Highly supercooled riming and unusual triple-frequency radar signatures over Antarctica
Riming of ice crystals by supercooled water droplets is an efficient ice growth process, but its basic properties are still poorly known. While it has been shown to contribute significantly to surface precipitation at mid-latitudes, little is known about its occurrence at high latitudes. In Antarcti...
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ftcopernicus:oai:publications.copernicus.org:acpd101509 2023-05-15T14:02:18+02:00 Highly supercooled riming and unusual triple-frequency radar signatures over Antarctica Tridon, Frédéric Silber, Israel Battaglia, Alessandro Kneifel, Stefan Fridlind, Ann Kalogeras, Petros Dhillon, Ranvir 2022-03-09 application/pdf https://doi.org/10.5194/acp-2022-136 https://acp.copernicus.org/preprints/acp-2022-136/ eng eng doi:10.5194/acp-2022-136 https://acp.copernicus.org/preprints/acp-2022-136/ eISSN: 1680-7324 Text 2022 ftcopernicus https://doi.org/10.5194/acp-2022-136 2022-03-14T17:22:16Z Riming of ice crystals by supercooled water droplets is an efficient ice growth process, but its basic properties are still poorly known. While it has been shown to contribute significantly to surface precipitation at mid-latitudes, little is known about its occurrence at high latitudes. In Antarctica, two competing effects can influence the occurrence of riming: the scarcity of supercooled liquid water clouds due to the extremely low tropospheric temperatures and the low aerosol concentration, which may lead to the formation of fewer and larger supercooled drops potentially resulting in an enhanced riming efficiency. In this work, by exploiting the deployment of an unprecedented number of multi-wavelength active and passive remote sensing systems (including triple-frequency radar measurements) in West Antarctica, during the Atmospheric Radiation Measurements West Antarctic Radiation Experiment (AWARE) field campaign, we evaluate the importance of riming incidence in Antarctica and find that riming occurs at much lower temperatures compared to the mid-latitudes. We then focus on a case study featuring a persistent layer of unexpectedly pronounced triple-frequency radar signatures but only a relatively modest amount of supercooled liquid water. In-depth analysis of the radar observations suggests that such signatures can only be explained by the combined effects of moderately rimed aggregates or similarly shaped florid polycrystals and a narrow particle size distribution (PSD). Simulations of this case study performed with a 1D bin model %by introducing an additional class corresponding to rimed ice indicate that similar triple frequency radar observations can be reproduced when narrow PSDs are simulated. Such narrow PSDs can in turn be explained by two key factors: (i) the presence of a shallow homogeneous droplet or humidified aerosol freezing layer aloft seeding an underlying supercooled liquid layer, and (ii) the absence of turbulent mixing throughout a stable polar atmosphere that sustains narrow PSDs, as hydrometeors grow from the nucleation region aloft to several millimeter ice particles, by vapor deposition and then riming. Text Antarc* Antarctic Antarctica West Antarctica Copernicus Publications: E-Journals Antarctic West Antarctica |
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Copernicus Publications: E-Journals |
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language |
English |
description |
Riming of ice crystals by supercooled water droplets is an efficient ice growth process, but its basic properties are still poorly known. While it has been shown to contribute significantly to surface precipitation at mid-latitudes, little is known about its occurrence at high latitudes. In Antarctica, two competing effects can influence the occurrence of riming: the scarcity of supercooled liquid water clouds due to the extremely low tropospheric temperatures and the low aerosol concentration, which may lead to the formation of fewer and larger supercooled drops potentially resulting in an enhanced riming efficiency. In this work, by exploiting the deployment of an unprecedented number of multi-wavelength active and passive remote sensing systems (including triple-frequency radar measurements) in West Antarctica, during the Atmospheric Radiation Measurements West Antarctic Radiation Experiment (AWARE) field campaign, we evaluate the importance of riming incidence in Antarctica and find that riming occurs at much lower temperatures compared to the mid-latitudes. We then focus on a case study featuring a persistent layer of unexpectedly pronounced triple-frequency radar signatures but only a relatively modest amount of supercooled liquid water. In-depth analysis of the radar observations suggests that such signatures can only be explained by the combined effects of moderately rimed aggregates or similarly shaped florid polycrystals and a narrow particle size distribution (PSD). Simulations of this case study performed with a 1D bin model %by introducing an additional class corresponding to rimed ice indicate that similar triple frequency radar observations can be reproduced when narrow PSDs are simulated. Such narrow PSDs can in turn be explained by two key factors: (i) the presence of a shallow homogeneous droplet or humidified aerosol freezing layer aloft seeding an underlying supercooled liquid layer, and (ii) the absence of turbulent mixing throughout a stable polar atmosphere that sustains narrow PSDs, as hydrometeors grow from the nucleation region aloft to several millimeter ice particles, by vapor deposition and then riming. |
format |
Text |
author |
Tridon, Frédéric Silber, Israel Battaglia, Alessandro Kneifel, Stefan Fridlind, Ann Kalogeras, Petros Dhillon, Ranvir |
spellingShingle |
Tridon, Frédéric Silber, Israel Battaglia, Alessandro Kneifel, Stefan Fridlind, Ann Kalogeras, Petros Dhillon, Ranvir Highly supercooled riming and unusual triple-frequency radar signatures over Antarctica |
author_facet |
Tridon, Frédéric Silber, Israel Battaglia, Alessandro Kneifel, Stefan Fridlind, Ann Kalogeras, Petros Dhillon, Ranvir |
author_sort |
Tridon, Frédéric |
title |
Highly supercooled riming and unusual triple-frequency radar signatures over Antarctica |
title_short |
Highly supercooled riming and unusual triple-frequency radar signatures over Antarctica |
title_full |
Highly supercooled riming and unusual triple-frequency radar signatures over Antarctica |
title_fullStr |
Highly supercooled riming and unusual triple-frequency radar signatures over Antarctica |
title_full_unstemmed |
Highly supercooled riming and unusual triple-frequency radar signatures over Antarctica |
title_sort |
highly supercooled riming and unusual triple-frequency radar signatures over antarctica |
publishDate |
2022 |
url |
https://doi.org/10.5194/acp-2022-136 https://acp.copernicus.org/preprints/acp-2022-136/ |
geographic |
Antarctic West Antarctica |
geographic_facet |
Antarctic West Antarctica |
genre |
Antarc* Antarctic Antarctica West Antarctica |
genre_facet |
Antarc* Antarctic Antarctica West Antarctica |
op_source |
eISSN: 1680-7324 |
op_relation |
doi:10.5194/acp-2022-136 https://acp.copernicus.org/preprints/acp-2022-136/ |
op_doi |
https://doi.org/10.5194/acp-2022-136 |
_version_ |
1766272489864822784 |