Case study of a humidity layer above Arctic stratocumulus and potential turbulent coupling with the cloud top
Specific humidity inversions (SHIs) above low-level cloud layers have been frequently observed in the Arctic. The formation of these SHIs is usually associated with large-scale advection of humid air masses. However, the potential coupling of SHIs with cloud layers by turbulent processes is not full...
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ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00056393 2023-05-15T14:58:02+02:00 Case study of a humidity layer above Arctic stratocumulus and potential turbulent coupling with the cloud top Egerer, Ulrike Ehrlich, André Gottschalk, Matthias Griesche, Hannes Neggers, Roel A. J. Siebert, Holger Wendisch, Manfred 2021-04 electronic https://doi.org/10.5194/acp-21-6347-2021 https://noa.gwlb.de/receive/cop_mods_00056393 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00056044/acp-21-6347-2021.pdf https://acp.copernicus.org/articles/21/6347/2021/acp-21-6347-2021.pdf eng eng Copernicus Publications Atmospheric Chemistry and Physics -- http://www.atmos-chem-phys.net/volumes_and_issues.html -- http://www.bibliothek.uni-regensburg.de/ezeit/?2069847 -- 1680-7324 https://doi.org/10.5194/acp-21-6347-2021 https://noa.gwlb.de/receive/cop_mods_00056393 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00056044/acp-21-6347-2021.pdf https://acp.copernicus.org/articles/21/6347/2021/acp-21-6347-2021.pdf https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/openAccess CC-BY article Verlagsveröffentlichung article Text doc-type:article 2021 ftnonlinearchiv https://doi.org/10.5194/acp-21-6347-2021 2022-02-08T22:34:05Z Specific humidity inversions (SHIs) above low-level cloud layers have been frequently observed in the Arctic. The formation of these SHIs is usually associated with large-scale advection of humid air masses. However, the potential coupling of SHIs with cloud layers by turbulent processes is not fully understood. In this study, we analyze a 3 d period of a persistent layer of increased specific humidity above a stratocumulus cloud observed during an Arctic field campaign in June 2017. The tethered balloon system BELUGA (Balloon-bornE moduLar Utility for profilinG the lower Atmosphere) recorded vertical profile data of meteorological, turbulence, and radiation parameters in the atmospheric boundary layer. An in-depth discussion of the problems associated with humidity measurements in cloudy environments leads to the conclusion that the observed SHIs do not result from measurement artifacts. We analyze two different scenarios for the SHI in relation to the cloud top capped by a temperature inversion: (i) the SHI coincides with the cloud top, and (ii) the SHI is vertically separated from the lowered cloud top. In the first case, the SHI and the cloud layer are coupled by turbulence that extends over the cloud top and connects the two layers by turbulent mixing. Several profiles reveal downward virtual sensible and latent heat fluxes at the cloud top, indicating entrainment of humid air supplied by the SHI into the cloud layer. For the second case, a downward moisture transport at the base of the SHI and an upward moisture flux at the cloud top is observed. Therefore, the area between the cloud top and SHI is supplied with moisture from both sides. Finally, large-eddy simulations (LESs) complement the observations by modeling a case of the first scenario. The simulations reproduce the observed downward turbulent fluxes of heat and moisture at the cloud top. The LES realizations suggest that in the presence of a SHI, the cloud layer remains thicker and the temperature inversion height is elevated. Article in Journal/Newspaper Arctic Beluga Beluga* Niedersächsisches Online-Archiv NOA Arctic Atmospheric Chemistry and Physics 21 8 6347 6364 |
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article Verlagsveröffentlichung |
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article Verlagsveröffentlichung Egerer, Ulrike Ehrlich, André Gottschalk, Matthias Griesche, Hannes Neggers, Roel A. J. Siebert, Holger Wendisch, Manfred Case study of a humidity layer above Arctic stratocumulus and potential turbulent coupling with the cloud top |
topic_facet |
article Verlagsveröffentlichung |
description |
