-2a6bd5e778da4a2e855c04bebd76082e2022-12-22T02:04:47ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482020-03-01131273128510.5194/amt-13-1273-2020Microphysical properties and fall speed measurements of snow ice crystals using the Dual Ice Crystal Imager (D-ICI)T. KuhnS. Vázquez-Martín<p>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.</p> <p>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 <span class="inline-formula">µ</span>m pixel<span class="inline-formula"><sup>−1</sup></span>. 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.</p> <p>The instrument has been tested in Kiruna, northern Sweden (67.8<span class="inline-formula"><sup>∘</sup></span> N, 20.4<span class="inline-formula"><sup>∘</sup></span> E). Measurements are demonstrated with images from different snow events, and the determined snow ice crystal properties are presented.</p>https://www.atmos-meas-tech.net/13/1273/2020/amt-13-1273-2020.pdf |
| spellingShingle | T. Kuhn S. Vázquez-Martín Microphysical properties and fall speed measurements of snow ice crystals using the Dual Ice Crystal Imager (D-ICI) Atmospheric Measurement Techniques |
| title | 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_short | 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 |
| url | https://www.atmos-meas-tech.net/13/1273/2020/amt-13-1273-2020.pdf |
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