Microphysical investigation of the seeder and feeder region of an Alpine mixed-phase cloud
<p>The seeder–feeder mechanism has been observed to enhance orographic precipitation in previous studies. However, the microphysical processes active in the seeder and feeder region are still being understood. In this paper, we investigate the seeder and feeder region of a mixed-phase cloud pa...
| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2021-05-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/21/6681/2021/acp-21-6681-2021.pdf |
| _version_ | 1818597059511451648 |
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| author | F. Ramelli J. Henneberger R. O. David J. Bühl M. Radenz P. Seifert J. Wieder A. Lauber J. T. Pasquier R. Engelmann C. Mignani M. Hervo U. Lohmann |
| author_facet | F. Ramelli J. Henneberger R. O. David J. Bühl M. Radenz P. Seifert J. Wieder A. Lauber J. T. Pasquier R. Engelmann C. Mignani M. Hervo U. Lohmann |
| author_sort | F. Ramelli |
| collection | DOAJ |
| description | <p>The seeder–feeder mechanism has been observed to enhance orographic precipitation in previous studies. However, the microphysical processes active in the seeder and feeder region are still being understood. In this paper, we investigate the seeder and feeder region of a mixed-phase cloud passing over the Swiss Alps, focusing on (1) fallstreaks of enhanced radar reflectivity originating from cloud top generating cells (seeder region) and (2) a persistent low-level feeder cloud produced by the boundary layer circulation (feeder region). Observations were obtained from a multi-dimensional set of instruments including ground-based remote sensing instrumentation (Ka-band polarimetric cloud radar, microwave radiometer, wind profiler), in situ instrumentation on a tethered balloon system, and ground-based aerosol and precipitation measurements.</p>
<p>The cloud radar observations suggest that ice formation and growth were enhanced within cloud top generating cells, which is consistent with previous observational studies. However, uncertainties exist regarding the dominant ice formation mechanism within these cells. Here we propose different mechanisms that potentially enhance ice nucleation and growth in cloud top generating cells (convective overshooting, radiative cooling, droplet shattering) and attempt to estimate their potential contribution from an ice nucleating particle perspective. Once ice formation and growth within the seeder region exceeded a threshold value, the mixed-phase cloud became fully glaciated.</p>
<p>Local flow effects on the lee side of the mountain barrier induced the formation of a persistent low-level feeder cloud over a small-scale topographic feature in the inner-Alpine valley. In situ measurements within the low-level feeder cloud observed the production of secondary ice particles likely due to the Hallett–Mossop process and ice particle fragmentation upon ice–ice collisions. Therefore, secondary ice production may have been partly responsible for the elevated ice crystal number concentrations that have been previously observed in feeder clouds at mountaintop observatories. Secondary ice production in feeder clouds can potentially enhance orographic precipitation.</p> |
| first_indexed | 2024-12-16T11:41:47Z |
| format | Article |
| id | doaj.art-e3816e0165d34d8babc0ce9f364b0ae5 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-16T11:41:47Z |
| publishDate | 2021-05-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-e3816e0165d34d8babc0ce9f364b0ae52022-12-21T22:32:56ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242021-05-01216681670610.5194/acp-21-6681-2021Microphysical investigation of the seeder and feeder region of an Alpine mixed-phase cloudF. Ramelli0J. Henneberger1R. O. David2J. Bühl3M. Radenz4P. Seifert5J. Wieder6A. Lauber7J. T. Pasquier8R. Engelmann9C. Mignani10M. Hervo11U. Lohmann12Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, SwitzerlandInstitute for Atmospheric and Climate Science, ETH Zurich, Zurich, SwitzerlandDepartment of Geosciences, University of Oslo, Oslo, NorwayLeibniz Institute for Tropospheric Research, Leipzig, GermanyLeibniz Institute for Tropospheric Research, Leipzig, GermanyLeibniz Institute for Tropospheric Research, Leipzig, GermanyInstitute for Atmospheric and Climate Science, ETH Zurich, Zurich, SwitzerlandInstitute for Atmospheric and Climate Science, ETH Zurich, Zurich, SwitzerlandInstitute for Atmospheric and Climate Science, ETH Zurich, Zurich, SwitzerlandLeibniz Institute for Tropospheric Research, Leipzig, GermanyDepartment of Environmental Sciences, University of Basel, Basel, SwitzerlandFederal Office of Meteorology and Climatology MeteoSwiss, Payerne, SwitzerlandInstitute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland<p>The seeder–feeder mechanism has been observed to enhance orographic precipitation in previous studies. However, the microphysical processes active in the seeder and feeder region are still being understood. In this paper, we investigate the seeder and feeder region of a mixed-phase cloud passing over the Swiss Alps, focusing on (1) fallstreaks of enhanced radar reflectivity originating from cloud top generating cells (seeder region) and (2) a persistent low-level feeder cloud produced by the boundary layer circulation (feeder region). Observations were obtained from a multi-dimensional set of instruments including ground-based remote sensing instrumentation (Ka-band polarimetric cloud radar, microwave radiometer, wind profiler), in situ instrumentation on a tethered balloon system, and ground-based aerosol and precipitation measurements.</p> <p>The cloud radar observations suggest that ice formation and growth were enhanced within cloud top generating cells, which is consistent with previous observational studies. However, uncertainties exist regarding the dominant ice formation mechanism within these cells. Here we propose different mechanisms that potentially enhance ice nucleation and growth in cloud top generating cells (convective overshooting, radiative cooling, droplet shattering) and attempt to estimate their potential contribution from an ice nucleating particle perspective. Once ice formation and growth within the seeder region exceeded a threshold value, the mixed-phase cloud became fully glaciated.</p> <p>Local flow effects on the lee side of the mountain barrier induced the formation of a persistent low-level feeder cloud over a small-scale topographic feature in the inner-Alpine valley. In situ measurements within the low-level feeder cloud observed the production of secondary ice particles likely due to the Hallett–Mossop process and ice particle fragmentation upon ice–ice collisions. Therefore, secondary ice production may have been partly responsible for the elevated ice crystal number concentrations that have been previously observed in feeder clouds at mountaintop observatories. Secondary ice production in feeder clouds can potentially enhance orographic precipitation.</p>https://acp.copernicus.org/articles/21/6681/2021/acp-21-6681-2021.pdf |
| spellingShingle | F. Ramelli J. Henneberger R. O. David J. Bühl M. Radenz P. Seifert J. Wieder A. Lauber J. T. Pasquier R. Engelmann C. Mignani M. Hervo U. Lohmann Microphysical investigation of the seeder and feeder region of an Alpine mixed-phase cloud Atmospheric Chemistry and Physics |
| title | Microphysical investigation of the seeder and feeder region of an Alpine mixed-phase cloud |
| title_full | Microphysical investigation of the seeder and feeder region of an Alpine mixed-phase cloud |
| title_fullStr | Microphysical investigation of the seeder and feeder region of an Alpine mixed-phase cloud |
| title_full_unstemmed | Microphysical investigation of the seeder and feeder region of an Alpine mixed-phase cloud |
| title_short | Microphysical investigation of the seeder and feeder region of an Alpine mixed-phase cloud |
| title_sort | microphysical investigation of the seeder and feeder region of an alpine mixed phase cloud |
| url | https://acp.copernicus.org/articles/21/6681/2021/acp-21-6681-2021.pdf |
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