Specific humidity inversions (SHIs) above low-level cloud layers have been frequently observed in the Arctic. The formation of these SHIs is usually associated with large-scale advection of humid air masses. However, the potential coupling of SHIs with cloud layers by turbulent processes is not fully understood. In this study, we analyze a 3 d period of a persistent layer of increased specific humidity above a stratocumulus cloud observed during an Arctic field campaign in June 2017. The tethered balloon system BELUGA (Balloon-bornE moduLar Utility for profilinG the lower Atmosphere) recorded vertical profile data of meteorological, turbulence, and radiation parameters in the atmospheric boundary layer. An in-depth discussion of the problems associated with humidity measurements in cloudy environments leads to the conclusion that the observed SHIs do not result from measurement artifacts. We analyze two different scenarios for the SHI in relation to the cloud top capped by a temperature inversion: (i) the SHI coincides with the cloud top, and (ii) the SHI is vertically separated from the lowered cloud top. In the first case, the SHI and the cloud layer are coupled by turbulence that extends over the cloud top and connects the two layers by turbulent mixing. Several profiles reveal downward virtual sensible and latent heat fluxes at the cloud top, indicating entrainment of humid air supplied by the SHI into the cloud layer. For the second case, a downward moisture transport at the base of the SHI and an upward moisture flux at the cloud top is observed. Therefore, the area between the cloud top and SHI is supplied with moisture from both sides. Finally, large-eddy simulations (LESs) complement the observations by modeling a case of the first scenario. The simulations reproduce the observed downward turbulent fluxes of heat and moisture at the cloud top. The LES realizations suggest that in the presence of a SHI, the cloud layer remains thicker and the temperature inversion height is elevated. |
format |
Article in Journal/Newspaper |
author |
Egerer, Ulrike Ehrlich, André Gottschalk, Matthias Griesche, Hannes Neggers, Roel A. J. Siebert, Holger Wendisch, Manfred |
author_facet |
Egerer, Ulrike Ehrlich, André Gottschalk, Matthias Griesche, Hannes Neggers, Roel A. J. Siebert, Holger Wendisch, Manfred |
author_sort |
Egerer, Ulrike |
title |
Case study of a humidity layer above Arctic stratocumulus and potential turbulent coupling with the cloud top |
title_short |
Case study of a humidity layer above Arctic stratocumulus and potential turbulent coupling with the cloud top |
title_full |
Case study of a humidity layer above Arctic stratocumulus and potential turbulent coupling with the cloud top |
title_fullStr |
Case study of a humidity layer above Arctic stratocumulus and potential turbulent coupling with the cloud top |
title_full_unstemmed |
Case study of a humidity layer above Arctic stratocumulus and potential turbulent coupling with the cloud top |
title_sort |
case study of a humidity layer above arctic stratocumulus and potential turbulent coupling with the cloud top |
publisher |
Copernicus Publications |
publishDate |
2021 |
url |
https://doi.org/10.5194/acp-21-6347-2021 https://noa.gwlb.de/receive/cop_mods_00056393 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00056044/acp-21-6347-2021.pdf https://acp.copernicus.org/articles/21/6347/2021/acp-21-6347-2021.pdf |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic Beluga Beluga* |
genre_facet |
Arctic Beluga Beluga* |
op_relation |
Atmospheric Chemistry and Physics -- http://www.atmos-chem-phys.net/volumes_and_issues.html -- http://www.bibliothek.uni-regensburg.de/ezeit/?2069847 -- 1680-7324 https://doi.org/10.5194/acp-21-6347-2021 https://noa.gwlb.de/receive/cop_mods_00056393 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00056044/acp-21-6347-2021.pdf https://acp.copernicus.org/articles/21/6347/2021/acp-21-6347-2021.pdf |
op_rights |
https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/openAccess |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.5194/acp-21-6347-2021 |
container_title |
Atmospheric Chemistry and Physics |
container_volume |
21 |
container_issue |
8 |
container_start_page |
6347 |
op_container_end_page |
6364 |
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1766330125892190208 |