Highly supercooled riming and unusual triple-frequency radar signatures over McMurdo Station, Antarctica
<p>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...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2022-09-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/22/12467/2022/acp-22-12467-2022.pdf |
| _version_ | 1811208893939843072 |
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| author | F. Tridon F. Tridon I. Silber A. Battaglia A. Battaglia A. Battaglia S. Kneifel S. Kneifel A. Fridlind P. Kalogeras P. Kalogeras R. Dhillon |
| author_facet | F. Tridon F. Tridon I. Silber A. Battaglia A. Battaglia A. Battaglia S. Kneifel S. Kneifel A. Fridlind P. Kalogeras P. Kalogeras R. Dhillon |
| author_sort | F. Tridon |
| collection | DOAJ |
| description | <p>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: (i) the scarcity of supercooled liquid water clouds due to the extremely low tropospheric temperatures and (ii) the low aerosol concentration, which may lead to the formation of fewer and larger supercooled drops potentially resulting in an enhanced riming efficiency.</p>
<p>In this work, by exploiting the deployment of an unprecedented number of multiwavelength 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 riming incidence at McMurdo Station and find that riming occurs at much lower temperatures when compared to previous results in the mid-latitudes. This suggests the possible occurrence of a common atmospheric state over Antarctica that includes a rather stable atmosphere inhibiting turbulent mixing, and a high riming efficiency driven by large cloud droplets.</p>
<p>We then focus on a peculiar case study featuring a persistent layer with a particularly pronounced riming signature in triple-frequency radar data 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 one-dimensional bin model 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 ice particles of several millimeters in size, by vapor deposition and then riming.</p> |
| first_indexed | 2024-04-12T04:29:34Z |
| format | Article |
| id | doaj.art-ec752cac02f14f4abec7526aca75630d |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-04-12T04:29:34Z |
| publishDate | 2022-09-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-ec752cac02f14f4abec7526aca75630d2022-12-22T03:47:58ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242022-09-0122124671249110.5194/acp-22-12467-2022Highly supercooled riming and unusual triple-frequency radar signatures over McMurdo Station, AntarcticaF. Tridon0F. Tridon1I. Silber2A. Battaglia3A. Battaglia4A. Battaglia5S. Kneifel6S. Kneifel7A. Fridlind8P. Kalogeras9P. Kalogeras10R. Dhillon11Institute for Geophysics and Meteorology, University of Cologne, Cologne, Germanynow at: DIATI, Politecnico di Torino, Turin, ItalyDepartment of Meteorology and Atmospheric Science, Pennsylvania State University, University Park, PA, USADIATI, Politecnico di Torino, Turin, ItalyDepartment of Physics and Astronomy, University of Leicester, Leicester, UKNational Center for Earth Observation, Leicester, UKInstitute for Geophysics and Meteorology, University of Cologne, Cologne, GermanyMeteorological Institute, Ludwig Maximilian University of Munich, Munich, GermanyNASA Goddard Institute for Space Studies, New York, NY, USADepartment of Physics and Astronomy, University of Leicester, Leicester, UKNational Center for Earth Observation, Leicester, UKDepartment of Physics and Astronomy, University of Leicester, Leicester, UK<p>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: (i) the scarcity of supercooled liquid water clouds due to the extremely low tropospheric temperatures and (ii) the low aerosol concentration, which may lead to the formation of fewer and larger supercooled drops potentially resulting in an enhanced riming efficiency.</p> <p>In this work, by exploiting the deployment of an unprecedented number of multiwavelength 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 riming incidence at McMurdo Station and find that riming occurs at much lower temperatures when compared to previous results in the mid-latitudes. This suggests the possible occurrence of a common atmospheric state over Antarctica that includes a rather stable atmosphere inhibiting turbulent mixing, and a high riming efficiency driven by large cloud droplets.</p> <p>We then focus on a peculiar case study featuring a persistent layer with a particularly pronounced riming signature in triple-frequency radar data 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 one-dimensional bin model 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 ice particles of several millimeters in size, by vapor deposition and then riming.</p>https://acp.copernicus.org/articles/22/12467/2022/acp-22-12467-2022.pdf |
| spellingShingle | F. Tridon F. Tridon I. Silber A. Battaglia A. Battaglia A. Battaglia S. Kneifel S. Kneifel A. Fridlind P. Kalogeras P. Kalogeras R. Dhillon Highly supercooled riming and unusual triple-frequency radar signatures over McMurdo Station, Antarctica Atmospheric Chemistry and Physics |
| title | Highly supercooled riming and unusual triple-frequency radar signatures over McMurdo Station, Antarctica |
| title_full | Highly supercooled riming and unusual triple-frequency radar signatures over McMurdo Station, Antarctica |
| title_fullStr | Highly supercooled riming and unusual triple-frequency radar signatures over McMurdo Station, Antarctica |
| title_full_unstemmed | Highly supercooled riming and unusual triple-frequency radar signatures over McMurdo Station, Antarctica |
| title_short | Highly supercooled riming and unusual triple-frequency radar signatures over McMurdo Station, Antarctica |
| title_sort | highly supercooled riming and unusual triple frequency radar signatures over mcmurdo station antarctica |
| url | https://acp.copernicus.org/articles/22/12467/2022/acp-22-12467-2022.pdf |
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